华北联网中的山西台网

从联网的系统构成、联网设备及软件配置、联网产生的效益３个方面介绍了华北联网中山西台网的情况，总结了孤立的小网联结成大跨度的现代化监测网络的经验。     

全国重力联网和精度评定

本文以收集现有全国各省地震局流动重力测量资料和图件为主，结合大区域联测资料，用绝对重力点控制联网并进行统一平差。平差程序采用经典相关间接平差方法，以压缩存贮方式解算法方程。计算结果表明：全国重力网段差平均精度为０．０１０７×１０－５ｍｓ－２。辽宁地区点值精度最高为０．０１９×１０－５ｍｓ－２，一般为０．０２０×１０－５－０．０３０×１０－５ｍｓ－２。     

华北联网短波通讯中CCU故障处理方法

华北联网短波通讯中ＣＣＵ故障处理方法杨志刚，徐良爱，黄百锁（中国山西０４１０００临汾中心地震台）华北地区遥测地震台网联网（简称华北联网）于１９９２年９月通过国家地震局专家组的验收，投入运行两年来，较好地监测了大华北地区的地震活动，增强了首都围及华北地...     

地震工程试验联网最新进展

地震工程试验联网(NEES)是新世纪地震工程学科最重要的事件。由美国国家自然科学基金会牵头,全美15家主要的地震工程研究单位共同实施一项旨在调动全部优势资源进行复杂结构体系的地震响应协同试验研究计划。该计划从1999年开始,将于2014年全部完成,目前多数成员单位进入设备安装调试阶段,有些单位利用新装备实现了某些利用传统手段无法完成的试验任务。建议工程力学研究所燕郊的结构实验室直接按照加入NEES的标准进行硬件配置和软件开发,使硬件的数量和技术指标满足NEES要求;使软件与硬件配套,实现与NEES联网,可远程快速通讯,实时监控,实时数值模拟计算,实现显式、隐式和显隐混合算法伪动力试验以及具有位移控制、力控制、位移和力混合控制功能。     

区域地震台网远震定位问题探讨：华北地区遥测地震台网联网…

用北京遥测地震台网的远震资料应用ＴＥＬ９２远震定位程序对６６个地震重新计算，将计算结果与《ＰＤＥ目录》对比分析，从中得出有益的结论。     

华北遥测地震台网联网定位能力

本文利用1992年北京遥测地震台网联网前和联网后所测定的957个近震的参数进行分析与比较,进而论证华北遥测地震台网联网的定位精度和范围。     

海南广东数字地震台网联网应用

描述了利用Internet将海南、广东数字地震台网连接,组建虚拟地震台网的技术途径,比较了海南本地台网和虚拟台网地震监控能力及海南虚拟台网应用效果。结果表明,联网后,扩展了对两省交界海域的监控范围,提高了定位精度,有利于地震速报和地球物理研究。     

临汾台网联网工作综述

本文从临汾台网的联网建设、考核运行及联网初步效益3个方面综述了临汾台网的联网工作。     

单机地震数据采集系统NCDAS：华北地区遥测地震台网联网论文续

设计了一套单机地震数据采集软件系统ＮＣＤＡＳ。文中描述了该软件的总体结构，各任务块的功能，事件检测算法以及硬件环境。     

In situ 2-D and 3-D measurements of radiation patterns of half-wave dipole GPR antennas

Dipole antennas for ground-penetrating radar (GPR) radiate and receive electromagnetic waves with a strong directional dependence. Thus, experiments to measure in situ antenna radiation as functions of direction and polarization are of practical interest. Three field experiments were performed. One experiment was over a layered fluvial/eolian sequence; the other two used controlled targets (buried pipes and a metal ball). The radiation patterns were sampled by incrementally varying the antenna orientations and separations while recording reflections from the known targets. The results show qualitative, but systematic, correspondence with approximate theoretical far-field radiation patterns. Slow variations of amplitude with antenna azimuth and dip indicate that antenna orientations within 20° in the standard TE and TM acquisition geometries are adequate for most field applications, but not if detailed amplitude analysis is to be performed. Variations in antenna orientation or height (particularly for heights less than one-quarter wavelength) above the free surface introduce corresponding biases or uncertainties into recorded amplitudes. The variance within any suite of measurements is, in part, a consequence of differences in ground impedance at each antenna location. The theoretically predicted sensitivity to antenna height is mediated by surface roughness at high frequencies. It is necessary to include, or compensate for, the antenna radiation pattern in analysis of field data amplitudes, in experiment design, and in selecting appropriate antennas for specific applications.     

GPS高精度重复测量中的天线相位中心偏差检测及改正

首先通过GPS接收机在超短基线上检测数据计算天线相位中心偏差,然后对民乐跨断层综合观测场地2007~2008年的GPS点位速率进行校正。从计算结果可知,所用GPS天线相位中心偏差多在亚毫米级。对于距离在几千米的点位,由于各期观测所用天线的不同,使得相位中心的偏差对水平运动速率的影响多在亚毫米级;若各期观测所用天线相同,则影响多在10-2毫米量级。对高精度GPS观测来说,多期观测尽可能采用同一天线。     

GPS扼径圈天线相位中心偏差检验

GPS接收机天线相位中心偏差是指GPS天线接收卫星信号的电气中心与其机械几何中心之差,在GPS高精度测量中,这是不容忽视的。讨论了采用基线测量相对定位法确定天线相位中心偏差的原理和方法,并利用这一方法计算出天线相位偏差结果。     

一种简易探地雷达天线的制作及其应用效果分析

由于商业探地雷达天线价格昂贵,又比较笨重,很多测量参数不能任意修改或修改起来比较困难,且在室内做实验又很不方便,所以,设计一种造价低,小巧方便且效果较好的天线显得很有意义.基于这样的考虑,本文从实用的角度出发,采用半定量化的方式较详细的介绍一种简易探地雷达天线的制作方法,并辅以网络分析仪对其实际应用效果进行分析研究.实验证明,对于常规的探地雷达实验研究,该天线在性能上已达了要求,是有效的,可行的.     

