Arsenic forensic modeling leads to decommission of downgradient/off-site monitoring wells

Arsenic was detected at concentrations exceeding the regulatory limit of 0.010 milligrams per liter (mg/L) in an off-site bedrock monitoring well downgradient of a former electroplating facility in Merrimack, New Hampshire. The bedrock underlying the site is associated with naturally occurring high concentrations of groundwater arsenic. Geochemical modeling was used to evaluate whether the arsenic in bedrock groundwater at the off-site monitoring location was site-related or naturally occurring. The hydrogeochemical signature of the off-site bedrock well did not resemble signatures of site-impacted bedrock wells. Multiple lines of evidence support that the arsenic observed in off-site bedrock groundwater was not a result of adverse impacts from site-related groundwater contamination.     

改进环境和职业健康安全管理整合体系适应GB/T24001-2004标准

建立与实施环境和职业健康安全管理整合体系有利于企业降低管理成本、提高管理效益。环境管理体系标准的改版加强了其与其他管理体系之间的协调性和兼容性,有利于进一步推动整合体系的建立与实施。在深入研究GB/T24001-2004版标准在结构框架、术语、要素名称及内容等方面变化情况的基础上,在环境和职业健康安全方针、目标、指标和方案的策划、资源,特别是基础设施的保障、合规性评价的完善、纠正措施和预防措施的实施以及一体化内部审核的开展等方面提出了建议对策,以供企业借鉴。改进环境和职业健康安全管理整合体系,以适应体系标准的发展变化,不断提高企业的现代安全健康管理水平是企业可持续发展的重要因素。     

高层综合楼排烟系统设计分析与计算校核

高层综合楼功能复杂,人员密集,火灾危险性大,而火灾中烟气的毒害和窒息作用是致人死亡的最主要原因。因此,对该类建筑进行必要的排烟设计,既可以保证人员疏散安全,也有利于进行消防扑救。以某高层综合楼的排烟设计为例,对其排烟系统设计进行分析,重点对其排烟风机的排烟量进行计算校核,并提出了在排烟系统设计时应注意的问题,为设计人员及消防设计审核人员提供参考。     

减推力起飞对NOx排放影响计算方法研究

伴随着航空公司对未来几年氮氧化物(NOx)排放量增长的预测,量化机场NOx排放量日益重要。根据国际民航组织认证的发动机排放数据,在研究推力对NOx排放的影响时,通常模拟4个推力级别:100%(起飞阶段)、85%(爬坡阶段)、30%(进近阶段)、7%(慢车阶段)。美国联邦航空局设计了模型——排放和扩散模拟系统,利用该模型对4个阶段分别进行模拟。结果表明,飞机在最大推力时产生的NOx量最多。分析了起飞阶段减推力下起飞对机场年NOx排放量的影响,通过排放和扩散模拟系统,研究了一系列算法,用于预测推力与NOx排放量的关系。     

Risk assessment of offshore crude oil pipeline failure

Failure of Leak Detection System (LDS) to detect pipeline leakages or ruptures may result in drastic consequences that could lead to excessive financial losses. To minimize the occurrence of such failure, the functionality of the LDS and the integrity of the pipeline should be assessed on a priority basis. This paper presents an integrated risk-based assessment scheme to predict the failure and the failure consequences of offshore crude oil pipelines. To estimate risk, two important quantities have to be determined, the joint probability of failure of the pipeline and its LDS and the consequences of failure. Consequences incorporate the financial losses associated with environmental damage, oil spill cleanup and lost production. The assessment provides an estimate of the risk in monetary value and determines whether the estimated risk exceeds a predefined target risk. Moreover, the critical year for the asset can be determined. In essence, the outcome of the assessment facilitates an informed decision-making about the future of the asset.     

The role of component arrangement in complex safety instrumented systems—A case study

The arrangement of components plays a key role in the performance of complex Safety Instrumented Systems (SIS), in which a SIS logic solver is interlocked with other logic solvers, to share a final element, for instance. The position of the components and the way they are utilized affects the reliability characteristics, such as the Probability of Failure on Demand (PFD), Spurious Trip Rate (STR), architectural sensitivity and model uncertainty. This case study uses quantitative and qualitative approaches to elaborate on various aspects of component arrangement in complex SIS. Numerous simplified models are analyzed; new classification is introduced for SIS components based on their response to demand; a set of guidelines are developed for SIS architecture design, with a focus on component arrangement; and the use of these guidelines is demonstrated in a real-life example, where an existing turbine SIS is modified to incorporate a new over-speed protection system. The simplified models and the turbine upgrade project are also used to explain the issue of unknowns and uncertainties in reliability analysis and how these issues can be addressed in SIS architecture by optimizing component arrangement.     

Numerical modeling of water spray suppression of conveyor belt fires in a large-scale tunnel

Conveyor belt fires in an underground mine pose a serious life threat to miners. Water sprinkler systems are usually used to extinguish underground conveyor belt fires, but because of the complex interaction between conveyor belt fires and mine ventilation airflow, more effective engineering designs are needed for the installation of water sprinkler systems. A computational fluid dynamics (CFD) model was developed to simulate the interaction between the ventilation airflow, the belt flame spread, and the water spray system in a mine entry. The CFD model was calibrated using test results from a large-scale conveyor belt fire suppression experiment. Simulations were conducted using the calibrated CFD model to investigate the effects of sprinkler location, water flow rate, and sprinkler activation temperature on the suppression of conveyor belt fires. The sprinkler location and the activation temperature were found to have a major effect on the suppression of the belt fire, while the water flow rate had a minor effect.     

营运驾驶员驾驶事故影响因素仿真研究

解决营运驾驶员驾驶事故频发的不安全行为问题,基于复杂适应系统（CAS）理论和多主体建模与仿真（ABMS）方法,构建营运驾驶员驾驶事故模型。通过调节车辆状况、管理者管理监督水平、营运驾驶员情绪状态、安全教育水平、驾驶经验和环境综合条件等因素,运用NetLogo仿真平台分析安全管理水平、营运驾驶员安全责任意识、心理负荷水平对驾驶事故的影响。研究表明:营运驾驶员驾驶事故的发生系统是一种典型的CAS,营运驾驶员驾驶事故是三大主体属性和行为环境交互的结果,且交互作用程度不同。因此,运输企业要考虑多种因素,采取相应的措施来降低营运驾驶员驾驶事故的发生。     

Safer Truck Front Design for Pedestrian Impacts*

Truck and bus frontal impacts account for a major proportion of pedestrian fatalities in many less motorized countries. To understand this phenomenon, we have collected injury data on pedestrian impacts with buses and trucks and performed computer simulations to identify critical design parameters at 15–45 km/h impact velocities for further investigation. A male dummy which was scaled to fifty percentile Indian dimensions has been used for simulations using MADYMO. Bumper height, bumper offset and grille inclination affect the pelvis and thorax forces and Head Injury Criterion values critically. Bumper width has less effect. Simulations were performed to optimize for the above–mentioned three parameters. Changes in front geometric parameters reduce injury to the upper body and head below safety limits for the existing force–displacement properties but do not affect leg injuries significantly. Hence bumpers need to be made less stiff. Injury data shows that pedestrians also sustain tibia fractures in bus/truck impacts in apparent low velocity impacts. The computer modeling does not offer adequate explanation for this phenomenon. These simulations confirm that it is theoretically possible to make truck/bus fronts safer for pedestrians in impacts up to 35 km/h.