中国科学院机构知识库网格系统: 检索

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.

Identification of degradation mechanisms of blue InGaN/GaN laser diodes 期刊论文 OAI收割
JOURNAL OF PHYSICS D-APPLIED PHYSICS, 2015, 卷号: 48, 期号: 41, 页码: 4
作者: Wen, PY(温鹏雁); Zhang, SM(张书明); Li, DY(李德尧); Liu, JP(刘建平); Zhang, LQ(张立群)

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InGaN/GaN laser diode degradation mechanism optical characteristic

Centroid localization algorithm based on bicubic interpolation gray square weighted (EI CONFERENCE) 会议论文 OAI收割
2012 3rd International Conference on Advances in Materials and Manufacturing Processes, ICAMMP 2012, December 22, 2012 - December 23, 2012, Beihai, China
作者: Zhou J.

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The 3D coordinates of measured point is embodied in 2D image coordinate of the optical characteristic point via the visual measurement system. Based on the gray square weighted centroid localization algorithm the paper presents bicubic interpolation gray square weighted centroid localization algorithm increases the number of effective pixels around the optical characteristic point imaging center and reduces noise error via the gray square weighted improves the imaging center location accuracy of optical characteristic point realizes the accurate location of the optical characteristic points. Results indicate application of the proposed algorithm to location the standard tolerance along the direction of x is 0.0022 Pixel the standard tolerance along the direction of y is 0.0023 Pixel compared with the others the standard tolerance is minimum and discrete to a lesser degree distancing ideal image point that is the proposed algorithm has higher location accuracy. The maximum tolerance along the direction of x is 0.008 Pixel the one along the direction of y is 0.007 Pixel compared with the other two algorithms the maximum tolerance is minimum.Results indicate that the stability of the proposed algorithm is better. (2013) Trans Tech Publications Switzerland.

Research on satellite platform vibration compensation technology for space optical communication (EI CONFERENCE) 会议论文 OAI收割
2012 International Meeting on Opto-Electronics Engineering and Materials Research, OEMR 2012, July 27, 2012 - July 29, 2012, Shenyang, Liaoning, China
Han C.; Li X.

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The piezo-electric steering control system is used to compensate the vibration of satellite platform. The mathematical model of piezo-electric steering system is built. The adaptive controller based on improved LMS filter algorithm is designed according to this system characteristic. The adaptive delay filter is designed to solve slow convergence speed problem of traditional algorithm. Meanwhile the adaptive delay filter can also compensate phase delay of control circuit. The adaptive deviation filter is introduced and it effectively compensates the vibration deviation which is low frequency and high amplitude. The experimental results show that the remained errors are rad which meets space optical communication requirement and proves that this control scheme is valid and feasible. (2012) Trans Tech Publications Switzerland.

The new approach for infrared target tracking based on the particle filter algorithm (EI CONFERENCE) 会议论文 OAI收割
International Symposium on Photoelectronic Detection and Imaging 2011: Advances in Infrared Imaging and Applications, May 24, 2011 - May 24, 2011, Beijing, China
作者: Sun H.; Han H.-X.; Sun H.

收藏 | 浏览/下载：59/0 | 提交时间：2013/03/25

Target tracking on the complex background in the infrared image sequence is hot research field. It provides the important basis in some fields such as video monitoring precision and video compression human-computer interaction. As a typical algorithms in the target tracking framework based on filtering and data connection the particle filter with non-parameter estimation characteristic have ability to deal with nonlinear and non-Gaussian problems so it were widely used. There are various forms of density in the particle filter algorithm to make it valid when target occlusion occurred or recover tracking back from failure in track procedure but in order to capture the change of the state space it need a certain amount of particles to ensure samples is enough and this number will increase in accompany with dimension and increase exponentially this led to the increased amount of calculation is presented. In this paper particle filter algorithm and the Mean shift will be combined. Aiming at deficiencies of the classic mean shift Tracking algorithm easily trapped into local minima and Unable to get global optimal under the complex background. From these two perspectives that "adaptive multiple information fusion" and "with particle filter framework combining" we expand the classic Mean Shift tracking framework.Based on the previous perspective we proposed an improved Mean Shift infrared target tracking algorithm based on multiple information fusion. In the analysis of the infrared characteristics of target basis Algorithm firstly extracted target gray and edge character and Proposed to guide the above two characteristics by the moving of the target information thus we can get new sports guide grayscale characteristics and motion guide border feature. Then proposes a new adaptive fusion mechanism used these two new information adaptive to integrate into the Mean Shift tracking framework. Finally we designed a kind of automatic target model updating strategy to further improve tracking performance. Experimental results show that this algorithm can compensate shortcoming of the particle filter has too much computation and can effectively overcome the fault that mean shift is easy to fall into local extreme value instead of global maximum value.Last because of the gray and fusion target motion information this approach also inhibit interference from the background ultimately improve the stability and the real-time of the target track. 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Evaluation of the operating range for ground-based infrared imaging tracking system (EI CONFERENCE) 会议论文 OAI收割
International Symposium on Photoelectronic Detection and Imaging 2011: Advances in Infrared Imaging and Applications, May 24, 2011 - May 24, 2011, Beijing, China
作者: Zhang Z.-D.

