An extension of the fuzzy improved risk graph and fuzzy analytical hierarchy process for determination of chemical complex safety integrity levels

The risk graph (RG) is widely used to evaluate the safety integrity level (SIL) of safety instrument systems (SIS). However, subjective opinion-based conventional RGs cannot provide successful results for the problems of risk parameters, such as shortages or lack of data; hence, the output of a conventional approach lacks sufficient reliability. We introduced the fuzzy improved risk graph (FIRG), an extension of fuzzy set theory, to deal with possible ambiguities during SIL study and increase the reliability of conventional RGs. In the present study, the levels of consequences defined as linguistic terms were converted into qualitative intervals; therefore, by correlating the proposed approach with experts’ opinions and attributing weight factors, a desired SIL value was obtained. The output of this new approach can be compared directly with quantitative risk assessment techniques to improve the safety performance of industrial systems.     

A meta‐analytic investigation into the moderating effects of situational strength on the conscientiousness–performance relationship

Debates about the utility of conscientiousness as a predictor of job performance have focused primarily on mean effect size estimates, despite theoretical and empirical reasons to expect variability across situations. The present study meta‐analytically demonstrates that occupation‐level situational strength is one important source of this variability. Consistent with theory, predicted uncorrected conscientiousness–performance correlations ranged from r = .09 to .23 (overall performance) and r = .06 to .18 (task performance), with stronger correlations observed in weak occupations. These results highlight the need for continued inquiry into the nature of situational strength, its impact on other predictor–outcome relationships, and the implications of these issues vis‐à‐vis theory and practice. Copyright © 2009 John Wiley & Sons, Ltd.     

Probationary and non-probationary drivers' nighttime crashes in Western Australia, 1996-2000

INTRODUCTION: This study was designed to explore the temporal aspects of crashes for probationary and non-probationary drivers. METHODS: Data from the West Australian Road Injury Database from 1996-2000 were used to calculate age-sex-specific crash rates per 100,000 person-days and to plot proportions of fatal and hospital crashes by time for probationary and non-probationary drivers. The population attributable risk was used to estimate the potential number of lives saved by nighttime driving restriction in the probationary period. RESULTS: Probationary drivers were seven times more likely to crash than non-probationary drivers. While the highest number of crashes was in the daytime, probationary drivers had a higher proportion of fatal or hospitalization crashes at night than non-probationary drivers. CONCLUSION: Restrictions on driving at night could form part of graduated driver training. Even if some probationary drivers disobeyed the restriction, a substantial reduction in car occupant fatalities and hospitalizations could result.     

Stress,work and professional satisfaction and militancy among Canadian physicians

The introduction of a national health care system in Canada has resulted in regular and increasing conflict between the medical profession, government and other political actors. The present study utilizes a stressor–strain framework to understand physician militancy in Canada. Data were collected from 2087 men and women physicians using questionnaires completed anonymously. Four groups of predictor variables identified in previous research were considered: individual demographic characteristics, practice characteristics, work stressors, and work and professional satisfactions. Empirical support for the model was found. Each panel of predictor variables had significant and unique relationships with measures of physician militancy.     

基于状态Petri网的矿区生态环境脆弱度动态评价方法

采用状态Petri网模型对矿区生态环境脆弱度进行动态评价,给出了状态Petri网中累积值、加权值、不变值和虚拟值4种不同状态值的计算及表示方法,提出了基于状态Petri网的矿区生态环境脆弱度计算方法。库所的累积值用于计算采矿过程中环境指标的总变化量。加权值主要用于脆弱度的计算。具有不变值的库所在相应的变迁被激发前后状态值均保持不变。没有实际意义的虚拟值在状态Petri网中仅起到逻辑或过渡作用。网结构描述了矿区生态环境脆弱度的组成结构,网系统的运行反映了生态环境脆弱化的状态变化过程,并且将脆弱度的计算融入了状态Petri网的运行中。在案例研究中,绘制了4种修复方案下脆弱度的变化情况曲线,表明该评价方法可以对矿区生态环境脆弱度进行动态评价。状态Petri网模型能将矿区生态环境脆弱化过程,以及人工修复和自然修复过程直观形象地展现出来,为预测矿区生态环境脆弱度的变化情况及制定相应的修复方案提供参考。该模型适用于矿山长期开采对生态环境造成破坏过程的建模及计算,而且对矿山的开采过程也不需要作特别的假设限制。     

A framework for human error risk analysis of coal mine emergency evacuation in China

Evacuation from underground coal mine in emergency as soon as possible makes the difference between life and death. Human factors have an important impact on a successful evacuation, but literature review shows that there is a lack of consideration of human error risk during coal mine emergency evacuation in China. To address the above problems, in this paper, we established a framework for human error risk analysis of coal mine emergency evacuation, consisting of scenario and task analysis, risk assessment and risk reduction. A general evacuation procedure which is applicable for different causes is detailed through the scenario and task analysis. A new method based on expert judgment, named OGI-Model, is proposed to evaluate the reliability of human safety barrier. In this new approach, human safety barrier is divided into three sub-barriers, i.e., organization safety sub-barrier (OSSB), group safety sub-barrier (GSSB), and individual safety sub-barrier (ISSB). Each sub-barrier consists of a series of concrete measures against specific evacuation actions. An example is provided in this paper to demonstrate the use of this framework and its effectiveness.     

