This thesis describes a methodology for the requirements analysis of critical real-time systems. The methodology is based on formal methods, and provides a systematic way in which requirements can be analysed and specifications produced. The proposed methodology consists of a framework with distinct phases of analysis, a set oftechniques appropriate for the issues to be analysed at each phase of the framework, a hierarchical structure of the specifications obtained from the process of analysis, and techniques to perform quality assessment of the specifications. The phases of the framework, which are abstraction levels for the analysis of the requirements, follow directly from a general structure adopted for critical real-time systems. The intention is to define abstraction levels, or domains, in which the analysis of requirements can be performed in terms of specific properties of the system, thus reducing the inherent complexity of the analysis. Depending on the issues to be analysed in each domain, the choice of the appropriate formalism is determined by the set of features, related to that domain, that a formalism should possess. In this work, instead of proposing new formalisms we concentrate on identifying and enumerating those features that a formalism should have. The specifications produced at each phase of the framework are organised by means of a specification hierarchy, which facilitates our assessment of the quality of the requirements specifications, and their traceability. Such an assessment should be performed by qualitative and quantitative means in order to obtain high confidence (assurance) that the level of safety is acceptable. In order to exemplify the proposed methodology for the requirements analysis of critical real-time systems we discuss a case study based on a crossing of two rail tracks (in a model railway), which raises safety issues that are similar to those found at a traditional level crossing (i.e. rail-road).

<p> Heat stress is a recognized occupational hazard present in many work environments. Its effects increase with increasing environmental heat loads. There is good evidence that exertional heat illness is associated with ambient thermal conditions in outdoor environments. Further, there is reason to believe that risk of acute injury may also increase with the ambient environment. For these reasons, the assessment of heat stress, which can be done through the characterization of the wet bulb globe temperature (WBGT), is designed to limit exposures to those that could be sustained for an 8-h day. The ACGIH Threshold Limit Value (TLV) for heat stress was based on limited data from Lind in the 1960s. Because there are practical limitations of using thermal indices, measurement of physiological parameters, such as body temperature and heart rate are used with environmental indices or as their alternative. </p><p> The illness and injury records from the Deepwater Horizon cleanup effort provided an opportunity to examine the effects of ambient thermal conditions on exertional heat illness and acute injury, and also the cumulative effect of the previous day&rsquo;s environmental conditions. The ability of the current WBGT-based occupational exposure limits to discriminate unsustainable heat exposures, and the proposal of alternative occupational limits was performed on data from two progressive heat stress protocol trials performed at USF. The USF studies also provided the opportunity to explore physiological strain indicators (rectal temperature, heart rate, skin temperature and the Physiological Strain Index) to determine the threshold between unsustainable and sustainable heat exposures. Analysis were performed using Poisson models, conditional logistic regressions, logistic regressions, and receiver operator curves (ROC curves).</p><p> It was found that the odds to present an acute event, either exertional heat illness or acute injuries increased significantly with rising environmental conditions above 20 &deg;C (RR 1.40 and RR 1.06, respectively). There was evidence of the cumulative effect from the prior day&rsquo;s temperature and increased risk of exertional heat illness (RRs from 1.0&ndash;10.4). Regarding the accuracy of the current TLV, the results of the present investigation showed that this occupational exposure limit is extremely sensitive to predict cases associated with unsustainable heat exposures, its area under the curve (AUC) was 0.85; however its specificity was very low (specificity=0.05), with a huge percentage of false positives (95%). The suggested alternative models improved the specificity of the occupational exposure limits (specificities from 0.36 to 0.50), maintaining large AUCs (between 0.84 and 0.89). Nevertheless, any decision in trading sensitivity for specificity must be taken with extreme caution because of the steeped increment risk of heat related illness associated with small increments in environmental heat found also in the present study. Physiologic heat strain indices were found as accurate predictors for unsustainable heat stress exposures (AUCs from 0.74 to 0.89), especially when measurements of heart rate and skin temperature are combined (AUC=0.89 with a specificity of 0.56 at a sensitivity=0.95). Their implementation in industrial settings seems to be practical to prevent unsustainable heat stress conditions.</p>

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Lasers have been used in the entertainment industry since 1964, when they were used in the film Goldfinger. Laser display shows commenced in about 1973. It would be reasonable to expect laser safety to have been adequately addressed over the last twenty-five years. This research showed that the industry was not able to assess the risks from its work. A national survey of the competence of enforcing officers showed that they rarely had the necessary expertise to judge the safety of shows. Therefore, there was often a wide gulf between the laser companies and those responsible for enforcing entertainment and health and safety legislation. A hazard assessment methodology has been developed which considers any laser show as a series of modules which may have different hazards associated with them at different stages of the life cycle, and different people would potentially be exposed to these hazards. A number of laser radiation exposure situations have been assessed, including audience scanning. A theoretical understanding of the laser scanning issues and the application of measurement techniques to enable assessments to be carried out against internationally recognised maximum permissible exposure levels were developed. The conclusion was that the practice of audience scanning was not acceptable in its current form. A number of laser companies worldwide have accepted this view as a direct result of this research. A means of presenting the risk assessment for a laser display has been developed which provides benefits for the laser company, the venue manager, event promoter and the enforcing officer. It is recognised that a complete assessment may not be possible in the time available and a focused approach to the assessment is presented. In summary, if audience scanning is intended, the assessment is complex, but if this practice is not intended then the assessment can be straightforward. Suggestions are made for applying the risk assessment methodology to other laser applications.

<p> This study is the first occupational safety and health evaluation of the cannabis industry of Colorado from an Occupational Health Psychology (OHP) perspective. Qualitative pilot data and common OHP theories provide a framework for project development, design, and rationale. This study investigated the following among cannabis industry workers: potential stressors, perceptions and awareness of physical safety hazards, strain outcomes, and organizational supports that might buffer relations between stressors and strain outcomes. Study results provide a first glimpse at the demographics of the cannabis industry and suggest that workers generally experience low strain and high levels of organizational supports in the presence of various physical and psychological stressors and hazards. However, results also suggest heterogeneous health and safety training, awareness, and regulation in the cannabis industry. Future research directions and practical implications for cannabis industry workers are provided.</p>

published_or_final_version / Business Administration / Master / Master of Business Administration

published_or_final_version / Geography / Master / Master of Arts in China Development Studies

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No description available.