Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Towards a Theory of Claim Making: Bridging Access and Property Theory
    Kronenburg García, Angela ; Dijk, Han van - \ 2020
    Society & Natural Resources 33 (2020)2. - ISSN 0894-1920 - p. 167 - 183.
    access - Claim making - land - natural resources - property - theory

    This article proposes a framework for studying and understanding how people make claims to land and other natural resources. We argue that a focus on claim-making practices of actors (individuals, groups, institutions, companies, the state), and the processes of appropriation, accessing and contestation that come along with it, best responds to Sikor and Lund’s call to examine “the grey zone” between access and property. We identify and discuss three practices of claim making: “grounding claims” is the practice of inscribing or altering the landscape with visible markers connoting ownership; “talking claims” is when speech is used strategically to make, justify and contest claims; and “representing claims” is when claims are represented on material objects (maps, title deeds) that are detached from the resource. We contribute to debates on enclosure, large-scale land acquisitions and resource grabbing by providing a lens of claim making through which these processes can be conceptualized.

    Competence for life: a review of developments and perspective for the future : Farewell address upon retiring as Professor of Education and Competence Studies at Wageningen University & Research on 20 October 2016
    Mulder, Martin - \ 2016
    Wageningen : Wageningen University & Research - ISBN 9789462579675 - 36
    education - competences - theory - research - onderwijs - bevoegdheden - theorie - onderzoek
    The concept of competence is probably as old as humanity. Introduced in the academic literature in the 1950s, it underwent a remarkable development. Used in the 1960s, criticised in the 1970s, discarded in the 1980s, renewed in the 1990s, and transformed in the 2000s, the global competence movement in the 2010s is stronger than ever. Started as an approach to train specific skills and teach for known jobs, it developed as a strategy to align the worlds of work and education and to prepare professionals for the labour market and lifelong learning. Now it is time to think about competencies for the unknown future and about ways to learn these.
    Aesthetic creation theory and landscape architecture
    Etteger, Rudi Van; Thompson, I.H. ; Vicenzotti, Vera - \ 2016
    Jola : Journal of Landscape Architecture 11 (2016)1. - ISSN 1862-6033 - p. 80 - 91.
    Aesthetic Creation Theory - criticism - landscape architecture - philosophical aesthetics - theory

    In recent decades the landscape architectural discourse has tended to eschew ideas of aesthetics while focusing instead on notions of functional and sustainable design. We offer the view that Aesthetic Creation Theory, whose principal exponent is the philosopher Nick Zangwill, has the potential to redress this imbalance by interpreting landscape architecture as art. Zangwill's account of art differs, however, from many other definitions found in philosophical aesthetics: it holds that works of art have aesthetic functions that are essential to them, but also allows that they have other, non-aesthetic functions, for example practical or ecological ones. It thus removes the strict distinction between fine art and the useful arts. After introducing Zangwill's theory, we discuss some rival theories of art and then explore the virtues of Aesthetic Creation Theory for the theory, practice, and pedagogy of landscape architecture.

    Peasants and the art of farming : A Chayanovian manifesto
    Ploeg, J.D. van der - \ 2013
    Winnipeg : Fernwood (Agrarian Change and Peasant Studies Series 2) - ISBN 9781552665657 - 157
    landbouw bedrijven in het klein - bedrijfssystemen - duurzame landbouw - plattelandsgemeenschappen - landbouw bedrijven - landbouw - verandering - theorie - geschiedenis - wereld - voedselsoevereiniteit - peasant farming - farming systems - sustainable agriculture - rural communities - farming - agriculture - change - theory - history - world - food sovereignty
    Many impressive studies on the changing nature of the global food system have been published, and nearly all address changes at the macro level. The far less visible changes occurring at the micro level have received relatively little attention, especially in the realm of critical rural studies. This book is a reflection of the far reaching and complex transformations of food systems that have occurred as a result of liberalization and globalization. This book focuses on the structure and dynamics of peasant farms and the historically highly variable relations that govern the processes of labour and production within the peasant farms. Jan Douwe van der Ploeg argues that peasant agriculture can play an important, if not central, role in augmenting food production and creating sustainability. However, peasants today, as in the past, are materially neglected. By building on the pioneering work of Chayanov, this book seeks to address this neglect and to show how important peasants are in the ongoing struggles for food, food sustainability and food sovereignty.
    On a landscape approach to design an eco-poetic interpretation of landscape
    Koh, J. - \ 2013
    Wageningen : Wageningen Universiteit - 43
    landschapsarchitectuur - landschap - ontwerp - theorie - landscape architecture - landscape - design - theory
    Rede Wageningen Universiteit, 30 mei 2013.
    The predictive adaptive response: modeling the life history evolution of the butterfly, Bicyclus anynana, in seasonal environments
    Heuvel, J. van den; Saastamoinen, M. ; Brakefield, P.M. ; Kirkwood, T.B.L. ; Zwaan, B.J. - \ 2012
    Wageningen UR
    ecology - evolutionary - evolution - physiological - life history - modeling - individual based - stochastic spatial - phenotypic plasticy - polymorphism - resource allocation - theory - trade offs
    A predictive adaptive response (PAR) is a type of developmental plasticity where the response to an environmental cue is not immediately advantageous but instead is later in life. The PAR is a way for organisms to maximize fitness in varying environments. Insects living in seasonal environments are valuable model systems for testing the existence and form of PAR. Previous manipulations of the larval and the adult environments of the butterfly Bicyclus anynana have shown that individuals that were food restricted during the larval stage coped better with forced flight during the adult stage compared to those with optimal conditions in the larval stage. Here, we describe a state-dependent energy allocation model, which we use to test whether such a response to food restriction could be adaptive in nature where this butterfly exhibits seasonal cycles. The results from the model confirm the responses obtained in our previous experimental work and show how such an outcome was facilitated by resource allocation patterns to the thorax during the pupal stage. We conclude that for B. anynana, early-stage cues can direct development toward a better adapted phenotype later in life and, therefore, that a PAR has evolved in this species.
    Technology and social theory
    Matthewman, S. - \ 2011
    Basingstoke : Palgrave Macmillan (Themes in social theory ) - ISBN 9780230577565 - 206
    technologie - sociologie - theorie - innovaties - technology - sociology - theory - innovations
    Real Tourism; Practice, Care, and Politics in Contemporary Travel Culture
    Minca, C. ; Oakes, T. - \ 2011
    Oxford, UK : Routledge (Contemporary geographies of leisure, tourism and mobility 26) - ISBN 9780415582247 - 280
    toerisme - reizen - theorie - toekomst - vrije tijd - sociologie - tourism - travel - theory - future - leisure - sociology
    Over the past decade, tourism studies has broken out of its traditional institutional affiliation with business and management programs to take its legitimate place as an interdisciplinary social science field of cutting edge scholarship. The field has emerged as central to ongoing debates in social theory concerning such diverse topics as postcolonialism, mobility, and postmodernism, to name just a few. While there has been a diverse body of empirical research on this transformation the theoretical discussions in tourism studies remain largely attached to theories of modernity and Anglo-centric assumptions about tourism. There is a need for the field to come to terms theoretically with the contemporary and future realities of tourism as a truly global phenomenon. This book puts forward new postmodernist ideas and arguments about tourism today and in the future.
    The operator hierarchy : a chain of closures linking matter, life and artificial intelligence
    Jagers op Akkerhuis, G.A.J.M. - \ 2010
    Radboud University Nijmegen. Promotor(en): H. Zwart. - [S.l. : S.n. - ISBN 9789032703899 - 286
    evolutie - theorie - leven - natuur - systeembiologie - oorsprong van het leven - theoretische biologie - natuurwetenschappen - kunstmatige intelligentie - evolution - theory - life - nature - systems biology - origin of life - theoretical biology - natural sciences - artificial intelligence
    Dit proefschrift beschrijft een nieuw ordenend principe met als doel daarmee bruggen te kunnen bouwen tussen de verschillende wetenschapsvelden. Bij het realiseren van dit doel is de evolutietheorie van Darwin als startpunt genomen. Het ontstaan van organisatieniveaus wordt vaak weergegeven als een hiërarchische volgorde van systemen. De literatuur geeft hiervan talrijke voorbeelden. De gepresenteerde opeenvolgingen van systemen zijn op het eerste gezicht heel logisch, zoals atoom, molecuul, organel, cel, weefsel, orgaan, organisme, populatie, gemeenschap, ecosysteem, planeet, zonnestelsel, sterrenstelsel, heelal ( figuur 2). Een dergelijke benadering van de hiërarchie in de natuur heeft breed opgang gedaan in de exacte wetenschappen. Echter, bij nadere bestudering blijkt deze hiërarchie niet consequent. Het doel van dit proefschrift is om ordenende principes in de natuurwetenschappen te vinden en deze toe te passen bij het bouwen van bruggen tussen de disciplines. Een beter begrip van deze regels zal het namelijk mogelijk maken om voorspellingen over de volgende stadia in de evolutie aan te scherpen en op basis hiervan nauwkeuriger uitspraken te doen over toekomstige operatoren. Dit zal wetenschappers en filosofen nieuwe mogelijkheden bieden om op verkenning te gaan in een domein waarvan men tot voor kort dacht dat het ontoegankelijk was voor een natuurwetenschappelijke benadering: de toekomst van de evolutie.
    Vrijheid of macht? Een filosofische reflectie op democratische planvorming
    Behagel, J.H. - \ 2009
    Topos : periodiek over landschapsarchitectuur, ruimtelijke planning en sociaal-ruimtelijke analyse 19 (2009)01. - ISSN 1572-302X - p. 14 - 17.
    regionale planning - participatie - theorie - regional planning - participation - theory
    Geen planvormingsproces, of er worden mensen en partijen uit het gebied zelf gevraagd om mee te denken. De laatste jaren heeft de participatieve aanpak zoveel aan kracht gewonnen dat het een vanzelfsprekendheid lijkt. Maar waarom vinden we dit eigenlijk belangrijk? Leiden gebiedsprocessen tot meer democratische beslissingen en vrijheid? Met behulp van grote denkers als Kant en Nietzsche weegt Jelle Behagel voor- en nadelen van publieke participatie af
    Emergence and embedding of innovation brokers in the agricultural innovation system
    Klerkx, L.W.A. ; Leeuwis, C. - \ 2009
    In: Theory and practice of advisory work in a time of turbulences - proceedings XIX ESEE, Assisi (Perugia), Italy, 15-19 September 2009. - Perugia : INEA / University of Perugia - p. 65 - 69.
    voorlichtingskunde - landbouw - voorlichting - adviescentra - efficiëntie - theorie - oefening - ontwikkelingslanden - wereld - landbouwvoorlichting - extension education - agriculture - extension - advisory centres - efficiency - theory - practice - developing countries - world - agricultural extension
    Theoretical perspectives on institutional variety in agri-food chains: an annotated bibliography.
    Vellema, S. ; Danse, M.G. ; Meijerink, G.W. ; Ton, G. ; Valk, O.M.C. van der; Wilbrink, H. - \ 2008
    Den Haag : LEI (LEI /Rapport ) - 60
    landbouwproducten - voedselproducten - bibliografieën - theorie - agro-industriële ketens - agricultural products - food products - bibliographies - theory - agro-industrial chains
    Water en olie, dat mengt niet vanzelf : onderzoek naar theoriegebruik bij leefstijlcampagnes
    Wevers, A. ; Renes, R.J. ; Woerkum, C.M.J. van - \ 2008
    [S.l.] : ZonMw - ISBN 9789085852292 - 99
    levensstijl - campagnes - ziektebestrijding - gezondheidseducatie - gezondheidsbevordering - informatieverspreiding - efficiëntie - theorie - onderzoek - kwalitatieve analyse - kwantitatieve analyse - volksgezondheid - nederland - kwalitatieve methoden - kwantitatieve methoden - lifestyle - campaigns - disease control - health education - health promotion - diffusion of information - efficiency - theory - research - qualitative analysis - quantitative analysis - public health - netherlands - qualitative methods - quantitative methods
    Sociale rechtvaardigheid en ruimtelijke diversiteit. Een Walzeriaanse visie op bereikbaarheid en toegankelijkheid.
    Keulartz, F.W.J. - \ 2007
    Filosofie en Praktijk 28 (2007)5. - ISSN 0167-2444 - p. 38 - 48.
    stedelijke planning - landgebruik - theorie - urban planning - land use - theory
    Met behulp van Walzers notie van complexe gelijkheid kan aannemelijk gemaakt worden dat er bij de discussie over spreiding versus verweving daadwerkelijk sprake is van een dilemma waarbij telkens weer gezocht zal moeten worden naar balans tussen marktwerking en overheidsbemoeienis. . Dit artikel gaat over open of gesloten buurten en subculturen; over gated comminities. Wat dat laatste betreft, is dat terug te vinden in de door Soetert ontworpen kasteelbouw (Haverleij bij Den Bosch of Brandevoort bij Helmond. Over harde en zwakke grenzen
    Designing sustainable landscapes: from experience to theory : a process of reflective learning from case-study projects in Kenya
    Duchhart, I. - \ 2007
    Wageningen University. Promotor(en): K. Kerkstra, co-promotor(en): F.R. Steiner. - [S.l.] : S.n. - ISBN 9789085046752 - 224
    landschap - duurzaamheid (sustainability) - ontwerp - landschapsarchitectuur - planning - ruimtelijke ordening - participatie - theorie - kenya - landscape - sustainability - design - landscape architecture - planning - physical planning - participation - theory - kenya
    Het betreft hier een actie-geörienteerd onderzoek naar een duurzame ontwikkeling van dorpen en steden (in Kenia). Naast de landschappelijke ingrepen (i.v.m. erosie en gezondheid), zijn ook nationale instituten en overheden in contact gebracht met lokale organisaties om zo kennisuitwisseling tot stand te brengen
    Reforms in turbulent times : a study on the theory and practice of three irrigation management policy reform models in Mashonaland, Zimbabwe
    Zawe, C. - \ 2006
    Wageningen University. Promotor(en): Linden Vincent, co-promotor(en): Alex Bolding. - [S.l.] : S.n. - ISBN 9789085045427 - 353
    irrigatie - bedrijfsvoering - zimbabwe - beleid - landbouwhervorming - theorie - oefening - irrigation - management - zimbabwe - policy - agrarian reform - theory - practice
    This thesis focuses on smallholder Irrigation Management Reform (IMR) policy models implemented in Mashonaland West and Mashonaland Central provinces of Zimbabwe. In particular it is concerned with how the models were negotiated, recursively shaped, adopted, transformed and accepted into policy by an array of actors spanning across international funding agencies, government ministries, local agencies responsible for smallholder irrigation development, the irrigators and their surrounding communities. The thesis intends to add to the growing body of debate on IMRs by providing information on ‘the reform process,’ an aspect that has been underplayed so far. It also aims to contribute to the development of an irrigation management policy for the smallholder irrigation sector in Zimbabwe that has been lacking to date.
    Architects of nature: environmental infrastructure and the nature-culture dichotomy
    Kreike, E.H.P.M. - \ 2006
    Wageningen University. Promotor(en): M. Wessel, co-promotor(en): Freerk Wiersum. - [S.l. ] : S.n. - ISBN 9789085044444 - 289
    milieu - cultuur - interacties - natuurbescherming - menselijke activiteit - milieubescherming - milieubeheer - theorie - environment - culture - interactions - nature conservation - human activity - environmental protection - environmental management - theory
    Kulturer & Organisationer
    Hofstede, G. ; Hofstede, G.J. - \ 2006
    Kopenhagen : Handelshøjskolens Forlag - ISBN 9788762902527 - 437
    intercultureel onderzoek - rassen (taxonomisch) - interraciale relaties - etnische groepen - karakteristieken - psychologie - cultuur - socialisatie - etnografie - sociologie - cultuursociologie - communicatie - niet-verbale communicatie - groepen - organisaties - wereld - theorie - bedrijfsvoering - internationale vergelijkingen - bedrijfsmanagement - denken - cross cultural studies - races - race relations - ethnic groups - characteristics - psychology - culture - socialization - ethnography - sociology - cultural sociology - communication - nonverbal communication - groups - organizations - world - theory - management - international comparisons - business management - thinking
    Lokales Denken, globales Handeln : Interkulturelle Zusammenarbeit und globales Management
    Hofstede, G. ; Hofstede, G.J. - \ 2006
    München : Deutscher Taschenbuch Verlag - ISBN 9783406533228 - 555
    intercultureel onderzoek - rassen (taxonomisch) - interraciale relaties - etnische groepen - karakteristieken - psychologie - cultuur - socialisatie - etnografie - sociologie - cultuursociologie - communicatie - niet-verbale communicatie - groepen - organisaties - wereld - theorie - bedrijfsvoering - internationale vergelijkingen - bedrijfsmanagement - denken - cross cultural studies - races - race relations - ethnic groups - characteristics - psychology - culture - socialization - ethnography - sociology - cultural sociology - communication - nonverbal communication - groups - organizations - world - theory - management - international comparisons - business management - thinking
    Allemaal andersdenkenden: omgaan met cultuurverschillen
    Hofstede, G. ; Hofstede, G.J. - \ 2005
    Amsterdam/Antwerpen : Contact - ISBN 9789025426811 - 431
    rassen (taxonomisch) - etnische groepen - psychologie - intercultureel onderzoek - cultuur - socialisatie - interraciale relaties - sociologie - cultuursociologie - communicatie - niet-verbale communicatie - groepen - organisaties - wereld - theorie - bedrijfsvoering - bestuur - bedrijfseconomie - races - ethnic groups - psychology - cross cultural studies - culture - socialization - race relations - sociology - cultural sociology - communication - nonverbal communication - groups - organizations - world - theory - management - administration - business management
    Onderwijsconcepten en professionele ontwikkeling van leraren vanuit praktijktheoretisch perspectief
    Vries, Y. de - \ 2004
    Wageningen University. Promotor(en): Martin Mulder, co-promotor(en): D. Beijaard. - [s.l.] : S.n. - ISBN 9789058089571 - 184
    lerarenopleiding - beroepsopleiding (hoger) - onderwijsmethoden - leertheorie - docenten - onderwijzen - oefening - theorie - nederland - professionaliteit - ontwikkeling - vakbekwaamheid - teacher training - professional education - teachers - teaching - teaching methods - learning theory - professionalism - development - professional competence - practice - theory - netherlands
    The focus of the study reported on in this dissertation is research among teachers with respect to their educational concepts and the extent to which their theories change or develop in the course of teachers' careers. The research is done from a practical knowledge perspective in which what teachers themselves regard as important in education and in teaching, plays a central role. The main research study focussed on a number of aspects that constitute the core of thinking about education; i.e., the aim of education, the content of education, and the role of the teacher and that of the pupil in the educational process. By means of interviews and observation in the classroom these aspects were studied. The results show that the teachers' educational concepts are strongly related to personal and context factors like experiences during childhood; the their education, working experience, the pupils they teach, the school organization, the subjects the teachers teach and social developments. In the second, complementary study, the focus was on the teachers' practical theories about how pupils learn, and on the extent to which these theories change or develop in the course of teachers' careers. The data indicate that all the teachers changed or developed their practical theory with respect to learning by pupils to a greater or lesser degree. As in the main study, personal and contextual factors played a role in the changes in, and development of, these theories. The teacher's own 'drive' to learn, the extent of internal or external steering, and the motivation to learn are important personal factors. Experiences gained in educational practice and the school organization are important context factors.
    CoP op Alterra; use the world around as a learning resource and be a learning resource for the world
    Kersten, P.H. ; Kranendonk, R.P. - \ 2002
    Wageningen : Alterra (Alterra-rapport 546) - 151
    kennis - ontwikkeling - managementbenaderingen - theorie - informatieverspreiding - kennistheorie - kennismanagement - kennisoverdracht - maatschappijwetenschappen - sociologie - knowledge - development - diffusion of information - management philosophies - theory - theory of knowledge
    Uitleg van het begrip Community of Practice (CoP). Het proces van kennisontwikkeling, zoals dat door Etienne Wenger is ontwikkeld
    Op zoek naar magische momenten in de ruimtelijke planvorming; deskstudie voor de etudes uit de nota "Natuur voor mensen, mensen voor natuur"
    Kersten, P.H. ; Eekhout, M.J.J. ; Kranendonk, R.P. ; Poel, K.R. de; Geenen, J.J.N. - \ 2001
    Wageningen : Alterra (Alterra-rapport 366) - 166
    ruimtelijke ordening - ontwerp - acteurs - gevalsanalyse - planning - theorie - landelijk gebied - landschapsarchitectuur - natuur - physical planning - design - actors - case studies - planning - theory
    Architectuur voor een 'standaard raamwerk water'; toepasbaar bij modelstudies in het waterbeheer
    Wal, T. van der - \ 1999
    H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 32 (1999)22. - ISSN 0166-8439 - p. 46 - 47.
    waterbeheer - hydrologie - theorie - methodologie - modellen - computer software - toepassingen - computers - ontwerp - systemen - automatisering - programmeren - integraal waterbeheer - software-ontwikkeling - water management - hydrology - theory - methodology - models - computer software - applications - computers - design - systems - automation - programming - integrated water management - software engineering
    Uitleg over de achtergronden en de architectuur van het in ontwikkeling zijnde 'Standaard Raamwerk Water'. Het wordt een gemeenschappelijk raamwerk voor alle modelapplicaties in het integraal waterbeheer
    Management, structuur en cultuur : over het gebruik van organisatietheorieën in Breda
    Polling, J. - \ 1999
    Agricultural University. Promotor(en): J.C. van Dalen. - S.l. : [s.n.] - ISBN 9789058080967 - 251
    overheidsorganisaties - organisatieontwikkeling - organisaties - theorie - verandering - bedrijfsvoering - overheid - plaatselijk bestuur - geschiedenis - nederland - noord-brabant - organisatie - government organizations - organizational development - organizations - theory - change - management - public authorities - local government - history - netherlands - noord-brabant - organization

