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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Development and Implementation of Rotorcraft Preliminary Design Methodology using Multidisciplinary Design Optimization

Khalid, Adeel S. 14 November 2006 (has links)
A formal framework is developed and implemented in this research for preliminary rotorcraft design using IPPD methodology. All the technical aspects of design are considered including the vehicle engineering, dynamic analysis, stability and control, aerodynamic performance, propulsion, transmission design, weight and balance, noise analysis and economic analysis. The design loop starts with a detailed analysis of requirements. A baseline is selected and upgrade targets are identified depending on the mission requirements. An Overall Evaluation Criterion (OEC) is developed that is used to measure the goodness of the design or to compare the design with competitors. The requirements analysis and baseline upgrade targets lead to the initial sizing and performance estimation of the new design. The digital information is then passed to disciplinary experts. This is where the detailed disciplinary analyses are performed. Information is transferred from one discipline to another as the design loop is iterated. To coordinate all the disciplines in the product development cycle, Multidisciplinary Design Optimization (MDO) techniques e.g. All At Once (AAO) and Collaborative Optimization (CO) are suggested. The methodology is implemented on a Light Turbine Training Helicopter (LTTH) design. Detailed disciplinary analyses are integrated through a common platform for efficient and centralized transfer of design information from one discipline to another in a collaborative manner. Several disciplinary and system level optimization problems are solved. After all the constraints of a multidisciplinary problem have been satisfied and an optimal design has been obtained, it is compared with the initial baseline, using the earlier developed OEC, to measure the level of improvement achieved. Finally a digital preliminary design is proposed. The proposed design methodology provides an automated design framework, facilitates parallel design by removing disciplinary interdependency, current and updated information is made available to all disciplines at all times of the design through a central collaborative repository, overall design time is reduced and an optimized design is achieved.
162

Kleene-Type Results for Weighted Tree-Automata / Kleeneartige Resultate für Gewichtete Baumautomaten

Pech, Christian 08 March 2004 (has links) (PDF)
The main result of this thesis is the generalization of the Kleene-theorem to formal tree-series over commutative semirings (the Kleene theorem states the coincidence between rational and recognizable formal languages). To this end weighted tree-languages are introduced and the Kleene-theorem is proved for them. The desired result for formal tree-series is then obtained through application of a homomorphism that relates weighted tree-languages with formal tree-series. In the second part of the thesis the connections to the theorie of Iteration-theories are discovered. In particular it is shown there that the grove-theory of formal tree-series forms a partial iteration-theory. / Hauptresultat dieser Arbeit ist die Verallgemeinerung des Satzes von Kleene über die Koinzidenz der rationalen und der erkennbaren Sprachen auf den Fall der formalen Baumreihen über kommutativen Semiringen. Zu diesem Zweck werden gewichtete Baumsprachen eingeführt, da sich diese ählich den klassischen Baumsprachen verhalten. Der Satz von Kleene wird also zunächst auf den Fall der gewichteten Baumsprachen verallgemeinert. Das erstrebte Resultat wird dann durch Anwendung eines Homomorphismus', der gewichteten Baumsprachen formle Baumreihen zuordnet, erhalten. Im zweiten Teil der Arbeit werden Kreuzverbindungen zur Theorie der Iterationstheorien aufgezeigt. Insbesondere wird z.B. gezeigt, dass die Grovetheorie der formalen Baumreihen eine partielle Iterationstheorie bildet.
163

