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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    Future urban energy systems : Harnessing demand side flexibility and managing data uncertainty
    Azari, Delaram - \ 2020
    Wageningen University. Promotor(en): H.H.M. Rijnaarts, co-promotor(en): K.J. Keesman; H.J. Cappon. - Wageningen : Wageningen University - ISBN 9789463954044 - 153

    This thesis looks into the impact of data uncertainty on the techno-economic decisions of the actors in a future energy system, with flexibility sources. It looks into the problem from the view point of three actors, namely, the distribution system operator, aggregators (as potential operators of a demand response program), and end-users, such as building energy managers and residential consumers. A comprehensive analytical sensitivity analysis framework is developed to quantify and monetize the impact of data uncertainty on the operation of different stylized energy systems with flexible resources.

    The proposed framework consists of four mathematical models: a data pre-processing module, an optimisation algorithm to model the operation of the energy system and the flexibility provider, a local (analytical) sensitivity analysis (LSA), and a global sensitivity analysis (GSA). Together, the framework is used to investigate the impact of uncertainty on the operation of a market-based energy system in the future, as well as the requirement of the existing and the emerging actors in such environment.

    On the sensitivity of local flexibility markets to forecast error : A bi-level optimization approach
    Azari, Delaram ; Torbaghan, Shahab Shariat ; Cappon, Hans ; Keesman, Karel J. ; Gibescu, Madeleine ; Rijnaarts, Huub - \ 2020
    Energies 13 (2020)8. - ISSN 1996-1073
    Bi-level optimization - Optimal flexibility dispatch - Sensitivity analysis - Transactive energy

    The large-scale integration of intermittent distributed energy resources has led to increased uncertainty in the planning and operation of distribution networks. The optimal flexibility dispatch is a recently introduced, power flow-based method that a distribution system operator can use to effectively determine the amount of flexibility it needs to procure from the controllable resources available on the demand side. However, the drawback of this method is that the optimal flexibility dispatch is inexact due to the relaxation error inherent in the second-order cone formulation. In this paper we propose a novel bi-level optimization problem, where the upper level problem seeks to minimize the relaxation error and the lower level solves the earlier introduced convex second-order cone optimal flexibility dispatch (SOC-OFD) problem. To make the problem tractable, we introduce an innovative reformulation to recast the bi-level problem as a non-linear, single level optimization problem which results in no loss of accuracy. We subsequently investigate the sensitivity of the optimal flexibility schedules and the locational flexibility prices with respect to uncertainty in load forecast and flexibility ranges of the demand response providers which are input parameters to the problem. The sensitivity analysis is performed based on the perturbed Karush-Kuhn-Tucker (KKT) conditions. We investigate the feasibility and scalability of the proposed method in three case studies of standardized 9-bus, 30-bus, and 300-bus test systems. Simulation results in terms of local flexibility prices are interpreted in economic terms and show the effectiveness of the proposed approach.

    Exploring the impact of data uncertainty on the performance of a demand response program
    Azari, Delaram ; Shariat Torbaghan, Shahab ; Cappon, Hans ; Keesman, Karel J. ; Rijnaarts, Huub ; Gibescu, Madeleine - \ 2019
    Sustainable Energy, Grids and Networks 20 (2019). - ISSN 2352-4677
    Data uncertainty - Demand response - Sensitivity analysis

    There is a significant interest in utilizing demand response (DR) programs to increase the flexibility of sustainable power systems. The DR operators (e.g., aggregator companies) need a robust means to assess the performance of a potential DR program that will be employed in the future. Such assessments should be based on data, some of which are hardly available. Knowledge about the DR providers (e.g., the behavior of proactive consumers) is key to the success of a DR program. In this paper, we devise a data-driven framework to assess the impact of uncertainties associated with future DR programs. The proposed framework comprises two modules: the DR simulation module, and the data analytics module. The DR module solves an optimization problem which simulates the operation of a hypothetical DR program. The data analytics module, firstly, selects subsets from historical load and price data. Secondly, it performs sensitivity analysis on the optimal solution to capture the impact of uncertainties. We consider two sources of uncertainty. First, we consider lack of information about DR providers due to the absence of a DR program in the current system. Second, we consider errors in load and price forecasts, whose impacts are investigated by formulating a sensitivity matrix from the perturbed KKT equations of the optimization problem solved by the DR module. The proposed framework provides insights regarding the potential of a prospective DR program. Such information can be useful for DR operators as a starting point to decide their position in the contractual agreement they will engage in with the (distribution) system operator and/or DR providers in the future.

