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991.
992.
针对现有相位延迟估计方法未利用双差模糊度网解约束的特点,提出了一种附加双差模糊度网解约束的相位延迟估计方法。首先以整周双差模糊度网解为真值更新精密单点定位(PPP)估计的非差浮点模糊度,再通过网平差法估计未校正相位延迟(UPD)。实验结果表明,PPP双差模糊度与双差模糊度网解一致性好,其宽、窄巷中误差分别为0.07周和0.11周,误差大于1周的PPP双差模糊度主要出现在卫星初升阶段。约束改变了非差浮点模糊度,从而改变了参与UPD网平差的测站,使14%新升起卫星的窄巷UPD在短时间内较无约束有大于0.2周的差异。附加约束/无约束的全天星间单差UPD差异在大于99.9%的置信水平下满足零均值假设,表明整周双差模糊度网解约束方法与无约束方法估计UPD相关产品具有等效性。研究结果可为参考网非差模糊度解算和PPP与网络实时动态定位(RTK)的融合工作提供参考。 相似文献
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996.
中国主导建设的国际GNSS监测评估系统(iGMAS)相比国际上比较成熟的IGS系统在产品精度等方面存在差别,目前实时精密单点定位应用多采用IGS实时、近实时产品.为改变这一现状,针对iGMAS产品特性以及实时精密单点定位对超快速精密星历的需求,对iGMAS超快速星历的精度和稳定性方面进行评估,设计了iGMAS产品实时/... 相似文献
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颜成瑗 《中国空间科学技术》1992,12(1):57-62
VSAT 卫星通信系统是80年代初发展起来的一种灵活方便的通信系统。文章介绍了一种VSAT 卫星数据收集系统的组成,主要技术特点以及卫星链路参数的计算。最后介绍了该系统在我国首次应用于水利自动化工程的情况。 相似文献
998.
T. Ondoh 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Precursory phenomena in the ionosphere, atmosphere and groundwater before large earthquakes (M > 6.5) are extensively investigated toward the earthquake prediction. Upward tornado type seismic clouds occurred near the epicenter associated with strong LF-VLF radio noises from lightning discharges in the evening of January 9, 1995 [Yamada, T., Oike, K. On the increase of electromagnetic noises before and after the 1995 Hyogo-Ken Nanbu earthquake. In: Hayakawa M. (Ed.), Atmospheric and Ionospheric Electromagnetic Phenomena Associated with Earthquakes. TERRAPUB, Tokyo, pp. 417–427, 1999] and anomalous foEs increases up to 10 MHz were detected at Shigaraki, 90 km of the epicenter and at Kokubunji, 500 km east of the epicenter [Ondoh, T. Anomalous sporadic-E layers observed before M7.2 Hyogo-ken Nanbu earthquake; Terrestrial gas emanation model. Adv. Polar Upper Atmos. Res. 17, 96–108, 2003; Ondoh, T. Anomalous sporadic-E ionization before a great earthquake, Adv. Space Research 34, 1830–1835, 2004] associated with strong ELF noises from lightning discharges in the daytime on January 15, 1995 [Hata, M., Fujii, T., Takumi, I. EM precursor of large-scale earthquakes in Japan, in: Abstracts of International Workshop on Seismo Electromagnetics (IWSE 2005), Univ. Electro-Communications, Chofu, Tokyo, Japan, March 15–17, pp. 182–186, 2005] before the M7.2 Hyogoken–Nanbu earthquake of January 17, 1995. The anomalous foEs increases occurred at epicentral distances within 500 km that are the same as those of the terrestrial gas emanations along active faults before large earthquakes [King, C.-Y. Gas geochemistry applied to earthquake prediction: An overview. J. Geophys. Res. 91(B12), 12269–12281, 1986]. The anomalous foEs increases seem to be a seismic precursor because geomagnetic and solar conditions were very quiet all day on January 15,1995 and the normal foEs in Japanese winter is below 6 MHz. No significant pre-seismic geomagnetic field variation was detected at epicentral distance of 100 km before this earthquake [Ondoh, T., Hayakawa, M. Anomalous occurrence of sporadic-E layers before the Hyogoken–Nanbu earthquake, M7.2 of January 17, 1995. In: Hayakawa, M. (Ed.), Atmospheric and Ionospheric Electromagnetic Phenomena Associated with Earthquakes, TERRAPUB, Tokyo, pp. 629–639, 1999; Ondoh, T., Hayakawa, M. Seismo discharge model of anomalous sporadic E ionization before great earthquakes. In: Hayakawa, M., O.A. Molchanov, (Eds.), Seismo