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Numerical modeling of DPSK pressure signals and their transmission characteristics in mud channels

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Petroleum Science 2009年第3期6卷 266-270页

作者： Shen Yue Su Yinao Li Gensheng Li Lin Tian Shouceng College of Physics Science and Technology China University of Petroleum Dongying Shandong 257061 China CNPC Drilling Research Institute Beijing 100083 China State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum Beijing 102249 China

A numerical model and transmission characteristic analysis of DPSK （differential phase shift keying） pressure signals in mud channels is introduced. With the control logic analysis of the rotary valve mud telemetry, a logical control signal is built from a Gate function sequence according to the binary symbols of transmitted data and a phase-shift function is obtained by integrating the logical control signal. A mathematical model of the DPSK pressure signal is built based on principles of communications by modulating carrier phase with the phase-shift function and a numerical simulation of the pressure wave is implemented with the mathematical model by MATLAB programming. Considering drillpipe pressure and drilling fluid temperature profile along drillpipes, the drillpipe of a vertical well is divided into a number of sections. With water-based drilling fluids, the impacts of travel distance, carrier frequency, drillpipe size, and drilling fluids on the signal transmission were studied by signal transmission characteristic analysis for all the sections. Numerical calculation results indicate that the influences of the viscosity of drilling fluids and volume fraction of gas in drilling fluids on the DPSK signal transmission are more notable than the others and the signal will distort in waveform with differential attenuations of the signal frequent component.

关键词： Measurement while drilling (MWD) modulation binary symbol mathematical model numerical simulation differential phase shift keying (DPSK) signal transmission characteristics

维普期刊数据库

Improvement and Realization of DSR Routing Protocol with QoS Support in Wireless Mesh Networks

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china communications 2009年第1期6卷 123-127页

作者： Gu Xiaoyan , Liu Feng Image Processing and Image communications Key Lab, Nanjing university of Posts and Telecommunications, Nanjing 210003, china Image Processing and Image communications Key Lab Nanjing University of Posts and Telecommunications Nanjing 210003 China

In Wireless Mesh Network,multimedia applications require the network to guarantee Quality-of-Service(QoS). A new QoS-aware routing protocol based on DSR named QDSR(QoS-DSR) is further proposed. QDSR guarantees the QoS of application, such as bandwidth and delay, defines routing cost function according to the number of hops of path and buffer and chooses the best path based on routing cost. Simulation results show that, compared with DSR, QDSR greatly improves the throughput, reduces the average end to end delay, improves the efficiency, satisfies the QoS of application better and has stronger applicability and expansibility.

关键词： Wireless Mesh network Quality-of-Service routing protocol bandwidth delay routing cost function

Long time behavior for damped generalized coupled nonlinear wave equations. Ⅱ.Unbounded domain

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communications in Nonlinear Science and Numerical Simulation 2001年第2期6卷 107-110页

作者： Shaomei FANG and Boling GUO Department of Mathematics, Shaoguan university, Shaoguan 512005, china Graduate School, china Academy of Engineering Physics, beijing 100088, china Center for Nonlinear Studies, Institute of Applied Physics and Computational Department of Mathematics Shaoguan University Shaoguan 512005 China Graduate School China Academy of Engineering Physics Beijing 100088 China Center for Nonlinear Studies Institute of Applied Physics and Computational mathematics Beijing 100088 China

In this paper, by using a priori estimates in the weighted space, the existence of the global attractor for the damped generalized coupled nonlinear wave equations in an unbounded domain is obtained.

关键词： unbounded domain weighted space attractor

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communications in Nonlinear Science and Numerical Simulation 1999年第3期4卷 186-190页

作者： Guoqian CHEN and J. H. W. LEE(Centre for Environmental Sciences, Peking university, beijing 100871, china) (Department of Civil Engineering, university of Hong Kong, Hong Kong, china) Centre for Environmental Sciences Peking University Beijing 100871 China Department of Civil Engineering University of Hong Kong Hong Kong China

IntroductionThethermal,abodyofbuoyalfluidinafluidwithwhichitcanmixandgivennamebygliderpilotstothosemassesofwarmairrisingfromhotgroundwarmedbysunshineinwhichtheycansoar,***],duetoi... 详细信息

IntroductionThethermal,abodyofbuoyalfluidinafluidwithwhichitcanmixandgivennamebygliderpilotstothosemassesofwarmairrisingfromhotgroundwarmedbysunshineinwhichtheycansoar,***],duetoi...

