• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 415
  • 243
  • 179
  • 117
  • 111
  • 76
  • 38
  • 20
  • 18
  • 16
  • 12
  • 10
  • 8
  • 8
  • 5
  • Tagged with
  • 1494
  • 207
  • 136
  • 112
  • 104
  • 104
  • 90
  • 82
  • 82
  • 80
  • 78
  • 76
  • 65
  • 54
  • 53
  • 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.
271

Marketingová strategie slavkovského zámku / The marketing strategy of the chateau in Slavkov u Brna

Mrvová, Irena January 2010 (has links)
The goal of graduation thesis is to describe current state of marketing mix in the chateau in Slavkov u Brna and to propose a new possibilities. The thesis is divided into two main parts. The first theoretical chapter has free parts: The genaral marketing strategy, The destination of tourism and The specification in tourism. The main goal of the first chapter is to describe differences in tourism. The second chapter (The aplication of theory to the concrete destination) is concentrated on chateau in Slavkov u Brna and South Moravian. The main topics are Characteristics of specific area, The situation analysis, The formulation of vision and goals in destination marketing, The selection of strategy and Marketing mix.
272

Uma linha de produtos de software orientada a serviços para sistemas de auxílio à visitação de museus / A service-oriented software product line for museum visitation assistance systems

Fuzeto, Ricardo 20 May 2019 (has links)
Os sistemas de auxílio à visitação de museus apresentam um grau de reúso de software baixo, dado que o volume de trabalhos publicados contendo a proposta de um novo sistema e/ou modelagem é consideravelmente elevado, e com grau de referenciação entre tais trabalhos próximo de zero. Além disso, diversos estudos neste domínio de aplicações utilizam técnicas de ciência de contexto e fazem uso de dispositivos de Internet das Coisas (IoT), o que agrava o grau de reúso devido à variedade de sensores e dispositivos existentes. Este trabalho apresenta a Museum Touring and Tutoring Product Line (MTTPL), linha de produtos orientada a serviços para o domínio dos sistemas de auxílio à visitação de museus. Os requisitos desta linha de produtos foram coletados principalmente dos resultados de um mapeamento sistemático feito sobre sistemas E-learning e dispositivos IoT. Como forma de avaliação preliminar da linha de produtos proposta, foi realizada uma prova de conceito em que a MTTPL foi instanciada, dando origem ao SmartICMC, um museu virtual para apoiar a visitação ao Museu da Fauna e Flora do ICMC-USP. A prova de conceito fornece indícios de que a linha de produtos proposta é válida e aplicável para sistemas de auxílio à visitação de museus. Como principal contribuição, espera-se que a MTTPL possa ser utilizada para instanciar outros sistemas deste domínio, aumentando o reúso dos assets providos pela linha de produtos. / Museum visitation assisting systems present a low software reuse degree, given that the amount of published papers containing a proposal for a new system and/or modeling is considerably elevated, and with a referring degree among those works near to zero. Besides, many studies on this application domain use context awareness techniques and Internet of Things (IoT) devices, aggravating software reuse degree due to the variety of existing IoT devices. This work presents the Museum Touring and Tutoring Product Line (MTTPL), a service-oriented product line for the museum visitation assisting systems domain. Requirements for this product line were collected mainly from the results of a systematic mapping about E-learning systems and IoT devices. As a preliminary evaluation of the proposed product line, a proof of concept was held in which MTTPL was instantiated, giving rise to SmartICMC, a virtual museum to support the visit to the ICMC-USP Museum of Fauna and Flora. The proof of concept provided evidence that the proposed product line is valid and applicable to museum visitation support systems. As a major contribution, it is expected that MTTPL can be used to instantiate other systems in this domain, increasing the reuse of the assets provided by the product line.
273

Influence des propriétés cristallochimiques de la calcite sur la diffusion de l'hélium et essai de datation (U-Th-Sm)/He de calcite filonienne et de remplissage de brèche / Crystallographic influence of calcite mineral on helium diffusion and (U-Th-Sm)/He datation experiment on calcite vein and breccia filling

