An extended cyclic MUSIC algorithm

Many modulated communication signals exhibit a cyclostationarity (or periodic correlation) property, corresponding to the underlying periodicity arising from carrier frequencies or baud rates. In this paper, we propose a new MUSIC-like direction-finding algorithm that exploits cyclostationarity in order to improve the direction-of-arrival (DOA) estimation. Both cyclic and conjugate cyclic correlation matrices are used in the proposed method so that it can be considered as an extension of the cyclic MUSIC algorithm . The proposed cyclic method allows an increase in resolution power and noise robustness. Depending on the modulation type of incoming signals, the proposed method is also able to handle more sources than the number of sensors.     

Efficient Subspace-Based Estimator for Localization of Multiple Incoherently Distributed Sources

In this paper, a new subspace-based algorithm for parametric estimation of angular parameters of multiple incoherently distributed sources is proposed. This approach consists of using the subspace principle without any eigendecomposition of the covariance matrix, so that it does not require the knowledge of the effective dimension of the pseudosignal subspace, and therefore the main difficulty of the existing subspace estimators can be avoided. The proposed idea relies on the use of the property of the inverse of the covariance matrix to exploit approximately the orthogonality property between column vectors of the noise-free covariance matrix and the sample pseudonoise subspace. The resulting estimator can be considered as a generalization of the Pisarenko's extended version of Capon's estimator from the case of point sources to the case of incoherently distributed sources. Theoretical expressions are derived for the variance and the bias of the proposed estimator due to finite sample effect. Compared with other known methods with comparable complexity, the proposed algorithm exhibits a better estimation performance, especially for close source separation, for large angular spread and for low signal-to-noise ratio.     

An improved cyclic beamforming method for signal DOA estimation

Modulated signals used in telecommunication are cyclostationary. This property can be exploited to improve the direction of arrival (DOA) estimation performance. In this work, we propose an improved cyclic beamforming algorithm exploiting cyclostationarity. The proposed method exploits the information of both cyclic correlation matrix and cyclic conjugate correlation matrix with different cyclic frequencies. Compared with the existing methods, the simulation results show that proposed method improves substantially the signal selectivity; also it allows an increase in resolution power.     

油气井中的切割弹研究综述

文章对切割弹的分类和现状进行了详细的论述，并对切割弹设计中的装药结构、药型罩结构、外壳的结构、炸高以及间隙的影响进行了详尽的叙述。从中可以看出，切割弹的结构将直接决定着射流状态的好坏，进而决定着切割效果的好坏。合理的炸高和间隙，将直接决定着切割效果的好坏以及下井的通畅。     

利福平壳聚糖蛋白微球的制备及性能研究

选择生物相容性好,可生物降解的壳聚糖蛋白为药物载体,并测定了微球粒径,药物组分含量及载体自身结构和释药过程等主要物理性能,考察了制备工艺中的W/O型分散体系程度、投药量等物理量对形态、粒度、分布和体外降解等的作用.结果表明自制的利福平壳聚糖蛋白微球符合临床使用要求,可作为新型缓释药物临床应用.