检索结果-南通市图书馆

Optimal power allocation for cognitive relay networks: amplify-and-forward versus selection relay

science China(Information sciences) 2011年第4期54卷 861-872页

作者： YUE WenJing 1,2.ZHENG BaoYu 1,2.MENG QingMin 1,YUE WenJie 3.& CUI JingWu 1 1 Institute of Signal Processing and Transmission,nanjing {2. of Posts and Telecommunications,nanjing 2.0003.China 2.{3. of Electronic engineering,Shanghai Jiaotong {2.,Shanghai 2.02.0,China 3.Shanxi Institute of Educational science,Taiyuan 03.009,China 1. Institute of Signal Processing and Transmission Nanjing University of Posts and Telecommunications Nanjing 210003 China2. Department of Electronic Engineering Shanghai Jiaotong University Shanghai 200240 China3. Shanxi Institute of Educational Science Taiyuan 030009 China

We consider a cognitive relay network which is defined by a source,a destination,and cognitive relay nodes and primary user *** this network,a source is assisted by cognitive relay nodes which allow coexisting with primary user nodes by imposing severe constraints on the transmission power so that they operate below the noise floor of primary user *** this paper,we mainly study the power allocation strategies of this system to minimize the outage probability subject to total and individual power constraints for cognitive relay nodes and subject to interference constraints for primary user nodes.A relay transmission scheme,namely amplify-and-forward (AF),is *** first present an optimal power allocation (OPA) scheme to minimize the system outage probability,based on instantaneous channel state information among the source,destination and relay nodes and mean channel gains between primary user nodes and cognitive ***,we propose a selection AF scheme (S-AF) where the single best relay is chosen to assist in the transmission and study power allocation strategy for S-AF to minimize outage *** analytical power allocation strategies have been validated through numerical *** results indicate that the AF with OPA and S-AF with OPA have significantly better outage behavior and average throughput than AF and S-AF schemes *** also find that S-AF with OPA achieves a higher throughput,and hence lower outage probability than AF with OPA.

关键词： cognitive radio (CR) relay networks power allocation outage probability

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Turbulent intensity and its similarity function over an Inner Mongolian grassland during spring

引用

science China Earth sciences 2010年第5期53卷 773-780页

作者： YUE Ping1,2.3. NIU ShengJie2. HU YinQiao4 & ZHANG Qiang1 1 Key Laboratory of Arid Climate Change and Reducing Disaster of Gansu Province, Key Laboratory of Arid Climate Change and Reducing Disaster of CMA, Institute of Arid Meteorology, CMA, Lanzhou 73.02., China 2.2. of Information science and Technology, {2. 2.0044, China 3.Zhangye National Meteorological Observatory, Zhangye 73.000, China 4 Cold and Arid Regions {3. and engineering Research Institute, Chinese Academy of science, Lanzhou 73.000, China 1. Key Laboratory of Arid Climate Change and Reducing Disaster of Gansu Province Key Laboratory of Arid Climate Change and Reducing Disaster of CMA Institute of Arid Meteorology CMA Lanzhou 730020 China2. Nanjing University of Information Science and Technology Nanjing 210044 China3. Zhangye National Meteorological Observatory Zhangye 734000 China4. Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Science Lanzhou 730000 China

Macroscopic reason for the development of turbulences in fluid is the conjunction action of velocity and temperature shears. We use the 2.08 spring flux observations in the surface layer over Inner Mongolian grassland, obtain the similarity functions of turbulent intensity under different stratification stability conditions, and calculate the clear day turbulent intensity in the spring, which is then analyzed and compared with the observed values of turbulent intensity. The results show that in the Inner Mongolian grassland, under the condition of spring unstable stratification of the surface layer, dependence of the similarity function of turbulent intensity on stratification stability follows a "2.3.power law". The structural function is a constant under the neutral stratification condition, and complicated under the stable condition. The calculated turbulent intensity has a close correlation with the observed one, which verifies the accuracy of the similarity functions and the suitability of the theorem of turbulent intensity in the grassland region.

