地下ELF线天线在地-电离层壳体中产生的场

为了研究地震产生的机理,需要分析和研究地下任意ELF线天线在地-电离层壳体中产生的电磁场。地下任意ELF线天线产生的电磁场可由地下ELF点源产生的电磁场进行叠加。首先导出了地下ELF点源在地-电离层壳体中产生的电磁场表达式,然后得到了地下任意ELF线天线在地-电离层壳体中产生的电磁场的表达式。分别讨论了地下单条和两条ELF线天线在地面上产生电磁场的场强空间分布图,用色标表示了场强值在空间分布的强弱。电磁场的水平分量在地面上产生电磁场的场强值要比垂直分量产生的场强值大,单条线天线在地面上产生电磁场的场强值要比两条线天线产生的场强值小。     

调相信号模拟与数字产生方法比较

介绍了调相信号的模拟产生方法和数字产生方法，并对2种调相信号产生方法的差异进行了分析，重点阐述了直接数字合成(DDS)器件产生调相信号的机理和特点。     

多通道可编程相参信号产生系统

1简介 多通道可编程相参信号产生系统由多通道信号产生卡,多通道信号产生控制软件及高性能工控机组成.系统软件控制界面及四通道产生的信号如图1和图2所示.     

强激光打靶产生电磁脉冲特性与传导防护研究

为了降低电磁脉冲的场强大小,加强强激光打靶产生电磁脉冲的传导防护性能,提出了强激光打靶产生电磁脉冲特性与传导防护研究.由于强激光打靶产生电磁脉冲对各种电子设备和电气设备都会造成一定威胁,采用双指数函数,分析了强激光打靶产生电磁脉冲的时域波形频谱,完成了强激光打靶产生电磁脉冲的特性研究;为了消除强激光打靶产生的电磁脉冲波...     

超短脉冲激光产生方法新说

到目前为止,关于产生超短脉冲激光的方法已有许多技术。为寻求新的产生方法和探索新的产生超短脉冲激光的技术途径,作者根据其产生过程的物理机制的不同,提出新的分类方法:     

长周期硬件高速任意位数随机数产生器

本文介绍的随机数产生方法利用m序列所特有的性质,完全采用硬件电路产生,产生速率快.若随机数为16Bit,则速率可达50MHz/16=3.125MHz;随机数周期长,若利用24级移位寄存器产生m序列,则16Bit随机数的周期至少为2~(24)/16=2~(20).因此该方法产生的伪随机数可以再现.由于完全利用硬件产生,因此该方法产生速率快,不占用CPU和存贮单元,且能保证足够长的周期.经过均匀性和独立性的检验,该方法产生的伪随机数紧密地近似于理想的随机数.     

极紫外阿秒脉冲产生过程的本征原子相位分析

为了研究高次谐波极紫外阿秒脉冲产生过程中的谐波相位匹配问题,基于光场电离高次谐波产生过程3步分析模型得出了高次谐波产生过程的理论描述解析式,并以此分析了阿秒脉冲产生过程中的高次谐波本征原子相位。由研究可知,除最高阶谐波外,对同一阶高次谐波产生有贡献的电子均有两类—长轨迹电子和短轨迹电子,各高次谐波长轨迹电子产生的谐波谱相之间几乎不存在线性关系,而短轨迹电子产生的高次谐波谱相之间则存在着良好的线性关系。结果表明,抑制各谐波长轨迹电子有助于产生更小脉宽阿秒脉冲。此结果对极紫外阿秒脉冲产生实验中的高次谐波相位匹配有重要的参考价值。     

离轴涡旋光束诱导空气等离子体产生太赫兹波

使用涡旋光束代替高斯光束作为产生光源,研究了涡旋光束产生太赫兹波的过程。探究了具有不同拓扑荷数的涡旋光束在产生太赫兹波时的差异,相位奇点的位置对产生太赫兹波的影响,不同脉冲强度和激光波长下涡旋光束产生的太赫兹波能量、频谱和偏振的变化。结果表明,产生的太赫兹波强度会随涡旋光束拓扑荷数的变化而变化,并且与涡旋中心的位置密切相关。涡旋光束所产生的太赫兹波随脉冲强度和激光波长的变化趋势与高斯光束一致。高斯光束与涡旋光束产生的太赫兹波在频谱和偏振上的变化趋势一致。     

