Hunan UniversityHunan

Hunan, China

Hunan UniversityHunan

Hunan, China
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Wang L.,Hunan University | Zhang G.,Hunan UniversityHunan | Zhang X.,Hunan University | Shi H.,Hunan University | And 5 more authors.
Journal of Materials Chemistry A | Year: 2017

Development of novel and scalable high-performance carbon nanomaterials and nanostructures is of critical importance for practical applications of flexible supercapacitors. In this study, we report a unique type of all-carbon nanofibrous non-woven web, in which carbon nanofibers are formed from well-connected porous ultrathin carbon nanobubbles. The foamed porous structures are achieved using ethanol as a carbon source coating on an electrospun ZnO nanofiber template followed by removing the ZnO template via a reduction and evaporation process. As a candidate for flexible supercapacitor applications, the fabricated integrated carbon nanofiber webs exhibit a long cycling life with 94.1% capacitance retention even after 35000 cycles at a current density of 10 A g-1 with a three-electrode configuration. The symmetric supercapacitors also show a high rate performance with 81.4% capacitance retention when the current density is increased 70 times from 0.5 to 35 A g-1. Furthermore, electrochemical testing of the flexible symmetric devices displays almost the same capacitive behavior in different bending states. These excellent electrochemical performances are attributed to the interconnected porous and bubbled structures of the carbon nanofiber webs. © 2017 The Royal Society of Chemistry.


Hawbani A.,Hefei University of Technology | Wang X.,Hefei University of Technology | Karmoshi S.,Hefei University of Technology | Kuhlani H.,Hefei University of Technology | And 3 more authors.
Wireless Communications and Mobile Computing | Year: 2017

The use of wireless sensor networks (WSN) in tracking applications is growing rapidly. In these applications, the nodes detect, monitor, and track a target, object, or event. In this paper, we consider the problem of tracking mobile objects in wireless sensor networks (WSN). We present a novel tracking model, named Grouping based Location Tracking (GLT), scaling well with the number of nodes and the number of mobile objects. GLT is based on theGrouping Hierarchy Structure, GHS. In GHS, nodes are partitioned into groups (not clusters) according to their maximum covered region (MCR) such that each group contains a number of nodes and a number of leaders. GLT consists of two tiers. The first tier, which is called the Notification Tree (NT), enhances the activation mechanism, the data cleaning mechanism, and the energy balancing mechanism. On the other hand, the second tier, which is called the Hierarchical Spanning Tree (HST), supports the data reporting mechanism and the lifetime prolonging mechanism. Simulations results show that GLT reduces the communication node selections overhead without diminishing object tracking accuracy and achieves a significant energy consumption reduction and network lifetime extension compared with the state-of-the-art approaches. © 2017 Ammar Hawbani et al.


Chen Z.,Nanchang Hangkong University | Li G.,Nanchang Hangkong University | Li G.,Hunan UniversityHunan | Zheng H.,Nanchang Hangkong University | And 3 more authors.
Applied Surface Science | Year: 2017

The mechanism of surface effect and selective catalytic performance of MnO2 nanorods remain mysterious at present. Using first-principles pseudo-potential plane wave method, the surface energy, cohesive energy, geometrical and electronic structure for MnO2 in the evolution of crystal → bulk surface → nanorod morphologies have been systematically calculated and analyzed. The results show that the surface energy is increased along with the decrease of geometry configuration in crystal → bulk surface → nanorod as a whole. However in three nanorod morphologies, the surface energy is increased along with the additional geometry configuration, wherein the largest nano(III) has the largest surface energy and lowest cohesive energy. These characters are originated from their changes in geometry structure and lost in Mulliken charges of atoms along surface planes. Electronic structure shows that the selective catalytic activity of MnO2 nanorods is originated from their unique states of valence electrons, which occupying the highest occupied molecular orbital (HOMO) only appears on (110) Miller surface layers and the lowest unoccupied molecular orbital (LUMO) only on (100) Miller surface layers, respectively. Such attracting phenomenon has significantly difference with that of MnO2 bulk surface. Thereinto, a transitional model of [(100 × 110)] microfacet model is found to exhibit much more approaching surface performance to MnO2 nanometer structure somewhere. Thus, our findings open an avenue for detailed and comprehensive studies on the growth and catalysis of MnO2 nanomaterials. © 2017 Elsevier B.V.


