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McKinney, Jessica, Fuschia M. Sirois, and Jameson K. Hirsch. "Posttraumatic Growth and Shame/Guilt in Veterans: Does Time (Perspective) Really Heal All Wounds?" Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etsu-works/620.
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Prevalence of PTSD is higher in veterans compared to the general population, with between 12 and 31% of veterans, across combat eras, developing PTSD during their lifetime, compared to 7-8% of civilians, perhaps as a result of military-related experiences (e.g., combat, sexual trauma). Such experiences contribute to the detrimental cognitive-emotional processes, including shame and guilt, which precipitate and maintain post-traumatic stress disorder. Yet, some persons experiencing trauma also experience post-traumatic growth as a result, exhibiting resiliency and, in some cases, even thriving. The mechanism of action for post-traumatic growth (PTG), which is conceptualized as a positive change following trauma (i.e., finding purpose and meaning in life), is unknown, but may involve adaptive schema restructuring (e.g., temporal shifts). Specifically, PTG may involve changes to time-perspective, or the tendency for a person to consider their life as a function of, or in the context of, the past (e.g., past trauma, nostalgia), present (e.g., positive/negative) or future (e.g., goals). The ability, for instance, to temporally transcend the past or present and focus on a more-adaptive future, may contribute to a reduction in the ruminative processes so often involved in shame and guilt, whereas maladaptive temporal views (e.g., negative past and present) may exacerbate guilt and shame. However, this premise has not been tested. We hypothesized that time perspective would mediate the association between PTG and shame/guilt, such that higher levels of PTG would be associated with higher levels of adaptive temporality/lower levels of maladaptive temporality and, in turn, to lower /higher levels of shame and guilt. Participants (N=545; 70.1% male (n=382); 86.4% Caucasian (n=469), Mean Age=49.86, SD=16.78) were community-dwelling veterans who self-identified as having experienced a trauma, and completed the PTG Inventory, Zimbardo Time Perspective Inventory, and Differential Emotions Scale-IV. Bivariate correlations and simple mediation analyses were conducted covarying age, sex, ethnicity, VHA usage, and service era. Supporting hypotheses, in simple mediation analyses (10000 bootstrapped samples), the direct effect of PTG on shame (DE=-.0134, SE=.0098, p=.1720, IE 95% CI=-.0327 to .0059) and guilt (DE=-.0085, SE=.0100, p=.3919, IE 95% CI=-.0281 to .0110) was reduced, and fell out of significance, when future time perspective was added as a mediator, indicating full mediation. The direct effects of PTG on shame and guilt were reduced, but remained significant, when present hedonistic, present fatalistic, past negative, and past positive were added as mediators, indicating partial mediation. Our results suggest that the relation between posttraumatic growth and shame/guilt may be due, in part, to changes in cognitive-emotional processing related to temporality. The PTG process may involve adaptive shifts in time perspective that, in turn, beneficially impact negative emotions associated with trauma exposure. Our findings may have clinical implications. Promotion of acceptance and meaning (e.g., via Acceptance and Commitment Therapy) to foster posttraumatic growth, and encouraging temporal holism (e.g., Cognitive Processing Therapy, Time Perspective Therapy), may reduce shame and guilt associated with trauma in the veteran population.
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Treiss, Stephanie. "TIME-DEPENDENT SURFACE TEMPERATURE and HEAT FLUX MEASUREMENTS on a SINGLE CYLINDER ENGINE HEAD and LINER." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1512061036731254.
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Enblom, Gustav, and Hannes Eskebaek. "Real Time Vehicle Diagnostics Using Head Mounted Displays." Thesis, Linköpings universitet, Programvara och system, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-119657.
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This thesis evaluates how a head mounted display (HMD) can be used to increase usability compared to existing computer programs that are used during maintenance work on vehicles. Problems identified during a case study in a vehicle workshop are first described. As an attempt to solve some of the identified problems a prototype application using a HMD was developed. The prototype application aids the user during troubleshooting of systems on the vehicle by leading the mechanic with textual information and augmented reality (AR). Assessment of the prototype application was done by comparing it to the existing computer program and measuring error rate and time to completion for a predefined task. Usability was also measured using the System Usability Scale. The assessment showed that HMDs can provide higher usability in terms of efficiency and satisfaction. Furthermore, the thesis describes and discusses other possibilities and limitations that usage of HMDs and AR can lead to that were identified both from theory and during implementation.
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Guo, Haiqing. "Head & base production optimization : setup time reduction." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55215.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 53).
At Schlumberger, the make-to-order strategy and number of Head & Base product types (about 1000 types) requires a flexible manufacturing system in which the machine setup is frequent. However, the lengthy CNC machine setup time in the Head & Base machining station directly affects the manufacturing capacity. This research implements Single Minute Exchange of Die (SMED) methodology and proposes a set of solutions, such as manufacturing sequence optimization, setup sequence optimization, setup operation simplification, etc, to reduce setup time without sacrificing quality. Most of the solutions have been implemented and the result is significant and impressive, the overall setup time has been reduced by up to 40 percent and the expected cost saving is about 50,000 USD.
by Haiqing Guo.
M.Eng.
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Kirichok, T. A. "Hyperbolic heat conduction in the layer with a time-dependent laser heat source." Thesis, Вид-во СумДУ, 2005. http://essuir.sumdu.edu.ua/handle/123456789/19911.
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Tolloczko, J. J. A. "Time dependent properties of heat cycled slag cement concretes." Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376503.
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MacKay, Robert Malcolm. "The Oregon Graduate Institute one dimensional time-dependent radiative convective model : theory and application /." Full text open access at:, 1990. http://content.ohsu.edu/u?/etd,202.
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Roxanas, Dimitrios. "Long-time dynamics for the energy-critical harmonic map heat flow and nonlinear heat equation." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61612.
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The main focus of this thesis is on critical parabolic problems, in particular, the
harmonic map heat from the plane to S2, and nonlinear focusing heat equations
with an algebraic nonlinearity.
The focus of this work has been on long-time dynamics, stability and singularity
formation, and the investigation of the role of special, soliton-like, solutions to the
asymptotic behaviour of solutions.
Harmonic Map Heat Flow: Flow: we consider m-corotational solutions to the
harmonic map heat flow from R2 to S2. We first work in a class of maps with
trivial topology and energy of the initial data below two times the energy of
the stationary harmonic map solutions. We give a new proof of global existence
and decay. The proof is based on the "concentration-compactness plus rigidity"
approach of Kenig and Merle and relies on the dissipation of the energy and a
profile decomposition. We also treat m-corotational maps (m greater than 3) with
non-trivial topology and energy of the initial data less than three times the energy
of the stationary harmonic map solutions. Through a new stability argument we
rule out finite-time blow-up and show that the global solution asymptotically
converges to a harmonic map.
