Biological responses inCaenorhabditis elegans to high magnetic fields

Here we describe a device for testing possible influences of high magnetic fields on biological processes, by which alternating-current magnetic stimuli as high as 1.7 T can be administered. Experiments with a simple multicellular organism, the nematodeCaenorhabditis elegans, revealed that intermittent exposure to the magnetic fields modestly inhibited the animal's reproduction as well as its post-embryonic development, and caused a marked but transient derangement in its locomotory behavior. Available evidence indicates that alternating high magnetic fields can elicit both chronic and acute biological effects, but that the effects may be well tolerated or compensated for by the living organism.     

冷轧变形对镀镍钢带腐蚀性能的影响

研究了冷轧变形对镀镍钢带耐腐蚀性能的影响.利用电化学方法表征镍镀层的腐蚀行为,金相显微镜观察表面形貌,XRD法确定不同轧制变形量镍镀层中的残余应力.结果表明:2%~4%冷轧变形可以改进镀镍钢带的腐蚀性能,而变形量超过4%会降低其性能.     

Phase behavior and properties of salt-free cationic/anionic surfactant mixtures of oleic acid and stearic acid

Cationic base surfactant, tetradecyltrimethylammonium hydroxide （TTAOH）, can be obtained through anion exchange from tetradecyltrimethylammonium bromide （TTABr）. Salt-free cationic and anionic （catanionic） surfactant mixtures were studied by mixing TTAOH with oleic acid （OA） or stearic acid （SA） in water. The phase behavior of TTAOH/OA/H2O is compared with that of TTAOH/SA/H2O. It was found that the phase behavior of TTAOH/OA/H2O and TTAOH/SA/H2O system differs from each other due to the existence of the unsaturated double carbon bond （C=C） in OA. At fixed total surfactant concentration （25 mg/mL） of TTAOH/ONH2O system at 25℃, one can observe an isotropic L1 phase, and a L1/Lα two-phase region with increasing OA content. The volume of top turbid Lα phase increases while the bottom phase changes gradually from transparently clear to a bit turbid until a single Lα-phase is reached. Finally at high OA concentration, excess OA is separated from the bulk aqueous solutions. TTAOH/SA/H2O system usually forms white precipitating at 25℃ due to the high chain melting temperature of SA. When heated to 60℃, however, the state of samples changes. At fixed total surfactant concentration of 25 mg/mL, an isotropic Lα phase and a milk-white or bluish Lα-phase are observed with increasing SA concentration. Transparent thin layers which are strongly birefringent form at the tops of some samples within the Lα-phase region. Finally, at high SA concentration, excess SA is separated from the bulk aqueous solutions. In addition to phase behavior study, we also measured the conductivity of TTAOH/OA/H2O system at 25℃ and TTAOH/SA/H2O system at 60℃, respectively. Surface tension and rheological measurements were also performed on typical samples.     

Tribological behaviors of some polymeric materials in sea water

Ocean tribology, a new research field of tribology, is being established and developing. The investigation on the tribology in sea water has important significance to ocean exploitation. In this paper, the tribological behaviors of UHMWPE, PTFE as well as Ekonol/PTFE, graphite/PTFE and CF/PTFE sliding against GCr15 steel and Ni-Cr-WC alloy in sea water were investigated, and compared with those in pure water. Results show that the main factors that affect the tribological behaviors of five polymeric materials in sea water are the corrosive effect and lubricating effect of sea water. When polymeric materials sliding against GCr15 in sea water, owing to serious corrosion of counterface by sea water, the surface roughness of the counterface increases largely. As a result, the lubricating effect of medium decreases sharply and the plowing effect of counterface increases greatly. So the friction coefficients and wear rates of five materials sliding against GCr15 in sea water are much larger than those under other conditions. Such wear model, depending on the corrosion of counterface by medium, can be called indirect corrosive wear. Under other three conditions, owing to the more superior lubricating effect of sea water than pure water and the better wettability of Ni-Cr-WC than GCr15, the friction coefficients and wear rates of five materials increase in the following order： sliding against Ni-Cr-WC in sea water 〈 sliding against Ni-Cr-WC in pure water 〈 sliding against GCr15 in pure water. Moreover, compared with other materials, CF/PTFE is the one with more superior plowing and wear resistance in pure and sea water, which is a potential frictional material well suitable for pure and sea water lubrication.     

