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Searching for AGN and pulsar candidates in 4FGL unassociated sources using machine learning

Research in Astronomy and Astrophysics 2021年第1期21卷 143-157页

作者： Ke-Rui Zhu shi-ju kang Yong-Gang Zheng Department of Physics Yunnan Normal UniversityKunmingYunnan650092China School of Physics and Electrical Engineering Liupanshui Normal UniversityLiupanshuiGuizhou553004China

In the fourth Fermi Large Area Telescope source catalog(4 FGL),5064γ-ray sources are reported,including 3207 active galactic nuclei(AGNs),239 pulsars,1336 unassociated sources,92 sources with weak association with blazars at low Galactic latitudes and 190 other *** employ two different supervised machine learning classifiers,combined with the direct observation parameters given by the 4 FGL fits table,to search for sources potentially classified as AGNs and pulsars in the 1336 unassociated *** order to reduce the error caused by the large difference in the sizes of samples,we divide the classification process into two separate steps in order to identify the AGNs and the ***,we select the identified AGNs from all of the samples,and then select the identified pulsars from the remaining *** the 4 FGL sources associated or identified as AGNs,pulsars and other sources with the features selected through the K-S test and the random forest(RF)feature importance measurement,we trained,optimized and tested our classifier ***,the models are applied to classify the 1336 unassociated *** to the calculation results of the two classifiers,we report the sensitivity,specificity,accuracy in each step and the class of unassociated sources given by each *** accuracy obtained in the first step is approximately 9595%;in the second step,the obtained overall accuracy is approximately 80%.Combining the results of the two classifiers,we predict that there are 583 AGN-type candidates,115 pulsar-type candidates,154 other types ofγ-ray candidates and 484 of uncertain types.

关键词： gamma rays:galaxies galaxies:active methods:statistical

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An explanation for 13 consecutive day activities of Mrk 421

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Research in Astronomy and Astrophysics 2021年第1期21卷 75-86页

作者： Yong-Gang Zheng Chu-Yuan Yang shi-ju kang Jin-Ming Bai Yunnan Observatories Chinese Academy of SciencesKunming 650011China Department of Physics Yunnan Normal UniversityKunming 650092China Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment-Shandong University Weihai 264209China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China Department of Physics and Electronics Science Liupanshui Normal UniversityLiupanshui 553004China

It is surprising to find an instance of migration in the peak positions of synchrotron spectral energy distribution components during the activity epochs of Markarian 421(Mrk 421),accompanying an orphan flare at the X-ray and GeV-TeVγ-ray bands.A geometric interpretation and standard shock or stochastic acceleration models of blazar emission have difficulty reproducing these observed *** present paper introduces a linear acceleration by integrating the reconnection electric field into the particle transport model for the observed behaviors of Mrk *** note that strong evidence for evolution in characteristic of multi-wavelength spectral energy distribution including shifting the peak frequency,accompanying an orphan flare at the X-ray and GeV-TeVγ-ray bands provides an important electrostatic acceleration diagnostic in a blazar *** suitable model parameters,we apply the results of the simulation to the 13-day flaring event in March 2010 of Mrk 421,concentrating on the evolution of multiwavelength spectral energy distribution characteristic by shifting the peak *** is clear that the ratio of the electric field and magnetic field strength plays an important role in temporal evolution of the peak frequency of synchrotron spectral energy distribution *** suggest it is reasonable that the electrostatic acceleration is responsible for the evolution of multi-wavelength spectral energy distribution characteristic by shifting the peak *** on the model results,we assert that the peak frequency of the synchrotron spectral energy distribution component may signify a temporary characteristic of blazars,rather than a permanent one.

关键词： radiation mechanisms:non-thermal BL Lacertae objects:individual:(Mrk 421) acceleration of particles

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On the intrinsic shape of the gamma-ray spectrum for Fermi blazars

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Research in Astronomy and Astrophysics 2018年第5期18卷 93-98页

作者： shi-ju kang Qingwen Wu Yong-Gang Zheng Yue Yin Jia-Li Song Hang Zou Jian-Chao Feng Ai-jun Dong Zhong-Zu Wu Zhi-Bin Zhang Lin-Hui Wu School of Electrical Engineering Liupanshui Normal University Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing School of Physics Huazhong University of Science and Technology Department of Physics Yunnan Normal University School of Physics and Electronic Science Guizhou Normal University Department of Physics College of Science Guizhou University

