Data fusion,ensemble and clustering to improve the classification accuracy for the severity of road traffic accidents in Korea

Increasing amount of road traffic in 1990s has drawn much attention in Korea due to its influence on safety problems. Various types of data analyses are done in order to analyze the relationship between the severity of road traffic accident and driving environmental factors based on traffic accident records. Accurate results of such accident data analysis can provide crucial information for road accident prevention policy. In this paper, we use various algorithms to improve the accuracy of individual classifiers for two categories of severity of road traffic accident. Individual classifiers used are neural network and decision tree. Mainly three different approaches are applied: classifier fusion based on the Dempster–Shafer algorithm, the Bayesian procedure and logistic model; data ensemble fusion based on arcing and bagging; and clustering based on the k-means algorithm. Our empirical study results indicate that a clustering based classification algorithm works best for road traffic accident classification in Korea.     

Experimental investigation of the lower flammability limit of volatile liquid fuel-aluminum powder mixtures in air

Aluminum powder was always chosen as an additive to improve the explosive performance. In this work, experiments were performed to investigate the lower flammability limit (LFL) of volatile liquid fuel-aluminum powder mixtures using a 20 L closed spherical stainless steel vessel at a temperature of 20 °C (293 K) and 40 °C (313 K). The volatile liquid fuels tested in the work were diethyl ether (DEE), epoxypropane (PO), n-pentane and n-hexane. DEE, PO and n-pentane are in the liquid phase at room temperature and can easily transition to the gas phase at 40 °C (313 K). Through a series of experiments carried out, it was found that the change in phase would affect the interaction between the components. Aluminum powder always has an inhibitory effect on the flammability of the mixtures when it is mixed with gas-phase fuels. The inhibition effect was most obvious when the aluminum powder concentration reached 200 g/m³. While the interaction between aluminum powder and liquid-phase volatile fuels was promotion and was influenced by the component proportion and the type of the volatile fuels.     

基于模糊综合评价的化工工艺本质安全指数研究

建立化工工艺的本质安全评价指标体系,包括可燃性、爆炸性、毒性、反应性、温度、压力、储量等7个指标。为解决前人指数法中的边界波动效应,采用模糊综合评价建立化工工艺本质安全评价指数模型,确定各指标的权重、危险分级及对各分级的隶属函数。以甲基丙烯酸甲酯的5条工艺路线为例进行分析,结论与前人提出的指数方法的评价结果相吻合,表明该指数方法可以用来进行化工工艺的本质安全评价,以指导设计初期的本质安全型工艺路线选择。     

The hazards and risks of hydrogen

An analysis was completed of the hazards and risks of hydrogen, compared to the traditional fuel sources of gasoline and natural gas (methane). The study was based entirely on the physical properties of these fuels, and not on any process used to store and extract the energy. The study was motivated by the increased interest in hydrogen as a fuel source for automobiles.The results show that, for flammability hazards, hydrogen has an increased flammability range, a lower ignition energy and a higher deflagration index. For both gasoline and natural gas (methane) the heat of combustion is higher (on a mole basis). Thus, hydrogen has a somewhat higher flammability hazard.The risk is based on probability and consequence. The probability of a fire or explosion is based on the flammability range, the auto-ignition temperature and the minimum ignition energy. In this case, hydrogen has a larger flammability zone and a lower minimum ignition energy—thus the probability of a fire or explosion is higher. The consequence of a fire or explosion is based on the heat of combustion, the maximum pressure during combustion, and the deflagration index. Hydrogen has an increased consequence due to the large value of the deflagration index while gasoline and natural gas (methane) have a higher heat of combustion. Thus, based on physical properties alone, hydrogen poses an increase risk, primarily due to the increased probability of ignition.This study was unable to assess the effects of the increased buoyancy of hydrogen—which might change the probability depending on the actual physical situation.A complete hazard and risk analysis must be completed once the actual equipment for hydrogen storage and energy extraction is specified. This paper discusses the required procedure.     

