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Schleussner, Sebastian Michael. "ZrN Back-Contact Reflectors and Ga Gradients in Cu(In,Ga)Se2 Solar Cells." Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-151402.
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Solar cells constitute the most direct way of converting solar energy to electricity, and thin-film solar-cell technologies have lately been growing in importance, allowing the fabrication of less expensive modules that nonetheless have good power-conversion efficiencies. This thesis focuses on solar cells based on Cu(In,Ga)Se2, which is the thin-film technology that has shown the highest conversion efficiency to date, reaching 20.3 % on the laboratory scale. Solar modules still have some way to go to become entirely competitive with existing energy technologies, and there are two possible paths to this goal: Firstly, reducing their manufacturing costs, for instance by minimizing the material usage per module and/or by increasing the throughput of a given factory; and secondly, increasing the power output per module in other words, the module efficiency. The subject matters of this thesis are related to those two approaches. The first issue investigated is the possibility for reducing the thickness of the Cu(In,Ga)Se2 layer and compensating for lost absorption by using a ZrN back reflector. ZrN layers are fabricated by reactive sputtering and I present a method for tuning the sputtering parameters so as to obtain a back reflector with good optical, electrical and mechanical properties. The reflector layer cannot be used directly in CIGS devices, but relatively good devices can be achieved with a precursor providing a homogeneous supply of Na, the addition of a very thin sacrificial Mo layer that allows the formation of a film of MoSe2 passivating the back contact, and optionally a Ga gradient that further keeps electrons away from the back contact. The second field of study concerns the three-stage CIGS coevaporation process, which is widely used in research labs around the world and has yielded small-area cells with highest efficiencies, but has not yet made it to large scale production. My focus lies on the development and the effect of gradients in the [Ga]/[In+Ga] ratio. On the one hand, I investigate 'intrinsic' gradients (ones that form autonomously during the evaporation), and present a formation model based on the differing diffusivity of Ga and In atoms in CIGS and on the development along the quasi-binary tie line between (In,Ga)2Se3 and Cu2Se. On the other hand, I determine how the process should be designed in order to preserve 'extrinsic' gradients due to interdiffusion. Lastly, I examine the electrical effects of Ga-enhancement at the back and at the front of the absorber and of In-enhancement at the front. Over a wide range, In-rich top layers prove to have no or a weakly beneficial effect, while Ga-rich top regions pose a high risk to have a devastating effect on device performance.
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Lewis, Brian Wellington. "Silica nanosphere textured back reflectors for increased absorption in thin film amorphous silicon solar cells." [Ames, Iowa : Iowa State University], 2010. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1476317.
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Curtin, Benjamin Michael. "Photonic crystal back-reflectors for light management and enhanced absorption in a-Si:H solar cells." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1468075.
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Boesch, Ryan Paul. "SiO₂ nanosphere textured back reflectors for enhanced light trapping in amorphous and nanocrystalline silicon solar cells." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1464182.
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Ramachandran, Adithya. "HEV fuel optimization using interval back propagation based dynamic programming." Thesis, Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/55054.
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In this thesis, the primary powertrain components of a power split hybrid electric vehicle are modeled. In particular, the dynamic model of the energy storage element (i.e., traction battery) is exactly linearized through an input transformation method to take advantage of the proposed optimal control algorithm. A lipschitz continuous and nondecreasing cost function is formulated in order to minimize the net amount of consumed fuel. The globally optimal solution is obtained using a dynamic programming routine that produces the optimal input based on the current state of charge and the future power demand. It is shown that the global optimal control solution can be expressed in closed form for a time invariant and convex incremental cost function utilizing the interval back propagation approach. The global optimality of both time varying and invariant solutions are rigorously proved. The optimal closed form solution is further shown to be applicable to the time varying case provided that the time variations of the incremental cost function are sufficiently small. The real time implementation of this algorithm in Simulink is discussed and a 32.84 % improvement in fuel economy is observed compared to existing rule based methods.
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Vardakos, Sotirios. "Back-analysis methods for optimal tunnel design." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/26124.
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A fundamental element of the observational method in geotechnical engineering practice is the utilization of a carefully laid out performance monitoring system which provides rapid insight of critical behavioral trends of the work. Especially in tunnels, this is of paramount importance when the contractual arrangements allow an adaptive tunnel support design during construction such as the NATM approach. Utilization of measurements can reveal important aspects of the ground-support interaction, warning of potential problems, and design optimization and forecasting of future behavior of the underground work.
The term back-analysis involves all the necessary procedures so that a predicted simulation yields results as close as possible to the observed behavior. This research aims in a better understanding of the back-analysis methodologies by examining both simplified approaches of tunnel response prediction but also more complex numerical methods. Today a wealth of monitoring techniques is available for tunnel monitoring. Progress has also been recorded in the area of back-analysis in geotechnical engineering by various researchers. One of the most frequently encountered questions in this reverse engineering type of work is the uniqueness of the final solution. When possible errors are incorporated during data acquisition, the back analysis problem becomes formidable. Up to the present, various researchers have presented back-analysis schemes, often coupled with numerical methods such as the Finite Element Method, and in some cases the more general approach of neural networks has been applied.
The present research focuses on the application of back-analysis techniques that are applicable to various conditions and are directly coupled with a widely available numerical program. Different methods are discussed and examples are given. The strength and importance of global optimization is introduced for geotechnical engineering applications along with the novel implementation of two global optimization algorithms in geotechnical parameter identification. The techniques developed are applied to the back-analysis of a modern NATM highway tunnel in China and the results are discussed.Ph. D.
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Mas, Baixeras Albert. "Optimization of inverse reflector design." Doctoral thesis, Universitat de Girona, 2011. http://hdl.handle.net/10803/22705.
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Aquesta tesi presenta un nou mètode pel disseny invers de reflectors. Ens hem centrat en tres temes principals: l’ús de fonts de llum reals i complexes, la definició d’un algoritme ràpid pel càlcul de la il•luminació del reflector, i la definició d’un algoritme d’optimització per trobar més eficientment el reflector desitjat.
Les fonts de llum estan representades per models near-field, que es comprimeixen amb un error molt petit, fins i tot per fonts de llum amb milions de raigs i objectes a il•luminar molt propers. Llavors proposem un mètode ràpid per obtenir la distribució de la il•luminació d’un reflector i la seva comparació amb la il•luminació desitjada, i que treballa completament en la GPU. Finalment, proposem un nou mètode d’optimització global que permet trobar la solució en menys passos que molts altres mètodes d’optimització clàssics, i alhora evitant mínims locals.This thesis presents new methods for the inverse reflector design problem. We have focused on three main topics: the use of real and complex light sources, the definition of a fast lighting simulation algorithm to compute the reflector lighting, and the definition of an optimization algorithm to more efficiently find the desired reflector. The light sources are represented by near-field datasets, that are compressed with a low error, even with millions of rays and for very close objects. Then, we propose a fast method to obtain the outgoing light distribution of a reflector and the comparison with the desired one, working completely in the GPU. Finally, a new global optimization method is proposed to search the solution in less steps than most other classic optimization methods, also avoiding local minima.
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Murray, Myles P. "DEVELOPMENT AND OPTIMIZATION OF BACK SURFACE ACRYLICSOLARMIRRORS TO ASSURE 25 YEAR LIFETIME PERFORMANCE." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1364987929.
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Johnson, Christian Axel. "Optimization-based biomechanical evaluation of isometric exertions on a brake wheel." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-03032009-041004/.
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Safi, Djamschid [Verfasser]. "Simulation of traveling-wave tubes for analysis and optimization in modulated back-off / Djamschid Safi." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2020. http://d-nb.info/1217326774/34.
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Mollica, Fabien. "Optimization of ultra-thin Cu(In,Ga)Se2 based solar cells with alternative back-contacts." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066556/document.
