Semi-analytical study of free vibration characteristics of shear deformable filament wound anisotropic shells of revolution

Free vibration characteristics of filament wound anisotropic shells of revolution are investigated by using multisegment numerical integration technique in combination with a modified frequency trial method. The applicability of multisegment numerical integration technique is extended to the solution of free vibration problem of anisotropic composite shells of revolution through the use of finite exponential Fourier transform of the fundamental shell equations. The governing shell equations comprise the full anisotropic form of the constitutive relations, including first-order transverse shear deformation, and all components of translatory and rotary inertia. The variation of the stiffness coefficients along the axis of the shell is also incorporated into the solution method. Filaments are assumed to be placed along the geodesic fiber path on the shell of revolution resulting in the variation of the stiffness coefficients along the axis of the composite shell of revolution with general meridional curvature. Sample solutions have been performed on the effect of the variation of the stiffness coefficients on the free vibration behavior of filament wound truncated conical and spherical shells of revolution.     

扫描隧道显微镜——20世纪重大科技成果之一

扫描隧道显微镜是利用探针尖端与物质表面原子间的不同种类的局域相互作用，来测量表面原子结构和电子结构的显微新技术，它的出现被科学界誉为是表面科学和表面现象分析技术的一次革命。     

The application of a modified method of discrete sources for solving the problem of wave scattering by group of bodies

A new universal and effective algorithm for solving the problems of wave diffraction on complicated structures composed of bodies of revolution is presented. The method is applied to diffraction on a group made of two impedance bodies of revolution. The method permits to get the pattern and the field with high accuracy.     

旋转二次曲面线圈轴线上的磁场

从普通物理电磁学角度出发,分别讨论了球状、椭球状、旋转抛物面状及双曲面状线圈旋转对称轴线上的磁场问题,最后得到了一个关于旋转二次曲面对称轴线上磁场的普适表达式.     

Embedding Misner and Brill–Lindquist Initial Data for Black-Hole Collisions

In this article we consider the isometrical immersions into Euclidean three-space of two-dimensional slices of the Misner and the Brill–Lindquist initial data for black-hole collisions. We show negativity of curvature and deduce other geometric properties of the slices. Under the assumption that ends behave strongly like paraboloid of revolution, we prove that Misner and the Brill–Lindquist slices cannot be isometrically immersed into R ³. This condition on an end is natural in general relativity because it holds for each end of a slice of the Schwartzschild metric where it is embedded as a paraboloid of revolution.     

Nonlinear Axisymmetric Deformation Model for Structures of Revolution

An axisymmetric formulation for modeling three-dimensional deformation of structures of revolution is presented. The axisymmetric deformation model is described using the cylindrical coordinate system. Large displacement effects and material nonlinearities and anisotropy are accommodated by the formulation. Mathematical derivation of the formulation is given, and an example is presented to demonstrate the capabilities and efficiency of the technique compared to the full three-dimensional model.     

Dynamics of damped rotating solids of revolution through an Eulerian modal approach

This article presents a technique for modelling the dynamic response of rotating flexible solids with internal modal damping. The method is applicable to solids with geometry of revolution that rotate around their main axis at constant spinning velocity. The model makes use of an Eulerian modal coordinate system which adopts the vibration modes in a non-rotating frame as basis functions. Due to the coordinate system, the technique is particularly suitable for studying the dynamic interaction between rotating solids and non-rotating structures and permits to obtain Frequency Response Functions. The current investigation presents the development of the proposed technique from a previous Lagrangian model, and consequently the mathematical relationships between the two coordinate sets are found. The approach has been adopted to study the dynamics of a simply supported cylinder including damping in order to obtain the receptance function and the modal properties of the rotating solid.     

Influence of small angles of attack and sweep on the rolling moment at a hypersonic flow around the bodies of revolution

The influence of small attack and sweep angles on the rolling moment variation at a supersonic flow around the bodies close to the bodies of revolution is considered. Based on the method of the differential hypothesis of locality the integral expressions are obtained for the derivatives of the rolling moment coefficient with respect to the attack and sweep angles. The norm of these derivatives is defined and the estimates for the norm are obtained.     

