Explicit models for elastic and piezoelastic surface waves

^** Email: julius.kaplunov{at}brunel.ac.uk Explicit models for the Rayleigh and Bleustein–Gulyaevsurface waves are extracted from the original 2D formulationswithin the general framework of linear elasticity and electroelasticity.The derivations are based on perturbing in slow time the self-similarsolutions for homogeneous surface wave. Both the proposed modelsinvolve hyperbolic equations on the surface along with ellipticequations over the interior, emphasizing the dual nature ofa surface wave. Comparisons with exact solutions are presented,including that for the plane Lamb problem.     

Transmission of sound through a pair of rectangular elastic plates

^** Email: f.leppington{at}ukonline.co.uk Two thin elastic plates, which may have different physical parameters,occupy the parallel regions 0 < x < a, 0 < y < b,z = – d and 0 < x < a, 0 < y < b, z = 0, ina Cartesian coordinate system, where the separation distanced is much less than the dimensions a and b. The plates are simplyconnected to a structure that occupies the rest of the region– d < z < 0. The side walls (x = 0 or a, 0 <y < b, – d < z < 0 and y = 0 or b, 0 < x <a, – d < z < 0) are taken to be acoustically soft;the surfaces z = – d and z = 0, outside the rectangularregions occupied by the plates, are taken to be acousticallyhard. Light compressible fluid (air) is in each of the half-spacesoutside the plates and in the rectangular region between them.A sound field is induced by a high-frequency plane wave. Allowanceis made for a small element of damping in the fluid trappedbetween the plates, as well as damping in the plates. Estimatesare derived for the transmitted power, averaged over a frequencyband and with respect to all incidence directions, in the asymptoticlimits of small fluid loading and high frequency. For the casewhere the two plates have identical physical properties, detailedasymptotic estimates are given for the form of the peaks inthe transmitted power, at a discrete set of operating frequencies,both above and below the plates' coincidence frequency.     

环状集输水平管内油-气-水三相流流型试验研究

目前我国东部陆上油田大部分已进入特高含水采油期,绝大多数油井综合含水率已超过85%,部分油井已达到95%。油-气-水三相流型是特高含水混输技术界限确定、水力热力计算方法研究及集输系统科学运行管理的基础。为了研究大庆低渗透油田环状集输水平管道内油-气-水三相流型,研制一套流型试验装置,进行了一系列试验研究,获得了1360组油气水三相流型图及相应的流动参数。对采集到的流型及试验数据进行分析,首次总结出水平环状集输管道中油-气-水三相流的五种流型,分别为分层流、三层扰动流、波浪冲击流、气弹掺混流和完全掺混流。同时给出了每种流型对应的参数范围,并对每种流动形态及典型特征进行了解释。     

Design study of an FEL oscillator with a waveguide

We present a design study of a free electron laser （FEL） oscillator for high power THz source experiments on the basis of the Shanghai femtosecond accelerator device. A circular groove guide is used as a new interaction structure. Plane metal meshes are used as upstream and downstream mirrors of the resonator. The general design parameters are presented. We analyzed the spontaneous emission and stimulated emission in the oscillator using these parameters.     

Direct and inverse measurement of thin films magnetostriction

Two techniques of measurements of thin film magnetostriction are compared: direct, when changes of the substrate curvature caused by the film magnetization are controlled, and inverse (“indirect”), when the modification of the magnetic anisotropy induced by the substrate deformation (usually bending) is measured. We demonstrate how both the elastic strength of the substrate and the effective magneto-mechanical coupling between the substrate deformation and magnetic anisotropy of the film depend on different conditions of bending. Equations to be used for magnetostriction value determination in typical cases are given and critical parameters for the corresponding approximations are identified.     

