两端绞紧微板弛豫动态过程分析

为探讨微机电系统中平板结构弛豫动力学特性,基于Euler-Bernoulli方程,计入空气滑膜阻尼与压膜阻尼对微板弛豫过程的影响,导出两端绞紧微板挠度弛豫表达式,并给出临界阻尼、过阻尼及欠阻尼时微板弛豫Ma-ple算例。利用ANSYS对微板临界阻尼、过阻尼以及欠阻尼弛豫进行仿真,结果显示不同长宽比微板仿真数据均与理论计算符合较好。     

Reexamination of slow relaxation of polymer chains in sol-gel transition

Using [2+2] photocycloaddition of coumarin groups attached to the PMMA chain backbone, we can gradually transfer a semidilute copolymer solution to a uniform speckle-free gel. We reexamined the effects of concentration, crosslinking density, solvent quality on the controversial scaling exponent (α_s) between the linewidth (Γ_s) of the slow mode and the scattering vector (q) during the sol-gel transition. Our results suggest that the slow mode is attributed to large thermally agitated density fluctuation and revealed that the variation of α_s is due to the relative length of 1/q to the correlation length (ξ) of the density fluctuation; namely, if ξ>1/q, α_s→3, while when ξ<1/q, α_s→2.     

Quenching of self-excited vibrations

Stable normal-mode vibrations in engineering can be undesirable and one of the possibilities for quenching these is by embedding the oscillator in an autoparametric system by coupling to a damped oscillator. There exists the possibility of destabilizing the undesirable vibrations by a suitable tuning and choice of nonlinear coupling parameters. An additional feature is that, to make the quenching effective in the case of relaxation oscillations, one also has to deform the slow manifold by choosing appropriate coupling; this is illustrated for Rayleigh and van der Pol relaxation.     

Nanoluminograph — A New Generation of Measuring Instruments

A nanoluminescent device, or nanoluminograph, has been developed, created, and patented. By means of the device, unique information about the physicochemical properties of surface and near-surface layers of solids and ultrathin coatings of thickness less than 0.4 μm may be obtained. There is also the hope of decreasing the thickness of the subject layer with further development of the detecting component of the device. __________ Translated from Izmeritel'naya Tekhnika, No. 8, pp. 28–31, August, 2005.     

Toward a unified description of nonlinearity and frequency dispersion of piezoelectric and dielectric responses in Pb(Zr,Ti)O3

A phenomenological approach is proposed describing both nonlinearity and frequency dispersion in dielectric and piezoelectric properties of lead zirconate titanate, Pb(Zr,Ti)O₃ (PZT), thin films and ceramics. The approach couples the frequency dependent response in form of the power law, 1/ω^β, with the rate-independent nonlinear response described by the Rayleigh law. The main experimental trends are well described by the model.     

Dielectric properties of sol-gel derived Ta2O5 thin films

The dielectric constant and the dielectric loss of tantalum pentoxide (Ta₂O₅) thin films, produced by sol-gel spin-coated process on Corning glass substrates, have been investigated in the frequency range of 20-10⁵ Hz and the temperature range of 183-403 K, using ohmic Al electrodes. The frequency and temperature dependence of relaxation time has also been determined. The capacitance and loss factor were found to decrease with increasing frequency and increase with increasing temperature. The activation energy values were evaluated and a good agreement between the activation energy values obtained from capacitance and dielectric loss factor measurements were observed.     

Topological improvement procedures for quadrilateral finite element meshes

This paper presents a set of procedures for improving the topology of unstructured quadrilateral finite element meshes. These procedures are based on the topology of the finite element mesh, and all operations act only on local regions of the mesh. The goal is to optimize the topology such that the smoothing process can produce the best possible element quality. Topological improvement procedures are presented both for elements that are interior to the mesh and for elements connected to the boundary. Also presented is a discussion of efficiency and optimal ordering of the procedures. Several example meshes are included to show the effectiveness of the current approach in improving element qualities in a finite element mesh.     

Effect of Ion Dose on Growth of Relaxed SiGe Layer on Ion Implantation Si Substrate

Thin strain-relaxed Si0.8Ge0.2 films (57.6 nm) on the 30 keV Ar ion implantation Si substrates for different dose (1 × 1014, 5 × 1014, 3 × 1015 cm-2) were grown by ultra high vacuum chemical vapor deposition (UHVCVD) system.Rutherford backscattering/ion channeling (RBS/C), high resolution X-ray diffraction (HRXRD), Raman spectra as well as atomic force microscopy (AFM) were used to characterize these SiGe films. Investigations by RBS/C as well as HRXRD demonstrate that these thin Sio.8Geo.2 films could indeed epitaxially grow on the Ar ion implantation Si substrates. Under low dose ( 1 × 1014 cm-2) and medium dose (5 × 1014 cm-2) implantation conditions, the relaxation extents of SiGe films are 60.6% and 63.6%, respectively. However, high dose implantation (3 × 1015 cm-2) prompt the strain in epitaxial SiGe film to be close to full relaxation status (relaxation extent of 96.6% ). On the other hand, determinations of RBS/C also indicate the crystalline quality of SiGe film grown on high dose implantation Si substrate is nearly identical to that grown on low dose (1 × 1014 cm-2) implantation Si substrate.     

军事物流选址分配模型及遗传算法优化

在每个物流中心的容量有限的情况下,为了解决军事物流中心选址和服务需求分配问题,建立了一种基于二维地理坐标平面的军事物流选址分配模型。针对这种非凸和非光滑的混合整数非线性规划模型,给出了一种改进遗传算法的全局最优化求解方法,其中由于适应度函数与各物流中心对应的需求分配情况密切相关,我们用拉格朗日松弛法解决了对于特定位置的物流中心服务需求分配的子问题,最终得到了模型的全局最优解或者近似全局最优解,最后的实例求解表明了该算法的有效性和稳定性。     

粘弹流变体数学模型和等价模型的研究

本文首次提出用复元件来建立粘弹流变力学模型的拉氏状态方程的新方法,建立这种新数学模型较易于微分状态方程的建立。本文还提出流变力学模型的结构式表示法和计算法,用结构式来判别各种等价模型非常便捷。