Xiangtan, China
Xiangtan, China

Xiangtan University, or XTU , is a university located in Xiangtan, Hunan. It was founded in 1958 and is organized into 22 Schools and Departments.Xiangtan University, located in Xiangtan City, the home town of Mao Zedong, is a comprehensive university operating under the joint support of the Hunan Provincial Government and the Ministry of Education. It is one of China’s first educational institutes authorized to award master’s degrees and is also among the earliest schools approved to enroll overseas students and students of national defense. In an evaluation conducted by the Ministry of Education, the university’s bachelor degree education was rated as excellent. Wikipedia.

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Kuang Y.,Peking University | Tang H.,Peking University | Tang H.,Xiangtan University
Journal of Statistical Physics | Year: 2017

This paper extends the model reduction method by the operator projection to the one-dimensional special relativistic Boltzmann equation. The derivation of arbitrary order globally hyperbolic moment system is built on our careful study of two families of the complicate Grad type orthogonal polynomials depending on a parameter. We derive their recurrence relations, calculate their derivatives with respect to the independent variable and parameter respectively, and study their zeros and coefficient matrices in the recurrence formulas. Some properties of the moment system are also proved. They include the eigenvalues and their bound as well as eigenvectors, hyperbolicity, characteristic fields, linear stability, and Lorentz covariance. A semi-implicit numerical scheme is presented to solve a Cauchy problem of our hyperbolic moment system in order to verify the convergence behavior of the moment method. The results show that the solutions of our hyperbolic moment system converge to the solution of the special relativistic Boltzmann equation as the order of the hyperbolic moment system increases. © 2017 Springer Science+Business Media New York

Xie J.,Xiangtan University | Zhong G.,Xiangtan University | Cai C.,Xiangtan University | Chen C.,Xiangtan University | Chen X.,Xiangtan University
Talanta | Year: 2017

As biomarkers of many diseases, glycoproteins are of great significance to clinical diagnostics. However, the determination of low abundant glycoproteins in complex biological samples without any pretreatment process is still a problem. In this study, a rapid and convenient separation method for highly efficient enrichment of glycoproteins is reported, based on pH double-responsive imprinted magnetic microspheres. Thin imprinted polymer shells were fabricated onto the surface of magnetic microspheres by free radical polymerization, using 2-(Dimethylamino) ethyl methacrylate as pH-sensitive monomer, 4-vinylphenylbronic acid as boronate affinity monomer, and ovalbumin (OVA) as template molecule. Combining the advantages of pH-sensitive monomer and boronate affinity monomer, rapidly capture-release of OVA could be modulated by changing solution pH. Moreover, high absorption ability (81.2 mg/g) was achieved within about 10 min. This study provided responsible way to imprint glycoproteins and showed great potential for glycoprotein detection in clinical diagnostic. © 2017 Elsevier B.V.

Nawaz A.,City University of Hong Kong | Mao W.G.,Xiangtan University | Lu C.,Curtin University Australia | Shen Y.G.,City University of Hong Kong
Journal of Alloys and Compounds | Year: 2017

The nanoscale elastic-plastic deformation behavior of single crystal 6H-SiC was systematically investigated by using nanoindentation with a Berkovich indenter. The effect of loading rates on the critical pop-in load, pop-in displacement and maximum shear stress was observed which indicates that phase transformation in 6H-SiC is highly unlikely. Results further indicated that the elastic-plastic transition was evidenced by stable pop-in events under conditions of an indentation load of 0.54 mN with a loading rate of 20 μN/s. In the load-independent region, hardness was determined as 33 ± 2 GPa and elastic modulus had a stabilized value of 393 ± 8 GPa. The significant indentation size effect and depth independent hardness in 6H-SiC was analyzed by Nix-Gao and proportional specimen resistance models. By coupling the Hertzian contact theory and Johnson's cavity model, elastic-plastic transitions were determined in detail. Johnson's cavity model was used to figure out the plastic zone size. The stress distribution was also calculated based on the critical load responsible for the elastic plastic transition. Theoretically, the calculated maximum tensile strength (13.5 GPa) and cleavage strength (31 GPa) revealed that the pop-in was not initiated by the cleavage fracture. The deformation behavior was further elaborated to confirm the slippage on the basal plane determined by the critical resolved shear stress and Schmidt factor analysis. © 2017

Hu Y.,Beijing Jiaotong University | Li D.,Beijing Jiaotong University | Shu S.,Xiangtan University | Niu X.,Shantou University
International Journal of Heat and Mass Transfer | Year: 2017

A multiple-relaxation-time (MRT) lattice Boltzmann (LB) model is proposed for simulating flow and heat transfer in the hydrodynamically and thermally anisotropic porous medium at the representative-elementary-volume (REV) scale. By selecting the appropriate equilibrium distributions, relaxation matrix and discrete force/heat source terms, the present MRT LB model can recover the correct Darcy–Brinkman–Forchheimer and energy equations with anisotropic permeability and thermal conductivity through the Chapman–Enskog procedure. Several natural convection problems in anisotropic porous medium are simulated to validate the present LB model. The corresponding numerical results are in good agreement with data in the available literature. Especially, natural convection in a cavity with two anisotropic porous layers is investigated. The numerical results indicates that, the use of anisotropic porous layer with some optimal parameters can produce higher rate of heat transfer compared with the isotropic porous layer. © 2016 Elsevier Ltd

Liu S.,Xiangtan University | Ge C.,Xiangtan University | Ling Y.,Xiangtan University | Tang H.,Xiangtan University
Australian Journal of Chemistry | Year: 2017

Polymers with ionic liquid (IL) moieties can undergo thermally induced solution phase transitions by adjusting the balance of hydrophilicity and hydrophobicity between the cations and anions of the IL moieties, thus making them attractive candidates towards various applications such as separation, sensing, and biomedicine. In the present study, a series of poly(γ-4-methylbenzyl-l-glutamate) pyridinium tetrafluoroborate conjugates (P1-P4) containing various pyridinium moieties (i.e. pyridinium, 2-methylpyridinium, 3-methylpyridinium, and 4-methylpyridinium) were prepared by nucleophilic substitution between poly(γ-4-chloromethylbenzyl-l-glutamate) and pyridine or methylpyridines with different substituent positions, followed by ion-exchange reaction in the presence of NaBF4. 1H NMR spectroscopy and Fourier transform infrared spectroscopy analyses confirmed the molecular structures of P1-P4. 1H NMR analysis additionally revealed that P1-P4 showed high grafting efficiency in the range of 93-97%. P1, P3, and P4 exhibited reversible UCST-type phase behaviours in both methanol and water, whereas P2 showed a reversible UCST-type phase behaviour in water only. Variable-temperature UV-visible spectroscopy was used to characterize the solution phase behaviours and UCST-type phase transition temperature (Tpt) values of P1-P4, which were in the range of 24.9-37.2°C in methanol (3mg mL-1) and 40.9-55.7°C in water (10mg mL-1). Tpt decreased significantly with decreasing polymer concentrations. © CSIRO 2017.

Ye R.,Shantou University | Xi Y.,Shantou University | Ma Y.,Xiangtan University
2016 1st IEEE International Conference on Computer Communication and the Internet, ICCCI 2016 | Year: 2016

In recent years, a lot of image encryption schemes based on chaotic systems have been extensively investigated to meet the increasing demand for real-time secure image transmission. In this paper, tent maps and swapping based confusion approach were applied to design an image encryption scheme so as to enhance the security and efficiency of chaos-based image cryptosystems. The security and performance of the proposed image encryption scheme have been analyzed thoroughly, including histograms, correlation coefficients, information entropy, key sensitivity analysis, key space analysis, differential analysis, etc. All the experimental results suggest that the proposed image encryption scheme is highly secure and robust to resist various common attacks, and therefore can be used for secure image and video communication applications. © 2016 IEEE.

Gong S.G.,Xiangtan University | Deng Y.B.,Xiangtan University | Xie G.L.,Xiangtan University | Zhang J.P.,Xiangtan University
IOP Conference Series: Earth and Environmental Science | Year: 2017

With the rising of wind power industry and the ever-growing scale of wind farm, the research for the wake performance of wind turbine has an important guiding significance for the overall arrangement of wind turbines in the large wind farm. The wake simulation model of 10kW horizontal-axis wind turbine is presented on the basis of Averaged Navier-Stokes (RANS) equations and the RNG k-ϵ turbulence model for applying to the rotational fluid flow. The sliding mesh technique in ANSYS CFX software is used to solve the coupling equation of velocity and pressure. The characters of the average velocity in the wake zone under rated inlet wind speed and different rotor rotational speeds have been investigated. Based on the analysis results, it is proposed that the horizontal spacing between the wind turbines is less than two times radius of rotor, and its longitudinal spacing is less than five times of radius. And other results have also been obtained, which are of great importance for large wind farms. © Published under licence by IOP Publishing Ltd.

Li Q.,Xiangtan University | Su Y.,Xiangtan University | Tan M.,Xiangtan University
2016 International Symposium on Electrical Engineering, ISEE 2016 | Year: 2016

As fatigue damage being the most important reason and basis of wind turbine maintenance, a novel active power dispatching approach was proposed to optimize the fatigue distribution of wind turbines in large-scale wind farms. In this approach, the relationship of fatigue and active power of a wind turbine was built. The grid demanded active power of a wind farm was dispatched to wind turbines according to the inverse proportion of fatigue of wind turbines. Especially, available power and lower limit power of a wind turbine were considered well over, so as to the reference active power of a wind turbine could be carried out. The results of simulation illustrate that the proposed solution is a feasible way to optimize fatigue distribution in wind farms and trace the grid demanded output of wind farms, which may contribute to lower visit of maintenance in a wind farm thus cutting down the maintenance cost of large-scale wind farms. © 2016 IEEE.

Lv Z.,Xiangtan University
Renewable and Sustainable Energy Reviews | Year: 2017

Using quantile regression technique, this paper explores the interaction effects of democracy and income on CO2 emissions in 19 emerging countries over the period 1997–2010. The results indicate a stronger and significant interaction impact on CO2 emissions only at the lower emission countries. Moreover, democracy reduces CO2 emissions but only if the country has already reached to a certain income level. The new empirical evidence from this study provides a more complete picture of the determinants of emissions throughout the conditional distribution, and these novel findings not only help advance the existing literature, but also can be of special interest to the country's policy makers, especially among the most democracy and least democracy nations. © 2017 Elsevier Ltd

Li Y.-X.,Xiangtan University | Wang Q.-Q.,CAS Beijing National Laboratory for Molecular | Yang L.,Xiangtan University | Yang L.,CAS Beijing National Laboratory for Molecular
Organic and Biomolecular Chemistry | Year: 2017

A convenient metal-free decarbonylative alkylation-aminoxidation of styrene derivatives with aliphatic aldehydes and N-hydroxyphthalimide (NHPI) to yield phthalimide protected alkoxyamines is developed. With DTBP as an oxidant and radical-initiator, this reaction smoothly converts aliphatic aldehydes into alkyl radicals and subsequently allows the cascade construction of C(sp3)-C(sp3) and C(sp3)-O bonds via radical-radical coupling. © The Royal Society of Chemistry.

Du W.,Anhui University | Jin S.,Anhui University | Xiong L.,Xiangtan University | Chen M.,Anhui University | And 5 more authors.
Journal of the American Chemical Society | Year: 2017

A large thiolate/phosphine coprotected Ag50(Dppm)6(SR)30 nanocluster was synthesized through the further growth of Ag44(SR)30 nanocluster and characterized by X-ray photoelectron spectroscopy (XPS), electrospray ionization mass spectrometry (ESI-MS), and single-crystal X-ray analysis. This new nanocluster comprised a 32-metal-atom dodecahedral kernel and two symmetrical Ag9(SR)15P6 ring motifs. The 20 valence electrons correspond to shell closure in the Jellium model. Moreover, this nanocluster could be alloyed by templated/galvanic metal exchange to the homologue AuxAg50-x(Dppm)6(SR)30 nanocluster; the latter showed much higher thermal stability than the Ag50(Dppm)6(SR)30 nanocluster. Further experiments were conducted to study the optical, electrical, and photoluminescence properties of both nanoclusters. Our work not only reports two new larger size nanoclusters but also reveals a new way to synthesize larger size silver and alloy nanoclusters, that is, controlled growth/alloying. (Figure Presented). © 2017 American Chemical Society.

Yang S.,Xiangtan University | He J.,Charles University | Zhou P.,Xiangtan University | Sun L.Z.,Xiangtan University
Journal of Magnetism and Magnetic Materials | Year: 2017

Using density function theory, we study the spin state control of transition metal doped MoS2 through H/F chemical decoration. The results indicate that the ground spin state of single TM (Mn, Fe, and Co) doped MoS2 is sensitive to its chemical environment. H/F chemical decoration on TM can effectively modulate their magnetic moment up to 1 μB, especially for the Mn doped system, the F decoration will produce the system show “spin ON” to “spin OFF” transition. Interestingly, the H decoration will increase the magnetic moment of TM doped MoS2 with 1 μB, however, the F decoration will reduce the magnetic moment of TM doped MoS2 with 1 μB. Such modulation derives from the anti-bonding and bonding nature between TM and H/F atom, respectively. Our results may open a new route to apply TM doped MoS2 to multistate memory. © 2016 Elsevier B.V.

Zha D.,Nanjing University of Science and Technology | Sun H.,Nanjing University of Science and Technology | Fu Y.,Nanjing University of Science and Technology | Ouyang X.,Xiangtan University | Wang X.,Nanjing University of Science and Technology
Electrochimica Acta | Year: 2017

As a widely concerned material for supercapacitors, nickel cobalt layered double hydroxides (NiCo-LDHs) often suffer from the inferior rate capability and cycling stability due to the low electrical conductivity and easy agglomeration. To address these shortcomings, a simple in-situ hydrolysis approach is successfully developed to construct a binder-free system consisting of acetate anion-intercalated nickel cobalt layered double hydroxides (A-NiCo-LDHs) and Ni foam (NF) without additional alkali sources. The resulting A-NiCoLDH/NF electrodes exhibited obviously enhanced capacitive properties owing to the unique nanostructure and strong synergistic effects. It is worth noting that the optimized A-Ni5Co5-LDH/NF electrode delivered the highest performance among the electrodes studied, including ultrahigh specific capacitance (2445 F g−1 at 0.5 A g−1) and superior rate capability (1644 F g−1 and 1383 F g−1 at 20 A g−1 and 50 A g−1, respectively), as well as satisfactory long-term endurance (∼93% capacitance retention after 10,000 cycles at 20 A g−1). The attractive performances and facile fabrication make the A-Ni5Co5-LDH/NF system a promising candidate for low-cost high-performance energy storage devices. © 2017 Elsevier Ltd

Wei X.,Xiangtan University | Li M.,Xiangtan University | Hu P.,Xiangtan University | Yang B.,Xiangtan University
Sensors and Actuators, B: Chemical | Year: 2017

Fluorescence imaging is a powerful tool to characterize cell membrane receptors which involve many important intracellular activities. However, the study of the membrane receptors’ senior behaviors is hindered by the static model characteristic of current fluorescence imaging strategies. To address this issue, we adapted a novel type of programmable binary chimera aptamer probes for intelligent fluorescence imaging of cell membrane receptors. Firstly, one binary chimera aptamer probe was successfully engineered to reiteratively image target receptor PTK7 on living cells. Besides, it also showed a distinct advantage of selectivity for signal regulation over conventional method such as trypsin treatment. Secondly, another probe was developed by employing a layered DNA nanostructure as the programmable signal regulating moiety. It allowed in situ visualizing the membrane receptor PTK7 in an AND logic manner using two DNA strands as inputs. Interestingly, it was among the first cell imaging probes which could differentiate the order-dependent interaction in a keypad-lock logic manner. Furthermore, an internal control was also successfully employed in these probes to improve imaging reliability by accounting for cell-to-cell variations and background. © 2016 Elsevier B.V.

Ye W.-B.,Xiangtan University
Applied Thermal Engineering | Year: 2017

Uniform air flow distribution is an important and fundamental issue to miscellaneous equipments. The detailed design method and design principle are presented in this work. The practical application for uniform air flow distribution is conducted according to the employed design method. Finite volume method (FVM) is used to verify the designed validation. The numerical treatment of convection terms in governing equations is based on the quadratic upwind interpolation of convective kinematics (QUICK) scheme. The well-know semi-implicit pressure-linked equation (SIMPLE) algorithm is used to treat the coupling of pressure and velocity fields. It is found that the design method is validated for the uniform air flow distribution. The unbalance rate of air flow distribution is less than 10%. Moreover, the uniform of air flow distribution can be further improved by adding vertical baffles. The developed design method is of great significance to obtain uniform air flow distribution. © 2016 Elsevier Ltd

Wu Y.,Xiangtan University | Duan X.,Xiangtan University | Jing G.,Xiangtan University | OuYang Q.,Xiangtan University | Tao N.,Xiangtan University
Postharvest Biology and Technology | Year: 2017

Sour rot is caused by Geotrichum citri-aurantii and is one of the devastating diseases in citrus fruit. This disease is difficult to control because of the lack of effective fungicides. In this study, cinnamaldehyde, a common food preservative, was evaluated to control postharvest sour rot in citrus fruit through in vivo and in vitro experiments. Results showed that cinnamaldehyde with a minimum inhibitory concentration and fungicidal concentration of 0.50 mL L−1 dose-dependently inhibited the mycelial growth of G. citri-aurantii. The application of wax with cinnamaldehyde (WCA; 0.50, 1.0, and 2.0 mL L−1) significantly reduced the incidence of sour rot on citrus fruit inoculated with G. citri-aurantii during storage. After 8 d of storage, the decay incidences in the fruit treated with WCA (0.50, 1.0, and 2.0 mL L−1) were only 80%, 77% and 50%, respectively. By contrast, the decay incidence in the control fruit was 100%. In addition, WCA treatment increased the activities of superoxide dismutase (SOD), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL), but did not affect the activities of catalase (CAT) and peroxidase (POD), and the total phenol content. Our results suggested that WCA might induce defense responses against sour rot in citrus fruit. © 2017 Elsevier B.V.

Wang L.,Changsha University of Science and Technology | Dai L.,Changsha University of Science and Technology | Zhang X.,Xiangtan University | Zhang J.,Changsha University of Science and Technology
Materials | Year: 2017

The filling of strand corrosion products during concrete crack propagation is investigated experimentally in the present paper. The effects of stirrups on the filling of corrosion products and concrete cracking are clarified. A prediction model of crack width is developed incorporating the filling proportion of corrosion products and the twisting shape of the strand. Experimental data on cracking angle, crack width, and corrosion loss obtained from accelerated corrosion tests of concrete beams are presented. The proposed model is verified by experimental data. Results show that the filling extent of corrosion products varies with crack propagation. The rust filling extent increases with the propagating crack until a critical width. Beyond the critical width, the rust-filling extent remains stable. Using stirrups can decrease the critical crack width. Stirrups can restrict crack propagation and reduce the rust filling. The tangent of the cracking angle increases with increasing corrosion loss. The prediction of corrosion-induced crack is sensitive to the rust-filling extent. © 2016 by the authors; licensee MDPI, Basel, Switzerland.

Yang W.C.,Xiangtan University | Liu Y.,Xiangtan University | Li B.,Xiangtan University | Cao C.,Xiangtan University
Progress in Electromagnetics Research Letters | Year: 2017

The effects of exposure to the electromagnetic field from base stations have received considerable attention. Currently, researches have shown that the exposure level from a base station varies with time due to the traffic. The traffic for mobile communications has a temporal and spatial correlation. In this paper, we develop an approach to study the variation law of exposure to the base stations and analyze the correlation of exposure in time and in space. We use a spectrum analyzer to measure the transmission power of the base stations at the different periods of a day. We obtain the analytical expressions for representing the variation of exposure with time using Genetic Algorithm. The self correlation of exposure to a single base station in time series and the cross correlation of exposure to base stations in the same area are both discussed. We find that the self correlation coefficients of exposure to a single base station are bigger than 0.9 in two hours and bigger than 0.5 in eleven hours. Particularly, the spatial correlation of exposure is slightly stronger than the time correlation, up to 0.99. © 2017, Electromagnetics Academy. All rights reserved.

Zhang L.,Xiangtan University | Duan Z.,Xiangtan University | Zhu H.,Xiangtan University | Yin K.,Xiangtan University
Materials and Manufacturing Processes | Year: 2017

Graphene exhibits both excellent stretch and specific surface area. As a consequence, graphene has attracted immense attention for its applications lately. It worked well when bonded with copper composites. Unfortunately, however, there are little of such composites. To facilitate researchers to work better in the future, this article reviews its synthesis. There are two routes, including direct synthesis and indirect synthesis, which could be used to prepare copper/graphene. Simultaneously, the development and prospects of copper/graphene composite material have been discussed. © 2017 Taylor & Francis.

Li X.,Hunan University of Technology | Li X.,Xiangtan University | Li Z.,Xiangtan University
Journal of Phase Equilibria and Diffusion | Year: 2017

The isothermal section of the Cu-Fe-Si ternary system at 650 °C was investigated by scanning electron microcopy, coupled with energy dispersive x-ray spectroscopy and x-ray diffraction. Seven three-phase regions exist in the isothermal section of the Cu-Fe-Si ternary system. No new ternary compound was found in this section. The solubility of Fe in η(Cu3Si), ε(Cu15Si4), γ(Cu5Si) and κ(Cu6.69Si) phases was low. The solubility of Fe in (Cu) was found to decrease when Si content was increased in the range from 5.3 at.% to 11.9 at.%. The maximum solubilities of Cu in FeSi, FeSi2 and (αFe) were 1.7 at.%, 3.3 at.% and 1.6 at.%, respectively, and the maximum solubilities of Si in (Cu) and (αFe) were 11.9 at.% and 27.1 at.%, respectively. © 2017 ASM International

Hong B.,Xiangtan University | Liu L.,Xiangtan University | Wang T.,Xiangtan University
Hanjie Xuebao/Transactions of the China Welding Institution | Year: 2017

As longeron automatic welding, the obstacles in welding area such as stiffening plates, partitions and holes must be automatically avoided. The location of the obstacles on the workpiece are random due to the products are varied and the low-precision of the clamping, we hardly predict the obstacles in a single way. To solve this problem, by the use of ultrasonic sensor collecting the date of the obstacles, raising a prediction model in longeron automatic welding based on the ameliorated fruit flies algorithm optimization generalized regression neural network (AFOA-GRNN). The method by introducing the information element and the sensitivity of the two factors in traditional fruit flies algorithm, improved optimization strategies and location updating of fruit flies position, to optimize the parameters of the generalized neural network, to predict the obstacles in longeron automatic welding. Experiments show that correction type AFOA-GRNN prediction model compared to FOA-GRNN, training speed is faster, and the predicting precision is higher. © 2017, Editorial Board of Transactions of the China Welding Institution, Magazine Agency Welding. All right reserved.

Wu K.,Peking University | Tang H.,Peking University | Tang H.,Xiangtan University
Astrophysical Journal, Supplement Series | Year: 2017

The ideal gas equation of state (EOS) with a constant adiabatic index is a poor approximation for most relativistic astrophysical flows, although it is commonly used in relativistic hydrodynamics (RHD). This paper develops high-order accurate, physical-constraints-preserving (PCP), central, discontinuous Galerkin (DG) methods for the one- and two-dimensional special RHD equations with a general EOS. It is built on our theoretical analysis of the admissible states for RHD and the PCP limiting procedure that enforce the admissibility of central DG solutions. The convexity, scaling invariance, orthogonal invariance, and Lax-Friedrichs splitting property of the admissible state set are first proved with the aid of its equivalent form. Then, the high-order central DG methods with the PCP limiting procedure and strong stability-preserving time discretization are proved, to preserve the positivity of the density, pressure, specific internal energy, and the bound of the fluid velocity, maintain high-order accuracy, and be L 1-stable. The accuracy, robustness, and effectiveness of the proposed methods are demonstrated by several 1D and 2D numerical examples involving large Lorentz factor, strong discontinuities, or low density/pressure, etc. © 2016. The American Astronomical Society. All rights reserved.

Kim H.H.,Kyung Hee University | Chung E.T.,Chinese University of Hong Kong | Wang J.,Chinese University of Hong Kong | Wang J.,Xiangtan University
Lecture Notes in Computational Science and Engineering | Year: 2017

BDDC (Balancing Domain Decomposition by Constraints) and FETI-DP (Dual-Primal Finite Element Tearing and Interconnecting) algorithms with adaptively enriched coarse spaces are developed and analyzed for second order elliptic problems with high contrast and random coefficients. Among many approaches to form adaptive coarse spaces, we consider an approach using eigenvectors of generalized eigenvalues problems defined on each subdomain interface, see Mandel and Sousedík (2007), Galvis and Efendiev (2010), Spillane et al. (2011), Spillane et al. (2013), Klawonn et al. (2015). © Springer International Publishing AG 2017.

Zhang J.-F.,Xiangtan University | Lu J.-F.,Xiamen University | Xiang F.-Y.,Xiangtan University
Astrophysical Journal | Year: 2017

We study the properties of polarized radiation in turbulent magnetic fields from X-ray binary jets. These turbulent magnetic fields are composed of large- and small-scale configurations, which result in the polarized jitter radiation when the characteristic length of turbulence is less than the non-relativistic Larmor radius. On the contrary, the polarized synchrotron emission occurs, corresponding to a large-scale turbulent environment. We calculate the spectral energy distributions and the degree of polarization for a general microquasar. Numerical results show that turbulent magnetic field configurations can indeed provide a high degree of polarization, which does not mean that a uniform, large-scale magnetic field structure exists. The model is applied to investigate the properties of polarized radiation of the black-hole X-ray binary Cygnus X-1. Under the constraint of multiband observations of this source, our studies demonstrate that the model can explain the high polarization degree at the MeV tail and predict the highly polarized properties at the high-energy γ-ray region, and that the dominant small-scale turbulent magnetic field plays an important role for explaining the highly polarized observation at hard X-ray/soft γ-ray bands. This model can be tested by polarization observations of upcoming polarimeters at high-energy γ-ray bands. © 2017. The American Astronomical Society. All rights reserved.

Yang X.J.,Xiangtan University | Yang X.J.,University of Missouri | Li A.,University of Missouri | Glaser R.,University of Missouri | Zhong J.X.,Xiangtan University
Astrophysical Journal | Year: 2017

The so-called unidentified infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 μm ubiquitously seen in a wide variety of astrophysical regions are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. Astronomical PAHs may have an aliphatic component, as revealed by the detection in many UIE sources of the aliphatic C-H stretching feature at 3.4 mm. The ratio of the observed intensity of the 3.4 mm feature to that of the 3.3 μm aromatic C-H feature allows one to estimate the aliphatic fraction of the UIE carriers. This requires knowledge of the intrinsic oscillator strengths of the 3.3 mm aromatic C-H stretch (A3.3) and the 3.4 μm aliphatic C-H stretch (A3.4). Lacking experimental data on A3.3 and A3.4 for the UIE candidate materials, one often has to rely on quantum-chemical computations. Although the second-order Møller-Plesset (MP2) perturbation theory with a large basis set is more accurate than the B3LYP density functional theory, MP2 is computationally very demanding and impractical for large molecules. Based on methylated PAHs, we show here that, by scaling the band strengths computed at an inexpensive level (e.g., B3LYP/6-31G), we are able to obtain band strengths as accurate as those computed at far more expensive levels (e.g., MP2/6-311+G(3df,3pd)). We calculate the model spectra of methylated PAHs and their cations excited by starlight of different spectral shapes and intensities. We find that (I3.4 I3.3)mod, the ratio of the model intensity of the 3.4 μm feature to that of the 3.3 μm feature, is insensitive to the spectral shape and intensity of the exciting starlight. We derive a straightforward relation for determining the aliphatic fraction of the UIE carriers (i.e., the ratio of the number of C atoms in aliphatic units NC,ali to that in aromatic rings NC,aro) from the observed band ratios (I3.4 I3.3)obs: NC,ali NC,aro ≈ 0.57 × (I3.4 I3.3)obs for neutrals and NC,ali NC,aro ≈ 0.26 × (I3.4 I3.3)obs for cations. © 2017. The American Astronomical Society. All rights reserved.

Yu Y.-X.,Xiangtan University | Zhang X.-D.,Xiangtan University | Hu K.,Xiangtan University | Xiang F.-Y.,Xiangtan University
New Astronomy | Year: 2017

The orbital period variations of two W UMa-type contact binaries, UY UMa and EF Boo, are analyzed by using all available times of light minimum. It is detected that the general trends of their (O−C) curves show an upward parabolic variation, which reveals their continuous period increases at the rates of dP/dt=2.545×10−7 days yr−1 and dP/dt=2.623×10−7 days yr−1, respectively. Meanwhile, UY UMa also shows a cyclic period variation with a small amplitude of A=0.0026 days superposed on the long-term increase. Due to their contact configurations, the secular period increases are interpreted as a result of mass transfer from the less massive component to the more massive one. The cyclic period variation of UY UMa may be interpreted in terms of either the magnetic activity or the light time effect. © 2017

Ma Z.,Xiangtan University | Xie Z.,Xiangtan University | Wang Y.,Hunan University | Lu C.,Curtin University Australia
Scripta Materialia | Year: 2017

Electrodes softening during lithium insertion may result in degeneration of their electrochemical performances. In this paper, based on a coupling multiple-slip crystal plasticity formulation with three (i.e., statistically-stored, geometrically-necessary and electrochemical reaction-induced) dislocation densities, a relationship is built up between hardness and the state of charge for electrodes in lithium-ion batteries, which can take into account the indentation size effect during charging and discharging progresses. It is shown that the relationship is helpful in monitoring the state of charge and providing new avenues for applications of high-performance rechargeable batteries. © 2016 Acta Materialia Inc.

Huang W.,Central South University | Liu D.,Central South University | Xia M.,Xiangtan University
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2017

Coal and gas outburst is a very complex dynamic disaster in underground coal mining process. In this paper, a numerical model was established based on the theory of particle flow to simulate the development of micro-cracks, displacement, force and velocity fields, and to investigate the microscopic mechanism of gas pressure and layer-stiffness ratio. The simulation results show that the coal and gas outburst is a relatively quick process. The shear cracks were mainly concentrated in the front tip of outburst, the tensile cracks occurred deep inside the coal. The gas outburst has great influence on the coal and rock damage. When the gas pressure is relatively small, the shear cracks occur at the front and the tensile crack reached deeper. When the gas pressure is relatively large, the shear cracks and tensile cracks penetrate into the same depth. The damage of coal and rock and the shear crack ratio increases. When the layer-stiffness ratios is not the same, the speed and shape of crack propagation are not the same. © 2017, Science Press. All right reserved.

Xiao Y.-X.,Xiangtan University | Wang B.,Xiangtan University | Li Z.-Y.,Xiangtan University
Jisuan Lixue Xuebao/Chinese Journal of Computational Mechanics | Year: 2017

Weak discontinuities problems (such as inclusion problems) are important problems in solid mechanics calculation. Higher-order finite element method is a method which can ensure the accuracy of the numerical solutions near the interfaces. However, they have much higher computational complexity than the linear elements. In this paper, we present a new algebraic multigrid method (GAMG) for higher-order finite element discretizations of the weak discontinuous problems based on some geometric and analytical information by using two-level method. The resulting GAMG method is then applied to the solution of the single inclusion problem in a circular domain. Numerical results have been shown that the iteration counts of the new GAMG method do not substantially depend on the size of the problem, the number of elements and the discontinuity of Young's modulus with compared to those commonly used GAMG methods, and the CPU time is also improved obviously. Thus, the overall efficiency of the finite element analysis is greatly improved for modeling weak discontinuities problems. © 2017, Editorial Office of Chinese Journal of Computational Mechanics. All right reserved.

Liu S.,Xiangtan University | Zhang Y.,Xiangtan University | Tong J.,Xiangtan University
Mocaxue Xuebao/Tribology | Year: 2017

Combining self-assembly technology and spray painting method, the dual self-assembled monolayers/Ionic liquids composite lubrication films (DA-LA-ILs), which including N-[3-(Trimethoxysilyl)propyl] ethylenediamine(DA), Lauroyl Chloricle(LA) and 1-Dodecyl-3-Methylimidazolium Hexafluorophosphate Ionic liquids (ILS), were prepared on silicon (Si) substrates. The water contact angle meter, Fourier transform infrared spectroscopy and atomic force microscope were used to characterize the wettability the molecular components, microscopic morphologies and microscale adhesion behaviors of the films. The tribological properties of the films were analyzed by a ball-on-plate tribolometer. The investigation reveals that the adhesion properties of Si surface were effectively improved after being modified by the DA-LA-ILs composite lubrication film. Meanwhile, compared with the DA-LA dual sel-assembled monolayers and ILs modified Si substrate, the composite lubricating film showed the best friction-reduction and wearresistance properties. The results provide theoretical foundation and experimental basis for the applications of DA-LAILs composite lubricating film to reduce the adhesion between micro surfaces and improved wear resistance in microelectro mechanical systems. © 2017, Science Press. All right reserved.

Yang Z.,Xiangtan University | Yang Z.,University of Chinese Academy of Sciences | Chen F.,University of Chinese Academy of Sciences | Zhang S.,University of Chinese Academy of Sciences | And 3 more authors.
Organic Letters | Year: 2017

The first asymmetric hydrogenation of phenanthridines catalyzed by chiral cationic ruthenium diamine complexes has been developed with up to 92% ee and full conversions. The choice of the counteranion of the catalyst was found to be critical for achieving high enantioselectivity. In addition, the obtained 5,6-dihydrophenanthridine could be used as a chiral hydride donor for organocatalytic asymmetric transfer hydrogenation. © 2017 American Chemical Society.

Xiong L.,Xiangtan University | Peng B.,Petrochina | Ma Z.,Xiangtan University | Wang P.,Xiangtan University | Pei Y.,Xiangtan University
Nanoscale | Year: 2017

The atomic structure of a ten-electron (10e) thiolate-protected gold cluster, denoted as Au29(SR)19, was theoretically predicted. Based on the prediction of the atomic structure of the 10e Au29(SR)19 cluster, we proposed a novel 'gold-atom insertion, thiolate-group elimination' mechanism to understand the structural evolution of the face-centered-cubic (fcc) thiolate-protected gold clusters. The key step of structural evolution from Au28(SR)20 to Au29(SR)19 and then to the Au30(SR)18 cluster, i.e. the growth of triangle-Au3 units in the gold cores, is understood from the first insertion of an exterior Au(0) atom into the ligand shell and then cleavage of μ3-SR groups. © The Royal Society of Chemistry 2017.

Wang P.,Xiangtan University | Sun X.,Xiangtan University | Liu X.,Xiangtan University | Xiong L.,Xiangtan University | And 2 more authors.
Journal of Physical Chemistry Letters | Year: 2017

As an important intermediate link between the smaller and larger size thiolate-protected gold nanoparticles (RS-AuNPs), the molecular formula and atomic structure of the ∼14 kDa core-mass RS-AuNP species (containing around 70 core gold atoms) have not been determined unambiguously. In this work, we theoretically predict an unprecedented ∼14 kDa core-mass AuNP species, denoted as Au68(SR)36, which is composed a symmetric, face-centered-cubic (fcc) 68-gold atom framework. The fcc gold kernel in the Au68(SR)36 is made of eight 13-atom Au-cubotahedrons sharing 12 square faces, showing a standard 2 × 2 × 2 magic cube formula. The Au68(SR)36 is thought to be a key intermediate NP bridging the evolution of Au44(SR)28 and Au92(SR)44. The DFT calculations indicate the Au68(SR)36 has a sizable HOMO-LUMO gap of 0.98 eV and relative high thermodynamic stability. The fcc 68-atom gold framework in the Au68(SR)36 also presents a new candidate to address the atomic structure of recently reported water-soluble mercaptobenzoic acid protected Au68NPs. © 2017 American Chemical Society.

