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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.
151

Dissolução de Foraminíferos Quaternários do Atlântico Sul: da perda de CaCO3 ao ganho de informação paleoceanográfica

Petró, Sandro Monticelli January 2018 (has links)
Estudos paleoceanográficos são baseados em indicadores indiretos, ou seja, informações sedimentológicas, paleontológicas e geoquímicas que refletem as condições ambientais dos oceanos no passado geológico. Processos tafonômicos como a dissolução podem enviesar a informação contida nestes indicadores. Porém, quando corretamente identificada, a dissolução pode se tornar uma ferramenta para caracterizar mudanças oceanográficas, como variações na distribuição das massas d’água e a acidificação dos oceanos. O objetivo deste estudo é entender como ocorre este enviesamento, identificar indicadores que determinam a presença ou ausência da dissolução e identificar alterações oceanográficas no Quaternário tardio da Bacia de Pelotas em função deste processo. Esta tese compreende várias etapas, incluindo a realização de experimentos de dissolução em varias espécies de foraminíferos provenientes do oeste do Atlântico Sul, a comparação entre dados de fauna de foraminíferos planctônicos de sedimento com as condições ambientais do oceano Atlântico Sul e, finalmente, as análises de testemunhos do Quaternário tardio da Bacia de Pelotas (foraminíferos, cocolitoforídeos, teor de carbonato, granulometria, δ18O, AMS 14C). Os experimentos geraram um ranking de susceptibilidade à dissolução para foraminíferos, identificando Orbulina universa e Hoeglundina sp. como bons indicadores de pouca dissolução, além de identificar a razão entre foraminíferos planctônicos e bentônicos como imprópria para indicar o grau de dissolução. A análise da fauna de foraminíferos planctônicos do Atlântico Sul identificou maior enviesamento por condições ambientais de fundo em áreas com massas d’água mais corrosivas provenientes do sul, bem como o viés observado nas espécies frágeis pode ser relacionado aos erros em estimativas de paleotemperaturas baseadas em censos de fauna. Baseado nos indicadores aqui elaborados, combinado com outros indicadores comuns, as alterações oceanográficas na Bacia de Pelotas indicam um aumento da dissolução em períodos glaciais em função do avanço da Água Antartica de Fundo e da Água Circumpolar Superior. Finalmente, na parte conceitual desta tese, é proposta uma definição de zona tafonômicamente ativa para sistemas pelágicos, que deve considerar a coluna d’água como seu limite superior. / Paleoceanographic studies are based on proxy data, i.e. sedimentological, paleontological and geochemical information that reflect the environmental conditions of the oceans in the geological past. Taphonomic processes such as dissolution may bias the information contained in these proxies. However, when correctly identified, dissolution can become a tool to characterize oceanographic changes, such as variations in the water masses distribution and acidification of the oceans. The purpose of this study is to understand how this bias occurs, to identify proxies that determine the presence or absence of dissolution and to identify late Quaternary oceanographic changes in the Pelotas Basin as a function of this process. This thesis comprises several stages, including dissolution experiments on several foraminifera species from the western South Atlantic, comparison between sediment plankton foraminifera fauna data with environmental conditions of the South Atlantic Ocean, and finally, the analyses of late Quaternary of the Pelotas Basin cores (foraminifera, coccolith, carbonate content, grain size, δ18O, and AMS 14C). The experiments generated a ranking of susceptibility to dissolution for foraminifera, identifying Orbulina universa and Hoeglundina sp. as good proxies of low dissolution, besides identifying the planktonic and benthic foraminifera ratio as inappropriate for indicating the degree of dissolution. The analysis of the planktonic foraminifera fauna of the South Atlantic identified greater bias due to bottom environmental conditions in areas with more corrosive water masses from the south, as well as the observed bias in fragile species may be related to errors in paleotemperature estimates based on fauna census counts. Based on the proxies developed here, and other indicators frequently used, the late Quaternary oceanographic changes in the Pelotas Basin indicate an increase of the dissolution in glacial periods due to the advance of Antarctic Bottom Water and Upper Circumpolar Deep Water. Finally, in the conceptual part of this thesis, a taphonomically active zone for pelagic systems is proposed, which should consider the water column as its upper limit.
152

