Papers by Keyword: Fourier Analysis

Abstract: Conventionally, the sin²ψ method has been used as X-ray stress measurement. However, in recent years, the XRD² method and the cos α method have been put into practical use and spreading. In addition, the Fourier analysis method that shares the same measurement principle of the cos α method has been developed and is attracting attention. Therefore, in this paper, the Fourier analysis method is examined from the measurement theory and the measurement accuracy is investigated. It is reviewed that the basic equation is a finite Fourier series, and that stress can be determined from the Fourier coefficients by using coordinate transformations. Then, while comparing it with the multiple regression analysis, the accuracy of the Fourier analysis method is discussed by using numerical calculations.

Abstract: This paper presents the study results of morphology contact and free surface at amorphous metal foils (Fe₇Co₇₁Ni₁₂(SiB)₁₀, Fe₇₀Ni₁₀(SiB)₁₀, Fe₆₀Co₃₀(SiB)₁₀) and their analysis of the elemental composition. Using spectral methods of research was allowed to make a comparative analysis size and anisotropy of distribution topological inhomogeneities. A parallel study of spinning foils by Mossbauer spectroscopy and Vibrating sample magnetometer (VSM) possible to determine the magnetic state of the samples.

Abstract: Nowadays, signal attracts more and more concerns from all walks of life as an information carrier in the information age. However, Fourier Transform which separately deals with time and frequency domains may not be fully competent as a signal processer in the digitization of communications system. Wavelet analysis is a strong signal processing method, which can not only fetch the features of the signal, but also achieve the signal denoising, compression, determine trends, and other functions .Image denoising and voice denoising were two empirical analyses in this study, which indicate certain research value of wavelet analysis for the development of signal processing.

Abstract: Commutation failure theory in HVDC transmission system is proposed and its reason is analyzed. Anomalous commutation failure phenomenon related to concurrent CF or successive CF in multi-infeed HVDC transmission system is presented. Six kinds of ac system strength are used in simulating the anomalous commutation failure, and the results show that this phenomenon is more and more serious at first as the system strength increases, and then become less serious as the strength becomes stronger. The reason of anomalous CF is found when analyzing phase A voltage with Fourier analysis in one period after fault, that is because of the major dc components and the low-order harmonics existing in voltage waves.

Abstract: The pioneering works in the area of mass transport in porous media go back to the end of last century. The partial differential equations governing the mass and heat transfer can be solved using numerical techniques, and in this paper we solve them analytically under different boundary conditions including time-periodic boundary conditions. The nature of these solutions is discussed. Analytic solutions provide valuable physical insight and are usually easier to compute. In addition, these solutions may help to experimentally determine the parameters in a setting where both the mass and temperature gradients are present, without resorting to a simplified set of equations that govern heat and mass transfer separately.

Abstract: In this paper, X-ray computed tomography was applied to obtain the aggregate images of asphalt concrete sample. Fourier analysis was utilized to describe the surface characteristics of the aggregates. With complex Fourier series function, the shape of the aggregates was quantified. The results indicate that Fourier morphological analysis can be used to mathematically represent the shape of particles in 2D micromechanical simulation of asphalt concrete.

Abstract: Power electronic converters produce not only characteristic harmonics, but also both non-characteristic harmonics and interharmonics. This paper presents the physical background of both non-characteristic harmonics and interharmonics. Generation causes are explored and discussed in detail. Extensive series of simulation of different power converter topologies are provided and compared with experimental results and existing standards. This research offers missing background for standards covering low-frequency EMC.

Abstract: Precise measurement of shape parameters of gear components is of ultimate importance for performance and service life of machinery. The conventional manual methods with aid of measurement tools rely largely on experiences of testing personnel. This study aims at developing an efficient and automatic methods for gear measurements, based on Fourier analysis with image processing software OPTIMAS. The shape parameters of gear are conveniently derived from the polar coordinates and the Fourier coefficients obtained from the image analysis software. The automatic methods are applied to two types of gear for illustration. The macro written for this purpose is presented and the measurement results are compared with conventional methods. It has been proven that Fourier analysis is a reliable and cost effective method for gear measurement. In addition, the results of Fourier analysis can be used to determine other parameters to characterize shape and size of the gear.

Abstract: The Fourier analysis is employed to study the effect of non-constant terms on the convergence properties of SIMPLE (Semi-Implicit Method for Pressure Linked Equations) algorithm formulated on a staggered grid in two-dimension. The results indicate the non-constant items can broaden the convergence range of pressure relaxation factor for a given velocity under-relaxation factor. What’s more, the non-constant items do well to the damping of the lowest error and can accelerate the convergence rate.

Abstract: This paper, based on the discrete wavelet thoughts, using the pressure fluctuations signal of the engine compressor, effectively remove high frequency interference, and keep useful information to signal. According to the different position of different states of the signal pressure pulsation multi-resolution analysis, reconstruction of the relevant frequency band pressure component signals, thus judgment that whether compressor enters a stall, the conventional only through the stall of engine after expressed by changes to the method of performance criterion.