<p>This thesis proposed and presented technical details of new probabilistic metrics of trust in the links wireless ad hoc networks for unobservable communications. In covert communication networks, only the end nodes are aware of the communication characteristics of the overall path. The most widely used protocols of ad hoc networks was overviewed. The routing protocols of ad hoc networks with trust considerations and select Destination Sequence Routing, a protocol that can be used in distributed ad hoc network settings for path discovery, was also reviewed. It establishes a path through which all packets sent by a source must pass to the destination. The end nodes are responsible for examining the statistics of the received packets and deriving inferences on path feature variations which are used for computing new trust metrics. When a path is judged not trustworthy based on the metrics, the Destination Sequence Routing is informed to undertake a new trusted path discovery between the end points. The thesis added a new feature based on the quality of service parameters of the path to create trust in the links in recognition of attacks.</p>

Thesis (Ph. D.)--Psychology, Georgia Institute of Technology, 2008. / Committee Chair: Richard Catrambone; Committee Member: James Foley; Committee Member: Mark Guzdial; Committee Member: Paul Corballis; Committee Member: Wendy Rogers.

This thesis sets out to examine contemporary organisational restructuring. In particular it documents and examines the role of engineers and systems analysts in designing and delivering new technologies and work systems. On the basis of fieldwork observations and detailed cross sectoral interviewing of over three hundred personnel in over sixty organisations, the thesis documents the kind of restructuring that is taking place and who is involved in the process. Whilst examining the role of trade unions, management and engineers within this process of restructuring the key focus is systems analysts - who hitherto, have remained a largely uncharted and under-researched group of workers. Through fieldwork, interviews and literature reviews the thesis highlights who systems analysts are and what is involved in the process of systems analysis and design. The thesis, First, documents and offers a critical assessment of the process of business restructuring and some of the key attempts to theorise this process. Second, it documents and examines a series of methods, values and techniques which constitute a design culture, or referral point, from which engineers and analysts interpret what is in the organisations interest, make sense of their own work, pass judgement on their designs and assess their relationships to others involved in the design process. Third, through an analysis of the tools and techniques used for systems analysis and design the thesis demonstrates that there is a profound contradiction between, on the one hand, attempts to develop tools and techniques to more accurately embody the social in the technical and, on the other hand, the influence which prevailing property relations and configurations of power have on the tools and techniques used in systems design. This influence is manifest in the continued existence of a software bottleneck and in system failure and user dissatisfaction. Fourth, the thesis highlights the nature of union involvement in the design process and demonstrates some of the key issues and concerns unions face in the 1990s. Finally, the thesis assesses a number of key attempts to analyse the class position of' intermediate strata' and demonstrates, on the basis of fieldwork studies and interviews the class position of engineers and systems analysts and how this influences the types of technologies and systems these groups design.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2005 / Having simple structure and high sensitivity, micro accelerometer is a type of popular transducer used to measure the acceleration in a great variety of conditions. The bridge-type micro accelerometer is a typical micro accelerometer and has many types. As one of research project of Kentron in South Africa, the thesis presented here analyzes the bridge-type capacitive nticro accelerometer (BTCMA) and the bridge-type micro accelerometer with two piezoelectric thin films read-out (BTPMA). In this thesis, the similar structures are used on BTCMA and BTPMA For proving the fundamental mode of the structure can measure acceleration and utilizing the structural and electric characteristic to avoid the effect of higher modes, the program CoventorWare for nticro-electric-mechanical system (MEMS) design and analysis is used here to analyze the modes of these two structures, The two group piezoelectric thin films of BTPMA can be connected in serial or parallel configurations. Integrating piezoelectric effect method, strength method and energy method, the analytical analysis of these two configurations has been done with particular emphasis on the elastic characteristics of the thin films. The analytical formulas of transducer, sensitivity, resonance frequency, noise, quality factor, ntinimum detectable signal and maximum detectable range are obtained. According to the comparison results between these two configurations, the charge output in parallel configuration is a little more than that in serial configuration and the sensitivity in serial configuration is much higher than that in parallel configuration. Finally, a calculation of certain practical nticro accelerometer size is used to prove the above conclusions. On the base of capacitance theory, strength method and energy method, the analytical analysis of the BTCMA has been done in this thesis.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2005. / Due to an increasing in industrial micromation need in recent years, the use of micro accelerometers has been highly increased. Consecutively, this has promoted research activities in this field; capacitive accelerometers also have got high concern at large. As a research project of the Kentron in South Africa, this thesis deals with a theoretical model for a one-dimensional micro capacitive accelerometer with U-shape cantilever beam. The properties of the small angle tilted-plate capacitor have been analyzed; the capacitance equation and electrostatic force equation of this kind capacitor have been derived. The sensing element of this accelerometer consists of an inertial mass connected with two cantilever beams. The vibration modes analysis to the sensing element was accomplished by using CoventorWare2004's MemMech module, the result indicates that the main vibration mode can cause the capacitance change observably and the effect of the other modes to the capacitance can be ignored, which satisfied the purpose of the design. In the process of deriving the linearizing acceleration equation, the angle of the inertial mass caused by the deformation of the U-shape cantilever beam was taken into account as well as the electrostatic force between the two electrodes, thus the more precise acceleration linear equation was obtained. The sensitivity equation was derived through the acceleration linear equation, the relationship between the main parameters of the system and the sensitivity has been analyzed. The differential structure of this micro capacitive accelerometer was also analyzed; the linearizing acceleration equation and sensitivity equation of this kind structure were derived, it has been proven that the sensitivity of this structure is twice than the normal structure approximately. The maximum detectable signal was obtained in terms of the fracture strength of the cantilever beam and the maximum displacement of the inertial mass. The minimum detectable signal was obtained in terms of the thermal noise analysis. In the process of the dynamic analysis, the forced vibration produced by the sinusoidal periodic force and sinusoidal periodic moment was analyzed and the transient capacitance equation was derived, this proved the system has good dynamic character in theory. The system was simulated and analyzed by using CoventorWare2004's Saber module. The initial capacitance analysis indicates the relationship between the voltage and the initial capacitance, the result is close to the analytic model. The resonance frequencies analysis indicates that the main dimensions of the sensing element can determine the resonance frequencies and each vibration mode's sequence, the initial dimensions of the sensing element was proved reasonable by analyzing. Sensitivity analysis and Monte Carlo analysis indicate the effect of the sensing element's normal manufacturing tolerance to the system's frequency is small. Impact of plate curvature analysis indicates the effect of the inertial mass's deformation caused by the surface stress to the capacitance is small. Transient analysis obtained the system's transient displacement curve of six directions and transient capacitance curve in normal terms; this proved the system has good dynamic character in the simulating environment.

