分类： 生物学 >> 生物物理学 提交时间： 2016-05-11
Wang, Wen-Liang
Li, Ran
Li, Da-Peng
Wang, Yi
Wang, Wen-Liang
Li, Ran
Ding, Jian
Tao, Louis
Tao, Louis
摘要： Luminance and contrast are two major attributes of objects in the visual scene. Luminance and contrast information received by visual neurons are often updated simultaneously. We examined the temporal response properties of neurons in the primary visual cortex (V1) to stimuli whose luminance and contrast were simultaneously changed by 50 Hz. We found that response tuning to luminance changes precedes tuning to contrast changes in V1. For most V1 neurons, the onset time of response tuning to luminance changes was shorter than that to contrast changes. Most neurons carried luminance information in the early response stage, while all neurons carried both contrast and luminance information in the late response stage. The early luminance response suggests that cortical processing for luminance is not as slow as previously thought.
分类： 地球科学 >> 地理学 提交时间： 2025-07-17 合作期刊: 《干旱区科学》
摘要： The Loess Plateau (LP), one of the most ecologically fragile regions in China, is affected by severe soil erosion and environmental degradation. Despite large-scale ecological restoration efforts made by Chinese government in recent years, the region continues to face significant ecological challenges due to the combined impact of climate change and human activities. In this context, we developed a kernal Remote Sensing Ecological Index (kRSEI) using Moderate Resolution Imaging Spectroradiometer (MODIS) products on the Google Earth Engine (GEE) platform to analyze the spatiotemporal patterns and trends in ecological environmental quality (EEQ) across the LP from 2000 to 2022 and project future trajectories. Then, we applied partial correlation analysis and multivariate regression residual analysis to further quantify the relative contributions of climate change and human activities to EEQ. During the study period, the kRSEI values exhibited significant spatial heterogeneity, with a stepwise degradation pattern in the southeast to northwest across the LP. The maximum (0.51) and minimum (0.46) values of the kRSEI were observed in 2007 and 2021, respectively. Trend analyses revealed a decline in EEQ across the LP. Hurst exponent analysis predicted a trend of weak anti-persistent development in most of the plateau areas in the future. A positive correlation was identified between kRSEI and precipitation, particularly in the central and western regions; although, improvements were limited by a precipitation threshold of 837.66 mm/a. A moderate increase in temperature was shown to potentially benefit the ecological environment within a certain range; however, temperature of –1.00°C–7.95°C often had a negative impact on the ecosystem. Climate change and human activities jointly influenced 65.78% of LP area on EEQ, primarily having a negative impact. In terms of contribution, human activities played a dominant role in driving changes in EEQ across the plateau. These findings provide crucial insights for accurately assessing the ecological state of the LP and suggest the design of future restoration strategies.
分类： 物理学 >> 地球物理学、天文学和天体物理学 提交时间： 2024-01-09 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： In this paper, we study five luminous supernovae (LSNe) Ibc (SN 2009ca, ASASSN-15mj, SN 2019omd, SN 2002ued, and SN 2021bmf) whose peak absolute magnitudes Mpeak are ≈ −19.5 to −21 mag by fitting their multi-band light curves (LCs) with different energy source models. We find that SN 2009ca might be powered by the 56Ni model since the required 56Ni mass (0.56 M⊙) is comparable to those of energetic SNe Ic, while the rest four SNe cannot be accounted for the 56Ni model since their derived 56Ni masses are ≳1 M⊙ or the ratios of the 56Ni mass to the ejecta mass are larger than 0.2. This indicates that some LSNe might be powered by 56Ni decay, while most of them need additional energy sources. We then use the magnetar plus 56Ni model and the fallback plus 56Ni model to fit the LCs of the four LSNe that cannot be explained by the 56Ni model, finding that the two models can account for the four SNe, and the derived parameters are comparable to those of LSNe or superluminous SNe in the literature, if they were (mainly) powered by magnetars or fallback. We suggest that the magnetar plus 56Ni model is more reasonable than the fallback plus 56Ni model, since the validity of the fallback plus 56Ni model depends on the value of accretion efficiency (η) and favors a large η value, and the magnetar plus 56Ni model yields smaller χ2/dof values. It should be pointed out that, however, the fallback plus 56Ni model is still a promising model that can account for the four SNe in our sample as well as other LSNe.
