Working conditions,psychological/physical symptoms and occupational accidents. Bayesian network models

Each day thousands of workers suffer occupational accidents of varying degrees of severity. Accidents at work render workers incapable of carrying out their day to day activities, either temporarily or permanently, and they also have detrimental effects on family life, the company, and the general public. In order to reduce the occupational accident rate, it is necessary to determine the causes of those accidents. Although there are many different types of accidents, they generally stem from poor working conditions. The purpose of this study was to analyze the influence of working conditions on occupational accidents from data gathered in the VI National Survey of Working Conditions (VI NSWCs) in 2007. This survey utilized a random sample of the active population of Spain. The sample comprised 11,054 people (5917 males and 5137 females). In order to carry out the study, a probabilistic model was built using Bayesian networks. The model included the following variables: hygiene conditions, ergonomic conditions, job demands, physical symptoms, psychological symptoms, and occupational accidents. The study demonstrated that there were strong relationships between hygiene conditions and occupational accidents; it has been shown that poor hygienic conditions duplicate the probability of accident. Physical symptoms increased almost 50% due to poor ergonomic conditions. And finally, high job demands almost duplicated the psychological symptoms. The investigation also showed a high degree of interdependence between physical and psychological symptomatologies and the relationship between these and occupational accidents.     

Providing the numerical context for British casualty reduction targets

The first national target for reducing road accident casualties in Great Britain was set in 1987, the target year being 2000. As the year 2000 approached, preparations were made for setting a subsequent target, the target year being 2010. A major part of the preparation consisted of forecasting the number of casualties that might be expected in 2010, conditional upon predictions about how the volume of road travel by the various transport modes might change and the type of new road safety measures that the Government might introduce. The forecasts provided the numerical context for the casualty reduction target that the Government announced in March 2000.This paper summarises the statistical analyses of accident data from 1983 to 1998 upon which the forecasts were based, and compares the approach with alternatives that have been adopted elsewhere. It also describes how progress towards the target has been monitored annually, allowing the Government to judge whether additional efforts might be needed to achieve the target. This examination of the actual data from 1999 to 2007 shows how far the original forecasts have proved to be successful.The improvement of car secondary safety over the past 15 years has probably been the development that has had the most significant effect on the national casualty total. A statistical model is used to quantify this effect by analysis of accident data, and the results of the most recent analyses are included.     

Assessment of four turbulence models in simulation of large-scale pool fires in the presence of wind using computational fluid dynamics (CFD)

Pool fires are the most common of all process industry accidents. Pool fires often trigger explosions which may result in more fires, causing huge losses of life and property. Since both the risk and the frequency of occurrence of pool fires are high, it is necessary to model the risks associated with pool fires so as to correctly predict the behavior of such fires.Among the parameters which determine the overall structure of a pool fire, the most important is turbulence. It determines the extent of interaction of various parameters, including combustion, wind velocity, and entrainment of the ambient air. Of the various approaches capable of modeling the turbulence associated with pool fires, computational fluid dynamics (CFD) has emerged as the most preferred due to its ability to enable closer approximation of the underlying physical phenomena.A review of the state of the art reveals that although various turbulence models exist for the simulation of pool fire no single study has compared the performance of various turbulence models in modeling pool fires. To cover this knowledge-gap an attempt has been made to employ CFD in the assessment of pool fires and find the turbulence model which is able to simulate pool fires most faithfully. The performance of the standard k–? model, renormalization group (RNG) k–? model, realizable k–? model and standard k–ω model were studied for simulating the experiments conducted earlier by Chatris et al. (2001) and Casal (2013). The results reveal that the standard k–? model enabled the closest CFD simulation of the experimental results.     

