Wave-like perturbations in the ionospheric F2-layer observed after the Ms8.1 Samoa earthquake of September 29, 2009

A study of the critical frequency foF2 variations after the large earthquake (M_s = 8.1) which occurred on 29 September, 2009 in the region of Samoa Islands in the Pacific Ocean is carried out using data of the ionospheric station of Kwajalein. The epicenter of the earthquake was located at about 184 km southwest from Apia (the capital of West Samoa). It was found that wave-like perturbations of foF2 were observed for ∼3 h above the station (located approximately 3560 km northwest from the epicenter). The amplitude of the disturbance was as large as ∼20% of the average magnetic quiet day foF2 values. A comparison of the observed perturbations of foF2 with the ones detected at Stanford ionospheric station after the Alaska earthquake of 28 March 1964 (M_s = 8.4) showed a close similarity of the wave-like perturbations of foF2 in both cases.     

Formation mechanism of great positive TEC disturbances prior to Wenchuan earthquake on May 12, 2008

The problems of physical explanation and possible mechanisms of the seismo-ionospheric effects formation are under discussion now. There are proposed different mechanisms of such effects, for example, large- and small-scale internal gravity waves (IGWs), atmospheric electric field, electromagnetic fields and emissions. However, the appearance of local large-scale seismo-ionospheric anomalies in Total Electron Content (TEC) is possible to explain only by two mechanisms: an atmospheric electric field and/or small-scale IGWs. In this paper, the simulation results for reproduction of the observed seismo-ionospheric great positive effects in TEC prior to strong Wenchuan earthquake are presented. The obtained results confirm the proposed mechanism of seismo-ionospheric effects formation by the penetration of the seismogenic electric field from the atmosphere into the ionosphere. It is suggested that so great TEC enhancement observed 3 days prior to Wenchuan earthquake could be explained by combined action of seismogenic vertical electric field and IGWs generated by the solar terminator.     

毫米波准光开放腔测试系统误差分析

给出用于毫米波频段精确测量介质片复介电常数的准光开放腔系统的误差分析,说明了近似理论引起的误差和被测量提取不准引起的误差。推导了相关的公式,给出了分析的数值结果和测量结果。     

螺栓连接松动的导波监测技术综述

螺栓连接件使结构易于安装或拆卸,同时还可以承受较大的载荷,广泛应用于航空航天结构中。然而,螺栓在复杂服役环境中很容易发生松动,因此准确监测螺栓预紧力对于确保结构的可靠性和安全性具有重要意义。经过多年的发展,基于超声导波的结构健康监测方法逐渐成为螺栓连接松动监测的重要技术手段之一。对典型的螺栓预紧力导波监测方法进行了综述,包括导波能量耗散法、时间反转法、接触声学非线性法和混沌超声法等方法,介绍了这些方法的基本原理和发展现状。同时,通过实验将目前应用较多的导波能量耗散法、时间反转法进行了对比,结果表明时间反转法的监测灵敏度更高。     

Dynamical Systems Approach to Space Environment Turbulence

Space plasmas are dominated by waves, instabilities and turbulence. Dynamical systems approach offers powerful mathematical and computational techniques to probe the origin and nature of space environment turbulence. Using the nonlinear dynamics tools such as the bifurcation diagram and Poincaré maps, we study the transition from order to chaos, from weak to strong chaos, and the destruction of a chaotic attractor. The characterization of the complex system dynamics of the space environment, such as the Alfvén turbulence, can improve the capability of monitoring Sun-Earth connections and prediction of space weather. This revised version was published online in August 2006 with corrections to the Cover Date.     

风扇转子前缘曲线相对掠对性能的影响

本文从叶片前缘曲线掠的形式入手,采用适合叶轮机械内三维流动特点的相对掠概念,把叶片前缘曲线相对掠应用到设计中,探讨叶片前缘曲线相对掠(包括相对前掠、相对无掠和相对后掠)对通道激波的方位、强度的影响,以及由此造成的对风扇性能的影响,并进行了数值模拟,从得到的结果可以看出转子前缘曲线对风扇/压气机的性能影响非常明显,并对设计在气动方面的优化有一定的指导作用。      

Effects of Superthermal Particles on Waves in Magnetized Space Plasmas

Distributions with excess numbers of superthermal particles are common in space environments. They are well modelled by the isotropic kappa distribution, or, where magnetic effects are important, the kappa-Maxwellian. This paper presents a review of some studies of electrostatic and electromagnetic waves in such plasmas, based on the associated generalized plasma dispersion functions, Z _κ and Z _κM. In particular, the effects of low values of κ are considered, i.e. strongly accelerated distribution functions. Recently the full susceptibility tensor for oblique propagation of electromagnetic waves in a kappa-Maxwellian magnetoplasma has been established and has been applied to the study of whistler waves.     

MHD Waves and Heating in Coronal Holes

Coronal holes have been identified as source regions of the fast solar wind, and MHD wave activity has been detected in coronal holes by remote sensing, and in situ in fast solar wind streams. I review some of the most suggestive wave observations, and discuss the theoretical aspects of MHD wave heating and solar wind acceleration in coronal holes. I review the results of single fluid 2.5D MHD, as well as multi-fluid 2.5D MHD models of waves in coronal holes, the heating, and the acceleration of the solar wind be these waves.     

运动激波绕射的数值模拟

用高分辨率的ＴＶＤ格式对复杂的激波反射过程做数值模拟。激波斜壁反射计算结果与实验干涉照片、压力分布、密度分布均符合得很好。通过对运动激波绕射凸起物的数值模拟,得到非定常反射流场发展过程及复杂流场间断的清晰图谱。