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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Integrated Communications and Thermal Management Systems for Microsystem-based Spacecraft : A Multifunctional Microsystem Approach

Kratz, Henrik January 2006 (has links)
This thesis explores the potential of multifunctional silicon-based microsystems for advanced integrated nanospacecraft (AIN). Especially, multifunctional microsystems with the coexistant functions of communications and thermal management implemented in multilayer silicon stacks are approached with systems study. Host vehicles, composed of microsystems, including micro/nano-spacecraft and spherical rovers are contemplated with respect to future performance and implications, system level design, and breadboard realizations. A module of great importance, named the "integrated communications and thermal management system for advanced integrated spacecraft" or ICTM, symbolizes the achievements within the field of self-contained microsystems and is a prioritized entity throughout the thesis. The ICTM is natively placable onboard all types of highly miniaturized craft. The single AIN spacecraft and future clusters of these are investigated with respect to future full scale implementation of space systems designed and implemented with the distributed reconfigurable nanospacecraft cluster (DRNC) concept. Here, a true entanglement of microsystems technology (MST) and miniaturized spacecraft technology can revolutionize the applications, cost, and span of conceivable space missions. An intended communications scenario supporting a data rate of 1 Mbps, for the transmitter, is achieved during 6 minutes with a maximum continuous power dissipation of 10 W. Thermal simulations support the expectation, of a thermally biased ICTM, that the module is capable of supporting this energy burst, by using the mechanisms of heat storage and heat switches, and still fulfilling the requirements imposed by AIN type of spacecraft. In addition, multiple functional surfaces for the ICTM are evaluated with respect to equilibrium temperature and process compatibility. The tailored surfaces provide temperature control using micromachining methods. A design of a micromachined Ka-band front end with several MST enabled features is presented including e.g. vias, phase-shifters, and antennas. Similar antennas have been manufactured resulting in an evaluation of ring- and slot-antennas on silicon substrate. Based on a primitive version of the ICTM, a S-band patch antenna has been successfully implemented and characterized. Included in the thesis is a microthruster, an enabling technology for DRNC.
42

Investigation of Dithiolenes for Propylene/Propane Membrane Separations

Sejour, Hensley 24 August 2007 (has links)
Polyimide membranes containing nickel dithiolenes were investigated for the separation of propylene and propane. Permeation and sorption experiments were conducted as well thermal property analyses. Results indicate that the dithiolene has an antiplasticizing effect on the polymers studied. Upon addition of the dithiolene there is a subsequent reduction in the permeability coefficient and the permeability selectivity remains relatively unchanged. There is some evidence of increases in solubility selectivity, but a larger decrease in diffusivity selectivity results in a decrease in the permeability selectivity. Investigation of the thermal and mechanical properties of dithiolene-containing films indicates a reduction in fractional free volume as well as the glass transition temperature when compared to the pure polymer. There is also an increase in the modulus of the films upon addition of the dithiolene. The implications of these results and their correlation with antiplasticization are discussed.
43

Molecular Characterization of Ductal Carcinoma In Situ: Pilot Studies

Desai, Neil Bipinchandra 28 September 2010 (has links)
Ductal carcinoma in situ (DCIS); is thought directly to precede invasive breast cancer (IBC). Screening mammography has driven the incidence of this key precursor lesion to >65,000 cases per year. However, little is known about the factors controlling the natural history or risk for recurrence following treatment of a particular patients DCIS. Though the heterogeneity of the disease is well established, no histologic or demographic criteria have been able to stratify DCIS for treatment. We hypothesize that at initial diagnosis there exist biologically distinct subsets of DCIS with associated prognoses that may be recognized by molecular markers. Molecular approaches have been limited by technical design issues related to the types of tissue available for analysis, namely degraded formalin-fixed paraffin embedded (FFPE) specimens and small core biopsy samples. However, new technologies promise to overcome these issues. In the first phase of our investigation, we aimed a) to pilot feasibility studies on the use of FFPE DCIS for molecular analyses including gene expression microarray and b) to pilot feasibility study of selective, high throughput sequencing through the use of "exon capture" on small input material that simulated expected DCIS core biopsy amounts. The results of this work offer specific technical guidelines for the molecular study of DCIS. Moreover, they have enabled the initiation of the second phase of this study, which aims to assess molecular profiles of DCIS recurrence and progression.
44