Forecasting turbine problems by means of the state space framework

A forecasting system is set up to improve the diagnosis in a Condition Monitoring Programme of a critical turbine placed at an industrial plant. The system is based on a statistical model in a State Space framework, such that the local mean level of the vibration state of the equipment is estimated directly from the data, based on a continuous-time set up. This model is combined with a cost model in Conditioned Monitoring, by which the time of preventive replacement is produced when the minimum of the expected cost per unit of time is reached into the future. Such measure is a combination of the costs of failure, the costs of a preventive replacement and the probabilities of reaching the alarm levels fixed by some criteria. The system is estimated by Maximum Likelihood and thoroughly tested on the equipment. The main tests relate to statistical properties of the model residuals and a comprehensive comparison with an alternative system, namely a linear trend regression model in continuous time. The system produced a reasonable forecasting performance and sensible time of preventive replacement prediction and outperformed the alternative forecasting system.     

事故预测分析的PETRI网

对事故预测分析Ｐｅｔｒｉ网模型中的事件、逻辑门表示及其模型构造进行了讨论；文中以一事故为例，对其ｐｅｔｒｉ网、ｐｅｔｒｉ网的可达标识图制作做了较为详细的介绍。在此基础上，分析可达标识图，求出导致事故发生的最小割集和最小径集，为控制事故的措施选择提供了可靠的理论依据。该方法表现直观，为事故的预测分析开辟了一条新的途径。     

From job-based to competency-based organizations

The efficacy of designing organizations around job structures is challenged. Although this approach has dominated the fields of organizational behavior and human resource management for decades, a number of forces have converged to suggest that a competency-based approach often is more appropriate. In the global competitive environment which large, complex organizations face, the competency-based approach and the capabilities that individuals need to acquire and develop should be the major focus. Reward systems, career tracks, selection systems, and the structure of organizations need to change to focus on competencies. The challenges and opportunities for research, theory, and practice development that a change to a competency-based approach raises are many and diverse. For example, new pay systems are needed, new selection systems are needed, indeed whole new concepts about what constitutes selection validity and career development are needed.     

共同管沟深基坑现场变形监测与数值模拟分析

为了分析共同管沟深基坑边坡的变形规律及其对邻近建筑物的影响作用,以三星深基坑工程为例,采用数值模拟分析并进行现场变形监测验证。结果表明:降水措施对深基坑开挖引起的水平位移作用不大,而对竖向位移作用较大;随着深基坑开挖深度的不断加大,边坡土体的水平位移和竖向位移总体呈现增大的趋势,最大水平位移值表现为从坡脚向坡脚上方移动;原地下水位线以上所开挖边坡的最大竖向位移都发生在坡脚处,采用降水措施后,原地下水位线以下所开挖边坡的最大竖向位移出现在原地下水位附近。现场变形监测与数值模拟计算结果吻合度较高,说明土体参数的选取合理。研究成果可提升城市共同管沟深基坑建设安全设计及施工水平、降低工程风险损失。     

Risk informed optimization of a hazardous material multi-periodic transportation model

This paper presents a systematic framework toward the development of a Transportation Model for Hazardous Materials (HazMat). In practice, the proposed modeling framework is realized through an appropriate generalization of the traditional transportation network problem in the presence of safety constraints that need to be satisfied. The objective is to minimize transportation cost while reducing risks at the desired levels.In particular, the present research study identifies and evaluates different risk factors that influence the HazMat transportation network. Next, the transportation model is depicted graphically using nodes and arcs and optimal conditions are identified by solving the associated minimum cost flow network problem. The results show safety levels that help making informed decisions on choosing the optimal transportation configuration for hazardous material shipments.Within the proposed methodological context, appropriately parameterized simulation studies elucidate the effects of occurrence probabilities of the different risk events on transportation cost. Furthermore, as the appropriate management decisions must consider the effect of actions in one time period on future periods, the proposed model is structured as a multi-periodic model.Finally, the proposed methodological approach is employed to demonstrate the utility of proper analytical tools in decision making and particularly in ensuring that scientifically informed safety procedures are in place while transporting goods that can be potentially proven dangerous to the public and the surroundings.     