Nonlinear Heat Equation: we also study solutions of the focusing energy-critical
nonlinear heat equation. We show that solutions emanating from initial data
with energy and kinetic energy below those of the stationary solutions
are global and decay to zero. To prove that global solutions dissipate to zero
we rely on a refined small data theory, L2-dissipation and an
approximation argument. We then follow the "concentration-compactness
plus rigidity" roadmap of Kenig and Merle (and in particular the approach taken
by Kenig and Koch for Navier-Stokes) to exclude finite-time blow-up.Science, Faculty of
Mathematics, Department of
Graduate
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Siqueira, Sunni Ann. "Calculation of Time-Dependent Heat Flow in a Thermoelectric Sample." ScholarWorks@UNO, 2012. http://scholarworks.uno.edu/honors_theses/24.
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In this project, the time-dependent one-dimensional heat equation with internal heating is solved using eigenfunction expansion, according to the thermoelectric boundary conditions. This derivation of the equation describing time-dependent heat flow in a thermoelectric sample or device yields a framework that scientists can use (by entering their own parameters into the equations) to predict the behavior of a system or to verify numerical calculations. Allowing scientists to predict the behavior of a system can help in decision making over whether a particular experiment is worthy of the time to construct and execute it. For experimentalists, it is valuable as a tool for comparison to validate the results of an experiment. The calculations done in this derivation can be applied to pulsed cooling systems, the analysis of Z-meter measurements, and other transient techniques that have yet to be invented. The vast majority of the calculations in this derivation were done by hand, but the parts that required numerical solutions, plotting, or powerful computation, were done using Mathematica 8. The process of filling in all the steps needed to arrive at a solution to the time-dependent heat equation for thermoelectrics yields many insights to the behavior of the various components of the system and provides a deeper understanding of such systems in general.
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North, Travis. "Experimental and analytical study of time varying electrical fields and their effect on convective boiling heat transfer /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1426090.
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Simmons, Stephen Gordon. "The simultaneous measurement of time-resolved surface heat flux and freestream turbulence at a stagnation point." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-06112009-063356/.
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Launila, Andreas. "Real-Time Head Pose Estimation in Low-Resolution Football Footage." Thesis, KTH, Computer Vision and Active Perception, CVAP, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12061.
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This report examines the problem of real-time head pose estimation in low-resolution football footage. A method is presented for inferring the head pose using a combination of footage and knowledge of the locations of the football and players. An ensemble of randomized ferns is compared with a support vector machine for processing the footage, while a support vector machine performs pattern recognition on the location data. Combining the two sources of information outperforms either in isolation. The location of the football turns out to be an important piece of information.
QC 20100707
Capturing and Visualizing Large scale Human Action (ACTVIS)
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Kopfer, Eva [Verfasser]. "Heat flows on time-dependent metric measure spaces / Eva Kopfer." Bonn : Universitäts- und Landesbibliothek Bonn, 2018. http://d-nb.info/1160594120/34.
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Reinarz, Anne. "Sparse space-time boundary element methods for the heat equation." Thesis, University of Reading, 2015. http://centaur.reading.ac.uk/49315/.
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The goal of this work is the efficient solution of the heat equation with Dirichlet or Neumann boundary conditions using the Boundary Elements Method (BEM). Efficiently solving the heat equation is useful, as it is a simple model problem for other types of parabolic problems. In complicated spatial domains as often found in engineering, BEM can be beneficial since only the boundary of the domain has to be discretised. This makes BEM easier than domain methods such as finite elements and finite differences, conventionally combined with time-stepping schemes to solve this problem. The contribution of this work is to further decrease the complexity of solving the heat equation, leading both to speed gains (in CPU time) as well as requiring smaller amounts of memory to solve the same problem. To do this we will combine the complexity gains of boundary reduction by integral equation formulations with a discretisation using wavelet bases. This reduces the total work to O(hₓ-(d-1)), when the solution of the linear system is performed with linear complexity. We show that the discretisation with a wavelet basis leads to a numerically sparse matrix. Further, we show that this matrix can be compressed without losing accuracy of the underlying Galerkin scheme. This matrix compression reduces the number of non-zero matrix entries from O(N2) to O(N). Thus, we can indeed solve the linear system in linear time. It has been shown theoretically that using sparse grid methods leads to considerably higher convergence rates in the energy norm of the problem. In this work we will show that the convergence can be further improved for some choices of polynomial degrees by using more general sparse grid spaces. We also give numerical results to verify the theoretical bounds from [Chernov, Schwab, 2013].
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Ali, A. A. A.-W. "The modelling, simulation and real time control of intercranial pressure." Thesis, University of Bradford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233661.
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Swisher, Stacey Elaine. "Time-resolved heat flux measurements of the turbulent junction vortex system." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-10312009-020052/.
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DÜBBEL, ANDRÉ. "Real-time Head Pose Estimation inLow-resolution Football Footage UsingRandom Forests." Thesis, KTH, Skolan för datavetenskap och kommunikation (CSC), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-142449.
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This report presents a method for real-time head pose estimation in low resolution football footage. The presented method uses a random forest trained on synthetically generated head images. The use of synthetic training images is shown to be a good substitute for the use of manually labelled images. The presented method compares favourably to support vector machines trained for the same task, both in terms of accuracy and speed. It is noted that the method relies on a good head detection to perform well. The report also examines ways of combining the image based head pose estimation with contextual features such as ball position and player position. It is shown that the relative direction to the ball can improve the accuracy of the pose estimate in certain situations. Furthermore, it is found that the random forest method can easily be extended to incorporate images from multiple cameras to improve accuracy.Denna rapport presenterar en metod för realtidsestimering av huvudets vridning i lågupplöst fotbollsvideo. Den presenterade metoden använder sig av en random forest tränad på syntetiskt skapade huvudbilder. Användandet av syntetisk data visar sig vara ett gott substitut för användandet av handmärkta bilder. Den presenterade metoden jämförs positivt mot stödvektormaskiner tränade för samma ändamål, både i avseende på precision och snabbhet. Det visas att metoden förlitar sig på god huvuddetektering för att prestera väl. Rapporten undersöker också sätt att kombinera den bildbaserade estimeringen med kontextuella faktorer så som bollposition och spelarposition. Det visas att den relative riktiningen till bollen kan förbättra precisionen i vissa lägen. Vidare visas att random forest-metoden enkelt kan utökas till att använda sig av bilder från flera kameror för att förbättra precisionen.