Li Y.,Xiangtan University | Wang P.,Xiangtan University | Bao Y.,Xiangtan University | Huang K.,Xiangtan University
Ceramics International | Year: 2017

Designing a high capacity and long cycle life MnO-based composite material for lithium ion batteries (LIBs) is still a great challenge because of the intrinsically low electrical conductivity and dramatic volume variations during lithiation/delithiation. In this paper, the MnO nanoparticles (MnO NPs) are recombined with multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (r-GO) to rationally construct a novel MnO NPs@MWCNTs/r-GO multilayer sandwich structure via electrostatic interaction self-assembly and vacuum filtration processes. As a result, the MnO NPs are closely attracted in the conductive MWCNTs network, and the MWCNTs adsorbed on the surface of MnO NPs can be served as a soft and flexible carbon coating layer to self-adapt the huge volume expansion. For another, the r-GO between two MnO NPs@MWCNTs layers is the cause to form a free-standing paper, enhancing the transverse conductivity of the whole electrode simultaneously. These features will contribute to achieve excellent cycling stability and improved rate capability. © 2017 Elsevier Ltd and Techna Group S.r.l.

Wang H.,Xiangtan University | Huang K.,Xiangtan University | Wang P.,Xiangtan University | Zhong J.,Xiangtan University
Journal of Alloys and Compounds | Year: 2017

The rechargeable Lithium-Sulfur battery has been regarded as a promising candidate for the next generation energy storage devices owing to its high energy density, low cost and environment friendliness. The further development of Li-S battery, however, is still hindered by capacity decay and kinetics sluggish caused by the poor electrochemical activity and polysulfide shuttle effect. Herein, a nitrogen-doped porous carbon framework is synthesized by a facial strategy, delivering large special surface area and narrow pore size distribution. As a result, the composited cathode with sulfur loading of 62% shows an excellent rate performance and extreme cycling stability (100 cycles at 1.0 C and 457 mAh g−1 after 500 cycles at 2.0 C), which demonstrates that the N-doped porous carbon host can effectively improve the transport of electron and ion, entrap the dissolved polysulfide, thus improving the electrochemical performance significantly in rate performance and cycle stability. © 2016 Elsevier B.V.

Yang W.,Xiangtan University | Peng S.,Xiangtan University
International Journal of Networking and Virtual Organisations | Year: 2016

In this paper, we propose a mobility model for opportunistic networks in a commercial area (MMCA). The commercial area is divided into two parts: internal and external areas. We modified the traditional susceptible-infected-removed (SIR) model for predicting the performance of the message forwarding in MMCA. Using the opportunistic networks environment (ONE) simulation platform, we validated this modified SIR by comparing the theoretical results and modelled data from ONE. We further analyse the performances of MMCA with the number of nodes, walking speeds, communication ranges and the size of areas. © 2016 Inderscience Enterprises Ltd.

Lan Z.,Xiangtan University | Wei X.,Xiangtan University | Chen L.,Xiangtan University
19th International Conference on Electrical Machines and Systems, ICEMS 2016 | Year: 2016

The increase of motor capacity cause the rise of motor internal temperature, the high temperature severely affected performance and reliable operation of motor. Considering influence of the permanent magnet eddy current loss on thermal field of motor, thermal field of PMSM has been analyzed by Lumped Parameter Thermal Network Method(LPTN), the thermal network model of 38 nodes has been established. Finally, the correctness of model is verified by comparison with the analysis results of Finite Element Method(FEM) and temperature test. © 2016 The Institute of Electrical Engineers of Japan.

Yang X.J.,Xiangtan University | Yang X.J.,University of Missouri | Glaser R.,University of Missouri | Li A.,University of Missouri | And 2 more authors.
New Astronomy Reviews | Year: 2017

The unidentified infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, 11.3 and 12.7 μ m are ubiquitously seen in a wide variety of astrophysical regions in the Milky Way and nearby galaxies as well as distant galaxies at redshifts z ≳ 4. The UIE features are characteristic of the stretching and bending vibrations of aromatic hydrocarbon materials. The 3.3 μ m feature which results from the C-H stretching vibration in aromatic species is often accompanied by a weaker feature at 3.4 μ m. The 3.4 μ m feature is often thought to result from the C-H stretch of aliphatic groups attached to the aromatic systems. The ratio of the observed intensity of the 3.3 μ m aromatic C-H feature (I 3.3) to that of the 3.4 μ m aliphatic C-H feature (I 3.4) allows one to estimate the aliphatic fraction (e.g., N C, aliph/N C, arom, the number of C atoms in aliphatic units to that in aromatic rings) of the carriers of the UIE features, provided that the intrinsic oscillator strengths (per chemical bond) of the 3.3 μ m aromatic C-H stretch (A 3.3) and the 3.4 μ m aliphatic C-H stretch (A 3.4) are known. In this review we summarize the computational results on A 3.3 and A 3.4 and their implications for the aromaticity and aliphaticity of the UIE carriers. We use density functional theory and second-order perturbation theory to derive A 3.3 and A 3.4 from the infrared vibrational spectra of seven polycyclic aromatic hydrocarbon (PAH) molecules with various aliphatic substituents (e.g., methyl-, dimethyl-, ethyl-, propyl-, butyl-PAHs, and PAHs with unsaturated alkyl chains). The mean band strengths of the aromatic (A 3.3) and aliphatic (A 3.4) C-H stretches are derived and then employed to estimate the aliphatic fraction of the carriers of the UIE features by comparing the ratio of the intrinsic band strength of the two stretches (A 3.4/A 3.3) with the ratio of the observed intensities (I 3.4/I 3.3). We conclude that the UIE emitters are predominantly aromatic, as revealed by the observationally-derived mean ratio of I 3.4/I 3.3[U+27E9] ≈ 0.12 and the computationally-derived mean ratio of A 3.4/A 3.3[U+27E9] ≈ 1.76 which suggest an upper limit of N C, aliph/N C, arom ≈ 0.02 for the aliphatic fraction of the UIE carriers. © 2017 Elsevier B.V.

Zhou Y.,Xiangtan University | Hu L.,Xiangtan University | Wang D.,Xiangtan University
Xitong Fangzhen Xuebao / Journal of System Simulation | Year: 2017

To attack the maneuvering target tracking problem in LOS/NLOS hybrid environments, an interacting multiple model (IMM) tracking algorithm based on "current" statistical (CS) model and unscented Kalman filter (UKF) was proposed (IMM-UKF-CS). In the framework of IMM, it took advantage of CS in maneuvering target tracking and chose UKF as the sub-filter for the high positioning accuracy and low computational cost. Simulation results show that IMM-UKF-CS possesses higher tracking accuracy, better robustness and lower time cost, which promises for maneuver target tracking in LOS/NLOS hybrid environments. © 2017, The Editorial Board of Journal of System Simulation. All right reserved.

Zhou Y.,Xiangtan University | Yang W.,Xiangtan University | Yang W.,Hunan University | Xu Z.,Xiangtan University | Shi X.,Xiangtan University
International Journal of Advanced Manufacturing Technology | Year: 2017

The hole series parts is widely used in the aerospace, automotive electronics, instrumentation, and hydraulic components. There are many of holes with the same machining parameter in this kind of parts, the consistency evaluation of these hole surface quality is one of the most important considerations. Based on wavelet packet energy spectrum, higher-order statistics, radar chart, and fuzzy c-means (FCM) algorithm, a method is presented to evaluate hole surface quality quickly and effectively. Vibration signal is used as the main source of information about the drilling process. In this paper, wavelet packet energy spectrum (WPES) and higher-order statistics, which can image the information on both time and frequency domain, are applied as preparatory work for cluster analysis. Then, a ten-dimensional feature vector for cluster analysis is constructed from the value of higher-order statistics and wavelet packet energy ratio of the frequency bands where the energy is abnormal. Finally, cluster analysis based on radar chart and FCM algorithm is conducted on the feature vector for classification. By comparison, it is found that the cluster analysis result is basically consistent with the artificial test result. The proposed method can be further extended to the quality evaluation of other machining processes. © 2017 Springer-Verlag London

Xu G.,Xiangtan University | Yang L.,Xiangtan University | Yang L.,City University of Hong Kong | Li Z.,Xiangtan University | And 2 more authors.
Journal of Materials Chemistry A | Year: 2017

Large-scale adoption of sodium-ion batteries in energy storage and conversion devices requires the development of electrode materials with high capacity, high-rate performance and long cycling life. Herein, a self-supporting electrode composed of mesoporous NaTi2(PO4)3 nanocrystals and multi-wall carbon nanotubes for Na storage is described. The fabrication process involves protein-assisted self-assembly, a vacuum filtration process, and thermal treatment. The self-supporting electrode possesses favorable features such as hierarchical porosity, interconnected conductive networks, plenty of sites for intercalation-based and interfacial Na storage, and high mechanical robustness, as well as strong synergistic coupling between each constituent. The electrode used directly as the anode in sodium-ion batteries delivers excellent performance such as a high capacity of 132 mA h g−1 at 1C, a high initial coulombic efficiency of 99%, and a high-rate capability of 62 mA h g−1 at 50C, as well as long-term cycling stability with a capacity of 87% at 10C after 3000 cycles. The freestanding anode possesses favorable properties up to a thickness of 50 μm boding well for a high volumetric/areal capacity. Our study has great potential to be applicable to a wide range of mesoporous nanocrystals of both anodes and cathodes for high-performance energy storage and conversion devices. © The Royal Society of Chemistry.

Luo S.,Xiangtan University | Qi X.,Xiangtan University | Yao H.,Xiangtan University | Ren X.,Xiangtan University | And 2 more authors.
Journal of Physical Chemistry C | Year: 2017

Tin selenide (SnSe) is a newly emerging layered material. SnSe with low dimensionality has been reported as an appealing material with a diverse range of applications such as rechargeable lithium-ion batteries, memory switching devices, solar energy conversion, thermoelectric energy conversion, and near-infrared optoelectronic devices. Here we synthesized SnSe ultrathin flakes on SiO2/Si substrates through simple vapor deposition route and investigated its temperature-dependent Raman spectroscopy behavior with 532, 633, and 785 nm excitation wavelengths. It was found that the Ag 2, Ag 3, and B3g modes soften as temperature increases from 98 to 298 K under all wavelengths. Our results revealed anharmonic phonon properties of SnSe, and they will benefit the advanced study of its thermal properties. This approach will also have large application in characterizing the optical, electronic, and thermal properties of other novel layered materials. Moreover, our results can be utilized to measure the temperature of SnSe-based nanodevices without destruction. (Graph Presented). © 2017 American Chemical Society.

PING P.,Xiangtan University | ZHU X.,Hengyang Normal University | WANG L.,Xiangtan University
Journal of Biological Systems | Year: 2017

In this paper, a novel method to analyze the similarity/dissimilarity of protein sequences based on Principal Component Analysis-Fast Fourier Transformation (PCA-FFT) is proposed, in which, the PCA is utilized to transform protein sequences into time series and the FFT is utilized to analyze the time series while considering them as signals. To test the effectiveness of our newly proposed method, it is applied to analyze the similarity/dissimilarity of 16 different ND5 protein sequences and 29 different spike protein sequences, respectively. Furthermore, the correlation analysis is presented for comparing with others methods, and the simulation results show that it has better performances in the aspects of computation complexity and recognition degree than some existing methods. © 2017 © The Author(s)

Jiang Q.,Xiangtan University | Ma L.,Xiangtan University
Applied System Innovation - Proceedings of the International Conference on Applied System Innovation, ICASI 2015 | Year: 2016

With the growing establishment of the Sound Design course of animation majors in colleges and universities, under the new situation, the content and teaching model of the Sound Design course has been demanded to be more professional to meet the requirements of the animation creation and industry market. The introduction of the “Performance” teaching model in the Sound Design course, which largely stimulates creative thinking in animation, is of significant importance in motivating the students to create animation works with initiative. In this teaching model, animation ideas and thinking skills will interact and improve under the guidance of sound theory, psychology, and performance, making the animation idea thinking modes even more diversified. Furthermore, the teaching model attempts to influence the teaching pattern of other courses in animation and strengthen the integration of the major, and makes it more adapted to the needs of the current market for college talents. © 2016 Taylor & Francis Group, London.

Huang Z.,Xiangtan University
Applied System Innovation - Proceedings of the International Conference on Applied System Innovation, ICASI 2015 | Year: 2016

To preserve the grass cloth-weaving techniques, recording and profiling are often employed to present the historical documents and relics about the traditional artistry. To promote it, innovating the technical procedures or reinventing the applications of the product (Chinese linen made of grass cloth) are usually adopted. However, the one-way recording, profiling or applying fails to deliver the touch, the texture, the charm and the whole experience to the audience; because the soul of grass cloth-weaving hides in the intricate and magic hand-making process. This paper has borrowed the information interaction theory to illustrate the traditional grass cloth-weaving techniques and to systematically analyze the following five aspects, namely, “feel”, “action”, “interpersonal”, “tools” and “Scene”. It intends to shed light on the nature of grass cloth-weaving and render the audience an alternative viewing perspective and a more touching, unforgettable and thought-provoking experience. © 2016 Taylor & Francis Group, London.

Mao L.-L.,Xiangtan University | Mao L.-L.,University of León
Applied System Innovation - Proceedings of the International Conference on Applied System Innovation, ICASI 2015 | Year: 2016

As the second-largest film market after the USA, China’s box-office sales totaled 29.6 billion RMB in 2014. However, Chinese films grossed only 1.87 billion RMB overseas. This makes the overseas box office of Chinese films an important and interesting topic. Expecting the statistic analysis of films by a certain director in certain marketing can bring some suggestion to the promotion of Chinese films abroad. This paper collected the box-office sales of all those 15 films directed by Zhang Yimou, released in Spain from 1987 to 2014. After the statistic analysis of the box office and audience numbers, this study found that: 1) different types of films have a different acceptance, but the acceptance is stable within the types; 2) the same type of film has a similar cultural discount for a Spanish audience; and 3) the Spanish audience is consistent with Chinese film critics for Chinese films. Then, through the comparison of the box office of Zhang Yimou’s works in Spain and the USA, the paper explored that: 1) the box-office gap between Spanish and American marketing has been steadily narrowing in recent years; 2) different from the American audience’s thinking of Chinese films as myths of martial arts and kung-fu, the Spanish audience has a more tolerant acceptance to the abundant Chinese culture, not only martial arts but also modern Chinese art and life. © 2016 Taylor & Francis Group.

Ma L.,Xiangtan University | Jiang Q.,Xiangtan University
Applied System Innovation - Proceedings of the International Conference on Applied System Innovation, ICASI 2015 | Year: 2016

This research mainly guides students to perceive the relationship between spaciousness and deepness of form during the process of sculpture creation through numerous approaches of “Empirical-Interaction,” in order to complete the interpretation of original purpose from artworks. This research establishes the logical system of “Empirical-Interaction,” leading the students to utilizing this logical system to think deeply and finally creating homologous artworks. The course comprises three modules: creation of original artworks, interposition of “Empirical-Interaction” teaching pattern, and recreation of artworks. On the theoretical basis, the “cone of experience” introduced by Dale involves the digital sculpture and makes students achieve a new perception to the judgment of spaciousness and create a sculpture with an even more profound expression. Based on the experimental process of leading the students to constructing the “Empirical-Interaction,” the cognitive transformation of the deepness of physical volume will be embodied in students’ sculptures. © 2016 Taylor & Francis Group, London.

Shen G.,Xiangtan University
Applied System Innovation - Proceedings of the International Conference on Applied System Innovation, ICASI 2015 | Year: 2016

VJing, a short form of “Video Jockeying”, is a new kind of media art, which has a short history but large influence in visual arts. It is a manifestation which has come to eminence and become a kind of prevalent art, music, and performance during the last 10 years. VJing is normally misinterpreted as a live form of MTV. However, VJing is actually to see how designers changing the rhythm, hue, or shape of the images in a live visual performance. Since people have no proper principle to evaluate the VJing works, artists are explaining and presenting the VJing works in their own ways. In addition, the relationship between screen and image is based on the connection of projector installation, so the designer and his/her crew have to do many hard works before the performance. The whole paper introduces VJing theory and elements, compares VJing with film, interprets VJing environment and audience and analyzes several VJing examples. According to the paper, VJing can be the media that connects these two aspects and makes a global party that will last permanently. © 2016 Taylor & Francis Group, London.

Qing L.,Xiangtan University | Li M.,Xiangtan University
Applied System Innovation - Proceedings of the International Conference on Applied System Innovation, ICASI 2015 | Year: 2016

The acquirement of target viewers’ feedback on an animated movie, plays a critical role in the movie’s post-production as well as its distribution strategy into market. The traditional acquisition methods, such as surveys, test screenings, and interviews, could be easily impacted by the viewers’ social desirability effect and recall errors. In this study, the team applied eye tracker, which has been used widely in advertising and marketing, to collect viewer’s visual responses to selected animation clips. The raw data collected by eye tracker were summarized into 4 key measurements we defined to suit the animation product’s unique features. The defined measurements are eye wandering rate, character attention density, visual guidance effect, and visual resistance. © 2016 Taylor & Francis Group, London.

Xiang F.Y.,Xiangtan University | Xiang F.Y.,University of Missouri | Li A.,University of Missouri | Zhong J.X.,Xiangtan University | Zhong J.X.,University of Missouri
Astrophysical Journal | Year: 2017

A large number of interstellar absorption features at ∼4000 A®-1.8 μm, known as the "diffuse interstellar bands" (DIBs), remains unidentified. Most recent works relate them to large polycyclic aromatic hydrocarbon (PAH) molecules or ultrasmall carbonaceous grains which are also thought to be responsible for the 2175 A® extinction bump and/or the far-ultraviolet (UV) extinction rise at λ-1>5.9μm-1. Therefore, one might expect some relation between UV extinction and DIBs. Such a relationship, if established, could put important constraints on the carrier of DIBs. Over the past four decades, whether DIBs are related to the shape of the UV extinction curves has been extensively investigated. However, the results are often inconsistent, partly due to the inconsistencies in characterizing UV extinction. Here we re-examine the connection between the UV extinction curve and DIBs. We compile the extinction curves and the equivalent widths of 40 DIBs along 97 sightlines. We decompose the extinction curve into three Drude-like functions composed of the visible/near-infrared component, the 2175Åbump, and the far-UV (FUV) λ-1>5.9μm-1extinction at . We argue that the wavelength-integrated FUV extinction derived from this decomposition technique best measures the strength of the FUV extinction. No correlation is found between the FUV extinction and most (∼90%) of the DIBs. We have also shown that the color excess E (1300-1700), the extinction difference at 1300 and 1700 A®often used to measure the strength of the FUV extinction, does not correlate with DIBs. Finally, we confirm the earlier findings of no correlation between the 2175 A ® bump and DIBs or between the 2175 A ® bump and the FUV extinction. © 2017. The American Astronomical Society. All rights reserved.

Yang B.,Xiangtan University | Gong H.,Xiangtan University | Chen C.,Xiangtan University | Chen X.,Xiangtan University | Cai C.,Xiangtan University
Biosensors and Bioelectronics | Year: 2017

We described a novel resonance light scattering (RLS) sensor for the specific recognition of trace quantities of Hepatitis A Virus (HAV); the sensor was based on a mussel-inspired hepatitis molecularly imprinted polymer. As a recognition element, polydopamine (PDA)-coated totivirus-imprinted polymer was introduced on the surface of SiO2 nanoparticles (virus-imprinted SiO2@PDA NPs) using an efficient one-step synthesis method. The target virus was selectively captured by the imprinted polymer films, thereby increasing the RLS intensity. A simple fluorescence spectrophotometer was employed to measure the changes in the intensity. The enhanced RLS intensity (∆IRLS) was proportional to the concentration of HAV in the range of 0.04–6.0 nmol∙L−1, with a low limit of detection of 8.6 pmol∙L−1. The selectivity study confirmed that the resultant HAV-imprinted SiO2@PDA NPs possessed high selectivity for HAV. The sensor was successfully applied for the direct detection of additional HAV from a 20,000-fold dilution of human serum. The proposed strategy is simple, eco-friendly, highly selective, and sensitive. © 2016 Elsevier B.V.

Xie E.Y.,Xiangtan University | Li C.,Xiangtan University | Yu S.,Guangdong University of Technology | Lu J.,CAS Academy of Mathematics and Systems Science
Signal Processing | Year: 2017

Utilizing complex dynamics of chaotic maps and systems in encryption was studied comprehensively in the past two and a half decades. In 1989, Fridrich's chaotic image encryption scheme was designed by iterating chaotic position permutation and value substitution some rounds, which received intensive attention in the field of chaos-based cryptography. In 2010, Solak et al. proposed a chosen-ciphertext attack on the Fridrich's scheme utilizing influence network between cipher-pixels and the corresponding plain-pixels. Based on their creative work, this paper scrutinized some properties of Fridrich's scheme with concise mathematical language. Then, some minor defects of the real performance of Solak's attack method were given. The work provides some bases for further optimizing attack on the Fridrich's scheme and its variants. © 2016 Elsevier B.V.

Gao Q.-F.,CNRS Study of Microstructures, Mechanics and Material Sciences lab | Gao Q.-F.,Xiangtan University | Dong H.,Xiangtan University | Deng Z.-W.,Hunan City University | Ma Y.-Y.,Tongji University
Computers and Geotechnics | Year: 2017

Wind loads are random variables, which induce significantly greater responses in structures than do static loads. We develop a finite-infinite element model of a 2 MW wind turbine using ABAQUS and then verify it with in situ data. The adopted dynamic constitutive model of the soil is based on the Davidenkov skeleton curve. The results demonstrate that the dynamic amplification factors (DAFs) strongly depend on wind speed and spatial position. Considerable values of the DAFs, ground acceleration, and ground velocity are observed, suggesting that the responses of the shallow foundation of a wind turbine are affected by dynamic wind loads. © 2017 Elsevier Ltd

Wang W.,Xiangtan University | Zeng Y.-C.,Xiangtan University | Sun R.-T.,Xiangtan University
Wuli Xuebao/Acta Physica Sinica | Year: 2017

A memristor is a nonlinear nanoscale-sized element with memory function, and it has an italic type "8" voltagecurrent relation curve that looks like a pinched hysteresis loop characteristic. The memristor is utilized to construct chaotic circuit, which has attracted the attention of the researchers. At present, most of studies focus on applying one or two memristors to the chaotic circuit. In order to study the multi memristor chaotic circuit, in this work we propose a sixorder chaotic circuit with two flux-controlled memristors and a charge-controlled memristor. A corresponding six-order nonlinear dynamic differential equation of the circuit state variables is established. The dynamic properties of the circuit are demonstrated in detail. The analyses of equilibria and equilibrium stability show that the circuit has an equilibrium located in the three-dimensional space which is constituted by memristor internal state variables, and it is found that the equilibrium stability is determined by the circuit parameters and the initial states of three memristors. The Lyapunov exponent spectra and bifurcation diagrams of the circuit imply that it can produce two bifurcation behaviors by adjusting its parameters, which are Hopf bifurcation and anti-period doubling bifurcation. The hyperchaos, transient chaos and intermittency cycle phenomena are found in the same system. The dynamical behavior of this circuit is dependent on the initial state of memristor, showing different orbits such as chaotic oscillation, periodic oscillation and stable sink under different initial states. Finally, the simulation results indicate that some strange attractors like lotus type and superposition type are observed when voltage and electricity signal in observing chaotic attractors are generalized to power and energy signal, respectively. And the attractor production between the energy signals of the memristors are studied. Specially, when different initial conditions of three memristors are used to simulate the circuit, we can find the coexistence phenomenon of chaotic attractors with different topological structures or quasi-periodic limit cycle and chaotic attractor. The six-order chaotic oscillating circuit is mainly composed of three parts: the parallel connection between a flux-controlled memristor and capacitor, the serial connection between a charge-controlled memristor and inductor, and another flux-controlled memristor that is alone and floating, which enriches the application of memristor in highorder chaotic circuit. Compared with most of other chaotic systems, it has many circuit parameters and very complex topological structure, which enhances the complexity of chaotic system and the randomness of the generated signal. It is more difficult to decipher the encrypted information in chaotic secure communication, and thus it has better security performance and safety performance. © 2017 Chinese Physical Society.

Qing L.,Xiangtan University | Wu L.,Xiangtan University
Proceedings of the IEEE International Conference on Advanced Materials for Science and Engineering: Innovation, Science and Engineering, IEEE-ICAMSE 2016 | Year: 2016

Animation products always attract attention. The business often pays more attention on animation production. There is a bigger issue they have to face, how to make animation products more attractive. The traditional warm-up pattern of animation marketing can't satisfy the demands of present society. Based on consumer psychology of different ages consumers this paper analysis the problem, 'positioning deviation, narrow classification, simplex media' of Chinese animation market by studying on the warm-up pattern of animation marketing of American, Japan and Korea and stand on the acceptable media features of present animation consumers. © 2016 IEEE.

Kuang R.,Xiangtan University
Proceedings of the IEEE International Conference on Advanced Materials for Science and Engineering: Innovation, Science and Engineering, IEEE-ICAMSE 2016 | Year: 2016

As a kind of ancient and mysterious folk behavior art, Changle Story integrates performances, painting, history, astronomy, geography, literature, customs, and the spirit of the times. Usually, children less than ten years old wear traditional clothes, and stand on a hathpace to perform a variety of Chinese folk stories. The performance form is unique. Essentially, it is a spontaneous performance activity of the masses, which pays attention to the image of feelings. With a comprehensive artistic meaning, it also has both sacrifice and entertainment functions. As is known to all, Changle Story is not a drama. However, it is closely related to the occurrence and development of drama from the perspective of embryology. In this paper, the drama elements of this ancient art will be presented through an analysis on the program and contents of Changle Story from both synchronic and diachronic dimensions. © 2016 IEEE.

Lu J.,Xiangtan University | Xiong M.,Xiangtan University | Xiong J.,Xiangtan University
Proceedings of the IEEE International Conference on Advanced Materials for Science and Engineering: Innovation, Science and Engineering, IEEE-ICAMSE 2016 | Year: 2016

The Generation and development of arts design depend on the specified culture background. Research on bamboo product, should be focused on the study of traditional culture of hunan province. The article is to analyse existing bamboo products based on the market and consumption situation, and to point out the main reasons about the decline of Hunan bamboo products and development lag. The article proposes the use of bamboo materials in contemporary design, not only the basic functions of the material should be considered a physical level, but also should explore personality traits and spiritual contents of the bamboo material. Product-carrier, expressed geographical and cultural characteristics of bamboo, to meet the dual demands of contemporary material and cultural consumer group. © 2016 IEEE.

Jiang K.,Peking University | Jiang K.,Xiangtan University | Wang C.,Peking University | Huang Y.,Xiangtan University | Zhang P.,Peking University
Communications in Computational Physics | Year: 2013

The ordered patterns formed by microphase-separated block copolymer systems demonstrate periodic symmetry, and all periodic structures belong to one of 230 space groups. Based on this fact, a strategy of estimating the initial values of self-consistent field theory to discover ordered patterns of block copolymers is developed. In particular, the initial period of the computational box is estimated by the Landau-Brazovskii model as well. By planting the strategy into the whole-space discrete method, several new metastable patterns are discovered in diblock copolymers. © 2013 Global-Science Press.

Sun Z.,Sun Yat Sen University | Zhang C.,Sun Yat Sen University | Wang B.,Guangdong University of Technology | Li Q.,Xiangtan University | Long D.,Sun Yat Sen University
Quantum Information Processing | Year: 2013

Recently, Liu et al. (Quantum Inf Process 12: 1797-1805, 2013) proposed a secure multiparty quantum key agreement (MQKA) protocol with single particles. Their protocol allows N parties to negotiate a secret session key in such away that (1) outside eavesdroppers cannot gain the session key without introducing any errors; (2) the session key cannot be determined by any non-trivial subset of the participants. However, the particle efficiency of their protocol is only 1/k+1)N(N-1). In this paper, we show that the efficiency of the MQKA protocol can be improved to 1/N(k+1) by introducing two additional unitary operations. Since, in some scenarios, the secret keys are confidential, neither party is willing to divulge any of the contents to the other. Therefore, in our protocol, no participant can learn anything more than its prescribed output, i.e., the secret keys of the participants can be kept secret during the protocol instead of being exposed to others, thus, the privacy of the protocol is also improved. Furthermore, we explicitly show the scheme is secure. © 2013 Springer Science+Business Media New York.

Zhao W.,U.S. Food and Drug Administration | Zhao W.,Xiangtan University | Zou W.,U.S. Food and Drug Administration | Chen J.J.,U.S. Food and Drug Administration
BMC Bioinformatics | Year: 2014

Background: The big data moniker is nowhere better deserved than to describe the ever-increasing prodigiousness and complexity of biological and medical datasets. New methods are needed to generate and test hypotheses, foster biological interpretation, and build validated predictors. Although multivariate techniques such as cluster analysis may allow researchers to identify groups, or clusters, of related variables, the accuracies and effectiveness of traditional clustering methods diminish for large and hyper dimensional datasets. Topic modeling is an active research field in machine learning and has been mainly used as an analytical tool to structure large textual corpora for data mining. Its ability to reduce high dimensionality to a small number of latent variables makes it suitable as a means for clustering or overcoming clustering difficulties in large biological and medical datasets. Results: In this study, three topic model-derived clustering methods, highest probable topic assignment, feature selection and feature extraction, are proposed and tested on the cluster analysis of three large datasets: Salmonella pulsed-field gel electrophoresis (PFGE) dataset, lung cancer dataset, and breast cancer dataset, which represent various types of large biological or medical datasets. All three various methods are shown to improve the efficacy/effectiveness of clustering results on the three datasets in comparison to traditional methods. A preferable cluster analysis method emerged for each of the three datasets on the basis of replicating known biological truths. Conclusion: Topic modeling could be advantageously applied to the large datasets of biological or medical research. The three proposed topic model-derived clustering methods, highest probable topic assignment, feature selection and feature extraction, yield clustering improvements for the three different data types. Clusters more efficaciously represent truthful groupings and subgroupings in the data than traditional methods, suggesting that topic model-based methods could provide an analytic advancement in the analysis of large biological or medical datasets. © 2014 Zhao et al.; licensee BioMed Central Ltd.

Huang Y.-C.,National Cheng Kung University | Liu Y.,Xiangtan University | Lin Y.-T.,National Cheng Kung University | Liu H.-J.,National Chiao Tung University | And 5 more authors.
Advanced Materials | Year: 2014

A large enhancement of nanodomain retention is shown in the mixed-phase region of a strained BiFeO3 epitaxial fi lm. The superior ferroelectric retention is attributed to a lower elastic-energy density at the phase boundaries, which act as periodic pinning centers for the domain wall motion. This study delivers a new pathway of incorporating an elastic-energy term to assist ferroelectric retention. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chen Y.,Xiangtan University | Chen Y.,Rensselaer Polytechnic Institute | Xie Y.,Xiangtan University | Yang S.A.,Singapore University of Technology and Design | And 4 more authors.
Nano Letters | Year: 2015

Carbon allotropes are subject of intense investigations for their superb structural, electronic, and chemical properties, but not for topological band properties because of the lack of strong spin-orbit coupling (SOC). Here, we show that conjugated p-orbital interactions, common to most carbon allotropes, can in principle produce a new type of topological band structure, forming the so-called Weyl-like semimetal in the absence of SOC. Taking a structurally stable interpenetrated graphene network (IGN) as example, we show, by first-principles calculations and tight-binding modeling, that its Fermi surface is made of two symmetry-protected Weyl-like loops with linear dispersion along perpendicular directions. These loops are reduced to Weyl-like points upon breaking of the inversion symmetry. Because of the topological properties of these band-structure anomalies, remarkably, at a surface terminated by vacuum there emerges a flat band in the loop case and two Fermi arcs in the point case. These topological carbon materials may also find applications in the fields of catalysts. © 2015 American Chemical Society.

Li Y.-F.,Xiangtan University
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2010

The design and synthesis of meso-tetra(p-methoxylpheny1)porphyrin (T(p-OCH3)PPH2) and its application in fluorescent detections of Ag(I) in aqueous solution are reported. The fluorescence quenching of T(p-OCH3)PPH2 is attributed to the formation of a complex between T(p-OCH3)PPH2 and Ag(I) by 1:1 complex ratio (K = 3.7 × 105), which has been utilized as the basis of the fabrication of the Ag(I)-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed Ag(I)-sensitive chemosensor were investigated. The chemosensor can be applied to the quantification of Ag(I) with a linear range covering from 1.0 × 10-7 to 5.0 × 10-5 M with a detection limit of 2.5 × 10-8 M. The experiment results show that the response behavior of T(p-OCH3)PPH2 towards Ag(I) is pH independent in medium condition(pH 4.0-8.0). Most importantly, the fluorescence changes of the chemosensor are remarkably specific for Ag(I) in the presence of other heavy and transition metal ions (even those that exist in high concentration), which meet the selective requirements for practical application. The proposed chemosensor has been used for direct measurement of Ag(I) content in river water samples with satisfying results, which further demonstrates its value of practical applications in environmental systems. © 2010 Elsevier B.V. All rights reserved.

Zhou W.,Xiangtan University | Fan W.,Xiangtan University | Jiang Q.,Xiangtan University | Liang Y.-F.,Peking University | Jiao N.,Peking University
Organic Letters | Year: 2015

A unique copper-catalyzed aerobic oxidative C-C bond cleavage of simple unstrained ketones with air and amines has been developed. In this chemistry, amides and oxo amides are easily synthesized through the selective C-C bond cleavage of simple ketones or unstrained cycloketones. The broad substrate scopes and use of an inexpensive copper catalyst and green molecular oxygen as an oxidant as well as an O-source make this protocol very attractive for potential synthetic applications. The control experiments reveal that the present copper-catalyzed oxidative C-C bond cleavage of simple ketones proceeds in a novel catalytic pathway rather than through the cleavage of a dioxetane intermediate. (Chemical Equation Presented). © 2015 American Chemical Society.

Wang J.,University Of Science And Technology Liaoning | Liu J.,Xiangtan University | Liu J.,Deakin University | Xu H.,University Of Science And Technology Liaoning | And 6 more authors.
Journal of Materials Chemistry A | Year: 2013

Ultralong SnS2 nanobelts with a high production yield up to ∼98% were synthesized via a gram-scale and template-free solvothermal route. The synthetic mechanism of these intriguing ultralong nanobelts was proposed to be from the synergetic effect of the layered CdI2-type structure of SnS2 and surface-modification of the capping reagent dodecanethiol. The resulting SnS2 nanobelts showed a high specific capacity of 640 mA h g-1 and stable cycling ability (560 mA h g-1 after 50 cycles), which is much better than a graphite anode. © The Royal Society of Chemistry 2013.

Xie G.,Xiangtan University | Guo Y.,Xiangtan University | Li B.,Xiangtan University | Yang L.,Xiangtan University | And 4 more authors.
Physical Chemistry Chemical Physics | Year: 2013

We present a kinetic model to investigate the anomalous thermal conductivity in silicon nanowires (SiNWs) by focusing on the mechanism of phonon-boundary scattering. Our theoretical model takes into account the anharmonic phonon-phonon scattering and the angle-dependent phonon scattering from the SiNWs surface. For SiNWs with diameter of 27.2 nm, it is found that in the case of specular reflection at lateral boundaries, the thermal conductivity increases as the length increases, even when the length is up to 10 μm, which is considerably longer than the phonon mean free path (MFP). Thus the phonon-phonon scattering alone is not sufficient for obtaining a normal diffusion in nanowires. However, in the case of purely diffuse reflection at lateral boundaries, the phonons diffuse normally and the thermal conductivity converges to a constant when the length of the nanowire is greater than 100 nm. Our model demonstrates that for observing the length dependence of thermal conductivity experimentally, nanowires with smooth and non-contaminated surfaces, and measuring at low temperature, are preferred. This journal is © the Owner Societies 2013.

