Numerical Simulation Research Papers - Academia.edu (original) (raw)

We propose a new prediction interval and band for the nonlinear regression model. The construction principle of this interval and band is based on an exact confidence region for parameters of the nonlinear regression model. This region, fully described in Vila & Gauchi (2007), provides a rigorous justification for the new prediction interval and band that we propose. This new band is then compared to the classical bands, and also to the band based on the bootstrap resampling method. The comparison of these bands is undertaken with simulated and real data from predictive modelling in food science.

- by and +1
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- Stochastic Process, Food Science, Prediction, Numerical Simulation

This work presents a three-dimensional CFD study of a two-phase flow field in a Gas-Liquid Cylindrical Cyclone (GLCC) using CFX4.3 TM , a commercial code based on the finite volume method. The numerical analysis was made for air-water mixtures at near atmospheric conditions, while both liquid and gas flow rates were changed. The two-phase flow behavior is modeled using an Eulerian-Eulerian approach, considering both phases as an interpenetrating continuum. This method computes the inter-phase phenomena by including a source term in the momentum equation to consider the drag between the liquid and gas phases. The gas phase is modeled as a bimodal bubble size distribution to allow for the presence of free-and entrapment gas, simultaneously. The results (interface vortex shape and liquid angular velocity) show a reasonable match with experimental data. The CFD technique here proposed, demonstrates to satisfactorily reproduce angular velocities of the phases and their spatial distribution inside the GLCC. The experiments showed gas volume fractions smaller than 150 ppm along the liquid exit, however it was not possible to reproduce numerically these small volume fractions, since they had approximately the same order of magnitude of the error in the numerical method.

- by Luis Rojas-Solórzano
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- Engineering, Computational Fluid Dynamics, Finite Volume Methods, Modeling

An intense low pressure system formed in the Bass Strait region of southeastern Australia during the Boxing Day long weekend of 25-28 December 1998. The explosive development of this low commenced on 26 December (Boxing Day) and reached peak intensity on 27 December 1998 with mean wind speeds reported in the 50-60kt range. The event is referred to, for simplicity, as the Boxing Day storm.

We consider the Euler discretisation of a scalar linear test equation with positive solutions and show for both strong and weak approximations that the probability of positivity over any finite interval of simulation tends to unity as the step size approaches zero. Although a.s. positivity in an approximation is impossible to achieve, we develop for the strong (Maruyama) approximation an asymptotic estimate of the number of mesh points required for positivity as our tolerance of non-positive trajectories tends to zero, and examine the effectiveness of this estimate in the context of practical numerical simulation. We show how this analysis generalises to equations with a drift coefficient that may display a high level of nonlinearity, but which must be linearly bounded from below (i.e. when acting towards zero), and a linearly bounded diffusion coefficient. Finally, in the linear case we develop a refined asymptotic estimate that is more useful as an a priori guide to the number of mesh points required to produce positive approximations with a given probability.

- by Cónall Kelly and +2
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- Applied Mathematics, Monte Carlo Simulation, Numerical Simulation, Stochastic differential equation

Key issues related to the modeling of ultra-high speed transmission are discussed in this paper. These topics include components modeling, link modeling and BER estimation. Different solutions for the transport of 100 Gb/s over a single wavelength including technologies such as coherent detection, polarization multiplexing, optical OFDM, and digital signal processing are reviewed and compared with means of numerical simulations.

- by Igor Koltchanov
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- Signal Processing, Modeling, Digital Signal Processing, Numerical Simulation

