Analysis of crater formation in buried NG pipelines: A survey based on past accidents and evaluation of domino effect

The formation of a crater by the abrupt and catastrophic rupture of a high-pressure pipeline can be highly relevant, especially when the crater uncovers other pipelines, which could undergo a domino effect with a significant increase of the consequences on people or on the environment. However, this scenario has been only partially studied in the literature. To assess the influence of the pipeline parameters on the dimensions of the resulting crater, a statistical analysis of accidental ruptures of buried natural gas pipelines that have involved the formation of a crater was carried out. Mathematical expressions are proposed to describe the proportionality relationships found, which can be very useful to support adequate separation distances in the design and construction of parallel corridors of pipelines after appropriate escalating effects are considered. Finally, detailed event trees were developed to calculate the probability of occurrence of the final outcomes, as well as the identified domino sequences, based on a qualitative and quantitative analysis of the data. The study of these accident scenarios, based on actual cases, represents a useful and needed advance in risk analysis of natural gas transportation through pipelines.     

Dynamic pressure induced by a methane–air explosion in a coal mine

The hazardous effect of dynamic pressure and strong gas flows induced by a methane–air mixture explosion in underground coal mines is studied. The dynamic pressure effect of a methane–air explosion was analyzed by numerical simulation, in a duct and tunnel. Compared to the overpressure generated by an explosion that can act on a body, the dynamic pressure caused by the high-speed flow of the gaseous combustion products can cause serious damage as well. At the structural opening of a coal mine, the destruction caused by the dynamic pressure induced by a methane–air explosion is more serious than the overpressure. For a tube or tunnel partially filled by a methane–air mixture, the dynamic pressure is lower than the overpressure in the region occupied by the flammable mixture. Beyond the premixed region, the dynamic pressure is of the same order of magnitude as the overpressure.     

生态补偿助力脱贫攻坚：协同、拮抗与对接

中央政府提出的“生态补偿脱贫一批”标志着生态补偿扶贫正逐步成为我国打赢脱贫攻坚战的重要途径之一。2020年是脱贫攻坚战的决胜之年，生态补偿如何有效助力脱贫攻坚成为研究的热点。本文以实践与政策为导向，运用文献研究法和逻辑分析法，在厘清生态补偿扶贫理念形成与发展的基础上，解析生态补偿与脱贫攻坚之间存在的协同效应和拮抗效应。研究发现生态补偿与脱贫攻坚在地理空间位置、实施主客体、标准、方式和途径等方面相耦合容易产生协同效应，在价值诉求、农户资源禀赋、政府部门工作等方面矛盾产生拮抗效应。生态补偿有效助力脱贫攻坚的关键在于构建对接机制以强化协同效应、弱化或去除拮抗效应。为此，通过建立精准的瞄准制度、稳定脱贫的长效机制、政府部门内部生态补偿扶贫协调机制等举措，构建生态补偿与脱贫攻坚的对接机制，以促进二者高效协同发展。     

不同孔径排放钻孔有效影响半径的时空响应

针对矿井在施工排放钻孔局部防突措施时,已知排放时间,如何确定排放钻孔孔径和钻孔间距这一难题,提出一种钻屑量和钻屑瓦斯解吸指标现场测试法,结合数值模拟计算,确定不同孔径排放钻孔有效排放半径随时间的变化规律。研究结果表明:同一孔径排放钻孔,随着排放时间的增加,有效排放半径呈幂指数增大;不同孔径排放钻孔,随着排放钻孔直径的增加,有效排放半径呈幂指数增大。研究结论对矿井选取合适的排放钻孔孔径及布置参数具有指导意义。     

惰性粉体对蔗糖粉尘最小点火能的影响研究

为了预防蔗糖粉尘爆炸,利用1.2 L哈特曼管研究了NH₄H₂PO₄与Al(OH₄对蔗糖粉尘爆炸的抑制作用。在蔗糖粉尘质量分数一定的条件下,通过改变 NH₄H₂PO₄与Al(OH)₄的粒径和质量分数,测定其对蔗糖粉尘爆炸的抑制效果。结果表明:随着NH₄H₂PO₄和Al(OH)₄质量分数的增加,粒径的减小,蔗糖粉尘的最小点火能均逐渐增大,当惰性粉体增加到一定质量时,蔗糖粉尘被完全惰化,在蔗糖粉尘中分别加入粒径为48~74,38~47,25~37 μm的NH₄H₂PO₄和Al(OH)₄,3种粒径的NH₄H₂PO₄使蔗糖粉尘完全惰化的质量分数分别为40%,35%,30%,3种粒径的Al(OH)₃使蔗糖粉尘惰化的质量分数均为60%。因此(NH₄)H₂PO₄抑制蔗糖粉尘爆炸的效果比Al(OH)₃更显著。     

生态建筑及其绿色生态住区环境效益

从生态建筑的内涵出发，以国内外生态建筑实例为理论依据，绿色生态住区为对象性，阐述了绿色生态住区的开发与建设，应遵循生态设计理论和生态美学观念，符合可持续发展规律，并将绿色生态住区的构建视为生态建筑的观察平台，指出生态建筑的规划与设计必须考虑环境的生态、社会及其经济效益的统一。     

刈割对香港草地干物质生产的影响

研究了刈割频率对香港草地于物质生产的影响。结果表明，刈割使干物质生产量下降，刈割频率越高生产量下降越大。禾本科植物受刈割影响比木本和非禾本科草本植物大，且停止刚割一年后生物量仍低于对照点。认为常年刈割是华南草地生产力下降的重要原因之一。     

支持人居环境健康发展的自然调和理论研究

人类聚居的城市环境和建筑环境，与人类自然气象环境之间持续着动态的自然调和作用，当然调和理论是支持人居环境可持续发展的基础理论之一；文中圈定了自然调和理论研究的框架体系；介绍了面向人居环境的可持续发展所进行的自然调和技术研究进展；剖析了自然调和理论问题研究的科学性。     

机械振荡对猕猴桃愈伤组织的生理效应

通过机械振荡处理中华猕猴桃（Actinidia chinensis planch)茎段的愈伤组织，研究模拟振荡方式的力学刺激对木本植物愈伤组织生长分化的生理生化效应。结果表明，猕猴桃对机械振荡的应激效应与本实验室此前对草本植物非洲雏菊（Gerbera jamesonii acrocarpous)的研究有相似的结果。即适度的机械振荡（频率2-3Hz)可促进猕猴桃愈伤组织的生长，使胞内可溶性蛋白质含量升高，SOD活性升高，而IAA氧化酶活性质膜的通透性降低；但当振动强度超过一定范围（3Hz)后，愈伤组织的生长受到明显的抑制，可溶性蛋白质含量下降，SOD活性降低，而IAA氧化酶活性升高，同时细胞膜的封闭和完整性受到损伤，透性增大，研究显示植物对外界应力刺激的响应（应激效应）是很明显的图1表2参17。     

河西走廊园林绿地复合系统的夏季小气候效应

选择17种不同结构的园林绿地复合系统，对光照、温度、湿度和防尘效应进行测定，综合评价这17种园林绿地复合系统在改善城市气候方面的作用．结论是：乔、灌、草园林绿地复合系统在改善城市气候方面的作用最大，表4参7