利用谱分析法估计GRACE Follow-On地球重力场的空间分辨率     

庞振兴  姬剑锋  肖云  李迎春 《测绘学报》2012,(3):333-338

利用轨道扰动引力谱和大地水准面累计误差谱分析的方法估计未来GRACE(gravity recovery and climateexperiment)Follow-On卫星反演地球重力场的空间分辨率。基于GRACE Follow-On卫星的轨道特性,计算其在高空所受到的径向扰动引力,并根据谱特性及星载加速度计的测量噪声水平分析该卫星能反演重力场的阶数。利用EGM96重力场模型分别计算200 km和250 km轨道高度处的扰动引力谱。分析其特性表明:在两个轨道高度处分别能反演281阶和242阶的地球重力场模型。给出大地水准面累计误差谱模型,并计算200 km和250 km轨道高度处大地水准面累计误差谱。分析其谱特性表明:在两个轨道高度处分别能反演至286阶和228阶的地球重力场模型。  相似文献   

考虑接连两次地震影响的群体建筑物震害预测方法     

马骏驰苏经宇  窦远明郭小东 《地震工程与工程振动》2005,25(5):91-94

利用文献[2]推荐的方法得到了不同地震组合情况下的等效地震影响系数,将其与传统的钢筋混凝土框架结构震害预测方法相结合,得到两次地震作用对建筑物所造成的损伤,进而得到了该类建筑物的群体震害预测结果。结果分析表明,接连两次地震对建筑物的累积破坏作用显著。最后以福建省泉州市规划区范围内的钢筋混凝土框架结构群体震害预测为例,证明了该方法具有简便实用的特点。  相似文献   

Comparative analysis of real-time precise point positioning zenith total delay estimates   总被引：1，自引：0，他引：1  

F. Ahmed  P. Václavovic  F. N. Teferle  J. Douša  R. Bingley  D. Laurichesse 《GPS Solutions》2016,20(2):187-199

The continuous evolution of global navigation satellite systems (GNSS) meteorology has led to an increased use of associated observations for operational modern low-latency numerical weather prediction (NWP) models, which assimilate GNSS-derived zenith total delay (ZTD) estimates. The development of NWP models with faster assimilation cycles, e.g., 1-h assimilation cycle in the rapid update cycle NWP model, has increased the interest of the meteorological community toward sub-hour ZTD estimates. The suitability of real-time ZTD estimates obtained from three different precise point positioning software packages has been assessed by comparing them with the state-of-the-art IGS final troposphere product as well as collocated radiosonde (RS) observations. The ZTD estimates obtained by BNC2.7 show a mean bias of 0.21 cm, and those obtained by the G-Nut/Tefnut software library show a mean bias of 1.09 cm to the IGS final troposphere product. In comparison with the RS-based ZTD, the BNC2.7 solutions show mean biases between 1 and 2 cm, whereas the G-Nut/Tefnut solutions show mean biases between 2 and 3 cm with the RS-based ZTD, and the ambiguity float and ambiguity fixed solutions obtained by PPP-Wizard have mean biases between 6 and 7 cm with the references. The large biases in the time series from PPP-Wizard are due to the fact that this software has been developed for kinematic applications and hence does not apply receiver antenna eccentricity and phase center offset (PCO) corrections on the observations. Application of the eccentricity and PCO corrections to the a priori coordinates has resulted in a 66 % reduction of bias in the PPP-Wizard solutions. The biases are found to be stable over the whole period of the comparison, which are criteria (rather than the magnitude of the bias) for the suitability of ZTD estimates for use in NWP nowcasting. A millimeter-level impact on the ZTD estimates has also been observed in relation to ambiguity resolution. As a result of a comparison with the established user requirements for NWP nowcasting, it was found that both the G-Nut/Tefnut solutions and one of the BNC2.7 solutions meet the threshold requirements, whereas one of the BNC2.7 solution and both the PPP-Wizard solutions currently exceed this threshold.  相似文献   

Mechanical Initiation and Propagation Mechanism of a Thrust Fault: A Case Study of the Yima Section of the Xiashi-Yima Thrust (North Side of the Eastern Qinling Orogen,China)     

Wu Cai  Linming Dou  Zhenlei Li  Jiang He  Hu He  Yanlu Ding 《Rock Mechanics and Rock Engineering》2015,48(5):1927-1945

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Roadway Stagger Layout for Effective Control of Gob-Side Rock Bursts in the Longwall Mining of a Thick Coal Seam     

Zhen-lei Li  Lin-ming Dou  Wu Cai  Gui-feng Wang  Yan-lu Ding  Yong Kong 《Rock Mechanics and Rock Engineering》2016,49(2):621-629

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Extracting damages caused by the 2008 Ms 8.0 Wenchuan earthquake from SAR remote sensing data     

Yanfang Dong  Qi Li  Aixia Dou  Xiaoqing Wang 《Journal of Asian Earth Sciences》2011,40(4):907-914

