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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    Better modelling practice : an ontological perpsective on multidisciplinary, model-based problem solving
    Scholten, H. - \ 2008
    Wageningen University. Promotor(en): Adrie Beulens, co-promotor(en): M.S. Elzas. - S.l. : S.n. - ISBN 9789085853046 - 314
    wiskundige modellen - probleemoplossing - kennis - simulatie - simulatiemodellen - kwaliteit - besluitvorming - ontologieën - modelleren - kwaliteitszorg - mathematical models - problem solving - knowledge - simulation - simulation models - quality - decision making - ontologies - modeling - quality management
    Mathematical models are more and more used to support to solve multidisciplinary, real world problems of increasing complexity. They are often plagued by obstacles such as miscommunication between modellers with different disciplinary backgrounds leading to a non-transparent modelling process. Other difficulties include bad modelling practices, i.e. improper data handling, insufficient calibration, validation and uncertainty analysis, overselling model capabilities and incorrect use of model results in the decision process.

    To tackle these difficulties, a body of knowledge on modelling, on the problem at hand and on the models itself to solve the problem, has been made explicit and organised in ontological knowledge bases with concepts and relations connecting the concepts. These ontological knowledge bases are furthermore structured in layers ranging from generic to detailed and specific. This facilitates communication between team members from different disciplines and also makes parts of the knowledge reusable. Tools to fill the knowledge bases and to support modelling projects (guidance from the knowledge base, logbook and project management) complete this better modelling practice framework.
    Improving support for greenhouse climate management : an exploration of a knowledge-based system
    Schotman, P.J. - \ 2000
    Agricultural University. Promotor(en): H. Challa; M.S. Elzas; R. Martin Clouaire. - S.l. : S.n. - ISBN 9789058082145 - 234
    kassen - bedrijfsvoering - controle - solanum lycopersicum - gewassen - gewassen, groeifasen - modellen - neusrot - tomaten - binnenklimaat - beslissingsondersteunende systemen - glastuinbouw - greenhouses - management - control - solanum lycopersicum - crops - crop growth stage - models - blossom-end rot - tomatoes - indoor climate - decision support systems - greenhouse horticulture

    This thesis discusses automated support for operational management of greenhouse crops and proposes a knowledge-based system to support the grower in his operational management task.

    Operational management is defined as the day-to-day decision making processes which directly or indirectly lead to activities that influence the growth and development of the crop. To improve automated support for operational management, the growers operational decision making has been analyzed in the light of theory related to problem solving. The analysis of the task environment has resulted in a model of the decision processes within operational crop production management. This model has been based on the intelligence - design - choice cycle of Simon (1997). During the design and choice phases of this model the grower has to convert his observations at the crop and environment level into actions that can be implemented at the control level. Since this conversion is considered a complex and knowledge intensive task, a knowledge-based system is proposed to support the grower. The main idea behind the approach is to allow the grower to tell the system what objectives it must pursue and have the system deduce the required device settings at the control level. As these objectives may be situated at the crop, environment and control level, both domain knowledge as well as a suitable inference mechanism is required to realize such an approach.

    Analysis of the knowledge in the domain of crop production shows that this knowledge is, or can be made available. Regarding the latter, the Blossom-end Rot example shows that knowledge can be made available in a suitable format.

    With respect to the inference mechanism past approaches have been surveyed. Based on the results of this survey, the characteristics of the inference problem, and the attributes of the domain knowledge, it has been concluded that constraint reasoning fits the requirements best.

    Simulation experiments with a prototype implementation show that the constraint reasoning can indeed be used as inference mechanism, however it is argued that the amount of work needed to realize and implementation in practice is formidable.

