Nature of the short wavelength excitations in vitreous silica: An X-Ray brillouin scattering study

Spontaneous emission in photonic crystals with anisotropic three-dimensional dispersion relation is studied. If the upper level is below a characteristic frequency omega(1), or above omega(2), or between omega(1) and omega(2), the radiation is a localized field with a frequency in the band gap, or a propagating field with a frquency in the band, or a diffusion field, respectively. An analytical expression for the Lamb shift is obtained. The Lamb shift for the current case is small compared to that in an ordinary vacuum or in one- or two-dimensional photonic crystals due to lower density of states.     

A moiré method of visualizing electromagnetic force lines

We propose a simple moiré method of visualizing electromagnetic force lines. The indicial equation is first derived for the tangent (or normal) curve to the electric field (or magnetic induction) around two parallel-line charges (or currents). The derived equation is then shown to have a one-to-one correspondence with that of the moiré fringe formed by two overlapped radial gratings. Since the tangent (or normal) curve to the electric field (or the magnetic induction) corresponds to the direction of the electric (or magnetic) force on a test charge (or current), the radial grating moirés can be used for the visualization of electric (or magnetic) force lines.     

绕凸包主动流动控制的初步数值研究

基于程序可靠性校验,本文对绕凸包流动进行了数值研究,其中主要对不同吹／吸气速度影响进行了参数化研究,并根据结果对吹／吸气控制分离机理予以了解释,表明:吹吸气对附面层的吹断／吸除作用以及其对主流的气动堵塞作用是正确分析其影响分离机理的关键。     

Focal Shift of Paraxial Gaussian Beams in a Left-Handed Material Slab Lens

Focal shift is inevitable in conventional lens systems due to the Fresnel number and angular aperture. In this Letter, we demonstrate that there is no focal shift when a paraxial Gaussian beam passes through a left-handed material slab lens without absorption or gain. However, the effect is exhibited in the presence of absorption or gain, and becomes larger as the absorption or gain increases. When the absorption is equal to the gain, the phenomenon of the focal shift caused by the gain is more obvious. In addition, the field distribution is not affected by the absorption or gain and always remains Gaussian both in internal and external focus planes.     

量子隐形传态网络的广播与组播

给出了广播与组播的物理原理.当Alice需要发送信息时, 就向与自己相连的交换机发送一连接请求信号,交换机收到连接请求信号后 通过检测目的地址判断是点到点的通信还是组播与广播;若目的地址是A类、 B类或C类地址,则进行点到点的通信操作;若目的地址是D类地址或是有特殊意义的地址(本地网络/指定网络广播), 则启动量子信息的广播与组播操作.广播与组播时的保真度随受话终端数的增加而减小,其极限为2/3.     

Damping properties of layered cylindrical shells,vibrating in axially symmetric modes

The damping of cylindrical shells coated with unconstrained layers of viscoelastic material either on one side of the shell (inside or outside) or on both sides is estimated. The basic equations of motion are derived which describe harmonic forced flexural damped vibrations in axisymmetric modes. For pure sinusoidal modes expressions for the overall loss factors are given. The damping properties of cylindrical shells of finite length, coated on the inside or outside, or on both sides (symmetrically or unsymmetrically) are compared. Classical thin shell theory is used for the analysis. It is shown how two-layered damped shells differ from two-layered damped beams. The extent of damping reduction in shells resulting from the fact that the shell cross-section is closed is discussed.     

激光传输模拟中基于衍射过程FFT算法的参量优化

为实现采用相位屏法正确模拟准直激光束经湍流大气的传输特性,根据湍流特性、抽样定理以及两屏间衍射过程FFT算法本身所决定的相邻两屏网格间距之间的关系,得出相位屏间距和网格间距确定网格数目最优取值的解析表达式,数值模拟高斯光束经自由空间和湍流大气传输的远场分布,网格数目取解析式求得的最优值848时,光束经自由空间传输的模拟结果与ABCD定律求得的解析结果完全一致;网格数目取836或860时,等效于光束通过偶数相位屏时被正透镜或负透镜阵列会聚或发散,削弱或夸大湍流大气对光束的影响,模拟结果出现严重偏差。     

量子纠缠与经典关联在双光子关联成像中的作用

关联成像引起了人们广泛的兴趣,特别是,二阶关联成像是一种纯粹的量子效应还是也可能是一种经典效应还存在争议.本文分析了三种关联成像方案,其中前两种方案中用经典关联和量子纠缠的双光子光源都能成像,而第三种只能用量子纠缠的双光子光源才能成像.对比发现,纠缠双光子同时存在动量和坐标两个自由度上的关联,在三种成像方案中都可用作光源.而经典关联的双光子不具有动量和坐标的双重关联,而仅仅存在其中一种关联(经典关联),关联成像的方式也因此受到限制.     

