KNbO_3:Fe自泵相位共轭

本文提出KNbO_3:Fe光折变晶体的异形切割和最佳实验配置,首次在室温下获得内环腔自泵相位共轭,反射率高达～60％。     

数字调谐系统在组合音响上的应用

本文介绍了NEC公司大规模专用集成电路μPD1715G——016及其在组合音响上的应用,讨论了设计中的几点关键性问题,并分析了解决问题的方法和途径。     

一种锁相式频率合成器的设计

介绍了一种锁相式频率合成器的总体设计和电路结构设计,并进行了实验制作。设计的电路工作频率在１００ＭＨｚ以上,可广泛应用于雷达,航空,航天,通讯,导航,锁相环路等领域。     

基于数字水印的证件防伪技术

证件防伪是人们广泛关注的社会问题。本文提出了一种基于数字水印的证件防伪技术方案。该方案将水印嵌入到证件持有人的数字照片中,通过对数字照片边界的RADON变换来矫正图像在打印扫描(简称PS)过程中引入的几何失真,以证件号码为种子,产生具有良好自相关特性的随机序列作为水印信号,为提高水印的鲁棒性,采用强度自适应的DCT系数局部调整法,将水印重复多次嵌入到图像的分块DCT中频系数中。水印的提取采用相似度检测法,无需原始的图像。实验结果证明了该方案的可行性和有效性。与其他防伪技术相比,基于数字水印的证件防伪技术具有隐蔽性好,保密性强,技术容易更新,无需特殊材料和工艺,成本较低等突出的优点。     

Formation Technologies of Fiber Bragg Gratings

The principle of fiber Bragg gratings(FBG)is briefly described.The formation technologies of FBG are systematically given and analyzed.In addition,the experiment is described in detail,e.g.,the phase mask method is used to write directly the period Bragg gratings into the Ge-doped single mode fiber with KrF excimer UV laser.The results of experiment are also presented and analyzed.     

First principles study of structural,electronic and optical properties of AgSbS2

In this work, we study the structural, electronic and optical properties of AgSbS₂, using full-potential linearized augmented plane wave and the pseudopotential plane wave scheme in the frame of generalized gradient approximation. Features such as the lattice constant, bulk modulus and its pressure derivative are reported. Our results suggest a phase transition from AF-IIb phase to rocksalt (B1) phase under high pressure. The calculated band structure and density of states show that the material under load has an indirect energy band gap X→(LГ) for AF-IIb phase (semiconductor) and a negative band gap W→(ГX) for B1 phase (semimetal). The optical properties are analyzed and the origin of some peaks in the spectra is discussed. Besides, the dielectric function, refractive index and extinction coefficient for radiation up to 14 eV have also been reported and discussed.     

Perceptual image quality assessment using phase deviation sensitive energy features

Full reference image quality assessment (FR-IQA) algorithms aim to establish generic measures of perceptual image quality independent of distortion types. Recent developments in FR-IQA have marked the use of phase congruency features. Phase congruency is a dimensionless, normalized feature calculated from the log-Gabor energy of the image, equipped to be relatively insensitive to noise variations due to calculation of noise circle. The underlying assumptions on the nature of the noise used in this calculation affect the performance of phase congruency based FR-IQA measures. In this work, we (a) test the hypothesis that using the phase deviation sensitive energy features obtained from the log-Gabor filtered image instead of the noise adjusted, normalized phase congruency features will improve the general applicability of an FR-IQA measure, (b) reduce execution time by omitting noise circle calculation and (c) study how the modifications in parameter values, changes the correlation between the subjective scores and objective image quality values. Experiments on six benchmark databases suggest the effectiveness of the proposed method which improves over the existing phase congruency based algorithms, achieves competitive performance with the state-of-the-art methods and delivers the best average performance across all databases in terms of prediction monotonicity and accuracy.     

由阵列相位加权实现雷达横向距离分辨

本文提出一种通过阵列相位加权实现雷达横向距离分辨的新方法。首先要测出阵列口径面上由回波信号产生的幅度和相位分布。这一过程是通过对各接收通道相位进行加权而实现的。接下来，由已取得的数据即可获得横向距离分辨率。理论分析表明，无论目标位于远场区还是近场区，本方法都是适用的     

基于FPGA的全数字锁相环电机调速系统设计

数字锁相环具有抗干扰能力强、锁相效果好等优点。而电机锁相控制系统调速精度高,易于用程序实现。本文介绍了一种基于FPGA的数字锁相环,用于电机调速系统的设计。     

Dramatically enhanced performances and ideally controlled nano-morphology via co-solvent processing in low bandgap polymer solar cells

The device performance of photovoltaics with a polymer:fullerene bulk heterojunction (BHJ) structure, consisting of DT-PDPP2T-TT donor polymer and poly(3-hexylthiophene):[6,6]phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) acceptor compound, was investigated as a function of co-solvent composition. An enhancement of the photocurrent density and fill factor is observed in diodes made by spin-coating with chloroform mixed with ortho-dichlorobenzene, which allows a significantly higher device efficiency of 5.55% compared to diodes made from neat chloroform (efficiency = 3.61%). To clarify the role of the co-solvent, we investigated the nanoscale morphology with AFM, TEM and 2D-GIWAXS techniques and also the free-charge carrier mobility via space-charge limited current theory. We obtained the result that, under such supersaturated conditions, co-solvents induce increased polymer crystalline aggregation into a 3D phase structure and boost charge-carrier transport characteristics. This provides a rational basis for the development of ideally-controlled BHJ films that yield efficient DT-PDPP2T-TT:PCBM solar cells. Therefore, carefully selecting solvent mixtures provides an approach toward efficient low bandgap polymer solar cells.