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Zun-Lei Xu Kai-Kai Duan Zhao-Qiang Shen Shi-Jun Lei Tie-Kuang Dong Fabio Gargano Simone Garrappa Dong-Ya Guo Wei Jiang Xiang Li Yun-Feng Liang Mario Nicola Mazziotta Maria Fernanda Munoz Salinas Meng Su Valerio Vagelli Qiang Yuan Chuan Yue Jing-Jing Zang Ya-Peng Zhang Yun-Long Zhang Stephan Zimmer 《天文和天体物理学研究(英文版)》2018,(3)
The DArk Matter Particle Explorer(DAMPE),also known as Wukong in China,which was launched on 2015 December 17,is a new high energy cosmic ray and γ-ray satellite-borne observatory.One of the main scientific goals of DAMPE is to observe Ge V-Te V high energy γ-rays with accurate energy,angular and time resolution,to indirectly search for dark matter particles and for the study of high energy astrophysics. Due to the comparatively higher fluxes of charged cosmic rays with respect to γ-rays,it is challenging to identify γ-rays with sufficiently high efficiency,minimizing the amount of charged cosmic ray contamination. In this work we present a method to identify γ-rays in DAMPE data based on Monte Carlo simulations,using the powerful electromagnetic/hadronic shower discrimination provided by the calorimeter and the veto detection of charged particles provided by the plastic scintillation detector. Monte Carlo simulations show that after this selection the number of electrons and protons that contaminate the selected γ-ray events at~10 Ge V amounts to less than 1% of the selected sample.Finally,we use flight data to verify the effectiveness of the method by highlighting known γ-ray sources in the sky and by reconstructing preliminary light curves of the Geminga pulsar. 相似文献
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为探明气候变化下干旱半干旱地区湿草甸参考作物蒸散发(ET0)影响因子,使用FAO 56 P-M模型对科尔沁湿草甸ET0进行模拟,利用涡度相关系统对模型的适用性进行评价,并通过通径分析及指标敏感性分析对ET0的影响因子进行辨识。结果表明:(1)小时尺度模拟精度最高,日尺度次之,月尺度较差,小时尺度上晴、阴、雨3种天气条件下模拟效果不同,晴天最优,阴雨天较差。(2)ET0年内变化呈单峰曲线状,生长季明显高于非生长季,集中在3—10月,占全年89.79%。生长季典型晴天ET0逐小时分布特征遵循倒“U”单峰型变化规律。(3)通径分析结果显示,对ET0的通径系数以及对回归方程估测可靠程度E的总贡献均表现为VPD(饱和水汽压差) > Tmin(最低气温) > Rn(冠层表面净辐射)>u2(2 m高度风速),即VPD为影响ET0最重要的因子;指标敏感性分析中,在去除VPD后引起的E变化最大,说明ET0对VPD的变化最为敏感,其次为u2、Tmin和Rn。 相似文献
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摘要:目的 探讨菌株Salinivibrio sp.YH4分泌的丝氨酸蛋白酶EYHS的耐盐性及结构特征。方法 明胶底物酶谱法分析EYHS的耐盐性。应用生物信息学手段对EYHS及6种耐盐的S8家族丝氨酸蛋白酶结构特征进行分析。结果 EYHS在4 mol/L的NaCl溶液中仍具有活性,属于耐盐蛋白酶。EYHS及6种S8家族丝氨酸蛋白酶分子表面的loop区等无规则卷曲所占比例较高,α-螺旋与β-片层则主要位于酶分子内部。EYHS分子表面酸性氨基酸含量较高,且具有弱疏水内核。多序列比对发现蛋白酶的催化三联体两侧存在高度保守的基序和保守的极性氨基酸及芳香族氨基酸,并存在多个保守的Gly与Ala。同源模建和表面电荷分布显示,α螺旋和β片层围成了蛋白酶的催化腔,EYHS活性中心包含由Asp32、His65与Ser215组成的催化三联体,且催化位点区域表面静电势为负。结论 上述结构特征可能有助于耐盐丝氨酸蛋白酶EYHS在高盐环境下维持其稳定性和适度柔性,并有助于其催化功能的发挥,为深入研究耐盐丝氨酸蛋白酶的高盐环境适应性提供了一定的理论依据。 相似文献
