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粗糙面声散射方法概述 总被引：3，自引：0，他引：3
给出了处理粗糙面声散射问题的不同方法,并对各种方法的优缺点进行了扼要说明,最后对常用的粗糙面声散射方法一一积分方程。法和小斜率近似方法的理论公式做了简单推导。 相似文献
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通过实验数据求松弛时间谱的近似方法,采用稳态应力松弛实验或动态剪切实验求得稳态松弛模量函数G（t）或动态模量函数G′（ω）、G″（ω）,由这些函数求取松弛时间谱H（λ）的各次近似解。通过动态线性小振幅剪切震荡实验所得的熔体储能模量G′（ω）和耗能模量G″（ω）数据,根据Schwarzl和staverman提出的近似公式,计算得到离散松弛时间谱,提出了计算参数和温度对离散松弛时间谱的影响。 相似文献
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将近代Shannon信息熵概念广义化,利用信息量的"可加性"特征及离散熵的一般表达式,与R＆D期望资金流贴现法相结合,推导出R＆D资金流贴现率的熵近似上限及熵近似下限公式,用于R＆D决策评估,实例计算分析,得到令人满意的结果.文中提出的理论,为寻求R＆D的决策方法开辟了新的途径. 相似文献
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在非线性极化理论框架下讨论饱和吸收时,采用三阶近似非线性模型,在入射光较强的条件下,三阶非线性吸收出现了明显的偏差,在非线性饱和吸收的理论研究或者实验分析中,在使用高能量的泵浦光强研究非线性饱和吸收效应时,应采用由速率方程严格推导的饱和吸收公式,而在低能量泵浦光强作用时,采用传统的三阶非线性吸收公式亦可。 相似文献
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一、激发学生的学习兴趣,启迪学生的思维(一)用实践操作唤起学生的兴趣教师在教学实践中动手操作或让学生自己动手操作,最能唤起学生的兴趣,保持学生稳定的注意力。如在推导圆柱体的体积公式时,我通过让学生自己推导将一个圆柱体拼割成一个近似的长方体,并让学生掌握了圆柱体的 相似文献
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将鱼骨型水平井的流场划分为主干井渗流区域和鱼骨分支渗流区域流,利用拟压力形式,根据压力叠加原理并采用采用保角变换和推导出不同分支数和夹角的情况下鱼骨型水平井非稳态产能的解析公式。根据推到的公式优化出最优的分支数和分支角度。然后,得出了最优分支角度下,不同生产时间下产量与压力的关系。 相似文献
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A procedure for approximating fractional-order systems by means of integer-order state-space models is presented. It is based on the rational approximation of fractional-order operators suggested by Oustaloup. First, a matrix differential equation is obtained from the original fractional-order representation. Then, this equation is realized in a state-space form that has a sparse block-companion structure. The dimension of the resulting integer-order model can be reduced using an efficient algorithm for rational L2 approximation. Two numerical examples are worked out to show the performance of the suggested technique. 相似文献
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In the paper, a control algorithm for output regulation problem of nonlinear pure-feedback systems with unknown functions is proposed. The main contributions of the proposed method are not only to avoid Assumptions of unknown functions, but also adopt a non-backstepping control scheme. First, a high-gain state observer with disturbance signals is designed based on the new system that has been converted. Second, an internal model with the observer state is established. Finally, based on Lyapunov analysis and the neural network approximation theory, the control algorithm is proposed to ensure that all the signals of the closed-loop system are the semi-globally uniformly ultimately bounded, and the tracking error converges to a small neighborhood of the origin. Three simulation studies are worked out to show the effectiveness of the proposed approach. 相似文献
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《Journal of The Franklin Institute》2023,360(7):5082-5091
In this article, an adaptive tracking control approach using Bernstein polynomial approximation is firstly proposed for an unknown nonlinear dynamic system. Bernstein polynomial approximation aims to compensate the unknown nonlinear dynamic function. However, if Bernstein theorem is directly used, the Bernstein polynomial's coefficients need to be derived from the system dynamic function. Nevertheless, the dynamic function is presumed to be unknown, hence the polynomial approximation still cannot be used for designing this control. In order to obtain the available function approximation, adaptive strategy is considered to estimate these coefficients. Finally, by learning from the classical adaptive algorithm, the undetermined coefficient problem is addressed, so that the valid tracking control is found for the unknown nonlinear dynamic system. According to Lyapunov stability analysis and simulation experiment, it is concluded that the new adaptive scheme can realize the control objective. 相似文献
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《Journal of The Franklin Institute》2023,360(7):4807-4829
The Discrete Tchebichef Transform (DTT) is widely used in signal processing applications such as image and video compression and digital watermarking due to its coding and decorrelation properties. In embedded systems and real-time applications, the need for fast, low complexity, and energy efficient algorithms is increasingly important. However, there is a limited number of such algorithms available for efficient computation of the DTT compared to the discrete cosine transform. To address this issue, a new DTT approximation is proposed, which provides a low-complexity and efficient solution by exploiting the deviation from orthogonality. The suggested algorithm requires fewer additions and bit-shifting operations compared to the existing ones. The implementation of this DTT approximation on the Xilinx Virtex-6 XC6VSX475T-1FF1759-2 FPGA resulted in a 19.20% decrease in hardware resources and 2% reduction in energy consumption for 1-D 8 inputs compared to the best candidate DTT approximation. With a low deviation from orthogonality, the efficiency of the proposed approximation has been confirmed in image compression and digital watermarking. The experimental results show an average quality improvement of 0.25 dB over the latest DTT approximation. 相似文献
