Computer implementation of Mason\u27s rule and software development of stochastic petri nets

A symbolic performance analysis approach for discrete event systems can be formulated based on the integration of Petri nets and Moment Generating Function concepts [1-3]. The key steps in the method include modeling a system with arbitrary stochastic Petri nets (ASPN), generation of state machine Petri nets with transfer functions, derivation of equivalent transfer functions, and symbolic derivation of transfer functions to obtain the performance measures. Since Mason\u27s rule can be used to effectively derive the closed-form transfer function, its computer implementation plays a very important role in automating the above procedure. This thesis develops the computer implementation of Mason\u27s rule (CIMR). The algorithms and their complexity analysis are also given. Examples are used to illustrate CIMR method\u27s application for performance evaluation of ASPN and linear control systems. Finally, suggestions for future software development of ASPN are made

Image analysis for translating English multimodal texts into Greek : a multimodal semiotics approach to translation training in a Greek higher education context

This study explores the image analysis practices of undergraduate translation trainees in a Greek. university. The key research questions focused on the trainees' perception of the role of visual literacy in translation, the nature of their verbal and visual associations and activities effective for developing this role. Visual literacy, semiotics, and translation theories provided the conceptual framework for this multimodal semiotics approach to translation training, which guided my examination of the way the trainees described semiotic resources, how they used verbal and visual elements of Cl. translation task, and the extent to which they focused on the visual. Expanding on the concept of mediation, I developed a 'verbo-visual' mediation model that included visual semiotic elements to provide a detailed description of the ways in which the trainees intervened in the translation process. Through an action research study I gauged the extent to which the trainees had developed visual literacy skills. I planned a series of tasks centred on the translation of a multimodal text from English into Greek. I used direct and video observation of the students as they performed the tasks and afterwards evaluated their translations. The main findings of my research reveal that the trainees found it difficult initially to consider all the semiotic elements of the data-text whilst simultaneously translating its verbal elements. However. by providing examples of potential verbal-visual interactions and reflecting on and modifying the tasks, I found that the trainees began to appreciate non-verbal elements as potential translational factors. I was thus able to demonstrate a raised level of awareness of the visual elements of multimodal texts to some extent for all trainees in this study. The research suggests that customized image analysis, photo-elicitation and visualization techniques may play a part in the improvement of translation training in a multimodal semiotics translation environment

Accomplishing task-invariant assembly strategies by means of an inherently accommodating robot arm

Despite the fact that the main advantage of robot manipulators was always meant to be their flexibility, they have not been applied widely to the assembly of industrial components in situations other than those where hard automation might be used. We identify the two main reasons for this as the 'fragility' of robot operation during tasks that involve contact, and the lack of an appropriate user interface. This thesis describes an attempt to address these problems.We survey the techniques that have been proposed to bring the performance of cur¬ rent industrial robot manipulators in line with expectations, and conclude that the main obstacle in realising a flexible assembly robot that exhibits robust and reliable behaviour is the problem of spatial uncertainty.Based on observations of the performance of position-controlled robot manipulators and what is involved during rigid-body part mating, we propose a model of assembly tasks that exploits the shape invariance of the part geometry across instances of a task. This allows us to escape from the problem of spatial uncertainty because we are 110 longer working in spatial terms. In addition, because the descriptions of assembly tasks that we derive are task-invariant, i.e. they are not dependent on part size or location, they lend themselves naturally to a task-level programming interface, thereby simplifying the process of programming an assembly robot.the process of programming an assembly robot. However, to test this approach empirically requires a manipulator that is able to control the force that it applies, as well as being sensitive to environmental constraints. The inertial properties of standard industrial manipulators preclude them from exhibiting this kind of behaviour. In order to solve this problem we designed and constructed a three degree of freedom, planar, direct-drive arm that is open-loop force-controllable (with respect to its end-point), and inherently accommodating during contact.In order to demonstrate the forgiving nature of operation of our robot arm we imple¬ mented a generic crank turning program that is independent of the geometry of the crank involved, i.e. no knowledge is required of the location or length of the crank. I11 order to demonstrate the viability of our proposed approach to assembly we pro¬ grammed our robot system to perform some representative tasks; the insertion of a peg into a hole, and the rotation of a block into a corner. These programs were tested on parts of various size and material, and in various locations in order to illustrate their invariant nature.We conclude that the problem of spatial uncertainty is in fact an artefact of the fact that current industrial manipulators are designed to be position controlled. The work described in this thesis shows that assembly robots, when appropriately designed, controlled and programmed, can be the reliable and flexible devices they were always meant to be

Generally speaking : exploring expressions of generality in secondary mathematics classrooms

It is widely recognised that generality is at the heart of the learning and teaching of mathematics. Motivated by a desire to understand what it is about generality which presents such an obstacle for so many students, this study examines the variety and complexity of ways in which generality is expressed in mathematics classrooms. Systematic reflection on my own experience of teaching over a year revealed a wide range of types of generalisation taking place in mathematics classrooms. The main study then analyses transcripts of fifty-two lessons taught by six teachers teaching at least four hundred students, sampled over a period of two months. The focus is on 'ordinary' lessons where expression of generality is not the main objective. Infonned by the literature, observation notes and student work, a framework is developed with five categories used to distinguish between types of generalisations, which emerge from the transcribed data . These categories are: the object of generalisation, its presumed longevity of relevance, its justification, its origin and the awareness being promoted. Having established the Ubiquitous richness and complexity of expression of generality in mathematics classrooms, the study looks in closer detail at the expression of generality pertinent to mathematical procedures and to mathematical concepts. The study uses the framework, and draws on second language education literature, to re-examine the fifty-two main study lessons. This analysis highlights the complexity of expressing generality through natural language, and suggests that natural language exhibits many of the pitfalls and ambiguities of algebraic expression. Further, it suggests that algebraic notation might offer a clearer means of expressing generality in many cases. The framework developed for considering characteristics of expressions of generality is then applied to the researcher's own classroom, demonstrating how awareness of ways in which generality is expressed can inform pedagogic choices as well as provide a structure for reflection on practice

Washington University Record, May 13, 1999

https://digitalcommons.wustl.edu/record/1830/thumbnail.jp

Software development management using metamodels and activity networks

This thesis develops the concept, management and control of metamodels for the management of software development projects. Metamodels provide a more flexible approach for managing and controlling the software engineering process and are based on the integration of several software development paradigms. Generalised Activity Networks are used to provide the more powerful planning techniques required for managing metamodels. In this thesis, both new node logics, that clarify previous work in this field, and Generalised Activity-on-the-Arrow and Generalised Activity-on-the-Node representations are developed and defined. Activity-on-the-Node representations reflect the current mood of the project management industry and allow constraints to be applied directly to logical dependencies between activities. The Generalised Activity Networks defined within this thesis can be used as tools to manage risks and uncertainties in both software developments and general engineering projects. They reflect the variation and uncertainties in projects more realistically and improve the planning and scheduling of such projects. [Continues.

Artificial intelligence and its application in architectural design

No abstract available.No abstract available