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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

Estudos de aminólise de ésteres em presença de micelas inversas / Studies of the ester aminolysis in the presence of reversed micelles

Farah, Joao Pedro Simon 14 March 1984 (has links)
Nesta dissertaçao foram estudadas as reações de aminólise de benzoatos por dodecilamina (DA), propionato de dodecilamôrtio (DAP) e suas misturas em ciclohexano. Foram usados os ésteres do tipo X-Ø-CO2-Ø-NO2 (X=NO2,CH3O,CH3,H e Cl) e NO2-Ø-CO2-Ø-Y (Y=CH3 , H, Cl e CN). A aminólise de ésteres por DA é de segunda ordem em amina e está associada com entropias de ativação altamente negativas e pequenas eutalpias de ativação. A reação é muito mais sensível à natureza do grupo abandonador que da acila. Na reaçao com DAP micelar mostrou-se claramente que o grupo carboxilato de detergente atua com base geral e não como nucleófilo. A reação é de segunda ordem em DAP e apresentou as mais altas entropias de ativação. O valor de ρ de Hammett era maior quando se variou o grupo Y, mostrando que a reação, como com DA, é mais sensível à natureza do grupo fugitivo. O valor da razão ρY/ρX mostrou que o grupo abandonador é o íon fenóxido p-substituido. Uma prova adicional deste fato, foi obtida dos resultados de aminólise em presença de água solubilizada. O DAP micelar aumentou a velocidade de aminólise por DA, por fatôres desde 132 vêzes (Cl/NO2) até 311 vêzes (NO2/NO2 ). A aminólise de ésteres por DA+DAP apresentou parâmetros de ativação, cujos valores são intermediários àqueles para as reações com DA e com DAP respectivamente. Os valores de ρ de Hammett foram similares aqueles obtidos para a reação com DAP somente. Baseados nos resultados previamente reportados, foram sugeridos esquemas para as reações. Eles envolvem a formação de intermediários tetraédricos (aniônicos para as reações com DA e com DAP e zwitteriônicos para a aminólise por DAP), cujo colapso é determinante da velocidade. / In this thesis the aminolysis of benzoate esters by dodecylamine (DA), dodecylammonium propionate (DAP) and their mixtures in cyclohexane was studied. The esters used were X-ØCO2ØNO2 (X=NO2CH3O,CH3,H e Cl) and NO2ØCO2ØY (Y=CH3,H,Cl e CN). Ester aminolysis by DA is second order in the amine and is associated with a highly negative entropies and small euthalpies of activation. The reaction is much more sensitive to the nature of the leaving group than that of the acyl one. In the reaction with micellar DAP it was clearly showed that the carboxylate group of the surfact and is acting as a general base, not as a nucleophile. The reaction was found to be second order in the surfactant and showed the highest entropies of activation. The Hammett ρ value was larger when was varied, showing that the reaction, like that with DA, is more sensitive to the nature of the leaving group. From the ratio ρY/ρX it was shown that the leaving group is the P-substituted phenoxide ion. Additional proof for this was reached from the results of aminolysis in the presence of solubilized water. Micellar DAP enhance the rate of aminolysis by DA by factors ranging from 132 times (Cl/NO2) to 311 times (NO2/ NO2). Ester aminolysis by DA+DAP has activation parameters which are intermediate between those for the reactions with DA, and with DAP, respectively. The Hammett ρ values were similar to those obtained for the reaction with DAP alone. Based on the previous data schemes for the reactions were suggested. They involve the formation of tetrahedral intermediates (anions for the reaction with DA and with DA+DAP, and zwitterion for the aminolysis by DAP) whose collapse are rate limiting.
152

Caracteriza??o qu?mica e atividades biol?gicas in vitro e in silico de Asemeia ovata (Polygalaceae)