Electromagnetics: Lithosphere–Atmosphere–Ionosphere Couplings, TERRAPUB, Tokyo, pp. 385–390, 2002; Ondoh. T., Hayakawa, M. Synthetic study of precursory phenomena of the M7.2 Hyogo-ken Nanbu earthquake. Phys. Chem. Earth 31, 378–388, 2006]. The foF2 decrease and h’F increase occurred before the M7.8 Hokkaido Nansei-Oki earthquake of July 12,1993 in a geomagnetic quiet period [Ondoh, T. Ionospheric disturbances associated with great earthquake of Hokkaido southwest coast, Japan of July 12, 1993. Phys. Earth Planet. Interiors. 105, 261–269, 1998; Ondoh, T. Seismo ionospheric phenomena. Adv. Space Res. 26, 8, 1267–1272, 2000]. Characteristic phase changes at terminator times of Omega 10.2 kHz waves passing 70 km of the epicenter extended toward darker local times by 1 h for 3 days before this earthquake due to lowering of the wave reflection height or ion density increases in the D region [Hayakawa, M., Molchanov, O. A., Ondoh, T., Kawai, E. The precursory signature effect of the Kobe earthquake on VLF subionospheric signals. J. Commun. Res. La., 43, 00. 169–180, 1996]. The radon concentration in the atmosphere over Ashiya fault, Kobe [Yasuoka, Y., Shinogi, M. Anomaly in atmospheric radon concentration: a possible precursor of the 1995 Kobe, Japan, earthquake. Health Phys. 72(5), 759–761, 1997] and in the groundwater at 17 m well in Nishinomiya, Japan [Igarashi, G., Saeki, S., Takahata, N., Sumikawa, K., Tasaki, S., Sasaki, Y., Takahashi, M., Sano, Y. Ground-water radon anomaly before the Kobe earthquake in Japan. Science 269, 60–61, 1995] had gradually increased since 2 months before the M7.2 earthquake, increased suddenly in December 1994, and rapidly returned to the normal low level of October, 1994 [Yasuoka, Y., Shinogi, M. 1997. Anomaly in atmospheric radon concentration: a possible precursor of the 1995 Kobe. Japan, earthquake. Health Phys. 72(5), 759–761.]. Radon concentration changes in the groundwater before the M 7.0 Izu-Oshima-kinkai earthquake, Japan on January 14, 1978 [Wakita, H., Nakamura, Y., Notsu, K., Noguchi, M., Asada, T. 1980. Radon anomaly: a possible precursor of the 1978 Izu-Oshima-kinkai earthquake. Science 207, 882–883] and the M6.8 Chengkung earthquake, Taiwan on December 10, 2003 [Kuo, T., Fan, K., Chen, W., Kuochen, H., Han, Y., Wang, C., Chang, T., Lee, Y. Radon anomaly at the Antung Hot Spring before the Taiwan M6.8 Chengkung earthquake. Proceedings, Thirty-First Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, January 30–February 1, 2006, SGP-TR-179, 2006] are also investigated to find common features of the groundwater radon concentration changes before large earthquakes (M > 6.5) in comparison with those before the M7.2 Hyogoken–Nanbu earthquake. Groundwater radon concentrations before the 3 large earthquakes had shown common characteristic changes of gradually initial ones from the normal level since about 2 months before the earthquake onsets, rapid decreases down to the minimum, and quick increases up to the maximum at 7–20 days before the earthquake onsets, respectively. These are very useful characteristics of pre-seismic radon anomaly for the earthquake prediction or warning. Promising observations toward the earthquake prediction are also discussed. 相似文献
999.
强磁场结构在行星际空间膨胀的数值模拟 总被引:1,自引:1,他引:0
本文研究了强磁场结构在18—240Rs的行星际空间的膨胀效应。模拟结果表明, 强磁场结构的膨胀能够形成典型的磁云剖面结构;膨胀速度明显依赖于磁场强度的大小;强磁场结构运动的速度直接影响到它的动力学特性。 相似文献
1000.