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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.
1

Modeling And Control Of High Temperature Oven For Low Temperature Co-fired Ceramic (ltcc) Device Manufacturing

Yucel, Ayse Tugce 01 October 2012 (has links) (PDF)
In the electronics the quality, reliability, operational speed, device density and cost of circuits are fundamentally determined by carriers. If it is necessary to use better material than plastic carrier, it has to be made of ceramics or glass-ceramics. This study dealt with the ceramic based carrier production system. The types of the raw ceramics fired at low temperature (below 1000&deg / C) are called Low Temperature Co-Fired Ceramics (LTCC). In this study, a comprehensive thermal model is described for the high temperature oven which belongs to a Low Temperature Co-fired Ceramic (LTCC) substance production line. The model includes detailed energy balances with conduction, convection and radiation heat transfer mechanisms, view factor derivations for the radiative terms, thermocouple balances, heating filaments and cooling mechanisms for the system. Research was conducted mainly on process development and production conditions along with the system modeling of oven. Temperature control was made in high temperature co-firing oven. Radiation View Factors for substrate and thermocouples are determined. View factors between substrate and top-bottom-sides of the oven are calculated, and then inserted into the energy balances. The same arrangement was made for 3 thermocouples at the bottom of the oven. Combination of both expressions gave the final model. Modeling studies were held with energy balance simulations on MATLAB. Data analysis and DOE study were held with JMP Software.
2

Assessment of thermal radiation arithmetic's for jet flames : A study involving generic calculation methods concerning radiation from jet flames with the purpose to determine the safety distance for flame effects

Anderson, Anne Lee January 2018 (has links)
Jet flames are commonly used as flame effects in pyrotechnical shows, and are also a possible risk in industries that uses pressurised flammable gas. For these users it is important to  make fire safety engineering calculations to minimise the risks. This project focus on jet flames that are used in pyrotechnic shows where, e.g. it is important to determine the safety distance to the audience. Up to now most studies made concerning jet flames regards jet flames in subsonic regiments, whilst there is a lack of studies concerning sonic jet flames and mathematical formulations for radiation from these cases are limited. This makes pre-determination of temperatures, safety distances, flame heights etc. a challenge. Based on information found, and assumptions when needed, calculations of the safety distance were made.
3

The relationship between sky view factor and the brightness of the night sky

Törmänen, Samuel January 2024 (has links)
Light pollution is a problem that affects both living creatures as well as the perception of the night sky. As artificial lighting becomes more affordable and energy efficient, more and more lights are being used, further increasing the light pollution produced by us humans where cities with larger populations experience the largest amount of light pollution. There is however a knowledge gap in the field of light pollution regarding the possibility of a relationship between sky view factor and the brightness of the night sky. This study attempts to reduce that knowledge gap. By using cameras to take photos in different locations, the brightness of the night sky can be compared and together with the sky view factor of each location in can be determined if there exist such a relationship. Based on the results of this study, trends suggesting that this relationship exists emerges, however not to the extent that any definite conclusions can be drawn without further studies.
4

Mitigating Urban Heat Island through Integration of Agriculture in the Built Environment in Arid Regions

Gaxiola Camacho, Ivan Eladio January 2016 (has links)
Consequences of human activity in natural environments can be observed in urban phenomena. Urban Heat Island is one of those consequences, it is characterized by higher temperature levels in surface-cover and air in urban centers compared with its surrounding rural areas. UHIs are present in cities of arid ecosystems such as Phoenix and Tucson. Existing urban development trends contribute to UHI episodes. Urban Agriculture (UA) is an emerging environmental strategy and, contrary to traditional and industrial agricultural methods, UA systems provide the option of not using soil, its geometrical arrangement lets grow crops disregarding of extensive surface of land to be consumed. UA systems can be implemented as building fabric components. Urban Agriculture provides access to healthier and economic food, it is more energy efficient and promotes a more vegetarian diet which can eventually contribute diminishing health problems such as obesity and toxicity. A response for achieving a decrease in temperature levels in an urban arid region scenario can be established by demonstrating the following premise: "Urban Heat Island effect in arid regions can be mitigated if vegetated surface in the form of agriculture is properly integrated in the built environment". Research procedures were applied at building scale. Results involved physical objective data acquisition. Research methods required the use of software and thermodynamic tools to measure thermal behavior of samples. The impact of vegetated cover in temperature levels and thermal comfort in an outdoor scenario was digitally simulated. The selected research case contributed as a source of data for comparison and baseline benchmarking of thermodynamic circumstances. Employment of green infrastructure in cities can contribute to the improvement of energy efficiency in buildings and developing self-sufficient communities. Urban agriculture comprises implications and side beneficial environmental consequences in arid habitats beyond decreasing temperature levels in cities, such effects are energy conservation, reducing air pollution, diminishing food security concerns, improving soil quality and runoff wastewater as well as cutting down fossil fuel use in transportation of food. In that sense, future research fields include water quality and availability, innovative emerging materials, climate analysis, societal and cultural value, Net zero development and energy efficiency as well as solid waste management.
5