Berechnung singulärer Punkte nichtlinearer Gleichungssysteme

Schnabel, Uwe 20 November 2000 (has links) (PDF)
Diese Arbeit beschäftigt sich mit der Berechnung singulärer Punkte nichtlinearer Gleichungssysteme F(x)=0. Dazu werden minimal erweiterte Systeme der Form F(x)+D*s=0, f(x)=0 betrachtet. Die allgemeine Vorgehensweise zur Berechnung singulärer Punkte mit solchen erweiterten Systemen wird geschlossen dargestellt. Dazu werden zuerst die (teilweise verallgemeinerten Ljapunov-Schmidt-)reduzierten Funktionen von Golubitsky und Schaeffer, Beyn, Jepson und Spence, Griewank und Reddien, Kunkel bzw. Govaerts verallgemeinert und zusammengefasst. Es wird die verallgemeinerte Kontaktäquivalenz all dieser verallgemeinerten reduzierten Funktionen und die Gleichheit der benötigten Regularitätsannahmen bewiesen. Für eine weitere, neu eingeführte reduzierte Funktion wird die in dieser Arbeit definierte Ableitungsäquivalenz zu den anderen reduzierten Funktionen gezeigt. Mit dieser neuen reduzierten Funktion wird eine Reihe singulärer Punkte klassifiziert. Aus dieser Klassifikation ergeben sich Funktionen f aus Ableitungen der neuen reduzierten Funktion. Mit den so eingeführten Funktionen f kann das zweistufiges Newtonverfahren nach Pönisch und Schwetlick effektiv angewendet werden. Alle benötigten Ableitungen werden mittels Automatischer Differentiation bestimmt. Die numerischen Ergebnisse für eine Reihe von Beispielen zeigen die Effizienz dieses Verfahrens. Beim Newtonverfahren werden lineare Gleichungssysteme mit geränderten Matrizen B gelöst. Es wird gezeigt, für welche Ränderungen die Konditionszahl von B minimal ist. Dies ist z.B. für gewisse Vielfache der Singulärvektoren zu den kleinsten Singulärwerten der Fall. Zur Bestimmung dieser Ränderungen wird die inverse Teilraumiteration für Singulärwerte in verschiedenen Algorithmen angewendet. Die Konvergenzeigenschaften werden untersucht. Für einen Algorithmus wird bewiesen, dass die Konditionszahlen der iterierten geränderten Matrizen monoton fallen. Die numerischen Experimente bestätigen diese Eigenschaften.
164

On numerical resilience in linear algebra / Conception d'algorithmes numériques pour la résilience en algèbre linéaire

