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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.
61

Diagnostics of ion generation and fluxes from cathodic arc spots for a better understanding of energetic deposition of thin films

Oh, Kyunghwan 31 March 2023 (has links)
This thesis is devoted to the investigation of ion generation and fluxes from cathodic arc spots for a better understanding of energetic deposition of thin film. The ion generation is related to the arc spot properties, and ion fluxes influence the film deposition. Significantly, the cathodic arc has the explosion characteristic for the ignition process, which is the generation process of ions. Thus, it is not easy to observe the spot characteristics, and some fundamental questions related to cathodic arc spot motion are still open. The multiply charged ions produced from the arc spot ignition process have a higher ion potential energy than ions of other deposition techniques; therefore, consideration of the effect of ion potential energy on film growth is required for the cathodic arc technique. The first part of this thesis deals with fundamental arc spot characteristics, especially the trend of spot motion in a magnetically steered arc source placed in vacuum or in a reactive gas atmosphere. This is investigated with a streak camera having high spatial and temporal resolutions. To answer the fundamental question of whether the spots have characteristic times, such as a 'periodic spot lifetime' or a 'the periodic characteristic time between spot ignitions”, the streak images were analyzed by fast Fourier transformation (FFT). It was found that the power spectrum of the arc spot fluctuations does not show any specific frequencies, which means the arc spot ignition process can be described by a fractal model, and the spectral slope in the log-log power-frequency diagram has a tendency to be reduced in the presence of a compound (for example oxide or nitride) layer on the cathode surface. Through the fractal analysis and measurements of optical emission spectroscopy, the fundamental limitation of the temporal resolution for the optical emission method is determined and considered. The second part of this thesis considers cathodic arc’s application aspects: the energetic deposition of thin films and coatings. Most studies related to energetic deposition have previously investigated the effects of ion kinetic energy on film deposition; however, this thesis focuses on the effects of ion potential energy on film growth. To investigate the effect of ion potential energy on film growth, plasma diagnostic by energy-resolved mass spectrometry and deposited film characterization by XRD, XRR, AFM, profilometry and SEM were carried out. The ion potential energy influences the preferential direction of film growth or a polycrystalline growth in the case of aluminum deposition. This result could be a starting point for further research into the effect of ion potential energy on film deposition.
62

A Theoretical Approach To Assessing Annual Energy Balance In Gray Whales (eschrichtius Robustus)

Greenwald, Nathalie Lucie Elizabeth 01 January 2005 (has links)
While direct measurements of energetic demands are nearly impossible to collect on large cetaceans, comprehensive bioenergetic models can give insights on such parameters by combining physiological and ecological knowledge. This model was developed to estimate necessary food intake of gray whales, Eschrichtius robustus, of the Eastern North Pacific stock. Field Metabolic Rates (FMR) for gray whales were first estimated based on various assumptions (e.g. volumetric representation of gray whales, extent of their feeding season, and blubber depth distribution) using morphometric data, energetic costs, and food assimilation according to age and gender specific requirements. Food intake rates for gray whales of varying maturity and gender were then estimated based on FMR and caloric value of prey and compared to food intake rates of previous studies. Monte Carlo simulations and sensitivity analysis were performed to assess the model's predictions compared to observed field data from previous studies. Predicted average food intakes for adult male, pregnant/ lactating female, and immature whales were 475 ± 300, 525 ± 300 and 600 ± 300 kg d-1, respectively. Estimated blubber depths resulting from these food intakes were comparable to field data obtained from whaling data. Sensitivity analysis indicated food intake, from all parameters, as having the highest impact on the percent change in ending mass from a simulation. These food intake estimates are similar to those found in a previous study and fall within the range of food intake per body mass observed in other species of cetaceans. Though thermoregulation can be a factor in some cetaceans, it appears not to be an additional cost for gray whales as the present model's predicted lower critical temperatures for the whales (TLC) were below ambient temperatures. With temperatures increasing in the Bering Sea, the main prey of gray whales, ampeliscid amphipods, could be adversely affected, possibly resulting in increased food shortages leading to a surge in gray whale strandings.
63

Prediction and warning system of SEP events and solar flares 4 for risk estimation in space launch operations

