Korte verblijftijd haalbaar bij mestvergisting
Timmerman, M. ; Eekert, M. ; Riel, J.W. van; Schuman, E. - \ 2013
V-focus 10 (2013)6. - ISSN 1574-1575 - p. 42 - 43.
veehouderij - mestvergisting - biogas - gasproductie - fermentatie - duur - glycerol - biobased economy - warmtekrachtkoppeling - livestock farming - manure fermentation - biogas - gas production - fermentation - duration - glycerol - biobased economy - cogeneration
Vergisting van mest bij verblijftijden van korter dan 15 dagen is haalbaar, maar mestsoort en mestkwaliteit blijken een groot effect te hebben op de biogasproductie bij deze korte verblijftijden. Het is mogelijk om bij deze korte verblijftijd een kleine hoeveelheid (<5%) glycerine toe te voegen waardoor de biogasproductie sterk toeneemt, zodat er een 2 tot 3 keer zo grote WKK kan worden neergezet als bij pure mestvergisting. Maar de biogasproductie van de glycerine hangt wel af van de mestkwaliteit.
Nieuw belichtingsmodel geeft een meer evenwichtige plantbelasting (interview met Arie de Gelder)
Bouwman-van Velden, P. ; Gelder, A. de - \ 2012
Onder Glas 9 (2012)5. - p. 59 - 59.
glastuinbouw - glasgroenten - belichting - duur - modellen - plantenontwikkeling - gebruikswaarde - groenten - greenhouse horticulture - greenhouse vegetables - illumination - duration - models - plant development - use value - vegetables
Afgelopen winter is bij het onderzoek met LED en SON-T belichting in tomaten ook gekeken naar wisselende belichtingsduur. Wageningen UR glastuinbouw ontwikkelde een belichtingsmodel dat eerder werd ingezet bij de gerbera. Het lijkt er op dat de plantbelasting rond de kortste dag beter is te sturen.
Extreme value modeling of areal rainfall from weather radar
Overeem, A. ; Buishand, T.A. ; Holleman, I. ; Uijlenhoet, R. - \ 2010
Water Resources Research 46 (2010). - ISSN 0043-1397
neerslag - frequentieverdeling - duur - meteorologische waarnemingen - radar - precipitation - frequency distribution - duration - meteorological observations - radar - precipitation annual maxima - frequency estimation - reduction factors - intervals - curves - sites
An 11 year high-quality radar rainfall data set is used to abstract annual maximum rainfall depths for durations of 15 min to 24 h and area sizes of 6 to 1.7 × 103 km2 for the Netherlands. Generalized extreme value (GEV) distributions are fitted to the annual maxima. A new method is presented to describe the distribution of extreme areal rainfall depths by modeling GEV parameters as a function of both duration and area size. This leads to a semiempirical expression from which quantiles of extreme rainfall depths can be obtained for a chosen duration, area size, and return period. The uncertainties in these quantiles are calculated using the bootstrap method. Radar-based areal reduction factors (ARFs) are derived. These ARFs are comparable to those based on high-density rain gauge networks derived from the literature. It is concluded that radar data, after careful quality control, are suitable to estimate extreme areal rainfall depths
Invulling lichteisen EU-welzijnsrichtlijn voor vleeskuikens, vier lichtschema's vergeleken = Comparison of four light schedules according to EU directive 2007/43 for broilers
Harn, J. van - \ 2009
Lelystad : Animal Sciences Group, Wageningen UR (Rapport / Animal Sciences Group 172) - 45
pluimveehouderij - kuikens - vleesproductie - huisvesting van kippen - verlichting - lichtsterkte - duur - dierenwelzijn - vleeskuikens - poultry farming - chicks - meat production - chicken housing - lighting - light intensity - duration - animal welfare - broilers
Four different light schedules according to EC Directive 2007/43 for broilers were compared. This study was done with five different broilers strains
Investment patterns in Dutch glasshouse horticulture
Goncharova, N. - \ 2007
Wageningen University. Promotor(en): Arie Oskam. - [S.l.] : S.n. - ISBN 9789085046684 - 180
investering - besluitvorming - onzekerheid - tuinbouw - kassen - nederland - akkerbouw- en tuinbouwbedrijven - tuinbouwbedrijven - duur - bedrijfsbeëindiging in de landbouw - econometrische modellen - investment - decision making - uncertainty - horticulture - greenhouses - netherlands - crop enterprises - market gardens - duration - farm closures - econometric models
Keywords: investment, uncertainty, investment spikes, entry, exit, duration model, GMM dynamic panel data estimator, Negative Binomial model, Heckman selection model, moving window ARIMA, Principal Component analysis, horticulture
This thesis focuses on the analysis of investment decision-making in order to better understand the variables that influence a firm's profit-maximizing strategy. The goal of a firm is to continue to exist, which can be achieved through the maximization of profit. Thus, the investment decision is considered as a realization of the firm's profit-maximizing objective.