Visibilidade web de universidades

Klinger, Augusto January 2011 (has links)
Visibilidade Web é a área de estudo das medidas de visibilidade de organizações, termos ou documentos na web, sendo um dos campos de pesquisa da ciência de Webmetria. Neste trabalho, uma fórmula para o cálculo de visibilidade na web é proposta, baseando-se na visão proporcionada por diferentes motores de busca. O resultado final é um indicador de Visibilidade Web para universidades. São apresentados e analisados rankings de universidades do mundo todo encontrados na web, tais como o ARWU, o WR e o THE. Tais rankings trabalham com indicadores compostos, mas abordam a questão da visibilidade na rede de maneiras diferentes. Também são discutidos alguns trabalhos recentes no campo de Visibilidade Web. O indicador elaborado baseia-se na classificação do site oficial da universidade nos buscadores como meio de pontuar a visibilidade, valendo-se de metabusca. Um método de fusão de rankings é utilizado para a pontuação. Siglas de universidades brasileiras foram submetidas ao cálculo de visibilidade e classificadas, mostrando uma aplicação da fórmula no mundo real. Dois rankings foram construídos, um deles apontando falhas no método proposto e o segundo contornando o problema encontrado, apresentando uma classificação justa, coerente com a realidade e com outros rankings de universidades brasileiras. A principal contribuição do trabalho é a definição de um indicador de visibilidade na web que mostra como são classificadas as instituições através dos principais pontos de entrada da rede: os motores de busca. / Web Visibility is the area of study of visibility measures of organizations, terms or documents on the web, one of the fields of the Webmetrics science. In this work, a formula for the calculation of visibility on the web is proposed, based on the vision provided by different search engines. The result is an indicator of Web Visibility for universities. In related works section are presented and analyzed rankings of universities around the world from the web, such as ARWU, WR and THE. Such rankings work with composite indicators, but address the issue of visibility on the network in different ways. Also are covered some resent works in the field of Web Visibility. The indicator developed is based on the classification of the universities’ official website in search engines as a means of scoring the visibility, using a metasearch engine. A method of rankings fusion is used for the scoring process. Acronyms of Brazilian universities were subjected to the calculation of visibility and classified, showing an application of the formula in the real world. Two rankings were built, one of them pointing out flaws in the proposed method and another solving the problem encountered with a fair rating, consistent with reality and with other rankings of universities. The main contribution of this work is a Web Visibility indicator that shows how the institutions are classified by the main entry points of the network: the search engines.
153

Visibilidade web de universidades

Klinger, Augusto January 2011 (has links)
Visibilidade Web é a área de estudo das medidas de visibilidade de organizações, termos ou documentos na web, sendo um dos campos de pesquisa da ciência de Webmetria. Neste trabalho, uma fórmula para o cálculo de visibilidade na web é proposta, baseando-se na visão proporcionada por diferentes motores de busca. O resultado final é um indicador de Visibilidade Web para universidades. São apresentados e analisados rankings de universidades do mundo todo encontrados na web, tais como o ARWU, o WR e o THE. Tais rankings trabalham com indicadores compostos, mas abordam a questão da visibilidade na rede de maneiras diferentes. Também são discutidos alguns trabalhos recentes no campo de Visibilidade Web. O indicador elaborado baseia-se na classificação do site oficial da universidade nos buscadores como meio de pontuar a visibilidade, valendo-se de metabusca. Um método de fusão de rankings é utilizado para a pontuação. Siglas de universidades brasileiras foram submetidas ao cálculo de visibilidade e classificadas, mostrando uma aplicação da fórmula no mundo real. Dois rankings foram construídos, um deles apontando falhas no método proposto e o segundo contornando o problema encontrado, apresentando uma classificação justa, coerente com a realidade e com outros rankings de universidades brasileiras. A principal contribuição do trabalho é a definição de um indicador de visibilidade na web que mostra como são classificadas as instituições através dos principais pontos de entrada da rede: os motores de busca. / Web Visibility is the area of study of visibility measures of organizations, terms or documents on the web, one of the fields of the Webmetrics science. In this work, a formula for the calculation of visibility on the web is proposed, based on the vision provided by different search engines. The result is an indicator of Web Visibility for universities. In related works section are presented and analyzed rankings of universities around the world from the web, such as ARWU, WR and THE. Such rankings work with composite indicators, but address the issue of visibility on the network in different ways. Also are covered some resent works in the field of Web Visibility. The indicator developed is based on the classification of the universities’ official website in search engines as a means of scoring the visibility, using a metasearch engine. A method of rankings fusion is used for the scoring process. Acronyms of Brazilian universities were subjected to the calculation of visibility and classified, showing an application of the formula in the real world. Two rankings were built, one of them pointing out flaws in the proposed method and another solving the problem encountered with a fair rating, consistent with reality and with other rankings of universities. The main contribution of this work is a Web Visibility indicator that shows how the institutions are classified by the main entry points of the network: the search engines.
154

