时频测控技术的发展   总被引：11，自引：1，他引：11  

周渭  王海 《时间频率学报》2003,26(2):87-95

目前，在所有的物理量中时间与频率标准的物理实现具有最高的准确度和稳定度，它们的发展不但在计量技术中，而且在几乎整个高科技领域中起着十分重要的作用。这方面的发展一直受到发达国家的高度重视。根据近年来与国外同行的技术交流和了解的情况，对时频测控技术的发展和影响等作了介绍。  相似文献   

2D stabilised analytic signal method in DC pole-pole potential data interpretation     

Paras R. Pujari  Rambhatla G. Sastry 《Journal of Earth System Science》2003,112(1):37-49

Using analytic signal method, interpretation of pole-pole secondary electric potentials due to 2D conductive/resistive prisms is presented. The estimated parameters are the location, lateral extent or width and depth to top surface of the prism. Forward modelling is attempted by 2D-Finite Difference method. The proposed stabilised analytic signal algorithm (RES2AS) uses Tikhonov’s regularization scheme and FFT routines. The algorithm is tested on three theoretical examples and field data from the campus of Roorkee University. The stability of RES2AS is also tested on synthetic error prone secondary pole-pole potential data.  相似文献   

长效振弦式锚索测力计应用研究   总被引：1，自引：0，他引：1  

王清标  吕爱钟  邓铁六 《岩土力学》2003,(Z1)

介绍了长效振弦式锚索测力计传感器的工作原理、结构特点、技术性能和配套仪器,并对主要相关技术的应用研究成果作了论述:(1)弱激发电路解决频率不一致问题;(2)微小变形原则解决长期稳定性问题;(3)新数学模型提高了传感器准确度,二次仪表提高了传感器准确度。  相似文献   

The impact of accelerometry on CHAMP orbit determination   总被引：6，自引：0，他引：6  

S. Bruinsma  S. Loyer  J. M. Lemoine  F. Perosanz  D. Tamagnan 《Journal of Geodesy》2003,77(1-2):86-93

 The contribution of the STAR accelerometer to the CHAMP orbit precision is evaluated and quantified by means of the following results: orbital fit to the satellite laser ranging (SLR) observations, GPS reduced-dynamic vs SLR dynamic orbit comparisons, and comparison of the measured to the modeled non-gravitational accelerations (atmospheric drag in particular). In each of the four test periods in 2001, five CHAMP arcs of 2 days' length were analyzed. The mean RMS-of-fit of the SLR observations of the orbits computed with STAR data or the non-gravitational force model were 11 and 24 cm, respectively. If the accelerometer calibration parameters are not known at least at the few percent level, the SLR orbit fit deteriorates. This was tested by applying a 10% error to the along-track scale factor of the accelerometer, which increased the SLR RMS-of-fit on average to 17 cm. Reference orbits were computed employing the reduced-dynamic technique with GPS tracking data. This technique yields the most accurate orbit positions thanks to the estimation of a large number of empirical accelerations, which compensate for dynamic modeling errors. Comparison of the SLR orbits, computed with STAR data or the non-gravitational force model, to the GPS-based orbits showed that the SLR orbits employing accelerometer observations are twice as accurate. Finally, comparison of measured to modeled accelerations showed that the level of geomagnetic activity is highly correlated with the atmospheric drag model error, and that the largest errors occur around the geomagnetic poles. Received: 7 May 2002 / Accepted: 18 November 2002 Correspondence to: S. Bruinsma Acknowledgments. The TIGCM results were obtained from the CEDAR database. This study was supported by the Centre National d'Etudes Spatiales (CNES). The referees are thanked for their helpful remarks and suggestions.  相似文献   

2002年6～7月安阳市连续性高温天气过程分析     

张文喜葛相英  陈海成王爱玲 《河南气象》2003,(2):26-27

利用1970～2000年安阳市高温天气资料和实时资料，分析了安阳市2000年6～7月两次区域性连续高温天气的天气形势、地面要素特征、地形影响及高温天气变化周期，揭示了高温天气的成因，找出了预报着眼点。  相似文献   

