Safety-related conclusions for the application of ultrasound in explosive atmospheres

International safety regulations such as EN 1127-1 consider ultrasound to be an ignition source. Currently, applications of ultrasound in explosive atmospheres have to comply with a threshold value of 1 mW/mm². However, it is unclear as to how this intensity has to be measured and, therefore, this threshold value is poorly defined. Moreover, it is based on theoretical estimations in analogy to other ignition sources and there are no publications or significant records on these estimations. Within a research project at PTB, it has now been investigated experimentally in relation to worst-case considerations including airborne ultrasound, focused MHz ultrasound in liquids and acoustic cavitation. On the basis of the results of the research it is now possible to revise the current regulations and to specify measures for safe operation of ultrasonic applications in explosive atmospheres. In this context, for ultrasound coupled directly to gaseous atmospheres a new threshold value of 170 dB (re. 20 μPa) can be suggested, and for ultrasonic applications in liquids, an augmentation can be made to the threshold to 400 mW/mm².     

温差拉深法在制造大型杯形件中的应用

用温差拉深法制造大型杯形件毛坯,可避免毛坯拉断和起皱,最大限度地降低拉深系数、减少拉深次数、降低加工成本。     

水质模拟及趋势分析

根据洛河、伊河河流及流经地区特征 ,选择具有代表性的断面 ,选用一维河流有限差分水质模型 ,计算洛河、伊河 1 995～2 0 0 0年主要断面污染物浓度 ,并对其进行评价。采用季节性肯达尔检验法 ,对计算出的洛河、伊河 1 995～ 2 0 0 0年主要断面污染物浓度进行趋势分析 ,并分析其变化特征及形成原因     

Pulse cleaning flow models and numerical computation of candle ceramic filters

ＩｎｔｒｏｄｕｃｔｉｏｎＣｌｅａｎｉｎｇｔｈｅｆｉｎｅｐａｒｔｉｃｌｅｓｉｎｈｉｇｈｔｅｍｐｅｒａｔｕｒｅ (450℃ -950℃ )ａｎｄｈｉｇｈｐｒｅｓｓｕｒｅｃｏｎｄｉｔｉｏｎｃａｎｅｎｈａｎｃｅｔｈｅｔｈｅｒｍａｌｅｆｆｉｃｉｅｎｃｙｏｆｃｌｅａｎｃｏａｌｔｅｃｈｎｏｌｏｇｉｅｓｓｕｃｈａｓＩＧＣＣｏｒＰＦＢＣ .Ｒｉｇｉｄｃｅｒａｍｉｃｆｉｌｔｅｒｓｏｆａｖａｒｉｅｔｙｏｆｓｔｒｕｃｔｕｒｅｓａｒｅｕｎｄｅｒｄｅｖｅｌｏｐｍｅｎｔｉｎｐｒｏｇｒａｍｓａｒｏｕｎｄｔｈｅｗｏｒｌｄ ,ｗｈｉｃｈｃａｎｆｉ…     

氯气和光气爆燃事故源强估算

在建立化学品泄漏的气体排放、液体排放、两相排放模式和爆炸燃烧的火球和气爆，蒸气云爆炸及绝热扩散和池蒸发扩展等模式的基础上，估计分析了氯气和光气爆燃事故源强，即爆炸能量及碎片抛射、冲击波、热辐射和毒云等后果影响     

Prevention of gasoline vapor explosions in portable fuel containers

Portable Fuel Containers (PFCs) made for consumer use can, under unusual circumstances, develop a flammable atmosphere in the container headspace. In order to prevent an inadvertent ignition from causing flame propagation into this headspace and a subsequent explosion or flame jetting, PFC manufacturers are developing prototype Flame Mitigation Devices (FMDs) for installation in the PFC. A test method is described in this paper to determine if the installed FMD will indeed prevent flame entry into the PFC in a high-challenge flame propagation scenario. The method entails the use of a butane-air mixture ignited in a 5 cm diameter, 12 cm long tube attached to either the container neck or a spout on the container neck. Two concept FMD designs have successfully prevented repeated attempts at flame propagation into the PFC and have also produced encouraging results in tests for fuel flow restriction, duel dispensing nozzle friction, and prolonged fuel exposure. Versions of these tests are currently being promulgated in a draft ASTM standard on PFC FMDs.     

水中氮类污染物的联系与区别

叙述了水体中含氮类污染物的来源，种类，相互转化方式和条件，表征意义等，以便对水中氮类污染物有一个全面，系统的认识。     

Effects of ecological factors on the diurnal activity rhythm of Yakutian black-capped marmots (Marmota camtschatica bungei) in the arctic

It is established that the activity of marmots (the genusMarmota) on the surface is timed to the daylight period. In the Arctic, under conditions of continuous illumination (the polar day), the diurnal rhythm of black-capped marmotsMarmota camtschatica bungei on the surface has a “daylight” pattern. The main external regulator of the diurnal rhythm is the altitude of the sun above the horizon. In the cold period, however, the effect of air temperature on animal activity becomes stronger.     

超低空航拍技术在输变电环评工作中的应用研究

分析了环评工作中收集的影像资料存在的问题,提出了超低空航拍的解决方法。通过对比分析,选择了多旋翼无人机作为超低空航拍平台。该设备具有携带方便,飞行稳性的优点。从实际应用效果来看,基于该技术获得的影像信息含量全面、工作效率高、评价结果更客观可信,为提高环评工作质量提供了一个可靠的技术方案。     

“一带一路”沿线国家粮食生产的时空格局分析

“一带一路”倡议是新时代下全球化发展的必然结果。粮食作为一种重要的战略资源,其生产对“一带一路”沿线国家乃至全球粮食安全意义重大。通过对沿线国家粮食生产数量、结构等方面的深入剖析,揭示了“一带一路”沿线国家近40年来粮食生产的时空格局。结果表明：（1）“一带一路”沿线国家是世界粮食的重要产区,粮食产量占全球比例50%~60%左右,1977-2016年粮食产量呈增长趋势,单产是其粮食总产增长的主要影响因素。1995-2016年人均粮食产量有所提高但国别差异显著,人粮关系逐步改善,区域粮食保障程度整体增强。（2）“一带一路”沿线国家粮食生产存在明显的地域差异,空间格局相对稳定,中国、印度、俄罗斯是其主要粮食生产国,东南亚和南亚国家的粮食产量普遍较高,阿拉伯半岛国家的粮食产量相对较低。（3）稻谷、小麦和玉米是“一带一路”沿线国家主要粮食作物,稻谷对粮食总产变化的贡献最大,1977-2016年玉米占比不断增加,三大作物区域分布特征明显。