Zounon, Mawussi 01 April 2015 (has links)
Comme la puissance de calcul des systèmes de calcul haute performance continue de croître, en utilisant un grand nombre de cœurs CPU ou d’unités de calcul spécialisées, les applications hautes performances destinées à la résolution des problèmes de très grande échelle sont de plus en plus sujettes à des pannes. En conséquence, la communauté de calcul haute performance a proposé de nombreuses contributions pour concevoir des applications tolérantes aux pannes. Cette étude porte sur une nouvelle classe d’algorithmes numériques de tolérance aux pannes au niveau de l’application qui ne nécessite pas de ressources supplémentaires, à savoir, des unités de calcul ou du temps de calcul additionnel, en l’absence de pannes. En supposant qu’un mécanisme distinct assure la détection des pannes, nous proposons des algorithmes numériques pour extraire des informations pertinentes à partir des données disponibles après une pannes. Après l’extraction de données, les données critiques manquantes sont régénérées grâce à des stratégies d’interpolation pour constituer des informations pertinentes pour redémarrer numériquement l’algorithme. Nous avons conçu ces méthodes appelées techniques d’Interpolation-restart pour des problèmes d’algèbre linéaire numérique tels que la résolution de systèmes linéaires ou des problèmes aux valeurs propres qui sont indispensables dans de nombreux noyaux scientifiques et applications d’ingénierie. La résolution de ces problèmes est souvent la partie dominante; en termes de temps de calcul, des applications scientifiques. Dans le cadre solveurs linéaires du sous-espace de Krylov, les entrées perdues de l’itération sont interpolées en utilisant les entrées disponibles sur les nœuds encore disponibles pour définir une nouvelle estimation de la solution initiale avant de redémarrer la méthode de Krylov. En particulier, nous considérons deux politiques d’interpolation qui préservent les propriétés numériques clés de solveurs linéaires bien connus, à savoir la décroissance monotone de la norme-A de l’erreur du gradient conjugué ou la décroissance monotone de la norme résiduelle de GMRES. Nous avons évalué l’impact du taux de pannes et l’impact de la quantité de données perdues sur la robustesse des stratégies de résilience conçues. Les expériences ont montré que nos stratégies numériques sont robustes même en présence de grandes fréquences de pannes, et de perte de grand volume de données. Dans le but de concevoir des solveurs résilients de résolution de problèmes aux valeurs propres, nous avons modifié les stratégies d’interpolation conçues pour les systèmes linéaires. Nous avons revisité les méthodes itératives de l’état de l’art pour la résolution des problèmes de valeurs propres creux à la lumière des stratégies d’Interpolation-restart. Pour chaque méthode considérée, nous avons adapté les stratégies d’Interpolation-restart pour régénérer autant d’informations spectrale que possible. Afin d’évaluer la performance de nos stratégies numériques, nous avons considéré un solveur parallèle hybride (direct/itérative) pleinement fonctionnel nommé MaPHyS pour la résolution des systèmes linéaires creux, et nous proposons des solutions numériques pour concevoir une version tolérante aux pannes du solveur. Le solveur étant hybride, nous nous concentrons dans cette étude sur l’étape de résolution itérative, qui est souvent l’étape dominante dans la pratique. Les solutions numériques proposées comportent deux volets. A chaque fois que cela est possible, nous exploitons la redondance de données entre les processus du solveur pour effectuer une régénération exacte des données en faisant des copies astucieuses dans les processus. D’autre part, les données perdues qui ne sont plus disponibles sur aucun processus sont régénérées grâce à un mécanisme d’interpolation. / As the computational power of high performance computing (HPC) systems continues to increase by using huge number of cores or specialized processing units, HPC applications are increasingly prone to faults. This study covers a new class of numerical fault tolerance algorithms at application level that does not require extra resources, i.e., computational unit or computing time, when no fault occurs. Assuming that a separate mechanism ensures fault detection, we propose numerical algorithms to extract relevant information from available data after a fault. After data extraction, well chosen part of missing data is regenerated through interpolation strategies to constitute meaningful inputs to numerically restart the algorithm. We have designed these methods called Interpolation-restart techniques for numerical linear algebra problems such as the solution of linear systems or eigen-problems that are the inner most numerical kernels in many scientific and engineering applications and also often ones of the most time consuming parts. In the framework of Krylov subspace linear solvers the lost entries of the iterate are interpolated using the available entries on the still alive nodes to define a new initial guess before restarting the Krylov method. In particular, we consider two interpolation policies that preserve key numerical properties of well-known linear solvers, namely the monotony decrease of the A-norm of the error of the conjugate gradient or the residual norm decrease of GMRES. We assess the impact of the fault rate and the amount of lost data on the robustness of the resulting linear solvers.For eigensolvers, we revisited state-of-the-art methods for solving large sparse eigenvalue problems namely the Arnoldi methods, subspace iteration methods and the Jacobi-Davidson method, in the light of Interpolation-restart strategies. For each considered eigensolver, we adapted the Interpolation-restart strategies to regenerate as much spectral information as possible. Through intensive experiments, we illustrate the qualitative numerical behavior of the resulting schemes when the number of faults and the amount of lost data are varied; and we demonstrate that they exhibit a numerical robustness close to that of fault-free calculations. In order to assess the efficiency of our numerical strategies, we have consideredan actual fully-featured parallel sparse hybrid (direct/iterative) linear solver, MaPHyS, and we proposed numerical remedies to design a resilient version of the solver. The solver being hybrid, we focus in this study on the iterative solution step, which is often the dominant step in practice. The numerical remedies we propose are twofold. Whenever possible, we exploit the natural data redundancy between processes from the solver toperform an exact recovery through clever copies over processes. Otherwise, data that has been lost and is not available anymore on any process is recovered through Interpolationrestart strategies. These numerical remedies have been implemented in the MaPHyS parallel solver so that we can assess their efficiency on a large number of processing units (up to 12; 288 CPU cores) for solving large-scale real-life problems.
165

既有建物作為空載光達系統點雲精度評估程序之研究 / The Study of Accuracy Assessment Procedure on Point Clouds from Airborne LiDAR Systems Using Existing Buildings