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En quelques années, l'efficacité des cellules solaires à base de Cu(In,Ga)Se2 (CIGS) est passée de 20% à 22.6%. La rapidité de ce développement montre que le CIGS est un matériaux idéal pour les technologies solaires en couches minces. Pourtant, le coût de production cette technologie doit encore être abaissé pour une meilleure compétitivité. La fabrication d'un module avec une couche CIGS plus fine permettrait d'augmenter la production d'une usine et de réduire sa consommation en métaux. Ce travail de thèse vise à réduire l'épaisseur du CIGS d'un standard de 2.0-2.5 µm à une épaisseur inférieure à 500 nm sans altérer les performances des cellules. Cependant, comme rapporté dans la littérature, nous avons observé une diminution des rendements, ce que nous avons analysé en détail en comparant simulations et caractérisations d'échantillons. Celle-ci est causée à la fois par une faible absorption de la lumière dans la couche de CIGS et par un impact important du contact arrière (fortes recombinaisons et faible réflectivité). Pour dépasser ces limites, nous démontrons à la fois théoriquement et expérimentalement que le contact arrière en molybdène peut être remplacé par un oxyde transparent conducteur couplé à un miroir métallique. Nous obtenons de cette manière de meilleurs rendements de cellules. Pour atteindre ce résultat, une optimisation du dépôt de CIGS a été nécessaire. De plus, nous prouvons qu'une couche d'oxyde perforée, insérée entre le CIGS et le contact arrière, limite les recombinaisons des porteurs de charges et réduit l'influence des courants parallèles. Au final, nous avons fabriqué une cellule avec un rendement de 10.7% sur SnO2:F passivé par Al2O3In the past three years, record efficiency of Cu(In,Ga)Se2 (CIGS) based solar cells has improved from 20% up to 22.6%. These results show that CIGS absorber is ideal for thin-film solar cells, even if this technology could be more competitive with a lower manufacture cost. The fabrication of devices with thinner CIGS absorbers is a way to increase the throughput of a factory and to reduce material consumption. This PhD thesis aims to develop cells with a CIGS thickness below 500 nm instead of the conventional 2.0-2.5 µm. However, as reported in the literature, we observed a decrease in cell performance. We carefully analyzed this effect by the comparison between simulations and sample characterizations: it is attributed, on one hand, to a lack of light absorption in the CIGS layer and, on the other hand, to an increased impact of the back-contact (high recombination and low reflectivity). To resolve these problems, we demonstrated theoretically and experimentally that the use of an alternative back-contact, other than molybdenum, such as a transparent conducting oxide coupled with a light reflector, improves the cell efficiency. To achieve this result, an optimization of the CIGS deposition was necessary. Moreover, we proved that a porous oxide layer inserted between the CIGS and the back-contact limits the charge-carrier recombination and removes some parasitic resistance. Finally, an efficiency of 10.7% was achieved for a 480-nm-thick CIGS solar cell with a SnO2:F back-contact passivated with a porous Al2O3 layer
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Smith, Frank A. "A framework for flexible comparison and optimization of X-ray digital tomosynthesis." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/dissertations/1667.
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Digital tomosynthesis is a novel three-dimensional imaging technology that utilizes limited number of X-ray projection images to improve the diagnosis and detection of lesions. In recent years, tomosynthesis has been used in a variety of clinical applications such as dental imaging, angiography, chest imaging, bone imaging, and breast imaging. The goal of our research is to develop a framework to enable flexible optimization and comparison of image reconstruction and imaging configurations.
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Lavelle, Jerome Philip. "An optimization of the placement of flexible reflective post delineators from a visual detection point of view." Ohio : Ohio University, 1986. http://www.ohiolink.edu/etd/view.cgi?ohiou1183139198.
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McMulkin, Mark L. "Investigation and empirical evaluation of inputs to optimization-based biomechanical trunk models." Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-10032007-172024/.
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Cafieri, Sonia. "From local to global and back : a closed walk in mathematical programming and its applications." Habilitation à diriger des recherches, Université Paul Sabatier - Toulouse III, 2012. http://tel.archives-ouvertes.fr/tel-00979273.
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Ce document propose un parcours de mes travaux de recherche en optimisation, en passant par l'optimisation mixte en variables entières, l'optimisation non-linéaire continue locale et le clustering dans les réseaux (graphes). Le premier chapitre traite de la programmation non linéaire mixte en variables entières et de l'optimisation globale déterministe. Il présente des contributions relatives à des investigations théoriques ainsi que des applications à des problèmes concrets. Nous discutons principalement de relaxations convexes et de reformulations automatiques de problèmes de programmation mathématique, dans le but d'améliorer l'efficacité des algorithmes de Branch-and-Bound. Dans le cadre de la programmation polynomiale, nous avons étudié des relaxations convexes pour les monômes multilinéaires et la génération de relaxations compactes de problèmes polynomiaux basés sur une technique spécifique de reformulation-linéarisation (RLT). Parmi les applications, une attention particulière est portée à des problèmes qui se posent dans la gestion du trafic aérien. Nous avons proposé de nouveaux modèles mathématiques et des approches de résolution basées d'une part sur l'optimisation mixte en variables entières et d'autre part sur le contrôle optimal. Deux thèmes de l'optimisation continue non-linéaire sont décrits au deuxième chapitre. Des méthodes de point intérieur pour la programmation quadratique et leurs noyaux d'algèbre linéaire (systèmes KKT) sont d'abord discutées. L'accent est mis sur les méthodes itératives pour les systèmes KKT et sur des questions connexes, telles que les techniques de préconditionnement et les propriétés de convergence. L'autre sujet discuté concerne, encore une fois, des problèmes de trafic aérien. Il porte sur les approches déjà mentionnées de contrôle optimal qui conduisent à des problèmes non-linéaires. Le troisième chapitre présente mes principaux résultats dans le domaine du clustering dans les réseaux. Le problème de l'identification de clusters dans les réseaux peut être formulé en utilisant la programmation mathématique et conduit généralement à un problème d'optimisation combinatoire. Mes contributions concernent les critères de classification et les méthodes de clustering correspondantes. Une attention particulière est portée aux méthodes exactes utilisées pour résoudre l'ensemble du problème d'optimisation ou, localement, les sous-problèmes survenant dans des heuristiques hiérarchiques, ou enfin dans le raffinement des solutions obtenues précédemment par d'autres méthodes.
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Ma, Tengfei. "A Graph Attention plus Reinforcement Learning Method for Antenna Tilt Optimization." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300111.
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Remote Electrical Tilt optimization is an effective method to obtain the optimal Key Performance Indicators (KPIs) by remotely controlling the base station antenna’s vertical tilt. To improve the KPIs aims to improve antennas’ cooperation effect since KPIs measure the quality of cooperation between the antenna to be optimized and its neighbor antennas. Reinforcement Learning (RL) is an appropriate method to learn an antenna tilt control policy since the agent in RL can generate the optimal epsilon greedy tilt optimization policy by observing the environment and learning from the state- action pairs. However, existing models only produced tilt modification strategies by interpreting the to- be- optimized antenna’s features, which cannot fully characterize the mobile cellular network formed by the to- be- optimized antenna and its neighbors. Therefore, incorporating the features of the neighboring antennas into the model is an important measure to improve the optimization strategy. This work will introduce the Graph Attention Network to model the neighborhood antenna’s impact on the antenna to be optimized through the attention mechanism. Furthermore, it will generate a low- dimensional embedding vector with more expressive power to represent the to- be- optimized antenna’s state in the RL framework through dealing with graph- structural data. This new model, namely Graph Attention Q- Network (GAQ), is a model based on DQN and aims to acquire a higher performance than the Deep Q- Network (DQN) model, which is the baseline, evaluated by the same metric — KPI Improvement. Since GAQ has a richer perception of the environment than the vanilla DQN model, it thereby outperforms the DQN model, obtaining fourteen percent performance improvement compared to the baseline. Besides, GAQ also performs 14 per cent better than DQN in terms of convergence efficiency.Optimering av fjärrlutning är en effektiv metod för att nå optimala nyckeltal genom fjärrstyrning av den vertikala lutningen av en antenn i en basstation. Att förbättra nyckeltalen innebär att förbättra sammarbetseffekten mellan antenner eftersom nyckeltalen är mått på kvalitén av sammarbetet mellan den antenn som optimeras och dess angränsande antenner. Förstärkande Inlärning (FI) är en lämplig metod för att lära sig en optimal strategi för reglering av antennlutningen eftersom agenten inom FI kan generera den optimala epsilongiriga optimeringsstrategin genom att observera miljön och lära sig från par av tillstånd och aktioner. Nuvarande modeller genererar dock endast lutningsstrategier genom att tolka egenskaperna hos den antenn som ska optimeras, vilket inte är tillräckligt för att karatärisera mobilnätverket bestående av antennen som ska optimeras samt dess angränsande antenner. Därav är inkluderingen av de angränsande antennernas egenskaper i modellen viktig för att förbättra optimeringsstrategin. Detta arbete introducerar Graf- Uppmärksammat Nätverk för att modellera de angränsande antennernas påverkan på den antenn som ska optimeras genom uppmärksamhetsmekanismen. Metoden genererar en lågdimensionell vektor med större förmåga att representera den optimerade antennens tillstånd i FI modellen genom att hantera data i struktur av en graf. Den nya modellen, Graf- Uppmärksammat Q- Nätverk (GUQ), är en modell baserad på DQN med mål att nå bättre prestanda än en standard DQN- modell, utvärderat efter samma mätvärde –– förbättring av nyckeltalen. Eftersom GUQ har en större upfattning av miljön så överträffar metoden DQN- modellen genom en fjorton procent bättre prestandaökning. Dessutom, så överträffar GUQ även DQN i form av snabbare konvergens.
