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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.
91

Design, modeling and control of a convertible mini airplane having four tiliting rotors / Conception, modélisation et commande d'un drone convertible à quatre hélices pivotantes

Flores Colunga, Gerardo Ramón 31 October 2014 (has links)
Cette thèse étudie certains problèmes plus importants dans le sens de guidage, navigation et contrôle présentés dans une catégorie particulière de mini véhicules aériens (MVA) : le MVA convertible avec des ailes fixes et disques pendulaires. Cet aéronef est capable de changer sa configuration de vol, du vol stationnaire au vol palier et vice versa, au moyen d’une manœuvre de transition. Motivé par des applications civiles, on étudie théoriquement et expérimentalement les principes de contrôle en fonction de Lyapunov pour les dynamiques présentées dans le MVA convertible. Des résultats de convergence asymptotique sont obtenus sur l’enveloppe de vol complet du véhicule : d’un vol vertical à basse vitesse à un vol vers l’avant à grande vitesse. Cette thèse est divisée en quatre parties principales : l’étude de 1) les aéronefs à voilure fixe ; 2) le quadrirotor (avion équipe de quatre moteurs) ; 3) l’aéronef convertible ; 4) les applications de vision en utilisant l’aéronef convertible. Dans la première partie, un principe de contrôle en fonction de Lyapunov est développé pour diriger un mini véhicule aérien à voilure fixe tout au long d’un chemin d’accès souhaité. En outre, un générateur de chemin d’accès est proposé. Le résultant de la stratégie du contrôle donne une convergence globale du chemin actuel du MVA au chemin d’accès souhaité. Dans la deuxième partie, un contrôle en fonction de Lyapunov à l’aide de la théorie de la perturbation du singulier est proposé et appliqué sur la dynamique du MVA. En effet, dans cette partie on a abordé le problème diagnostic et la détection de pannes fault detection and diagnosis (FDD) pour un quadrirotor. Dans la troisième partie une nouvelle stratégie de contrôle pour effectuer la transition d’un avion convertible entre le mode avion et le mode hélicoptère, et vice versa, est présenté. L’analyse est effectuée pour le modèle longitudinal du PVHAT (Planar Vertical Helicopter-Airplane Transition) aéronef, lequel est un avion ayant disques pendulaires afin de réaliser la manœuvre de transition. L’algorithme de contrôle de boucle fermée qui en résulte, est prouvé être globalement asymptotiquement stable. Finalement, dans la quatrième partie de cette thèse, le problème de l’estimation et suivi d’un chemin à l’aide de vision système embarqué dans l’avion PVHAT est résolu. La stabilité globale exponentielle de la position sous-système ainsi que le contrôleur de commutation est démontrée. Des simulations illustratives et résultats expérimentaux sont obtenus sur plusieurs plateformes expérimentales développées dans cette thèse, pour évaluer l’applicabilité des principes contrôle proposés et mettre en valeur les mérites de l’approche. / This thesis studies some of the most relevant problems in the sense of guidance,navigation and control presented in a particular class of mini aerial vehicles (MAV) : the convertible MAV with fixed wings and tilting rotors. This aircraft is able to change its flight configuration from hover to level flight and vice-versaby means of a transition maneuver. Motivated by civilian applications, we theoretically and experimentally study Lyapunov-based control laws for dynamics presented in the convertible MAV. Results of asymptotic convergence are obtained over the complete flight envelope of the vehicle : from low-speed vertical flight through high-speed forward flight. We have divided this thesis in four main parts : the study of 1) the fixed-wingaircraft; 2) the quadrotor; 3) the convertible aircraft and 4) vision applications by using the convertible aircraft. In a first part, a Lyapunov-based controllaw is developed to steer a fixed wing mini aerial vehicle along a desired path. Furthermore a path generator is proposed. The resulting control strategy yields global convergence of the current path of the MAV to the desired path. In a second part, a Lyapunov-based control using singular perturbation theory is proposed and applied on dynamics of the MAV. Furthermore, in this part we address the problem of fault detection and diagnosis (FDD) for a quad-rotor. In the third part a new control strategy for the transition between airplane and helicopter mode, and vice versa, in convertible planes is presented. The analysis is carried out for the longitudinal model of the PVHAT (Planar VerticalHelicopter-Airplane Transition) aircraft, which is an airplane having tilting rotors in order to achieve the transition maneuver. The resulting closed loop control algorithm is proved to be globally asymptotically stable. Finally in thefourth part of this thesis the problem of estimation and tracking of a road using avision embedded system in the PVHAT aircraft is solved. The global exponential stability of the position subsystem together with the switching controller is demonstrated. Illustrative simulations and experimental results obtained on several experimental platforms developed in this thesis, assess the implementability of the proposed control laws and highlight the merits of the approach.
92