    Relevant ...?
    Elzas, M.S. - \ 1999
    Wageningen : Wageningen Universiteit - 46
    Kettenis, D.L. - \ 1999
    In: M.S. Elzas: Een bloemlezing uit zijn werk / Kettenis, D.L., - p. 9 - 11. M.S. Elzas: Een bloemlezing uit zijn werk
    Kettenis, D.L. - \ 1999
    Wageningen : Wageningen UR, Sectie Informatica - 174 p.
    Il faut cultiver son jardin
    Hofstede, G.J. - \ 1999
    In: M.S. Elzas: Een bloemlezing uit zijn werk / Kettenis, D.L., - p. 121 - 122.
    Bijdrage van Drs. E.W. van Ammers
    Ammers, E.W. van - \ 1999
    In: M.S. Elzas: Een bloemlezing uit zijn werk / Kettenis, D.L., - p. 49 - 50.
    Computer architecture: single and parallel systems (boekbespreking).
    Elzas, M.S. - \ 1997
    Computing Reviews 38 (1997)11. - ISSN 0010-4884
    An introduction to high-performance scientific computing (boekbespreking).
    Elzas, M.S. - \ 1997
    Computing Reviews 38 (1997)7. - ISSN 0010-4884 - p. 342 - 323.
    INFO Society 2000.
    Elzas, M.S. - \ 1995
    Agro Informatica 95 (1995)2. - ISSN 0925-4455 - p. 21 - 22.
    Evaluating probabilistic risk assessment models.
    Elzas, M.S. - \ 1995
    In: Proc. 1995 Summer Computer Simulation Conf., T.I. Ören, L.G. Birta (eds.). SCSC, San Diego - p. 957 - 966.
    Proposal for a CEPIS World Wide Web Structure.
    Elzas, M.S. - \ 1995
    Unknown Publisher
    Review of the AECL Post Closure Assessment and related documents.
    Elzas, M.S. - \ 1995
    Hull, Quebec Canada : Canadian Environmental Assessment Agency/MTC Inc. - 61 p.
    A knowledge - based system to assist in the design of soil survey schemes
    Domburg, P. - \ 1994
    Agricultural University. Promotor(en): M.S. Elzas; J.J. de Gruijter. - S.l. : Domburg - ISBN 9789054853121 - 191
    bodemkarteringen - landevaluatie - horizonten - bodemgeschiktheid - grondanalyse - bemonsteren - computersimulatie - simulatie - simulatiemodellen - geostatistiek - soil surveys - land evaluation - horizons - soil suitability - soil analysis - sampling - computer simulation - simulation - simulation models - geostatistics

    Soil survey information with quantified accuracy is relevant to decisions on land use and environmental problems. To obtain such information statistical strategies should be used for collecting and analysing data. A survey project based on a statistical sampling strategy requires a soil survey scheme specifying which sites are to be sampled, which data are to be recorded and how they are to be analysed statistically. The efficiency of such a scheme is determined by the accuracy of the survey results and the cost of operation. This accuracy and cost depend mainly on the method of determination and the sampling design in the scheme.

    This study aimed at formulating the basic design considerations of a knowledge-based system (KBS) to assist in the design of soil survey schemes. This system should incorporate pedological and statistical knowledge. The domain of the system has provisionally been limited to surveys for which a design-based approach, i.e. the use of classical sampling theory, is appropriate.

    Initially, the domain of the system has been structured in three layers: (i) an entity structure clarifying the position of the system in a soil survey project; (ii) a model describing the design process as a number of interrelated steps, and (iii) a conceptual framework defining the main concepts and their relations.

    Further analysis made it possible to specify the tasks in which the KBS should assist: definition of the survey request, selection of prior information, design of outlinear schemes, evaluation and optimization of outlinear schemes, generation of a report, and evaluation a posteriori .

    The system will primarily assist in the statistical decisions in the design process. Since there was no suitable classification of sampling designs available, a hierarchical framework of sampling designs has been constructed, in which sampling designs are grouped into types of designs, and types are grouped into classes of designs. Furthermore the main classes of sampling designs treated in the literature have been ordered in a taxonomy. Decision trees have been developed to guide the selection of an appropriate sampling approach (designbased versus model-based), and, in the case of a design-based approach, to guide the search for an appropriate class of sampling designs.

    To ensure that the available means for a project, such as budget, personnel, and equipment, are used adequately schemes should be evaluated and optimized beforehand. Models related to the features of sampling designs have been developed for predicting the accuracy and cost of survey schemes, the so-called prior evaluation. Furthermore the use of dynamic programming is proposed to search for the optimal sampling design within an outlinear scheme. The procedure enables objective comparison of schemes taking into account differences in spatial variability or sampling cost among sub-regions.

    Finally, basic design considerations are presented consisting of an initial requirements definition, a description of the intended use of the KBS, and a specification of the components for an actual KBS. Five components are distinguished: a database, a knowledge base, a model base, a problem-solving model, and a user interface. The system will assist in its own maintenance through continuous storage of knowledge from executed projects. This will facilitate the re-use of information. A KBS which is based on these basic design considerations will assist in controlling the quality of soil survey projects.

