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CONDITIONS FOR UNIFORMLY NON-CONFOUNDING OF CAUSAL DISTRIBUTION EFFECTS OVER MULTIPLE COVARIATES

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Journal of Systems Science & Complexity 2010年第4期23卷 796-803页

作者： Xueli WANG School of Science,beijing university of posts and telecommunications,beijing 100876,china. School of Science Beijing University of Posts and Telecommunications Beijing China

Causation is a distinct concept from association and more important than association inepidemiologic *** paper proposes the concept of uniform non-confounding for causal distributioneffects over multiple covariates,and gives the sufficient conditions for uniform non-confoundingover a covariate set C including confounders or non-confounders,and also shows the conditions forconditionally non-confounding in the *** these conditions can be tested by observeddata.

关键词： Causal distribution effect confounding covariates uniform non-confounding

Neighborhood-following algorithms for linear programming

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Science china Mathematics 2004年第6期47卷 812-820页

作者： Al WenbaoSchool of Science, beijing university of posts and telecommunications, beijing 100876, china School of Science Beijing University of Posts and Telecommunications Beijing China

In this paper, we present neighborhood-following algorithms for linear programming. When the neighborhood is a wide neighborhood, our algorithms are wide neighborhood primal-dual interior point algorithms. If the neighborhood degenerates into the central path, our algorithms also degenerate into path-following algorithms. We prove that our algorithms maintain the O9√nL) -iteration complexity still, while the classical wide neighborhood primal-dual interior point algorithms have only the O(nL-iteration complexity. We also proved that the algorithms are quadratic convergence if the optimal vertex is nondegenerate. Finally, we show some computational results of our algorithms.

关键词： linear programming primal-dual interior point methods wide neighborhood methods quadratic convergence

Analyzing the Switching Characteristics of a NOLM Demultiplexer with on Analytic and Numrical Methods

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Chinese Journal of Lasers 1999年第5期8卷 419-424页

作者： LIU XianbinG YE Peida(telecommunications Engineering School, beijing university of posts and telecommunications, beijing 100876 china) 北京邮电大学电信工程学院北京

The switching characteristics of a NOLM demultiplexer are investigated by using an analytic and numerical method. The results reveal that the switching characteristics of a NOLM demultiplexer depend on parameters such as the power coupling ratio of the coupler,the peak power of control pulses, the walk-off and the initial time delay between signal pulses and control pulses, etc. The efficiency of NOLM is dependent on the peak power of controlpulses However, the switching window profile begins to oscillate as the power exceeds a critica value and this will be detrimental to the demultiplexed signals. The signal-control pulse walk-off can broaden the switching window of NOLM, make the window profile deviate fromits central position, and decrease its switching efficiency.

关键词： OTDM NOLM demultiplexer all-optical switch

STABILITY OF GENERALIZED JACKSON NETWORKS WITH INFINITE SUPPLY OF WORK

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Journal of Systems Science & Complexity 2008年第2期21卷 283-295页

作者： Yongjiang GUO School of Science Beijing University of Posts and Telecommunications Beijing 100876 China

A general Jackson network （GJN） with infinite supply of work is considered. By fluid limit model, the author finds that the Markov process describing the dynamics of the GJN with infinite supply of work is positive Harris recurrent if the corresponding fluid model is stable. Furthermore, the author proves that the fluid model is stable if the usual traffic condition holds.

关键词： Fluid limit model general Jackson network (GJN) infinite supply positive Harris recurrent stability.

SVM-based loss differentiation algorithm for wired-cum-wireless networks

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The Journal of china Universities of posts and telecommunications 2009年第4期16卷 104-111页

作者： DENG Qian-hua ,CAI An-ni School of Telecommunication Engineering,beijing university of posts and telecommunications,beijing 100876,china School of Telecommunication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

In a hybrid wired-cum-wireless network environment, packet loss may happen because of congestion or wireless link errors. Therefore, differentiating the cause is important for helping transport protocols take actions to control congestion only when the loss is caused by congestion. In this article, an end-to-end loss differentiation mechanism is proposed to improve the transmission performance of transmission control protocol （TCP）-friendly rate control （TFRC） protocol. Its key design is the introduction of the outstanding machine learning algorithm - the support vector machine （SVM） into the network domain to perform multi-metric joint loss differentiation. The SVM is characterized by using end-to-end indicators for input, such as the relative one-way trip time and the inter-arrival time of packets fore-and-aft the loss, while requiring no support from intermediate network apparatus. Simulations are carried out to evaluate the loss differentiation algorithm with various network configurations, such as with different competing flows, wireless loss rate and queue size. The results show that the proposed classifier is effective under most scenarios, and that its performance is superior to the ZigZag, mBiaz and spike （ZBS） scheme.