The curvature of the γ-ray spectrum in blazars may reflect the intrinsic distribution of emitting electrons, which will further give some information on the possible acceleration and cooling processes in the emitting region. The γ-ray spectra of Fermi blazars are normally fitted either by a single power-law（PL） or a log-normal（call Logarithmic Parabola, LP） form. The possible reason for this difference is not clear. We statistically explore this issue based on the different observational properties of 1419 Fermi blazars in the 3 LAC Clean Sample. We find that the γ-ray flux（100 Me V–100 Ge V） and variability index follow bimodal distributions for PL and LP blazars, where the γ-ray flux and variability index show a positive correlation. However, the distributions of γ-ray luminosity and redshift follow a unimodal distribution. Our results suggest that the bimodal distribution of γ-ray fluxes for LP and PL blazars may not be intrinsic and all blazars may have an intrinsically curved γ-ray spectrum, and the PL spectrum is just caused by the fitting effect due to less photons.

关键词： galaxies active - galaxies jets - gamma rays galaxies - galaxies statistics

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Double [5]carbohelicene: facile synthesis, chiroptical properties,isomerization study, and lasing application

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Science China Chemistry 2025年第1期 233-240页

作者： Peipei Liu Yantong Li Meng-Xiang Wu Hao kang Xiao-Li Zhao Lin Xu Linlin Liu Xiaodong Li junfeng Fang Zhiwei Fang Ya Cheng Hai-Bo Yang Huakang Yu Xueliang shi State Key Laboratory of Petroleum Molecular & Process Engineering Shanghai Key Laboratory of Green Chemistry and Chemical ProcessesSchool of Chemistry and Molecular Engineering East China Normal University School of Physics and Optoelectronics South China University of Technology Institute of Polymer Optoelectronic Materials & Devices State Key Laboratory of Luminescent Materials & Devices South China University of Technology School of Physics and Electronic Science Engineering Research Center of Nanophotonics & Advanced Instrument Ministry of EducationEast China Normal University State Key Laboratory of Precision Spectroscopy School of Physics and Electronic Science East China Normal University

Double carbohelicenes have attracted considerable attention due to their aesthetic structures, distinct π-conjugation extension, inherent chirality, and intriguing optical and electronic properties. Herein, the concise de novo synthesis of a new double[5]carbohelicene 1 together with its chiroptical properties, isomerization process and lasing application is presented. 1 was synthesized by a simple protocol involving the formation of a 6,6′-bipentacene as the key intermediate. It is worth noting that1 existed as two diastereomers 1-PP/MM and 1-PM, which were successfully isolated and unambiguously confirmed by Xray crystallography. The optical resolution of the racemic 1-PP/MM was successfully achieved by chiral-phase highperformance liquid chromatography（HPLC）, and 1-PP and 1-MM were characterized by circular dichroism. Interestingly, it was found that 1-PP/MM could be completely isomerized to 1-PM upon heating, and the detailed thermodynamics and kinetics of the isomerization process were systematically investigated. 1-PM exhibited deep-red luminescence with emission maximum at 723 nm and fluorescence quantum yield as high as 32.95%. Consequently, we can showcase the lasing application of 1-PM by doping with epoxy resin to assemble a bottle microlaser spontaneously, which the lasing wavelength is 796.6 nm at a threshold of 0.8 m J cm-2. We believe that our studies, including the facile synthesis methodology, detailed isomerization studies, and lasing application, will shed some light on the design and synthesis of novel carbohelical systems with more functions.

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Analysis of the anti-T2DM components in dichloromethane fraction of Schisandra sphenanthera and its mechanism

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Traditional Medicine Research 2025年第1期10卷 27-43页

作者： shi-Bo Feng Hai-Hui Jiang Hui-Li kang Yi Jiang Hua-Wei Zhang Xiao-Mei Song Yu-Ze Li Wen-Li Huang Dong-Dong Zhang Chong Deng School of Pharmacy Shaanxi University of Chinese MedicineXianyang 712046China School of Pharmacy and Shaanxi Qinling Application Development and Engineering Center of Chinese Herbal Medicine Shaanxi University of Chinese MedicineXianyang 712046China Key Laboratory for Research and Development of“Qin Medicine”of Shaanxi Administration of Traditional Chinese Medicine Xianyang 712046China Shaanxi Key Laboratory of Research and Application of“Taibai Qi Yao” Xianyang 712046China

