Theermal Stress and Fracture in Transparent Optical Materials due to Laser Energy-Absorption by a Defect

利用热弹性理论分析了在光学材料中由于缺陷吸收激光能量引起的温度和热应力分布,并且针对一个简单的裂纹模型分析了热应力产生的应力强度因子,给出了一些主要参数对于应力强度因子的影响的规律。

Enhanced cycling performance and high energy density of LiFePO4 based lithium ion batteries

LiFePO4 attracts a lot of attention as cathode materials for the next generation of lithium ion batteries. However, LiFePO4 has a poor rate capability attributed to low electronic conductivity and low density. There is seldom data reported on lithium ion batteries with LiFePO4 as cathode and graphite as anode. According to our experimental results, the capacity fading on cycling is surprisingly negligible at 1664 cycles for the cell type 042040. It delivers a capacity of 1170 mAh for 18650 cell type at 4.5C discharge rate. It is confirmed that lithium ion batteries with LiFePO4 as cathode are suitable for electric vehicle application. (c) 2007 Elsevier B.V. All rights reserved.

On the formation of well-aligned ZnO nanowall networks by catalyst-free thermal evaporation method

Two-dimensional ZnO nanowall networks were grown on ZnO-coated silicon by thermal evaporation at low temperature without catalysts or additives. All of the results from scanning electronic spectroscope, X-ray diffraction and Raman scattering confirmed that the ZnO nanowalls were vertically aligned and c-axis oriented. The room-temperature photoluminescence spectra showed a dominated UV peak at 378 nm, and a much suppressed orange emission centered at similar to 590 nm. This demonstrates fairly good crystal quality and optical properties of the product. A possible three-step, zinc vapor-controlled process was proposed to explain the growth of well-aligned ZnO nanowall networks. The pre-coated ZnO template layer plays a key role during the synthesis process, which guides the growth direction of the synthesized products. (C) 2007 Elsevier B.V. All rights reserved.

闭合水平环状日珥的磁流体静力学平衡

对太阳进行的H_α单色光观测有时会看到水平环状日珥。本文着重讨论了这种等离子体环的静力学平衡。对于这种轴对称和闭场条件的情形,求得磁场和密度的解析解。本文的结论表明,在不同的重力场和线性无力因子α的影响下,磁面形状和热力学参量的分布会有很大的变化。

高频感应等离子体动力学及其应用

<正> 高频感应等离子体技术是近十多年发展起来的一门新技术,由于它具有无电极污染,弧区大,温度均匀,能提供纯净热源,工质不受限制等特点,在化工、冶金等工业和各个科学技术领域中有着潜在的应用前景.因为过去对能够稳定并控制热等离子体流的某些方法和装置,以及对高频放电理论,等离子体动力学进行了卓有成效的研究,所以促使这个新方向得

在强激光下Ge平行板的动态F-P干涉效应

实验表明,在连续CO_2激光辐照下,Ge平行板透射光强度随时间呈准周期性的变化。基于平行平面板的多光束干涉理论,并考虑激光引起的温升对Ge片折射率和厚度的影响,得到的计算结果与实验相符合。这说明平行平面Ge在高功率连续CO_2激光作用下因折射率和厚度随温度的变化而具有一种动态的法布里-珀罗干涉效应。

广义WKB方法及其对浅水波问题的应用

本文首先指出WKB方法可适用于更广泛的一类方程,并把它应用于线性化浅水波方程。对浅水波焦散区的非线性情形,用广义WKB方法进行了讨论,把文献[4]的结果推广到一般弯曲焦散线的情形。