Garcia-Rigo, A., Nunez, M., Qahwaji, Rami S.R., Ashamari, Omar, Jiggens, P., Perez, G., Hernández-Pajares, M., Hilgers, A. 08 July 2016 (has links)
Yes / A web-based prototype system for predicting solar energetic particle (SEP) events and solar flares for use by space launch operators is presented. The system has been developed as a result of the European Space Agency (ESA) project SEPsFLAREs (Solar Events Prediction system For space LAunch Risk Estimation). The system consists of several modules covering the prediction of solar flares and early SEP Warnings (labeled Warning tool), the prediction of SEP event occurrence and onset, and the prediction of SEP event peak and duration. In addition, the system acquires data for solar flare nowcasting from Global Navigation Satellite Systems (GNSS)-based techniques (GNSS Solar Flare Detector, GSFLAD and the Sunlit Ionosphere Sudden Total Electron Content Enhancement Detector, SISTED) as additional independent products that may also prove useful for space launch operators. / This work has been developed in the frame of 34 SEPsFLAREs project (ESA Contract Number 4000109626/13/NL/ 35 AK), which is an activity funded by ESA/ESTEC Space Environ- 36 ment (TEC-EES) section. The authors of this work are grateful to 37 ESA’s MONITOR project (Contract Number 4000100988/2010/F/ 38 WE) for allowing the use of GSFLAD and SISTED products. 39 We also thank AGAUR (Generalitat de Catalunya) for the financial 40 support from Grant PDJ 2014 00074.
64

CHARACTERIZATION OF INKJET PRINTED HIGH NITROGEN ENERGETIC MATERIALS AND BILAYER NANOTHERMITE

Adarsh Patra (6897383) 15 August 2019 (has links)
<p>This thesis presents work on two major areas of research. The first area of research involves the use of a dual-nozzle piezoelectric inkjet printing system to print bilayer aluminum bismuth (III) oxide nanothermite samples. The combinatorial printing method allows for separate fuel and oxidizer inks to be printed adjacent to each other at prescribed offset distances. The effect of the bilayer thickness on the burning rate of the samples is investigated using high-speed imaging. Analysis of the burning rate data revealed that there is no statistically significant relationship between these two parameters. This result was used to determine the dominant processes that control the propagation rate in nanothermite systems. It was concluded that convective processes dominate the burning rate rather than diffusive processes. The second area of research involved synthesizing inks suitable for inkjet printing using two promising high nitrogen energetic materials called BTATz and DAATO<sub>3.5</sub>. The performance of the developed inks was characterized using four experiments. The thermal stability and exothermic behavior of the inks were determined using DSC and TGA analysis. The results revealed that the inks are more thermally stable than the base materials. The inks were used to print lines that were subsequently used to determine burning rates. DAATO<sub>3.5</sub> samples were determined to have faster burning rates than BTATz. Closed pressure bomb experiments were conducted to determine the gas producing capability of the high nitrogen inks. BTATz samples showed better performance in terms of peak static pressures and pressurization rates. 3D printed microthrusters were developed to test the thrust performance of the inks. Peak thrust, total impulse, and specific impulse values are reported and were determined to be suitable for use with Class 1 micro-spacecraft. Finally, a microthruster array prototype was developed to demonstrate the capability to use additive manufacturing to create high packing density arrays.</p>
65

Análise de aproveitamento energético em aterros sanitários baseada em cenários de produção de efluentes

Thomazoni, André Luis Ribeiro January 2014 (has links)
O aumento da preocupação de soluções ambientalmente adequadas e energeticamente eficientes, aliado às recentes mudanças nas diretrizes políticas Brasileiras em relação à gestão e ao gerenciamento de resíduos sólidos e suas práticas de disposição final, permite a oportunidade de investigar a recuperação energética e o abatimento dos efluentes gerados por aterros sanitários. O presente trabalho explora, separadamente, o uso de modelo de previsão de produção de biogás baseado no decaimento de primeira ordem, e para a estimativa de produção de lixiviado, aplica-se o método do balanço hídrico (MBH). A partir de variação dos principais parâmetros de entrada de cada modelo, obtêm-se cenários de produção de biogás e estimativas da capacidade de geração máxima e mínima de lixiviado para o aterro sanitário de Guajuviras (Canoas - RS, Brasil). Tomando os resultados de geração de lixiviado e de biogás calculados, estima-se o potencial energético disponível e o desempenho de três diferentes sistemas de conversão energética propostos: geração elétrica por motogeradores, evaporação de lixiviado em regime de cogeração com motogeradores, motogeradores com trocadores de calor em regime de cogeração e sistema de evaporação de lixiviado (LES). Resultados obtidos para o período analisado, mostram que a produção elétrica do cenário mais conservador está na faixa entre 17.300 a 18.800 MWh, enquanto que a produção de energia elétrica do cenário otimista atinge valores entre 416.976 e 459.900 MWh. Já para a evaporação de lixiviado, os volumes evaporados em regime de cogeração variaram de 1 a 70% em relação ao volume de lixiviado gerado pelo aterro sanitário, enquanto que o LES, considerando o cenário otimista, foi capaz de evaporar 100% do lixiviado durante 18 anos. / The growing concern on environmentally suitable and energy efficient solutions allied with the recent changes in the Brazilian policies on the solid waste management and its final disposal practices, enables an opportunity to investigate the energy recovery and abatement of landfills emissions. The present work explores separately the utilization of 1st order decay model for assess the landfill gas (LFG) production, and applies the water budget method for prediction of leachate generation. Ranging the main input parameters on each model, were obtained distinct scenarios for LFG production and the maximum and minimum leachate generation capacity of Guajuviras landfill (Canoas- RS, Brazil). Based in the calculated results for leachate and LFG production were assessed the available energetic potential and the performance of three distinct energetic conversion systems: motogenerators, heat exchangers in cogeneration with motogenerators and leachate evaporation system (LES). Results for the analyzed period show that the electric generation for conservative scenario ranges between 17.300 to 18.800 MWh, whereas, the electricity production for more optimistic scenario ranges between 416.976 to 459.900 MWh. As for the leachate evaporation, the evaporated volume by the cogeneration system reaches values between 1 to 70% of the leachate produced by the landfill, whereas, the LES, considering the optimistic scenario, is able to evaporate all the generated leachate by the landfill among 18 years.
66

