用改进的离散坐标法计算炉内三维辐射传热

采用离散坐标法进行炉内三维辐射传热的计算。在正方体炉膛内验证了该法的精确性，计算结果与区域法进行比较，表明离散坐标法算法可靠，计算工作量小，适合于炉内辐射传热的计算。针对长方体炉膛计算了吸收-发射-散射介质的传热问题，表明传统的离散坐标法不适合计算具有复杂相函数曲线的辐射传热问题，因此采用改进的离散坐标法，并得到了合理的结果。对于煤粉燃烧炉膛将辐射传热问题和炉内流动、燃烧过程耦合起来进行计算，表明离散坐标法是一种很有工程应用价值的炉内辐射传热计算方法。

Elasticity, stability, and ideal strength of beta-SiC in plane-wave-based ab initio calculations

On the basis of the pseudopotential plane-wave method and the local-density-functional theory, this paper studies energetics, stress-strain relation, stability, and ideal strength of beta-SiC under various loading modes, where uniform uniaxial extension and tension and biaxial proportional extension are considered along directions [001] and [111]. The lattice constant, elastic constants, and moduli of equilibrium state are calculated and the results agree well with the experimental data. As the four SI-C bonds along directions [111], [(1) over bar 11], [11(1) over bar] and [111] are not the same under the loading along [111], internal relaxation and the corresponding internal displacements must be considered. We find that, at the beginning of loading, the effect of internal displacement through the shuffle and glide plane diminishes the difference among the four Si-C bonds lengths, but will increase the difference at the subsequent loading, which will result in a crack nucleated on the {111} shuffle plane and a subsequently cleavage fracture. Thus the corresponding theoretical strength is 50.8 GPa, which agrees well with the recent experiment value, 53.4 GPa. However, with the loading along [001], internal relaxation is not important for tetragonal symmetry. Elastic constants during the uniaxial tension along [001] are calculated. Based on the stability analysis with stiffness coefficients, we find that the spinodal and Born instabilities are triggered almost at the same strain, which agrees with the previous molecular-dynamics simulation. During biaxial proportional extension, stress and strength vary proportionally with the biaxial loading ratio at the same longitudinal strain.

Metallographic Sample Prepared by Ion Beam Etching

Ion beam etching technique was used to reveal the metallograhpic microstructure and interface morphology of electroplating chromium coating, in particular, whose substrate surface layer was treated in advance by laser quenching. Chemical etchings were, also conducted for comparison. The reveal microstructures were observed and analyzed by scanning electron microscopy. The results show that ion beam etching can reveal well the whole microstructures of composite coating-substrate materials.

Measuring Receptor/Ligand Interaction at the Single-Bond Level: Experimental and Interpretative Issues

There is increased interest in measuring kinetic rates, lifetimes, and rupture forces of single receptor/ligand bonds. Valuable insights have been obtained from previous experiments attempting such measurements. However, it remains difficult to know with sufficient certainty that single bonds were indeed measured. Using exemplifying data, evidence supporting single-bond observation is examined and caveats in the experimental design and data interpretation are identified. Critical issues preventing definitive proof and disproof of single-bond observation include complex binding schemes, multimeric interactions, clustering, and heterogeneous surfaces. It is concluded that no single criterion is sufficient to ensure that single bonds are actually observed. However, a cumulative body of evidence may provide reasonable confidence. 0 2002 Biomedical Engineering Society.

对流扩散方程的变步长摄动有限差分格式

摄动有限差分(PFD)方法是构造高精度差分格式的一种新方法。变步长摄动有限差分方法是等步长摄动有限差分方法的发展和推广。对需要局部加密网格的计算问题，变步长PFD格式不需要对自变量进行数学变换，且和等步长PFD格式一样，具有如下的共同特点：从变步长一阶迎风格式出发，通过把非微商项(对流系数和源项)作变步长摄动展开，展开幂级数系数通过消去摄动格式修正微分方程的截断误差项求出，由此获得高精度变步长PFD格式。该格式在一、二和三维情况下分别仅使用三、五和七个基点，且具有迎风性。文中利用变步长PFD格式对对流扩散反应模型方程，变系数方程及Burgers方程等进行了数值模拟，并与一阶迎风和二阶中心格式及其问题的精确解作了比较。数值试验表明，与一阶迎风和二阶中心格式相比，变步长PFD格式具有精度高，稳定性与收敛性好的特点。变步长PFD格式与等步长PFD格式相比，变步长PFD解在薄边界层型区域的分辨率得到了明显的提高。

