Changsha, China
Changsha, China

Hunan University , located in Changsha, Hunan province, is one of the oldest and most important national universities in China. Wikipedia.

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An intelligent and information multi-vehicle collaboratively operating municipal refuse collection and transfer system and method are provided. The system comprises an automated system with multiple-degree of freedom intelligent dustbin grabbing, an operating system with two types of refuse vehicles collaborating, a multi-vehicle collaborative operation information system, and a fixed-point refuse collection operation confirmation and remote monitoring information management system for coordinating overall operation of the systems. The automated system with multiple-degree of freedom intelligent dustbin grabbing system is used for the refuse vehicles to automatically collect dustbins; the operating system with two types of refuse vehicles collaborating comprises a plurality of small- and medium-sized refuse vehicles and large capacity refuse vehicles. The small- and medium-sized refuse vehicles collect refuse in the dustbins according to multi-vehicle collaborative operation information with the support of the multi-vehicle collaborative operation information system, and the large capacity refuse vehicles are used to dock with the collected refuse and transport the refuse out of town with the support of the multi-vehicle collaborative operation information system. The method is the implementation of the above system. The system and method have good operability and high degree of intelligence and provide good results of refuse disposal.

Hunan University and Changsha Boli Electrical Corporation | Date: 2014-09-15

A steady state control method for a three-phase double-mode inverter. Off-grid steady state control is composed of outer loop power droop control, voltage feed-forward quasi-resonant control, and inner current loop dead-beat control. Therefore, the response speed of the inverter is raised, and the influence caused by the load fluctuation of a micro-grid is inhibited. Based on the off-grid steady state control, grid-connected steady state control introduces phase lead control to the power droop control. Therefore, the output voltage of the inverter is always slightly ahead of the power grid voltage, which avoids the energy pour backward phenomenon of the inverter due to a phase error, and realizes stable and reliable running in the grid-connected mode.

Wu Y.,Wayne State University | Lake R.,Wayne State University | Cao L.,University of Ontario Institute of Technology | Cao L.,Hunan University
Justice Quarterly | Year: 2015

Relying on survey data collected from over 1,300 students of 13–18 years old across multiple US cities, this study attempts to integrate race into social bond theory to explain the variation in juvenile perceptions of the police. Results indicate significant differential outlooks between white and black teenagers, and to a lesser extent, between white and Hispanic juveniles. Social bonds, especially commitment to school and conventional beliefs, have significant effects on juveniles’ attitudes. The effects of race and social bonds are more independent and social bonds do not mediate the race-attitudes relationship. Other factors, such as juvenile delinquency, victimization, and sense of safety, are also related to juvenile assessments of the police. Implications of the findings are discussed. © 2013, Academy of Criminal Justice Sciences.

Qu B.,Hunan University | Qu B.,National University of Singapore | Ma C.,University of California at San Diego | Ji G.,National University of Singapore | And 5 more authors.
Advanced Materials | Year: 2014

A layered SnS2-reduced graphene oxide (SnS2-RGO) composite is prepared by a facile hydrothermal route and evaluated as an anode material for sodium-ion batteries (NIBs). The measured electrochemical properties are a high charge specific capacity (630 mAh g-1 at 0.2 A g-1) coupled to a good rate performance (544 mAh g-1 at 2 A g-1) and long cycle-life (500 mAh g-1 at 1 A g -1 for 400 cycles). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhang H.,Shenzhen University | Zhang H.,National University of Singapore | Lu S.B.,Hunan University | Zheng J.,National University of Singapore | And 4 more authors.
Optics Express | Year: 2014

The nonlinear optical property of few-layered MoS2 nanoplatelets synthesized by the hydrothermal exfoliation method was investigated from the visible to the near-infrared band using lasers. Both open-aperture Z-scan and balanced-detector measurement techniques were used to demonstrate the broadband saturable absorption property of fewlayered MoS2. To explore its potential applications in ultrafast photonics, we fabricated a passive mode locker for ytterbium-doped fibre laser by depositing few-layered MoS2 onto the end facet of optical fiber by means of an optical trapping approach. Our laser experiment shows that few-layer MoS2-based mode locker allows for the generation of stable mode-locked laser pulse, centered at 1054.3 nm, with a 3-dB spectral bandwidth of 2.7 nm and a pulse duration of 800 ps. Our finding suggests that few-layered MoS2 nanoplatelets can be useful nonlinear optical material for laser photonics devices, such as passive laser mode locker, Q-switcher, optical limiter, optical switcher and so on. © 2014 Optical Society of America.

Zhang Z.,Hunan University | Zhou D.,Yunnan University
Neural Networks | Year: 2012

In this paper, we first discuss the existence of a unique equilibrium point of a generalized Cohen-Grossberg BAM neural networks of neutral type delays by means of the Homeomorphism theory and inequality technique. Then, by applying the existence result of an equilibrium point and constructing a Lyapunov functional, we study the global asymptotic stability of the equilibrium solution to the above Cohen-Grossberg BAM neural networks of neutral type. In our results, the hypothesis for boundedness in the existing paper, which discussed Cohen-Grossberg neural networks of neutral type on the activation functions, are removed. Finally, we give an example to demonstrate the validity of our global asymptotic stability result for the above neural networks. © 2011 Elsevier Ltd.

Huang H.-J.,Jiangxi Agricultural University | Yuan X.-Z.,Hunan University
Progress in Energy and Combustion Science | Year: 2015

Energy from biomass, bioenergy, is a promising source to replace fossil fuels in the future, as it is abundant, clean, and carbon dioxide neutral. Thermochemical liquefaction of biomass is widely investigated as a promising method to produce one kind of liquid biofuel, namely bio-oil. This review presents the recent research progress in the liquefaction of typical biomass from a new perspective. Particularly, this article summarizes five aspects of related work: first, the effect of solvent type on the liquefaction behaviors of biomass; second, the effect of biomass type on the liquefaction behaviors of biomass; third, the liquefaction of biomass in sub-/super-critical ethanol; fourth, the liquefaction of biomass in organic solvent-water mixed solvents; fifth, the liquefaction of sewage sludge. Meanwhile, the research advance in the migration and transformation behavior of heavy metals during the liquefaction of sewage sludge was also summarized in this review. This review can offer an important reference for the study of biomass liquefaction. © 2015 Elsevier Ltd. All rights reserved.

Lei Y.,Hunan University | Murmu T.,University of Limerick | Adhikari S.,University of Swansea | Friswell M.I.,University of Swansea
European Journal of Mechanics, A/Solids | Year: 2013

The dynamic characteristics of damped viscoelastic nonlocal beams are studied in this paper. The Kelvin-Voigt and three-parameter standard viscoelastic models, velocity-dependent external damping and nonlocal Euler-Bernoulli beam theory are employed to establish the governing equations of motion for the bending vibration of nanobeams. A transfer function method (TFM) is developed to obtain closed-form and uniform solution for the vibration analysis of Euler-Bernoulli beams with different boundary conditions. New analytical expressions for critical viscoelastic parameters, damping parameters and limiting frequencies are obtained. Considering a carbon nanotube as a numerical example, the effects of the nonlocal and viscoelastic constants on the natural frequencies and damping factors are discussed. The results demonstrate the efficiency of the proposed modeling and analysis methods for free vibration analysis of viscoelastic damped nonlocal Euler-Bernoulli beams. © 2013 Elsevier Masson SAS. All rights reserved.

Yao K.X.,National University of Singapore | Yin X.M.,Hunan University | Wang T.H.,Hunan University | Zeng H.C.,National University of Singapore
Journal of the American Chemical Society | Year: 2010

In this work, we describe a solution-based synthesis of monodisperse Cu2O nanocrystals with controllable sizes in the nanoscale regime. Two types of nanocrystals, cubes and rhombic dodecahedra unifaceted with either {001} or {110} crystal planes, have been prepared at a 100% morphological yield. In particular, synthetic parameters and formation processes of the Cu 2O nanocrystals have been investigated in detail, and a range of well-oriented supercrystals/superlattices built from the two types of nanobuilding blocks have been attained for the first time. It has been revealed that n-hexadecylamine used in the present work plays multiple roles: it serves as a chelating ligand to form [Cu(NH2C16H 33)4]2+ complex precursor, as a phase-transferring agent to transfer divalent Cu2+ ions into the organic phase, as a reducing agent to generate monovalent Cu+ (i.e., Cu2O), as a passivating adsorbate to control crystal morphology, and as a surface capping agent to generate self-assemblies of nanocrystals via van der Waals interaction. Apart from synthesis and self-assembly, disassembly and reassembly of Cu2O nanocrystals have also been investigated. The disassembly processes are accompanied with aggregative growths of nanocrystals, which can be attributed to a combined process of "oriented attachment" and Ostwald ripening, leading to permanent engagement and enlargement of nanocrystals. Finally, our self-assembled nanocrystals of Cu2O show a lower detection limit, lower operating temperature, and higher sensitivity in ethanol vapor detection, compared with other Cu2O-based alcohol sensors reported in the recent literature. A greater depletion layer of carrier and a relatively small contact potential may account for the observed sensing enhancement in the sensors made from the organized Cu2O nanocrystals. © 2010 American Chemical Society.

Zhang J.,University of Swansea | Fu Y.,Hunan University
Meccanica | Year: 2012

A new beam model is developed for the viscoelastic microbeam based on a modified couple stress model which contains only one material length scale parameter. The governing equations of equilibrium together with initial conditions and boundary conditions are obtained by a combination of the basic equations of modified couple stress theory and Hamilton's principle. This new beam model is then used for an electrically actuated microbeam-based MEMS structure. The dynamic and quasi-static governing equations of an electrically actuated viscoelastic microbeam are firstly given where the axial force created by the midplane stretching effect is also considered. Galerkin method is used to solve above equation and this method is also validated by the finite element method (FEM) when our model is reduced into an elastic case. The numerical results show that the instantaneous pull-in voltage, durable pull-in voltage and pull-in delay time predicted by this newly developed model is larger (longer) than that predicted by the classical beam model. A comparison between the quasi-static model results and the dynamic model results is also given. © 2012 Springer Science+Business Media B.V.

Hu A.,Hunan University | Cao G.,Guangdong Pharmaceutical University
Tetrahedron Asymmetry | Year: 2011

The hydrobromide and nitrate of 4-(tert-butyl)-5-(4-chlorobenzyl)thiazol-2- amine have been synthesized, and their chiral symmetry breaking in the solid-state has been investigated. It is shown that each molecule is connected by continuous N-H⋯Br/N-H⋯O hydrogen bonds to afford left- or right-handed helical assemblies in the crystal packing. Mirror-image CD spectra were obtained for the right- and left-handed helical-type chiral crystals. © 2011 Elsevier Inc. All rights reserved.

Xiao L.,Hunan University | Huang S.,Hunan University | Lu K.,University of Aalborg
IET Power Electronics | Year: 2013

Unbalanced grid voltage will cause large dc-bus voltage ripple and introduce high harmonic current components on the grid side. This will severely threaten the safety of the grid-connected voltage source converter (VSC) and consequently, affect the healthy operation condition of the load. In this study, a new proportional-integral-resonant (PI-RES) controller-based, space vector modulated direct power control topology is proposed to suppress the dc-bus voltage ripple and in the same time, controlling effectively the instantaneous power of the VSC. A special ac reactive power reference component is introduced in the controller, which is necessary in order to reduce the dc-bus voltage ripple and active power harmonics at the same time. The proposed control topology is implemented in the lab. Simulation and experimental results are provided to validate its performance and the analysis presented in this study. © The Institution of Engineering and Technology 2013.

Liu D.,Xi'an Jiaotong - Liverpool University | Lee M.-C.,Chinese University of Hong Kong | Pun C.-M.,University of Macau | Liu H.,Hunan University
IEEE Transactions on Vehicular Technology | Year: 2013

One major concern of existing wireless localization systems is the identification of nonline-of-sight (NLOS) signal propagation, since NLOS can be considered the dominant source of localization error. Present identification methods usually assume that NLOS could make it not possible to perform localization in a consistent manner. However, the validity of the foregoing assumption has not been properly investigated. This paper presents a theoretical analysis of mobile user localization involving one or more NLOS beacons and shows the given assumption as being invalid when the estimated user location is outside the convex hull of the beacons used in the localization. It also proposes an efficient algorithm for checking whether the estimated location of a mobile user is inside the convex-hull region in both 2-D and 3-D space. Extensive localization experiments on different wireless networks demonstrate that using current NLOS identification methods and classical localization algorithms could yield localization results with grossly underestimated errors. © 2012 IEEE.

Yuan L.,Hunan University | Jin F.,Hunan University | Zeng Z.,Hunan University | Liu C.,Hunan University | And 2 more authors.
Chemical Science | Year: 2015

Two-photon excitation (TPE) probe-based fluorescence imaging has become one of the most attractive diagnostic techniques to investigate biomolecules and biological events in live cells and tissues. At the current stage most of the TPE-based sensing is reflected by fluorescence intensity changes. Nevertheless the mere altering of intensity could be facilely affected by ambient conditions. On the other hand, TPE probes based on an intramolecular charge transfer (ICT) strategy could solve this problem to some extent with a morphology change-induced emission shift. However their applications are yet constrained due to the inherent limitation of ICT, e.g. the high degree of overlap of two emissions bands and shifts of the TPE maxima. To achieve the desired TPE-based sensing and to circumvent the problems stated above, we adapted a Förster resonance energy transfer (FRET) strategy to develop small molecule ratiometric TPE fluorescent probes. Our FRET-based ratiometric TPE fluorescent probe displays a remarkable emission shift (up to 125 nm) with two well-resolved emission bands. Hence the ratio of these two emission bands could enable the measurement of fluorescence changes more accurately, thus further improving imaging in live cells and deep tissues. To the best of our knowledge, the current reported probe has the largest emission shift among all the small molecule ratiometric TPE fluorescent probes while the maximum TPE wavelength remains unchanged. This work has provided a FRET approach to fabricate novel small molecule ratiometric TPE fluorescent probes that improve imaging in deep tissues. This journal is © The Royal Society of Chemistry.

Lu K.,Shanghai Maritime University | Lu K.,University of Aalborg | Lei X.,Hunan University | Blaabjerg F.,University of Aalborg
IEEE Transactions on Energy Conversion | Year: 2013

The back EMF-based sensorless control method is very popular for permanent magnet synchronous machines (PMSMs) in the medium- to high-speed operation range due to its simple structure. In this speed range, the accuracy of the estimated position is mainly affected by the inductance, which varies at different loading conditions due to saturation effects. In this paper, a new concept of using a constant artificial inductance to replace the actual varying machine inductance for position estimation is introduced. This facilitates greatly the analysis of the influence of inductance variation on the estimated position error, and gives a deep insight into this problem. It also provides a simple approach to achieve a globally minimized position error. A proper choice of the artificial machine inductance may reduce the maximum position error by 50% without considering the actual inductance variation in the control algorithm. Analytical and experimental results are given for validating the proposed theory. © 1986-2012 IEEE.

Lu L.-M.,Jiangxi Agricultural University | Lu L.-M.,Hunan University | Zhang X.-B.,Hunan University | Shen G.-L.,Hunan University | Yu R.-Q.,Hunan University
Analytica Chimica Acta | Year: 2012

In this paper, for the first time, Cu nanoparticles (CuNPs) were prepared by seed-mediated growth method with Au nanoparticles (AuNPs) playing the role of seeds. Carbon nanotubes (CNTs) and AuNPs were first dropped on the surface of glassy carbon (GC) electrode, and then the electrode was immersed into growth solution that contained CuSO 4 and hydrazine. CuNPs were successfully grown on the surface of the CNTs. The modified electrode showed a very high electrochemical activity for electrocatalytic oxidation of glucose in alkaline medium, which was utilized as the basis of the fabrication of a nonenzymatic biosensor for electrochemical detection of glucose. The biosensor can be applied to the quantification of glucose with a linear range covering from 1.0×10 -7 to 5×10 -3M and a low detection limit of 3×10 -8M. Furthermore, the experiment results also showed that the biosensor exhibited good reproducibility and long-term stability, as well as high selectivity with no interference from other oxidable species. © 2011 Elsevier B.V.

Mu Y.,Zhejiang Normal University | Jia D.,Zhejiang Normal University | He Y.,Zhejiang Normal University | Miao Y.,Zhejiang Normal University | And 2 more authors.
Biosensors and Bioelectronics | Year: 2011

Development of fast and sensitive sensors for glucose determination is important in food industry, clinic diagnostics, biotechnology and many other areas. In these years, considerable attention has been paid to develop non-enzymatic electrodes to solve the disadvantages of the enzyme-modified electrodes, such as instability, high cost, complicated immobilization procedure and critical operating situation et al. Nano nickel oxide (NiO) modified non-enzymatic glucose sensors with enhanced sensitivity were investigated. Potential scanning nano NiO modified carbon paste electrodes up to high potential in alkaline solution greatly increases the amount of redox couple Ni(OH)2/NiOOH derived from NiO, and thus improves their electrochemical properties and electrocatalytical performance toward the oxidation of glucose. The non-enzymatic sensors response quickly to glucose and the response time is less than 5s, demonstrating excellent electrocatalytical activity and assay performance. The calibration plot is linear over the wide concentration range of 1-110μM with a sensitivity of 43.9nA/μM and a correlation coefficient of 0.998. The detection limit of the electrode was found to be 0.16μM at a signal-to-noise ratio of 3. The proposed non-enzymatic sensors can be used for the assay of glucose in real sample. © 2010 Elsevier B.V.

Cui X.Y.,Hunan University | Cui X.Y.,National University of Singapore | Liu G.R.,National University of Singapore | Li G.Y.,Hunan University | Zhang G.Y.,National University of Singapore
International Journal for Numerical Methods in Engineering | Year: 2011

A formulation for thin plates with only the deflection as nodal variables has been proposed using the generalized gradient smoothing technique and the radial point interpolation method (RPIM). The deflection fields are approximated using the RPIM shape functions which possess the Kronecker Delta property for easy impositions of essential boundary conditions. Three types of smoothing domains, which are also serving as the numerical integrations domains, are constructed based on the background three-node triangular cells and the generalized gradient smoothing operation is performed over each of them to obtain the smoothed curvatures. The generalized smoothed Galerkin weak form is then used to create the discretized system equations. The essential boundary conditions of rotations are imposed in the process of constructing the curvature field, and the translation boundary conditions are imposed as in the standard FEM. A number of numerical examples, including both static and free vibration analysis, are studied using the present methods and the numerical results are compared with the analytical ones and those in the open literatures. The results show that the present formulation can obtain very stable and accurate solutions, even for the extremely irregular background cells. © 2010 John Wiley & Sons, Ltd.

Li C.C.,Hunan University | Li C.C.,National University of Singapore | Li Q.H.,Hunan University | Chen L.B.,Hunan University | Wang T.H.,Hunan University
ACS Applied Materials and Interfaces | Year: 2012

A facile, green strategy is explored to synthesize mesoporous Au/Li 4Ti 5O 12 spheres based on in situ conversion of titanium glycolate in LiOH aqueous solution. Compared with TiO 2 precursors, titanium glycolate possesses some strengths: (i) fast and easy preparation; (ii) direct reaction with LiOH without introduce of TiO 2 impurity. In the synthesis, the produced chemical waste is only the mixed solvent of acetone and ethylene glycol (EG). Furthermore, acetone and EG in chemical waste can be easily separated by distillation and reused in the next synthesis process due to the great difference between their boiling points. In particular, the as-prepared mesoporous Au/Li 4Ti 5O 12 spheres combines the advantages of large specific surface area (166 m 2/g) and good electronic conduction enhanced by Au nanoparticles when used as an anode electrode material. The electrochemical tests show that the mesoporous Au/Li 4Ti 5O 12 spheres display excellent high rate capability and cycling performance. © 2012 American Chemical Society.

Li C.C.,Hunan University | Li C.C.,National University of Singapore | Li Q.H.,Hunan University | Chen L.B.,Hunan University | Wang T.H.,Hunan University
Journal of Materials Chemistry | Year: 2011

Cobalt oxide nanowire array films have been prepared on large-area metallic substrates via a topochemical conversion route and have been demonstrated as advanced anode materials for high-performance lithium-ion batteries. Compared to previous reports, the cobalt oxide nanowire array electrodes will have good contact with the conducting substrates and an open space between neighboring nanowires, which provide an express pathway for charge transfer and facilitate diffusion of electrolyte into the inner region of the electrode. Besides these strengths, other ancillary materials such as binders and conductive additives are not required to enhance the system's conductivity and stability. After 50 successive cycles, the cobalt nanowire arrays are capable of retaining a specific capacity of 743 mAh g-1 with a very small capacity fading of 0.13% per cycle. © The Royal Society of Chemistry 2011.

Wei D.,National University of Singapore | Xie L.,National University of Singapore | Lee K.K.,National University of Singapore | Hu Z.,National University of Singapore | And 6 more authors.
Nature Communications | Year: 2013

Graphene is often regarded as one of the most promising candidates for future nanoelectronics. As an indispensable component in graphene-based electronics, the formation of junctions with other materials not only provides utility functions and reliable connexions, but can also improve or alter the properties of pristine graphene, opening up possibilities for new applications. Here we demonstrate an intramolecular junction produced by the controllable unzipping of single-walled carbon nanotubes, which combines a graphene nanoribbon and single-walled carbon nanotube in a one-dimensional nanostructure. This junction shows a strong gate-dependent rectifying behaviour. As applications, we demonstrate the use of the junction in prototype directionally dependent field-effect transistors, logic gates and high-performance photodetectors, indicating its potential in future graphene-based electronics and optoelectronics. © 2013 Macmillan Publishers Limited. All rights reserved.

Pan S.,Hunan University | Guo R.,Hunan University | Xu W.,Hunan University
Soft Matter | Year: 2014

Dynamically tuning the surface wettability has long been a scientific challenge, but of great importance in surface science. Robust superhydrophobic surfaces, displaying switchable and tunable extreme wetting behaviors, are successfully developed by spraying photoresponsive hydrophobic nanoparticles onto various substrates. The surface wettability can be intelligently adjusted by applying irradiation with UV or visible light, which is assumed to initiate large conformation changes of azobenzene units at the coating surface, resulting in distinct surface energy change and thus controlled wetting behaviors. The underlying wetting mechanism about the resulting surfaces is systematically investigated and supported by the estimation of water contact angles using newly rewritten Cassie-Baxter and Wenzel relations and also by the evaluation of solid surface free energy adopting the Owens-Wendt approach. The methodology proposed may provide a novel way of tuning surface wettability and investigating the wetting transition mechanism and also promote applications in self-cleaning and smart fluid control. This journal is © the Partner Organisations 2014.

Pan S.,Hunan University | Guo R.,Hunan University | Xu W.,Hunan University
Soft Matter | Year: 2014

For the first time, the surface composite Cassie-Baxter wetting state is carefully investigated using ginkgo biloba as natural model. Investigations follow two directions: (a) low local solid contact areal fraction leading to high apparent contact angles; and (b) thick air plastron trapped at the contacting interface leading to stable dewetting state. This journal is © the Partner Organisations 2014.

Li Z.,Guangxi University for Nationalities | Xie T.,Guangxi University | Li Q.,Hunan University
Computers and Mathematics with Applications | Year: 2012

In this paper, we investigate some properties of (X, τθ) such as compactness, separate property, Lindelf property and connectedness, where (X, τθ) is induced by a reflexive relation θ on X which may be infinite. Moreover, we introduce the concept of approximating spaces and research their characterizations and properties. Particularly, we obtain a sufficient and necessary condition that topological spaces are approximating spaces. These will be not only conducive to better understanding basic concepts and properties of a rough set, but also have theory and actual significance to topology. © 2012 Published by Elsevier Ltd.

Lei Y.,Hunan University | Adhikari S.,University of Swansea | Friswell M.I.,University of Swansea
International Journal of Engineering Science | Year: 2013

This paper investigates the dynamic behavior of nonlocal viscoelastic damped nanobeams. The Kelvin-Voigt viscoelastic model, velocity-dependent external damping and Timoshenko beam theory are employed to establish the governing equations and boundary conditions for the bending vibration of nanotubes. Using transfer function methods (TFM), the natural frequencies and frequency response functions (FRF) are computed for beams with different boundary conditions. Unlike local structures, taking into account rotary inertia and shear deformation, the nonlocal beam has maximum frequencies, called the escape frequencies or asymptotic frequencies, which are obtained for undamped and damped nonlocal Timoshenko beams. Damped nonlocal beams are also shown to possess an asymptotic critical damping factor. Taking a carbon nanotube as a numerical example, the effects of the nonlocal parameter, viscoelastic material constants, the external damping ratio, and the beam length-to-diameter ratio on the natural frequencies and the FRF are investigated. The results demonstrate the efficiency of the proposed modeling and analysis methods for the free vibration and frequency response analysis of nonlocal viscoelastic damped Timoshenko beams. © 2013 Elsevier Ltd.

Li C.C.,Hunan University | Li C.C.,National University of Singapore | Mei L.,Hunan University | Chen L.B.,Hunan University | And 2 more authors.
Journal of Materials Chemistry | Year: 2012

We have demonstrated an extremely facile procedure for the preparation of 3D porous manganese oxide nanostructures by pyrolysis of Mn-based coordination polymer nanowires. The highly aligned and ultralong Mn-based polymer nanowires with high chemical purities were prepared using nitrilotriacetic acid (NA) as a chelating agent by a one-step hydrothermal approach. In the synthesis, NA was slowly dissolved in water and bonded with manganese ions by carboxyl groups to form one-dimensional polymer nanowires under the protection of isopropyl alcohol, and then form highly aligned nanowire bundles. Control experiments show that the morphologies of polymer nanowires greatly depend on the precursor salts and ratios between deionized water and isopropyl alcohol. Based on the elemental analysis results, the probable molecular formula and growth mechanism have been proposed. The catalytic reaction results demonstrated that the as-prepared 3D porous manganese oxide nanostructure was a good support for aerobic oxidation of benzyl alcohol. Moreover, the catalysts can be easily separated and recycled. © 2012 The Royal Society of Chemistry.

Ye Y.,Hunan University | Li K.,Hunan University
Computers and Fluids | Year: 2013

Entropic Lattice Boltzmann Method (ELBM) is used for the stable computational simulation of high Reynolds number fluid flows, due to it alleviates the obstacle of numerical instabilities by restoring the second law of thermodynamics (Boltzmann's H-theorem). In general, this stability is gained at the price of some computational overhead, associated with the requirement of adjusting the local relaxation parameter of the standard Lattice Boltzmann Method (LBM) in such a way as to guarantee compliance with H-theorem. In this paper, we present a very efficient implementation strategy for ELBM based high Reynolds number flow simulation on nVIDIA graphics processing unit (GPU) with optimization approaches. Some algorithms for H-α solver on GPU which solve the relaxation adjusting parameter are also proposed in our study. We demonstrate the ELBM-GPU parallel approach for fluid flows simulation which can reduce the computational cost of ELBM implementation and obtain an excellent performance. Meanwhile, we find that the direct approximate method of parameter solution is more efficient than other methods on the whole. The results show that: (1) the whole ELBM-GPU implementation results in average speedups of 3.14 over the single-core ELBM-CPU result; (2) comparison of two types of methods for H-α solver, the direct approximate method can save an average 31.7% of computation time than the iteration method; and (3) the implementation of ELBM on GPU allows us to achieve up to 50% global memory bandwidth utilization ratio. © 2013 Elsevier Ltd.

Zhou Y.-H.,Hunan University | Zhou Y.-H.,Gannan Medical University | Zeng J.,Hunan University | Chen K.-Q.,Hunan University
Carbon | Year: 2014

The electronic transport properties of zigzag 6, 6, 12-graphyne nanoribbons (6, 6, 12-Z GYNRs) are investigated by first-principles calculations. The results show that the two bands around the Fermi level of 4-6, 6, 12-ZGYNR are not flat but cambered, which is different from that of zigzag graphene and α-graphyne nanoribbons, and is also different from that of 5-6, 6, 12-ZGYNR. In non-magnetic states, the current across the 5-6, 6, 12-ZGYNR system is almost forbidden even at rather large bias voltages, while in 4-6, 6, 12-ZGYNR system, the current increases linearly with the increase of bias voltage. In spin-polarized state, fine spin filtering effect is gained in anti-parallel configuration of 5-6, 6, 12-ZGYNR system. Moreover, it is found that magnetoresistance exists in the 5-6, 6, 12-ZGYNR system, but not in the 4-6, 6, 12-ZGYNR system. © 2014 Elsevier Ltd. All rights reserved.

Huang H.-J.,Jiangxi Agricultural University | Yuan X.-Z.,Hunan University
Bioresource Technology | Year: 2016

Various hydrothermal treatment methods, including hydrothermal carbonization, liquefaction and sub/super-critical water gasification, have been applied to the disposal of sewage sludge for producing bio-materials or bio-fuels. It has become a research hotspot whether the heavy metals contained in sewage sludge can be well treated/stabilized after the hydrothermal treatments. This review firstly summarized the methods of assessing heavy metals' contamination level/risk and then discussed the migration and transformation behaviors of heavy metals from the following aspects: the effect of reaction temperature, the effect of additives (catalysts and other biomass), the effect of the type of solvent and the effect of reaction time. This review can provide an important reference for the further study of the migration and transformation behaviors of heavy metals during the hydrothermal treatment of sewage sludge. © 2015 Elsevier Ltd.

Agency: Cordis | Branch: FP7 | Program: CP-FP-SICA | Phase: HEALTH.2010.1.1-3 | Award Amount: 4.87M | Year: 2011

Protein glycosylation is a post-translational phenomenon that is involved in most physiological and disease processes including cancer. Most of the known cancer-associated glycobiomarkers were discovered individually using liquid chromatography and mass spectroscopy. Though valuable, there is room for improvement in these approaches for the discovery phase. There is also a critical need for innovative, rapid, and high-throughput (HTP) technologies that will translate the discovery of cancer-associated glycobiomarkers from basic science to clinical application. The GlycoHIT consortium brings a highly experienced, innovative and interdisciplinary team of researchers from Europe, China and USA representing academia, industry and clinical fields to significantly enhance some of the existing glycoanalytical technologies and to advance novel HTP glycoanalytical technologies beyond current state of the art. Microchip technology and novel partitioning methods will be exploited for nanoscale HTP separations of serum glycoproteins for analysis by HPLC or LCMS. In parallel, lectin array technology will be radically improved by the innovative use of recombinant human lectins and lectin mimics derived by screening large phage displayed combinatorial libraries. Aptamer libraries will be exploited for identification of lectin mimics and development of a glycosignature platform Compatibility of the lectin/lectin mimic array technologies with novel label-free biosensors will be explored. Newly-developed technologies will be validated by analysis of serum samples from a variety of cancer patient cohorts and will be supported throughout by experimental interaction analysis, complex structural modelling and informatics. Effective project management, commercially-aware intellectual property management and targeted dissemination activities supplement the core science and ensure maximum impact for the project.

Zeng H.,Hunan University | Zeng H.,University of Illinois at Urbana - Champaign | Zeng H.,Yangtze University | Hu H.,Hunan University | Leburton J.-P.,University of Illinois at Urbana - Champaign
ACS Nano | Year: 2010

We use first principles density functional theory combined with nonequilibrium Green*s function technique to investigate the electronic and transport properties of metallic armchair and zigzag carbon nanotubes (CNTs) with different kinds of multivacancy defects. While the existence of a small band gap in pristine zigzag (12,0) CNTs lowers its conductance compared to pristine armchair (7,7) CNTs, transport properties in the presence of multi (hexa)-vacancy are superior in the former nanostructure, that is more sensitive to defect size and topology than the latter. In addition, in the zigzag structures hexavacancy nanotubes have higher conductance than divancancy nanotubes, which is due to the presence of midgap states that reduce the transmission gap and enhance the conductance. © 2010 American Chemical Society.

Chen Z.,Hunan University | Liu J.,Hunan University | Han Z.,Hunan University | Du B.,Hunan University | And 2 more authors.
Energy | Year: 2013

In this work, the commercially available diesel fuel (Bu00), butanol(20%)-diesel(80%) (by vol.) (Bu20), butanol(30%)-diesel(70%) (Bu30), and butanol(40%)-diesel (60%) (Bu40) fuels were tested. Experiments were conducted on a high-speed direct injection (DI) diesel engine for passenger-car application for varied loads at two representative engine speeds. The results showed that butanol-diesel blends slightly increased combustion pressure and accelerated burning rate. As fueled by the Bu40 blend, the maximum power output of the engine cannot be affected. Besides, butanol-diesel blends increased BSFC and brake thermal efficiency. Moreover, the effects of butanol addition on diesel engine exhaust emissions were varied with loads. Under low-load conditions, CO emissions obviously increased while NOx emissions decreased as butanol blending ratio increased. Under high-load conditions, on the contrary, CO emissions decreased but NOx emission increased. For the 40% butanol-diesel blend, in addition, HC emissions were higher than the neat diesel and lower percentage of butanol-diesel blends, especially at low-load. It is interesting that smoke decreased significantly at all conditions with the use of butanol-diesel blends, and the more butanol blending ratio the less smoke. Overall butanol is a potentially promising biofuel, which could be used conveniently up to high blending ratio with diesel fuel in diesel engines. © 2013.

Shi C.,Hunan University | Yang J.,Yancheng Institute of Technology | Yang N.,Hunan University | Chang Y.,Hunan University
Cement and Concrete Composites | Year: 2014

This paper studied the influence of waterglass on the early water stability of potassium magnesium phosphate cement (MKPC). Mass loss and residual strength were used to reflect the water stability of MKPC pastes exposed to different curing conditions. Experimental results indicated that the addition of waterglass could accelerate early hydration of MKPC, reduce the crystallinity of hydration products, and improved the pore structures significantly. The early water stability of MKPC was greatly improved due to the significant decreased dissolution of hydration products and pore volume of hardened MKPC. © 2014 Published by Elsevier Ltd.

Qin Z.,Shanghai JiaoTong University | Xie G.,Shanghai JiaoTong University | Zhang H.,University of Science and Technology of China | Zhao C.,Hunan University | And 3 more authors.
Optics Express | Year: 2015

Black phosphorus, a newly emerged two-dimensional material, has attracted wide attention as novel photonic material. Here, multilayer black phosphorus is successfully fabricated by liquid phase exfoliation method. By employing black phosphorus as saturable absorber, we demonstrate a passively Q-switched Er-doped ZBLAN fiber laser at the wavelength of 2.8 μm. The modulation depth and saturation fluence of the black phosphorus saturable absorber are measured to be 15% and 9 μJ/cm2, respectively. The Q-switched fiber laser delivers a maximum average power of 485 mW with corresponding pulse energy of 7.7 μJ and pulse width of 1.18 μs at repetition rate of 63 kHz. To the best of our knowledge, this is the first time to demonstrate that black phosphorus can realize Q-switching of 2.8-μm fiber laser. Our research results show that black phosphorus is a promising saturable absorber for mid-infrared pulsed lasers. © 2015 Optical Society of America.

Gui R.,Shanghai JiaoTong University | Wan A.,Shanghai JiaoTong University | Liu X.,Hunan University | Jin H.,Shanghai JiaoTong University
Chemical Communications | Year: 2014

Gold nanoclusters and doxorubicin dual-loaded liposomes were prepared by using a supercritical CO2 method, and developed toward intracellular fluorescent thermometry, photothermal-triggered drug release and tumor therapy. This journal is © The Royal Society of Chemistry.

Gui C.,University of Connecticut | Gui C.,Hunan University
Archive for Rational Mechanics and Analysis | Year: 2012

In this paper, we prove even symmetry of monotone traveling wave solutions to the balanced Allen-Cahn equation in the entire plane. Related results for the unbalanced Allen-Cahn equation are also discussed. © 2011 Springer-Verlag.

Chen Z.,Hunan University | Wu Z.,Hunan University | Liu J.,Hunan University | Lee C.,University of Illinois at Urbana - Champaign
Energy Conversion and Management | Year: 2014

In this work, the combustion and emission fundamentals of high n-butanol/diesel ratio blend with 40% butanol (i.e., Bu40) in a heavy-duty diesel engine were investigated by experiment and simulation at constant engine speed of 1400 rpm and an IMEP of 1.0 MPa. Additionally, the impact of EGR was evaluated experimentally and compared with neat diesel fuel (i.e., Bu00). The results show that Bu40 has higher cylinder pressure, longer ignition delay, and faster burning rate than Bu00. Compared with Bu00, moreover, Bu40 has higher NOx due to wider combustion high-temperature region, lower soot due to local lower equivalence ratio distribution, and higher CO due to lower gas temperature in the late expansion process. For Bu40, EGR reduces NOx emissions dramatically with no obvious influence on soot. Meanwhile, there is no significant change in HC and CO emissions and indicated thermal efficiency (ITE) with EGR until EGR threshold is reached. When EGR rate exceeds the threshold level, HC and CO emissions increase dramatically, and ITE decreases markedly. Compared with Bu00, the threshold of Bu40 appears at lower EGR rate. Consequently, combining high butanol/diesel ratio blend with medium EGR has the potential to achieve ultra-low NOx and soot emissions simultaneously while maintaining high thermal efficiency level. © 2013 Elsevier Ltd. All rights reserved.