PSemRef: personalização de consultas em ambientes distribuídos e dinâmicos

NEVES, Thiago Arruda 31 January 2010 (has links)
Made available in DSpace on 2014-06-12T15:57:22Z (GMT). No. of bitstreams: 2 arquivo3186_1.pdf: 4312700 bytes, checksum: dc73d3362ddcea01428e6624d0d875a0 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2010 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O processamento de consultas é um tema de pesquisa muito importante em ambientes distribuídos e dinâmicos, tais como os Peer Data Management Systems. Uma questão crucial nesse processo é a reformulação da consulta em um ponto de origem em termos de um ponto destino, considerando as correspondências existentes entre eles. Como parte do projeto SPEED (Semantic Peer-to-Peer Data Management System) uma ferramenta de reformulação de consultas, chamada SemRef (Semantic Reformulator), foi desenvolvida. Por seu intermédio, as consultas submetidas pelo usuário são reformuladas, executadas e os resultados integrados para exibição. O SemRef explora um conjunto de correspondências semânticas para enriquecimento da consulta na sua reformulação. A idéia é produzir um conjunto de resultados que expresse o que os usuários consideram importante no momento em que submetem suas consultas, considerando a dinamicidade do sistema. De uma maneira geral, os resultados das consultas são gerados de forma única sem refletir as preferências e perfis dos usuários. Neste trabalho, o objetivo é estender o módulo SemRef, passando a ser chamado PSemRef (Personalized Semantic Reformulator), propondo uma abordagem na qual as consultas sejam personalizadas e seus resultados ordenados de acordo com as preferências dos usuários e um conjunto de informações contextuais. Abordamos o problema da personalização de consultas no SPEED, bem como a especificação de nossa proposta para solucioná-lo, a qual envolve a obtenção de uma informação contextual estática (na forma de perfil do usuário) e dinâmica (localização do usuário). Capturamos as preferências do usuário na seleção e na priorização de um conjunto de variáveis de enriquecimento, as quais estão ligadas diretamente à reformulação da consulta. Todas essas informações citadas influenciam na geração de um conjunto ordenado de resultados das consultas. Detalhamos também os aspectos de implementação do nosso trabalho e, por fim, apresentamos a experimentação realizada envolvendo um estudo de caso com os resultados que foram obtidos
155

Identification of cloud service use-cases and quality aspects:end-user perspective : Learnability, Operability and Security quality attributes and their corresponding use cases

Haghverdian, Pol, Olsson, Martin January 2016 (has links)
Context. With the entry of smart-phones on the market in the beginningof 2007, the integration of an mp3 player, camera and gps into an all in onedevice. As the integration was realized, creating and storing own contentbecame easier. Therefore the need of more storage became a problem as thesmart-phones were limited in capacity. The 3G network was on the rise andthe cloud solutions could help to contribute to the storage problems usersstarted to have. Objectives. In this study we will evaluate what can be done with use casesin terms of quality attributes, seeing it from a users perspective by havingusers rank use cases for cloud services. With further investigation we willmake a contribution of what the differences between public and personalclouds are. Methods. Use-cases were found by the conducted empirical study andwere based on a Systematic mapping review. In this review, a number ofarticle sources are used, including Google search, Bth summon and Googlescholar. Studies were selected after reading the articles and checked if thepapers matched our defined inclusion criteria. We also designed a surveywith variable amount of questions depending on what the participant wouldanswer. The questions were featured in terms of functionality interpretedfrom the use-cases found in the SLM. Results. Through our SLM we found six different use-cases which were Recovery, Collaborative working, Password protection, Backup, Version tracking and Media streaming. The identified quality attributes gave two or moremappings to their corresponding use-case. As for the comparison betweendifferent clouds, only two out of six use-cases where implemented for the Personal cloud. Conclusions. This gave us the conclusion that the vendors have beenmostly focusing on the storage part of the Personal cloud, but there are solutions in order to increase the functionalities. Those solutions will probably not fit everyone as it includes open source software, with skills of handling installation and other procedures by the user.
156

