• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 75
  • 18
  • 11
  • 8
  • 3
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 160
  • 25
  • 20
  • 16
  • 14
  • 13
  • 13
  • 13
  • 12
  • 12
  • 10
  • 10
  • 10
  • 10
  • 9
  • 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.
41

Behavior of Precast Bridge Deck Joints with Small Bend Diameter U-Bars

Chapman, Cheryl Elizabeth 01 August 2010 (has links)
The Interstate Highway System plays a vital role in our economic development by providing a continuous corridor for transporting goods and services. Currently, there is a need for repair and expansion of the existing highways, which include all bridges along its path. Because of the high demand for the highway system, repair and expansion must occur rapidly and efficiently. In recent years, precast bridge deck systems have become an efficient way to reduce construction time during repair. This thesis presents the experimental research of the behavior of the U-Bar joint detail used in precast bridge deck systems. This detail consists of staggered reinforcement extending beyond the precast deck portion into the joint. Six specimens utilizing the U-Bar detail were constructed and tested. Three specimens were tested in flexure to simulate the forces applied in a longitudinal deck joint, while three specimens were tested in pure tension to simulate the forces experienced in a transverse deck joint located over an interior pier. A tight 180° bend at 3db was desired in order to minimize the thickness of the deck. To achieve this tight bend, deformed wire reinforcement was chosen for the U-Bar detail due to the favorable material properties of deformed wire reinforcement. The purpose of the testing was to determine if the joint details could generate a precast deck system that could emulate the monolithic cast-in-place deck systems already in use. For monolithic behavior in a precast deck system, the joints must be able transfer shear, tension and moments. In this research, the joint overlap length was the most dominant variable, and should not be less than 152.4 mm (6”). The precast bridge deck joint should consist of high strength concrete with f’c of at least 68.9 MPa (10 ksi). The longitudinal reinforcement spacing should be no greater than 152.4 mm (6”).
42

Indian Diasporic Films as Quantum (Third) Spaces: A Curriculum of Cultural Translation

Ausman, Tasha 27 June 2012 (has links)
This thesis examines narrative articulations in the films Bend It Like Beckham, Bhaji on the Beach, and American Chai as a complicated conversation in relation to bicultural-identity construction in the Indian diaspora. Unpacking the way desi identities are managed in/as a quantum (third) space – one that is continuously shifting and deferred – the films exemplify how "desi" is a heterogeneous cultural "group" without a homeland from which to speak or to return. The narratives of these films are considered cultural translations that expose inter-generational culture-clashes in the spaces between Indian and Western cultures. Screenplay pedagogy was used as a methodology to (re)read analysis of the films, revealing the ways that different movies employ and reinscribe themes of the multicultural pastoral, the carnivalesque, and melodrama, respectively. This thesis concludes by opening up some of the places from which individuals enunciate their desi identities, including the possibilities for (self)reflection.
43

