A CSP Approach to Action Systems

The communicating sequential processes (CSP) formalism, introduced by Hoare, is an event-based approach to distributed computing. The action-system formalism, introduced by Back & Kurki-Suonio, is a state-based approach to distributed computing. Using weakest-precondition formulae, Morgan has defined a correspondence between action systems and the failures-divergences model for CSP. Simulation is a proof technique for showing refinement of action systems. Using the correspondence of Morgan, Woodcock & Morgan have shown that simulation is sound and complete in the CSP failures-divergences model. In this thesis, Morgan's correspondence is extended to the CSP infinite- traces model in order to deal more properly with unbounded nondeterminism. It is shown that simulation is sound in the infinite-traces model, though completeness is lost in certain cases. The new correspondence is then extended to include a notion of internal action. This allows the definition of a hiding operator for action systems that is shown to correspond to the CSP hiding operator. Rules for simulation steps involving internal actions are developed. A parallel operator for action systems is defined, in which interaction is based on synchronisation over shared actions. This operator is shown to correspond to the CSP parallel operator. The correspondence between action systems and CSP is extended again so that actions may have input and output parameters. This allows parallel action- systems to pass values on synchronisation. The original motivation for the work described in this thesis was the use of the action system formalism in the development of telecommunications systems, where interaction is often based on synchronised value-passing. The techniques developed here are applied to a series of case studies involving telecommunications-type systems. The techniques are used to refine and decompose abstract specifications of these systems into parallel sub-systems that interact via synchronised value-passing

Implementation of quality management in the public sector versus the private sector: a cultural analysis

This thesis reviews the Total Quality Management (TQM) literature and concludes that core to the introduction of TQM in any organisation is a need to be acutely sensitive to the cultural aspects of the organisation. This thesis proceeds to review the Organisational Culture literature and concludes that culture can be measured and changed. It also identifies four factors of Organisational Culture which facilitate measurement of the concept. As the research programme is situated in the public sector the thesis considers the very different and indeed opposing views regarding the development of the public sector and concludes, that irrespective of the strategy used, that the human factor is a key area in public sector reform. This people focus requires culture change and time to implement. The methodology employed to measure and compare organisational culture in both private and public sector organizations at two different times in the quality journey was primarily positivist and quantitative. Cartwright’s 9-dimension culture questionnaire was employed to capture the human facets of organisational culture. The results indicate a significant difference in culture between the private and public sectors at both times but that the variation in culture had reduced during the time interval between the two surveys. The implications of this study will assist in the understanding of organisational culture particularly in the public sector. Due to the shortage of research in this sector the results will assist in the development of public sector reform or modernisation programmes

Spiny lobster recruitment in South Florida: quantitative experiments and management implications

Understanding recruitment and identifying factors critical to that process are imperative if adult spiny lobster Panulirus argus stocks are to be conserved and properly managed. The goal of our research has been to obtain ecological information linking inshore postlarval spiny lobster recruitment to later life stages, thereby providing the basic framework for assessing and predicting adult stock. Since 1983, we have investigated various aspects of spiny lobster recruitment including: postlarval time-to-metamorphosis, postlarval/juvenile habitat selection and selection cues, postlarval/juvenile crypticity and susceptibility to predation, juvenile food preference and emigration, juvenile sociality, and the effect of habitat degradation (i.e., siltration) on postlarval/juvenile habitat selection and mortality. From this research we have established many of the basic biological and ecological determinants of the so-called missing stage of the spiny lobster (i.e., settlement through first 3-4 months of benthic life). Currently, we are conducting quantitative field experiments evaluating: 1. The relationship between surface collector catch (a standard measure of recruitment), postlarval settlement in algal clumps, and benthic juvenile abundance, and 2. The relative importance of settlement versus habitat carrying capacity in determining local lobster abundances. This research is ongoing, but preliminary results suggest that in Florida Bay: 1. Settlement is patchy and highest near the keys 2. Surface collectors are poor indicators of local settlement or recruitment 3. Suitable Habitat may Limit recruitment to the postalgal juvenile stage more than settlement

Updated opacities from the opacity project

Using the code autostructure, extensive calculations of inner-shell atomic data have been made for the chemical elements He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Cr, Mn, Fe and Ni. The results are used to obtain updated opacities from the Opacity Project (OP). A number of other improvements on earlier work have also been included. Rosseland-mean opacities from the OP are compared with those from OPAL. Differences of 5-10 per cent occur. The OP gives the 'Z-bump', at log(T) 5.2, to be shifted to slightly higher temperatures. The opacities from the OP, as functions of temperature and density, are smoother than those from OPAL. The accuracy of the integrations used to obtain mean opacities can depend on the frequency mesh used. Tests involving variation of the numbers of frequency points show that for typical chemical mixtures the OP integrations are numerically correct to within 0.1 per cent. The accuracy of the interpolations used to obtain mean opacities for any required values of temperature and density depends on the temperature-density meshes used. Extensive tests show that, for all cases of practical interest, the OP interpolations give results correct to better than 1 per cent. Prior to a number of recent investigations which have indicated a need for downward revisions in the solar abundances of oxygen and other elements, there was good agreement between properties of the Sun deduced from helioseismology and from stellar evolution models calculated using OPAL opacities. The revisions destroy that agreement. In a recent paper, Bahcall et al. argue that the agreement would be restored if opacities for the regions of the Sun with 2 × 106T 5 × 106 K (0.7-0.4 R) were larger than those given by OPAL by about 10 per cent. In the region concerned, the present results from the OP do not differ from those of OPAL by more than 2.5 per cent

Two Nucleons on a Lattice

The two-nucleon sector is near an infrared fixed point of QCD and as a result the S-wave scattering lengths are unnaturally large compared to the effective ranges and shape parameters. It is usually assumed that a lattice QCD simulation of the two-nucleon sector will require a lattice that is much larger than the scattering lengths in order to extract quantitative information. In this paper we point out that this does not have to be the case: lattice QCD simulations on much smaller lattices will produce rigorous results for nuclear physics.Comment: 13 pages, 6 figure

A Calculus for Orchestration of Web Services

We introduce COWS (Calculus for Orchestration of Web Services), a new foundational language for SOC whose design has been influenced by WS-BPEL, the de facto standard language for orchestration of web services. COWS combines in an original way a number of ingredients borrowed from well-known process calculi, e.g. asynchronous communication, polyadic synchronization, pattern matching, protection, delimited receiving and killing activities, while resulting different from any of them. Several examples illustrates COWS peculiarities and show its expressiveness both for modelling imperative and orchestration constructs, e.g. web services, flow graphs, fault and compensation handlers, and for encoding other process and orchestration languages