Nybyggnad av konverteringsbara kontor : Praktiska och ekonomiska konsekvenser / Construction of convertible offices : Practical and Economical consequences

Löwstett, Johan, Norberg, Emil January 2015 (has links)
Frågan om hur kontorsbyggnader som är anpassade för att konverteras till bostäder är idag inte utredd för svenska förhållanden. I arbetet så visar vi hur marknadens aktörer ställer sig till konceptet. Vi redovisar vilka ekonomiska och byggtekniska förutsättningar som bör beaktas i en projektering och vilken påverkan dessa har på utformning och ekonomi. Den främsta förutsättningen för att konceptet ska fungera är var byggnaden är placerad. Det bästa läget har visat sig vara i områden där vilken verksamhet som kommer dominera är osäker eller verkar kunna ändras de kommande 10-20 åren. I det läget kan olika ekonomiska strategier användas, antingen som riskminimering vid osäker framtid eller för att på ett effektivare sätt använda marken i ett område där kommersiell verksamhet är lämpligast idag, men bostäder kommer passa bäst inom överskådlig framtid. Ifall konceptet är något som kommer kunna stärka miljöprofilen får idag sägas vara oklart. Idén har väckt störst intresse hos fastighetsägare som ser sig själva som långsiktiga med ett perspektiv som överstiger 10 år.   Byggnadstekniskt så har de största utmaningarna vid konvertering av konventionella kontor identifierats till installationer och geometri. Det är inte möjligt att lösa dessa problem utan att göra avkall på andra faktorer som smalare huskroppar för att kunna placera lägenheter på ett lämpligare sätt eller andra typer av bjälklag som antingen bygger med i höjd eller ger längre produktionstid. Ekonomiskt så är den största utmaningen risken att förlora uthyrningsbar area som kan uppstå för att uppnå godtagbar geometri för bostäder. Konvertering leder till lägre nyttjande av fastigheten. Konceptet kan fungera som en lönsam försäkringspremie förutsatt att krav på exploateringen kan tillgodoses, vilket får anses vara svårt i dagsläget. Dessutom finns ett motstånd i branschen mot att betala för de merkostnader som uppstår. Risken för en fördröjd planprocess bör även ses som en kostsam faktor som minimierar möjligheter av konceptet. / The question about the construction of office buildings which are prepared to be converted into dwellings has not yet been sufficiently explored for Swedish conditions. In this report we will show how the markets participants approach the subject. We will show which conditions are necessary to consider during the construction process and the effects these have on the design and economy. The primary condition has been identified as the location of the building. It has been shown that an area where the future functions are uncertain, or susceptible to change in the coming 10-20 years, is the most suitable.  In such an event different economic strategies may be applied, either as reduction of risks to answer to an uncertain future or to use the property in a more efficient way where a commercial function might be preferred today but residence will be the most suitable in a foreseeable future. As of construction, the biggest problem during conversions from offices to residence has been identified as geometry and installations. It is not possible to solve these without sacrificing different factors and may cause thinner buildings and different type of floor structures that may cause taller buildings or increased construction time. Economical, the toughest challenge is the risk of losing rentable area due to the adaptation of the buildings geometry, although key indicators are showing the efficiency of the property compared in this study indicates that there is no significant difference in that aspect. The concept might work as a profitable insurance provided that demands of development rate are met, which are considered difficult. Investment analysis shows that the building needs high vacancy rates for it to be profitable to convert the building. Apart from that there is also a resistance in the industry to pay for the additional costs that arises.
93