Numerical Study of Abutment Scour in Cohesive Soils

Chen, Xingnian 16 January 2010 (has links)
This research is part of the extension of the SRICOS-EFA method for predicting the maximum scour depth history around the bridge abutment. The basic objective is to establish the equation for predicting the maximum bed shear stress around the abutment at the initial condition of scouring. CHEN3D (Computerized Hydraulic ENgineering program for 3D flow) program is utilized to perform numerical simulations and predict bed shear stress before scouring. The Chimera technique incorporated in CHEN3D makes the program capable of simulating all kinds of complex geometry and moving boundary. CHEN3D program has been proven to be an accurate method to predict flow field and boundary shear stress in many fields and used in bridge scour study in cohesive soils for more than ten years. The maximum bed shear stress around abutment in open rectangular channel is studied numerically and the equation is proposed. Reynolds number is the dominant parameter, and the parametric studies have been performed based on the dimensional analysis. The influence of channel contraction ratio, abutment aspect ratio, water depth, abutment shape, and skew angle has been investigated, and the corresponding correction This research is part of the extension of the SRICOS-EFA method for predicting the maximum scour depth history around the bridge abutment. The basic objective is to establish the equation for predicting the maximum bed shear stress around the abutment at the initial condition of scouring. CHEN3D (Computerized Hydraulic ENgineering program for 3D flow) program is utilized to perform numerical simulations and predict bed shear stress before scouring. The Chimera technique incorporated in CHEN3D makes the program capable of simulating all kinds of complex geometry and moving boundary. CHEN3D program has been proven to be an accurate method to predict flow field and boundary shear stress in many fields and used in bridge scour study in cohesive soils for more than ten years. The maximum bed shear stress around abutment in open rectangular channel is studied numerically and the equation is proposed. Reynolds number is the dominant parameter, and the parametric studies have been performed based on the dimensional analysis. The influence of channel contraction ratio, abutment aspect ratio, water depth, abutment shape, and skew angle has been investigated, and the corresponding correction factors have been proposed. The study of the compound channel configuration is conducted further to extend the application of the proposed equation. Numerical simulations of overtopping flow in straight rectangular channel, straight compound channel and channel bend have been conducted. The bridge deck is found to be able to change the flow distribution and the bed shear stress will increase significantly once overtopping. The influence of the channel bend curvature, abutment location in the channel bend, and the abutment shape is also investigated. The corresponding variation of the bed shear stress has been concluded. The scour models, including the erosion rate function, roughness effect, and the turbulence kinetic energy, have been proposed and incorporated into the CHEN3D program. One flume test case in NCHRP 24-15(2) has been simulated to determine the parameters for the roughness and the turbulence kinetic energy. The prediction of the maximum scour depth history with the proposed model is in good agreement with the measurement for most cases. The influence of overtopping flow on the abutment scour development is also studied and the corresponding correction factor is proposed.
44

Behavior of Precast Bridge Deck Joints with Small Bend Diameter U-Bars

Chapman, Cheryl Elizabeth 01 August 2010 (has links)
The Interstate Highway System plays a vital role in our economic development by providing a continuous corridor for transporting goods and services. Currently, there is a need for repair and expansion of the existing highways, which include all bridges along its path. Because of the high demand for the highway system, repair and expansion must occur rapidly and efficiently. In recent years, precast bridge deck systems have become an efficient way to reduce construction time during repair. This thesis presents the experimental research of the behavior of the U-Bar joint detail used in precast bridge deck systems. This detail consists of staggered reinforcement extending beyond the precast deck portion into the joint. Six specimens utilizing the U-Bar detail were constructed and tested. Three specimens were tested in flexure to simulate the forces applied in a longitudinal deck joint, while three specimens were tested in pure tension to simulate the forces experienced in a transverse deck joint located over an interior pier. A tight 180° bend at 3db was desired in order to minimize the thickness of the deck. To achieve this tight bend, deformed wire reinforcement was chosen for the U-Bar detail due to the favorable material properties of deformed wire reinforcement. The purpose of the testing was to determine if the joint details could generate a precast deck system that could emulate the monolithic cast-in-place deck systems already in use. For monolithic behavior in a precast deck system, the joints must be able transfer shear, tension and moments. In this research, the joint overlap length was the most dominant variable, and should not be less than 152.4 mm (6”). The precast bridge deck joint should consist of high strength concrete with f’c of at least 68.9 MPa (10 ksi). The longitudinal reinforcement spacing should be no greater than 152.4 mm (6”).
45

Developing a comprehensive system for making disciples at Calvary Baptist Church of South Bend, Indiana

Jenkins, David G. January 2001 (has links)
Thesis (D. Min.)--Trinity Evangelical Divinity School, 2001. / Abstract. Includes bibliographical references (leaves 209-211).
46

An Experimental and Numerical Investigation of Evaporative Spray Cooling for a 45 degree Bend near a Gas Turbine Exhaust

