Dissertations / Theses: 'Valve seats'

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Smith, Ryan Thomas. "Development of a Nitrogen-Modified Stainless-Steel Hardfacing Alloy." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440156184.

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Durango, Deisson Alexander Zuleta. "Influência da temperatura, velocidade e força no desgaste e no coeficiente de atrito de materiais para válvulas e sedes de válvulas de motores flex-fuel." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3151/tde-18012017-141613/.

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Na maioria dos equipamentos mecânicos há movimento relativo entre componentes, e como resultado desse deslizamento relativo, as forças de atrito na superfície geram deformação plástica e/ou remoção de massa (ou volume) do material. Nos motores de combustão interna a geração da potência é realizada pela transformação da energia química em calor por meio da combustão do combustível com o ar, gerando o movimento alternativo de mecanismos (pistões, biela, virabrequim). Já no caso dos motores flex-fuel, o etanol como combustível aumenta a potência, levando a maiores carregamentos termomecânicos e, consequentemente, tribológicos nos seus componentes. Um dos sistemas do motor mais afetado pela mudança no combustível é o par válvula-sede, motivo pelo qual é necessário investigar os mecanismos de desgaste, os efeitos dos parâmetros de operação no comportamento frente ao atrito, e escolher apropriadamente pares deslizantes de materiais que apresentem baixas perdas de massa (taxas de desgaste) e coeficientes de atrito. Ensaios do tipo reciprocating tinham sido empregados para realizar estudos tribológicos de materiais de válvulas e com tratamentos superficiais. As condições de ensaio mais representativas são de operação do motor. Portanto, a seleção de parâmetros como carga, velocidade e temperatura não é fácil: para alguns equipamentos de teste, as variáveis não são independentes. Além disso, devido à complexidade do sistema tribológico, a interação entre as variáveis afeta os resultados. O objetivo deste trabalho de pesquisa foi dividido em duas frentes. A primeira, analisar isoladamente o efeito da temperatura, força normal e velocidade no coeficiente de atrito e no desgaste. O tribômetro SRV-4 do tipo reciprocating foi usado com uma esfera de aço AISI 52100 e distintos materiais de disco (aços e ligas intermetálicas sinterizadas de Nb). A segunda parte consistiu na caracterização dos mecanismos de desgaste de válvulas e sedes de motores distintos, após diferentes tipos de ensaios (dinamômetro e campo em veiculo). O coeficiente de atrito (?) e a perda de massa foram medidos para determinar o desempenho tribológico dos sistemas estudados. Além disso, as superfícies das marcas de desgaste tanto no disco quanto na esfera, assim como das válvulas e sedes foram analisadas por microscopia óptica (MO), microscopia eletrônica de varredura (MEV) com espectroscopia de energia dispersiva de raios-X (EDS) e espectroscopia Raman. Para as distintas ligas intermetálicas de Nb ensaiadas com esfera de aço AISI 52100, encontrou-se que os mecanismos de desgaste nas superfícies após uma análise de MEV-EDS foram particularmente abrasão, adesão e oxidação. Já no caso dos motores que foram avaliados, muitos dos danos observados estavam presentes em ambas as válvulas e sedes de admissão e escape; no entanto, a oxidação ocorreu apenas nas válvulas de escape, provavelmente produzido pela alta temperatura durante a operação do motor.
In most of the mechanical assemblies there is relative motion between components, and as a result of this relative sliding action, frictional forces on the sliding surface result in removal or displacement of mass (or volume) of the material. The power generation of internal combustion engines comes from chemical energy transformation into heat through air fuel combustion with further expansion of gases generating the reciprocating movement of power cell (pistons, rod and crankshaft). For flex fuel engines, the ethanol increases power, leading to higher thermo-mechanical forces and consequently higher friction between its components. The valve/valve seat pair is one of the most affected system due to this change, leading to the need of more accurate analysis of its wear mechanisms, its operating parameters effects and his behavior regarding the friction so making possible to choose properly materials with lower mass loss (wear rate) and coefficient of friction. Reciprocating tests had been used to tribological studies of valve materials with surface treatment purpose. The most important test boundary conditions are the engine operating conditions. Therefore, the load, speed and temperature parameters definition is not easy since for some test equipment those variables are not independent. Besides due to tribological system complexity the variable interaction affects its results. The present research goal was divided in two groups. The first one analyzes the normal force, frequency and temperature effect on friction coefficient and wear, independently of each other. It was used a SRV-4 reciprocating tribometer with a sphere (AISI 52100 steel) against several disc materials (steel and sintered intermetallic alloys of Nb). The second one consisted in the characterization of wear mechanisms of valve/valve seat from different engines that were submitted to different test (engine dynamometer test bench and vehicle). The coefficient of friction (?) and mass loss were measured in order to define the studied systems tribological performance. Besides the both disc and sphere wear scars such as valve/valve seat were analyzed using optical microscopy (OM), scanning electron microscopy (SEM) with energy dispersive spectroscopy of X-ray (EDS) and Raman spectroscopy. For the tested intermetallic alloys of Nb with AISI 52100 sphere it was found the following wear mechanisms after SEM-EDS analyses: abrasion, adhesion and oxidation. In the case of the evaluated engines, several damages were observed in both intake and exhaust valves/valve seats; however, the oxidation occurred only on exhaust valves, probably due to high operating temperature.

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Foral, Martin. "Optimalizace sacího potrubí zážehového motoru." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228432.

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The work deals with design solutions to the intake manifold modern contemporary internal combustion engines. Then describes the types of flow and structural design of ports, including the intake of their basic properties. The thesis also compare the results of the analysis and design optimization based on simulation of flow inlet port and measure the actual inlet port.

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Lewis, Roger. "Wear of diesel engine inlet valves and seats." Thesis, University of Sheffield, 2000. http://etheses.whiterose.ac.uk/10238/.

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Valve wear has been a serious problem to engine designers and manufacturers for many years. Although new valve materials and production techniques are constantly being developed, these advances have been outpaced by demands for increased engine performance. The drive for reduced oil consumption and exhaust emissions, the phasing out of leaded petrol, reductions in the sulphur content of diesel fuel and the introduction of alternative fuels such as gas all have implications for valve and seat insert wear. The aim of the project has been, through the use of a representative bench test and engine testing, to diagnose the predominant wear mechanisms in diesel engine inlet valves and seats. This information was then to be used with other test data to develop a model for predicting valve recession and other tools to assist in solving valve failure problems. Test apparatus has been developed that is capable of providing a simulation of the wear of both inlet valves and seats used in automotive diesel engines. Investigations carried out using the apparatus have shown that the valve and seat wear problem involves two distinct mechanisms; impact of the valve on the seat insert on valve closure and sliding of the valve on the seat under the action of the combustion pressure. Wear has been shown to increase with valve closing velocity, combustion load and misalignment of the valve relative to the seat. Lubrication of the valve/seat interface leads to a significant reduction in valve recession. Valve rotation ensures even wear and promotes debris removal from the valve/seat interface. During testing it was established that resistance to impact was the key seat material property determining the amount of recession that occurred. A semi-empirical wear model for predicting valve recession has been developed based on the fundamental mechanisms of wear determined during test work. Model predictions were compared with engine tests and tests run on the bench test-rig. The model can be used to give a quantitative prediction of the valve recession to be expected with a particular material pair or a qualitative assessment of how parameters need to be altered in order to reduce recession. Flow charts have also been developed, based on the review of literature, failure analysis and modelling carried out, to assist in diagnosing and rectifying valve/seat failures and to help in reducing valve recession by design. The test apparatus, valve recession model and design tools can be integrated into an industrial environment in order to help reduce costs and timescales involved in solving valve/seat wear problems using the current trial and error methods.

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Abdel-Fattah, Yahia. "The mechanics of valve cooling in internal-combustion engines : investigation into the effect of VSI on the heat flow from valves towards the cooling jacket." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4333.

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Controlling the temperature of the exhaust valves is paramount for proper functioning of engines and for the long lifespan of valve train components. The majority of the heat outflow from the valve takes place along the valve-seat-cylinder head-coolant thermal path which is significantly influenced by the thermal contact resistance (TCR) present at the valve/seat and seat/head interfaces. A test rig facility and experimental procedure were successfully developed to assess the effect of the valve/seat and seat/head interfaces on heat outflow from the valve, in particular the effects of the valve/seat interface geometry, seat insert assembly method, i.e. press or shrink fit, and seat insert metallic coating on the operating temperature of the valve. The results of tests have shown that the degree of the valve-seat geometric conformity is more significant than the thermal conductivity of the insert: for low conforming assemblies, the mean valve head temperature recorded during tests on copper-infiltrated insert seats was higher than that recorded during tests on noninfiltrated seats of higher conformance. The effect of the insert-cylinder head assembly method, i.e. shrink-fitted versus press-fitted inserts, has proved negligible: results have shown insignificant valve head temperature variations, for both tin-coated and uncoated inserts. On the other hand, coating the seat inserts with a layer of tin (20-22μm) reduced the mean valve head temperature by approximately 15°C as measured during tests on uncoated seats. The analysis of the valve/seat and seat/head interfaces has indicated that the surface asperities of the softer metal in contact would undergo plastic deformation. Suitable thermal contact conductance (TCC) models, available in the public domain, were used to evaluate the conductance for the valve/seat and seat/cylinder head interfaces. Finally, a FE thermal model of the test rig has been developed with a view to assess the quality of the calculated TCC values for the valve/seat and seat/head interfaces. The results of the thermal analysis have shown that predicted temperatures at chosen control points agree with those measured during tests on thermometric seats with an acceptable level of accuracy, proving the effectiveness of the used TCC models.