Cheng Y.,Hunan University | Matykina E.,Complutense University of Madrid | Skeldon P.,University of Manchester | Thompson G.,University of Manchester
Electrochimica Acta | Year: 2011

Plasma electrolytic oxidation was undertaken on Zircaloy-4 in alkaline silicate and pyrophosphate electrolytes, with a square waveform AC current regime. The resultant coatings were examined using scanning electron spectroscopy, X-ray diffraction and nanoindentation. The coatings formed in silicate electrolyte comprised mainly a porous inner layer and a more compact outer layer, with characteristic solidification structures being evident following prolonged treatment. The coatings contained monoclinic and tetragonal ZrO2, the latter being mainly present in the outer layer, which was of hardness up to ∼8 GPa. In contrast, extensively cracked coatings resulted from use of pyrophosphate electrolyte; the coating integrity was improved by the addition of silicate to the pyrophosphate electrolyte. The different morphologies of the coatings appeared to be related to the differing nature of the microdischarges and to the incorporation of silicon species that enhanced the formation of t-ZrO2. © 2011 Elsevier Ltd.

Zhang X.Z.,Hunan University | Zhang X.Z.,Hunan Institute of Engineering | Wang Y.N.,Hunan University
Energy Conversion and Management | Year: 2011

This paper presents the design and implementation of a high performance position-sensorless control scheme for the extensively used brushless DC (BLDC) motors. In the proposed method, with proper PWM strategy, instead of detecting the zero-crossing point (ZCP) of the nonexcited motor back electromagnetic force (EMF) or the average motor terminal to neutral voltage, the true zero-crossing points of back EMF are extracted directly from the difference of the specific average line-to-line voltages with simple RC circuits and comparators. In contrast to conventional methods, the neutral voltage is not needed and the diode freewheeling currents in the nonconducted phase are eliminated completely; therefore, the commutation signals are more accurate and insensitive to the common-mode noise. Moreover, 100% pulse-width-modulation (PWM) duty ratio control of BLDC motors is provided with the presented method. As a result, the proposed method makes it possible to achieve good motor performance over a wide speed range and to simplify the starting procedure. The detailed circuit model is analyzed and some experimental results obtained from a sensorless prototype are shown to verify the analysis and confirm the validity of the proposed method. © 2010 Elsevier Ltd. All rights reserved.

Cao E.,Hunan University | Cao E.,University of Illinois at Urbana - Champaign
International Journal of Production Research | Year: 2014

This paper examines optimal decisions and coordination models for a dual-channel supply chain when the two end competition market demands are simultaneously disrupted. Firstly, we developed the pricing and production decisions models without demand disruptions and propose a revenue sharing contract to coordinate the dual-channel supply chain where the manufacturer is a Stackelberg leader and the retailer is a follower. We derived the conditions under which the maximum profit can be achieved in detailed. We compared the profits under normal case and disrupted case and quantified the information value of knowing demand disruptions. We proposed an improved revenue sharing contract to coordinate the dual-channel supply chain with demand disruptions. The results indicate that the adjusting prices and production quantity are the optimal decisions whether the demand disruptions case or normal case. We also find that the original revenue sharing contract is a special case of improved revenue sharing contract and the market scale change, channel substitutability and deviation cost affected the improved revenue sharing contract under demand disruptions. Finally, we further conduct numerical experiments to show how the demand disruption affects the decisions. © 2014 Taylor & Francis.

Gui R.,Shanghai JiaoTong University | Wan A.,Shanghai JiaoTong University | Liu X.,Hunan University | Yuan W.,Michigan State University | Jin H.,Shanghai JiaoTong University
Nanoscale | Year: 2014

Hydrodynamic size-minimized quantum dots (QDs) have outstanding physicochemical properties for applications in multicolor molecular and cellular imaging at the level of single molecules and nanoparticles. In this study, we have reported the aqueous synthesis of Ag2S QDs by using thiol-based multidentate polymers as capping reagents. By regulating the composition of the precursors (AgNO3 and sulfur-N2H4·H 2O complex) and multidentate polymers (poly(acrylic acid)-graft-cysteamine-graft-ethylenediamine), as well as the reaction time, Ag2S QDs (2.6-3.7 nm) are prepared, displaying tunable photoluminescence (PL) emission from red to the second near-infrared region (687-1096 nm). The small hydrodynamic thickness (1.6-1.9 nm) of the multidentate polymers yields a highly compact coating for the QDs, which results in the bright fluorescent QDs with high PL quantum yields (QYs: 14.2-16.4%). Experimental results confirm that the QDs have high PL stability and ultralow cytotoxicity, as well as high PLQYs and small hydrodynamic sizes (4.5-5.6 nm) similar to fluorescent proteins (27-30 kDa), indicating the feasibility of highly effective PL imaging in cells and living animals. This journal is © the Partner Organisations 2014.

Yang J.,Hunan Institute of Engineering | Hu W.,Hunan University | Tang J.,Hunan Agricultural University
RSC Advances | Year: 2014

The impact deposition of Al (or Fe) atoms on the rhombohedron of Fe (or the truncated octahedron of Al) nanoparticles is investigated by performing a molecular dynamics simulation using the embedded atom method. These simulations are performed in different incident energies (from 10 eV to 50 eV). The dependence of the incident energy of deposited atoms on the growth configurations of Fe-Al nanoparticles is analyzed. For the deposition of Al atoms on the Fe nanoparticle, some Al atoms are incorporated into the Fe core as the incident energy of Al increases. A nanoparticle configuration with Fe-core and Al-shell is usually observed at all incident energies considered. In this case, the substrate Fe atoms and the deposited Al atoms are arranged in body-centered cubic configuration. For the impact deposition of Fe atoms on the Al nanoparticle, an onion-like nanoparticle is observed at incident energy of 10 eV. A configuration with Al-shell and alloyed Fe-Al core is obtained as the incident energy increases. This study proposes a method of artificially controlling nanoalloy configuration. © 2014 The Royal Society of Chemistry.

Long M.,Changsha University of Science and Technology | Chen Y.,University of Warwick | Peng F.,Hunan University
IEEE Communications Letters | Year: 2011

A simple yet accurate analysis of the bit error rate performance for differential chaos shift keying communication system is proposed for an additive white Gaussian noise channel by using the non-central F distribution of the decision variable and assuming variable bit energy in the calculation. The new method has much higher accuracy or much lower computational complexity than the existing methods in the literature. Numerical results show that in most cases, the predicted bit error rate from the new method is indistinguishable from the simulated bit error rate, showing the effectiveness of our result. © 2011 IEEE.

Chen H.,Hunan University | Lin W.,Hunan University | Lin W.,Institute of Fluorescent Probes for Biological Imaging | Cui H.,Hunan University | Jiang W.,Hunan University
Chemistry - A European Journal | Year: 2015

The development of near-infrared (NIR) functional fluorescent dyes has gained increasing attention over the last few decades. Herein, we describe the development of a unique type of xanthene-cyanine fused NIR fluorophores, XC dyes, formed by reacting chloro-substituted cyanine with resorcin or its analogues under anhydrous conditions. XC dyes are a hybrid of cyanine and xanthene. The preliminary mechanistic studies indicate that the formation of XC compounds likely includes a sequence of cyclization and oxidation. XC dyes have absorption and emission in the NIR region, and their fluorescence properties can be controlled by modifications of the key hydroxyl and amine groups. The novel XC NIR dyes are advantageous over previously developed merocyanine dyes NIR dyes in their chemical stability against strong nucleophiles. Quantum chemical calculations reveal that the distinct properties of XC and HD dyes can be attributed to their structural differences. By taking advantage of the superior properties of XC dyes, we have further constructed a new NIR fluorescent probe, XC-H2S , which is capable of monitoring both the concentration- and time-dependent variations of H2S in living animals, highlighting the value of XC NIR dyes. We expect that the unique XC NIR dyes developed herein will find broader applications than HD NIR dyes as fluorescent platforms for the development of a wide variety of NIR fluorescent probes, in particular, those suitable for targets of interest that have strong nucleophilic character. @copy;2015 Wiley-VCH Verlag GmbH & Co. KGaA , Weinheim.

Cao E.,Hunan University | Cao E.,Hunan Province Key Laboratory of Logistics Information and Simulation Technology | Wan C.,Hong Kong Polytechnic University | Lai M.,Hunan University | Lai M.,Hunan Province Key Laboratory of Logistics Information and Simulation Technology
International Journal of Production Economics | Year: 2013

This paper develops a coordination mechanism for a supply chain consisting of one manufacturer and n Cournot competing retailers when the production cost and demands are simultaneously disrupted. This differs from traditional supply chain coordination models under a static case and the case with only demand or cost disruption. The coordination mechanism with revenue sharing is considered, and the effects of production cost and demand disruptions on revenue sharing contract are discussed to investigate the optimal strategies of players with disruptions. The penalty cost is introduced explicitly to obtain the production deviation cost caused by the disruptions. In this study, it is obtained that the coordination contract considering the production deviation cost differs from that without disruption. Besides that, the disruptions may affect the order quantities, wholesale prices as well as revenue sharing contract. Then, the optimal strategies for different disruption levels under the centralized decision-making mode are proposed. Concerning the decentralized mode, the improved revenue sharing contract can be used to coordinate the decentralized decision-making supply chain effectively. Finally, the theoretical results are illustrated by conducting some numerical examples. © 2012 Elsevier B.V. All rights reserved.

Fu Y.,Hunan University | Wang J.,FAW CAR Co. | Hu S.,Hunan University
Acta Mechanica | Year: 2014

Based on the first-order shear deformation beam theory, considering geometric nonlinearity, the governing equations for symmetric laminated composite beams subjected to uniform temperature rise are derived by using Hamilton's principle, and then three solving methods are presented to deal with it. By introducing an auxiliary function, which is shown in method one, the governing equations are reduced to be a single fourth-order integral- differential equation, and the exact solutions for the thermal buckling and postbuckling of symmetric laminated composite beams with combination of in-plane immovable simply supported and clamped boundary conditions are presented for the first time. On the basis of the results given in the method one, the explicit solutions for the thermal buckling and postbuckling of the beams are presented by giving accurate displacement functions (method two) and Ritz method (method three), respectively. Then, the effects of the transverse shear effects and boundary conditions on the thermal buckling and postbuckling of the beams are qualitatively discussed. What is more, a preliminary discussion on the probability and difference of extending the giving methods to the higher-order shear deformation beam theory with various boundary conditions is conducted. In the numerical examples, the good agreements between the present results and existing solutions verify the validity and efficiency of the present analysis and numerical results. And then the symmetric cross-ply laminated composite beam (0/90/0) is taken as an example to numerically evaluate the effects of the length-to-thickness ratio, beam theories, and boundary conditions on the thermal buckling and postbuckling of symmetric laminated composite beams. Some meaningful conclusions have been drawn. © 2013 Springer-Verlag Wien.

Cheng Y.,Hunan University | Wu F.,Hunan University | Matykina E.,Complutense University of Madrid | Skeldon P.,University of Manchester | Thompson G.E.,University of Manchester
Corrosion Science | Year: 2012

Plasma electrolytic oxidation coatings were formed in alkaline silicate electrolyte on Zircaloy-2. The evolution of the types of discharges, the microstructures, phase compositions and the corrosion resistance of the coatings were studied by real time imaging, SEM, XRD, and electrochemical tests. Characteristic solidification structures were revealed in the PEO coatings, the formation of the solidification structures is related to the long lasting discharges during the PEO process and the very low thermal conductivity of zirconium oxide. Thermal effect in the coatings and silicate content in the electrolyte affect the phase compositions of the coatings. © 2012 Elsevier Ltd.

Xiao W.-Z.,Hunan Institute of Engineering | Wang L.-L.,Hunan University | Tan Z.,Hunan University
Computational Materials Science | Year: 2014

We employ spin-polarized density functional theory (DFT) calculations within generalized gradient approximation (GGA) to study the electronic structure and magnetic properties of C-doped SnO2 (SnO2:C) bulk and thin films. Our results indicate that a singly substitutional C (CO) does not induce magnetism, while the CO-CO pairs can unexpectedly activates short-range ferromagnetism in SnO2 bulk. The intrinsic defect O vacancy (VO) triggers local moment on the isolated CO atom but do not enhance the ferromagnetic (FM) coupling between CO atoms. When the substitutional CO atoms located at the surface of SnO2 thin films, system exhibits anti-ferromagnetic (AFM) feature, which is inconsistent with experimental observation. This diversity of magnetic behavior in SnO2:C system highlights the delicate interplay between electron correlations and localization. The magnetic properties are closely related to the intrinsic defect VO and the reduction of some Sn+4 ions to Sn +2 as a possible charge compensation mechanism. © 2013 Elsevier Ltd. All rights reserved.

Ke S.,Hunan University | Feser E.,University of Illinois at Urbana - Champaign
Regional Studies | Year: 2010

KE S. and FESER E. Count on the growth-pole strategy for regional economic growth? Spread-backwash effects in Greater Central China. Regional Studies. This paper investigates spread-backwash effects associated with non-agricultural gross domestic product and employment growth across 922 cities and counties in Central China between 2000 and 2005. Simultaneous equation estimates find mixed spread-backwash effects from prefecture and higher-level cities to comparable or lower-level cities and counties. Spread effects of gross domestic product and employment growths are also indicated between county-level cities. However, county-level cities exerted backwash effects on rural counties. The paper discusses the implications of these findings in relation to the construction of urban economic growth zones in Central China as an important strategy of Central Rise. © 2010 Regional Studies Association.

Chen Z.,Hunan University | Liu J.,Hunan University | Wu Z.,Hunan University | Lee C.,University of Illinois at Urbana - Champaign
Energy Conversion and Management | Year: 2013

An experimental investigation was conducted on a direct injection (DI) diesel engine with exhaust gas recirculation (EGR), coupled with port fuel injection (PFI) of n-butanol. Effects of butanol concentration and EGR rate on combustion, efficiency, and emissions of the tested engine were evaluated, and also compared to a DI mode of diesel-butanol blended fuel. The results show butanol concentration and EGR rate have a coupled impact on combustion process. Under low EGR rate condition, both the peak cylinder pressure and the peak heat release rate increase with increased butanol concentration, but no visible influence was found on the ignition delay. Under high EGR rate condition, however, the peak cylinder pressure and the peak heat release rate both decrease with increased butanol concentration, accompanied by longer ignition delay and longer combustion duration. As regard to the regulated emissions, HC and CO emissions increase with increased butanol concentration, causing higher indicated specific fuel consumption (ISFC) and lower indicated thermal efficiency (ITE). It is also noted that butanol PFI in combination with EGR can change the trade-off relationship between NOx and soot, and simultaneously reduce both into a very low level. Compared with the DI mode of diesel-butanol blended fuel, however, the DI diesel engine with butanol PFI has higher HC and CO emissions and lower ITE. Therefore, future research should be focused on overcoming the identified shortcomings by an improved injection strategy of butanol PFI. © 2013 Elsevier Ltd. All rights reserved.

Fang F.,Beijing Technology and Business University | Xu J.,Hunan University
Nonlinear Analysis: Real World Applications | Year: 2016

Let Ω be a bounded smooth domain in ℝN with N≥2, C=Ω×(0,∞) and (Formula presented.)(C) be a (P.S.) sequence of the functional (Formula presented.) We study the limit behaviour of un and obtain a global compactness result. © 2015 Elsevier Ltd.

Cao Y.,Hunan University | Tang S.,Hunan University | Li C.,Hunan University | Zhang P.,University of Connecticut | And 3 more authors.
IEEE Transactions on Smart Grid | Year: 2012

Large-scale deployment of electric vehicles (EVs) is anticipated in the foreseeable future. Heavy intermittent charging load of EVs will create bottlenecks in supplying capacity and expose power system to severe security risks. In this paper, we propose an intelligent method to control EV charging loads in response to time-of-use (TOU) price in a regulated market. First, an optimized charging model is formulated to minimize the charging cost. Then, a heuristic method is implemented to minimize the charging cost considering the relation between the acceptable charging power of EV battery and the state of charge (SOC). Finally, the charging cost and energy demand in different time intervals are compared for both typical charging pattern and optimized charging pattern. Results show that the optimized charging pattern has great benefit in reducing cost and flatting the load curve if the peak and valley time periods are partitioned appropriately. © 2011 IEEE.

Jiang C.,Hunan University | Ni B.Y.,Hunan University | Han X.,Hunan University | Tao Y.R.,Hunan University | Tao Y.R.,Hunan Institute of Engineering
Computer Methods in Applied Mechanics and Engineering | Year: 2014

In this paper, we propose a method for time-variant uncertainty analysis, namely, the "non-probabilistic convex model process", which provides an effective mathematical tool for the analysis of structural dynamic uncertainty when lacking relevant information. In the convex model process, we express the variables at any time with intervals and establish the corresponding auto-covariance function and correlation coefficient function to depict the correlation between variables at different times. We also define several important characteristic parameters for the uni- and bi-dimensional convex model processes, including the mid-value function, variance function, auto-covariance function, and cross-covariance function; we provide the definition for the stationary convex model process and its ergodicity. Then, by combining the convex model process with the first-passage failure mechanism, we propose a non-probabilistic analysis model of structural dynamic reliability and formulate the solving algorithm based on Monte Carlo simulation. Finally, through the analysis of numerical examples, we verify the effectiveness of the convex model process and the model of dynamic reliability analysis proposed in this paper. © 2013 Elsevier B.V.

Zhang X.-B.,Hunan University | Kong R.-M.,Hunan University | Lu Y.,University of Illinois at Urbana - Champaign
Annual Review of Analytical Chemistry | Year: 2011

Metal ion sensors are an important yet challenging field in analytical chemistry. Despite much effort, only a limited number of metal ion sensors are available for practical use because sensor design is often a trial-and-error-dependent process. DNAzyme-based sensors, in contrast, can be developed through a systematic selection that is generalizable for a wide range of metal ions. Here, we summarize recent progress in the design of DNAzyme-based fluorescent, colorimetric, and electrochemical sensors for metal ions, such as Pb2+, Cu2+, Hg2+, and UO22+. In addition, we also describe metal ion sensors based on related DNA molecules, including T-T or C-C mismatches and G-quadruplexes. Copyright © 2011 by Annual Reviews. All rights reserved.

Chen T.,Hunan University | Hu Y.,Hunan University | Cen Y.,Hunan University | Chu X.,Hunan University | Lu Y.,University of Illinois at Urbana - Champaign
Journal of the American Chemical Society | Year: 2013

A novel nanocomplex displaying single-excitation and dual-emission fluorescent properties has been developed through a crown-like assembly of dye-encapsulated silica particles decorated with satellite AuNCs for live cell imaging of highly reactive oxygen species (hROS), including •OH, ClO - and ONOO-. The design of this nanocomplex is based on our new finding that the strong fluorescence of AuNCs can be sensitively and selectively quenched by these hROS. The nanocomplex is demonstrated to have excellent biocompatibility, high intracellular delivery efficiency, and stability for long-time observations. The results reveal that the nanocomplex provides a sensitive sensor for rapid imaging of hROS signaling with high selectivity and contrast. © 2013 American Chemical Society.

Yang J.,Hunan Institute of Engineering | Hu W.,Hunan University | Wu Y.,Hunan University of Science and Technology | Dai X.,Hunan University
Surface Science | Year: 2012

The structure of nickel (Ni), iron (Fe), and magnesium (Mg) adatoms on the aluminum (Al) truncated octahedron is studied using molecular dynamics and the analytic embedded atom method. First, the energy barriers of several typical diffusion processes of Ni, Fe, and Mg adatoms on the Al truncated octahedral cluster were calculated using the nudged elastic band method. The calculated energy barriers were found to be related to the surface energy and atomic radius of the adatom and substrate atom. The result shows that the incorporation of Ni and Fe atoms into Al core easily occurs, and the Mg atom should segregate at the surface of the Al cluster. Thus, the growth of Ni, Fe and Mg on the Al truncated octahedron with 1289 atoms was simulated at several temperatures. In the Ni-Al and Fe-Al cases, the core-shell structure was not obtained. For the Mg-Al system, a good Mg shell on the Al core was found at lower temperatures, and an almost perfect truncated octahedron with more Al shells emerged with an increase in temperature. © 2012 Elsevier B.V. All rights reserved.

Xiao W.-Z.,Hunan Institute of Engineering | Wang L.-L.,Hunan University
Physica Status Solidi (B) Basic Research | Year: 2014

Using first-principles calculations, we have studied the structural, electronic, and magnetic properties in CdS monolayer doped with nonmagnetic (NM) atoms X (X=B, C, N, and O). The total magnetic moments are about 1.0, 2.0, 1.0, and 0.0μB per supercell for the B-, C-, N-, and O-doped systems, respectively. As the electronegativity of X element increases, the local magnetic moment tends to localize and the impurity states gradually approach the valence band maximum of the host CdS. We find that the CdS monolayer with one S atom per supercell substituted by a B or C atom is half-metallic (HM), while that with an N atom per supercell is a ferromagnetic (FM) semiconductor. As for the one-oxygen doped case, the system still remains a semiconductor. Upon two S atoms per supercell substituted by X (=B, C, and N) atom, the X-doped CdS systems exhibit various magnetic ground states. As a consequence of the competition between double-exchange and super-exchange, the two-B-doped CdS system displays NM and anti-magnetic (AFM) behaviors, while the two-C-doped CdS system shows HM ferromagnetism with a Curie temperature of 280K. However, the two-N-doped CdS system is a semiconductor with weakly AFM ground state. Our study demonstrates that the NM elements doping is an efficient route to tune the magnetic and electronic properties in CdS monolayers. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sun Z.,Hunan University | Zeng J.,Dongguan University of Technology
Optimization Methods and Software | Year: 2011

The mixed linear complementarity problem is reformulated as a non-smooth equation by the use of the median operator. On the basis of slant differentiability, a damped semismooth Newton method for solving the non-smooth equation is presented. Both monotone and finite termination properties of the proposed method are proved. © 2011 Taylor & Francis.

Deng Y.,University of Nebraska at Omaha | Tuan C.Y.,Hunan University | Tuan C.Y.,University of Nebraska at Omaha | Xiao Y.,Hunan University | Xiao Y.,University of Southern California
Journal of Structural Engineering (United States) | Year: 2012

Nine simply supported circular steel concrete-filled tubes (CFTs), two circular steel posttensioned concrete-filled tubes (PTCFTs), and one circular steel fiber-reinforced concrete-filled tube (FRCFT) have been tested in an instrumented drop-weight impact facility. The weight and the height of the drop-weight were varied to cause failure in some test specimens. The failure modes and local damages in those specimens have been investigated extensively. Failure in the steel tubes was commonly tensile facture or rupture along the circumference. Concrete core in the impact area commonly crushed under compression and cracked under tension. The use of prestressing strands and steel fibers significantly restrained the concrete tension cracks in the PTCFT and FRCFT specimens, respectively. The experimental results are analyzed in the context of principles of energy and momentum conservation. © 2012 American Society of Civil Engineers.

Wang Y.,Hunan University | Zhang X.,Hunan Institute of Engineering | Yuan X.,Hunan University | Liu G.,Hunan Institute of Engineering
IEEE Transactions on Vehicular Technology | Year: 2011

This paper proposes an efficient and robust control scheme for the position-sensorless electric vehicle (EV) with a brushless dc motor. The back electromotive force detection method is first adopted and improved to implement sensorless control of the motor. The equivalent circuits of the control system are depicted, and the mathematical models under normal driving and energy regeneration are then derived, respectively. By combining the advantages of nonsingular terminal sliding mode with the high-order sliding-mode method, a hybrid terminal sliding-mode (HTSM) control scheme for EV is put forward to guarantee both system performance and robust stability. Experimental results show that the scheme can perfectly implement position-sensorless control without Hall sensors and that the HTSM exhibits better performance and higher efficiency than the proportionalintegraldifferential (PID) controller. Furthermore, more energy is recovered, and by the proposed scheme, the driving range is improved 5.7% more than using the traditional controller. © 2006 IEEE.

Yang J.,Hunan Institute of Engineering | Hu W.,Hunan University | Wu Y.,Hunan University of Science and Technology | Dai X.,Hunan University
Crystal Growth and Design | Year: 2012

The surface diffusion of Co atoms on the Cu clusters with decahedral, cuboctahedral, and icosahedral structures are studied using the nudged elastic band method along with an analysis embedded atom method. The calculated energy barriers show that the exchange is easier than the hopping as the Co atom diffuses from the {111} to {100} facet. The hopping mechanism is favored for the diffusion between the adjacent {111} facets as the Co adatom on the decahedron and icosahedron. On this basis, atom-by-atom growth molecular dynamics simulations are used to study the structure of the Co-Cu cluster. As Co atoms are deposited onto the Cu decahedron or cuboctahedron, we found that Co atoms only occupy {100} facets. So a Co atom belt on the surface of the Cu decahedral cluster is observed. For Co atoms on the Cu icosahedron, an anomalous core-shell structure, where the Co atoms with a larger surface energy lie on the shell and the Cu atoms with smaller surface energy occupy the core, is observed. © 2012 American Chemical Society.

Zhang X.-B.,Hunan University | Zhang X.-B.,University of Illinois at Urbana - Champaign | Wang Z.,University of Illinois at Urbana - Champaign | Xing H.,University of Illinois at Urbana - Champaign | And 2 more authors.
Analytical Chemistry | Year: 2010

The catalytic beacon has emerged as a general platform for sensing metal ions and organic molecules. However, few reports have taken advantage of the true potential of catalytic beacons in signal amplification through multiple enzymatic turnovers, as existing designs require either equal concentrations of substrate and DNAzyme or an excess of DNAzyme in order to maintain efficient quenching, eliminating the excess of substrate necessary for multiple turnovers. On the basis of the large difference in the melting temperatures between the intramolecular molecular beacon stem and intermolecular products of identical sequences, we here report a general strategy of catalytic and molecular beacon (CAMB) that combines the advantages of the molecular beacon for highly efficient quenching with the catalytic beacon for amplified sensing through enzymatic turnovers. Such a CAMB design allows detection of metal ions such as Pb 2+ with a high sensitivity (LOD = 600 pM). Furthermore, the aptamer sequence has been introduced into DNAzyme to use the modified CAMB for amplified sensing of adenosine with similar high sensitivity. These results together demonstrate that CAMB provides a general platform for amplified detection of a wide range of targets. © 2010 American Chemical Society.

Manfrinato V.R.,Massachusetts Institute of Technology | Zhang L.,Brookhaven National Laboratory | Su D.,Brookhaven National Laboratory | Duan H.,Hunan University | And 3 more authors.
Nano Letters | Year: 2013

We investigated electron-beam lithography with an aberration-corrected scanning transmission electron microscope. We achieved 2 nm isolated feature size and 5 nm half-pitch in hydrogen silsesquioxane resist. We also analyzed the resolution limits of this technique by measuring the point-spread function at 200 keV. Furthermore, we measured the energy loss in the resist using electron-energy-loss spectroscopy. © 2013 American Chemical Society.

Fan J.C.,KTH Royal Institute of Technology | Fan J.C.,Anhui University of Technology | Sreekanth K.M.,KTH Royal Institute of Technology | Sreekanth K.M.,Amrita University | And 3 more authors.
Progress in Materials Science | Year: 2013

In the past 10 years, ZnO as a semiconductor has attracted considerable attention due to its unique properties, such as high electron mobility, wide and direct band gap and large exciton binding energy. ZnO has been considered a promising material for optoelectronic device applications, and the fabrications of high quality p-type ZnO and p-n junction are the key steps to realize these applications. However, the reliable p-type doping of the material remains a major challenge because of the self-compensation from native donor defects (VO and Zni) and/or hydrogen incorporation. Considerable efforts have been made to obtain p-type ZnO by doping different elements with various techniques. Remarkable progresses have been achieved, both theoretically and experimentally. In this paper, we discuss p-type ZnO materials: theory, growth, properties and devices, comprehensively. We first discuss the native defects in ZnO. Among the native defects in ZnO, VZn and O i act as acceptors. We then present the theory of p-type doping in ZnO, and summarize the growth techniques for p-type ZnO and the properties of p-type ZnO materials. Theoretically, the principles of selection of p-type dopant, codoping method and XZn-2VZn acceptor model are introduced. Experimentally, besides the intrinsic p-type ZnO grown at O-rich ambient, p-type ZnO (MgZnO) materials have been prepared by various techniques using Group-I, IV and V elements. We pay a special attention to the band gap of p-type ZnO by band-gap engineering and room temperature ferromagnetism observed in p-type ZnO. Finally, we summarize the devices based on p-type ZnO materials. © 2013 Elsevier Ltd. All rights reserved.

« Mitsubishi Electric showcases EMIRAI 3 xDAS assisted-driving concept car at CES | Main | Virginia Tech report finds national crash rate for conventional vehicles higher than crash rate of self-driving cars » Researchers at Georgia Tech, with colleagues at Hunan University and the Institute of Metal Research, Chinese Academy of Sciences, have devised a novel, efficient electrolysis approach for hydrogen evolution directly from native biomasses—cellulose, lignin and even wood and grass powders—to hydrogen at low temperature. A paper on their work is published in the RSC journal Energy and Environmental Science. Using an aqueous polyoxometalate (POM)—phosphomolybdic acid (H [PMo O ] and silicotungstic acid (H SiW O )—as a catalyst at the anode, the raw biomass is oxidized and electrons are transferred to POM molecules by heating or light-irradiation. Polyoxometalates (POMs) are a subset of metal oxides that represent a diverse range of molecular clusters with an almost unmatched range of physical properties and the ability to form dynamic structures that can range in size from the nano- to the micrometer scale. Heavy interest in POMs began in the 1990s. In the current work, protons from biomass diffuse to the cathode and are reduced to hydrogen. The electric energy consumption can be as low as 0.69 kWh per normal cubic meter of H (Nm−3 H ) at 0.2 A cm−2—only 16.7% of the energy consumed for the reported water electrolysis. Unlike the traditional electrolysis of alcohols, a noble-metal catalyst is not required at the anode.

Zeng J.,Hengyang Normal University | Chen K.-Q.,Hunan University
Carbon | Year: 2016

By using nonequilibrium Green's functions in combination with the density functional theory, the spin transport properties of a single-molecule spintronic device are investigated. The computational results show that when the magnetic configuration of the device is set as parallel, the perfect spin-filtering effect can be observed. Especially, this perfect spin-filtering effect is independent of the number of carbon atoms in the carbon chain. However, when the magnetic configuration is set in antiparallel, the spin-filtering effect displays a strong odd-even oscillatory characteristic, namely, the spin-filtering efficiencies of odd-numbered chain systems have a higher values than even-numbered chain systems. Moreover, the magnetoresistance effect can also be observed in this single-molecule spintronic device. In contrast to the odd-even oscillatory characteristic of the spin-filtering effect in the antiparallel magnetic configuration, high magnetoresistance ratios belong to even-numbered chain systems while low magnetoresistance ratios belong to odd-numbered chain systems. The mechanisms are suggested for these interesting phenomena. © 2016 Elsevier Ltd. All rights reserved.

Wu Z.,Hunan University | Zhang P.,Hunan University | Zhang P.,Beijing Forestry University | Zeng G.,Hunan University | And 2 more authors.
Journal of Environmental Engineering (United States) | Year: 2012

Humic acid (HA) removal from water with inorganic polyaluminum coagulants is reported in this paper. Polyaluminum chloride (PAC) and three kinds of polyaluminum chloride sulfate (PACS) with a [SO42-]/[Al3+] (S) molar ratio of 0.02, 0.06, and 0.10 were prepared. The coagulation behaviors of these coagulants were investigated in the view of coagulant dosage, initial pH, and aging time. PACS (S=0.06) showed the best HA removal efficiency, and there was no restabilization within a broad effective dosage range. The proper initial pH range was broad and was 4.0-9.0 for PACS (S=0.06). The stability of PACS (S=0.06) reduced with a long aging time, so the proper aging time should not exceed 1 month. The aluminum species distribution, particle mean size, charge neutralization, and infrared spectrum of prepared coagulants were tested. Results showed that SO42-addition promoted the hydrolysis/polymerization of aluminum and reduced the charge neutralization capacity of PACS. Besides charge neutralization, the bridge-aggregation and sweep-flocculation mechanisms may play important roles for HA removal. The coexisting Ca2+ and kaolin slightly promoted the HA removal with polyaluminum coagulants. © 2012 American Society of Civil Engineers.

Wen H.,Hunan University | Teng Z.,Hunan University | Wang Y.,Hunan University | Zeng B.,Hunan University | Hu X.,Beihang University
IEEE Transactions on Power Electronics | Year: 2011

This paper focuses on the low-computation harmonic-analysis procedure with sufficient suppression of spectral leakage and picket-fence effect. The interpolated FFT algorithm based on the minimized sidelobe window is considered, and its calculate procedure and formulas are given, which is free of solving high-order equations. The implementation of the proposed algorithm in the digital-signal-processor (DSP) based three-phase harmonic ammeter is also introduced. The proposed algorithm has the major advantages that the calculate formulas for harmonic parameters can be easily implemented by hardware multipliers, making the method a good choice for real-time applications. The simulation and application results validate the accuracy and efficiency of the proposed algorithm. © 2011 IEEE.

Yuan Z.,Hunan University | Ma Z.,Guilin University of Electronic Technology | Tang X.,University of South China
Nonlinear Dynamics | Year: 2012

Under the assumption that the incidence rate of the infection and the removal rate of the infective by cytotoxic T lymphocytes are nonlinear, we study the global dynamics of a HIV infection model with the response of the immune system using characteristic equation, the Fluctuation lemma, and the direct Lyapunov method. The existence of a threshold parameter, i.e., the basic reproduction number or basic reproductive ratio is established and the global stability of the equilibria is discussed. © 2011 Springer Science+Business Media B.V.

Li S.,Hunan University | Tan M.,Nanyang Technological University | Tsang I.W.,Nanyang Technological University | Kwok J.T.-Y.,Hong Kong University of Science and Technology
IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics | Year: 2011

Particle swarm optimizer (PSO) is a powerful optimization algorithm that has been applied to a variety of problems. It can, however, suffer from premature convergence and slow convergence rate. Motivated by these two problems, a hybrid global optimization strategy combining PSOs with a modified Broyden-Fletcher-Goldfarb-Shanno (BFGS) method is presented in this paper. The modified BFGS method is integrated into the context of the PSOs to improve the particles' local search ability. In addition, in conjunction with the territory technique, a reposition technique to maintain the diversity of particles is proposed to improve the global search ability of PSOs. One advantage of the hybrid strategy is that it can effectively find multiple local solutions or global solutions to the multimodal functions in a box-constrained space. Based on these local solutions, a reconstruction technique can be adopted to further estimate better solutions. The proposed method is compared with several recently developed optimization algorithms on a set of 20 standard benchmark problems. Experimental results demonstrate that the proposed approach can obtain high-quality solutions on multimodal function optimization problems. © 2011 IEEE.

Chen H.,Hunan University | Cao L.,Hunan University | Logan D.B.,Monash University
Traffic Injury Prevention | Year: 2012

Objective: The objective of this research was to study the risk factors that significantly influence the severity of intersection crashes for vehicle occupants, as well as for pedestrians and other vulnerable road users.Methods: Logistic regression was applied as the method in this study to analyze a data set of intersection crashes involving casualties in Victoria, Australia, for the period January 2000 to December 2009.Results: Seven risk factors obtained were found to be significantly associated with the severity of intersection crashes, including driver age and gender, speed zone, traffic control type, time of day, crash type, and seat belt usage.Conclusions: This study found that male drivers as well as older drivers (age 65 and above) had higher odds of being involved in fatal intersection crashes. Intersection crashes occurring between midnight and early morning (12:00 a.m. to 5:59 a.m.), in 100 km/h speed zones, or with no traffic control had a higher odds of a fatal outcome than their counterpart categories. Furthermore, intersection crashes involving pedestrians or a non-seat belt-wearing driver were more likely to lead to a fatal outcome. In general, identification of risk factors and the discussion of the odds ratio between levels on the impact of the intersection crash severity would be beneficial for road safety stakeholders to develop initiatives to reduce the severity of intersection crashes. © 2012 Copyright Taylor and Francis Group, LLC.

Yin K.,University of South China | Liao D.,Hunan University | Tang C.-K.,University of South China
Molecular Medicine | Year: 2010

Atherosclerosis is characterized by a chronic inflammatory condition that involves numerous cellular and molecular inflammatory components. A wide array of inflammatory mediators, such as cytokines and proteins produced by macrophages and other cells, play a critical role in the development and progression of the disease. ATP-binding membrane cassette transporter A1 (ABCA1) is crucial for cellular cholesterol efflux and reverse cholesterol transport (RCT) and is also identified as an important target in antiatherosclerosis treatment. Evidence from several recent studies indicates that inflammation, along with other atherogenic- related mediators, plays distinct regulating roles in ABCA1 expression. Proatherogenic cytokines such as interferon (IFN)-γ and interleukin (IL)-1β have been shown to inhibit the expression of ABCA1, while antiatherogenic cytokines, including IL-10 and transforming growth factor (TGF)-β1, have been shown to promote the expression of ABCA1. Moreover, some cytokines such as tumor necrosis factor (TNF)-α seem to regulate ABCA1 expression in species-specific and dose-dependent manners. Inflammatory proteins such as C-reactive protein (CRP) and cyclooxygenase (COX)-2 are likely to inhibit ABCA1 expression during inflammation, and inflammation induced by lipopolysaccharide (LPS) was also found to block the expression of ABCA1. Interestingly, recent experiments revealed ABCA1 can function as an antiinflammatory receptor to suppress the expression of inflammatory factors, suggesting that ABCA1 may be the molecular basis for the interaction between inflammation and RCT. This review aims to summarize recent findings on the role of inflammatory cytokines, inflammatory proteins, inflammatory lipids, and the endotoxin-mediated inflammatory process in expression of ABCA1. Also covered is the current understanding of the function of ABCA1 in modulating the immune response and inflammation through its direct and indirect antiinflammatory mechanisms including lipid transport, high-density lipoprotein (HDL) formation and apoptosis. © 2010 The Feinstein Institute for Medical Research.

