Papers by Keyword: Windowed Fourier Transform

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Authors: Qian Kemao, Seah Hock Soon
Abstract: Phase unwrapping is an important and challenging process in optical interferometry. Difficulties in phase unwrapping are usually caused by either noise (“bad” pixels) or invalid areas (“bad” regions). If the “bad” pixels can be removed, the problems due to the noise are solved. Further, if the “bad” regions can be identified, they can be avoided in phase unwrapping. In our previous work the noise can be successfully removed using a windowed Fourier transform [Optics and Lasers Technology, 37:458-462 (2005)]. In this paper we will show that the invalid areas can be identified by the same windowed Fourier transform. Thus a single windowed Fourier transform is able to process both “bad” pixels and “bad” regions simultaneously, which makes the phase unwrapping simple and effective.
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Authors: Fei Yu Wang, Zi Wei Zheng, Wei Hua Li
Abstract: In the current study, using methods of signal processing to manage gene prediction has attracted great attention. At first, the voss mapping which can map the DNA alphabetic sequence into the numerical sequence and the 3-base periodicity of exon are introduced. Then a fixed-length sliding window approach and its feasibility are analyzed. It can be proved that when two exons are very close, gene prediction by only setting a threshold to the spectrum could not have good effect. To overcome this shortcoming, a new method based on one-dimensional image segmentation is proposed. Finally, simulation shows the short introns are culled commendably. Two evaluation indices are also introduced to demonstrate the effectiveness of this method.
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Authors: Yan Bin He, Xin Zhong Li, Wei Min Chen, Jun Song Wen
Abstract: Phase unwrapping is one of the key technologies in electronic speckle pattern interferometry. A new phase unwrapping algorithm, based on windowed Fourier transform is proposed. The high noisy phase map is denoised by the window Fourier transform approach and then is uwrapped by the discrete cosine transform. The method is tested in this paper using a circumferentially fixed circular plate with a point load at the centre and compared with not denoised wrapped phase map and unwrapped phase map. The result shows the new proposed phase unwrapping method in denoising and improving image quality has obvious superiority.
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