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Naicker, Kovilen Manikum. "Unlocking the economic value of empty seats in South African stadia." Diss., University of Pretoria, 2020. http://hdl.handle.net/2263/75270.

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In a country known for its love of major sports such as cricket, football (soccer) and rugby, it seems counterintuitive that attendance at live sport events is declining. With high-performing international teams, star personalities, and beautiful sport venues, emptier sports stadia need investigation. This decline negatively affects sports revenues and has a depressive effect on microeconomies in and around sporting venues as well. This research sought to understand the South African sport consumers’ behaviour. It draws on insights from literature on sport consumer behaviour and related psychological fields. An understanding of the antecedent psychological drivers for behavioural intentions to attend live sport events was assessed, grounded by the theory of planned behaviour. A deductive research design employed a distributed survey that gathered 171 observations for analysis and used a multiple regression methodology, with weighted least squares transformations. The findings illustrate that sport consumers’ attitudes, subjective norms, and perceived behavioural control all positively influence their behavioural intentions to attend live sport events. The influence of digital media in creating a more competitive sport consumption category – a key insight for stakeholders looking to future-proof their sports marketing and event offerings was highlighted. This research contributes to literature in the fields of behavioural psychology, social science, sport management and sport marketing, among others. Further actionable recommendations to sports industry stakeholders are offered to derive broad-based business value.
Mini Dissertation (MBA)--University of Pretoria, 2020.
Gordon Institute of Business Science (GIBS)
MBA
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Rai, Sweta. "Identification of factors influencing the valve seat pressing process." Thesis, KTH, Industriell produktion, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-215974.

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Van, der Westhuizen Anriette. "The verification of seat effective amplitude transmissibility (SEAT) value as a reliable metric to evaluate dynamic seat comfort." Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16453.

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Thesis (MScIng)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: A rough road vibration stimulus was reconstructed on a shaker platform to assess the dynamic comfort of seven seats by six human subjects. The virtual seat method was combined with a paired comparison procedure to assess subjective dynamic seat comfort. The psychometric method of constants, 1-up-1-down Levitt procedure and a 2-up-1-down Levitt procedure were compared experimentally to find the most accurate and efficient paired comparison scheme. A two-track interleaved, 2-up-1-down Levitt procedure was used for the subjective dynamic seat comfort assessment. SEAT value is an objective metric and has been widely used to determine seat vibration isolation efficiency. There was an excellent correlation (R2 = 0.97) between the subjective ratings and estimated SEAT values on the seat top when the values are averaged over the six subjects. This study suggests that the SEAT values, estimated from averaged seat top transmissibility of six carefully selected subjects, could be used to select the best seat for a specific road vibration input.
AFRIKAANSE OPSOMMING: Ses persone het deelgeneem aan ‘n eksperiment, om die dinamiese ritgemak van sewe stoele te karakteriseer. ‘n Rowwe padvibrasie is vir die doel op ‘n skudplatform geherkonstrueer. Subjektiewe ritgemak is bepaal deur die virtuelestoel metode met ‘n gepaarde, vergelykingstoets te kombineer. Die psigometriese metode van konstantes, die 1-op-1-af Levitt procedure en die 2-op- 1-af Levitt procedure is vergelyk om die mees effektiewe en akkurate vergelykingstoets te vind. ‘n Tweebaan, vervlegde , 2-op-1-af Levitt prosedure het die beste resultate gelewer en is gekies vir die subjektiewe evaluasie van dinamiese ritgemak. SEAT-waarde is ‘n objektiewe maatstaf, wat gebruik word om te bepaal hoe effektief ‘n stoel die insittende van voertuigvibrasie isoleer. Daar was ‘n uitstekende korrelasie (R2 = 0.97) tussen subjektiewe dinamiese ritgemakevaluesies en SEAT-waardes in die vertikale rigting op die stoelkussing as die gemiddelde oor die ses persone bereken word. Uit die resultate van hierdie studie blyk dit dat SEAT-waardes, wat bereken is vanaf die gemiddelde sitplektransmissie van die ses persone, wat verteenwoordigend van die teikenbevolking is, gebruik kan word om die beste stoel vir ‘n spesifieke vibrasieinset te kies.

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Ritchie, Greg. "Minimizing pressure relief valve seat leakage through optimization of design parameters." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/31013.

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Lind, Sofia. "Wear reduction between disc edge and seat in a butterfly valve." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-62586.

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This thesis was written on behalf of SOMAS instruments AB. SOMAS develops, manufactures and markets valves. The mission was to reduce the wear between the disc edge and the seat in a butterfly valve that are used at high temperatures. This study investigated the possibility of using a surface treatment or coating that can reduce wear or if a new base material is better to use than the current steel 316 material. Possible materials, surface treatments and coatings were investigated and compared in a material study. In discussion with the company, four test pairs were chosen; • Steel 316 - Steel 316 • Steel 316 - Nitronic 60 • Nitronic 60 - Nitronic 60 • Steel 316 - Steel 316 with a surface coating of Tribaloy T-400 The wear behavior of the selected materials was investigated using a test rig at Karlstad University based on the method of block-on-ring. The machine spins a cylinder that corresponds to the seat against a block which in this case corresponds to the disc edge. The tests were carried out at room temperature, 250 ˚C and 500 ˚C. The cylinder was spinning at a speed of 100 rpm while the block pressed against with a load of 50 N. A profilometer, micro-hardness tester and scanning electron microscope (SEM) were used to investigate the wear. A comparison was made based on the volume of material removed from the blocks, the maximum wear depth of the blocks and the maximum wear depth of the cylinder. Wear mechanisms, chemical composition and hardness profiles were used to explain differences in results. The results were compared with the steel 316 to steel 316 solution. The Tribaloy T-400 showed good properties to reduce the wear at room temperature. Block made of Tribaloy T-400 showed no wear, instead steel from the cylinder had been adhered to the blocks. At higher temperatures, the amount of adhered material on the tribaloy T-400 increased, resulting in more wear at the surface of the cylinder than at room temperature. The wear on the cylinder was comparable to the wear of a steel cylinder that slid against a steel block. Nitronic 60 against nitronic 60 exhibited a significant reduction in wear compared with steel to steel at room temperature. At higher temperatures, nitronic 60 against nitronic 60 was the test pair that exhibited least wear. Nitronic 60 is recommended for further examination as a material in both the disc edge and the seat in a butterfly valve to be used at both room temperature and elevated temperatures.
Detta examensarbete skrevs på uppdrag från SOMAS instruments AB. SOMAS utvecklar, tillverkar och marknadsför ventiler. Uppdraget gick ut på att minska nötningen mellan spjällkanten och sätet i en vridspjällsventil som ska användas i höga temperaturer. Denna studie undersökte möjligheten det att använda en ytbehandling eller ytbeläggning som kan minska nötningen eller om ett nytt basmaterial är bättre att använda än det nuvarande materialet stål 316. Möjliga material, ytbehandlingar och ytbeläggningar undersöktes och jämfördes i en materialstudie. I diskussion tillsammans med företaget så valdes fyra stycken testpar; • stål 316 - stål 316 • stål 316 - nitronic 60 • nitronic 60 - nitronic 60 • stål 316 - stål 316 med en ytbeläggning av tribaloy T-400 Nötningsbeteendet hos de valda materialen undersöktes med hjälp av en testrigg på Karlstad universitet som bygger på metoden ”block-on-ring”. Maskinen snurrar en cylinder som motsvarar sätet mot ett block som i detta fall motsvarar spjällkanten. Testerna utfördes i rumstemperatur, 250 ˚C och 500 ˚C. Cylindern snurrade med en hastighet av 100 rpm medan blocket tryckte mot med en last på 50 N. En profilometer, mikrohårdhetstestare och svepelektronmikroskåp användes för att undersöka nötningen. En jämförelse gjordes baserad på volymen av det bortnötta materialet från blocken, maximala nötningsdjupet på blocken och maximala nötningsdjupet på cylindern. Slitagemekanismer, kemisk sammansättning och hårdhetsprofiler användes för att kunna förklara skillnader i resultaten. Resultaten jämfördes mot stål 316 mot stål 316. Tribaloy T-400 visade upp bra egenskaper för att kunna minska nötningen i rumstemperatur. Block gjorda av Tribaloy T-400 uppvisade ingen nötning, istället hade material från stål cylindern adderats på blocken. Vid högre temperaturer så ökade mängden adderat material på tribaloy T-400 vilket resulterade i att ytan på cylindern uppvisade mer nötning än i rumstemperatur. Nötningen på cylindern kunde jämföras med nötningen hos en stålcylinder som glidit mot ett stål block. Nitronic mot nitronic uppvisade vid rumstemperatur en stor minskning av nötning jämfört med stål mot stål. Vid högre temperatur var nitronic 60 mot nitronic 60 det test par som uppvisade minst nötning. Nitronic 60 rekommenderas för vidare undersökning som material i både spjällkanten och sätet i en vridspjällsventil som ska användas i både rumstemperatur och i höga temperaturer.

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Penhalbel, Luciano Tadeu Baffi. "Avaliação tribológica do par válvula e sede de válvula de admissão de um motor ciclo diesel em condições reais de funcionamento." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-07122017-093905/.