Rocha, Jos? Luiz Carneiro da 26 August 2016 (has links)
Submitted by Luis Ricardo Andrade da Silva (lrasilva@uefs.br) on 2017-01-11T21:46:05Z No. of bitstreams: 1 Boneco 97-2003-corre??es.pdf: 20164603 bytes, checksum: 78fbb46841fee330fc6bc340e1af3756 (MD5) / Made available in DSpace on 2017-01-11T21:46:06Z (GMT). No. of bitstreams: 1 Boneco 97-2003-corre??es.pdf: 20164603 bytes, checksum: 78fbb46841fee330fc6bc340e1af3756 (MD5) Previous issue date: 2016-08-26 / Funda??o de Amparo ? Pesquisa do Estado da Bahia - FAPEB / Polygalaceae family species are traditionally used in many regions of the world and because of this, research is being conducted to evaluate the biological activities, as well as phytochemicals aspects of these plants. In this way, the present study was to carry out the proposed chemical characterization and evaluation of biological activity in vitro of the extract and prediction of new biological activities in silico of the substances identified in Asemeia ovata (Polyagalaceae). The chemical characterization was made through previous phytochemical screening tests and fingerprint by HPLC-DAD. The isolation and identification of compounds was performed by classical chromatography techniques, HPLC-DAD and 1H and 13C NMR. The evaluation of the antioxidant activity in vitro was taken by Scavenging of DPPH free radical method, acetylcholinesterase activity by adapting the method of Ellman and Artemia salina lethality. The prediction of activity was made by tools for in silico target fishing, followed by docking the DOCK 6.7 program and evaluation of interaction profiles by Protein-Ligand Interaction server profiler. The chemical characterization showed that the extracts are rich in flavonoids and phenolic acids. It was possible to identify and quantify using HPLC-DAD substances: rutin, luteolin-7-O-glucoside, caffeic acid, p-coumaric acid and trans-ferulic acid. Moreover, it was possible to isolate the rutin substance, poligalen and a possible new alkaloid. The ethyl acetate extract was superior in the evaluation of in vitro activity with EC50 = 5.46 mg/mL for antioxidant activity, and LC50 = 71.91 mg/mL A. salina lethality. Acetylcholinesterase activity did not yield significant results (AChEIs% <20%). Tools for in silico target fishing allowed, through the ChemProt 2.0 and DRAR- CPI-servers, to select the molecular targets carbonic anhydrase 12 and epidermal growth factor receptor for routine; for luteolin-7-O-glucoside targets cotransporter 2 sodium / glucose and CDC42-activated protein kinase 1; poligalen to the target protein tyrosine kinase JAK2; and for caffeic acid, p-coumaric acid and trans-ferulic the best targets were epidermal growth factor receptor and Ras-related C3 botulinum toxin substrate 1, carbonic anhydrase 12 and Ornithine carbamoyltransferase, mitochondrial. This work provides new results for the species, both from a chemical and biological point of view, there is good prospects of study with interesting potential to be discovered. / Esp?cies da fam?lia Polygalaceae s?o utilizadas tradicionalmente em muitas regi?es do mundo e, devido a isso, pesquisas est?o sendo realizadas para avaliar as atividades biol?gicas, como tamb?m os aspectos fitoqu?micos desses vegetais. Desta forma, o presente trabalho teve como proposta realizar a caracteriza??o qu?mica e avalia??o de atividades biol?gicas in vitro de extratos da planta inteira e predi??o in silico de novas atividades biol?gicas das subst?ncias identificadas de Asemeia ovata (Polyagalaceae). A caracteriza??o qu?mica foi feita atrav?s de testes de triagem fitoqu?mica pr?via e fingerprint por CLAE-DAD. O isolamento e identifica??o de subst?ncias foi realizado por t?cnicas de cromatografia cl?ssica, CLAE-DAD e RMN de 1H e 13C. A avalia??o da atividade antioxidante in vitro foi feita pelo m?todo de sequestro de radical livre DPPH, atividade anticolinester?sica pela adapta??o do m?todo de Ellman e letalidade frente Artemia salina. A predi??o de atividades in silico foi feita por m?todos de Triagem Virtual Inversa (TVI), seguido de reacoplamento pelo programa DOCK 6.7 e avalia??o dos perfis de intera??o pelo servidor Protein-Ligand Interaction Profiler. A caracteriza??o qu?mica mostrou que os extratos s?o ricos em ?cidos fen?licos e flavonoides. Foi poss?vel identificar e quantificar, atrav?s de CLAE-DAD, as subst?ncias: rutina, luteolina-7-O-glicos?deo, ?cido cafeico, ?cido p-cum?rico e ?cido trans-fer?lico. Al?m disso, foi poss?vel isolar as subst?ncias rutina, poligaleno e um poss?vel novo alcaloide. O extrato acetato de etila mostrou-se superior na avali??o das atividades in vitro, com CE50 = 5,46 mg/mL para atividade antioxidante, e CL50 = 71,91 ?g/mL para letalidade frente a A. salina. Para a atividade anticolinester?sica n?o obteve-se resultados significativos (%IAChE < 20%). A TVI permitiu selecionar, atrav?s dos servidores ChemProt 2.0 e DRAR-CPI, os alvos moleculares Anidrase carb?nica 12 e Receptor de fator de crescimento epid?rmico para a rutina; para a luteolina-7-O-glicos?deo os alvos Cotransportador 2 de s?dio/glicose e Prote?na quinase CDC42 ativada 1; para o poligaleno o alvo Prote?na tirosina quinase JAK2; e para os ?cidos cafeico, p-cum?rico e trans-fer?lico os melhores alvos foram Receptor de fator de crescimento epid?rmico e Ras-relacionada ao substrato C3 da Toxina botul?nica 1, Anidrase carb?nica 12 e Ornitina carbamoiltransferase, mitocondrial. Esse trabalho fornece resultados in?ditos para a esp?cie, tanto do ponto de vista qu?mico, como biol?gico, apresentando boas perspectivas de estudo, com interessante potencial a ser descoberto.
153