To understand the investment decision, investments in fixed capital in Dutch glasshouse horticulture were studied. Because an investment decision is dynamic by nature, investment patterns were analysed during the period 1975-1999, thereby providing a longer term overview. The salient characteristic of Dutch glasshouse horticulture firms is that they remain small-scale family firms with respect to labour and land, but are highly capital-intensive. Moreover, in recent decades, the sector has experienced many transformations in the fields of evolution and adaptation to new technologies, consumer preferences, and market and environmental requirements. This makes the Dutch glasshouse horticulture sector an attractive case for studying investment patterns. This is done by considering an investment decision as having three components: decisions about participation, about level, and about time. These components are a tangible part of investment decision-making; they reflect the latent factors of: investment thresholds, adjustment costs, irreversibility, and risk and uncertainty, all of which predetermine investments.
Results from this research show the relevance of separating the participation and level decisions since the set of significant variables differ (e.g. energy- and land prices are not significant for the level decision), and some of the variables exhibited contrasting signs (e.g. debts, revenue, labour cost). The impact of thresholds is tested on different types of entry and exit, which are considered as investment or disinvestment decisions. The raising of a threshold discourages firms from action; they prefer to delay any decision that can be related to the irreversibility of an investment. The results of this study do not provide strong support for the Real Option theory, which postulates that the effect of the uncertainty can be observed through the changes in investment threshold. While the model based onMarshalliantrigger points, which suggests the direct impact of the sector-characterizing variables (such as expectation of output prices, interest rate and uncertainty), explains the participation investment decision better.
A phenomenon that has not been studied in any depth is the effect of uncertainty on investment, which is considered in many studies as ambiguous. This study argues that risk and uncertainty should be distinguished from each other. The estimation leads to the conclusion concerning the difference in their effects on the level of investment, which sometimes contrast with each other. Moreover, the asymmetry in the effect of uncertainty is confirmed.The timing of investment addresses the phenomenon of lumpy and intermittent patterns of investment, as estimated by a duration model. The timing of investments can be explained by the irreversibility of investment, with the lumpiness suggesting the fixed component in adjustment costs. A 6-year investment cycle was revealed at firm level and confirmed at average level. This implies that new policy instruments for increasing the adoption of new technologies will not necessarily lead to an immediate increase in investments, but will depend on, amongst others, factors associated with the degree of vintage of the installed technologies.
|De OEEI-methodiek toegepast - Een methodiek voor de kosten-batenanalyse van infraprojecten
Straaten, J.W. van der; Heijman, W.J.M. ; Fanoy, J.A. - \ 2003
Wegen 77 (2003)6. - ISSN 0043-2067 - p. 10 - 13.