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A indústria automotiva exige produtos que trabalhem em condições extremas. O desenvolvimento de componentes é uma ação de aperfeiçoar os motores de combustão interna para que atinjam a vida requerida com níveis de desgaste aceitáveis, respeitando os limites legais de operação, como por exemplo, valores de emissões de poluentes. Diante dessas exigências, se faz necessário estudar componentes considerados críticos que conhecidamente influenciam no desempenho do motor. A tribologia do par válvula e sede de válvula de admissão é um importante conjunto que se deve ter atenção quanto ao seu desgaste, visto que pode influenciar na degradação do motor quanto aos parâmetros de emissões de poluentes e requisitos operacionais de manutenção e de vida do produto. O objetivo foi avaliar o comportamento do par tribológico, válvula e sede de válvula de admissão, submetidos a ensaios em dinamômetro e veiculares (condições reais de operação), quanto ao nível e tipo de desgaste ocorrido no par. Os resultados obtidos foram correlacionados com os requisitos de desempenho legais e operacionais de um motor ciclo diesel, como também foi realizada a caracterização do tipo de desgaste ocorrido no par tribológico e comparada com a literatura específica. Com base nos resultados, concluiu-se que ocorreu uma excelente compatibilidade entre a válvula e a sede da válvula de admissão; o nível de desgaste não prejudicou o desempenho do motor e as emissões de poluentes; o par tribológico atendeu aos requisitos de trabalho extremos, como operação em altas temperaturas e pressão de combustão com baixas taxas de desgaste; e os tipos de desgastes observados foram classificados como desgaste adesivo e sinais de deformação plástica.
Automotive industry demands products that work under extreme conditions. The development of components for internal combustion engines is an action to improve this product, so that it reaches the required life with acceptable levels of wear and respecting the legal operating limits, such as values of emission pollutants. In view of these requirements, it is necessary to study components considered critical, which are known to influence the performance of the engine. So within this universe the tribology of the intake valve and valve seat insert is an important set, that must receive attention to its wear and consequently its influence to the engine degradation in the parameters of emission pollutants and performance related to the operational maintenance requirements and life of the product. The aim of this work is to evaluate the behavior of the tribological intake pair, valve and valve seat insert, submitted to dynamometer and vehicular tests (real operating conditions), regarding the level and type of wear occurred in the pair. The results were compared with legal and operational performance requirements of a diesel cycle engine, as well as the characterization of the wear type occurred in the tribological pair, with the related literature. Based on the results it was concluded that there was excellent compatibility between the valve and the valve seat material; the wear level did not impar the engine performance and emissions of pollutants; the tribological pair meeting extreme work requirements, such as high temperature operation and combustion pressure while maintaining low wear rates. The wear types observed were classified as adhesive wear and slight signs of shear strain wear.

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Aryal, Ashok. "Geometry of mean value sets for general divergence form uniformly elliptic operators." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/36205.

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Doctor of Philosophy
Department of Mathematics
Ivan Blank
In the Fermi Lectures on the obstacle problem in 1998, Caffarelli gave a proof of the mean value theorem which extends to general divergence form uniformly elliptic operators. In the general setting, the result shows that for any such operator L and at any point [chi]₀ in the domain, there exists a nested family of sets { D[subscript]r([chi]₀) } where the average over any of those sets is related to the value of the function at [chi]₀. Although it is known that the { D[subscript]r([chi]₀) } are nested and are comparable to balls in the sense that there exists c, C depending only on L such that B[subscript]cr([chi]₀) ⊂ D[subscript]r([chi]₀) ⊂ B[subscript]Cr([chi]₀) for all r > 0 and [chi]₀ in the domain, otherwise their geometric and topological properties are largely unknown. In this work we begin the study of these topics and we prove a few results about the geometry of these sets and give a couple of applications of the theorems.

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Taylor, John Abner. "Effects of a Surface Engineered Metallic Coating on Elastomeric Valve Stem Seal Leakage." Thesis, University of North Texas, 2000. https://digital.library.unt.edu/ark:/67531/metadc2690/.

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Valve stem seal leakage is a major source of fugitive emissions, and controlling these emissions can result in added expense in leak detection and repair programs. Elastomeric O-rings can be used as valve stem seals, and O-ring manufacturers recommend lubrication of elastomeric seals to prevent damage and to assure proper sealing. In this research, a metallic coating was applied as a lubricant using a vacuum vapor deposition process to the surface of elastomeric valve stem seals. Valve stem leak measurements were taken to determine if the coated O-rings, alone or with the recommended lubrication, reduced valve stem seal leakage. This research determined that the metallic coating did not reduce valve stem leakage.

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Kendall, Guy. "Analogues of Picard sets for meromorphic functions with a deficient value." Thesis, University of Nottingham, 2004. http://eprints.nottingham.ac.uk/10062/.

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Picard's theorem states that a non-constant function which is meromorphic in the complex plane C omits at most two values of the extended complex plane C*. A Picard set for a family of functions F is a subset E of the plane such that every transcendental f in F takes every value of C*, with at most two exceptions, infinitely often in C-E. If f is transcendental and meromorphic in the plane, then: (i) [Hayman and others] if N is a positive integer, f^Nf' takes all finite non-zero values infinitely often; (ii) [Hayman] either f takes every finite value infinitely often, or each derivative f^(k) takes every finite non-zero value infinitely often. We can seek analogues of Picard sets ie subsets E of the plane and an associated family of functions F, such that (for case (i)) f^Nf' takes all finite non-zero values infinitely often in C-E, for all f in F. Similarly for case (ii). In this thesis we improve or extend the results previously known, both for Picard sets proper and for the analogous cases (i) and (ii) mentioned above, when the family of functions F consists of meromorphic functions which have deficient poles (in the sense of Nevanlinna).

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McDonell, Erin E. "An evaluation of methods used to cover bunker silos with oxygen barrier plastic to maintain the nutritive value of silage." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 88 p, 2008. http://proquest.umi.com/pqdweb?did=1459918791&sid=13&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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Thiodoro, Leonardo Andrioli. "Caracterização do desgaste do par válvulas e sede de válvula de motores a combustão interna ciclo Otto flex-fuel." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3151/tde-28112017-081305/.

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Desde a sua invenção, o motor a combustão interna sofreu significantes evoluções, como redução do consumo de combustível, aumento da sua potência e durabilidade a um menor custo. Outros setores também evoluíram, como a busca por alternativas de combustível, tendo como exemplo o etanol hidratado combustível, que trouxe vantagens tais como maior desempenho e menor emissão de poluentes, porém com solicitações mecânicas, térmicas e termomecânicas mais severas. Sua menor lubricidade, quando comparada a da gasolina tipo C também intensificou o desgaste no par tribológico válvula e sede de válvula. Neste trabalho foram analisados diversos pares de válvulas e sedes de válvulas provenientes de quatro motores pós teste, sendo dois deles de mesma especificação técnica e submetidos às mesmas condições de ensaio, variando somente o combustível utilizado (etanol hidratado combustível e gasolina comum tipo C). A topografia da superfície de contato foi avaliada através de exames das superfícies com lupa estereoscópica, microscópio eletrônico de varredura e perfilômetro óptico a fim de identificar os danos encontrados. Ao término das análises foi realizada a comparação dos danos encontrados entre a superfície de contato das válvulas e sedes do motor que operou com etanol hidratado combustível e gasolina comum tipo C, de forma a evidenciar as diferenças proporcionadas pelos combustíveis. Este trabalho faz parte do \"Consórcio de P&D e Desafios Tribológicos em Motores Flex-Fuel\" patrocinado pela FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo) com participação da indústria automotiva, para identificar os modos de desgaste atuantes.
Since its invention the internal combustion engine presented significant improvements like lower fuel consumption, higher power and durability increase at reduced costs. Other industries sectors did also improve as the search for new alternative fuels such as hydrated ethanol fuel which brought advantages like higher performance with lower pollutant emissions, although with it came more severe mechanical, thermal and thermo-mechanic stresses. Ethanol lower lubricity when compared to type C gasolines did also increase the valve/ valve seat insert wear. This study presents the results of contact surface analysis of several pairs valve/ valve seat insert from four engines after test being two of them of same technical specification and submitted to the same test cycle with only difference their fuel (hydrated ethanol and regular type C gasoline). The contact surface topography was evaluated through surface exams using optical microscopy, scanning electron microscope and non-contact profiler, to evaluate damages. At the end of analysis, a comparison between valves and valve seats from the engines that operated with hydrated ethanol and regular type C gasoline in order to put in evidence the damage difference provided by the fuels. This study is part of \"Consórcio de P&D e Desafios Tribológicos em Motores Flex-Fuel\", sponsored by FAPESP (\"Fundação de Amparo à Pesquisa do Estado de São Paulo\") with participation of automotive industries, to characterize the existent wear.

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Bentil, Ekua Fesuwa. "Identification of Differentially Expressed Genes and Gene Sets Using a Modified Q-Value." Thesis, North Dakota State University, 2014. https://hdl.handle.net/10365/27313.

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Gene expression technologies allow expression levels to be compared across treatments for thousands of genes simultaneously. Statistical methods exist for identifying differentially expressed (DE) genes and gene sets while controlling multiple testing error. Most methods do not take into account the distribution of effect sizes or the overrepresentation of observed patterns. This paper compares a recently proposed modified q-value method that takes into account such patterns to a traditional q-value method for experiments with three treatments. The results of simulation studies performed suggest that the proposed methods improve upon the traditional method in the identification of DE genes in certain settings, but are outperformed by the traditional method in other settings. Analysis of data sets from real microarray.

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Sekonyela, Malira Patience. "Integrating Lesotho economy into the regional automotive value chain : manufacturing of car-seat covers." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/17421.

