Browsing by Issue Date, starting with "2004-07"
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- Using system dynamics and multicriteria analysis for performance management: a case studyPublication . Santos, Sérgio Pereira dos; Belton, Valerie; Howick, Susan; Neely, A.; Kennerley, M.; Walters, A.The case study described in this paper aims to illustrate how qualitative and quantitative system dynamics modelling and multicriteria analysis can be used in an integrated way to enhance the process of performance measurement and management in the radiotherapy department of a major UK cancer treatment centre. The complexity of the radiotherapy process, which is used for both radical and palliative treatments, and its significance for patients, present particular challenges for performance measurement and management. The paper will discuss the benefits arising and the practical difficulties faced in the study.
- An efficient parallel collision detection algorithm for virtual prototype environmentsPublication . Figueiredo, Mauro; Terrence, FernandoThe automatic recognition of geometric constraints in virtual assembly and maintenance operations relies in the determination of intersecting surfaces between virtual prototypes. This is a key challenge in many virtual prototype applications, where it is necessary to find collisions precisely and interactively. This paper presents a novel algorithm to determine intersecting surfaces at interactive speed in a virtual prototyping environment. The proposed algorithm is based on the Overlapping AxisAligned Bounding Box (OAABB). The OAABB concept is used effectively to eliminate the number of surfaces that cannot intersect and improve performance. The algorithm also facilitates the implementation using parallel computing methods. OpenMP is used, taking advantage of shared memory multiple processors and reducing the overall time complexity of the collision detection algorithm. To achieve an efficient parallel simulation, it is necessary to provide an efficient load balancing scheme. Our experiences in parallelising the code to achieve a better work distribution are also described. Results show that the proposed collision detection achieves interactive rates in real industrial applications as desired.
- Modelos de avaliação de hipotecas: uma revisão de literaturaPublication . Viegas, Cristina; Pereira, José AzevedoEste artigo analisa os modelos de avaliação de activos hipotecários baseados na técnica de análise de fluxos contingentes. Trata-se de modelos que tendem a considerar duas fontes de incerteza: o risco de taxa de juro e o risco de incumprimento. Tal facto permite-lhes incorporar, em simultâneo, o efeito induzido pela opção de compra americana inerente à possibilidade detida pelo devedor de terminar o contrato antecipadamente, mediante o pagamento do empréstimo, e o efeito induzido pela opção de venda, que corresponde à possibilidade de incumprimento, também detida pelo devedor. A coexistência de ambas as opções e das correspondentes fontes de risco tende a dificultar significativamente o desenvolvimento dos respectivos modelos de avaliação. Esta área de investigação tem sido marcada durante os últimos anos pela emergência de modelos de avaliação mais sofisticados e aproximados da realidade, que tomam em consideração outros aspectos capazes de influenciar a decisão de antecipar o pagamento ou de incumprir, tais como os custos de transacção e outras motivações de natureza não puramente financeira.