An improved vehicle-pedestrian near-crash identification method with a roadside LiDAR sensor

Problem: Potential conflicts between pedestrians and vehicles represent a challenge to pedestrian safety. Near-crash is used as a surrogate metric for pedestrian safety evaluations when historical vehicle–pedestrian crash data are not available. One challenge of using near-crash data for pedestrian safety evaluation is the identification of near-crash events. Method: This paper introduces a novel method for pedestrian-vehicle near-crash identification that uses a roadside LiDAR sensor. The trajectory of each road user can be extracted from roadside LiDAR data via several data processing algorithms: background filtering, lane identification, object clustering, object classification, and object tracking. Three indicators, namely, the post encroachment time (PET), the proportion of the stopping distance (PSD), and the crash potential index (CPI) are applied for conflict risk classification. Results: The performance of the developed method was evaluated with field-collected data at four sites in Reno, Nevada, United States. The results of case studies demonstrate that pedestrian-vehicle near-crash events could be identified successfully via the proposed method. Practical applications: The proposed method is especially suitable for pedestrian-vehicle near-crash identification at individual sites. The extracted near-crash events can serve as supplementary material to naturalistic driving study (NDS) data for safety evaluation.     

Self-Organizing Map and clustering algorithms for the analysis of occupational accident databases

Data mining techniques are a powerful method for extracting information from large databases. Among these techniques, clustering and projection of data from high-dimensional spaces hold a main role, since they allow to discover hidden structures in the data set. Following this approach, this paper presents a data analysis method designed to help the management and investigation of occupational accident databases. The purpose is to discover the most common sequences of events leading to accidents for devising preventive actions. To this aim, we developed a two-level approach based on the joint use of the Kohonen’s Self-Organizing Map and the k-means clustering algorithm. This approach allows not only to group the accidents in different classes but also to visualize them in a way understandable for the analyst. The method has been applied with satisfactory results to a large database of occupational accidents occurred in the Italian wood processing industry. A comparison with the Hierarchical Clustering method confirmed the effectiveness of the proposed approach.     

Effect of initial pressure on explosion characteristics of 2, 3, 3, 3–tetrafluoropropene

With the popularity of refrigerants in the process industries, the potential safety problems caused by the use of refrigerants have attracted worldwide attention as people have realized their inherent explosion characteristics of refrigerants. This paper studied the explosion characteristics of refrigerant 2, 3, 3, 3–tetrafluoropropene (R1234yf) at different concentrations and initial pressures based on a 20 L experimental apparatus. The experimental results illustrated the peak overpressure of R1234yf increased with the rise of initial pressure. At a constant ambient temperature of 25 °C, the maximum rate of pressure rise and deflagration index showed an N-shaped trend with the increase of the refrigerant concentration from 6.8% to 10%. The maximum rate of pressure rise and deflagration index increased first and then decreased with the increase of the refrigerant concentration at atmospheric pressure, while they presented an M-shaped trend at pressurization condition. The peak overpressure, the maximum rate of pressure rise, and deflagration index reached 0.742 MPa, 4.04 MPa s⁻¹, and 1.1 MPa.m.s⁻¹ with a refrigerant concentration of 7.6%, respectively, which were less than those of refrigerant propane and difluoromethane (R32) at the optimal concentration. Furthermore, R1234yf exhibited better safety performance compared with refrigerant R32 in the same flammability classification.     

北京市危险化学品企业安全生产风险评估分级研究

为对北京市危化品企业基本情况的全面掌握,开展了危险化学品企业安全生产风险评估分级研究,借鉴国外经验和国内有关科研成果,提出了固有风险和动态风险相结合的危化品安全生产风险评估方法。固有风险为企业的基本风险水平,主要由危险化学品物质量、工艺水平、安全监控和周边环境决定,为共性指标;动态风险,反映企业安全生产管理绩效的水平,主要包括安全基础管理和现场管理,为个性指标,不同企业类型,评估动态风险指标有差异。从大量数据中抽取了最能反应企业安全生产状态的指标因素,通过专家组打分法和层次分析法确定评价因素的权重,该评估方法具有较强的实用性和可操作性,是本质安全和安全绩效的创新结合,为企业安全生产评估分级提供了新思路。通过分级,按照"风险优先"原则,政府部门实行差别监管,降低安全监管成本,促进危险化学品安全生产工作向规范化、科学化转变。同时,研制了危化品企业安全生产风险分级系统,为建立北京市危化品企业风险分级数据库奠定了基础。     

Prediction of flammability limits of fuel-air and fuel-air-inert mixtures from explosivity parameters in closed vessels