Background:The type 2 diabetes mellitus(T2DM)pharmacodynamic study of various parts of Schisandra sphenanthera was conducted in the previous stage,and it was found that dichloromethane extracted part(SDP)had a significant hypoglycemic ***,the components of SDP were analyzed,and the specific mechanism of its anti-T2DM was ***:We used a high-fat,high-sugar diet in combination with streptozotocin to induce a T2DM rat model,and the model rats were divided into two groups according to body weight and blood ***,oral glucose tolerance test,fasting blood glucose,low density lipoprotein cholesterol,superoxide dismutase,insulin,glycated hemoglobin,total cholesterol,nonesterified free fatty acids,alanine aminotransferase,high-density lipoprotein cholesterol,aspartate aminotransferase,malondialdehyde,and glutathione peroxidase were measured,organ indices were calculated,and pathological sections of pancreas and liver were *** 16S rRNA V3–V4 region of intestinal flora was sequenced to explore the effect of SDP on biochemical indicators and intestinal *** on the above indicators,the anti-T2DM mechanism of SDP in Schisandra sphenanthera was ***:After six weeks of administration,the biochemical indices of diabetic rats were diminished compared to the control *** SDP could significantly increase the gut microbialα-diversity index,resulting in significant changes in the flora of T2DM rats,with increased richness and diversity,reduced harmful flora,and significantly back-regulated the levels of acetic acid,propionic acid,and butyric ***:SDP can improve the symptoms associated with elevated blood glucose,dyslipidemia,elevated fasting insulin levels,and damaged glucose tolerance in *** against T2DM may be through the control of intestinal flora to normalize and exert anti-diabetic effect;its main active components may be lignans and terpenoids.

关键词： Schisandra sphenanthera T2DM intestinal flora HPLC

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Investigations on methane hydrate formation,dissociation,and viscosity in gas-water-sand system

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Petroleum Science 2022年第5期19卷 2420-2430页

作者： Shang-Fei Song Shun-kang Fu Qing-Yun Liao Bo-Hui shi Hong-ju Chen Jing Gong State Key Laboratory of Natural Gas Hydrates/National Engineering Laboratory for Pipeline Safety China University of PetroleumBeijing102249China PipeChina West East Pipeline Company Shanghai200122China Key Lab of Deepwater Engineering CNOOC Research InstituteBeijing100028China

Understanding the kinetics and viscosity of hydrate slurry in gas-water-sand system is of great significance for the high-efficiency and high-safety development of natural gas *** effect of micronsized sands with various concentrations and particle sizes on the hydrate formation,dissociation,and viscosity in gas-water-sand system are investigated in this *** experimental results show that the hydrate induction time in the sandy system is slightly prolonged compared to the pure gas-water system,and the inhibition effect first strengthens and then weakens as the sand concentration increases from0 wt%to 5 wt%.Besides,the difference of hydrate formation amount in various cases is not *** concentration and particle size of sand have little effect on the kinetics of hydrate *** promoting and inhibiting effects on hydrate formation have been found in the sandy multiphase *** the viscosity characteristics,there are three variations of hydrate slurry viscosity during the formation process:Steep drop type,S-type and Fluctuation ***,appropriate sand size is helpful to reduce the randomness of slurry viscosity ***,even at the same hydrate volume fraction,the slurry viscosity in the formation process is significantly higher than that in dissociation process,which needs further *** work provides further insights of hydrate formation,dissociation,and viscosity in gas-water-sand system,which is of great significance for safe and economic development of natural gas hydrates.

关键词： Hydrate slurry Micron-sized sands Hydrate formation Hydrate dissociation Viscosity characteristics

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Integrated criteria for covert channel auditing

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第6期9卷 737-743页

作者： Chang-da WANG shi-guang ju School of Computer Science and Telecommunications Engineering Jiangsu University Zhenjiang 212013 China School of Computer Science Carleton University Ottawa Ontario K1S 5B6 Canada

A new concept, the security level difference of a covert channel, is presented, which means the security level span from the sender to the receiver of the covert channel. Based on this, the integrated criteria for covert channel auditing are given. Whereas TCSEC (Trusted Computer System Evaluation Criteria) or CC (Common Criteria for Information Technology Security Evaluation) only use the bandwidth to evaluate the threat of covert channels, our new criteria integrate the security level difference, the bandwidth sensitive parameter, bandwidth, duration and instantaneous time of covert channels, so as to give a comprehensive evaluation of the threat of covert channels in a multilevel security system.

