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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Thermal modelling and optimisation of building-integrated photo-voltaic thermal systems.

McDowell, Alastair Kieran Joel January 2015 (has links)
This Masters project has involved detailed thermal analysis of a unique renewable energies building. A TRNSYS model of this building has been developed and validated by real measurements and has shown to be capable of accurately predicting room temperatures and total heat gain from a solar-thermal roofing system. Supporting experiments were conducted experimentally and numerically. An experimental solar thermal testing unit constructed for the purpose of validating the solar-thermal roof concept. This experimental apparatus has been used to evaluate the effect of various operating procedures on the total heat gain from the system under a range of meteorological conditions. The validated thermal building model is used to conduct long-term simulations to provide a measure of year-round thermal performance of the building and estimated gains from renewable energy systems. Similar techniques are used to assist in the design and optimisation of a new transportable sustainable building concept in association with StoneWood Homes. It was found that a 4.5kW BIVP/T system could supply the small building with 100% of the yearly electrical energy and space heating requirements.
52

Cristallisation et transferts thermiques dans un polymère thermoplastique semi-cristallin en refroidissement rapide sous pression

Tardif, Xavier 22 October 2012 (has links) (PDF)
Une description précise des transferts de chaleurs est indispensable dans la simulation et l'optimisation de procédés, la qualité des pièces thermoplastiques semi-cristallines étant fortement liée à l'histoire thermique pendant la mise en forme. Cela requiert de connaître précisément les propriétés thermophysiques du polymère pour obtenir des résultats fiables. L'objectif de ce travail est de développer des dispositifs expérimentaux associés à des méthodes d'identifications afin de mesurer les propriétés thermiques et la cinétique de cristallisation du polymère dans les conditions de mise en œuvre. Une première étude expérimentale a permis de mettre au point un protocole de mesure et d'identification des propriétés thermiques ainsi que la cinétique de cristallisation de polypropylène par méthodes inverses sous faible pression et à faible vitesse de refroidissement. En parallèle, un nouvel appareil PvT fonctionnant jusqu'à 400°C et 200 MPa a été conçu et validé expérimentalement. La conductivité thermique et la cinétique de cristallisation ont été mesurées sous forte vitesse de refroidissement et sous forte pression. Un capteur de luminance combinant une fibre optique et un photodétecteur a été installé sur un banc expérimental du laboratoire pour mesurer la température de surface d'un polypropylène et ainsi identifier sa cinétique de cristallisation en refroidissement très rapide. Le capteur a ainsi été calibré et validées expérimentalement. La dernière partie traite du procédé d'injection thermoplastique en présentant une méthodologie d'identification de la cinétique de cristallisation à partir de la mesure de pression.
53

Development of PVT methodology and mounting experimental apparatus / Desenvolvimento de metodologia PVT e montagem de aparato experimental

