Dislocations emission and crack extension at the atomistic crack tip in body-centered-cubic metal Mo

The behaviors of a crack in body-centered-cubic metal Mo under different loading modes were studied using the molecular dynamics method. Dislocation emission was observed near the crack tip in response to mode II loading with theta = 0 degrees in which theta is the inclination angle of the slip plane with respect to the crack plane, and two full dislocations were observed at the stress level of K-II = 1.17 MPa m(1/2) without any evidence of crack extension. Within the range of 0 degrees less than or equal to theta less than or equal to 45 degrees, crack extension was observed in response to mode I loading, and the effect of crystal orientation on the crack propagation was studied, The crack propagated along the [111] slip direction without any evidence of dislocations emission.

激光点热源作用下动态微变形的数值模拟与校验

采用MSC．Marc非线性有限元软件，对试件在激光点热源作用下动态微变形过程进行了数值模拟。通过激光反射放大系统测量了试件在激光点热源作用下的动态微变形过程。模拟值与实测值的结果表明：热应力和相变应力的共同作用使得试件产生微变形，最终试件的变形方向取决于热应变和相变共同作用的结果，朝向激光束或背向激光束。比较实验值和模拟值，发现变形的最大值相近，变形过程却略有不同。考虑到激光点热源作用下有限厚度的试件内，温度场分布出现的反常效应，即内部的温度大于边界温度，提出采用波动理论修正经典的热传导计算模型，可望有效地提高模拟过程的计算精度。结论为进一步研究薄板激光弯曲的变形机理及变形过程莫定了基础。

Ce：Mn：LiNbO3晶体紫外记录研究

采用紫外光作记录光在Ce：Mn：LiNbO3晶体中实现非挥发全息记录，灵敏度可达0．0803cm／J，衍射效率（固定）为5．07％，比采用红光为记录光，紫外光为敏化光的非挥发双中心记录方案均提高了50多倍。分析表明，采用紫外光作为记录光，深能级电子被激发比例极大提高，参与光折变过程的电子平均运动周期变短．提高了衍射效率和灵敏度；深浅能级电子光栅的同相位，使得固定空间电荷场变强。文中还研究了退火对记录性能的影响。

不同类型蒸发源对平面夹具薄膜均匀性的影响

分析了几种可能的实际蒸发源与薄膜均匀性的关系，其中包括扩展的平面蒸发源和曲面蒸发源。通过实验论证了薄膜均匀性对蒸发源尺寸和蒸发特性的依赖关系。得到的分析结果表明：当蒸发源半径和夹具高度的比值小于1／17时，蒸发源可以被视为一个点面源；大于1／10时，应当把蒸发源视为面面源进行考虑。当挖坑深度和蒸发源半径的比值介于0和0．5之间时，挖坑对薄膜均匀性造成的影响基本可以忽略；大于0．6时，挖坑效应明显影响薄膜的均匀性。

咖啡灭字虎天牛研究综述

咖啡灭字虎天牛是危害咖啡树的重大害虫,从本世纪初以来,国内外对该虫做了许多研究、这些研究包括生活史、取食危害习性、寄主植物、化学防治、生物防治等方面.与农林害虫相比,对咖啡灭字虎天牛的研究工作仍相当落后.到目前为止,人们对该虫的自然种群数量变动规律及其发生机制还不清楚.今后加强这方面的研究,对于该虫的综合治理具有重大意义.

双链RNA病毒诱导的牙鲆胚胎细胞差减cDNA文库的构建

以紫外线灭活的dsRNA病毒草鱼出血病病毒(GCHV)诱导和模拟诱导的牙鲆胚胎细胞为材料,利用抑制性差减杂交(SSH)技术,成功构建了双链RNA病毒诱导的牙鲆胚胎细胞(FEC)差减cDNA文库。以管家基因αtub lin作为差减指标,经检测,该文库差减效率达210倍,表明经病毒诱导后某些差异表达基因也得到了相应倍数的富集。将获得的cDNA片段连接到pGEM T载体,PCR检测显示差减片段在250bp~2 000bp之间。该差减cDNA文库的构建为从分子水平研究牙鲆培养细胞对dsRNA病毒的免疫反应、以及进

Synthesis and structures of morphology-controlled ZnO nano- and microcrystals

Zinc oxide flower-like bunches were directly synthesized on indium-doped tin oxide (ITO) glass substrates through a simple chemical bath deposition process. By adjusting precursor concentration, other morphologies ( spindles and rods) were also obtained. All of them are hexagonal and single crystalline in nature and grow along the [ 0001] crystallographic direction. The possible growth mechanisms for these nano- and microcrystals were proposed. It was revealed that both the inherent highly anisotropic structure of ZnO and the precursor concentration play crucial roles in determining final morphologies of the products. In addition, vibrational properties of ZnO crystals with different morphologies were investigated by Raman spectroscopy.

FET ACTIVE SLOTLINE NOTCH ANTENNAS FOR QUASI-OPTICAL POWER COMBINING

A new active antenna structure with applications in quasi-optical power combining is described. The active antenna combines a slotline FET oscillator with a notch antenna. The new structure was successfully used to create both E-plane and H-plane linear arrays as well as a 2-D array. Preliminary results of radiation patterns and the power combining efficiencies of the arrays are discussed.

Cu导线表面起伏程度对早期失效的影响

使用两种化学机械抛光剂得到的单层大马士革Cu导线表面起伏程度不同．扫描电镜观察到明显的缺陷出现在大起伏的Cu导线表面．这种表面缺陷导致早期失效比率剧增至几乎100％、电迁移寿命猛降至早期失效的量级、失效时间分布从多模变为单模，其相应的失效机制激活能为0．744-0．02eV，这说明失效主要是由Cu原子沿导线表面扩散引起的．最弱链接近似被用来分析单根Cu导线