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Optimal user scheduling and power control in multi-user cognitive broadcast systems

Science china(Information Sciences) 2012年第6期55卷 1402-1414页

作者： WANG QunHuan 1,2,3.WANG HuiMing 1,2,3.& YIN QinYe 1,3.1 School of electronic and Information Engineering,xi'an jiaotong university,xi'an {3.,china 2 State key Lab for Integrated Services Networks,xidian university,xi'an 710071,china 3.ministry of education key Lab for Intelligent Networks and Network Security,xi'an jiaotong university,xi'an 710071,china. 1. School of electronic and Information Engineering Xi’an Jiaotong University Xi’an 710049 China2. State Key Lab for Integrated Services Networks Xidian University Xi’an 710071 China3. Ministry of Education Key Lab for Intelligent Networks and Network Security Xi’an Jiaotong University Xi’an 710071 China

Cognitive radio systems should not only have the ability to sense and exploit "frequency spectrum holes",but also the ability to sense and utilize "spatial spectrum holes".In this paper,we consider the issue of maximizing the throughput of the cognitive systems by fully utilizing "spatial spectrum holes" brought in by multiple cognitive users,in the scenario where a pair of licensed users and a cognitive broadcast system share multiple spectrum *** exploiting the channel reciprocity under the premise that the licensed system adopts the time-division-duplexing (TDD) mode,we propose a more practical cognitive access scheme that can sense the interference at the licensed user caused by the cognitive transmitter,based on the existing feedback signals from the licensed user to the licensed base *** both interferences from the licensed base station to the cognitive receiver and from the cognitive transmitter to the licensed user into consideration,we investigate the optimal user scheduling and power allocation scheme that can maximize the ergodic sum rate of the cognitive *** show that scheduling the user whose channel gain to interference and noise ratio (CGINR) is the largest for each frequency band is *** also derive the dynamic power allocation scheme meeting the three practical constraints,i.e.,the transmitter's average transmission power constraint,the power amplifier's instantaneous transmission power constraint,and the interference power constraint at the licensed *** result shows that in different coherent time intervals and different frequency bands,the power allocation has a multi-level waterfilling *** analysis shows that the strategy scheduling user with the largest CGINR introduces significant performance improvement compared with the traditional strategy scheduling user with the largest channel gain to noise ratio (CGNR).We also illustrate the impact of power constraints and the number of users on system p

关键词： cognitive radio distributed spatial spectrum holes opportunistic scheduling power allocation

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Influence of Molecular Weight of PEO on Performance of Quasi-solid-state Dye-sensitized Solar Cells

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Journal of Wuhan university of Technology(materials Science) 2010年第2期25卷 218-222页

作者：沈小林 School of materials Science & Engineering Xi’an Jiaotong University

Quasi-solid-state dye-sensitized solar cells （DSCs） were prepared using gel electrolyte gelated by poly（ethylene-oxide）（PEO） with different molecular weight. With the increase in PEO molecular weight, the short circuit current densities （Jsc） increase significantly, which is related to the increase in I - diffusion due to the increase in free volume of gel electrolyte. However, only a slight increase in open voltage （Voc） is observed, which is explained by the decrease in dark current arising from the reduction of triiodide （I3.-） by conduction band electrons.

关键词： dye-sensitized solar cell poly(ethylene oxide) gel electrolyte molecular weight

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Crystal structures and electronic properties of BaC_2 isomers by theoretical study based on DFT

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Science china Chemistry 2008年第6期51卷 545-550页

作者： FENG Jing1,xiAO Bing2 & CHEN JingChao1 1 key Laboratory of Advanced materials of Precious-Nonferrous Metals,education {3. of china,and key Lab of Advanced materials of Yunnan Province,Kunming university of Science and Technology,Kunming 650093.china 2 School of materials Science and Engineering,xi’an jiaotong university,xi’an 710049,china 1. key Laboratory of Advanced materials of Precious-Nonferrous Metals Education Ministry of China Kunming China 3. key Lab of Advanced materials of Yunnan Province Kunming University of Science and Technology Kunming 650093 China 2. School of materials Science and Engineering Xi’an Jiaotong University Xi’an 710049 China

Band structures and electronic properties of two BaC2 isomers were calculated by using density func-tional theory(DFT) *** ionic bond features are all typical between cation(Ba) and anion clusters(C2) in both structures of the ***,a much stronger covalent bond exists in anion clusters which can be seen by inspecting the electron distribution contour that has a dull bell like shape between two carbon *** shortest distance between Ba2+ and C22? and the bond length in anion clusters are different in these isomers of BaC2,which are 0.2945 nm and 0.1185 nm for the structure with the I4/mmm space group and 0.2744 and 0.113. nm with the C2/c type,*** structures were clarified by combining the DOS to indicate the ionic bonding features more *** analysis provided further evidence on these *** calculation results reveal that the transition temperature of these two polymorphs of BaC2 locates near 13. K,which is consistent with the recent experimental results.

