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A HIGH-ORDER FINITE DIFFERENCE METHOD FOR UNSTEADY CONVECTION-DIFFUSION PROBLEMS WITH SOURCE TERM

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Journal of Hydrodynamics 1999年第2期11卷 97-102页

作者： Yang Zhi-feng Wang Xuan(State key laboratory of Environment Simulation and Pollution Control, Institute of Environmental Sciences, beijing normal university, beijing 100875, P. R. china.) beijing normal Univ Beijing China

The convection and diffusion are the basic processes in fluid flow and heat& mass transfer. The upwind and evolution functions for the convection term are introduced to give a comprehensive transformation to one-dimensional unsteady convection-diffusion equation involving source term. The corresponding compact fourth-order finite difference methed is developed. With the trans formation, the authors overcome the difficultyin dealing with the convection term, and the high-order expression for the convection-diffusion term can be conveniently obtained. The proposed difference scheme with thefourth-order accuracy and unconditional stability can fully reflect the upwind and evolutioneffects of the convection. The calculated results show that the errors of the referencescheme are 600 or 6000 times those of the proposed scheme for the same computationalgrid. With the one time decrease of the space grid, the errors of the proposed scheme andthe reference scheme reduce about 20 times and 2 times respectively. It is evident that theaccuracy of the proposed scheme is remarkably higher than that of the reference scheme.

关键词： convection-diffusion compact difference method comprehensive transformation unsteady computational fluid dynamics

Feature extraction without phase error for THz reflective spectroscopy

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Science china.Information Sciences) 2012年第1期55卷 127-132页

作者： ZHANG LiangLiang,ZHONG Hua,ZHU DeChong,ZUO Jian&ZHANG CunLin beijing key laboratory for Terahertz Spectroscopy and Imaging,key laboratory of Terahertz Optoelectronics,Ministry of Education of china.capital normal university,beijing 100048,china beijing key laboratory for Terahertz Spectroscopy and Imaging Key Laboratory of Terahertz Optoelectronics Ministry of Education of China Capital Normal University Beijing China

We propose two methods for avoiding misplacement phase error in terahertz reflection time-domain spectroscopy(THz-RTDS).The absorption signatures of the materials are extracted directly from the second-order derivative of the phase of the sample beam or the first derivative of the relative reflectance with respect to *** techniques provide straightforward and fast solutions to solve the phase-retrieval problem in RTDS.

关键词： feature extraction phase error reflective spectroscopy

Development and application of ergodicity model with FRCM and FLAR for hydrological process

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Science china.Technological Sciences) 2009年第2期52卷 379-386页

作者： WANG HongRui1, FENG QiLei2, LIN Xin3 & ZENG WenYi4 1 College of Water Science, key laboratory for Water and Sediment Sciences of the Ministry of Education, beijing normal university, beijing 100875, china.2 School of Science, beijing Institute of Education, beijing 100011, china.3 School of Mathematical Sciences, beijing normal university, beijing 100875, china.4 College of Information Science and Technology, beijing normal university, beijing 100875, china College of Water Science Key Laboratory for Water and Sediment Sciences of the Ministry of Education Beijing Normal University Beijing China School of Science Beijing Institute of Education Beijing China School of Mathematical Sciences Beijing Normal University Beijing China College of Information Science and Technology Beijing Normal University Beijing China

In this paper, a new ergodic property analysis model of hydrological process is proposed based on fuzzy-rough c-means clustering (FRCM), autocorrelogram, and fuzzy least absolute regression (FLAR). A precipitation time series (1951―2004) from Shanghai Hydrology Station is then analyzed with the model. The results show that the precipitation time series of April, May, June, and September has er-godic property. We conclude that in the long run, the precipitation of April, May, June, and September will not keep decreasing; it will converge to its mean value in some period.

关键词： hydrological process ergodic autocorrelogram fuzzy-rough c-means clustering fuzzy least absolute regression

Information flow and controlling in regularization inversion of quantitative remote sensing

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Science china.Earth Sciences 2005年第1期48卷 74-83页

作者： YANG Hua, XU Wangli, ZHAO Hongrui, CHEN Xue & WANG Jindi Research Center for Remote Sensing and GIS, School of Geography, beijing normal university, State key laboratory of Remote Sensing Science, beijing key laboratory for Remote Sensing of Environment and Digital Cities, beijing 100875, china.Department of Mathematics, beijing normal university, beijing 100875, china Research Center for Remote Sensing and GIS School of Geography Beijing Normal University State Key Laboratory of Remote Sensing Science Beijing Key Laboratory for Remote Sensing of Environment and Digital Cities Beijing China Department of Mathematics Beijing Normal University Beijing China