Métodos cuantitativos para la generación de rankings de selecciones de fútbol y su aplicación a la confección de grupos balanceados en la copa del mundo

Cea Bontá, Sebastián Alejandro January 2016 (has links)
Magíster en Gestión de Operaciones / Ingeniero Civil Industrial / El presente trabajo se centra en la confección de distintas metodologías de creación de ratings, mediante técnicas estadísticas para el ordenamiento de las selecciones de fútbol internacionales con el fin de mejorar el ya existente y conocido mundialmente Ranking FIFA. Los métodos utilizados en este trabajo integran los datos de partidos de fútbol entre selecciones adultas desde el año 2005 al 2013 y que permitieron la asignación de los cabezas de serie para el Mundial de fútbol acontecido en Brasil durante los meses de Junio y Julio del 2014. Para el estudio de las variables más importantes que determinan el resultado de un encuentro se utilizaron 4 modelos predictivos. El principal enfoque utilizado fue el uso de modelos Logit Multinomiales. El modelo que permita explicar de mejor manera la data utilizando el mínimo número de variables será la primera metodología que se utilizará como propuesta al ranking FIFA actual. El modelo de predicción que mejor se ajustó a la data fue el basado en 2 atributos: Diferencia de ranking entre los equipos, y el factor localía. De esta manera variables como pertenecer a cierta confederación o la localía continental no fueron incluidas en las propuestas finales. Además de lo recién señalado se realizan modificaciones estructurales al modelo FIFA existente, que permiten corregir ciertos defectos. Luego de proponer metodologías diferentes a la actual, se evalúan los resultados de cada una de ellas bajo métricas de comparación. Primero que todo se debe notar que una metodología será evaluada de acuerdo al ranking que de ella se desprenda. Estos rankings serán comparados mediante la métrica "mean squared error" (MSE) a partir de Rankings de Referencias. En la segunda parte de esta tesis se propone un modelo lineal que sea capaz de generar propuestas para mundiales con fase de grupos mucho más equilibradas que los que se han visto en las últimas ediciones mundialistas, en las cuales la disparidad en el nivel de los equipos intergrupos ha sido tema recurrente.
157

Computing a journal meta-ranking using paired comparisons and adaptive lasso estimators

Vana, Laura, Hochreiter, Ronald, Hornik, Kurt 01 1900 (has links) (PDF)
In a "publish-or-perish culture", the ranking of scientific journals plays a central role in assessing the performance in the current research environment. With a wide range of existing methods for deriving journal rankings, meta-rankings have gained popularity as a means of aggregating different information sources. In this paper, we propose a method to create a meta-ranking using heterogeneous journal rankings. Employing a parametric model for paired comparison data we estimate quality scores for 58 journals in the OR/MS/POM community, which together with a shrinkage procedure allows for the identification of clusters of journals with similar quality. The use of paired comparisons provides a flexible framework for deriving an aggregated score while eliminating the problem of missing data.
158

Development of a preference ranking procedure with dogs

Li, Han January 1900 (has links)
Master of Science / Department of Human Nutrition / Kadri Koppel / Palatability of pet food is an important factor influencing food purchase decision of pet owners. In industry, single- or two-bowl methods are traditionally used to determine food acceptance or preference by pets but shortcomings exist to these methods. The first objective of this study was to propose and develop a preference ranking procedure. Preliminary testing consisted of five phases each lasting five days. Each day twelve beagles were presented 5 treats encased in identical rubber toys (“kongs”). The order of selection was considered as the ranking of preference. The five phases consisted of training, testing lab-baked treats formulations with five varieties of fats, starches and proteins, and commercial foods. The dogs generally ranked 1-2 flavors above others, indicating this procedure could be a more efficient method to determine preference since more samples can be evaluated simultaneously. The second objective was to validate this procedure by following the same process as the preliminary test. The results from phases 2 to 4 showed a similar pattern. For phase 5, various treat formulations were tested by combining the most to least preferred ingredients in each category. The results proved that the ranking of the formulations resembled the preference of the dogs for individual ingredients. Therefore, this procedure was concluded to be reliable. The third objective was to use descriptive sensory analysis to study the sensory characteristics of the treats and gain insights on the drivers of dogs’ preference. Five highly trained panelists profiled the aroma of the treats and the data was analyzed with the preference results collected from the dogs. The external preference maps showed that fish and meaty aromatics tended to be liked by the dogs and grain and musty/dusty aromatics appeared to be disliked. The last objective of this study was to further explore the applications of this procedure by studying the effect of toy/puzzle toy of the treat and ingredient dosage/ratio. With the same dogs, Styrofoam cups (puzzle toy alternative) and kongs were evaluated separately with the same treats. The results collected with Styrofoam cups were similar but less discriminating than kongs. It potentially suggested that the difficulty level of the toy can affect the significance of the dogs’ preferences. No significant preference was observed when testing the treats with different ratio of the most and the least preferred protein sources, although the human descriptive panel was able to provide different profiles for the samples. In conclusion, the preference ranking procedure is a reliable test method but more research is necessary to further explore applications.
159

