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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.
681

CFD Flame Spread Model Validation: Multi-Component Data Set Framework

Wong, William Chiu-Kit 30 July 2012 (has links)
"Review of the literature shows that the reported correlation between predictions and experimental data of flame spread vary greatly. The discrepancies displayed by the models are generally attributed to inaccurate input parameters, user effects, and inadequacy of the model. In most experiments, the metric to which the model is deemed accurate is based on the prediction of the heat release rate, but flame spread is a highly complex phenomenon that should not be simplified as such. Moreover, fire growth models are usually made up of distinctive groups of calculation on separate physical phenomena to predict processes that drive fire growth. Inaccuracies of any of these “sub-models” will impact the overall flame spread prediction, hence identifying the sources of error and sensitivity of the subroutines may aid in the development of more accurate models. Combating this issue required that the phenomenon of flame spread be decomposed into four components to be studied separately: turbulent fluid dynamics, flame temperature, flame heat transfer, and condensed phase pyrolysis. Under this framework, aspects of a CFD model may be validated individually and cohesively. However, a lack of comprehensive datasets in the literature hampered this process. Hence, three progressively more complex sets of experiments, from free plume fires to fires against an inert wall to combustible wall fires, were conducted in order to obtain a variety of measurements related to the four inter-related components of flame spread. Multiple permutations of the tests using different source fuels, burner size, and source fire heat release rate allowed a large amount of comparable data to be collected for validation of different fire configurations. FDS simulations using mostly default parameters were executed and compared against the experimental data, but found to be inaccurate. Parametric study of the FDS software shows that there are little definitive trends in the correlation between changes in the predicted quantities and the modeling parameters. This highlights the intricate relationships shared between the subroutines utilized by FDS for calculations related to the four components of flame spread. This reveals a need to examine the underlying calculation methods and source code utilized in FDS."
682

BRANDSKYDDAT TRÄ : Jämförelse mellan obehandlat, brandskyddsmålat och brandskyddsimpregnerat trä