As educators and instructional designers consider educational practices nationally and internationally, they find themselves questioning the traditional ways of teaching and learning which seems to be outdated in an era defined by the World Wide Web and globalisation. Instructional designers and educators worldwide recognise that there is a need for learning facilitation that builds upon the diverse needs and diverse experiences of learners and that is open to change. Instructional design can be regarded as one way of addressing the needs of learner groups with diverse needs as learners attach much value to the quality of their learning materials. In fact, many learners depend on the quality of their learning materials to complete their courses successfully and to enter the labour market as qualified people. Well-designed learning materials and environments, therefore, play an important role in contributing to improved student pass rates and, in the broader South African context, to the skills development and socio-economic development of our country. It is thus a huge challenge for instructional designers to ensure successful learning facilitation by means of the learning programmes and environments they design. The intellectual contribution of this dissertation lies within the area of instructional designers’ personal views on teaching and learning. More specifically, the focus of this research inquiry is on investigating the extent to which the personal teaching and learning philosophies of a group of instructional designers at a higher education institution influence their design decisions. A review of the literature reveals that instructional designers are dependent on learning theories that have been tested in order to make design decisions that would best suit the requirements of a particular teaching and learning situation. For this inquiry I contend that the personal teaching and learning philosophies of instructional designers are based on established theories of human learning, but that their personal teaching and learning philosophies change over time as they address the demands of changing socio-cultural contexts. Considering the focus of this study, it is thus important to establish what a grounded instructional design approach entails as well as what views socio-cultural theory and activity theory hold on humanlearning and how these relate to the personal teaching and learning philosophies of the research participants. A grounded approach uses theories of human learning as a foundation for making decisions on the design of learning experiences and environments that would result in effective learning. According to activity theory, if human behaviour is to be understood, a study of surrounding social practices should be part and parcel of the inquiry. In this regard the decision-making process of instructional designers can be seen as an activity system. Within this system the design activities of instructional designers are mediated by tools aiming at effective learning programmes and environments. Tools, activity theory states, are created and transformed during the development of the activity itself. As such the personal teaching and learning philosophies of the designers are viewed as design tools that are continuously shaped and modified during the design process. This inquiry is concerned with the emergence of the everyday knowledge and actions of a group of identified instructional designers. Therefore a qualitative, ethnomethodological strategy is followed allowing me to examine the nature of the personal teaching and learning philosophies of the designers and how these philosophies are shaped and used to make instructional design decisions in their place of work. Activity theory is used as both the theoretical framework and data analysis tool for this inquiry. The findings of the study make it clear that instructional designers regard personal teaching and learning philosophies as essential tools in their daily design activities. The findings also demonstrate that personal teaching and learning philosophies are individual user tools, and as such the unique qualities of the tools remain with the individual instructional designer. / Dr. G. V. Lautenbach

