基于RankClus算法的机场流程日志活动挖掘

流程挖掘技术可以提取机场流程日志中的有用信息用于流程分析。但机场流程日志处于细节化的低抽象层次,不符合分析者的预期。对机场流程日志挖掘得到的流程模型呈现意面状的复杂结构,流程模型的含义难于理解。解决该问题的一种方法是通过活动挖掘,将低抽象层次活动聚类为流程模型中表征高抽象层次活动的活动类簇。为此提出了一种基于RankClus算法的活动挖掘方法,将机场流程日志的活动聚类与活动排序评分计算相结合,从而构建更易理解的活动聚类流程模型。实验结果表明,RankClus活动聚类流程模型的日志回放一致性与原生日志流程模型大致相当,但在结构复杂度上要显著低于原生日志流程模型。     

基于脊波变换的图像压缩算法

自然图像包括大量的具有明显“直线边缘”的图像,而且边缘表示了图像的主要信息。利用脊波对“直线奇异”的良好刻画,针对具有直线特征的图像,设计基于脊波变换的有损压缩算法。首先对图像进行脊波变换,然后对变换系数进行标量量化、扫描、游程编码和熵编码。仿真实验表明,与基于小波变换的JPEG 2000压缩算法相比,该算法能获得更高的压缩率,同时保持较高的信噪比。     

分布式光纤传感技术在架空线路中的应用

设计了一种分布式光纤传感器,该传感器基于光时域反射原理,通过测量光纤中的背向散射光强度随时间的变化来进行光纤传输特性的测试。构造了用于实时监测的分布式光纤测试系统,在架空线路中有较好的监测应用。并对该分布式光纤传感器性能进行了监测,结果验证该传感器有较好的稳定性,测温精度误差范围在±0.5℃左右。     

基于nRF401的无线呼叫服务系统设计

无线呼叫服务系统为点对多点通信,存在信道冲突问题.文中采用呼号广播的方法分配信道,即以中央控制器广播各呼叫器的编码呼号,统一了时分复用的计时基准点和计时时钟,实现各受服务时间片的准确分配.系统硬件设计本着低成本原则,呼叫器以AT89C2051和nRF401为核心,并做到零功耗空闲,中央控制器结构与呼叫器基本相同,以七彩LED(发光二极管)和数码管进行呼叫显示,并通过串行口与PC机相连接.基于VC 设计服务系统软件安装于PC机上,以激活的消息框提醒需要服务客人的编号.     

一种基于飞机目标CFD图的目标特征提取算法研究

随着雷达目标微多普勒现象的发现,目标的微动特性在雷达自动目标识别中逐渐受到了广泛的关注。微动目标回波中包含了精细的目标微多普勒特征信息,因此,可以从其中推断出目标特有的独立特征。而基于目标微动回波时频图的特征更是因为其信息量充足的特点,成为了一种新兴有效的目标分类特征。文中主要研究了飞机目标的韵律频率图(Cadence Frequency Diagram,CFD)特征分类算法,详细叙述了算法的具体步骤。仿真分析了CFD特征在飞机目标分类中的特点和优势,并且研究了相关参数对CFD特征的影响。     

Preventive Replacement of a 1-Unit System with a Wearout State

This paper is concerned with a 1-unit system with 3 types of states: usual, wearout, and failure; the hazard rate is constant in the usual state and is monotonically increasing and unbounded in the wearout state. In order to deal with this system in detail, we introduce two models: model 1 in which the period of normal operation is fixed and model 2 in which it is a random variable with a negative exponential distribution function. The models have different preventive replacement policies based on both age and state. Moreover we give the conditions under which these policies are effective.     