考量信用風險下之海外可轉債評價 / Pricing Euro-Convertible Bonds with Credit Risk

吳岱恩, Wu, Tai En Unknown Date (has links)
鑒於近年全球海外可轉換公司債發行檔數大增,然而以此商品為研究主題的文獻並不多,於是決定以此為研究目標。   影響海外可轉換公司債的價格因素包括股票價格、匯率、國內利率、國外利率和發行公司的違約機率,因此可買回、可賣回海外可轉換公司債是一個複雜的商品,而評價也較為困難。本文採用三維度二項樹和最小平方蒙地卡羅法建立評價海外可轉債的數值模型。為了更貼近真實世界,本文考量各變數間相關性和動態信用風險;另外,為了使評價更為精準,於股價過程中加入跳躍過程。   本文將模型運用至兩檔台灣公司所發行的海外可轉債,發現理論價格傾向於高估,但是理論價格與市價極為接近,尤其當以最小平方蒙地卡羅法評價時。另外本文也針對發行條件和模型中各個變數作敏感度分析,其中重要的是發現股票波動度、股票與匯率間相關係數在海外可轉債評價中扮演重要的角色。 / The number of Euro-convertible bonds issued has highly increased in the early 2010s. However, the related literature is barely found. This paper studies the pricing models of this investment product. Euro-convertible bonds are complex instruments affected by the credit risk of the issuers, the dynamic process of stock prices, the term structure of the interest rate and the movement of the exchange rate in the same time. Accordingly, building the ECB pricing model is a hard work. This paper presents a model considering the dynamic credit risk and jump in stock price process to make valuation more precise. Another advantage of models in this paper is use of stochastic interest rates for both local and foreign so as to make the model more staying with the real world. The other advantage is taking the correlation between each random variables into account. For pricing the Euro-convertible bonds, the numerical methodologies used in this paper are three-dimension binomial tree and least squares Monte Carlo approach. For purpose of assessing the performance of the model, two Euro-convertible bonds issued by Taiwan companies are chosen as samples and the difference between the theoretical price and market price during its issue period are provided. The results demonstrate that in spite of pretty slight overestimation, the least squares Monte Carlo simulation does a better job. In addition, this paper performs several kinds of sensitivity analysis to have in-depth understanding about the models. The consequence shows that the volatility of a stock return and the correlation between stock and exchange rate play a central role in ECB valuations.
94

海外可轉換公司債的評價-考慮平均重設條款、信用風險及利率期間結構

張世東, CHANG SHIH TUNG Unknown Date (has links)
影響海外可轉換公司債的因素有許多,包括股價、國內利率、國外利率、匯率,若將時間變數也加入計算,其變動因子高達5階,這種「高維度」的問題已非有限差分法或樹狀方法能處理;且海外可轉債常附有平均式條款、回顧式條款等「路徑相依」性質的選擇權,更是格狀結構數值法(Lattice)難以處理的問題。若使用蒙地卡羅模擬,雖然可以處理高維度及路徑相依的問題,但遇到美式契約時,則會有無法判斷轉換時點的問題,更遑論還必須處理的重設條款或界限型契約。 本論文研究海外可轉換公司債的評價,特點是可以處理其契約中各種可能的複雜條款,本文所使用的最小平方蒙地卡羅模擬,由Longstaff and Schwartz [2000]提出,對於美式契約、路徑相依及高維度問題皆可處理。本文並以Hull and White利率三元樹配適公司債利率符合市場利率期間結構。此外本研究加入海外可轉換公司債評價中最重要的信用風險因素,過去可轉債文獻理論價格大都高於實際市價,這是由於忽略了公司的信用風險溢酬,本文所使用的信用風險模型是由Lando [1998]所提出,特點是不以信用等級作為考量,探討公司特性與所屬產業,並考慮總體因素對違約機率的影響,從市場價格中估計違約密度參數,進而求得信用價差。 本研究對仁寶電腦在2002年所發的ECB做實證研究,比較LSM理論價格與實際市價之誤差,及對Takahashi[2001]所提出之歐式模型做比較,發現本文提出模型之評價結果相當不錯,誤差僅有0.83%;此外並對建華金控2002所發之ECB,探討各種複雜新奇條款對ECB價格的影響,發現市場上嚴重低估了重設條款所提高的價值,而實際市價卻十分接近僅含賣回條款的理論價格。
95

