웹 서버 클러스터에서 Cyber Foraging 응용을 위한 비주기적 부하 갱신을 통한 부하 분산 기법

XiaoYi Lu,Zhen Fu,최원일,강정훈,옥민환,박명순 한국정보처리학회 2007 정보처리학회논문지. 컴퓨터 및 통신시스템 Vol.14 No.1

본 논문에서 웹 서버 클러스터 환경에서 웹 요청들의 분산을 위한 부하 분산 기법을 제안한다. 전통적인 주기적 부하 정보 갱신 기반의 부하 분산 기법에서는 동기화된 부하 정보와 동적 페이지에 포함된 스크립트들의 갱신 정보 때문에 Cyber Foraging 서비스 같은 동적 웹 응용 프로그램에서는 적합하지 않다. 이를 해결하기 위해 Update-on-Finish 부하 분산 알고리즘은 비주기적인 부하 갱신 방법을 사용하고 있다. 웹 스위치는 비주기적인 부하 리포팅 후, 서버들의 실제 부하 정보를 알 수 있다. 그런후 실제 정보에 따라 부하 분산 스케줄을 재배열 한다. 하지만 Update-on-Finish 알고리즘의 경우 부하 정보를 유지하기 위한 통신 부하가 크다는 문제점을 가진다. 본 논문에서는 각 서버가 K%의 작업을 마친 후 비주기적 부하 정보 보고를 통하여부하감소시킨 방법을 제안한다. 또한 서버의 처리능력이 다른 환경을 고려하여 서로 다른 threshold Ti값을 적용함으로써, 다양한 처리 능력을 가진 서버들을 위한 로드 밸런싱 알고리즘으로 확장하여 제안하고 있다. 시뮬레이션 결과에서 제안된 K-Percent-Finish Reporting 방법은 Update-on-Finish 방법보다 최소 50% 이상의 통신 부하를 감소시키면서, 기존 주기적 부하 정보 갱신 기반의 관련 연구들보다 향상된 시스템 처리 능력을 보여주고 있다. This paper introduces a load-balancing algorithm focusing on distributing web requests evenly into the web cluster servers. The load-balancing algorithms based on conventional periodic load-information update mechanism are not suitable for dynamic page applications, which are common in Cyber Foraging services, due to the problems caused by periodic synchronized load-information updating and the difficulties of work load estimation caused by embedded executing scripts of dynamic pages. Update-on-Finish algorithm solves this problem by using non-periodic load-update mechanism, and the web switch knows the servers’ real load information only after their reporting and then distributes new loads according to the new load-information table, however it results in much communication overhead. Our proposed mechanism improve update-on-finish algorithm by using K-Percents-Finish mechanism and thus largely reduce the communication overhead. Furthermore, we consider the different capabilities of servers with a threshold Ti value and propose a load-balancing algorithm for servers with various capabilities. Simulation results show that the proposed K-Percents-Finish Reporting mechanism can at least reduce 50% communication overhead than update-on-finish approach while sustaining better load balancing performance than periodic mechanisms in related work.

Optimization and application of multiple tuned mass dampers in the vibration control of pedestrian bridges

Zheng Lu,Xiaoyi Chen,Xiaowei Li,Peizhen Li 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.1

An effective design approach for Multiple Tuned Mass Dampers (MTMDs) in pedestrian bridges was proposed by utilizing the transfer function to obtain each TMD’s optimum stiffness and damping. A systematic simulation of pedestrian excitations was described. The motion equation of a typical MTMD system attached to a Multi-degree-of-freedom (MDOF) system was presented, and the transfer function from the input pedestrian excitations to the output acceleration responses was defined. By solving the minimum norm of the transfer function, the parameters of the MTMD which resulted in the minimum overall responses can be obtained. Two applications of lightly damped pedestrian bridges attached with MTMD showed that MTMDs designed through this method can significantly reduce the structural responses when subjected to pedestrian excitations, and the vibration control effects were better than the MTMD when it was considered as being composed of equal number and mass ratios of TMDs designed by classical Den Hartog method.