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Includes bibliographical references
The purpose of this study was to analyse the Automotive Industry in Southern Africa, to assess how best Lesotho can contribute to this supply chain. This analysis was done to better understand the sector, to identify Lesotho's potential to produce car seat covers for South African automotive assembly plants, and find the best trade policies and programmes to support value chains in the sector. The plan was to assess the possibility for Lesotho made automotive components manufacturers to supply the Original Equipment Manufacturers (OEMs - the main automotive assembly plants), and use the South African Automotive Industry as the entry point for the Lesotho components to penetrate the Regional Automotive Value Chain. The main focus of this study was the manufacturing of car-seat covers to supply the seven Original Equipment Manufacturers namely: Volkswagen, BMW, Renault, Toyota, Daimler Chrysler, Ford and Mercedes Benz. The impact of Motor Industry Development Programme (MIDP) and Automotive Production and Development Programme (APDP) on the industry was assessed. The impact of the APDP on relocation of components manufacturers to other Southern African Customs Union (SACU) countries was assessed, Lesotho being used as a case study. It set out to find out if Lesotho firms have the potential to contribute to the automotive value chains through manufacture of car seat covers.

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Clatworthy, Jane. "The theoretical and statistical value of cluster analysis in health psychology : an empirical investigation using artificial and existing data sets." Thesis, University of Brighton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404065.

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Vávrovec, Jiří. "Optimalizace sacího potrubí zážehového motoru." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-228906.

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This thesis focus with construction design intake manifold of four stroke engine rallyecross division 1A. For improvement observant come into operating here derive benefit from theory tuned supercharging, which is based on tuning longitudes sucking conduit. Derive benefit woolen effect. Driving unit is here used four cylinders, water-cooled, atmospheric combustion engine from car VW Polo 6N GTI. Design is created so, to answer condition division 1A.

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21

Musengi, Sandra. "Passing the spear : a grounded theory study of the influence of family business value sets on succession planning in black family-owned businesses." Thesis, Rhodes University, 2007. http://hdl.handle.net/10962/d1007056.

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Literature suggests that a small number of family businesses are able to make the transition from the founder to other family members with a common reason cited being the lack of planning. This study aims to build understanding of leadership succession in family businesses by focusing on the influence of a founder's family business value set on the succession planning process in Black family-owned businesses. Using the Strauss and Corbin (1990) grounded theory method, this study develops a theory of succession planning of Black familyowned businesses labelled Passing the Spear which is comprised of three stages based on an analysis of 21 qualitative interviews. The Spear was an analogy used to represent both the values of the founder and the family business, thus in Passing the Spear, founders where essentially performing a dual transfer of their values and leadership to the successor. The implementation of the process Passing the Spear was influenced by the family business value set of the founder, which in this study, were labelled as Traditional, Progressive, and Transitional. These value sets were distinguished by their behaviour regarding their choice of successor where founders with a traditional value set exhibited gatekeeping behaviour, while the behaviour of founders with a progressive value set was labelled navigating, and finally, founders with a transitional value set demonstrated behaviour labelled exploring. Furthermore, it was found that after the successor had been chosen, founders appeared to follow a generic succession planning process, however, the ease and timing of implementation was influenced by the family business context, evidence of being proactive and the degree of family business resilience. The process of Passing the Spear comprised of three stages of (a) Showing the spear where the founder's focus is on the induction and socialization of the successor using the strategies of bringing the successor into the family business and managing the family-business interface using relationships; (b) Explaining the spear entailed founders using the strategies of sharing knowledge and teaching the successors about the family business; and ( c) Sharing the spear was where founders focused on empowering the successors by implementing strategies of sharing responsibilities and learning from the successor.The process provides insights into the influence of family business values on the succession planning process and can be useful for founders of Black family-owned businesses in planning for succession in their businesses. In addition, the study provides another perspective of succession planning and offers a contribution to the literature for understanding succession in Black family-owned businesses.

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22

Ounaies, Senda. "Optimal investment in friction markets and equilibrium theory with unbounded attainable sets." Thesis, Paris 1, 2018. http://www.theses.fr/2018PA01E022/document.

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Cette thèse traite des phénomènes liés aux mathématiques financières et économiques. Elle est composée de deux sujets de recherche indépendants. La première partie est consacrée à deux contributions au problème de Merton. Pour commencer, nous étudions le problème de l’investissement optimal et de la consommation de Merton dans le cas de marchés discrets dans un horizon infini. Nous supposons qu’il y a des frictions sur les marchés en raison de la perte due aux échanges financières. Ces frictions sont modélisées par des fonctions de pénalités non linéaires où les modèles classiques de coût de transactions étudiés par Magill et Constantinides [31] et les marchés illiquides étudiés par Cetin, Jarrow et Protter dans [6] sont inclus dans cette formulation. Dans ce contexte, la région de solvabilité est définie en tenant compte de cette fonction de pénalité et chaque investisseur doit maximiser son utilité, dérivée de la consommation. Nous donnons la programmation dynamique du modèle et nous prouvons l’existence et l’unicité de la fonction valeur. Des stratégies optimales d’investissement et de consommation sont également construites. Ensuite, nous étendons le modèle de Merton à un problème à plusieurs investisseurs. Notre approche consiste à construire un modèle d’équilibre général déterministe dynamique. Nous prouvons ensuite l’existence d’un équilibre du problème qui est un ensemble de contrôles composés de processus de consommation et de portefeuille, ainsi que les processus de prix qui en découlent afin que la politique de consommation de chaque investisseur maximise son profil. Les résultats obtenus dans cette partie étendent principalement les résultats récemment obtenus par Chebbi et Soner [10] ainsi qu’aux d’autres résultats obtenus dans ce cadre dans la littérature. Dans la deuxième partie, nous traitons le problème de l’existence d’un équilibre d’une économie de production avec des ensembles d’allocations réalisables non-bornés où les consommateurs peuvent avoir des préférences non-transitives non-complètes. Nous introduisons une propriété asymptotique sur les préférences pour les consommations réalisables afin de prouver l’existence d’un équilibre. Nous montrons que cette condition est vraie lorsque l’ensemble des allocations réalisables est compact ou aussi lorsque les préférences sont représentées par des fonctions d’utilité dans le cas où l’ensemble des niveaux d’utilité rationnels individuels réalisables est compact. Cette hypothèse généralise la condition de CPP de Allouch [1] et couvre l’exemple de Page et al. [40] lorsque les niveaux d’utilité disponibles définis ne sont pas compacts. Nous étendons donc les résultats existants dans la littérature avec des ensembles réalisables non bornés de deux façons en ajoutant la production et en prenant en compte des préférences générales
This PhD dissertation studies two independent research topics dealing with phenomena issues from financial and economic mathematics.This thesis is organized in two parts. The first part is devoted to two contributions tothe Merton problem. First, we investigate the problem of optimal investment and consumption of Merton in the case of discrete markets in an infinite horizon. We suppose that there is frictions in the markets due to loss in trading. These frictions are modeled through nonlinear penalty functions and the classical transaction cost studied by Magill and Constantinides in [31] and illiquidity models studied by Cetin, Jarrow and Protter in [6] are included in this formulation. In this context, the solvency region is defined taking into account this penalty function and every investigator have to maximize his utility, that is derived from consumption, in this region. We give the dynamic programming ofthe model and we prove the existence and uniqueness of the value function. Optimalinvestment and consumption strategies are constructed as well. We second extend the Merton model to a multi-investors problem. Our approach is to construct a dynamic deterministic general equilibrium model. We then provide the existence of equilibrium of the problem which is a set of controls that is composed of consumption and portfolio processes, as well as the resulting price processes so that each investor’s consumption policy maximizes his lifetime expected. The results obtained in this part extends mainly the results recently obtained by Chebbi and Soner [10] and other corresponding results in the litterature.The second part of this thesis deals with the problem of the existence of an equilibrium of a production economy with unbounded attainable allocations sets where the consumers may have non-complete non-transitive preferences. We introduce an asymptotic property on preferences for the attainable consumptions in order to prove the existence of an equilibrium. We show that this condition holds true if the set of attainable allocations is compact or, when preferences are representable by utility functions, if the set of attainable individually rational utility levels is compact. This assumption generalizes the CPP condition of Allouch [1] and covers the example of Page et al. [40] when the attainable utility levels set is not compact. So we extend the previous existence results with unbounded attainable sets in two ways by adding a production sector and considering general preferences

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Horák, Milan. "Svoboda usazování obchodních společností v evropském právu." Master's thesis, Vysoká škola ekonomická v Praze, 2012. http://www.nusl.cz/ntk/nusl-125124.

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States have traditionally dealt with foreign companies on their territory within their private international law. The arrival of European law and enactment of freedom of establishment though considerably constrained capabilities of member states, whereas companies gained the right of establishment. The aim of this thesis is characterization and specification of the relationship between the freedom of establishment, member states and companies incorporated under laws of member states. The main focus of this thesis is analysis of ten most important cases by the Court of Justice of the European Union concerning the freedom of establishment of companies, which significantly transformed mentioned relationship. Subsequently the thesis summarizes the conclusions of analyzed cases by subject of evolution of primary and secondary freedom of establishment, standing of pseudoforeign companies, conformity with incorporation theory and real seat theory and lastly ways of statutory and/or real seat transfer. The main contribution of the thesis is the very detailed case law analysis, including the newest case Vale from July 12th 2012, and also the case law classification by object.

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Antonio, Filho Fadel David. "O caminho novo : o Vale Histórico da Serra da Bocaina - opulência e decadência da sub-região paraibana paulista (reintegração de um espaço geográfico 'deprimido') /." Rio Claro : [s.n.], 2009. http://hdl.handle.net/11449/116118.

