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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
191

Thermal Transport and Heat Exchanger Design for the Space Molten Salt Reactor Concept

Flanders, Justin M. 31 August 2012 (has links)
No description available.
192

Bronze-Age Crete and Art Nouveau: A Diachronic Dialog

Hsu, Sheng-Chieh January 2017 (has links)
This dissertation examines the relationship between Minoan art and Art Nouveau. The Minoan civilization was rediscovered at the turn of the twentieth century when the Art Nouveau movement reached its peak. Due to this coincidental timing, their artistic resemblance has raised questions about whether Minoan art had inspired Art Nouveau and whether Art Nouveau played a role in the restoration of Minoan art. The possibility of a Minoan influence on Art Nouveau is considered through a number of aspects, which include news reports on the excavations, Minoan collections acquired by museums, reference to the Minoans in various fields, application of Minoan motifs, and the attractiveness of the Minoans to Art Nouveau artists. As for the reversed influence, the research analyzes how archaeologists came to see the Minoans as a “modern” civilization, investigates the background of the restorers of Minoan objects, and provides examples of fresco restorations that illustrate an Art Nouveau preference of the early archaeologists and restorers. With the evidence and the discussion, I argue that the existing connection between Minoan art and Art Nouveau is beyond doubt. / Art History
193

The Sickly Female Body in Edvard Munch's The Dance of Life (1899-1900)

McEwen, Rebecca January 2018 (has links)
In interpretations of The Dance of Life (1899-1900) by Edvard Munch, the femme fragile and the femme fatale have been considered jointly (i.e. as allusions to the cyclicality of life) or as individuals. Their unique characteristics have been recognized as such: whereas the femme fragile dons white to signify her prepubescent state and thus her innocence, the femme fatale wears red to suggest her sexuality and even her availability. Yet, scholars have failed to probe their iconographical complexities. Doing so would not only lend greater conviction to Munch’s historical identity as a Symbolist (as his archetypes would be recognized for their multivalence), but it would also reveal the didactic possibilities of the work of art itself. Given this void in the literature, the purpose of this thesis will be to elaborate on the formal and narrative qualities of the femme fragile and femme fatale in this painting. These archetypes ultimately allude to misogynistic anxieties, with the femme fragile in particular representing the sickly female body. / Art History
194

Haar Wavelet Collocation Method for Thermal Analysis of Porous Fin with Temperature-dependent Thermal Conductivity and Internal Heat Generation

Oguntala, George A., Abd-Alhameed, Raed January 2017 (has links)
Yes / In this study, the thermal performance analysis of porous fin with temperature-dependent thermal conductivity and internal heat generation is carried out using Haar wavelet collocation method. The effects of various parameters on the thermal characteristics of the porous fin are investigated. It is found that as the porosity increases, the rate of heat transfer from the fin increases and the thermal performance of the porous fin increases. The numerical solutions by the Haar wavelet collocation method are in good agreement with the standard numerical solutions.
195

Thermal Analysis of Convective-Radiative Fin with Temperature-Dependent Thermal Conductivity Using Chebychev Spectral Collocation Method

Oguntala, George A., Abd-Alhameed, Raed 15 March 2018 (has links)
Yes / In this paper, the Chebychev spectral collocation method is applied for the thermal analysis of convective-radiative straight fins with the temperature-dependent thermal conductivity. The developed heat transfer model was used to analyse the thermal performance, establish the optimum thermal design parameters, and also, investigate the effects of thermo-geometric parameters and thermal conductivity (nonlinear) parameters on the thermal performance of the fin. The results of this study reveal that the rate of heat transfer from the fin increases as the convective, radioactive, and magnetic parameters increase. This study establishes good agreement between the obtained results using Chebychev spectral collocation method and the results obtained using Runge-Kutta method along with shooting, homotopy perturbation, and adomian decomposition methods.
196

Effects of Louver Length and Vortex Generators to Augment Tube Wall Heat Transfer in Louvered Fin Heat Exchangers