Li K.,Hunan University | Zheng W.,Hunan University | Li K.,State University of New York at New Paltz
IEEE Transactions on Signal Processing | Year: 2015

Discrete Fourier transform (DFT) is widely used in almost all fields of science and engineering. Fast Fourier transform (FFT) is an efficient tool for computing DFT. In this paper, we present a fast Fourier transform (FFT) algorithm for computing length-q× 2m DFTs. The algorithm transforms all q-points sub-DFTs into three parts. In the second part, the operations of subtransformation contain only multiplications by real constant factors. By transformation, length-2m-scaled DFTs (SDFT) are obtained. An extension of scaled radix-2/8 FFT (SR28FFT) is presented for computing these SDFTs, in which, the real constant factors of SDFTs are attached to the coefficients of sub-DFTs to simplify multiplication operations. The proposed algorithm achieves reduction of arithmetic complexity over the related algorithms. It can achieve a further reduction of arithmetic complexity for computing a length-N=q× 2m IDFT by 2N-4m real multiplications. In addition, the proposed algorithm is applied to real-data FFT, and is extended to 6m DFTs. © 2014 IEEE.

Jin J.,Hunan University | Jin J.,Southwest Petroleum University | Li Q.,Hunan University | Li Y.,Shaanxi Normal University
Information Sciences | Year: 2013

Fuzzy automata theory on lattice-ordered monoids was introduced by Li and Pedrycz. Dropping the distributive laws, fuzzy finite automata (L-FFAs for short) based on a more generalized structure L, named a po-monoid, are presented and investigated from the view of algebra in this paper. The notions of (strong) successor and source operators, fuzzy successor and source operators which are shown to be closure operators on certain conditions are introduced and discussed in detail. Using the weak primary submachines, a unique decomposition theorem of a fuzzy finite automaton based on a lattice-ordered monoid is obtained. Taking L as a quantale, fuzzy subsystems are proved to be the same as fuzzy submachines of an L-FFA. In particular, intrinsic connections between algebraic properties of L and properties of some operators of an L-FFA are discovered. It is shown that the join-preserving property of fuzzy successor and source operators can be fully characterized by the right and left distributive laws respectively, and the idempotence of successor operator can be characterized equivalently by the nonexistence of zero divisors when L is a lattice-ordered monoid. © 2013 Elsevier B.V. All rights reserved.

Xu Y.,Hunan University | Li K.,Hunan University | Hu J.,Oklahoma State University | Li K.,State University of New York at New Paltz
Information Sciences | Year: 2014

On parallel and distributed heterogeneous computing systems, a heuristic-based task scheduling algorithm typically consists of two phases: task prioritization and processor selection. In a heuristic based task scheduling algorithm, different prioritization will produce different makespan on a heterogeneous computing system. Therefore, a good scheduling algorithm should be able to efficiently assign a priority to each subtask depending on the resources needed to minimize makespan. In this paper, a task scheduling scheme on heterogeneous computing systems using a multiple priority queues genetic algorithm (MPQGA) is proposed. The basic idea of our approach is to exploit the advantages of both evolutionary-based and heuristic-based algorithms while avoiding their drawbacks. The proposedalgorithm incorporates a genetic algorithm (GA) approach to assign a priority to each subtask while using a heuristic-based earliest finish time (EFT) approach to search for a solution for the task-to-processor mapping. The MPQGA method also designs crossover, mutation, and fitness function suitable for the scenario of directed acyclic graph (DAG) scheduling. The experimental results for large-sized problems from a large set of randomly generated graphs as well as graphs of real-world problems with various characteristics show that the proposed MPQGA algorithm outperforms two non-evolutionary heuristics and a random search method in terms of schedule quality. © 2014 Elsevier Inc. All rights reserved.

Chen Z.,Hunan University | Lovett D.,Daresbury Innovation Center | Morris J.,Newcastle University
Journal of Process Control | Year: 2011

Process analytical technologies (PAT) are increasingly being explored and adopted by pharmaceutical and industrial biotechnology companies for enhanced process understanding, Quality by Design (QbD) and Real Time Release (RTR). To achieve these aspirations there is a critical need to extract the most information, and hence understanding, from complex and often 'messy' spectroscopic data. This contribution reviews a number of new approaches that have been shown to overcome the limitations of existing calibration/modelling methodologies and describes a practical system which would enhance robustness of the closed loop process control system and overall 'control strategy'. Application studies are described of the use of on-line spectroscopy for the monitoring and control of a downstream solvent recovery column, batch cooling crystallization and pharmaceutical fermentation. © 2011 Elsevier Ltd. All rights reserved.

Wang H.-Q.,Hunan University | Liu W.-Y.,University of South China | Wu Z.,Hunan University | Tang L.-J.,Hunan University | And 3 more authors.
Analytical Chemistry | Year: 2011

Genotyping of single nucleotide polymorphisms (SNPs) is a central challenge in disease diagnostics and personalized medicine. A novel label-free homogeneous SNP genotyping technique is developed on the basis of ligationmediated strand displacement amplification (SDA) with DNAzyme- based chemiluminescence detection. Discrimination of single-base mismatches is first accomplished using DNA ligase to generate a ligation product between a discriminant probe and a common probe. The ligated product then initiates two consecutive SDA reactions to produce a great abundance of aptamer sequences against hemin, which can be probed by chemiluminscence detection. The developed strategy is demonstrated using a model SNP target of cytochrome P450 monooxygenase CYP2C19*2, a molecular marker for personalized medicines. The results reveal that the developed technique displays superb selectivity in discriminating single-base mismatches, very low detection limit as low as 0.1 fM, a wide dynamic range from 1 fM to 1 nM, and a high signal-to-background ratio of 150. Due to its label-free, homogeneous, and chemiluminescence-based detection format, this technique can be greatly robust, cost-efficient, readily automated, and scalable for parallel assays of hundreds of samples. The developed genotyping strategy might provide a robust, highly sensitive, and specific genotyping platform for genetic analysis and molecular diagnostics. © 2011 American Chemical Society.

Xiao C.,Oakland University | Xiao C.,Hunan University | Rehman A.,Oakland University | Zeng X.,Oakland University
Analytical Chemistry | Year: 2012

Motivated by the use of ionic liquids (ILs) as green replacers of traditional electrolytes, a mechanistic study has been systematically conducted to comprehend various design principles responsible for electrochemical profiling of redox-active species in ILs. The full spectrum of properties associated with ILs is exploited to assess the viability of this platform, thus revealing the correlation between the redox properties and the physiochemical parameters of the species involved. This includes the evaluation of (1) the variation of redox responses toward analytes with similar molecular structures or functionalities of ILs, (2) the influence in terms of physical criteria of the system such as viscosity and conductivity as well as chemical structure of ILs, and (3) the sustainability in harsh conditions (high temperature or humidity) and interferences. The principle is exemplified via trinitrotoluene (TNT) and dinitrotoluene (DNT) with inherent redox activity as analytes and IL membranes as solvents and electrolytes using glassy carbon (GC) electrodes. A discrete response pattern is generated that is analyzed through linear discriminant analysis (LDA) leading to 100% classification accuracy even for the mixture of analytes. Quantitative analysis through square wave voltammetry (SWV) gave rise to the detection limits in liquid phase of 190 and 230 nM for TNT and DNT, respectively, with a linear range up to 100 μM. Gas-phase analysis shows strong redox signals for the estimated concentrations of 0.27 and 2.05 ppm in the gas phase for TNT and DNT, respectively, highlighting that ILs adopt a role as a preconcentrator to add on sensitivity with enhanced selectivity coming from their physiochemical diversity, thus addressing the major concerns usually referred to most sensor systems. © 2011 American Chemical Society.

Wang G.-J.,Hunan University | Xie C.,Hunan University | He L.-Y.,China Agricultural University | Chen S.,Hunan University
Physica A: Statistical Mechanics and its Applications | Year: 2014

In this paper, based on the detrended fluctuation analysis (DFA) method and the detrended cross-correlation analysis (DCCA) method, we propose an improved method of minimum-variance (MV) hedge ratio, i.e., the detrended minimum-variance (D-MV) hedge ratio, which can measure the hedge ratio at different time scales. The proposed D-MV hedge ratio is defined as the detrended covariance function between spot and futures returns divided by the detrended variance function of futures returns. Through the simulated and empirical analysis, we find that (i) the outcomes of the hedge ratio and the corresponding hedging effectiveness for the D-MV hedge ratio are diverse at different time scales, which can meet needs of various hedging participants with different hedging horizons; (ii) our proposed D-MV hedge ratio has a better hedging performance and a greater potential to determine the hedge ratio because its results of hedging effectiveness at most of time scales are better than those of the traditional MV hedge ratio; and (iii) as for the method of D-MV hedge ratio for different polynomial orders m in the fitting procedure, the D-MV-1 hedge ratio (i.e., the linear polynomial in the fitting procedure) has the best hedging capability for determining the hedge ratio. © 2014 Elsevier B.V. All rights reserved.

Wang J.,Hunan University | Katafygiotis L.S.,Hong Kong University of Science and Technology
Structural Safety | Year: 2014

In this paper the problem of reliability-based optimal design of linear structures subjected to stochastic excitations is considered. A global optimization method based on Transitional Markov chain Monte Carlo (TMCMC) is used to address the problem, where the optimization problem is converted into the task of generating sample points (designs) according to a probability density function (PDF) suitably constructed on the feasible space of designs satisfying all the constraints. TMCMC is used for generating sample points, in order to get higher convergence rate of the stationary distribution of the Markov chain states to the constructed PDF. The generation of sample points uniformly distributed in the feasible space, which is required at the initial stage of TMCMC, is achieved by using Subset Simulation. To apply Subset Simulation and TMCMC in the concerned reliability-based optimization problem, Domain Decomposition Method (DDM) is used to examine the reliability constraint, that is, whether the failure probability at a given design exceeds a specified threshold. Based on the statistical properties of the failure probability estimator given by DDM, a 'minimum' computational effort, in terms of providing a reliable judgment on the reliability constraint, is defined so that a further reduction in the computational cost can be achieved in the proposed reliability-based optimization (RBO) algorithm. Illustrative examples are presented to show the application and the advantages of the proposed global RBO algorithm. © 2014 Elsevier Ltd.

Zhao M.,Hunan University | Li S.,Hunan University | Kwok J.,Hong Kong University of Science and Technology
Image and Vision Computing | Year: 2010

Text detection is important in the retrieval of texts from digital pictures, video databases and webpages. However, it can be very challenging since the text is often embedded in a complex background. In this paper, we propose a classification-based algorithm for text detection using a sparse representation with discriminative dictionaries. First, the edges are detected by the wavelet transform and scanned into patches by a sliding window. Then, candidate text areas are obtained by applying a simple classification procedure using two learned discriminative dictionaries. Finally, the adaptive run-length smoothing algorithm and projection profile analysis are used to further refine the candidate text areas. The proposed method is evaluated on the Microsoft common test set, the ICDAR 2003 text locating set, and an image set collected from the web. Extensive experiments show that the proposed method can effectively detect texts of various sizes, fonts and colors from images and videos. © 2010 Elsevier B.V. All rights reserved.

Zheng W.,Hunan University | Li K.,Hunan University | Li K.,State University of New York at New Paltz
IEEE Transactions on Circuits and Systems II: Express Briefs | Year: 2014

In this brief, we present a fast algorithm for computing length-q × 2m discrete Fourier transforms (DFT). The algorithm divides a DFT of size- N = q × 2m decimation in frequency into one length- N/2 DFT and two length-N/4 DFTs. The length-N/2 sub-DFT is recursively decomposed decimation in frequency, and the two size-N/4 sub-DFTs are transformed into two dimension and the terms with the same rotating factor are arranged in a column. Thus, the scaled DFTs (SDFTs) are obtained, simplifying the real multiplications of the proposed algorithm. A further improvement can be achieved by the application of radix-2/8, modified split-radix FFT (MSRFFT), and Wang's algorithm for computing its length-2m and length- q sub-DFTs. Compared with the related algorithms, a substantial reduction of arithmetic complexity and more accurate precision are obtained. © 2014 IEEE.

Guan X.,Tongji University | Sun Y.,Tongji University | Qin H.,Tongji University | Li J.,Tongji University | And 3 more authors.
Water Research | Year: 2015

Over the past 20 years, zero-valent iron (ZVI) has been extensively applied for the remediation/treatment of groundwater and wastewater contaminated with various organic and inorganic pollutants. Based on the intrinsic properties of ZVI and the reactions that occur in the process of contaminants sequestration by ZVI, this review summarizes the limitations of ZVI technology and the countermeasures developed in the past two decades (1994-2014). The major limitations of ZVI include low reactivity due to its intrinsic passive layer, narrow working pH, reactivity loss with time due to the precipitation of metal hydroxides and metal carbonates, low selectivity for the target contaminant especially under oxic conditions, limited efficacy for treatment of some refractory contaminants and passivity of ZVI arising from certain contaminants. The countermeasures can be divided into seven categories: pretreatment of pristine ZVI to remove passive layer, fabrication of nano-sized ZVI to increase the surface area, synthesis of ZVI-based bimetals taking advantage of the catalytic ability of the noble metal, employing physical methods to enhance the performance of ZVI, coupling ZVI with other adsorptive materials and chemically enhanced ZVI technology, as well as methods to recover the reactivity of aged ZVI. The key to improving the rate of contaminants removal by ZVI and broadening the applicable pH range is to enhance ZVI corrosion and to enhance the mass transfer of the reactants including oxygen and H+ to the ZVI surface. The characteristics of the ideal technology are proposed and the future research needs for ZVI technology are suggested accordingly. © 2015 Elsevier Ltd.

Zheng W.,Hunan University | Li K.,Hunan University | Li K.,State University of New York at New Paltz
IEEE Transactions on Signal Processing | Year: 2014

This paper presents a scaled radix-2/8 fast Fourier transform (FFT) (SR28FFT) algorithm for computing length-N=2m discrete Fourier transforms (DFTs) scaled by complex number rotating factors. The idea of the SR28FFT algorithm is from the modified split radix FFT (MSRFFT) algorithm, and its purpose is to furnish other algorithms with high efficiency but without shortcomings of the MSRFFT algorithm. A novel radix-2/4 FFT (NR24FFT) algorithm and a novel radix-2/8 FFT (NR28FFT) algorithm are proposed. These two algorithms use SR28FFT to calculate their sub-DFTs of odd-indexed terms. Several aspects of the two algorithms such as computational complexity, computation accuracy, and coefficient evaluations or accesses to the lookup table all are improved. The bit-reverse method can be used for their order permutation and no extra memory is required to store their extra coefficients by the two novel algorithms, which contribute significantly to the performance of the FFT algorithms. The SR28FFT algorithm can also be applied to other algorithms whose decomposition contains sub-DFTs of powers-of-two. The Appendix presents an algorithm named SR28FFT-2 for further reducing the number of arithmetic operations, and NR24FFT and NR28FFT algorithms based on SR28FFT-2 requires fewer real operations than that required by the MSRFFT algorithm. © 1991-2012 IEEE.

Wu G.,National Science Foundation | Zhang Y.-J.,Hunan University
Energy Policy | Year: 2014

Whether China's crude oil imports are the culprit of oil price volatility these years has not been quantitatively confirmed. Therefore, this paper empirically investigates the role of China's crude oil net imports in Brent price changes from October 2005 to November 2013 based on an econometric analysis. The results indicate that, during the sample period, China's crude oil imports do not significantly affect Brent price changes, no matter in the long run or short run. Therefore, the blame for China's crude oil imports to cause the dramatic fluctuations of international oil price has no solid evidence. Also, there exists significant uni-directional causality running from the Brent price to China's crude oil imports at the 5% level. Besides, the response of the Brent price to China's crude oil imports is found positive but slight, and the Brent price responds more significantly to US dollar exchange rate and OECD commercial inventory than to China's crude oil imports in the short run. Finally, the contribution of China's crude oil imports to Brent price movement is about 10%, which is less than that of US dollar exchange rate but larger than that of Indian crude oil imports or OECD commercial inventory. © 2014 Elsevier Ltd.

Zhang Z.,Hunan University | Hou Z.,University of South China
Nonlinear Analysis: Real World Applications | Year: 2010

In this paper, we investigate a non-autonomous ratio-dependent predator-prey model with exploited terms. By means of using coincidence degree theory, we establish the existence of at least four positive periodic solutions for the above model. © 2009 Elsevier Ltd. All rights reserved.

Wen H.,Hunan University | Teng Z.,Hunan University | Wang Y.,Hunan University | Hu X.,Beihang University
IEEE Transactions on Industrial Electronics | Year: 2013

A novel approach to harmonic analysis for industrial power systems based on windowed fast Fourier transform is presented. First, the desirable sidelobe window (DSW) is constructed through self-convolution of the maximum decay sidelobe window (MDW) in the time domain. Then, the power system signal parameters, i.e., frequency, phase, and amplitude, are calculated by the DSW-based discrete phase difference correction algorithm. It has been shown that the spectral leakage and harmonic interferences can be reduced considerably by weighting samples with the DSW because of its good sidelobe behaviors, i.e., the peak sidelobe level and the sidelobe rolloff rate are proportional to the order of the window (or the times of self-convolution). The DSW-based discrete phase difference correction algorithm can be easily implemented in embedded systems due to the low computation burden. Both simulative and experiment data tests have been performed to verify the effectiveness and practicability of the proposed method. © 2012 IEEE.

Zuo Z.,Hunan University | Zuo Z.,University of California at Los Angeles | Liu H.,University of California at Los Angeles | Liu B.,Chinese Academy of Agricultural Sciences | And 3 more authors.
Current Biology | Year: 2011

Cryptochromes are blue light receptors that mediate light regulation of gene expression in all major evolution lineages, but the molecular mechanism underlying cryptochrome signal transduction remains not fully understood [1, 2]. It has been reported that cryptochromes suppress activity of the multifunctional E3 ubiquitin ligase CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) to regulate gene expression in response to blue light [3, 4]. But how plant cryptochromes mediate light suppression of COP1 activity remains unclear. We report here that Arabidopsis CRY2 (cryptochrome 2) undergoes blue light-dependent interaction with the COP1-interacting protein SUPPRESSOR OF PHYTOCHROME A 1 (SPA1) [5, 6]. We demonstrate that SPA1 acts genetically downstream from CRY2 to mediate blue light suppression of the COP1-dependent proteolysis of the flowering-time regulator CONSTANS (CO) [7, 8]. We further show that blue light-dependent CRY2-SPA1 interaction stimulates CRY2-COP1 interaction. These results reveal for the first time a wavelength-specific mechanism by which a cryptochrome photoreceptor mediates light regulation of protein degradation to modulate developmental timing in Arabidopsis. © 2011 Elsevier Ltd.

Yin X.,Changsha University of Science and Technology | Fang Z.,Hunan University | Cai C.S.,Louisiana State University
Journal of Bridge Engineering | Year: 2011

When studying the vibration of a bridge-vehicle coupled system, most researchers focus on the vertical vibration of bridges under moving vehicular loads. In reality, the moving vehicular loads can also induce significant lateral vibrations of high-pier bridges. This study is focused on establishing a new methodology considering the bridge's lateral vibration induced by moving vehicles. The vehicle tire is modeled as a three-dimensional elementary spring model, and the contact patch is assumed to be a rectangle. Three significant factors that affect the lateral forces, including the slip angle, camber angle, and vehicle tires moving with an S shape, are introduced in studying the effect of the lateral forces on the lateral vibration of bridges. The bridge-vehicle coupled equations are established by combining the equations of motion of both the bridge and vehicles using the displacement relationship and interaction force relationship at the contact patch. The accuracy and efficiency of the present method are verified by comparing the simulations and the field test results of a typical high-pier bridge, showing that the proposed method can rationally simulate the lateral vibration of the bridge under moving vehicular loads. © 2011 American Society of Civil Engineers.

Xiao Y.,Hunan University | Xiao Y.,University of California at Los Angeles | Yang R.Z.,Hunan University | Shan B.,Hunan University
Construction and Building Materials | Year: 2013

Bamboo is well-known because of its characteristics of being fast-growing, eco-friendly and of high strength/weight ratio. In today's trend of sustainable development, there is a renewed interest to use bamboo for modern building and bridge structures. However, traditional use of raw bamboo culms is not the only and the most effective application in construction. Studies on glue laminated forms of bamboo have emerged around the world. The authors developed a laminated bamboo or glubam for general structural applications. This paper introduces the manufacturing process of glubam, investigates and analyzes its energy consumption and carbon dioxide emission, and provides main mechanical properties through material testing. Analysis results and comparison with other comparable construction materials show the eco-friendly performance of glubam. The mechanical properties of glubam are found using methods developed for timber material. The results show that glue laminated bamboo or glubam is promising for general use in construction. © 2013 Elsevier Ltd. All rights reserved.

Guo J.,Hunan University | Yang C.,Zhejiang GongShang University | Yang C.,Hunan University | Zeng G.,Hunan University
Bioresource Technology | Year: 2013

Sterilization, alkaline-thermal and acid-thermal treatments were applied to activated sludge and the pre-treated sludge was used as raw material for Rhodococcus R3 to produce polymeric substances. After 60h of fermentation, bioflocculant of 2.7 and 4.2gL-1 were produced in sterilized and alkaline-thermal treated sludge as compared to that of 0.9gL-1 in acid-thermal treated sludge. Response surface methodology (RSM) was employed to optimize the treatment process of swine wastewater using the composite of bioflocculant and zeolite modified by calcining with MgO. The optimal flocculating conditions were bioflocculant of 24mgL-1, modified zeolite of 12gL-1, CaCl2 of 16mgL-1, pH of 8.3 and contact time of 55min, and the corresponding removal rates of COD, ammonium and turbidity were 87.9%, 86.9%, and 94.8%. The use of the composite by RSM provides a feasible way to improve the pollutant removal efficiencies and recycle high-level of ammonium from wastewater. © 2013 Elsevier Ltd.

Niu H.,Hunan University | Niu H.,University of Science and Arts of Iran | Huang D.,Hunan University | Niu C.,Hunan University
Sensors and Actuators, B: Chemical | Year: 2014

A time-gated fluorescence sensor for water content determination in organic solvents was proposed in this paper. A europium ternary complex (ETC) was synthesized and used as the fluorescence indicator in the fabrication of the fluorescence water sensor. To prevent leakage of the fluorophore, ETC was photo-copolymerized with acrylamide, (2-hydroxyethyl)methacrylate, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and triethylene glycol dimethacrylate on a glass surface treated with a silanizing agent. The ETC has long life-time fluorescence, and time-gated fluorescence intensity was used in this paper instead of fluorescence intensity. The time-gated fluorescence intensity of ETC decreased with increasing of water content in organic solvents. In the range of 0.0-8.0% (v/v), the time-gated fluorescence intensity of ETC changed as a linear function of water content. The detection limits were 0.056%, 0.042%, and 0.033% for ethanol, tetrahydrofuran, and 1,4-dioxane, respectively. The sensor exhibited satisfactory reproducibility, reversibility, and a short response time. The sensing membrane was found to have a lifetime of at least one mouth. © 2013 Elsevier B.V. All rights reserved.

Zhang H.,Hunan University | Jia X.,Wuhan University of Technology | Yu J.,Wuhan University of Technology | Xue L.,Wuhan University of Technology
Construction and Building Materials | Year: 2013

Organic expanded vermiculites (OEVMTs) were prepared using cetyltrimethyl ammonium bromide (CTAB) and octadecyl dimethyl benzyl ammonium chloride (ODBA) as intercalation agents. Effect of EVMT organic modification on physical and aging properties of styrene-butadiene-styrene (SBS) modified bitumen was investigated. The microstructures of the binders were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. EVMT/SBS modified bitumen forms a phase-separated structure, while OEVMT/SBS modified bitumens form the exfoliated nanostructures according to XRD analysis. OEVMTs show the more obvious influence on physical properties of SBS modified bitumen in comparison with EVMT. The compatibility between the EVMT and SBS modified bitumen is also improved after organic modification of EVMT. AFM analysis indicates that the contrast between the dispersed phase and the matrix phase in SBS modified bitumen increases with the addition of ODBA-EVMT. As a result of thin film oven test (TFOT), the viscosity aging index of SBS modified bitumen decreases, while the retained ductility and penetration increase obviously with the introduction of EVMT and OEVMTs. ODBA-EVMT/SBS modified bitumen has more pronounced improvements in aging resistance of SBS modified bitumen in comparison with CTAB-EVMT/SBS modified bitumen by preventing the phase-separated trend of the SBS modified bitumen during TFOT. © 2012 Elsevier Ltd. All rights reserved.

Liu B.,Chinese Academy of Agricultural Sciences | Liu B.,University of California at Los Angeles | Zuo Z.,University of California at Los Angeles | Zuo Z.,Hunan University | And 4 more authors.
Genes and Development | Year: 2011

Plant photoreceptors mediate light suppression of the E3 ubiquitin ligase COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1) to affect gene expression and photomorphogenesis. However, how photoreceptors mediate light regulation of COP1 activity remains unknown. We report here that Arabidopsis blue-light receptor cryptochrome 1 (CRY1) undergoes blue-light-dependent interaction with the COP1-interacting protein SPA1 (SUPPRESSOR OF PHYTOCHROME A). We further show that the CRY1- SPA1 interaction suppresses the SPA1-COP1 interaction and COP1-dependent degradation of the transcription factor HY5. These results are consistent with a hypothesis that photoexcited CRY1 interacts with SPA1 to modulate COP1 activity and plant development. © 2011 by Cold Spring Harbor Laboratory Press.

Wang X.,Hunan University | Zhang Q.,Hunan University | Wan Q.,Hunan University | Dai G.,Micro nano Technology Center | And 3 more authors.
Journal of Physical Chemistry C | Year: 2011

Controllable ZnO architectures with different morphologies were synthesized via an ethanolamine-assisted one-pot hydrothermal method. By adjusting reaction conditions such as the molar ratio between Zn(OAc)2 and NaOH and the volume ratio of the ethanolamine/water, the flowerlike, spindlelike, swordlike, and umbellarlike ZnO architectures of the hexagonal phase have been obtained. The as-prepared ZnO products were characterized by FE-SEM, TEM, XRD, BET, PL, and Raman spectroscopy. The ethanolamine significantly influenced the morphology of ZnO products, which is related to the competitive adsorption between ethanolamine and [Zn(OH)4]2- to ZnO nuclei. Their PL spectra depend on their morphologies and phase structures. The morphology-dependent photocatalytic performances in the degradation of methylene blue under UV illumination were observed, in which the flowerlike ZnO structures exhibit highest activity for their most irregular surface Zn sites. © 2011 American Chemical Society.

Xiao Y.,Hunan University | Xiao Y.,University of Southern California | Ma J.,Zhejiang Prov Institute Of Architectural Design And Research
Construction and Building Materials | Year: 2012

A fire simulation experiment of a full-scale room unit model was carried out to study the fire safety of lightweight glue-laminated bamboo (glubam) frame buildings. Wooden crib with its quantity determined based on typical fire load intensity for residential buildings was stacked and ignited in the experimental room unit. The test was finished after 1 h. Temperature histories of several points on walls and upper floor slab, fire behavior of the over-all structure and the damage to the members were examined. Numerical simulation was conducted using fire-driven fluid dynamics software Fire Dynamics Simulator (FDS) developed by National Institute of Standards and Technology (NIST). The simulated results were compared with the experimental observations, demonstrating that the FDS is a useful tool to provide visual simulation of the experimental testing. Fire design measures using gypsum boards and rock wool insulation suggested for the new bamboo building are found adequate from this research. © 2012 Elsevier Ltd. All rights reserved.

Li C.C.,Hunan University | Zheng Y.P.,Xiamen University | Wang T.H.,Hunan University
Journal of Materials Chemistry | Year: 2012

In this work, we reported several kinds of highly stable, effective mesoporous Au/TiO 2 sphere-based solid acid catalysts with large specific surface areas and good monodispersity in the reaction medium. In this process, monodisperse titanium glycolate spheres were first formed by an antisolvent precipitation route, and were then converted to mesoporous TiO 2 by in situ hydrolysis under hydrothermal conditions. The resultant uniform TiO 2 spheres were subsequently functionalized with sulfate anions at different temperatures or incorporated with tungstophosphoric acid (TPA); the solid acid catalysts were thus fabricated. In particular, our monodisperse spherical catalysts with large specific surface area have shown remarkable performance in a wide range of acid-catalyzed reactions such as Friedel-Crafts alkylation, esterification and hydrolysis of acetate. The TiO 2-based catalysts could be separated and reused showing no deactivation. © 2012 The Royal Society of Chemistry.

Zeng Q.,Hunan University | Cheng J.,Tsinghua University | Tang L.,Tsinghua University | Liu X.,Hunan University | And 3 more authors.
Advanced Functional Materials | Year: 2010

The self-assembly of sodium dodecyl benzene sulphonate (SDBS) functionalized graphene sheets (GSs) and horseradish peroxidase (HRP) by electrostatic attraction into novel hierarchical nanostructures in aqueous solution is reported. Data from scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction demonstrate that the HRP-GSs bionanocomposites feature ordered hierarchical nanostructures with well-dispersed HRP intercalated between the GSs. UV-vis and infrared spectra indicate the native structure of HRP is maintained after the assembly, implying good biocompatibility of SDBS-functionalized GSs. Furthermore, the HRP-GSs composites are utilized for the fabrication of enzyme electrodes (HRP-GSs electrodes). Electrochemical measurements reveal that the resulting HRP-GSs electrodes display high electrocatalytic activity to H2 O2 with high sensitivity, wide linear range, low detection limit, and fast amperometric response. These desirable electrochemical performances are attributed to excellent biocompatibility and superb electron transport effi ciency of GSs as well as high HRP loading and synergistic catalytic effect of the HRP-GSsbionanocomposites toward H2O2 . As graphene can be readily non-covalently functionalized by "designer" aromatic molecules with different electrostatic properties, the proposed self-assembly strategy affords a facile and effective platform for the assembly of various biomolecules into hierarchically ordered bionanocomposites in biosensing and biocatalytic applications. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zheng K.,Hunan University | Lin W.,Hunan University | Lin W.,University of Jinan | Tan L.,Hunan University | And 2 more authors.
Chemical Science | Year: 2014

Two-photon fluorescent probes are favorable as powerful molecular tools for studies in biology and medicine. To construct two-photon fluorescent probes, it is necessary to have suitable two-photon fluorescent platforms. Herein, we present the rational design, synthesis, and spectral properties of carbazole-coumarin (CC) derivatives, a unique family of two-photon fluorescent dyes. Significantly, the action cross-sections of CC are tunable by modifications at the 4′-position of the coumarin moiety, implying that CC could be exploited as a novel platform to design two-photon fluorescent probes. Carbon monoxide (CO) plays an important role in many physiological and pathological processes. Although the tracking of CO in living cells has been previously reported, the detection of CO in much thicker biosamples, for instance, living tissues, has not been realized. It is known that two-photon fluorescent probes are favorable for monitoring biomolecules in living tissues. Thus, based on the unique CC platform, we rationally engineered CC-CO as the first two-photon fluorescent CO probe, and we further demonstrated that CC-CO could monitor the changes of CO levels not only in living cells but also in living tissues for the first time, demonstrating the value of our two-photon fluorescent CO probe. The CC platform is complementary to the current two-photon fluorescent platforms and it may be used to develop a wide variety of two-photon fluorescent probes. In addition, we expect that CC-CO and its next generation analogues may be useful for unraveling the functions of CO in complicated living systems. © 2014 the Partner Organisations.

Zhou Y.,Japan National Institute of Advanced Industrial Science and Technology | Yin S.,Hunan University | Gao Y.,Xiamen University | Zhao Y.,Xiamen University | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2010

(Chemical Equation Presented) Different copper complexes selectively catalyze the aerobic oxidative coupling of H-phosphonates to afford either hypophosphates and pyrophosphates in high yields with high selectivity (see scheme; tmeda = N, N, N', N'-tetramethylethylenediamine). © 2010 Wiley-VCH Verlag GmbH &. Co. KGaA, Weinheim.

Wu J.-C.,Hunan University | Wu J.-C.,Hunan Normal University | Song R.-J.,Hunan University | Wang Z.-Q.,Hunan University | And 5 more authors.
Angewandte Chemie - International Edition | Year: 2012

Keeping options open: The new and mild title reaction involving indoles selectively furnishes 1 and 2 with the aid of tert-butyl hydroperoxide (TBHP). The method represents the first example of a copper-catalyzed α arylation of α-amino carbonyl substrates leading to α-aryl α-imino and α-aryl α-oxo carbonyl compounds using a C-H oxidation strategy. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wu X.,Guilin University of Electronic Technology | Wang Y.,Hunan University | Dang X.,Guilin University of Electronic Technology
Fuzzy Sets and Systems | Year: 2014

This paper presents a robust adaptive sliding-mode control (RASMC) scheme for a class of condenser-cleaning mobile manipulator (CCMM) in the presence of parametric uncertainties and external disturbances. The development of control system is based on the fuzzy wavelet neural network (FWNN). First, a dynamic model is obtained in view of the practical CCMM system. Second, the FWNN is used to identify the unstructured system dynamics directly due to its ability to approximate a nonlinear continuous function to arbitrary accuracy. Using learning ability of neural networks, RASMC can coordinately control the condenser-cleaning mobile platform and the mounted manipulator with different dynamics efficiently. The implementation of the control algorithm is dependent on the adaptive sliding-mode control. Finally, based on the Lyapunov stability theory, the stability of the whole control system, the boundedness of the neural networks weight estimation errors, and the uniformly ultimately boundedness of the tracking error are all strictly guaranteed. Moreover, simulation results validate the superior control performance of the proposed adaptive control method. © 2013 Elsevier B.V.

Zhou H.,Hunan University | Xie S.-J.,Hunan University | Zhang S.-B.,University of Science and Arts of Iran | Shen G.-L.,Hunan University | And 2 more authors.
Chemical Communications | Year: 2013

A novel template-dependent extension based isothermal amplification (TEIA) system with high single-base discrimination capability is developed, where the interference caused by non-specific reaction in isothermal strand displacement amplification (SDA) technique is substantially avoided via using a functionalized template probe, showing potential value in the development and application of SDA based detection devices. © 2013 The Royal Society of Chemistry.

Huang J.,Hunan University | Wu Y.,University of Florida | Chen Y.,Hunan University | Zhu Z.,University of Florida | And 4 more authors.
Angewandte Chemie - International Edition | Year: 2011

Make it a double: Complementary probes with two pyrene labels were engineered for the amplification of a target DNA sequence. In the stem-closed conformation of the probes in the absence of the target, the two pyrene moieties were separated. The target propagated hybridization chain reactions to bring pyrene moieties on neighboring probes close together to form fluorescent pyrene excimers (see picture). © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Duan M.-Y.,Hunan University | Liang R.,Hunan University | Tian N.,Xiamen University | Li Y.-J.,Hunan University | Yeung E.S.,Hunan University
Electrochimica Acta | Year: 2013

Au-Pt core-shell nanoparticles (Au-Pt NPs) as an effective bimetallic electrocatalyst for methanol oxidation has been extensively explored. However, the conventional drop-coating method for fabricating Au-Pt NP electrodes did not fully exploit the small size of the NPs. Here, self-assembly of Au-Pt NPs into monolayer arrays is proposed as an alternative for the preparation of Au-Pt NP catalytic electrode to ensure the exposure of each NP to electrolyte. Under the optimized condition, the Pt mass activity of the Au-Pt monolayer array was ∼6 times better than that of the commercial Pt/C catalyst, and 3 times better than that of Au-Pt NP electrodes fabricated by a drop-coating method, indicating superior electrocatalytic activity. © 2012 Elsevier Ltd.

Xu J.,Hunan University | Ma L.,Hunan University | Guo P.,Hunan University | Zhuang X.,Hunan University | And 4 more authors.
Journal of the American Chemical Society | Year: 2012

Nanoscale dual-wavelength lasers are attractive for their potential applications in highly integrated photonic devices. Here we report the growth of nanoribbon lateral heterostructures made of a CdSxSe1-x central region with epitaxial CdS lateral sides using a multistep thermal evaporation route with a moving source. Under laser excitation, the emission of these ribbons indicates sandwich-like structures along the width direction, with characteristic red emission in the center and green emission at both edges. More importantly, dual-wavelength lasing with tunable wavelengths is demonstrated at room temperature based on these single-nanoribbon heterostructures for the first time. These achievements represent a significant advance in designing nanoscale dual-wavelength lasers and have the potential to open up new and exciting opportunities for diverse applications in integrated photonics, optoelectronics, and sensing. © 2012 American Chemical Society.

Duong T.,Hunan University | Duong T.,Industry University of Hochiminh City | Jiangang Y.,Hunan University | Truong V.,University of Technical Education Hochiminh City
International Journal of Electrical Power and Energy Systems | Year: 2013

In the deregulated power industry, private power producers are increasing rapidly to meet the increase demand. The purpose of the transmission network is to pool power plants and load centers in order to supply the load at a required reliability, maximum efficiency and at lower cost. As power transfer increases, the power system becomes increasingly more difficult to operate and insecure with unscheduled power flows and higher losses. FACTS devices such as Thyristor Controlled Series Compensator (TCSC) can be very effective to power system security. Proper location of TCSC plays key role in optimal power flow solution and enhancement of system performance without violating the security of the system. This paper applied min cut algorithm to select proper location of TCSC for secured optimal power flow under normal and contingencies operating condition. Proposed method requires a two-step approach. First, the optimal location of the TCSC in the network must be ascertained by min cut algorithm and then, the optimal power flow (OPF) with TCSC under normal and contingencies operating condition is solved. The proposed method was tested and validated for locating TCSC in Six bus, IEEE 14-, IEEE-30 and IEEE-118 bus test systems. Results show that the proposed method is good to select proper location of TCSC for secured OPF.