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Banca: Adler Guilherme Viadana
Banca: Silvio Carlos Bray
Banca: José Bueno Conti
Banca: Maria Geralda de Almeida
Banca: Oswaldo Bueno Amorim Filho
Resumo: A pesquisa resgata o trecho paulista do "Caminho Novo", antiga estrada geral de São Paulo, ligação terrestre com o Rio de Janeiro, a partir do século XVIII. No chamado Vale Histórico da Serra da Bocaina, cujo relevo se apresenta muito movimentado, a cultura do café penetrou em território paulista. Esta sub-região do Vale do Paraíba tornou-se uma das mais prósperas do país. A fase posterior, de queda na produção cafeeira, transformou-a numa região "deprimida" e estagnada. Atualmente, existem esforços para, através dos diversos ramos do turismo, reativar e dinamizar esta região vale-paraibana paulista, de modo a reintegrá-la ao pujante sistema econômico de São Paulo.
Abstract: The research rescues part of Paulista's "New Way", an old general highway of Sao Paulo, a linking land conection with Rio de Janeiro, from eighteenth century on. Through the known as Historical Bocainas's Valley, whose relief presents itself as a turnover, the coffee culture penetrated in the paulista's territory. This sub-region of Paraíba's Valley became one of the most prosperous regions of the Country. The later faze, of a drop in coffee production, transformed it in a depressed and stagnant region. Currently there are efforts, through various branches of tourism, and re-energize the region of Paraibana Paulista valley, to reinstate her to the vibrant economic system of São Paulo.

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Mount, David, Charles Putnam, Sara Centouri, Ann Manziello, Ritu Pandey, Linda Garland, and Jesse Martinez. "Using logistic regression to improve the prognostic value of microarray gene expression data sets: application to early-stage squamous cell carcinoma of the lung and triple negative breast carcinoma." BioMed Central, 2014. http://hdl.handle.net/10150/610040.

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BACKGROUND:Numerous microarray-based prognostic gene expression signatures of primary neoplasms have been published but often with little concurrence between studies, thus limiting their clinical utility. We describe a methodology using logistic regression, which circumvents limitations of conventional Kaplan Meier analysis. We applied this approach to a thrice-analyzed and published squamous cell carcinoma (SQCC) of the lung data set, with the objective of identifying gene expressions predictive of early death versus long survival in early-stage disease. A similar analysis was applied to a data set of triple negative breast carcinoma cases, which present similar clinical challenges.METHODS:Important to our approach is the selection of homogenous patient groups for comparison. In the lung study, we selected two groups (including only stages I and II), equal in size, of earliest deaths and longest survivors. Genes varying at least four-fold were tested by logistic regression for accuracy of prediction (area under a ROC plot). The gene list was refined by applying two sliding-window analyses and by validations using a leave-one-out approach and model building with validation subsets. In the breast study, a similar logistic regression analysis was used after selecting appropriate cases for comparison.RESULTS:A total of 8594 variable genes were tested for accuracy in predicting earliest deaths versus longest survivors in SQCC. After applying the two sliding window and the leave-one-out analyses, 24 prognostic genes were identified
most of them were B-cell related. When the same data set of stage I and II cases was analyzed using a conventional Kaplan Meier (KM) approach, we identified fewer immune-related genes among the most statistically significant hits
when stage III cases were included, most of the prognostic genes were missed. Interestingly, logistic regression analysis of the breast cancer data set identified many immune-related genes predictive of clinical outcome.CONCLUSIONS:Stratification of cases based on clinical data, careful selection of two groups for comparison, and the application of logistic regression analysis substantially improved predictive accuracy in comparison to conventional KM approaches. B cell-related genes dominated the list of prognostic genes in early stage SQCC of the lung and triple negative breast cancer.

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Gomes, Maurilio Pereira. "Efeito de tratamentos térmicos em insertos de assentos de válvulas sinterizados." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-06092017-104226/.

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Atualmente, uns dos grandes desafios para a indústria automobilística é aumentar o desempenho do conjunto mecânico responsável por selar a câmara de combustão interna de motores automotivos e também reduzir os seus custos de obtenção. O objetivo deste trabalho foi o de tratar termicamente insertos de assentos de válvulas (do inglês valve seat insert, VSI) obtidos pela rota de metalurgia do pó. Esta técnica possibilitou a substituição do cobalto e do chumbo, devido ao seu elevado custo e efeito toxicológico, respectivamente. Ao longo do trabalho foram avaliados VSI obtidos com três misturas de pós diferentes, sendo que os elementos comuns nestas três misturas foram os pós de ferro, sulfeto de manganês, carboneto de nióbio, grafite, estearato de zinco e cobre. Em cada uma destas misturas variou-se apenas os tipos de pós de aços rápidos e aço ferramenta utilizado, sendo estes o aço rápido AISI M3:2 (Mistura 1), aço rápido AISI M2 (Mistura 2) e aço ferramenta AISI D2 (Mistura 3). Os tratamentos térmicos aplicados aos VSI consistiram em têmpera ao ar e têmpera ao óleo, ambas seguidas de duplo revenimento em sete temperaturas equidistantemente diferentes, variando de 100 °C a 700 °C. Os ciclos dos tratamentos térmicos foram determinados por meio da utilização de termopares do tipo k acoplados à um sistema de aquisição de dados. As propriedades físicas e mecânicas dos VSI foram determinadas através da dureza aparente, densidade aparente e resistência à ruptura radial. A caracterização microestrutural foi realizada utilizando-se a microscopia óptica e microscopia eletrônica de varredura. A composição química foi determinada por meio da análise elementar e por espectrometria de fluorescência de energia dispersiva de raios X. Os melhores resultados em relação às propriedades mecânicas dos VSI foram obtidas para os insertos temperados ao ar e duplamente revenido a 600 °C para a Mistura 1 e Mistura 2, e a 500 °C para Mistura 3. Já para a têmpera ao óleo, as melhores respostas foram para os VSI obtidos com a Mistura 1 duplamente revenida a 400 °C e a, 300 °C para os componentes obtidos com a Mistura 2 e Mistura 3.
Currently, one of the biggest challenges for the automobile industry is to increase the performance of the mechanical set responsible for sealing the internal combustion chamber in automotive engines and reduce its cost of production. The aim of the present work was to heat treat valve seat inserts (VSI) obtained through the powder metallurgy route. This procedure made possible the substitution of cobalt and lead, due to its high cost and toxicological effect, respectively. Throughout the work, it was evaluated VSI obtained with three different types of powders mixtures, and common elements at the three different powders mixtures were iron powder, manganese sulfide, niobium carbide, graphite, zinc stearate and copper. In each of these powders mixtures, it was changed only the type of high-speed steels and tool steel, consisting of high-speed steel AISI M3:2 (Mixture 1), high-speed steel AISI M2 (Mixture 2) and tool steel AISI D2 (Mixture 3). The heat treatments applied to the VSI were air quenching and oil quenching, both followed by double tempering at seven different equidistantly temperatures, ranging from 100 °C up to 700 °C. The heat treatments thermal cycles were determined using a thermocouple type k attached to a data acquisition system. The physical and mechanical properties of the VSI were measured in terms of apparent hardness, apparent density and crush radial strength. Microstructural characterization was performed using optical and scanning electron microscopy. The chemical composition was determined using gas analysis and energy dispersive X-ray fluorescence spectrometry. The best results regarding the mechanical properties of the VSI were obtained for the VSI air-quenched and double tempered at 600 °C for the powder Mixture 1 and Mixture 2, and at 500 °C for Mixture 3. For the oil quenching, the best response was reached for the VSI obtained with Mixture 1 double tempered at 400 °C, and at 300 °C for the components obtained with Mixture 2 and Mixture 3.

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Crozet, Martial. "Analyse tribologique du contact siège-soupape d'un moteur diesel." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI106.

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Au sein du moteur diesel, le contact siège-soupape est l’un des rares contacts secs. Cette absence de lubrification couplée avec la répétition des cycles de combustion (500 millions) et les conditions sévères de fonctionnement (pression de combustion de 18 MPa) l’expose à des dégradations importantes. Celles-ci se matérialisent par des enlèvements de métal au niveau de la soupape d’admission, aboutissant à terme à des fuites de gaz et au dysfonctionnement du moteur. Dans ce contexte, l’objectif est de comprendre les mécanismes de dégradation du contact siège-soupape, afin d’identifier les paramètres influençant l’usure et de proposer des solutions correctives. Pour y répondre, la démarche choisie s’appuyant sur les notions de triplet tribologique et de débit de matière au sein du contact a fait intervenir une double analyse numérique et expérimentale. Un modèle dynamique et un banc de culbuterie ont permis de montrer que les débits d’usure pouvaient être activés par l’architecture du mécanisme d’ouverture de la soupape. Par conséquent, la limitation de ces débits est obtenue par le contrôle de la géométrie « globale » du système et donc sans modification des matériaux. De la même manière, un modèle par éléments finis se focalisant sur la réponse locale des 1ers corps (siège-soupape) a permis de mettre en évidence l’impact de la géométrie « locale » du contact. Le changement de cette géométrie est un levier pour limiter le cisaillement des 1ers corps ce qui réduit l’arrachement de particules (débit source interne) et donc l’usure. Enfin, des essais réalisés sur le moteur et sur un banc d’essais spécifiquement adapté ont permis de finaliser la compréhension des mécanismes de dégradation (débit source, débit d’usure…). Les interprétations morphologiques des faciès d’usure du contact en terme de débits de matière ont permis de comprendre les mécanismes de formation d’une couche protectrice : le 3e corps (débit interne). Une solution pour favoriser ce débit interne est l’utilisation optimisée de polluants issus de la combustion. Par exemple, l’huile brûlée dans le contact (débit source externe), qui est a priori néfaste, devient ici une opportunité. De la même manière, les hydrocarbures imbrûlés issus de la combustion du biodiesel contribuent à protéger le contact
Within diesel engines, the valve-seat contact is one of the few non-lubricated contacts. Due to the lack of lubrication it is exposed to significant degradation. It is put in evidence by material removal at the intake valve. This material pull out is promoted by the replication of combustion cycles (500 million) and by severe operating conditions (pressure 18 MPa). The wear can possibly lead to gas leakage and to the engine failure. In this context, the target of this work was to understand degradation mechanisms of the valve-seat contact in order to identify parameters affecting its wear. To address this question, the chosen approach based on the tribological triplet and material flows within the contact involved a double numerical and experimental vision. A dynamic model and a valvetrain test bench showed that the wear flows could be activated by the architecture of the valve opening system. Therefore, the limitation of these flows is obtained by the control of the "global" geometry of the system and thus without modification of materials. In the same way, a finite element model focusing on the local response of the 1st bodies (seat-valve) made it possible to highlight the impact of the "local" geometry of the contact. The change of this geometry is a lever to limit shear stresses applied to 1st bodies which reduces the tearing of particles (internal source flow) and therefore wear. Finally, tests carried out on the engine and on a specifically adapted test bench made it possible to finalize the understanding of degradation mechanisms (source flow, wear flow ...). Morphological interpretations of worn surfaces in terms of material flows made it possible to understand the build up stages of a protective layer : the 3rd body (internal flow). One solution to promote this internal flow is the optimized use of pollutants from combustion. For example, the burned oil in contact (external source flow), which is a priori harmful, becomes an opportunity here. In the same way, un-burned hydrocarbons from the combustion of biodiesel help to protect the contact

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Misák, Petr. "Možnosti řízení a minimalizace rizik technologie výroby stavebních materiálů a výrobků pomocí fuzzy logiky a dalších nástrojů risk managementu." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-233814.

