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center, Limit Cycles and Isochronous center of a Z_4-equivariant Quintic System

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Acta Mathematica Sinica,English Series 2010年第6期26卷 1183-1196页

作者： Chao Xiong DU Hei Long MI Yi Rong LIU Department of Hu'nan Shaoyang University Shaoyang 422000 P. R. China and School of Mathematics Central South University Changsha 410083 P. R. China Department of Information Science Hu'nan Commercial University Changsha 410083 P. R. China School of Mathematics Central South University Changsha 410083 P. R. China

In this paper, we study the limit cycles bifurcations of four fine focuses in Z4-equivariant vector fields and the problems that its four singular points can be centers and isochronous centers at the same time. By computing the Liapunov constants and periodic constants carefully, we show that for a certain Z4-equivariant quintic systems, there are four fine focuses of five order and five limit cycles can bifurcate from each, we also find conditions of center and isochronous center for this system. The process of proof is algebraic and symbolic by using common computer algebra soft such as Mathematica, the expressions after being simplified in this paper are simple relatively. Moreover, what is worth mentioning is that the result of 20 small limit cycles bifurcating from several fine focuses is good for Z4-equivariant quintic system and the results where multiple singular points become isochronous centers at the same time are less in published references.

关键词： Z4-equivariant focal value center limit cycles isochronous center

Discrete element method study of solid descending and residence properties in COREX shaft furnace with center gas supply device

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Journal of Iron and Steel Research International 2019年第7期26卷 669-678页

作者： Heng Zhou Qin-fu Hou Ming-yin Kou Shun Yao Sheng-li Wu School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China Department of Chemical Engineering Monash University Clayton VIC 3800 Australia

Solid descending and residence properties in COREX shaft furnace with a center gas supply device (CGSD) were studied using the discrete element method. Solid flow pattern, residence time distribution, and local solid residence time (SRT) were analyzed. Moreover, the effects of the rotation speed of screws, the radius, and height of CGSD were investigated. The results show that the solid flow is dominantly a plug flow in the shaft furnace with the CGSD. In the upper region of the shaft furnace for gas-solid reduction, uniform distribution of local SRT is observed, which is preferable to match the even gas distribution expected due to the CGSD and slots. For different rotation speeds of the screws, the distribution of solid flow patterns is similar. The averaged residence time, dispersed plug volume fraction, and dead volume fraction decrease with increasing the rotation speed of the screws. The radius of the CGSD affects the solid residence in the shaft furnace. Local SRT above the CGSD increases with the increase in the radius of CGSD, possibly leading to the formation of more agglomerates. Hence, the radius of CGSD should be chosen carefully. The height of CGSD has a minor effect on solid residence in the shaft furnace.

关键词： COREX shaft furnace Solid residence time Discrete element method center gas supply device Solid descending

Task-Aware Flow Scheduling with Heterogeneous Utility Characteristics for Data center Networks

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Tsinghua Science and Technology 2019年第4期24卷 400-411页

作者： Fang Dong Xiaolin Guo Pengcheng Zhou Dian Shen the School of Computer Science and Engineering Southeast University

With the continuous enrichment of cloud services, an increasing number of applications are being deployed in data centers. These emerging applications are often communication-intensive and data-parallel, and their performance is closely related to the underlying network. With their distributed nature, the applications consist of tasks that involve a collection of parallel flows. Traditional techniques to optimize flow-level metrics are agnostic to task-level requirements, leading to poor application-level performance. In this paper, we address the heterogeneous task-level requirements of applications and propose task-aware flow scheduling. First, we model tasks' sensitivity to their completion time by utilities. Second, on the basis of Nash bargaining theory, we establish a flow scheduling model with heterogeneous utility characteristics, and analyze it using Lagrange multiplier method and KKT condition. Third, we propose two utility-aware bandwidth allocation algorithms with different practical constraints. Finally, we present Tasch, a system that enables tasks to maintain high utilities and guarantees the fairness of utilities. To demonstrate the feasibility of our system, we conduct comprehensive evaluations with realworld traffic trace. Communication stages complete up to 1.4 faster on average, task utilities increase up to 2.26,and the fairness of tasks improves up to 8.66 using Tasch in comparison to per-flow mechanisms.

