Engineering and Information Technology Collected Works - Theses
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ItemModelling wavelength-dependence of optical gain and ultrafast behaviour in semiconductor lasers(University of Melbourne, 1997)
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ItemObject-oriented concepts for land and geographic information systems(University of Melbourne, 1991)
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ItemStability of boreholes in saturated porous anisotropic shales(University of Melbourne, 1996)
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ItemA mechanics of cutting approach for the prediction of forces and power in some commercial machining operations(University of Melbourne, 1986)
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ItemThe influence of geometrical variables and cutting conditions on twist drill performance(University of Melbourne, 1988)
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ItemNegation and control in PROLOG(University of Melbourne, 1985)We investigate ways of bringing PROLOG closer to the ideals of logic programming, by improving its facilities for negation and control. The forms of negation available in conventional PROLOG systems are implemented unsoundly, and can lead to incorrect solutions. We discuss several ways in which negation as failure can be implemented soundly. The main forms of negation considered are not, not-equals, if-then-else and all solutions predicates. The specification and implementation of all solutions predicates is examined in detail. Allowing quantifiers in negated calls is an extension which is easily implemented and we stress its desirability, for all forms of negation. We propose other enhancements to current implementations, to prevent the computation aborting or looping infinitely, and also outline a new technique for implementing negation by program transformation. Finally, we suggest what forms of negation should be implemented in future PROLOG systems. The poor control facilities of conventional PROLOG lead to infinite loops and inefficiency. More flexible computation rules can often overcome these problems. We first introduce control primitives for database and recursive predicates, then show how control information can be generated automatically, using these primitives. Automatically reordering subgoals in clauses is also considered. This allows programmers to concentrate more on the logic of a problem, making programming simpler. We give examples using several different styles of programming. The implications of automatic control for the design of control primitives is also discussed. Next, we re-examine the theoretical foundations of PROLOG systems with flexible computation rules. The SLD resolution model is extended, to correct a previous over-simplification. The extension also brings to light a much greater flexibility of computation rules, which has previously been overlooked. A rule which behaves like intelligent backtracking is given as an example. Finally, we take an overview of the many approaches to control in PROLOG. Some general principals for evaluating and classifying control rules are given. These show the deficiencies of current systems more clearly. We make suggestions for future implementations of PROLOG with extra control facilities.
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ItemFixpoint semantics(University of Melbourne, 1985)
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ItemPrivacy protection, technological change and law reform(University of Melbourne, 1985)Some parts of this thesis have appeared elsewhere in an earlier form. In particular, Chapter 6 and the first section of Appendix C is based on a paper written with Peter Thorne which appeared in The Australian Computer Journal m November 1983 [Thom 83]. Parts of Chapters 4 to 9 appeared in another paper written with Peter Thorne which has been submitted for publication in 1985 [Thom 85]. These two papers were based on two technical reports ([Thom 82] and [Thom 84]), portions of which also appear in this thesis. The remainder of Appendix C and section 6.2 are substantially from a technical report written with Lee Naish [Naish 83a]; this describes the implementation of the MU-PROLOG deductive database system. In broad terms. Chapters 1 to 5 are a review of the work of others; whereas Chapters 6 to 9 constitute original research. I have endeavoured to acknowledge sources of quotes, ideas and other information via the specific references in the text and in the bibliography. I would like thank Margaret Thom and Rodney Topor who read and made many helpful detailed comments on a draft of this thesis. I would also like to thank all those, including numerous staff and students of the Computer Science Department who have-supported and encouraged me over the years. Finally, I would like to thank Peter Thorne, my supervisor, and acknowledge all his help. We have shared so many ideas together and he has read and commented on numerous drafts of this thesis.
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ItemThe influence of microstructure on the wear behaviour of rail and wheel materials(University of Melbourne, 1985)
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ItemDesign of a distributed UNIX kernel and its modelling in CSP(University of Melbourne, 1984)The thesis presented is firstly that the standard UNIX kernel may be partitioned and distributed over a very local network resulting in increased processing power without unacceptable delays due to associated message passing, and secondly that CSP may be used to model the distributed kernel. That the UNIX kernel was selected for study is largely due to the impact that the facilities supported by and supplied with the operating system have made on teaching institutions and, more recently, industry. However, the approach that is taken need not be limited to UNIX and may be applicable to other operating systems. For the partitioning of the kernel, we establish a suitable division of labour through the examination of a standard Version 7 UNIX system. The anticipated message passing throughput is considered in relation to commercially available hardware for a very local network providing very fast, reliable, variable length message transfers. An approach to implementation of the distributed kernel is presented which considers the residence of system tables and the use of existing source code. A more precise notion of the processes involved in the distribution is presented by a model in CSP. This model shows, at a functional level, the interactions of processes in the network. The distributed model relies on the semantics of CSP and in particular uses language extensions for managing priority and preemption. We define operational semantics for CSP including commands for exceptions and interruptions. The contribution that extended CSP makes to potentially real-time applications is examined and a scheme is given for the implementation of synchronized message passing in the presence of preemption.