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Electronic structure and optical properties of Sn_(2x)Ga_(2(1-x))O_3 compounds

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Science China(Physics,Mechanics & Astronomy) 2011年第3期54卷 459-464页

作者： YAN JinLiang zhang yijun School of Physics Ludong University Yantai 264025 China

Band structure, density of states, electron density difference, and optical properties of intrinsic β-Ga2O3 and Sn2xGa2(1-x)O3 (x= 3.125%-6.25%) compounds are studied using first-principle calculations based on the density functional theory. The anisotropic optical properties are investigated by means of the complex dielectric function, which are explained by the selection rule of band-to-band transitions. All the calculation results indicate that the conductivity of Sn2xGa2(1-x)O3 is super to β-Ga2O3, and the calculated results consist with experiments that have been reported.

关键词： electronic structure optical properties β-Ga2O3 Sn2xGa2(1-x)O3 compounds

A Review of Atmospheric Electricity Research in China from 2011 to 2018

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Advances in Atmospheric Sciences 2019年第9期36卷 994-1014页

作者： Xiushu QIE yijun zhang Key Laboratory of Middle Atmosphere and Global Environment Observation Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Department of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences Fudan UniversityShanghai 200438China Collaborative Innovation Centre on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and TechnologyNanjing 210044China College of Earth and Planetary Science University of Chinese Academy of SciencesBeijing 100049China

Atmospheric electricity research has been conducted actively in China,having profited from the development and application of high temporal and spatial resolution lightning detection and location *** paper reviews the scientific advances made in the field of atmospheric electricity in China from 2011 to 2018,covering the following five aspects:(1)lightning detection and location techniques;(2)discharge processes and parameters associated with rocket-triggered lightning;(3)physical processes in natural lightning and attachment to the ground;(4)lightning activities and charge structure in different thunderstorms;and(5)effects of thunderstorms on the upper *** addition,some outstanding questions for future research are outlined.

关键词： atmospheric electricity lightning thunderstorm lightning location techniques

Application of Lightning Data Assimilation to Numerical Forecast of Super Typhoon Haiyan (2013)

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Journal of Meteorological Research 2020年第5期34卷 1052-1067页

作者： Rong zhang Wenjuan zhang yijun zhang Jianing FENG Liangtao XU State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesChina Meteorological Administration(CMA)Beijing 100081 Key Laboratory for Cloud Physics of CMA Chinese Academy of Meteorological SciencesCMABeijing 100081 Department of Atmospheric and Oceanic Sciences&Institute of Atmospheric Sciences Fudan UniversityShanghai 200438

Previous observations from World Wide Lightning Location Network(WWLLN) and satellites have shown that typhoon-related lightning data have a potential to improve the forecast of typhoon intensity. The current study was aimed at investigating whether assimilating TC lightning data in numerical models can play such a role. For the case of Super Typhoon Haiyan in 2013, the lightning data assimilation(LDA) was realized in the Weather Research and Forecasting(WRF) model, and the impact of LDA on numerical prediction of Haiyan’s intensity was *** data from WWLLN were used to adjust the model’s relative humidity(RH) based on the method developed by Dixon et al.(2016). The adjusted RH was output as a pseudo sounding observation, which was then assimilated into the WRF system by using the three-dimensional variational(3DVAR) method in the cycling mode at 1-h intervals. Sensitivity experiments showed that, for Super Typhoon Haiyan(2013), which was characterized by a high proportion of the inner-core(within 100 km from the typhoon center) lightning, assimilation of the inner-core lightning data significantly improved its intensity forecast, while assimilation of the lightning data in the rainbands(100–500 km from the typhoon center) led to no obvious improvement. The improvement became more evident with the increase in LDA cycles, and at least three or four LDA cycles were needed to achieve obvious intensity forecast improvement. Overall, the improvement in the intensity forecast by assimilation of the inner-core lightning data could be maintained for about 48 h. However, it should be noted that the LDA method in this study may have a negative effect when the simulated typhoon is stronger than the observed, since the LDA method cannot suppress the spurious convection.

