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See detailModeling and computing ternary projective relations between regions
Clementini, Eliseo; Billen, Roland ULg

in IEEE Transactions on Knowledge and Data Engineering (2006), 18(6), 799-814

Current spatial database systems offer limited querying capabilities beyond binary topological relations. This paper introduces a model for projective relations between regions to support other ... [more ▼]

Current spatial database systems offer limited querying capabilities beyond binary topological relations. This paper introduces a model for projective relations between regions to support other qualitative spatial queries. The relations are ternary because they are based on the collinearity invariant of three points under projective geometry. The model is built on a partition of the plane into separate zones that are obtained from projective properties of two reference objects: Then, by considering the empty/ nonempty intersections of a primary object with these zones, the model is able to distinguish between 34 different projective relations. Then, the paper proposes original algorithms for computing the relations under the assumption that regions of the plane are stored as vector polygons in a spatial database. These algorithms run in optimal O(n log n) time. [less ▲]

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See detailModeling and experimental investigation of an Organic Rankine Cycle using scroll expander for small scale solar applications
Quoilin, Sylvain ULg; Orosz, Matthew; Lemort, Vincent ULg

(2008, October)

This study aims at developing and optimizing an Organic Rankine Cycle (ORC) for a small scale, decentralized parabolic trough system. A numerical model the Organic Rankine Cycle is developed and an ... [more ▼]

This study aims at developing and optimizing an Organic Rankine Cycle (ORC) for a small scale, decentralized parabolic trough system. A numerical model the Organic Rankine Cycle is developed and an experimental study is carried out on an ORC prototype working with refrigerant HCFC-123, and whose heat sources consist in two hot air flows. The ORC model is built by connecting different sub-models: the heat exchanger models, a volumetric pump model and a scroll expander model. Measured performances of the ORC prototype are presented and allow the validation of the ORC model. [less ▲]

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See detailModeling and experimental validation in partially wet conditions of an air-to-air heat recovery exchanger
Gendebien, Samuel ULg; Bertagnolio, Stéphane ULg; Lemort, Vincent ULg

in Proceedings of the 12th Conference of The International Building Performance Simulation Association (2011, November)

Nowadays, important efforts are deployed to reduce our current residential building consumption. The most common retrofit option concerns the air tightness and the thermal insulation improvement. However ... [more ▼]

Nowadays, important efforts are deployed to reduce our current residential building consumption. The most common retrofit option concerns the air tightness and the thermal insulation improvement. However, this latter retrofit option could decrease the air indoor quality because of a reduction of air infiltration flow rate. Installation of an air-to-air heat recovery system allows for an efficient combination between consumption reduction due to the air tightness improvement and acceptable air indoor quality. The study presented in this paper has been realized in the frame of the „Green +‟ project, which aims at developing decentralized heat recovery ventilation systems. The present paper focuses on modeling and experimental validation of an air-to-air heat recovery exchanger in partially wet conditions (i.e. where condensation might occur in one of the two air streams). The knowledge of the thermal performance in dry and wet regimes is essential since it highly impacts on the heat recovered from the vitiated air flow rate (extracted from the building) to the fresh air flow rate (coming from the outdoor). The first part of the paper briefly describes a solving procedure able to determine the regime (completely dry, completely wet and partially wet). A moving boundary model for the partially wet regime is applied in order to predict performance of such device. Secondly, the experimental apparatus (and its control) designed to characterize thermal performance in different operating conditions (dry and wet regime) is presented. [less ▲]

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See detailModeling and experimental validation of an industrial sheet metal forming process
CELENTANO, D.; GARCIA, C.; FLORES, F. et al

in Computational Mechanics, WCCM VI (2004)

Detailed reference viewed: 5 (1 ULg)
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See detailModeling and finite element analysis of mechanical behavior of flexible MEMS components
Pustan, Marius ULg; Paquay, Stéphane; Rochus, Véronique et al

in Microsystem Technologies (2011), 17(4), 553-562

This paper describes the studies of the mechanical characteristics of flexible MEMS components including theoretical approaches, finite element analysis and experimental investigations. Modeling and ... [more ▼]

This paper describes the studies of the mechanical characteristics of flexible MEMS components including theoretical approaches, finite element analysis and experimental investigations. Modeling and finite element analyses together with theoretical and experimental investigations are performed to estimate the elastic behavior of MEMS components as microcantilevers, microbridges and micromembranes. Finite element analysis of microcomponents deflections under different loading and the stress distribution in beams are determined and compared with the experimental measurements performed using an atomic force microscope. The modeling of a micromembrane supported by four hinges that enable out-of-plane motion is presented. Finite element analysis and experimental investigations are performed to visualize the deflection of the mobile part of the micromembrane under an applied force and the stress distribution in hinges. In additional, this paper provides analytical relations to compute the stiffness and the stress of the investigated flexible MEMS components. [less ▲]