Bad weather conditions usually limit the acquisition of optical remote sensing images, while all day and all weather synthetic aperture radar (SAR) shows the ability of providing timely remote sensing data for emergency response and rescue works after earthquake. Because SAR is sensitive to the surface changes caused by earthquake, the modified electromagnetic behaviour by geological disasters and the collapse of buildings can be recorded in SAR images as backscattering intensity changes. Absolute radiometric calibration was performed to SAR products to derive backscattering coefficient sigma nought from image digital number (DN). Based on change detection methods, Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) data and TerraSAR-X data acquired for the Ms 8.0 Wenchuan earthquake were used to extract earthquake damage information. This study revealed that landslides showed stronger backscattering and barrier lakes showed lower backscattering in post-earthquake 10 m ALOS PALSAR images comparing to pre-earthquake, and collapsed buildings showed lower backscattering compared to un-collapsed buildings in 1 m TerraSAR-X image. Results showed that SAR data with different spatial resolutions are useful for different earthquake damage information extraction: medium spatial resolution SAR data, e.g. 10 m ALOS PALSAR data, were efficient for secondary geological disaster extraction; high-resolution SAR data, e.g. 1 m TerraSAR-X data, with the help of ancillary GIS data or high-resolution optical data, could be used to extract building collapse information in urban areas. This study indicates that SAR remote sensing data can provide earthquake damage information at early emergency stage and assist the field surveying, further damage assessment and post-earthquake reconstruction.  相似文献   

The simulation of snowmelt runoff in the ungauged Kaidu River Basin of TianShan Mountains,China   总被引：6，自引：1，他引：5  

Yan Dou  Xi Chen  Anmin Bao  Lanhai Li 《Environmental Earth Sciences》2011,62(5):1039-1045

Snowmelt runoff is an important source of water resources in the arid mountain area. Modelling snowmelt runoff for cold regions remains a problematic aspect because of the lack of data by gauges in large basins. In order to overcome the shortage of measured data in the snowmelt runoff modelling, the temperature interpolation method would greatly help in improving the simulation accuracy and describing the snow-hydrological behaviours of the study catchments. In this study, the temperature is the principal variable used to estimate the importance of the melting of snow cover using the snowmelt runoff model. Five different temperature interpolation attempts were performed over the Kaidu River Basin for the snowmelt season of the year 2000. Three temperature inputs were taken directly from the individual weather stations in or near the study area, and the other two temperature inputs were interpolated from the three weather stations. The results indicated that the temperature estimated from different methods could result in quite a difference in runoffs in comparison with the observed ones. The simulation results using average temperature from the three stations showed good results; the simulation run with the weighted average temperature generated a lower R ² than the average temperature of three stations and using temperature directly adopted from three individual stations gave various results. The weather stations used to perform the snowmelt runoff simulation should be located in the place which is most representative of the mountain weather conditions, and the land cover and topography that those stations represented also play an important role in the snowmelt runoff simulation.  相似文献   

A pattern recognition approach to evaluation of soil liquefaction potential using piezocone data     

Dou Yiqiang  John B. Berrill 《Soil Dynamics and Earthquake Engineering》1993,12(2)

A pattern recognition approach to liquefacation evaluation is propoesed. The state of any soil layer at a level ground site subject to seismic loads is represented by a pattern in a seven-dimensional feature space and can be classified into one of three classes: liquefiable cohesive soil, and non-liquefiable cohesionless soil. The liquefaction potential of the soil layer can be assessed according to the probabilities of the pattern belonging to the three classes. Training patterns derived from field data (piezocone (CPTU) data and maximum ground acceleration) from sites which liquefied or did not liquefy during earthquakes in New Zealand are randomly chosen to design a pattern recognition system to provide an optimal estimation of the liquefaction potential of any soil stratum of interest. Two recognition systems have been set up to estimate the state-conditional probability density function. One is based on a Parzen window approach in which no knowledge of the probabilistic structure of the training patterns is assumed; the other is based on a parameter estimation approach assuming a multivariate normal distribution. The error rate of recognition by the Parzen window approach is 6·9% when taking the window size as 1·5, and the error rate by the parameter estimation approach, which can be easily, is 7·7%. implemented without reference to our training patterns  相似文献   

地球化学场分解的理论与方法   总被引：3，自引：0，他引：3  

孟宪伟  余先川 《地球科学进展》1994,9(6):59-64

由于多期地质地球化学作用的相互叠加，地球化学场通常表现为复杂的叠加场。在叠加场内，元素组合的成因特征、变差函数的多级套合结构和多标度分形谱能有效地反映地质地球化学的多期性。相应地，用Ｒ型因子分析法、单变量因子克立格法和多标度分形谱便能有效地实现地球化学场的分解。  相似文献   

TRAJECTORY ANALYSES OF THE DUSTSTORMS OVER EAST ASIA^*          下载免费PDF全文

Sheng Peixuan  Meng Guangli  Dou Wenyu  Qin Yu 《Acta Meteorologica Sinica》1994,8(2):239-246

The transports of dust are calculated using 3-dimensional(3-D) trajectory method for three cases of duststorms in the terrain-following coordinate system,and the synoptic processes are also discussed for each case.The case of 17-20 April 1980,a severe duststorm was associated with the rapid development of a cyclone over the Mongolia Plateau.The dust moved from west to east across several deserts,formed a typical dust path in spring.The other two were weaker and the dust was triggered by the strong wind behind the cold front from northwest or north.Because the vertical velocity is considered in 3-D trajectory analysis,trajectories calculated should better reveal the transport rule of the dust particles and the results seem to be more consistent with the synoptic processes.The trajectory analysis on the 2-D isobaric surfaces is simpler but can be used only in the conditions with weak vertical wind shear and weak vertical velocity.The difference of trajectories at lower levels between two methods may be caused by the different treatment of orography.  相似文献