A water-filled geomembrane tube is considered for the purpose of temporary flood protection. With proper design, this tube can be a cheap and efficient breakwater, temporary levee, or cofferdam. This thesis considers a single tube resting on clay and sand foundations. A finite difference program, FLAC, is used in the numerical analyses. The tube is assumed to be infinitely long, and it is modeled two-dimensionally. Beam elements are used to model the tube. The tube is inflated with water. The hydrostatic pressure in the tube is converted to point loads and applied at the beam nodes in the direction perpendicular to the chord connecting two adjacent nodes. Two of FLAC's built-in soil models are used: elastic and Mohr-Coulomb. The Mohr-Coulomb model is used in all the cases except the preliminary analyses, in which the elastic soil model is used. The Mohr-Coulomb soil model is able to model the soil's nonlinear stress-strain and path-dependent deformation behavior. A tube without external water is placed on clay with various shear strengths to study how the clay consistency affects the height and the stresses in the tube. A tube with external water on one side is placed on medium dense sand. A wooden block is placed on the side opposite the floodwater. Three types of block geometry and two sizes are studied. The floodwater level is increased until the system fails. Three failure modes, rolling, sliding, and piping, are studied. The effect of pore pressure on these failure modes is examined. The influence of a filter placed under part of the tube and block is also investigated. The tube's tensile forces, shear forces, moments, and settlements are included. Soil stresses and pore pressures at the soil-tube interfaces are computed. The cross-section of the tube at various external water levels, and the pore pressures in the soil, are calculated. These results are compared with experimental results that were obtained by graduate students in geotechnical engineering at Virginia Tech. / Master of Science

