The past two decades have seen an ethno-religious revival in China, one which is spurred by the development of ethnic tourism with the introduction of the Chinese-state-market economy. The success of recreating, branding, and selling the Yi torch festival, as among the Liangshan Yi people, draws public attention. While some intellectuals are in favor of ethnic elites' effort in promoting cultural difference and authenticity in a festive context, others dispute the changing meanings that are brought about by this "invented tradition". My thesis is intended to bridge the disputants' concern of ritual knowledge and ritual reproduction with a lack of discussion of a stereotypically "primordial" form of the torch festival, dutzie, or "the sacrifice to the fire". I examine how cultural difference is reified and projected upon Morganian-Marxist scales of human societal development through the state-initiated projects of ethnic identification and "minority work" in the early years of nation-state building, and how subsequent radicalized state policies generate forced assimilation and give rise to the Yi's own appropriation of a state-designated category of ethnicity. By exploring both the retraditionalization of the Yi torch festival and the rural Yi's long-held practice of dutzie in the reform era, I investigate ritual changes and cultural continuity among the Liangshan Yi, and therefore highlight Yi identity formation in historical and social processes of producing ethnic dimension in China.

Research conducted at Virginia Tech has examined plasma torch operational characteristics using a feedstock gas of mixed hydrocarbons representing a cracked JP-7 surrogate. The tests were part of a program to examine the torch as an igniter and flame-holder for hydrocarbon-fueled scramjet engines. Previous research has shown that the plasma torch has promise as a robust igniter and flame-holder using gaseous fuels such as methane, ethylene and propylene when combined with an aeroramp to assist with the combustion process. The present investigation tested the plasma torch with a feedstock mixture of gaseous hydrocarbons that simulates thermally cracked JP-7 jet fuel. This simulation of a cracked hydrocarbon fuel was studied to lay the foundation for work with liquid hydrocarbon fuel, which is of interest for today's aerospace vehicles. The cracked JP-7 surrogate consists of a 15/25/60 mixture of methane/ethane/ethylene. The research results include torch operational characteristics such as downstream plume temperatures and emission spectroscopy within the combustion plume, as well as the power supplied to the torch over a range of mass flow rates. Filtered photographs of the emissions plume were studied to aid torch plume diagnostics. Other observations made were erosion and alignment of the electrodes, which will help determine the potential lifespan of the torch using cracked JP-7 fuel. The results show successful operation over a range of powers with simulated cracked JP-7 feedstock flows. Measured spectra, current, and voltage are compared with similar results for other hydrocarbon feedstock gases. The torch operating on the JP-7 surrogate feedstock appears to be a satisfactory device for ignition, flame-holding, and combustion enhancement of cracked hydrocarbons in supersonic combustion. / Master of Science

As the flight speeds of aircraft are increased above Mach 5, efficient methods of propulsion are needed. Scramjets may be a solution to this problem. Supersonic combustion is one of the main challenges involved in the operation of a Scramjet engine. In general, both an igniter and a flameholder are needed to achieve and maintain supersonic combustion. The current work examines a plasma torch-strut combination as an igniter-flameholder. The plasma torch-strut combination was tested in the Virginia Tech unheated supersonic wind tunnel at Mach 2.4. Pressure and temperature sampling, filtered photography, and spectroscopic measurements were used to compare different test cases. These results provide both qualitative and quantitative results on how the combination responds to changes in the mass flow rate of fuel and the power to the plasma torch. The key conclusions of the work were the following: 1. Tests showed that an exothermic reaction takes place. 2. The amount of heat release increases with an increase in the mass flow rate of fuel. 3. The plasma torch-fuel injector interaction caused the heat release to be well above the tunnel floor and sometimes off the strut centerline 4. One change in the fuel injector pattern caused more temperature rise near the floor of the tunnel. 5. The flow penetration height of the plasma torch alone was reduced by the fuel-plasma torch interaction. 6. Moving the strut upstream reduced the measured temperature rise at a fixed downstream location, but increased the penetration height of the plasma torch. 7. The computed heat release was found to be small compared to the potential heat release from all the fuel burning. 8. The amount of temperature rise caused by the fuel is not greatly affected by the power to the plasma torch. / Master of Science