    GO-FRESH: Valorisatie kansrijke oplossingen voor een robuuste zoetwatervoorziening : Rendabel en duurzaam watergebruik in een zilte omgeving
    Veraart, J.A. ; Oude Essink, G. ; Pauw, P. ; Baaren, E. van; Zuurbier, K. ; Louw, P. de; MacAteer, E. ; Schoot, M. van der; Groot, N. ; Cappon, H. ; Waterloo, M. ; Hu-a-ng, K. ; Groen, M. - \ 2018
    Deltares - 187 p.
    Model-based management strategy for resource efficient design and operation of an aquaponic system
    Reyes Lastiri, Daniel ; Geelen, Caspar ; Cappon, Hans J. ; Rijnaarts, Huub H.M. ; Baganz, Daniela ; Kloas, Werner ; Karimanzira, Divas ; Keesman, Karel J. - \ 2018
    Aquacultural Engineering 83 (2018). - ISSN 0144-8609 - p. 27 - 39.
    Aquaponics - Mathematical model - Resource efficiency

    Aquaponics is a technique that combines aquaculture with hydroponics, i.e. growing aquatic species and soilless plants in a single system. Commercial aquaponics is still in development. The main challenge consists in balancing the conditions required for the growth of multiple species, leading to dynamic a system with high complexity. Mathematical models improve our understanding of the complex dynamics in aquaponics, and thus support the development of efficient systems. We developed a water and nutrient management strategy for the production of Nile tilapia (Oreochromis niloticus) and tomato (Solanum lycopersicum) in an existing INAPRO aquaponic demonstration system in Abtshagen, Germany. This management strategy aims for improved water and nutrient efficiency. For this purpose, we developed a system-level mathematical model and simulation. In our simulations, we found that the existing configuration and water management of the Abtshagen aquaponic system results in an excessive amount of water discharged from the RAS. Therefore, sending more nutrient-rich water from fish to plants can help reducing water and fertilizer consumption. However, this water transfer may lead to excess concentrations of some nutrients, which could stress fish, plants or both. For the Abtshagen system, our simulations predicted excess concentrations of total suspended solids (TSS) for the fish, and sodium (Na+) and ammonium nitrogen (NH4 +-N) for the plants. Furthermore, our simulations predicted excess calcium (Ca2+) and magnesium (Mg2+) for plants, due to the use of local fresh water with relatively high concentrations of those ions. Based on our simulations, we developed an improved management strategy that achieves a balance between resource efficiency and water quality conditions. This management strategy prevents excess levels of TSS for fish, and Na+ and NH4 +-N for plants. Under the improved management strategy, simulated water requirements (263 L/kg fish and 22 L/kg tomato) were similar to current commercial RAS and greenhouse horticulture. Simulated fertilizer requirements for plants of N, Ca and Mg (52, 46 and 9 mg/kg tomato, respectively) were one order of magnitude lower than in high efficient commercial closed greenhouse production.

