矢量喷管数学模型研究

采用计算流体力学的有限体积法和神经网络方法,对矢量喷管的统一数学模型进行了研究,并得到了一种以神经网络描述形式的数学模型。该模型为矢量喷管控制规律和带有推力矢量的飞行／推进系统综合控制的研究提供了一定基础。     

The hemispheric asynchrony of polar faculae during solar cycles 19–22

We investigate the north–south (N–S) asynchrony of the polar faculae and compare it with the hemispheric asynchrony of solar activity at low latitudes. We find that, (1) both the solar activity at high and low latitudes do not synchronously occur in the northern and southern hemispheres, there is phase shifts between the two hemispheres; (2) the N–S asynchrony of the polar faculae is a function of latitudes, implying that the asynchrony of the polar faculae between the two hemispheres is related to the hemispheric asymmetry and latitudinal distribution of the polar faculae.     

A new approach to solar cycle forecasting

We describe a novel approach for determining the timing of the solar cycle and tracking its evolution relative to other cycles. This method also has predictive capability for forecasting the cycle “onset.” Based on current trends, we expect that Cycle 23 will be about 1 year longer than the previous two cycles.     

Classification of hyperspectral remote-sensing data with primal SVM for small-sized training dataset problem

With recent technological advances in remote sensing, very high-dimensional (hyperspectral) data are available for a better discrimination among different complex land-cover classes having similar spectral signatures. However, this large number of bands makes very complex the task of automatic data analysis. In the real application, it is difficult and expensive for the expert to acquire enough training samples to learn a classifier. This results in a classification problem with small-size training sample set. Recently, a regularization-based algorithm is usually proposed to handle such problem, such as Support Vector Machine (SVM), which usually are implemented in the dual form with Lagrange theory. However, it can be solved directly in primal formulation. In this paper, we introduces an alternative implementation technique for SVM to address the classification problem with small-size training sample set. It has been empirically proven that the effectiveness of the introduced implementation technique which has been evaluated by benchmark datasets.     

Correlation between solar flare productivity and photospheric vector magnetic fields

Studying the statistical correlation between the solar flare productivity and photospheric magnetic fields is very important and necessary. It is helpful to set up a practical flare forecast model based on magnetic properties and improve the physical understanding of solar flare eruptions. In the previous study ([Cui, Y.M., Li, R., Zhang, L.Y., He, Y.L., Wang, H.N. Correlation between solar flare productivity and photospheric magnetic field properties 1. Maximum horizontal gradient, length of neutral line, number of singular points. Sol. Phys. 237, 45–59, 2006]; from now on we refer to this paper as ‘Paper I’), three measures of the maximum horizontal gradient, the length of the neutral line, and the number of singular points are computed from 23990 SOHO/MDI longitudinal magnetograms. The statistical relationship between the solar flare productivity and these three measures is well fitted with sigmoid functions. In the current work, the three measures of the length of strong-shear neutral line, total unsigned current, and total unsigned current helicity are computed from 1353 vector magnetograms observed at Huairou Solar Observing Station. The relationship between the solar flare productivity and the current three measures can also be well fitted with sigmoid functions. These results are expected to be beneficial to future operational flare forecasting models.     

The Progress of the Taiwan Oscillation Network Project

We describe the present status of the project of the Taiwan Oscillation Network (TON) and discuss a scientific result using the TON data. The TON is a ground-based network to measure solar intensity oscillations for the study of the solar interior. Four telescopes have been installed in appropriate longitudes around the world. The TON telescopes take K-line full-disk solar images of diameter 1000 pixels at a rate of one image per minute. The data has been collected since October of 1993. The TON high-spatial-resolution data are specially suitable for the study of local properties of the Sun. In 1997 we developed a new method, acoustic imaging, to construct the acoustic signals inside the Sun with the acoustic signals measured at the solar surface. From the constructed signals, we can form intensity map and phase-shift map of an active region at various depths. The direct link between these maps and the subsurface wave-speed perturbation suffers from the poor vertical resolution of acoustic imaging. Recently an inversion method has been developed to invert the measured phase travel time perturbation to estimate the distribution of wave-speed perturbation based on the ray approximation. This technique of acoustic imaging has been used to image the far-side of the Sun that could provides information on space weather prediction. The TON Team includes: Antonio Jimenez (Instituto Astrofisica de Canarias, Spain); Guoxiang Ai and Honqi Zhang (Huairou Solar Observing Station, P.R.C.); Philip Goode and William Marquette (Big Bear Solar Observatory, U.S.A.); Shuhrat Ehgamberdiev and Oleg Ladenkov (Ulugh Beg Astronomical Institute, Uzbekistan) This revised version was published online in August 2006 with corrections to the Cover Date.     

基于矢量数据的三维航迹规划方法

提出了基于矢量数据的三维航迹规划方法。通过将威胁数据以矢量的方式与地形等高线结合起来对规划空间进行灵活表述，使得航迹规划可以充分考虑地形／威胁的影响，同时在规划时考虑了低空飞行器性能及其他约束。试验结果表明，该方法可以快速有效地完成三维航迹规划，给出的结果既满足各种约束条件又符合人的直觉。     

一种基于光流计算的机器人视觉与行为模型

主动环境探测与准确的行为控制近来已成为机器人领域的重点研究课题，它直接关系到机器人对环境的适应能力，以及能否根据周围环境做出及时、准确的动作规划。该研究背景是月球探测机器人的智能导航，阐述了如何建立机器人视觉与电机行为关系的视觉与行为模型。在此模型中，机器人根据运动所引起的地面图像光流场变化来计算当前机器人运动状态。在实验室环境中，该方法具有运行速度快，工作稳定等特点。这种视觉与行为模型可以用于今后的自主机器人主动目标跟踪和动态避障等实际导航项目中，具有一定的现实意义。     

S频段星载相控阵天线在轨标校技术

针对星载相控阵天线在轨标校技术,重点研究了S频段星载相控阵天线标校方法,论证了标校站的数量及配置要求,同时分析了标校时间和标校流程,从而提出了使用1个标校站进行粗略标校,然后再使用3个标校站进行精确标校,即改进的粗略标校+精确标校的在轨标校方法。在保证标校精度的同时,使标校站天线口径从3个7m天线降低为1个7m天线和2个0.5m天线,大大降低了系统对标校站的建设要求。当相控阵天线波束合成损失大于1dB,系统可采用单站粗略标校+三站精确标校的改进算法进行天线标校;当相控阵天线波束合成损失在1dB以内,系统可省略单站粗略标校过程直接进行三站精确标校。     

引射喷管的气动性能和传热计算

对某型飞机引射喷管装三种机尾罩时的推力性能和机尾罩温度进行了计算，主流和次流的特性分别用特征线法和一维方法计算，为了计算机尾罩的温度，建立了一种简化的一维模型，计算结果与试飞实测数据吻合良好，引射喷管装三种机尾罩的比较表明：切短的机尾罩可以在推力下降不太多的同时改善机尾罩温度。