The oscillating plasma torch is proposed as a potential device that will produce an oscillating shock and resulting control of the supersonic combustion process. This research will capitalize on previous results [Gallimore, 1998] which indicate that the plasma torch oscillations originate from the inherent oscillations of the voltage applied to the torch. The aim of this research is to thoroughly investigate the oscillation behavior of the plasma torch with the plan of ultimately controlling the oscillation at chosen frequencies. A modulating power system used for dynamic control of the plasma torch oscillation was designed and tested in quiescent conditions (no flow), Mach 2.4 cold supersonic flow, and Mach 2 heated supersonic flow conditions. The oscillating plasma torch used nitrogen feedstock and was operated over a frequency range of 2Hz- 4kHz. A dynamic torch model using the hybrid Mayr-Cassie electric arc model was developed to predict the plasma torch electric arc response at appropriate frequencies for interaction with supersonic combustion. In quiescent conditions, the dynamic response of the plasma torch power system and plasma jet were characterized using signal processing techniques and high speed video imaging. High speed Schlieren images were used to determine the behavior of the oscillating plasma jet in Mach 2.4 cross flow and its influence on the induced shock structure. The unsteady nitrogen-fed torch was integrated with the flush walled 4-hole aerodynamic ramp injector using hydrogen and hydrocarbon fuels at the University of Virginia Aerospace Research Lab (ARL) heated Mach 2 supersonic flow. Unsteady pressure variations from the oscillating shock produced by the plasma torch were recorded using recess-mounted Kulite pressure transducers. Also, measurements of the static pressure of the combustion produced by the oscillating plasma torch were obtained. The oscillating torch system performed well over a range of different flow conditions. It will enable active control input to the combustion process. The controllable unsteady blockage might provide a type shock interaction needed to increase turbulence and mixing augmentation [Kumar, et al. 1987]. / Master of Science

A newly designed liquid fuel (kerosene) aeroramp injector/plasma igniter was tested in cold flow using the Virginia Tech supersonic wind tunnel at Mach 2.4. The liquid fuel (kerosene) injector is flush wall mounted and consists of a 2 hole aeroramp array of impinging jets that are oriented in a manner to improve mixing and atomization of the liquid jets. The two jets are angled downstream at 40 degrees and have a toe-in angle of 60 degrees. The plasma torch used nitrogen and air as feedstocks and was placed downstream of the injector as an ignition aid. First, schlieren and shadowgraph photographs were taken of the injector flow to study the behavior of the jets, shape of the plume, and penetration of the liquid jet. The liquid fuel aeroramp was found to have better penetration than a single, round jet at 40 degrees. However, the liquid fuel aeroramp does not penetrate as well as an upstream/downstream impinging jet in a plane aligned with the flow. Next, the Sauter mean droplet diameter distribution was measured downstream of the injector. The droplet diameter was found to vary from 21 to 37 microns and the atomization of the injector does not appear to improve beyond 90 effective jet diameters from the liquid fuel aeroramp. These results were then used to decide on an initial location for the plasma torch. The combined liquid injector/plasma torch system was tested in an unheated (300 K) Mach 2.4 flow with a total pressure of 345 kPa. The liquid fuel (kerosene) volumetric flow rate was varied from 0.66 lpm to 1.22 lpm for the combined liquid injector/plasma torch system. During this testing the plasma torch was operated from 1000 to 5000 watts with 25 slpm of nitrogen and air as feedstocks. The interaction between the spray plume and the plasma torch was observed with direct photographs, videos, and photographs through an OH filter. It is difficult to say that any combustion is present from these photographs. Of course, it would be surprising if much combustion did occur under these cold-flow, low-pressure conditions. Differences between the interaction of the spray plume and the plasma torch with nitrogen and air as feedstocks were documented. According to the OH wavelength filtered photographs the liquid fuel flow rate does appear to have an effect on the height and width of the bright plume. As the liquid fuel flow rate increases the bright plume increases in height by 30% and increases in width slightly (2%). While, a decrease in liquid fuel flow rate resulted in an increase in height by 9% and an increase in width by 10%. Thus, as the liquid fuel flow rate varies the width and height of the bright plume appear to always increase. This can be explained by noticing that the shape of the bright plume changes as the liquid fuel flow rate varies and perhaps anode erosion during testing also plays a part in this variation of the bright plume. From the OH wavelength filtered photographs it was also shown that the bright plume appears to decrease in width by 9% and increase in height by 22% when the plasma torch is set at a lower power setting. When air is used as the torch feedstock, instead of nitrogen, the penetration of the bright plume can increase by as much as 19% in width and 17% in height. It was also found that the height and width of the bright plume decreased slightly (2%) as the fuel flow rate increased when using air as the torch feedstock. Testing in a hot-flow facility is planned. / Master of Science

