计算机2000年问题对地震观测的影响及其预防方法

简要分析了计算机２０００ 年问题对地震观测的影响．这些影响主要表现在各种应用软件方面．提出了几种预防方法,除了更换必要的观测仪器之外,还要解决各类软件的２０００ 年问题     

地下流体地震前兆多层次跟踪法在华南及沿海地区的应用

利用多层次跟踪法,对８０年代以来华南及沿海地区发生的９次大于Ｍｓ５．０级和２次陆区接近Ｍｓ５．０级地震的发震时间进行了系统验证。在１１个震例中预测时段正确的有：中期１０个、短期５个和短临２个,表明该方法应用于华南及其沿海地区未来中强震发震时间的预报。     

Possible configurations of the magnetic field in the outer magnetosphere during geomagnetic polarity reversals

Possible configurations of the magnetic field in the outer magnetosphere during geomagnetic polarity reversals are investigated by considering the idealized problem of a magnetic multipole of order m and degree n located at the centre of a spherical cavity surrounded by a boundless perfect diamagnetic medium. In this illustrative idealization, the fixed spherical (magnetopause) boundary layer behaves as a perfectly conducting surface that shields the external diamagnetic medium from the compressed multipole magnetic field, which is therefore confined within the spherical cavity. For a general magnetic multipole of degree n, the non-radial components of magnetic induction just inside the magnetopause are increased by the factor 1 + [(n + 1)/n] relative to their corresponding values in the absence of the perfectly conducting spherical magnetopause. An exact equation is derived for the magnetic field lines of an individual zonal (m = 0), or axisymmetric, magnetic multipole of arbitrary degree n located at the centre of the magnetospheric cavity. For such a zonal magnetic multipole, there are always two neutral points and n – 1 neutral rings on the spherical magnetopause surface. The two neutral points are located at the poles of the spherical magnetopause. If n is even, one of the neutral rings is coincident with the equator; otherwise, the neutral rings are located symmetrically with respect to the equator. The actual existence of idealized higher-degree (n > 1) axisymmetric magnetospheres would necessarily imply multiple (n + 1) magnetospheric cusps and multiple (n) ring currents. Exact equations are also derived for the magnetic field lines of an individual non-axisymmetric magnetic multipole, confined by a perfectly conducting spherical magnetopause, in two special cases; namely, a symmetric sectorial multipole (m = n) and an antisymmetric sectorial multipole (m = n – 1). For both these non-axisymmetric magnetic multipoles, there exists on the spherical magnetopause surface a set of neutral points linked by a network of magnetic field lines. Novel magnetospheric processes are likely to arise from the existence of magnetic neutral lines that extend from the magnetopause to the surface of the Earth. Finally, magnetic field lines that are confined to, or perpendicular to, either special meridional planes or the equatorial plane, when the multipole is in free space, continue to be confined to, or perpendicular to, these same planes when the perfectly conducting magnetopause is present.Also Honorary Research Associate, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK and Visiting Reader in Physics. University of Sussex, Falmer, Brighton BN1 9QH, UK     

用水氡最大变化率法对强震时间作中短期预报

介绍了水氡变化率的物理含义以及变化率动态图象的生成方法,强震前在动态图象上存在着变化率≥０．０６高值异常区,异常区中心的最大变化率随时间有规律地演化,且与发震时间有着良好的统计关系。据此提出４个时间预测指标。检验性预测结果表明,预测的发震时间段长短大多数为２至６个月,可满足强震的中短期预报尺度的需要。     

