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101.
102.
K. Arai M. Saka K. Seto 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,37(12):2197-II
A method for reconstruction of cross-section of rainfall situations with precipitation radar data based on wavelet analysis of multi-resolution analysis (MRA) which allows extract a peak of the radar reflectivity is proposed in order to detect bright band height. It is found that the bright band height can be estimated by using the MRA with the basis of Daubechies wavelet family. It is also found that the boundaries in rainfall structure can be clearly extracted with MRA. 相似文献
103.
Ralph D. Lorenz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(7):2219-2230
Winds near the ground on Titan for the Dragonfly landing site (near Selk crater, 10°N) for the mid-2030s (Titan late southern summer, Ls ~ 310°) are estimated for mission design purposes. Prevailing winds due to the global circulation are typically 0.5 m/s, and do not exceed 1 m/s. Local terrain-induced flows such as slope winds appear to be similarly capped at 1 m/s. At various landing sites and times, these two contributions will vectorially combine to yield steady winds (for part of a Titan day, Tsol) of up to 2.0 m/s, but typically less – the slope wind component will be small in the mid-morning. In early afternoon, as on Earth and Mars, solar-driven convection in the planetary boundary layer will cause wind fluctuations of the order of 0.1 m/s, varying with a typical timescale of ~1000 s. Occasionally this convection organizes into coherent ‘dust devil’ vortices: detectable vortices with speeds of 1 m/s are predicted about once per Titan day. We have introduced the convective velocity scale combined with the advection time of PBL cells as a metric to derive the frequency of occurrence of gusts associated with convective vortices (‘dust devils’). Maximum possible vortex winds on Titan of 2.8 m/s may be expected only once per 40 Tsols, and define the maximum wind (4.8 m/s at 10 m height) that Dragonfly must tolerate without damage. The applicability of different wind combinations, scaled to the height of relevant Dragonfly components above the ground (e.g. the maximum corresponds to 3.9 m/s at 1.3 m height) by a logarithmic wind profile, to Dragonfly design and operations are discussed. 相似文献
104.
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
105.
利用时域有限差分(FDTD)方法,结合理想匹配层(PML)吸收边界条件,对无限长柱形散射体的总场计算进行分析并得出数值解。证明了该方法在散射体总场计算中的实用性和有效性,并在此基础上给出了不同入射波源及PML参数对计算结果的影响。 相似文献
106.
107.
S.M. Park H. Kim S. Min J. Park J.H. Lee H. Kil L.J. Paxton S.-Y. Su J. Lee K.W. Min 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
We have studied the topside nighttime ionosphere of the low latitude region using data obtained from DMSP F15, ROCSAT-1, KOMPSAT-1, and GUVI on the TIMED satellite for the period of 2000–2004, during which solar activity decreased from its maximum. As these satellites operated at different altitudes, we were able to discriminate altitude dependence of several key ionospheric parameters on the level of solar activity. For example, with intensifying solar activity, electron density was seen to increase more rapidly at higher altitudes than at lower altitudes, implying that the corresponding scale height also increased. The density increased without saturation at all observed altitudes when plotted against solar EUV flux instead of F10.7. The results of the present study, as compared with those of previous studies for lower altitudes, indicate that topside vertical scale height increases with altitude and that, when solar activity increases, topside vertical scale height increases more rapidly at higher altitudes than at lower altitudes. Temperature also increased more rapidly at higher altitudes than at lower altitudes as solar activity increased. In addition, the height of the F2 peak was seen to increase with increasing solar activity, along with the oxygen ion fraction measured above the F2 peak. These results confirm that the topside ionosphere rises and expands with increasing solar activity. 相似文献
108.
针对微机电系统(MEMS)中微小器件的表面刻蚀沟槽及台阶的测量,研制采用步进电机运动平台和微力电感测头,用变截面片簧作回转运动的测头支撑机构,对运动平台存在的偏心作用力和振动噪声问题做了分析和研究,提出了有效的解决方案。 相似文献
109.
110.
星载SAR多普勒频率计算与全零多普勒中心导引 总被引:1,自引:1,他引:1
讨论了在天线坐标系中多普勒频率的计算方法和全零多普勒中心的条件及其实现。证明对近圆轨道SAR卫星,采用与时间延迟积分-电荷耦合器件(TDI-CCD)空间相机相同的计算公式和偏流角补偿技术,能以偏航控制方式实现星载SAR的全零多普勒中心导引。由此可将回波多普勒中心频率的全球变化范围减至最小,显著降低了SAR成像处理的难度。研究具重要的应用价值。 相似文献