Spelling suggestions: "subject:"nonlinearity"" "subject:"noncolinearity""
181 |
Understanding and Accelerating the Optimization of Modern Machine LearningLiu, Chaoyue January 2021 (has links)
No description available.
|
182 |
Is peacebuilding a phase? – Analyzing the peacebuilding in El Salvador 30 years after the civil warOlsson, Gabriella January 2022 (has links)
Even if the messiness of peacebuilding has been recognized for some time, peacebuilding has still been viewed as quite linear, meaning there’s a transition from war to peace and that peacebuilding is a phase. Recently, other voices have been raised claiming we need a paradigm shift and to stop seeing peacebuilding as linear and instead see it as a never-ending constantly adapting practice. The question then arises, if it is possible to distinguish that peacebuilding connected to a specific conflict ends at some point and if society adapts to conduct peacebuilding for new tensions within society. That is what this thesis aims to find out, and it does so by mapping the activities of the civil society in a post-conflict country, as civil society constitutes an excellent indicator of what kind of peacebuilding is being done. The case studied is El Salvador, which ended a 12-year-long civil war with a peace agreement in 1992. The activities are mapped with the help of a framework for analyzing civil society peacebuilding. The study concludes that much of the peacebuilding activities connected to the civil war seem to have ended, except for when it comes to the rights of people who became disabled by the civil war, as well as trauma treatment activities addressing trauma from the civil war. Civil society also shows certain adaptation to the gang violence, by addressing it with trauma treatment activities and activities aiming at building a culture of peace.
|
183 |
Simultaneous Aircraft Localization and Mapping using Signals of Opportunity and Inverse Depth ParametrizationRamsberg, Oskar, Wigström, Elin January 2024 (has links)
In modern combat aircraft, the most common localization method integrates a Global Navigation Satellite System (GNSS) with an Inertial Navigation System (INS). Although GNSS is the optimal choice for navigation, there are situations when the GNSS satellite signal is unavailable. This can happen due to various reasons such as jamming, physical obstacles, or technical failures. An alternative method to GNSS is utilizing Signals of Opportunity (SOP), which leverages signals not intended for navigation, such as those from cellular towers. These signals are transmitted from non-controllable sources, and challenges may arise due to the lack of guarantee regarding their quality and availability. Therefore, it is crucial that any estimation method utilizing SOP is robust to ensure accurate aircraft localization. This thesis investigates three different localization approaches to address this challenge. This study explores SOP sources with both known and unknown positions. For known signal source positions, an Extended Kalman Filter (EKF) based solution is utilized as a baseline to evaluate how well unknown signal sources can be used to estimate the aircraft's location. To address the challenge of unknown signal source positions, an EKF combined with a Simultaneous Localization and Mapping (SLAM) method, referred to as EKF SLAM, is used. In this case, the sources are introduced through two different approaches. The first approach, undelayed initialization, introduces the signal source directly when observed. The second approach, delayed initialization, involves inverse depth parameterization (IDP) and preprocessing of the signal source position before fully introducing it into the aircraft system. While both approaches outperform an unassisted INS approach, they do not achieve the same level of performance as when the source positions are known. Moreover, various factors, including the aircraft's trajectory, measurement noise, measurement frequency, and the initial covariance of new landmarks, influence the performance of the EKF SLAM approaches. Additionally, delayed initialization is strongly influenced by a threshold assessing landmark position estimate linearity, underscoring its sensitivity to accuracy. The concept behind delayed initialization aims to reduce the error of the signal source position before it is introduced to the system. This method has been proven to significantly reduce the signal source position error. However, its robustness is influenced by several factors, including the parallax angle, sudden changes in the aircraft's direction, and particularly the initial covariance of a landmark estimate. The accuracy of the aircraft's