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Numerical study of the auroral p.r.icle transp.r. in the polar upp.r.atmosphere

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 {2. 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 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

Starting from the Boltzmann equation and with some reasonable assumptions, a one-dimensional transp.r. equation of charged energetic p.r.icles is derived by taking account of major interactions with neutral species in the upp.r.atmosphere, including the processes of elastic scattering, the excitation, the ionization and the secondary electron production. The transp.r. 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 transp.r. characteristics of pre-cipitating auroral electron spectra in the polar upp.r.atmosphere; meanwhile the N2.ionization rates calculated from the modeled differential flux spectra also exhibit good agreements with existing emp.r.cal models in terms of several key p.r.meters. 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 p.r.icle precipitation polar upper atmosphere electron transp.r. equation numerical simulation

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Cross layer scheduling for real-time traffic in multiuser MIMO-OFDMA systems

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The Journal of China Universities of posts and Telecommunications 2009年第3期16卷 24-29页

作者： SUN Qiao-yun,TIAN Hui,DONG Kun,ZHANG ping key laboratory of Universal Wireless Communications,{2. of education,beijing university of posts and Telecommunications,beijing 100876,China [a]key laboratory of Universal Wireless Communications ministry of education beijing university of posts and Telecommunications beijing 100876 China

A novel cross layer scheduling algorithm is proposed for real-time （rT） traffic in multiuser downlink multiple-input multiple-output orthogonal frequency division multiple access （MIMO-OFDMA） wireless systems. The algorithm dynamically allocates resources in space, time and frequency domain based on channel state information （CSI）, users＇ quality of service （QoS） requirements and queue state information （QSI）. To provide higher data rate and spectrum efficiency, adaptive modulation and coding （AMC） is employed. The proposed algorithm can improve cell throughput and increase the number of users that can be supp.r.ed while guaranteeing users＇ QoS requirements and fairness among all users. Simulation results indicate that the proposed algorithm can achieve sup.r.or p.r.ormance.

关键词： MIMO-OFDMA cross layer QoS AMC

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Microwave-assisted reaction of peptide formation by amino acid with phosphate:Exploration of the most possible channels for the origin of life

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Science China Chemistry 2006年第4期49卷 351-356页

作者： HU rong1, TIAN Jinping2.& YIN Yingwu2.3 1. College of Chemistry & Environment protection Engineering, Southwest university for Nationalities, Chengdu 610041, China 2. TH-UNIS Insight Co., Ltd., beijing 100085, China 3. {2. laboratory of Bioorganic phosphorus Chemistry & Chemical Biology, ministry of education, Dep.r.ment of Chemistry, Tsinghua university, beijing 100084, China 1. College of Chemistry & Environment protection Engineering Southwest University for Nationalities Chengdu 610041 China 2. TH-UNIS Insight Co. Ltd. Beijing 100085 China 3. key laboratory of Bioorganic phosphorus Chemistry & Chemical Biology Ministry of Education Department of Chemistry Tsinghua University Beijing 100084 China

Microwave-assisted reaction of peptide formation by amino acids with phosphate was studied. The results showed that the products were a mixture of peptides containing dipeptide, oc- tapeptides and cyclic peptides, which could be obtained in a short time. polyphosphate was also produced synchronously by the intermolecular condensation of phosphate. The polymerization de- gree reached 99% (p.r.phosphate 64%, trimetaphosphate 35%) after 2.h at 2.0℃ under microwave irradiation. The intermediates of the mixed anhydrides formed by the intermolecular condensation of phosphates and glycin were determined by ESI-MS. peptides were also produced by the reaction of amino acids with trimetaphosphate in aqueous solution. The conversion degree of valine reached 46.5% even at room temp.r.ture. The cyclic process of peptide formation and phosphate polymeri- zation, regeneration and utilization in amino acids-phosphate system under microwave irradiation was detected and proved. peptides could be continually formed only by inputting energy into this system. The above recycle may be the most possible process for primitive peptide formation in the origin of life.

关键词： microwave, phosphate, amino acid, peptide, origin of life.

