共查询到20条相似文献,搜索用时 0 毫秒
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Presents a parameter-smoothing technique for discrete hidden Markov models in speech recognition using fuzzy vector quantisation and the Parzen window. The technique is compared with existing smoothing techniques by experiments with speaker-independent isolated word recognition. The results suggest that this technique is more effective than the others in terms of improved recognition.<> 相似文献
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位相叠加效应对连续位相板束匀滑特性的影响 总被引:1,自引:0,他引:1
在大型激光系统的运行过程中,为了对相位畸变导致的焦斑分布不均匀进行改善,在光路通常会使用连续位相板(CPP) 来进行远场束匀滑。根据CPP 面型的随机特性,利用统计的方法对位相板与畸变波前相位的叠加特性进行了计算,系统研究了连续位相板对光束波前分布实现控制的机理。从CPP面形的概率密度与远场直方图之间的关系出发,推导了畸变波前通过CPP 后远场光强分布的表达式,从理论上解释了这种束匀滑器件的工作原理及特性。通过数值模拟计算了不同畸变光束经过CPP后的远场直方图,对结果进行比较并分析了不同面型特性对最终束匀滑效果的影响。结果证明:位相板能在焦斑光强上起到卷积滤波的作用,从而实现光束匀滑效果。从原理上解释了CPP 在具有小相关长度时具有更高匀滑效果这一特性,为实际面型设计和优化提供理论基础。另外,应用统计几何光学方法进行分析,可有效降低波前叠加分析的难度。 相似文献
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The estimation of the instantaneous frequency (IF) of a harmonic complex-valued signal with an additive noise using the Wigner distribution is considered. If the IF is a nonlinear function of time, the bias of the estimate depends on the window length. The optimal choice of the window length, based on the asymptotic formulae for the variance and bias, can be used in order to resolve the bias-variance tradeoff. However, the practical value of this solution is not significant because the optimal window length depends on the unknown smoothness of the IF. The goal of this paper is to develop an adaptive IF estimator with a time-varying and data-driven window length, which is able to provide quality close to what could be achieved if the smoothness of the IF were known in advance. The algorithm uses the asymptotic formula for the variance of the estimator only. Its value may be easily obtained in the case of white noise and relatively high sampling rate. Simulation shows good accuracy for the proposed adaptive algorithm 相似文献
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高空环境对航空遥感器光学窗口的影响 总被引:1,自引:0,他引:1
为提高航空遥感器光学窗口的光学性能,从空气动力学环境和大气环境两个方面分析了高空环境对光学窗口的影响。根据空气动力学原理,计算出飞行马赫数和雷诺数,以确定光学窗口所处的飞行环境;依据纵掠平壁理论,计算出光学窗口外表面的平均对流换热系数,仿真光学窗口温度分布,分析了轴向温差对光学窗口的影响。分析高空大气环境下光学窗口玻璃出现结霜原因及影响,并提出预防结霜的解决方案。最后针对某航空遥感器光学窗口进行飞行试验,结果表明分析的结论正确,提出的解决方案合理可靠,可为其他航空光学窗口设计提供依据。 相似文献
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基于平行光通过倾斜的平板玻璃会使光线发生平移的现象,从几何光学的角度分析了三折式光学窗口对航空相机成像分辨率的影响,在窗口玻璃厚度为25 mm,窗口玻璃之间的夹角为45,照相距离为5 000m的条件下,对焦距1 000 mm 的相机成像偏移量进行了分析计算,计算结果成像偏移量为3.34 m,大于设计要求的1/3 像元.最后,通过试验检验了成像偏移对相机成像分辨率的影响,分析及试验结果表明,相机焦距、窗口玻璃厚度和窗口玻璃之间的夹角越大,相机照相距离越小,使相机成像分辨率越低,尤其是采用三折式窗口玻璃的长焦距相机,不适宜在较近照相距离下照相。 相似文献
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The influence of horn length on the radiation pattern of an oblique-flare-angle corrugated horn is described. Two experiments with a 110° horn are reported. These show that a horn with three slots has a radiation pattern which is essentially the same as that of a horn with five slots. It is also demonstrated that the innermost slot has a dominant effect on the pattern. 相似文献
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K. Bock B. Keppens V. De Heyn G. Groeseneken L. Y. Ching A. Naem 《Microelectronics Reliability》2001,41(3)
ESD-performance of grounded-gate nMOS protection structures has been observed for a standard 0.25 μm CMOS epitaxial layer based technology. The shortest gate lengths show unexpectedly lower ESD-thresholds, leading to an optimum performance for longer gate length devices attributed to the trade off between power dissipation and melt volume of the parasitic bipolar. 相似文献