Tan Z.,Xiangtan University | Tan Z.,Peking University | Wang X.,Xiangtan University | Zhou H.,Peking University
Electrochimica Acta | Year: 2013

Highly energy density olivine LiMn0.7Fe0.3PO 4/C composite was synthesized by coprecipitation method followed by ball milling. The composite was characterized by elemental analysis, XRD, SEM, TEM and its electrochemical property was also studied. This electrode presents an enhanced electrochemical intercalation performance of lithium ions, a narrow particle size distribution, and an excellent electrochemical performance. Especially, the coprecipitation method reduces Mn dissolution into the electrolyte, a common problem in LiMnPO4 which influence its energy density, due to the homogeneous distribution of transition metals. The electrochemical performance of LiMn0.7Fe0.3PO 4/C and the Mn dissolution rate with long term cycles were investigated by CV and EIS to further understand the intrinsic properties of the high Mn content LiMn0.7Fe0.3PO4/C materials. Our results indicate that homogeneous distribution of Mn and Fe is very important to achieve a higher energy density. © 2012 Elsevier Ltd.

Wang X.,National University of Singapore | Yang J.,National University of Singapore | Yu H.,Xiangtan University | Li F.,National University of Singapore | And 8 more authors.
Chemical Communications | Year: 2014

We demonstrate an efficient D-A-π-A sensitizer with a benzothiazole-cyclopentadithiophene moiety as the spacer in a triphenylamine organic dye for dye-sensitized solar cells. The dye has a broad visible light absorption range up to 800 nm. A power conversion efficiency >9% has been achieved using a [Co(bpy)3]2+/3+-based electrolyte. © 2014 the Partner Organisations.

Jiang K.,Xiangtan University | Jiang K.,Peking University | Xu W.,Peking University | Zhang P.,Peking University
Communications in Computational Physics | Year: 2015

This paper concerns the analytic structure of the self-consistent field theory (SCFT) energy functional of multicomponent block copolymer systems which contain more than two chemically distinct blocks. The SCFT has enjoyed considered success and wide usage in investigation of the complex phase behavior of block copolymers. It is well-known that the physical solutions of the SCFT equations are saddle points, however, the analytic structure of the SCFT energy functional has received little attention over the years. A recent work by Fredrickson and collaborators [see the monograph by Fredrickson, The Equilibrium Theory of Inhomogeneous Polymers, (2006), pp. 203-209] has analysed the mathematical structure of the field energy functional for polymeric systems, and clarified the index-1 saddle point nature of the problem caused by the incompressible constraint. In this paper, our goals are to draw further attention to multicomponent block copolymers utilizing the Hubbard-Stratonovich transformation used by Fredrickson and co-workers. We firstly show that the saddle point character of the SCFT energy functional of multicomponent block copolymer systems may be high index, not only produced by the incompressible constraint, but also by the Flory-Huggins interaction parameters. Our analysis will be beneficial to many theoretical studies, such as the nucleation theory of ordered phases, the mesoscopic dynamics. As an application, we utilize the discovery to develop the gradient-based iterative schemes to solve the SCFT equations, and illustrate its performance through several numerical experiments taking ABC star triblock copolymers as an example. © Global-Science Press 2015.

Hu J.,Peking University | Huang Y.,Xiangtan University
Advances in Applied Mathematics and Mechanics | Year: 2011

In this paper, we apply an a posteriori error control theory that we develop in a very recent paper to three families of the discontinuous Galerkin methods for the Reissner-Mindlin plate problem. We derive robust a posteriori error estimators for them and prove their reliability and efficiency. © 2011 Global Science Press.

Hu G.,University of Macau | Hu G.,UM Zhuhai Research Institute | Yi N.,Xiangtan University
Journal of Computational Physics | Year: 2016

In this paper, we present an adaptive finite volume method for steady Euler equations with a non-oscillatory k-exact reconstruction on unstructured mesh. The numerical framework includes a Newton method as an outer iteration to linearize the Euler equations, and a geometrical multigrid method as an inner iteration to solve the derived linear system. A non-oscillatory k-exact reconstruction of the conservative solution in each element is proposed for the high order and non-oscillatory behavior of the numerical solutions. The importance on handling the curved boundary in an appropriate way is also studied with the numerical experiments. The h-adaptive method is introduced to enhance the efficiency of the algorithm. The numerical tests show successfully that the quality solutions can be obtained smoothly with the proposed algorithm, i.e., the expected convergence order of the numerical solution with the mesh refinement can be reached, while the non-oscillation shock structure can be obtained. Furthermore, the mesh adaptive method with the appropriate error indicators can effectively enhance the implementation efficiency of numerical method, while the steady state convergence and numerical accuracy are kept in the meantime. © 2016 Elsevier Inc.

Xie H.-L.,Xiangtan University | Xie H.-L.,Peking University | Jie C.-K.,Xiangtan University | Yu Z.-Q.,Peking University | And 5 more authors.
Journal of the American Chemical Society | Year: 2010

The liquid-crystalline (LC) phase structures and transitions of a combined main-chain/side-chain LC polymer (MCSCLCP) 1 obtained from radical polymerization of a 2-vinylterephthalate, poly(2,5-bis{[6-(4-butoxy-4′- oxybiphenyl) hexyl]oxycarbonyl}styrene), were studied using differential scanning calorimetry, one- and two-dimensional wide-angle X-ray diffraction (1D and 2D WAXD), and polarized light microscopy. We have found that 1 with sufficiently high molecular weight can self-assemble into a hierarchical structure with double orderings on the nanometer and subnanometer scales at low temperatures. The main chains of 1, which are rodlike as a result of the "jacketing" effect generated by the central rigid portion of the side chains laterally attached to every second carbon atom along the polyethylene backbone, form a 2D centered rectangular scaffold. The biphenyl-containing side chains fill the space between the main chains, forming a smectic E (SmE)-like structure with the side-chain axis perpendicular to that of the main chain. This biaxial orientation of 1 was confirmed by our 2D WAXD experiments through three orthogonal directions. The main-chain scaffold remains when the SmE-like packing is melted at elevated temperatures. Further heating leads to a normal smectic A (SmA) structure followed by the isotropic state. We found that when an external electric field was applied, the main-chain scaffold greatly inhibited the motion of the biphenyls. While the main chains gain a sufficiently high mobility in the SmA phase, macroscopic orientation of 1 can be achieved using a rather weak electric field, implying that the main and side chains with orthogonal directions can move cooperatively. Our work demonstrates that when two separate components, one offering the "jacketing" effect to the normally flexible backbone and the other with mesogens that form surrounding LC phases, are introduced simultaneously into the side chains, the polymer obtained can be described as an MCSCLCP with a fascinating hierarchically ordered structure. © 2010 American Chemical Society.

Chen X.-J.,Xiangtan University | Dai Y.-Z.,Xiangtan University | Wang X.-Y.,Xiangtan University | Guo J.,Xiangtan University | And 3 more authors.
Journal of Hazardous Materials | Year: 2015

A series of visible-light responsive photocatalysts prepared using Ag3PO4 immobilized with graphene oxide (GO) with varying GO content were obtained by an electrostatically driven method, and 2,4-dichlorophenol (2,4-DCP) was used to evaluate the performance of the photocatalysts. The composites exhibited superior photocatalytic activity and stability compared with pure Ag3PO4. When the content of GO was 5%, the degradation efficiency of 2,4-DCP could reach 98.95%, and 55.91% of the total organic (TOC) content was removed within 60min irradiation. Meanwhile, the efficiency of 91.77% was achieved for 2,4-DCP degradation even after four times of recycling in the photocatalysis/Ag3PO4-GO (5%) system. Reactive species of O2-, OH and h+ were considered as the main participants for oxidizing 2,4-DCP, as confirmed by the free radical capture experiments. And some organic intermediates including 4-chlorophenol (4-CP), hydroquinone (HQ), benzoquinone (BZQ), 2-chlorohydroquinone and hydroxyhydroquinone (HHQ) were detected by comparison with the standard retention times from the high performance liquid chromatography (HPLC). In short, the enhanced photocatalytic property of Ag3PO4-GO was closely related to the strong absorption ability of GO relative to 2,4-DCP, the effective separation of photogenerated electron-hole pairs, and the excellent electron capture capability of GO. © 2015 Published by Elsevier B.V.

Feng B.,Xiangtan University | Huang S.,Xiangtan University | Ge F.,Xiangtan University | Jia D.,Hubei University | Dai Y.,Xiangtan University
Biosensors and Bioelectronics | Year: 2011

The amount of active capture antibodies immobilized per unit square is crucial to developing effective antibody chips, biosensors, immunoassays and other molecular recognition technologies. In this study, we present a novel yet simple method for oriented antibody immobilization at high density based on the formation of an orderly, organized aggregation of immunoglobulin G (IgG) and staphylococcal protein A (SPA). Following the chelation of His-tag with Ni 2+, antibodies were immobilized on a solid surface in a three-dimensional (3D) manner and exposed the analyte receptor sites well, which resulted in a substantial enhancement of the analytical signal with more than 64-fold increase in detection sensitivity. Pull-down assays confirmed that IgG antibody can only bind to Ni 2+ matrix indirectly via a SPA linkage, where the His-tag is responsible for binding Ni 2+ and homologous domains are responsible for binding IgG Fc. The immobilization approach proposed here may be an attractive strategy for the construction of high performance antibody arrays and biosensors as long as the antibody probe is of mammalian IgG. © 2011 Elsevier B.V.

Hu J.,Peking University | Huang Y.,Xiangtan University | Lin Q.,CAS Academy of Mathematics and Systems Science
Journal of Scientific Computing | Year: 2014

The paper is to introduce a new systematic method that can produce lower bounds for eigenvalues. The main idea is to use nonconforming finite element methods. The conclusion is that if local approximation properties of nonconforming finite element spaces are better than total errors (sums of global approximation errors and consistency errors) of nonconforming finite element methods, corresponding methods will produce lower bounds for eigenvalues. More precisely, under three conditions on continuity and approximation properties of nonconforming finite element spaces we analyze abstract error estimates of approximate eigenvalues and eigenfunctions. Subsequently, we propose one more condition and prove that it is sufficient to guarantee nonconforming finite element methods to produce lower bounds for eigenvalues of symmetric elliptic operators. We show that this condition hold for most low-order nonconforming finite elements in literature. In addition, this condition provides a guidance to modify known nonconforming elements in literature and to propose new nonconforming elements. In fact, we enrich locally the Crouzeix-Raviart element such that the new element satisfies the condition; we also propose a new nonconforming element for second order elliptic operators and prove that it will yield lower bounds for eigenvalues. Finally, we prove the saturation condition for most nonconforming elements. © 2014 Springer Science+Business Media New York.

Jiang K.,Peking University | Jiang K.,Xiangtan University | Zhang P.,Peking University
Journal of Computational Physics | Year: 2014

Quasicrystals are one kind of space-filling structures. The traditional crystalline approximant method utilizes periodic structures to approximate quasicrystals. The errors of this approach come from two parts: the numerical discretization, and the approximate error of Simultaneous Diophantine Approximation which also determines the size of the domain necessary for accurate solution. As the approximate error decreases, the computational complexity grows rapidly, and moreover, the approximate error always exits unless the computational region is the full space. In this work we focus on the development of numerical method to compute quasicrystals with high accuracy. With the help of higher-dimensional reciprocal space, a new projection method is developed to compute quasicrystals. The approach enables us to calculate quasicrystals rather than crystalline approximants. Compared with the crystalline approximant method, the projection method overcomes the restrictions of the Simultaneous Diophantine Approximation, and can also use periodic boundary conditions conveniently. Meanwhile, the proposed method efficiently reduces the computational complexity through implementing in a unit cell and using pseudospectral method. For illustrative purpose we work with the Lifshitz-Petrich model, though our present algorithm will apply to more general systems including quasicrystals. We find that the projection method can maintain the rotational symmetry accurately. More significantly, the algorithm can calculate the free energy density to high precision. © 2013 Elsevier Inc.

Fu X.,South China University of Technology | Fu X.,Xiangtan University | He X.,South China University of Technology | Wang Y.,Peking University
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2011

Silica hollow microspheres with an eccentric interior and varied porous shell structures, including mesoporous, macroporous and monoporous shells, were prepared by a simple and efficient precipitation-phase separation method. We found that the morphology, size and porous shell structures of the silica hollow microspheres depended strongly on process parameters such as the amount of ammonia, the ratio of TEOS/polystyrene and the organic solvent. The prepared silica hollow microspheres were characterized by scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption measurements and thermogravimetric analysis. Based on our results, we propose a possible formation mechanism of the hollow and eccentric structure. © 2011 Elsevier B.V.

Wang J.,University Of Science And Technology Liaoning | Liu J.,Xiangtan University | Liu J.,Deakin University | Zhou Y.,Xiangtan University | And 2 more authors.
RSC Advances | Year: 2013

Semiconductor α-MnO2 hierarchical hollow microspheres constructed with nanotubes have been facilely synthesized through a bubble template-based self-scrolling solution route. An energy-minimizing-driven self-assembly of α-MnO2 nanoparticles on the base of O 2 bubbles is responsible for the formation of hierarchical hollow microsphere structure. The as-obtained α-MnO2 products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and UV-vis-NIR spectrophotometry. The Li ion storage and water treatment performances of these α-MnO2 hierarchical hollow microspheres constructed with nanotubes were tested. A discharge capacity as high as 983 mA h g-1 during the 30th cycle has been delivered at a current density of 300 mA g-1. These as-prepared samples were also used as adsorbents in water treatment, and showed an excellent ability to remove organic pollutants without any other additives. © 2013 The Royal Society of Chemistry.

Jiang K.,Xiangtan University | Huang Y.,Xiangtan University | Zhang P.,Peking University
Journal of Computational Physics | Year: 2010

A numerical method in Fourier-space is developed to solve the polymeric self-consistent field equations. The method does not require a priori symmetric information. More significantly, periodic structure can be adjusted automatically during the iteration process. In this article, we apply our method to AB linear diblock copolymer melt, thus reproduce all known stable phases, and reveal some meta-stable phases. It is worthy to point out that we also give an efficient strategy to estimating initial values for diblock copolymer system. Finally, by comparing with Matsen-Schick's method, we show some advantages of our method. © 2010 Elsevier Inc.

Vasudevan R.K.,University of New South Wales | Liu Y.,Xiangtan University | Liu Y.,University of Washington | Li J.,University of Washington | And 7 more authors.
Nano Letters | Year: 2011

Development of magnetoelectric, electromechanical, and photovoltaic devices based on mixed-phase rhombohedral-tetragonal (R-T) BiFeO3 (BFO) systems is possible only if the control of the engineered R phase variants is realized. Accordingly, we explore the mechanism of a bias induced phase transformation in this system. Single point spectroscopy demonstrates that the T → R transition is activated at lower voltages compared to T → -T polarization switching. With phase field modeling, the transition is shown to be electrically driven. We further demonstrate that symmetry of formed R-phase rosettes can be broken by a proximal probe motion, allowing controlled creation of R variants with defined orientation. This approach opens a pathway to designing next-generation magnetoelectronic and data storage devices in the nanoscale. © 2011 American Chemical Society.

Xu J.-J.,Xiangtan University | Ren W.,National University of Singapore | Ren W.,Institute of High Performance Computing of Singapore
Journal of Computational Physics | Year: 2014

A level-set method for two-phase flows with moving contact line and insoluble surfactant is presented. The mathematical model consists of the Navier-Stokes equation for the flow field, a convection-diffusion equation for the surfactant concentration, together with the Navier boundary condition and a condition for the dynamic contact angle derived by Ren et al. (2010) [37]. The numerical method is based on the level-set continuum surface force method for two-phase flows with surfactant developed by Xu et al. (2012) [54] with some cautious treatment for the boundary conditions. The numerical method consists of three components: a flow solver for the velocity field, a solver for the surfactant concentration, and a solver for the level-set function. In the flow solver, the surface force is dealt with using the continuum surface force model. The unbalanced Young stress at the moving contact line is incorporated into the Navier boundary condition. A convergence study of the numerical method and a parametric study are presented. The influence of surfactant on the dynamics of the moving contact line is illustrated using examples. The capability of the level-set method to handle complex geometries is demonstrated by simulating a pendant drop detaching from a wall under gravity. © 2014 Elsevier Inc.

Jiang K.,Xiangtan University | Tong J.,Peking University | Zhang P.,Peking University | Shi A.-C.,McMaster University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

The relative stability of two-dimensional soft quasicrystals in systems with two length scales is examined using a recently developed projection method, which provides a unified numerical framework to compute the free energy of periodic crystal and quasicrystals. Accurate free energies of numerous ordered phases, including dodecagonal, decagonal, and octagonal quasicrystals, are obtained for a simple model, i.e., the Lifshitz-Petrich free-energy functional, of soft quasicrystals with two length scales. The availability of the free energy allows us to construct phase diagrams of the system, demonstrating that, for the Lifshitz-Petrich model, the dodecagonal and decagonal quasicrystals can become stable phases, whereas the octagonal quasicrystal stays as a metastable phase. © 2015 American Physical Society.

Zhang D.C.,Xiangtan University | Lin J.G.,Xiangtan University | Wen C.,Swinburne University of Technology
Journal of Materials Chemistry B | Year: 2014

The influences of cold rolling (CR), recovery and recrystallization on the microstructure, mechanical properties and superelasticity of the suction cast Ti-7.5Nb-4Mo-2Sn alloy were investigated. It has been found that, with the increase of the CR thickness reduction rate, the volume fraction of the strain-induced martensite transiting from the β phase increases. During annealing treatment, the precipitation of α and ω phases occurred at 700 and 800 °C, respectively, and the volume fraction of the α and ω phases increases with increasing CR thickness reduction rate. The high density of dislocations introduced by cold rolling can accelerate the course of α and ω transformation. The cold rolled alloy after annealing at 700 °C exhibits excellent superelasticity with a high first yielding stress (σSIM), a large recoverable strain (ε recoverable) and a high strain recovery rate (η) due to the retention of massive dislocations and α phase precipitates in the recovery process. The grain size shows a strong effect on the martensitic transformation, and the relationship between the critical stress for the martensite transformation and grain size follows the Hall-Petch equation with a slope of approximately 0.27 MN m-3/2. This journal is © the Partner Organisations 2014.

Cheng F.,Peking University | Wan W.,Peking University | Tan Z.,Peking University | Tan Z.,Xiangtan University | And 4 more authors.
Electrochimica Acta | Year: 2011

A nano-LiFePO4/C composite has been directly synthesized from micrometer-sized Li2CO3, NH4H 2PO4, and FeC2O4·2H 2O by the lauric acid-assisted solid-state reaction method. The SEM and TEM observations demonstrate that the synthesized nano-LiFePO4/C composite has well-dispersed particles with a size of about 100-200 nm and an in situ carbon layer with thickness of about 2 nm. The prepared nano-LiFePO 4/C composite has superior rate capability, delivering a discharge capacity of 141.2 mAh g-1 at 5 °C, 130.9 mAh g-1 at 10 C, 121.7 mAh g-1 at 20 °C, and 112.4 mAh g-1 at 30 °C. At -20 °C, this cathode material still exhibits good rate capability with a discharge capacity of 91.9 mAh g-1 at 1 °C. The nano-LiFePO4/C composite also shows excellent cycling ability with good capacity retention, up to 100 cycles at a high current density of 30 °C. Furthermore, the effect of lauric acid in the preparation of nano-LiFePO4/C composite was investigated by comparing it with that of citric acid. The SEM images reveal that the morphology of the LiFePO 4/C composite transformed from the porous structure to fine particles as the molar ratio of lauric acid/citric acid increased. © 2011 Elsevier Ltd. All rights reserved.

Hu K.,Xiangtan University
Physica A: Statistical Mechanics and its Applications | Year: 2012

Community detection is of considerable interest for analyzing the structure and function of complex networks. Recently, a type of multi-resolution methods in community detection was introduced, which can adjust the resolution of modularity by modifying the modularity function with tunable resolution parameters, such as those proposed by Arenas, Fernández and Gómez and by Reichardt and Bornholdt. In this paper, we show that these methods still have the intrinsic limitation-large communities may have been split before small communities become visible-because it is at the cost of the community stability that the enhancement of the modularity resolution is obtained. The theoretical results indicated that the limitation depends on the degree of interconnectedness of small communities and the difference between the sizes of small communities and of large communities, while independent of the size of the whole network. These findings have been confirmed in several example networks, where communities even are full-completed sub-graphs. © 2012 Elsevier B.V. All rights reserved.

Zhang H.,Polytechnic University of Catalonia | Tan Y.,Xiangtan University | Shu S.,Xiangtan University | Niu X.,Xiangtan University | And 4 more authors.
Computers and Fluids | Year: 2014

Particle collisions play a very important role in determining the fluid-particle multiphase flow, and thus it is crucial to treat the particle-particle interaction using a felicitous method in numerical simulations. A novel combined lattice Boltzmann method (LBM)-immersed boundary method (IBM)-discrete element method (DEM) scheme is presented in this study with its application to model the sedimentation of 2D circular particles in incompressible Newtonian flows. The hydrodynamic model of the incompressible Newtonian flow is based on the Bhatnagar-Gross-Krook LBM, and a momentum exchange-based IBM is adopted to calculate the fluid-solid interaction force. The kinematics and trajectory of the discrete particles are evaluated by DEM, in which the particle-particle interaction rules are governed by theoretical contact mechanics to enable the direct use of real particle properties. This eliminates the need of artificial parameters and also improves the reliability of the numerical results. By using a more accurate and physical description of particle interaction, a 'safe zone' or threshold is also no longer required. Case studies of single particle settling in a cavity, and two particles settling in a channel were carried out, the velocity characteristics of the particle during settling and near the bottom were examined. A numerical example of sedimentation involving 504 particles was finally presented to demonstrate the capability of the combined scheme. © 2014 Elsevier Ltd.

Yu X.,Hunan Institute of Engineering | Yi B.,Hunan Institute of Engineering | Wang X.,Xiangtan University | Chen J.,Hunan Institute of Engineering
Atmospheric Environment | Year: 2012

The reaction rate constants of ozone with organic compounds in the atmosphere were predicted by a quantitative structure-activity relationship (QSAR) model. Density functional theory (DFT) calculations, for the first time, were carried out on the radicals from organic compounds, at the UB3LYP level of theory with 6-31G(d) basis set. A set of quantum chemical descriptors calculated from the radicals, the energy of the highest occupied molecular orbital of beta spin states (E βHOMO), the molecular average polarizability (α), and the total energy (E T), were used to build the general QSAR model for aliphatic compounds, applying the genetic algorithm (GA) technique and support vector machine (SVM) regression. The root mean square errors (RMSE) are 0.680 for the training set (68 compounds), 0.777 for the validation set (36 compounds) and 0.709 for the test set (35 compounds). Investigated results indicate that the SVM model given here has good predictivity for aliphatic compounds. © 2012 Elsevier Ltd.

Liu S.,SUNY College of Environmental Science and Forestry | Liu S.,South China University of Technology | Lu H.,University of Sichuan | Hu R.,SUNY College of Environmental Science and Forestry | And 4 more authors.
Biotechnology Advances | Year: 2012

Woody biomass is renewable only if sustainable production is imposed. An optimum and sustainable biomass stand production rate is found to be one with the incremental growth rate at harvest equal to the average overall growth rate. Utilization of woody biomass leads to a sustainable economy. Woody biomass is comprised of at least four components: extractives, hemicellulose, lignin and cellulose. While extractives and hemicellulose are least resistant to chemical and thermal degradation, cellulose is most resistant to chemical, thermal, and biological attack. The difference or heterogeneity in reactivity leads to the recalcitrance of woody biomass at conversion. A selection of processes is presented together as a biorefinery based on incremental sequential deconstruction, fractionation/conversion of woody biomass to achieve efficient separation of major components. A preference is given to a biorefinery absent of pretreatment and detoxification process that produce waste byproducts. While numerous biorefinery approaches are known, a focused review on the integrated studies of water-based biorefinery processes is presented. Hot-water extraction is the first process step to extract value from woody biomass while improving the quality of the remaining solid material. This first step removes extractives and hemicellulose fractions from woody biomass. While extractives and hemicellulose are largely removed in the extraction liquor, cellulose and lignin largely remain in the residual woody structure. Xylo-oligomers, aromatics and acetic acid in the hardwood extract are the major components having the greatest potential value for development. Higher temperature and longer residence time lead to higher mass removal. While high temperature (> 200 °C) can lead to nearly total dissolution, the amount of sugars present in the extraction liquor decreases rapidly with temperature. Dilute acid hydrolysis of concentrated wood extracts renders the wood extract with monomeric sugars. At higher acid concentration and higher temperature the hydrolysis produced more xylose monomers in a comparatively shorter period of reaction time. Xylose is the most abundant monomeric sugar in the hydrolysate. The other comparatively small amounts of monomeric sugars include arabinose, glucose, rhamnose, mannose and galactose. Acetic acid, formic acid, furfural, HMF and other byproducts are inevitably generated during the acid hydrolysis process. Short reaction time is preferred for the hydrolysis of hot-water wood extracts. Acid hydrolysis presents a perfect opportunity for the removal or separation of aromatic materials from the wood extract/hydrolysate. The hot-water wood extract hydrolysate, after solid-removal, can be purified by Nano-membrane filtration to yield a fermentable sugar stream. Fermentation products such as ethanol can be produced from the sugar stream without a detoxification step. © 2012 Elsevier Inc.

Wu M.-M.,Guangxi University | Wen L.,Guangxi University | Tang B.-Y.,Guangxi University | Tang B.-Y.,Xiangtan University | And 2 more authors.
Journal of Alloys and Compounds | Year: 2010

The structural, electronic and elastic properties of typical hexagonal-close-packed MgZn2 and ScZn2 phases in Mg-Sc-Zn alloy were investigated by means of first-principles calculations within the framework of density functional theory (DFT). The calculated lattice constants were in good agreement with the experimental values. The obtained cohesive energy and formation enthalpy of both phases are negative, showing their structural stability from energetic point of view. The five independent elastic constants were calculated, and then the bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν of polycrystalline aggregates were derived. The ductility and plasticity of the MgZn2 and ScZn2 phases were further discussed. The elastic anisotropy of the two phases was also analyzed. Finally, the electronic density of states (DOS) and charge density distribution were also calculated to reveal the underlying mechanism of structural stability and mechanical properties. © 2010 Elsevier B.V. All rights reserved.

Yi B.,Hunan Institute of Engineering | Yi B.,Xiangtan University | He H.-P.,Xiangtan University | Fan Q.-H.,CAS Institute of Chemistry
Journal of Molecular Catalysis A: Chemical | Year: 2010

A new series of dendritic ligands with a chiral diphosphine located at the focal point have been synthesized through coupling of (R,R)-3,4-bis(biphenylphosphino)pyrrolidine (pyrphos) with peripherally alkyl-functionalized benzoic acid dendrons. These ligands were employed in the Rh-catalyzed asymmetric hydrogenation of prochiral dehydroamino acids, exhibiting excellent catalytic activities and enantioselectivities. The second-generation dendritic catalyst could be recovered by simple liquid-liquid biphasic separation and reused four times without serious loss of its activity and selectivity. © 2009 Elsevier B.V. All rights reserved.

Yu X.,Hunan Institute of Engineering | Wang X.,Xiangtan University | Li B.,Hunan Institute of Engineering
Colloid and Polymer Science | Year: 2010

To construct reliable quantitative structureproperty relationship models of Q and e parameters, density functional theory (DFT) calculations were carried out for 56 radicals with structure C 1 H 3-C 2 HR 3 • (formed from the monomer + H•) at the B3LYP level of theory with 6-31G(d) basis set. The multiple linear regression technique was used to select the descriptors as inputs for the artificial neural network (ANN). A three-descriptor ANN for the parameter lnQ was developed that produced training set root mean square (rms) error=0.317 and rms error=0.313 for an external prediction set. A two-descriptor ANN for the parameter e was built with rms errors of 0.264 for the training set and 0.271 for the prediction set. Comparing to existing models, our ANN models show better or comparable statistical characteristics, which shows that calculating quantum chemical descriptors from radicals to develop ANN models and predict lnQ and e values is feasible. © Springer-Verlag 2010.

Yang K.,Xiangtan University | Yang K.,University of the Basque Country | Chen Y.,Xiangtan University | D'Agosta R.,University of the Basque Country | And 4 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

The thermoelectric properties of hybrid graphene/boron nitride nanoribbons (BCNNRs) are investigated using the nonequilibrium Green's function approach. We find that the thermoelectric figure of merit (ZT) can be remarkably enhanced by periodically embedding hexagonal BN (h-BN) into graphene nanoribbons (GNRs). Compared to pristine GNRs, the ZT for armchair-edged BCNNRs with width index 3p+2 is enhanced 10-20 times, while the ZT of nanoribbons with other widths is enhanced by just 1.5-3 times. As for zigzag-edge nanoribbons, the ZT is enhanced 2-3 times. This improvement comes from the combined increase in the Seebeck coefficient and the reduction in the thermal conductance outweighing the decrease in the electrical conductance. In addition, the effect of the component ratio of h-BN on the thermoelectric transport properties is discussed. These results qualify BCNNRs as a promising candidate for building outstanding thermoelectric devices. © 2012 American Physical Society.

Zhou Y.,Xiangtan University | Zhou Y.,Shanghai JiaoTong University | Li J.,Shanghai JiaoTong University | Wang D.,Xiangtan University
Science China Information Sciences | Year: 2012

Quantization/compression is usually adopted in wireless sensor networks (WSNs) since each sensor node typically has very limited power supply and communication bandwidth. We consider the problem of target tracking in a WSN with quantized measurements in this paper. Attention is focused on the design of measurement quantizer with adaptive thresholds. Based on the probability density function (PDF) of the signal amplitude measured at a random location and by maximizing the entropy, an adaptive design method for quantization thresholds is proposed. Due to the nonlinear measuring and quantization models, particle filtering (PF) is adopted in the fusion center (FC) to estimate the target state. Posterior Cramér-Rao lower bounds (CRLBs) for tracking accuracy using quantized measurements are also derived. Finally, a simulation example on tracking single target with noisy circular trajectories is provided to illustrate the effectiveness of the proposed approach. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg.

Lan Y.-H.,Xiangtan University | Li W.-J.,Xiangtan University | Zhou Y.,Xiangtan University | Luo Y.-P.,Hunan Institute of Engineering
International Journal of Automation and Computing | Year: 2013

This paper is concerned with the problem of the full-order observer design for a class of fractional-order Lipschitz nonlinear systems. By introducing a continuous frequency distributed equivalent model and using an indirect Lyapunov approach, the sufficient condition for asymptotic stability of the full-order observer error dynamic system is presented. The stability condition is obtained in terms of LMI, which is less conservative than the existing one. A numerical example demonstrates the validity of this approach. © 2013 Institute of Automation, Chinese Academy of Sciences and Springer-Verlag Berlin Heidelberg.

Xinrong S.,Hunan Institute of Engineering | Kunyang S.,Hunan Institute of Engineering | Sha D.,Xiangtan University | Yaping C.,Xiangtan University | Yuanbin L.,Xiangtan University
Journal of Industrial and Engineering Chemistry | Year: 2013

Poly[N,N'-(2-amino-5-carboxybutyl-1,3-phenylenedimethylene)-2,2'-diamino-4,4'-bithiazole] was synthesized and characterized with Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Anhydrous electrorheological (ER) fluids were prepared using the polymer particles as disperse phase and bromodiphenylmethane as a disperse medium. Rheological measurements were carried out via a rotational rheometer to investigate the effects of electric field strength and the polymer particle content on the ER properties. Results indicate that suspensions of the polymer particles containing amino and carboxybutyl groups in bromodiphenylmethane exhibit a substantial ER effect. © 2012 The Korean Society of Industrial and Engineering Chemistry.

Nie C.,Hunan Institute of Engineering | Yu H.,Xiangtan University
Applied Mechanics and Materials | Year: 2012

To approximate some problems with strongly discontinuous coefficients, we present the large jump asymptotic method for parabolic interface problems, focus on the derivation and proof of the asymptotic error estimates for our approximation, and show it is of order two. Numerical experiments verify the theoretical results.

Zhang Q.,Xiangtan University | Fan T.-W.,Xiangtan University | Fu L.,Xiangtan University | Tang B.-Y.,Xiangtan University | And 3 more authors.
Intermetallics | Year: 2012

The effects of RE (RE = Pr, Nd, Gd, Tb, Dy) solute atoms on four basal stacking faults of Mg solid solutions have been studied using density functional theory. From the generalized stacking fault energy surface, both stable and unstable stacking fault energies are reduced obviously with the addition of RE elements, and the effect becomes weak with increase of the atomic number of RE elements. Due to the decrease of fault energies of I 2 stacking fault, the extended dislocation configuration tends to be stabilized and the ductility could also be improved by the addition of RE atoms. Then the deformation mechanisms are further studied by means of both the Rice and ZCT criterions. Finally, the electronic structure further reveals the underlying mechanisms for the effects of RE solutes on stacking faults of Mg solid solutions. © 2012 Elsevier Ltd. All rights reserved.

Liao Y.,Xiangtan University | Liao Y.,Hunan Institute of Engineering | Jiang P.,Xiangtan University | Chen S.,Xiangtan University | And 2 more authors.
Green Chemistry | Year: 2013

A novel method for the formation of 2-arylsulfanylphenols from thiols and cyclohexanones is described. Iodine was used as an effective catalyst for this kind of transformation. Cyclohexanones were used as a phenol source via a dehydrogenation and tautomerization reaction. © 2013 The Royal Society of Chemistry.

Zhao J.,University of Wollongong | Ding H.,Northeastern University China | Zhao W.,Xiangtan University | Jiang Z.,University of Wollongong
Journal of Alloys and Compounds | Year: 2013

Hot deformation behaviour of Ti-6Al-4V alloy with different hydrogen contents (0, 0.35 and 0.6 wt.%) was investigated over the temperature range from 1050 to 1100 °C and strain rate range from 0.005 to 5 s1. The effects of hydrogen on the microstructural evolution, flow stress, work hardening, strain energy density and strain rate sensitivity were systematically analysed. Constitutive models for Ti-6Al-4V alloy with different hydrogen contents were established by using a stepwise multiple-linear regression method. The results show that δ hydride with an FCC crystal structure exists in the deformed matrix of the hydrogenated specimens. The size of δ hydride is refined when the deformation temperature is raised from 1050 to 1100 °C. The work hardening rate increases with hydrogen when the strain is lower than 0.01. When the strain is higher than 0.01, however, hydrogen does not show significant effect on the work hardening rate. Both the flow stress and the strain rate sensitivity show an increasing trend with hydrogen, and the strain rate sensitivity increases gradually with strain and temperature. The selected optimum variables for the constitutive equations after stepwise multiple-linear regression are different for the Ti-6Al-4V alloy with different hydrogen contents. The calculated flow stress is in good agreement with the tested value. © 2013 Elsevier B.V. All rights reserved.

Fang Z.,Central South University | Fang Z.,Hunan Institute of Engineering | Cao C.,Hunan University of Science and Technology | Cao C.,Xiangtan University
Journal of Molecular Structure | Year: 2013

The relationship between the molecular conformation and spectroscopic properties of symmetrical bis-Schiff bases was explored experimentally. Seven samples of compounds p-X-C6H4CHNC6H 4NCHC6H4-p-X (X = OMe, Me, Et, Cl, F, CF 3, or CN) were prepared for this study, and their crystal structures were measured by X-ray diffraction. Their λmax values in ethanol, acetonitrile, chloroform and cyclohexane solvents were measured, and their δC(CN) values in chloroform-d were determined. The results show that the νmax is dependent on the substituents at the benzylidene ring and the dihedral angle τ of the titled molecules, and the term sin(τ) is suitable to modify the substituent effects on the νmax. However, experimental investigations indicate that the dihedral angle τ has a limited effect on the values of δ C(CN). This study provides a new understanding for the molecular conformation on spectroscopic properties of symmetrical Schiff bases. © 2012 Elsevier B.V. All rights reserved.