El tubo capilar con intercambio de calor líquido-succión (CT-LSHX) es un componente ampliamente utilizado en refrigeradores domésticos. Trabajos recientes han indicado que la entrada del tubo capilar era bifásica, aunque condiciones subenfriadas estaban medidas a la salida del condensador. El objetivo de esta tesis doctoral es examinar las condiciones reales a la entrada del tubo capilar de un refrigerador doméstico mediante el uso de un banco de pruebas innovador. Se instalaron tubos transparentes a la salida del condensador y a la entrada del tubo capilar con el fin de visualizar el flujo. La campaña de visualización experimental revela que el flujo a la entrada del tubo capilar era bifásico a pesar de la medición de un cierto subenfriamiento, independientemente de la posición del filtro instalado a la entrada del capilar (horizontal o vertical), la dirección del flujo (hacia arriba o hacia abajo) y la carga de refrigerante. Este estudio demuestra también que el filtro no estaba actuando como un acumulador ya que el nivel de líquido del capilar siempre siguió la entrada del tubo capilar, independientemente de la longitud del tubo capilar dentro del filtro. Se plantearon dos hipótesis para explicar el fenómeno: una condición de no equilibrio del refrigerante y/o un desequilibrio entre el caudal másico del compresor y del capilar, es decir, el sistema estaría equipado con un capilar no bastante restrictivo en comparación con las necesidades del compresor. El condensador original refrigerante-aire fue reemplazado por un condensador refrigerante-agua para evaluar, a partir del balance de calor en el condensador de agua, las condiciones del refrigerante a la salida del condensador y, por lo tanto, a la entrada del tubo capilar. Las mediciones indican un flujo bifásico no equilibrado compuesto de vapor y líquido subenfriados a la entrada del tubo capilar. Para verificar si la presencia de flujo bifásico se debía a un desequilibrio entre el caudal másico del compresor y del capilar, el diseño del banco de prueba se modificó utilizando un diámetro de tubo capilar más pequeño y aumentando la velocidad del compresor. Con esta nueva configuración, se alcanzó a llenar de líquido el filtro y, por lo tanto, tener condiciones exclusivamente líquidas a la entrada del tubo capilar. Se realizó una comparación de prestaciones entre un flujo bifásico y un flujo únicamente líquido a la entrada del capilar. Los resultados revelan que el COP fue mayor cuando la entrada del capilar era sólo líquida. / El tub capil·lar amb intercanvi de calor líquid-succió (CT-LSHX) és un component àmpliament utilitzat en refrigeradors domèstics. Treballs recents han indicat que l'entrada del tub capil·lar era bifàsica, encara que condicions sub-refredades estaven mesurades a l'eixida del condensador. L'objectiu d'aquesta tesi doctoral és examinar les condicions reals a l'entrada del tub capil·lar d'un refrigerador domèstic mitjançant l'ús d'un banc de proves innovador. Es van instal·lar tubs transparents a l'eixida del condensador i a l'entrada del tub capil·lar amb la finalitat de visualitzar el flux. La campanya de visualització experimental revela que el flux a l'entrada del tub capil·lar era bifàsic malgrat el mesurament d'un cert sub-refredament, independentment de la posició del filtre instal·lat a l'entrada del capil·lar (horitzontal o vertical), la direcció del flux (cap amunt o cap avall) i la càrrega de refrigerant. Aquest estudi demostra també que el filtre no estava actuant com un acumulador ja que el nivell de líquid del capil·lar sempre va seguir l'entrada del tub capil·lar, independentment de la longitud del tub capil·lar dins del filtre. Es van plantejar dues hipòtesis per a explicar el fenomen: una condició de no equilibri del refrigerant i/o un desequilibri entre el cabal màssic del compressor i del capil·lar, és a dir, el sistema estaria equipat amb un capil·lar no bastant restrictiu en comparació amb les necessitats del compressor. El condensador original refrigerant-aire va ser reemplaçat per un condensador refrigerant-aigua per a avaluar, a partir del balanç de calor en el condensador d'aigua, les condicions del refrigerant a l'eixida del condensador i, per tant, a l'entrada del tub capil·lar. Els mesuraments indiquen un flux bifàsic no equilibrat compost de vapor i líquid sub-refredats a l'entrada del tub capil·lar. Per a verificar si la presència de flux bifàsic es devia a un desequilibri entre el cabal màssic del compressor i del capil·lar, el disseny del banc de prova es va modificar utilitzant un diàmetre de tub capil·lar més xicotet i augmentant la velocitat del compressor. Amb aquesta nova configuració, es va aconseguir omplir de líquid el filtre i, per tant, tindre condicions exclusivament líquides a l'entrada del tub capil·lar. Es va realitzar una comparació de prestacions entre un flux bifàsic i un flux únicament líquid a l'entrada del capil·lar. Els resultats revelen que el COP va ser major quan l'entrada del capil·lar era només líquida. / Capillary tube with liquid-to-suction heat exchanger (CT-LSHX) is a component widely used in household refrigerators. Recent works have indicated that even when measuring subcooled conditions at the condenser outlet, the actual capillary tube inlet is two phase-flow. The aim of this PhD thesis is to examine the actual conditions at the capillary tube inlet of a household refrigerator by using an innovative test bench. Transparent tubes were set up at the condenser outlet and capillary tube inlet. The experimental visualisation campaign reveals that the capillary tube inlet was two-phase flow despite the measurement of a certain subcooling, regardless of the filter position (horizontal or vertical), flow direction (upward or downward) and refrigerant charge. This study also demonstrates that the filter was not acting as an accumulator since the liquid level of the capillary always followed the capillary tube entrance, regardless of the capillary tube length inside the filter. Two hypotheses were then posed to explain the phenomenon: a non-equilibrium condition of the refrigerant and/or an unbalanced matching between compressor and capillary tube, that is, the system would be equipped with a capillary tube with a notably large expansion capacity compared to the needs of the compressor. The original refrigerant-to-air condenser was replaced by a refrigerant-to-water condenser to assess, from the heat balance at the water condenser, the refrigerant conditions at the condenser outlet and therefore, at the capillary tube inlet. Measurements indicate a non-equilibrium two-phase flow composed of subcooled vapour and liquid at the capillary tube inlet. To verify if the presence of two-phase flow was due to unbalanced matching between the capillary tube and compressor, the test bench design was modified by using a smaller capillary tube diameter and increasing compressor speed. Fully liquid conditions at the capillary tube inlet were reached with this new configuration. A performance analysis comparison between a capillary tube inlet composed of vapour and liquid and a capillary tube inlet composed of only liquid was also performed. Results reveal that COP were higher in cases of fully liquid conditions at the capillary tube inlet. / Bardoulet, LV. (2018). Non-adiabatic capillary tubes in high efficiency household refrigerator: an experimental study [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/113170

