基于改进UCT算法的国际跳棋博弈系统研究

国际跳棋的博弈系统中,UCT算法是一个比较新颖的算法,其效果得到了广泛认可.但是UCT算法的缺点也同样明显,终局下的处理明显不如稳定性更强的Alpha-Beta算法.为避免UCT算法的不稳定性,本文采取限制搜索深度和增加扩展条件的方法对UCT算法进行改进,改进后的UCT算法胜率远超过改进前的UCT算法胜率,使得博弈水平...     

Community based feedback techniques to improve video search

In this paper, we present a novel approach to aid users in the difficult task of video search. We use a graph based model based on implicit feedback mined from the interactions of previous users of our video search system to provide recommendations to aid users in their search tasks. This approach means that users are not burdened with providing explicit feedback, while still getting the benefits of recommendations. The goal of this approach is to improve the quality of the results that users find, and in doing so also help users to explore a large and difficult information space. In particular we wish to make the challenging task of video search much easier for users. The results of our evaluation indicate that we achieved our goals, the performance of the users in retrieving relevant videos improved, and users were able to explore the collection to a greater extent.     

一种基于协议的提高RS 485实时性的方法

RS 485总线因其结构简单、成本低廉、通信速率高、传输距离远等优点,在工业控制领域得到了广泛应用。因为RS 485采用半双工通信,所以RS 485通信系统一般由一个主节点、多个从节点组成,采用主节点轮询从节点、从节点受控发送数据的通信方式。这种方式造成系统的通信效率低、实时性差。目前已有的一些研究采用硬件改造和CSMA/CD的方法使系统具有多主结构,从而提高实时性,但是实现较为复杂。提出一种基于协议的提高RS 485实时性的新方法,该方法不需要修改硬件,不需要额外资源,只需要进行简单的程序修改。实验结果表明该方法能有效提高系统的实时性。     

一种提高基于WSN农业监测系统覆盖率的方案

在基于无线传感网络(WSNs)农业监测系统中,传感节点需周期收集环境数据,如温度、湿度,并且以尽可能少的传感节点实现对监测区域的随时监测。为此,提出一种基于太阳能的调度节点移动的覆盖率优化(SPMSC)方案。在SPMSC方案中,每个移动节点能够利用太阳板获取能量。通过预测太阳能的数量决定节点的移动方案,实现以最少节点和最小的能量消耗最大化覆盖区域。仿真结果表明,与同类方案相比,提出SPMSC方案的节点数下降了4%,网络寿命提高了10%。     

On-state voltage drop based derating/uprating on a MW converter to improve reliability

Power semiconductor devices are the most fragile components limiting reliability of power converters, where major stresses are temperature dependent parameters. Typically, the operating virtual maximum junction temperature is specified by a manufacturer for each individual device. The thermal system and operating load are designed based on this number. Online monitoring of an on-state collector–emitter voltage (υ_ce,on) and a junction temperature is necessary to ensure the design performance within a safe limit and also to make this method applicable for derating/uprating power. This paper presents the real time measurement of υ_ce,on and thereby the junction temperature estimation in high power converters. Knowing these parameters online, the maximum power capability can be detected. The operating maximum junction temperature is selected and thereby based on the operating condition the derating of power is shown for a megawatt (MW) converter. An experimental setup including online monitoring is described and the measurement of power derating is presented at the specified conditions.     

Growth,X-ray peak broadening studies,and optical properties of Mg-doped ZnO nanoparticles

Undoped and Mg-doped ZnO nanoparticles (NPs) (Zn_1?xMg_xO, x=0.01, 0.03, and 0.05) were grown by the sol–gel method. X-ray results showed that the products were crystalline with a hexagonal wurtzite phase. Microscopy studies revealed that the undoped ZnO NPs and Zn_1?xMg_xO NPs had nearly spherical and hexagonal shapes. The size–strain plot (SSP) method was used to study the individual contributions of crystallite sizes and lattice strain on the peak broadening of the undoped and Mg-doped ZnO NPs. Some physical parameters such as strain, stress, and energy-density values were calculated for all reflection peaks of the XRD corresponding to the wurtzite hexagonal phase of ZnO in the 20–100° range from the SSP results. The effect of doping on the band-gap was also investigated by a photoluminescence (PL) spectrometer. The PL results showed that Mg²⁺ is a good dopant to control band gap of the ZnO properties.     

