跟瞄激光雷达扫描图像的实时滤波算法

为实现跟瞄激光雷达的高精度实时跟瞄,对雷达三维信息实时滤波算法进行了研究。对方位信息,用卡尔曼滤波算法滤波,在保证实时性的同时获得了较好的滤波效果;对距离信息,用去边缘点3×3小窗口中值滤波算法,实现了对距离信息的准实时性滤波。研究表明:该信息处理滤波算法既有优良的滤波性能,又能保证实时性,可提高测角和测距精度,改善整机的实时跟踪性能。     

基于组字典学习的逆合成孔径雷达成像方法

基于压缩感知(compressive sensing, CS)的逆合成孔径雷达(inverse synthetic aperture radar, ISAR)成像方法可以使用非常少的数据来获得高质量的图像。但基于CS的ISAR成像方法中目标场景不准确的稀疏表示限制了成像方法的性能。结合字典学习(dictionary learning, DL)技术的CS ISAR成像方法能够寻找到目标场景图像块的最优稀疏表示,提高成像质量,但每一个图像块被单独考虑,而忽略了彼此之间的相互依赖关系。为了实现进一步提高成像质量的目标,针对ISAR图像分块重建的问题,首次提出一种基于组字典学习(group dictionary learning,GDL)的ISAR成像方法。将具有相似结构的图像块聚类并构建出多个图像块组,利用奇异值分解(singular value decomposition, SVD)从图像块组中学习出最优组稀疏变换字典。学习好的组稀疏变换字典可以寻找到待重建图像块组的最优稀疏表示,进而重建出高质量的目标场景图像。实验结果表明:与现有的CS ISAR成像方法相比,基于GDL的ISAR成像方法能获得更好的成像效果,并具有更高的计算效率。     

An analysis of the topside ionosphere parameters based on the long-duration Irkutsk incoherent scatter radar measurements

The topside ionosphere parameters are studied based on the long-duration Irkutsk incoherent scatter radar (52.9N, 103.3E) measurements conducted in September 2005, June and December 2007. As a topside ionosphere parameter we chose the vertical scale height (VSH) related to the gradient of the electron density logarithm above the peak height. For morphological studies we used median electron density profiles. Besides the median behavior we also studied VSH disturbances (deviations from median values) during the magnetic storm of September 11th 2005. We compared the Irkutsk incoherent scatter radar data with the Millstone Hill and Arecibo incoherent scatter radar observations, the IRI-2007 prediction (using the two topside options) and VSH derived from the Irkutsk DPS-4 Digisonde bottomside measurements.     

XANES analysis of organic residues produced from the UV irradiation of astrophysical ice analogs

Organic residues formed in the laboratory from the ultraviolet (UV) photo-irradiation or ion bombardment of astrophysical ice analogs have been extensively studied for the last 15 years with a broad suite of techniques, including infrared (IR) and UV spectroscopies, as well as mass spectrometry. Analyses of these materials show that they consist of complex mixtures of organic compounds stable at room temperature, mostly soluble, that have not been fully characterized. However, the hydrolysis products of these residues have been partly identified using chromatography techniques, which indicate that they contain molecular precursors of prebiotic interest such as amino acids, nitrile-bearing compounds, and amphiphilic compounds. In this study, we present the first X-ray absorption near-edge structure (XANES) spectroscopy measurements of three organic residues made from the UV irradiation of ices having different starting compositions. XANES spectra confirm the presence of different chemical functions in these residues, and indicate that they are rich in nitrogen- and oxygen-bearing species. These data can be compared with XANES measurements of extraterrestrial materials. Finally, this study also shows how soft X rays can alter the chemical composition of samples.     

试论引进教材与国内教材的合理使用

教材作为高校系统授课的重要资料,它是依据教育的目标与内容所编著的,有利于教学活动的展开和学生的学习与掌握.当前在外语院校的教学中,引进教材和使用国内原版教材已成为一种趋势,但是实现二者阃的互补,注重引进教材中存在的问题,结合实际,为我所用,才能起到培养应用型人才的目的.     

