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Simulation study of the performance of the Very Large Area gamma-ray Space Telescope

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Nuclear Science and Techniques 2024年第09期 43-59页

作者： Xu Pan Wei Jiang Chuan Yue shi-jun lei Yu-Xin Cui Qiang Yuan Key Laboratory of Dark Matter and Space Astronomy Purple Mountain Observatory Chinese Academy of Sciences School of Astronomy and Space Science University of Science and Technology of China

The Very Large Area gamma-ray Space Telescope （VLAST） is a mission concept proposed to detect gamma-ray photons through both Compton scattering and electron–positron pair production mechanisms, thus enabling the detection of photons with energies ranging from MeV to TeV. This project aims to conduct a comprehensive survey of the gamma-ray sky from a low-Earth orbit using an anti-coincidence detector, a tracker detector that also serves as a low-energy calorimeter, and a high-energy imaging calorimeter. We developed a Monte Carlo simulation application of the detector using the GEANT4 toolkit to evaluate the instrument performance, including the effective area, angular resolution, and energy resolution, and explored specific optimizations of the detector configuration. Our simulation-based analysis indicates that the current design of the VLAST is physically feasible, with an acceptance above 10 m2sr which is four times larger than that of the Fermi-LAT,an energy resolution better than 2% at 10 GeV, and an angular resolution better than 0.2° at 10 GeV. The VLAST project promises to make significant contributions to the field of gamma-ray astronomy and enhance our understanding of the cosmos.

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Nuclear Starburst Activity in the Seyfert 2 Galaxy NGC 2273

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Chinese Journal of Astronomy and Astrophysics 2003年第3期3卷 203-211页

作者： Qiu-Sheng Gu, lei shi, shi-jun lei, Wen-Hao Liu and Jie-Hao Huang Department of Astronomy, Nanjing University, Nanjing 210093 qsgu@*** Department of Astronomy Nanjing University

We present spectrophotometric results of the Seyfert 2 galaxy NGC 2273. Thepresence of high-order Balmer absorption lines (H8, H9, H10) and weak equivalent widths of CaII Kλ3933, CN λ4200, G-band λ4300 and MgIb λ5173 clearly indicate recent star-forming activity inthe nuclear region. Using a simple stellar population synthesis model, we find that for the bestfit, the contributions of a power-law featureless continuum, an intermediate-age (～ 10~8 yr) and anold (> 10~9 yr) stellar population to the total light at the reference normalization wavelength are10.0%, 33.4% and 56.6%, respectively. The existence of recent starburst activity is also consistentwith its high far-infrared luminosity (log L_(FIR.)/L☉ = 9.9), its infrared color indexes[α(25,60) = ― 1.81 and α(60,100) = ― 0.79, typical values for Seyfert galaxies withcircumnuclear starburst], and its q-value (2.23, ratio of infrared to radio flux, very similar tothat of normal spirals and starburst galaxies). Byrd et al. have suggested that NGC 2273 might haveinteracted with NGC 2273B in less than 10~9 yr ago, so the starburst activity in this galaxy couldhave been triggered by tidal interaction, as indicated in recent numerical simulations.

关键词： galaxies: seyfert galaxies: starburst galaxies: stellar content

The boresight alignment of the DArk Matter Particle Explorer

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Research in Astronomy and Astrophysics 2020年第6期20卷 223-228页

作者： Wei Jiang Xiang Li Kai-Kai Duan Zhao-Qiang Shen Zun-lei Xu Jing-Jing Zang shi-jun lei Qiang Yuan Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210023China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China University of Chinese Academy of Sciences Beijing 100049China

The DArk Matter Particle Explorer(DAMPE)can measureγ-rays in the energy range from a few GeV to about 10 *** direction of eachγ-ray photon is reconstructed in the DAMPE payload reference *** convert this to celestial coordinates,we require the celestial orientation of the payload system,which,however,may slightly deviate from that of the satellite system provided by the *** this paper,we adopt a maximum likelihood method and use theγ-rays centered around several bright point-like sources to measure and correct the angular deviations between the DAMPE payload and satellite system,the so-called"boresight alignment".We also check our method of boresight alignment for some sets of simulation data with artificial orientations and obtain consistent *** time-dependent boresight alignment analysis does not show evidence for significant variation of the parameters.