Ou G.-C.,Sun Yat Sen University | Ou G.-C.,Hunan University | Feng X.-L.,Sun Yat Sen University | Lu T.-B.,Sun Yat Sen University
Crystal Growth and Design | Year: 2011

The reaction of a racemic four-coordinated nickel(II) complex [Ni(α-rac-L)](ClO 4) 2 with l-Leu - in acetonitrile/water under basic conditions gave two six-coordinated diastereomers of {[Ni(SS-L)(l-Leu)](ClO 4)} n (Δ-1) and {[Ni(RR-L)(l-Leu)](ClO 4)} n (a-2). While the reaction of [Ni(α-rac-L)](ClO 4) 2 with d-Leu - in acetonitrile/water under basic condition generated two six-coordinated diastereomers of {[Ni(RR-L)(d-Leu)](ClO 4)} n (Λ-1) and {[Ni(SS-L)(d-Leu)](ClO 4)} n (b-2) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, Leu - = leucine anion). Δ-1 and Λ-1 belong to supramolecular stereoisomers in which the [Ni(SS-L)(l-Leu)] + and [Ni(RR-L)(d-Leu)] + monomers are linked through the intermolecular hydrogen bonding interactions to form 1D homochiral right- and left-handed helical chains, respectively, while the connections of [{Ni(RR-L)}(l-Leu)] +/[{Ni(SS-L)}(d-Leu)] + in a-2/b-2 through similar intermolecular hydrogen bonding interactions give 1D zigzag chains instead of 1D helical chains. In contrast, the reactions of [Ni(α-rac-L)](ClO 4) 2 with l/d-leucine in acetonitrile/water under acidic condition gave the left-handed helical chains of {[Ni(SS-L)(l-HLeu)](ClO 4) 2} n (Λ-3) and right-handed helical chains of {[Ni(RR-L)(d-HLeu)](ClO 4) 2} n (Δ-3), respectively, demonstrating the helicity of 1D helical chains is pH dependent The homochiral nature of Δ-1/Λ-1 and a-2/b-2 are confirmed by the results of CD spectra measurements. © 2011 American Chemical Society.

Wei W.-T.,Hunan University | Zhou M.-B.,Hunan University | Fan J.-H.,Hunan University | Liu W.,Hunan University | And 7 more authors.
Angewandte Chemie - International Edition | Year: 2013

Difunctionalization: Inexpensive and environmentally benign FeCl 3 catalyzes the oxidative 1,2-alkylarylation of activated alkenes with an aryl C(sp2)-H bond and a C(sp3)-H bond adjacent to a heteroatom. This reaction is a new strategy for the synthesis of oxindoles and makes use of DBU as ligand and TBHP as oxidant (see scheme, TBHP=tert-butyl hydrogenperoxide). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Deng G.-B.,Hunan University | Wang Z.-Q.,Hunan University | Xia J.-D.,Hunan University | Qian P.-C.,Hunan University | And 4 more authors.
Angewandte Chemie - International Edition | Year: 2013

Ray of light: 10a,11-Dihydro-10H-benzo[b]fluorenes were synthesized by a visible-light-catalyzed tandem cyclization of 1,6-enynes with arylsulfonyl chlorides. This method extends the scope of enyne cyclizations and represents a new synthetic application of arylsulfonyl chlorides. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chen T.,University of Florida | Wu C.S.,University of Florida | Jimenez E.,University of Florida | Zhu Z.,Xiamen University | And 6 more authors.
Angewandte Chemie - International Edition | Year: 2013

Lighting the way with DNA: Molecular beacon micelle flares (MBMFs), based on self-assembly of diacyllipid-molecular-beacon conjugates (L-MBs; see figure), have been developed for combined mRNA detection and gene therapy. These MBMFs were shown to inhibit a model gene in vitro and decrease the viability of cancer cells in culture. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

He L.,Hunan University | Lin W.,Hunan University | Lin W.,University of Jinan | Xu Q.,Hunan University | Wei H.,Hunan University
Chemical Communications | Year: 2015

We introduce a new FRET strategy to construct a ratiometric fluorescent H2S sensor. The ratio emission signal of the coumarin-naphthalimide dyad is modulated by the FRET process, which works in coordination with the ICT mechanism. The FRET process on/off is controlled through tuning the overlap level of the donor emission spectrum with the acceptor absorption via modulation of the acceptor fluorophore absorption wavelength. CN-N3 was applied to visualize both the intracellular exogenous and endogenous H2S through blue and green emission channels. This journal is © The Royal Society of Chemistry.

Guo J.,Chengdu University of Information Technology | Yang C.,Zhejiang GongShang University | Yang C.,Hunan University | Peng L.,Hunan University
Bioresource Technology | Year: 2014

Sterilization, alkaline-thermal, and acid-thermal treatments were applied to different suspended sludge solids (SSS) concentrations and the pre-treated sludge was used as raw material for bioflocculant-producing bacteria R3 to produce bioflocculant. After 60h of fermentation, three forms of bioflocculant (broth, capsular, and slime) were extracted, and maximum broth bioflocculant of 2.9 and 4.1gL-1 were produced in sterilized and alkaline-thermal treated sludge as compared to that of 1.8gL-1 in acid-thermal treated sludge. Higher bioflocculant quantity was produced in SS of 15, 25, and 35gL-1 compared to that produced in SS of 45, 55, and 65gL-1. Bioflocculant combined with 0.5g Ca2+ in 1.0L kaolin suspension acted as conditioning agent, and maximum flocculating activity of 94.5% and 92.8% was achieved using broth and slime bioflocculant, respectively. The results demonstrated that wastewater sludge could be used as sources to prepare bioflocculants. © 2013 Elsevier Ltd.

Liu Q.H.,Hunan University | Xiao S.F.,Zhanjiang Normal University
International Journal of Geometric Methods in Modern Physics | Year: 2015

With acceptance of the Dirac's observation that the canonical quantization entails using Cartesian coordinates, we examine the operator erPr rather than Pr itself and demonstrate that there is a decomposition of erPr into a difference of two self-adjoint but noncommutative operators, in which one is the total momentum and another is the transverse one. This study renders the operator Pr indirectly measurable and physically meaningful, offering an explanation of why the mean value of Pr over a quantum mechanical state makes sense and supporting Dirac's claim that Pr "is real and is the true momentum conjugate to r". © 2015 World Scientific Publishing Company.

He X.,Stanford University | He X.,Hunan University | Gao J.,Stanford University | Gao J.,Xiamen University | And 2 more authors.
Trends in Molecular Medicine | Year: 2010

Near-infrared fluorescence (NIRF) imaging promises to improve cancer imaging and management; advances in nanomaterials allow scientists to combine new nanoparticles with NIRF imaging techniques, thereby fulfilling this promise. Here, we present a synopsis of current developments in NIRF nanoprobes, their use in imaging small living subjects, their pharmacokinetics and toxicity, and finally their integration into multimodal imaging strategies. We also discuss challenges impeding the clinical translation of NIRF nanoprobes for molecular imaging of cancer. Whereas utilization of most NIRF nanoprobes remains at a proof-of-principle stage, optimizing the impact of nanomedicine in cancer patient diagnosis and management will probably be realized through persistent interdisciplinary amalgamation of diverse research fields. © 2010 Elsevier Ltd.

Hu D.,Hunan University | Li Q.,Hunan Normal University
IEEE Communications Letters | Year: 2010

In asymmetric fingerprinting, the merchant can trace the traitors from a pirated copy by means of the embedded unique fingerprint, while the customer is immune of being framed due to the asymmetric property. In this letter, we propose an asymmetric fingerprinting scheme based on 1-out-of-n oblivious transfer (OT1n), which is efficient from the bandwidth usage point of view. First, multicast that is an efficient transport technology for one-to-many communication is exploited, which can reduce the bandwidth usage significantly. Second, symmetric encryption instead of public-key encryption is performed on the multimedia content, which also can reduce the complexity and communication cost. © 2010 IEEE.

Chang H.,Tsinghua University | Tang L.,Tsinghua University | Wang Y.,Tsinghua University | Jiang J.,Hunan University | Li J.,Tsinghua University
Analytical Chemistry | Year: 2010

Combining nanomaterials and biomolecule recognition units is promising in developing novel clinic diagnostic and protein analysis techniques. In this work, a highly sensitive and specific fluorescence resonance energy transfer (FRET) aptasensor for thrombin detection is developed based on the dye labeled aptamer assembled graphene. Due to the noncovalent assembly between aptamer and graphene, fluorescence quenching of the dye takes place because of FRET. The addition of thrombin leads to the fluorescence recovery due to the formation of quadruplex-thrombin complexes which have weak affinity to graphene and keep the dyes away from graphene surface. Because of the high fluorescence quenching efficiency, unique structure, and electronic properties of graphene, the graphene aptasensor exhibits extraordinarily high sensitivity and excellent specificity in both buffer and blood serum. A detection limit as low as 31.3 pM is obtained based on the graphene FRET aptasensor, which is two orders magnitude lower than those of fluorescent sensors based on carbon nanotubes. The excellent performance of FRET aptasensor based on graphene will also be ascribed to the unique structure and electronic properties of graphene. © 2010 American Chemical Society.

Zeng Q.,Hunan University | Cheng J.-S.,Tsinghua University | Liu X.-F.,Hunan University | Bai H.-T.,Hunan University | Jiang J.-H.,Hunan University
Biosensors and Bioelectronics | Year: 2011

Graphene (GR) was covalently functionalized with chitosan (CS) to improve its biocompatibility and hydrophilicity for the preparation of biosensors. The CS-grafted GR (CS-GR) rendered water-soluble nanocomposites that were readily decorated with palladium nanoparticles (PdNPs) using in situ reduction. Results with TEM, SEM, FTIR, Raman and XRD revealed that CS was successfully grafted without destroying the structure of GR, and PdNPs were densely decorated on CS-GR sheets with no aggregation occurring. A novel glucose biosensor was then developed through covalently immobilizing glucose oxidase (GOD) on a glassy carbon electrode modified with the PdNPs/CS-GR nanocomposite film. Due to synergistic effect of PdNPs and GR, the PdNPs/CS-GR nanocomposite film exhibited excellent electrocatalytical activity toward H2O2 and facilitated high loading of enzymes. The biosensor demonstrated high sensitivity of 31.2μAmM-1cm-2 for glucose with a wide linear range from 1.0μM to 1.0mM as well as a low detection limit of 0.2μM (S/N=3). The low Michaelis-Menten constant (1.2mM) suggested enhanced enzyme affinity to glucose. These results indicated that PdNPs/CS-GR nanocomposites held great potential for construction of a variety of electrochemical biosensors. © 2011 Elsevier B.V.

Chen S.,Hunan University | Chen S.,Tohoku University | Yoshino H.,Tohoku University | Li N.,Hunan University
Energy and Buildings | Year: 2010

The purposes of this paper are to analyse energy consumption characteristics and to find out influence factors of residential energy consumption in summer in typical cities of China. The investigated residences were located in seven cities of five architecture thermotechnical design zones. Questionnaire surveys revealed housing unit characteristics, household characteristics, the possession and utilization of domestic energy consuming appliances and indoor thermal environment in summer. Energy consumption analyses show that summer energy consumption amounts in different cities bear distinct regional characteristics: the household amounts of electricity use are largest in Hongkong, and the values are smaller but still at a high level in Beijing, Shanghai and Changsha, and at the smallest level in Kunming, Harbin and Urumqi, while the difference in gas use is small among these cities. Influence factor analyses show that city locations, housing unit characteristics, the utilization of space coolers and water heaters, household characteristics, and subjective evaluation of indoor thermal environment all contribute to the residential energy consumption in summer when taking all the families in the seven cities as the sample collectivity, while detail analyses for separate cities shows each city has its own characteristics. In Shanghai, the satisfaction rate of thermal environment, the possession and operation of air conditioners and housing unit characteristics greatly affect the summer energy consumption, but the electrical fan is judged as the non-influence factor, while in Urumqi, the possession and operation of electrical fans and the categories of water heaters have remarkable effect, and the influence of housing unit characteristics is also distinct, but the number of air conditioners and their usage contribute little to energy use due to the cool climate. © 2009 Elsevier B.V. All rights reserved.

Zhang Y.,Huaqiao University | Sun G.,Hunan University | Li G.,Hunan University | Luo Z.,University of Technology, Sydney | Li Q.,University of Sydney
Materials and Design | Year: 2012

Thin-walled structures have been widely used as key components in automobile and aerospace industry to improve the crashworthiness and safety of vehicles while maintaining overall light-weight. This paper aims to explore the design issue of thin-walled bitubal column structures filled with aluminum foam. As a relatively new filler material, aluminum foam can increase crashworthiness without sacrificing too much weight. To optimize crashworthiness of the foam-filled bitubal square column, the Kriging meta-modeling technique is adopted herein to formulate the objective and constraint functions. The genetic algorithm (GA) and Non-dominated Sorting Genetic Algorithm II (NSGA II) are used to seek the optimal solutions to the single and multiobjective optimization problems, respectively. To compare with other thin-walled configurations, the design optimization is also conducted for empty bitubal column and foam-filled monotubal column. The results demonstrate that the foam-filled bitubal configuration has more room to enhance the crashworthiness and can be an efficient energy absorber. © 2012 Elsevier Ltd.

Peng X.-F.,Hunan University | Chen K.-Q.,Hunan University | Wan Q.,Hunan University | Zou B.S.,Hunan University | Duan W.,Tsinghua University
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

The thermal conductance associated with the lowest six types of ballistic phonon modes in quantum wire with catenoidal contacts is investigated. The results show that the cutoff frequency for the four types of acoustic modes is zero while two types of optical modes are of nonzero cutoff frequency. For a perfect quantum wire, a quantized thermal-conductance plateau can be observed. While for the structure with catenoidal contacts, the thermal-conductance plateau is broken and a decrease in thermal conductance appears. The results also show that the reduced thermal conductance contributed from different vibrational modes has different characteristics. © 2010 The American Physical Society.

Xu S.,Tsinghua University | Xu S.,Hunan University | Liu Y.,Tsinghua University | Wang T.,Hunan University | Li J.,Tsinghua University
Analytical Chemistry | Year: 2011

In this work, we report a cathodic electrogenerated chemiluminescence (ECL) of luminol at a positive potential (ca. 0.05 V vs Ag/AgCl) with a strong light emission on the graphene-modified glass carbon electrode. The resulted graphene-modified electrode offers an excellent platform for high-performance biosensing applications. On the basis of the cathodic ECL signal of luminol on the graphene-modified electrode, an ECL sandwich immunosensor for sensitive detection of cancer biomarkers at low potential was developed with a multiple signal amplification strategy from functionalized graphene and gold nanorods multilabeled with glucose oxidase (GOx) and secondary antibody (Ab2). The functionalized graphene improved the electron transfer on the electrode interface and was employed to attach the primary antibody (Ab1) due to it large surface area. The gold nanorods were not only used as carriers of secondary antibody (Ab2) and GOx but also catalyzed the ECL reaction of luminol, which further amplified the ECL signal of luminol in the presence of glucose and oxygen. The as-proposed low-potential ECL immunosensor exhibited high sensitivity and specificity on the detection of prostate protein antigen (PSA), a biomarker of prostate cancer that was used as a model. A linear relationship between ECL signals and the concentrations of PSA was obtained in the range from 10 pg mL-1 to 8 ng mL-1. The detection limit of PSA was 8 pg mL-1 (signal-to-noise ratio of 3). Moreover, the as-proposed low-potential ECL immunosensor exhibited excellent stability and reproducibility. The graphene-based ECL immunosensor accurately detected PSA concentration in 10 human serum samples from patients demonstrated by excellent correlations with standard chemiluminescence immunoassay. The results suggest that the as-proposed graphene ECL immunosensor will be promising in the point-of-care diagnostics application of clinical screening of cancer biomarkers. © 2011 American Chemical Society.

Dregely D.,University of Stuttgart | Neubrech F.,University of Stuttgart | Neubrech F.,Kirchhoff Institute for Physics | Duan H.,Hunan University | And 2 more authors.
Nature Communications | Year: 2013

Nanoantennas confine electromagnetic fields at visible and infrared wavelengths to volumes of only a few cubic nanometres. Assessing their near-field distribution offers fundamental insight into light-matter coupling and is of special interest for applications such as radiation engineering, attomolar sensing and nonlinear optics. Most experimental approaches to measure near-fields employ either diffraction-limited far-field methods or intricate near-field scanning techniques. Here, using diffraction-unlimited far-field spectroscopy in the infrared, we directly map the intensity of the electric field close to plasmonic nanoantennas. We place a patch of probe molecules with 10 nm accuracy at different locations in the near-field of a resonant antenna and extract the molecular vibrational excitation. We map the field intensity along a dipole antenna and gap-type antennas. Moreover, this method is able to assess the near-field intensity of complex buried plasmonic structures. We demonstrate this by measuring for the first time the near-field intensity of a three-dimensional plasmonic electromagnetically induced transparency structure. © 2013 Macmillan Publishers Limited. All rights reserved.

Zou S.,Hunan University | Wu J.,York University | Chen Y.,Wilfrid Laurier University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

We consider a delayed susceptible-infected-recovered epidemic model on an uncorrelated complex network and address the effect of time lag on the shape and multiple waves of epidemic curves. We show that when the transmission rate is above a threshold, a large delay can cause multiple waves with larger amplitudes in the second and subsequent waves. © 2011 American Physical Society.

Xu S.,Tsinghua University | Xu S.,Hunan University | Liu Y.,Tsinghua University | Wang T.,Hunan University | Li J.,Tsinghua University
Analytical Chemistry | Year: 2010

A novel electrogenerated chemiluminescence (ECL) biosensor using gold nanoparticles as signal transduction probes was described for the detection of kinase activity. The gold nanoparticles were specifically conjugated to the thiophosphate group after the phosphorylation process in the presence of adenosine 59-[c-thio] triphosphate (ATP-s) cosubstrate. Due to its good conductivity, large surface area, and excellent electroactivity to luminol oxidization, the gold nanoparticles extremely amplified the ECL signal of luminol, offering a highly sensitive ECL biosensor for kinase activity detection. Protein kinase A (PKA), an important enzyme in regulation of glycogen, sugar, and lipid metabolism in the human body, was used as a model to confirm the proof-of-concept strategy. The as-proposed biosensor presented high sensitivity, low detection limit of 0.07 U mL-1, wide linear range (from 0.07 to 32 U mL-1), and excellent stability. Moreover, this biosensor can also be used for quantitative analysis of kinase inhibition. On the basis of the inhibitor concentration dependent ECL signal, the half-maximal inhibition value IC50 of ellagic acid, a PKA inhibitor, was estimated, which was in agreement with those characterized with the conventional kinase assay. While nearly no ECL signal change can be observed in the presence of Tyrphostin AG1478, a tyrosine kinase inhibitor, but not PKA inhibitor, shows its excellent performance in kinase inhibitor screening. The simple and sensitive biosensor is promising in developing a high-through assay of in vitro kinase activity and inhibitor screening for clinic diagnostic and drug development. © 2010 American Chemical Society.

Duan X.,Hunan University | Wang C.,University of California at Los Angeles | Pan A.,Hunan University | Yu R.,Hunan University | Duan X.,University of California at Los Angeles
Chemical Society Reviews | Year: 2015

The discovery of graphene has ignited intensive interest in two-dimensional layered materials (2DLMs). These 2DLMs represent a new class of nearly ideal 2D material systems for exploring fundamental chemistry and physics at the limit of single-atom thickness, and have the potential to open up totally new technological opportunities beyond the reach of existing materials. In general, there are a wide range of 2DLMs in which the atomic layers are weakly bonded together by van der Waals interactions and can be isolated into single or few-layer nanosheets. The van der Waals interactions between neighboring atomic layers could allow much more flexible integration of distinct materials to nearly arbitrarily combine and control different properties at the atomic scale. The transition metal dichalcogenides (TMDs) (e.g., MoS2, WSe2) represent a large family of layered materials, many of which exhibit tunable band gaps that can undergo a transition from an indirect band gap in bulk crystals to a direct band gap in monolayer nanosheets. These 2D-TMDs have thus emerged as an exciting class of atomically thin semiconductors for a new generation of electronic and optoelectronic devices. Recent studies have shown exciting potential of these atomically thin semiconductors, including the demonstration of atomically thin transistors, a new design of vertical transistors, as well as new types of optoelectronic devices such as tunable photovoltaic devices and light emitting devices. In parallel, there have also been considerable efforts in developing diverse synthetic approaches for the rational growth of various forms of 2D materials with precisely controlled chemical composition, physical dimension, and heterostructure interface. Here we review the recent efforts, progress, opportunities and challenges in exploring the layered TMDs as a new class of atomically thin semiconductors. © The Royal Society of Chemistry 2015.

Xie Z.-X.,Hunan University | Tang L.-M.,Hunan University | Pan C.-N.,Hunan University | Li K.-M.,Hunan University | And 2 more authors.
Applied Physics Letters | Year: 2012

The thermoelectric properties in graphene nanoribbons modulated with stub structures are studied using atomistic simulation of electron and phonon transport. The results show that the phonon transport is dramatically suppressed by the elastic scattering of the stub structure; while the thermopower S can be enhanced by a few times of magnitude. This leads to a strong enhancement of the figure of merit (ZT). Moreover, it is found that the enhancement of ZT can be effectively tuned by modulating geometric parameters of the stub and edge shapes, which offers an effective way to improve the thermoelectric performance of graphene nanoribbons. © 2012 American Institute of Physics.

Hu A.,Hunan University | Chen X.,Hunan University | Tang Y.,Hunan University | Tang Q.,Hunan University | And 2 more authors.
Electrochemistry Communications | Year: 2013

Fe3O4 nanorod graphene composites (FNGC) have been successfully prepared via in situ self-assembly by mild chemical reduction of graphite oxide and (NH4)2Fe(SO4)2 in water with hydrazine as reducing agent under normal pressure. Scanning electron microscopy and transmission electron microscopy observations confirmed that the as-formed Fe3O4 nanorods, about 11 nm in diameter and more than 100 nm in length, were uniformly anchored on graphene nanosheets. Electrochemical investigation showed that the FNGC exhibited improved cycling stability and superior rate capacity in comparison with Fe3O 4 nanoparticles. A charge specific capacity of 867 mA h g - 1 was maintained with only 5% capacity loss after the 100th cycle at 1 C. At a current density of 5 C, its charge capacity was 569 mA h g - 1. The results suggested that FNGC is a promising candidate for practical application as lithium ion battery anode material. © 2012 Elsevier B.V.

Li X.,Hunan University | Zhou S.,Hunan Normal University | Wang D.,Hunan University
International Journal of Wireless and Mobile Computing | Year: 2013

In this work we present a sighting-aware obstacle mobility model for ad hoc network. In natural or man-made disasters, military activities or healthcare services scenarios, people's line of sight is obstructed by the obstacles. In the proposed mobility model, the nodes of the network move around the obstacles in a natural and realistic way. A recursive procedure is followed by each node according to which every time an obstacle is encountered between the node's current position and the final destination point, the node moves to the obstacle's vertex which makes the path the current shortest path from the source point to the destination point. This process is repeated until the destination is reached. Simulation results show that the proposed model has significant difference with other obstacle mobility models on the network pathway selection. And also the proposed model has different impacts on network topology and routing performance. Copyright © 2013 Inderscience Enterprises Ltd.

Deng L.,Hunan University | Hu W.,Hunan University | Deng H.,Hunan University | Xiao S.,Hunan University | And 2 more authors.
Journal of Physical Chemistry C | Year: 2011

Monte Carlo simulations were performed to study systematically the surface segregation behaviors and atomic-scale structural features of Au-Ag nanoparticles for a range of alloy compositions, particle sizes, and temperatures. Segregation of Ag to the surface was observed in all the particles considered. The surface segregation was promoted by increasing the particle sizes or Ag compositions and decreasing nanoparticles' temperatures. It was found that the most stable mixing patterns are the onionlike structure with Ag-rich shell for small particles, and the alloyed-core/layered-shell structure for large particles. Accordingly, the calculated alloying extents based on Monte Carlo simulations are consistent with experimental EXAFS analysis, which indicates more obvious alloying features in nanoparticles with larger sizes or at higher temperatures, and more obvious segregated features in nanoparticles under the opposite conditions. The size distribution of Au ensembles on different coordinated sites was analyzed quantitatively, which presented varied composition-and temperature-dependent effects. The possible effects of size and shape distribution of surface ensembles on tuning the catalytic activity and selectivity of bimetallic nanoparticles were also discussed. © 2011 American Chemical Society.

Liang H.,Hunan University | Zhang X.-B.,Hunan University | Lv Y.,Hunan University | Gong L.,Hunan University | And 5 more authors.
Accounts of Chemical Research | Year: 2014

ConspectusDNA performs a vital function as a carrier of genetic code, but in the field of nanotechnology, DNA molecules can catalyze chemical reactions in the cell, that is, DNAzymes, or bind with target-specific ligands, that is, aptamers. These functional DNAs with different modifications have been developed for sensing, imaging, and therapeutic systems. Thus, functional DNAs hold great promise for future applications in nanotechnology and bioanalysis. However, these functional DNAs face challenges, especially in the field of biomedicine. For example, functional DNAs typically require the use of cationic transfection reagents to realize cellular uptake. Such reagents enter the cells, increasing the difficulty of performing bioassays in vivo and potentially damaging the cell's nucleus. To address this obstacle, nanomaterials, such as metallic, carbon, silica, or magnetic materials, have been utilized as DNA carriers or assistants. In this Account, we describe selected examples of functional DNA-containing nanomaterials and their applications from our recent research and those of others. As models, we have chosen to highlight DNA/nanomaterial complexes consisting of gold nanoparticles, graphene oxides, and aptamer-micelles, and we illustrate the potential of such complexes in biosensing, imaging, and medical diagnostics.Under proper conditions, multiple ligand-receptor interactions, decreased steric hindrance, and increased surface roughness can be achieved from a high density of DNA that is bound to the surface of nanomaterials, resulting in a higher affinity for complementary DNA and other targets. In addition, this high density of DNA causes a high local salt concentration and negative charge density, which can prevent DNA degradation. For example, DNAzymes assembled on gold nanoparticles can effectively catalyze chemical reactions even in living cells. And it has been confirmed that DNA-nanomaterial complexes can enter cells more easily than free single-stranded DNA.Nanomaterials can be designed and synthesized in needed sizes and shapes, and they possess unique chemical and physical properties, which make them useful as DNA carriers or assistants, excellent signal reporters, transducers, and amplifiers. When nanomaterials are combined with functional DNAs to create novel assay platforms, highly sensitive biosensing and high-resolution imaging result. For example, gold nanoparticles and graphene oxides can quench fluorescence efficiently to achieve low background and effectively increase the signal-to-background ratio. Meanwhile, gold nanoparticles themselves can be colorimetric reporters because of their different optical absorptions between monodispersion and aggregation.DNA self-assembled nanomaterials contain several properties of both DNA and nanomaterials. Compared with DNA-nanomaterial complexes, DNA self-assembled nanomaterials more closely resemble living beings, and therefore they have lower cytotoxicity at high concentrations. Functional DNA self-assemblies also have high density of DNA for multivalent reaction and three-dimensional nanostructures for cell uptake. Now and in the future, we envision the use of DNA bases in making designer molecules for many challenging applications confronting chemists. With the further development of artificial DNA bases using smart organic synthesis, DNA macromolecules based on elegant molecular assembly approaches are expected to achieve great diversity, additional versatility, and advanced functions. © 2014 American Chemical Society.

Tan W.,Hunan University | Tan W.,University of Florida | Donovan M.J.,Hunan University | Donovan M.J.,University of Florida | And 2 more authors.
Chemical Reviews | Year: 2013

The development of aptamers and their use in biomarker discovery, detection, sensing, profiling, and characterizing of cells is discussed. Through the process of cell-SELEX (systematic evolution of ligands by exponential enrichment), aptamers may be selected with high selectivity and specificity toward a targeted cell line. Not only can aptamers bind to certain molecules with high affinity, they can also be chemically modified with relative ease. Cell-selected aptamers are able to recognize subtle differences among cellular membranes. These differences can be exploited for cell detection, capture, and imaging. Similar to aptamers selected against purified proteins, aptamers from cell-SELEX can also be analyzed to obtain the binding motif and be post engineered to enhance their affinity or functionality. Specifically, with their ability to distinguish cancer cells from normal cells, aptamers allow a comparative strategy to identify differences at the molecular level and promote the discovery of molecular features of cancer cells.

Peng L.,University of Florida | You M.,Hunan University | Wu C.,University of Florida | Han D.,University of Florida | And 5 more authors.
ACS Nano | Year: 2014

An azobenzene-containing surfactant was synthesized for the phase transfer of α-cyclodextrin (α-CD)-capped gold nanoparticles between water and toluene phases by host-guest chemistry. With the use of the photoisomerization of azobenzene, the reversible phase transfer of gold nanoparticles was realized by irradiation with UV and visible light. Furthermore, the phase transfer scheme was applied for the quenching of a reaction catalyzed by gold nanoparticles, as well as the recovery and recycling of the gold nanoparticles from aqueous solutions. This work will have significant impact on materials transfer and recovery in catalysis and biotechnological applications. © 2014 American Chemical Society.

Huang F.,Anhui University of Science and Technology | Xu H.,Anhui University of Science and Technology | Tan W.,University of Florida | Tan W.,Hunan University | Liang H.,Anhui University of Science and Technology
ACS Nano | Year: 2014

The immobilization of DNA molecules onto a solid support is a crucial step in biochip research and related applications. In this work, we report a DNA photolithography method based on photocleavage of 2-nitrobenzyl linker-modified DNA strands. These strands were subjected to ultraviolet light irradiation to generate multiple short DNA strands in a programmable manner. Coupling the toehold-mediated DNA strand-displacement reaction with DNA photolithography enabled the fabrication of a DNA chip surface with multifunctional DNA patterns having complex geometrical structures at the microscale level. The erasable DNA photolithography strategy was developed to allow different paintings on the same chip. Furthermore, the asymmetrical modification of colloidal particles was carried out by using this photolithography strategy. This strategy has broad applications in biosensors, nanodevices, and DNA-nanostructure fabrication. © 2014 American Chemical Society.

Jin Z.,Hunan University | Xie D.-X.,Hunan University | Zhang X.-B.,Hunan University | Gong Y.-J.,Hunan University | And 2 more authors.
Analytical Chemistry | Year: 2012

Several heavy metal ions (HMIs), such as Cd 2+, Pb 2+, and Hg 2+, are highly toxic even at very low concentrations. Although a large number of fluoroionphores have been synthesized for HMIs, only a few of them show detection limits that are below the maximum contamination levels in drinking water (usually in the nM range), and few of them can simultaneously detect and remove HMIs. In this work, we report a new fluoroionphore-ionic liquid hybrid-based strategy to improve the performance of classic fluoroionphores via a synergistic extraction effect and realize simultaneous instrument-free detection and removal of HMIs. As a proof-of-concept, Hg 2+ was chosen as a model HMI, and a rhodamine thiospirolactam was chosen as a model fluoroionphore to construct bifunctional fluoroionphore-ionic liquid hybrid 1. The new sensing system could provide obviously improved sensitivity by simply increasing the aqueous-to-ionic liquid phase volume ratio to 10:1, resulting in a detection limit of 800 pM for Hg 2+, and afford extraction efficiencies larger than 99% for Hg 2+. The novel strategy provides a general platform for highly sensitive detection and removal of various HMIs in aqueous samples and holds promise for environmental and biomedical applications. © 2012 American Chemical Society.

You M.,University of Florida | Chen Y.,University of Florida | Zhang X.,Hunan University | Liu H.,University of Florida | And 5 more authors.
Angewandte Chemie - International Edition | Year: 2012

Regulatable nanorobots: A DNA-based walking device was designed that is capable of autonomous locomotion, with light control of initiation, termination, and velocity (see picture). This device is reminiscent of cellular protein motors in nature, especially those of green plants. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fang X.,CAS Beijing National Laboratory for Molecular | Tan W.,University of Florida | Tan W.,Hunan University
Accounts of Chemical Research | Year: 2010

Molecular medicine is an emerging field focused on understanding the molecular basis of diseases and translating this information into strategies for diagnosis and therapy. This approach could lead to personalized medical treatments. Currently, our ability to understand human diseases at the molecular level is limited by the lack of molecular tools to identify and characterize the distinct molecular features of the disease state, especially for diseases such as cancer. Among the new tools being developed by researchers including chemists, engineers, and other scientists is a new class of nucleic acid probes called aptamers, which are ssDNA/RNA molecules selected to target a wide range of molecules and even cells. In this Account, we will focus on the use of aptamers, generated from cell-based selections, as a novel molecular tool for cancer research. Cancers originate from mutations of human genes. These genetic alterations result in molecular changes to diseased cells, which, in turn, lead to changes in cell morphology and physiology. For decades, clinicians have diagnosed cancers primarily based on the morphology of tumor cells or tissues. However, this method does not always give an accurate diagnosis and does not allow clinicians to effectively assess the complex molecular alterations that are predictive of cancer progression. As genomics and proteomics do not yet allow a full access to this molecular knowledge, aptamer probes represent one effective and practical avenue toward this goal. One special feature of aptamers is that we can isolate them by selection against cancer cells without prior knowledge of the number and arrangement of proteins on the cellular surface. These probes can identify molecular differences between normal and tumor cells and can discriminate among tumor cells of different classifications, at different disease stages, or from different patients. This Account summarizes our recent efforts to develop aptamers through cell-SELEX for the study of cancer and apply those aptamers in cancer diagnosis and therapy. We first discuss how we select aptamers against live cancer cells. We then describe uses of these aptamers. Aptamers can serve as agents for molecular profiling of spedfic cancer types. They can also be used to modify therapeutic reagents to develop targeted cancer therapies. Aptamers are also aiding the discovery of new cancer biomarkers through the recognition of membrane protdn targets. Importantly, we demonstrate how molecular assemblies can integrate the properties of aptamers and, for example, nanoparticles or microfluidic devices, to improve cancer cell enrichment, detection and therapy. Figure Presented. © 2010 American Chemical Society.

Lu S.B.,University of Science and Technology of China | Miao L.L.,Hunan University | Guo Z.N.,University of Science and Technology of China | Qi X.,Xiangtan University | And 6 more authors.
Optics Express | Year: 2015

Black phosphorous (BP), the most thermodynamically stable allotrope of phosphorus, is a high-mobility layered semiconductor with direct band-gap determined by the number of layers from 0.3 eV (bulk) to 2.0 eV (single layer). Therefore, BP is considered as a natural candidate for broadband optical applications, particularly in the infrared (IR) and mid-IR part of the spectrum. The strong light-matter interaction, narrow direct band-gap, and wide range of tunable optical response make BP as a promising nonlinear optical material, particularly with great potentials for infrared and mid-infrared opto-electronics. Herein, we experimentally verified its broadband and enhanced saturable absorption of multi-layer BP (with a thickness of ∼10 nm) by wide-band Z-scan measurement technique, and anticipated that multi-layer BPs could be developed as another new type of two-dimensional saturable absorber with operation bandwidth ranging from the visible (400 nm) towards mid-IR (at least 1930 nm). Our results might suggest that ultra-thin multi-layer BP films could be potentially developed as broadband ultra-fast photonics devices, such as passive Q-switcher, mode-locker, optical switcher etc. © 2015 Optical Society of America.

You M.,Hunan University | You M.,University of Florida | Peng L.,University of Florida | Shao N.,University of Florida | And 5 more authors.
Journal of the American Chemical Society | Year: 2014

Cell types, both healthy and diseased, can be classified by inventories of their cell-surface markers. Programmable analysis of multiple markers would enable clinicians to develop a comprehensive disease profile, leading to more accurate diagnosis and intervention. As a first step to accomplish this, we have designed a DNA-based device, called "Nano-Claw". Combining the special structure-switching properties of DNA aptamers with toehold-mediated strand displacement reactions, this claw is capable of performing autonomous logic-based analysis of multiple cancer cell-surface markers and, in response, producing a diagnostic signal and/or targeted photodynamic therapy. We anticipate that this design can be widely applied in facilitating basic biomedical research, accurate disease diagnosis, and effective therapy. © 2013 American Chemical Society.

Kong R.-M.,Hunan University | Zhang X.-B.,Hunan University | Chen Z.,Hunan University | Tan W.,Hunan University | Tan W.,University of Florida
Small | Year: 2011

Aptamers represent a class of single-stranded DNA or RNA oligonucleotides that play important roles in biosensing and biomedical applications. However, aptamers can gain more flexibility as molecular recognition tools by taking advantage of the unique chemical and physical properties provided by nanomaterials. Such aptamer-nanomaterial conjugates are having an increasing impact in the fields of biosensing, bioimaging, and therapy. The recent advances and limitations of aptamer-assembled nanomaterials in biosensing and biomedical applications are briefly introduced and discussed. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Li Y.,TU Dortmund | Rehtanz C.,TU Dortmund | Ruberg S.,TU Dortmund | Luo L.,Hunan University | Cao Y.,Hunan University
IEEE Transactions on Power Systems | Year: 2012

This paper proposes a hybrid method to assess and select suitable control inputs for multiple HVDC and FACTS supplementary wide-area damping controllers (WADCs) of large-scale interconnected power system. This method can not only reduce the interaction among different WADCs, but also get good performance of damping multiple inter-area oscillations. The residue analysis method based on observability/controllability index is used to preselect the input signal candidates for each WADC. Then, the relative gain array (RGA) analysis, including the steady-state values and the dynamic behavior, is carried out to evaluate and determine the suitable input signals for multiple WADCs. Since the undesired interaction among multiple WADCs is reduced significantly by the proposed method, we can design each WADC independently without considering the coordination of controllers, which can reduce the design difficulty of multiple WADCs. A detailed case study validates the proposed method, and indicates that the multiple WADCs adopting the selected wide-area signals can effectively damp multiple inter-area oscillations at different operating scenarios (e.g., line fault, line outage, and load shedding). © 1969-2012 IEEE.

