Thesis (Ph. D.)--University of Wisconsin--Madison, 1980. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

This thesis presents a novel current-controlled oscillator (CCO). It charges and discharges a source-coupled capacitor periodically with well-controlled current sources. Its current-to-frequency conversion relies on passive components, which are insensitive to the temperature and process variations. The proposed CCO is compact and area-efficient. Moreover, compared to ring-oscillator and LC-tank oscillator, it exhibits much wider tuning range and better linearity. Therefore, it suits the modern system-on-chip (SoC) design. / text

No description available.

This thesis presents the development of a generalised computer program to calculate harmonic currents and voltages in six and twelve-pulse thyristor controlled reactors under non-ideal conditions. Thyristor controlled reactors are a relatively new source of harmonic distortion in power systems. The steady state characteristic harmonics are well known. Other non-characteristic harmonics can, however, be generated. A detailed representation is therefore necessary. Apart from the most common non-ideal conditions, such as voltage, impedance and firing pulse unbalances, this work allows voltage harmonic distortions, two firing pulse control methods, the effect of the feedback control in the equally spaced firing pulse control and the effect of the step-down transformer saturation. The effect of the a.c. system impedance, filters and capacitor banks is also included. Four different models of filters were implemented. With non-infinite a.c. systems, the harmonic currents generated are not totally absorbed by the filters. The remaining distortion may affect the main busbar voltages. Therefore, an iterative method was adopted in which the distorted voltages calculated at the end of one iteration are used to calculate the new currents and voltages. The process is repeated until convergence is reached. Several cases were then studied using this program which was then joined to an existing steady-state converter harmonic program. For instance, the need for a more complete representation of controlled reactors, converters and a.c. system network is illustrated. This study begins considering an hvdc station under ideal conditions which are then gradually moved towards more real conditions. The influence of the a.c. system representation in harmonic studies is also discussed. This analysis also compares the performance of two filter designs, namely the tuned and the damped filters. A study of harmonic magnification in the presence of a.c. and d.c. resonances is also included. The harmonic calculations program presented in this thesis is able to study so many conditions of operation of converters and/or thyristor controlled reactors that it is impractical to show all the possible cases. For instance, filters and capacitor banks can be installed at the converter busbar or at any controlled reactor busbar. Furthermore, the three-phase calculation approach allows studies in which some abnormal operation, such as the absence of a filter branch or capacitor bank at one phase, can be observed.

Sustained concentrations of active compound were maintained in vitro and in vivo for an oral and a parenteral dosage form respectively. The vehicle of a oral dosage form was modified and the molecular structure of a parenteral dosage form was modified. An oral dosage form was tested in vitro using dissolution apparatus. A parenteral dosage form was tested in vivo using rats. A new oral suspension dosage form for acetylsalicylic acid was compared to two controlled release forms and two immediate release dosage forms which are currently commercially available. A parenteral thrombomodulin analogue conjugated to polyethylene glycol was compared to the unconjugated thrombomodulin analogue. In each case the goal was to maintain sustained concentrations of active compound. / Graduation date: 1991

The benefits of controlled release drug delivery are important to the pharmaceutical industry. With a controlled release device, local administration of a drug is possible and release profiles can be created that remain within therapeutic limits for prolonged periods. Made from biodegradable and bioerodable polymers, unwanted side effects and the need of return trips for treatment diminish. However, a usable device must be free of organic solvents normally used to dissolve large drug molecules. Many of these solvents are toxic themselves. Therefore, steps must be taken to either remove residual solvent from the final device or limit their use during synthesis. Ideally, it is desirable to remove the organic solvents from the process entirely. Supercritical carbon dioxide (scCO2) has been used as a replacement for these solvents. Carbon dioxide is inexpensive, environmentally acceptable, and safe for use in human consumables. However, many drug molecules have very low solubility in scCO2, resulting in extended polymer impregnation times. An organic co-solvent can be used to increase drug solubility, leading to a more efficient polymer impregnation. Using only a small amount of organic co-solvent, a single phase stream is possible that results in significantly increased solubility. This meets the original task of limiting organic solvents in the process and increases efficiency over scCO2 alone. This study uses supercritical carbon dioxide with ethanol as a co-solvent. Ethanol increases the solubility of β-estradiol in scCO2 for impregnation into the glassy polymer polyvinylpyrrolidone (PVPP). Experimental conditions cover a range of temperatures from 40 °C to 50 °C and pressure up to 2500 psi. The effect of polymer swelling time on the sorption process is also studied. A dual mode sorption model describes the sorption of drug into the glassy polymer, and a plug flow and stirred tank compartmental model predicts breakthrough profiles. The determined sorption parameters allow analysis of polymer conformation and suggest optimum impregnation conditions.

published_or_final_version / Medicine / Master / Doctor of Medicine

No description available.

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 318-327).

Thesis (M.D.)--University of Hong Kong, 2004. / Also available in print.