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ABSTRACT: TiO2 array film fabricated by potentiostatic anodization of titanium is characterized by X-ray diffraction (XRD), scanning electron
microscopy (SEM), and charge–discharge measurements. The XRD results indicated that the TiO2 array is amorphous, and after calcination at 500 °C, it has the anatase form. The pore size and wall thickness of TiO2 nanotube arrays synthesized at different anodization voltages are highly dependent on the applied voltage. The electrochemical
performance of the prepared TiO2 nanotube array as an electrode material for lithium batteries was evaluated by galvanostatic charge–discharge measurement.
The sample prepared at 20V shows good cyclability but low discharge capacity of 180mAh cm−3, while the sample prepared at 80V has the highest discharge capacity of 340mAh cm−3.
KeywordsTiO2 nanotube-TiO2 array film-Anodization-Lithium ion intercalation
Journal of Solid State Electrochemistry 04/2012; 14(6):1045-1050. · 2.13 Impact Factor
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ABSTRACT: The performance of multi-service applications are known to be determined mainly by the interactions between workload and behaviors of the application. The change of workload can lead to dynamic service demands on system resources, and even cause dynamic bottleneck switches between services inside the application. In this paper, to profiling large-applications' behaviors, and help to locate the bottleneck and optimize their capacities, we focus on modeling their behavior according to the workload. Although this topic has been well studied at testing stage, building such a model under live workload remains a challenge, because the workload and application behaviors are time-varying. To tackle this problem, we propose an adaptive approach to build and rebuild performance model according to log files. Both the user behaviors and their corresponding internal service relations are modeled, and the CPU time consumed by each service is also obtained through Kalman filter, which can "absorb" some level of noise in real-world data. Our model can explain the behaviors of both the whole application and the individual services, and provide valuable information for capacity planning and bottleneck detection. At last, our work is evaluated with TPC-W bench mark, whose results can demonstrate the effectiveness of our approach.
Computer Software and Applications Conference (COMPSAC), 2011 IEEE 35th Annual; 08/2011
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ABSTRACT: With the rapid development of cloud computing, traditional TP applications are evloving into the Extreme Transaction Processing (XTP) applications which are characterized by exceptionally demanding performance, scalability, availability, security, manageability and dependability require requirements, elastic caching platforms (ECPs) are introduced to help meet these requirements. Three popular cache strategies for ECPs have been proposed, say replicated strategy, partitioned strategy and near strategy. According to our investigations, many ECPs support multiple cache strategies. In this paper, we evaluate the impact of the three cache strategies using the TPC-W benchmark. To the best of our knowledge, this paper is the first evaluation of distributed cache strategies for ECPs. The main contribution of this work is guidelines that could help system administrators decide effectively which cache strategy would perform better under different conditions. Our work shows that the selection of the best cache strategy is related with workload patterns, cluster size and the number of concurrent users. We also find that four important metrics (number of "get" operations, message throughput, get/put ratio, and cache hit rate) could be used to help characterize the current condition.
Quality Software (QSIC), 2011 11th International Conference on; 08/2011
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ABSTRACT: Runtime monitoring of Web service compositions has been widely acknowledged as a significant approach to understand and guarantee the quality of services. However, existing runtime monitoring solutions consider only the constraints on the sequence of messages exchanged between partner services and ignore the actual data contents inside the messages. As a result, it is difficult to monitor some dynamic properties such as how message data of interest is processed between different participants. To address this issue, we propose an efficient, non-intrusive online monitoring approach to dynamically analyze data-centric properties for service-oriented applications involving multiple participants. By introducing Par-BCL - a Parametric Behavior Constraint Language for web services - to define monitoring parameters, various data-centric temporal behavior properties for Web services can be specified and monitored. This approach broadens the monitored patterns to include not only message exchange orders, but also the data contents bound to the parameters. To reduce runtime overhead, we statically analyze the monitored properties to generate parameter state machine from the event pattern automata to optimize monitoring. The experiments show that our solution is efficient and promising.
Web Services (ICWS), 2011 IEEE International Conference on; 08/2011
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Proceedings of the 11th International Conference on Quality Software, QSIC 2011, Madrid, Spain, July 13-14, 2011.; 01/2011
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Proceedings of the 35th Annual IEEE International Computer Software and Applications Conference, COMPSAC 2011, Munich, Germany, 18-22 July 2011; 01/2011
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Proceedings of the 35th Annual IEEE International Computer Software and Applications Conference, COMPSAC 2011, Munich, Germany, 18-22 July 2011; 01/2011
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ABSTRACT: In this paper, the polarization of an oxygen electrode in rechargeable lithium oxygen batteries was investigated and found
to be closely related to the fading of discharge capacity and ceasing of cycling. Electrochemical tests showed that with an
catalyzed air electrode, the cell could deliver a high initial discharge capacity of
of carbon with rapid fading to
at the fourth cycle. When the cell was cycled at a restricted depth of discharge, the cycle life could be prolonged. Electrochemical
impedance spectra responses and scanning electron microscopy observations indicated that the discharged product could block
the air pathway, increase electrochemical resistance, and lose electrical contact. To improve the electrochemical performance
of lithium oxygen batteries, the oxygen reduction catalyst and the structure of the
electrode deserve further investigation.