ARMITAGE, GRANT 03 January 2014 (has links)
The research performed in this work investigated evaporative spray cooling systems using water near a 45 degree bends in gas turbine exhaust piping systems. Both experimental data and numerical data were generated with the goal of evaluating the ability of Fluent 6.3.26 to predict the performance of these systems for the purpose of design using only modest computational resources. Three cases were investigated in this research: single phase exhaust flow with no water injection, injecting water before the bend and injecting water after the bend. Various probes were used to measure dry bulb temperature, total pressure and water mass flux of the two phase flow at the exit of the pipe. Seven hole probes and pitot static probes were used to measure single phase flow properties. Numerical simulations were performed using mass flow boundary conditions which were generated from experimental results. A turbulence model was selected for the simulations based on comparisons of single phase simulations with experimental data and convergence ability. Using Fluent’s discrete phase model, different wall boundary conditions for the discrete phase were used in order to find the model which would best match the evaporation rates of the experimental data. Mass flux values through the exit plane of the pipe were found to be the most reliable of all the two phase data collected. Results from numerical simulations revealed the shortcomings of the available discrete phase wall boundary conditions to accurately predict the interaction of the liquid phase with the wall. Experimental results for both cases showed extensive areas of the wall which had liquid film layers running down the length of the pipe. Simulations resulted in particles either failing to impact the wall and create a liquid film, or creating a liquid film which was much smaller than the film present in experimental results. This led to 8% and 15% discrepancy in evaporation amounts between numerical and experimental results for water injection upstream and downstream of the bend respectively. Under-prediction of areas wetted with a wall film in the simulations also led to gross over predictions of wall temperature in numerical results. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2014-01-02 11:02:00.955
47

Experimental study of third (HFC) and fourth generation (HFO) refrigerants during flow boiling in singularities

Padilla Gomez, Miguel David 18 November 2011 (has links) (PDF)
The refrigerant charge reduction in HVAC\R systems is an important issue because it falls within environmental policies regarding refrigerants contributions to the greenhouse effect. A way to move toward charge reduction is to increase the compactness of heat exchangers, which means more complex designs of the evaporators. Nevertheless, while a large amount of studies have has been published on the thermal and hydraulic analysis of flow boiling of refrigerants in horizontal tubes, very little attention has been given to flow boiling in geometries different from straight tubes. This PhD thesis aims at studying the flow boiling characteristics of third generation (HFC) and fourth generation fluids such as HFO-1234yf in geometries which modify the fluid dynamics and two-phase flow with respect to horizontal straight tubes. To achieve this goal, an experimental test facility was specifically designed and built to conduct refrigerant evaporation experiments. This test facility allowed to perform flow regimes visualizations and pressure drop measurements in singularities (such as sudden contractions and return bends). First, two-phase flow regimes visualizations have been carried out using HFO-1234yf, R-134a and R-410A either in straight tubes or in singularities. A qualitative analysis of the flow behavior and also several comparisons to flow pattern prediction methods from the literature were conducted. The second objective of this work was to characterize the flow disturbances caused by singularities such as sudden contractions and return bends, and to study their effects on the hydrodynamic performance (e.g. pressure drop) of refrigerants.Lastly, pressure drop databases for third and fourth generation refrigerants are presented.
48

Cikliškai lenkiamų srieginių jungčių deformavimas ir stiprumas / Deformation and Strength af a Cyclically Bent Threaded Connection

