Дисертації з теми "SOFC stack"
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Tan, Wee Choon. "Numerical Investigation of Ammonia-fueled Planar SOFC Stack-Internal and External Cooling Effects." Kyoto University, 2018. http://hdl.handle.net/2433/235990.
Повний текст джерелаMarra, Dario. "Development of solid oxide fuel cell stack models for monitoring, diagnosis and control applications." Doctoral thesis, Universita degli studi di Salerno, 2013. http://hdl.handle.net/10556/1014.
Повний текст джерелаIn the present thesis different SOFC stack models have been presented. The results shown were obtained in the general framework of the GENIUS project (GEneric diagNosis Instrument for SOFC systems), funded by the European Union (grant agreement n° 245128). The objective of the project is to develop “generic” diagnostic tools and methodologies for SOFC systems. The “generic” term refers to the flexibility of diagnosis tools to be adapted to different SOFC systems. In order to achieve the target of the project and to develop stack models suitable for monitoring, control and diagnosis applications for SOFC systems, different modeling approaches have been proposed. Particular attention was given to their implementability into computational tools for on-board use. In this thesis one-dimensional (1-D), grey-box and blackbox stack models, both stationary and dynamic were developed. The models were validated with experimental data provided by European partners in the frame of the GENIUS project. A 1-D stationary model of a planar SOFC in co-flow and counter-flow configurations was presented. The model was developed starting from a 1- D model proposed by the University of Salerno for co-flow configuration (Sorrentino, 2006). The model was cross-validated with similar models developed by the University of Genoa and by the institute VTT. The crossvalidation results underlined the suitability of the 1-D model developed. A possible application of the 1-D model for the estimation of stack degradation was presented. The results confirmed the possibility to implement such a model for fault detection. A lumped gray-box model for the simulation of TOPSOE stack thermal dynamics was developed for the SOFC stack of TOPSOE, whose experimental data were made available in the frame of the GENIUS project. Particular attention was given to the problem of heat flows between stack and surrounding and a dedicated model was proposed. The black-box approach followed for the implementation of the heat flows and its reliability and accuracy was shown to be satisfactory for the purpose of its applications. The procedure adopted turned out to be fast and applicable to other SOFC stacks with different geometries and materials. The good results obtained and the limited calculation time make this model suitable for implementation in diagnostic tools. Another field of application is that of virtual sensors for stack temperature control. Black-box models for SOFC stack were also developed. In particular, a stationary Neural Network for the simulation of the HEXIS stack voltage was developed. The analyzed system was a 5-cells stack operated up to 10 thousand hours at constant load. The neural network exhibited very good prediction accuracy, even for systems with different technology from the one used for training the model. Beyond showing excellent prediction capabilities, the NN ensured high accuracy in well reproducing evolution of degradation in SOFC stacks, especially thanks to the inclusion of time among model inputs. Moreover, a Recurrent Neural Network for dynamic simulation of TOPSOE stack voltage and a similar one for a short stack built by HTc and tested by VTT were developed. The stacks analyzed were: a planar co-flow SOFC stack (TOPSOE) and a planar counter-flow SOFC stack (VTT-HTc). All models developed in this thesis have shown high accuracy and computation times that allow them to be implemented into diagnostic and control tool both for off-line (1-D model and grey-box) and for on-line (NN and RNNs) applications. It is important noting that the models were developed with reference to stacks produced by different companies. This allowed the evaluation of different SOFC technologies, thus obtaining useful information in the models development. The information underlined the critical aspects of these systems with regard to the measurements and control of some system variables, giving indications for the stack models development. The proposed modeling approaches are good candidates to address emerging needs in fuel cell development and on-field deployment, such as the opportunity of developing versatile model-based tools capable to be generic enough for real-time control and diagnosis of different fuel cell systems typologies, technologies and power scales. [edited by author]
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Al-Masri, Ali [Verfasser], Detlef [Akademischer Betreuer] Stolten, and Wilfried [Akademischer Betreuer] Becker. "Numerische Modellierung der thermomechanischen Fluid-Struktur-Interaktion im SOFC-Stack / Ali Al-Masri ; Detlef Stolten, Wilfried Becker." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/113059064X/34.
Повний текст джерелаBRUNACCINI, GIOVANNI. "Investigation on low and high temperature fuel cell components and their evaluation in short stack configuration." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2010. http://hdl.handle.net/2108/1300.
Повний текст джерелаResearch activities on solid oxide (SOFC) or polymer electrolyte membrane (PEMFC) fuel cells are currently focused on performance and lifetime enhancement as well as costs reduction. These aspects are relevant to make such systems more attractive for the market, both for stationary and automotive applications. From this point of view, an increase of temperature (from 80°C to 110-120°C) appears necessary for PEMFC technology (high temperature PEMFC, or HTPEMFC). This would allow more resistance to CO contaminants in the fuel, better thermal and water management and a better efficiency for co-generation. On the contrary, SOFC technology is moving towards intermediate temperature (IT-SOFC); this would allow cost reduction while developing planar cells, due to less critical construction processes and an increase of stability. These ways to enhance the fuel cells applications are well studied for single cell but the scale-up process to significant power production devices needs specific investigations. Moreover, different technologies need different field test procedures, tailored on the specific application sectors. In this Ph.D. thesis, fuel cell devices exploiting either solid oxide or polymer electrolyte technologies, were tested for specific applications. In particular, 1kW fuel cell stacks were tested in order to verify the possibility of fuel cell use in small size applications. Nowadays, HT-PEMFC devices are creating lot of interest for FC technology development. Anyway, despite a deep knowledge of material properties, the assessment of the new materials at stack level have undergone only few studies. In this research activity this aspect was investigated. Moreover, IT-SOFC technology is considered valuable for stationary applications and distributed energy production, using cheap fuels and a highly efficient electrochemical process. Nevertheless, for residential energy consumption, the studied SOFC device can be considered not as a downscaled device for laboratory study, but as the base to develop a complete system. This Ph.D. thesis involves considerations for both stationary and automotive applications, by analysing fuel cells stack with a size large enough to be considered a proof-of-concept. In other words, the size appears sufficient to investigate main phenomena visible in larger stack oriented to real world applications. The whole activity can be divided in two lines: 1) tests of HT-PEMFC short stacks that were carried out to evaluate their performance in typical automotive working conditions (current, temperature, humidification, pressure) and to establish an optimal operating point. 2) tests of IT-SOFC stacks in natural gas, in order to evaluate performance decay and its response to detrimental effects due to thermal and redox cycles that can appear in "out of laboratory" usage. Diagnostic analysis such as current interrupt method and electrochemical impedance spectroscopy completed the study by supplying information about the optimization of stack assembling procedure. The whole experimental activities were carried out in laboratory, to accurately control the process variables; nevertheless, the recorded performances are anyway meaningful with respect to real world applications, once defined tailored working conditions by a good compromise between performances and costs.