Zeolitic imidazolate framework (ZIF)-based membranes and sorbents for advanced olefin/paraffin separations

Zhang, Chen 08 June 2015 (has links)
Propylene is one of the most important feedstocks of the petrochemical industry with an estimated 2015 worldwide demand of 100 million tons. Retrofitting conventional C3 splitters is highly desirable due to the huge amount of thermal energy required to separate propylene from propane. Membrane separation is among the alternatives that both academia and industry have actively studied during the past decades, however; many challenges remain to advance membrane separation as a scalable technology for energy-efficient propylene/propane separations. The overarching goal of this research is to provide a framework for development of scalable ZIF-based mixed-matrix membrane that is able to deliver attractive transport properties for advanced gas separations. Zeolitic imidazolate frameworks (ZIFs) were pursued instead of conventional molecular sieves (zeolites and carbon molecular sieves) to form mixed-matrix membrane due to their intrinsic compatibility with high Tg glassy polymers. A systematic study of adsorption and diffusion in zeolitic imidazolate framework-8 (ZIF-8) suggests that this material is remarkably kinetically selective for C3 and C4 hydrocarbons and therefore promising for membrane-based gas separation and adsorptive separation. As a result, ZIF-8 was used to form mixed-matrix dense film membranes with polyimide 6FDA-DAM at varied particle loadings and it was found that ZIF-8 significantly enhanced propylene/propane separation performance beyond the “permeability-selectivity” trade-off curve for polymeric materials. Eventually, this research advanced ZIF-based mixed-matrix membrane into a scalable technology by successfully forming high-loading dual-layer ZIF-8/6FDA-DAM asymmetric mixed-matrix hollow fiber membranes with attractive propylene/propane selectivity.
45

Latent Heat Thermal Energy Storage Device for Automobile Applications

Shih, Po-Chen 28 November 2013 (has links)
Driving with the cold engine increases fuel consumption and greenhouse gases emissions. A latent heat energy storage device has been proposed to recover waste heat and reduce engine warm-up time by using phase change materials (PCMs) as an energy storage medium. Two types of paraffin waxes and 50/50 mixture of the two have been examined to characterize their behaviors under repetitive heating/freezing. From the results, the heat transfer is more effective in the case of narrower spacing distances between the cooling plates and high circulating flow rate of the heat transfer fluid. A 50/50 mixture of two paraffin waxes also provides better heat transfer due to the possible existence of both conduction and natural convection. The results of the metal block simulation experiments demonstrated the potential of latent heat TES’s for use in engine warm-up.
46

Latent Heat Thermal Energy Storage Device for Automobile Applications

Shih, Po-Chen 28 November 2013 (has links)
Driving with the cold engine increases fuel consumption and greenhouse gases emissions. A latent heat energy storage device has been proposed to recover waste heat and reduce engine warm-up time by using phase change materials (PCMs) as an energy storage medium. Two types of paraffin waxes and 50/50 mixture of the two have been examined to characterize their behaviors under repetitive heating/freezing. From the results, the heat transfer is more effective in the case of narrower spacing distances between the cooling plates and high circulating flow rate of the heat transfer fluid. A 50/50 mixture of two paraffin waxes also provides better heat transfer due to the possible existence of both conduction and natural convection. The results of the metal block simulation experiments demonstrated the potential of latent heat TES’s for use in engine warm-up.
47

[en] EXPERIMENTAL VALIDATION OF MODELS FOR PREDICTING THE FORCES FOR REMOVING WAX DEPOSITS IN PIPELINES USING PIGS / [pt] AVALIAÇÃO DE MODELOS PARA A REMOÇÃO DE DEPÓSITOS DE PARAFINA EM DUTOS UTILIZANDO PIGS

