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361.
B. Bidaine R. Warnant 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The ionospheric effect remains one of the main factors limiting the accuracy of Global Navigation Satellite Systems (GNSS) including Galileo. For single frequency users, this contribution to the error budget will be mitigated by an algorithm based on the NeQuick global ionospheric model. This quick-run empirical model provides flexible solutions for combining ionospheric information obtained from various sources, from GNSS to ionosondes and topside sounders. Hence it constitutes an interesting simulation tool not only serving Galileo needs for mitigation of the ionospheric effect but also widening the use of new data. 相似文献
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高建鸽 《沈阳航空工业学院学报》1998,15(1):40-46
本文介绍了利用EPROM芯片构成步进电机的驱动电源,并对驱动电源及频率混同电路进行了分析和设计。 相似文献
366.
Sophie Pireaux Pascale Defraigne Laurence Wauters Nicolas Bergeot Quentin Baire Carine Bruyninx 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
The stability of GPS time and frequency transfer is limited by the fact that GPS signals travel through the ionosphere. In high precision geodetic time transfer (i.e. based on precise modeling of code and carrier phase GPS data), the so-called ionosphere-free combination of the code and carrier phase measurements made on the two frequencies is used to remove the first-order ionospheric effect. In this paper, we investigate the impact of residual second- and third-order ionospheric effects on geodetic time transfer solutions i.e. remote atomic clock comparisons based on GPS measurements, using the ATOMIUM software developed at the Royal Observatory of Belgium (ROB). The impact of third-order ionospheric effects was shown to be negligible, while for second-order effects, the tests performed on different time links and at different epochs show a small impact of the order of some picoseconds, on a quiet day, and up to more than 10 picoseconds in case of high ionospheric activity. The geomagnetic storm of the 30th October 2003 is used to illustrate how space weather products are relevant to understand perturbations in geodetic time and frequency transfer. 相似文献
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A kind of wireless sensor was previously developed,which is powered and transmit signals wirelessly instead of using an electrical connection to the embedded reinforcement.Based on this technique,the relationship between diameters of corroded sensing steel wires and corrosion levels of steel bars is established by experiments.Quadratic function is utilized to fit the experiment results,and the correlation coefficients are all larger than 0.95.Estimated corrosion levels of commonly used steel bars are given for different diameters of corroded sensing steel wires fractured due to corrosion. 相似文献
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温度漂移是影响超声波流量计测量精度的一个重要因素,本文从算法上提出一种不受其影响的数学模型,以使相应的硬件简单化.该方法已应用在超声波流量计中,收到了很好的效果. 相似文献
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S.O. Ikubanni J.O. Adeniyi O.K. Obrou 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
We have employed the hourly values of the ionospheric F-region critical frequency (foF2) obtained from Ouagadougou ionosonde, Burkina Faso (geographic coordinates 12° N, 1.8° W) during the interval of 1985–1995 (solar cycle 22) and solar radio flux of 10 cm wavelength (F10.7) to develop a local model (LM) for the African low-latitude station. The model was developed from regression analysis method, using the two-segmented regression analysis. We validated LM with foF2 data from Korhogo observatory, Cote d’Ivorie (geographical coordinates 9.3° N, 5.4° W). LM as well as the International Reference Ionosphere (IRI) agrees well with observations. LM gave some improvement on the IRI-predicted foF2 values at the sunrise (06 LT) at all solar flux levels and in all seasons except June solstice. The performance of the models at the representing the salient features of the equatorial foF2 was presented. Considering daytime and nighttime performances, LM and IRI are comparable in low solar activity (LSA), LM performed better than IRI in moderate solar activity (MSA), while IRI performed better than LM in high solar activity (HSA). CCIR has a root mean square error (r.m.s.e), which is only 0.10 MHz lower than that of LM while LM has r.m.s.e, which is about 0.05 MHz lower than that of URSI. In general, our result shows that performance of IRI, especially the CCIR option of the IRI, is quite comparable with the LM. The improved performance of IRI is a reflection of the numerous contributions of ionospheric physicists in the African region, larger volume of data for the IRI and the diversity of data sources, as well as the successes of the IRI task force activities. 相似文献