Allen, Jeremy L. "The Effect of Baffle Arrangements on Flow Uniformity in a Manifold for a Unique Solid Oxide Fuel Cell Stack Design." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1320851931.
Повний текст джерелаSivasankaran, Visweshwar. "Manufacturing and characterization of single cell intermediate-temperature solid oxide fuel cells for APU in transportation application." Thesis, Dijon, 2014. http://www.theses.fr/2014DIJOS027/document.
Повний текст джерелаThe fabrications of large area IT-SOFC planar cell by new simple and cost effective process were explained. The optimization of the new process with respect to pore formers, thickness of layers, sintering temperature were performed. The electrochemical results of 10cm2 performed in Fiaxell open flange set up were detailed with respect to different configuration. Long term ageing performance tests of single cells were conducted in Fiaxell device and results are discussed. Preparation of new test bench and stacking process performed till now were briefed
Price, Robert. "Metal/metal oxide co-impregnated lanthanum strontium calcium titanate anodes for solid oxide fuel cells." Thesis, University of St Andrews, 2018. http://hdl.handle.net/10023/16018.
Повний текст джерелаHyde, Andrew Justin. "A Portable Generator Incorporating Mini-Tubular Solid Oxide Fuel Cells." The University of Waikato, 2008. http://hdl.handle.net/10289/2582.
Повний текст джерелаKornely, Michael [Verfasser], and E. [Akademischer Betreuer] Ivers-Tiffée. "Elektrische Charakterisierung und Modellierung von metallischen Interkonnektoren (MIC) des SOFC-Stacks / Michael Kornely ; Betreuer: E. Ivers-Tiffée." Karlsruhe : KIT Scientific Publishing, 2012. http://d-nb.info/1184493332/34.
Повний текст джерелаLiu, Zhengyang. "Characterization and Failure Mode Analysis of Cascode GaN HEMT." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/49580.
Повний текст джерелаMaster of Science
Sarda, Venkatesh Verfasser], Lorenz [Akademischer Betreuer] Singheiser, and Werner [Akademischer Betreuer] [Lehnert. "Degradation phenomena in the anode side of solid oxide fuel cell (SOFC) stacks / Venkatesh Sarda ; Lorenz Singheiser, Werner Lehnert." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1156924243/34.
Повний текст джерелаTARALASHVILI, TAMAR. "Interstate soft conflicts, trade and FDI." Doctoral thesis, Università Politecnica delle Marche, 2021. http://hdl.handle.net/11566/291111.
Повний текст джерелаThis thesis contributes to the literature on the economic impact of interstate conflicts. The thesis contributes by focusing on the empirical analysis of effect of soft conflicts on bilateral trade and FDI. Interstate soft conflicts arising from the failure of diplomacy, when a military operation seems too radical, can act as a policy tool and have a negative impact on bilateral relations. And since nowadays countries tend to avoid violence and militarized intervention, interstate soft conflicts become explicitly interesting to study. The empirical approach is based on the use of balanced panel data with annual observations and on a theory-consistent structural gravity framework augmented by a new measure of interstate soft conflict. The results from standard gravity estimators show that interstate soft conflicts have a statistically significant and sustained negative impact on both bilateral trade and FDI stocks, regardless of the control for omitted variables (presence of regional trade agreements, different types of sanctions and militarized interstate disputes) and different model specifications. The results demonstrate that the impact of different types of interstate soft conflicts – indirect, against the country in general and direct, against a specific organization or firm - is quite heterogeneous between trade and FDI. Both types of soft conflicts have a significant negative impact on trade, while in case of FDI, we found significance only for direct cases.
Ferreira, Ronaldo Rodrigues. "The transactional HW/SW stack for fault tolerant embedded computing." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/114607.
Повний текст джерелаFault tolerance implementation in embedded systems is challenging because the physical constraints of area occupation, power dissipation, and energy consumption of these systems. The need for optimizing these three physical constraints while doing computation within the available performance goals and real-time deadlines creates a conundrum that is hard to solve. Classical fault tolerance solutions such as triple and dual modular redundancy are not feasible due to their high power overhead or lack of efficient and deterministic error recovery. Existing techniques, although some of them reduce the power and area overhead, incur heavy perfor- mance penalties and most of the time do not assume a feasible fault model. This dissertation introduces the Transactional HW/SW Stack, or simply Stack, to effi- ciently manage the area, power, fault coverage, and performance conundrum. The Stack introduces a new compilation strategy that assembles programs into Transac- tional Basic Blocks, together with a novel microprocessor, the TransactiOnal Basic Block Architecture (ToBBA), which provides fine-grained error detection and deter- ministic error rollback and elimination using the Transactional Basic Blocks (TBBs) both as a container for errors and as a small unit of data checkpointing. Two so- lutions to sustain the TBB semantics in hardware are introduced: software- and hardware-based. Stack’s area, power, performance, and coverage were evaluated using ToBBA’s hardware implementation model. The Stack attains an error correc- tion coverage of 99.35% with 2.05 power overhead within an area overhead of 2.65. The Stack also presents a performance overhead of 1.33 or 1.54, depending on the hardware model adopted to support the TBB.
