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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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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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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.

Development of a series of dummy loads in S-band 期刊论文 OAI收割
HIGH POWER LASER AND PARTICLE BEAMS, 2015, 卷号: 27, 期号: 6, 页码: 65105
作者: He X(贺祥); Zhao FL(赵风利); Wang XJ(王湘鉴); Zhang JR(张敬如); Shu G(束冠)

收藏 | 浏览/下载：26/0 | 提交时间：2016/04/18

Frequency band width High power High power performance Long-time operation Low-voltage standing wave ratios Pulse repetition frequencies Simulation and optimization Voltage standing-wave ratio

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.

Debris flows in Mozi gully, China following the 2008 Wenchuan earthquake 会议论文 OAI收割
Padua, 2011
作者: Su, Pengcheng; Wei, Fangqian; Cheng, Zunlan; Liu, Jingjing

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收藏 | 浏览/下载：30/0 | 提交时间：2018/11/08

Comprehensive fuzzy evaluation methods Glacial debris flows Glacial lake outburst flood High and steep slope In-situ investigations International Karakorum Highway (KKH) Occurrence frequencies Risk evaluation

Model identification and closed-loop confirmation for opto-electronic platform of seeker (EI CONFERENCE) 会议论文 OAI收割
2010 2nd International Conference on Industrial Mechatronics and Automation, ICIMA 2010, May 30, 2010 - May 31, 2010, Wuhan, China
作者: Liu H.; Zhang J.; Zhang J.; Zhang J.; Chen J.

收藏 | 浏览/下载：32/0 | 提交时间：2013/03/25

A mathematical model of seeker opto-electronic platform is the basis for researching performance designing a servo control system and simulating. Focusing on high frequencies of mechanical resonant restriction of gimbaled axis rotation a new model identification method was proposed under the pseudo-random invert-M-sequences. The testing signal data acquisition the calculating of frequency response and least square identification were investigated. The realized steps are explicitly illustrated and the testing example is given in this paper the results confirm that the proposed method is effective and practical. 2010 IEEE.

Three-dimensional angle measurement based on auto-collimation and moire fringe (EI CONFERENCE) 会议论文 OAI收割
2008 International Conference on Optical Instruments and Technology: Optoelectronic Measurement Technology and Applications, November 16, 2008 - November 19, 2008, Beijing, China
Cai S.; Liang S.; Qiao Y.-F.

收藏 | 浏览/下载：28/0 | 提交时间：2013/03/25

A method for small three-dimensional (3D) angle measurement based on auto-collimation and moire fringe is proposed and analyzed. A right-angle prism is used as the indicator of angle change. The inclined plane indicates the pitch and yaw angles and roll angle in indicated by the rib which is the intersection of two right-angle sides. Pitch and yaw angles measurement are implemented by auto-collimation based on reticule and roll angle measurement is measured based on moire fringe. Roll angle measurement is separated from pitch and yaw by using two light sources with different frequencies. Any small change of pitch and roll angles will induce the shift of the reticule image after reflecting by inclined plane. And any small roll angle will induce a change in moire fringe width that is generated by scale grating image which is reflected by the prism and index grating. The math model of this method is built up and error analysis is presented. The theoretical calculation results show that the proposed method is feasible and can achieve high accuracy. 2009 SPIE.

First-Principle Calculations for Elastic and Thermodynamic Properties of Diamond 期刊论文 OAI收割
Communications in Theoretical Physics, 2009, 卷号: 51, 期号: 6, 页码: 1129-1134
Z. J. Fu; G. F. Ji; X. R. Chen; Q. Q. Gou

收藏 | 浏览/下载：21/0 | 提交时间：2012/04/13

density functional theory elastic constants thermodynamic properties diamond ab-initio calculations vibrational frequencies high-pressure bulk modulus temperature constants exchange accurate energy phase

The pressure-induced phase transition of the solid -HMX 期刊论文 OAI收割
Molecular Physics, 2009, 卷号: 107, 期号: 22, 页码: 2373-2385
L. Y. Lu; D. Q. Wei; X. R. Chen; G. F. Ji; X. J. Wang; J. Chang; Q. M. Zhang; Z. Z. Gong

收藏 | 浏览/下载：18/0 | 提交时间：2012/04/13

-HMX crystal octahydro-1 molecular dynamics 3 high pressure compression 5 phase 7-tetranitr transition vibrational frequencies beta-cyclotetramethylene tetranitramine molecular-dynamics simulations compass force-field vibrational-spectra crystal structure

Correction method for detection of the frequencies of railway fsk signals (EI CONFERENCE) 会议论文 OAI收割
2008 9th International Conference on Signal Processing, ICSP 2008, October 26, 2008 - October 29, 2008, Beijing, China
作者: Yu J.

收藏 | 浏览/下载：63/0 | 提交时间：2013/03/25

In order to acquire the information of railway binary frequency-shift keying signals which include upper/down side frequencies and base low-frequency with high-accuracy a novel frequency detection algorithm for France UM-71 system is proposed. Combining fast Fourier transform with the ratio correction method the carrier frequency and the base frequency are obtained. Furthermore the hardware consumption has been decreased. And it possesses the advantage of simple algorithm and fast operation speed. Comparing with the detection of the base frequency the upper/down side frequency of railway signal is more difficult. Based on spectrum analysis and the spectrum correction a new method which adopts the sliding window is put forward in this paper. The absolute differences between the upper side frequencies and the down side frequencies obtained are regarded as the criterion for judgment. Then the set of data in which the maximum absolute value is is to be the result of the upper/down side frequency. Because the sliding window will go through every stage when the upper/down side frequency changes therefore it is not sensitive enough to the position of data which need to be transformed. Using the method mentioned above the experiment results show that the accuracy requirement of the side frequency is satisfied well. 2008 IEEE.