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simulation of freezing and melting of soil on the northeast Tibetan Plateau

Chinese Science Bulletin 2011年第20期56卷 2145-2155页

作者： XIA Kun 1,2,3,LUO Yong 2,4,5 & LI WeiPing 2 1 Institute of Atmospheric Physics,Chinese Academy of Sciences,beijing 100029,china 2National Climate Center,china Meteorological Administration,beijing 100081,china 3Graduate University of Chinese Academy of Sciences,beijing 100049,china 4 Center for earth system Science,Tsinghua University,beijing 100084,china 5key laboratory of earth system numerical simulation,ministry of education,beijing 100084,china Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China National Climate Center China Meteorological Administration Beijing China Graduate University of Chinese Academy of Sciences Beijing China Center for earth system Science Tsinghua University Beijing China key laboratory of earth system numerical simulation Ministry of Education Beijing China

Using observational data spanning the period from February to December 2009 and recorded at the Suli station in Qinghai Province,the land-surface model CLM3.0 was employed to simulate the freezing and melting of *** results indicate that the simulated soil temperature is higher than the observed soil temperature and the ultimate thawing date is earlier than the observed date during the melting *** the freezing period,the simulated soil temperature is lower than the observed soil temperature and the ultimate freezing of the deep soil is earlier than that ***,the simulation of freezing is better than that of melting,and the simulation of a shallow layer is better than that of a deeper *** the original CLM3.0,it is assumed that frozen soil begins to melt when the soil temperature exceeds 0C,which is inconsistent with *** critical freeze-thaw temperature was calculated according to thermodynamics equations and the freeze-thaw condition was *** this work,the melting rate for frozen soil was reduced using the modified scheme,and the simulated soil temperature was lowered. Meanwhile,the refreezing of soil during the melting season was well simulated and more closely matched ***,it was found that the rates of melting and freezing differ,with the former being slower than the latter,but refreezing during the melting season is rather quick.

关键词：土壤温度冻结期青藏高原东北部模拟融化观测数据热力学方程表面模型

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Hopping control channel MAC protocol for opportunistic spectrum access networks

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The Journal of china Universities of Posts and Telecommunications 2010年第6期17卷 65-71页

作者： FU Jing-tuan,JI Hong,MAO Xu key laboratory of Universal Wireless Communications,ministry of education,beijing University of Posts and Telecommunications,beijing 100876,china key laboratory of Universal Wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

Opportunistic spectrum access （OSA） is considered as a promising approach to mitigate spectrum scarcity by allowing unlicensed users to exploit spectrum opportunities in licensed frequency bands. Derived from the existing channel-hopping multiple access （CHMA） protocol,we introduce a hopping control channel medium access control （MAC） protocol in the context of OSA networks. In our proposed protocol,all nodes in the network follow a common channel-hopping sequence; every frequency channel can be used as control channel and data channel. Considering primary users＇ occupancy of the channel,we use a primary user （PU） detection model to calculate the channel availability for unlicensed users＇ access. Then,a discrete Markov chain analytical model is applied to describe the channel states and deduce the system throughput. Through simulation,we present numerical results to demonstrate the throughput performance of our protocol and thus validate our work.

关键词： channel hopping MAC protocol OSA Markov chain

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numerical study of the auroral particle transport in the polar upper atmosphere

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Science china(Technological Sciences) 2008年第10期51卷 1759-1771页

作者： CAI HongTao1,2, MA ShuYing1,2 & PU ZuYin3 1 School of Electronic Information, Wuhan University, Wuhan 430079, china 2 key laboratory of Geospace Environment and Geodesy, ministry of education of PRC, Wuhan 430079, china 3 School of earth and Space Sciences, Peking University, beijing 100871, china School of Electronic Information Wuhan University Wuhan China key laboratory of Geospace Environment and Geodesy Ministry of Education of PRC Wuhan China School of earth and Space Sciences Peking University Beijing China

Starting from the Boltzmann equation and with some reasonable assumptions, a one-dimensional transport equation of charged energetic particles is derived by taking account of major interactions with neutral species in the upper atmosphere, including the processes of elastic scattering, the excitation, the ionization and the secondary electron production. The transport equation is numerically solved, for a simplified atmosphere consisting only of nitrogen molecules (N2), to obtain the variations of incident electron fluxes as a function of altitude, energy and pitch angle. The model results can describe fairly the transport characteristics of pre-cipitating auroral electron spectra in the polar upper atmosphere; meanwhile the N2 ionization rates calculated from the modeled differential flux spectra also exhibit good agreements with existing empirical models in terms of several key parameters. Taking the energy flux spectra of precipitating electrons observed by FAST satellite flying over EISCAT site on May 15, 1997 as model inputs, the model-calculated ionization rate profile of neutral atmosphere consists reasonably with that recon-structed from electron density measurements by the radar.

