基于LC-SLM的CT图像全息三维重构与实时显示

提出了一种将计算全息技术与液晶空间光调制器相结合的CT图像三维重构与实时显示的方法。用计算全息技术对一系列CT图片进行三维信息融合,并根据CT图片数目的不同,制作了不同的计算全息图,基于CT图片本身是数字化二维图像的特点,采用了快速傅里叶变换算法。用液晶空间光调制器作为全息图显示载体,设计了CT图像三维实时显示系统,利用计算机控制实时输出不同的计算全息图到空间光调制器,通过光学再现获得不断变化的三维再现像,实现CT图像的三维实时显示。     

On-Line Blood and Respiratory Gas Analysis

Data from a patient receiving ventilatory assistance are processed by computer to calculate pulmonary shunt, dead space/tidal volume ratio, oxygen uptake and delivery, and carbon dioxide elimination and delivery. The computations are based on routines described by Kelman and by Severinghaus, but modified to match limitations of testing imposed by the requirements for ventilatory assistance. Analyses are performed sequentially on arterial and venous blood samples and on respiratory gas samples. The output of the blood gas analyzers is fed on-line to a computer together with other data, such as patient identification, which are manually entered at a keyboard and with thumb-wheel switches. The computer processing begins with determining the concentration of oxygen and carbon dioxide in whole blood and of bicarbonate in plasma. The shunt equation is used to calculate a virtual shunt at therapeutic concentrations of inspired oxygen. Dead space/tidal volume ratios are corrected for mechanical dead space in the respiratory circuit. The analyzed results are returned to the operator within seconds via a video display. Since the data include blood samples from multiple patient sites, a cross-comparison is made by the computer and the operator is informed of unusually large differences in values.     

磷酸盐双芯光纤的制作和自锁相激光输出

利用堆积法制作出Nd掺杂的磷酸盐玻璃双芯光纤(TCF)。结合管棒法,设计一种能够任意调节芯径与芯间距比例的制备方法。激光实验采用808 nm激光二极管(LD)作为抽运源,以长为6 cm,外径为620 μm的TCF作为增益介质,宽带高反双色镜和TCF另一端的菲涅耳反射形成的F-P腔作为激光谐振腔。抽运功率大于阈值时,CCD观察到清晰的远场干涉条纹,表明得到自锁相激光输出。激光最大输出功率达到52 mW,对应斜率效率为27.1%,并研究了不同抽运功率时,TCF激光的光谱性能。     

远距离复杂背景鲁棒的步态特征提取与表示方法

远距离复杂背景下步态图像通常受到噪声的影响很大。Gabor特征在此类步态识别中显示了良好的特性,然而一些基于Gabor特征的算法使用较多的模板从而导致计算量增大。为解决这个问题,本文提出了一种新的基于改进Gabor特征的步态特征提取与表示方法。首先突出步态能量图中的有效区域,并抑制易受噪声干扰的区域。然后构造一个同时具有两个方向互补特性的基本的滤波器,经过缩放和旋转,生成一系列滤波器。使用这些滤波器对改进的步态能量图以及步态差异图像进行卷积,得到两个特征向量集合以表示此步态对象。使用最近邻分类计算出本文方法在USF步态数据库上的识别率,与相关算法的比较证实了此步态特征提取与表示方法的有效性。对算法的计算量分析表明,本文算法所需的计算量比相关算法有较大降低。      

基于Kinect的虚拟视点生成技术

传统的多视点生成方法是基于多相机阵列系统的关键技术。现提出了基于Kinect的多视点成像计算方法。首先对Kinect的深度图使用三边滤波器进行平滑,根据修复好的深度图配合彩色图,利用DIBR技术生成多个存在空缺信息的彩色视点;最后结合彩色图的纹理结构信息和深度图的背景信息对有丢失信息的彩色图进行修复。实验结果表明,文中提出的深度修复方法能够有效地修补Kinect的深度图,生成的虚拟视点图在3DTV上效果明显,立体视觉效果显著。     