    This book deals with organizational change in two different ways. One way is the historical description of several attempts to implement organizational change in one particular organization. That organization is the local civil service of Breda, a city in the southern part of the Netherlands with a history that goes back to the thirteenth century. This book covers the period of about thirty years from 1965 until 1996. In this period Breda had between 120.000 and 130.000 inhabitants and the civil service varied between 1200 and 1800 employees. The historical description focuses not only on the changes as such but also on the situation that existed when the attempts to change were undertaken (the environmental conditions). Main goal in this part of the study is to create a basis for an answer to the question: What factors or conditions were decisive for the claimed success of the changes that took place in 1992, where similar attempts at earlier dates seemed to have failed?

    The other way to treat organizational change in this study is induced by the question: Which organization theory or theories were used in the reorganizations described in the historical part? In order to obtain an answer to this question it was necessary to go into the character of organizations theory - which is thought to be a body of knowledge - and into the relevancy of organizations theory for practical use - which is thought to be small. A theoretical model for research is proposed in part 2. This model is based upon three major assumptions.

    guidelines and directions derived from organizations theory are insufficient to support organizational change in practice. This causes "changers" (those who initiate the desired change) to develop their own, "private" organization theory. An important part of this study is concerned with the reconstruction of those private theories.the private theories of changers are expressed one way or another in the documents used to realise the desired organizational change. In the addendum to this study quotes from the documents used are translated into "central concepts" of the changers. These central concepts are considered to be the framework of the private organization theories.organizational change is realised on one or more of three organizational dimensions: management, structure and culture. These dimensions are influenced strongly by environmental factors. Technologic possibilities available, the actual economic situation, prevailing social values and political and governmental conditions are considered to be the most important environmental conditions.

    The last section of part 2 (chapter 6) gives a short analysis of the specific character of Dutch local government and public service. In the local civil service the position of the town clerk in most cities has evolved to that of city manager in the period considered.

    The historical account in part 3 is subdivided into 5 chapters, the first being a short and global sketch of the history of the Netherlands since World War II in order to give a general background for the developments in Breda. Each of the other four give a description of one of the successive attempts to reorganize the civil service of Breda. In these chapters attention is also given to several problems of local policy that filled, for the most part, the political agenda.

    In part 4, the model developed in part 2 is applied on documents used to realise the desired changes described in part 3. The private theories for each period are reconstructed and compared to the general organization theory existing at the time. An important aspect of this analysis is that private and general organization theory and the desired and realised organization are described in terms of the three dimensions (management, structure and culture) of the proposed referential model in part 2. Each chapter of part 4 closes with a summary of conclusions with respect to that period.

    General conclusions derived from the whole study and a few suggestions for further research are gathered in part 5. The most important conclusions can be presented in the following statements.

    Writers on organizations agree to a large extent on the fact that environmental conditions have a bearing on the structure and functioning of organizations. Many of them even agree on the fact that organizations theories are influenced by the economic and social forces of their time. Nevertheless proposed organization theories hardly ever try to specify the situation in which they are developed.An explanation for this lack of attention may be found in the emphasis on comparative analysis of organizational research. In comparing organizations in a specific historical period, technological economic, social and political conditions can be viewed as the same for all organizations at the time. In that case those environmental conditions have no bearing on the results of the research and need not be made explicit.Organizational change can be considered as change on the three dimensions: management, structure and culture. In the case observed in this study the same set of rather simple rules was used for creating change in each of the four successive periods on the dimensions management: (replace sitting managers) and structure (enhance line-staff relations, put together what belongs together; though criteria to do this differ from period to period; and decrease span of control).The most important motive to introduce large scale changes in the case observed, therefore, seems to be the need to change organizational culture. In the case considered, the organization started with a power oriented culture. The first attempt on change tried to implement a role oriented culture but failed for the most part as a result of the existing power structure.

    The second attempt was accompanied by the wave of democratization of the late sixties and early seventies which undermined the power structure in the organization. The rather low pressure on reinforcing role relations, except for those belonging to project management, caused a major shift towards a task culture in which hardly anybody seemed to have authority. In this situation project management played a major role.

    In the third attempt, under pressure of the economic recession, legitimate authority, the political power of mayor and aldermen, reinforced a strong role culture. As a result of this change the existing structural elements of project management were practically eliminated. The position of the chief executive level (the town clerk) was weak.

    In the fourth attempt power shifted from the political to the chief executive level. This shift was enabled by the weak political position of mayor and aldermen and the authority bestowed on the town clerk.

    Modelstructuren voor het schatten van het volume c.q. gewicht van komkommers met computer vision
    Langers, R.A. - \ 1998
    Wageningen : IMAG-DLO (Nota / Dienst Landbouwkundig Onderzoek, Instituut voor Milieu- en Agritechniek P98-25) - 20
    cucumis sativus - komkommers - plantenfysiologie - plantenanatomie - plantenmorfologie - modellen - theorie - onderzoek - machine vision - cucumis sativus - cucumbers - plant physiology - plant anatomy - plant morphology - models - theory - research - machine vision
    STIMEST versie 1.0 : een model voor mineralenstromen en mestbewerking op vleesvarkensbedrijven
    Adriaenssens, R.S. ; Willers, H.C. ; Lamaker, E.J.J. - \ 1998
    Wageningen : IMAG-DLO (Nota / Dienst Landbouwkundig Onderzoek, Instituut voor Milieu- en Agritechniek P 98-14) - 25
    mest - vloeibare meststoffen - rundveedrijfmest - varkens - zoötechniek - mineralen - voedingsfysiologie - modellen - theorie - onderzoek - mestoverschotten - mestverwerking - manures - liquid manures - cattle slurry - pigs - zootechny - minerals - nutrition physiology - models - theory - research - manure surpluses - manure treatment
    Duurzaam gewasproductiesysteem voor de toekomst
    Bakker, J.C. - \ 1998
    Agrabeton 8 (1998)1. - ISSN 0167-3246 - p. 4 - 4.
    duurzaamheid (sustainability) - kassen - forceren van planten - landbouw - klimaatverandering - natuurlijke hulpbronnen - hulpbronnengebruik - bescherming - herstel - theorie - ontwerp - toekomst - sustainability - greenhouses - forcing - agriculture - climatic change - natural resources - resource utilization - protection - rehabilitation - theory - design - future
    Korte presentatie van een concept dat aan de Duurzame Technologische Ontwikkeling (DTO) moet kunnen voldoen. Omdat het een ontwerp voor de toekomst betreft wordt het ook wel afgekort tot 'KAS 2020'
    Global optimization at work
    Hendrix, E.M.T. - \ 1998
    Agricultural University. Promotor(en): P. van Beek; A.J.M. Beulens. - Renkum : Hendrix - ISBN 9789054858744 - 248
    modellen - theorie - wiskundige modellen - onderzoek - wetenschap - models - theory - mathematical models - research - science

    In many research situations where mathematical models are used, researchers try to find parameter values such that a given performance criterion is at an optimum. If the parameters can be varied in a continuous way, this in general defines a so-called Nonlinear Programming Problem. Methods for Nonlinear Programming usually result in local optima. A local optimum is a solution (parameter values) which is the best with respect to values in the neighbourhood of that solution, not necessarily the best over the total admissible, feasible set of all possible parameter values, solutions.

    For mathematicians this results in the research question: How to find the best, global optimum in situations where several local optima exist?, the field of Global Optimization (GLOP). Literature, books and a specific journal, has appeared during the last decades on the field. Main focus has been on the mathematical side, i.e. given assumptions on the structure of the problems to be solved and specific global optimization methods and properties are derived. Cooperation between mathematicians and researchers (in this book called 'the modeller' or 'the potential user'), who saw global optimization problems in practical problems has lead to application of GLOP algorithms to practical optimization problems. Some of those can be found in this book. In this book we started with the question:

    Given a potential user with an arbitrary global optimization problem, what route can be taken in the GLOP forest to find solutions of the problem?

    From this first question we proceed by raising new questions. In Chapter 1 we outline the target group of users we have in mind, i.e. agricultural and environmental engineers, designers and OR workers in agricultural science. These groups are not clearly defined, nor mutually exclusive, but have in common that mathematical modelling is used and there is knowledge of linear programming and possibly of combinatorial optimization.

    In general, when modellers are confronted with optimization aspects, the first approach is to develop heuristics or to look for standard nonlinear programming codes to generate solutions of the optimization problem. During the search for solutions, multiple local optima may appear. We distinguished two major tracks for the path to be taken from there by the potential user to solve the problem. One track is called the deterministic track and is discussed in Chapters 2, 3 and 4. The other track is called the stochastic track and is discussed in Chapters 5 and 6. The two approaches are intended to reach a different goal.

    The deterministic track aims at:

    The global optimum is approximated (found) with certainty in a finite number of steps.

    The stochastic track is understood to contain some stochastic elements and aims at:

    Approaching the optimum in a probabilistic sense as effort grows to infinity.

    Both tracks are investigated in this book from the viewpoint of a potential user corresponding to the way of thinking in Popperian science. The final results are new challenging problems, questions for further research. A side question along the way is:

    How can the user influence the search process given the knowledge of the underlying problem and the information that becomes available during the search?

    The deterministic approach
    When one starts looking into the deterministic track for a given problem, one runs into the requirements which determine a major difference in applicability of the two approaches.

    Deterministic methods require the availability of explicit mathematical expressions of the functions to be optimized.

    In many practical situations which are also discussed in this book, these expressions are not available and deterministic methods cannot be applied. The operations in deterministic methods are based on concepts such as Branch-and-Bound and Cutting which require bounding of functions and parameters based on so-called mathematical structures.

    In Chapter 2 we describe these structures and distinguish between those which can be derived directly from the expressions, such as quadratic, bilinear and fractional functions and other structures which require analysis of the expressions such as concave and Lipschitz continuous functions. Examples are given of optimization problems revealing their structure. Moreover, we show that symmetry in the model formulation may cause models to have more than one extreme.

    In Chapter 3 the relationship between GLOP and Integer Programming (IP) is highlighted for several reasons.

    • Sometimes practical GLOP problems can be approximated by IP variants and solved by standard Mixed Integer Linear Programming (MILP) techniques.
    • The algorithms of GLOP and IP can similarly be classified.
    • The transformability of GLOP problems to IP problems and vice versa shows that difficult problems in one class will not become easier to solve in the other.
    • Analysis of problems, which is common in Global Optimization, can be used to better understand the complexity of some IP problems.

