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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.
81

Experimental Investigations Of Surface Interactions Of Shock Heated Gases On High Temperature Materials Using High Enthalpy Shock Tubes

Jayaram, V 06 1900 (has links)
The re-entry space vehicles encounter high temperatures when they enter the earth atmosphere and the high temperature air in the shock layer around the body undergoes partial dissociation. Also, the gas molecules injected into the shock layer from the ablative thermal protection system (TPS) undergo pyrolysis which helps in reducing the net heat flux to the vehicle surface. The chemical species due to the pyrolysis add complexity to the stagnation flow chemistry (52 chemical reactions) models which include species like NOx, CO and hydrocarbons (HCs). Although the ablative TPS is responsible for the safety of re-entry space vehicle, the induced chemical species result in variety of adverse effects on environment such as global warming, acid rain, green house effect etc. The well known three-way-catalyst (TWC) involves simultaneous removal of all the three gases (i.e, NOx, CO, Hydrocarbons) present in the shock layer. Interaction of such three-way-catalyst on the heat shield materials or on the wall of the re-entry space vehicle is to reduce the heat flux and to remove the gases in the shock layer, which is an important issue. For the re-entry vehicle the maximum aerodynamic heating occurs at an altitude ranging about 68 to 45 km during which the vehicle is surrounded by high temperature dissociated air. Then the simplest real gas model of air is the five species model which is based on N2, O2, O, NO and N. This five species model assumes no ionization and no pyrolysis gases are emitted from the heat shield materials. The experimental research work presented in this thesis is directed towards the understanding of catalytic and non-catalytic surface reactions on high temperature materials in presence of strong shock heated test gas. We have also explored the possibility of using shock tube as a high enthalpy device for synthesis of new materials. In the first Chapter, we have presented an overview of re-entry space vehicles, thermal protection system (TPS) and importance of real gas effects in the shock layer. Literature survey on TPS, ablative materials and aerothermochemistry at the stagnation point of reentry capsule, in addition to catalytic and non-catalytic surface reactions between the wall and dissociated air in the shock layer are presented. In Chapters 2 and 3, we present the experimental techniques used to study surface reactions on high temperature materials. A brief description of HST2 shock tunnel is presented and this shock tunnel is capable of generating flow stagnation enthalpies ranging from 0.7 to 5 MJ/kg and has an effective test time of ~ 800 µs. High speed data acquisition system (National Instruments and Yokogawa) used to acquire data from shock tube experiments. The experimental methods like X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Raman and FTIR spectroscopy have been used to characterize the shock-exposed materials. Preliminary research work on surface nitridation of pure metals with shock heated nitrogen gas is discussed in Chapter 2. Surface nitridation of pure Al thin film with shock heated N2 is presented in Chapter 3. An XPS study shows that Al 2p peak at 74.2 eV is due to the formation AlN on the surface of Al thin film due to heterogeneous non-catalytic surface reaction. SEM results show changes in surface morphology of AlN film due to shock wave interaction. Thickness of AlN film on the surface increased with the increase in temperature of the shock heated nitrogen gas. However, HST2 did not produce sufficient temperature and pressure to carry out real conditions of re-entry. Therefore design and development of a new high enthalpy shock tunnel was taken up. In Chapter 4, we present the details of design and fabrication of free piston driven shock tunnel (FPST) to generate high enthalpy test gas along with the development of platinum (Pt) and thermocouple sensors for heat transfer measurement. A free piston driven shock tunnel consists of a high pressure gas reservoir, compression tube, shock tube, nozzle, test section and dump tank connected to a vacuum pumping system. Compression tube has a provision to fill helium gas and four ports, used to mount optical sensors to monitor the piston speed and pressure transducer to record pressure at the end of the compression tube when the piston is launched. Piston can attain a maximum speed of 150 m/s and compress the gas inside the compression tube. The compressed gas bursts the metal diaphragm and generates strong shock wave in the shock tube. This tunnel produces total pressure of about 300 bar and temperature of about 6000 K and is capable of producing a stagnation enthalpy up to 45 MJ/kg. The calibration of nozzle was carried out by measuring the pitot tube pressure in the dump tank. Experimentally recorded P5 pressure at end of the shock tube is compared with Numerical codes. Calibrated pressure P5 values are used to calculate the temperature T5 of the reflected shock waves. This high pressure and high temperature shock heated test gas interacts with the surface of the high temperature test materials. For the measurement of heat transfer rate, platinum thin film sensors are developed using DC magnetron sputtering unit. Hard protective layer of aluminum nitride (AlN) on Pt thin film was deposited by reactive DC magnetron sputtering to measure heat transfer rate in high enthalpy tunnel. After the calibration studies, FPST is used to