Investigation on Depth of Heat Affected Zone of Discharge Spot by High Repetitive Rate YAG Laser-Induced Discharge Texturing

It is known that the press formability and the elongation of laser textured sheet are improved, and the service life of textured roll is longer than that of the un-textured roll due to hardening of the treated surface. One of the goals to develop high repetitive rate YAG laser-induced discharge texturing (LIDT) is to get deeper hardening zone. By observing and measuring cross-section of LIDT spots in different discharge conditions, it is found that the single-crater, which is formed by the discharge conditions of anode, which is covered by an oil film and with rectangular current waveform, has the most depth of heat affected zone (HAZ) comparing with other crater shapes when discharge energy is the same. The depth of HAZ is mainly depends on pulse duration when the discharge spot is single-crater. The results are analyzed.

禹城地区陆气相互作用耦保模式和观测研究

论述了陆气相互作用研究在人类生存环境与发展区域经济中的重要意义与研究现状。在原有研究工作基础上，针对中国科学院禹试验城站地区麦田陆气水热传输过程，提出了一个多层陆气耦合模式。对植被内部湍流交换的物理过程作了深入研究，特别考虑了叶片气孔为非饱和水汽条件下的交换情况，并且给出了修正后的根系吸水模式。陆气耦合模式分别对大气、植被、土壤作多层划分，以助于细致了解沿高度分布的各物理量。利用本模式对中国科学院禹城试验站地区小麦地陆气水热交换过程进行了数值模拟，模拟结果与实测值吻合较好。证明该模式成功地模拟了陆气相互作

气泡初始尺寸对泡弹状流型转换的影响

本文对气液两相泡状流向弹状流转换的机制进行了分析,认为气泡合并是影响该流型转换的主要机制,并据此用随机数值模拟方法,对气泡初始尺寸对泡状流向弹状流转换的影响进行了研究。计算结果表明,无量纲气泡碰撞率是一条通用曲线,根据该曲线可以确定气泡初始尺寸产生影响的区域及其大小,与实验结果的比较令人满意。

Flow Characteristics and Its Friction Coefficient of Laminar Near-Wall Boundary Layer in Dusty Atmosphere

采用双向耦合的双流体模型,研究了大气悬浮沙尘的存在对大气边界层中层流底层流动特性及摩阻系数的影响,计算并讨论了不同沙尘含量下含尘大气相对于无尘大气摩阻系数的变化。结果表明：摩阻系数的变化取决于悬浮沙尘的初始运动状态和质量载荷率。

颗粒级配和结构对粉砂力学性质的影响

分析了几组原状、重塑和配制土样的静三轴试验结果,认为颗粒级配和结构性是影响粉砂应力-应变关系和强度特性的两个主要因素.当颗粒级配不同时,结构性原状粉砂土样和不具有结构性的配制土的强度均不同.相同颗粒级配的原状和重塑粉砂的强度也不同.而颗粒级配稍有不同的一种配制粉砂与原状粉砂在应力-应变关系和强度特性方面相接近.此种配制粉砂可替代原状粉砂做为模型试验用土.

Quantifying the Effects of Contact Duration, Loading Rate, and Approach Velocity on P-Selectin-PSGL-1 Interactions Using AFM

Kinetics and its regulation by extrinsic physical factors govern selectin-ligand interactions that mediate tethering and rolling of circulating cells on the vessel wall under hemodynamic forces. While the force regulation of off-rate for dissociation of selectin-ligand bonds has been extensively studied, much less is known about how transport impacts the on-rate for association of these bonds and their stability. We used atomic force microscopy (AFM) to quantify how the contact duration, loading rate, and approach velocity affected kinetic rates and strength of bonds of P-selectin interacting with P-selectin glycoprotein ligand I (PSGL-1). We found a saturable relationship between the contact time and the rupture force, a biphasic relationship between the adhesion probability and the retraction velocity, a piece-wise linear relationship between the rupture force and the logarithm of the loading rate, and a threshold relationship between the approach velocity and the rupture force. These results provide new insights into how physical factors regulate receptor-ligand interactions.

