Many of the applications of geometric modelling are concerned with the computation of well-defined properties of the model. The applications which have received less attention are those which address questions to which there is no unique answer. This thesis describes such an application: the automatic production of a dimensioned engineering drawing. Dna distinctive feature of this operation is the requirement for sophisticated decision-making algorithms at each stage in the processing of the geometric model. Hence, the thesis is focussed upon the design j development and implementation of such algorithms. Various techniques for geometric n~odell:i.ng are briefly examined and then details are given of the modelling package that was developed for this project, The principles of orthographic projection and dimensionj.n.g are treated and some published work on the theory of dimensioning is examined. A new theoretical approach to dimensioning is presented and discussed. The existing body of knowledge on decision-making is sampled and the~author then shows how methods which were originally developed for management decisions may be adapted to serve the purposes of this project. The remainder of the thesis is devoted to reports on the development of decision-making algorithms for orthographic view selection, sectioning and crosshatching, the preparation of orthographic views with essential hidden detail, and two approaches to the actual insertion of dimension lines and text. The thesis concludes that the theories of decisionmaking can be applied to work of this kind. It may be possible to generate computer solutions that are closer to the optimum than some man-made dimensioning schemes. Further work on important details is required before a commercially acceptable package could be produced.

The growth and advances made in computer technology have led to the present interest in picture processing techniques. When considering image data compression the tendency is towards trans-form source coding of the image data. This method of source coding has reached a stage where very high reductions in the number of bits representing the data can be made while still preserving image fidelity. The point has thus been reached where channel errors need to be considered, as these will be inherent in any image comnunication system. The thesis first describes general source coding of images with the emphasis almost totally on transform coding. The transform technique adopted is the Discrete Cosine Transform (DCT) which becomes common to both transform coders. Hereafter the techniques of source coding differ substantially i.e. one tech­nique involves zonal coding, the other involves threshold coding. Having outlined the theory and methods of implementation of the two source coders, their performances are then assessed first in the absence, and then in the presence, of channel errors. These tests provide a foundation on which to base methods of protection against channel errors. Six different protection schemes are then proposed. Results obtained, from each particular, combined, source and channel error protection scheme, which are described in full are then presented. Comparisons are made between each scheme and indicate the best one to use given a particular channel error rate.

No description available.

This thesis addresses the viability of automatic speech recognition for control room systems; with careful system design, automatic speech recognition (ASR) devices can be useful means for human computer interaction in specific types of task. These tasks can be defined as complex verbal activities, such as command and control, and can be paired with spatial tasks, such as monitoring, without detriment. It is suggested that ASR use be confined to routine plant operation, as opposed the critical incidents, due to possible problems of stress on the operators' speech. Some solutions to the problems of stress are given. From a series of studies, it is concluded that the interaction be designed to capitalise upon the tendency of operators to use short, succinct, and task specific styles of speech. From studies comparing different types of feedback, it is concluded that operators be given screen based feedback rather than auditory feedback. Feedback will take two forms: the use of the ASR device will require recognition feedback, which will be best supplied using text; the performance of a process control task will require feedback integrated into the mimic display. This latter feedback can be either textual or symbolic, but it is suggested that symbolic feedback will be more beneficial. Related to both interaction style and feedback is the issue of handling recognition errors. These should be corrected by simple command repetition practices, rather than use error handling dialogues. This thesis also addresses some of the problems of user error in ASR use, and provides a number of recommendations for its reduction. Before using the ASR device, new operators will require some form of training. It is shown that a demonstration by an experienced user of the device can lead to superior performance than instructions. Thus a relatively cheap and very efficient form of operator training can be supplied by demonstration by experienced ASR operators

Automated fault diagnosis in induction machines is a difficult task and normally requires background information of electrical machines. Here a different methodology to the condition monitoring problem is devised. The approach is based entirely on Digital Signal Processing (DSP) and Statistical Pattern Recognition (PR). Description of machine conditions is extracted from empirical data. The main tasks that must be carried out by a PR-based condition monitoring system are: condition identification, knowledge reinforcement and knowledge creation for previously unseen conditions. The DSP operations are employed to quickly isolate sensor faults and to remove noise using data acquired from a single channel. DSP transformations may seem promising in making the monitoring system portable. Most importantly, they can compensate for operational changes in the machine. These changes affect the supply line currents and the primary signal quantities to be measured, i.e. the current and the axial leakage flux. The data which is input to the statistical monitoring system may be transformed, in the form of features, or remain unaltered. The system exploits the statistical properties of the feature vectors. The particular features, namely the LAR coefficients, convey short-term, high-resolution spectral information. For a long record, the feature vector sequence may provide information about changes in the record spectral characteristics, with time. Many induction machine processes are stationary and they can be properly be dealt with by a simple statistical classifier, e.g. a Gaussian model. For nonstationary processes, the system may employ a more comprehensive tool, namely the Hidden Markov Model. which may track the changing behaviour of the process in question. Initially a limited number of machine conditions are available to the process engineer. By identifying their boundaries, new faulty conditions could be signalled for and adopted into the database.

No description available.

This thesis deals with the development of a microprocessor controlled CCD based camera for digital imaging of the nightglow. A brief description of the techniques used to image the nightglow is given and the reasons for choosing a CCD as the detector are discussed. The fundamentals of CCD operation are then described with particular emphasis on buried channel CCD image sensors as the P8603 CCD used in the camera is of this type. A major part of the thesis is devoted to the detailed design of the camera electronics which consists of three main sections; (i) a MC6802 based microprocessor controller with 4 K of ROM and 64 K of dynamic RAM; (ii) a display interface which allows an on-line display of the images to be produced on an oscilloscope for monitoring purposes while observing; and (iii) the CCD interface which consists of the drive pulse buffers for the image, store and readout sections of the CCD, the bias voltage generators for the CCD on-chip charge amplifier, and the signal processing electronics which has a choice of four software selectable gains and uses correlated double sampling to achieve low noise levels. The design of a digital cassette system for recording the image data is also described. The system, which is based on a low cost stereo cassette recorder, accepts and produces data in the same RS232 serial format used by the camera and is capable of operating at up to 9600 baud on two channels. A further section deals with the optical, structural and cryogenic design. This includes a description of the camera optical system which is based on a commercial FI.4 CCTV lens, theoretical calculations of the expected response of the camera to a range of nightglow emissions, the design of the liquid nitrogen cryostat which is used to cool the CCD, the design of the camera chassis, and calculations to determine (i) the CCD temperature required to reduce the dark current to an acceptable level; and (ii) the capacity of the liquid nitrogen reservoir which is necessary to allow a whole night's observing without refilling. The detailed operation of the camera control program, which is written in 6800 assembly language, is then described with the aid of flowcharts. Currently the control program is set up to give a one minute integration period using half-frame imaging and a 3 x 2 pixel amalgamation. The final section of the thesis deals with the testing and performance of the camera. Several experiments were carried out including the measurement of the various possible ampilifier gains, the noise performance of the system, the angular response of the camera optics, and the calibration of the camera using a standard light to allow the absolute intensity of nightglow emissions to be calculated. Theoretical calculations of the expected noise levels and the expected response of the camera to the standard light are also included. A suite of image processing programs, written in Pascal for an Apple II microcomputer, are then described. These programs allow various operations to be performed such as scanning the images stored on tape, and correcting for the defective columns on the CCD and the angular response of the camera optics. Lastly, the performance of the camera in the field is discussed and the results of observations made locally, which include photographs of images believed to show hydroxyl airglow structure, are presented.

No description available.

No description available.

No description available.