Weisser, Peter. "The Admiral's Carrot and Stick: Zheng He and the Confucius Institute." CSUSB ScholarWorks, 2018. https://scholarworks.lib.csusb.edu/etd/625.
Повний текст джерелаYan, Yulin Verfasser], Werner [Akademischer Betreuer] [Lehnert, and Lorenz [Akademischer Betreuer] Singheiser. "Degradation study of SOC stacks with impedance spectroscopy / Yulin Yan ; Werner Lehnert, Lorenz Singheiser." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1186069570/34.
Повний текст джерелаYan, Yulin [Verfasser], Werner [Akademischer Betreuer] Lehnert, and Lorenz [Akademischer Betreuer] Singheiser. "Degradation study of SOC stacks with impedance spectroscopy / Yulin Yan ; Werner Lehnert, Lorenz Singheiser." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1186069570/34.
Повний текст джерелаFürthauer, Sebastian [Verfasser], Frank [Akademischer Betreuer] Jülicher, and Holger [Akademischer Betreuer] Stark. "Active Chiral Processes in Soft Biological Matter / Sebastian Fürthauer. Gutachter: Frank Jülicher ; Holger Stark. Betreuer: Frank Jülicher." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://d-nb.info/1068148063/34.
Повний текст джерелаLongbottom, Todd L. M. S. "Climatic and topographic controls on soil carbon storage and dynamics in the Indian Himalaya: Potential carbon cycle and climate change feedbacks." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342106746.
Повний текст джерелаCicero, Simone. "Modelli statistici per il calcolo dello stock di carbonio nei suoli: applicazione al database della Regione Emilia Romagna." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Знайти повний текст джерелаRussi, Luigi. "modeling the pressure drop and thermal profile of a novel solid oxide fuel cell stack design with a homogenized approach." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Знайти повний текст джерелаThull, Jean-Paul. "Management of stock effluent spillage from trucks in New Zealand." Lincoln University, 1999. http://hdl.handle.net/10182/778.
Повний текст джерелаHuling, Kelsey Rose Stark. "Tubules to Tracebacks: Animating sensation through material." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555451814841903.
Повний текст джерелаQuibel, Edouard. "Impacts de la préparation du sol lors de la phase de plantation sur la dynamique des matières organiques et la fonction de stockage du Carbone dans les sols forestiers Impact du travail du sol localisé sur le stock de carbone organique du sol et la communauté microbienne en condition de plantation en forêt tempérée Changes in soil organic carbon stock by mechanical site preparation in oak and pine plantations on an acidic soil Impact du travail du sol localisé sur le stock de carbone organique du sol et la communauté microbienne en condition de plantation sur sol à engorgement temporaire en eau." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR017.
Повний текст джерелаIn the current context of climate change, forests are seen as a carbon sinj, i. e. they can contribute to C storage. This storage can take place in the medium term in woody biomass and in the longer term in soils. In order to preserve forests and their C storage capacity, foresters have to carry out artificial regeneration (i. e. planting) to adapt stands to future conditions. To ensure the success of this planting stage, it is sometimes necessary to remove some constraints such as the presence of blocking vegetation, compaction or waterlogging of soil. To do this, a Mechanical Soil Preparation (MSP) can be carried out prior to plantin. This PMS work may cause a Soil Organic Carbon (SOC) loss by mineralization. In order to limit the negative effects of PMS, tools have been developed to prepare the soil only in a localized area, on the future line of plants. These tools have been developed to respond to some situations. The Reversible Scarifier® (RS) tool and the Multifunction Subsoiler (MFSS) are designed to prepare soils compacted and/or invaded by eagle fern (Pteridium aquilinum). The Razherb® (RAZ) and the Culti 3B® (C3B) tools are designed to prepare compacted and/or waterlogged soils invaded by Molinia caerulea (Molinia caerulea). First, based on 6 sites belonging to the ALTER network, the impact of the RS tool alone and in combination with MFSS on COS was evaluated 5 years after the PMS. This evaluation therefore focused on the quantity and quality of SOC. The impact of the tools on the microbial functioning of the soil was also tested. This part showed a decrease in the stock of C and mineralized C by the microbial community under controlled conditions localized to the prepared area but impacts at the forest stand scale depend on soil characteristics. Second, based on 3 sites belonging to the PILOTE network, the impact of the combination of RAZ+C3B tools on SOC stocks and potential mineralization was evaluated. On these soils with temporary waterlogging, adecrease in SOC stock was observed in the prepared area only in the topsoil (0-30 cm). On the other hand, both SOC stock on the full profile and the potential mineralization did not have a significant effect on the prepared area. At the forest stand scale, the RAZ+C3B combination had no effect on SOC stock or potential mineralization. This thesis work suggests that although they had an impact on the prepared area, the tools used in this study had low influence on the soil at the forest plot scale. However, these observations may vary according to the soil type and have a significant impact on the forest plot
Oliveira, Daniele Costa de. "Potencial de sequestro de carbono no solo e dinâmica da matéria orgânica em pastagens degradadas no Brasil." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-17072018-184226/.