关键词： data center networks coflow flow scheduling data-intensive applications

Design and Optimization of VLC Enabled Data center Network

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Tsinghua Science and Technology 2020年第1期25卷 81-92页

作者： Yudong Qin Deke Guo Xu Lin Geyao Cheng Science and Technology on Information Systems Engineering Laboratory National University of Defense TechnologyChangsha 410073China School of Computer Science and Technology Xidian UniversityXi’an 710000China

Visible-Light Communication(VLC) has the potential to provide dense and fast connectivity at low cost. In this paper we propose SFNet, a novel VLC-enabled hybrid data center network that extends the design of wireless Data center Networks(DCNs) into three further dimensions:(1) fully wireless at the inter-rack level;(2) no need for a centralized control mechanism on wireless links;and(3) no need for any infrastructure-level alterations to data centers. Previous proposals typically cannot realize these three rationales simultaneously. To achieve this vision,the proposed SFNet augments fat-tree by organizing all racks into a wireless small-world network via VLC links. The use of VLC links eliminates hierarchical switches and cables in the wireless network, and thus reduces hardware investment and maintenance costs. To fully exploit the benefits of the topology of SFNet, we further propose its topology design and optimization method, routing scheme, and online flow scheduling algorithm. Comprehensive experiments indicate that SFNet exhibits good topological properties and network performance.

关键词： Data center Network(DCN) Visible Light Communication(VLC) topology design

Accurate and Robust Eye center Localization via Fully Convolutional Networks

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IEEE/CAA Journal of Automatica Sinica 2019年第5期6卷 1127-1138页

作者： Yifan Xia Hui Yu Fei-Yue Wang the School of Creative Technologies University of PortsmouthPortsmouthPO1 2DJUK the State Key Laboratory of Management and Control for Complex Systems Institute of AutomationChinese Academy of SciencesBeijing 100190China

Eye center localization is one of the most crucial and basic requirements for some human-computer interaction applications such as eye gaze estimation and eye tracking. There is a large body of works on this topic in recent years, but the accuracy still needs to be improved due to challenges in appearance such as the high variability of shapes, lighting conditions, viewing angles and possible occlusions. To address these problems and limitations, we propose a novel approach in this paper for the eye center localization with a fully convolutional network(FCN),which is an end-to-end and pixels-to-pixels network and can locate the eye center accurately. The key idea is to apply the FCN from the object semantic segmentation task to the eye center localization task since the problem of eye center localization can be regarded as a special semantic segmentation problem. We adapt contemporary FCN into a shallow structure with a large kernel convolutional block and transfer their performance from semantic segmentation to the eye center localization task by *** experiments show that the proposed method outperforms the state-of-the-art methods in both accuracy and reliability of eye center localization. The proposed method has achieved a large performance improvement on the most challenging database and it thus provides a promising solution to some challenging applications.

关键词： Deep learning eye center localization eye gaze estimation eye tracking fully convolutional network (FCN) humancomputer interaction

On Maximum Elastic Scheduling in Cloud-Based Data center Networks for Virtual Machines with the Hose Model

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Journal of Computer Science & Technology 2019年第1期34卷 185-206页

作者： Shuai-Bing Lu Jie Wu Huan-Yang Zheng Zhi-Yi Fang College of Computer Science and Technology Jilin UniversityChangchun 13012China Department of Computer and Information Sciences Temple UniversityPhiladelphiaPA19122U.S.A.

With the growing popularity of cloud-based data center networks (DCNs),task resource allocation has become more and more important to the efficient use of resource in *** paper considers provisioning the maximum admissible load (MAL)of virtual machines (VMs)in physical machines (PMs)with underlying tree-structured DCNs using the hose model for *** limitation of static load distribution is that it assigns tasks to nodes in a once-and-for-all manner,and thus requires a priori knowledge of program *** avoid load redistribution during runtime when the load grows,we introduce maximum elasticity scheduling,which has the maximum growth potential subject to the node and link *** paper aims to find the schedule with the maximum elasticity across nodes and *** first propose a distributed linear solution based on message passing,and we discuss several properties and extensions of the *** on the assumptions and conclusions,we extend it to the multiple paths case with a fat tree DCN,and discuss the optimal solution for computing the MAL with both computation and communication *** that,we present the provision scheme with the maximum elasticity for the VMs,which comes with provable optimality guarantee for a fixed flow scheduling strategy in a fat tree *** conduct the evaluations on our testbed and present various simulation results by comparing the proposed maximum elastic scheduling schemes with other *** simulations validate the effectiveness of the proposed policies,and the results are shown from different perspectives to provide solutions based on our research.

