Dissertations / Theses on the topic 'Thermal time'
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Feldgoise, Jeffrey. "Thermal design through space and time." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/65983.
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Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 1997.Includes bibliographical references (p. 89-90).
One of the primary roles of architecture is to control the environment at the service of a building's inhabitants. Thermal qualities are a significant factor in the overall experience one has inside and outside a building. However, thermal issues are not often considered within the context of the architectural design process, resulting in buildings that are not responsive to thermal concerns. Heat has the potential to influence the form of architectural space. The methods by which architects can use thermal energy as a formative element in design is open to further exploration. In this thesis, I explore new methods for architects to describe thermal intentions and visualize thermal qualities of design proposals. Beyond the economic issue of energy conservation, the thermal qualities of building spaces affect the quality of human inhabitation. The capability to describe and visualize heat would allow architects to adjust the building's thermal characteristics to modify a person's experience of the place. With a more complete understanding of thermal qualities of their building proposals, architects would be able to design for the complete gamut of thermal sensations that humans can experience. What is needed is a working vocabulary that describes the range of thermal conditions possible in buildings. In this work, I describe a vocabulary for a building's thermal qualities using four sets of measurable, opposing terms: open versus protected, bright versus dim, warm versus cool, and active versus still. Next, I then articulate the thermal qualities of a co-housing project to create a thermal experience that enhances the community aspects of co-housing. Using a variety of visualization techniques, I verify that the design proposal is achieving the intended thermal goals. Using the knowledge gained from this and future thermal design exercises, we can begin to reflect on the general relationships between thermal phenomena and physical building forms, learning about the thermal qualities of architecture.
Jeffrey Feldgoise.
M.Arch.
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Alshatshati, Salahaldin Faraj. "Estimating Envelope Thermal Characteristics from Single Point in Time Thermal Images." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1512648630005333.
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Michiorri, Andrea. "Power system real-time thermal rating estimation." Thesis, Durham University, 2010. http://etheses.dur.ac.uk/469/.
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This Thesis describes the development and testing of a real-time rating estimation algorithm developed at Durham University within the framework of the partially Government-funded research and development project “Active network management based on component thermal properties”, involving Durham University, ScottishPower EnergyNetworks, AREVA-T&D, PB Power and Imass. The concept of real time ratings is based on the observation that power system component current carrying capacity is strongly influenced by variable environmental parameters such as air temperature or wind speed. On the contrary, the current operating practice consists of using static component ratings based on conservative assumptions. Therefore, the adoption of real-time ratings would allow latent network capacity to be unlocked with positive outcomes in a number of aspects of distribution network operation. This research is mainly focused on facilitating renewable energy connection to the distribution level, since thermal overloads are the main cause of constraints for connections at the medium and high voltage levels. Additionally its application is expected to facilitate network operation in case of thermal problems created by load growth, delaying and optimizing network reinforcements. The work aims at providing a solution to part of the problems inherent in the development of a real-time rating system, such as reducing measurements points, data uncertainty and communication failure. An extensive validation allowed a quantification of the performance of the algorithm developed, building the necessary confidence for a practical application of the system developed.
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Gaffney, Eamonn Andrew. "Aspects of imaginary time thermal field theory." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627526.
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LeVett, Marshall Allan. "Parallel Time-Marching for Fluid-Thermal-Structural Interactions." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1452178897.
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Babich, Francesco. "Thermal comfort in non-uniform environments : real-time coupled CFD and human thermal regulation modelling." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/32835.
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Energy consumption in buildings contributes more greenhouse gas emissions than either the industrial or transportation sectors, primarily due to space cooling and heating energy use, driven by the basic human need for thermal comfort and good indoor air quality. In recent years, there has been a proliferation of air conditioning in both residential and commercial buildings especially in the developing economic areas of the world, and, due to the warming climate and the growing disposable income in several densely populated developing countries, the energy demand for space cooling is dramatically increasing. Although several previous studies focused on thermal comfort, there are only a few works on asymmetrical environments or transient conditions, such as those expected when mixed mode ventilation or other low energy techniques such as elevated air movement generated by ceiling fans are adopted in the residential sector. Moreover, even fewer studies addressed the accuracy of computer predictions of human thermal comfort in non-uniform environmental conditions. However, focusing on non-uniform thermal environments is important because the space conditioning systems that generate them are often likely to be less energy consuming than those which provide more homogeneous conditions. This is due to the fact that these less energy-intensive space conditioning systems tend to condition the occupants, and not the entire room. The aim of this research was to investigate human thermal comfort in non-uniform transient environmental conditions, focusing in particular on the capability of predicting human thermal comfort in such conditions in residential buildings. Furthermore, this research investigated the energy savings that can be achieved in residential buildings when the same level of thermal comfort is delivered using less conventional, but lower-energy, approaches. In this research, a combination of computer based modelling, experimental work in controlled environments, and data from field studies was used. Computer modelling comprised CFD coupled with a model of human thermal physiology and human thermal comfort, and dynamic thermal modelling. In the experimental work, environmental chambers were used to collect data to validate the coupled CFD model. The data from field studies on real domestic buildings in India and in the UK was used to identify the most relevant configurations to be modelled using the coupled system. This research led to three main conclusions concerning thermal comfort in non-uniform environments: (i) the coupled model is able to predict human thermal comfort in complex non-uniform indoor configurations, as long as the environment around the human body is accurately modelled in CFD, and is superior to the traditional PMV model as both temporal and spatial variation and non-uniform conditions can be taken into account; (ii) dynamic thermal simulation completed using a dynamic cooling set-point showed that the energy demand for space cooling can be reduced by as much as 90% in mixed mode buildings by using ceiling fans, without jeopardising occupants' thermal comfort; and (iii) the accurate and validated transient three-dimensional CFD model of a typical Indian ceiling fan developed in this research can be used for any study that requires the air flow generated by a ceiling fan to be modelled in CFD.
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Acomb, Simon. "Applications of nonlinear dynamics to time dependent thermal convection." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305477.
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Cosma, Andrei Claudiu. "Real-Time Individual Thermal Preferences Prediction Using Visual Sensors." Thesis, The George Washington University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=13422566.
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The thermal comfort of a building’s occupants is an important aspect of building design. Providing an increased level of thermal comfort is critical given that humans spend the majority of the day indoors, and that their well-being, productivity, and comfort depend on the quality of these environments. In today’s world, Heating, Ventilation, and Air Conditioning (HVAC) systems deliver heated or cooled air based on a fixed operating point or target temperature; individuals or building managers are able to adjust this operating point through human communication of dissatisfaction. Currently, there is a lack in automatic detection of an individual’s thermal preferences in real-time, and the integration of these measurements in an HVAC system controller.
To achieve this, a non-invasive approach to automatically predict personal thermal comfort and the mean time to discomfort in real-time is proposed and studied in this thesis. The goal of this research is to explore the consequences of human body thermoregulation on skin temperature and tone as a means to predict thermal comfort. For this reason, the temperature information extracted from multiple local body parts, and the skin tone information extracted from the face will be investigated as a means to model individual thermal preferences.
In a first study, we proposed a real-time system for individual thermal preferences prediction in transient conditions using temperature values from multiple local body parts. The proposed solution consists of a novel visual sensing platform, which we called RGB-DT, that fused information from three sensors: a color camera, a depth sensor, and a thermographic camera. This platform was used to extract skin and clothing temperature from multiple local body parts in real-time. Using this method, personal thermal comfort was predicted with more than 80% accuracy, while mean time to warm discomfort was predicted with more than 85% accuracy.
In a second study, we introduced a new visual sensing platform and method that uses a single thermal image of the occupant to predict personal thermal comfort. We focused on close-up images of the occupant’s face to extract fine-grained details of the skin temperature. We extracted manually selected features, as well as a set of automated features. Results showed that the automated features outperformed the manual features in all the tests that were run, and that these features predicted personal thermal comfort with more than 76% accuracy.