Повний текст джерелаPastures are the main land use in the world, occupying two-thirds of the world\'s arable land and three quarters of agricultural areas of Brazil. When well-managed, pastures have a high capacity to store SOC, but they may lose up to 50 % of stock SOC when in an advanced stage of degradation. The objective of this work was to quantify the potential of carbon sequestration and to evaluate soil organic matter dynamics in the conversion of degraded pastures to well-managed in Brazil. We evaluated changes in stocks SOC in pastures in Brazil through a meta-analysis, determining the management factors and the rates of stocks SOC changes in different pasture status. In seven cronossequences located in Vila Bela da Santíssima Trindade (MT), Nova Xavantina (MT), Conquista D\'Oeste (MT), Dueré (TO), Carmolândia (TO) and Paraíso (TO) were determined the changes in the quantity and quality of soil organic matter (SOM). C and N stocks and rates of local variations were determined. The quality of the SOM was evaluated through isotopic analysis, physical fractionation, C management index (CMI), degree of humification (HFIL) and C content in microbial biomass (MB-C). Through the meta-analysis it was estimated that in Brazil degraded pastures present a reduction of stocks SOC of 0.13 Mg ha-1 year -1. Nominal pastures were able to increase stock SOC, while improved pastures did not always maintain stocks similar to native vegetation. The recovery of pastures promotes the accumulation of C in the soil at the rate of 0.40 Mg ha-1 year -1. Meeting the recovery goal of 30 million ha of pasture will result in the accumulation of 12 Tg C ha-1year -1. The degradation of pastures in the states of Mato Grosso and Tocantins reduces C stocks in the soil at a rate of 0.06 Mg C ha-1 year-1. While the recovery of degraded pastures has the potential to increase C stocks in the soil with rate of 0.12 Mg C ha-1 year-1. In the pastures evaluated, about 54% of the C originates from the cultivated grasses. The organic fraction was the most sensitive to LUC, promoting the decrease of C stocks in this fraction. Pasture implantation has a negative impact on SOM quality, with a reduction in the CMI of up to 70%; however, if managed well, the CMI of pastures may be higher than that of native vegetation. The MB-C and degree of humification were not altered after the implantation or the recovery of the pastures. Changes in C stocks in SOM fractions and CMI were the most efficient indicators of changes in SOM quality in pastures. The recovery of degraded pastures promotes an increase in C stock in the soil and an improvement in the quality of the MOS.
Chen, Tsung-Ting, and 陳宗廷. "Thermal stress analysis of a planar SOFC stack." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/a2gy3r.
Повний текст джерела國立中央大學
機械工程研究所
94
Solid oxide fuel cells (SOFCs) utilize ceramics as the anode, electrolyte, and cathode (often called a positive electrode-electrolyte-negative electrode, PEN) and operate at high temperatures such that they have the highest efficiencies of all fuel cells. The high-temperature operation, however, gives rise to significant thermal stresses caused from the mismatch of coefficient of thermal expansion (CTE) and temperature gradients in the SOFC system. Therefore, a comprehensive thermal stress analysis of SOFC stack is necessary for the success in design and operation of a SOFC system. The aim of this study is, by using finite element simulation, to characterize the thermal stress distribution in a planar SOFC stack during transients and steady operation. An integrated electrochemical and thermal analysis was first conducted to generate the temperature profiles in a 3-cell SOFC stack during various start-up and steady stages. The obtained temperature fields within the cell stack were subsequently applied to a thermal stress analysis using a 3-D finite element model of a 3-cell stack. Each unit cell consists basically of a PEN assembly, interconnect, nickel mesh, and gas-tight glass-ceramic seals. Incorporation of the glass-ceramic sealant, which was never considered in other previous studies, into the 3-cell FEA model would produce more realistic results in thermal stress analysis. In particular, the effect of viscous behavior of glass-ceramic sealant on thermal stress distribution within the cell stack was investigated. In addition, the effects of stack support condition, temperature gradient, cyclic operation were also characterized. Modeling results indicated that a change in the support condition at the bottom frame of the 3-cell stack would not cause significant changes in the thermal stress distribution. Thermal stress distribution did not differ significantly in each unit cell within the 3-cell stack due to a negligible out-of-plane thermal stress gradient. By considering the viscous characteristics of glass-ceramic sealant at temperatures above the glass-transition temperature (Tg), relaxation of thermal stresses in PEN and glass-ceramic sealant was predicted. Effect of operating cycles on the variation of thermal stress was also simulated and the results indicated that a significant increase in thermal stress in PEN and glass-ceramic sealant would be expected with increasing cycle number.
Chen, Chen-yin, and 陳貞吟. "Development and Modification of Interconnet Materials for SOFC Cell Stack." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/41798682149762083371.
Повний текст джерела國立中央大學
能源工程研究所
95
Two choices for interconnect materials are ceramic and metallic alloy materials. To combine the advantages of these materials, we’ll coat high electronic conductivity ceramic materials, such as lanthanide series metal oxides (La1-xCaxCrO3, LCC). LCC powder materials were synthesized by the glycine-nitrate-process(GNP). Our study included different sintering times and temperatures, concentrations of coating ceramic materials, and thickness of coating. The effects of different test conditions are related to performance. From XRD results, longer sintering time could also induce the undesired formation of FeCr¬2O4. From SEM results, we clearly saw that the coating layer was quite smooth and the LCC20-coated Crofer22 composite was suitable as an interconnect in SOFC since it could prevent Cr from oxidation and volatilization at high internal temperatures under SOFC operation conditions. For ASR measurements, the ASR of fresh Crofer22 was measured at 1.0361 mΩ-cm2. After 100 hr oxidation, the result of non-coated sample was 3.0740 mΩ-cm2. With a similar setup to LCC20-coated samples, results were 0.9263 mΩ-cm2. These results improved the ability of the composite interconnect to promote electronic conductivity at high internal temperatures. Through comprehensive studies, we seek to develop ceramic/metal composite interconnect materials with low cost, high electronic conductivity, great high temperature characteristics, high oxidation resistance, puncture resistance, and stability under multiple chemical gases.