分类： 化学 >> 物理化学 提交时间： 2017-11-05 合作期刊: 《结构化学》
摘要： In this work, the photovoltaic properties of BFBPD-PC61BM system as a promising high-performance organic solar cell (OSC) were theoretically investigated by means of quantum chemistry and molecular dynamics calculations coupled with the incoherent charge-hopping model. Moreover, the hole carrier mobility of BFBPD thin-film was also estimated with the aid of an amorphous cell including 100 BFBPD molecules. Results revealed that the BFBPD-PC61BM system possesses a middle-sized open-circuit voltage of 0.70 V, large short-circuit current density of 17.26 mA·cm-2, high fill factor of 0.846, and power conversion efficiency of 10%. With the Marcus model, in the BFBPD-PC61BM interface, the exciton-dissociation rate, kdis, was predicted to be 2.684×1013 s-1, which is as 3～5 orders of magnitude large as the decay (radiative and non-radiative) one (108～1010 s-1), indicating a high exciton-dissociation efficiency of 100% in the BFBPD-PC61BM interface. Furthermore, by the molecular dynamics simulation, the hole mobility of BFBPD thin-film was predicted to be as high as 1.265×10-2 cm2·V-1·s-1, which can be attributed to its dense packing in solid state.
分类： 物理学 >> 核物理学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： An accurate and fast sampling method was developed on the modeling of a voxel phantom called Rad-HUMAN for radiation protection of MC-based radiation transport and simulation. The segmented organ voxels, which were assigned with three dimensional (3D) coordinates, were simplified through a two-step hybrid sampling algorithm. Firstly, certain voxels were sampled into a coordinate matrix by the nearest neighbor sampling. Secondly, the coordinate matrix was renewed using a weighted sampling. To compare visualization with the sampling, the resultant matrix was used to extract the contour of organs/tissues for constructing polygon-surface phantom. The feasibility and effectiveness of the sampling method was verified through the modeling of large organs (e.g. skeleton system) and application of transformation to MC computational geometries.
分类： 天文学 >> 天文学 提交时间： 2024-10-08 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： In this paper, we perform the detailed modeling for the light curves (LCs) of PTF 10iuv which is a calcium-rich (Ca-rich) supernova (SN) to constrain the physical properties of its ejecta and the energy sources, as well as the explosion mechanism. We find that the 56Ni model and the 56Ni plus circumstellar interaction model fail to explain the LCs, while the four-element (56Ni, 48Cr, 52Fe, and 44Ti) model can account for the LCs. The ejecta mass of PTF 10iuv derived by the model (1.52−0.25+0.34M⊙) is consistent with that of the merger of a sub-Chandrasekhar mass white dwarf. The early-time LCs were mainly powered by 56Ni whose mass is ∼0.03 M⊙, while the contributions of 48Cr and 52Fe can be neglected. The derived 44Ti mass (∼0.25 M⊙) is ∼1.8 times the upper limit of the derived 44Ti mass of Ca-rich SN 2005E. We suggest that subtracting the contributions of the host-galaxy, which are unknown, and including the flux from other long-lived elements (e.g., 57Co, 55Fe, 60Co) can reduce the amount of 44Ti, and that this value can be regarded as an upper limit.
