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An underlying clock in the extreme flip-flop state transitions of the black hole transient Swift J1658.2-4242 期刊论文 OAI收割
Astronomy and Astrophysics, 2020, 卷号: 641, 页码: A101
作者: HXMT

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accretion accretion disks black hole physics X-rays: binaries time Astrophysics - High Energy Astrophysical Phenomena Abstract:
Aims: Flip-flops are top-hat-like X-ray flux variations, which have been observed in some transient accreting black hole binary systems, and feature simultaneous changes in the spectral hardness and the power density spectrum (PDS). They occur at a crucial time in the evolution of these systems, when the accretion disc emission starts to dominate over coronal emission. Flip-flops remain a poorly understood phenomenon, so we aim to thoroughly investigate them in a system featuring several such transitions.
Methods: Within the multitude of observations of Swift J1658.2-4242 during its outburst in early 2018, we detected 15 flip-flops, enabling a detailed analysis of their individual properties and the differences between them. We present observations by XMM-Newton, NuSTAR, Astrosat, Swift, Insight-HXMT, INTEGRAL, and ATCA. We analysed their light curves, searched for periodicities, computed their PDSs, and fitted their X-ray spectra, to investigate the source behaviour during flip-flop transitions and how the interval featuring flip-flops differs from the rest of the outburst.
Results: The flip-flops of Swift J1658.2-4242 are of an extreme variety, exhibiting flux differences of up to 77% within 100 s, which is much larger than what has been seen previously. We observed radical changes in the PDS simultaneous with the sharp flux variations, featuring transitions between the quasi-periodic oscillation types C and A, which have never been observed before. Changes in the PDS are delayed, but more rapid than changes in the light curve. Flip-flops occur in two intervals within the outburst, separated by about two weeks in which these phenomena were not seen. Transitions between the two flip-flop states occurred at random integer multiples of a fundamental period of 2.761 ks in the first interval and 2.61 ks in the second. Spectral analysis reveals the high and low flux flip-flop states to be very similar, but distinct from intervals lacking flip-flops. A change of the inner temperature of the accretion disc is responsible for most of the flux difference in the flip-flops. We also highlight the importance of correcting for the influence of the dust scattering halo on the X-ray spectra.

Automated Parallel and Body-Fitted Mesh Generation in Finite Element Simulation of Macromolecular Systems 期刊论文 OAI收割
COMMUNICATIONS IN COMPUTATIONAL PHYSICS, 2016, 卷号: 19, 期号: 3, 页码: 582-602
作者: Xie, Yan; Liu, Tiantian; Tu, Bin; Lu, Benzhuo; Zhang, Linbo

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Parallel mesh generation body-fitted PHG biomolecules finite element simulation

The application of the maximum criteria optimizing technique in generation of body-fitted grids 期刊论文 OAI收割
CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION, 2014, 卷号: 57, 期号: 4, 页码: 1275-1283
作者: Jia Yan-Yan; Xing Xue-Jun; Shi Ji-An; Sun Guo-Qiang

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收藏 | 浏览/下载：14/0 | 提交时间：2018/09/26

Body-fitted grid Maximum length criteria Maximum area criteria Improved single particle optimizer Limited step length

The application of the maximum criteria optimizing technique in generation of body-fitted grids 期刊论文 OAI收割
CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION, 2014, 卷号: 57, 期号: 4, 页码: 1275-1283
作者: Jia Yan-Yan; Xing Xue-Jun; Shi Ji-An; Sun Guo-Qiang

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收藏 | 浏览/下载：17/0 | 提交时间：2018/09/26

Body-fitted grid Maximum length criteria Maximum area criteria Improved single particle optimizer Limited step length

Space optical remote sensor of the CAE thermal control index calculation method (EI CONFERENCE) 会议论文 OAI收割
2011 International Conference on Advanced Design and Manufacturing Engineering, ADME 2011, September 16, 2011 - September 18, 2011, Guangzhou, China
作者: Li L.

收藏 | 浏览/下载：28/0 | 提交时间：2013/03/25

The thermal control indicators CAE methods of Space optical remote sensor are analyzed in the presented work. We sat up a thermal optical analysis model for space optical remote sensor. By assuming fully covered by in-orbit temperature load and using the finite element method for thermal deformation analysis we obtained the optical remote sensor surface deformation and displacement under various thermal loading. Using ZERNIKE polynomial wave was fitted to obtain ZERNIKE polynomial coefficients which were incorporated into the optical system design. Using CODE V optical calculation software heat-ray machines under elastic deformation of the system point spread function transfer function (MTF) wave front differential (WFE) etc. were calculated. Image quality changes of remote sensors are discussed in variety assumed cases such as temperature loads of quality change. By repeated iteration critical value of temperature fields meeting the design requirements are obtained for the optical system. Optical indicators were converged to the temperature field indicator then reasonable indicators of thermal control for remote sensors were obtained. For the thermal control design this method provided a reliable basis for design. (2011) Trans Tech Publications Switzerland.

Adaptive Wiener filtering with Gaussian fitted point spread function in image restoration (EI CONFERENCE) 会议论文 OAI收割
2011 IEEE 2nd International Conference on Software Engineering and Service Science, ICSESS 2011, July 15, 2011 - July 17, 2011, Beijing, China
作者: Yang L.; Zhang X.; Zhang X.; Zhang X.; Yang L.