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Ma, Jiya. "A Genetic Algorithm for Solar Boat." Thesis, Högskolan Dalarna, Datateknik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:du-3488.
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Genetic algorithm has been widely used in different areas of optimization problems. Ithas been combined with renewable energy domain, photovoltaic system, in this thesis.To participate and win the solar boat race, a control program is needed and C++ hasbeen chosen for programming. To implement the program, the mathematic model hasbeen built. Besides, the approaches to calculate the boundaries related to conditionhave been explained. Afterward, the processing of the prediction and real time controlfunction are offered. The program has been simulated and the results proved thatgenetic algorithm is helpful to get the good results but it does not improve the resultstoo much since the particularity of the solar driven boat project such as the limitationof energy production
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Kim, Doo-Il. "Development and application of integrated ozone contactor design and optimization tools." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-05182007-120642/.
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Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008.Jae-Hong Kim, Committee Chair ; Philip J.W. Roberts, Committee Member ; E. Michael Perdue, Committee Member ; Sotira Yiacoumi, Committee Member ; Thorsten Stoesser, Committee Member.
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Badalamenti, Bryan M. "OpenCL Based Digital Image Projection Acceleration." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1438277905.
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Aguilar, David P. "A radial basis neural network for the analysis of transportation data." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000515.
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Pelaio, Bruna Pilz Moraes. "Avaliação funcional lombopélvica: comparação entre indivíduos com e sem dor lombar crônica." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/17/17152/tde-20112018-111242/.
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Alguns pacientes com dor lombar crônica classificados no grupo de otimização funcional pelo método de classificação Treatment based classification (TBC), apesar de apresentarem bons resultados em questionários funcionais, ainda referem dor e limitação em várias tarefas funcionais. Este estudo teve como objetivo explorar as diferenças de performance entre os pacientes com dor lombar crônica e indivíduos saudáveis submetidos a um conjunto de testes de força isométrica do quadril e resistência lombopélvica, além de identificar valores de corte classificatórios com acurácia aceitável de testes e razões entre esses testes que possam discriminar significativamente os pacientes com dor lombar crônica e indivíduos saudáveis. Trezentos e cinquenta indivíduos (saudáveis n = 170 e pacientes com dor lombar crônica n = 180) foram estratificados por idade, gênero e nível de atividade física. Os pacientes com dor lombar crônica foram incluídos se apresentassem resultado no questionário de função Oswestry Disability Index (ODI) <20%. O conjunto de testes consistiram de: testes de força isométrica de abdutores, extensores e flexores de quadril, teste de resistência da musculatura abdominal profunda e testes de resistência de ponte lateral, ponte frontal, flexores e extensores lombares. Os pacientes com dor lombar crônica apresentaram maiores valores de força isométrica dos flexores do quadril (p> 0,001) e teste de resistência da musculatura abdominal profunda (p> 0,001), mas menor resistência na ponte lateral (p> 0,05), ponte frontal (p> 0,001), flexores (p> 0,001) e extensores lombares (p> 0,05) em comparação com saudáveis. A acurácia foi considerada aceitável para os valores de corte do teste de flexores lombares (91,4seg; AUC = 0,84), flexores/extensores lombares (0,95; AUC = 0,82), ponte lateral/flexores lombares (0,57; AUC = 0,79), ponte frontal/flexores lombares (0,79; AUC = 0,75) e extensores /flexores de quadril (0,67; AUC = 0,73). Sendo assim, conclui-se que pacientes com dor lombar crônica classificados no grupo de otimização funcional pelo TBC, apesar de apresentarem boa pontuação no questionário funcional, apresentaram diferenças de performance em alguns testes. Além disso, as análises de acurácia dos valores de corte de testes e razões permitiram discriminar os pacientes com dor lombar, o que pode auxiliar no programa de tratamento e decisão de alta no retorno á atividades com níveis de demanda elevada no trabalho, atividade física ou mesmo diárias.Some chronic low back pain (LBP) patients classified on the functional optimization subgroup by the Treatment based classification method (TBC), although presenting acceptable score in functional questionnaires, they still experience pain and limitations in several functional tasks and in sports activities. This study aimed to explore differences in performance between chronic LBP patients and healthy individuals submitted to a set of isometric hip strength and lumbar endurance tests, and to identify accurate tests and ratios classificatory cut-off values to significantly discriminate patients with chronic low back pain and healthy individuals. Three hundred and fifty subjects (Healthy n=170 and chronic LBP patients n=180) were stratified by age, gender and physically active or sedentary. LBP patients were included if they had Oswestry Disability Index (ODI) < 20%. The set of tests consisted of: Isometric strength tests of hip abductors, extensors, flexors, deep abdominal functional test, and endurance tests of lateral bridge, frontal bridge, lumbar flexors and extensors. The LBP patients presented higher strength values of hip flexors (p> 0.001) and deep abdominal function test (p>0.001), but lower endurance on lateral bridge (p>0.05), frontal bridge (p>0.001), lumbar flexors (p>0.001) and extensors tests (p>0.05) compared to healthy individuals. The accuracy was considered acceptable for lumbar flexors test (91.4 sec; AUC = 0.84), lumbar flexors/extensors (0.95; AUC = 0.82), lateral bridge/ lumbar flexors (0.57; AUC = 0.79), frontal bridge/lumbar flexors (0.79; AUC = 0.75) and hip extensors/flexors (0.67; AUC = 0.73). Some chronic LBP patients, despite having acceptable score in functional scores, presented differences in lumbopelvic and hip performance tests and, based on some accurate cut-off classificatory ratios and tests, allowed to discriminate LBP patients, what may be considered in treatment program and decision making for patient\'s discharge when returning to higher demand levels of work, physical or even daily activity.
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Hammoud, Mohamad. "Etude et conception d'antennes imprimées sectorielles à faibles lobes arrière pour réseau Wi-Fi outdoor maillé." Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTS032.
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Dans le cadre du réseau maillé Wi-Fi sur la bande 2,4 GHz en environnement outdoor, nous concevons des antennes sectorielles à très faible rapport de rayonnement avant – arrière. Ceci permet de limiter les interférences co-canales. Nous étudions tout d'abord des éléments rayonnants associés à un plan réflecteur en métamatériau. Ce dernier est basé sur une structure de Sievenpiper dite structure « champignon ». Cette structure est constituée de motifs périodiques imprimés sur un substrat. A l’aide de simulations des diagrammes de dispersion, et de la phase du coefficient de réflexion sur ces structures, avec de nombreux résultats issus de la littérature, nous caractérisons ces plans réflecteurs. Nous sommes alors en mesure de proposer des critères sur la géométrie des motifs pour que le comportement haute impédance de la structure coïncide avec la bande électromagnétique interdite. Le comportement des antennes, élément rayonnant et réflecteur, présente des performances de rayonnement et de bandes passantes très intéressantes. Pour des raisons budgétaires cette structure n'est pas retenue. Une partie de cette thèse explore alors l'effet de la géométrie des éléments rayonnants imprimés associés aux réflecteurs sur les performances en gain et sur le rapport avant/arrière. Le choix se porte sur une géométrie de type boucle. Ce travail est mené tant grâce à des simulations électromagnétiques 3D ainsi qu'à des expérimentations. Des mesures sur terrain d'un prototype d'un système constitué de trois antennes tri-sectorielles munis d'un radôme valide et clôt l'étudeIn the frame of outdoor meshed Wi-Fi network operating in the 2.4 GHz frequency band, we conceive sectoral antennas with very low front to back radiation ratio. This should limit co-channel interferences between neighboring base stations. We first study radiating elements in microstrip technology associated with a reflector based on metamaterials. The latter is based on the structure of Sievenpiper, the so-called "mushroom" structure. This structure comprises periodic pattern sprinted on a substrate. Simulations of the dispersion diagram and of the phase of the reflection coefficient, linked to numerous results from the literature, allow us to perform a full-through characterization of these reflectors. We can therefore propose a criterion on the geometry of the patterns bringing the high-impedance frequency band within the forbidden electromagnetic bandgap. The behavior of the overall antenna, radiant element and reflector, exhibits very interesting performances considering bandwidth and radiation lobes. For economic reasons, this structure is not retained and we switch to a simple perfect electric conductor plane. A part of this thesis explores the impact of printed antenna geometry and its associated reflector on the gain and front to back ratio characteristics. We finally choose a loop geometry. This work is achieved with 3D electromagnetic simulations and with outdoor measurements. On-field experiments on a prototype comprising 3 tri-sectoral antennas assembled under a Radome validate and concludes the study
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Rama, Venkat Siddhartha. "Optimization Study of a Combined Wind-Solar Farm for a Specified Demand." Wright State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=wright1592391472670774.
