表面波在表面活性剂流变学研究中的应用

论述了表面波的原理及其发展,文中进一步讨论了毛细波和纵向波的特点,较为详细地介绍了纵向波的实验方法和装置以及在表面活性剂流学变性质研究中的应用。     

外部边界球可达域上拟共形映射的Lipschitz连续性

定义了外部边界球可达域,利用曲线族的模获得如下结果:设D是R~n中的有界拟凸域,f:D→B~n是K-拟共形映射,若D是外部边界球可达域,则f∈Lip_α(D),其中α=K~(1/(1-n)).     

柴油高压物理特性的研究

 柴油物理特性是模拟计算高压燃油喷射系统的基础。针对柴油的密度、体弹性模量和运动粘度等进行了试验研究，在其基础上得出了柴油密度、弹性模量和运动粘度随压力和温度变化的经验公式，能较好地把柴油的密度、弹性模量和声速统一起来，与试验的误差小于3%，相关系数大于0.998，能满足高精度燃油喷射系统仿真的精度要求。     

固体杨氏模量的测量

通过测量超声波在固体介质中传播的纵波传播速度,进一步测量该固体的杨氏模量,得到了测量固体杨氏模量的一种新方法。     

Sound transmission prediction by 3-D elasticity theory

The problem of sound transmission through layered panel structures is studied with the exact theory of three-dimensional (3-D) elasticity. The exact solution to the 3-D elasticity equations is obtained by the use of the Fourier spectral method. Based on this analytical solution, a transfer matrix is derived that relates the spectral displacements and stresses on the one surface of the panel to those on the opposite panel surface. The transfer matrix is then used to develop the analytical solutions for sound reflection and transmission coefficients. Explicit, concise expressions are obtained for the analytical solutions of the acoustic transmission and reflection coefficients under the general conditions of layered anisotropic panels. Examples are given for both single-layer and sandwich panels. Predictions on sound transmission from the 3-D elasticity theory are compared with available data from other methods, and the results are discussed.     

激光干涉法测量弹性模量

从光的干涉原理出发，讨论了金属丝弹性模量的光电测量方法．设计了激光干涉法测量长度微变量的测量装置，并介绍了测量原理，给出了动镜移动方向判别电路．     

磁流变弹性体若干物理量的数值分析

应用有限元方法,考虑了颗粒的磁化饱和过程与非线性磁化过程,计算得到了磁流变弹性体中的磁场分布,进而研究了在不同磁场大小、不同颗粒体积比浓度下磁流变弹性体在成链方向的相对磁导率,计算结果和实验结果取得了一致。利用Maxwell应力张量,计算了磁场引起的磁流变弹性体的附加剪切模量。分析了颗粒体积比浓度、外加磁场对磁流变弹性体的磁致剪切模量的影响。研究了颗粒为旋转椭球形状时,颗粒的放置方式与其长短轴之比对磁流变弹性体的磁致剪切模量的影响。计算结果表明,磁流变弹性体的相对磁导率随颗粒体积比浓度的增大而增大,随磁场强度的增大而减小,颗粒的形状和放置方式对磁流变效应有很大的影响。     

Changes in electronic,magnetic and bonding properties from Zr2FeH5 to Zr3FeH7 addressed from ab initio

Potential hydrogen storage ternaries Zr₃FeH₇ and Zr₂FeH₅, are studied from ab initio with the purpose of identifying changes in electronic structures and bonding properties. Cohesive energy trends: E_coh. (ZrH₂) > E_coh. (Zr₂FeH₅) > E_coh. (Zr₃FeH₇) > E_coh. (hypothetic-FeH) indicate a progressive destabilization of the binary hydride ZrH₂ through adjoined Fe so that Zr₃FeH₇ is found less cohesive than Zr₂FeH₅. From the energy volume equations of states EOS the volume increase upon hydriding the intermetallics leads to higher bulk moduli B₀ explained by the Zr/Fe–H bonding. Fe–H bond in Zr₂FeH₅ leads to annihilate magnetic polarization on Fe whereas Fe magnetic moment develops in Zr₃FeH₇ identified as ferromagnetic in the ground state. These differences in magnetic behaviors are due to the weakly ferromagnetic Fe largely affected by lattice environment, as opposed to strongly ferromagnetic Co. Hydrogenation of the binary intermetallics weakens the inter-metal bonding and favors the metal–hydrogen bonds leading to more cohesive hydrides as with respect to the pristine binaries. Charge analyses point to covalent like Fe versus ionic Zr and hydrogen charges ranging from covalent H^−0.27 to more ionic H^−0.5.     

On stress-based piecewise elasticity for limited strain extensibility materials

A one-dimensional stress-based elasticity model with limited strain extensibility is developed in this paper, based on thermodynamics arguments. Such nonlinear elastic models can be used to model certain rubber-like and biological materials with limiting chain extensibility. The derived constitutive function is a non-smooth piecewise expression, which can be regularized for numerical or physical considerations. This non-smooth constitutive expression is derived from a Gibbs potential. A three-dimensional extension of this stress-based model is also proposed in the paper. Some simple structural examples are investigated for a bar composed of this non-smooth elastic body. A homogeneous bar composed of this new class of nonlinear elastic material that is loaded is studied for different tension states, namely for concentrated or distributed axial loading. It is shown that the displacement limit extensibility can be observed at the structural scale, with finite or infinite axial load parameters.     

Impact of chain architecture (branching) on the thermal and mechanical behavior of polystyrene thin films

The modulus and glass transition temperature (T_g) of ultrathin films of polystyrene (PS) with different branching architectures are examined via surface wrinkling and the discontinuity in the thermal expansion as determined from spectroscopic ellipsometry, respectively. Branching of the PS is systematically varied using multifunctional monomers to create comb, centipede, and star architectures with similar molecular masses. The bulk‐like (thick film) T_g for these polymers is 103 ± 2 °C and independent of branching and all films thinner than 40 nm exhibit reductions in T_g. There are subtle differences between the architectures with reductions in T_g for linear (25 °C), centipede (40 °C), comb (9 °C), and 4 armed star (9 °C) PS for ≈ 5 nm films. Interestingly, the room temperature modulus of the thick films is dependent upon the chain architecture with the star and comb polymers being the most compliant (≈2 GPa) whereas the centipede PS is most rigid (≈4 GPa). The comb PS exhibits no thickness dependence in moduli, whereas all other PS architectures examined show a decrease in modulus as the film thickness is decreased below ～40 nm. We hypothesize that the chain conformation leads to the apparent susceptibility of the polymer to reductions in moduli in thin films. These results provide insight into potential origins for thickness dependent properties of polymer thin films. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012