两种基于分数阶模糊函数的运动目标检测方法

针对海杂波中运动目标较微弱的特点,推导了单频信号、LFM信号以及相位含有三次项回波信号的分数阶模糊函数的时移特性及正负对称旋转角的分数阶模糊函数,得到2个有用的结论:(1)延时单频信号和延时LFM信号的分数阶模糊函数模函数与时域延时无关,而对于相位含有三次项的回波信号,其延时信号与原信号的分数阶模糊函数模值相等,但其最大值位置不同,与延时有关;(2)单频信号和LFM信号的正负对称旋转角的分数阶模糊函数模处处相等,而对于相位含有三次项的回波信号,其模幅度差别很大。根据此特性提出了2种基于分数阶模糊函数的运动目标检测方法。IPIX实测数据验证表明了文中方法的有效性。     

XGM波长变换器网络的性能分析

目前对有限范围波长变换器的研究或者是针对能变换到较长和较短波长的FWM(SOA(Semiconductor Optical Amplifier) in Four-Wave Mixing,基于半导体光放大器的四波混合)波长变换器的,或者是针对具有卷绕(Wraprounds)功能的变换器.本文研究了只具有单边变换且不具有卷绕的XGM(SOA(Semiconductor Optical Amplifier) in Cross-Gain Modulation,基于半导体光放大器的交叉增益调制)有限范围波长变换器对网络性能的影响,从网络的阻塞率方面比较了FWM与XGM波长变换器对网络性能的影响.研究结果表明,XGM波长变换器的性能虽然只相当于具有10-20%左右变换范围的FWM波长变换器,但较无波长变换器网络的性能已经有了较大的改善,同时与全范围波长变换器网络的性能相差并不太远.     

MIMO系统中一种自适应的迭代检测译码算法

针对常用的非穷尽列表形式后验概率检测算法直接采用恒定且较大的列表长度,导致列表冗余度大的问题,该文提出了一种自适应长度的列表球形译码算法(Adaptive Size List Sphere Decoding, ASLSD)。在算法中通过更新检测半径和设置停止条件,使检测列表长度可随信噪比和迭代次数自适应变化。而且通过将列表操作与LSD (List Sphere Decoding)检测相结合,避免了符号序列在不同半径下的重复检测。仿真表明,在较小性能损失的前提下,该算法可以大大减小所需检测列表的长度,进而有效降低接收机的复杂度。     

193nm准分子激光飞点扫描角膜的研究

本文详细叙述了 193nm准分子激光切削角膜屈光矫正的几种治疗模式 ,并以近视加散光为例 ,对准分子激光消融角膜量的数学模型进行了定量的推导。研究了准分子激光切削角膜的机理 ,提出了确定角膜切削所需的激光脉冲的数目和脉冲位置的方法。在此基础上研究了准分子激光飞点扫描的几种算法 ,并进行了相应的临床实验 ,通过比较得到了两种较好的飞点扫描算法 ,现已在手术中使用。     

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.     

Regularities in the formation of dislocation networks on the boundary of bonded Si(001) wafers

The dislocation networks in structures with hydrophilically bonded Si (001) wafers are investigated by transmission electron microscopy. Networks with differing geometry and type of dominant dislocations are observed. One type of networks, which is typical of bonded structures, is formed on the basis of a square network of screw dislocations and contains a system of unidirectional 60° zigzag-shaped dislocations. It is established that such dislocation networks are flat in structures with an azimuthal misorientation of wafers exceeding 2°, whereas they are three-dimensional at smaller misorientation angles. A unique network of another type is formed only by 60° dislocations, the majority of which are extended along one direction, which does not coincide with the 〈110〉 directions in the boundary plane and has a number of specific features, the explanation of which is impossible within the framework of conventional representations.     

基于Atmegal6L的智能温控饮水机设计

介绍了一种基于ATmegal6L,利用DS18820温度传感器进行测温并控制,具有闲置断电功能的节能型饮水机的实现方案。方案应用了液晶显示,利用红外光电传感器进行热水阀门监控,选用了固态继电器（SSR）进行加热电路控制,具有使用方便,节能安全的特点。     