Magnetic spectra of Fe-based nanocrystalline wires with axial or transverse domains

The circular permeability μ′=μ′−jμ″ of two Fe-based soft magnetic wires with axial and transverse domains, has been determined from the measurements of impedance Z=R+jX as functions of frequency (f=10-10⁵ Hz) and AC current amplitude (I=0.1-100 mA). From the magnetic spectra of μ′−f and μ″−f for a few circular fields (H_φ=0.4, 1.2, 4, 12, 40 A/m), we found that the sample with axial domain structure exhibits a relaxational feature, while for the one with transverse domain resonance-like spectra were observed when the circular field H_φ≥4 A/m. These results have been discussed in terms of domain structure and circular magnetization processes.     

Number of elastic scatterings on free stationary nuclei to slow down a neutron

We report the formulation of the number of elastic scatterings required to slow down a neutron. By establishing its analytical expression, we show that this number displays a discontinuity and an oscillatory transient that progressively dampens when the neutron energy decreases. This result does not apply to neutrons with energies lower than a few eV, as we restrict our study to scatterings on free stationary nuclei.     

Analyzing the prices of the most expensive sheet iron all over the world: Modeling, prediction and regime change

The private car license plates issued in Shanghai are bestowed the title of “the most expensive sheet iron all over the world”, more expensive than gold. A citizen has to bid in a monthly auction to obtain a license plate for his new private car. We perform statistical analysis to investigate the influence of the minimal price P_min of the bidding winners, the quota of private car license plates, the number of bidders, as well as two external shocks including the legality debate of the auction in 2004 and the auction regime reform in January 2008 on the average price of all bidding winners. It is found that the legality debate of the auction had marginal transient impact on the average price in a short time period. In contrast, the change of the auction rules has significant permanent influence on the average price, which reduces the price by about 3020 yuan Renminbi. It means that the average price exhibits nonlinear behaviors with a regime change. The evolution of the average price is independent of the number of bidders in both regimes. In the early regime before January 2008, the average price was influenced only by the minimal price P_min in the preceding month with a positive correlation. In the current regime since January 2008, the average price is positively correlated with the minimal price and the quota in the preceding month and negatively correlated with the quota in the same month. We test the predictive power of the two models using 2-year and 3-year moving windows and find that the latter outperforms the former. It seems that the auction market becomes more efficient after the auction reform since the prediction error increases.     

Design and construction of a compact end-station at NSRRC for circular-dichroism spectra in the vacuum-ultraviolet region

A synchrotron‐radiation‐based circular‐dichroism end‐station has been implemented at beamline BL04B at the National Synchrotron Radiation Research Center (NSRRC) in Taiwan for biological research. The design and performance of this compact end‐station for measuring circular‐dichroism spectra in the vacuum‐ultraviolet region are described. The linearly polarized light from the beamline is converted to modulated circularly polarized light with a LiF photoelastic modulator to provide a usable wavelength region of 130–330 nm. The light spot at the sample position is 5 mm × 5 mm at a slit width of 300 µm and provides a flux greater than 1 × 10¹¹ photons s^?1 (0.1% bandwidth)^?1. A vacuum‐compatible cell made of two CaF₂ windows has a variable path length from 1.3 µm to 1 mm and a temperature range of 253–363 K. Measured CD spectra of (1S)‐(+)‐10‐camphorsulfonic acid and proteins demonstrated the ability of this system to extend the wavelength down to 172 nm in aqueous solution and 153 nm in hexafluoro‐2‐propanol.     

Temperature-dependent vortex matter in a superconducting mesoscopic circular sector

Nonlinear time-dependent Ginzburg–Landau (TDGL) equations were solved in the present work using the link variables method. Vortex configurations were investigated in a superconducting circular sector immersed in an external magnetic field applied perpendicular to its plane. Magnetization and free energy were calculated as a function of the applied magnetic field at several temperatures. This paper illustrates how the vortices moved around at the transition fields before they become accommodated into an equilibrium configuration. A linear dependence of the magnetization dependence on temperature has been found for a certain magnetic field.