詹立丞, Chan, Li Cheng Unknown Date (has links)
空載光達系統於建置國土測繪基本資料扮演關鍵角色,依國土測繪法,為確保測繪成果品質,應依測量計畫目的及作業精度需求辦理儀器校正。國土測繪中心已於102年度建置航遙測感應器系統校正作業中,提出矩形建物之平屋頂面做為空載光達系統校正之可行性,而其所稱之校正,是以點雲精度評估待校件空載光達系統所得最終成果品質,並不對儀器做任何參數改正,但其校正成果可能因不同人員操作而有差異,因此本研究嘗試建立一套空載光達點雲半自動化精度評估程序,此外探討以山形屋脊線執行點雲精度評估之可行性。 由於光達點雲為離散的三維資訊,不論是以山形屋脊線或矩形建物之平屋頂面作為標物執行點雲精度評估,均須先萃取屋頂面上之點,為避免萃取成果受雜訊影響,本研究引入粗差偵測理論,發展最小一乘法結合李德仁以後驗變方估計原理導出的選擇權迭代法(李德仁法)將非屋頂點視為粗差排除。研究中分別對矩形建物之平屋頂面及山形屋脊線進行模擬及真實資料實驗,其中山形屋脊線作為點雲精度評估之可行性實驗中發現不適合用於評估點雲精度,因此後續實驗僅以萃取矩形建物之平屋頂面點雲過程探討粗差比率對半自動化點雲精度評估程序之影響。模擬實驗成果顯示最小一乘法有助於提升李德仁法偵測粗差數量5%至10%;真實資料實驗,以含有牆面點雲的狀況為例,則有助提升5%的偵測粗差數量。本研究由逐步測試結果提出能夠適用於真實狀況的半自動化之點雲精度評估程序,即使由不同人員操作,仍能獲得一致的成果,顯示本研究半自動化精度評估程序之可信度。 / The airborne LiDAR system plays a crucial role in building land surveying data. Based on the Land Surveying and Mapping Act, to ensure the quality of surveying, instrument calibration is required. The approach proposed by National Land Surveying and Mapping Center (NLSC) in 2013 was confirmed the feasibility for airborne LiDAR system calibration using rectangular horizontal roof plane. The calibration mean to assess the final quality of airborne LiDAR system based on the assessment of the accuracy of the point cloud, and do not adjust the instrument. But the results may vary according to different operators. This study attempts to establish a semi-automatic procedure for the accuracy assessment of point clouds from airborne LiDAR system. In addition, the gable roof ridge lines is discussed for its feasibility for the accuracy assessment of point cloud. No matter that calibration is performed using rectangular horizontal roof plane or gable roof ridge line, point clouds located on roof planes need to be extracted at first. Therefore, Least Absolute Deviation (LAD) combined with the Iteration using Selected Weights (Deren Li method) is developed to exclude the non-roof points which regarded as gross errors and eliminate their influences. The simulated test and actual data test found that gable roof ridge lines are not suitable for accuracy assessment. As for the simulated test using horizontal roof planes, LAD combined with Deren Li method prompts the rate of gross error detection about 5% to 10% than that only by Deren Li method. In actual test, data contains wall points, LAD combined with Deren Li method can prompt about 5%. Meanwhile, a semi-automatic procedure for real operations is proposed by the step-by-step test. Even different operators employ this semi-automatic procedure, consistent results will be obtained and the reliability can achieve.
166

Sustainability in practice : a study of how reflexive agents negotiate multiple domains of consumption, enact change, and articulate visions of the 'good life'