Cao J.,Xiangtan University | Cao J.,CAS National Center for Nanoscience and Technology | Zhang W.,CAS National Center for Nanoscience and Technology | Xiao Z.,CAS National Center for Nanoscience and Technology | And 4 more authors.
Macromolecules | Year: 2012

Two low-bandgap polymers P1 and P2 were synthesized by copolymerization of benzo[1,2-b:4,5-c']-dithiophene-4,8-dione (BDTD) with benzo-[1,2-b:4,5-b'] dithiophene (BDT) and dithieno[3,2- b:2',3'-d]silole (DTS), respectively. Thermogravimetric analyses of P1 and P2 were found and the temperature of 5% weight-loss was selected as the onset point of decomposition. Both the polymers are found to exhibit low-lying HOMO and good light-absorption properties. The absorption spectra of the polymers in chloroform and films are found to be of the range of 500-650 nm. The optimized weight ratios for P1 and P2 both are found to be 1:1.5. The AFM images show the morphology change for the polymer/PC61BM composite films and the rms roughness for the film is found to decrease from 6.94 to 0.47 nm. P2 device exhibits higher external quantum efficiency (EQE) than that of P1, which is due to stronger sunlight absorption of P2 film.

Zhao J.,University of Wollongong | Ding H.,Northeastern University China | Zhao W.,Xiangtan University | Huang M.,Northeastern University China | And 2 more authors.
Computational Materials Science | Year: 2014

Hot deformation characteristics of a Ti600 titanium alloy were investigated by a Gleeble 1500D thermo-mechanical test simulator over the temperature range from 760 to 920 °C and strain rate range from 0.01 to 10 s-1. The flow behaviour and microstructural evolution were studied. Dynamic recrystallisation (DRX) grains exhibit different shapes at different deformation temperatures, and more severe distortion around the DRX grains exists in the matrix deformed at low temperature compared with that at relatively high temperature. Phenomenological and empirical constitutive equations were established based on the hyperbolic sine Arrhenius-type model and the multiple-linear regression, respectively. An artificial neural network (ANN) model was developed to predict the flow stress. A comparative study was made on the capability of the developed models to represent the hot deformation behaviour of this alloy. The results indicate that the flow stress of Ti600 alloy is sensitively dependent on the strain rate and deformation temperature. The multiple-linear model shows a higher accuracy in tracking the flow behaviour of Ti600 alloy than the Arrhenius-type model. The ANN model is much more efficient and has higher accuracy in predicting the hot deformation flow behaviour of Ti600 alloy than both the Arrhenius-type and multiple-linear models. © 2014 Elsevier B.V. All rights reserved.

Yang J.,Hunan Institute of Engineering | Yang J.,Xiangtan University
International Journal of Computer Mathematics | Year: 2015

Discontinuous Galerkin (DG) approximations for non-linear parabolic problems are investigated. To linearize the discretized equations, we use a two-grid method involving a small non-linear system on a coarse gird of size H and a linear system on a fine grid of size h. Error estimates in H1-norm are obtained, O(hr+Hr+1) where r is the order of the DG space. The analysis shows that our two-grid DG algorithm will achieve asymptotically optimal approximation as long as the mesh sizes satisfy h=O(H(r+1)/r). The numerical experiments verify the efficiency of our algorithm. © 2014 Taylor & Francis.

Luo X.Q.,Xiangtan University | Wang D.L.,Xiangtan University | Zhang Z.Q.,Xiangtan University | Ding J.W.,Xiangtan University | Liu W.M.,CAS Institute of Physics
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

We study analytically the characteristics of optical absorption and slow-light solitons in an asymmetrical four-level N configuration semiconductor quantum wells with the cross-coupling relaxation of longitudinal-optical phonons (CCRLOP). It is shown that, in the linear range, the electromagnetically induced transparency (EIT) depends on the coherence control of both the optical fields and the CCRLOP. A double EIT is obtained under a relatively strong optical field which is from the hole and antibonding states in the wide well. Especially, the double EIT becomes perfect under the condition of increasing the CCRLOP. In the nonlinear range, the CCRLOP has an important effect on both the amplitude and the group velocity of the solitons. The amplitude of solitons reveals parabolic changes which obtain a maximum value with the increase of CCRLOP. The group velocity of the solitons continuously slows down if there are fixed three-photon detunings. These results may have potential applications for all-optical switching and some optical information engineering in solid systems. © 2011 American Physical Society.

Li L.,Hunan Institute of Engineering | Yi J.,Hunan University of Technology | Zhu J.,Xiangtan University
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2011

This paper proposes a new method of parameter estimation of power quality disturbances based on modified incomplete S-transform, which combines the modified S-transform with incomplete S-transform. The method complementary advantages in time frequency resolutions and computation speed. First, the computational procedure is provided. After that the optimal windowing coefficients in connection with different disturbances are discussed. Then the extraction of characteristic quantities is introduced, which are the module vectors obtained from the modified incomplete S-transform. The computation of each vector based on adaptive selection of optimal windowing coefficient. Finally, the parameters estimation method which utilizes these characteristic quantities are illustrated. Simulation results verified that the proposed method has characteristics of lower complexity, less computation and high precision.

Lan Y.-H.,Xiangtan University | Gu H.-B.,Xiangtan University | Chen C.-X.,Xiangtan University | Zhou Y.,Xiangtan University | Luo Y.-P.,Hunan Institute of Engineering
Neurocomputing | Year: 2014

This paper concerns with the problem of the observer-based robust control for a class of fractional-order complex dynamic networks. First, by introducing a continuous frequency distributed equivalent model and using indirect Lyapunov approach, the sufficient condition for robust asymptotic stability of the closed-loop systems via state observer-based control is presented. Next, using matrix[U+05F3]s singular value decomposition (SVD) and linear matrix inequality (LMI) techniques, the existence condition and method of designing a robust non-fragile observer-based controller are derived. Finally, the validity of the proposed methods are demonstrated by a numerical example. © 2014 Elsevier B.V.

Chen S.,Xiangtan University | Liao Y.,Xiangtan University | Liao Y.,Hunan Institute of Engineering | Zhao F.,Xiangtan University | And 3 more authors.
Organic Letters | Year: 2014

A novel palladium catalyzed approach to 3-arylindoles was developed from indoles and cyclohexanones. Various cyclohexanones acted as aryl sources via an alkylation and dehydrogenation sequence using molecular oxygen as the hydrogen acceptor. This method showed good regioselectivity and afforded 3-arylindoles as the sole products. © 2014 American Chemical Society.

Xiao Y.,Jiangnan University | Song G.,Wuxi Institute of Technology | Liao Y.,Xiangtan University | Ding R.,Jiangnan University
International Journal of Control, Automation and Systems | Year: 2012

This paper proposes a multi-innovation stochastic gradient (MISG) parameter estimation algorithm for an input nonlinear controlled autoregressive (IN-CAR) model, i.e., a Hammerstein nonlinear CAR system, by expanding the innovation length. The analysis and simulation results indicate that the proposed MISG algorithm can generate more accurate parameter estimates for IN-CAR systems compared with the stochastic gradient algorithm. © ICROS, KIEE and Springer 2012;.

Wang R.-N.,Guangxi University | Tang B.-Y.,Guangxi University | Tang B.-Y.,Xiangtan University | Peng L.-M.,Shanghai JiaoTong University | Ding W.-J.,Shanghai JiaoTong University
Computational Materials Science | Year: 2012

First-principles calculations were performed to investigate the structural, elastic and electronic properties of L1 2-Al 3(Sc 1-xZr x) (x = 0.25, 0.5 and 0.75) based on special quasi-random structures (SQSs) with 32 atoms. As the content of Zr atoms increased, the lattice parameters of L1 2-Al 3(Sc 1-xZr x) were increased whereas thermodynamical stability was lowered. The obtained C 11 and C 44 were reduced slightly, indicating that the incompressibility along the principle axes and the resistance to shear in 〈0 0 1〉 direction on the {1 0 0} plane were lowered, the shear and Young's modulus were also reduced while the bulk modulus were slightly larger. The ductility was improved due to increase of the B/G ratio and Cauchy pressure. The electronic structures revealed that the dominant hybridization between the Al p states and transition-metal d states became weaker with increasing of the content of Zr. © 2012 Elsevier B.V. All rights reserved.

Zeng M.-X.,Guangxi University | Wang R.-N.,Guangxi University | Tang B.-Y.,Guangxi University | Tang B.-Y.,Xiangtan University | And 2 more authors.
Modelling and Simulation in Materials Science and Engineering | Year: 2012

A detailed theoretical study of structural, elastic and electronic properties of tI26-type Mg 12RE (RE=Ce, Pr and Nd) phases has been carried out by means of first-principles calculations based on density functional theory. The optimized lattice parameters at T=0K are in excellent agreement with the available experimental value at room temperature, and the obtained formation enthalpies show that with increasing atomic number of RE, the stability of Mg 12RE alloys becomes lower. The elastic constants of tI26 Mg 12RE are further calculated, then the bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio of polycrystalline aggregates are derived, and the relevant mechanical properties of Mg 12RE alloys are also discussed. The elastic anisotropy of the three alloys is studied in detail using several methods, and the three-dimensional directional representation reveals the variation of Young's modulus along the crystallographic direction visually and completely. Finally, electronic density of states, charge density distribution and Bader charges are also calculated to reveal the underlying mechanism of structural stability and mechanical properties. © 2012 IOP Publishing Ltd.

Zhou Y.,Xiangtan University | Li J.,Shanghai JiaoTong University
Proceedings of the 2012 24th Chinese Control and Decision Conference, CCDC 2012 | Year: 2012

Target tracking by two airborne platforms with bearings-only measurements has obtained distinct interest recently. It is a nonlinear problem that Kalman filter (KF) can not be applied directly. Using extended Kalman filter (EKF) to solve this problem will get high computational burden involved because the Jacoby and Hessian matrices for the measuring equation should be calculated online. In this paper, the triangular ranging formula is derived for two bearings-only platforms first. Then the location error is proved to be zero mean Gaussian noises. This enables the traditional Kalman filter applicable. To further improve the tracking accuracy, interactive multiple model (IMM) is adopted to estimate the target state from the converted measurements. Simulation for both non-maneuvering and maneuvering target is also included to illustrate the proposed approach has high accuracy with much lower computational burden. © 2012 IEEE.

Chen Y.,South China Normal University | Dai L.,Mathematics Teaching and Research Group | Lu Z.,Xiangtan University
Advances in Applied Mathematics and Mechanics | Year: 2010

We investigate the superconvergence properties of the constrained quadratic elliptic optimal control problem which is solved by using rectangular mixed finite element methods. We use the lowest order Raviart-Thomas mixed finite element spaces to approximate the state and co-state variables and use piecewise constant functions to approximate the control variable. We obtain the superconvergence of O(h 1+s) (0

Li Q.,Xiangtan University | Chan W.H.,The Hong Kong Institute of Education | Wu C.,Guangdong University of Finance | Wen Z.,Xiangtan University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

Blind quantum computation allows a client who does not have enough quantum resources or technologies to achieve quantum computation on a remote quantum server such that the client's input, output, and algorithm remain unknown to the server. Up to now, single- and double-server blind quantum computation have been considered. In this work, we propose a triple-server blind computation protocol where the client can delegate quantum computation to three quantum servers by the use of entanglement swapping. Furthermore, the three quantum servers can communicate with each other and the client is almost classical since one does not require any quantum computational power, quantum memory, and the ability to prepare any quantum states and only needs to be capable of getting access to quantum channels. © 2014 American Physical Society.

Fan T.-W.,Xiangtan University | Tang B.-Y.,Xiangtan University | Tang B.-Y.,Guangxi University | Peng L.-M.,Shanghai JiaoTong University | Ding W.-J.,Shanghai JiaoTong University
Scripta Materialia | Year: 2011

Multi-stacking fault structures in pure magnesium similar to long-period stacking ordered phases of Mg-Y-Zn alloys have been investigated systematically from first-principles calculations. Based on stacking fault energy, the favorable multi-stacking fault structures are in general accordance with experimental observations. Furthermore, the present investigations indicate that inter-transformation occurs mainly between long-period stacking ordered structures with the same type of stacking faults when their lower stacking fault energies are closer. Calculated electronic structures reveal two different mechanisms for I1-I1 and I2-I2 interactions. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Luo M.,Chinese University of Hong Kong | Leung Y.,Chinese University of Hong Kong | Zhou Y.,Xiangtan University | Zhang W.,Nanjing University of Information Science and Technology
Journal of Climate | Year: 2015

Temporal scaling properties of the monthly sea surface temperature anomaly (SSTA) in global ocean basins are examined by the power spectrum and detrended fluctuation analysis methods. Analysis results show that scaling behaviors of the SSTA in most ocean basins (e.g., global average, South Pacific, eastern and western tropical Pacific, tropical Indian Ocean, and tropical Atlantic) are separated into two distinct regimes by a common crossover time scale of 52 months (i.e., 4.3 yr). It is suggested that this crossover is modulated by the El Niño/La Niña-Southern Oscillation (ENSO), indicating different scaling properties at different time scales. The SSTA time series is nonstationary and antipersistent at the small scale (i.e., crossover). It is, however, stationary and long range correlated at the large scale (i.e.,.crossover). For both time scales, scaling behaviors of SSTA are heterogeneously distributed over the ocean, and the fluctuation of SSTA intensifies with decreasing latitude. Stronger fluctuation appears over the tropical regions (e.g., centraleastern tropical Pacific, tropical Atlantic, tropical Indian Ocean, and South China Sea), which are directly or indirectly linked to ENSO. Weaker fluctuation and stronger persistence are found in id- and high-latitude areas, coinciding with the ''reemergence'' areas. © 2015 American Meteorological Society.

Cai B.,Hunan Institute of Engineering | Zhu J.,Xiangtan University
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2012

In order to realize the effective following of output current along grid voltage and the maximum power point tracking, the working principle and control principle of PV grid-connected inverter are analyzed and the control and parameter setting of ADRC (Auto Disturbance Rejection Controller) are discussed. A current tracking control scheme based on ADRC is then designed for PV grid-connected inverter. The closed-loop current is tracked and controlled to realize the unity power factor operation, feed electricity to grid and make the grid current following along grid voltage. Experimental results show that, the ADRC suppresses various disturbances effectively and quickly, and the performance of system startup and stability are superior to conventional controllers.

Yu X.,Hunan Institute of Engineering | Wang X.,Xiangtan University | Chen J.,Hunan Institute of Engineering
Journal of the Chilean Chemical Society | Year: 2011

Recently, the support vector machine (SVM), as a novel type of learning machine, has been introduced to solve chemical problems. In this study, ε- support vector regression (ε-SVR) and ν-support vector regression (ν-SVR) were, respectively, used to construct quantitative structure-property relationship (QSPR) models of Q and e parameters in the Q-e scheme, which is remarkably useful in the interpretation of the reactivity of a monomer in free-radical copolymerizations. The quantum chemical descriptors used to developed the SVR models were calculated from styrene and radicals with structures CH 3CH 2C 1H 2-C 2HR 3• (C 1H 2= C 2HR 3 + CH 3CH 2• → CH 3CH 2C 1H 2- C 2HR 3•). The optimum ε-SVR model of lnQ (C= 9, ε =0.05 and γ =0.2) and the optimum ν-SVR model of e (C=100, ν = 0.5 and γ =0.4) produced low root mean square (rms) errors for prediction sets: 0.318 and 0.266, respectively. Thus, applying SVR to predict parameters Q and e is successful.

Zeng L.,Xiangtan University | Xiao Y.,Changde Vocational Technical College | Liu J.,Xiangtan University | Tan L.,Xiangtan University
Journal of Molecular Structure | Year: 2012

Three new ruthenium(II) complexes, [Ru(MeIm)4phen]2+ (1), [Ru(MeIm)4ip]2+ (2) and [Ru(MeIm)4pip] 2+ (3), have been synthesized and characterized. The binding properties of the three complexes towards calf-thymus DNA were investigated by different spectrophotometric methods and viscosity measurements. In addition, the cytotoxicity of these complexes has been evaluated by MTT method and Giemsa staining experiment. The main results reveal that the plane area and hydrophobicity of intercalative ligands have a significant effect on the DNA-binding behaviors and the IC50 value of complex 2 against MCF-7 cells is close to that of cis-Pt(NH3)2Cl2. © 2012 Elsevier B.V. All rights reserved.

Deng P.,Hengyang Normal University | Fei J.,Xiangtan University | Feng Y.,Hengyang Normal University
Analyst | Year: 2011

Chitosan was modified by salicylaldehyde via Schiff's base reaction and the resulting product was modified on the surface of an acetylene black paste electrode (ABPE) by the drop-coating method. In 0.5 mol L -1 acetate buffer (pH 4.2), a substantial increase in the anodic stripping peak current of tryptophan (Trp) (compared to conventional bare carbon paste electrode (CPE) and bare ABPE) is observed at the Schiff's base chitosan-modified electrode. The parameters influencing voltammetric determination of Trp have been optimized. Under the selected conditions, the linearity between the anodic peak currents and concentrations of Trp demonstrated a wide range of 6.0 × 10 -8 mol L -1 to 2.0 × 10 -6 mol L -1, 2.0 × 10 -6 mol L -1 to 4.0 × 10 -5 mol L -1 and 4.0 × 10 -5 mol L -1 to 1.0 × 10 -4 mol L -1, a low detection limit of 2.0 × 10 -9 mol L -1 was obtained after a 60 s accumulation. In addition, the developed electrochemical sensor has been successfully applied for the determination of Trp in pharmaceutical and biological samples with satisfactory assay results. This journal is © The Royal Society of Chemistry.

Huang C.,Xiangtan University | Huang C.,China Agricultural University | Ren A.,China Agricultural University | Feng C.,China Agricultural University | Yang N.,Xiangtan University
Sensors and Actuators, B: Chemical | Year: 2010

A two-photon sensor for silver ion derived from twin-cyano-stilbene as the fluorophore is reported. The sensor exhibits remarkably large two-photon absorption cross sections (δTPA) whose value is as high as 950 GM in MeCN, high sensitivity to and selectivity for silver ion, and emits strong two-photon fluorescence when excited by 790 nm laser photons. The sensor can be used to detect trace Ag+, and its binding constant (log K) for Ag+ is as high as 5.76 ± 0.05. The successful applications of the sensor provide a brilliant prototype for the development of ideal two-photon fluorescence probes. © 2010 Elsevier B.V. All rights reserved.

Deng P.-H.,Hengyang Normal University | Fei J.-J.,Xiangtan University | Feng Y.-L.,Hengyang Normal University
Journal of Electroanalytical Chemistry | Year: 2010

A sensitive and simplified voltammetric method is developed for the determination of trace amounts of vanadium(V) by adsorptive anodic stripping voltammetry using an acetylene black (AB) paste electrode. The method is based on the preconcentration of the V(V)-alizarin violet (AV) complex at open circuit while stirring the solution for 90 s in 0.15 mol dm-3 hexamethylenetetraamine-hydrochloric acid buffer (pH 4.4), the adsorbed complex is then oxidized, producing a response with a peak potential of 564 mV when scanning linearly from 0 to 1000 mV. For voltammetric determination of V(V), the parameters influencing the peak current have been optimized. Under the selected conditions, the peak current and concentration of V(V) accorded with linear relationship in the range of 8.0 × 10-10 mol dm -3-1.0 × 10-7 mol dm-3 (cAV = 2.0 × 10-6 mol dm-3) and 1.0 × 10-7 mol dm-3-8.0 × 10-6 mol dm-3 (c AV = 2.0 × 10-5 mol dm-3), the detection limit (three times signal to noise) was estimated to be 6.0 × 10 -10 mol dm-3 for 90 s accumulation. The relative standard deviation (RSD) is 1.9% and 2.3% for V(V) concentrations of 1.0 × 10 -7 mol dm-3 and 1.0 × 10-8 mol dm -3 respectively. Finally, this proposed method was successfully applied to the determination of V(V) in natural water samples. © 2010 Elsevier B.V. All rights reserved.

Ouyang T.,Xiangtan University | Chen Y.,Xiangtan University | Liu L.-M.,Beijing Computational Science Research Center | Xie Y.,Xiangtan University | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Graphyne, a new allotrope of carbon, is a current topic of focus in the nanomaterial research community. We investigate the thermal transport property of graphyne nanoribbons (GYNRs) by using the nonequilibrium Green's-function method. The thermal conductance of GYNRs is only approximately 40% that of graphene nanoribbons. A distinct width dependence of the thermal property is observed in GYNRs as well. The conductance of armchair-edged GYNRs (A-GYNRs) shows a linear width dependence, while a steplike width dependence is displayed in the conductance of zigzag-edged GYNRs (Z-GYNRs). Moreover, the conductance of an A-GYNR is larger than that of a Z-GYNR of the same width, indicating obvious anisotropic transport in graphyne (twice that in graphene). In addition, the thermal transport in graphyne family nanoribbons is also explored. The results show that the conductance of graphyne family nanoribbons is insensitive to the acetylenic linkages, but depends on the number of benzene rings. These findings could offer useful guidelines for the design and performance improvement of the graphyne-based nanodevices. © 2012 American Physical Society.

Deng C.-S.,Xiangtan University | Xu H.,University of South China
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2012

The localization behaviors of electronic states and the role of long-range correlation (LRC) in a one-dimensional tight-binding Anderson model with long-range correlated diagonal disorder were numerically studied at the band center by using the transfer matrix method. Two different kinds of localized states with anomalous properties were found in two special localized regimes: regime I with both weak correlation and weak disorder and regime II with both strong correlation and strong disorder. Further calculations show that the LRC plays inverse role in these two regimes: by increasing the degree of LRC, the localization is suppressed in regime I while the localization is enhanced in regime II. © 2011 Elsevier B.V.

Sun W.,Chalmers University of Technology | Ma Z.,Linköping University | Dang D.,Chalmers University of Technology | Dang D.,Xiangtan University | And 4 more authors.
Journal of Materials Chemistry A | Year: 2013

Unlike normal donor-acceptor (D-A) polymers containing only one electron-deficient segment in their repeating unit, the incorporation of two electron-deficient moieties with different absorption behaviors, forming a D-A1-D-A2 internal structure in the alternating copolymer, showed a broader absorption spectrum than its constituent parts and enhanced photovoltaic performance. This work is anticipated to open the door to the design of new low bandgap polymers with a broader absorption range for efficient polymer solar cells. © 2013 The Royal Society of Chemistry.

Deng C.-S.,Xiangtan University | Xu H.,University of South China
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2012

The combined effects of long-range correlations and disorder strength on critical properties of electronic states in one-dimensional systems with long-range correlated off-diagonal disorder are investigated for the whole energy band. Numerical studies on the localization length demonstrate the existence of disorder-induced delocalization-to-localization transition (DLT) and energy-induced DLT in such systems when the correlations of hopping terms are strong enough to generate extended states. Further calculations confirm that the critical disorder strength and critical energy related to these DLTs are Wc=2 t0-|E| and ± Ec=±|2 t0-W|, respectively. Based on these critical points, the detailed phase diagrams in different parameter spaces are obtained. © 2012 Elsevier B.V.

Xiao L.,Xiangtan University | Deng Z.,Xiangtan University | Fung Ka.Y.,Hong Kong University of Science and Technology | Ng Ka.M.,Hong Kong University of Science and Technology
International Journal of Hydrogen Energy | Year: 2013

Biohydrogen generated from the anaerobic digestion of a synthetic food waste with constant composition and a real food waste collected in Hong Kong were studied. This study aims at using a monoculture to increase biohydrogen production and determining optimum conditions for maximumbiohydrogen production. Among the nine bacteria screened for biohydrogen production, Escherichia cloacae and Enterobacter aerogenes produced the largest amount of biohydrogen from the anaerobic digestion of synthetic food waste. The optimum anaerobic digestion conditions were determined: initial pH of 7, a water to solids ratio of 5 (w/w), a mesophilic temperature (37 ± 1 °C), and in the presence of 40 mg/L FeSO4·7H2O. Anaerobic digestion at the optimum operating conditions using collected food waste with E. cloacae as the bacterial source was also performed. By adjusting the pH in the range of 5e6, a specific biohydrogen production of 155.2 mL/g of volatile solids (VS) in food waste was obtained. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Deng P.-H.,Hengyang Normal University | Feng Y.-L.,Hengyang Normal University | Fei J.-J.,Xiangtan University
Journal of Electroanalytical Chemistry | Year: 2011

A sensitive procedure was developed for the determination of trace molybdenum(VI) by adsorptive anodic stripping voltammetry based on the oxidation of molybdenum(VI)-2′,3,4′,5,7-pentahydroxyflavone (morin) complex at a sodium dodecyl sulfate modified carbon paste electrode (denoted as SDS/CPE). Compared with the poor response at a conventional paste electrode, the electrooxidation of molybdenum(VI)-morin complex at the SDS/CPE was greatly improved, as confirmed from the significant enhancement of peak current and the negative shift of peak potentials. The optimum conditions for the analysis of molybdenum(VI) include 0.1 M sulfuric acid, 3.0 × 10 -5 M or 3.0 × 10 -6 M morin, an accumulation potential of -0.1 V (versus SCE), an accumulation period of 60 s or 120 s and a scan rate of 0.1 V s -1. Under the selected conditions, the linearity between peak currents and concentrations of molybdenum(VI) existed for a wide range of 8.0 × 10 -10-6.0 × 10 -8 M (c morin = 3 × 10 -6 M) for 120 s accumulation and 6.0 × 10 -8-6.0 × 10 -6 M (c morin = 3 × 10 -5 M) for 60 s accumulation, a low detection limit (three times signal to noise) of 4.0 × 10 -10 M was obtained after a 120 s preconcentration. The proposed method was successfully applied to the determination of molybdenum(VI) in real samples with enhanced selectivity. © 2011 Elsevier B.V. All rights reserved.

Deng P.,Hengyang Normal University | Fei J.,Xiangtan University | Zhang J.,Hengyang Normal University | Feng Y.,Hengyang Normal University
Food Chemistry | Year: 2011

A reliable and sensitive procedure for the determination of trace levels of molybdenum by adsorptive anodic stripping voltammetry is proposed. The method is based on adsorptive accumulation of the molybdenum (Mo)-alizarin violet (AV) complex onto an acetylene black paste electrode (ABPE), followed by oxidation of the adsorbed species by voltammetric scan using a second-order derivative modulation. For voltammetric determination of molybdenum, the parameters influencing the peak current have been optimized. Under the selected conditions, the electrode demonstrated linear response over a wide range of Mo(VI) concentration (6.0×10-9-1.0×10-5mol/L), the detection limit was 2.0×10-9mol/L (S/N=3) for 120s accumulation. The effects of potential interfering ions were studied, and it was found that the proposed procedure was free from most interferences. The method has been applied to the determination of molybdenum in plant foodstuffs, and satisfied results were obtained. © 2010 Elsevier Ltd.

Zhou G.,Xi'an Jiaotong University | Zhou G.,Hong Kong Baptist University | Wang Q.,CAS Changchun Institute of Applied Chemistry | Wang X.,Xiangtan University | And 5 more authors.
Journal of Materials Chemistry | Year: 2010

A new series of phosphorescent platinum(II) cyclometalated complexes with distinct electronic structures has been developed by simple tailoring of the phenyl ring of ppy (Hppy = 2-phenylpyridine) with various main-group moieties in [Pt(ppy-X)(acac)] (X = B(Mes)2, SiPh3, GePh3, NPh2, POPh2, OPh, SPh, SO2Ph substituted at the para position). Their distinctive electronic characters, resulting in improved hole-injection/hole-transporting or electron-injection/electron-transporting features, have confined/consumed the electrons in the emission layer of organic light-emitting diodes (OLEDs) to achieve good color purity and high efficiency of the devices. The maximum external quantum efficiency of 9.52%, luminance efficiency of 30.00 cd A-1 and power efficiency of 8.36 lm W -1 for the OLEDs with Pt-B (X = B(Mes)2) as the emitter, 8.50%, 29.74 cd A-1 and 19.73 lm W-1 for the device with Pt-N (X = NPh2), 7.92%, 22.06 cd A-1 and 13.64 lm W -1 for the device with Pt-PO (X = POPh2) as well as 8.35%, 19.59 cd A-1 and 7.83 lm W-1 for the device with Pt-SO2 (X = SO2Ph) can be obtained. By taking advantage of the unique electronic structures of the Pt-Ge (X = GePh3) and Pt-O (X = OPh) green emitters and the intrinsic property of blue-emitting hole-transport layer of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), single-dopant white OLEDs (WOLEDs) can be developed. These simple WOLEDs emit white light of very high quality (CIE at (0.354, 0.360), CRI of ca. 97 and CCT at 4719 K) even at high brightness (>15000 cd m-2) and the present work represents significant progress to address the bottle-neck problem of WOLEDs for the efficiency/color quality/brightness trade-off optimization that is necessary for pure white light of great commercial value. © 2010 The Royal Society of Chemistry.

Zhang Y.,Nanjing Southeast University | Liu Y.,University of Washington | Ye H.-Y.,Nanjing Southeast University | Fu D.-W.,Nanjing Southeast University | And 8 more authors.
Angewandte Chemie - International Edition | Year: 2014

Molecular ferroelectric thin films are highly desirable for their easy and environmentally friendly processing, light weight, and mechanical flexibility. A thin film of imidazolium perchlorate processed from aqueous solution is an excellent molecular ferroelectric with high spontaneous polarization, high Curie temperature, low coercivity, and superior electromechanical coupling. These attributes make it a molecular alternative to perovskite ferroelectric films in sensing, actuation, data storage, electro-optics, and molecular/flexible electronics. Molecular ferroelectric thin films and block crystals along crystal face (10\bar 2) of imidazolium perchlorate display perfect hexagonal domains similar to that of the trigonal crystal system LiNbO3. The high spontaneous polarization, high Curie temperature, low coercivity, and superior electromechanical coupling make it a molecular alternative to perovskite ferroelectric films. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ma Z.,Linköping University | Dang D.,Chalmers University of Technology | Dang D.,Xiangtan University | Tang Z.,Linköping University | And 8 more authors.
Advanced Energy Materials | Year: 2014

A series of conjugated polymers containing benzodithiophene as donor and isoindigo as acceptor with no, one, two and three thiophene spacer groups is synthesized and characterized. The polymer with bithiophene as a spacer has a superior efficiency of 7.31% in solar cells. This demonstrates an important design strategy to produce polymers for high-performance solar cells by inserting thiophene spacer groups. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Geng S.,Xiangtan University | Zhang L.,University of South China
Zeitschrift fur Angewandte Mathematik und Physik | Year: 2013

This paper is concerned with the asymptotic behavior of the solution for quasilinear hyperbolic equations with nonlinear damping. The main novelty in this paper is that we obtain the Lp(2 ≤ p ≤ +∞) convergence rates of the solution to the quasilinear hyperbolic equations, and we need none of the additional technical assumptions for the nonlinear damping f(v) given by Li and Saxton (Q Appl Math 61:295–313, 2003). © 2013, Springer Basel.

Zhang Y.,Xiangtan University | Wang Z.,Beijing Computational Science Research Center | Cao J.,Xiangtan University | Cao J.,Beijing Computational Science Research Center
Journal of Materials Chemistry C | Year: 2014

Based on density functional theory, we investigated the magnetic properties of 5d transition metal (TM) atoms at the porous sites of graphene-like carbon nitride (g-C3N4). Our results show that the TM adatoms bind to g-C3N4 much more strongly than to graphene, due to the unique porous structure of g-C3N4. The magnetic anisotropy energies (MAEs) for TM-doped g-C3N4 were investigated using the torque method. Huge MAEs are obtained, especially for Ir@g-C3N4 (12.4 meV per atom), with an easy axis perpendicular to the plane. Moreover, the MAE can be enhanced to 56.9 meV per atom by applying an electric field of up to 1.0 V Å-1. © 2014 the Partner Organisations.

We report on a novel electrochemical method for the sensitive determination of trace zirconium (Zr) at a glassy carbon electrode modified with a film of acetylene black containing dihexadecyl hydrogen phosphate and in the presence of alizarin violet (AV). The method is based on the preconcentration of the Zr(IV)-AV complex at a potential of -200 mV (vs. SCE). The adsorbed complex is then oxidized, producing a response with a peak potential of 526 mV. Compared to the poor electrochemical signal at the unmodified GCE, the electrochemical response of Zr(IV)-AV complex is greatly improved, as confirmed by the significant increase in peak current. The effects of experimental conditions on the oxidation current were studied and a calibration plot established. The oxidation current is linearly related to the Zr(IV) concentration in the 8.0 pM to 10 nM concentration range (c AV = 0.2 μM) and 10 nM ~0.6 μM (c AV = 2.0 μM), and the detection limit (S/N = 3) is as low as 4.0 pM for a 3-min accumulation time. The method was successfully employed to the determination of zirconium in standard ore samples. © 2011 Springer-Verlag.

Yang Y.,Xiangtan University | Yang Y.,Chinese Academy of Sciences | Xie H.,Chinese Academy of Sciences | Xie H.,Dalian National Laboratory for Clean Energy | Liu E.,Xiangtan University
Green Chemistry | Year: 2014

1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU), in conjunction with methanol after CO2 capture in DMSO created a new solvent capable of dissolving up to 8 wt% of cellulose, which could be applied as a highly efficient reaction media for the synthesis of cellulose esters under mild conditions. This journal is © the Partner Organisations 2014.

Zhang Y.,Xiangtan University | Zheng X.,Xiangtan University | Zhang T.,Jilin University
Sensors and Actuators, B: Chemical | Year: 2011

Bi0.5Na0.5TiO3-Bi0.5K 0.5TiO3 (BNT-BKT) powder is synthesized by a metal-organic decomposition method and characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). A humidity sensor, which is consisted of five pairs of Ag-Pd interdigitated electrodes and an Al2O3 ceramic substrate, is fabricated by spin-coating the BNT-BKT powder on the substrate. Good humidity sensing properties such as high response value, short response and recovery times, and small hysteresis are observed in the sensing measurement. The impedance changes more than four orders of magnitude within the whole humidity range from 11% to 95% relative humidity (RH) at 100 Hz. The response time and recovery time are about 20 and 60 s, respectively. The maximum hysteresis is around 4% RH. The results indicate that BNT-BKT powder is of potential applications for fabricating high performance humidity sensors. © 2011 Elsevier B.V. All Rights Reserved.

Yi Z.,Hunan Normal University | Yi Z.,Xiangtan University | Lu W.,Hong Kong Polytechnic University | Liu H.,Hunan Normal University | Zeng S.,Hunan Normal University
Nanoscale | Year: 2015

Polyacrylic acid (PAA) modified NaYF4:Gd/Yb/Er upconversion nanorods (denoted as PAA-UCNRs) are demonstrated for tri-modal upconversion (UC) optical, computed X-ray tomography (CT), and magnetic resonance imaging (MRI). The hydrophilic PAA-UCNRs were obtained from hydrophobic oleic acid (OA) capped UCNRs (denoted as OA-UCNRs) using a ligand exchange method. The as-prepared UCNRs with a hexagonal phase structure present high monodispersity. These PAA-UCNRs are successfully used as ideal probes for in vivo UC luminescence bioimaging and synergistic X-ray and UC bioimaging. Moreover, X-ray CT imaging reveals that PAA-UCNRs can act as contrast agents for improved detection of the liver and spleen. In addition, a significant signal enhancement in the liver is observed in in vivo MRI, indicating that PAA-UCNRs are ideal T1-weighted MRI agents. More importantly, in vivo long-term tracking based on these PAA-UCNRs in the live mice and the corresponding ex vivo bioimaging of isolated organs also verify the translocation of PAA-UCNRs from the liver to the spleen, and the observed intense UC signals from the feces reveal the biliary excretion mechanism of these UCNRs. These findings contribute to understanding of the translocation and potential route for excretion of PAA-UCNRs, which can provide an important guide for the diagnosis and detection of diseases based on these UCNRs. This journal is © The Royal Society of Chemistry.