Osmose inversa aplicada no reúso da água do rio Sarapuí em processos industriais / Reverse osmosis applied in Sarapuí river water reuse in industrial processes

Raphael da Rocha Sixel 14 December 2009 (has links)
O objetivo deste estudo foi analisar o desempenho de um sistema de captação e tratamento de água do rio Sarapuí, por meio de uma estação de tratamento composta por um sistema de pré-tratamento convencional, ligado a um sistema de separação por membranas de osmose inversa, no Município de Belford Roxo RJ, instalado para fornecer água de processo a instalações industriais. Foi verificado que a água captada encontra-se em condição bastante degradada e que a unidade de tratamento removeu, em média, 97% do teor dos poluentes presentes na água, enquadrando-a nos parâmetros requeridos pelo processo industrial. Foi possível comprovar que o processo de separação por osmose inversa pode ser utilizado em escala industrial, proporcionando ganhos econômicos consideráveis, além de evitar o consumo de água potável para fins de processos industriais e, ainda, contribuir para a retirada de carga orgânica de uma fonte degradada / The objective of this study was to analyze the performance of a system to capture and treat water from Sarapuí river through a treatment system consisting of a conventional pré-treatment stage, linked to a reverse osmosis separation system membranes, in the city of Belford Roxo - RJ, installed to provide process water for industrial plants. It was found that the water is captured in highly degraded condition and the treatment plant removed an average of 97% of the pollutants in the water, fitting the parameters required by the industrial process. It could be demonstrated that the separation process by reverse osmosis can be used on an industrial scale, providing significant economic gains, and avoid the consumption of potable water for industrial processes and also contribute to the removal of organic pollutants from a degraded source
154

Logística e Sustentabilidade : Análise de casos de estudo e tendências

Fernandes, Maria Cristina da Silva January 2008 (has links)
In the last decades, the negative environment impacts of entreprise activities have gained wide recognition. Environmental issues affect numerous logistical decisions troughout the value chain. As concerns rises, companies must take more account of the external logistics cost related with the environment problems (such as climate change, pollution and scarcity of natural resources) and social problems (poverty, violence, unemployment...) Several studies suggest that green logistics strategies such as reducing consumption, recycling and reusing materials can bring large benefits. Companies should be able to create measures and strategies in order to achieve sustainable balance between economic, environmental and social objectives. This research intends to identify logistics-related environmental impacts in activities such as purchasing (raw materials acquisition), Transport, Warehousing/Distribution; to interpret concepts such as Green Logistics and Inverse Logistics; to present an international Case Study (Procter & Gamble) and a Portuguese Case Study (Unicer), showing the best practices employed by leading firms; finnaly, an overview of managers opinion about environmental and social problems, sustainable reports and environmental responsible logistics activities.
155

Usando o Sistema de Inferência Neuro Fuzzy - ANFIS para o cálculo da cinemática inversa de um manipulador de 5 DOF /