Research was conducted at Virginia Tech on a high-pressure uncooled plasma torch to study torch operational characteristics with hydrocarbon feedstocks and to determine the feasibility of using the torch as an igniter in scramjet applications. Operational characteristics studied included electrical properties, such as arc stability, voltage-current characteristics and start/re-start capabilities, and mechanical properties, such as coking, electrode erosion and transient to steady-state torch body temperature trends. Possible use of the plasma torch as an igniter in high-speed combustion environments was investigated through the use of emission spectroscopy and a NASA chemical kinetics code. All feedstocks tested; argon, methane, ethylene and propylene, were able to start. The voltage data indicated that there were two preferred operating modes, which were well defined for methane. For all gases, a higher current setting, on the order of 40 A, led to more stable torch operation. A low intensity, high frequency current applied to the torch, along with the primary DC current, resulted in virtual elimination of soot deposits on the anodes. Electrode erosion was found to multiply each time the complexity of the hydrocarbon was increased. Audio and high-speed visual analysis led to identification of 180 Hz plasma formation cycle, related to the three-phase power supply. The spectroscopic analysis aided in the identification of combustion enhancing radicals being produced by the torch, and results of the chemical kinetics analysis verified combustion enhancement and radical production through the use of a basic plasma model. Overall, the results of this study indicate that the plasma torch is a promising source for scramjet ignition, and further study is warranted. / Master of Science

This thesis attempts to explore the discursive construction of Olympic ideology in the 2008 Torch Relay news coverage by the British and the Chinese media. It applies a corpus-based Discourse-Historical Approach in Critical Discourse Analysis (DHA-CDA) to analyse how and why the complexity, contradiction and conflicts in linguistic interpretations of Olympism are demonstrated by the media discourse between East and West. This study first focuses on the underpinning ideology and the study of the media, considering the historical development of Olympic ideology (Olympism) along with the respective mainstream ideologies in Britain (Liberalism) and China (Harmony), as well as the philosophical foundations and prominence of CDA. It then draws on the elaborated analytical approach-corpus-based CDA-in detail to analyse four specially constructed corpora drawn from the China Daily, BBC News and The Guardian. Thereafter corpus techniques including frequency and concordance analysis are applied and results obtained that reveal comparative differences and diachronic shifts across the corpora. Having first described the data, they are then interpreted in their linguistic contexts, and subsequently explained in the broader historical and socio-political contexts surrounding the dynamic life of the Olympic Torch Relay. This study demonstrates that there are contrasting expressions of Olympic ideology in the media discourse of the two countries. At a deeper level, this social practice is revealed to be dominated by the mainstream ideologies of the hosting and participating nations, which have been entrenched throughout their respective histories. The involvement of Britain and China in Olympic history and the relevant socio-political events surrounding the 2008 Torch Relay are explored in order to inform our analysis. The conclusion to this thesis reinforces its significant contribution to the study of Olympism. The Olympic philosophy of integrating diversified ideologies was certainly not manifest in the confrontation between the eastern and western media in 2008. Liberalism and harmony had never confronted each other face to face on the world stage before or attempted to find a common ground on which to coexist as revealed in this study. Based on this, respect for and tolerance of diverse ideology, history and culture will hopefully promote the solidarity and prosperity represented by Olympism in the new era.

