The New Vacuum Solar Telescope (NVST) is a one meter vacuum solar telescope that aims to observe fine structures on the Sun. The main goals of NVST are high resolution imaging and spectral observations, including me...The New Vacuum Solar Telescope (NVST) is a one meter vacuum solar telescope that aims to observe fine structures on the Sun. The main goals of NVST are high resolution imaging and spectral observations, including measurements of the solar magnetic field. NVST is the primary ground-based facility used by the Chinese solar research community in this solar cycle. It is located by Fuxian Lake in southwest China, where the seeing is good enough to perform high resolution observations. We first introduce the general conditions at the Fuxian Solar Observatory and the primary science cases of NVST. Then, the basic structures of this telescope and instruments are described in detail. Finally, some typical high resolution data of the solar photosphere and chromosphere are also shown.展开更多
The binocular stereo vision is the lowest cost sensor for obtaining 3D information.Considering the weakness of long‐distance measurement and stability,the improvement of accuracy and stability of stereo vision is urg...The binocular stereo vision is the lowest cost sensor for obtaining 3D information.Considering the weakness of long‐distance measurement and stability,the improvement of accuracy and stability of stereo vision is urgently required for application of precision agriculture.To address the challenges of stereo vision long‐distance measurement and stable perception without hardware upgrade,inspired by hawk eyes,higher resolution perception and the adaptive HDR(High Dynamic Range)were introduced in this paper.Simulating the function from physiological structure of‘deep fovea’and‘shallow fovea’of hawk eye,the higher resolution reconstruction method in this paper was aimed at ac-curacy improving.Inspired by adjustment of pupils,the adaptive HDR method was proposed for high dynamic range optimisation and stable perception.In various light conditions,compared with default stereo vision,the accuracy of proposed algorithm was improved by 28.0%evaluated by error ratio,and the stability was improved by 26.56%by disparity accuracy.For fixed distance measurement,the maximum improvement was 78.6%by standard deviation.Based on the hawk‐eye‐inspired perception algorithm,the point cloud of orchard was improved both in quality and quantity.The hawk‐eye‐inspired perception algorithm contributed great advance in binocular 3D point cloud recon-struction in orchard navigation map.展开更多
Microblade assemblages are among the most common prehistoric archaeological materials found on the Tibetan Plateau(TP)and are thought to indicate large scale migration to and settlement of the TP.Few microblade sites,...Microblade assemblages are among the most common prehistoric archaeological materials found on the Tibetan Plateau(TP)and are thought to indicate large scale migration to and settlement of the TP.Few microblade sites,however,have been systematically excavated,especially in the remotest,highest-elevation regions of the TP.The timing of the large-scale arrival,spread,and permanent settlement of people on the TP therefore remains controversial.In this paper,we report on a recently excavated site,Locality 3 of the Nwya Devu Site(ND3),located at 4600 meters above sea level(masl),near the shore of Ngoin Lake,on the interior TP.Our analyses reveal a fairly typical microblade technological orientation and two types of microblade cores:wedge-shaped and semi-conical,which are similar to those found throughout North China.Using Optically Stimulated Luminescence(OSL)dating and AMS^(14)C dating,the age of ND3 ranges from 11 to 10 ka.This date range indicates ND3 is the oldest microblade site yet recorded in the remote,high-elevation regions of the TP and thus provides important information about when and how hunter-gatherers using microblades began exploiting the higher altitudes of the TP.Taken together,studies at ND3 and throughout the TP suggest that a microblade adaptation is associated with the first prolonged human occupation of the plateau and that microblades played a significant role in mediating the risks and facilitating the mobility necessary to permanently inhabit the TP.展开更多
