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.     

移动式环保公厕车防震抗风安全性研究

移动式环保公厕车工作地点范围广、环境复杂,且没有地基固定,要求其具有特别高的抗地震能力、抗风载变形能力。利用有限元仿真的方法,研究了移动式环保公厕车在不同地震载荷、风力载荷条件下的变形和应力状况,分析了地震载荷和风力载荷对移动式环保公厕车破坏程度和破坏机理,对比了单一载荷作用与复合载荷作用的区别,从而为移动式环保公厕车使用环境的选择、安全检查的合理安排等提供有力的参考依据。     

The role of agri‐environment schemes in conservation and environmental management

Over half of the European landscape is under agricultural management and has been for millennia. Many species and ecosystems of conservation concern in Europe depend on agricultural management and are showing ongoing declines. Agri‐environment schemes (AES) are designed partly to address this. They are a major source of nature conservation funding within the European Union (EU) and the highest conservation expenditure in Europe. We reviewed the structure of current AES across Europe. Since a 2003 review questioned the overall effectiveness of AES for biodiversity, there has been a plethora of case studies and meta‐analyses examining their effectiveness. Most syntheses demonstrate general increases in farmland biodiversity in response to AES, with the size of the effect depending on the structure and management of the surrounding landscape. This is important in the light of successive EU enlargement and ongoing reforms of AES. We examined the change in effect size over time by merging the data sets of 3 recent meta‐analyses and found that schemes implemented after revision of the EU's agri‐environmental programs in 2007 were not more effective than schemes implemented before revision. Furthermore, schemes aimed at areas out of production (such as field margins and hedgerows) are more effective at enhancing species richness than those aimed at productive areas (such as arable crops or grasslands). Outstanding research questions include whether AES enhance ecosystem services, whether they are more effective in agriculturally marginal areas than in intensively farmed areas, whether they are more or less cost‐effective for farmland biodiversity than protected areas, and how much their effectiveness is influenced by farmer training and advice? The general lesson from the European experience is that AES can be effective for conserving wildlife on farmland, but they are expensive and need to be carefully designed and targeted.     

中国农田N_2O排放量的估算

排放量估算是温室效应气体研究的重要内容。本文论述了影响农田Ｎ２Ｏ排放量估算准确性的因素，讨论如何提高农田Ｎ２Ｏ排放量估算的准确性，并估算了中国农田Ｎ２Ｏ排放总量。     

湿地冷湿效应初探

对湿地周围不同距离农田的近地面气温、湿度、地温以及典型湿地地温的测定表明 ,湿地冷湿效应与湿地植被及其积水深度有关。在所选择的 3种湿地植被中 ,漂筏苔草积水最深 ,冷湿效应最大 ,其次为毛果苔草 ,小叶章最小。不同距离农田的近地面气温和湿度变化不同 ,随距离增加 ,温度增大 ,湿度减小。这种变化主要是由湿地的局部冷湿作用造成的。农田地温平均值高出小叶章湿地 4℃之多 ,高出漂筏苔草湿地近 5℃ ,表明湿地的制冷作用很明显     

有机农业与常规农业对农田生物多样性影响的比较研究进展

一些研究者认为,有机农业不仅在理念上而且在实践上,都有助于促进农田生物多样性的维持和保护.为了促进我国科学界对有机农业与农田生物多样性关联性研究的关注,综述了有机农业对农田生态系统内杂草、地表节肢动物、土壤生物以及鸟类等不同生物类群种类、数量及其多样性的影响.     

煤矿井下气候参数和劳动强度对矿工生理参数影响的研究

对机械化采煤工作面的采煤机司机和支柱工的劳动心率和能量代谢进行了现场实测。就气候参数和劳动强度对作业人员的生理参数影响进行了模拟实验,取得一些实验研究成果。对改善劳动条件和作业环境,提高生产效率,保护井下矿工的身心健康与安全,提供了科学依据。     

Long-term temporal-spatial dynamics of marine coastal water quality in the Tolo Harbor, Hong Kong, China

IntroductionToloHarborislocatedinthenortheasternpartofHongKong .Itisanearlyland lockedwaterbodywithonlyonenarrowexittotheopenseaatMirsBay(Fig .1) .Itslengthandsurfaceareaareapproximately 15kmand 5 2km2 ,respectively .Theaveragedepthvariesfromlessthan10min…     

渗滤液回灌设计中一些参数的理论研究

考虑填埋场中微生物对污染物的生物降解作用 ,建立了描述回灌条件下填埋场内渗滤液迁移规律的数值模型。通过建立的模型分析了回灌设计中的一些技术参数 (如水力负荷、有机负荷及配水次数等 )对回灌处理效果的影响规律 ,以供实际工程参考     

混凝-生物接触氧化法处理城市污水的研究

采用混凝-生物接触氧化法处理生活小区废水,考察了不同混凝剂用量对COD、NH4-N、SS、TP的去除效果,同时研究了生物接触氧化法对COD、NH4-N等的去除以及耐冲击负荷能力.结果表明,随混凝剂用量的增加,COD、SS、TP的去除率随之增加,生物接触氧化法具有较高的抗冲击负荷能力,最大NH4-N去除负荷达到0.55 kg/(m3·d),最大有机去除负荷达到4.32 kg/(m3·d)