Journal of The Electrochemical Society. 02/2010; 157(3):A362-A365.
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ABSTRACT: Pt nanocatalysts supported on glassy carbon (GC) were electrochemically deposited by cyclic voltammetry (CV) with different scanning potential ranges. The lower limit of potential was fixed at -0.25 V vs. saturated calomel electrode, whereas the upper limit of potential was adjusted to be 0.0, 0.20, 0.60, and 1.0 V. Scanning electron microscopy images showed that Pt microparticles are uniformly dispersed on the GC substrate and the agglomerated microparticles are composed of numerous nanoparticles. In addition, the catalytic capabilities of Pt/GCs for methanol electrooxidation were examined by CV, chronoamperometry, and electrochemical impedance spectroscopy in a solution of 0.5 M CH(3)OH and 0.5 M H(2)SO(4). The results demonstrate that the catalytic activities and stabilities of Pt catalysts prepared by the potential ranges from -0.25 to both 0.60 and 1.0 V for methanol electrooxidation were higher than the others, which may be due to their higher electrochemical active surface area, lower charge transfer resistance, and more preferred Pt crystallographic orientation.
Journal of Solid State Electrochemistry 01/2010; 14(1):101-107. · 2.13 Impact Factor
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24th IEEE International Conference on Advanced Information Networking and Applications, AINA 2010, Perth, Australia, 20-13 April 2010; 01/2010
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IEEE International Conference on Web Services, ICWS 2010, Miami, Florida, USA, July 5-10, 2010; 01/2010
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ABSTRACT: PtRuMe (Me = Fe, Co, Ni) catalysts dispersed on multi-wall carbon nanotubes (MWCNTs) were prepared by ultrasonic-assisted chemical reduction. X-ray diffraction (XRD) showed that Pt existed as face-centered cubic structure, while Ru and Me alloyed with Pt. The calculated particle sizes from XRD data are of 3.40, 3.40, 2.61 and 3.06 nm for PtRu, PtRuFe, PtRuCo and PtRuNi, respectively, and are consistent with TEM results. The electrochemical measurements showed that the addition of Me to PtRu enhances the electrocatalytic properties for methanol oxidation and PtRuNi has the best catalytic activity and stability. (C) 2009 Elsevier B.V. All rights reserved.
Electrochemistry Communications 03/2009; 11(3):643-646. · 4.86 Impact Factor
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ABSTRACT: PtRuSnOx supported on multi-wall carbon nanotubes (MWCNTs) was prepared by ultrasonic-assisted chemical reduction method. The as-prepared catalyst was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns indicate that Pt exists as the face-centered cubic structure, Ru is alloyed with platinum, while non-noble metal oxide SnOx exists as an amorphous state. From TEM observation, PtRuSnOx is well dispersed on the surface of MWCNTs with the particle size of several nanometers. The electrochemical properties of the as-prepared catalyst for methanol electrooxidation were studied by cyclic voltammetry (CV) and chronoamperometry (CA). The onset potential of methanol oxidation on PtRuSnOx and PtRu catalysts is much more negative than that on Pt catalyst, shifting negatively by about 0.20 V, while the peak current density of methanol oxidation on PtRuSnOx is higher than that on PtRu. Electrochemical impedance spectroscopy (EIS) studies also show that the reaction kinetics of methanol oxidation is improved with the presence of SnOx. The addition of non-noble metal oxide SnOx to PtRu promotes the catalytic activity for methanol electrooxidation and the possible reaction mechanism is proposed. (C) 2009 Elsevier Ltd. All rights reserved.
Electrochimica Acta 01/2009; 54(18):4436-4440. · 3.83 Impact Factor
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ABSTRACT: PtRuMoOx and PtRuWOx catalysts supported on multi-wall carbon nanotubes (MWCNTs) are prepared by ultrasonic-assisted chemical reduction method. XRD measurements indicate that Pt exists as face-centered cubic structure, Ru is alloyed with platinum, and the metal oxides exist as an amorphous structure. TEM pictures show that PtRuMoOx and PtRuWOx catalysts are well dispersed on the surface of MWCNTs with the particle size of about 3 nm and a narrow particle size distribution. The electrochemical properties of the catalysts for methanol electrooxidation are studied by cyclic voltammetry (CV), chronoamperometry (CA) and chronopotentiometry (CP). The onset potentials for methanol oxidation on PtRuMoOx and PtRuWOx are more negative than that of pure Pt catalyst, shifting negatively by about 0.20V and have better electrocatalytic activities than PtRu/MWCNTs. (C) 2009 Elsevier B.V. All rights reserved.
