Dissertations / Theses on the topic 'Cell cycling performance simulation'

In line with the company-wide CS09 project being carried out at Volvo CE Components, Cell 14 will have changes in terms of distribution of machines and parts routing to meet the lean manufacturing goals established.  These changes are of course dependant on future production volumes, as well as lot sizing and material handling considerations.

In this context, an important emphasis is given to the awareness of the performance measures that support decision making in these production development projects.  By using simulation as a confirmation tool, it is possible to re-assess these measures by testing the impact of changes in complex situations, in line with the lean manufacturing principles.

The aim of the project is to develop a discrete event simulation model following the methodology proposed by Banks et al (1999).  A model of Cell 14 will be built using the software Technomatix Plant Simulation ® which is used by the Company and the results from the simulation study will be analyzed.

Le développement des lasers ultra-courts à de hautes intensités a permis l’émergence de nouveaux domaines de recherche en relation avec l’interaction laser-plasma. En particulier, les lasers petawatt femtoseconde ont ouvert la voie vers la possibilité de concevoir une nouvelle génération d’accélérateurs de particules. La modélisation numérique a largement contribué à l’essor de ce domaine d’accélération des électrons par sillage laser. Dans ce contexte, les codes Particle-In-Cell sont les plus répandus dans la communauté. Ils permettent une description fiable de l’interaction laser plasma et surtout de l’accélération par sillage laser.Cependant, une modélisation précise de la physique en jeu nécessite de recourir à des simulations 3D particulièrement coûteuses. Une manière pour accélérer efficacement ce type de simulations est l’utilisation de modèles réduits qui, tout en assurant un gain en temps de calcul très important, garantissent une modélisation fiable du problème. Parmi ces modèles, la décomposition des champs en modes de Fourier dans la direction azimutale est particulièrement adaptée à l’accélération laser plasma.Dans le cadre de ma thèse, j’ai implémenté ce modèle dans le code open-source SMILEI, dans un premier temps, avec un schéma différences finies (FDTD) pour discrétiser les équations de Maxwell. Néanmoins, ce type de solveur peut induire un effet de Cherenkov numérique qui corrompt les résultats de la simulation. Pour mitiger cet artéfact, j’ai également implémenté une version pseudo-spectrale du solveur de Maxwell qui présente de nombreux avantages en termes de précision numérique.Cette méthode est ensuite mise en oeuvre pour étudier l’impact de profils de lasers réalistes sur la qualité du faisceau d’électrons en exploitant des mesures réalisées sur le laser Apollon. Sa capacité à modéliser correctement les processus physiques présents est analysée en déterminant le nombre de modes nécessaires et en comparant les résultats avec ceux issus des simulations 3D en géométrie Cartésienne. Cette étude montre qu’inclure les défauts du laser mène à des différences dans les résultats et que ces derniers dégradent la performance des accélérateurs-laser plasma notamment en termes de quantité de charge injectée. Ces simulations, instructives pour les futures expériences d’accélération d’électrons par le laser Apollon, mettent en avant la nécessité d’inclure les mesures expérimentales dans la simulation et particulièrement celle du front de phase, pour aboutir à des résultats précis
The advent of ultra-short high-intensity lasers has paved the way to new and promising, yet challenging, areas of research in laser-plasma interaction physics. The success of building petawatt femtosecond lasers offers a promising path for designing future particle accelerators and light sources.Achieving this goal intrinsically relies on the combination of experiments and numerical modeling. So far, Particle-In-Cell (PIC) codes have been the ultimate tool to accurately describe the laser-plasma interaction especially in the field of Laser WakeField Acceleration (LWFA). Nevertheless, the numerical modeling of laser-plasma accelerators in 3D can be a very challenging task due to their high computational cost.A useful approach to speed up such simulations consists of employing reduced numerical modes which simplify the problem while retaining a high fidelity.Among these models, Fourier field decomposition in azimuthal modes for the cylindrical geometry is particularly well suited for physical problems with close to cylindrical symmetry, which is the case in LWFA.During my Ph.D., I first implemented this method in the open-source code SMILEI in the Finite Difference Time Domain (FDTD) discretization scheme for the Maxwell solver. However, this kind of solvers may suffer from numerical Cherenkov radiation (NCR). To mitigate this artifact, I also implemented Maxwell’s solver in the Pseudo Spectral Analytical Domain (PSATD) scheme which offers better accuracy of the results.This method is then employed to study the impact of realistic laser profiles from the Apollon facility on the quality of the accelerated electron beam. Its ability to correctly model the involved physical processes is investigated by determining the optimal number of modes and benchmarking its results with full 3D Cartesian simulations. It is shown that the imperfections in the laser pulse lead to differences in the results compared to theoretical profiles. They degrade the performance of laser-plasma accelerators especially in terms of the quantity of injected charge. These simulations, insightful for the future experiments of LWFA that will be held soon with the Apollon laser, put forward the importance of including realistic lasers in the simulation to obtain reliable results