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See detailModeling and Finite Element Analysis of Mechanical Behavior of Flexible MEMS Components
Pustan, Marius ULg; Paquay, Stéphane; Rochus, Véronique ULg et al

in Courtois, Bernard (Ed.) DTIP 2010 (2010, May 05)

This paper describes the studies of the mechanical characteristics of flexible MEMS components including theoretical approach, finite element analysis and experimental investigations. Modeling and finite ... [more ▼]

This paper describes the studies of the mechanical characteristics of flexible MEMS components including theoretical approach, finite element analysis and experimental investigations. Modeling and finite element analyses together with theoretical and experimental investigations are performed to estimate the mechanical behaviour of MEMS components as microcantilevers, microbridges and micromembranes. The finite element analysis of microcomponents deflections under different loading and the stress distribution in beams is determined and compared with the experimental measurements performed using atomic force microscope. The modeling of a micromembrane supported by four hinges that enable out-of-plane and in-plane motions is presented. Finite element analysis and experimental investigations are performed to estimate the deflection of the mobile plate of the micromembrane under an applied force and to visualize the distribution of the stress in hinges. In additional, this paper provides analytical relations for stiffness and stresses of the investigated flexible MEMS components. [less ▲]

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See detailModeling and observation of an upwelling filament off Cape Ghir (NW Africa) during the CAIBEX survey
Troupin, Charles ULg; Sangrà, Pablo; Arístegui, Javier et al

Poster (2010, February 22)

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See detailModeling and observation of an upwelling filament off Cape Ghir (NW~Africa) during the CAIBEX campaign
Troupin, Charles ULg; Arístegui, Javier; Barton, Eric Desmond et al

Poster (2009, November 27)

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See detailModeling and Prediction of Nonlinear Environmental System Using Bayesian Methods
Mansouri, Majdi; Dumont, Benjamin ULg; Destain, Marie-France ULg

in Computers & Electronics in Agriculture (2013), 92

An environmental dynamic system is usually modeled as a nonlinear system described by a set of nonlinear ODEs. A central challenge in computational modeling of environmental systems is the determination ... [more ▼]

An environmental dynamic system is usually modeled as a nonlinear system described by a set of nonlinear ODEs. A central challenge in computational modeling of environmental systems is the determination of the model parameters. In these cases, estimating these variables or parameters from other easily obtained measurements can be extremely useful. This work addresses the problem of monitoring and modeling a leaf area index and soil moisture model (LSM) using state estimation. The performances of various conventional and state-of-the-art state estimation techniques are compared when they are utilized to achieve this objective. These techniques include the extended Kalman filter (EKF), the particle filter (PF), and the more recently developed technique variational filter (VF). Specifically, two comparative studies are performed. In the first comparative study, the state variables (the leaf-area index LAI , the volumetric water content of the soil layer 1, HUR1 and the volumetric water content of the soil layer 2, HUR2) are estimated from noisy measurements of these variables, and the various estimation techniques are compared by computing the estimation root mean square error (RMSE) with respect to the noise-free data. In the second comparative study, the state variables as well as the model parameters are simultaneously estimated. In this case, in addition to comparing the performances of the various state estimation techniques, the effect of number of estimated model parameters on the accuracy and convergence of these techniques are also assessed. The results of both comparative studies show that the PF provides a higher accuracy than the EKF, which is due to the limited ability of the EKF to handle highly nonlinear processes. The results also show that the VF provides a significant improvement over the PF because, unlike the PF which depends on the choice of sampling distribution used to estimate the posterior distribution, the VF yields an optimum choice of the sampling distribution, which also accounts for the observed data. The results of the second comparative study show that, for all techniques, estimating more model parameters affects the estimation accuracy as well as the convergence of the estimated states and parameters. However, the VF can still provide both convergence as well as accuracy related advantages over other estimation methods. [less ▲]

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See detailModeling and Prediction of Time-Varying Environmental Data Using Advanced Bayesian Methods
Mansouri, Majdi ULg; Dumont, Benjamin ULg; Destain, Marie-France ULg

in Masegosa, Antoçnio; Villacorta, Pablo; Cruz-Corona, Carlos (Eds.) et al Exploring Innovative and Successful Applications of Soft Computing (2013)

The problem of state/parameter estimation represents a key issue in crop models which are nonlinear, non-Gaussian and include a large number of parameters. The prediction errors are often important due to ... [more ▼]