You M.,University of Florida | Huang F.,University of Florida | Chen Z.,Hunan University | Wang R.-W.,University of Florida | And 2 more authors.
ACS Nano | Year: 2012

Recently, the specific hybridization of DNA molecules has been used to construct self-assembled devices, such as the mechanical device to mimic cellular protein motors in nature. Here, we present a new light-powered DNA mechanical device based on the photoisomerization of azobenzene moieties and toehold-mediated strand displacement. This autonomous and controllable device is capable of moving toward either end of the track, simply by switching the wavelength of light irradiation, either UV (365 nm) or visible (>450 nm). This light-controlled strategy can easily solve one main technical challenge for stepwise walking devices: the selection of routes in multipath systems. The principle employed in this study, photoisomerization-induced toehold length switching, could be further useful in the design of other mechanical devices, with the ultimate goal of rivaling molecular motors for cargo transport and macroscopic movement. © 2012 American Chemical Society.

Wang Q.-Y.,Hunan University | Kang Y.-J.,Jiangnan University
Nanoscale Research Letters | Year: 2016

In this study, we have developed an efficient method based on single-stranded DNA (ssDNA) aptamers along with silica fluorescence nanoparticles for bacteria Salmonella typhimurium detection. Carboxyl-modified Tris(2,2′-bipyridyl)dichlororuthenium(II) hexahydrate (RuBPY)-doped silica nanoparticles (COOH-FSiNPs) were prepared using reverse microemulsion method, and the streptavidin was conjugated to the surface of the prepared COOH-FSiNPs. The bacteria S. typhimurium was incubated with a specific ssDNA biotin-labeled aptamer, and then the aptamer-bacteria conjugates were treated with the synthetic streptavidin-conjugated silica fluorescence nanoprobes (SA-FSiNPs). The results under fluorescence microscopy show that SA-FSiNPs can be applied effectively for the labeling of bacteria S. typhimurium with great photostable property. To further verify the specificity of SA-FSiNPs out of multiple bacterial conditions, variant concentrations of bacteria mixtures composed of bacteria S. typhimurium, Escherichia coli, and Bacillus subtilis were treated with SA-FSiNPs. In addition, the feasibility of SA-FSiNPs for bacteria S. typhimurium detection in chicken samples was assessed. All the results display that the established aptamer-based nanoprobes exhibit the superiority for bacteria S. typhimurium detection, which is referentially significant for wider application prospects in pathogen detection. © 2016, Wang and Kang.

Chen M.,Hunan University | Xu P.,Hunan University | Zeng G.,Hunan University | Yang C.,Hunan University | And 2 more authors.
Biotechnology Advances | Year: 2015

Increasing soil pollution problems have caused world-wide concerns. Large numbers of contaminants such as polycyclic aromatic hydrocarbons (PAHs), petroleum and related products, pesticides, chlorophenols and heavy metals enter the soil, posing a huge threat to human health and natural ecosystem. Chemical and physical technologies for soil remediation are either incompetent or too costly. Composting or compost addition can simultaneously increase soil organic matter content and soil fertility besides bioremediation, and thus is believed to be one of the most cost-effective methods for soil remediation. This paper reviews the application of composting/compost for soil bioremediation, and further provides a critical view on the effects of this technology on microbial aspects in contaminated soils. This review also discusses the future research needs for contaminated soils. © 2015 Elsevier Inc.

Bamrungsap S.,University of Florida | Chen T.,University of Florida | Shukoor M.I.,University of Florida | Chen Z.,University of Florida | And 5 more authors.
ACS Nano | Year: 2012

Biocompatible magnetic nanosensors based on reversible self-assembly of dispersed magnetic nanoparticles into stable nanoassemblies have been used as effective magnetic relaxation switches (MRSw) for the detection of molecular interactions. We report, for the first time, the design of MRSw based on aptamer-conjugated magnetic nanoparticles (ACMNPs). The ACMNPs capitalize on the ability of aptamers to specifically bind target cancer cells, as well as the large surface area of MNPs to accommodate multiple aptamer binding events. The ACMNPs can detect as few as 10 cancer cells in 250 μ L of sample. The ACMNPs' specificity and sensitivity are also demonstrated by detection in cell mixtures and complex biological media, including fetal bovine serum, human plasma, and whole blood. Furthermore, by using an array of ACMNPs, various cell types can be differentiated through pattern recognition, thus creating a cellular molecular profile that will allow clinicians to accurately identify cancer cells at the molecular and single-cell level. © 2012 American Chemical Society.

Zhu G.,Hunan University | Zhu G.,University of Florida | Hu R.,Hunan University | Zhao Z.,Hunan University | And 4 more authors.
Journal of the American Chemical Society | Year: 2013

DNA nanotechnology has been extensively explored to assemble various functional nanostructures for versatile applications. Mediated by Watson-Crick base-pairing, these DNA nanostructures have been conventionally assembled through hybridization of many short DNA building blocks. Here we report the noncanonical self-assembly of multifunctional DNA nanostructures, termed as nanoflowers (NFs), and the versatile biomedical applications. These NFs were assembled from long DNA building blocks generated via rolling circle replication (RCR) of a designer template. NF assembly was driven by liquid crystallization and dense packaging of building blocks, without relying on Watson-Crick base-pairing between DNA strands, thereby avoiding the otherwise conventional complicated DNA sequence design. NF sizes were readily tunable in a wide range, by simply adjusting such parameters as assembly time and template sequences. NFs were exceptionally resistant to nuclease degradation, denaturation, or dissociation at extremely low concentration, presumably resulting from the dense DNA packaging in NFs. The exceptional biostability is critical for biomedical applications. By rational design, NFs can be readily incorporated with myriad functional moieties. All these properties make NFs promising for versatile applications. As a proof-of-principle demonstration, in this study, NFs were integrated with aptamers, bioimaging agents, and drug loading sites, and the resultant multifunctional NFs were demonstrated for selective cancer cell recognition, bioimaging, and targeted anticancer drug delivery. © 2013 American Chemical Society.

Mao X.,Central China Normal University | Su H.,Central China Normal University | Tian D.,Central China Normal University | Li H.,Central China Normal University | Yang R.,Hunan University
ACS Applied Materials and Interfaces | Year: 2013

1,2-bis-(2-pyren-1-ylmethylamino-ethoxy) ethane (NPEY) was synthesized and brought to the surface of graphene nanosheets (GNs) via π-π stacking, which provided a simple and convenient route for processing "turn-on" fluorescent sensor by simply mixing the diluted aqueous solutions of both components. The synthesized NPEY modified graphene nanosheets (NPEY-GNs) not only allows good selectivity toward Mn2+ with the detection limit of 4.6 × 10-5 M, but also shows "turn-on" response for Mn2+ both in vitro and in living cells. These sensing capabilities of NPEY-GNs in living cells make it a robust candidate for many biological fields, such as intracellular tracking, intracellular imaging, etc. © 2013 American Chemical Society.

Liu Y.,Wenzhou University | Yao B.,Wenzhou University | Deng C.-L.,Wenzhou University | Tang R.-Y.,Wenzhou University | And 2 more authors.
Organic Letters | Year: 2011

Chemical equations presented. A new, simple method for selectively synthesizing alkyl aryl ketones has been developed by palladium-catalyzed oxidative coupling of trialkylamines with aryl iodides. In the presence of PdCl2(MeCN)2, TBAB, and ZnO, a variety of aryl iodides underwent an oxidative coupling reaction with tertiary amines and water to afford the corresponding alkyl aryl ketones in moderate to excellent yields. It is noteworthy that this method is the first example of using trialkylamines as the carbonyl sources for constructing alkyl aryl ketone skeletons. © 2011 American Chemical Society.

Tang R.-Y.,Hunan University | Tang R.-Y.,Wenzhou University | Xie Y.-X.,Hunan University | Xie Y.-L.,Wenzhou University | And 2 more authors.
Chemical Communications | Year: 2011

The first example of molecular sieve-promoted TBHP-mediated direct oxidative thiolation of an sp3 C-H bond adjacent to a nitrogen atom with disulfides under metal-free conditions, which allows for preparation of numerous S,N-containing compounds, is presented. Moreover, diverse benzothiazoles and a fipronil analog can be synthesized through this strategy. © 2011 The Royal Society of Chemistry.

Lu L.-M.,Hunan University | Zhang X.-B.,Hunan University | Kong R.-M.,Hunan University | Yang B.,Hunan University | And 2 more authors.
Journal of the American Chemical Society | Year: 2011

Many types of fluorescent sensing systems have been reported for biological small molecules. Particularly, several methods have been developed for the recognition of ATP or NAD +, but they only show moderate sensitivity, and they cannot discriminate either ATP or NAD + from their respective analogues. We have addressed these limitations and report here a dual strategy which combines split DNAzyme-based background reduction with catalytic and molecular beacon (CAMB)-based amplified detection to develop a ligation-triggered DNAzyme cascade, resulting in ultrahigh sensitivity. First, the 8-17 DNAzyme is split into two separate oligonucleotide fragments as the building blocks for the DNA ligation reaction, thereby providing a zero-background signal to improve overall sensitivity. Next, a CAMB strategy is further employed for amplified signal detection achieved through cycling and regenerating the DNAzyme to realize the true enzymatic multiple turnover (one enzyme catalyzes the cleavage of several substrates) of catalytic beacons. This combination of zero-background signal and signal amplification significantly improves the sensitivity of the sensing systems, resulting in detection limits of 100 and 50 pM for ATP and NAD +, respectively, much lower than those of previously reported biosensors. Moreover, by taking advantage of the highly specific biomolecule-dependence of the DNA ligation reaction, the developed DNAzyme cascades show significantly high selectivity toward the target cofactor (ATP or NAD +), and the target biological small molecule can be distinguished from its analogues. Therefore, as a new and universal platform for the design of DNA ligation reaction-based sensing systems, this novel ligation-triggered DNAzyme cascade method may find a broad spectrum of applications in both environmental and biomedical fields. © 2011 American Chemical Society.

Zhou M.-B.,Hunan University | Pi R.,Hunan University | Hu M.,Hunan University | Yang Y.,Hunan University | And 4 more authors.
Angewandte Chemie - International Edition | Year: 2014

This study describes a new rhodium(III)-catalyzed [3+2] annulation of 5-aryl-2,3-dihydro-1H-pyrroles with internal alkynes using a Cu(OAc)2oxidant for building a spirocyclic ring system, which includes the functionalization of an aryl C(sp2)-H bond and addition/protonolysis of an alkene C=C bond. This method is applicable to a wide range of 5-aryl-2,3-dihydro-1H-pyrroles and internal alkynes, and results in the assembly of the spiro[indene-1,2′-pyrrolidine] architectures in good yields with excellent regioselectivities. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA.

Yang Z.,Wenzhou University | Nie H.,Wenzhou University | Chen X.,Wenzhou University | Chen X.,Hunan University | Huang S.,Wenzhou University
Journal of Power Sources | Year: 2013

The fuel cell (FC), as a clean and high-efficiency device, has drawn a great deal of attention in terms of both fundamentals and applications. However, the high cost and scarcity of the requisite platinum catalyst as well as a sluggish oxygen reduction reaction (ORR) at the cathode in FC have become the greatest barrier to large-scale industrial application of FC. The development of novel non-precious metal catalysts (NPMC) with excellent electrocatalytic performance has been viewed as an important strategy to promote the development of FC. Recent studies have proven that metal free carbon materials doped with heteroatom (e.g. N, B, P, S or Se) have also shown striking electrocatalytic performance for ORR and become an important category of potential candidates for replacing Pt-based catalysts. This review summarizes recent achievements in heteroatom doped carbon materials as ORR catalysts, and will be beneficial to future development of other novel low-cost NPMCs with high activities and long lifetimes for practical FC applications. © 2013 Elsevier B.V. All rights reserved.

Yang W.,Hunan University | Zhou J.,Hunan University | Xu W.,China Academy of Building Research | Zhang G.,Hunan University
Energy Policy | Year: 2010

As a renewable energy technology, the ground-source heat pump (GSHP) technologies have increasingly attracted world-wide attention due to their advantages of energy efficiency and environmental friendliness. This paper presents Chinese research and application on GSHP followed by descriptions of patents. The policies related to GSHP are also introduced and analyzed. With the support of Chinese government, several new heat transfer models and two new GSHP systems (named pumping and recharging well (PRW) and integrated soil cold storage and ground-source heat pump (ISCS&GSHP) system) have been developed by Chinese researchers. The applications of GSHP systems have been growing rapidly since the beginning of the 21st century with financial incentives and supportive government policies. However, there are still several challenges for the application of GSHP systems in large scale. This paper raises relevant suggestions for overcoming the existing and potential obstacles. In addition, the developing and applying prospects of GSHP systems in China are also discussed. © 2009 Elsevier Ltd. All rights reserved.

Yang M.-G.,Central South University | Li C.-Y.,T.Y. Lin International Engineering Consulting China Co. | Chen Z.-Q.,Hunan University
Engineering Structures | Year: 2013

Non-linear hysteresis is a complicated mechanical characteristic for magneto-rheological (MR) damper. In this paper, a new simple non-linear hysteretic model for MR damper is proposed to represent the hysteretic behavior. First, the force-displacement and force-velocity loops under a range of currents, amplitudes and frequencies are obtained by mechanical behavior test of a RD1097 type MR damper. Then the model's parameters are identified by the non-linear least square method from test data and fitted by the polynomials as functions of the supplied current. Finally, the accuracy and the effectiveness of the model are demonstrated by the RMS errors comparison between the reconstructed hysteretic curves and the experimental ones, and further are verified by seismic response reduction experiment under three excitations including the sinusoidal wave, the Pingsheng Bridge earthquake wave and the El-Centro wave. The results show that the proposed model has higher accuracy than some of existing models with explicit functions and is easier to be identified than those models with non-linear differential equations. Therefore, the proposed model can be effectively applied to simulation analysis in engineering control subjected to frequency-fixed or random excitations. © 2013 Elsevier Ltd.

Zhao C.,Hunan University | Zhang H.,Hunan University | Qi X.,Xiangtan University | Chen Y.,Hunan University | And 3 more authors.
Applied Physics Letters | Year: 2012

Under strong laser radiation, a Dirac material, the topological insulator (TI) Bi2Te3, exhibits an optical transmittance increase as a result of saturable absorption. Based on an open-aperture Z-scan measurement at 1550 nm, we clearly show that the TI, Bi2Te3 under our investigation, is indeed a very-high-modulation-depth (up to 95%) saturable absorber. Furthermore, a TI based saturable absorber device was fabricated and used as a passive mode locker for ultrafast pulse formation at the telecommunication band. This contribution unambiguously shows that apart from its fantastic electronic property, a TI (Bi2Te3) may also possess attractive optoelectronic property for ultrafast photonics. © 2012 American Institute of Physics.

Response surface methodology along with Box-Behnken design was firstly applied to optimize the extraction conditions for the polysaccharides from the roots of Isatis tinctoria L. The experimental data obtained were fitted to a second-order polynomial equation using multiple regression analysis. The 3-D response surface and the contour plots derived from the mathematical models were applied to determine the optimal conditions. The optimal conditions were extraction temperature (X1) 99.5 °C, extraction time (X 2) 3.75 h and ratio of water to raw material (X3) 11.84 (v/w). Under these conditions, the maximal observed value extraction yield of Isatis root polysaccharides (IRPSs) was (11.19 ± 0.04)%, which was agreed with predicted value 11.17%. Pharmacological experiments indicated that IRPS have an appreciable ABTS radical scavenging ability in vitro and could increase IL-4 and IFN-γ mRNA expression in chicken lymphocytes obtaining maximum promoted effects of 70% and 115%, respectively. This study may facilitate a deeper understanding of IRPS to provide theoretical references. © 2011 Elsevier Ltd. All rights reserved.

Jin G.,University of Waterloo | Jin G.,National University of Defense Technology | Matthews D.E.,University of Waterloo | Zhou Z.,Hunan University
Reliability Engineering and System Safety | Year: 2013

The paper presents a Bayesian framework consisting of off-line population degradation modeling and on-line degradation assessment and residual life prediction for secondary batteries in the field. We use a Wiener process with random drift, diffusion coefficient and measurement error to characterize the off-line population degradation of secondary battery capacity, thereby capturing several sources of uncertainty including unit-to-unit variation, time uncertainty and stochastic correlation. Via maximum likelihood, and using observed capacity data with unknown measurement error, we estimate the parameters in this off-line population model. To achieve the requirements for on-line degradation assessment and residual life prediction, we exploit a particle filter-based state and static parameter joint estimation method, by which the posterior degradation model is updated iteratively and the degradation state of an individual battery is estimated at the same time. A case study of some Li-ion type secondary batteries not only shows the effectiveness of our method, but also provides some useful insights regarding the necessity of on-line updating and the apparent differences between the population and individual unit degradation modeling and assessment problems. © 2012 Elsevier Ltd.

Li H.,Hunan University | Lei J.,North China Electrical Power University | Liu Q.,CAS Institute of Engineering Thermophysics
International Journal of Heat and Mass Transfer | Year: 2012

The inverse heat conduction problems (IHCP) analysis method provides an efficient approach for estimating the thermophysical properties of materials, the boundary conditions, or the initial conditions. Successful applications of the IHCP method depend mainly on the efficiency of the inversion algorithms. In this paper, a generalized objective functional, which has been developed using a generalized stabilizing functional and a combinational estimation that integrates the advantages of the least trimmed squares (LTS) estimation and the M-estimation, is proposed. The objective functional unifies the regularized M-estimation, the regularized least squares (LS) estimation, the regularized LTS estimation, the regularized combinational estimation of the LTS estimation and the M-estimation, and the regularized combinational estimation of the LS estimation and the M-estimation into a concise formula. The filled function method, which is coupled with the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm, is developed for searching a possible global optimal solution. Numerical simulations are implemented to evaluate the feasibility and effectiveness of the proposed algorithm. Favorable numerical performances and satisfactory results are observed, which indicates that the proposed algorithm is successful in solving the IHCP. © 2012 Elsevier Ltd. All rights reserved.

Wang Q.,Hunan University | Chen Z.,Hunan University | Li L.,Hunan University | Yang G.,Ganzhou Zhangyuan Tungsten New Materials Co.Ltd
Surface and Coatings Technology | Year: 2012

In this work, the spray parameters of the bimodal WC-12Co powder are optimized by Taguchi experiment program by using liquid fuel JP-8000 HVOF spray system with mass flow meter controlling the flux of the medium. The phase composition, microstructure, hardness, porosities, fracture toughness, per-pass deposited thickness and the abrasive wear mechanism of the coatings have been studied in detail. The results indicate that the varying of the spraying parameters shows little effect on the phase composition of the WC-12Co coatings but great influence on their other performance such as hardness, porosity, fracture toughness and the per-pass thickness of coatings. High hardness of the coatings usually means low porosity, low fracture toughness, low per-pass thickness and high wear resistance for the HVOF WC-12Co coatings. The bimodal coating deposited under the optimal spray parameter exhibits excellent performance, which can be attributed to its small mean free path of the cobalt binder resulting from the bimodal distribution of WC particles. As last, three groups of spray parameters, named as economic, moderate and high level spray parameters, are suggested according to the results of Taguchi experiment program and the applied situation of the coated parts as well as their preparation cost. © 2011 Elsevier B.V.

Yuan Y.-Q.,Lishui University | Guo S.-R.,Lishui University | Guo S.-R.,Hunan University | Xiang J.-N.,Hunan University
Synlett | Year: 2013

Cu(OAc)promoted TBHP oxidative coupling reaction of formamides with thiols successfully proceeded through direct C-H bond activation of formamides. The corresponding S-phenyl dialkyl thiocarbamate compounds were formed with high yield under solvent-free conditions. © Georg Thieme Verlag Stuttgart · New York.

Dou S.,Hunan University | Shen A.,Hunan University | Tao L.,Hunan University | Wang S.,Hunan University | Wang S.,University of Manchester
Chemical Communications | Year: 2014

In this work, we successfully, for the first time, perform the molecular doping of graphene as metal-free electrocatalysts for oxygen reduction reaction. The doped small molecule onto graphene could induce the charge transfer between graphene and the molecules, which leads to significantly enhanced electrocatalytic activity for oxygen reduction reaction. This journal is © the Partner Organisations 2014.

Zhang Y.,Hunan University | Yin S.,Hunan University | Luo S.,Hunan University | Au C.T.,Hunan University | Au C.T.,Hong Kong Baptist University
Industrial and Engineering Chemistry Research | Year: 2012

Carboxyl-functionalized imidazolium-based ionic liquid was grafted onto cross-linked divinylbenzene polymer (PDVB-CEIMBr) for the first time. The catalyst was characterized and used for the cycloaddition of CO 2 to epoxides under relatively mild reaction conditions without any use of cocatalyst and organic solvent. The effects of reaction conditions (temperature, initial CO 2 pressure, and time) and water addition on the yield of cyclic carbonate were investigated systematically. Under optimal conditions (140 °C, initial CO 2 pressure 2.0 MPa and 4 h), propylene carbonate selectivity and yield was 99.8% and 96.1%, respectively. Moreover, the catalyst shows good stability and reusability. A plausible reaction mechanism was proposed for the catalytic reaction. It is suggested that synergetic effect among Brønsted acid COOH, Lewis base Br - and the support facilitates the coupling reaction. From the viewpoint of industrial application, the catalyst is attractive because of its excellent catalytic efficiency. © 2012 American Chemical Society.

Guo S.-R.,Hunan University | Guo S.-R.,Lishui University | He W.-M.,Hunan University | Xiang J.-N.,Hunan University | Yuan Y.-Q.,Lishui University
Chemical Communications | Year: 2014

A new method for the preparation of alkyl aryl sulfides through direct oxidative thiolation of alkanes or ethers with arylsulfonyl hydrazides using di-tert-butyl peroxide (DTBP) as an oxidant catalyzed by Pd(OAc)2 has been reported. The C-H bonds in various alkanes or ethers were successfully converted into C-S bonds to yield the corresponding sulfides in moderate to good yields. © the Partner Organisations 2014.

Ding Y.,Hunan University of Technology | Su D.,Hunan University
Energy Procedia | Year: 2011

Using the rice husk as raw material, the native in-situ mastoid SiO 2 is purified by acid and alkali pretreatment. The morphologies and structures of the native in-situ mastoid SiO2 are characterized and analyzed with SEM, HRTEM, FT-IR, EDS and XRD. The results show that the native in-situ SiO2 is mastoid and amorphous. Si content is increasing from the outer surface to the inner surface of the rice husk. © 2011 Published by Elsevier B.V. Selection and/or peer-review under responsibility of International Materials Science Society.

Guo S.-R.,Lishui University | Guo S.-R.,Hunan University | Yuan Y.-Q.,Lishui University | Xiang J.-N.,Hunan University
Organic Letters | Year: 2013

A novel method for the preparation of alkyl aryl sulfides through direct oxidation thiolation of commercial ethers with diaryl disulfides using di-tert-butyl peroxide (DTBP) as the oxidant without a metal catalyst was established. The C(sp3)-H bond in various ethers was successfully converted into a C-S bond, and the corresponding sulfides were achieved with moderate to high yields. © 2013 American Chemical Society.

Song H.,Hunan University | Song H.,Hong Kong Baptist University
International Journal of Computer Mathematics | Year: 2015

We present the numerical methods for the Cahn–Hilliard equation, which describes phase separation phenomenon. The goal of this paper is to construct high-order, energy stable and large time-stepping methods by using Eyre's convex splitting technique. The equation is discretized by using a fourth-order compact difference scheme in space and first-order, second-order or third-order implicit–explicit Runge–Kutta schemes in time. The energy stability for the first-order scheme is proved. Numerical experiments are given to demonstrate the performance of the proposed methods. © 2014 Taylor & Francis.

Kang Q.,Hunan University | Liu S.,Hunan University | Yang L.,Hunan University | Yang L.,Nanchang Hangkong University | And 2 more authors.
ACS Applied Materials and Interfaces | Year: 2011

TiO2 nanotube arrays (NTAs) are modified with PbS nanoparticles by successive ionic layer adsorption and reaction (SILAR) or electrodeposition, with an aim towards tuning the photoelectrochemical cell to the visible region. The PbS modification of the TiO2 NTAs results in an increase in the visible light adsorption, however the increase in photocurrent is dependent on the modification method. PbS/TiO2 NTAs prepared by SILAR and electrodeposition show, respectively, photocurrents of 11.02 and 5.72 mA/cm 2. The increase in photocurrent is attributed to enhanced charge separation efficiency and improved electron transport. © 2011 American Chemical Society.

Zhang Z.,Hunan Institute of Science and Technology | Xia F.-L.,Hunan University | Li X.-P.,Hunan Institute of Science and Technology
Pramana - Journal of Physics | Year: 2013

In this paper, we investigate the bifurcations and dynamic behaviour of travelling wave solutions of the Klein-Gordon-Zakharov equations given in Shang et al, Comput. Math. Appl. 56, 1441 (2008). Under different parameter conditions, we obtain some exact explicit parametric representations of travelling wave solutions by using the bifurcation method (Feng et al, Appl. Math. Comput. 189, 271 (2007); Li et al, Appl. Math. Comput. 175, 61 (2006)). © Indian Academy of Sciences.

Zhang Y.,Huaqiao University | Sun G.,Hunan University | Xu X.,Huaqiao University | Li G.,Hunan University | Li Q.,University of Sydney
Thin-Walled Structures | Year: 2014

Much attention of current design analysis and optimization of crashworthy structures have been largely paid to the scenarios with single load case in literature. Nevertheless the designed structures may often have to be operated in other load conditions, thus raising a critical issue of optimality. This paper aims to understand and optimize the dynamic responses and energy absorption of foam-filled conical thin-walled tubes under oblique impact loading conditions by using multiobjective optimization method. The crashworthiness criteria, namely specific energy absorption (SEA) and crushing force efficiency (CFE), are related to loading parameters and design variables by using D-optimal design of experiments (DoE) and Kriging model. To obtain the optimal Pareto solutions of hollow and foam-filled conical tubes, design optimization is first performed under different loading case (DLC) using multiobjective particle swarm optimization (MOPSO) algorithm separately. The optimal designs indicate that hollow tube has better crashing performance than the foam-filled tube under relatively high impacting velocity and great loading angle. To combine multiple load cases (MLC) for multiobjective optimization, a double weight factor technique is then adopted. It is found that the optimal foam-filled tube has better crashing performance than empty conical tube under any of overall oblique loading cases concerned. The study gains insights in deriving multiobjective optimization for multiple load cases, providing a guideline for design of energy absorber under multiple oblique loading. © 2014 Elsevier Ltd.

Hong G.,Stanford University | Tabakman S.M.,Stanford University | Welsher K.,Princeton University | Chen Z.,Hunan University | And 4 more authors.
Angewandte Chemie - International Edition | Year: 2011

In the best light: Plasmonic gold substrates were used to image cells by near-infrared fluorescence microscopy. Two fluorophores (single-walled carbon nanotubes (SWNTs) functionalized by the RGD sequence as well as the organic fluorophore IR800) tag cells in two different spectral regions. The fluorescence of SWNTs sandwiched between a cell membrane and a gold film was enhanced relative to the fluorescence observed on a quartz substrate (see picture). © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wang D.,Hunan University | Wang D.,Huaqiao University | Huang L.,Hunan University
Neural Networks | Year: 2014

In this paper, we investigate the periodic dynamical behaviors for a class of general Cohen-Grossberg neural networks with discontinuous right-hand sides, time-varying and distributed delays. By means of retarded differential inclusions theory and the fixed point theorem of multi-valued maps, the existence of periodic solutions for the neural networks is obtained. After that, we derive some sufficient conditions for the global exponential stability and convergence of the neural networks, in terms of nonsmooth analysis theory with generalized Lyapunov approach. Without assuming the boundedness (or the growth condition) and monotonicity of the discontinuous neuron activation functions, our results will also be valid. Moreover, our results extend previous works not only on discrete time-varying and distributed delayed neural networks with continuous or even Lipschitz continuous activations, but also on discrete time-varying and distributed delayed neural networks with discontinuous activations. We give some numerical examples to show the applicability and effectiveness of our main results. © 2013 Elsevier Ltd.

Lu X.,Hunan University | Lu X.,Wuhan University | Chen S.,Wuhan University | Lu J.,CAS Academy of Mathematics and Systems Science
IET Control Theory and Applications | Year: 2013

This study investigates the finite-time tracking for double-integrator multi-agent systems with bounded control input under the conditions of fixed and switching jointly reachable digraphes. In detail, two continuous distributed tracking protocols are designed to track the virtual leader in finite time with the same velocity and converging position. In particular, one introduces a special continuous distributed tracking protocol with bounded control input to track the virtual leader in finite time and reduce the chatter together. An example is also given to validate the proposed approaches. © The Institution of Engineering and Technology 2013.

Yuan Q.,Hunan University | Yuan Q.,Wuhan University | Wu Y.,Hunan University | Wang J.,Wuhan University | And 5 more authors.
Angewandte Chemie - International Edition | Year: 2013

Target practice: A novel photodynamic therapy system has been constructed by taking advantage of the specific molecular recognition of an aptamer, loading capability of a G-quadruplex, and upconversion of nanoparticles using near-infrared (NIR) light. This system selectively delivers a photosensitizer to targeted cells and upon irradiation with NIR light demonstrates phototoxicity effects. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhu H.-Y.,Taizhou University | Zhu H.-Y.,Hubei University | Fu Y.-Q.,Taizhou University | Jiang R.,Taizhou University | And 3 more authors.
Bioresource Technology | Year: 2012

Novel magnetic chitosan/poly(vinyl alcohol) hydrogel beads (m-CS/PVA HBs) were prepared by an instantaneous gelation method and characterized by X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and thermogravimetric analysis (TGA). Results of characterization indicated that m-CS/PVA HBs have been prepared successfully without damaging the crystal structure of Fe 3O 4 and their saturation magnetization were about 21.96emug -1. The adsorption capacity of Congo Red on the m-CS/PVA HBs was 470.1mgg -1. The adsorption was well described by pseudo-second-order kinetics and Langmuir equation. Positive value of enthalpy change (ΔH °) (13.32kJmol -1) showed that the adsorption was endothermic and physical in nature. The values of Gibbs free energy change (ΔG °) were found to be -3.321kJmol -1 at 298K for m-CS/PVA HBs, indicating the spontaneity of Congo Red adsorption. Therefore, the m-CS/PVA HBs could be employed as a low-cost alternative to other adsorbents in the removal of dyes from aqueous solution. © 2011 Elsevier Ltd.

Chen M.,Hunan University | He J.,Hunan University | Fan Q.,Hunan University | Dong Z.,Huaqiao University | Chen L.,Hunan University
Journal of Lightwave Technology | Year: 2015

In this paper, high-level quadrature amplitude modulation (QAM)-encoded real-time orthogonal frequency division multiplexing (OFDM) transceivers are implemented with two field programmable gate arrays and high-resolution digital-to-analog converter (DAC) and analog-to-digital converter (ADC). Some key digital signal processing (DSP) algorithms for real-time direct-detection optical OFDM (DDO-OFDM) system are presented and described in detail. To improve the effective number of bits of ADC and reduce quantization noise, the DAC operates at 5 GS/s with an oversampling factor of 2. Meanwhile, the optimal digital clipping ratio at the transmitter is also investigated by numerical simulation to optimize the performance of the real-time transmitter. The results show that the real-time measured BERs after 10-km SSMF are below the hard-decision forward error correction threshold of $3.8 \times 10^{-3}$. For comparison, the off-line BER performance is also analyzed using off-line DSP approaches. It shows that there is a negligible power penalty between the offline and real-time processing results. To the best of our knowledge, we have achieved the highest modulation format (1024-QAM) for real-time optical OFDM systems. © 2015 IEEE.

Peng C.,Huaqiao University | Liu Y.,Hunan University
Applied Physics A: Materials Science and Processing | Year: 2013

A well-organized hierarchical structure of ZnO was developed by chemical bath deposition and used as templates for making gold-coated ZnO (Au/ZnO) hybrid nanostructures. The coverage of Au nanoparticles (Au NPs) on ZnO was controlled by changing the amount of the Au precursor. The Au/ZnO hybrids were applied as gas sensing materials to detect acetone. The improved sensor response, selectivity and short response, and recovery time to acetone vapor due to Au NPs on ZnO nanostructures has been observed and explained by considering the formation of Au/ZnO heterostructures, which are favorable for the diffusion of gas molecules. In addition, the dependence of Au amount on gas sensor properties was systematically investigated. ZnO decorated by 6 wt% Au NPs displayed a 9.05-fold enhancement in gas response to 100 ppm of acetone at 280 C compared to pristine ZnO. © 2012 Springer-Verlag Berlin Heidelberg.

Yuan Z.,Hunan University | Wang L.,University of New Brunswick
Nonlinear Analysis: Real World Applications | Year: 2010

For a multigroup SEIR epidemiological model with nonlinear incidence rates, the basic reproduction number is identified. It is shown that, under certain group mixing patterns and nonlinearity and/or nonsmoothness in the incidence of infection, the basic reproduction number is a global threshold parameter in the sense that the disease free equilibrium is globally stable if the basic reproduction number is less than one and the endemic equilibrium is globally stable if the basic reproduction number is greater than one. © 2009 Elsevier Ltd. All rights reserved.

Zhang Y.-J.,Hunan University | Wang A.-D.,Beijing Institute of Technology | Da Y.-B.,Beijing Institute of Technology
Energy Policy | Year: 2014

It is an important task for China to allocate carbon emission quotas among regions so as to realize its carbon reduction targets and establish the national cap-and-trade carbon market. Meanwhile, it is supposed to be cost-effective to jointly reduce China's carbon emissions through some collaborative activities among regions. Then a natural question is how to allocate the quotas among regions in light of the collaboration. For this purpose, the Shapley value method is adopted and the results show that, first, the regions with higher GDP, higher carbon outflow and higher carbon reduction connection should be allocated more carbon quotas. Moreover, when the collaboration is considered, the optimal allocation of carbon quotas among regions will change significantly compared to the basic quotas by the entropy method; and the Central region is allocated the largest proportion of carbon quota among regions, which indicates its largest radiation effect. Besides, the collaboration between the Central region and Northern coast region, and that between the Central region and the Eastern region should be paid close attention. These results may provide insightful support for decision makers to promote collaborative carbon reduction and allocate carbon quotas in China. © 2014 Elsevier Ltd.

Xu F.,Hunan University | Xu F.,Chongqing University of Technology | Sun G.,Hunan University | Li G.,Hunan University | Li Q.,University of Sydney
Thin-Walled Structures | Year: 2014

This paper aims to investigate the crushing behaviors of tailor-welded blank (TWB) thin-walled structures. A series of TWB high-strength steel (HSS) square tubes with different weld line locations is used to perform the crushing tests for evaluating the effects of different TWB parameters, such as weld line locations and material combinations, on crushing characteristics. These TWB specimens are fabricated through the laser welding process to ensure sufficiently narrow weld line. In the study, the center edge of TWB square specimens is not welded so that such special TWB structures have open cross section. The crushing test results exhibit excellent repeatability. The collapse modes and force-displacement relationships are compared with each other. It is found that the crushing behaviors of different material combinations are fairly significant for a given weld line location. Such key crushing characteristics as specific energy absorption (SEA), average crush force (Favg), peak force (Fmax) are also evaluated for understanding crashworthiness of these TWB structures. The experimental results provide us with some insightful guidance to crashworthiness design of TWB thin-walled HSS structures. © 2013 Published by Elsevier Ltd.

Zhang Y.-J.,Hunan University | Da Y.-B.,Beijing Institute of Technology
Renewable and Sustainable Energy Reviews | Year: 2015

In order to find the efficient ways to reduce carbon emission intensity in China, we utilize the LMDI method to decompose the changes of China's carbon emissions and carbon emission intensity from 1996 to 2010, from the perspectives of energy sources and industrial structure respectively. Then we introduce the decoupling index to analyze the decoupling relationship between carbon emissions and economic growth in China. The results indicate that, on the one hand, economic growth appeared as the main driver of carbon emissions increase in the past decades, while the decrease of energy intensity and the cleaning of final energy consumption structure played significant roles in curbing carbon emissions; meanwhile, the secondary industry proved the principal source of carbon emissions reduction among the three industries and had relatively higher potential. On the other hand, when the decoupling relationship is considered, most years during the study period saw the relative decoupling effect between carbon emissions and economic growth, which indicated that the reduction effect of inhibiting factors of carbon emissions was less than the driving effect of economic growth, and the economy grew with increased carbon emissions; there appeared the absolute decoupling effect in 1997, 2000 and 2001, which implied that the economy grew while carbon emissions decreased; whereas no decoupling effect was identified in 2003 and 2004. © 2014 Elsevier Ltd.