Spacca, Jordy Luiz Cerminaro January 2019 (has links)
Orientador: Suely Cunha Amaro Mantovani / Resumo: No estudo dos manipuladores são utilizados os conceitos da cinemática direta e a inversa. No cálculo da cinemática direta tem-se a facilidade da notação de Denavit-Hartenberg, mas o desafio maior é a resolução da cinemática inversa, que se torna mais complexa conforme aumentam os graus de liberdade do manipulador, além de apresentar múltiplas soluções. As variáveis angulares obtidas pelas equações da cinemática inversa são utilizadas pelo controlador, para posicionar o órgão terminal do manipulador em um ponto específico de seu volume de trabalho. Na busca de alternativas para contornar estes problemas, neste trabalho utilizam-se os Modelos Adaptativos de Inferência Neuro-Fuzzy - ANFIS para a resolução da cinemática inversa, por meio de simulações, para obter o posicionamento de um manipulador robótico de 5 graus de liberdade, composto por sete servomotores controlados pela plataforma de desenvolvimento Intel® Galileo Gen 2, usado como caso de estudo. Nas simulações usamse ANFIS com uma arquitetura com três e quatro funções de pertinência de entrada, do tipo gaussiana. O desempenho da arquitetura da ANFIS implementada foi comparado com uma Rede Perceptron Multicamadas, demonstrando com os resultados favoráveis a ANFIS, a sua capacidade de aprender e resolver com baixo erro quadrático médio e com precisão, a cinemática inversa para o manipulador em estudo. Verifica-se também, que a performance das ANFIS melhora, quanto à precisão dos resultados, demonstrado pelo desvio médio d... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In the study of manipulator’s, the concepts of direct and inverse kinematics are used. In the computation of forward kinematics, it has of the ease of Denavit-Hartenberg notation, but the biggest challenge is the resolution of the inverse kinematics, which becomes more complex as the manipulator's degrees of freedom increase, besides presenting multiple solutions. The angular variables obtained by the inverse kinematics equations are used by the controller to position the terminal organ of the manipulator at a specific point in its work volume. In the search for alternatives to overcome these problems, in this work, the Adaptive Neuro-Fuzzy Inference Models (ANFIS) are used to solve the inverse kinematics, by means of simulations, to obtain the positioning of a robot manipulator of 5 degrees of freedom, consisting of seven servomotors controlled by the Intel® Galileo Gen 2 development platform, used as a case's study . In the simulations ANFIS's architecture are used three and four Gaussian membership functions of input. The performance of the implemented ANFIS architecture was compared to a Multi-layered Perceptron Network, demonstrating with the favorable results the ANFIS, its ability to learn and solve with low mean square error and with precision, the inverse kinematics for the manipulator under study. It is also verified that the performance of the ANFIS improves, as regards the accuracy of the results in the training process, , demonstrated by the mean deviation of the... (Complete abstract click electronic access below) / Mestre
156

A desconsideração inversa da personalidade jurídica da Empresa Individual de Responsabilidade Limitada (EIRELI) e o tratamento constitucional favorecido das micro e pequenas empresas: uma análise crítica / The inverse disregard of the legal personality of the Individual Limited Liability Company (EIRELI) and the favored constitutional treatment of micro and small enterprises: a critical analysis

Moraes, Maria Elisa Palomine Bonato 07 November 2018 (has links)
A desconsideração inversa da personalidade jurídica goza, hoje, de previsão expressa no Código de Processo Civil (artigo 133, §2º), embora já fosse anteriormente estudada pela doutrina e aplicada pela jurisprudência brasileira. Da mesma forma, é recente a inserção, no ordenamento jurídico pátrio, da figura da Empresa Individual de Responsabilidade Limitada (EIRELI), inaugurada pela Lei nº 12.441/2011. A maior novidade trazida por este diploma foi a possibilidade de um único indivíduo constituir uma pessoa jurídica com a celebrada vantagem da separação entre o seu patrimônio e o da empresa que erigiu. Tal particularidade permite, por sua vez, que a desconsideração inversa da personalidade jurídica também atinja as EIRELIs, sendo justamente este o foco da presente pesquisa, a qual se pautou pela análise de acórdãos que se debruçaram sobre o tema, oriundos dos cinco maiores tribunais de justiça no país. Uma vez que as EIRELIs são comumente erigidas sob a forma de micro e pequenas empresas (Lei Complementar nº 123/2006), se sujeitam ao tratamento diferenciado e favorecido dispensado a esta categoria tanto pela Constituição Federal quanto por leis hierarquicamente inferiores. Não obstante, tal atenção especial costuma se restringir à teoria e aos textos legais, sendo raramente constatada na prática jurídica. Por isso, o foco deste trabalho foi o exame crítico de decisões datadas de 2012 a 2017, no bojo das quais foram encontrados equívocos e inconsistências que não condizem com o aludido tratamento, o que, devido à notória relevância das pequenas empresas no cenário econômico-social, prejudica consideravelmente o desenvolvimento nacional. / The inverse disregard of legal personality is now expressly provided for in the Code of Civil Procedure (article 133, §2), although it was previously studied by the doctrine and applied by the Brazilian jurisprudence. In the same way, the insertion in the legal order of the figure of the Individual Company for Limited Liability (EIRELI), inaugurated by Law 12,441/2011, is recent. The greatest novelty brought by this law was the possibility of a single individual to constitute a legal entity with the well-known advantage of the separation between its assets and the one of the company that he/she erected. This particularity allows, in turn, that the inverse disregard of the legal personality also affects the EIRELIs, being precisely this the focus of the present research, which was based on the analysis of judgments that dealt with the subject, coming from the five major courts of justice in the country. Since EIRELIs are commonly erected in the form of micro and small enterprises (Complementary Law 123/2006), they are subject to the differentiated and favored treatment granted to this category both by the Federal Constitution and by lower hierarchical laws. Nevertheless, such special attention is usually confined to theory and legal texts, and is rarely found in legal practice. Therefore, the focus of this work was the critical examination of decisions dating from 2012 to 2017, in which were found misunderstandings and inconsistencies that do not fit the aforementioned treatment, which, due to the notorious relevance of small companies in the economic- development, considerably undermines national development.
157