利用多数据处理方法提高LIBS谱信号质量

基于分段光谱特征值提取法和小波变换算法等多个数据预处理方法,分别针对分段基线差异及光谱噪声等严重影响激光诱导击穿光谱(LIBS)信号质量的主要影响因素,开展光谱信号预处理研究.基于实验室LIBS实验装置,通过实验验证,基于多通道光谱仪不同波段光谱特征值提取,提出了一种简单易行的多组数据中特征值点连接的方法,有效地提高了LIBS光谱信号的基线平直度,并得出以小波变换算法进行LIBS谱线信号去噪的最佳算法参数.在上述工作的基础上,使用基于误差反向传播的人工神经网络方法,实现了纯铜和不锈钢等物质种类的有效识别,研究结果表明,综合利用多数据处理方法进行LIBS技术中光谱信号处理可以有效提高谱线分析和识别的质量.     

Iterative reconstruction in X-ray fluorescence tomography based on radon inversion

We describe a new approach for the inversion of the generalized attenuated radon transform in X-ray fluorescence computed tomography (XFCT). The approach consists of using the radon inverse as an approximation for the actual one, followed by an iterative refinement. Also, we analyze the problem of retrieving the attenuation map directly from the emission data, giving rise to a novel alternating method for the solution. We applied our approach to real and simulated XFCT data and compared its performance to previous inversion algorithms for the problem, showing its main advantages: better images than those obtained by other analytic methods and much faster than iterative methods in the discrete setting.     

一种基于IPV4子网划分IP地址有效利用的方法

基于IPV4的子网划分,传统的划分方法由于保留了部分IP地址而严重影响IP地址的有效利用,提出一种基于VLSM的子网划分表示方法,将IP地址利用率从传统划分方法的71%,提高到94%,解决了在子网划分过程中IP地址浪费严重的问题。     

基于纳米针尖反射靶的X射线显微系统

本文利用电化学腐蚀方法制备出曲率半径＜100 nm 的钨针尖,并在 FEI Quantum 600型扫描电镜（ SEM）中作为反射靶材以搭建微焦点X射线显微系统。通过SEM发射电子束轰击纳米钨针尖,以减少电子束和靶材的物理作用区域,进而减小X射线源的光斑尺寸,实现高分辨率的X射线显微成像。采用线对卡来评价系统的最佳成像分辨率,实验结果表明：系统在加速电压30 kV、电子束束流120 nA、SEM的工作距离5 mm、放大倍数为100倍、探测器采集时间为180 s的条件下,可以获得优于1μm的分辨率图像。     

X-ray and synchrotron studies of porous silicon

The results of comprehensive studies of layers of porous silicon of different conductivity types, grown by anodizing standard Si(111) substrates in an electrolyte based on fluoric acid and ethanol with the addition of 5% of iodine and kept in air for a long time, are discussed. Measurements are performed by scanning electron microscopy, high-resolution X-ray diffraction, and ultrasoft X-ray spectroscopy using synchrotron radiation. The structural parameters of the layers (thickness, strain, and porosity) and atomic and chemical composition of the porous-silicon surface are determined. It is found that an oxide layer 1.5–2.3-nm thick is formed on the surface of the silicon skeleton. The near-edge fine structure of the Si 2p absorption spectrum of this layer corresponds to the fine structure of the 2p spectrum of well coordinated SiO₂. In this case, the fine structure in the Si 2p-edge absorption region of the silicon skeleton is identical to that of the 2p absorption spectrum of crystalline silicon.     

X-ray photoelectron spectroscopy and X-ray electron-microprobe analysis of single crystals based on bismuth telluride

Experimental data on the distribution and atomic fractions of elements in Bi₂Te_2.94Se_0.06, Bi₂Te_2.88Se_0.12, Bi_1.99Sn_0.01Te_2.94Se_0.06, and Bi_1.99Sn_0.01Te_2.88Se_0.12 are discussed; these data were obtained using X-ray electron-microprobe analysis and X-ray photoelectron spectroscopy. It is ascertained that Sn impurity introduced with a concentration amounting to x=0.01 increases the uniformity of the Bi and Te distributions in solid solutions, whereas an increase in the Se content from y=0.06 to 0.12 gives rise to fluctuations in the composition; the fluctuations range from 0.5 at. % in undoped solid solutions based on Bi₂Te₃ to 0.3 at. % in these solutions doped with Sn. The binding energies of the core electrons in the single crystals under consideration were determined; variation in the total density of electronic states in the valence band in the vicinity of the Fermi level was observed.     

Transmit scheme to improve coverage in simulcast system based on wideband channel measurement in indoor at 6 GHz

Array gain would be well exploited to improve power coverage if some powerful multipath components from different radio links can coherently combine at the receiver (Rx). Thus, in this paper, an algorithm is proposed for transmission in simulcast system, where partial channel state information (CSI) is needed. Based on measured multipath channel, performance of the proposed algorithm is evaluated. According to simulation results, the proposed algorithm outperforms the direction summation (DS) scheme and multipath antenna diversity (MAD) algorithm, with 2~4 dB advantage over the latters. Especially in line of sight (LOS) scenario, the advantage is more obvious. Besides, the proposed algorithm brings more gain with increasing number of transmit antennas without additional power. Finally, robustness of the proposed algorithm is examined with imperfect CSI.     