具有水上事故特征的目标P-中位应急救助选址优化及方法

科学地进行应急救助基地选址是提高应急资源利用效率和应急服务水平的关键,以南京海事辖区为例,对事故多发水域应急救助基地的布局规划和覆盖分配进行了优化研究。总结了辖区水域中影响应急救助站点选址的因素,有辖区事故重点水域分布、桥区水域、锚地3个因素,运用DBSCAN算法确定了辖区事故重点水域的分布情况,结合桥区水域、锚地影响因素,引入安全风险权重系数,利用P-中位建立了应急救助站点选址数学模型。构建的选址模型目标函数在满足设置的约束条件下取最小值,即实现了救援用时最少或救援距离最短。最后运用免疫算法求解选址优化数学模型。经过计算,在考虑时效性的基础上,较好地实现了应急救助对辖区水域的全覆盖和重点水域的重点覆盖。     

基于大气退化物理模型恢复算法的露天矿车辆助驾技术

露天矿汽车运输是大型露天矿主要运输方式之一,是影响露天矿生产能力和经济效益的关键因素。本文分析了露天矿车辆运输事故原因,针对露天矿卡车运输道路环境特点与天气因素,通过安装于车体外的高清CCD摄像设备,来消除卡车盲区的安全隐患,并基于大气退化物理模型恢复算法,实现了在雨、雪、雾、灰尘等恶劣天气条件下的露天矿车辆运输道路环境探测影像增强技术,提高露天矿卡车司机的可视距离,降低事故发生率。本文的研究对于提高露天矿车辆运输安全,降低露天矿事故发生率具有重要意义,并以某大型露天煤矿为应用实例验证了其可行性。     

蒙德安全评价法的改进及其计算机实现

蒙德安全评价法是一种广泛应用于石化领域的安全评价方法,相对于其它指数型安全评价方法具有评价全面、实施便捷的特点,在工程中被大量应用。但是蒙德法有它难以克服的缺点：定量参数查找困难、定性参数估计困难、手动计算繁琐、分析流程不确定。本文针对这些问题提出了一种自动化的蒙德评价方法,克服了上述缺点,具有分析简便、快速、准确的特点。并开发完成了基于此方法的软件,经过案例测试表明此方法具有实用性,在工程应用中具有实际价值。     

Prediction models for the flash point of pure components

The flash point for a liquid is defined as the lowest temperature at which its vapor forms a spontaneously ignitable mixture when brought in contact with air. Having a good estimation of the flash point temperature at normal conditions is relevant because it is one of the main properties used to characterize fire and explosion hazards for liquids. Most of predictive correlations in the literature include a physical effect by including the normal boiling temperature in their formulation. To achieve combustion, sufficient evaporation is required and then a part of the liberated energy from the combustion is used to support the evaporation. Thus the evaporation energy and a chemical effect given by the heat of reaction are incorporated in this work. It is firstly verified that the relation between the flash point temperature and the normal boiling temperature tends to be a constant. Thus a heuristic approach based on 611 chemical species of diverse families indicates that this relation is around 0.75. The dispersion of the error has been reduced by using two proposed correlations where both physical and chemical properties are included in the model. In particular, the second equation is based on the group contributions method, which has been developed for alkanes. This method is in fact a combination of the group contributions method and the first model to overcome the difficulties in predicting isomeric differences.     

海河干流流域暴雨径流非点源污染负荷解析与控制策略

随着点源污染逐渐得到有效控制,非点源污染对海河干流流域水环境污染的贡献日益增大,对其污染负荷进行科学测算成为海河干流水质达标方案制订的重要前提。基于GIS技术,通过土地利用类型划分,利用PLOAD模型对海河干流的暴雨径流非点源污染负荷进行了计算。结果表明,海河干流流域建设用地的比例依海河流向自上而下逐渐递减,而涉农用地逐渐增加,城区地表径流与农业面源污染分别是上、下游地区重要的非点源污染负荷来源。关于流域的暴雨径流非点源污染负荷,CODCr为15 619.29 t/a,NH3-N为369.16 t/a,TN为851.20 t/a,TP为250.29 t/a。为改善海河干流水质,非点源污染控制应纳入流域的污染物总量控制计划中,与点源污染一起参与环境容量的分配与控制。     

Influence of trunk muscle activity and stability in front and back holding

Purpose. A tandem carrying style is often used in the workplace, but carrying approaches are different for two people because of the holding load in the tandem posture. To understand these carrying styles, this study aimed to investigate the patterns of muscle activity and stability of the trunk influenced by front and back holding of a heavy load. Methods. Electromyography data of eight trunk and two hip muscles, as well as displacements of the trunk, were recorded for analysis while subjects stood statically holding a handle in the front and back of the body with and without load. Results. Without load, muscle activities during front holding mirrored those during back holding. With load, greater muscle activities were observed in the dorsal muscles of the trunk and lesser activities were noted in the ventral muscles in the two holding styles. More frequencies of trunk oscillations occurred in front holding with and without load. Conclusions. The results revealed that back holding of load created more stability of the upper body, whereas front holding resulted in more instability of the trunk.     

