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Constraining the X-Ray-Infrared Spectral Index of Second-timescale Flares from SGR 1935+2154 with Palomar Gattini-IR 期刊论文 OAI收割
The Astrophysical Journal, 2020, 卷号: 901, 页码: L7
作者: HXMT

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Radio transient sources Magnetars Soft gamma-ray repeaters 2008 992 1471 Astrophysics - High Energy Astrophysical Phenomena Astrophysics - Instrumentation and Methods for Astrophysics Abstract: The Galactic magnetar SGR 1935+2154 has been reported to produce the first example of a bright millisecond-duration radio burst (FRB 200428) similar to the cosmological population of fast radio bursts (FRBs). The detection of a coincident bright X-ray burst represents the first observed multiwavelength counterpart of an FRB. However, the search for similar emission at optical wavelengths has been hampered by the high inferred extinction on the line of sight. Here, we present results from the first search for second-timescale emission from the source at near-infrared (NIR) wavelengths using the Palomar Gattini-IR observing system in the J band, enabled by a novel detector readout mode that allows short exposure times of ?0.84 s with 99.9% observing efficiency. With a total observing time of ?12 hr (?47,728 images) during its 2020 outburst, we place median 3Ҡlimits on the second-timescale NIR fluence of ?18 Jy ms (13.1 AB mag). The corresponding extinction-corrected limit is ?125 Jy ms for an estimated extinction of A_J = 2.0 mag. Our observations were sensitive enough to easily detect an NIR counterpart of FRB 200428 if the NIR emission falls on the same power law as observed across its radio to X-ray spectrum. We report nondetection limits from epochs of four simultaneous X-ray bursts detected by the Insight-HXMT and NuSTAR telescopes during our observations. These limits provide the most stringent constraints to date on fluence of flares at 10¹⁴ Hz, and constrain the fluence ratio of the NIR emission to coincident X-ray bursts to R_NIR ? 0.025 (fluence index ?0.35).

Advanced astigmatism-corrected tandem Wadsworth mounting for small-scale spectral broadband imaging spectrometer (EI CONFERENCE) 会议论文 OAI收割
作者: Lin G.-Y.

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Tandem gratings of double-dispersion mount make it possible to design an imaging spectrometer for the weak light observation with high spatial resolution high spectral resolution and high optical transmission efficiency. The traditional tandem Wadsworth mounting is originally designed to match the coaxial telescope and large-scale imaging spectrometer. When it is used to connect the off-axis telescope such as off-axis parabolic mirror it presents lower imaging quality than to connect the coaxial telescope. It may also introduce interference among the detector and the optical elements as it is applied to the short focal length and small-scale spectrometer in a close volume by satellite. An advanced tandem Wadsworth mounting has been investigated to deal with the situation. The Wadsworth astigmatism-corrected mounting condition for which is expressed as the distance between the second concave grating and the imaging plane is calculated. Then the optimum arrangement for the first plane grating and the second concave grating which make the anterior Wadsworth condition fulfilling each wavelength is analyzed by the geometric and first order differential calculation. These two arrangements comprise the advanced Wadsworth mounting condition. The spectral resolution has also been calculated by these conditions. An example designed by the optimum theory proves that the advanced tandem Wadsworth mounting performs excellently in spectral broadband. 2012 Optical Society of America.

Optimization of the two parameters of classical blaze grating in Littrow mount (EI CONFERENCE) 会议论文 OAI收割
2nd International Conference on Advanced Engineering Materials and Technology, AEMT 2012, July 6, 2012 - July 8, 2012, Zhuhai, China
作者: Zhang S.

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On the base of electromagnetic theory of gratings we analyse the effects of both of two important parameters of classical blaze grating in Littrow mount to diffraction efficiency and the two parameters are optimized for obtaining highest diffraction efficiency. It is presented that not only blaze angle but apex angle affect diffraction efficiency. The investigation has been performed on the design and fabrication of classical blaze grating which has high diffraction efficiency. (2012) Trans Tech Publications Switzerland.

Rotation and scaling invariant feature lines for image matching (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
作者: Wang Y.; Wang Y.; Wang Y.; Wang Y.; Wang Y.

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Image matching has been one of the most fundamental issues computer vision over the decades. In this paper we propose a novel method based on making use of feature lines in order to achieve more robust image matching. The feature lines have the properties of rotation and scaling invariance coined RIFLT(Rotation invariant feature line transform). Experimental results demonstrate the effectiveness and efficiency of the proposed method. Compare with the famous powerful algorithm Scale Invariant Feature Transform(SIFT) the proposed method is more insensitive to noise. And for certain sequence of images which contain clear lines the proposed method is more efficiency. Using the feature lines obtained by our method it is possible to matching two scene images with different rotation angles scale and light distort. 2011 IEEE.

Fabrication of high-efficiency ultraviolet blazed gratings by use of direct Ar2-CHF3 ion-beam etching through a rectangular photoresist mask (EI CONFERENCE) 会议论文 OAI收割
International Symposium on Photoelectronic Detection and Imaging 2011: Sensor and Micromachined Optical Device Technologies, May 24, 2011 - May 26, 2011, Beijing, China
Tan X.

