A multi-mode sonar transmitter

This project was initiated to evaluate appropriate microprocessor and digital logic techniques that could increase the flexibility and effectiveness of a sonar transmitter. The study led to a multi-channel signal synthesis concept designed to exploit 'phased array' steering techniques. Two versions of the equipment have now been built and evaluated. Mk.I is a relatively low power 15 channel system with 2 kilowatts total electrical power using a 40 kHz 15 λ x 1 line array. This system proved the practicability of the basic concept and its success led to the 16 kilowatt Mk2 high power version which drives a 16λ x 16 λ wideband transducer array. The study included: The design and construction of a multi-channel signal generator. The writing of control and signal synthesis software. The design, evaluation and commissioning of suitable linear power amplifiers . Investigations into suitable transducers and phased array design, leading to the manufacture of suitable matched wide band multi-channel 'staved' transducer arrays. Finally, a series of trials were made in a variety of open water conditions to evaluate the systems performance and investigate the multiple modes of operation that have been developed. The system has successfully demonstrated that transmitter beam steering is both practical and flexible. The techniques implemented permit sector interrogation by 'within-pulse' type sweeps, by 'Ripple-fire' and by transmitting steered 'Pings' sequentially on prededermined bearings. Each mode allows considerable flexibility in the generated waveform shape and frequency. The 'Multi-Mode' capability of this approach was conceived primarily as a research tool but many of the modes can be isolated and exploited in dedicated applications

Measuring Complexity and Stability of Web Programs�

Software maintenance engineers spend at least half of their time trying to understand the system they are to modify. This is due partially to the fact that often the only documentation available is the source code itself. The literate programming paradigm provides the incentive and the capability to produce high quality documentation and code simultaneously. The goal is to create "works of literature" which have all the extras (table of contents, cross references, and indices) to help readers to comprehend the programs quickly and thoroughly. The purpose of this thesis is to explore the similarities and differences in measurements of complexity and stability of literate programs compared to those of traditionally developed code.Computer Scienc

An annotated and classified bibliography of software metrics publications : 1988 to 1994

With the growth of the software industry, the measurement of software plays an ever increasing role. In order to provide software metric researchers and practitioners with references so they can quickly identify the references of particular interest to them, over 60 of the many publications on software metrics that have appeared since 1988 are classified into four tables that comprise, respectively, (1) Metrics through the Life Cycle, (2) Classic Metrics, (3) Programming Language Metrics, and (4) New Metrics. Table 1 serves as a complete list of all the classified publications while Table 2, Table 3 and Table 4 are subsets of Table 1. The subset tables present more detailed information than Table 1. The bibliographic reference section contains brief summaries of the publications in the classified tables. As a continuation of the 1988 survey done by V. Cote, P. Bourque, S. Oligny and N. Rivard through the paper, "Software metrics: an overview of recent results", this project was conducted to discover the current trends in software metrics practice, and to report the trend movement from the 1988 paper until now by comparison of the results from the two surveys. All the table comparisons from the two surveys are given in percentages. As a survey, we are fully aware of the limitations of our collection out of the wealth of the publications in the software metrics field, but we are confident that our survey is a good indicator of the practice in the software metrics field. [Résumé abrégé par UMI]

Brexit Dilemmas: Shaping Postwithdrawal Relations with a Leaving State

How do voters want their governments to respond when another country unilaterally withdraws from an international institution? We distinguish between negotiation approaches that vary in the degree to which they accommodate the withdrawing state's demands and argue that negotiation preferences are shaped by two issues. The first is voters’ exposure to the costs and benefits of accommodation. This exposure varies across issues, and we argue that citizens will generally prefer non-accommodation on zero-sum issues, but support more accommodation on cooperation issues, where non-accommodation puts existing cooperation gains at risk. Second, withdrawal negotiations create precedents, and citizens should therefore be less willing to accommodate the more they are concerned about the ripple effects of accommodation on the institution's stability. These concerns also confront citizens with two types of dilemmas depending on how favorably they view the institution themselves. To test our argument, we use survey evidence and a conjoint experiment conducted in Germany and Spain during the Brexit negotiations. We find that respondents overall are more willing to accommodate the UK on cooperation issues than on zero-sum issues, but also find evidence that Euroskeptics and Europhiles confront different issue-specific dilemmas. Our paper contributes to a better understanding of the dynamics surrounding the challenges to multilateralism that have proliferated in recent years