关键词： functional materials metal diaries phase transition electron density first principle calculation orbital bonding state

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Preparation and characterization of CoFe_2O_4/TiO_2 magnetic composite films

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Science china Chemistry 2008年第9期51卷 842-847页

作者： TIAN xiaoxia1, QU ShaoBo1,2, PEI ZhiBin1 & WANG BinKe1,2 1 College of Science, Air Force Engineering university, xi’an 710051, china 2 electronic {3. research Laboratory, key Laboratory of ministry of education, xi’an jiaotong university, xi’an 710049, china College of Science Air Force Engineering University Xi’an 710051 China electronic materials research Laboratory Key Laboratory of Ministry of Education Xi’an Jiaotong University Xi’an 710049 China

CoFe2O4/TiO2 magnetic composite films were prepared using the sol-gel method with tetrabutyltitanate and metallic chlorates as starting materials. The effects of heat treatment temperatures on micro- structures and on magnetic properties were studied. The microstructure and properties of the samples at different heat treatment temperatures were characterized by X-ray diffraction, Raman spectrum, scanning electron microscopy, polarized microscopy and vibrating sample magnetometry. The results show that crystals of different substances grow up independently. Cobalt ferrite is evenly embedded into the titanium dioxide matrix in the prepared composite films. The magnetism of the composite films is enhanced with an increase of the heat temperature.

关键词： CoFe2O4/TiO2 composite films magnetism sol-gel

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Asynchronous cooperative communication systems:A survey on signal designs

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Science china(Information Sciences) 2011年第8期54卷 1547-1561页

作者： WANG HuiMing 1,2 & xiA xiangGen 3.1 School of electronic and Information Engineering, xi’an jiaotong university, xi’an 710049,{3. 2 State key Laboratory of Integrated Services Networks, xidian university,xi’an 710049, china 3.Department of Electrical and Computer Engineering,university of Delaware,Newark,DE 19716,USA 1. School of electronic and Information Engineering Xi’an Jiaotong University Xi’an 710049 China2. State Key Laboratory of Integrated Services Networks Xidian University Xi’an 710049 China3. Department of Electrical and Computer Engineering University of Delaware Newark DE 19716 USA

Cooperative communications is a promising technique for future high speed wireless *** systems may be formulated as virtual multi-input multi-output (MIMO) systems where spatial/cooperetive diversity is a key advantage. However,different from MIMO systems,one of the major chal- lenges for cooperative communications systems is that the cooperative transmissions in cooperative systems may be neither time nor frequency synchronized,since the transmissions are from multiple cooperative nodes at different *** existing signal designs for co-located MIMO systems may not be able to collect the cooperative diversity in cooperative communications *** paper gives an overview of recent research efforts on combating the time and frequency asynchronism of the cooperative communication *** focus on the signal designs (or space-time codings/modulations) to achieve full cooperative diversity,and summarize some of the resent distributed space-timing coding and space-frequency coding techniques to combat timing errors and frequency offsets,and in the meantime to achieve full cooperative diversity,in both one-way and two-way cooperative networks.

关键词： cooperative communications time and frequency offsets space-time coding space-frequency codes full cooperative diversity linear receiver

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Efficient optimization of electron transfer pathway by constructing phosphide/ceria interface boosts seawater hydrogen production

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Journal of Energy Chemistry 2024年第8期95卷 490-498,I0011页

作者： Yifan Zhao Lingfeng Yang Youyu Long Min xi Anran Chen Hua Zhang School of materials and Energy Yunnan UniversityKunming 650091YunnanChina Electron Microscopy Centre of Yunnan university Yunnan UniversityKunming 650091YunnanChina

Developing efficient and durable hydrogen evolution reaction(HER)electrocatalysts is one of the most important issues for the commercialization of seawater electrolysis,but it remains ***,we report a CeO_(2)-CoP nanoneedle array catalyst loaded on Ti mesh(CeO_(2)-CoP/TM)with workfunction-induced directional charge transport *** CeO_(2)-CoP/TM catalyst showed superior HER catalytic activity and stability,with over potentials of 41 and 60 mV to attain 10 mA cm^(-2),in 1 M KOH and 1 M KOH+seawater electrolyte,*** results and theoretical calculations reveal that the work function drives the charge transfer from CeO_(2)to CoP,which effectively balances the electronic density of CoP and CeO_(2),optimizes the d-band center,and accelerates the water activation kinetics,thus enhancing the HER *** solar-driven water electrolysis device displays a high and stable solar-to-hydrogen conversion efficiency of 19.6%.This study offers a work function-induced directional charge transport strategy to design efficient and durable catalysts for hydrogen production.

