基于旋度计算的流面生成算法研究

三维流场可视化一直以来是个很具有挑战性的问题.介绍了基于流线连接的流面生成方法,针对发散场中流线间距过大的问题,提出基于旋度计算的流面生成方法,通过流线法向量连线生成具有较好视觉效果的流带和流面,最后选取CDC风场数据对算法进行检验.     

叶芝与乔伊斯对比研究

探索叶芝、乔伊斯两位爱尔兰作家在信仰、创作手法、历史观、爱尔兰民族运动和人生感悟方面的相同点、不同点，供评阅参考。叶芝、乔伊斯不信仰基督教，有各自的哲理，但有相似的历史观——循环论。乔伊斯充分利用象征主义，以荷马《奥德赛》中的人物、故事情节、地点作为意识流小说《尤利西斯》的框架——各章的题目，揭示了深奥的道理。叶芝参加爱尔兰民族的解放运动，成为爱尔兰文艺的领导人，而乔伊斯却放逐自己于海外，拯救自己的理想——文学。两人在创作中得出各自的结论，以劝谏他人。     

全国内地非典型肺炎疫情自回归预报模型

利用时序分析方法研究从2003年4月27日开始卫生部办公厅发布的全国内地新增传染性非典型肺炎疫情报告，建立全国内地非典型肺炎疫情ARMAV预报模型，对模型进行适用性检验后，可以用所建模型对未来疫情进行外延预测。用时序分析方法进行监测、分析及预报，对非典型肺炎的疫情发展和关键影响因素等提供精度较高的预测结果。     

基于鲁棒H∞滤波的追踪卫星相对导航算法研究

针对追踪卫星存在轨道机动的情况,在模型存在不确定参数和非高斯噪声输入时,研究了基于鲁棒H∞滤波理论的相对导航算法.该算法采用线性不等式技术,根据Lyapunov稳定性原理推导出具有范数有界不确定参数离散系统的鲁棒H∞滤波器存在的充要条件,并将滤波器的设计转化为一个凸优化的求解问题.将该算法应用到追踪卫星导航中,仿真结果表明该算法在大轨道机动下有效且能消除模型不确定性和非高斯噪声对系统造成的不利影响.     

基于直流换向方法的电阻测量技术

随着现代制造业的飞速发展,电子元器件的体积将变得越来越小,于是测试功率受到了很大的限制,都需要降低测试电流,这就对系统测试小电压信号时的噪声抑制能力提出了极大的挑战,本文在经典偏置补偿测量电阻方法的基础上,介绍了基于直流电流换向方法的电阻测量技术,并对这两种方法进行了比较,得出基于直流电流换向方法在抑制噪声能力上的优越性。     

聚能爆破切割清理弹射通道技术

 考虑到飞机隐身等因素,飞机驾驶舱顶部为金属结构而不是传统的座舱盖结构,在弹射救生过程中,采用聚能爆破切割技术,切割金属结构形成"座舱盖"并抛放以清理弹射通道,且已在B-1B、B2飞机上采用。利用座舱顶部金属结构平板件,对聚能切割器装药量、切割厚度,切割过程冲击噪声对飞行员的影响、爆破飞溅物对飞行员的损伤防护等进行了分析和试验研究,并将冲击噪声对飞行员的影响与国军标的要求进行了对比。通过本次研究,将为以后的工程应用提供基础性依据。     

外涵静子后掠对某风扇/增压级气动特性的影响

针对某大涵道比风扇/增压级外涵静子后掠降噪的优化设计目标,采用1种周向平均快速特性预测计算方法和3维数值模拟软件NUMECA,对其100％设计转速下外涵静子无后掠及轴向后掠22.5°和30°算例的特性曲线及流场进行了对比分析,以研究外涵静子轴向后掠对风扇/增压级特性及气动性能的影响规律.结果表明:一定程度的轴向后掠角度会使静子表面静压在叶尖处增强,而根部的叶片表面静压分布更趋均匀,风扇/增压级的外涵气动特性在裕度上无明显恶化;但严重的后掠角度则会导致叶尖叶片表面载荷显著增加,从而造成外涵的喘振裕度减小,进而影响整个风扇/增压级的气动性能.     