枸杞子四种原性状的FTIR光谱法鉴别

本文利用傅里叶变换红外（FTIR）光谱法无损快速鉴别了枸杞了的四种原性状。结果表明：不同颜色、不同味道、不同质地及不同形状的枸杞子的红外光谱谱图较为特征,各种枸杞子的红外官能团吸收均遵循一定的变化规律。该方法快速、简便、直观、样品不需要分离提取。     

基于双三角形金属条的二维可衍生超材料性能分析

基于两宽金属条中间引入两交叉细长金属线的双三角形结构, 提出了一种新型二维超材料结构.利用HFSS软件对该结构及其衍生结构进行仿真分析, 结果表明: 该类形结构在电磁波垂直和平行两种入射情况下都能实现双负特性, 通过比较分析归纳出该类形结构的一般规律: 电磁波以垂直和水平两种方式入射时, 中间引入的金属线个数每增加一根, 结构的谐振频率向高频方向分别移动0.5 GHz和4 GHz左右.对多维左手材料的发展提供了参考.     

激光致盲干扰效果评估方法研究

研究了激光致盲干扰设备对光电制导系统、光电成像系统和激光测距机干扰效果的评估方法,分别提出了相应的干扰效果评估准则。对于光电制导系统,可以根据实施激光致盲干扰后制导武器的脱靶量是否超出正常制导精度的三倍或杀伤半径判定干扰是否有效,并根据干扰成功率的大小划分干扰等级。对观瞄用光电成像系统的干扰效果,可以按照致盲激光对成像功能的损伤、破坏程度划分为四个等级;对跟踪用光电成像系统的干扰效果可以根据实施干扰后成像系统能否输出有效跟踪脱靶量,以及脱靶量是否超出正常跟踪精度的三倍判定干扰是否有效。对激光测距机的干扰效果可以依据致盲激光对测距机测距精度、测距能力的影响程度划分为四个等级。     

高能飞秒激光系统中空间滤波器的研究和设计

 由于透镜传输时间延迟效应（PTD），飞秒激光脉冲经过空间滤波器产生脉冲波前变形。讨论了用双胶合透镜或双分离透镜代替空间滤波器中的单透镜，以消除或减小PTD效应，设计了适用于飞秒激光装置的空间滤波器。     

Determination of the 2D amplitude-phase structure of an optical field and the transfer function in the case of a convolution-like effect of a medium

A solution of the phase problem in optics as applied to the simultaneous detection and analysis of the phase-amplitude structure of image-forming or image-transmitting 2D optical fields and the phase-amplitude structure of probed media or objects, transfer or instrumental functions of signal-transmitting media, or field-or image-forming systems is considered. The effect of media or objects is described by the operation of convolution. The essence of the method applied is the introduction of two additional modulators, which in some way perform the function of visualizing the phase information. Optical schemes of two types are considered. In both cases, the first additional modulation precedes the action of a medium or an object. The second additional modulation takes place either in the plane immediately behind the probed medium (first type of scheme) or in the plane of spatial frequencies formed by the optical system (second type of scheme). In the first variant, the plane of detection is that of the spatial frequencies; in the second variant, it is the plane of the image formation. The resulting intensity distributions yield a solution to the problem.     

Comparison of Pareto and tapered Pareto distributions for environmental phenomena

The Pareto distribution is often used to describe environmental phenomena such as the sizes of earthquakes or wildfires, or the interevent times or distances between such environmental disturbances. Because it is heavy-tailed, the Pareto distribution, or power-law distribution as it is occasionally called, suggests that a higher frequency of extremely large values occur compared to other, more familiar distributions such as the normal, exponential, or uniform. However, an alternative distribution called the tapered Pareto has been shown in some cases to fit as well or better to data than the Pareto distribution, and the tapered Pareto distribution is not heavy-tailed, suggesting a far lower frequency of extreme events. Even with rather large datasets, it is often quite difficult to distinguish which of these distributions is preferable, as they only differ markedly in the extreme upper tail where few, if any, observations are recorded. This article reviews the evidence and arguments related to these two competing distributions, especially in the context of earthquakes and wildfires.     