Tan S.,Hunan University | Tan S.,CAS Academy of Mathematics and Systems Science | Lu J.,CAS Academy of Mathematics and Systems Science | Hill D.J.,University of Hong Kong | Hill D.J.,University of Sydney
IEEE Transactions on Automatic Control | Year: 2015

It is well known that evolution is a fundamental phenomenon driving nature. And random drift is a basic force for population evolution. This technical note aims at constructing a unified theoretical framework for analyzing and intervening in random drift of binary states on general networks. In detail, a general methodology is developed for calculating the fixation probability with different dynamics, including the Wright-Fisher (WF), birth-death (BD), and death-birth (DB) processes. In particular, we prove that the fixation probability of a mutant at node $k$ corresponds to the $k$-th element of stationary distribution of a stochastic matrix deduced from the weight matrix of the networks. Intuitively, it provides an effective way to discover the invasion hubs of structured population and further to intervene in random drift on networks. Finally, a typical example is then given to validate the above theoretical results. © 1963-2012 IEEE.

Zhang P.,Beijing Forestry University | Zhang G.,Renmin University of China | Dong J.,Hunan University | Fan M.,University of Wyoming | Zeng G.,Hunan University
Separation and Purification Technology | Year: 2012

Recently there has been increasing concerns on widespread occurrence of endocrine disrupting chemicals (EDCs) in aquatic environment. Bisphenol A (BPA) in water was oxidized as a target EDC by K2FeO4 (Fe(VI)) in this study. The results showed that BPA was effectively removed within a broad initial water pH range of 5.0-9.5, especially under a weak acidic condition between the initial pH 5 and 6. When the initial BPA concentration was about 1.5 mg L-1, BPA could be completely removed with a oxidation time of 30 min and a Fe(VI)/BPA molar ratio of 3.0. After Fe(VI) oxidation, UV254 of the water samples significantly increased, indicating that BPA degradation intermediates and end products still contained phenyl ring. Further online UV scanning showed that the UV absorbance obviously changed within the UV range of 190-215 nm and 230-300 nm during Fe(VI) oxidation. The DOC of water samples reduced with the increase of Fe(VI) dosage and prolonging of oxidation time, and about 50% of BPA was mineralized after Fe(VI) oxidation under a Fe(VI)/BPA molar ratio of 4.0. The influences of coexisting constituents such as humic acids, SiO32-, HCO3- and tert-butanol were studied. The results showed that humic acids and SiO32- notably inhibited the BPA removal; tert-butanol slightly decreased the BPA removal; and the existence of HCO3- slightly enhanced the BPA removal. © 2011 Elsevier B.V. All rights reserved.

Zhang C.-P.,CAS Shanghai Institute of Organic Chemistry | Wang Z.-L.,Hunan University | Chen Q.-Y.,CAS Shanghai Institute of Organic Chemistry | Zhang C.-T.,Hunan University | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2011

Copper is king! A convenient method for the synthesis of trifluoromethylated heteroaromatic compounds under mild conditions has been developed based on the observation that 1 can be reduced by certain metals (see scheme). Substrate 1 is assumed to be reduced by copper via a single-electron transfer mechanism, and CuCF3 is the most probable intermediate in this reaction. DMF=N,N-dimethylformamide, Tf=triflate. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yang H.,Hunan University | Prudencio E.E.,University of Texas at Austin | Cai X.-C.,University of Colorado at Boulder
International Journal for Numerical Methods in Engineering | Year: 2012

We develop a parallel fully implicit domain decomposition algorithm for solving optimization problems constrained by time-dependent nonlinear partial differential equations. In particular, we study the boundary control of unsteady incompressible Navier-Stokes equations. After an implicit discretization in time, a fully coupled sparse nonlinear optimization problem needs to be solved at each time step. The class of full space Lagrange-Newton-Krylov-Schwarz algorithms is used to solve the sequence of optimization problems. Among optimization algorithms, the fully implicit full space approach is considered to be the easiest to formulate and the hardest to solve. We show that Lagrange-Newton-Krylov-Schwarz, with a one-level restricted additive Schwarz preconditioner, is an efficient class of methods for solving these hard problems. To demonstrate the scalability and robustness of the algorithm, we consider several problems with a wide range of Reynolds numbers and time step sizes, and we present numerical results for large-scale calculations involving several million unknowns obtained on machines with more than 1000 processors. © 2012 John Wiley & Sons, Ltd.

Fang Q.H.,University of New South Wales | Fang Q.H.,Hunan University | Zhang L.C.,University of New South Wales
Acta Materialia | Year: 2013

This paper establishes an analytical model to predict the normal threshold load that causes the emission of partial dislocations in silicon during nanoscratching. In the modeling, the deformation mechanisms and the sequence of microstructural changes already explored by experiment and molecular dynamics will be exactly followed; that is, with increasing the normal load of nanoscratching, phase transformation first takes place, followed by partial dislocation emission from the interface between the phase transformed zone and the original crystalline silicon when the scratching load reaches its threshold. The model postulates that the emission process represents the generation of a dipole of Shockley partial dislocations. One partial dislocation of the dipole, located at the interface, is considered immobile, while the other partial dislocation moves into the bulk of the crystalline silicon. The mobile partial dislocation slips along a crystallographic plane, and a stacking fault is formed in its wake. Based on the above, the threshold normal scratching load for the emission of a partial dislocation is determined by means of the energy criterion. The influence of the indenter geometry and the location of dislocation nucleation on the threshold normal scratching load is then investigated. Compared with the deformation of silicon under nanoindentation, the present study concludes that the threshold load under scratching is always smaller, and that a sharp indenter leads to a relatively smaller threshold load. The model prediction is well verified by scratching experiments. Copyright © 2013 Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved.

Zhang C.-P.,CAS Shanghai Institute of Organic Chemistry | Wang Z.-L.,CAS Shanghai Institute of Organic Chemistry | Wang Z.-L.,Hunan University | Chen Q.-Y.,CAS Shanghai Institute of Organic Chemistry | And 3 more authors.
Chemical Communications | Year: 2011

The CF3 radical was generated from the reaction of S-(trifluoromethyl)diphenylsulfonium triflate with Na2S 2O4 or HOCH2SO2Na under suitable conditions without further reduction. Based on this, a method for the synthesis of α-trifluoromethylated ketones has been successfully developed. © 2011 The Royal Society of Chemistry.

Li J.,Hunan University | Fang Q.,Hunan University | Liu Y.,Hunan University | Zhang L.,University of New South Wales
Applied Surface Science | Year: 2014

This paper investigates the mechanisms of subsurface damage and material removal of monocrystalline copper when it is under a nanoscale high speed grinding of a diamond tip. The analysis was carried out with the aid of three-dimensional molecular dynamics simulations. The key factors that would influence the deformation of the material were carefully explored by analyzing the chip, dislocation movement, and workpiece deformation, which include grinding speed, depth of cut, grid tip radius, crystal orientation and machining angle of copper. An analytical model was also established to predict the emission of partial dislocations during the nanoscale high speed grinding. The investigation showed that a higher grinding velocity, a larger tip radius or a larger depth of cut would result in a larger chipping volume and a greater temperature rise in the copper workpiece. A lower grinding velocity would produce more intrinsic stacking faults. It was also found that the transition of deformation mechanisms depends on the competition between the dislocations and deformation twinning. There is a critical machining angle, at which a higher velocity, a smaller tip radius, or a smaller depth of cut will reduce the subsurface damage and improve the smoothness of a ground surface. The established analytical model showed that the Shockley dislocation emission is most likely to occur with the crystal orientations of (0 0 1)[1 0 0] at 45° angle. © 2014 Elsevier B.V. All rights reserved.

Jiang H.-J.,Hunan University | Dai H.-L.,Hunan University | Dai H.-L.,Chongqing University of Technology
International Journal of Heat and Mass Transfer | Year: 2015

Three-dimensional thermodynamic analysis of simply supported high strength and low alloy (HSLA) rectangular steel plates under laser shock processing are carried out in this paper. Three-dimensional transient temperature field of the laser shock processing the rectangular HSLA steel plate is solved by the method of separation of variables. Meanwhile, the displacement and stress fields are derived by using the state-space method. It could be found that some parameters such as laser moving speed and thickness to length ratio do not affect the temperature field only, but also have great influences on the displacement and stress field. The closer the laser from the center of plate is, the greater is the revulsion amplitude of HSLA steel plate's temperature on laser area. The vibration frequency of HSLA steel plate is proportional to the increasing of laser moving speed. The thickness to length ratio affects HSLA plate's displacement and stress, but the variation law of in-plane displacement U∗ is not consistent with other displacement and stress components. It can be observed that applied loading form affects the deflection greatly, both on the order of magnitude and displacement shape. © 2014 Elsevier Ltd.

Yuan Z.,Hunan University | Zou X.,University of Western Ontario
Mathematical Biosciences and Engineering | Year: 2013

We consider a mathematical model that describes the interactions of the HIV virus, CD4 cells and CTLs within host, which is a modification of some existing models by incorporating (i) two distributed kernels reecting the variance of time for virus to invade into cells and the variance of time for invaded virions to reproduce within cells; (ii) a nonlinear incidence function f for virus infections, and (iii) a nonlinear removal rate function h for infected cells. By constructing Lyapunov functionals and subtle estimates of the derivatives of these Lyapunov functionals, we shown that the model has the threshold dynamics: if the basic reproduction number (BRN) is less than or equal to one, then the infection free equilibrium is globally asymptotically stable, meaning that HIV virus will be cleared; whereas if the BRN is larger than one, then there exist an infected equilibrium which is globally asymptotically stable, implying that the HIV-1 infection will persist in the host and the viral concentration will approach a positive constant level. This together with the dependence/ independence of the BRN on f and h reveals the effect of the adoption of these nonlinear functions.

Long X.Y.,Hunan University | Jiang C.,Hunan University | Han X.,Hunan University | Gao W.,University of New South Wales | Bi R.G.,Hunan University
Computer Methods in Applied Mechanics and Engineering | Year: 2014

As a semi-analytical structural analysis algorithm, the scaled boundary finite-element method (SBFEM) only discretizes the boundary of the analyzed domain without the need of fundamental solutions, which makes it powerful for problems with stress singularity or unbounded foundation media. In this paper, a sensitivity analysis method of SBFEM is proposed for elastostatics, through which the first order derivatives of the structural responses with respect to the design parameters can be obtained efficiently and accurately. An approach is suggested to compute the eigenvalue and eigenvector sensitivities of the Hamilton matrix, which are then used to calculate the analytical derivative of the stiffness matrix. Based on these calculations, the sensitivities of displacements and stresses are further obtained by a series of differential equations. The proposed sensitivity analysis method is also applied to the fracture mechanics problems. Three numerical examples are investigated to demonstrate the validity of the proposed method. © 2014 Elsevier B.V.

Liu Q.,Guangzhou University | Lin Y.,Guangzhou University | Zong Z.,Guangzhou University | Sun G.,Hunan University | Li Q.,University of Sydney
Composite Structures | Year: 2013

Design of composite appears more challenging compared with metallic counterparts because of its microstructural heterogeneity and behavioral sophistication. This paper aims to develop a multiscale approach for predicting three-dimensional elastic model of carbon twill weave fabric composite which will be applied to crashworthiness analysis of body structure of electric vehicle. The geometric parameters were obtained by measuring the microstructure of T300 carbon twill weave fabric composite through optical microscopy. The finite element model of representative volume element (RVE) in laminate composite was established to characterize the elastic properties of the materials using the homogenization technique. The numerical results of property were compared with those from uniaxial tensile and three point bending tests. Finally, the constitutive model of such composite was employed to crashworthiness analysis for electric vehicle body structure under the roof crash and side pole impact. The study indicates that the deformation behaviors of laminate calculated by using the elastic properties are in good agreement with tensile and bending experimental results with maximum relative errors of 4.04% and 7.79%, respectively. Meanwhile, a 28% savings of body weight is achieved using the carbon twill weave fabric composite compared to its predecessor made of glass fiber reinforced plastics (GFRP). © 2012 Elsevier Ltd.

Wang X.-J.,Henan Normal University | Wang W.,Henan Normal University | Liu Y.-L.,Hunan University
Sensors and Actuators, B: Chemical | Year: 2012

ZnO flowers functionalized by Au nanoparticles (NPs) with various Au contents have been developed. The gas sensing properties of the sensors fabricated from these materials were examined and compared at varied working temperatures. Improved sensor response, selectivity and short response and recovery times to acetone vapor were achieved by suitably modulating the weight percent of Au NPs. Experimentally, the formation of Au/ZnO hybrids and surface coarsening of ZnO flowers were found to lead to apparent further enhancement of the sensor performance. © 2012 Elsevier B.V.

Yuan Z.,Hunan University | Zou X.,University of Western Ontario
Nonlinear Analysis: Real World Applications | Year: 2010

In this paper, a general mathematical model is proposed with detailed justifications to describe the spread of a disease with latency in a heterogeneous host population which includes many existing ones as special cases. For a simpler version that assumes an identical natural death rate for all groups, and with a gamma distribution for the latency, the model is shown to demonstrate the global threshold dynamics in terms of the basic reproduction number R0 of the model: if R0≤1, the disease-free equilibrium is globally asymptotically stable in the positive orthant, whereas if R0>1, a unique endemic equilibrium exists and is globally asymptotically stable in the interior of the positive orthant. The proofs of the main results make use of the theory of non-negative matrices, persistence theory in dynamical systems, Lyapunov functions and a subtle grouping technique in estimating the derivatives of Lyapunov functions guided by graph theory, which was recently developed and applied by several authors to some relateted epidemic models. © 2009 Elsevier Ltd. All rights reserved.

Xu F.,Hunan University | Xu F.,Chongqing University of Technology | Sun G.,Hunan University | Li G.,Hunan University | Li Q.,University of Sydney
Journal of Materials Processing Technology | Year: 2014

This paper aims to investigate mechanical characteristics of the new tailor-welded blank (TWB) components made of high strength steel (HSS). A series of HSS-TWB thin plates with different orientations of weld line are studied through three-point bending tests to evaluate the effects of different design parameters, such as weld line locations and material combinations, on the deformation behaviors. The experimental results exhibit good repeatability of tests. And the relative shift phenomenon between indenter and specimen is observed and analyzed for the TWB steel sheets with different weld line orientations at parallel and 45° to the bending moment, respectively. The results from the experiment include the force versus displacement curves and some detailed photographical images throughout the loading process. It is found that the discrepancy of different combinations is quite noteworthy. In this paper, the peak force, absorbed energy and bending strength are presented to evaluate the mechanical characteristics of HSS-TWB thin plates with different weld line orientations and material combinations. The comparison demonstrates that the TWB structures with the weld orientation at 45° angle to the bending moment have the greatest advantages of different TWB steel sheets. © 2013 Published by Elsevier B.V.

Gai H.,Xuzhou Normal University | Gai H.,Hunan University | Li Y.,Hunan University | Yeung E.S.,Hunan University
Topics in Current Chemistry | Year: 2011

Optical detection continues to dominate detection methods in microfluidics due to its noninvasive nature, easy coupling, rapid response, and high sensitivity. In this review, we summarize two aspects of recent developments in optical detection methods on microfluidic chips. The first aspect is free-space (off-chip) detection on the microchip, in which the conventional absorption, fluorescence, chemiluminescence, surface plasmon resonance, and surface enhanced Raman spectroscopies are involved. The second aspect is the optofluidic (inside-chip) detection. Various miniaturized optical components integrated on the microfluidic chip, such as waveguide, microlens, laser, and detectors are outlined. © 2011 Springer-Verlag Berlin Heidelberg.

Yi T.,Hunan University | Zou X.,University of Western Ontario
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2010

In this paper, we consider a class of delay reaction-diffusion equations (DRDEs) with a parameter ε > 0. A homogeneous Neumann boundary condition and non-negative initial functions are posed to the equation. By letting ε → 0, such an equation is formally reduced to a scalar difference equation (or map dynamical system). The main concern is the relation of the absolute (or delay-independent) global stability of a steady state of the equation and the dynamics of the nonlinear map in the equation. By employing the idea of attracting intervals for solution semiflows of the DRDEs, we prove that the globally stable dynamics of the map indeed ensures the delay-independent global stability of a constant steady state of the DRDEs. We also give a counterexample to show that the delayindependent global stability of DRDEs cannot guarantee the globally stable dynamics of the map. Finally, we apply the abstract results to the diffusive delay Nicholson blowfly equation and the diffusive Mackey-Glass haematopoiesis equation. The resulting criteria for both model equations are amazingly simple and are optimal in some sense (although there is no existing result to compare with for the latter). © 2010 The Royal Society.

Zhang Y.-J.,Hunan University | Zhang L.,Beijing Institute of Technology
Applied Energy | Year: 2015

Since 2009, global financial crisis has eased gradually and world economy has begun to recover slowly. Meanwhile, both Brent and WTI (West Texas Intermediate) crude oil prices have entered into a new round of increase and volatility, and the abnormal price spreads between them have been identified. Under this circumstance, this paper employs the Markov regime switching model with dynamic autoregressive coefficients to explore the price regimes of Brent and WTI after the financial crisis. Then it analyzes the causes of the abnormal spreads between the two benchmark crude oil prices based on the statistical observations of their typical regime differences. The results show that there are three main regimes in both Brent and WTI crude oil price returns, i.e., sharply downward, slightly downward and sharply upward regimes for Brent whilst sharply downward, relatively stable and sharply upward regimes for WTI. Meanwhile, the typical price regimes of Brent and WTI are the "sharply upward" and "relatively stable" regimes after the financial crisis, respectively. Besides, their different movement regimes in recent years are mainly attributed to their different market fundamental situations and the dynamics in crude oil markets, which also lead to the occurrence of their abnormal price spreads. © 2015 Elsevier Ltd.

Yuan Z.,Hunan University | Zou X.,University of Western Ontario
Nonlinear Analysis: Real World Applications | Year: 2010

In this paper, we consider a reaction diffusion model for competing pioneer and climax species. A previous work has established the existence of traveling wave fronts connecting two competition-exclusion equilibria in certain range of the parameters, while in this paper, we explore the possibility of traveling wave fronts connecting the pioneer-invasion-only equilibrium and the co-invasion equilibrium. By combining the Schauder's fixed point theorem with a pair of the so called desired functions, we show that the model does support such co-invasion waves in some other ranges of parameters. We also determine the minimal speed for such co-invasion waves in terms of the parameters, and discuss some biological implications and significance of the results. © 2008 Elsevier Ltd.

Feng H.,Hunan University | Fang Q.H.,Hunan University | Fang Q.H.,University of New South Wales | Zhang L.C.,University of New South Wales | Liu Y.W.,Hunan University
International Journal of Plasticity | Year: 2013

A grain size-dependent model is theoretically suggested to describe the combined effects of special rotational deformation and dislocations near a mode I crack tip on the fracture toughness of nanocrystalline metals and ceramics. In the model, the special rotation deformation is driven by the external stress concentration near the crack tip, and serves as a toughening mechanism by releasing part of local stresses. The lattice dislocations consist of triple junction dislocation produced by intergrain sliding and edge dislocations emitted from the crack tip. The emitted dislocations are stopped at grain boundaries. The stress fields of these dislocations suppress future dislocation emission, and the suppression depends on grain size. The results indicate that the combination of special rotational deformation and dislocations near the crack tip can lead to an increase of critical crack intensity factor (effective fracture toughness) by several times in nanocrystalline materials at finest grain size. It is also found that the fracture toughness of nanocrystalline materials is highly sensitive to grain size and there is an ideal grain size corresponding to the best toughening effects, which is qualitatively consistent with the conclusion in previous work. © 2012 Elsevier Ltd. All rights reserved.

Zhou X.,Hunan University | Li X.,Hunan University | Luo H.,Hunan University | Wen S.,Hunan University
Applied Physics Letters | Year: 2014

Photonic spin Hall effect (SHE) holds great potential applications in precision metrology. How to obtain a high measurement precision is an important issue to detect the photonic SHE. In this Letter, we propose using optimal preselection and postselection in weak measurements to enhance the measurement precision. We find that the maximum weak value and pointer shift can be obtained with an optimal overlap of preselection and postselection states. These findings offer the possibility for improving the precision of weak measurements and thereby have possible applications for accurately characterizing the parameters of nanostructures. © 2014 AIP Publishing LLC.

Liu C.,Hunan University | Zhang H.,Hunan University | Tang Y.,Hunan University | Luo S.,Hunan University
Journal of Materials Chemistry A | Year: 2014

Graphene is a promising support for nanosized electrocatalysts, however the conventional stacking arrangement of its graphene sheets substantially decreases the catalytic sites on the catalyst. We report here the fabrication of a graphene/Cu electrocatalyst by the simple cyclic voltammetric electrolysis of graphene oxide (GO) and copper ethylenediamine tetraacetate (Cu-EDTA), and find that the electrochemically reduced GO (RGO) and Cu nanoparticles can be sequentially self-assembled into layer-by-layer, 3D sandwich-type, and homogenous architectures as the concentration ratio of Cu-EDTA/GO increases. The 3D sandwich-type RGO/Cu composite (S-RGO/Cu) shows RGO sheets decorated with Cu nanoparticles which stand nearly perpendicular on the electrode, leading to a significant increase in the electrochemically accessible surface area (0.685 cm2) relative to those of the horizontal layer-by-layer RGO/Cu composite (0.147 cm2) and the homogenous RGO/Cu composite (0.265 cm2). Stemming from its high electrochemical surface area, the S-RGO/Cu composite exhibits a high electrocatalytic activity in hydrazine oxidation in terms of current density and overpotential. Mechanistic analysis of the electrode reactions reveals the reaction pathways of hydrazine on RGO/Cu are closely related to the electrochemical surface area of the RGO/Cu electrocatalyst. The correlation between the architectures and their performances in electrocatalysis presented here can guide the design of novel structures with enhanced properties. © 2014 The Royal Society of Chemistry.

Chen Y.,Hunan University | Zhuo M.,Hunan University | Deng J.,Hunan University | Xu Z.,Hunan University | And 2 more authors.
Journal of Materials Chemistry A | Year: 2014

Transition metal oxides are promising high-capacity anode materials for next-generation lithium-ion batteries. However, their cycle life remains a limiting factor with respect to their commercial applications. The development of transition-metal oxide anode materials with long lifespans through a facile route has become an important issue. A straightforward strategy is designed for the fabrication of a NiCo2O4 nanoplates-reduced graphene oxide sheets (NiCo2O4-RGO) composite. It displays a high reversible capacity of 816 mA h g-1 over 70 cycles with 80.1% capacity retention of the 2nd cycle and excellent rate capability. Its rate capability and cycling stability are enhanced in comparison with those of pure NiCo2O4 nanoplates. The as-obtained nanocomposite avoids the problems of dispersion and aggregation induced by cracking or pulverization of the transition-metal oxide upon cycling. The graphene or reduced graphene oxide not only works as a substrate to provide room for loading scattered grains, but also serves as a conductive network to facilitate the collection and transportation of electrons during the cycling, indirectly increasing the conductivity of NiCo2O4. © 2014 The Royal Society of Chemistry.

Ning X.,Hunan University | Zhong W.,Hunan University | Li S.,Hunan University | Wang Y.,Beijing University of Chemical Technology | Yang W.,Beijing University of Chemical Technology
Journal of Materials Chemistry A | Year: 2014

Nitrogen-doped porous graphene/carbon (NPGC) framework electrode materials have been synthesized via chemical activation of graphene oxide/polypyrrole (GOP) composites with KOH. The effects of the mass ratio of KOH/GOP and activation temperature on the electrochemical performance of NPGC have been discussed. It is found that the NPGC prepared by activating GOP (GO:Py = 1:40) with 3.5 times mass of KOH at 650 °C (NPGC650) exhibits the highest specific capacitance of 405 F g-1 at a current density of 0.2 A g -1. Particularly, the specific capacitance still remains at 249 F g-1 even at a current density as high as 10 A g-1. Moreover, 96% of the capacitance can be retained after 1000 cycles even under a high operation current of 10 A g-1. The present work provides a novel strategy to synthesize NGPC electrode material for supercapacitors. This journal is © the Partner Organisations 2014.

Li F.,Hunan University | Chen Y.,Hunan University | Ma J.,Hunan University
Journal of Materials Chemistry A | Year: 2014

Porous SnO2 nanoplates have been successfully prepared by the oxidization conversion of hydrothermally synthesized SnS2 nanoplates at 500 °C. When exposed to NO gas, such porous SnO2 nanoplate sensors exhibited fast response, enhanced sensitivity and excellent selectivity due to their unique structural characteristics in comparison with commercial SnO2 nanoparticles. © the Partner Organisations 2014.

Zhang L.,Hunan University | Li L.,Hunan University | Ju H.,Hunan University | Zhu B.,Hunan University
Energy Conversion and Management | Year: 2010

The effect of the heat transfer coefficient at the casting-mold interface is of prime importance to improve the casting quality, especially for castings in metal molds. However, it is difficult to determine the values of heat transfer coefficient from experiments due to the influence of various factors, such as contacting pressure, oxides on surfaces, roughness of surfaces, coating material, coating thickness and gap formation caused by the deformation of casting and mold, etc. In the present paper, the interfacial heat transfer coefficient (IHTC) between the casting and metal mold is identified by using the method of inverse analysis based on measured temperatures, neural network with back-propagation algorithm and numerical simulation. Then, by applying the identified IHTC in finite element analysis, the comparison between numerical calculated and experimental results is made to verify the correctness of method. The results show that the numerical calculated temperatures are in good agreement with experimental ones. These demonstrate that the method of inverse analysis is a feasible and effective tool for determination of the casting-mold IHTC. In addition, it is found that the identified IHTC varies with time during the casting solidification and varies in the range of about 100-3200 Wm -2K-1. The characteristics of the time-varying IHTC have also been discussed. © 2010 Elsevier Ltd. All rights reserved.

Hu G.,University of Northern British Columbia | Li J.,University of Northern British Columbia | Zeng G.,Hunan University
Journal of Hazardous Materials | Year: 2013

Oily sludge is one of the most significant solid wastes generated in the petroleum industry. It is a complex emulsion of various petroleum hydrocarbons (PHCs), water, heavy metals, and solid particles. Due to its hazardous nature and increased generation quantities around the world, the effective treatment of oily sludge has attracted widespread attention. In this review, the origin, characteristics, and environmental impacts of oily sludge were introduced. Many methods have been investigated for dealing with PHCs in oily sludge either through oil recovery or sludge disposal, but little attention has been paid to handle its various heavy metals. These methods were discussed by dividing them into oil recovery and sludge disposal approaches. It was recognized that no single specific process can be considered as a panacea since each method is associated with different advantages and limitations. Future efforts should focus on the improvement of current technologies and the combination of oil recovery with sludge disposal in order to comply with both resource reuse recommendations and environmental regulations. The comprehensive examination of oily sludge treatment methods will help researchers and practitioners to have a good understanding of both recent developments and future research directions. © 2013 Elsevier B.V.

Liu G.Q.,Hunan University
Advanced Materials Research | Year: 2014

One of the research works of network control systems is the effect of network upon control systems. A simulation platform of networked control systems is designed for this purpose. Matlab is used to build models of real systems. Communication between controller and process is fulfilled with Winsock. The simulation platform supports many control algorithms and gives good environment for the analysis and gives good environment for the analysis and design of networked control systems. © (2014) Trans Tech Publications, Switzerland.

Yin H.,Hunan University | Wen G.,Hunan University | Liu Z.,Hunan University | Qing Q.,Hunan University
Thin-Walled Structures | Year: 2014

Foam-filled thin-walled structure and multi-cell thin-walled structure both have recently gained attentions for their excellent energy absorption capacity. As an integrator of the above two kinds of thin-walled structures, foam-filled multi-cell thin-walled structure (FMTS) may have extremely excellent energy absorption capacity. This paper firstly investigates the energy absorption characteristics of FMTSs by nonlinear finite element analysis through LS-DYNA. Based on the numerical results, it can be found that the FMTS with nine cells has the most excellent crashworthiness characteristics in our considered cases. Thus, the FMTSs with cell number n=9 are then optimized by adopting a multi-objective particle swarm optimization (MOPSO) algorithm to achieve maximum specific energy absorption (SEA) capacity and minimum peak crushing force (PCF). During the process of multi-objective optimization design (MOD), four kinds of commonly used metamodels, namely polynomial response surface (PRS), radial basis function (RBF), Kriging (KRG) and support vector regression (SVR) for SEA and PCF, are established to reduce the computational cost of crash simulations by the finite element method. In order to choose the best metamodel for optimization, the accuracies of these four kinds of metamodels are compared by employing the error evaluation indicators of the relative error (RE) and the root mean square error (RMSE). The optimal design of FMTSs with nine cells is an extremely excellent energy absorber and can be used in the future vehicle body. © 2013 Elsevier Ltd. All rights reserved.

Xiao Z.,Hunan University | Luo H.,Hunan University | Wen S.,Hunan University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

In this paper, we present a systematic study of beam shifts and angular momenta of paraxial vortex beams at air-left-handed-material (LHM) interfaces. It is shown that, compared to their counterparts at air-right-handed-material (RHM) interfaces, the spatial Goos-Hänchen (GH) and Imbert-Fedorov (IF) shifts remain the same, while the angular GH and IF shifts are reversed at air-LHM interfaces. The spatial and angular shifts of paraxial vortex beams have their respective origins in transverse angular momenta and transverse linear momenta. The spatial GH and IF shifts remain unreversed as a result of both reversions of transverse angular momenta and z-component linear momentum, while the angular GH and IF shifts are reversed because the z-component linear momentum is reversed and the transverse linear momenta are unreversed at air-LHM interfaces. In addition, we perform a quantitative analysis on spin-orbit angular momentum conversion and orbit-orbit angular momentum conversion, which further helps us understand the essence of vortex beam shifts at air-LHM interfaces and their fundamental distinctions from those at air-RHM interfaces. © 2012 American Physical Society.

Jin J.,Hunan University | Wang C.,Hunan University
International Journal of Electronics | Year: 2014

This paper presents two new current differencing transconductance amplifiers (CDTAs)-based electronically tunable current-mode four-phase quadrature oscillators (QO). The proposed QOs consist of two CDTAs, one resistor and two grounded capacitors, respectively, which are suitable for monolithic integration. The condition of oscillation (CO) and frequency of oscillation (FO) can be independently controlled, and the FO can be electronically tunable by adjusting the bias current of the CDTA. Moreover, the QOs can provide four quadrature output currents at high-output-impedance nodes, which enable the QOs can be connected directly to the next stage without any impedance matching requirements. Cadence IC Design Tools 5.1.41 (Cadence Design Systems Inc., San Jose, CA) post-layout simulation results and experimental evidence are included to confirm the theory. © 2013 © 2013 Taylor & Francis.

Yin H.,Hunan University | Wen G.,Hunan University | Hou S.,Hunan University | Chen K.,Qingdao Sifang Rolling Stock Research Institute Co.
Materials and Design | Year: 2011

Honeycomb-filled tubes have recently gained attention for their enhanced energy absorption capacity. This paper firstly investigates the energy absorption characteristics of honeycomb-filled single and bitubular polygonal tubes (HSBPT) by nonlinear finite element analysis through LS-DYNA. By employing a six-level judgement method, we find that both of the honeycomb-filled single and honeycomb-filled bitubular tubes with enneagonal configuration have very excellent energy absorption characteristics among the considered cases. Next, the HSBPTs with enneagonal configuration are optimized by adopting multiobjective particle swarm optimization (MOPSO) algorithm to achieve maximum specific energy absorption (SEA) capacity and minimum peak crushing force (PCF). During the process of multiobjective optimization design (MOD), accurate metamodels of SEA and PCF of the HSBPTs with enneagonal configuration are established to reduce the computational cost of crash simulations by finite element method. Numerical experiments show that the quartic polynomial functions of SEA and PCF are the suitable metamodels for both honeycomb-filled single and bitubular enneagonal tubes. © 2011 Elsevier Ltd.

Sun X.,Hunan University | Sun X.,University of Kansas | Zhang Q.,Hunan University | Medina M.A.,University of Kansas | And 2 more authors.
Applied Energy | Year: 2014

A technology that combines phase change materials (PCMs) with a natural cold source is proposed to reduce the space cooling energy of telecommunications base stations (TBSs). First, a mathematical model was developed to assess this technology. Then, a full-scale prototype, named latent heat storage unit (LHSU), was designed, built, and tested in an enthalpy difference laboratory. The energy efficiency ratio (EER) and the adjusted energy efficiency ratio (AEER) were used as the criteria to evaluate the performance of this unit and to compare it with conventional air conditioners. LHSU performance simulations were carried out based on the unit's operation in TBSs located in five Chinese cities with different climates. The simulated average annual AEER was 14.04. W/W, which is considerably higher than the limiting value of 3.2. W/W for air conditioners with a cooling capacity of less than 4500. W. The estimated average energy savings potential of the LHSU was 50%. Based on these results, it was concluded that LHSUs could be used in TBSs to reduce a significant amount of their energy consumed in space cooling. © 2013 Elsevier Ltd.

Gu J.,Hunan University | Zhang J.,Hunan University | Zhang J.,Dalian University of Technology | Li G.,Hunan University
Engineering Analysis with Boundary Elements | Year: 2012

The isogeometric analysis is introduced in the Boundary Integral Equation (BIE) for solution of 3-D potential problems. In the solution, B-spline basis functions are employed not only to construct the exact geometric model but also to approximate the boundary variables. And a new kind of B-spline function, i.e., local bivariate B-spline function, is deducted, which is further applied to reduce the computation cost for analysis of some special geometric models, such as a sphere, where large number of nearly singular and singular integrals will appear. Numerical tests show that the new method has good performance in both exactness and convergence. © 2011 Elsevier Ltd. All rights reserved.

Jiang T.-Y.,Changsha University of Science and Technology | Fang Z.,Hunan University
Zhongguo Gonglu Xuebao/China Journal of Highway and Transport | Year: 2011

Aimed at anchorage problems that carbon fiber reinforced polymer/plastics (CFRP) was used as prestress tendon and cable reactive powder concrete (RPC) was regarded as bond medium and based on it, a new bond-type anchorage was developed. The calculated formulas of average bond strength and its corresponding slip, critical anchorage length, and bond-slip constitutive model were proposed. Influences of surface shape, bond length, number and space of CFRP tendons, slope angle of inner wall of steel sleeve and pretensioning load on anchorage performance were studied by static test. Test results show that the surface shape of CFRP tendon is significant to the anchorage performance of the bond-type anchorage. When the tensile strength of the indented surface CFRP tendon is less than 3000 MPa and compressive strength of RPC is more than 130 MPa, the critical anchorage length is 20 diameters of general CFRP tendon for common bond specimen, the shortest critical anchorage length in anchorage system is 13 diameters of pretensioning CFRP tendon with ratio of 56% of pretensioning load. The appropriate rod space is not less than rod diameter for the anchorage system with multiple CFRP tendons.

Zhang L.,Hunan University | Zhang Z.,National University of Defense Technology | Huang L.,Hunan University
Nonlinear Dynamics | Year: 2012

This paper undertakes an analysis of a double Hopf bifurcation of a maglev system with timedelayed feedback. At the intersection point of the Hopf bifurcation curves in velocity feedback control gain and time delay space, the maglev system has a codimension 2 double Hopf bifurcation. To gain insight into the periodic solution which arises from the double Hopf bifurcation and the unfolding, we calculate the normal form of double Hopf bifurcation using the method of multiple scales. Numerical simulations are carried out with two pairs of feedback control parameters, which show different unfoldings of the maglev system and we verify the theoretical analysis. © Springer Science+Business Media B.V. 2011.

He Q.,Hunan University | Yi W.,Hunan University
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2011

Under blast or impact loads, disproportionate collapse would be likely for a majority of high-rise buildings without special collapse-resistant design. Five axially restrained beam tests with various reinforcement ratios, various classes of steel bar, and various loading velocity, were conducted. The collapse-resistance behavior of beam-column sub-structures was studied considering catenary action under the failure of RC column. Both ends of the specimens were pin-connected and fixed on steel boxes and two steel tubes were embedded in both ends of the specimen. The load was continuously applied on the top of the middle column in scheduled time by the servo-hydraulic actuator with displacement-controlled mode, and the pin-supported RC beam-column experienced elastic, plastic and catenary stages. The collapse occurred at a vertical displacement of about 400 mm due to the rupture of the bottom steel bars, and the member ultimate capacity was about 2 times as much as the plastic stage, but the displacement was nearly 20 times more. Based on the experimental results, the applied load process was analyzed and the transition process of the applied load mechanism was discussed, and a simplified calculation method for catenary action was presented for collapse-resistant design of beam-column sub-structures.

Xu Y.,Hunan University | Chan E.H.W.,Hong Kong Polytechnic University
Journal of Urban Planning and Development | Year: 2012

The community question, referring to the transformation of social networks when rural residents move into urban areas, has been extensively debated by urbanists and sociologists in Western countries. This paper, focusing on the urbanization of rural villages caused by urban expansion and land requisition, examines the community question in the context of transitional China. It aims to investigate whether the unique institutional settings in China will lead to a different answer to the community question. Compared with the existing studies, there are two improvements in the design of this research, which include: (1) adding a middle stage to divide the urbanization process into the three stages of rural village, semiurbanization village, and urban resettlement housing district, thereby identifying and comparing the status of personal social ties at each stage of the state-led urbanization process; and (2) controlling the features of sampled villages and characteristics of respondents that may affect social life patterns, therefore understanding the exact effects of urbanization on neighborhood social life. This study found that (1) the conventional community- lost argument finds support in transitional China with state-led urbanization; (2) the decline of social ties is nonlinear during the urbanization process, which is different from the common statement of linear transformation in the literature. Instead, the decline reaches the lowest point at the stage of semiurbanized village; and (3) the structure of personal networks also changes along with the process of community lost. © 2011 American Society of Civil Engineers.