Computing the limits of risk aversion

Utility theory can be used to model the decision process involved in evaluating the cost-effectiveness of systems that protect against a risk to assets. A key variable in the model is the coefficient of relative risk aversion (or simply “risk-aversion”) which reflects the decision maker's reluctance to invest in such safety systems. This reluctance to invest is the scaled difference in expected utility before and after installing the safety system and has a minimum at some given value of risk-aversion known as the “permission point”, and it has been argued that decisions to sanction safety systems would be made at this point. As the cost of implementing a safety system increases, this difference in utility will diminish. At some point, the “point of indiscriminate decision”, the decision maker will not be able to discern any benefit from installing the safety system. This point is used to calculate the maximum reasonable cost of a proposed safety system. The value of the utility difference at which the decision maker is unable to discern any difference is called the “discrimination limit”.By considering the full range of accident probabilities, costs of the safety system and potential loss of assets, an average risk-aversion can be calculated from the model. This paper presents the numerical and computational techniques employed in performing these calculations. Two independent approaches to the calculations have been taken, the first of which is the derivative-based secant method, an extension of the referred derivative method employed in previous papers. The second is the Golden Bisection Method, based on a Golden Section Search algorithm, which was found to be more robust but less efficient than the secant method. The average risk-aversion is a function of several key parameters: the organisation's assets, the probability and maximum cost of an incident, and the discrimination limit. An analysis of the sensitivity of the results to changes in these parameters is presented. An average risk-aversion of 0.8–1.0 is found for a wide range of parameters appropriate to individuals or small companies, while an average risk-aversion of 0.1 is found for large corporations. This reproduces the view that large corporations will be risk neutral until faced with risks that pose a threat to their viability.     

Applying machine learning approaches to analyze the vulnerable road-users' crashes at statewide traffic analysis zones

Introduction: In this paper, we present machine learning techniques to analyze pedestrian and bicycle crash by developing macro-level crash prediction models. Methods: We collected the 2010–2012 Statewide Traffic Analysis Zone (STAZ) level crash data and developed rigorous machine learning approach (i.e., decision tree regression (DTR) models) for both pedestrian and bicycle crash counts. To our knowledge, this is the first application of DTR models in the burgeoning macro-level traffic safety literature. Results: The DTR models uncovered the most significant predictor variables for both response variables (pedestrian and bicycle crash counts) in terms of three broad categories: traffic, roadway, and socio-demographic characteristics. Additionally, spatial predictor variables of neighboring STAZs were considered along with the targeted STAZ in both DTR models. The DTR model considering spatial predictor variables (spatial DTR model) were compared without considering spatial predictor variables (aspatial DTR model) and the model comparison results discovered that the prediction accuracy of the spatial DTR model performed better than the aspatial DTR model. Finally, the current research effort contributed to the safety literature by applying some ensemble techniques (i.e. bagging, random forest, and gradient boosting) in order to improve the prediction accuracy of the DTR models (weak learner) for macro-level crash count. The study revealed that all the ensemble techniques performed slightly better than the DTR model and the gradient boosting technique outperformed other competing ensemble techniques in macro-level crash prediction models.     

Dependability modelling of instrumentation and control systems: A comparison of competing architectures

The purpose of this paper is to present a framework for comparing different candidate architectures for the same system. To this end, we propose a rigorous approach for homogeneously modelling different architectures. Starting with the functional specifications of the system, we derive a functional-level model that is used to construct a high-level dependability model for each architecture, using well-defined, formal construction rules. Our modelling approach is then applied to three possible architectures of an instrumentation and control system, and an example of a comparative analysis of these systems is provided.     

Why dual leaders will drive innovation: Resolving the exploration and exploitation dilemma with a conservation of resources solution

Using conservation of resources theory, we challenge traditional unity of command models of leadership and propose that a dual‐leadership framework can serve as a potential solution to the inherent challenges of innovation. Leading for innovation demands are depicted as uniquely disparate from other forms of leadership, resulting in several types of conflict and resource depletion for individual leaders. We contend that this exploration–exploitation role conflict and the resulting need to manage incongruent role identities produce stress, strain, and resource depletion that in turn hamper innovative goal achievement for both a single leader directly and via subordinates more indirectly. We propose, however, that as an extension of the resource investment tenet of the conservation of resources theory, a dual‐leadership approach may alleviate many of these challenges for innovation. Specifically, the addition of a second leader can add resources to innovation and in turn decrease the role conflict inherent in managing the generation and implementation of creative ideas. Limitations and areas for future research are offered.     

