The lack of availability of a single, complete paper on the analysis of a digital data acquisition system for in situ oceanographic measurements brought about the present work. In order to compile an accurate technical paper on such a complex system, it was necessary to design, construct, and calibrate a system for the in situ measurement of various physical and chemical properties of sea water. A unique digital encoding circuit was developed which utilizes the basic principles of null balance, resistance ratio bridge and potentiometer measurements. The circuit is a uniquely loaded binary ladder resistance network. Variation of the loading allows resistance ratio and potentiometric measurements to be made over different ranges with a constant high degree of resolution. The developed system has the capability of measuring any parameter which can be converted into a varying voltage, current, or resistance. The range over which the measurement can be made is adjustable; and the resolution equals ± 0.006% of the full range value. The resolution is constant over the full range, as a result of the analog-to- digital converter linearity characteristics. / Graduation date: 1968

Regression testing is an expensive software engineering activity intended to provide confidence that modifications to a software system have not introduced faults. Test case prioritization techniques help to reduce regression testing cost by ordering test cases in a way that better achieves testing objectives. In this thesis, we are interested in prioritizing to maximize a test suite's rate of fault detection, measured by a metric, APED, trying to detect regression faults as early as possible during testing. In previous work, several prioritization techniques using low-level code coverage information had been developed. These techniques try to maximize APED over a sequence of software releases, not targeting a particular release. These techniques' effectiveness was empirically evaluated. We present a larger set of prioritization techniques that use information at arbitrary granularity levels and incorporate modification information, targeting prioritization at a particular software release. Our empirical studies show significant improvements in the rate of fault detection over randomly ordered test suites. Previous work on prioritization assumed uniform test costs and fault seventies, which might not be realistic in many practical cases. We present a new cost-cognizant metric, APFD[subscript c], and prioritization techniques, together with approaches for measuring and estimating these costs. Our empirical studies evaluate prioritization in a cost-cognizant environment. Prioritization techniques have been developed independently with little consideration of their similarities. We present a general prioritization framework that allows us to express existing prioritization techniques by a framework algorithm using parameters and specific functions. Previous research assumed that prioritization was always beneficial if it improves the APFD metric. We introduce a prioritization cost-benefit model that more accurately captures relevant cost and benefit factors, and allows practitioners to assess whether it is economical to employ prioritization. Prioritization effectiveness varies across programs, versions, and test suites. We empirically investigate several of these factors on substantial software systems and present a classification-tree-based predictor that can help select the most appropriate prioritization technique in advance. Together, these results improve our understanding of test case prioritization and of the processes by which it is performed. / Graduation date: 2004

Traditionally, research into end-user programming has focused on how to make programming more accessible to end users. However, few researchers have considered providing end users with devices to help improve the reliability of the programs they create. To help improve the reliability of spreadsheets created by end users, we are working to allow users to communicate the purpose and other underlying information about their spreadsheets using a form of requirement specifications we call "guards." Guards were initially designed for individual cells but, for large spreadsheets, with replicated/shared formulas across groups of rows or columns, guards can only be practical if users can enter them across these groups of rows or columns. The problem is, this introduces many-to-many relationships, at the intersection of rows and columns with guards. It is not clear how the system should reason and communicate about many-to-many relationships in a way that will make sense to end users. In this thesis, we present the human-centric design rationale for our approach to how the system should reason about such many-to-many relationships. The design decisions are presented with their reasons gleaned from two design-time models--Cognitive Dimensions and Attention Investment--and from the users themselves in a small think-aloud study. / Graduation date: 2003

As the performance gap between processor and memory grows, memory latency will be a major bottleneck in achieving high processor utilization. Multithreading has emerged as one of the most promising and exciting techniques used to tolerate memory latency by exploiting thread-level parallelism. The question however remains as to how effective multithreading is on tolerating memory latency. Due to the current availability of powerful microprocessors, high-speed networks and software infrastructure systems, a cost-effective parallel machine is often realized using a network of workstations. Therefore, we examine the possibility and the effectiveness of using multithreading in a networked computing environment. Also, we propose the Multithreaded Virtual Processor model as a means of integrating multithreaded programming paradigm and modern superscalar processor with support for fast context switching and thread scheduling. In order to validate our idea, a simulator was developed using a POSIX compliant Pthreads package and a generic superscalar simulator called Simple Scalar glued together with support for multithreading. The simulator is a powerful workbench that enables us to study how future superscalar design and thread management should be modified to better support multithreading. Our studies with MVP show that, in general, the performance improvement comes not only from tolerating memory latency, but also due to the data sharing among threads. / Graduation date: 1999

The application of the personal computer in the area of real-time process control is investigated. Background information is provided regarding factory automation and process control. The current use of the PC in the factory for data acquisition is presented along with an explanation of the advantages and disadvantages associated with extending the use of the PC to real-time process control. The use of interrupt-driven and polled I/O to obtain real-time response is investigated and contrasted with the use of a real-time operating system. A unique compilation of information provides guidelines for selecting an implementation method for real-time control. Experimental work is performed to evaluate the access time and latency periods for the hard drive, video monitor, and I/O devices operating in a DOS environment. The execution speeds of C and assembly language programs are investigated. A method to estimate the performance of a real-time control system using polled or interrupt-driven I/O is developed. / Graduation date: 1997

A sophisticated computer program is developed to analyze flow linear dichroism data on nucleic acids for individual base inclinations. Measured absorption and linear dichroism data for synthetic AT and GC polymers and natural DNAs are analyzed. The reliability of the program is tested on data for the synthetic polymers, and the results are similar to earlier, more straightforward analyses. For the first time, specific base inclinations are derived for all bases individually from the linear dichroism data for natural deoxyribonucleic acids. For B-form DNA in aqueous solution at moderate salt concentrations, the inclinations from perpendicular are as follows: d(A)=16.1 �� 0.5; d(T)=25.0 �� 0.9; d(G)=18.0 �� 0.6; d(C)=25.1 �� 0.8 deg. Our results indicate that the bases in synthetic and natural DNAs are not perpendicular to the helix axis, even in the B form. The mathematical bases and numerical analyses are presented in detail since both are the keys for successful spectral decompositions in this study, and could be applied to nonlinear optimization problems encountered in other types of biochemistry and biophysics measurements. The interplay between computer programming and scientific measurements can not be overemphasized for modern research. / Graduation date: 1994

<p>Investor confidence is a concept many investors are constantly trying to gauge. In practice however these concepts are usually not easy to measure. This study attempts to capture the total sum of investor perception in South Africa by examining market behaviour. Data from the JSE/FTSE (1995-2009) will be used to determine an Equity Risk Premium. Bond Yield Spreads will also be calculated from data provided by I-NET BRIDGE. An amalgamation of these components will produce the proposed Investment Confidence Index. Similar indices currently on the South African Market are based on subjective surveys and might therefore be biased. The proposed index which is a first in SA will prove invaluable to practitioners in the financial sector.</p>

The non-ideal aqueous electrolyte simulator (NAELS) is composed of three major parts: a Newton-Raphson non-linear optimization program written by Weare, et al (1987); an activity coefficient subroutine for non-ideal electrolyte systems based on Pitzer's model; and an extensive, user expandable database. It is robust, stable, and requires neither thermodynamic data nor initial guesses as input. NAELS provides very good estimates of equilibrium speciation and solubility in concentrated electrolyte systems. NAELS was assembled as a technical utility package for use on IBM-compatable microcomputers. / Graduation date: 1992

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (M.B.A.)--University of Hong Kong, 1988.