The St. Lawrence Lowlands platform, Quebec, Canada, is a densely-populated area, heavily dependent on groundwater resources. In 1999, the Geological Survey of Canada initiated a large-scale hydrogeological assessment study over a 1,500 km2 region northwest of Montreal. The objectives were to define the regional groundwater flow, and to give quantitative estimates of the groundwater dynamic parameters and of the available groundwater resources. The applied approach consisted of defining the hydrogeologic framework, hydraulic properties of the aquifer units, and groundwater dynamic components. Lower Paleozoic sedimentary rocks represent regional aquifer units. Coarse Quaternary fluvio-glacial sediments locally overlay the rock sequence and constitute an interface aquifer unit. Fine marine sediments confine most of the regional aquifers. Collected GIS based information was synthesized in a finite element numerical model. The regional saturated steady-state flow was calibrated under current stress conditions assuming an equivalent porous medium approach. Water budget calculations show that the total groundwater flow in regional aquifers amounts to 97.7 Mm3/y. Infiltration from precipitation provides 86.6% of the groundwater supply, while 9.6% comes from subsurface inflow and the remaining 3.8% is induced recharge from surface waters. Discharge from regional aquifers occurs through flow to streams (76.9%), groundwater withdrawal (18.4%), and underground outflow (4.7%). La plateforme Lowllands du Saint-Laurent, Québec, Canada, est une aire densément peuplée, dépendant grandement des ressources en eau souterraine. En 1999, le Service Géologique du Canada a initié une étude hydrogéologique à grande-échelle sur 1500 km2 au Nord-Ouest de Montréal. Le sobjectifs ont été de définir la dynamique de l’écoulement régional, et de donner des estimations quantitatives des paramètres dynamiques des ressources disponibles en eau souterraine. L’approche utilisée consista à définir le cadre hydrogéologique de travail, les propriétés hydrauliques des unités aquifères, et les composantes dynamiques des eaux souterraines. Les roches sédimentaires du Paléozoïque Inférieur représentent les unités aquifères régionales. Les sédiments marins fins confinent la plus grande partie des aquifères régionaux. Les informations de base, collectées dans un SIG, ont été synthétisées dans un modèle numérique aux éléments finis. L’écoulement permanent régional, en zone saturée, a été calibré en conditions de stress en assumant une approche de milieu poreu équivalent. Les calculs du bilan hydrologique montrent que l’écoulement total des eaux souterraines dans les aquifères régionaux atteind 97,7 Mm3/an. L’infiltration à partir des précipitations apporte 86.6% de l’eau souterraine exploitée; sachant que 9,6% proviennent d’écoulement de subsurfaces, et que les 3,8% restants proviennent de la recharge via les eaux de surface. Le débit pompé des aquifères régionaux apparaît à travers l’écoulement des cours d’eau, le rabattement des eaux souterraines (18.4%), et l’écoulement ascendant (4.7%). La plataforma de Tierras Bajas San Lorenzo, Quebec, Canadá, es un área densamente poblada que depende fuertemente de recursos de agua subterránea. En 1999 el Servicio Geológico de Canadá inició un estudio de evaluación hidrogeológica a gran escala sobre un área de 1,500 km2 en la región noroeste de Montreal. Los objetivos fueron definir el flujo regional de agua subterránea y aportar estimados cuantitativos de los parámetros dinámicos de agua subterráne y de los recursos disponibles de agua subterránea. El enfoque aplicado consistió en definir el marco hidrogeológico, propiedades hidráulicas de las unidades acuíferas, y los componentes dinámicos de agua subterránea. Rocas sedimentarias del Paleozoico Inferior representan unidades regionales de acuíferos. Sedimentos fluvio-glaciares Cuaternarios gruesos sobreyacen localmente la secuencia rocosa y constituyen una unidad acuífera interfacial. Sedimentos marinos finos confinan la mayoría de acuíferos regionales. Información colectada basada en SIG se sintetizó en un modelo numérico de elemento finito. El flujo regional saturado en régimen permanente se calibró bajo condiciones de stress asumiendo un enfoque de medio poroso equivalente. Los cálculos de balance hídrico muestran que el flujo total de agua subterránea en acuíferos regional alcanza 97.7 Mm3/año. Infiltración a partir de lluvia aporta el 86.6% del abastecimiento al agua subterránea, mientras que el 9.6% proviene de entradas subsuperficiales y el restante 3.8% consiste de recarga inducida a partir de aguas superficiales. La descarga proveniente de acuíferos regionales ocurre a través de flujo a ríos (76.9%), utilización de agua subterránea (18.4%), y salida subterránea (4.7%).

- by Ana Rivera
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- Engineering, Earth Sciences, Hydrogeology, Finite Element

To predict the performance of an aquifer thermal energy storage system, an understanding of the system's hydrothermal behavior is needed. One possibility is to run a detailed numerical simulation of the system. However, for a single-well system in which fluid flow is limited to steady radial flow, a characterization scheme based on a set of four dimensionless parameter groups allows production temperatures and energy recovery factors to be read from graphs. The assumption of radial fluid flow is valid when buoyancy flow can be neglected and a well is fully screened in a horizontal aquifer which is confined above and below by impermeable layers. Criteria for little buoyancy flow include a low permeability or vertically stratified aquifer, a small temperature difference between injected and ambient water. and short cycle leneth The ha.•ie enerov tranannrt ., ,.., ........ •,.• ....... r layer system with steady radial fluid flow in the aquifer are nondimensionalized to derive the key parameter groups. Next a numerical model which calculates the heat transfer in the aquifer and confining layers for an injection-storage-production cycle is run for a range of values of these groups. The calculated production temperatures and energy recovery factors are then presented graphically as a function of the parameter groups. Comparisons between results of field experiments and recovery factors read from the graphs show good agreement. ATES cycl• [Tsang eta!., 1977; Fabris et al., 1977]. Recently, Sauty et al. [1980a] have studied the thermal behavior of a simplified single-well ATES system in terms of , a set of dimensionless groups. A few heat storage field experiments in either confined

- by Johan Claesson
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- Environmental Engineering, Civil Engineering, Water resources, Heat Transfer

A first principles-based model has been developed to simulate the capacity fade of Li-ion batteries. Incorporation of a continuous occurrence of the solvent reduction reaction during constant current and constant voltage ͑CC-CV͒ charging explains the capacity fade of the battery. The effect of parameters such as end of charge voltage and depth of discharge, the film resistance, the exchange current density, and the over voltage of the parasitic reaction on the capacity fade and battery performance were studied qualitatively. The parameters that were updated for every cycle as a result of the side reaction were state-of-charge of the electrode materials and the film resistance, both estimated at the end of CC-CV charging. The effect of rate of solvent reduction reaction and the conductivity of the film formed were also studied.

