区域短波通信台网选频的研究

河南省地震局短波通信台网的工作频率被限制在短波的低频段，受干扰严重，中心台又位于市中心，环境噪声电平很高，加之，局网内可用的电台大部分发射功率小、抗干扰性能差。这些因素给通信台网的工作频率选择带来困难。为提高区域通信的质量，在对短波电离层信道传播特性进行分析的基础上，结合本地大气噪声和环境噪声的实际情况，对河南省地震局通信网的选频问题进行了研究，给出了选频的原则和方法，介绍了选频试验的结果和体会。     

Simulation of structural response under high‐frequency ground excitation

The structural response to high‐frequency ground motions is complicated due to the involvement of local‐mode vibration. At present such a characteristic is not well recognized and this can cause confusion over the analytical and experimental modelling of the corresponding response and damage. The fact that most existing regulatory guides for limits on allowable construction vibrations are necessarily simplified for administrative reasons calls upon the derivation of more sophisticated approaches for special cases. This requires accumulation of pertinent experimental evidence. This paper attempts to provide some insights into the local‐mode dynamic response characteristics, with emphasis on appropriate modelling techniques and experimental measurements. A preliminary testing program is reported, in which efforts were made to reproduce high‐frequency response with a reduced scale reinforced concrete model with shaking table facilities. The results demonstrate the dependence of the response amplitudes with the excitation frequency. On a ppv‐basis, the current test results indicate that a substantial increase of the allowable ppv value from those specified by various standards may be considered for structural damage to reinforced concrete building structures. More analytical and experimental data are needed for further evaluation of the local‐mode effects and to quantify their impact on the structural damage process. Copyright © 2001 John Wiley & Sons, Ltd.     

亚洲季风区ITCZ对华北雨季异常的可能影响

分析了冬、春季亚洲季风区ITCZ活动对华北夏季降水的影响。用OLR资料定义了ITCZ综合指数，分析表明该指数能比较清晰、客观地综合反映出亚洲季风区深对流活动的强度和位置。用该指数分析了华北多雨年和少雨年前期热带大范围对流活动的变化特征。印度和东亚季风区的ITCZ活动在多雨和少雨年显示出明显不同。华北夏季降水与2-4月ITCZ综合指数的时滞相关性最明显。这种时滞相关可能与球面Rossby波的频散相联系，并可以为华北夏季降水的长期预报提供新的参考依据。低频振荡分析表明，多雨年南北两个半球的低频振荡强度较强，范围较大，并不断由南向北传播，这种传播很可能与副热带高压的北跳有关。而少雨年低频振荡在南半球或热带地区呈准静止状态。     

Asynchronism-synchronism of regional precipitation in South-to-North Water Transfer planned areas

1 IntroductionThe geographical feature of China is quite complex with an obvious spatial heterogeneity. At the sense of spatial distribution of precipitation, under the impacts of the relative position of land to ocean and the monsoon climate, the amount of precipitation tends to decrease from south to north and from southeast to northwest. According to the hydrological regionalization, the North China Plain, one of the social and economic centers of China[1,2], is a region short of water re…     

核转变能与理论地质年表

本文讨论了地球内部长寿期放射性同位素衰变能的存量 ,给出地球脉动频率和频数公式 ,并据以重新建立了理论地质年表 ,解释了地球自转变化、地磁场倒转和黄赤交角变化等。     

Ultra low frequency electromagnetic wave anomaly and its spectrum characteristics before earthquakes

Many observations and researches show that abundant and intense ultra low frequency (ULF) electromagnetic anomalies appeare before local earthquakes. In order to understand this phenomenon systematically, the transmission property and the formation of the seismic-electric dipole are discussed in this paper. The results show that the vertical component of the ULF electric anomaly before earthquake has the properties of better penetration, less disturbance and high signal-to-noise ratio. The signal can be easily extracted and received. The anomaly should be an important way to seek for reliable short-term and imminent earthquake precursors. After the spectrum analysis of the (ULF) electric field anomalies, we found that the periods of the anomaly related to local earthquakes are from a few minutes to a dozens minutes. There is a relation between the spectrum of the anomaly and the epicentral distance. The ULF electric field anomalies strongly rely on the orientation of the seismogenic zone. The percolation electric field anomaly and its spectrum amplitude do not have obvious relation with the size of local earthquakes. Contribution No. 94A0097, Institute of Geophysics, SSB, China. The English version is improved by Prof. Guo-Hua FAN, Institute of Geophysics, State Seismological Bureau.     

Ultra low frequeney electromagnetic wave anomaly and its spectrum characteristics before earthquakes

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A possible UL Fseismice lectro-magnetic emission

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Appraisal of regional and index flood quantile estimators

Our results illustrate the performance of at-site and regional GEV/PWM flood quantile estimators in regions with different coefficients of variation, degrees of regional heterogeneity, record lengths, and number of sites. Analytic approximations of bias and variance are employed. For realistic GEV distributions and short records, the index-flood quantile estimator performs better than a 2-parameter GEV/PWM quantile estimator with a regional shape parameter, or a 3-parameter at-site GEV/PWM quantile estimator, in both humid and especially in arid regions, as long as the degree of regional heterogeneity is moderate. As regional heterogeneity or record lengths increases, 2-parameter estimators quickly dominate. Flood frequency models that assign probabilities larger than 2% to negative flows are unrealistic; experiments employing such distributions provide questionable results. This appraisal generally demonstrates the value of regionalizing estimators of the shape of a flood distribution, and sometimes the coefficient of variation.