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Cavity flow regime for spillway aerators

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Science China(Technological Sciences) 2013年第4期56卷 818-823页

作者： WU JianHua ma fei College of Water Conservancy and Hydropower Engineering Hohai University

It is well known that the effect of air entrainment for cavitation damage controls is related not only to the air discharge into aerator devices but also the flow regime of the cavity below *** the basis of the hydraulic characteristics of the flow,the aerator devices were for the first time *** theoretical considerations were performed about the jet length and cavity flow regime with the influencing *** with the behavior of the flow through the aerator of discharge tunnels,the flow regimes of the cavity below spillway aerators were experimentally investigated,and the empirical expressions were presented to identify the conversions of the cavity flow regimes,including fully filled cavity,partially filled cavity,and net air *** issues of the design of the aerator devices were suggested in the present work.

关键词： aerator air entrainment cavity discharge tunnel flow regime spillway

FLOW REGIMES BELOW AERATORS FOR DISCHARGE TUNNELS

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Journal of Hydrodynamics 2012年第3期24卷 378-382页

作者： ma fei WU Jian-hua College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 China

The flow regimes below an aerator influence directly the air entrainment and the cavitation damage control. Based on the theoretical considerations, the experiments of the aerator for a discharge tunnel were conducted, and the relationships between the flow regime and hydraulic and geometric parameters were investigated. The results showed that, there are two kinds of threshold values for the flow regime conversions. One is Fr1-2 standing for the conversion from the fully filled cavity to the partially filled cavity, and the other is Fr2-3 which shows the change from the partially filled cavity to the net air cavity. Two empirical expressions were obtained for the conversions of the flow regimes, which can be used in the designs of the aerators.

关键词： aerator discharge tunnel flow regime filling water jet length

Spatial-temporal dynamics of alpine grassland coverage and its response to climate warming in *** Nature Preserve during 2000-2019

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Journal of Mountain Science 2022年第8期19卷 2297-2311页

作者： ma fei PENG Pei-hao College of Earth Sciences Chengdu University of TechnologyChengdu 610059China

The Qinghai-Tibet Plateau(QTP)has the largest and highest alpine grassland ecosystem in the world,which is considered to be the most sensitive and vulnerable ecosystem to climate *** dynamic changes and driving mechanism have always been widely *** Qomolangma National Nature Preserve(QNNP),with the largest altitude difference in the world,was selected as the study area to analyse the spatial-temporal dynamics of grassland coverage and the different characteristics of elevation gradients at the southern slope(SS)and northern slope(NS)with MODIS MOD13Q1 NDVI and MOD11A2 land surface temperature data from 2000to 2019 using the mann-Kendall trend test and Theil-Sen slope ***,the response mechanism of grassland coverage to climate warming is *** results revealed that from 2000 to 2019,the grassland coverage change in the study area is mainly *** increased area proportion of grassland coverage on the southern slope is significantly higher than that on the northern slope,and the decreased area proportion of grassland coverage on the northern slope is significantly greater than that on the southern *** change characteristics of grassland coverage in the QNNP exhibit an obvious elevation gradient;the higher the elevation,the greater the increased area proportion of grassland coverage,particularly on the *** land surface temperature can be used as a proxy for analysing the temporal and spatial variation trends of air temperature in the *** the increase of the altitude,the land surface temperature rise rate on both the southern slope and northern slope exhibited an increasing trend,and the sensitivity of grassland coverage to temperature rise was higher on the northern *** water condition was the decisive factor for the horizontal and vertical spatial heterogeneity of the dynamic change of grassland coverage,and the melting of glaciers and thawing of permafrost were important sources of water for grassland gro

关键词： Alpine grassland Global warming Vegetation dynamic Elevation gradient Qomolangma

Hydraulic characteristics of stepped spillway dropshafts

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Science China(Technological Sciences) 2019年第5期62卷 868-874页

作者： SHEN JieYi WU JianHua ma fei College of Water Conservancy and Hydropower Engineering Hohai University

Nowadays, "Sponge Cities" are being built to provide a valid solution to the glaring drainage problems in the urban areas of China. The hydraulics of a dropshaft, especially discharge capacity, energy dissipation and cavitation damage control, evidently affect its safety and the city's underground tunnel system, due to the high dropshaft and large discharge. The hydraulic characteristics of stepped spillway dropshafts are experimentally investigated for the variable step rotation angles and end sill heights. Flow regimes inside the dropshafts are classified under the different approach flow discharges. The results illustrate that there is high energy dissipation in the present dropshafts with the stepped spillway and the cavitation damage could be effectively avoided thanks to the effect of the air entrainment to the flow.

