It was the purpose of this investigation to study the effect of varying the direct to reverse time ratio of periodically-reversed, direct current from 1.0 to 20.0 at an anode current density of 4.5 amperes per square centimeter, and to study the effect of alternating current of 60, 240, and 500 cycles per second, 0.2 to 4.5 amperes per square centimeter, superimposed on direct current on the electrolytic production of peroxydisulfuric acid. Electrolyses of 200 milliliters of sulfuric acid of specific gravity 1.4, at a temperature of 5 to 10 °C were performed with direct current. The anode current density was varied. The surface area of platinum anode and lead cathode was 2.0 and 221.8 square centimeters, respectively. For one hour of electrolysis, the yields were 7.9, 14.0, 20.2, and 22.9 grams of peroxydisulfuric acid at the anode current density of 1.5, 3.0, 4.5, and 6.0 amperes per square centimeter, respectively. The current efficiencies corresponding to these anode current densities were 85.0, 77.0, 61.5, and 53.4 per cent. The results showed that the yield was increased and the current efficiency was decreased with increase in the anode current density. Electrolysis of the same concentration and volume of sulfuric acid using periodically-reversed, direct current yielded 14.2 grams at an anode current density of 4.5 amperes per square centimeter and at a temperature of 5 to 8 °C. The time of electrolysis was one hour and the time ratio of direct to reverse electrolysis was 20. The current efficiency obtained under these conditions was 42.6 per cent. Decreasing the direct to reverse time ratio gave lower yields and current efficiencies. Apparently, there is no advantage in using periodically-reversed, direct current over the use of direct current for this reaction under the above experimental conditions. Electrolyses of 200 milliliters of sulfuric acid of the same concentration were performed with 60 cycles per second, alternating current superimposed on direct current. The direct current density was 4.5 amperes per square centimeter for the ten tests, but the surface area of the platinum anode was changed from two to one square centimeter and the direct current was decreased from 9.0 to 4.5 amperes. The current efficiency decreased sharply from 61.5 to approximately 31.0 per cent as the ratio of peak alternating to direct current increased from zero to 0.2 and then it remained constant until the ratio reached one. The current efficiency decreased suddenly to almost zero when the ratio was greater than one. The same sulfuric acid was electrolyzed under the same experimental conditions with 240 and 500 cycles per second, alternating current superimposed on direct current. Both direct and alternating anode current densities were varied. The direct current density was 2.2 and 4.5 amperes per square centimeter. The current efficiencies obtained during these tests were almost the same as that obtained with 60 cycles per second, alternating current within a specific limit of the ratio of peak alternating to direct current. The ratio of peak alternating current to direct current at which the current efficiencies suddenly dropped to zero was 0.75 for 240 cycles per second, and 0.5 for 500 cycles per second, instead of one for 60 cycles per second, superimposed alternating current. The platinum anode was activated and dissolved into the sulfuric acid when the ratio of peak alternating to direct current was greater than 1.0, 0.75, and 0.5 for 60, 240, and 500 cycles per second, alternating current superimposed on direct current. Apparently, there is no advantage in using alternating current superimposed on direct current over the use of direct current for electrolytic production of peroxydisulfuric acid. / Master of Science

No description available.

A one-dimensional analytical model of dark current has been developed to facilitate the investigation and analysis of dark current from gate-controlled photovoltaic InSb arrays. The applied gate voltage is an essential parameter in the model. The expressions relating this parameter to surface potential are derived separately for the cases of accumulation and depletion at the surface of n-type InSb material under the gate. In addition, the measured dark current is compared with that from the analytical model, and the discrepancy is discussed in terms of the intrinsic carrier concentration, surface recombination velocity, and geometry of the array. The components of dark current are mainly associated with surface state generation-recombination, field induced tunneling, and the depletion region from the bulk and surface. The experimental results are obtained at temperatures between 30K and 40K.

Assumindo elétrons e buracos se movimentando em suas bandas próprias e centros de recombinação independente para ambos, Hughes e Sokel calcularam as características e distribuição de cargas para o oxido de chumbo (PbO) quando este se encontra sob radiação. O cálculo também inclui a corrente de difusão e segundo os autores, esta possui um importante papel em muitos aspectos. Neste trabalho a característica para o PbO foi recalculado sem considerar a contribuição da corrente de difusão e essencialmente foi obtido o mesmo resultado. Foram desenvolvidos aproximações para baixo e alto campo. Em seguida, foram assumidos iguais parâmetros para ambos portadores (isto é, iguais mobilidades, tempos de captura, coeficientes de recombinação e densidades de centros de captura) e obtido as características para 18 combinações de três conjuntos de parâmetros convenientemente definidos. Aproximações de campo baixo e campo alto foram também derivadas para este caso / Assuming electron and hole bands and independent recombination centers or both carriers, Hughes and Sokel calculated the characteristics and charge distributions for lead oxide PbO under irradiation. The calculation also included the diffusion current and it was asserted that such a current was important in some aspects. In this work the characteristic for PbO was recalculated without the diffusion component and essentially the same result was obtained. Side this; approximations were derived for low and high fields. Next, assuming equal parameters for both carriers (that is, equal mobilities, trapping times, recombination rates and density of trap), characteristics were obtained for 18 combinations of three conveniently defined set of parameters. Low and high field approximation were also derived for this case

No description available.

Thèse : Physique : Paris, Faculté des sciences : 1828. / Titre provenant de l'écran-titre.

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 64-67). Also available in print.

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 64-67). Also available online.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 98-100). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 98-100). Also available on the Internet.