The last proposed study analyzed the thermoregulation activity at the face level to predict skin temperature in the context of thermal comfort assessment. This solution uses a single color camera to model thermoregulation based on the side effects of the vasodilatation and vasoconstriction. To achieve this, new methods to isolate skin tone response to an individual’s thermal regulation were explored. The relation between the extracted skin tone measurement and the skin temperature was analyzed using a regression model.
Our experiments showed that a thermal model generated using noninvasive and contactless visual sensors could be used to accurately predict individual thermal preferences in real-time. Therefore, instantaneous feedback with respect to the occupants' thermal comfort can be provided to the HVAC system controller to adjust the room temperature.
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Mackwood, Andrew. "Numerical simulations of thermal processes and welding." Thesis, University of Essex, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272572.
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Huang, Huang. "Power and Thermal Aware Scheduling for Real-time Computing Systems." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/610.
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Over the past few decades, we have been enjoying tremendous benefits thanks to the revolutionary advancement of computing systems, driven mainly by the remarkable semiconductor technology scaling and the increasingly complicated processor architecture. However, the exponentially increased transistor density has directly led to exponentially increased power consumption and dramatically elevated system temperature, which not only adversely impacts the system's cost, performance and reliability, but also increases the leakage and thus the overall power consumption. Today, the power and thermal issues have posed enormous challenges and threaten to slow down the continuous evolvement of computer technology. Effective power/thermal-aware design techniques are urgently demanded, at all design abstraction levels, from the circuit-level, the logic-level, to the architectural-level and the system-level.
In this dissertation, we present our research efforts to employ real-time scheduling techniques to solve the resource-constrained power/thermal-aware, design-optimization problems. In our research, we developed a set of simple yet accurate system-level models to capture the processor's thermal dynamic as well as the interdependency of leakage power consumption, temperature, and supply voltage. Based on these models, we investigated the fundamental principles in power/thermal-aware scheduling, and developed real-time scheduling techniques targeting at a variety of design objectives, including peak temperature minimization, overall energy reduction, and performance maximization.
The novelty of this work is that we integrate the cutting-edge research on power and thermal at the circuit and architectural-level into a set of accurate yet simplified system-level models, and are able to conduct system-level analysis and design based on these models. The theoretical study in this work serves as a solid foundation for the guidance of the power/thermal-aware scheduling algorithms development in practical computing systems.
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Yu, Ying Diana. "Real-time computer control for wafer in rapid thermal processing." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq20891.pdf.
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Rogers, John Ashley. "Real time impulsive stimulated thermal scattering of thin polymer films." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13130.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemistry and Dept. of Physics, 1992.Title as it appears in the M.I.T. Graduate List, Feb. 1992: Real time impulsive stimulated thermal scattering from supported thin polymer films.
Includes bibliographical references (p. 163-165).
by John Ashley Rogers.
M.S.
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Daniel, Kyle Andreas. "Space-time Description of Supersonic Jets with Thermal Non-uniformity." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/95942.
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The supersonic jet plumes that exhaust from the engines of tactical aircraft produce intense noise signatures that expose the Navy personnel working on the deck of aircraft carriers to dangerously high levels of noise that often results in hearing damage. Reducing the noise radiated by these supersonic plumes is of interest to the Department of Defense and is the primary motivation of this research. Fundamentally, jet noise reduction is achieved by manipulating the nozzle boundary condition to produce changes in the turbulence development and decrease the acoustic efficiency of coherent structures. The research presented here focuses on a novel jet noise reduction technique involving a centered thermal non-uniformity that alters the base flow by introducing a temperature-driven centerline velocity deficit into a perfectly expanded Mach 1.5 jet. The results indicate $2 pm 0.5$ dB reductions in peak narrowband spectral sound pressure levels upstream of peak directivity directions for the non-uniform jet compared to a thermally uniform baseline, even for static thrust matched conditions. This reduction is hypothesized to be related to perturbations induced by the thermal non-uniformity that convect inside the irrotational core and reduce the correlation length scales of turbulence at locations far downstream. This hypothesis was evaluated by studying the coherent turbulence via its convective hydrodynamic footprint in the near-field. An indirect investigation of the near-field using a far-field-informed model of the wavenumber-frequency spectra indicate a reduction in the energy contained in the tail of the wavenumber spectra amplitude, suggesting a reduction in the size of large scale structures. A direct evaluation of the spatio-temporal behavior of the near-field was performed using temporally resolved schlieren images. Space-time correlations of the frequency-filtered near-field identified high frequency acoustic waves radiated by compactly coherent turbulent structures and low frequency Mach waves produced by large scale instabilities. In the thermally non-uniform case these features and their sources were found to be decorrelated at downstream regions. These results provide strong evidence that a centered thermal non-uniformity reduces the radiated noise compared to a uniform baseline by shortening the correlation length scales of coherent structures in regions far from the nozzle exhaust.Doctor of Philosophy
A more complete understanding of the intense noise sources present in supersonic jet plumes is of value to both government and industry, and is a necessary step towards optimizing noise reduction techniques. Tactical aircraft that operate on the deck of aircraft carriers expose Navy personnel to dangerously high levels of noise that often results in permanent hearing damage. Supersonic jet noise reduction is also of relevance to the recent efforts to revitalize supersonic air transport over land. For supersonic air transport to become a reality, the noise produced by these future aircraft during takeoff and landing must meet the increasingly stringent community noise requirements. Fundamental jet noise research is needed to guide the design of future engine architectures for these aircraft to ensure their commercial success. The research presented herein examines a novel noise reduction technique that involves a centered thermal non-uniformity consisting of a heated jet plume with a spot of locally cooler, slower moving air concentrated along the centerline of a Mach 1.5 jet. This temperature driven velocity deficit is shown to reduce the radiated noise by up to 2.5 dB at peak frequencies and at angles just outside of the peak directivity direction. The cause of the noise reduction is hypothesized be related to a reduction in the size of the coherent structures that radiate a majority of the noise produced by turbulent jets. This hypothesis is evaluated by examining the 'footprint' of the coherent structures in the ambient field directly outside of the jet shear layer in an area called the near-field. An indirect investigation of the near-field using a far-field informed analytic model suggests a reduction in the size of large scale structures. A direct evaluation of the space time structure of the near-field was performed using temporally resolved schlieren images. Statistical processing of the density gradient provided by the schlieren images revealed acoustically intense structures known as Mach waves and high frequency acoustic waves. These features and their sources, large scale instabilities and compactly coherent turbulence, were found to be decorrelated by the introduction of the thermal non-uniformity. These results provide strong evidence that the centered thermal non-uniformity produces a noise benefit by reducing the size of the turbulent structures.
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Thomas, Kevin P. "System architecture for real time power management." Thesis, University of Bristol, 1996. http://hdl.handle.net/1983/b4d196a1-d1f8-4141-b6e3-a32eb4f2073f.