Filipe Xavier Feitosa 25 February 2013 (has links)
CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / The aim of this work was to assemble an experimental apparatus PVT skilled labor in obtaining phase equilibria at high pressures and determining efficient methodology. Tests were performed mounting apparatus in order to develop methodology. During these tests, the data bubble point of pure carbon dioxide were determined at temperatures of 25, 26, 27 and 28  C and compared with data obtained for similar equipment, providing average deviation of 0.4 Bar, 0.6% on the extent being of the same order of magnitude compared to similar equipment. For testing systems in which one liquid component is introduced at ambient pressure in the analysis phase equilibrium torque was analyzed ethanol-CO2 at 40  C, and also compared with the literature data. The results obtained in steps preliminary analyzes showed that the system was capable of developing new data phase equilibrium. The study continued with the application development methodology for systems of viscera from fish oil + carbon dioxide oil, fish viscera + carbon dioxide + ethanol, corn oil + carbon dioxide and corn oil + ethanol + carbon dioxide at temperatures of 40, 50, 60, 70, 80, 90 and 110  C for systems without ethanol at temperatures of 40, 60, 80 and 110  C, for others. The phase diagrams obtained for all systems studied were of type IV according to the classification of Von Konynen and Scott, which is similar to that found in literature phase diagrams for systems consisting of triglycerides and carbon dioxide, showing the ability development of new data for the set-apparatus developed methodology. / O objetivo desta dissertaÃÃo foi montar um aparato experimental PVT hÃbil ao trabalho na obtenÃÃo de equilÃbrio de fases em altas pressÃes e a determinaÃÃo de metodologia eficiente. Testes de montagem no aparato foram realizados com o intuito de desenvolver a metodologia. Durantes estes testes, dados do ponto de bolha do diÃxido de carbono puro foram determinados em temperaturas de 25, 26, 27 e 28 ÂC e comparados com dados obtidos para equipamentos similares, fornecendo desvio mÃdio de 0,4 Bar, 0,6 % relativo à medida, sendo da mesma ordem de grandeza em relaÃÃo a equipamentos similares. Para testes de sistemas em que um componente lÃquido à pressÃo ambiente fosse introduzido nas anÃlises de equilÃbrio de fases o binÃrio etanol-CO2 foi analisado a 40 ÂC, e tambÃm comparado com dados da literatura. Os resultados obtidos nas etapas de anÃlises preliminares mostraram que o sistema estava apto a desenvolver novos dados de equilÃbrio de fases. Os estudos prosseguiram com o desenvolvimento da aplicaÃÃo da metodologia para os sistemas de Ãleo de vÃscera de peixe + diÃxido de carbono, Ãleo de vÃscera de peixe + etanol + diÃxido de carbono, Ãleo de milho + diÃxido de carbono e Ãleo de milho + etanol + diÃxido de carbono nas temperaturas de 40, 50, 60, 70, 80, 90 e 110 ÂC para os sistemas sem etanol e nas temperaturas de 40, 60, 80 e 110 ÂC, para os demais. Os diagramas de fases obtidos para todos os sistemas estudados foram do tipo IV de acordo com a classificaÃÃo de Von Konynen e Scott, o que se assemelha ao encontrado na literatura de diagramas de fase para sistemas constituÃdos de triglicerÃdeos e diÃxido de carbono, mostrando a capacidade de desenvolvimento de novos dados para o conjunto metodologia-aparato desenvolvido.
54

Barriers in Implementation of Green Supply Chain Management : Case Study on Synthite Industries Pvt Ltd, India

JOY, EDWIN, VIJAYAN, ARCHANA January 2023 (has links)
No description available.
55

NUMERICAL MODELLING OF A NOVEL PVT COLLECTOR AT CELL RESOLUTION

Schön, Gustav January 2017 (has links)
Solar photovoltaic-thermal (PVT) modules produce heat and power via a heat exchanger attached to the rear of the PV cells. The novel PVT collector in this study is previously untested and therefore its behaviour and thermo-electric performance due to fluid channel configuration and in various climate and operating conditions are unknown. Moreover, the working fluid flowing through the heat exchanger cause a temperature gradient across the module such that a cell near the inlet and a cell near the outlet may have significant temperature differences. PV cells are sensitive to temperature; however the most common way to simulate power output from a PVT is to use the average temperature and ignore the gradient. In this study, a single diode PV model is incorporated into a commercial thermal solver to co-simulate the thermal and electrical output of a novel PVT module design with cell level resolution. The PVT system is modelled in steady state under various wind speeds, inlet temperatures, ambient temperatures, flow rates, irradiation, convection coefficients from coolant and back of the module and two different fluid channel configurations. The results show that of the controllable variables, the inlet temperature has the highest influence of the total power output and that a parallel flow of the fluid channel configuration is preferable. The difference between the cell resolution and the module resolution simulations do not motivate the use of a higher resolution numerical simulation. / En kombinerad solcellspanel och solvärmefångare (PVT) producerar värme och elenergi på samma yta genom att en värmeväxlare upptar värmen från baksidan av solcellspanelen. Den PVT som berörs i denna studien är nyutvecklad och har aldrig tidigare testats, vilket medför att data för hur den beter sig samt dess termo-elektiska prestanda saknas för olika driftförhållanden samt flödeskonfigurationer. Vidare ger mediet som flödar genom värmeväxlaren upphov till en temperaturgradient, vilken kan innebära en påtaglig skillnad i temperatur mellan solcellerna i solcellspanelen vid mediets in- respektive utlopp. Trots solcellers temperaturkänslighet, så sker simulering i allmänhet med avseende på panelens medeltemperatur istället för att hänsyn tas till denna temperaturgradient. I den här studien implementeras en så kallad  ”single diode”-modell i en kommersiell numerisk mjukvara termiska beräkningar för att samsimulera termiskt och elektriskt effektuttag ur den nyutvecklade PVT-designen. Designen modelleras statiskt under givna variationer av vindhastighet, inloppstemperatur, omgivande temperatur, flödeshastighet, solinstrålning och konvektionskoefficienter för mediet samt baksidan av modulen. Resultaten visar att kontrollerbara variabler som inloppstemperatur har högst inverkan på den totala effekten samt att en parallell flödeskonfiguration lämpar sig bäst. Studien visar också att skillnaden mellan simulering på cellnivå och modulnivå inte motiverar en numerisk beräkningsmetod med upplösning satt till solcellsnivå.
56