阈值电压对超深亚微米SRAM存储单元SNM的影响

采用基于物理模型的 α指数 MOSFET模型 ,对超深亚微米 (VDSM:Very Deep Submicron) SRAM存储单元的静态噪声容限 (SNM:Static Noise Margin)进行了解析分析 ,分析中考虑了随机工艺涨落造成的VDSM SRAM存储单元阈值失配对 SNM的影响 ,结果与 HSPICE仿真相符 ;文中同时分析了栅宽与 SNM的关系 ,其结论与实验结果一致 ,并给出了 VDSM SRAM存储单元设计中应注意的问题     

Cross-coupled phase conjugation through two-frequency four-wave mixing in dyes

Two-frequency four-wave mixing in a dye is demonstrated, in which degenerate four-wave mixing is performed simultaneously within the absorption and emission frequency spectra, with two separate sets of beams. The coupling between the two bands gives rise to backward output waves at both frequencies, which are proportional to the phase conjugate of a single probe which can be at either of the two frequencies. Forward-propagating waves which are not conjugated are also generated at both frequencies. The frequency shifted outputs are tunable over the bandwidth of the spectrum in which they lie. A theoretical analysis is performed which is based on a four-level system model of the ground and first excited singlet states in a dye. Resulting are coupled equations, which are solved to yield the efficiencies of the various outputs. Experiments give results in good agreement with the theory.     

LiNbO3光纤型行波光调制器的有限元分析与设计

文中提出一种新型的LiNbO3行波光调制器——LiNbO3矩形光纤型行波光调制器,它用LiNbO3晶体光纤代替传统的LiNbO3波导,耦合效率高,调制带宽达500GHz,能保证很好的阻抗匹配和小驻波比。文中采用有限元法对调制器的尺寸形状进行模拟分析,并进行了优化设计,得到了最优化尺寸及其主要性能指标。最后,探讨了双电极LiNbO3矩形光纤型行波光调制器的制作工艺。     

A Technique for Determination of Filter Insertion Loss as a Function of Arbitrary Generator and Load Impedances

Insertion loss is derived in terms of generator impedance, load impedance, and filter open-circuit and short-circuit impedances. This expression contains a difference term which places great weight on the accuracy with which filter impedances are measured. It is shown that the use of this difference term can be avoided by introducing the filter insertion loss in a circuit with known generator and load impedances. The resulting exact expression contains terms which are easily measurable with sufficient accuracy to provide reliable insertionloss values for the filter for any combination of generator and load impedances. Also shown is a simplified approximate expression for insertion loss which is applicable in a filter attenuation band. A discussion of experimental verification of the expressions is followed by curves showing application of the approximate insertion-loss expression to a particular filter.     

Amplified spontaneous emission model for quantum-well distributedfeedback lasers

An amplified spontaneous emission model for quantum-well (QW) distributed feedback (DFB) lasers is presented, which takes into account local spontaneous emission, stimulated emission, and real refractive index change which are calculated from the Fermi-Dirac occupancy functions in a self-consistent manner. The local-normal-mode transfer-matrix method is used, which allows a coupling of the local DFB effect with the local QW spontaneous emission and gain. As an example, an analysis is given of a partly gain-coupled DFB laser with periodically etched QWs, which has a large discontinuity of spontaneous emission and gain in high- and low-corrugation regions. It is shown that the side-mode suppression improves with the increase of the number of etched QW's, due to the carrier-density-dependent gain-coupling     

Design and realization of a digital ΔΣ modulator forfractional-n frequency synthesis

The basic operation of a fractional-n frequency synthesizer has been published, but to date little has been presented on the digital ΔΣ modulators which are required to drive such synthesizers. This paper provides a tutorial overview, which relates digital ΔΣ modulation to other applications of ΔΣ modulation where the literature is more complete. The paper then presents a digital ΔΣ modulator architecture which is economical and efficient and which is practical to realize with commercially available components in comparison with other possible implementations which require extensive custom very large-scale integration (VLSI). A demonstration is made of a 28-b modulator using the architecture presented, which provides a 25-MHz tuning bandwidth and <1-Hz frequency resolution. The modulator is demonstrated in an 800-MHz frequency synthesizer having phase noise of -90 dBC/Hz at a 30-kHz offset