冷摆辗模具的材料选择及其热处理

模具寿命是冷摆辗的关键问题之一。选择合理的模具材料以及采用适宜的热处理工艺可以提高冷摆辗模具的强韧性,从而提高模具寿命。基于摆动辗压工艺的基本原理,分析研究了冷摆辗模具的受力情况,并对冷摆辗模具材料的选择及热处理工艺作了探讨。     

An experimental study on the burning rate of a continuously released n-heptane spill fire on an open water surface

Spill fires are common during oil product storage and transportation after a loss of containment. Since the burning fuel is moving and the fuel depth is quite shallow, the burning rate in a spill fire is different from that of a pool fire with a static burning zone. Unlike pool fires, which have been studied for decades and have well-established correlations for burning rate, research on spill fires is inadequate. In this paper, continuously released n-heptane spill fire experiments were conducted on open water surfaces with varying fuel discharge rates. The pool diameters were measured, and the spill fire burning rates were estimated based on a dynamic balance between fuel supply and combustion. The burning rates in n-heptane pool fires from the literature were reviewed and compared with the estimated burning rates in spill fires of the same dimension. The spill fire burning rate was found to be close to that in a pool fire during the initial burning phase but lower than that in a bulk burning pool fire and that in a “fuel-level-controlled” pool fire. The distinction between the burning rates of spill fires and pool fires is explained by the heat balance analysis of the fuel layer. A model for the spill fire burning rate was proposed accordingly. The results calculated with the presented model are closer to the measured data than those calculated with pool fire models.     

烟气深度余热回收技术对燃气锅炉NOx排放扩散迁移规律的影响研究

运用Fluent计算软件对北京市丰台区某燃气锅炉排放烟气中NOx的转化和扩散过程进行了数值模拟,定量地研究了烟气深度余热回收技术对燃气锅炉排放NOx在大气中的迁移规律产生的影响,并与Screen 3模型模拟的结果进行了对比.研究发现:烟气深度余热回收技术的应用使NOx的最大落地浓度与烟气直排时相比增加了2.5倍,NOx对本地地表的影响面积增大了15750 m2,增加了本地环境污染的风险.结合燃气锅炉的NOx控制技术提出了缓解局部环境风险的解决方案.结果表明,烟气深度余热回收技术与低氮燃烧技术联用,NOx的控制效率达到70%以上时,在有效提升锅炉热效率的同时,可以缓解由于烟温大幅下降造成的本地环境污染恶化的风险.     

香港城市固体废物系统管理

本文以大量翔实的数据介绍了香港对城市固体废物的系统管理,即分类、收集、监测分析、处理和预测评价。香港环保署自８０ 年代开始对城市固体废物进行监测并系统管理。在全港设置了３ 个大型策略性填埋场、５ 个垃圾转运站、１ 个垃圾焚烧厂（１９９７ 年５ 月关闭） 和１个化学废物处理中心。目前,香港政府正筹建一个新的、技术先进的焚烧厂。从１９８６ ～１９９７年,这些废物处理设施处理全港废物量为８９６０ ～２４３００ｔ／ｄ,其中城市固体废物比例每年不等,最低为３０ ．７ ％ ,最高为６５ ．５ ％ 。１９９７ 年,这些废物中可循环再利用物接近５０ ％ ,出口部分达１２０ 多万吨,回收资金２０ 多亿港元。根据历年来城市固体废物量与本地生产总值（ＧＤＰ）和人口数量的密切相关性,预测出２０１１ 年城市固体废物人均产率为２ ．５６ｋｇ／ 人·ｄ, 城市固体废物量为１２８１０ ｔ／ｄ。城市固体废物系统管理紧迫而重要,香港的经验是值得我们借鉴的。     

低浓度Pb2+、Cd2+对鲫鱼肝脏组织中 HSP70诱导的影响

以鲫鱼(Carassius auratus)作为实验对象,经过40 d Pb2+、Cd2+不同浓度的暴露后,运用SDS-PAGE和Western Blotting方法检测鱼肝脏组织内应激蛋白HSP70的诱导表达情况.结果表明,在实验浓度下,与对照组相比,Pb2+、Cd2+对鱼肝脏内HSP70有显著的诱导(P＜0.05),但在Cd2+浓度为0.2 mg/L有停止表达HSP70的现象,可能是由于浓度过高造成了组织病理损伤而破坏了诱导表达机制.实验还发现,在实验浓度低于国家渔业用水标准时,HSP70仍然表现为明显诱导(P＜0.05),充分说明运用分子生物学指标要比传统的环境检测指标敏感,具有对污染物早期预警的作用.     

