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991.
INTRODUCTIONFromthe1990’s,thescallop,C.farreri,culturedinthenorthernChinaSea,deterioratedinsize,healthandoutputbecauseofhighstockingdensities,shortageofnaturalfoodanddiseases.Massmortalityof50%-90%occurredinJiaozhouBay,Qingdao,andSishiliwanBay,Yantai,fromJulyto… 相似文献
992.
Li Zhixiong Zhang Guomin Fu Zhengxiang and Zhang YongxianState Seismological Bureau Beijing China Center for Analysis Prediction SSB Beijing China 《中国地震研究》1996,(4)
In this paper,characteristics of spatial and temporal variation of linear fitting goodness before some moderately strong earthquakes(Ms≥5.0)in the eastern part of China(east of longitude 180)are studied according to the famous Gutenberg-Richter's relation expressed as lgN=a-bM,by using the moderate and small events that occurred in and around the source area.The results show that the linear goodness of fitting varies abnormally prior to these moderately strong earthquakes.In the early stage of the earthquake preparatory process,distribution of the energy released through small events in and around the source area is isostatic and the fitting goodness approximates 1,while the distribution of the energy turns to be isostatic before moderately strong earthquakes,leading to the obvious decrease of the linear goodness of fitting.This phenomenon could be a medium term anomaly and a medium term criterion for moderately strong earthquake prediction. 相似文献
993.
郭东屏 《地球科学与环境学报》1993,(Z2)
本文采用连续介质水电比拟法,对不完整河旁三维井流与完整河旁二维井流作了对比研究。结果表明,当其他条件相同时,前者水井出水量只能达到后者出水量的80%左右;实测的两类流场图,显示出三维井流与二维井流的许多重要特征和区别,对此作了详细对比分析,阐明了流量显著变小的机理;指出不完整河旁井流问题按三维流计算的必要性;对当前工作提出了重要且可行的建议。 相似文献
994.
制备了配合物键合异构体[Co(NH3)5NO2]Cl2和[Co(NH3)5ONO]Cl2,并用红外光谱测定了它们的结构. 相似文献
995.
用线性规划法求解瞬变电磁场反射系数 总被引:1,自引:0,他引:1
讨论了在水平层状介质中的反射系数的物理意义 ,推出时间域含有以反射系数序列为未知项的欠定方程组 ,提出用线性规划法求解瞬变电磁场反射系数序列 ,并给出求解思路和程序框图。对两个理论模型进行了处理 ,计算出了其反射系数。算例分析结果表明 ,算法可靠 ,程序可行。这一方法可用于瞬变电磁成像数值计算中。 相似文献
996.
997.
Initial results of centralized autonomous orbit determination of the new-generation BDS satellites with inter-satellite link measurements 总被引:3,自引:0,他引:3
Chengpan Tang Xiaogong Hu Shanshi Zhou Li Liu Junyang Pan Liucheng Chen Rui Guo Lingfeng Zhu Guangming Hu Xiaojie Li Feng He Zhiqiao Chang 《Journal of Geodesy》2018,92(10):1155-1169
Autonomous orbit determination is the ability of navigation satellites to estimate the orbit parameters on-board using inter-satellite link (ISL) measurements. This study mainly focuses on data processing of the ISL measurements as a new measurement type and its application on the centralized autonomous orbit determination of the new-generation Beidou navigation satellite system satellites for the first time. The ISL measurements are dual one-way measurements that follow a time division multiple access (TDMA) structure. The ranging error of the ISL measurements is less than 0.25 ns. This paper proposes a derivation approach to the satellite clock offsets and the geometric distances from TDMA dual one-way measurements without a loss of accuracy. The derived clock offsets are used for time synchronization, and the derived geometry distances are used for autonomous orbit determination. The clock offsets from the ISL measurements are consistent with the L-band two-way satellite, and time–frequency transfer clock measurements and the detrended residuals vary within 0.5 ns. The centralized autonomous orbit determination is conducted in a batch mode on a ground-capable server for the feasibility study. Constant hardware delays are present in the geometric distances and become the largest source of error in the autonomous orbit determination. Therefore, the hardware delays are estimated simultaneously with the satellite orbits. To avoid uncertainties in the constellation orientation, a ground anchor station that “observes” the satellites with on-board ISL payloads is introduced into the orbit determination. The root-mean-square values of orbit determination residuals are within 10.0 cm, and the standard deviation of the estimated ISL hardware delays is within 0.2 ns. The accuracy of the autonomous orbits is evaluated by analysis of overlap comparison and the satellite laser ranging (SLR) residuals and is compared with the accuracy of the L-band orbits. The results indicate that the radial overlap differences between the autonomous orbits are less than 15.0 cm for the inclined geosynchronous orbit (IGSO) satellites and less than 10.0 cm for the MEO satellites. The SLR residuals are approximately 15.0 cm for the IGSO satellites and approximately 10.0 cm for the MEO satellites, representing an improvement over the L-band orbits. 相似文献
998.
