弹体在内摩擦介质中的斜侵彻深度计算

考虑介质处于内摩擦状态下,利用球腔膨胀理论及内摩擦介质侵彻近区运动方程求得刚性弹体在侵彻过程中的阻力。在此基础上,考虑自由表面对弹体斜侵彻的影响,将斜侵彻分为3个阶段,推导了斜向侵入弹体表面上任一点的应力公式,进而得出了新的刚性弹体的斜侵彻解析解。该解与别列赞公式在形式上一致,计算结果也符合较好,从而在理论上对别列赞经验公式进行了解释。     

Stress state of a piezoceramic body with a plane crack opened by a rigid inclusion

The paper establishes a relationship between the solutions for cracks located in the isotropy plane of a transversely isotropic piezoceramic medium and opened (without friction) by rigid inclusions and the solutions for cracks in a purely elastic medium. This makes it possible to calculate the stress intensity factor (SIF) for cracks in an electroelastic medium from the SIF for an elastic isotropic material, without the need to solve the electroelastic problem. The use of the approach is exemplified by a penny-shaped crack opened by either a disk-shaped rigid inclusion of constant thickness or a rigid oblate spheroidal inclusion in an electroelastic medium __________ Translated from Prikladnaya Mekhanika, Vol. 44, No. 7, pp. 47–60, July 2008.     

Influence of culture conditions on lipopeptide production by Bacillus subtilis

Bacillus subtilis produces various families of lipopeptides with different homologous compounds. To produce “new molecules” with improved activities and to select strains that produced a reduced number of homologs or isomers, we studied the effects of different media on the nature of the synthesis of fatty acid chains for each lipopeptide family. This study focused on two B. subtilis strains cultivated in flasks. Optimized medium for lipopeptide production and Landymedium modified by replacing glutamic acid with other α-amino acids were used. We found that the intensity of production of homologous compounds depends on the strain and the culture medium. Analysis of these lipopeptides by high-performance liquid chromatography showed that the strain B. subtilis NT02 yielded various homologous compounds when cultivated in Landy medium (L-Glu), but primarily one homologous product in high relative amounts when cultivated in the optimized medium. Mass spectrometric analysis and determination of the amino acid composition of this molecule enabled us to identify it as Bacillomycine L c15.     

A C>1 Completion of the Kerr Space–Time at Spacelike Infinity Including I+ and I−

It is well known that, for asymptotically flat spacetimes, one cannot in general have a smooth differentiable structure at spacelike infinity, i ⁰. Normally, one uses direction dependent structures, whose regularity has to match the regularity of the (rescaled) metric. The standard C ^>1-structure at i ⁰ ensures sufficient regularity in spacelike directions, but examples show very low regularity on I ⁺ and I ^–. The alternative C ¹⁺-structure shows that both null and spacelike directions may be treated on an equal footing, at the expense of some manageable logarithmic singularities at i ⁰. In this paper, we show that the Kerr spacetime may be rescaled and given a structure which is C ^>1 in both null and spacelike directions from i ⁰.     

PtMn/Co多层薄膜结构及磁光克尔效应的研究

用磁控溅射法制备了不同Mn含量的PtMn/Co多层膜,通过大,小角X射线衍射谱对该多层膜进行结构分析,研究了该多层膜的层状结构同磁光克尔效应的关系,通过测定该多层膜在不同杂质浓度下的克尔谱,椭偏率谱及克尔回线,发现克尔角随Mn含量增加的变化规律,并分析了它的产生机制。     

含克尔介质微波激射器的原子辐射率

建立了含克尔介质微波激射器(micromaser with Kerr medium)的基本量子原理,分析计算了处于不同方式(热原子和超冷原子状态)下的二能级原子沿z轴穿过处于相干态的含克尔介质微腔的原子辐射率,并着重讨论了克尔介质与单模辐射场作用的耦合强度χ、失谐量Δ和原子注入速率r对原子辐射概率的影响. 关键词： 含克尔介质微波激射器 热原子和超冷原子 原子辐射率     

贵金属Ag中光学和磁光性质的研究实验

关键词：     

LARGE AND EXTREMELY FAST THIRD-ORDER NON-LINEARITY OF Ag NANOPARTICLES EMBEDDED INTO A CsxO SEMICONDUCTOR MATRIX

The third-order optical nonlinearity of Ag-O-Cs thin films, where Ag nanoparticles are embedded into a Cs_xO semiconductor matrix, was measured by the femtosecond optical Kerr technique. The third-order nonlinear optical susceptibility, χ⁽³⁾, of the thin films was estimated to be 1.1×10^-9 esu at the incident wavelength of 820 nm. The response time, i.e. the full width at half-maximum of the Kerr signal, is as fast as 114 fs only. The intrinsic third-order optical nonlinearity can be attributed to the intraband transition of electrons from the occupied state near the Fermi level to the unoccupied state. It is suggested that such a nonlinearity is further enhanced by the local field effect that is present in the metallic nanoparticles composite thin films.     

Deformation due to time harmonic sources in micropolar thermoelastic medium possessing cubic symmetry with two relaxation times

The response of a micropolar thermoelastic medium possessing cubic symmetry with two relaxation times due to time harmonic sources is investigated. Fourier transform is employed and the transform is inverted by using a numerical inversion technique. The components of displacement, stress, microrotation and temperature distribution in the physical domain are obtained numerically. The results of normal displacement, normal force stress, tangential couple stress and temperature distribution are compared for micropolar cubic crystal and micropolar isotropic solid. The numerical results are illustrated graphically for a particular material. Some special cases are also deduced.     

变温度荷载作用下半无限成层饱和介质的热固结分析

对半无限成层饱和多孔介质作用随时间变化的温度荷载的热固结问题进行解析求解．其中,热-水-力耦合线性弹性控制方程考虑了热渗效应和等温热流效应的影响．先采用Laplace变换求其在变换域上的解,然后用数值方法求逆变换．对半无限体表面作用呈指数衰减热荷载的双层体系进行研究,分析了两层介质热固结系数、弹性模量等的差异性对热固结特征的影响．研究表明:位移场和应力场对温度场的耦合作用可以忽略,而热渗效应对温度和孔压有显著影响．