    In Chapter 4 we analyze the use of deterministic methods, demonstrating the application of the Branch-and-Bound concept. The following can be stated from the point of view of the potential user:

    • Analysis of the expressions is required to find useful mathematical structures (Chapter 2). It should be noted that also interval arithmetic techniques can be applied directly on the expressions.
    • The elegance of the techniques is the guarantee that we are certain about the global optimality of the optimum, when it has been discovered and verified.
    • The methods are hard to implement. Thorough use should be made of special data structures to store the necessary information in memory.

    Two cases are elaborated. The quadratic product design problem illustrates how the level of Decision Support Systems can be reached for low dimensional problems, i.e. the number of variables, components or ingredients, is less than 10. The other case, the nutrient problem, shows how by analysis of the problem many useful properties can be derived which help to cut away large areas of the feasible space where the optimum cannot be situated. However, it also demonstrates the so-called Curse of Dimensionality; the problem has so many variables in a realistic situation that it is impossible to traverse the complete Branch-and-Bound tree. Therefore it is good to see the relativity of the use of deterministic methods:

    No global optimization method can guarantee to find and verify the global optimum for every practical situation, within a humans lifetime.

    The stochastic approach
    The stochastic approach is followed in practice for many optimization problems by combining the generation of random points with standard nonlinear optimization algorithms. The following can be said from the point of view of the potential user.

    • The methods require no mathematical structure of the problem and are therefore more generally applicable.
    • The methods are relatively easy to implement.
    • The user is never completely certain that the global optimum has been reached.
    • The optimum is approximated in a probabilistic sense when effort increases to infinity.

    In Chapter 5 much attention is paid to the question what happens when a user wants to spend a limited (not infinite) amount of time to the search for the optimum, preferably less than a humans lifetime:

    What to do when the time for solving the problem is finite?

    First we looked at the information which becomes available during the search and the instruments with which the user can influence the search. It appeared that besides classical instruments which are also available in traditional nonlinear programming, the main instrument is to influence the trade-off between global (random) and local search (looking for a local optimum). This lead to a new question:

    Is there a best way to rule the choice between global and local search, given the information which becomes available?

    Analyzing in a mathematical way with extreme cases lead to the comfortable conclusion that a best method of choosing between global and local search -thus a best global optimization method- does not exist. This is valid for cases where further information (more than the information which becomes available during the search) on the function to be optimized is not available, called in literature the black-box case. The conclusion again shows that mathematical analysis with extreme cases is a powerful tool to demonstrate that so-called magic algorithms -algorithms which are said in scientific journals to be very promising, because they perform well on some test cases- can be analyzed and 'falsified' in the way of Popperian thinking. This leads to the conclusion that:

    Magic algorithms which are going to solve all of your problems do not exist.

    Several side questions derived from the main problem are investigated in this book.

    In Chapter 6 we place the optimization problem in the context of parameter estimation. One practical question is raised by the phenomenon

    Every local search leads to a new local optimum.

    We know from parameter estimation that this is a symptom in so called non-identifiable systems. The minimum is obtained at a lower dimensional surface or curve. Some (non-magic) heuristics are discussed to overcome this problem.

    There are two side questions of users derived from the general remark:

    "I am not interested in the best (GLOP) solution, but in good points".

    The first question is that of Robust Solutions, introduced in Chapter 4, and the other is called Uniform Covering, concerning the generation of points which are nearly as good as the optimum, discussed in Chapter 6.

    Robust solutions are discussed in the context of product design. The robustness is defined as a measure of the error one can make from the solution so that the solution (product) is still acceptable. Looking for the most robust product is looking for that point which is as far away as possible from the boundaries of the feasible (acceptable) area. For the solution procedures, we had a look at the appearance of the problem in practice, where boundaries are given by linear and quadratic surfaces, properties of the product.

    • For linear boundaries, finding the most robust solution is an LP problem and thus rather easy.
    • For quadratic properties the development of specific algorithms is required.

    The question of Uniform Covering concerns the desire to have a set of "suboptimal" points, i.e. points with low function value (given an upper level of the function value); the points are in a so-called level set. To generate "low" points, one could run a local search many times. However, we want the points not to be concentrated in one of the compartments or one sub-area of the level set, we want them to be equally, uniformly spread over the region. This is a very difficult problem for which we test and analyze several approaches in Chapter 6. The analysis taught us that:

    It is unlikely that stochastic methods will be proposed which solve problems in an expected calculation time, which is polynomial in the number of variables of the problem.

    Final result
    Whether an arbitrary problem of a user can be solved by GLOP requires analysis. There are many optimization problems which can be solved satisfactorily. Besides the selection of algorithms the user has various instruments to steer the process. For stochastic methods it mainly concerns the trade-off between local and global search. For deterministic methods it includes setting bounds and influencing the selection rule in Branch-and-Bound. We hope with this book to have given a tool and a guidance to solution procedures. Moreover, it is an introduction to further literature on the subject of Global Optimization.

    Keuze van een nieuwe structuur : eindrapport van de Werkgroep Organisatiestructuur : intern rapport
    Anonymous, - \ 1997
    Wageningen : IMAG-DLO (Nota / DLO Instituut voor Milieu- en Agritechniek P 97-13) - 30
    organisaties - theorie - bedrijfsvoering - bestuur - onderzoeksinstituten - proefstations - bedrijfseconomie - organizations - theory - management - administration - research institutes - experimental stations - business management
    Biologische en chemische bestrijding van de gegroefde lapsnuitkever (Otiorhynchus sulcatus)
    Tol, R.W.H.M. van - \ 1997
    Boskoop : Proefstation voor de Boomkwekerij (Rapport / Boomteeltpraktijkonderzoek nr. 50) - 50
    bestrijdingsmethoden - plantenplagen - plantenziekten - geïntegreerde plagenbestrijding - geïntegreerde bestrijding - gewasbescherming - biologische bestrijding - pesticiden - houtachtige planten als sierplanten - rapporten - theorie - systemen - nederland - otiorhynchus sulcatus - wetenschap - control methods - plant pests - plant diseases - integrated pest management - integrated control - plant protection - biological control - pesticides - ornamental woody plants - reports - theory - systems - netherlands - otiorhynchus sulcatus - science
    Speelveld voor nieuwe buitenplaatsen : een verkennende studie naar de invloed van hun variabele eigenschappen op ruimtelijke kwaliteit en rentabiliteit
    Berg, L.M. van den; Wintjes, A.L.W. - \ 1997
    Wageningen : DLO-Staring Centrum (Rapport / DLO-Staring Centrum 511) - 102
    landschap - landschapsbouw - ruimtelijke ordening - landhuizen - theorie - ontwerp - nederland - kastelen - landscape - landscaping - physical planning - country houses - theory - design - netherlands - castles
    Continuous soil maps - a fuzzy set approach to bridge the gap between aggregation levels of process and distribution models
    Gruijter, J.J. de; Walvoort, D.J.J. ; Gaans, P.F.M. van - \ 1997
    Geoderma 77 (1997)2/4. - ISSN 0016-7061 - p. 169 - 195.
    bodemtaxonomie - bodemclassificatie - bodemtypen - theorie - controle - systemen - systeemanalyse - geostatistiek - regeltheorie - soil taxonomy - soil classification - soil types - theory - control - systems - systems analysis - geostatistics - control theory
    Soil maps as multi-purpose models of spatial soil distribution have a much higher level of aggregation (map units) than the models of soil processes and land-use effects that need input from soil maps. This mismatch between aggregation levels is particularly detrimental in the context of precision agriculture. It is argued that, in order to bridge the gap, soil distribution modelling should be based on a new classification paradigm: that of fuzzy set theory. In geographic space, this enables representation of gradual as well as abrupt transitions, i.e., soil distribution models that can predict variables at pedon level. In a case study we used fuzzy k-means with extragrades to derive a continuous classification from data on thicknesses of 25 layers measured in 552 soil profiles. For interpolation of the class memberships we developed a new method, Compositional Kriging, which takes into account that the memberships have the structure of compositional data: they must be positive and add up to a constant (1) for each individual. These conditions were added to the regular Kriging equations. For cartographic representation of the continuous soil distribution models we developed a new technique, the Pixel Mixture technique, by which we generated a large number of small coloured pixels in each raster cell of the map. The colours of the pixels symbolize the classes, and the proportions of iso-coloured pixels in a cell symbolize the grades of the class memberships as predicted for that cell. The combination of continuous classification and Compositional Kriging convincingly bridged the gap between aggregation levels, and with the aid of the Pixel Mixture technique the resulting soil distribution model could also be visualized at the appropriate level of aggregation. The continuous soil map showed both the general landscape structure, as well as the varying degree of variability within the study area. Based on this multi-purpose continuous soil model, functional models of soil processes and land-use effects can be developed.
    Lagekostenbedrijf is een feit
    Ooijen, J.H. van; Braam, C.R. - \ 1997
    Agrabeton 7 (1997)5. - ISSN 0167-3246 - p. 2 - 4.
    kostenanalyse - stallen - bouwmaterialen - beton - asbest - bouwconstructie - constructieonderdelen - structuren - constructie - theorie - ontwerp - cost analysis - stalls - building materials - concrete - asbestos - building construction - structural components - structures - construction - theory - design
    Op de 'Waiboerhoeve', de centrale proefboerderij van het Praktijkonderzoek Rundvee, Schapen en Paarden (PR) in Lelystad, is een zogenoemd lagekostenbedrijf gebouwd. In dit artikel wordt ingegaan op het ontwerp en de uitvoering van enkele betonnen bouwdelen
    Manure Management. Treatment strategies for sustainable agriculture
    Burton, C.H. ; Beck, J. ; Bloxham, P.F. ; Derikx, P.J.L. ; Martinez, J. - \ 1997
    Silsoe : Silsoe Research Institute - ISBN 9780953128204 - 181
    mest - vloeibare meststoffen - rundveedrijfmest - dierlijke meststoffen - drijfmest - organisaties - theorie - bedrijfsvoering - bestuur - duurzaamheid (sustainability) - mestoverschotten - mestverwerking - bedrijfseconomie - manures - liquid manures - cattle slurry - animal manures - slurries - organizations - theory - management - administration - sustainability - manure surpluses - manure treatment - business management
    HOPSY: instrument voor afwegen van beheersalternatieven
    Edelenbosch, N.H. - \ 1997
    Bosbouwvoorlichting 36 (1997)7. - ISSN 0166-8986 - p. 119 - 122.
    bosbouw - opbrengsten - theorie - houtaanwas - staande opstand - bossen - rotaties - aanbodsevenwicht - vraag - aanbod - econometrische modellen - wiskundige modellen - bosbedrijfsvoering - opbrengstregeling - velling - bosexploitatie - forestry - yields - theory - increment - growing stock - forests - rotations - supply balance - demand - supply - econometric models - mathematical models - forest management - yield regulation - felling - forest exploitation
    Prognoses ontwikkeling houtoogst met Hopsy. Het houtoogstprognose-systeem Hopsy is een instrument dat consequenties voor strategische beheerskeuzen voor de toekomstige houtoogst en houtvoorraad laat zien
    Gevraagd: een verbeterd ontwerp
    Guldemond, J.L. - \ 1997
    Groen : vakblad voor groen in stad en landschap 53 (1997)3. - ISSN 0166-3534 - p. 20 - 24.
    ontwerp - onderhoud - bedrijfsvoering - bestrating - wegen - oppervlakten - theorie - design - maintenance - management - pavements - roads - surfaces - theory
    A geo-information theoretical approach to inductive erosion modelling based on terrain mapping units
    Suryana, N. - \ 1997
    Agricultural University. Promotor(en): M. Molenaar; A.C. Imeson. - S.l. : [s.n.] - ISBN 9789054856306 - 234
    bodem - erosie - geografische informatiesystemen - cartografie - theorie - remote sensing - fotointerpretatie - afbeelden - modellen - onderzoek - soil - erosion - geographical information systems - mapping - theory - remote sensing - photointerpretation - imagery - models - research
    Three main aspects of the research, namely the concept of object orientation, the development of an Inductive Erosion Model (IEM) and the development of a framework for handling uncertainty in the data or information resulting from a GIS are interwoven in this thesis. The first and the second aspect of the thesis discuss simultaneously the application of a terrain mapping unit (TA" in hierarhical observational procedures and an IEM in a GIS environment. These aspects were aimed at providing an alternative solution to the traditional approach to data acquisition, data capture and producing aggregated information for a GIS.

    The third aspect discusses the application of standard deviation, probability of misclassification, membership degree and plausibility reasoning for handling error and uncertainty associated with data inputs and information outputs handled by a GIS in general and into and from the Indonesian Field Engineering Design Plan (FEDP) in particular. It is aimed mainly at establishing a framework for representing uncertainty in geographical data manipulation. GIS logical models, the characteristics of logical GIS models, types of uncertainty including error due to variability, imprecision, ambiguity and a proposed conceptual framework based on the concept of certainty factors are discussed.

    The research involved the establishment of stable basic mapping units that allow the definition of repeatable and hierarchical observational procedures. This solution was addressed especially to the situation when sophisticated software and good quality data are not available. In this research, TMUs are defined as areas with a particular combination of geology, geomorphology, morphometry and soil characteristics, usually obtained by interpretation of aerial photo or SPOT images. Terrain areas having similar relief characteristics are identified, delineated and verified in the field. The delineated TMUs represent natural divisions of the terrain often with distinct boundaries.

    Attributes associated with the established TMUs were selected and used to clasify TMUs. A classification hierarchy of TMU was established in the fight of object oriented modelling including abstraction, inheritance, aggregation and association of terrain objects. The hierarchy has three levels, namely level +1 (superclass level refered to as TMU), level 0 (class level refered to as sub TMU) and level -1 (elementary object refered to as subsub TMU). A lower level in the classification hierarchy represents more refined or specialised information.

    The well known deductive erosion model, the Universal Sod Loss Equation (USLE) is incomplete in predicting spatial erosion processes. More sophisticated models (i.e. CREAMS, ANSWERS, EPIC, WEPP, GAMES) have failed to account for the complexity of erosion processes and there are no means for validation of model predictions. An alternative to the problem is suggested through an inductive (bottom-up) approach. This approach involves an Inductive Erosion Model (IEM), which was built on observations including dynamic (resilience) and static (inertia) site specific erosion influencing factors in one or more sample areas, made on site at the farmer's field level which is the best functional unit to describe erosion class at local level. An IEM model therefore is region specific. Once an IEM is built and tested for each type of TMU then it can be incorporated within the GIS environment as an acceptable means to predict safely the severity of sod erosion for the entire study area. Erosion severity classes predicted by an IEM are considered as active or dynamic attributes of the established TMUs. By definition TMU provides inherently erosion influencing factors, so called terrain characteristics including morphometry, geology, soil and ground cover. An IEM is intended to predict homogeneous erosion severity classes, related to TMUs at different aggregation or hierarchical levels. The aggregation levels are related to point observations, farmers field level (FFL) and larger parts of the terrain. The discussion of this aspect is focused on the role of the TMU in the observational procedure providing input for an IEM.

    The established hierarchical mapping units served as a basis for inductive erosion modelling, incorporating expert knowledge-based inference rules. The inductive erosion modelling followed a multi-scale approach and was implemented in a GIS environment. Application of the concepts of regionalization, observed pattern, and decision rules in predicting and modelling purposes are discussed. At regional level patterns associated with the main erosive processes such as sheet, rill, gully and ravine features are generally still identifiable on the aerial photos at scale 1 : 50 000. However, more detailed information on these types of active process at local level can be obtained only by more detailed study, i.e., erosion study at the FFL. In this regard, the FFL is considered as a suitable basic functional unit to describe erosion at local level.

    Instead of using probability reasoning, which must follow statistical constraints, production rules allow the introduction of a Certainty Factor (CF) for handling both uncertainty in data, models and the resulting information. The C17 can be obtained as a subjective judgment made by experts and comes naturally to experts either in inferring underlying processes or estimating quality of data and models being used. With special reference to the situation when all procedures and techniques for determining probability and obtaining quantitative information particularly in data poor environment are unlikely to be performed, this study demonstrated sufficiently the application of the concept of CF.

    In the fight of evidence theory, an IEM for predicting erosion severity at a specific TMU was built as a function of various certainty factors of spatial erosion influencing factors. The certainty factor has a value between -1 and +1 and its value indicates the estimated change in belief of allocation of a TMU to a particular erosion class as evidence (from maps, air photos, field observations etc.) is gathered, for each contributing factor. The erosion severity class to which a TMU is finally allocated is the one with overall certainty factor closest to +1. It is proposed as a method of handling uncertain information caused by incompleteness such as inferences established and derived by experts from a set of observations including the effect of causal relationships among various uncertain evidences.

