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X windows is a graphic display management system. It is designed to work on a variety of machines and display adapters, however it is not designed for terminals with local graphics capabilities. X windows can be made to work on this type of terminal, although in a slower and restricted form. The problem with designing a variation of X for these terminals is the translation from X requests to native graphics commands, and the mapping of terminal input into X events. These implementation issues are discussed and example code is provided. / Department of Computer Science

The purpose of the X-Form package is for use in the classroom as an instructional aid for teaching the algorithms and data used to represent, transform, and display objects in three-dimensional space. The program provides various areas containing graphic and textual representations of the data structures used in the creation and transformation of a three-dimensional object. Another area, containing the menu items, serves as an interface to the available demonstration items. These items include various object and viewing parameters which can be input by the user. The user then sees the result of the entered data, including animated graphics and changes in data structures. The graphic areas show the object at various stages of development, so that the user can understand the progression of the required manipulations. The textual representations are also designed to assist the user in understanding how useful information is derived from entered data. Through testing and statistical analysis, XForm has proven to be an effective tool for instruction of three-dimensional graphics. / Department of Computer Science

Canada’s forests are believed to contain 86 gigatons of carbon, stored above and below ground. These forests are large in area, making them difficult to monitor using conventional means. Understanding the carbon cycle and the role of forests as carbon sinks is crucial in the investigation and mitigation of climate change to address national obligations. One economical solution for monitoring the carbon content of Canada’s forests is the development of an automated computer system which uses multisource remotely sensed data to estimate the aboveground carbon of trees. The process involves data fusion of remotely sensed hyperspectral data for tree species information and lidar (light detection and ranging) and radar (radio detection and ranging) for tree height. The size and dimensionality of the data necessitate the efficient use of computing resources for analysis. The outcome is a useful carbon measuring system. The three research questions are: (1) How do we map with remote sensing aboveground carbon in the forests? (2) How do we determine the accuracies of these aboveground carbon maps? (3) How can an automated system be designed for creating aboveground carbon maps? / Graduate

This thesis is a reapproachment of diverse design concepts, brought to bear upon the computer system engineering problem of identification and control of highly constrained multiprocessing (HCM) computer machines. It contributes to the area of meta/general systems methodology, and brings a new insight into the design formalisms, and results afforded by bringing together various design concepts that can be used for the construction of highly constrained computer system architectures. A unique point of view is taken by assuming the process of identification and control of HCM computer systems to be the process generated by the Activity Structures Methodology (ASM). The research in ASM has emerged from the Neuroscience research, aiming at providing the techniques for combining the diverse knowledge sources that capture the 'deep knowledge' of this application field in an effective formal and computer representable form. To apply the ASM design guidelines in the realm of the distributed computer system design, we provide new design definitions for the identification and control of such machines in terms of realisations. These realisation definitions characterise the various classes of the identification and control problem. The classes covered consist of: 1. the identification of the designer activities, 2. the identification and control of the machine's distributed structures of behaviour, 3. the identification and control of the conversational environment activities (i.e. the randomised/ adaptive activities and interactions of both the user and the machine environments), 4. the identification and control of the substrata needed for the realisation of the machine, and 5. the identification of the admissible design data, both user-oriented and machineoriented, that can force the conversational environment to act in a self-regulating manner. All extent results are considered in this context, allowing the development of both necessary conditions for machine identification in terms of their distributed behaviours as well as the substrata structures of the unknown machine and sufficient conditions in terms of experiments on the unknown machine to achieve the self-regulation behaviour. We provide a detailed description of the design and implementation of the support software tool which can be used for aiding the process of constructing effective, HCM computer systems, based on various classes of identification and control. The design data of a highly constrained system, the NUKE, are used to verify the tool logic as well as the various identification and control procedures. Possible extensions as well as future work implied by the results are considered.

The interaction of steep waves with structures is a complex problem which is still not fully understood, and is of great importance for the design of offshore structures. A particular problem of interest is the phenomenon of ringing which is highly nonlinear. In this thesis a number of inviscid free surface flow problems are simulated using a finite element model. The free surface boundary condition is fully nonlinear, meaning nonlinear effects up to very high order can be simulated, depending on mesh resolution. The model uses a fully automatic unstructured mesh generator; this allows the mesh to change its shape and structure as the free surface deforms. Two unstructured mesh generators have been developed, one based on the advancing front method, the other on the Voronoi technique. Variations of each method are examined. Both methods give good quality meshes. The advancing front technique is found to be faster, but the Voronoi method is more robust and reliable. In addition to the standard finite element method, a sigma transformed version of the finite element formulation has been developed as an alternative. Both techniques have been used for the numerical simulations. The sigma transformation involves stretching of the mesh between the bed and free surface, and so has the advantage that remeshing is avoided. The standard finite element method is straightforward to apply to problems involving submerged arbitrary shaped bodies. Simulations have been performed of a number of test cases, such as a standing wave of large amplitude, a base excited tank and steep travelling waves. Convergence tests were carried out and results found to be in close agreement with analytical and alternative numerical solutions of Wu and Eatock Taylor (1994), Wu et al. (1998) and Chern et al. (1999). The force on a submerged horizontal cylinder due a travelling wave has been calculated. First and second order components have been obtained by Fourier analysis. The results have been compared with the theoretical predictions of Ogilvie (1963), Vada (1987) and Wu and Eatock Taylor (1990) and the experimental results of Chaplin (1984).

Three studies in the machine assisted proof of recursion implementation are described. The verification system used is Edinburgh LCF (Logic for Computable Functions). Proofs are generated, in LCF, in a goal-oriented fashion by the application of strategies reflecting informal proof plans. LCF is introduced in Chapter 1. We present three case studies in which proof strategies are developed and (except in the third) tested in LCF. Chapter 2 contains an account of the machine generated proofs of three program transformations (from recursive to iterative function schemata). Two of the examples are taken from Manna and Waldinger. In each case, the recursion is implemented by the introduction of a new data type, e.g., a stack or counter. Some progress is made towards the development of a general strategy for producing the equivalence proofs of recursive and iterative function schemata by machine. Chapter 3 is concerned with the machine generated proof of the correctness of a compiling algorithm. The formulation, borrowed from Russell, includes a simple imperative language with a while and conditional construct, and a low level language of labelled statements, including jumps. We have, in LCF, formalised his denotational descriptions of the two languages and performed a proof of the preservation of the semantics under compilation. In Chapter 4, we express and informally prove the correctness of a compiling algorithm for a language containing declarations and calls of recursive procedures. We present a low level language whose semantics model a standard activation stack implementation. Certain theoretical difficulties (connected with recursively defined relations) are discussed, and a proposed proof in LCF is outlined. The emphasis in this work is less on proving original theorems, or even automatically finding proofs of known theorems, than on (i) exhibiting and analysing the underlying structure of proofs, and of machine proof attempts, and (ii) investigating the nature of the interaction (between a user and a computer system) required to generate proofs mechanically; that is, the transition from informal proof plans to behaviours which cause formal proofs to be performed.

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<p>As the need for large elections increases and computer networking becomes more widely used, e-voting has become a major topic of interest in the field of cryptography. However, lack of cryptography knowledge among the general public is one obstacle to widespread deployment. In this paper, we present an e-voting scheme based on an existing scheme. Our scheme features an efficient location anonymization technique built on homomorphic encryption. This technique does not require any participation from the voter other than receiving and summing location shares. Moreover, our scheme is simplified and offers more protection against misbehaving parties. We also give an in-depth security analysis, present performance results, compare our scheme with existing schemes, and describe how our research can be used to enhance cybersecurity education.</p>

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 147-155). Also available via the Internet.