position is crucial, resulting in a trade-off between preprocessing and rapidly initializing a signal source position to the aircraft system. In contrast, undelayed initialization is less sensitive to trajectory changes, even though it introduces the signal sources with greater initial error. There is a significant difference in computational time when comparing known and unknown sources. As the number of sources increases, the computational time for unknown sources is more affected than for known sources. The delayed source initialization method increases computational time due to its preprocessing, especially as more sources are used. Conversely, initializing sources directly reduces the computational time, as no preprocessing is required. / I moderna stridsflygplan är den vanligaste lokaliseringsmetoden att integrera ett Global Navigation Satellite System (GNSS) med ett Inertial Navigation System (INS). Även om GNSS är det optimala valet för navigation finns det situationer när GNSS-satellitsignalen inte är tillgänglig. Detta kan inträffa på grund av olika orsaker som störningar, fysiska hinder eller tekniska fel. En alternativ metod till GNSS är att använda Signals of Opportunity (SOP), som utnyttjar signaler som inte är avsedda för navigation, till exempel de från mobilmaster. Dessa signaler kommer från okontrollerbara källor, vilket kan medföra utmaningar på grund av att deras kvalitet och tillgänglighet inte kan garanteras. Därför är det viktigt att varje lokaliseringsmetod som använder SOP är robust för att säkerställa en bra och korrekt flygplans positionering. Detta examensarbete undersöker tre olika lokaliseringsmetoder för att hantera denna utmaning. Denna studie utforskar SOP-källor med både kända och okända positioner. För kända positioner används en lösning baserad på ett Extended Kalman Filter (EKF) som en baslinje för att utvärdera hur väl okända signalkällor kan användas för att uppskatta flygplanets position. För att hantera utmaningen med okända signalkällors positioner används ett EKF kombinerad med en metod vid namn Simultaneous Localization and Mapping (SLAM), även kallad EKF SLAM. I detta fall introduceras källorna genom två olika tillvägagångssätt. Det första tillvägagångssättet, ofördröjd initialisering, introducerar signalkällan direkt när den observeras. Det andra tillvägagångssättet, fördröjd initialisering, involverar inverse depth parameterization (IDP) och förbearbetning av signalkällans position innan den introduceras i flygplanets lokaliseringssystem. Även om båda tillvägagångssätten presterar bättre än en oassisterad INS-metod uppnår de inte samma prestandanivå som när källornas position är kända. Dessutom påverkar olika faktorer prestandan hos EKF SLAM-metoderna, vilka främst är flygplanets flygbana, mätbrus, mätfrekvens och den initiala kovariansen av nya landmärken. Dessutom påverkas fördröjd initialisering starkt av en tröskel som bedömer linjäritet hos landmärkes positionen, vilket understryker dess känslighet för noggrannhet. Konceptet bakom fördröjd initialisering syftar till att minska felet i signalkällans position innan den introduceras i lokaliseringssystemet. Denna metod har visat sig kunna minska felet i signalkällans position avsevärt. Emellertid påverkas dess robusthet av flera faktorer, inklusive parallaxvinkeln, plötsliga förändringar i flygplanets riktning och särskilt den initiala kovariansen av uppskattningen av ett landmärkes position. Noggrannheten i flygplanets position är avgörande, vilket resulterar i en avvägning mellan förbearbetning och snabb initialisering av en signalkällas position till flygplanets lokaliseringssystem. Till skillnad från fördröjd initialisering är ofördröjd initialisering mindre känslig för förändringar i flygbanan, även om den introducerar signalkällorna med större initialt fel. Det finns en anmärkningsvärd skillnad i beräkningstid när man jämför kända och okända källors. När antalet källor ökar påverkas beräkningstiden för okända källor mer än för kända källor. Den fördröjda källinitialiseringsmetoden ökar beräkningstiden på grund av dess förbearbetning, särskilt när många källor används. Däremot minskar beräkningstiden när källor initialiseras direkt, eftersom ingen förbearbetning krävs.
|
184 |
A Unified Measure of Audio System FidelityTedesco, Lawrence A., Jr. 15 December 2007 (has links)
A new technique to qualitatively measure distortion in dynamically controlled audio systems using non-stationary noise sequences is explored and compared to traditional methods based upon stationary test signals. This technique can easily be adapted to give a qualitative measure of distortion as a function of the perceived Sound Pressure Level (SPL).
