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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.
141

Degradation of Shear Performance of Beams due to Bond Deterioration and Longitudinal Bar Cutoffs

Masukawa, Junji 30 August 2012 (has links)
Experimental and analytical research has been conducted to investigate the degradation of shear performance of beams due to bond deterioration and longitudinal bar cutoffs. To achieve the controlled rate of bond degradation, the method of adjustment of the rib height by machining was adopted. Bond behaviour of the milled bars were measured in tension stiffening tests with internally installed strain gauges. Maximum bond stresses for the milled bars were reduced by up to 50% compared to those for normal deformed bar. The bond behaviour of the milled bars were compared with those of the bars subjected to accelerated corrosion. It was confirmed that the stripped bar had the possibility to simulate corroded bars to some extent. Based on the calculations of average tensile stresses in the cracked concrete for each specimen, appropriate tension stiffening factors for each type of bar were suggested and then verified with the 2-dimensional nonlinear finite element analysis program VecTor2. Next, eight simply supported beams were tested. In four of them half of the longitudinal bars were cut off near the supports. Various combinations of normal and machined reinforcing bars were selected for both longitudinal and transverse reinforcement. The predicted shear failure load for the cutoff beam based on the general method for shear design in CSA A23.3-04 was unconservatively estimated. Cutoffs of longitudinal reinforcement resulted in much more significant drops of shear resistance than did bond deterioration of reinforcement. The inclinations of diagonal cracks for the cutoff series were larger than those for the no-cutoff series due to significant concentrations of longitudinal strains near the cutoff locations. Finally modifications to the general shear design method in CSA A23.3-04 were proposed based on the results of VecTor2 analyses for the beam tests. It was found that the influence of bond deterioration on the shear strength of reinforced concrete member can be accounted for by adjusting the tension stiffening factor applied to the equation for β. With respect to bar cutoffs, its influence on shear strength can be expressed by the strain concentration factor applied to the equation for ε_x.
142

Degradation of Shear Performance of Beams due to Bond Deterioration and Longitudinal Bar Cutoffs

Masukawa, Junji 30 August 2012 (has links)
Experimental and analytical research has been conducted to investigate the degradation of shear performance of beams due to bond deterioration and longitudinal bar cutoffs. To achieve the controlled rate of bond degradation, the method of adjustment of the rib height by machining was adopted. Bond behaviour of the milled bars were measured in tension stiffening tests with internally installed strain gauges. Maximum bond stresses for the milled bars were reduced by up to 50% compared to those for normal deformed bar. The bond behaviour of the milled bars were compared with those of the bars subjected to accelerated corrosion. It was confirmed that the stripped bar had the possibility to simulate corroded bars to some extent. Based on the calculations of average tensile stresses in the cracked concrete for each specimen, appropriate tension stiffening factors for each type of bar were suggested and then verified with the 2-dimensional nonlinear finite element analysis program VecTor2. Next, eight simply supported beams were tested. In four of them half of the longitudinal bars were cut off near the supports. Various combinations of normal and machined reinforcing bars were selected for both longitudinal and transverse reinforcement. The predicted shear failure load for the cutoff beam based on the general method for shear design in CSA A23.3-04 was unconservatively estimated. Cutoffs of longitudinal reinforcement resulted in much more significant drops of shear resistance than did bond deterioration of reinforcement. The inclinations of diagonal cracks for the cutoff series were larger than those for the no-cutoff series due to significant concentrations of longitudinal strains near the cutoff locations. Finally modifications to the general shear design method in CSA A23.3-04 were proposed based on the results of VecTor2 analyses for the beam tests. It was found that the influence of bond deterioration on the shear strength of reinforced concrete member can be accounted for by adjusting the tension stiffening factor applied to the equation for β. With respect to bar cutoffs, its influence on shear strength can be expressed by the strain concentration factor applied to the equation for ε_x.
143

Evaluation of e-beam SiO2 for MIM application

Guo, Wei 06 1900 (has links)
A metal-insulator-metal (MIM) device is used to rectify high frequency radiation received through an antenna coupled to it. In this study, a Ta-SiO2-Ta MIM device was fabricated and characterized. SiO2 layers with different thicknesses of 2nm, 5nm and 8nm were deposited and evaluated both electrically and optically. Tantalum was deposited using a sputtering system, while the oxide was evaporated using an E-beam evaporator. A Keithley 4200-SCS system combined with a four-probe station was adopted to measure both current-voltage and capacitance-voltage (C-V) characteristics. The I-V curves for all MIM devices were almost linear except the one with 8nm of SiO2 exhibited some nonlinearity. The C-V measurement that was carried out at AC frequency showed changing resistance for all samples and the resistance decreased as the thickness decreased. However, the E-beam SiO2 was found not to be a desirable oxide for MIM application due to the existence of many defects. / Materials Engineering
144

Laser assisted machining of high chromium white cast-iron

Armitage, Kelly. January 2006 (has links)
Thesis (MEng) - Swinburne University of Technology, Industrial Research Institute Swinburne - 2006. / A thesis submitted in fulfillment of the requirement for the degree of Master of Engineering by Research, Industrial Research Institute Swinburne, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology - 2006. Typescript. Includes bibliographical references (p. 113-116).
145

Studies of far from equilibrium condensed matter systems Euler buckling instability and molecular beam epitaxy /

Moldovan, Dorel, January 1999 (has links)
Thesis (Ph. D.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains xiv, 170 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.
146

The adaptive control of optical beam jitter /

Watkins, R. Joseph. January 2004 (has links) (PDF)
Thesis (Ph. D. in Mechanical Engineering)--Naval Postgraduate School, December 2004. / Thesis advisor(s): Brij N. Agrawal, Young S. Shin. Includes bibliographical references (p. 163-165). Also available online.
147

High performance 1300 nm photodetectors grown by molecular beam epitaxy

Sun, Xiaoguang. January 2002 (has links) (PDF)
Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.
148

MBE growth and charaterization of GaN film /

Zhu, Wenkai. January 1999 (has links)
Thesis (M. Phil.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 65-66).
149

Novel III-Nitride growth by ultraviolet radiation assisted metal organic molecular beam epitaxy

Pritchett, David Chu. January 2009 (has links)
Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Doolittle, W. Alan; Committee Member: Carter, W. Brent; Committee Member: Ferguson, Ian T.; Committee Member: Frazier, A. Bruno; Committee Member: Rincon-Mora, Gabriel A.
150

Electron beam irradiation of polystyrene/poly(vinyl methyl ether) blends /

Pietri, Valerie, January 1993 (has links)
Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 169-172). Also available via the Internet.

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