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Macdonald, John Charles. "Efficient Estimation for Small Multi-Rotor Air Vehicles Operating in Unknown, Indoor Environments." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3496.
Full textAbstract:
In this dissertation we present advances in developing an autonomous air vehicle capable of navigating through unknown, indoor environments. The problem imposes stringent limits on the computational power available onboard the vehicle, but the environment necessitates using 3D sensors such as stereo or RGB-D cameras whose data requires significant processing. We address the problem by proposing and developing key elements of a relative navigation scheme that moves as many processing tasks as possible out of the time-critical functions needed to maintain flight. We present in Chapter 2 analysis and results for an improved multirotor helicopter state estimator. The filter generates more accurate estimates by using an improved dynamic model for the vehicle and by properly accounting for the correlations that exist in the uncertainty during state propagation. As a result, the filter can rely more heavily on frequent and easy to process measurements from gyroscopes and accelerometers, making it more robust to error in the processing intensive information received from the exteroceptive sensors. In Chapter 3 we present BERT, a novel approach to map optimization. The goal of map optimization is to produce an accurate global map of the environment by refining the relative pose transformation estimates generated by the real-time navigation system. We develop BERT to jointly optimize the global poses and relative transformations. BERT exploits properties of independence and conditional independence to allow new information to efficiently flow through the network of transformations. We show that BERT achieves the same final solution as a leading iterative optimization algorithm. However, BERT delivers noticeably better intermediate results for the relative transformation estimates. The improved intermediate results, along with more readily available covariance estimates, make BERT especially applicable to our problem where computational resources are limited. We conclude in Chapter 4 with analysis and results that extend BERT beyond the simple example of Chapter 3. We identify important structure in the network of transformations and address challenges arising in more general map optimization problems. We demonstrate results from several variations of the algorithm and conclude the dissertation with a roadmap for future work.
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Ghazavizadeh, Akbar. "Modeling and simulation of the micromechanical behavior of semi-crystalline polyethylene including the effect of interphase layer." Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAD048/document.
Full textAbstract:
Dans ce travail, la caractérisation mécanique de l’interphase entre les zones amorphes et cristallines dans le polyéthylène a été abordée. La caractérisation élastique est effectuée en appliquant deux approches micromécaniques à partir des données de la simulation moléculaire pour la zone interlamellaire. Ces approches micromécaniques sont d’une part le modèle étendu d’inclusion composite, et d’autre part la méthode de double inclusion. Les résultats des deux approches s’accordent parfaitement. Il a été mis en évidence que le tenseur de rigidité de l’interphase n’est pas défini positif, l’interphase est donc mécaniquement instable. La comparaison avec les résultats expérimentaux valide la méthodologie proposée. Pour la caractérisation hyperélastique, l’algorithme hybride proposé consiste à appliquer la loi de comportement d’un milieu continu isotrope, compressible et hyperélastique aux résultats de la simulation de la dynamique moléculaire d’un élément unitaire de polyéthylène. La notion d’optimisation d’un ensemble de fonctions coûts non négatives est l’idée clé de cette partie. Les paramètres hyperélastiques identifiés sont en bon accord avec ceux qui ont été estimés expérimentalement. L’évolution des frontières de l’interphase avec la déformation est le second résultat de cette analyse. La fin du travail est dédiée à la simulation numérique de la grande déformation viscoplastique d’un agrégat de polyéthylène. Le modèle de Gent adopté pour la contrainte de rappel, le tenseur de projection proposé pour l’approche modifiée de Taylor, et l’optimisation multiniveau font parties des contributions apportéesElastic characterization of the interphase layer in polyethylene is implemented by applying the relationships of two micromechanical approaches, “Extended Composite Inclusion Model” and “Double-Inclusion Method”, to the Monte Carlo molecular simulation data for the interlamellar domain. The results of the two approaches match perfectly. The interphase stiffness lacks the common feature of positive definiteness, which indicates its mechanical instability. Comparison with experimental results endorses the proposed methodology. For the hyperelastic characterization of the interlamellar domain and the interphase layer, the proposed hybrid algorithm consists in applying the constitutive equations of an isotropic, compressible, hyperelastic continuum to the molecular dynamics simulation results of a polyethylene stack. Evolution of the interphase boundaries are introduced as auxiliary variables and the notion of minimizing a set of nonnegative objective functions is employed for parameter identification. The identified hyperelastic parameters for the interlamellar domain arein good agreement with the ones that have been estimated experimentally. Finally, the large, viscoplastic deformation of an aggregate of polyethylene is reexamined. The Gent model adopted for the back stress of the noncrystalline phase, correcting the projection tensor for the modified Taylor approach, and the idea of multilevel optimization are among the contributions made
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Berberovic, Adnan, and Alexander Eriksson. "A Multi-Factor Stock Market Model with Regime-Switches, Student's T Margins, and Copula Dependencies." Thesis, Linköpings universitet, Produktionsekonomi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-143715.
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Investors constantly seek information that provides an edge over the market. One of the conventional methods is to find factors which can predict asset returns. In this study we improve the Fama and French Five-Factor model with Regime-Switches, student's t distributions and copula dependencies. We also add price momentum as a sixth factor and add a one-day lag to the factors. The Regime-Switches are obtained from a Hidden Markov Model with conditional Student's t distributions. For the return process we use factor data as input, Student's t distributed residuals, and Student's t copula dependencies. To fit the copulas, we develop a novel approach based on the Expectation-Maximisation algorithm. The results are promising as the quantiles for most of the portfolios show a good fit to the theoretical quantiles. Using a sophisticated Stochastic Programming model, we back-test the predictive power over a 26 year period out-of-sample. Furthermore we analyse the performance of different factors during different market regimes.
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"Optimization of Back Reflectors for Bifacial Photovoltaic Modules." Master's thesis, 2019. http://hdl.handle.net/2286/R.I.53954.
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abstract: Demand for green energy alternatives to provide stable and reliable energy
solutions has increased over the years which has led to the rapid expansion of global
markets in renewable energy sources such as solar photovoltaic (PV) technology. Newest
amongst these technologies is the Bifacial PV modules, which harvests incident radiation
from both sides of the module. The overall power generation can be significantly increased
by using these bifacial modules. The purpose of this research is to investigate and maximize
the effect of back reflectors, designed to increase the efficiency of the module by utilizing
the intercell light passing through the module to increase the incident irradiance, on the
energy output using different profiles placed at varied distances from the plane of the array
(POA). The optimum reflector profile and displacement of the reflector from the module
are determined experimentally.
Theoretically, a 60-cell bifacial module can produce 26% additional energy in
comparison to a 48-cell bifacial module due to the 12 excess cells found in the 60-cell
module. It was determined that bifacial modules have the capacity to produce additional
energy when optimized back reflectors are utilized. The inverted U reflector produced
higher energy gain when placed at farther distances from the module, indicating direct
dependent proportionality between the placement distance of the reflector from the module
and the output energy gain. It performed the best out of all current construction geometries
with reflective coatings, generating more than half of the additional energy produced by a
densely-spaced 60-cell benchmark module compared to a sparsely-spaced 48-cell reference
module.ii
A gain of 11 and 14% was recorded on cloudy and sunny days respectively for the
inverted U reflector. This implies a reduction in the additional cells of the 60-cell module
by 50% can produce the same amount of energy of the 60-cell module by a 48-cell module
with an inverted U reflector. The use of the back reflectors does not only affect the
additional energy gain but structural and land costs. Row to row spacing for bifacial
systems(arrays) is reduced nearly by half as the ground height clearance is largely
minimized, thus almost 50% of height constraints for mounting bifacial modules, using
back reflectors resulting in reduced structural costs for mounting of bifacial modulesDissertation/Thesis
Masters Thesis Mechanical Engineering 2019
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Chen, Ji-Siao, and 陳紀孝. "Modeling and Optimization of Phosphor-converted LEDs with Omni-directional Reflectors." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/45022580387697383018.
