A counterexample to questions on the integrality property of virtual signature

Wall (1961), defined the virtual Euler Characteristic χ(Γ) of an arbitrary group Γ of finite homological type as , where Γ′ is any torsion free subgroup of finite index in Γ. Analogous to virtual Euler Characteristic, we define the Virtual signature of an oriented virtual Poincare Duality group, a rational number. We show that two of Ken Brown's results on questions regarding the integrality property of virtual Euler Characteristics when formulated in the Virtual signature case is false.     

Experimental investigations on the external cavity time signature in chaotic output of an incoherent optical feedback external cavity semiconductor laser

Chaotic dynamics of a semiconductor laser subject to incoherent optical feedback (IOF) are experimentally investigated, and the external cavity time are retrieved and measured from intensity time series of the laser output by using self-correlation function and the mutual information. Through moderating feedback strength and injection current of the laser, the external cavity time signature of the laser chaotic output is effectively attenuated, and then the security of such chaos encryption system can be assured to a certain degree.     

基于ID的一次性盲公钥的密码学分析

为保护用户的隐私又可以避免用户犯罪,ZHANG等提出了基于ID的一次性盲公钥协议.本文给出了两种伪造攻击方案,任何注册用户和非注册用户都可以伪造私钥和证书并可以对任何消息产生有效的签名,而可信中心无法在法院授权的情况下揭示签名者的真实身份,从而指出他们的方案无法阻止用户犯罪,而且是全局可伪造的.     

Nonuniversal transport behavior in heterogeneous high‐density polyethylene/graphite nanosheet composites

The direct‐current resistivity of high‐density polyethylene/graphite nanosheet composites above the percolation threshold has been measured and fitted to a power law, which gives a conductivity critical exponent (0.10 ± 0.01) and a percolation threshold (2.97 ± 0.03). These fitted parameters are in disagreement with universal theoretical predictions, and plausible explanations of the observed discrepancies are given. The sample‐to‐sample fluctuations in the relative resistivity seem to obey a power law. This fluctuation behavior, if interpreted in terms of correlation‐length fluctuations, yields a correlation‐length critical exponent, 0.52 ± 0.06, that is consistent with the mean‐field value of 1/2. Interpretations of these experimental results imply that nonuniversal transport behavior in disordered composites is caused by composites being in a nonuniversal scaling regime. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1846–1852, 2006     

双通道视频信息处理数据融合技术

“飞鱼”类掠海反舰导弹已对水面大型舰艇的生存构成重大威胁，而近程反导舰炮武器系统是反“飞鱼”类掠海反舰导弹的最后防线。因此，实现成功拦截掠海反舰导弹，精确稳定地自动跟踪目标，是近程反导舰炮武器系统的关键技术之一。阐述了适合自动跟踪高速飞行掠海导弹的双通道视频处理器的构成。对工作原理、去噪预处理、图像分割、特征抽取、识别和位置检测等技术作了简要说明，并对核心部分——双通道视频信息的资源利用和数据融合处理作了较详细的论述。双通道并行处理数据融合技术在国内首次应用于××近程反导舰炮武器系统光电跟踪仪中，在海上定型试验中取得了很好的跟踪效果。     

Study on the optical properties of rapidly grown KDP crystals

KDP crystals were grown at growth rates from 5.0 to 19.0 mm/d. Transmittance, laser damage threshold and light scatter were detected. It has been shown that laser damage thresholds of KDP crystals decrease with the increase of the absorption coefficients. Large-scale impurity is an important factor that causes light absorption in UV range and reduces the damage threshold.     

Best simultaneous approximations: Norms, signatures, and asymptotic directions

Results concerning the distribution of directions of best simultaneous approximations in various norms are obtained. Translated fromMatematicheskie Zametki, Vol. 67, No. 5, pp. 730–737, May, 2000.     

Nonlinear optical phenomena at the interface with photorefractive crystals

Characteristics of nonlinear optical phenomena in reflection of light at the interface with photorfractive crystals having photovoltaic nonlinearity are studied. it is shown that under total reflection, hysteretic behavior of the reflection coefficient is possible as a function of the incident radiation intensity or the angle of incidence. It is important that previously required threshold intensities are rather low (≤1 W/cm²) in comparison with the known case of reflection from media with Kerr nonlinearity. The present results are of doubtless interest in view of the development of possible devices for controlling laser radiation. Interdepartmental Institute of Advanced Training of Personnel in New Trends in Engineering and Technology at the State Polytechnical Academy of Belarus, 77, Partizanskii Ave., Minsk-107, 220600 Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 915–920, November–December, 1998.     

ZrO2/ SiO2多层膜的化学法制备研究

 分别以ZrOCl₂·8H₂O 和正硅酸乙酯为原料,采用溶胶-凝胶工艺制备了性能稳定的ZrO₂和SiO₂溶胶。用旋转镀膜法分别在K9玻璃和单晶硅片上制备了ZrO₂/ SiO₂多层膜。采用溶剂替换和紫外光处理等手段,有效地解决了ZrO₂/SiO₂多层膜中膜层开裂和膜间渗透等问题。应用扫描电子显微镜观测了薄膜的表面和剖面微观形貌,并用椭偏仪测得薄膜的厚度和折射率,研究了薄膜厚度、折射率与热处理温度、紫外光处理时间的关系,对所获得薄膜的紫外-可见、红外光谱进行了分析。用输出波长1064nm ,脉宽15ns 的电光调Q光系统产生的强激光进行了单层膜的辐照实验,结果发现溶剂替换后激光损伤阈值有所提高。     

强紫外激光在空气中长程传输受激旋转拉曼散射效应

 采用瞬态受激旋转拉曼散射（SRRS）模型，详细考虑了激光脉冲波形、介质的非线性极化、泵浦光的衰减、斯托克斯光的非线性放大以及拉曼线宽等诸多因素，对强紫外激光束在空气中长程传输过程产生的SRRS效应进行了研究。讨论了产生SRRS效应的阈值条件，详细分析了SRRS效应对激光光束质量的影响。