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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.
821

An adaptive autopilot design for an uninhabited surface vehicle

Annamalai, Andy S. K. January 2014 (has links)
An adaptive autopilot design for an uninhabited surface vehicle Andy SK Annamalai The work described herein concerns the development of an innovative approach to the design of autopilot for uninhabited surface vehicles. In order to fulfil the requirements of autonomous missions, uninhabited surface vehicles must be able to operate with a minimum of external intervention. Existing strategies are limited by their dependence on a fixed model of the vessel. Thus, any change in plant dynamics has a non-trivial, deleterious effect on performance. This thesis presents an approach based on an adaptive model predictive control that is capable of retaining full functionality even in the face of sudden changes in dynamics. In the first part of this work recent developments in the field of uninhabited surface vehicles and trends in marine control are discussed. Historical developments and different strategies for model predictive control as applicable to surface vehicles are also explored. This thesis also presents innovative work done to improve the hardware on existing Springer uninhabited surface vehicle to serve as an effective test and research platform. Advanced controllers such as a model predictive controller are reliant on the accuracy of the model to accomplish the missions successfully. Hence, different techniques to obtain the model of Springer are investigated. Data obtained from experiments at Roadford Reservoir, United Kingdom are utilised to derive a generalised model of Springer by employing an innovative hybrid modelling technique that incorporates the different forward speeds and variable payload on-board the vehicle. Waypoint line of sight guidance provides the reference trajectory essential to complete missions successfully. The performances of traditional autopilots such as proportional integral and derivative controllers when applied to Springer are analysed. Autopilots based on modern controllers such as linear quadratic Gaussian and its innovative variants are integrated with the navigation and guidance systems on-board Springer. The modified linear quadratic Gaussian is obtained by combining various state estimators based on the Interval Kalman filter and the weighted Interval Kalman filter. Change in system dynamics is a challenge faced by uninhabited surface vehicles that result in erroneous autopilot behaviour. To overcome this challenge different adaptive algorithms are analysed and an innovative, adaptive autopilot based on model predictive control is designed. The acronym ‘aMPC’ is coined to refer to adaptive model predictive control that is obtained by combining the advances made to weighted least squares during this research and is used in conjunction with model predictive control. Successful experimentation is undertaken to validate the performance and autonomous mission capabilities of the adaptive autopilot despite change in system dynamics.
822

The ecology of dispersal in lions (Panthera leo)

Elliot, Nicholas Bryant January 2014 (has links)
As ecosystems become increasingly fragmented, there has been a proliferation of research into fields such as resource use, movement ecology and habitat connectivity. To understand how species may adapt to threats associated with habitat fragmentation it is necessary to study these processes in dispersing individuals. However, this is seldom done. Dispersal is one of the most important life-history traits involved in species persistence and evolution, but the consequences of dispersal are determined primarily by those that survive to reproduce. Although dispersal is most effectively studied as a three-stage process (departure, transience and settlement), empirical studies rarely do so and an investigation into the entire process has probably never been carried out on any one species. Here I investigate the survival, resource use, movement ecology and connectivity of African lions (Panthera leo) in all three dispersal phases in addition to adulthood. I make use of a longterm dataset incorporating radio-telemetry and observational data from lions in Hwange National Park, Zimbabwe. Dispersal is inherently risky and my results show that male lions that disperse while young suffer high mortality, young dispersal being brought about by high off-take of territorial males. Dispersing males may be aware of risks associated with territorial adults as they position themselves far from them and utilise habitats and resources differently. However, dispersers, compared to adult males and females, are far less averse of risky, anthropogenic landscapes, suggesting they are the demographic most prone to human-lion conflict. The ontogenetic movement behaviour of lions reflects a transition from directional movement during transience, suggestive of sequential search strategies, to random or periodic use of a fixed territory after settlement. In terms of habitat connectivity, I show that radically different conclusions emerge depending on which demographic is used to parameterise connectivity models. Understanding the shifting mechanisms that species adopt throughout ontogeny is critical to their conservation in an increasingly fragmented world.
823

Éthique du dissensus : la complétude du deux au service du soin / Dissensus ethics : completness of both, help to care