Comparative Analysis of PVT Scintillators for the Development of a Fast Neutron Imager

Shawger, Richard Elwood 22 September 2016 (has links)
No description available.
57

Effects of pulse-modulated microwave radiation from mobile phones on the sleep/waking EEG and psychomotor vigilance

Hung, Ching-Sui January 2008 (has links)
This study employed multiple assessments, including sleep/resting waking EEG (visual scoring and power spectral analysis) and psychomotor vigilance task, to access effects of varying pulse-modulated microwaves (such as: 'talk', 'listen' and 'standby' mode signals) emitted from a standard mobile phone. The idea was prompted by a finding that the pulse modulation frequencies of mobile phone signals correspond to the frequencies of brain delta and alpha waves. Thereby it is possible the brain is able to recognize and respond to the low-frequency components of the mobile phone signals. Supporting evidence comes from repetitively reported EEG alpha and spindle effects of the 2, 8 and 217-Hz pulsed microwave exposure. Furthermore, brain imaging (EEG and PET) studies reveal 'low-frequency pulse-modulated waves' rather than the 'microwave frequency carrier waves' is the sine qua non for inducing these brain physiological effects [Huber et al., 2002, 2005; Regel et al., 2007a]. On the other hand, recent converging evidence, from molecular, behavioural and electrophysiological level, have shown that brain plasticity is a continuous process from waking to sleep and, sleep, a well-defined physiological condition, is 'shaped' by the waking experiences. The latter findings suggest certain sleep EEG features may characterize levels of cortical plasticity during wakefulness. The work presented in this thesis was inspired by these studies and aimed to understand how the real mobile phone signals with different low-frequency pulsing components [such as 'talk' (8, 217 Hz pulsed), 'listen' (2, 8, 217 Hz pulsed) and 'stand by' mode < 2 Hz pulsed)] change human brain electrical activities from waking to sleep. We approached this question based on EEG analysis in two domains: (1) EEG visual scoring; (2) EEG spectral analysis from relaxed waking to the deeper stages of non-NREM sleep. We also looked at the effects on the psychomotor vigilance performance. Results suggest 'talk' and 'Iisten/standby' modes have inverse effects on the distinctive thalamo-cortical oscillation modes and may thus impart inverse effects on their sleep structures. The implications of this study are of practical importance as it suggests the thalamo-cortical oscillations can be modulated by synchronizing rTMS/tDCS/DBS and sleeplwaking EEG. This concept may be applied to modulate the brain oscillation modes for enhancing sleep-dependent brain plastiCity or information processing.
58

Filtros RC-Ativo ULV e ULP combinando OTA de único estágio e transcondutância negativa de entrada para receptores RF de baixa energia. / ULV and ULP active-RC filters combining single-stage OTA and negative input transconductance for low energy RF receivers.

