无尾飞机翼尖失速问题研究

首先分析了无尾飞机翼尖失速的特点，包括与其他布局形式共有的和自身特有的特点，重点是翼尖失速对无尾飞机飞行品质的影响。讨论了后掠角和尖削比这两个机翼外形参数对翼尖失速特性的影响。从空气动力学角度出发，根据2种不同的思路，综述了5种解决翼尖失速的方法，分析它们各自的作用原理。最后提出改善无尾飞机翼尖失速特性的若干建议。     

盲源分离及盲信号提取的研究进展

盲源分离和盲信号提取是从观测信号中恢复源信号的有效方法,目前已成为信号处理领域的研究热点。介绍了盲信号处理的数学模型,给出盲源分离与盲信号提取的基本思想,阐述了各方法的原理、特点及性能,并对它们之间的区别与联系进行分析,最后指出盲源分离及盲信号提取的发展方向。     

Research on Feature Extraction of Remnant Particles of Aerospace Relays

The existence of remnant particles, which significantly reduce the reliability of relays, is a serious problem for aerospace relays. The traditional method for detecting remnant particles—particle impact noise detection (PIND)—can be used merely to detect the existence of the particle; it is not able to provide any information about the particles’ material. However, information on the material of the particles is very helpful for analyzing the causes of remnants. By analyzing the output acoustic signals from a PIND tester, this paper proposes three feature extraction methods: unit energy average pulse durative time, shape parameter of signal power spectral density (PSD), and pulse linear predictive coding coefficient sequence. These methods allow identified remnants to be classified into four categories based on their material. Furthermore, we prove the validity of this new method by processing PIND signals from actual tests.     

Constraints on injection parameters of cosmic rays in the Galactic center from resolved HESS observations

In this study, we investigate how restrictive the γ-ray emission from the Galactic center region, as seen by HESS and other Cherenkov air shower arrays, is against various models for cosmic ray injection. We derive diffusion coefficients which fit the observed spatial scales of diffuse γ-ray emission from the extended emission associated with the molecular clouds SgrA, B and C. Using these diffusion coefficients, we then obtain a limit for time scale of assumed recent proton acceleration near the SMBH, as the spatial size of SgrA^∗ in VHE γ-rays has to be consistent with the observed unresolved HESS point source size at this position. The signal from this hadronic component may be mixed with the expected VHE inverse Compton emission from the nearby unresolved pulsar wind nebula.     

Italian polar data center for capacity building associated with the IHY

The International Heliophysical Year offers a good opportunity to develop and coordinate studies on the Sun–Earth system by using a large variety of simultaneous data obtained by satellite/spacecraft and ground based instruments. Among these data we recall the ones coming from solar and interplanetary medium observations, auroral, neutron monitor, geomagnetic field, ionospheric, meteorological, and other atmospheric observatories. In this context, an Information System for the Italian Research in Antarctica has started in 2003, aiming to collect information on the scientific research projects funded by the National Antarctic Research Program of Italy since its establishment (1985). It belongs to Joint Committee on Antarctic Data Management of Scientific Committee on Antarctic Research as Italian Antarctic Data Center. This project, as the Italian Polar Database, gathers also information on research activities conducted in North Pole regions. This Information System can be a relevant resource for capacity building associated with the International Heliophysical Year, especially for people involved in interdisciplinary researches. We describe the present status of the Italian Polar Data Center and its potential use.     

多通道投影图像的几何自动拼接技术

以低端摄像头产品为测量元件构造了实用的可扩展的多通道投影图像自动拼接系统;利用二次校准方法细化求解一致性矩阵,在投影屏幕上实现了多通道投影图像间的几何无缝拼接;特征图案的正确选择和二次校准方法最大限度地降低了摄像头性能对校准精度的影响;在满足相邻投影图像有重叠区域和摄像头能拍摄到重叠区域两个基本条件时,系统可实现自动拼接校准.实验表明,二次校准方法使校准时间明显缩短,使校准精度达到了亚像素级;低端摄像头、高效率的特征提取方法和一致性矩阵求解算法使系统扩展成本大大降低.      

基于多时间尺度特征的语音识别模型

提出了基于多时间尺度特征的语音识别模型.该模型采用描述谱参数轨迹的段特征,在段尺度上实现了对语音信号帧间相关性的显式建模;采用段特征依赖的非平稳时间序列产生模型,实现了不同尺度特征间的相关性建模,并在帧尺度上通过参数化的均值轨迹函数,实现了对语音信号帧间相关性的隐式建模.给出了基于多时间尺度特征联合统计距离优化的分段算法及基于最大似然准则的模型参数估计算法.识别实验表明,该模型的识别性能优于标准HMM及趋势HMM.     

叶片弦中区内部气膜孔局部换热特性实验

对叶片弦中区内部有、无冲击射流的气膜出流冷却方式中,冷气侧气膜孔局部换热特性进行了实验研究。无冲击射流时,主要研究了来流雷诺数、气膜出流与横流密流比的变化对气膜孔局部换热特性的影响;研究发现,气膜孔局部的换热均随两者的增加而强化,且孔后的换热要好于孔前的换热,越靠近孔的地方换热越强,并对倾角为30°和90°时气膜孔的“溢流效应”进行了比较。有冲击射流时,改变冲击雷诺数、横流射流密流比等流动参数,通过对数据整理得出了这些参数对其局部换热特性的影响规律。      

Walsh变换对冲击信号序列特征提取的研究

提出使用Walsh变换和小波包相结合的方法,对滚动轴承故障产生的冲击信号序列提取故障特征, 并给出了计算的有效算法. 对滚动轴承故障特征分析和计算表明,用改进小波包分解、重构公式能有效地剔除冲击信号序列中高频共振信号和噪声, 使用快速Walsh变换(FWT)求取其功率谱,优于Fourier变换,可很好地提取故障特征,仿真和实际数据计算的结果,证实了上述方法的有效性.      

基于遗传算法的故障诊断规则提取方法的研究

针对粗糙集应用于故障诊断过程中存在的决策表属性连续值离散化和属性约简之间分离的问题,根据粗糙集的约简思想,本文研究了一种新的基于遗传算法的规则自动提取方法,可以在知识获取过程中同时实现属性连续值离散和属性约简。将该方法用于卫星电源系统故障诊断,可以从故障决策表中直接提取规则,得到超过90%的故障诊断准确率,进一步验证了这种方法的可行性和有效性。