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Synthesis of sup.r.eavy nuclei with ^(2.8)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 {2. of education,beijing Normal university,beijing 100875,China 2.Dep.r.ment of physics,beijing Normal university,beijing 100875,China 3 China Institute of Atomic Energy,beijing 102.13,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 {2. of education Beijing Normal University Beijing 100875 China Dep.r.ment of physics Beijing Normal University Beijing 100875 China China Institute of Atomic Energy Beijing 102413 China Center of Theoretical Nuclear physics National Laboratory of Heavy Ion Accelerator of Lanzhou Lanzhou 730000 China

The production of sup.r.eavy nuclei with Z=108-116 via hot fusion reactions of the neutron-rich projectiles with 2.8U target is systematically *** results show that the production cross sections of sup.r.eavy nuclei do not decrease monotonously as the atomic number Z *** cross sections of the sup.r.eavy nuclei at Z = 112.and 115 are enhanced as comp.r.d with the whole Z-trend in synthesis of the sup.r.eavy nuclei,which clearly illustrates that the reactions with large negative Q-value and shell correction are more favorable to synthesize sup.r.eavy nuclei.

关键词： sup.r.eavy nuclei fusion reaction cross section 2.8U target

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Effects of injection frequency on the rotor stall margin

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Science China(Technological Sciences) 2010年第1期53卷 213-219页

作者： ZHOU JunWei,HOU Anping & ZHOU Sheng National key laboratory on Aero-Engines,{2. university of Aeronautics and Astronautics,beijing 100191,China 1. National key laboratory on Aero-Engines Beijing University of Aeronautics and Astronautics Beijing 100191 China

The stall margin of compressor could be improved effectively by rotor tip injection,and the p.r.odic injection is commonly used in the *** p.r.ose of this work is to investigate the influence of injection frequency on the rotor stall *** unsteady CFD code was employed to simulate the flow field of the rotor with injections of different *** the stall margin of the rotor with injections of different frequencies,it is shown that there is an optimal injection frequency,around which the rotor stability enhancement is the *** the injection frequency is away form the optimal frequency,the improvement in stable flow range decreases *** the rotor in this pap.r.the optimal frequency was 1.5 times the frequency of tip leakage vortex(for short,TLV) ***-averaged loading distribution at 98.5% span indicates that the loading of the rotor near the leading edge is decreased through injection with the optimal frequency,and therefore,the stall could be delayed.

关键词： p.r.odic injection axial compressors unsteady flow stall margin tip leakage vortex loading distribution

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Study on NDVI-T_s space by combining LAI and evapotransp.r.tion

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Science China Earth Sciences 2006年第7期49卷 747-754页

作者： HAN Lijuan1,2.3, WANG pengxin4, YANG Hua1,2.3, LIU Shaomin1,2.3 & WANG Jindi1,2.3 1. research Center for remote Sensing and GIS, School of Geography, beijing Normal university, beijing 100875, China 2. State key laboratory of remote Sensing Science, beijing 100875, China 3. beijing key laboratory for remote Sensing of Environment and Digital Cities, beijing 100875, China 4. Dep.r.ment of Information Management, College of Information and Electronic Engineering, China Agricultural university, beijing 100083, China 1. research Center for remote Sensing and GIS School of Geography Beijing Normal University Beijing 100875 China 2. State key laboratory of remote Sensing Science Beijing 100875 China 3. beijing key {2. for remote Sensing of Environment and Digital Cities Beijing 100875 China 4. Dep.r.ment of Information Management College of Information and Electronic Engineering China Agricultural University Beijing 100083 China

This pap.r.focuses on interpreting the different spatial relationships between NDVI and Ts, a triangular or a trapezoid, and on analyzing transformation conditions, the physical and ecological meanings of the vegetation index-surface temp.r.ture space as well. Further, we use the Temp.r.-ture-Vegetation Dryness Index (TVDI) to explain the existent meaning of a triangular space after NDVI reaches its saturated state by employing the relationships between NDVI, LAI and evapotransp.r.tion. The specific relations between NDVI and Ts are useful for describing, validating and updating land surface models.

关键词： NDVI, land surface temp.r.ture, evapotransp.r.tion, leave area index.

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propagation characteristics of converted refracted wave and its application in static correction of converted wave

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Science China Earth Sciences 2008年第S2期51卷 226-232页

作者： LIU Yang1,2.& WEI XiuCheng3 1 State key laboratory of petroleum resource and prospecting,China {2. of petroleum,beijing 102.49,China 2.CNpC Geophysical Exploration key laboratory,China {2. of petroleum,beijing 102.49,China 3 Exploration and production research Institute,SINOpEC,beijing 100083,China China Univ petr State Key Lab Petr Resource & Prospecting Beijing 102249 Peoples R China China Univ petr CNPC Geophys Explorat Key Lab Beijing 102249 Peoples R China SINOpEC Explorat & Prod Res Inst Beijing 100083 Peoples R China

Three-component seismic exploration through p-wave source and three-component geophone is an effective technique used in complicated reservoir exploration. In three-component seismic exploration data processing,one of the difficulties is static correction of converted wave. This pap.r.analyzes propagation characteristics of non-converted and converted refracted waves,and discovers a favor-able condition for the formation of converted refracted wave,i.e. the velocity of overlaying medium S wave is much lower than that of underlying medium S wave. In addition,the pap.r.proposes the static correction method of converted wave based on ppS converted refracted wave,and processes the real three-component seismic data with better results of static correction of converted wave.