The first generation solar adaptive optics (AO) system, which consists of a fine tracking loop with a tip-tilt mirror (TTM) and a correlation tracker, and a high-order correction loop with a 37-element deformable ...The first generation solar adaptive optics (AO) system, which consists of a fine tracking loop with a tip-tilt mirror (TTM) and a correlation tracker, and a high-order correction loop with a 37-element deformable mirror (DM), a correlating Shack-Hartmann (SH) wavefront sensor (WFS) based on the ab- solute difference algorithm and a real time controller (RTC), has been developed and installed at the 1-m New Vacuum Solar Telescope (NVST) that is part of Fuxian Solar Observatory (FSO). Compared with the 37-element solar AO system developed for the 26-cm Solar Fine Structure Telescope, administered by Yunnan Astronomical Observatories, this AO system has two updates: one is the subaperture arrangement of the WFS changed from square to hexagon; the other is the high speed camera of the WFS and the corre- sponding real time controller. The WFS can be operated at a frame rate of 2100 Hz and the error correction bandwidth can exceed 100 Hz. After AO correction, the averaged residual image motion and the averaged RMS wavefront error are reduced to 0.06" and 45 nm, respectively. The results of on-sky testing obser- vations demonstrate better contrast and finer structures of the images taken with AO than those without AO.展开更多
The high frequency (HF) channel simulators with time-varying parameters based on the Watterson model are analyzed. The methods of simulating the HF channel with time-varying parameters are proposed. The linearly time-...The high frequency (HF) channel simulators with time-varying parameters based on the Watterson model are analyzed. The methods of simulating the HF channel with time-varying parameters are proposed. The linearly time-varying delay spread is introduced into the channel simulators to simulate the transition states between two channel modes of CCIR520-1. Two signals, including a 500 Hz and a 1 000 Hz bandwidth signal are respectively input into the standard Watterson HF channel model and the proposed channel model with time-varying parameters. Some simulation results prove that the proposed HF channel model with time-varying parameters can reflect the time-varying characteristics of frequency selected fading of HF channel.展开更多
We report efficient power scaling of the laser output with an adaptive bemn profile from an Nd:YAG dual-cavity master oscillator using a three-stage end-pumped Nd:YVO4 amplifier. We succeed ill the last switching of...We report efficient power scaling of the laser output with an adaptive bemn profile from an Nd:YAG dual-cavity master oscillator using a three-stage end-pumped Nd:YVO4 amplifier. We succeed ill the last switching of an excited laser mode by modulating an acousto-optic modulator loss in a dual-cavity master oscillator, thereby achieving temporal modulation of the output beam profile. The outputs from the master oscillator are amplified via a three-stage power amplifier yielding 36.6, 40.5, and 45.4 W of the maximum output at 116.8 W of incident pump power for the transverse electromagnetic, Laguerre-Gaussian, and quasi-top-hat beam, respectively. The prospects for further power scaling and applications via the dual-cavity master-oscillator power-amplifier (MOPA) system are considered.展开更多
A mode field adapter (MFA) fabricated by the thermal expanded core (TEC) technique is investigated. Firstly, the mode field characteristics of the TEC large mode area fiber (LMAF) are analyzed. Compared with the...A mode field adapter (MFA) fabricated by the thermal expanded core (TEC) technique is investigated. Firstly, the mode field characteristics of the TEC large mode area fiber (LMAF) are analyzed. Compared with the single-mode fiber (SMF), the mode field diameter of the LMAF enlarged slower than that of the SMF. Secondly, the mode field characteristics of the different fibers with TEC treatment are discussed. Thirdly, the transmission efficiency of the MFA fabricated by the SMF and LMAF is also investigated. Finally, we used the 6/125 μm SMF and 15/130 μm LMAF to fabricate an MFA with transmission efficiency of 92% and the handling power as high as 100 W.展开更多
