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在压缩采样中,测量矩阵应该和表达字典有尽可能小的相干性,随机测量矩阵一直被使用是因为其和任何表达字典都有较小的相干性。提出一种基于梯度迭代最小化方法,作为格拉斯曼框架设计的一种变体,通过优化一个初始的随机测量矩阵来得到相干性更小的测量矩阵。仿真结果表明所设计的测量矩阵具有更好的性能。 相似文献
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A high detection efficiency calorimeter which is used to detect γ-rays with energies from 1 MeV up to 10 MeV as well as light charged particles has been proposed. Design of the geometry, results of the crystal tests and Monte Carlo simulations are present 相似文献
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苗泉 《湖南工业职业技术学院学报》2005,5(2):7-9
ETF是一种可同时在一级市场和二级市场交易的消极管理型指数基金,它的许多优点使其近年来在全球各大主要资本市场上获得了迅猛的发展。我国也已于2004年11月29日推出第一支ETF——上证50ETF,因此了解并借鉴美国这一世界上最为发达和成熟的ETF市场的发展经验将对我国发展自己的ETF市场大有裨益。 相似文献
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在传统ETF(Exact transfer function)成像算法的基础上,根据SAS(synthetic aperture sonar)应用中较为普遍的发射器和接收器收发分置的基本模型,该文详细推导得到了一种应用于SAS成像的改进的最优ETF算法,分析并推导得到了算法使用中应该满足的分块处理条件。由于该改进算法推导过程中聚焦函数的方位相位的计算不作近似截取而是做准确计算,使得该算法具有最优的相位精度。同时,分块处理条件的推导,为数据的并行运算提供了依据。该算法对数据分块进行并行处理,使得算法运算速度得到提高,有利于算法应用的快速实现。最后,该文使用点目标回波仿真数据对算法的效果进行了验证,成像结果证明了该改进算法的有效性。 相似文献
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从字典的相干性边界条件出发, 提出一种基于极分解的非相干字典学习方法(Polar decomposition based incoherent dictionary learning, PDIDL), 该方法将字典以Frobenius范数逼近由矩阵极分解获取的紧框架, 同时采用最小化所有原子对的内积平方和作为约束, 以降低字典的相干性, 并保持更新前后字典结构的整体相似特性. 采用最速梯度下降法和子空间旋转实现非相干字典的学习和优化. 最后将该方法应用于合成数据与实际语音数据的稀疏表示. 实验结果表明, 本文方法学习的字典能逼近等角紧框架(Equiangular tight-frame, ETF), 实现最大化稀疏编码, 在降低字典相干性的同时具有较低的稀疏表示误差. 相似文献
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《Thin》2014
This paper presents the details of an experimental study of a cold-formed steel hollow flange channel beam known as LiteSteel beam (LSB) subject to web crippling under End Two Flange (ETF) and Interior Two Flange (ITF) load cases. The LSB sections with two rectangular hollow flanges are made using a simultaneous cold-forming and electric resistance welding process. Due to the geometry of the LSB, and its unique residual stress characteristics and initial geometric imperfections, much of the existing research for common cold-formed steel sections is not directly applicable to LSB. Experimental and numerical studies have been carried out to evaluate the behaviour and design of LSBs subject to pure bending, predominant shear and combined actions. To date, however, no investigation has been conducted on the web crippling behaviour and strength of LSB sections. Hence an experimental study was conducted to investigate the web crippling behaviour and capacities of LSBs. Twenty-eight web crippling tests were conducted under ETF and ITF load cases, and the ultimate web crippling capacities were compared with the predictions from the design equations in AS/NZS 4600 and AISI S100. This comparison showed that AS/NZS 4600 and AISI S100 web crippling design equations are unconservative for LSB sections under ETF and ITF load cases. Hence new equations were proposed to determine the web crippling capacities of LSBs based on experimental results. Suitable design rules were also developed under the direct strength method (DSM) format. 相似文献
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Shu-Wen Tang Shi-Tao Wang Li-Min Duan Zhi-Yu Sun Yu-Hong Yu Xue-Heng Zhang Ke Yue Chen-Gui Lu He-Run Yang Peng Ma Fang Fang Duo Yan Yu Sun 《核技术(英文版)》2017,28(5)
A tracking system composed of three multiwires proportional chambers(MWPCs) for the external target facility of the Cooler Storage Ring is reported in this paper. The active areas of the MWPCs are 518 mm 9400 mm, 582 mm 9 450 mm, and 710 mm 9 500 mm Each MWPC consists of a series of alternately placed cathode and anode wire planes and can measure position along the directions of-30°, 0°, and 30° relative to horizontal. The construction and operation of the detectors are described, and a method for track reconstruction is introduced. A track-finding efficiency of about 62% and a spatial resolution of 1.21 mm have been achieved. The pion and proton can be identified clearly with the tracking system combined with a time-of-flight system. 相似文献