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In ultraviolet spectroscopy groove irregularity and surface roughness of nanometer magnitude can cause a significant loss of diffraction efficiency. Therefore there is a constant need to improve the diffraction efficiency. A blazed grating can concentrate most of the light intensity into a desired diffraction order it is important to control the groove shape precisely so it is the optimum choice among gratings of different kinds of profile. As the operating wavelength of most UV spectral applications is less than 200 nm especially the blaze angle and the apical angle. We have presented a direct shaping method to fabricate EUV blazed gratings by using an ion-beam mixture of Ar+ and CHF2 +to etch K9 glass with a rectangular photoresist mask. With this method the required blaze angle is small we have succeeded in fabricating well-shaped UV blazed gratings with a 1200 line/mm groove density and 8.54 blaze angles and 1200 line/mm groove density and 11.68 blaze angles and the metrical efficiency is about 81% and 78%. The good performance of the gratings was verified by diffraction efficiency measurements. When one uses the etching model the conditions on the ion-beam grazing incident angle and the CHF3partial pressure should be noted. Besides since the etched groove shape depends on the aspect ratio of the photoresist mask ridge if we wish to fabricate larger gratings with this method we must improve the uniformity of the photoresist mask before ion-beam etching. 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Parallel estimation of translation for video stabilization (EI CONFERENCE) 会议论文 OAI收割
2010 6th International Conference on Wireless Communications, Networking and Mobile Computing, WiCOM 2010, September 23, 2010 - September 25, 2010, Chengdu, China
作者: Wang H.; Liu G.; Wang H.; Wang H.; Wang H.

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Translation motion estimation is the major aspect of video motion compensation especially in two-dimensional turntable. This paper presents a robust parallel estimation algorithm of translation in video stabilization system. The equivalent model of translation that derived is accorded with small rotation angle comparatively. A parallel algorithm based on grey mapping is used in local motion estimation to shorten the estimation time and improve the computation efficiency. After local motion vectors are calculated a fast filter can detect the spurious vectors avoiding possible jerks. The suggested translation estimation algorithm has been implemented on NVIDIA GTX 260 the experimental results show that the average time of the estimation and compensation finished in 16 ms/frame and stabilize 1k1k pixels sequence gray video up to 60 frames/s. 2010 IEEE.

Design of CAN bus application layer protocol for aerocraft control system (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: Zhang Y.; Zhang H.; Zhang H.; Zhang W.; Zhang W.

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A special Controller Area Network (CAN) bus application layer protocol is designed for the highly reliable communication of microcomputer-based systems in aerocraft control system by analyzing the practical time sequence of data transmission data priority data type and data function etc in this paper. Identifier distribution data storage form data type data exchange method and fault handling mechanism of the application layer protocol are specified in detail in the background of a real aerocraft control system. At last a simulation platform based on CAN bus for aerocraft control system is built to validate the design. Experimental results show that this application layer protocol meets the requirements of data transmission reliability real-time and high efficiency. The bus load rate is low and there is great room for expansion. 2010 IEEE.

Optimizing control mode of optical payloads based on multi-population genetic algorithm (EI CONFERENCE) 会议论文 OAI收割
2009 IEEE International Conference on Mechatronics and Automation, ICMA 2009, August 9, 2009 - August 12, 2009, Changchun, China
Xu W.; Jin G.

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Optimizing the control mode of optical payload could improve the payload's work efficiency. When the mathematic model of payload's control mode was established optimization problems could be boiled down to seek the maximal value of the function with many variables. This paper put forward a calculational method to base the mathematic model the calculational method was multi-population genetic algorithm (MPGA). After the 0-1 variables and real multidimensional ones had been coded separately the algorithm established the populations independently made the multidimensional variables as the centrosome and combined 0-1 ones to work out the maximal value of the function which was established to describe the control mode of the optical payload. Moreover the emulational experiment had been done with the material arithmetic operators. The result indicates that the method using MPGA can hurdle the disadvantage of traditional ones which calculate slowly and get into local best value trap easily . It has the characters that not only fits large scale area scout but also gets the best value in full scale rapidly so this algorithm can better satisfy the technology demand for the intelligent control of optical payload. 2009 IEEE.

High power diode laser with beam coupling (EI CONFERENCE) 会议论文 OAI收割
Optoelectronic Materials and Devices III, October 27, 2008 - October 30, 2008, Hangzhou, China
作者: Wang L.; Liu Y.; Wang L.; Liu Y.; Liu Y.

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As the increasing applications of the semiconductor lasers in the laser processing the single 2-D stack optic-power density has not satisfied the actual requirements. It demands to couple several diode laser stack beams to one to improve the brightness and it becomes the central issue to adopt the appropriate beam coupling technology which would offer high quality and high efficiency. In this paper it mainly introduces the beam shaping and the technology of spatial coupling polarization coupling and wavelength coupling. The coupling key elements are presented and indicated. Finally the development of the diode laser on beam coupling in our country fell behind through analyzing the statement of the world. Our lab is studying on polarization coupling and wavelength coupling. We gain some results by phase which the polarization coupling efficiency can achieve 90% for two LD stacks with seven bars whose luminous wavelength is 975nm and980nm.By two 808nm diode laser coupling the efficiency of 60% can be achieved after focusing to the beam size of 22mm2. 2008 SPIE.

Fabrication of multilayer laminar grating with high efficiency for extreme ultraviolet (EI CONFERENCE) 会议论文 OAI收割
3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies, AOMATT 2007: Advanced Optical Manufacturing Technologies, July 8, 2007 - July 12, 2007, Chengdu, China
作者: Jin C.-S.; Zhang L.-C.

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The main goal for investigations on multilayer laminar gratings working at the EUV region is to enhance their efficiency. In this article second third we demonstrate a routine to fabricate multilayer laminar gratings with high efficiency. This routine comprises three steps: first optimizing fabricating techniques to obtain multilayer coatings with high reflectivity strictly controlling errors of multilayer grating parameters to ensure the coinciding of the optical performance with the expectation. Results demonstrate that this routine is feasible. The measured peak efficiency of -1 order at 12.8nm was 14.3%. Some related issues about efficiency curves such as wavelength separation and suppression of zero order are discussed. preparing grating substrates with ideal groove profile and low roughness by holographic recording and ion beam etching process