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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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收藏 | 浏览/下载：24/0 | 提交时间：2022/02/08

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).

Design of high speed and parallel compression system used in the big area CCD of high frame frequency (EI CONFERENCE) 会议论文 OAI收割
2011 International Conference on Precision Engineering and Non-Traditional Machining, PENTM 2011, December 9, 2011 - December 11, 2011, Xi'an, China
作者: Li G.-N.; Jin L.-X.; Zhang R.-F.; Wang W.-H.; Li G.-N.

收藏 | 浏览/下载：51/0 | 提交时间：2013/03/25

According to the area CCD camera of characteristics such as high resolution capacity and high frame frequency this paper puts forward a high speed and parallel image compression system of high integration degree. Firstly according to the work principle of the area CCD FPGA is adopted to realize the timing driving and multichannel and parallel analog signal handling to raise the export frame frequency of the area CCD. Secondly with an image compression scheme based on FPGA embedded processor MicroBlaze and ADV212 compression chip real time image compression and the high speed area CCD are realized. Finally by detecting the analog signal of the area CCD output the real time compression of the big area CCD image is carried out in different compression ratios and the compression performance is analyzed. Experiment result shows that this scheme can realize real time image compression with the biggest data rate of 520Mbps. When compression bit ratio is 0.15 the signal-to-noise ratio of peak value can reach 36 dB. Image collection and image compression are integrated which reduces the data transmission between them and improves systematic integration degree.

Three-loop autopilot design and simulation (EI CONFERENCE) 会议论文 OAI收割
2012 9th IEEE International Conference on Mechatronics and Automation, ICMA 2012, August 5, 2012 - August 8, 2012, Chengdu, China
作者: Zhang Y.

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In order to realize missile real-time change flight trajectory three-loop autopilot is setting up. The structure characteristics autopilot model and control parameters design method were researched. Firstly this paper introduced the 11th order three-loop autopilot model. With the principle of systems reduce model order the 5th order model was deduced. On that basis open-loop frequency characteristic and closed-loop frequency characteristic were analyzed. The variables of velocity ratio dynamic pressure ratio and elevator efficiency ratio were leading to correct system nonlinear. And then autopilot gains design method were induced. System flight simulations were done and result shows that autopilot gains played a good job in the flight trajectory autopilot satisfied the flight index. 2012 IEEE.

MAC protocol with dynamic priority adjustment for light trail networks (EI CONFERENCE) 会议论文 OAI收割
Network Architectures, Management, and Applications VIII, December 8, 2010 - December 12, 2010, Shanghai, China
作者: Fang W.; Li S.

收藏 | 浏览/下载：22/0 | 提交时间：2013/03/25

In order to improve the wavelength utilization as well as the fairness of the light trail networks we modified the FP MAC from the view point of weight balance by introducing a weight mode. The weight mode is composed of two factors real-time factor and node activity ratio. Moreover the weight mode is used as a bid by each LT node to compute the priority. Hence the priority of the LT node is adjusted dynamically in every round and the MAC protocol with dynamic priority adjustment is entitled as DPA MAC. Simulation results show that the performances of DPA MAC protocol are much better than that of FP MAC protocol in terms of packet loss rate and activity percentile. 2011 Copyright SPIE - The International Society for Optical Engineering.

Design and demonstration of micro multi-step mirrors and light source in micro FTIR (EI CONFERENCE) 会议论文 OAI收割
6th IEEE International Conference on Nano/Micro Engineered and Molecular Systems, NEMS 2011, February 20, 2011 - February 23, 2011, Kaohsiung, Taiwan
Liang Z.; Fu J.; Feng C.; Liang J.

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To obtain high resolution high signal-to-noise ratio (SNR) high reliability and real time in wide spectral range we study the space modulation Micro Fourier Transform Spectrometer (FTS) based on multi-step mirrors covering the spectral range of 3-5m and 8-12 m in theory and experiment. The influences of spectrum reconstruction caused by the diffraction and extended light source in Fourier Transform Infrared Spectrometer (FTIR) are analyzed. A method to reduce the noises in spectrum reconstruction and the relationship between coherent intensity and solid angle of light source are discussed. An extended light source with suitable size is chosen considering the requirement of SNR and spectrum resolving power in the optical design. Furthermore the fabrication of micro multi-step mirrors which is the core part of FTS is investigated. Three methods for fabricating multi-step micro mirrors are demonstrated. 2011 IEEE.

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.

Fabrication and photoluminescence of ZnS: Mn2+ nanowires/ZnO quantum dots/SiO2 heterostructure (EI CONFERENCE) 会议论文 OAI收割
作者: Yang L.; Wang D.; Wang Y.; Wang Y.; Wang Y.