Full textAbstract:
碩士國立清華大學
光電工程研究所
96
ABSTRACT White LEDs based on UV LED pumping visible phosphors have the advantages of stable color temperature, high color rendition, good color uniformity, easy fabrication, and low cost. However, the electrical-to-optical conversion efficiency is lower than that of the mainstream white LEDs technology based on blue LEDs pumping yellow phosphor. The low efficiency is due to two factors. One is the low efficiency of current UV LED. The other is the low phosphor conversion efficiency. This study proposes a way to improve the efficiency of UV pumped phosphor-converted LED using omni-directional reflector (ODR) film. A one-dimensional model to approximate the light extraction is derived to predict the light extraction and to optimize its design. According to experimental result, the present method using ODR film can enhance the light extraction. Prediction of the proposed model is consistent with the experimental result. The LED using ODR films has higher efficiency with thinner phosphor layer, higher reflectance of bottom-boundary of phosphor layer for UV light, and smaller light absorption of silicone resin. A theoretical maximum improvement of 2.62X is predicted.
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Yang, Tsung-Lung, and 楊宗龍. "Engineering design optimization using back-propagation network." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/41407894209919924542.
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Patabandi, Maddumage Chathura Jeevantha. "Co-Simulation of Back-to-Back VSC Transmission System." 2011. http://hdl.handle.net/1993/4770.
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With the increased complexity of modern power systems, it may be required more than
one platform to do an intended study efficiently and accurately. This research was carried out to investigate the use of co-simulation in an application of power system.
A back-to-back Voltage Source Converter (VSC) transmission system was modeled
in PSCAD/EMTDC which is an Electro-Magnetic Type (EMT) software. Results were
analyzed for some operating points of the system.
Then the control system of the above system was modelled in MATLAB/SIMULINK
while the rest of the system was modeled in PSCAD/EMTDC. Both of these systems
were interfaced to obtain the complete system and results were analyzed under same operating points as the original PSCAD case.
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Pinto, Cristiana Sofia Santos. "Core back moulding, adhesion optimization in the joining area." Master's thesis, 2020. http://hdl.handle.net/1822/69578.
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Dissertação de mestrado em Polymer EngineeringWhen industries need to make components with two or more materials using just one mould and one machine, they use multi-material injection moulding techniques. One of these techniques is the core back moulding that allows the subsequent injection of two different materials without opening the mould, commonly used for parts with simple geometry, normally a rigid part involved with an elastomer. These moulds are very complex in its structure, therefore the design of the mould, its construction and assembly need to be carefully done to avoid part defects. Moreover, multi-material injection moulding may be a challenge regarding the adhesion between materials, being dependent on materials compatibility, materials rheological characteristics and injection moulding conditions used. The present dissertation addresses the development of a core back mould for the production of a complex bi-material part for the automotive industry and the study of the processing conditions that best promote the adhesion between the materials used. For that different tools where used such as Solidworks for the mould design, and DOE for the design of experiments. The mould development went through several steps such as the design of the injection, cooling, ejection and gas trap systems. Then the mould components were machined and assembled. Finally, the mould was tested and the parts were analysed. A study about the adhesion of the materials in this type of moulds and how the processing conditions influence the interface quality was realised. To simplify that study, a Design of Experiments was performed. This method is used to reduce the number of tests, assuring the reliability of the results. Finally, to analyse the adhesion of the parts, tensile tests were performed. It was concluded that the mould had a good performance. Parts were successfully made and the strength of the joints evaluate. It was concluded that the adhesion between materials was more efficient in the part extremities comparing with the middle zones. These results are attributed to the location of the gate and also the complex geometry of the part. Furthermore, the processing conditions influence the strength of the joint region. The set of values that would optimise PP/EPDM joints are the injection temperature of the second material of 200ºC, the mould temperature of 40ºC and the injection pressure of 80bar.
Quando as indústrias necessitam de fazer componentes com dois ou mais materiais utilizando apenas um molde e uma máquina, utilizam técnicas de moldação por injeção multi-material. Uma destas técnicas é a moldação core back que permite a subsequente injeção de dois materiais diferentes sem abertura do molde, normalmente utilizada para peças com geometria simples, como uma peça rígida envolvida com um elastómero. Estes moldes são muito complexos, pelo que a conceção do molde, a sua construção e montagem precisam de ser realizadas cuidadosamente para evitar defeitos nas peças. Além disso, a moldação multi-material pode ser um desafio no que respeita à adesão entre os materiais, dependendo da compatibilidade dos materiais, características reológicas e condições de processamento. A presente dissertação aborda o desenvolvimento de um molde core back para a produção de uma peça bi-material para a indústria automóvel e o estudo das condições de processamento que melhor promovem a adesão entre os materiais utilizados. Para isso são utilizadas diferentes ferramentas, tais como Solidworks para o desenho do molde, e DOE. O desenvolvimento do molde passou por várias etapas, tais como a conceção dos sistemas de injeção, arrefecimento, ejeção e escape de gás. Em seguida, os componentes do molde foram maquinados e montados. Finalmente, o molde foi testado e as peças foram analisadas. Foi realizado um estudo sobre a adesão dos materiais neste tipo de moldes e como as condições de processamento influenciam a qualidade da interface. Para simplificar esse estudo, foi realizado um Design of Experiments. Este método é utilizado para reduzir o número de ensaios, assegurando a fiabilidade dos resultados. Finalmente, para analisar a adesão das peças, foram realizados ensaios de tração. Concluiu-se que o molde tinha um bom desempenho. As peças foram produzidas com sucesso e a resistência da zona de união foi avaliada. Concluiu-se que a adesão entre os materiais era mais eficiente nas extremidades das peças, em comparação com as zonas médias. Estes resultados devem-se à localização do ponto de injeção e também à complexa geometria da peça. Além disso, as condições de processamento influenciam a resistência da zona de união. O conjunto de valores que otimizariam a adesão da peça PP/EPDM são a temperatura de injeção do segundo material de 200ºC, a temperatura do molde de 40ºC e a pressão de injeção de 80bar.
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Wu, Wan-Cheng, and 吳萬成. "Parameter Optimization of Back-Propagation Network and Feature Selection Using Particle Swarm Optimization Approach." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/74104438758229482008.
Full textAbstract:
碩士華梵大學
資訊管理學系碩士班
96
Abstract The back-propagation network (BPN) is a popular tool and can be applied in various fields. But, different problems may require different parameter settings for network architectures. On the other hand, a dataset may contain many features, but not all of the features are beneficial for classification in BPN. Particle swarm optimization (PSO) is a novel meta -heuristic technique in the artificial intelligence field. PSO imitates the rasorial mechanism of bird in nature and has been successfully imple mented to solve the problems in many fields. , thesis , we proposed the best PSO-based approach named PSOBPN, to obtain the parameter and select a subset of feature to degrade the classification accuracy rate of PSO. In order to evaluate the proposed approa ch, we use twelve datasets in UCI Machine Learning Repository to evaluate the performance and apply the 10-fold cross-validation to calculate the classification result. The experimental results are compared with MONNA proposed by Leazoray and Cardot, DISTAL proposed by Yang and Honavar and SA+BPN proposed by Lin et al. As a result, PSOBPN’s classification accuracy rate is better than MONNA and DISTAL. So the PSOBPN can enhance the classification accuracy. Keyword： Back-propagation neural network, Particle swarm optimization, Parameter Optimization, Features selection.
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Kang, Shih-Huang, and 康詩凰. "Back analyses of earthdam seepage problems using heuristic optimization method." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/97563619349681806887.
Full textAbstract:
碩士國立交通大學
土木工程學系
99
Embankment dam is the most common type of dams in Taiwan. Besides dam failure caused by overflow erosion, piping due to seepage is one of the major reason that may result in the breach of an embankment dam. Piping failure tends to take place unexpectedly and catastrophically. A proper program of monitoring for seepage and water pressure can help to reduce the chance of piping failure. When unusual monitored data occurs, an appropriate diagnosis will be essential to look for the real cause and timely solve the problem. This thesis aims to propose a diagnosis procedure by means of back analyses of earth-dam seepage problems using one of the heuristic optimization methods - the harmonic search method. This procedure incorporates the harmonic search algorithm into MATLAB as the optimization server and a commercial numerical simulation tool FLAC as the simulation engine to allow the simulated results match the monitoring data. A common data file serves as the interface communicating between MATLAB and FLAC. This work also makes use of two earth-dam seepage problems to demonstrate the feasibility and applicability of the proposed diagnosis procedure.