邱重銘. "Cold Start-up Dynamic Simulation of a Micro SOFC Stack." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/23912456521776763420.
Повний текст джерелаChen, An-Hsin, and 陳安信. "Thermal Stress Analysis of a Planar SOFC Stack with Mica Sealants." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/46605163957270321781.
Повний текст джерела國立中央大學
機械工程研究所
95
The aim of this study is, by using finite element analysis (FEA), to characterize the thermal stress distribution in a planar solid oxide fuel cell (SOFC) stack with a compressive sealing design at various stages. The temperature profiles generated by an integrated thermo-electrochemical model were applied to calculate the thermal stress distributions in a multiple-cell SOFC stack by using a three-dimensional (3-D) FEA model. The constructed 3-D FEA model consists of the complete components used in a practical SOFC stack, including positive electrode-electrolyte-negative electrode (PEN) assembly, interconnect, nickel mesh, glass-ceramic seals, and compressive mica seals. Incorporation of the compressive mica sealant, which was never considered in previous studies, into the 3-D FEA model would produce more realistic results in thermal stress analysis and enhance the reliability of predicting potential failure locations in an SOFC stack. The stress fields at different assembly temperatures and the effect of anisotropic elastic moduli of mica sealant were investigated. The thermal stresses in each component at room temperature after assembly were increased when the assembly temperature was increased form 200 oC to 300 and 400 oC. However, the assembly temperature did not affect the thermal stress distributions significantly at steady-operation and shutdown stages. Two different elastic moduli of mica material were used in the FEA model and the simulation results indicated that the critical stresses in each component at a specific stage were comparable except for the mica sealants. Thermal stress distributions obtained in the current study were also made a comparison with those in a rigid-bonding sealing design. The thermal stresses in each component were larger at the after-assembly and shutdown stages but lower in the operation condition for the rigid-bonding type of sealing design. That trend of stress distribution was opposite to that for a compressive sealing design used in the current study.
Huang, Ling-Hao, and 黃令豪. "Effect of Sealing Design on the Thermal Stresses in SOFC Stack." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/gxsju4.
Повний текст джерела國立中央大學
機械工程研究所
96
Solid oxide fuel cell (SOFC) usually operates at a high temperature with a good fuel flexibility and a high efficiency. However, the coefficient of thermal expansion mismatch between ceramic electrodes and metallic components under this high temperature gives rise to a large amount of stresses in the cell stack. In order to predict the durability and reliability of a SOFC stack, a comprehensive three-dimensional finite element analysis (FEA) model based on a stack design being developed at the Institute of Nuclear Energy Research (INER) was constructed. The model was designed for using mica sealant in a compressive sealing design. The first objective of this study is using FEA to calculate the thermal stress distribution in a three-cell planar SOFC stack with a compressive mica sealing design under cyclic thermal loading and to investigate the effects of the applied assembly load on the stress distribution. Simulation results indicate that an applied compressive load of 0.6 MPa could eliminate the bending deformation of the PEN and frame leading to a well joined structure. For a greater applied load, the critical stresses in the glass-ceramic and mica sealants were increased. The glass-ceramic and mica sealants might fail for an applied compressive load of 6 MPa. In this regard, a 0.6 MPa compressive load might be an optimal assembly load. When the SOFC stack was subjected to cyclic thermal loading, the stress accumulation behavior was observed at the inner corners of the frames. The critical stress in the metallic interconnect/frame was increased with increasing number of operating cycles. However, the critical stresses in the PEN, nickel mesh, mica gasket, and glass-ceramic sealant barely changed with cycle number. The second objective of the current study is to make a comparison of the stress distributions between two sealing designs, namely the rigid and compressive seals. Changing a rigid type of glass-ceramic sealant to a compressive type of mica gasket would influence the stress distribution, especially in the PENs. The critical stress in the PEN was decreased at room temperature but significantly increased at operation temperature. Such difference in the stress distribution could be ascribed by the difference in the constrained conditions at the interface of connecting components under various sealing designs. The third objective of this work is to assess the structural reliability of the PEN subjected to such a high thermal stress by measuring the flexural strength of two anode materials, namely Slip-41 and Slip-48. The Slip-48 anode material has a higher flexural strength than does the Slip-41 anode material. The difference in the strength might be caused by their different porosity. Fractography analysis results indicate the Slip-48 anode has a smoother fracture surface and a less amount of defects, compared to the Slip-41. Both anode materials have no obvious temperature dependence on the flexural strength. By importing the mechanical properties of the Slip-48 anode material into stress analysis, the critical stress in the PENs at steady-operation stage would exceed its strength. Therefore, the strength of the tested anode materials needs to be improved for future use in the given SOFC stack design.
Chien, Wei-Ming, and 簡暐珉. "Experimental Simulation and Analysis of Flow Visualization and Uniformity in a Planar SOFC Stack." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/52987355174763757303.