ROBSON DE OLIVEIRA SOUZA 26 October 2005 (has links)
[pt] Pigs ainda são a ferramenta mais utilizada pela indústria para remover depósitos de parafina em linhas submarinas de petróleo. A passagem de Pigs é considerada uma operação de risco, pois existe a possibilidade do gradiente de pressão disponível para deslocar o Pig não ser suficiente para vencer as forças de contato entre o Pig e a parede do tubo e as forças necessárias para remoção do depósito de parafina. Neste trabalho realizou-se um estudo experimental visando o levantamento de dados de laboratório sobre as forças de contato Pig-tubo para alguns tipos de Pigs comumente usados em operações de campo. Além disso, foram também determinadas forças para remoção de depósitos de parafina fabricados no laboratório sob condições controladas. Foi projetada e construída uma seção de testes onde os Pigs ensaiados eram puxados com velocidade constante através de trechos de tubo, sendo a força trativa de puxada monitorada continuamente por células de carga. Os resultados de força de contato Pig-tubo sem depósito de parafina foram comparados com modelos teóricos disponíveis na literatura. Para o caso dos experimentos onde depósitos estavam presentes, as forças necessárias para a quebra dos depósitos foram também comparadas com o único modelo disponível na literatura. Os resultados obtidos mostraram que, para Pigs de disco e de espuma os modelos disponíveis prevêem as forças de contato Pig-tubo com incerteza aceitável. Para o caso de remoção de parafina a comparação com os experimentos desenvolvidos mostrou que o modelo disponível consegue estimar a força inicial para a quebra do depósito dentro de uma faixa de incerteza de ± 30% para os Pigs de disco e de espuma. / [en] Pigging is still the most widely used method to remove wax deposits in subsea pipelines. The passage of a pig is still considered a risky operation, since the pressure gradient available for driving the pig might not be sufficient to overcome the contact forces between the pig and the wall, as well as the forces required to remove the wax deposit. If this is the case, the pig will be stuck, and costly remediation procedures will have to be implemented. In the present work, an experimental study was carried out aimed at collecting reliable data on the contact forces developed between pigs and the pipe wall for some types of pigs commonly used in field operations. Also, as part of the work, the forces required to remove wax deposits prepared under controlled conditions were recorded. To this end, a test section was specially designed and constructed. In the tests, the pigs were pulled through a set of pipes at constant speed by a winch, while the pulling force was continuously recorded by load cells. The results obtained for the contact forces between disc, foam and conical cup pigs and the pipe wall without wax deposits were compared with models available in the literature. Good level of agreement was obtained. Experimental results obtained for the cases where the test pipes had controlled wax deposits where compared with the only model available in the literature for predicting the forces required to break the wax deposits. The comparisons demonstrated that the measured forces required for breaking the wax deposit can be estimated by the available models within an uncertainty of ±30%.
48

Desenvolvimento de cimento ósseo de fosfato de cálcio como suporte para o crescimento de tecidos