- by Branko Popov
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- Materials Engineering, Ab initio calculations, Numerical Simulation, The

An analytical model for gas-solid suspension flow through an inclined section of pipe was developed. This model predicts the ratio of the total pressure drop in an inclined pipe to that of a horizontal pipe. The model has been used to predict the critical pipe angle, which is defined as the angle at which the maximum pressure drop for a given solids flow rate is achieved. This angle differs from 90 ° (found in a single-phase flow) and is directly proportional to the ratio between the gas superficial velocity and the particle terminal velocity. The three-dimensional conservation equations for steady-state two-phase flow in an inclined pipe were solved numerically for constant solids and gas flow rates at different pipe inclinations. This model was based on the continuum theory for describing the mass and momentum balance equations for the fluid and solid phases. A packing model, describing the shear stress of the solid phase as a function of its volume fraction, is suggested in order to limit the maximum value of the solid volume fraction. A new model for particle-wall interaction was developed taking into account the angle of inclination of the pipe. The prediction of the numerical model was compared with experimental data obtained in a specially designed test rig. In general, the agreement between the experimental data and the models was satisfactory. The results of the numerical simulation also confirmed that the critical pipe angle for gas-solid flow is lower than 90 ° . The assumptions made during the development of the models were assessed in order to explain the differences between the predicted and measured values of the flow parameters for different flow regimes. © 1997 Elsevier Science S.A.

- by David Mason
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- Mechanical Engineering, Chemical Engineering, Two Phase Flow, Powder technology

The majority of concrete dams worldwide have behaved relatively well during seismic events. However, there are several cases where global failure or substantial damages have occurred. The need for new dam construction and retrofitting of existing dams necessitates the use of advanced design approaches that can take realistically into account the potential dam-reservoir-foundation interaction. Seismic design of concrete dams is associated with difficulties to estimate the dynamic distress of the dam as well as the response of the damreservoir-foundation system and to assess the impact of the various parameters involved. In this chapter, after an extensive literature review on the dynamic interaction of concrete dams with retained water and underlying soil, results from numerical simulations are presented. Initially, analytical closed-form solutions that have been widely used for the calculation of dam distress are outlined. Subsequently, the numerical methods based on the finite element method (FEM) which is unavoidably used for complicated geometries of the reservoir and/or the dam, are reviewed. Emphasis is given on FEM-based procedures and especially the boundary conditions and interactions involved. Numerical results are presented to illustrate the impact of various key parameters on the distress and response of concrete dams considering dam-foundation interaction phenomena. In general, a good agreement is observed between the results of analytical and numerical approaches for the examined characteristic dam configuration.

This article presents a new method to pre-cure natural rubber-compounding (NRc) by using microwave energy at a frequency of 2.45 GHz with a rectangular wave guide. The influences of microwave power input, specimen thicknesses, and vulcanized sulfur contents on the dielectric and thermal characteristics and crosslinked contents of microwave-cured NRc are studied. Furthermore, a generalized mathematical model for predicting temperature distribution inside the specimen during pre-heating is proposed. Significant results show that microwave energy can produce partial cross-linking at temperatures below the actual vulcanizing process. The numerical results from the model agree well with the results from the experiments.

- by Natt Makul
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- Mechanical Engineering, Materials Science, Microwave, Modeling

A detailed urban heat exchange simulation software, the Town Energy Balance (TEB), has been used to analyse the impact of urban parameters on energy balance during a summer and a winter day under Paris, France, climatic conditions. Computer runs were conducted to explore the influence of each of the urban parameters selected. The results showed that impacts of these parameters

- by Morgane Colombert and +1
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- Heat Exchanger, Seasonality, Numerical Simulation, Urban heat island

The speed of golf balls can be regarded as the fastest in all ball games. The flying distance of a golf ball is influenced not only by its material, but also by the aerodynamics of the dimple on its surface. By using Computational Fluid Dynamics method, the flow field and aerodynamics characteristics of golf balls can be studied and evaluated before the golf balls are actually manufactured. This work uses FLUENT as its solver and numerical simulations were carried out to estimate the aerodynamics parameters and noise levels for various kinds of golf balls having different dimple configurations. With the obtained aerodynamics parameters, the flying distance and trajectory for a golf ball were determined and visualized. The results showed that the lift coefficient of the golf ball increased if small dimples were added between the original dimples. When launched at small angles, golf balls with deep dimples were found to have greater lift effects than drag effects. Therefore, the golf balls would fly further. As far as noise generation was concerned, deep dimples produced lower noise levels.

- by Chang-hsien Tai and +2
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- Mechanical Engineering, Numerical Simulation, Computation Fluid Dynamics
- by Burdon Rowland
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- Genetics, Molecular Biology, Polymorphism, Quantitative Genetics

Plant-based fibers have been selected as suitable reinforcements for composites due to their good mechanical performances and environmental advantages. This paper describes the development of a simulation procedure to predict the temperature profile and the curing behavior of the hemp fiber/thermoset composite during the molding process. The governing equations for the non-linear transient heat transfer and the resin cure kinetics were presented. A general purpose multiphysics finite element package was employed. The procedure was applied to simulate one-dimensional and three-dimensional models. Experiments were carried out to verify the simulated results. Experimental data shows that the simulation procedure is numerically valid and stable, and it can provide reasonably accurate predictions. The numerical simulation was performed for a three-dimensional complex geometry of an automotive part to predict the temperature distribution and the curing behavior of the composite during the molding process.