Повний текст джерела國立中央大學
能源工程研究所
96
This thesis investigates experimentally flow distributions in a planar SOFC short-stack using various designs of external manifolds and thus increases flow uniformity of the short-stack. A hydraulic platform combined with laser-induced fluorescence (LIF) and dye visualization (DV) techniques are established to obtain flow fields in the short-stack including three layers, each layer having 12 rib-channels. A Matlab-based code is used to process these flow field images by the binary method and thus corresponding velocities in each of 12 channels for all three different layers can be extracted. Results from both LIF and DV methods are roughly the same with the largest difference up to 10 %, when the channel Reynolds number(Re = VDh/???are within 25~100, where V is the velocity, Dh is the hydraulic diameter of the rib channel, and ? is the kinematic viscosity of fluid. The focus is placed on the effect of different flow directions in both the feed header (FH) and the exhaust header (EH) to flow uniformity of the short-stack. There are five arrangements: (1) The Conventional-type, where both FH and EH are in the same streamwise direction of flow channels; (2) Z-type, where FH and EH are in the same spanwise direction of flow channels; (3) TZ-type, both FH and EH in the same transverse direction of flow channels; (4) U-type, similar to (2) but FH and EH are in opposite directions; (5) TU-type, similar to (3) but FH and EH are in opposite directions. These experimental results show that the fourth design (U-type) has the best flow uniformity among all different designs. In attempt to further improve flow uniformity of the U-type design, a triangular pyramid is placed in the feed header, which can further increase flow uniformity in each layer of the short-stack. Based on the best knowledge of the author, the present study is the first experimental measurement on the flow distributions in the short-stack of planar SOFC and should be useful for numerical simulations.
Huang, Sheng-Wei, and 黃陞緯. "Innovative Solid Oxide Fuel Cell (SOFC) Stack Design For Asymmetric Membrane Electrode Assembly (MEA) Structure." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/69696476351786189161.
Повний текст джерела元智大學
機械工程學系
93
This study is focused on the design and evaluation of the solid oxide fuel cell (SOFC) based on asymmetric membrane electrode assembly (MEA). In the beginning, the planar SOFC single cell is built and its performance is evaluated. We found that the ohmic resistance can be decreased with proper pressing between stainless steel current collector and MEA. In addition, the reduction of NiO within anode to Ni under dilute H2 environment also further decreases the ohmic resistance. The decrease of ohmic resistance results in higher performance. Meanwhile, increasing the cell temperature promotes the cell performance due to lower electrolyte resistivity and higher electrode activities as expected. Based on the experience built on the single cell, two-cell stack were further built and its performance is also evaluated. By properly distributing the air and dilute H2 to corresponding parts with proper sealing, the voltage doubles at a certain current density comparing to the single cell. However, the cell performance decays after long-term operation probably due to cathode poison from the Cr oxide formed on the stainless steel current collector.
Huang, Yau-De, and 黃耀德. "Numerial Analysis of Thermal and Flow Field in SOFC Stacks." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/54359072046629487258.
Повний текст джерела徐瑞民. "The Application of Soft Computing in Investing Taiwan Stock Exchange Capitalization Weighted Stock Index Options." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/01854143811981826438.
Повний текст джерела明新科技大學
企業管理研究所
100
TAIEX options were launched in the end of 2001. The trading volume of 2001 was 5,137 followed by 1,566,446 in 2002 and 125,767,624 in 2010. With trading volume increasing by 80 times in 10 years, TAIEX options trading has accounted for about 68.73% of the total, making it one of the most important financial derivative commodities. However, TAIEX options trading is involved with combinations of the buyer, the seller, the right to buy and the right to sell coupled with factors including time value and intrinsic value, the operations of TAIEX options are more complex than the stock market or the future market. The buyer of TAIEX options enjoys the power to determine the contract performance or not by paying the royalties. In other words, it can regulate investment risk. To reduce investment risk, general investors tend to take the buyer operations. However, in most cases, Taiwan’ stock market is in the trend of consolidation. Investors in the buyer position may lose royalties due to the special operational characteristics of the options and cannot profit from the TAIEX options market as expected. This paper employs four forecasting methods including the multiple stepwise regression, back-propagation neural networks, support vector regression, and genetic programming. The research period is January 19, 2011 to January 18, 2012. With the daily closing number of the TAIEX index as the subject, this paper divides the research period into 13 intervals to build the forecast model. In forecasting operation, this paper selects the most accurate forecast model from the four forecasting methods to use the stock market index closing number of 10 consecutive days to predict the stock market closing number after five days. Coupled with the simple operational strategies mainly in the buyer position of buying call options when the option forecast value after price gap computation is bullish and buying put options when the option forecast value after price gap computation is bearish, this paper simulates the operations of the entire year in 2011. According to the results, the genetic programming is the most accurate forecasting method, and the Strategy No. 3 of “conservative operating principles” with investment return rate at 45.25% is the best investment strategy. Keywords:TAIEX options, Multiple stepwise regression, Back-propagation neural networks, Support vector regression, Ggenetic programming
Tang, Shao-Yuan, and 湯韶元. "The Application of Soft Computing for Investing Taiwan Stock Futures." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/69865850882756111669.
Повний текст джерела明新科技大學
管理研究所
101
With rapid development of Taiwan's economy, the market provides more and more financial products for investors. Among them, stock futures combine stocks and futures, involving the robustness of stocks and high leverage of futures. The stock futures have surprising growth potential and multi-dimension functions. This thesis uses genetic programming and support vector regression with technical indicators. Moreover, three factor model and liquidity indicator are used to construct stock price prediction model, and investment strategies are established to help investors to invest stock futures. The research period is between December 1, 2009 and July 31, 2012. The stock futures derived from stocks is the research object. There are eight investment cases during the research period. The empirical results show that the proposed prediction model combined with investment operation strategies can obtain the average rate of return, which is greater than the market index return rate and interest rate of three-month fixed deposit in the banks of Taiwan.
Peng, Da-Hsiung, and 彭大雄. "Experimental study on the effect of a stack of rings with soft blades for pier scour prevention." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/58553138137551172006.