    Hydrodynamics, sediment transport and light extinction off Cape Bolinao, Philippines
    Rivera, P.C. - \ 1997
    Agricultural University. Promotor(en): L. Lijklema; W. van Vierssen. - Rotterdam : Balkema - ISBN 9789054104087 - 244
    delta's - estuaria - hydraulica - hydrodynamica - rivieren - waterlopen - kanalen - water - geologische sedimentatie - kusten - modellen - theorie - onderzoek - oceanografie - deltas - estuaries - hydraulics - hydrodynamics - rivers - streams - canals - water - geological sedimentation - coasts - models - theory - research - oceanography

    Observational and numerical modelling studies of the hydrodynamics, sediment transport, and light extinction were undertaken in the marine environment around Cape Bolinao in the Lingayen Gulf (Northwest Philippines). Abundant with ecologically important seagrasses and benthic organisms, Cape Bolinao is presently threatened with siltation and eutrophication problems. For this reason intensive field measurements of relevant enviromnental variables which include currents, tides, temperature, salinity, total suspended solids (TSS), ash-free dry weight (AFDW), sedimentation flux, grain size distribution and organic content of bottom sediments, gilvin absorption, phytoplankton concentration, and light extinction were executed from August 1993 to June 1995. Laboratory experiments were simultaneously undertaken to determine the sedimentation and light extinction characteristics of various sediment fractions. Using time series and regression analyses, the results were analyzed and presented. A set of numerical models were developed and applied in the area around Cape Bolinao and the Lingayen Gulf. A prognostic model for the hydrodynamics, driven by realistic wind and tide forces, was developed independently for the cape (fine-resolution model) and the gulf (coarse resolution model). An operational open boundary condition based on the method of wave propagation is discussed. The hydrodynamical predictions were used, in conjunction with a diagnostic surface wave model, to force the suspended sediment transport model. The transport model, which is based on the time-dependent advection-diffusion equation, is third order accurate in space and time. For a realistic description of the suspended sediment transport process in Cape Bolinao, resuspension and sedimentation fluxes were included in the numerical model using existing parameterizations. The predicted suspended sediment concentrations were used in a diagnostic model for light extinction. This later model is based on the assumption that the contributions of the optically active components to the attenuation of the photosynthetically available radiation (PAR) are linearly additive. Calibration of the numerical models using field observations produced a set of parameter values which is deemed representative for the area of investigation. Using these parameter values, the overall model predictions were in good agreement with field observations. Finally, using the integrated model, the impact of river sediment loads (treated as a conservative tracer) in the Bolinao reef system was quantified.

    Non-timber forest products of East Kalimantan : Potentials for sustainable use.
    Valkenburg, J.L.C.H. van - \ 1997
    Wageningen : Tropenbos Foundation - ISBN 9789051130300 - 202
    bosbouw - bosproducten - bosbedrijfsvoering - theorie - duurzaamheid (sustainability) - opbrengsten - flora - plantengeografie - kalimantan - borneo - ericaceae - sierplanten - bosproducten anders dan hout - forestry - forest products - forest management - theory - sustainability - yields - flora - phytogeography - kalimantan - borneo - ericaceae - ornamental plants - non-wood forest products
    Neural - fuzzy approach for system identification
    Tien, B.T. - \ 1997
    Agricultural University. Promotor(en): G. van Straten. - S.l. : Tien - ISBN 9789054857266 - 154
    theorie - controle - systemen - systeemanalyse - neurale netwerken - regeltheorie - theory - control - systems - systems analysis - neural networks - control theory

    Most real-world processes have nonlinear and complex dynamics. Conventional methods of constructing nonlinear models from first principles are time consuming and require a level of knowledge about the internal functioning of the system that is often not available. Consequently, in such cases a nonlinear system identification procedure from observational data is a more attractive alternative. If the model structures to be investigated are purely chosen from a set of mathematically convenient structures, without incorporation of knowledge about the internal functioning, this is called black-box modeling. In case that some qualitative a priori information can be used in the above modeling procedure, it is sometimes referred to as gray-box modeling.

    Artificial neural network models and fuzzy models are typical examples of black-box and gray-box modeling, respectively. They have the same property of parallel processing and both serve as universal function approximators to perform nonlinear mapping. Each of them has its own weak and strong points. The fuzzy model has a transparent knowledge representation but has restricted learning ability. A neural network model can easily learn from new data, but it is difficult to interpret the information contained in its internal configuration.

    This thesis investigates how to construct an integrated neural-fuzzy model that can perform approximation of an unknown system via a set of given input-output observations. The result is the integrated neural-fuzzy model NUFZY, which combines the advantages of the above two paradigms, and concurrently compensates for their weaknesses. Thus, it has a transparent network structure and a self-explanatory representation of fuzzy rules.

    The NUFZY system is a special type of neural network, which is characterized by partial connections in its first and second layers. Through its network connections the NUFZY system carries out a particular type of fuzzy reasoning. Also, the NUFZY system is functionally equivalent to a zero th -order Takagi-Sugeno fuzzy model, so that it is an universal function approximator as well.

    Two existing learning methods, i.e., the orthogonal least squares and the prediction error algorithms, can be applied directly to the developed NUFZY model. The former method, referred to as batch learning, can be used to detect redundant fuzzy rules from the prototype rule base and to find the weight parameters of the NUFZY model by one-pass estimation. The latter, referred to as recursive learning, allows a fast adaptation of parameters of the NUFZY model. Several practical examples with real data of agricultural problems, which address the tomatoes growth and the greenhouse temperature, have been presented in this thesis, showing the capability of the NUFZY system for modeling nonlinear dynamic systems.

    Two questions concerning the integrated neural-fuzzy model are addressed by studying the equivalent T-S fuzzy model: how to obtain a linguistic interpretation of fuzzy rules deduced by learning from training examples, and how to incorporate a priori knowledge into the T-S fuzzy model.

    It is found out that it is possible to have linguistic interpretations of the crisp consequent of the T-S fuzzy rules by transforming them into Mamdani - like fuzzy rules. A new parameter set, the consequent significance level, is associated to the consequent of each Mamdani fuzzy rule to form an extended Mamdani fuzzy model. This model has a more flexible modeling ability than the ordinary Mamdani fuzzy model and has a comparable model accuracy as that of the T-S fuzzy model.

    Regarding the second question, an optimization approach is employed to systematically incorporate the a priori knowledge into the T-S fuzzy model. If the knowledge about the system behavior outside the identification data range is expressed in the form of a qualitative Mamdani fuzzy model, then this model can be incorporated in the objective function of the parameter estimation problem as an additional penalty term. Thus, the estimation of the parameters of the T-S fuzzy model from the identification data is constrained by the involvement of a priori knowledge. As a consequence, the resultant fuzzy model becomes more robust in the extrapolation domain. This approach can be extended to neural -fuzzy modeling without difficulty.

    To conclude, the beauty of the integrated neural-fuzzy model, NUFZY, developed in this thesis is that it is a neural network, enabling the implementation of efficient learning algorithms in an easy way, and that it is a fuzzy model at the same time, allowing incorporation of priori knowledge and transparent interpretation of its internal network structure. So, among the various methods of nonlinear system identification, the NUFZY model can serve as an attractive alternative.

    See also

    Gebiedsdekkende basisinformatie voor het regionale waterbeheer in het waterschap Rijn en IJssel; programmeringsstudie
    Finke, P.A. ; Bierkens, M.F.P. ; Droesen, W. ; Stolp, J. - \ 1996
    Wageningen [etc.] : DLO-Staring Centrum [etc.] - 86
    toepassingen - capaciteit - hydrologie - kaarten - methodologie - bodemkarteringen - theorie - waterbeheer - watervoorraden - nederland - betuwe - raden - gelderland - waterschappen - applications - capacity - hydrology - maps - methodology - soil surveys - theory - water management - water resources - netherlands - betuwe - boards - gelderland - polder boards
    Voor het waterschap Rijn en IJssel is de gegevensbehoefte voor het regionaal waterbeheer onderzocht. De gegevensbehoeften van verschillende instrumenten zijn vergeleken, waarna variabelen geodentificeerd zijn die bij vrijwel alle instrumenten nodig zijn (het basispakket). Ook zijn twee uitbreidingspakketten gedefinieerd. Daarnaast zijn opties voor de gewenste ruimtelijke dichtheid van gegevensverzameling uitgewerkt. Combinaties van variabelenpakket en ruimtelijke dichtheid zijn geanalyseerd op kostendoorlooptijd en prioriteiten. De beste optie is verzameling van bodemgegevens en actualisatie van grondwatertrappen op een schaal van 1 : 50 000, alsmede het aanmaken van een gedetailleerd digitaal hoogtemodel.
    Changing forest management strategies in Sudan : a challenge for forestry educational systems
    Mahir, S.S. - \ 1996
    Agricultural University. Promotor(en): W. van den Bor; N.G. Röling. - S.l. : Mahir - ISBN 9789054854951 - 263
    bosbouw - bosbedrijfsvoering - theorie - duurzaamheid (sustainability) - opbrengsten - bosbouwkundige handelingen - sociale economie - voorlichting - onderwijs - sociale bosbouw - landgebruik - pachtstelsel - bebossing - inheemse kennis - sociale verandering - sudan - sociale processen - forestry - forest management - theory - sustainability - yields - forestry practices - socioeconomics - extension - education - social forestry - land use - tenure systems - afforestation - indigenous knowledge - social change - sudan - social processes

    This study is an effort to understand the way various categories of social actors go about their interaction with the management of forest resources in Sudan. By providing an overview and description of the motives, perceptions, and management objectives and strategies of social actors, the study tries to contribute towards better understanding of the social, economic and cultural factors influencing the resource management. The specific objectives of this study include:
    (1) Investigation of how social actors interact with forest resources in an era of rapidly changing conditions.
    (2) Get a better understanding of how changes in management objectives and strategies are influencing and are influenced by knowledge processes.
    (3) Analyze present forestry education's curriculum.
    (4) Explore possibilities of incorporating what we learn during the course of this study to propose a model for development of curriculum for forestry education in Sudan.

    This dissertation is written on the basis of empirical data collected from various individuals, groups and institutions involved in forest resources management in Sudan. The field work for the study was carried out mainly in the Central region of Sudan. However, the author's own experiences and those of other officials who worked in other locations, made the scope of the study not limited to geographical boundaries of the region.

    For the data collection, a combination of methodological instruments such as discussions, semi-structured interviews and participant observation, were used iteratively. Besides, taking a social actor as a unit of analysis, the study has used a hybrid of the systems' and the actors' perspectives as the main analytical tool.

    The main findings of this study indicate that:

    First, whereas, a forest is the unit of concern for officials, it is the tree which draws villagers' attention more than the forest as such. However, in general social actors see trees and forests as sources and signs of life. Besides, various actors attach different social, economic and/or cultural meanings to trees/forests. Consequently, they develop varying management objectives and strategies. In this regard, this study shows that similarity between foresters' and villagers' objectives is the exception rather than the rule. Foresters' management objectives are focused on management of forests for provision of forest goods and services for the nation, whereas villagers keep trees for social-cultural-spiritual-economic reasons, but rarely for firewood alone. Sometimes, what is important for villagers is seen as of 'minor importance' to foresters.

    Second, villagers traditionally, did not care about ownership of forests. However, ownership of valued-trees was well known. Notwithstanding such a situation, the government in Sudan intervened to manage the resource. Nonetheless, abolishment of the traditional Native Administrative system together with many other factors led to the situation where the state was unable to manage the resources on a sustainable basis. Hence, some of the tree/forest resources acquired the characteristics of the unowned, none-property resources.

    Third, most of the foresters see forest management mainly as consisting of a series of context-free technical activities, while villagers perform trees/forests management as part and parcel of their overall land use.

    Fourth, this study exposes social actors' appreciation concerning positive changes in each other's attitudes and behaviours and their willingness to manage forest resources jointly. Nevertheless, villagers and their leaders as well as officials have to be aware of and prepared for their new rights and responsibilities.

    Fifth, this study manifests that the formal forestry knowledge in Sudan is based on the assumption that wood is the main product. In most of their experiments forestry researchers look mainly into wood, and did not pay enough attention to non-timber- products. In addition, extension officers tend to disseminate unified, ready-made messages to various clients' segments. As well, in spite of the shown appreciation of local people's forestry knowledge, foresters rarely take villagers' observations and comments seriously.

    Sixth, women are becoming increasingly involved in forestry activities and the number of female foresters is increasing. Taking into consideration the fact that the rural Sudanese culture in many places does not allow easy interaction between male extension officers and village women, the need for female forestry extension officers seems to be well understood.

    Seventh, the following are among the learning points in relation to villagers' knowledge activities as depicted from this study:
    (1) For villagers researching and learning are inseparable. Deploying their surrounding environment in its totality, villagers carefully observe and learn experientially.
    (2) Local people's knowledge is embedded into different kinds of rituals and spiritual beliefs.
    (3) Villagers do not tend to reach to consensus and unified kind of knowledge and solutions.
    (4) Villagers normally exchange information among themselves during greetings; direct and indirect asking; certain occasions and locations such as funerals, market places and days, and religious/cultural feasts.

    Eighth, the findings of this study reveal that none of social actors alone has the technical/managerial capacity pertinent to sustainable management of forest resources. The necessary knowledge base is rather fragmented and unevenly scattered among different actors. Hence, we argued that in the absence of a suitable knowledge and information system, appropriate management of forest resources will be difficult. Forestry education has a role to play in facilitation of such knowledge and information system. Nonetheless, many economic, didactical and organizational problems remain as constraints for present institutions to perform better roles.

    Ninth, the results of this study came to support the idea that education is but one element which influences foresters' attitudes and behaviour. In reality, foresters' performance is determined by a composite of inter-related factors such as the work environment. Under the prevailing situation, learners and educators have neither enough time nor good motivation for creation of favourable learning environments.

    The main recommendations of this study are:
    (1) Foresters should take other social actors' perceptions, knowledge and management objectives into consideration when deciding about official management objectives and strategies.
    (2) Forestry educational institutions will and should have a role to play in facilitating various forest resources managers getting around a platform and discuss, learn and coordinate their resources to manage the resources on a sustainable basis. However, before being able to play such a role, they should start to see their roles as "experts' bureaux", but instead try to develop networking institutions.
    (3) Moreover, in an era of fast change, forest managers should learn more about learning. Nevertheless, to facilitate such kinds of learning, forestry educational institutions need to restructure their curricula involving other social actors and create channels for ongoing monitoring.
    (4) However, all the above mentioned requirements will be of limited effect in the absence of an overall conducive environment. Again, educators should not wait for these improvements to come, instead they should work very hard for the creation of such a conducive educational and learning environment.

    As a contribution towards development of such educational and learning environment, a model for forestry curriculum development has been proposed.

    Sparse canopy parameterizations for meteorological models
    Hurk, B.J.J.M. van den - \ 1996
    Agricultural University. Promotor(en): J. Wieringa, co-promotor(en): H.A.R. de Bruin. - S.l. : Van den Hurk - ISBN 9789054854913 - 271
    microklimaat - bodem - landschap - modellen - theorie - klimaatzones - klimatologie - microclimate - soil - landscape - models - theory - climatic zones - climatology
    Meteorological models for numerical weather prediction or climate simulation require a description of land surface exchange processes. The degree of complexity of these land-surface parameterization schemes - or SVAT's - that is necessary for accurate model predictions, is yet unclear. Also, the calibration of these SVAT's for relatively complex terrain, such as sparse canopies, is not completely resolved. This thesis pays attention to the sensitivity of the atmospheric boundary layer to the parameterization of surface exchange processes for a sparse canopy surface.

    During two experimental campaigns carried out in a sparsely vegetated vineyard surface in La Mancha, Spain, detailed measurements were collected, including the flux densities of sensible, soil and latent heat, radiative fluxes, aerodynamic properties, and soil and vegetation characteristics. These measurements were used for calibration and validation of various SVAT-models and their components.