    How to analyse urban resource cycles : a dynamic systems approach to facilitate decision-making
    Bozileva, Elvira ; Leusbrock, Ingo ; Cappon, Hans J. ; Rijnaarts, Huub H. ; Keesman, Karel J. - \ 2018
    IFAC-PapersOnLine 51 (2018)2. - ISSN 2405-8963 - p. 541 - 546.
    decision support - modelling - optimisation - sensitivity analysis - urban resources

    Individual technologies allowing and enabling sustainable resource management in urban areas are available on the market. Modelling and analysis tools to aid in tailoring these technologies for a specific context are abundant as well. However, compartmentalization of scientific knowledge does not allow researchers and practitioners to take full advantage of the available information and work towards the common goal of sustainability. The aim of this paper is to present a methodology, which can support researchers, engineers and planners who intend to use a modelling approach to tailor the technological solutions for a specific urban system. The methodology encompasses a systematic inventory of tools and techniques that can be used at different stages of model-based decision-making, such as objective formulation, model development, sensitivity analysis and optimisation. Whereas the methodology is intended to be generic, its applicability is illustrated with an example related to a residential water-energy cycle.

    Assessing the flexibility potential of the residential load in smart electricity grids - A data-driven approach
    Azari, Delaram ; Torbaghan, Shahab Shariat ; Cappon, Hans ; Gibescu, Madeleine ; Keesman, Karel ; Rijnaarts, Huub - \ 2017
    In: 2017 14th International Conference on the European Energy Market, EEM 2017. - IEEE computer society - ISBN 9781509054992
    Data-driven framework - Demand Response (DR) - Prosumers' preferences - Sensitivity analysis
    This paper proposes a framework for assessing the sensitivity of the performance of a hypothetical demand response (DR) program to consumers' preferences, should they enable DR and become prosumers. The proposed framework contains a data analytics module and a DR simulation module. The data analytics module, processes the historical data to select informative subsets and define simulation scenarios to investigate the performance of the DR module. The DR module is, in essence, an optimization problem that seeks to meet the objective of the distribution system operator (DSO); it minimizes active power losses, by utilizing the potential flexibility prosumers can provide. The optimization problem is solved subject to physical and economic constraints. It considers the fact that cost of energy for the prosumers, after implementing DR, remains less than or equal to its value before that. We defined six scenarios to investigate the sensitivity of the performance of DR on prosumers preferences, in four representative days (so called case studies). Our results demonstrate the effectiveness of the proposed framework in helping the DSO assessing the potential flexibility of various users, and from there, improving the success rate of implementing DR in energy systems of the future.
    Numerical design and experimental evaluation of an acoustic separator for water treatment
    Cappon, H.J. ; Keesman, K.J. - \ 2016
    In: Acoustofluidics 2016, Thursday 22 - Friday 23 September 2016, Technical University of Denmark. - DTU - p. 63 - 64.
    Acoustofluidics 2016 Conference
    Cappon, Hans - \ 2016
    Numerical design and experimental evaluation of an acoustic separator for water treatment
    Model of an aquaponic system for minimised water, energy and nitrogen requirements
    Reyes Lastiri, D. ; Slinkert, T. ; Cappon, H.J. ; Baganz, D. ; Staaks, G. ; Keesman, K.J. - \ 2016
    Water Science and Technology 74 (2016)1. - ISSN 0273-1223 - p. 30 - 37.
