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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    Day-to-night heat storage in greenhouses: 4. Changing the environmental bounds
    Seginer, Ido ; Straten, Gerrit van; Beveren, Peter J.M. van - \ 2020
    Biosystems Engineering 192 (2020). - ISSN 1537-5110 - p. 90 - 107.
    Control bounds - Greenhouse control - Greenhouse model - Heat buffer

    Controlling the greenhouse environment usually involves bounds (restrictions) on the indoor conditions. In model-based control, these bounds are meant to keep the plant environment away from high risk zones, the effects of which are not sufficiently well described by the model. The objective is to estimate the potential energy saving and gain in profit resulting from relaxing the bounds. The calculations employed a previously developed simulation-optimization program in conjunction with a new, solar-driven evapotranspiration model. Spanning a whole year, the simulations were carried out for a typical Dutch tomato-greenhouse configuration, utilising a gas-fired boiler for both heat and CO2 production, and a water tank for day-to-night heat storage. The main findings are as follows: Provided that the crop is not damaged by the change, the expected gain from increasing the permissible humidity is about 0.74 € m−2y−1 per one percent relative humidity, and from reducing the minimum temperature − about 0.87 € m−2y−1 per degree. Roughly 2% of the energy is saved by a 1K reduction of temperature or a 1% increase of the relative humidity. Adding a heat buffer has no noticeable effect on the total amount of gas used. It does, however, increase the effectiveness of CO2 enrichment, thus increasing the yield and the economic gain (by 3.4 €m−2y−1). Replacing the profit goal by energy-use-minimisation goal, results in a substantial loss (−11.5 € m−2y−1).

    Optimal utilization of a boiler, combined heat and power installation, and heat buffers in horticultural greenhouses
    Beveren, P.J.M. van; Bontsema, J. ; Straten, G. van; Henten, E.J. van - \ 2019
    Computers and Electronics in Agriculture 162 (2019). - ISSN 0168-1699 - p. 1035 - 1048.
    Dynamic optimization - Energy cost saving - Equipment deployment - Greenhouse - Greenhouse operational management - Zero-or-range constraint

    In the daily operation of a greenhouse, decisions must be made about the best deployment of equipment for generating heat and electricity. The purpose of this paper is twofold: (1)To demonstrate the feasibility and flexibility of an optimal control framework for allocating heat and electricity demand to available equipment, by application to two different configurations used in practice. (2)To show that for a given energy and electricity demand benefit can be obtained by minimizing costs during resource allocation. The allocation problem is formulated as an optimal control problem, with a pre-defined heat and electricity demand pattern as constraints. Two simplified, yet realistic, configurations are presented, one with a boiler and heat buffer, and a second one with an additional combined heat and power generator (CHP)and a second heat buffer. A direct comparison with the grower is possible on those days where the other equipment that was at the grower's disposal was not used (63 days in the available 2012 data set). On those days overall costs savings of 20% were obtained. This shows that a given heat demand does not come with a fixed price to pay. Rather, benefits can be obtained by determining the utilization of the equipment by dynamic optimization. It also appears that prior knowledge of gas and electricity prices in combination with dynamic optimization has a high potential for cost savings in horticultural practice. To determine the factors influencing the outcome, different sensitivities to the optimization result were analyzed.

    Improving climate monitoring in greenhouse cultivation via model based filtering
    Mourik, Simon van; Beveren, Peter J.M. van; López-Cruz, Irineo L. ; Henten, Eldert J. van - \ 2019
    Biosystems Engineering 181 (2019). - ISSN 1537-5110 - p. 40 - 51.
    Climate monitoring - Extended Kalman filter - Moving average filter - Protected horticulture - Sensitivity analysis - Unscented Kalman filter

