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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.
11

The Importance of Prior Geologic Information on Hydraulic Tomography Analysis at the North Campus Research Site (NCRS)

Tang, Han, Tang, Han January 2016 (has links)
The purpose of this study is to investigate the importance of prior information about hydraulic conductivity (K) by Kriging, using point K data and/or residual covariance, on improvements of K estimates at the North Campus Research Site (NCRS). Among many methods that can characterize the mean or detail distribution of hydraulic conductivity (K), the Cooper-Jacob straight line solution, Kriging using point K data, single-well pumping tests inversion and Hydraulic Tomography (HT) have been compared in this study, using the head data collected from 15 cross-hole pumping tests collected at NCRS, where 9 existing wells were installed with packer system and the pressure responses at different intervals in different wells were monitored with transducers. It is found that the HT method, which fuse all the available pumping test data, yields more accurate and consistent results. However, many studies have indicated that the hydraulic data combined with geologic investigation will improve the HT estimates. Thus, in this study, hard data of K obtained by permeameter (227 data points) are brought in using Kriging and combined with HT to yield better estimate K field. Moreover, the validations of unused tests indicate that the estimated K obtained using collected K information makes more accurate predictions.
12

Matching And Reconstruction Of Line Features From Ultra-high Resolution Stereo Aerial Imagery

Ok, Ali Ozgun 01 September 2011 (has links) (PDF)
In this study, a new approach for the matching and reconstruction of line features from multispectral stereo aerial images is presented. The advantages of the existing multispectral information in aerial images are fully taken into account all over the steps of pre-processing and edge detection. To accurately describe the straight line segments, a principal component analysis technique is adapted. The initial correspondences between the stereo images are generated using a new pair-wise stereo matching approach which involves a total of seven relational constraints. The final line to line correspondences between the stereo images are established in a precise matching stage in which the final line matches are assigned by means of three novel measures and a final similarity voting scheme. Once the line matches are established, the stereo reconstruction of those matches is performed by an innovative reconstruction approach that manipulates the redundancy inherent in line pair-relations. By this way, the reconstruction of the stereo matches that are observed in a nearly-parallel geometry with the epipolar lines can also be performed accurately. The proposed approach is tested over two different urban test sites with various built-up characteristics, and as a result, very successful and promising stereo line matching and reconstruction performances are reached. Besides, the comparison of the results of the proposed approach with the results of one of the state-of-the-art stereo matching approaches proves the superiority and the potential of proposed approach.
13

Är progressiva avskrivningar en förutsättning för nyproduktion? : En studie av effekterna vid en övergång till raka avskrivningar för bostadsrättsföreningar / Is progressive depreciations a prerequisite for production of new dwellings? : A study of the effects of a transition to straight  line depreciation for housing cooperatives

Wyckman, Oscar, Eriksson Funke, Lina January 2014 (has links)
Bakgrund: Den senaste tiden har en debatt blossat upp i media om huruvida det är rimligt att bostadsrättsföreningar får tillämpa progressiva avskrivningar och om raka avskrivningar är ett bättre alternativ. Bokföringsnämnden beslöt under våren år 2014 att progressiva avskrivningar inte är en tillämplig avskrivningsmetod för byggnader. I media har många uttalat sig om vad detta kommer få för effekt på marknaden för bostadsrätter, men det har ännu inte utretts ur ett vetenskapligt perspektiv. Syfte: Uppsatsen syftar till att bidra med detta vetenskapliga perspektiv genom att analysera huruvida progressiva avskrivningar är en förutsättning för nyproduktion. I uppsatsen ämnas även undersöka om detta skiljer mellan olika regioner i Sverige. Metod: För att besvara de i syftet ställda problemformuleringarna har en teoretisk modell utvecklats med grundantagandet att köpare av bostadsrätter ska vara indifferenta till vilken avskrivningsmetod som används. Regler och praxis kring avskrivningar i bostadsrättsföreningar har kartlagts för att kunna ge modellen adekvat utformning. Modellens slutresultat visar hur en övergång från progressiva till raka avskrivningar påverkar lönsamheten i nyproduktion av bostadsrätter. En diskussion har förts kring rimligheten i de antaganden som gjorts i modellen och det framtagna resultatet, med utgångspunkt i mikroekonomisk teori och en generell analys av bostadsmarknaden. Slutsats: Enligt de antaganden som gjorts i denna studie och den modell som tagits fram har slutsatsen dragits att de progressiva avskrivningarna på kort sikt är en förutsättning för nyproduktion. Det finns dock ett antal omständigheter som tyder på att reaktionen i verkligheten blir något mildare än vad resultatet från modellen visar. Vidare tycks effektens storlek minska ju högre marknadspriset för bostadsrätter var innan övergången till raka avskrivningar. På lång sikt är inte progressiva avskrivningar en förutsättning för nyproduktion av bostadsrätter. / Background: In Sweden, there has been a recent debate about the reasonability of the use of progressive depreciations by housing cooperatives and if straight line depreciations is a better alternative. The Swedish Accounting Standards Board decided during the spring of 2014 that progressive depreciation is not an applicable depreciation method for buildings. In media, many have discussed the effect on the market for housing cooperative shares but it has not yet been investigated with a scientific perspective. Purpose: The aim of the thesis is to contribute with this scientific perspective by analyzing if progressive depreciations is a prerequisite for production of new dwellings. The thesis is also meant to look into regional differences of this matter. Method: To answer the two problem formulations above, a theoretical model has been developed with the basic assumption that buyers of housing cooperative shares should be indifferent to which depreciation method is applied. Rules and practices of housing cooperative depreciations have been charted in order to make the model adequate. The end result of the model shows how a transition from progressive to straight line depreciation affects the profitability of production of new dwellings. With respect to microeconomic theory and a general analysis of the housing market, a discussion has been carried out about the model assumptions and the model results. Conclusions: According to the used model and its assumptions, the conclusion has been made that progressive depreciations is a short term prerequisite for production of new dwellings. Although, there are circumstances that indicate that the market reaction would be milder than what the model results show. Furthermore, the effect of the depreciation method transition seems to decrease with higher market prices for the housing cooperative shares. In the long term, progressive depreciations is not a prerequisite for production of new dwellings.
14