Photosystem I(PSI)is one of two photosystems involved in oxygenic photosynthesis.PSI of cyanobacteria exists in monomeric,trimeric,and tetrameric forms,in contrast to the strictly monomeric form of PSI in plants and a...Photosystem I(PSI)is one of two photosystems involved in oxygenic photosynthesis.PSI of cyanobacteria exists in monomeric,trimeric,and tetrameric forms,in contrast to the strictly monomeric form of PSI in plants and algae.The tetrameric organization raises questions about its structural,physiological,and evolutionary significance.Here we report the3.72 A˚resolution cryo-electron microscopy structure of tetrameric PSI from the thermophilic,unicellular cyanobacterium Chroococcidiopsis sp.TS-821.The structure resolves 44 subunits and 448 cofactor molecules.We conclude that the tetramer is arranged via two different interfaces resulting from a dimer-of-dimers organization.The localization of chlorophyll molecules permits an excitation energy pathway within and between adjacent monomers.Bioinformatics analysis reveals conserved regions in the PsaL subunit that correlate with the oligomeric state.Tetrameric PSI may function as a key evolutionary step between the trimeric and monomeric forms of PSI organization in photosynthetic organisms.展开更多
This paper presents a VHF(30-300 MHz) RF programmable gain amplifier(PGA) with an adaptive phase correction technique.The proposed technique effectively mitigates phase errors over the VHF band,and the RFPGA as a ...This paper presents a VHF(30-300 MHz) RF programmable gain amplifier(PGA) with an adaptive phase correction technique.The proposed technique effectively mitigates phase errors over the VHF band,and the RFPGA as a whole satisfies all the specifications of the China mobile multimedia broadcasting VHF band applications.The RFPGA is implemented with a TSMC 0.25μm CMOS process.Measurement results reveal a gain range of around 61 dB,an ⅡP3 of-7 dBm at maximum gain,a power consumption of 10.2 mA at maximum gain,and a phase imbalance of less than 0.3 degrees.展开更多
基金Supported by the National Natural Science Foundation of China
文摘The New Vacuum Solar Telescope (NVST) is a one meter vacuum solar telescope that aims to observe fine structures on the Sun. The main goals of NVST are high resolution imaging and spectral observations, including measurements of the solar magnetic field. NVST is the primary ground-based facility used by the Chinese solar research community in this solar cycle. It is located by Fuxian Lake in southwest China, where the seeing is good enough to perform high resolution observations. We first introduce the general conditions at the Fuxian Solar Observatory and the primary science cases of NVST. Then, the basic structures of this telescope and instruments are described in detail. Finally, some typical high resolution data of the solar photosphere and chromosphere are also shown.
基金funded by the National Natural Science Foundation of China(No.51979275)Key Laboratory of Spatial‐temporal Big Data Analysis and Application of Nat-ural Resources in Megacities,MNR(No.KFKT‐2022‐05)+3 种基金Open Fund of Key Laboratory of Urban Land Resources Monitoring and Simulation,Ministry of Natural Resources(No.KF‐2021‐06‐115)Open Project Program of State Key Laboratory of Virtual Reality Technology and Systems,Bei-hang University(No.VRLAB2022C10)Jiangsu Province and Education Ministry Co‐sponsored Synergistic Innovation Center of Modern Agricultural Equipment(No.XTCX2002)2115 Talent Development Program of China Agricultural University and Chinese Universities Scientific Fund(No.2021TC105).
文摘The binocular stereo vision is the lowest cost sensor for obtaining 3D information.Considering the weakness of long‐distance measurement and stability,the improvement of accuracy and stability of stereo vision is urgently required for application of precision agriculture.To address the challenges of stereo vision long‐distance measurement and stable perception without hardware upgrade,inspired by hawk eyes,higher resolution perception and the adaptive HDR(High Dynamic Range)were introduced in this paper.Simulating the function from physiological structure of‘deep fovea’and‘shallow fovea’of hawk eye,the higher resolution reconstruction method in this paper was aimed at ac-curacy improving.Inspired by adjustment of pupils,the adaptive HDR method was proposed for high dynamic range optimisation and stable perception.In various light conditions,compared with default stereo vision,the accuracy of proposed algorithm was improved by 28.0%evaluated by error ratio,and the stability was improved by 26.56%by disparity accuracy.For fixed distance measurement,the maximum improvement was 78.6%by standard deviation.Based on the hawk‐eye‐inspired perception algorithm,the point cloud of orchard was improved both in quality and quantity.The hawk‐eye‐inspired perception algorithm contributed great advance in binocular 3D point cloud recon-struction in orchard navigation map.
