Adaptive and vector directional processing applied to video colour images

The adapted K-nearest neighbour and adaptive vector median filters together with vector directional processing to filter 3D images are presented. Vector median, median and adaptive vector median filters have been modified and proved to suppress impulsive noise in the video sequences.     

激光束整形为正方框形光束的DOE的设计及实验

以几何理论为基础来设计将激光束整形为正方框形光束的衍射光学元件(DOE),推导出了衍射光学元件表面上的相位表达式;以高斯光束整形为例,将其整形为所需要的光强分布;进行了计算机模拟,得到了比较好的结果;同时也进行了实验验证,实验结果证明了设计方法、理论推导以及程序设计的正确性。     

像素的形状和大小与LCD的视角特性

通过对相邻像素的投影和杂散光的研究,很好地解释了 Ｌ Ｃ Ｄ 像素的形状和大小与对比度和视角特性的关系,并指出当 Ｌ Ｃ Ｄ 器件在 Ｃｒ ＞ １ 的有效显示区中,其大像素的对比度比小像素的大,同时也强调了相邻像素的选通态对 Ｌ Ｃ Ｄ 测量结果的影响。     

激光束整形为矩形光束的DOE的设计及实验

本文以几何理论为基础来设计把激光束整形为矩形光束的衍射光学元件 (DOE) ,推导出了衍射光学元件的相位表达式 ;并以高斯光束整形为例 ,把其整形为所需要的光强分布 ;进而进行了计算机模拟 ,得到了令人满意的结果 ;同时也进行了实验验证 ,实验结果证明了设计方法、理论推导以及程序设计的正确性     

Measures of folding applied to the development of the human fetal brain

Previous work has suggested the existence of differences between the cerebral cortex of normal individuals, and those of patients with diseases such as epilepsy and schizophrenia. These shape abnormalities may be of developmental origin. Improved shape measures could provide useful tools for neuroscience research and patient diagnosis. We consider the theoretically desirable properties of measures of brain shape. We have implemented seven measures, three from the neuroscience literature, and four new to this field. Three of the measures are zero-order and four are second-order with respect to the surface. We validate the measures using simple geometrical shapes, and a collection of magnetic resonance scans of ten histologically normal ex vivo fetal brains with gestational ages from 19-42 weeks. We then apply the measures to MR scans from two histologically abnormal ex vivo brains. We demonstrate that our implementation of the measures is sensitive to anatomical variability rather than to the discreteness of the image data. All the measures were sensitive to changes in shape during fetal development. Several of the measures could distinguish between the normal and abnormal fetal brains. We propose a multivariate approach to studying the shape of the cerebral cortex, in which both zero-order and second-order measures are used to quantify folding.     

Electromagnetic coupling to a conducting wire behind an aperture of arbitrary size and shape

The electromagnetic coupling to a conducting wire behind an aperture in a plane conducting screen is analyzed. The aperture can be of arbitrary size and shape. The wire can be of finite length, with or without terminating loads, or of infinite length. The electric current on the wire and the equivalent magnetic current over the aperture region are calculated by the method of moments. An equivalent circuit for the effect of the aperture on the transmission line mode of the wire is derived.     

不同尺寸、形状和组成的金纳米颗粒的光热特性:在癌症治疗中的应用

光热疗法由于其安全和高效的优点,作为一种非破坏性方法在癌症治疗中有广泛的应用前景。光热疗法中,所采用的纳米颗粒在近红外波段的光热转换效率取决于纳米颗粒的光谱吸收特性。采用时域有限差分法对球型、壳型、杆型、片型、笼型、星型和花型等七种不同金纳米颗粒的光谱吸收特性进行了仿真计算,结果表明纳米颗粒的几何参数和结构对其光谱吸收效率和共振波长产生了显著的影响。通过对比七种金纳米颗粒的体积吸收系数,发现金纳米片在近红外波段的光热转换效率优于其他六种金纳米颗粒。从电流密度矢量分布得出,金纳米颗粒内部产生共振电流是导致金纳米颗粒在近红外波段具有明显的单色吸收特性的原因。     

一种度量目标散射相似性的新参数

针对目标相似性参数度量分布式目标与典型目标散射相似程度不准确的问题,本文利用规范散射Pauli基矢量和分布式目标相干矩阵,定义了一个度量目标散射相似性程度的新参数--目标散射相似性.由于该参数综合考虑了分布式目标主散射机制、次要散射机制与规范散射的相似性,以及不同散射机制对廊的发生概率,因而它能准确反映分布式目标与规范目标散射的平均近似程度.与相似性参数一样,新参数具有目标旋转不变性、尺度无关性等特性.作为一种实际应用,给出了分布式目标与金属球、角反射器等典型目标的散射相似性.结合旧金山地区AIRSAR极化数据,讨论了这些相似性测度在地物分类方面的应用.     

Segmentation, registration, and measurement of shape variation via image object shape

A model of object shape by nets of medial and boundary primitives is justified as richly capturing multiple aspects of shape and yet requiring representation space and image analysis work proportional to the number of primitives. Metrics are described that compute an object representation's prior probability of local geometry by reflecting variabilities in the net's node and link parameter values, and that compute a likelihood function measuring the degree of match of an image to that object representation. A paradigm for image analysis of deforming such a model to optimize a posteriori probability is described, and this paradigm is shown to be usable as a uniform approach for object definition, object-based registration between images of the same or different imaging modalities, and measurement of shape variation of an abnormal anatomical object, compared with a normal anatomical object. Examples of applications of these methods in radiotherapy, surgery, and psychiatry are given.     