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A major characteristic of aircraft evolution is the rapid growth in the electrical and electronic content of each subsequenat ircraft generation.T he dominant technology used in an aircraft electrical power distribution network to switch power and to protect the aircraft wiring from hazardous electrical faults is the electro-mechanical relay switch and the electro-thermal circuit breaker. Despite the maturity of these devices they do however suffer from a number of problems relating to reliability, accuracy, and limited operational lifetime. The design, fabrication and testing of a novel Solid State Power Controller (SSPC) is described. The design uses power MOSFET's to provide both the power switching operation of a relay, and the power interruption capability of a circuit breaker. The majority of the control functions required by this device are performed digitally by virtue of a real time program executed on an embedded microcontroller. A number of methods are derived for characterising existing I2t wire protection trip response curves. Reproduction of a true 1 2t trip response in real time using iterative computational methods is described. An examination of the semiconductor thermal characteristics was undertaken. The methods adopted for extracting the power semiconductor thermal response involved direct measurement using infrared thermal imaging techniques and simulation using a computer based modelling tool. Knowledge of the semiconductor die temperature is of vital importance in the context of the overall protection strategy. A finite difference calculation performed in real time has been demonstrated as a viable method to predict the operational temperature of the MOSFET power switching devices used in the design
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Romano, Valerio. "Interaction of pulsed laser radiation with tissue : determination of the thermal damage with time resolved thermal microscopy /." Bern, 1991. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Beggs, Clive. "The use of ice thermal storage with real time electricity pricing." Thesis, De Montfort University, 1995. http://hdl.handle.net/2086/10674.
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The thesis investigates the application of ice thermal storage technology to situations where the price of electricity varies continuously with instantaneous network demand. A central hypothesis is postulated in chapter 1, which states: "A variable electricity pricing structure, in which unit price continuously varies in response to instantaneous network demand, enhances the opportunities and benefits of ice thermal storage. The benefits both financial and environmental are dependent on the establishment of control and design strategies which optimise performance by matching refrigeration load with the instantaneous electricity price. " For ease of reference, the form of pricing described above is referred to in the thesis as 'real time' electricity pricing. The 'pool price' which is used to facilitate the competitive electricity awkct in England and Wales, is one of the foremost examples of real time pricing. The thesis therefore uses the electricity supply industry in the UK as its research vehicle. Notwithstanding this, the work contained in the thesis can be applied to any country which applies real time electricity pricing mechanisms. The validity of the hypothesis is assessed in the thesis through the development of a variety of numerical and computer models. These models fall into two distinct categories; those concerned with predicting and optimising the financial benefits of ice thermal storage, and those concerned with predicting and optimising the environmental benefits of ice thermal storage. Chapters 2,3 and 4 should be treated as support chapters, which equip the reader with the prerequisite knowledge necessary to understand the research work contained in the later chapters. As such, these chapters contain, respectively, a description of the electricity supply industry in the UK, a discussion of demand side management in the UK, and a description of the technology involved in ice thermal storage. The parametric study contained in chapter 4 is however an original piece of research work by the author. The models developed to evaluate and optimise the economic benefits of ice thermal storage are presented in chapters 5 and 6, and are applied to contrasting theoretical case study applications, namely an office building and a dairy. In chapter 5a 'long hand' numerical analysis technique is used. In chapter 6 this technique is rationalised and developed into a computer model for optimising both the design and control of ice storage installations in real time electricity pricing applications. The environmental studies are presented in chapter 7. These concentrate on the ability of ice thermal storage to reduce carbon dioxide emissions. Although the overall objective of the chapter is to evaluate the carbon dioxide emissions associated with ice thermal storage, the bulk of the chapter is concerned with the development of a model for predicting the carbon dioxide emissions per kWh of delivered electrical energy in England and Wales on a time related basis. The development of this 'time of day' carbon dioxide model is one of the main objectives of the thesis. Having established this model, it is then used to analyse the carbon dioxide emissions associated with the dairy case study.
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Riedel, Gernot Jurgen. "Time Resolved Raman Thermography : Thermal Dynamics of GaN-based Electronic Devices." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520665.
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Jelger, Pär. "High Performance Fiber Lasers with Spectral, Thermal and Life Time Control." Doctoral thesis, KTH, Laserfysik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11711.
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This thesis contains the results of research in the fields of spectral control, efficiency andlifetime of high-power, rare-earth doped fiber lasers, properties which are of greatimportance for scientific and industrial applications. Volume Bragg gratings (VBGs) has forthe first time been used together with fiber lasers and the laser performance in terms ofspectral purity, thermal stability, and tunability was evaluated. It was found that VBGs arean excellent high-contrast spectral filter for many fiber laser designs where bulk optics arenecessary, or for speciality fibers such as photonic crystal fibers or large-mode area fibers. Itis also shown that they work equally well in low power and very high-power configurations,i.e. for fiber lasers ranging three orders of magnitude in output power, from ~100 mW to >100 W. Furthermore, VBGs are shown to work very well as tunable spectral filters,producing a narrow emission linewidth in a compact setup. Concerning efficiency, it was shown how cryogenic cooling of the fiber gain-mediasubstantially increased the efficiency. The reasons are an increased pump absorption, anincreased gain cross-section, and a decreased threshold. The broad spectral output resultingfrom the low temperatures is shown to be easily mitigated by implementing a VBG as oneof the cavity mirrors. The low operating temperature is also shown to efficiently suppressself-pulsing in the fiber laser, which, if left unchecked, can lead to catastrophic break-downof the fiber end-faces. The increased absorption and suppressed self-pulsing allowed a fiberlength long enough to almost completely absorb the pump, which meant that, for the samepump power, more than 60 % higher output-power was attained. Finally, the lifetime issue of Yb-doped fiber lasers was addressed. It was found that Cecodopingsubstantially reduced the photodarkening-rate while leaving other fiber parametersessentially unchanged. This is especially important for Yb-doped fiber lasers emitting at 980nm, as the high inversion required make them very susceptible to photodarkening. It wasshown that the output power in Yb-doped fiber lasers degraded quickly when no Cecodopingwas present and, conversely, with the right Yb/Ce-codoping ratio, degradationfreelasing could be achieved for many hours. The research results obtained in this work could be of great interest to scientists andengineers working with spectroscopy, display systems, non-linear optics to just name a fewexamples.QC 20100721
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Tucker, Gary. "Development and application of time-temperature integrators to thermal food processing." Thesis, University of Birmingham, 2008. http://etheses.bham.ac.uk//id/eprint/144/.
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This thesis describes the research and development into a range of time-temperature integrators (TTIs) for the measurement of process values for food heat treatments. The TTIs are based on the first order thermal degradation of bacterial \(\alpha\)-amylases. Two new TTIs are described, one for mild pasteurisation treatments of a few minutes at 70°C and one for full sterilisation of >3 minutes at 121.1°C. Examples are given of how these TTIs are applied to a variety of industrial thermal processes. These include traditional methods such as canning, but also more complex systems such as tubular heat exchangers and batch vessels, together with novel systems such as ohmic heating. Some of the industrial experiments dealt with processes in which the thermal effects had not been previously quantified. For sterilisation, a highly innovative solution is required. A candidate TTI material is identified based on an amylase secreted by the hyperthermophilic microorganism Pyrococcus furiosus. This microorganism exists in extreme conditions where it metabolises in boiling volcanic pools; with elemental sulphur readily available, in water of high salinity, and in a reducing atmosphere. The amylase it secretes is naturally thermostable and withstands a full thermal sterilisation process.
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Nagarajan, Vivek Krishna. "REAL-TIME ASSESSMENT OF THERMAL TISSUE DAMAGE USING DIFFUSE REFLECTANCE SPECTROSCOPY." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1494313847936136.
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Hedbrant, Johan. "On the thermal inertia and time constant of single-family houses." Licentiate thesis, Linköpings universitet, Energisystem, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-123878.