Neumann, Dorothea January 2015 (has links)
Environmental issues and the housing shortage is an ongoing debate among politicians. Wood is a building material that Sweden has plenty of and it is a material that, according to research, does not contribute to as much carbon dioxide emissions during production, compared to other construction materials such as concrete and steel. Therefore the demand for timber, in both facade claddings and external wall constructions, is increasing. In light of this, the purpose with this degree project is to study different fire protection methods for wood and compare it to untreated wood. Collecting the facts and information for this degree project at Mälardalens University, is done through literature studies, surveys, and two experiments conducted on two selected fire retardants. The experiments were conducted to test untreated, fire protection impregnated and wood with fire proof paint. One of the experiments tested the load-carrying capacity of the beams after being charred with a gas burner. The other experiment investigated the surface layer and measured the fire spread rate and both experiments tested the fire resistance. The experiments that were conducted concluded that out of the three different methods for facades and beams, fire protection impregnation was the best choice in all five chosen categories: load-carrying capacity, fire resistance, surfaces, environmental impact and health safety for workers. / Miljöfrågan och bostadsbristen är två pågående debatter bland politikerna. Ett byggmaterial som både är miljövänligt och lätt att bygga med är trä. Det är ett byggmaterial som Sverige har gott om och enligt forskning bidrar det inte med lika mycket koldioxidutsläpp vid produktionen jämfört med andra konstruktionsmaterial som betong och stål. Enligt äldre bygglagstiftningar var det enbart tillåtet att bygga hus med två våningar i trä. Det var godkänt att bygga hus med tre våningar om den nedersta våningen bestod utav sten och de två översta i trä. Den nya bygglagstiftningen har inga begränsningar på att använda trä i ytterväggar, oberoende av byggnadsklass så länge de uppfyller funktionskraven. Byggsektorn har varit medveten om att de fick bygga flervåningshus i trä men inte hur det skulle utföras och samtidigt uppfylla bygglagstiftningens krav. Resultatet av ändringarna i bygglagstiftningen, Boverkets byggregler, ökade efterfrågan och utbudet på brandskyddsmedel till trä. De vanligaste produkterna som finns ute för konsumenten är brandskyddsfärg och brandskyddsimpregnering. Trä kan genom brandskyddsimpregnering eller brandskyddsfärg få en brandteknisk klass enligt det europeiska systemet, EN 13501-1, upp mot B-s1,d0 som är högre än för obehandlat trä, Ds1, d0. Tekniskt sett går det att bygga Br1-byggnader med obehandlat trä, dock så krävs det ett antal åtgärder för att uppfylla Boverkets byggreglers funktionskrav, till exempel att installera automatiska släcksystem eller enbart ha trä på en begränsad del av fasaden. Med brandskyddsbehandling går det idag endast att uppnå brandteknisk ytskiktsklass B-s1,d0, vilket inte är tillräckligt enligt Boverkets byggregler som kräver lägst obrännbara fasadbeklädnader i ytskiktsklass A2-s1,d0 för att uppfylla allmänna råden. Fasadbeklädnader av trä, oavsett brandteknisk klass, kan testas med provmetoden SP FIRE 105 och därmed uppfylla föreskriftens krav på ytterväggskonstruktioner med avseende på brandspridning längs fasadytan. Syftet med arbetet är att jämföra olika brandskyddsmetoder av trä och undersöka vilken eller vilka som är bäst lämpad att använda i flervåningshus ur bland annat miljö-, arbetsmiljö- och brandsynpunkt. Detta uppnås genom en litteraturstudie som fokuserar på ämnet brandskyddsmetoder av trä och genom två försök genomfördes för att testa obehandlat, brandskyddsimpregnerat och brandskyddsmålat trä. Ett försök testade bärförmågan efter brandpåverkan, andra undersökte ytskikt, och båda försöken testade brandmotstånd. Bärförmågan testades genom att brandpåverkade reglar blev utsatta för en central punktlast i en Instron- maskin. Ytskikten prövades genom ett enklare försök baserad på testmetoden SP FIRE 105 på tre fasader. En obehandlad, en brandskyddsimpregnerad och en brandskyddsmålad. Mätningar och dokumentation gjordes med bland annat mätinstrument som plattermoelement och filmkamera. Båda typerna av brandskyddsmetoder kräver en kemisk framställning som varken är bra för naturen eller människan. Produktionen är automatiserad och därmed inte någon risk för någon människa. Den färdiga produkten är varken skadlig för miljön, människor eller djur, sålänge inte produkterna förtärs i större omfattning. Resultatet från undersökningen av de tre olika fasaderna visade att det brandskyddsimpregnerade virket klarade sig bäst i alla fem kategorier: bärförmåga, brandmotstånd, ytskikt, miljöpåverkan och arbetsmiljö. Slutsatsen är av det två typer av brandsskyddsmedel för trä som testades, är brandskyddsimpregnering den mest lönsammaste alla fem kategorier. Produkten är lätthanterad, avger inga farliga gaser och är i snitt inte dyrare än det obehandlade materialet. Dock är det viktigt att tänka på brandskyddsarbete och inte släppa på säkerheten för att konstruktionen byggs med brandskyddsimpregnerat trä.
683

LOW COST SUBMINIATURE TELEMETRY SPREAD SPECTRUM TECHNOLOGY DEMONSTRATION/VALIDATION

Thursby, William R. Jr, Shirley, Benjamin M. 11 1900 (has links)
International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / Eglin Air Force Base (AFB) plans to demonstrate subminiature telemetry (SMT) spread spectrum technology, via an upgraded prototype SMT system, to validate its cost-effectiveness for both Department of Defense (DoD) and commercial use. The goal is to develop new and/or modify current SMT instrumentation using existing production methods to provide increased capabilities at lower costs and reduced size. The transmitter is to require less than 2 cubic inches of space and have a cost goal of $500/unit "in quantity." The cost goal of a ground-based, 24-channel capable ground receiver is $4000/unit "in quantity". The SMT project as well as its schedule, flight and ground demonstrations, validation criteria and goals, and various benefits are discussed.
684