Schröder, Thomas January 2013 (has links)
A small proportion of people claim to live and consume in ways they consider more sustainable in social and environmental terms. As yet, we do not know how many exactly, but possibly no more than 5-10% of the population. The thesis intentionally focuses on this minority finding there are at least three reasons why it is interesting to do so. First because they are all but ignored in sociologies of practice in the context of sustainable consumption which considers this minority an insignificance and focuses almost exclusively on 'mainstream' majority which more closely maps onto the stereotype of 'consumer society'. Second because we think we can learn much from juxtapositioning this group empirically against the spectrum of theories of practice to devise more robust and appropriate theoretical explanation of how these subjects, in the context of everyday practice, negotiate the many interpretations and contradictions involved in trying to put 'sustainability' into practice. Third because by understanding them better we can reflect on theoretical, empirical and policy implications for nudging this minority of the population to a higher percentage. The thesis sits at one end of a spectrum of positions in theories of practice applied to consumption, and in particular with a normative interest in sustainable consumption. It aligns with those who seek to re-insert the reflexive agent into accounts of practice, with particular reference to the conceptual construct of the 'citizen-consumer' and the context of political consumption (Spaargaren & Oosterveer 2010). Referring to theories of consumption, the thesis adds perspectives on how people negotiate multiple domains of consumption simultaneously since everyday practice involves interactions across multiple domains (such as eating, mobility, householding); and yet typically in theories of practice these are artificially separated into single domains. The study therefore considers the implications which domains have on how particular practices are carried out, first separately (per domain) and then as they come together (in a cross-cutting domain perspective). The study then takes theories of practice as a springboard to develop a theoretical position and framework which better fits the narrated accounts of the 37 subjects who participated in this study. In iteratively co-developing a theoretical framework and multiple 'stages' of empirical research (using grounded theory methodology) the study seeks to explain theoretically how subjects justify their 'doings' (drawing on 'conventions' and 'orders of worth' (Boltanski & Thévenot 2006)); how they appear to muddle through as best they can (introducing 'bricolage' (Lévi-Strauss 1972)); and how subjects appear to devise decision short-cuts when approaching decisions characterised by the multiple contradictions of sustainable consumption and incomplete or 'too much' information (introducing heuristics (Gigerenzer & Gaissmaier 2011)). In joining calls to re-insert the reflexive agent to account for how, when and why subjects enact changes towards trajectories which they consider 'more sustainable' in their own terms, the study takes inspiration from Margaret Archer's morphogenesis approach (1998) and explores her model of multiple modes of reflexivity, announcing certain modes as 'better fitting' conditions of late modernity. The study finally finds that contrary to a notion of the un-reflexive agent, the citizen-consumer is able to articulate visions of the 'good life'. In addition she is able to fold these visions back onto everyday practices performed in the past, present and future, laying out normative guidelines and positive accounts of how to achieve personal or societal well-being and happiness. The overarching positioning of the study is much inspired by Andrew Sayer's (2011; 2000) 'normative turn' calling upon social sciences to re-instate research into the things about which people care. The study is therefore guided by the overarching question of how people translate their environmental and/or social concerns into the ways in which they live and consume.
167

Berechnung singulärer Punkte nichtlinearer Gleichungssysteme

Schnabel, Uwe 27 October 2000 (has links)
Diese Arbeit beschäftigt sich mit der Berechnung singulärer Punkte nichtlinearer Gleichungssysteme F(x)=0. Dazu werden minimal erweiterte Systeme der Form F(x)+D*s=0, f(x)=0 betrachtet. Die allgemeine Vorgehensweise zur Berechnung singulärer Punkte mit solchen erweiterten Systemen wird geschlossen dargestellt. Dazu werden zuerst die (teilweise verallgemeinerten Ljapunov-Schmidt-)reduzierten Funktionen von Golubitsky und Schaeffer, Beyn, Jepson und Spence, Griewank und Reddien, Kunkel bzw. Govaerts verallgemeinert und zusammengefasst. Es wird die verallgemeinerte Kontaktäquivalenz all dieser verallgemeinerten reduzierten Funktionen und die Gleichheit der benötigten Regularitätsannahmen bewiesen. Für eine weitere, neu eingeführte reduzierte Funktion wird die in dieser Arbeit definierte Ableitungsäquivalenz zu den anderen reduzierten Funktionen gezeigt. Mit dieser neuen reduzierten Funktion wird eine Reihe singulärer Punkte klassifiziert. Aus dieser Klassifikation ergeben sich Funktionen f aus Ableitungen der neuen reduzierten Funktion. Mit den so eingeführten Funktionen f kann das zweistufiges Newtonverfahren nach Pönisch und Schwetlick effektiv angewendet werden. Alle benötigten Ableitungen werden mittels Automatischer Differentiation bestimmt. Die numerischen Ergebnisse für eine Reihe von Beispielen zeigen die Effizienz dieses Verfahrens. Beim Newtonverfahren werden lineare Gleichungssysteme mit geränderten Matrizen B gelöst. Es wird gezeigt, für welche Ränderungen die Konditionszahl von B minimal ist. Dies ist z.B. für gewisse Vielfache der Singulärvektoren zu den kleinsten Singulärwerten der Fall. Zur Bestimmung dieser Ränderungen wird die inverse Teilraumiteration für Singulärwerte in verschiedenen Algorithmen angewendet. Die Konvergenzeigenschaften werden untersucht. Für einen Algorithmus wird bewiesen, dass die Konditionszahlen der iterierten geränderten Matrizen monoton fallen. Die numerischen Experimente bestätigen diese Eigenschaften.
168

