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Heavy Traffic Limit Theorems for a Queue with Poisson ON/OFF Long-range Dependent Sources and General Service Time Distribution

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Acta Mathematicae Applicatae Sinica 2012年第4期28卷 807-822页

作者： wan-yang DAI Department of Mathematics and State Key Laboratory of Novel Software TechnologyNanjing University

In Internet environment, traffic flow to a link is typically modeled by superposition of ON/OFF based sources. During each ON-period for a particular source, packets arrive according to a Poisson process and packet sizes （hence service times） can be generally distributed. In this paper, we establish heavy traffic limit theorems to provide suitable approximations for the system under first-in first-out （FIFO） and work-conserving service discipline, which state that, when the lengths of both ON- and OFF-periods are lightly tailed, the sequences of the scaled queue length and workload processes converge weakly to short-range dependent reflecting Gaussian processes, and when the lengths of ON- and/or OFF-periods are heavily tailed with infinite variance, the sequences converge weakly to either reflecting fractional Brownian motions （FBMs） or certain type of long- range dependent reflecting Gaussian processes depending on the choice of scaling as the number of superposed sources tends to infinity. Moreover, the sequences exhibit a state space collapse-like property when the number of sources is large enough, which is a kind of extension of the well-known Little＇s law for M/M/1 queueing system. Theory to justify the approximations is based on appropriate heavy traffic conditions which essentially mean that the service rate closely approaches the arrival rate when the number of input sources tends to infinity.

关键词： reflecting fractional Brownian motion reflecting Gaussian process long-range dependence queueing process weak convergence

Effect of Wavefront Properties on Numerical Aperture of Fresnel Hologram in Incoherent Holographic Microscopy

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Chinese Physics Letters 2014年第4期31卷 60-63页

作者： wan Yu-Hong Institute of Information Photonics Technology Beijing University of Technology Beijing 100124 College of Applied Sciences Beijing University of Technology Beijing 100124

Fresnel incoherent correlation holographic （FINCH） microscopy is a recently developed new technique, which employs a spatial light modulator （SLM） as the beam splitter. Light originating from the same object point is split into two beams by the wavefront-division phase mask displayed on SLM, and a Fresnel-zone plate-like hologram is formed by the interference of the two beams. The numerical aperture NAH of the recorded Fresnel hologram is introduced as a comprehensive parameter for evaluating the imaging characteristics in the FINCH scheme. The effect of wavefront properties on NAH of the hologram is investigated theoretically in the sense of optimizing imaging resolution. The variation trends of NAH are described and an optimal NAH is achieved by implementing an appropriate phase mask for a given recording distance between SLM and CCD; thus optimized imaging resolution and signal-to-noise ratio are demonstrated experimentally.

关键词： FRESNEL function HOLOGRAPHY WAVEFRONTS (Optics) GIRDERS NUMERICAL apertures

Real-time camera tracking using hybrid features in mobile augmented reality

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Science China(Information Sciences) 2015年第11期58卷 211-223页

作者： wanG WeiJie wan HuaGen State Key Laboratory of CAD&CG Zhejiang University

Often only simple features are employed in mobile augmented reality(AR) due to the limited computational capacity of mobile terminals, which often leads to unsteadiness of the camera tracking. In this paper, we propose a novel approach to real-time camera tracking in mobile AR using hybrid features to alleviate this problem. By integrating feature points and lines as scene features, hybrid features are generated through the process of point/line features extraction, optimization and fusion, and are used in the real-time estimation of camera parameters. A method for image feature optimization is proposed based on the scene structural analysis to meet the computational constraints of mobile terminals. In order to improve the stability of camera tracking, an iterative screening method is proposed to choose a set of stable feature lines, and hybrid features are adaptively constructed based on the composition and geometry of scene features. It is shown from the experimental results that the proposed method produces more stable and smoother camera trajectories in comparison with the method only using feature points, and a good balance is achieved between the stability and the real-time computation of the camera tracking on a mobile platform.

关键词： mobile augmented reality feature extraction camera tracking hybrid feature mobile platform

Method for multi-attribute group decision-making based on the compromise weights

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Journal of Systems Engineering and Electronics 2010年第4期21卷 591-597页

作者： Shengbao Yao wan'an Cui School of Business Administration Zhongnan University of Economics and Law Wuhan 430073 P. R. China College of Management Guangxi University for Nationalities Nanning 530006 P. R. China

Multi-attribute group decision-making problems are considered where information on both attribute weights and value scores of consequences is *** group decision analysis,if preference information about alternatives is provided by participants,it should be verified whether there exist compromise weights that can support all the preference *** different compromise weight vectors may differ for the ranking of the *** the case that compromise weights exist,the method is proposed to find out all the compromise weight vectors in order to rank the *** on the new feasible domain of attribute weights determined by all the compromise weight vectors and the incomplete information on value scores of consequences,dominance relations between alternatives are checked by a nonlinear goal programming model which can be transformed into a linear one by adopting a *** checked dominance relations uniformly hold for all compromise weight vectors and the incomplete information on value scores of consequences.A final ranking of the alternatives can be obtained by aggregating these dominance relations.

关键词： group decision-making incomplete information preference relation compromise weight.

Halogen effects on phenylethynyl palladium(Ⅱ) complexes for living polymerization of isocyanides

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Science China Chemistry 2019年第7期62卷 883-886页

作者： Xinhua wan Beijing National Laboratory for Molecular Sciences Key Laboratory of Polymer Chemistry and Physics Ministry of Education College of Chemistry & Molecular Engineering Peking University

Polyisocyanides belong to one of the most important artificial helical polymers. The rigid-rod helical conformation makes them to exhibit wide potential applications in chiral recognition, enantioseparation, asymmetrical catalysis, and liquid crystals [1]. Up to now, quite a few metal-promoted polymerization methods have been developed to synthesize polyisocyanides. Especially, it is a great challenge for synthetic chemists to synthesize polyisocyanides in living/controllable fashion that afford well-defined and high isotactic helical polymers.