Ensaio sobre o regime jurídico das debêntures / Essay on the legal regime of debentures

Amaral, Jose Romeu Garcia do 31 March 2014 (has links)
Este trabalho propõe-se a estudar, mediante abordagem teórica e prática, o regime jurídico das debêntures, tendo em vista as recentes alterações introduzidas pela Lei nº 12.431, de 24 de junho de 2011, que promoveu mudanças significativas em sua disciplina, bem como examinar os problemas e questões atuais das debêntures em um contexto evolutivo da doutrina e dos casos práticos que lhe são submetidos à análise, tendo em vista o uso cada vez mais frequente desse mecanismo de financiamento das sociedades. Busca-se, também, examinar o funcionamento do mercado de debêntures e as novas propostas para incentivar a circulação dos títulos de dívida. Dentre as questões mais controvertidas a serem estudadas neste trabalho, destacam-se as seguintes: (i) evolução da natureza jurídica do instituto, em que as debêntures são vistas como títulos de dívida pertencentes à categoria dos valores mobiliários; (ii) criação do novo mercado de debêntures, como avanço à proposta do Novo Mercado de Renda Fixa; (iii) possibilidade de emissão de debêntures por sociedades limitadas e cooperativas, em razão da ausência de vedação legal e da existência de normas que lhe dão suporte jurídico; (iv) realização de negócios jurídicos com debêntures que vão além da sua função econômica de financiamento da empresa; (v) existência da organização dos debenturistas, em complemento à ideia de comunhão de interesses, tendo em vista o seu caráter orgânico; e, por fim, (vi) se os deveres fiduciários dos administradores se voltariam também aos interesses dos debenturistas, como credores especiais da sociedade emitente. / This work aims to study, through a theoretical and practical approach, the legal system of debentures in view of the recent changes introduced by Law No. 1431, of June 24, 2011, affecting significantly their discipline, and also to examine their current problems and issues within the evolutionary context of the doctrine and the case studies that are submitted to analysis, since the use of this financing mechanism by companies has been increasingly frequent. It also seeks to examine the functioning of the debenture market and the new proposals to stimulate the circulation of debt bonds. Amongst the most controversial issues to be studied in this work, the following are highlighted: (i) the evolution of the legal nature of this institute, in which debentures are seen as debt notes pertaining to the category of securities; (ii) the creation of a new debenture market as an advancement to the proposal of the New Fixed Income Market; (iii) the possibility of limited partnerships and cooperatives issuing debentures in view of the absence of a legal prohibition and the existence of norms that give legal support to it; (iv) the consummation of legal transactions with debentures that go beyond their economic function of business financing; (v) the existence of a debenture holder organization as a complement to the idea of pooling of interests, in view of its organic character; and, finally, (vi) whether the fiduciary duties of the administrators would also accommodate the interests of the debenture holders, while in their position of special creditors to the issuing business.
96

兩段迴歸結合蒙地卡羅模擬對可轉債定價之研究 / Pricing Convertible Bonds by Piecewise Regression and Monte Carlo Simulation

