Search for superfluidity of3He in3He-4He solution

We have tried to cool a³He-⁴He solution down to the microkelvin temperature region to search for a superfluid transition of the³He component in the solution. The contact surface area between the solution and a sintered powder has been increased enormously by the use of a fine platinum powder, to reduce the effect of the residual heat leak directly entering into the solution. Although the heat leak was found to be time dependent, the ultimate ratio of the heat leak to the surface area is about 0.046 pW/m², improved very much from those by the other groups. But the lowest temperature of the solution is still around 0.2 mK, and no evidence of the transition has been observed yet.     

一起井下煤巷锚杆支护冒顶事故的剖析

通过对2612l上顺槽锚杆支护冒顶事故的剖析，提出了针对防范措施，在以后类似条件下施工中杜绝事故的发生。     

德兴铜矿资源多角化经营战略的思考

根据国家可持续发展战略的要求，对德兴铜矿资源优势及资源利用中存在的主要问题进行了分析，从矿山发展战略方面提出实行资源多角化经营战略的对策，并论述了实行这一对策的必要性、应遵循的原则和应处理好的几个关系。     

磨矿细度对胡家峪矿选铜指标影响

针对胡家峪矿选矿指标下降的问题，对工艺技术条件及现场操作状况进行了综合分析，找出了原因，进行了工业试验，制定了改进措施。     

矿山井下光电测距三角高程测量精度的探讨

本文根据武山铜矿井下 7″级基本导线控制测量工作中量取仪器高和反光镜高 ,通过对光电测边三角高程高差误差的分析 ,其测量精度可以满足井下I级水准测量精度的要求。     

堆浸厂实现达产目标的可行性分析

本文紧扣德兴铜矿堆浸现状与设计 ,对达产 2 0 0 0t/a电铜的能力进行了适当的分析 ,并对提高德兴铜矿堆浸电铜产量提出了有效的措施。     

Permeation and Sorption of Water and Gases Through EVA Copolymers Films

The transport of water and gases (pure oxygen and carbon dioxide) through poly(ethylene-co-vinyl acetate) (EVA) films of different VA contents and through a low density polyethylene LDPE (used as reference with 0 wt.% VA), was analysed by permeation and sorption measurements. In the case of water, for EVA of 70 wt.% VA, a plasticization effect on the material was observed. For EVA of 19 wt.% VA, there was no plasticization, while for EVA of 4.5 wt.% VA and for LDPE, the water diffusion coefficient decreases with increasing water. An empirical law was then found to account for the reduction of the water diffusivity. A negative plasticization effect was attributed to the formation of water clusters in these rather non polar polymers. This latter result was confirmed by sorption measurements and infra-red spectroscopy. The increase in water sorption extent with the VA content leads to a steady increase in the water permeability in the EVA copolymers. In the case of gas permeation, both for O₂ and CO₂ and whatever the VA content of the copolymer used, the experimental curves are characterized by a constant diffusion coefficient. This is confirmed by sorption experiments. In terms of gas permeability, EVA copolymers are characterized by low coefficients especially for oxygen. In the EVA rubbery copolymers, The O₂ solubility coefficient does not increase with the VA content due to the lack of polar interactions, while the CO₂ one increases due to the overall interactions between CO₂ induced dipoles and the polar the VA carbonyl groups. For these copolymers, the H₂O/CO₂ and H₂O/O₂ selectivities are very high. The experimental values of the selectivities indicate that these EVA copolymers appear as good candidates for applications using high perm-selectivity properties. Electronic Publication     

On Failure-Time Distributions for Systems of Dissimilar Units

Certain reliability problems of systems of dissimilar units with repair are described. The mean time to system failure is based on the relation of mean first passage times between states of the system. The failure-time distribution is obtained from an integral equation of the renewal type. The two approaches can be also applied to a system of dissimilar units under an overload. Finally, it is shown that these results include many earlier results as special cases.