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Since the nineteen-seventies, electricity has become a common heating source in Swedish single-family houses. About one million smallhouses can use electricity for heating, about 600.000 have electricity as the only heating source. A liberalised European electricity market would most likely raise the Swedish electricity prices during daytime on weekdays and lower it at other times. In the long run, electrical heating of houses would be replaced by fuels, but in the shorter perspective, other strategies may be considered. This report evaluates the use of electricity for heating a dwelling, or part of it, at night when both the demand and the price are low. The stored heat is utilised in the daytime some hours later, when the electricity price is high. Essential for heat storage is the thermal time constant. The report gives a simple theoretical framework for the calculation of the time constant for a single-family house with furniture. Furthermore the “comfort” time constant, that is, the time for a house to cool down from a maximum to a minimum acceptable temperature, is derived. Two theoretical model houses are calculated, and the results are compared to data from empirical studies in three inhabited test houses. The results show that it was possible to store about 8 kWh/K in a house from the seventies and about 5 kWh/K in a house from the eighties. The time constants were 34 h and 53 h, respectively. During winter conditions with 0°C outdoor, the “comfort” time constants with maximum and minimum indoor temperatures of 23 and 20°C were 6 h and 10 h. The results indicate that the maximum load-shifting potential of an average single family house is about 1 kW during 16 daytime hours shifted into 2 kW during 8 night hours. Up-scaled to the one million Swedish single-family houses that can use electricity as a heating source, the maximum potential is 1000 MW daytime time-shifted into 2000 MW at night.
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Hellweg, Stefanie Hellweg Stefanie Hellweg Stefanie. "Time- and site-dependent life-cycle assessment of thermal waste treatment processes /." Berlin : dissertation.de, 2000. http://www.dissertation.de.
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Chaturvedi, Vivek. "Leakage Temperature Dependency Aware Real-Time Scheduling for Power and Thermal Optimization." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/870.
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Catering to society’s demand for high performance computing, billions of transistors are now integrated on IC chips to deliver unprecedented performances. With increasing transistor density, the power consumption/density is growing exponentially. The increasing power consumption directly translates to the high chip temperature, which not only raises the packaging/cooling costs, but also degrades the performance/reliability and life span of the computing systems. Moreover, high chip temperature also greatly increases the leakage power consumption, which is becoming more and more significant with the continuous scaling of the transistor size. As the semiconductor industry continues to evolve, power and thermal challenges have become the most critical challenges in the design of new generations of computing systems.
In this dissertation, we addressed the power/thermal issues from the system-level perspective. Specifically, we sought to employ real-time scheduling methods to optimize the power/thermal efficiency of the real-time computing systems, with leakage/ temperature dependency taken into consideration. In our research, we first explored the fundamental principles on how to employ dynamic voltage scaling (DVS) techniques to reduce the peak operating temperature when running a real-time application on a single core platform. We further proposed a novel real-time scheduling method, “M-Oscillations” to reduce the peak temperature when scheduling a hard real-time periodic task set. We also developed three checking methods to guarantee the feasibility of a periodic real-time schedule under peak temperature constraint. We further extended our research from single core platform to multi-core platform. We investigated the energy estimation problem on the multi-core platforms and developed a light weight and accurate method to calculate the energy consumption for a given voltage schedule on a multi-core platform. Finally, we concluded the dissertation with elaborated discussions of future extensions of our research.
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Gim, Taeweon. "Modelling and evaluation of time-varying thermal errors in machine tool elements." Thesis, Cranfield University, 1997. http://dspace.lib.cranfield.ac.uk/handle/1826/3682.
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This thesis addresses a comprehensive approach to understanding the time-varying thermal errors in machine tools. Errors in machine tools are generally classified as being time or spatial dependent. Thermal errors are strongly dependent on the continuously changing operating conditions of a machine and its surrounding environment. Uniform temperature rises or stable temperature gradients, which produce time-invariant thermal errors, are considered to be rare in ordinary shop floor environments. Difficulties in analysing time-varying thermal errors are that, first of all, the temperature distribution within the components of a machine should be evaluated, and secondly, the distribution is continuously changing with time. These difficulties can be overcome by introducing a point-wise description method with three thermal parameters. From the theoretical analysis of simple machine elements such as bars, beams and cylinders, and extensive finite-element simulation data for a straightedge subject to room temperature variations, three thermal parameters, i. e. time-delay, time-constant and gain, were identified to obtain a precise description of the thermal deformation of a point of a machine body. Time-delay is dependent largely on thermal diffusivity, and the heat transfer mechanism. The time-constant is governed by heat capacity, heat transfer mechanism and body size. Gain, on the other hand, is determined by the thermal expansion coefficient, heat transfer mechanism and mechanical constraint. The three thermal parameters, in turn, imply that thermal deformation of a point in a body can be described by a simple first- order differential equation. Regarding their dependence on the heat transfer mechanism, a more refined description requires a time-varying linear first-order differential equation. Such an equation can be applied to each point of interest of a machine body. The final form of modelling, using the parameters, is a state-space equation gathering the governing equations for the points of interest. By adopting the point-wise discrete modelling method, we can overcome the difficulty of the spatial distribution of the temperature. Indeed, the calibration of a machine tool is usually performed at discrete points. The completion of this approach was made by presenting the methods by which the three thermal parameters can be evaluated. The first method employs analytical tools based on simplifying assumptions about the shape and boundary conditions of machine components. The second method was to apply numerical techniques to complex machine components. Because there are many drawbacks in theoretical approaches, experimental techniques are essential to complement them. The three thermal parameters can be easily identified using popular parameter identification techniques which can be applied to time-varying cases by their recursive forms. The techniques described were applied to modelling the thermal errors in a single-point diamond turning research machine. It was found that the dominant error component was spindle axial growth. The predictive model for the time-constant was shown to be in agreement with both the machine and with the scaled physical model rig.
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Miller, Brent Adam. "Loosely Coupled Time Integration of Fluid-Thermal-Structural Interactions in Hypersonic Flows." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429828070.
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Abbass, Mohamed A. M. S. "Real-time Control of Ultrasound Thermal Ablation using Echo Decorrelation Imaging Feedback." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535468911083998.
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Gill, Arshdeep Singh. "Thermal Evolution of Moon." DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1726.
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In August, 2014 three experiments were conducted using infrared systems deployed at White Mountain Research center, CA. The data was acquired for the whole month of August. Teams of 3-4 students from Cal Poly San Luis Obispo and UC Santa Barbara were stationed at the research center for 2-3 days to operate the equipment. The three experiments were:(1) creating spatial-temporal time series of lunar surface temperatures;(2) identifying atmospheric meteor trails;(3) search for meteor impacts on the Moon surface. Out of the three this thesis focusses on experiment 1 and the results from this experiment could also help with the other experiments.
We propose to use a thermal infrared camera mounted on a telescope to acquire time-series observations of lunar surface temperatures to get a novel insight into the thermal evolution of the Moon over a complete lunar cycle. Half a lunar cycle would account from morning to night and lasts for approximately 14.75 days. Seeing how the pixel value changes from morning to night the pixel and temperature trends can be observed throughout the day. Apart from that one can get the two temperature peaks that could maybe help to get an estimate for the Thermal inertia of the surface in the presence of Moon regolith. The temperature trends and the thermal inertia could potentially provide some insight for methods that seek to determine the properties of asteroids from ground based observations.
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Messenger, Robert K. "Modeling and Control of Surface Micromachined Thermal Actuators." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd434.pdf.
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Hioe, Yunior. "Mold thermal design and quasi steady state cycle time analysis in injection molding." Connect to resource, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1141840509.
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Chen, Huifeng. "Correcting the effect of thermal ageing for Real-Time power device Temperature Estimators." Thesis, University of Newcastle Upon Tyne, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519582.
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Muizzu, Mohamed. "Thermal and time-dependent effects on monolithic reinforced concrete roof slab-wall joints." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509019.
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Spiers, Hayley Ileana. "Time resolved x-ray diffraction and thermal imaging studies of magnesium zinc ferrites." Thesis, University College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415415.
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Gaskill, David M. "Real-Time Auxiliary Display Devices Enhance the Performance of Thermal Array Chart Recorders." International Foundation for Telemetering, 1991. http://hdl.handle.net/10150/612938.