|
185 |
O MEC e o MEF aplicados à análise de problemas viscoplásticos em meios anisotrópicos e compostos / The BEM and FEM applied for analysis of viscoplastics problems in the anisotropic and composites mediasVanalli, Leandro 06 August 2004 (has links)
O objetivo do presente trabalho é o desenvolvimento de formulações e de códigos computacionais que possibilitem a análise bidimensional estática de meios contínuos anisotrópicos viscoplásticos reforçados ou não por fibras. Especificamente, as análises numéricas envolvem aplicações dos métodos dos elementos de contorno (MEC) e dos elementos finitos (MEF), comparando-se os resultados obtidos com respostas analíticas e experimentais, disponíveis na literatura, buscando-se assim, subsídios teóricos que permitam o entendimento de problemas mais gerais envolvendo meios anisotrópicos. Para tanto são empregados elementos finitos triangulares com aproximações cúbica e quadrática para os deslocamentos na modelagem dos domínios. Na consideração do reforço com fibras, elementos finitos de barras simples são empregados. A formulação desenvolvida proporciona também a consideração de distribuição randômica das fibras imersas no meio sem qualquer aumento dos graus de liberdade do problema analisado, diferindo-se assim, das formulações conhecidas até o momento. Com o MEC, a análise de plasticidade e viscoplasticidade em meios com anisotropia geral é feita de maneira original no trabalho, destacando-se a consideração de lei de fluxo plástico não-associativa e o tratamento de viscosidade apenas com integrais de contorno, sem a utilização de aproximações de domínio. Uma quantidade significativa de exemplos é apresentada, possibilitando a verificação da eficiência das formulações e dos códigos desenvolvidos / The objective of the present work is the development of formulations and computational codes that enable the static bidimensional analysis of the viscoplastic anisotropic medias reinforced, or not, by fibers. Specifically, the numerical analysis involve applications of the boundary elements method (BEM) and finite elements (FEM), comparing the results obtained with analytical and experimental solutions available in the literature, allowing the understanding of general problems in anisotropic media. Two-dimensional finite elements with cubic and quadrate approximations for the displacements are used to model domains. Reinforcements are modeled by truss finite elements. The developed formulation provides the consideration of random distribution of the fibers, without any additional degree of freedom of the problem. With the BEM, the plasticity and viscoplasticity analysis in general anisotropic medias is originally developed in the present work, emphasizing the consideration of non-associative plastic flow and the treatment of viscosity just with boundary integrals, without domain approximation. Various examples are shown in order to verify the efficiency of the proposed formulation and developed computational codes
|
186 |
Aplicação do acoplamento entre o MEC e o MEF para o estudo da interação dinâmica elastoplástica entre o solo e estruturas / BEM/FEM coupling application to the study of the elastoplastic dynamic interaction between soil and structuresAlmeida, Francisco Patrick Araujo 24 October 2003 (has links)
O objetivo do presente trabalho é o desenvolvimento de um código computacional que possibilite a análise dinâmica de estruturas tridimensionais em regime elástico-linear acopladas ao solo, tratado como meio infinito elastoplástico. As superestruturas são tratadas por elementos finitos simples de casca e de barra geral, as estruturas de fundações são tratadas por elementos de casca que simulam o contato com o solo, modelando radiers, túneis e reservatórios enterrados. Blocos são modelados por elementos de contorno tridimensionais. O solo é modelado de duas maneiras distintas: na região plastificada emprega-se a solução fundamental de Kelvin (estática) e na região não plastificada (elástica) adota-se a solução fundamental do problema de Stokes. O acoplamento entre os meios é feito aplicando-se a técnica de subregiões. Deve ficar claro que todo procedimento estático equivalente foi implementado. Vários exemplos numéricos são apresentados, onde se percebe a eficiência do código computacional desenvolvido / The objective of the present work is the development of a computational code that makes possible dynamic analyses of three-dimensional structures in elastic-linear behavior coupled to the soil, modeled as elastoplastic infinite medium. Simple finite elements, shell and general bars, are used to model elastic structures. The structures of foundations are modeled by shells elements which simulate the contact with the soil, modeling radiers, tunnels and buried reservoirs. Blocks are modeled by three-dimensional boundary elements. The soil is modeled in two different ways: in the plastic region Kelvins fundamental solution (static) is used and in the elastic region the fundamental solution of the Stokes problem is adopted. The coupling among the media is done applying the sub-region technique. It is important to note that the equivalent static procedure has been implemented. Several numerical examples are presented, demonstrating the efficiency of the developed computational code
|
187 |
Hyperfiction, creativity and postmodern novel / L'hyperfiction, la créativité et le roman postmoderneDarougari, Baharak 29 September 2018 (has links)
