Semantics, Implementation and Pragmatics of Clear, a Program Specification Language

Specifications are necessary for communicating decisions and intentions and for documenting results at many stages of the program development process. Informal specifications are typically used today, but they are imprecise and often ambiguous. Formal specifications are precise and exact but are more difficult to write and understand. We present work aimed toward enabling the practical use of formal specifications in program development, concentrating on the Clear language for structured algebraic specification. Two different but equivalent denotational semantics for Clear are given. One is a version of a semantics due to Burstall and Goguen with a few corrections, in which the category-theoretic notion of a colimit is used to define Clear's structuring operations independently of the underlying 'institution' (logical formalism). The other semantics defines the same operations by means of straightforward set-theoretic constructions; it is not institutionindependent but it can be modified to handle all institutions of apparent interest. Both versions of the semantics have been implemented. The settheoretic implementation is by far the more useful of the two, and includes a parser and typechecker. An implementation is useful for detecting syntax and type errors in specifications, and can be used as a front end for systems which manipulate specifications. Several large specifications which have been processed by the set-theoretic implementation are presented. A semi-automatic theorem prover for Clear built on top of the Edinburgh LCF system is described. It takes advantage of the structure of Clear specifications to restrict the available information to that which seems relevant to proving the theorem at hand. If the system is unable to prove a theorem automatically the user can attempt the proof interactively using the high-level primitives and inference rules provided. We lay a theoretical foundation for the use of Clear in systematic program development by investigating a new notion of the implementation of a specification by a lower-level specification. This notion extends to handle parameterised specifications. We show that this implementation relation is transitive and commutes with Clear's structuring operations under certain conditions. This means that a large specification can be refined to a program in a gradual and modular fashion, where the correctness of the individual refinements guarantees the correctness of the resulting program

Performance analysis of text-oriented printing using PostScript

POSTSCRIPT is a page description language which is used to transmit printing information from a host computer (i.e. Apple Macintosh) to a printer (i.e. Apple LaserWriter Plus). It has the ability to describe pages consisting of text, vector graphics, and scanned bit-map images. Printing text is the area of concentration for this thesis. Specifically several variables that affect the printing speed of a common POSTSCRIPT printer, the Apple LaserWriter Plus, are looked at when printing text in a variety of fonts, sizes, and orientations. The variables that affect printer performance include: - use of outline vs. bit-map fonts; - the outline font rasterization process; - the use of pre-cached bit-map fonts; - background outline font rasterization; - arbitrary scaling and rotation; - downloading host-resident fonts; - Adobe and Third Party host-resident downloadable fonts vs. printer-resident fonts; - Appletalk vs. RS-232 communications interfaces; - use of the POSTSCRIPT show, ashow, and widthshow instructions; - targeting the POSTSCRIPT instructions at a particular engine resolution; - print engine overhead A sequence of POSTSCRIPT files were transmitted to the Apple LaserWriter Plus printer. The experiments were carefully constructed to exercize each of the variables listed above. Performance measurements were carefully recorded and analyzed. Where applicable, improvements were proposed to improve printer performance

Nonlinear buckling of delaminated panels

Laminated structures have increasingly gained popularity in engineering applications owing to their advantageous properties. Particularly in aerospace applications, laminated components, typically comprising fibre-reinforced composites, have a soaring demand owing to their high strength to weight ratio. However, owing to the complex nature of the material, several different failure mechanisms may occur; amongst them is delamination, i.e. the separation at the interface between two laminates. This defect is often difficult to detect, yet may significantly reduce a component's load carrying capacity and subsequently may severely affect its safe working conditions. It is therefore of utmost importance to assess the effects of delaminations on the structural elements carefully. Since components in aerospace applications often comprise laminated panels, a geometrically nonlinear plate delamination model is derived analytically by extending a previously developed two-layer strut model. This type of structural component is commonly analysed as an engineering simplification since at plates are often used as an archetype to simplify more complex structural forms. Thus, an isotropic plate is currently considered, which re ects the simplest constitutive behaviour, and it can represent to some extent the behaviour of a laminated composite that has a uniform or symmetric lay-up sequence. A rectangular defect is located in the centre of this uniformly compressed, isotropic rectangular plated panel representing the delamination. Whilst trigonometric out-of-plane displacement functions are used in a Rayleigh{Ritz procedure yielding the governing equations that describe the mechanical behaviour of the plate, in-plane deformations are obtained via von Karman's compatibility equation. An indication of the residual capacity of the panel after critical buckling is obtained by investigating the nonlinear postbuckling range, where delamination propagation is incorporated by introducing a discrete cohesive zone model at the boundaries of the delaminated region. Different configurations are investigated in the neighbourhood of the previously evaluated transitional depth of delamination, which constitutes the boundary between local and global buckling. Initially, a uniformly spreading defect is investigated for various different defect sizes and depths. Subsequently, geometric parameters are linked to the response of the panel to generalize the outcomes with quantitative comparisons being undertaken against previous results and those obtained with the commercial nite element software ABAQUS. It is found that the model compares well and several criteria for the initial design of the damaged panels are proposed such that delamination growth may be accommodated safely and e ciently. Furthermore, uni-directional growth of the delamination is considered in a pilot study with suggestions being made regarding the growth direction tendency