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The thesis proposes management options and risk minimizing in the field of building materials production technologies and related products using fuzzy logic and other risk management tools. The thesis indicates why some methodologies are not commonly used. The main purpose of this work (thesis) is to propose possible upgrades of standard methods in process capability and risk minimizing related to building materials and products. Markov analysis and fuzzy Markov chains are applied.

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Filho, Edson Souza de Jesus. ""PROCESSAMENTO, USINAGEM E DESGASTE DE LIGAS SINTERIZADAS PARA APLICAÇÕES AUTOMOTIVAS"." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-28062007-123420/.

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O objetivo deste trabalho foi desenvolver potenciais materiais para aplicações automotivas, em particular como insertos para assento de válvula em motores de combustão interna à gasolina. O desenvolvimento compreendeu as etapas de processamento dos materiais via metalurgia do pó, tratamento térmico, caracterização microestrutural e mecânica, usinagem e desgaste dos mesmos. O desenvolvimento objetivou principalmente a redução de custo e a aplicação de elementos menos poluentes, excluindo-se, por exemplo, a aplicação do Co devido ao seu alto custo e do Pb devido aos seus efeitos toxicológicos e prejudiciais ao meio ambiente. A realização de uma pesquisa minuciosa na busca de patentes relacionadas indicou que os materiais estudados apresentam composições particulares, e, portanto inéditas. Os resultados encontrados nos ensaios de dureza e de resistência à compressão radial nas amostras tratadas termicamente apresentaram resultados superiores aos da liga comercial atualmente em uso. Testes de usinabilidade em amostras sem tratamento térmico apresentaram comportamento similar ao da liga comercial, indicando que a usinabilidade do material praticamente não foi afetada com a mudança na composição química. Após a etapa de tratamento térmico, as ligas obtidas apresentaram valores de esforços de corte superiores aos do material comercial. Os resultados dos testes de desgaste abrasivo em amostras tratadas termicamente apresentaram menores valores de coeficientes de atrito e perda de massa em todos os casos em relação ao material comercial. Este comportamento é devido aos benefícios introduzidos pelo tratamento térmico executado e pela adição de alguns elementos resistentes ao desgaste na forma de carbonetos de Nb e Ti/W. Os resultados dos esforços de corte apresentaram boa concordância com os resultados dos ensaios de desgaste. Os materiais produzidos apresentam-se como potenciais candidatos para substituir, com vantagens, inserto para assento de válvula a base de Fe-Co em motores de combustão interna a gasolina.
The aim of this work was the development of materials for automotive applications, in particular, valve seat inserts for gasoline combustion engines. The development involved the following activities: processing by powder metallurgy techniques, heat treatment, mechanical and microstructural characterization, machining and wear of materials. This work was undertaken aiming cost reduction of this component by the use of cheaper and less pollutant elements, eliminating the presence of Co and Pb due to their high cost and toxicological effects, respectively. The accomplishment of a thorough research into patents revealed that the materials studied here present particular compositions and were not yet produced. The results of hardness measurements and the transverse radial strength of the studied materials, after heat treatment, revealed superior properties than the commercial alloys applied at the moment. The machining tests of the material without heat treatment indicated a similar behaviour in comparison to the commercial alloy, suggesting that the new alloy chemistry composition was not deleterious in this sense. After heat treatment, the obtained alloys presented a cutting force increase in relation to the commercial alloy. Wear tests results of heat treated materials presented smaller friction coefficient and mass loss than the commercial alloy, in all cases. This was especially achieved due to the advantages offered by heat treatment allied to the addition of NbC and Ti/W carbides. The materials obtained here showed to be potential candidates to substitute with advantages, valve seat inserts made of Fe-Co alloys for gasoline combustion engines.

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30

Ghoudi, Hamza. "Propriétés statistiques des réseaux des applications couplées et récurrence des applications des dendrites locales." Thesis, Toulon, 2019. http://www.theses.fr/2019TOUL0019.

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Cette thèse est divisée en deux grandes parties : la première est consacrée aux propriétés statistiques des systèmes dynamiques et l’autre porte sur des propriétés des systèmes dynamiques topologiques.Dans la première partie, d’abord nous rappelons quelques notions de base des systèmes dynamiques aléatoire et de la théorie des valeurs extrêmes. Ensuite, par l’application de cette théorie aux réseaux des applications couplées nous montrons que la probabilité de l’apparition de la synchronisation dans ces réseaux est liée à la distribution du maximum d’une certaine observable évaluée le long de presque toutes les orbites. De plus, nous montrons qu’une telle distribution appartient à la famille des lois des valeurs extrêmes, où le paramètre de cette distribution (indice extrémal) nous permet d’obtenir une description détaillée de la probabilité de synchronisation. Enfin, nous illustrerons les résultats théoriques par des calculs numériques robustes qui nous permettent d’aller au-delà du cadre théorique fourni.Dans la seconde partie, nous commençons par introduire quelques notions de base des systèmes dynamiques topologiques. Ensuite, nous étudions la relation entre les ensembles des points récurrents et périodiques d’une application continue de dendrites locales dans lui-même dans lequel l’ensemble des points d’extrémité est dénombrable
This thesis is divided into two parts the first is devoted to the study of the statistical properties of Dynamical systems and the other is about properties of topological dynamical systems.ln the first part, we recall the basic notions of random dynamical systems and the theory of extreme values. Then, by applying this theory to the cou pied map lattices, we show that the probability of the appearance of synchronization is related to the distribution of the maximum of a certain observable evaluated a long almost ail orbits. Moreover, we show that such a distribution belongs to the family of extreme value laws, where the parameter of this distribution (extremal index) allows us to obtain a detailed description of the probability of synchronization. Finally, we support the theoretical results by robust numerical computations that allow us to go beyond the theoretical framework. ln a second part, we give some basic notions of topological dynamical systems. Next, we study the relations between the sets of recurrent points and periodic points of a continuous self mapping of a local dendrite whose the endpoints set is countable

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31

Beisler, Matthias Werner. "Modelling of input data uncertainty based on random set theory for evaluation of the financial feasibility for hydropower projects." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2011. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-71564.

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The design of hydropower projects requires a comprehensive planning process in order to achieve the objective to maximise exploitation of the existing hydropower potential as well as future revenues of the plant. For this purpose and to satisfy approval requirements for a complex hydropower development, it is imperative at planning stage, that the conceptual development contemplates a wide range of influencing design factors and ensures appropriate consideration of all related aspects. Since the majority of technical and economical parameters that are required for detailed and final design cannot be precisely determined at early planning stages, crucial design parameters such as design discharge and hydraulic head have to be examined through an extensive optimisation process. One disadvantage inherent to commonly used deterministic analysis is the lack of objectivity for the selection of input parameters. Moreover, it cannot be ensured that the entire existing parameter ranges and all possible parameter combinations are covered. Probabilistic methods utilise discrete probability distributions or parameter input ranges to cover the entire range of uncertainties resulting from an information deficit during the planning phase and integrate them into the optimisation by means of an alternative calculation method. The investigated method assists with the mathematical assessment and integration of uncertainties into the rational economic appraisal of complex infrastructure projects. The assessment includes an exemplary verification to what extent the Random Set Theory can be utilised for the determination of input parameters that are relevant for the optimisation of hydropower projects and evaluates possible improvements with respect to accuracy and suitability of the calculated results
Die Auslegung von Wasserkraftanlagen stellt einen komplexen Planungsablauf dar, mit dem Ziel das vorhandene Wasserkraftpotential möglichst vollständig zu nutzen und künftige, wirtschaftliche Erträge der Kraftanlage zu maximieren. Um dies zu erreichen und gleichzeitig die Genehmigungsfähigkeit eines komplexen Wasserkraftprojektes zu gewährleisten, besteht hierbei die zwingende Notwendigkeit eine Vielzahl für die Konzepterstellung relevanter Einflussfaktoren zu erfassen und in der Projektplanungsphase hinreichend zu berücksichtigen. In frühen Planungsstadien kann ein Großteil der für die Detailplanung entscheidenden, technischen und wirtschaftlichen Parameter meist nicht exakt bestimmt werden, wodurch maßgebende Designparameter der Wasserkraftanlage, wie Durchfluss und Fallhöhe, einen umfangreichen Optimierungsprozess durchlaufen müssen. Ein Nachteil gebräuchlicher, deterministischer Berechnungsansätze besteht in der zumeist unzureichenden Objektivität bei der Bestimmung der Eingangsparameter, sowie der Tatsache, dass die Erfassung der Parameter in ihrer gesamten Streubreite und sämtlichen, maßgeblichen Parameterkombinationen nicht sichergestellt werden kann. Probabilistische Verfahren verwenden Eingangsparameter in ihrer statistischen Verteilung bzw. in Form von Bandbreiten, mit dem Ziel, Unsicherheiten, die sich aus dem in der Planungsphase unausweichlichen Informationsdefizit ergeben, durch Anwendung einer alternativen Berechnungsmethode mathematisch zu erfassen und in die Berechnung einzubeziehen. Die untersuchte Vorgehensweise trägt dazu bei, aus einem Informationsdefizit resultierende Unschärfen bei der wirtschaftlichen Beurteilung komplexer Infrastrukturprojekte objektiv bzw. mathematisch zu erfassen und in den Planungsprozess einzubeziehen. Es erfolgt eine Beurteilung und beispielhafte Überprüfung, inwiefern die Random Set Methode bei Bestimmung der für den Optimierungsprozess von Wasserkraftanlagen relevanten Eingangsgrößen Anwendung finden kann und in wieweit sich hieraus Verbesserungen hinsichtlich Genauigkeit und Aussagekraft der Berechnungsergebnisse ergeben