Li W.,University of Sydney | Li W.,Monash University | Li W.,Northwestern University | Luo Z.,Hunan UniversityHunan | And 4 more authors.
Materials and Design | Year: 2016

A 100 mm-diameter split Hopkinson pressure bar (SHPB) was applied to investigate effects of nanoparticles on the dynamic mechanical properties of recycled aggregate concrete (RAC) under impact loading. The nano-SiO2 (NS) and nano-CaCO3 (NC) were incorporated to replace cement by mass of 1 and 2% in RACs. The impact velocities were set as 7.7, 9.8 and 11.6 m/s in the SHPB tests. The effects of nanoparticles on failure patterns, compressive strengths, elastic modulus, peak strain and dynamic increase factor (DIF) of RACs under different strain rates were analyzed and discussed. The results show that nanomodified RACs exhibit higher both quasi-static and dynamic compressive strengths compared to control RAC. Dynamic elastic modulus of RAC seems not be affected by nanoparticle dosages and impact velocities. Compared to NC, NS is more effective to improve dynamic compressive strengths of RAC. On the other hand, the nanoparticles modified RACs exhibit lower DIF values than that of the control RAC. Moreover, NC obviously more reduces the DIF values of nanomodified RAC than NS. © 2016 Elsevier Ltd


Pan L.,Hunan International Economics University | Wang H.,Hunan UniversityHunan | Li R.,Hunan UniversityHunan | Cao Y.,Hunan UniversityHunan
Industrial Engineering and Manufacturing Technology - Proceedings of the 2014 International Conference on Industrial Engineering and Manufacturing Technology, ICIEMT 2014 | Year: 2015

The multi-dimensional trend of the grid resource service has made its trust assessment complex. State of the art works hold the limitations in that they use simple or subjective methods to evaluate the trustworthiness of the service, which leads to misinformation or inaccurate assessments. In this regard, this paper proposes schemes to specify the trustworthiness of each service type, based on the multi-dimensional attributes of the service; in particular, we construct models to derive the desired trust value of the provided services with respect to both the user and recommender transaction records. Such mechanisms can better reflect the user’s actual demand whilst also achieving satisfactory performance in grid resource transactions. © 2015 Taylor & Francis Group, London.


Pan L.,Hunan International Economics University | Wang H.,Hunan UniversityHunan | Li R.,Hunan UniversityHunan | Cao Y.,Hunan UniversityHunan
Industrial Engineering and Manufacturing Technology - Proceedings of the 2014 International Conference on Industrial Engineering and Manufacturing Technology, ICIEMT 2014 | Year: 2015

The IEEE 802.16j based Broadband Wireless Access(BWA) is a brand-new technology to support high speed and wide coverage communications. However, the application of such communication networks faces significant challenges due to the time-varying character of the communication channels. In this regard, we first propose a novel scheme to exploit the optimal channel transmission capacity based on the state of each communication channel. Then we design an effective channel usage scheme to fully utilize the channel transmission bandwidth with respect to users’ requirements. Moreover we also make the performance analysis on the proposed schemes with respect to various metrics. Experiment results validate the efficiency and efficacy of the proposed schemes. © 2015 Taylor & Francis Group, London.


