Estimation of the elastic Earth parameters (h2, l2) using SLR data

We present results for the global elastic parameters h₂ and l₂ derived from the analysis of Satellite Laser Ranging (SLR) data. SLR data for the two satellites LAGEOS 1 and LAGEOS 2 observed during 2.5 years from January 3, 2005 until July 1, 2007 with 18 globally distributed ground stations were analysed using different approaches. The analysis was done separately for the two satellites and approaches to estimate the two elastic parameters independently and together were performed. We do a sequential analysis and study the stability of the estimates as a function of length of the data set used. The adjusted final values for h₂ equal to 0.6151 ± 0.0008 and 0.6152 ± 0.0008, and those for l₂ equal to 0.0886 ± 0.0003 and 0.0881 ± 0.0003 for LAGEOS 1 and LAGEOS 2 tracking data are compared to other independently derived estimates. These parameters and their errors achieve stability at about the 24 and 27 month time interval for h₂ and l₂, respectively.     

基于 SMS P和 C & I 方式的假目标干扰效果研究

SM SP和C&I是美国科学家提出的两种新型假目标干扰产生方式,其主要是对DRFM 技术截获的雷达信号进行抽取、复制、组合,生成干扰信号,可在雷达接收端形成密集假目标干扰,并具有一定的移频和压制效果。建立了两种假目标干扰的数学模型,通过研究脉压后的干扰波形,分析子脉冲数目、时隙等因素对干扰效果的影响。     

灰色系统研究进展（2004--2014）

从灰数及其运算、灰色序列算子与灰色预测模型、灰色关联分析与灰色聚类评估模型、灰色决策模型、灰色组合模型和灰色控制几个方面介绍了灰色系统理论2004—2014年的研究进展及部分应用成果。梳理了基于"核"和灰度的灰数运算法则、一般灰数的概念、灰度合成公理及缓冲算子的一般形式,总结了4种GM(1,1)基本模型,即均值GM(1,1)模型(EGM)、离散GM(1,1)模型(DGM)、均值差分GM(1,1)模型(EDGM)、原始差分GM(1,1)模型(ODGM),及其适用的序列类型。介绍了灰色相似关联度、灰色接近关联度、三维灰色绝对关联度,以及基于中心点和端点混合三角白化权函数的灰色聚类评估模型、多目标加权智能灰靶决策模型、两阶段综合测度决策模型、灰色博弈模型、灰色投入产出模型,并且阐述了分布型、中立型和中立-分布型灰色随机时滞系统的指数鲁棒稳定性等新概念、新模型、新方法。同时提出了有待进一步研究解决的问题。     

高雷诺数下交叉圆柱涡激振动的数值分析

基于能量捕获应用场景,利用数值仿真的方法研究了高雷诺数下交叉圆柱的涡激振动(Vortex Induced Vibration, VIV)现象。首先建立了三维VIV数值模型,通过与已有文献试验数据对比验证了该数值模型的准确性。进而在该模型的基础上,对交叉圆柱的VIV进行了仿真研究,并与普通圆柱做了对比分析。研究发现,受竖圆柱的影响,交叉圆柱在中低流速的涡强度有所减小,使低流速下的柱体振幅减小,启动流速变大;在中流速范围,涡脱落位置的改变,使得振幅增加;在高流速范围涡强度和涡脱落位置变化并不明显,振幅也与普通圆柱相近。     

等维灰数递补动态预测在机场客运量预测中的应用

基于灰色系统等维灰数递补动态预测和残差GM（1，1）修正模型，对其应用的可行性进行了有益的探讨，并结合实例，对首都国际机场中短期客运量进行了预测。通过调整原始样本中的变异数据，得到比较理想的预测结果．经检验预测结果是可信的。该研究为机场客运量预测提供了一种方法，可供借鉴。     

小高径比扰流柱冷却通道的换热和流动特性

采用数值模拟的方法,对涡轮叶片尾缘处圆形小高径比扰流柱冷却通道的换热和流动特性进行了研究,分析进口雷诺数和扰流柱间距对冷却通道换热和流动特性的作用过程.结果表明:进口雷诺数的提高能够有效改善冷却通道端壁的换热性能,但这种改善能力随着进口雷诺数的提高而逐渐减弱,同时降低冷却通道的压力损失系数.在两种扰流柱间距中,流向间距是影响端壁换热性能的主要因素,随着流向间距的减小,冷却通道换热性能逐渐变好,压力损失系数降低;横向间距是影响冷却通道流动损失的主要因素,两者大小成反比关系.在通道计算中,扰流柱平均换热性能约是端壁平均换热性能的1.8倍,端壁换热权重约是换热面积比0.824倍,同时该权重几乎不受进口雷诺数的影响.      

