Evaluation of the Energy Release Rate of Three-point-bending Beam Using Finite Element Method

Calculation of the energy release rate with finite element method (FEM ) is conducted. The concrete beam model is meshed using a method without need of considering the crack-tip singular element. Two columns of nodes, which belong to the right-and left-parts of the beam, respectively, are generated on the central line of the model and released one after another in a proper sequence. Energy release rate is evaluated based on the virtual crack closure technique. Comparison between the calculated values and theoretical values is made, which shows that they are in good agreement.     

Experimental Analysis on Heat Release Rate of Materials

The heat release rate is the key factor that determines fire hazards. In order to find out the characters of heat release rate and their relation with other parameters. The authors introduce the oxygen consumption principle which cone calorimeter applies, and then expound the calculation of heat release rate in detail. The heat release rate of several kinds of representative materials has been studied by means of cone calorimeter in the different irradiances. Test results shows that HRR and TFI^-1/2 vary linearly with the irradiances.     

The Core in Performance -Based Building Fire Protection Study and Its Development

The core of performance-based building fire protection design consists of the establishment of fire scenario,the enactment of fire and the simulation of fire and smoke-flow development.These are most important for performance-based building fire protection design.An unreasonable enactment or pre-digestion could result in a biggish error between the simulation outcome and the actual condition.In this paper,several emphases and some issues worth much attention are introduced and analyzed.In addition,a few important issues in simulating the fire and smoke-flow development related to Field Model are analyzed in detail.     

Adsorption & Release of Nitrogen of Soils in Three Gorges Reservoir

The effects of flooding and subsequent air-drying on NH_4~+ adsorption and the release of nitrogen of typical soils adsorbed ammonia in Three Gorges reservoir were studied in the laboratory.The influence of adsorption and release of soils in Three Gorges Reservoir on Aquatic Environment Quality was also studied.The results show that: 1) The adsorption ability is enhanced by flooding and subsequent air-drying.The capacity of the ammonia adsorption capacity was increased from 666 mg/kg to 833 mg/kg.2) Nitrogen,which has been adsorbed by sample soils in drawdrown area of Three Gorge area,is released under simulating flooding condition.The more the soil adsorbed,the more the nitrogen released.The ratio between aerobic condition and anaerobic condition is 1.2~1.4.3) The soils in drawdrown area of Three Gorge Reservoir can adsorb nitrogen from surface runoff,and during submersion periods the nitrogen is released.The risk of Eutrophication is increased in Three Gorges Reservoir.     

乙醇气体缓释处理对鲜食葡萄保鲜效果的影响

采用不同剂量(1.5、3.0、6.0 m L/kg)的乙醇缓释保鲜剂处理鲜食葡萄(品种:户太八号),以空白处理为对照,分别于室温(25±1)℃及低温(0.5±1)℃条件下避光贮藏7 d和60 d,分析鲜食葡萄在贮藏期间果实腐烂指数等主要品质指标以及呼吸代谢的变化。结果表明,持续低剂量的乙醇气体缓释处理能够有效抑制病原微生物对葡萄果实的侵染(室温贮藏7 d各处理组果实的腐烂指数均低于0.15,低温贮藏60 d三种剂量处理的腐烂指数均低于0.05),延缓葡萄果实失水、褐变及因果梗老化引起的落粒,同时可大大降低贮藏期果实VC及可溶性固形物的损失,抑制果实在贮藏期内的呼吸代谢,其保鲜效果与乙醇缓释剂的处理剂量呈正相关。该方法安全无害,成本低廉,是一种简便高效的果蔬保鲜技术方法。     

乙醇/柴油混合燃料对发动机燃烧特性的影响

通过试验研究,分析了在柴油机上燃用柴油/乙醇混合燃料对发动机燃烧特性、燃油效耗率及排气烟度的影响,为柴油/乙醇混合燃料在柴油机上的推广应用提供了有价值的参考依据。     

中国转基因油菜的环境安全性分析

根据中国转基因油菜研究和环境释放的现状，对中国环境条件下转基因油菜的生存竞争能力、基因扩散风险以及对生物多样性影响等环境安全问题进行了分析。分析认为，中国是许多十字花科植物进化起源中心和生物多样性中心，生态环境类型复杂；转基因油菜的外源基因可以通过花粉向油菜（Brassica napus）、白菜（B．rapa）和芥菜（B．juncea）类植物扩散；中国转基因油菜的基因扩散风险高于其它作物．存中国，油菜的转基因技术相当成熟，油菜的转基因实验频次很高，涉及的基因种类繁多，进口的转基因油菜数量巨大，隐患不容忽视。在中国，转基因油菜的安全性管理和研究相当薄弱，检测和监测手段无法满足安全管理需求，这一现状必将阻碍中国转基困油菜的产业化进程，并对中国环境安全带来隐患。作者提出，加强转基因油菜的环境安全意识，加强中国转基冈油菜的安全管理及其措施的落实，加强转基因油菜检测和监测等技术平台的建设。     

淀粉黏结剂对颗粒有机复混肥养分释放的影响

以自制的两种淀粉基黏结剂作为有机复混肥造粒黏结剂，以无机黏结剂硅酸钠为对照处理，以废物堆肥和市售无机化肥作为原料，经圆盘造粒获得3种不同颗粒有机复混肥。3种有机复混肥颗粒平均抗压碎力都达到了中国国家标准(≥6 N)的要求；无机黏结剂C颗粒经24 h的水浸泡后，其崩解率为6.1%；而A和B淀粉黏结剂颗粒保持完好，崩解率为0。通过168 h养分溶出试验发现，有机黏结剂A和B能明显降低颗粒肥中营养元素的释放速率；PVA(聚乙烯醇)改性淀粉黏结剂B作为有机复混肥造粒黏结剂，能明显延缓颗粒肥中NH⁺₄-N、全氮、全磷和全钾释放速率。虽然黏结剂A比黏结剂B延缓颗粒肥无机养分释放的效果差，但与无机黏结剂C相比，其延缓颗粒肥无机养分释放速率的效果要好的多。试验结果表明：用改性淀粉黏结剂作为有机复混肥造粒黏结剂，可以同步实现对速溶无机养分的控制释放，也为新型非包膜控施肥的研制和开发提供新的思路和参考。     

聚合物/膨润土复合控释材料的应用研究

用聚合物/膨润土复合材料与肥料混合制备混合型缓/控释肥和用复合材料包裹尿素制备包膜型缓/控释肥进行盆栽试验。结果表明,聚合物和膨润土都具有控释作用,二者复合具有更好的控释效果。几种混合型缓/控释肥处理的玉米生物量均较对照有显著提高,以添加含膨润土0.5倍(相对于聚合物质量)的复合材料配制的缓/控释肥效果最好。几种包膜型缓/控释肥处理的玉米生物量较对照有所提高,差异达显著水平,以含膨润土2倍的复合材料制备的缓/控释肥效果最好。     

控释尿素施用对水稻吸氮量及产量的影响

以15N标记尿素及用其制成的有机-矿质材料控释尿素为供试肥料,探讨其在黑土水稻田上使用后水稻对N的吸收利用及水稻产量的变化。结果表明:控释尿素比普通尿素氮肥利用率提高了3.64%～19.92%,土壤中N的残留量增加6.37%～20.86%,可提高水稻产量8.66%～25.70%。