塑封电子器件负极端变色原因分析

利用X—RAY光电子能谱仪对125°下,通电15kV,96h后负极一端出现白色物质的塑封电容器进行分析。对比分析性氧化铝结发现,负极一端白色物质为氧化铝富集所致。造成该现象的原因是,环氧塑封料中含有活性氧化铝,由于固化不完全或吸潮导致环氧塑封料中残留水分,残留的水分与活合,在电应力的作用下,有向电源负极迁移的趋势;同时,由于温度效应的存在,塑封树脂软化,加速了水分与活性氧化铝向电源负极迁移的速度,形成了氧化铝在负极端富聚现象,使电容器负极端呈现白色。     

SiC衬底AlGaN/GaN HEMT的热分析与测试

对SiC衬底AlGaN/GaN HEMT的结温进行了理论计算与实测。计算中考虑了衬底材料热导率随温度的变化以及器件源、漏电阻上的热损耗,不同耗散功率下的理论计算与红外显微镜实测结果比较表明,两者相差最大不超过10℃。由于理论计算结果是在解析解的基础上运用计算机迭代计算获得,所耗时间较短,故这一结果对于改善器件结构以提高AlGaN/GaN HEMT及其MMIC电路的性能将有较大帮助。     

氨气预氮化制备超薄氮化硅薄膜及电学性能

为寻求制备性能良好的纳米厚度氮化硅(SiN_x)薄膜的方法,采用NH_3等离子体氮化、SiH_4/NH_3等离子增强化学淀积法及先氮化后淀积的方法制备了三种SiN_x薄膜,研究比较了三种薄膜的性质。用X射线光电子谱检测了NH_3等离子体氮化Si片得到的SiN_x薄膜的组分,利用椭圆偏振光谱仪测量薄膜厚度,估算了氮化速率。用NH_3和SiH_4作为反应气,分别在原始硅片和经过NH_3预氮化后的硅片上淀积厚度为5 nm、10 nm和50 nm的SiN_x薄膜。用电容-电压法研究了薄膜样品的电学性质,发现单纯用NH_3等离子体氮化的薄膜不适合做介质膜,而先用NH_3氮化再淀积SiN_x的样品比直接淀积SiN_x的样品界面性能明显改善,界面态密度降低到1～2×10~(11)eV~(-1) cm~(-2)。     

Coherent网络中的纠错码

网络编码对网络中的传输错误或恶意攻击十分敏感,如果网络拓扑和网络码对于网络的收点和发点都是已知的,这种类型的网络称为Coherent网络。在Coherent网络中,网络汉明重量的概念拉近了网络纠错码和传统纠错码之间的距离,传统纠错码的一些理论和方法有望在将来应用于网络纠错码。类似于传统纠错码,极小距离反映了网络纠错码的纠错能力。利用陪集码理论去描述和研究网络纠错码是一个令人感兴趣的研究方向。     

Changes of peripheral blood flow in patients with cancer of the lungs, esophagus and cardia under the effect of anesthesia and surgery

The authors report the data on changes in peripheral circulation, depending on the kind of anesthesia, the amount of operative blood loss, alterations in circulating blood volume and localization of tumor in patients with cancer of the lung, esophagus and cardia. Totally, 35 patients (15--lung cancer, 10--esophageal cancer, 10--cancer of the cardia) were explored. In 25 cases fluothane was used as the main anesthetic, in 10--neuroleptanalgesia. The state of peripheral circulation was estimated by the period semielimination of radioactive xenon-133 from the muscle depot. It was found that alterations in peripheral circulation were not dependent on tumor localization, the use of fluothane and neuroleptanalgesia is associated with similar changes in peripheral blood flow and, finely, an increased loss of blood results in more pronounced alterations in peripheral circulation.     