study the heat transfer rate and to investigate catalytic/non-catalytic surface reaction on high temperature materials. In Chapter 5, an experimental investigation of non-catalytic surface reactions on pure carbon material is presented. The pure carbon C60 films and conducting carbon films are deposited on Macor substrate in the laboratory to perform shock tube experiments. These carbon films were exposed to strong shock heated N2 gas in the shock tube portion of the FPST tunnel. The typical shock Mach number obtained is about 7 with the corresponding pressure and temperature jumps of about 110 bar and 5400 K after reflection at end of the shock tube. Shock exposed carbon films were examined by different experimental techniques. XPS spectra of C(1s) peak at 285.8 eV is attributed to sp2 (C=N) and 287.3 eV peak is attributed to sp3 (C-N) bond in CNx due to carbon nitride. Similarly, N(1s) core level peak at 398.6 eV and 400.1 eV observed are attributed to sp3-C-N and sp2-C=N of carbon nitride, respectively. SEM study shows the formation of carbon nitride crystals. Carbon C60 had melted and undergone non-catalytic surface reaction with N2 while forming carbon nitride. Similar observations were made with conducting carbon films but the crystals were spherical in shape. Micro Raman and FTIR study gave further evidence on the formation of carbon nitride film. This experimental investigation confirms the formation of carbon nitride in presence of shock-heated nitrogen gas by non-catalytic surface reaction. In Chapters 6 and 7, we present a novel method to understand fully catalytic surface reactions after exposure to shock heated N2, O2 and Ar test gas with high temperature materials. We have employed nano ZrO2 and nano Ce0.5Zr0.5O2 ceramic high temperature materials to investigate surface catalytic reactions in presence of shock heated test gases. These nano crystalline oxides are synthesized by a single step solution combustion method. Catalytic reaction was confirmed for both powder and film samples of ZrO2. As per the theoretical model, it is known that the catalytic recombination reaction produces maximum heating on the surface of re-entry space vehicles. This was demonstrated in this experiment when a metastable cubic ZrO2 changed to stable monoclinic ZrO2 phase after exposure to shock waves. The change of crystal structure was seen using XRD studies and needle type monoclinic crystal growth with aspect ratio (L/D) more than 15 was confirmed by SEM studies. XPS of Zr(3d) core level spectra show no change in binding energy before and after exposure to shock waves, confirming that ZrO2 does not change its chemical nature, which is the signature of catalytic surface reaction. When a shock heated argon gas interacted with Ce0.5Zr0.5O2 compound, there was a change in colour from pale yellow to black due to reduction of the compound, which is the effect of heat transfer from the shock wave to the compound in presence of argon gas. The reduction reaction shows the release of oxygen from the compound due to high temperature interaction. The XPS of Ce(3d) and Zr(3d) spectra confirm the reduction of both Ce and Zr to lower valent states. The oxygen storage and release capacity of the Ce0.5Zr0.5O2 compound was confirmed by analyzing the reduction of Ce4+ and Zr4+ with high temperature gas interaction. When Ce0.5Zr0.5O2 (which is same as Ce2Zr2O8) in cubic fluorite structure was subjected to strong shock, it changed to pyrochlore (Ce2Zr2O7) structure by releasing oxygen and on further heating it changed to Ce2Zr2O6.3 which is also crystallized in pyrochlore structure by further releasing oxygen. If this heating is carried out in presence of argon test gas, fluorite structure can easily change to pyrochlore Ce2Zr2O6.3 structure, which is a good electrical conductor. Due to its oxygen storage capability (OSC) and redox (Ce4+/Ce3+) properties, Ce0.5Zr0.5O2 had been used as oxygen storage material in three-way-catalyst. Importance of these reactions is that the O2 gas released from the compound will react with gas released from the heat shield materials, like NOx, CO and hydrocarbon (HCs) species which results in reduction of temperature in the shock layer of the re-entry space vehicle. The compound Ce0.5Zr0.5O2 changes its crystal structure from fluorite to pyrochlore phase in presence of shock heated test gas. The results presented in these two Chapters are first of their kind, which demonstrates the surface catalytic reactions. In Chapter 8, we present preliminary results of the oxygen recombination on the surface of heat shield material procured from Indian Space Research Organization (ISRO) used as TPS in re-entry space capsule (Space capsule Recovery Experiment SRE-1) and on thin film SiO2 deposited on silicon substrate. The formation of SiO between the junctions of SiO2/Si was confirmed using XPS study when shock exposed oxygen reacted on these materials. The surface morphology of the ablated SiO2 film was studied using SEM. The damage induced due to impact of shock wave in presence of oxygen gas was analyzed using Focused Ion Beam (FIB) microscope. The results reveal the damage on the surface of SiO2 film and also in the cross-section of the film. We are further investigating use of FIB, particularly related to residual stress developed on thin films due to high pressure and high temperature shock wave interaction. In Chapter 9, conclusions on the performance of FPST, synthesis of high temperature materials, catalytic and non-catalytic surface reactions on the high temperature material due to shock-heated test gases are presented. Possible scope for future studies is also addressed in this Chapter.
82