Nonlinear internal waves in a one-dimensional channel

Summary By applying a perturbation technique to the Euler equation for a two-layer fluid we show that the evolution of the interface is described by a Korteweg-de Vries equation. This model is applied to describe the tide generation of internal waves in the Straits of Gibraltar.

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Riassunto Applicando tecniche perturbative all'equazione di Eulero per un fluido a due strati si può mostrare che l'evoluzione dell'interfaccia tra i due fluidi è descritta dall'equazione di Korteweg-de Vries. Questo modello è applicato per analizzare la generazione di onde interne di tipo solitonico nello Stretto di Gibilterra, considerando come forzante l'onda di marea.

     

Recent studies of physisorbed films

Recent developments in the field of physisorption have brought about qualitative changes in this relatively hoary branch of surface science. Rapid advances have been under way for the last 10 years or so, comparable to the time scale of the revolution in the rest of surface science, and as in the case of the overall field, they involve improvements in experimental technique, materials technology, and theoretical understanding. The progress in physisorption carries wide-ranging implications for substrate characterization, chemisorption, and catalysis, and beyond surface science for certain aspects of general statistical mechanics, the physics of condensed matter, and superfluidity. This review is a survey of some of these developments. The focus here will be on results; details of experimental and theoretical technique are omitted for brevity's sake.     

Scanning probe microscopy of graphene

A material with novel fundamental properties that challenge our current understanding is always exciting for research. If the novel properties extend to the realm of device engineering and promise a revolution in applications, then the scope of its research knows no bounds. The story of graphene, the two dimensional form of carbon, has followed this path. Graphene has been the subject of numerous experimental and theoretical investigations since 2004 when an elegant and a simple technique to make monolayer graphene set the stage for extensive research. Many other techniques to make graphene were developed in parallel to this technique. As graphene is replete with unique structural and electronic properties scanning probe microscopy has proved to be an exciting and a rewarding venture. In this review we discuss the findings of scanning probe microscopy and how it has served as an indispensable tool to understand the properties of graphene and further graphene research.     

Analysis of diffraction of a plane wave on a grating consisting of impedance bodies of revolution

The problem of wave scattering by a grating consisting of coaxial impedance bodies of revolution is solved. The efficient numerical algorithm based on the modified null field method is offered. The method is applied both to scalar and vector formulations of the problem. The numerical results are obtained for various geometries of the grating elements.     

脉冲平面波斜入射旋转对称体电磁散射的FDTD算法

提出一种应用时域有限差分算法求解脉冲平面波斜入射时旋转对称体散射问题的方法.对斜入射脉冲平面波在圆柱坐标系下进行分解、应用总场/散射场连接边界、PML吸收边界条件.通过与矩量法分析结果的比较,验证了该方法的有效性.     

钇原子亚稳态寿命的测量

利用基态原子无穷长的寿命以及亚稳态原子在飞行过程中的衰减,比较由激光感应荧光法测量到的钇原子束基态和亚稳态的速度分布曲线,经过拟合处理计算,得到钇原子亚稳态a~2D_(5/2)的寿命为(0.8±0.2)ms.     

纸质胶带胶层厚度在线测量

在纸质胶带生产过程中 ,胶层厚度及均匀性是很重要的技术指标 ,因此需要对胶层厚度进行在线测量。介绍了一种红外纸质胶带胶层厚度测量仪。它是依据胶质对一定波长的红外光具有特征吸收的原理 ,采用了能量比参考平衡技术 ,使仪器性能稳定、可靠     

