Papers by Keyword: Wavelet Transform (WT)

Abstract: For soft threshold function are likely to cause a constant deviation with the original signal, hard threshold function can not fully remove noise and the selection of semi threshold function parameters is complex, we presented a critical threshold function, and analyzed the parameter selection for the new threshold. The simulation experiments prove that the denoising of critical threshold method is much better, and it also can make up for the deficiencies of traditional threshold.

Abstract: A new detecting method for apples’ early defects which was based on the image fusion of infrared and visible images was introduced in order to distinguish and separate the fruits with mechanical damage. Using apple as the research object, the basic detecting process was expounded, and the process of image registration was introduced emphatically. An improved algorithm of image fusion, which was based on wavelet transform, was proposed. Then the experimental result was provided as well as the objective evaluation for it.

Abstract: In this article, a new method for multi-focus image fusion via multiple wavelet bases is proposed.Firstly the wavelet transform is used to perform a multiscale decomposion on each image , then based on local gradient in the fusion to get primary fusion image .And then a set of the primary fusion images are obtained.Next these primary fusion images are fused to obtain final fusion iamge within spatial domain based on local variances weighted average rule.Experimental results show the new method is better than the traditional single wavelet base method in fusion effect.

Abstract: From the prospect of the printing forgery prevention technology, this paper systematically analyzed the principles of digital watermark in printing forgery prevention technology, based on this, it proposed wavelet transforming printing forgery prevention algorithm based on chaotic characteristics, in this paper, by using digital watermark image scrambling technology based on chaotic mapping to encrypt the wavelet transforming coefficient, then choose the different K value in chaotic mapping and the size of the scrambling image to combine the the cryptography technology and the wavelet transforming technology for resisting the various printing forgery attack effectively. In the end, the author made a detailed design about the wavelet transform printing forgery prevention system which based on chaotic characteristics and put it into fact by VC++, then validated the algorithm by experimental result, then compared it to the traditional watermark algorithm from the aspect of the image compression and anti attack ability to prove the stability and robustness of the algorithm this paper proposed.

Abstract: Taking the wavelet decomposed approximate image as the main research object, a direction estimation method for moving object was proposed in this paper. Firstly, the approximate image for the frame of the video was obtained via wavelet decomposition; and furthermore, the motion estimation on the approximate image was achieved to obtain the motion vectors. Finally, the motion vectors were described as polar coordinate form to compute the number of motion vectors in specified angles and the information entropy of the motion directions. The experiment results show that the proposed method can remove the effect of noise and the results of direction estimation are consistent with the actual motion directions.

Abstract: Biometrics technology is an important security technology and the research of it has become a new hot spot for its superior security features. Then hand vein recognition is a new biological feature recognition which has many advantages, such as safety, non-contact. According to the features of human hand vein image, a hand vein preprocessing method based on wavelet transform and windows maximum between-class difference method threshold (OTSU) segmentation algorithm is proposed. In this paper, the hand vein image is enhanced by adaptive histogram equalization in low frequency part of the hand vein image after wavelet decomposition and filtering before feature extraction. Then the windows OTSU threshold segmentation algorithm is used to get the features. The experimental results show that this method is simple and easy to realize and has laid a good foundation for the latter part of the vein recognition.

Abstract: The frequency and time of precipitation can influence the storage, allocation and management of water resources. But the precipitation frequency becomes more random and the precipitation process becomes more complexity due to the climate change and human activities, which increases the difficulty of technology and management. In this research, the fractal dimension based on Continuous Wavelet Transform (CWT) as the index of the precipitation complexity is applied to describe the precipitation process; using it, the complexity distributions of different precipitation processes in Liu-Kuang zone of Qingzhang basin China in different periods is illuminated respectively. The result indicates that in research region: (1) the annual precipitation frequency in the late period is less than that in the early period; (2) the urbanization and human activities increase the precipitation frequency. This result can reflect the frequency change of precipitation in changing environment and provide reference for the decision-making of water resources management in the local basin.

Abstract: A multichannel computer screen recording system based on Field Programmable Gate Array (FPGA) and Advanced RISC Machines (ARM) is introduced in this paper. This system has both Video Graphics Array (VGA) and Digital Video Interface (DVI) inputs, and supports the resolution of 1920x1080 and any common resolutions that do not exceed 1600x1200. The system can simultaneously record VGA and DVI signal by using the FPGA as the MUX of VGA and DVI. The experimental results showed that the algorithm used in this system, which combined the wavelet transform and listless zerotree entropy coding, achieved significantly higher quality of the decoded images than JPEG with the same compression ratio. The mapping of FPGA to SRAM method ensures the bit stream band width between FPGA and ARM. With the compression ratio of 50, the system can record 20 frames per second at the resolution of 1600x1200.

Abstract: The early fault detection of mechanical equipment is the technical support of automation equipment to run efficiently. Because of various faults have the characteristics of sudden, transient degeneration, so the traditional Fourier transform based on signal processing method can't meet the needs of the transient signal. This paper discusses time-frequency analysis technology of local wave from signal denoising, signal singularity detection and signal frequency band energy distribution analysis to extract the transient signal characteristics, and the motor bearing fault is put forward as an example, the effectiveness of the proposed method is verified.

Abstract: This paper is based on the wavelet transform theory and the Hilbert transform, it aims at researching on the pressure fluctuation characteristics in the bed, through analyzing and comparing the calculated envelope spectrum of pressure signal after transforms. On the basis of self-built cold fluidized bed, we choose to change the air flow and diameter of particle in fluidized bed as the two influencing factors. For researching the pressure fluctuation characteristics of fluidized bed, we collect pressure signal of the large particle fluidized bed which under normal operation conditions. The experimental results reveal that: as the increasing of the air flow, the energy of pressure increases; and with the increase of particle size in fluidized bed, the pressure fluctuation decreases in the bed.