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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.
41

Development and Characterization of a Regeneratively Amplified Ultrafast Laser System with an All-Glass Stretcher and Compressor

Walker, Stephen January 2006 (has links)
High-peak power laser systems are defined along with a brief introduction of the technology used in their development and application to the project. A review of concepts surrounding optical pulses, focusing on the particular phenomena involved with the ultrafast, follows. Numerical models involving optical pulses are introduced and verified. An extensive description of the laser system is presented, including models used in its design. Data verifying the correct operation of the laser system is presented and interpreted. A dispersion compensation system, including a function model, is introduced, and its application to the laser system is analyzed. An introduction to pulse characterization techniques is presented followed by the design and verification of two different characterization devices. Experiments utlizing the dispersion compensation system and pulse characterization devices are presented and the results are interpreted. Conclusions are made regarding the performance of the laser system models and pulse characterization devices, along with suggested improvements for each. The results of the experiments are discussed including suggestions for future work.
42

Development and Characterization of a Regeneratively Amplified Ultrafast Laser System with an All-Glass Stretcher and Compressor

Walker, Stephen January 2006 (has links)
High-peak power laser systems are defined along with a brief introduction of the technology used in their development and application to the project. A review of concepts surrounding optical pulses, focusing on the particular phenomena involved with the ultrafast, follows. Numerical models involving optical pulses are introduced and verified. An extensive description of the laser system is presented, including models used in its design. Data verifying the correct operation of the laser system is presented and interpreted. A dispersion compensation system, including a function model, is introduced, and its application to the laser system is analyzed. An introduction to pulse characterization techniques is presented followed by the design and verification of two different characterization devices. Experiments utlizing the dispersion compensation system and pulse characterization devices are presented and the results are interpreted. Conclusions are made regarding the performance of the laser system models and pulse characterization devices, along with suggested improvements for each. The results of the experiments are discussed including suggestions for future work.
43

Tidal Exchange Process at Ta-pon Bay

Cheng, Po-Hsin 29 August 2002 (has links)
The study site, Ta-pon Bay, is located in southwestern Taiwan that has the total volume of 9.92 x 106 m3, surface area of 4.46 x 106 m2, and an average depth of 2.19 m. The Ta-pon Bay is a shallow and semi-enclosed lagoon. The tidal regime at the Ta-pon Bay inlet is mixed, with diurnal dominance. There is noticeable amount of land-derived freshwater inflow in Ta-pon Bay and the mixing between the sea water and freshwater is largely determined by the tide. In order to understand the tidal exchange process between Ta-pon Bay and the coastal sea, the observation focused on the physiographic and hydrographic characteristics of this lagoon. The bathymetry of the study area was also surveyed. From the spatial sediment grain-size distribution pattern, the high energy region is at the inlet and the low energy region is in the interior of the lagoon. Our observation results indicate that freshwater outflow from the Kao-ping River was not transported into Ta-pon Bay. Tides are also the dominant cause for the water level fluctuations in the lagoon. In our winter observation, the local wind effects and atmospheric forcing dominated the subtidal sea surface fluctuations. In summer observation, the subtidal variability was strongly influenced by freshwater inflow. In Ta-pon Bay, the spatial salinity distribution was controlled by the flood and ebb tides, and the spatial temperature distribution was controlled by the different seasons. The tidal prism model can help us understand the tidal exchange between a shallow coastal lagoon and the open sea, and estimate the volume of freshwater inflow, return flow factor, and the turn-over time. Furthermore, we used a one-dimensional model to simulate the hydrodynamics of tidal inlet. The model results show good agreement with observations. We found that the superelevation of the lagoon was 20 cm. This mean sea level difference was caused by freshwater inflow and accumulation of lagoonward tidal transport of water.
44