基站设备的电磁兼容验证

1基站设备的电磁干扰验证 基站设备的电磁干扰验证包括传导干扰验证和辐射干扰验证。传导干扰是基站设备产生的干扰信号通过电源线或信号线对外传导产生的干扰。辐射干扰是基站设备产生的干扰信号通过空间耦合的形式对外辐射产生的干扰。     

产生区宽度W_g＝W－ξW_f中参数ξ的估计

产生参数（产生寿命、表面产生速度）的测量是半导体材料和器件工艺质量检验的重要内容，产生区宽度的Ｐｉｅｒｒｅｔ模型形式简单，但其含有一待定参数，本文主要就是研究这一参数的估计方法。     

A linear, time-varying system framework for noniterativediscrete-time band-limited signal extrapolation

A technique for the analysis and design of noniterative algorithms for discrete-time, band-limited signal extrapolation is described. The approach involves modeling the extrapolation process as a linear, time-varying (LTV) system, or filter. Together with a previously developed Fourier theory for LTV systems, this model provides a frequency-domain transfer function representation for the extrapolation system. This representation serves as a powerful tool for characterizing and comparing the reconstruction properties of several well-known least squares optimal algorithms for band-limited extrapolation. Moreover, the frequency-domain setting provides a conceptually attractive means for understanding the process of extrapolation itself. Additionally, a least squares approximation methodology for designing LTV filters for band-limited extrapolation is developed. The design technique is shown to unify a broad class of algorithms for extrapolating discrete-time data and, further, to provide a means for designing new and improved extrapolation algorithms     

Detection of Modulated Gaussian Signals in Noise

A method using Hermite polynomials is utilized for analyzing the outputs of νth-law devices for inputs of modulated Gaussian signals and zero-mean Gaussian noise. New results are developed for the output correlation functions, and techniques for obtaining closed-form expressions are pointed out. Output signal-to-noise ratios for various input carrier-to-noise-power ratios are calculated, and plots are shown for a single sinusoidal modulating signal. Results are derived to show the existence of a theoretical maximum for the output signal-to-noise ratio. The method can be directly applied for the case of general Fourier expandable signals modulating a Gaussian carrier.     

Rain attenuation measurements over New Delhi with a microwave radiometer at 11 GHz

Rain attenuation measurements over New Delhi carried out with a microwave radiometer installed at the National Physical Laboratory (NPL), New Delhi and operating on 11 GHz for a period of more than three years are presented. For 0.01 percent of time for the period June 1977-April 1978, the attenuation exceeded for the monsoon period is 14.0 dB whereas for the whole year, it exceeds 10.4 dB. During the winter for the same percentage of time, the attenuation exceeded 1.5 dB, whereas for March-April it exceeds 0.5 dB. For the period May 1978-June 1980, it is observed that for 0.01 percent of time the attenuation for the whole year exceeds 9.0 dB. During the winter for the same percentage of time, the attenuation exceeds 1.4 dB whereas for March-April it exceeds 0.4 dB. A comparison of attenuation over New Delhi and those reported elsewhere are discussed. Yearly and worst month time ratio over New Delhi are given also as the values reported for the European region. Comparison of the attenuation distribution and the rate of surface rainfall measured with a rapid-response rain gauge are also given. The comparison shows that for the monsoon period and for 0.01 percent of time, the attenuation value exceeded for 14 dB corresponds to the surface rainfall rate of 140 mm/h. For the monsoon of 1978, 1979, comparison shows that for 0.1 percent of time, the attenuation value exceeded for 9.0 dB corresponds to the surface rainfall rate of 90 mm/h. Variation of attenuation and effective path length for various rainfall rates and elevation angles are also given.     

Image Processing of Biological Liquids Films for Medical Diagnostics

In this paper, the development of smart medical autonomous technology is considered. An example of a smart medical autonomous distributed system for diagnostics is also discussed. To develop this system for medical image analysis we review several processing methods. The use of the cuneiform dehydration method for medical diagnosis is considered. The experimental results obtained for blood serum dehydrated films are presented. The author proposes an algorithm for the primary identification of structures formed in the films and their use for automated detection of various structures for diagnostic purposes. The paper describes the first stage of image processing, i.e. the selection of filtering types for the correct identification of structural features and characteristics of the images. The results of filtering and some computational results of various types of structures in the films are presented.     