Severo, Lucas Compassi 04 February 2019 (has links)
Este trabalho propõe novas topologias de circuitos e técnicas de projeto para filtros ativos e amplificadores de ganho programável (PGA) com operação em ultra baixa tensão (ULV) e ultra-baixa potência (ULP). Os receptores de RF do tipo Bluetooth de baixa energia (BLE), utilizados nos circuitos de internet das coisas (IoT), são as aplicações alvo dos circuitos propostos neste trabalho. Na faixa de ULV são utilizados filtros do tipo RC-ativo, uma vez que possuem uma maior linearidade em relação aos filtros do tipo gmC. A operação em ULP é alcançada neste trabalho utilizando uma nova topologia de amplificador operacional de transcondutância (OTA), com único estágio, que apresenta uma alta eficiência e reduzida sensibilidade às variações de processo, tensão e temperatura (PVT). O baixo ganho de tensão do amplificador de estágio único e os efeitos das cargas resistivas de realimentação são compensados usando um transcondutor negativo, robusto a variações em PVT, conectado às entradas do OTA. A faixa dinâmica dos circuitos é elevada usando topologias totalmente diferenciais e as taxas de rejeição de modo comum e de fonte de alimentação são melhoradas utilizando circuitos de realimentação de modo-comum. Para possibilitar a operação na faixa de ULV todos os circuitos usam apenas dois transistores empilhados e o nível de inversão do canal é elevado através da polarização direta do substrato. Neste trabalho são propostas também uma ferramenta de análise do ponto de operação do transistor, baseando-se na simulação elétrica, e algumas metodologias de projetos para circuitos operando em ULV. Os circuitos e metodologias desenvolvidos foram utilizados para o projeto de um filtro passa-faixa complexo RC-ativo de terceira ordem, um amplificador de ganho programável e um filtro biquadrático do tipo Tow-Thomas com ganho programável, compatíveis com receptores de RF do padrão BLE. Para a implementação do PGA, uma nova topologia de transconductor negativo programável foi desenvolvida para permitir a compensação ótima do amplificador operacional em todos os modos de ganho. Todos os circuitos foram projetados para operar com uma tensão de alimentação de 0,4 V e foram prototipados em processos de fabricação CMOS e BiCMOS de 180 nm e 130 nm, respectivamente. Os resultados experimentais e de simulação pós-layout demonstram uma operação adequada em 0,4 V, uma ultra-baixa dissipação de potência, atingindo o mínimo de 10.9 ?W/polo, e a melhor figura-de-mérito (FoM) em relação aos outros filtros ativos e amplificadores disponíveis na literatura. / This thesis proposes novel circuit topologies and design techniques of ultra-low voltage (ULV) and ultra-low power (ULP) active-filters and programmable gain amplifiers (PGA) suitable for the Bluetooth low energy (BLE) RF receivers used in the Internet of Things (IoT) applications. The active-RC filters are preferred to the gm-C topologies at the ULV operation due to its improved linearity. However, the closed-loop operation increases the operational amplifier required voltage gain and its capacity to drive the resistive feedback load. In this work, the ULP dissipation is obtained by proposing a very efficient single-stage inverter-based operational transconductance amplifier (OTA) and a proper forward bulk biasing to reduce the sensitivity to process, voltage and temperature (PVT) variations. The low voltage gain and the resistive load effects on the single-stage OTA are completely compensated by using a PVT robust negative transconductor connected at the OTA inputs. The dynamic range is increased by using fully-differential topologies and common-mode feedback to improve the common-mode and power supply rejection rates. The operation at the ULV range is reached by using only two-stacked transistors in all the circuit implementations and bulk forward bias in some transistors to reduce the threshold voltage and to increase the channel inversion level. An operation point simulation-based tool and some design methodologies are also proposed in this work to design the ULV circuits. The proposed circuits were used to design a third-order active-RC complex band-pass filter (CxBPF), a programmable gain amplifier (PGA) and a Tow-Thomas biquad, with integrated programmable gain capability, suitable for BLE RF receivers. The PGA implementation uses a new programmable input negative transconductor to obtain the optimal closed-loop amplifier compensation in all the gain modes. The circuits were designed to operate at the power supply voltage of 0.4 V and are prototyped in 180 nm and 130 nm low-cost CMOS and BiCMOS process, respectively. The experimental and post-layout simulation results have demonstrated the proper ULV operation at 0.4 V, the ultra-low power dissipation down to 10.9 ?W/pole and the best figure-of-merit (FoM) among the state-of-the-art active-filters and amplifiers from the literature.
59