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Nonlinear force-free magnetic field(NLFFF) extrapolation based on the observed photospheric magnetic field is the most important method to obtain the coronal magnetic field nowadays.However, raw photospheric magnetograms contain magnetic forces and small-scale noises, and fail to be consistent with the force-free assumption of NLFFF models. The procedure for removing the forces and noises in observed data is called preprocessing. In this paper, we extend the preprocessing code of Jiang Feng to spherical coordinates for a full sphere. We first smooth the observed data with Gaussian smoothing, and then split the smoothed magnetic field into a potential field and a non-potential field.The potential part is computed by a numerical potential field model, and the non-potential part is preprocessed using an optimization method to minimize the magnetic forces and magnetic torques. Applying the code to synoptic charts of the vector magnetic field from SDO/HMI, we find it can effectively reduce the noises and forces, and improve the quality of data for a better input which will be used for NLFFF extrapolations applied to the global corona. 相似文献
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东天山博格达造山带晚石炭世柳树沟组为一套由玄武岩和流纹岩组成的双峰式火山岩,形成于晚石炭世,其Si O_2含量介于46.18%~46.56%和76.06%~76.25%之间,具有明显的Daly成分间断。其中,玄武岩具富Na贫K特征,Ti O_2、Al_2O_3、Ca O和MgO含量均较高,∑REE为75.54×10~(-6)~80.22×10~(-6),LREE/HREE值为3.00~3.12,以富集Ba、Rb等大离子亲石元素(LILE)和不相容元素(P、K),相对亏损Ti、Ta、Nb等高场强元素(HFSE)和不相容元素(U、Th)为特征;流纹岩Na_2O/K_2O值为0.32~0.36,属低Ti、低Mg类流纹岩,∑REE为520.72×10~(-6)~595.26×10~(-6),LREE/HREE值为5.60~6.53,具有Rb、Th、K、La、Ce、Zr、Hf、Sm等元素的富集以及Ba、U、Ta、Nb、Sr、P和Ti元素的亏损特征。柳树沟组双峰式火山岩形成于大陆裂谷环境,具板内成因特征,玄武岩可能为亏损尖晶石相地幔橄榄岩向石榴石相地幔橄榄岩过渡相较高程度部分熔融的产物,受到地壳物质混染;流纹岩具典型的A型花岗岩的地球化学特征。 相似文献
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Zaiyong Zhang Wenke Wang Chengcheng Gong Zhoufeng Wang Lei Duan Tian‐chyi Jim Yeh Peiyuan Yu 《水文研究》2019,33(9):1338-1348
In cold climates, the process of freezing–thawing significantly affects the ground surface heat balance and water balance. To better understand the mechanism of evaporation from seasonally frozen soils, we performed field experiments at different water table depths on vegetated and bare ground in a semiarid region in China. Soil moisture and temperature, air temperature, precipitation, and water table depths were measured over a 5‐month period (November 1, 2016, to March 14, 2017). The evaporation, which was calculated by a mass balance method, was high in the periods of thawing and low in the periods of freezing. Increased water table depth in the freezing period led to high soil moisture in the upper soil layer, whereas lower initial groundwater levels during freezing–thawing decreased the cumulative evaporation. The extent of evaporation from the bare ground was the same in summer as in winter. These results indicate that a noteworthy amount of evaporation from the bare ground is present during freezing–thawing. Finally, the roots of Salix psammophila could increase the soil temperature. This study presents an insight into the joint effects of soil moisture, temperature, ground vegetation, and water table depths on the evaporation from seasonally frozen soils. Furthermore, it also has important implications for water management in seasonally frozen areas. 相似文献