Theses and Dissertations

The purpose of this work is to clarify the causes of non-ideal behavior observed in the current-voltage characteristics of chromium to n-type gallium-arsenide surface barrier diodes.

One particularly attractive application for Light Emitting Diodes is in planar arrays. A process has been developed to diffuse ion-implanted Zn in GaP over distances for the production of plug diffusion contacts in thin epitaxial layers.

This thesis proposes several optimization methods that utilize parallel algorithms for large-scale machine learning problems. The overall theme is network-based machine learning algorithms; in particular, we consider two machine learning models: graphical models and neural networks. Graphical models are methods categorized under unsupervised machine learning, aiming at recovering conditional dependencies among random variables from observed samples of a multivariable distribution.

This dissertation explores the effect of competition among physicians on the technology diffusion and treatment choices in health care market. In Chapter 2, I study the effect of competition among physicians on their use of a new technology for coronary heart disease in Pennsylvania from 2003-2008: drug-eluting stents in percutaneous coronary intervention (PCI) procedures.

The adhesion of gold to sapphire has been investigated in an effort to develop a bonding model for Au/A12o3 system. Ultra-pure gold was bonded to sapphire by melting it on sapphire disks in a furnace with a controlled atmosphere.

Previous research on the effect of recovery interval was performed in Skinner boxes under either food or water deprivation. One purpose of the present experiment was to determine whether a growth function would adequately describe the data over the wider range of intervals. Another purpose of the present study was to test Estes’ (1955) model for spontaneous recovery and regression.

A partially ordered set (poset), P =(X;<), is a set X together with a relation, <,that is irreexive and transitive. An interval order is a poset which has an intervalrepresentation: an assignment of a closed interval, I_x, in the real number line toeach x in X so that x<y if and only if I_x is completely to the left of I_y. Wienerand Fishburn characterized interval orders as posets which do not contain a 2+2as an induced suborder [5, 22]. Define P[p, q] to be posets for which there existsan interval representation with interval lengths in [p, q].

This thesis details the author's contributions to the fields of difluoromethylation and polydifluoromethylation chemistries. State-of-the-art methodology in difluoromethylation is achieved in our lab either by nickel-catalyzed conventional cross-coupling between electrophiles and the nucleophile (DMPU)2Zn(CF2H)2 or by reductive cross-coupling to join HCF2Cl and aryl halides with a nickel catalyst. Chapter 1 introduces the benefits of incorporating fluorinated moieties in drug candidates and general methods to install CF3, (CF2)n and CF2H moieties into arenes and heteroarenes.

An explanation is presented of the physical mechanisms involved when PIN and varactor diodes operate as switches, and an analysis is made of the changes that occur in their equivalent circuits as a consequence of exposure to high RF power.

The method of determining energy distribution of surface states at silicon silicon-dioxide interface by using very low frequency signals following the Kuhn's quasi-static method is described. A general description of the solid-solid interface, the surface space charge region in silicon, and their modifications in the presence of interface states is given.

A concept which allows the development of efficient finite element techniques for the analysis of plane elastic structures containing cracks is discussed. It consists in combining a special finite element covering a small area around each crack tip, with conventional CST elements in the rest of the region.

This report describes an experimental investigation of the design of chip breakers. In this experiment the effect of the use of a coolant on the formation of the chip, and on the design of the chip breaker has been investigated.

The basic objective of this investigation is to provide a method for quantitatively analyzing the effect of autmation on the staff time requrements of a university library circulation system. This is accomplished by characterizing the various levels of sophistication in circulation systems in terms of the degree of automation involved, and then analyzing the components of existing circulation systems at each level of automation.