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由于基于最坏情况困难假设等优点,基于格的密码被认为是最具前景的抗量子密码研究方向。作为格密码的常用的两个主要困难问题之一,含错学习(LWE)问题被广泛用于密码算法的设计。为了提高格密码算法的性能,Zhang等人(2019)提出了非对称含错学习问题,该文将从理论上详细研究非对称含错学习问题和标准含错学习问题关系,并证明在特定错误分布下非对称含错学习问题和含错学习问题是多项式时间等价的,从而为基于非对称含错学习问题设计安全的格密码算法奠定了理论基础。 相似文献
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《Signal Processing, IEEE Transactions on》2006,54(8):3111-3124
Approximation of digital signals by means of continuous-time functions is often required in many tasks of digital to analog conversion, signal processing, and coding. In many cases the approximation is performed based on an$l^2$ optimality criterion; in this paper we study approximations of one-dimensional signals under the$l^infty$ norm. We first introduce approximations in linear spaces, for which linear programming methods are known. For the particular case of linear approximations (i.e., first-order polynomials), we propose a geometric solution that is shown to be computationally more efficient than the linear programming approach. Then, we study the problem of piecewise approximations, i.e., dividing the domain into intervals and approximating the signal in linear spaces within every segment independently, so as to reach an optimal noncontinuous approximation. Given an error bound$delta$ , we establish a strategy to determine the minimum number$k$ of segments for which the approximation is guaranteed to produce an error within$delta$ . We then show how to find the optimal partition that gives the piecewise$l^infty$ optimal solution with$k$ segments. The computational complexity of the algorithms is studied, showing that in many practical situations, the number of operations is$O(n)$ , with$n$ being the number of samples. 相似文献
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A formulation based on Lagrangian optimization and spheroidal vector wave functions is presented for the vector electromagnetic inverse source problem of deducing a time-harmonic current distribution that is confined within a spheroidal volume, that generates a prescribed radiation field, and that is subject to given constraints on the source functional energy, which characterizes antenna current level, and the source's reactive power, which models antenna resonance matching. The paper includes computer simulation results illustrating the derived inverse theory. 相似文献
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Peverini O. A. Addamo G. Tascone R. Virone G. Orta R. 《Microwave Theory and Techniques》2010,58(2):440-450
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On the Complexity of Hardness Amplification 总被引:2,自引:0,他引:2
《IEEE transactions on information theory / Professional Technical Group on Information Theory》2008,54(10):4575-4586
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车牌字符的预处理研究 总被引:4,自引:0,他引:4
由于在汽车牌照自动识别系统中,因天气或拍摄角度等原因造成车牌图像模糊、倾斜和光照不均等现象,给车牌的处理带来了很大困难。本文针对这些问题,提出了相应的处理方法,高效地完成了车牌字符的预处理。 相似文献
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针对飞参数据的特点.从野值剔除和属性选择两个方面对飞参数据预处理进行了研究,提出了基于残差检验的野值别除方法和基于神经网络的两阶段属性选择方法。在野值剔除方法中,首先计算原始序列和拟合序列的残差.再用门限值对残差进行检验;在属性选择方法中,先用神经网络对属性的相对重要度进行排序,再用神经网络进行属性选择。最后用实验验证了两方法的有效性。 相似文献
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针对飞参数据的特点,从野值剔除和属性选择两个方面对飞参数据预处理进行了研究,提出了基于残差检验的野值剔除方法和基于神经网络的两阶段属性选择方法。在野值剔除方法中,首先计算原始序列和拟合序列的残差,再用门限值对残差进行检验;在属性选择方法中,先用神经网络对属性的相对重要度进行排序,再用神经网络进行属性选择。最后用实验验证了两方法的有效性。 相似文献
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文章对用智能车载预警系统获取的夜间图像进行了预处理,包括平滑滤波、锐化、阈值分割、数学形态学和求连通域。通过算法的对比试验,选择出了适合所获取的图像的一套方法。 相似文献
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When designing a system, there are two methods that can be used to improve the system's reliability without changing the nature of the system: 1) using more reliable components, and/or 2) providing redundant components within the system. The redundancy allocation problem attempts to find the appropriate mix of components & redundancies within a system in order to either minimize cost subject to a minimum level of reliability, or maximize reliability subject to a maximum cost and weight. Redundancy allocation problems can be classified into two groups; one allows the system to have a mix of components with different characteristics incorporated in the system, while the other only allows one type of each component. The former group has a much larger solution space compared to the latter, and therefore obtaining an exact optimal or even a high quality solution for this problem may be more difficult. Optimization techniques, based on meta-heuristic approaches, have recently been proposed to solve the redundancy allocation problem with a mix of components. However, an exact solution method has not been developed. In this paper, we develop an exact solution method, based on the improved surrogate constraint (ISC) method, and use this method to find optimal solutions to problems previously presented in the literature 相似文献
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A pulsewidth-modulated (PWM) voltage applied to a squirrel-cage induction motor (SQIM) can cause high bearing currents, heating of rotor shaft, voltage spike across the motor terminals, etc. Filtering of this PWM voltage to obtain a sinusoidal output voltage can be a solution to this problem. However, a passive L-C filter makes the dynamic performance of the drive poor for high-performance control application. In this paper, a feed-forward control strategy for the L-C filter is proposed to have a good bandwidth for the filter output voltage. This filter control strategy is introduced along with a sensorless vector control strategy for the SQIM drive. This complete strategy retains the high dynamic performance of the drive even with the L-C filter. In this paper, a three-level converter is used as a voltage source inverter for the drive to have a less filter-size requirement. The control strategy is verified on a 7.5-hp SQIM drive with a three-level insulated-gate bipolar-transistor inverter and L-C filter. Experimental results validate the high dynamic performance of the drive with filter. 相似文献
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交流电动机矢量控制变压变频调速系统(一) 第一讲 矢量控制的基本概念 总被引:1,自引:0,他引:1
本文首先对直流电动机电磁转矩和异步电动机电磁转矩之间的内在联系进行了介绍,在此基础上,给出矢量控制的基本概念,最后,讨论了异步电动机矢量控制方法的基本思想,给出了矢量控制系统的总体(思路)框图。 相似文献
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The Regulator Problem for Linear Systems With Saturations on the Control and its Increments or Rate: An LMI Approach 总被引:1,自引:0,他引:1
Benzaouia A. Tadeo F. Mesquine F. 《IEEE transactions on circuits and systems. I, Regular papers》2006,53(12):2681-2691
This paper solves the problem of designing stabilizing regulators for linear systems subject to control saturations and asymmetric constraints on its increment or rate, using reduced dimension linear matrix inequalities (LMIs) developed on a reduced-order state space. Compared with previous approaches, the proposed technique is valid for asymmetric constraints on the increment or rate of the control while the computing time is improved by resolving LMIs of reduced dimensions 相似文献
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本文对网络安全进行技术分析,从不同角度阐述网络安全的隐患,在设计中采用相应对策,确保Internet/Intranet网络安全运行。 相似文献