Measuring liquefaction-induced deformation from optical satellite imagery

Martin, Jonathan Grant 11 September 2014 (has links)
Liquefaction-induced deformations associated with lateral spreading represent a significant hazard that can cause substantial damage during earthquakes. The ability to accurately predict lateral-spreading displacement is hampered by a lack of field data from previous earthquakes. Remote sensing via optical image correlation can fill this gap and provide data regarding liquefaction-induced lateral spreading displacements. In this thesis, deformations from three earthquakes (2010 Darfield, February 2011 Christchurch, and 2011 Tohoku Earthquakes) are measured using optical image correlation applied to 0.5-m resolution satellite imagery. The resulting deformations from optical image correlation are compared to the geologic conditions, as well as field observations and measurements of liquefaction. Measurements from optical image correlation are found to have a precision within 0.40 m in all three cases, and results agree well with field measurements. / text
685

指數分布的聯立統計推論之研究

毛又安, MAO, YOU-AN Unknown Date (has links)
本文主要是研究統計理論中的聯立信賴區間估計法,針對雙特徵數的指數母體,研究 位置特徵數的差異狀況。也就是要找出位置特徵數的所有複合比,所有對比的聯立信 賴區間。全文共分四章。第一章緒論,說明研究動機、目的及方法。第二章指數分布 的順序統計式,由於本文所使用的估計方法會使用到順序統計式,所以在本章中特別 研究順序統計式的某些線性組合,找出某些特殊的性質;並且將Tanis (1963) 提出的理論擴展至第二型設限數據。第三章位置特徵數的聯立信賴區間,藉由第二章 中導出的定理以Tukey 法及Holder不等式法找出聯立信賴區間,並且比較這些方法的 優劣。第四章結論及建議。全文共一冊,約兩萬字。
686

Sosnovskio barščio (Heracleum sosnowskyi Manden) ir uosialapio klevo (Acer negundo L.) plitimo ypatumai / Spread peculiarities of Sosnowski's hogweed (Heracleum sosnowskyi Manden) and box elder (Acer negundo L.)

Valantinaitė, Audronė 01 June 2011 (has links)
Sosnovskio barščio ir uosialapio klevo plitimo tyrimai buvo atliekami Pasvalio ir Kauno rajonuose. Tyrimo metu buvo nustatoma šių augalų plitimo ypatumai, efektyviausios kontrolės priemonės, invazijos agresyvumo lygmenys. Gauti tyrimai parodė, kad vanduo daro didesnę įtaką uosialapio klevo išplitimo atstumams nei vėjas, nes jų buvo aptinkama visame 10 km tirtos upės pakrantės ruože, o toliausiai vėjo pagalba atsiradę savaiminukai buvo aptikti iki 100 metrų nuo motininio medžio. Šie augalai dera gausiai, vidutiniškai vienas uosialapio klevo medis subrandina 70 tūkst. Sėklų. Sosnovskio barščio 1 m2 aptikta apie 7,5 tūkst. sėklų. Veiksmingiausia kontrolės priemonė uosialapiui klevui yra mažų savaiminukų naikinimas, nes kertant paaugusius medžius jie sėkmingai atželia iš kelmo ataugų. Sosnovskio barščio kontrolei, jų kasimas yra veiksmingiau nei purškimas, nes kasant atželia 45 % naikinamų augalų, o tik purškiant – 85 %. Apskaičiuotas invazyvumo lygmuo parodo, jog Sosnovskio barštis yra invazyvesnis nei uosialapis klevas. Uosialapio klevo invazyvumo lygmuo yra 0,42, o Sosnovskio barščio - 0,56. / The research on the spread of heracleum sosnowskyi and acer negundo was carried out in the regions of Pasvalys and Kaunas. The research focuses on the spread features of these plants, most effective control measures and the level of invasion. The results showed that water had larger influence on the spread of acer negundo than wind as some spontaneous trees were found in all 10 kilometers onshore area. The longest distance from the parent tree revealed to be approximately 100 meters. These plants fruit abundantly, approximately one mature tree of acer negundo produces 70 thousands of seeds. Heracleum sosnowskyi matures about 7.5 thousands of seeds / 1 m2. The most effective control measure of acer negundo is destroying spontaneous seedlings because cutting of the grown trees isn’t effective, they regrow from the stumps. For a control of heracleum sosnowskyi digging is more effective than spraying, because 45 % of the spontaneous seedlings regrow after digging while 85 % of them regrow after spraying. Calculated level of invasion shows that heracleum sosnowskyi is more invasive than acer negundo. A level of invasion of acer negundo is 0.42, heracleum sosnowskyi – 0.56.
687