The greening of air transport is the driver for developing technologies to reduce the environmental impact of aviation with the aim of halving the amount of carbon dioxide (COଶ) emitted by air transport, cutting specific emissions of nitrogen oxides (NO୶) by 80% and halving perceived noise by the year 2020. Fuel Cells (FC) play an important role in the new power generation field as inherently clean, efficient and reliable source of power especially when comparing with the traditional fossil-fuel based technologies. The project investigates the feasibility of using an electric hybrid system consisting of a fuel cell and battery to power a small model aircraft (PiperCub J3). In order to meet the desired power requirements at different phases of flight efficiently, a simulation model of the complete system was first developed, consisting of a Proton Exchange Membrane hybrid fuel cell system, 6DoF aircraft model and neural network based controller. The system was then integrated in one simulation environment to run in real-time and finally was also tested in hardware-in-the-loop with real-time control. The control strategy developed is based on a neural network model identification technique; specifically Model Reference Control (MRC), since neural network is well suited to nonlinear systems. To meet the power demands at different phases of flight, the controller controls the battery current and rate of charging/discharging. Three case studies were used to validate and assess the performance of the hybrid system: battery fully charged (high SOC), worst case scenario and taking into account the external factors such as wind speeds and wind direction. In addition, the performance of the Artificial Neural Network Controller was compared to that of a Fuzzy Logic controller. In all cases the fuel cell act as the main power source for the PiperCub J3 aircraft. The tests were carried-out in both simulation and hardware-in-the-loop.

This thesis is based on a project "Bifacial Photovoltaic Energy Production Analysis" to build a detailed simulation model system accurately simulate bifacial panel performance under real field radiation conditions and deployment configuration, and to predict its corresponding energy yield. To the author’s up-to-date knowledge, the model system is unpreceded among same type simulation software in complexity, details in consideration, ranges of deployment and parameters. The model system can also be used as a platform for more components and variables to be added on, such as adding on more rows of panel arrays to simulate bifacial solar farm scenario; and adding spectral information for more accurate analysis. The system components’ sub-models were carefully chosen based on a broad literature review in related aspects; especially in sky diffuse radiance, ground reflection, and bifacial solar cells. Built in MATLAB© based on mathematical expressions from above said models, the system consists of 5 bifacial panels and their racking as shading objects and the central panel performance is under investigation and has taken consideration of all possible panel azimuth and elevation combinations. Model simplification and resolution are carefully considered so to achieve a good balance in complexity, computation load and output accuracy. Output reliability is confirmed with other people’s work. Furthermore, the model has been fully checked and peer tested. Outputs under different parameter settings are analysed and discussed. Conclusions and recommended future work are provided at the end of the thesis.