Повний текст джерела國立成功大學
水利及海洋工程學系碩博士班
95
This research proposed a device consisting of a stack of rings with soft blades to prevent pier scouring. The device was tested in the flume under the following four arrangements: Type A- pier has no scour prevention device; Type B-pier surrounded by a device consisting of a stack of rings with soft blades; Type C-a “stack of rings with soft blades” device placed before pier; Type D-a “stack of rings with soft blades” device placed before and after pier. Scour behavior was oberserved, as each configuration was subjected to a passing flood. All scour-prevention configurations effectively decrease scour and vortex phenomenon. But type D devices arrangement which before the pier included a triangular stack of rings with soft blades, while those placed after the pier consisted of a “U” type’s stack of rings with soft blades, does so most effectively.
Liao, Wen-Hsiang, and 廖文祥. "A Study on the Application of Soft Computing to Trading Timing in Taiwan Stock Market." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/22380791262613501261.
Повний текст джерела長庚大學
資訊管理研究所
93
In the recent years, applying artificial intelligence to financial transaction has become more and more popular. This study combines the advantages of genetic algorithm and neural network, and it takes the technical indicators of the stocks as inputs to decide the right time of transaction. It also investigates whether the proposed trading strategy is better than single technical indicator strategy and buy-and-hold strategy. This study adopts moving-window to evaluate TSEC Taiwan 50 between Jan 4, 2000 and Dec 31, 2004 on the proposed trading, single technical indicator, and buy-and-hold strategies. The capability of making profits by the proposed trading strategy is more effective and stable than single indicator and buy-and-hold strategies during the 3-years evaluation. Although the study on technical indicators shows valuable reference for stock exchange, investors should not take it as the best index for trading strategy.
Shie, Yi-Da, and 謝易達. "Measurements and Analyses of Anode-Supported and Electrolyte-Supported Single-Cell Stacks for Pressurized SOFCs." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/16403717118737202833.
Повний текст джерела國立中央大學
能源工程研究所
102
This study applies a recently-established high-pressure double-chamber solid oxide fuel cell (SOFC) testing platform together with the self-assembled single cell stacks (a full cell with flow distributors in both anode and cathode), so that cell performance and electrochemical impedance spectroscopy (EIS) of both anode-supported and electrolyte-supported SOFCs can be measured. Fixed flow rates are used for all experiments, 500 sccm hydrogen and 400 sccm nitrogen for the anode and 900 sccm air for the cathode. To investigate effects of system pressure (p) and temperature (T), five different p varying from 1 atm to 5 atm and four different T varying from 700℃ to 800℃ are independently controlled and varied. The major objective is to compare advantages/disadvantages and similarities/differences between anode-supported and electrolyte-supported SOFC single stacks. Results show that cell performances of both anode-supported and electrolyte-supported SOFC singlel stacks increase with increasing p and T. For example, when T = 850℃ at 0.7 V, the power densities (PD) of anode-supported/electrolyte-supported single-cell stacks are respectively 309/193 mW cm-2 at p = 1 atm, values of PD modestly increase to 422/228 mW cm-2 rather quickly as p increases at 3 atm, and values of PD can only increase modestly to 476/250 mW cm-2 at p = 5 atm. These results reveal that pressurization for the increase of PD is most significant from 1 atm to 3 atm and such enhancement becomes more gradually when p > 3 atm. Furthermore, the aforesaid that cell performance results are to be explained by EIS measurements. We use equivalent an circuit model to analyze EIS data. It is found that the ohmic polarization resistance is independent of p, but it decreases with increasing T. Moreover, both of activation and concentration polarization resistances decrease with increasing T and/or p. Such resistance results due to effects of increasing p and T are similar for both anode-supported and electrolyte-supported single-cell stacks. When compared, it is also found that the increase of PD due to pressurization is more significant in the anode-supported single-cell stack than in the electrolyte-supported SOFC single-cell stack. However, the latter is more sensitive to the temperature effect as compared to the former. Generally speaking, the temperature effect is more effective than the pressurization effect in terms of the increase of cell performance. This is because increasing T can effectively decrease the ohmic polarization resistance. The present study is important, because it is the first step toward the development of pressurized SOFCs combined with micro gas turbines for future power generation.
Ribeiro, André Filipe da Silva. "Implementação de nó sensor baseado em SoC ARM e ZigBee." Master's thesis, 2018. http://hdl.handle.net/1822/57432.
Повний текст джерелаOs acidentes rodoviários são uma das principais causas de mortalidade no mundo e representam um custo considerável para a sociedade. A elevada percentagem de autoestradas na rede rodoviária nacional em relação à rede rodoviária europeia levou ao desenvolvimento de instrumentos de avaliação das infraestruturas e de ferramentas de gestão da segurança. Neste sentido, foi criado um sistema de gestão das infraestruturas rodoviárias, em que uma das principais funções é detetar a ocorrência de acidentes em tempo real, alertando os gestores da própria Wireless Sensor Network (WSN) e os utilizadores da autoestrada. O objetivo do presente estudo foi transferir todas as funcionalidades de software do elemento desse sistema de gestão que deteta a ocorrência de acidentes, ou seja, o nó sensor, recorrendo a um System-on-Chip (SoC) que possui um transceiver de rádio frequência (RF) e um processador que pertence à família ARM Cortex M3. Avaliou-se igualmente o consumo energético do nó sensor desenvolvido. Os resultados mostram que as funcionalidades de software foram transferidas com sucesso e que o novo nó sensor apresenta um consumo energético mais baixo do que o anterior. Conclui-se que o nó sensor desenvolvido possui mais autonomia e poderá ser uma boa opção para implementação em sistemas de gestão das infraestruturas rodoviárias. Sugerem-se posteriores análises para otimização e ajustamento do sistema às reais condições de utilização.