- by Mohini Sain
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- Engineering, Kinetics, Modeling, Heat Transfer

Hydrometeors spectra evolution induced by coalescence processes is simulated using a microphysical model of the Berry and Reinhard (1974) type including hydrometeors of seven kinds: water drops, plate-like and columnar crystals, dendrites, snowflakes, graupel and hail. The sensitivity of spectra evolution to several parameters, such as air temperature, drop freezing rate, initial liquid water and ice particles content is studied. The Berry and Reinhard (1974) method was used for numerical integration of corresponding stochastic coalescence equations. A remarkable impact of ice processes on the evolution of hydrometeors of all types is demonstrated. The amount of large droplets in mixed phase experiments is significantly less than that in the experiment without the ice phase. The main factor causing the cessation of water spectrum broadening is connected with a crucial decrease of the coalescence rate between water droplets due to permanent elimination of the largest droplets from the drop spectrum as a result of ice-water interaction and drop freezing. The results of simulations show that when only coalescence processes are considered, relative amounts of snowflakes and graupel crucially depend on air temperature. Under comparably high temperatures it is snowflakes that are the dominating hydrometeor type, while under low temperatures graupel can be the dominating hydrometeor type due to an increased rate of drop freezing. A high sensitivity of snowflake/graupel content ratio to the initial size of crystals is demonstrated. Initial liquid water content in model experiments appears to be one of the most important factors determining the formation not only of graupel, but of snowflakes as well. Results indicate the existence of a "critical" minimum concentration of water drops and minimum broadness of the drop size spectrum, which means that when the corresponding values are smaller there is no large snowflake or graupel generation.

The processing of hard and liquid silicone rubbers (LSR) are compared by means of modeling and simulation. The curing process for both, hard and liquid silicone, are modeled using the auto-catalytic Kamal-Sourour model and a nonlinear regression method is used to find the kinetic parameters. The fitted kinetic model is then combined with the heat balance equations to simulate real processing conditions. Both resins are compared in terms of process perform-ance and consistency of the final part. The results show that even though hard silicone rubbers are less expensive resins, its processing conditions present several issues of consistency and quality control when compared with LSR.

- by Juan Hernández-ortiz
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- Engineering, Kinetics, Modeling, Heat Transfer

Determining the epithelium's contribution to corneal biomechanics is important for the predictive numerical simulation of corneal biomechanical behaviour in which the cornea's five main layers are represented separately. Twenty-four corneal buttons were tested under posterior inflation conditions while monitoring their behaviour using non-contact methods. The corneas were divided into two groups of 12; one with and one without the epithelium. Control of specimen hydration, temperature and pressure application rate, and limiting the programme to specimens within a small age range resulted in a narrow scatter of test results. On average, intact specimens were able to carry slightly more pressure at the same deformation, and experienced less average stress for the same strain, compared with specimens without the epithelium. These results indicated that the stiffness of the epithelium was considerably lower than that of the stroma, and might therefore be ignored in numerical simulation studies.

- by Ahmed Elsheikh
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- Biomechanics, Cornea, Elasticity, Numerical Simulation

We employ a three-dimensional (3D) particle-in-cell method coupling with finitedifference time domain scheme to simulate the electron emission in surface conduction electron-emitter displays (SEDs). This computational technique includes the space charge effects automatically. We thus explore the conducting mechanism, the emission efficiency, and the current density distribution on the anode plate with one field emission emitter.

- by Chineng Mo
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- Materials Science, Field emission, Numerical Simulation, Current Density

Based on a dynamic (i.e. time-dependent) one-dimensional approach, this work applied lattice Boltzmann method (LBM) to computationally model biospecific affinity chromatography (BAC). With governing equations expressed in lattice-based dimensionless form, LBM was implemented in D1Q2 lattice by assigning particle distribution functions to adsorbate concentration in both fluid and solid phases. The LBM simulator was firstly tested in view of a classic BAC work on lysozyme and the streaming step relating to adsorbate concentration in the solid-phase was suppressed from the LBM code with no loss of functionality. Expected behaviour of breakthrough curves was numerically reproduced and the influence of lattice-based dimensionless parameters was examined. The LBM simulator was next applied so as to assess lattice-based dimensionless parameters regarding an experimental BAC work on lipase.