关键词： machine learning SVM TCP-friendly rate control (TFRC) congestion control

TWO-AGENT PARETO OPTIMAL COOPERATIVE INVESTMENT IN INCOMPLETE MARKET:AN EQUIVALENT CHARACTERIZATION

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Journal of Systems Science & Complexity 2011年第4期24卷 701-710页

作者： Qing ZHOU School of Science Beijing University of Posts and Telecommunications Beijing 100876 China.

This paper studies the following cooperative investment game with two agents. At the start of the game, both the agents＇ capital are collected. The total capital are then invested according to a certain trading strategy. At a certain time To one agent quits the cooperation and they divide the wealth among themselves. During the remaining period [To, T], the other agent invests his/her capital following a possibly different trading strategy. By stochastic optimization method combined with the theory of Backward Stochastic Differential Equations （BSDEs, for short）, we give an equivalent characterization of the Pareto optimal cooperative strategies.

关键词： Backward stochastic differential equation cooperative investment incomplete market,Pareto optimum stochastic utility.

Search recommendation model based on user search behavior and gradual forgetting collaborative filtering strategy

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The Journal of china Universities of posts and telecommunications 2010年第3期17卷 110-117页

作者： LIU Chuan-chang State Key Laboratory of Networking and Switching Technology, beijing university of posts and telecommunications, beijing 100876, china State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications Beijing 100876 China

The existing search engines are lack of the consideration of personalization and display the same search results for different users despite their differences in interesting and purpose. By analyzing user＇s dynamic search behavior, the paper introduces a new method of using a keyword query graph to express user＇s dynamic search behavior, and uses Bayesian network to construct the prior probability of keyword selection and the migration probability between keywords for each user. To reflect the dynamic changes of the user＇s preference, the paper introduces non-lineal gradual forgetting collaborative filtering strategy into the personalized search recommendation model. By calculating the similarity between each two users, the model can do the recommendation based on neighbors and be used to construct the personalized search engine.

关键词： search recommendation model search behavior expression keyword query graph gradual forgetting collaborative filtering

Novel limited feedback scheme under the MIMO broadcast system

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The Journal of china Universities of posts and telecommunications 2009年第6期16卷 11-16页

作者： CHENG Tie-zheng,YUAN Chao-wei School of Information and Communication Engineering,beijing university of posts and telecommunications,beijing 100876,china School of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

By deducing the distribution of the normalized channel covariance matrix,a novel limited feedback scheme is proposed under multiple users（MU） multiple-input multiple-output（MIMO） broadcast channel（BC） *** proposed scheme has advantages in three ***,it has no constraints on the number of users or ***,each user＇s feedback bits are independent of the number of receiving ***,the proposed scheme avoids the storage of large-size codebook on the *** results show that the performance of the proposed scheme is close to the perfect channel state information（CSI） case and it just needs a small number of feedback bits.

关键词： MIMO broadcast channel limited feedback normalized channel covariance

Synchronization of MIMO OFDM systems by perfect complete generalized complementary orthogonal loosely synchronous code groups

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The Journal of china Universities of posts and telecommunications 2009年第2期16卷 1-7页

作者： WANG Jian YANG Xun LI Dao-ben School of Information Engineering,beijing university of posts and telecommunications,beijing 100876,china School of Information Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

This article proposes a time/frequency synchronization algorithm in the multiple input multiple output （MIMO） systems, in which the perfect complete generalized complementary orthogonal loosely synchronous code groups are used as the synchronization sequence. The synchronization algorithm is divided into four stages： 1） synchronization in time domain by signal autocorrelation; 2） synchronization in frequency domain by fast Fourier transform （FFT）; 3） multipath dissociation using coherent detection and fine time synchronization; 4） fine frequency offset estimation by phase rotation. As per the perfect complete generalized complementary orthogonal loosely synchronous code groups, the cross-correlation and out-of-phase auto-correlation for any relative shift between any two codes is always zero. This ideal property makes the time/frequency synchronization algorithm simple and efficient. The simulation results show that even in the multipath fast fading channel with low signal noise ratio （SNR）, the MIMO system can get synchronized both in the time domain and frequency domain with high stability and reliability.

关键词： MIMO OFDM synchronization complementary orthogonal code loosely synchronous (LS) code