一种基于CCD的非接触尺寸测量系统

设计了一种基于CCD的非接触尺寸测量系统.运用亚像素边缘检测法对圆环进行边缘检测,完成对圆环的非接触尺寸测量.利用数据库实现对测量数据的存储管理及网络传输.通过实验证明:对圆环测量精度外径误差0.005 mm,内径误差0.001 mm,壁厚误差0.015 mm,整体绝对误差小于0.02 mm,相对误差小于0.07％,满足了工程高精度测量要求.本系统适合有危害性的工业现场环境,数据的存储管理功能也给实际应用带来很大便利.     

Communication over fading dispersive channels with feedback

An intermittent on-off noiseless feedback scheme for binary communication over the slow- and fast-fading Rayleigh channels is proposed and analyzed. At high energy-to-noise ratios, doubling the number of feedback iterations yields a 3-dB power saving for the slowly fading channel. Power savings ranging from 1 dB for one feedback iteration to 9 dB for 16 iterations are typical for the fast-fading model. Also for the fast-fading model, by picking the optimum number of forward transmissions for each value of energy-to-noise ratio, the best achievable performance requires approximately 7.5 dB more energy than the minimum predicted by the rate-distortion bound. Also presented is a feedback communication system for wide-sense stationary, uncorrelated-scatterer, fading, and dispersive forward and feedback channels. The model used for both forward and feedback channels is Kennedy's. Upper and lower bounds on the error probability for block orthogonalM-ary communication are presented for this system.     

An efficient method for terminal and multiterminal pathset enumeration

The literature is abundant with algorithms for determining separately the paths for the single terminal pair, paths for multiterminal pairs and cuts for a specified terminal pair of any network, from knowledge of the reliability logic diagram (RLD). However, very few methods are available as efficient algorithms for enumerating simultaneously the paths between any single terminal pair, paths for multiterminal pairs and cuts for the specified terminal pair.The present paper provides a conceptually simple and computationally efficient algorithm to obtain simultaneously the paths between any single pair of terminals, paths for multiterminal pairs and the cuts for the specified terminal pair of interest of any complex network. The algorithm is easy and computationally economical and also applicable to graphs having both nodes and branches of finite non-zero failure probability.An illustrative example is provided to demonstrate the effectiveness of the proposed algorithm.     

信息系统如何开展定级备案工作

信息系统定级、备案工作是开展等级保护工作的前提和基础。介绍了信息安全等级保护定级备案工作目标、内容流程和方法,为政府机关、企事业信息系统开展信息安全等级保护定级备案工作提供了借鉴。     

Analysis of stochastic gradient tracking of time-varying polynomialWiener systems

This paper presents analytical and Monte Carlo results for a stochastic gradient adaptive scheme that tracks a time-varying polynomial Wiener (1958) system [i.e., a linear time-invariant (LTI) filter with memory followed by a time-varying memoryless polynomial nonlinearity]. The adaptive scheme consists of two phases: (1) estimation of the LTI memory using the LMS algorithm and (2) tracking the time-varying polynomial-type nonlinearity using a second coupled gradient search for the polynomial coefficients. The time-varying polynomial nonlinearity causes a time-varying scaling for the optimum Wiener filter for Phase 1. These time variations are removed for Phase 2 using a novel coupling scheme to Phase 1. The analysis for Gaussian data includes recursions for the mean behavior of the LMS algorithm for estimating and tracking the optimum Wiener filter for Phase 1 for several different time-varying polynomial nonlinearities and recursions for the mean behavior of the stochastic gradient algorithm for Phase 2. The polynomial coefficients are shown to be accurately tracked. Monte Carlo simulations confirm the theoretical predictions and support the underlying statistical assumptions     

General coupling matrix synthesis methods for Chebyshev filteringfunctions

Methods are presented for the generation of the transfer polynomials, and then the direct synthesis of the corresponding canonical network coupling matrices for Chebyshev (i.e., prescribed-equiripple) filtering functions of the most general kind. A simple recursion technique is described for the generation of the polynomials for even- or odd-degree Chebyshev filtering functions with symmetrically or asymmetrically prescribed transmission zeros and/or group delay equalization zero pairs. The method for the synthesis of the coupling matrix for the corresponding single- or double-terminated network is then given. Finally, a novel direct technique, not involving optimization, for reconfiguring the matrix into a practical form suitable for realization with microwave resonator technology is introduced. These universal methods will be useful for the design of efficient high-performance microwave filters in a wide variety of technologies for application in space and terrestrial communication systems