Numerical solutions of rotational normal modes of a triaxial two-layered anelastic Earth

The Earth's rotational normal modes depend on Earth model used, including the layer structures,principal inertia moments of different layers and the compliances. This study focuses on providing numerical solution of the rotational normal modes of a triaxial two-layered anelastic Earth model without external forces but with considering the complex forms of compliances and the electromagnetic coupling between the core and mantle. Based on the present knowledge of the Chandler wobble(CW) and Free Core Nutation(FCN), we provide a set of complete compliances which could be used for reference in further investigations. There are eight rotational normal mode solutions, four of which might exist in nature. However, in reality only two of these four solutions correspond to the present motion status of the prograde CW and the retrograde FCN. On one hand, our numerical calculations show that the periods and quality factors(Qs) of CW and FCN are respectively 434.90 and 429.86 mean solar days(d) and 76.56 and 23988.47 under frequency-dependent assumption, and the triaxiality prolongs CW about 0.01 d and has hardly effect on FCN. On the other hand, we analyze the sensibility of compliances and electromagnetic coupling parameter on the periods and Qs of CW and FCN and find the sensitive parameters with respect to them.

Probing signals of atmospheric gravity waves excited by the July 29,2021 M_(W)8.2 Alaska earthquake

It is commonly believed that the atmosphere is decoupled from the solid Earth.Thus,it is difficult for the seismic wave energy inside the Earth to propagate into the atmosphere,and atmospheric pressure wave signals excited by earthquakes are unlikely to exist in atmospheric observations.An increasing number of studies have shown that earthquakes,volcanoes,and tsunamis can perturb the Earth's atmosphere due to various coupling effects.However,the observations mainly focus on acoustic waves with periods of less than 10 min and inertial gravity waves with periods of greater than 1 h.There are almost no clear observations of gravity waves that coincide with observations of low-frequency signals of the Earth's free oscillation frequency band within 1 h.This paper investigates atmospheric gravity wave signals within1 h of surface-atmosphere observations using the periodogram method based on seismometer and microbarometer observations from the global seismic network before and after the July 29,2021 M_(w)8.2 Alaska earthquake in the United States.The numerical results show that the atmospheric gravity wave signals with frequencies similar to those of the Earth's free oscillations _(0)S_(2) and _(0)T_(2) can be detected in the microbaro meter observations.The results con firm the existence of atmospheric gravity waves,indicating that the atmosphere and the solid Earth are not decoupled within this frequency band and that seismic wave energy excited by earthquakes can propagate from the interior of the Earth to the atmosphere and enhance the atmospheric gravity wave signals within 1 h.

Detection and interpretation of the Earth's free oscillations excited by the great Sumatra-Andaman earthquake with GGP station data

The mode serials of the Earth’s free oscillation provide some important information on the Earth’s deep structure and superconducting gravimeters （SG） can investigate the phenomena of the Earth’s free oscillations with high accuracy. The great Sumatra-Andaman earthquake fully excited the Earth’s free oscillations and these signals were perfectly recorded by five superconducting gravimeters in the globe. After the pre-treatment and spectral analysis on the SG observation data, we obtained the experimented mode serials of the Earth’s free oscillations consisting of 147 modes with GGP station data. These observed modes were themselves some new important data for the study of the Earth’s deep structure. On the basis of the discussions on some checked inner-core-sensitive modes, we distinguished three layers from the inner core, and the boundary of the upper layer was compatible with the formerly known transition zone in the inner core based on seismic body waves and supported that there were the hemispherical variation and very lower shear velocity zone in the lower inner core.

Effects of rotation and gravity on an electro-magneto-thermoelastic medium with diffusion and voids by using the Lord-Shulman and dual-phase-lag models

The effects of rotation and gravity on an electro-magneto-thermoelastic medium with diffusion and voids in a generalized thermoplastic half-space are studied by using the Lord-Shulman (L-S) model and the dual-phase-lag (DPL) model. The analytical solutions for the displacements, stresses, temperature, diffusion concentration, and volume fraction field with different values of the magnetic field, the rotation, the gravity, and the initial stress are obtained and portrayed graphically. The results indicate that the effects of gravity, rotation, voids, diffusion, initial stress, and electromagnetic field are very pronounced on the physical properties of the material.

The focal mechanism solution of the Ms6.5 Wuding earthquake in Yunnan Province of October 24,1995

The focal mechanism of Wuding earthquake with magnitude M =6.5 on October 24, 1995 is estimated by the method of inversion of seismic tensor in this paper. The two principal axes are nearly horizontal, the principal compressive axis is about N30°E, the nodal plane which strikes about N105°E (N75°W) is probably consistent with the actual rupture plane.

