共查询到7条相似文献,搜索用时 0 毫秒
1.
Xu Baowen Zhang Weifeng 《电子科学学刊(英文版)》2002,19(4)
The users' interest can be mined from the web cache and can be used widely. The interest can be specialized by the two-tuple (term, weight) in the simple interest model, in which the association relations are not mined, and then the interest cannot be associated in expressing the users' interest. Based on analyzing the WWW cache model, this letter brings forward a two-dimensional interest model and gives the interrelated methods on how to store the two-dimensional interest model effectively. 相似文献
2.
Traditional approaches of spatial spectral estimation are usually based on the second-order statistics. The higher-order cumulants and the poly-spectrum contain more information and are capable of reducing the Gaussian noise. In this paper, we present a new spectrum estimation method for direction-finding, the FOMUSIC algorithm, which is based on the eigen-structure analysis of the fourth-order cumulants. The derivation of the algorithm is given in detail and its performance is illustrated by both the computer simulations and the experiments of a direction-finding system. The obtained results demonstrate that the fourth-order cumulants based method outperforms the traditional methods, especially when the noise is an unknown colored one. 相似文献
3.
Yu Shuijun Liang Diannong 《电子科学学刊(英文版)》1996,13(3):211-215
The cost function for eigenstructures extraction is discussed in detail in this paper, one can obtain the largest eigenvector by minimizing the cost function. In order to obtain other eigenvectors, a covariance matrix series is constructed. If one compares the cost function with the energy function of a neural networks, the neural networks can be easily introduced to extract the eigenvectors. Theoretical analysis and computer simulations show that the proposed method is reasonable and feasible. 相似文献
4.
By using correlation-detection technique and improving structure of the test tube,the background noise of thermionic-electrons and space charge effect are restrained.The sec-ondary emission coefficient δ of thermionic cathode at high temperature has been studied.Theδ of impregnated scandate cathodes increases exponentially with increasing temperature at lowenergy and current of the bombardment electrons;at high energy or current of the bombardmentelectrons the temperature has little effect on δ.The research shows that an enhanced thermionicemission occurred when the cathode works at high temperature and under electron bombardment.These phenomena are discussed in terms of “internal field model”. 相似文献
5.
A definition of combined phase center for horn feeds is given.Formulas of E-planeand H-plane combined phase center for conical horns and the corresponding Optimal model arepresented,and a fast optimization method for solving this model is described.By using thismethod,the phase center of corrugated horn is discussed and calculated,and the variation of thephase center with distance and operating frequency is given. 相似文献
6.
Zhang Mengyang Feng Kongyu 《电子科学学刊(英文版)》1997,14(1):82-89
The virtual-ray method for treating HF electromagnetic scattering problems is derived from the plane wave of free space, and using this the plane wave scattering by an impedance wedge is studied. In the solution process a novel concept of generalized circle is introduced so that the complete amplitude function is obtained. And a reasonable physical interpretation for the term W2, which was neglected previously, is given. The calculated results agree well with those of the analytical solution obtained by G.D. Maliuzhinets(1958). 相似文献