中国科学院机构知识库网格系统: 检索

Interannual moisture variability on the Qinghai Plateau: Trends, patterns, and implications 期刊论文 OAI收割
JOURNAL OF HYDROLOGY, 2024, 卷号: 645, 页码: 132074
作者: Yang, Yanxi; Wang, Junbang; Zhang, Xiujuan; Ye, Hui; Yuan, Bin

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收藏 | 浏览/下载：8/0 | 提交时间：2024/12/20

Climate change Moisture Index (IM) Quasi-periodic EEMD Qinghai Plateau (QP)

Fluctuation characteristics and topological interface states in the quasi-periodic structures of shallow-water waves 期刊论文 OAI收割
JOURNAL OF HYDRODYNAMICS, 2024, 页码: 9
作者: Guan X(关雪); Xiao BY(肖伯雅); Liu Y(刘宇); Chen M(陈猛)

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收藏 | 浏览/下载：4/0 | 提交时间：2024/12/23

Water wave metamaterial quasi-periodic structure Fibonacci sequence topological interface states

Clusters of Solar Radio Spikes Modulated by Quasi-Periodic Pulsations in a Confined Flare 期刊论文 OAI收割
UNIVERSE, 2022, 卷号: 8, 期号: 7, 页码: 14
作者: Huang, Jing; Tan, Chengming; Chen, Xingyao; Tan, Baolin; Yan, Yihua

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收藏 | 浏览/下载：36/0 | 提交时间：2022/09/19

solar flare solar radio burst spike quasi-periodic pulsation particle acceleration

Nonlinear dynamic responses of high-speed railway vehicles under combined self-excitation and forced excitation considering the influence of unsteady aerodynamic loads 期刊论文 OAI收割
NONLINEAR DYNAMICS, 2021, 页码: 36
作者: Ceng XH(曾晓辉); Shi HM(史禾慕); Wu H(吴晗); Shi HM(史禾慕); Zeng XH(曾晓辉)

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收藏 | 浏览/下载：40/0 | 提交时间：2021/09/08

High-speed railway vehicle Unsteady aerodynamic loads Self-excited vibration Forced vibration Quasi-periodic motion

Synchronous X-ray/Optical QPOs from the Black Hole LMXB MAXI J1820+070 期刊论文 OAI收割
Monthly Notices of the Royal Astronomical Society, 2021
作者: HXMT

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收藏 | 浏览/下载：52/0 | 提交时间：2022/02/08

black hole physics Low Mass X-ray Binaries accretion accretion discs stars: individual (MAXI J1820+070) Astrophysics - High Energy Astrophysical Phenomena Abstract: We present high-speed optical photometry from SAAO and SALT on the black hole LMXB MAXI J1820+070 (ASSASN-18ey), some of it simultaneous with NICER, Swift and Insight-HXMT X-ray coverage. We detect optical Quasi-Periodic Oscillations (QPOs) that move to higher frequencies as the outburst progresses, tracking both the frequency and evolution of similar X-ray QPOs previously reported. Correlated X-ray/optical data reveal a complex pattern of lags, including an anti-correlation and a sub-second lag that evolve over the first few weeks of outburst. They also show correlated components separated by a lag equal to the QPO period roughly centered on zero lag, implying that the inter-band variability is strongly and consistently affected by these QPOs at a constant phase lag of roughly ±Ю The synchronisation of X-ray and optical QPOs indicates that they must be produced in regions physically very close to each other we thus propose that they can be explained by a precessing jet model, based on analogies with V404 Cyg and MAXI J1348-630.

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

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收藏 | 浏览/下载：25/0 | 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.

A criterion on a repeller being a null set of any limit measure for stochastic differential equations 期刊论文 OAI收割
SCIENCE CHINA-MATHEMATICS, 2020, 页码: 18
作者: Chen, Lifeng; Dong, Zhao; Jiang, Jifa

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收藏 | 浏览/下载：22/0 | 提交时间：2020/05/24

stationary measure limit measure support Lyapunov function repelling limit cycle repelling quasi-periodic orbits

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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收藏 | 浏览/下载：58/0 | 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.

Quasi-Periodic Solutions for Differential Equations with an Elliptic-Type Degenerate Equilibrium Point Under Small Perturbations 期刊论文 OAI收割
JOURNAL OF DYNAMICS AND DIFFERENTIAL EQUATIONS, 2019, 卷号: 31, 期号: 2, 页码: 653-681
作者: Li, Xuemei; Shang, Zaijiu

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收藏 | 浏览/下载：77/0 | 提交时间：2020/01/10

Delay differential equation Degenerate equilibrium point Quasi-periodic solution Perturbation

A Second-Order Two-Scale Algorithm for Thermo-Mechanical Coupling Problems in Quasi-Periodic Porous Materials 期刊论文 OAI收割
COMMUNICATIONS IN COMPUTATIONAL PHYSICS, 2019, 卷号: 25, 期号: 4, 页码: 1144-1176
作者: Yang, Zhiqiang; Sun, Yi; Cui, Junzhi; Guan, Tianyu; Yuan, Zifeng

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收藏 | 浏览/下载：65/0 | 提交时间：2019/03/05

SOTS model radiation effect thermo-mechanical performance quasi-periodic structures