Effect of longitudinal or inplane deformation and inertia on the large amplitude flexural vibrations of slender beams and thin plates

Large amplitude flexural vibrations of slender beams, and thin circular and rectangular plates have been studied when a compatible longitudinal or inplane mode is coupled with the fundamental flexural mode. It is shown that the effect of longitudinal or inplane deformation and inertia is to reduce the non-linearity in the flexural frequency-amplitude relationship. Further, for slender beams and thin plates, the effect of longitudinal or inplane inertia is negligible.     

Electrical conducting properties of proton-conducting terbium-doped strontium cerate membrane

The electrical conduction behavior of SrCe_0.95Tb_0.05O_3−δ (SCTb) was investigated in different gases at high temperatures. In air, oxygen or nitrogen SCTb shows small electronic-hole conduction below 800°C and oxygen ionic conduction over 800°C with activation energy about 30 kJ/mol and 164–181 kJ/mol respectively. SCTb becomes a protonic conductor in hydrogen or methane in 500–900°C, with the proton conductivity in the range of 10⁻³–10⁻² S/cm, two to three orders of magnitude higher than electronic or oxygen ionic conductivity of SCTb in air or oxygen. The activation energy for protonic conduction in SCTb is 49 kJ/mol in methane and 54 kJ/mol in hydrogen. The electrical conductivity of SCTb in water vapor-saturated nitrogen, air or oxygen is higher than in corresponding gas without water vapor. Presence of water vapor does not affect the electrical conduction of SCTb in hydrogen or methane. Gas permeation measurements show that SCTb membrane is impermeable to hydrogen when the membrane is exposed to hydrogen or methane upstream and nitrogen or oxygen downstream. These results confirm that SCTb is a pure protonic conductor with very low electronic and oxygen ionic conductivity. SCTb will find applications as a high temperature electrolyte in fuel cells or hydrogen sensors.     

Spin wave spectrum of a magnonic crystal with an internally structured defect

We report a theoretical investigation of the spin wave spectrum of a magnonic crystal with a defect. The latter is considered as either a single or double layer with parameters (the values of the uniaxial anisotropy and/or layer thickness) different from those of the constituent layers of the magnonic crystal. It is shown that, depending upon the parameters of the defect, the spectrum may contain either one or several additional discrete (localized) modes within the magnonic band gaps, or even a mini-band of those.     

Solution Transformations and Their Effects on the Systems with Open Boundary Conditions

The solution transformations and properties of the R-matrices for two-component systems under these transformations are analyzed in details.Not all transformed R-matrices can be put into the Skalyanin‘s formalism.For those R-matrices with all required properties,the effects of solution transformations to the six-and eight-vertex systems with open boundary conditions are discussed.these effects can be one of the following types:the Hamiltonian is invariant or transposition-invariant or made in a similarity transformation,or its coupling coefficients are multiplied by an overall factor,or the spin of the system is rotated around the z axis or/and reflected with respect to some plane.In these cases,the transformed systems remain to be integrable.     

人体硬组织替代材料的研究进展

硬组织（骨、牙等）损伤或病变是临床上常见的事件，如果损伤或病变严重到无法进行药物治疗的程度，需要采取硬组织替代材料进行修复或置换。文章对人体硬组织替代材料的类型、力学性能及生物学性能等方面进行了综述，并指出了硬组织替代材料的发展方向。     

Generalization of the Kelvin equation for arbitrarily curved surfaces

Capillary condensation, which takes place in confined geometries, is the first-order vapor-to-liquid phase transition and is explained by the Kelvin equation, but the equation's applicability for arbitrarily curved surface has been long debated and is severe problem. Recently, we have proposed generic dynamic equations for moving surfaces. Application of the equations to the vapor/fluid interfaces in chemical equilibrium conditions nearly trivially solves the generalization problem for the Kelvin equation. The equations are universally true for any surfaces: atomic, molecular, micro or macro scale, real or virtual, Riemannian or pseudo-Riemannian, active or passive.