Compact heat exchangers are widely used by the automotive industry in systems that cool engine components. Louvered fin heat exchangers are used over their continuous fin counterparts because of the significant advantages they provide in heat transfer efficiency, while only causing small increases in overall pressure losses. With the recent emphasis that has been placed on reducing fuel consumption, decreasing the size of the compact heat exchanger has become an important concern. With reduction in size comes not only weight savings, but also a decrease in frontal area in a vehicle that must be dedicated to the heat exchanger, allowing for more aerodynamic vehicle designs. Air-side resistance on the tube wall and louvered fin surfaces comprises over 85% of total resistance to heat transfer in louvered fin heat exchangers. The tube wall surface is considered the primary surface for heat transfer, where the temperature between the working fluid and convecting air is at a maximum. Recent studies have shown that implementing delta winglets on louvered fins along the tube wall is an effective method of augmenting tube wall heat transfer. In this thesis, the effect of delta winglets is investigated in both two- and three-dimensional louvered fin arrays. For both geometries, winglets are simulated in a manufacturable configuration, where piercings in the louvered fins that would result from the winglet manufacturing process are modeled. Using the two-dimensional geometry to model tube wall heat transfer was shown not to accurately predict heat transfer coefficients. In a two-dimensional geometry, winglets were found not to be an effective means for augmenting tube wall heat transfer and caused only 8% augmentation. Using the three-dimensional geometry, winglets with simulated piercings were observed to cause up to 24% tube wall heat transfer augmentation, with a corresponding increase in pressure losses of only 10%. / Master of Science

No / This paper presents a series of test results of elliptical concrete filled steel tubular (CFST) beams and columns to explore their performance under bending and compression. A total of twenty-six specimens were tested, including eight beams under pure bending and eighteen columns under the combination of bending and compression. The main parameters were the shear span to depth ratio for beams, the slenderness ratio and the load eccentricity for columns. The test results showed that the CFST beams and columns with elliptical sections behaved in ductile manners and were similar to the CFST members with circular sections. Finally, simplified models for predicting the bending strength, the initial and serviceability-level section bending stiffness of the elliptical CFST beams, as well as the axial and eccentric compressive strength of the composite columns were discussed.

Hydroxyl-terminated polybutadiene (HTPB) is a common solid rocket fuel that is used in solid-fueled ramjets (SFRJs) for hypersonic propulsion. Renewed interest in hypersonic systems has developed a need to simulate HTPB combustion using computational fluid dynamics (CFD). However, the current chemical kinetic mechanisms lack the experimental data necessary to accurately simulate SFRJ conditions. Shock tube experiments at the University of Central Florida (UCF) were carried out to study the interaction of HTPB pyrolysis products (ethylene, propene, 1,3-butadiene, benzene, and toluene) with air. Experiments were conducted at 5 ± 0.5 atm and 1100 – 1800 K. Mixtures ranged from fuel lean to fuel rich (Φ = 0.5, 1.0, 4.0, 4.76) and contained individual fuel components or a fuel blend of the HTPB pyrolysis products. Species time-history of carbon monoxide (CO) and time-resolved temperature were measured with a quantum cascade laser (QCL) in the mid-infrared (MIR) region and compared against chemical kinetics models: AramcoMech3.0, HyChem, and NUIG 1.3. Additional OH* measurements were taken with an emission detector to capture ignition delay time (IDT). The data is used to develop an improved chemical kinetic mechanism for simulating HTPB combustion in air at SFRJ conditions.