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Cordea, Marius Daniel. "Real time 3D head pose recovery for model-based video coding." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0015/MQ48145.pdf.
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Yuk, Shun-cho Jacky. "A probabilistic framework for real-time head shape detection and tracking." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39558861.
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Yuk, Shun-cho Jacky, and 郁順祖. "A probabilistic framework for real-time head shape detection and tracking." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39558861.
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Andersen, Arden Bruce. "Validation of the USF Safe Exposure Time Equation for Heat Stress." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/2985.
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Heat stress conditions are prevalent in the working environment around the world. Often they are not readily engineered out. Administrative controls and, in extreme/toxic environments, personal protective gear are the means available to protect workers. For every combination of metabolic work rate, clothing ensemble and environmental WBGT, there is a time of exposure threshold, beyond which the worker can no longer compensate for the heat stress, and signs and symptoms of heat strain appear. Increasingly, worker environments require specialty clothing either for worker protection or to maintain a clean/sanitary environment. Prior to the publication of the USF safe exposure time equation, no simple method was available for determining safe worker exposure time based on a clothing adjustment factor. To demonstrate the validity of the USF SET equation, both direct and indirect data from different environments, metabolic rates, and clothing ensembles were collected to compare observed tolerance times to the predicted safe exposure time. Statistical analysis was performed using the Kolmogorov-Smirnov test. The USF SET equation predicted an acceptable safe exposure time, 19 % of the trials. Based upon this data, the USF safe exposure time heat stress equation over estimates safe exposure time for workers in hot environments, in various clothing ensembles at various metabolic work rates.
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Mukherjee, Smarajit. "Time- and Space-resolved Heat Transfer Model for Spark-Ignition Engines." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1517440404339384.
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Shukla, Nitin. "Heat Transport across Dissimilar Materials." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/27820.
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All interfaces offer resistance to heat transport. As the size of a device or structure approaches nanometer lengthscales, the contribution of the interface thermal resistance often becomes comparable to the intrinsic thermal resistance offered by the device or structure itself. In many microelectronic devices, heat has to transfer across a metal-nonmetal interface, and a better understanding about the origins of this interface thermal conductance (inverse of the interface thermal resistance) is critical in improving the performance of these devices. In this dissertation, heat transport across different metal-nonmetal interfaces are investigated with the primary goal of gaining qualitative and quantitative insight into the heat transport mechanisms across such interfaces. A time-domain thermoreflectance (TDTR) system is used to measure the thermal properties at the nanoscale. TDTR is an optical pump-probe technique, and it is capable of measuring thermal conductivity, k, and interface thermal conductance, G, simultaneously.
The first study examines k and G for amorphous and crystalline Zr47Cu31Al13Ni9 metallic alloys that are in contact with poly-crystalline Y2O3. The motivation behind this study is to determine the relative importance of energy coupling mechanisms such as electron-phonon or phonon-phonon coupling across the interface by changing the material structure (from amorphous to crystalline), but not the composition. From the TDTR measurements k=4.5 W m-1 K-1 for the amorphous metallic glass of Zr47Cu31Al13Ni9, and k=5.0 W m-1 K-1 for the crystalline Zr47Cu31Al13Ni9. TDTR also gives G=23 MW m-2 K-1 for the metallic glass/Y2O3 interface and G=26 MW m-2 K-1 for the interface between the crystalline Zr47Cu31Al13Ni9 and Y2O3. The thermal conductivity of the poly-crystalline Y2O3 layer is found to be k=5.0 W m-1 K-1. Despite the small difference between k and G for the two alloys, the results are repeatable and they indicate that the structure of the alloy plays a role in the electron-phonon coupling and interface conductance.
The second experimental study examines the effect of nickel nanoparticle size on the thermal transport in multilayer nanocomposites. These nanocomposites consist of five alternating layers of nickel nanoparticles and yttria stabilized zirconia (YSZ) spacer layers that are grown with pulsed laser deposition. Using TDTR, thermal conductivities of k=1.8, 2.4, 2.3, and 3.0 W m-1 K-1 are found for nanocomposites with nickel nanoparticle diameters of 7, 21, 24, and 38 nm, respectively, and k=2.5 W m-1 K-1 for a single 80 nm thick layer of YSZ. The results indicate that the overall thermal conductivity of these nanocomposites is strongly influenced by the Ni nanoparticle size and the interface thermal conductance between the Ni particles and the YSZ matrix. An effective medium theory is used to estimate the lower limits for the interface thermal conductance between the nickel nanoparticles and the YSZ matrix (G>170 MW m-2 K-1), and the nickel nanoparticle thermal conductivity.Ph. D.
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Dias, Wiranjith Priyan Solomon. "Time dependent deformations of hardened cement paste from 20°C to 725°C." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/37992.
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Kreitzer, Paul Joseph. "Spray cooling simulation implementing time scale analysis and the Monte Carlo method." Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/11173.
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Thesis (Ph. D.)--West Virginia University, 2010.Title from document title page. Document formatted into pages; contains viii, 136 p. : ill. (some col.) + 1 AVI file and 1 JPEG image file. Includes AVI and JPEG image files. Includes abstract. Includes bibliographical references (p. 102-104).
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Fannin, Christopher A. "Linear Modeling and Analysis of Thermoacoustic Instabilities in a Gas Turbine Combustor." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/28400.
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A dynamic model is developed for the purpose of predicting stability characteristics of an industrial-scale, swirl-stabilized premixed combustor located at the National Energy Technology Laboratory (NETL) in Morgantown, WV. The model consists of modular blocks that assemble into an open-loop transfer function depicting the frequency response of the thermoacoustic system. These blocks include the system acoustic response to unsteady heat release forcing, the air-side coupling of acoustic particle velocity to inlet fuel mass fraction, transport delays present in the mixing nozzle and combustion chamber, and dynamic heat release excitation from unsteady inlet fuel mass fraction. By examing the frequency response with linear stability techniques, the existence of limit cycles due to linear instabilities is predicted. Further, the frequency response analysis is used to predict limit cycle frequencies in the case of predicted instability. The analysis predictions are compared with the results of tests performed at NETL, demonstrating a capability of replicating many of the observed stability characteristics.Ph. D.
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Cordea, Marius Daniel. "Real time three-dimensional head pose recovery for model-based video coding." Thesis, University of Ottawa (Canada), 1999. http://hdl.handle.net/10393/8860.