Pacific, Christophe 17 December 2008 (has links)
Le consensus a pour finalité d’éliminer le conflit. Il aimerait pouvoir sacraliser de nouvelles normes dans une société en crise de rituel. Hélas, la réalité nous montre que l’étoffe du consensus est tissée de soumission librement consentie, de nécessités et de jeux de pouvoir très liés aux plaisirs immédiats. A force d’habitude, l’exigence de consensus change le remède en poison. Le consensus sonne le glas de l’éthique. En cherchant l’unité, le consensus diabolise le conflit et cherche expressément à l’éliminer du fait de son chaos apparent. Le dissensus, lui, en mettant la parole en tension, assure le lien fécond du vivreensemble. La dualité est la clef naturelle qui rationalise la sociabilité des contraires. Le dissensus privilégie l’association des différences pour assurer la représentation de chacune d’entre elles. Ce n’est qu’à partir d’une heuristique naturelle et holiste de l’altérité que le sujet peut se développer en tant que soimême et différent. De cette façon, un « double-je » se construit, capable à la fois de dire courageusement « me voici », face à la menace potentielle de l’autre mais surtout capable de ce même courage pour palier la vulnérabilité de cet autre quand ses forces de résistance l’abandonnent. Le dissensus signe l’émancipation et le dépli du sujet visant le dépassement de soi. La réussite de cette démarche d’ipséité se confirme quand la puissance de déploiement se met au service de la vulnérabilité d’autrui en termes de sollicitude. Ce travail essaie de proposer le dissensus comme un conflit sain et nécessaire, garant d’une éthique d’ouverture, une voie d’excellence pour ceux qui sont concernés par ce que l’homme peut offrir de meilleur : un soin / Finality of consensus is to eliminate conflict. It tries to sacrilize news Norms in a rituals crisis Society. Reality shows that consensus material is woven of submission freely agreed, of necessities and power games closely linked to instantaneous pleasures. By dint of habits, consensus demand substitute Poison for Remedy; consensus sounds Ethics kneel death. Consensus demonizes conflict by seeking unity, and explicitly seeks with elimination of it, regarding its visible chaos. A contrario, Dissensus assures ethics blow of the ‘living-together’ concept by fertile speech link. Duality is the natural solution, which rationalizes opposites’ sociability. Dissensus privileges differences coexistences, rather than weakest shakeout. Subject can build himself up by his self fulfillment, and as a different man, only from a natural and holist heuristic otherness. Thereby, a ‘double-I’ build itself, able to say courageously ‘Here I am’ to other one’s potential threaten, and especially able to face other one’s vulnerability with the same courage, when his resistance forces give-up. Dissensus signs subject emancipation and opening, aiming at going beyond of oneself. Displaying process goes thought an ipseity reasoning, which emerges from otherness, free itself from the latter, to finally return to it, in solicitude terms: live with, against and for other one. This work tries to show Dissensus as a sound and required conflict which guarantees an opening Ethics, an excellence way for the ones who are concerned by the best thing a human being can offer : a Care
824

Object Detection and Tracking Using Uncalibrated Cameras

Amara, Ashwini 14 May 2010 (has links)
This thesis considers the problem of tracking an object in world coordinates using measurements obtained from multiple uncalibrated cameras. A general approach to track the location of a target involves different phases including calibrating the camera, detecting the object's feature points over frames, tracking the object over frames and analyzing object's motion and behavior. The approach contains two stages. First, the problem of camera calibration using a calibration object is studied. This approach retrieves the camera parameters from the known locations of ground data in 3D and their corresponding image coordinates. The next important part of this work is to develop an automated system to estimate the trajectory of the object in 3D from image sequences. This is achieved by combining, adapting and integrating several state-of-the-art algorithms. Synthetic data based on a nearly constant velocity object motion model is used to evaluate the performance of camera calibration and state estimation algorithms.
825

Control of a Multivariable Lighting System

Halldin, Axel January 2017 (has links)
This master’s thesis examines how a small MIMO lighting system can be identified and controlled. Two approaches are examined and compared; the first approach is a dynamic model using state space representation, where the system identification technique is Recursive Least Square, RLS, and the controller is an LQG controller; the second approach is a static model derived from the physical properties of light and a feedback feed-forward controller consisting of a PI controller coupled with a Control Allocation, CA, technique. For the studied system, the CA-PI approach significantly outperforms the LQG-RLS approach, which leads to the conclusion that the system’s static properties are predominant compared to the dynamic properties.
826

Význam cestovního ruchu pro ekonomiky nejméně rozvinutých zemí (LDC) / Significance of tourism for the economies of the Least Developed Countries (LDCs)

Kaliberka, Jan January 2010 (has links)
The Least developed countries represent the weakest and poorest segment of the Word economy. Members of this this specific group are countries with the lowest incomes per capita, low human development and high economic vulnerability. Dealing with problems of these countries including extreme poverty isn't successful in the long run. Many advanced, developing as well as the LDCsstart to concentrate on tourism development, thank to its wide impacts on the economy and regional development. Also the UN strengthens its support to the LDCs in sustainable tourism development. The goal of this thesis is to analyze the significance of tourism for the economies of the LDCs and its potential for boosting the socio-economic development in these countries and for solving their problems includingtha alleviation of poverty.
827

