Proving Temporal Properties of Z Specifications Using Abstraction

This paper presents a systematic approach to proving temporal properties of arbitrary Z specifications. The approach involves (i) transforming the Z specification to an abstract temporal structure (or state transition system), (ii) applying a model checker to the temporal structure, (iii) determining whether the temporal structure is too abstract based on the model checking result and (iv) refining the temporal structure where necessary. The approach is based on existing work from the model checking literature, adapting it to Z.

Thermal/mechanical simulation and laboratory fatigue testing of an alternative yttria tetragonal zirconia polycrystal core-veneer all-ceramic layered crown design

This study evaluated the stress levels at the core layer and the veneer layer of zirconia crowns (comprising an alternative core design vs. a standard core design) under mechanical/thermal simulation, and subjected simulated models to laboratory mouth-motion fatigue. The dimensions of a mandibular first molar were imported into computer-aided design (CAD) software and a tooth preparation was modeled. A crown was designed using the space between the original tooth and the prepared tooth. The alternative core presented an additional lingual shoulder that lowered the veneer bulk of the cusps. Finite element analyses evaluated the residual maximum principal stresses fields at the core and veneer of both designs under loading and when cooled from 900 degrees C to 25 degrees C. Crowns were fabricated and mouth-motion fatigued, generating master Weibull curves and reliability data. Thermal modeling showed low residual stress fields throughout the bulk of the cusps for both groups. Mechanical simulation depicted a shift in stress levels to the core of the alternative design compared with the standard design. Significantly higher reliability was found for the alternative core. Regardless of the alternative configuration, thermal and mechanical computer simulations showed stress in the alternative core design comparable and higher to that of the standard configuration, respectively. Such a mechanical scenario probably led to the higher reliability of the alternative design under fatigue.

Lattice-dome design using a knowledge-based system approach

In the design of lattice domes, design engineers need expertise in areas such as configuration processing, nonlinear analysis, and optimization. These are extensive numerical, iterative, and lime-consuming processes that are prone to error without an integrated design tool. This article presents the application of a knowledge-based system in solving lattice-dome design problems. An operational prototype knowledge-based system, LADOME, has been developed by employing the combined knowledge representation approach, which uses rules, procedural methods, and an object-oriented blackboard concept. The system's objective is to assist engineers in lattice-dome design by integrating all design tasks into a single computer-aided environment with implementation of the knowledge-based system approach. For system verification, results from design examples are presented.

Specification, refinement and verification of concurrent systems - An integration of Object-Z and CSP

This paper presents a method of formally specifying, refining and verifying concurrent systems which uses the object-oriented state-based specification language Object-Z together with the process algebra CSP. Object-Z provides a convenient way of modelling complex data structures needed to define the component processes of such systems, and CSP enables the concise specification of process interactions. The basis of the integration is a semantics of Object-Z classes identical to that of CSP processes. This allows classes specified in Object-Z to he used directly within the CSP part of the specification. In addition to specification, we also discuss refinement and verification in this model. The common semantic basis enables a unified method of refinement to be used, based upon CSP refinement. To enable state-based techniques to be used fur the Object-Z components of a specification we develop state-based refinement relations which are sound and complete with respect to CSP refinement. In addition, a verification method for static and dynamic properties is presented. The method allows us to verify properties of the CSP system specification in terms of its component Object-Z classes by using the laws of the the CSP operators together with the logic for Object-Z.

A formal model of real-time program compilation

Program compilation can be formally defined as a sequence of equivalence-preserving transformations, or refinements, from high-level language programs to assembler code, Recent models also incorporate timing properties, but the resulting formalisms are intimidatingly complex. Here we take advantage of a new, simple model of real-time refinement, based on predicate transformer semantics, to present a straightforward compilation formalism that incorporates real-time constraints. (C) 2002 Elsevier Science B.V. All rights reserved.