Cros, Alexandre 02 July 2012 (has links)
La datation des carbonates est un enjeu important en géosciences car ces minéraux sont présents dans tous les grands cycles superficiels terrestres. Actuellement, l’âge de formation des cristaux de calcite de failles peut être déterminé par la méthode de déséquilibre U-Th ou par la méthode U-Pb. La potentialité de la méthode (U-Th-Sm)/He a été envisagée à partir des premiers résultats de diffusion de l’hélium dans les carbonates (Copeland et al. 2007) qui montrent que l’hélium est rétentif à basse température, inférieure à 70°C. Le développement de cette méthode nécessite une identification des propriétés cristallochimiques et du comportement de la calcite afin de discuter la validité des âges obtenus. Une zone de déformation au contact d’une faille normale du fossé d’effondrement de Gondrecourt à Augeville (Est du bassin de Paris) et des cristaux de calcite géodique des argilites de Tournemire (Aveyron) ont été étudiés. Une étude pétrographique et géochimique (analyse des isotopes stables δ18O et δ13C et des éléments mineurs et traces) a permis d’identifier les phases de remplissage de la zone de déformation d’Augeville. Sur les phases de remplissages une étude cristallographique par DRX (diffraction des rayons X) et ATG (analyse thermogravimétrique) a permis d’identifier les propriétés mécaniques de la calcite à différentes températures. Des expériences de diffusion de l’hélium ont été conduites selon un protocole différent de celui de Copeland et al. (2007) : temps de chauffage inférieur à 12 heures au lieu de paliers de chauffage de plusieurs heures à semaines. Des datations (U-Th-Sm)/He ont été réalisées sur toutes les phases de remplissage de la zone de déformation ainsi que sur les cristaux géodiques de Tournemire. Les résultats pour Gondrecourt mettent en évidence une zone de déformation à remplissage calcitique pluriphasée qui marque chaque étape de l’évolution tectonique de la zone. Il s’agit majoritairement de remplissages de brèches hydrauliques à brèches chaotiques avec, pour finir, la mise en place de filons. Sur ces minéralisations les résultats cristallochimiques montrent que lorsqu’ils sont soumis à une température croissante, de température ambiante à 400°C, ou sur le long terme à 200°C, il y a un accroissement du nombre de microfissures qui aboutit à la formation de clivage. L’évolution cristallochimique sous l’effet de la température présente des modifications structurales pour chacune des phases étudiées. Les expériences de diffusion dépendent de ces microfissures et de cette évolution microstructurale. Ces résultats mettent en évidence les mécanismes de diffusion de l’hélium dans la calcite à travers de multiples domaines de diffusion différents de la taille du grain. Ces domaines de diffusion dépendent de l’état microstructural de l’échantillon. Les résultats de datation (U-Th-Sm)/He présentent une large dispersion de 0,1 Ma à 35 Ma pour la zone de déformation de Gondrecourt et de 0,4 Ma à 20 Ma pour les cristaux géodiques de Tournemire. La variation des âges est en partie liée à la position des cristaux de calcite dans la succession paragénétique qui entraine un continuum de fracturation qui génère de multiples domaines de diffusion dans les cristaux de calcite. / Carbonate dating is a major issue in geosciences due to their widespread terrestrial environments presence . Precipitation ages determination are actually provide by U-Th disequilibrium series for young <1 Ma carbonates crystal and/or U-Pb method for older samples. In addition, Copeland et al. (2007) have proposed the development of (U-Th-Sm)/He dating method based on retentive helium behavior at surface temperature, conclusion issue of their first diffusion coefficients determined on carbonates samples. In this thesis work, the intention was to get an identification of crystallo-chemical properties and behavior of helium in calcite to date samples by (U-Th-Sm)/He and finally discuss the validity of this method. Deformation zones in contact to the normal fault of the Gondrecourt trench close to Augeville (eastern side of Basin of Paris) and calcite crystals geodic Tournemire argillites (Aveyron) were studied. Petrographic and geochemical couples studies (analysis of stable isotopes δ18O and δ13C and minor and trace elements) have allow the filling phases identification of the Augeville deformation zone. Based on the filling phases results, a crystallographic study by XRD (X-ray diffraction) and TGA (Thermogravimetric analysis) have been performed to identify the mechanical properties of calcite at different temperatures. Then, diffusion experiments on natural helium were conducted using a protocol differing than Copeland et al. (2007): heating time less than 12 hours instead of heating stages from hours to weeks. (U-Th-Sm)/He analyses were performed on all filling phases of the deformation zone and on the crystal geodes of Tournemire. Results for Gondrecourt samples show a deformation zone that marks several calcitic fillings corresponding to each stage of the tectonic evolution of the area. Calcite filling mainly corresponds to breccia and/or vein fillings which have precipitated approximatively in the same time. Crystallochemical results of these samples, show an increased number of microcracks leading to the formation of cleavage when samples are subjected to temperature increasing, from room temperature to 400 °C, or several days the long term at 200 °C. The crystallochemical evolution under the effect of temperature exhibits structural modifications for each studied phase. Diffusion experiments depend on these microcracks abundance and the microstructural evolution. These results emphasize the mechanisms of helium diffusion in calcite across multiple diffusion domains at different grain size. These multiple diffusion domains are linked to microstructural state of the sample. The results of dating (U-Th-Sm)/He ages show a wide dispersion of 0.1 to 35 Ma for the deformation zone Gondrecourt and from 0.4 to 20 Ma for Tournemire crystal geodes. Ages variation are partly related to the calcite crystals position in the paragenetic sequence. When a mineral undergoes deformations it becomes less retentive.
274

Desenvolvimento de método de recuperação de 131I no processo de produção de 99Mo pela fissão de 235U / Development of a recovery method of 131I in the 99Mo process through the fission of 235U