La méthode LS-STAG est une méthode de type frontière immergée/cut-cell pour le calcul d’écoulements visqueux incompressibles qui est basée sur la méthode MAC pour grilles cartésiennes décalées, où la frontière irrégulière est nettement représentée par sa fonction level-set, résultant en un gain significatif en ressources informatiques par rapport aux codes MFN commerciaux utilisant des maillages qui épousent la géométrie. La version 2D est maintenant bien établie et ce manuscrit présente son extension aux géométries 3D avec une symétrie translationnelle dans la direction z (configurations extrudées 3D). Cette étape intermédiaire sera considérée comme la clé de voûte du solveur 3D complet, puisque les problèmes de discrétisation et d’implémentation sur les machines à mémoire distribuée sont abordés à ce stade de développement. La méthode LS-STAG est ensuite appliquée à divers écoulements newtoniens et non-newtoniens dans des géométries extrudées 3D (conduite axisymétrique, cylindre circulaire, conduite cylindrique avec élargissement brusque, etc.) pour lesquels des résultats de références et des données expérimentales sont disponibles. Le but de ces investigations est d’évaluer la précision de la méthode LS-STAG, d’évaluer la polyvalence de la méthode pour les applications d’écoulement dans différents régimes (fluides newtoniens et rhéofluidifiants, écoulement laminaires stationnaires et instationnaires, écoulements granulaires) et de comparer ses performances avec de méthodes numériques bien établies (méthodes non structurées et de frontières immergées)
The LS-STAG method is an immersed boundary/cut-cell method for viscous incompressible flows based on the staggered MAC arrangement for Cartesian grids where the irregular boundary is sharply represented by its level-set function. This approach results in a significant gain in computer resources compared to commercial body-fitted CFD codes. The 2D version of LS-STAG method is now well-established and this manuscript presents its extension to 3D geometries with translational symmetry in the z direction (3D extruded configurations). This intermediate step will be regarded as the milestone for the full 3D solver, since both discretization and implementation issues on distributed memory machines are tackled at this stage of development. The LS-STAG method is then applied to Newtonian and non-Newtonian flows in 3D extruded geometries (axisymmetric pipe, circular cylinder, duct with an abrupt expansion, etc.) for which benchmark results and experimental data are available. The purpose of these investigations is to evaluate the accuracy of LS-STAG method, to assess the versatility of method for flow applications at various regimes (Newtonian and shear-thinning fluids, steady and unsteady laminar to turbulent flows, granular flows) and to compare its performance with well-established numerical methods (body-fitted and immersed boundary methods)

碩士
國立高雄應用科技大學
機械與精密工程研究所
96
ABSTRACT PEMFC’s multiphysics models have established on the logical postulate. To illustrate, proton exchange membranes emphasize the model of water molecule transfer (migration, electroosmosis and diffusion), catalyst layer accents on a model of reaction dynamic, diffusion layer should consider the mix gas in a mathematics model of porous transfer, and gas channel and manifoldmodel have to focus on momentum transfer model. If we want to build a completed multiphysics model of PEMFC, we should resolve equations such as Migration’s Law, Diffusion’s Law and Convection’s Law such as basic Transfer Law and chemical electric electrochemistry reactive equation with Fuel cell. The complicated equations will accompany the increase of parameter to enlarge. In this article, we use COMSOL Multiphysics Modeling Multiphysics software to simulate and analyze proton exchange membrane fuel cell’s current density in cathode. In addition, we use the mass fraction of oxygen, water, and azotes to approximate the result of current distribute. We evidence the Cross-Flow Fields of PEMFC model, and analyze the speed of fluid and water flowing distribution to evaluate the efficiency of fuel cell. In this article, we use mathematics include describing Stefan-Maxwell equations of gas diffuse, Bulter-Volume equations of three phase electrochemical reaction in catalyst layer, energy equations of heat transfer and Darcy’s law of momentum transfer in the diffusion layer. As a consequence, we can find out three points in this article. First, increasing entrance pressure not only raises entrance hydrogen but also increases the concentration of oxygen mass fraction. Moreover, adding convection effective makes more hydrogen and oxygen to participate reaction to the catalyst layer. When the pressure increases to 2atm, the efficiency has postponed. Second, while the temperature becomes higher in inlet, and it makes current lower. Third, we can find the electrochemistry reaction rate of catalyst layer thickness minimum difference under 1μm in different distributed conditions of catalyst layer thickness. Key word：Proton Exchange Membrane、Fuel Cell、COMSOL