Violência sexual doméstica contra crianças e adolescentes: um estudo sobre o município de Foz do Iguaçu-Pr / Domestic sexual violence against children and adolescentes: a study of the cuty of Foz do Iguaçu-Pr

Ziglioli, Claires Salete 21 January 2016 (has links)
Made available in DSpace on 2017-07-10T18:17:57Z (GMT). No. of bitstreams: 1 Claires Salete Ziglioli.pdf: 2940196 bytes, checksum: 13a8350913e2ffc09c286e378e49f608 (MD5) Previous issue date: 2016-01-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This Master's Dissertation study aimed to analyze the domestic sexual violence against children and adolescents: a study of the city of Foz do Iguaçu-Pr, city of the Triple Frontier of Brazil, Argentina and Paraguay. The procedure began with the approach of the phenomenon of violence in its forms of structural violence and domestic violence. Subsequently, reference was made to the Integral Protection System, highlighting the Law Guarantee System, represented by Service Network in combating sexual violence, as well as the Combat Plans Sexual Violence against Children and National Teenagers, State and Municipal. The research took place in the SINAN, and in the organs (Guardianship Councils I and II, CREAS, NUCRIA, MP, Shelter and IML) identified as full protection in Foz do Iguaçu. It tried, thus, understand the coping flow to sexual violence against children and adolescents, as well as compliance with the actions of the Municipal Plan to Combat Sexual Violence against Children and Adolescents in the city. The methodology privileged the qualitative-quantitative approach, enriched with information obtained through the questionnaire and survey data online and on-site, next to the sectors in the year 2014. The data analysis was performed with a qualitative reading in the light of the theoretical framework, key to highlight some categories such as online data type of sexual violence; consequences of violence; author data aggression; referrals to the sectors that make up the organizational and functional structure of children and adolescents rights guarantee system; research on the spot, next to the Guardianship Councils I and II, the CREAS, the NUCRIA, the prosecutor, the Shelter and the IML, to map the number of cases received, accompanied and directed by them to other sectors; yet the actions undertaken by sectors, in relation to compliance with the structural axes of the Municipal Plan to Combat Sexual Violence against Children and Adolescents. According to the survey results, it was concluded that the flow of service and the Municipal Plan does not advocate in the city of Foz do Iguaçu in fighting domestic sexual violence against children and adolescents. Still, regarding the relationship between the Municipal Plan to Combat Sexual Violence against Children and Adolescents and the flow of care to sexual violence, it was found that children and adolescents remain being raped not only within the family, but by the institucions that should ensure their full protection. / Este estudo de Dissertação de Mestrado teve por objetivo analisar a violência sexual doméstica contra crianças e adolescentes: um estudo sobre o município de Foz do Iguaçu-Pr, cidade da Tríplice Fronteira do Brasil-Argentina-Paraguai. O procedimento iniciou-se com a abordagem sobre o fenômeno da violência, nas suas formas de violência estrutural e de violência doméstica. Posteriormente, fez-se referência ao Sistema de Proteção Integral, destacando-se o Sistema de Garantia de Direito, representado pela Rede de Atendimento no enfrentamento da violência sexual, como também os Planos de Enfrentamento à Violência Sexual contra Crianças e Adolescentes Nacional, Estadual e Municipal. A pesquisa realizou-se no SINAN e junto aos órgãos (Conselhos Tutelares I e II, CREAS, NUCRIA, MP, Casa Abrigo e IML), identificados como de proteção integral em Foz do Iguaçu. Procurou-se, assim, compreender o fluxo de enfrentamento à violência sexual contra crianças e adolescentes, bem como o cumprimento das ações do Plano Municipal de Enfrentamento à Violência Sexual contra Crianças e Adolescentes no município. A metodologia utilizada privilegiou a abordagem qualiquantitativa, enriquecida com informações obtidas por meio de questionário e de levantamento de dados online e in loco, junto aos setores no ano de 2014. A análise dos dados foi realizada a partir da leitura qualitativa à luz do referencial teórico, fundamental para evidenciar algumas categorias como: os dados online do tipo da violência sexual; as consequências da violência; os dados do autor da agressão; os encaminhamentos para os setores que compõem a estrutura organizativa e funcional do sistema de garantia de direitos de crianças e adolescentes; a pesquisa in loco, junto aos Conselhos Tutelares I e II, ao CREAS, ao NUCRIA, ao Ministério Público, a Casa Abrigo e ao IML, para mapear o número de casos recebidos, acompanhados e encaminhados por eles para outros setores; e, ainda, as ações realizadas pelos setores em relação ao cumprimento dos eixos estruturantes do Plano Municipal de Enfrentamento à Violência Sexual contra Crianças e Adolescentes. De acordo com os resultados da pesquisa, conclui-se que o fluxo de atendimento e o Plano Municipal não se preconizam no município de Foz do Iguaçu no enfrentamento da violência sexual doméstica contra crianças e adolescentes. Ainda no que concerne à articulação entre o Plano Municipal de Enfrentamento à Violência Sexual contra Crianças e Adolescentes e o fluxo de atendimento à violência sexual, verificou-se que as crianças e adolescentes permanecem sendo violentadas não somente dentro do ambiente familiar, mas também pelos órgãos que deveriam assegurar a proteção integral.
83