    In a theoretical analysis the traditional treatment of aerodynamic transport of heat and moisture between a sparse canopy surface and the atmosphere was considered, and compared by an alternative formulation based on Lagrangian diffusion theory. An analysis of field observations was carried out to quantify the spatial and temporal variability of the surface albedo of a sparsely vegetated surface. Furthermore, a model for the stomatal conductance, based on the calculation of leaf photosynthesis and its relations with stomatal water vapour transport, was tested and scaled- up to the canopy level.

    Various existing SVAT's, designed for sparse canopies, were described and compared to field measurements in a zero-dimensional mode, that is, with forcings measured at reference height close above the surface. These models were all based on different physical treatment of soil heat flux, aerodynamic exchange and canopy resistance. None of the included models gave an optimum description of the observed fluxes, but a model could be constructed that combined the best parts of each of these SVAT's.

    In an additional model study, this new description has been coupled to a onedimensional planetary boundary-layer (PBL) model. Parts of the SVAT were replaced by other components, and the impact on simulated PBL-dynamics has been evaluated. Large effects are found when (a) the reference two-layer model was replaced with a single layer ('big leaf') model, (b) soil heat flux was simulated with a resistance scheme rather than a diffusion or force-restore scheme, and (c) the aerodynamic resistance between the reference level and the bare soil was chosen too low. Since vegetation cover was small, smaller effects resulted from an alteration of the canopy resistance formulation. Also, it was found that the simulated entrainment of heat at the top of the boundary layer is low compared to entrainment ratios cited in literature.

    Scaling up in hydrology using remote sensing.
    Stewart, J.B. ; Engman, E.T. ; Feddes, R.A. ; Kerr, Y. - \ 1996
    Chichester [etc.] : Wiley - ISBN 9780471968290 - 255
    toepassingen - hydrologie - modellen - remote sensing - theorie - applications - hydrology - models - remote sensing - theory
    Economic modelling of pork production-marketing chains
    Ouden, M. den - \ 1996
    Agricultural University. Promotor(en): A.A. Dijkhuizen; J.A. Renkema; R.B.M. Huirne. - Wageningen : Wageningen Agricultural University - ISBN 9789054855644 - 168
    verticale integratie - varkens - investering - kosten-batenanalyse - economische evaluatie - prijzen - prijsvorming - kosten - dierenwelzijn - huisvesting, dieren - milieubescherming - milieubeheer - milieu - kwaliteit - wiskundige modellen - econometrische modellen - econometrie - theorie - nederland - vertical integration - pigs - investment - cost benefit analysis - economic evaluation - prices - price formation - costs - animal welfare - animal housing - environmental protection - environmental management - environment - quality - mathematical models - econometric models - econometrics - theory - netherlands - cum laude
    The research described in this thesis was focused on the development of economic simulation and optimization computer models to support decision making with respect to pork production- marketing chains. The models include three production stages: pig farrowing, pig fattening and pig slaughtering including cutting of carcasses. Transportation of live pigs between these stages was also considered. The pork chain simulation model was developed and described to simulate technical and economic performance of both individual stages and pork chains as a whole. Special attention was focused on the quantification of the way in which stages can influence each other's performance and profitability. The simulation model was used to analyse the distribution of costs and benefits along the stages of the pork chain using various transfer pricing systems. Besides the chain producing standard pork, three differentiated pork chain concepts were evaluated. The simulation model was also used to quantify the impact of pig welfare demands on the economics of the pork chain. Pig welfare perceptions were assessed from animal welfare experts, retailers and other consumer-related respondents using a questionnaire based on conjoint analysis. The estimated pig welfare perceptions and corresponding economics were used as input parameters for static and dynamic linear programming models to analyse the development of least-cost chain concepts satisfying increasing demands on pig welfare. Additionally, the optimization models were extended using multi-criteria- decision-making techniques to include the effects on nitrogen and phosphorus emissions and energy consumption in pig farming as well.
    Integrated economy - energy - environment policy analysis : a case study for the People's Republic of China
    Zhang, Z. - \ 1996
    Agricultural University. Promotor(en): H. Folmer; P. van Beek. - Wageningen : Zhang - 328
    kooldioxide - economie - klimaatverandering - paleoklimatologie - energiebeleid - energie - probleemanalyse - luchtverontreiniging - milieu - schade - milieueffect - energiebronnen - elektrotechniek - elektrische apparatuur - elektriciteit - elektrificatie - wiskundige modellen - econometrische modellen - econometrie - theorie - China - carbon dioxide - economics - climatic change - palaeoclimatology - energy policy - energy - problem analysis - air pollution - environment - damage - environmental impact - energy sources - electrical engineering - electrical equipment - electricity - electrification - mathematical models - econometric models - econometrics - theory - China

    This study is the first systematic and comprehensive attempt to deal with the economic implications of carbon abatement for the Chinese economy in the light of the economics of climate change, of which this dissertation is the results. It consists of nine chapters. After a brief introduction, Chapter 2 discusses some economic aspects of climate change. This in turn will serve as a good guide to pursuing the case study for CO 2 emissions in China. Chapter 3 analyses the Chinese energy system in the CO 2 context. Chapter 4 discusses alternative economic modelling approaches to cost estimates for limiting CO 2 emissions. The purpose is to show the rationale for choosing a computable general equilibrium (CGE) approach for the macroeconomic analysis of CO 2 emission limits and linking such a CGE model of the Chinese economy with a power planning model of China's electricity sector. Chapter 5 presents a time-recursive dynamic CGE model of the Chinese economy. Chapter 6 deals with some essential work done for empirical application of the CGE model. Chapter 7 analyses the economywide impacts of alternative carbon limits for China through counterfactual policy simulations, while Chapter 8 analyses the impacts of compliance with CO 2 limits in China's power industry by means of a technology- oriented dynamic optimization model for power system expansion planning. Finally, Chapter 9 summarizes the conclusions of this study and points out some areas where there is a need for further methodological and empirical work to enrich the policy relevance of the study.

    Analysis of the Chinese energy system: implications for future CO 2 emissions

    At present China contributes 11% of global CO 2 emissions. This means that China ranks second if the Soviet emissions are distributed over the new independent republics. Given the global characteristics of climate change and China's potential importance as a source Of CO 2 emissions, advocates of controlling CO 2 emissions call for substantial efforts in China. However, the Chinese authorities have argued that China cannot be expected to make a significant contribution to the carbon emission problem unless China receives substantial international aid for this purpose. This contrasts sharply with the wishes of proponents of controlling CO 2 emissions. Chapter 3 is devoted to explaining this difference in opinion by examining China's energy resources and their development, the Chinese energy consumption patterns, the achievements and remaining problems of electricity generation in China, China's energy conservation in an international perspective, historical CO 2 emissions in China, and environmental challenges for the Chinese energy system. At the same time, it sheds light on the implications for China's future CO 2 emissions.

    From examining these aspects, it has become clear that, driven by the threat of further degradation of the environment, great pressure on the severely congested railways, and the harmful economic effects of energy shortages, China is already determined to make great efforts towards energy conservation and enhanced energy efficiency in general, and towards using coal much more efficiently in particular. A number of policy measures, which have been and will continue to be implemented, have been outlined. They are the so-called 'noregrets' measures in the sense that they are taken without considering the greenhouse effect. These measures include increase in proportion of raw coal washed; retrofitting and replacement of small inefficient industrial boilers; substituting direct burning of coal by electricity through development of largesize, high-temperature and high-pressure efficient coal-fired power plants; speeding up hydropower exploitation; popularizing domestic use of coal briquette; increased penetration of town gas into urban households; expanding district heating systems; and relaxing restrictions on energy trade. Moreover, success in the implementation of these measures will largely depend on the extent to which a reform of China's energy pricing will be carried out. With respect to reducing CO 2 emissions, because the 'regrets' policies are often costly, 'getting prices right' and implementing these 'no-regrets' actions above should have priority over the imposition of a carbon tax. This suggests that the implementation of these measures will be accelerated if curbing global CO 2 emissions requires special action on China's part.

    While China makes such drastic efforts, fundamental reform of aid and loan practices also needs to be undertaken in the industrialized countries, so that bilateral and multilateral assistance be channelled less towards expanding energy supplies and more towards promoting energy efficiency improvements, thus reducing CO 2 emissions. Related to this, joint implementation projects for increased energy efficiency should be encouraged.

    Macroeconomic analysis of CO 2 emission limits for China

    Given that China is the world's most populous country and largest coal producer and consumer, its coal-dominated energy structure and carbon-intensive economy, and that carbon dioxide is the greatest contributor to global warming, its economic development and the resulting CO 2 emissions are of great concern. Chapter 4 argues that a CGE approach is generally considered an appropriate tool for analysing the economic impacts of limiting CO 2 emissions.

    For this purpose, a time-recursive dynamic CGE model of the Chinese economy has been developed. This model includes ten production sectors, distinguishes four energy inputs, and is made up of nine blocks. Moreover, the CGE model highlights the relationships between economic activity, energy consumption and CO 2 emissions. Thus, the model makes it possible to analyse the Chinese economy-energy-environment system interactions simultaneously, at both sectoral and macroeconomic levels. The model is also able to calculate the welfare impacts of carbon abatement policies. Furthermore, the CGE model incorporates an explicit tax system. This makes it suitable for estimating the 'double dividend' from the imposition of a carbon tax that is incorporated as a cost-effective means of limiting CO 2 emissions. Finally, the model is solved directly with a numerical solution technique included in GAMS.

    Using this CGE model, a baseline scenario for the Chinese economy has first been developed under a set of assumptions about the exogenous variables. Counterfactual policy simulations have then been carried out to compute the macroeconomic implications of two less restrictive scenarios, under which China's CO 2 emissions in 2010 will be cut by 20% and 30% respectively relative to the baseline, and to determine the efficiency improvement of four indirect tax offset scenarios relative to the tax retention scenarios. Finally, a comparison with other studies for China has been made. The following conclusions can be drawn.

    First, a rapid growth of the Chinese economy will take place until the year 2010. Consequently, this will lead to increased energy consumption and hence CO 2 emissions, despite substantial energy efficiency improvement. Second, large reductions in carbon emissions can only be achieved by ever-larger increases in carbon taxes and hence prices of fossil fuels. Third, the associated GNP and welfare losses tend to rise more sharply as the degree of the carbon emission reduction increases. Fourth, although aggregate gross production tends to decrease at an increasing rate as the carbon dioxide emission target becomes more stringent, changes in gross production vary significantly among sectors in both absolute and relative terms. This suggests that special attention should be paid to the sectoral implications when designing a domestic carbon tax. Fifth, although a change in level and structure of economic activity and a change in direct energy consumption by households play a role in reducing total energy consumption, lower energy input coefficients contribute to the bulk of energy reduction and hence CO 2 emissions. Sixth, the negative impacts of carbon taxes on GNP and welfare would be reduced if the carbon tax revenues were used to offset reductions in indirect taxes. Moreover, it would become more worthwhile to lower indirect taxes as the target of CO 2 emissions becomes more stringent. Seventh, our estimates of the reduction in GNP growth are higher than those by GLOBAL 2100 and GREEN in order to achieve the same reductions in CO 2 emissions relative to the baseline. Moreover, the carbon taxes required in China are much lower than those for both the industrialized countries and the world average. This suggests that the joint implementation mechanism as a preliminary step towards a global regime of tradeable carbon permits should be considered a means of reducing global CO 2 emissions effectively.

    Cost-effective analysis of carbon abatement options in China's electricity sector

    Chapter 8 attempts to shed light on technological aspects of carbon abatement in China's power industry and is thus devoted to satisfying electricity planning requirements. To that end, a technology-oriented optimization model for power system expansion planning has been developed. This model has been adapted from the MARKAL model. It chooses the minimization of discounted cost over the entire planning horizon as its objective function and incorporates a number of power- related constraints adopted by MARKAL. In the power planning model, 15 types of power plants are represented in terms of their technical, economic and environmental parameters. The model allows for substitution from highcarbon fossil fuels and technologies towards low-carbon and carbon-free counterparts and for interactions between periods to cope with carbon limits.

    Using the power planning model, a comparison of the 15 types of power plants considered has been made in terms of both the levelized cost of generation and the marginal Cost Of CO 2 reduction at a 10% discount rate. Driven by the baseline electricity demands that are estimated by the CGE model, the model has then been used to develop a baseline scenario for China's electricity supply and to analyse the impacts of compliance with CO 2 limits in the power industry. The main findings are as follows.

    First, large coal-fired plants and hydroelectric plants should be given priority in future electricity planning. Thus, efforts should be directed towards expanding domestic capacity for manufacturing large units, mobilizing the necessary large investment resources, and towards resolving the disappointing performance of domestically-produced large units.

    Second, a rapid growth of China's power industry will take place until the year 2010. Accordingly, capital investment in the industry as a share of GNP is calculated to go up from the current level. Given that coal-fired power plants still predominate, the amount of coal consumed for electricity generation accordingly grows rapidly, thus increasing its share in total coal consumption. This will lead to an increase in CO 2 emissions within the power sector itself, although the decreasing direct use of coal will alleviate the environmental impacts of coal use as a whole. Moreover, it has been shown that more large units are expected to be put into operation during the period under consideration compared with the current composition of plants. This will bring the average gross coal consumption of coal- fired plants down. Besides, the calculations show that nuclear power begins to make a useful contribution to China's electricity supply, although there is little prospect of dramatic increases until the year 2010.

    Third, compliance with carbon limits in the electricity sector requires accelerated expansion of hydroelectric power and nuclear power. This finding is in line with the government investment priority, which has been set with aims to reduce pressure on transportation and air pollution, but without considering the greenhouse effect. This suggests that the development of hydroelectric power and nuclear power needs to be accelerated in China if curbing CO 2 emissions is taken into account. This provides a precondition for developing joint implementation projects in China's electricity sector. In practice, however, to make these projects operational will depend on the far-reaching negotiations for joint implementation mechanism.

    Protocol voor het cultuur- en gebruikswaarde onderzoek van snijmais
    Ebskamp, A.G.M. ; Bonthuis, H. - \ 1995
    Wageningen : CPRO-DLO - 16
    ontwerp - maïs - theorie - rassenproeven - zea mays - design - maize - theory - variety trials - zea mays
    Modelling studies of fish production in integrated agriculture - aquaculture systems
    Dam, A.A. van - \ 1995
    Agricultural University. Promotor(en): E.A. Huisman; R. Rabbinge; F.W.T. Penning de Vries. - S.l. : Van Dam - ISBN 9789054853879 - 163
    landbouw - visteelt - bedrijfsvoering - computersimulatie - simulatie - simulatiemodellen - modellen - theorie - onderzoek - geïntegreerde systemen - agriculture - fish culture - management - computer simulation - simulation - simulation models - models - theory - research - integrated systems

    The general objective of this thesis is to formulate a general model for fish production in integrated ponds and ricefields as a means of obtaining a better understanding of these production systems. Integrated culture systems produce fish without large industrial energy inputs and have positive effects on the whole farm system. A main characteristic is their environmental variability, notably dissolved oxygen concentration and temperature. A systems approach using mathematical models is advocated because it can lead to insights that have universal applicability while avoiding the pitfalls of site- and species-specific, expensive experimental work. Two modelling approaches are distinguished: descriptive models, generally the result of statistical analysis of datasets; and explanatory models, based on knowledge of the biological processes underlying fish production.

    Multiple regression analysis (a descriptive modelling technique) was used for the analysis of data from 15 integrated rice-fish production experiments with the Nile tilapia (Oreochromis niloticus L.) in the Philippines. Results showed that this technique led to insights that had not been obtained through separate analysis of the experiments. Main drawback of this method was that the models were not applicable to other production environments.

    An explanatory model (called Fish Growth Simulator, or FGS) for growth of O.niloticus was developed on the basis of an existing simulation model for the African catfish Clarias gariepinus Burchell (1822). After parameterization and calibration, the model gave good predictions of fish growth in independent datasets. Parameterization and calibration of the same model for the rainbow trout Onchorhynchus mykiss (Walbaum) demonstrated the generality of the model and it was concluded that, provided that enough data are available, the model may be used to predict growth in a wide range of fish species. Food amount and composition, and temperature were the environmental variables upon which the model based its predictions.

    FGS was expanded with a dissolved oxygen module to accomodate oxygen as an environmental variable. The module was based on the hypothesis that oxygen is needed in sufficient amounts for aerobic metabolism, and that gill surface area limits the supply of oxygen to fish. The resulting model allowed the simulation of fish growth under low dissolved oxygen concentration and also provided an explanation for differences in the final weight of fishes, both within and between species.