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This thesis presents an Interactive Facial Animation Testbed (IFAT) for a low bit-rate videophone system based on a face (head) model. The effects of head motion and facial expressions are combined in the 3D head model. The head "pose" (p&barbelow;osition, o&barbelow;rientation, and s&barbelow;cale e&barbelow;stimation) has to be accurately recovered before attempting to recover the face expressions. For the specification of the facial expressions we adopted the "muscle-based" facial model parameterization. This topology independent system incorporates 16 muscles and 10 parameters controlling mouth opening, jaw rotation, eye movement, eyelid opening, and head orientation. Two algorithms were developed for automatic head pose recovery: 2½D pose recovery of the 3D position and 2D orientation using a 2D elliptical head model, and 3D pose recovery of the 3D position and 3D orientation using a 3D wireframe head model. The developed global motion tracking system is meant to work in a realistic videoconferencing environment with no makeup highlighting the speaker's facial features, uncalibrated camera, unknown lighting conditions and unknown scene background. In order to validate the accuracy of the 3D head tracking system, we developed a rapid calibration technique using a sequence of images of a synthetic "standard" 3D head in lieu of real life head.
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Gong, Zhen-Xiang. "Time-dependent melting and freezing heat transfer in multiple phase change materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ29948.pdf.
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Gong, Zhen-Xiang. "Time-dependent melting and freezing heat transfer in multiple phase change materials." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42043.
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Based on an analysis of the causes of non-convergence in the effective heat capacity methods a new conservative effective heat capacity method is developed for general phase change heat transfer problems. Numerical experiments verified the accuracy and efficiency of the new method.A multi-layer phase change material (PCM) heat transfer module is proposed for latent heat energy storage. Cyclic heat transfer in the module was modelled using the finite element technique. A parametric study was performed to investigate the energy charge/discharge rates for the new design.
A second-law thermodynamic analysis was carried out for thermal energy storage using multiple PCMs. The exergy efficiency of energy storage units using two, three as well as five different PCMs was analyzed and compared with that using a single PCM.
A novel cone-cylinder design configuration is proposed for a shell-and-tube latent heat energy storage exchanger. A finite element model was developed to simulate the coupled convection and cyclic melting/freezing phase change heat transfer occurring outside the tube. The advantages of the new configuration are examined and discussed with the help of numerical experiments. Following the new design configuration a novel multi-exchanger energy storage system is proposed. Finite element simulation results validated and extended the thermodynamic analytical results.
A new solar thermal storage unit using multiple PCMs was proposed and analyzed by a finite element model. A parametric study was carried out to investigate the advantages of the new design when compared with conventional single PCM designs.
Finally, a finite element model for melting and freezing heat transfer including free convection in the melt region was developed. The streamline upwind/Petrov-Galerkin method was employed to enhance both the stability and accuracy of the numerical solution. Using this finite element model simulations were carried out for melting of a PCM in a rectangular cavity heated from below. Flow patterns and local heat flux distributions at the heating surface are presented and discussed. In addition, melting of a PCM in a rectangular cavity with an isothermal vertical wall was simulated. To enhance the heat transfer rate during the last stage of the melting process, inverting the PCM container is shown to be an effective technique; this idea was examined with a parametric study.
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Dale, Paul David. "Time heals all wounds? : mathematical models of epithelial and dermal wound healing." Thesis, University of Oxford, 1995. http://ora.ox.ac.uk/objects/uuid:aaa4717f-a115-4a34-bb03-d64ce81841d9.
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The mechanisms responsible for the healing of corneal surface wounds are the subject of biological controversy. In particular, the role and source of the regulatory chemical epidermal growth factor (EGF) is an area of intense debate. In the first part of this thesis, we propose a reaction-diffusion model which focuses on the stimulus for increased mitotic and migratory activity due to secretion of EGF. A detailed numerical study of various possible models, with parameter values based on biological data, reveals that, for realistic healing times, EGF must be released by the underlying layers of the cornea, in addition to the tear film source. The model exhibits travelling wave solutions and further analysis elucidates the interaction and role of the parameters in determining the speed of healing. Furthermore, we consider the effect of topical application of EGF and investigate the effect of curvature of the eye. We show that our model is consistent with many of the key features of corneal wound healing. Adult dermal wounds, in contrast to foetal wounds, heal with the formation of scar tissue. A crucial factor in determining the nature of the healed tissue is the ratio of collagen 1 to collagen 3, which indicates the fibril diameter. We develop a reaction-diffusion model which focuses on the stimulus for collagen synthesis due to the secretion of the different isoforms of the regulatory chemical transforming growth factor β (TGFβ). Numerical simulations of the model without diffusion lead to a value of this ratio consistent with that of healthy tissue for the foetus but corresponding to scarring in the adult. The model equations evolve to waves moving into the wound, but addition of TGFβ only has a transient effect on the final collagen levels. We investigate this effect by developing a caricature model. The model indicates that the main source of the fibroblasts is the underlying subcutaneous tissue and we determine key parameters which explain the difference between adult and foetal wound healing. Furthermore we make clinically testable predictions on the effects that topical application of various chemicals will have on scar formation.
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Stenlund, Lars. "Experimentella studier av värmeflöden och värmelagring i ett bebott flerbostadshus." Doctoral thesis, Umeå universitet, Institutionen för fysik, 1987. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-100376.
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The study is experimentally inclined, with a high target precision for performance measurement. A comprehensive programme of measurements was carried out in a two-storey building, having a massive structure and dating from 1970. Measurements were made continuously during the heating season from a total of about 70 points. Readings were taken every 30 seconds, and the mean values stored in a computer every 15 minutes. Analysis of the results have been concentrated on: * Thermal inertia, and particularly that of cooling mechanisms. * Time delays in heat flows through the building envelope in response to variations in ambient temperature. * The amount of solar input beneficially retained when operating with night setback and with normal operation. The results indicate that the building has both a long time constant, of about 200 h, and a short one, of about 1.5 h. The magnitude of the shorter time constant depends on the thermal capacity of the interior of the building (furniture, curtains etc.), and can be regarded as having some validity for other apartment building stock. Analyses of temperature gradients in the internal surfaces of the exterior walls indicate that the building's ventilation system, which was originally constructed as an exhaust air ventilation system, but with the inflow of fresh air blocked off, generates a dynamic insulation effect. Calculations indicate that this effect can provide a saving of 6 % of the total heating requirement, excluding that for domestic hot water. Investigation of the static heat requirement with and without night set-back indicate a considerable potential annual saving of heating energy, amounting to a maximum of 13 %, provided that the building is heated in accordance with a prescribed strategy. A 'comfort indoor temperature' has also been determined, being the temperature above which the occupants of the building consume excessive heating energy. Theoretical models have been derived to illustrate the short time constant and to analyse the dynamic insulation effect noted.Diss. Umeå : Umeå universitet, 1987
digitalisering@umu
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Shaw, Martin Fraser. "Modelling the time-series of cerebrovascular pressure transmission variation in head injured patients." Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3287/.