In order to minimize uncertainty of the inversed parameters to the largest extent by making full use of the limited information in remote sensing data, it is necessary to understand what the information flow in quantitative remote sensing model inversion is, thus control the information flow. Aiming at this, the paper takes the linear kernel-driven model inversion as an example. At first, the information flow in different inversion methods is calculated and analyzed, then the effect of information flow controlled by multi-stage inversion strategy is studied, finally, an information matrix based on USM is defined to control information flow in inversion. It shows that using Shannon entropy decrease of the inversed parameters can express information flow more properly. Changing the weight of a priori knowledge in inversion or fixing parameters and partitioning datasets in multi-stage inversion strategy can control information flow. In regularization inversion of remote sensing, information matrix based on USM may be a better tool for quantitatively controlling information flow.

关键词： regularization inversion, information flow, Shannon entropy decrease, information matrix.

Quantitative exploration of the mechanisms behind the urban thermal environment in beijing

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Progress in Natural Science:Materials International 2009年第12期19卷 1757-1763页

作者： Dan Meng,Xiaojuan Li~*,Wenji Zhao,Huili Gong key laboratory of 3D Information Acquisition and Application,Ministry of Education,key laboratory of Resource,Environment and GIS in beijing,College of Resources Environment and Tourism,capital normal university,beijing 100048,china key laboratory of 3D Information Acquisition and Application Ministry of Education Key Laboratory of Resource Environment and GIS in Beijing College of Resources Environment and Tourism Capital Normal University Beijing 100048 China

The driving mechanism behind the formation of urban thermal environments is the result of a combination of *** was chosen as the study area,and the technique of principal component analysis(PCA) was used.A spatial regression method was also applied for quantitative explanation of the thermal *** Landsat thematic mapper images were used to quantify potential causing *** the eigenvalues of each factor and its relationship with land surface temperature,the first three principal components(PCs) are regarded as the main causative factors explaining the mechanism as independent *** first three PCs mainly reflect urban construction,road density and the normalized difference vegetation index(NDVI),*** least squares,spatial lag and spatial error regression models were established separately for the relationships between the first three PCs and land surface temperature(LST).In the two spatial regression models,z-statistics for both the spatial lag parameter(ρ) and spatial residual parameter(λ) are significant,indicating the necessity of using spatial regression to replace the OLS regression model,as well as indicating that the spatial error regression model is superior to the spatial lag regression ***,the normalized difference built-up index(NDBI) and road density are the most significant positive contributions to LST.

关键词： Urban thermal environment Drive mechanism Spatial regression beijing

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Science china.Life Sciences) 2009年第8期52卷 780-788页

作者： YANG Bo1,YANG SuYong2,ZHAO Lun3,YIN LiuHua1,LIU Xu1& AN ShaSha1 1 laboratory of Psychology,School of Sociology,china.university of Political Science and Law,beijing 102249,china.2 National key laboratory of Cognitive Neurosciences and learning,beijing normal university,beijing 100875,china.3 Institute of Language,Xuzhou normal university,Xuzhou 221116,china laboratory of Psychology School of Sociology China University of Political Science and Law Beijing China National key laboratory of Cognitive Neurosciences and learning Beijing Normal University Beijing China Institute of Language Xuzhou Normal University Xuzhou China

Inhibitory control dysfunction is regarded as a core feature in *** major objective of this study was to explore the time course of response inhibition in chronic heroin addicts and provide the neurophysiological evidence of their inhibitory control *** amplitudes and latencies of ERP components were studied in fourteen heroin addicts(mean duration of heroin use being(13.54±5.71) years(Mean±SD),average abstinence being((4.67±6.44) months)) and fourteen matched healthy controls with a visual Go/Nogo *** results showed that heroin addicts demonstrated significantly larger Go-N2 amplitudes which results in a decreased N2 Go/Nogo effect,but no statistically significant differences were found between heroin addicts and controls in *** ERP data suggest that fronto-central areas of heroin addicts were impaired during the inhibition process(200-300 ms) and over-activated to *** impaired early process might reflect an abnormal conflict monitoring process in heroin *** results consolidate the inhibitory control dysfunction hypothesis in chronic heroin users.

