单本振二次变频方案浅析

介绍了一种新型的变频方案,采用单本振源即可实现二次变频,还能保留传统二次变频方案的优点,简化了本振源的实现,有利于小型化和集成化.对该新方案进行了理论分析,进而对这种改进二次变频方案提出了采用的频率配置关系和中频滤波器参数设计准则,并结合一个工程实例完成了相关设计.文中所讨论的方案也同样适用于其它频段.     

一种安全完备的秘密图像分存方案

基于二维细胞自动机原理提出了一种新的秘密图像分存方案,该方案把秘密图像作为细胞自动机的一个初始配置,通过二维阶可逆存贮细胞自动机将影子图像分解成份,再利用其逆细胞自动机对份的影子图像中连续的份进行反向迭代来重构所分存的秘密图像.分析表明:该方案实现简单,在计算上是安全的,并且是一个完备的方案,而且易于在软件和硬件上实现.     

三粒子量子态隐形传送的正交完备基展开与算符变换

席拥军等提出了一个利用三对任意纠缠的粒子作为量子通道对一个任意的三粒子态实现隐形传送的方案.在此方案中,接受者需要引入一个辅助二态粒子.由波函数的叠加原理与变换算符出发,提出一种方法,不需要引入一个辅助二态粒子,将体系的总量子态按Bell基展开,接受者直接对自己拥有的粒子进行相应的变换,可使这三粒子恢复原始量子态,从而实现概率为1的量子态的隐形传送.     

新的可转移电子现金方案

提出一种新的可转移离线电子现金方案.引入一种新的限制性盲签名机制,实现了对用户身份的限制性盲化;引入一种基于身份的公钥机制,实现了一个多重代理签名机制,进而实现了用户现金的不可追踪性.方案检查二次消费上的优势非常明显,通过重复消费的货币就能够直接计算出重复消费者的身份信息.     

一种基于二维细胞自动机的秘密图像共享方案

基于二维细胞自动机提出了一种新的秘密图像共享方案,该方案把秘密图像作为细胞自动机的一个初始配置,通过利用二维n阶可逆存贮细胞自动机进行分解成n为份的影子图像,再利用其逆细胞自动机进行反向迭代来重构所共享的秘密图像.分析表明,该方案实现简单,在计算上是安全的,并且是一个完备的(n,n)方案.     

一种单脉冲二次雷达接收通道幅相一致性的调整方案

对单脉冲二次雷达接收通道的幅相一致性进行了简要分析，并提出了一种利用CPLD闭环控制实现通道幅相一致性的方案。实验表明，该方案可行。     

基于非线性光纤环镜的OCDMA全光码字转换方法

提出了一种利用非线性光纤环镜(NOLND实现二维全光码字转换方法,设计了基于NOLM的码字转换方案,并进行了系统性能仿真分析.研究结果表明:该方法能够成功实现系统的数据传输;采用这种码字转换方法,系统误码率性能远远高于没有进行码字转换的系统性能.     

空管二次雷达S模式询问机目标捕获与监视实现方案

提出了一种空管二次雷达S模式询问机捕获与监视空中S模式目标的工程实现方案.方案既考虑了S模式询问机的具体使用条件,又完全符合国际民航组织附件10的相关规定.采用S模式与A/C模式的兼容组合技术实现了过渡时期对空域目标的全面监视,采用自适应随机捕获技术实现空域中S模式目标的捕获和锁定,采用S模式多目标询问时序编排技术实现对同一波束内多个S模式目标的选址询问和监视.该方案已经在实际二次雷达S模式询问机研制过程中得以应用和验证,效果良好.     

二维综合孔径微波辐射计成像理论与方法研究

本文在顺轨方向孔径综合技术的理论研究的基础之上,对星载二维成像综合孔径微波辐射计的成像理论进行了分析,讨论了二种不同的基线结构方案,并对相应的可见度函数采样方案和成像反演算法进行了讨论.最后通过数值模拟说明了本文提出的成像理论和基线结构方案具有可行性.     

GSMR射频通信接收机的设计

本文分析了一种应用于GSMR信号的接收机方案和部分实现.采用二次变频宽中频接收机的技术,结构明了,实用性强.文中叙述了接收机总体方案的考虑和设计.并结合实际硬件电路对该方案进行了分析和讨论.     

Wavelet-based image denoising using a Markov random field a priorimodel

This paper describes a new method for the suppression of noise in images via the wavelet transform. The method relies on two measures. The first is a classic measure of smoothness of the image and is based on an approximation of the local Holder exponent via the wavelet coefficients. The second, novel measure takes into account geometrical constraints, which are generally valid for natural images. The smoothness measure and the constraints are combined in a Bayesian probabilistic formulation, and are implemented as a Markov random field (MRF) image model. The manipulation of the wavelet coefficients is consequently based on the obtained probabilities. A comparison of quantitative and qualitative results for test images demonstrates the improved noise suppression performance with respect to previous wavelet-based image denoising methods.     