Plasmas térmicos vêm sendo utilizados em um crescente número de aplicações industriais. Na maioria dessas aplicações, as tochas de plasmas (o equipamento utilizado para gerar o plasma) necessitam ser utilizadas por várias centenas de horas antes de qualquer manutenção, a fim de permitir um contínuo processo industrial. Os eletrodos da tocha de plasma, particularmente o catodo, eventualmente irão apresentar sinais de desgaste (erosão), forçando uma substituição dos mesmos e, conseqüentemente, obrigando a uma parada na operação da tocha. Desse modo, a erosão dos eletrodos de uma tocha de plasma (em particular, a erosão do catodo) deve ser minimizada sempre que possível. Este trabalho visa estudar materiais para eletrodos e condições de operação de tochas de plasma a fim de se diminuir a erosão dos eletrodos, particularmente do catodo. Nesse sentido, uma câmara de testes foi construída para simular eletrodos concêntricos de uma tocha de plasma. Um campo magnético externo foi utilizado para movimentar um arco elétrico que foi estabelecido entre os eletrodos concêntricos. Nessa câmara foram estudados diferentes tipos de gases e materiais para o catodo, para tentar aumentar o tempo de vida dos catodos de tocha de plasma. Os resultados obtidos mostraram que: a) A presença de contaminantes nos gases utilizados como gases de plasma alteram as condições da superfície do catodo, diminuindo as taxas de erosão; b) Misturas de gases inertes com gases poliatômicos, quando utilizadas como gases de plasma, contaminam a superfície do catodo, alterando as condições das mesmas, diminuindo as taxas de erosão; c) A presença de contaminantes no material utilizado no catodo, como também a utilização de ligas de cobre como material para os eletrodos, também alteram as características da superfície, aumentando o tempo de vida dos catodos. / Thermal plasmas have shown a growing number of industrial applications. In most of those applications, the plasma torch (the device used to generate the thermal plasma) would need several hundred hours of using before anykind of maintenance, in spite of permit a continuous industrial process. The electrodes of the plasma torch, particularly the cathode, eventually will present signs of erosion, forcing their replacement and, consequently, a stoppage of the torch operation. However, electrode erosion of a plasma torch (cathode erosion in particular) must be minimized as often as possible. The objective of this work is to study materials for plasma torch electrodes and the operation condition of the plasma torch, in order to diminish the erosion of the electrodes (cathode in particular). Therefore, an experimental chamber was built in order to simulate concentric electrodes of a plasma torch. An external magnetic field was used for moving the electric arc that was stablished between the concentric electrodes. Different types of gases and cathode materials have been studied using that chamber. The results obtained so far showed that: a) Contaminants present in the gases used as plasma gases, change the cathode surface conditions, decreasing the erosion rates; b) Mixtures of inert gases with potiatomic gases, when used as plasma gases, contaminate the cathode surface, changing their conditions, decreasing the erosion rates; c) Contaminants in the composition of the materials used in the cathode, and even the use of copper alloys as material for electrodes, changes the surface characteristics, increasing the cathode lifetime.

Plasmas térmicos vêm sendo utilizados em um crescente número de aplicações industriais. Na maioria dessas aplicações, as tochas de plasmas (o equipamento utilizado para gerar o plasma) necessitam ser utilizadas por várias centenas de horas antes de qualquer manutenção, a fim de permitir um contínuo processo industrial. Os eletrodos da tocha de plasma, particularmente o catodo, eventualmente irão apresentar sinais de desgaste (erosão), forçando uma substituição dos mesmos e, conseqüentemente, obrigando a uma parada na operação da tocha. Desse modo, a erosão dos eletrodos de uma tocha de plasma (em particular, a erosão do catodo) deve ser minimizada sempre que possível. Este trabalho visa estudar materiais para eletrodos e condições de operação de tochas de plasma a fim de se diminuir a erosão dos eletrodos, particularmente do catodo. Nesse sentido, uma câmara de testes foi construída para simular eletrodos concêntricos de uma tocha de plasma. Um campo magnético externo foi utilizado para movimentar um arco elétrico que foi estabelecido entre os eletrodos concêntricos. Nessa câmara foram estudados diferentes tipos de gases e materiais para o catodo, para tentar aumentar o tempo de vida dos catodos de tocha de plasma. Os resultados obtidos mostraram que: a) A presença de contaminantes nos gases utilizados como gases de plasma alteram as condições da superfície do catodo, diminuindo as taxas de erosão; b) Misturas de gases inertes com gases poliatômicos, quando utilizadas como gases de plasma, contaminam a superfície do catodo, alterando as condições das mesmas, diminuindo as taxas de erosão; c) A presença de contaminantes no material utilizado no catodo, como também a utilização de ligas de cobre como material para os eletrodos, também alteram as características da superfície, aumentando o tempo de vida dos catodos. / Thermal plasmas have shown a growing number of industrial applications. In most of those applications, the plasma torch (the device used to generate the thermal plasma) would need several hundred hours of using before anykind of maintenance, in spite of permit a continuous industrial process. The electrodes of the plasma torch, particularly the cathode, eventually will present signs of erosion, forcing their replacement and, consequently, a stoppage of the torch operation. However, electrode erosion of a plasma torch (cathode erosion in particular) must be minimized as often as possible. The objective of this work is to study materials for plasma torch electrodes and the operation condition of the plasma torch, in order to diminish the erosion of the electrodes (cathode in particular). Therefore, an experimental chamber was built in order to simulate concentric electrodes of a plasma torch. An external magnetic field was used for moving the electric arc that was stablished between the concentric electrodes. Different types of gases and cathode materials have been studied using that chamber. The results obtained so far showed that: a) Contaminants present in the gases used as plasma gases, change the cathode surface conditions, decreasing the erosion rates; b) Mixtures of inert gases with potiatomic gases, when used as plasma gases, contaminate the cathode surface, changing their conditions, decreasing the erosion rates; c) Contaminants in the composition of the materials used in the cathode, and even the use of copper alloys as material for electrodes, changes the surface characteristics, increasing the cathode lifetime.