Development of a generic crop model template in the cropping system model APSIM

The Agricultural Production Systems slMulator, APSIM, is a cropping system modelling environment that simulates the dynamics of soil-plant-management interactions within a single crop or a cropping system. Adaptation of previously developed crop models has resulted in multiple crop modules in APSIM, which have low scientific transparency and code efficiency. A generic crop model template (GCROP) has been developed to capture unifying physiological principles across crops (plant types) and to provide modular and efficient code for crop modelling. It comprises a standard crop interface to the APSIM engine, a generic crop model structure, a crop process library, and well-structured crop parameter files. The process library contains the major science underpinning the crop models and incorporates generic routines based on physiological principles for growth and development processes that are common across crops. It allows APSIM to simulate different crops using the same set of computer code. The generic model structure and parameter files provide an easy way to test, modify, exchange and compare modelling approaches at process level without necessitating changes in the code. The standard interface generalises the model inputs and outputs, and utilises a standard protocol to communicate with other APSIM modules through the APSIM engine. The crop template serves as a convenient means to test new insights and compare approaches to component modelling, while maintaining a focus on predictive capability. This paper describes and discusses the scientific basis, the design, implementation and future development of the crop template in APSIM. On this basis, we argue that the combination of good software engineering with sound crop science can enhance the rate of advance in crop modelling. Crown Copyright (C) 2002 Published by Elsevier Science B.V. All rights reserved.

Desenvolvimento e implanta????o do sistema Sancad

Recentemente, a expans??o do n??mero de munic??pios conveniados com a FNS fez aumentar a demanda por novos projetos de melhoria dos sistemas de ??gua e esgotos. Ao mesmo tempo, a FNS enfrentava car??ncia de pessoal t??cnico especializado, dificuldades de admiss??o de novos profissionais e limita????o de recursos para a contrata????o de projetos atrav??s de empresas privadas, inviabilizando o atendimento das demandas pela forma tradicional. Diante disso, servidores da FNS desenvolveram um software para projetos de redes de esgotos sanit??rios, utilizando os recursos modernos da computa????o gr??fica (CAD ??? Computer Aided Design). Acoplado ao CAD, prop??s-se a cria????o de um m??dulo de dimensionamento, resultando numa ferramenta completa de elabora????o de projetos, em ambiente computacional Windows, contemplando as v??rias etapas t??picas de um trabalho na ??rea, desde a digitaliza????o do levantamento topogr??fico, lan??amento da rede, c??lculos, planilhas, desenho e montagem final das pranchas geradas. Este sistema foi denominado Sancad. A utiliza????o do Sancad permitiu uma redu????o m??dia de 60 a 70% no tempo de elabora????o de projetos, significando uma forma de atender a um n??mero maior de demandas e de suprir a car??ncia de profissionais na FNS. Al??m disso, a utiliza????o do Sancad tem mostrado ganhos em termos de qualidade, corre????o e confiabilidade do produto final obtido. As previs??es iniciais quanto ?? abrang??ncia de utiliza????o do Sancad foram amplamente superadas, tendo o mesmo se tornado um padr??o para a ??rea de projetos de saneamento da FNS, estando instalado em 12 unidades da Funda????o em todo o Brasil e em processo de instala????o em outras. O Sancad tornou-se objeto de interesse de t??cnicos de saneamento e de estudantes de engenharia e arquitetura de institui????es p??blicas e privadas, que receberam treinamento a fim de conhec??-lo e utiliz??-lo. Finalmente, o sucesso da experi??ncia tem contribu??do para a dissemina????o da cultura de computa????o gr??fica e a ades??o dos profissionais da FNS e das autarquias municipais conveniadas ?? nova tecnologia. Neste mesmo sentido, ressalta-se a utiliza????o de teodolitos eletr??nicos ??? conhecidos como Esta????o Total ??? para a gera????o de plantas topogr??ficas j?? em formato digital, para serem usadas pelo Sancad, com novos ganhos de qualidade e produtividade na elabora????o dos projetos de saneamento