基金supported by the National Key Research and Development Project of China(Grant No.2021YFC1523603)the Second Tibetan Plateau Scientific Expedition and Research(Grant No.2019QZKK0601)+1 种基金the National Natural Science Foundation of China(Grant Nos.42072033&41977380)the National Social Science Foundation of China(Grant Nos.23&ZD268&21@WTK001)。
文摘Microblade assemblages are among the most common prehistoric archaeological materials found on the Tibetan Plateau(TP)and are thought to indicate large scale migration to and settlement of the TP.Few microblade sites,however,have been systematically excavated,especially in the remotest,highest-elevation regions of the TP.The timing of the large-scale arrival,spread,and permanent settlement of people on the TP therefore remains controversial.In this paper,we report on a recently excavated site,Locality 3 of the Nwya Devu Site(ND3),located at 4600 meters above sea level(masl),near the shore of Ngoin Lake,on the interior TP.Our analyses reveal a fairly typical microblade technological orientation and two types of microblade cores:wedge-shaped and semi-conical,which are similar to those found throughout North China.Using Optically Stimulated Luminescence(OSL)dating and AMS^(14)C dating,the age of ND3 ranges from 11 to 10 ka.This date range indicates ND3 is the oldest microblade site yet recorded in the remote,high-elevation regions of the TP and thus provides important information about when and how hunter-gatherers using microblades began exploiting the higher altitudes of the TP.Taken together,studies at ND3 and throughout the TP suggest that a microblade adaptation is associated with the first prolonged human occupation of the plateau and that microblades played a significant role in mediating the risks and facilitating the mobility necessary to permanently inhabit the TP.
基金funded by the National Natural Science Foundation of China(Grant No.11178004)
文摘The first generation solar adaptive optics (AO) system, which consists of a fine tracking loop with a tip-tilt mirror (TTM) and a correlation tracker, and a high-order correction loop with a 37-element deformable mirror (DM), a correlating Shack-Hartmann (SH) wavefront sensor (WFS) based on the ab- solute difference algorithm and a real time controller (RTC), has been developed and installed at the 1-m New Vacuum Solar Telescope (NVST) that is part of Fuxian Solar Observatory (FSO). Compared with the 37-element solar AO system developed for the 26-cm Solar Fine Structure Telescope, administered by Yunnan Astronomical Observatories, this AO system has two updates: one is the subaperture arrangement of the WFS changed from square to hexagon; the other is the high speed camera of the WFS and the corre- sponding real time controller. The WFS can be operated at a frame rate of 2100 Hz and the error correction bandwidth can exceed 100 Hz. After AO correction, the averaged residual image motion and the averaged RMS wavefront error are reduced to 0.06" and 45 nm, respectively. The results of on-sky testing obser- vations demonstrate better contrast and finer structures of the images taken with AO than those without AO.
文摘The high frequency (HF) channel simulators with time-varying parameters based on the Watterson model are analyzed. The methods of simulating the HF channel with time-varying parameters are proposed. The linearly time-varying delay spread is introduced into the channel simulators to simulate the transition states between two channel modes of CCIR520-1. Two signals, including a 500 Hz and a 1 000 Hz bandwidth signal are respectively input into the standard Watterson HF channel model and the proposed channel model with time-varying parameters. Some simulation results prove that the proposed HF channel model with time-varying parameters can reflect the time-varying characteristics of frequency selected fading of HF channel.