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Ground-based infrared imaging tracking system (GIITS) is of great importance for aerial target warning and guard. The operating range is one of the key performance specifications on the other which should be calculated calculate the radiation power received on the detector in order to analysis whether the output signal meets the detection requirements or not analyzed and studied during the whole GIITS design process. The operating range is mostly influenced by a few factors without considering the effect of the background radiation. By improving of the traditional method including atmospheric attenuation a new operating range calculation model of the GIITS was established based on two requirements. One is that the image size of observed target should meet the requirement of the processor signal extraction. The number of the pixel occupied by target image should be more than 9. The other is that the signal noise ratio (SNR) of the GIITS should not be less than 5 to meet the requirements of the target detection probability and spatial frequency. The SNR calculation equation in form of energy is deduced and the radiation characteristic of the observed target and background are analyzed. When evaluate the operating range of the GIITS using the new method the performance of GIITS and feature of target and background. This paper firstly makes analysis and summarization on the definite localizations of the traditional operating range equation of the GIITS. The localizations are mainly in two aspects. On one hand we should successively calculate two operating range values according to two requirements mentioned above and choose the minimum value as the analytic result. In the end the dispersion of the image and the effect of image dispersion are not considered in the traditional method an evaluation of operating range for fighter aircraft is accomplished as an example. The influence factors in every aspect on operating range were explored by the calculated result. The new operating range calculation model provides the theoretical basis for the design and applications as well as the comprehensive evaluation of a GIITS. 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Realization of the imaging-auto-focus on the APRC using splicing- CCD (EI CONFERENCE) 会议论文 OAI收割
International Conference on Graphic and Image Processing, ICGIP 2011, October 1, 2011 - October 2, 2011, Cairo, Egypt
Lu Z.; Guo Y.; Xue X.; Ma T.; Lv H.

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It is difficult to deal with the auto-focus of aerial push-broom remote sensing camera (APRC) based on image processing. First of all this paper recommended the Splicing structure of CCD in the APRC Based on this auto-focus method which is made use of the overlapping area of CCD mosaic structure was proposed combined with the characteristic of the imaging mode. After analyzing of experiments about all kinds of focus-examine functions based on image processing the gradient square function has been chosen. The experimental results show that the proposed auto-focus method for the APRC is proved to be feasible and real-time. 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

MTF-based research on the minimum fill factor in optical sparse aperture system (EI CONFERENCE) 会议论文 OAI收割
2011 4th International Conference on Intelligent Computation Technology and Automation, ICICTA 2011, March 28, 2011 - March 29, 2011, Shenzhen, Guangdong, China
作者: Liu Z.

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To avoid the loss of image information when it is transferred through optical sparse aperture system with excessively diluted apertures arrangement we propose a method in the frequency domain termed characteristic triangle to calculate the minimum fill factor. This method is based on the characteristics of MTF and demonstrates that when the characteristic triangle is equilateral with each side 3th power of sub-MTF cutoff frequency MTF has no zero value below cutoff frequency thus we can obtain the minimum fill factor. Furthermore we apply it to some typical sparse arrays such as Golay3 Golay6 Ring6 and Tri-arm7 and get their fill factors of 33.33% 15.16% 30.11% and 11.14% correspondingly which are consistent with numerical results. 2011 IEEE.

Brazing RB-SiC used in large aperture space optical system (EI CONFERENCE) 会议论文 OAI收割
2011 International Conference on Materials and Products Manufacturing Technology, ICMPMT 2011, October 28, 2011 - October 30, 2011, Chengdu, China
Zhang B.; Zhang Z.

收藏 | 浏览/下载：24/0 | 提交时间：2013/03/25

Because of the sic material's superior optical characteristic machine characteristic and hot characteristic it becomes currently the space big aperture reflector choose firstly1. For larger aperture sic mirror it is not economical and safe to make the monolithic body directly 2 3. The SiC mirror brazed assembly with several segments can solve these problems. In this paper one 600 mm sic plane mirror as demonstration welded with 3 radial segments is roughly grinded to the required figure at first then the mirror is finely grinded and polished by the technology of CCOS the mirror figure error is less than 1/20 ( = 632.8nm) in RMS finally. The problems of the preferential removal near braze joint are solved. The methods of reducing the residual stress of mirror are discussed. At last some measurements and experiments are carried on and the results conclude that the brazed SiC mirror can meet the requirement of large aperture optical systems. (2011) Trans Tech Publications.

Research on radiometric calibration of interline transfer CCD camera based on TDI working mode (EI CONFERENCE) 会议论文 OAI收割
5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, April 26, 2010 - April 29, 2010, Dalian, China
作者: Liu J.-G.; Wu X.-X.

收藏 | 浏览/下载：24/0 | 提交时间：2013/03/25

Interline transfer CCD camera can be designed to work in time delay and integration mode similar to TDI CCD to obtain higher responsivity and spatial resolution under poor illumination condition. However it was found that outputs of some pixels were much lower than others' as interline transfer CCD camera work in TDI mode in laboratory radiometric calibration experiments. As a result photo response non-uniformity(PRNU) and signal noise ratio(SNR) of the system turned for the worse. This phenomenon's mechanism was analyzed and improved PRNU and SNR algorithms of interline transfer CCD camera were advanced to solve this problem. In this way TDI stage was used as a variant in PRNU and SNR algorithms and system performance was improved observably with few influences on use. In validation experiments the improved algorithms was applied in radiometric calibration of a camera with KAI-0340s as detector. Results of validation experiments proved that the improved algorithms could effectively improve SNR and lower PRNU of the system. At the same time characteristic of the system could be reflected better. As working in 16 TDI stages PRUN was reduced from 2.25% to 0.82% and SNR was improved about 2%. 2010 Copyright SPIE - The International Society for Optical Engineering.