套筒式张线天平的研制

根据民机张线测力试验的特殊要求,研制了一台套筒结构形式的张线天平。详细介绍了该天平在研制中遇到的难点、关键技术的解决措施以及研制的结果。天平元件布置在58mm的外套筒上,内杆直径为44mm,外套筒和内杆通过楔块焊接在一起。法向力、俯仰力矩和滚转力矩为拉压变形,横向力和偏航力矩为＂S＂形变形,轴向力为弯曲变形,元件支撑部分受拉压变形且刚度较强。通过对天平进行有限元分析,在法向力和俯仰力矩作用下,得出的应变结果与实际输出基本吻合。风洞试验结果表明：天平设计合理,天平外套筒、内杆及张线支撑系统刚度好,天平各分量测量精度高。     

The damping of small-amplitude oscillations in quiescent prominences

The presence of small-amplitude oscillations in prominences is well-known from long time ago. These oscillations, whose exciters are still unknown, seem to be of local nature and are interpreted in terms of magnetohydrodynamic (MHD) waves. During last years, observational evidence about the damping of these oscillations has grown and several mechanisms able to damp these oscillations have been the subject of intense theoretical modelling. Among them, the most efficient seem to be radiative cooling and ion-neutral collisions. Radiative cooling is able to damp slow MHD waves efficiently, while ion-neutral collisions, in partially ionised plasmas like those of solar prominences, can also damp fast MHD waves. In this paper, we plan to summarize our current knowledge about the time and spatial damping of small-amplitude oscillations in prominences.     

激光干涉仪测量刚性转子动不平衡量技术浅析

介绍了采用激光干涉仪测量刚性转子运转时支撑上振动信号的原理,并简要分析了刚性转子动不平衡量的提取和解算技术.     

采用航路动态规划的时间控制技术研究

针对巡航导弹射程远的特点,考虑到导弹在中制导段的时间约束要求,利用导弹在线剩余时间预测方法,根据实际剩余时间和预测剩余时间得出了时间误差信号。在预定航路基础上利用时间误差信号生成侧向机动指令,通过航路动态规划,实现对攻击时间的控制。最后进行了仿真,仿真结果表明了该方法的有效性。     

Modeling Pulsar Wind Nebulae

In the last few years, new observations by CHANDRA and XMM have shown that Pulsar Wind Nebulae present complex but similar inner features, with the presence of axisymmetric rings and jets, which are generally referred to as a jet-torus structure. Due to the rapid growth in accuracy and robustness of numerical schemes for relativistic fluid-dynamics, it is now possible to model the flow and magnetic structure of the relativistic plasma responsible for the emission. Recent results have clarified how the jet and rings are formed, suggesting that the morphology is strongly related to the wind properties, so that, in principle, it is possible to infer the conditions in the unshocked wind from the nebular emission. I will review here the current status in the modeling of Pulsar Wind Nebulae, and, in particular, how numerical simulations have increased our understanding of the flow structure, observed emission, polarization and spectral properties. I will also point to possible future developments of the present models.     

Solar Isotopic Composition as Determined Using Solar Energetic Particles

Solar energetic particles (SEPs) provide a sample of the Sun from which solar composition may be determined. Using high-resolution measurements from the Solar Isotope Spectrometer (SIS) onboard NASA’s Advanced Composition Explorer (ACE) spacecraft, we have studied the isotopic composition of SEPs at energies ≥20 MeV/nucleon in large SEP events. We present SEP isotope measurements of C, O, Ne, Mg, Si, S, Ar, Ca, Fe, and Ni made in 49 large events from late 1997 to the present. The isotopic composition is highly variable from one SEP event to another due to variations in seed particle composition or due to mass fractionation that occurs during the acceleration and/or transport of these particles. We show that various isotopic and elemental enhancements are correlated with each other, discuss the empirical corrections used to account for the compositional variability, and obtain estimated solar isotopic abundances. We compare the solar values and their uncertainties inferred from SEPs with solar wind and other solar system abundances and find generally good agreement.     