关键词： instrumentation detectors-gamma rays general-methods data

The orbital phase resolved spectroscopy of X-ray binary 4U 1822–371 with Suzaku

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Research in Astronomy and Astrophysics 2016年第4期16卷 37-46页

作者： Shu Niu Shu-Ping Yan shi-jun lei Michael A.Nowak Norbert S.Schulz Li Ji Purple Mountain Observatory Chinese Academy of SciencesNanjing 210008China MIT Kavli Institute for Astrophysics and Space Research CambridgeMA 02139USA

4U 1822-371 is a typical edge-on eclipsing low mass X-ray binary and the prototype of accre- tion disk coronal sources. We report on the results of a spectral analysis over the energy range 0.5-45 keV observed by Suzaku in 2006. We extract spectra from five orbital phases. The spectra can be equally well described by various previously proposed models： an optically thick model described by a partially cov- ered cutoff power law and an optically thin model described by a blackbody plus a cutoff power law. The optically thick model requires a covering fraction of about 55%, while the optically thin model requires a temperature of the central source of about 0.16 keV. The spectrum in the optically thick model also shows the previously detected cyclotron line feature at ~30 keV with the same Suzaku observation. This fea- ture confirms the presence of a strong magnetic field. The Fe Ks fluorescent line strengths as well as the detected Fe xxvI strengths are similar to previous Chandra and XMM-Newton detections in our phased spectral analysis; however, we also observe strong Fe xxvI during the eclipse, which indicates a slightly larger central corona.

关键词： accretion accretion disks -- binaries: eclipsing -- line: formation -- binaries: spectroscopic-- X-rays: binaries

Optimal gamma-ray selections for monochromatic line searches with DAMPE

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Frontiers of physics 2022年第3期17卷 1-6页

作者： Zun-lei Xu Kai-Kai Duan Wei Jiang shi-jun lei Xiang Li Zhao-Qiang Shen Tao Ma Meng Su Qiang Yuan Chuan Yue Yi-Zhong Fan Jin Chang Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210023China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China

The DArk Matter Particle Explorer (DAMPE) is a space high-energy cosmic-ray detector covering a wide energy band with a high energy resolution. One of the key scientific goals of DAMPE is to carry out indirect detection of dark matter by searching for high-energy gamma-ray line structure. To promote the sensitivity of gamma-ray line search with DAMPE, it is crucial to improve the acceptance and energy resolution of gamma-ray photons. In this paper, we quantitatively proved that the photon sample with the largest ratio of acceptance to energy resolution is optimal for line search. We therefore developed a line-search sample specifically optimized for the line-search. Meanwhile, in order to increase the statistics, we also selected the so-called BGO-only photons that convert into e^(+)e^(-) pairs only in the BGO calorimeter. The standard, the line-search, and the BGO-only photon samples are then tested for line-search individually and collectively. The results show that a significantly improved limit could be obtained from an appropriate combination of the date sets, and the increase is about 20% for the highest case compared with using the standard sample only.

关键词： DArk Matter Particle Explorer(DAMPE) gamma-ray line-search

A low-melting-point metal doping strategy for the synthesis of small-sized intermetallic Pt_(5)Ce fuel cell catalysts

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Nano Research 2024年第9期17卷 8112-8118页

作者： Zi-jun Zou shi-Yi Yin Yao Tang Sheng-Liang Zhong lei Wang shi-Long Xu Hai-Wei Liang College of Chemistry and Chemical Engineering Jiangxi Normal UniversityNanchang 330022China Department of Chemistry University of Science and Technology of ChinaHefei 230026China School of Materials and Chemical Engineering Anhui Jianzhu UniversityHefei 230601China

Carbon-supported platinum-lanthanum(Pt-Ln)intermetallic compound(IMC)nanoparticles with high activity and robust stability have been demonstrated as promising cathode catalysts for proton-exchange membrane fuel ***,the preparation of Pt-Ln IMC catalysts needs high-temperature annealing treatment that inevitably causes nanoparticle sintering,resulting in significant reduction of the electrochemical surface area and mass-based ***,we prepare small-sized M-doped Pt_(5)Ce(M=Ga,Cd,and Sb)IMCs catalysts via a low-melting-point metal doping *** speculate that the doping of low-melting-point metals can facilitate the generation of vacancies in the crystal lattice through thermal activation and thus reduce the kinetic barriers for the formation of intermetallic Pt_(5)Ce *** prepared Ga-doped Pt_(5)Ce catalyst exhibits a higher electrochemical active surface area(81 m^(2)·gPt^(-1))and a larger mass activity(0.45 A·mgPt^(-1)at 0.9 V)over the undoped Pt_(5)Ce and commercial Pt/C *** the membrane electrode assembly test,the Ga-doped Pt_(5)Ce cathode delivers a power density of 0.98 W·cm^(-2)at 0.67 V,along with a voltage loss of only 27 mV at 0.8 A·cm^(-2)at the end of accelerated stability test.

