published_or_final_version / Physics / Master / Master of Philosophy

Thesis--M. Phil., University of Hong Kong.

Thesis (M.S.)--University of Michigan, 1977. / Project completed January 1978. Degree awarded December 1977.

The thesis of this paper is that proportional representation is a desirable reform and that it could be applied to the election of the legislative bodies in Canada to a far greater extent than has been admitted by its opponents. In Chapter 1 the two main types of porportional representation, or P.R. as it is called generally, the Hare system, preferred on the English speaking countries, and the 'list' type, preferred on the Continent of Europe, are examined and compared. The two basic premises of P.R.: that every substantial group in the community is entitled to representation at all times; and that no one, in his capacity as a member of a substantial group, can be represented by someone for whom he has not voted; are evaluated and found logical. In Chapter II the past and present uses of P.R. in Canada are surveyed. This reform came about as a result of the renewed interest in effective democratic government occasioned by World War 1. P.R. was tried in both municipal and provincial elections, and, although a failure in the municipal field, was never repealed for the election of some M.L A.'s in Alberta and Manitoba. The conclusion reached is that the factor of party had a great deal to do with the retention or rejection of P.R.; and that P.R. was not given a fair trial in the civic field. Chapter III surveys the history of P.R. as an issue in the House of Commons. The subject was debated at considerable length in the early 1920's; the only recorded division in the House on P.R. is analysed. The Report of the 1936 Special Committee on the Election and Franchise Act is examined and found too shallow for acceptance. In Chapter IV an attempt has been made to meet the geographic objection of the Special Committee, namely, that constituencies would be far too large, by proposing a partial application of P.R. to federal elections. Appendix I is a map upon which the proposed scheme has been drawn. Some indications of the extent to which P.R. could be applied for the elections of provincial legislators are given. In Chapter V the other main objection of the Special Committee, namely, that P.R. would cause the disintegration of political parties into groups and seriously endanger the operation of cabinet government is rejected because the paradoxical integrating effect of a federal system, and the similar effect of the Crown, are ignored. The conclusion is that P.R. is a logical extension of the democratic election, but that in the past it has been supported from the wrong point of view, and, that, therefore, the initiative will now have to come from the voters. / Arts, Faculty of / Political Science, Department of / Graduate

Inaugural-Dissertation--Universität Zürich. / "Separatabdruck aus der 'Zeitschrift für schweizerische Statistik', Jahrgang 1901." "Literatur": p. 472-480.

Thesis (LL. M.)--University of Toronto, 2007. / Source: Masters Abstracts International, Volume: 46-06, page: 3065.

Tissue equivalent proportional counters (TEPCs) are commonly used for radiation monitoring in areas where a mixture of neutron and photon radiations may be present, such as those commonly encountered in nuclear power plants. In such radiation fields, the dose rate of each component can vary drastically from extremely low to very high. Among these possible combinations of radiation fields with very different dose rates, a mixed field of an intense photon and a weak neutron dose component is the more commonly encountered. This study describes the measurement of lineal energy spectra carried out with a 5.1 cm (2 inch) diameter spherical TEPC simulating a 2 μm diameter tissue site in low energy (33 – 330 keV neutrons) mixed photon-neutron fields with varying dose rates generated by the McMaster University 1.25 MV double stage Tandetron accelerator. The Tandetron accelerator facility was employed to produce neutrons using thick 7Li targets via the 7Li(p, n)7Be reaction. A continuous spectrum of neutrons is generated at any selected proton beam energy which is very narrow at beam energies very close to the threshold of the reaction 1.88 MeV and becomes wider as the proton beam energy moves further away from the threshold energy of the reaction. Dose rates which resulted in dead times as high as 75% for the data acquisition system were employed to study the effect of dose rate on the measured quality factors, microdosimetric averages (y ̅_f and y ̅_D)absorbed dose and dose equivalent. The dose rate at a given beam energy was varied by changing the accelerator beam current. A variety of mixed neutron gamma fields was generated using neutron beams with mean energies extending approximately from 33 keV to 330 keV with the 7Li target using proton beam energies ranging from 1.89 to 2.5 MeV. In direct beams, 478 keV photons which are produced in the 7Li target via inelastic scattering interaction 7Li(p, p'γ)7Li dominate the low LET component of the mixed field of radiation. When a 2 cm thick polyethylene moderator was inserted between the neutron producing target and the counter, the low LET component of the mixed radiation field also contained 2.20 MeV gamma rays originating from 1H(n, γ)2H capture interactions in the moderator. We have observed that high dose rates due to both photons and neutrons in a mixed field of radiation result in pile up of pulses and distort the lineal energy spectrum measured under these conditions. The pile up effect and hence the distortion in the lineal energy spectrum becomes prominent with dose rates which result in dead times larger than 25% for the high LET radiation component. In intense neutron fields, which may amount to 75% dead time, a 50% or even larger increase in values for the measured microsdosimetric averages and the neutron quality factor was observed. This study demonstrates that moderate dose rates which do not result in dead times of more than 20-25% due to either of the component radiations or due to both components of mixed field radiation generate results which are acceptable for operational health physics mixed neutron-gamma radiation monitoring using tissue equivalent proportional counters. / UOIT

This project was designed to determine the feasibility of constructing a multichamber proportional counter. A multi-chamber detector is designed to increase the total surface area which will increase the number of radiation interactions that occur per unit dose. Surface area can be changed without changing the detector volume by subdividing the active volume into several smaller volumes that can then be used as mini detectors whose data can be summed and used to determine the absorbed dose. This will allow the total surface area to remain the same as that of the more common 12.5 cm (5 in.) spherical detector and a decreased total volume resulting in a more compact detector design. However, subdividing those volumes causes problems with electric field fringing at the ends of the mini detectors. In order to correct this, guard ring and field tube designs which operate at a lower voltage than the detector cathode were tested. Results from this study showed that the field tube design provided the best overall resolution but it only outperformed the other designs by a maximum of 5%. However the field tube design doubles the length of the detector which would result in a larger overall detector package. The performance of the single and double ring configurations was suitable for radiation monitoring applications. These findings show that it is feasible to use an array of subdivided detector volumes instead of a spherical detector.

Thesis (M. Ec.)--University of Sydney, 1958. / Also available in print form.

Thesis (M.S.)--University of Michigan, 1961. / Degree awarded in Aug. 1961. Project completed in July 1962.