Application of time-variable process noise in terrestrial reference frames determined from VLBI data

In recent years, Kalman filtering has emerged as a suitable technique to determine terrestrial reference frames (TRFs), a prime example being JTRF2014. The time series approach allows variations of station coordinates that are neither reduced by observational corrections nor considered in the functional model to be taken into account. These variations are primarily due to non-tidal geophysical loading effects that are not reduced according to the current IERS Conventions (2010). It is standard practice that the process noise models applied in Kalman filter TRF solutions are derived from time series of loading displacements and account for station dependent differences. So far, it has been assumed that the parameters of these process noise models are constant over time. However, due to the presence of seasonal and irregular variations, this assumption does not truly reflect reality. In this study, we derive a station coordinate process noise model allowing for such temporal variations. This process noise model and one that is a parameterized version of the former are applied in the computation of TRF solutions based on very long baseline interferometry data. In comparison with a solution based on a constant process noise model, we find that the station coordinates are affected at the millimeter level.     

Ionospheric and geomagnetic Pc5 oscillations as observed by the ionosonde and magnetometer at Sodankylä

The study is based on the data of the rapid-run ionosonde at the Sodankylä Geophysical Observatory at auroral latitude (L?=?5.25) which routinely performs one-minute sounding since 2007. This dataset allows a unique opportunity for investigating possible effects of ultra-low frequency (ULF, 1–7?mHz) waves in the auroral ionosphere. Suitable observations were made during moderately disturbed geomagnetic conditions typically at recovery of the geomagnetic storms caused by solar wind high-speed streams, in the daytime between 9 and 16 MLT. The ionospheric oscillations corresponding to Pc5 geomagnetic pulsations were found in variations of the virtual height of the F layer and the power of ionosonde reflections from E and F layers. The later are most probably caused by modulation of electron precipitation, which is also manifested in weak (about 0.01–0.06?dB) variations of cosmic noise absorption. The most important and novel result is that the pulsations of power of reflection from E and F layers typically has a spectral maximum at nearly half the periodicity of the Pc5 geomagnetic pulsations, whereas such spectral peak is negligible in the geomagnetic pulsations.     

Preliminary analysis of the quality and positioning performance of BDS-3 global interoperable signal B1C&B2a

BeiDou-3 Navigation Satellite System (BDS-3) satellites are equipped with the new generation GNSS signals B1C and B2a, which support the interoperability with GPS and Galileo systems. In this study, the pseudo-range multipath error and carrier phase observation noise of the BDS-3 B1C and B2a signals were evaluated based on zero baseline measurements from the day of year (DOY) 113 to 116, 2020. Further, the precision and performance of the single point positioning (SPP) and precise point positioning (PPP) are assessed at 9 stations. This assessment manifests that the standard deviations (STDs) of the pseudo-range multipath error are about 0.09 ~ 0.22 m, while STDs of the carrier phase observation noise are about 0.075 mm. For the single-frequency SPP, its positioning precision is about 2.03 ~ 4.85 m and 3.29 ~ 10.73 m at the 99.99% confidence level in horizontal and vertical directions, respectively, while the dual-frequency SPP precision is about 1.92 ~ 8.02 m and 4.81 ~ 12.77 m in horizontal and vertical directions, respectively. For the daily static PPP, the convergence time is about 20 ~ 30 min, while the daily positioning precision can reach 1.38 ~ 4.42 cm and -1.31 ~ 4.34 cm in horizontal and vertical directions, respectively. In general, the quality and the SPP and PPP performance of the BDS-3 B1C&B2a signals are comparable to the GPS and Galileo.