Sanders, Paul Alan 21 October 2005 (has links)
There are several different types of compact heat exchangers used in applications where small size and weight are required. One particular type of compact heat exchanger, the louvered fin heat exchanger, has been used heavily in the automotive and air conditioning industries. Over the last several decades, the majority of the work towards improving louvered fin exchanger efficiency has focused on designing more efficient fins by optimizing fin parameters like louver angle, fin pitch, louver pitch, and louver length. At this point in time, many improvements to standard louver geometry have been made, so other surfaces and methods of enhancing exchanger performance need to be studied if any significant future efficiency gains are to be expected. This thesis presents a detailed experimental study that has two major foci relative to the performance of the louvered fin compact heat exchanger. The first is to determine the effect of louver length on pressure drop and tube wall heat transfer, which is the primary heat transfer surface in the heat exchanger. The second is to augment tube wall heat transfer with the use of delta winglets placed on the fins near the tube wall. These studies were completed on a 20X scale model of a louvered fin exchanger with a fin pitch to louver pitch ratio of 0.76 and a louver angle of 27°, over a Reynolds number range based on louver pitch of 230 < ReLp < 1016. The three louver lengths evaluated were 100%, 82%, and 70% of the fin height and delta winglet experiments were performed for louver length to fin pitch ratios of 100% and 70%. Heat transfer results for the louver length tests show that decreasing louver length leads to increases in tube wall heat transfer of 0% to 50% depending on Reynolds number. Also, delta winglets placed on the fins near the tube wall have been shown to produce average tube wall heat transfer augmentations of up to 52%. / Master of Science
197

Aerodynamic Force and Pressure Loss Measurements on Low Aspect Ratio Pin Fin Arrays

Thrift, Alan Albright 20 February 2007 (has links)
The desire to achieve higher heat transfer augmentation for turbine blades is fueled by the increased power output and efficiency that is achievable with high turbine inlet temperatures. The use of internal cooling channels fitted with pin fin arrays serves as one method of accomplishing this goal. Consequently, the addition of pin fin arrays comes at the expense of increased pressure drop. Therefore the pin fin geometry must be judiciously chosen to achieve the required heat transfer rate while minimizing the associated pressure drop. This project culminates in the measurement of both pin fin force and array pressure drop as they related to changes in the array geometry. Specifically, the effects of Reynolds number, spanwise pin spacing, streamwise pin spacing, pin aspect ratio, and flow incidence angle. Direct two-component force measurement is achieved with a cantilever beam force sensor that uses highly sensitive piezoresistive strain gauges, relating the strain at the base of the beam to the applied force. With proper characterization, forces as small as one-tenth the weight of a paper clip are successfully measured. Additionally, array pressure drop measurements are achieved using static pressure taps. Experiments were conducted over a range of Reynolds numbers between 7,500 and 35,000. Changes in the spanwise pin spacing were shown to substantially alter the pin fin drag and array pressure drop, while changes in the streamwise pin spacing were less influential. The experimental results also showed a dramatic reduction in the pin fin drag and array pressure drop for an inline flow incidence angle. Finally, changes in the pin aspect ratio were shown to have little effect on the array pressure drop. / Master of Science
198

Development of a Methodology to Measure Aerodynamic Forces on Pin Fins in Channel Flow

Brumbaugh, Scott J. 23 January 2006 (has links)
The desire for smaller, faster, and more efficient products places a strain on thermal management in components ranging from gas turbine blades to computers. Heat exchangers that utilize internal cooling flows have shown promise in both of these industries. Although pin fins are often placed in the cooling channels to augment heat transfer, their addition comes at the expense of increased pressure drop. Consequently, the pin fin geometry must be judiciously chosen to achieve the desired heat transfer rate while minimizing the pressure drop and accompanying pumping requirements. This project culminates in the construction of a new test facility and the development of a unique force measurement methodology. Direct force measurement is achieved with a cantilever beam force sensor that uses sensitive piezoresistive strain gauges to simultaneously measure aerodynamic lift and drag forces on a pin fin. After eliminating the detrimental environmental influences, forces as small as one-tenth the weight of a paper clip are successfully measured. Although the drag of an infinitely long cylinder in uniform cross flow is well documented, the literature does not discuss the aerodynamic forces on a cylinder with an aspect ratio of unity in channel flow. Measured results indicate that the drag coefficient of a cylindrical pin in a single row array is greater than the drag coefficient of an infinite cylinder in cross flow. This phenomenon is believed to be caused by an augmentation of viscous drag on the pin fin induced by the increased viscous effects inherent in channel flow. / Master of Science
199

