820 resultados para Risk assessment Mathematical models


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Computer based mathematical models describing the aircraft evacuation process have a vital role to play in the design and development of safer aircraft, the implementation of safer and more rigorous certification criteria, in cabin crew training and post-mortem accident investigation. As the risk of personal injury and the costs involved in performing full-scale certification trials are high, the development and use of these evacuation modelling tools are essential. Furthermore, evacuation models provide insight into the evacuation process that is impossible to derive from a single certification trial. The airEXODUS evacuation model has been under development since 1989 with support from the UK CAA and the aviation industry. In addition to describing the capabilities of the airEXODUS evacuation model, this paper describes the findings of a recent CAA project aimed at investigating model accuracy in predicting past certification trials. Furthermore, airEXODUS is used to examine issues related to the Blended Wing Body (BWB) and Very Large Transport Aircraft (VLTA). These radical new aircraft concepts pose considerable challenges to designers, operators and certification authorities. BWB concepts involving one or two decks with possibly four or more aisles offer even greater challenges. Can the largest exits currently available cope with passenger flow arising from four or five aisles? Do we need to consider new concepts in exit design? Should the main aisle be made wider to accommodate more passengers? In this paper we discuss various issues evacuation related issues associated VLTA and BWB aircraft and demonstrate how computer based evacuation models can be used to investigage these issues through examination of aisle/exit configurations for BWB cabin layouts.

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Self-compacting concrete (SCC) is generally designed with a relatively higher content of finer, which includes cement, and dosage of superplasticizer than the conventional concrete. The design of the current SCC leads to high compressive strength, which is already used in special applications, where the high cost of materials can be tolerated. Using SCC, which eliminates the need for vibration, leads to increased speed of casting and thus reduces labour requirement, energy consumption, construction time, and cost of equipment. In order to obtain and gain maximum benefit from SCC it has to be used for wider applications. The cost of materials will be decreased by reducing the cement content and using a minimum amount of admixtures. This paper reviews statistical models obtained from a factorial design which was carried out to determine the influence of four key parameters on filling ability, passing ability, segregation and compressive strength. These parameters are important for the successful development of medium strength self-compacting concrete (MS-SCC). The parameters considered in the study were the contents of cement and pulverised fuel ash (PFA), water-to-powder ratio (W/P), and dosage of superplasticizer (SP). The responses of the derived statistical models are slump flow, fluidity loss, rheological parameters, Orimet time, V-funnel time, L-box, JRing combined to Orimet, JRing combined to cone, fresh segregation, and compressive strength at 7, 28 and 90 days. The models are valid for mixes made with 0.38 to 0.72 W/P ratio, 60 to 216 kg/m3 of cement content, 183 to 317 kg/m3 of PFA and 0 to 1% of SP, by mass of powder. The utility of such models to optimize concrete mixes to achieve good balance between filling ability, passing ability, segregation, compressive strength, and cost is discussed. Examples highlighting the usefulness of the models are presented using isoresponse surfaces to demonstrate single and coupled effects of mix parameters on slump flow, loss of fluidity, flow resistance, segregation, JRing combined to Orimet, and compressive strength at 7 and 28 days. Cost analysis is carried out to show trade-offs between cost of materials and specified consistency levels and compressive strength at 7 and 28 days that can be used to identify economic mixes. The paper establishes the usefulness of the mathematical models as a tool to facilitate the test protocol required to optimise medium strength SCC.

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The adoption of agile software development methodologies may appear to be a rather straightforward process yielding instantly improved software in less time and increasingly satisfied customers. This paper will show that such a notion is a misunderstanding and can be harmful to small software development organisations. A more reasonable approach involves a careful risk assessment and framework for introducing agile practices to address specific risks. A case study with a small software development organisation is provided to show the assessment in practice and the resulting risk mitigation strategies for process improvement.

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Drawing on research in Northern Ireland into the process of release under the Belfast/Good Friday Agreement, this article explores the identification and classification of risk in relation to prisoners released early under the Sentences (NI) Act. The main argument is that conflict, post-conflict and transitional conditions expose more starkly the political underpinnings of risk-management strategy and the article demonstrates the particular variant of Politicized Risk Assessment (PRA) recently used in the release of prisoners in Northern Ireland

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We examined the trade-off between the behaviours associated with predator avoidance and mate acquisition in the mate-guarding amphipod crustacean Gammarus duebeni. We used laboratory experiments to investigate the impact of olfactory predator cues on activity, mate choice and mate-guarding behaviour of males and females. Pair formation declined under perceived risk of predation, reflecting reduced activity of both males and females and hence a reduced likelihood of encountering a mate. We also observed a reduction in the choosiness of both males and females. Under increased perceived predation risk, assessment of the female by the male was more likely to be followed by pair formation, and males showed a nonsignificant trend towards reduced discrimination in favour of large females and were less tenacious in their pair bond when they paired during exposure to predator cues. Females also showed less resistance behaviour, suggesting that both males and females trade off the costs of maximizing current reproductive success against the benefits of predator avoidance for survival and reproduction in the future. We discuss the implications of such context-dependent mating behaviours for ecological interactions between species and suggest that predators, via the effects of perceived predation risk on mate choice and mate guarding in the prey species, induce trait-mediated indirect effects with the potential to influence population dynamics and community structure. (C) 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