基金supported by the National Research Foundation of Korea(NRF)(No.501100003725)the Basic Science Research Program(No.NRF-2014R1A1A2A16053885)+1 种基金the Korean National Police Agency(No.501100003600)the Projects for Research and Development of Police science and Technology(No.Pa-B000001)
文摘We report efficient power scaling of the laser output with an adaptive bemn profile from an Nd:YAG dual-cavity master oscillator using a three-stage end-pumped Nd:YVO4 amplifier. We succeed ill the last switching of an excited laser mode by modulating an acousto-optic modulator loss in a dual-cavity master oscillator, thereby achieving temporal modulation of the output beam profile. The outputs from the master oscillator are amplified via a three-stage power amplifier yielding 36.6, 40.5, and 45.4 W of the maximum output at 116.8 W of incident pump power for the transverse electromagnetic, Laguerre-Gaussian, and quasi-top-hat beam, respectively. The prospects for further power scaling and applications via the dual-cavity master-oscillator power-amplifier (MOPA) system are considered.
基金supported by the Shenzhen Peacock Plan(No.KQCX2015033110182368)the project of Shenzhen Science and Technology Innovation Committee(No.JCYJ20160301114759922)
文摘A mode field adapter (MFA) fabricated by the thermal expanded core (TEC) technique is investigated. Firstly, the mode field characteristics of the TEC large mode area fiber (LMAF) are analyzed. Compared with the single-mode fiber (SMF), the mode field diameter of the LMAF enlarged slower than that of the SMF. Secondly, the mode field characteristics of the different fibers with TEC treatment are discussed. Thirdly, the transmission efficiency of the MFA fabricated by the SMF and LMAF is also investigated. Finally, we used the 6/125 μm SMF and 15/130 μm LMAF to fabricate an MFA with transmission efficiency of 92% and the handling power as high as 100 W.
基金Support has been provided by the Gibson Family Foundation,the Bredesen Center for Interdisciplinary Research and Education,the Dr Donald L.Akers Faculty Enrichment Fellowship,and National Science Foundation(DGE-0801470 and EPS-1004083)support to B.D.B.In addition,J.M.and B.D.B.have been supported via a JDRD award from University of Tennessee(UTK)/Oak Ridge National Lab Science Alliance to B.D.B.,M.L.has been supported as a CIRE Fellow at University of Tennessee,Knoxville,C.J.C.was supported by a UTK NSF GFRP award(grant no.2017219379)K.S.has been supported by the Tickle College of Engineering,UTK.
文摘Photosystem I(PSI)is one of two photosystems involved in oxygenic photosynthesis.PSI of cyanobacteria exists in monomeric,trimeric,and tetrameric forms,in contrast to the strictly monomeric form of PSI in plants and algae.The tetrameric organization raises questions about its structural,physiological,and evolutionary significance.Here we report the3.72 A˚resolution cryo-electron microscopy structure of tetrameric PSI from the thermophilic,unicellular cyanobacterium Chroococcidiopsis sp.TS-821.The structure resolves 44 subunits and 448 cofactor molecules.We conclude that the tetramer is arranged via two different interfaces resulting from a dimer-of-dimers organization.The localization of chlorophyll molecules permits an excitation energy pathway within and between adjacent monomers.Bioinformatics analysis reveals conserved regions in the PsaL subunit that correlate with the oligomeric state.Tetrameric PSI may function as a key evolutionary step between the trimeric and monomeric forms of PSI organization in photosynthetic organisms.
文摘This paper presents a VHF(30-300 MHz) RF programmable gain amplifier(PGA) with an adaptive phase correction technique.The proposed technique effectively mitigates phase errors over the VHF band,and the RFPGA as a whole satisfies all the specifications of the China mobile multimedia broadcasting VHF band applications.The RFPGA is implemented with a TSMC 0.25μm CMOS process.Measurement results reveal a gain range of around 61 dB,an ⅡP3 of-7 dBm at maximum gain,a power consumption of 10.2 mA at maximum gain,and a phase imbalance of less than 0.3 degrees.