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International Telemetering Conference Proceedings / November 04-07, 1991 / Riviera Hotel and Convention Center, Las Vegas, NevadaChart recorders are needed both for producing a permanent record for post-mission analysis and for providing real-time information during a test. Immediate feedback is important when test conditions may require mid-course warnings or corrections. In the traditional galvanometer based chart recorder, the operator can look directly at the pens moving on the paper and quickly judge speed and amplitude. When using a thermal array recorder, there is a small delay between the time of printing and the time when the trace is visible. This is due to the construction of the thermal array itself. Individual printing elements are deposited on a ceramic substrate which eliminates all motion from the printing process and physically blocks the operator’s view of the printhead so that for a short time there are no visual clues as to the exact waveform position. At higher chart speed this gap only represents milliseconds of elapsed time, well below human reaction time, and therefore of no real importance. At trending speeds, however, the delay could be half a second or even more and could be a problem in some situations. The first solution offered by manufacturers of thermal array recorders was a row of LED’s that stretched across the recorder directly over the printheads and reflected printing activity in real-time and indicated the actual position of the individual waveform traces. This was found to be a satisfactory solution by most telemetrists who wanted to change to the new technology in order to take advantage of the thermal array recorder’s higher frequency response and flexible formats. While the LED array satisfies basic real-time response requirements, there are many other applications for auxiliary displays which include variable chart labeling and graphic display of waveforms.
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Greenwood, David Michael. "Quantifying the benefits and risks of real-time thermal ratings in electrical networks." Thesis, University of Newcastle upon Tyne, 2014. http://hdl.handle.net/10443/2586.
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Real-Time Thermal Rating (RTTR) is a technology that allows the rating of electrical conductors to be estimated using real-time, local weather conditions. In many cases this leads to an increased rating with respect to conventional approaches. It also identifies some instances in which the conventional, static, rating is greater than the true rating, and is therefore potentially unsafe. The work in this thesis comprises methodologies to improve the planning and implementation of RTTR. Techniques commonly employed in the wind energy industry have been modified for use with RTTR. Computational wind simulations were employed to allow the identification of determining conductor spans, to inform network designers of the rating potential of different conductor routes, to estimate the additional wind energy that could be accommodated through the enhanced line rating and to allow informed placement of the monitoring equipment required to implement RTTR. Furthermore, the wind simulation data were also used to allow more accurate estimation of conductor ratings during operation. Probabilistic methods have been devised to estimate the level of additional load that could be accommodated through RTTR, and quantify the risk in doing so. Finally, a method has been developed to calculate the benefit RTTR can provide to system wide reliability. State sampling and sequential Monte Carlo simulations were used to evaluate the probabilistic functions associated with the ratings, the load and failures on both the existing network and the RTTR system itself. These methods combine to address fundamental barriers to the wide scale adoption and implementation of RTTR. The majority of existing research has focussed on improving technical solutions, which are of little benefit if it is not possible to quantify the benefits of RTTR before it is implemented. This work allows quantification not only of those benefits, but of the associated risks and uncertainties as well.
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Pelletier, Maude. "Geomorphological, ecological and thermal time phase of permafrost degradation, Tasiapik, Nunavik (Québec, Canada)." Master's thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/25766.
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Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2014-2015Six places-échantillons représentatives de la séquence temporelle écologique associée à la dégradation du pergélisol ont été sélectionnées sur un plateau silteux à pergélisol riche en glace à proximité d'Umiujaq, au Nunavik. Le présent travail a pour objectif de déterminer les changements qui se produisent dans les flux de chaleur entre les trois niveaux de l'écosystème (végétation / couverture de neige, couche active, pergélisol) ainsi que les rétroactions qui surviennent lors de la dégradation du pergélisol et à quantifier la vitesse de la transition à partir de photographies aériennes et la dendrochronologie. Pour répondre aux objectifs, la méthodologie utilisée suit le protocole du programme Adaptation et Dévelopement de l’Arctique sur le Pergélisol en Transition (ADAPT), intégrant l’analyse de données écologiques, climatiques, stratigraphiques et thermiques. Les résultats obtenus illustrent une évolution exponentielle des facteurs de dégradation du pergélisol sur une période estimée à environ 90 ans; lent durant les 60 premières années, et significativement plus rapide durant les 30 dernières années.
Six plots, representative of the regional ecological time sequence associated with permafrost degradation, were selected on a silty ice-rich permafrost plateau near Umiujaq, Nunavik. The objective of the present work is to determine the changes that occur in the flow of energy between the three layers of the ecosystem (vegetation / snow cover, active layer, permafrost) and the feedbacks that occur during the degradation of permafrost and to quantify the rate of the transition using time-lapse aerial photographs and tree ring analysis. In order to respond to these objectives, the methodology follows the ADAPT (Arctic Development and Adaptation on Permafrost in Transition) protocol, including ecological, climate, stratigraphic and thermal data analysis. The results show exponential evolution of permafrost degradation factors over a period of time of about 90 years; slowly during the first 60 years, and significantly faster during the last 30 years.
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Shrestha, Kristina. "Time-Resolved Temperature Measurements and Thermal Imaging using Nano-Thermometers in Different Environments." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1593706274306985.
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Bin, Ja'afar Mohamad Fakri Zaky. "Domestic air conditioning in Malaysia : night time thermal comfort and occupants adaptive behaviour." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1444280/.
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This is the first study of night time thermal comfort in Malaysia as well as the first study of sleeping comfort level. The focus of the investigation, the use of air-conditioners in homes clearly indicates a problem. Evidences of overcooling (76% of the cases) and sleep interruptions (45% of cases) to adjust control are found. In around 38% of the cases, the internal thermal profiles never reached a stable condition instead they keep cooling throughout the night until the units are turned off in the morning. The act of putting on a thicker, comforter type blanket, more of a psychological choice than a physiological need, during air-conditioned occupancy, results in people operating their air-conditioners at lower than the optimum temperature level. A thermal comfort field survey was conducted by monitoring 29 air-conditioned bedrooms, investigating the environmental conditions, the corresponding comfort perceptions and occupants' adaptive behaviour. Thermal neutralities and thermal acceptability for night-time occupancy in air-conditioned homes are established. Statistically significant difference is found between the neutral air temperature of normal blanket users (27.5 °C) and that of comforter users (25.2 °C). Thermal acceptability and comfort range for each group have also been established. A simulation study was conducted and it shows that the choice of using a comforter as opposed to a normal blanket results in an increase of up to 52% in the cooling load of a bedroom. This finding suggests that adaptive behaviour does not always result in less energy being used for comfort provision when active cooling is employed.
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Liao, Hao-Hsiang. "Thermal and thermoelectric properties of nanostructured materials and interfaces." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/19198.
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Many modern technologies are enabled by the use of thin films and/or nanostructured composite materials. For example, many thermoelectric devices, solar cells, power electronics, thermal barrier coatings, and hard disk drives contain nanostructured materials where the thermal conductivity of the material is a critical parameter for the device performance. At the nanoscale, the mean free path and wavelength of heat carriers may become comparable to or smaller than the size of a nanostructured material and/or device. For nanostructured materials made from semiconductors and insulators, the additional phonon scattering mechanisms associated with the high density of interfaces and boundaries introduces additional resistances that can significantly change the thermal conductivity of the material as compared to a macroscale counterpart. Thus, better understanding and control of nanoscale heat conduction in solids is important scientifically and for the engineering applications mentioned above.
In this dissertation, I discuss my work in two areas dealing with nanoscale thermal transport: (1) I describe my development and advancement of important thermal characterization tools for measurements of thermal and thermoelectric properties of a variety of materials from thin films to nanostructured bulk systems, and (2) I discuss my measurements on several materials systems done with these characterization tools.