Precision-integrated scalable monitoring

Jain, Navendu 27 April 2015 (has links)
Scalable system monitoring is a fundamental abstraction for large-scale networked systems. The goal of this dissertation is to design and build a scalable monitoring middleware that provides system introspection for large distributed systems and that will facilitate the design, development, and deployment of distributed monitoring applications. This middleware will enable monitoring applications to flexibly control the tradeoff between result precision and communication cost and to improve result accuracy in the face of node failures, network delays, and system reconfigurations. We present PRISM (PRecision-Integrated Scalable Monitoring), a scalable monitoring middleware that provides a global aggregate view of large-scale networked systems and that can serve as a building block for a broad range of distributed monitoring applications by coordinating views of multiple vantage points across the network. To coordinate a global view for system introspection, PRISM faces two key challenges: (1) scalability to large systems and high data volumes and (2) safeguarding accuracy in the face of node and network failures. To address these challenges, we design, implement, and evaluate PRISM, a system that defines precision as a new unified abstraction to enable scalable monitoring. PRISM quantifies (im)precision along a three-dimensional vector: arithmetic imprecision (AI) and temporal imprecision (TI) balance precision against monitoring overhead for scalability while network imprecision (NI) addresses the challenge of providing consistency guarantees despite failures. Our prototype implementation of PRISM addresses the challenge of providing these metrics while scaling to a large number of nodes and attributes by (1) leveraging Distributed Hash Tables (DHTs) to create scalable aggregation trees, (2) self-tuning AI budgets across nodes in a principled, near-optimal manner to shift precision to where it is useful, (3) pipelining TI delays across tree levels to maximize batching of updates, and (4) applying dual-tree prefix aggregation which exploits symmetry in our DHT topology to drastically reduce the cost of the active probing needed to maintain NI. Through extensive simulations and experiments on four large-scale testbeds, we observe that PRISM provides a key substrate for scalable monitoring by (1) reducing monitoring load by up to two orders of magnitude compared to existing approaches, (2) providing a flexible framework to control the tradeoff between accuracy, bandwidth cost, and response latency, (3) characterizing and improving confidence in the accuracy of results in the face of system disruptions, and (4) improving the observed accuracy by up to an order of magnitude despite churn. We have built several monitoring applications on top of PRISM including a distributed heavy hitter detection service, a distributed monitoring service for Internet-scale systems, and a detection service for monitoring distributed-denial-of-service (DDoS) attacks at the source-side in distributed networked systems. Finally, we demonstrate how the unified precision abstraction enables new monitoring applications by presenting experiences from these applications. / text
45

Measuring the efficacy of low-income residential sustainability interventions

Steubing, Jacob Wayne 05 August 2011 (has links)
Volatile and rising global fuel prices present a tremendous challenge to our energy-dependent economy, and the ramifications are especially great for low-income households. Residential weatherization programs represent a tremendous opportunity to shield vulnerable populations, but the allocation of funding and assessment of efficacy has historically been fraught with political and procedural hurdles. This report examines the methods of assessing the efficacy of low-income weatherization and proposes a set of best practices. / text
46

Implementation of 2-Step Intensity Modulated Arc Therapy

Sun, Jidi January 2010 (has links)
Intensity modulated arc therapy is a novel treatment technique that has shown great potential to be superior to conventional intensity modulated radiotherapy, both in terms of treatment plan quality as well as treatment delivery. Based on previous literature, a simplified technique called two-step intensity modulated arc therapy (2-step IMAT) was implemented into a treatment planning system. In order to automatically generate treatment plans for this technique, a beam portal shaping method was developed to generate beam segments. A sensitivity analysis was carried out on a geometric phantom to determine optimal parameters for the 2-step IMAT implementation for that particular phantom. The segment weights were optimized using the dose-based and dose-volume-based objective functions. The optimal solution search was based on the gradient-descend algorithm. The dose-based objective function was implemented using a so-called lambda-value-dose-based objective function developed in this work in order to increase both speed and flexibility of the optimization. The successful implementation demonstrated the feasibility of automatic 2-step IMAT treatment planning. A comparison of conventional arc therapy and 2-step IMAT showed improvements in the target dose uniformity by about 50% for both geometric phantom and clinical paraspinal tumor case, whilst also improving the organ sparing. The comparisons between the lambda-value-dose-based and dose-volume-based optimizations showed a speed advantage of the former by a factor of over five in the phantom study. The current beam portal shaping approach can be improved by optimizing the segment width and including multiple organs-at-risk in the segment generation algorithm. Future work will also include the implementation of a stochastic optimization to minimize the chance of getting trapped in local minima during the segment weight optimization. In summary, the work of this research showed that the automatic 2-step IMAT planning is a viable technique that can result in highly conformal plans while keeping the treatment planning and delivery simple and straightforward.
47