Depuis l’invention du terme hypertexte par Ted Nelson en 1965, il y a eu des débats fréquents à propos des mérites et des dangers des textes numériques, pour savoir si le développement des technologies informatiques causerait l’obsolescence des supports imprimés. Les prophéties étaient apocalyptiques et l’avenir des livres semblait sombre. Environ cinquante ans plus tard, tant les supports imprimés qui étaient condamnés que les hypertextes numériques qui semblaient être leurs exécuteurs existent encore. Les romans sont toujours populaires et les hypertextes aussi. Nul n’est dépassé ou éradiqué par l’autre. Au contraire, la coexistence des livres et leurs homologues numériques a affecté notre perception des textes, des lecteurs, des auteurs et de l’expérience de lecture. Plus important, l’échange entre les deux médias a eu comme résultat l’apparition d’une fiction expérimentale exceptionnelle à la fois sur écran et sur papier. La conjonction entre la fiction et les technologies numériques est au centre de ce projet qui vise à d’étudier l’hyperfiction, ses racines dans la fiction traditionnelle et ses descendants imprimés. / Since Ted Nelson coined the term “hypertext” in 1965, there have been frequent debates on the merits and dangers of digital texts and whether the development of digital technology would outdate the print-based medium. The prophecies were apocalyptic and the future of books seemed bleak. About fifty years later, the doomed print-based medium and the digital hypertexts, their would-be executioners,both still exist. Novels are still popular and so is hyperfiction. Neither outdated or eradicated the other. Instead, the coexistence of books and their digital counterparts has affected ourperception of text, reader, writer and the reading experience. More importantly, the exchange between the two media has resulted in exceptional experimental fiction both on screen and on paper. The conjunction between fiction and digital technology is of concern to this project which attempts to study hyperfiction, its roots in fiction and its printed descendants.
|
188 |
Contributions à la réduction de dimensionKuentz, Vanessa 20 November 2009 (has links)
Cette thèse est consacrée au problème de la réduction de dimension. Cette thématique centrale en Statistique vise à rechercher des sous-espaces de faibles dimensions tout en minimisant la perte d'information contenue dans les données. Tout d'abord, nous nous intéressons à des méthodes de statistique multidimensionnelle dans le cas de variables qualitatives. Nous abordons la question de la rotation en Analyse des Correspondances Multiples (ACM). Nous définissons l'expression analytique de l'angle de rotation planaire optimal pour le critère de rotation choisi. Lorsque le nombre de composantes principales retenues est supérieur à deux, nous utilisons un algorithme de rotations planaires successives de paires de facteurs. Nous proposons également différents algorithmes de classification de variables qualitatives qui visent à optimiser un critère de partitionnement basé sur la notion de rapports de corrélation. Un jeu de données réelles illustre les intérêts pratiques de la rotation en ACM et permet de comparer empiriquement les différents algorithmes de classification de variables qualitatives proposés. Puis nous considérons un modèle de régression semiparamétrique, plus précisément nous nous intéressons à la méthode de régression inverse par tranchage (SIR pour Sliced Inverse Regression). Nous développons une approche basée sur un partitionnement de l'espace des covariables, qui est utilisable lorsque la condition fondamentale de linéarité de la variable explicative est violée. Une seconde adaptation, utilisant le bootstrap, est proposée afin d'améliorer l'estimation de la base du sous-espace de réduction de dimension. Des résultats asymptotiques sont donnés et une étude sur des données simulées démontre la supériorité des approches proposées. Enfin les différentes applications et collaborations interdisciplinaires réalisées durant la thèse sont décrites. / This thesis concentrates on dimension reduction approaches, that seek for lower dimensional subspaces minimizing the lost of statistical information. First we focus on multivariate analysis for categorical data. The rotation problem in Multiple Correspondence Analysis (MCA) is treated. We give the analytic expression of the optimal angle of planar rotation for the chosen criterion. If more than two principal components are to be retained, this planar solution is used in a practical algorithm applying successive pairwise planar rotations. Different algorithms for the clustering of categorical variables are also proposed to maximize a given partitioning criterion based on correlation ratios. A real data application highlights the benefits of using rotation in MCA and provides an empirical comparison of the proposed algorithms for categorical variable clustering. Then we study the semiparametric regression method SIR (Sliced Inverse Regression). We propose an extension based on the partitioning of the predictor space that can be used when the crucial linearity condition of the predictor is not verified. We also introduce bagging versions of SIR to improve the estimation of the basis of the dimension reduction subspace. Asymptotic properties of the estimators are obtained and a simulation study shows the good numerical behaviour of the proposed methods. Finally applied multivariate data analysis on various areas is described.
