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| 1 | Impervious surface extraction based on different methods from multiple spatial resolution images:a comprehensive comparison显示文摘Many efforts have been devoted to extracting impervious surfaces based on different methods from multiple spatial resolution images.Differences in extraction methods and spatial resolutions are significant and have led to discrepant performances in terms of the impervious surface extraction accuracy.However,which extraction method is more suitable for which kind of spatial resolution image in practice is poorly understood.This study systematically compared the performances of 12 methods of impervious surface extraction for four spatial resolution images(i.e.Landsat 8[30 m],Sentinel-2A[20 m],Sentinel-2A[10 m],and Gaofen-2[4 m])in three testing areas.The results indicated that for the mediumspatial resolutions of 30 and 20 m,the support vector machine(SVM)method was considered as the optimal classification method with the highest accuracy of impervious surface extraction.For the high-spatial resolutions of 10 and 4 m,the object based image analysis(OBIA)method obtained the highest accuracy of the impervious surface distribution.Furthermore,the perpendicular impervious surface index(PISI)outperformed the other indices in obtaining the impervious surface distribution,with the highest accuracy for four spatial resolution images.These comprehensive assessments can provide a valuable guidance for future impervious surface extraction from different spatial resolutions. | Shanshan Feng Fenglei Fan | 2021 | International Journal of Digital Earth2021，14，9： | 4 |
| 2 | Exploration of spatial and temporal characteristics of PM2.5 concentration in Guangzhou, China using wavelet analysis and modified land use regression model显示文摘This article attempts to detail time series characteristics of PM2.5 concentration in Guangzhou(China)from 1 June 2012 to 31 May 2013 based on wavelet analysis tools,and discuss its spatial distribution using geographic information system software and a modified land use regression model.In this modified model,an important variable(land use data)is substituted for impervious surface area,which can be obtained conveniently from remote sensing imagery through the linear spectral mixture analysis method.Impervious surface has higher precision than land use data because of its sub-pixel level.Seasonal concentration pattern and day-by-day change feature of PM2.5 in Guangzhou with a micro-perspective are discussed and understood.Results include:(1)the highest concentration of PM2.5 occurs in October and the lowest in July,respectively;(2)average concentration of PM2.5 in winter is higher than in other seasons;and(3)there are two high concentration zones in winter and one zone in spring. | Fenglei Fan Runping Liu | 2018 | Geo-Spatial Information Science2018，21，4： | 2 |
| 3 | Temporal and spatial change detecting (1998–2003) and predicting of land use and land cover in Core corridor of Pearl River Delta (China) by using TM and ETM+ images显示文摘 | Fenglei Fan Yunpeng Wang Zhishi Wang | 2008 | Environmental Monitoring and Assessment (-)2008，，1： | 1 |
| 4 | Land use and land cover change in GangZhou China from 1998 to2003 based on landsat TM/ETM+ imagery显示文摘 | FAN Fenglei WENG Qihao WANG Yunpeng | 2007 | Sensors2007，7，7： | 1 |
| 5 | Research on the quasi-isentropic driving model of aluminized explosives in the detonation wave propagation direction显示文摘Taking CL-20(Hexanitrohexaazaisowurtzitane)-based aluminized explosives with high gurney energy as the research object, this research experimentally investigates the work capability of different aluminized explosive formulations when driving metal flyer plates in the denotation wave propagation direction.The research results showed that the formulations with 43 μm aluminum(Al) powder particles(The particle sizes of Al powder were in the range of 2~43 μm) exhibited the optimal performance in driving flyer plates along the denotation wave propagation direction. Compared to the formulations with Al powder 13 μm, the formulations with Al powder 2 μm delivered better performance in accelerating metal flyer plates in the early stage, which, however, turned to be poor in the later stage. The CL-20-based explosives containing 25% Al far under-performed those containing 15% Al. Based on the proposed quasi-isentropic hypothesis, relevant isentropy theories, and the functional relationship between detonation parameters and entropy as well as Al reaction degree, the characteristic lines of aluminized explosives in accelerating flyer plates were theoretically studied, a quasi-isentropic theoretical model for the aluminized explosive driving the flyer plate was built and the calculation methods for the variations of flyer plate velocity, Al reaction degree, and detonation product parameters with time and axial positions were developed. The theoretical model built is verified by the experimental results of the CL-20-based aluminized explosive driving flyer plate. It was found that the model built could accurately calculate the variations of flyer plate velocity and Al reaction degree over time. In addition, how physical parameters including detonation product pressure and temperature varied with time and axial positions was identified. The action time of the positive pressure after the detonation of aluminized explosives was found prolonged and the downtrend of the temperature was slowed down and even reversed to a slight rise due to the aftereffect reaction between the Al powder and the detonation products. | Hongfu Wang Yan Liu Fan Bai Chao He Yingliang Xu Qiang Zhou Chuan Xiao Fenglei Huang | 2024 | Defence Technology(防务技术)2024，32，2： | 0 |
| 6 | Experimental and numerical analyses of the effect of fibre content on the close-in blast performance of a UHPFRC beam显示文摘Limited research has been conducted on the influences of fiber content on close-in blasting characteristics for ultrahigh-performance fiber-reinforced concrete(UHPFRC)beams.This paper aims to address this knowledge gap through experimental and mesoscale numerical methods.Experiments were conducted on ten UHPFRC beams built with varying steel fiber volumetric fractions subjected to close-in explosive conditions.Additionally,this study considered other parameters,such as the longitudinal reinforcement type and ratio.In the case of UHPFRC beams featuring normal-strength longitudinal reinforcement of diametersΦ12,Φ16,andΦ20,a reduction in maximum displacement by magnitudes of19.6%,19.5%,and 17.4%was observed,respectively,as the volumetric fractions of fiber increased from1.0%to 2.5%.In addition,increasing the longitudinal reinforcement ratio and using high-strength steel longitudinal reinforcement both significantly reduced the deformation characteristics and increase the blasting resistances of UHPFRC beams.However,the effects on the local crushing and spalling damage were not significant.A mesoscale finite element model,which considers the impacts of fiber parameters on UHPFRC beam behaviors,was also established and well correlated with the test findings.Nevertheless,parametric analyses were further conducted to examine the impacts of the steel fiber content and length and the hybrid effects of various types of microfibers and steel fibers on the blasting performance of UHPFRC beams. | Junbo Yan Qiyue Zhang Yan Liu Yingliang Xu Zhenqing Shi Fan Bai Fenglei Huang | 2024 | Defence Technology(防务技术)2024，31，1： | 0 |
| 7 | Analysis on Torque-angle Characteristic of Special Motor for CFR600 Safety Rod Drive Mechanism显示文摘CFR600safety rod drive mechanism is driving device powered by mechanical,which turns rotational movement into up-and-down movement of movable body through driving chain.The special motor is not only power supplier,but also one of the key components for safety rod drive mechanism. | XIA Fan JIN Fenglei | 2017 | Annual Report of China Institute of Atomic Energy2017，，1： | 0 |
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