- by Lifescience Global Canada and +1
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- Numerical Simulation, Lattice Boltzmann Method

We have developed a modified physical vapor transport (M-PVT) growth technique for the preparation of SiC single crystals which makes use of an additional gas pipe in order to control the gas phase composition of the conventional physical... more

- by Francis Baillet
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- Materials Science, Crystal Growth, Phosphorus, Numerical Simulation
- by Jørgen Amdahl
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- Engineering, Civil Engineering, Numerical Simulation, Marine Structures

Under the two initial 1-D one parameter velocity distribution forms (one is normal, the other is exponential), the z direction scale height evolution of normal neutron stars in the Galaxy is studied by numerical simulation. We do statistics for the cases at different time segments, also do statistics for the cumulative cases made of each time segment. The results show in the cumulative cases the evolution curves of the scale heights are smoother than in the each time segment, i.e., the cumulation improve the signal-to-noise ratio. Certainly the evolution cases are different at different Galactic disk locations, which also have very large difference from the average cases in the whole disk. In the initial stages of z evolution of normal neutron stars, after the beginning transient states, the cumulative scale heights increase linearly with time, and the cumulative scale height increasing rates have linear relationship with the initial velocity distribution parameters, which have larg...

- by Luo A-Li
- •
- Physics, Theoretical astrophysics, Numerical Simulation, Signal to Noise Ratio

The purpose is to propose an improved method for inverse boundary value problems. This method is presented on a model problem. It introduces a higher order problem. BEM numerical simulations highlight the efficiency, the improved accuracy, the robustness to noisy data of this new approach, as well as its ability to deblur noisy data. Keywords Cauchy problem • inverse problem • boundary values • boundary element method • regularization

- by A. Cimetière
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- Mechanical Engineering, Civil Engineering, Mathematics, Computational Mechanics

The feasibility of linear and nonlinear geostatistical estimation techniques for optimal merging of rainfall data from raingage and radar observations is investigated in this study by use of controlled numerical experiments. Synthetic radar and raingage data are generated with their hypothetical error structures that explicitly account for sampling characteristics of the two sensors. Numerically simulated rainfall fields considered to be ground-truth fields on 4x4 km grids are used in the generation of radar and raingage observations. Ground-truth rainfall fields consist of generated rainfall fields with various climatic characteristics that preserve the space-time covariance function of rainfall events in extratropical cyclonic storms. Optimal mean areal precipitation estimates are obtained based on the minimum variance, unbiased property of kriging techniques under the second order homogeneity assumption of rainfall fields. The evaluation of estimated rainfall fields is done based on the refinement of spatial predictability over what would be provided from each sensor individually. Attention is mainly given to removal of measurement error and bias that are synthetically introduced to radar measurements. The influence of raingage network density on estimated rainfall fields is also examined.

- by dongjun seo
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- Engineering, Environmental Science, Numerical Simulation, stochastic Hydrology

This paper reports on the development of an automated planning and scheduling system supporting terminal operations of the vehicle transshipment hub in Bremerhaven. We describe terminal operations and derive an integral decision model for manpower planning and inventory control. Thereby we propose a hierarchical separation of the integral model into sub-models and develop heuristics to solve the arising sub-problems.

- by Herbert Kopfer
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- Operations Management, Heuristics, Logistics, Scheduling

The behavior of two spherical bubbles with different sizes near a solid wall is investigated in consideration of the effects of the vapor and noncondensable gas in the bubbles, and then the equations of motion of the bubbles are derived. Further, the effects of a solid wall on the variation with time of the bubble radius and the pressure at bubble wall are clarified by numerical calculations.

- by toru fujiwara
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- Mechanical Engineering, Applied Mathematics, Interaction, Growth

The digital waveguide mesh is an extension of the onedimensional (1-D) digital waveguide technique. The mesh can be used for simulation of two-and three-dimensional (3-D) wave propagation in musical instruments and acoustic spaces. The original rectangular digital waveguide mesh algorithm suffers from direction-dependent dispersion. Alternative geometries, such as the triangular mesh, have been proposed previously to improve the performance of the mesh. In this paper, we show that the dispersion problem may be reduced using various other techniques. These methods include multidimensional interpolation, optimization of the point-spreading function, and frequency warping. We compare the accuracy and computational complexity of these techniques in the two-dimensional (2-D) case and conduct numerical simulations of a membrane. A rectangular mesh using second-order Lagrange interpolation can be implemented without multiplications, but its accuracy is worse than that of other enhanced structures. The most accurate technique in terms of the relative frequency error is the warped triangular mesh whose maximum error is 0.6%. The warped rectangular mesh with optimized weighting coefficients is not as exact, but still offers a 1.2% accuracy.

- by Vesa Välimäki
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- Engineering, Computational Complexity, Mesh generation, Optimization

In this paper, we numerically investigate the hyperchaotic behaviors in the fractional-order Chen hyperchaotic systems. By utilizing the fractional calculus techniques, we find that hyperchaos exists in the fractional-order Chen hyperchaotic system with the order less than 4. We found that the lowest order for hyperchaos to have in this system is 3.72. Our results are validated by the existence of two positive Lyapunov exponents. The generalized projective synchronization method is also presented for synchronizing the fractional-order Chen hyperchaotic systems. The present technique is based on the Laplace transform theory. This simple and theoretically rigorous synchronization approach enables synchronization of fractional-order hyperchaotic systems to be achieved and does not require the computation of the conditional Lyapunov exponents. Numerical simulations are performed to verify the effectiveness of the proposed synchronization scheme.