“优师计划”背景下师范生U-G-S培养模式价值、问题及对策

从“优师计划”背景下师范生U-G-S培养模式价值分析入手,剖析“优师计划”背景下师范生U-G-S培养模式中地方政府、师范院校、中小学校、师范生四个基本要素各自存在问题,提出“四位一体”师范生U-G-S培养模式提升对策,以当地政府为主导、以师范院校为引领、以中小学校为核心、以师范生为主体,统筹各方培养资源和优势力量,激活多方利益主体意愿,助力乡村卓越教师的培养。

Earth's Free Toroidal Oscillations Observed by the JCZ-1 Seismometer

We firstly detected the Earth's free toroidal oscillations excited by three large earthquakes in Japan,2011,Chile,2010 and Indonesia,2005 from the observed data of the JCZ-1 seismometer at Wuhan Seismic Station. The eigenperiods of basic modes (0T2 - 0T67 ) and first modes (1T2 ～ 1T50 ) were detected,and their error ratios were less than 0. 5% by comparing the observed eigenvalues with the theoretical eigenvalues in PREM. We supplemented some modes- 0T11,0T15 , 0T19 , 1T4 , 1T5 and 1T14 ,which were not mentioned in PREM,and also observed the spectral line multi-peak phenomenon from 0T2, 0T6 , 0T7 and 0T8 . These results show that the JCZ-1 seismometer is able to precisely observe the Earth's long period toroidal free oscillations.

A Simple Mechanism for Generating a Geomagnetic Field

On the basis of the ideal gas model, the polarization of charges in the mantle was obtained, a physical and mathematical model was constructed, and estimated calculations of the dipole mode of the Earth’s magnetic field were performed, taking into account the speed of its angular rotation, the parameters of density and temperature, the chemical composition, the ionization potential, the dielectric constant and the percentage of the main chemical compounds of the mantle substance.

SNRVEI地球模型连续分布的简正模及其意义

基于Peltier等建立的粘弹地球表面负荷形变理论，运用简正模分析法，实现了SNRVEI粘弹地球模型表面负荷勒夫数从拉氏域至时间域的变换．数值结果印证了韩大仲关于真实地球存在“连续分布的简正模”的结论，同时还表明在保证较高计算精度前提下，为便于计算，将地球核慢边界以上部分划分成较少个物性均匀层是可行的．本文的方法和结果经过数值检验，可用于冰后相对海平面变化、地球自转非潮汐加速度变化等地表负荷均衡动态响应观测量的研究．

一种ADS-B报头互相关检测方法

广播式自动相关监视(ADS-B)报头检测方法的优劣直接决定着接收机的性能。为了解决脉冲匹配检测方法受脉冲能量影响较大的不足,提出了一种基带归一化的互相关报头检测方法。首先将基带信号根据动态门限进行归一化,然后将其与标准报头作互相关,最后通过相关峰检测来判定信号的存在和到达时间。与主流基于脉冲位置和上升沿的检测方法相比,该方法隐含地利用了脉冲位置、上升沿、下降沿、脉冲宽度、非脉冲区等多个信息用于检测报头,且无需进行下行格式(DF)认证。仿真结果表明:该方法在信噪比大于2 d B时检测性能略优,在信噪比小于2 d B时检测性能与主流检测方法相差1 d B。在实际接收实验中,以该方法为基础的信号接收效果良好,在视距内可以形成稳定连续的航迹,证明了该方法的实用性。

“S注入法”与电压互感器的特殊接线方式

基于"S注入法"的选线定位保护新原理的TY系列选线定位保护已大量运行于国内电力系统。"S注入法"需通过电压互感器向故障系统注入检测信号,而为了消谐等目的,电压互感器有多种特殊的接线方式。对这些特殊的接线方式进行了分析,论证说明了这些特殊接线方式既能够满足消谐的需要,又适合于"S注入法"选线定位。

基于Galerkin方法构建MEMS器件宏模型

将器件结构单元的线性模态振型函数(或是本征正交模态)作为全局基函数集合,结合Galerkin方法,获得具有足够仿真精度的微机电系统(MEMS)器件自由度缩减模型.宏模型中相关的状态变量数目很少,可以被快速计算,便于植入系统仿真器中进行模拟.文中分别阐述了这两种自由度缩减模型构造方法的优缺点及存在的问题,认为宏模型研究的重点将是器件非线性特性的有效表达以及建模过程自动化的计算机实现;并对非线性MEMS器件宏模型的研究发展给出了建议.

Thomson effect with hyperbolic two-temperature on magneto-thermo-visco-elasticity

The study considers a homogeneous isotropic thermo-visco-elastic solid with hyperbolic two-temperature to cope up with its two-dimensional(2 D)deformations.The heat conduction equation is influenced by the Thomson coefficient.Lord-Shulman’s theory is used to modify the basic governing equations.A method called"normal mode analysis"is utilized to attain the magnetic field,stress,conductive and thermodynamic temperature,and displacement components.Also,a number of numerical calculations are performed and discussed to understand the impact of hyperbolic two-temperatures,Thomson parameter,and viscosity on the material mentioned above.