The development of an intelligent ray launching algorithm for wireless network planning

Lai, Zhihua January 2010 (has links)
Current propogation models are no longer sufficient for wireless network planning. They are neither accurate (empirical) nor fast enough (deterministic) to be applicable in the applications of Automated Cell Planning. This thesis focuses on the development of a new method, namely Intelligent Ray Launching Algorithm (IRLA), which is based on a fast, accurate and robust algorithm that is especially suitable for wireless network planning. The infrastructure of IRLA is thoroughly analysed in this thesis and the results are presented. Foster's design methodology has been used to parallelise the new model. Various scenarios for outdoor, indoor, indoor-to-outdoor and outdoor-to-indoor settings have been employed to test the effectiveness and efficiency of IRLA. The field strengths (path loss) and multipath information were calculated, which were used to demonstrate the application of IRLA. The accuracy of IRLA is guaranteed via the use of a meta-based heuristics calibration procedure. In order to achieve a simulation within a realistic time scale, acceleration techniques such as avoid double marking, multi-threading and the use of Parallel Object-Oriented Programming C++ have been employed. Since multipath for a large number of receiver locations can be easily obtained via IRLA, the study of delay spread has been presented. The success of the integration with a wireless network planning platform exemplifies that IRLA is suitable for wireless network planning and optimisation, which is beneficial to relevant academics and industries. Testing demonstrated that depending on various scenarios, IRLA obtains industrially-recognised accuracy ranging from 5 to 8 dB Root-Mean-Square-Error. This model is highly-efficient because its required runtime for most simulations is from a few seconds to a few minutes.
688

Approche cartésienne pour le calcul du vent en terrain complexe avec application à la propagation des feux de forêt

Proulx, Louis-Xavier 01 1900 (has links)
La méthode de projection et l'approche variationnelle de Sasaki sont deux techniques permettant d'obtenir un champ vectoriel à divergence nulle à partir d'un champ initial quelconque. Pour une vitesse d'un vent en haute altitude, un champ de vitesse sur une grille décalée est généré au-dessus d'une topographie donnée par une fonction analytique. L'approche cartésienne nommée Embedded Boundary Method est utilisée pour résoudre une équation de Poisson découlant de la projection sur un domaine irrégulier avec des conditions aux limites mixtes. La solution obtenue permet de corriger le champ initial afin d'obtenir un champ respectant la loi de conservation de la masse et prenant également en compte les effets dûs à la géométrie du terrain. Le champ de vitesse ainsi généré permettra de propager un feu de forêt sur la topographie à l'aide de la méthode iso-niveaux. L'algorithme est décrit pour le cas en deux et trois dimensions et des tests de convergence sont effectués. / The Projection method and Sasaki's variational technique are two methods allowing one to extract a divergence-free vector field from any vector field. From a high altitude wind speed, a velocity field is generated on a staggered grid over a topography given by an analytical function. The Cartesian grid Embedded Boundary method is used for solving a Poisson equation, obtained from the projection, on an irregular domain with mixed boundary conditions. The solution of this equation gives the correction for the initial velocity field to make it such that it satisfies the conservation of mass and takes into account the effects of the terrain. The incompressible velocity field will be used to spread a wildfire over the topography with the Level Set Method. The algorithm is described for the two and three dimensional cases and convergence tests are done.
689