- by Xiangjun Wu
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- Engineering, Nonlinear dynamics, Numerical Simulation, Mathematical Sciences

The study of the dynamics of a simple batch distillation usually assumes the equilibrium between the liquid and vapour phases. In contrast to that approach, this work considers the analysis of the dynamic behaviour of a nonequilibrium simple batch distillation. A simple batch distillation device is similar to an evapouration unit because no reflux is employed. A mathematical model and their singular points are analysed through the usual technique of linearization followed by the eigenvalues analysis. The stability nature of those points is presented for ideal solutions. Phase plane plots are made to show the occurrence of some unexpected behaviours such as 'dynamic azeotropic points' and 'inversion of the distillation order'. The dependence of these phenomena on the vapour withdrawal flowrate is established for simple batch distillation. #

- by Antonio Meirelles
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- Chemical Engineering, Mass Transfer, Stability, Numerical Simulation

The microstructure simulation of spinodal decomposition was carried out in the aged Cu-70 and 90 at.% Ni alloys, based on a solution of the non-linear Cahn-Hilliard partial differential equation by the finite difference method. The calculated concentration profiles were compared with the experimental ones determined by atom-probe field ion microscope analyses of the solution treated and aged Cu-70 at.% Ni alloy samples. Both the numerically simulated and experimental results showed a good agreement for the concentration profiles and microstructure evolution in the aged Cu-Ni alloys. A very slow growth kinetics of phase decomposition was observed to occur in this type of alloy. The morphology of decomposed phases consists of an irregular shape with no preferential alignment in any crystallographic direction. The wavelength of composition modulation was determined numerically to be about 2 nm and it remained constant after aging at 573 K for times as long as 8889 h. No phase decomposition was observed to occur for the numerical simulation of aging at temperatures lower than 523 K for a time as long as 1 year.

We report on our empirical studies of a new controller for a two-link brachiating robot. Motivated by the pendulum-like motion of an ape's brachiation, we encode this task as the output of a "target dynamical system." Numerical simulations indicate that the resulting controller solves a number of brachiation problems that we term the "ladder," "swing-up," and "rope" problems. Preliminary analysis provides some explanation for this success. The proposed controller is implemented on a physical system in our laboratory. The robot achieves behaviors including "swing locomotion" and "swing up" and is capable of continuous locomotion over several rungs of a ladder. We discuss a number of formal questions whose answers will be required to gain a full understanding of the strengths and weaknesses of this approach.

- by Toshio Fukuda
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- Mechanical Engineering, Motion control, Control Systems, Actuators

Predictions of dense non-aqueous phase liquid (DNAPL) releases are sensitive to the nonwetting phase relative permeability-saturation (k r,N -S) constitutive relationships employed in numerical models. In this study, hysteretic k r,N -S curves were measured for a variety of sands, revealing trends in k r,N -S function shapes that were correlated to sand type. To explore the significance of this conclusion, numerical simulations of a fixed volume DNAPL release were conducted using 10 realisations of a spatially correlated, random permeability field. Simulations assuming homogeneity of relative permeability were compared to those employing the determined functional dependence of relative permeability on porous media properties. The simulations demonstrate both temporal and spatial sensitivity. The time for DNAPL migration to cease is shorter, and the ultimate extent of DNAPL invasion is greater, in those simulations using the traditional assumption that k r,N -S is uniform and not correlated to porous media type.

- by Jason Gerhard
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- Numerical Simulation, Porous Media, Numerical Model, Spatial Correlation

In this paper, lab tests coupled to a semi-pilot test section are used to derive data for the calibration of a numerical model. The paper is aimed at proposing a set of experiments, which can be used to calibrate a numerical model before using it on defined soils. The complexity of the phenomenon of transport of reactive pollutants in soil has to be faced in the most complete way. The different behaviour of soil after wet/dry cycles with respect to the fluidodynamic characteristics and the importance to consider the local biomass behaviour in case of organic contaminant has been underlined. An optimal approach has to take into account all the different components and here a simple series of experimental procedure is presented. The sensitivity analysis of the numerical model has shown that its results are not so much dependent on the classical numerical aspects (time or space increments) but mainly on a set of parameters related to soil structure which must then be derived through a good calibration. (P. Viotti). produced contamination of several aquifers all over the world. Contaminants dispersed at the land surface migrate through the vadose zone before being advected and dispersed by flowing groundwater. Solute transport in unsaturated soils has been the topic of experimental, theoretical research and studies above numerical simulation aspects . The behaviour and fate of chemicals in the vadose zone is complex , being a process occurring in conditions strongly influenced 0304-3800/$ -see front matter

- by Paolo Viotti
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- Unsaturated soil, Sensitivity Analysis, Multidisciplinary, Ecological Modelling

The impact energy absorption by helmets is of vital importance to the safety of motorcyclists during accidents. The paper is concerned with the study of damage and delamination, which are the principal modes of failure and energy absorption, in a composite shell and their influence on the impact performance of a helmet. Numerical simulations were conducted with different composite shells made of cross-ply laminate, woven fabric, and glass mat. The effectiveness of the numerical model is established using available experimental results from the literature. Hashin failure criteria and cohesive zone model (CZM) were used for predicting the in-plane damage and delamination in composite plies, respectively. An interface layer having a bilinear relationship between traction and relative displacement was placed between the plies of the composite shell to predict the delamination. The influence of damage and delamination in shells made of composite materials on impact-induced forces is evaluated and their performance is compared with helmet shells made of Acrylonitrile Butadiene Styrene (ABS).