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This paper proposes a new approximation to be used for the correction function in the turbo decoding algorithm, called Linear-Constant-log Map. Max-log Map, Linear-log Map and Constant-log Map are the well known simplified versions of Jacobi-log Map (Maximum a Posteriori) algorithm already in use but they cannot meet a proper performance in term of output BER and clock consumption of the CPU decoding encoded bits. The proposed algorithm first breaks the correction function domain of the Jacobi logarithm to three subsections by determining the border points between these sections and then uses a linear function and two constant values as an approximation of this function. Using an AWGN channel model, simulation results show that the new algorithm is almost more than six times faster than Jacobi-log Map algorithm with a Bit Error Rate (BER) very close to it. 相似文献
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J.P. Den Hartog 《Journal of The Franklin Institute》1933,216(4):459-473
Two new approximate graphical solutions are given for the problem of forced vibration of an undamped single degree of freedom vibrating system with a non-linear spring, whose characteristic is given in the form of a curve. One of these solutions gives much more accurate results than the approximation known so far. 相似文献
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In this paper, the approximation problem of T–S fuzzy linear singular system for a class of nonlinear singular system with derivative of input is considered and the nonlinear singular system has impulses. Consider a numerical example and a two-wheel drive robot, the T–S fuzzy singular systems are calculated for original system with derivative of input. According to solvability and steps of solving of the two examples, the results are extended to more generally nonlinear singular system with derivative of input. The theorem and algorithm that are given if input-state system is bounded impulse-free item and separable impulse item, it can be approximated by T–S fuzzy singular system with arbitrary accuracy. Finally, a numerical simulation is carried out to show the consistency with theoretical analysis and illustrate the effectiveness of approximation. 相似文献
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A new transitional filter based on the sum of filter polynomials is proposed and discussed. It shall be shown that the approach allows for greater flexibility in adjusting passband and stopband gain shapes. The sensitivity of the filter transfer function is analyzed and related to the approximation problem. Some new modified classical filters are also derived including maximally flat (Butterworth) and equiripple (Chebyshev) types. Several examples of combining Butterworth, Chebyshev and sync-tuned filters are presented and compared to those obtained using the conventional product method. The new transitional filter provides an alternative to other forms and provides a means for isolating the effects of non-uniformly distributed pole angles. 相似文献
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Shi Jun 《中国科学院研究生院学报》1992,(4)
In this paper, we present a new more efficient Galerkin approximation method for a class of non-smooth Fredholm integral equations and show that this method is not only a high order method but also an adaptive one. 相似文献
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Dragan Antić Bratislav Danković Saša Nikolić Marko Milojković Zoran Jovanović 《Journal of The Franklin Institute》2012,349(1):323-336
In this paper, we define a class of almost orthogonal rational functions of Legendre type in a new manner. Relations of these functions with classical exponentional functions orthogonal over interval (0, ∞), as well as classical polynomials orthogonal over (0, 1) are explained. Defining relations of these functions can be used for designing almost orthogonal filters. These filters are generators of orthogonal signals and can be successfully applied in finding the best signal approximation in the sense of the mean square error. The filters orthogonal property enables building of physical (in this case electrical) models of dynamical systems (the sources of signals to be approximated) either with less components for the same model accuracy or higher accuracy for the same number of components than the other known models. New filters represent further improvement of previously designed filters, by the same authors, in the sense of simplicity, higher accuracy, lesser approximation time and even a possibility to approximate signals generated by systems with built-in imperfections. Series of experiments were performed to analyze the dependence of approximation accuracy and the number of filters sections. 相似文献