钦州市7月旱涝的异常环流特征及前期强信号初探     

何小娟 《气象研究与应用》2003,24(3):28-30

选取钦州市7月8个重旱、13个重涝年,从天气气候角度着重对其前期冬季(12～2月)500hPa环流形势、环流特征指数以及青藏高原冬季积雪、北太平洋海温进行对比诊断分析,发现7月旱涝年前冬大型环流已出现较大的差异,其前一年12月的极涡强度、高原高度场,北太平洋赤道海温,以及前冬(12～2月)西太平洋副高面积指数、前冬青藏高原冬季积雪的多少,在旱涝年也有明显的不同,可作为旱涝发生的前期强信号,并确定其描述指标。  相似文献   

利用数字图像处理技术提高地震剖面图像信噪比   总被引：1，自引：2，他引：1  

陈凤  李金宗  黄建明  李冬冬 《地球物理学进展》2003,18(4):758-764

提出了利用数字图像处理技术提高地震剖面信噪比的新方法，首先根据数字图像处理要求的格式，对地震剖面数据进行转换，得到地震剖面图像，分析了地震数据特点和初步地震图像的实验结果后，设计了新的预处理方法——“二维沿层滤波”，在此基础上，利用可以计算帧间运动速度及其变化都较大的改进的光流分析技术，计算出多幅地震剖面对应点的偏移量，然后应用图像积累技术对这多幅地震剖面进行积累，实现对三维地震数据体提高信噪比的处理，该方法充分利用了三维地震信息，不但可以提高整个数据体的信噪比，而且可以减少信号能量的损失，并保持原来的信号能量关系，使地震剖面的质量得到明显提高，为地震解释奠定良好的基础。  相似文献   

长江巨洪的强信号探讨     

冯利华 《地球物理学进展》2003,18(4):772-775

分析了1900年以来长江3次巨洪的3个强信号：(1)太阳黑子活动，(2)厄尔尼诺事件，(3)青藏高原南部大震，它们对大气环流异常的影响分别称为日气作用、海气作用、地气作用，依据长江巨洪和3个强信号的基本事实，讨论了长江发生巨洪的统计规律，指出当3个强信号的出现时间互相重叠时，长江很可能发生巨洪，如果再叠加其它信号，长江发生巨洪的量级更大，这对长江巨洪的超长期预期具有重要的指示作用。  相似文献   

室内土工模型试验的新方法——桩基渗水力土工模型试验     

方磊  李广信 《高校地质学报》1997,3(4):451-457

本文通过桩基渗水力工模型试验实例，介绍了一种新的室内土工模型试验方法－渗水力土工模型试验。它利用水在土体中的渗流来提供土工模型试验中必须的体积力，因而克服了常规模型试验和离心模型试验中一些缺陷。该方法在桩基研究及工程实际中具有良好的应用前景。  相似文献   

Candidate precursors: pulse-like geoelectric signals possibly related to recent seismic activity in Japan   总被引：1，自引：0，他引：1  

Yuji Enomoto  Akito Tsutsumi  Yukio Fujinawa  Minoru Kasahara  Hiroshi Hashimoto 《Geophysical Journal International》1997,131(3):485-494

Telemetric network observations of pulse-like geoelectric charge signals using a vertical dipole buried under the ground were undertaken at various observation sites over a wide area in Japan from April 1996. From continuous records of the signals during the six months following that, we attempted to select anomalous signals, possibly related to seismic electric activity. Special attention was paid to the elimination of noise resulting from industrial and meteorological electric activity, comparison with other electromagnetic signals in the VLF band and the relation between the precursor period and the distance from the eventual main shock that occurred in Japan. Four candidate precursor electric signals, which were not contaminated by industrial and meteorological electric activity, were then selected, of which the second appeared before the Akita-ken Nairiku-nanbu earthquake swarm, for which the maximum M = 5.9 occurred on 1996 August 11, and the third and fourth before the Chiba-ken Toho-oki earthquake, M = 6.6, on 1996 September 11. A tentative qualitative model explaining why the candidate precursory signal is related to stress building up before an earthquake is presented in terms of the electrification of gases released from fracturing rocks immediately prior to the main shock.  相似文献