Nastavení ochranných funkcí pro zadanou rozvodnu VN / Protection setting concept for given MV substation

Váhala, Václav January 2017 (has links)
The thesis is focused on the protection concept for medium voltage substation. The first theoretical part of thesis describes given medium voltage substation. Substation consists of two incoming feeders and six outgoing feeders. Due to the size of the substation was selected one outgoing feeder which is the subject of description and protection concept. Next part of the thesis is a description of the protective functions used to protect the elements in the selected feeder. This part contains a detailed description of the function and setting options for protection. The main part of the thesis describes calculation of specific protection functions and consequently with secondary testing of protective functions. Tests were performed on protective functions in the digital protections REF615 and REM620. The final part of the thesis deals with the evaluation of the secondary test results and verification saturation of the specified current transformers.
84

Zugbeeinflussungssysteme in Polen, der Slowakei und Tschechien

Dorka, Moritz 31 August 2012 (has links)
In dieser Arbeit sollen die maßgeblichen nationalen Zugbeeinflussungssysteme der Länder Polen (SHP, Radio-Stop, KHP), Slowakei und Tschechien (LS, MIREL VZ1) vorgestellt und miteinander verglichen werden. Der Fokus liegt dabei auf einer funktionellen Betrachtung, wobei auch der technische Hintergrund nicht unberücksichtigt bleibt. Ein Ausblick auf die zukünftigen Bemühungen hinsichtlich ETCS rundet den Überblick ab.:1 Übersicht . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 LS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 Zielstellung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Funktionsweise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Betriebsmodi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.4 MIREL VZ1-Erweiterungen . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.5 Weitere Entwicklungen in der Slowakei und in Tschechien . . . . . . . . . . 13 3 SHP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.1 Zielstellung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.2 Funktionsweise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.3 KHP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.4 Radio-Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.5 Weitere Entwicklungen in Polen . . . . . . . . . . . . . . . . . . . . . . . . 19 4 Literaturverzeichnis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 / This paper compares the major national train protection systems of Poland (SHP, Radio-Stop, KHP), the Slovak Republic and Czechia (LS, MIREL VZ1). The emphasis is placed on a functional description, while mentioning the relevant technical background where necessary. An outlook on future developments regarding ETCS in the respective countries concludes each chapter.:1 Übersicht . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 LS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 Zielstellung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Funktionsweise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Betriebsmodi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.4 MIREL VZ1-Erweiterungen . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.5 Weitere Entwicklungen in der Slowakei und in Tschechien . . . . . . . . . . 13 3 SHP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.1 Zielstellung . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.2 Funktionsweise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.3 KHP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.4 Radio-Stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.5 Weitere Entwicklungen in Polen . . . . . . . . . . . . . . . . . . . . . . . . 19 4 Literaturverzeichnis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

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