The performance of solid oxide fuel cells (SOFCs) at the cell and system levels is studied using computer simulation. At the cell level, a new model combining the cell micro and macro models is developed. Using this model, the microstructural variables of porous composite electrodes can be linked to the cell performance. In this approach, the electrochemical performance of porous composite electrodes is predicted using a micro-model. In the micro-model, the random-packing sphere method is used to estimate the microstructural properties of porous composite electrodes from the independent microstructural variables. These variables are the electrode porosity, thickness, particle size ratio, and size and volume fraction of electron-conducting particles. Then, the complex interdependency among the multi-component mass transport, electron and ion transports, and the electrochemical and chemical reactions in the microstructure of electrodes is taken into account to predict the electrochemical performance of electrodes. The temperature distribution in the solid structure of the cell and the temperature and species partial pressure distributions in the bulk fuel and air streams are predicted using the cell macro-model. In the macro-model, the energy transport is considered for the cell solid structure and the mass and energy transports are considered for the fuel and air streams. To demonstrate the application of the cell level model developed, entitled the combined micro- and micro-model, several anode-supported co-flow planar cells with a range of microstructures of porous composite electrodes are simulated. The mean total polarization resistance, the mean total power density, and the temperature distribution in the cells are predicted. The results of this study reveal that there is an optimum value for most of the microstructural variables of the electrodes at which the mean total polarization resistance of the cell is minimized. There is also an optimum value for most of the microstructural variables of the electrodes at which the mean total power density of the cell is maximized. The microstructure of porous composite electrodes also plays a significant role in the mean temperature, the temperature difference between the hottest and coldest spots, and the maximum temperature gradient in the solid structure of the cell. Overall, using the combined micro- and micro-model, an appropriate microstructure for porous composite electrodes to enhance the cell performance can be designed. At the system level, the full load operation of two SOFC systems is studied. To model these systems, the basic cell model is used for SOFCs at the cell level, the repeated-cell stack model is used for SOFCs at the stack level, and the thermodynamic model is used for the balance of plant components of the system. In addition to these models, a carbon deposition model based on the thermodynamic equilibrium assumption is employed. For the system level model, the first SOFC system considered is a combined heat and power (CHP) system that operates with biogas fuel. The performance of this system at three different configurations is evaluated. These configurations are different in the fuel processing method to prevent carbon deposition on the anode catalyst. The fuel processing methods considered in these configurations are the anode gas recirculation (AGR), steam reforming (SR), and partial oxidation reformer (POX) methods. The application of this system is studied for operation in a wastewater treatment plant (WWTP) and in single-family detached dwellings. The evaluation of this system for operation in a WWTP indicates that if the entire biogas produced in the WWTP is used in the system with AGR or SR fuel processors, the electric power and heat required to operate the plant can be completely supplied and the extra electric power generated can be sold to the electrical grid. The evaluation of this system for operation in single-family detached dwellings indicates that, depending on the size, location, and building type and design, this system with all configurations studied is suitable to provide the domestic hot water and electric power demands. The second SOFC system is a novel portable electric power generation system that operates with liquid ammonia fuel. Size, simplicity, and high electrical efficiency are the main advantages of this environmentally friendly system. Using a sensitivity analysis, the effects of the cell voltage at several fuel utilization ratios on the number of cells required for the SOFC stack, system efficiency and voltage, and excess air required for thermal management of the SOFC stack are studied.

碩士
國立臺灣海洋大學
輪機工程系
94
The main aim of this thesis study is to perform an investigation into the performance related problems with proton exchange membrane fuel cell (PEMFC) using CFDRC software. There are a great number of operating and physical parameters, such as pressure, temperature, humidity, fuel composition, and flow channel influencing the performance of a PEMFC. Mathematical model for a three-dimensional fuel cell are performed including fluid flows, heat transfer, mass transfer, electrochemical kinetics, and electric charge transport. Numerical simulation area includes the channel of positive and negative poles, catalyst, diffusion layers, and membrane within the fuel cell. The numerical model is coupled with a computational fluid dynamics technology that includes the porous gas diffusion electrodes and the reactant flow channels. Three-dimensional spatial distributions of current, temperature, species concentrations, pressure and water are illustrated and discussed in detail by numerical simulation. In proton exchange membrane fuel cells it is particularly important to maintain appropriate pressure and water content in the electrolyte membrane. The water balance depends on the coupling between diffusion of water, pressure variation, and the electro-osmotic drag in the membrane. Last, effects of pressure and humidification temperature of inlet stream and rib-to-channel ratio on the cell performance have been analyzed.

