Xiang-jun Chen

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In order to obtain the useful information from the raw data which contain the state data reflecting the structure condition and the noise, de-noising and feature extraction techniques based on Wavelet analysis were studied. An improved wavelet thresholding algorithm to eliminate the noise for vibration signals was proposed. Comparison analysis with other(More)
A direct perturbation theory for solitons of the derivative nonlinear Schrödinger (DNLS) equation is developed based on a closure of eigenfunctions of the linearized DNLS equation around a one-soliton solution. The slow evolution of soliton parameters and the perturbation-induced radiation are obtained. Under the known simple gaugelike transformation, these(More)
We present a simple and effective method for denoising phase patterns based on a discrete model. The proposed filtering method transforms the image denoising problem to solving the energy diffusion problem of a system with complex-valued fields. We establish an appropriate cost function that uses the discrete form of complex-valued Markov random fields. The(More)
Data processing is important to the structure health monitoring system which produces large volumes of raw data containing the useful information and the noise. Wavelet analysis is a newly emerging theory in data processing field, which has good localization characteristics in both frequency and time domains compared to most traditional methods used for(More)
The application of the neural network in the structure damage identification is studied using a combination of theoretical and experimental methods. A multi-layer neural network models based on the BP algorithm is designed for the damage identification of existing model structure. The model is trained with the data from an engineering beam to filter(More)
The derivative nonlinear Schr6dinger (DNLS) equation arises as a physical model for ultra-short pulse propagation. In this article, linearization operators of solitons in the DNLS hierarchy are studied. It is shown that these operators commute with the recursion operator of the hierarchy. In addition, they can be factored into the recursion operator and the(More)
OBJECTIVE To select Chinese characters for Chinese visual acuity chart by using the method of Fourier frequency spectrum analysis. METHODS BMP images were made for 1062 Chinese characters with small or medium number of strokes. The images were processed to derive frequency spectrum at the frequency domain by using a MatLab program. Euclidean distance from(More)
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