C³TO (Chatter Call Centre/Tutoring Online) is a scalable architecture to support mobile online tutoring using chat protocols over cell phones. It is the scalability of this architecture which is the primary focus of this dissertation. Much has been written lamenting the state of mathematics education in South Africa. It is not a pretty story. In order to help solve this mathematical crisis, the “Dr Math” research project was started in January, 2007. “Dr Math” strove to assist school pupils with their mathematics homework by providing access to tutors from a nearby university to help them. The school pupils used MXit on their cell phones and the tutors used normal computer workstations. The original “Dr Math” research project expected no more than twenty to thirty school pupils to participate. Unexpectedly thousands of school pupils started asking “Dr Math” to assist them with their mathematics homework. The original software could not scale. The original software could not cater for the thousands of pupils needing help. The scalability problems which existed in the original “Dr Math” project included: hardware scalability issues, software scalability problems, lack of physical office space for tutors, and tutor time being wasted by trivial questions. C³TO tackled these scalability concerns using an innovative three level approach by implementing a technological feature level, a tactical feature level, and a strategic feature level in the C³TO architecture. The technological level included specific components, utilities, and platforms which promoted scalability. The technological level provided the basic building blocks with which to construct a scalable architecture. The tactical level arranged the basic building blocks of the technological level into a scalable architecture. The tactical level provided short term solutions to scalability concerns by providing easy configurability and decision making. The strategic level attempted to answer the pupils questions before they actually arrived at the tutor thereby reducing the load on the human tutors. C³TO was extensively tested and evaluated. C³TO supported thousands of school pupils with their mathematics homework over a period of ten months. C³TO was used to support a small conference. C³TO was used to encourage people to volunteer their time in participation of Mandela Day. C³TO was used to support “Winter School” during the winter school holiday. In all these cases, C³TO proved itself to be scalable.

This dissertation studies the issues raised by the parallel execution of rules in a pattern-matching production system. There are two main areas of concern: maintaining correctness during the course of simultaneous rule executions, and controlling the execution of productions without introducing serial bottlenecks. It is demonstrated that guaranteeing program correctness using a serializability criterion introduces an unacceptable overhead and reduces the potential parallel speedup to a single order of magnitude. Instead of attempting to automatically extract coexecutable sets of parallel rules, the approach taken in this research is to define a minimal set of language constructs which allow correct parallel programs to be designed. The view that the rule-based computation has an algorithmic structure allows us to attach a semantic interpretation to rule firing. By examining the role of each rule in the overall computation, we can understand and begin to find a solution to the problems of controlling rule firing and ensuring correctness while maximizing effective use of parallel processing resources. When rules are executed in parallel, the conventional control mechanisms applied to rule-based systems act to limit parallel activity. Two novel rule-firing policies are described: an asynchronous rule-firing policy that causes rules to be executed as soon as they become enabled, and a task-based scheduler that allows multiple independent tasks to run asynchronously with respect to each other while allowing rules to execute either synchronously or asynchronously within the context of each task. Because the asynchronous execution of rules reduces the opportunities for performing conflict resolution, methods for performing heuristic discrimination at various points in the rule execution cycle are discussed. The experimental results of this research are presented in the context of UMass Parallel OPS5, a rule-based language that incorporates parallelism at the rule, action, and match levels, and provides language constructs for supporting the design of parallel rule-based programs including a locking scheme for working memory elements and operators for specifying local synchronization of rules and actions. Results are presented for a number of programs illustrating common AI paradigms including search, inference, and constraint satisfaction problems.