    The possibility of improving the accuracy of climate monitoring in greenhouse cultivation by way of model based filtering was explored. The focus was on estimating the average climate inside a greenhouse compartment. Starting point was employing an extended Kalman filter (EKF), combined with a greenhouse climate differential equation model. In two different greenhouses (A and B), temperature and humidity were monitored with a 5-min sampling resolution with a sensor grid. The available data sets spanned 1 and 0.5 years. With the average over all sensors as reference signal, the root mean squared errors (RMSEs) of the unfiltered signals (coming from single sensors) were 0.43 °C and 0.48 g m −3 for greenhouse A, and 0.80 °C and 0.64 g m −3 for greenhouse B. The filter was compared with a moving average (MA) filter, and an unscented Kalman filter (UKF). Overall, monitoring accuracy was not improved by any of the filters, and in most cases it deteriorated. Performance was strongly linked to the choice of filter, where the EKF outperformed the other filters by a considerable difference. The violations on the assumptions of whiteness and normality of the noise were severe but had a moderate effect on the RMSEs (0.11 °C and 0.10 g m −3 for greenhouse A). A clear link was found between model accuracy and monitoring accuracy. A 10–15 fold decrease of state errors was associated with an RMSE reduction down to 0.1 °C and 0.1 g m −3 , the expected equivalent of increasing the number of climate sensors from 1 to 25.