- by praveen pinnoji
- •
- Materials Science, Fracture and cohesive zone model, Numerical Simulation, Impact

In this study, turbulent compressible gas flow in a rectangular micro-channel is numerically investigated. The gas flow assumed to be in the subsonic regime up to Mach number about 0.7. Five low and high Reynolds number RANS turbulence models are used for modeling the turbulent flow. Two types of mesh are generated depending on the employed turbulence model. The computations are performed for Reynolds number up to 19000 and two inlet pressures of 1102 kPa and 499 kPa. The longitudinal variations of flow characteristics such as pressure, temperature, Mach number and friction factor are investigated. The experimental data are also used for the sake of comparison and to find which turbulence model has the best performance. The results show that the turbulence models with wall functions have generally better agreement with the experimental data than those one without wall function. The numerical results are different for normal size pipe flow.

In this paper we discuss the development of a valuation system of asset-liability management of portfolios of life insurance policies on advanced architectures. According to the new rules of the Solvency II project, numerical simulations must provide reliable estimates of the relevant quantities involved in the contracts; therefore, valuation processes have to rely on accurate algorithms able to provide solutions in a suitable turnaround time. Our target is to develop an effective valuation software. At this aim we first introduce a change of numéraire in the stochastic processes for risks sources, thus providing estimates under the forward risk-neutral measure that result in a gain in accuracy. We then parallelize the Monte Carlo method to speed-up the simulation process.

- by Zelda Marino
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- Cognitive Science, Stochastic Process, Computer Science, Distributed Computing

The dynamics of a prey-predator system, where predator population has two stages, juvenile and adult with harvesting are modelled by a system of delay differential equation. Our analysis shows that, both the delay and harvesting effort may play a significant role on the stability of the system. Numerical simulations are given to illustrate the results.

This paper describes how to optimize the energy performance of single-story multiple-skin facades (MSF) by changing the settings of the facades and HVAC-system according to the net energy demand of the building. The annual energy performance is analyzed for typical Belgian climatic conditions using a whole building simulation tool. Three MSF are scrutinised: a mechanically ventilated airflow window, a naturally ventilated double-skin facade and a mechanically ventilated supply window. Their performance is compared against the performance of two traditional facades: a traditional window with exterior and interior shading device. It is shown that both the heating and cooling demand may significantly be improved by implementing control strategies such as controlling the airflow rate and the recovery of air returning from the multiple-skin facades.

- by H. Hens
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- Engineering, Architecture, Modeling, Energy Management

In this work a methodology to automatically balance the flow in profile extrusion dies is used. For this purpose a computational code, based on the finite-volume method, was developed and used to perform the required threedimensional numerical simulations of the flow. The methodology is illustrated using two case studies, each one leading to the adoption of a different constructive solution (with and without flow separators). In order to evaluate the quality of the automatically generated die geometries, an objective function, that takes into account the flow balancing and the ratio L/t of the parallel zone, is proposed.

- by O. Carneiro
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- Numerical Simulation, Case Study, Design Tool, Finite Volume

Among numerous techniques for the hydrogen production without harmful emissions, especially avoiding the carbon dioxide emissions, hydrogen technologies driven by geothermal energy represent an attractive solution. This paper is interested in the process by which the electricity generated from geothermal power plant that is operated using CO 2 as heat transmission fluid is exploited for hydrogen production through water electrolysis. A numerical simulation is used to evaluate the potential for hydrogen production and to estimate the levelized cost of electrolytic hydrogen. We also present a brief analysis of environmental issues, including the carbon tax. The results show that the process has a good potential for geothermal hydrogen production, is capable of producing about 22 kg/h of electrolytic hydrogen for the geothermal source of carbon dioxide mass flow rate of 40 kg/s and a temperature of 296 K. In economic regard, the electric energy system costs are the major component of t...

- by modou diop
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- Numerical Simulation, Hydrogen Production, Environmental Impact

This paper describes the RT-LAB real-time simulator implementation of the Hardware-In-the-Loop simulation of a fuel cell hybrid electric vehicle system with several 10 kHz converters. The paper demonstrates the necessity to use special IGBT bridge models that implements interpolation techniques within fixed time step simulation scheme. The paper reports on the latest advances from Opal-RT to simulate this kind of system with a 10 µs sample time. HIL computational time measurement are provided as well as a model fidelity comparison made by Toyota Motor Corp. of the RT-LAB Electrical Drive Simulator versus an actual fuel cell hybrid electric vehicle. In this paper, we describe an the methodology and simulation techniques used to make the real-time simulation of a fuel-cell hybrid vehicle with DC-DC converter and several PMSM inverter drives running with 10 kHz carrier frequency. The paper is organized in the following manner. First, typical problems regarding the real-time simulation ...

