微小电势的精密测量方法

用电位计直接测量0.5μV以下的微小电势,由于检流计零位飘移(简称零位电势)及寄生电势的影响,有时测量误差可达1μV左右。零位电势和寄生电势是随着仪器工作条件的改变而变化的,所以采用电流换向及零电势补偿的方法,都难以消除两者的影响,故不能取得满意的测量结果。下面介绍一种偏差法可以较好地解决这一问题。使用这一方法时,电位计的最小步值应小于或等于0.1μV。测量时,将电位计工作电流标准化以后,调整检流计光电放大倍数,使检流计电压分度值为(0.01～0.001)μV/每格左右,按被测电势大约范围,在测量盘上预置一定数值,并记下检流计偏转格数(称为预置数     

环境因素对碳钢点蚀临界电势的影响

采用动电势扫描法测定了不同体系中碳钢发生点蚀的临界电势Eb。结果表明 :当Cl- 浓度 <0 .0 1mol/L时 ,随Cl- 浓度增加 ,临界电势负移并与Cl- 浓度成线性关系 ;pH值在 7～ 11之间 ,随pH值增加 ,临界电势正移并与pH值成线性关系 ;随温度增加 ,临界电势负移并与温度成线性关系。     

消隐电势谱及其特性的实验证明

本文介绍自制的消隐电势谱仪及其实验结果。证明消隐电势谱与出现电势谱有所不同,现场分析蒸发钡膜的结果还表明它更为表面灵敏。     

高空间分辨率的出现电势谱

在PHI-590型扫描俄歇微探针上扩展了出现电势谱的测量功能,此出现电势谱具有上靶电子束流小(几个微安)、空间分辨率高(小于一个微米)的特点,并可用在线计算机控制测量过程。     

静电场中场强和电势关系的研究与讨论

从功能关系出发给出电势与场强的关系式并在此基础上证明各种不同的电场中延电场线电势降低最快的结论,这对研究电场线与等势面的关系具有一定的意义。     

静电电压表校准装置中平板电极对电势分布的影响

静电电压表校准装置中的平板电极是该装置的重要组成部分,它的几何参数影响了其周围的电势分布。通过理论分析和仿真计算,分析计算了平板电极直径、形状、厚度、边缘平滑度和离地高度等因素对电势分布的影响。计算结果表明:在测试距离100mm时,以直径为600mm,厚度为1mm的圆形平板电极做参考,直径增加至1000mm,其纵向的电势分布只增强了1.3%;增加平板电极厚度100mm,其纵向电势分布的增强大于5.4%,更加趋近无限大平板电极所产生的电势分布;尺寸相当时,形状对电势分布的影响可以忽略;边缘平滑度对电势的影响可以忽略;距离地面0.5m会形成明显的畸变电势分布。这一结果对校准装置中平板电极的设计具有一定的参考意义。     

空心阴极放电中的电势垒和电场反转

利用流体-亚稳态原子模型对柱型空心阴极放电中电场反转和电势垒进行了研究。模拟得到了稳态放电时电势、电子密度、离子密度、电场和粒子流密度等的分布特性。220 V阳极电压和133 Pa氩气下,电子和离子密度峰值位于放电单元中心处,为2.4×1010cm-3;在阴极位降区,离子密度远高于电子密度。负辉区电势高于阳极电势,放电的轴向存在电场反转现象,放电单元的中心处形成一电势垒。电子扩散流密度和电子流密度之比对电场反转的形成有重要影响。文章同时研究了阳极电压对电场反转特性的影响。结果表明,电压升高时,电子扩散流密度升高,电场反转和电势垒现象增强。模拟结果同时表明空心阴极放电模式下有利于电场反转的形成。该研究对于分析空心阴极放电中电场反转的成因有重要的参考价值。     

利用专用过渡电阻检定低电势电位差计

由于直流比较仪式电位差计的价格昂贵及其在检定低电势电位差计时存在零漂和热稳定等问题,所以很多单位仍然采用元件检定电位差计的方法来检定标准电位差计。众所周知,高电势电位差计的元件检定精度可优于5ppm,经过这样检定的电位差计用作检定同级电位差计的标准是相当满意的了。但是,低电势电位差     

GaAs霍尔元件不等位电势的调制消除

测试了MESFET工艺条件下制作的霍尔片的基本性能。对设计出的GaAs集成霍尔元件进行了不等位电势的测试，采用霍尔元件并联和自旋电流的方法对GaAs方形霍尔元件的不等位电势进行了静态和动态调制消除。实验结果表明GaAs霍尔元件的不等位电势引起的偏差可以控制在可以忽略的范围内。     

