Mechanical Properties of Sialic Foamed Ceramic and Applications in Defense Structure

Mechanical properties of a closed-cellular sialic foamed ceramic are investigated by compressive tests. The sialic foamed ceramic under uniaxial stress compression shows brittleness and the flow stress increases with the strain rate. The engineering stress-engineering strain curve under uniaxial strain compression could be divided into three stages： linear elasticity, collapsed plateau and densification. The unloading elastic modulus, Poisson ratio and energy absorption ability are discussed. Shelly cellular material made by sialic foamed ceramic is applied into the stress distribution layer in the defense structure. Field explosion experiments are performed for the sand based stress distribution layer and shelly cellular material based layer. Compared with sand, the shelly cellular material reduces the peak stress of the blast wave.     

一种推广伊辛自旋模型的实空间重正化群理论

本文提出了一种推广的伊辛自旋模型。它包括了伊辛自旋模型、Schofield和Bowers提出的混合自旋模型以及一种特殊的格点稀释伊辛自旋模型作为特例。运用实空间重正化群得到了这个推广模型的相变流图和三个非平庸不动点(一个伊辛不动点,一个三相不动点和一个一级相变不动点)。结果表明:混合自旋模型和伊辛模型属于同一普适类。证实了Schofield和Bowers通过直接对混合自旋模型临界指数的计算所做的结论。 关键词：     

上海市黄瓜上市高峰量预报因子的选择和模型的建立

本文通过对上海市黄瓜上市高峰期产量预报因子的选择和模型的建立,摸索出上海市蔬菜上市的规律,对保证城市蔬菜均衡供应具有一定的意义。众所周知,黄瓜产量不仅与品种、栽培措施有关,而且与气象因素有着相当密切的关系.黄瓜生长期中,各种气象因子对其上市高峰量的影响是不同的。以往都是凭经验来确定某气象因子的时段.(所谓时段,是指某一段相隔一定天数的时间).这种方法所得到的结果并非最佳因子;而用这些因子组建的回归方程就带有极大的主观性,影响预测的结果.因此,为避免不     

Time-Resolved Femtosecond Degenerate Four-Wave Mixing in LiNbO3：Fe,Mg Crystal

Forward degenerate four-wave mixing （DFWM） processes are investigated with a femtosecond pulsed laser in lithium niobate crystal doubly-doped with magnesium and iron （LiNbO3：Fe, Mg）. The pulse energy dependence reveals a pure third-order nonlinear response, and the third-order nonlinear susceptibility x^（3） in the material is evaluated to be 4.96 × 10^-13 esu. The time-resolved DFWM process shows a response time of x^（3） shorter than 100fs, which is due to the nonresonant electronic nonlinearities. Our results indicate that LiNbO3 crystals have potentials for ultrafast real-time optical processing systems, which require a large and fast x^（3） optical nonlinearity.     

扰动模糊集的粗糙度

首先,将扰动模糊集和粗糙集理论相结合,提出了粗糙扰动模糊集的概念并研究了其基本性质.接着,通过引进扰动模糊集水平上、下边界区域的概念,克服了粗糙集理论中普遍存在的两个集合的上近似的交不等于两个集合的交的上近似(两个集合的下近似的并不等于两个集合的并的下近似)的缺陷.最后,定义了依参数的扰动模糊集的粗糙度的定义,讨论了其基本性质.     

Spatial soliton by cascading χ(2) effect and its self-induced wave-guide in quasi-phase-matched media

The formation of the spatial solitons in the quadratic nonlinearity χ(2) media by cascading second harmonicgeneration (SHG) in quasi-phase-matched (QPM) sample is studied on the basis of nonlinear Schrodingerequation (NLSE). When the solitary wave propagates in the QPM media, it formed optical wave-guidesthrough cascading χ(2) effect called self-induced soliton wave-guide. Transverse refractive index distribu-tion of the self-induced soliton wave-guide of fundamental and SHG wave is obtained by cascading process.Analysis of guided-mode of such self-induced soliton wave-guide is first proposed to our knowledge. Be-cause the power needed for forming the spatial solitons in cascading process is much lower than that inKerr media, this kind of self-induced soliton wave-guide shows potential applications in all-optical signalprocess.     

伊辛模型的四分支临界面及其临界行为

本文通过等标度同普适类变换理论,使严格的重正化群递推方程得以直接应用。对伊辛模型的计算产生了四个不动点、四支临界面。对应于铁磁及反铁磁相变,其结果与已知的严格解及最好近似解一致。对于超反铁磁相变,本文提出临界曲面方程为—ch(h)=sh(2K_x)sh(2K_y)。 关键词：     

高效红外变可见上转换磷光体——CdF_2:YbF_3,ErF_3

掺YbF_3和ErF_3的CdF_2单晶能够把GaAS:Si二极管发出的红外辐射转换为红色或翠绿色可见光。Er~(3 )浓度为1克分子％左右时,发光亮度最大,而且红色(6450～     

THE TWO-BOSON SCATTERING PHASE SHIFTS IN THE GENERAL φ6 THEORY WITH THE GAUSSIAN WAVE-FUNCTIONAL APPROACH

The two-particle scattering phase shifts with a λφ⁴ +ξφ⁶ interaction are com-puted in (1 + 1) and (2 + 1) dimensions using the Gaussian wave-functional approach.Through numerical analysis, we give the phase-shift curves with respect to the scat-tering energy for most cases of this theory. In (1 + 1) and (2 + 1 ) dimensions, for the symmetry vacuum the phase shifts are positive or negative depending on the signs of the renormalized parameter, while for the asymmetric vacuum the phase shifts are negative.