Bignardi, Aline Moraes Teixeira 24 June 2013 (has links)
O 131I é um radioisótopo de iodo amplamente utilizado em medicina nuclear, pode ser utilizado tanto para diagnóstico quanto para tratamento devido às suas características físicas de decaimento - e sua elevada emissão de raios-y. Sua produção no IPEN é realizada utilizando um reator nuclear a partir da reação indireta: 130Te (n,y) 131mTe 131Te 131I, onde são irradiados alvos contendo Te. Pode também ser produzido via produto de fissão de 235U, onde, o 235U irradiado produz cerca de 300 elementos diferentes, entre eles o 131I. O 131I produzido nesse método apresenta altas atividade específica e concentração radioativa, o que facilita a produção de compostos marcados com o radionuclídeo. O objetivo deste trabalho é desenvolver um método de recuperação de 131I no processo de produção de 99Mo pela rota de dissolução ácida de alvos de 235U, com a qualidade necessária para ser utilizado em Medicina Nuclear. O 131I encontra-se em 2 fases no processo, tanto na fase gasosa produzida na dissolução ácida dos alvos de U metálico e a menor parte em solução. Foram utilizados diversos materiais para captura e recuperação de 131I nas 2 fases do processo, a fase gasosa e a solução de dissolução dos alvos de U. Foram testadas colunas de alumina com Cu, alumina ácida com Cu, nanoesferas de Ag, cartuchos aniônicos, resina aniônica, colunas de carvão ativado, microesferas de Ag e microesferas de Cu. Soluções contendo 131I em NaOH 0,1 mol.L-1 foram percoladas pelos materiais e os eluídos foram analisados em calibrador de dose. Foi também estudada a precipitação de AgI e dissolução desse precipitado em NH4OH 0,1 mol L-1 e Na2S2O3 5%. Dentre os testes realizados, a princípio, os resultados de recuperação variaram de acordo com o material, o carvão ativado apresentou rendimento de recuperação entre 42% a 83%. Já o rendimento de recuperação da coluna de alumina com Cu variou de 20% a 85%. Os testes com nanoesferas de Ag apresentaram rendimento de recuperação de 26% utilizando NaOH 0,1 mol L-1 e 72% utilizando Na2S2O3 como eluentes. Testes com cartuchos aniônicos apresentaram os melhores resultados com uma porcentagem de recuperação de 81 a 90%. Testes utilizando 131I na sua forma gasosa apresentaram uma retenção de 66,45% e não foram realizados testes para recuperação do 131I retido. Nos testes utilizando precipitação de AgI a porcentagem de retenção de 131I foi de 100%. É possível concluir que os cartuchos aniônicos e a precipitação de AgI foram as melhores opções para a retenção de 131I, e as colunas de alumina com Cu tem um grande potencial para eluição do radionuclídeo 131I na forma química adequada. / 131I is an iodine radioisotope widely used in nuclear medicine that can be used either for diagnostic or for treatment due to its physical decay by - and its high emission of -rays. It is produced at IPEN using the indirect reaction: 130Te(n,)131mTe 131Te 131I where TeO2 targets are irradiated in a Nuclear Reactor. There is also the possibility of producing 131I by the fission of 235U, where about 300 different elements are produced together with 131I. The 131I produced through this method presents high specific activity and radioactive concentration suitable for the labeling of molecules. The aim of this work was to develop a recovery method of 131I with the required quality to be used in Nuclear Medicine in the 99Mo production process through the route of acid dissolution of metallic 235U targets. 131I can appear in two phases of the process, both in the gaseous phase produced during the dissolution of metallic U targets and in the dissolution solution. This work studied the recovery of 131I in these two phases. Several materials were used for the capture and recovery of 131I at the two phases of the process, the gaseous one and the solution of dissolution of U targets. Columns of alumina with Cu, acid alumina with Cu, Ag microspheres, Cu microspheres, Ag nanospheres, anionic cartridges, Ag cartridges, anion exchange resin and activated charcoal columns were tested. Solutions containing 131I in 0.1 mol.L-1 NaOH were percolated through the materials and the eluted solutions were analyzed in a dose calibrator. The precipitation of AgI was also studied wth further dissolution of this precipitate with 0.1 mol L-1 NH4OH and 5% Na2S2O3. The recovery results varied according to the material, activated charcoal showed recovery yields between 42% and 83% but the recovery yield of the alumina column with Cu ranged from 20% to 85%. Tests with Ag nanospheres showed recovery yield of 26% using 0.1 mol L-1NaOH and 72% for Na2S2O3. Tests with anionic cartridges showed the best results with a recovery percentage ranging between 81 to 90%. Tests using 131I in the gaseous phase presented retention of 66.45% and its elution was not studied. The experiments with the AgI precipitation showed total retention of 131I. It can be concluded that the anionic cartridges and the precipitation of AgI have higher affinity for the retention of 131I, and alumina columns with Cu have great potential for its elution in a suitable chemical form.
275