    Water and nutrient savings can be established by coupling water streams between interacting processes. Wastewater from production processes contains nutrients like nitrogen (N), which can and should be recycled in order to meet future regulatory discharge demands. Optimisation of interacting water systems is a complex task. An effective way of understanding, analysing and optimising such systems is by applying mathematical models. The present modelling work aims at supporting the design of a nearly emission-free aquaculture and hydroponic system (aquaponics), thus contributing to sustainable production and to food security for the 21st century. Based on the model, a system that couples 40 m3 fish tanks and a hydroponic system of 1,000 m2 can produce 5 tons of tilapia and 75 tons of tomato yearly. The system requires energy to condense and recover evaporated water, for lighting and heating, adding up to 1.3 GJ/m2 every year. In the suggested configuration, the fish can provide about 26% of the N required in a plant cycle. A coupling strategy that sends water from the fish to the plants in amounts proportional to the fish feed input, reduces the standard deviation of the NO3− level in the fish cycle by 35%.
    Modelling of aquaculture-hydroponic systems
    Reyes Lastiri, D. ; Slinkert, Thomas ; Keesman, K.J. ; Cappon, H.J. - \ 2015
    Towards implementation of farm animal welfare monitoring in practice: example from the veal industry
    Reenen, C.G. van; Wolthuis, M. ; Heeres, J. ; Wesselink, M.M.C. ; Cappon, M. ; Bokkers, E.A.M. - \ 2014
    In: Proceedings of the 6th International Conference on the Assessment of Animal Welfare at Farm and Group Level. - Wageningen, The Netherlands : Wageningen Academic Publishers - ISBN 9789086862474 - p. 202 - 202.
    Between 2005 and 2009, a system for on-farm monitoring of veal calf welfare was developed by a consortium of scientific and commercial partners from France, Italy and the Netherlands. The system comprised of protocols for the recording of primarily animal-based measures of behaviour, clinical health, and post-mortem pathology, and an assessment model based on threshold values for individual welfare measures and the integration of these measures into aggregate scores according to the Welfare Quality® approach. Currently, in the Netherlands, a follow-up study is in progress aiming to support the implementation in the veal industry of a welfare monitoring system. In this study we try to establish a so-called ‘quality cycle’ whereby (1) the welfare status of a batch of veal calves is assessed by an external, trained assessor, (2) the assessment information is reported and interpreted, and fed back to the farmer by one of his own advisors, (3) remedial steps in terms of e.g. feeding, housing, and management are taken by the farmer if needed and on a voluntary basis; these steps are also laid down in a concise report, and (4) an assessment of the welfare of the next batch of calves takes place. In our project welfare assessments are carried out by inspectors of the Foundation for Quality Guarantee of the Veal Sector, which is an independent inspection body performing food safety and legal compliance audits on Dutch veal farms. Depending on the type of farm and system of veal production, either professional advisors of the veal or feed industry, who already attend veal farms participating in the study, or regular veterinarians act as advisors with regard to the interpretation and possible implications of welfare assessment outcomes. A total of 65 veal farmers voluntarily enrolled in the study. On each farm four consecutive batches of calves will be followed-up and systematically monitored. Wageningen University is responsible for the training and instruction of assessors and advisors, and for data handling and reporting. Throughout the study, we also interview farmers and their advisors, and have feedback meetings with groups of assessors, advisors and farmers. We will address some limitations and advantages of our approach. We suggest that the active involvement of stakeholders within the veal sector in welfare assessment and in providing advice to farmers will facilitate the future adoption of the welfare monitoring system in practice.
    Numerical and experimental design of ultrasonic particle filters for water treatment
    Cappon, H.J. - \ 2014
    Wageningen University. Promotor(en): Gerrit van Straten, co-promotor(en): Karel Keesman. - Wageningen : Wageningen University - ISBN 9789461738592 - 202
    waterzuivering - terugwinning - ultrasone behandeling - geluidsleer - scheidingstechnologie - wiskundige modellen - water treatment - recovery - ultrasonic treatment - acoustics - separation technology - mathematical models