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32

邱俊瑋. "Design and Verification of Metal Seats for Double Eccentric Butterfly Valves." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/68878003383098478684.

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碩士
國立彰化師範大學
機電工程學系
100
In this study, computer-aided design (CAE) tool and finite element method (FEM) are applied to analyze performance of a double eccentric butterfly valve with metal seat. An experimental system was developed to measure the amount of valve leakage and the strain of the metal seat at various operation conditions with different pressures and temperatures where they can be drawn back to the design to improve the performance of the valve. Experimental results show that the higher pressure lead more leakage, and simultaneously the greater positive strain of the metal seat. The corresponding results to the analysis in FEM is that the strain of valve disc located in the back-end support rod is greater than that of the disc front contacted with the metal ring resulting in the dramatically decrease of the contact force which is the main factor of increasing the valve leakage. In situation of the high temperatures, the experimental results represent that the higher temperatures leads less valve leakage in case of the highest operation pressure, 300 psi. It indicates that the thermal deformation of the metal seat make the greater contact force with the disc to reduce valve leakage.

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33

"Self-similar sets and Martin boundaries." Thesis, 2008. http://library.cuhk.edu.hk/record=b6074537.

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In [DS1,2,3], Denker and Sato initiated a new point of view to study the problem. They identified the Sierpinski gasket as a Martin boundary of some canonical Markov chain and used the associated theory to consider the problem. In this thesis, we will extend their result so as to be applicable to all single-point connected monocyclic post critically finite (m.p.c.f.) self-similar sets.
In the first chapter, we review some basic facts of the self-similar sets and the Martin boundaries, and we prove that every m.p.c.f. self-similar set K is homeomorphic to the quotient space of the symbolic space associated with K, moreover, the homeomorphism is a Lipschitz equivalence for some special m.p.c.f. self-similar sets.
In the second chapter, we first prove that the quotient space of the symbolic space associated with K is homeomorphic to the Martin boundary with respect to the state space associated with K if K is a single-point connected m.p.c.f. self-similar set. Combining this result and the result in the first chapter, we conclude that every single-point connected m.p.c.f. self-similar set can be identified with the Martin boundary of some canonical Markov chain. Then for the 3-level Sierpinski gasket, we prove that there exists a one to one relation between the strongly P-harmonic functions on the 3 state space and K-harmonic functions constructed by Kigami.
In the third chapter, we define a new Markov chain on the pentagasket K which is a single-point connected m.p.c.f. self-similar also. Under the new Markov chain, we prove that K can be identified with the Martin boundary of the new Markov chain and that there exists a one to one relation between the strongly P-harmonic functions and the K-harmonic functions.
One of the fundamental problems in fractal analysis is to construct a Laplacian on fractals. Since fractals, like the Sierpinski gasket and the pentagasket, do not have any smooth structures, it is not possible to construct it from the classical point of view. Hence, until now there is no systematic way to define such a notion on the general class of fractals.
There are two approaches for the problem which have achieved some success in certain special situations. The first one is a probabilistic approach via constructing Brownian motions on self-similar sets. The second approach is an analytical one proposed by Kigami. He approximated the underlying self-similar set K by an increasing sequence of finite sets equipped with the discrete Laplacians Hm in a consistent way. He showed that if K is strongly symmetric, then Hm converge to a Laplacian on K.
by Ju, Hongbing.
"March 2008."
Adviser: Lau Ka Sing.
Source: Dissertation Abstracts International, Volume: 70-03, Section: B, page: 1702.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2008.
Includes bibliographical references (p. 91-94).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts in English and Chinese.
School code: 1307.

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34

Gallestey, Eduardo [Verfasser]. "Theory and numerics of spectral value sets / von Eduardo Gallestey Alvarez." 1998. http://d-nb.info/959500413/34.

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35

Lupienski, Jason. "Data analysis capability and traceability strategy throughout a cylinder head seat and valve guide process." 2007. http://proquest.umi.com/pqdweb?did=1320956681&sid=5&Fmt=2&clientId=39334&RQT=309&VName=PQD.

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Thesis (M.S.)--State University of New York at Buffalo, 2007.
Title from PDF title page (viewed on Nov. 15, 2007) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Wobschall, Darold. Includes bibliographical references.

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36

Lin, Sung-Chieh, and 林松杰. "Classifying the Value of Downstream Supply Chain Firm Using Rough Sets Theory." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/45588283129202875384.

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碩士
國立雲林科技大學
資訊管理系碩士班
95
Data Mining has been a maturely technology and it has been successfully applied to Customer Relationship Management (CRM). This research proposes a new method of valuation Analysis for Downstream Supply Chain Firm, which combined several technology of Data Mining. The proposed method could be more easy and efficient to discriminate who is the loyal customers, and provide the useful information to company for setting up the best selling strategy. This research focuses on two purposes：(1) Propose the method of attribute discretization to enhance classifier of Rough Sets; (2) Find out the target customers and characteristics of customers to do well customer relationship management for companies. In verification, this study collects a real dataset to verify the proposed method, the real dataset is the purchased records of customers from database of Company C. ie., firstly, utilize RFM(Recently、Frequency、Monetary) Model to get measure point for Customer Valuation. Secondly, take aggregated measure point to cluster customers by K-means. Lastly, use customer clustering as class and related attributes to produce the rule of Customer Valuation from Rough Sets classifier. The results can help C Company to differentiate and manage customers quickly. And, those rules could be applied to the other business to create the best benefit for the target customers.

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37

Tsai, Hong Wen, and 蔡鴻文. "Computation the Value Sets of Transfer Functions of Parametric Uncertainty Systems Using Interval Arithmetic." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/90304373689779711001.

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碩士
國立中正大學
化學工程研究所
88
The problem of robust stability analysis using interval arithmetic tools for a parametric uncertain system is to determine the locations of roots of characteristic polynomial whose coefficients are multi-linear with known bounds. Frequency domain properties of transfer functions provide the information of the feedback control design and computation the $H^\infty$-norm as well as the robust close-loop stability against parametric perturbations. An interval arithmetic converging with certainty is to compute arbitrarily good and reliable range enclosures of function value and solution of interval equations. This dissertation presents an algorithm of constructing the boundary of robust root locus and frequency response templates for uncertain plant in the complex plane with zero inclusion,and exclusion tests and the pivoting procedure. The robust root locus is the smallest set of regions in the complex plane in which all the roots of the characteristic polynomial p(s;q) lies when the feedback system under parameter variation. Find the locus of area in the complex plane such that p(s;q)=0 and the parameters lies in the given domain. Such areas are said to lie on the robust root loci applying the zero inclusion ,exclusion checking whether the value set includes the zero. The frequency response template of parametric transfer function G(jw;q)=N(jw;q)/D(jw;q)=z ,such that p(jw;q)=N(jw;q)-z*D(jw;q), can be found if z exists and satisfies p(jw;q)=0. Templates with sweeping frequency are useful in determining the $H^\infty$-norm. Being together with the pivoting procedure to trace the outer boundary of robust root locus and the frequency response template. The use of interval arithmetic was motivated by an effort to find accuracy bounds of solutions in numerical computations with generalized Gauss-Seidel iteration, and extend the original methods to analysis and design of systems. Instead of a particular value from the perturbation, complete variation interval in corresponding parameter is automatically guaranteed. Worked examples with computational results are included.

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Cho, Yu-Ju, and 卓昱汝. "Effects of Seat Surface Parameters and the Optimum Value on Schoolchildren of Different Heights." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/3yt3fs.

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碩士
國立臺北科技大學
創新設計研究所
102
Users’ physical and psychological needs are continued dynamically changing with time, environments and ages, in response to users'' dynamic needs under different conditions, furniture design should be added "dynamic" concepts. School-age is the important critical period for musculoskeletal growth and correct posture developing, we should emphasize whether the seat is conforming to the growing needs of children. Studies have found that the height, depth and width of the seat surface affect human’s postures, the stability of the center of gravity, and even the concentration and relaxation. Therefore, the research proposes that seat surface should be designed with dynamic concepts by modular method that is to swap the seat surface in a manner consistent demand for children of different heights. The research includes two stages: (1) collecting the ranges of different seat surface parameters with psychophysical methods; (2) investigate the effects of seat surface parameters on children od different heights, including posture, the center of gravity, concentration and relaxation. Results are as followings, (1) the effects of children’s posture and center of gravity of seat surface of height, depth and width are with significant differences, and the effects of children’s concentration and relaxation of seat surface of height are with significant difference. (2)The dynamic modular specifications of seat surface: length×width×height is 28×29×33cm, 30×35×36cm, 36×39×40.5cm, 40×45×43.5cm. The suggests of children’s dynamic modular specifications is to provide for future research and design reference, expect that children could develop correct postures in suitable seat surface parameters, and improves their learning concentration.