Análise de aproveitamento energético em aterros sanitários baseada em cenários de produção de efluentes

Thomazoni, André Luis Ribeiro January 2014 (has links)
O aumento da preocupação de soluções ambientalmente adequadas e energeticamente eficientes, aliado às recentes mudanças nas diretrizes políticas Brasileiras em relação à gestão e ao gerenciamento de resíduos sólidos e suas práticas de disposição final, permite a oportunidade de investigar a recuperação energética e o abatimento dos efluentes gerados por aterros sanitários. O presente trabalho explora, separadamente, o uso de modelo de previsão de produção de biogás baseado no decaimento de primeira ordem, e para a estimativa de produção de lixiviado, aplica-se o método do balanço hídrico (MBH). A partir de variação dos principais parâmetros de entrada de cada modelo, obtêm-se cenários de produção de biogás e estimativas da capacidade de geração máxima e mínima de lixiviado para o aterro sanitário de Guajuviras (Canoas - RS, Brasil). Tomando os resultados de geração de lixiviado e de biogás calculados, estima-se o potencial energético disponível e o desempenho de três diferentes sistemas de conversão energética propostos: geração elétrica por motogeradores, evaporação de lixiviado em regime de cogeração com motogeradores, motogeradores com trocadores de calor em regime de cogeração e sistema de evaporação de lixiviado (LES). Resultados obtidos para o período analisado, mostram que a produção elétrica do cenário mais conservador está na faixa entre 17.300 a 18.800 MWh, enquanto que a produção de energia elétrica do cenário otimista atinge valores entre 416.976 e 459.900 MWh. Já para a evaporação de lixiviado, os volumes evaporados em regime de cogeração variaram de 1 a 70% em relação ao volume de lixiviado gerado pelo aterro sanitário, enquanto que o LES, considerando o cenário otimista, foi capaz de evaporar 100% do lixiviado durante 18 anos. / The growing concern on environmentally suitable and energy efficient solutions allied with the recent changes in the Brazilian policies on the solid waste management and its final disposal practices, enables an opportunity to investigate the energy recovery and abatement of landfills emissions. The present work explores separately the utilization of 1st order decay model for assess the landfill gas (LFG) production, and applies the water budget method for prediction of leachate generation. Ranging the main input parameters on each model, were obtained distinct scenarios for LFG production and the maximum and minimum leachate generation capacity of Guajuviras landfill (Canoas- RS, Brazil). Based in the calculated results for leachate and LFG production were assessed the available energetic potential and the performance of three distinct energetic conversion systems: motogenerators, heat exchangers in cogeneration with motogenerators and leachate evaporation system (LES). Results for the analyzed period show that the electric generation for conservative scenario ranges between 17.300 to 18.800 MWh, whereas, the electricity production for more optimistic scenario ranges between 416.976 to 459.900 MWh. As for the leachate evaporation, the evaporated volume by the cogeneration system reaches values between 1 to 70% of the leachate produced by the landfill, whereas, the LES, considering the optimistic scenario, is able to evaporate all the generated leachate by the landfill among 18 years.
67

Análise de aproveitamento energético em aterros sanitários baseada em cenários de produção de efluentes