Chen Y.Q.,Xiangtan University | Zheng X.J.,Xiangtan University | Feng X.,Tsinghua University
Nanotechnology | Year: 2010

Zn1-xVxO (x = 0.015, 0.02, 0.025, 0.03, V-ZnO) nanofibers were synthesized by electrospinning, and a butterfly-shaped piezoelectric response was measured by scanning force microscopy. The diameters of V-ZnO nanofibers with hexagonal wurtzite phase are in the range of 50-300nm. The large piezoelectric coefficient d33 of 121pmV-1 was obtained and the high piezoelectric property may be attributed to the switchable spontaneous polarization induced by V dopants and the easier rotation of V-O bonds under an electric field. The result shows that the V-ZnO nanofiber is a promising candidate for nanoscale piezoelectric devices. © 2010 IOP Publishing Ltd.

Zhang X.,Nanyang Technological University | Zhang X.,China Jiliang University | Huang Y.,Xiangtan University | Ma Z.,Xiangtan University | And 4 more authors.
Physical Chemistry Chemical Physics | Year: 2014

Consistency in experimental observations, numerical calculations, and theoretical predictions have revealed that the skins of water and ice share the same attribute of supersolidity characterized by an identical H-O vibration frequency of 3450 cm-1. Molecular undercoordination and inter-electron-pair repulsion shortens the H-O bond and lengthens the O:H nonbond, leading to a dual process of nonbonding electron polarization. This relaxation-polarization process enhances the dipole moment, elasticity, viscosity, and thermal stability of these skins with a 25% density loss, which is responsible for the hydrophobicity and toughness of the water skin and results in the slippery behavior of ice. This journal is © the Partner Organisations 2014.

Li C.P.,Chinese University of Hong Kong | Yu Z.G.,Xiangtan University | Yu Z.G.,Queensland University of Technology | Han G.S.,Xiangtan University | Chu K.H.,Chinese University of Hong Kong
PLoS ONE | Year: 2012

Background: The composition vector (CV) method has been proved to be a reliable and fast alignment-free method to analyze large COI barcoding data. In this study, we modify this method for analyzing multi-gene datasets for plant DNA barcoding. The modified method includes an adjustable-weighted algorithm for the vector distance according to the ratio in sequence length of the candidate genes for each pair of taxa. Methodology/Principal Findings: Three datasets, matK+rbcL dataset with 2,083 sequences, matK+rbcL dataset with 397 sequences and matK+rbcL+trnH-psbA dataset with 397 sequences, were tested. We showed that the success rates of grouping sequences at the genus/species level based on this modified CV approach are always higher than those based on the traditional K2P/NJ method. For the matK+rbcL datasets, the modified CV approach outperformed the K2P-NJ approach by 7.9% in both the 2,083-sequence and 397-sequence datasets, and for the matK+rbcL+trnH-psbA dataset, the CV approach outperformed the traditional approach by 16.7%. Conclusions: We conclude that the modified CV approach is an efficient method for analyzing large multi-gene datasets for plant DNA barcoding. Source code, implemented in C++ and supported on MS Windows, is freely available for download at http://math.xtu.edu.cn/myphp/math/research/source/Barcode_source_codes.zip. © 2012 Li et al.

Wang Y.-F.,Queensland University of Technology | Yu Z.-G.,Queensland University of Technology | Yu Z.-G.,Xiangtan University | Anh V.,Queensland University of Technology
International Journal of Data Mining and Bioinformatics | Year: 2013

Microarray techniques have revolutionised genomic research by making it possible to monitor the expression of thousands of genes in parallel. The Fuzzy C-Means (FCM) method is an efficient clustering approach devised for microarray data analysis. However, microarray data contains noise, which would affect clustering results. In this paper, we propose to combine the FCM method with the Empirical Mode Decomposition (EMD) for clustering microarray data to reduce the effect of the noise. The results suggest the clustering structures of denoised microarray data are more reasonable and genes have tighter association with their clusters than those using FCM only. Copyright © 2013 Inderscience Enterprises Ltd.

Liu H.-J.,Xiangtan University | Yang D.-W.,Xiangtan University | Liu H.-H.,Xiangtan University | Liu H.-H.,Wuhan Textile University
Analytical Methods | Year: 2012

A poly(brilliant cresyl blue) (PBCB) functionalized single walled-carbon nanotube (SWCNT) modified glassy carbon electrode (PBCB/SWCNT/GCE) is fabricated by electropolymerization. The electrocatalytic activity of the PBCB/SWCNT/GCE towards the reduction of hydrogen peroxide is then investigated. The electrode shows high sensitivity [4.1 nA (μM) -1] to the electrocatalytic reduction of H 2O 2 at an applied potential of -0.30 V (vs. SCE). Important practical advantages such as a fast response time (within 5 s), a low detection limit (0.12 μM), wide linear dynamic range (4.9 × 10 -7 to 2.3 × 10 -4 M, R 2 = 0.994) and stability (remains ∼93% of its original activity after 30 days) are achieved with the PBCB/SWCNT/GCE. Further, the presence of probable interferences such as glucose, ascorbic acid, dopamine and uric acid does not interfere during the detection of H 2O 2. The application of the sensor to determine H 2O 2 in tap water with recovery values of 96% to 102% shows the sensor is suitable for routine analysis. © 2012 The Royal Society of Chemistry.

Wang H.,Hunan Normal University | Wang H.,Xiangtan University | Yi Z.,Hunan Normal University | Yi Z.,Xiangtan University | And 4 more authors.
Journal of Materials Chemistry C | Year: 2013

In this paper, optical/magnetic multi-functional NaErF4 nanocrystals with high quality, different phases and shapes were synthesized by a simple hydrothermal method using oleic acid as the capping agent. The structure, upconversion luminescence and magnetic properties were characterized by various techniques. The transmission electron microscopy results reveal that the nanocrystals are of high quality and can be self-assembled into a two-dimensional ordered structure. Moreover, the crystal phase and shape can be readily controlled by adjusting the reaction temperature and F- content. The results reveal that high temperature can favor the formation of a hexagonal phase structure and promote the phase transformation from the cubic to hexagonal phase. The phase transformation mechanism based on the free energy theory was discussed in detail. In addition, the F- content plays a critical role in determining the morphology of the final products. A high F - content is beneficial for the formation of the one-dimensional rod-like shape. Interestingly, phase-induced upconversion luminescence color tuning from red to green was observed. All of the as-prepared NaErF4 nanocrystals possess paramagnetic properties at room temperature and the magnetizations of the nanocrystals with spherical-like cubic, cubic, and rod-like shapes were measured as 1.69 emu g-1, 2.53 emu g -1and 2.29 emu g-1 at 20 kOe, respectively, which are larger than most previously reported Gd-based nanocrystals. In addition, T 2-weighted magnetic resonance imaging based on these NaErF 4 nanocrystals was demonstrated for the first time. Therefore, these tunable upconversion fluorescent NaErF4 nanocrystals with excellent paramagnetic properties can be used as promising dual-modal nanoprobes for optical bioimaging and magnetic resonance imaging, and may have potential applications in bioseparation. This journal is © The Royal Society of Chemistry 2013.

Wang J.,Guizhou University | Zhou Y.,Xiangtan University | Wei W.,Guizhou University
Systems and Control Letters | Year: 2012

In this paper, we study optimal feedback controls of a system governed by semilinear fractional evolution equations via a compact semigroup in Banach spaces. By using the Cesari property, the Fillippove theorem and extending the earlier work on fractional evolution equations, we prove the existence of feasible pairs. An existence result of optimal control pairs for the Lagrange problem is presented. © 2012 Elsevier B.V. All rights reserved.

Agarwal R.P.,Florida Institute of Technology | Zhou Y.,Xiangtan University | Wang J.,Guizhou University | Luo X.,Xiangtan University
Mathematical and Computer Modelling | Year: 2011

In this paper, we study the fractional functional differential equations with causal operators in an arbitrary separable Banach space. By means of the techniques of the measure of noncompactness, the existence and continuation of solutions are given. Further, some topological properties of solution sets are discussed and the existence of optimal solutions of the associated control problem are presented. An example is given to illustrate the result. © 2011 Elsevier Ltd.

Sun C.Q.,Xiangtan University | Sun C.Q.,Nanyang Technological University | Zhang X.,Nanyang Technological University | Zhang X.,China Jiliang University | And 4 more authors.
Journal of Physical Chemistry Letters | Year: 2013

Goldschmidt-Pauling contraction of the H-O polar-covalent bond elongates and polarizes the other noncovalent part of the hydrogen bond (O:H-O), that is, the O:H van der Waals bond, significantly, through the Coulomb repulsion between the electron pairs of adjacent oxygen (O-O). This process enlarges and stiffens those H2O molecules having fewer than four neighbors such as molecular clusters, hydration shells, and the surface skins of water and ice. The shortening of the H-O bond raises the local density of bonding electrons, which in turn polarizes the lone pairs of electrons on oxygen. The stiffening of the shortened H-O bond increases the magnitude of the O1s binding energy shift, causes the blue shift of the H-O phonon frequencies, and elevates the melting point of molecular clusters and ultrathin films of water, which gives rise to their elastic, hydrophobic, highly-polarized, ice-like, and low-density behavior at room temperature. © 2013 American Chemical Society.

Huang C.,Xiangtan University | Huang C.,Shaoguan University | Ding C.,Sun Yat Sen University
Analytica Chimica Acta | Year: 2011

A novel two-photon fluorescence probe for Pb2+ derived from 4-methyl-2,5-dicyano-4′-amino stilbene as a two-photon fluorophore and bis[2-(2-aminophenylsulfanyls)ethyl]amine as a novel Pb2+ ligand was developed. The probe possesses small molecule size, large two-photon absorption cross-section (1020GM), noncytotoxic effect, long-wavelength emission at 609nm, large Stokes shift (209nm), excellent photostability, moderate water-solubility, good cell-permeability, and pH-insensitivity in the biologically relevant pH range. The probe can selectively detect Pb2+ ions in live cells and living tissues without interference from other metal ions and the membrane-bound probes, and its quenching constant (KSVTP) is 7.58×105M-1. © 2011 Elsevier B.V.

Sun C.Q.,Xiangtan University | Sun C.Q.,Nanyang Technological University | Zhang X.,Nanyang Technological University | Zhang X.,China Jiliang University | And 6 more authors.
Journal of Physical Chemistry Letters | Year: 2013

The specific-heat difference between the O:H van der Waals bond and the H-O polar-covalent bond and the Coulomb repulsion between electron pairs on adjacent oxygen atoms determine the angle-length-stiffness relaxation dynamics of the hydrogen bond (O:H-O), which is responsible for the density and phonon-stiffness oscillation of water ice over the full temperature range. Cooling shortens and stiffens the part of relatively lower specific-heat, and meanwhile lengthens and softens the other part of the O:H-O bond via repulsion. Length contraction/elongation of a specific part always stiffens/softens its corresponding phonon. In the liquid and in the solid phase, the O:H bond contracts more than the H-O elongates, hence, an O:H-O cooling contraction and the seemingly "regular" process of cooling densification take place. During freezing, the H-O contracts less than the O:H elongates, leading to an O:H-O elongation and volume expansion. At extremely low temperatures, the O:H-O angle stretching lowers the density slightly as the O:H and the H-O lengths change insignificantly. In ice, the O-O distance is longer than it is in water, resulting in a lower density, so that ice floats. © 2013 American Chemical Society.

Tang H.,Xiangtan University | Tang H.,Louisiana State University | Zhang D.,Louisiana State University
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2013

A series of pyrenyl-terminated poly(γ-benzyl-l-glutamate)s (py-PBLGs) with controlled polymer molecular weight (MW = 2.3-14.8 kg mol -1) and molecular weight distribution (PDI = 1.17-1.55) have been prepared from 1-pyrenemethylamine hydrochloride-mediated ring-opening polymerization (ROP) of γ-benzyl-l-glutamic acid based N-carboxyanhydride (BLG-NCA). FTIR analysis revealed that the py-PBLG9 was conformationally heterogeneous with 35.0% α-helix, 55.6% β-sheet, and 9.4% random coil conformations in the solid state, whereas the py-PBLG 66 adopts 100% α-helix conformation. Py-PBLGs promote the dispersion of SWCNTs in organic solvents and in the PBLG solid through π-π interaction, as evidenced by the Raman spectroscopic studies. WAXD analysis revealed that the SWCNTs significantly affect the ordering of the py-PBLG self-assembly: the long range hexagonal packing of py-PBLG66 rods is notably enhanced by the addition of SWCNTs, whereas the lamellar packing of py-PGLG9 β-sheets is weakened. In the hexagonal lattice, the SWCNTs are intercalated parallel to the py-PBLG66 rods, in contrast to the normal orientation of the SWCNTs with respect to the extended py-PBLG9 chains in the β-sheets. The relative packing structure also affects the intermolecular interaction among the PBLGs: SWCNTs promote the interaction among the py-PBLG9 chains packed in a lamellar structure and weaken the intermolecular interaction among the py-PBLG66 columnar hexagonal array. © 2013 Wiley Periodicals, Inc.

Zhang Y.,Xiangtan University | Zheng X.,Xiangtan University | Zhang T.,Jilin University | Gong L.,Xiangtan University | And 2 more authors.
Sensors and Actuators, B: Chemical | Year: 2010

As a novel humidity sensing material, Bi0.5K0.5TiO3 (BKT) powder was synthesized by a chemical solution method, and the humidity sensor was composed of BKT powder, Ag-Pd interdigitated electrodes and Al2O3 ceramic substrate. The humidity sensing properties were measured by using LCR analyzer. The experimental results show that the impedance changes about four orders of magnitude within the whole humidity range from 11% to 95% relative humidity (RH). At the frequency of 100 Hz, the response time and recovery time are about 12 and 25 s, and the maximum hysteresis is around 3% RH. They indicate that BKT powder has good humidity sensing properties, and it is of the potential applications for fabricating high performance humidity sensors. © 2010 Elsevier B.V. All rights reserved.

Chen F.,Xiangnan University | Nieto J.J.,University of Santiago de Compostela | Zhou Y.,Xiangtan University
Nonlinear Analysis: Real World Applications | Year: 2012

We present some results for the global attractivity of solutions for fractional differential equations involving RiemannLiouville fractional calculus. The results are obtained by employing Krasnoselskii's fixed point theorem. Similar results for fractional differential equations involving Caputo fractional derivative are also obtained by using the classical Schauder's fixed point theorem. Several examples are given to illustrate our main results. © 2011 Elsevier Ltd. All rights reserved.

Zheng W.-T.,Jilin University | Sun C.Q.,Nanyang Technological University | Sun C.Q.,Xiangtan University
Energy and Environmental Science | Year: 2011

As a new class of materials, carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) have been continuing fascinating the community with properties that can be seen from neither bulk graphite nor diamond. Although the physics and chemistry of these carbon allotropes have been intensively investigated from various perspectives, the laws governing the fascinations and their interdependence remain as yet undetermined. From the perspectives of bond and nonbond formation, dissociation, relaxation, vibration, and the associated energetics and dynamics of charge repopulation, polarization, densification, and localization, this article aims to show that the broken-bond-induced local bond contraction and bond strength gain, quantum entrapment and densification of charge and energy, polarization of the unpaired edge dangling σ-bond electrons, and the formation of the pseudo-π-bond between the dangling σ-bond electrons along the edges are responsible for the anomalies. Theoretical reproduction of the experimentally observed elastic modulus enhancement, melting point depression, layer-number, strain, pressure and temperature induced Raman shift, C 1s core-level positive shift, work function reduction, band gap expansion, edge and defect selective generation of the Dirac-Fermi polarons and the associated magnetism consistently confirmed that the shorter and stronger bonds between undercoordinated carbon atoms modulate locally the atomic cohesive energy, the Hamiltonian, and hence the detectable bulk properties. The polarization of the unpaired dangling σ-bond electrons by the densely, deeply, and locally entrapped core and bonding electrons generates the massless, magnetic and mobile Dirac-Fermi polarons at sites surrounding vacancies and zigzag-GNR edges. The pseudo-π-bond formation between the nearest dangling σ-bond electrons along the armchair-GNR and the reconstructed zigzag-GNR edges discriminates them from the zigzag-GNR edges or vacancies in the electronic and magnetic properties. Consistency between predictions and observations confirmed that the C-C bond contracts by up to 30% with a 152% bond strength gain at the edges with respect to those in the bulk diamond. © 2011 The Royal Society of Chemistry.

Zhao B.,Xiangtan University | Huang H.,Xiangtan University | Jiang P.,Xiangtan University | Zhao H.,Xiangtan University | And 5 more authors.
Journal of Physical Chemistry C | Year: 2011

Flexible counter electrodes (CEs) are designed and fabricated by depositing the composite film of carbon materials (carbon aerogel, carbon black, and active carbon) and poly(tetrafluoroethylene) on stainless steel mesh and applied in dye-sensitized solar cells (DSSCs). The effect of pore structure of the carbon materials on the electrocatalytic activity was investigated by cyclic voltammogram and electrochemical impedance spectroscopic analysis. The carbon aerogel with a mesopore structure showed the highest double-layer capacitance and best electrocatalytic activity. The DSSC, based on the carbon aerogel CE and a ruthenium dye (N719), showed a high power conversion efficiency of 9.06%, which is 99% of that based on a Pt CE (9.14%) under the same experimental conditions. © 2011 American Chemical Society.

Li Y.,Sun Yat Sen University | Zhang Q.,Sun Yat Sen University | Zhu J.,Sun Yat Sen University | Wei X.-L.,Xiangtan University | Shen P.K.,Sun Yat Sen University
Journal of Materials Chemistry A | Year: 2014

A rational design of MnO2/3D porous graphene-like (PG) (denoted as 3D PG-Mn) composites and their fabrication via a simple and cost-effective redox process have been achieved for the first time. The 3D PG can provide a highly conductive structure in conjunction with a large surface area to support good contact between the MnO2 nanoparticles and effectively enhance the mechanical strength of the composite during volume changes as well as suppress the aggregation of MnO2 nanoparticles during Li ion insertion/extraction. As a result, the 3D PG-Mn composite with a content of 62.7 wt% MnO2 shows a highly stable capacity of up to 836 mA h g -1 after 200 cycles at a current density of 100 mA g-1 and reversible high rate charge-discharge performance. Such a highly stable 3D PG-Mn composite can be produced on a large-scale and might have even wider applications as an anode material in lithium-ion batteries. © 2014 The Royal Society of Chemistry.

Yi Z.,Hunan Normal University | Yi Z.,Xiangtan University | Zeng S.,Hunan Normal University | Lu W.,Hong Kong Polytechnic University | And 6 more authors.
ACS Applied Materials and Interfaces | Year: 2014

In this work, the amine-functionalized NaYbF4:Er nanoparticles were developed as dual-modal nanoprobes for synergistic upconversion (UC) luminescence and X-ray imaging in a single system by a simple one-step method of simultaneous synthesis and surface modification. The water-soluble NaYbF 4:Er nanoparticles present excellent green and dominant red UC emissions. The in vitro cell imaging shows that the high-contrast green and intense red UC emissions can be observed from HeLa cells treated with these nanoparticles, indicating the successful labeling of HeLa cells. Moreover, the localized spectra measured from HeLa cells and background presented significant green and dominant red UC emissions with the absence of any autofluorescence, further verifying that these nanoparticles can be successfully used as ideal probes for optical UC bioimaging with high contrast and non-autofluorescence. In addition, the amine-functionalized NaYbF4:Er nanoparticles maintained low cell toxicity in HeLa cells evaluated by the 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. More importantly, these amine-functionalized NaYbF4:Er nanoparticles can also be used as X-ray imaging, owing to the large X-ray absorption efficiency of the Yb ion. The synergistic in vivo UC and X-ray imaging present significant UC luminescence and X-ray signals in the same region of a nude mouse, and the two signals are matched very well, which provides direct evidence for simultaneous UC luminescence and X-ray imaging in a single compound of lanthanide-doped material. Moreover, ex vivo UC imaging shows that these nanoparticles are first accumulated in the lung and gradually translocated from the lung into the liver. These results demonstrate that the amine-functionalized NaYbF4:Er nanoparticles presented here are very attractive nanoprobes for dual-modal UC luminescence and X-ray imaging with low cytotoxicity, autofluorescence free, and synergistic combination of the advantages of the two imaging modalities. © 2014 American Chemical Society.

Zeng S.,Hunan Normal University | Yi Z.,Xiangtan University | Lu W.,Hong Kong Polytechnic University | Qian C.,Hunan Normal University | And 7 more authors.
Advanced Functional Materials | Year: 2014

A strategy is demonstrated for simultaneous phase/size manipulation, multicolor tuning, and remarkably enhanced upconversion luminescence (UCL), particularly in red emission bands in fixed formulae of general lanthanide-doped upconverting nanoparticles (UCNPs), namely NaLnF4:Yb/Er (Ln: Lu, Gd, Yb), simply through transition metal Mn2+-doping. The addition of different Mn2+ dopant contents in NaLnF4:Yb/Er system favors the crystal structure changing from hexagonal (β) phase to cubic (α) phase, and the crystal size of UCNPs can be effectively controlled. Moreover, the UCL can be tuned from green through yellow and to dominant red emissions under the excitation of 980 nm laser. Interestingly, a large enhancement in overall UCL spectra of Mn2+ doped UCNPs (59.1 times for NaLuF4 host, 39.3 times for NaYbF4 host compared to the UCNPs without Mn2+ doping) is observed, mainly due to remarkably enhanced luminescence in the red band. The obtained result greatly benefits in vitro and in vivo upconversion bioimaging with highly sensitive and deeper tissue penetration. To prove the application, a select sample of nanocrystal is used as an optical probe for in vitro cell and in vivo bioimaging to verify the merits of high contrast, deeper tissue penetration, and the absence of autofluorescence. Furthermore, the blood vessel of lung of a nude mouse with the injection of Mn2+-doped NaLuF4: Yb/Er UCNPs can be readily visualized using X-ray imaging. Therefore, the Mn2+ doping method provides a new strategy for phase/size control, multicolor tuning, and remarkable enhancement of UCL dominated by red emission, which will impact on the field of bioimaging based on UCNP nanoprobes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Li Q.,University of Southampton | Luo K.H.,University of Southampton | Luo K.H.,Tsinghua University | Li X.J.,Xiangtan University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

In this paper, we aim to address several important issues about the recently developed lattice Boltzmann (LB) model for relativistic hydrodynamics. First, we study the conservation law of the particle number in the relativistic LB model. Through the Chapman-Enskog analysis, it is shown that in the relativistic LB model the conservation equation of the particle number is a convection-diffusion equation rather than a continuity equation, which makes the evolution of the particle number dependent on the relaxation time. Furthermore, we investigate the origin of the discontinuities that appeared in the relativistic problems with high viscosities, which were reported in a recent study. A multiple-relaxation-time relativistic LB model is presented to examine the influences of different relaxation times on the discontinuities. Numerical experiments show the discontinuities can be eliminated by setting the relaxation time τ e (related to the bulk viscosity) to be sufficiently smaller than the relaxation time τ ν (related to the shear viscosity). Meanwhile, it is found that the relaxation time τ ε, which has no effect on the conservation equations at the Navier-Stokes level, will affect the numerical accuracy of the relativistic LB model. Moreover, the accuracy of the relativistic LB model for simulating moderately relativistic problems is also investigated. © 2012 American Physical Society.

Sun C.Q.,Nanyang Technological University | Sun C.Q.,Jilin University | Sun C.Q.,Xiangtan University | Zhang X.,Nanyang Technological University | Zheng W.,Jilin University
Chemical Science | Year: 2012

Coulomb repulsion between the unevenly-bound bonding "-" and nonbonding ":" electron pairs in the "O 2-:H +/p-O 2-" hydrogen bond is shown to originate the anomalies of ice under compression. Consistency between experimental observations, density functional theory and molecular dynamics calculations confirmed that the resultant force of the compression, the repulsion, and the recovery of electron-pair dislocations differentiates ice from other materials in response to pressure. The compression shortens and strengthens the longer-and-softer intermolecular "O 2-:H +/p" lone-pair virtual bond; the repulsion pushes the bonding electron pair away from the H +/p and hence elongates and weakens the intramolecular "H +/p-O 2-" real bond. The virtual-bond compression and the real-bond elongation symmetrize the "O 2--H +/p:O 2-" as observed at ∼60 GPa and result in the abnormally low compressibility of ice. The virtual-bond stretching phonons (<400 cm -1) are thus stiffened and the real-bond stretching phonons (>3000 cm -1) softened upon compression. The cohesive energy loss of the real bond dominates and lowers the critical temperature for the VIII-VII phase transition. The polarization of the lone electron pairs and the entrapment of the bonding electron pairs by compression expand the band gap consequently. Findings should form striking impact to understanding the physical anomalies of H 2O. © 2012 The Royal Society of Chemistry.

Han G.S.,Xiangtan University | Yu Z.G.,Xiangtan University | Yu Z.G.,Queensland University of Technology | Anh V.,Queensland University of Technology | And 2 more authors.
PLoS ONE | Year: 2013

Background: Predicting protein subnuclear localization is a challenging problem. Some previous works based on non-sequence information including Gene Ontology annotations and kernel fusion have respective limitations. The aim of this work is twofold: one is to propose a novel individual feature extraction method; another is to develop an ensemble method to improve prediction performance using comprehensive information represented in the form of high dimensional feature vector obtained by 11 feature extraction methods. Methodology/Principal Findings: A novel two-stage multiclass support vector machine is proposed to predict protein subnuclear localizations. It only considers those feature extraction methods based on amino acid classifications and physicochemical properties. In order to speed up our system, an automatic search method for the kernel parameter is used. The prediction performance of our method is evaluated on four datasets: Lei dataset, multi-localization dataset, SNL9 dataset and a new independent dataset. The overall accuracy of prediction for 6 localizations on Lei dataset is 75.2% and that for 9 localizations on SNL9 dataset is 72.1% in the leave-one-out cross validation, 71.7% for the multi-localization dataset and 69.8% for the new independent dataset, respectively. Comparisons with those existing methods show that our method performs better for both single-localization and multi-localization proteins and achieves more balanced sensitivities and specificities on large-size and small-size subcellular localizations. The overall accuracy improvements are 4.0% and 4.7% for single-localization proteins and 6.5% for multi-localization proteins. The reliability and stability of our classification model are further confirmed by permutation analysis. Conclusions: It can be concluded that our method is effective and valuable for predicting protein subnuclear localizations. A web server has been designed to implement the proposed method. It is freely available at http://bioinformatics.awowshop.com/snlpred_page.php. © 2013 Han et al.

Wang J.,Guizhou University | Zhou Y.,Xiangtan University | Wei W.,Guizhou University
Nonlinear Analysis: Real World Applications | Year: 2012

In this paper, we study fractional Schrödinger equations with potential and optimal controls. The first novelty is a suitable concept on a mild solution for our problems. Existence, uniqueness, local stability and attractivity, and data continuous dependence of mild solutions are also presented respectively. The second novelty is an initial study on the optimal control problems for the controlled fractional Schrödinger equations with potential. Existence and uniqueness of optimal pairs for the standard Lagrange problem are obtained. © 2012 Elsevier Ltd. All rights reserved.

Liu Y.Y.,Xiangtan University | Liu Y.Y.,University of Washington | Zhu Z.X.,Tsinghua University | Li J.-F.,Tsinghua University | Li J.Y.,University of Washington
Mechanics of Materials | Year: 2010

It is well known that the structures and properties of ferroelectric films can be remarkably different from their bulk counterpart, and a nonlinear phenomenological theory of ferroelectrics is applied to study phase structures and electromechanical properties of epitaxial Pb(Zr1-xTi x)O3 (PZT) thin films, focusing on the effects of substrate and film thickness. The effective misfit strain induced by lattice mismatch between film and substrate has been calculated, and the misfit strain-composition, temperature-composition, and thickness-composition phase diagrams of PZT films have been constructed. The temperature-composition phase diagram differs substantially from that of bulk PZT ceramics, and the calculated phase structures in thin films allow us to explain numerous previous experimental observations. In particular, it is confirmed that the morphotropic phase boundary (MPB) of PZT films is shifted from that of bulk PZT, resulting in substantially different electromechanical response in PZT thin films. Good agreement with experimental data is observed in general. © 2010 Elsevier Ltd.

Wang J.,Guizhou University | Zhou Y.,Xiangtan University | Feckan M.,Comenius University | Feckan M.,Slovak Academy of Sciences
Nonlinear Dynamics | Year: 2013

In this paper, a generalized Darbo's fixedpoint theorem associated with Hausdorff measure of noncompactness is established. Then we apply this new variant fixed-point theorem to study some fractional differential equations in Banach spaces via the technique of measure of noncompactness. Many novel existence and uniqueness results for solutions are obtained under the more general conditions. © Springer Science+Business Media B.V. 2012.

Zhang X.,Nanyang Technological University | Nie Y.,Nanyang Technological University | Zheng W.,Jilin University | Kuo J.-L.,Academia Sinica, Taiwan | And 2 more authors.
Carbon | Year: 2011

Using a combination of the bond order-length-strength correlation theory, the spin-polarized tight binding method, the first-principles calculations, and the atomistic photoelectron distillation experiments, we investigated the mechanisms of edge-selective generation and hydrogenated modulation of Dirac-Fermi polarons (DFPs) surrounding the atomic vacancies at a graphite surface and at the edges of graphene nanoribbons (GNR). We found that: (i) the DFPs with a high-spin density at a zigzag-GNR edge and at an atomic vacancy result from the isolation and polarization of the dangling σ-bond electrons of √3d (d is the C-C bond length) distance along the edge by the locally and densely entrapped bonding electrons; (ii) along an armchair-GNR edge and a reconstructed-zigzag-GNR edge, however, the formation of quasi-triple-bond between the nearest edge atoms of d distance prevents the DFPs from generation; and (iii) hydrogenation reduces the spin density substantially and turns the asymmetric dumb-bell-like density into the spherical-like p z density. A further C 1s photoelectron spectroscopic purification has confirmed that the generation of the DFPs is associated with two extra peaks of energy states located at the bottom and the top edge of the C 1s band. © 2011 Elsevier Ltd. All rights reserved.

Yin T.,Xiangtan University | Liu D.,Tsinghua University | Ou Y.,Xiangtan University | Ma F.,University of Washington | And 4 more authors.
Journal of Physical Chemistry C | Year: 2010

A novel technique is developed to process nanocrystalline Ca 3Co4O9 ceramics with much enhanced thermoelectric properties. Nanocrystalline Ca3Co4O 9 nanofibers are synthesized first using sol-gel based electrospinning, and then consolidated into bulk ceramics by spark plasma sintering with preferred grain orientation distribution and without substantial grain growth. The nanofiber-sintered ceramic has a grain size much smaller than that sintered from sol-gel synthesized powders with improved texture, and has simultaneously enhanced Seebeck coefficient, electric conductivity, and thermal resistivity, resulting in substantial enhancement in thermoelectric figure of merit ZT. This technique is promising for high-efficiency thermoelectric conversion of waste heat directly into electricity. © 2010 American Chemical Society.

Yang X.X.,Xiangtan University | Li J.W.,Xiangtan University | Zhou Z.F.,Xiangtan University | Wang Y.,Hunan University of Science and Technology | And 4 more authors.
Nanoscale | Year: 2012

From the perspective of bond relaxation and bond vibration, we have formulated the Raman phonon relaxation of graphene, under the stimuli of the number-of-layers, the uni-axial strain, the pressure, and the temperature, in terms of the response of the length and strength of the representative bond of the entire specimen to the applied stimuli. Theoretical unification of the measurements clarifies that: (i) the opposite trends of the Raman shifts, which are due to the number-of-layers reduction, of the G-peak shift and arises from the vibration of a pair of atoms, while the D- and the 2D-peak shifts involve the z-neighbor of a specific atom; (ii) the tensile strain-induced phonon softening and phonon-band splitting arise from the asymmetric response of the C 3v bond geometry to the C 2v uni-axial bond elongation; (iii) the thermal softening of the phonons originates from bond expansion and weakening; and (iv) the pressure stiffening of the phonons results from bond compression and work hardening. Reproduction of the measurements has led to quantitative information about the referential frequencies from which the Raman frequencies shift as well as the length, energy, force constant, Debye temperature, compressibility and elastic modulus of the C-C bond in graphene, which is of instrumental importance in the understanding of the unusual behavior of graphene. © 2012 The Royal Society of Chemistry.

Jiang C.,Xiangtan University | Li W.,Hubei University | Li W.,Changchun University
Materials Letters | Year: 2014

We describe a simple method to prepare Co3O4 films on glass slides fabricated via solvothermal synthesis at 160 C for 90 min. After the surface modification, the prepared films show extraordinary superhydrophobicity and good self-cleaning performance. The results indicate that the maximum water contact angle is approximately 169.2 and sliding angle is less than 3. More importantly, such films exhibit excellent anti-icing properties: for a spherical-like water droplet placed on the surface at -4.6 to -5.0 C, ice cannot be formed for more than 66 min. The super-hydrophobic films could have significant industrial applications in the future. © 2014 Elsevier B.V.

Wang H.,Hunan Normal University | Wang H.,Xiangtan University | Lu W.,Hong Kong Polytechnic University | Zeng T.,Hunan Normal University | And 6 more authors.
Nanoscale | Year: 2014

In this paper, multi-functional hexagonal phase NaErF4:Yb nanorods were synthesized by a facile hydrothermal method. The upconversion luminescence (UCL) intensity and red to green ratio of the multi-functional NaErF4 nanorods can be improved by Yb3+ doping. More importantly, owing to the decreased distance of Er and Yb, the significant enhancement of red UCL can be obtained, which is different to the usual green UCL of Yb/Er doped NaYF4 host. In addition, the intensity of UCL is strongest when the Yb3+-doped concentration reached 30%. The in vitro cell imaging and localized UCL spectra taken from HeLa cells revealed that these NaErF4: 30% Yb3+ nanorods are ideal nanoprobes with absence of autofluorescence for optical bioimaging. Moreover, these nanorods possess large X-ray absorption ions (Er3+ and doped Yb3+), and were successfully used as contrast agents for in vivo X-ray bioimaging for the first time. In addition to the excellent UCL and X-ray absorption properties, these nanorods present significant paramagnetic properties and can be used as T2-weighted magnetic resonance imaging (MRI) agents. Therefore, these enhanced red UCL NaErF4 nanocrystals with excellent paramagnetic properties and X-ray absorption properties can be used as promising multi-modal nanoprobes for optical bioimaging, MRI, computed X-ray tomography (CT), and may have potential applications in bioseparation. © 2014 The Royal Society of Chemistry.

Chen A.,Xiangtan University | Chen A.,Xiangnan University | Chen F.,Xiangnan University | Deng S.,Xiangnan University
Computers and Mathematics with Applications | Year: 2010

This paper investigates almost automorphic mild solutions of the fractional semilinear equation Dα x (t) = A x (t) + f (t, x (t)), 0 < α < 1, considered in a Banach space X, where A is a linear operator of sectorial type ω < 0. Some sufficient conditions are given for the existence, uniqueness and uniform stability of almost automorphic mild solutions to this semilinear equation. © 2009 Elsevier Ltd. All rights reserved.

Tan J.,Xiangtan University | Yang X.,Hunan Normal University | Yang X.,HPCSIP Key Laboratory
Journal of Systems Science and Complexity | Year: 2012

Consider the compound binomial risk model with interest on the surplus under a constant dividend barrier and periodically paying dividends. A system of integral equations for the arbitrary moments of the sum of the discounted dividend payments until ruin is derived. Moreover, under a very relaxed condition, the solutions for arbitrary moments are obtained by setting up iteration processes because of a special property of the system of integral equations. © 2012 Institute of Systems Science, Academy of Mathematics and Systems Science, CAS and Springer-Verlag Berlin Heidelberg.

Li Q.,Xiangtan University | Li Q.,Sun Yat Sen University | Li Q.,Hong Kong Baptist University | Chan W.H.,Hong Kong Baptist University | Long D.-Y.,Sun Yat Sen University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

Secret sharing is a procedure for sharing a secret among a number of participants such that only the qualified subsets of participants have the ability to reconstruct the secret. Even in the presence of eavesdropping, secret sharing can be achieved when all the members are quantum. So what happens if not all the members are quantum? In this paper, we propose two semiquantum secret sharing protocols by using maximally entangled Greenberger-Horne- Zeilinger-type states in which quantum Alice shares a secret with two classical parties, Bob and Charlie, in a way that both parties are sufficient to obtain the secret, but one of them cannot. The presented protocols are also shown to be secure against eavesdropping. © 2010 The American Physical Society.

