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41.
研究了图像傅立叶变换过程中的振幅与位相问题,突出了位相在整个变换中的重要性,并利用双位相函数对图像进行加密编码和解码,计算机模拟表明双位相编码和解码能有效的抑制附加噪声。 相似文献
42.
W. Whaling W. H. C. Anderson M. T. Carle J. W. Brault H. A. Zarem 《Journal of research of the National Institute of Standards and Technology》2002,107(2):149-169
We report precision measurements by Fourier transform spectroscopy of the vacuum wavenumber, line width, and relative signal strength of 928 lines in the Ar I spectrum. Wavelength in air and classification of the transition are supplied for each line. A comparison of our results with other precision measurements illustrates the sensitivity of Ar I wavelengths to conditions in the light source. 相似文献
43.
V.V. Korolkov I.I. Kulakova B.N. Tarasevich G.V. Lisichkin 《Diamond and Related Materials》2007,16(12):2129-2132
High temperature hydrogen stream treatment of nanodiamond was shown to produce nanodiamond with bifunctional surface. OH- and different CH-groups were shown to be the main functional groups on the surface. In this article we proposed two main strategies for further chemical modification of hydrogenated nanodiamond. OH-groups were shown to react with different types of acylating agents: anhydrides and chloranhydrides. Chlorination of hydrogenated nanodiamond with molecular chlorine and its subsequent treatment with alkyllithium reagents resulted in formation of alkyl-nanodiamonds. Chlorination was shown to reduce the size of nanodiamonds aggregates. We have also applied suspension-state NMR-H1 spectroscopy to study suspensions of alkyl-nanodiamonds for the first time. 相似文献
44.
Bradley T. Ewing Jamie Brown Kruse Douglas A. Smith 《Journal of Wind Engineering & Industrial Aerodynamics》2007,95(3):209-219
This research examines the interdependence in time series wind speed data measured in the same location at four different heights. A multiple-equation system known as a vector autoregression is proposed for characterizing the time series dynamics of wind. Additionally, the recently developed method of generalized impulse response analysis provides insight into the cross-effects of the wind series and their responses to shocks. Findings are based on analysis of contemporaneous wind speed time histories taken at 13, 33, 70 and 160 ft above ground level with a sampling rate of 10 Hz. The results indicate that wind speeds measured at 70 ft was the most variable. Further, the turbulence persisted longer at the 70-ft measurement than at the other heights. The greatest interdependence is observed at 13 ft. Gusts at 160 ft led to the greatest persistence to an “own” shock and led to greatest persistence in the responses of the other wind series. 相似文献
45.
关于移动平均过程两系数的推导 总被引:1,自引:0,他引:1
杜德文 《石油化工高等学校学报》1995,(2)
对经济预测方法中两公式给出了证明,两公式的系数被显式推导出来,这两个公式是时间序列模型公式,广泛用于经济预测之中,但文献上很难找到推导过程,本文的证明是基本的,无需高深数学知识即可理解. 相似文献
46.
Berlin Wu 《Computational Economics》1994,7(1):37-53
In this paper, the methods of time series for nonlinearity are briefly surveyed, with particular attention paid to a new test design based on a neural network specification. The proposed integrated expert system contains two main components: an identification environment and a robust forecasting design. The identification environment can be viewed as a integrated dynamic design in which cognitive capabilities arise as a direct consequence of their self-organizational properties. The integrated framework used for discussing the similarities and differences in the nonlinear time series behavior is presented. Moreover, its performance in prediction proves to be superior than the former work. For the investigation of robust forecasting, we perform a simulation study to demonstrate the applicability and the forecasting performance. 相似文献
47.
48.
基于信号样本可以重建信号频谱包络,本文提出一种简单、实用的内插方法,将此方法的有效性和FFT的优越性结合起来应用于细化频率分辨率,以适应需要获取信号较多频谱信息的应用场合。 相似文献
49.
Abstract. A vector time series model of the form A(L)y(t) + B(L)x(t) =ε(t) is known as a vector autoregressive model with exogenous variables (VARX model) and involves a regressand vector y(t) and a regressor vector x(t). This paper provides a method for the recursive fitting of subset VARX models. It suggests the use of ascending recursions in conjunction with an order selection criterion to choose an 'optimum' subset VARX model. 相似文献
50.
详细介绍了在改进红外焊缝检测仪的过程中实时信号的一种抗干扰方法--自相关方法。重点离自相关方法的数学模型,软件框图及设计思想,并给出了实验结果。 相似文献