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Cheng, Yung-Lung, and 鄭詠隆. "TFT-LCD TV Back Cover Research for the Optimization of Warpage." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/88286249980969860266.
Full textAbstract:
碩士中原大學
機械工程研究所
97
Abstract Through the rapid progress of technology, the size of LCD get larger and the exterior of product are two main concern of TV. Thus, CRT Monitor has been gradually replaced by light TFT-LCD TV. For 3C market is gradually mature and competitive, the demand of exterior, complexity of product, and the quality of the product are all raised. To decrease the error of mold design and shorten time, the experiences and inheritances of designers and aged engineers are trusted in product design. Through tests, the standards of mold design and product quality have been set up. However, the complicate of TFT-LCD TV formation can’t be manufactured easily. The purpose of this study is to discuss the 28 inch TFT-LCD TV products that might make warpage abnormal with products in the molding development which belong to appearance of back cover plastic injection molding. Moldflow is used to analysis TFT-LCD TV back cover and finding out the best parameter setup of TFT-LCD TV, for its outstanding ability on plastic mold analysis. Through the analysis、mold temperature、compressed pressure、cooling time and dissolved plastic liquid temperature are the for crucial parameters that affects warpage abnormal. Moreover, Taguchi Optimization Methods is also used to find out Smaller-is-better. According to the study, the smallest parameter setup of warpage could prevent the exterior from out of shape product which could help to reduce the cost、the usage of material. It could increase the competitive the ability of products at the same time. Finally, it would give a contribution on TFT-LCD TV in the future by comparing the result between the best parameters set up and actual result.
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Tsai, Meng-chi, and 蔡孟頎. "Multi-Pin Optimization of Image Registration using Back Propagation Neural Network." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/237p9f.
Full textAbstract:
碩士國立中央大學
機械工程研究所碩士在職專班
96
Image registration are skillful of machine vision, the commerce service package was adopted as the drawing of equipment most of the time , software source code library and database or image capture hardware and research assistant sold by professional vendor , they have unique authority of agency or own vision technique, there are differences as the basis principles of image processing, characteristics of different software systems that have merit and demerit , the system are linear programming could not to process non-linear problem of multi-pin interlace location optimizated .This research method combine Back Propagation Neural Network to image alignment software we design for multi-pin alignment optimization and capture two hundred pieces of sample image with random , that could be mantle over 90% whole and each of pin location , using MSE to find the best speed learn rate 0.1 and momentum coefficient 0.1 . During 2000 times training for BPNN , network showing convergence , than promote bias and weight , these could be drawing curve approach truely , the cruve solve non-linear phenomenon , input any grid in range the Neural network running forward counting and directly to output result with optimization .
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Li, ChiaLin, and 李佳霖. "Optical Design Optimization for Light Guide Film and Slimmed Back Light Module." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/16677717160497995671.
Full textAbstract:
碩士國立暨南國際大學
光電科技碩士學位學程在職專班
100
Digital products bring convenience and entertainment to people’s everyday life. Commonly, observable and readable contents were presented through display interfaces in digital products. Among various display interfaces, the TFT LCD (thin-film-transistor liquid-crystal-display) has been recognized as the mainstream display technology for having the advantages of light weight, slim body, energy saving and low radiation. TFT LCD itself does not emit light, however, and back-lighting module is necessary for TFT LCD to provide illumination for depicting the images. Light guiding plate is one of the core accessories in back-light module, which controls the display lumens and uniformity through using different micro structures on its surface. Currently, there are three different fabrication techniques, injection formation, extrusion formation, and thermal embossing formation, for the light guiding plate. Among these three techniques, thermal embossing formation is the only one that has the ability to make the light guiding plate with a thickness less than 0.1mm. For those extremely thin light guiding plates, it is often called light guiding films (LGF) rather than light guiding plates. The low power consumption and slim body of the LGF make it having been adopted as lighting keyboard in compact products such as personal computers and cell phones since 2010, which can also reduce the number of LEDs used in these products. The main focus of this thesis is to optimize the optical performance of the LGF for its application in slim back-light module. In this work, we take 13.3” TFT LCD and 3.5” TFT LCD as our design object, trying to find the optimum design of the back-light module by using thermal embossing LGF with different thicknesses and micro surface structures. From our experimental results, it is found that using thicker LGF can improve the overall luminescence, smoother edge of the LGF gives more uniform light distribution, and facilitating 120o V-cut at the edge of the LGF reduces the hot-spot when using the LED light bar as the light source.
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Hsu, Shih-Huan, and 許世煥. "Optimization by Pairwise Linkage Detection, IncrementalLinkage Set, and Restricted / Back Mixing:DSMGA-II." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/79004402954781747596.
Full textAbstract:
碩士國立臺灣大學
電機工程學研究所
103
This thesis proposes a new evolutionary algorithm, called DSMGA-II, to efficiently solve optimization problems via exploiting problem substructures. The proposed algorithm adopts pairwise linkage detection and stores the information in the form of dependency structure matrix (DSM). A new linkage model, called the incremental linkage set, is then constructed by using the DSM. Inspired by the idea of optimal mixing, the restricted mixing and the back mixing are proposed. The former aims at efficiently exploration under certain constrains. The latter aims at exploitation by re ning the DSM so as to reduce unnecessary evaluations. Experimental results show that DSMGA-II outperforms LT-GOMEA and hBOA in terms of number of function evaluations on the concatenated/folded/cyclic trap problems, NK-landscape problems with various degrees of overlapping, 2D Ising spin-glass problems, and MAX-SAT. The investigation of performance comparison with P3 is also included.
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Lin, Hsin-Chih, and 林欣志. "Optimization of Back-Propagation Network and Feature Selection Using Simulated Annealing Approach." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/37500654928580964653.
Full textAbstract:
碩士華梵大學
資訊管理學系碩士班
94
The back-propagation network (BPN) is a popular data mining technique. Nevertheless, different problems may require different network architectures and parameters. Therefore, rule of thumb or "try and error" methods are usually used to determine them. However, these methods may lead worse network architectures and parameters. On the other hand, a dataset may contain many features; however, not all features are beneficial for classification in BPN. Therefore, a simulated annealing (SA) approach is proposed to obtain the better network architectures and parameters, and to select the beneficial subset of features which result in a better classification. In order to evaluate the proposed approach, the datasets in UCI Machine Learning Repository are used to evaluate the performance and the 10-fold cross-validation is applied to calculate the classification result. The experimental results show that the network architectures and parameters obtained by the proposed approach are better than those of other approaches. When the feature selection is taken into consideration, the classification accurate rates of most dataset are increased. Therefore, the developed approach can be utilized to find out the network architecture and parameters of BPN, and discover the useful features effectively.
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Cheng, Ming-Chia, and 鄭明嘉. "Optimization of Light Guide Plate Micro-Structure by Back-Propagation Neural Network." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/jzvey2.
Full textAbstract:
碩士國立高雄第一科技大學
光電工程研究所
96
This research proposes a newly developed optimization method for light guide plate (LGP) of extra thin back light system. The design goal will be focused at 13 to 15 inches monitor, which might be specific for notebook computer. Traditionally, LGP is optimized either by curve fitting or time-consuming try errors, which might have disadvantages in case uniformity and brightness has to perfectly be balanced. Besides, extra-thin back light system might complicate optical design. In this paper, the Back-Propagation Neural Network (BPNN) is employed to optimize the distribution of LGP micro-structure in order to achieve the well-balanced for uniformity for backlight systems. In this paper, distribution spacing of each region of the LGP is employed as the input values of the input layer in BPNN. After calculation, luminance values of each regions are treated as the target output values of the output layer of the BPNN; then have both the weighting values and the bias values well and repeatedly trained in the hidden layer of the BPNN in order to get most optimal results. The experiment shows successful results in system uniformity after finding out the input values with the best inferential output values in BPNN and Genetic Algorithms (GA). Well-balanced uniformity for extra-thin backlight system might be achieved by this newly developed optimization method.
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Wu, Chang-Rong, and 吳昌榮. "DRAM Leakage Current and Retention Time Improvement by Back-end Passivation Film Optimization." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/10750742516799731979.
