共查询到19条相似文献,搜索用时 140 毫秒
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本文在已有文献基础上,提出最佳和次佳Лypbe函数概念,并给出寻找方法。这些结果既可以用来作理论分析,又可以用来实际确定绝对稳定角域中的K值,与传统的频率方法相比,优点是能较方便地给出相应的 Лypbe型V函数。 相似文献
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布尔置换和bent函数在密码学中起着非常重要的作用。在Coulter和Mesnager所提出的三元组布尔置换广义构造方法(该三元组布尔置换可以用来构造bent函数)的基础上,给出了一个等价的构造三元组布尔置换的具体方法。利用此具体方法,提供了一个构造三元组布尔置换的算法。对三个置换之间的依赖关系做了进一步研究,提出了一个三元组置换成立的充要条件,并给出了一个构造三元组布尔置换的新算法。分析了利用三元组布尔置换所得bent函数的性质。 相似文献
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由经典的函数逼近理论衍生的很多数值算法有共同的缺点:计算量大、适应性差、对模型和数据要求高,在实际应用中受到限制。神经网络可以被用来计算复杂输入与输出结果之间的关系,故神经网络具有很强的函数逼近功能。该文给出了径向基函数网络(RBFNN)的结构及学习过程,重点阐述了RBFNN在函数逼近、求解非线性方程组以及散乱数据插值中的应用,结合MATLAB神经网络工具箱给出了数值实例,并与BP网络进行了比较。应用结果表明RBFNN是数值计算的一个有力工具,与传统方法比较具有编程简单、实用的特点,在工程和科学研究上若将其制成软件包则具有很好的使用价值。 相似文献
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Sarka等人在文献[1]中给出了弹性布尔函数的一种构造方法,利用该方法可以构造出非线性度、弹性阶和代数次数等密码学性质均较理想的奇数元弹性布尔函数。对其构造得到的弹性布尔函数的谱值分布进行了研究,分析了由该方法所构造得到的5元1阶和7元1阶弹性布尔函数的谱值,给出了这两类弹性布尔函数的谱值分布情形,并给出了相应谱值点的计数结果。 相似文献
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给出一种基于核函数的主成分分析方法,它主要用来解决大规模非线性数据的特征提取问题。文中给出了简化的协方差矩阵的计算方法与推导过程,还给出了KPCA方法的详细推导过程。最后使用核主成分分析的方法分别对线性与非线性分布的数据进行了分析,取得了比传统主成分分析方法更好的结果。 相似文献
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在对Snakes能量函数进行了改进之后,将其用于处理航空影象中的目标提取,动态规划方法被用来解决优化求解问题。最后给出了利用这种方法对目标进行提取的例子。 相似文献
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In this paper, absolute stability condition is investigated when a hysteresis nonlinearity is connected to a linear subsystem via positive feedback in Lur'e system framework. In particular, the nonlinearity is considered to belong to the time-invariant slope-restricted counter-clockwise hysteresis class. An absolute stability criterion is proposed in terms of the negative-imaginary system properties. In effect, the stability condition requires the linear subsystem to belong to the strongly strict negative-imaginary (SSNI) system class along with satisfying a matrix condition involving the DC-gain of the linear subsystem and the slope-upper-bounds of the nonlinearities. Compliance to the conditions guarantees asymptotic convergence of state-trajectories to an equilibrium set. Invoking the stability result and exploiting the relaxed minimality assumption of SSNI systems, a static state-feedback synthesis method is proposed to ensure absolute stability for such hysteretic systems. Tractable conditions in the form of linear matrix inequalities can be solved to obtain a stabilising state-feedback gain matrix. Finally, a numerical example of multi-input–multi-output system is presented to illustrate the usefulness of the proposed results. 相似文献
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Necessary and suffcient conditions for the existence of a Lyapunov function in the Lur‘e form to guarantee the absolute stability of Lur‘e control systems with multiple non-linearities are discussed in this paper. It simplifies the existence problem to one of solving a set of linear matrix inequalities (LMIs). If those LMIs are feasible, free parameters in the Lyapunov function, such as the positive definite matrix and the coefficients of the integral terms, are given by the solution of the LMIs. Otherwise, this Lyaptmov function does not exist. Some sufficient conditions are also obtained for the robust absolute stability of uncertain systems. A numerical example is provided to demonstrate the effectiveness of the proposed method. 相似文献
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Necessary and suffcient conditions for the existence of a Lyapunov function in the Lur'e form to guarantee the absolute stability of Lur'e control systems with multiple non-linearities are discussed in this paper. It simplifies the existence problem to one of solving a set of linear matrix inequalities (LMIs), If those LMIs are feasible, free parameters in the Lyapunov function,such as the positive definite matrix and the coefficients of the integral terms, are given by the solution of the LMIs. Otherwise, this Lyapunov function does not exist. Some sufficient conditions are also obtained for the robust absolute stability of uncertain systems.A numerical example is provided to demonstrate the effectiveness of the proposed method. 相似文献
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Robotic gas tungsten arc (GTA)-based additive manufacturing (AM) is a promising technique to produce high-quality and large-scale metal parts with low cost. Despite this fact, the key issue of ensuring deposition height stability has not been fully solved. In this study, an arc voltage sensing and control approach with little delay is proposed to increase the forming height stability in GTA-based AM. The deposition height stability is indirectly characterized by arc voltage signals sampled using a designed arc voltage detection system. A novel de-noising method, combining the anti-impulse interference moving average with the wavelet packet transform, is proposed to filter out interferences in the original arc voltage. A Fuzzy-PID controller is developed to control the arc voltage by adjusting the wire feed speed on next deposition layer. Constant parameter and closed-loop control experiments are compared via fabricating thin-walled parts. The more stable arc voltage and more excellent forming appearance in the closed-loop control test indicate that applying the arc voltage sensing and control system can greatly improve the forming height stability in robotic GTA-based AM. 相似文献
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为解决均匀参数采样在许多情况下得到质量不高的采样点,进而生成不理想的B样条拟合曲线,提出空间曲线基于内在几何量的均匀采样方法,以获得给定总数且具有代表性的采样点.首先定义基于弧长、曲率和挠率加权组合的特征函数,通过调整组合参数更好匹配不同的曲线形状;然后提出空间曲线基于内在几何量的自适应采样方法,迭代生成满足给定距离阈值的采样点.采用最大绝对误差和均方根误差作为评价指标,与均匀弧长采样方法和基于弧长和曲率平均的均匀采样方法进行对比,并通过实例进行验证.结果表明,文中方法在采样质量和B样条拟合结果上获得明显改善. 相似文献
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The present paper establishes results for the robust absolute stability of a class of nonlinear continuous-time systems with time-varying matrix uncertainties of polyhedral type and multiple time-varying sector nonlinearities. By using the variational method and the Lyapunov Second Method, criteria for robust absolute stability are obtained in different forms for the given class of systems. Specifically, the parametric classes of Lyapunov functions are determined which define the necessary and sufficient conditions of robust absolute stability. The piecewise linear Lyapunov functions of the infinity vector norm type are applied to derive an algebraic criterion for robust absolute stability in the form of solvability conditions of a set of matrix equations. Several simple sufficient conditions of robust absolute stability are given which become necessary and sufficient for special cases. Two examples are presented as applications of the present results to a particular second-order system and to a specific class of systems with time-varying interval matrices in the linear part. 相似文献