关键词： Work function Heterostructure Charge transport Seawater splitting Solar-to-hydrogen

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Simulation on the Melt Flow in Laser Full Penetration Welding with a Model Including a Non-Rotational Symme-try keyhole Based on Energy Balance

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稀有金属材料与工程 2011年第S4期40卷 120-124页

作者： Zhang L J1,Zhang J X1,Wu B1,2,Chen L2,Gong S L2,Wang H R3.1 State key Laboratory of Mechanical Behavior for materials,xi’an jiaotong {3.,xi’an 710049,china2 Power Beam Processing Dept.,Avic Beijing Aeronautical Manufacturing Technology research Institute,Beijing 100024,china3.School of Energy and Power Engineering,xi’an jiaotong {3.,xi’an 710049,china xi An Jiao Tong Univ Sch Energy & Power Engn Xian 710049 Peoples R China xi An Jiao Tong Univ State Key Lab Mech Behav Mat Xian 710049 Peoples R China Avic Beijing Aeronaut Mfg Technol Res Inst Power Beam Proc Dept Beijing 100024 Peoples R China

A three dimensional model including a non-rotational symmetry keyhole of which the geometry is calculated base on the energy balance at keyhole wall is created to simulate the heat transfer and fluid flow within the molten pool during laser full penetration welding of titanium alloy *** order to take into account the effects of multiple reflections within the keyhole,a ray tracing method is employed and the coordinate dependent heat flux obtained is exerted on keyhole wall during the simulation on the heat transfer and fluid flow within molten ***,the computed weld cross sectional profile is compared with the experimental result to verify the model and it is fond that the simulation result is consists with experimental result.

关键词： laser welding titanium alloy non-rotational symmetry keyhole simulation

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X-ray spectra induced in highly charged 40Ar^q+ interacting with Au surface

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Science china(Physics,Mechanics & Astronomy) 2006年第2期49卷 203-212页

作者： ZHANG xiao’an1,2, xiAO Guoqing1, YANG Zhihu1, CHEN ximeng3. ZHAO Yongtao1, LI Fuli4, ZHANG Yinping1, CUI Ying3. ZHANG Hongqiang3. XU Xu3. SHAO Jianxiong3.& ZHAN Wenlong11. Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 73.000, china 2. Department of Physics, xianyang Normal university, xianyang 712000, china 3. Department of Modern Physics, Lanzhou university, Lanzhou 73.000, china 4. Department of Applied Physics, xi’an jiaotong university, xi’an 710049, china 1. Institute of Modern Physics Chinese Academy of Sciences Lanzhou 730000 China 2. Department of Physics Xianyang Normal University Xianyang 712000 China 3. Department of Modern Physics Lanzhou University Lanzhou 730000 China 4. Department of Applied Physics Xi’an Jiaotong University Xi’an 710049 China

By use of optical spectrum technology, the spectra of X-ray induced by highly charged 40Arq+ ions interacting with Au surface have been studied. The results show that the argon Kα X-ray were emitted from the hollow atoms formed below the surface. There is a process of multi-electron exciting in neutralization of the Ar16+ion, with electronic con-figuration 1s2 in its ground state below the solid surface. The yield of the projectile Kα X-ray is related to its initial electronic configuration, and the yield of the target X-ray is related to the projectile kinetic energy.

关键词： highly charged ion hollow multi-electron excitation X- ray.

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Relationship between disorder,magnetism and band topology in Mn(Sb_(1-x)Bi_(x))_(2)Te_(4) single crystals

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Chinese Physics B 2024年第6期33卷 102-107页

作者：席明雷和畅 Department of Physics and Beijing key Laboratory of Opto-electronic Functional materials&Micro-nano Devices Renmin University of ChinaBeijing 100872China key Laboratory of Quantum State Construction and Manipulation(ministry of education) Renmin University of ChinaBeijing 100872China

We investigate the evolution of magnetic properties as well as the content and distribution of Mn for Mn(Sb_(1-x)Bi_(x))_(2)Te_(4) single crystals grown by large-temperature-gradient chemical vapor transport *** is found that the ferromagnetic MnSb_(2)Te_(4) changes to antiferromagnetism with Bi doping when x≥*** analysis implies that the occupations of Mn ions at Sb/Bi site Mn_(Sb/Bi) and Mn site Mn_(Mn) have a strong influence on the magnetic ground states of these *** the decrease of Mn_(Mn) increase of Mn_(Sb/Bi),the system will favor the ferromagnetic ground *** addition,the rapid decrease of T_(C/N) with increasing Bi content when x ≤0.25 and the insensitivity of T_(N) to x when x> 0.25 suggest that the main magnetic interaction may change from the Ruderman-Kittel-Kasuya-Yosida type at low Bi doping region to the van-Vleck type in high Bi doped samples.

关键词： magnetic topological insulator magnetic properties antisite defects chemical vapor transport

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Nonlinear V-I property of Ag /BaTiO_3.composite materials

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Chinese Science Bulletin 1997年第12期42卷 1046-1048页

作者： KONG Lingbing, FAN Huiqing, ZHANG Liangying and YAO xielectronic materials research Laboratory,{3., xi’an 710049, china electronic materials research Laboratory Xi\'an Jiaotong University Xi\'an 710049 China

THE composites formed by mixing metal particles into matrices have special optical and electri-cal properties. Up to now, main work has been laid on the investigation of optical propertyof the composites, rather than on that of electrical property. As well known, the structure of ZnO varistors can be described as semiconducting grainssurrounded by a thin layer of insulator. The thin layer of insulator is of electrical tunneling ef-fect leading to function of varistors. Because the resistance of the semiconducting grains

关键词： composite metal ferroeletrics nonlinear V-I property.

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