Derivatives of the energy functional for 2D‐problems with a crack under Signorini and friction conditions

We consider the two‐dimensional elasticity problem for an elastic body with a crack under unilateral constraints imposed at the crack. We assume that both the Signorini condition for non‐penetration of the crack faces and the condition of given friction between them are fulfilled. The problem is non‐linear and can be described by a variational inequality. Varying the shape of the crack by a local coordinate transformation of the domain, the first derivative of the energy functional to the problem with respect to the crack length is obtained, which gives the criterion for the crack growing. The regularity of the solution is discussed and the singular solution is performed. Copyright © 2000 John Wiley & Sons, Ltd.     

翼型跨音速流动计算和外形设计的变域变分有限元方法

在气体动力学问题研究中经常会碰到诸如激波、翼型设计等未知界面问题。未知界面的存在为该类问题的理论分析和数值求解带来了很大困难。刘高联针对未知界面问题发展了一种变域变分有限元方法,该方法将未知界面看作是一个变化区域的边界,采用变域变分将未知界面结合在变分泛函中,使其与求解流场的控制方程结合起来,从而将未知界面的求解和流场的求解完全耦合进行,因而是一种处理未知界面的独特工具,极适合于气动外形的设计求解。本文运用变域变分有限元方法对翼型跨音速流动正、反命题进行了数值研究。由于在跨音速翼型绕流中存在激波,所以为了得到压缩激波解,采用了“人工密度”办法。几个算例均得到了满意的计算结果和设计结果,证明了本文方法的有效性和优越性。     

Comparison between formulas of rotational band for axially symmetric deformed nuclei

The experimental rotational spectra of the deformed nuclei available in even-even and odd-A nuclei in the rare-earth and actinide regions are systematically analyzed with several rotational spectra formulas,including Bohr-Mottelson's I(I+l)-expansion,Harris'w2-expansion,ab and abc formulas.It is shown that the simple 2-parameter ab formula is much better than the widely used 2-parameter Bohr-Mottelson's AB formula and Harris'αβ formula.The available data of the rotational spectra of both ground-state band in even-even nuclei and one-quaasiparticle band in odd-A nuclei can be conveniently and rather accurately reproduced by ab formula and abc formula.The moment of inertia and the variation with rotational frequency of angular momentum can be satisfactorily reproduced by ab and abc formulas.     

河台金矿中稀土元素在韧性剪切过程中迁移行为的研究

通过对两类糜棱岩及其原岩的稀土元素含量的分析研究, 结果表明, 稀土元素在韧性剪切过程中发生有规律的成分变异. 在云母石英片岩及混合岩形成糜棱岩、超糜棱岩过程中, 即随着变形强度的增强, 单个稀土元素、轻稀土、重稀土和稀土总量均出现有规律的增加或减少, 而稀土元素配分模式不变. 通过对构造岩变形前后的等比分析, 认为两类不同的糜棱岩类中稀土元素的成分变异极小, 但存在少量稀土元素的迁入和迁出, 变化的原因是在岩石变形过程中发生了体积的改变和大量的流体作用影响, 并导致轻稀土相对富集、重稀土相对亏损的分异作用.     

有限变形非对称弹性理论变分原理

应用有限变形S-R分解定理,将体力矩重新定义为内外两种体力矩之和,给出了相应的变形能增率表达式及其物理意义,并进一步补充和完善了有体力矩作用下的有限变形力学的功率变分原理和余功率变分原理。     

Polymerization of Methyl Methacrylate with Ni(II) α‐Diimine/MAO and Fe(II) and Co(II) Pyridyl Bis(imine)/MAO

Polymerizations of methyl methacrylate with (α‐diimine)nickel(II)/methylaluminoxane (MAO) and (pyridyl bis(imine))iron(II) and (pyridyl bis(imine))cobalt(II)/MAO are reported. Effects of structural variation of the ligand on the activities of catalysts and polymer microstructure are described. The catalyst systems gave syndio‐rich poly(methyl methacrylate). The α‐diimine system showed much higher activity than the pyridyl bis(imine) systems under similar polymerization conditions.

     

四芯光纤的远场干涉特性研究

设计了芯间距较小的特殊结构四芯光纤,可用于生成格子光场或用于制作光纤传感器.研究了在采用相干长度较短的LD光源的情况下,经过一段既弯曲又扭转的四芯光纤远程传输后的纤端光场干涉特性.基于叠加原理,出射光场可视为每个独立纤芯的多光源相干叠加和圆孔衍射调制共同作用的结果,推导了相应的理论公式,给出了四芯光纤远场干涉的理论与实验相一致的结果.对光纤弯曲所导致的光程差累积和偏振态衰变效应进行了分析和讨论,并给出了相应的实验结果.     

Comparison of Dechlorane Plus Concentrations in Sequential Blood Samples of Pregnant Women in Taizhou,China

To develop an appropriate sampling strategy to assess the intrauterine exposure to dechlorane plus (DP), we investigated DP levels in sequential maternal blood samples collected in three trimesters of pregnancy, respectively, from women living in Taizhou. The median concentration of DPs (sum of syn-DP and anti-DP) in all samples was 30.5 pg g⁻¹ wet-weight and 5.01 ng g⁻¹ lipid-adjusted weight, respectively. The trimester-related DP concentrations were consistently strongly correlated (p < 0.01), indicating that a single measurement of DP levels could represent intrauterine exposure without sampling from the same female repeatedly; however, the wet-weight levels significantly increased across trimesters (p < 0.05), while the lipid-adjusted levels did not significantly vary. Notably, whether lipid-adjusted weight or wet-weight levels, the variation extent of DP across trimesters was found to be less than 41%, and those for other persistent organic pollutants (POPs) reported in the literature were also limited to 100%. The limitation in variation extents indicated that, regardless of the time of blood collection during pregnancy and how the levels were expressed, a single measurement could be extended to screen for exposure risk if necessary. Our study provides different strategies for sampling the maternal blood to serve the requirement for assessment of in utero exposure to DP.     

用不同光强点定位测量线偏振光旋转角时检测灵敏度的研究

通过实验验证马吕斯定律,分别在消光位置和最大光强位置作检测点,测量待测旋光物质的旋光度,研究物理实验中普遍存在的在光强极大值和光强最大相对变化率位置检测灵敏度的问题。根据实验结果的分析,得出了在消光位置测量线偏振光旋转角最精确的结论。     

电爆炸过程中金属丝阻抗的变化

为了掌握金属丝阻抗的变化规律,通过分压器和罗氏线圈分别测量出电爆炸过程中金属丝上的电压和电流,并由此计算出金属丝阻抗等相关电参数随时间变化的规律;采用F.D.Bennett和A.Hobson模型对金属丝阻抗进行了数值模拟,得到金属丝阻抗随时间的变化规律。实验结果和模拟结果的比较表明:两个模型的模拟结果均在金属丝气化前和部分初始放电电压下有效;当放电时电容器初始电压较大时,能量沉积速度更快,金属丝液化、气化、完全气化所用的时间更短;在金属丝爆炸过程中,金属丝阻抗存在一个最大值。