Time-Domain Cavity Oscillations Supported by a Temporally Dispersive Dielectric

Forced time-domain oscillations in a cavity filled with a temporally dispersive polar dielectric are studied. The cavity is bounded by a singly connected closed perfect electric conductor surface$S$of rather arbitrary shape. A given source pumps a signal of finite duration to the cavity. Hence, the principle of causality is involved in the formulation of the problem. The temporal cavity oscillations are obtained as a self-consistent solution to the system of Maxwell's equations and Debye equation supplemented with appropriate initial conditions . Analytical solution is obtained by using the evolutionary approach to electromagnetics proposed and implemented recently. Temporal oscillations of the cavity modes are studied. Obtained results are compared with the finite-difference time-domain solutions.     

A digital approach to clock recovery in generalized minimum shiftkeying

A method for clock recovery to be used with generalized minimum-shift-keying (MSK) modulations is presented. Attractive features of the method are that it is suited for digital implementation and that its performance is not affected by the carrier-phase recovery process. Clock reference is extracted by passing the sampled baseband waveform through the cascade of a nonlinearity, followed by a digital differentiator whose average output represents the error signal to be employed in a tracking loop. The performance of this scheme is analyzed by means of simulation in steady-state and in transient conditions. Tracking errors are compared with those attained by the well-known De Buda synchronizer and with the Cramer-Rao lower bound     

A reconfigurable aperture antenna based on switched links between electrically small metallic patches

A reconfigurable aperture (RECAP) antenna is described in which a planar array of electrically small, metallic patches are interconnected by switches. The antenna can be reconfigured to meet different performance goals by changing the switches that are open and closed. The switch configuration for a particular goal is determined using an optimizer, such as the genetic algorithm. First, the basic concept for the RECAP antenna is verified by comparing theoretical results with measurements for configurations in which the switches are simply wires connecting the patches. Next, details are given for a prototype antenna in which field-effect transistor based electronic switches are used with optical control. Theoretical results for the prototype antenna are then compared with measurements for cases in which electronic reconfiguration is used to change the bandwidth of operation or steer the pattern of the antenna. Finally, an overview of alternate switch/control strategies, some of which were tested, is given along with suggestions for improving the next generation of this antenna.     

Perturbation-Based Stochastic Modeling of Nonlinear Circuits

This paper presents a general model for a nonlinear circuit, in which, the circuit parameters (e.g. resistance and capacitance) are subject to random fluctuations due to noise, which vary with time. The fluctuating amplitudes of these parameters are assumed to be Ornstein–Uhlenbeck (O.U.) processes and not the white noise owing to temporal correlations. The nonlinear circuit is represented by a system of nonlinear differential equations depending upon a set of parameters that fluctuate slowly with time. To model these fluctuations, we use the theory of Ito’s stochastic differential equations (SDEs). Then the driving force of the circuit dynamics is in accordance with the general perturbation theory decomposed into the sum of a strong linear component and a weak nonlinear component by the introduction of a small perturbation parameter. The circuit states are expanded in the powers of this small perturbation parameter and recursive solutions to the various approximates obtained. Finally, the approximate expressions for the output states are obtained as stochastic integrals with respect to Brownian motion processes. The proposed method is applied to a half-wave rectifier circuit which is built out of a diode, a resistor and a capacitor. The diode is represented by nonlinear voltage–current equation, and resistance and capacitance are subject to random fluctuations due to noise, which vary slowly with time. The results, obtained using the proposed method, are compared with those obtained via the conventional perturbation-based deterministic differential equations model for a nonlinear circuit. Hence, the noise process component, present at the output, is obtained.     

Bayesian class discovery in microarray datasets

A novel approach to class discovery in gene expression datasets is presented. In the context of clinical diagnosis, the central goal of class discovery algorithms is to simultaneously find putative (sub-)types of diseases and to identify informative subsets of genes with disease-type specific expression profile. Contrary to many other approaches in the literature, the method presented implements a wrapper strategy for feature selection, in the sense that the features are directly selected by optimizing the discriminative power of the used partitioning algorithm. The usual combinatorial problems associated with wrapper approaches are overcome by a Bayesian inference mechanism. On the technical side, we present an efficient optimization algorithm with guaranteed local convergence property. The only free parameter of the optimization method is selected by a resampling-based stability analysis. Experiments with Leukemia and Lymphoma datasets demonstrate that our method is able to correctly infer partitions and corresponding subsets of genes which both are relevant in a biological sense. Moreover, the frequently observed problem of ambiguities caused by different but equally high-scoring partitions is successfully overcome by the model selection method proposed.     