关键词： living polymerization isocyanides chiral recognition

Effect of stress ratio on HCF and VHCF properties at temperatures of 20 °C and 700 °C for nickel-based wrought superalloy GH3617M

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Chinese Journal of Aeronautics 2019年第9期32卷 2199-2210页

作者： Aoshuang wan Junjiang XIONG School of Transportation Science and Engineering Beihang University

This paper attempts to investigate the effects of stress ratio and high temperature on the HCF(high-cycle-fatigue) and VHCF(very-high-cycle-fatigue) behaviors of nickel-based wrought superalloy GH3617 M. Fatigue tests over the full HCF and VHCF regimes were conducted on superalloy GH3617 M subjected to constant-amplitude loading at five stress ratios of -1, -0.5, 0,0.4, and 0.8 in environments of 20 °C and 700 °C temperatures. From experimental observation and fractographic analysis, fatigue mechanisms were deduced to reveal the synergistic interaction between high temperature and stress ratio on the HCF and VHCF behaviors of superalloy GH3617 M. A phenomenological model was crafted from available fatigue design knowledge to evaluate the synergistic interaction, and a good correlation between predictions and experiments has been achieved.

关键词： High cycle fatigue High-temperature Nickel-based superalloy Stress ratio Very high cycle fatigue

A PENALTY FUNCTION METHOD FOR SOLVING ILL-POSED BILEVEL PROGRAMMING PROBLEM VIA WEIGHTED SUMMATION

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Journal of Systems Science & Complexity 2013年第6期26卷 1019-1027页

作者： JIA Shihui wan Zhongping Math Department School of ScienceWuhan University of Science and Technology Hubei Province Key Laboratory of Systems Science in Metallurgical Process Wuhan University of Science and Technology School of Mathematics and Statistics Wuhan University

For ill-posed bilevel programming problem,the optimistic solution is always the best decision for the upper level but it is not always the best choice for both levels if the authors consider the model's satisfactory degree in *** acquire a more satisfying solution than the optimistic one to realize the two levels' most profits,this paper considers both levels' satisfactory degree and constructs a minimization problem of the two objective functions by weighted ***,using the duality gap of the lower level as the penalty function,the authors transfer these two levels problem to a single one and propose a corresponding ***,the authors give an example to show a more satisfying solution than the optimistic solution can be achieved by this algorithm.

关键词： Bilevel programming duality gap penalty function satisfactory degree weighted sum-mation.

Hybrid Bayesian estimation tree learning with discrete and fuzzy labels

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Frontiers of Computer Science 2013年第6期7卷 852-863页

作者： Zengchang QIN Tao wan Intelligent Computing and Machine Learning Lab School of Automation Science and Electrical Engineering Beihang University Beijing 100191 China School of Biological Science and Medical Engineering Beihang University Beijing 100191 China Department of Biomedical Engineering Case Western Reserve University Cleveland OH 44106 USA

Classical decision tree model is one of the classical machine learning models for its simplicity and effectiveness in applications. However, compared to the DT model, probability estimation trees （PETs） give a better estimation on class probability. In order to get a good probability estimation, we usually need large trees which are not desirable with respect to model transparency. Linguistic decision tree （LDT） is a PET model based on label semantics. Fuzzy labels are used for building the tree and each branch is associated with a probability distribution over classes. If there is no overlap between neighboring fuzzy labels, these fuzzy labels then become discrete labels and a LDT with discrete labels becomes a special case of the PET model. In this paper, two hybrid models by combining the naive Bayes classifier and PETs are proposed in order to build a model with good performance without losing too much transparency. The first model uses naive Bayes estimation given a PET, and the second model uses a set of small-sized PETs as estimators by assuming the independence between these trees. Empirical studies on discrete and fuzzy labels show that the first model outperforms the PET model at shallow depth, and the second model is equivalent to the naive Bayes and PET.

关键词： fuzzy labels label semantics random set probability estimation tree mass assignment linguistic decision tree naive Bayes

New understanding achieved from 2 years of Chinese ionospheric investigations

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Science Bulletin 2016年第7期61卷 524-542页

作者： Libo Liu Weixing wan Key Laboratory of Earth and Planetary Physics Institute of Geology and Geophysics Chinese Academy of Sciences Beijing National Observatory of Space Environment Institute of Geology and Geophysics Chinese Academy of Sciences Geoscience School University of the Chinese Academy of Sciences

In the mainland of China, the number of ionospheric research groups is more than 10. Around 110 articles related to ionospheric physics have been published during 2014–2015. In this annual national report of the Committee on Space Research(COSPAR), we will outline some recent progresses in ionospheric studies conducted by the Chinese mainland scientists in the past 2 years. These investigations cover(1) the ionosphere responses to geomagnetic activities;(2) ionospheric climatology and structures;(3) couplings between the ionosphere, plasmasphere and lower atmosphere, and possible seismic signatures in the ionosphere;(4) ionospheric irregularities and scintillation;(5) ionospheric models, data assimilation and simulations;(6) ionospheric dynamics and electrodynamics;(7) progresses in the observation methodology and technique; and(8) planetary ionospheres. Such investigations will strengthen our ability to monitor the ionosphere,provide a better understanding of the ionospheric states and the underlying fundamental processes, and improve the ionospheric modeling, forecasting, and related applications.

关键词： Ionosphere Ionospheric climatology Ionospheric dynamics Ionospheric coupling Planetary ionospheres Ionospheric disturbance