Equilibrium-dialysis studies of the interaction between cholic acid and 100000g-supernatant preparations from the rat liver

1. The binding of cholic acid to 100000g supernatants from rat livers was investigated by equilibrium dialysis and gel-exculsion chromatography. 2. Supernatants were found to contain at least two classes of binding site for cholic acid. 3. These recptor molecules are probably proteins since incubation with proteolytic enzymes resulted in complete loss of cholic acid binding. 4. Supernatants were added to columns of Sephadex G-75, and two groups of fractions were shown to bind cholic acid. One of these contained low-affinity binding sites and the other contained both low- and high-affinity binding sites. 5. Feeding cholestyramine had no effect on cholic acid binding. 6. Increased cholic acid binding occurred after injection of phenobarbitone. There was an increase in the amount of the low-affinity component but no change in the high-affinity component. 7. The dissociation constants of the binding of cholic acid suggest that the binding proteins may be involved in bile acid transport.     

Mathematical models of strontium-90 behavior in a "water--fresh-water fish spawn" system in several individual cases of radionuclide entry into bodies of water

A group of 72 gilts, aged between eight and nine months, were treated 20 days each by administration of 5 g Suisynchronpr?mix (Zinc Metallibur/Sui), followed by 24-hour treatment with 750 IU PMS (Prolosanserum). Fifty per cent of the group received 500 IU per animal of HCG (Gonabion) at 11 a.m., on the fourth day after Sui. All animals were artificially inseminated at 3.30 p.m. on the fifth day after Sui. and at 7.30 a.m. on the sixth day after Sui. Laparotomy was performed on 50 per cent of the HCG-treated and untreated animals in the afternoon of the sixth day after Sui. Animals with no recordable ovulation had to undergo another laparotomy in the morning of the seventh day. The above approach resulted in regrouping by four therapeutic categories: 1. HCG with laparotomy, 2. No HCG, 3. HCG with no laparotomy, 4. No HCG and no laparotomy. In the afternoon of the sixth day after Sui (51-56 hours after HCG) ovulation had begun in all 17 measurable animals of the first group, but only in one of 18 animals of the second. The animals were slaughtered between the seventh and twelfth days after Sui, and the following ovulation percentages were established: 100 per cent in the first group, 83.3 per cent in the second, 55.6 per cent in the third, and 72.2 per cent in the fourth. The animals that had been given HCG treatment (Groups 1 and 3) were found to be superior in terms of percentual ovulation to the untreated animals (Groups 2 and 4). However, Group 2 was the only group that had been exposed to the extraordinary stress of two laparotomies, and this should be borne in mind for evaluation. Ovarian cysts (more than 10 mm) began to develop on the eighth day on the laparotomised groups (1 and 2) and on the tenth day on the non-laparotomized groups (3 and 4). Cysts developed in 41.1 per cent of all animals in Group 1, 38.9 per cent in Group 2, 27.8 per cent in Group 3, and 22.2 per cent in Group 4. Therefore, cyst formation is thought to have been stimulated by laparotomy. Ovocyte tests suggested fertilisation of all animals in the first group. The embryonation rates of the second, third, and fourth groups are discussed with reference to the dates of insemination.     

Pathogenicity of K. ozaenae for mice and chick embryos

The authors tested the virulence of K. ozaenae--its old museum strains, the freshly isolated ones and those passaged on meat-peptone agar; experiments were carried out on mice and chick embryos. To mice the culture was administered intraperitoneally, subcutaneously, intranasally, and to embryos--into the allantoic cavity and on the chorioallantoic membrane. Irrespective of the method of administration, the freshly isolated strains were highly virulent both for mice and for chick embryos. The virulence of such strains decreased in the process of passaging on the nutrient medium. Old museum strains were of low virulence for albino mice and avirulent for chick embryos. In comparing the virulent and avirulent strains there were found no differences in the antigenic structure and toxicity of the Boiven complex, cytoplasm, membrane, capsular polysaccharide or whole virulent and avirulent bacteria killed by heating.