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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.

No pulsed radio emission during a bursting phase of a Galactic magnetar 期刊论文 OAI收割
Nature, 2020, 卷号: 587, 页码: 63-65
作者: HXMT

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收藏 | 浏览/下载：44/0 | 提交时间：2022/02/08

Astrophysics - High Energy Astrophysical Phenomena Abstract: Fast radio bursts (FRBs) are millisecond-duration radio transients of unknown physical origin observed at extragalactic distances^1-3. It has long been speculated that magnetars are the engine powering repeating bursts from FRB sources^4-13, but no convincing evidence has been collected so far¹⁴. Recently, the Galactic magnetar SRG 1935+2154 entered an active phase by emitting intense soft íray bursts¹⁵. One FRB-like event with two peaks (FRB 200428) and a luminosity slightly lower than the faintest extragalactic FRBs was detected from the source, in association with a soft íray/hard-X-ray flare^18-21. Here we report an eight-hour targeted radio observational campaign comprising four sessions and assisted by multi-wavelength (optical and hard-X-ray) data. During the third session, 29 soft-íray repeater (SGR) bursts were detected in íray energies. Throughout the observing period, we detected no single dispersed pulsed emission coincident with the arrivals of SGR bursts, but unfortunately we were not observing when the FRB was detected. The non-detection places a fluence upper limit that is eight orders of magnitude lower than the fluence of FRB 200428. Our results suggest that FRB-SGR burst associations are rare. FRBs may be highly relativistic and geometrically beamed, or FRB-like events associated with SGR bursts may have narrow spectra and characteristic frequencies outside the observed band. It is also possible that the physical conditions required to achieve coherent radiation in SGR bursts are difficult to satisfy, and that only under extreme conditions could an FRB be associated with an SGR burst.

Optimized Design of Integrated Ultra-Light Main Supporting Structure for Micro-Nano Remote-Sensing Camera 期刊论文 OAI收割
Guangxue Xuebao/Acta Optica Sinica, 2019, 卷号: 39, 期号: 7
作者: T.Wang; L.Zhang; X.Jia; G.Gao

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收藏 | 浏览/下载：49/0 | 提交时间：2020/08/24

Structural design,Cameras,Electric power utilization,Functions,Natural frequencies,Optical systems,Remote sensing,Shape optimization,Titanium alloys,Topology

Structural design for the imaging unit of space optical remote camera 期刊论文 OAI收割
Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering, 2019, 卷号: 48, 期号: 11
作者: X.Liu; Z.Cheng; D.Wang

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收藏 | 浏览/下载：34/0 | 提交时间：2020/08/24

Cameras,Convergence of numerical methods,Finite element method,Natural frequencies,Optical testing

Optimum design of braced structure for optical fiber image transmission module based on inert strength 期刊论文 OAI收割
Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering, 2019, 卷号: 48, 期号: 5
作者: F.Yang; H.Tian; C.Yan; C.Wu; D.Mu

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收藏 | 浏览/下载：37/0 | 提交时间：2020/08/24

Light transmission,Ground supports,Imaging systems,Natural frequencies,Optical fibers,Optical glass,Optical instrument lenses,Shape optimization,Structural design,Structural optimization,Topology

Design of two-axis flexible support structure for fast steering mirror in space cameras 期刊论文 OAI收割
Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering, 2019, 卷号: 48, 期号: 12
作者: K.Wang; H.Xin; N.Cao; Z.Shi

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收藏 | 浏览/下载：28/0 | 提交时间：2020/08/24

Optical testing,Cameras,Differential equations,Earth (planet),Ground supports,Mirrors,Modal analysis,Motion compensation,Natural frequencies,Orbits,Position control,Stiffness

Optimization design of strengthening components for linear motion system of the novel optical testing target 期刊论文 OAI收割
Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering, 2018, 卷号: 47, 期号: 6
作者: Zhang, Shaojun; Gao, Yunguo; Xue, Xiangyao

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收藏 | 浏览/下载：28/0 | 提交时间：2019/09/17

Ability testing Continuum mechanics Modal analysis Natural frequencies Optical testing Reinforcement Structural analysis Structural design Vibration analysis

Stiffness improvement methods and its application on design and optimization of large lens hood for space camera 期刊论文 OAI收割
Journal of Vibroengineering, 2018, 卷号: 20, 期号: 7, 页码: 2668-2679
作者: Gong, Xiaoxue; Zhang, Lei; Wei, Lei; Jia, Xuezhi; Xuan, Ming

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收藏 | 浏览/下载：19/0 | 提交时间：2019/09/17

Design Cameras Lenses Natural frequencies Optical systems Plates (structural components) Stiffness

Optical axis stabilization of semi-strapdown seeker based on disturbance observer (EI CONFERENCE) 会议论文 OAI收割
2011 International Conference on Information and Automation, ICIA 2011, June 6, 2011 - June 8, 2011, Shenzhen, China
Sun G.; Zhu M.; Yin S.; Jia H.

收藏 | 浏览/下载：21/0 | 提交时间：2013/03/25

Based on the kinematics of semi-strapdown seeker the framework coordinate of the seeker is established. The optical axis stability equation of semi-strapdown seeker is deduced by using attitude transformation matrix. Then the stability control principle block diagram of semi-strapdown seeker is shown based on the stability equation. The main factors that influence the stabilization precision are pointed out such as friction disturbance velocity-measuring noise and missile disturbance. In order to improve the stabilization precision disturbance observer was proposed in semi-strapdown seeker stability control. The low frequency external disturbance and high frequency velocity measurement noise are effectively restrained by the disturbance observer as shown in hardware-in-loop simulation and optical axis stabilization precision is improved nearly 20 times and 5 times due to two different frequencies with same amplitude. 2011 IEEE.

A 350MHz Ti:sapphire laser comb based on monolithic scheme and absolute frequency measurement of 729nm laser 期刊论文 OAI收割
OPTICS EXPRESS, 2009, 卷号: 17, 期号: 8, 页码: 6059
Zhang, W; Han, HN; Zhao, YY; Du, Q; Wei, ZY

收藏 | 浏览/下载：28/0 | 提交时间：2013/09/17

TI-SAPPHIRE LASER MODE-LOCKED LASERS OPTICAL FREQUENCIES FEMTOSECOND TI PHASE-CONTROL GHZ GENERATION METROLOGY STANDARD 633-NM