Accident models and organisational factors in air transport: The need for multi-method models

Event analysis is needed to learn and improve safety. In air transport, ‘occurrences’ are routinely reported by pilots and air traffic controllers, and in-flight data analysis systems automatically monitor aircraft system behaviour and capture parameter threshold exceedances. The safety analyst of a large airline has to analyse dozens of occurrences each day. To understand why events happened the analyst has to go beyond the given information and make causal inferences. The analyst is able to do this for causal factors closely related in time and space to the event itself by applying individual knowledge and expertise. But typically the result of the analysis is ad hoc reaction to each individual event. Systematic analysis is needed to find areas of improvement for factors that are further removed from the event (latent factors). New tools are needed to help the analyst in this respect. There is a need for models that represent possible causal event sequence scenarios that include technical, human, and organisational factors. Building such models is a huge task, and requires the combination of detailed knowledge of all aspects of the system, processing huge amounts of data, a substantial mathematical background and the ability to capture this all in a user friendly software tool to be used by the safety analysts. Experience in Causal Modelling of Air Transportation System (CATS) in the Netherlands and similar projects in FAA and Eurocontrol in aviation shows that this is indeed a formidable task, but it has to be done to further improve safety.     

通信铁塔影响建筑物防雷安全计算公式之合理性探讨

以一个发生过严重雷灾事故的屋顶通信铁塔为例,分别利用国际电信联盟ITU-K56《无线通讯基站的雷电防护》和国际电报电话咨询委员会CCITT《防雷手册》中的公式计算出建筑物安装了通信铁塔后的年预计雷击次数,并将之与未安装通信铁塔时的年预计雷击次数进行对比,两者的计算结果存在显著差异。基于雷击条件相似原则,参照移动公司通信铁塔每年遭受雷击次数的实际统计数据,对这两个计算公式的合理性问题进行了探讨。研究结果表明,CCITT《防雷手册》中的计算公式更具合理性,计算结果更加接近实际值,计算方法更能准确地评估铁塔对所在区域的建筑物及电子电气设备的防雷安全所造成的影响。     

A protocol for the evaluation of LNG vapour dispersion models

The international transport, storage and utilisation of LNG is growing rapidly. Whilst the LNG industry has an excellent safety record, the possibility of an accidental release cannot be discounted. Internationally-accepted standards, such as the 59A Standard of the US National Fire Protection Association (NFPA), provide direction on the assessment of LNG spill hazards and hazard range criteria which must be met. Modelling of the atmospheric dispersion of LNG vapour from accidental spills is one of the critical steps in such hazard analyses. This paper describes a comprehensive evaluation protocol devised for the 59A Standard, specifically for the assessment of LNG vapour dispersion models. The evaluation protocol is based on methodologies developed in previous European Union studies, which have been extended, significantly adapted and tailored to the specific requirements of the evaluation of models for the dispersion of LNG vapour. The protocol comprises scientific evaluation of the numerical and physical basis of models for the dispersion of LNG vapour, model verification, and validation; resulting in a comprehensive model evaluation report which includes qualitative and quantitative criteria for model acceptance. A supporting suite of validation data, and guidance on the use of this data, has also been produced. The NFPA 59A (2009) standard states that LNG vapour dispersion models are acceptable for use if they have been evaluated in accordance with this protocol.     

网格划分及开口处计算区域延展对FDS模拟结果的影响

结合具体算例,引入相关性分析方法对FDS应用中出现的网格独立性问题进行了量化研究,就火源区、羽流区和烟气层区对网格密度敏感性的差别进行了讨论,并且分析了开口处计算区域设置对计算结果的影响.随着网格密度的增大.不同计算结果之间的相关性值不断增大至0.99以上,且火源区的相关性值受网格密度影响最大,浮力羽流区次之,烟气层区最小.不延展计算区域和延展计算区域情况下的计算结果的相关性值较低,而不同计算区域延展范围下的计算结果之间的相关性均较高.结果表明,相关性值可以用来衡量计算结果的网格独立性.火源区、浮力羽流区、烟气层区对于网格密度的敏感程度依次递减,加密火源区在控制计算时间的同时可以有效提高计算精度.计算区域设置对于建筑开口处的烟气溢流和补气情况将产生重要影响.进而将影响到建筑内部的热流场,将开口处的计算区域适当向外延展,是保证计算结果精确度的有效手段.     

