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Search Results: 1 - 10 of 36997 matches for " Chunming Zhao "
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Outage probability of selective decode and forward relaying with secrecy constraints
Xiaojun Sun,Chunming Zhao
Mathematics , 2011,
Abstract: We study the outage probability of opportunistic relay selection in decode-and-forward relaying with secrecy constraints. We derive the closed-form expression for the outage probability. Based on the analytical result, the asymptotic performance is then investigated. The accuracy of our performance analysis is verified by the simulation results.
An Impulse Model for Computer Viruses
Chunming Zhang,Yun Zhao,Yingjiang Wu
Discrete Dynamics in Nature and Society , 2012, DOI: 10.1155/2012/260962
Abstract: Computer virus spread model concerning impulsive control strategy is proposed and analyzed. We prove that there exists a globally attractive infection-free periodic solution when the vaccination rate is larger than 0. Moreover, we show that the system is uniformly persistent if the vaccination rate is less than 1. Some numerical simulations are finally given to illustrate the main results.
Low complexity Chase-2 decoding of concatenated codes
XiaoJian Liu,ChunMing Zhao,XiaoJun Sun
Chinese Science Bulletin , 2010, DOI: 10.1007/s11434-009-3572-y
Abstract: The concatenated codes are widely used in current communication systems, such as satellite communication systems and WiMAX system. The objective of this study was to present a low complexity iterative soft decoding algorithm for concatenated codes. The concatenation was between a Reed-Solomon (RS) code and recursive systematic convolutional (RSC) code. The reduction in computational complexity was achieved by simplifying the Chase-2 decoder for RS codes with limited usage of test patterns. The processing of soft information between inner and outer decoders was also discussed. Simulation results showed that the proposed algorithm could achieve a good trade-off between complexity and performance.
Research advances in the catalysts for the selective oxidation of ethane to aldehydes
Zhang Zhe,Zhao Zhen,Xu Chunming
Chinese Science Bulletin , 2005, DOI: 10.1007/BF02897374
Abstract: Selective oxidation of ethane to aldehydes is one of the most difficult processes in the catalysis researches of low alkanes. The development of selective oxidation of ethane to aldehydes (formaldehyde, acetaldehyde and acrolein) is discussed. The latest progress of the catalysts, including bulk or supported metal oxide catalysts, highly dispersed and isolated active sites catalysts, and the photo-catalytic ethane oxidation catalysts, partial oxidation of ethane in the gas phase, and the proposed reaction pathways from ethane to aldehydes are involved.
Closed-Form Expressions for Relay Selection with Secrecy Constraints
Xiaojun Sun,Chunming Zhao,Ming Jiang
Mathematics , 2010,
Abstract: An opportunistic relay selection based on instantaneous knowledge of channels is considered to increase security against eavesdroppers. The closed-form expressions are derived for the average secrecy rates and the outage probability when the cooperative networks use Decode-and-Forward (DF) or Amplify-and-Forward (AF) strategy. These techniques are demonstrated analytically and with simulation results.
Closed-Form Expressions for Secrecy Capacity over Correlated Rayleigh Fading Channels
Xiaojun Sun,Chunming Zhao,Ming Jiang
Mathematics , 2010,
Abstract: We investigate the secure communications over correlated wiretap Rayleigh fading channels assuming the full channel state information (CSI) available. Based on the information theoretic formulation, we derive closed-form expressions for the average secrecy capacity and the outage probability. Simulation results confirm our analytical expressions.
Joint LDPC and Physical-layer Network Coding for Asynchronous Bi-directional Relaying
Xiaofu Wu,Chunming Zhao,Xiaohu You
Mathematics , 2011,
Abstract: In practical asynchronous bi-directional relaying, symbols transmitted by two sources cannot arrive at the relay with perfect frame and symbol alignments and the asynchronous multiple-access channel (MAC) should be seriously considered. Recently, Lu et al. proposed a Tanner-graph representation of the symbol-asynchronous MAC with rectangular-pulse shaping and further developed the message-passing algorithm for optimal decoding of the symbol-asynchronous physical-layer network coding. In this paper, we present a general channel model for the asynchronous MAC with arbitrary pulse-shaping. Then, the Bahl, Cocke, Jelinek, and Raviv (BCJR) algorithm is developed for optimal decoding of the asynchronous MAC channel. For Low-Density Parity-Check (LDPC)-coded BPSK signalling over the symbol-asynchronous MAC, we present a formal log-domain generalized sum-product-algorithm (Log-G-SPA) for efficient decoding. Furthermore, we propose to use cyclic codes for combating the frame-asynchronism and the resolution of the relative delay inherent in this approach can be achieved by employing the simple cyclic-redundancy-check (CRC) coding technique. Simulation results demonstrate the effectiveness of the proposed approach.
On the BCJR Algorithm for Asynchronous Physical-layer Network Coding
Xiaofu Wu,Chunming Zhao,Xiaohu You
Mathematics , 2011,
Abstract: In practical asynchronous bi-directional relaying, symbols transmitted by two source nodes cannot arrive at the relay with perfect symbol alignment and the symbol-asynchronous multiple-access channel (MAC) should be seriously considered. Recently, Lu et al. proposed a Tanner-graph representation of symbol-asynchronous MAC with rectangular-pulse shaping and further developed the message-passing algorithm for optimal decoding of the asynchronous physical-layer network coding. In this paper, we present a general channel model for the asynchronous multiple-access channel with arbitrary pulse-shaping. Then, the Bahl, Cocke, Jelinek, and Raviv (BCJR) algorithm is developed for optimal decoding of asynchronous MAC channel. This formulation can be well employed to develop various low-complexity algorithms, such as Log-MAP algorithm, Max-Log-MAP algorithm, which are favorable in practice.
A Stochastic Dynamic Model of Computer Viruses
Chunming Zhang,Yun Zhao,Yingjiang Wu,Shuwen Deng
Discrete Dynamics in Nature and Society , 2012, DOI: 10.1155/2012/264874
Abstract: A stochastic computer virus spread model is proposed and its dynamic behavior is fully investigated. Specifically, we prove the existence and uniqueness of positive solutions, and the stability of the virus-free equilibrium and viral equilibrium by constructing Lyapunov functions and applying Ito's formula. Some numerical simulations are finally given to illustrate our main results.
Modeling of kiwifruit metallothionein kiwi503
Chunming Zhu,Tun Lü,Riqing Zhang,Nanming Zhao,Jinyuan Liu
Chinese Science Bulletin , 2000, DOI: 10.1007/BF02886249
Abstract: Kiwifruit metallothionein, kiwi503, is a typical plant metallothionein protein. It has 63 amino acid residues in two cysteine-rich regions and one spacer region of about 32 residues. In this note, the two cysteine-rich regions and the spacer region have been modeted separatety by the distance geometry and the homology method. The three parts are then connected to generate a three-dimensional structural modet of kiwifruit metallothionein kiwi503. The result shows that there is no structural or energy barrier preventing either cysteine rich domain from independently forming a metal-sulfur chetating cluster. The method can also be applied to predicting the structures of the same type of other proteins.
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