关键词： aurora particle precipitation polar upper atmosphere electron transport equation numerical simulation

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Efficiency of sediment transport by flood and its control in the Lower Yellow River

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Science china(Technological Sciences) 2004年第Z1期47卷 173-185页

作者： NI Jinren1, LIU Xiaoyong2, LI Tianhong1, ZHAO Ye’an3 & JIN Ling1 1. Department of Environmental Engineering, Peking University The key laboratory of Water and Sedi- ment Sciences, ministry of education, beijing 100871, china 2. General Institute of Water Resources and Hydropower Planning and Design, ministry of Water Re- sources, beijing 100011, china 3. The Yellow River Conservancy Commission, Zhengzhou 450003, china Department of Environmental Engineering Peking University Beijing China The key laboratory of Water and Sediment Sciences Ministry of Education Beijing China General Institute of Water Resources and Hydropower Planning and Design Ministry of Water Resources Beijing China The Yellow River Conservancy Commission Zhengzhou China

This paper presents the characteristics of sediment transport by flood in the Lower Yellow River with the reach from Huayuankou to Gaocun, which is regarded as a typical braided pattern. The Artificial Neural Network Model on Water Use for Sediment Transport (WUST) by flood was established based on the measured data from 1980 to 1998. Consequently, simulations of controlling process of sediment transport by flood were made in terms of the control theory under different scenarios. According to the situation of sediment transport by flood in the Lower Yellow River, Open-Loop control system and feedback control system were adopted in system design. In the Open-Loop control system, numerical simulations were made to reveal the relationship between average discharge of flood and the WUST with varying sediment concentrations. The results demonstrate that sediment concentration has significant influence on the controlling process of flood flow to WUST. It is practical and efficient to control WUST if sediment concentration is less than 20 kg/m3. In the feedback control system, controlling processes of sediment concentration and flood discharge for sediment transport were simulated respectively under given conditions, and it was found that sediment transport process could be controlled completely by sediment concentration and discharge at the inlet of the reach from Huayuankou to Gaocun. Using the same method, controlling processes of sediment transport by flood in other reaches in the Lower Yellow River were also simulated. For the case of sediment concentration being 20 kg/m3, the optimized controlling discharge ranges from 2390 to 2900 m3/s in the lower reach of Huayuankou. This study is also of significance to flood control and flushing sediment in the Lower Yellow River with proper operation modes of Xiaolangdi Reservoir.

关键词： the Lower Yellow River, flood, sediment transport, efficiency, simulation, control.

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A Circular aperture-array structure optical system for digital sun sensor

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Optoelectronics Letters 2008年第1期4卷 62-65页

作者： WEN Zhi-ming,JIANG Jie, ZHANG Guang-jun,and FAN Qiao-yun key laboratory for Precision Opto-mechatronic. Techonology of ministry of education ,beijing University of Aeronautics and Astronautics, beijing 100083,china key laboratory for Precision Opto-mechatronic. Techonology of ministry of education Beijing University of Aeronautics and Astronautics Beijing China

Based on the first type of Rayleigh Sommerfeld diffraction formula, an imaging model of circular aperture-array structure digital sun sensor optical system is developed. Then a 6×6 circular aperture-array structure optical system is designed. The results of numerical simulation show that the optical system is designed well and is conformed to the requirements of miniaturization and high accuracy of sun sensor.

关键词：数字太阳传感器圆孔结构光学系统光衍射角度测量

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Improvement of fabrication precision of focused ion beam by introducing simultaneous electron beam

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Progress in Natural Science:Materials International 2010年第1期20卷 111-115页

作者： Hu LUO,Ran JING,Yi-min CUI,Hai-long WANG,Rong-ming WANG key laboratory of Micro-Nano Measurement-Manipulation and Physics,ministry of education, Department of Physics,beijing University of Aeronautics and Astronautics,beijing 100191,china key laboratory of Micro-Nano Measurement-Manipulation and Physics Ministry of Education Department of Physics Beijing University of Aeronautics and Astronautics Beijing 100191 China

The introduction of electron beam(EB)brings features of both simultaneous observation of ion milling process and improvement of ion-milling accuracy in a dual beam system consisting of focused ion beam(FIB)and scanning electron microscope (SEM).The experiments reveal that simultaneous EB can also decrease the fabrication line width significantly during the ion milling *** the Coulomb interaction between ions and electrons,the effect of simultaneous EB on the diameter of FIB in the course of milling was studied by numerical *** experiments and simulation indicate that the achievable fabrication line width can be dramatically reduced under appropriate conditions by introducing *** provides a convenient and effective way to improve the fabrication precision in the SEM-FIB dual beam system.

