Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 112-118). Also available via the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 490-494).

A differential Pirani molecular-beam detector was developed with a sensitivity for noncondensable gases about five times greater than that of the previous most sensitive Pirani beam-detector. With a circular entrance channel of pressure-accumulation factor 28, at room temperature a one-microvolt signal was produced for a helium beam intensity of 5.4 x 10¹² atoms/sec/cm² . At liquid-nitrogen temperature, the sensitivity increased almost four times. This detector was used to investigate the directivity characteristics of molecular beams of helium, argon and nitrogen, produced with several circular, cylindrical tubes, mounted on a rotatable oven. In the molecular-flow region, the angular distributions were somewhat narrower than those reported by previous workers. With increasing source pressure, the full-width at half-maximum of the distribution for each tube with any gas became 75 to 78 degrees, but with further increase of source pressure, the full-width depended on the particular gas used. The electric circuit of the Pirani detector was easily modified so that the entrance channel and beam cavity could be used as a combination Pitot tube and pressure gauge for determining the Mach numbers of supersonic beams in vacuum. It was found that a 0.214-mm. conical converging nozzle produced a Mach 2.2 helium beam when the pressure ratio across the nozzle was about 120. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The optimal design of a plywood-web beam, as for any structural element, is usually found by trial and error in which an initial design is modified until a solution which maximizes the beam's efficiency and meets a set of prescribed design criteria is found. To automate this process, a reliability-based optimization program which computes the optimal dimensions of a plywood-web beam is formulated and tested in this study. The program minimizes the cost of a plywood-web beam subject to constraints imposed upon its performance expressed in terms of acceptable levels of safety with respect to a set of limit states. A plywood-web beam model which incorporates the effects of shear deformations in the web components and the effects of non-rigid connections between the beam's flanges and webs is developed and used to compute a plywood-web beam's response under load. The beam's performance is evaluated by means of a reliability analysis in order to rationally account for any uncertainty associated with the beam's material properties and the loads acting on it. An existing non-linear optimization routine computes the optimal continuous design of a plywood-web beam using the results of the structural and reliability analyses. A discrete solution, representing the optimal practical design which uses only available or allowable dimensions for the beam's components, is found by means of an exhaustive search of a restricted region of the design variable space near the optimal continuous solution. As an example, the program is used to optimize the design of a ply wood-web box girder. Sensitivity analyses are performed on the optimal design in order to identify and quantify the critical input parameters in the optimization process. The effects of errors in the problem's formulation, analytical errors arising from the structural analysis and statistical errors resulting in an inaccurate representation of the problem's probabilistic characteristics are studied. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The multiple Coulomb scattering of negative pions has significant effects on the dose distributions resulting from pion beams incident on thick targets. The use of negative pions in radiotherapy requires a detailed knowledge of the distribution of dose and biological effect. Thus it is important to have an accurate description for the lateral distributions of pions which result from multiple scattering. It has been proposed by Fowler and Perkins that these lateral distributions are of a Gaussian nature for incident pencil beams. In this study an attempt has been made to determine experimentally and theoretically the appropriate value for the standard deviation of the Gaussian in the pencil beam description. The experimental determination involved placing medical x-ray films in a homogeneous water phantom, perpendicular to the beam axis of the M8 biomedical channel at TRIUMF. The distributions recorded on film for circularly collimated beams were measured for optical density and compared to calculated distributions in order to extract the pencil beam information. The presence of contaminating electrons and muons as well as the difficulty in achieving a parallel beam complicated the determination of the standard deviation of the Gaussian for pions. The experimental determination at the end of a 20.1 cm range in water is only 7% greater than the preferred theoretical calculation for pions alone. This calculation is based on the first (Gaussian) term of Moliere’s theory modified for the Fano correction and energy loss and yields results 20% lower than those of the "standard reference" of Fowler and Perkins. The agreement between the theory for pions and the experiment for a real beam in water indicates that the theory presented should be adequate for treatment planning calculations. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No description available.

No description available.

Thesis (M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (ℓ. 202-207)

Thesis (Ph.D.) - University of Glasgow, 1999. / Ph.D. thesis submitted to the Department of Civil Engineering, University of Glasgow, 1999. Print version also available.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Includes bibliographical references (p. 214-223) Also available in print.