Lu B.,Hunan Mechanical and Electrical Polytechnic | Huang W.,Hunan University
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2011

This paper proposes a novel hybrid wavelet-energy operator method for accurate voltage sag detection and measurement. In the proposed method, the voltage sag is decomposed into two signal parts by wavelet transform: one is a detail signal, the other is an approximation signal. And in the detail signal, the start time and the end time of the sag signal can be detected. By applying an energy operator to the approximation signal, the temporary sag decline in value can be measured accurately and quickly. At the same time, the wavelet transform (WT) in this method acts like a filter. WT can weaken or remove the high frequency disturbance from voltage sag to enhance the noise immunity and accuracy of the energy operator. Simulation and experimental results verify the effectiveness of the algorithm.

Xiao Y.,Hunan University | He Y.,Hunan University
Neurocomputing | Year: 2011

We have developed a neural-network-based fault diagnosis approach of analog circuits using maximal class separability based kernel principal components analysis (MCSKPCA) as preprocessor. The proposed approach can detect and diagnose faulty components efficiently in the analog circuits by analyzing their time responses. First, using wavelet transform to preprocess the time responses obtains the essential and reduced candidate features of the corresponding response signals. Then, the second preprocessing by MCSKPCA further reduces the dimensionality of candidate features so as to obtain the optimal features with maximal class separability as inputs to the neural networks. This simplifies the architectures reasonably and reduces the computational burden of neural networks drastically. The simulation results show that our resulting diagnostic system can classify the faulty components of analog circuits under test effectively and achieves a competitive classification performance. © 2010 Elsevier B.V.

Chen J.-H.,Hunan University | Liu C.-H.,Hunan University
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2011

The performances of AlMgSi(Cu) alloys widely used in the industry, largely correlate with the precipitates formed in the thermal process. The morphologies, the structural features and the phase stabilities of all well-known precipitates that possibly form in the AlMgSi(Cu) alloys were reviewed. In order to understand the structural transformations between the early-stage hardening precipitates in the alloys, and their relations with the mechanical properties of the materials, a concept of dynamic structure to describe the evolution of the hardening particles was introduced. For further development of the high-strength 6××× series alloys, a few un-answered questions about the structural transformations in Cu-containing 6××× series alloys are crucial.

Deng L.,Hunan University | Hu W.,Hunan University | Deng H.,Hunan University | Xiao S.,Hunan University
Journal of Physical Chemistry C | Year: 2010

Monte Carlo simulations were carried out to systematically investigate the effects of composition, size, and temperature on the surface segregation and structural features of Au-Pt nanoparticles in the present paper. A strong surface Au enrichment was observed in all of the nanoparticles, and the surface segregation of Au was promoted by increasing the particle sizes. It is found that the core-shell structure was preferred in the equilibrium Au-Pt nanoparticles with low Au composition, and three-shell onion-like structure was formed at high Au composition. The competitive multisite segregation was predicted in the core-shell nanoparticles in which Au atoms favor sites at the vertices, edges, and facets. The reverse temperature dependency of segregation for different surface sites has also been discussed. © 2010 American Chemical Society.

Chen D.,Hunan University | Xiao T.,Hunan University
Journal of the American Ceramic Society | Year: 2010

Single-phase ZnO nanoparticles were successfully prepared by solid-liquid reaction ball milling assisted by ultrasonic wave. The samples were characterized by X-ray diffraction and transmission electron microscopy. By the comparison of the as-milled products with and without the help of ultrasonic wave, it is found that ultrasonic wave is a key factor promoting the transformation from Zn(OH)2 to ZnO. Based on hot-spot theory, the formation mechanism of the single-phase ZnO nanoparticles under ultrasonic wave assistance is determined. © 2010 The American Ceramic Society.

Zeng J.,Hunan University | Chen K.-Q.,Hunan University | Sun C.Q.,Nanyang Technological University
Physical Chemistry Chemical Physics | Year: 2012

By applying the nonequilibrium Green's functions and the density-functional theory, we investigate the electronic structures and transport properties of fluorinated zigzag-edged boron nitride nanoribbons. The results show that the transition between half-metal and semiconductor in zigzag-edged boron nitride nanoribbons can be realized by fluorination at different sites or by the change of the fluorination level. Moreover, the negative differential resistance and varistor-type behaviors can also be observed in such fluorinated zigzag-edged boron nitride nanoribbon devices. Therefore, the fluorination of zigzag-edged boron nitride nanoribbons will provide the possibilities for a multifunctional molecular device design. © 2012 the Owner Societies.

Liu Y.,Hunan University | Ling X.,Hunan University | Yi X.,Hunan University | Zhou X.,Hunan University | And 4 more authors.
Optics Letters | Year: 2015

Observation of photonic spin Hall effect (SHE) in dielectric metasurfaces whose local optical axes are spatially rotated is presented. The photonic SHE manifests itself as a spin-dependent splitting in momentum space due to the space-variant Pancharatnam-Berry phase. We show that no spin-dependent splitting occurs when keeping the rotational symmetry of local optical axes. However, the splitting can be observed when the rotational symmetry is broken. The spin-dependent splitting in position space can be observed in the far field due to the high transmission efficiency of dielectric metasurfaces. Moreover, it can be enhanced by increasing the rotation rate of local optical axes in the metasurfaces. © 2015 Optical Society of America.

Li G.,Hunan University | Liu Y.,Hunan University
Materials Science in Semiconductor Processing | Year: 2013

ZnO nanoparticles were synthesized by calcining composites of zinc nitrate and poly(vinyl pyrrolidone) (PVP, molecular weight 30 000) at a mass ratio of 1:2 at 500 °C for 2 h. X-Ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques were used to characterize the as-synthesized ZnO nanoparticles. The particles ranged in size from 30 to 50 nm. Infrared spectra of PVP and the PVP+Zn(NO3) 2·6H2O composite revealed coordination between the carbonyl (C=O) of PVP and Zn2+ of zinc nitrate, which led to a uniform nanoparticle morphology. The gas-sensing properties and photocatalytic performance of the final product were systematically investigated. The results show that the ZnO nanoparticles exhibit both a high response for ethanol detection and excellent photocatalytic activity for degradation of methyl orange under UV irradiation for 30 min. © 2013 Elsevier Ltd. All rights reserved.

Zhou J.,Hunan University | Liu Y.,Hunan University | Ke Y.,Hunan University | Luo H.,Hunan University | Wen S.,Hunan University
Optics Letters | Year: 2015

We propose a novel method for the generation of Airy vortex and Airy vector beams based on the modulation of dynamic and geometric phases. In our scheme, the Airy beam is generated by the dynamic phase with a spatial light modulator, and the vortex phase or the vector polarization is modulated by the geometric phase with a dielectric metasurface. The modulation of the geometric phase provides an extra degree of freedom to manipulate the phase and the polarization of Airy beams. This scheme can be extended to generate any other types of optical beams with desirable phase and polarization. © 2015 Optical Society of America.

Li S.,Hunan University | Yin H.,Hunan University
Optical Engineering | Year: 2011

Image fusion combines multiple images of the same scene into a single image which is suitable for human perception and practical applications. Different images of the same scene can be viewed as an ensemble of intercorrelated images. This paper proposes a novel multimodal image fusion scheme based on the joint sparsity model which is derived from the distributed compressed sensing. First, the source images are jointly sparsely represented as common and innovation components using an over-complete dictionary. Second, the common and innovations sparse coefficients are combined as the jointly sparse coefficients of the fused image. Finally, the fused result is reconstructed from the obtained sparse coefficients. Furthermore, the proposed method is compared with some popular image fusion methods, such as multiscale transform-based methods and simultaneous orthogonal matching pursuit-based method. The experimental results demonstrate the effectiveness of the proposed method in terms of visual effect and quantitative fusion evaluation indexes. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Cao Y.,Hunan University | Wang G.,Jinhua Electrical Power Bureau
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2010

The power system complexity and its related research progress are introduced in terms of existence and evolution, and the relationship between existence complexity and evolution complexity is analyzed. The existence complexity contains the multilayer & inter-relevancy, nonlinear dynamics, randomness, real-time, social economics, openness, etc., and the evolution complexity contains the self-organization, synergetics, mutagenicity, and fractal dimension, etc. The theoretical framework of power system complexity study is proposed, including its basic concept, its comprehensive analysis method and system, the power system self -organized criticality, the power system network features, the simulation and prediction methods of power system cascading failures based on the complexity theory, its comprehensive integration technology, etc. The important topics and future work related to the research of power system complexity are pointed out.

Ling X.,Hunan University | Zhou X.,Hunan University | Luo H.,Hunan University | Wen S.,Hunan University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

An inhomogeneous anisotropic medium with specific structure geometry can apply the tunable spin-dependent geometrical phase to the light passing through the medium, and thus can be used to steer the spin-dependent splitting (SDS) of light. In this paper, we exemplify this inference by the q plate, an inhomogeneous anisotropic medium. It is demonstrated that when a linearly polarized light beam normally passes through a q plate, k-space SDS first occurs, and then the real-space SDS in the far-field focal plane of a converging lens is distinguishable. Interestingly, the SDS, described by the normalized Stokes parameter S3 shows a multilobe and rotatable splitting pattern with rotational symmetry. Further, by tailoring the structure geometry of the q plate and/or the incident polarization angle of light, the lobe number and the rotation angle both are tunable. Our result suggests that the q plate can serve as a potential device for manipulating the photon spin states and enable applications such as in nano-optics and quantum information. © 2012 American Physical Society.

Wang C.,Hunan University
Zhen ci yan jiu = Acupuncture research / [Zhongguo yi xue ke xue yuan Yi xue qing bao yan jiu suo bian ji] | Year: 2010

OBJECTIVE: To observe the effect of electroacupuncture (EA) on contents of myocardial nitric oxide (NO), nitric oxide synthase (NOS), and intracellular Ca2+ levels in experimental myocardial ischemia-reperfusion injury (MI/RI) rats, so as to provide some evidence for acupuncture treatment of cardiovascular disorders and for the correlation between the acupoints and the internal organs. METHODS: Fifty male Wistar rats were randomly divided into sham-operation (sham), model, Neiguan (PC 6), Lieque (LU 7), and Hegu (LI 4) groups (n = 10/group). MI/RI model was established by occlusion of the descending anterior branch of the left coronary artery for 40 min and reperfusion for 60 min. EA (30 Hz/100 Hz, 2-4 mA) was applied to the bilateral PC 6, LU 7 and LI 4 for 20 min. The myocardial tissue of the ischemic area was taken, homogenated and centrifuged, separated for assaying NO and NOS activity by using spectrophotometer and their contents with nitrate reductase colorimetric assay. Another part of the myocardium tissue was processed to be cell suspension (added with Fluo-3/AM dye) for assaying intracellular free [Ca2+]i concentration under the laser confocal microscope. RESULTS: Compared with sham group, myocardial NO and NOS contents of model group decreased mildly and significantly (P < 0.05), while myocardial fluorescence intensity (content) of intracellular Ca2+ increased evidently (P < 0.01). In comparison with model group, the contents of myocardial NO and NOS were upregulated considerably in PC 6 group (P < 0.05), and intracellular Ca2+ content in PC 6 group reduced significantly (P < 0.01). No significant differences were found between LU 7 and model groups and between LI 4 and model groups in the above mentioned 3 indexes (P > 0.05). CONCLUSION: EA of PC 6 can upregulate myocardial NO and NOS contents and downregulate myocardial intracellular Ca2+ level in MI/RI rats, which may contribute to its effect in relieving myocardial injury. Neiguan (PC 6) and the heart have a relatively specific correlation.

Liu Y.F.,Hunan University
Green Building, Materials and Civil Engineering - Proceedings of the 4th International Conference on GreenBuilding, Materials and Civil Engineering, GBMCE 2014 | Year: 2015

In the modern design field, the lack of Chinese design style and the overflow of new Chinese style are being criticized. In this paper, the orientation of Chinese elements is expounded, the abstraction and expression of Chinese elements in interior design are discussed, and the innovative integration between Chinese elements and interior design is studied. The focus of this study is to identify a reasonable corresponding point for heritage and development of Chinese elements under the cultural globalization context. The purpose is to promote the heritage of Chinese elements and communication with the Western culture in the design field. © 2015 Taylor & Francis Group, London.

Yuan L.,Hunan University | Lin W.,Hunan University | Zheng K.,Hunan University | He L.,Hunan University | Huang W.,Hunan University
Chemical Society Reviews | Year: 2013

The long wavelength (far-red to NIR) analyte-responsive fluorescent probes are advantageous for in vivo bioimaging because of minimum photo-damage to biological samples, deep tissue penetration, and minimum interference from background auto-fluorescence by biomolecules in the living systems. Thus, great interest in the development of new long wavelength analyte-responsive fluorescent probes has emerged in recent years. This review highlights the advances in the development of far-red to NIR fluorescent probes since 2000, and the probes are classified according to their organic dye platforms into various categories, including cyanines, rhodamine analogues, BODIPYs, squaraines, and other types (240 references). © The Royal Society of Chemistry 2013.

Xu B.,Hunan University | Xu B.,University of Houston | Zhang T.,Hunan University | Song G.,University of Houston | Gu H.,University of Houston
Mechanical Systems and Signal Processing | Year: 2013

Concrete-Filled Steel Tube (CFST) has been widely adopted in high-rise buildings and bridges as a typical structural member carrying vertical loads in recent years. The debonding between the steel tube and the concrete can dramatically reduce the confinement effect of steel tube on the concrete and decrease the load-carrying capacity and the ductility of the CFST. It is still challenging to develop reliable debonding monitoring and detection techniques for CFST because of the inaccessibility of the interface. In this study, an active interface condition monitoring approach for CFST by the use of lead zirconate titanate (PZT) piezoceramics based functional smart aggregates (SAs) embedded in concrete as actuator and PZT patches bonded on the surface of the steel tube as sensors is proposed and verified experimentally. Laboratory tests are performed on the CFST column, in which the deboning is mimicked by setting four thin styrofoam plates with different sizes on different locations of the four internal surfaces of the steel tube, respectively, before casting the concrete. The responses of the PZT sensors are measured when each SA is excited with sweep sinusoidal signals. According to the Fourier spectra and two evaluation indices based on the wavelet packet analysis on the PZT sensors measurements, the artificially mimicked debonding areas are detected successfully. Analysis on the sensitivity of the two evaluation indices shows that the indices based on wavelet packet analysis are more sensitive to the debonding defect. The proposed PZT based active debonding monitoring method provides an innovative approach to detect the debonding damage of CFST columns. © 2011 Elsevier Ltd. All rights reserved.

Zhou X.,Hunan University | Xiao Z.,Hunan University | Luo H.,Hunan University | Wen S.,Hunan University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

We theorize the spin Hall effect of light (SHEL) on a nanometal film and demonstrate it experimentally via weak measurements. A general propagation model to describe the relationship between the spin-orbit coupling and the thickness of the metal film is established. It is revealed that the spin-orbit coupling in the SHEL can be effectively modulated by adjusting the thickness of the metal film, and the transverse displacement is sensitive to the thickness of metal film in a certain range for horizontal polarization light. Importantly, a large negative transverse shift can be observed as a consequence of the combined contribution of the ratio and the phase difference of Fresnel coefficients. © 2012 American Physical Society.

Zeng J.,Hunan University | Chen K.-Q.,Hunan University | He J.,Hunan University | Zhang X.-J.,Hunan University | Sun C.Q.,Nanyang Technological University
Journal of Physical Chemistry C | Year: 2011

By using nonequilibrium Green's functions in combination with the density functional theory, we investigate the electronic transport properties of edge hydrogenated zigzag-edged graphene nanoribbon heterojunctions. Results show that a perfect spin-filtering effect with 100% spin polarization and a rectifying behavior with a ratio larger than 10 5 can be realized by dihydrogenation, which can also be modulated by changing the widths of the two component ribbons. © 2011 American Chemical Society.

Sun D.,Hunan University | Luo S.-N.,Hunan University
European Journal of Mechanics, A/Solids | Year: 2011

In this paper, the wave propagation and dynamic response of the rectangular FGM plates with completed clamped supports under impulse load are analyzed. The effective material properties of functionally graded materials (FGMs) for the plate are assumed to vary continuously through the plate thickness and be distributed according to a volume fraction power law along the plate thickness. Considering the effects of transverse shear deformation and rotary inertia, the governing equations of the wave propagation in the functionally graded plate are derived by using the Hamilton's principle. A complete discussion of dispersion of the FGM plates is given. Using the dispersion relation and integral transforms, exact integral solutions for the FGM plates under impulse load are obtained. The influence of volume fraction distributions on wave propagation and dynamic response of the FGM plates is analyzed. © 2011 Elsevier Masson SAS. All rights reserved.

Wan Q.,Hunan University | Wang C.,Hunan University
Microelectronics Journal | Year: 2011

This paper presents a low-voltage low-power transmitter front-end using current mode approach for 2.4 GHz wireless communication applications, which is fabricated in a chartered 0.18 μm CMOS technology. The direct up-conversion is implemented with a current mode mixer employing a novel input driver stage, which can significantly improve the linearity and consume a small amount of DC current. The driver amplifier utilizes a transimpedance amplifier as the first stage and employs an inter-stage capacitive cross-coupling technique, which enhances the power conversion gain as well as high linearity. The measured results show that at 2.4 GHz, the transmitter front-end provides 15.5 dB of power conversion gain, output P-1 dB of 3 dBm, and the output-referred third-order intercept point (OIP3) of 13.8 dBm, while drawing only 6 mA from the transmitter front-end under a supply voltage of 1.2 V. The chip area including the testing pads is only 0.9 mm×1.1 mm. © 2010 Elsevier Ltd. All rights reserved.

Fu Y.,Hunan University | Zhang J.,Hunan University | Wan L.,Hunan University
Current Applied Physics | Year: 2011

In this paper, the energy balance method has been successfully used to study a nonlinear oscillator arising in the microbeam-based microelectromechanical system (MEMS). Firstly, the governing equation of the free vibration of a microbeam is governed based on the Euler-Bernoilli hypothesis where the midplane stretching effect and distributed electrostatic force are both considered. Then this PDE problem is simplified into an ODE problem by using the Galerkin method. Finally, the nonlinear ODE equation is solved by a powerful mathematical tool, the energy balance method. The good agreement of results got from energy balance method with results from fourth-order Runge-Kutta method indicates that the obtained period is of high accuracy. © 2010 Elsevier B.V. All rights reserved.

Qin Y.,Max Planck Institute of Microstructure Physics | Pan A.,Hunan University | Liu L.,Max Planck Institute of Microstructure Physics | Moutanabbir O.,Max Planck Institute of Microstructure Physics | And 2 more authors.
ACS Nano | Year: 2011

This paper reports on a novel and versatile method to synthesize sharp-edged crescent-shaped half-nanotubes (HNTs) using a flexible template-based nanofabrication method assisted by atomic layer deposition. This was achieved by electrodeposition inside crescent-shaped nanochannels created by a controlled removal of a sacrificial layer, which was deposited by atomic layer deposition onto the pore walls of an anodic aluminum oxide template. This method provides a high degree of freedom in the manipulation of the morphological properties of HNTs such as the edge sharpness, opening, gap size, and the wall thickness. Initial optical investigations of the HNTs reveal distinct surface plasmon resonance by dark field scattering spectra and surface enhanced Raman spectrum. © 2011 American Chemical Society.

Yuan L.,Hunan University | Lin W.,Hunan University | Song J.,Hunan University
Chemical Communications | Year: 2010

The first ratiometric fluorescent probe for hydroxyl radical ratiometric imaging in living cells was rationally designed based on a hybrid coumarin-cyanine platform. © 2010 The Royal Society of Chemistry.

Tan H.,Hunan University | Yang S.,Hunan University | Shen G.,Hunan University | Yu R.,Hunan University | Wu Z.,Hunan University
Angewandte Chemie - International Edition | Year: 2010

No cloudiness with a silver lining: Deposition of metallic silver on a liquid-crystal substrate with attached DNA strands greatly alters the surface topology and induces a homeotropic-to-tiled transition of the LC molecules surrounding them, resulting in an obvious change in appearance from dark to birefringent (see picture; Ag: spheres). This enzymatic silver deposition is an excellent signal-enhancement strategy for LC optical amplification. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wang M.-H.,Hunan University | Hu J.-W.,Hunan University | Li Y.-J.,Hunan University | Yeung E.S.,Hunan University
Nanotechnology | Year: 2010

An environment-friendly method is developed to fabricate close-packed Au nanoparticle (AuNP) monolayers with sub-10nm interparticle spacing simply by covering n-butanol on the surface of an Au aqueous colloid. The close-packed nanostructure can further transform into two-dimensional (2D) aggregates with different aggregation degrees upon aging for severaldays. This structural evolution process was disclosed by transition electron microscopy (TEM) and UV-vis spectroscopy and its influence on the ensemble optical properties was further demonstrated by surface-enhanced Raman scattering (SERS). It was revealed that creating sub-10nm interparticle spacing and particle dimers are highly desirable for engendering strong SERS activity under a 632.8nm excitation. Further aging the film leads to the formation of larger aggregates, which moves the surface plasmon resonance of the aggregates gradually 'off-resonance' from the 632.8nm excitation line and costs some numbers of sub-10nm interparticle spacings. The two parameters together decrease the SERS activity of the close-packed AuNP monolayers. The present strategy thus provides an easy way to finely tune the SERS properties of thin nanoparticle films and other ensemble properties, which can easily be realized by creating sub-10 interparticle spacing, controlling the particle aggregation degree and by adopting suitable particle sizes and shapes. © 2010 IOP Publishing Ltd.

He D.,Hunan University | He X.,Hunan University | Wang K.,Hunan University | Cao J.,Hunan University | Zhao Y.,Hunan University
Langmuir | Year: 2012

In this paper, a reversible light-responsive molecule-gated system based on mesoporous silica nanoparticles (MSN) functionalized with thymine derivatives is designed and demonstrated. The closing/opening protocol and release of the entrapped guest molecules is related by a photodimerization-cleavage cycle of thymine upon different irradiation. In the system, thymine derivatives with hydrophilicity and biocompatibility were grafted on the pore outlets of MSN. The irradiation with 365 nm wavelength UV light to thymine-functionalized MSN led to the formation of cyclobutane dimer in the pore outlet, subsequently resulting in blockage of pores and strongly inhibiting the diffusion of guest molecules from pores. With 240 nm wavelength UV light irradiation, the photocleavage of cyclobutane dimer opened the pore and allowed the release of the entrapped guest molecules. As a proof-of-the-concept, Ru(bipy) 3 2+ was selected as the guest molecule. Then the light-responsive loading and release of Ru(bipy) 3 2+ were investigated. The results indicated that the system had an excellent loading amount (53 μmol g -1 MSN) and controlled release behavior (82% release after irradiation for 24 h), and the light-responsive loading and release procedure exhibited a good reversibility. Besides, the light-responsive system loaded with Ru(bipy) 3 2+ molecule could also be used as a light-switchable oxygen sensor. © 2012 American Chemical Society.

Tang Y.,Hunan University | Ma J.,Hunan University
RSC Advances | Year: 2014

In this work, In2O3 nanorods and nanoparticles have been successfully prepared by solvothermal methods followed by annealing of the precursors at 300 °C. Experimental results show that the morphology and phase are strongly influenced by the solvents used. Moreover, we have developed gas sensors based on ultrathin In2O3 nanorods, which demonstrate excellent o-dichlorobenzene and chlorobenzene sensing properties, superior to those of nanoparticles with a similar size. It is expected that our as-synthesized In2O3 nanorods could potentially be applied in real-time monitoring of polychlorobenzene concentrations in the future. © the Partner Organisations 2014.

Li Q.,Chinese University of Hong Kong | Zhang C.,Chinese University of Hong Kong | Ma J.,Hunan University | Wang G.,CAS Hefei Institutes of Physical Science | Ng D.H.L.,Chinese University of Hong Kong
ChemCatChem | Year: 2014

The ultra-small Ag nanocrystallite-decorated TiO2 hollow sphere heterostructures were fabricated by using a two-step hydrothermal method. These heterostructures demonstrated an excellent photodegradation performance of rhodamine B. The photodegradation efficiency could reach up to 100 % within 20 min under simulated sunlight irradiation. XRD, field emission SEM, TEM, scanning TEM, high-resolution TEM coupled with energy-dispersive X-ray spectroscopy, UV/Vis absorption and photoluminescence spectroscopy, X-ray photoelectron spectroscopy, Mott-Schottky analysis, and hydroxyl radical measurements were used to correlate the structure, surface property, and energy band alignment of rhodamine B to its photocatalytic activity. In these metal-semiconductor heterostructures, the Ag nanocrystallites were highly crystalline and were distributed evenly on the surface of TiO2 hollow spheres with compact interfaces. They reduced the recombination rate of charge carriers and favoured the charge transfer across the interfaces. The increased surface adsorbed oxygen facilitated the generation of hydroxyl radicals, and the reduced surface defects increased the lifetime of charge carriers upon Ag loading. The Schottky barriers between Ag and illuminated TiO2, the upward shift of the Fermi level, and increased electron density due to Ag coupling contributed to the charge transfer and increase in quantum efficiency. These key factors involved in photocatalysis are of great importance to design functional and effective photocatalysts. Hollow, Hollow, Hollow: Ag-TiO2 hollow sphere heterostructures demonstrate an excellent photodegradation efficiency of rhodamine B under simulated sunlight irradiation owing to the excellent dispersion of Ag nanocrystallites, increase in surface adsorbed oxygen, and increased lifetime of charge carriers. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Liu K.,Hunan University | Zhang Q.,Huazhong University of Science and Technology | Chen J.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Zhang J.,Hunan University
IEEE Transactions on Industrial Electronics | Year: 2011

The ill-convergence of multiparameter estimation due to the rank-deficient state equations of permanent-magnet synchronous machines (PMSMs) is investigated. It is verified that the PMSM model for multiparameter estimation under id = 0 control is rank deficient for simultaneously estimating winding resistance, rotor flux linkage, and winding inductance and cannot ensure them to converge to the correct parameter values. A new method is proposed based on injecting a short pulse of negative id current and simultaneously solving two sets of simplified PMSM state equations corresponding to id = 0 and id ≠ 0 by using an Adaline neural network. The convergence of solutions is ensured, while the minimum |i d| is determined from the error analysis for nonsalient-pole PMSMs. The proposed method does not need the nominal value of any parameter and only needs to sample the winding terminal currents and voltages, and the rotor speed for simultaneously estimating the dq-axis inductances, the winding resistance, and the rotor flux linkage in nonsalient-pole PMSMs. Compared with existing methods, the proposed method can eliminate the estimation error caused by the variation of rotor flux linkage and inductance as a result of state change due to the injected d-axis current in the surface-mounted PMSM. The method is verified by experiments, and the results show that the proposed method has negligible influence on output torque and rotor speed and has good performance in tracking the variation of PMSM parameters due to temperature variation. © 2010 IEEE.

Gao T.,Norwegian University of Science and Technology | Wang T.,Hunan University
Crystal Growth and Design | Year: 2010

A one-dimensional (1D) to two-dimensional (2D) topotactic transformation has been proposed for the synthesis of 2D CdS nanosheets by promoting the lateral growth of 1D CdS nanobelts. The as-prepared nanosheets are single crystal with hexagonal structure, usually 20-100 nm in thickness, 20-100 μm in width, and up to several millimeters in length. CdS nanosheets show enhanced multiphonon responses and exciton-phonon couplings, which are correlated to their extraordinary anisotropic geometry. Photoluminescence measurement reveals three emission bands at about 1.61, 2.39, and 2.45 eV, which are attributed to the radiative transitions related to surface states, bandgap, and excitonic molecules, respectively; moreover, the formation of the surface states and the excitonic molecules are significantly enhanced due to the anisotropic geometry of the 2D nanosheets. CdS nanosheets show also pronounced photoconduction under visible light irradiation, indicating potentials in assembly of optoelectronic nanodevices. © 2010 American Chemical Society.

He X.,Hunan University | Zhao Y.,Hunan University | He D.,Hunan University | Wang K.,Hunan University | And 2 more authors.
Langmuir | Year: 2012

Adenosine-5′-triphosphate (ATP) is a multifunctional nucleotide, which plays a vital role in many biological processes, including muscle contraction, cells functioning, synthesis and degradation of important cellular compounds, and membrane transport. Thus, the development of ATP-responsive controlled release system for bioorganism application is very significative. Here, an original and facile ATP-responsive controlled release system consisting of mesoporous silica nanoparticles (MSN) functionalized with an aptamer as cap has been designed. In this system, the ATP aptamer was first hybridized with arm single-stranded DNA1 (arm ssDNA1) and arm single-stranded DNA2 (arm ssDNA2) to form the sandwich-type DNA structure and then grafted onto the MSN surface through click chemistry approach, resulting in blockage of pores and inhibition of guest molecules release. In the presence of ATP, the ATP aptamer combined with ATP and got away from the pore, leaving the arm ssDNA1 and ssDNA2 on the surface of MSN. The guest molecules can be released because single-stranded DNA is flexible. The release of the guest molecules from this system then can be triggered by the addition of ATP. As a proof-of-principle, Ru(bipy) 32+ was selected as the guest molecules, and the ATP-responsive loading and release of Ru(bipy)32+ have been investigated. The results demonstrate that the system had excellent loading efficiency (215.0 μmol g1 SiO2) and the dye release percentage can reach 83.2% after treatment with 20 mM ATP for 7 h. Moreover, the ATP-responsive behavior shows high selectivity with ATP analogues. However, the leakage of Ru(bipy)32+ molecule is neglectable if ATP was not added, indicating an excellent capping efficiency. Interestingly, this system can respond not only to the commercial ATP but also to the ATP extracted from living cells. By the way, this system is also relatively stable in mouse serum solution at 37 °C. This proof of concept might promote the application of ATP-responsive devices and can also provide an idea to design various target-responsive systems using other aptamers as cap. © 2012 American Chemical Society.

Zeng B.,Hunan University | Teng Z.,Hunan University
IEEE Transactions on Power Delivery | Year: 2011

Parameter estimation is an important topic in power system signal-processing tasks. A new class of windows, the cosine self-convolution window (CSCW), is proposed. The main-lobe and side-lobe behaviors of the first to the third order CSCWs are studied. A CSCW-based improved fast Fourier transform algorithm (FFT) for estimating power system signal parameters, such as frequency, phase, and amplitude, is given. The CSCW has a low peak side-lobe level, a high side-lobe decaying rate, and a simple spectral representation. Leakage errors and harmonic interferences are thus reduced considerably by weighting samples with the CSCW. The CSCW-based improved FFT algorithm can be easily implemented in embedded systems. The effectiveness of the proposed method was analyzed by means of computer simulations and practical experiments for multifrequency signals with the variations of the power system frequency as well as the presence of white noise and interhamonics. © 2010 IEEE.

Liu C.-X.,Hunan University | Liu Q.,Hunan University | Guo C.-C.,Hunan University
Catalysis Letters | Year: 2010

In this paper, a series of nanoparticle bonded metalloporphyrins with different saturation magnetization were synthesized by a modified silanation method. Under geomagnetic field (5 × 10-5 T), with the increase of the saturation magnetizations, the growth rate of yields of cyclohexanol in the cyclohexane oxidation with iodosylbenzene catalyzed by these nanoparticle bonded metalloporphyrins followed the order of ironporphyrin > manganeseporphyrin > cobaltporphyrin. Graphical Abstract: A series of nanoparticle bonded metalloporphyrins with different saturation magnetization were synthesized by a modified silanation method. Under geomagnetic field (5 × 10-5 T), with the increase of the saturation magnetizations, the growth rate of yields of cyclohexanol in the cyclohexane oxidation with iodosylbenzene catalyzed by these nanoparticle bonded metalloporphyrins followed the order of ironporphyrin > manganeseporphyrin > cobaltporphyrin. © 2010 Springer Science+Business Media, LLC.

Lin W.,Hunan University | Long L.,Hunan University | Chen B.,Hunan University | Tan W.,Hunan University | Gao W.,Hunan University
Chemical Communications | Year: 2010

A fluorescence turn-on probe for Cu2+ based on the novel copper-mediated dihydrorosamine oxidation reaction has been constructed and employed in the detection of Cu2+ in water, new born calf serum, and living cells, and the new copper-mediated dihydrorosamine oxidation reaction likely proceeds by a copper redox mechanism. © 2010 The Royal Society of Chemistry.

Xia B.,Hunan University | Yu D.,Hunan University | Liu J.,Hunan University
Computer Methods in Applied Mechanics and Engineering | Year: 2013

For the acoustic field prediction without sufficient information, an interval random model is introduced to treat with the uncertain parameters in which the probability distribution parameters of random variables are modeled as interval variables instead of given precise values. Based on the interval random model, the hybrid uncertain acoustic dynamic equilibrium equation is constructed and a hybrid uncertain analysis method is proposed. In the proposed method, the interval random matrix and vector are expanded by the first-order Taylor series and the sound pressure response vector is obtained by the matrix perturbation technique. A monotonic analysis is conducted for the sound pressure response vector and based on it the lower and upper bounds of the sound pressure response vector are obtained by the vertex method. According to the response bounds, the intervals of expectation and variance of the sound pressure response vector are calculated by the random interval moment method. Two numerical examples which include a simple problem with explicit expression and a complex engineering application are presented to demonstrate the effectiveness of the present method. © 2012 Elsevier B.V.

Zheng K.,Hunan University | Lin W.,Hunan University | Tan L.,Hunan University
Organic and Biomolecular Chemistry | Year: 2012

We have constructed a new fluorescence turn-on chemosensor for hydrogen sulfide based on a phenanthroimidazole scaffold, and the novel sensor is suitable for imaging hydrogen sulfide in living cells. This journal is © The Royal Society of Chemistry 2012.

Metoprolol (MET) is a β1-adrenoceptor antagonist, which is widely used in the treatment of cardiovascular diseases, and α-hydroxymetoprolol (α-OHM) is its hydroxylated metabolite. Owing to their similar structures, optimization of the condition for the chromatography approach, which is in common use for determination, is both time consuming and laborious. A new and effective strategy that combines the excitation-emission matrix fluorescence with second-order calibration methods was developed for simultaneous determination of MET and α-OHM in human plasma. Although the fluorescence spectra of MET and α-OHM overlapped and a large number of unknown and uncalibrated fluorescent components coexisted, the developed method enables accurate concentrations together with reasonable resolution of excitation and emission profiles for the analytes of interest. An additional advantage of the proposed method is that there is no need for separation and sample pretreatment, in addition to lower cost than traditional methods.

Jiang C.,Hunan University | Bi R.G.,Hunan University | Lu G.Y.,Hunan University | Han X.,Hunan University
Computer Methods in Applied Mechanics and Engineering | Year: 2013

By using the convex model approach, the bounds of the uncertain parameters are only required rather than their precise probability distributions, based on which it can be made possible to conduct the reliability analysis for many complex engineering problems with limited information. In this paper, a non-probabilistic reliability model is given for structures with convex model uncertainty, which is defined as a ratio of the multidimensional volume falling into the reliability domain to the one of the whole convex model. A Monte Carlo simulation is then formulated for the reliability model to obtain a reference solution. A first order approximation method (FOAM) is proposed to solve the reliability model based on a linear approximation of the failure surface. A second order approximation method (SOAM) is further formulated to improve the reliability analysis precision for limit-state functions with relatively strong nonlinearity. By introducing the suggested reliability model, a convex-model-based system reliability method is also formulated. Eight numerical examples are provided to demonstrate the effectiveness of the present methods. © 2012 Elsevier B.V.

Lin W.,Hunan University | Yuan L.,Hunan University | Cao Z.,Hunan University | Feng Y.,Hunan University | Song J.,Hunan University
Angewandte Chemie - International Edition | Year: 2010

"Chemical Equation Presented" Cassette recording: A new class of coumarin-rhodamine through-bond energy-transfer (TBET) cassettes with minimal spectral overlap between the donor emission and the acceptor absorption (see picture) show large pseudo-Stokes shifts (up to 230 nm) and emission shifts (up to 170 nm). The utility of this TBET platform for TBET-based probe development was demonstrated by a new ratiometric fluorescence pH probe. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

Zhang M.,Hunan University | Chen G.,Hunan University | Zhou Y.,Hunan University | Li S.,Hunan University
Optics Express | Year: 2013

Keyhole formation is a prerequisite for deep penetration laser welding. Understanding of the keyhole dynamics is essential to improve the stability of the keyhole. Direct observation of the keyhole during deep penetration laser welding of a modified "sandwich" specimen with a 10 kW fiber laser is presented. A distinct keyhole wall and liquid motion along the wall are observed directly for the first time. The moving liquid "shelf" on the front keyhole wall and the accompanying hydrodynamic and vapor phenomena are observed simultaneously. Micro-droplets torn off the keyhole wall and the resultant bursts of vapor are also visualized. The hydrodynamics on the keyhole wall has a dominant effect on the weld defects. The emission spectrum inside the keyhole is captured accurately using a spectrometer to calculate the characteristics of the keyhole plasma plume. ©2013 Optical Society of America.