Fractal curves to improve the reversible data embedding for VQ-indexes based on locally adaptive coding

The VQ reversible data embedding technology allows an original VQ coding to be completely restored after the extraction of embedded data. In this paper, we propose a new reversible scheme based on locally adaptive coding for VQ-compressed images. The fractal Hilbert curve is applied to replace the traditional trace of processing the VQ index table. The VQ index table is pre-processed to create a fractal Hilbert curve. Following the curve to process the VQ index table can get better compression rates in the data embedding procedure. Besides, compared to Chang et al.’s scheme, which compressed the inputted VQ index value only when the to-be-embedded bit b is 0, our method performs compressing operations in both cases that the to-be-embedded bits b are 0 and 1. The experimental results show that the proposed method has the best compression rate and the highest embedding capacity compared with other reversible VQ embedding methods.     

X射线果品品质在线检测系统研究

针对果品品质检测中内在品质检测的难点,研究了果品X射线检测系统及关键技术,分析了系统各部分组成及工作流程,研究了DM642 EVM嵌入式系统的实时通信技术,根据果品的X射线图像特点,提出了基于一类支持向量机分类器和外轮廓检测的X射线果品品质在线检测算法。实验表明,该系统识别率达88%,并满足在线检测的实时性要求。     

基于X射线焊缝图像缺陷特征提取的研究

本文针对X射线焊缝图像的复杂性,提出了准确快速的提取焊缝区域和缺陷的方法。由于检测到的X射线图像具有对比度不高、光照不均、缺陷边缘模糊、图像噪声多、存在较大的背景起伏等缺点,首先对含有缺陷的焊缝图像进行一系列的图像预处理;然后采用自适应阈值分割算法来提取焊缝缺陷区域,为缺陷特征测量做准备工作;最后,在图像本身所包含的几何特征、灰度特征、结构信息、颜色信息等特征中,对缺陷图像进行几何特征的测量,以便对缺陷类型进行分类。结果表明,该方法能较准确地提取射线图像的焊接缺陷,并能较准确的获取该缺陷的几何和代数特征,具有良好的适应性和实用性。     

基于OSEM算法的X射线荧光CT重建算法研究

X射线荧光CT作为一种新颖的无损检测手段,能够有效获取样本内部物质的属性和分布,并以图像的形式直观展示。文章以XFCT图像重建为出发点,研究了基于OSEM的XFCT重建算法,讨论了重建质量、重建时间与子集划分个数之间的关系,并进行相关仿真和验证,获得良好的结果。     

基于SDD的太阳X射线探测器脉冲成形电路设计

设计应用在风云二号03批空间环境探测器上的太阳X射线探测器在研制过程中需要一套完善的地面测控系统,太阳X射线探测器采用性能优越的SDD(Silicon Drift Detector,硅漂移传感器),主要对地面测控系统的脉冲成形电路进行了详细的电路分析,改进了电路结构,采用高速运算放大器实现了脉冲信号的滤波成形,用较少级数进行滤波即得到准高斯波形。利用Multisim12.0软件对成形电路的不同参数进行仿真测试,实验结果表明,设计电路达到了设计指标要求,具有移植性和通用性,使其能够在后端的脉冲幅度分析电路中被有效利用。     

Application of SEM-modified X-ray microscope to entomology and histology, and effects of X-ray coherence in imaging

A projection X-ray microscope has been constructed by modifying a scanning electron microscope (HITACHI S-2500CX). Characteristic internal structures and their changes in an aphid, a fly, an ant, a water bear and a beetle are observed first, non-destructively, by X-ray microscope. Stereo-pair X-ray micrographs of Golgi-stained sections of porcine liver show a network of bile canaliculi and stellate cells. The very clear micrographs presented indicate the usefulness of the microscope in studies of entomology and histology. In some micrographs, very thin whiskers or hairs are visible, which suggests that a phase-contrast effect is present in the imaging. X-ray micrographs of an ant hair taken at various distances between the X-ray source and the specimen, D(s), indicate that the image enhancement due to the phase contrast increases with increasing D(s). Degree of the lateral coherence of X-rays of wave length 0.1 nm is theoretically estimated near the hair, with the result that the coherence increases from about zero (almost complete incoherence) at D(s) = 0.1 mm to about unity (almost complete coherence) at D(s) = 6 mm, in agreement with the observation.