    Day-to-night heat storage in greenhouses : 3 Co-generation of heat and electricity (CHP)
    Seginer, Ido ; Beveren, Peter J.M. van; Straten, Gerrit van - \ 2018
    Biosystems Engineering 172 (2018). - ISSN 1537-5110 - p. 1 - 18.
    Co-generation of heat and electricity - CO enrichment - Greenhouse environmental control - Heat storage
    Day-to-night heat storage in water tanks (buffers) is common practice for cold-climate greenhouses, where gas is burned during the day for carbon-dioxide enrichment. In Seginer, I., van Straten, G., van Beveren, P. (2017). Biosystems Engineering, 161, 188–199, an optimal environmental control approach was outlined for conventional greenhouses, the idea being that a virtual value of the stored heat (its ‘co-state’) could be used to guide instantaneous control decisions. The value of the co-state was heuristically adjusted to minimise the time the buffer was ineffective (being empty or full). Here the same approach is applied to greenhouses with co-generation of heat and electricity (CHP). The parameters-set and weather are characteristic of tomato greenhouses in The Netherlands. The main results are: (1) The heuristic control method is easily adapted to systems with CHP; (2) Buffers are more useful to CO2 enrichment in the summer than to heating in the winter; (3) There is strong synergy between the two production systems – tomatoes and electricity. The tomato crop benefits from the by-products of electricity generation, namely CO2 and heat, sharing this benefit to support low electricity prices; (4) The combined system produces less CO2 pollution than the two production systems operating independently; (5) The contribution of the CHP and buffer to the economic performance of the system is very significant, while that of the thermal screen and boiler is marginal; (6) Flexibility in the system is important. A buffer and/or continuously controlled boiler and CHP are essential to achieving high profitability.
    Day-To-night heat storage in greenhouses : A simulation study
    Seginer, I. ; Straten, G. Van; Beveren, P.J.M. Van - \ 2017
    In: 5th International Symposium on Models for Plant Growth, Environment Control and Farming Management in Protected Cultivation, HortiModel 2016 International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462611788 - p. 119 - 127.
    Co-state-based policy - Co2 enrichment - Day-To-night heat storage - Greenhouses
    In cold-climate locations, where natural gas is burned during the day to enrich greenhouses with carbon dioxide, water tanks (buffers) are often used to store the surplus daytime heat for nighttime heating. A practical control strategy for filling (charging) and emptying (discharging) of the buffer, based on a virtual value (costate) of the stored heat (the state), is suggested and illustrated by simulation. Heating and ventilation decisions are obtained by maximizing, at each time step, the virtual increase in value of the greenhouse system (including stored heat). As long as the heat buffer is neither empty nor full, the virtual value (co-state) of the stored heat remains constant. When the buffer is full (towards the end of a day), this value is gradually decreased, until the buffer starts to discharge. When the buffer empties (towards the end of a night), the virtual value is gradually increased, until recharging of the buffer starts again. This heuristic strategy is meant to minimize the time that the buffer is empty or full, because in these states the buffer is inactive (ineffective). Simulations with an annual weather sequence show the following: (1) the winter-Time virtual value of stored heat is about equal to the actual cost of heat, while in summer it is close to zero; (2) the utilization of the buffer, judged by the time on the storage bounds (full or empty), is roughly uniform along the year; (3) the performance of the system improves asymptotically with an increase of the installed capacity of the buffer; (4) expensive energy (heat) results in reduced intensity of cultivation (less heat and less yield).
    Performance of extended and unscented Kalman filters for state and parameter estimation of a greenhouse climate model
    López-Cruz, I.L. ; Beveren, P.J.M. Van; Mourik, S. Van; Henten, E.J. Van - \ 2017
    In: International Symposium on New Technologies and Management for Greenhouses - GreenSys2015 International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462611665 - p. 175 - 181.
    Data assimilation - Dynamic model - Greenhouse environment - Model calibration - Uncertainty
    In dynamic modeling of the greenhouse climate, prediction errors are a significant issue due to uncertainties in initial state values, input variables, model parameters and model structure, all propagating in time in a nonlinear way. We investigated a data assimilation approach using two non-linear Kalman filters in light of prediction uncertainty. An extended (EKF) and an unscented (UKF) Kalman filters were designed to estimate climate states, and also both the states and model parameters. The states to be estimated were air temperature, absolute humidity and carbon dioxide concentration inside a greenhouse. Year round measurements from a Dutch greenhouse with a rose crop were used. The dynamic model was first calibrated manually by estimating ten of its parameters. Uncertainties of the measurements needed for designing EKF and UKF were specified via literature sources whereas the uncertainties related to the process were tuned. Both filters increased the model predictive power several orders of magnitude with respect to mean squared error (MSE) statistics and one order of magnitude with respect to mean absolute error (MAE) analyzed during autumn-winter and spring-summer seasons when only the model states were estimated. However, no improvement on the one step ahead state predictions were achieved when both states and model parameters were estimated by both nonlinear filters. Results showed that data assimilation based on nonlinear Kalman filters is advantageous over data assimilation that uses only model calibration. Therefore, improved model of the greenhouse climate by data assimilation can be used in controlling and optimizing more efficiently the greenhouse system.
