牙形石HistiodellaHass四个种的讨论及地层对比意义

作者描述了产自塔里木盆地的HistiodellaHass的四个种,并探讨了它们与中国北方和北美中大陆暖水型牙形石及中国南方和北大西洋冷水型牙形石的对比关系。认为Histiodellasinuosa带对比北美中大陆牙形石动物群3的下部、中国南方Amorphognathusvariabilis带下部和中国北方Aurilobodusleptosomatus-Loxodusdissectus带下部。Histiodellaholodentata带下部相当于中国北方Aurilobodusleptosomatus-Loxodusdissectus带中部或中国南方的Amorphognathusvariabilis带至Eoplacognathussuecicus带的下部。Histiodellakristinae带对比北大西洋区的Eoplacognathussuecicus带中上部和中国北方的Tangshanodustangshanensis带。Histiodellabellburnensis带对比北大西洋区的Eoplacognathussuecicus带的上部到Eoplacognathusfoliaceus带下部。HistiodellaHass与北大西洋区和中国北方区典型牙形石的共同出现可以作为一个桥梁,建立起北美中大陆、北大西洋、塔里木盆地及华北地区牙形石的对比关系。

一种噪声环境的语音端点检测方法

端点检测是语音识别系统的一个重要组成,尤其是在噪声环境中,其准确性对语音识别系统性能有直接影响。提出了一种基于小波子带倒谱系数(SBC)的语音信号端点检测方法,利用小波变换对频带进行尺度划分,采用小波子带倒谱能量检测语音端点。通过与MFCC的仿真对比以及大量实验分析,小波子带倒谱特征在语音端点检测中具有更好的识别性能。

基于能量检测的复杂环境下的鸟鸣识别

针对实际环境噪声使得鸟鸣识别准确率受到影响的问题,提出一种基于能量检测的抗噪鸟鸣识别方法。首先,对包含有噪声的鸟鸣信号用能量检测方法检测并筛选出有用鸟鸣信号;其次,根据梅尔尺度的分布,对有用鸟鸣信号提取小波包分解子带倒谱系数(WPSCC)特征;最后,用支持向量机(SVM)分类器分别对提取的小波包分解子带倒谱系数(WPSCC)和梅尔频率倒谱系数(MFCC)特征进行建模分类识别。同时还对比了在添加不同信噪比的噪声下15类鸟鸣在能量检测前后的识别性能差异。实验结果表明,提取的WPSCC特征具有较好的抗噪功能,且经过能量检测后的识别性能更佳,更适用于复杂环境下的鸟鸣识别。

Transmission spectra of one-di mensional photonic crystals including negative-refractive-index media

We introduce a new model of one-dimensional （1D） photonic crystal composed of alternately arranged RHM and LHM layers with positive and negative refractive indices respectively, for which the transmission spectra of the model are calculated numerically with the transfer matrix method, and the bandgap structure and the polarization properties are analyzed. We found that the introduction of negative refractive index layers （i.e. LHM medium layers） gives rise to some peculiar band-gap structure and polarization properties as follows. Firstly, the forbidden bands are extremely wide and the transmission bands are very sharp without oscillation;and secondly, the change of incident angle has different influences on the forbidden bands of TE and TM modes. For the TM mode, the forbidden band width decreases substantially and finally vanishes, and for the TE mode with central wavelength, the total reflection happens at anv incident anale.

Cooperative Anti-Interference Spectrum Sharing with Secondary User Selection

In this paper, we propose a cooperative anti-interference spectrum sharing strategy with secondary user selection where the secondary system can gain spectrum access along with the primary system. Specifically, secondary user and are selected to transmit the primary and secondary signal through different bandwidth in the second transmission slot which occupies fraction of the time. Thus, the primary and secondary systems will not interfere with each other. We study the joint optimization of time and bandwidth allocation such that the transmission rate of the secondary system is maximized, while guaranteeing the primary system to achieve its target rate. Simulation results confirm efficiency of the proposed spectrum sharing strategy, and the significant performance improvement of the cognitive system.

RECENT PROGRESS IN MULTI-BEAM KLYSTRON IN IECAS

Recent research progresses in Multi-Beam Klystron (MBK) in IECAS are briefly introduced in the letter. The S-band MBKs of IECAS have peak power of 120-250 kW, average power of 4-9 kW, efficiency of 35-45%, gain of 41-46 dB, beam voltage of 15-19 kV, and weight of 40-45 kg. Some key technical problems of MBK are also described and discussed. Among them,improving the design of MBK to obtain the required bandwidth, raising beam transmission to increase average power, eliminating oscillation and spray spectrum, overcoming window breakdown caused by magic mode, reducing breakdown times of electrongun, are most important things for the practical MBK. Besides, further research work in MBK in IECAS is commented.

A portable single-cell analysis system integrating hydrodynamic trapping with broadband impedance spectroscopy

In this paper, we present a portable single-cell analysis system with the hydrodynamic cell trapping and the broadband electrical impedance spectroscopy （EIS）. Using the least flow resistance path principle, the hydrodynamic cell trapping in serpentine arrays can be carried out in a deterministic and automatic manner without the assistance of any external fields. The experimental results show that a cell trap rate of higher than 95% can be easily achieved in our ceil trapping microdevices. Using the maximum length sequences （MLS） technique, our home-made EIS is capable of measuring the impedance spectrum ranging from 1.953 kHz to 1 MHz in approximately 0.5 ms. Finally, on the basis of the developed single-cell analysis system, we precisely monitor the trapping process of human breast tumor cells （MCF-7 cells） according to the changes of electrical impedance. The MCF-7 cells with different trapping conditions or sizes can also be clearly distinguished through the impedance signals. Our portable single-cell analysis system may provide a promising tool to monitor single cells for long periods of time or to discriminate cell types.