    Due to limited water resources available in the world and the ever growing world population, there is an increasing need for water recycling, recovery and multi-sourcing strategies. One of the new physical process technologies being investigated for water purification and/or constituent recycling is ultrasonic particle separation. This technology is especially interesting for harvesting particles with an almost neutral buoyancy. An ultrasonic particle filter does not use a filter medium, like sand or a membrane, but filters on a basis of acoustic forces in ultrasonic standing waves, which are able to immobilise particles in flowing water.

    The objective of this study was to develop an ultrasonic separation device for particle recovery and water purification. This separator should be fit for industrial applications treating cubic meters of water per hour. In order to reach this objective, a combined numerical-experimental approach was proposed to develop a model-based design of an ultrasonic separator. Each individual component of this separator was modelled using a finite element (FE) approach. The numerical simulations were continuously cross-checked with experiments in order to find the best solution possible.

    In this thesis, the source of the acoustic wave is a piezoelectric transducer attached to a glass matching layer of the acoustic cavity, which couples the transducer to the fluid inside the cavity, forming an acoustic resonator/separator. In order to obtain a valid FE transducer model, a limited set of material parameters for the piezoelectric transducer were obtained from the manufacturer, thus preserving prior physical knowledge to a large extent. The remaining unknown parameters were estimated from impedance (admittance) analysis combined with a numerical optimisation routine using 2D and 3D FE models. Thus, a full set of physically interpretable material parameters was obtained. The approach provided adequate accuracy of the estimates of the material parameters, near 1%.

    A similar approach as used for the transducer was applied to an existing ultrasonic separator, again preserving known physical parameters and estimating the remaining unknown or less certain parameters. The results showed that the approach led to a fully calibrated 2D model of the emptyseparator, which was subsequently validated with experiments on a filledseparator chamber. The large sensitivity of the separator to small variations indicated that either such system should be made and operated within tight specifications to obtain the required performance. Alternatively, the operation of the system should be adaptable to cope with a slightly off-spec system, requiring a feedback controller.

    Starting from a fully characterised existing separator with all material parameters found so far, the subsequent step was the actual design of, or extrapolation to, a new separator. A basic design for an industrial scale acoustic separator was obtained based on simulated flow characteristics inside the separation chamber, on acoustic analysis within the chamber and simulated particle trajectories combining these two analyses. Results showed that positioning the piezoelectric transducer surfaces perpendicular to the flow direction and introducing chamber partitioning with multiple flow lanes to enforce laminar flow, resulted in high particle retention. The average particle displacement was found to be related to acoustic pressure in the fluid, showing large retention at peak pressures above 1 MPa or average pressures above 0.5 MPa for small (10 µm), near buoyant (1100 kg/m3) particles at a flow speed of 3.5 cm/s, thus providing comprehensible criteria for subsequent optimisation.

    This basic ultrasonic standing wave separator design was optimised with respect to separation efficiency, throughput and energy consumption. The methodology, using a design of experiments (DOE) approach, showed that it was possible to improve system performance based on acoustic pressure profiles, separation efficiency and flow robustness. Compromising the energy consumption and aiming for maximum separation efficiency with a laminar stable flow up to 5 ml/s resulted in a separator with inner dimensions of 70 mm length, 20 mm width and 28.5 mm height using two transducers perpendicular to the direction of flow and three parallel flow lanes with 9.5 mm height each. The lowest power consumption (with an average of 30 W) with adequate pressure to trap the particles was obtained when it was not operated at the main eigenfrequency.

    Finally, this new ultrasonic particle filter was built and evaluated experimentally. The particle filter was a three channel device, manufactured from glass with four in/outlet ports made of ABS. It was operated in sequenced batch mode and the separation efficiency was determined at three flow rates ranging from 1 to 3 ml/s, using a stock suspension of insoluble potato starch of 1 g/l (1000 ppm). Concentrations of stock, filtrate and concentrate were measured using a turbidity meter and significant effects of acoustic particle concentration were measured at both outlets of the process. The maximum filtration efficiency and concentration efficiency were 54% and 76%, respectively. The performance found was lower than the 100% that was expected for 10 µm particles from the model based design study. The deviation in performance is mainly a result of (i) the pulsation of the feed pump, (ii) differences between the model and the actual prototype, (iii) the limited power supply of only 10 W used and (iv) (too) small particles, below 10 µm, occurring in the starch suspension.

    The best dimensions for an acoustic separator were obtained, but thus far operational characteristics were not yet studied. Operational characterisation and optimisation is the last step in the process of obtaining the best possible solution for operation. With the aim to achieve a high separation efficiency with minimal energy consumption, a model-based open-loop switching control strategy was designed for the commercially available BioSep, using a numerical-experimental approach. Firstly, a dynamic BioSep model structure was derived from mass balances and its system properties were studied. Then, the unknown system parameters were estimated from steady state and dynamic experimental data and subsequently, the switching times of the control input were determined. The model with switching control outputs was then validated by experiments. Finally, the control strategy was implemented in an experimental setup and tested using suspended potato starch. Results showed that the optimal control strategy reached a mass separation efficiency of 96%, which was an improvement of 4% with respect to the initial settings, while using less energy.

