基于特征值分解的时间反转超声成像技术

由于声波衍射的关系,超声成像系统的检测效果会受到检测深度、传播介质等因素的影响,难以取得理想的高分辨率成像结果。文中基于时间反转声学理论,将基于时间反转矩阵特征值分解的成像算法引入超声成像技术中。在该算法中,每一个非零的特征值均对应一个散射体,通过对时间反转矩阵进行特征值分解得到包含检散射体相位信息的特征向量,将得到的时间反转信号反向发射从而实现对不同散射体的成像。仿真实验结果表明,该算法对于一定深度的缺陷具有更好的检测效果,且缺陷的横向分辨率明显优于一般超声成像算法,这一结果有益于提升超声系统区分多个近距离目标的能力。     

基于时间反转的探地雷达多目标成像算法研究

时间反转成像算法用于探地雷达多目标成像时,由于各个目标体的能量聚焦时刻和聚焦能量的强度都不相同,使得智能识别局部能量聚焦时刻成为该算法的瓶颈。为了实现时间反转成像算法用于探地雷达多目标成像,首先在B-Scan 中检测到潜在目标双曲线位置,然后用窗口框出各个潜在目标体的“空间-时间”位置,之后将该“空间-时间”窗口转化为待成像区域中的“位置-埋深”窗口,并对各个潜在目标窗口分别进行时间反转成像,虚假目标不存在能量聚焦,进而剔除虚假目标,实现多目标成像。实验结果表明:该算法能较好地实现多目标成像,由于该算法只对潜在目标窗口进行成像,而不是对整个待成像区域进行成像,大大提高了成像效率。     

时间反转技术在LFMCW雷达目标检测中的应用

为提高复杂环境下线性调频连续波(LFMCW)雷达的目标检测性能,分析了多路径对目标检测的影响,针对时间反转(TR)技术的优点,提出了基于时间反转技术的检测模型,并探讨了该模型的可行性,最后通过仿真比较了不同检测算法的检测性能。仿真结果表明,基于时间反转技术的检测模型相比于传统目标检测算法具有更好的检测性能。     

一种水声通信中的多阵元Turbo均衡算法

Turbo均衡应用在水声通信中的问题主要在于水声信道时间扩展长,多接收阵元处理复杂度较高。该文研究了将时间反转与马尔可夫链蒙特卡罗(MCMC)均衡联合优化算法用于实现Turbo均衡。首先进行时间反转实现多接收阵元较长多径时延的压缩,再利用白化滤波器解决时间反转造成的噪声模型失配问题,最后利用复杂度较低的MCMC均衡器结合软迭代信道估计对时间反转合并后得到的信号进行均衡。结合真实实验信道条件对信道响应估计的误差建立模型,通过仿真比较得出, 该算法在相同条件下相对于多阵元直接自适应Turbo均衡算法复杂度降低67%,且有1.6 dB的误码率性能增益。通过对湖上试验数据进行处理,进一步验证了该算法的优势。     

MIMO无线认知传感网超宽带频谱效率研究

无线资源管理是无线认知传感网的基本功能,而频谱效率是无线资源管理的关键性能指标。文章围绕无线认知传感网超宽带通信系统中的频谱效率开展深入研究,首先给出频谱效率的通用表达式,然后分析充水、恒功率充水、时间反转、信道反转、恒功率谱密度、MMSE(最小均方误差)等频谱成形滤波器设计方法中的频谱效率。     

基于布谷鸟算法的光纤激光网络异质信息入侵检测

采用以往入侵检测方法时,通过随机方式对参数进行初始化处理,检测精度低,为此,提出一种基于布谷鸟算法的光纤激光网络异质信息入侵检测方法。分析了布谷鸟算法寻优过程,针对常规布谷鸟算法受参数改变的影响相对较大,具有收敛速度慢、准确率低以及容易陷入局部最优的弊端,依据差分进化方法,通过在新鸟巢位置公式中结合别的鸟巢位置完成简易交叉变异,提升种群多样性,同时利用惯性权重减少迭代次数,保证整体寻优速度。对光纤激光网络异质信息入侵的历史数据进行采集,提取关键特征,通过布谷鸟算法对极限学习机进行改进,获取最优入侵检测分类器,通过分类器构建异质信息入侵检测模型,实现光纤激光网络异质信息入侵检测。实验结果表明,所提方法收敛速度快,误报率低且入侵检测精度高。     

混沌激光实现等角型扇形束扫描成像

将混沌激光作为激光光源，利用混沌互相关信号具有类delta函数的特性，结合等角型扇形光束扫描技术实现了对组织仿体中异质物的尺寸、位置、光学特性和结构重建。等角型扇形束扫描系统包含1个准直混沌光源和2个光电探测器。准直后的混沌激光穿过组织仿体被光电探测器接收，通过混沌光源和光电探测器同步旋转，获取不同角度下出射光的时域信息；对出射光与参考光进行互相关运算，提取互相关峰值，得到光在组织仿体内的衰减信息，通过异质物与仿体背景衰减系数的对比，实现对组织仿体内异质物的检测。根据光在仿体中散射和吸收引起的衰减规律，建立了混沌信号互相关峰值作为投影数据的理论模型，采用滤波反投影算法实现图像重建。结果表明，基于混沌激光的等角型扇形束扫描成像方法有较高的检测精度，能够区分不同衰减系数的异质物。     

结合暗通道和Retinex理论的图像去雾算法

针对雾天环境下拍摄的图像模糊、亮度低等问题,提出了一种利用图像颜色反转,并结合暗通道先验和Retinex理论的图像去雾算法.该方法采用四分加权算法准确估计大气光值,导向滤波方法对透射率进行细化;然后利用大气散射模型对反转图像进行去雾处理后再反转,得到初步复原的无雾图像;最后采用MSR算法进一步处理,提升图像的亮度和清晰度.实验结果表明,采用本算法得到的第一组和第二组图像信息熵分别为7.548 3和7.5121,峰值信噪比分别为7.763 8和11.374 7,平均梯度值分别为11.566 0和13.572 0,各组数据均优于其他三种算法,运行时间也具有一定优势,证明了所提算法的有效性.     

利用互相关和Hough变换快速检测探地雷达目标

考虑到探地雷达目标检测效率低的问题,该文基于目标回波能量空间分布的三参数双曲线模型,提出了一种快速的地下目标检测算法.算法首先利用相邻1维回波的相关性提取回波双曲线,再能量加权拟合曲线以估计出回波模型的两个参数,最后通过1维Hough变换来完成目标检测与定位.实测数据实验结果表明该文算法在不降低目标检测性能和定位精度的同时,计算时间只有传统基于Hough变换检测算法的1.5%左右,计算量的理论分析证明了该文算法在计算效率上的优势.     

雷电辐射源定位的时间反转方法与应用

将频域时间反转（time reversal，TR）聚焦技术应用于雷电辐射源探测定位，介绍了雷电辐射源探测系统的基本组成和TR定位算法，讨论了定位精度的影响因素，给出了典型应用实例.通过与传统的方法进行对比，发现该方法具有较好的鲁棒性，无需提取波形的到达时刻等信息，可直接利用检测波形的反向传播进行自动聚焦定位，并具有多辐射源同时定位的潜力.     

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.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

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.     

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.     

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.     

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.     

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.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.