重离子与~(nat)W���互作用中Hf的生成研究

用放射化学方法研究了6.3、8.5、11.8、14.7、18.4、24.6、40 MeV/nucleon ~(40)Ar + ~(nat)W���10.5 MeV/nucleon ~(84)Kr + ~(nat)W���80 MeV/nucleon ~(16)O + ~(nat)W���135 MeV/nucleon ~(12)C + ~(nat)W���应中的Hf的生成，得到了Hf同位素的激发函数、反冲性质和同位素分布。研究结果指出利用HIRFL能量的重离子和丰中子靶核作用，能以一定的截面生成A > 170区丰中子新核素。重炮弹更有利于丰中子新核素的生成。使用厚靶，可以明显地提高丰中子新核素的产额。过高的入射能量对丰中子新核素的生成无明显贡献，相反却极大地增加了缺中子同位素产额，这对丰中子新核素的分离和鉴别是非常不利的

SFC 200K W���频系统计算机控制的改进探讨

本文是关于对HIRFL SFC 200KW 高频系统实施计算机控制的专题讨论。首先对HIRFL SFC 200KW 高频系统各部分的运行情况进行了详细分析，在此基础上对原有计算机控制系统进行了剖解，并针对原有计算机控制系统存在的缺陷进行了一些改进和实验，使之投入实际运行工作中；然后，对计算机控制系统中普遍采用的电路从理论上进行了讨论，给出了一些有益于工程实践的结论；最后，为了实现对整个SFC 200KW 高频系统的计算机控制，从软、硬件两个方面，提出了对HIRFL SFC 200KW 高频系统进行该造的方案。

《保护生态学:生物圈和生物存活》简介

<正> 保护生态学从1969年沿用开始,一直作为一个概念和术语,没有发展成为一门有明确研究对象、范畴和方法论的独立学科。直到1993年由George W.Cox编辑,由Wm.C.Brown Publishers出版的《保护生态学:生物圈和生物存活》(Conservation Ecology:Biosphere and Biosurvival)才奠定了保护生态学理论和实践的基础。该书中G.W.Cox将传统生态学与其它相关学科的相关知识结合起来,运用了保护生物学的理论和方法。全书短小精悍,结构明快,共352页分为三大部分。第一部分回顾了生态学的概念,介绍了生态学的发展历史。接着介绍了"绝灭生态学"(The ecology of extinction),作者回顾了过去及近代生物的绝灭率,绝灭物种的生活史足迹等,认为:近代物种绝灭率由于人

A novel (W-Al)-C-Co composite cemented carbide prepared by mechanical alloying and hot-pressing sintering

Novel cemented carbides (W0.4Al0.6)C-0.5-Co With different cobalt contents were prepared by mechanical alloying and hot-pressing technique. Hot-pressing technique as a common technique was performed to fabricate the bulk bodies of the hard alloys. The novel cemented carbides have good mechanical properties compared with WC-Co. The density and operation cost of the novel material were much lower than the WC-Co system. It was easy to process submicroscale sintering with the novel materials and obtain the rounded particles in the bulk materials. There is almost no eta-phase in the (W0.4Al0.6)C-0.5-CO cemented carbides system although the carbon deficient obtains the astonishing value of 50%.

Preparation and characterization of W-Type hexaferrite doped with La3+

A series of W-type ferrites with the composition of Ba1-xLaxCo2Fe16O27 (where, x = 0.0, 0.05, 0.10, 0.15, 020 and 0.25) were prepared by solid-state reaction method. The structure transformations of the ferrites were examined by XRD, DTA-TG and XPS, and the microwave-absorbing properties were investigated by evaluating the permeability and permittivity of materials (mu(r), epsilon(r)). The results showed that the phase-transition temperature increased with the addition of La2+ content, and a single-phase was formed at 1250 degrees C at last. Microwave properties were obviously improved as a result of the substitution of La3+ for Ba2+ at the frequency range of 0.5 similar to 18.0 GHz.

Preparation of W-Al-Mo ternary alloys by mechanical alloying

Single phase WxAl(50)Mo(50)-X (X=40, 30, 20 and 10) powders have been synthesized directly by mechanical alloying (MA). The structural evolutions during MA and subsequent as-milled powders by annealing at 1400 degrees C have been analyzed using X-ray diffraction (XRD). Different from the Mo50Al50 alloy, W40Al50Mo10 and W30Al50Mo20 alloys were stable at 1400 degrees C under vacuum. The results of high-pressure sintering indicated that the microhardnesses of two compositions, namely W40Al50Mo10 and W30Al50Mo20 alloys have higher values compared with W50Al50 alloy.

High strength Ni based composite reinforced by solid solution W(Al) obtained by powder metallurgy

The solid-solution-particle reinforced W(Al)-Ni composites were successfully fabricated by using mechanical alloying (MA) and hot-pressing (HP) technique when the content of Ni is between 45 wt% and 55 wt%. Besides, samples of various original component ratio of Al50W50 to Ni have been fabricated, and the corresponding microcomponents and mechanical properties such as microhardness, ultimate tensile strength and elongation were characterized and discussed. The optimum ultimate tensile strength under the experiment conditions is 1868 MPa with elongation of 10.21 % and hardness of 6.62 GPa. X-ray diffraction (XRD), FE-SEM and energy dispersive analysis of X-rays (EDS) were given to analysis the components and morphology of the composite bulk specimens.