NUMERICAL MODEL FOR MICROCHANNEL CONDENSERS AND GAS COOLERS WITH AN IMPROVED AIR-SIDE APPROACH

Martínez Ballester, Santiago 10 October 2012 (has links)
La presente tesis se ha llevado a cabo en el Instituto de Ingeniería Energética de la Universitat Politècnica de València y durante una estancia en el National Institute of Standards and Technology (NIST). El objetivo principal de la tesis es desarrollar un modelo de alta precisión para intercambiadores de calor de microcanales (MCHX), que tiene que ser útil, en términos de coste computacional, para tareas de diseño. En la opinión del autor, existen algunos inconvenientes cuando los modelos existentes se aplican a algunos diseños recientes de intercambiador de calor, tales como MCHXs, bien de tubos en serpentín o en paralelo. Por lo tanto, la primera etapa de la tesis identifica los fenómenos que tienen el mayor impacto en la precisión de un modelo para MCHX. Adicionalmente, se evaluó el grado de cumplimiento de varias simplificaciones y enfoques clásicos. Con este fin, se desarrolló el modelo de alta precisión Fin2D como una herramienta para llevar a cabo la investigación mencionada. El modelo Fin2D es una herramienta útil para analizar los fenómenos que tienen lugar, sin embargo requiere un gran coste computacional, y por tanto no es útil para trabajos de diseño. Es por ello que en base a los conocimientos adquiridos con el modelo Fin2D, se ha desarrollado un nuevo modelo, el Fin1Dx3. Este modelo tan sólo tiene en cuenta los fenómenos más importantes, reteniendo casi la misma precisión que Fin2D, pero con una reducción en el tiempo de cálculo de un orden de magnitud. Se introduce una novedosa discretización y un esquema numérico único para el modelado de la transferencia de calor del lado del aire. Este nuevo enfoque permite modelar los fenómenos existentes de forma consistente con mayor precisión y con mucho menos simplificaciones que los modelos actuales de la literatura. Por otra parte, se logra un coste razonable de cálculo para el objetivo fijado. La tesis incluye la validación experimental de este modelo tanto para un condensador y un enfriador de gas. Con e / Martínez Ballester, S. (2012). NUMERICAL MODEL FOR MICROCHANNEL CONDENSERS AND GAS COOLERS WITH AN IMPROVED AIR-SIDE APPROACH [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17453
200

Projection of TaSiOx/In0.53Ga0.47As Tri-gate transistor performance for future Low-Power Electronic Applications

Saluru, Sarat K. 12 June 2017 (has links)
The aggressive scaling of silicon (Si) based complementary metal-oxide-semiconductor (CMOS) transistor over the past 50 years has resulted in an exponential increase in device density, which consequentially has increased computation power rapidly. This has pronounced the necessity to scale the device's supply voltage (VDD) in to order to maintain low-power device operation. However, the scaling of VDD can degrade drive current significantly due to the low carrier mobility of Si. To overcome the key challenges of dimensional and voltage scaling required for low-power electronic operation without degradation of device characteristics, the adoption of alternate channel materials with low bandgap with superior transport properties will play a crucial role to improve the computation ability of the standard integrated circuit (IC). The requirement of high-mobility channel materials allows the industry to harness the potential of III-V semiconductors and germanium. However, the adoption of such high mobility materials as bulk substrates remains cost-prohibitive even today. Hence, another key challenge lies in the heterogeneous integration of epitaxial high-mobility channel materials on the established cost-effective Si platform. Furthermore, dimensional scaling of the device has led to a change in architecture from the conventional planar MOSFET to be modified to a 3-D Tri-gate architecture which provides fully depleted characteristics by increasing the inversion layer area and hence, providing superior electrostatic control of the device channel to address short channel effects such as subthreshold slope (SS) and drain induced barrier lowering (DIBL). The Tri-gate configuration provides a steeper SS effectively reducing leakage current (IOFF), thereby decreasing dynamic power consumption and increasing device performance. Recently, Tantalum silicate (TaSiOx) a high-k dielectric has been shown to exhibit superior interfacial quality on multiple III-V materials. However, there is still ambiguity as to the potential of short-channel devices incorporating alternate channel (III-V) materials which is the basis of this research, to demonstrate the feasibility of future high-mobility n-channel InGaAs material integration on Si for high- speed, low-power, high performance CMOS logic applications. / Master of Science / Everyone today is dependent on some sort of an electronic device be it a computer, laptop, tablet or a phone powered by the boom of the Silicon Valley. All of which have witnessed significant improvement in performance due to the increase in the number of transistors in a microprocessor (similar to horsepower of a car) which is made possible due to the dimensional scaling of the transistor device features (currently at 14nm). With increased transistor density, a higher power consumption is consequential creating a trade-off between performance and power consumption (battery life). However, there are limitations as to how small a transistor can be scaled. This has provided precedence to employ alternate materials such as III-V alloys and Germanium to reduce power consumption (due to a lower band gap; which dictates how much energy is consumed) while simultaneously improving device performance by providing a mobility boost (which is a property of the aforementioned materials that allows current to flow faster, thereby improving device performance). The aim of this work is evaluate leading device architectures incorporating alternate channel materials (InGaAs in particular which is a very suitable III-V alloy) to develop a simulation model that is calibrated to existing data to project device performance future transistor nodes.

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