    Concluding, a stepwise numerical-experimental approach to acoustic separator design was presented in this study. The minimum power required was estimated to be 22-34 W, resulting in an average electric energy consumption of 1-1.5 kWh/m3. The practical concentration efficiency obtained was 76% at a flow rate of 2 ml/s and a filtration efficiency of 54% at 1 ml/s with a real power input of 8.8 W. An optimal open loop control strategy showed that it is possible to operate an acoustic separator with high separation efficiency using the least power possible. Parallelisation, instead of enlarging the separator, is recommended to scale this system up to larger, industrial flows.

    Ultrasound standing-wave bio-reactor design and testing on aerobic activated sludge
    Keesman, K.J. ; Beus, N. de; Cappon, H.J. - \ 2013
    In: Proceedings of the Ultrasonics Symposium (IUS), 2013 IEEE International. - - p. 1331 - 1332.
    This study experimentally investigated the ultrasonic separation efficiency of water-activated sludge suspensions, which is in line with our previous work on modeling and control in acoustic separation of suspensions using a numerical-experimental approach. The main conclusion is that ultrasound separation provides a promising technique that could have industrial application for activated sludge separation in the future.
    Design basis of industrial acoustic separators
    Cappon, H.J. ; Keesman, K.J. - \ 2013
    In: Proceedings of the IEEE UFFC International Ultrasonics Symposium, 2013. - - p. 299 - 302.
    This study presents the process of obtaining a basic design for an industrial scale acoustic separator based on flow characteristics inside the separation chamber, on acoustic analysis within the chamber and calculated particle trajectories combining these two analyses. Adequate criteria for subsequent optimisation were evaluated. Results showed that positioning the piezoelectric transducer surfaces perpendicular to the flow direction and introducing chamber partitioning with multiple flow lanes to enforce laminar flow, resulted in high particle retention. The average particle displacement was found to be related to acoustic pressure in the fluid, showing large retention at peak pressures above 1 MPa or average pressures above 0.5 MPa for small (10 µm), near buoyant (1100 kg/m3) particles at a flow speed of 3.5 cm/s, thus providing comprehensible criteria for subsequent optimisation.
    Numerical modeling, calibration, and validation of an ultrasonic separator
    Cappon, H.J. ; Keesman, K.J. - \ 2013
    IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 60 (2013)3. - ISSN 0885-3010 - p. 614 - 621.
    suspended particles - layered resonators - standing waves - filter
    Our overall goal is to apply acoustic separation technology for the recovery of valuable particulate matter from wastewater in industry. Such large-scale separator systems require detailed design and evaluation to optimize the system performance at the earliest stage possible. Numerical models can facilitate and accelerate the design of this application; therefore, a finite element (FE) model of an ultrasonic particle separator is a prerequisite. In our application, the particle separator consists of a glass resonator chamber with a piezoelectric transducer attached to the glass by means of epoxy adhesive. Separation occurs most efficiently when the system is operated at its main eigenfrequency. The goal of the paper is to calibrate and validate a model of a demonstrator ultrasonic separator, preserving known physical parameters and estimating the remaining unknown or less-certain parameters to allow extrapolation of the model beyond the measured system. A two-step approach was applied to obtain a validated model of the separator. The first step involved the calibration of the piezoelectric transducer. The second step, the subject of this paper, involves the calibration and validation of the entire separator using nonlinear optimization techniques. The results show that the approach lead to a fully calibrated 2-D model of the empty separator, which was validated with experiments on a filled separator chamber. The large sensitivity of the separator to small variations indicated that such a system should either be made and operated within tight specifications to obtain the required performance or the operation of the system should be adaptable to cope with a slightly off-spec system, requiring a feedback controller