关键词： fabrication line width numerical simulation simultaneous electron beam Coulomb interaction

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Bionic Design and Finite Element Analysis of Elbow in Ice Transportation Cooling system

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Journal of Bionic Engineering 2010年第3期7卷 301-306页

作者： Dejun Miao~(1,2), Xiuhua Sui~3, Linjing Xiao~3 1. key laboratory of Mine Hazard Prevention and Control (ministry of education, china), Shandong University of Science and Technology, Qingdao 266510, P. R. china 2. School of Architecture, Tsinghua University, beijing 100084, P. R. china 3. College of Mechanical and Electronic Engineering, Shandong University of Science and Technology, Qingdao 266510, P. R. china key laboratory of Mine Hazard Prevention and Control (ministry of education China) Shandong University of Science and Technology Qingdao P. R. China School of Architecture Tsinghua University Beijing P. R. China College of Mechanical and Electronic Engineering Shandong University of Science and Technology Qingdao P. R. China

With the increase in mining depth, mine heat harm has appeared to be more prominent. The mine heat harm could be resolvedor reduced by ice refrigeration. Thus, ice transportation through pipeline becomes a critical problem; typically flowresistance occurs in the elbow. In the present study, according to the analysis of the surface morphology of fish scale, abiomimetic functional surface structure for the interior wall of elbow is designed. Based on the theory of liquid-solid two phaseflow, a CFD numerical simulation of ice-water mixture flowing through the elbow is carried out using finite element *** experiments of pressure drop and flow resistance for both bionic and common elbows are conducted to test theeffect of the bionic elbow on flow resistance reduction. It is found that with the increase in the ice mass fraction in the ice-watermixture, the effect of bionic elbow on resistance reduction becomes more obvious.

关键词： bionic elbow two phase flow ice transportation flow resistance reduction pressure loss

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Random Vibration Analysis of the Electronic Equipment Cabinet

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武汉理工大学学报 2006年第S2期28卷 709-713页

作者： LIU Yanping~1 LIU Dongqing~2 1.key laboratory of Condition Monitoring and Control for Power Plant Equipment of ministry of education,North china Electric Power University,beijing 102206 ,china 2.beijing University of Science and Technology,beijing 100083,china key laboratory of Condition Monitoring and Control for Power Plant Equipment of ministry of education North China Electric Power UniversityBeijing 102206China beijing University of Science and Technology Beijing 100083China

In order to understand the vibration characteristic of system structure of electronic equipment cabinet within the particular vibration frequency,the finite element analysis software-ANSYS is used to simulate the tests of random vibrations of the cabinet system and obtain the isopleths graph of deformation and stress of the *** can confirm maximum of deformation and stress of the cabinet and position *** more analysis of the frequency response curve,which can confirm harm- ful consequences random vibrations caused and weak link of the cabinet *** numerical simulation results are in good a- greement with the experimental *** shows that this research provides an efficient method for the anti-seismic design and the dynamic optimization design.

关键词： random vibrations test vibration characteristic numerical simulation finite element analysis electronic equipment cabinet ANSYS software

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VORTEX INDUCED VIBRATIONS OF FINNED CYLINDERS

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Journal of Hydrodynamics 2008年第2期20卷 195-201页

作者： SHA Yong WANG Yong-xue Postdoctoral Programme Technology Research Department CNOOC Research Beijing 100027 China State key laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian 116024China

This article presents the results of a numerical simulation on the vortex induced vibration of various fumed cylinders at low Reynolds number. The non-dimensional, incompressible Navier-Stokes equations and continuity equation were adopted to simulate the fluid around the cylinder. The cylinder （with or without fins） in fluid flow was approximated as a mass-spring system. The fluid-body interaction of the cylinder with fins and uniform flow was numerically simulated by applying the displacement and stress iterative computation on the fluid-body interfaces. Both vortex structures and response amplitudes of cylinders with various arrangements of fins were analyzed and discussed. The remarkable decrease of response amplitude for the additions of Triangle60 fins and Quadrangle45 fins was found to be comparable with that of bare cylinder. However, the additions of Triangle00 fins and Quadrangle00 fins enhance the response amplitude greatly. Despite the assumption of two-dimensional laminar flow, the present study can give a good insight into the phenomena of cylinders with various arrangements of fins.

关键词： vortex induced vibration cylinder with fins fluid-body interaction

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Retrospect and prospect of watershed hydrological model

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Communications in Nonlinear Science and numerical simulation 2001年第3期6卷 172-177页

作者： B. CHEN, L. Z. XIA, Z. F. YANG and G. Q. CHEN State key laboratory for Studies of Turbulence and Complex systems / Center for Environmental Sciences, Peking University, beijing 100871, china Institute of Environmental Sciences, beijing Normal Universitg, State key Lab. Studs. T./C.S. Center for Environmental Sciences Peking University Beijing 100871 China Institute of Environmental Sciences Beijing Normal University Beijing 100875 China

A brief review is presented of the development of watershed hydrological models. Conventional Hydrological Model, Grey Hydrological Model, Digital Hydrological Model and Intelligent Hydrological Model are analyzed. The frameworks of Fuzzy Cognitive Hydrological Model and Integrated Digital Watershed Hydrological Model are presented.

关键词： watershed hydrological model digital watershed complex system

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