Juchnevičius, Žilvinas 06 February 2012 (has links)
Disertacijoje, taikant apkrovų pasiskirstymo sriegio vijose modeliavimą, nagrinėjamos lenkiamų srieginių jungčių mažaciklio stiprumo problemos. Mo-dernesnės daugiaciklio ir mažaciklio ilgaamžiškumo skaičiavimo metodikos detaliai kiekybiškai įvertina ašinės apkrovos pasiskirstymą vijose, kuris leidžia detaliau ir tiksliau įvertinti konstrukcijos ypatumų įtaką. Disertacijoje siekiama ir cikliškai lenkiamoms srieginėms jungtims sukurti apkrovos pasiskirstymo sriegyje skaičiavimo metodą ir pritaikyti jį ciklinio stiprumo skaičiavimui Sudaryta lenkiamos srieginės jungties elementų poslinkių darnos lygtis įga-lino sukurti trijų ruožų ir daugiaruožį lenkimo apkrovos pasiskirstymo jung¬tyje modelius ir įdiegti juos į norminio mažaciklio ilgaamžiškumo skaičiavimo gran-dinę. Pirmame skyriuje pateikta literatūros šaltinių analizė. Jame apžvelgiama sunkiai apkrautų srieginių jungčių taikymo sritis ir apkrovimo sąlygos, apžvel¬giami ir analizuojami atlikti tyrimai, susiję su srieginių jungčių cikliniu stipru-mu. Antrame skyriuje pateikti sriegio vijų poros deformavimo savybių eksperi¬mentinio tyrimo rezultatai ir anksčiau literatūroje neminėtų nukraunamos ir pa-kartotinai apkraunamos vijų poros savybių analizė. Trečiame skyriuje pateikta srieginės jungties elementų deformavimo sche¬ma, poslinkių darnos diferencialinės lygtys, diferencialinių lygčių analitiniai sprendiniai ir lenkiamos srieginės jungties modeliai – trijų ruožų ir daugiaruožis tamprieji modeliai lenkimo apkrovos... [toliau žr. visą tekstą] / Industry equipment such as pressure vessels, mining equipment, heat exchang-ers, steam generators and other structures are provided with bolted closures for the purpose of in-service inspection and maintenance of internal components. Threaded connections often experience variable cyclic loads due to temperature, inner pressure and variation in the deformation of connection fittings. Often, studs and screws are not only affected by an axial load, but also by bending moments. More sophisticated high-cycle and low-cycle durability calculation meth-odologies have been already developed for threaded connections experiencing cyclic axial loads, and in these methodologies the distribution of axial load among turns is assessed quantitatively. The quantitative data of load distribu-tion in the thread enables a more accurate assessment of the influence of the constructional design particularities (connection length, material, nut and turn’s form) and the deformation stages of the connection element. These durability calculation methodologies are not applied for threaded connections that are cyclically bent, as the analytical models that are suitable for practical application in the load distribution of the turns have not been cre-ated for bent threaded connections. In this field, no models have been created to be calculated by the BE method. As the threaded connection is a complex node consisting of deformed el-ements, the load distribution among turns is influenced by the... [to full text]
49

Supercritical Fluid Deposition of Thin Metal Films: Kinetics, Mechanics and Applications

Karanikas, Christos F. 01 February 2009 (has links)
In order to meet the demands of the continuous scaling of electronic devices, new technologies have been developed over the years. As we approach the newest levels of miniaturization, current technologies, such as physical vapor deposition and chemical vapor deposition, are reaching a limitation in their ability to successfully fabricate nano sized electronic devices. Supercritical fluid deposition (SFD) is a demonstrated technology that provides excellent step coverage for the deposition of metals and metal oxides within narrow, high aspect ratio features. This technique shows the potential to satisfy the demands of integrated circuit miniaturization while maintaining a cost effective process needed to keep the technology competitive. In order to complement SFD technology heuristics for scale-up, an understanding of the deposition mechanism and kinetics and resolution of integration issues such as interfacial film adhesion must be resolved. It is critical to have a fundamental understanding of the chemistry behind the reaction process in supercritical fluid deposition. For this purpose, a detailed kinetic study of the deposition of ruthenium from bis(2,2,6,6-tetramethyl-3,5-heptanedionato) (1,5-cyclooctadiene) ruthenium(II) is carried out so that growth rate orders and a mechanism can be established. These predictive kinetic results provide the means to control the reaction which allows for overall optimization of the process. Reliability is of the utmost importance for fabricated devices since they must withstand harsh steps in the fabrication process as well as perform and last under standard and extreme usage conditions. One issue of reliability is assessed by addressing the adhesion of the metallization layers deposited by SFD. A quantitative determination of the interfacial adhesion energy of as deposited and pretreated copper metallization layers from SFD onto barrier layers is used to determine the potential for integration of these films for industry standards. Extension of the basics of SFD by performing co-deposition of multiple compounds, layer-by-layer deposition for device fabrication and integration with other unique technologies for novel applications demonstrates the ability of this technique to satisfy a wide range of commercial applications and be used as the basis for new technologies. Co-depositions of Ce/Pt, Co/Pt, Ba/Ti and Nd/Ni for the fabrication of functional direct methanol fuel cell electrodes, magnetic alloys for media storage applications, high k dielectric films for alternative energy storage devices and alternative materials for solid oxide fuel cell cathodes, respectively, are performed. Layer-by-layer deposition with masking is used to fabricate nanometer scale capacitors. Finally, plasma spray technology is combined with the rapid expansion of supercritical solvents technique to form a novel, patent pending, process that is used to fabricate next generation photovoltaic cells.
50