    The effects of model reduction and data assimilation on greenhouse climate predictions
    Mourik, S. Van; Beveren, P.J.M. Van; López-Cruz, I.L. ; Henten, E.J. Van - \ 2017
    In: International Symposium on New Technologies and Management for Greenhouses - GreenSys2015 International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462611665 - p. 235 - 241.
    Black box models - Control - First principle models - Modelling - Uncertainty analysis
    We investigated the effect of model reduction and data assimilation on prediction accuracy of greenhouse climate. For this, a first-principle model was reduced, and calibrated with measurement data. Calibration data consisted of a time series of temperature, humidity, and carbon-dioxide concentration in a rose greenhouse, together with 15 variables related to outside climate and control actions. The results indicate that model reduction does not produce a crucial loss of prediction accuracy. In contrast, data assimilation decreases the size and variance of prediction errors drastically, making predictions much more reliable. A static linear model seems to predict the most essential input-output response for temperature and humidity, but the predictive power for carbon-dioxide concentration is limited. The prediction errors have standard deviations of typically 2°C, for temperature, 5-10% for relative humidity, and 200-300 ppm for CO2. The prediction errors have biases of the same order, which differ per period for which the predictions are made. We believe these results are promising for modelling climate via a static black box approach, in combination with data assimilation. The relatively low computational demand for uncertainty analysis and easy model building provide a suitable starting point for investigating augmented systems, such as plant development based on controlled climate.
    Day-to-night heat storage in greenhouses : 2 Sub-optimal solution for realistic weather
    Seginer, Ido ; Straten, Gerrit van; Beveren, Peter J.M. van - \ 2017
    Biosystems Engineering 161 (2017). - ISSN 1537-5110 - p. 188 - 199.
    CO enrichment - Greenhouse - Heat buffer - Optimal control - Self-adjusting co-state
    Day-to-night heat storage in water tanks (buffers) is common practice in cold-climate greenhouses, where gas is burned during the day for carbon dioxide enrichment. In Part 1 of this study, an optimal control approach was outlined for such a system, the basic idea being that the virtual value (shadow price) of the stored heat (its 'co-state') could be used to guide the instantaneous control decisions. The results for daily-periodic weather showed: (1) The optimal co-state is constant in time. (2) The optimal solution is associated with minimum time on the storage bounds (buffer empty or full). With these conclusions as guidelines, a semi-heuristic procedure of optimisation for realistic (i.e. not strictly periodic) weather is developed. The co-state remains constant while the storage trajectory is between the heat storage bounds. It is gradually increased while the buffer is empty, and decreased when the buffer is full, attempting to push the trajectory away from the bounds, thus minimising the time that the buffer is idle. The main outcomes are: (1) No information about the future is required. (2) The algorithm changes the co-state automatically, producing the correct annual variation (high in winter and low in summer). (3) The predictions of yield and heat requirement compare favourably with practice. (4) The gain in performance achievable with the suggested method is probably 75% or more of the true optimum. (5) The procedure can be used in the design stage to determine the optimal buffer size and the usefulness of other modifications of the system.
    Day-to-night heat storage in greenhouses : 1 Optimisation for periodic weather
    Seginer, Ido ; Straten, Gerrit van; Beveren, Peter J.M. van - \ 2017
    Biosystems Engineering 161 (2017). - ISSN 1537-5110 - p. 174 - 187.
    CO enrichment - Constant co-state - Greenhouse - Heat buffer - Optimal control - Periodic weather
    Day-to-night heat storage using water tanks (buffers) is common practice in cold-climate greenhouses, where gas is burned during the day for carbon dioxide enrichment. In this study an optimal control approach is outlined for such a system, based on the idea that the virtual value (shadow price) of the stored heat, its 'co-state', could be used to guide the instantaneous control decisions. If this value is high, the system has an incentive to fill the heat storage (buffer), and vice versa if the co-state is low. The optimal co-state trajectory maximises the net income (performance criterion). To illustrate the method, a system description and a parameter-set roughly representative of tomato greenhouses in The Netherlands is used. The results, for daily-periodic weather, show: (1) The optimal co-state is constant (same value night and day), in contrast to the varying set-points and control fluxes. (2) The optimal solution is associated with minimum time on the storage bounds (minimum time of full or empty buffer). (3) The optimal virtual value (co-state) of stored heat is about the same as the actual cost of boiler heat during winter and about zero in summer. (4) The gain from installing a buffer is highest during spring and minimal in winter. (5) The intensive utilisation of the heat buffer in summer and its low utilisation in winter indicate that the justification of the heat storage practice, under the assumed conditions, is more the need for CO2 enrichment in summer than the need for heating in winter.
    Digital growth response maps for assessment of cooling requirement in greenhouse production of tomato
    Shamshiri, R. ; Che Man, H. ; Zakaria, A.J. ; Beveren, Peter van; Wan Ismail, W.I. ; Ahmad, D. - \ 2017
    Acta Horticulturae 1152 (2017). - ISSN 0567-7572 - p. 117 - 124.
    Computer simulation - Cooling requirement - Greenhouse - Growth response map - Temperature - Tomato - Tropical lowland