Machado, Jeferson Luis de Moraes January 2007 (has links)
O crescimento de células em arcabouços tridimensionais porosos tem se tornado progressivamente ativo na engenharia de tecidos. Os arcabouços guiam o crescimento celular, sintetizam uma matriz extracelular e outras moléculas biológicas, e facilitam a formação de tecidos e órgãos funcionais. Um cimento deste tipo pode ser preparado misturando um sal de fosfato de cálcio com uma solução aquosa para que se forme uma pasta que possa reagir à temperatura corporal dando lugar a um precipitado que contenha hidroxiapatita (Ca10(PO4)6(OH)2). A similaridade química e morfológica entre este biomaterial e a parte mineral dos tecidos ósseos permite a osteocondução, sendo o cimento substituído por tecido ósseo novo com o tempo e com a vantagem de não desencadear processos inflamatórios e de corpo estranho, com eventual expulsão do material implantado. O objetivo do presente trabalho foi a obtenção e caracterização de suportes tridimensionais para a engenharia de tecido, com o uso de matérias-primas nacionais, por meio da utilização de microesferas de parafina como corpos geradores de poros. As microesferas foram produzidas por suspensão em solução aquosa de poli (álcool vinílico) (PVA) e sulfato de sódio (Na2SO4). Foram analisadas as fases presentes no cimento sintetizado e após a reação de cura do mesmo, a variação do tamanho de partícula e da resistência mecânica com o tempo de moagem. Foi analisada a porosidade dos suportes e a forma de extração da parafina daqueles que a utilizaram na sua formação. O tamanho de poro dos suportes gerados com a variação da quantidade de fase líquida ficou aquém do tamanho considerado ideal para o crescimento de tecido ósseo. A porosidade dos arcabouços fabricados com esferas de parafina foi observada por microscopia eletrônica de varredura (MEV), e seu comportamento foi analisado a partir de ensaios in vitro em solução SBF (simulated body fluid) e em cultura de células. A utilização de esferas de parafina permitiu a formação de poros com tamanho tal que possibilitam potencialmente o crescimento tecidual e celular. / The growth of cells in three-dimensional porous scaffolds has been extensively studied for use in tissue engineering. They guide grow of cells, synthesize extra cellular matrix and other biological molecules, and facilitate the formation of functional tissues and organs. Bone cements has been developed for biomedical applications for a decade approximately. This kind of cement can be prepared mixing a calcium phosphate salt with aqueous solution forming a paste that can react at body temperature generating a hydroxyapatite precipitated (Ca10(PO4)6(OH)2). The chemical and morphological similarity between the cement composition and the mineral part of the bones allows osteoconduction in the tissue with replacement of cement by new bone formed with the advantage to not unchain inflammatory processes and of strange body. The objective of this work was the use of the α-TCP cement for making these scaffolds, through the variation of the amount of liquid phase in the cement and of the use of paraffin spheres as pore source. These spheres were produced by suspension in water solution of poly (vinyl alcohol) and sodium sulphate (Na2SO4). The phases had been analyzed in the synthesized cement and after the reaction of cure of cement, beyond variation of the particle size and the resistance mechanics with the milling time. It was analyzed the porosity of the scaffolds and the extraction of the paraffin in that supports. The pore size of the supports generated with the variation of the amount of liquid phase was on this side of the size considered ideal for the bone tissue growth. The porosity of scaffolds manufactured with paraffin spheres was observed by Scanning Electron Microscopy (SEM), and its behavior was analyzed from test in vitro in SBF solution (simulated body fluid). The use of paraffin spheres allowed the formation of pores size able to permit tissue growth.
49

Diagnostics for Rift Valley fever virus

Upreti, Deepa January 1900 (has links)
Master of Science / Department of Diagnostic Medicine/Pathobiology / A. Sally Davis / Rift Valley fever virus (RVFV) is a mosquito-borne, zoonotic Phlebovirus that is a significant threat to ruminants and humans. RVFV is categorized as an overlap Select Agent by the Department of Health and Human Services and US Department of Agriculture. Therefore, the study of RVFV’s pathogenesis and the development of novel diagnostic tools for the prevention and control of outbreaks and virus spread is crucial. RVF is endemic to sub-Saharan Africa but has spread beyond the continent to the Arabian Peninsula indicating the competence of the virus to emerge in new areas. Thus, the high likelihood of RVF’s spread to other non- endemic countries also spurs the need for development and implementation of rapid diagnostic tests and surveillance programs. In the US, RVFV is a Select Agent, requiring BSL-3 enhanced containment practices for research work. First, we developed a method for the detection of RVFV RNA by reverse transcriptase real-time PCR (RT-qPCR) using non-infectious, formalin- fixed, paraffin-embedded tissues (FFPET). The results from FFPET RT-qPCR were compared to prior results for fresh-frozen tissues (FFT) RT-qPCR, as well as immunohistochemistry and histopathology completed on the same FFPET blocks. We developed a novel technique using a rapid and low cost magnetic bead extraction method for recovery of amplifiable RVFV RNA from FFPET. FFPET RT-qPCR can serve as an alternative tissue-based diagnostic test, which does not require a BSL-3 research facility. Second, we assessed the diagnostic accuracy and precision of a recombinant RVFV nucleoprotein based competitive ELISA (cELISA) assay to detect RVFV antibodies. The cELISA results were compared to the virus neutralization test, the gold standard serological assay for RVFV. This prototype cELISA is easy to implement, sensitive, specific, and safe test for the detection of antibodies to RVFV in diagnostic and surveillance applications. RVF is an important transboundary disease that should be monitored on a regular basis. The diagnostic tests developed and validated in this thesis could be used in endemic or non-endemic countries for the early detection of RVF and assist with the implementation of countermeasures against RVFV.
50