Neural tube defects (NTDs) are the second most common type of congenital birth defect that affect infants worldwide. There are several proposed mechanisms for NTDs, but no definitive mechanism has yet been described. One possible mechanism is oxidative disruption of normal developmental signaling. The purpose of this study is to culture whole mouse embryos with three common developmental toxicants, mono-2-ethylhexyl phthalate (MEHP, a plastic pollutant), Fumonisin B1 (FB1, a corn mold), and valproic acid (VPA, an anticonvulsant drug), all of which are known to cause NTDs, and compare their shifts in redox potential and changes to important signaling pathways through transcriptomic analysis. To determine if prevention of oxidative stress decreases the likelihood of developing an NTD, preventative measures were taken by pretreating pregnant dams with 3H-1,2-dithiole-3-thione (D3T), an effective nuclear factor erythroid 2-related factor 2 (NRF2) inducer. It was found that between the three chemicals, two genes were significantly dysregulated, Makorin-2 (MKRN2) and Microtubule Associated Protein-6 (MAP6), both of which are implicated in NTDs. After staining embryos with lysotracker red (for apoptosis) or DCP-Rho1 (for oxidative stress), it was found that D3T pretreatment generally lowers the amount of apoptosis and oxidative stress in toxicant treated embryos. However, it only decreased the prevalence of NTDs seen in embryos cultured with FB1 or VPA. These results demonstrate common mechanisms that are potentially related in the formation of NTD and will help to target possible preventative measures.

yes / In this work, the interfacial bond performance of recycled aggregate concrete filled stainless steel tube (RAC-FSST) members was investigated through the repeated push-out tests. Three coarse recycled aggregate (CRA) replacements (0, 50% and 100%) and two cross-sectional dimensions were considered in the experimental program. The failure pattern, bond stress-slip response and strain development of stainless steel tube were obtained, and the bond mechanisms under different loading stages were analyzed. Test results showed that the ultimate bond stress increases with the increasing CRA content and decreasing cross-sectional dimensions. Compared with CFST members having carbon steel, RAC-FSST members present lower bond stress. The macro-interlocking effect is obvious in the later loading stage, resulting in a significant increase in the post-peak bond slip curves. Finally, the ultimate bond strength and idealized bond stress-slip models for the RAC-FSST members were suggested on the basis of the test results.

The Internet today has become a powerful tool-that has greatly improved the lives of all peoples across the globe. Simply put, the Internet has brought us into a new century of interconnectedness unlike any other period in human history. However, in terms of politics the effects of the Internet have been rather difficult to monitor, making the recent developments in the country of Iran unique. The Islamic Republic of Iran has become increasingly hostile towards moderate reforms and has steadfastly refused to grant greater freedoms, resulting in the disillusionment of many Iranians with their government. Coupled with this rising discontent has been a meteoric rise of Internet activity. With other outlets of expression dominated by the regime, the Internet has become the sole battlefield for political discussion. This research focuses on how the Internet is being used by both the government and the opposition as a political tool in the struggle for democracy. The intent of this thesis is to analyze the effects- of the Internet through the emergence of three different Internet trends. The expansion of blogging has led to greater political discourse as it has allowed Iranians to provide their opinion in an open environment for the first time. Social networking has given Iranians the ability to meet and learn about each other in ways that would never have been originally possible Lastly, the inception of the "YouTube Effect" has brought the events'oflran worldwide. Different from a typical news piece, these Internet videos are unedited showing the gravity of the situation to outsiders. Above all, the Islamic Republic of Iran presents a unique case study for analyze of the abilities of the Internet in institutionalizing democracy.

The addition of hydrogen and oxygen to a hydrocarbon fuel mixture has a significant effect on its sooting tendencies at high pressures. Understanding the mechanism behind and rates of soot formation is key to proper chemical modeling of fireballs. This research aims to investigate the soot formation rates and soot induction times of several intermediary chemicals found in energetic material (EM) combustion. Three common EM combustion intermediaries, acetylene, ethylene, and propyne are studied. Hydrogen and oxygen are added to the hydrocarbon fuel to observe their effect on parameters such as induction time and total soot yield. A laser absorption spectroscopy system was utilized to measure soot formation time history during experiments. The diagnostic instrument employs a low-noise continuous wave laser at 635 nm. The laser was transmitted through the test section of a shock tube device and its intensity during an experiment was measured. The data was used to determine estimated soot yield and soot induction times. This work will extend the chemical modeling capabilities of the National Nuclear Security Administration (NNSA) with an improved understanding of soot formation in fireball conditions.