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In this paper we demonstrated the encapsulation of ZnS: Mn2+ nanowires (NWs) and ZnO quantum dots (QDs) with a layer of mesoporous SiO 2 shell for the purpose of integrating dual emission property into one common nanostructure. The average diameter of ZnS: Mn2+ NWs ZnO QDs and ZnS: Mn2+ / ZnO@SiO2 heterostructure was about 10 nm 6 nm and 22 nm respectively. Within ZnS: Mn2+ / ZnO@SiO 2 nanocomposites the intensity of the yellow-orange emission contributed by ZnS: Mn2+ NWs and the UV emission contributed by ZnO QDs was three and ten times higher than their individual components respectively. The fluorescence intensity ratio of the dual emission can be tuned by adjusting the hydrolysis time of tetraethyl orthosilicate. The peak energy of the yellow-orange and UV emission showed blueshift and redshift as increasing the temperature respectively. The anomalous enhancement of the integrated intensity for the UV emission with the temperature indicated that the high surface state density existing in ZnO QDs can overrun the influence of temperature quenching and even alter the photoluminescent properties. 2010 American Institute of Physics.

An improved fast parallel SPIHT algorithm and its FPGA implementation (EI CONFERENCE) 会议论文 OAI收割
2010 2nd International Conference on Future Computer and Communication, ICFCC 2010, May 21, 2010 - May 24, 2010, Wuhan, China
作者: Jin L.-X.; Tao H.-J.; Wu Y.-H.

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In view of the current stringent need to the real-time compression algorithm of the high-speed and high-resolution image such as remote sensing or medical image and so on in this paper No List SPIHT (NLS) algorithm has been improved and a fast parallel SPIHT algorithm is proposed which is suitable to implement with FPGA. It can deal with all bit-planes simultaneously and process in the speed of 4pixels/period so the encoding time is only relative to the image resolution. The experimental results show that the processing capacity can achieve 200MPixels/s when the input clock is 50MHz the system of this paper need 2.29ms to complete lossless compression of a 512x512x8bit image and only requires 1.31ms in the optimal state. The improved algorithm keeps the high SNR unchanged increases the speed greatly and reduces the size of the needed storage space. It can implement lossless or lossy compression and the compression ratio can be controlled. It could be widely used in the field of the high-speed and high-resolution image compression. 2010 IEEE.

OFDM baseband modulation technology based on VHDL (EI CONFERENCE) 会议论文 OAI收割
2010 IEEE International Conference on Advanced Computer Control, ICACC 2010, March 27, 2010 - March 29, 2010, 445 Hoes Lane - P.O.Box 1331, Piscataway, NJ 08855-1331, United States
Lin L.; Qiao Y.-F.; Su W.-X.

收藏 | 浏览/下载：16/0 | 提交时间：2013/03/25

In order to improve the transmission velocity in mulitipath fading wireless channel two main advantages are obtained via discussing spectrum utilization ratio of OFDM. Then the high speed OFDM technology receives increasing attentions in mobile communication. Modulation programs are designed with VHDL based on the principle of OFDM in the paper. First from the results of VHDL simulation after OFDM fundamental is introduced the realization of baseband operations such as interleaver subcarrier modulation IFFT and adding CP are presented. Finally implemented programs are validated on the actual implement system. Experimental results indicate that setup time corresponding to transmission velocity is only 71.05s and steady time is approximately 6 times as setup time that is not only achieving the high speed transmission but also supplying adequate modulation time. 2010 IEEE.

Design and analysis of power system of micro-electromechanical actuator (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 J.; Zhang J.; Zhang J.

收藏 | 浏览/下载：23/0 | 提交时间：2013/03/25

In order to apply the electromechanical actuator to tactical mini-missiles maximum rotational speed of output shafts is greater than 250/s. Test results basically correspond to the requirement of technical indexes. It is proved that this analysis and design method is congruent with the design of micro-electromechanical actuators this paper researches on the key technology such as load-bearing ability the system bandwidth can reach 25.3Hz on the condition of no load and 23.4Hz on the condition of load thus the method is feasible. 2010 IEEE. rapidity and miniaturization of the micro-electromechanical actuator power system based on the ball screw. First according to specific technical indexes the power electromechanical time constant and the size of the motors are screened originally through theoretical analysis. Finally based on the characteristics of ball screw transmission load locus of the micro-electromechanical actuator dynamic system is theoretically analyzed and the optimum speed ratio is determined through parameter optimization. The results of the double closed loop controlled test on the principle prototype show: the system can operate normally with 2.5N.m hinge moment