关键词： environmental fluid mechanics thermal turbulence modeling

Exact Periodic-Wave Solutions for(2+1)-Dimensional Boussinesq Equation and (3+1)-Dimensional KP Equation

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communications in Theoretical Physics 2004年第8期42卷 239-241页

作者： ZHAO Qiang LIU Shi-Kuo FU Zun-Tao School of Physics, Peking university, beijing 100871, china School of Physics Peking University Beijing 100871 China

The(2+1)-dimensional Boussinesq equation and(3+1)-dimensional KP equation are studied by using theextended Jacobi elliptic-function *** exact periodic-wave solutions for the two equations are obtained.

关键词： Jacobi elliptic-function method (2+l)-dimensional Boussinesq equation (3+l)-dimensional KP equation periodic-wave solutions

Multi-user MIMO downlink eigen-mode transmission over jointly correlated MIMO channels

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Science china(Information Sciences) 2011年第10期54卷 2124-2137页

作者： LI Xiao ,JIN Shi & GAO XiQi National Mobile communications Research Laboratory,Southeast university,Nanjing 210096,china National Mobile communications Research Laboratory Southeast University Nanjing China

The study of multi-user multiple-input multiple-output (MU-MIMO) systems has emerged recently as an important research topic because such systems have the potential to combine the high capacity that can be achieved through MIMO processing with the benefits of spatial-division ***,receiver and transmitter channel state information (CSI) is generally required,especially for the downlink *** this paper,MU-MIMO downlink transmission systems with statistical CSI at the transmitter are studied for jointly correlated MIMO ***-mode space division multiple access transmission is derived based on the maximization of the ergodic sum rate,and two eigen-mode power allocation algorithms are proposed using matrix permanent and convex optimization *** new algorithms can overcome the limitations of the existing multi-user downlink transmission algorithm in practical applications.

关键词： MIMO eigen-mode multi-user downlink

Measurement of Mean Burst Period in WallTurbulence by Wavelet Analysis

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communications in Nonlinear Science and Numerical Simulation 1999年第3期4卷 3-5页

作者： Li LI Chunxiao XU Zhaoshun ZHANG and Guialang CUI(Department of Engineering Mechanics, Tsinghua university, beijing 100084, china) Department of Engineering Mechanics Tsinghua University Beijing 100084 China

IntroductionInwallturbulence,theejectionoflow-speedfluidfromthewallandthesweepofth***urst,andwhentheflowisbursting,therealwaysea... 详细信息

IntroductionInwallturbulence,theejectionoflow-speedfluidfromthewallandthesweepofth***urst,andwhentheflowisbursting,therealwaysea...

关键词： turbulence burst phenomena wavelet analysis

Study on near-wall turbulence structures with local Reynolds stress

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communications in Nonlinear Science and Numerical Simulation 2000年第3期5卷 105-117页

作者： Li LI Chunxiao XU Guixiang CUI and Zhaoshun ZHANG(Department of Engineering Mechanics, Tsinghua university, beijing 100084, china) Department of Engineering Mechanics Tsinghua University Beijing 100084 China

The direct- numerical- simulated ch annel turbulence is analyzed with two-dimensional wavelet transform. Considering the relation between turbulence coherent structure and Reynolds stress in near wall region, the local Reynolds stress (LRS) is defined.A new method for extracting coherent signals from turbulence based on the LRS is developed. Velocity fiuctuations are decomposed to coherent signals and background signals. It is found that the scaling exponents of coherent signals have a considerable deviation from the Kolmogorov scaling law q/3 (K41 theory), while that of background signals is very close to q/3. It is confirmed that coherent signals are mainly responsible for the anomalous *** characterized by the positive peaks of LRS, the typical structures in near wall region are obtained by conditional statistical averaging. It is shown that the local character of near-wall turbulence structures can be effectively described with LRS.

关键词： wavelet channel turbulence the local Reynolds stress

Effective capacity region of two-user opportunistic spectrum access

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Science china(Information Sciences) 2011年第9期54卷 1928-1937页

作者： XU YuHua,WANG JinLong & WU QiHui Institute of communications Engineering,PLA university of Science and Technology,Nanjing 210007,china Institute of communications Engineering PLA University of Science and Technology Nanjing China

The effective capacity region of the two-user opportunistic spectrum access (OSA) system in Rayleigh fading environment is derived in this *** OSA is a contemporary research topic,little attention has been given to the capacity analysis under quality-of-service (QoS) ***,we use the effective capacity,which is a powerful tool to analyze the QoS requirements in wireless communication systems,to study the sustainable packet arrival rate of the secondary users while meeting statistical QoS *** derive the effective capacity region of the two-user OSA system and propose a method to obtain the capacity region *** addition,by combining the finite state channel model and the activity of the primary user,an extended finite state channel model for the two-user OSA system is also proposed.

关键词： cognitive radio opportunistic spectrum access effective capacity