A Wide-Band High-Linearity Down-Conversion Mixer for Cable Receptions

分析了一种宽带高线性度的用于有线接收机的下变频混频器.该设计采用0.35μm SiGe BiCMOS工艺.射频输入信号频率范围设计为1～1.8GHz,测得的1dB压缩点达到 14.23dBm,最大转换增益为8.31dB,最小噪声系数为19.4dB,在5V供电情况下,直流功耗为54mW.     

Electromagnetic analysis of axially symmetric diffractive lenses with the method of moments

We present the electromagnetic analysis of axially symmetric diffractive lenses. Analysis is performed by numerically solving the electric and magnetic field integral equations using the method of moments, and it exploits axial symmetry to reduce computational cost. Formulations for the analysis of loss less dielectric and perfectly conducting lenses are presented. The analysis of binary and eight-level lenses are performed to illustrate the utility of the technique.     

Three-dimensional analysis of subwavelength diffractive optical elements with the finite-difference time-domain method

We present a three-dimensional (3D) analysis of subwavelength diffractive optical elements (DOE's), using the finite-difference time-domain (FDTD) method. To this end we develop and apply efficient 3D FDTD methods that exploit DOE properties, such as symmetry. An axisymmetric method is validated experimentally and is used to validate the more general 3D method. Analyses of subwavelength gratings and lenses, both with and without rotational symmetry, are presented in addition to a 2 x 2 subwavelength focusing array generator.     

Point-tracked quantitative analysis of left ventricular surface motion from 3-D image sequences

We propose and validate the hypothesis that we can use differential shape properties of the myocardial surfaces to recover dense field motion from standard three-dimensional (3-D) image sequences (MRI and CT). Quantitative measures of left ventricular regional function can be further inferred from the point correspondence maps. The noninvasive, algorithm-derived results are validated on two levels. First, the motion trajectories are compared to those of implanted imaging-opaque markers of a canine model in two imaging modalities, where subpixel accuracy is achieved. Second, the validity of using motion parameters (path length and thickness changes) for detecting myocardial injury area is tested by comparing algorithms derived results to postmortem analysis TTC staining of myocardial tissue, where the achieved Pearson product-moment correlation value is 0.968.     

Effect of the Structure of Cations and Anions of Ionic Liquids on Separation of Aromatics from Hydrocarbon Mixtures

1. Introduction Benzene is a key chemical in the chemical industry, used as the raw material for producing polymer precursors, solvents, dyes, drugs, herbicides, and so on. The world production of benzene is more than 2.0×107 tons/year (Vervalin, 1991; Weissermel and Arpe, 1993; Villaluenga and Tabe-Mohammadi, 2000). Before World War II, benzene was mainly produced from coal, but nowadays more than 90% is obtained from petroleum, mainly from catalytic reformates and FCC gasoline, and by …     

Design and Implementation of a Concurrency Control Mechanism in an Object-Oriented Database System

This paper presents a practical concurrency control mechanism-Object-Locking in OODBMS.Object-Locking can schedule transactions,each of them can be considered as a sequence of high level operations defined on classes.By the properties of parallelity and commutativity between high level operations,proper lock modes for each operation are designed and the compatibility matrix is constructed.Wiht these lock modes,phantoms are kept away from databases and a high degree of concurrency is achieved.     

Diffusion boundary layer of a rotating disk electrode as a thin-layer spectroelectrochemical cell

A UV-visible rapid scan spectrophotometer (RSS) was coupled to a Au rotating disk electrode (RDE) for monitoring at near-normal incidence the reflection-absorption spectrum of the diffusion boundary layer in [Fe(CN)(6)](4)(-) aqueous solutions over a potential region in which [Fe(CN)(6)](4-) oxidizes, generating highly absorbing [Fe(CN)(6)](3-) (lambda(max) = 420 nm). Measurements were performed under steady-state conditions at rotation rates, omega, in the range 300 相似文献   

Optical implementation of the hopfield neural network with matrix gratings

We propose a new method for the optical implementation of the Hopfield neural network with a universal tool. The tool is a matrix grating constituted with a group of element gratings. The algorithms for designing a matrix grating are proposed, and a matrix grating is created to execute recognition experiments by use of the Hopfield neural network. The experimental results demonstrate that the proposed method performs well. The stability of the light efficiencies of different optical components used in optical networks is also considered.     

Temperature-sensitive cuts for surface acoustic waves in quartz

Temperature is the main parameter that affects the stability of surface acoustic wave (SAW) devices such as the external and internal stress. The temperature sensitivity of the frequency as a function of quartz crystal anisotropy is presented by a perturbation equation because of a temperature change. The analytical result shows which cut is suitable for high temperature sensitivity of the quartz and which cut is associated with low temperature sensitivity. The theoretical sensitivity values are compared with experimental results. Both the experimental and theoretical results are in good agreement.