低压下近熄灭极限区域纸火蔓延实验研究

对低压下的近熄灭极限区域水平纸火蔓延进行了实验研究。通过降低环境压力和氧气浓度,确定了水平纸火蔓延的着火极限,并得出了在极限氧气浓度条件下的火蔓延速度变化规律。在相同氧气浓度下(43%)进行了不同压力的水平纸火蔓延实验。结果表明,火蔓延速度在近熄灭极限区域内非线性增加,通过比较分析前人火蔓延速度实验结果,确定了火蔓延近熄灭极限区域和线性增长区域的分界压力值。此外,得出了压力分界处的火焰变化特征,并根据火焰图像与理论分析,得出了不同区域内的火蔓延传热机制。     

中国农业净碳汇时空演化特征分析

论文以全国范围县级单元为研究对象,对1991—2011年长达21 a的农业净碳汇时空格局变化规律展开了深入分析。研究表明：1）从时间变化角度可以发现,整体上我国农业在长达21 a内均以净碳汇为主,并且总体上处于波动上升趋势,农业净碳汇净增93.7%;2）我国农业碳汇结构相对比较稳定,稻谷、小麦和玉米三者共同占到了80%左右,而碳源结构则在1991—2011年间发生了较大变化,由1991年农药为主,化肥、牛为辅转变成为化肥为主,农药、地膜、牛为辅的结构;3）空间分布方面,我国县域农业净碳汇量地区间差距在不断缩小,存在4种农业碳生态类型区;4）1991—2011年间净碳汇为负值的县级单元数量增多,并且在空间上主要分布于西南地区与内蒙古。农业种植量相对较小,作物生长碳吸收不明显,单位产量农业投入要素多以及农业类型以畜牧业为主是这些地区农业净碳汇为负值的主要原因。     

The interaction of heat shock proteins and some components of plant viruses北大核心CSCD

Considerable research has indicated that heat shock proteins (Hsp), as molecular chaperones, carry out many biological activities of plant viruses by folding, transporting, translocating, assembling, or degrading client proteins. It is fundamental to develop resistant plant varieties and novel anti-viral agents by determining the interaction mechanisms between plant viruses and hosts. In this study, we first reviewed the classification, gene and protein structure, and biological significances. We then analyzed the assembling mechanism of Hsp70 or Hsp90, plant host cofactors, and RNA-dependent RNA polymerases in a viral replicase complex, and the mechanism of interaction and subcellular localization between Hsp70 and some plant virus components. We highlighted the mechanism of interaction and movement between Hsp70 and some plant virus components and the effect of Hsp expression of plant hosts or viruses. The results indicated where the mechanism occurred, the participating factors, energy supply, and material conversion between Hsps and the plant virus components for the course of the intracellular movement, local movement between cells, and long-distance movement, and showed the Hsp type specificity and the law of dynamic Hsp expression in plant hosts infected by viruses. The studies mainly focused on the two Hsp factors and the plant viral components, indicating limited coordination mechanisms among many nucleic acids, proteins, and polysaccharides in macromolecular protein complexes (MRC). Future research should analyze the translocation mechanism between client proteins and Hsps, the coordination mechanism between Hsps and MRC components, and the relation between MRC and the plant tissue structure. © 2018 Science Press. All rights reserved.     

Theoretical and Experimental Investigation of a Novel Hybrid Heat-Pipe Solar Collector

Abstract

This article describes a novel flat plate heat-pipe solar collector, namely, the hybrid heat-pipe solar collector. An analytical model has been developed to calculate the collector efficiency as well as simulate the heat transfer processes occurring in the collector. The effects of heat pipes/absorber, top cover, flue gas channel geometry, and flue gas temperature and flow rate, on the collector efficiency were investigated based on three modes of operation, i.e., solar only operation, solar/exhaust gas combined, and solar, exhaust gas and boiler combined. Experimental testing of the collector was also carried out for each of these modes of operation under real climatic conditions. The results were used to estimate the efficiency of the collector and determine the relation between the efficiency and general external parameter. The modeling and experimental results were compared and a correlation factor was used to modify the theoretical predictions. It was found that the efficiency of the collector was increased by about 20–30% compared to a conventional flat-plate heat pipe solar collector.     

植物碳酸酐酶对岩溶作用的影响及其生态效应

广泛存在各种类型生物细胞中的碳酸酐酶（cA）,通过催化C02和HCO3^-之间的相互转化,驱动岩溶过程。文章通过分析我国西南典型岩溶区植物叶片和根系CA活性,探讨其与岩溶作用的相互关系,结果表明：岩溶生态系统中植物的碳酸酐酶活性差异较大,并在植物的生长期发生变动,植株根系CA活性〉成熟叶片CA活性,因而在土壤水分充足的条件下．根系分泌的CA催化CO2＋H2O←→HCO3^-＋H^＋过程,促进石灰岩溶解,加快成土速率,并通过固定根呼吸和土壤微生物分解所释放的CO2产生岩溶碳汇效应;非岩溶生态系统由于土壤碳酸钙含量低,造成植物根系CA表达活性较低。