Numerical simulation of far-field blast loads arising from large TNT equivalent explosives

Large TNT equivalent explosions usually arise from accidents occurring during the transportation, storage, and manufacturing of chemicals relevant to process industries. The blast wave generated by the explosion will spread and interact with the surrounding factories and storehouses, damaging the building structures within several kilometers and causing significant casualties and property losses. This study aims to develop an efficient numerical simulation method to predict blast loads to estimate the consequences of accidents involving far-field free air bursts or surface burst explosions. Before its interaction with the interested target, a blast wave is generated in the numerical model by specifying the initial and boundary conditions of the disturbed air. Based on empirical data of incident overpressure, an explicit formula to calculate the air particle velocity is derived from the governing equations of a perfect inviscid gas. A simplified path line method is proposed to calculate the air density. The proposed method is applied to the LS-DYNA CESE solver to simulate the blast loads on building structures in the far field. Validations against empirical data and experiments indicate that the proposed method is sufficiently accurate for engineering applications and, through a case study, presents a more efficient performance than the LOAD_BLAST_ENHANCED (LBE) and mapping methods.     

环保型塑料产业进展

本文在持续跟踪环保型塑料产业动态的基础上,从原料开发、产品设计、废弃物回收利用等方面,综述了生物基和石油基环保型塑料产业的最新进展,旨在为塑料研发人员和相关产业工作者开拓思路。指出:环保型塑料是未来塑料产业发展的重要方向,非环保型塑料的市场份额将逐步被环保型塑料占据,最后稳定在较低的水平上。     

基于SHERPA的环境空气质量减排情景模拟评估

分析了SHERPA综合评价模型的基本原理和主要建模理念,重点介绍了其在环境空气质量减排情景模拟评估方面的作用,以及在排放源与受体关系(SRR)方面的处理方法,比较了其与欧盟常用的其他情景模拟模型的优缺点。SHERPA模型的特点是空间灵活性较好,对于任何给定地点,可以快速评估不同地区对该研究地点空气质量的影响。SHERPA模型的3个主要功能为污染物来源分析、决策支持和情景模拟。基于SHERPA模型对法国环境空气中PM_(2.5)、PM_(10)和NO_2年均浓度进行污染来源分析、决策支持分析和减排情景模拟评估,展示了模型在环境治理措施优先级筛选和政府间联合治理措施协调建议方面的功能和作用,以期为中国环境空气质量预测预报、环境质量管理措施的制定和成效评估等环境服务与管理工作提供借鉴。     

Toward harmonizing prospective effectiveness assessment for road safety: Comparing tools in standard test case simulations

Abstract

Objective: With the overall goal to harmonize prospective effectiveness assessment of active safety systems, the specific objective of this study is to identify and evaluate sources of variation in virtual precrash simulations and to suggest topics for harmonization resulting in increased comparability and thus trustworthiness of virtual simulation-based prospective effectiveness assessment.

Methods: A round-robin assessment of the effectiveness of advanced driver assistance systems was performed using an array of state-of-the-art virtual simulation tools on a set of standard test cases. The results were analyzed to examine reasons for deviations in order to identify and assess aspects that need to be harmonized and standardized. Deviations between results calculated by independent engineering teams using their own tools should be minimized if the research question is precisely formulated regarding input data, models, and postprocessing steps.

Results: Two groups of sources of variations were identified; one group (mostly related to the implementation of the system under test) can be eliminated by using a more accurately formulated research question, whereas the other group highlights further harmonization needs because it addresses specific differences in simulation tool setups. Time-to-collision calculations, vehicle dynamics, especially braking behavior, and hit-point position specification were found to be the main sources of variation.

Conclusions: The study identified variations that can arise from the use of different simulation setups in assessment of the effectiveness of active safety systems. The research presented is a first of its kind and provides significant input to the overall goal of harmonization by identifying specific items for standardization. Future activities aim at further specification of methods for prospective assessments of the effectiveness of active safety, which will enhance comparability and trustworthiness in this kind of studies and thus contribute to increased traffic safety.     