关键词： P5Ce low-melting-point metal small-sized intermetallic compound catalysis fuel cells

Effect of electrical parameters and slag system on macrostructure of electroslag ingot

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China Foundry 2024年第1期21卷 44-50页

作者： Bing-jie Wang Yu Wang Meng-jun Wang lei Zhao Li-zhong Chang Xiao-fang shi School of Metallurgy engineering Anhui University of TechnologyMa'anshan 243002AnhuiChina

To investigate the influence of electric parameters and slag system on the solidification quality of electroslag ingot during electroslag remelting,different power supply modes,current strengths and remelting slag systems were used to conduct electroslag remelting experiments on 304L austenitic stainless steel,and the macrostructure of electroslag ingots was *** results indicate that the depth of the metal pool decreases with the reduction of remelting frequency in the low frequency power supply *** effects of different power supply modes,such as low-frequency,direct current straight polarity(DCSP),and direct current reverse polarity(DCRP),on reducing the depth of the metal pool increase in that *** reducing the remelting current strength in the same power supply mode,the depth of metal pool is *** compared to the binary slag system of 70%CaF2+30%Al2O3,the ternary slag system of 60%CaF2+20%Al2O3+20%CaO is more effective in reducing the depth of the metal pool during *** the 60%CaF2+20%Al2O3+20%CaO ternary slag system results in a shallower and flatter metal pool,with columnar crystal growth occurring closer to the axial *** effect is observed for both low frequency and direct current(DC)power supply modes.

关键词： electroslag remelting frequency slag system solidification quality

Unveiling the Re,Cr,and I diffusion in saturated compacted bentonite using machine-learning methods

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Nuclear Science and Techniques 2024年第6期35卷 65-77页

作者： Zheng-Ye Feng jun-lei Tian Tao Wu Guo-jun Wei Zhi-Long Li Xiao-Qiong shi Yong-Jia Wang Qing-Feng Li Department of Engineering Huzhou UniversityHuzhou 313000China Institute of Theoretical Physics Shanxi UniversityTaiyuan 030006China College of Physics Science and Technology Shenyang Normal UniversityShenyang 110034China

The safety assessment of high-level radioactive waste repositories requires a high predictive accuracy for radionuclide diffusion and a comprehensive understanding of the diffusion *** this study,a through-diffusion method and six machine-learning methods were employed to investigate the diffusion of ReO_(4)^(−),HCrO_(4)^(−),and I−in saturated compacted bentonite under different salinities and compacted dry *** machine-learning models were trained using two *** dataset contained six input features and 293 instances obtained from the diffusion database system of the Japan Atomic Energy Agency(JAEA-DDB)and 15 *** other dataset,comprising 15,000 pseudo-instances,was produced using a multi-porosity model and contained eight input *** results indicate that the former dataset yielded a higher predictive accuracy than the *** gradient-boosting exhibited a higher prediction accuracy(R2=0.92)and lower error(MSE=0.01)than the other machine-learning *** addition,Shapley Additive Explanations,Feature Importance,and Partial Dependence Plot analysis results indicate that the rock capacity factor and compacted dry density had the two most significant effects on predicting the effective diffusion coefficient,thereby offering valuable insights.

关键词： Machine learning Effective diffusion coefficient Through-diffusion experiment Multi-porosity model Global analysis

A low-power Bluetooth-based wireless sensor network and its global confliction-solving impact localization method

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Chinese Journal of Aeronautics 2024年第1期37卷 153-161页

作者： Yuanjia WANG lei QIU Qiyun XU Liming shi College of Aerospace Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China Department of Electrical and Electronic Engineering University of EdinburghEdinburgh EH89YLUK

During the whole service lifetime of aircraft structures with composite materials,impacts are inevitable and can usually cause severe but barely visible *** the occurrences of impact are random and unpredictable,it is a hotspot direction to develop an online impact monitoring system that can meet strict limitations of aerospace applications including small size,light weight,and low power ***(PZT)sensor,being able to generate impact response signals with no external power and cover a large-scale structure with only a small amount of them,is a promising ***,for real systems,networks with multiple nodes are normally required to monitor large-scale structures in a global way to identify any impact localization confliction,yet the existing studies are mostly evaluated with single nodes instead of ***,in this paper,based on a new low-power node designed,a Bluetooth-based digital impact monitoring PZT sensor network is proposed for the first time with its global confliction-solving impact localization *** of the system as a network are researched and analyzed on a complex real aircraft wing box for a global confliction-solving impact localization,showing a satisfying high accuracy.

关键词： Bluetooth-based low-power design Confliction-solving evaluation Complex composites Piezoelectric sensors Wireless impact monitoring network