Xiaopeng Gong Shengfeng Gu Yidong Lou Fu Zheng Maorong Ge Jingnan Liu 《Journal of Geodesy》2018,92(7):797-809
Global navigation satellite systems (GNSS) are acting as an indispensable tool for geodetic research and global monitoring of the Earth, and they have been rapidly developed over the past few years with abundant GNSS networks, modern constellations, and significant improvement in mathematic models of data processing. However, due to the increasing number of satellites and stations, the computational efficiency becomes a key issue and it could hamper the further development of GNSS applications. In this contribution, this problem is overcome from the aspects of both dense linear algebra algorithms and GNSS processing strategy. First, in order to fully explore the power of modern microprocessors, the square root information filter solution based on the blocked QR factorization employing as many matrix–matrix operations as possible is introduced. In addition, the algorithm complexity of GNSS data processing is further decreased by centralizing the carrier-phase observations and ambiguity parameters, as well as performing the real-time ambiguity resolution and elimination. Based on the QR factorization of the simulated matrix, we can conclude that compared to unblocked QR factorization, the blocked QR factorization can greatly improve processing efficiency with a magnitude of nearly two orders on a personal computer with four 3.30 GHz cores. Then, with 82 globally distributed stations, the processing efficiency is further validated in multi-GNSS (GPS/BDS/Galileo) satellite clock estimation. The results suggest that it will take about 31.38 s per epoch for the unblocked method. While, without any loss of accuracy, it only takes 0.50 and 0.31 s for our new algorithm per epoch for float and fixed clock solutions, respectively. 相似文献
999.
顾及大气延迟效应的YG-13A斜距标定 总被引:2,自引:1,他引:1
针对大气延迟时变误差影响遥感卫星十三号(YG-13A)斜距标定精度的问题,提出利用顾及大气延迟时变误差的斜距标定方法提高其斜距标定精度的策略。首先,利用基于NCEP气象资料和全球TEC数据的大气延迟改正方法来计算各标定景的大气延迟改正量。其次,将各标定景的大气延迟改正量代入斜距标定模型中。最后,在地面布设高精度角反射器控制点的情况下通过顾及大气延迟时变误差的斜距标定模型求解斜距测量系统误差,从而提高和验证斜距测量精度,角反射器控制点的平面和高程精度均优于0.1 m。利用嵩山遥感定标场地区的4组不同拍摄模式下获得的YG-13A卫星影像数据对比试验表明,相较于传统的斜距定标方法,在顾及大气延迟时变误差的情况下,4组数据的斜距改正值离散度均有所下降。利用太原、天津两个区域3景影像验证斜距改正后的精度,最小值为0.55 m,最大值为0.91 m,均值为0.70 m。试验结果证明了顾及大气延迟时变误差的斜距标定方法的有效性和可行性。 相似文献
1000.
深部矿井开采极易诱发矿柱型岩爆,矿柱型岩爆严重威胁着矿山的安全高效开采,为探究矿柱型岩爆破坏机制和前兆信息,选用自贡红砂岩进行单轴压缩试验,并采用主动超声和被动声发射对破裂过程进行监测,联合主动超声与被动声发射监测数据对波速进行层析成像反演,分析试样破裂过程中波速演化规律。研究结果表明:砂岩试样在加载过程中速度模型呈现高度非均质性,在加载过程中会出现低速区,且声发射事件集中出现在低速区内部;P波速度离散度可反映全局波速变化特征,在峰值附近变化剧烈,随荷载增加P波速度离散度持续增大;声发射事件在峰前、峰后定位结果相差较大,峰前阶段声发射事件随机分布,峰后阶段声发射事件定位结果集中。此外,研究发现选用均质速度模型进行声发射事件定位会增大定位误差,试样最终失稳前b值的降低表明试样大尺度裂纹活动加剧,导致岩石非均质性增大,也间接证明了采用非均质速度模型进行声发射震源定位的必要性。该研究结果可用于现场矿柱稳定性监测,定期反演获得矿柱波速变化为矿柱型岩爆提供先兆预警信息。 相似文献