    FGS was used for simulation of food and oxygen limitations in waste-fed fish ponds in Honduras, Thailand and Rwanda. The model simulated fish growth for various combinations of environmental conditions: temperature, food availability and dissolved oxygen concentration. Validation, using data from Indonesia and Panama, was not successful because estimates of the food consumption rate in these countries were not reliable.

    In the last chapter methodology, the role of oxygen in fish metabolism and growth, model implications for the management of integrated agriculture-aquaculture systems and implications for further work are discussed.

    Sudden change in second order nonlinear systems : slow passage through bifurcation
    Maree, G.J.M. - \ 1995
    Agricultural University. Promotor(en): J. Grasman, co-promotor(en): F. Verhulst. - S.l. : Maree - ISBN 9789054854319 - 155
    wiskundige modellen - theorie - wiskunde - analyse - mathematical models - theory - mathematics - analysis

    Dynamical systems modelling physical processes often evolve on several time- scales with different orders of magnitude. In modelling oscillating systems some simplifying assumptions have to be made. When the short-term behaviour of a natural system is considered the parameters that appear in mathematical models of such systems can be assumed constant. In the long term, however, these parameters will vary slowly because of gradual changes in the nature of the system. Moreover, system parameters can be varied deliberately by the experimenter. This slow change of the system parameter can produce an enormous effect on the state of the system at a certain moment, which can lead to undesirable responses; "small causes produce large effects". In this thesis we study sudden changes in systems that can be modeled by second order nonlinear differential equations. The model parameter slowly changes in a dynamical way and is a function of the (slow) time.

    Outside a certain transition region the system exhibits on a large time-scale a damped oscillation around a stable, slowly varying, parameter-dependent equilibrium solution. The dynamics of the regarded problems on a large time-scale are described with the aid of averaging methods. When the bifurcation parameter approaches a critical value, however, this asymptotic averaged approximation is not valid anymore. A sudden, rapid transition takes place, since the stability of an equilibrium changes or an equilibrium vanishes. In order to offer a quantitative analysis it is important to understand in what way the solutions of the differential equations behave in the vicinity of the bifurcation point. In order to describe a bifurcation or jump phenomenon a local approximation has to be made. Local analysis yields that Painlevé equations can play an important role in the bifurcation process. In specific cases the solutions of the nonlinear transition equations can exhibit algebraic growth or they can explode (via a singularity). In this study the validity of the local approximations has been proven for a large class of systems. With the aid of matching techniques and a thorough analysis of the transition equation an accurate prediction has been made of the behaviour of solutions after passage of the bifurcation point. Examples of nonlinear systems that are of the same type as the problems which are considered in this thesis can be found in mechanics, climatology, biology, astronomy, and space craft technology. The power of the mathematical analysis, that has been performed in this thesis, is that it can be applied to a large class of dynamical systems. The analysis in this thesis has been carried out with the use of singular perturbation techniques. The problems that we consider are related to physical systems. We distinguish between variables, which are related to the dynamics of the system, and parameters that exhibit a slow change on a large time-scale. The problem is treated dynamically, since we take into consideration a slowly varying parameter.

    In chapter 2 an elementary bistable system is considered that corresponds qualitatively to the Euler arc from mechanics. For this system a sudden moment of snap- through occurs, since the parameter that describes the "stiffness" of the problem slowly varies in time and causes a dynamical bifurcation. Solutions of the system, that originally oscillate around a slowly decreasing equilibrium solution, exhibit a sudden jump behaviour and a transition to an other equilibrium state occurs. From the point of view of the qualitative analysis it is important to make a good prediction of the moment in time at which this jump will take place. The significant degeneration, which describes the jump phenomenon, is a nonlinear differential equation that can not be solved in terms of known functions or combinations of known functions; the local transition behaviour is described by the first Painlevé transcendent. Although it is not possible to deduce an asymptotic expression for the exact moment of snap-through, we are able to obtain an expression for the upper and lower limit of the expected moment of snap-through. In order to achieve this goal we apply numerical methods. A specific solution of the first Painlevé equation can be derived that matches the parameter-dependent equilibrium solution which had existed before the jump took place. The zero of this specific solution can be considered as a natural constant for the first Painlevé equation. The limit expansion of this solution has an asymptotic series. The zero of the solution of the first Painlevé equation with certain matching conditions yields a better approximation for the moment that the system snaps through. The matching condition (and therefore also the approximation of the jump moment) depend on the amplitude and the phase of the original oscillation, and on the velocity at which the parameter slowly changes.

    In chapters 3 and 4 systems are analyzed which are modelled by second order nonlinear differential equations that pass a pitchfork bifurcation. In the vicinity of a certain critical value of the state parameter a transition occurs from a stable "straight" equilibrium to a parabolic equilibrium curve. The leading order transition equation, which describes the pitchfork bifurcation, is the second Painlevé transcendent. The transcendental solutions of this equation either algebraically grow, which corresponds with a transition from the linear equilibrium to one of the two stable branches of the parabolic equilibrium curve, or exponentially decay, which corresponds with a transition to the unstable, slowly varying equilibrium solution after bifurcation.

    In chapter 3 we analyze the validity of the different asymptotic expansions. In order to obtain a global picture of the system we apply matching techniques and approximation theorems, that are obtained by extending existing first and second order averaging methods, and we extend the local solutions. It is proven that the different local solutions overlap. The matching conditions depend on the initial conditions and on the values of the parameters. Analytical analysis of the transition equation provides information about the required matching procedures. Moreover, it is seen that the asymptotic approximation remains valid before, during, and after the pitchfork bifurcation. There is a connection between the slowly oscillating solutions before and after passage of the bifurcation point. It is possible to predict accurately which stable branch of the parabolic equilibrium curve win be followed after bifurcation dependent on the state of the system "far away" from the bifurcation point. In this thesis an interesting connection has been discovered between the recent theory of Painlevé equations and the applications of singular perturbation techniques.

    In chapter 4 we are concerned with the dynamics of a slowly varying Hamiltonian system for which the phase portrait for a fixed value of the forcing function qualitatively changes with time. This phase portrait periodically changes and a figure-eight separatrix periodically disappears and reappears. As the system parameter changes a double homclinic loop is born which grows to a maximum, shrinks back into the origin, lies dormant, and then is born again; the bifurcation parameter periodically crosses a critical value corresponding to a supercritical pitchfork bifurcation. Dependent on the initial state of the system and the values of the parameters the system can exhibit chaotic or (quasi) periodic behaviour. The sequence of stable upper and lower branches which a given trajectory follows after passage of the pitchfork bifurcation can be irregular and so the system can exhibit sensitive dependence on initial conditions. The attraction properties can be analyzed with the aid of a Poincaré map. Chaotic dynamics almost always occur in a system without friction. For a dissipative system it is more likely that it win exhibit a periodic behaviour from a certain moment in time. The validity of the approximating Poincaré map and of the matched asymptotic approximations can be proven on a large time- scale. The proof of this validity has been carried out with the aid of an approximation theorem that concerns the averaging of oscillating functions with a slowly varying frequency, an extension theorem, matching techniques, and connection formulas for the solutions of the second Painlevé equation. Numerical simulations confirm the results that are obtained with analytical methods. A mechanical example is the motion of a simple pendulum that is connected to a rotating, rigid body.

    Finally, in chapter 5 we study the general class of nonlinear second order problems with a slowly varying parameter that passes a critical value corresponding to a transcritical. bifurcation. The jump phenomenon and the pitchfork bifurcation can be generalized in the same way as the transcritical bifurcation problem has been generalized in chapter 5. In this case, in the vicinity of a certain critical value of the parameter a transition occurs from a stable "straight" equilibrium to an other "straight" equilibrium, whereas the originally stable equilibrium becomes unstable. Again, the local solution that is obtained with averaging methods is valid outside a certain nonlinear transition layer and yields matching conditions for the second order differential equation that is generic for this type of bifurcation. This significant degeneration, however, does not possess the Painlevé property. Solutions of the transition equation decrease exponentially, explode or exhibit algebraic growth, which corresponds to a transition from the one stable equilibrium to another. The chance of an explosion becomes larger when the amplitude of the original oscillation is larger. With the aid of local asymptotic approximations and an analysis of the transition equation it can be investigated whether or not the system win explode on a certain moment. The "explosion condition" depends on the initial conditions and the values of the parameters.

    Monetarisering in de huishouding: een analyse van de huishoudvoering van relatief welgestelden.
    Ophem, J. ; Hoog, K. de - \ 1995
    Huishoudstudies 5 (1995)2. - p. 8 - 19.
    automatisering - consumentengedrag - voedsel - voedselinkoop - voedingsmiddelen - huishoudkunde - huishoudens - huishoudelijk werk - inkomen - arbeid (werk) - levensstijl - bedrijfsvoering - mechanisatie - Nederland - prijzen - inkopen - dienstensector - theorie - handarbeid - organisatie - personen - automation - consumer behaviour - food - food purchasing - foods - home economics - households - housework - income - labour - lifestyle - management - mechanization - Netherlands - prices - purchasing - services - theory - manual work - organization - persons
    Empirische data worden geanalyseerd op de vraag in hoeverre er onder relatief welgestelde Nederlanders sprake is van monetarisering en of dit een element van een levensstijl is
    Monetarisering in de huishouding: een historiserende beschouwing.
    Hoog, K. de; Ophem, J. van - \ 1995
    Huishoudstudies 5 (1995)2. - p. 1 - 8.
    automatisering - consumentengedrag - efficiëntie - voedsel - voedselinkoop - voedingsmiddelen - geschiedenis - huishoudkunde - huishoudens - huishoudelijk werk - arbeid (werk) - levensstijl - bedrijfsvoering - mechanisatie - prijzen - productiviteit - inkopen - dienstensector - theorie - handarbeid - organisatie - automation - consumer behaviour - efficiency - food - food purchasing - foods - history - home economics - households - housework - labour - lifestyle - management - mechanization - prices - productivity - purchasing - services - theory - manual work - organization
    Verkennend en beschouwend artikel over monetarisering : vermindering van huishoudelijke taken/activiteiten door ingehuurde dienstverlening en door gebruik van huishoudelijke apparatuur en geprefabriceerd voedsel. Nagegaan wordt hoe deze strategie, gezien als element van een levensstijl, zich in de loop van de tijd ontwikkeld heeft
    Space and time scale variability and interdependencies in hydrological processes.
    Feddes, R.A. - \ 1995
    Cambridge [etc.] : Cambridge University Press [etc.] - ISBN 9780521495080 - 181
    methodologie - hydrologie - theorie - geostatistiek - methodology - hydrology - theory - geostatistics
    Technisch model varkensvoeding : informatiemodel
    Peet - Schwering, C.M.C. van der; Vos, H.J.P.M. ; Peet, G.F.V. van der - \ 1994
    S.l. : Werkgroep TMV
    varkens - diervoedering - voer - modellen - theorie - onderzoek - pigs - animal feeding - feeds - models - theory - research
    Community biodiversity development and conservation programme : proposal to DGIS, IDRC and SIDA for implementation phase 1, 1994 - 1997
    Anonymous, - \ 1994
    Wageningen : CPRO-DLO - 182
    ontwerp - ontwikkelingslanden - genenbanken - genetische bronnen - germplasm - inheemse kennis - genetische bronnen van plantensoorten - hulpbronnenbehoud - zaadcontrole - zaden - theorie - design - developing countries - gene banks - genetic resources - germplasm - indigenous knowledge - plant genetic resources - resource conservation - seed testing - seeds - theory
    Duurzame verzorging als technologische uitdaging.
    Terpstra, M.J. - \ 1994
    Wageningen : Landbouwuniversiteit Wageningen - 29
    samenstelling - economische ontwikkeling - milieu - milieubeheer - milieubescherming - gezinnen - huishoudkunde - huishoudens - colleges (hoorcolleges) - bedrijfsvoering - natuurlijke hulpbronnen - bescherming - kwaliteit - herstel - hulpbronnengebruik - plattelandsontwikkeling - sociale ontwikkeling - sociale voorzieningen - sociaal welzijn - structuur - duurzaamheid (sustainability) - technische vooruitgang - technologie - theorie - welzijnsvoorzieningen - milieuwetenschappen - natuurwetenschappen - organisatie - wetenschap - sociaal werk - composition - economic development - environment - environmental management - environmental protection - families - home economics - households - lectures - management - natural resources - protection - quality - rehabilitation - resource utilization - rural development - social development - social services - social welfare - structure - sustainability - technical progress - technology - theory - welfare services - environmental sciences - natural sciences - organization - science - social work
    Geboeid door ketens
    Dalen, J. van - \ 1994
    Wageningen : LU - 43
    industrie - organisaties - theorie - bedrijfsvoering - bedrijven - ondernemingen - bestuur - colleges (hoorcolleges) - hogere agrarische scholen - universiteiten - nederland - veluwe - gelderland - industry - organizations - theory - management - businesses - enterprises - administration - lectures - agricultural colleges - universities - netherlands - veluwe - gelderland
    Rede Landbouwuniversiteit Wageningen, 3 maart 1994
    Proceedings First International Conference on Management of agri-chains.
    Hagelaar, G. - \ 1994
    Dept. Management Studies. Wageningen Agricultural University - 350
    landbouwindustrie - industrie - landbouw - organisaties - theorie - bedrijfsvoering - bestuur - verticale integratie - materialen - wereld - bedrijfseconomie - logistiek - agribusiness - industry - agriculture - organizations - theory - management - administration - vertical integration - materials - world - business management - logistics
    Community biodiversity development and conservation programme : working document [2] for implementation phase [1] - 1994 - 1997 : as agreed by partners in Buga, Colombia, September 1993
    Anonymous, - \ 1993
    Wageningen : CGN - 35
    ontwerp - ontwikkelingslanden - genenbanken - genetische bronnen - germplasm - inheemse kennis - genetische bronnen van plantensoorten - hulpbronnenbehoud - zaadcontrole - zaden - theorie - design - developing countries - gene banks - genetic resources - germplasm - indigenous knowledge - plant genetic resources - resource conservation - seed testing - seeds - theory
    Melkvee, 1975 - 1995 : bedrijfseconomische beschouwingen
    Everdingen, W.H. van - \ 1993
    Den Haag : LEI-DLO (Periodieke rapportage / Landbouw-Economisch Instituut 6-91) - 134
    melkvee - melkveehouderij - statistiek - productiviteit - rentabiliteit - dierhouderij - bedrijfsresultaten in de landbouw - organisaties - theorie - bedrijfsvoering - bestuur - nederland - bedrijfseconomie - dairy cattle - dairy farming - statistics - productivity - profitability - animal husbandry - farm results - organizations - theory - management - administration - netherlands - business management
    Het schrijven van onderzoeksvoorstellen : [verslag van een cursus]
    Zwart, L.H. - \ 1993
    Wageningen : Wetenschapswinkel (Rapport / Wetenschapswinkel 74) - 23
    onderzoek - theorie - wetenschap - wetenschappelijk onderzoek - research - theory - science - scientific research
    The importance of weather data in crop growth simulation models and assessment of climatic change effects
    Nonhebel, S. - \ 1993
    Agricultural University. Promotor(en): C.T. de Wit; J. Goudriaan. - S.l. : Nonhebel - ISBN 9789054851141 - 144
    groei - gewassen - Triticum aestivum - tarwe - hexaploïdie - klimaatverandering - paleoklimatologie - oogsttoename - oogstverliezen - opbrengsten - modellen - theorie - klimaatzones - klimatologie - agrometeorologie - computersimulatie - simulatie - simulatiemodellen - onderzoek - growth - crops - Triticum aestivum - wheat - hexaploidy - climatic change - palaeoclimatology - yield increases - yield losses - yields - models - theory - climatic zones - climatology - agricultural meteorology - computer simulation - simulation - simulation models - research

    Yields of agricultural crops are largely determined by the weather conditions during the growing season. Weather data are therefore important input variables for crop growth simulation models. In practice, these data are accepted at their face value. This is not realistic. Like all measured values, are weather data subject to inaccuracies. Crop growth simulation models are sensitive to weather data used as input, so inaccuracies in weather data can affect the simulation results. The errors in weather data were estimated and their effects on the simulation results of a spring wheat crop growth simulation model were determined. Inaccuracies in weather data caused deviations in simulated yields of 10-15 %.