|
189 |
臨床實驗藥量特性之研究 / Characterizing dose response curve in clincal trials方廷企 Unknown Date (has links)
在製藥工業中,藥量特性之研究常被應用於藥理學、毒物學及臨床試驗中。藥量特性之研究同時在臨床試驗中的第一階段的藥物安全性及第二階段的藥物有效性中扮演著重要的角色。透過藥量特性的研究,使我們對於藥物的開發有著更深一層的認識,並可藉此縮短藥物核准上市的時間。
在多數的情況下,我們對於藥物動力學之參數與藥物劑量間的線性關係,有著特別的興趣。基於這個目的,一些典型的方法即是由一般線性模式發展而成的。然而,這些典型的統計方法常遇到下列的難題而違反其假設:(一)不同藥物劑量間的異質變異性。(二)不滿足常態性的假設。針對這些問題,我們藉由比較不同劑量間的斜率關係的無母數檢定程序來評估其線性關係並刻劃出藥物的反應曲線,文中並藉此方法舉出交叉實驗之實例。 / The problem of characterizing dose response curve for a pharmacokinetic parameter over a specific dose range is considered. In many cases, it is of interest to determine dose linearity (or dose proportionality) between the pharmacokinetic parameters and dose levels. For this purpose, several classical methods based on a general linear model procedure are available. However, two difficulties commonly encountered, namely (i) heterogeneity of the varibility at different dose levels and (ii) violation of the normality assumptions, often make the classical methods not applicable. To account for these problems, we propose a general nonparametric test procedure by comparing the slopes at different dose level to asses dose linearity and to characterize dose response curve. An example concerning the study of dose response of a compound based on a four-way crossover experiment is presented.
|
190 |
Golanhöjderna, den strategiska betydelsen 1967-1973Bengtsson, Kristofer January 2009 (has links)
<p>The topic of this essay is the strategic importance of the <em>Golan Heights</em> during the period <em>1967-1973, </em>specifically targeting the following<em> </em>questions;</p><p>- <em>Why were the heights strategically important</em>?</p><p>- <em>What are the gains of either of the states in controlling the Golan Heights?</em></p><p>A theoretical framework based on Jerker Widén´s and Jan Ångström´s <em>Militärteorins grunder</em> (The fundamentals in Military Theory) and its chapter regarding the strategic context will be used as an analytical framework.</p><p>The framework has been applied on the specific conditions of the Golan Heights during a given and limited period of time; stretching from 1967 to 1973, however, the study will <em>not</em> deal with the <em>war of attrition</em> in 1970 as the impact on the Golan Heights and the surrounding geographical strategically important area was limited if at all. The two wars waged during this particular time are used in an attempt to give a somewhat objective picture of the strategic importance of the area.</p><p>The conclusions are that the importance of the Golan heights during the selected period was significant as the Golan Heights provided a “strategic lock” both ways and provides a favourable area to deploy artillery, intelligence and surveillance sensors.</p> / <p>Denna uppsats behandlar främst de grundläggande teorierna kring strategi applicerade på referensobjektet Golanhöjderna under åren 1967-1973.</p><p>Syftet är att svara på frågorna:</p><p><em>Varför var höjderna viktiga ur ett strategiskt perspektiv?</em></p><p><em>Vilka fördelar vinner endera</em> <em>staten på att besitta dem?</em></p><p>Tidsrymden har valts med tanke på att det är under denna tid som de häftigaste striderna ägde rum på detta specifika terrängavsnitt. Utnötningskriget 1970 berörs ej då det inte berörde terrängavsnittet. De parter som behandlas är Israel och Syrien då dessa gränsar till varandra runt Golanhöjderna.</p><p>De bägge parternas planer och mål under stridigheterna kommer att analyseras enligt en deskriptivt-analyserande metod och även till viss del jämföras vad avser deras avsikter och önskade slutläge.</p><p>Den teoretiska referensramen, vilken skall fungera som ett analysverktyg, består huvudsakligen av sex belysande aspekter som tillsammans kan beskriva den strategiska bilden, hämtade ur Jerker Widéns och Jan Ångströms bok <em>Militärteorins grunder</em>. Utöver dessa sex aspekter kommer även manöverkrig, linjaritet samt rysk krigskonst att beskrivas. Dessa operationaliseras sedan på referensobjektet och leder fram till en diskussion som sedan mynnar ut i ett antal slutsatser.</p><p>De slutsatser som har dragits är att Golanhöjderna har en strategisk vikt i området 1967-1973 då de fungerade som ett ”strategiskt lås” för bägge sidor samt att höjderna var värdefulla ur underrättelse-/spaningshänseende.</p>
|
Page generated in 0.0577 seconds