Icke-triviala billigaste väg-ruttningskonflikter - klassificering och sökmetoder / Non-triivial shortest path routing conflicts - classification and search methods

Morén, Björn January 2010 (has links)
<p>Within telecommunication and routing of traffic in IP-networks a protocol named“Open Shortest Path First” (OSPF) is widely used. This means that a server dealswith the routing over a network with given weights by calculating shortest paths touse for routing. If we assume that a desired traffic pattern is given the problem isto find out if it is possible to set the weights so that the desired traffic pattern is apart of a shortest path graph. In this thesis we assume that it is a unique shortestpath. To search for weights that solve the problem leads to a complex LP-model. Analternative is to search in the LP-dual under certain restrictions. These solutions tothe LP-dual are called conflicts and a conflict means that there exists no weights sothat the desired traffic pattern is obtained. The goal of this thesis is to study, classifyand search for conflicts. An algorithm has been developed that finds some kind ofconflicts in polynomial time with respect to the size of the graph.</p> / <p>Inom telekommunikation och ruttning av datatrafik i IP-nätverk så används oftaett protokoll som kallas “Open Shortest Path First” (OSPF). Det innebär att enserver sköter ruttningen över ett nätverk genom att utifrån givna bågkostnaderberäkna billigaste vägar som används för ruttningen. Frågeställningen utgårfrån att vi har ett önskat ruttningsschema och vi vill ta reda på om det gåratt sätta bågkostnader så att det önskade ruttningsschemat ingår i en billigasteväg-graf. I det här examensarbetet splittas inte trafik utan varje billigaste vägär unik mellan två noder. Att söka efter bågkostnader som löser problemet geren krävande LP-modell och ett alternativ är att utgå från LP-dualen undervissa restriktioner. Dessa lösningar till LP-dualen benämns konflikter och enkonflikt motsvarar att det inte finns några bågkostnader så att det önskaderuttningsschemat fås. Målet med examensarbetet är att studera, klassificeraoch söka efter konflikter. En algoritm har tagits fram som hittar vissa typer avsådana konflikter i polynomiell tid, sett till storleken på grafen.</p>
158

Icke-triviala billigaste väg-ruttningskonflikter - klassificering och sökmetoder / Non-triivial shortest path routing conflicts - classification and search methods

Morén, Björn January 2010 (has links)
Within telecommunication and routing of traffic in IP-networks a protocol named“Open Shortest Path First” (OSPF) is widely used. This means that a server dealswith the routing over a network with given weights by calculating shortest paths touse for routing. If we assume that a desired traffic pattern is given the problem isto find out if it is possible to set the weights so that the desired traffic pattern is apart of a shortest path graph. In this thesis we assume that it is a unique shortestpath. To search for weights that solve the problem leads to a complex LP-model. Analternative is to search in the LP-dual under certain restrictions. These solutions tothe LP-dual are called conflicts and a conflict means that there exists no weights sothat the desired traffic pattern is obtained. The goal of this thesis is to study, classifyand search for conflicts. An algorithm has been developed that finds some kind ofconflicts in polynomial time with respect to the size of the graph. / Inom telekommunikation och ruttning av datatrafik i IP-nätverk så används oftaett protokoll som kallas “Open Shortest Path First” (OSPF). Det innebär att enserver sköter ruttningen över ett nätverk genom att utifrån givna bågkostnaderberäkna billigaste vägar som används för ruttningen. Frågeställningen utgårfrån att vi har ett önskat ruttningsschema och vi vill ta reda på om det gåratt sätta bågkostnader så att det önskade ruttningsschemat ingår i en billigasteväg-graf. I det här examensarbetet splittas inte trafik utan varje billigaste vägär unik mellan två noder. Att söka efter bågkostnader som löser problemet geren krävande LP-modell och ett alternativ är att utgå från LP-dualen undervissa restriktioner. Dessa lösningar till LP-dualen benämns konflikter och enkonflikt motsvarar att det inte finns några bågkostnader så att det önskaderuttningsschemat fås. Målet med examensarbetet är att studera, klassificeraoch söka efter konflikter. En algoritm har tagits fram som hittar vissa typer avsådana konflikter i polynomiell tid, sett till storleken på grafen.
159

