关于一次性使用产品可靠性增长管理方法的探讨

本文对尚未明确讨论过的一次性使用产品的可靠性增长管理问题,参照与时间有关的系统的可靠性增长管理方法,提出了一整套相应的方法。并用数值例说明了这种方法。     

电镀的Ag,Cu,Zn层在边界润滑状态下摩擦学性能

在GCr15钢球上电镀软金属 Ag,Cu,Zn 层,在32~# 机械油的边界润滑状态下,其上、下球镀层分别是无镀层抗胶合能力的 9.84,5.4,4.0倍。经过 40 min低载荷运转证明,镀层可有效地减少基体的磨损,而且磨痕面光滑。测定了在一定载荷范围内的摩擦系数。镀 Ag 层的摩擦系数较低,其值稳定在0.05左右;镀Cu层摩擦系数值稳定在0.055左右。对镀液的性质、镀层的厚度进行了相应的探讨。对试验结果及现象做了一定的分析。     

大型电站锅炉炉墙振动研究

大型电站锅炉炉墙结构振动的原因很复杂,主要有燃料燃烧不均匀或爆发性连续脉冲;烟气流过管束时形成的卡门涡街;炉膛空腔的声学共振;从结构外振源传来的振动等。炉墙振动过大会造成绝热层开裂、焊接松脱等恶劣后果,锅炉内爆则会引起灾难性的破坏,但目前锅炉结构设计从未考虑其动态特性。本文对国产大型电站锅炉(主要是30万千瓦电站直流锅炉)的炉墙和刚性梁振动进行了较全面的实测,对测试数据进行了谱分析和传递函数分析,研究了炉墙各区域的振幅分布及频率分布,又从相关分析中研究了振动的随机性,定性地分析了燃烧、卡门涡街、声学共振等所引起的振动的频率范围,从而肯定了目前国产30万千瓦电站锅炉炉墙振动的主要振源在于燃烧。     

AP1轨钢的应力腐蚀试验研究

本文首先阐述了研究轨钢应力腐蚀的意义。在国内首次开展了对轨钢应力腐蚀门槛应力强度因子K_(ISCC)的测定研究,并取得了AP1轨钢在蒸馏水和3.5％盐水下的K_(ISCC)值。从而为轨道的设计和维修提供了依据。     

Functional link between ataxia-telangiectasia and Nijmegen breakage syndrome gene products

Ataxia-telangiectasia (A-T) and Nijmegen breakage syndrome (NBS) are recessive genetic disorders with susceptibility to cancer and similar cellular phenotypes. The protein product of the gene responsible for A-T, designated ATM, is a member of a family of kinases characterized by a carboxy-terminal phosphatidylinositol 3-kinase-like domain. The NBS1 protein is specifically mutated in patients with Nijmegen breakage syndrome and forms a complex with the DNA repair proteins Rad50 and Mrel1. Here we show that phosphorylation of NBS1, induced by ionizing radiation, requires catalytically active ATM. Complexes containing ATM and NBS1 exist in vivo in both untreated cells and cells treated with ionizing radiation. We have identified two residues of NBS1, Ser 278 and Ser 343 that are phosphorylated in vitro by ATM and whose modification in vivo is essential for the cellular response to DNA damage. This response includes S-phase checkpoint activation, formation of the NBS1/Mrel1/Rad50 nuclear foci and rescue of hypersensitivity to ionizing radiation. Together, these results demonstrate a biochemical link between cell-cycle checkpoints activated by DNA damage and DNA repair in two genetic diseases with overlapping phenotypes.     

受弹性约束的双层圆柱壳的振动分析

本文采用传递矩阵法对受弹性约束的双层圆柱壳进行自由振动和稳态响应研究,并运用复阻尼理论分析材料内阻尼对结构响应的影响。本文所用的分析方法对于承受各种荷载作用而只有任意齐次边界条件的圆柱壳结构都能适用,并可应用于求解多层圆柱壳的振动问题。     

用于燃气轮机装置反命题计算中的最优子集回归法

本文介绍了最优子集回归法及其在求解燃气轮机反命题问题中的应用。该算法采用“分支—界限”原则和由作者发展的一种新的变量组合秩序,结果使计算工作量大大减少。文中也讨论了改进回归方程精度的方法。     

Thermostability of subtilisin nattokinase obtained by site-directed mutagenesis

To study the thermostability of Nattokinase(subtilisin NAT,NK),three double mutant plasmids(pET-28a-NKG61C/S98C,pET-28a-NKT22C/S87C,pET-28a-NKS24C/S87C)were constructed by site-directed mutagenesis.Target enzymes were detected using SDS-PAGE and disulfide bond formation was detected using Western blotting analysis.Thermostability was tested by rates of inactivation at certain temperature.The results showed that disulfide bond was not formed within two cysteines and the thermostability of three double mutants was not increased compared with the wild-type NK.The thermostability of NK performed in Ca2+was stronger than in ethylenediaminetetraacetic acid(EDTA).But when the temperature reached 62℃,the enzymes rapidly denatured and inactivated even in the presence of Ca2+.Although the thermostability of mutants was not increased,this study shows a tendency of improving thermostability of NK in protein engineering.