Li X.,Hunan University | Liao B.,Hunan University | Chen H.,Hunan University
Journal of Theoretical Biology | Year: 2015

Complex diseases usually involve complex interactions between multiple loci. The artificial intelligent algorithm is a plausible strategy to evade combinatorial explosion. However, the randomness of solution of this algorithm loses decreases the confidence of biological researchers on this algorithm. Meanwhile, the lack of an efficient and effective measure to profile the distribution of cases and controls impedes the discovery of pathogenic epistasis. Here we present an efficient method called maximum dissimilarity-minimum entropy (MDME) to analyze breast cancer single-nucleotide polymorphism (SNP) data. The method searches risky barcodes, which to increase the odds ratio and relative risk of the breast cancer. This method based on the hypothesis that if a specific barcode is associated with a disease, then the barcode permits distinction of cases from controls and more importantly it shows a relative consistent pattern in cases. An analysis based on simulated dataset explains the necessity of minimum entropy. Experimental results show that our method can find the most risky barcode that contributes to breast cancer susceptibility. Our method may also mine several pathogenic barcodes that condition the different subtypes of cancer. © 2014 Elsevier Ltd.

Luo Z.-C.,South China Normal University | Liu M.,South China Normal University | Liu H.,South China Normal University | Zheng X.-W.,South China Normal University | And 5 more authors.
Optics Letters | Year: 2013

We report on the generation of passive harmonic mode locking of a fiber laser using a microfiber-based topological insulator (TI) Bi2Te3 saturable absorber (SA). The optical deposition method was employed to fabricate the microfiber-based TISA. By virtue of the excellent nonlinear optical property of the proposed TISA, the fiber laser could operate at the pulse repetition rate of 2.04 GHz under a pump power of 126 mW, corresponding to the 418th harmonic of fundamental repetition frequency. The results demonstrate that the microfiber-based TI photonic device can operate as both the high nonlinear optical component and the SA in fiber lasers, and could also find other applications in the related fields of photonics. © 2013 Optical Society of America.

Li F.,Hunan University | Li F.,Zte United States Inc. | Yu J.,Zte United States Inc. | Fang Y.,Fudan University | And 3 more authors.
Optics Express | Year: 2014

We experimentally demonstrated a 256-ary quadrature amplitude modulation (256QAM) direct-detection optical orthogonal frequency division multiplexing (DDO-OFDM) transmission system utilizing a costeffective directly modulated laser (DML). Intra-symbol frequency-domain averaging (ISFA) is applied to suppress in-band noise while the channel response estimation and Discrete Fourier Transform-spread (DFT-spread) is used to reduce the peak-to-average power ratio (PAPR) of the transmitted OFDM signal. The bit-error ratio (BER) of 15-Gbit/s 256QAM-OFDM signal has been measured after 20-km SSMF transmission that is less than 7% forward-error-correction (FEC) threshold of 3.8 × 10-3 as the launch power into fiber is set at 6dBm. For 11.85-Gbit/s 256QAM-OFDM signal, with the aid of ISFA-based channel estimation and PAPR reduction enabled by DFT-spread, the BER after 20-km SSMF transmission can be improved from 6.4 × 10-3 to 6.8 × 10-4 when the received optical power is -6dBm. © 2014 Optical Society of America.

Xia B.,Hunan University | Yu D.,Hunan University | Liu J.,Hunan University
Journal of Sound and Vibration | Year: 2013

In this paper, hybrid perturbation Monte-Carlo method (HPMCM) and hybrid perturbation vertex method (HPVM) are developed for the hybrid uncertain structural-acoustic problem with random and interval variables. The random variables are used to treat the uncertain parameters with sufficient information; whereas, the interval variables are used to treat the uncertain parameters with limited information. In HPMCM, the intervals of expectation and variance of the frequency response vector are calculated by a combination of random interval matrix perturbation method, random interval moment method and Monte-Carlo method. In HPVM, a monotonicity analysis is conducted for the frequency response vector based on the random interval matrix perturbation method; and then the intervals of expectation and variance of the frequency response vector are calculated by employing the random interval moment method and the vertex method. Numerical results on a shell structural-acoustic problem verify the effectiveness and high efficiency of HPVM compared with HPMCM. © 2012 Elsevier Ltd.

Liu F.,Hunan University
Lecture Notes in Electrical Engineering | Year: 2015

The evaluation index system of influence of Chinese golf websites includes website scale, inbound link, website traffic, website utilization rate, etc. Choosing 17 Chinese golf websites as the object of the research, this chapter evaluates their influence on the basis of grey relational analysis and finds that the influence of golf vertical portals is comparatively high, but the impact of most of the Chinese golf websites is low, which are badly in need of reinforcement and promotion. © Springer International Publishing Switzerland 2015.

Chen M.,Hunan University | He J.,Hunan University | Tang J.,Hunan University | Wu X.,Beijing Jiaotong University | Chen L.,Hunan University
Optics Express | Year: 2014

In this paper, a FPGAs-based real-time adaptively modulated 256/64/16QAM-encoded base-band OFDM transceiver with a high spectral efficiency up to 5.76bit/s/Hz is successfully developed, and experimentally demonstrated in a simple intensity-modulated direct-detection optical communication system. Experimental results show that it is feasible to transmit a raw signal bit rate of 7.19Gbps adaptively modulated real-time optical OFDM signal over 20km and 50km single mode fibers (SMFs). The performance comparison between real-time and off-line digital signal processing is performed, and the results show that there is a negligible power penalty. In addition, to obtain the best transmission performance, direct-current (DC) bias voltage for MZM and launch power into optical fiber links are explored in the real-time optical OFDM systems. © 2014 Optical Society of America.

Liu H.,South China Normal University | Zheng X.-W.,South China Normal University | Liu M.,South China Normal University | Zhao N.,South China Normal University | And 6 more authors.
Optics Express | Year: 2014

We reported on the generation of femtosecond pulse in a fiber ring laser by using a polyvinyl alcohol (PVA)-based topological insulator (TI), Bi2Se3 saturable absorber (SA). The PVA-TI composite has a low saturable optical intensity of 12 MW/cm2 and a modulation depth of ∼3.9%. By incorporating the fabricated PVA-TISA into a fiber laser, mode-locking operation could be achieved at a low pump threshold of 25 mW. After an optimization of the cavity parameters, optical pulse with ∼660 fs centered at 1557.5 nm wavelength had been generated. The experimental results demonstrate that the PVA could be an excellent host material for fabricating high-performance TISA, and also indicate that the filmy PVA-TISA is indeed a good candidate for ultrafast saturable absorption device. © 2014 Optical Society of America.

Xu D.,Hunan University | Yu Q.,China Automotive Technology and Research Center | Zhou J.,Hunan University | Bishop S.R.,University College London
Journal of Sound and Vibration | Year: 2013

This paper presents a nonlinear magnetic low-frequency vibration isolator designed with the characteristic of quasi-zero stiffness (QZS). An approximate expression of the magnet repulsive force is proposed and a unique analytical relationship between the stiffness of vertical spring and initial gap settings of the magnet springs is derived for the QZS system. Based on the harmonic balance (HB) method, the force transmissibility is formulated and the jumping frequencies, effect of excitation force and damping ratio are discussed for characteristic analysis. An experimental prototype is developed and tested. The performance of the QZS system is verified through a series of experimental studies showing that the new model greatly outperforms standard linear isolation systems especially in low-frequency domain. The tuning techniques for adapting to the change of loading mass and adjusting the QZS property in practice are also addressed. © 2013 Elsevier Ltd. All rights reserved.

Fu Y.,Hunan University | Chen Y.,Hunan University | Zhang P.,Hunan University
Meccanica | Year: 2013

The thermal buckling problem of functionally graded beam with longitudinal crack is presented in the paper. The whole beam is divided into four sub-beams and each one is modeled as a Timoshenko beam. The buckling governing equation of each sub-beam in thermal environment is established by using Hamilton Principle. Combining with the boundary conditions, the continuous conditions of the displacements and the forces, the buckling governing equations are solved by both the analytical and numerical methods. The buckling modes and critical buckling temperatures are obtained, and the effects of the functionally graded index, crack length, crack depth, and crack longitudinal location on the buckling characteristics of beams are discussed in numerical examples. © Springer Science+Business Media 2012.

Yin J.,Norwegian University of Science and Technology | Yin J.,Hunan University | Yang J.,Chalmers University of Technology | Pantaleev M.,Chalmers University of Technology | Helldner L.,Chalmers University of Technology
IEEE Transactions on Antennas and Propagation | Year: 2013

Future ultra-wideband (UWB) radio telescopes require UWB feeds for reflector antennas, and many new UWB feed technologies have gained substantial progress to satisfy the tough specifications for future radio telescope projects, such as the square kilometer array (SKA). It has been noticed that, different from traditional narrow-band horn feeds, all UWB feeds are non-BOR (Body of Revolution) antennas. Therefore, BOR1 efficiency becomes an important characterization for the modern UWB feed technologies. We present a novel circular Eleven feed, constructed of 'circularly' curved folded dipoles printed on flat circuit boards, in order to have high BOR1 efficiency at a low manufacture cost. The Genetic Algorithm (GA) optimization scheme has been applied to the design for achieving a low reflection coefficient. Simulated and measured results show that the circular Eleven feed has a reflection coefficient below-6 dB over 1.6-14 GHz and below-10 dB over 78% of the band, and an aperture efficiency higher than 60% over 1-10 GHz and 50% up to 14 GHz. © 2013 IEEE.

Xia B.,Hunan University | Yu D.,Hunan University
Journal of Vibration and Acoustics, Transactions of the ASME | Year: 2013

To calculate the probability density function of the response of a random acoustic field, a change-of-variable perturbation stochastic finite element method (CVPSFEM), which integrates the perturbation stochastic finite element method (PSFEM) and the change-ofvariable technique in a unified form, is proposed. In the proposed method, the response of a random acoustic field is approximated as a linear function of the random variables based on a first order stochastic perturbation analysis. According to the linear relationship between the response and the random variables, the formal expression of the probability density function of the response of a random acoustic field is obtained by the change-of-variable technique. The numerical examples on a two-dimensional (2D) acoustic tube and a three-dimensional (3D) acoustic cavity of an automobile cabin verify the accuracy and efficiency of the proposed method. Hence, the proposed method can be considered as an effective method to quantify the effects of the parametric randomness of a random acoustic field on the sound pressure response. Copyright © 2013 by ASME.

Yuan L.,Hunan University | Lin W.,Hunan University | Chen B.,Hunan University | Xie Y.,Hunan University
Organic Letters | Year: 2012

Coumarin-rhodamine-based compounds 1a,b were rationally designed and synthesized as novel FRET ratiometric fluorescent chemodosimeters. Ratiometric chemodosimeters 1a,b exhibit several favorable features, including a large variation in the emission ratio, well-resolved emission peaks, high sensitivity, high selectivity, low cytotoxicity, and good cell membrane permeability. Importantly, these excellent attributes enable us to demonstrate ratiometric imaging of Cu 2+ in living cells by using these novel ratiometric fluorescent chemodosimeters. © 2011 American Chemical Society.

Wu H.,Hunan University | Liu S.,Hunan University | Jiang J.,Hunan University | Shen G.,Hunan University | Yu R.,Hunan University
Chemical Communications | Year: 2012

A novel electrochemical biosensor was developed for activity assay of DNA methyltransferase and its inhibitor based on methylation-sensitive cleavage, which activated a primer for terminal transferase-mediated extension of biotinylated dUTP followed by sensitive detection via enzymatic amplification. © The Royal Society of Chemistry 2012.

Wang M.-F.,Hunan University
International Journal for Numerical Methods in Biomedical Engineering | Year: 2011

On the basis of the applied loadings simulated by piecewise interpolation polynomials, a precise integration method using the Ritz vectors and a modified Krylov precise integration method are presented. The Ritz method is used to reduce the dimension of structural dynamic equations and the Krylov subspace method is applied to reduce the dimension of the exponential matrix required in the evaluation. The Padé approximation is employed in computing the initial matrices required for the recurrence evaluations of the exponential matrices of reduced size. The new cut-off criteria proposed in this paper are used to determine the required number of the Ritz vectors and the required size of the Krylov subspace. The accuracy of the time integration schemes presented is studied and compared with those of other commonly used schemes. The time integration schemes presented have arbitrary order of accuracy, wider application and are less time-consuming. Two numerical examples are also presented to demonstrate the applicability of the proposed methods. © 2010 John Wiley & Sons, Ltd.

Wang H.,Hunan University | Li E.,Central South University | Li G.Y.,Hunan University
Computational Mechanics | Year: 2011

This paper presents a crashworthiness design optimization method based on a metamodeling technique. The crashworthiness optimization is a highly nonlinear and large scale problem, which is composed various nonlinearities, such as geometry, material and contact and needs a large number expensive evaluations. In order to obtain a robust approximation efficiently, a probability-based least square support vector regression is suggested to construct metamodels by considering structure risk minimization. Further, to save the computational cost, an intelligent sampling strategy is applied to generate sample points at the stage of design of experiment (DOE). In this paper, a cylinder, a full vehicle frontal collision is involved. The results demonstrate that the proposed metamodel-based optimization is efficient and effective in solving crashworthiness, design optimization problems. © 2010 Springer-Verlag.

Wang Q.,Hunan University | Yang L.,Hunan University | Yang X.,Hunan University | Wang K.,Hunan University | And 3 more authors.
Chemical Communications | Year: 2012

Based on the "Y" junction structure and restriction endonuclease-aided target recycling strategy, an electrochemical biosensor for DNA detection was developed. This universal biosensor was suitable for detecting different sequences of target DNA by changing the sequence of capture and assistant strands. © 2012 The Royal Society of Chemistry.

Tan Z.P.,Hunan University
Applied Mechanics and Materials | Year: 2014

With the increasing development of modern social information degree, the multimedia technology and network technology have rapid development, and the society puts forward new requirements for the education industry. Accordingly, this paper uses virtual design of Flash3D animation to development and design demonstration system of track and field action. The system uses the built-in method to extract the feature of track and field action, and uses the wavelet reconstruction algorithm to reconstruct the action, so as to achieve the function of action learning. We use Adobe Flash CS65 of the system to extract 5 groups of 1025 movements and reconstruct 10 groups of 2256 movements. Comparing the reconstructed image with the actual image frames, we found the new images reconstructed by the demonstration system are consisting with the real images frame. It provides a new computer method for teaching track and field action. © (2014) Trans Tech Publications, Switzerland.

Ouyang X.,Hunan University | Liu J.,Hunan University | Li J.,Hunan University | Yang R.,Hunan University
Chemical Communications | Year: 2012

Combining a DNA intercalator, SYBR Green I, and enzyme-linkage reactions with carbon nanoparticles, a low-background biosensing platform for label-free and sensitive fluorescent assay of DNA methylation is reported. © 2012 The Royal Society of Chemistry.

Stand-alone hybrid photovoltaic(PV)-wind-diesel-battery system is becoming an appropriate choice of power supply system for remote areas far from the power grid. However, the sizing optimization of the stand-alone hybrid PV-wind-diesel-battery system is difficult because of the system’s complexity. In this paper, a novel improved fruit fly optimization algorithm-based multi-objective optimization method is proposed for the optimization design of this system. Here, the objectives to be minimized are the annual total cost and the pollutant emission of the system. The obtained solutions of the best Pareto front can help decision-makers to choose the prior one. The simulation conducted in this paper is based on real data collected from Dongao Island. Simulation results show the excellent properties of the proposed optimization method and demonstrate the feasibility of the stand-alone hybrid PV-wind-diesel-battery system in Dongao Island. © 2015 Springer-Verlag Berlin Heidelberg

This paper concerns with the anti-periodic solutions for a class of shunting inhibitory cellular neural networks model with oscillating coefficients in leakage terms. By applying contraction mapping fixed point theorem and differential inequality techniques, we establish some sufficient conditions for the existence and exponential stability of anti-periodic solutions for the model, which complement with some recent ones. Moreover, an example and its numerical simulation are given to support the theoretical results. © 2015 Elsevier B.V.

Chen C.-F.,Hunan University | Wu M.-T.,Hunan University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

The upper-geosynthetic-encased stone column (UGESC) is widely used in engineering practice as a composite foundation. Its failure modes are analyzed herein. Two models are established for the swelling failure mode of UGESC based on the Meyerhof approach and the Terzaghi approach for calculating the bearing capacity of deep foundations by introducing the block limit equilibrium method and considering the effect of self-weight of soils and surrounding skin friction of the encased segment. The stochastic optimization algorithm is employed to search for the critical slip surface, and the corresponding ultimate bearing capacity can be obtained by solving the established models. The comparative analysis of the test results and those from other approaches demonstrates that this novel computing method coincides more with the engineering practice. With respect to the bearing capacity, the optimal encased depth of UGESC is approximately four times the diameter of the stone columns.

Yang L.,Hunan University | Chen B.,Hunan University | Luo S.,Hunan University | Li J.,Hunan University | Liu R.,Hunan University
Environmental Science and Technology | Year: 2010

CdTe quantum dots (QDs) are prepared on TiO2 nanotubes (TiO 2 NTs), for the first time, with pulse electrodeposition. A novel single-drop optical sensor is prepared with the CdTe QDs-modified TiO 2 NTs, and applied for the detection of polycyclic aromatic hydrocarbons (PAHs) based on fluorescence resonance energy transfer (FRET). Excited at 270 nm, the sensor shows fluorescence emission at around 370 nm. As PAHs are with absorption/fluorescence emission at around 364/410 nm, FRET happens between the CdTe QDs and PAHs with the CdTe QDs as donors and PAHs as receptors. The sensitivity is dependent on the number of rings of the PAHs, with the highest sensitivity observed in the response to benzo(a)pyrene (BaP). Using FRET, the sensitivity to BaP is enhanced by about 2 orders with respect to the direct fluorescent spectrometry. The proposed sensor shows a linear response to the logarithm of BaP concentration in the range of 400 nM to 40 pM, with a detection limit of 15 pM, which is much close to the quality criteria (15.1 pM) in drinking water set by U.S. Environment Protection, suggesting that the proposed sensor can be used for quick scanning of PAHs. The achieved sensitivity is much higher than that of the published sensor-based methods. As PAHs are quantified based on the relative fluorescence intensity at 410-370 nm, the sensor need no calibration with a standard sensor, avoiding the influence from the sensor-to-sensor difference. The practicability of the sensor is tested by analyzing PAHs in Xiangjiang River water, the PAHs contents ranges from 0.045 to 2.847 ng/L based on the sampling spots. © 2010 American Chemical Society.

Yuan L.,Hunan University | Zuo Q.-P.,First Hospital of Changsha
Sensors and Actuators, B: Chemical | Year: 2014

Hydrogen sulfide (H2S) is now recognized as an important biological regulator and plays an important role in a vast number of physiological and pathological processes. However, understanding the important functions of H2S has remained challenging, in part due to the lack of tools for detecting endogenous H2S. Here, compound 2 was synthesized with one step reaction as a novel fluorescent turn-on probe for H2S on the basis of H2S-promoted thiolysis of dinitrophenyl ether. This free probe displayed almost no background signals due to both PET and ICT double signaling quenching mechanism. Thus, this probe shows large fluorescent turn-on and selectivity response to H2S and can be used for the fluorescence detection of both exogenous and endogenous H2S in cells with satisfactory sensitivity. Moreover, it was also applied for direct visualization of H2S in living tissues with two-photon microscopy. In addition to providing a highly sensitive and selective reaction-based fluorescent probe for H2S, the insights into the double signaling quenching mechanism controlling the signal-to-noise ratio of fluorescent turn-on probe may guide the design of fluorescent turn-on probes with better signal-to-noise ratio. © 2014 Elsevier B.V.

The flow field around a box girder of a large span cable-stayed bridge, under Reynolds number of 1.27×105, is computed by using three-dimensional large eddy simulation (LES). The flow results under various angles of attack are obtained and compared with wind tunnel tests. The distribution of mean and RMS value of pressure around the girder surface are also provided. Investigation on fluctuating pressure on the girder surface is carried out through power spectrum density (PSD) and spatial coherent analysis. The research shows that the flow structure around the girder is characterized by the flow separated from the girder windward corners, reattachment on the girder upper surface, the primary vortices shedding within the reattachment region, vortex convection and alternatively shedding in the wake. The fluctuating pressure on the girder surface is clearly dominated by the presence of primary vortices. It is found that the primary vortices are not shed synchronously in girder span-wise direction, and the vortex shedding energy is concentrated on a narrow band of frequency. The fluctuating pressure on the girder lower surface, on the area upstream the reattachment region on girder upper surface is in phase, which is out of phase with that on the upper surface of leeward air fairing and area close to the upper leeward corner. The recognized flow mechanism may help to optimize the aerodynamic shape of girder cross section for long-span bridges against wind loading. © 2014 Elsevier Ltd.

Cao X.,Hunan University | Lin W.,Hunan University | Wan W.,Hunan University
Chemical Communications | Year: 2012

We have constructed a novel NIR fluorescent turn-on Cu+ probe suitable for imaging endogenous Cu+ ions in living cells based on a tricarbocyanine scaffold and a high affinity Cu+ receptor. © The Royal Society of Chemistry 2012.

Wu D.,Hunan University | Zhang Q.,Hunan University | Chu X.,Hunan University | Wang H.,Hunan University | And 2 more authors.
Biosensors and Bioelectronics | Year: 2010

A novel electrochemical sensor has been developed for sensitive and selective detection of mercury (II) based on target-induced structure-switching DNA. A 33-mer oligonucleotide 1 with five self-complementary base pairs separated by seven thymine-thymine mismatches was first immobilized on the electrode via self-assembly of the terminal thiol moiety and then hybridized with a ferrocene-tagged oligonucleotide 2, leading to a high redox current. In the presence of Hg2+, mercury-mediated base pairs (T-Hg2+-T) induced the folding of the oligonucleotide 1 into a hairpin structure, resulting in the release of the ferrocene-tagged oligonucleotide 2 from the electrode surface with a substantially decreased redox current. The response characteristics of the sensor were thoroughly investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The effect of the reaction temperature on the response of the sensor was also studied in detail. The results revealed that the sensor showed sensitive response to Hg2+ in a concentration range from 0.1 nM to 5 μM with a detection limit of 0.06 nM. In addition, this strategy afforded exquisite selectivity for Hg2+ against other environmentally related metal ions, which was superior to that of previous anodic stripping voltammetry (ASV)-based techniques. The excellent sensitivity and selectivity signified the potential of the sensor for Hg2+ detection in real environmental samples. © 2009 Elsevier B.V. All rights reserved.

Zhu D.,Hunan University | Mobasher B.,Arizona State University | Vaidya A.,Arizona State University | Rajan S.D.,Arizona State University
Composites Science and Technology | Year: 2013

Woven fabrics are used in many applications, including ballistic armors, propulsion engine containment systems and fabric reinforced composites. In order to facilitate the design and improvement of such applications, this paper investigates the stress-strain response in warp and fill directions, the apparent Poisson's ratio, and the in-plane shear response of Kevlar 49 fabric including the possible effects of specimen size and pre-loading on the mechanical responses of the fabric. Full-field image analysis of the fabric under shear deformation is used to better understand the mechanisms related to in-plane shear. The experimental results show that the fabric exhibits non-linear and orthogonal behavior in tension, and can deform up to 20% before complete failure. It has identical Young's modulus (pre-peak elastic stiffness) in warp and fill directions, but has different crimp strain, tensile strength and ultimate strain. The apparent Poisson's ratio is a nonlinear function of strain and dependent upon the levels of pre-loading. It increases with strain quickly at the beginning and decreases gradually until the fabric fails. The shear response is highly nonlinear and has four distinct regions: linear elastic rotation region, dissipative rotation region, yarn compression region and shear locking region, and it is not dependent upon specimen size after normalization. © 2012 Elsevier Ltd.

Chen J.M.,Hunan University
Communications in Computer and Information Science | Year: 2012

This paper proposed an improved partition entropy coefficient (IPE) index by making using of the trend of partition entropy coefficient (PE) index to increase as the cluster number increases. Comparisons between IPE index and PE index and two existed cluster validity indexes are conducted on four real data sets. Experimental results show that IPE is able to identify the cluster number underlying the data set in the case that PE index is unable to do and outperforms the two existed cluster validity indexes. © Springer-Verlag Berlin Heidelberg 2012.

Jin J.,Hunan University | Wang C.,Hunan University
AEU - International Journal of Electronics and Communications | Year: 2012

This letter presents a single CDTA (Current Differencing Transconductance Amplifier)-based current-mode quadrature oscillator (QO). The proposed circuit structure is very simple, which only consists of one CDTA, one resistor and two capacitors, and it is easy for monolithic integration. The oscillation frequency of the QO can be electronically controlled by the bias current of the CDTA. Moreover, the oscillator can provide two quadrature current outputs. PSPICE simulation results are provided to verify all the theoretical analysis. © 2012 Elsevier GmbH.

Wu Y.,Hunan University | Chen Y.,Hunan University | Zhou J.,Hunan University
Materials Letters | Year: 2013

A facile aqueous solution synthesis of La(OH)3 nanorods and La2O3 nanoplates, only using La(NO3) 3·6H2O as the lanthanide source and formamide as the alkaline source at room temperature, is reported for the first time. After high temperature calcination, the 1D La(OH)3 nanorods evolved into 2D La2O3 nanoplates. A possible evolution mechanism during heat treatment was proposed. The photoluminescence (PL) characteristics of both La(OH)3 nanorods and La2O3 nanoplates were investigated with purple light under UV excitation, which showed potential applications in fluorescent devices. © 2012 Elsevier B.V.

Wu C.,Hunan University | Luo A.,Hunan University | Shen J.,University of Central Florida | Ma F.J.,Hunan University | Peng S.,Hunan University
IEEE Transactions on Power Electronics | Year: 2012

This paper presents a negative sequence compensation system based on a novel two-phase three-wire converter to eliminate a negative sequence current for the high-speed railway traction power system with a three-phase V/V traction transformer. In this compensation system, the proposed two-phase three-wire converter is fed by two single-phase power sources formed with two step-down transformers connecting to the two feeder sections. The proposed converter contains three switch legs, one of which is connected to the common ground wire of two single-phase voltages. Hence, a switch leg is saved compared with two conventional single-phase converters, and the ratings of the power switches are not increased. In order to enhance the dynamic and steady-state performances of the compensation system, a compound control method composed of hysteresis control and dividing frequency control is presented. Simulation and experimental results are presented to demonstrate that the proposed compensator and its control strategy are very effective. © 2011 IEEE.

Ge J.,Hunan University | Huang Z.-M.,Hunan University | Xi Q.,Hunan University | Yu R.-Q.,Hunan University | And 2 more authors.
Chemical communications (Cambridge, England) | Year: 2014

A novel fluorescent nanosensor has been developed for detecting biothiols including cysteine and glutathione using graphene oxide based hairpin DNA-selective fluorescence quenching and thymine-Hg(II)-thymine coordination-controlled hybridization chain reaction, which provides a simple but the most sensitive platform for biothiol assays.

Zhu L.,Hunan University | Bai S.,Hunan University | Chen K.,Hunan University
Surface and Coatings Technology | Year: 2012

Chemical vapor deposition (CVD) of rhenium coatings on a gourd shaped graphite substrate is studied. Effects of deposition temperature, chlorine flow rate, total pressure and chlorination temperature on deposition rate, yield, morphology and texture of rhenium coating are investigated, respectively. Uniform rhenium coatings have been obtained by using proper combination of deposition conditions at an acceptable deposition rate and yield. The rhenium coatings consist of two sub-layers, i.e., an inner nucleation layer of fine equiaxed grains and an outer layer comprising oriented columnar grains. Although different surface morphologies have been observed, the grains of rhenium coatings are all <002> oriented. The tendency of the preferred orientation <002> is more significant with decreasing surface roughness of the coating. © 2012 Elsevier B.V.

Li S.,Hunan University | Kang X.,Hunan University
IEEE Transactions on Consumer Electronics | Year: 2012

This paper proposes a weighted sum based multi-exposure image fusion method which consists of two main steps: three image features composed of local contrast, brightness and color dissimilarity are first measured to estimate the weight maps refined by recursive filtering. Then, the fused image is constructed by weighted sum of source images. The main advantage of the proposed method lies in a recursive filter based weight map refinement step which is able to obtain accurate weight maps for image fusion. Another advantage is that a novel histogram equalization and median filter based motion detection method is proposed for fusing multi-exposure images in dynamic scenes which contain motion objects. Furthermore, the proposed method is quite fast and thus can be directly used for most consumer cameras. Experimental results demonstrate the superiority of the proposed method in terms of subjective and objective evaluation. © 1975-2011 IEEE.

Fang Z.,Hunan University | Wang J.-Q.,Hunan University
Journal of Bridge Engineering | Year: 2012

The tension force of cables must be measured accurately during construction and maintenance stages for cable-supported bridge systems. On the basis of the transverse vibration equation of a cable and by using a curve-fitting technique to replace the numerical iterative process, a practical formula to estimate the cable tension is proposed in a simply explicit form, in which the bending stiffness of the cable is included, and the sag effect is neglected for simplicity by using the frequencies relative to antisymmetric or higher vibration modes of the cable. The capability of this formulation is verified through comparison with available experimental results and finite-element solutions, which indicate that the formula developed in this paper is sufficiently accurate and can be conveniently applied to field measurement for cable-supported bridge systems. © 2012 American Society of Civil Engineers.

He D.,Hunan University | He X.,Hunan University | Wang K.,Hunan University | Cao J.,Hunan University | Zhao Y.,Hunan University
Advanced Functional Materials | Year: 2012

A novel photon-fueled gate-like mesoporous silica nanoparticles (MSN)-based delivery system is reported. In this system, the malachite green carbinol base (MGCB) is immobilized on the nanochannel wall of MSN as a light-induced hydroxide ion emitter and i-motif DNA is grafted on the surface of MSN as a cap. Photoirradiation with 365 nm wavelength UV light makes MGCB molecules dissociate into malachite green (MG) cations and OH - ions, which induce the i-motif DNA to unfold into the single-stranded form due to the increase of the pH in the solution. Therefore, the pores are uncapped and the entrapped guest molecules are released. After the light is turned off, the MG cations recombine with the OH - ions and return to the MGCB forms. The pH value thus decreases and the single-stranded DNA switches back to i-motif structure to cap the pore again. Because of the photon-fueled MGCB-dependent DNA conformation changes, the i-motif DNA-gated switch can be easily operated by turning the light on or off. Importantly, the opening/closing protocol is highly reversible and a partial cargo release can be easily achieved at will. This proof-of-concept may promote the application of DNA in the controlled release and can also provide a way to design various photon-fueled controlled-release systems using a combination of some photoirradiated pH-jump systems and other kinds of pH-sensitive linkers. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yan H.,Hunan University | Li X.,Hunan University
Dianwang Jishu/Power System Technology | Year: 2013

With the promotion of low-carbon electricity, a large-amount of new energy sources such as wind farm and so on are connected to power grid. On the basis of the uncertainty of wind farms and small hydropower stations connected to the busbar in a certain provincial power grid, based on differential evolution and rough sets attribute reduction integrated with least square support vector machine (LSSVM) a method to analyze uncertainty of net load forecasting for busbar connected with distributed energy sources is proposed. Firstly, the output characteristics of wind farms and small hydropower stations connected to a busbar are researched and analyzed, and based on historical data the fitting of distribution function is performed; secondly, adopting thresholds with different confidence level, which obey to the output distribution of wind farms and small hydropower stations, the random output data of wind farms and small hydropower stations, which obeys to thresholds with different confidence under the same distribution is taken as the perturbation of load data, then based on differential evolution and rough sets attribute reduction integrated with LSSVM the uncertainty of busbar net load forecasting is analyzed. Simulation results of net load forecasting of busbar in a certain 220 kV substation show that the proposed method can be used to the net load forecasting of busbar connected with wind farms and small hydropower stations.

Zeng J.,Hunan University | Chen K.-Q.,Hunan University
Applied Physics Letters | Year: 2014

By using nonequilibrium Green's functions in combination with the density functional theory, we investigate the spin-dependent transport properties in a Fe-porphyrin-like carbon nanotube spintronic device. The results show that magnetoresistance ratio is strongly dependent on the magnetic configuration of the Fe-porphyrin-like carbon nanotube. Under the application of the external magnetic field, the magnetoresistance ratio of the device can be increased from about 19% to about 1020% by tuning the magnetic configuration in the device. Our results confirm that the magnetic configuration is a key factor for obtaining a high-performance spintronic device. © 2014 AIP Publishing LLC.

Dai H.-L.,Hunan University | Zheng H.-Y.,Hunan University
European Journal of Mechanics, A/Solids | Year: 2011

In this paper, investigation on buckling and post-buckling behaviors of a laminated cylindrical shell of functionally graded material (FGM) with the piezoelectric fiber reinforced composite (PFRC) actuators subjected to thermal and axial compressed loads is presented. Based on the Donnell assumptions, the material properties of the FGM layer vary smoothly through the laminated cylindrical shell thickness according to a power law distribution of the volume fraction of constituent materials. In the present study, a numerical procedure for the laminated cylindrical shell is used based on the Ritz energy method and the nonlinear strain-displacement relations. Some useful discussion and numerical examples are presented to show various effects of temperature field, volume fraction and geometric parameters on the buckling and post-buckling behaviors of the laminated cylindrical shell with PFRC. © 2011 Elsevier Masson SAS. All rights reserved.

Huang W.,Hunan University | Lin W.,Hunan University | Guan X.,Hunan University
Tetrahedron Letters | Year: 2014

In this work, we first studied the pH-dependent characteristic of chromenoquinoline. Based on this, we then designed and synthesized two novel chromenoquinoline derivatives that can act as fluorescent pH sensors. The pKa values of two novel chromenoquinoline derivatives can be modulated from 2.32 to 4.38 and 6.27 by introducing EDG on the backbone of chromenoquinoline. Furthermore, we demonstrate that the sensor 4 can be used as a ratiometric fluorescent pH sensor for fluorescence imaging in living cells. © 2013 Elsevier Ltd. All rights reserved.

Lin Y.,Hunan University | Bao L.,East China University of Science and Technology | Wei Y.,Fudan University
IEEE Transactions on Automatic Control | Year: 2010

In this technical note, we investigate the numerical solution of the projected generalized Sylvester equations via a matrix sign function method. Such equations arise in stability analysis and control problems for descriptor systems including model reduction based on balanced truncation. Unlike the classical matrix sign function iteration, we propose a modification of the matrix sign function method that converges quadratically for pencils of arbitrary index. Numerical experiments report the effectiveness of the modified method. © 2006 IEEE.

Wang H.,Hunan University | Li G.Y.,Hunan University | Li E.,Central South University
Computer Methods in Applied Mechanics and Engineering | Year: 2010

In automotive industry, structural optimization for crashworthiness criteria is of special importance in the early design stage. To reduce the vehicle design cycle, metamodeling techniques have become so widespread... In this study, a time-based metamodeling technique is proposed for the vehicle design. The characteristics of the proposed method are the construction of a time-based objective function and establishment of a metamodel by support vector regression (SVR). Compared with other popular metamodel-based optimization methods, the design space of the proposed method is expanded to time domain. Thus, more information and features can be extracted in the expanded time domain. To validate the performance of the time-based metamodeling technique, cylinder impacting and full vehicle frontal collision are optimized by the proposed method. The results demonstrate that the proposed method has potential capability to solve the crashworthiness vehicle design. © 2010 Elsevier B.V.

Chen X.,Hunan University | Huang L.,Hunan University | Guo Z.,Hunan University
Neurocomputing | Year: 2013

Based on the tangency or non-tangency of the periodic solution to certain surface, this paper gives a set of conditions ensuring global convergence in finite time toward a unique periodic solution for Hopfield neural networks with discontinuous activations. Moreover, two numerical examples are provided to illustrate the theoretical results. © 2012 Elsevier B.V.

Wang K.,Hunan University
The Analyst | Year: 2013

Living cell studies can offer tremendous opportunities for biological and disease studies. Due to their high sensitivity and selectivity, minimum interference with living biological systems, ease of design and synthesis, fluorescent nucleic acid probes (FNAPs) have been widely used in living cell studies, such as for intracellular detection, cell detection, and cell-to-cell communication. Here, we review the general requirements and the recent developments in FNAPs for living cell studies. We broadly classify these designs as hybridization probes and aptamer probes. For hybridization probes, we describe recently developed designs, such as nanomaterial-based and amplification-based hybridization probes. For aptamer probes, we discuss four general paradigms that have appeared most frequently in the literature: nanomaterial-based, nanomachine-based, cell surface-anchored and activatable aptamer probe designs in vivo. FNAPs promise to open up new and exciting opportunities in biological marks detection for a wide range of biological and medical applications.

Liu G.,Hunan University | Shi H.,Hunan University | Yang Y.,North China Electrical Power University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

As power system is a non-analytical complex variable system, node voltages are not analytical complex-variable function of load current. In the plural domain, node voltages are not directly derivative of the load current, so there are still no papers using dynamic analytic method to study power system voltage stability. In this paper, the dynamic analytic method of non-analytical complex was derived; the comprehensive dynamic equivalent impedance of power system was defined; and the necessary condition when power system achieves limit transmission is that the comprehensive dynamic equivalence impedance mode is equal to load static equivalent impedance mode. By simulation and calculations, it proved that the necessary condition was right; load impedance modulus margin can accurately describe the system load node voltage stability level. Dynamic analytic method set a theoretical foundation to establish power system nonlinear equivalent model, and to apply nonlinear equivalent model to calculate limit power quickly and accurately. The maximum transmission power judgment criterion can be used to judge whether it is feasible to the solution of power flow equation for large-scale power system. © 2013 Chin. Soc. for Elec. Eng.

Liu G.,Hunan University | Yang Y.,North China Electrical Power University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

Voltage stability and angle stability are only two extreme conditions of power system stability analysis. When Jacobian matrix is singular, it's not only critical point of voltage stability, but static critical point of angle stability. According to the general principle of extreme value analysis of nonlinear equations, the equivalence relation of static angle stability and voltage stability