储存环HIAF-SRing等时性模式的非线性磁场影响研究

高精度环形谱仪SRing（Spectrometer Ring）是强流重离子加速器装置（HIAF）的重要组成部分,其等时性模式为远离β稳定线的短寿命原子核质量和寿命的精确测量提供国际领先的科研条件。为了扩大短寿命原子核质量测量精度和范围,SRing等时性模式设计了两种光学:γ_t=1.43和1.67。质量分辨是衡量等时性储存环的最重要参数。二极磁铁的高阶场以及磁铁的边缘场能强烈地引起束流光学高阶畸变,对质量分辨产生影响,因此需要高极磁铁对其进行校正。介绍了SRing等时性模式的线性计算,对非线性磁场的影响进行了详细研究。应用六极磁铁和八极磁铁对非线性场和发射度的影响进行了校正后,离子的循环时间标准偏差σ（T）/T达到3.5×10-7,质量分辨△m/m达到1×106。The isochronous mode of the Spectrometer Ring at the High Intensity heavy-ion Accelerator Facility (HIAF) project in China offers the capacity of measuring the mass and half-life of short-lived nuclides. The transition energy settings of the SRing are 1.43 and 1.67, which have been calculated in the same injection scheme. The resolution of mass or revolution time is the most important parameter of the isochronous mode design of a storage ring. The nonlinear magnetic field errors, including high-order magnet field of dipole, fringe field of magnets, have strongly effect to the resolution of revolution time. High-order corrections are required to improve the resolution of revolution time and mass. In this paper, the SRing linear isochronous optical were shown. The influence of nonlinear magnetic field errors on the revolution time resolving power were investigated. With 3 sextupole families and 1 octupole family corrections, the relative variation of revolution time reaches 4.6×10-7 with the momentum spread of ±0.2%. The relation of the relative standard revolution time deviation σ(T)/T and revolution turns was researched. With corrections of high-order isochronous condition and emittance influence by 3 sextupole families and 1 octupole family, one can reach a resolution of up to σ(T)/T=3.5×10-7, which corresponds to the mass resolution of △m/m=1×106.     

利用自差法研究激光二极管泵浦Nd:YVO_4激光器的线宽

用光纤延时自差法测量二极管激光纵向泵浦单频运转的Nd：YVO4激光器的线宽。在1秒时间内，激光线宽为25kHz。还测量了线宽与激光器腔长和输出功率的关系。     

Effect of small total pulse on development of a wake behind the self-propelled bodies

Experimental studies on the wakes behind the self-propelled bodies of revolution have been analysed, and results of stereometric studies on the co-current flows behind autonomous streamlined and bluff bodies of revolution are presented for the times of their development corresponding to the coordinate system of a distant wake of 2400 and 1200 body diameters, correspondingly. Possible modelling of axisymmetric co-currents by the flows generated by a string at its pulse motion along the axis is examined. It is shown that supposed solutions based on the model of interferential development of wakes behind the self-propelled bodies of revolution can approximate both the known results of experimental studies of wakes behind the self-propelled bodies of revolution and the flows generated by corresponding pulse transportation of a string.     

具有密度跃层分层流体中回转体激发内波特性实验

在具有连续密度跃层的分层流体中,对长径比为7:1的回转体在迎水和背水运动下激发体积效应与尾迹效应内波特性开展了系列实验.结果表明,体积效应激发内波属于一种相对于回转体定常的多模态Lee波结构,而尾迹效应激发主控内波为相对于回转体非定常的拟Lee波结构,这是一类由湍流尾迹中大尺度相干结构作为移动源激发的内波结构,在Lee波与拟Lee波之间存在一个与长径比近似为线性关系的临界转捩Froude数Fr_c,当FrFr_c 时拟Lee波为主控内波,而且拟Lee波相关速度Froude数近似为一个常数0.8,其无因次峰-峰幅值随Fr的增大近似线性增大,其中Fr为回转体特征直径Froude数.结果还表明,回转体头部与尾部几何形式并不影响其激发内波临界转捩Froude数Fr_c、 拟Lee波相关速度Froude数及其峰-峰幅值变化特性.     

行星的视运动与圆外旋轮线

用简化模型（行得在同一平面内绕太阳作匀速圆周运动）分析了行星相对于地球的运动（视运动）。给出了视运动的运动方程，证明了行星视运动的轨迹与圆外旋轮线，讨论了行星的顺向运动与逆向运动，给出了关于水星、金星、火星、土星、木星的数值结果。