9 resultados para Specification searching

em Aston University Research Archive


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This study examines the forecasting accuracy of alternative vector autoregressive models each in a seven-variable system that comprises in turn of daily, weekly and monthly foreign exchange (FX) spot rates. The vector autoregressions (VARs) are in non-stationary, stationary and error-correction forms and are estimated using OLS. The imposition of Bayesian priors in the OLS estimations also allowed us to obtain another set of results. We find that there is some tendency for the Bayesian estimation method to generate superior forecast measures relatively to the OLS method. This result holds whether or not the data sets contain outliers. Also, the best forecasts under the non-stationary specification outperformed those of the stationary and error-correction specifications, particularly at long forecast horizons, while the best forecasts under the stationary and error-correction specifications are generally similar. The findings for the OLS forecasts are consistent with recent simulation results. The predictive ability of the VARs is very weak.

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This paper reports ongoing work that is attempting to find out ‘what is good practice for knowledge management’. The data we have to analyse this issue is 109 maps of knowledge (on knowledge management) which were built during 18 group workshops with 152 people from 15 different organisations. The maps contain data on the aspirations and action plans which UK managers have to improve knowledge management practices in their organisation. So far we have attempted a number of approaches to analysing this data, both inductive and deductive, but we still feel there is more to be learned from the rich data set we have. The paper presents a flavour of the work we have done, have considered doing, and have resisted doing. The aim of the paper is to stimulate debate on the strengths of our analyses and, more importantly, on amassing views of how it can be further strengthened, and the difficulties and dilemmas which might need to be overcome.

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Investment in capacity expansion remains one of the most critical decisions for a manufacturing organisation with global production facilities. Multiple factors need to be considered making the decision process very complex. The purpose of this paper is to establish the state-of-the-art in multi-factor models for capacity expansion of manufacturing plants within a corporation. The research programme consisting of an extensive literature review and a structured assessment of the strengths and weaknesses of the current research is presented. The study found that there is a wealth of mathematical multi-factor models for evaluating capacity expansion decisions however no single contribution captures all the different facets of the problem.

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The purpose of this research has been to investigate the extent to which Lean techniques have been applied to indirect or White Collar activities within manufacturing operations. The work has been based on a systematic review of the literature and six UK based case studies. Both are described in the paper. The findings from this work include, for example, that there are few reports off the application of Lean in this context. The more substantive papers focus on NPI and Project Management, where as, Support and ‘Front Office’ activities are covered only briefly in ‘trade journal’ articles. These do demonstrate that Lean techniques can be applied successfully to non-production related activities, and there are significant opportunities for work in this area. However, the definition of Lean is evolving and practitioners do not share a common understanding of terminology. This may undermine their accuracy when reporting the application of Lean techniques.

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Self-adaptive systems have the capability to autonomously modify their behaviour at run-time in response to changes in their environment. Self-adaptation is particularly necessary for applications that must run continuously, even under adverse conditions and changing requirements; sample domains include automotive systems, telecommunications, and environmental monitoring systems. While a few techniques have been developed to support the monitoring and analysis of requirements for adaptive systems, limited attention has been paid to the actual creation and specification of requirements of self-adaptive systems. As a result, self-adaptivity is often constructed in an ad-hoc manner. In this paper, we argue that a more rigorous treatment of requirements explicitly relating to self-adaptivity is needed and that, in particular, requirements languages for self-adaptive systems should include explicit constructs for specifying and dealing with the uncertainty inherent in self-adaptive systems. We present RELAX, a new requirements language for selfadaptive systems and illustrate it using examples from the smart home domain. © 2009 IEEE.

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Resilience is a term that is gaining currency in conservation and sustainable development, though its meaning and value in this context is yet to be defined. Searching for Resilience in Sustainable Development examines ways in which resilience may be created within the web of ecological, socio-economic and cultural systems that make up the world in. The authors embark upon a learning journey exploring both robust and fragile systems and asking questions of groups and individuals actively involved in building or maintaining resilience.

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Cloud computing is a new technological paradigm offering computing infrastructure, software and platforms as a pay-as-you-go, subscription-based service. Many potential customers of cloud services require essential cost assessments to be undertaken before transitioning to the cloud. Current assessment techniques are imprecise as they rely on simplified specifications of resource requirements that fail to account for probabilistic variations in usage. In this paper, we address these problems and propose a new probabilistic pattern modelling (PPM) approach to cloud costing and resource usage verification. Our approach is based on a concise expression of probabilistic resource usage patterns translated to Markov decision processes (MDPs). Key costing and usage queries are identified and expressed in a probabilistic variant of temporal logic and calculated to a high degree of precision using quantitative verification techniques. The PPM cost assessment approach has been implemented as a Java library and validated with a case study and scalability experiments. © 2012 Springer-Verlag Berlin Heidelberg.