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- 저자 : ( Wenqing Cheng ) (검색결과 4 건)
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Performance Evaluation of Web-based Cloud Services in a Browser-Scripting Approach
( Chengwei Zhang ),( Xiaojun Hei ),( Wenqing Cheng ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.6
Cloud services are often provisioned to their customers using user-friendly web browsers with flexible and rich plug-in environments. Delay is one of the fundamental performance metrics of these web-based services. Commonly-used network measurement tools usually only measure network delay and it may be difficult to infer the web-delay performance using only network layer measurement approaches. In this paper, we propose to evaluate the application layer delay in a browser-based network measurement platform using engineered scripts. We conducted a delay measurement study using instrumented scripts in the proposed browser-based measurement platform. Our investigation included a comparison study of three browser-scripting delay measurement methods, including Java applet, JSP and Flash ActionScript. We developed a browser-based delay measurement testbed over the Internet so that different delay measurement tools could be evaluated in the same real network environment including typical Internet paths and the Baidu cloud. We also decomposed the components of the end-to-end delay process of the above measurements to reveal the difference and relationship between the network-layer delay and the application-layer delay. Our measurement results characterize the stochastic properties of the application-layer delay over real Internet paths, and how these properties vary from the underlying network layer delay. This browser-scripting measurement approach can be easily deployed on different cloud service platforms to inspect their application-layer delay performance between end clients and the cloud platforms. Our measurement results may provide insights into designing new cloud services with enhanced quality-of-experience perceived by cloud users.
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Yuqiang Han,Qinghua Que,Ran Cheng,Ran Cheng,Chunfa Lin,Wenqing Han,Enhao Wang,Junyi Zhu,Haoran Yan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10
In present work, a novel SiCfreinforced (Al3Ti + Al3Ni)-based metallic–intermetallic laminate (Ti–(Al3Ti + Al3Ni)/SiCf-MIL) composite without centerline defect was prepared using Ti, Al foils, NiTi wires and SiC fibers by vacuum hot pressingsintering method. Electron backscatter diffraction was employed to characterize the microstructure and phase constituents ofTi–(Al3Ti + Al3Ni)/SiCf-MIL composite during various stages of preparation process. The elimination mechanism of intermetalliccenterline was discussed. Besides, quasi-static compressive performance and fracture toughness of the synthesizedcomposite were investigated. The experimental results indicated that as reaction time increasing, the NiTi/Al interfacialreaction occurred prior to the Ti/Al interfacial reaction to form an Al3Ti/Al3Ni zone. Then, the oxides gathered at the frontof Ti/Al interfacial reaction layer were dispersed in the intermetallic layer rather than being pushed together to generate thecenterline due to the Al3Ti/Al3Ni zone. After reaction, there were no residual NiTi phases and intermetallic layers mainlyconsisting of Al3Tiand Al3Niphases were obtained in this composite. In addition, high angle grain boundaries in Al3Tigrains occupied a large proportion, conversely, low angle grain boundaries dominated in Al3Nigrains. Furthermore, stressconcentration appears at the interface between layers instead of along the middle plane of intermetallic layer. Moreover,both compressive strength and fracture toughness of the composite are superior in comparison with SiCfreinforced Ti–Al3Timetallic–intermetallic laminate composite (Ti–Al3Ti/SiCf-MIL) ascribed to the elimination of centerline.
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( Xu Du ),( Nguyen-son Vo ),( Wenqing Cheng ),( Trung Q. Duong ) 한국인터넷정보학회 2011 KSII Transactions on Internet and Information Syst Vol.5 No.11
In this research, we consider the replication strategy for the applications of video streaming in wireless mesh networks (WMNs). In particular, we propose a closed-form of optimal replication densities for a set of frames of a video streaming by exploiting not only the skewed access probability of each frame but also the skewed loss probability and skewed encoding rate-distortion information. The simulation results demonstrate that our method improves the replication performance in terms of user-perceived quality (UPQ) which includes: 1) minimum average maximum reconstructed distortion for high peak signal-to-noise ratio (PSNR), 2) small reconstructed distortion fluctuation among frames for smooth playback, and 3) reasonable average maximum transmission distance for continuous playback. Furthermore, the proposed strategy consumes smaller storage capacity compared to other existing optimal replication strategies. More importantly, the effect of encoding rate is carefully investigated to show that high encoding rate does not always gain high performance of replication for video streaming.
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Jing Zhu,Aidong Deng,Jing Li,Minqiang Deng,Wenqing Sun,Qiang Cheng,Yang Liu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.11
A resonance-based sparse improved fast independent component analysis (ICA) (RSIFICA) is proposed to extract the fault characteristics of planetary gearbox. First, the signal is decomposed using resonance sparse signal decomposition (RSSD). Second, highresonance components were retained while others were eliminated. Finally, the signal after dimension reduction was analyzed using ICA, and the fault characteristic frequency was extracted through envelope spectrum analysis. In this process, the preset Q parameter of RSSD is optimized on the basis of fuzzy entropy and ant-lion optimization algorithm. The accuracy of RSSD was improved by performing time-frequency entropy component selection. FastICA was improved, and the slow convergence problem of ICA was solved. Results showed that RSIFICA could extract the fault characteristic frequency accurately, and the calculation efficiency of FastICA increased by 21.49 %. In terms of extracting the fault features, its performance could be better than EMD-FastICA.
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