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In the imaging process of the space remote sensing camera there was degradation phenomenon in the acquired images. In order to reduce the image blur caused by the degradation the remote sensing images were restored to give prominence to the characteristic objects in the images. First the frequency-domain notch filter was adopted to remove strip noises in the images. Then using the ground characters with the knife-edge shape in the images the point spread function of the imaging system was estimated. In order to improve the accuracy the estimated point spread function was corrected with Gaussian fitting method. Finally the images were restored using the adaptive Wiener filtering with the fitted point spread function. Experimental results of the real remote sensing images showed that almost all strip noises in the images were eliminated. After the denoised images were restored its variance and its gray mean gradient increased also its laplacian gradient increased. Restoration with Gaussian fitted point spread function is beneficial to interpreting and analyzing the remote sensing images. After restoration the blur phenomenon of the images is reduced. The characters are highlighted and the visual effect of the images is clearer. 2011 IEEE.

Timing generator of scientific grade CCD camera and its implementation based on FPGA technology (EI CONFERENCE) 会议论文 OAI收割
5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optoelectronic Materials and Devices for Detector, Imager, Display, and Energy Conversion Technology, April 26, 2010 - April 29, 2010, Dalian, China
作者: Li Y.; Li Y.; Li Y.; Li Y.

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The Timing Generator's functions of Scientific Grade CCD Camera is briefly presented: it generates various kinds of impulse sequence for the TDI-CCD video processor and imaging data output acting as the synchronous coordinator for time in the CCD imaging unit. The IL-E2TDI-CCD sensor produced by DALSA Co.Ltd. use in the Scientific Grade CCD Camera. Driving schedules of IL-E2 TDI-CCD sensor has been examined in detail the timing generator has been designed for Scientific Grade CCD Camera. FPGA is chosen as the hardware design platform schedule generator is described with VHDL. The designed generator has been successfully fulfilled function simulation with EDA software and fitted into XC2VP20-FF1152 (a kind of FPGA products made by XILINX). The experiments indicate that the new method improves the integrated level of the system. The Scientific Grade CCD camera system's high reliability stability and low power supply are achieved. At the same time the period of design and experiment is sharply shorted. 2010 Copyright SPIE - The International Society for Optical Engineering.

Remote sensing image restoration using estimated point spread function (EI CONFERENCE) 会议论文 OAI收割
2010 International Conference on Information, Networking and Automation, ICINA 2010, October 17, 2010 - October 19, 2010, Kunming, China
作者: Yang L.; Yang L.

收藏 | 浏览/下载：34/0 | 提交时间：2013/03/25

In order to reduce image blur caused by the degradation phenomenon in the imaging process the acquired images of the space remote sensing camera are restored. First the frequency-domain notch filter is adopted to remove strip noises in the images. Then degradation function which is referred to as the point spread function (PSF) of the imaging system is estimated using the knife-edge method. To improve the accuracy of the estimation the estimated PSF is adjusted with Gaussian fitting. Finally the images are restored by Wiener filtering with the fitted PSF. The restoration results of the remote sensing images show that almost all strip noises are eliminated by the notch filter. After denoising and restoration the variance of the remote sensing image worked with in this paper increases 30.979 and the gray mean gradient increases 3.312. Due to Gaussian fitting the accuracy of the PSF estimation is heightened. Image restoration with the final PSF is benefit to interpreting and analyzing the remote sensing images. After restoration the contrasts of the restored images are increased and the visual effects become clearer. 2010 IEEE.

The adaptive immersed interface finite element method for elliptic and Maxwell interface problems 期刊论文 OAI收割
JOURNAL OF COMPUTATIONAL PHYSICS, 2009, 卷号: 228, 期号: 14, 页码: 5000-5019
作者: Chen, Zhiming; Xiao, Yuanming; Zhang, Linbo

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收藏 | 浏览/下载：15/0 | 提交时间：2018/07/30

Adaptive finite element method Interface problems Non-body-fitted meshes Elliptic equation Maxwell's equations

Ion beam sputter deposition of zirconia thin films (EI CONFERENCE) 会议论文 OAI收割
International Symposium on Photoelectronic Detection and Imaging, ISPDI 2007: Optoelectronic System Design, Manufacturing, and Testings, September 9, 2007 - September 12, 2007, Beijing, China
作者: Liu L.; Yang H.; Liu L.

收藏 | 浏览/下载：22/0 | 提交时间：2013/03/25

We determined the optical constants (the refractive index n and the extinction coefficient k) of ion beam sputter deposited zirconia thin films with spectroscopic ellipsometry (SE). First we obtained the structure information (the layer thickness surface roughness and layer diffusion) by fitting the grazing x-ray reflection (GXRR) spectra. The fitted surface roughness is verified by atomic force micrometer (AFM) measurement. Second based on the acquired structure information the measured ellipsometry spectra are fitted in the range of 240-800nm at an incident angle of 70.25 degree. The optical constants are solved based on the Tauc-Lorentz dispersion. The optical band gap extracted by SE is 4.79eV. Finally the optical band gap is verified by Taue plot method which is well consistent with that of SE.