通风系统可靠性和稳定性数学模型研究

通风系统的可靠性和稳定性是矿井通风网络理论的两大核心内容之一,本文从通风系统分析的角度出发,对通风系统可靠性和稳定性数学模型进行了研究.可靠性用来衡量通风系统保持其通风参数的性能,稳定性是衡量风量波动大小的,二者既存在联系又有一定的区别.     

基于有序Logit与Probit模型的交通事故严重性影响因素分析

为准确分析影响交通事故严重性的各项因素,引入有序选择模型中的Ordinal Logit模型和Ordinal Probit模型,研究驾驶员、车辆、环境、管理因素与事故严重程度之间的耦合关系,利用计量经济学理论和统计学方法对模型进行显著性检验。并选择美国北卡罗来纳州2010年至2014年385个翻车事故样本进行严重性影响因素分析,所得回归模型参数估计均符合Wald检验(p≤0.0001)和似然比检验(p≤0.0001),模型的拟合度也都符合Pearson检验(p=0.7976)、偏差检验(p=0.6006)和信息准则检验,模型预测精度指标值均大于0.7。所得两个模型中变量"安全带"(p≤0.001)、"路面状况"(p=0.0071)、"道路线形"(p=0.0077)、"路面类型"(p=0.0251)都对翻车事故的严重性具有显著影响,表明有序Logit模型和有序Probit模型均适用于分析和揭示影响交通事故严重性的各个因素。     

Methodology for global sensitivity analysis of consequence models

A methodology is presented for global sensitivity analysis of consequence models used in process safety applications. It involves running a consequence model around a hundred times and using the results to construct a statistical emulator, which is essentially a sophisticated curve fit to the data. The emulator is then used to undertake the sensitivity analysis and identify which input parameters (e.g. operating temperature and pressure, wind speed) have a significant effect on the chosen output (e.g. vapour cloud size). Performing the sensitivity analysis using the emulator rather than the consequence model itself leads to significant savings in computing time.To demonstrate the methodology, a global sensitivity analysis is performed on the Phast consequence model for discharge and dispersion. The scenarios studied consist of above-ground, horizontal, steady-state discharges of dense-phase carbon dioxide (CO₂), with orifices ranging in diameter from ½ to 2 inch and the liquid CO₂ stagnation conditions maintained at between 100 and 150 bar. These scenarios are relevant in scale to leaks from large diameter above-ground pipes or vessels.Seven model input parameters are varied: the vessel temperature and pressure, orifice size, wind speed, humidity, ground surface roughness and height of the release. The input parameters that have a dominant effect on the dispersion distance of the CO₂ cloud are identified, both in terms of their direct effect on the dispersion distance and their indirect effect, through interactions with other varying input parameters.The analysis, including the Phast simulations, runs on a standard office laptop computer in less than 30 min. Tests are performed to confirm that a hundred Phast runs are sufficient to produce an emulator with an acceptable degree of accuracy. Increasing the number of Phast runs is shown to have no effect on the conclusions of the sensitivity analysis.The study demonstrates that Bayesian analysis of model sensitivity can be conducted rapidly and easily on consequence models such as Phast. There is the potential for this to become a routine part of consequence modelling.     

危险化学品中毒事故应急预案编制与响应关注要点

大工业的发展导致各类职业中毒事件的发生日益严重,除人员伤亡等影响外,也会对于社会公众安全带来影响。应急预案编制中强调应急准备的重要性和针对性。职业危害事故识别和分类分级处理以及对于社会公共安全影响的危机处理能力是应急工作中应该关注的重要内容。应急响应中强调第一目击者的处理能力的培养、现场的实时监测、事故报告与事态演变的持续预警、有效应急资源应对危机处理的能力。