    Concentration based flow control in acoustic separation of suspensions
    Cappon, H.J. ; Stefanova, L.A. ; Keesman, K.J. - \ 2013
    Separation and Purification Technology 103 (2013). - ISSN 1383-5866 - p. 321 - 327.
    standing waves
    Acoustic separation is a relatively new method for recovering valuable particulate matter from suspensions. This separation method is mainly used in medical technology, but may well be applicable as water purification and material recovery technique. The key question then is what separation efficiency can be reached and whether this can be realised in an energy-efficient way. In the current study, a commercially available acoustic separator, named BioSep, which employs ultrasound enhanced sedimentation, was used. With the aim to achieve a high separation efficiency with minimal energy consumption, a model-based open-loop switching control strategy was designed for the BioSep, using a numerical-experimental approach. Firstly, a dynamic BioSep model structure was derived from mass balances and its system properties were studied. Then, the unknown system parameters were estimated from steady state and dynamic experimental data and subsequently, the switching times of the control input were determined. The model with switching control outputs was then validated by experiments. Finally, the control strategy was implemented in the experimental setup and tested using suspended potato starch. Results showed that the optimal control strategy reached a mass separation efficiency of 96%, which was an improvement of 4% with respect to the initial settings, while using less energy.
    Numerical Modeling of Piezoelectric Transducers Using Physical Parameters
    Cappon, H. ; Keesman, K.J. - \ 2012
    IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 59 (2012)5. - ISSN 0885-3010 - p. 1023 - 1032.
    Design of ultrasonic equipment is frequently facilitated with numerical models. These numerical models, however, need a calibration step, because usually not all characteristics of the materials used are known. Characterization of material properties combined with numerical simulations and experimental data can be used to acquire valid estimates of the material parameters. In our design application, a finite element (FE) model of an ultrasonic particle separator, driven by an ultrasonic transducer in thickness mode, is required. A limited set of material parameters for the piezoelectric transducer were obtained from the manufacturer, thus preserving prior physical knowledge to a large extent. The remaining unknown parameters were estimated from impedance analysis with a simple experimental setup combined with a numerical optimization routine using 2-D and 3-D FE models. Thus, a full set of physically interpretable material parameters was obtained for our specific purpose. The approach provides adequate accuracy of the estimates of the material parameters, near 1%. These parameter estimates will subsequently be applied in future design simulations, without the need to go through an entire series of characterization experiments. Finally, a sensitivity study showed that small variations of 1% in the main parameters caused changes near 1% in the eigenfrequency, but changes up to 7% in the admittance peak, thus influencing the efficiency of the system. Temperature will already cause these small variations in response; thus, a frequency control unit is required when actually manufacturing an efficient ultrasonic separation system.
    Onderzoek naar de beperking van grondtarra bij de oogst van suikerbieten
    Bouma, J. ; Cappon, A. - \ 1988
    Wageningen : IMAG (Rapport / Instituut voor Mechanisatie, Arbeid en Gebouwen 101) - 97
    oogsten - beta vulgaris - suikerbieten - bietenrooiers - oogstverliezen - landbouwproducten - schoonmaakapparaten - sorteermachines - wortels - knollen - schoonmaken - indeling - afpellen - wassen (activiteit) - harvesting - beta vulgaris - sugarbeet - beet harvesters - yield losses - agricultural products - cleaners - sorters - roots - tubers - cleaning - grading - peeling - washing
    Alternatieve huisvesting voor leghennen : technisch verslag
    Cappon, A. ; Beek, C. ter; Frederiks, W.F. - \ 1986
    Wageningen : IMAG (Rapport / Instituut voor Mechanisatie, Arbeid en Gebouwen no. 83) - 14
    huisvesting, dieren - dierenwelzijn - hennen - pluimveehokken - animal housing - animal welfare - hens - poultry housing
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