关键词： turbulent intensity variance of velocity similarity function grassland

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Characteristics of Li diffusion on silicene and zigzag nanoribbon

引用

Chinese Physics B 2016年第1期25卷 742-745页

作者：郭艳华曹觉先徐波 College of Materials science and engineering Nanjing Tech UniversityNanjing 210009China department of Physics Xiangtan UniversityXiangtan 411105China department of Materials science and {2. and National Laboratory of Solid State Microstructures Nanjing UniversityNanjing 210093China

We perform a density functional study on the adsorption and diffusion of Li atoms on silicene sheet and zigzag nanoribbons. Our results show that the diffusion energy barrier of Li adatoms on silicene sheet is 0.2. eV, which is much lower than on graphene and Si bulk. The diffusion barriers along the axis of zigzag silicene nanoribbon range from0. 1 to 0.2. eV due to an edge effect, while the diffusion energy barrier is about 0.5 eV for a Li adatom to enter into a silicene nanoribbon. Our calculations indicate that using silicene nanoribbons as anodes is favorable for a Li-ion battery.

关键词： Li diffusion silicene sheet silicene nanoribbons density functional theory

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

A STUDY ON NUMERICAL METHOD OF NAVIER-STOKES EQUATION AND NON-LINEAR EVOLUTION OF THE COHERENT STRUCTURES IN A LAMINAR BOUNDARY LAYER

引用

Journal of Hydrodynamics 2006年第3期18卷 372-377页

作者： LU Chang-gen CAO Wei-dong QIAN Jian-hua State KeyLaboratory of Hydrology-Water Resources and Hydraulic engineering and College of environmental {2. and engineering Hohai University Nanjing 210098 China College of environmental science and {2. Hohai University Nanjing 210098 China

A new method for direct numerical simulation of incompressible Navier-Stokes equations is studied in the paper. The compact finite difference and the non-linear terms upwind compact finite difference schemes on non-uniform meshes in x and y directions are developed respectively. With the Fourier spectral expansion in the spanwise direction, three-dimensional N-S equation are converted to a system of two-dimensional explicit-implicit The treatment of equations. The third-order mixed scheme is employed the three-dimensional for time integration. non-reflecting outflow boundary conditions is presented, which is important for the numerical simulations of the problem of transition in boundary layers, jets, and mixing layer. The numerical results indicate that high accuracy, stabilization and efficiency are achieved by the proposed numerical method. In addition, a theory model for the coherent structure in a laminar boundary layer is also proposed, based on which the numerical method is implemented to the non-linear evolution of coherent structure. It is found that the numerical results of the distribution of Reynolds stress, the formation of high shear layer, and the event of ejection and sweeping, match well with the observed characteristics of the coherent structures in a turbulence boundary layer.

关键词： non-uniform meshes compact finite differences scheme Fourier spectral expansion coherent structure boundary layer

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

CALCULATION AND ANALYSIS ON CHANGE OFAGRICULTURAL WATER CONSUMPTIONIN THE CHANGJIANG DELTA

引用

Chinese Geographical science 2001年第4期11卷 35-39页

作者： ZHANG Yong-qin1, MIAO Qi-long2. PENG Bu-zhuo1(1. department of Urban and Resources sciences,{2.,{3., P. R. China 2. department of environmental sciences, nanjing Institute of Meteorology, nanjing 2.0044, P. department of Urban and Resources sciences Nanjing University Nanjing P. R. China department of environmental {2.s Nanjing Institute of Meteorology Nanjing P. R. China

ABSTRACT: The potential evapotranspiration of specific crops in the Changjiang Delta is calculated by using Pen-man-Monteith method, and an agricultural water consumption model in the area is developed on the basis of agricultural production situation. This model has higher precision compared with actual data and can reflect the actual status of agriculture water need. Considering the meteorological, hydrological, economical development situation of the Changjiang Delta, this paper calculates and analyzes the volumes of agricultural water consumption in 2.00, 2.10, 2.3. and 2.50 under different climate change conditions and different development speeds of urbanization in future. The result shows agriculture water demand increases with temperature rising and decreases obviously with cultivated area reducing. For the Changjiang Delta, the volume of agricultural water consumption in the future will less than that of present.