用单片机实现水声遥控指令的脉冲周期编码（PTC）信号

本文介绍用单片机实现脉冲周期编码（ＰＴＣ）的电路,给出硬件和软件的配置,其特点是灵活、简单、可靠,适合用于水下传输多个声遥控指令     

斑石鲷(Oplegnathus punctatus)游泳性能研究

流速作为深远海养殖海区选址的重要依据,也是影响鱼类游泳能力的重要因素之一,为评价深远海养殖良种斑石鲷(Oplegnathus punctatus)的游泳能力,明确最适放养规格,分别以体重50、150、250、350g的斑石鲷为研究对象,利用鱼类游泳能力及运动消耗检测装置,在24℃条件下,解析了不同规格的斑石鲷在四种流速下的续航时间、暴发游泳速度(U_burst)、临界游泳速度(U_crit)和运动耗氧率(MO₂),并计算出其单位位移耗能(COT)和最适游泳速度(U_opt)。结果表明,鱼体规格和流速均会对实验鱼续航时间产生影响显著(P<0.001,F=25.401,df=1),50g斑石鲷在60cm/s流速下续航时间显著小于其他三种规格(P<0.05),在大于60cm/s流速下,四种规格斑石鲷续航时间均小于30min;250g和350g斑石鲷暴发游泳速度显著高于50g与150g(P<0.05);斑石鲷临界游泳速度与体重成正相关(R=0.96),不同规格下临界游泳速度存在显著差异(P<0.05);各规格实验鱼间最适游泳速度无显著差别(P>0.05)。以上结果表明,不同规格斑石鲷游泳能力存在显著差异,其中250g和350g斑石鲷耐流能力显著优于50g和150g。综上所述,斑石鲷在深远海海域进行陆海接力养殖时,建议放养250g以上规格,且养殖海域流速不超过60cm/s。     

Is the September 5, 2022, Luding MS6.8 earthquake an ‘unexpected’ event?

Whether the September 5, 2022, Luding M_S6.8 earthquake is an ‘expected’ event in the context of earthquake forecast? This commentary discusses this issue mainly using the recently proposed ‘earthquake nowcasting’ approach.     

长时效的正压原始方程能量完全守恒(拟)谱模式

遵循误差反演补偿新计算原理,对正压原始方程传统气象全球拟谱模式方案进行了改造,构造了正压原始方程能量完全守恒全球拟增模式新计算方案,解决了正压原始方程的（非线性）计算稳定性问题和能量守恒整体性质保持问题,改进了相应正压原始方程传统气象全球拟谱模式方案的计算效能。新方案的数值试验表明：在计算实践上,新方案在解决能量守恒问题的同时,可解决（非线性）计算稳定性问题,并在一定条件下可解决非线性计算收敛性问题。进一步的比较数值试验还表明：在计算实践上,新方案具有在提高相应传统气象方案的计算精度,减少其计算量的同时,延长其计算时效,解决其中一类特定“气候漂移”问题方面的效用。本工作原理也适用于斜压原始方程情形。     

Compensation of time‐delay for control of civil engineering structures

Time‐delay is an important issue in structural control. Applications of unsynchronized control forces due to time‐delay may result in a degradation of the control performance and it may even render the controlled structures to be unstable. In this paper, a state‐of‐the‐art review for available methods of time‐delay compensation is presented. Then, five methods for the compensation of fixed time‐delay are presented and investigated for active control of civil engineering structures. These include the recursive response method, state‐augmented compensation method, controllability based stabilization method, the Smith predictor method and the Pade approximation method, all are applicable to any control algorithm to be used for controlled design. Numerical simulations have been conducted for MDOF building models equipped with an active control system to demonstrate the stability and control performance of these time‐delay compensation methods. Finally, the stability and performance of the phase shift method, that is well‐known in civil engineering applications, have also been critically evaluated through numerical simulations. Copyright © 2000 John Wiley & Sons, Ltd.     

添加正则化项的黏声逆时偏移成像方法研究

在实际地球介质中传播的地震波会产生衰减和频散现象,因此其更接近于黏弹性介质,在地震处理中补偿这些黏性影响是十分必要的。基于波动方程的叠前深度偏移中进行吸收衰减补偿更准确,也更有物理意义,直接求解双程波动方程的逆时偏移(RTM)能够成像大倾角复杂构造,具有诸多优势。然而当考虑吸收衰减补偿时通常会产生不稳定现象,大部分研究都是在逆时偏移的波场延拓中进行波数域的低通滤波来解决这个问题。本文采用广义标准线性固体的黏声波动方程进行吸收衰减补偿的Q--RTM方法,通过添加正则化项的方式来稳定延拓过程。添加正则化项本质上是低通滤波,滤波窗口是指数形式,在时空域有明确的形式,可以阻止发生高频不稳定。与直接滤波相比,正则化参数可以是空变的,因此比较适合剧烈变化的区域,我们还发现震源归一化互相关成像条件更适合Q--RTM方法。