褶皱结构对蜻蜓后翅的气动特性影响分析

褶皱结构是否能对蜻蜓后翅气动性能产生正面的影响,对蜻蜓后翅气动性能的影响是否与雷诺数(Re)相关。建立接近真实蜻蜓后翅的三维蜻蜓后翅褶皱模型和拥有同样外形的三维平板模型,利用计算流体力学方法分别计算两个模型在不同Re、不同攻角(α)下滑翔飞行时的气动特性。结果表明:褶皱结构的存在会明显提高蜻蜓后翅的升力,但是同时也会增大其阻力;不同Re情况下,褶皱结构对蜻蜓后翅气动性能的影响不同,当Re=1 000,α=0°～25°时,蜻蜓后翅的气动效能始终略优于三维平板;褶皱结构对蜻蜓后翅气动特性的影响与α也相关,α较大时蜻蜓后翅的气动效能略优于三维平板。     

飞翼式微型飞行器飞行动力学特性研究

微型飞行器(MAV)非线性飞行力学特性研究是MAV设计中的一个重要环节。由于MAV具有自身尺寸微小,飞行速度低等特点,其空气动力学低雷诺数效应十分明显。飞翼式MAV的非常规气动布局也使得其飞行力学特性与常规飞行器有很大差异。以低雷诺数风洞实验为基础,研究了飞翼式MAV空气动力学特性,提出了1种针对飞翼式飞行器的动阻尼导数计算方法。在飞翼式MAV飞行速度范围内将其运动方程分段线性化以研究其飞行力学特性数值规律。结果表明,飞翼式MAV各项飞行品质指标与常规飞行器存在很大差异,在整个飞行范围内其飞行动力学特性呈非线性变化规律。本文的研究对实现飞翼式MAV自主飞行控制具有重要意义。     

用n表示第n个素数

给出一个用ｎ 表示第ｎ 个素数的公式ｐ１ ＝ ２ｐｎ ＝ ３ ＋ ∑∞ｋ＝ １ １ ＋ ｎ － １２ － ∑ｋｉ＝ １ ｓｉｎ （２ｉ）２ｉ＋ １πｓｉｎ π２ｉ ＋ １ｎ － １２ － ∑ｋｉ＝ １ ｓｉｎ （２ｉ）２ｉ＋ １πｓｉｎ π２ｉ ＋ １ 　　（ｎ ＝ ２,３,４,…）     

Evolutionary features of polar and non-polar coronal holes during solar cycle 24 and the rising phase of cycle 25

This paper presents the results of the analysis of the evolution of coronal holes (CHs) on the Sun during the period May 13, 2010 – March 20, 2022, covering Solar Cycle 24. Our study uses images in the extreme-ultraviolet iron line (Fe XII 193 Å) obtained with the Atmospheric Imager Assembly of the Solar Dynamics Observatory (AIA/SDO). To localize CHs and determine their areas, we used the Heliophysics Event Knowledgebase (HEK). We separate the CHs into polar and non-polar and study the evolutionary features of each group. During this period, an asymmetry between the Northern (N) and Southern (S) Hemispheres (N-S or hemispheric asymmetry) is detected both in the solar activity (SA) indices and in the localization of the maximum areas of the polar and non-polar CHs. It is shown that the hemispheric asymmetry of the areas of polar and non-polar CHs varies significantly over time and that the nature of these changes is clearly related to the SA cycle. We find that for most of the period, the polar CHs were predominated generated in the S- hemisphere while the non-polar CHs were dominant in the N- hemisphere. It is found that the maximum and minimum of the hemispheric imbalance in the areas of non-polar CHs are close in time to the maximum and minimum of the asymmetry of the SA indices (the number and areas of sunspots). The maximum hemispheric imbalance of the polar CH areas is observed at the maximum of Cycle 24, and the minimum imbalance is found at the cycle minimum. These results confirm our assumption that these two types of CHs are of a different nature and that the non-polar CHs, like sunspots, are elements of the general magnetic activity.