Aligning Brand Identity with Brand Image : An evaluation of a proposed method

Hultman, Emma, Razafimandimbison, Sylvio Hardy, Nazem, Ramin January 2015 (has links)
Branding and the management of brands has become a highly prioritized aspect for com-panies to maintain lasting competitive advantage and to provide meaning to consumption. Therefore companies have adopted an inside-out approach in order to manage their brand. The challenge with an inside-out approach is to align the internal brand identity,what brands communicate, with the external brand image, what consumers perceive. Therefore two questions are crucial to answer; how does the brand want to be perceived and how is the brand actually perceived? There is a risk that gaps occur in the communication of the brand, and these gaps are crucial to monitor and prevent for effective brand management. This paper proposes a method on how to measure and align brand identity and brand im-age, based on existing theories and models regarding brand management. The method is evaluated through a case study, where the difference between Happy Plugs’ brand identity and brand image is analyzed. The method was designed using Kapferer’s Brand Pyramid and Brand Identity Prism. Both qualitative and quantitative data is used to examine how wide the gap between Happy Plugs’ brand identity and brand image is. The Happy Plugs brand is solely used as a tool to apply the designed method and evaluate the validity of it. The findings show that a gap in brand identity and brand image does occur, at higher levels of the brand pyramid, or brand identity. The results from the case study indicate that the designed model is an effective tool in identifying and measuring possible gaps, and is a use-ful approach for companies who wish to align their brand identity with brand image.
48

Domination of a generalized Cartesian product

Benecke, Stephen 12 August 2009 (has links)
Let $G\ensuremath{\mathbin{\raisebox{0.3mm}{$\scriptstyle\square$}}} H$ denote the Cartesian product of the graphs $G$ and $H$. Domination of the Cartesian product of two graphs has received much attention, with a main objective to confirm the truth of Vizing's well-known conjecture. The conjecture states that the domination number of the Cartesian product of two graphs is at least as large as the product of the respective domination numbers. The potential truth of Vizing's conjecture gives rise to investigating the domination of graph products that generalizes the Cartesian product. The generalized prism $\pi G$ of $G$ is the graph consisting of two copies of $G$, with edges between the copies determined by a permutation $\pi$ acting on the vertices of $G$. A generalized Cartesian product $G\ensuremath{\mathbin{\raisebox{0.3mm}{${\scriptstyle \square}$}\hspace{-1.99mm}\raisebox{0.65mm}{${\scriptstyle \pi}$}}} H$ is defined here, incorporating structural properties of both the Cartesian product of two graphs as well as the generalized prism of a graph. Conditions on the isomorphism of two generalized Cartesian products are explored first, establishing a characterization in the case of natural isomorphisms. A comparison of the diameter of the generalized Cartesian product and the corresponding Cartesian product graph is used to illustrate the structural differences between these graph products. This comparison is continued through a study of the validity of an inequality similar to Vizing's conjecture for Cartesian products. Graphs that attain equality in the general bounds for the domination number of the Cartesian product and generalized Cartesian product are investigated in more detail. For any graph $G$ and $n\geq 2$, $\min\{|V(G)|,\gamma(G)+n-2\}\leq\gamma(G\ensuremath{\mathbin{\raisebox{0.3mm}{$\scriptstyle\square$}}} K_{n})\leq n\gamma(G)$. A graph $G$ is called a consistent Cartesian fixer if $\gamma(G\ensuremath{\mathbin{\raisebox{0.3mm}{$\scriptstyle\square$}}} K_{n})=\gamma(G)+n-2$ for each $n$ such that $2\leq n<|V(G)|-\gamma(G)+2$. A graph attaining equality in the stated upper bound on $\gamma(G\ensuremath{\mathbin{\raisebox{0.3mm}{$\scriptstyle\square$}}} K_{n})$ is called a Cartesian $n$-multiplier. Both of these classes are characterized. Concerning the generalized Cartesian product, $\gamma(G\ensuremath{\mathbin{\raisebox{0.3mm}{${\scriptstyle \square}$}\hspace{-1.99mm}\raisebox{0.65mm}{${\scriptstyle \pi}$}}} K_{n})\leq n\gamma(G)$ for any graph $G$, permutation $\pi$ and $n\geq 2$. A graph attaining equality in the upper bound for all $\pi$ is called a universal multiplier. Such graphs are characterized similar to a known result for generalized prisms. A similar problem for the product $G\ensuremath{\mathbin{\raisebox{0.3mm}{${\scriptstyle \square}$}\hspace{-1.99mm}\raisebox{0.65mm}{${\scriptstyle \pi}$}}} C_{n}$ is considered, with conditions on a graph being a so-called cycle multiplier provided. A graph attaining equality in the lower bound $\gamma(G\ensuremath{\mathbin{\raisebox{0.3mm}{${\scriptstyle \square}$}\hspace{-1.99mm}\raisebox{0.65mm}{${\scriptstyle \pi}$}}} H)\geq\gamma(G)$ for some permutation $\pi$ is called a $\pi$-$H$-fixer. A brief investigation is conducted into the existence of universal $H$-fixers, i.e.~graphs that are $\pi$-$H$-fixers for some $H$ and all permuations $\pi$ of $V(G)$, and it is shown that no such graphs exist when $n\geq 3$. A known efficient algorithm for determining $\gamma(G\ensuremath{\mathbin{\raisebox{0.3mm}{$\scriptstyle\square$}}} P_{n})$ is surveyed, and modified to accommodate any Cartesian product $G\ensuremath{\mathbin{\raisebox{0.3mm}{$\scriptstyle\square$}}} H$, thereby establishing a general framework for evaluating the domination number of $G\ensuremath{\mathbin{\raisebox{0.3mm}{$\scriptstyle\square$}}} H$ for a fixed graph $G$ and any $H$. An algorithm to determine $\gamma(G\ensuremath{\mathbin{\raisebox{0.3mm}{$\scriptstyle\square$}}} T)$ for any tree $T$ is provided, and it is observed to be polynomial for trees of bounded maximum degree. The general framework for $G\ensuremath{\mathbin{\raisebox{0.3mm}{$\scriptstyle\square$}}} H$ is also modified to accommodate the generalized Cartesian product $G\ensuremath{\mathbin{\raisebox{0.3mm}{${\scriptstyle \square}$}\hspace{-1.99mm}\raisebox{0.65mm}{${\scriptstyle \pi}$}}} H$. The study diverts from the main topic of domination to investigate the planarity of the generalized Cartesian product graph. If both $G$ and $H$ are 2-connected graphs, then $G\ensuremath{\mathbin{\raisebox{0.3mm}{${\scriptstyle \square}$}\hspace{-1.99mm}\raisebox{0.65mm}{${\scriptstyle \pi}$}}} H$ is nonplanar. A known simple polynomial-time planarity testing algorithm is surveyed, and used to establish conditions on the planarity of $P_{m}\ensuremath{\mathbin{\raisebox{0.3mm}{${\scriptstyle \square}$}\hspace{-1.99mm}\raisebox{0.65mm}{${\scriptstyle \pi}$}}} P_{n}$, the generalized Cartesian product of two paths. This research aims to lay the foundation on which further properties of the generalized Cartesian product and further generalizations may be studied, as well as to provide various open problems to spark interest in the research area.
49

