He+ 辐照剂量对钨纳米丝生长的影响

采用低能(50eV)大流强的He+ 辐照多晶钨材料,辐照温度1420±50K,辐照剂量从1.0×1024ions/m2逐渐增加到1.0×1027ions/m2,用扫描电子显微镜、透射电子显微镜、称重等手段分析辐照后钨样品表面微观结构的形貌改变及质量损失的情况,系统的研究了He+ 辐照剂量对钨纳米丝生长的影响.结果表明,随着He+ 辐照剂量的增加,钨纳米丝的厚度最终达到饱和,由于辐照后钨表面存在致密的钨纳米丝层,进而导致到达钨纳米丝层底部的He+ 数量和能量降低,从而导致钨纳米丝生长速率显著降低,且当钨纳米丝生长速率和和钨纳米丝的侵蚀速率相等时,钨纳米丝生长将会达到平衡.     

双正交小波滤波器簇代数结构及构造

研究了一类向量多项式两种特殊分解结构,由此引进了与双正交小波滤波器簇相应的多相向量概念,分析了多相向量分解代数结构,得到了在低通滤波器给定条件下,满足任意阶可和规则的对偶低通滤波器构造方法.分析并证明了双正交滤波器簇对应多相向量至多具有的3种代数分解结构,根据其分解的形式得到了双正交小波基构造的新方法,该方法便于双正交小波构造计算机程序化.     

液Zn对Fe2Al5涂层侵蚀的相变过程研究

本文对Fe₂Al₅涂层在液态Zn中的侵蚀相变过程进行了研究,实验结果表明：在侵蚀初期,靠界面张力平衡的作用,先发生热侵蚀,在试样表面形成热蚀沟,当热蚀沟达到一定程度后, 液Zn与Fe₂Al₅相由不浸润变为浸润;同时Zn原子扩散进入Fe₂Al₅相并形成Fe₂Al₅-Zn_x固溶体相(η相);随着侵蚀时间的增加,发生在腐蚀界面上的液Zn对Fe₂Al₅涂层的侵蚀过程是恒温相变过程,相变过程使Fe₂Al₅涂层发生定向熔化. 相变的驱动力来自于相成分的改变所引起的各相自由能的变化及各相间的相平衡的重新建立.     

Sources of electrochemical noise in corroding systems

The electrochemical noise method is reasonably well established as a technique that can estimate corrosion rate through the electrochemical noise resistance or impedance. A more interesting potential application is the identification of the nature of the corrosion process. In this paper, a number of corrosion types are examined, and it is concluded that the majority constitute a form of shot noise, possibly with a superimposed baseline current. Methods by which parameters describing the shot noise process can be estimated from the measured data are presented. It appears to be feasible to extract the charge in the shot noise events, and their frequency, providing all of the anodic or cathodic current, is associated with these events. However, the analysis requires a number of assumptions that are not always valid, and these are discussed. Finally, some alternative methods that have been used to identify the type of corrosion are briefly discussed. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 5, pp. 557–566. The text was submitted by the author in English.     

Numerical calculations of erosion in an abrupt pipe contraction of different contraction ratios

Erosion predictions in a pipe with abrupt contraction of different contraction ratios for the special case of two‐phase (liquid and solid) turbulent flow with low particle concentration are presented. A mathematical model based on the time‐averaged governing equations of 2‐D axi‐symmetric turbulent flow is used for the calculations of the fluid velocity field (continuous phase). The particle‐tracking model of the solid particles is based on the solution of the governing equation of each particle motion taking into consideration the effect of particle rebound behaviour. Models of erosion were used to predict the erosion rate in mg/g. The effect of Reynolds number and flow direction with respect to the gravity was investigated for three contraction geometries considering water flow in a carbon steel pipe. The results show that the influence of the contraction ratio on local erosion is very significant. However, this influence becomes insignificant when the average erosion rates over the sudden contraction area are considered. The results also indicate the significant influence of inlet velocity variations. The influence of buoyancy is significant for the cases of low velocity of the continuous flow. A threshold velocity below which erosion may be neglected was indicated. Copyright © 2004 John Wiley & Sons, Ltd.     

超声清洗槽内空化强度的测量

对洗涤槽内超声空化的相对强度及其分布进行了研究。采用铝箔腐蚀法,应用图像、数据处理软件对试验结果进行处理,最后对实验结果进行了讨论。     

REE示踪研究坡面侵蚀时空演变过程

在室内人工模拟降雨条件下, 通过沿坡面垂直分段和分层结合布设不同的稀土元素, 研究坡面侵蚀的时空演变规律. 结果表明: 次降雨条件下在产流开始20 min内, 坡面片蚀和细沟侵蚀的平均侵蚀加速度、平均侵蚀率和累积侵蚀量之比分别为1:1, 1:1.5和1:1.3, 坡面下1/3区域的平均侵蚀加速度、平均侵蚀率和累积侵蚀量分别是坡面中部的5, 12, 13倍; 后期细沟平均侵蚀加速度、平均侵蚀率和累积侵蚀量分别为片蚀的43, 7, 5倍. 连续小雨强降雨条件下, 产流35 min内, 细沟侵蚀平均加速度是片蚀的7～10倍, 35 min后, 坡面处于稳定状态; 降雨产流10 min内, 坡面下1/3区域平均侵蚀加速度是坡面中部的5倍, 沟头激活后, 坡面中部的平均侵蚀加速度达到坡面下1/3区域的4倍; 坡顶部存在一个相对稳定区. 说明REE示踪技术能够同时量化随时间和空间变化的坡面侵蚀过程.     

Dynamics of erosion plasma formation and formation of a plasma flame with a condensed disperse phase when quasi-continuous laser radiation acts on bismuth

The dynamics of near-surface plasma formation and the formation of an erosion plasma flame was investigated for quasi-continuous laser radiation (λ=1.06 μm, q=0.1–10 MW/cm², τ∼1.5 msec) acting on bismuth targets in air. The absence of low-threshold plasma formation at q<2 MW/cm² was established and explained. Instabilities in the plasma formation were revealed and the range of laser radiation power densities (2≤q≤4 MW/cm²) at which these instabilities take place was determined. At q≥5.4 MW/cm², brightening of the flame was noted. The dependence of the luminescence temperature of the flame on the laser radiation power density q was determined. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 126–133, January–February, 1998.     

供应链上两类不同信用风险的关联及传染效应研究

在一个典型的存在资金约束的二级供应链上,通常存在两类不同的信用风险:一是供应商向银行信用贷款所形成的信贷信用风险;二是供应商为零售商提供商业信用而形成的商业信用风险。本文针对上述两类不同信用风险之间的关联性及传染问题展开研究,揭示了两类风险之间的传染机理,度量了风险的传染强度,并分析了传染强度的影响因素。研究表明:两类不同信用风险之间的关联性,导致供应链上存在由非同类信用风险构成的关联信用风险(Different types of associated credit risk),本文简称为供应链上的D类关联信用风险。结合数值分析发现:D类关联信用风险的传染强度与供应商的生产成本及无风险利率正相关,而与商品的市场价格负相关。特别地,当市场需求服从指数分布时,关联信用风险的传染强度与商业信用成本和零售商的特质有关,供应商通过调整商业信用成本和选择零售商类型可以降低D类关联信用风险的传染强度,进而降低自身的银行信贷风险。本文将同类型信用风险之间的关联和传染问题引申到不同类型的信用风险之间,进一步深化和拓展了关联信用风险的内涵。