关键词： lightning three-dimensional variational(3DVAR)data assimilation Typhoon Haiyan typhoon intensity

Hawking Evaporation for the 2+1 Dimensional Radiating Black Hole

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Chinese Physics Letters 1995年第7期12卷 446-448页

作者： CAI Ronggen zhang yijun SU Rukeng Department of Physics Fudan UniversityShanghai 200433 CCAST(World Laboratory) P.O.Box 8730Beijing 100080

By using a metric which is a counterpart of four dimensional Vaidya metric,we have investigated the Hawking evaporation of the 2+1 dimensional radiating black *** Hawking temperature of this radiating black hole is **... 详细信息

关键词： Hawking black radiating

Assimilation of Total Lightning Data Using the Three-Dimensional Variational Method at Convection-Allowing Resolution

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Journal of Meteorological Research 2017年第4期31卷 731-746页

作者： Rong zhang yijun zhang Liangtao XU Dong ZHENG Wen YAO State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081 College of Earth Sciences University of Chinese Academy of Sciences Beijing 100049 Laboratory of Lightning Physics and Protection Engineering Chinese Academy of Meteorological Sciences Beijing 100081

A large number of observational analyses have shown that lightning data can be used to indicate areas of deep convection. It is important to assimilate observed lightning data into numerical models, so that more small-scale information can be incorporated to improve the quality of the initial condition and the subsequent forecasts. In this study, the empirical relationship between flash rate, water vapor mixing ratio, and graupel mixing ratio was used to adjust the model relative humidity, which was then assimilated by using the three-dimensional variational data assimilation system of the Weather Research and Forecasting model in cycling mode at 10-min intervals. To find the appropriate assimilation time-window length that yielded significant improvement in both the initial conditions and subsequent forecasts, four experiments with different assimilation time-window lengths were conducted for a squall line case that occurred on 10 July 2007 in North China. It was found that 60 min was the appropriate assimilation time-window length for this case, and longer assimilation window length was unnecessary since no further improvement was present. Forecasts of 1-h accumulated precipitation during the assimilation period and the subsequent 3-h accumulated precipitation were significantly improved compared with the control experiment without lightning data assimilation. The simulated reflectivity was optimal after 30 min of the forecast, it remained optimal during the following 42 min, and the positive effect from lightning data assimilation began to diminish after 72 min of the forecast. Overall,the improvement from lightning data assimilation can be maintained for about 3 h.

关键词： lightning data assimilation three-dimensional variational (3DVAR) method Wether Research and Forecasting (WRF) model

First-principles study on electronic structure and optical properties of N-doped P-type β-Ga_2O_3

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Science China(Physics,Mechanics & Astronomy) 2012年第1期55卷 19-24页

作者： zhang LiYing YAN JinLiang zhang yijun LI Ting DING XingWei School of Physics Ludong University Yantai 264025 China

The band structure, density of states, electron density difference and optical properties of intrinsic β-Ga2O3 and N-doped β-Ga2O3 were calculated using first-principles based on density functional theory. After N doping, the band gap decreases, shallow acceptor impurity levels are introduced over the top of the valence band and the absorption band edge is slightly red-shifted compared to that of the intrinsic one. The anisotropic optical properties are investigated by means of the complex dielectric function, which are explained by the selection rule of the band-to-band transitions. All calculation results indicate that N-doping is a very promising method to get P-type β-Ga2O3.

关键词： P-type β-Ga2O3 N-doped β-Ga2O3 first-principles electronic structure optical properties

Semantic-Oriented Sentiment Classification for Chinese Product Reviews: An Experimental Study of Book and Cell Phone Reviews

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Tsinghua Science and Technology 2005年第Z1期10卷 797-802页

作者： YE Qiang LI yijun zhang Yiwen School of Management Harbin Institute of Technology Harbin 150001 China School of Management Harbin Institute of Technology Harbin 150001 China Department of Management Information Systems University of Arizona Tucson 85705 U.S.A.

Sentiment classification is an automatic opinion classification method to classify the product reviews on web into positive or negative opinions to help consumers or sellers to understand the opinions and evaluations from existing customers. Semantic-oriented approach is one of the recent developments in sentiment classification. Up to now, most research of sentiment classification is on English reviews,and little work has been done on Chinese reviews using sentiment classification. The detailed techniques used in English review cannot be applied directly to Chinese reviews due to the different characteristics between these two languages. This study modified and improved the semantic-oriented approach to a 6-step process for Chinese review, focusing on the modification and improvement on the text segmentation and reference words pairs (RWPs) identification. Two experiments were conducted on book reviews and cell phone reviews. The results show that the performances of the proposed approach are comparable to those of the existing English reviews classification studies.