Graph compression using graph grammars

Peternek, Fabian Hans Adolf January 2018 (has links)
This thesis presents work done on compressed graph representations via hyperedge replacement grammars. It comprises two main parts. Firstly the RePair compression scheme, known for strings and trees, is generalized to graphs using graph grammars. Given an object, the scheme produces a small context-free grammar generating the object (called a “straight-line grammar”). The theoretical foundations of this generalization are presented, followed by a description of a prototype implementation. This implementation is then evaluated on real-world and synthetic graphs. The experiments show that several graphs can be compressed stronger by the new method, than by current state-of-the-art approaches. The second part considers algorithmic questions of straight-line graph grammars. Two algorithms are presented to traverse the graph represented by such a grammar. Both algorithms have advantages and disadvantages: the first one works with any grammar but its runtime per traversal step is dependent on the input grammar. The second algorithm only needs constant time per traversal step, but works for a restricted class of grammars and requires quadratic preprocessing time and space. Finally speed-up algorithms are considered. These are algorithms that can decide specific problems in time depending only on the size of the compressed representation, and might thus be faster than a traditional algorithm would on the decompressed structure. The idea of such algorithms is to reuse computation already done for the rules of the grammar. The possible speed-ups achieved this way is proportional to the compression ratio of the grammar. The main results here are a method to answer “regular path queries”, and to decide whether two grammars generate isomorphic trees.
15

Rovinné mechanismy / Planar mechanisms

HOFFMAN, Jan January 2013 (has links)
This work thesis is dealing with planar mechanisms. It?s concentrated on definition the topic, enumeration methods of mathematical description of mechanisms and occasion of simulation with usage information technology. It?s going mainly on GeoGebra program, in which were created most of schemes and models mechanisms. Created models are recorded on attached CD. Important charter of this theses are mechanisms used to draving planar curves, ending with mechanisms used to drawing straight line.
16

A Variable-Stiffness Compliant Mechanism for Stiffness-Controlled Haptic Interfaces

Hawks, Jeffrey C 01 December 2014 (has links) (PDF)
In this research a variable-stiffness compliant mechanism was developed to generate variable force-displacement profiles at the mechanisms coupler point. The mechanism is based on a compliant Roberts straight-line mechanism, and the stiffness is varied by changing the effective length of the compliant links with an actuated slider. The variable-stiffness mechanism was used in a one-degree-of-freedom haptic interface to demonstrate the effectiveness of varying the stiffness of a compliant mechanism. Unlike traditional haptic interfaces, in which the force is controlled using motors and rigid links, the haptic interface developed in this work displays haptic stiffness via the variable-stiffness compliant mechanism. The force-deflection behavior of the mechanismwas analyzed using the Pseudo-Rigid Body Model (PRBM), and two key parameters, KQ and g,were optimized using finite element analysis (FEA) to match the model with the behavior of the device. One of the key features of the mechanism is that the inherent return-to-zero behavior of the compliant mechanism was used to provide the stiffness feedback felt by the user. A prototype haptic interface was developed capable of simulating the force-displacement profile of Lachmans Test performed on an injured ACL knee. The compliant haptic interface was capable of displaying stiffnesses between 4200 N/m and 7200 N/m.
17