Risk based assessment of subsynchronous resonance in AC/DC systems

Adrees, Atia January 2014 (has links)
This thesis investigates the phenomenon of subsynchronous resonance (SSR) in meshed series compensated AC/DC systems in the presence of operational uncertainties. The main contribution of this research is the novel application of risk assessment methods to SSR studies. In terms of network topology, future electric power transmission networks alongside the current power networks are expected to be meshed, and consequently, exposed to relative low risk of subsynchronous resonance. However, power systems are increasingly operated closer to stability limits in order to enhance efficiency and economics of their use. These stressed operating conditions may contribute to the deterioration in the system reliability. Uncertainty associated with the loads will also further diversify in the future due to new type of devices connected to the network whilst the integration of stochastic renewable generation sources will add another layer of uncertainty to system operation. There is a growing necessity to explore the challenges created by the increased uncertainty in generation and loads, and quantify risk to keep a balance between avoiding potentially catastrophic systems failures and mitigating for extremely rare event. This research work introduces risk assessment in subsynchronous resonance studies. Two indices are developed to quantify the severity of dynamic instability and transient torque amplification. Using these indices generators in the network can be ranked based on potential exposure to SSR. Following the development of indices, a methodology is proposed to evaluate the risk of SSR. The developed methodology takes into account the severity of SSR problem and probabilities of different contingencies and different operating conditions of a turbine generator. A robust investigation, into the effect of uncertainties on both aspects of SSR with symmetrical and asymmetrical compensation schemes, is also performed. The results of the analysis reveal that a critically compensated system in normal meshed network configuration may become dynamically unstable with as low as ±5% uncertainty in mechanical parameters. The critical compensation level with asymmetrical compensation in normal network configuration and each contingency becomes higher. It is also shown that the risk level assessed with the developed methodology does not change under the influence of ±5% uncertainties in the mechanical parameters. After establishing, that risk, based approach provides a better picture of all credible scenarios and risk of SSR in compensated power network, a methodology based on risk evaluation of SSR for selecting an optimal combination of TCSCs and fixed series capacitors for compensation of transmission lines is presented. This proposed methodology maximizes the use of fixed capacitors whilst maintaining the risk of SSR within an acceptable level in all credible contingencies and operating conditions.
160

Measuring and Ranking Efficiency of Major Airports in the United States Using Data Envelopment Analysis

Lee, Myunghyun 03 August 2004 (has links)
An airport is an important piece of infrastructure in air transportation system. This project focuses on measuring and ranking the efficiency of airports in the United States using the basic DEA, Ranking DEA, Goal programming and DEA and TOPSIS. In general, airport authorities of relatively inefficient airports are trying to benchmark the operational strategies of efficient airports. This project focuses on evaluating hub airports in the United States. ATL, LAX, and MEM airports are relatively efficient among forty four hub airports in the United States based on the performances and airport facilities of the 2000 year when the results of all applied methods in this project, the basic DEA ranking, the Cross Efficiency ranking, the Andersen-Petersen ranking and TOPSIS ranking method, are compared. The implication of this project is that airport authorities in the United States would benchmark these three airports to maximize operation and management efficiency for their airports. In general, most of the airports are handling passengers and freight. Therefore, ATL and LAX would be the most efficient hub airports in the United States. The capacities of airport facilities and more appropriate input data like financial data should be considered in the follow up research. / Master of Science

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