    In most weather data sets missing values occur and since crop growth models require daily data the values of the missing data have to be estimated. Several methods to estimate missing values were discussed and their effects on simulation results were studied. Large differences in quality of the estimation methods were found. Some of them resulted in deviations in simulated yields up to 30 %.

    Daily weather data are not always available and often average weather data are used instead. The effects of using average weather data on simulation results were studied for three sites in different climates. For all sites large deviations in simulation results were found.

    The increasing CO 2 concentration is affecting agricultural production in two ways: via a climatic change and via effects on assimilation and transpiration rates. The spring wheat model was used to study the overall effects of higher CO 2 levels on wheat yields in Western Europe. A temperature rise of 3 °C resulted in a yield decline, doubled CO 2 concentration in a yield increase and the combination of both in a yield increase of about 2 ton ha -1.

    Population growth, income distribution and economic development - theory, methodology, and empirical results.
    Heerink, N. - \ 1993
    Berlin : Springer Verlag - ISBN 9783540573234 - 401
    correlatieanalyse - demografie - econometrische modellen - econometrie - economische ontwikkeling - bevolking - inkomen - inkomensverdeling - wiskundige modellen - multivariate analyse - populatiegroei - regressieanalyse - statistiek - theorie - vermogensverdeling - correlation analysis - demography - econometric models - econometrics - economic development - human population - income - income distribution - mathematical models - multivariate analysis - population growth - regression analysis - statistics - theory - wealth distribution
    Enkele informatie theoretische aspecten van GIS.
    Molenaar, M. - \ 1993
    Agro Informatica 6 (1993)2. - ISSN 0925-4455 - p. 9 - 13.
    ontwerp - geografische informatiesystemen - theorie - design - geographical information systems - theory
    Automated spatial and thematic generalization using a context transformation model : integrating steering parameters, classification and aggregation hierarchies, reduction factors, and topological structures for multiple abstractions
    Richardson, D.E. - \ 1993
    Agricultural University. Promotor(en): M. Molenaar. - S.l. : Richardson - ISBN 9780969704300 - 149
    cartografie - theorie - geografische informatiesystemen - mapping - theory - geographical information systems

    This dissertation presents a model for spatial and thematic digital generalization. To do so, the development of digital generalization over the last thirty years is first reviewed

    The approach to generalization taken in this research differs from other existing works as it tackles the task from a database perspective rather than a representation perspective. Accordingly, a context transformation model is presented that can automatically decrease representation density (the density of objects and object classes appearing on maps) through the application of steering parameters, classification and aggregation hierarchies, and topological data structures.

    The underlying philosophy in the development has been to provide a user environment with as much flexibility as possible.

    Agrarisch ondernemerschap in een bedrijfskundig perspectief
    Ziggers, G.W. - \ 1993
    Agricultural University. Promotor(en): A.A. Kampfraath; J.A. Renkema. - S.l. : Ziggers - ISBN 9789054850700 - 156
    landbouw - organisaties - theorie - bedrijfsvoering - bestuur - ondernemingen - economie - bedrijven - agrarische bedrijfsvoering - nederland - bedrijfseconomie - agriculture - organizations - theory - management - administration - enterprises - economics - businesses - farm management - netherlands - business management

    The aim of this study is to gain insight into the relations which leads to financial success. These relations concern the environment of the organization and levels of management levels of management and financial success and finally the environment of the organization' and financial succes. When insight is gained into these relations one can improve management in such a way that the best fit between environment and management can be obtained in order to get optimal financial results. The research was carried out in the pot-plant nursery branch. For this purpose these three variables were defined, measured and their interrelations analyzed. The measurement tools have been tested on validity and reliability. Hypotheses have been formulated and tested. The observation sessions were conducted at thirty nine pot-plant nurseries. The hypotheses concern the interrelations between complexity of the organization, personal traits of the entrepreneur, level of management and financial success.

    Rundvleesmarkt en rundvleesbeleid in de EG : een modelmatige verkenning
    Leeuwen, M.G.A. van - \ 1992
    Den Haag : LEI-DLO (Onderzoekverslag / Landbouw-Economisch Instituut (LEI-DLO), Afdeling Algemeen Economisch Onderzoek en Statistiek 100) - ISBN 9789052421797 - 149
    rundvlees - kalfsvlees - rundvee - markten - marketing - marktconcurrentie - aanbodsevenwicht - overheidsbeleid - landbouwbeleid - agrarisch recht - econometrische modellen - wiskundige modellen - econometrie - theorie - landen van de europese unie - beef - veal - cattle - markets - marketing - market competition - supply balance - government policy - agricultural policy - agricultural law - econometric models - mathematical models - econometrics - theory - european union countries
    Programmadag urgentieprogramma bollenziekte- en veredelingsonderzoek 1992 : samenvattingen van de programmadag, 30 september 1992
    Holsteijn, H.M.C. van; Toussaint, H.A.J.M. - \ 1992
    Wageningen : CPRO-DLO - ISBN 9789073771079 - 17
    ontwerp - ziekteresistentie - bloembollen - plaagresistentie - plantenveredeling - theorie - design - disease resistance - ornamental bulbs - pest resistance - plant breeding - theory
    Nieuwe situatie in het plantenveredelings- en reproduktieonderzoek : voorlichtings- en discussiebijeenkomst, 18 maart 1992
    Anonymous, - \ 1992
    Wageningen : CPRO-DLO - 9
    ontwerp - proefstations - plantenveredeling - onderzoek - onderzoeksinstituten - zaadcontrole - zaden - theorie - nederland - gelderland - veluwe - design - experimental stations - plant breeding - research - research institutes - seed testing - seeds - theory - netherlands - gelderland - veluwe
    Ontwikkelingsvisie 1993 - 1996
    Heusinkveld, G.W.H. ; Middelkoop, J.H. van; Jonge, G. de; Haar, J.W. van der - \ 1992
    Beekbergen : Praktijkonderzoek Pluimveehouderij (PP uitgave : praktijkonderzoek pluimveehouderij 1) - 41
    pluimvee - kippen - konijnen - pelsdieren - nederland - theorie - ontwerp - toekomst - poultry - fowls - rabbits - furbearing animals - netherlands - theory - design - future
    The corporate image concept : a strategic approach
    Vos, M.F. - \ 1992
    Agricultural University. Promotor(en): C.M.J. van Woerkum; A. van der Meiden. - S.l. : Vos - ISBN 9789090052267 - 199
    organisaties - theorie - bedrijfsvoering - bestuur - ondernemingen - economie - bedrijven - agrarische bedrijfsvoering - public relations - openbare mening - bedrijfseconomie - organizations - theory - management - administration - enterprises - economics - businesses - farm management - public relations - public opinion - business management

    Following a clarification of the concept of corporate image using the available literature as a basis, the process of image-formation and the nature of the influence of corporate image on behaviour are explored. The relationship with corporate identity is then discussed. This exploration leads us to considerations on corporate image policy and recommendations relating to methods of measurement.

    The core of the publication consists of the Corporate Image Concept, developed to provide a framework of ideas in the structuring of corporate image policy for public relations managers, public relations consultants and advice bureaus. Finally, a trial is set up to test the constructed Corporate Image Concept in Dutch universities, leading to the formulation of general conclusions.

    Bedrijfskundige aspecten van milieuvriendelijkere bedrijfssystemen in de glastuinbouw : perspectieven van het minimaliseren van de meststofuitspoeling bij grondteelten
    Ruijs, M.N.A. ; Os, E.A. van - \ 1991
    Naaldwijk : Proefstation voor Tuinbouw onder Glas (Verslag / Proefstation voor Tuinbouw onder Glas nr. 2) - 20
    plantenvoeding - kunstmeststoffen - mest - aquatisch milieu - kostenanalyse - industrie - organisaties - theorie - bedrijfsvoering - bedrijven - ondernemingen - bestuur - glastuinbouw - plant nutrition - fertilizers - manures - aquatic environment - cost analysis - industry - organizations - theory - management - businesses - enterprises - administration - greenhouse horticulture
    Onderzoeksplan boomteeltpraktijkonderzoek 1991 - 1995 : strategische benadering boomteelt-praktijkonderzoek op proefstation en regionale onderzoekscentra
    Anonymous, - \ 1991
    Boskoop : Proefstation voor de Boomkwekerij (Rapport / Boomteeltpraktijkonderzoek nr. 12) - 13
    ontwerp - houtachtige planten als sierplanten - onderzoek - theorie - design - ornamental woody plants - research - theory
    Het arbeids- en organisatie-onderzoek : een hele geschiedenis! : vijf en veertig jaren: 1946 - 1991
    Krolis, K.E. - \ 1991
    Wageningen : IMAG (Rapport / IMAG 236) - 64
    agrarische bedrijfsvoering - geschiedenis - arbeid (werk) - Nederland - werkorganisatie - theorie - werk - arbeidskunde - arbeid in de landbouw - farm management - history - labour - Netherlands - organization of work - theory - work - work study - farm labour
    Vooronderzoek bedrijfsregistratie in de boomteelt
    Wilms, G.J. - \ 1991
    Boskoop : Proefstation voor de Boomkwekerij (Rapport / Boomteeltpraktijkonderzoek nr. 14) - 26
    houtachtige planten als sierplanten - organisaties - theorie - bedrijfsvoering - bestuur - bedrijfseconomie - ornamental woody plants - organizations - theory - management - administration - business management
    Milieu gemodelleerd : de rol van systeemanalyse in de milieukunde
    Hordijk, L. - \ 1991
    Wageningen : Landbouwuniversiteit - 30
    ecologie - biogeografie - hydrobiologie - theorie - controle - systemen - systeemanalyse - regeltheorie - openbare redes - ecology - biogeography - hydrobiology - theory - control - systems - systems analysis - control theory - public speeches
    Hoe verder met landbouw en ruimte?
    Hetsen, H. ; Hidding, M.C. - \ 1991
    Landbouwkundig Tijdschrift 103 (1991)11. - ISSN 0927-6955 - p. 10 - 13.
    landbouw - ontwerp - landbouw bedrijven - landgebruik - bedrijfsvoering - natuurbescherming - nederland - ruimtelijke ordening - planning - plattelandsontwikkeling - plattelandsplanning - theorie - stedelijke planning - agrarisch natuurbeheer - agriculture - design - farming - land use - management - nature conservation - netherlands - physical planning - planning - rural development - rural planning - theory - urban planning - agri-environment schemes
    Een aanzet voor de discussie: hoe ruimtelijke vraagstukken die verband houden met de ontwikkeling van de landbouw moeten worden opgelost
    Van kaalkap naar selectieve kap. Een nieuwe strategie voor het beheer van bos in Nederland?
    Klein, J.P.G. de - \ 1991
    Nederlands Bosbouwtijdschrift 63 (1991). - ISSN 0028-2057 - p. 126 - 132.
    kaalslag - bosbedrijfsvoering - bosbouw - Nederland - selectiesysteem - selectiekap - shelterwoodsysteem - houtteelt conversie - opstandsontwikkeling - opstandsstructuur - duurzaamheid (sustainability) - theorie - opbrengsten - gelijkjarige opstanden - ongelijkjarige opstanden - clear felling - forest management - forestry - Netherlands - selection system - selective felling - shelterwood system - silvicultural conversion - stand development - stand structure - sustainability - theory - yields - even-aged stands - uneven-aged stands
    Modelling the escape of Chondrostereum purpureum spores from a larch forest with biological control of Prunus serotina.
    Jong, M.D. de; Wagenmakers, P.S. ; Goudriaan, J. - \ 1991
    Netherlands Journal of Plant Pathology 97 (1991). - ISSN 0028-2944 - p. 55 - 61.
    celdifferentiatie - demonstratiebossen - afsterving - ziekten - bosschade - achteruitgang, bossen - bosplagen - bosbouw - micro-organismen - modellen - natuurlijke vijanden - parasitaire planten - plantenziekteverwekkende schimmels - sporen - theorie - bomen - onkruiden - larix - prunus serotina - chondrostereum purpureum - bosbescherming - experimentele bossen - bospathologie - wetenschap - cell differentiation - demonstration forests - dieback - diseases - forest damage - forest decline - forest pests - forestry - microorganisms - models - natural enemies - parasitic plants - plant pathogenic fungi - spores - theory - trees - weeds - larix - prunus serotina - chondrostereum purpureum - protection of forests - experimental forests - forest pathology - science
    Risico-analyse van gebeurtenissen die leiden tot infectie van non-target planten. Middels een theoretische benadering in de vorm van gesimuleerde spore-verspreiding binnen en buiten het bos, wordt de sporefractie berekend die zou kunnen ontsnappen uit het bos
    Probabilistic models of perception
    Ennis, D.M. - \ 1991
    Agricultural University. Promotor(en): J.E.R. Frijters. - S.l. : Ennis - 212
    perceptie - beeldverwerking - statistiek - waarschijnlijkheidsanalyse - wiskunde - wiskundige modellen - theorie - patroonherkenning - perception - image processing - statistics - probability analysis - mathematics - mathematical models - theory - pattern recognition
    Mental representations of objects may fluctuate or change from moment to moment. Many models of similarity, identification, classification, and preferential choice are deterministic. These models cannot formally account for perceptual fluctuations. In this thesis, it is assumed that there exists a probability density function for psychological magnitudes (usually assumed to be multivariate normal) and a judgment function which defines how these magnitudes are used to make a particular decision. Based on these ideas, probabilistic models of triad discrimination, similarity, identification and preferential choice are derived and evaluated. Several of these models can account for differences in self-similarity, asymmetric similarities and violations of the triangle inequality because the metric axioms are not assumed to apply to proximity measures among stimulus means. A paradox, created when deterministic models of identification are compared, concerning the universal form of the similarity function and the distance metric, is resolved using a probabilistic model. The use of nonlinear least squares to estimate parameters is illustrated in the case of several of the models. Fechner-Thurstone models, in which stimulus variability, a psychophysical transformation, and psychological variability are formally included, are discussed.
    Besturen van organisaties : een inleiding tot de bedrijfskunde.
    Zuurbier, P.J.P. ; Bots, J.M. ; Edwards, A.R. ; Heck, E. van; Hendriks, J.A. ; Meer, C.J. van der; Stemne, S.I. ; Zwanenberg, A.C.M. - \ 1991
    Culemborg : Educaboek - ISBN 9789011019225 - 382
    industrie - organisaties - theorie - bedrijfsvoering - bedrijven - ondernemingen - bestuur - bedrijfseconomie - industry - organizations - theory - management - businesses - enterprises - administration - business management
    De zorg voor het milieu in economisch perspectief (3).
    Koeijer, T.J. de; Wossink, G.A.A. ; Renkema, J.A. - \ 1991
    Landbouwkundig Tijdschrift 103 (1991)5. - ISSN 0927-6955 - p. 24 - 26.
    veldgewassen - akkerbouw - landbouw bedrijven - natuurbescherming - landbouw - teeltsystemen - agrarische economie - bestrijdingsmethoden - plantenplagen - plantenziekten - geïntegreerde plagenbestrijding - geïntegreerde bestrijding - modellen - theorie - geïntegreerde bedrijfssystemen - wetenschap - milieuhygiëne - agrarisch natuurbeheer - field crops - arable farming - farming - nature conservation - agriculture - cropping systems - agricultural economics - control methods - plant pests - plant diseases - integrated pest management - integrated control - models - theory - integrated farming systems - science - environmental hygiene - agri-environment schemes
    De vakgroep Agrarische Bedrijfseconomie en de vakgroep Landbouwpolitiek, hebben in 1989 een begin gemaakt met het ontwikkelen van een milieu-economisch model voor de akkerbouw. In deze bijdrage wordt aangegeven wat de wenselijke en mogelijke gebruiksvoorwaarden zijn op bedrijfs- en regionaal niveau bij de beleidsvorming in landbouw
    In pursuit of progress.
    Verrips, K. ; Becker, H.A. ; Leeuw, F.L. - \ 1991
    Amsterdam : SISWO - ISBN 9789067060967 - 144
    methodologie - nederland - sociale wetenschappen - sociologie - theorie - methodology - netherlands - social sciences - sociology - theory
    A hundred and more years of plant protection in The Netherlands.
    Zadoks, J.C. - \ 1991
    Netherlands Journal of Plant Pathology 97 (1991). - ISSN 0028-2944 - p. 3 - 24.
    ziektebestrijding - geschiedenis - nederland - plagenbestrijding - gewasbescherming - systemen - theorie - wetenschap - disease control - history - netherlands - pest control - plant protection - systems - theory - science
    Kenschetsing van ontwikkelingen in de Nederlandse gewasbescherming sinds de oprichting van de Nederlandse Plantenziektenkundige Vereniging. Gedurende deze periode worden een drietal gedachtenstromen onderscheiden
    Heer en meester? : systeemtechnologie in landbouw en milieu
    Straten, G. van - \ 1991
    Wageningen : Landbouwuniversiteit - 41
    engineering - automatische regeling - theorie - engineering - automatic control - theory
    Rede Wageningen, 7 februari 1991
    Digital optimal control of rigid manipulators.
    Willigenburg, L.G. van - \ 1991
    Delft : Delftse Universitaire Pers - ISBN 9789062756612 - 278
    automatische regeling - engineering - robots - theorie - automatic control - theory
    Gap models : a general description of the structure and assumptions underlying forest succession models, including a brief manual for the model ZELIG
    Bartelink, H.H. - \ 1990
    Wageningen : Dorschkamp (Rapport / De Dorschkamp Instituut voor Bosbouw en Groenbeheer nr. 607) - 49
    bosbouw - plantensuccessie - plantengemeenschappen - modellen - theorie - onderzoek - meting - experimenten - statistiek - simulatie - forestry - plant succession - plant communities - models - theory - research - measurement - experiments - statistics - simulation
    HOPSY-2, een instrument voor de normatieve en strategische planning van houtoogst = HOPSY-2, a tool for strategic planning of timber harvest
    Hinssen, P.J.W. - \ 1990
    Wageningen : Dorschkamp (Rapport / De Dorschkamp Instituut voor Bosbouw en Groenbeheer nr. 606) - 123
    econometrie - aanbodsevenwicht - vraag - aanbod - econometrische modellen - wiskundige modellen - bosbouw - opbrengsten - theorie - houtaanwas - staande opstand - bossen - rotaties - bosbedrijfsvoering - opbrengstregeling - velling - bosexploitatie - econometrics - supply balance - demand - supply - econometric models - mathematical models - forestry - yields - theory - increment - growing stock - forests - rotations - forest management - yield regulation - felling - forest exploitation
    Houtoogst uit het Nederlandse blijvende opgaande bos van 1985 tot 2035 : de prognoses in 1990 met toepassing van het houtoogstprognoseprogramma HOPSY-2 = The Dutch standing forest wood supply forecast 1990 : an application of the wood supply forecasting computer program HOPSY-2
    Hinssen, P.J.W. ; Daamen, W.P. - \ 1990
    Wageningen : Dorschkamp (Rapport / De Dorschkamp Instituut voor Bosbouw en Groenbeheer nr. 605) - 156
    bosbouw - bosbedrijfsvoering - opbrengsten - theorie - houtaanwas - staande opstand - bossen - rotaties - opbrengstregeling - velling - markten - marketing - vraag - aanbod - hout - houtproducten - prijzen - aanbodsevenwicht - econometrische modellen - wiskundige modellen - nederland - bosexploitatie - forestry - forest management - yields - theory - increment - growing stock - forests - rotations - yield regulation - felling - markets - marketing - demand - supply - wood - wood products - prices - supply balance - econometric models - mathematical models - netherlands - forest exploitation
    Bedrijfseconomische gevolgen van vitaliteitsvermindering : eerste methodiekontwikkeling voor het kwantificeren van de financiele schade door vitaliteitsvermindering op bosbedrijfsniveau
    Jans, M.F.F.W. - \ 1990
    Wageningen : De Dorschkamp (Rapport / De Dorschkamp, Instituut voor Bosbouw en Groenbeheer nr. 597) - 83
    bosbouw - achteruitgang, bossen - levensvatbaarheid - houtaanwas - opstandsontwikkeling - opstandsstructuur - biomassa - bosbedrijfsvoering - bosbouweconomie - staande opstand - bossen - taxatie - opbrengsten - theorie - nederland - bosopstanden - boswaardebepaling - forestry - forest decline - viability - increment - stand development - stand structure - biomass - forest management - forest economics - growing stock - forests - valuation - yields - theory - netherlands - forest stands - forest valuation
    A simple model of P uptake by crops as a possible basis for P fertilizer recommendations
    Noordwijk, M. van; Willigen, P. de; Ehlert, P.A.I. ; Chardon, W.J. - \ 1990
    Netherlands Journal of Agricultural Science 38 (1990)3A. - ISSN 0028-2928 - p. 317 - 332.
    fosfor - mestbehoeftebepaling - vloeistoffen (liquids) - absorptie - wortels - modellen - theorie - fosfaten - fosforpentoxide - derivaten - wetenschap - phosphorus - fertilizer requirement determination - liquids - absorption - roots - models - theory - phosphates - phosphorus pentoxide - derivatives - science
    Tungabhadra irrigation pilot proje[c]t : final report, conclusions and recommendations
    Jurriens, M. ; Landstra, W. - \ 1990
    Wageningen : International Institute for Land Reclamation and Improvement
    ontwerp - india - irrigatie - theorie - design - india - irrigation - theory
    Visie vermeerdering boomkwekerijgewassen : ontwikkeling, knelpunten, prioriteiten en mogelijkheden voor onderzoek
    Kunneman, B.P.A.M. - \ 1990
    Boskoop : Proefstation voor de Boomkwekerij (Rapport / Boomteeltpraktijkonderzoek nr. 5) - 35
    ontwerp - bosbouw - houtachtige planten als sierplanten - plantenvermeerdering - geslachtelijke voortplanting - theorie - vegetatieve vermeerdering - design - forestry - ornamental woody plants - propagation - sexual reproduction - theory - vegetative propagation
    Geintegreerd bedrijfsmodel voor de akkerbouw op de noordoostelijke zand- en dalgronden, met name in grondwaterbeschermingszones
    Vereijken, P.H. - \ 1990
    Gewasbescherming 21 (1990)6. - ISSN 0166-6495 - p. 165 - 171.
    akkerbouw - veldgewassen - grondwater - modellen - zandgronden - waterbronnen - theorie - putten - geïntegreerde bedrijfssystemen - noord-holland - wetenschap - arable farming - field crops - groundwater - models - sandy soils - springs (water) - theory - wells - integrated farming systems - noord-holland - science
    Aanzet tot een geintegreerd bedrijfsmodel, waarbij als werkwijze is gekozen voor de formulering van een programma van eisen, het ontwerpen van een vruchtwisselingsmodel dat aan deze eisen voldoet en tenslotte een verkenning van de technische, milieuhygienische en bedrijfseconomische perspectieven van een hierop gebaseerde bedrijfsvoering
    Tien jaar verzorgingstechnologie in perspectief.
    Groot-Marcus, J.P. - \ 1990
    Tijdschrift voor huishoudkunde 11 (1990). - ISSN 0169-1295 - p. 1 - 7.
    higher education - home economics - households - management - theory - organization
    Bedrijfsbegeleiding in de melkveehouderij: economisch aantrekkelijk?
    Dijkhuizen, A.A. - \ 1990
    Landbouwkundig Tijdschrift 102 (1990)4. - ISSN 0927-6955 - p. 12 - 16.
    automatisering - melkvee - melkveehouderij - agrarische bedrijfsvoering - agrarische bedrijfsplanning - informatiesystemen - bedrijfsvoering - modellen - theorie - wetenschap - automation - dairy cattle - dairy farming - farm management - farm planning - information systems - management - models - theory - science
    Beschouwing van mogelijkheden ter voorkoming van gezondheidsstoornissen en vruchtbaarheidsproblemen middels bedrijfsbegeleiding. Aandacht voor de theoretische haalbaarheid, afgeleid uit modelberekeningen, en de praktische realisatie
    Analysis of the exit problem for randomly perturbed dynamical systems in applications
    Roozen, H. - \ 1990
    Agricultural University. Promotor(en): J. Grasman. - S.l. : Roozen - 156
    wiskundige modellen - theorie - stochastische processen - dynamisch programmeren - markov-processen - mathematical models - theory - stochastic processes - dynamic programming - markov processes