Flammability limits of fuel-air and fuel-air-inert gaseous mixtures, especially at non-atmospheric conditions, are essential properties required for establishing safety operating conditions for handling and processing flammable gases. For pure fuels, an important data pool exists, formed by the flammability limits of fuel-air and fuel-air-inert gaseous mixtures at ambient initial conditions measured by standard methods. Such methods can be used for experimental determination of flammability limits for multi-fuels mixed with air, with or without additives, under non-atmospheric conditions. Their use is however a time- and material-consuming process; in addition, the flammability limits obtained by various standard methods may be scattered as a result of different choices in the operating parameters, for each standard method. It appears that a preliminary estimation of the flammability limits for fuel-air and fuel-air-inert gaseous mixtures can minimize the effort of measuring them in specific initial conditions.The present paper describes a new method for estimating the flammability range of fuel-oxidizer gaseous mixtures based on measurements of explosivity properties e.g. the peak explosion pressure and maximum rate of pressure rise recorded during closed vessel laminar explosions of fuel-oxidizer mixtures far from limits. Data obtained for several hydrocarbon-air gaseous mixtures with or without inert gas addition are used to examine the accuracy of estimated flammability limits (LFL – the lower and UFL – the upper flammability limit) as well as of the Limiting Oxygen Concentration (LOC) and the Minimum Inert Concentration (MIC). The predictive ability of the proposed method is examined against the predictive ability of other recently described methods.     

细水雾对油池火热释放速率影响规律的实验研究

热释放速率是描述火灾现象的重要参数,可以表征火灾发展的强烈程度。利用大尺寸的热释放速率实验测量平台开展细水雾对不同种类油池火灭火效率的实验研究,同时分析细水雾对燃烧产物一氧化碳含量的影响。结果表明,热释放速率曲线能直接反映出细水雾对火源的作用,细水雾作用下三种燃料的热释放速率均被有效抑制,且细水雾的流量越大,对油池火的灭火效果越好。燃烧产物一氧化碳在施加细水雾时出现陡增,表明细水雾隔绝氧气,造成不完全燃烧或者燃烧熄灭。     

建筑材料及制品燃烧性能试验规范概述

建筑材料和制品燃烧性试验规范对保证建筑物内人的生命安全和财产安全是极为重要的。笔者对美国、加拿大、欧盟、日本以及中国的建筑材料燃烧性能试验规范进行分析、比较和综述。通过研究认为美国和加拿大对建筑材料燃烧性能的要求和试验方法基本相似,他们主要针对材料的燃烧性、火焰传播进行检测;欧盟于2001年颁布了新的燃烧性分级体系,该分级体系包括专门针对铺地材料部分和针对其他所有建筑构件材料和产品部门;日本采用锥形量热计法(ISO5660)将内装饰材料分为不燃、准不燃和阻燃材料3个等级;我国对建筑材料的试验方法包括不燃性试验方法、墙和天花板内装饰材料的三级分级体系和铺地材料两级分级体系。     

2007-2011年我国烟花爆竹事故统计分析研究

燃放烟花爆竹的习俗由于其在中国民俗中的特殊含义而延续至今,但是,因其自身的易燃、易爆性,烟花爆竹生产具有很高的风险性和危害性,引发的各类安全事故时有发生,不仅对社会财产造成严重损失,更危害到人民的生命安全。依据不同分类方法对2007—2011年间我国烟花爆竹事故进行了综合统计分析,得出了事故总体情况,不同方法统计下的事故比例,以及事故原因分类等,并进一步基于原因分析,从法律法规、技术手段以及安全管理三方面提出了一系列相关措施建议。     

基于自适应灰色面板聚类的城市公共安全风险测度*

为科学评估城市公共安全风险,基于“脆弱性—能力”综合评估框架从公共安全风险事件维度入手,构建城市公共安全风险评估指标体系;选取2015—2019年与脆弱性和风险承载能力相关的22个指标,采用改进后的自适应灰色面板聚类从绝对量、增量和波动量3方面进行测度。聚类结果将全国城市的公共安全风险水平分为6个类型;基于研究结果进一步分析造成不同类型特征的原因,明确各城市公共安全管理存在的薄弱点,提出相关改进建议。研究结果表明:北京和上海在3个层面上均有较好表现,属于低风险城市;全国大部分地区呈现出绝对量水平中等或较差,增量和波动量水平较好的特征。     

Experimental investigation on the lower flammability limits of diethyl ether/ n-pentane/epoxypropane-air mixtures