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Cerebral autoregulation is the process by which blood ow is maintained over a changing cerebral perfusion pressure. Clinically autoregulation is an important topic because it directly effects overall patient management strategy. However accurately predicting autoregulatory state or even modelling the underlying general physiological processes is a complex task. There are a number of models published within the literature but there has been no active attempt to compare and classify these models. Starting with the hypothesis that a physiologically based model would be a better predictor of autoregulatory state than a purely statistically based one has led us to investigate approaches to model comparison. Using three different models: a new mathematical arrangement of a physiological model by Ursino, the Highest Model Frequency (HMF) model by Daley and the Pressure reactivity index (PRx) statistical model by Czosnyka, a general comparison was carried out using the Matthews correlation coecient against a known autoregulatory state. This showed that the Ursino model was approximately three times as predictive as both the HMF model and the PRx model. However, in general, all of the models predictive accuracies were relatively poor so a number of optimisation strategies were then assessed. These optimisation strategies ultimately were formed into a generalised modelling framework. This framework draws on the ideas of mathematical topology to underpin and explain any change or optimisation to a model. Within the framework different optimisations can be grouped into four categories, each of which are explored in the text of this thesis: 1) Model Comparison. This is the simplest technique to apply where the number of models under examination are reduced based on the predictive accuracy. 2) Parameter restriction. A classical form of optimisation by constraining a model parameter to cause a better predictive accuracy. In the case of both the HMF and PRx we showed between a two hundred and six hundred percent increase in predictive accuracy over the initial assessment. 3) Parameter alteration. This change allows for related parameters to be substituted into a model. Four different alterations are explored as a surrogate measure for arterial-arteriolar blood volume the most clinically applicable of which is a transcranial impedance technique. This latter technique has the potential to be a non invasive measure correlated with both mean ICP and ICP pulse amplitude. 4) Model alteration. Allows for larger changes to the underlying structure of the model. Two examples are presented: firstly a new asymmetric sigmoid curve to overcome computational issues in the Ursino model and secondly a novel use of fractal characterisation which is applied in a wavelet noise reduction technique. The framework also gives an overview of the autoregulatory research domain as a whole as a result of its abstract nature. This helps to highlight some general issues in the domain including a more standardised way to record autoregulatory status. Finally concluding with research addressing the requirement for easier access to data and the need for the research community to cohesively start to address these issues.
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Henderson, Alistair. "Predicting Ignition Time Under Transient Heat Flux Using Results from Constant Flux Experiments." University of Canterbury. Civil Engineering, 1998. http://hdl.handle.net/10092/8273.
Full textAbstract:
This project investigated if ignition could be mathematically predicted when a material is subjected to a transient heat flux.
Six timbers commonly used in New Zealand for construction and indoor furnishing timbers were tested in a cone calorimeter at the University of Canterbury. The experiments were run at 50, 35, 20 and 15 kW/m2 incident heat flux. The sample surface temperature and heat release data was collected for each test. From the ignition time data a value for thermal inertia was calculated and using specific heat data from the literature the thermal properties of each material was inserted into a One Dimensional Heat Transfer Model.
A second series of tests were conducted on each of the materials tested at constant flux. These new tests involved subjecting the sample to a transient heat flux based on t² fire growth curves. Again surface temperature and heat release data was obtained from the tests.
The one dimensional heat transfer model was used to attempt to predict the surface temperature profile and the ignition time when the test conditions were entered into it.
It was found that the predicted surface temperature profile generally matched the shape of the measured temperature profile. However the model was unsuccessful in accurately predicting the ignition time in either the constant or transient flux conditions.
It is considered that accurate values for the thermal conductivity and the specific heat would be required before the ignition time and temperature profile could be accurately modelled.
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Gibson, Borbor Auzzel Kwaku Kudar. "Residence time investigation of artificial silver ores in heap leaching using cyanide lixiviant." Master's thesis, Faculty of Engineering and the Built Environment, 2020. http://hdl.handle.net/11427/32642.
Full textAbstract:
Heap Leaching has gained much relevance in the processing of low-grade mineral resources - ores considered uneconomical for beneficiation through conventional concentration and tank leaching. However, it is at the same time characterized by extended leaching periods due to slow mineral conversion and low rates of recovery as a major challenge. Interactions within the heap bed are not fully understood as chemical leaching and hydrodynamics interact in a complex manner. To study these interactions, a number of investigations have focused on the hydrodynamic interaction using conventional residence time distribution (RTD) studies in laboratory columns. In these RTD studies, the flows of tracer exiting through the effluent stream provide information of its paths, where some flows might relate to fast movement, slow convoluted channels, or micro/macro stagnated regions. This information is usually interpreted through simplified reactor models representing the bed as a combination of plug flow reactors (PFRs), continuous stirred tank reactors (CSTRs) and dead zones. Using columns as reactors to approximate heap leaching on a laboratory scale, it is anticipated that the RTD flow distribution response should be similar to the distribution of a PFR with associated dead zones. While some literature sources have alluded to the response in columns being similar to a plug flow response, recent sources using a similar hydrodynamic RTD approach reported column reactor distribution resembling flow more typical of a continuous stirred tank, CSTR, system instead of plug flow. Given that packed ore beds are not agitated, this appears paradoxical. It is hypothesised that the CSTR-like response is a result of the distribution of convoluted flow channels through the ore bed, which perform overall like a bundle of PFRs of different lengths. To discern the two patterns the use of a reactive leaching on a well characterized ore material is proposed. Therefore, this work aims to study simultaneously the flow and leach performance of a laboratory column reactor, utilizing a novel reactive leaching approach with a lixiviant amendable to a well-characterized homogeneous solid material. The objective of this work is to establish flow distribution performance in packed bed columns and correlate such performance to the ultimate extraction from the packed bed. The study was performed using a nonreactive solution tracer (potassium nitrate) to characterise flow through a column packed with an artificial silver ‘ore' (silver grains embedded in concrete), followed by a reactive leaching study using sodium cyanide which would leach the silver. The artificial silver ore was developed with the aim to exhibit four ideal properties, namely homogeneous porosity, uniform grain size, homogenous dispersion of the grains throughout the ore, and even grade distribution of the different size fractions after crushing. Leaching and micro-XCT characterization studies were performed in order to determine the leaching properties