Comparação de métodos de estimação para problemas com colinearidade e/ou alta dimensionalidade (p > n ) / Comparison of estimation methods for problems with collinear and/or high dimensionality (p > n)

Casagrande, Marcelo Henrique 29 April 2016 (has links)
Este trabalho apresenta um estudo comparativo do poder de predição de quatro métodos de regressão adequados para situações nas quais os dados, dispostos na matriz de planejamento, apresentam sérios problemas de multicolinearidade e/ou de alta dimensionalidade, em que o número de covariáveis é maior do que o número de observações. No presente trabalho, os métodos abordados são: regressão por componentes principais, regressão por mínimos quadrados parciais, regressão ridge e LASSO. O trabalho engloba simulações, em que o poder preditivo de cada uma das técnicas é avaliado para diferentes cenários definidos por número de covariáveis, tamanho de amostra e quantidade e intensidade de coeficientes (efeitos) significativos, destacando as principais diferenças entre os métodos e possibilitando a criação de um guia para que o usuário possa escolher qual metodologia usar com base em algum conhecimento prévio que o mesmo possa ter. Uma aplicação em dados reais (não simulados) também é abordada. / This paper presents a comparative study of the predictive power of four suitable regression methods for situations in which data, arranged in the planning matrix, are very poorly multicolinearity and / or highdimensionality, wherein the number of covariatesis greater the number of observations. In this study, the methods discussed are: principal component regression,partial least squares regression,ridge regression and LASSO. The work includes simulations, where in the predictive power of each of the techniques is evaluated for different scenarios defined by the number of covariates, sample size and quantity and intensity ratios (effects) significant, high lighting the main dffierences between the methods and allowing for the creating a guide for the user to choose which method to use based on some prior knowledge that it may have. An applicationon real data (not simulated) is also addressed.
828

The relationship between inflation and economic growth in Ethiopia

Abis Getachew Makuria 14 July 2014 (has links)
The main purpose of this study is to empirically assess the relationship between inflation and economic growth in Ethiopia using quarterly dataset from 1992Q1 to 2010Q4. In doing so, an interesting policy issue arises. What is the threshold level of inflation for the Ethiopian economy? Based on the Engle-Granger and Johansen co-integration tests it is found out that there is a positive long-run relationship between inflation and economic growth. The error correction models show that in cases of short-run disequilibrium, the inflation model adjusts itself to its long-run path correcting roughly 40% of the imbalance in each quarter. In addition, based on the conditional least square technique, the estimated threshold model suggests 10% as the optimal level of inflation that facilitates growth. An inflation level higher or lower than the threshold level of inflation affects the economic growth negatively and hence fiscal and monetary policy coordination is vital to keep inflation at the threshold. / Economics / M. Com. (Economics)
829

[en] IDENTIFICATION OF MECHANICAL SYSTEMS PARAMETERS THROUGH INVERSE PROBLEM S RESOLUTION WITH BAYESIAN STATISTICAL INFERENCE / [pt] IDENTIFICAÇÃO DE PARÂMETROS EM SISTEMAS MECÂNICOS ATRAVÉS DA RESOLUÇÃO DO PROBLEMA INVERSO COM INFERÊNCIA ESTATÍSTICA BAYESIANA