Zeng W.,Hunan UniversityHunan | Zhang G.,Hunan UniversityHunan | Hou S.,Hunan UniversityHunan | Wang T.,Hunan UniversityHunan | Duan H.,Hunan UniversityHunan
Electrochimica Acta | Year: 2015

Graphene@NiO/MoO3 composite nanosheet arrays (CSAs) were grown on the nickel foam via a one-step hydrothermal way. The composite of NiO and MoO3 showed a promising synergistic effect for capacitors. Graphene had been integrated to the composite nanosheets to further enhance the electrochemical performance. The prepared samples were characterized by scanning electron microscopy and transmission electron microscopy, X-ray diffraction spectroscopy and Raman spectroscopy. A possible growth mechanism was proposed to explain the formation of the composite nanosheets by carrying out a series of time-dependent experiments. Benefiting from the improved electron conductivity and effective buffering of the volume variation induced by redox reactions, the composite exhibited a high area capacitance of 1.372 F cm-2 even at a high current density of 42 mA cm-2, and showed excellent cycle stability (62.7% of the initial capacitance after 7500 cycles, while 87.9% remained in the latter 7000 cycles). © 2014, Elsevier Ltd. All rights reserved.


Fang Y.,Hunan UniversityHunan | Yi X.,Guilin Normal CollegeGuangxi | Qin W.,Guilin Normal CollegeGuangxi | Zhang Y.,Guilin Normal CollegeGuangxi | Liao Y.,Guangxi Academy of Fishery science
Asian Journal of Chemistry | Year: 2014

A series of 2-oxo-quinoline-3-Schiff-base derivatives (4a1-4n2) have been designed and synthesized as new antitumor agents. in vitro Antitumor activities were evaluated against four cancer cell lines including MGC80-3, BEL-7404, A549 and NCI-H460. Compounds 4a1, 4a2, 4c2, 4d1, 4d2 and 4l2 exhibited better inhibition activities than commercial antitumor drug 5-fluorouracil (5-fluorouracil, IC50 = 44 ±0.54 μM) on NCI-H460, with IC50 of 35.52 ± 0.86, 16.22 ± 0.71, 11.62 ± 0.52, 5.16 ± 0.37, 7.62 ± 0.46 and 7.66 ± 0.65 μM, respectively. © 2014, Chemical Publishing Co. All rights reserved.


Yan L.,Hunan UniversityHunan | He J.,Hunan UniversityHunan | Chen M.,Hunan UniversityHunan | Tang J.,Hunan UniversityHunan | Chen L.,Hunan UniversityHunan
Energy Science and Applied Technology - Proceedings of the 2nd International Conference on Energy Science and Applied Technology, ESAT 2015 | Year: 2015

The performance of blind equalization and frequency offset estimation scheme in coherent optical Minimum-Shift Keying (MSK) communication is investigated. At the receiver, blind equalization scheme is used to compensate fiber dispersion and nonlinearity in the electrical field. Meanwhile, a frequency offset scheme based on Fast Fourier Transform (FFT) and Chirp Z-Transform (CZT) can be used to frequency offset estimation and recovery. The simulation results show that the 10-Gb/s MSK signals can be recovered successfully using the blind equalization and frequency offset estimation scheme. © 2016 Taylor & Francis Group, London.


Zhu Q.,Hunan UniversityHunan | Miao L.,Hunan UniversityHunan
Energy Science and Applied Technology - Proceedings of the 2nd International Conference on Energy Science and Applied Technology, ESAT 2015 | Year: 2015

Currently, Hadoop is widely used in a growing number of network applications. Based on the advantages of its open source framework for distributed systems, it implements Hadoop distributed file system and Map Re-duce distributed computing framework. Therefore, how to conduct performance monitoring nodes in the cluster to ensure the normal and efficient operation of the whole cluster is one of the key studies on Hadoop. Although there are a large number of third-party monitoring tools to achieve monitoring for Hadoop cluster, limitations of monitoring indicators lead to inadequate monitoring granularity. This article is a supplement of Ganglia, which is a real-time monitoring system. Using JMX interface which Hadoop supports to get more monitoring indicators, we can achieve full performance monitoring of Hadoop cluster when running tasks. Meanwhile, it makes use of the advantages of Nagios and MongoDB, and resolves the problem that Ganglia cannot store data permanently. © 2016 Taylor & Francis Group, London.

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