Contributions to ionospheric electron density retrieval

Aragón Àngel, Angela 22 February 2010 (has links)
La transformada de Abel es una técnica de inversión usada frecuentemente en radio ocultaciones (RO) que, en el contexto ionosférico, permite deducir densidades electrónicas a partir de datos de STEC (Slant Total Electron Content) derivados a partir de observaciones de la fase portadora. Esta técnica está basada en medidas precisas en doble frecuencia de fase portadora ( banda L) de un receptor GPS a bordo de un satélite de órbita baja (Low Earth Orbit -LEO-) rastreando un satélite GPS detrás del limbo de la tierra. Al combinar tales medidas con la información de posiciones y velocidades de los satélites GPS y LEO, es posible deducir el cambio en el camino de la señal debido a la presencia de la atmósfera y, consecuentemene, convertirlo en ángulos de curvatura (bending angles). A partir de ellos, información sobre el índice de refracción vertical puede ser obtenida a través de técnicas de inversión, y transformarlo en perfiles verticales de densidad electrónica y/o perfiles de atmósfera neutra. Una de las hipótesis básicas de la inversión clásica es suponer que el campo de densidades electrónicas tiene simetría esférica en la vecindad de una ocultación. Sin embargo, a la práctica, la huella de una ocultación generalmente cubre regiones de miles de km que puede presentar variabilidad ionosférica importante; por lo cuál, la hipótesis de simetría esférica no puede ser garantizada. De hecho, las inhomogeneidades de la densidad electrónica en la dirección veritcal para una ocultación dada son una de las principales causas de error cuando se usa la inversión de Abel inversion. Para corregir el error debido a la hipótesis de simetría esférica, se introduce el concepto de separabilidad. Ello implica que la densidad electrónica puede ser expresada como una combinación de datos de Vertical Total Electron Content (VTEC) derivados externamente, los cuales asumen la dependencia horizontal de la densidad, y una función de forma, que a su vez asume la dependencia en altura que es común a todas las observaciones para una ocultación dada. Nótese que el espesor de capa permanece constante cerca de la región de la ocultación debido a la hipótesis de separabilidad en vez de la densidad, como ocurriría en el caso de usar simetría esférica. Esta técnica fue aplicada exitosamente a la combinación lineal de fases de GPS L1 y L2, , LI= L1-2, la cuál proporcionar un observable libre de geometría que depende sólo del retraso ionosférico, la ambigüedad de fase, biases instrumentales y wind-up. Los resultados presentaban una mejora del 40% en RMS al comparar frecuencias del pico de la capa F2 con datos de ionosonda respecto la inversión clásica de Abel. Sin embargo, la potencial influencia de la diferencia de caminos ópticos entre L1 y L2 fue despreciada. Esta tesis doctoral muestra que ello no es un problema para la inversión a alturas ionosféricas. Una alternativa para la inversión de perfiles que evita esta desventaja es usar la curvatura de la señal como dato principal. La implementación de la separabilidad para ángulos de curvatura no es inmediata y ha sido uno de los objetivos de esta tesis. En este sentido, el principio de la separabilidad ha sido aplicado a los ángulos de curvatura de L1 en vez de la la combinación LI como en trabajos anteriores. Además, trabajando con ángulos de curvatura, la separabilidad puede ser también trasladada a la obtención de perfiles troposféricos. Varias aproximaciones para obtener la contribución de las partes altas de la ionosfera han sido también estudiadas, aparte del hecho de simplemente prescindir de esta contribución. Se ha usado un modelo climatológico, una extrapolación exponencial y el hecho de considerar las implicaciones de usar separabilidad. También se ha propuesto una manera para obtener funciones de mapeo (mapping functions) deducidas a partir de perfiles RO. Sin embargo, trabajando sólo con datos derivados únicamente de RO, se está sistematicamente despreciando la contribución de la protonosfera al TEC. Con la propuesta inicial de función de mapeo sólo la contribución ionosférica es tenida en cuenta. La solución ideal para aplicaciones de datos de tierra GNSS sería usar un modelo de dos capas, una para modelar la ionosfera y otra para la protonosfera, o alternativamente, si se quisiera alta resolución tomográfica, combinar observaciones RO y con elevación positiva de LEOs con datos de tierra. Se ha probado que modelando con dos capas, los resultados que se habían obtenido con el análisis de datos RO han podido ser validados. La conclusión más importante es que la proporción entre la contribución ionosférica y protonosférica es el parámetro que explica la localización de las alturas efectivas. / La transformada d’Abel és una tècnica emprada freqüentment en radio ocultacions (RO) que, en el context ionosfèric, permet deduir densitats electròniques a partir de dades de STEC (Slant Total Electron Content) derivats a partir d’observacions de la fase portadora. Aquesta tècnica està basada en mesures precises en doble freqüència de fase portadora (banda L) d’un receptor GPS a bord d’un satèl·lit d’òrbita baixa (Low Earth Orbit-LEO-) rastrejant un satèl·lit GPS darrere del limb de la terra. En combinar les dites mesures amb la informació de posicions i velocitats dels satèl·lits GPS i LEO, és possible deduir el canvi en el camí del senyal degut a la presència de l’atmosfera i, conseqüentment, convertir-lo en angles de curvatura (bending angles). A partir d’ells, informació sobre l’índex de refracció vertical pot ser obtinguda mitjançant tècniques d’inversió i transformar-lo en perfils verticals de densitat electrònica i/o perfils d’atmosfera neutra. Una de les hipòtesis bàsiques de la inversió clàssica és suposar que el camp de densitats electròniques té simetria esfèrica en el veïnatge d’una ocultació. Tanmateix, a la pràctica, la petjada d’una ocultació generalment cobreix regions de milers de quilòmetres que pot presentar variabilitat ionosfèrica important; per la qual cosa, la hipòtesi de simetria esfèrica no pot ser garantida. De fet, les inhomogeneitats de la densitat electrònica en la direcció vertical per a una ocultació donada són una de les principals causes d’error quan es fa servir la inversió d’Abel. Per a corregir l’error a causa de la hipòtesi de simetria esfèrica, s’introdueix el concepte de separabilitat. Això implica que la densitat electrònica pot ser expressada com una combinació de dades de Vertical Total Electron Content (VTEC) derivats externament, els quals assumeixen la dependència horitzontal de la densitat, i una funció de forma, la qual alhora assumeix la dependència en altura que és comuna a totes les observacions per a una ocultació donada. Cal notar que l’espessor de capa roman constant a prop de la regió de l’ocultació a causa de la hipòtesi de separabilitat en comptes de la densitat, tal i com succeiria en el cas de fer servir simetria esfèrica. Aquesta tècnica fou aplicada amb èxit a la combinació lineal de fases de GPS L1 i L2, LI=L1-2, la qual