MARIO GERMAN SANDOVAL 12 January 2015 (has links)
[pt] O problema de estimação pode ser entendido como um caso particular dos problemas inversos. Dadas observações da resposta de um sistema para certas causas, deseja-se estimar certas características do sistema. Essas características, em um sistema dinâmico, geralmente são representadas por parâmetros. Assim, para uma representação físico-matemática do sistema, dada uma excitação e observando a resposta, é possível obter uma estimação dos parâmetros. A estimação paramétrica é de grande importância e utilizada em diversas situações, desde experimentalistas, ao observar fenômenos no laboratório, até quem estuda o comportamento de setores sociais por amostras populacionais. A parte inicial desta dissertação apresenta uma breve introdução ao problema inverso do marco da estatística Bayesiana. Neste marco trata-se a estimação paramétrica como resultado da resolução de um problema inverso. Duas técnicas de estimação s ao deduzidas a partir da inferência estatística Bayesiana. A primeira delas, mínimos quadrados, coleta todos os dados e logo faz a estimação. A segunda, filtro de Kalman (e filtro de Kalman extendido), melhora o estado do conhecimento dos parâmetros a serem estimados a cada nova observação. Para a abordagem destas técnicas de estimação, de modo de poder compará-las, é apresentada a resolução analítica de um sistema harmônico de um e dois graus de liberdade. Por último, é apresentada uma modelagem de uma bancada experimental, em escala de laboratório, que emula uma coluna de perfura ção acoplada a um motor. Esta bancada foi desenvolvida para estudos de dinâmica torcional, na dissertação de mestrado de Bruno C. Cayres A., de modo que aqui só é de interesse a caracterização da mesma. As técnicas de estimação paramétrica são usadas de forma teórica, simulando os dados a partir de soluções analíticas para diferentes parâmetros da modelagem do motor e da coluna. Também usa-se medições feitas na bancada para estimar os parâmetros da modelagem, obtendo assim um conhecimento melhorado dos parâmetros envolvidos no sistema coluna-motor. / [en] The estimation problem can be understood as a particular case of an inverse problem. Given observations of the response of a system, due to certain causes, one wants to estimate certain characteristics of the problem. These features, in a dynamic system, are usually represented by parameters. Thus, for a mathematical representation of the physical system, given an excitation and given the observing response, it is possible to give an estimation of the parameters. The parameter estimation is of great importance and used in countless situations, such as experimental obseration of a phenomena in the laboratory or even by those who study the behaviors social sectors by population samples. The initial part of this dissertation presents a brief introduction to the inverse problem the framework of the Bayesian statistics. In this context, the parametric estimation is a result of the resolution of an inverse problem. Two estimation techniques are derived from the Bayesian statistical inference. The first of these, least squares, collects all the data and then makes the estimation. The second, Kalman filter (and extended filter Kalman), improves the state of knowledge of the parameters to be estimated, with each new observation. To address these estimation techniques, in order to be able to compare them, presents the analytical resolution of a harmonious system of one and two degrees of freedom. Finally, it is presented a model for an experimental setup, in laboratory scale, which emulates a drillstring coupled to a motor. This experimental setup was developed to study the dynamic torsional and by the author of the dissertation of Bruno C. Cayres A., the mode that is of interest here only the characterization of it. These techniques are used for parameter estimation in theoretical way, simulating data from the analytical solutions, for different parameters involved in the column-motor modeling. Also, we use measurements obtained from the experimental setup to estimate the parameters of the column-motor model. Thereby, we obtain an improved knowledge of the parameters involved in the column-motor.
830

Is constructivism a prerequisite to unlock the power of web based platforms in teacher training? : A case study on the enablers for web based learning platforms for teacher training in Cambodia

Peacock, Maria Natasha January 2019 (has links)
This case study, executed in school network driven by a private foundation for underprivileged children in Cambodia, provides a perspective from a unique situation of technology enablement in an environment with a predominantly instructivist teaching tradition.   The said environment is strongly influenced by private sector donors with strong constructivist traditions and expectations. The environment is thus unique in the sense that a relatively asset rich environment, with expectations of 21st century pedagogical skills, is transported into an asset poor environment that was/is strongly rooted in instructivism. The case study thus give a perspective on if technology itself is a possible solution for better teacher education/educational delivery, or if the underlying pedagogy first needs to be evolved to allow web-based platforms and tools to be fully leveraged.     In the specific environment being studies, teacher in-service training plays a larger role than formal teacher qualifications, and peer-to-peer, in-person, learning is the cornerstone of development (offline connectivism). Rather than changing the way the teachers learn, there should be opportunity in further strengthening the current practices of communities. Connectivist MOOCs (Massive Open Online Courses) do provide the community engagement and together with technology mediated professional learning platforms there should be opportunity to provide enhanced support for teachers’ education.   The two main hurdles to overcome, beyond functioning technology assets and web access, are teachers own comfort levels with technology platforms, as well as provision of platforms that support local language options. The comfort level with technology is important to address as, assuming technology and web access works, the openness and lack of control in a web environment is in direct contradiction to instructivist teaching. Unlocking the potential of the web requires that teachers are comfortable with the web itself and also truly support inquiry based learning over didactic teaching, and that they have the skills to help children navigate the openness of the web.   As economies shift towards becoming knowledge societies, collaborative problem-solving and navigation to knowledge are skills of increasing in importance, relative static knowledge recall that was previously viewed as value adding. This case study contributes to pedagogical theory and in particularly gives one more perspective on the shift from instructivist to constructivist teaching as a pre-requisite for capturing the power of the internet, and the shift to leveraging networks in a connectivist pedagogical approach. This case study also calls out the need for evolved frameworks to better describe technology mediated learning in least developing country environments. The case study also provides contribution to practice to technology mediated teacher education as it specifically addresses some of the opportunities in strengthening the support to teacher education in least developed countries.

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