基于编码发射与自适应波束形成的超声成像

与传统的延时叠加(DAS)波束形成的成像方法相比,Capon算法可以有效地提高医学超声成像的横向分辨率,但不能提高成像的对比度。该文提出一种新的成像方法Chirp_Capon算法,即将超声编码发射技术与Capon算法相结合,利用编码信号优异的相关特性来弥补Capon算法在对比度上的不足,从而得到了较好的成像结果。仿真结果表明相对于Capon算法,该算法不仅具有较高横向分辨率,而且可以有效提高图像的对比度和信噪比。     

基于语义分析的电子邮件过滤系统设计

文章介绍了一个基于语义分析的电子邮件过滤系统的设计。该系统首先基于关键词匹配对电子邮件进行检索，对普通的垃圾邮件可直接予以删除，对包含敏感话题关键词的邮件则进入语义分析的过程，根据对敏感话题关键词出现的单句进行语义分析的结果对邮件进一步分流处理。并采用CORBA技术来解决异构环境处理的问题。     

Development of 2-DOF tilting actuator with remote center of rotation for human operated non-contact handling tool

This paper describes the development of a new and unique 2-DOF tilting actuator that has a remote center of rotation. The tilting actuator is part of a non-contact handling tool that allows thin contact sensitive objects like silicon wafers or coated sheet metal to be manipulated without any contact between the tool and the object. Tilting is necessary to keep the object aligned with the levitator during large planar accelerations, similar to how a waiter tilts a tray of beverages during transport. A feed-forward tilt implementation based on known acceleration eliminates the need of sensor, but it requires that the center of rotation coincides with the center of mass of the levitated object to avoid disturbances by the tilting action. This is realized by a mechanical solution of a dome-shaped structure that is supported by three ball bearings on the inner surface. The tilting actuator is attached to an in-house developed admittance controlled SCARA-type haptic device, which allows both automated and human operated manipulation. In this collaborative system, where the haptic device assists the human operator in real time, the human operator can successfully perform the manipulation task with ease and without failure, which would not have been possible without the haptic assistance.     

Synthesis of Some New Biologically Active Sulfur Compounds Containing Pyrazolo[3,4-d] pyrimidine Moiety

A novel series of the pyrazolo[3,4-d]pyrimidines having biologically active sulfur moieties 3-20 were prepared via reaction of 4-mercapto-1-phenyl-1 H -pyrazolo[3,4-d]pyrimidine 3 with different reagents. Identification of the new compounds was established by elemental analyses, IR, 1 H-NMR, and mass spectral data. Some of the obtained compounds showed the interesting antimicrobial activity comparable to antibiotic chloramphenicol as standard antibacterial agent and Terbinafin as a standard antifungal agent.     

Analytical model, analysis and parameter optimization of a super linear electro-optic modulator (SFDR > 130 dB)

An analytical model of a super linear optical modulator with high spurious-free-dynamic-range (SFDR > 130 dB) is presented and analyzed. The linear modulator is referred to as IMPACC which stands for Interferometric Modulator with Phase-modulating And Cavity-modulating Components. The modulator is based on a unique combination of a RF-driven phase-modulator (PM) and a ring resonator (RR) within a Mach-Zehnder interferometer (MZI) configuration. Our analysis shows that our design can achieve SFDR values which are ~ 20 dB higher than the standard MZI modulator and 3-5 dB from the Ring Assisted Mach-Zehnder Interferometer (RAMZI) modulator. Both PM and RR in the IMPACC are simultaneously driven by a RF signal of the same frequency, but not necessarily the same amplitudes. The analytical model shows that the combination of these two optical elements, with the proper choice of RF-driving and device parameters, can lead to four important and compelling consequences. First, it offers a wholistic and elegant model in which the standard MZI modulator and the RAMZI modulator are just special cases of IMPACC. Second, the model offers an excellent parameter optimization methodology for fast parameter (internal and/or external) selection and performance evaluation. Third, it provides additional degree of control through the introduction of an external control parameter, the RF power split ratio (F). Lastly, it demonstrates one unique feature of IMPACC such as adaptive SFDR characteristics, where manufacturing tolerances in the transmission coefficient (τ) of the RR can be compensated with proper adjustments of the external parameter of the power split ratio (F).     

基于变分贝叶斯双尺度自适应时变噪声容积卡尔曼滤波的同步定位与建图算法

为解决移动机器人在同步定位与建图(SLAM)中因系统噪声和观测噪声时变导致状态估计精度降低的问题,该文提出一种基于变分贝叶斯的双尺度自适应时变噪声容积卡尔曼滤波SLAM算法(DSACKF SLAM)。该算法采用逆 Wishart 分布对一步预测误差协方差矩阵 P _k|k–1和观测噪声协方差矩阵 R _k建模,分别用来降低系统噪声和观测噪声的影响,并利用变分贝叶斯滤波实现对移动机器人状态向量 X _k, P _k|k–1和 R _k的联合估计。分别在系统噪声和观测噪声时变和时不变的条件下进行仿真实验,结果表明与基于无迹卡尔曼滤波的 SLAM 算法(UKF SLAM) 、自适应更新观测噪声的容积卡尔曼滤波的SLAM 算法(VB-ACKF SLAM) 相比,所提DSACKF SLAM算法在噪声时变时,平均位置误差分别减小1.54 m, 3.47 m;噪声时不变时,平均位置误差分别减小0.62 m, 1.41 m,证明DSACKF SLAM算法有更好的估计性能。     

FPGA通用开关盒层次化建模与优化

国际上权威的通用布局布线工具（Versatile Place and Route tool,VPR）所支持的开关盒（Switch Box,SB）结构限定在Disjoint,Wilton和Universal3种类型,并且通道内同种类型的互连线必须相邻排列。针对这两个约束,该文提出了FPGA（Field Programmable Gate Array）层次化通用开关盒模型,可涵盖FPGA中的任意开关盒结构,并基于这种模型,提出了具有更高布通率的新型开关盒结构JSB（Joint Switch Box,JSB）,与Disjoint,Wilton和Universal结构相比,布通率分别提高了10.1%,3.3%和4.6%;还通过优化分布FPGA中互连线,大幅度减小了电路延时,在相同工艺参数和相同开关盒的条件下,比VPR的布线时延关键路径平均缩短了10.4%。     

机载相控阵雷达TAS方式的实现

相控阵雷达具有灵活的波束指向、驻留时间、可控的空间功率及时间资源分配等特点,使相控阵雷达具有支持跟踪加搜索(TAS)的能力,即能同时完成搜索和对多个目标的精密跟踪。该文从任务调度机制和跟踪滤波两项关键技术论述了机载相控阵雷达TAS方式的算法。通过计算机仿真验证,表明这种方法能够使相控阵雷达具有很好的跟踪加搜索(TAS)能力。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Nevanlinna-Pick interpolation: Pick matrices have bounded number of negative eigenvalues

The Nevanlinna-Pick interpolation problem is studied in the class of functions defined on the unit disk without a discrete set, with the property that all their Pick matrices have not more than a prescribed number of negative eigenvalues. It is shown, in particular, that the degenerate problem always has a unique solution, not necessarily meromorphic. A related extension problem to a maximal function in the class is also studied.