Impact of floodplain and Stage 0 stream restoration on flood attenuation and floodplain exchange during small frequent storms

River flooding impacts human life and infrastructure, yet provides habitat and ecosystem services. Traditional flood control (e.g., levees, dams) reduces habitat and ecosystem services, and exacerbates flooding elsewhere. Floodplain restoration (i.e., bankfull floodplain reconnection and Stage 0) can also provide flood management, but has not been sufficiently evaluated for small frequent storms. We used 1D unsteady Hydrologic Engineering Center's River Analysis System to simulate small storms in a 5 km-long, second-order generic stream from the Chesapeake Bay watershed, and varied % channel restored (starting at the upstream end), restoration location, restoration bank height (distinguishes bankfull from Stage 0 restoration), and floodplain width/Manning's n. Stream restoration decreased (attenuated) peak flow up to 37% and increased floodplain exchange by up to 46%. Floodplain width and % channel restored had the largest impact on flood attenuation. The incremental effects of new restoration projects on flood attenuation were greatest when little prior restoration had occurred. By contrast, incremental effects on floodplain exchange were greatest in the presence of substantial prior restoration, setting up a tradeoff. A similar tradeoff was revealed between attenuation and exchange for project location, but not bank height or floodplain width. In particular, attenuation and exchange were always greater for Stage 0 than for bankfull floodplain restoration. Stage 0 thus may counteract human impacts such as urbanization.     

武汉市一次污染过程的局地流场和边界层结构的数值模拟

利用2013年11月武汉市逐日空气质量资料、地面气象观测资料、NCEP/NCAR再分析资料和L波段雷达探空资料，通过WRF模式模拟空气污染生消过程中的局地气象条件变化，探讨特殊地形条件下边界层结构变化和局地环流在污染物生消过程中的作用和影响。结果表明：（1）武汉地区当背景环流场强的时候，由地形引起的局地流场对污染物扩散的影响就弱，反之当背景环流场弱的时候, 地形对流场影响明显:夜间为山风，白天为谷风。夜间山风与偏西北气流及偏东气流在武汉及周边地区辐合，形成气流汇聚带，在武汉地区形成一个反复污染带,即由地形引起的局地流场对污染物扩散的贡献就大；（2）武汉地区发生空气污染时，地面湿度较高，边界层呈上干下湿状态，其特征为暖而干且有偏东小风，这导致污染物不断堆积和重污染过程的形成。     

高含盐废水脱盐处理技术研究进展

综述了几种常见的高含盐废水脱盐处理技术的发展历程、工艺原理、优缺点及目前的研究进展，分析了热分离、膜分离、电渗析、离子交换、电吸附、微生物脱盐等方法的优缺点，展望了未来废水脱盐工艺的发展方向。指出：脱盐方法将根据各类水体的水质特点更加精细化；多种脱盐技术联合应用也是今后废水脱盐的发展方向。     

基于FDS的加油站便利店火灾模拟

为了研究加油站便利店火灾的发展规律，选择合理的疏散路线，使用 FDS软件对某加油站便利店进行火灾数值模拟。通过观察烟气扩散和动态升温过程，分析便利店的烟气扩散和升温规律，对比分析不同疏散路线上温度、烟气层高度和能见度的数据变化规律，分析选择不同疏散路线对人员安全疏散的影响。结果表明:在无火灾报警设备的情况下，卫生间等有隔断的设施会延迟设施内人员获得火灾信息的时间,不利于安全疏散；同等高度下靠墙区域受高温烟气影响较中央开阔区域更大；疏散时选择合理的疏散路线可以显著延长安全疏散时间。     

土压平衡矩形顶管施工引起的地表沉降规律研究

为了分析与掌握矩形顶管施工引起的地表沉降变形规律，提出基于MIDAS-GTS有限元软件的分析方法，首先，通过工程实例验证MIDAS-GTS有限元软件在分析顶管施工引起地表沉降变形的有效性；其次，通过影响因素的敏感性分析确定不同影响因素作用下的地表沉降变形特性，这些影响因素主要包括开挖面支护压力、侧摩阻力、地层结构特性等；最后，通过地表沉降变形特性分析得出矩形顶管的适用范围。研究结果表明:基于MIDAS-GTS有限元软件的地表沉降规律分析方法和结果，可为矩形顶管施工过程提供相关参考和借鉴。     

行为经济学视角下矿工不安全行为仿真分析

为了分析影响矿工不安全行为决策的成本收益因素，扩展不安全行为的研究方向，基于行为经济学，构建矿工不安全行为决策模型，模型包括矿工属性、管理者属性以及矿工之间的交互影响规则。利用Netlogo工具进行仿真模拟，探讨不同影响因素对不安全行为产生的影响程度。结果表明:正向激励水平对抑制不安全行为效果显著，同时，维持合理的工作时间对保障安全生产意义重大，从而为煤矿企业控制不安全行为提供思路。