The stress driven instability in elastic crystals: Mathematical models and physical manifestations

Summary Equilibrium equations and stability conditions for the simple deformable elastic body are derived by means of considering a minimum of the static energy principle. The energy is supposed to be sum of the volume (elastic) and the surface terms. The ability to change relative positions of different material particles is taken into account, and appropriate natural definitions of the first and second variations of the energy are introduced and calculated explicitly. Considering the case of negligible magnitude of the surface tension, we establish that an equilibrium state of a nonhydrostatically stressed simple elastic body (of any physically reasonable elastic energy potential and of any symmetry) possessing any small smooth part of free surface is always unstable with respect to relative transfer of the material particles along the surface. Surface tension suppresses the mentioned instability with respect to sufficiently short disturbances of the boundary surface and thus can probably provide local smoothness of the equilibrium shape of the crystal. We derive explicit formulas for critical wavelength for the simplest models of the internal and surface energies and for the simplest equilibrium configurations. We also formulate the simplest problem of mathematical physics, revealing peculiarities and difficulties of the problem of equilibrium shape of elastic crystals, and discuss possible manifestations of the above-mentioned instability in the problems of crystal growth, materials science, fracture, physical chemistry, and low-temperature physics.     

Comparison of a pump-around, a diffusion-driven, and a shear-driven system for the hybridization of mouse lung and testis total RNA on microarrays

In the present study, we demonstrate the benefits of a shear-driven rotating microchamber system for the enhancement of microarray hybridizations, by comparing the system with two commonly used hybridization techniques: purely diffusion-driven hybridization under coverslip and hybridization using a fully automated hybridization station, in which the sample is pumped in an oscillating manner. Starting from the same amount of DNA for the three different methods, a series of hybridization experiments using mouse lung and testis DNA is presented to demonstrate these benefits. The gain observed using the rotating microchamber is large: both in terms of analysis speed (up to tenfold increase) and in final spot intensity (up to sixfold increase). The gain is due to the combined effect of the hybridization chamber miniaturization (leading to a sample concentration increase if comparing iso-mass conditions) and the transport enhancement originating from the rotational shear-driven flow induced by the rotation of the chamber bottom wall.     

用VB来开发辅助教学软件

本文首先介绍了基于中文Ｗｉｎｄｏｗｓ９５平台的最新版ＶｉｓｕａＬ Ｂａｓｉｃ５．０的特点,然后以纵横码辅助教学软件开发为便,阐述了用ＶＢ开发多媒体辅助教学软件的方法、步骤,并给出了开发过程中的关键技术。     

Strong coupling expansion for classical statistical dynamics

We discuss the simple, randomly driven systemdx/dt = –x –x³ +f(t), wheref(t) is a Gaussian random function or stirring force with f(t)f(t) = (t – t). We show how to obtain approximately the coefficients of the expansion of the equal-time Green's functions as power series in (1/R)ⁿ, whereR is the internal Reynolds number ()^1/2/, by using a new expansion for the path integral representation of the generating functional for the correlation functions. Exploiting the fact that the action for the randomly driven system is related to that of a quantum mechanical anharmonic oscillator with Hamiltonianp ²/2 +m ² x ²/2 +vx ⁴ +x ⁶/2, we evaluate the path integral on a lattice by assuming that thex ⁶ term dominates the action. This gives an expansion of the lattice theory Green's functions as power series in 1/(a)^1/3, wherea is the lattice spacing. Using Padé approximants to extrapolate toa = 0, we obtain the desired large-Reynolds-number expansion of the two-point function.Supported financially by the National Science Foundation and the U.S. Department of Energy.     

Phase separation dynamics in driven diffusive systems

We study phase separation dynamics in a driven diffusive system. Our simulations are based on the Cahn-Hilliard equation with an additional flux term due to an external field. We study the dynamical scaling parallel and perpendicular to the field. A crossover is observed from isotropic domains at early times to extremely anisotropic domains at later times. We find that the inverse interfacial density (an isotropic measure of the domain size) increases ast , with =1/3, from early times independent of the field strength, even though we do not observe dynamical scaling during these times. Our results indicate that a growth exponent =1/3 may be more universal than previously expected. We analyze the dynamics in terms of surface driven instabilities and one-dimensional solitary waves.     

软件开发统一过程应用研究

Rational Unified Process(RUP)是一个先进的较成熟的软件过程框架，Rational Suite是一个可视化的RUP支持软件包，两者结合提供了一个较好的软件工程环境。结合一个物业管理系统的开发过程，介绍了RUP过程的特点和实践过程。     

应用于加速器驱动次临界系统的程序开发

开发了应用输运理论方法的两套程序系统：蒙特卡罗－燃耗程序系统和输运－燃耗程序系统。针对蒙特卡罗程序不能计算燃料的同位素成分变化，提出将它和燃耗计算程序耦合以完成燃耗计算。燃耗程序所使用的单群截面由蒙特卡罗程序计算。将用于常规反应堆的计算方法和策略推广到输运－燃耗程序系统，这使得计算步序大大简化，并改进了精度。对加速器驱动次临界系统的基准题进行了校核计算，其结果和其他国家的计算结果符合良好，这表明所提出的计算方法与程序系统是成功的。     

单辊传动和异径轧制在镍带轧机上的实验

本文实验证明，在四辊薄带轧机上，实行“单辊传动和异径轧制”方案是可行的．通过实验数据分析和比较，单辊传动异径轧制可降低轧制力２１％～４０％，保证了轧机受力零件的安全．通过增加压下率，减少轧制道次，可以提高轧机的生产率．     

高速铁路列车运行调整的状态空间模型及算法

列车运行调整的优化属超大规模的组合优化问题，具有因素多、各因素之间关系复杂的特点，很难给出一个简洁、易解的规划模型．基于面向事件的状态空间模型良好的描述能力和具有接近系统自然特性的特点，本文在前人研究的基础上，结合我国高速铁路的特点，建立了行车调整的事件驱动的状态空间模型．针对前人研究中状态转移方程的表达及在冲突确认和疏解上的缺陷，结合算法的求解特点和列车运行的实际可能性，提出了改进方法．特别是冲突确认和疏解的新方法和策略，清除了事件驱动的状态空间模型和与之相应的调整算法在实用时的主要难点之一．仿真表明模型和算法是有效的．     

时延驱动的门阵和标准单元布图系统——Tiger

Ｔｉｇｅｒ可以完成从布局到详细布线的整个布图全过程。在整个布图过程中，根据ＲＣ延迟模型计算所有连线的延迟，并把整个芯片的时延最小作为优化目标。在Ｔｉｇｅｒ系统中，应用了性能驱动的布局和总体布线算法、ＤＲＡＦＴ通道布线算法和基于垂直通道模型的走线道分配算法。实验结果表明，Ｔｉｇｅｒ的布图速度要比ＴｉｍｂｅｒＷｏｌｆ６．０快很多。它在保证芯片性能的同时，其芯片面积与ＴｉｍｂｅｒＷｏｌｆ差不多。