关键词： Multilevel security Covert channel Covert channel auditing

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Effects of 24-Epibrassinolide on Antioxidant System in Cucumber Seedling Roots Under Hypoxia Stress

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Agricultural Sciences in China 2007年第3期6卷 281-289页

作者： kang Yun-yan GUO shi-rong LI juan DUAN Jiu-ju College of Horticulture Nanjing Agricultural University Nanjing 210095 P.R.China

This article aims to study the effects of exogenous 24-epibrassinolide （EBR） on the changes in ROS, activities of antioxidative enzymes and antioxidants in cucumber （Cucumis sativus L.） seedling roots under hypoxia stress. Seedlings of a hypoxiaresistant cultivar, Lühachun 4, and a hypoxia-sensitive cultivar, Zhongnong 8, were hydroponically grown for 8 d in normoxic or hypoxic nutrient solutions that were added or not added with 10^-3 mg L^-1 EBR. Under hypoxia stress, the ROS levels and the lipid peroxidation were significantly increased in the roots upon exposure to hypoxia stress, which were inhibited by EBR application. The EBR treatment significantly increased the seedlings growth and SOD, APX, GR activities, and contents of AsA and GSH under hypoxia stress. From the results obtained in this study, it can be concluded that oxidative damage on seedling roots by hypoxia stress can be considerably alleviated and the tolerance of plants was elevated.

关键词： cucumber (Cucumis sativus L.) 24-epibrassinolide seedlings hypoxia stress antioxidative system lipid peroxidation

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Synthesis plasmonic Bi/Bi VO4 photocatalysts with enhanced photocatalytic activity for degradation of tetracycline(TC)

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Chinese Journal of Chemical Engineering 2019年第12期27卷 3053-3059页

作者： Nianjun kang Dongbo Xu Weidong shi School of Chemistry and Chemical Engineering Jiangsu UniversityZhenjiang 212013China

In recent years,the excessive use of antibiotics has become a serious problem for human ***04 regarded as one of the most promising visible-light-driven photocatalysts was used to degrade the *** this paper,we fabricated Bi/BiV04 plasmonic photocatalysts which enhanced the photocatalytic activity of BiV04 for degradation of tetracycline(TC)*** Bi/BiV04 photocatalysts were characterized by X-ray diffraction,X-ray photoelectron spectroscopy,scanning electron microscopy,transmission electron microscopy and high-resolution transmission electron *** addition,the photocatalytic experiment results show that the 0.04-Bi/BiVO4 sample has the best photocatalytic activity for 2 times than the pure BiV04 *** cycle experiments,after four repetitions of the experiments,showed the sample still maintained a high photocatalytic ***,the photocatalytic reaction mechanism was also studied by free radical capture experiments and electron paramagnetic resonance spectroscopy.

关键词： Bi/BiVO4 Plasmonic Photocatalysts Tetracycline(TC) Visible light

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Climate effects of the GlobeLand30 land cover dataset on the Beijing Climate Center climate model simulations

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Science China Earth Sciences 2016年第9期59卷 1754-1764页

作者： shi XueLi NIE SuPing ju WeiMin YU Le National Climate Center Beijing 100081 China International Institute for Earth System Science (ESSI) Nanjing University Nanjing 210093 China Ministry of Education Key Laboratory for Earth System Modeling Center for Earth System Science Tsinghua University Beijing 100084 China Joint Center for Global Change Studies Beijing 100875 China

Land cover is one of the most basic input elements of land surface and climate models. Currently, the direct and indirect effects of land cover data on climate and climate change are receiving increasing attentions. In this study, a high resolution(30 m) global land cover dataset(Globe Land30) produced by Chinese scientists was, for the first time, used in the Beijing Climate Center Climate System Model(BCC_CSM) to assess the influences of land cover dataset on land surface and climate simulations. A two-step strategy was designed to use the Globe Land30 data in the model. First, the Globe Land30 data were merged with other satellite remote sensing and climate datasets to regenerate plant functional type(PFT) data fitted for the BCC_CSM. Second, the up-scaling based on an area-weighted approach was used to aggregate the fine-resolution Globe Land30 land cover type and area percentage with the coarser model grid resolutions globally. The Globe Land30-based and the BCC_CSM-based land cover data had generally consistent spatial distribution features, but there were some differences between them. The simulation results of the different land cover type dataset change experiments showed that effects of the new PFT data were larger than those of the new glaciers and water bodies(lakes and wetlands). The maximum value was attained when dataset of all land cover types were changed. The positive bias of precipitation in the mid-high latitude of the northern hemisphere and the negative bias in the Amazon, as well as the negative bias of air temperature in part of the southern hemisphere, were reduced when the Globe Land30-based data were used in the BCC_CSM atmosphere model. The results suggest that the Globe Land30 data are suitable for use in the BCC_CSM component models and can improve the performance of the land and atmosphere simulations.

关键词： Land cover Climate model Application strategy Numerical simulation Air temperature Precipitation

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