关键词： agricultural water consumption Changjiang Delta climate change impact

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Size distributions and magic number characteristics of cluster configurations formed during solidification processes of liquid metal Al

引用

science China(Technological sciences) 2006年第2期49卷 172-187页

作者： LIU Rangsu1, LIU Fengxiang1, DONG Kejun1, ZHENG Caixing1, LIU Hairong2. PENG Ping2.& LI Jiyong3.1. department of Physics, Hunan {2., Changsha 410082. China 2. department of Material {3. and engineering, Hunan {2., Changsha 410082. China 3. department of Chemistry, Hunan {2., Changsha 410082. China 1. department of Physics Hunan University Changsha 410082 China 2. department of Material science and {2. Hunan University Changsha 410082 China 3. department of Chemistry Hunan University Changsha 410082 China

A molecular dynamics simulation study has been performed for a large systemconsisting of 100000 liquid metal Al atoms to investigate the formation and magic numbercharacteristics of the cluster configurations formed during the rapid solidification processes. Thecluster-type index method (CTIM) has been adopted to describe various types of clusterconfigurations. The results indicate that the icosahedral clusters (12.0 12.0) and theircombinations play the most important role in the rnicrostructure transitions during solidificationprocesses; for the cluster configurations of different levels formed by various combinations withdiffering numbers of basic clusters, their size distributions possess obvious magic number sequencewhich is in turn as 13.13., 19(2.), 2.-2.(2.), 3.-3.(3.), 3.-40, 43.44, 48..., (those in bracket arethe corresponding value in liquid state); the magic numbers correspond to the peak value positionsof the cluster numbers for corresponding level formed with various combinations by 1, 2. 3. 4, 5, 6,7, ...basic clusters, respectively. This magic number sequence is in good agreement with theexperimental results obtained by Harris et al. At the same time, this simulation study also gives ascientific and reasonable explanation to these experimental results.

关键词： liquid metal, solidification processes, cluster configuration, magic numbers, computer simulation.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

DYNAMIC CHARACTERISTICS OF LIQUID SLOSHING IN A RECTANGULAR TANK UNDER LOW GRAVITY

引用

Journal of Hydrodynamics 2006年第2期18卷 170-176页

作者： CHENG Xu-duo HU Mei-zhu LIU Zhi-yun School of Food science and engineering Nanjing University of Finance and Economics Nanjing 210003 China department of Physics Anqing Teachers College Anqing 246011 China School of Food science and engineering Nanjing University of Finance and Economics Nanjing 210003 China

In this paper, the dynamics of liquid sloshing in a rectangular tank under low gravity was investigated. The basic frequencies and the velocity potentials of sloshing of liquid were obtained by expansion of the Fourier series. The characteristics of force and moment of the liquid acting on a rectangular tank were analyzed. The equivalent mechanical models of spring-vibrator-damper of sloshing of liquid were established with mechanical equivalent principle and numerical results were given. The numerical results show that the equivalent sloshing mass increases with the increase of gravity, and that the basic frequency and the equivalent sloshing mass increase with the increase of the liquid depth.

关键词： low gravity liquid sloshing equivalent mechanical model

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

A possible Younger Dryas-type event during Asian monsoonal Termination 3

引用

science China Earth sciences 2006年第9期49卷 982-990页

作者： CHEN Shitao1, WANG Yongjin1, KONG Xinggong1, LIU Dianbing1, CHENG Hai2.& R.L. Edwards2.1. College of Geography science, nanjing Normal {2., Jiangsu Key Laboratory of {3. Change and Ecological Construction, nanjing 2.0097, China 2. department of Geology and Geophysics, {2. of Minnesota, Minneapolis MN55455, USA 1. College of Geography science Nanjing Normal University Jiangsu Key Laboratory of Environmental Change and Ecological Construction Nanjing 210097 China 2. department of Geology and Geophysics University of Minnesota Minneapolis MN 55455 USA