碩士
國立臺北科技大學
工業工程與管理研究所
97
The product differentiation and customization strategy force the production system to shift from mass to high variety low volume production. In recent years, cell production system is proposed to cope with the requirement. In this research, we use the example case from a reference book "Learning to See" for experimental study. Six cell production models were constructed with simulation tool eM-Plant. The number of cells, batch size, rate of setup reduction, methods of kanban assignment are the experimental factors. In supermarket pull supply mode, the multi-cell production system with multi-skill operator, one-piece transfer batch, and dedicated cell rule performs better for demands with high variety low volume and low variety high volume. Setup reduction will make the gap of performance measure among the six cell production models smaller. In make-to-order supply mode, the multi-cell production system with multi-skill operator, one-piece transfer batch, and dedicated cell rule performs better for demands with high variety low volume. However, the single-cell production system with one-piece transfer batch performs better for demands with low variety high volume. In make-to-order supply mode, number of cells should be adjusted according to the shifting of product variety and volume.

碩士
國立高雄第一科技大學
運籌管理所
98
Due to rapid changes in business operation environments, ordering patterns have been shifted from low ordering frequencies with large volumes to that of higher frequencies and smaller volumes. Traditional production lines based on large volume requirement assumption have also been re-designed in cell production lines. Simulation performance analyses among different types of production lines are the focus of the research. A Taiwan hardware (door lock) manufacturer is taken as the study case. Current assembly-line conveyor layout of the case company was designed on mass production basis, which divided processes as detailed as possible to simplify the task and the process handled by each operator. However, such design required a large number of operators and reduced production flexibility. When it handles orders with higher ordering frequencies and smaller quantities, idle labor and labor cost will increase. Bottleneck stations will also shift from being managed effectively. Based on literatures, three types of cell production lines are considered along with current conveyor production line. Simulation mode for each line is constructed using AREA and is tested. Performances among these production lines are compared under selected criteria. Based on simulation results, following conclusions are drawn: 1. Balancing the production lines, different production lines are designed and are compared under the same basis. The short flow line results in a unit operation cost NTD2.97 which is NTD0.82 less than that of current conveyer production line. 2. Meanwhile, only NTD 0.80 unit line-change cost will be caused for short flow line, compared with NTD 1.04 of conveyer flow line. 3. However, cell production lines are usually designed by deleting, combining, or re-arranging tasks. Job enrichment and job training are usually required for operators.

Cereal rye (Secale cereale, L., CR) is the most commonly utilized cover crop species within the United States. Yet, the total land area planted to CR on an annual basis remains relatively low despite its numerous proven environmental benefits. The relatively low rates of CR adoption could be due to a dearth of knowledge surrounding certain agronomic and economic components of CR adoption. Currently, there exists knowledge gaps within the scientific literature regarding CR performance, N cycling, and associated economic risk. Thus, to address the above-mentioned knowledge gaps, three individual studies were developed to: i) investigate the fate of scavenged CR nitrogen (N) amongst soil N pools, ii) assess the suitability of visible-spectrum vegetation indices (VIs) to predict CR biomass and nutrient accumulation (BiNA), and iii) characterize the economic risk of CR adoption at a regional scale over time.

In the first study, ¹⁵N, a stable isotope of N, was used in an aerobic incubation to track the fate of CR root and shoot N among the soil microbial biomass, inorganic, and organic N pools, as well as explore CR N bioavailability over a simulated corn growing season. In this study, the C:N ratio of the shoot residues was 16:1 and the roots was 31:1 and differences in residue quality affected the dynamics of CR N release from each residue type. On average, 14% of whole plant CR N was recovered in the soil inorganic N pool at the final sample date. Correspondingly, at the final sampling date 53%, 33%, and less than 1% of whole plant CR N was recovered as soil organic N, undecomposed residue, and as microbial biomass N, respectively. Most CR N remained unavailable to plants during the first cash crop growing season subsequent to termination. This knowledge could support the advancement of N fertilizer management strategies for cropping systems containing cereal rye.