Les espaces publics au prisme de l’art à Johannesburg (Afrique du Sud) : quand la ville fait œuvre d’art et l’art œuvre de ville / Publics spaces through art in Johannesburg (South Africa) : when the city makes art and art makes the city

Guinard, Pauline 28 November 2012 (has links)
Cette thèse porte sur les espaces publics à Johannesburg, capitale économique de l’Afrique du Sud. Dans le contexte contemporain, l’utilisation de la notion occidentale d’espaces publics pose problème : d’une part, du fait des ségrégations passées qui ont eu tendance à faire de ces espaces des lieux de séparation et de mise à distance des différents publics ; et d’autre part, du fait des forts taux de violence et du fort sentiment d’insécurité, qui tendent à encourager la sécurisation et la privatisation de ces mêmes espaces. L’enjeu est alors de comprendre les éventuels processus de construction de la publicité (au sens de caractère public) de ces espaces, à la fois sur le plan juridique, social et politique. Pour ce faire, l’art qui se déploie dans les espaces juridiquement publics de la métropole depuis la fin de l’apartheid, est utilisé comme une clef de lecture privilégiée de ces phénomènes, en tant qu’il permettrait, ainsi que nous entendons le montrer, de créer des espaces de rencontre et de débats ou, à l’inverse, de mieux réguler et contrôler ces espaces. Selon une approche qualitative, notre étude se base à la fois sur des observations de terrain et sur des entretiens conduits auprès des producteurs mais aussi des récepteurs de cet art qui a lieu dans les espaces publics. A la croisée de la géographie urbaine et de la géographie culturelle, nous envisageons donc de réexaminer la notion d’espaces publics au prisme de l’art à Johannesburg en vue de saisir – entre tentative de normalisation et résistance à cette normalisation – quelle ville est aujourd’hui à l’œuvre non seulement à Johannesburg, mais aussi, à travers elle, dans d’autres villes du monde. / This Ph.D. thesis deals with public spaces in Johannesburg, the economic capital of South Africa. In the current context, the issues raised by the use of the western notion of public spaces are explored. On one hand, the previous segregations tended to mark off spaces into different publics completely separated from each other. On the other hand, the high rates of violence and sense of insecurity enhance securitization and privatization of these same spaces. What is at stake is to understand how the publicness of these spaces can be legally, socially, and politically built. In that framework, art spread in legally public spaces of Johannesburg since the end of apartheid is used as a tool to understand and reveal these phenomena since it is presented, as we aim at demonstrating, as a mean to create spaces of encounter and debate or, conversely, to regulate and control better these spaces. In a qualitative approach, our study is based on field observations and interviews with both producers and receivers of this art which takes place in public spaces. At the crossroads of urban geography and cultural geography, we are therefore re-examining the concept of public spaces through the prism of art in Johannesburg to figure out – between normalization and resistance to this normalization – which city is today at work not only in Johannesburg, but also, through her, in other cities of the world.
50