基于碳纤维复合材料的电容式燃油油位测量传感器

利用解析法和Ansys软件对基于碳纤维复合管材的电容式燃油油位测量传感器设计进行了计算和分析，给出了传感器的结构设计和中和电流法测量电路，实现了碳纤维复合材料在电容式油位测量中的应用。对传感器和测量系统的标定和稳定性、可靠性、高低温等试验，结果表明碳纤维复合管材电容式油位测量传感器在飞机燃油测量中的应用是可行的。     

Multi-function radar emitter identification based on stochastic syntax-directed translation schema

To cope with the problem of emitter identification caused by the radar words＇ uncertainty of measured multi-function radar emitters, this paper proposes a new identification method based on stochastic syntax-directed translation schema（SSDTS）. This method, which is deduced from the syntactic modeling of multi-function radars, considers the probabilities of radar phrases appearance in different radar modes as well as the probabilities of radar word errors occurrence in different radar phrases. It concludes that the proposed method can not only correct the defective radar words by using the stochastic translation schema, but also identify the real radar phrases and working modes of measured emitters concurrently. Furthermore, a number of simulations are presented to demonstrate the identification capability and adaptability of the SSDTS algorithm.The results show that even under the condition of the defective radar words distorted by noise,the proposed algorithm can infer the phrases, work modes and types of measured emitters correctly.     

Parallel Distributed CFAR Detection Optimization Based on Genetic Algorithm with Interval Encoding

Aiming at parallel distributed constant false alarm rate (CFAR) detection employing K/N fusion rule, an optimization algorithm based on the genetic algorithm with interval encoding is proposed. N-1 local probabilities of false alarm are selected as optimization variables. And the encoding intervals for local false alarm probabilities are sequentially designed by the person-by-person optimization technique according to the constraints. By turning constrained optimization to unconstrained optimization, the problem of increasing iteration times due to the punishment technique frequently adopted in the genetic algorithm is thus overcome. Then this optimization scheme is applied to spacebased synthetic aperture radar (SAR) multi-angle collaborative detection, in which the nominal factor for each local detector is determined. The scheme is verified with simulations of cases including two, three and four independent SAR systems. Besides, detection performances with varying K and N are compared and analyzed.     

Long-period meteor radar temperature variations over Collm (51°N, 13°E) and Kazan (56°N, 49°E)

We have estimated temperatures from meteor radar measurements using the gradient method and the full width at half maximum method over Kazan (56°N 49°E) and Collm (51°N, 13°E). The time series cover the period 2016–2019. The temperature gradient model is constructed from SABER temperature observations. We demonstrate that annual mean, amplitudes and phases of the annual and semiannual oscillations of the radar temperatures are close to those of the MLS and SABER temperatures. The annual mean temperatures over Kazan and Collm differ non-significantly. The seasonal variability of the radar temperature is mostly due to the annual cycle which tends to grow with latitude. The gradient method produces temperatures which agree with the SABER temperatures better than with the MLS ones. The harmonics of the annual oscillations from periods of 73 days up to periods of about 40 days are the most significant day-to-day temperature oscillations and have zonal wavenumber zero. Their periods and phases are in good correspondence with those of the MLS and SABER ones. We also show some results which demonstrate that at 56°N the FWHM method is not as robust as the gradient method.     

Connection between winter mesopause region temperatures and diurnal LF reflection height variations measured at Collm

Scale height, H, estimates are calculated from the decrease/increase of ionospheric virtual reflection heights of low-frequency (LF) radio waves at oblique incidence in suitably defined morning intervals around sunrise during winter months. The day-to-day variations of H qualitatively agree with daily mean temperature variations around 90 km from meteor radar measurements. Since mesospheric long-period temperature variations are generally accepted to be the signature of atmospheric planetary waves, this shows that LF reflection height measurements can be used for monitoring the dynamics of the upper middle atmosphere. The long-term variations of monthly mean H estimates have also been analysed. There is no significant trend, which is in agreement with other measurements of mesopause region temperature trends.