    The objective of this work was to generate a series of digital growth response maps that address specific times of cooling requirement for tomato production in a tropical lowland greenhouse. Collected data from a net-screen covered greenhouse were processed by a computer model that utilized a mathematical approach to simulate tomato's growth responses (GR) to air temperature at early growth and development growth stages. Orthogonal projection was applied on three-dimensional GR plots to create top-view sketch to demonstrate variations with respect to changes in hours and days. Results indicated that air temperature inside the greenhouse was 65% optimal at the early growth stage and 72% optimal at the development growth stage of tomato.

    Membership function model for defining optimality of vapor pressure deficit in closed-field cultivation of tomato
    Shamshiri, R. ; Che Man, H. ; Zakaria, A.J. ; Beveren, Peter van; Wan Ismail, W.I. ; Ahmad, D. - \ 2017
    Acta Horticulturae 1152 (2017). - ISSN 0567-7572 - p. 281 - 290.
    Greenhouse - Growth response - Membership functions - Optimal value - Tomato - Vapor pressure deficit

    Estimation of plant's evapotranspiration (ET) or water loss to the atmosphere depends on the vapor pressure deficit (VPD) of the closed-field environment (greenhouse). The objective of this work was to develop a membership function model for defining optimal VPD of greenhouse air for tomato cultivation (Lycopersicon esculentum) at different growth stages (GS) and light conditions (sun, cloud, night). Mathematical descriptions of a peer-reviewed published growth response (GR) model for optimal greenhouse air temperature (T) and relative humidity (rH) were derived and implemented in a computer program. An incremental algorithm was written in MATLAB

    Dynamic assessment of air temperature for tomato (Lycopersicon esculentum mill) cultivation in a naturally ventilated net-screen greenhouse under tropical lowlands climate
    Shamshiri, R. ; Beveren, P. van; Che Man, H. ; Zakaria, A.J. - \ 2017
    Journal of Agricultural Science and Technology (JAST) 19 (2017)1. - ISSN 1680-7073 - p. 59 - 72.
    Greenhouse - Growth response - Natural ventilation - Optimal Temperature - Tomato
    Net-screen covered greenhouses operating on natural ventilation are used as a sustainable approach for closed-field cultivation of fruits and vegetables and to eliminate insect passage and the subsequent production damage. The objective of this work was to develop a real-time assessment framework for evaluating air-temperature inside an insect-proof net-screen greenhouse in tropical lowlands of Malaysia prior to cultivation of tomato. Mathematical description of a growth response model was implemented and used in a computer application. A custom-designed data acquisition system was built for collecting 6 months of air-temperature data, during July to December 2014. For each measured air-Temperature (T), an optimality degree, denoted by Opt(T), was calculated with respect to different light conditions (sun, cloud, night) and different growth stages. Interactive three-dimensional plots were generated to demonstrate variations in Opt(T) values due to different hours and days in a growth season. Results showed that air temperature was never less than 25% optimal for early growth, and 51% for vegetative to mature fruiting stages. The average Opt(T) in the entire 6 months was between 65 and 75%. The presented framework allows tomato growers to automatically collect and process raw air temperature data and to simulate growth responses at different growth stages and light conditions. The software database can be used to track and recor Opt(T)d values from any greenhouse with different structure design, covering materials, cooling system, and growing seasons and to contribute to knowledge-based decision support systems and energy balance models.
    Stochastic control of crop growth, a simulation study
    Mourik, S. van; Vellekoop, Michel ; Beveren, P.J.M. van; Ooster, A. van 't; Henten, E.J. van - \ 2016
    In: Proceedings of the International Conference on Agricultural Engineering, Aarhus, Denmark. -
    stochastic control - Crop growth simulation model - climate change - metamodel - Regression analysis - LINTUL2
    Comparative evaluation of naturally ventilated screenhouse and evaporative cooled greenhouse based on optimal vapor pressure deficit
    Shamshiri, Ramin ; Ahmad, Desa ; Wan Ismail, Wan Ishak ; Man, Hasfalin Che ; Zakaria, Abd Jamil ; Beveren, Peter Van; Yamin, Muhammad - \ 2016
    In: 2016 American Society of Agricultural and Biological Engineers Annual International Meeting, ASABE 2016. - American Society of Agricultural and Biological Engineers - ISBN 9781510828759 - 10 p.
    Evaporative cooling - Greenhouse - Natural ventilation - Optimal - Screenhouse - Tomato - Vapor pressure deficit
    The objective of this study was to compare two closed-field plant production environments for tomato cultivation based on optimal vapor pressure deficit (VPD). Experiment was carried out in tropical lowlands of Malaysia by collecting 11 days of sample data during March (2014), from an evaporative cooled Polycarbonate Panel (PP) covered greenhouse and a naturally ventilated Screenhouse (SH). A computer application was designed and used for VPD calculation and data processing with respect to three light conditions (night, sun and cloud). The average and maximum VPD were respectively equal to 0.97 and 3.81 kPa for SH and 1.19 and 5.1 kPa for PP. The largest differences in the VPD of the two environments were between 2.9 and 3.1 kPa and were observed between hours of 12:30 and 17:30 at sun conditions. Results did not show significant differences in the two environments between hours of 00:00 and 8:00, when inside air temperature was between 24 to 26°C, and relative humidity was near 90%. The hypothesis that the PP, compared to SH, provides VPD closer to the optimal range was rejected. Further analysis of the results showed that linear correlations with R2>0.9 exist between daily averaged VPD of each greenhouses. It was concluded that VPD in the SH was closer to the optimal range in the entire days of experiment. The outcome of this study contributes to knowledge-based information for greenhouse growers by addressing questions about trends in VPD data, peak-hours and light conditions associated with maximum and minimum values.
    Optimal Day-to-Night Greenhouse Heat Storage : Square-Wave Weather
    Seginer, Ido ; Straten, Gerrit van; Beveren, Peter van - \ 2016
    IFAC-PapersOnLine 49 (2016)16. - ISSN 2405-8963 - p. 375 - 380.
    Co-state - Constrained optimum - Greenhouse - Heat storage - Optimal control - Time on bounds