Diethyl ether (DEE), epoxypropane (PO) and n-pentane have excellent ignition and combustion performance; hence, they have a wide variety of applications in industry and advanced aviation propulsion systems. As these fuels are flammable at normal temperature and pressure, their explosive characteristics need to be explored. In this study, the lower flammability limits (LFLs) of vapor mixtures of DEE/PO/n-pentane in air were measured in 20 L, closed, stainless steel spherical vessels. Experimental results were obtained at ambient atmospheric pressure and an initial temperature of 40 °C. The experimental results show that the LFLs of DEE-air, n-pentane -air, and PO-air are 1.81 vol%, 1.41 vol% and 2.44 vol%, respectively. The LFLs of binary/ternary fuel mixtures under different compositions were tested, and the experimental results are compared with the classical Le Chatelier's formula. The results show that, for the binary fuels (i.e., DEE/PO, DEE/n-pentane, PO/n-pentane)-air mixtures, the maximum difference of the LFLs between Le Chatelier's formula and the experimental results is 6.10%. For the ternary fuels (i.e., DEE/PO/n-pentane)-air mixtures, the maximum difference of the LFLs between the two results is 6.33%. Due to the adiabatic flame temperature of each single fuel mixture being close, the Le Chatelier's formula is applicable for an estimation of the LFL for DEE/PO/n-pentane-air mixtures.     

危险品道路运输风险分级指数法研究

危险品道路运输过程风险影响因素多,随机性和不确定性大,定量风险评价比较复杂,至今没有统一的风险评估模型.为了有效预防危险品运输事故和进行快速风险评估,基于运输危险品本身特性和相关的风险影响因素探讨了运输危险品现实风险分级指数法.该方法由危险品风险分级指数、路线影响因素和安全措施补偿因子3部分构成.危险品风险分级指数由危险品加权平均风险等级和运输危险品量、泄漏点与居民区距离以及危险品扩散因子等级确定.危险品加权平均风险等级涉及其健康危害性、可燃性、化学反应活性以及特殊危险性(氧化性和与水反应性)等级的确定.路线影响因素包含运输道路特征、气象条件、交通状况和影响人员分布4类.安全措施补偿因子为车辆、设备、容器、包装因子,人员素质因子和安全管理因子3类.该方法可对运输危险品的潜在风险进行快速分级,有利于采取有效的安全预防和控制措施,降低运输事故概率和沿线影响人员风险.     

A societal risk study for transportation of class-3 hazmats – A case of Indian state highways

United Nations Class-3 hazardous materials (hazmats) are basically liquid products and transported in road tankers under ambient temperature and atmospheric pressure. They are mostly flammables and some of them are toxic (e.g. benzene) as well. The spillages due to collision related incidents involving the road tankers, carrying such hazmats through highways, pose not only flammability hazards due to pool fire, flash fire and vapor cloud explosion (VCE), but create substantial toxic hazards also. The paper presents the risk-based study of route evaluation of two state highways and one urban city road in western India on account of transportation of class-3 hazmats, namely benzene, toluene, p-xylene, methanol, cyclohexane and acetone. A comparative evaluation of study routes was undertaken based on their societal risks presented in terms of F–N curves and assessed against HSE, UK as well as VROM, The Netherlands risk acceptance criteria. Societal risks contribution of cyclohexane to the overall flammability risk mainly VCE is found to be the highest followed by acetone and benzene compared to other study hazmats. This is due to highly explosive nature of cyclohexane resulting into vapor cloud explosion. While acetone and methanol pool fires are likely to cause larger area of damage compared to others, benzene supersedes others as far as toxicity risk is concerned and larger evacuation area is encountered, as it poses greater Immediately Dangerous to Life or Health (IDLH) distance than others. Besides, study of initial isolation distance following an accident in case of benzene tanker found that benzene spillage requires larger initial isolation distance than others and so are the day and night protective action zone distances.     