infrastructuur - wegtransport - duur - tijd - investering - kosten-batenanalyse - methodologie - noord-holland - flevoland - road transport - infrastructure - duration - time - investment - cost benefit analysis - methodology - noord-holland - flevoland
In 1998 is het "Onderzoeksprogramma economische effecten infrastructuur" (OEEI) gestart, om te komen tot een eenduidige kosten-baten analyse. In totaal hebben 9 onderzoeken plaats gehad, die vervolgens geëvalueerd zijn. In dit artikel is de methode voor het eerst in de praktijk getoetst, en wel voor het wegverkeer binnen de regio Amsterdam, Almere en 't Gooi. Ondertussen is in 2000 de MKBA verplicht gesteld bij grote infrastructurele projecten
Energiezuinig drogen van bloembollen en ontvochtigen van drooglucht
Bot, G.P.A. ; Loon, W.K.P. van; Campen, J.C. van - \ 2002
Wageningen : IMAG - 21
bloembollen - drogen - duur - energiebesparing - luchtstroming - gewaskwaliteit - verwarming - energiegebruik - landbouwkundig onderzoek - ornamental bulbs - drying - duration - energy saving - air flow - crop quality - heating - energy consumption - agricultural research
Het droogproces van bloembollen (tulpen) is modelmatig en experimenteel onderzocht. Het laagste energiegebruik treedt op bij droging met buitenlucht maar dit vraagt ook de langste droogtijd. Het hangt van de cultivar af of dit verantwoord is. Een kortere droogtijd wordt verkregen bij voorverwarmen, hierdoor wordt echter meer energie gebruikt. Bij de in de praktijk gebruikelijke droogwanden treedt inhomogene droging op. Deze wordt vooral veroorzaakt door een niet gelijkmatige doorstroming van de verschillende kisten in de kistenstapeling voor de droogwand. Door de langere droogtijd van de langzaam drogende kisten blijven deze te lang vochtig terwijl de sneller drogende kisten lang worden blootgesteld aan warme drooglucht. Beide aspecten hebben een negatieve invloed op de kwaliteit. Verbetering van de homogeniteit van de doorstroming zal de droogpotentieel van de drooglucht beter benutten en de totale droogtijd verkorten waardoor zowel met als zonder bijverwarming van de drooglucht energie wordt bespaard.
|Bergings- en bemalingscapaciteit van polders
Schuurmans, W. ; Hamaker, P. ; Kolff, J. van de; Bentschap Knook, L.A. - \ 1996
Het Waterschap 81 (1996)5. - ISSN 1380-4251 - p. 164 - 167.
analogen - drainage - drainage uitrusting - duur - hydrologie - modellen - polders - neerslag - pompen - noord-holland - analogues - drainage equipment - duration - hydrology - models - precipitation - pumps
|Vier jaar kwalificatiestructuur: een tussenbalans.
Lazonder, A. - \ 1996
Agrarisch Onderwijs 38 (1996)19. - ISSN 0925-837X - p. 16 - 17.
voortgezet onderwijs - agrarisch onderwijs - leerplan - scholen - onderwijsprogramma's - onderwijs - onderwijzen - participatie - beroepsopleiding - onderwijshervorming - onderwijsvernieuwing - onderwijsplanning - onderwijsbeleid - methodologie - evaluatie - grootte - duur - groepsgrootte - middelbaar beroepsonderwijs - organisatie - studie - secondary education - agricultural education - curriculum - schools - education programmes - education - teaching - participation - vocational training - educational reform - educational innovation - educational planning - educational policy - methodology - evaluation - size - duration - group size - intermediate vocational training - organization - study
Aandacht voor doorstroommogelijkheden en rendementsverbetering
|Final report of the Dutch contribution to the CEC project Weather radar and flood storm hazard.
Uijlenhoet, R. ; Stricker, J.N.M. - \ 1993
Wageningen : Wageningen Agricultural University - 21
duur - overstromingen - neerslag - radar - remote sensing - stormen - technieken - duration - floods - precipitation - storms - techniques
Spatial variability and interpolation of daily precipitation amount.