Synthesis of Porous Carbon Supported Palladium Nanoparticle Catalysts by Atomic Layer Deposition: Application for Rechargeable Lithium–O₂ Battery

Lei, Yu,Lu, Jun,Luo, Xiangyi,Wu, Tianpin,Du, Peng,Zhang, Xiaoyi,Ren, Yang,Wen, Jianguo,Miller, Dean J.,Miller, Jeffrey T.,Sun, Yang-Kook,Elam, Jeffrey W.,Amine, Khalil American Chemical Society 2013 Nano letters Vol.13 No.9

<P>In this study, atomic layer deposition (ALD) was used to deposit nanostructured palladium on porous carbon as the cathode material for Li–O<SUB>2</SUB> cells. Scanning transmission electron microscopy showed discrete crystalline nanoparticles decorating the surface of the porous carbon support, where the size could be controlled in the range of 2–8 nm and depended on the number of Pd ALD cycles performed. X-ray absorption spectroscopy at the Pd K-edge revealed that the carbon supported Pd existed in a mixed phase of metallic palladium and palladium oxide. The conformality of ALD allowed us to uniformly disperse the Pd catalyst onto the carbon support while preserving the initial porous structure. As a result, the charging and discharging performance of the oxygen cathode in a Li–O<SUB>2</SUB> cell was improved. Our results suggest that ALD is a promising technique for tailoring the surface composition and structure of nanoporous supports in energy storage devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2013/nalefd.2013.13.issue-9/nl401833p/production/images/medium/nl-2013-01833p_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl401833p'>ACS Electronic Supporting Info</A></P>

Compatibility of lithium salts with solvent of the non-aqueous electrolyte in Li–O₂ batteries

Du, Peng,Lu, Jun,Lau, Kah Chun,Luo, Xiangyi,Bareñ,o, Javier,Zhang, Xiaoyi,Ren, Yang,Zhang, Zhengcheng,Curtiss, Larry A.,Sun, Yang-Kook,Amine, Khalil The Royal Society of Chemistry 2013 Physical chemistry chemical physics Vol.15 No.15

<P>The stability of lithium salts, especially in the presence of reduced oxygen species, O<SUB>2</SUB> and H<SUB>2</SUB>O (even in a small amount), plays an important role in the cyclability and capacity of Li–O<SUB>2</SUB> cells. This combined experimental and computational study provides evidence that the stability of the electrolyte used in Li–O<SUB>2</SUB> cells strongly depends on the compatibility of lithium salts with solvent. In the case of the LiPF<SUB>6</SUB>–1NM3 electrolyte, the decomposition of LiPF<SUB>6</SUB> occurs in the cell as evidenced by <I>in situ</I> XRD, FT-IR and XPS analysis, which triggers the decomposition of 1NM3 solvent due to formation of HF from the decomposition of LiPF<SUB>6</SUB>. These reactions lead to degradation of the electrolyte and cause poor cyclability of the cell. The same reactions are not observed when LiTFSI and LiCF<SUB>3</SUB>SO<SUB>3</SUB> are used as the lithium salts in 1NM3 solvent, or LiPF<SUB>6</SUB> is used in TEGDME solvent.</P> <P>Graphic Abstract</P><P>We provided evidence that the stability of the electrolyte used in Li–O<SUB>2</SUB> cells strongly depends on the compatibility of lithium salts with solvent. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cp50500f'> </P>

MOPSO-based Data Scheduling Scheme for P2P Streaming Systems

( Pingshan Liu ),( Yaqing Fan ),( Xiaoyi Xiong ),( Yimin Wen ),( Dianjie Lu ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.10

In the Peer-to-Peer (P2P) streaming systems, peers randomly form a network overlay to share video resources with a data scheduling scheme. A data scheduling scheme can have a great impact on system performance, which should achieve two optimal objectives at the same time ideally. The two optimization objectives are to improve the perceived video quality and maximize the network throughput, respectively. Maximizing network throughput means improving the utilization of peer’s upload bandwidth. However, maximizing network throughput will result in a reduction in the perceived video quality, and vice versa. Therefore, to achieve the above two objects simultaneously, we proposed a new data scheduling scheme based on multi-objective particle swarm optimization data scheduling scheme, called MOPSO-DS scheme. To design the MOPSO-DS scheme, we first formulated the data scheduling optimization problem as a multi-objective optimization problem. Then, a multi-objective particle swarm optimization algorithm is proposed by encoding the neighbors of peers as the position vector of the particles. Through extensive simulations, we demonstrated the MOPSO-DS scheme could improve the system performance effectively.

Efficient Privacy Protection in Radio Frequency Identification Systems

Yuan Yang,이태석(Tae-seok Lee),XiaoYi Lu,인호(Hoh In),박명순(Myong-Soon Park) 한국정보과학회 2005 한국정보과학회 학술발표논문집 Vol.32 No.2

In today’ s hyper-competitive business environment, Radio Frequency Identification (RFID) technology is expected to enhance the operation efficiency of supplying chain management in both manufactures and retail industries. However, the widespread deployment of RFID tags may create new threats to user privacy, due to the powerful tracking capability of the tags. Many authentication protocols for RFID have been proposed. They are helpful preventing passersby being scanned to determine what articles they are carrying. However, most of them would not prevent the bigger physical tracking problem of RFID, especially when being tracked by the “constellation” of products they carry. We proposed this RFID scheme to prevent these tracking problems.