Full textAbstract:
碩士長庚大學
電子工程研究所
92
DRAM data retention time has nearly doubled for each generation due to the demand of high density for high speed and low power DRAMs. However, the electric field in memory cell is also becoming stronger and leakage current has been increasing with each generation resulting in poor retention characteristics. In the work, it was found that the back-end passivation films were skipped in the standard process flow of 0.14µm 256Mb DRAMs, the performance of the leakage current and the data retention time were significantly improved. Hence, the optimization of the passivation process was studied in detail. It's well known that hydrogen penetration to the gate oxide interface is responsible for the degradation of the leakage current and the retention time. Our results also indicated that the minimization of hydrogen released from the passivation nitride is an effective way of improving the leakage current and the retention time. Another effective way is to deposit an oxide layer with higher density of dangling bonds under the passivation nitride. Interestingly, the increase of the passivation nitride thickness would not lead to a better leakage current and retention performance. A reasonable explanation is that only Si-H bonds at the interface of oxide and nitride diffuse to the gate oxide interface. All experiments in this work were performed on ASM Eagle-10 PE CVD System. A three-stage DOE was applied to optimize the properties of passivation oxide and nitride films. And then, the key parameters of each film were identified for minimizing leakage current. A model to explain the leakage current and data retention degradation phenomenon was established successfully.
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Chen, Chien Ming, and 陳建銘. "Simulation Optimization for Hybrid Flow Shop Scheduling Problem in Semiconductor Back-end Assembly." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/75563476548176832846.
Full textAbstract:
博士國立清華大學
工業工程與工程管理學系
103
This study presents a simulation optimization approach for a hybrid flow shop scheduling problem in an actual semiconductor back-end assembly facility. The complexity of the problem is determined on the basis of demand and supply. Demand varies with orders, which are in turn characterized by different quantities, product types, and release times. Supply varies with the number of flexible manufacturing routes; however, this factor is constrained in a multi-line, multi-stage production system that utilizes specific types and numbers of both identical and unrelated parallel machines. This study addresses a non-deterministic polynomial-time-hard and stochastic discrete optimization problem that is subject to numerous constraints, such as product—machine dedication and lot split and merge due to charateristics of production process. Die bond, wire bond and mold were considered as bottlenecks. Due to unbalance throughput during these three stage, there is a split behavior at die bond stage, then to wire bond for reducing flow time by parallel processing; thre is a batch behavior before mold, then batch processing at mold stage due to economic scale. In the latter, jobs that belong to the same order must be processed by the same machine type at each stage under stochastic processing and sequence-dependent setup times. A simulation optimization approach is developed in view of the complex and stochastic nature of the problem. The approach includes a simulation model for performance evaluation, an optimization strategy that applies either a genetic algorithm or particle swarm optimization, and a technique for acceleration via optimal computing budget allocation. Flow time is improved because of optimal assignment in terms of production line and machine type. Scenarios depicting the different levels of demand, product mix, and lot-split size are analyzed to reveal the advantages of the proposed simulation approach. Furthermore, lot split-size (limited 2 options) is included as a decision variable and is coupled with different meta-heuristics to enhance solution quality and practical heuristics. Future research directions are then recommended on the basis of the computational results.
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Yang, Hsiang-ti, and 楊翔廸. "Parameter Optimization and Dynamic Analysis of a Back Pull Type Impact Sustentation System." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/05066649418477909166.
Full textAbstract:
碩士逢甲大學
機械工程學所
98
he main concept of back pull impact sustentation systems focuses on by-guided vibration suppression. The design of this structure is to absorb the external substance force shock. This bumper is able to transmit the input shock into the far back of the vehicle and transfer the force into different directions. The original force will push the vehicle into the pull direction; meanwhile, it is being pulled by the internal spring in order to avoid the vehicle crash. This paper will apply SIMULINK simulation analysis software to discuss how influential this structure design is related to parameter hypothesis. The crucial point is to find out how the main body of this design receives the minimum impact in accordance with its parameter combination by using Taguchi Methods. The following step is using actual parameter to carry on the computer analogue result. Its goal is to discover the smallest target performance as soon as the structure’s main body is hit by the external impact. The result then utilizes Taguchi Methods in this paper. After being evaluated, we designate the proper controlled factor in response to the extent of influence. Subsequently, we are able to propose some improvements, redesign the structure and make parameter adjustments according to the object’s mass, damping coefficient and spring coefficient. When the structure is under the outside force impact, the alternative of Taguchi Methods factor and the level of hypothesis will result in the structure’s anti-collision and shock absorption effect. The experiment outcome thus shows the target performance presents high quality of guiding vibration suppression.
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Lin, Hwun-Fong, and 林煥豐. "The Biped Robot Motion Control Using Back-Propagation Neural Network with Particle Swarm Optimization." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/10805052763785858623.
Full textAbstract:
碩士龍華科技大學
工程技術研究所
97
This research is based on particle swarm algorithm combined with back-propagation neural network to improve the optimization of robot AI motor and the training strategy of the biped robot. The system is applied with AI motor feedback signals to compute the transfer function of the AI motor, and then through the manual mode to teach the motion trajectory for the motion control parameters of the biped robot . The system is implemented by Visual Basic and Matlab as a tool for program developments. In the research method and procedure, the PD parameters of AI motors are first optimized by the particle swarm algorithm, and then the biped robot motion trajectories are trained by manual mode. The feedback signals of all angle information are recorded as the input foot information of the hip and knee angle. Afterward, the system used the back-propagation neural network training to approach the output value as the ankle angle for the assurance the center of robot gravity located within two soles of the feet. The experimental results are shown that the particle swarm algorithm is optimized the PD parameters of AI motors as well as of the back-propagation neural network training through input angles automatically approach the corresponding ankle angles so that the motion stability of the biped is ensured. Importantly, the system is successfully applied to the robot motion learning of the upstairs walking motion.
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Lin, Ih-Siang, and 林義翔. "The Back Analysis on the Ground Temperature of Artificial Ground Freezing Using Optimization Method." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/83704559711254398183.
Full textAbstract:
碩士國立雲林科技大學
營建工程系碩士班
95
Due to its reversibility, flexibility and environmental benignity, artificial ground freezing (AGF) has been widely utilized on civil engineering projects for the construction of shafts, large open excavations, and tunnels. Practically, due to the difficulty in estimating the related thermal parameters of soil, the prediction on the ground temperature is usually based on empirical rule or oversimplified calculation methods. In view of the above, a two dimensional finite-element method coupling with nonlinear optimization method was adopted in this study to study the effect of the locations of measured temperatures, the period for temperature measuring, and the initial guess values of parameters of the model on the calculated ground temperature. A sensitivity analysis of the independent parameters of the model on the calculated temperature was also performed. The results showed the error of calculated temperature decreased with an increase in the locations of measured temperatures. The results showed the errors of calculated temperature increased with an increase in the errors of predicted diameter of frozen zone. Using the measured temperatures during longer period to establish the objective function can reduce the error of the predicted ground temperature. The optimization results of the parameters related to the unfrozen water content and the content of quartz were found to be seriously affected by its corresponding initial guess values. The results also found that volumetric water content is the most sensitive parameter to the calculated ground temperature.
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Liu, Mi-Ni, and 劉宓霓. "Study of Fabrication Process Optimization of Interdigitated Back Contact (100) Mono-crystalline Silicon Solar Cells." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/17829008227727595667.
Full textAbstract:
碩士國立雲林科技大學
機械工程系
102
This thesis is mainly to study the fabrication process optimization of interdigitated back contact (IBC) (100) mono-crystalline silicon solar cells (SCs). In this study, the 6 inch, (100), n-type CZ silicon wafer with a minority carrier lifetime of 30 μs, a thickness of 200 μm and a resistivity (ρ) of 2-7 ohm-cm is used as the starting substrate to fabricate IBCSCs by using the standard ICs and crystalline silicon (c-Si) solar cells processes. After the IBCSCs are completed, the solar simulator is used to measure and analyze the photovoltaic characteristic of IBCSCs. The research topics of this thesis include (1) the influence of nickel silicide on contact resistance of cells, (2) optimal design of the width ratio of p+ emitter to n+ emitter and contact holes opening ratio, and (3) copper metallization process. In the present result, first, the fill factors can be significantly confined in a range from 77.5 % to 81.5% and the average efficiency is also higher for the samples integrated with nickel silicide process. Second, the sample designed with a width ratio of p+ emitter to n+ emitter of 6:1 (p+/n+=300 μm/50 μm) and a contact hole opening ratio of 5 % obtains a highest efficiency of 18.01 % in this study. Third, the copper metallization process integrated with thermal evaporation of seed bilayer of Ti/Cu and Cu electro chemical deposition (ECD) has been successfully demonstrated in IBCSC process. The efficiency can be improved by 1-2 % for the sample using the rapid thermal annealing (RTA) process at 420 oC for 20 sec compared with the one without using RTA after copper metallization. In this study, for best result, the efficiency, Voc, Jsc and fill factor of IBCSC are 18.01 %, 0.59 V, 37.9 mA/cm2 and 79.1 %, respectively. Keywords: interdigitated back contact (IBC), mono-crystalline silicon solar cells, nickel silicide, width ratio of p+ emitter to n+ emitter, copper metallization
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Sundareswaran, Savithri. "Statistical characterization for timing sign-off : from silicon to design and back to silicon." 2009. http://hdl.handle.net/2152/6658.