Beek, E.G. ; Stein, A. ; Janssen, L.L.F. - \ 1992
Stochastic hydrology and hydraulics 6 (1992). - ISSN 0931-1955 - p. 304 - 320.
duur - hydrologie - neerslag - geostatistiek - duration - hydrology - precipitation - geostatistics
Estimation of rainfall in Zambia using meteosat - TIR data
Huygen, J. - \ 1989
Wageningen : SC-DLO (Report / The Winand Staring Centre 12) - 71
toepassingen - duur - hydrologie - infraroodfotografie - neerslag - remote sensing - zambia - applications - duration - hydrology - infrared photography - precipitation - remote sensing - zambia
A study of upstream boundary conditions for overland flow
Lima, J.L.M.P. - \ 1988
Wageningen : Landbouwuniversiteit Wageningen (Research report / Agricultural University, Department of Hydraulics and Catchment Hydrology 89) - 23
duur - stroming - hydrodynamica - hydrologie - meting - oppervlakteafvoer - neerslag - regen - relaties - oppervlakkige afvoer - snelheid - duration - flow - hydrodynamics - hydrology - measurement - overland flow - precipitation - rain - relationships - runoff - velocity
|Analysis of rainfall data relating to the number of days available for tillage and planting in some selected locations in Niger.
Hoogmoed, W.B. - \ 1986
Wageningen : Agricultural University [etc.] - 54
grondbewerking - zaaibedbereiding - beplanten - neerslag - hydrologie - duur - niger - tillage - seedbed preparation - planting - precipitation - hydrology - duration
Heterogeneity of Dutch rainfall
Witter, J.V. - \ 1984
Landbouwhogeschool Wageningen. Promotor(en): L.C.A. Corsten, co-promotor(en): D.A. Kraijenhoff van de Leur. - Wageningen : Witter - 204
neerslag - duur - hydrologie - meteorologische waarnemingen - weersgegevens - precipitation - duration - hydrology - meteorological observations - weather data
Rainfall data for the Netherlands have been used in this study to investigate aspects of heterogeneity of rainfall, in particular local differences in rainfall levels, time trends in rainfall, and local differences in rainfall trend. The possible effect of urbanization and industrialization on the distribution of rainfall has also been studied. Consideration has been given to whether local differences in rainfall justify a partition of the Netherlands into regions. Finally, the degree of areal reduction which is possible in hydrological design because of variation of rainfall in time and space has been investigated.A statistical analysis of these aspects is useful because they frequently appear in the hydrological literature. The statistical analysis presented in this thesis uses hydrological concepts, such as the statistical areal reduction factor, and attention is focused on moderately low return period events. Only rainfall levels and trends in rainfall have been investigated and not more complicated aspects, such as, trends in the variance of rainfall. Further, rainfall variations in time and space have been analysed separately.Estimates of the levels of the rainfall characteristics used in the investigation of homogeneity in time and space are given in Section 2.2. These are annual frequencies of exceedance during the summer or the winter period of a certain threshold value and the total annual rainfall (Tables 2.1 and 2.2). The expected daily rainfall has also been estimated for return periods in excess of half a year (Table 2.4, Figure 2.2). Time trends in rainfall averaged over the Netherlands have been estimated. For the period 1951-1979, the time trend is negative for the summer period; and for the period 1906-1979, the time trend is positive for the winter period (Table 2.5). Time trends in rainfall series were found to be related to the occurrence of circulation types (Figure 2.4).In Section 2.4 local differences in these rainfall characteristics have been investigated using the kriging method that gives the
best linear unbiased predictor. As may be expected, there are local differences, both in rainfall level (Figure 2.7), and in time trends in the rainfall series which were reduced by the annual mean (Figure 2.9). Many of the rainfall series investigated exhibit inhomogeneities (Table 2.7). Two possible causes of these inhomogeneities, changes in the frequency of occurrence of circulation types and anthropogenic activities, such as urbanization and industrialization, are discussed in Section 2.6.A possible partition of the Netherlands into regions is investigated by using rainfall data for the period 1951-1979. Earlier studies on the geographical distribution of certain rainfall characteristics in the Netherlands are presented in Section 2.5.1. The model to test the statistical significance of the partitions used in this study is presented in Section 2.5.2.One of the proposed partitions, an a posteriori partition based on mean annual