Effect of different atmospheres on dry friction behavior of steel sliding against brass at high speed

The atmosphere components have an influence on tribological behaviors of tribo-pairs. Through changing the atmosphere component, the effect of atmosphere component on the tribological behaviors of CrNiMo steel against brass at high sliding velocity was investigated. The wear test was carried out on a high-speed friction and wear test rig whose test atmosphere could be controlled. The tests were performed at four sliding velocities （30, 40, 50, 60 m/s）, one contact pressure （1.33 MPa） and two atmosphere components （N2 or O2）. The morphologies of the worn surfaces of various pins were observed with a scanning electron microscope. The chemical compositions of the surfaces and subsurfaces for steels were determined with an energy dispersion spectroscopy. The results showed that the wear rate of the steel pins were low all the time with the sliding velocity increasing in oxygen atmosphere, and that the wear rate of the steel pin in nitrogen atmosphere was higher than that of the steel pin in oxygen atmosphere. It was found that the thin and compact oxidation layer formed on the worn surface of the steel in oxygen atmosphere played a key role in wear resistance. However, the wear rate of the steel pin increased rapidly with the sliding velocity increasing in nitrogen atmosphere, which was attributed to the thick and loose surface layer formed on the worn surface of the steel.     

有限状态马氏过程的自相关函数的单调性

使用生成元(转移速率矩阵)的若当分解,给出了以自相关函数描述的可逆性和不可逆性之间的区别。对于有限状态的马氏过程,证明了不可逆性蕴涵着存在状态空间上的实值观测函数,使得它的自相关函数在［0,∞)上不单调,且在某个时间间隔内,它是负值的;而可逆性则蕴涵着状态空间上所有的实值观测函数的自相关函数在［0,∞)上单调,且为正值的。     

TC4钛合金压坯的吸氢行为

利用管式氢处理炉研究了TC4钛合金压坯的温度-平衡氢分压关系以及吸氢动力学行为,测定了吸氢速率常数和激活能,并分析了吸氢反应各个阶段的反应机理.结果表明,随着吸氢温度的升高,达到平衡所需要的时间缩短,吸氢后的平衡氢分压升高.在350℃吸氢时,反应机制分别是形核长大、幂函数定律和三维扩散.在400℃吸氢时,反应机制分别是幂函数定律和三维扩散.在450～750℃吸氢时,反应机制均是三维扩散.TC4钛合金压坯吸氢反应的激活能为14.55kJ·mol-1.     

单晶硅片化学机械抛光材料去除特性

根据化学机械抛光(CMP)过程中硅片表面材料的磨损行为,建立了硅片CMP时的材料去除率模型,设计了不同成分的抛光液并进行了材料去除率实验,得出了机械、化学及其交互作用所引起的材料去除率.结果表明,磨粒的机械作用是化学机械抛光中的主要机械作用,磨粒的机械作用与抛光液的化学作用交互引起的材料去除率是主要的材料去除率.     

WEB日志中基于KNN算法的注入式攻击行为检测方法研究

阐述了注入式攻击及KNN算法的相关概念并探讨了注入式攻击行为检测与文本分类技术的关系.结合KNN算法的优点及注入式攻击行为检测与文本分类的相似性,提出了Web日志中基于KNN算法的注入式攻击检测方法,给出了其计算模型,并进行了检测对此.结果表明,该方法具有良好的检测准确度.     

含二茂铁基树形两亲性分子的合成及其电化学行为

合成了2, 3, 4-三-（11-二茂铁基）十一烷氧基苯甲酸, 用元素分析、核磁共振谱, 红外及紫外光谱等对产物进行了表征. 利用循环伏安法（CV）, 线性扫描伏安法（LSV）, 常规脉冲伏安法（NPV）, 计时电流法（CA）和计时电量法（CC）研究了该物质的电化学行为, 测定了其电化学参数. 结果表明该二茂铁基两亲性分子在溶液中具有良好的氧化还原可逆性, 是由扩散控制的可逆过程, 且三个二茂铁基团之间没有强相互作用而显示等同的氧化还原性.