Journal of Power Sources 01/2009; 192(2, SI):285-290. · 4.95 Impact Factor
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ABSTRACT: Porous ternary PtRuCo catalyst supported on a glassy carbon substrate was prepared by one-step electrochemical codeposition using an adsorbed hydrogen gas bubble as a dynamic template. The as-prepared catalyst was characterized by scanning electron microscopy and transmission electron microscopy. Methanol electro-oxidation on the as-prepared catalyst was investigated by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy, and the results show that porous ternary PtRuCo catalyst has excellent electrocatalytic performance.
Electrochemical and Solid-State Letters 01/2009; 12(7):B112-B115. · 2.00 Impact Factor
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ABSTRACT: As the Internet increases explosively, the QoS support in e-business server is becoming more and more important. However, the implementation of a fine-grained QoS control model in the e-business servers is a challenging task. In this paper, we propose a WorkManager-based QoS scheduling framework (WMQ) for e-business servers. This framework hides the complexity of QoS scheme implementations and provides a flexible architecture supporting fine-grained QoS control. A prototype of our framework has been implemented within the open-source server Tomcat. The evaluation of this prototype shows that our approach allows Tomcat to effectively meet the QoS requirement of the applications by fine-grained QoS control. Our experience also shows that the WMQ framework can efficiently simplify and reduce the implementation effort involved in developing QoS-enabled e-business servers.
e-Business Engineering, 2007. ICEBE 2007. IEEE International Conference on; 11/2007
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ABSTRACT: High dynamic computing environment makes quality of service (QoS) guarantee more important to distributed system. It should possess self-tuning capability reacting to external environment variation such as fluctuating workload. This paper proposed an adaptive self- configuration framework for EJB platform, which can automatically tune configuration parameters to preserve QoS when workload changed. The key point of this framework is a performance model based on layered queuing network, which guides the search for the best combination of configuration parameters to satisfy performance requirement of EJB application. We have prototyped this self-configuration framework on an EJB server named OnceAS, and the experiment results showed that through the framework's control, system performs well on QoS goal.
e-Business Engineering, 2007. ICEBE 2007. IEEE International Conference on; 11/2007
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ABSTRACT: The overload of Web Application Servers (WAS) is a typical and critical problem encountered in nowaday Web commerce. This problem imposes greater demands on WAS to provide QoS support under overload conditions. However, even with a practical solution, the implementation of a flexible QoS model to enable fine- grained QoS control in WAS is still a challenging task. In this paper we propose a QoS-enabled WorkManager Model (WMQ), which hides the complexity of QoS mechanisms implementations and provides a flexible QoS architecture. Hybrid QoS schemes are proposed base on this model to support self-optimization and fine-grained QoS control. We implement this model and integrate it in a Web Application Server. Our integrating experience shows that the WMQ model significantly reduces the implementation effort in developing a QoS-enabled WAS. We evaluate this model by a TPC-W workload generator in a typical e-commerce application. Evaluation results show that, our overload control allows consistent performance and improves the system throughput up to 22% during extreme overload. In addition, compared with other widely used scheduling policies, our hybrid request scheduling policy shows better performance on improving the system throughput and minimizing the number of aborted requests. Keywords: QoS, performance tuning, Web Application Servers
Quality Software, 2007. QSIC '07. Seventh International Conference on; 11/2007
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ABSTRACT: -silicon nitride nanorods have been synthesized through solid-state reduction–nitridation of silica using NaNH2 as both a reductant and a nitriding reagent. X-ray powder diffraction patterns show that the products have a hexagonal phase with lattice parameters a=7.767 Å and c=5.630 Å. Transmission electron microscopy reveals that the as-synthesized products are pure nanorods with an average size about 30 nm in diameter and 400 nm in length. X-ray photoelectron spectra indicate that the molar ratio of Si/N is 2.988:4. Fourier-transform infrared spectrum yields a strong Si–N absorption at 926 cm−1 that may be a red shift due to size effect.
Journal of the American Ceramic Society 03/2007; 90(4):1243 - 1245. · 2.27 Impact Factor
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ABSTRACT: Novel kelp-like crystalline β-SiC nanobelts have been synthesized through direct pyrolysis of methyltrichlorosilane at 600°C in an autoclave. The products are characterized by X-ray powder diffraction, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, electron diffraction, and Raman spectroscopy. On the basis of morphology and structural characterization, an apical growth mechanism is proposed to clarify the formation of as-prepared nanobelts. Also, at 420 nm, a broad peak is observed in the visible photoluminescence emission.
Journal of the American Ceramic Society 01/2007; 90(2):653 - 656. · 2.27 Impact Factor