proporciona un observable lliure de geometria que depèn només del retard ionosfèric, l’ambigüitat de fase, biases instrumentals i wind-up. Els resultats presenten una millora del 40% en RMS en comparar freqüències del pic de la capa F2 amb dades de ionosonda respecte la inversió clàssica d’Abel. No obstant, la potencial influència de la diferència de camins òptics entre L1 i L2 fou menyspreada. Aquesta tesi doctoral mostra que això no és pas un problema per a la inversió a altures ionosfèriques. Una alternativa per a la inversió de perfils que evita aquesta desavantatge és emprar la curvatura del senyal com a dada principal. La implementació de la separabilitat per a angles de curvatura no és immediata i ha estat un dels objectius d’aquesta tesi. En aquest sentit, el principi de la separabilitat ha esta aplicat als angles de curvatura de L1 en comptes de la combinació LI com en treballs anterior. A més, treballant amb angles de curvatura, la separabilitat pot ser també traslladada a l’obtenció de perfils troposfèrics. Varies aproximacions per a obtenir la contribució de les parts altes de la ionosfera han estat també estudiades, apart del fet de prescindir simplement d’aquesta contribució. S’ha fet servir un model climatològic, una extrapolació exponencial i el fet de considera les implicacions d’usar separabilitat. També s’ha proposat una manera pera obtenir funcions de mapeo (mapping functions) deduïdes a partir de perfils RO. Tanmateix, treballant només amb dades derivades únicament de RO, s’està menyspreant sistemàticament la contribució de la protonosfera al TEC. Amb la proposta inicial de funció de mapeo només tenim en compte la contribució ionosfèrica. La solució ideal per a aplicacions de dades de terra GNSS seria fer servir un model de dues capes, una per a modelar la ionosfera i una altra per la protonosfera, o alternativament, si es volgués alta resolució tomogràfica, combinar observacions RO i amb elevació positiva de LEOs amb dades de terra. S’ha provat que modelant amb dues capes, els resultats obtinguts amb l’anàlisi de dades RO han pogut estar validats. La conclusió més important és que la proporció entre la contribució ionosfèrica i protonosfèrica és el paràmetre que explica la localització de les altures efectives. / The Abel transform is a frequently used radio occultation (RO) inversion technique which, in the ionospheric context, allows retrieving electron densities as a function of height from STEC (Slant Total Electron Content) measurements derived from carrier phase observations. The GPS RO technique is based on precise carrier dual-frequency phase measurements (L-band) of a GPS receiver onboard a Low Earth Orbit satellite (LEO) tracking a rising or setting GPS satellite behind the limb of the earth. When combining such measurements with the information from the positions and velocities of GPS and LEO satellites, it is possible to derive the phase path change due to the atmosphere during an occultation event which subsequently can be converted into bending angles. From these, information about the vertical refraction index can be obtained by means of inversion techniques, which can then be converted into ionospheric vertical electron density profiles and/or neutral atmospheric profiles. One of the basic assumptions in the classical approach is to assume the spherical symmetry of the electron density field in the vicinity of an occultation. However, in practice, the footprint of an occultation generally covers wide regions of thousands of kilometres in length that may show significant ionospheric variability; therefore this hypothesis cannot be guaranteed. Indeed, inhomogeneous electron density in the horizontal direction for a given occultation is believed to be one of the main sources of error when using the Abel inversion. In order to correct the error due to the spherical symmetry assumption, the separability concept is introduced and applied. This implies that the electron density can be expressed by a combination of externally derived Vertical Total Electron Content (VTEC) data, which assumes the horizontal dependency, and a shape function, which in turn assumes the height dependency that is common to all the observations for a given occultation. Note that the slab thickness remains constant near the occultation due to the separability hypothesis instead of the density as is the case of the spherical symmetry. This technique was successfully applied to the linear combination of the GPS carrier phases L1 and L2, , LI= L1-2 which is a geometric free observable that depends only on the ionospheric delay, phase ambiguity, instrumental bias and wind-up. The result was an improvement of about 40% in RMS when comparing frequencies of the F2 layer peak with ionosonde data and the classical Abel inversion. The main advantage of such developed technique is its simple computation. Nevertheless, the potential influence of the different signal paths between L1 and L2 was neglected. Regarding this aspect, this Ph.D. dissertation shows that is not a problem for inversion at ionospheric heights. An alternative to inverting the profile, which overcomes this disadvantage, is to use the bending angle of the signal as the main input data. The implementation of separability when using the bending angle is not immediate and was, actually, one of the goals of this thesis. In this sense, the separability approach has been applied to measured L1 bending angle, instead of LI combination as reported in previous work. Additionally, this approach could also be translated to tropospheric profile retrievals. Several approaches to account for the upper ionospheric contribution have been also tackled, apart from the fact of neglecting such contribution: a climatological model, an exponential extrapolation and condisering the nature of the separability concept. it has been proposed a way to obtain mapping functions derived from RO profiles. Such mapping functions can be easily derived from usual ionospheric parameters. For the contribution of this part of the ionosphere, it has been shown that it is capable to account for the total electron content (TEC). However, by working solely with RO derived data, we are systematically neglecting the contribution of the protonosphere to the total electron content. With the initial proposed mapping function based on the analysis of effective heights derived from RO, only the ionospheric contribution is accounted for. The ideal solution for ground-based GNSS data applications would be to use a two-layer model, one to model the ionosphere and another one for the protonosphere, or alternatively, if we are looking for high tomographic resolution, to combine RO and topside LEO observations with ground data. It has been shown that by modelling in such way, the results that were obtained with RO data analysis can be validated. The most important conclusion is that the ratio between ionospheric and protonospheric contribution is the driver for the location of the effective heights.
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Reverse logistics: models and applications