Song H.,Sun Yat Sen University | Li N.,Sun Yat Sen University | Cui H.,Sun Yat Sen University | Wen X.,Xiangtan University | And 2 more authors.
CrystEngComm | Year: 2013

Novel nanostructures, e.g. core-shell or yolk-shell, sword-sheath, coaxial nanotubes, etc., are extensively explored for their potential application in modifying electrode durability in lithium-ion batteries (LIBs). Herein, hybrid nanostructures of monodisperse tin dioxide nanocrystals inclusion in highly ordered mesotunnels of mesoporous carbon (CMK-3) are hydrothermally synthesized. Benefiting from ultrafine nanocrystals of mainly 2 nm or so and their good distribution throughout the highly ordered tunnels and the outer surface of the CMK-3, the hybrid shows a strongly coupled synergistic effect. When used as anode materials for LIBs, the hybrid composite exhibits excellent cycling and rate performance superior to both components involved with high reversible capacity retention above 95% for 200 cycles and recoverable initial reversible capacity at large rates of 10 A g-1. Insights into the electrochemical process reveal the total capacity is contributed by two different factors: redox capacitance and interfacial capacitance. Once solid electrolyte interfaces (SEIs) are formed, the hybrid composite exhibits stable interfaces and robust structures indicated by the enhanced interfacial capacitance. © 2013 The Royal Society of Chemistry.

Shen L.,Sun Yat Sen University | Song H.,Sun Yat Sen University | Cui H.,Sun Yat Sen University | Wen X.,Xiangtan University | And 2 more authors.
CrystEngComm | Year: 2013

Fe3O4-carbon nanocomposites have been synthesized simply with a hydrothermal method free of template that is followed by an annealing process. The morphological and compositional analysis reveals that the inter-separated Fe3O4 nanocrystals with a size of ~10 nm are homogeneously embedded within the mesoporous carbon matrix. The interesting configuration is evaluated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Benefiting from the advantages of good buffering and electric conductivity, the nanocomposite delivers an initial capacity of 1706 mAh g-1 at 0.2 C (1 C = 1 A g-1). Besides excellent lithium storage capability, it exhibits a superior cycling stability with more than 100% capacity retention after 100 cycles at 0.2 C and 1 C. When successively discharging at variable rates, the nanocomposite retains a reversible capacity of 1249 mAh g-1 at 0.1 C, 690 mAh g-1 at 1 C, and 311 mAh g-1 at 10 C. With excellent capability and rate performance, the Fe3O4-carbon nanocomposites may be a promising anode material of lithium ion batteries (LIBs) for the green large-scale production. © 2013 The Royal Society of Chemistry.

Liu H.,Hunan Normal University | Lu W.,Hong Kong Polytechnic University | Wang H.,Xiangtan University | Rao L.,Xiangtan University | And 4 more authors.
Nanoscale | Year: 2013

In this work, we developed a novel and biocompatible dual-modal nanoprobe based on single-phase amine-functionalized BaYF5:Yb/Er nanoparticles (NPs) for upconversion (UC) fluorescence and in vivo computed X-ray tomography (CT) bioimaging for the first time. High-quality water-soluble amine-functionalized BaYF5:Yb/Er NPs with an average size of 24 nm were synthesized by a facile environmentally friendly hydrothermal method for simultaneous synthesis and surface functionalization. Structure investigation based on the Rietveld refinement method revealed that the as-synthesized BaYF5:Yb/Er NPs present a cubic phase structure, which differs from the previously reported tetragonal structure. Under 980 nm excitation, high-contrast green and red UC emissions were observed from HeLa cells incubated with these amine-functionalized NPs. The UC spectra measured from the NPs incubated with HeLa cells presented only green and red UC emissions without any autofluorescence, further revealing that these NPs are ideal candidates for fluorescent bioimaging. In addition, the cell cytotoxicity test showed low cell toxicity of these NPs. These amine-functionalized NPs were also successfully used as CT agents for in vivo CT imaging because of the efficient X-ray absorption efficiency of Ba and doped Yb ions. A prolonged (2 h) signal enhancement of the spleen in a mouse was observed in CT imaging, which can improve the detection of splenic diseases. More importantly, the simultaneous X-ray and UC in vivo bioimaging was demonstrated in a nude mouse for the first time, indicating the as-prepared UCNPs can be successfully used as dual-modal bioprobes. These results demonstrate that BaYF5:Yb/Er NPs are ideal nanoprobes for dual-modal fluorescent/CT bioimaging with low cytotoxicity, non-autofluorescence, and enhanced detection of the spleen. © 2013 The Royal Society of Chemistry.

Tan L.,Xiangtan University | Shen J.,Xiangtan University | Shen J.,Sun Yat Sen University | Liu J.,Xiangtan University | And 3 more authors.
Dalton Transactions | Year: 2012

Two functional Ru(ii) mixed-ligand complexes, [Ru(phen) 2(ttbd)] 2+ (1) (ttbd = 4-(6-propenyl-pyrido[3,2-a]phenzain-10-yl-benzene-1,2- diamine, phen = 1,10-phenanthroline) and [Ru(bpy) 2(ttbd)] 2+ (2) (bpy = 2,2′-bipyridine), have been synthesized and characterized. The spectral characteristics of complexes 1 and 2 were investigated using fluorescence spectroscopy and revealed that both complexes were very sensitive to solvent polarity and oxygen molecules in nonaqueous solvents. The binding properties of the two complexes towards calf thymus DNA (CT-DNA) were investigated with different spectrophotometric methods, viscosity measurements and quantum chemistry calculations, indicating that both complexes could enantioselectively bind to CT-DNA by means of intercalation, but with different binding strengths and discrimination. On the other hand, the cytotoxicity of both complexes have been evaluated by MTT assays and Giemsa staining experiments. The main results reveal that the hydrophobicity and surface area of the ancillary ligands have a significant effect on their DNA binding behavior and both complexes are likely to be useful for optically probing nonaqueous and oxygen-free environments. © 2012 The Royal Society of Chemistry.

Wang J.,Guizhou University | Zhou Y.,Xiangtan University
Nonlinear Analysis: Real World Applications | Year: 2011

This paper concerns the existence of mild solutions for semilinear fractional evolution equations and optimal controls in the α-norm. A suitable α-mild solution of the semilinear fractional evolution equations is introduced. The existence and uniqueness of α-mild solutions are proved by means of fractional calculus, singular version Gronwall inequality and LeraySchauder fixed point theorem. The existence of optimal pairs of system governed by fractional evolution equations is also presented. Finally, an example is given for demonstration. © 2010 Published by Elsevier Ltd. All rights reserved.

Li B.-G.,Xiangtan University | Yu Z.-G.,Xiangtan University | Yu Z.-G.,Queensland University of Technology | Zhou Y.,Xiangtan University
Journal of Statistical Mechanics: Theory and Experiment | Year: 2014

In this work, we study the fractal and multifractal properties of a family of fractal networks introduced by Gallos et al (2007 Proc. Nat. Acad. Sci. USA 104 7746). In this fractal network model, there is a parameter e which is between 0 and 1, and allows for tuning the level of fractality in the network. Here we examine the multifractal behavior of these networks, the dependence relationship of the fractal dimension and the multifractal parameters on parameter e. First, we find that the empirical fractal dimensions of these networks obtained by our program coincide with the theoretical formula given by Song et al (2006 Nature Phys. 2 275). Then from the shape of the τ(q) and D(q) curves, we find the existence of multifractality in these networks. Last, we find that there exists a linear relationship between the average information dimension D(1) and the parameter e. © 2014 IOP Publishing Ltd and SISSA Medialab srl.

Li Q.,University of Southampton | Luo K.H.,University of Southampton | Luo K.H.,Tsinghua University | Li X.J.,Xiangtan University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

The pseudopotential lattice Boltzmann (LB) model is a widely used multiphase model in the LB community. In this model, an interaction force, which is usually implemented via a forcing scheme, is employed to mimic the molecular interactions that cause phase segregation. The forcing scheme is therefore expected to play an important role in the pseudoepotential LB model. In this paper, we aim to address some key issues about forcing schemes in the pseudopotential LB model. First, theoretical and numerical analyses will be made for Shan-Chen's forcing scheme and the exact-difference-method forcing scheme. The nature of these two schemes and their recovered macroscopic equations will be shown. Second, through a theoretical analysis, we will reveal the physics behind the phenomenon that different forcing schemes exhibit different performances in the pseudopotential LB model. Moreover, based on the analysis, we will present an improved forcing scheme and numerically demonstrate that the improved scheme can be treated as an alternative approach to achieving thermodynamic consistency in the pseudopotential LB model. © 2012 American Physical Society.

Wang J.,Guizhou University | Zhou Y.,Xiangtan University
International Journal of Dynamical Systems and Differential Equations | Year: 2011

In this paper, we consider a time optimal control problem of a system governed by a class of fractional semilinear evolution equations in the sense of the Caputo fractional derivative operator. The existence and uniqueness of mild solutions is proven. Then fractional time optimal control problem of the target varying with time is formulated. The existence of fractional time optimal controls is also presented. Finally, an example is given to illustrate the effectiveness of the results obtained. © 2011 Inderscience Enterprises Ltd.

Wang J.,Guizhou University | Zhou Y.,Xiangtan University
Nonlinear Analysis: Real World Applications | Year: 2011

In this paper, we prove the existence and controllability results for fractional semilinear differential inclusions involving the Caputo derivative in Banach spaces. The results are obtained by using fractional calculation, operator semigroups and BohnenblustKarlin's fixed point theorem. At last, an example is given to illustrate the theory. © 2011 Elsevier Ltd. All rights reserved.

Wang J.,Guizhou University | Wei W.,Guizhou University | Zhou Y.,Xiangtan University
Journal of Dynamical and Control Systems | Year: 2011

This paper concerns the fractional finite time delay evolution systems and optimal controls in infinite-dimensional spaces. A suitable mild solution of the fractional finite time delay evolution systems is introduced. Using the singular version of the Gronwall inequality with finite time delay, we obtain some sufficient conditions for the existence, uniqueness and continuous dependence of mild solutions of these control systems. A formulation for the fractional Lagrange problem is introduced. The existence of optimal pairs of fractional-time-delay evolution systems is also presented. Finally, an example is given for demonstration. © 2011 Springer Science+Business Media, LLC.

Sun C.Q.,Nanyang Technological University | Sun C.Q.,Xiangtan University | Sun C.Q.,Jilin University
Nanoscale | Year: 2010

Although they exist ubiquitously in human bodies and our surroundings, the impact of nonbonding lone electrons and lone electron pairs has long been underestimated. Recent progress demonstrates that: (i) in addition to the shorter and stronger bonds between under-coordinated atoms that initiate the size trends of the otherwise constant bulk properties when a substance turns into the nanoscale, the presence of lone electrons near to broken bonds generates fascinating phenomena that bulk materials do not demonstrate; (ii) the lone electron pairs and the lone pair-induced dipoles associated with C, N, O, and F tetrahedral coordination bonding form functional groups in biological, organic, and inorganic specimens. By taking examples of surface vacancy, atomic chain end and terrace edge states, catalytic enhancement, conducting-insulating transitions of metal clusters, defect magnetism, Coulomb repulsion at nanoscale contacts, Cu3C2H2 and Cu3O 2 surface dipole formation, lone pair neutralized interface stress, etc, this article will focus on the development and applications of theory regarding the energetics and dynamics of nonbonding electrons, aiming to raise the awareness of their revolutionary impact to the society. Discussion will also extend to the prospective impacts of nonbonding electrons on mysteries such as catalytic enhancement and catalysts design, the density anomalies of ice and negative thermal expansion, high critical temperature superconductivity induced by B, C, N, O, and F, the molecular structures and functionalities of CF 4 in anti-coagulation of synthetic blood, NO signaling, and enzyme telomeres, etc. Meanwhile, an emphasis is placed on the necessity and effectiveness of understanding the properties of substances from the perspective of bond and nonbond formation, dissociation, relaxation and vibration, and the associated energetics and dynamics of charge repopulation, polarization, densification, and localization. Finding and grasping the factors controlling the nonbonding states and making them of use in functional materials design and identifying their limitations will form, in the near future, a subject area of "nonbonding electronics and energetics", which could be even more challenging, fascinating, promising, and rewarding than dealing with core or valence electrons alone. © The Royal Society of Chemistry 2010.

Han G.-S.,Xiangtan University | Yu Z.-G.,Xiangtan University | Yu Z.-G.,Queensland University of Technology | Anh V.,Queensland University of Technology
Journal of Theoretical Biology | Year: 2014

Membrane proteins play important roles in many biochemical processes and are also attractive targets of drug discovery for various diseases. The elucidation of membrane protein types provides clues for understanding the structure and function of proteins. Recently we developed a novel system for predicting protein subnuclear localizations. In this paper, we propose a simplified version of our system for predicting membrane protein types directly from primary protein structures, which incorporates amino acid classifications and physicochemical properties into a general form of pseudo-amino acid composition. In this simplified system, we will design a two-stage multi-class support vector machine combined with a two-step optimal feature selection process, which proves very effective in our experiments. The performance of the present method is evaluated on two benchmark datasets consisting of five types of membrane proteins. The overall accuracies of prediction for five types are 93.25% and 96.61% via the jackknife test and independent dataset test, respectively. These results indicate that our method is effective and valuable for predicting membrane protein types. A web server for the proposed method is available at http://www.juemengt.com/jcc/memty-page.php. © 2013 Elsevier Ltd.

Li Q.,University of Southampton | Luo K.H.,University of Southampton | Luo K.H.,Tsinghua University | Li X.J.,Xiangtan University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2013

Owing to its conceptual simplicity and computational efficiency, the pseudopotential multiphase lattice Boltzmann (LB) model has attracted significant attention since its emergence. In this work, we aim to extend the pseudopotential LB model to simulate multiphase flows at large density ratio and relatively high Reynolds number. First, based on our recent work, an improved forcing scheme is proposed for the multiple-relaxation-time pseudopotential LB model in order to achieve thermodynamic consistency and large density ratio in the model. Next, through investigating the effects of the parameter a in the Carnahan-Starling equation of state, we find that the interface thickness is approximately proportional to 1/√a. Using a smaller a will lead to a wider interface thickness, which can reduce the spurious currents and enhance the numerical stability of the pseudopotential model at large density ratio. Furthermore, it is found that a lower liquid viscosity can be gained in the pseudopotential model by increasing the kinematic viscosity ratio between the vapor and liquid phases. The improved pseudopotential LB model is numerically validated via the simulations of stationary droplet and droplet oscillation. Using the improved model as well as the above treatments, numerical simulations of droplet splashing on a thin liquid film are conducted at a density ratio in excess of 500 with Reynolds numbers ranging from 40 to 1000. The dynamics of droplet splashing is correctly reproduced and the predicted spread radius is found to obey the power law reported in the literature. © 2013 American Physical Society.

Zhou Y.,Chinese University of Hong Kong | Leung Y.,Chinese University of Hong Kong | Yu Z.-G.,Xiangtan University | Yu Z.-G.,Queensland University of Technology
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2013

Multifractal detrended fluctuation analysis (MF-DFA) is a generalization of the conventional multifractal analysis. It is extended from the detrended fluctuation analysis (DFA) which is developed for the purpose of detecting long-range correlation and fractal property in stationary and nonstationary time series. The MF-DFA and some corresponding relationships of the exponents have been subsequently extended to the two-dimensional space. We reexamine two extended relationships in this study and demonstrate that: (i) The invalidity of the relationship h(q)≡H for two-dimensional fractional Brownian motion, and h(q=2)≡H between the Hurst exponent H and the generalized Hurst exponent h(q) in the two-dimensional case. Two more logical relationships are proposed instead as h(q=2)=H for the stationary surface and h(q=2)=H+2 for the nonstationary signal. (ii) The invalidity of the expression τ(q)=qh(q)- Df stipulating the relationship between the standard partition-function-based multifractal exponent τ(q) and the generalized Hurst exponent h(q) in the two-dimensional case. Reasons for its invalidity are given from two perspectives. © 2013 American Physical Society.

Liu Y.,Xiangtan University | Yan X.,Tsinghua University | Yang N.,Xiangtan University | Xi C.,Tsinghua University
Catalysis Communications | Year: 2011

FeCl 2 ligated with 2-(benzimidazolyl)-6-(1-(arylimino)ethyl) pyridine in the presence of zinc powder and zinc iodide could effectively catalyze cyclotrimerization of intermolecular alkynes to afford benzene derivatives in high regioselectivity. The synthetic usefulness of this catalytic system consisting of Fe(II) complex C1, Zn and ZnI 2 in acetonitrile was tested with various terminal alkynes. In the cases of using aryl substituted alkynes, the 1,2,4-trisubstituted benzenes 2 were found to be the major products. © 2010 Elsevier B.V. All rights reserved.

Zeng S.,Hunan Normal University | Wang H.,Xiangtan University | Lu W.,Hong Kong Polytechnic University | Yi Z.,Xiangtan University | And 3 more authors.
Biomaterials | Year: 2014

Visualization of blood vessel of lung can improve the detection of the lung and pulmonary vascular diseases. However, research on visualization of blood vessel of lung using the new generation upconversion nanoprobes is still scarce. Herein, high quality hexagonal phase NaLuF4:Gd/Yb/Er nanorods were synthesized by a simple hydrothermal method through doping Gd3+. Doping Gd can not only promote the phase transformation from cubic to hexagonal and the shape evolution from microtube to rod-like, but also provide an additional magnetic properties for biomedical application. The as-prepared nanorods were further converted to water solubility by treating with HCl for eliminating the capped oleic acid. The ligand-free nanorods were successfully used for high-contrast upconversion fluorescent bioimaging of HeLa cells. Moreover, the in vivo synergistic upconversion fluorescent and X-ray imaging of nude mice were demonstrated by subcutaneously and intravenously administrated the ligand-free nanorods. The X-ray signals were matched well with the upconversion signal, indicating the successfully synergistic bioimaging. The ex-vivo X-ray and upconversion fluorescent imaging of various organs revealed that the nanorods were mainly accumulated in liver and lung. More importantly, the blood vessel of the lung can be readily visualized when these ligand-free nanorods are intravenously injected. Apart from the synergistic X-ray and upconversion bioimaging, the ligand-free nanorods can also possess excellent paramagnetic property for potential magnetic resonance imaging contrast agent. Our results have demonstrated the enhanced visualization of blood vessel of lung performed by dual-modal bioimaging of X-ray and upconversion fluorescence, revealing the great promise of these nanoprobes in angiography imaging. Such a new technique enables the integration of the two bioimaging techniques by combining their collective strengths and minimizing their shortcomings. © 2013 Elsevier Ltd.

Chen F.,Xiangnan University | Zhou Y.,Xiangtan University
Computers and Mathematics with Applications | Year: 2011

In this paper, some attractivity results for fractional functional differential equations are obtained by using the fixed point theorem. By constructing equivalent fractional integral equations, research on the attractivity of fractional functional and neutral differential equations is skillfully converted into a discussion about the existence of fixed points for equivalent fractional integral equations. Two examples are also provided to illustrate our main results. © 2011 Elsevier Ltd. All rights reserved.

Wang J.,Guizhou University | Zhou Y.,Xiangtan University | Wei W.,Guizhou University | Xu H.,Guizhou University | Xu H.,Curtin University Australia
Computers and Mathematics with Applications | Year: 2011

This paper investigates nonlocal problems for a class of fractional integrodifferential equations via fractional operators and optimal controls in Banach spaces. By using the fractional calculus, Hölder inequality, p-mean continuity and fixed point theorems, some existence results of mild solutions are obtained under the two cases of the semigroup T(t), the nonlinear terms f and h, and the nonlocal item g. Then, the existence conditions of optimal pairs of systems governed by a fractional integrodifferential equation with nonlocal conditions are presented. Finally, an example is given to illustrate the effectiveness of the results obtained. © 2011 Elsevier Ltd. All rights reserved.

Liu J.-L.,Xiangtan University | Yu Z.-G.,Xiangtan University | Yu Z.-G.,Queensland University of Technology | Anh V.,Queensland University of Technology
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

Many studies have shown that we can gain additional information on time series by investigating their accompanying complex networks. In this work, we investigate the fundamental topological and fractal properties of recurrence networks constructed from fractional Brownian motions (FBMs). First, our results indicate that the constructed recurrence networks have exponential degree distributions; the average degree exponent ©λ increases first and then decreases with the increase of Hurst index H of the associated FBMs; the relationship between H and ©λ can be represented by a cubic polynomial function. We next focus on the motif rank distribution of recurrence networks, so that we can better understand networks at the local structure level. We find the interesting superfamily phenomenon, i.e., the recurrence networks with the same motif rank pattern being grouped into two superfamilies. Last, we numerically analyze the fractal and multifractal properties of recurrence networks. We find that the average fractal dimension ©dB of recurrence networks decreases with the Hurst index H of the associated FBMs, and their dependence approximately satisfies the linear formula ©dB2-H, which means that the fractal dimension of the associated recurrence network is close to that of the graph of the FBM. Moreover, our numerical results of multifractal analysis show that the multifractality exists in these recurrence networks, and the multifractality of these networks becomes stronger at first and then weaker when the Hurst index of the associated time series becomes larger from 0.4 to 0.95. In particular, the recurrence network with the Hurst index H=0.5 possesses the strongest multifractality. In addition, the dependence relationships of the average information dimension ©D(1)and the average correlation dimension ©D(2) on the Hurst index H can also be fitted well with linear functions. Our results strongly suggest that the recurrence network inherits the basic characteristic and the fractal nature of the associated FBM series. © 2014 American Physical Society.

Huang Y.,Xiangtan University | Zhang X.,Shenzhen University | Zhang X.,China Jiliang University | Zhang X.,Nanyang Technological University | And 5 more authors.
Coordination Chemistry Reviews | Year: 2015

We present recent progress in understanding the anomalous behavior of water ice under mechanical compression, thermal excitation, and molecular undercoordination (with fewer than four nearest neighbors in the bulk) from the perspective of hydrogen (O:HO) bond cooperative relaxation. We modestly claim the resolution of upwards of ten best known puzzles. Extending the Ice Rule suggests a tetrahedral block that contains two H2O molecules and four O:HO bonds. This block unifies the density-geometry-size-separation of molecules packing in water ice. This extension also clarifies the flexible and polarizable O:HO bond that performs like a pair of asymmetric, coupled, H-bridged oscillators with short-range interactions and memory as well as extreme recoverability. Coulomb repulsion between electron pairs on adjacent oxygen atoms and the disparity between the O:H and the HO segmental interactions relax the O:HO bond length and energy cooperatively under stimulation. A Lagrangian solution has enabled mapping of the potential paths for the O:HO bond at relaxation. The HO bond relaxation shifts the melting point, O 1s binding energy, and high-frequency phonon frequency whereas the O:H relaxation dominates polarization, viscoelasticity, and the O:H dissociation energy. The developed strategies have enabled clarification of origins of the following observations: (i) pressure-induced proton centralization, phase transition-temperature depression and ice regelation; (ii) thermally induced four-region oscillation of the mass density and the phonon frequency over the full temperature range; and (iii) molecular-undercoordination-induced supersolidity that is elastic, hydrophobic, thermally stable, with ultra-low density. The supersolid skin is responsible for the slipperiness of ice, the hydrophobicity and toughness of water skin, and the bi-phase structure of nanodroplets and nanobubbles. Molecular undercoordination mediates the O:H and HO bond Debye temperatures and disperses the quasi-solid phase boundary, resulting in freezing point depression and melting point elevation. O:HO bond memory and water-skin supersolidity ensures a solution to the Mpemba paradox - hot water freezes faster than its cold. These understandings will pave the way toward unveiling anomalous behavior of H2O interacting with other species such as salts, acids and proteins, and excitation of H2O by other stimuli such as electrical and magnetic fields. © 2014 Elsevier B.V.

Wang J.,Guizhou University | Zhou Y.,Xiangtan University | Feckan M.,Comenius University | Feckan M.,Slovak Academy of Sciences
Computers and Mathematics with Applications | Year: 2012

In this paper, the first purpose is treating Cauchy problems and boundary value problems for nonlinear impulsive differential equations with Caputo fractional derivative. We introduce the concept of piecewise continuous solutions for impulsive Cauchy problems and impulsive boundary value problems respectively. By using a new fixed point theorem, we obtain many new existence, uniqueness and data dependence results of solutions via some generalized singular Gronwall inequalities. The second purpose is discussing Ulam stability for impulsive fractional differential equations. Some new concepts in stability of impulsive fractional differential equations are offered from different perspectives. Some applications of our results are also provided. © 2011 Elsevier Ltd. All rights reserved.

Wang J.,Guizhou University | Zhou Y.,Xiangtan University | Feckan M.,Comenius University | Feckan M.,Slovak Academy of Sciences
Computers and Mathematics with Applications | Year: 2012

This paper is motivated from some recent papers treating the boundary value problems for impulsive fractional differential equations. We first make a counterexample to show that the formula of solutions in cited papers are incorrect. Second, we establish a general framework to find the solutions for impulsive fractional boundary value problems, which will provide an effective way to deal with such problems. Third, some sufficient conditions for the existence of the solutions are established by applying fixed point methods. Meanwhile, data dependence is obtained by using a new generalized singular Gronwall inequality. Finally, three examples are given to illustrate the results. © 2011 Elsevier Ltd. All rights reserved.

Tan L.-F.,Xiangtan University | Liu J.,Xiangtan University | Shen J.-L.,Sun Yat Sen University | Liu X.-H.,Xiangtan University | And 2 more authors.
Inorganic Chemistry | Year: 2012

Stabilization of triple helical structures is extremely important for carrying out their biological functions. Nucleic acid triple helices may be formed with DNA or RNA strands. In contrast to many studies in DNA, little has been reported concerning the recognition of the RNA triplex by transition-metal complexes. In this article, [Ru(phen) 2(mdpz)] 2+ (Ru1) is the first metal complex able to enhance the stability of the RNA triplex Poly(U)̇Poly(A)*Poly(U) and serve as a prominent molecular "light switch" for the RNA triplex. © 2012 American Chemical Society.

Wen X.,Xiangtan University | Wei X.,Xiangtan University | Yang L.,Xiangtan University | Shen P.K.,Sun Yat Sen University
Journal of Materials Chemistry A | Year: 2015

A novel composite of reduced graphene oxide (RGO) and FeS2 microparticles self-assembled from small size cubes as a high-performance anode material for lithium-ion batteries (LIBs) has been prepared via a facile one-pot hydrothermal method. The prepared composite shows interconnected networks of reduced graphene oxide sheets and well-dispersed FeS2 microparticles which were composed of small-size cubic FeS2 crystals. The composite not only provides a high contact area between the electrolyte and the electrode, favorable diffusion kinetics for both electrons and lithium ions, but also provides the protection against the volume changes of electroactive FeS2 materials and excellent electrical conductivity of the overall electrode during electrochemical processes as well as an enhanced synergistic effect between cubic FeS2 and RGO. As an anode material for LIBs, it exhibits a very large initial reversible capacity of 1147 mA h g-1 at a current rate of 100 mA h g-1 and maintains 1001.41 mA h g-1 over 60 cycles, which is much higher than that of the theoretical capacity of graphite (372 mA h g-1) and indicates high stability. The results demonstrate that the composite can be a promising candidate for electroactive materials in LIBs. © The Royal Society of Chemistry 2015.

Yu Z.-G.,Queensland University of Technology | Yu Z.-G.,Xiangtan University | Chu K.H.,Chinese University of Hong Kong | Li C.P.,Chinese University of Hong Kong | And 3 more authors.
BMC Evolutionary Biology | Year: 2010

Background. The vast sequence divergence among different virus groups has presented a great challenge to alignment-based analysis of virus phylogeny. Due to the problems caused by the uncertainty in alignment, existing tools for phylogenetic analysis based on multiple alignment could not be directly applied to the whole-genome comparison and phylogenomic studies of viruses. There has been a growing interest in alignment-free methods for phylogenetic analysis using complete genome data. Among the alignment-free methods, a dynamical language (DL) method proposed by our group has successfully been applied to the phylogenetic analysis of bacteria and chloroplast genomes. Results. In this paper, the DL method is used to analyze the whole-proteome phylogeny of 124 large dsDNA viruses and 30 parvoviruses, two data sets with large difference in genome size. The trees from our analyses are in good agreement to the latest classification of large dsDNA viruses and parvoviruses by the International Committee on Taxonomy of Viruses (ICTV). Conclusions. The present method provides a new way for recovering the phylogeny of large dsDNA viruses and parvoviruses, and also some insights on the affiliation of a number of unclassified viruses. In comparison, some alignment-free methods such as the CV Tree method can be used for recovering the phylogeny of large dsDNA viruses, but they are not suitable for resolving the phylogeny of parvoviruses with a much smaller genome size. © 2010 Yu et al; licensee BioMed Central Ltd.

Yuan B.,Xiangtan University | Zheng X.J.,Xiangtan University | Chen Y.Q.,Xiangtan University | Yang B.,Xiangtan University | Zhang T.,Jilin University
Solid-State Electronics | Year: 2011

Photoconductive semiconductor switch (PCSS) based on ZnO single nanobelt (NB) was fabricated by controlling the concentration of mixed solution and using the probe technique, and applied into a test circuit to control the circuit state. The current-voltage characteristics and voltage spectra were investigated by system source meter and oscillograph, and the results show that the PCSS is of high photosensitivity of ∼104, low dark current of ∼10-3 μA, low power consumption of ∼2.45 μW, typical rise time 0.12 s, and decay time 0.15 s. Within the wavelength range of 280-340 nm, the shorter the wavelength is, the higher the voltage response is. The test circuit state conversion between "1" and "0" is obviously corresponding to UV illumination "on" and "off". The high photosensitivity and low dark current of PCSS can be reasonably explained by using the view point of light absorption and oxygen chemisorption mechanism. © 2010 Elsevier Ltd. All rights reserved.

Yang X.,Xiangtan University | Feng B.,Xiangtan University | He X.,Xiangtan University | Li F.,Xiangtan University | And 3 more authors.
Microchimica Acta | Year: 2013

This review describes recent advances in the use of carbon nanomaterials for electroanalytical detection of biogenic amines (BAs). It starts with a short introduction into carbon nanomaterials such as carbon nanotubes, graphene, nanodiamonds, carbon nanofibers, fullerenes, and their composites. Next, electrochemical sensing schemes are discussed for various BAs including dopamine, serotonin, epinephrine, norepinephrine, tyramine, histamine and putrescine. Examples are then given for methods for simultaneous detection of various BAs. Finally, we discuss the current and future challenges of carbon nanomaterial-based electrochemical sensors for BAs. The review contains 175 references. [Figure not available: see fulltext.] © 2013 Springer-Verlag Wien.

Zhang H.,Fudan University | Zhou T.,Fudan University | Xie G.,Xiangtan University | Cao J.,Xiangtan University | Yang Z.,Fudan University
Applied Physics Letters | Year: 2014

Thermal conductivities of graphene nanoribbons (GNRs) and carbon nanotubes (CNTs) are systematically investigated by employing nonequilibrium molecular dynamics. It is found that with the same size, the thermal conductivity of armchair GNR (AGNR) is smaller than that of zigzag CNT, while thermal conductivity of zigzag GNR (ZGNR) is larger than that of armchair CNT. The phonon participation ratios and local vibrational densities of states of GNRs (CNTs) demonstrate that the edges of the ZGNR are beneficial to the heat transport, while the edges of the AGNR are completely opposite. All these results are very helpful for us to understand the thermal transport mechanism in carbon-based nanostructures. © 2014 AIP Publishing LLC.

Zhang D.,Xiangtan University | Zhao Y.,Xiangtan University
IEEE Journal of Biomedical and Health Informatics | Year: 2016

A novel accurate and fast optic disc (OD) detection method is proposed by using vessel distribution and directional characteristics. A feature combining three vessel distribution characteristics, i.e., local vessel density, compactness, and uniformity, is designed to find possible horizontal coordinate of OD. Then, according to the global vessel direction characteristic, a General Hough Transformation is introduced to identify the vertical coordinate of OD. By confining the possible OD vertical range and by simplifying vessel structure with blocks, we greatly decrease the computational cost of the algorithm. Four public datasets have been tested. The OD localization accuracy lies from 93.8% to 99.7%, when 8-20% vessel detection results are adopted to achieve OD detection. Average computation times for STARE images are about 3.4-11.5 s, which relate to image size. The proposed method shows satisfactory robustness on both normal and diseased images. It is better than many previous methods with respect to accuracy and efficiency. © 2014 IEEE.

Zhang H.,Xiangtan University | Li W.,Xiangtan University | Fang G.,University of Alberta
Applied Surface Science | Year: 2012

Superhydrophobic surfaces have shown inspiring applications in microfluidics, and self-cleaning coatings owing to water-repellent and low-friction properties. However, thermodynamic mechanism responsible for contact angle hysteresis (CAH) and free energy barrier (FEB) have not been understood completely yet. In this work, we propose an intuitional 3-dimension (3D) droplet model along with a reasonable thermodynamic approach to gain a thorough insight into the physical nature of CAH. Based on this model, the relationships between radius of three-phase contact line, change in surface free energy (CFE), average or local FEB and contact angle (CA) are established. Moreover, a thorough theoretical consideration is given to explain the experimental phenomena related to the superhydrophobic behavior. The present study can therefore provide some guidances for the practical fabrications of the superhydrophobic surfaces. © 2011 Elsevier B.V. All rights reserved.

Xiang F.Y.,Xiangtan University | Xiang F.Y.,University of Missouri | Li A.,University of Missouri | Zhong J.X.,Xiangtan University | Zhong J.X.,University of Missouri
Astrophysical Journal | Year: 2011

The diffuse interstellar bands (DIBs) are ubiquitous absorption spectral features arising from the tenuous material in the space between stars - the interstellar medium (ISM). Since their first detection nearly nine decades ago, over 400 DIBs have been observed in the visible and near-infrared wavelength range in both the Milky Way and external galaxies, both nearby and distant. However, the identity of the species responsible for these bands remains as one of the most enigmatic mysteries in astrophysics. An equally mysterious interstellar spectral signature is the 2175 Å extinction bump, the strongest absorption feature observed in the ISM. Its carrier also remains unclear since its first detection 46 years ago. Polycyclic aromatic hydrocarbon (PAH) molecules have long been proposed as a candidate for DIBs as their electronic transitions occur in the wavelength range where DIBs are often found. In recent years, the 2175 Å extinction bump is also often attributed to the π-π* transition in PAHs. If PAHs are indeed responsible for both the 2175 Å extinction feature and DIBs, their strengths may correlate. We perform an extensive literature search for lines of sight for which both the 2175 Å extinction feature and DIBs have been measured. Unfortunately, we found no correlation between the strength of the 2175 Å feature and the equivalent widths of the strongest DIBs. A possible explanation might be that DIBs are produced by small free gas-phase PAH molecules and ions, while the 2175 Å bump is mainly from large PAHs or PAH clusters in condensed phase so that there is no tight correlation between DIBs and the 2175 Å bump. © 2011. The American Astronomical Society. All rights reserved.

Huang Y.,Xiangtan University | Li J.,University of Nevada, Las Vegas | Wu C.,Xiangtan University
Computer Methods in Applied Mechanics and Engineering | Year: 2013

In this paper, a simple averaging technique for edge elements is justified to improve the standard convergence rate (hence achieving superconvergence) when they are used to solve the Maxwell's equations. For simplicity, here we focus on the lowest-order triangular edge element, which is widely used in practice. Though there exists no natural superconvergence points for the numerical solution obtained on such an edge element, superconvergence can be obtained after a simple average of solutions over the neighboring elements. A comprehensive analysis for the lowest-order triangular edge element is carried out, and one-order higher convergence rate than the standard interpolation error estimate is proved for the averaged solution at midpoints of those interior edges of parallelograms (formed by two triangles), i.e., superconvergence happens at the parallelogram centers. We also provide detailed analysis to explain why several cases do not have superconvergence. Extensive numerical results consistent with our analysis are presented. © 2012 Elsevier B.V.