Thomazoni, André Luis Ribeiro January 2014 (has links)
O aumento da preocupação de soluções ambientalmente adequadas e energeticamente eficientes, aliado às recentes mudanças nas diretrizes políticas Brasileiras em relação à gestão e ao gerenciamento de resíduos sólidos e suas práticas de disposição final, permite a oportunidade de investigar a recuperação energética e o abatimento dos efluentes gerados por aterros sanitários. O presente trabalho explora, separadamente, o uso de modelo de previsão de produção de biogás baseado no decaimento de primeira ordem, e para a estimativa de produção de lixiviado, aplica-se o método do balanço hídrico (MBH). A partir de variação dos principais parâmetros de entrada de cada modelo, obtêm-se cenários de produção de biogás e estimativas da capacidade de geração máxima e mínima de lixiviado para o aterro sanitário de Guajuviras (Canoas - RS, Brasil). Tomando os resultados de geração de lixiviado e de biogás calculados, estima-se o potencial energético disponível e o desempenho de três diferentes sistemas de conversão energética propostos: geração elétrica por motogeradores, evaporação de lixiviado em regime de cogeração com motogeradores, motogeradores com trocadores de calor em regime de cogeração e sistema de evaporação de lixiviado (LES). Resultados obtidos para o período analisado, mostram que a produção elétrica do cenário mais conservador está na faixa entre 17.300 a 18.800 MWh, enquanto que a produção de energia elétrica do cenário otimista atinge valores entre 416.976 e 459.900 MWh. Já para a evaporação de lixiviado, os volumes evaporados em regime de cogeração variaram de 1 a 70% em relação ao volume de lixiviado gerado pelo aterro sanitário, enquanto que o LES, considerando o cenário otimista, foi capaz de evaporar 100% do lixiviado durante 18 anos. / The growing concern on environmentally suitable and energy efficient solutions allied with the recent changes in the Brazilian policies on the solid waste management and its final disposal practices, enables an opportunity to investigate the energy recovery and abatement of landfills emissions. The present work explores separately the utilization of 1st order decay model for assess the landfill gas (LFG) production, and applies the water budget method for prediction of leachate generation. Ranging the main input parameters on each model, were obtained distinct scenarios for LFG production and the maximum and minimum leachate generation capacity of Guajuviras landfill (Canoas- RS, Brazil). Based in the calculated results for leachate and LFG production were assessed the available energetic potential and the performance of three distinct energetic conversion systems: motogenerators, heat exchangers in cogeneration with motogenerators and leachate evaporation system (LES). Results for the analyzed period show that the electric generation for conservative scenario ranges between 17.300 to 18.800 MWh, whereas, the electricity production for more optimistic scenario ranges between 416.976 to 459.900 MWh. As for the leachate evaporation, the evaporated volume by the cogeneration system reaches values between 1 to 70% of the leachate produced by the landfill, whereas, the LES, considering the optimistic scenario, is able to evaporate all the generated leachate by the landfill among 18 years.
68

Energy Release Rate Characterization of Additively Manufactured Al/PVDF with Varying Infill Densities and Patterns

Alexander Charles Ca Hoganson (12879233) 16 June 2022 (has links)
<p>  </p> <p>The additive manufacturing of energetic materials is a novel way to alter the properties of an energetic material without necessarily changing its chemical structure. There are many methods of additive manufacturing which can be applied to energetic material fabrication, each of which have unique advantages and disadvantages. The most well characterized additive manufacturing method is the commercially refined technique of fused filament fabrication (FFF) printing. FFF manufacturing techniques can be applied to additively manufacture thermoplastic energetic materials. The thermoplastic aluminum and polyvinylidene difluoride (Al/PVDF) system is suitable for manufacture with FFF techniques, shapeable into pyrotechnics with custom geometries using commonly available FFF printers. This theoretically allows Al/PVDF systems to be tailored for a wide variety of multifunctional needs, such as reactive structures. Following a literature review describing energetic material additive manufacturing techniques, this thesis focuses on the creation of outwardly identical Al/PVDF samples and the use of a geometric correction factor to control for uneven feedstock diameter. By varying the infill pattern, infill density, and interior geometry, different sample energy densities were obtained and observed during combustion. High speed videography measurements and the mass of individual samples were used to estimate the overall energy release rate. An Ashby plot contrasting the energy density and energy release rate was obtained. While full density printed samples burned similar to cast propellant strands in a linear burn, the energy release rates of additively manufactured Al/PVDF could be increased via convective combustion by varying the infill type and density. These results have significance for the fields of structural energetic materials and for additive manufacturing studies of energetic materials.</p>
69

