计算空气动力学

  《计算空气动力学》总结了多年来作者在计算空气动力学方面的主要研究工作．介绍了采用差分方法求解气体动力学方程，数值模拟航天飞行器的跨声速、超声速和高超声速绕流的研究工作．
    书中既给出了在实际工作中作者提出的计算方法，也给出了采用各种计算方法解决实际问题的实例．内容重点是解决实际问题，也简述了各种计算方法的理论基础，而且尽可能地反映了当前计算空气动力学的最新成果．
    《计算空气动力学》可供大专院校流体力学专业的本科生、研究生、教师和从事这方面研究工作的科学工作者参考．

Conical emission of Ti : sapphire femtosecond laser pulses propagating in water

Conical emission is investigated for Ti:sapphire femtosecond laser pulses propagating in water. The colored rings can be observed in the forward direction due to the constructive and destructive interference of transverse wavevector, which are induced by the spatio-temporal gradient of the free-electron density. With increasing input laser energy, due to filamentation and pulse splitting induced by the plasma created by multiphoton excitation of electrons from the valence band to the conduction band, the on-axis spectrum of the conical emission is widely broadened and strongly modulated with respect to input laser spectrum, and finally remains fairly constant at higher laser energy due to intensity clamping in the filaments.

卫星激光通信Ⅱ地面检测和验证技术

星间激光通信终端的主要技术指标和运行性能必须事先在地面实验室条件下进行模拟检验, 因此在研制卫星激光通信终端的同时必须发展相应的系统性检测和验证平台, 主要包括激光通信性能检验、光跟瞄性能检验和光束质量检验。本文综述了卫星激光通信终端检验技术的国外进展, 介绍了我们全物理模拟的地面检测验证思路和方法。

相位延迟器复合旋光器技术及其应用

提出了一种将相位延迟器复合为旋光器的技术，利用米勒矩阵对其原理与应用进行了分析。相位延迟器复合为旋光器时，将相位延迟器置于两块1／4波片之间，使两块1／4波片的快轴相互垂直且与相位延迟器的快轴分别成±45°角。利用相位延迟器复合为旋光器技术，可以将相位调制器转换为偏振方向调制器。实验验证了相位延迟器复合为旋光器和相位调制器转换为偏振方向调制器的可行性。

Calculations of bond dissociation energies and dipole moments in energetic materials using density-functional methods

We compare the effectiveness of six exchange/correlation functional combinations (Becke/Lee, Yang and Parr; Becke-3/Lee, Yang and Parr; Becke/Perdew-Wang 91; Becke-3/Perdew-Wang 91; Becke/Perdew 86; Becke-3/Perdew 86) for computing C-N, O-O and N-NO2 dissociation energies and dipole moments of five compounds. The studied compounds are hexabydro-1,3,5-trinitro-1,3,5-triazine (RDX), dimethylnitramine, cyanogen, nitromethane and ozone. The Becke-3/Perdew 86 in conjunction with 6-31G

Beam combination of a radial laser array: Flat-topped beam

An analytical expression of a radial laser array for flat-topped beam is derived based on the generalized Collins formula. The intensity distribution of the resulting beam focused by a lens at the focus plane, for phase-locked and nonphase-locked cases, is studied numerically. The effect of the Fresnel number and normalized radius on intensity distribution for phase-locked and nonphase-locked cases is also presented. It is found that intensity distribution for nonphase-locked case is much less sensible to the Fresnel number and normalized radius than that of phase-locked case. (C) 2008 Elsevier Ltd. All rights reserved.

Enhanced luminescence from transparent Ni2+-doped MgO-Al2O3-SiO2 glass ceramics by Ga2O3 addition

Transparent Ni2+-doped MgO-Al2O3-SiO2 glass ceramics without and with Ga2O3 were synthetized. The precipitation of spinel nanocrystals, which was identified as solid solutions in the glass ceramics, could be favored by Ga2O3 addition and their sizes were about 7.6 nm in diameter. The luminescent intensity of the Ni2+-doped glass ceramics was largely enhanced by Ga2O3 addition which could mainly be caused by increasing of Ni2+ in the octahedral sites and the reduction of the mean frequency of phonon density of states in the spinel nanocrystals of solid solutions. The full width at half maximum (FWHM) of emissions for the glass ceramics with different Ga2O3 content was all more than 200 nm. The emission lifetime increased with the Ga2O3 content and the longest lifetime is about 250 mu s. The Ni2+-doped transparent glass ceramics with Ga2O3 addition have potential application as broadband optical amplifier and laser materials. (C) 2007 Elsevier Ltd. All rights reserved.

Effect of La3+ on microwave dielectric properties of (Pb0.45Ca0.55) (Fe0.5Nb0.5)O-3 ceramics

In this work, microwave dielectric properties of A-site substitution by La3+ in (Pb0.45Ca0.55) (Fe0.5Nb0.5) 03 system were investigated. Microwave dielectric properties of A-site charge unbalance substitution of [(Pb0.45Ca0.55)(1-x) La-x] (Fe0.5Nb0.5)O-3(+) (P45CLFN) were improved because the solid solution of small amount of surplus La3+ with (Pb, Ca)(2+) could eliminate oxygen vacancies, and the formation of secondary phase (pyrochlore) was also caused by surplus La3+. The decreasing of dielectric constant with the increase of La3+ content is due to the formation of pyrochlore. The grain size is changed slightly and Q(f) values (7000 similar to 7300 GHz) are almost unchanged at x = 0.02 similar to 0.10, but the temperature coefficient of resonant frequency (TCF) are increased and changed from negative to positive. TCF is zero at x 0.075 with Q(f) = 7267 GHz and K = 89. TCF of all specimens are within +/- 5 x 10(-6)degrees C-1.

基于光栅传感器的位移测量仪的研制

本文介绍一种基于光栅传感器的位移测量仪。它通过硬件电路对2个光栅传感器输出的信号分别进行20细分,然后对细分后的信号分别进行辨向和计数,再使用一个微处理器对辨向信号和计数信号进行处理,得到X-Y工作台在坐标X和坐标Y方向的位移值,最后根据误差修正算法对位移测量值进行修正,得到该仪器的测量分辨率为1μm且测量精度达±2μm（1σ）。此外,所研制的测量仪具有可靠、易于扩展和调试方便的特点。