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991.
通过在圆锥喇叭内壁加磁介导涂层的方法,成功地设计了具有低副瓣、低交叉极化和方向图对称的喇叭天线。该磁介质涂层既是良导电体,又是良导磁体。通过选择合适的喇叭张角,该喇叭天线与波纹喇叭性能相同,而且比波纹喇叭设计简单。  相似文献   
992.
曲线顶管初探   总被引:7,自引:0,他引:7  
王承德 《特种结构》1998,15(4):18-21
本文对曲线顶管的最重要参数——最小曲线半径进行了探讨,得出最小曲线半径与管段长度、管径成正比,与木垫片厚度成反比的关系。另外还指出曲线半径还受土体承载力的制约,要防止管道在施工中发生纵向失稳。  相似文献   
993.
A robust method is presented for computing rotation angles of image sequences from a set of corresponding points containing outliers. Assuming known rotation axis, a least-squares (LS) solution are derived to compute the rotation angle from a clean data set of point correspondences. Since clean data is not guaranteed, we introduce a robust solution, based on the M-estimator, to deal with outliers. Then we present an enhanced robust algorithm, called the annealing M-estimator (AM-estimator), for reliable robust estimation. The AM-estimator has several attractive advantages over the traditional M-estimator: By definition, the AM-estimator involves neither scale estimator nor free parameters and hence avoids instabilities therein. Algorithmically, it uses a deterministic annealing technique to approximate the global solution regardless of the initialization. Experimental results are presented to compare the performance of the LS, M- and AM-estimators for the angle estimation. Experiments show that in the presence of outliers, the M-estimator outperforms the LS estimator and the AM-estimator outperforms the M-estimator.  相似文献   
994.
On chaotic simulated annealing   总被引:25,自引:0,他引:25  
Chen and Aihara (1995) proposed a chaotic simulated annealing approach to solving optimization problems. By adding a negative self coupling to a network model proposed earlier by Aihara et al. and gradually removing this negative self-coupling, they used the transient chaos for searching and self-organizing, thereby achieving great improvement over other neural-network approaches to optimization problems with or without simulated annealing. In this paper we suggest a new approach to chaotic simulated annealing with guaranteed convergence and minimization of the energy function by gradually reducing the time step in the Euler approximation of the differential equations that describe the continuous Hopfield neural network. This approach eliminates the need to carefully select other system parameters. We also generalize the convergence theorems of Chen and Aihara to arbitrarily increasing neuronal input-output functions and to less restrictive and yet more compact forms.  相似文献   
995.
A novel principle “electret” microphone, i.e., floating electrode electret microphone, is proposed and implemented in this study. Single-chip fabrication and corrugation technique are used in the design and fabrication of the microphone. The floating electrode is encapsulated by highly insulated materials to ensure that there is no electric-leakage passage between the floating electrode and the electrodes of the microphone. Net-free electronic charges (not “bonded” charges as in traditional electret) in the floating electrode can excite the electric field, which is similar to that of the traditional electret. The floating electrode can be easily charged by use of the “hot” electron technique, available using the avalanche breakdown of the p+-n junction. Therefore, the electret microphone is rechargeable, which can greatly increase the lifetime of the device. The preamplifier has been on-chip integrated in a junction-field-effect transistor (JFET) source-follower type with resistors by use of ion implantation. Electret charges are banded in a deep potential trap, thus, this microphone can operate at a high temperature (as high as 300°C) and has high stability and reliability. Experiments show that the prototype has a 3-mV/Pa sensitivity and a larger than 21-kHz frequency bandwidth in a 1 mm ×1-mm diaphragm area. Microphone performance can be further improved by optimized process and design. The fabrication is completely integrated-circuit (IC) compatible, hence, the microphone shows promise in integrated acoustic systems  相似文献   
996.
闫玉娥  王宝树 《微处理机》1998,(1):52-54,61
本文介绍了IC卡处理系统的基本组成,详述了一种IC卡处理系统的软硬件实现方法,说明了I^2C总线在系统中的应用。  相似文献   
997.
本文将虚拟仪器技术与光频转换器件TSL230B相结合,设计新型浑浊度数字化测试仪.阐述该系统的工作原理、硬件构成及软件设计方案;实现浑浊度的自动在线测量.实验结果表明,该仪器数据处理能力强,图形化显示直观,保存与打印结果方便,测量的重复性好,精确度高.  相似文献   
998.
本文分析了发电企业生产项目招标的现状、特点以及存在的问题,提出了完善和改进发电企业生产项目招标管理的一些措施,从而建立科学合理、规范的监督制度与运作程序,保证项目质量,提高经济效益。  相似文献   
999.
The problem of stabilizing multiple independent linear systems sharing one conmmon network cable is presented and solved. Both the quanfization and time sequencing are studied in the field of control over networks by providing the formulated stabilizing sufficient condition which illustrates the relationship between the system instability, quanfization and time sequencing, and the data rate is also presented in temps of the quanfization and time sequencing. A numerical example is given to illustrate the result.  相似文献   
1000.
分布式防火墙技术研究   总被引:1,自引:0,他引:1  
王霞 《电脑学习》2004,(5):41-43
介绍了分布式防火墙的产生、体系结构、主要特点及存在的问题.  相似文献   
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