SAW电视中频滤波器三次行程的分析方法

随着立体声电视和高清晰度电视等的发展,对声表面波电视中频滤波器的性能提出了更严格的要求,首先介绍了声表面波电视中频滤波器三次行程反射问题形成的主要原因,由于它与主信号的幅度只差12dB,将会使滤波器的通带波动达到不可容许的地步,因此必须加以抑制,本文讨论了分别采用同相位法;声表面波单相单向换能器（Single Phase Unidirectional Transducer,SPUDT）来消除三次行程信号的影响。     

Probability density function estimation using the MinMax measure

The problem of initial probability assignment which is consistent with the available information about a probabilistic system is called a direct problem. E.T. Jaynes' (1957) maximum entropy principle (MaxEnt) provides a method for solving direct problems when the available information is in the form of moment constraints. On the other hand, given a probability distribution, the problem of finding a set of constraints which makes the given distribution a maximum entropy distribution is called an inverse problem. A method based on the MinMax measure to solve the above inverse problem is presented. The MinMax measure of information, defined by Kapur, Baciu and Kesavan (1995), is a quantitative measure of the information contained in a given set of moment constraints. It is based on both maximum and minimum entropy. Computational issues in the determination of the MinMax measure arising from the complexity in arriving at minimum entropy probability distributions (MinEPD) are discussed. The method to solve inverse problems using the MinMax measure is illustrated by solving the problem of estimating a probability density function of a random variable based on sample data     

Random forest-based tuberculosis bacteria classification in images of ZN-stained sputum smear samples

In this paper, we present a robust hybrid watermarking method applied to color images for authentication, which presents robustness against several distortions. Due to the different nature of common signal processing and geometrical attacks, two different techniques for embed a same watermark are used in this method. In the first one, the luminance component (Y) information is used to embed the watermark bit sequence into the magnitude of the middle frequencies of the Discrete Fourier Transform (DFT). In the second one, a selected region of 2D histogram composed by blue-difference and red-difference (Cb–Cr) chrominance components is modified according to the watermark bit sequence. The quality of the watermarked image is measured using the following well-known indices peak signal to noise ratio (PSNR), visual information fidelity (VIF) and structural similarity index (SSIM). The difference color of the watermarked image is obtained using the normalized color difference (NCD) measure. The experimental results show that the proposed method provides robustness against several geometric distortions, signal processing operations, combined distortions and photo editing. The comparison with the previously reported methods based on different techniques is also provided.     

Two-dimensional object recognition through two-stage stringmatching

A two-stage string matching method for the recognition of two-dimensional (2-D) objects is proposed in this work. The first stage is a global cyclic string matching. The second stage is a local matching with local dissimilarity measure computing. The dissimilarity measure function of the input shape and the reference shape are obtained by combining the global matching cost and the local dissimilarity measure. The proposed method has the advantage that there is no need to set any parameter in the recognition process. Experimental results indicate that the hostage string matching approach significantly improves the recognition rates compared to the one-stage string matching method.     

Picosecond time-resolved laser mass spectroscopy

The extension of laser mass spectroscopy to the picosecond time domain and the application of this method to the study of fast surface processes is described. The technique is based on a pump-probe scheme in which a first pulse stimulates the desorption of surface material, and a second delayed pulse is used to photoionize the desorbed particles to allow detection with a mass spectrometer. Measurements on picosecond-laser-heated GaAs surfaces demonstrate the feasibility of the method. For example, it was possible to measure the thermal desorption of Ga and of Ga₂O with picosecond time resolution     

基于三级邻居的复杂网络节点影响力度量方法

已有的节点影响力度量方法均存在一定的局限性。该文基于三度影响力原则,综合考虑局部度量的适宜层次及大规模网络的可扩展性,提出一种基于3级邻居的节点影响力度量方法(TIM)。该方法将节点2, 3级具有传播衰减特性的邻居视为整体,用于度量节点的影响能力。利用传染病模型及独立级联模型,在3个真实数据集验证了该方法的有效性。实验结果表明,基于3级邻居的节点影响力度量方法在影响力一致性、区分度、排序性等指标中表现优越,且能够有效求解影响力最大化问题。     

Polarization-mode dispersion measurements along installed opticalfibers using gated backscattered light and a polarimeter

We describe two new techniques that utilize a polarimeter for studying the state of polarization of gated Rayleigh backscattered or Fresnel backreflected light along optical fibers in real time on the Poincare sphere. The first method, using Rayleigh backscattered light, is here applied to measure the accumulation of polarization-mode dispersion (PMD) along an 11.5 km section of installed fiber link. With a simplified configuration, the second technique is developed and applied for measuring the PMD of individual fiber subsections in a 37 km long link. This is achieved by using the Fresnel-reflections which arise from the fiber connectors that join the link     

Translational motion compensation for coronary angiogram sequences

A method of compensating for the lag of the video cameras typically used in angiographic systems is presented for use in sequences of digitized X-ray images. The lag effect is reduced by a straightforward weighted subtraction, which has the undesirable side effect of increasing noise. By superimposing several lag-corrected and appropriately shifted images, however, the signal-to-noise ratio can be restored. The algorithm uses the phase-correlation method to measure the two-dimensional shift of a mobile coronary arterial structure. Processing is confined to a rectangular area of interest (AOI), which encloses a feature of clinical significance. The differences of the phases of the Fourier transforms of two frames is computed, combined with an appropriate filter, and inverse Fourier-transformed to produce a phase-correlation image. The vector separation from the origin of image space of the peak of the phase-correlation image is the estimate of the shift of the artery's position in the second frame as compared to the first. The isolation of the AOI from the surrounding image is achieved by the application of a window and correction for any linear trend in the background intensity.     

Electrical Derivative Measurement of High-Power InGaAs LDs Under Scanning Current with Variable Step

For the large driving current of high-power semiconductor Laser diodes (LDs), a modified method to measure the electrical derivative of LDs under scan-ning driving current with variable step length is proposed, which is to achieve the fast and accurate measurement of optical and electrical characteristic parameters of LDs with a relatively small data acquisition. The experimental re-sults show that, with fewer measurements, this method can effectively and accurately measure and extract the LDs corresponding parameters including threshold cur-rent (Ith), voltage-current characteristic (V-I), luminous power-current relation (P-I), electrical derivative curve (IdV/dI-I). The wavelet transformation singularity testing results of the threshold current also verify the accuracy, reliability, and advantage of this method.