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HBD:Towards Efficient Reactive Rule Dispatching in Software-Defined Networks

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Tsinghua Science and Technology 2016年第2期21卷 196-209页

作者： Chang Chen Xiaohe Hu Kai Zheng xiang Wang yang xiang Jun Li Department of Automation Research Institute of Information TechnologyTsinghua UniversityBeijing 100084China. IBM China Research Lab Beijing 100084China Research Institute of Information Technology Tsinghua UniversityBeijing 100084China. Research Institute of Information Technology Tsinghua National Lab for Information Science and TechnologyTsinghua UniversityBeijing 100084China.

Most types of Software-Defined Networking （SDN） architectures employ reactive rule dispatching to enhance real-time network control. The rule dispatcher, as one of the key components of the network controller, generates and dispatches the cache rules with response for the packet-in messages from the forwarding devices. It is important not only for ensuring semantic integrity between the control plane and the data plane, but also for preserving the performance and efficiency of the forwarding devices. In theory, generating the optimal cache rules on demands is a knotty problem due to its high theoretical complexity. In practice, however, the characteristics lying in real-life traffic and rule sets demonstrate that temporal and spacial localities can be leveraged by the rule dispatcher to significantly reduce computational overhead. In this paper, we take a deep-dive into the reactive rule dispatching problem through modeling and complexity analysis, and then we propose a set of algorithms named Hierarchy-Based Dispatching （HBD）, which exploits the nesting hierarchy of rules to simplify the theoretical model of the problem, and trade the strict coverage optimality off for a more practical but still superior rule generation result. Experimental result shows that HBD achieves performance gain in terms of rule cache capability and rule storage efficiency against the existing approaches.

关键词： Software-Defined Networking (SDN) reactive rule dispatching rule cache performance

Photoelectron momentum distributions of single-photon ionization under a pair of elliptically polarized attosecond laser pulses

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Chinese Physics B 2020年第7期29卷 313-320页

作者： Hui-Fang Cui xiang-yang Miao College of Physics and Information Engineering Shanxi Normal UniversityLinfen 041004China Key Laboratory of Spectral Measurement and Analysis of Shanxi Province Shanxi Normal UniversityLinfen 041004China

The attosecond ionization dynamics of atoms has attracted extensive attention in these ***,the role of the initial state is not clearly *** address this question,we perform simulations on the neon atom and its model atom with different initial states by numerically solving the corresponding two-dimensional time-dependent Schrodinger¨*** theoretically investigate atomic photoelectron momentum distributions(PMDs)by a pair of elliptically polarized attosecond laser *** find that the PMD is sensitive not only to the ellipticities of the pulses,the relative helicity,and time delay of the pulses,but also to the symmetry of the initial electronic *** are analyzed by the first-order time-dependent perturbation theory(TDPT)and offer a new tool for detecting the rotation direction of the ring currents.

关键词： photoelectron momentum distributions elliptically polarized attosecond laser pulses magnetic quantum numbers rotation direction of the ring currents

Unified Characteristic Numbers and Solutions of Equations for Birth and Death Processes with Barriers

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Acta Mathematicae Applicatae Sinica 2010年第3期26卷 443-454页

作者： xiang-qun yang He-song Wang College of Mathematics and Computer Science Hunan Normal University. Changsha 410081 China College of Mathematics and Computer Science Changsha University of Science and Technology Changsha410076 China

The state 0 of a birth and death process with state space E = {0, 1, 2,....} is a barrier which can be classified into four kinds： reflection, absorption, leaping reflection, quasi-leaping reflection. For the first, second and fourth barriers, the characteristic numbers of different forms have been introduced. In this paper unified characteristic numbers for birth and death processes with barriers were introduced, the related equations were solved and the solutions were expressed by unified characteristic numbers. This paper concerns work solving probability construction problem of birth and death processes with leaping reflection barrier and quasi-leaping reflection barrier.