    Day-to-night heat storage is often practiced in cold-climate greenhouses. It is suggested to manage the heat storage by considering the co-state (virtual value) of the stored heat in the on-line optimization of the greenhouse environment. Examples worked out for a periodic square-wave weather show that a properly selected constant co-state can produce an optimal solution to the control problem. The optimal co-state is shown to change with time over the year. Maximizing the performance criterion can also be achieved by minimizing the time that the heat buffer is either completely empty or completely full.

    Optimal control of greenhouse climate using minimal energy and grower defined bounds
    Beveren, P.J.M. van; Bontsema, J. ; Straten, G. van; Henten, E.J. van - \ 2015
    Applied Energy 159 (2015). - ISSN 0306-2619 - p. 509 - 519.
    Cooling - Energy - Greenhouse climate - Heating - Optimal control

    Saving energy in greenhouses is an important issue for growers. Here, we present a method to minimize the total energy that is required to heat and cool a greenhouse. Using this method, the grower can define bounds for temperature, humidity, CO2 concentration, and the maximum amount of CO2 available. Given these settings, optimal control techniques can be used to minimize energy input. To do this, an existing greenhouse climate model for temperature and humidity was expanded to include a CO2 balance. Heating, cooling, the amount of natural ventilation, and the injection of industrial CO2 were used as control variables.Standard optimization settings were defined in order to compare the grower's strategy with the optimal solution. This optimization resulted in a theoretical 47% reduction in heating, 15% reduction in cooling, and 10% reduction in CO2 injection for the year 2012. The optimal control does not need to maintain a minimum pipe temperature, in contrast to current practice. When the minimum pipe temperature strategy of the grower was implemented, heating and CO2 were reduced by 28% and 10% respectively.We also analyzed the effect of different bounds on optimal energy input. We found that as more freedom is given to the climate variables, the higher the potential energy savings. However, in practice the grower is in charge of defining the bounds. Thus, the potential energy savings critically depend on the choice of these bounds. This effect was analyzed by varying the bounds. However, because the effect can be demonstrated to the grower, the outcome has value to the grower with respect to decision making, an option that is not currently available in practice today.

    Optimale besturing kasklimaat met minimale energie
    Beveren, P.J.M. van; Bontsema, J. ; Straten, G. van; Henten, E.J. van - \ 2015
    Kas Magazine / TuinbouwCommunicatie 2015 (2015)12. - ISSN 1878-8408 - p. 28 - 30.
    De huidige kasklimaatregeling in de glastuinbouw is gebaseerd op veel regels. Veel instellingen kunnen worden aangepast in de klimaatcomputer om temperatuur, luchtvochtigheid, CO2 concentratie en licht te regelen en zo de plant te kunnen sturen. Het beheren van die instellingen is een complexe uitdaging voor de tuinder. Nog lastiger wordt het als instellingen gericht op goede groei en ontwikkeling van het gewas moeten worden gecombineerd met bijvoorbeeld het minimaliseren van de energie input.
    Optimal control of greenhouse climate with grower defined bounds
    Beveren, P.J.M. van; Bontsema, J. ; Straten, G. van; Henten, E.J. van - \ 2015
    Optimal management of energy resources in greenhouse crop production systems
    Beveren, Peter van - \ 2015
    Optimal control of greenhouse climate with grower defined bounds
    Beveren, P.J.M. van; Bontsema, J. ; Straten, G. van; Henten, E.J. van - \ 2015
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