rainfall (Figure 2.11D), is in agreement with the resulting spatial patterns of the levels of the rainfall characteristics considered (Table 2.10). Also, the level of hourly rainfall was found to be related to mean annual rainfall (Figure 2.18A), but, with a simple urban runoff model with a time-step of one hour, no differences were found between the number and quantity of overflow for 12 rainfall stations, classified according to this partition (Section 2.5.3).These partitions into regions are not satisfactory for rainfall trends, except for an a posteriori partition based on time trends for the period 1951-1979 (Figure 2.12). But both the geographical distribution of trends and the degree of trend in some long-term rainfall records are not in agreement with this partition. Apparently, the changes in rainfall pattern are recent. Because the partition is based on trends in reduced rainfall series (reduced by the annual mean), the changes are also local. Thus on the basis of data used in this study, it was not possible to devise a satisfactory partition of the Netherlands for rainfall trends. With regard to rainfall level it is suffice to assume that the design rainfall at a given location is proportionate to the mean summer or winter rainfall; therefore, a partition of the Netherlands into regions is not necessary. This has already been suggested in Buishand and Velds (1980).The influence of urbanization and industrialization on precipitation (urban effects) has been investigated by using the method of Lowry (1977), which allows for changes in frequency of occurrence of circulation types. In Section 2.6, this method is discussed and the findings of other studies on the occurrence, causes, and magnitude of urban effects are presented. In Section 2.6.1, the occurrence of urban effects is discussed, for instance, on the basis of changes in mean daily rainfall for 32 rainfall stations between the industrialized and urbanized period (1956-1979) and the non-industrialized period (1932-1955), with a stratification of days according to season and circulation type (according to Hess, 1977), see Figure 2.22. Although the results were sometimes inconclusive and not always in. accordance with the hypothesis of an urban effect, there are indications of urban effects for the zonal circulation type and for three of the meridional circulation types (Tables 2.16 and 2.17; Figure 2.22). Moderate rainfalls were also found to be affected (Table 2.17, where a threshold value for daily rainfall of 15 mm has been considered), and urban effects in the summer period increase with rainfall depth.In Chapter 3 consideration is given to the degree of areal reduction which is possible in hydrological design because. of variations of rainfall in time and space. Use has been made of the IRF-0 kriging theory, and semi-variograms were estimated by the multi-realization approach. The applicability of the IRF-0 theory to predict the mean areal rainfall is discussed in section 3.2.1. Contrary to what had been expected, in a substantial number of cases the estimated order of the intrinsic random function differs from zero (Tabel 3.1). Further research is needed on the structure identification, both on the statistical aspects (estimation of the order k of the intrinsic random function and of the coefficients of the generalized covariance model) and on the physical aspects (semi-variogram or generalized covariance model to be expected under certain assumptions regarding rainfall). The variation in semi-variogram estimates for individual rainfall events was found to be large (Figure 3.3). In Section 3.2.2, the kriging predictor of areal rainfall is compared with the more commonly used arithmetic mean and Thiessen predictor. All three predictors yield similar results (Table 3.5), but the kriging predictor is more efficient (Table 3.4).Methods to estimate the statistical areal reduction factor (ARF) are presented in Section 3.3.1. With the methods proposed in USWB (1957-1960), NERC (1975), Bell (1976), and Rodríguez-Iturbe and Mejía (1974) and Buishand (1977c), the areal reduction factor for daily rainfall (ARF 24 ) has been estimated for three areas each of about 1000 km 2in the Netherlands, for the summer period, the winter period, and the complete year. In Section 3.3.3, the variance of ARF 24 is estimated. All four estimators of ARF 24 were found to produce similar results (Tabel 3.12), and the three areas considered do not clearly differ with respect to ARF 24 . These estimates of ARF 24 are somewhat lower than those of USWB (1957-1960) for the United States and those of NERC (1975) for the United Kingdom (Figure 3.22), and they are in reasonable agreement with earlier estimates of ARF 24 for the Netherlands (Table 3.14). For small areas, ARF 