Wang L.,Xiangtan University
Journal of Internet Technology | Year: 2012

Research on the anti-monitoring problem of mobile object in the heterogeneous sensory field, a new Exposure model is proposed, which can be used to estimate the risk approximately when a mobile object is moving along a path to traverse the sensory field deployed with anisotropic sensor nodes. And based on the newly proposed Exposure model, a novel decision algorithm is designed by combing with the Anisotropic Voronoi Tessellation schemes, which guarantee the mobile object can select a suitable path with approximately minimal risk to travel across the anisotropic sensory field. Theoretical analyses and simulation results show that, the new algorithm has good anti-monitoring performance, and requires only that the mobile object shall know the local information in its detection radius, so it is distributed and practical also.

Zhang J.,Xiangtan University | Liu J.,Xiangtan University
2011 International Conference on Electric Information and Control Engineering, ICEICE 2011 - Proceedings | Year: 2011

In this paper, by constructing the equivalent form of the continuous algebraic Riccati equation (CARE), applying the properties of matrix's Schur complement and special matrix inequality, we propose new series lower bounds for the solution of the CARE. Further, new lower matrix bounds for the solution of the CARE are developed. Finally, we give a corresponding numerical example to illustrate the effectiveness of the derived results. © 2011 IEEE.

Jiao P.,Xiangtan University | Liu Y.,Xiangtan University | Wang X.,Xiangtan University | Chen J.,Xiangtan University
Computational Materials Science | Year: 2013

The structural, electronic and magnetic properties of Sr1- xNaxRuO3 have been investigated using the pseudo-potential plane wave method within the generalized gradient approximation GGA + U method by first principles. The results show that all structures of Sr1-xNaxRuO3 (x = 0, 0.125, 0.25) are ferromagnetic phase. There is a more strong Jahn-Teller distortion of the RuO6 octahedra in Na doped compounds. Na doping cannot induce magnetic phase transition in SrRuO3. A Stoner mechanism for ferromagnetism in SrRuO3 is weakened by Na doping, which can lead to a reduction of effective magnetic moment. Na doping lowers the density of states at Fermi lever and decreases the number of electrons above the Fermi energy, which indicates that the pure SrRuO3 is more metallic than Sr 0.875Na0.125RuO3 and Sr0.75Na 0.25RuO3. However, the metal-insulator transition has not happened when Na only substitutes on the Sr site in SrRuO3. © 2012 Elsevier B.V. All rights reserved.

Tang Y.,Xiangtan University | Chen Y.,South China Normal University
Journal of Systems Science and Complexity | Year: 2012

This paper studies variational discretization for the optimal control problem governed by parabolic equations with control constraints. First of all, the authors derive a priori error estimates where {double pipe}{pipe}u - U h{double pipe}{pipe} L∞(J;L2(Ω)) = O(h 2 + k). It is much better than a priori error estimates of standard finite element and backward Euler method where {double pipe}{pipe}u - U h{double pipe}{pipe} L∞(J;L2(Ω)) = O(h + k). Secondly, the authors obtain a posteriori error estimates of residual type. Finally, the authors present some numerical algorithms for the optimal control problem and do some numerical experiments to illustrate their theoretical results. © 2012 Institute of Systems Science, Academy of Mathematics and Systems Science, CAS and Springer-Verlag Berlin Heidelberg.

Huang H.,South China University of Technology | Huang H.,Xiangtan University | Ji X.,South China University of Technology | Ji X.,Xiangtan University | And 2 more authors.
Chemical Society Reviews | Year: 2015

The transition metal-catalyzed C-H functionalization with hydroxylamine derivatives serving as both reactants and internal oxidants has attracted a lot of interest. These reactions obviate the need for external oxidants and therefore result in high reactivity and selectivity, as well as excellent functional group tolerance under mild reaction conditions, and moreover, water, methanol or carboxylic acid is generally released as the by-product, thus leading to reduced waste. This review focuses on the transition metal-catalyzed oxidative C-H functionalization of N-oxyenamine internal oxidants, with an emphasis on the scope and limitations, as well as the mechanisms of these reactions. This journal is © The Royal Society of Chemistry.

Ma M.M.,Xiangtan University | Ding J.W.,Xiangtan University
Solid State Communications | Year: 2010

The electronic structures and the persistent currents of diamond-like graphene rings (DGRs) are investigated within the tight-binding formalism. The calculations show that an armchair DGR is a metallic ring only at selected ring width N=3m-1 (m is an integer), while a zigzag one appears to be metallic regardless of its geometry. The persistent currents in DGRs are calculated, depending strongly on their geometries. It is found that the persistent current in a metallic armchair DGR is near an order of magnitude larger than that in a metallic zigzag hexagonal graphene ring (HGR) of equivalent size [M.M. Ma, J.W. Ding, N. Xu, Nanoscale 1 (2009) 387]. In the metallic zigzag DGRs, the persistent currents are declined generally by two orders of magnitude compared with the sizable metallic armchair DGRs. © 2010 Elsevier Ltd. All rights reserved.

Liu Y.,Xiangtan University | Huang K.,Xiangtan University | Luo H.,Xiangtan University | Li H.,Xiangtan University | And 2 more authors.
RSC Advances | Year: 2014

A well-organized flexible composite of nitrogen-doped graphene-Fe 3O4 (N-G-Fe3O4) is successfully synthesized through a green and facile chemical method. The half cells based on the synthesized N-G-Fe3O4 composite exhibit a reversible specific capacity approaching about 800 mA h g-1, after 100 cycles at a current density of 100 mA g-1. For the composite, the graphene plays a flexible confinement function to encapsulate Fe3O4 particles, accommodating the volume change and preventing the agglomeration of Fe3O4 nanoparticles. Furthermore, the nitrogen doping can greatly improve the electrical conductivity of graphene, and decrease the energy barrier for Li ion penetration and effectively modify the surface chemistry at the anode/electrolyte interface to form a stable solid electrolyte interface (SEI) layer. As a result, this unique N-G-Fe3O4 composite can dramatically improve the cycling performance and rate capacity as an anode material for lithium ion batteries. This journal is © the Partner Organisations 2014.

Pei Y.,University of Nebraska - Lincoln | Pei Y.,Xiangtan University | Shao N.,Oak Ridge National Laboratory | Li H.,University of Nebraska - Lincoln | And 2 more authors.
ACS Nano | Year: 2011

Using ab initio methods, we investigate the structural evolution of a family of gold-sulfide cluster anions (AumSn -). We show that this family of clusters exhibits simple size-evolution rules and novel hollow polyhedron structures. The highly stable AumS n - species such as Au6S4 -, Au9S5 -, Au9S 6 -, Au10S6 -, Au 11S6 -, Au12S8 -, and Au13S8 - detected in the recent ion mobility mass spectrometry experiment of Au25(SCH 2CH2Ph)18 (Angel et al. ACS Nano2010, 4, 4691) are found to possess either quasi-tetrahedron, pyramidal, quasi-triangular prism, or quasi-cuboctahedron structures. The formation of these polyhedron structures are attributed to the high stability of the S-Au-S structural unit. A unique "edge-to-face" growth mechanism is proposed to understand the structural evolution of the small AumSn - cluster. A 3:2 ratio rule of Au/S is suggested for the formation of a hollow polyhedron structure among small-sized AumSn clusters. © 2011 American Chemical Society.

Xie Y.,Xiangtan University | Zhang F.,Xiangtan University | Liu P.,Xiangtan University | Hao F.,Xiangtan University | Luo H.,Xiangtan University
Journal of Molecular Catalysis A: Chemical | Year: 2014

Metalloporphyrin-catalysed direct functionalization of saturated CH bonds is one among the topical and challenging areas within the chemical industry. In this work, three types of unsupported and boehmite supported trans-A 2B2-metalloporphyrin chloride complexes (Co-D(p-Cl)PPCl, Fe-D(p-Cl)PPCl, Mn-D(p-Cl)PPCl) were prepared and characterized. It has been found that these trans-A2B2-metalloporphyrins have high catalytic activity in cyclohexane oxidation under dioxygen. The boehmite supported metalloporphyrins show better catalytic performance and are more stable than unsupported metalloporphyrins. Among these supported metalloporphyrin catalysts, Co-D(p-Cl)PPCl/BM was better than Fe-D(p-Cl)PPCl/BM and Mn-D(p-Cl)PPCl/BM, the cyclohexane conversion and selectivity to KA oil are 6.83% and 83.30%, respectively, and the turnover number is 1.05 × 10 7. The Co-D(p-Cl)PPCl/BM catalyst can be facilely recovered and was recycled up to six times without significant decrease in catalytic performance. © 2014 Elsevier B.V. All rights reserved.

Ma K.L.,Nanjing University of Aeronautics and Astronautics | Yan X.H.,Nanjing University of Aeronautics and Astronautics | Xiao Y.,Nanjing University of Aeronautics and Astronautics | Chen Y.P.,Xiangtan University
Solid State Communications | Year: 2010

We studied theoretically the electronic transport of metallic graphene nanoribbons (GNRs) with two vacancies using the tight-binding model and Green's function method. The results show that the conductance of zigzag GNR (ZGNR) varies with the relative position of two vacancies. However, when two vacancies reside on the edges, the conductance remain unchanged compared to that of perfect GNRs due to the interaction between vacancy state and edge state. Moreover, the conductance at the Fermi level for armchair GNR (AGNR) can be zero or finite depending on the position of vacancies on the GNRs. The demonstrated features of electronic transport open extremely attractive perspectives for designing well-defined GNR-based nanoelectronic devices. © 2010 Elsevier Ltd. All rights reserved.

Jiang W.,Xiangtan University | Zeng W.,Xiangtan University | Ma Z.,Xiangtan University | Pan Y.,Xiangtan University | And 2 more authors.
RSC Advances | Year: 2014

An amorphous nanoporous stannous oxide (ANSO) composite with carbon nanotubes (CNTs) electrode material is synthesized by electrodeposition and anodic oxidation methods. The ANSO@CNTs as an anode material for lithium-ion batteries exhibits a highly reversible specific capacity, stable cycling ability and good rate capabilities. The first discharge capacity is as high as 1895.3 mA h g-1with a reversible capacity of 1608.2 mA h g-1at a current density of 100 mA g-1. Furthermore, an electrochemical performance with a highly reversible capacity and enhanced rate capability can be found due to the highly uniform distribution and superior electrochemical and mechanical performances of the CNTs. The preparation approach for the ANSO@CNTs anode material reported in this paper may be applied to large-scale production of anode materials for high performance lithium-ion batteries. © the Partner Organisations 2014.

Wang D.,Xiangtan University | Xiao A.,Xiangtan University | Yang W.,Xiangtan University
Journal of Computational Physics | Year: 2013

In this paper, the Crank-Nicolson (CN) difference scheme for the coupled nonlinear Schrödinger equations with the Riesz space fractional derivative is studied. The existence of this difference solution is proved by the Brouwer fixed point theorem. The stability and convergence of the CN scheme are discussed in the L2 norm. When the fractional order is two, all those results are in accord with the difference scheme developed for the classical non-fractional coupled nonlinear Schrödinger equations. Some numerical examples are also presented. © 2013 Elsevier Inc.

Yi N.,Xiangtan University | Huang Y.,Xiangtan University | Liu H.,Iowa State University
Journal of Computational Physics | Year: 2013

A direct discontinuous Galerkin method for solving the generalized Korteweg-de Vries (KdV) equation with both periodic data and non-homogeneous boundary data is developed. A class of numerical fluxes is identified so that the method preserves both momentum and energy for the initial value problem. The method with such a property is numerically shown robust with less error in both phase and amplitude after long time simulation. Numerical examples are given to confirm the theoretical result and the capacity of this method for capturing soliton wave phenomena and various boundary wave patterns. © 2013 Elsevier Inc.

Cao X.,Xiangtan University | Bai Y.,Xiangtan University | Xie Y.,Xiangtan University | Deng G.-J.,Xiangtan University | Deng G.-J.,CAS Institute of Chemistry
Journal of Molecular Catalysis A: Chemical | Year: 2014

Pd-catalyzed intermolecular aerobic dehydrogenative aromatizations have been developed for the arylation of aryl sulfonamides with cyclohexanones. Various N-aryl sulfonamides were selectively obtained in good yields using molecular oxygen as oxidant. The reaction tolerated a wide range of functionalities. © 2013 Elsevier B.V.

Wang D.,Xiangtan University | Xiao A.,Xiangtan University | Li X.,Xiangtan University
Computer Physics Communications | Year: 2013

Based on W-transformation, some parametric symplectic partitioned Runge-Kutta (PRK) methods depending on a real parameter α are developed. For α=0, the corresponding methods become the usual PRK methods, including Radau IA-IĀ and Lobatto IIIA-IIIB methods as examples. For any α≠0, the corresponding methods are symplectic and there exists a value α * such that energy is preserved in the numerical solution at each step. The existence of the parameter and the order of the numerical methods are discussed. Some numerical examples are presented to illustrate these results. © 2012 Elsevier B.V. All rights reserved.

Xiao F.,Xiangtan University | Chen W.,Xiangtan University | Liao Y.,Xiangtan University | Deng G.-J.,Xiangtan University
Organic and Biomolecular Chemistry | Year: 2012

The copper-promoted three-component coupling sequence for substituted quinoline formation from aldehydes, anilines and acetone is described. Various 2-arylquinolines were selectively obtained in good yields under mild conditions. The reaction tolerated a wide range of functionalities. © 2012 The Royal Society of Chemistry.

Wang F.-F.,Xiangtan University | Luo C.-P.,Xiangtan University | Wang Y.,Xiangtan University | Deng G.,Xiangtan University | Yang L.,Xiangtan University
Organic and Biomolecular Chemistry | Year: 2012

A practical Bronsted acid promoted benzylic C-H functionalization of 2-methylazaarenes and nucleophilic addition to aldehydes was developed in good to excellent yields. A six-membered hydrogen-bonding transition state is proposed to be crucial for the reaction. Ready availability of the two starting materials, the use of acetic acid as the catalyst and the facile reaction conditions will guarantee this synthetic method attractive to the synthesis of bioactive pyridine and quinoline derivatives. © 2012 The Royal Society of Chemistry.

Zeng H.,Xiangtan University | Li T.,Xiangtan University | Yan Z.,Xiangtan University | Luo S.,Xiangtan University | Li F.,Xiangtan University
Crystal Growth and Design | Year: 2010

Two metal-organic frameworks (MOFs) with one-dimensional channels were successfully synthesized from the reactions of flexible paraffinic polycarboxylate with Zn(NO3)2 and CeCl3, respectively (([Zn2(BTCA)] · 5H2O}., (1) and ([CeNa(BTCA)(H2O)3] • 4H2O}., (2), H 4BTCA = 1,2,3,4-butanetetracarboxylic acid). With similar reaction conditions, reactions of the same organic ligand with different metals selected from different blocks (d-block and f-block) result in different coordination modes of carboxylate groups and final frameworks of 1 and 2. It is interesting that pores in 1 and 2 exhibit different behaviors to sodium cation, showing unique properties of MOFs based on flexible ligands. © 2010 American Chemical Society.

Tang K.,Hunan Institute of Science and Technology | Luo J.,Xiangtan University | Zhang P.,Hunan Institute of Science and Technology | Zhou C.,Hunan Institute of Science and Technology | Yi J.,Hunan Institute of Science and Technology
Chemical Engineering Research and Design | Year: 2013

Kinetics data is important for the reliable scale-up of a lab-scale process and for selection, design and operation of related equipment. This paper reports on the kinetics study for reactive extraction of hydroxy-(2-methyl-phenyl)-acetic acid (HA) enantiomers by hydroxypropyl-β-cyclodextrin (HP-β-CD) from the organic phase to the aqueous phase. The theory of extraction with chemical reaction was used. The effects of agitation speed, interfacial area, pH value of aqueous phase, initial concentration of HA enantiomers and initial concentration of extractant on the specific rate of extraction were investigated. The reactions have been found to be first order in HA and second order in HP-β-CD with the forward rate constants of 4.873×10-4m6/(mol2s) for R-HA and 4.343×10-4m6/(mol2s) for S-HA, respectively. © 2012 The Institution of Chemical Engineers.

Wang W.,Xiangtan University | Zhang K.,Xiangtan University | Liu H.,Xiangtan University | Qiao Z.,Xiangtan University | And 2 more authors.
Catalysis Communications | Year: 2013

Unsupported Ni-P catalysts were prepared from the mixed precursor of NiCl2 and NaH2PO2 by thermal decomposition method, and their catalytic activities were measured using the hydrodeoxygenation (HDO) of p-cresol as probe. The effects of the H 2PO2 -/Ni2 + molar ratio in the precursor and the thermal decomposition temperature on the catalyst purity, crystallite size and HDO activity were studied. The HDO of p-cresol on these Ni-P catalysts proceeded with two parallel pathways yielding methylbenzene and methylcyclohexane as final products. The higher HDO catalytic activity of the catalyst was attributed to its bigger crystallite size and purer phase of Ni2P. © 2013 Published by Elsevier B.V. All rights reserved.

Liu H.-H.,Xiangtan University | Wang Y.,Xiangtan University | Deng G.,Xiangtan University | Yang L.,Xiangtan University
Advanced Synthesis and Catalysis | Year: 2013

A direct transition metal-free regioselective C-3 amidation of indoles has been developed with the commercially available N-fluorobenzenesulfonimide (NFSI) as the amino source under external oxidant-free conditions. This amidation requires only a catalytic amount of base and exhibits excellent functional group tolerance and regioselectivity. The C-3 regioselectivity was proposed to realize by a free radical mechanism. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ma Y.,Xiangtan University | Ma Y.,Rutgers University | Lockwood G.K.,Rutgers University | Garofalini S.H.,Rutgers University
Journal of Physical Chemistry C | Year: 2011

A variable charge potential is developed that is suitable for the simulations of energy conversion materials FeF 2 and FeF 3. Molecular dynamics simulations using this potential show that the calculated structural and elastic properties of both FeF 2 and FeF 3 are in good agreement with experimental data. Such a transferability of this potential rests in the fact that the difference in the bond characteristic between FeF 2 and FeF 3 is properly accounted for by the variable charge approach. The calculated equilibrium charges are also in excellent agreement with first-principles Bader charges. Surface energies obtained by the variable charge method are closer to the first-principles data than are fixed charge models, indicating the importance of variable charge method for the simulations of the surface. A significant decrease in atomic charges is observed only for the outermost one or two layers, which is also observed in the first-principles calculations. © 2011 American Chemical Society.

Tang R.-J.,Xiangtan University | Luo C.-P.,Xiangtan University | Yang L.,Xiangtan University | Li C.-J.,McGill University
Advanced Synthesis and Catalysis | Year: 2013

An electrophilic amidation via a cationic rhodium(III)-catalyzed C(sp 2)-H activation has been developed with the commercially available N-fluorobenzenesulfonimide as the amino source under external oxidant-free conditions. This amidation requires only a catalytic amount of base and exhibits excellent functional group tolerance and regioselectivity, providing a new avenue in direct C(sp2)-H amidation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Deng J.,Xiangtan University | Deng Z.,Port Machinery BU of Sany Group Co. Changsha
Neurocomputing | Year: 2016

In this paper, applying the fixed point theorem and a new method, we study the existence, uniqueness, and global exponential stability of solutions of NNs with continuously distributed delays and obtain some new results in terms of system parameters. In our results, the exponentially convergent rate is given and the conditions are less restrictive than previously known criteria. Therefore they can be applied to NNs with a broad range of activation functions though these functions are neither differentiability nor strict monotonicity. © 2015 Elsevier B.V.

Li J.,Xiangtan University | Li J.,University of Nevada, Las Vegas | Huang Y.,Xiangtan University | Yang W.,Xiangtan University
Journal of Computational Physics | Year: 2013

In this paper we develop an adaptive edge finite element method based on a reliable and efficient recovery type a posteriori error estimator for time-harmonic Maxwell equations. The asymptotically exact a posteriori error estimator is based on the superconvergence result proved for the lowest-order edge element on triangular grids, where most pairs of triangles sharing a common edge form approximate parallelograms. The efficiency and robustness of the proposed method is demonstrated by extensive numerical experiments for electromagnetic cloaking problems with highly anisotropic permittivity and permeability. © 2013 Elsevier Inc.

Fan Y.,Nanyang Technological University | Zhang Q.,Nanyang Technological University | Xiao Q.,Nanyang Technological University | Wang X.,Nanyang Technological University | Huang K.,Xiangtan University
Carbon | Year: 2013

We report a carbon nanotube (CNT)-silicon core-shell nanowire for lithium ion battery anodes. In this material, the core consists of vertically aligned CNTs synthesized through plasma enhanced chemical vapor deposition. The CNTs exhibit quite large diameters and large inter-wire spacing and are advantageous in strain accommodation and electrolyte access. The silicon shell is tailored with a thickness gradient along its length to eliminate excessive strain accumulation at the nanowire roots and cater for free space distribution in the CNT core array. In addition, the silicon shell exhibits a unique vertically opened pore structure, which is expected to have further improved strain accommodation and Li+ transport. As a result, the CNT-silicon anode demonstrates excellent cyclability with a capacity retention of more than 90% over 100 cycles. It also shows remarkable rate performance that is to our knowledge, the best among all core-shell nanowires reported. © 2013 Elsevier Ltd.

Li X.,Xiangtan University | Xiao A.,Xiangtan University
International Journal of Modeling, Simulation, and Scientific Computing | Year: 2014

The Hagedorn wavepacket method is an important numerical method for solving the semiclassical time-dependent Schrödinger equation. In this paper, a new semidiscretization in space is obtained by wavepacket operator. In a sense, such semidiscretization is equivalent to the Hagedorn wavepacket method, but this discretization is more intuitive to show the advantages of wavepacket methods. Moreover, we apply the multi-time-step method and the Magnus-expansion to obtain the improved algorithms in time-stepping computation. The improved algorithms are of the Gauss-Hermite spectral accuracy to approximate the analytical solution of the semiclassical Schrödinger equation. And for the given accuracy, the larger time stepsize can be used for the higher oscillation in the semiclassical Schrödinger equation. The superiority is shown by the error estimation and numerical experiments. © World Scientific Publishing Company.

Wang W.-y.,Xiangtan University | Yang Y.-q.,Xiangtan University | Luo H.-a.,Xiangtan University | Liu W.-y.,Xiangtan University
Catalysis Communications | Year: 2010

Ni-Mo-B amorphous catalysts promoted by Co and La were prepared by chemical reduction of the corresponding metal salts with sodium borohydride. The effects of additives for the catalytic activity were studied using the hydrodeoxygenation of phenol as model reaction. Co- and La-promoted Ni-Mo-B amorphous catalysts exhibited higher catalytic activity. The total selectivity of oxygen-free products was increased to 93.1% with a selectivity of 3.2% aromatics on Co-Ni-Mo-B and the total H/C atomic ratio in the products was improved to 1.99 on La-Ni-Mo-B. Crown Copyright © 2010.

Liu H.,Xiangtan University | Liu P.,Xiangtan University | You K.,Xiangtan University | Luo H.,Xiangtan University
Catalysis Communications | Year: 2010

The liquid-phase ammoximation of cyclohexanone over a titanium silicate sieve is followed in real time using on-line ATR-FTIR spectroscopy. We have discovered the formation and the vanishment of an intermediate during the reaction with the aid of on-line ATR-FTIR spectroscopy. A new possible reaction mechanism is proposed according to the experimental results. Hydrogen peroxide is firstly adsorbed on titanium silicate sieves, forming a complex peroxidic species of titanium, which can react with cyclohexanone to form an intermediate. Then the intermediate reacts with ammonia to give cyclohexanone oxime. The infrared spectra indicate that the intermediate has strong absorption of C-O bond. © 2010 Elsevier B.V. All rights reserved.

Wang W.,Xiangtan University | Yang Y.,Xiangtan University | Luo H.,Xiangtan University | Liu W.,Xiangtan University
Reaction Kinetics, Mechanisms and Catalysis | Year: 2010

Different contents of promoter (Co) in Co-Ni-Mo-B amorphous catalysts were prepared by chemical reduction of the precursors of metal salts with a sodium borohydride aqueous solution. The catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Adding a proper content of the promoter Co into Ni-Mo-B amorphous catalyst could increase the MoO2 content and decrease the particle size, but doping excess Co would cover some of the active sites and increase the particle size of the catalysts. The effect of Co content on the catalytic hydrodeoxygenation activity of the amorphous catalysts was studied using phenol as a model compound. The main route for the HDO of phenol on these amorphous catalysts was hydrogenation-dehydration and the content of aromatic compounds in HDO products was decreased obviously. The pseudo first-order reaction rate constant of the phenol HDO on Co-Ni-Mo-B amorphous catalyst was much greater than that of MoS2 when adding proper promoter Co. © 2010 Akadémiai Kiadó, Budapest, Hungary.

She Y.,Xiangtan University | Wang D.,Xiangtan University | Zhang W.,Tongren University | He Z.,Xiangtan University | Ding J.,Xiangtan University
Journal of the Optical Society of America B: Optical Physics | Year: 2010

By using the multiple-scale method, we study analytically the formation and stability of two-component spatial optical solitons in a cold, lifetime-broadened resonant four-level double-∧ type atomic system via electromagnetically induced transparency. It is shown that stable two-component (1+1) dimension spatial optical solitons with extremely weak light intensity can occur, which is different from the passive ones with photorefractive and planar waveguides. Furthermore, the interaction characteristics between two solitons are studied by numerical simulations. We find that the collisional dynamics and the energy transfer of the two solitons are closely correlated with their relative phase shift. Our results may provide a good idea to obtain useful spatial optical solitons for application in optical soliton communications. © 2010 Optical Society of America.

Xiao S.,Xiangtan University | Yang X.,Xiangtan University | Ding J.W.,Xiangtan University
Applied Physics B: Lasers and Optics | Year: 2010

Er3+/Yb3+ co-doped YF3 powder is prepared by combining a nitrate decomposition method with a NH4HF2 fluorization process, from which efficient energy transfer induced down-conversion is achieved. An absorbed 365 nm near ultraviolet photon is split into two photons of 650 nm red and 1000 nm near infrared radiations, both falling in the responding region of Si-based solar cells. The quantum cutting mechanism has been proposed and discussed and the energy transfer efficiency for the quantum cutting is evaluated by developing an emission intensity ratio contrast method. The investigation might offer a new possible approach to achieve Si-based solar cells of high efficiency by down-converting the near ultraviolet part of the solar spec-trum. © Springer-Verlag 2010.

Pang C.-Y.,Sichuan Normal University | Zhou R.-G.,East China Jiaotong University | Zhou R.-G.,Xiangtan University | Ding C.-B.,Sichuan Normal University | Hu B.-Q.,Chengdu University of Technology
Quantum Information Processing | Year: 2013

The operations of data set, such as intersection, union and complement, are the fundamental calculation in mathematics. It's very significant that designing fast algorithm for set operation. In this paper, the quantum algorithm for calculating intersection set C=A∩B is presented. Its runtime is O (√|A|×|B|×|C|)for case |C|≠ φ and O(√|A|× |B|) for case |C|= φ (i.e. C is empty set), while classical computation needs O (|A| × |B|) steps of computation in general, where |.| denotes the size of set. The presented algorithm is the combination of Grover's algorithm, classical memory and classical iterative computation, and the combination method decrease the complexity of designing quantum algorithm. The method can be used to design other set operations as well. © 2012 Springer Science+Business Media, LLC.

Guo F.,University of California at San Diego | Wang L.,University of California at San Diego | Zhou G.,Xiangtan University
Journal of Global Optimization | Year: 2014

This paper considers the optimization problem of minimizing a rational function. We reformulate this problem as a polynomial optimization problem by the technique of homogenization. These two problems are shown to be equivalent under some generic conditions. The exact Jacobian SDP relaxation method proposed by Nie is used to solve the resulting polynomial optimization problem. We also prove that the assumption of nonsingularity in Nie's method can be weakened to the finiteness of singularities. Some numerical examples are given in the end. © 2013 Springer Science+Business Media New York.

Liu J.,CAS Institute of Process Engineering | Liu J.,University of Chinese Academy of Sciences | Shen W.,Xiangtan University | Cui D.,CAS Institute of Process Engineering | And 4 more authors.
Catalysis Communications | Year: 2013

A comparative study was conducted for laboratory syngas methanation over a self-made Ni-Mg/Al2O3 catalyst to demonstrate the technical advantages of fluidized bed over fixed bed reactor. At different reaction temperatures, gas velocities and pressures, the CO conversion and selectivity to CH4 in fluidized bed were shown to be higher than in fixed bed, and much closer to the thermodynamic equilibriums. The spent catalysts from fluidized bed methanation had distinctively low and easy-oxidizing deposited carbon in comparison with that from fixed bed. The results were attributed to the bigger effective catalytic surface, better heat and mass transfer in fluidized bed reactor. © 2013 Elsevier B.V. All rights reserved.

Shu W.,Xiangtan University | Jiang L.,Xiangtan University | Xiao S.,Xiangtan University | Yang X.,Xiangtan University | Ding J.W.,Xiangtan University
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2012

In order to search efficient red-emitting phosphors for white LEDs application, CaAl 12O 19:Mn 4+ phosphors have been prepared by a combustion method assisted with GeO 2 flux. The influence of GeO 2 concentration and annealing temperature on the structure and luminescence intensity for the phosphors has been investigated. The mechanism for luminescence enhancement has been discussed. At GeO 2 doping concentration of 1.5 mol%, the red emission intensity increases by 81% under 330 nm UVA excitation. More isolated luminescence center Mn 4+ ions rather than pairs of Mn 4+-Mn 2+ ions are formed in the lattice with the introduction of GeO 2 at high temperature oxidation, leading to the enhancement of the red emission. A feasible new way to enhance the red emission in CaAl 12O 19:Mn 4+ phosphor is obtained. © 2011 Elsevier B.V. All rights reserved.

Chen Q.,Xiangtan University | Chen Q.,Guilin University of Technology | Wang Y.,Xiangtan University | Zhang T.,Xiangtan University | And 3 more authors.
Electrochimica Acta | Year: 2012

The cycle performance of spinel LiMn 2O 4 at 25 and 55 °C is improved by LaF 3 modification via a chemical deposition method. The physical and electrochemical performances of pristine and LaF 3-coated LiMn 2O 4 cathode materials are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical measurements. The coated LiMn 2O 4 with 2.92 wt% LaF 3 (LaF 3-3-LMO) displays capacity retentions of 90.1% and 84.2% at 25 and 55 °C, respectively, after 100 cycles, much higher than those of pristine LiMn 2O 4, 72.7% and 54.8%. The concentration of manganese dissolved from LaF 3-3-LMO in electrolyte is much lower than that from pristine LiMn 2O 4. The analysis of AC impedance indicates that the charge transfer resistance (R ct) and the increase of R ct for LaF 3-3-LMO during cycling are much lower than those for pristine LiMn 2O 4. The significantly improved electrochemical performance of the LaF 3-coated LiMn 2O 4 can be attributed to the reduction of manganese dissolution in electrolyte and charge transfer resistance with the help of LaF 3 coating. © 2012 Elsevier Ltd. All rights reserved.

Yamaguchi H.,Doshisha University | Niu X.-D.,Doshisha University | Ye X.-J.,Doshisha University | Ye X.-J.,Wuhan Institute of Technology | And 2 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2012

The dynamic rheological properties of viscoelastic magnetic fluids in externally applied uniform magnetic fields are investigated by a laboratory-made cone-plate rheometer in this study. In particular, the effects of the magnetic field on the viscoelastic properties (the complex dynamic modulus) of the viscoelastic magnetic fluids are studied. In the investigation, three viscoelastic magnetic fluids are made by mixing a magnetic fluid and a viscoelastic fluid with different mass ratios. As a supplementation to the experimental investigation, a theoretical analysis is also presented. The present study shows that the viscosity and elasticity of the viscoelastic magnetic fluids are significantly influenced by the magnetic field and the concentrations of the magnetic particles in the test fluids. Theoretical analysis qualitatively explains the present findings. © 2012 Elsevier B.V. All rights reserved.

Wang M.,Xiangtan University | Zhou J.,Xiangtan University | Mao G.,Xiangtan University | Zheng X.,Xiangtan University
Industrial and Engineering Chemistry Research | Year: 2012

TS-1 has been synthesized from an inorganic reactant system using Ti(SO 4) 2 as the titanium source, TPABr as the templating agent, and ammonia as the base to provide the alkalinity needed for crystallization. The effects of preparation parameters, such as titanium sources, crystallization temperature and time, SiO 2/TiO 2, TPABr/SiO 2, ammonia/SiO 2 and seed crystals on the physicochemical and catalytic properties of TS-1 were investigated in detail. The TS-1 samples were characterized by XRD, FT-IR, UV-vis, SEM, and ICP-AES, and the catalytic performance of TS-1 was evaluated in the epoxidation of allyl chloride. The results show that the catalytic performance of TS-1 synthesized using Ti(SO 4) 2 was excellent, and the crystal size of the catalyst was small. The synthesis conditions had a great influence on the properties of TS-1. The optimum synthesis conditions for the present system should employ a gel composition of SiO 2/TiO 2/NH 3/TPABr/H 2O = 1:0.022:2.5:0.15:35 and carry out the crystallization at 443 K for 3 days; the addition of seed in the synthesis gel played an important role in the crystallization of TS-1. Moreover, the stability and reusability of TS-1 prepared from this system was fine. © 2012 American Chemical Society.

Shen P.,Xiangtan University | Shen P.,CAS Beijing National Laboratory for Molecular | Bin H.,Xiangtan University | Bin H.,CAS Beijing National Laboratory for Molecular | And 2 more authors.
Organic Electronics: physics, materials, applications | Year: 2013

Two donor-acceptor (D-A) copolymers, PEHBDT-BTz and PODBDT-BTz, containing the same backbone of benzodithiophene (BDT) and bithiazole (BTz) units but different side chains were designed and synthesized. Effects of the side chains of BDT and BTz units on solubility, absorption spectra, energy levels, film morphology, and photovoltaic properties of the polymers were investigated. Results showed that the more branched side chains could increase the molecular weight and the introduction of alkylthienyl groups into BTz unit benefits to broaden the absorption and lower the bandgaps as well as deepen HOMO levels, which are propitious to improve the short-circuit current density (J sc) and open-circuit voltage (Voc) of photovoltaic cells. Polymer solar cells (PSCs) were prepared with the polymers as electron donors and PCBM as an acceptor. The device fabrication conditions, including the additive, the different acceptor and blend ratio of the polymer donor and acceptor, have been optimized. PCE of PSCs based on the copolymers varied from 2.92% for PODBDT-BTz to 3.71% for PEHBDT-BTz, depending on the type and topology of the side chains on the BDT moiety. The results indicate that an appropriate choice of side chains on the backbone is an effective way to improve photovoltaic performance of the related PSCs. © 2013 Elsevier B.V. All rights reserved.

Huang H.,Xiangtan University | Tang L.,Xiangtan University | Cai J.,Xiangtan University | Deng G.-J.,Xiangtan University
RSC Advances | Year: 2016

A mild and ambient pyrrole synthesis via copper-catalyzed aerobic cyclization of alkylamines and arylacetaldehydes is described. This method provided alternative access to a range of 1,3,4-trisubstituted pyrroles under environmentally friendly reaction conditions. © 2016 The Royal Society of Chemistry.