Radiation and Convection Heat Transfer in Wildland Fire Environments

Frankman, David J. 14 July 2009 (has links) (PDF)
Wildland fire research has been extensive and on going since before 1950. The motivation behind this research is to prevent loss of property and lives. In spite of this research, the heat transfer of fuel ignition and flame spread is not well understood. This dissertation seeks to fill gaps in this understanding through modeling and also by experimentation. The effect of water vapor on the transmission of thermal radiation from the flame to the fuel was investigated. The Spectral Line Weighted-sum-of-gray-gases approach was adopted for treating the spectral nature of the radiation. The study reveals that water vapor has only a moderate effect even at 100 percent humidity. Experiments were conducted wherein wood shavings and Ponderosa pine needles in quiescent air were subjected to an imposed radiant heat flux. The internal temperature of these particles was measured and compared to steady-state model predictions. Excellent agreement was observed between the model predictions and the experimental data. Exercise of the model led to the conclusion that ignition of the fuel element by radiation heating alone is unlikely. Time-resolved radiation and convection heat flux were measured in a series of experimental laboratory fires designed to explore heat transfer behavior during combustion of discontinuous fuel beds. Convection heat flux was shown to fluctuate between positive and negative values during flame engulfment, indicating the presence of alternating packets of hot combustion gas and cool ambient air within the flame. Rapid temporal fluctuations were observed in both radiation and convection. Spectral analysis revealed content at frequencies as high as 150 to 200 Hz. Time-resolved radiation and convection heat flux histories were also collected on fourteen controlled burns and wildfires. The data reveal significant temporal fluctuations in both radiation and convection heat flux. Spectral analysis using a Fast Fourier Trans-form (FFT) revealed content as high as 100 Hz using data sets that were sampled at 500 Hz. The role of the higher frequency convective content in fuel thermal response was explored using a one-dimensional transient conduction model with a convective boundary condition. It was shown that high-frequency (i.e., short-duration) convective pulses can lead to fine fuel ignition.
6

The Effect of Baffles and Entrance Ports on the Measured Reflectance of Diffuse and Specular Samples in the Integrating Sphere

Duncan-Chamberlin, Katherine V. 03 June 2015 (has links)
No description available.
7

Detekce terénních hran s využitím nástroje sky view faktor / Terrain break-lines detection based on Sky View Factor

Englmaierová, Tereza January 2019 (has links)
Terrain Breakline Detection Using Sky-view factor Abstract The subject of this diploma thesis is to propose the procedure of detecting of terrain breaklines using Sky-view factor. The theoretical part of the diploma thesis first introduces the issue of terrain breaklines detection, which presents the methods known to date and Sky- view factor, which is the focal point of the proposed method. Implementation over real data takes place at four locations in the Czechia (Vítkovice, Hradiště, Strnady and Velenka). Data in the form of raster format is tested. At the end, the results of the proposed method and its verification using two selected methods of field edge detection are presented and evaluated. Achieved results point to Sky-view factor for terrain edge detection. Keywords: terrain breakline, digital terrain model, Sky-view factor, detection terrain breaklines methods
8

Detekce terénních hran s využitím nástroje sky view faktor / Terrain break-lines detection based on Sky View Factor

Englmaierová, Tereza January 2019 (has links)
Terrain Breakline Detection Using Sky-view factor Abstract The subject of this diploma thesis is to propose the procedure of detecting of terrain breaklines using Sky-view factor. The theoretical part of the diploma thesis first introduces the issue of terrain breaklines detection, which presents the methods known to date and Sky- view factor, which is the focal point of the proposed method. Implementation over real data takes place at four locations in the Czechia (Vítkovice, Hradiště, Strnady and Velenka). Data in the form of raster format is tested. At the end, the results of the proposed method and its verification using two selected methods of field edge detection are presented and evaluated. Achieved results point to Sky-view factor for terrain edge detection. Keywords: terrain breakline, digital terrain model, Sky-view factor, detection terrain breaklines methods
9

Staden i Arenastaden / The city within Arenastaden

Öberg, Marcus, Valdebenito, Marcelo January 2014 (has links)
Ett mycket högexploaterat förslag utformas där en egen identitet skapas åt Arenastaden i Växjö. Solens gång, bullerkällor, brandrisker, kulturhistoriska värden och många mål i kommunens visionsbild för Arenastaden väger in vid utformning av förslaget. Förslagets nya upplevelsevärden och andra kvalitéer analyseras med hjälp av en solstudie, bullerkällsundersökning och analysmetod av Kevin Lynch. Projektuppgiften är baserad på att en mycket hög exploatering drar ner på områdets upplevelsevärden. Då analysens resultat föll annorlunda erhölls ett annat resultat – metoden; att bygga på höjden besparar grönytor och de värden som mäts vid en Lynchanalys.
10