Evaluation of a Flat-Plate Photovoltaic Thermal (PVT) Collector prototype

Linde, Daniel January 2016 (has links)
This Master thesis, in collaboration with Morgonsol Väst AB, was completed as a part of the Solar Energy engineering program at Dalarna University. It analyses the electrical and thermal performance of a prototype PVT collector developed by Morgonsol Väst AB. By following the standards EN 12975 and EN ISO 9806 as guides, the thermal tests of the collector were completed at the facility in Borlänge. The electrical performance of the PVT collector was evaluated by comparing it to a reference PV panel fitted next to it. The result from the tests shows an improved electrical performance of the PVT collector caused by the cooling and a thermal performance described by the linear efficiency curve ηth=0.53-21.6(Tm-Ta/G). The experimental work in this thesis is an initial study of the prototype PVT collector that will supply Morgonsol Väst with important data for future development and research of the product.
60

Laboratory and modelling studies on the effects of injection gas composition on CO₂-rich flooding in Cooper Basin, South Australia.

Bon, Johannes January 2009 (has links)
This Ph.D. research project targets Cooper Basin oil reservoirs of very low permeability (approximately 1mD) where injectivities required for water flooding are not achievable. However, the use of injection gases such as CO₂ would not have injectivity problems. CO₂ is abundant in the region and available for EOR use. CO₂ was compared to other CO₂-rich injection gases with a hydrocarbon content including pentane plus components. While the effect of hydrocarbon components up to butane have been investigated in the past, the effect of n-pentane has on impure CO₂ gas streams has not. One particular field of the Cooper Basin was investigated in detail (Field A). However, since similar reservoir and fluid characteristics of Field A are common to the region it is expected that the data measured and developed has applications to many other oil reservoirs of the region and similar reservoirs elsewhere. The aim of this Ph.D. project is to determine the applicability of CO₂ as an injection gas for Enhanced Oil Recovery (EOR) in the Cooper Basin oil reservoirs and to compare CO₂ with other possible CO₂-rich injection gases. The summarised goals of this research are to: • Determine the compatibility of Field A reservoir fluid with CO₂ as an injection gas. • Compare CO₂ to other injection gas options for Field A. • Development of a correlation to predict the effect of nC₅ on MMP for a CO₂- rich injection gas stream. These goals were achieved through the following work: • Extensive experimental studies of the reservoir properties and the effects of interaction between CO₂-rich injection gas streams and Field A reservoir fluid measuring properties related to: • Miscibility of the injection gas with Field A reservoir fluid • Solubility and swelling properties of the injection gas with Field A reservoir fluid • Change in viscosity-pressure relationship of Field A reservoir fluid due to addition of injection gas • A reservoir condition core flood experiment • Compositional simulation of the reservoir condition core flood to compare expected recoveries from different injection gases • Development of a set of Minimum Miscibility Pressure (MMP) measurements targeted at correlating the effect of nC₅ on CO₂ MMP. The key findings of this research are as follows: • Miscibility is achievable at practical pressures for Field A and similar reservoir fluids with pure CO₂ or CO₂-rich injection gases. • For Field A reservoir fluid, viscosity of the remaining flashed liquid will increase at pressures below ~2500psi due to mixing the reservoir fluid with a CO₂-rich injection gas stream. • Comparison of injection gases showed that methane rich gases are miscible with Field A so long as a significant quantity of C₃+ components is also present in the gas stream. • There is a defined trend for effect of nC₅ on MMP of impure CO₂. This trend was correlated with an error of less than 4%. • Even though oil composition is taken into account with the base gas MMP, it still affects the trend for effect of nC₅ on MMP of a CO₂-rich gas stream. • An oil characterisation factor was developed to account for this effect, significantly improving the results, reducing the error of the correlation to only 1.6%. The significance of these findings is as follows: • An injection pressure above ~3000psi should be targeted. At these pressures miscibility is achieved and the viscosity of the reservoir fluid injection gas mix is reduced. • CO₂ should be compared to gases such as Tim Gas should after considering the cost of compression, pipeline costs and distance from source to destination will need to be considered. • The addition of nC₅ will reduce the MMP and increase the recovery factor, however the cost of the nC₅ used would be more than the value of increased oil recovered. • The developed correlation for the effect of nC₅ on impure CO₂ MMP can be used broadly within the limits of the correlation. • Further research using more oils is necessary to validate the developed oil characterisation factor and if successful, using the same or similar method used to improve other correlations. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1369016 / Thesis (Ph.D.) -- University of Adelaide, Australian School of Petroleum, 2009.

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