关键词： sentiment classification Chinese customer reviews books cell phones semantic orientation

Catalytic synthesis of acetals and ketals with H3PW12O40/PAn

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Rare Metals 2008年第1期27卷 89-94页

作者： YANG Shuijin zhang yijun DU Xinxian Philippe G. Merle Hubei Key Laboratory of Bioanalytical Technique Department of Chemistry and Environmental Engineering Hubei Normal University Huangshi 435002 China Department of Chemistry and Biochemistry Concordia University Montreal H4B 1R6 Canada

A new environmental friendly catalyst H3PW12O40/PAn was prepared and identified by means of FT-IR,XRD,and TG/*** optimum conditions have been found;that is,the mass ratio of PAn to H3PW12O40 is 1：1.5,the volume of methanol is 20 mL,and the reflux reaction time is 3 *** structural identity of Keggin units is preserved after the incorporation into polyaniline *** activities of H3PW12O40/PAn in synthesizing 2-methyl-2-ethoxycarbonylmethyl-1,3-dioxolane,2,4-dimethyl-2-ethoxycarbonylmethyl-1,3-dioxolane,cyclohexanone ethylene ketal,cyclohexanone 1,2-propanediol ketal,butanone ethylene ketal,butanone 1,2-propanediol ketal,2-phenyl-1,3-dioxolane,4-methyl-2-phenyl-1,3-dioxolane,2-propyl-1,3-dioxolane,and 4-methyl-2-propyl-1,3-dioxolane were *** has been demon-strated that H3PW12O40/PAn is an excellent *** factors concerned in these reactions were *** optimum conditions are as follows：the molar ratio of aldehyde/ketone to glycol（r） is 1：1.5,the mass ratio of the catalyst used to the reactants is 0.6%,and the reaction time is 1.0 *** these conditions,the yield is as follows：2-methyl-2-ethoxycarbonylmethyl-1,3-dioxolane,69.0%;2,4-dimethyl-2-ethoxycarbonylmethyl-1,3-dioxolane,79.5%;cyclohexanone ethylene ketal,78.9%;cyclohexanone 1,2-propanediol ketal,85.3%;butanone ethylene ketal,56.9%;butanone 1,2-propanediol ketal,78.1%;2-phenyl-1,3-dioxolane,76.3%;4-methyl-2-phenyl-1,3-dioxolane,94.2%;2-propyl-1,3-dioxolane,70.7%;and 4-methyl-2-propyl-1,3-dioxolane,79.2%.

关键词： phosphotungstic acid acetal ketal polyaniline catalysis

Analysis of the Spectral Characteristics of Triggered Lightning

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Advances in Atmospheric Sciences 2019年第11期36卷 1265-1272页

作者： Huaming zhang yijun zhang Weitao LYU Yang zhang Qi QI Yanfeng FAN Institute Laboratory of Lightning Physics and Protection Engineering State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081 China Institute of Atmospheric Sciences Fudan University Shanghai 200439 China Meteorological Disaster Prevention Technology Center of Shanxi Province Taiyuan 030002 China

The spectra with wavelength range of 390 nm to 660 nm of triggered lightning were observed in Guangdong Area using a slitless spectrograph. The characteristics of the lightning spectra during the initial continuous current and return strokes were analyzed, and the differences between the metal section and air section of the lightning channel were compared. The results showed that the metal spectra were contained in the metal section during the initial continuous current. As for the lightning channel of the return strokes, the line spectra for both the metal section and the air section were identical;neither of the two sections contained the metal spectra, but the relative intensity of its emission spectrum was different. Owing to different radiation mechanisms, the spectral structures and luminance of the two sections were not the same. Combined with the current data, it was found that there was a good positive correlation between the total spectral strength and the transferred charge. The total intensity of the lightning channel spectrum increased with the height of the channel, indicating that the radiation sequence of the lightning channel was different. High temporal resolution observations showed that the spectral line duration could be divided into three categories, in which the lines with higher excitation energy appear first and decay rapidly, while those with lower excitation energy appear later but last longer.

关键词： triggered lightning lightning spectra metal channel air channel current