董恆元, Tung, Heng Yuan Unknown Date (has links)
可轉換公司債兼具了選擇權以及債券的性質,價值又會受到股價之影響,以傳統的方法定價十分不易。由於蒙地卡羅模擬能解決定價問題上狀態變數或許為多維度及路徑相依的問題,Kind 與Wilde 在2004 年提出以蒙地卡羅模擬對可轉債定價,且以最小平方迴歸法估計繼續持有價值,並在僅考慮轉換及還本兩種選擇權及沒有違約風險之下,以數值範例呈現單一迴歸模式無法適當估計繼續持有價值。然而,他們並未進行實證。本研究乃以民國99 年台灣發行的可轉債為研究對象,除考慮發行時的合約條件外,另加上信用評等的考量以將違約機率透過現金流量套入定價過程中,並分別以兩段迴歸及單一迴歸估計繼續持有價值以結合蒙地卡羅模擬,實證結果顯示就可轉債之起始定價的偏差比而言,兩段迴歸得到的結果優於單一迴歸。惟在兩段迴歸之下,超過八成的可轉債其模擬價格依然高於市場價格。實證結果也顯示價性(moneyness)及擔保狀況與定價的偏差有關。 / Convertible bonds (CBs) possess features of both bonds and options, and their prices are affected by the underlying stocks, which make the pricing problem an uneasy task for traditional methods. Since Monte Carlo simulation can handle the problems of path-dependence and multivariate dimensions faced by pricing, Kind and Wilde (2004) suggested to price CBs via least-squares Monte Carlo simulations (LSM), which estimate the continuation values by least squares regression. They also demonstrated that a single regression line could not appropriately estimate the continuation value even only conversion and redemption were allowed and the CB was free of default. So the idea of piecewise regression was recommended to improve the estimation process. However, they didn’t apply piecewise regression to real data. Therefore, piecewise regression together with Monte Carlo simulation were employed to investigate the pricing issue of Taiwan’s CBs. CBs issued on 2010 were selected, besides reviewing the contents of CB’s contracts, default risks based on credit ratings were taken into account to evaluate the discounted cash flows in the pricing procedure. Comparing the estimated model prices of LSM with initial selling prices, the mispricing rates of single regression model and piecewise regression model were obtained for further analysis. Result shows that the modified piecewise regression method performs better in mispricing rate. However, similar to previous findings, 80% of the estimated model prices based on piecewise regressions are still higher than market prices. It also shows that moneyness and guaranteed condition will relate to mispricing rate.
97

Ensaio sobre o regime jurídico das debêntures / Essay on the legal regime of debentures

Jose Romeu Garcia do Amaral 31 March 2014 (has links)
Este trabalho propõe-se a estudar, mediante abordagem teórica e prática, o regime jurídico das debêntures, tendo em vista as recentes alterações introduzidas pela Lei nº 12.431, de 24 de junho de 2011, que promoveu mudanças significativas em sua disciplina, bem como examinar os problemas e questões atuais das debêntures em um contexto evolutivo da doutrina e dos casos práticos que lhe são submetidos à análise, tendo em vista o uso cada vez mais frequente desse mecanismo de financiamento das sociedades. Busca-se, também, examinar o funcionamento do mercado de debêntures e as novas propostas para incentivar a circulação dos títulos de dívida. Dentre as questões mais controvertidas a serem estudadas neste trabalho, destacam-se as seguintes: (i) evolução da natureza jurídica do instituto, em que as debêntures são vistas como títulos de dívida pertencentes à categoria dos valores mobiliários; (ii) criação do novo mercado de debêntures, como avanço à proposta do Novo Mercado de Renda Fixa; (iii) possibilidade de emissão de debêntures por sociedades limitadas e cooperativas, em razão da ausência de vedação legal e da existência de normas que lhe dão suporte jurídico; (iv) realização de negócios jurídicos com debêntures que vão além da sua função econômica de financiamento da empresa; (v) existência da organização dos debenturistas, em complemento à ideia de comunhão de interesses, tendo em vista o seu caráter orgânico; e, por fim, (vi) se os deveres fiduciários dos administradores se voltariam também aos interesses dos debenturistas, como credores especiais da sociedade emitente. / This work aims to study, through a theoretical and practical approach, the legal system of debentures in view of the recent changes introduced by Law No. 1431, of June 24, 2011, affecting significantly their discipline, and also to examine their current problems and issues within the evolutionary context of the doctrine and the case studies that are submitted to analysis, since the use of this financing mechanism by companies has been increasingly frequent. It also seeks to examine the functioning of the debenture market and the new proposals to stimulate the circulation of debt bonds. Amongst the most controversial issues to be studied in this work, the following are highlighted: (i) the evolution of the legal nature of this institute, in which debentures are seen as debt notes pertaining to the category of securities; (ii) the creation of a new debenture market as an advancement to the proposal of the New Fixed Income Market; (iii) the possibility of limited partnerships and cooperatives issuing debentures in view of the absence of a legal prohibition and the existence of norms that give legal support to it; (iv) the consummation of legal transactions with debentures that go beyond their economic function of business financing; (v) the existence of a debenture holder organization as a complement to the idea of pooling of interests, in view of its organic character; and, finally, (vi) whether the fiduciary duties of the administrators would also accommodate the interests of the debenture holders, while in their position of special creditors to the issuing business.

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