检索结果-南通市图书馆

Efficient Dual Algorithms for Image Segmentation Using TV-Allen-Cahn Type Models

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Computational Physics 2011年第4期9卷 859-877页

作者： Li-Lian Wang Ying Gu Division of Mathematical Sciences School of Physical and Mathematical SciencesNanyang Technological University637371Singapore

Variational image segmentation based on the Mumford and Shah model[31],together with implementation by the piecewise constant level-set method(PCLSM)[26],leads to fully nonlinear Total Variation(TV)-Allen-Cahn *** commonlyused numerical approaches usually suffer from the difficulties not only with the nondifferentiability of the TV-term,but also with directly evolving the discontinuous piecewise constant-structured *** this paper,we propose efficient dual algorithms to overcome these *** use of a splitting-penalty method results in TVAllen-Cahn type models associated with different"double-well"potentials,which allow for the implementation of the dual algorithm of Chambolle[8].Moreover,we present a new dual algorithm based on an edge-featured penalty of the dual variable,which only requires to solve a vectorial Allen-Cahn type equation with linear∇(div)-diffusion rather than fully nonlinear diffusion in the Chambolle’s ***,more efficient numerical algorithms such as time-splitting method and Fast Fourier Transform(fft.can be *** numerical tests show that two dual algorithms are much faster and more stable than the primal gradient descent approach,and the new dual algorithm is at least as efficient as the Chambolle’s algorithm but is more *** demonstrate that the new method also provides a viable alternative for image restoration.

关键词： Variational models image segmentation TV-Allen-Cahn type equations dual algorithms splitting-penalty methods fft.

AM ultrasound-modulated optical tomography with real-time fft

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2001年第22期46卷 1869-1872页

作者： Yong Yao Da Xing Yonghong He S China Normal Univ Inst Laser Life Sci Guangzhou 510631 Peoples R China

We report on a novel ultrasound-modulated optical tomographic technique applied in dense tissue-simulating turbid media. A 1 MHz ultrasound beam is focused into the media to modulate and tag the scattering laser light passing through the ultrasonic focused zone. A 10 kHz sinusoidal wave, as a detection wave, is carried by the ultrasound beam through amplitude-modulation (AM). The scattering photons that come from the focused zone carry the modulated information, received by detector and demodulated by real-time fast Fourier transform (fft.. The optical tomographic images of the tissue simulating media and buried object are reconstructed with AM spectral intensity. This method can be applied to imaging three-dimensional tissue structures with different optical parameters. For the first time, we obtained the tomography of buried objects in biological tissue phantoms with a detecting depth of 30 mm.

关键词： optical tomography ultrasonic modulation amplitude modulation optical imaging fft.

维普期刊数据库

Accurate determination of the spherical aberration coefficient of a field-emission gun electron microscope using digital electron micrographs

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 1997年第4期 50-59页

作者：任罡段晓峰彭练矛 Beijing 100080 Beijing Laboratory of Electron Microscopy China Chinese Academy of Sciences

It is shown that for a weak phase object the image formation process in a field-emission gun (FEG) electron microscope is the same as in a conventional transmission electron microscope, and that the spherical aberration coefficient of an FEG electron microscope may be measured by using an amorphous thin film. Methods were developed for accurate determination of the spherical aberration coefficient of an FEG electron microscope using digital electron micrographs.

关键词： spherical aberration coefficient FEG electron microscope digital electron micrograph fft.

Sampling theorem and digital electron microscopy

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 1997年第1期 112-116页

作者：彭练矛 Beijing 100080 Beijing Laboratory of Electron Microscopy China Chinese Academy of Sciences

The sampling problem is important in digital electron microscopy which deals with discrete digital micrographs. In recording a digital electron micrograph using a digital CCD camera, the camera size is usually limited to less than 1024 ×1024. This limitation results mainly *** consideration of the cost of the CCD camera and the exposure time needed to record the digital mi-

关键词： digital electron microscopy sampling theorem imaging processing fft.

DETECTION OF SINUSOIDAL SIGNALS IN FREQUENCY DOMAIN

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

DETECTION OF SINUSOIDAL SIGNALS IN FREQUENCY DOMAIN

Design and Implementation of GNSS-R Software Receiver Based on fft

2006 CIE International Conference on Radar

作者： Fathy M.Ahmed Khairy A.Elbarbary Abdel Rahman H.Elbardawiny Military Technical College CairoEgypt

Periodogram is a simple and efficient way to detect and estimate parameters of sinusoidal *** this paper,we evaluate the detection performance of the periodogram and its variants such as Bartlett,Welch methods,and a proposed Bartlett-based *** evaluation through the Receiver Operating Characteristics （ROCs） of the mentioned methods are presented and *** studies showed that,the standard periodogram used to give the best detection *** the present work,analytical derivation and simulation results showed that,the proposed method gives a better detection performance outperforming the standard periodogram at the expense of tolerable reduction of the frequency resolution.

关键词： Detection Periodogram Bartlett fft.

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Design and Implementation of GNSS-R Software Receiver Based ...

第三届中国卫星导航学术年会

作者： LI MingLi,YANG DongKai,LI WeiQiang,Huang Yi,Zhang YiqiangSchool of Electronic and Information Engineering,Beihang University,Beijing,100191,China

The advantages of software receiver are its flexibility,better performance on system update and algorithm *** paper mainly focused on study a software receiver which could be used in GNSS-R research,not only gives the structure of the signal collection system,but also describes the design of the software receiver *** open-loop tracking method and fft.based correlation power processing method of the reflected signals are introduced in the *** data analysis result of the signal processing experiments shows that the design of the GNSS-R software receiver can provide reliable and effective correlation data of the reflected signals,and can be used as an effective tool for the further study of GNSS-R.

关键词： GNSS (Global Navigation Satellite System) reflected signal software receiver fft.

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

基于频域批处理的直扩系统窄带干扰抑制技术

哈尔滨师范大学自然科学学报 2006年第3期22卷 59-62页

作者：秦显荣大庆石油学院

针对直接序列扩频系统中窄带干扰问题,采用频域批处理LMS算法进行干扰抑制.文中推导了算法的数学过程,并进行了计算机仿真,仿真结果表明,采用该算法可以较大幅度提高系统的抗干扰性能.

关键词：直序扩频系统窄带干扰抑制 fft.

维普期刊数据库