Soto Zuluaga, Juan Pablo 12 January 2006 (has links)
En los últimos años la Logística Inversa se ha hecho relevante no solo para el mundo académico sino también para el empresarial. Las empresas dan cada día más importancia a esta área, debido a los factores medioambientales y a los beneficios derivados del mejoramiento de su proceso de devoluciones. Así mismo, para tener unos procesos de Logística Inversa eficientes y exitosos, es necesaria la colaboración entre los miembros de la cadena de suministro. Esta tesis se concentra en ambos aspectos, Colaboración y Logística Inversa.El propósito de esta tesis es doble; primero, analizar los problemas que sufren hoy en día las empresas en esta área, partiendo de una perspectiva general, y posteriormente analizando la industria editorial española. En segundo lugar, nosotros proponemos cuatro modelos matemáticos concernientes a los problemas de planificación que presentan las empresas cuando incorporan las devoluciones, y finalmente proponemos unas metodologías para solucionarlos. / During last years Reverse Logistics has become a relevant topic not only for academics but also for the business world. Companies are giving each day more and more importance to this field, because the environmental issues and the benefits that the company can obtain by the improvement of their return's processes. To obtain a successful and efficient Reverse Logistics processes there exist the need to collaborate along the supply chain. This thesis focuses on both of these two topics, Collaboration and Reverse Logistics. The aim of this thesis is twofold; first, we try to understand the returns processes' problems that companies are facing today from the management point of view, from a general perspective and afterwards on the editorial industry. Secondly, we propose some mathematical models and solution methods related to real planning problems faced by the companies when the returns are incorporated.

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