Social identity and applicant attraction: Exploring the role of multiple levels of self

Applicant attraction is a critical objective of recruitment. Common predictor variables of applicant attraction are limited in that they do not provide a comprehensive understanding of the process that shapes the perceptions and beliefs of job applicants about the firms for which they aspire to work for. Because individuals have the inherent desire to expand and enhance their social identities (e.g., personal, relational, and collective identities), they are likely to be attracted to organizations that allow them to do so. Building on recent work on levels of self, our paper suggests that social identities mediate the relation between currently established predictor variables of applicant attraction (e.g., compensation, type of work, and organizational image) and important applicant attraction outcomes. Common predictor variables of applicant attraction can lead to the activation, evaluation, and identification processes described by social identity theory. A theoretical framework is presented that illustrates the mediating influence of social identity on the relations between common predictor variables and applicant attraction outcomes. This framework may lead to more effective recruitment strategies. Copyright © 2015 John Wiley & Sons, Ltd.     

Pitfalls in the application of utility functions to the valuation of human life

Safety strategies in the process and other industries depend ultimately on how much the owners and operators decide should be spent on protection systems to protect workers and the public from potential plant hazards. An important input to decisions of this sort is the value of life, which needs to be assessed in a valid manner so that safety decisions can be made properly. A key reference point for decisions on safety investment decisions in the UK is a 1999 study on the “value of a prevented fatality” (VPF), which employs a two-injury chained model that has been shown previously by the present authors to possess internal inconsistencies. The 1999 study made extensive use of utility functions to interpret survey data, and it is this feature that is explored in this paper. It will be explained here how different forms of utility function of the Exponential family can produce the same figure for an intermediate parameter in the calculation of the VPF from the two-injury chained model. Exponential utility functions are, however, unlikely to provide a realistic representation if their calculated risk-aversions need to be negative or zero in order to match survey data, which would imply an incautious attitude amongst those taking decisions on safety. The use of an incompletely specified wealth threshold in the utility modelling is explored in the light of a proposal by the authors of the 1999 study that a second utility function can be used to determine the individual's utility when his wealth lies below the threshold, which constitutes the lower limit of validity of the first utility function. The proposition is shown to be untenable. The results presented in this paper raise further concerns about the lack of validity of the 1999 study on which the UK VPF is based and hence on the safety decisions that have been made in consequence.     

Risk-based maintenance policy selection using AHP and goal programming

Maintenance policy selection is a multiple criteria decision making. The criteria often considered are cost and reliability of maintenance. There has been a growing interest in using risk of accidents as a criterion for maintenance selection. This paper presents an approach of maintenance selection based on risk of equipment failure and cost of maintenance. Analytic hierarchy process (AHP) and goal programming (GP) are used for maintenance policy selection. A case study in a benzene extraction unit of a chemical plant was done. The AHP results show that considering risk as a criterion, condition based maintenance (CBM) is a preferred policy over time-based maintenance (TBM) as CBM has better risk reduction capability than TBM. Similarly, considering cost as a criterion, corrective maintenance (CM) is preferred. However, considering both risk and cost as multiple criteria, the AHP–GP results show that CBM is a preferred approach for high-risk equipment and CM for low risk equipment.     

基于证据推理客运索道安全性评估

在比较分析现有各种评估方法的基础上,提出基于证据推理的安全性评估方法。在评估过程中,首先确定评价因素集及相应的权重和评价等级及评价等级效用值,然后利用解析算法进行证据的合成,并根据方案最终效用值到各评语等级效用值之间距离的大小确定评价等级。最后,将该方法运用于某客运索道安全评估,得出客运索道安全性评价为较好,并通过与模糊综合评价方法相比,进一步论证了该方法的可行性和有效性。     

Guidelines for life extension process management in oil and gas facilities

Facilities life extension has caught the attention among the capital-intensive industries, like oil and gas. By extending the life cycle of the industrial assets, a wide range of benefits is obtained, comparing with other life ending management strategies. This article first contextualizes the implementation of the life extension concept in the oil and gas industry, showing global data about life extension. Despite the importance of the ageing process, due to its great economic impact and the risk it poses to the production sector, regulatory entities, even in countries more advanced in that sector or that have already experienced the extension process, developed only superficial material about the topic without defining a structured methodology for the assessment of the possibility of useful life extension. The available references do not allow a comprehensive analysis of that possibility, which highlights the importance the methodology proposed. Thus, this article proposes a guideline for the life extension process management, strengthening a framework containing the main evaluation stages, aiming to facilitate the analysis of issues related to ageing and to support the decision-making process. Lastly, real case studies regarding current life extension processes submitted to the Brazilian regulatory body were evaluated against the proposed framework stages, evidencing their lack of necessary details to support the decision-making. Upon the realization that the real cases identified do not allow for the assessment of the contribution and adequacy of the proposed framework in its entirety, the same was also applied to a hypothetical case. The latter was developed based on facts reported by a major operator in Brazil. The result was the determination that the use of the proposed methodology transformed the assessment of the possibility of life extension into a systematic and transparent process, leading to easier and better-founded decision-making procedures, and improving the management of the asset during its extended life.