    In the preface of his book entitled 'Theory and applications of stochastic differential equations', Z. Schuss (1980) noticed a gap between the theory of stochastic differential equations and its applications. In addition to the work of Schuss and many others in the field, the present work aims at narrowing this gap.

    This thesis deals with randomly perturbed dynamical systems. Such systems frequently arise in the modelling of phenomena in biology, mechanics, chemistry, and physics. In some cases random perturbations form a minor aspect of the problem under study. Then a deterministic description can be used. In the present work the behaviour of the dynamical systems depends essentially on the random perturbations. We encounter systems with so-called 'diffusion across the flow' (Chapters 1,2) and systems with 'diffusion against the flow' (Chapters 1,3-5). The stability of equilibria of these systems (and thus, the lifetime, reliability of these systems) is affected by random perturbations.

    In the study of so-called 'exit problems' we consider a domain in the state space of the dynamical system and try to compute statistical quantities related to escape from this domain, such as the probability density function of the exit-time, the probability density function of exit points on the boundary of the domain (or, less ambitiously, the first few statistical moments of these densities: mean, variance, etc.). The expectation value of the exit-time can be used to express the stochastic stability of the system.

    We speak of randomly perturbed dynamical systems, so we assume that the stochastic fluctuations are small. This is often a realistic assumption. To derive expressions for the statistical quantities mentioned above, we employ asymptotics where the small parameter is related to the intensity of the random perturbations. The asymptotic method used in Chapter 2 is well-established. The asymptotics in Chapters 3-6 are of a formal character. The asymptotic analysis is performed to the lowest order necessary to incorporate the essential effects. In view of the complexity of this simplest approach, we did not carry out higher order calculations.

    The first chapter forms an introduction to some important topics in the theory of exit problems. We discuss the relevant (initial-) boundary-value problems, the classification of boundaries of domains of stochastic dynamical systems, and we give elementary examples of systems with 'diffusion across the flow' and 'diffusion against the flow' and their asymptotic solution. This chapter facilitates access to literature on exit problems and to the remaining chapters of this thesis. A more detailed treatment of the topics touched upon in this chapter is found in the cited literature.

    Chapter 2 is concerned with the dynamics of a loaded stiff rod. The load consists of a deterministic part and a small stochastic part. An accumulation of stochastic load fluctuations may drive the energy of the rod across some critical level. The expectation value of the time to reach this critical energy level is a measure for the reliability of the system that contains the rod. According to the directions in which the loads act, various cases are distinguished. We derive expressions for the expectation value of the exit-time and (for some of the cases) of a number of other statistical quantities, as the exit-time density, its moments and cumulants and the probability density function of the square root of the energy (as a function of time). We use an asymptotic method known as the averaging technique. As a matter of fact, the model is a randomly loaded slightly damped oscillator. Since many practical systems near equilibrium behave essentially like a slightly damped oscillator, the. results obtained may be expected to have a wide range of application.

    In Chapter 3 we study the exit problem for a stochastic dynamical system of interacting biological populations. Exit from the domain (the positive orthant) corresponds with extinction of a population. We start with a birth and death process, having a discrete state space, and subsequently formulate an 'approximate' Fokker- Planck (or forward Kolmogorov) equation in a continuous state space. It is assumed that the deterministic system associated with the stochastic dynamical system has a point attractor in the positive orthant. The biological system will remain for some (probably long) time in a neighbourhood of the attracting point, but after a (rare) succession of random fluctuations, one of the populations will get extinct. Determining the expected time of exit (of whichever of the populations), and of which population will probably get extinct first, requires the numerical solution of a system of so-called 'ray equations' (obtained from the Fokker-Planck equation by the WKB-method). In literature these differential equations are provided with initial conditions, which entails difficulties in the numerical construction of contours in the state space on which the eikonal function attains a constant value (confidence contours). We define boundary conditions instead of initial conditions and thereby resolve these difficulties. The ideas are illustrated by a two-dimensional generalized Lotka-Volterra model. This model allows a nice demonstration of the concepts of deterministic stability and stochastic stability. Numerically constructed confidence contours are shown for predator-prey, mutualism and competition variants of the model. We carry out numerical simulations of birth- death processes to check the results.

    A discussion of various ways of numerical solution of the system of ray equations is found in Chapter 4. In particular we explain the boundary-value method referred to above. Moreover we give some details on the numerical construction of rays and confidence contours. At the end we present an example with intersecting rays. This phenomenon is investigated analytically in Chapter 6.

    In Chapter 5 we are concerned again with a stochastic version of the two- dimensional generalized Lotka-Volterra model. The approach differs from that in Chapter 3 in that now we pay attention to what happens near the boundaries of the domain (the positive coordinate axes). The main difficulty is caused by the fact that the normal components of both the drift and the diffusion coefficients vanish near the boundaries, as linear functions of the distance to the boundaries. To obtain expressions for the statistical quantities of interest, we generalize a method of other authors in the study of a similar one-dimensional problem. The asymptotic expressions contain some unknown constants, that can be obtained numerically. Explicit calculations are carried out for a predator-prey system as an example,

    Applying the WKB-method to the forward Kolmogorov equation, we obtain the ray equations. In the solution of the ray equations one sometimes observes intersecting rays forming caustic surfaces. This phenomenon is studied in Chapter 6. Near locations of intersecting rays, the WKB-approximation does not hold. We derive a uniform asymptotic expansion in terms of new canonical integrals whose validity extends over regions containing caustics. We start with the simple case of a cusp arising in a diffusion problem for which explicit results can be obtained. Subsequently, we generalize it to a formal approach to singularities arising in the forward Kolmogorov equation.
    The text of each of the chapters has appeared as a report or a publication in a scientific journal.

    Retributieheffing bij het Staatsbosbeheer in bezoekerscentra en tijdens ekskursies
    Setten, T.A. van - \ 1989
    Wageningen : Dorschkamp (Rapport / "De Dorschkamp" Instituut voor Bosbouw en Groenbeheer nr. 575) - 129
    belastingen - theorie - recreatie - milieueducatie - bosbouw - conferenties - bezoeken - nederland - taxes - theory - recreation - environmental education - forestry - conferences - visits - netherlands
    De bruikbaarheid van het houtoogstprognosesysteem "Hopsy" als hulpmiddel bij bosbedrijfsplanning : een case study in de boswachterij Smilde
    Hinssen, P.J.W. - \ 1989
    Wageningen : De Dorschkamp (Rapport / Rijksinstituut voor Onderzoek in de Bos- en Landschapsbouw "De Dorschkamp" nr. 546) - 142
    bosbouw - opbrengsten - theorie - houtaanwas - staande opstand - bossen - rotaties - aanbodsevenwicht - vraag - aanbod - econometrische modellen - wiskundige modellen - bosbedrijfsvoering - opbrengstregeling - velling - bosexploitatie - forestry - yields - theory - increment - growing stock - forests - rotations - supply balance - demand - supply - econometric models - mathematical models - forest management - yield regulation - felling - forest exploitation
    De gemiddeld jaarlijkse waterbalans van bos-, heide- en graslandvegetaties
    Visser, P.H.B. de; Vries, W. de - \ 1989
    Wageningen : STIBOKA (Rapport / Stichting voor Bodemkartering nr. 2085) - 136
    graslanden - bosbouw - bodemwater - permeabiliteit - absorptie - hygroscopiciteit - heidegronden - waterbalans - methodologie - hydrologie - theorie - modellen - bodemwaterbalans - nederland - grasslands - forestry - soil water - permeability - absorption - hygroscopicity - heathland soils - water balance - methodology - hydrology - theory - models - soil water balance - netherlands
    De gemiddeld jaarlijkse waterbalans van een aantal combinaties van bos- en heidesystemen op zandgronden is berekend met het simulatiemodel SWATRE. Bij bos is daarbij onderscheid gemaakt in een 3-tal bostypen: douglas, grove den en eik. Ook is gekeken naar een aantal combinaties van grasland met natte zandgronden en veengronden, alsmede een aantal kale zandgronden. Het totale aantal onderscheiden zandgronden is 14, terwijl het totale aantal doorgerekende combinaties 58 bedraagt
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