Proceedings of the 26th International Symposium on Theoretical Aspects of Computer Science (STACS'09)

The Symposium on Theoretical Aspects of Computer Science (STACS) is held alternately in France and in Germany. The conference of February 26-28, 2009, held in Freiburg, is the 26th in this series. Previous meetings took place in Paris (1984), Saarbr¨ucken (1985), Orsay (1986), Passau (1987), Bordeaux (1988), Paderborn (1989), Rouen (1990), Hamburg (1991), Cachan (1992), W¨urzburg (1993), Caen (1994), M¨unchen (1995), Grenoble (1996), L¨ubeck (1997), Paris (1998), Trier (1999), Lille (2000), Dresden (2001), Antibes (2002), Berlin (2003), Montpellier (2004), Stuttgart (2005), Marseille (2006), Aachen (2007), and Bordeaux (2008). ..

Classroom Façade Design for Daylighting in a Tropical Hot-humid Climate

Previous studies have confirmed that the learning performance of school students can improve when good levels of daylight are available in classrooms. In tropical climates, it might be difficult to utilise and control natural light due to its high levels. Various activities in classrooms, such as taking notes and viewing screens and whiteboard, can also become difficult. Consequently, daylight in tropical classrooms may be less welcome and utilised less frequently. In order to deal with natural light utilisation, building facade is one of significant architectural design elements influencing energy consumption and human comfort. This study aims to investigate classroom facade designs that attempt to optimise visual and thermal comfort while reducing energy consumption. Focusing on facade appearance, daylighting systems and occupants’ behaviour, there are three stages of study using occupants and classrooms in the Faculty of Architecture, Urban Design and Creative Arts, Mahasarakham University, Thailand as the case study. The research commenced the first stage with finding the actual problems of daylight utilisation in tropical classrooms in terms of room form, brightness levels, and users’ behaviours and attitudes. In order to study brightness pattern and human sensation several survey methods: illumination measurements, observations, questionnaires and interviews; were applied. In the second stage, computer simulation was undertaken in order to analyse the problems and suggest solutions using DesignBuilder package. The suggestions were verified in the last stage by surveying occupants’ satisfaction comparing the modified classroom to the existing classrooms. The measurements and surveys demonstrated availability of the daylight and positive attitude in using natural light of the occupants whereas façade and systems are not appropriated for applying natural light: provided insufficient daylight level and allowed occurrence of glare. Daylight environment appeared to proper for general visual tasks while more control was required for using projector. The simulation result showed the significance of window area, shading device and window orientation respectively. The use of two opposite fully glazed walls with shading depth of 50% of optimised device is recommended for all orientations. The suggested size of shading device usually allowed penetration of the sun into the classroom. The influence of direct sun which theoretically could be a serious problem was confirmed acceptable by occupants. It implies that direct sunlight can rather be a daylighting opportunity if correct shading design is applied. A limitation of this research is that, although the DesignBuilder package can facilitate study in both daylighting and thermal aspects, its daylighting analysis function has limit capacity for light reflected strategies. Results of this research are recommendations of facade characteristics and their operation systems which are suitable for the case study. The visually environmental improvement of one specific building which can be adapted for general classrooms and other types of low maintenance buildings. Moreover, research findings can be extended to be public guidelines for designers in their approach to sustainability

Stand-up as interaction : performance and audience in comedy venues

This thesis explores stand-up comedy as live performance focusing on the manner in which audience, performer, jokes and venue combine to make a unique interactiveexperience. It outlines the failure of previous literature in humour research to move beyond simple stimulus models of joking and laughter. It argues for a shift in the study of humour towards in situ observation which draws on both conversation analysis and audience research. Through the observation of stand-up interaction the thesis demonstrates that audience laughter is organised in a consistent fashion and that the transition between comedian's talk and audience laughter is socially organised. In turn the thesis examines the openings, middles and closings of standup routines. It demonstrates that despite a considerable variety of performance style,comperes' introductions, the commencement of the comedians' routines themselves and the closing of acts, are organised around a set of common features each with a preferred order. Further, it demonstrates the active role played by the audience as well as the performer in maintaining this ordering. It shows how a feeling of"liveness" is built up out of these sequences as they are constructed specifically for,and respond to, individual audiences. Looking at the central section of stand-uproutines this work demonstrates how jokes told by comedians incorporate a series of rhetorical and performance specific techniques which work towards announcing to an audience that a point of completion is approaching and that laughter is the preferred response. It is argued that this serves to minimise the audience's risk in laughing in a group situation and so is beneficial for both performer and audience. A new system for understanding stand-up is presented which pivots on notions of performance, interaction and liveness