Estudos microestruturais  sobre interações químicas na liga U-Mo com Al / Microstructural studies on chemical interactions in U-10Mo alloy with Al

Ilson Carlos Martins 01 December 2010 (has links)
Objetiva-se, com a pesquisa da liga U-Mo, a obtenção de material nuclear para confecção de elementos combustíveis de alta densidade de urânio para reatores de pesquisa de alto desempenho. A política internacional de não proliferação de armas nucleares limita o nível de enriquecimento para reatores de pesquisa em 20% U235. Ligas de U-Mo com 6-10 % peso de Mo podem levar a uma densidade de até 9 gU/cm3, no núcleo da placa combustível. As placas do elemento combustível MTR (Materials Testing Reactor), são fabricadas a partir de briquetes (U-Mo + pó Al) encapsulados em placas de Al, soldadas e laminadas. No entanto, a liga U-Mo é muito reativa na presença de Al. Os produtos dessa reação são indesejáveis, do ponto de vista nuclear, pois geram uma camada de interação química (IL) formada durante ciclagens térmicas e exposição a fissões nucleares. Como a IL tem baixa condutividade térmica, falhas estruturais no elemento combustível, em operação, podem ser causadas. O presente estudo oferece uma nova técnica de formação de pares de interdifusão que promove os contatos da liga U-Mo, na forma de tabletes, envolvidos em matriz de A1 (placas), selada por laminação. Criam-se, assim, condições ideais para a investigação da difusão, com reduzida possibilidade de oxidação nas interfaces de contato, simulando-se, ainda, as condições de laminação a quente no primeiro passe de redução, durante a fabricação da placa combustível MTR. Optou-se por trabalhar com um teor de Mo de 10% em peso na liga U-Mo, para se garantir uma maior formação da fase , uma vez que esse teor favorece uma maior estabilidade química dessa fase. A liga de Al utilizada como matriz dos pares de interdifusão foi a AA1050, por apresentar menores teores de impureza. Os pares de interdifusão U-10Mo/AA1050 foram tratados, termicamente, em duas faixas de temperaturas (1500C e 5500C) e em três tempos de aquecimento (5h, 40h e 80h), visando-se simular o processo de interdifusão e formação da camada de interação química. As análises da camada de interação U-10Mo/AA1050, feitas por MEV/EDS e por difração de Raios X, revelaram uma interdifusão de baixa evolução em Al (cerca de 8% atômico), na região U-Mo. Não houve a formação dos produtos típicos esperados, como (U,Mo)Alx=2,3,4. Associou-se esse fato, provavelmente, à presença do silício na liga AA1050 que, potencialmente, criou uma barreira de poucos micrômetros, impedindo o Al de se difundir de forma mais efetiva para o interior da liga U-10Mo. Sugeriu-se a possível formação de um produto intermetálico de Al com Si, U e Mo. Em especial, foi citada a possibilidade da ocorrência do intermetálico Al3.21 Si0.47, causando esse efeito de bloqueio. / This research refers to the study of U-Mo alloy as an alternative material for producing nuclear fuel elements with high density of uranium, for research reactors of high perfor-mance. The international non-proliferation of nuclear weapons has enrichment level li-mited to 20% U235. U-Mo alloys with 6-10 wt% Mo can lead to a density up to 9 gU/cm3, inside the fuel core. The MTR fuel element plates are made from briquettes (U-Mo powder + Al) encapsulated in Al plates, then welded and rolled However, the U-Mo alloy is very reactive in the presence of Al. The reaction products of this interaction are undesirable from the standpoint of nuclear usage, since they cause a chemical interaction layer (IL) formed during thermal cycling and exposure to nuclear fission neutrons. As the IL has low thermal conductivity, they may cause structural failure in the fuel element during opera-tion. The present study provides a new preparation technique for interdiffusion pairs made by hot rolling. The U-Mo alloy, in tablet format, is involved by matrix Al-plates, which is sealed and then hot rolled. This way to prepare the diffusion couples is an ideal condition to avoid the oxidation at the contact interface at U-Mo/Al. The hot rolling preparation also simulates the first reduction pass during MTR fuel plate manufacture. We chose to work with a Mo content of 10 wt% in U-Mo alloy to ensure greater phase formation, since this level favors a greater chemical stability in this phase. The Al alloy matrix was used as the AA1050 since it contains small impurity amounts. The interdiffusion couples U-10Mo/AA1050 were thermally treated in two temperature ranges (1500C and 5500C) and three soaking times (5h, 40h and 80h) to simulate the interdiffusion process and formation of chemical interaction layer. The analysis of the interaction layer U-10Mo/AA1050 was made by SEM/EDS and X-ray diffraction. It revealed a general trend of low interdiffusion of Al (about 8 atomic %) inside U-Mo. There was no formation of typical products as ex-pected (U, Mo)Alx= 2,3,4. This fact is probably linked to the silicon presence, co-diffusing in the system. Connected with this fact, there was the presence of silicon in the alloy AA1050, which potentially created a barrier that prevented Al to diffuse more effectively, beyond few micrometers into the U-10Mo bulk. A possible formation of intermetallic Al with Si, U and Mo was suggested. In particular, the occurrence of the intermetallic Al3.21Si0.47, causing this blocking effect, was mentioned.
276

