人造地球卫星VLBI观测的相对论时延模型

理论研究表明，VLBI观测技术将为空间目标的监测提供一种先进的、有效的技术手段，能够对高空和深空目标进行全天时、全天候的高精度监测定位。以太阳系质心参考系和非旋转地球质心参考系的坐标转换关系为基础，推导了人造地球卫星地面VLBI观测的相对论时间延迟模型，给出了一个通用的解析表达式式(14)，这一公式严格解析又无误差，建议采用本公式。同时详细地讨论了公式的适用范围和各种舍掉项的量级估计，并详细给出了时间延迟理论模型的计算步骤。     

河外射电源地面VLBI观测的相对论时延模型

重新研究了河外射电源地面VLBI观测的相时论时间延迟模型，给出了一个严格解析的表达式。根据公式可以得到数据处理中常用的Zhu-Groten模型、Shapiro模型和IERS推荐模型，详细地给出了时间延迟理论模型的计算步骤，介绍了各种时间系统的转换和使用方法。     

高精度GPS城市沉降监测网的数据处理与精度分析

为了研究用GPS观测取代常规的水准测量方法来监测城市沉降变化的可行性，在宁波市建立了有7个点组成的GPS基准网和14个点组成的GPS监测网。在观测中采取了一定的措施，以获得高精度的高程分量。用Bernese软件对数据进行处理时顾及到对流层延迟的影响，采用Saastamoinen模型，获得了mm级的高程精度，这将有助于提高沉降监测的效率。     

Radio Tomography: A New Experimental Technique

The technique of radio tomography has developed during the past fifteen years from a theoretical concept to an established experimental method, used for geophysical investigations ofsolar-terrestrial processes. It also has potential in the mapping and modelling of the ionised atmosphere for application to practical radio systems. The method involves measurement of the electron content of the ionosphere along a large number of intersecting satellite-to-receiver ray paths, with tomographic inversion of the data to give a two-dimensional image of the spatial distribution of plasma density in the region of ray-path intersection. The emphasis in this review is on experimental tomographic observations, which have highlighted the capabilities and potential of the technique. Examples are presented from the equatorial sector where the equatorial anomaly is a significant feature, the mid-latitude sector where radio propagation is often influenced by the presence of the main ionisation trough, and the auroral and polar regions where footprints of solar-terrestrial coupling processes are frequently to be seen.     

Active interaction control of civil structures. Part 1: SDOF systems

This paper presents a family of semi‐active control algorithms termed as active interaction control (AIC) used for seismic response control of civil structures. AIC control algorithms include active interface damping (AID), optimal connection strategy (OCS) and tuned interaction damping (TID). A typical SDOF AIC system consists of a primary structure, an auxiliary structure and an interaction element. The auxiliary structure typically has stiffness comparable to that of the primary structure while its natural frequency is much higher than that of the primary structure. Interactions between the primary and the auxiliary structures are defined by specific AIC control logic such that vibrational energy is extracted from the primary structure into the auxiliary structure during a locking phase and dissipated in the auxiliary structure in the subsequent unlocking phase. The stability of AIC control algorithms is shown using the Lyapunov direct method. The efficacy of AIC control algorithms is demonstrated by the results of numerical simulations of SDOF systems subjected to seismic ground motions. Practical issues such as sampling period and time delay are also investigated in this study. Copyright © 2001 John Wiley & Sons, Ltd.     

Interdecadal Variations of Phase Delays Between Two Nino Indices at Different Time Scales

Phase delays between two Nino indices-sea surface temperatures in Nino regions 1 2 and 3.4 (1950-2001)-at different time scales are detected by wavelet analysis. Analysis results show that there are two types of period bifurcations in the Nifio indices and that period bifurcation points exist only in the region where the wavelet power is small. Interdecadal variation features of phase delays between the two indices vary with different time scales. In the periods of 40-72 months, the phase delay changes its sign in 1977: Nino 1 2 indices are 2-4 months earlier than Nino 3.4 indices before 1977, but 3-6 months later afterwards. In the periods of 20-40 months, however, the phase delay changes its sign in another way:Nino 1 2 indices are 1-4 months earlier before 1980 and during 1986-90, but 1-4 months later during 1980-83 and 1993-2001.     

地震数据采集系统延迟时研究与分析

详细介绍了地震采集系统延迟时的因素,并根据系统的理论对产生的原因进行了论证。同时对实际生产中的测试方法进行了研究和分析;最后提出了新的测试方法,并对实际生产提出了合理的建议,取得了预期的效果。     

导航卫星信号湿延迟参数化模型和数值模式的比较

对高精度导航卫星处理软件(GAMIT)确定的卫星信号湿延迟和香港天文台中尺度数值模式(ORSM)所计算的湿延迟进行了比较,发现二者相关系数为0.99,偏差为3mm,平均绝对偏差为26.7mm,基本不存在系统性的偏差。卫星在天顶时,两者偏差最小,随着卫星仰角的降低,偏差增大,在天顶角70-80°时,两者确定信号湿延迟平均绝对偏差可达30mm。     

Comparison of flux measurement by open-path and close-path eddy covariance systems

For flux measurement, the eddy covariance technique supplies a possibility to directly measure the exchange between vegetation and atmosphere; and there are two kinds of eddy covariance systems, open-path and close-path systems. For the system error, it may result in difference of flux measurements by two systems. Therefore, it is necessary to compare the measured results from them. ChinaFLUX covers of eight sites applied the micrometeorological method, in which Changbai Mountains (CBS) and Qianyanzhou (QYZ) carried out open-path eddy covariance (OPEC) and close-path eddy covariance (CPEC) measurements synchronously.In this paper the data sets of CBS and QYZ were employed. The delay time of close-path analyzer to the open-path analyzer was calculated; the spectra and cospectra of time-series data of OPEC and CPEC were analyzed; the open-path flux measurement was used as a standard comparison, the close-path flux measurement results were evaluated. The results show that, at two sites the delay time of CO2 density for close-path analyzer was about 7.0-8.0 s, H2O density about 8.0-9.0 s; the spectrum from the open-path, close-path and 3D sonic anemometer was consistent with the expected -2/3 slope (log-log plot), and the cospectra showed the expected slope of -4/3 in the internal subrange; the CO2 flux measured by the close-path sensor was about 84% of that of open-path measurement at QYZ, about 80% at CBS, and the latent heat flux was balanced for two systems at QYZ, 86% at CBS. From the flux difference between open-path and close-path analyzers, it could be inferred that the attenuation of turbulent fluctuations in flow through tube of CPEC affected H2O flux more significantly than CO2 flux. The gap between two systems was bigger at CBS than at QYZ; the diurnal variation in CO2 flux of two measurement systems was very consistent.     

中国中部地区TID激发源的统计分布

利用武汉电离层观象台1985-1990年间的高频多普勒台阵观测资料，采用射线追踪方法，对观测到的电离层重力波扰动（TID）进行了定源研究，从统计上分析了扰动源的地理分布、季节变化以及与地磁活动的关系．结果表明，中国中部上空TID的激发源主要出现在春夏季的四川盆地和冬半年的山口地区．扰动的激发可能与青藏高原地形隆起对这两个地区的气象活动的影响有关．此外，有少部分尺度较大的扰动出现在冬半年，它们可能来自极区．