关键词： heroin addicts events-related potentials inhibitory control conflict monitoring response inhibition

Synthesis of superheavy nuclei with ^(238)U target

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Science china.Physics,Mechanics & Astronomy) 2009年第10期52卷 1482-1488页

作者： LIU ZuHua1,3 & BAO JingDong2,4 1 key laboratory of Beam Technology and Material Modification of Ministry of Education,beijing normal university,beijing 100875,china.2 Department of Physics,beijing normal university,beijing 100875,china.3 china.Institute of Atomic Energy,beijing 102413,china.4 Center of Theoretical Nuclear Physics,National laboratory of Heavy Ion Accelerator of Lanzhou,Lanzhou 730000,china key laboratory of Beam Technology and Material Modification of Ministry of Education Beijing Normal University Beijing China china.Institute of Atomic Energy Beijing China Department of Physics Beijing Normal University Beijing China Center of Theoretical Nuclear Physics National Laboratory of Heavy Ion Accelerator of Lanzhou Lanzhou China

The production of superheavy nuclei with Z=108-116 via hot fusion reactions of the neutron-rich projectiles with 238U target is systematically *** results show that the production cross sections of superheavy nuclei do not decrease monotonously as the atomic number Z *** cross sections of the superheavy nuclei at Z = 112 and 115 are enhanced as compared with the whole Z-trend in synthesis of the superheavy nuclei,which clearly illustrates that the reactions with large negative Q-value and shell correction are more favorable to synthesize superheavy nuclei.

关键词： superheavy nuclei fusion reaction cross section 238U target

Study on Water Consumption Coefficient of People's Living and Its Regional Disparity in the North of china

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Chinese Journal of Population,Resources and Environment 2005年第2期3卷 20-26页

作者： Wang Jing’ai 1-3, Mao Rui 3,4, Yang Mingchuan 3,4 & Zhou Junju 11 College of Geography & Remote Sensing 2 key laboratory of Regional Geography of beijing normal university 3 key laboratory of Environmental Change and Natural Disaster of Ministry of Education of china.4 College of Resources Science & Technology, beijing normal university, beijing 100875, china College of Geography and Remote Sensing Beijing 100048 China key laboratory of Environmental Change and Natural Disaster of Ministry of Education of china Beijing 100048 China College of Resources Science and Technology Beijing Normal University Beijing 100875 China

By employing the information-reshufflingmethod that integrates census data, precipitation dataand inquiry data of water consumption, this paperdiscusses 5 (water consumption coefficient of people’sliving) in allusion to different precipitation zones anddifferent periods of time. The study shows that 5-(water consumption coefficient of urban people’sliving), 5. (water consumption coefficient of ruralpeople’s living) and increase with time passing, andthe increasing extent of 5 is 1.84, 2.62, 2.84 and 2.68times respectively from the west to the east, whichresults from the total quantity of water resources andthe speed of urbanization. 5- and 5. of eachprecipitation zone increased with 5- increasing morequickly than 5., and the difference between the twoalso increased when time passed. In the past fifty years(1950-2000), the increasing extent of 5- was 1.71,2.96, 2.41 and 2.33 times respectively from the westto the east, in which 200-400mm precipitation zoneincreased more than others. Meanwhile the increasingextent of 5. is 1.55, 1.60, 1.53 and 1.64 timesrespectively from the west to the east with eachprecipitation zone increasing similarly. The change of5-is due to the speed of urbanization and the stabilityof water resources. This study provides basis forcalculating the water demand of people’s living andrevealing the impact of water demand of people’s livingon ecological drought in different zones.

关键词： The north of china precipitation zone water consumption coefficient of people’s living

Theoretical analysis of transcranial Hall-effect stimulation based on passive cable model

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Chinese Physics B 2015年第12期24卷 373-378页

作者：袁毅李小俚 Institute of Electrical Engineering Yanshan University State key laboratory of Cognitive Neuroscience and learning & IDG Mc Govern Institute for Brain Research Beijing Normal University Center for Collaboration and Innovation in Brain and learning Sciences Beijing Normal University

Transcranial Hall-effect stimulation（THS） is a new stimulation method in which an ultrasonic wave in a static magnetic field generates an electric field in an area of interest such as in the brain to modulate neuronal activities. However, the biophysical basis of simulating the neurons remains unknown. To address this problem, we perform a theoretical analysis based on a passive cable model to investigate the THS mechanism of neurons. Nerve tissues are conductive; an ultrasonic wave can move ions embedded in the tissue in a static magnetic field to generate an electric field（due to Lorentz force）.In this study, a simulation model for an ultrasonically induced electric field in a static magnetic field is derived. Then,based on the passive cable model, the analytical solution for the voltage distribution in a nerve tissue is determined. The simulation results showthat THS can generate a voltage to stimulate neurons. Because the THS method possesses a higher spatial resolution and a deeper penetration depth, it shows promise as a tool for treating or rehabilitating neuropsychiatric disorders.

关键词： Hall-effect stimulation passive cable model neurons