Zeng C.,Carnegie Mellon University | Liu C.,Xiangtan University | Pei Y.,Xiangtan University | Jin R.,Carnegie Mellon University
ACS Nano | Year: 2013

We report a disproportionation mechanism identified in the transformation of rod-like biicosahedral Au38(SCH2CH2Ph) 24 to tetrahedral Au36(TBBT)24 nanoclusters. Time-dependent mass spectrometry and optical spectroscopy analyses unambiguously map out the detailed size-conversion pathway. The ligand exchange of Au 38(SCH2CH2Ph)24 with bulkier 4-tert-butylbenzenethiol (TBBT) until a certain extent starts to trigger structural distortion of the initial biicosahedral Au38(SCH 2CH2Ph)24 structure, leading to the release of two Au atoms and eventually the Au36(TBBT)24 nanocluster with a tetrahedral structure, in which process the number of ligands is interestingly preserved. The other product of the disproportionation process, i.e., Au40(TBBT)m+2(SCH2CH2Ph) 24-m, was concurrently observed as an intermediate, which was the result of addition of two Au atoms and two TBBT ligands to Au 38(TBBT)m(SCH2CH2Ph) 24-m. The reaction kinetics on the Au38(SCH 2CH2Ph)24 to Au36(TBBT)24 conversion process was also performed, and the activation energies of the structural distortion and disproportionation steps were estimated to be 76 and 94 kJ/mol, respectively. The optical absorption features of Au 36(TBBT)24 are interpreted on the basis of density functional theory simulations. © 2013 American Chemical Society.

Chen Q.N.,University of Washington | Ma F.,University of Washington | Xie S.,Xiangtan University | Liu Y.,University of Washington | And 2 more authors.
Nanoscale | Year: 2013

Accurate scanning probing of magnetic materials at the nanoscale is essential for developing and characterizing magnetic nanostructures, yet quantitative analysis is difficult using the state of the art magnetic force microscopy, and has limited spatial resolution and sensitivity. In this communication, we develop a novel piezomagnetic force microscopy (PmFM) technique, with the imaging principle based on the detection of magnetostrictive response excited by an external magnetic field. In combination with the dual AC resonance tracking (DART) technique, the contact stiffness and energy dissipation of the samples can be simultaneously mapped along with the PmFM phase and amplitude, enabling quantitative probing of magnetic materials and structures at the nanoscale with high sensitivity and spatial resolution. PmFM has been applied to probe magnetic soft discs and cobalt ferrite thin films, demonstrating it as a powerful tool for a wide range of magnetic materials. © 2013 The Royal Society of Chemistry.

Pan K.,Xiangtan University | Liu Y.Y.,Xiangtan University | Xie S.H.,Xiangtan University | Liu Y.M.,University of Washington | Li J.Y.,University of Washington
Acta Materialia | Year: 2013

Piezoresponse force microscopy (PFM) has emerged as one of the most powerful tools for characterizing and manipulating electromechanical responses of piezoelectric and ferroelectric materials at the nanoscale, yet the interpretation and quantitative analysis of PFM data remains difficult and is not well established. In this paper, we develop a rigorous analysis of PFM using the Hankel integral transform and the effective point charge model, which accounts for the electromechanical coupling of the transversely isotropic piezoelectric medium, the concentrated electric field induced by scanning probe microscopy tip, and the coupling of the electromechanical field at the interface of air and piezoelectric half-space. Using this method, the contact mode is first considered in comparison with the decoupled method, followed by a detailed analysis of the non-contact mode considering the effects of experimental conditions. We note that the decoupled method is only valid for materials with weak piezoelectricity, and the effective piezoelectric coefficient derived from PFM shows nonlinear dependence on the complete set of specimen electromechanical moduli, as well as on the experimental conditions. The analysis thus sheds considerable insight into PFM and could enable determination of intrinsic piezoelectric coefficients through PFM measurement using inverse calculations. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Wu Y.-S.,Xiangtan University | Li C.-Y.,Xiangtan University | Li Y.-F.,Xiangtan University | Tang J.-L.,Xiangtan University | Liu D.,Xiangtan University
Sensors and Actuators, B: Chemical | Year: 2014

A pyrene compound (1) containing piperazine was synthesized and used as ratiometric fluorescent chemosensor to recognize Cr3+. The ratiometric fluorescent signal change of the chemosensor is on the basis of monomer-excimer conversion of 1 induced by Cr3+. As far as we know, it is the first ratiometric chemosensor based on pyrene that is developed for Cr3+. The analytical performance characteristics of the proposed Cr3+-sensitive chemosensor were investigated. The chemosensor can be applied to the quantification of Cr3+ with a linear range covering from 2.0 × 10-7 to 1.0 × 10-5 M with the detection limit is 4 × 10-8 M. The experiment results show that the response behavior of 1 towards Cr3+ is pH independent in medium condition (pH 6.0-8.0). Most importantly, the fluorescence changes of the chemosensor are remarkably specific for Cr3+ in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the response of the chemosensor toward Cr3+ is fast (response time less than 2 min). In addition, the chemosensor has been used for determination of Cr3+ in real sample such as river and pond water with satisfactory results. © 2014 Elsevier B.V. All rights reserved.

Wang R.,Xiangtan University | Wang D.,University of Shanghai for Science and Technology | Zhang Y.,Xiangtan University | Zheng X.,Xiangtan University
Sensors and Actuators, B: Chemical | Year: 2014

Bi0.5(Na0.85K0.15)0.5Ti 0.97Zr0.03O3 (BNKTZ) sensing materials were successfully synthesized via a simple metal-organic decomposition method. Their morphological feature was characterized as regular shaped microspheres, and it was observed that a large quantity of nanoparticles with the size, of 50-100 nm were present on microspheres surfaces. The introduction of a small quantity of Zr4+ in, the reaction system was played an important role in the size-control. At room temperature, humidity, sensing properties of the BNKTZ were investigated in detail. At 100 Hz, the curve of impedance versus relative humidity (RH) was of good linearity and the variation of BNKTZ humidity sensor's impedance was more than four orders of magnitude when humidity changed from 11% to 95% RH. The response time and recovery time were found to be about 18 s and 60 s, respectively. Furthermore, the maximum, hysteresis was only 4% RH. Comparing with A site substituted materials, with the similar response and sensing range, the A and B sites co-substituted BNKTZ humidity sensor possessed lower impedance, better linearity and wider operating frequency. The results indicated that BNKTZ microspheres have broader application for fabricating high performance room temperature humidity sensors. © 2013 Elsevier B.V.

Zou D.,Xiangtan University | Xie S.,Xiangtan University | Liu Y.,Xiangtan University | Lin J.,Xiangtan University | Li J.,University of Washington
Journal of Alloys and Compounds | Year: 2013

The electronic structure of CuGaTe2 has been investigated using first-principles calculations, and it was discovered that it has a mixture of heavy and light bands near the valence band maximum and a combination of electronically conducting and insulating units near the gap edges, highly desirable for good thermoelectric performance. Semi-classic Boltzmann transport theory was then used to calculate the thermoelectric properties of CuGaTe 2, and the optimal p- or n-type doping concentrations have been estimated based on the predicted maximum power factors. The phonon dispersion, phonon density of states, and specific heat of CuGaTe2 were evaluated by density functional perturbation theory in combination with the quasi-harmonic approximation, and the calculated phonon frequencies at the Γ point as well as the specific heat are in agreement with experimental data. The relatively high thermal conductivity of CuGaTe2 at low temperature is attributed to the lack of low-frequency vibrational modes, suggesting that its thermal conductivity can be reduced by introducing additional phonon scattering. © 2013 Elsevier B.V. All rights reserved.

Wang L.,Xiangtan University | Wu L.,Xiangtan University | Li Z.,Xiangtan University | Lei G.,Xiangtan University | And 2 more authors.
Electrochimica Acta | Year: 2011

Li2ZnTi3O8 fibers are synthesized by thermally treating electrospun Zn(CH3COO)2/LiOAc/TBT/PVP fibers and utilized as an energy storage material for rechargeable lithium-ion batteries. The material is characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermal analysis. Scanning electron microscopy results show that the Li2ZnTi3O 8 fibers have an average diameter of 200 nm. Electrochemical properties of the material are evaluated using cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy. The results show that as-prepared Li2ZnTi3O8 has a high specific discharge capacity of 227.6 mAh g-1 at the 2nd cycle. Its electrochemical performance at subsequent cycles shows good cycling capacity and rate capability. The obtained results thus strongly support that the electrospinning method is an effective method to prepare Li2ZnTi 3O8 anode material with higher capacity and rate capability. © 2011 Elsevier Ltd.

Zhou G.,Xiangtan University | Zhu P.,Xiangtan University
ICIC Express Letters | Year: 2011

Nonlinear algebraic equation originates from mathematics, physics, engineering and so on. Finding its roots efficiently has widespread applications in many fields. In this paper, based on homotopy analysis method, a series of efficient numerical algorithms for solving the roots of nonlinear equation quickly is presented. Firstly, primal nonlinear algebraic equation is replaced by a three-order approximative equation. Homotopy analysis method is used to solve the approximative equation, and a series of iterative algorithms is gotten. Secondly, the conclusion that the convergent order of one of the series of algorithms can reach four-order is proved. Thirdly, based on Newton-Raphson method, a scheme about how to define a convergent parameter is discussed, and a corresponding iterative algorithm for solving nonlinear algebraic equation is gotten. Finally, numerical results illustrate that the new algorithms are efficient and a good convergent parameter can in crease convergent region and rate of solution. ICIC International © 2011 ISSN 1881-803X.

Li T.,Xiangtan University | Li Q.,Xiangtan University | Yan J.,Xiangtan University | Li F.,Xiangtan University
Dalton Transactions | Year: 2014

Superhydrophobic and superoleophilic MnWO4:Dy3+ microbouquets were successfully fabricated via a facile hydrothermal process. The surface morphologies and chemical composition were investigated by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The wettability of the as-synthesized MnWO4:Dy3+ microbouquet film was studied by measuring the water contact angle (CA). A static CA for water of 165° and a very low sliding angle (SA) were observed, which were closely related to both the MnWO4:Dy3+ microbouquet structure and chemical modification. Furthermore, the as-prepared MnWO4:Dy 3+ surface showed superhydrophobicity for some corrosive liquids such as aqueous basic and salt solutions. © 2014 the Partner Organisations.

Wang B.,Xiangtan University | Qin H.,Xiangtan University
Chinese Control Conference, CCC | Year: 2013

A high quality unstructured triangular mesh scheme for adaptive finite element methods (AFEM) is presented. The algorithm is based on Superconvergent Cluster Recovery (SCR), and coupled with remeshing procedure and centroidal Voronoi tessellation (CVT) optimization techniques. The advantage for SCR is robust and easy to implementation. Normalized edge lengths which based on a metric are employed as the remeshing criterion. A high quality mesh can be obtained by CVT. Numerical test shows that the scheme can be applied successfully to a typical elliptic equation problem and other relevant steady-state problems in engineering. © 2013 TCCT, CAA.

Liu L.,Xiangtan University | Wang X.,Xiangtan University | Tian F.,Xiangtan University | Yi L.,Xiangtan University
Electrochimica Acta | Year: 2011

Bismuth-vanadium oxyfluoride (Bi2VO5F) has been synthesized using a simple, solid-state reaction process at different sintering temperatures. The structure and performance of the samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge experiments. The results show that bismuth-vanadium oxyfluoride belongs to a tetragonal crystal system with space group I4mm. The sample that was synthesized at 550 °C (P550) exhibits relatively good electrochemical properties. Sample P550 shows a high, initial discharge capacity of 222 mAh g-1 at a rate of 100 mA g-1 between 1.4 and 3.5 V. Sample P550 also shows acceptable electrochemical cycling properties. After the first cycle, the discharge specific capacity remains between 106 and 155 mAh g-1, which plateaus between 2.1 and 1.9 V during the first 15 cycles. © 2011 Elsevier Ltd. All rights reserved.

Li T.,Xiangtan University | Li Q.,Xiangtan University | Yan J.,Xiangtan University | Li F.,Xiangtan University
Dalton Transactions | Year: 2014

New photocatalysts (La3+-H3PW12O 40 and Ce3+-H3PW12O40) were prepared, and the degradation activity of these products was evaluated. These photocatalysts were synthesized by the hydrothermal method assisted by PEG-1000 from the reactions of LaCl3 or CeCl3 and phosphotungstic acid. The prepared catalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), ultraviolet-visible diffuse reflection spectroscopy (UV-vis) and thermal gravimetric analysis (TGA). The catalytic activity of La3+-H3PW12O40 and Ce 3+-H3PW12O40 was evaluated by adopting methyl orange (MO) and Rhodamine B (RhB) as model dyes, and the reaction was carried out under UV- and visible light irradiation. © the Partner Organisations 2014.

Ni B.,Xiangtan University | Liao J.,Xiangtan University | Chen S.,Xiangtan University | Zhang H.-L.,Xiangtan University
RSC Advances | Year: 2015

A series of end-on side-chain liquid crystalline polymers (SCLCPs) based on the biphenyl mesogen which were directly attached to the polymer backbone without the flexible spacer, poly(4,4′-alkoxybiphenylyl methacrylate) (PMBi-m, m = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16) were successfully synthesized by free radical polymerization. The chemical structures of the monomers were confirmed by 1H NMR and mass spectrometry. The molecular characterizations of the polymers were performed with 1H NMR, GPC and TGA. The phase behaviors were investigated by a combination of techniques including DSC, POM and 1D/2D WAXD. The experimental results showed that the alkoxy tail played an important role in the phase behaviors of the SCLCPs without the spacer. Firstly, all polymers form the smectic phase. Secondly, the clearing temperatures decrease with a small odd-even effect as the length of the alkyl tail increases and then increase slightly. Lastly, compared with the influence of the alkyl spacer length on liquid crystal properties of end-on SCLCPs with the biphenyl mesogen, the end-on SCLCPs without the spacer and with the different alkyl tail lengths (PMBi-m) exhibit a high glass transition temperature and a stable LC phase. © The Royal Society of Chemistry 2015.

Wu M.,University of Nebraska - Lincoln | Pei Y.,Xiangtan University | Dai J.,University of Nebraska - Lincoln | Li H.,University of Nebraska - Lincoln | Zeng X.C.,University of Nebraska - Lincoln
Journal of Physical Chemistry C | Year: 2012

Using density-functional theory (DFT), we show that edge-passivated zigzag graphene nanoribbons by a metal ligand M (ZGNR-M) can form various nanostructures through a single-file metal-chain joint. We have investigated structural properties of ZGNR-M (M = Al, Sc, Ti, V, Cr, Mn, Fe, or Co) based bi-wing nanostructures and tri-wing "nano-paddle-wheels", named as bi-ZGNR and tri-ZGNR, respectively. In particular, we explore whether one or more wings in bi-ZGNR or tri-ZGNR nanostructures can entail a strip of planar tetracoordinated carbon (ptC), a concept originally proposed by Hoffman et al. (J. Am. Chem. Soc.1970, 92, 4992) for molecular species. We find that although the ptC is energetically less favorable than nonplanar tetracoordinated carbon in bi-ZGNR nanostructures (M = Al, Sc, Ti, V, Cr, Mn, Fe, or Co), surprisingly, the ptC strip can be fully stabilized in two wings of tri-ZGNR and in all three wings of tri-ZGNR "nano-paddle-wheel". We also show that tri-ZGNR can be a structural unit for building a three-dimensional (3D) titanium-graphene framework (TiGF), the first predicted 3D porous material with segments of ptC strips. © 2012 American Chemical Society.

Li C.,Xiangtan University | Li C.,Hong Kong Polytechnic University | Lo K.-T.,Hong Kong Polytechnic University
Signal Processing | Year: 2011

Recently, an image scrambling encryption algorithm of pixel bit based on chaos map was proposed. Considering the algorithm as a typical binary image scrambling/permutation algorithm exerting on plaintext of size M×(8N), this paper proposes a novel optimal method to break it with some known/chosen-plaintexts. The spatial complexity and computational complexity of the attack are only O(32·MN) and O(16·n0·MN) respectively, where n0 is the number of known/chosen-plaintexts used. The method can be easily extended to break any permutation-only encryption scheme exerting on plaintext of size M×N and with L different levels of values. The corresponding spatial complexity and computational complexity are only O(MN) and O(logL(MN)⌉·MN) respectively. In addition, some specific remarks on the performance of the image scrambling encryption algorithm are presented. © 2010 Elsevier B.V. All rights reserved.

Xu G.,Xiangtan University | Yang L.,City University of Hong Kong | Wei X.,Xiangtan University | Ding J.,Xiangtan University | And 2 more authors.
Advanced Functional Materials | Year: 2016

Rational nanoscale surface engineering of electroactive nanoarchitecture is highly desirable, since it can both secure high surface-controlled energy storage and sustain the structural integrity for long-time and high-rate cycling. Herein, ultrasmall MoS2 quantum dots (QDs) are exploited as surface sensitizers to boost the electrochemical properties of Li4Ti5O12 (LTO). The LTO/MoS2 composite is prepared by anchoring 2D LTO nanosheets with ultrasmall MoS2 QDs using a simple and effective assembly technique. Impressively, such 0D/2D heterostructure composites possess enhanced surface-controlled Li/Na storage behavior. This unprecedented Li/Na storage process provides a LTO/MoS2 composite with outstanding Li/Na storage properties, such as high capacity and high-rate capability as well as long-term cycling stability. As anodes in Li-ion batteries, the materials have a stable specific capacity of 170 mAhg-1 after 20 cycles and are able to retain 94.1% of this capacity after 1000 cycles, i.e., 160 mAhg-1, at a high rate of 10 C. Due to these impressice performance, the presented 0D/2D heterostructure has great potential in high-performance LIBs and sodium-ion batteries. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chen H.,Xiangtan University
Chinese Journal of Organic Chemistry | Year: 2016

Significant progress has been made in polymeric semiconductors and their organic field-effect transistors (OFETs) since 1980s. To date, hundreds of polymeric semiconductors have been reported and used for OFETs. The hole mobility above 36.3 cm2·V-1·s-1 has been achieved, which can be competitive with organic small semiconductors and even amorphous silicon. In this review, the recent progress in high-mobility polymeric semiconductor materials has been summarized from the perspective of design, synthesis, and OFET devices performance. Moreover, the recent developments are systematically summarized and analyzed according to different types of polymeric semiconductors, including p-type, n-type, and ambipolar polymeric semiconductors. The analysis about the relationship among the molecular structure-aggregation structure-OFET devices performance may guide the rational molecule design in the polymeric semiconductor materials with excellently comprehensive performance in the future. © 2016 Chinese Chemical Society & SIOC, CAS.

Xie S.-H.,Xiangtan University | Xie S.-H.,University of Washington | Liu Y.-Y.,Xiangtan University | Li J.-Y.,University of Washington
Frontiers of Physics | Year: 2012

Multiferroic materials with two or more types of ferroic orders have attracted a great deal of attention in the last decade for their magnetoelectric coupling, and new ideas and concepts have been explored recently to develop multiferroic materials at nano-scale. Motivated by theoretical analysis, we synthesized single-phase BiFeO 3 (BFO) nanofibers, Pb(Zr 0.52Ti 0.48)O 3-CoFe 2O 4 (PZT-CFO) and Pb(Zr 0.52Ti 0.48)O 3-NiFe 2O 4 (PZT-NFO) composite nanofibers, and CoFe 2O 4-Pb(Zr 0.52Ti 0.48)O 3 (CFO-PZT) core-shell nanofibers using sol-gel based electrospinning. These nanofibers typically have diameters in the range of a few hundred nanometers and grain size in the range of 10s nanometers, and exhibits both ferroelectric and ferromagnetic properties. Piezoresponse force microscopy (PFM) based techniques have also been developed to examine the magnetoelectric coupling of the nanofibers, which is estimated to be two orders of magnitude higher than that of thin films, consistent with our theoretical analysis. These nanofibers are promising for a variety of multiferroic applications. © 2012 Higher Education Press and Springer-Verlag Berlin Heidelberg.

Zhang G.,Xiangtan University | Xiao A.,Xiangtan University
International Journal of Computer Mathematics | Year: 2015

The purpose of this paper is devoted to studying the implicit–explicit (IMEX) one-leg methods for stiff delay differential equations (DDEs) which can be split into the stiff and nonstiff parts. IMEX one-leg methods are composed of implicit one-leg methods for the stiff part and explicit one-leg methods for the nonstiff part. We prove that if the IMEX one-leg methods is consistent of order 2 for the ordinary differential equations, and the implicit one-leg method is A-stable, then the IMEX one-leg methods for stiff DDEs are stable and convergent with order 2. Some numerical examples are given to verify the validity of the obtained theoretical results and the effectiveness of the presented methods. © 2015 Taylor & Francis

Cao G.,Xiangtan University | Zhang Y.,Xiangtan University | Cao J.,Xiangtan University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2015

The topological properties of silicene and Sn film decorated with chemical functional groups (-H, -F, -Cl, -Br, -I) are investigated by the first-principle calculations. It is found that Sn films decorated with F, Cl, Br and I are topological insulators with sizable gap while the other combinations are normal insulators. The phase transition of X decorated silicene and Sn film was investigated by applying external strain. Our results pointed out that the normal insulators can transform into topological insulators with sizable gap under critical strain. The research provided new routes to design 2D topological insulator with sizable gap which has wide applications in next-generation spintronics devices. © 2015 Elsevier B.V. All rights reserved.

Yang Y.,University of Washington | Ma F.Y.,University of Washington | Lei C.H.,University of Washington | Liu Y.Y.,Xiangtan University | Li J.Y.,University of Washington
Journal of the Mechanics and Physics of Solids | Year: 2013

Thermoelectric materials are promising in converting heat directly into electricity, and composite materials are often used to enhance thermoelectric figure of merit. In this work, we develop a nonlinear asymptotic homogenization theory to analyze the effective behavior of layered thermoelectric composite with coupled transport of electricity and heat. The nonlinearly coupled thermoelectric transport equations are homogenized using asymptotic analysis, from which the macroscopic field distributions are derived with local fluctuation averaged out, and overall thermoelectric conversion efficiency is established using an idealized thermoelectric module. It is discovered that the thermoelectric field distributions in the composite are different from those in a homogeneous material, and they are difficult to be fitted by homogeneous solution. Furthermore, it is noted that while the effective thermoelectric properties of the composite can be defined through a set of equivalency principle, these effective properties depend on specific boundary conditions, resulting in effective figure of merit that is not correlated with thermoelectric conversion efficiency directly. The analysis thus sheds considerable insight into the effective behavior of thermoelectric composites for their design and optimization. © 2013 Elsevier Ltd.

Liu Y.,Xiangtan University | Wang Y.,Xiangtan University | Guo H.,Xiangtan University | Zhu M.,Xiangtan University | And 4 more authors.
Journal of Physical Chemistry C | Year: 2011

A triphenylamine-functionalized ternary europium(III) complex of Eu(DBM)3(DTPA-Phen), in which DTPA-Phen is 3,8-bis[4-(diphenylamino) phenyl]-1,10-phenanthroline and DBM is dibenzoylmethanato, was designed, synthesized and characterized. This complex emits the characteristic red emission of trivalent europium ion due to the 5D0 → 7Fj (j = 0-4) transitions under photoexcitation and exhibits high thermal stability (432 °C). Using this complex as a guest and a blend of poly(9,9-dioctylfluorene) (PFO) along with 2-(tert-butylphenyl)-5- biphenylyl-1,3,4-oxadiazole (PBD) as a host matrix yielded the double-layer polymer light-emitting devices (PLEDs) with high performance. The narrow-bandwidth red emission that peaked at 612 nm with a full width at half-maximum of 10 nm was observed in these devices at the dopant concentrations from 1 to 8 wt %. The highest external quantum efficiency of 1.8% photons per electron at a current density of 1.2 mA/cm2, with a maximum brightness of 1333 cd/m2 at 173.2 mA/cm2, was achieved from the device at 1 wt % dopant concentration. The results indicate that an introduction of triphenylamine groups into phenanthroline ligand can improve the performance of its Eu-organometallic compound-doped PLEDs. © 2011 American Chemical Society.

Ren G.,Xiangtan University | Ren G.,Science and Technology on Electro Optical Information Security Control Laboratory | Zeng S.,Xiangtan University | Zeng S.,Hong Kong Polytechnic University | Hao J.,Hong Kong Polytechnic University
Journal of Physical Chemistry C | Year: 2011

In this paper, highly monodispsered ultrasmall hexagonal phase NaGdF 4 nanorods were synthesized via a hydrothermal method using oleic acid as a stabilizing agent. The tunable multicolor upconversion (UC) emissions, including green, yellow, blue, and white emissions, can be readily achieved from lanthanide (Ln)-doped NaGdF 4 nanorods under the excitation of a 980 nm diode laser. The calculated chromaticity coordinates (CIE-X = 0.346, CIE-Y = 0.357) are close to those of the standard white light (CIE-X = 0.33, CIE-Y = 0.33), and the white UC emissions can be tuned from blue-white to white by adjusting the doped contents of Ho 3+ in the Yb 3+/ Tm 3+/Ho 3+ triply doped NaGdF 4 nanorods. In addition, the ultrasmall NaGdF 4 nanocrystals also exhibit paramagnetic properties at 293 K. The measured magnetizations of the NaGdF 4:20%Yb 3+/0.2% Er 3+ and NaGdF 4 nanocrystals were about 1.49 and 1.86 emu/g at 20 kOe, respectively, which were close to the reported values of other nanoparticles for bioseparation. Moreover, the NaGdF 4 nanocrystals can be readily attracted by a small magnet, which shows it has potential application in cell isolating. It is expected that these multifunctional ultrasmall NaGdF 4 nanorods including tunable UC colors and intrinsic paramagnetic properties may have potential applications in color displays, biolables, bioseparation, and magnetic resonance imaging. © 2011 American Chemical Society.

Su N.,Xiangtan University | Su N.,James Cook University
Journal of Hydrology | Year: 2010

The majority of infiltration equations in use today were developed for infiltration into rigid porous media based either on the classic diffusion equation or empirical formulation. In this paper, we present new equations of infiltration into swelling soils derived from the fractional Fokker-Planck equation (fFPE) of flow in swelling porous media formulated in a material coordinate. The cumulative infiltration we derived is I(t)=At+Stβ/2, where S is the fractional sorptivity, A the final infiltration rate, and β the order of fractional derivative in the fFPE. Using the data published in the literature on cumulative infiltration against time, β, S and A are determined. The determined value of β=0.2385 for this reported soil is much less than 1.0 which implies that infiltration into this specific swelling soil belongs to the category of sub-diffusion. We show that the new cumulative infiltration equation not only fits the reported data exceptionally better than Philip's two-term infiltration equation, more importantly, it provides fresh explanation and understanding of infiltration into swelling media. The new infiltration equation deviates from the majority of infiltration equations which were developed for rigid soils and ignore the realistic swelling and shrinking properties of the soils. © 2010 Elsevier B.V.

Hu M.L.,Xiangtan University | Yu Z.,Xiangtan University | Zhang K.W.,Xiangtan University | Sun L.Z.,Xiangtan University | Zhong J.X.,Xiangtan University
Journal of Physical Chemistry C | Year: 2011

Using density functional theory and nonequilibrium Green's function method, we investigate the tunneling magnetoresistance (TMR) of the magnetotunnel junctions (MTJs) based on bilayer hexagonal boron nitride and its response to external uniaxial strain. The TMR ratio increases linearly with the increasing uniaxial strain because the increasing uniaxial strain reduces the bandgap of bilayer hexagonal boron nitride gradually. Interestingly, the TMR ratio exceeds 95% when the uniaxial strain increases to 2.51%, which is close to that of the perfect spin filter. Our results indicate that the bilayer hexagonal boron nitride is a promising candidate for the spacer of MTJs. Moreover, its TMR ratio can be linearly modulated by external uniaxial strain. © 2011 American Chemical Society.

Zhou C.,Fudan University | Gao Y.,Fudan University | Gao Y.,Xiangtan University | Chen D.,Fudan University
Journal of Physical Chemistry B | Year: 2012

Poly(propargyl pyridinium bromide), a kind of conjugated polyelectrolyte with polyacetylene as the backbone and pyridinium as side groups, was synthesized simply via reaction between pyridine and propargyl bromide under mild conditions. The resultant polymer was characterized by 1H NMR, elemental analysis, FT-IR, and GPC-MALLS. An alkyne group was confirmed as the end group of the polymer chains by the alkyne/azide click chemistry, which reveals that the polymerization is terminated by the reaction between propargyl bromide and carbon anions. It is known that monosubstituted polyacetylenes reported have very weak fluorescence intensities, which limit their applications. As a monosubstituted polyacetylene, the freshly prepared poly(propargyl pyridinium bromide) also has a very weak fluorescence. However, we confirmed that addition of some anions to the polymer solution in DMF or DMSO leads to the fluorescence enhancements up to 25 times. Besides, heating the polymer solution at a temperature between 70 and 130 °C for longer than 0.5 h greatly enhanced the fluorescence intensity. The interaction with the anions or the heating enhances the effective exciton confinement within the conjugated backbone and thus results in the fluorescence enhancements. After the fluorescence enhancements, poly(propargyl pyridinium bromide) has relatively strong fluorescence emissions, which will make it promising in fluorescence-based applications. © 2012 American Chemical Society.

Huang Y.,Xiangtan University | Li J.,University of Nevada, Las Vegas | Yang W.,Xiangtan University | Sun S.,King Abdullah University of Science and Technology
Journal of Computational Physics | Year: 2011

Numerical simulation of metamaterials has attracted more and more attention since 2000, after the first metamaterial with negative refraction index was successfully constructed. In this paper we construct a fully-discrete leap-frog type finite element scheme to solve the three-dimensional time-dependent Maxwell's equations when metamaterials are involved. First, we obtain some superclose results between the interpolations of the analytical solutions and finite element solutions obtained using arbitrary orders of Raviart-Thomas-Nédélec mixed spaces on regular cubic meshes. Then we prove the superconvergence result in the discrete l2 norm achieved for the lowest-order Raviart-Thomas-Nédélec space. To our best knowledge, such superconvergence results have never been obtained elsewhere. Finally, we implement the leap-frog scheme and present numerical results justifying our theoretical analysis. © 2011 Elsevier Inc.

Huang Y.,Xiangtan University | Li J.,University of Nevada, Las Vegas | Yang W.,Xiangtan University
Journal of Computational Physics | Year: 2011

In this paper, we develop a fully-discrete interior penalty discontinuous Galerkin method for solving the time-dependent Maxwell's equations in dispersive media. The model is described by a vector integral-differential equation. Our scheme is proved to be unconditionally stable and achieve optimal error estimates in both L 2 norm and energy norm. The scheme is implemented and numerical results supporting our analysis are presented. © 2011 Elsevier Inc.

Jing Yu.,Nankai University | Tan X.,Xiangtan University | Zhou Z.,Nankai University | Shen P.,Nankai University
Journal of Materials Chemistry A | Year: 2014

Density functional theory computations were performed to investigate the adsorption of four organic molecules, including tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE), tetrathiafulvalene (TTF) and benzyl viologen (BV) on the basal plane of MoS2 monolayer (MoS2ML). There mainly exist non-covalent weak interactions between these organic molecules and MoS2ML with considerable charge transfer. Due to the adsorption of organic molecules, the band gap of MoS2ML can be efficiently reduced as the flat molecular levels lie in the band gap region of MoS2ML. Moreover, the adsorption of TCNQ can significantly enhance the optical absorption of MoS2ML in the infrared region of solar spectrum, whereas the adsorption of other molecules has negligible effect on the optical properties of MoS2ML. Our computations provide a flexible approach towards tuning the electronic and optical properties of MoS2ML. This journal is © the Partner Organisations 2014.

Li C.,Xiangtan University | Liu Y.,Xiangtan University | Zhang L.Y.,City University of Hong Kong | Wong K.-W.,City University of Hong Kong
Signal Processing: Image Communication | Year: 2014

As a fundamental theorem in number theory, the Chinese Reminder Theorem (CRT) is widely used to construct cryptographic primitives. This paper investigates the security of a class of image encryption schemes based on CRT, referred to as CECRT. Making use of some properties of CRT, the equivalent secret key of CECRT can be recovered efficiently. The required number of pairs of chosen plaintext and the corresponding ciphertext is only (1+⌈ ( log2L)/l⌉), the attack complexity is only O(L), where L is the plaintext length and l is the number of bits representing a plaintext symbol. In addition, other defects of CECRT, such as invalid compression function and low sensitivity to plaintext, are reported. The work in this paper will help clarify positive role of CRT in cryptology. © 2014 Elsevier B.V.

Yu D.,University of Washington | Yu D.,Chongqing University | Chen C.,Chongqing University | Xie S.,University of Washington | And 8 more authors.
Energy and Environmental Science | Year: 2011

Mesoporous V2O5 nanofibers were fabricated by a method combining sol-gel processing with electrospinning followed by annealing in air. The resultant nanofibers were 350 nm in diameter and consisted of porous polycrystalline vanadium oxide with a specific surface area of ∼97 m 2 g-1. The mesoporous V2O5 nanofibers demonstrated a significantly enhanced Li ion storage capacity of above 370 mA h g-1 and a high charge/discharge rate of up to 800 mA g-1 with little cyclic degradation. © 2011 The Royal Society of Chemistry.

Xu X.,Xiangtan University | Ji S.,Xiangtan University | Gao R.,China National Petroleum Corporation | Liu J.,Xiangtan University
RSC Advances | Year: 2015

Sodium-ion batteries have received great attention because of the abundant sodium resources and low cost. As a typical kind of cathode material for Na-ion batteries, sodium manganese oxides have shown great potential in cathode application due to their high specific capacity and good rate capability. Herein, we successfully synthesized P2-type Na0.4Mn0.54Co0.46O2 nanosheets via a two-step annealing route. The morphology and structural information of the Na0.4Mn0.54Co0.46O2 products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) technologies. The electrochemical performances of Na0.4Mn0.54Co0.46O2 were measured by charge-discharge tests, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). As the cathode for Na-ion batteries, the layered Na0.4Mn0.54Co0.46O2 nanosheets showed a high second charge capacity of 194 mA h g-1 and delivered a specific capacity of 125 mA h g-1 at a current of 20 mA g-1 after 60 cycles. © The Royal Society of Chemistry 2015.

Lan Y.-H.,Xiangtan University | Huang H.-X.,Xiangtan University
International Journal of Dynamical Systems and Differential Equations | Year: 2012

A combined controller-observer design procedure for a class of timedelay uncertain systems is proposed. First, a sufficient condition for robust asymptotical stability of the closed-loop systems is presented based on Lyapunov function theory. Next, by using matrix's Singular Value Decomposition (SVD) and Linear Matrix Inequality (LMI) techniques, the existence condition and method of designing an observer-based feedback controller is derived. The result is obtained in terms of LMI, which make all the gain matrices can be easily obtained by Matlab's LMI toolbox. Finally, the developed design techniques are applied to an engine idle speed control problem. The simulation results demonstrate the validity of this approach. © 2012 Inderscience Enterprises Ltd.

Yuquan X.,Xiangtan University
Mathematical Methods in the Applied Sciences | Year: 2012

In this paper, we consider a relation between two-parameter and one-parameter transition functions for Markov processes and obtain a very useful result to be regarded as relation theorem. Copyright © 2012 John Wiley & Sons, Ltd.

Liu B.-X.,Xiangtan University
Jisuan Lixue Xuebao/Chinese Journal of Computational Mechanics | Year: 2012

Aimed at the shortcoming of traditional parameters identification methods for LuGre friction model, a new parameters identification method based on genetic algorithms and modified chain code recognition method was presented. Firstly, LuGre friction model was briefly introduced. Secondly, the optimization objective function with measured and simulated friction force in stead state was established. Thirdly, the relationships among displacement-friction force curve in presliding regime, stiffness coefficient and damping coefficient of LuGre friction model were studied. Many displacement-friction force curves with different shape were simulated using different stiffness coefficients. The shape characteristics of those simulated displacement-friction force curves were extracted using modified chain code and Fourier descriptor. The Euclidean distance based on shape characteristics was employed as the measurement of similar degree between measured displacement-friction force curves and simulated displacement-friction force curves. When the distance is less than the given error, the corresponding stiffness coefficient of simulated displacement-friction force curve is regarded as the true one. In the end, a numerical example was given to show the correctness and effectiveness of the presented method.