of the artificial silver ore and validate the ore corresponds to these ideal properties. This validation was indeed achieved; however, the inner-particle pores were not found to be continuous at the scale of resolution of the instrument (4.8 microns). Poor extraction from the coarse particles in both the leaching characterization and reactive column leaching investigations suggested that this network was not well established and may exist only at the sub-micron scale. Leach tests were performed on individual particle sizes in both shake flask and circulating bed reactor tests. Extraction from the leaching of the coarse synthetic silver ore particles was observed to be very low relative to dissolution from pure silver metal grains. Diagnostic shrinking core and the extended mixed topology models were used to determine the controlling dissolution mechanism. Both models demonstrated that a diffusion-reaction mechanism governed the dissolution extraction from the large particles. RTD column leaching studies were performed utilizing flow rate and PSD as investigated parameters. The nonreactive tracer produced a step-change flow response that was more similar to a characteristic plug flow type distribution but showed distinct deviations towards CSTR behavior, especially for the beds containing a higher degree of fines. Reactive column leaching experiments were performed under similar conditions as the nonreactive RTD, introducing a step-change of the cyanide reagent. Rapid silver leaching occurred initially, but equally rapidly declined to very low rates. The leach curves were interpreted by translating the information obtained from the nonreactive RTDs into a distribution of parallel plug flow channels. The extent of reaction for each of these channels is derived from the surface reaction model for the individual size classes, put together for the corresponding PSD in each experiment. RTD specific PSDs tested using this approach assumed that longer residence times correspond to the prevalence of finer material. The validity of the approach was tested by comparing the extraction determined from the particle leaching kinetics studies to the reactive column data through modelling. The model is based on the weighted average leaching from a population of particles, calibrated against kinetic models formulated for individual size classes. This model is further linked to a distribution of flow channels determined from the RTD studies. The prediction of the model did not compare too well against the raw silver dissolution data of the columns. This was attributed to the model having been calibrated against kinetic data that did not fully consider the smaller size classes below -4/+2.8 mm – considered to be the key source of rapid surface reaction in the packed bed. Although the concept proposed in this project was not fully proven, further test work is recommended to expand on the approach presented here.
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Yoon, Il. "Two-phase flow dynamics by real-time neutron imaging in oscillating heat pipe." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5694.
Full textAbstract:
Thesis (M.S.)--University of Missouri-Columbia, 2008.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 19, 2009) Includes bibliographical references.
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Yang, Bo. "Spatio-temporal Analysis of Urban Heat Island and Heat Wave Evolution using Time-series Remote Sensing Images: Method and Applications." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1552398782461458.
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Alhamdan, Abdullah M. "Particle Residence Time Distribution and Bulk Heat Transfer Coefficients of Two-Phase Flow in Scraped Surface Heat Exchanger and Holding Tubes /." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487929230742153.
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Lee, Michael. "Finite time analysis of hydrogen compression using metal hydride and the experimental investigation of porous metal hydride compacts." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1447632.
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Thaokar, Chandrajit. "Development and Experimental Validation of Mathematical Tools for Computerized Monitoring of Cryosurgery." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/716.
Full textAbstract:
Cryosurgery is the destruction of undesired biological tissues by freezing. Modern cryosurgery is frequently performed as a minimally-invasive procedure, where multiple hypodermic, needle-shaped cryoprobes are inserted into the target area to be treated. The aim of the cryosurgeon is to maximize cryoinjury within a target region, while minimizing damage to healthy surrounding tissues. There is an undisputed need for temperature-field reconstruction during minimally invasive cryosurgery to help the cryosurgeon achieve this aim. The work presented in this thesis is a part of ongoing project at the Biothermal Technology Laboratory (BTTL), to develop hardware and software tools to accomplish real-time temperature field reconstruction. The goal in this project is two-fold: (i) to develop the hardware necessary for miniature, wireless, implantable temperature sensors, and (ii) to develop mathematical techniques for temperature-field reconstruction in real time, which is the focus of the work presented in this thesis. To accomplish this goal, this study proposes a computational approach for real-time temperature-field reconstruction, combining data obtained from various sensing modalities such as medical imaging, cryoprobe-embedded sensors, and miniature, wireless, implantable sensors. In practice, the proposed approach aims at solving the inverse bioheat transfer problem during cryosurgery, where spatially distributed input data is used to reconstruct the temperature field. Three numerical methods have been developed and are evaluated in the scope of this thesis. The first is based on a quasi-steady approximation of the transient temperature field, which has been termed Temperature Field Reconstruction Method (TFRM). The second method is based on analogy between the fields of temperature and electrical potential, and is thus termed Potential Field Analogy Method (PFAM). The third method is essentially a hybrid of TFRM and PFAM, which has shown superior results. Each of these methods has been benchmarked against a full-scale finite elements analysis using the commercial code ANSYS. Benchmarking results display an average mismatch of less than 2 mm in 2D cases and less than 3 mm in 3D cases for the location of the clinically significance isotherms of -22°C and -45°C. In an advanced stage of numerical methods evaluation, they have been validated against experimental data, previously obtained at the BTTL. Those experiments were conducted on a gelatin solution, using proprietary liquid-nitrogen cryoprobes and a cryoheater to simulate urethral warming. The design of the experiment was aimed at creating a 2D heat-transfer problem. Validation results against experimental data suggest an average mismatch of less than 2 mm, for the hybrid of TFRM + PFAM method, which is of the order of uncertainty in estimating the freezing front location based on ultrasound imaging.
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Marsili, Paolo. "Short time asymptotic behaviors of Heat kernel and Brownian motion on a Riemannian manifold." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13541/.
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Ziraknejad, Nima. "Driver head pose sensing using a capacitive array and a time-of-flight camera." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50186.
Full textAbstract:
Improving the safety of vehicle occupants has gained increasing attention among automotive manufacturers and researchers over the past three decades. There is increased potential for injury mitigation techniques to be applied more effectively to vehicle safety systems if the pose (i.e. the position and orientation) of the driver’s head with respect to the Head Restraint (HR) device can be provided to such safety systems in real-time during vehicle operation. This information is valuable to a range of systems including: adaptive HR positioning for whiplash injury mitigation, advanced driver assistance, driver inattention and fatigue detection, and other possible applications.