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39

Ma, Ke-Ping, and 馬克平. "Study on the Mechanism of Environmental Corrosion and Failure for 304 Stainless Steel and Copper Alloy Valve Sets." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/9b3x29.

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碩士
崑山科技大學
機械工程研究所
96
The structure materials of stainless steel and parts of copper alloy valve sets, employed to ship, were usually occurred by serious conditions of corrosion and fracture when they had immersed the sea and endured complex stress for a long time. Therefore, the systemic investigation of mechanism for the corrosion and fracture is employed in this study. The structure material of under water exhaust system and water tank reinforced material was made by 304L stainless steel and stayed in the seawater for a long time. The failure of 304L stainless steel endured complex stress corrosion was investigated in this study. The failures of slip-oil pump steady pin bolt and slip-oil separated valve made by copper alloy for the part of component was studied and analysis. In the experiment of this study, the failure structures of pipeline of exhaust system, rib material of water tank, slip-oil steady pin bolt and slip-oil separated valve made by copper alloy under water were cut individual with suit size for specimen. The X-ray, PT non-fracture detection, observation of metal micro-structure, hardness test, element spectrometer, SEM and EDS were used to investigate the mechanism of corrosion and failure. Based on the experimental results, the structure material of under water exhaust system and water tank reinforced material made by 304L stainless steel will induce serious stress corrosion failure because of staying in the seawater with chloride corrosion, the effect of internal combustion exhaust system with sulfur corrosion, microbiologically influenced corrosion, the corrosion of action of non-linear complex stress or platform of ship endure the vary forces from different sea-wave. On the other hand, the slip-oil steady pin bolt and slip-oil system separated tank valve were endured by action of tension or repeated stress, and then the fatigue and fracture failure will be occurred. In this study, the exact reasons of failure parts were found, and based on the results, we can support the reference of design ship and the material selection method.

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40

Atkinson, Matthew J. "Extreme value methods in body-burden analysis with application to inference from long-term data sets /." 2004. http://purl.galileo.usg.edu/uga%5Fetd/atkinson%5Fmatthew%5Fj%5F200405%5Fms.

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41

Zeng, Y., L. Zhang, Yakun Guo, J. Qian, and C. Zhang. "The generalized Hamiltonian model for the shafting transient analysis of the hydro turbine generating sets." 2014. http://hdl.handle.net/10454/7791.

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yes
Traditional rotor dynamics mainly focuses on the steady- state behavior of the rotor and shafting. However, for systems such as hydro turbine generating sets (HTGS) where the control and regulation is frequently applied, the shafting safety and stabilization in transient state is then a key factor. The shafting transient state inevitably involves multiparameter domain, multifield coupling, and coupling dynamics. In this paper, the relative value form of the Lagrange function and its equations have been established by defining the base value system of the shafting. Takingthe rotation angle and the angular speed of the shafting as a link, the shafting lateral vibration and generator equations are integrated into the framework of generalized Hamiltonian system. The generalized Hamiltonian control model is thus established. To make the model more general, additional forces of the shafting are taken as the input excitation in proposed model. The control system of the HTGS can be easily connected with the shafting model to form the whole simulation system of the HTGS. It is expected that this study will build a foundation for the coupling dynamics theory using the generalized Hamiltonian theory to investigate coupling dynamic mechanism among the shafting vibration, transient of hydro turbine generating sets, and additional forces of the shafting.
National Natural Science Foundation of China under Grant Nos. 51179079 and 50839003

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42

Adeyefa, Segun Adeyemi. "Satisficing solutions for multiobjective stochastic linear programming problems." Thesis, 2011. http://hdl.handle.net/10500/5703.

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Multiobjective Stochastic Linear Programming is a relevant topic. As a matter of fact, many real life problems ranging from portfolio selection to water resource management may be cast into this framework. There are severe limitations in objectivity in this field due to the simultaneous presence of randomness and conflicting goals. In such a turbulent environment, the mainstay of rational choice does not hold and it is virtually impossible to provide a truly scientific foundation for an optimal decision. In this thesis, we resort to the bounded rationality and chance-constrained principles to define satisficing solutions for Multiobjective Stochastic Linear Programming problems. These solutions are then characterized for the cases of normal, exponential, chi-squared and gamma distributions. Ways for singling out such solutions are discussed and numerical examples provided for the sake of illustration. Extension to the case of fuzzy random coefficients is also carried out.
Decision Sciences

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43

Adeyefa, Segun Adeyemi. "Satisticing solutions for multiobjective stochastic linear programming problems." Thesis, 2011. http://hdl.handle.net/10500/5703.

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Multiobjective Stochastic Linear Programming is a relevant topic. As a matter of fact, many real life problems ranging from portfolio selection to water resource management may be cast into this framework. There are severe limitations in objectivity in this field due to the simultaneous presence of randomness and conflicting goals. In such a turbulent environment, the mainstay of rational choice does not hold and it is virtually impossible to provide a truly scientific foundation for an optimal decision. In this thesis, we resort to the bounded rationality and chance-constrained principles to define satisficing solutions for Multiobjective Stochastic Linear Programming problems. These solutions are then characterized for the cases of normal, exponential, chi-squared and gamma distributions. Ways for singling out such solutions are discussed and numerical examples provided for the sake of illustration. Extension to the case of fuzzy random coefficients is also carried out.
Decision Sciences

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44

Beisler, Matthias Werner. "Modelling of input data uncertainty based on random set theory for evaluation of the financial feasibility for hydropower projects." Doctoral thesis, 2010. https://tubaf.qucosa.de/id/qucosa%3A22775.

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The design of hydropower projects requires a comprehensive planning process in order to achieve the objective to maximise exploitation of the existing hydropower potential as well as future revenues of the plant. For this purpose and to satisfy approval requirements for a complex hydropower development, it is imperative at planning stage, that the conceptual development contemplates a wide range of influencing design factors and ensures appropriate consideration of all related aspects. Since the majority of technical and economical parameters that are required for detailed and final design cannot be precisely determined at early planning stages, crucial design parameters such as design discharge and hydraulic head have to be examined through an extensive optimisation process. One disadvantage inherent to commonly used deterministic analysis is the lack of objectivity for the selection of input parameters. Moreover, it cannot be ensured that the entire existing parameter ranges and all possible parameter combinations are covered. Probabilistic methods utilise discrete probability distributions or parameter input ranges to cover the entire range of uncertainties resulting from an information deficit during the planning phase and integrate them into the optimisation by means of an alternative calculation method. The investigated method assists with the mathematical assessment and integration of uncertainties into the rational economic appraisal of complex infrastructure projects. The assessment includes an exemplary verification to what extent the Random Set Theory can be utilised for the determination of input parameters that are relevant for the optimisation of hydropower projects and evaluates possible improvements with respect to accuracy and suitability of the calculated results.
Die Auslegung von Wasserkraftanlagen stellt einen komplexen Planungsablauf dar, mit dem Ziel das vorhandene Wasserkraftpotential möglichst vollständig zu nutzen und künftige, wirtschaftliche Erträge der Kraftanlage zu maximieren. Um dies zu erreichen und gleichzeitig die Genehmigungsfähigkeit eines komplexen Wasserkraftprojektes zu gewährleisten, besteht hierbei die zwingende Notwendigkeit eine Vielzahl für die Konzepterstellung relevanter Einflussfaktoren zu erfassen und in der Projektplanungsphase hinreichend zu berücksichtigen. In frühen Planungsstadien kann ein Großteil der für die Detailplanung entscheidenden, technischen und wirtschaftlichen Parameter meist nicht exakt bestimmt werden, wodurch maßgebende Designparameter der Wasserkraftanlage, wie Durchfluss und Fallhöhe, einen umfangreichen Optimierungsprozess durchlaufen müssen. Ein Nachteil gebräuchlicher, deterministischer Berechnungsansätze besteht in der zumeist unzureichenden Objektivität bei der Bestimmung der Eingangsparameter, sowie der Tatsache, dass die Erfassung der Parameter in ihrer gesamten Streubreite und sämtlichen, maßgeblichen Parameterkombinationen nicht sichergestellt werden kann. Probabilistische Verfahren verwenden Eingangsparameter in ihrer statistischen Verteilung bzw. in Form von Bandbreiten, mit dem Ziel, Unsicherheiten, die sich aus dem in der Planungsphase unausweichlichen Informationsdefizit ergeben, durch Anwendung einer alternativen Berechnungsmethode mathematisch zu erfassen und in die Berechnung einzubeziehen. Die untersuchte Vorgehensweise trägt dazu bei, aus einem Informationsdefizit resultierende Unschärfen bei der wirtschaftlichen Beurteilung komplexer Infrastrukturprojekte objektiv bzw. mathematisch zu erfassen und in den Planungsprozess einzubeziehen. Es erfolgt eine Beurteilung und beispielhafte Überprüfung, inwiefern die Random Set Methode bei Bestimmung der für den Optimierungsprozess von Wasserkraftanlagen relevanten Eingangsgrößen Anwendung finden kann und in wieweit sich hieraus Verbesserungen hinsichtlich Genauigkeit und Aussagekraft der Berechnungsergebnisse ergeben.

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Dissertations / Theses on the topic 'Valve seats'

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