机载探地雷达数值模拟及逆时偏移成像

机载探地雷达可以用于人类无法到达的危险地区、植被严重覆盖的地下目标体探测,然而由于机载探地雷达的特殊性,影响机载探地雷达探测效果的因素包括天线的极化方向、天线的飞行高度以及地表粗糙度等.为了研究这些影响因素与探测效果之间的关系,用三维时间域有限差分模拟电磁波的传播过程,以沙漠地区地下空洞掩体的机载探地雷达探测为实例,分别模拟了不同天线极化方向、天线高度及地表粗糙度情况下的机载探地雷达剖面,分析了各因素对机载探地雷达探测地下空洞目标体的影响.天线极化方向与目标体走向垂直更有利于地下目标体探测;天线距离地表越近,可以获得更高分辨率的雷达剖面;沙漠地表起伏越大,雷达剖面中的散射杂波能量越强,浅部地下目标体信号容易被掩盖.为了消除起伏地形造成的散射杂波,提出用逆时偏移成像技术对共炮集机载探地雷达数据进行偏移成像,成像结果优于基尔霍夫偏移成像结果.     

GAMIT/GLOBK中区域网和全球网绑定问题的探讨

高精度GPS分析软件GAMIT/GLOBK广泛应用于地壳运动研究,在地震监测预报中发挥了重要的作用.为了利用GAMIT/GLOBK软件得到精确的GPS定位结果,必须解决GPS区域网与全球网绑定过程中出现的一些问题.通过分析和总结,发现天线相位中心改正模型、卫星天线和测站天线信息误差,是影响绑定中兼容性的3个主要因素.最后根据处理经验提出了相应的解决方案,并介绍了具体的调试技巧.     

一款用于乳腺癌成像的低轮廓单极子天线设计

本文利用基于两层双共轭梯度-快速傅立叶变换的矩量法研究了一种新颖的宽带微带单极天线,该天线具有低轮廓特性,尺寸为24×31.7×1.6mm^3。设计的天线具有宽带特性,在3.1 GHz到11 GHz之间的反射系数Sn〈-10dB。详细探讨了上述天线的设计步骤和测试结果,结果证明该天线可以用于乳腺癌成像。     

岩石电学参数扫频测量

介绍了一种线圈法岩心复电参数扫频测量系统,并运用该系统对岩心进行了实验测量分析.结果表明,线圈法测量结果与电极法结果同样具有电频散特性,二者具有明显的相关性;测量响应与岩心的含水饱和度有着规律性的对应关系;虚部响应比实部响应对含水饱和度的变化更敏感.研究结果为发展电频谱测井新方法奠定了理论基础.     

Differences in GPS coordinate time series resulting from the use of individual instead of type-mean antenna phase center calibration model

It is well-known that the phase center of a Global Navigation Satellite System (GNSS) antenna is not a stable point coinciding with a mechanical reference. The phase center position depends on the direction of the received signal, and is antenna-and signaldependent. Phase center corrections (PCC) models of GNSS antennas have been available for several years. The first method to create antenna PCC models was the relative field calibration procedure. Currently only absolute calibration models are generally recommended for use. In this study we investigate the differences between position estimates obtained using individual and type-mean absolute antenna calibrations in order to better understand how receiver antenna calibration models contribute to the Global Positioning System (GPS) positioning error budget. The station positions were estimated with two absolute calibration models: the igs08.atx model, which contains typemean calibration results, and individual antenna calibration models. Continuous GPS observations from selected Polish European Permanent Network (EPN) stations were used for these studies. The position time series were derived from the precise point positioning (PPP) technique using the NAPEOS scientific GNSS software package. The results show that the differences in the calibrations models propagate directly into the position domain, affecting daily as well sub-daily results. In daily solutions, the position offsets, resulting from the use of individual calibrations instead of type-mean igs08.atx calibrations, can reach up to 5 mm in the Up component, while in the horizontal one they generally stay below 1 mm. It was found that increasing the frequency of sub-daily coordinate solutions amplifies the effects of type-mean vs individual PCC-dependent differences, and also gives visible periodic variations in time series of GPS position differences.     

Theoretical analysis and simulation for avoiding antenna oscillations without distributed resistance

The so-called Wu and King antenna pattern is widely used in GPR because of its simple design and construction features. The main disadvantage is its limited efficiency due to transmitter energy losses which occur through lumped resistors. Based on the analysis of the electromagnetic field behaviour across the antenna, it is possible to replace the effect of the resistors by either storing the energy of the electric pulses, or damp them by means of one matched resistor, which will theoretically improve the efficiency of the antenna. In this paper we provide a theoretical analysis using a modified transmission line model together with simulation based on delayed potentials among other electromagnetic software, and measurement results using an impulse transmitter with fast MOSFET switches and a matched resistor that support this idea.