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	Detection of Flare Multiperiodic Pulsations in Mid-ultraviolet Balmer Continuum, Lyl Hard X-Ray, and Radio Emissions Simultaneously 期刊论文 OAI收割 The Astrophysical Journal, 2021, 卷号: 921, 页码: 179 作者: HXMT \| 收藏 \| 浏览/下载：27/0 \| 提交时间：2022/02/08 Solar flares Solar oscillations Solar ultraviolet emission Solar x-ray emission Solar radio emission 1496 1515 1533 1536 1522 Astrophysics - Solar and Stellar Astrophysics Abstract: Quasi-periodic pulsations (QPPs), which usually appear as temporal pulsations of the total flux, are frequently detected in the light curves of solar/stellar flares. In this study, we present the investigation of nonstationary QPPs with multiple periods during the impulsive phase of a powerful flare on 2017 September 6, which were simultaneously measured by the Hard X-ray Modulation Telescope (Insight-HXMT), as well as the ground-based BLENSW. The multiple periods, detected by applying a wavelet transform and Lomb-Scargle periodogram to the detrended light curves, are found to be ~20-55 s in the Ly`and mid-ultraviolet Balmer continuum emissions during the flare impulsive phase. Similar QPPs with multiple periods are also found in the hard X-ray emission and low-frequency radio emission. Our observations suggest that the flare QPPs could be related to nonthermal electrons accelerated by the repeated energy release process, i.e., triggering of repetitive magnetic reconnection, while the multiple periods might be modulated by the sausage oscillation of hot plasma loops. For the multiperiodic pulsations, other generation mechanisms could not be completely ruled out.
	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 \| 收藏 \| 浏览/下载：61/0 \| 提交时间：2022/02/08 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.
	SSA based decomposition of tool position trajectory for diamond turning of freeform optical surfaces (EI CONFERENCE) 会议论文 OAI收割 2009 International Conference on Manufacturing Science and Engineering, ICMSE 2009, December 26, 2009 - December 28, 2009, Zhuhai, China 作者: Liu Q.; Lin C. 收藏 \| 浏览/下载：21/0 \| 提交时间：2013/03/25 The radial spiral feed of the tool and the tool nose radius compensation are taken into consideration for the tool position trajectory (TPT) generation in diamond turning of freeform optical surfaces. Using the coarse sampling and the fine interpolation a novel approach based on singular spectrum analysis (SSA) is presented to decompose the generated TPT into a slowly varying trend and a quickly varying quasi-periodic oscillation. The numerical experiments of the TPT decomposition of toroidal surfaces have been carried out. The results verify that the proposed approach is very effective for the TPT decomposition. (2010) Trans Tech Publications.
	Numerical modeling of non-linear characteristics for barotropic atmosphere with external forcing 期刊论文 iSwitch采集 Acta physica sinica, 2005, 卷号: 54, 期号: 10, 页码: 4961-4970 作者: Wang, P; Dai, XG 收藏 \| 浏览/下载：31/0 \| 提交时间：2019/05/10 Barotropic atmosphere Thermal forcing Topography Oscillated solution Quasi-periodic oscillation