固体混合电势型CO传感器的研究进展

由于对环境问题的关注,近年来固体电解质CO传感器得到了广泛的研究。其中由于固体混合电势型CO传感器具有优异的性能和独特的工作机理,因此受到了人们的关注。文章简要阐述了固体混合电势型CO传感器的工作机理以及研究概况。     

Potential sputtering

The potential energy stored in multiply charged ions is liberated when the ions recombine during impact on a solid surface. For certain target species this can lead to a novel form of ion-induced sputtering, which, in analogy to the usual kinetic sputtering, has been termed 'potential sputtering'. This sputtering process is characterized by a strong dependence of the observed sputtering yields on the charge state of the impinging ion and can take place at ion-impact energies well below the kinetic sputtering threshold. We summarize a series of recent careful experiments in which potential sputtering has been investigated for hyperthermal highly charged ions' impact on various surfaces (e.g. Au, LiF, NaCl, SiO(2), Al(2)O(3) and MgO), present the different models proposed to explain the potential sputtering phenomenon and also discuss possible applications of potential sputtering for nanostructure fabrication.     

Corrosion Potential oscillations

The corrosion potentials of stainless steels in chloride solutions for conditions significantly removed from those leading to pitting and crevice corrosion are constant and to a first approximation largely independent of temperature and chloride ion concentration. With increasing temperature and/or chloride ion concentration or with decreasing corrosion resistance there comes a situation when the corrosion potential begins to oscillate, between two and values roughly corresponding to E_p and E_pp. These potential oscillations are often associated with pitting and crevice corrosion, although there are clear cases when no corrosion attack was visible even after prolonged exposure. The oscillations are attributed to unstable passivity.     

Embedded-atom Potential for Oxygen

The analytic embedded-atom potential for oxygen is developed from the experimental data and the results of the first-principle. The potential is used to predict the geometries and energies of O3, fcc, bcc, sc and diamond. The predictions are in good agreement with experimental data available and other theoretical results.     

Potential parameterization from proxy systems

We give an analysis and critique of a procedure for sequential multi-scale parameterization of so-called ab initio potentials. Such potentials are based upon a small selection of reference data generated at relatively low levels refinement of quantum mechanical (QM) methodology. Two closely related potentials for silica, BKS and TTAM, are explored in some depth because both have found frequent use in the literature of molecular dynamics simulation. The use of a single small molecular cluster as a proxy for the behavior of larger silica structures is shown to be perilous. Choices of ionic charge, basis set size, inclusion of electron correlation at some prescribed level of approximation, and parameterization data are each shown to have a substantial impact on the final potential parameterization. The analysis and critique provide the logical foundation for the different approach to the problem of parameterization and use of classical potentials that is treated in detail elsewhere in this collection. The use of extended model systems, force data calculated from QM methods, and a focused (limited) range of application are shown to be essential for a consistent (and ultimately, predictive) embedding approach to concurrent multi-scale materials simulation.     

Potential of the single-screw compressor

The single-screw compressor has the potential to become the dominant form of compressor in the 50–150 kW power range. It is capable of high energy efficiency because losses due to leakage, frictional effects and heat transfer factors are capable of being reduced to a low level. A new gaterotor design for this purpose is described. Low cost is possible because the compressor is compact, the new gaterotor is less expensive to manufacture, the bearings can be simplified, and the casing can become a simple pressure vessel.     

A Potential Superhard Material m-BCN

We here propose a new superhard material m-BCN with comparable Vickers hardness to cBN by the use of first-principles calculations. The calculations show that the mentioned m-BCN is a thermodynamically and kinetically stable semiconductor. Hydrostatic calculation shows that it is anisotropic and its incompressibility is very close to cBN. Structural analysis shows that its excellent mechanical property and thermodynamically stability are inherited from diamond and cBN. These results provide a new clue to find new superhard phase.     

纳米复合材料实用化技术前景

从纳米技术的基本概念出发综述纳米复合材料的制备方法及其实用化的技术前景。     

几种结构钢在人造海水中自腐蚀电位和析氢电位的研究

本文介绍了16Mn钢和2 1/4Cr-1Mo钢[注1]在人造海水中的自腐蚀电位和析氢电位的测量原理和方法。在实验中用怛电位仪测量不同试样的自腐蚀电位和析氢电位;研究了温度对试样自腐蚀电位的影响;不同热处理方法对试样自腐蚀电位和析氢电位的影响。     

Potential of PET in Tumor Theranostics

Radiochemistry - Targeted radionuclide therapy (TRT) is today one of the most effective methods for tumor treatment. The use of the theranostic concept allows personalized approach to the choice of...