Design of Linear Series Elastic Actuators for a Humanoid Robot

Knabe, Coleman Scott 23 June 2015 (has links)
Series elastic actuators (SEAs) have numerous benefits for force controlled robotic applications. This thesis presents the design and assembly of a set of compact, lightweight, low-friction linear SEAs for the legs of the Tactical Hazardous Operations Robot (THOR). The THOR SEA pairs a ball screw driven linear actuator with a configurable titanium leaf spring. A removable pivot changes the effective cantilever length, setting the compliance to either 372 or 655 kN/m. Unlike typical SEAs which measure actuator load through spring deflection, an in-line axial load cell directly measures actuator forces up to the commandable peak of 2225 N. The continuous operating range of the actuator is computed, along with an evaluation of the range of motion and torque profiles for the parallel hip and ankle joints. With a focus on a large power-to-weight ratio and small packaging size, the THOR SEAs are well-suited for accurate torque control of the parallel joints on the robot. Linearly actuated joints, especially ones driven through a crank arm, tend to suffer from a loss of mechanical advantage toward the ends of its limited range of motion. To augment the range of motion and mechanical advantage profile on THOR, an inverted Hoeken's linkage straight line mechanism is paired with a linear SEA at the hip and knee pitch joints on the robot. The resulting linkage assembly is capable of delivering nearly constant peak torque of 115 Nm across its 150 degree range of motion. The mechanical advantage profile of the Hoeken's linkage actuator is computed for the nominal case, as well the deviation resulting from maximum deflection of the titanium beam. / Master of Science
18

Stavrogins lockelse : Om orientering och desorientering i Dostojevskijs Onda andar / The attractive Stavrogin : On orientation and disorientation in Dostoevsky's The Possessed

Egermo, Anna-Corinne January 2015 (has links)
This essay aims to explain the attraction toward the main character Stavrogin that the other characters experience in Dostoevsky's The Possessed, his great novel from 1871. I will mainly employ the terms “orientation” and “disorientation” in my analysis of Stavrogin's power of attraction. The theory used for this reading is principally inspired by Sara Ahmed's Queer Phenomenology – Orientation, Objects, Others (2006), and the meaning I attach to the terms “orientation” and “disorientation” is derived from Ahmed's use of them. Ahmed's queer phenomenology helps us to reflect upon how Stavrogin functions as a point of orientation in the novel. This makes him a demonic influence on the other characters, in the sense that he disorientates them. The Possessed asks us what happens when we “lose our way”, and confusion as well as disorientation is a general theme of the novel. This topic has been raised before, but few have connected the demonic disorientation with the underlying unconventional desires, such as Peter Verchovensky's desire for Stavrogin. In this essay I attempt to show how Stavrogin can be thought of as a “new” orientation for the other characters, and how their following him causes them to follow lines that lead to destruction.
19

Algoritmos Evolutivos aplicados ao Classificador baseado em Segmentos de Reta / Evolutive Algorithms applied to the Straight Line Segment Classifier

Rodríguez, Rosario Alejandra Medina 03 July 2012 (has links)
Nos ultimos anos o uso de tecnicas de aprendizado computacional tornou se uma das tarefas comumente realizadas, pois tem inumeras aplicacoes de reconhecimento de padroes, tais como: reco- nhecimento de voz, classificacao de texto, reconhecimento facial, diagnostico por imagens medicas, entre outras. Dessa forma, um grande numero de tecnicas que lidam com este tipo de problema tem sido desenvolvido ate o momento. Neste trabalho apresentamos uma alternativa para melhorar a taxa acerto de classificacao do classificador binario SLS, que apresentou resultados comparaveis com as SVMs. Nesse metodo, o Gradiente Descendente e utilizado para otimizar a posicao final dos conjuntos de segmentos de reta que representarao cada classe. Embora convirja rapidamente a um valor otimo, muitas vezes e possivel o algoritmo parar em uma regiao de otimos locais, que nao representa o minimo global. Dado esse problema, foram utilizados diferentes algoritmos evolutivos em combinacao com o Gradiente Descendente a fim de melhorar a acuracia do classificador SLS. Adicionalmente a aplicacao de algoritmos evolutivos na fase de treinamento do classificador SLS, foram exploradas duas propostas: (i) explorar o uso de diferente numero de segmentos de reta para representar a distribuicao de dados de cada classe. Dado que no algoritmo original do metodo SLS o numero de segmentos de reta e igual para cada classe, o qual pode significar alguma perda de acuracia ou sobreposicao dos segmentos de reta; (ii) estimar a melhor combinacao de segmentos de reta a serem usados para cada classe. O uso de diferentes quantidades de segmentos de reta por classe pode ser de ajuda na obtencao de melhores porcentagens de acerto, mas determinar uma quantidade otima que permita representar cada classe, e um trabalho dificil. Assim, usamos o algoritmo X-Means, que e um algoritmo de agrupamento, para estimar o numero de segmentos de reta. As propostas exibiram bons resultados que possibilitam a aplicacao do classificador SLS, com um algoritmo de treinamento hibrido, em problemas reais. / During the past years, the use of machine learning techniques have become into one of the most frequently performed tasks, due to the large amount of pattern recognition applications such as: voice recognition, text classification, face recognition, medical image diagnosis, among others. Thus, a great number of techniques dealing with this kind of problem have been developed until now. In this work, we propose an alternative training algorithm to improve the accuracy of the SLS binary Classifier, which produces good results that can be compared to Support Vector Machines. In that classifier, the Gradient Descent method has been used to optimize the final positions of two sets of straight line segments that represent each class. Although, this method quickly converges to an optimum, it is possible that the algorithm stops at a local optimum region, which does not guarantee a global minimum. Given that problem, we combine evolutive optimization algorithms with the gradient descent method to improve the accuracy of the SLS Classifier. In addition to our proposal of using evolutive algorithms, we also developed two proposals: (i) we explore the use of different number of straight line segments to represent the data distribution. Since the original SLS classifier algorithm uses the same number of segments for each class, which could lead to a loss of accuracy or straight line segments overlapping. So, using different number of segments could be the way to improve the accuracy; (ii) estimate the best combination of straight line segments to represent each class. Finding an optimal combination, can be a very difficult problem, so we propose the X-Means algorithm to determine the number of segments. The proposed methodology showed good results which can be used to solve some other real problems with the SLS classifier using the proposed hybrid training algorithm.
20

