基于随机共振的双门限协作频谱感知算法

针对现有频谱感知算法在低信噪比（SNR）环境中性能检测不佳的问题以及传统随机共振（SR）检测弱信号的方法在实际应用中存在的局限性,通过设置最优门限,计算出最优的协作用户数量,提出了一种基于随机共振的双门限协作频谱感知算法,并对提出的算法进行了性能分析。DCSSR算法通过将位于双门限不确定区域的统计数据经过随机共振系统,进一步提高频谱感知算法在低信噪比下的检测性能。仿真结果表明,在不同信噪比和虚警概率下,DCSSR算法相较于传统单门限能量协作算法、双门限能量协作算法以及单门限随机共振协作算法,检测性能都得到了提升。在信噪比为-20 dB时,提出的DCSSR算法相较于传统单门限能量检测协作算法,检测概率提高了80%。     

改进双门限能量检测分簇协作频谱感知算法

针对传统频谱感知算法在低信噪比环境下检测概率较低的问题,提出改进双门限能量检测分簇协作频谱感知算法。算法将感知节点分簇,簇间信息采用OR准则硬融合,簇内双门限外节点发送1 bit判决结果进行硬融合,双门限内节点发送能量值和信噪比值进行加权软融合。加权软融合阶段构造检测概率与节点权重系数函数,利用压缩因子粒子群算法选择权重系数进行函数寻优,以最大化检测概率。仿真结果表明,在低信噪比和不同感知用户数目环境下,算法仍具有较高的检测概率。     

基于统计可信度的压缩感知协作频谱检测算法

压缩感知为认知无线电的宽频谱感知提供了一种新的方法和思路。基于压缩感知的原理,提出了一种多认知用户协作场景下基于用户统计可信度的协作频谱检测算法。该算法使用正交匹配协作追踪算法获得认知区域内的频谱占用情况,根据不同认知用户频谱检测的历史准确度综合判定用户感知结果的统计可信度。仿真结果表明,该算法在不同用户数、不同采样值、不同信噪比变化范围下其检测性能均优于传统算术平均方法,有效改善了检测性能。     

基于阈值选择信噪比的协作频谱检测

频谱感知是实现认知无线电的关键技术之一,协作能一定程度上消除多径和阴影影响,为了提高频谱检测性能,提出一种基于阈值选择信噪比的协作频谱检测的方法,该方法利用空间位置信息估计出信噪比,将检测数据和估计的信噪比送往融合中心,利用阈值设置,对信噪比进行算法选择,选出具有较好的SNR感知用户数据,结合能量检测法进行判断。仿真结果表明：在信噪比分布不均匀的情况下,该方法能较好的提高系统的检测性能,减少融合的用户数目。     

基于能量检测与Sevcik分形维数的协作频谱感知算法

在认知无线网络中,针对单节点频谱感知易受到噪声不确定性的影响和传统的能量检测法在高噪声功率场景中检测性能较差等问题,根据Sevcik分形维数(Sevcik fractal dimension, SFD)对噪声不敏感、能够区分信号与噪声波形的特点,提出一种将自适应门限的能量检测法与SFD相结合的协作频谱感知方法.通过能量检测法对接收信号进行检测判决,然后由SFD对判定为主用户不存在的信号进行复检,并将所有检测结果进行K秩融合,根据融合结果得出最终判决.仿真结果表明,本文提出的频谱感知方法对噪声不敏感,在低信噪比下的检测性能得到显著提高.     

基于节点选择的能量高效的协作频谱感知算法

针对认知无线电中协作频谱感知能耗高的问题,提出一种基于节点选择的能量高效的协作频谱感知算法。该算法在保证感知性能的同时优化感知节点数量,从而达到高效节能的目的,其核心是采用能量高效的节点选择算法。该算法综合考虑了感知性能和能耗,仿真结果表明该算法在保证感知性能的同时能有效降低协作频谱感知的系统能耗。     

认知网络中的协作频谱感知技术研究

认知无线电技术通过感知频谱后进行动态频谱资源分配,极大地提高了频谱利用效率。频谱感知是实现认知无线电技术的前提和基础,文中针对频谱感知技术中单节点检测的局限性对能够改善频谱感知能力的协作感知技术进行了分析及讨论,重点分析了基于能量检测法的协作感知中的各种数据融合算法,并在此基础上提出了目前协作感知中存在的问题及未来的研究方向。     

一种新的认知无线电频谱感知算法

频谱感知是认知无线电的关键技术之一,通过检测授权用户信号的有无来发现频谱空穴,以提高频谱利用率。基于接收信号的统计协方差理论,提出一种新的认知无线电频谱感知算法,无需信号的先验信息,且计算复杂度较低。仿真分析了该算法,结果表明其在低信噪比环境下,较传统能量检测法有更好的感知性能。     

认知无线电差分协作压缩频谱估计算法

在分布式认知无线网络场景下,针对传统协作压缩频谱估计收敛速度慢、计算复杂度高的问题,提出了一种差分协作压缩频谱估计算法用于宽带频谱感知。算法通过利用不同认知用户感知的宽带信号所满足的相同频谱支撑集特征,实现了在邻居节点感知先验信息条件下,本地认知用户基于压缩测量向量差值的宽带频谱迭代估计。仿真分析结果表明,所提算法在频谱估计精度、检测性能与计算复杂度方面均获得了明显改善。     

基于图像K-means聚类分析的频谱感知算法

近年来,基于能量检测的协作频谱感知算法被广泛应用于频谱感知领域。由于该方法在计算能量检测的判决门限受噪声影响较大以及受限于认知用户的数量等问题,导致其检测性能受到影响。为了解决这一问题,本文提出一种基于图像K-means聚类分析的频谱感知算法。这种方法利用主用户信号存在与否的两种认知信号状态映射成图像,经过调整图像强度和高斯滤波预处理之后利用提取图像像素分布直方图的方法提取出特征向量,然后利用改进的K均值聚类算法对这些特征向量进行训练得到分类模型。最后利用训练好的分类模型对未知信号进行检测,从而实现频谱感知。仿真结果表明,本文所提出的频谱感知算法,在检测性能上优于传统能量检测以及协作频谱感知算法,尤其在低虚警概率、低信噪比的环境下效果更加突出。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.