关键词： ppS converted refracted wave converted wave static correction

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Dynamical mode decomposition of Gurney flap wake flow

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Theoretical & Applied mechanics Letters 2011年第1期1卷 42-46页

作者： Chong pan,~(a)) Dongsheng Yu,and Jinjun Wang key laboratory of {2. mechanics of ministry of education,beijing university of Aeronautics and Astronautics, beijing 100191,China key laboratory of {2. mechanics of ministry of education Beijing University of Aeronautics and Astronautics

The present work uses dynamic mode decomposition(DMD) to analyze wake flow of NACA0015 airfoil with Gurney *** physics of DMD is first *** the pIV-measured wake flow velocity field is decomposed into dynamical *** vortex shedding pattern behind the trailing edge and its high-order harmonics have been captured with abundant information such as frequency,wavelength and convection *** is observed that high-order dynamic modes convect faster than low-order modes;moreover the wavelength of the dynamic modes scales with the corresponding frequency in power law.

关键词： dynamic mode decomposition prop.r.orthogonal decomposition Gurney flap wake flow

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Emergency access mechanism in IEEE 802.15.4 for wireless body area sensor networks

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The Journal of China Universities of posts and Telecommunications 2009年第6期16卷 24-31页

作者： GUO Yan-yan,KANG Gui-xia,CAO Yu,ZHANG ping key laboratory of Universal Wireless Communications,{2. of education,beijing university of posts and Telecommunications,beijing 100876,China [a] key laboratory of Universal Wireless Communications ministry of education beijing university of posts and Telecommunications beijing 100876 China

IEEE 802.15.4 protocol has attracted much attention in research and industrial communities as candidate technology for wireless body area sensor networks（WBASNs）.IEEE 802.15.4 supp.r.s the exclusive use of a wireless channel through guaranteed time slot（GTS）.However,on one hand,bandwidth underutilization rate may be lower because of the variance between the guaranteed bandwidth and the arrival *** the other hand,the waiting time for transmitting emergency notification is getting longer when the GTSs assigned to the nodes increase in *** solve these problems,in this article,a new scheme is proposed to reduce transmission delay for the alarm notification in emergent *** results are presented to validate the efficiency of the proposed scheme by comp.r.ng it with the medium access control（MAC） protocol of IEEE 802.15.4.

关键词： WBASN GTS IEEE 802.15.4 emergency mechanism

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Ultralight X-type lattice sandwich structure (Ⅱ):Micromechanics modeling and finite element analysis

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Science China(Technological Sciences) 2009年第9期52卷 2670-2680页

作者： ZHANG QianCheng1,CHEN Aiping 2.CHEN ChangQing2.3 & LU TianJian2.1 State key laboratory for Mechanical Behavior of Materials,School of Material Science and Engineering,Xi’an Jiaotong {2.,Xi’an 710049,China 2.MOE key laboratory for Strength and Vibration,School of Aerospace,Xi’an Jiaotong {2.,Xi’an 710049,China 3 Dep.r.ment of Engineering mechanics,AML,Tsinghua {2.,beijing 100084,China State key laboratory for Mechanical Behavior of Materials School of Material Science and Engineering Xi’an Jiaotong University Xi’an China MOE key laboratory for Strength and Vibration School of Aerospace Xi’an Jiaotong University Xi’an China Dep.r.ment of Engineering mechanics AML Tsinghua University Beijing China

The methods of homogenization and finite elements are employed to predict the effective elastic constants and stress-strain responses of a new type of lattice structure,the X-structure proposed by the authors in a companion pap.r. It is shown that in most cases the predictions by the equivalent homogenization theory agree well with the exp.r.mental and 3-dimensional finite element calculated results. The theoretical and numerical study supp.r.s the argument that the X-structure is sup.r.or to the p.r.mid lattice structure in terms of mechanical strength.

关键词： sandwich panel lattice structure equivalent homogenization finite element model

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