Late Neogene stratigraphy and sedimentation across the Murray Basin, southeastern Australia

Miranda, J. A. January 2007 (has links)
The Late Neogene sedimentary sequence of the Murray Basin provides an excellent opportunity to examine paleoenvironmental change across southeastern Australia. A detailed stratigraphic analysis of sediments deposited within the basin in the last 10 Ma was undertaken to assess the influence of tectonic and eustatic processes on deposition. / Stratigraphic observations and radiogenic isotope analysis reveals the onset of deposition by 7.2 Ma with a transgressive episode that deposited the marine marls of the Bookpurnong Beds. Deposition was restricted to the central and eastern parts of the basin due to the Hamley Fault. In the west, subsurface elevation contours indicate the presence of incised paleodrainage channels above Miocene limestones, which facilitated the formation of a large estuary system at 5.3 Ma. The sediments of the Norwest Bend Formation were deposited within this western region, while further east, the Loxton-Parilla Sands strandplain deposited over 214 coastal ridges. The basal parts of this unit occur as lateral equivalents to the sediments of the Lower Norwest Bend Formation (in the west). Topographic and magnetic data reveal that tectonism was active during this period and resulted in the erosion and truncation of strandlines. / Tectonic evidence and an estimated minimum 28,037 year cyclicity between strandline sets, suggests that the Loxton-Parilla Sands strandlines do not represent an unbroken record of glacioeustatic change. The subaerial exposure of these sediments at approximately 3.0 Ma caused the formation of a calcareous karst above the Norwest Bend Formation and a ferruginous and/or silicious cap (the Karoonda Surface) above the Loxton-Parilla Sands. The stratigraphic position of these surfaces are indicative of a regional widespread unconformity. / The Douglas-Blackburn paleodrainage system in western Victoria was dammed during the Mid-Late Pliocene by uplift associated with the Padthaway High, which caused the formation of a 400,000 km2 lacustrine system, known as Lake Bungunnia. Topographic analysis indicates that Lake Bungunnia comprised at least four distinct sub-basins with water depths of up to 30 metres, with lake shorelines indicating that active tectonism occurred during this period. The resulting lack of sediment input to the coast caused the formation of the Kanawinka Escarpment, a large erosional scarp along the southern margin of the Padthaway High. / The geomorphology of the modern Murray Basin can be directly attributed to the demise of the Lake Bungunnia system. Movement along the Morgan Fault in the west at approximately 700 Ka, resulted in the draining and progressive drying of Lake Bungunnia as a breach was created along the Padthaway High. The Murray River gorge as observed today was incised following this episode. The modern Murray River (and playa lakes such as Lake Tyrell) occupy the lowest elevations along the former sub-basins of Lake Bungunnia. / The Late Neogene sedimentary sequence across the Murray Basin illustrates a complex interaction of eustatic and tectonic processes on deposition. Sedimentation within strandline, estuarine and lacustrine systems, particularly in the western Murray Basin, display evidence of significant tectonic control. This highlights the important role that neotectonic processes have played in shaping southeastern Australia.

Page generated in 0.6983 seconds