The problem of state/parameter estimation represents a key issue in crop models which are nonlinear, non-Gaussian and include a large number of parameters. The prediction errors are often important due to uncertainties in the equations, the input variables, and the parameters. The measurements needed to run the model (input data), to perform calibration and validation are sometimes not numerous or known with some uncertainty. In these cases, estimating the state variables and/or parameters from easily obtained measurements can be extremely useful. In this work, we address the problem of modeling and prediction of leaf area index and soil moisture (LSM) using state estimation. The performances of various conventional and state-of-the-art state estimation techniques are compared when they are utilized to achieve this objective. These techniques include the extended Kalman filter (EKF), unscented Kalman filter (UKF), particle filter (PF), and the more recently developed technique variational Bayesian filter (VF). The objective of this work is to extend the state and parameter estimation techniques (i.e., EKF, UKF, PF and VF) to better handle nonlinear and non-Gaussian processes without a priori state information, by utilizing a time-varying assumption of statistical parameters. In this case, the state vector to be estimated at any instant is assumed to follow a Gaussian model, where the expectation and the covariance matrix are both random. The randomness of the expectation and the covariance of the state/parameter vector are assumed here to further capture the uncertainty of the state distribution. One practical choice of these distributions can be a Gaussian distribution for the expectation and a multi-dimensional Wishart distribution for the covariance matrix. The assumption of random mean and random covariance of the state leads to a probability distribution covering a wide range of tail behaviors, which allows discrete jumps in the state variables. [less ▲]

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See detailModeling and Prediction of Time-Varying Environmental Data Using Advanced Bayesian Methods
Mansouri, Majdi ULg; Dumont, Benjamin ULg; Destain, Marie-France ULg

in Masegosa, Antoçnio; Villacorta, Pablo; Cruz-Corona, Carlos (Eds.) et al Exploring Innovative and Successful Applications of Soft Computing (2013)

The problem of state/parameter estimation represents a key issue in crop models which are nonlinear, non-Gaussian and include a large number of parameters. The prediction errors are often important due to ... [more ▼]

The problem of state/parameter estimation represents a key issue in crop models which are nonlinear, non-Gaussian and include a large number of parameters. The prediction errors are often important due to uncertainties in the equations, the input variables, and the parameters. The measurements needed to run the model (input data), to perform calibration and validation are sometimes not numerous or known with some uncertainty. In these cases, estimating the state variables and/or parameters from easily obtained measurements can be extremely useful. In this work, we address the problem of modeling and prediction of leaf area index and soil moisture (LSM) using state estimation. The performances of various conventional and state-of-the-art state estimation techniques are compared when they are utilized to achieve this objective. These techniques include the extended Kalman filter (EKF), unscented Kalman filter (UKF), particle filter (PF), and the more recently developed technique variational Bayesian filter (VF). The objective of this work is to extend the state and parameter estimation techniques (i.e., EKF, UKF, PF and VF) to better handle nonlinear and non-Gaussian processes without a priori state information, by utilizing a time-varying assumption of statistical parameters. In this case, the state vector to be estimated at any instant is assumed to follow a Gaussian model, where the expectation and the covariance matrix are both random. The randomness of the expectation and the covariance of the state/parameter vector are assumed here to further capture the uncertainty of the state distribution. One practical choice of these distributions can be a Gaussian distribution for the expectation and a multi-dimensional Wishart distribution for the covariance matrix. The assumption of random mean and random covariance of the state leads to a probability distribution covering a wide range of tail behaviors, which allows discrete jumps in the state variables. [less ▲]

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See detailModeling and simulation of an air conditioning chilled water system
Lebrun, Jean ULg; Lemort, Vincent ULg; Teodorese, Ion

(2006, December)

This paper is giving an overview of problems encountered and solutions available for the simulation of an air conditioning system. Focus is given on the chilling water subsystem (from the chiller to the ... [more ▼]

This paper is giving an overview of problems encountered and solutions available for the simulation of an air conditioning system. Focus is given on the chilling water subsystem (from the chiller to the cooling coil). Main component simulation models (chillers, pumps, piping, valves, cooling coils and fans) are presented; they are tuned on manufacturer’s catalogue data. The way of integrating these models into a global HVAC system simulation is illustrated thanks to one example: the simulation of (a part of) a real chilled water loop, which is submitted to an exhaustive monitoring. Cooling demands and corresponding energy consumptions are systematically simulated and measured on one-minute time basis. This provides the opportunity for a global checking of the simulation by comparing simulated and measured cooling coil outputs. Further work should also include comparisons on chiller consumptions. [less ▲]