Excimer-laser-induced modifications of optical surfaces

The work in this thesis is a study of the interactions of a well characterized high power ultra violet excimer laser beam with solid optical quality surfaces, principally Al and Ge but with limited work on dielectrics. In order to characterize the beam and to monitor the changes induced on test surfaces by the beam, a computer controlled image processing system was developed. The system used the fluorescence from a UV absorbing glass to image the excimer beam and Schlieren imaging of the test surfaces with cw HeNe or pulsed dye laser illumination to monitor the induced changes. [Continues.

Enhancing the Impact of Cross-Sector Partnerships. Four Impact Loops for Channeling Partnership Studies

This paper addresses the topic of this special symposium issue: how to enhance the impact of cross-sector partnerships. The paper takes stock of two related discussions: the discourse in cross-sector partnership research on how to assess impact and the discourse in impact assessment research on how to deal with more complex organizations and projects. We argue that there is growing need and recognition for cross-fertilization between the two areas. Cross-sector partnerships are reaching a paradigmatic status in society, but both research and practice need more thorough evidence of their impacts and of the conditions under which these impacts can be enhanced. This paper develops a framework that should enable a constructive interchange between the two research areas, while also framing existing research into more precise categories that can lead to knowledge accumulation. We address the preconditions for such a framework and discuss how the constituent parts of this framework interact. We distinguish four different pathways or impact loops that refer to four distinct orders of impact. The paper concludes by applying these insights to the four papers included in this special issue

ON THE ECONOMICS OF THE-SOFTWARE REPLACEMENT PROBLEM

Software maintenance constitutes a significant fraction of the software budget. The cost of maintaining old applications has been escalating and this trend is likely to continue in the foreseeable future. The study of software maintenance strategies has become important to both researchers and practitioners in Information Systems. While there is a rich literature on the technical aspects of software maintenance, research on the economics of maintenance is in its infancy. In particular, the tradeoffs between maintaining and rewriting old software have not been investigated from a theoretical standpoint. In this paper, we present an economic model of the software replacement problem. Based on available empirical evidence, we hypothesize that, with frequent modifications and enhancements, the complexity of software increases rapidly. This deterioration of the code leads to a sharp increase in the maintenance cost. Thus, there may exist a time when it is optimal (in an economic sense) to rewrite the system, which reduces the system complexity and the subsequent maintenance cost. The proposed model allows us to compare the economics of various rewriting strategies and to determine the optimal rewriting point(s). Some interesting results with implications for the systems manager are obtained from the analysis. These include the impacts of system size, structuredness of the underlying technology, and the availability of superior technologies upon the rewriting point(s) and life cycle costs. A numerical example is provided to demonstrate the applicability of the model

Design and control of a synchronous reluctance machine drive

This thesis investigates the design, performance and control of a synchronous reluctance machine (Synchrel) drive. The Synchrel machine is proposed for variable speed drives because of its advantages over other machines. The rotor has no cage winding, brushes or slip rings. The torque ripple levels are lower in the Synchrel machine than the switched reluctance machine as it operates from a standard sine wave supply. An axially laminated rotor was designed based on finite element analysis, with the aim of producing the same output power as obtained from an induction motor (M) with a similar stator. Using vector control, the developed torque is controlled by regulating the stator current vector. Two vector control schemes are used, maximum torque per ampere and constant current in the direct axis. The output torque characteristics of the machine have been confirmed by finite element analysis. Slotine's approach of sliding mode control is used for position control of the vector controlled synchronous reluctance machine. A comparison is undertaken between the performance of a fixed gain controller with two sliding mode controllers, for both the regulator and servo cases. Invariant performance is obtained using Slotine's sliding mode control approach, unlike with a fixed gain controller. Robustness to parameter variation is an important feature of this technique. This robustness can be achieved through the control law design, assuming parameter variation bounds are known. These improvements are demonstrated for variations in load inertia. Inductance ripple affects machine performance, for example decreasing output torque and increasing core losses. A state space model for the machine that incorporates this inductance effect, yields drive simulation results that agree with experimental results