Brandspridning i äldre trähusbebyggelse : Brandskyddsinventering av Rademachersmedjorna i centrala Eskilstuna

Ingelmark, Oscar January 2014 (has links)
It is very important to protect buildings against fire. Especially older wooden buildings and areas with a historically important heritage, i.e. areas that cannot be restored to their original condition upon loss. In Eskilstuna one such area is located - Rademachersmedjorna. On behalf of Eskilstuna Kommunfastigheter AB a documentation of Rademachersmedjorna’s constructional fire protection has been conducted in this report in order to have the area's fire protection level documented. The purpose of this study has been, via systematic field studies, to provide an overview of Rademachersmedjorna and document the area’s current fire protection level. Based on this information, a visualization of the area's constructional fire protection and risk zones has been developed to give a simple overview for users, managers and owners. The inventory can be used by Eskilstuna Kommunfastigheter AB for a quick and easy visualization of Rademachersmedjorna’s fire protection level and risk zones. Furthermore, this information could be used as a basis for planning future safety prevention efforts. The documentation over the area is based on the assessment method Bedömning av brandskydd i kulturbebyggelse (hereafter referred to as BSV-k) and the parts this method includes. There are a total of 16 buildings at the Rademacher area and only one building achieved an acceptable fire protection level according to BSV-k. There are several zones in the area that pose a higher risk for the occurrence of fire and fire spread. These higher vulnerable fire hazard zones are spread out over Rademachersmedjorna which means that the whole area quickly can get involved in case of fire. In this context it is important to avoid fire what so ever may arise. Removing combustible material in escape routes, in attics and combustible materials nearby the buildings are some fire prevention measures which can be applied. It is also important to note objects such as bins and wooden planks that exist between the buildings being potential fire carriers. In cases where the buildings distance to a nearby located building is very short, the potential fire carriers pose little threat as the fire can spread directly from building to building. To achieve an acceptable level of fire protection for Rademachersmedjorna - according to this study's assessment method - is sufficient in many cases to apply fire prevention.
690

The Regulatory Arbitrage between Basel III and Solvency II: The Role of Alternative Risk Transfers Demonstrated on CDS Spreads - The Case of Italy / The Regulatory Arbitrage between Basel III and Solvency II: The Role of Alternative Risk Transfers Demonstrated on CDS Spreads - The Case of Italy

Budská, Petra January 2014 (has links)
Different capital regulatory requirements in the bank and insurer markets lead to finding and using of new more complex financial tools linked with capital release and subsequent optimization of the investment objectives, but they are also linked with promises and risk transfers that could cause a collapse or a systemic risk of the financial markets, as evidence by the recent financial crisis. The aim of my work is to examine the behavior of credit default swap spreads on the securitization and reinsurance markets, followed by analyzing arbitrage conditions between securitization and reinsurance markets by cointegration analysis. The thesis focuses on Italy because it is one of four main European players in the securitization market and it has highly developed bank and insurer markets. Moreover, it still faces to consequences of the recent financial crisis that is indicator of strong possible bases for above mentioned complex financial instruments. On the dataset of Top 8 Italian banks and insurer companies in the period 2006 - 2012 I showed by cointegration analysis a presence of just one cointegration relationship between securitization and reinsurance market, therefore I rejected possibility of arbitrage between these markets. But on the other hand, they converge to long term equilibrium slowly...

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