Helicopter turboshaft engines may ingest large amounts of foreign particles (most commonly sand/dust), which can cause significant compressor blade damage and even engine failure. In many helicopters, this issue is mitigated by separating the particles from the intake airstream. An effective device for engine air-particle separation is the vortex tube separator (VTS), which uses centrifugal forces in a vortical flow to radially filter foreign particles from a duct with an annular exit. Dozens or hundreds of these devices are linked together on a shared manifold known as a VTS array. There is a distinct lack of scientific literature regarding these arrays, which likely feature significantly more complex flowfields than singular VTSs due to aerodynamic interactions between the devices. The research presented in this dissertation identifies and explains flow features unique to arrays by means of an experimental investigation downstream of various VTS configurations in a wind tunnel. Mean PIV flowfields reveal that the VTS array rapidly generates a strong central recirculation zone while a single VTS does not, implying the existence of axial flow gradients within associated separators that could affect filtration efficiency. The key factor here is the global swirl intensity, which is increased in array flows due to high angular momentum contributions from separators that are radially distant from the duct center. A preliminary momentum integral model is constructed to predict the onset of recirculation in VTS flows. Analysis is then extended to the unsteady flowfield, where it is shown that VTS-generated turbulence contains only low levels of anisotropy. Spectral proper orthogonal decomposition is conducted on the array flow; it reveals the existence of low-frequency harmonic behavior composed of back-and-forth pumping motions downstream of the central VTS. Additionally, a unique precession motion is found in the same region at a slightly higher frequency. Similar precessing vortex cores have been shown to reduce separation efficiency in other cyclone separators. Both of these coherent structures may be associated with the central recirculation zone and may interfere with VTS array filtration given their timescales relative to potential particle relaxation timescales. This dissertation opens the door for future experimental and computational studies of fluid and particle dynamics in VTS flows with the goal of improving VTS array-specific design philosophies. / Doctor of Philosophy / Vortex tube separators (VTSs) help protect helicopter engines by filtering harmful particles (sand, dust, snow, ash, sea spray, etc.) they would otherwise ingest. This is done by creating a vortex in which centrifugal forces eject particles outwards, separating them from the main airstream. These devices are effective when dozens are grouped together into VTS arrays, but little is understood of the complex air and particle dynamics that result from the many interacting vortices both in and around such arrays. This dissertation describes an early effort to study these aerodynamics and open the door for subsequent particle dynamics research. A laser-based measurement technique called particle image velocimetry is used to determine flow velocities downstream of a VTS array placed in a wind tunnel. When velocities are averaged together over time, they reveal a central recirculation zone (a known feature of intensely swirling flows) downstream of the VTS array that vanishes when only a single separator in the array is active. A mathematical model is developed to predict such recirculation. It demonstrates that a VTS array comprises many separators that are far from the center of the duct they are contained within, and these contribute greatly to the overall swirl intensity. Other data analysis techniques are used to investigate the instantaneous velocity flowfield, which differs significantly from averaged quantities. One such technique is spectral proper orthogonal decomposition, which extracts so-called "coherent structures" from the flow - correlated high-energy motions that exist at certain frequencies and may not be visible in the raw data. This analysis finds two interesting structures at the very center of the duct, possibly associated with the recirculation zone: a back-and-forth pumping motion at a very low frequency (and some of its harmonic frequencies), and a "precessing" (unsteadily rotating) vortex at a slightly higher frequency. These motions, as well as the central recirculation zone itself, are impactful because they may affect the filtration process within the VTS upstream of where they were measured. Such effects will be investigated in future experiments and, if confirmed, may influence the design of VTS arrays.