Geração e avaliação de ortoimagem ALOS/PRISM 1B1: estudo de caso para São Gabriel, RS / Generation and evaluation of orthoimage ALOS/PRISM 1B1: study of case to São Gabriel-RS

Nakahori, Angela Akemi Goto January 2010 (has links)
O objetivo deste trabalho foi a geração e avaliação de ortoimagens ALOS/PRISM, utilizandose para isso MDEs (Modelos Digitais de Elevação) obtidos através das diferentes combinações de visadas desse sensor de uma imagem com nível de processamento 1B1. Na primeira etapa foram gerados os MDEs a partir das combinações das três visadas, utilizando-se para isso pontos de controle obtidos através de levantamento de campo, onde foram testados a quantidade mínima necessária de pontos de controle para geração de MDE e outros parâmetros tais como nível de processamento, tamanho de janela, entre outros. Na etapa seguinte, comparou-se o resultado da extração com os Modelos Digitais de Elevação do ASTER (GDEM) e o SRTM (Shuttle Radar Topographic Mission), este gerado a partir do Projeto TOPODATA do INPE (Instituto Nacional de Pesquisas Espaciais). Na etapa final avaliaram-se os MDEs com os pontos de checagem. Através de análises estatísticas selecionaram-se os melhores MDEs para ortorretificação. Os resultados demonstraram que, para este caso específico, todos os MDES da combinação de visada Backward – Foward (gerados a partir de 6 pontos de controle) seriam aprovados por apresentarem os menores valores de RMS (entre 2,94 e 3m) e que, ao se utilizar outros MDEs oriundos de outras combinações, as ortoimagens obtidas também atendem ao Padrão de Exatidão Cartográfica (PEC) Classe A para escala 1:25.000, bem como as ortoimagens geradas com os Modelos de Elevação Globais SRTM e GDEM. A área de estudo escolhida foi uma região rural do município de São Gabriel – RS, que possui relevo com média altimétrica de 160m, podendo ser considerado plano, o que justifica o bom desempenho do SRTM em conjunto com os MDEs gerados a partir do PRISM. / The aim of this work was the generation and evaluation of orthoimages ALOS / PRISM, using the MDEs (Digital Elevation Models) obtained using different combinations of sensor views of an image with 1B1 processing level. In the first step the MDEs were created from combinations of three views, using for it the ground control points obtained by field survey, where the minimum amount necessary of control points for DEM generation and other parameters as processing level, size of the windows, among others were tested. In the further step, the result of extraction was compared to Digital Elevation Models from ASTER (GDEM) and SRTM (Shuttle Radar Topographic Mission), this one generated from the Project TOPODATA from INPE (National Institute for Space Research). In the final step, the MDEs were evaluated with the checkpoints. Through statistical analysis the best MDEs were selected for orthorectification. The results showed that, for this specific case, all MDEs combination of Backward - Foward (generated from 6 control points) would be approved by submitting the lowest values of RMS (between 2.94 and 3 m) and, when using other MDEs from another combinations, obtained orthoimages also satisfies the Cartographic Accuracy Standard (PEC) for Class A 1:25,000 scale, as the orthoimages generated from the SRTM and GDEM. The chosen study area was a rural region of São Gabriel - RS, which has average altitude of 160 m, can be considered plane, which explains the good performance of the SRTM in conjunction with the MDEs generated from PRISM.

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