Full textAbstract:
With aggressive technology scaling, within-die random variations are becoming the
most dominant source of process variations. Gate-level statistical static timing is becoming
a widely accepted approach as an alternative to static timing analysis. However, statistical
timing approaches lack good models for handling timing variations due to within-die random
variations. Before performing statistical timing analysis on a design or System On Chip
(SoC), the cells in the library are pre-characterized for delay as well as constraints due to
these random variations. This is referred to as statistical characterization of the cells. The
major contribution of this dissertation is the development of novel techniques for statistical
characterization and optimization of cells. The methods couple the knowledge of circuits
along with the significant factor analysis methods to compute the sensitivities, to perform
statistical timing and to perform sensitivity-aware cell optimizations.
The first contribution of this dissertation is a statistical delay characterization
method developed for computing delay sensitivities of standard cells considering both global
and mismatch process variations. In addition to the cells being characterized for delay, the sequential cells are characterized for timing constraints like setup and hold time constraints.
The second contribution of this dissertation addresses the problem of constraint sensitivity
characterization in sequential cells.
Block-based statistical timing approaches lack accurate consideration of the impact
of slew variations on both delay and arrival time variations. Specifically, the delay variations
due to within-die random variables (mismatch variables) result in a slew-based correlation
during timing propagation. Handling within-die random variations more accurately during
statistical timing propagation is the topic of the third contribution of this dissertation.
Clock networks are more prone to these within-die random variations and can result in significant
clock-skew variations. In the fourth contribution, a timing margining methodology
is presented that accurately accounts for the clock skew variations in a timing sign-off flow.
Typically, the standard cells are designed very early in the design cycle and long before
the process reaches production maturity. Any subtle improvements to reduce variability
in standard cells can improve parametric yield significantly. Statistical characterization of
cells for timing provides a key baseline for understanding the circuit behavior due to different
sources of variation. The sensitivity information can also help increase yield by reducing
the variability during the circuit design itself. The final contribution in the dissertation addresses
this by defining key cell and device criticality metrics. A sensitivity-aware standard
cell layout optimization is demonstrated using the proposed criticality metrics.text
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Lee, Ming-Shun, and 李明勳. "A Study of the Deformation Behavior of Gravel Tunnel based on Back Analysis by Optimization Method." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/38456753461549298624.
Full textAbstract:
碩士國立臺灣科技大學
營建工程系
89
This research studied the excavation behavior of “Pakuashan tunnel”, which is being excavated in central Taiwan and is part of the Hanbau-Tsaotun Expressway. Two dimensional finite difference program, FLAC,was adopted to build a two dimensional numerical model to simulate multi-staged excavation of tunnel. This case was stuied with the simplex method of the optimization theory to reduce the analysis time of three dimensional program. By comparing the measurement data collected on the site with the analysis results, the elastic modulus (E) and the coefficient of at-rest earth pressure (K) of the minimum total objective function are obtained. Besides, according to the results, this research investigates the deformation behavior of excavation of gravel tunnels. The conclusions of the research are as follows: 1.It could reduce much analysis time by using two dimensional analysis. 2.By using the simplex method to back-analyze the left and right lanes of the east and west portal of Pakuashan tunnel, results show that the E value is about 200 to 1500 MPa and the K value is about 0.70 to 1.10. 3.The measurement data collected on the site illustrate that the defo- rmations occurred during top heading excavation are about 80~90% of the total deformations after bench excavation. 4.If the delay of the first measurement is long, the measured deformations will be 70~98% of the total deformations. The accuracy of the deformation data will be affected by construction work quite easily.
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Liao, Ying-Tzong, and 廖英宗. "A Study of Global Optimization Algorithms for Back Propagation - A Case Study of Freeway Incident Resource Allocation." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/48289535504478894579.
Full textAbstract:
碩士淡江大學
運輸管理學系
88
Due to the significant learning ability, the Neural Network algorithm has been applied to all kinds of domains recently. However, the existence of local optimal points, using global searching algorithm to improve the performance for Back Propagation Network (BPN) becomes a common research topic. The investigation declared that Threshold Accepting (TA), Great Deluge Algorithm (GDA) and Simulated Annealing (SA) have better performance in solving problems with local optimal points. So, this study employs architecture of Neural Network as the kernel and combines with global optimization search algorithm to improve the performance of traditional BPN algorithm. Regarding the allocation process of rescue resources, the quality of current resource assignment processes is depended upon dispatcher’s work experiences. In usual, the assignments are completed by hand and responses must be made right away, so it's easy to happen the mismatches of the resource allocation in turn the needs of extra efforts for re-allocation. Although there is no any application instance of BPN in Taiwan now, using BPN can easily establish the mapping relations between accident information and the work load for the resource allocation. From this study, we can draw a few significant results as follows. 1.With fewer nodes, TA, GDA and SA have better performance in convergence for problem learning mechanism than the traditional Neural Network algorithm. 2.For single event, the modified algorithm has accuracy in average more than 80%. 3.To cope with the local optimal points and improve inferior solution, the global optimal search algorithm can improve the quality of convergent solution and save computation time. 4.Due to the ineffective incident management procedures, the needs to develop an automatic identification surveillance system using self learning BNP algorithm for incident management are the urgent task.
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Huang, Yi-Jie, and 黃義傑. "Using Back-Propagation Neural Network Optimization for Digital Watermarking Identification of the Spatial Domain and Frequency Domain." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/74p3d6.
Full textAbstract:
碩士國立虎尾科技大學
電機工程研究所
102
The digital watermark is a popular way to protect intellectual properties and copyrights. Although the digital watermark is robust, environmental interference to images or artificial modification through network can ruin it. As the damage exceed the limit, the digital watermark can’t be extracted. This thesis talks about the identification of noise-interfered digital watermarks. We use a 32x32 image of our school’s badge as the watermark identification code. Three methods are used to embed this watermark into a 256x256 image of Lena. The first method is the least significant bit(LSB) replacement, which is the most popular method is spatial domain. The other two are discrete cosine transform(DCT) and discrete wavelet transform(DWT) in frequency domain. We compare the peak signal to noise ratio(PSNR) of the naturally damaged image and the geometrically distorted image whose watermark is embedded in spatial domain or frequency domain. And we extract the normalized correlations(NC) of the watermarks. To emulate the noise of natural damage, we introduce the Pepper and Salt noise and the Gaussian noise; To emulate the noise of geometric distortion, we introduce the median filter, clipping, rotation, and the JPEG compression. These three image of Lena with embedded watermarks are damaged to a certain level. The extracted watermarks can be barely recognized as the original watermark. But the overly damaged noises can’t be recognized. To enhance the normalized correlation(NC) of the watermark, we use the back-propagation neural network to optimize the recognition process. And we find that the watermark, which is recognized by the back-propagation neural network, is more identical to the original one.
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Li, Hao-Wei, and 李皓瑋. "Applying Moving Bootstrap and Back-Propagation Neural Network for the Optimization Demand Forecasting Model of Spare Parts." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/64z45d.
Full textAbstract:
碩士國立臺中科技大學
流通管理系碩士班
105
Inventory control of spare parts has been an essential to many organizations since it is one of the most expensive assets. Most of the spare parts are to belong to intermittent demand and Bootstrapping has been claimed to be of great value for forecasting. While a small proportion of spare parts are regard to regular demand, Moving Average, frequently used to deal with this type of demand. We address combination forecasting model by the Moving Bootstrap based on Bootstrapping and Moving Average to classify the appropriate method. Then use the Back-Propagation Neural Network to construct the classification model which can be used to automatically select the better approach of forecasting. We find that the main explanatory variables about consumption of daily average, the ratio of days with zero consumption and standard deviation of daily consumption can exact classify the demand forecasting approach. In the future, enterprise arranges to purchase new spare parts, this combination model will assist in concluding the forecasting method and reducing the forecast error. Moreover, it leads to lower stock costs and improves operational performance.