First, I describe the development, assembly, and modification of a time-domain thermoreflectance (TDTR) system that we use to measure the thermal conductivity and the interface thermal conductance of a variety of samples including nanocrystalline alloys of Ni-Fe and Co-P, bulk metallic glasses, and other thin films. Next, a unique thermoelectric measurement system was designed and assembled for measurements of electrical resistivity and thermopower of thermoelectric materials in the temperature range of 20 to 350 °C. Finally, a commercial Anter Flashline 3000 thermal diffusivity measurement system is used to measure the thermal diffusivitiy and heat capacity of bulk materials at high temperatures. With regards to the specific experiments, I examine the thermal conductivity and interface thermal conductance of two different types of nanocrystalline metallic alloys of nickel-iron and cobalt-phosphorus. I find that the thermal conductivity of the nanocrystalline alloys is reduced by a factor of approximately two from the thermal conductivity measured on metallic alloys with larger grain sizes. With subsequent molecular dynamics simulations performed by a collaborator, and my own electrical conductivity measurements, we determine that this strong reduction in thermal conductivity is the result of increased electron scattering at the grain boundaries, and that the phonon component of the thermal conductivity is largely unchanged by the grain boundaries.
We also examine four complex bulk metallic glass (BMG) materials with compositions of Zr₅₀Cu₄₀Al₁₀, Cu46.25Zr44.25Al7.5Er₂, Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Er₂, and Ti41.5Zr2.5Hf₅Cu42.5Ni7.5Si₁. From these measurements, I find that the addition of even a small percentage of heavy atoms (i.e. Hf and Er) into complex disordered BMG structures can create a significant reduction in the phonon thermal conductivity of these materials. This work also indicates that the addition of these heavy atoms does not disrupt electron transport to the degree with which thermal transport is reduced.Ph. D.
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Xu, Ming. "Critical current density and time-dependent magnetization of the high transition temperature superconductors." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/30033.
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Nagaraj, Mahavir. "Short time scale thermal mechanical shock wave propagation in high performance microelectronic packaging configuration." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1087.
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The generalized theory of thermoelasticity was employed to characterize the coupled thermal and mechanical wave propagation in high performance microelectronic packages. Application of a Gaussian heat source of spectral profile similar to high performance devices was shown to induce rapid thermal and mechanical transient phenomena. The stresses and temporal gradient of stresses (power density) induced by the thermal and mechanical disturbances were analyzed using the Gabor Wavelet Transform (GWT). The arrival time of frequency components and their magnitude was studied at various locations in the package. Comparison of the results from the classical thermoelasticity theory and generalized theory was also conducted. It was found that the two theories predict vastly different results in the vicinity of the heat source but that the differences diminish within a larger time window. Results from both theories indicate that the rapid thermal-mechanical waves cause high frequency, broadband stress waves to propagate through the package for a very short period of time. The power density associated with these stress waves was found to be of significant magnitude indicating that even though the effect, titled short time scale effect, is short lived, it could have significant impact on package reliability. The high frequency and high power density associated with the stress waves indicate that the probability of sub-micron cracking and/or delamination due to short time scale effect is high. The findings demonstrate that in processes involving rapid thermal transients, there is a non-negligible transient phenomenon worthy of further investigation.
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Collins, Kimberlee C. (Kimberlee Chiyoko). "Studies of non-diffusive heat conduction through spatially periodic and time-harmonic thermal excitations." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97836.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 127-133).
Studies of non-diffusive heat conduction provide insight into the fundamentals of heat transport in condensed matter. The mean free paths (MFPs) of phonons that are most important for conducting heat are well represented by a material's thermal conductivity accumulation function. Determining thermal conductivity accumulation functions experimentally by studying conduction in non-diffusive regimes is a recent area of study called phonon MFP spectroscopy. In this thesis, we investigate nondiffusive transport both experimentally and theoretically to advance methods for determining thermal conductivity accumulation functions in materials. We explore both spatially periodic and time-harmonic thermal excitations as a means for probing the non-diffusive transport regime, where the Fourier heat diffusion law breaks down. Boltzmann transport equation calculations of one-dimensional (1D) spatially sinusoidal thermal excitations are performed for gray-medium and fully spectral cases. We compare our calculations to simplified transport models and demonstrate that a model based on integrating gray-medium solutions can reasonably model materials with a narrow range of dominant heat-carrying phonon MFPs. We also consider the inverse problem of determining thermal conductivity accumulation functions from experimental measurements of thermal-length-scale-dependent effective thermal conductivity. Based on experimental measurements of Si membranes of varying thickness, we reproduce the thermal conductivity accumulation function for bulk Si. To investigate materials with short phonon MFPs, we developed an experimental approach based on microfabricating 1D wire grid polarizers on the surface of a material under study. This work finds that the dominant thermal length scales in polycrystalline Bi 2Te3 are smaller than 100 nm. We also determine that even small amounts of direct sample optical excitation, which occurs when light transmits through the grating and directly excites electron-hole pairs in the substrate, can appreciably influence the measured results, suggesting that an alternate approach that prevents all direct optical excitation is preferable. To study thermal length scales smaller than 100 nm without the need for microfabrication, we develop a method for extracting high frequency response information from transient optical measurements. For a periodic heat flux input, the thermal penetration depth in a semi-infinite sample depends on the excitation frequency, with higher frequencies leading to shallower thermal penetration depths. Prior work using frequencies as high as 200 MHz observed apparent non-diffusive behavior. Our method allows for frequencies of at least 1 GHz, but we do not observe any deviation from the heat diffusion equation, suggesting that prior observations attributed to non-diffusive effects were likely the result of transport phenomena in the metal transducer.
by Kimberlee Chiyoko Collins.
Ph. D.
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Zhou, Linjing. "Transient natural convection in a cavity with time-varying thermal forcing on a sidewall." Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/28833.
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Motivated by the environmental application of the diurnal heating and cooling effect of a water wall on a building, the present thesis considers natural convection flows in rectangular enclosures subjected to a temporal thermal forcing. The rectangular enclosure has all walls non-slip, and the upper and lower boundaries and one wall are adiabatic. The other wall is at a spatially uniform temperature or heat flux that varies with time as a sine wave. Direct numerical simulations have been conducted, and the fully developed stage of the flow, when the flow is periodic, is of interest.
To obtain an accurate solution, a new fourth-order compact finite difference spatial discretisation is proposed. Unlike the standard high order approach for local methods, such as finite-difference or finite-volume, which produces large stencils and thus introduces complexity in the boundary treatment and parallelisation, the proposed fourth-order compact scheme iteratively applies a low order spatial discretisation method to achieve higher accuracy. The scheme allows for a simple application of boundary conditions, can be applied on a non-uniform grid and allows a standard parallelisation approach to be used. The scheme is implemented and tested in an unsteady finite-difference heat equation solver and benchmarked against the analytical solution to validate the order of accuracy. It has been included in a full fractional-step Navier-Stokes solver and validated for the lid-driven cavity and natural convection problems.
