Papers by Keyword: Power Spectrum

Abstract: A newly proposed pseudopotential has been put forwardwith a novel scheme of determining potential parameters. Based on the criteria that the (i) potential and its first derivative are continuous at the core radius,(ii) exponential decay of columbic tail outside the core and, (iii) non-singular character with finite derivative at r→0; a pseudopotential is designed. Of the total five parameters, only two parameters are independently tuned to cohesive properties at ambient (T = 0 K and zero-pressure) condition, while the remaining three parameters are computed consistently following above mentioned criteria. However in the present study, we have examined the atomic transport properties of liquid phase for the case of aluminum. Results for velocity autocorrelation function (VACF), cosine power spectrum and mean square displacement are evaluated and compared with available MD results. From the computed results for diffusion co-efficient at various temperatures, activation energy is also calculated. Good agreement for diffusion co-efficient and activation energy with experimental findings confirm the transferability of pseudopotential even in the liquid phase.

Abstract: It is the precondition of vibration fault diagnosis technology that appropriate signal analysis method is applied to separate mechanical fault character message from vibration monitoring signal. Based on the characteristics of multi-exciting, multi-model, non-stationary, nonlinear of the complex mechanical vibration signal, the EMD (Empirical Mode Decomposition) method is firstly applied to decompose the most refined IMF (Intrinsic Mode Function) components of vibration monitoring signal, and then the time series analysis method is applied to estimate power spectrums of IMF components and separate the fault character messages. The feasibility and advantage of the associated method are proved by analyzing the diesel engine crankshaft vibration monitoring signal in the paper.

Abstract: Low-voltage power lines are not designed to transmit communication data; it is not ideal channel characteristics using power line as a data communication medium, especially the noise generated by the several of household electrical appliances will have a significant impact on the power line communication system. First, low-voltage power line carrier communication and channel noise characteristics are analyzed, and based on pure electricity environment UPS, the experimental results obtained with different electric appliances for data processing, and analyze the impact of the electric appliances noise on the power line carrier communication.

Abstract: According to satellite communication, a novel parameter estimation method based on spectrum feature analysis is proposed. For the satellite communication signals shaped by raised cosine, the scheme enhance the efficiency of power spectrum and the square power spectrum of signals. The proposed method can estimate symbol rate and carrier frequency exactly in the satellite channel without any prior knowledge.

Abstract: Power spectrum analysis is one of the important part of digital signal processing, various characteristics of the main signal in the frequency domain, is designed based on the limited data and extract the useful signal is submerged in the noise in the frequency domain. In this paper, the VB language to realize the power spectrum analysis can extract the useful signal was drowned in noise in frequency domain based on power spectrum, frequency structure and physical meaning analysis reflected the more obvious, monitoring and diagnosis in rotating machinery fault, power spectrum analysis is very wide.

Abstract: Tool wear condition monitoring has been an effective method in improving the production efficiency and process automation. In this paper, to analysis the cutting force features in tool wear condition monitoring of difficult to cut materials, we first remove the direct current components and apply a fast Fourier transformation to the cutting force to observe the features in different frequency bands. A wavelet packet transformation is then adopted to the cutting force to observe the relationship of energy ratio and tool wear states.

Abstract: The static signal is collected through the experiment, and the probability density function model is established. The static random signal noise is analyzed by frequency spectrum, power spectrum and high order spectrum analysis. It is found that the third order spectrum of the laser static signal is zero by the high order spectrum analysis. Noise signal is only to analyze on the frequency spectrum and power spectrum. The results show that the static laser signal has the characteristics of stationary Gauss random signal.

Abstract: Continuous phase modulation (CPM) signal has the advantages of high bandwidth efficiency, continuous phase, faster decay speed of power spectrum, constant envelope and so on, which is widely used in communication systems. The degree of the phase smoothing is one of main factors that affect the decay speed of CPM signal power spectrum. One method of smoothing CPM signal phase based on different power sine function as the frequency modulation function is proposed. We draw the phase trajectory of baseband signal and the normalized power spectrum by using the MATLAB software. The spectrum characteristics of the signal generated have great improvement compared with MSK signal, which reach the desired goal.

Abstract: In this paper, 2 high-rise building models with ladder and cascade irregularities of elevation were tested in a wind tunnel respectively to measure the mean and fluctuating wind pressure distributions. The mean and RMS (root-mean-square) coefficients of the drag, lift and torsion moment on the measuring layer were obtained from the wind pressures. In the direction which the buildings were positive in the wind, the variation of these above mentioned coefficients with height and the power spectrum densities of the fluctuating wind loads on sudden changed positions were analyzed in detail. Compared with the elevation regular tall building, the wind load characteristics of irregular ones were more complicated.

Abstract: Magnetic Barkhausen noise (MBN) is a new technique on non-destructive testing of residual stress. The testing system based on virtual instrument was explored. It can achieve the MBN and deal with it in time. The technique is applied to analyze residual stress in the welding line of iron materials back and forth the heat treatment. Through comparing with the data of blind-hole method, the corresponding change between Barkhausen signals and residual stress is verified.