Road accidents constitute one of the major’s world mortality cause and represent a considerable cost to society. High percentage of motorways in portuguese national road network compared to european road network has conducted to the development of assessment instruments of infrastructures and safety management tools. In this sense, a road infrastructure management system was created to detect live incidents occurrence and alert Wireless Sensor Netwok (WSN) managers and highroad drivers. The present study aimed to transfer all the software functionalities of a dedicated embedded system in a System-on-Chip (SoC) with a transceiver of Radio Frequency (RF), wherein the processor belongs to family ARM Cortex M3. The developed sensor node energetic consumption was assessed. Results indicate that the functionalities were successfully transfered and the new sensor node consumes lower energy than the previous one. Conclusions about the better autonomy of the developed sensor node indicate that it might constitute a good option to implement in road infrastructures management systems. Further analyses to optimize and adjust the system to real conditions are suggested.
Yu, Shih-Ban, and 尤仕邦. "The comparison of cluster based Soft – Computing methods on the trend forecasting with the weighted stock price index." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/28777945982161194188.
Повний текст джерела開南大學
財務金融學系
97
This study utilized Back-Propagation Neural Network (BPNN)、Support Vector Machine(SVM) and Genetic Algorithm Fuzzy Decision Tree (GAFDT) as three primary prediction models to forecast the stock trading signals. And the data clustered or not will be compared in both models. The object of this research was the Weighted Price Index of the Taiwan Stock Exchange. In 25 technical indices, we first used stepwise regression analysis to sieve out relative important factors, and k-means cluster analysis was adopted for data clustering. Then five-full alternation was applied in the experimental design process. Model from one to three are utilized to predict by BPNN, SVM and GAFDT, respectively. GAFDT began with transferring continuous data to discrete data by fuzzy sets so as to increase the comprehensibility of decision tree, and then utilized Genetic Algorithms to optimize the parameters like fuzzy term numbers. Finally, we compare the different intervals between Weighted Price Index of the Taiwan Stock Exchange and S&P 500 by GAFDT. Empirical findings revealed that the highest accurate rate was GAFDT (82.93%), followed by SVM (76.12%) and BPNN (75.53%). The more clusters GAFDT and SVM swarm off, the higher the accurate rate is. The accurate rate of falling of stock was higher than correction and rising in Weighted Price Index of the Taiwan Stock Exchange. The accurate rate of rising of stock is higher than correction and falling in S&P 500. Consequently, the prediction will be affected by training and testing in different stock markets and tendencies.
Júnior, Eládio João Munar. "Implementação de uma rede de sensores sem fios baseada em SoC Arm e ZigBee." Master's thesis, 2019. http://hdl.handle.net/1822/72246.
Повний текст джерелаAs vias de comunicação terrestres são elementos fulcrais para o desenvolvimento das sociedades. A sinistralidade rodoviária é uma das principais ameaças à integridade dos elementos que constituem o sistema rodoviário. No sentido de minimizar este impacto negativo, surge esta dissertação cujo objetivo é apresentar um sistema de monitorização que informa com precisão a ocorrência de colisões de veículos com os guardas de segurança das autoestradas e alertar as entidades responsáveis pela gestão do sistema em tempo real sobre o sucedido. A presente dissertação está orientada em melhorar o projeto, Sustainable Infrastructure Management System (SustIMS), desenvolvido pelo grupo de investigação Embedded System Research Group (ESRG) do Centro ALGORITMI da Universidade do Minho em co-promoção com a empresa Ascendi. Através da implementação de uma rede de sensores sem fios baseada em ZigBee, recorrendo a um System-on-Chip (SoC) comtransceiver Radio Frequency (RF) da família Arm Cortex-M3, equipado com sensor acelerómetro Microelectromechanical Systems (MEMS). O ZigBee, é um protocolo que assenta sobre as camadas definidas no standard IEEE 802.15.4, rede de baixo débito, mas com longa autonomia e baixa complexidade. De forma a cumprir com esses requisitos foi utilizado um processador Arm Cortex-M3 e um acelerómetro MEMS, os quais são caracterizados pelo seu baixo consumo energético. Os resultados desta dissertação são: (1) melhorias na solução atual com o principal foco de reduzir o consumo de energia do sistema; (2) o aumento do alcance da comunicação dos dispositivos; (3) o porting da aplicação para nova versão da Z-Stack; e (4) compatibilização do sistema com os microserviços web, desenvolvidos pelo ESRG.
Road communication is an essential component when it comes to society development. Road accidents are one of the main threats to the integrity of the elements that compose the road system. In order to minimize this negative impact, this dissertation aims to present a monitoring system that informs, with precision, the occurrence of vehicle collision against highway security rails and alert the entities responsible for the real-time management of the system about the event. The present dissertation aims to improve the project, Sustainable Infrastructure Management System, developed by the University of Minho’s Embedded System Research Group (ESRG) in co-promotion with the company Ascendi. By implementing a ZigBee-based wireless sensor network (WSN) using an Arm Cortex-M3 family Radio Frequency (RF) transceiver System-on-Chip (SoC) equipped with an Microelectromechanical Systems (MEMS) accelerometer sensor. ZigBee is a protocol based on the layers defined in the IEEE 802.15.4 standard, low speed network, but with long autonomy and low complexity. In order to meet this requirements an Arm Cortex-M processor and MEMS accelerometer were used, which are characterized by their low power consumption. The results of this dissertation are: (1) improvements on the current solution with the main focus on reducing the system energy consumption; (2) increasing the communication range of the devices; (3) the application porting for the new version of Z-Stack; (4) System compatibility with the microservices developed by the ESRG.