Estudos microestruturais  sobre interações químicas na liga U-Mo com Al / Microstructural studies on chemical interactions in U-10Mo alloy with Al

Martins, Ilson Carlos 01 December 2010 (has links)
Objetiva-se, com a pesquisa da liga U-Mo, a obtenção de material nuclear para confecção de elementos combustíveis de alta densidade de urânio para reatores de pesquisa de alto desempenho. A política internacional de não proliferação de armas nucleares limita o nível de enriquecimento para reatores de pesquisa em 20% U235. Ligas de U-Mo com 6-10 % peso de Mo podem levar a uma densidade de até 9 gU/cm3, no núcleo da placa combustível. As placas do elemento combustível MTR (Materials Testing Reactor), são fabricadas a partir de briquetes (U-Mo + pó Al) encapsulados em placas de Al, soldadas e laminadas. No entanto, a liga U-Mo é muito reativa na presença de Al. Os produtos dessa reação são indesejáveis, do ponto de vista nuclear, pois geram uma camada de interação química (IL) formada durante ciclagens térmicas e exposição a fissões nucleares. Como a IL tem baixa condutividade térmica, falhas estruturais no elemento combustível, em operação, podem ser causadas. O presente estudo oferece uma nova técnica de formação de pares de interdifusão que promove os contatos da liga U-Mo, na forma de tabletes, envolvidos em matriz de A1 (placas), selada por laminação. Criam-se, assim, condições ideais para a investigação da difusão, com reduzida possibilidade de oxidação nas interfaces de contato, simulando-se, ainda, as condições de laminação a quente no primeiro passe de redução, durante a fabricação da placa combustível MTR. Optou-se por trabalhar com um teor de Mo de 10% em peso na liga U-Mo, para se garantir uma maior formação da fase , uma vez que esse teor favorece uma maior estabilidade química dessa fase. A liga de Al utilizada como matriz dos pares de interdifusão foi a AA1050, por apresentar menores teores de impureza. Os pares de interdifusão U-10Mo/AA1050 foram tratados, termicamente, em duas faixas de temperaturas (1500C e 5500C) e em três tempos de aquecimento (5h, 40h e 80h), visando-se simular o processo de interdifusão e formação da camada de interação química. As análises da camada de interação U-10Mo/AA1050, feitas por MEV/EDS e por difração de Raios X, revelaram uma interdifusão de baixa evolução em Al (cerca de 8% atômico), na região U-Mo. Não houve a formação dos produtos típicos esperados, como (U,Mo)Alx=2,3,4. Associou-se esse fato, provavelmente, à presença do silício na liga AA1050 que, potencialmente, criou uma barreira de poucos micrômetros, impedindo o Al de se difundir de forma mais efetiva para o interior da liga U-10Mo. Sugeriu-se a possível formação de um produto intermetálico de Al com Si, U e Mo. Em especial, foi citada a possibilidade da ocorrência do intermetálico Al3.21 Si0.47, causando esse efeito de bloqueio. / This research refers to the study of U-Mo alloy as an alternative material for producing nuclear fuel elements with high density of uranium, for research reactors of high perfor-mance. The international non-proliferation of nuclear weapons has enrichment level li-mited to 20% U235. U-Mo alloys with 6-10 wt% Mo can lead to a density up to 9 gU/cm3, inside the fuel core. The MTR fuel element plates are made from briquettes (U-Mo powder + Al) encapsulated in Al plates, then welded and rolled However, the U-Mo alloy is very reactive in the presence of Al. The reaction products of this interaction are undesirable from the standpoint of nuclear usage, since they cause a chemical interaction layer (IL) formed during thermal cycling and exposure to nuclear fission neutrons. As the IL has low thermal conductivity, they may cause structural failure in the fuel element during opera-tion. The present study provides a new preparation technique for interdiffusion pairs made by hot rolling. The U-Mo alloy, in tablet format, is involved by matrix Al-plates, which is sealed and then hot rolled. This way to prepare the diffusion couples is an ideal condition to avoid the oxidation at the contact interface at U-Mo/Al. The hot rolling preparation also simulates the first reduction pass during MTR fuel plate manufacture. We chose to work with a Mo content of 10 wt% in U-Mo alloy to ensure greater phase formation, since this level favors a greater chemical stability in this phase. The Al alloy matrix was used as the AA1050 since it contains small impurity amounts. The interdiffusion couples U-10Mo/AA1050 were thermally treated in two temperature ranges (1500C and 5500C) and three soaking times (5h, 40h and 80h) to simulate the interdiffusion process and formation of chemical interaction layer. The analysis of the interaction layer U-10Mo/AA1050 was made by SEM/EDS and X-ray diffraction. It revealed a general trend of low interdiffusion of Al (about 8 atomic %) inside U-Mo. There was no formation of typical products as ex-pected (U, Mo)Alx= 2,3,4. This fact is probably linked to the silicon presence, co-diffusing in the system. Connected with this fact, there was the presence of silicon in the alloy AA1050, which potentially created a barrier that prevented Al to diffuse more effectively, beyond few micrometers into the U-10Mo bulk. A possible formation of intermetallic Al with Si, U and Mo was suggested. In particular, the occurrence of the intermetallic Al3.21Si0.47, causing this blocking effect, was mentioned.
277

