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Discussion on the geometric factor in the detection of high energy electrons in geospace

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Science China(Technological Sciences) 2008年第1期51卷 1-9页

作者： chen hongfei SHI WeiHong ZOU Hong ZOU JiQing Institute of Space Physics and Applied Technology School of Earth and Space SciencesPeking UniversityBeijing 100871China

High energy electron is a kind of sources to be detected in the geospace environ- ment. Generally, the particle telescope with much thick semiconductor detector is used as the sensor for energetic electrons because they can penetrate deeply into the detector. The more energy of the electrons is, the deeper they can penetrate into, so that the geometric factor varies with energy of the incident electrons. We discuss the geometric factor of particle radiation detector (PRD), which is a payload on ZY-1 (CBERS-1 and CBERS-2) satellites to monitor the high energy particle ra- diation inside the satellites. According to the NASA’s AE8 model, the geometric factors of electrons for the low energy bin (0.5―1.0 MeV) and the high energy bin (> 2.0 MeV) are 2.468 and 1.736 cm2·sr, respectively. These results are much differ- ent from the traditional calculation of the geometric factor that is 1.18 cm2·sr. The angle-response function of the telescope is also derived, which can be useful for design of the telescope and analysis of the directional distribution.

关键词： geometric factor high energy electrons particle radiation space exploration

Oxidation behavior of Hf-modified platinum aluminide coatings during thermal cycling

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Progress in Natural Science:Materials International 2018年第1期28卷 34-39页

作者： Liya Ye hongfei chen Guang Yang Bin Liu Yanfeng Gao School of Materials Science and Engineering Shanghai University Huaiyin Institute of Technology

Platinum aluminide coatings with different Hf contents were fabricated by using HfCl;. The oxidation kinetics and the rumpling behavior of oxide scale were investigated. After thermal cycling, the coating with 0.46 wt% Hf showed least weight gain. With the increase of Hf content, rumpling extent of the scale decreased. Meanwhile, HfO;preferentially formed in the scale resulting in the increase of scale thickness. The oxidation of excessive Hf even caused the spallation of the scale. The results in the present study indicate that although Hf plays an important role in decreasing rumpling extent of TGO, the oxidation of Hf decreases the adhesion of the scale.

关键词： Pt-Al coating Hf Oxidation Rumpling

Estimating Influence of Crystallizing Latent Heat on Cooling-Crystallizing Process of a Granitic Melt and Its Geological Implications

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Acta Geologica Sinica(English Edition) 2008年第2期82卷 438-443页

作者： ZHANG Bangtong WU Junqi LING hongfei chen Peirong State Key Laboratory for Mineral Deposits Research and Department of Earth Sciences Nanjing University Nanjing 210093 China

Based on the theory of thermal conductivity, in this paper we derived a formula to estimate the prolongation period （AtL） of cooling-crystallization process of a granitic melt caused by latent heat of crystallization as follows：△tL=QL×△tcol/（TM-TC）×CP where TM is initial temperature of the granite melt, Tc crystallization temperature of the granite melt, Cp specific heat, △tcol cooling period of a granite melt from its initial temperature （TM） to its crystallization temperature （Tc）, QL latent heat of the granite melt. The cooling period of the melt for the Fanshan granodiorite from its initial temperature （900℃） to crystallization temperature （600℃） could be estimated -210,000 years if latent heat was not considered. Calculation for the Fanshan melt using the above formula yields a AtL value of -190,000 years, which implies that the actual cooling period within the temperature range of 900°-600℃ should be 400,000 years. This demonstrates that the latent heat produced from crystallization of the granitic melt is a key factor influencing the cooling-crystallization process of a granitic melt, prolongating the period of crystallization and resulting in the large emplacement-crystallization time difference （ECTD） in granite batholith.