Desenvolvimento de cimento ósseo de fosfato de cálcio como suporte para o crescimento de tecidos

Machado, Jeferson Luis de Moraes January 2007 (has links)
O crescimento de células em arcabouços tridimensionais porosos tem se tornado progressivamente ativo na engenharia de tecidos. Os arcabouços guiam o crescimento celular, sintetizam uma matriz extracelular e outras moléculas biológicas, e facilitam a formação de tecidos e órgãos funcionais. Um cimento deste tipo pode ser preparado misturando um sal de fosfato de cálcio com uma solução aquosa para que se forme uma pasta que possa reagir à temperatura corporal dando lugar a um precipitado que contenha hidroxiapatita (Ca10(PO4)6(OH)2). A similaridade química e morfológica entre este biomaterial e a parte mineral dos tecidos ósseos permite a osteocondução, sendo o cimento substituído por tecido ósseo novo com o tempo e com a vantagem de não desencadear processos inflamatórios e de corpo estranho, com eventual expulsão do material implantado. O objetivo do presente trabalho foi a obtenção e caracterização de suportes tridimensionais para a engenharia de tecido, com o uso de matérias-primas nacionais, por meio da utilização de microesferas de parafina como corpos geradores de poros. As microesferas foram produzidas por suspensão em solução aquosa de poli (álcool vinílico) (PVA) e sulfato de sódio (Na2SO4). Foram analisadas as fases presentes no cimento sintetizado e após a reação de cura do mesmo, a variação do tamanho de partícula e da resistência mecânica com o tempo de moagem. Foi analisada a porosidade dos suportes e a forma de extração da parafina daqueles que a utilizaram na sua formação. O tamanho de poro dos suportes gerados com a variação da quantidade de fase líquida ficou aquém do tamanho considerado ideal para o crescimento de tecido ósseo. A porosidade dos arcabouços fabricados com esferas de parafina foi observada por microscopia eletrônica de varredura (MEV), e seu comportamento foi analisado a partir de ensaios in vitro em solução SBF (simulated body fluid) e em cultura de células. A utilização de esferas de parafina permitiu a formação de poros com tamanho tal que possibilitam potencialmente o crescimento tecidual e celular. / The growth of cells in three-dimensional porous scaffolds has been extensively studied for use in tissue engineering. They guide grow of cells, synthesize extra cellular matrix and other biological molecules, and facilitate the formation of functional tissues and organs. Bone cements has been developed for biomedical applications for a decade approximately. This kind of cement can be prepared mixing a calcium phosphate salt with aqueous solution forming a paste that can react at body temperature generating a hydroxyapatite precipitated (Ca10(PO4)6(OH)2). The chemical and morphological similarity between the cement composition and the mineral part of the bones allows osteoconduction in the tissue with replacement of cement by new bone formed with the advantage to not unchain inflammatory processes and of strange body. The objective of this work was the use of the α-TCP cement for making these scaffolds, through the variation of the amount of liquid phase in the cement and of the use of paraffin spheres as pore source. These spheres were produced by suspension in water solution of poly (vinyl alcohol) and sodium sulphate (Na2SO4). The phases had been analyzed in the synthesized cement and after the reaction of cure of cement, beyond variation of the particle size and the resistance mechanics with the milling time. It was analyzed the porosity of the scaffolds and the extraction of the paraffin in that supports. The pore size of the supports generated with the variation of the amount of liquid phase was on this side of the size considered ideal for the bone tissue growth. The porosity of scaffolds manufactured with paraffin spheres was observed by Scanning Electron Microscopy (SEM), and its behavior was analyzed from test in vitro in SBF solution (simulated body fluid). The use of paraffin spheres allowed the formation of pores size able to permit tissue growth.

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