潮汐是怎样使地球自转速度变慢的

本文说明月球引起地球海水的潮汐如何减慢地球的自转,就中特别说明了海水与海底的摩擦的作用,也简述了海水潮汐的“反作用”对月球运行的影响。     

从刚体的转动角谈地球的自转周期

从刚体转动角的计算入手，结合地球自转和公转运动的几种周期，分析了地球自转的真正周期－恒星日的长度，纠正了某些献和日常生活中关于地球自转周期的错误说法。     

康普顿早期验证地球自转的“水管”实验

对美国著名物理学家A.H.康普顿在大学本科阶段对地球自转的验证性实验进行原理简述,将其与最早证明地球自转的实验——傅科摆实验并行讨论,从实验原理、背景及影响方面对2个实验的差别作简要分析.     

与地球引力有关的一例谐振动

本文讨论了考虑地球自转时有关地球穿透隧道的一例谐振劝，并给出三种情况下的振动周期．同时，还得到两个非常有趣的结果．     

利用布拉维摆测量地球自转的实验研究

地球自转会带来许多非惯性系效应,利用这些效应定量测量地球的自转角速度,是物理学实验研究的一个重要方面,其中,布拉维摆不仅可以定性地体现出地球自转的效应,更是一种精密测定其自转周期的一种方法.深入研究了利用圆锥摆顺时针和逆时针旋转的周期不同测量地球自转角速度的实验,分析了实验中影响测量精度的关键因素并探讨了控制实验误差的方法,最终得到了与标准值偏差2.3%的结果.由于地球自转所导致的顺逆周期的差十分微小,而影响周期测量的因素很多,如何控制其中关键因素的误差就成为实验成功的重要环节.介绍了如何控制实验条件,以及一些重要的误差来源的分析和控制,对于在普通物理实验条件下成功进行地球自转角速度的测量具有借鉴意义.     

壳模型的综述

本文首先对壳模型历史上几个重要进展做一简单回顾,随后讨论发展的目标,对诸如有效相互作用的选择以及入侵态的存在予以更详细的讨论。最后展望一下将来简化大规模壳模型计算的可能途径。     

关于三体碰撞简化模型的讨论

三体碰撞在一定条件下可简化为两体碰撞处理，本文计算三体碰撞问题的几种简化模型与数值实验结果的偏差，讨论了简化模型的适用条件。     

冰冻地球的进动与章动

基于贾尼别科夫效应网上流传的一些观点认为,当地球南北两极的海冰增加或者减少将导致地球重量分布不平衡,地球将会发生翻转.本文基于简单的刚体地球模型,首先计算了地球南北纬度结冰时导致的地球总转动惯量变化,并利用欧拉动力学方程分析转动惯量变化引起的地球的进动与章动.研究指出,不论是不受外力作用的潘索情况还是考虑了潮汐力的情况,地球在南北纬度30°结冰的情况下旋转最不稳定.此外,即使地球表面冰冻到深度33公里,贾尼别科夫效应也不会在地球上发生.通过本文简单的计算终结了网络流言,并且有利于人们对地球进动和章动的理解.     

嫦娥四号月球背面探秘之旅

<正>在地-月系统长期的演化过程中,地球和月球之间的潮汐力使月球的自转逐渐减缓,最终导致月球被地球潮汐锁定,使得月球总是同一面朝向地球,所以从地球上始终不能完全看见月球的另一面(仅有18%因天平动效应和视差而被观测),因此被称为月球背面。月球背面的第一张影像由前苏联的"月球3号"环月探测器在1959年10月拍摄,揭开了月球背面的神秘面纱,直到1968年12月的阿波罗8号任务环绕月球时,才直接用眼睛看见月球背面。2007年中国发射了嫦娥一号,获取了分辨率为120     

用流体静力学观点解释潮汐现象

考虑地球自转因素,用流体静力学的方法讨论海潮表面形状与涨落问题.     

Quasiparticle approach to the modulational instability of drift waves coupling to zonal flows

The interaction between broadband drift mode turbulence and zonal flows has been studied through the wave-kinetic approach. Simulations have been conducted in which a particle-in-cell representation is used for the quasiparticles, while a fluid model is employed for the plasma. The interactions have been studied in a plasma edge configuration which has applications in both tokamak physics and magnetopause boundary layer studies. Simulation results show the development of a zonal flow through the modulational instability of the drift wave distribution, as well as the existence of solitary zonal flow structures about an ion gyroradius wide, drifting towards steeper relative density gradients.     

On the approach to Maxwellian distribution

The relaxation to equilibrium of a gas governed by the Boltzmann equation is studied for various collision models. For certain initial distributions evidence is presented that it can be characterized by a state in which there is an over-population of high-velocity particles.     

Contribution to the lattice thermal conductivity due to the correction term in the frame of the generalized callaway integral: Application to Ge

The contribution to the lattice thermal conductivity due to the correction term (due to the three phonon normal processes) has been studied at very low temperatures in the frame of the generalized Callaway integral by deriving analytical expressions for it. The contribution of the correction term towards total phonon conductivity of Ge has been calculated in the temperature range 1–5 K and negligible contribution is found due to it.     

Overlapping contributions to the pion-deuteron scattering length

The dependence of the pion-deuteron scattering length on the overlapping region of the two scatterers is studied. It is found that this region contributes almost 30 % to the total result.     

Letters to the editor

Abstract

Optical absorption spectra of TeO₂ crystals, irradiated at room temperature by up to 2·10¹⁸ cm^?2 10-MeV electrons and subsequently annealed to 575K, are studied. The dependence of Urbach absorption edge parameters in TeO₂ on the electron beam fluence is discussed. The irradiation-induced near-edge broad (2.5–3.5eV) absorption band is shown to be related to oxygen vacancies, annealing at 475–525K.     

Density matrix approach to the Hartree-Fock problem

The problem of determining the best one-body density matrix which minimizes the total energy of a many fermion system is studied, with the idea of providing an alternative approach to the method of Roothaan for solving the Hartree-Fock equation.     

Heavy quark production at the TESLA collider and its sensitivity to the gluon content in the photon

Heavy quark production is studied at the TESLA high energy linear collider (LC) both in its nominal and photon collider (PC) mode. Leading order cross-sections are calculated for the production of heavy quarks, , at high transverse momenta. The sensitivity of this process to the gluon content in the photon is studied. Received: 26 November 2001 / Published online: 21 June 2002     

Ten Approaches to Define the Field Emission Area

Technical Physics - The emission area is one of the main parameters of field emission systems. A variety of formal determination techniques for the emission area is studied. Using the model...     

On the collective contribution to the surface energy of simple metals

A recent analysis by Feibelman of the contribution of collective modes to the surface energy is re-examined. When sum rule considerations are studied, his negative energy results are found to be spurious.     

受迫振动法研究压强变化对气体阻尼系数的影响

采用弹性摆受迫振动时幅频特性对阻尼的依赖关系为依据,借助非接触电磁激振装置和（AX1001）单片机,通过测量所得的幅频特性曲线算出相应的阻尼系数。在密闭的环境下,改变空气的压强得到相应数值下的空气阻尼系数,最终,给出空气阻尼系数与压强之间的关系。