24 is underestimated by the method which uses the marginal distribution of point rainfall and the fitted correlationdistance function. This is also evidenced by the higher ARF 24 values in Kraijenhoff (1963). ARF 24 depends heavily on season and return period (Table 3.7). Averaged over the three areas, the maximum areal rainfall occurs in the winter period in 33% of the years considered.In Section 3.4 ARF for hourly rainfall (ARF 1 ) is estimated. As a function of areal size and return period, ARF 1 has been estimated for the summer and the winter period (Figure 3.28) and for the complete year (Figure 3.21). These ARF 1 estimates are somewhat lower than those of USWB (1957-1960) and NERC (1975) (Table 3.18), probably because few hourly rainfall data were available for this study. Especially the correlation-distance function for hourly rainfalls could not be estimated very satisfactorily.The storm-centred areal reduction factor (SRF) is discussed in Section 3.5. Models for SRF based on a literature survey of minimum-rainfall curves are presented in Table 3.19. For equal areal size, SRF values from network data are generally lower than ARF values (Figure 3.29). The smaller the areal size and the shorter the period for which rainfall totals are considered, the closer SRF and ARF values.In this study, rainfall variations in time and space have been analysed separately. Because of this simplification of the problem, the results presented in Chapter 3 may be of less relevance to practical design issues related to areal rainfall. Areal reduction is partly caused by spatial differences in rainfall patterns in time. This aspect of areal reduction is not taken into account, when time aggregates of rainfall over a measurement interval are considered, and rainfall depths over consecutive intervals are assumed to be independent. For this reason, the degree of areal reduction applicable to regional transport systems of sewerage water cannot be determined by using the statistical areal reduction factor.When rainfall variations in time and space are analysed as being interdependent, the need for knowledge and understanding of meteorology increases because the rainfall events described have first to be classified. Further, instead of the univariate statistical methods as used almost exclusively in this study, multivariate methods are required. However, at present, data from a dense network of rainfall recorders, necessary for such an investigation, are not available for the Netherlands.Further research on the causes of homogeneities in rainfall series is necessary. Although this study of homogeneity has been restricted to rainfall records of good and even quality, many rainfall series are statistically inhomogeneous, and local differences in trend often seem inexplicable. To explain this, meteorological knowledge and knowledge of the station history of rainfall series used is essential.
|Rainfall interstation correlation functions derived for a class of generalized storm models
Stol, P.T. - \ 1983
Wageningen : ICW (Report / Institute for Land and Water Management Research no. 7) - 47
analogen - duur - hydrologie - modellen - neerslag - analogues - duration - hydrology - models - precipitation
The complete derivation and solution of the rainfall interstation correlation function is described. The report emphasizes the mathematical treatment and the way in which the analytical solution can be obtained by calculus
De invloed van het neerslagoverschot op de vorm van overschrijdingsduurlijnen
Buys, J. - \ 1979
Wageningen : Instituut voor Cultuurtechniek en Waterhuishouding (Nota / Instituut voor Cultuurtechniek en Waterhuishouding 1130) - 33
grondwaterspiegel - neerslag - hydrologie - duur - water table - precipitation - hydrology - duration
De variantie van de gebiedsneerslag als functie van puntneerslagen en hun onderlinge samenhang
Buishand, T.A. - \ 1977
Wageningen : Veenman (Mededelingen Landbouwhogeschool 77-10) - 12
atmosfeer - berekening - gegevens verzamelen - duur - hydrologie - meteorologische waarnemingen - methodologie - neerslag - atmosphere - calculation - data collection - duration - hydrology - meteorological observations - methodology - precipitation
Transformation of storm models caused by stochastic components
Stol, P.T. - \ 1977
Wageningen : I.C.W. (Nota / Instituut voor Cultuurtechniek en Waterhuishouding no. 1028) - 34
neerslag - hydrologie - duur - modellen - analogen - precipitation - hydrology - duration - models - analogues
|Het groeiverloop van het vee op het I.V.V.O. "Hoorn" te Lelystad
Dool, M. van den - \ 1975
Lelystad : Instituut voor Veevoedingsonderzoek "Hoorn" (Documentatierapport / Instituut voor Veevoedingsonderzoek "Hoorn" nr. 9) - 20
kalveren - duur - groei - calves - duration - growth