期刊文献+
共找到3篇文章
< 1 >
每页显示 20 50 100
INDEX OF DIRECTION CHANGE OF ZONALLY AVERAGED WIND AND CHANGE OF SEASON
1
作者 朱敏 徐建霞 张铭 《Journal of Tropical Meteorology》 SCIE 2011年第2期128-135,共8页
In this paper, a Wind Direction Change Index (WI), which can describe four-dimensional spatiotemporal changes of the atmospheric circulation objectively and quantitatively, is defined to study its evolution and season... In this paper, a Wind Direction Change Index (WI), which can describe four-dimensional spatiotemporal changes of the atmospheric circulation objectively and quantitatively, is defined to study its evolution and seasonal variation. The first four modes can be obtained by EOF expansion of the zonally averaged WI. The first mode reveals the basic spatial distribution of the annually averaged WI. The second mode reflects the quasi-harmonic parts of the WI deviations. Tropical, subtropical and extratropical monsoon areas can be clearly reflected by this mode. The third mode reflects the non-harmonic parts of the WI deviations. It shows the so-called February reverse in stratospheric atmosphere as well as the asymmetric seasonal changes from spring to fall and from fall to spring due to both the land-sea distribution contrast between the Northern and Southern Hemispheres and the nonlinear effect of atmospheric and ocean fluids. The fourth mode reveals the northward advancing of the global reversed wind fields from spring to summer and their southward withdrawal from summer to autumn. 展开更多
关键词 Wind Direction Change index (WI) Empirical Orthogonal Function (EOF) four-dimensional space-time changes February stratospheric reverse
下载PDF
Beam Pattern Design and Performance Analyses for Circular Array with Spherical Baffles
2
作者 Cheng Zhang Ke-An Chen Guo-Yue Chen 《Journal of Electronic Science and Technology of China》 2009年第3期240-245,共6页
The influence of a rigid spherical baffle on the response of a uniform circular microphone array (UCA) is analyzed and two eigen-beam beamforming arrays are designed in the eigen-beam subspaee derived from the sound... The influence of a rigid spherical baffle on the response of a uniform circular microphone array (UCA) is analyzed and two eigen-beam beamforming arrays are designed in the eigen-beam subspaee derived from the soundfield decomposition. Expressions of white noise gain (WNG) and directivity index (DI) are derived for the designed arrays. Performance analyses are carried out for the designed arrays and compared between those of the delay-and-sum beamforming array using UCA with and without a rigid sphere. Computer simulations demonstrate that the designed arrays have frequency-independent directivity with the cost of reduced robustness at low frequency band. The delay-and-sum beamforming array has constant WNG at all frequencies, while its directivity of which is reduced at low frequency band. The rigid sphere can improve the robustness for all the arrays. 展开更多
关键词 BEAMFORMING directivity index uniform circular array white noise gain
下载PDF
Constrained minimum power combination for broadband beamformer design in the STFT domain
3
作者 Zhong-Hua FU 《Frontiers of Computer Science》 SCIE EI CSCD 2017年第3期408-418,共11页
Beamforming using sensor array is widely used in spatial signal processing since it offers better spatial focusing capability than single sensor. However, in practical appli- cations for broadband signal, there always... Beamforming using sensor array is widely used in spatial signal processing since it offers better spatial focusing capability than single sensor. However, in practical appli- cations for broadband signal, there always exists a trade-off issue between the directivity capability of an array and its robustness on system errors. In this paper, in order to combine merits of different beamformers instead of trade-off their per- formances, we propose a constrained minimum-power com- bination method. We firstly analyze two optimal beamform- ers that maximize Directivity Factor (DF) and White Noise Gain (WNG) respectively. Then we propose a non-linear combination method, which automatically selects the best beamformer that has the minimum output power, so as to control the unwanted white noise amplification and keep the maximum DF if possible. Two solutions to the proposed com- bination strategy are given. They do not need to determine the correct trade-off factor used in linear combination method, and avoid challenge ~stimations on noise and target statistics required in adaptive beamforming. The performance of the proposed beamformer is evaluated in ideal noise fields and complicated noise fields respectively. It is shown that the proposed beamformer integrates merits of different beamform- ers. It always achieves the best speech quality and biggest noise reduction compared to other popular beamformers. 展开更多
关键词 robust beamforming directivity index white noise gain BROADBAND STFT domain speech enhancement
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部