Tilts and polarity separation in the sunspot groups and active regions at the ascending and descending phases of the cycle 23

The Solar Feature Catalogues for sunspots and active regions measured with SOHO/MDI instrument and Ca II K3 spectroheliograph of the Paris-Meudon Observatory are analyzed with the automated classification technique for sunspot groups and active region polarities. We report the first classification results for daily variations of tilt angles (normal and trigonometric ones) in sunspot groups (SG) and active (AR) regions in the cycle 23. The average normal tilts are presented for every year at the ascending and descending phases of the cycle 23 which are similar to those deduced by other authors for the cycles 19–22. The normal tilts of both the sunspot groups and active regions are shown to increase in the ascending phase and a decrease in the descending phase. Similar to SG and AR areas, the trigonometric tilts are shown to have the noticeable North–South asymmetry with the Southern hemisphere dominant in the selected ascending and descending periods. The normal tilt variations with latitude follow Joy’s law revealing a periodicity along the meridian of about 10° and reaching the maximum of 14° at the latitude of about 32° corresponding to the top of the ‘royal zone’ where the sunspots appear. The variations of polarity separation with a latitude are in an anti-phase with those of the tilts reaching a maximum at the latitude of 35° and showing a small positive separation for the groups/active regions in a vicinity of the average tilts ±40°. The ratio R of the polarity separation to the trigonometric tilt fits the linear function of a latitude φ as R = −0.0213φ − 0.1245 confirming positive separation for the polarities of active regions with the average tilts, or the dominance of activity in the Southern hemisphere activity, for the selected period of observations.     

过失速下俯敏捷性及纵向控制效能需求研究

结合飞行安全和作战效能需求,对过失速战斗机的大迎角/过失速迎角下俯敏捷性指标及纵向控制效能需求进行了研究.为了满足飞行品质和过失速敏捷性指标要求,采用非线性动态逆方法设计了某推力矢量飞机快回路和慢回路飞行控制律.在此基础上,根据过失速下俯敏捷性和滚转敏捷性指标要求,对所需的最小俯仰推力矢量偏角进行了计算分析,所得结果对先进战斗机的设计有一定的参考价值.     

Intermediate-term periodicities in relativistic solar electron fluences during solar cycles 22 and 23

In this paper, we have investigated the intermediate-term periodicities of the relativistic (E > 10 MeV) solar electron flares measured by IMP-8 satellite of NASA for the time period of 1986–2001. This period of investigation includes the entire solar cycle 22; ascending, maximum and a part of descending phase of the current solar cycle 23. To determine accurately the occurrence rate of electron flux, we have employed three different spectral decomposition techniques, viz. fast Fourier transformation (FFT); maximum entropy method (MEM) and Lomb–Scargle periodogram analysis method. For solar cycle 22, in the low frequency range, power spectrum analysis exhibits statistically significant periodicities at ∼706, ∼504 and ∼392 days. In the intermediate frequency range, we have found a series of significant periodicities ∼294, ∼221, ∼153, ∼86, ∼73 and ∼66 days. For short term, periodicities of ∼21–23, ∼31 and ∼37 days were found in power spectrum. When solar cycle 23 is considered the significant periodicities are ∼20, ∼23, ∼29, ∼39, ∼54, ∼63, ∼118, ∼133 and ∼154 days. These results provide evidence that the best known Rieger period (∼153 days), appeared in the high energetic electron flux data for cycle 22 and also likely during maxima of cycle 23. The existence of these periodicities has been discussed in the light of earlier results.     

先进云纹测量技术及应用

本文着重介绍了高灵敏度云纹法的发展及其在结构和材料力学行为测量方面的应用,包括云纹干涉法、微米云纹法、纳米云纹法及其相移技术。介绍了清华大学工程力学系光测实验室近年来利用云纹干涉法在材料科学、激光焊接、微电子封装等力学行为测量方面的应用成果。讨论了微米/纳米云纹法分别在微电子封装、微机械系统(MEMS)、纳观变形场测量中的应用。