This thesis proposes, implements, and evaluates a new integrated hybrid sensing approach to providing the driver’s head pose both accurately and in real-time by employing two different sensing subsystems inside the vehicle: 1) a novel capacitive proximity sensing array, and 2) an Illumination-Compensated (IC) Time-of-Flight (ToF) range imaging camera. Firstly, for position sensing, a capacitive proximity sensing electrode and array were developed through electrostatic field analysis and then optimized using numerical modeling studies. Experiments (including environmental testing) using a full system prototype of the position sensing array were performed for numerical modeling validation and accuracy testing. Secondly, since orientation sensing (found to be inaccurate with capacitive sensing alone), this work demonstrated how a ToF camera can be utilized to obtain an accurate measurement of the driver’s head pose using a novel light IC technique. A laboratory testbed was also built to accommodate the aforementioned hybrid system. The capacitive array was incorporated inside the frontal compartment of a customized HR device as part of the testbed, and the ToF camera was installed in front of the driver.
Laboratory experiments have demonstrated that the head position can be estimated with a mean Euclidean distance error of 0.33 cm and a Mean Absolute Error in orientation of 3.45° and 1.61° for head yaw and pitch angles, respectively. The thesis also contains a comprehensive introduction to the problem, review of relevant current literature in the area, comparison with the findings of previous related investigations, discussion of the implications of the work and suggestions for future work.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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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.
Full textAbstract:
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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Tsakiraki, Eleni. "Real-time Head Motion Tracking for Brain Positron Emission Tomography using Microsoft Kinect V2." Thesis, KTH, Skolan för teknik och hälsa (STH), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189973.
Full textAbstract:
The scope of the current research work was to evaluate the potential of the latest version of Microsoft Kinect sensor (Kinect v2) as an external tracking device for head motion during brain imaging with brain Positron Emission Tomography (PET). Head movements constitute a serious degradation factor in the acquired PET images. Although there are algorithms implementing motion correction using known motion data, the lack of effective and reliable motion tracking hardware has prevented their widespread adoption. Thus, the development of effective external tracking instrumentation is a necessity. Kinect was tested both for Siemens High-Resolution Research Tomograph (HRRT) and for Siemens ECAT HR PET system. The face Application Programming Interface (API) ’HD face’ released by Microsoft in June 2015 was modified and used in Matlab environment. Multiple experimental sessions took place examining the head tracking accuracy of kinect both in translational and rotational movements of the head. The results were analyzed statistically using one-sample Ttests with the significance level set to 5%. It was found that kinect v2 can track the head with a mean spatial accuracy of µ0 < 1 mm (SD = 0,8 mm) in the y-direction of the tomograph’s camera, µ0 < 3 mm (SD = 1,5 mm) in the z-direction of the tomograph’s camera and µ0 < 1 ◦ (SD < 1 ◦ ) for all the angles. However, further validation needs to take place. Modifications are needed in order for kinect to be used when acquiring PET data with the HRRT system. The small size of HRRT’s gantry (over 30 cm in diameter) makes kinect’s tracking unstable when the whole head is inside the gantry. On the other hand, Kinect could be used to track the motion of the head inside the gantry of the HR system.
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Jamison, John S. "Time and Space Resolved Spin-Heat Transport in the Magnetic Insulator Yttrium Iron Garnet." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1586740671277489.
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Brack, Stefan [Verfasser]. "Time-resolved Transient Convective and Conjugate Heat Transfer Experiments Using IR Thermography / Stefan Brack." München : Verlag Dr. Hut, 2020. http://d-nb.info/1219476323/34.
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Kilic, Arif Nesimi 1963. "A multi-region transient erosion model for concrete with time-dependent surface heat flux." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/290695.
Full textAbstract:
A multi-region, transient concrete ablation and decomposition model is developed. The model consists of four regions of concrete containing a thermally affected region, a dry (evaporated and chemically dehydrated) region, and a gas-free (decarboxylated) region with ablated concrete at the melt/concrete interface. Each region has an interface where the latent heat of local decomposition reactions is taken into account as heat sinks due to endothermic characteristics of the reactions. The time dependent temperature profiles, and depth and growth rate of the regions are evaluated by use of the heat balance integral method. Solutions are obtained for surface heat fluxes in forms of constant, e ⁻(λ)ᵗ, t⁻(λ) and -At to analyze various melt cooldown schemes. The erosion front progresses with a constant rate proportional to the surface heat flux in case of constant heat flux, and terminates at a finite erosion depth that is logarithmically proportional to the cooldown rate for surface heat flux in forms of ⁻(λ)ᵗ and t⁻(λ). Sensitivity analyses are performed to investigate the effects of important thermophysical parameters. Larger erosion depth and rate is observed for higher thermal conductivity. Decomposition temperatures are found to be significant in ablation. Model results were compared with previous experiments and models, and determined to be valid and accurate for different types of melt/concrete interaction. The model presented in this study is simple yet very detailed and accurate in simulating the actual molten core/concrete interaction (MCCI) phenomena, and in investigating the concrete reaction to the molten core. It not only can be embodied into the MCCI codes currently being developed, but also can be used to determine the containment integrity, and fission products released into the environment and to the public as a stand alone code.
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Gummesson, Patrik. "Evaluation of heat pump concepts in ice rinks." Thesis, KTH, Tillämpad termodynamik och kylteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-141149.