关键词： data center network (DCN) cloud distributed algorithm elasticity hose model optimization

Influence of center of Gravity Location on Flight Dynamic Stability in a Hovering Tailless FW-MAV: Lateral Motion

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Journal of Bionic Engineering 2020年第1期17卷 148-160页

作者： Loan Thi Kim Au Hoon Cheol Park Department of Smart Vehicle Engineering and Artificial Muscle Research center Konkuk UniversitySeoul 05029Korea

This paper reports the effect of the center of Gravity(CG)position on lateral flight dynamic stability of hovering KUBeetle,a tailless FW-MAV,providing further insights on the effects of asymmetries in body mass distribution and wing *** the current study,the standard linearized equations of motion were applied as in the previous work on longitudinal dynamic *** stability derivatives were acquired using the computational fluid dynamic methods via the commercial software of ANSYS *** exists a stable region for CG between 2.6%and 3.5%of the mean chord below the wing pivot point,in which the lateral motion of hovering KUBeetle is passively *** CG below the stable region,because of an unstable oscillatory mode,the lateral motion of the FW-MAV is unstable but can be stabilized using rolling rate *** CG above the stable region,because of a divergence mode,the system remains unstable even with the rolling rate *** with other works on an FW-MAV based on a quasi-steady aerodynamic model and on insect showed similar characteristics for flapping *** is also interesting to note that the asymmetries in body mass and wing kinematics can enlarge the stable region of the system by a non-zero Ixz which approaches the root square of√IxIz,a negative LrNp,and a positive Ix2(Ir+Np).Combining the current result with that of the previous work on longitudinal motion,the most beneficial region of the CG for full 6-DOF flight dynamic stability of hovering KUBeetle was suggested.

关键词： FW-MAV center of gravity flight dynamic stability lateral motion asymmetry computational fluid dynamics bioinspired flight

The center Problem and Time-Reversibility with Respect to a Quadratic Involution for a Class of Polynomial Differential Systems with Order 2 or 3

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Journal of Systems Science & Complexity 2022年第4期35卷 1608-1636页

作者： YANG Jing YANG Ming LU Zhengyi Chengdu Institute of Computer Application Chinese Academy of SciencesChengdu610041China University of Chinese Academy of Sciences Beijing100049China School of Mathematical Sciences Sichuan Normal UniversityChengdu610068China

Most studies of the time-reversibility are limited to a linear or an affine *** this paper,the authors consider the case of a quadratic *** a polynomial differential system with a linear part in the standard form(-y,x)in R~2,by using the method of regular chains in a computer algebraic system,the computational procedure for finding the necessary and sufficient conditions of the system to be time-reversible with respect to a quadratic involution is *** the system is quadratic,the necessary and sufficient conditions can be completely obtained by this *** some cubic systems,the necessary and sufficient conditions for these systems to be time-reversible with respect to a quadratic involution are also *** conditions can guarantee the corresponding systems to have a ***,a property of a center-focus system is discovered that if the system is time-reversible with respect to a quadratic involution,then its phase diagram is symmetric about a parabola.

关键词： center polynomial differential systems quadratic involution regular chains time-reversibility

Abnormal Shift of center Wavelength in Annealing Long-Period Gratings

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Chinese Physics Letters 2000年第1期17卷 28-30页

作者： QIN Li WEI Zhan-Xiong WANG Qing-Ya LI Hui-Ping ZHANG Yu-Shu GAO Ding-San Department of Electronics Engineering Jilin UniversityChangchun 130023

During annealing process of long-period gratings,the center wavelengths of some inodes shift to red wavelength while those of others shift to blue compared with their original written ones,and the magnitudes of the shifts are related to the decay of the grating *** red shifts of center wavelength are more evident in lower-order inodes of the *** suggest that part of the photodissociated-H2 combines continuously with Ge-defect centers within 2 h after UV-exposure,and with which the observed abnormal shifts can be explained successfully.

关键词： center Shift annealing