    Software Industry Working Group Interim Report.
    Elzas, M.S. ; Sprangenberg-Carlier, M. - \ 1994
    Unknown Publisher - 40 p.
    An ICT strategy for Europe.
    Elzas, M.S. - \ 1994
    Unknown Publisher - 20 p.
    Kees de Wit.
    Elzas, M.S. - \ 1994
    NGI-Magazine 3 (1994)4.
    First Report to the Scientific Review Group of the Canadian Environmental Assessment.
    Elzas, M.S. - \ 1994
    Unknown Publisher - 100 p.
    Second Report to the Scientific Review Group of the Canadian Environmental Assessment.
    Elzas, M.S. - \ 1994
    Unknown Publisher - 12 p.
    Software verification, model validation and hydrogeologic modelling aspects in nuclear waste disposal system simulations : a paradigm shift
    Sheng, G.M. - \ 1994
    Agricultural University. Promotor(en): M.S. Elzas. - S.l. : Sheng - 295
    kernenergiecentrales - gevaren - opslag - kernenergie - radionucliden - radioactief afval - afvalverwijdering - huisvuilverwijdering - afvalstortplaatsen - stortterreinen - vuilnisbelten - computersimulatie - simulatie - simulatiemodellen - computer software - toepassingen - grondwaterstroming - programmeren - software-ontwikkeling - nuclear power stations - hazards - storage - nuclear energy - radionuclides - radioactive wastes - waste disposal - municipal refuse disposal - waste disposal sites - landfills - refuse tips - computer simulation - simulation - simulation models - computer software - applications - groundwater flow - programming - software engineering

    This work (1) reviews the current concept ad~ internationally on the disposal of highlevel nuclear wastes; (2) discusses some of the major challenges facing this disposal technology; (3) presents an evaluation of the Canadian performance assessment work as a case study; and (4) introduces a new paradigm within which to site an underground. disposal facility that offers many significant advantages over the existing concept.

    Chapter 1 explains the setup of the work and forms the "General Introduction" to the subject material.

    Chapter 2 describes the current internationally-accepted concept of underground disposal in stable, terrestrial, geologic media using a multi-barrier system of engineered (man-made) and natural barriers to prevent or retard the movement of radionuclides from depth to man's environment at the surface. Various aspects of the research and development work being conducted internationally to demonstrate the efficacy of this technology are described with emphasis paid to the Canadian Nuclear Fuel Waste Management Program (CNFWMP).

    Chapter 3 examines some of the technical challenges of the current disposal concept including (a) the present focus on the lithologic aspects of the geologic/geotechnic research; (b) the unsatisfactory situation in attempts at "validating" models used in computer simulations to forecast very long-term future conditions; and (c) the unsatisfactory state of software quality assurance in such computer simulations. The collection of papers in this chapter points out these problems and presents some of the software engineering tools and techniques used for software verification and quality assurance. Paper 3.4 introduces a comprehensive and systematic approach with which a rigorous process of validating models can be applied.

    Chapter 4 presents a review of some aspects of the Canadian performance assessment code, its models, as a case study to illustrate the application of principles, and tools and techniques described in Chapter 3. As such, various widely-recognized ANSI/IEEE software engineering standards were used to carry out the evaluation. This review is the first m-depth evaluation done externally and will likely serve, m part, as a basis for the ultimate judgement as to the quality and credibility of the Canadian performance assessment work.

    Chapter 5 introduces a completely new approach, called the Regional Recharge Concept (RRC), to the siting of underground waste repositories. The emphasis of this new concept is on achieving understanding of regional groundwater flow patterns so as to exploit such knowledge to locate a repository in an area where escaping contaminants will be carried by the groundwater into "stagnant zones" or on a flow trajectory long enough to render decaying radionuclides harmless if and when they do ever surface. The theoretic basis of the RRC is developed in this chapter and the many advantages of the concept are shown through a modelling exercise. Because of the "passive safety" philosophy inherent in this new concept, as well as the move away from the current international focus on lithologic studies (where experience has shown the great difficulties in characterizing fractures and predicting their future behaviour), the RRC being advocated in this work represents a true paradigm shift from the current concept of nuclear waste disposal.

    Chapter 6 summarizes the results from previous chapters in the form of conclusions relevant to future work in this area.

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