关键词： dropshaft end sill height hydraulic characteristics step rotation angle stepped spillway

Hierarchical Feature-Based Detection Method for SAR Targets Under Complex Environment

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Chinese Journal of Electronics 2017年第3期26卷 647-653页

作者： GAO fei ma fei LUO Xiling WANG Jun SUN Jinping School of Electronic and Information Engineering Beihang University

A reliable target detection method for Synthetic aperture radar(SAR)images is needed urgently with the wide application of SAR *** performance of conventional detection algorithms,such as Constant false alarm rate(CFAR),degrade significantly in low SCR or complex regions while the Human visual system(HVS)can identify targets of interest without knowing characteristics of the background even in complicated *** combination of HVS with the SAR-ATR system may effectively achieve real-time multi-target detection in complex occlusion scenes.A new effective target detection algorithm is put forward using hierarchical characteristics of *** by different roles of the retina and visual cortex in the HVS,this detection algorithm is divided into coarse detection and fine detection *** kinds of features based on the correlation between target features and suspicious targets,namely overall feature and refined feature,are used in these two stages respectively to extract real *** results verify its correctness and effectiveness in complex environment.

关键词： Synthetic aperture radar(SAR) Targets detection Human visual system(HVS) Complex background Hierarchical model and X(HmaX)

A study on comprehensive recycling of waste diamond tools

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Rare Metals 2012年第1期31卷 88-91页

作者： Wang, Limin Zhang, Guocheng ma, fei General Research Institute for Nonferrous Metals Beijing 100088 China General Research Institute for Powder Metals Advanced Materials Co. Ltd Beijing 101407 China

This article puts forward a new method of recycling materials in diamond tools comprehensively and efficiently by means of analyzing and summarizing various methods of recycling waste diamond *** the waste diamond tools were decomposed in a mixed acid,metals contained in it went into solution in their ionic forms,while diamond and tungsten carbide particles formed into residues to be *** amounts of metal ions in the leaching solution were adjusted according to the contents of metals in the diamond tools;then,the leaching solution was co-precipitated using oxalic acid as precipitation agent,and ammonia water was added to adjust the pH value of the oxalic *** the right conditions,the comprehensive precipitation rate of metals reached above 98%.Finally,ultrafine pre-alloy powder was obtained by hydrogen reduction of oxalate.

关键词： diamond tools leaching co-precipitation hydrogen reduction

Reference direction based immune clone algorithm for many-objective optimization

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Frontiers of Computer Science 2014年第4期8卷 642-655页

作者： Ruochen LIU Chenlin ma fei HE Wenping ma Licheng JIAO Key Laboratory of Intelligent Perception and Image Understanding of Ministry of Education International Research Center for Intelligent Perception and Computation Xidian University Xi'an 710071 China

In this paper, a new preference multi-objective optimization algorithm called immune clone algorithm based on reference direction method （RD-ICA） is proposed for solving many-objective optimization problems. First, an intelligent recombination operator, which performs well on the functions comprising many parameters, is introduced into an immune clone algorithm so as to explore the potentially excellent gene segments of all individuals in the antibody pop- ulation. Second, a reference direction method, a very strict ranking based on the desire of decision makers （DMs）, is used to guide selection and clone of the active population. Then a light beam search （LBS） is borrowed to pick out a small set of individuals filling the external population. The proposed method has been extensively compared with other recently proposed evolutionary multi-objective optimization （EMO） approaches over DTLZ problems with from 4 to 100 objectives. Experimental results indicate RD-ICA can achieve competitive results.

关键词： many-objective optimization preference multiobjective optimization artificial immune system reference direction method light beam search intelligent recombination operator

Inception point of air entrainment over stepped spillways

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Journal of Hydrodynamics 2013年第1期25卷 91-96页

作者： WU Jian-hua ZHANG Bin ma fei College of Water Conservancy and Hydropower Engineering Hohai University

The location of the inception point of the air entrainment directly affects the energy dissipation ratio, the cavitation damage control, and the training wall height designs for a stepped spillway and a stilling basin. In this paper, the boundary layer theory of plates is used to predict the location of the inception point of the air entrainment over the stepped spillways by assuming the steps on the spillways as a kind of roughness. An empirical formula is presented based on the physical model experiments, with the maximum error less than 1% except at one point where the error is 1.6%, as compared to the experimental data. Meanwhile, it is shown that the location of the inception point of the air entrainment for the stepped spillway is much nearer to the top of the spillway than that for a smooth spillways, which explains why the high ratio of the energy dissipation is provided for the stepped spillway.

关键词： air entrainment cavitation energy dissipation inception point stepped spillway unit discharge

Energy Saving for Automatic Train Control in Moving Block Signaling System

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China Communications 2014年第A02期11卷 12-22页

作者： GU Qing MENG Yu ma fei School of Mechanical Engineering University of Science and Technology Beijing Beijing 100083 E R. China

With rapid development of the railway traffic, the moving block signaling system （MBS） method has become more and more important for increasing the track capacity by allowing trains to run in a shorter time-headway while maintaining the required safety margins. In this framework, the tracking target point of the following train is moving forward with its leading train. This paper focuses on the energy saving tracking control of two successive trains in MBS. Nonlinear programming method is used to optimize the energy-saving speed trajectory of the following train. The real-time location of the leading train could be integrated into the optimization process. Due to simplicity, it can be used for online implementation. The feasibility and effectiveness are verified through simulation. The results show that the new method is efficient on energy saving even when disturbances present.

关键词： moving block signaling (MBS) energy saving automatic train protection (ATP) automatic train operation (ATO) tracking train speed trajectory