In the second study, a commercially available unmanned aerial vehicle (UAV) outfitted with a standard RGB sensor was used to collect aerial imagery of growing CR from which visible-spectrum VIs were computed. Computed VIs were then coupled with weather and geographic data using linear multiple regression to produce prediction models for CR biomass, carbon (C), N, phosphorus (P), potassium (K), and sulfur (S). Five visible-spectrum VIs (Visible Atmospherically Resistant Index (VARI), Green Leaf Index (GLI), Modified Green Red Vegetation Index (MGRVI), Red Green Blue Vegetation Index (RGBVI), and Excess of Green (ExG)) were evaluated and the results determined that MGRVI was the best predictor for CR biomass, C, K, and S and that RGBVI was the best predictor for CR N and P. Furthermore, the final prediction models for the VIs selected as the best predictors developed in this study performed satisfactorily in the prediction of CR biomass, C, N, P, K, and S producing adjusted R² values of 0.79, 0.79, 0.75, 0.81, 0.81, and 0.78, respectively. The results of this study have the potential to aid producers in making informed decisions regarding CR and fertility management.

In the final study, agronomic data for corn and soybean cropping systems with and without CR was collected from six states (Illinois, Indiana, Iowa, Minnesota, Missouri, and Wisconsin) and used within a Monte-Carlo stochastic simulation to characterize the economic risk of adopting CR at a regional scale over time. The results of this study indicate that average net returns to CR are always negative regardless of CR tenure primarily due to added costs and increased variability in cash crop grain yields associated with CR adoption. Further, the results demonstrate that the additional risk assumed by adopting CR is not adequately compensated for with current CR adoption incentive programs and that the risk premium necessary can be 1.7 to 15 times greater than existing incentive payments. Knowledge gained from this study could be used to reimagine current incentive programs to further promote adoption of CR.

碩士
南榮科技大學
工程科技研究所碩士班
105
A three-dimensional numerical model of multi-component mixture transport is presented and implemented in COMSOL Multiphysics to study the affections of the operation parameters and the physical properties on the performance and the electric fields in the high temperature proton exchange membrane fuel cell (PEMFC) with 0.7847mm×1.0mm×20mm. The modeled section of the high temperature PEMFC consist of the gas channels, the anode, the cathode, and the electrodes. The model contains the conservation of mass, momentum, species, and charge with electrochemical reactions. According to the numerical results, both the hydrogen mass fraction in the anode and the oxygen mass fraction in the cathode decrease along the flow direction, but the water mass fraction will increase. The maximum normal current density occurs at the inlet of the cathode. All the parameters, such as the physical properties of the porous electrodes and the operation conditions of the fuel cells, have unapparent effects upon the fuel cell performance and the electric fields at low current density. For high current density, increasing the fuel cell operation temperature, inlet pressure and outlet pressure, the porous material permeability, the porous material conductivity, the bipolar plate conductivity, the cathode stoichiometry, and reducing the fuel cell tortuosity of the porous media can improve the PEMFC performance and the electric fields.

碩士
華梵大學
電子工程學系碩士班
99
The main purpose of this thesis is to study the characteristic optimization of the structure of an amorphous silicon thin-film solar cell. The experiment is divided into two major parts. In the first part, we used 3D TCAD simulation software to study the thickness of amorphous p, i, and n layers as well as concentration of p and n layers of a typical amorphous silicon thin-film solar cell for characteristic optimization. In the second part, we studied the grating structure of an amorphous silicon thin-film solar cell by applying the best result of the first part to it. In the beginning, for the study of a typical amorphous silicon thin-film solar cell, we started our experiment with a sequence of adjusting the thickness of p, i, and n layers with other parameters fixed to obtain the optimum photoelectric conversion efficiency. We then changed the doping concentration of p, and n layers and finally got the best characteristic result of a typical amorphous silicon thin-film solar cell. For the second part of the study, we made use of the result obtained from the first part as a foundation. Afterward, we added a grating structure on it. We tried seven different grating structures on a typical amorphous silicon thin-film solar cell by varying the height, period, and duty cycle of each grating inorder to improve its photoelectric conversion efficiency. We have designed a special amorphous silicon thin-film solar cell structure which can improve photoelectric conversion efficiency more than 20%.