Zabezpečení vysokorychlostních komunikačních systémů / Protection of highspeed communication systems

Smékal, David January 2015 (has links)
The diploma thesis deals with 128–bit AES data encryption and its implementation in FPGA network card using VHDL programming language. The theoretical part explains AES encryption and decryption, its individual steps and operating modes. Further was described the VHDL programming language, development environment Vivado, FPGA network card Combo–80G and configurable framework NetCOPE. The practical part is the implementation of AES–128 in VHDL. A simulation was used to eliminate errors, then the synthesis was performed. These steps were made using Vivado software. Last step of practical part was testing of synthesized firmware on COMBO–80G card. Total of 4 projects were implemented in FPGA card. Two of them were AES encryption and decryption with ECB mode and another two describe the encryption and decryption with CBC mode.
169

Ustálený chod a zkratové poměry v síti 110 kV E.ON napájené z transformovny Sokolnice / Steady state and short-circuit conditions in 110kV E.ON network fed from Sokolnice transformer station

Vyčítal, Václav January 2015 (has links)
This thesis can be divided into five main parts. The first part deals with theoretical analysis of power flow calculation in power network during steady state condition. Load flow calculation is presented here as a linear and nonlinear problem. Newton iteration method is proposed for solving power flow as nonlinear problem. The second part of this thesis deals with the analysis of short-circuit calculation in accordance with valid International Standard IEC 60909. The equivalent voltage source method is adopted in case of the short-circuit calculation. For the calculation of unbalanced short-circuit currents, the symmetrical components method is also presented. The last three parts of this paper are focused on calculations of power flow and short-circuit conditions in power grid Sokolnice. So in the third part is the description of nodal area Sokolnice with its substations and the calculation of load flow and short-circuit conditions for two different power supply options. For each supply option is also considered an abnormal (fault) grid condition. (overall there are solved four different options) The fourth part of this thesis deals with the result analysis and also the results of different power supply options are compared. In the last part there are presented necessary technical improvements for fault-free operation of power grid Sokolnice based on the result of power flow and short-circuit conditions in that grid.
170

Kleene-Type Results for Weighted Tree-Automata

Pech, Christian 18 August 2003 (has links)
The main result of this thesis is the generalization of the Kleene-theorem to formal tree-series over commutative semirings (the Kleene theorem states the coincidence between rational and recognizable formal languages). To this end weighted tree-languages are introduced and the Kleene-theorem is proved for them. The desired result for formal tree-series is then obtained through application of a homomorphism that relates weighted tree-languages with formal tree-series. In the second part of the thesis the connections to the theorie of Iteration-theories are discovered. In particular it is shown there that the grove-theory of formal tree-series forms a partial iteration-theory. / Hauptresultat dieser Arbeit ist die Verallgemeinerung des Satzes von Kleene über die Koinzidenz der rationalen und der erkennbaren Sprachen auf den Fall der formalen Baumreihen über kommutativen Semiringen. Zu diesem Zweck werden gewichtete Baumsprachen eingeführt, da sich diese ählich den klassischen Baumsprachen verhalten. Der Satz von Kleene wird also zunächst auf den Fall der gewichteten Baumsprachen verallgemeinert. Das erstrebte Resultat wird dann durch Anwendung eines Homomorphismus', der gewichteten Baumsprachen formle Baumreihen zuordnet, erhalten. Im zweiten Teil der Arbeit werden Kreuzverbindungen zur Theorie der Iterationstheorien aufgezeigt. Insbesondere wird z.B. gezeigt, dass die Grovetheorie der formalen Baumreihen eine partielle Iterationstheorie bildet.

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