航空物探对华南某地区天然放射性辐射环境的调查

在华南某地区开展了航空物探调查,发现该地区天然放射性辐射水平相当高,并查明了引起的地质因素和分布特征,评估了天然放射性高辐射地区居民平均有效接收剂量,讨论了人类活动导致富含放射性石料的搬运、扩散所致使的危害.航空物探资料的利用为环境保护和治理规划提供了重要依据.     

Investigation of the Calibration Function of Local Earthquake Magnitude （ ML ） in the Fujian-Taiwan Region

The author carefully selected earthquakes with M_L=4.0～5.0, 215 occurring in the crust in the Taiwan region. The attenuation characteristics of maximum displacement recorded by the Fujian digital network have been obtained by multi-analysis as follows:logA=2.07 231.1/Δ (150km≤Δ≤650km) And the corresponding expression of calibration function is, R(Δ)=3.45-231.1(1/Δ-0.01) (150km≤Δ≤650km) Then, the author determined the magnitude and its error with the data from the Fujian network using the calibration function brought forward in 1997 and the above formula for 790 earthquakes occurring in the crust in the Taiwan region from September 1997 ～ August 2005. The result indicates that the average error of the network is 0.20 with the former and 0.18 with the latter. The average error is 0.13 with the latter with station correction. Compared with the magnitude determined by Taiwan seismologists, the magnitude value with the former is lower by 0.50 on average and that with the latter is higher by 0.08 on average.     

Towards error‐free hybrid simulation using mixed variables

Two procedures are developed and implemented in a hybrid simulation system (HSS) with the aim of enhancing the accuracy and reliability of the online, i.e. pseudo‐dynamic, test results. The first procedure aims at correcting the experimental systematic error in executing the displacement command signal. The error is calculated as the difference between command and feedback signals and correlated to the actuator velocity using the least‐squares method. A feed‐forward error compensation scheme is devised leading to a more accurate execution of the test. The second procedure employs mixed variables with mode switching between displacement and force controls. The newly derived force control algorithm is evaluated using a parametric study to assess its stability and accuracy. The implementation of the mixed variables procedure is designed to adopt force control for high stiffness states of the structural response and displacement control otherwise, where the resolution of the involved instruments may favour this type of mixed control. A simple pseudo‐dynamic experiment of steel cantilever members is used to validate the HSS. Moreover, two experiments as application examples for the two developed procedures are presented. The two experiments focus on the seismic response of (a) timber shear walls and (b) reinforced concrete frames with and without unreinforced masonry infill wall. Copyright © 2007 John Wiley & Sons, Ltd.     

Stability and accuracy analysis of outer loop dynamics in real‐time pseudodynamic testing of SDOF systems

Real‐time pseudodynamic (PSD) testing is an experimental technique for evaluating the dynamic behaviour of a complex structure. During the test, when the targeted command displacements are not achieved by the test structure, or a delay in the measured restoring forces from the test structure exists, the reliability of the testing method is impaired. The stability and accuracy of real‐time PSD testing in the presence of amplitude error and a time delay in the restoring force is presented. Systems consisting of an elastic single degree of freedom (SDOF) structure with load‐rate independent and dependent restoring forces are considered. Bode plots are used to assess the effects of amplitude error and a time delay on the steady‐state accuracy of the system. A method called the pseudodelay technique is used to derive the exact solution to the delay differential equation for the critical time delay that causes instability of the system. The solution is expressed in terms of the test structure parameters (mass, damping, stiffness). An error in the restoring force amplitude is shown to degrade the accuracy of a real‐time PSD test but not destabilize the system, while a time delay can lead to instability. Example calculations are performed for determining the critical time delay, and numerical simulations with both a constant delay and variable delay in the restoring force are shown to agree well with the stability limit for the system based on the critical time delay solution. The simulation models are also used to investigate the effects of a time delay in the PSD test of an inelastic SDOF system. The effect of energy dissipation in an inelastic structure increases the limit for the critical time delay, due to the energy removed from the system by the energy dissipation. Copyright © 2007 John Wiley & Sons, Ltd.     

Variability of Convective Activity over the North Indian Ocean and its Associations with Monsoon Rainfall over India

The present study is an attempt to examine the variability of convective activity over the north Indian Ocean (Bay of Bengal and Arabian Sea) on interannual and longer time scale and its association with the rainfall activity over the four different homogeneous regions of India (viz., northeast India, northwest India, central India and south peninsular India) during the monsoon season from June to September (JJAS) for the 26 year period (1979 to 2004). The monthly mean Outgoing Long-wave Radiation (OLR) data obtained from National Oceanic and Atmospheric Administration (NOAA) polar orbiting spacecraft are used in this study and the 26-year period has been divided into two periods of 13 years each with period-i from 1979 to 1991 and period -ii from 1992 to 2004. It is ascertained that the convective activity increases over the Arabian Sea and the Bay of Bengal in the recent period (period -ii; 1992 to 2004) compared to that of the former period (period -i; 1979 to 1991) during JJAS and is associated with a significantly increasing trend (at 95% level) of convective activity over the north Bay of Bengal (NBAY). On a monthly scale, July and August also show increase in convective activity over the Arabian Sea and the Bay of Bengal during the recent period and this is associated with slight changes in the monsoon activity cycle over India. The increase in convective activity particularly over the Arabian Sea during the recent period of June is basically associated with about three days early onset of the monsoon over Delhi and relatively faster progress of the monsoon northward from the southern tip of India. Over the homogeneous regions of India the correlation coefficient (CC) of OLR anomalies over the south Arabian Sea (SARA) is highly significant with the rainfall over central India, south peninsular India and northwest India, and for the north Arabian Sea (NARA), it is significant with northwest India rainfall and south peninsular rainfall. Similarly, the OLR anomalies over the south Bay of Bengal (SBAY) have significant CC with northwest India and south peninsular rainfall, whereas the most active convective region of the NBAY is not significantly correlated with rainfall over India. It is also found that the region over northeastern parts of India and its surroundings has a negative correlation with the OLR anomalies over the NARA and is associated with an anomalous sinking (rising) motion over the northeastern parts of India during the years of increase (decrease) of convective activity over the NARA.     

带权约束参数平差在工程控制网优化中的应用

介绍用带权约束平差原理编制的工程控制网试验修正法设计和平差程序,并用于设计工程导线和平差变形观测控制网等实际工程的例子,据此提供一些结论和建议.     

矢量GIS数据位置精度评价

论述了采用野外测量法评价矢量GIS数据位置精度的过程，为精确评价位置精度提出了相应的质量控制措施，讨论了必要的检测点数目、检测点选择等，并对该方法的适用范围作了说明。     

光学测微器的原理、检定及误差分析

着重讨论了高精度光学测微器的基本工作原理、检定方法及误差分析。     

经纬仪i角检定中的符号问题

通过对经纬仪横轴与竖轴垂直度的测试分析，就检定规程JJG414-94中所得供的计算公式的符号问题，提出了更正意见。