- by Jean Belanger
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- Fuel Cell, Hybrid Vehicle, Numerical Simulation, Dc-Dc Boost Converter

Two-color laser systems based on a semiconductor laser device and spectrally filtered feedback are studied. By use of a broadband numerical simulator and realistic active-structure optical responses, various two-color lasing configurations are investigated. Five characteristic dynamic regimes are observed and classified as semicoherent, coherent, multimode, chaotic, and multimode chaotic. Practical implications for gigahertz or terahertz signal-generation applications are discussed.

A wave equation on a one-dimensional interval I has a van der Pol type nonlinear boundary condition at the right end. At the left end, the boundary condition is fixed. At exactly the midpoint of the interval I, energy is injected into the system through a pair of transmission conditions in the feedback form of anti-damping. We wish to study chaotic wave propagation in the system. A cause of chaos by snapback repellers has been identified. These snapback repellers are repelling fixed points possessing homoclinic orbits of the non-invertible map in 2D corresponding to wave reflections and transmissions at, respectively, the boundary and the middleof-the-span points. Existing literature ͓F. R. Marotto, J. Math. Anal. Appl. 63, 199-223 ͑1978͔͒ on snapback repellers contains an error. We clarify the error and give a refined theorem that snapback repellers imply chaos. Numerical simulations of chaotic vibration are also illustrated.

- by Goong Chen
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- Mathematical Physics, Numerical Simulation, Mathematical Sciences, Physical sciences
- by M. Bristeau
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- Granular Flow, Multidisciplinary, Numerical Simulation, Reference Frame

Application of slump failure mechanism in the numerical modeling of the free meandering is the recent advancement towards dealing the real phenomena on the outer bends of meandering rivers with the numerical models. Recently numerous numerical simulations are performed using two-dimensional morphodynamic model for bed and bank with consideration of effects of slump blocks. Four different cases are simulated separately for steady and unsteady flow condition for about 6 h with and without slump block consideration. The measured bank erosion, channel migration and the channel width evolution show significant difference in the results due to inclusion of slump block effects. Long term simulation has been performed for 24 h to predict the free meandering behavior with variation of different slump block parameters. The result shows clear bar formation and projection, channel formation and migration towards the outer bends, making longer length of the flow path and increasing the sinuosity with the time which is very similar with the natural rivers.

- by gary parker
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- Engineering, Earth Sciences, Numerical Simulation, Unsteady flow

Synthesized-reference-wave holographic techniques offer relatively simple and cost-effective measurement of antenna radiation characteristics and reconstruction of complex aperture fields using near-field intensity-pattern measurement. These methods allow utilization of advantages of methods for probe compensations for amplitude and phasing near-field measurements for the planar and cylindrical scanning including accuracy analyses. The paper analyzes periodic errors, which can be created during scanning, using both theoretical results and numerical simulations.

- by Vladimir Schejbal
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- Numerical Simulation, Cost effectiveness, Near Field

Properties of concentration waves of solutes affected by nonlinear sorption, precipitation/ dissolution and homogeneous reactions in the mobile and stationary phases are established when the number of phases is constant. These properties essentially depend on the structure of a stoichiometric matrix which describes the chemical interactions. A reduction procedure of the stoichiometric matrix gives the number of waves or peaks together with their propagation velocities, and the retardation factors of species at trace levels. The location of the peaks and their broadening behavior due to the nonlinear equilibria are estimated. The number of waves and the properties of suitable linear combinations of concentrations provide a method for discriminating among rival interaction mechanisms irrespective of the equilibrium constants. This cannot be done using conventional methods based on the comparison between numerical simulations and experimental curves. Bryant et al., 1986] are devoted to the consequences of the set of elementary interactions (homogeneous reactions, adsorption and/or exchange reactions, precipitation, dissolution, degassing processes, etc.) on the structure and properties of the corresponding breakthrough curves (BTC). Predicting qualitative properties of BTCs or elucidating the main features of an interaction mechanism from experimental BTCs can be performed using numerical computer codes. Unfortunately, these calculations can be time consuming and they require that the interaction parameters (i.e., equilibrium constants, kinetic constants, etc.) be known. There is thus a need for some general properties relating the structure (i.e., shape, number, and existence of waves or peaks) of the BTCs to the structure of the solid-fluid interaction mechanism. These properties should be as independent as possible of the interaction parameters, and they should help one both to discriminate among rival mecHanisms and to estimate the sensitivity of the shape of the BTCs to physicochemical parameters. This first of two papers describes the underlying concepts

- by Michel Sardin
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- Environmental Engineering, Civil Engineering, Water resources, Carbon Dioxide

We present a robust null space method for linear equality constrained state space estimation. Exploiting a degeneracy in the estimator statistics, an orthogonal factorization is used to decompose the problem into stochastic and deterministic components, which are then solved separately. The resulting dimension reduction algorithm has enhanced numerical stability, solves the constrained problem completely, and can reduce computational load by reducing the problem size. The new method addresses deficiencies in commonly used pseudo-observation or projection methods, which either do not solve the constrained problem completely or have unstable numerical implementations, due in part to the degeneracy in the estimator statistics. We present a numerical example demonstrating the effectiveness of the new method compared to other current methods.

- by Mark Butala
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- Signal Processing, Algorithm, Multidisciplinary, Parameter estimation