“U-G-S”协同视角下师范生教育实习模式优化研究

“U-G-S”协同教育实习模式是协同理论在教育领域的应用,强调高校、政府和中小学共同致力于师范生实习工作。“U-G-S”协同教育实习有助于形成师范生培养合作共同体,促进教育理论与实践对话,提高师范生教育实习质量。然而,通过田野调查发现,目前的教育实习模式存在政府对教育实习管理不到位、高校对教育实习不重视与实习基地指导能力不足等问题。借鉴英国、加拿大的教育实习经验,优化我国教育实习模式的可行路径是:强化政府对“U-G-S”协同教育实习的治理责任,优化高校对“U-G-S”协同教育实习的教学管理,提升实习基地的指导能力。

“U-G-S”协作培育师范生教育情怀:现实困境、生成逻辑与实践进路

教育情怀是师范生成为“四有好老师”的核心要素。虽然“U-G-S”模式为师范生教育情怀培育提供了实践场域,但师范生教育情怀培育面临着目标遮蔽、进程割裂、评价单一等现实困境。师范生教育情怀生成经历初始萌发、具身认知、实践磨砺阶段,按照“U-G-S”模式协作开展对师范生教育情怀的培育,需要明确目标并落实各主体培育职责,发挥多主体协作优势;丰富培育途径,建立教育情怀养成档案袋,发挥档案袋在毕业要求和新入职教师考核中的评价作用。

“U-G-S”教师教育模式优化研究

国内外学者提出的“U-G-S”教师教育模式正在实践中进行多方面实验。但作为一种协同机制,各主体之间存在差异,例如办学主体的办学能力有待提高,教师教育的反馈机制有待进一步健全,协同机制有待进一步完善等等。为了促进“U-G-S”教师教育模式的进一步完善和发展,构建各主体间协同机制、构建教师教育信息资源共享平台、构建“互联网企业+U-G-S”教师教育模式很有必要。

U-G-S模式下物理专业本科生培养的探索与实践

提高师范类物理专业本科生的教育质量是培养适应现代化中学物理教学的优质师资的必由之路。在详细讨论目前物理教育教学中一些关键问题后,本文着重阐述了在U-G-S教学模式下联合地方性师范类本科院校、师范院校的实习基地(主要是中学)和当地政府三方共同促进物理类师范教育,并利用一个具体例子总结了相关的经验,为物理类师范生教育提供一些参考。

近似解析解方法在简正模计算中的应用

利用合理的参数近似,导出分层、球形、弹性各向同性和含自重的地球变形的常系数微分方程组,从而给出矩阵形式的解析解。同时,采用一种高效稳定的传播矩阵方法,计算地球简正模的本征周期和本征函数。为了验证方法的正确性,首先将本征周期与均匀球模型的解析解进行比较,结果表明,球型和环型简正模若要实现10^(-2)s的本征周期精度,模型的分层厚度分别为50 m和0.1 m;本征函数与解析解一致,且收敛性较好;当地球模型的层厚足够小时,近似解析解可认为是真实解。最后,采用近似解析解方法计算PREM模型的本征周期,并对Mineos的计算结果进行精度检验,发现环型简正模和球型简正模的本征周期精度分别为10^(-3)s和10^(-2)s,可以满足当前观测的需求。

Earth's density flattening and hypothesis of latitudinal normal density

In this paper, the definition of latitudinal density and density flattening of the level ellipsoid is given, and integral formulas of latitudinal density for pole gravity and equator gravity are derived. According to the pole gravity condition and equator gravity condition for the level ellipsoid, latitudinal density distribution function of the level ellipsoid is obtained. It is proved mathematically that latitudinal density of the earth's equator is larger than that of the pole, the earth's density flat-tening calculated preliminarily is 1/322, and hypothesis of the earth's latitudinal normal density is further proposed, so that theoretical preparation for studying the forming cause of the earth gravity in problems such as continent drift, mantle convection, and submarine extension is made well.

内核地球自转动力学理论的研究进展(Ⅵ)——章动转换函数和内核的动力学效应

本文是序列文章的第六篇,其主要内容包括:讨论了两种章动转换函数表达式以及它们系数之间的关系,指出了前人给出系数值的缺陷,以及某些公式表述的错误;基于内核地球模型的有关参数,利用Mathematica数学分析软件计算了PREM和1066A地球模型在FULL理论、MTIC和FIC近似下的章动本征模频率和章动转换函数的有关系数;计算了内核动力学对受迫章动的影响,结果表明其影响已在目前VLBI可检测的量级内.本文对地球章动转换函数进行了较完整的论述,期望对进一步研究地球自转动力学起重要作用.