Desenvolvimento de método de recuperação de 131I no processo de produção de 99Mo pela fissão de 235U / Development of a recovery method of 131I in the 99Mo process through the fission of 235U

Aline Moraes Teixeira Bignardi 24 June 2013 (has links)
O 131I é um radioisótopo de iodo amplamente utilizado em medicina nuclear, pode ser utilizado tanto para diagnóstico quanto para tratamento devido às suas características físicas de decaimento - e sua elevada emissão de raios-y. Sua produção no IPEN é realizada utilizando um reator nuclear a partir da reação indireta: 130Te (n,y) 131mTe 131Te 131I, onde são irradiados alvos contendo Te. Pode também ser produzido via produto de fissão de 235U, onde, o 235U irradiado produz cerca de 300 elementos diferentes, entre eles o 131I. O 131I produzido nesse método apresenta altas atividade específica e concentração radioativa, o que facilita a produção de compostos marcados com o radionuclídeo. O objetivo deste trabalho é desenvolver um método de recuperação de 131I no processo de produção de 99Mo pela rota de dissolução ácida de alvos de 235U, com a qualidade necessária para ser utilizado em Medicina Nuclear. O 131I encontra-se em 2 fases no processo, tanto na fase gasosa produzida na dissolução ácida dos alvos de U metálico e a menor parte em solução. Foram utilizados diversos materiais para captura e recuperação de 131I nas 2 fases do processo, a fase gasosa e a solução de dissolução dos alvos de U. Foram testadas colunas de alumina com Cu, alumina ácida com Cu, nanoesferas de Ag, cartuchos aniônicos, resina aniônica, colunas de carvão ativado, microesferas de Ag e microesferas de Cu. Soluções contendo 131I em NaOH 0,1 mol.L-1 foram percoladas pelos materiais e os eluídos foram analisados em calibrador de dose. Foi também estudada a precipitação de AgI e dissolução desse precipitado em NH4OH 0,1 mol L-1 e Na2S2O3 5%. Dentre os testes realizados, a princípio, os resultados de recuperação variaram de acordo com o material, o carvão ativado apresentou rendimento de recuperação entre 42% a 83%. Já o rendimento de recuperação da coluna de alumina com Cu variou de 20% a 85%. Os testes com nanoesferas de Ag apresentaram rendimento de recuperação de 26% utilizando NaOH 0,1 mol L-1 e 72% utilizando Na2S2O3 como eluentes. Testes com cartuchos aniônicos apresentaram os melhores resultados com uma porcentagem de recuperação de 81 a 90%. Testes utilizando 131I na sua forma gasosa apresentaram uma retenção de 66,45% e não foram realizados testes para recuperação do 131I retido. Nos testes utilizando precipitação de AgI a porcentagem de retenção de 131I foi de 100%. É possível concluir que os cartuchos aniônicos e a precipitação de AgI foram as melhores opções para a retenção de 131I, e as colunas de alumina com Cu tem um grande potencial para eluição do radionuclídeo 131I na forma química adequada. / 131I is an iodine radioisotope widely used in nuclear medicine that can be used either for diagnostic or for treatment due to its physical decay by - and its high emission of -rays. It is produced at IPEN using the indirect reaction: 130Te(n,)131mTe 131Te 131I where TeO2 targets are irradiated in a Nuclear Reactor. There is also the possibility of producing 131I by the fission of 235U, where about 300 different elements are produced together with 131I. The 131I produced through this method presents high specific activity and radioactive concentration suitable for the labeling of molecules. The aim of this work was to develop a recovery method of 131I with the required quality to be used in Nuclear Medicine in the 99Mo production process through the route of acid dissolution of metallic 235U targets. 131I can appear in two phases of the process, both in the gaseous phase produced during the dissolution of metallic U targets and in the dissolution solution. This work studied the recovery of 131I in these two phases. Several materials were used for the capture and recovery of 131I at the two phases of the process, the gaseous one and the solution of dissolution of U targets. Columns of alumina with Cu, acid alumina with Cu, Ag microspheres, Cu microspheres, Ag nanospheres, anionic cartridges, Ag cartridges, anion exchange resin and activated charcoal columns were tested. Solutions containing 131I in 0.1 mol.L-1 NaOH were percolated through the materials and the eluted solutions were analyzed in a dose calibrator. The precipitation of AgI was also studied wth further dissolution of this precipitate with 0.1 mol L-1 NH4OH and 5% Na2S2O3. The recovery results varied according to the material, activated charcoal showed recovery yields between 42% and 83% but the recovery yield of the alumina column with Cu ranged from 20% to 85%. Tests with Ag nanospheres showed recovery yield of 26% using 0.1 mol L-1NaOH and 72% for Na2S2O3. Tests with anionic cartridges showed the best results with a recovery percentage ranging between 81 to 90%. Tests using 131I in the gaseous phase presented retention of 66.45% and its elution was not studied. The experiments with the AgI precipitation showed total retention of 131I. It can be concluded that the anionic cartridges and the precipitation of AgI have higher affinity for the retention of 131I, and alumina columns with Cu have great potential for its elution in a suitable chemical form.
278