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白天天空背景对昼夜大气相干长度仪数据影响 总被引:1,自引:0,他引:1
昼夜大气相干长度仪实现了全天候连续观测恒星,是一种大气相干长度的常规观测仪器。主要分析了白天天空背景光引起的大气相干长度测量误差,提出了适合于工程应用的图像消噪方法,并进行了数值仿真,结果表明:该消噪方法能有效抑制白天天空背景引起的图像传感器噪声,使其在最大天空亮度观测3.5等星时所引起的大气相干长度测量误差减小到1.434%,扩大了选星跟踪范围,证实了该消噪方法应用于提高仪器测量精度的可行性和白天星像质心提取的准确性。 相似文献
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The optimization of a SiO2/TiO2,SiO2/ZnS double layer antireflection coating(ARC)on Ga0.5In0.5P/In0.02Ga0.98As/Ge solar cells for terrestrial application is discussed.The Al0.5In0.5P window layer thickness is also taken into consideration.It is shown that the optimal parameters of double layer ARC vary with the thickness of the window layer. 相似文献
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为实现激光传输内通道密封,会在末端加装带倾斜角的窗口,但窗口的回射杂散光辐照管壁会引起结构温升,加热通道内气体引起热效应。针对密封窗口的回射杂散光辐照加热直管道问题,建立了直管道部分结构场-气体密度场-光场的耦合仿真模型,分析了不同管道材料、管壁厚度、管道结构形式对光束波前畸变的影响。分析结果表明:等质量的铝、铜、钢三种材料中,铝管道引起的光束波前畸变最小,仅为钢、铜的约50%;通过管道外侧增加散热翅片以及高导热碳膜的方式来降低壁温、改善波前畸变的效果并不理想,波前RMS值下降不超过3%;增加受辐照段管道壁厚、提升管道热沉是降低光束波前畸变最有效的方案,铝管壁厚由8 mm增加至16 mm可使管道出口处的波像差RMS值从36.1 nm下降到21.4 nm,各阶像差均得到改善。研究结果能够为内通道部分管道设计和热效应评估提供一定的参考。 相似文献
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Roof-edge preserving image smoothing based on MRFs 总被引:1,自引:0,他引:1
A novel Markov random field (MRF) model is proposed for roof-edge (as well as step-edge) preserving image smoothing. Image surfaces containing roof-edges are represented by piecewise continuous polynomial functions governed by a few parameters. Piecewise smoothness constraint is imposed on these parameters rather than on the surface heights as is in traditional models for step-edges. In this way, roof edges are preserved without the necessity to deal with unstable higher order derivatives. 相似文献
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Si-Woong Lee Jae Gark Choi Byoung-Ju Yun 《Electronics letters》2003,39(9):712-714
An adaptive contour smoothing algorithm designed as a preprocessor for shape coders is presented. In the method, the degree of the adaptive smoothing is controlled based on the significance of each contour point, which is quantified according to inter-region contrast in an intensity image. The actual smoothing consists of an expansion operator and a thinning algorithm. 相似文献
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在GIS基础数据的采集过程中,地理信息数据总量非常大,是海量数据,这就要求我们在数据处理的初级阶段采取合理有效的手段控制数据质量。针对这种情况,需要对数据进行圆滑或抽稀处理,这里介绍了对自动生成的等高线进行圆滑和抽稀处理的一种算法。 相似文献
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In order to improve the learning speed and reduce computational complexity of twin support vector hypersphere(TSVH), this paper presents a smoothed twin support vector hypersphere (STSVH) based on the smoothingtechnique. STSVH can generate two hyperspheres with each one covering as many samples as possible from thesame class respectively. Additionally, STSVH only solves a pair of unconstraint differentiable quadraticprogramming problems (QPPs) rather than a pair of constraint dual QPPs which makes STSVH faster than theTSVH. By considering the differentiable characteristics of STSVH, a fast Newton-Armijo algorithm is used forsolving STSVH. Numerical experiment results on normally distributed clustered datasets ( NDC) as well asUniversity of California Irvine (UCI) data sets indicate that the significant advantages of the proposed STSVH in terms of efficiency and generalization performance. 相似文献