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The paper focuses on the ways in which medical discourses of HIV transmission risk, personal bodily meanings and reproductive decision-making are re-negotiated within the context of sero-different relationships, in which one partner is known to be HIV-positive. Eighteen in-depth interviews were conducted with 10 individuals in Northern Ireland during 2008–2009. Drawing on an embodied sociological approach, the findings show that physical pleasure, love, commitment, a desire to conceive without medical interventions and a dislike of condoms within regular ongoing relationships, shaped individuals' sense of biological risk. In addition, the subjective logic that a partner had not previously become infected through unprotected sex prior to knowledge of HIV status and the added security of an undetectable viral load significantly impacted upon women's and, especially, men's decisions to have unprotected sex in order to conceive. The findings speak to the importance of reframing public health campaigns and clinical counselling discourses on HIV risk transmission to acknowledge how couples negotiate this risk, alongside pleasure and commitment within ongoing relationships.

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This paper tests empirically whether pension information derived by corporate pension accounting disclosures is priced in corporate bond spreads. The model represents a hybrid of more traditional accounting ratio-based models of credit risk and structural models of bond spreads initiated by Merton (1974). The model is fitted to 5 years of data from 2002 to 2006 featuring companies from the US and Europe. The paper finds that while unfunded pension liabilities are priced in the overall sample, they are not priced as aggressively as traditional leverage. Furthermore, an extended model shows that the pension–credit risk relation is most evident in the US and Germany, where unfunded pension liabilities are priced more aggressively than traditional forms of leverage. No pension–credit risk relation is found in the other countries sampled, notably the UK, Netherlands and France.

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To quantify how much of the coronary heart disease (CHD) mortality decline in Northern Ireland between 1987 and 2007 could be attributed to medical and surgical treatments and how much to changes in population cardiovascular risk factors.

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Anthelmintic drugs are widely used to control parasitic infections in cattle. The ProSafeBeef project addressed the need for data on the exposure of European consumers of beef to potentially harmful drug residues. A novel analytical method based on matrix solid-phase dispersive extraction and ultra-performance liquid chromatography-tandem mass spectrometry was validated for 37 anthelmintic drugs and metabolites in muscle (assay decision limits, CCa, = 0.15-10.2 µg kg -1). Seven European countries (France, Spain, Slovenia, Ireland, Italy, Belgium and Portugal) participated in a survey of retail beef purchased in local shops. Of 1061 beef samples analysed, 26 (2.45%) contained detectable residues of anthelmintic drugs (0.2-171 µg kg -1), none above its European Union maximum residue limit (MRL) or action level. Residues detected included closantel, levamisole, doramectin, eprinomectin, moxidectin, ivermectin, albendazole and rafoxanide. In a risk assessment applied to mean residue concentrations across all samples, observed residues accounted for less than 0.1% of the MRL for each compound. An exposure assessment based on the consumption of meat at the 99th percentile of consumption of adults in 14 European countries demonstrated that beef accounted for less than 0.02% of the acceptable daily intake for each compound in each country. This study is the first of its kind to apply such a risk-based approach to an extensive multi-residue survey of veterinary drug residues in food. It has demonstrated that the risk of exposure of the European consumer to anthelmintic drug residues in beef is negligible, indicating that regulation and monitoring is having the desired effect of limiting residues to non-hazardous concentrations. © 2012 Copyright Taylor and Francis Group, LLC.

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Health professionals are expected to support family caregivers of patients requiring palliative care. However, there is a dearth of empirical evidence to help clinicians identify caregivers who might be at risk of poor psychosocial functioning.

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To determine the feasibility of educating adults about their risk of prediabetes/diabetes in a community pharmacy, to determine the common risk factors for prediabetes/diabetes in adults visiting a community pharmacy, and to assess any association between risk factors and age.

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The aim of this paper is to explore the ‘natural attitude’ underpinning risk practices in child welfare. This refers to various taken-for-granted approaches to risk that social workers and other human service professionals draw upon in their everyday practice. The approach proceeds by identifying and critically examining three key, meta-theoretical paradigms on risk which typically shape the natural attitude. They are labelled ‘objectivist’, ‘subjectivist’ and ‘critical’. The ontological, epistemological, axiological and methodological premises supporting each paradigm, and how they shape risk practices, are then reviewed leading to a composite, meta-theoretical position on risk termed ‘methodological pragmatism’. This position draws on the strengths of each paradigm and is formulated into ten propositions which consider how risk should be approached in child welfare. Within this corpus of thought salient themes are endorsed such as the need for method triangulation, an examination of ‘deep causality’, and the promotion of emancipatory perspectives. By critically reflecting on meta-theory, the paper contributes to the development of substantive theories of risk assessment and management in child welfare.

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To develop and implement a risk assessment process for all unlicenced medicinal products in use within the Belfast City Hospital.
Over half 65% of the unlicenced medicinal products currently in use were rated low or minor risk and therefore required no recording upon supply.
This has greatly improved the way unlicensed medicines are prescribed, procured, supplied and administered within the Belfast City Hospital.

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To test the applicability of the sex-specific 2008 Framingham general cardiovascular risk equation for coronary heart disease (CHD) and stroke in European middle-aged men from Ireland and France.