Effects of U-Turns on Capacity at Signalized Intersections And Simulation of U-Turning Movement by Synchro

Wang, Xiaodong 28 March 2008 (has links)
The primary objective of this study is to evaluate the operational effects of U-turn movement at signalized intersections. More specifically, the research objectives include the following parts: To identify the factors affecting the operational performance of U-turning vehicles. In this case, we are particularly interested in the U-turn speeds of U-turning vehicles. To evaluate the impacts of U-turns on capacity of signalized intersections, and To simulate U-turn movement at signalized intersections using Synchro and validate the simulation results. To achieve the research objectives, extensive field data collection work was conducted at sixteen selected sites at Tampa Bay area of Florida. The data collected in the field include: U-turning speed Left turning speed Turning radius Queue discharge time Control delay Hourly traffic volume, and Percentage of U- turning vehicles in left turn lane. Based on the collected field data, a linear regression model was developed to identify the factors affecting the turning speeds of U-turning vehicles at signalized intersections. The model shows the turning speed is significantly impacted by the turning radius and the speed of U-turning vehicles increases with the increase of turning radius. On the basis of field data field data collection, a regression model was developed to estimate the relationship between the average queue discharge time for each turning vehicle and the various percentages of U-turning vehicles in the left turn traffic stream. Adjustment factors for various percentages of U-turning vehicles were also developed by using the regression model. The adjustment factors developed in this study can be directly used to estimate the capacity reduction due to the presence of various percentages of U-turning vehicles at a signalized intersection. The developed adjustment factors were used to improve the simulation of U-turn movement at signalized intersection by using Synchro. The simulation model was calibrated and validated by field data. It was found that using the developed adjustment factors will greatly improve the accuracy of the simulation results for U-turn movement.
279

Från kulturchock till anpassning : Påverkar ett företags storlek, bransch och verksamhetstid svenska utlandstjänstgörandes anpassning till den kinesiska kulturen?

Rehn, Mikaela, Choudhury, Sabrina January 2009 (has links)
<p>Allt fler svenskar är utlandsstationerade i Kina (Sveriges Ambassad 2008) och att anpassa sig till den kinesiska kulturen kan vara påfrestande för en utlandstjänstgörande. Problematiken kring kulturanpassning har lett till att olika teorier testats och utvecklats (Black & Mendenhall 1991). En av de modeller som tagits fram är U-kurvan som beskriver individens anpassningsprocess genom faserna kulturchock och kulturanpassning (Zapf 1991). Individuella faktorer, som exempelvis språkkunskaper och kulturell erfarenhet har varit centrala inom forskningsområdet (Earley & Mosakowski 2004, Shay & Baack 2004) och denna studie undersöker därför företagsrelaterade faktorer då en utlandstjänstgörandes förmåga att utföra sina arbetsuppgifter påverkas av hur pass anpassad individen är till kulturen (Aycan 1997, Jun m. fl. 2001). Syftet med denna uppsats är därför att ta reda på hur en svensk utlandstjänstgörandes anpassningsprocess till den kinesiska kulturen påverkas av faktorerna företagsstorlek, bransch och verksamhetstid i Kina.</p><p>Materialet till undersökningen har huvudsakligen samlats in genom webbenkäter som skickats ut till utlandstjänstgörande svenskar i Kina. Resultaten visar att det är branschen i vilken den utlandstjänstgörandes företag verkar som har högst påverkan på en utlandstjänstgörandes anpassningsprocess. Undersökningen visade även att utlandstjänstgörande i företag med mindre än 50 anställda i detaljindustrin som etablerade sig i Kina under 1990-talet var bäst anpassade till den kinesiska kulturen. Då resultaten från studien presenterades i diagram framgick att i två fall av tre var den bästa anpassningsprocessen den som mest liknade en U-kurva vilket tyder på att den bästa anpassningsprocessen är den då en utlandstjänstgörande går igenom faserna på ett balanserat sätt. Detta är dock ingen slutsats som kan dras av undersökningen eftersom resultaten inte gällde för alla faktorer.</p> / <p>The numbers of Swedish expatriates in China are increasing (Swedish Embassy 2008) and adaption to the Chinese culture can be demanding for an individual. The complexity of cultural adjustments has led to different theories being tested and developed (Black & Mendenhall 1991). One of the models that have been developed is the U-curve, which describes the process of individual adaption through the two phase's culture shock and cultural adaption (Zapf 1991). Factors related to the individual, such as language skills and cultural experience have been central in research of cultural adaption and this study therefore examines company related factors because an individual's ability to perform his/her work tasks is affected by the individual's adjustment to the culture (Aycan 1997, Jun et al. 2001). The purpose of this study is therefore to verify how a Swedish expatriate's process of adaption to the Chinese culture is affected by the company related factors firm size, industry and time of operation in China.</p><p>The data of the study has mainly been collected by web surveys which were sent to Swedish expatriates in China. The results show that the industry has the largest influence on the adaption process. The study also showed that expatriates in companies with less than 50 employees in the retail- and manufacturing industry which were established in China during the 1990s, were the ones that were the most adjusted. When the results were presented as diagrams it showed that the best adaption process was the one that most reminded of a U-curve which indicates that the best adaption process occurs when the expatriate passes the phases in balance. However, this is not a conclusion that can be drawn from this study since these results are not valid for all the factors.</p>
280