Using water and air as working fluids, the time-varying temperature forcing on the wall produces an alternating direction vertical natural convection boundary layer that rises in the heating phase and falls in the cooling phase, entraining fluid from the cavity interior and discharging it alternatively at the top and bottom of the cavity, while the boundary layer is bi-directional during the transition from heating to cooling with a falling flow in the upper near wall region and a rising flow in the lower near wall region, and vice-versa for the cooling to heating transition. A stable stratification is maintained in the cavity core. The flow behaviour is dependent on the forcing frequency with low and high frequency regimes and an intermediate region, based on three characteristic time scales, the forcing period, the development time for the boundary layer and the filling time of the cavity. In the low frequency regime the filling time is less than the forcing period and the time average stratification S ̅ is well approximated by S ̅~f^(4/5). In the high frequency regime the forcing period is smaller than the boundary layer development time and S ̅~f^(-2). The maximum S ̅ occurs in the intermediate region, between the low and high frequency regimes. The maximum value of S ̅ increases with increasing Rayleigh number, approaching S ̅≅1.0 for the highest values of Rayleigh number considered. Scaling analysis has been conducted for Pr>1 fluid in a square enclosure. Scaling relations are obtained for the development of the natural convection boundary layer, the passage of the outflow intrusion, the filling of the cavity with the boundary layer outflow and resulting thermal stratification based on the Rayleigh number and forcing frequency in the low and high frequency regimes. Numerical simulations are carried out with the Rayleigh number and non-dimensional forcing frequency in the ranges 1×10^4≪Ra≪1×10^8 and 0.0001≪f≪10, and the results show that the proposed scaling relations give good predictions of the flow behaviours in the two regimes. The flow is also dependent on the aspect ratio of the cavity, with the transition frequency from the low frequency regime to the intermediate region increasing with increasing aspect ratio, while the boundary between the intermediate region and high frequency regime is not dependent on the aspect ratio.
Natural convection flow in an air-filled cavity subjected to a periodic temperature boundary condition exhibits an increased non-linearity and instability, especially at a high Rayleigh number Ra=1×10^8. The stratification parameter responds at a dominant frequency of two times the forcing frequency, together with its super-harmonics at four times, six times, eight times the forcing frequency. At f≅0.125 a resonant effect is observed with an amplification of the stratification variation at the response frequency of f_strat=0.25, and the appearance of super- and sub-harmonic modes. This effect is believed to be a result of the interaction of the forcing mode and the mode one internal wave. The resonance can also be observed in shallow cavities, featuring seiching motions of isotherms, supporting the hypothesis that the internal wave motions are excited by the forcing mode.
In addition to the temperature boundary condition, a heat flux boundary condition has also been applied. The flow structure is similar to the temperature boundary condition case with an alternating direction boundary layer and a stratified core. Instead of a spatially uniform temperature on the wall for the temperature boundary condition, the temperature on the wall increases with increasing y location for the heat flux boundary condition. The boundary layer is always uni-directional. Scaling analysis has been conducted for the low and high frequency regimes for Pr>1, with the characteristic time scales being the forcing period and the boundary layer development time. The scaling relations are then verified using the simulations, with the results showing overall good agreement with the derived scaling relations.
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SHA, SHI. "The Thermal-Constrained Real-Time Systems Design on Multi-Core Platforms -- An Analytical Approach." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3713.
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Over the past decades, the shrinking transistor size enabled more transistors to be integrated into an IC chip, to achieve higher and higher computing performances. However, the semiconductor industry is now reaching a saturation point of Moore’s Law largely due to soaring power consumption and heat dissipation, among other factors. High chip temperature not only significantly increases packing/cooling cost, degrades system performance and reliability, but also increases the energy consumption and even damages the chip permanently. Although designing 2D and even 3D multi-core processors helps to lower the power/thermal barrier for single-core architectures by exploring the thread/process level parallelism, the higher power density and longer heat removal path has made the thermal problem substantially more challenging, surpassing the heat dissipation capability of traditional cooling mechanisms such as cooling fan, heat sink, heat spread, etc., in the design of new generations of computing systems. As a result, dynamic thermal management (DTM), i.e. to control the thermal behavior by dynamically varying computing performance and workload allocation on an IC chip, has been well-recognized as an effective strategy to deal with the thermal challenges.
Over the past decades, the shrinking transistor size, benefited from the advancement of IC technology, enabled more transistors to be integrated into an IC chip, to achieve higher and higher computing performances. However, the semiconductor industry is now reaching a saturation point of Moore’s Law largely due to soaring power consumption and heat dissipation, among other factors. High chip temperature not only significantly increases packing/cooling cost, degrades system performance and reliability, but also increases the energy consumption and even damages the chip permanently. Although designing 2D and even 3D multi-core processors helps to lower the power/thermal barrier for single-core architectures by exploring the thread/process level parallelism, the higher power density and longer heat removal path has made the thermal problem substantially more challenging, surpassing the heat dissipation capability of traditional cooling mechanisms such as cooling fan, heat sink, heat spread, etc., in the design of new generations of computing systems. As a result, dynamic thermal management (DTM), i.e. to control the thermal behavior by dynamically varying computing performance and workload allocation on an IC chip, has been well-recognized as an effective strategy to deal with the thermal challenges.
Different from many existing DTM heuristics that are based on simple intuitions, we seek to address the thermal problems through a rigorous analytical approach, to achieve the high predictability requirement in real-time system design. In this regard, we have made a number of important contributions. First, we develop a series of lemmas and theorems that are general enough to uncover the fundamental principles and characteristics with regard to the thermal model, peak temperature identification and peak temperature reduction, which are key to thermal-constrained real-time computer system design. Second, we develop a design-time frequency and voltage oscillating approach on multi-core platforms, which can greatly enhance the system throughput and its service capacity. Third, different from the traditional workload balancing approach, we develop a thermal-balancing approach that can substantially improve the energy efficiency and task partitioning feasibility, especially when the system utilization is high or with a tight temperature constraint. The significance of our research is that, not only can our proposed algorithms on throughput maximization and energy conservation outperform existing work significantly as demonstrated in our extensive experimental results, the theoretical results in our research are very general and can greatly benefit other thermal-related research.
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Wei, Xiaomin. "FUNDAMENTAL CHARACTERIZATION OF TRIBOLOGICAL, THERMAL, FLUID DYNAMIC AND WEAR ATTRIBUTES OF CONSUMABLES IN CHEMICAL MECHANICAL PLANARIZATION." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/195125.
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This dissertation presents several studies relating to fundamental characterization of CMP consumables in planarization processes. These are also evaluated with the purposes of minimizing environmental impact and reducing cost of ownership (COO).The first study is conducted to obtain the retaining ring wear rate in a typical ILD CMP process and is specifically intended to investigate the effect of retaining ring materials and slot designs during the CMP process. The results show that retaining ring materials have effect on the COF, pad temperature and retaining ring wear rate, while retaining ring slot designs affect the pad surface abruptness. The second study is performed to compare the effect of different retaining ring slot designs on the slurry film thickness within the pad-wafer interface. A novel non-intrusive optical technique, dual emission UV-enhanced fluorescence (DEUVEF), was applied to accurately measure the film thickness of the slurry underneath the wafer during polishing. It is indicated that the optimized retaining ring slot design can significantly reduce the COO of CMP processes by increasing slurry utilization.A COF method is applied to measure the slurry mean residence time (MRT) during CMP. This technique uses transient COF data induced by a shift in slurry concentration to determine MRT. Variations in consumables as well as sliding velocity, pressure and slurry flow rate can affect the slurry MRT. One study in this dissertation focus on the effect of retaining ring slot designs on the slurry MRT. Another study compares the slurry MRT under same polishing conditions using pads with different groove width. Both studies are conducted on multiple sliding velocity, pressure and slurry flow rate variations to understand the characteristics of consumable designs. The method of measuring MRT during polishing presented in this dissertation can be easily applied in general CMP processes.The subsequent studies focus in the diamond conditioner discs characterization techniques. A newly developed method for determining active diamonds and aggressive diamonds on a diamond conditioner disc under a certain vertical load is elaborated in this dissertation. Later, this technique together with scanning electron microscopy (SEM) imaging is implemented to analyze diamond pullout and fracture in CMP. Five different types of diamond conditioner discs are subjected to a novel accelerated wear test respectively to compare the extent of diamond pullout and fracture under the same conditioning condition
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Venkatasamy, Vasanth Kumar. "Analysis of in-cavity thermal and pressure characteristics in aluminum alloy die casting." Connect to this title online, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1100721824.