弱粘性流体中垂直激励表面波的阻尼效应

在竖直振动的圆柱形容器中，将Navier-Stokes方程线性化，利用两时间尺度奇异摄动展开法研究了弱粘性流体的单一自由面驻波运动．整个流场被分为外部势流区和内部边界层区两部分，对两部分区域分别求解，得到包含阻尼项和外驱动影响的线性振幅方程．利用稳定性分析，得到形成稳定表面波的条件，给出了临界曲线．此外，还获得了阻尼系数的解析表达式．最后，将线性阻尼加到理想流体条件下所得到的色散关系中对其进行修正，理论结果证明修正后的驱动频率更加接近实验的结果．通过计算发现，当驱动的频率较低时，流体的粘性对表面波模式选择有重要影响，而表面张力的影响不明显；但当驱动频率较高时，流体的表面张力起主要作用，而流体的粘性影响甚小．

微孔泡沫塑料力学行为的研究综述

对微孔泡沫塑料力学行为的研究文献进行了综述，简单介绍了微孔泡沫塑料的制备和表征方法，重点介绍了微孔泡沫塑料力学性能的研究工作，其中也包括作者近期在该领域的一些工作。这些工作主要讨论了微孔泡沫塑料的压缩、拉伸、冲击、疲劳和黏弹性效应。最后，给出了对该领域工作的一些讨论和展望。

Neutron source from thin foil confined by two laser pulses

Neutron production from a thin deuterium-tritium (D-T) foil irradiated by two intense femtosecond laser pulses from opposite sides with zero phase difference is studied analytically and numerically. For the interaction of a laser pulse of amplitude a = 7, focal area 100 mu m(2) and areal density 4.4 x 10(18) cm(-2) with a D-T plasma foil, about 1.17 x 10(21) neutron s(-1) can be obtained, much more than from other methods. The profiles of the ion and electron densities are also calculated.

Efficient two-step digit-set-restricted modified signed-digit algorithm based on optoelectronic shared content-addressable memory

A two-step digit-set-restricted modified signed-digit (MSD) adder based on symbolic substitution is presented. In the proposed addition algorithm, carry propagation is avoided by using reference digits to restrict the intermediate MSD carry and sum digits into {(1) over bar ,0} and {0, 1}, respectively. The algorithm requires only 12 minterms to generate the final results, and no complementarity operations for nonzero outputs are involved, which simplifies the system complexity significantly. An optoelectronic shared content-addressable memory based on an incoherent correlator is used for experimental demonstration. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

一种硅微机械谐振器的单光源激振测振方法

提出一种用于硅微机械谐振传感器研究的单光源激振测振新方法，即微谐振器的激励及其谐振信号的测量使用同一光源。该方法采用全光纤斐索干涉仪结构，将干涉信号与光源强度变化信号进行运算后，通过选频技术解调出谐振器的振动信息，同时采用贝塞耳函数比值法扩大了振动幅度的测量范围，省去了一些难以获得准确数值的工作参数的计算。采用该方法实现了微悬臂梁结构形式的谐振器件的单光源激振与测振，获得了器件的谐振频率约为8．81kHz以及谐振状态下的振动幅度约为135nm。实验结果与采用其他双光源激振测振方法基本一致，新方法的可行性得

Analysis on fluorescence intensity reverse photonic phenomenon between red and green fluorescence of oxyfluoride nanophase vitroceramics

An interesting fluorescence intensity reverse photonic phenomenon between red and green fluorescence is investigated. The dynamic range. of intensity reverse between red and green fluorescence of Er( 0.5) Yb( 3): FOV oxyfluoride nanophase vitroceramics, when excited by 378.5nm and 522.5nm light respectively, is about 4.32 x 10(2). It is calculated that the phonon- assistant energy transfer rate of the electric multi- dipole interaction of {(4)G(11/2)( Er3+) -> F-4(9/2)( Er3+), F-2(7/2)( Yb3+). F-2(5/2)( Yb3+)} energy transfer of Er( 0.5) Yb( 3): FOV is around 1.380 x 10(8) s(-1), which is much larger than the relative multiphonon nonradiative relaxation rates 3.20 x 10(5) s(-1). That energy transfer rate for general material with same rare earth ion's concentration is about 1.194 x 10(5) s(-1). These are the reason to emerge the unusual intensity reverse phenomenon in Er( 0.5) Yb( 3): FOV. (C) 2007 Optical Society of America.