Comparação de indicadores de eficiência energética e exergética em duas indústrias do setor sucroalcooleiro / Comparison of indicatives of energetic and exergetic efficiency in two industries of sugar-alcohol sector

Schirmer, Florian 27 June 2006 (has links)
Made available in DSpace on 2017-07-10T19:25:07Z (GMT). No. of bitstreams: 1 Florian Schirmer.pdf: 2016231 bytes, checksum: 57aa2561433d1c4c0448c03930721ca7 (MD5) Previous issue date: 2006-06-27 / This work has an objective to study and to compare energetic and exergetic indicatives of two sugar and alcohol sector industry. The study was realized in 2005 harvest time at both industries. It was opted in doing the experiment collecting datas from individual boilers in each industry, quantity of ground cane, properties of cane and bagasse, quantity of energy involved in process per sectors, commercialized energy with the concession of each region and characteristics of each equipment involved in the process. The data were collected from respective department data-bank and through interviews with the responsibles for each sector, being the work based on studies done by diary and monthly average from collected data. The results pointed that each analyzed industry has different indicators for each studied data. The study states that both factories need more efficient equipments. And exergetic indicators presented results next to the studies done to Vale do Rosário Factory and mentioned on this work. / Este trabalho teve como objetivo estudar e comparar indicativos energéticos e exergéticos de duas indústrias do setor sucroalcooleiro. O estudo foi realizado no período de safra 2005 em ambas as indústrias. Optou-se em se fazer o experimento utilizando-se dados das caldeiras individualmente em cada indústria, quantidade de cana moída, propriedades da cana e do bagaço, quantidade de energia envolvida no processo por setores, energia comercializada com a concessionária de cada região e características de cada equipamento envolvido no processo. Os dados foram colhidos dos bancos de dados dos respectivos departamentos e por meio de entrevistas com os responsáveis de cada setor, sendo o trabalho baseado em estudos feitos pelas médias diárias e mensais dos dados coletados. Os resultados apontaram que cada indústria analisada tem indicadores diferentes para cada dado estudado. O estudo comprova que ambas as usinas necessitam de equipamentos mais eficientes. Já os indicadores exergéticos apresentaram resultados muito próximos aos do estudo feito para a Usina Vale do Rosário e mencionados neste trabalho.
70

Comparação de indicadores de eficiência energética e exergética em duas indústrias do setor sucroalcooleiro / Comparison of indicatives of energetic and exergetic efficiency in two industries of sugar-alcohol sector

Schirmer, Florian 27 June 2006 (has links)
Made available in DSpace on 2017-05-12T14:48:29Z (GMT). No. of bitstreams: 1 Florian Schirmer.pdf: 2016231 bytes, checksum: 57aa2561433d1c4c0448c03930721ca7 (MD5) Previous issue date: 2006-06-27 / This work has an objective to study and to compare energetic and exergetic indicatives of two sugar and alcohol sector industry. The study was realized in 2005 harvest time at both industries. It was opted in doing the experiment collecting datas from individual boilers in each industry, quantity of ground cane, properties of cane and bagasse, quantity of energy involved in process per sectors, commercialized energy with the concession of each region and characteristics of each equipment involved in the process. The data were collected from respective department data-bank and through interviews with the responsibles for each sector, being the work based on studies done by diary and monthly average from collected data. The results pointed that each analyzed industry has different indicators for each studied data. The study states that both factories need more efficient equipments. And exergetic indicators presented results next to the studies done to Vale do Rosário Factory and mentioned on this work. / Este trabalho teve como objetivo estudar e comparar indicativos energéticos e exergéticos de duas indústrias do setor sucroalcooleiro. O estudo foi realizado no período de safra 2005 em ambas as indústrias. Optou-se em se fazer o experimento utilizando-se dados das caldeiras individualmente em cada indústria, quantidade de cana moída, propriedades da cana e do bagaço, quantidade de energia envolvida no processo por setores, energia comercializada com a concessionária de cada região e características de cada equipamento envolvido no processo. Os dados foram colhidos dos bancos de dados dos respectivos departamentos e por meio de entrevistas com os responsáveis de cada setor, sendo o trabalho baseado em estudos feitos pelas médias diárias e mensais dos dados coletados. Os resultados apontaram que cada indústria analisada tem indicadores diferentes para cada dado estudado. O estudo comprova que ambas as usinas necessitam de equipamentos mais eficientes. Já os indicadores exergéticos apresentaram resultados muito próximos aos do estudo feito para a Usina Vale do Rosário e mencionados neste trabalho.

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