关键词： birth and death process with barrier reflection and absorption leaping reflection andquasi-reflection characteristic numbers solutions of equations

Criterion of Semi-Markov Dependent Risk Model

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Acta Mathematica Sinica,English Series 2014年第7期30卷 1273-1280页

作者： Xiao Yun MO xiang Qun yang Department of Basic Subjects Hu’nan University of Finance and Economics College of Mathematics and Computer Science Hu’nan Normal University

A rigorous definition of semi-Markov dependent risk model is given. This model is a generalization of the Markov dependent risk model. A criterion and necessary conditions of semi- Markov dependent risk model are obtained. The results clarify relations between elements among semi-Markov dependent risk model more clear and are applicable for Markov dependent risk model.

关键词： Semi-Markov dependent risk model Markov dependent risk model criterion necessarycondition Markov chain

A COMPARISON OF DIFFERENT CONTRACTION METHODS FOR MONOTONE VARIATIONAL INEQUALITIES

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Journal of Computational Mathematics 2009年第4期27卷 459-473页

作者： Bingsheng He xiang Wang Junfeng yang Department of Mathematics Nanjing University Nanjing 210093 China

It is interesting to compare the efficiency of two methods when their computational loads in each iteration are equal. In this paper, two classes of contraction methods for monotone variational inequalities are studied in a unified framework. The methods of both classes can be viewed as prediction-correction methods, which generate the same test vector in the prediction step and adopt the same step-size rule in the correction step. The only difference is that they use different search directions. The computational loads of each iteration of the different classes are equal. Our analysis explains theoretically why one class of the contraction methods usually outperforms the other class. It is demonstrated that many known methods belong to these two classes of methods. Finally, the presented numerical results demonstrate the validity of our analysis.

关键词： Monotone variational inequalities Prediction-correction Contraction methods.

On a class of measure-valued processes:singular cases

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Science China Mathematics 2006年第10期49卷 1315-1326页

作者： WANG Bin xiang Kainan yang xiangqun Department of Mathematics Hunan Normal University Changsha 410081 China Department of Mathematics Hunan Normal University Changsha 410081 China Department of Mathematics Hunan Normal University Changsha 410081 China

A measure-valued diffusion process describing how the measures evolve under flows or "imaginary" flows on Rd is constructed in this paper. The interest of the process is that on the one hand, it can be viewed as a mea... 详细信息

关键词： flow, "imaginary" flow, measure-valued process.

Complex patterns of precipitation and extreme events during 1951-2011 in Sichuan Basin, Southwestern China

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Journal of Mountain Science 2018年第2期15卷 340-356页

作者： ZHOU xiang-yang LEI Wen-juan Guizhou Provincial Key Laboratory of Public Big Data Guizhou University State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University College of Architecture & Environment Sichuan University

Sichuan Basin is located in southwestern China and affected by a complex water vapor （WV） sources. Here, the spatial and temporal patterns of precipitation and extreme events are investigated by six indices of World Meteorology Organization Commission, including annual precipitation total （AP）, maximum daily precipitation （Maxld）, intensity of rainfall over 1 mm/d （IR1）, maximum and mean consecutive dry days （Max CDD, Mean CDD） and coefficient of variance. Based on 24 daily precipitation time series from 1951 to 2o11, Mann-Kendall test is employed to quantify the significant level of these indices, from which the classification of precipitation change and its spatial patterns are obtained. Meanwhile, the probability distributions of these indices are identified by L-moment analysis and the Goodness-of-fit test, and the corresponding values are calculated by theoretical model at different return periods. The results reveal that the western basin displays normal drought： less AP and precipitation intensity while longer drought. The southern basin shows normal increase： larger AP and precipitation intensity but shorter CDD. However, in hilly region of the central basin and the transition zone between basin and mountains, precipitation changes abnormally： increasing both drought （one or both of Mean CDD and MaxCDD） and precipitation intensity （one or both of Maxld and trend of AP is. Probability IR1） no matter what the distribution models also demonstrate the complex patterns： a negative correlation between Maxld and Max CDD in the west （R2≥0.61） while a positive correlation in the east （R2≥0.41） at all return periods. These patterns are induced by the changes in WV sources and the layout of local terrain. The increase of WV in summer and decrease in spring leads to the heavier rainfall and longer drought respectively. The large heat island effect of the basin contributes to a lower temperature in transition zones and more precipitation in the downwind area. These resul