分类： 天文学 >> 天文学 提交时间： 2024-07-15 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： Lunar optical polarization is a fascinating phenomenon that occurs when sunlight reflects off the surface of the Moon and becomes polarized. This study employs a novel split-focus plane polarimetric camera to conduct the initial white light polarimetric observations on the near side of the Moon. We obtained the linear degree of polarization (DOP) parameters of white light by observation from the eastern and western hemispheres of the Moon. The findings indicate that the white light polarization is lower in the lunar highland than in the lunar maria overall. Combining the analysis of lunar soil samples, we noticed and determined that the DOP parameters of white light demonstrate high consistency with iron oxide on the Moon. This study may serve as a new diagnostic tool for the Moon.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
YU Guang-You
CAO De-Wen
HUANG Ai-Zhong
Yu Lei
LOH Chang-Wei
WANG Wen-Wen
QIAN Zhi-Qiang
YANG Hai-Bo
HUANG Huang
XU Zong-Qiang
ZHU Xue-Yuan
XU Bin
Qi Ming
摘要： Linear alkyl benzene (LAB) will be used as the solvent of a liquid scintillator mixture for the JUNO antineutrino experiment in the near future. Its light absorption property should therefore be understood prior to its effective use in the experiment. Attenuation length measurements at a light wavelength of 430 nm have been performed on samples of LAB prepared for the purpose of the JUNO experiment. Inorganic impurities in LAB have also been studied for their possibilities of light absorption in our wavelength of interest. In view of a tentative plan by the JUNO collaboration to utilize neutron capture with hydrogen in the detector, we have also presented in this work, a study on the carbon-hydrogen ratio and the relationship thereof with the attenuation length of the samples.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
LEI Xiang-Cui
HENG Yue-Kun
QIAN Sen
XIA Jing-Kai
LIU Shu-Lin
WU Zhi
YAN Bao-Jun
XU Mei-Hang
WANG Zheng LI Xiao-Nan
RUAN Xiang-Dong
Wang Xiao-Zhuang
YANG Yu-Zhen
WANG Wen-Wen
FANG Can
LUO Feng-Jiao
LIANG Jing-Jing 1,4 YANG Lu-Ping 1,7 YANG Biao 1,2
摘要： The neutrino detector of the Jiangmen Underground Neutrino Observatory (JUNO) is designed to use 20 kilotons of liquid scintillator and approximately 16,000 20-inch photomultipliers (PMTs).One of the options is to use the 20-inch R12860 PMT with high quantum efficiency which has recently been developed by Hamamatsu Photonics. The performance of the newly developed PMT preproduction samples is evaluated. The results show that its quantum efficiency is�0%燼t�00nm. Its Peak/Valley (P/V) ratio for the single photoelectron is 4.75 and the dark count rate is�7kHz燼t the threshold of 3 mV while the gain is at��07. The transit time spread of a single photoelectron is2.86ns. Generally the performances of this new 20-inch PMT are improved over the old one of R3600.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
WANG Wen-Wen
QIAN Sen
QI Minga XIA Jing-Kai
CHENG Ya-Ping
NING Zhe
LUO Feng-Jiao
HENG Yue-Kun
LIU Shu-Lin
SI Shu-Guang
Sun Jian-Ning
LI Dong
WANG Xing-Chao
HUANG Guo-Rui
TIAN Jing-Shou
WEI Yong-Lin
LIU Hu-Lin
LI Wei-Hua
WANG Xing
XIN Li-Wei
摘要： Aging experiments of a novel type of large area MCP-PMT made by JUNO collaboration were conducted.In these aging experiments, the multi-photoelectron spectrum and single photoelectron spectrum were measured daily,as well as the MCP resistance of the second PMT before and after the experiment. Two PMTs were aged successivelyfor cross check. The first PMT was aged for 52 days, while the other one was aged for 84 days. In order to study the mechanism of the aging process, the high voltage on the second PMT was increased to accelerate its aging process when the cumulative output of charge from its anode was about 4 C. From our study, it can be known that large area MCP-PMT aging had a strong relationship with the related MCPs. In accordance with the PMT aging curve,a PMT aging model was setup and a general aging formula was given.
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