激光散射研究絮凝剂在水中的自然构象

用激光散射技术测量了无机高分子絮凝剂PAC,PAC-V在水中自然状态下的分子量、其颗粒的流体力学半径、回转半径、第2维里系数等参数,并根据流体力学半径和回转半径的比值导出絮凝剂的颗粒形态。从而较全面地了解絮凝剂在水中的自然构象,并证实了絮凝剂的分子量、其颗粒大小及形状不随浓度的改变而变化,但对絮凝效果有较大影响,这为确切探知絮凝机理提供实验数据和理论依据。     

An information-theoretic approach to spectral variability,similarity, and discrimination for hyperspectral image analysis

A hyperspectral image can be considered as an image cube where the third dimension is the spectral domain represented by hundreds of spectral wavelengths. As a result, a hyperspectral image pixel is actually a column vector with dimension equal to the number of spectral bands and contains valuable spectral information that can be used to account for pixel variability, similarity and discrimination. We present a new hyperspectral measure, the spectral information measure (SIM), to describe spectral variability and two criteria, spectral information divergence and spectral discriminatory probability for spectral similarity and discrimination, respectively. The spectral information measure is an information-theoretic measure which treats each pixel as a random variable using its spectral signature histogram as the desired probability distribution. Spectral information divergence (SID) compares the similarity between two pixels by measuring the probabilistic discrepancy between two corresponding spectral signatures. The spectral discriminatory probability calculates spectral probabilities of a spectral database (library) relative to a pixel to be identified so as to achieve material identification. In order to compare the discriminatory power of one spectral measure relative to another, a criterion is also introduced for performance evaluation, which is based on the power of discriminating one pixel from another relative to a reference pixel. The experimental results demonstrate that the new hyperspectral measure can characterize spectral variability more effectively than the commonly used spectral angle mapper (SAM)     

美国有线电视企业处理与因特网之间关系的新近议论和举措

1引言 本刊2009年第7期“从新近企业实践观察广电网与因特网之间关系”一文中,综述了主要发达国家中关于公众接纳多屏幕接收的调研结果、对多平台一多屏幕传播前景的评估以及美国规模最大的两家有线电视企业——康喀斯特公司和时代华纳有线电视公司开拓万维网传播的打算,     

A new approximate solution for scattering by thin dielectric disks of arbitrary size and shape

In this paper, an approximate solution for electromagnetic scattering by a very thin planar homogeneous dielectric object is presented. This solution is obtained from a volumetric integral equation using Fourier transform and is shown to be uniformly valid from low to high frequencies at all incidence angles including edge-on incidence. Validity of the solution is demonstrated through a comparison with canonical objects such as an infinite dielectric slab, and a number of two-dimensional (2-D) and three-dimensional (3-D) dielectric scatterers. For 2-D, and 3-D scatterers, the approximate solution is compared with a method of moments solution. In all cases examined the approximate formulation provides very accurate results except for situations where the dielectric constant is very high.     

Measurement of gain and delay inequalities between the luminance and chrominance channels in colour television

A recently proposed method of measuring gain and delay inequalities in colour television is subject to ambiguities when applied to links having certain other linear distortions. A method of resolving these ambiguities is described.     

A simple,direct and reliable extraction method applied to GaN devices

In this article, a simple, direct and reliable extraction method has been developed and applied to different sizes of Gallium Nitride (GaN) high electron mobility transistors (HEMTs). Instead of high-voltage gate-forward measurements with risk of device damage, the proposed approach uses only uncritical cold S-parameters at pinch-off (V_GS < V_p, V_DS = 0 V) and in the off-state (V_GS = 0 V, V_DS = 0 V). The extraction procedure is validated by small- and large-signal measurements. Very good agreement is obtained. Scaling of parasitic elements with the device size is confirmed.     

Very-long-baseline interferometry techniques applied to problems of geodesy, geophysics, planetary science, astronomy, and general relativity

Very-long-baseline interferometry (VLBI) techniques have already been used to determine the vector separations between antennas thousands of kilometers apart to within 2 m and the directions of extragalactic radio sources to 0.1", and to track an artificial satellite of the earth and the Apollo Lunar Rover on the surface of the moon. The relative locations of the Apollo Lunar Surface Experiment Package (ALSEP) transmitters on the lunar surface are being measured within 1 m, and the moon's libration is being measured to 1" of selenocentric arc. Attempts are under way to measure the solar gravitational deflection of radio waves more accurately than previously possible, by means of VLBI. A wide variety of scientific problems is being attacked by VLBI techniques, which may soon be two orders of magnitude more accurate than at present.     

The influence of aperture size and shape on crosstalk level in free-space grating demultiplexers for WDM networks

A simple method is presented to calculate crosstalk caused by aberrations and diffraction at the aperture edges in free-space grating demultiplexers for wavelength-division multiplexed (WDM) communication systems. The influence of circular and square aperture sizes is described for ideal and aberrated optical systems. It is shown that aperture enlargement is not critical to aberrations whilst providing significant crosstalk reduction. The minimum crosstalk value is obtained when the dispersion plane is parallel to the diagonal of the square aperture. -60 dB crosstalk is attainable for moderately aberrated systems with 80 channels (0.5 nm spacing) in the range 1530-1570 nm.     

用于SoC的SPI接口设计与验证

给出了一个可用于SoC设计的SPI接口IP核的RTL设计与功能仿真。采用AMBA2．0总线标准来实现SPI接口在外部设备和内部系统之间进行通信,在数据传输部分,摒弃传统的需要一个专门的移位传输寄存器实现串／并转换的设计方法,采用复用寄存器的方法,把移位传输寄存器和发送寄存器结合在一起,提高了传输速度,也节约了硬件资源。采用SoC验证平台进行SoC环境下对IP的验证,在100MHz时钟频率下的仿真和验证结果表明,SPI接口实现了数据传榆,且满足时序设计要求。