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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 \| 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).
	Band Selection for Forest Stock Volume Estimation in Southern China 会议论文 OAI收割 Advanced Materials in Microwaves and Optics, Stafa-Zurich Song, Chenxi; Xia, Zhongsheng; Shao, Yun; Zhang, Fengli; Li, Kun; Wan, Zi 收藏 \| 浏览/下载：13/0 \| 提交时间：2014/12/07 Forest stock volume variance expansion factor RMSq ratio of band remote sensing
	Wavelet-based contourlet coding using SPECK algorithm (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 Xiu-Wei T.; Xi-Feng Z.; Tie-Fu D. 收藏 \| 浏览/下载：55/0 \| 提交时间：2013/03/25 We proposed a new still image compression algorithm called CSPECK witch was constructed by the wavelet-based contourlet transform (WBCT) and set partitioning embedded block coding (SPECK). In the WBCT the high frequency sub-band decomposed by the wavelet transform was further decomposed into multiple directional sub-bands by directional filter bank so as to explain the edge and texture of the image more sparsely. The SPECK algorithm exhibits lower complexity and more efficient compression ratio than SPIHT based on WBCT. Experimental results demonstrate that the proposed method is efficient in coding images that possess mostly textures and contours. The simulation results also show that this new coding algorithm increases the PSNR over CSPIHT. 2008 IEEE.
	UV-VUV spectral irradiance responsivity calibration for space remote sensing spectroradiometer (EI CONFERENCE) 会议论文 OAI收割 Advanced Materials and Devices for Sensing and Imaging III, November 12, 2007 - November 14, 2007, Beijing, China 作者: Yu H. 收藏 \| 浏览/下载：29/0 \| 提交时间：2013/03/25 In order to overcome the irradiance responsivity calibration troubles caused by the weak response of most spectral radiometers in ultraviolet band and poor ratio of signal to noise and to meet special calibration condition for some remote sensing spectroradiometers in space a spectral irradiance responsivity calibration unit based on parallel light illumination mode is established it is composed of a 150W deuterium lamp and a spherical mirror. The calibration unit gets the output standard value of spectral irradiance by irradiance transfer this way avoids the spectral reflectance measurement difficulty of the spherical mirror. A flight spectral radiometer model used for space remote sense was calibrated in range from 160nm to 300nm the calibration error of spectral irradiance responsivity is 4.7%. Some factors which contribute to calibration uncertainties are discussed.
	Energy transfer and red phosphorescence in strontium aluminates doped with Cr3+, Eu2+ and Dy3+ (EI CONFERENCE) 会议论文 OAI收割 Dielectrics in Emerging Technologies -and- Persistent Phosphors - International Symposia, May 15, 2005 - May 20, 2005, Quebec City, QC, Canada 作者: Wang X.; Wang X.; Wang X.; Zhang X.; Zhang X. 收藏 \| 浏览/下载：30/0 \| 提交时间：2013/03/25 Cr3+ activated red (694 nm) long persistent phosphorescence originating from 2E-4A2 transition is observed in 4SrO·7Al2O3: Cr3+ Eu2+ Dy3+ system. It is demonstrated that the red phosphorescence is resulted from the conversion of Eu2+ activated blue phosphorescence through persistence energy transfer from Eu2+ to Cr3+. The excitation spectra of the 694 nm emission exhibit strong f-d band of Eu 2+ indicating the existence of the energy transfer. The dependence of lifetimes and intensities of the red and blue emissions on Cr3+ concentrations are studied. The intensity ratio of the red to blue emission bands obtained from photoluminescence spectra is in good agreement with that obtained from fluorescence lifetime measurements. The decay curves of the red phosphorescence at 694nm are also studied.