关键词： Extreme precipitation events Climatechange Sichuan Basin Trend analysis Probability distribution

Scaling analysis of the circulation growth of leading-edge vortex in flapping flight

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Acta Mechanica Sinica 2021年第10期37卷 1530-1543,I0002页

作者： yang xiang Haotian Hang Suyang Qin Hong Liu J.C.Wu Center for Aerodynamics School of Aeronautics and AstronauticsShanghai Jiao Tong UniversityShanghai200240China School of Aeronautics and Astronautics Shanghai Jiao Tong UniversityShanghai200240China

In this paper,an experiment of a robotic model at Reynolds number of approximately 240 is performed with the aim of establishing a scaling law for describing the circulation growth of the leading-edge vortex(LEV)on a flapping *** typical modes of wing rotation,i.e.,advanced,symmetric,and delayed modes,are considered to examine the effects of wing rotation on the scaling formation of *** streamwise velocity fields of the LEV along the span of the wing are measured by particle image velocimetry *** results demonstrated that a spirally three dimensional(3D)LEV with spanwise distribution of circulation rolls up on the upper surface of wing and the circulation of LEV usually obtains the peak before the end of wing *** on the concept of vortex formation time,the formation time of the 3D LEV are defined in two distinct ***(denoted by T∗LEV)is defined based on the LEV circulation,and the other(denoted by T∗∗LEV)is defined based on the wing *** is found that T∗∗LEV increases monotonously during the upstroke and downstroke,whereas T∗LEV generally arrives peaks and then *** peak value of T∗LEV indicates the formation number of LEV,which stays in the range of 2.5–5.5,agrees with the scaling formation number predicted by other ***,the mode of wing rotation plays a controllable role in the formation number of LEV by modulating the characteristic length scale that feeds the formation of *** reaching the formation number,the LEVs stably remain attached on the flapping wing and even further grow at some spanwise locations because of vorticity ***,the linear relationship between T∗LEV and T∗∗LEV before reaching the formation number can suggest a potential model for predicting the circulation growth of LEV based on wing kinematics.

关键词： Leading-edge vortex Circulation Formation number Scaling formation

Lagrangian analysis of the fluid transport induced by the interaction of two co-axial co-rotating vortex rings

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Journal of Hydrodynamics 2020年第6期32卷 1080-1090页

作者： Hai-yan Lin yang xiang Su-yang Qin Hui Xu Hong Liu J.C.wu center for aerodynamics school of aeronautics and astronauticsshanghai jiao tong universityshanghai200240china

In this paper,the fluid transport in the interaction of two co-axial co-rotating vortex rings are *** rings are generated using the piston-cylinder apparatus,and the resulting velocity fields are measured using digital particle image *** interaction process is analysed by means of vorticity contour,as well by investigation of the Lagrangian coherent structures(LCSs)defined by the ridges of the finite-time Lyapunov exponent(FTLE).Experimental results demonstrate that two types of vortex interaction are identified,namely strong and weak interactions,*** the strong interaction,the Lagrangian boundaries of the two vortex rings are merged together and form a flux window for fluid *** weak interaction,only the Lagrangian drift induced by the motion of the front vortex ring is observed and affects the Lagrangian boundary of the rear vortex ***,the fluids transported in the strong interaction carry considerable momentum but no *** contrast,there are nearly no fluxes occurring in the weak *** tracking the variations of circulation and impulse occupied by the separated regions distinguished by the LCSs,it is found that the circulation nearly has no change,but the impulse occupied by vortex core region has significant *** the strong interaction,the impulse of rear vortex ring decreases but the impulse of the front vortex ring *** on the impulse law,it is speculated that the fluid force generated by the formation of the rear vortex rings can be ***,the strong interaction between wake vortices can actually improve the propulsive efficiency of the biological systems by operating the formation of large-scale vortices.

关键词： Vortex rings Lagranagian coherent structures(LCSs) fluid transport