Scaling relationships in indentation of power-law creep solids using self-similar indenters

We use dimensional analysis to derive scaling relationships for self-similar indenters indenting solids that exhibit power-law creep. We identify the parameter that represents the indentation strain rate. The scaling relationships are applied to several types of indentation creep experiment with constant displacement rate, constant loading rate or constant ratio of loading rate over load. The predictions compare favourably with experimental observations reported in the literature. Finally, a connection is found between creep and 'indentation-size effect' (i.e. changing hardness with indentation depth or load).

考虑压头曲率半径的J_2形变理论压痕有限元分析

采用经典J2形变理论,在考虑压头曲率半径的前提下,针对几组微压痕实验进行了有限元数值模拟,给出理论计算结果并与实验进行了系统比较.结果发现考虑了压头曲率半径后的经典J2形变理论得到的整段计算曲线不能和实验曲线吻合,可以推理出即使考虑压头曲率半径的的影响,经典J2形变理论也不能很好地解释实验现象.

几种高性能纤维束的冲击动力学性能实验研究

利用直拉式Hopkinson装置研究了碳纤维、无碱E玻璃纤维、Kevlar 49/964/964c、Twaron2000、Dyneema Sk66等纤维的动态拉伸性能。与准静态加载条件下相比，纤维束的拉伸强度基本与应变速率无关（玻璃纤维除外），而纤维束的弹性模量和失效应变随应变率的升高而明显变大。从高分子物理以及两种无机纤维的内部微观结构特征对纤维的力学性能与加载速率的关系进行了初步的物理阐释。讨论了实验数据的发散原因。

Localized Solid-State Amorphization at Grain Boundaries in a Nanocrystalline Al Solid Solution Subjected to Surface Mechanical Attrition

Using high-resolution electron microscopy, localized solid-state amorphization (SSA) was observed in a nanocrystalline (NC) Al solid solution (weight per cent 4.2 Cu, 0.3 Mn, the rest being Al) subjected to a surface mechanical attrition treatment. It was found that the deformation-induced SSA may occur at the grain boundary (GB) where either the high density dislocations or dislocation complexes are present. It is suggested that lattice instability due to elastic distortion within the dislocation core region plays a significant role in the initiation of the localized SSA at defective sites. Meanwhile, the GB of severely deformed NC grains exhibits a continuously varying atomic structure in such a way that while most of the GB is ordered but reveals corrugated configurations, localized amorphization may occur along the same GB.

Frequency characteristics and dynamical behaviors of self-modulation in vertical-cavity surface-emitting lasers

The frequency characteristics of a VCSEL with a quarter-wave plate (QWP) and an external reflector are investigated with the translation matrix of the vectorial field. Two series of eigenmode with a shift of half the free spectrum range are linearly polarized, respectively, along the neutral axes of QWP. We also numerically explore the polarization self-modulation phenomenon by using a vectorial laser equation and considering the inhomogeneous broadening of the gain medium. If the external cavity is so short that the shift is bigger than the homogeneous broadening, two stable longitudinal modes oscillate, respectively, on the neutral axes of QWP because they consume different carriers. With a long external cavity, the competition of the modes for the common carriers causes the intensity fluctuation of the modes with a period of one round-trip time of the external cavity.

蒸发两层流系统的对流不稳定性分析

关于蒸发液层的Rayleigh-Marangoni-Bénard不稳定性的研究中,早期文献中普遍采用的是单层流模型.近年来,一些学者采用两层流模型对蒸发稳定性进行了理论分析,有的文献中没有考虑蒸发率与饱和蒸汽压的耦合关系,所以得到的结果不能完全反应蒸发对系统稳定性的影响.本文建立了一种新的两层流模型,考虑了界面变形对系统稳定性的影响.采用线性稳定性方法对带有蒸发界面的两层流的Rayleigh-Marangoni-Bénard对流不稳定性进行了分析,得到了临界Marangoni数与波数的关系,重点讨论了蒸发系数以及重力对汽液两层流系统的不稳定性的影响.