Full textAbstract:
In Sweden there are about 350 ice rinks in operation today which consume approximately 300 GWh per year. The average energy consumption for a Swedish ice rink is approximately 1000 MWh per year. Ice rink dose not only consume energy it also rejects heat. The rejected heat comes from the refrigeration system that cools down the ice floor. The refrigeration system rejects heat around 700 to 1000 MWh per season. The reason for this study is because of the rejected heat which leads to the question how the rejected heat can be used.The object is to find a heat pump concept that can use the rejected heat or another heat source in an ice rink. Three different heat pump concepts were evaluated. The first heat pump concept use the ice floor as a heat source (called BHP), the second concept use the rejected heat as a heat source (called CHP) and the third concept use the rejected heat to charge an energy storage (called GHP).To accomplish the objective a heat analysis of two ice rinks were made to be able to simulate the heat pump concepts. With the simulation results a life cycle cost was made for a better evaluation. The results from the heat analysis were used for simulating the heat pump concepts. The two ice rinks that were analyzed were Järfälla ice rink and Älta ice rink. The main heat source the two ice rinks uses today is district heating and electricity. Järfälla only use district heating (DH) as a heat source and Älta ice rink use recovery heat, electricity and district heating.The heat analysis of the two the ice rinks showed that the highest district heating consumer was the domestic hot water at 47% of the DH followed by the dehumidifier at 32% of the DH and last the space heating at 22% of the DH. This shows how the heat is used in a general ice rink in Sweden. The temperature levels for the dehumidifier is around 65 °C (only DH part), the domestic hot water at 55 °C and last the space heating at 20 °C. However the heat demand for the ice rinks resulted in 443 MWh for Järfälla and 192 MWh for Älta. To know the size of the heat pump used for the heat pump concepts a heat profile for the ice rinks were made. The result of heat profiles lead to a heat pump size of 105 kW in Järfälla and 45 kW in Älta. The rejected heat for one season in Järfälla is 1000 MWh and 780 MWh in Älta.With the results from the heat analysis the evaluation the heat pump concepts was possible. The COP1 for the CHP resulted at 3,8 and the COP1 for the GHP was assumed to be the same as for the CHP. The COP1 calculations for the BHP concept resulted at 2,5. COP was calculated with collected data from the respective ice rinks refrigeration system. The simulations results were that the BHP and the CHP concept could fulfill the heat demand up to around 79% and the GHP up to around 84% in both ice rinks. The rest of the heat demand is heated with supplementary heat. The life cycle cost (LCC) showed that the CHP concept had the lowest cost followed by the GHP concept. The BHP concept had the highest LCC, because of the low COP. The LCC model dos not include the running cost, the maintenance cost and the energy tariffs for the district heating.The recommended solution is the GHP concept. This is because it is a good investment for the future since other buildings can be connected to the energy storage. The GHP concept is also the solution that fulfills the heat demand best and has the lowest annual energy cost.
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Nakamura, Chikara. "Asymptotic behaviors of random walks; application of heat kernel estimates." Kyoto University, 2018. http://hdl.handle.net/2433/232222.
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Hubble, David Owen. "An experimental investigation of the mechanism of heat transfer augmentation by coherent structures." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/26784.
Full textAbstract:
The mechanism by which convective heat transfer is augmented by freestream turbulence in the stagnation region was studied experimentally. Previous work has suggested that the primary mechanism for the observed augmentation is the amplification of vorticity into strong vortices which dominate the flow field near the surface. Therefore, two separate experimental investigations were performed to further study this phenomenon. In the first, the spatiotemporal convection from a heated surface was measured during the normal collision of a vortex ring. The convection was observed to increase dramatically in areas where vortices forced outer fluid through the natural convection boundary layer to the surface. Regions where fluid was swept along the surface experienced much smaller increases in convection. These observations led to the development of a mechanistic model which predicted the heat transfer based on the amount of time that fluid remained within the thermal boundary layer prior to reaching the surface. In subsequent testing, the model was able to accurately predict the time-resolved convection based solely on the transient properties of the vortex present. In the second investigation, the model was applied to the vortices which form in a stagnating turbulent flow. Three turbulence conditions were tested which changed the properties of the vortices produced. Again, the model was successful in predicting the time-resolved convection over much of the experimental measurement time.
The work of designing and calibrating the heat flux sensor used is also reported. A new sensor was developed specifically for the convection research performed herein as no existing sensor possessed the required spatiotemporal resolution and underwater capabilities. Utilizing spot-welded foils of thermoelectric alloys resulted in a very robust and sensitive sensing array which was thoroughly analyzed and calibrated. In the final section, the hybrid heat flux (HHF) method is presented which significantly increases the performance of existing heat flux sensors. It is shown (both numerically and experimentally) that by combining the spatial and temporal temperature measurements from a standard sensor, the time response increases by up to a factor of 28. Also, this method causes the sensor to be insensitive to the material to which it is mounted.Ph. D.
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Gifford, Andrew R. "The Physical Mechanism of Heat Transfer Augmentation in Stagnating Flows Subject to Freestream Turbulence and Related Studies." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/26097.
Full textAbstract:
The mechanism of heat transfer augmentation due to freestream turbulence in
classic Hiemenz stagnation flow was studied experimentally for the first time using time-resolved digital particle image velocimetry (TRDPIV) and a new thin film
heat flux sensor called the Heat Flux Array (HFA). Unique measurements of simultaneous, time-resolved velocity and surface heat flux data were obtained along the
stagnation line on a simple, rectangular flat plate model mounted in a water tunnel
facility. Identification and tracking of coherent structures in the stagnation region
lends support to the theory that coherent structures experience stretching and amplification of vorticity by the mean flow strain rate upon approaching the stagnation
surface. The resulting flow field in the near-wall region is comprised primarily of high
strength, counter-rotating vortex pairs with decreased integral length scale relative to
the imposed freestream turbulence. It is hypothesized that the primary mechanism
of heat transfer augmentation is the movement of cooler freestream fluid into the
heated near-wall region by these coherent structures. Furthermore, the level of heat
transfer augmentation is dictated by the integral length scale, circulation strength,
and core-to-surface distance of the coherent structures. To test this hypothesis, these
properties were incorporated into a mechanistic model for predicting the transient,
turbulent heat transfer coefficient. The model was successful in predicting the shape
and magnitude of the measured heat transfer coe±cient over much of the experimental
measurement time.
In a separate yet related set of studies, heat flux sensors and calibration methods
were examined. The High Temperature Heat Flux Sensor (HTHFS) was designed
and developed to become one of the most durable heat flux sensors ever devised for
long duration use in high temperature, extreme environments. Extensive calibrations
in both conduction and convection were performed to validate the performance of the
sensor near room temperature. The measured sensitivities in conduction and convection were both very close to the predicted sensitivity using a thermal resistance model
of the HTHFS. The sensor performance was unaffected by repeated thermal cycling
using kiln and torch firing. Finally, the performance of Schmidt-Boelter heat flux
sensors were examined in both shear and stagnation flow using two custom designed
convection calibration facilities. Calibration results were evaluated using an analytical sensitivity model based on an overall sensor thermal resistance from the sensor
to the heat sink or mounting surface. In the case of convection the model included
a term for surface temperature differences along the boundary layer. In stagnation
flow the apparent sensitivity of the Schmidt-Boelter sensors decreased non-linearly
with increasing heat transfer coefficient. Estimations of the sensor's internal thermal
resistance were obtained by fitting the model to the stagnation calibration data. This
resistance was then used with the model to evaluate the effects of non-uniform surface
temperature on the shear flow sensitivity. A more pronounced non-linear sensitivity
dependence on heat transfer coefficient was observed. In both cases the main result
is that convection sensitivity varies a great deal from standard radiation calibrations.Ph. D.