Seven U-Th dates, 560 δ 18O data and microscopic sequences were measured for sta- lagmites from two high-altitude caves in Shennongjia area, Hubei Province. Variations of the de- cadal-resolution stalagmite δ 18O record from Swan Cave (1600 m elevation) reflect large spatial changes in circulation strength and precipitation of Asian monsoon. The evidence comes from a great similarity among the stalagmite δ 18O records from nanjing, Jiangsu Province; Libo, Guizhou Province and here studied area during the last deglaciation, including a part interval of Younger-Dryas event and Bolling-Allerod. A 3.-year-resolution stalagmite δ 18O record from Yongxing Cave (1400 m eleva- tion), 70 km away from Swan Cave, reveals a rapid transition of Asian monsoon climate during Ter- mination 3.at about 2.5±5 kaBP. Based on 3.U-Th dates and about 5000 continuous annual bands, a millennial dry episode has been observed during Asian monsoonal Termination 3.from the Yongxing δ 18O profile. With respect to its structure, duration and transition, the dry reversal, as indicated by our stalagmite δ 18O record, generally agrees with the pattern of the YD event well-expressed in the Chi- nese stalagmite δ 18O records. This YD-type event is characterized by a large decrease in δ 18O value as much as 2.3.‰, more than half of the δ 18O excursion between glacial/interglacial periods, and lasts 13.1±59 a determined by the annual counting chronology. After this event, the monsoon climate shifted abruptly into the interglacial period within 74±4 a. Our data corroborate the view that the re- peated occurrence of YD-type event was not an “accident”, possibly resulted from the coupling of ice-sheet and oceanic/atmospheric circulations.

关键词： stalagmite, Termination 3. Asian monsoon, YD-type event, Shennongjia, Hubei Province.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Israeli Water Achievements Today and Enlightenment to China

引用

Chinese Journal of Population,Resources and Environment 2008年第4期6卷 72-77页

作者： Sun Lei1,2. Xu Lanqing3.1. Institute of environmental {2. and {2., Ocean {3. of China, Qingdao Shandong 2.6100, China 2. department of Soil and Water {2.s, Faculty of Agricultural, Food and environmental Quality {2.s, the Hebrew {3. of Jerusalem, 76100, Israel 3. Logistics Group of Ocean {3. of China, Qingdao Shandong 2.6100, China Institute of environmental science and {2. Ocean University of China Qingdao Shandong 266100 China department of Soil and Water sciences Faculty of Agricultural Food and Environmental Quality Sciences the Hebrew University of Jerusalem 76100 Israel Logistics Group of Ocean university of China Qingdao Shandong 266100 China

Despite the endemic drought, arid climate and associated limited freshwater resources, as well as difficult geopolitical realities, Israel can provide a reliable supply of high quality water to a rapidly growing population. The achievements of water supply in Israel can be summarized as water technologies (like water transportation and purification, desalination, wastewater treatment, effluent reuse, storm water catchment, control systems, rain enhancement and drip irrigation, etc.), water management and legislation as well as water industry. In view of the national concern regarding the quality and quantity of the water, the skills, technologies and know-how that Israel has accumulated in water supply and irrigation can give us enlightenment that is also presented in this paper.

关键词： Israel China water technology water management water industry

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

DYNAMIC CHARACTERISTICS OF LIQUID SLOSHING IN A TRANSVERSELY VIBRATING SPHERICAL TANK WITH A SPACER UNDER LOW GRAVITY

引用

Journal of Hydrodynamics 2008年第6期20卷 762-769页

作者： CHENG Xu-duo HU Mei-zhu WEN Ji-hua School of Food science and engineering Nanjing University of Finance and Economics Nanjing 210003 China department of Physics Anqing Teachers College Anqing 246011 China

The dynamic characteristics of liquid sloshing in a transversely vibrating spherical tank with spacer under low gravity were investigated. By expanding the characteristic functions, the frequencies and velocity potentials of liquid free-sloshing were obtained. The dynamic equations and boundary conditions of liquid sloshing in the traverse vibrational spherical tank with spacer under low gravity were derived. By modifying the velocity potentials of liquid free-sloshing, the velocity potentials of liquid sloshing in the traverse vibrating spherical tank with a spacer were obtained. Furthermore, the forces and the moments acting on tank wall were given. The numerical results show when a spacer is inserted in the tank, the sloshing frequencies of liquid and the forces acting on tank wall will decrease, but the moment of force to the centre of the tank which is caused by the force of liquid acting on the spacer will occur.

关键词： low gravity liquid forced sloshing sloshing suppression

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：