Oblique scattering from lossy periodic surfaces with applicationsto anechoic chamber absorbers

Plane wave scattering from lossy, periodic surfaces with periodicity in one direction is considered for arbitrary polarization and incidence angles. The material is assumed to be homogeneous and characterized by complex values of permittivity and permeability. Muller-type coupled integral equations are derived for the surface electric and magnetic currents. The power reflection coefficient is defined in terms of the scattered far fields. The integral equations are solved by the boundary element method (BEM) with constant elements. Arbitrary surfaces are accommodated by approximating the actual profile by means of linear segments. Other speed-up techniques are utilized to generate a numerically efficient solution. Substantial comparison is made for special cases to verify the formulation. The reflection coefficient is calculated for a variety of surface shapes. A new profile shape is presented that results in a lower reflection coefficient than the commonly used triangular shape     

一种提高无杂散动态范围的多通道信号接收方法

当大功率信号进入接收机后,将迫使模数转换器工作在非线性区,并导致接收信号中含有大量非线性杂散.为了抑制杂散并提高接收机对小信号的侦测能力,提出了一种具有无杂散高动态范围(Spurious-free Dynamic Range,SFDR)的信号接收方法.首先通过两路不同的通道同时接收信号,然后利用信号之间的频率差异识别杂...     

红外多光谱遥感数据的校准

主要介绍了一种对由特定红外图谱一体化系统采集的光谱数据进行校准与分析的方法。在实验部分,首先对得到的设定已知特定温度的黑体红外光谱数据进行归类和整理,然后在最大保留特征信号的条件下利用不同的滤波算法与滤波窗宽尽量消除信号噪声,并采用偏最小二乘算法对所得信号进行校准,使之与理论值相符。最后利用校准结果构建数学模型,并考虑主成分个数这一概念,检验模型准确度。通过数据分析可知,由这个特定红外图谱一体化系统采集的光谱数据经偏最小二乘算法校正后与理论值相近,此时能够拟合出校正数列与波数之间的函数关系,且受温度影响较小。     

A visual servoing algorithm using fuzzy logics and fuzzy-neural networks

A visual servoing algorithm is proposed for a robot with a camera in the hand to track a moving object in terms of image features and their variations, where fuzzy logics and fuzzy-neural networks are involved to learn feature Jacobian-based kinematic control law. Specifically, novel image features are suggested by employing a viewing model of the perspective projection to estimate the relative pitching and yawing angles. Such perspective projection-based features would not interact with the relative distance between the object and the camera, and, desired feature trajectories for learning the visually guided line-of-sight robot motion are obtained by measuring features by the camera in the hand not in the entire workspace, but on a single linear path along which the robot moves under the control of a commercially provided function of linear motion, and then, control actions of the camera are approximately found by fuzzy-neural networks to follow such desired feature trajectories.To show the validity of the proposed algorithm, some experimental results are illustrated, where a four-axis SCARA robot with a BW CCD camera is used.     

Theory of spontaneous emission noise in multisection semiconductor lasers

Calculations of spontaneous emission noise in semiconductor lasers are mainly based on a fundamental theory developed by Henry in 1986, which is useful for simple systems, together with a formulation in terms of transfer matrices by Makino and others, which facilitates application of the theory to more complicated multisection systems. The aim of this review is to present a unified account of this theoretical work in a transparent form intended to encourage its further use in complex systems. The opportunity is taken to strengthen the existing theory by including the effects of differing optical wave vectors in different sections and the consequent reflections at interfaces, which are important in some applications. Sample calculations are presented for a range of systems with one, two, three, and four sections and the predictions compared with other theoretical and experimental results.     

