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	The braking index of PSR B0540-69 and the associated pulsar wind nebula emission after spin-down rate transition 期刊论文 OAI收割 Monthly Notices of the Royal Astronomical Society, 2020, 卷号: 494, 页码: 1865-1870 作者: HXMT \| 收藏 \| 浏览/下载：57/0 \| 提交时间：2022/02/08 stars: magnetic field stars: neutron pulsars: general Astrophysics - High Energy Astrophysical Phenomena Abstract: In 2011 December, PSR B054-69 experienced a spin-down rate transition (SRT), after which the spin-down power of the pulsar increased by $\sim 36{{\ \rm per\ cent}}$. About 1000 d after the SRT, the X-ray luminosity of the associated pulsar wind nebula (PWN) was found to brighten by $32\pm 8{{\ \rm per\ cent}}$. After the SRT, the braking index n of PSR B0540-69 changes from n = 2.12 to 0.03 and then keeps this value for about five years before rising to n = 0.9 in the following years. We find that most of the current models have difficulties in explaining the measured braking index. One exceptive model of the braking index evolution is the increasing dipole magnetic field of PSR B0540-69. We suggest that the field increase may result from some instabilities within the pulsar core that enhance the poloidal component at the price of toroidal component of the magnetic field. The increasing dipole magnetic field will result in the X-ray brightening of the PWN. We fit the PWN X-ray light curve by two models: one assumes a constant magnetic field within the PWN during the brightening and the other assumes an enhanced magnetic field proportional to the energy density of the PWN. It appears that the two models fit the data well, though the later model seems to fit the data a bit better. This provides marginal observational evidence that magnetic field in the PWN is generated by the termination shock. Future high-quality and high-cadence data are required to draw a solid conclusion.
	The application of Kalman filtering technique on the multi-position strap-down north seeking system (EI CONFERENCE) 会议论文 OAI收割 2012 5th International Symposium on Computational Intelligence and Design, ISCID 2012, October 28, 2012 - October 29, 2012, Hangzhou, China 作者: Liu S.-J. 收藏 \| 浏览/下载：22/0 \| 提交时间：2013/03/25 In order to fit the sin wave curve of a multiposition strap-down north seeking system and to calculate the real north angle accurately the data collected from the Dynamically tuned gyro(DTG) must be filtered firstly to reduce the noise jamming. The principles of the system are introduced. The factors influencing the measuring precision are also analyzed. Then The DTG data are processed by second-order Butterworth filtering and Kalman filtering together. Experimental results indicate that the built-up filtering method can reduce noise jamming more effectively than second-order Butterworth filtering in the low frequency. 2012 IEEE.
	The application of template matching arithmetic on Strap-down North Seeking System (EI CONFERENCE) 会议论文 OAI收割 2011 International Conference on Mechatronic Science, Electric Engineering and Computer, MEC 2011, August 19, 2011 - August 22, 2011, Jilin, China Li D.-N.; Zhu W.; Chen T. 收藏 \| 浏览/下载：19/0 \| 提交时间：2013/03/25 In order to solve the problem of self-determination directional of theodolite equipment based on dynamically tuned gyroscope is proposed. The principle of the Multi-position Strap-down North Seeking System is introduced. Mathematical model of the system is discussed. The factors that influence the precision are analyzed. In order to fit the curve of sampling data back-propagation neural network arithmetic is used in data processing. As templates curve model is saved at database of the VC software. The template matching arithmetic advanced the measure precision of this system. The measure time of the system is shortened within 1 minute so it can save time for theodolite. 2011 IEEE.
	Data processing method of multi-position strap-down north seeking system based on SVD (EI CONFERENCE) 会议论文 OAI收割 2011 International Conference on Mechatronic Science, Electric Engineering and Computer, MEC 2011, August 19, 2011 - August 22, 2011, Jilin, China Shen C.-W.; Liu C.; Yu S.-B.; Wang Z.-Q.; Li J.-R. 收藏 \| 浏览/下载：36/0 \| 提交时间：2013/03/25 With the aim to fit the sin wave curve of a multi-position strap-down north seeking system and to calculate the real north angle accurately the principles of the system and the algorithm of singular value decomposition(SVD) are introduced. The factors influencing the measuring precision are also analyzed. Then the algorithm is adopted to fit curves. Experimental results indicate that the singular value decomposition is very precise for its error sum is 1.1102V and the squared error is 2.8mV. Moreover for phase angle measurement measured six times in same direction the squared error is 24 (1). The method based on SVD can satisfy the system precision requirements of curve-fitting north seeking systems. 2011 IEEE.
	Graph fitting test method for the interpolation error of Moire fringe (EI CONFERENCE) 会议论文 OAI收割 9th International Conference on Electronic Measurement and Instruments, ICEMI 2009, August 16, 2009 - August 19, 2009, Beijing, China 作者: Sun Y.; Sun Y. 收藏 \| 浏览/下载：30/0 \| 提交时间：2013/03/25 In order to realize the fast test for the interpolation error the graph fitting test method for the interpolation error of Moire fringe is put forward in this paper. Firstly the triangular wave Moire fringe photoelectric signal of the encoder whose phase difference is 90 are sampled to get the Lissajous graph of the two signals. Secondly the single wave represented by the founded subsection function is used to fit the practical Moire fringe Lissajous graph. Then the fitting result is tested to verify whether it satisfies the accuracy requirement. Lastly the founded subsection function instead of the practical wave function is used to calculate the interpolation error. Using the graph fitting method to sample the Moire fringe single of 15-bits photoelectric encoder to get the interpolation error curve the tested maximum interpolation error is 70" and the minimum error is - 69". Comparing with the interpolation error which is received from traditional test method the change trend of the interpolation error curve is similar and peak-peak value is almost equality. The results of experiment indicate that: the equipment is convenient and the examination method is efficient and feasible. The measure speed is fast and the manifestation result is intuitionistic. The system can be used in the working field. The method can avoid the speed influence and realize the dynamic interpolation error measure which is significant for the research of encoder's dynamic accuracy characteristics. 2009 IEEE.
	Study and calibration of azimuth effect in multi-position strap-down north seeking system (EI CONFERENCE) 会议论文 OAI收割 7th World Congress on Intelligent Control and Automation, WCICA'08, June 25, 2008 - June 27, 2008, Chongqing, China 作者: Wang Z.; Zhao J.; Wang Z. 收藏 \| 浏览/下载：10/0 \| 提交时间：2013/03/25 In order to reduce the influence of azimuth effect in multi-position strap-down north seeking system its cause of formation is studied based on the precession principle of the dynamically tuned gyro. A detecting system composed by true north prism two Leica theodolites and benchmark prism fixed in the strap-down north seeking system was designed to calibrate the azimuth effect. By two steps many measurements are gone on in every position to eliminate the random error. According to the homologous between the error and the position a sinusoid is made a fit as compensate curve after the error of twelve positions is measured. Then the azimuth effect of the arbitrary position can be corrected by the curve. The experiment result shows that the seeking north standard deviation is only 11.77 after compensation which is considerably less than the 87.75 without correction. 2008 IEEE.
	Relative radiometric correction on panchromatic images of the Beijing-1 micro-satellite - art. no. 67900W 会议论文 OAI收割 Remote Sensing and Gis Data Processing and Applications; and Innovative Multispectral Technology and Applications, Pts 1 and 2, Bellingham Liu, Xiang; Chen, ZhengChao; Zhang, Hao; Luo, WenFei; Zhang, Xia 收藏 \| 浏览/下载：27/0 \| 提交时间：2014/12/07 Beijing-1 micro-satellite relative radiometric correction array response de-striping FIR filter curve fit