Orientador: Edison Bittencourt / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-26T21:57:48Z (GMT). No. of bitstreams: 1 Silva_SoniaFonsecaCostae_D.pdf: 7122538 bytes, checksum: 168b9088ec0fd3c2e7dc5392747cded0 (MD5) Previous issue date: 2015 / Resumo: Compósitos ablativos são vastamente utilizados em divergentes de motores usados em veículos espaciais, em particular nos veículos em desenvolvimento no Instituto de Aeronáutica e Espaço, como por exemplo, o Veículo Lançador de Satélite. Tais divergentes podem ser produzidos por diversos processos, entre eles a bobinagem. Atualmente é empregado o processo de bobinagem paralela para a fabricação desses elementos. Porém, visando obter-se um melhor desempenho ablativo e otimização da massa para os divergentes, propõe-se uma inovação no processo de fabricação para estruturas ablativas, a bobinagem inclinada em fitas tecidas. Neste trabalho foi realizado um estudo teórico experimental da ablação em compósitos bobinados obtidos através dos dois processos de bobinagem, paralela e inclinada. Uma tocha de plasma é usada para simular as condições de operação do material em um divergente. O material utilizado como reforço do compósito foi um tecido de fibra de carbono e o polímero utilizado como matriz foi uma resina fenólica tipo resol. Nestas condições, foram avaliadas a taxa de perda de massa e as temperaturas atingidas na face exposta a tocha, tendo como parâmetro o fluxo térmico do jato de plasma. Os dados experimentais foram comparados com os resultados numéricos de uma simulação computacional. Embora não tenha sido obtida uma perfeita concordância entre os resultados numéricos e experimentais, a ordem de magnitude e o comportamento de variação dos parâmetros avaliados podem ser considerados fisicamente coerentes e dentro dos limites do modelo teórico proposto. Os resultados obtidos permitem estimar a taxa de perda de massa de acordo com o fluxo térmico e indicam um melhor desempenho ablativo das amostras obtidas por bobinagem inclinada em comparação com as amostras obtidas por bobinagem paralela / Abstract: Ablative composites are widely used in nozzles of propeller engines used in space vehicles, as the Satellite Launching Vehicle in development at Aeronautics and Space Institute, for example. Such nozzle extension can be produced by various processes, including wrapping tape. Currently is employed the parallel wrapping process to manufacture these elements. However, in order to get a better ablative performance and mass optimization for the nozzle extensions, it has been proposed an innovation in the manufacturing process for ablative structures, biased tape wrapping. In this paper is presented a theoretical study of experimental ablation in wound composite obtained by the two wrapping processes, parallel and biased tape. A plasma torch has used to simulate the operating conditions of the material in the nozzle extension. The composite has used as reinforcement a carbon fiber fabric with a resol phenolic resin matrix. Thus, it has evaluated the weight loss rate and the temperatures reached on the face to the side exposed to the torch, with the heat flux parameter of the plasma jet. The experimental data were compared with the numerical results of a computer simulation. Although not obtained a perfect agreement between the numerical and experimental results, the order of magnitude and the pattern of variation of the evaluated parameters can be considered physically consistent and within the limits of the proposed theoretical model. The results obtained allow us to estimate the mass loss rate in accordance with the thermal flow and indicate a better ablative performance of samples obtained by biased tape wrapping in comparison with the samples obtained by parallel wrapping / Doutorado / Ciencia e Tecnologia de Materiais / Doutora em Engenharia Quimica