Diffraction by Thick Conducting Haft-Plane and a Dielectric-Loaded Waveguide

This paper investigates the problem of diffraction of an incident plane wave by a half-plane with a finite thickness. The generalized scattering matrix procedure, which has been found useful for attacking waveguide discontinuity problems, is shown to apply to open region problems as well. Based on this procedure, a highly convergent Neumann Series solution is derived, and numerical calculations are presented for a wide range of parameters. The method of solution is not restricted to sufficiently thin half-planes only, as is the one discussed by Jones, although the labor in numerical calculation increases with increasing thickness. Comparisons with Jones' results show good agreement in the range where his results are valid. New results are presented for the extended range of thickness of the half-plane. Two other related problems, viz., those of radiation from a waveguide loaded with a dielectric or plasma medium, and diffraction by an inhomogeneously loaded waveguide, are also investigated in this paper.     

Applications of universal context modeling to lossless compressionof gray-scale images

Inspired by theoretical results on universal modeling, a general framework for sequential modeling of gray-scale images is proposed and applied to lossless compression. The model is based on stochastic complexity considerations and is implemented with a tree structure. It is efficiently estimated by a modification of the universal algorithm context. Several variants of the algorithm are described. The sequential, lossless compression schemes obtained when the context modeler is used with an arithmetic coder are tested with a representative set of gray-scale images. The compression ratios are compared with those obtained with state-of-the-art algorithms available in the literature, with the results of the comparison consistently favoring the proposed approach.     

2-D simulation of kink-related sidegating effects in GaAs MESFETs

Sidegating (backgating) effects in a planar structure with sidegate on the same side as MESFET are studied by two-dimensional simulation and the results are compared with those for a structure with a backgate on the back side of the substrate. The kink-related sidegating is reproduced in the planar structure, too. Its mechanism is discussed and is attributed to the change of EL2's role from an electron trap to a recombination center by capturing holes, which are generated by impact ionization and flow into the semi-insulating substrate including EL2 (deep donor). The dependence of shallow acceptor density in the semi-insulating substrate is also studied. It is shown that the kink-related sidegating is less remarkable in the case with lower acceptor density in the substrate. Potential dependence of sidegating effects on the sidegate (backgate) position is also discussed.     

The consequences of the application of a floating gate on d.c.-MISFET characteristics

In the literature the influence of the conducting layer, sometimes called a floating gate, upon d.c.-MISFET characteristics is ignored or only treated in a phenomenological way. Our intentions in this paper are to present a study of the consequences of a conducting layer in an exact way by using the MISFET theory described earlier.It is found that the d.c.-characteristics are influenced by parasitic capacitances from the conducting layer to source and drain and the charge-voltage relations along the channel of the MIS transistor.The theoretical considerations are verified by simulations with Spice 2 and some experimental results and are in agreement with the characteristics already given in the literature referred to.     

Dynamical Analysis of Full-Range Cellular Neural Networks by Exploiting Differential Variational Inequalities

The paper considers the full-range (FR) model of cellular neural networks (CNNs) in the case where the neuron nonlinearities are ideal hard-comparator functions with two vertical straight segments. The dynamics of FR-CNNs, which is described by a differential inclusion, is rigorously analyzed by means of theoretical tools from set-valued analysis and differential inclusions. The fundamental property proved in the paper is that FR-CNNs are equivalent to a special class of differential inclusions termed differential variational inequalities. A sound foundation to the dynamics of FR-CNNs is then given by establishing the existence and uniqueness of the solution starting at a given point, and the existence of equilibrium points. Moreover, a fundamental result on trajectory convergence towards equilibrium points (complete stability) for reciprocal standard CNNs is extended to reciprocal FR-CNNs by using a generalized Lyapunov approach. As a consequence, it is shown that the study of the ideal case with vertical straight segments in the neuron nonlinearities is able to give a clear picture and analytic characterization of the salient features of motion, such as the sliding modes along the boundary of the hypercube defined by the hard-comparator nonlinearities. Finally, it is proved that the solutions of the ideal FR model are the uniform limit as the slope tends to infinity of the solutions of a model where the vertical segments in the nonlinearities are approximated by segments with finite slope.