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Jo, Young Gyun. "Development of a thermal neutron imaging facility for real time neutron radiography and computed tomography /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Sjölund, Johannes. "Real-time Thermal Flow Predictions for Data Centers : Using the Lattice Boltzmann Method on Graphics Processing Units for Predicting Thermal Flow in Data Centers." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-70530.
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The purpose of this master thesis is to investigate the usage of the Lattice Boltzmann Method (LBM) of Computational Fluid Dynamics (CFD) for real-time prediction of indoor air flows inside a data center module. Thermal prediction is useful in data centers for evaluating the placement of heat-generating equipment and air conditioning. To perform the simulation a program called RAFSINE was used, written by Nicholas Delbosc at the University of Leeds, which implemented LBM on Graphics Processing Units (GPUs) using NVIDIA CUDA. The program used the LBM model called Bhatnagar-Gross-Krook (BGK) on a 3D lattice and had the capability of executing thermal simulations in real-time or faster than real-time. This fast rate of execution means a future application for this simulation could be as a predictive input for automated air conditioning control systems, or for fast generation of training data sets for automatic fault detection systems using machine learning. In order to use the LBM CFD program even from hardware not equipped with NVIDIA GPUs it was deployed on a remote networked server accessed through Virtual Network Computing (VNC). Since RAFSINE featured interactive OpenGL based 3D visualization of thermal evolution, accessing it through VNC required use of the VirtualGL toolkit which allowed fast streaming of visualization data over the network. A simulation model was developed describing the geometry, temperatures and air flows of an experimental data center module at RISE SICS North in Luleå, Sweden, based on measurements and equipment specifications. It was then validated by comparing it with temperatures recorded from sensors mounted in the data center. The thermal prediction was found to be accurate on a room-level within ±1° C when measured as the average temperature of the air returning to the cooling units, with a maximum error of ±2° C on an individual basis. Accuracy at the front of the server racks varied depending on the height above the floor, with the lowest points having an average accuracy of ±1° C, while the middle and topmost points had an accuracy of ±2° C and ±4° C respectively. While the model had a higher error rate than the ±0.5° C accuracy of the experimental measurements, further improvements could allow it to be used as a testing ground for air conditioning control or automatic fault detection systems.
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Smith, Robert Merrill. "Real-Time Control of Polysilicon Deposition in Single-Wafer Rapid Thermal Chemical Vapor Deposition Furnaces." NCSU, 1998. http://www.lib.ncsu.edu/theses/available/etd-19981020-131153.
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This thesis describes the development of a real-time control system for depositing polysilicon films on silicon wafers by means of rapid thermal chemical vapor deposition. Results are presented which characterize the ability of the control system to deposit films of an average desired thickness and predict the film?s spatial thickness distribution.A rapid thermal chemical vapor deposition system was used to individually process wafers. During processing, a mass spectrometer monitored the chemical species present in the exhaust gases to determine the total volume of material deposited. Simultaneously, optical probes resolved the spatial temperature distribution of the wafer. The mass spectrometry and optical temperature data were combined with an Arrhenius equation to model the deposition process. Validation of the model was exsitu. After processing, film thickness measurements were made on each wafer and compared to the computer model?s predictions.Experimental results identified hydrogen, a by-product of the deposition reaction, as the metric for determining the total volume of polysilicon deposited. Process recipe control (today?s standard control technique) produced films varying over a range of 280 Å when repeatedly employed to deposit film?s of 900 Å. Application of the real-time control system produced films varying a maximum of 74 Å when attempting to deposit films of average thickness ranging from 800 to 1200 Å. Modeling results predicted the thickness of the deposited film to within 20 Å at the center of the wafer. Predictions at the wafers edge were off by a maximum of 160 Å.From the experience gained during this project, the following two recommendations are made to guide future efforts. First, the mass spectrometer?s reaction time to an event occurring in the furnace was found to be one second. Employing an optical sensor could improve control by reducing the time lag of the system. Second, designing the furnace with the necessary optical access so that the sensors can be located outside the vacuum system would greatly facilitate the accuracy and reliability of the system. This would eliminate exposure of the sensors to the high temperatures and corrosive gases present inside the furnace which can adversely affect their performance.
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GOMES, LEONARDO LIMA. "EVALUATING THERMAL PLANTS IN BRAZIL STUDIND THE BEST TIME TO INVEST USING REAL OPTIONS MODELS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2002. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=2772@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOAté 1997 o Setor Elétrico Brasileiro (SEB) era basicamente um monopólio estatal administrado por empresas federais e estaduais. A partir do segundo semestre de 1997 foram iniciadas as privatizações, e em paralelo a reestruturação do setor. Antes do processo de reestruturação do SEB, o planejamento da expansão da geração era feito de forma coordenada e centralizada, com o objetivo de minimizar os custos de investimento e operação. A expansão da geração era uma variável de decisão do problema. No entanto, um dos pressupostos da reestruturação do setor foi e continua sendo a realização pelo agente privado de grande parte dos novos investimentos em geração e transmissão. Dessa maneira, a decisão sobre a expansão da geração deixa de ser centralizada e passa a depender da disposição de investimento deste agente, acarretando no aumento do nível de incertezas no processo de planejamento. Neste contexto, o presente trabalho visa estudar a dinâmica de investimentos privados em geração termelétrica no Brasil utilizando a Teoria das Opções Reais. A dinâmica de investimentos em termelétricas será estudada em três situações diferentes. Na primeira, será utilizado um modelo de opções reais / análise de decisão para determinar as estratégias de escolha do melhor momento de construção de um empreendimento considerando que há incerteza exógena na expansão da oferta de termelétricas. Na segunda, será utilizado o mesmo modelo para determinar as estratégias de momento de construção de uma termelétrica considerando que há incerteza na demanda, e que a expansão da oferta permanece constante. Na terceira, a expansão da oferta ocorre em resposta às incertezas e à interação entre os agentes. Será utilizado um modelo de opções reais / análise de decisão / teoria dos jogos. Os principais resultados obtidos no trabalho foram os prêmios de risco exigidos pelo investidor para realizar o investimento imediato e a determinação do melhor momento de investimento em função de algumas variáveis do problema. Foi possível comparar as diferentes situações estudadas, mostrando que a concorrência pode atrasar investimentos.
Until 1997 The Brazilian Electric Sector was basically a monopoly administrated by federal and state enterprises. In the second semester of 1997 it was begun privatizations and the restructuring process. Before Brazilian Electric Sector restructuring process, the planning of generation expansion was made through a centralized program which focus in minimize the investment and operation costs. The generation expansion was a decision variable of the problem. However, one of the assumptions of the restructuring sector process was and continues to be the private agent realization of a big share of the new investment in generation. So, the generation expansion is not more centralized, becoming a variable, which depends of the investment affordability of this agent. In this context, the present thesis studies the private investment dynamics in thermoelectric generation using Real Options. The dynamic of investment in thermal Plants will be studied in three different situations: In the first, it will be used a model of real options / decision analysis to determine the best timing of construction, considering that exists an exogenous uncertainty in the thermal supply expansion. In the second situation, the same model will be used to define the best timing of investment in thermal plants, considering that exists demand uncertainty, and that the supply expansion remains constant. In the third situation, the supply expansion occurs in response of the demand uncertainty evolution and the strategic interactions between the agents. It will be used a real options/ decision analysis/ game theory model. The main results obtained were the threshold contracted prices and the determination of the best time to invest as a function of some problem variables. It was possible to compare the different studied situations, showing that the competition could delay investments.
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Yunus, Mamoon I. (Mamoon Iqbal). "Spatial- and time-dependent thermal and electrical behavior of quenching high-temperature superconducting composite tapes." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/35046.
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