Revendo o problema da detecção de retas através dos olhos da aranha. / Straight Line detection revisited: Through the eyes of the spider.

Costa, Felipe Miney Gonçalves da 06 July 1999 (has links)
Visão é um processo que envolve uma grande quantidade de informações, as quais precisam ser otimizadas de alguma forma para propiciar um processamento eficiente. Grande parte das informações visuais estão contidas nos contornos de uma imagem e uma grande redução no volume dos dados pode ser conseguida com a análise dos contornos. Além dos contornos, a detecção de segmentos de reta é o próximo passo na compressão das informações visuais. A detecção de retas ocorre no sistema visual humano, e também no de outros seres vivos. Entre os invertebrados terrestres, o melhor sistema de visão é o das aranhas da família Salticidae e este apresenta características que facilitam a detecção de retas. Este trabalho propõe um novo método de detecção de retas, baseado no sistema visual das aranhas saltadoras, que aborda este problema através de um enfoque inédito, por otimização. O método realiza a busca por retas através de janelas lineares. Para isso, a detecção de retas será feita em um espaço de parâmetros, com a utilização do algoritmo de maximização de funções \"Downhill Simplex\". O método desenvolvido leva em consideração a natureza discreta da imagem e do espaço de parâmetros utilizado, e este trabalho inclui um estudo detalhado destes espaços discretos. O método incorpora, para lidar adequadamente com as peculiaridades do problema, características como \"Simulated Annealing\" e largura adaptativa. O desempenho do método depende de um conjunto de parâmetros cujo comportamento é de difícil previsão, e a escolha de um conjunto foi realizada através de um algoritmo genético. O trabalho envolve também a construção de um protótipo para a realização de testes utilizando o método desenvolvido. Os resultados foram analisados quanto a precisão na detecção de retas, ao tempo de processamento e a movimentação das janelas lineares, relacionada aos esforços na busca por retas. / Vision is a process that involves a large amount of information that need to be somehow optimized to allow efficient processing. Most of the visual information is contained in the contours of an image and a considerable reduction in the amount of data can be achieved by fmding and processing these contours. The next step to further compress the visual data is to fmd straight segments, and represent the contours in terms of these entities. Straight-line segment detection is performed by the human visual system, as well as by other creatures. Among terrestrial invertebrates, the best visual system is that of the Salticidae family of spiders, also known as jumping spiders. This visual system presents some characteristics that facilitate the detection of straight-lines. The present work proposes a new method for straight-line detection, based on the visual system of the jumping spiders, using linear windows. This method approach the straight-line detection problem through an optimization point of view yet unexplored in literature. The detection will be accomplished in a parameter space, using the \"Downhill Simplex\" maximization algorithm. The method considers the discrete nature of both the image and the parameter spaces, and this work includes a detailed analysis of these discrete spaces. The method also incorporates, to adequately deal with the specific characteristics of the problem, resources such as \"Simulated Annealing\" and adaptive width of the linear windows. The performance of the method depends on a set of parameters, which behavior is hard to predict, and the choice of an adequate set was made using a genetic algorithm. The work also involves the project and construction of a prototype, to evaluate the proposed method. Results were analyzed regarding their precision, processing time and the movements of the linear windows, related to the effort made to detect the straight lines.

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