神经网络在覆盖件模具表面激光硬化虚拟过程中的应用

基于人工神经网络技术对覆盖件模具表面激光硬化虚拟过程的仿真建模,结合几何因素分析了模型的主要影响参数,对BP网络的结构和训练进行了说明。预测了激光表面硬化的加工效果 (表面硬度、硬化层深、相对耐磨性和表面粗糙度),实现激光加工工艺参数的优化,为实际生产和加工提供了依据。并以C语言为开发语言,利于实现各平台间的集成。

Characteristic Dimensionless Numbers in Multi-Scale and Rate-Dependent Processes

For this sake, the macroscopic equations of mechanics and the kinetic equations of the microstructural transformations should form a unified set that be solved simultaneously. As a case study of coupling length and time scales, the trans-scale formulation

Capillary Effect on Vertically Excited Surface Wave in Circular Cylindrical Vessel

In a vertically oscillating circular cylindrical container, singular perturbation theory of two-time scale expansions was developed in inviscid fluids to investigate the motion of single free surface standing wave including the effect of surface tension.

连铸电磁冶金技术, 第七讲, 电磁连铸技术

连铸生产的要求是在高拉速下获得高质量的铸坯，即高质量与高生产率的统一；连铸技术的发展趋势是实现连铸连轧甚或近终形连铸，两者都要求有良好的铸坯表面质量。实践表明，铸坯表面质量实质上是由弯月面处发生的初期凝固决定的。为消除表面缺陷，提出了各种控制初期凝固的电磁连铸技术。

通过虚拟驱动程序（VxD）实现稳定的串口通信

本文主要介绍在Ｗｉｎｄｏｗｓ９５／９８环境下，利用ＶｘＤ开发工业激光器通信程序，以实现稳定的通信。同时还介绍了Ｗｉｎ３２应用程序与底层ＶｘＤ交换数据的方法。文中给出了开发的程序以及所实现的功能。

应变梯度理论进展

应变梯度理论是近10年来为解释材料在微米尺度下的尺寸效应现象而发展起来的一种新理论.首先综述了应变梯度理论近年的发展及其对材料力学行为研究方面的进展.其次主要介绍了不含高阶应力的一类应变梯度理论及其应用;最后对应变梯度理论的发展做了展望.

泥石流的启动分析

分析了由于振动或冲刷等动载荷引起散体堆积物的液化或流态化而导致的泥石流。 据此， 认为这是在小坡角(10°以内)条件下泥石流形成的主要原因。

重庆西山坪西园建材厂滑坡应急抢险治理工程

以西山坪西园建材厂滑坡体工程地质勘察资料为依据，分析了滑坡体的岩土组成和物理力学性质以及造成滑坡的原因。认为影响山体滑坡的因素除与边坡地层岩性。微地貌特征。气象及水文条件有关外，修建厂房开挖与切割边坡坡脚则是重要的诱发原因。定性得出该滑坡的形成机制和类型为牵引式、浅层、小型土质新型滑坡。在此基础上，应用规范所推荐的极限平衡法，对该滑坡体的3个主要地质剖面(A-A'、B-B、C-C)进行了稳定性计算与分析，得到不同工况下滑坡体稳定系数值。其中，在最不利组合工况（自重十暴雨十地震）下，滑坡体稳定系数仅为0.99-1.03，处于不稳定状态）根据计算结果，按照《长江三峡库区滑坡灾害防治规范》要求及“技术可行、安全可靠、经济合理、简单易实施”的设计原则，对该滑坡的应急抢险方案进行了设计，提出以抗滑桩拦挡工程为主、坡顶修筑截排水沟。地表裂缝回填夯实等综合治理方案。抗滑桩设置1排，分3段，根据每段不同的剩余下滑力设计抗滑桩的断面尺寸和埋设深度，使该滑坡体治理后，其安全系数分别满足不同工况下的规范要求。该方案已通过了三峡库区滑坡灾害防治专家组的审核，目前，正处于实施阶段。