This research is designed to study the effects of highly developed information technologies and logistic strategies on freight transportation. A simulation model called TTMNet is formulated as a multi-level product supply chain system that integrates the financial, informational, logistic, and physical aspects of transportation networks, to address freight transportation problems within a much broader decisionmaking and policy sensitive environment. It simulates freight movement in a regional supply chain, given real-time information, to help understand the mechanisms or principles followed by system operation, freight flow patterns, and evolution and interaction of prices and costs across the networks over time. TTMNet is implemented using micro-simulation techniques and GIS tools, and several simulators are involved, including a dynamic freight traffic simulator, a supply chain decision making simulator, and a real-time information simulator. The construction of a prototype dynamic freight traffic simulation model called DyFTS is the focus of this research. DyFTS is designed as a discrete event simulation system, highly adaptable to more comprehensive transportation simulation models. Various decision-making processes are formulated within DyFTS, such as goods-to-vehicle assignment, departure time choice and pre-trip routing, and en-route vehicle redirection. Descriptive real-time traffic information is simulated to study its influence on freight traffic operations. A knowledge-based learning process is established to refine the perceptions of decision-makers to the transportation network based on past experience. The inclusion of the simulation of regional ITS system makes the DyFTS a powerful tool to evaluate the information. A preliminary study is conducted herein to construct an integrated logistic and transportation system, a simplified version of TTMNet. It simulates enterprise-wide freight movements in a comprehensive product supply chain system that integrates the logistic, informational, and physical aspects of transportation networks. The resulting simulation model developed in this dissertation can be applied widely in freight transportation industry, such as, the study of commercial vehicle operations with and without real-time information, freight transportation of different delivery time requirements and different fleet configurations, and freight traffic patterns by product demand. It may also help direct or justify the development of real-time surface transportation information systems.

The work presented in this thesis deals with techniques to improve problem solving control skills of cooperative agents through machine learning. In a multi-agent system, the local problem solving control of an agent can interact in complex and intricate ways with the problem solving control of other agents. In such systems, an agent cannot make effective control decisions based purely on its local problem solving state. Effective cooperation requires that the global problem-solving state influence the local control decisions made by an agent. We call such an influence cooperative control. An agent with a purely local view of the problem solving situation cannot learn effective cooperative control decisions that may have global implications, due to the uncertainty about the overall state of the system. This gives rise to the need for learning more globally situated control knowledge. An agent needs to associate appropriate views of the global situation with the knowledge learned about effective control decisions. We call this form of knowledge situation-specific control. This thesis investigates learning such situation-specific cooperative control knowledge. Despite the agreement among researchers in multi-agent systems about the importance of the ability for agents to learn and improve their performance, this work represents one of the few attempts at demonstrating the utility and viability of machine learning techniques for learning control in complex heterogeneous multi-agent systems. More specifically, this thesis empirically demonstrates the effectiveness of learning situation-specific control for three aspects of cooperative control: (1) Organizational roles. Organizational roles are policies for assigning responsibilities for various tasks to be performed by each of the agents in the context of global problem solving. This thesis studies learning organizational roles in a multi-agent parametric design system called L-TEAM. (2) Negotiated search. One way the agents can overcome the partial local perspective problem is by engaging in a failure-driven exchange of non-local requirements to develop the closest possible approximation to the actual composite search space. This thesis uses a case-based learning method to endow the agents with the capability to approximate non-local search requirements in a given situation, thus avoiding the need for communication. (3) Coordination strategies. Coordination mechanisms provide an agent with the ability to behave more coherently in a particular problem solving situation. The work presented in this thesis deals with incorporating learning capabilities into agents to enable them to choose a suitable subset of the coordination mechanisms based on the present problem solving situation to derive approximate coordination strategies.