关键词： granitic melt latent heat of crystallization Beijing Fanshan granodiorite cooling-crystallization process

Normal Reference Value of Red Blood Cell Count of Chinese Presenile Men and Geographical Factors

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Chinese Geographical Science 2007年第1期17卷 92-98页

作者： HE Jinwei GE Miao SU Huimin LIANG Wei chen hongfei Department of Geography Shaanxi Normal University Xi＇ an 710062 China

This paper aims at providing a scientific basis for unifying the normal reference value standards of red blood cell count of Chinese presenile men. The paper, using microscopical counting method, studies the relationship between the normal reference values of 38,061 samples of red blood cell count of presenile men and eight geographical factors in 297 units in China. It is found that the correlation of geographical factors and the normal reference value of red blood cell count of presenile men is quite significant （F=303.00, P=-0.000）. By using the method of stepwise regression analysis, one regression equation is inferred. It is concluded that if geographical data are obtained in a certain area, the normal reference value of red blood cell count of presenile men in this area can be reckoned by using the regression analysis. Furthermore, according to the geographical factors, China can be divided into eight regions： Northeast China Region, North China Region, Shanxi-Shaanxi-Irmer Mongolia Region, Middle and Lower Reaches of the Changjiang River Region, Southeast China Region, Northwest China Region, Southwest China Region and Qinghai-Tibet Plateau Region.

关键词： red blood cell count normal reference value geographical factors regression analysis

Analysis of the internal charging data in medium earth orbit with numerical simulation and ground experiment

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Science China(Technological Sciences) 2022年第4期65卷 977-986页

作者： SONG SiYu chen hongfei YU XiangQian ZOU Hong ZONG QiuGang chen Ao SHI WeiHong YE YuGuang Institute of Space Physics and Applied Technology School of Earth and Space SciencesPeking UniversityBeijing 100871China

The deep dielectric charging effect monitor(DDCEM)has been designed to study the internal charging effect by measuring the charging currents and potentials inside the *** is equipped on three Chinese navigation satellites in a circular medium earth orbit(MEO)with 22000 km average height and 55°*** simulation based on the Geant4-RIC method was used to evaluate the data of *** data during May to November 2019 on one of the three satellites show that the charging currents of DDCEM were negatively enhanced when the satellite moved into the outer radiation *** currents reached the negative maximum during a significant electron enhancement in September *** currents were also detected besides negative currents that were caused by the deposition of electrons in the *** causation of positive currents in the space environment may be that the low-energy electrons cannot penetrate the satellite skin and make it charging to negative potential,the reference ground of DDCEM that is connected to the satellite skin drops below zero by the low-energy electrons so that the output currents turn to *** experiment was used to simulate the causation of positive currents and the result verified our theory.

关键词： deep dielectric charging effect monitor internal charging effect charging currents and potentials medium earth orbit space environment

Investigation of electrons inside the satellite by the Geant4 simulation

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Science China(Technological Sciences) 2011年第9期54卷 2271-2275页

作者： LI XiaoCan chen hongfei HAO YongQiang ZOU Hong SHI WeiHong Institute of Space Physics and Applied Technology School of Earth and Space Sciences Peking University Beijing 100871 China

The measurement of the electron radiation inside the satellite is important for engineering and space environment *** particle radiation detectors (PRD) on board CBERS-1 and CBERS-2 made great contribution to understanding of the space ***,what is the radiation relationship between inside and outside the satellite? The Monte Carlo simula-tion with Geant4 was implemented to study the *** boundaries of the energy bins of 0.5 and 2 MeV were precisely corresponding to outside energies of 0.99 and 2.52 MeV,*** the changes of the energy bins,the fluxes inside were smaller than those of the corresponding bins *** spectrum inside the satellite was harder than that *** indicator was that the flux ratio of the high energy bin to the low energy bin increased more than 20% from outside to *** geometric factor (GF) relates to the incident energy of *** using the AE-8 model to derive the incident spec-trum,the GFs of the low and high energy bins were 1.15 and 0.70 cm2 sr,*** of the low energy bin was larger than that of the high energy *** they were both smaller than the previous *** was due to the scattering,straggle and shielding effects.