Maintenance-related major accidents: Classification of causes and case study

The potential for major accidents is inherent in most industries that handle or store hazardous substances, for e.g. the hydrocarbon and chemical process industries. Several major accidents have been experienced over the past three decades. Flixborough Disaster (1974), Seveso Disaster (1976), Alexander Kielland Disaster (1980), Bhopal Gas Tragedy (1984), Sandoz Chemical Spill (1986), Piper Alpha Disaster (1988), Philips 66 Disaster (1989), Esso Longford Gas Explosion (1998), Texas City Refinery Explosion (2005), and most recently the Macondo Blowout (2010) are a few examples of accidents with devastating consequences.Causes are being exposed over time, but in recent years maintenance influence tends to be given less attention. However, given that some major accidents are maintenance-related, we intend to concentrate on classifying them to give a better insight into the underlying and contributing causes.High degree of technological and organizational complexity are attributes of these industries, and in order to control the risk, it is common to deploy multiple and independent safety barriers whose integrity cannot be maintained without adequate level of maintenance. However, maintenance may have a negative effect on barrier performance if the execution is incorrect, insufficient, delayed, or excessive. Maintenance can also be the triggering event.The objectives of this article are: (1) To investigate how maintenance impacts the occurrence of major accidents, and (2) To develop classification schemes for causes of maintenance-related major accidents.The paper builds primarily on model-based and empirical approaches, the latter being applied to reports on accident investigation and analysis. Based on this, the Work and Accident Process (WAP) classification scheme was proposed in the paper.     

Sam Mannan and his scientific publications: A life in process safety research

Dr. M. Sam Mannan is one of the true pioneers in the process safety area, spending almost his entire lifetime in process safety and risk research. He was dedicated to ‘make safety second nature’ and published an impressive body of work. An overview of his research helps understanding the process safety area and provides insight in the legacy of this process safety pioneer. In this paper, 327 publications authored by Dr. Mannan from 1999 to 2019 in Web of Science core collection were downloaded and visually analyzed from four perspectives: his publication outputs, collaboration networks, topic areas, and highly cited papers and cited references. The results show a rapidly increasing trend in his research activity, mostly through journal publications. He published in 53 different outlets, with Journal of Loss Prevention in the Process Industries being most frequently selected. Dr. Mannan had a very active and diverse worldwide network, and collaborated with 18 different countries/regions, nearly 90 different institutions and 387 authors. His publications addressed process safety-related topics widely, including safety related to liquefied natural gas, explosions, runaway reactions, inherent safety, flammability and aerosol, and more recently resilience. Dr. Mannan's most cited paper focused on ‘fuzzy risk matrix’, whereas the most frequently cited reference in his work is ‘thermal hazard evaluation by an accelerating rate calorimeter’ by Townsend DI in 1980. Based on his most recent research activity, promising future directions for process safety research include resilience linked to risk assessment and management, for instance through the ‘safety triad’ concept he promoted shortly before passing away.     

Predicting the flammable region reach of propane vapor clouds

Liquified gas fuels are widely used around the world, and the growth of LNG and LPG consumption continues to increase. However, using these fuels can lead to accidents if they are released to the environment. Consequently, the challenge to control and predict such hazards has become an objective in emergency planning and risk analysis. In a previous article the “Dispersion Safety Factor” (DSF) was proposed, defined as the ratio between the distance at which the lower flammability limit concentration occurs and that corresponding to the visible contour of a vapor cloud. Its interest was demonstrated by applying it to the specific case of an LNG spill. With the appropriate modifications, this factor may be applied to the dispersion of other substances; in this communication it is applied to the atmospheric dispersion of propane, and two expressions are proposed to estimate it. Due to the similarity between the properties of both gases, these expressions could probably be applied as well to the dispersion of propylene.     

Experimental investigation of spark ignition energy in kerosene,hexane, and hydrogen

Quantifying the risk of accidental ignition of flammable mixtures is extremely important in industry and aviation safety. The concept of a minimum ignition energy (MIE), obtained using a capacitive spark discharge ignition source, has traditionally formed the basis for determining the hazard posed by fuels. While extensive tabulations of historical MIE data exist, there has been little work done on ignition of realistic industrial and aviation fuels, such as gasoline or kerosene. In the current work, spark ignition tests are performed in a gaseous kerosene–air mixture with a liquid fuel temperature of 60 °C and a fixed spark gap of 3.3 mm. The required ignition energy was examined, and a range of spark energies over which there is a probability of ignition is identified and compared with previous test results in Jet A (aviation kerosene). The kerosene results are also compared with ignition test results obtained in previous work for traditional hydrogen-based surrogate mixtures used in safety testing as well as two hexane–air mixtures. Additionally, the statistical nature of spark ignition is discussed.