Conforto térmico e tempo de permanência em espaços abertos de lazer: Influência de diferentes níveis de sombreamento / Thermal comfort and exposure time in open spaces of leisure: Influence of different levels of shading

Faustini, Fabiana Benevenuto 20 October 2017 (has links)
Submitted by Fabiana Benevenuto Faustini null (fab_bf@hotmail.com) on 2018-09-26T04:31:37Z No. of bitstreams: 1 DISSERTAÇAO FINAL_ULTIMA CORREÇÃO.pdf: 4446072 bytes, checksum: f8eb255af14f0286951d1f51ea8e76bb (MD5) / Approved for entry into archive by Lucilene Cordeiro da Silva Messias null (lubiblio@bauru.unesp.br) on 2018-09-26T16:43:56Z (GMT) No. of bitstreams: 1 faustini_fb_me_bauru.pdf: 4446072 bytes, checksum: f8eb255af14f0286951d1f51ea8e76bb (MD5) / Made available in DSpace on 2018-09-26T16:43:56Z (GMT). No. of bitstreams: 1 faustini_fb_me_bauru.pdf: 4446072 bytes, checksum: f8eb255af14f0286951d1f51ea8e76bb (MD5) Previous issue date: 2017-10-20 / A sensação de conforto térmico experimentada pelos usuários de espaços abertos de lazer, como praças, parques, bosques, entre outros, pode afetar positiva ou negativamente a quantidade de usuários, atividades desenvolvidas, além do tempo de permanência das pessoas. No entanto, essa relação entre conforto térmico e tempo de permanência ainda é pouco estudada, fato que justifica a importância desta pesquisa, que busca investigar essa relação em um espaço aberto de lazer. O estudo foi desenvolvido em um parque Zoológico, na cidade de Bauru-SP, através da coleta de dados objetivos (medições microclimáticas e quantificação de pessoas), e subjetivos (aplicação de questionários) em dois subespaços com mesma atratividade (área de felinos) e diferentes Fatores de Visão do Céu (FVC), em duas condições de tempo, quente e ameno. Esses dados permitiram identificar os Votos de Sensação Real (ASV), calcular o índice PET (Temperatura Equivalente Fisiológica), verificar a preferência térmica dos usuários e registrar o tempo de permanência em cada subespaço, nas condições de tempo analisadas. Os resultados evidenciam a estreita relação entre FVC e o tempo de permanência em determinado espaço. Destaca-se ainda: 1. Maior frequência de sensação térmica de conforto dos usuários na área com maior sombreamento, nas condições de tempo quente, e frequências de sensação térmica equivalentes nos dois subespaços em condições de tempo ameno. 2. Nas condições de tempo quente, permanência de curta duração dos usuários nas áreas de alta incidência de radiação solar direta e faixa de neutralidade do índice PET variada em relação aos dois subespaços. 3. Em situações de desconforto por calor, o tempo de permanência é reduzido em função do FVC, e a atração passa a ser um aspecto secundário, ou seja, o maior interesse se torna a busca por um local mais confortável. / The sensation of thermal comfort experienced by the users of leisure open places, such as squares, parks, woods, among others, may positively or negatively affect the amount of users, developed activities, and permanency time of people. However, this relation between thermal comfort and exposure time is still poorly studied, fact that justifies the importancy of this research, that seeks to investigate this relation in an leisure open place. The study was developed in a Zoo Park, in Bauru-SP, trough objective data collect (microclimatic measurements and quantification of people), and subjective data collect (questionnaires application) in two subspaces with the same attractiveness (feline area) and different Sky View Factors (SVF), under two weather conditions, hot and mild. These data allowed to indentify the Actual Sensation Votes (ASV), to calculate the PET index (Physiological Equivalent Temperature), verify the thermal preference of the users and record the exposure time in each subspace, under the microclimatic conditions analyzed. The results show the narrow relation between SVF and the exposure time in a given space. It also shows: 1. Higher frequency of thermal sensation of comfort of the users in the area with greater shading, in hot weather conditions, and equivalent thermal sensation frequencies in the two subspaces in mild weather conditions. 2. In hot weather conditions, permanency of short duration of the users in the areas of high incidence of direct solar radiation and neutrality range of the PET index varied in relation to the two subspaces. 3. In situations of heat discomfort, the permanecy time is reduced in function of the SVF, and the attraction turns into a secondary aspect, that is, the greater interest becomes the search for a more comfortable place.

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