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61.
S.G. Wang J.K. Shi X. Wang G.J. Wang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
NeQuick ionospheric electron density model, which has been developed to version 2, produces the full electron density profile in the ionosphere. Each part of the profile is modeled using Epstein layer formalism. Simple empirical relations are used to compute the thicknesses of each layer. In order to validate the B2bot parameter in the NeQuick model during high solar activity, we use the data at Hainan, China (109.1°E, 19.5°N; Geomagnetic coordinates: 178.95°E, 8.1°N), measured with DPS-4, and study the diurnal and seasonal variations of B2bot, ΔB2 (B2best − B2NeQuick 2) and the seasonal median values of B2best/B2NeQuick 2 at that region. The results show that, (1) The differences between B2best and B2NeQuick 2 have diurnal and seasonal variations. (2) The diurnal variations of B2NeQuick 2 are smaller than those of B2best. (3) Generally, except for early morning the experimental values are properly reproduced. (4) Generally, during morning the NeQuick model has an underestimation. The magnitude of underestimation varies with LT and season. 相似文献
62.
Man-Lian Zhang Libo Liu Weixing Wan Baiqi Ning 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
In this paper, we present our recent work on developing an updated global model of the ionospheric F2 peak height hmF2 parameter by combining data from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC/FORMOSAT-3) radio occultation (RO) measurements and from the extended global ionosonde stations. In particular, 10 Chinese ionosonde stations’ data are newly introduced into this study. The modeling technique used is based on a two-layer empirical orthogonal function (EOF) expansion. Global distributions of hmF2 maps calculated using the newly constructed global model and the one provided by the International Reference Ionosphere model (IRI-ITU-R) are compared with the global distributions of hmF2 obtained by the COSMIC RO measurements and quantitative statistical analysis of the differences between the model results and those of the COSMIC RO measurements is made for the low (2008) and high (2012) solar activity years. The obtained average root-mean-square differences (RMSEs) for our model are 27.7 km (11.1%) and 31.0 km (9.8%), respectively for the years 2008 and 2012, whereas those for the IRI-ITU-R model are 39.9 km (16.9%) and 35.0 km (11.6%), respectively. Comparison of the results calculated both by our model and the IRI-ITU-R model with the digisonde observation is also made. The comparisons show that the newly constructed global hmF2 model can reproduce reasonably well the observations and perform better than IRI-ITU-R model. 相似文献
63.
Man-Lian Zhang Chunxu LiuWeixing Wan Libo LiuBaiqi Ning 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
Global modeling of M(3000)F2 and hmF2 based on three alternative EOF (empirical orthogonal function) expansion methods is described briefly. Data used for the model construction is the monthly median hourly values of M(3000)F2 from the ionosonde/digisonde stations distributed around the world for the period of 1975–1985 and the hmF2 data of the same period converted from the measured M(3000)F2 based on the strong anti-correlation existing between them. Independent data of a low (1965) and a high (1970) solar activity year are used to validate the three alternative models based on different EOF expansion methods. Comparisons between the modeled results and observed data for both the low (1965) and high (1970) solar activity years showed good agreement for both M(3000)F2 and hmF2 parameters. Statistical analysis on the differences between model values and observed data showed that all the three alternative models (Model A, B and C) based on the different EOF expansion methods have better agreement with the observed data than the models currently used in IRI. All three alternative EOF based models have almost the same accuracy. Discussion on the preference of the three alternative EOF based models is given. 相似文献
64.
轻型直升机的滑橇式起落架结构简单,有着广泛的实际应用。本文针对某项目直升机的设计需要,用机械能守恒定律和材料力学的方法对该型起落架的着陆载荷做出定量分析,并校核了起落架的垂直过载和强度。 相似文献
65.
D. Altadill S. Magdaleno J.M. Torta E. Blanch 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
Monthly average electron density profiles have been calculated from hourly electron density N(h) recorded in 26 digisonde stations distributed worldwide encompassing the time interval 1998–2006. The ionospheric electron density peak height of the F2 region, hmF2, and the effective scale height at the hmF2, Hm, deduced from average profiles have been analyzed to obtain the quiet-time behavior and have been analytically modeled by the spherical harmonic analysis (SH) technique using the modip latitude as the coordinate of the reference system. The coefficients of the SH models of hmF2 and Hm are bounded to the solar activity, and the temporal and seasonal variations are considered by Fourier expansion of the coefficients. The SH models provide a tool to predict hmF2 and Hm located anywhere in the range of latitudes between of 70°N and 70°S and at any time. The SH analytical model for hmF2 improves the fit to the observations by 10% in average compared to the IRI prediction, and it might improve the IRI prediction of hmF2 by more than 30% at high and low latitudes. The analytical model for Hm predicts the quiet behavior of the effective scale height with accuracy better than 15% in average which enables to obtain a good estimation of vertical profiles. These results could be useful to estimate information for the topside profile formulation. 相似文献
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卫星自主完好性监测(SAIM)技术是地面完好性监测手段的重要技术补充,可以有效缩短告警时间,有助于从根本上提高完好性性能。从SAIM技术出发提出多通道相关峰监测算法,实现多点异步采样,恢复相关峰。通过MATLAB软件仿真验证算法并给出典型异常模型及监测结果,并用普通接收机验证工程可实现性。通过软件仿真和实测结果对比论证了方法的可行性,采用成熟的商业星载接收机进行软件修改有效地降低了卫星完好性接收装置的研发难度。 相似文献
70.
在不改变激光重复频率、焊接速率、脉冲宽度、离焦量等参数的情况下,只改变峰值功率,采用Nd:YAG脉冲激光对石英加速度计表芯装配组件进行热传导焊接,通过X射线显微镜和超声波无损检测系统对焊接样件的焊缝形态与焊接质量进行检测分析,并对样件拉伸强度进行测试.结果表明:脉冲激光热传导焊接中的热输入量对焊缝形态和焊接质量有直接的影响,较低的热输入量可以实现边界轮廓整齐、表面光亮、热影响区较小、残余应力较低的焊缝形态,并且没有裂纹缺陷,同时焊接样件的拉伸强度是环氧胶粘接样件的3倍以上.因此,脉冲激光热传导焊接技术在组件装配连接上的应用具有潜在的优势. 相似文献