关键词： electron radiation in satellite electron detector Monte Carlo simulation Geant4

Anti-proton contamination design of the imaging energetic electron spectrometer based on Geant4 simulation

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Science China(Technological Sciences) 2015年第8期58卷 1385-1391页

作者： LUO Lin ZOU Hong ZONG QiuGang WANG LingHua chen hongfei SHI WeiHong YU XiangQian Institute of Space Physics and Applied Technology School of Earth and Space SciencePeking University

The measurement of energetic particles plays an important role in the space environment monitoring and space weather *** accuracy of the energetic electron measurement is seriously influenced by the proton *** anti-proton contamination design for the sensor of imaging energetic electron spectrometer is introduced in this *** to the electron and proton spectrum on the typical satellite orbits calculated by the radiation belt models,the efficiency of the anti-proton contamination design is estimated by the Geant4 simulation and the design is optimized based on the simulation results.

关键词： energetic particle measurement imaging energetic electron spectrometer anti-proton design Geant4 simulation

An analysis of the correlation between the fluxes of high-energy electrons and low-middle-energy electrons in the magnetosphere

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Science China(Technological Sciences) 2016年第7期59卷 1130-1136页

作者： LI chenFang ZOU Hong ZONG QiuGang JIA XiangHong chen hongfei SHI WeiHong YU XiangQian Institute of Space Physics and Applied Technology School of Earth and Space Science Peking University State Key Laboratory of Space Medicine Fundamentals and Application Chinese Astronaut Research and Training Center

The variation of the flux of energetic electrons in the magnetosphere has been proven to be strongly related to the solar wind speed. Observations of GEO orbit show that the flux of low-energy electrons is not only modulated by the solar wind speed, but, if a time delay is added, is also positively correlated to the flux of high-energy electrons. This feature provides a possible method to forecast the flux of high-energy electrons in GEO orbit. In this study, the correlations of the fluxes between the high-energy electrons and low-middle-energy electrons obtained at different L values and in different orbits are investigated to develop the application of this feature. Based on the analysis of long–term data observed by NOAA POES and GOES, the correlations between the fluxes of high-energy electrons and low–middle–energy electrons are good enough at different L values and in different orbits in quiet time, but this correlation is strongly affected by CME–driven geomagnetic storms.

关键词： magnetosphere high-energy electrons low-middle energy electrons forecast model

Native point defects and oxygen migration of rare earth zirconate and stannate pyrochlores

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Journal of Materials Science & Technology 2021年第14期73卷 23-30页

作者： Juanli Zhao Yuchen Liu Yun Fan Wei Zhang chengguan Zhang Guang Yang hongfei chen Bin Liu School of Materials Science and Engineering Shanghai UniversityShanghai200444China

Various excellent properties of rare earth zirconate and stannate pyrochlores are close related with their native point ***-principles calculations are performed to systematically investigate the point defect mechanism and the oxygen diffusion behavior of A_(2)B_(2)O_(7)(A=La,Ce,Pr,Nd,Pm,Sm,Eu,Gd;B=Zr,Sn).The possible defect complexes and their associated reactions under stoichiometric and nonstoichiometric conditions are *** O Frenkel pairs are the most stable defect structure in stoichiometric zirconates,whereas the cation antisite defects are the predominant one in stoichiometric *** the case of BO_(2) excess zirconates and stannates,the BA cation antisite defect with the A vacancy and/or the oxygen interstitial is energetically favorable,whereas the ABantisite defect together with the oxygen vacancy and/or the A interstitial is preferable under the A_(2)O_(3) excess ***,the maximum point defect concentrations of zirconates are much higher than those of ***,the oxygen migration barriers are similar in these compounds,ranging in 0.68 eV–0.80 *** predicted point defects and oxygen diffusion mechanisms play the critical role in their engineering applications and are expected to guide the future property improvement of pyrochlores through the control of point defects and/or composition.

关键词： Density-functional theory Pyrochlore Defect Migration Formation energies