围压与径向荷载共同作用下巴西盘裂纹应力强度因子的解析解

利用权函数法推导了围压和径向荷载共同作用下,考虑裂纹面摩擦的预制裂纹巴西盘应力强度因子计算公式,从理论上分析了围压、径向荷载和裂纹面摩擦对巴西盘应力强度因子的影响。结果表明,围压对I型应力强度因子有很大影响,I型应力强度因子随围压的增大而减小。当裂纹面闭合后围压和摩擦系数对II型应力强度因子同样具有显著影响,考虑裂纹面有效剪应力的权函数法理论解与有限元数值解相吻合,表明理论分析的正确性。     

A generalized structured doubling algorithm for the numerical solution of linear quadratic optimal control problems

We propose a generalization of the structured doubling algorithm to compute invariant subspaces of structured matrix pencils that arise in the context of solving linear quadratic optimal control problems. The new algorithm is designed to attain better accuracy when the classical Riccati equation approach for the solution of the optimal control problem is not well suited because the stable and unstable invariant subspaces are not well separated (because of eigenvalues near or on the imaginary axis) or in the case when the Riccati solution does not exist at all. We analyze the convergence of the method and compare the new method with the classical structured doubling algorithm as well as some structured QR methods. Copyright © 2012 John Wiley & Sons, Ltd.     

Complexation of Hg2+ with α‐Lipoic and Dihydrolipoic Acids: Study by Differential Pulse Voltammetry on Rotating Au‐Disk Electrode and ESI‐MS

The complexation of the natural antioxidants α‐lipoic acid (ALA) and its reduced form dihydrolipoic acid (DHLA) with Hg²⁺ was investigated by a recently proposed differential pulse voltammetric (DPV) method using the rotating Au‐disk electrode. Complexation processes are proposed from the multivariate curve resolution by alternating least squares (MCR‐ALS) analysis of DPV titration data. Main complexes were both 1 : 1 Hg : ALA and Hg : DHLA, although the formation of 1 : 2 complexes can be also deduced. ALA and DHLA show different Hg²⁺‐binding patterns at different pH. Voltammetric findings are completed with the data obtained by electrospray ionization mass‐spectrometry (ESI‐MS), especially in negative mode.     

Perpendicular magnetic recording—Its development and realization—

The principle of conventional magnetic recording is that magnetic fields are applied parallel to the plane of the magnetic medium. As described in this paper, the invention and development of a new method of placing the magnetized information perpendicular to the plane of the magnetic recording medium is presented. The yield in the mass production of high-density hard disk drives (HDDs) for perpendicular recording is much higher than that of HDDs for conventional recording. Consequently, it is estimated that as many as 75% of the 500 million HDDs to be shipped this year will use this technology.     

Influence of periodic excitation on self-sustained vibrations of one disk rotors in arbitrary length journals bearings

Interaction of forced and self-sustained vibrations of one disk rotor is described by nonlinear finite-degree-of-freedom dynamical system. The shaft of the rotor is supported by two journal bearings. The combination of the shooting technique and the continuation algorithm is used to study the rotor periodic vibrations. The Floquet multipliers are calculated to analyze periodic vibrations stability. The results of periodic motions analysis are shown on the frequency response. The quasi-periodic motions are investigated. These nonlinear vibrations coexist with the periodic forced vibrations.     

A 12.1-W SESAM mode-locked Yb:YAG thin disk laser

Pumped by a 940 nm fiber-coupled diode laser, a passively mode-locked Yb:YAG thin disk oscillator was demonstrated with a semiconductor saturable absorber mirror(SESAM). 12.1 W mode-locked pulses were obtained with pulse duration of 698 fs at the repetition rate of 57.43 MHz. Measurement showed that the beam quality was close to the diffraction limit.     

基于能量分布的红外像点定位分析方法

在红外探测器的应用中,常用统计分析、算例验证等方法研究目标成像精确定位问题。鉴于上述方法难以充分阐释物理意义与揭示普遍规律,提出基于能量分布及成像特征的分析方法,针对红外探测目标成像精确定位问题,利用能量分布和数字图像中成像规律,研究像点定位及精度分析。研究了红外目标成像和数字图像特点,建立了定位模型和方法流程;分析了定位误差影响因素,实现了定位结果精度评定;最后结合典型应用实例,进行了计算验证。该方法与已有方法相比,分析过程更直观,获取了红外像点定位分析的理论依据,并给出了定位结果的精度水平:通常红外成像应用中,精度优于1/6像元;在成像较大时,精度可达1/10像元以上。该研究结论对红外探测应用中目标准确定位具有重要意义。     

Flow of micropolar fluid between two orthogonally moving porous disks

The unsteady,laminar,incompressible,and two-dimensional flow of a micropolar fluid between two orthogonally moving porous coaxial disks is considered.The extension of von Karman’s similarity transformations is used to reduce the governing partial differential equations(PDEs) to a set of non-linear coupled ordinary differential equations(ODEs) in the dimensionless form.The analytical solutions are obtained by employing the homotopy analysis method(HAM).The effects of various physical parameters such as the expansion ratio and the permeability Reynolds number on the velocity fields are discussed in detail.