Från kulturchock till anpassning : Påverkar ett företags storlek, bransch och verksamhetstid svenska utlandstjänstgörandes anpassning till den kinesiska kulturen?

Rehn, Mikaela, Choudhury, Sabrina January 2009 (has links)
Allt fler svenskar är utlandsstationerade i Kina (Sveriges Ambassad 2008) och att anpassa sig till den kinesiska kulturen kan vara påfrestande för en utlandstjänstgörande. Problematiken kring kulturanpassning har lett till att olika teorier testats och utvecklats (Black &amp; Mendenhall 1991). En av de modeller som tagits fram är U-kurvan som beskriver individens anpassningsprocess genom faserna kulturchock och kulturanpassning (Zapf 1991). Individuella faktorer, som exempelvis språkkunskaper och kulturell erfarenhet har varit centrala inom forskningsområdet (Earley &amp; Mosakowski 2004, Shay &amp; Baack 2004) och denna studie undersöker därför företagsrelaterade faktorer då en utlandstjänstgörandes förmåga att utföra sina arbetsuppgifter påverkas av hur pass anpassad individen är till kulturen (Aycan 1997, Jun m. fl. 2001). Syftet med denna uppsats är därför att ta reda på hur en svensk utlandstjänstgörandes anpassningsprocess till den kinesiska kulturen påverkas av faktorerna företagsstorlek, bransch och verksamhetstid i Kina. Materialet till undersökningen har huvudsakligen samlats in genom webbenkäter som skickats ut till utlandstjänstgörande svenskar i Kina. Resultaten visar att det är branschen i vilken den utlandstjänstgörandes företag verkar som har högst påverkan på en utlandstjänstgörandes anpassningsprocess. Undersökningen visade även att utlandstjänstgörande i företag med mindre än 50 anställda i detaljindustrin som etablerade sig i Kina under 1990-talet var bäst anpassade till den kinesiska kulturen. Då resultaten från studien presenterades i diagram framgick att i två fall av tre var den bästa anpassningsprocessen den som mest liknade en U-kurva vilket tyder på att den bästa anpassningsprocessen är den då en utlandstjänstgörande går igenom faserna på ett balanserat sätt. Detta är dock ingen slutsats som kan dras av undersökningen eftersom resultaten inte gällde för alla faktorer. / The numbers of Swedish expatriates in China are increasing (Swedish Embassy 2008) and adaption to the Chinese culture can be demanding for an individual. The complexity of cultural adjustments has led to different theories being tested and developed (Black &amp; Mendenhall 1991). One of the models that have been developed is the U-curve, which describes the process of individual adaption through the two phase's culture shock and cultural adaption (Zapf 1991). Factors related to the individual, such as language skills and cultural experience have been central in research of cultural adaption and this study therefore examines company related factors because an individual's ability to perform his/her work tasks is affected by the individual's adjustment to the culture (Aycan 1997, Jun et al. 2001). The purpose of this study is therefore to verify how a Swedish expatriate's process of adaption to the Chinese culture is affected by the company related factors firm size, industry and time of operation in China. The data of the study has mainly been collected by web surveys which were sent to Swedish expatriates in China. The results show that the industry has the largest influence on the adaption process. The study also showed that expatriates in companies with less than 50 employees in the retail- and manufacturing industry which were established in China during the 1990s, were the ones that were the most adjusted. When the results were presented as diagrams it showed that the best adaption process was the one that most reminded of a U-curve which indicates that the best adaption process occurs when the expatriate passes the phases in balance. However, this is not a conclusion that can be drawn from this study since these results are not valid for all the factors.

Page generated in 0.0338 seconds