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See detailModeling and Simulation of Heat and Mass Transfer During Convective Drying of Wastewater Sludge with Introduction of Shrinkage Phenomena
Bennamoun, Lyes ULg; Fraikin, Laurent ULg; Léonard, Angélique ULg

in Drying Technology (2014), 32(1), 13-22

Wastewater sludge is dried in a convective dryer using air temperatures varying from 80°C to 200°C, velocities changing from 1 m · s−1 to 2 m · s−1, and humidities ranging from . The convective dryer is ... [more ▼]

Wastewater sludge is dried in a convective dryer using air temperatures varying from 80°C to 200°C, velocities changing from 1 m · s−1 to 2 m · s−1, and humidities ranging from . The convective dryer is equipped with a camera and an infrared pyrometer to follow respectively the external surface and the temperature of the product. The experimental results show that drying kinetic can be divided into three phases: two short first phases, called adaptation and constant drying phases, and a long third phase, called falling drying rate phase. As the moisture content decreases, the camera confirms simultaneous shrinkage effect with the volume reduction of the product of about 30–45% of the initial volume. Moreover, an increase of the product temperature towards air temperature was measured with the infrared pyrometer. In a second step of this study, the experimental results are modeled and simulated using heat and mass balances applied to the product and the heated air. The drying curve is rightly expressed with fourth-degree polynomial model with a correlation coefficient that approximates the unity and with low calculated errors. An outstanding determination of the heat transfer coefficient has permitted calculating the product temperature with good agreement with experimental results. The heat transfer coefficient expressed by means of Nusselt number is presented as a function of Reynolds and Prandlt numbers, changeable with air and product characteristics taking into account shrinkage effect. Moreover, as the applied air temperatures are sufficiently high, transfer by radiation is not neglected and is introduced in the mathematical model. [less ▲]

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See detailModeling and simulation of the domestic energy use in Belgium following a bottom-up approach
Georges, Emeline ULg; Gendebien, Samuel ULg; Bertagnolio, Stéphane ULg et al

in Proceedings of the CLIMA 2013 11th REHVA World Congress & 8th International Conference on IAQVEC (2013, June)

The present paper presents a “bottom-up” approach dedicated to the modeling and simulation of the domestic energy use. This methodology focuses first on a microanalysis (i.e. modeling and simulation of a ... [more ▼]

The present paper presents a “bottom-up” approach dedicated to the modeling and simulation of the domestic energy use. This methodology focuses first on a microanalysis (i.e. modeling and simulation of a set of representative households). Results from this micro-analysis are then used and extended to allow drawing conclusions at a macro-scale. The methodology can be validated by comparing simulation results to annual national energy consumption indexes or synthetic load profiles (energy consumption profiles generated from values of predefined past periods). Once the method is validated, it can be used to study the impact of different retrofit scenarios on the annual energy use and on the energy demand profiles. This paper describes the methodology developed for Belgium. [less ▲]

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See detailModeling and Uncertainty Quantification of Thermoelastic Damping in Micro-Resonators
Lepage, Séverine; Golinval, Jean-Claude ULg

Conference given outside the academic context (2006)

In the design of micro-electromechanical systems (MEMS) such as micro-resonators, dissipation mechanisms may have detrimental effects on the quality factor, which is directly related to the response ... [more ▼]

In the design of micro-electromechanical systems (MEMS) such as micro-resonators, dissipation mechanisms may have detrimental effects on the quality factor, which is directly related to the response amplitude of the system that is excited at its natural frequency. One of the major dissipation phenomena to be considered in such micro-systems is thermoelastic damping. Hence, the performance of such MEMS is directly related to their thermoelastic quality factor which has to be predicted accurately. Moreover, the performance of MEMS depends on manufacturing processes which may cause substantial uncertainty in the geometry and in the material properties of the device. The reliability of MEMS devices is affected by the inability to accurately predict the behavior of the system due to the presence of these uncertainties. The aim of this paper is to provide a framework to account for uncertainties in the finite element analysis. Particularly, the influence of uncertainties on the performance of a micro-beam is studied using Monte- Carlo simulations. A random field approach is used to characterize the variation of the material as well as the geometric properties. Their effects on the thermoelastic quality factor of a micro-beam are studied. [less ▲]

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See detailA modeling approach to determine the contribution of plant hydraulic conductivities on the water uptake dynamics in the soil-plant-atmosphere system
Lobet, Guillaume ULg; Pagès, Loïc; Draye, Xavier

in Plant Growth Modeling, Simulation, Visualization and Applications (PMA), 2012 IEEE Fourth International Symposium on (2012)

Detailed reference viewed: 14 (2 ULg)
See detailModeling argon dynamics in first-year sea ice
Moreau, S.; Vancoppenolle, M.; Tison, J.-L. et al

Poster (2012, July)

Detailed reference viewed: 16 (1 ULg)