Showing papers by "Nanjing University of Science and Technology published in 2010"
TL;DR: This method provides a facile and straightforward approach to deposit MnO(2) nanoparticles onto the graphene oxide sheets (single layer of graphite oxide) and may be readily extended to the preparation of other classes of hybrids based on GO sheets for technological applications.
Abstract: A composite of graphene oxide supported by needle-like MnO2 nanocrystals (GO−MnO2 nanocomposites) has been fabricated through a simple soft chemical route in a water−isopropyl alcohol system. The formation mechanism of these intriguing nanocomposites investigated by transmission electron microscopy and Raman and ultraviolet−visible absorption spectroscopy is proposed as intercalation and adsorption of manganese ions onto the GO sheets, followed by the nucleation and growth of the crystal species in a double solvent system via dissolution−crystallization and oriented attachment mechanisms, which in turn results in the exfoliation of GO sheets. Interestingly, it was found that the electrochemical performance of as-prepared nanocomposites could be enhanced by the chemical interaction between GO and MnO2. This method provides a facile and straightforward approach to deposit MnO2 nanoparticles onto the graphene oxide sheets (single layer of graphite oxide) and may be readily extended to the preparation of othe...
1,953 citations
TL;DR: A flexible graphene/polyaniline hybrid material as a supercapacitor electrode was synthesized by an in situ polymerization-reduction/dedoping-redoping process and showed better electrochemical performances than the pure individual components.
Abstract: A flexible graphene/polyaniline hybrid material as a supercapacitor electrode was synthesized by an in situ polymerization-reduction/dedoping-redoping process. This product was first prepared in an ethylene glycol medium, then treated with hot sodium hydroxide solution to obtain the reduced graphene oxide/polyaniline hybrid material. Sodium hydroxide also acted as a dedoping reagent for polyaniline in the composite. After redoping in an acidic solution, the thin, uniform and flexible conducting graphene/polyaniline product was obtained with unchanged morphology. The chemical structure of the materials was characterized by X-ray photoelectron spectroscopy and Raman spectroscopy. The composite material showed better electrochemical performances than the pure individual components. A high specific capacitance of 1126 F g−1 was obtained with a retention life of 84% after 1000 cycles for supercapacitors. The energy density and power density were also better than those of pure component materials.
574 citations
TL;DR: The enhanced specific capacitance and cycling life implies a synergistic effect between two components, of significance for developing new doped PANI materials for supercapacitors.
Abstract: Graphene oxide, a single layer of graphite oxide (GO), has been used to prepare graphene oxide/polyaniline (PANI) composite with improved electrochemical performance as supercapacitor electrode by in situ polymerization using a mild oxidant. The composites are synthesized under different mass ratios, using graphite as start material with two sizes: 12 500 and 500 mesh. The result shows that the morphology of the prepared composites is influenced dramatically by the different mass ratios. The composites are proposed to be combined through electrostatic interaction (doping process), hydrogen bonding, and π−π stacking interaction. The highest initial specific capacitances of 746 F g−1 (12 500 mesh) and 627 F g−1 (500 mesh) corresponding to the mass ratios 1:200 and 1:50 (graphene oxide/aniline) are obtained, compared to PANI of 216 F g−1 at 200 mA g−1 by charge−discharge analysis between 0.0 and 0.4 V. The improved capacitance retention of 73% (12 500 mesh) and 64% (500 mesh) after 500 cycles is obtained for...
568 citations
TL;DR: Three antipyrine derivatives of o-, m- and p-chlorobenzylideneaminoantipyrines were characterized by spectral techniques and density functional calculations and represent that the pi-conjugated moieties linked by Schiff base imines are responsible for the excellent Raman scattering activities of these compounds.
344 citations
TL;DR: A fundamental result called the equation of optimality in uncertain optimal control is given, and as an application, this result is used to solve a portfolio selection model.
Abstract: Optimal control is a very important field of study not only in theory but in applications, and stochastic optimal control is also a significant branch of research in theory and applications. Based on the concept of uncertain process, an uncertain optimal control problem is dealt with. Applying Bellman's principle of optimality, the principle of optimality for uncertain optimal control is obtained, and then a fundamental result called the equation of optimality in uncertain optimal control is given. Finally, as an application, the equation of optimality is used to solve a portfolio selection model.
343 citations
03 Dec 2010
TL;DR: An SRC oriented unsupervised MFL algorithm is proposed in this paper and the experimental results on benchmark face databases demonstrated the improvements brought by the proposed M FL algorithm over original SRC.
Abstract: Face recognition (FR) is an active yet challenging topic in computer vision applications. As a powerful tool to represent high dimensional data, recently sparse representation based classification (SRC) has been successfully used for FR. This paper discusses the metaface learning (MFL) of face images under the framework of SRC. Although directly using the training samples as dictionary bases can achieve good FR performance, a well learned dictionary matrix can lead to higher FR rate with less dictionary atoms. An SRC oriented unsupervised MFL algorithm is proposed in this paper and the experimental results on benchmark face databases demonstrated the improvements brought by the proposed MFL algorithm over original SRC.
341 citations
TL;DR: In this article, a dielectric loaded substrate integrated waveguide (SIW) H-plane sectoral horn antenna has been proposed and two antennas with rectangular and elliptical shaped loaded dielectrics were designed and fabricated.
Abstract: A dielectric loaded substrate integrated waveguide (SIW) H-plane sectoral horn antenna has been proposed in this paper. The horn and the loaded dielectric are integrated by using the same single substrate resulting in easy fabrication and low cost. Two antennas with rectangular and elliptical shaped loaded dielectrics were designed and fabricated. These antennas have high gain and narrow beamwidths both in the E-plane and in the H-plane. The results from the simulation and those from the measurement are in good agreement. To demonstrate applications of the array, the small aperture elliptical dielectric loaded antenna has been used to form an array to obtain higher gain and to form a one-dimensional monopulse antenna array.
331 citations
TL;DR: In this paper, a facile soft chemical approach was proposed to fabricate graphene−Co(OH)2 nanocomposites in a water−isopropanol system.
Abstract: The well-documented novel performances of graphene make it a potential candidate for a wide range of utilizations, driving research into exploiting unusual properties of this wonder material. This paper reports a facile soft chemical approach to fabricate graphene−Co(OH)2 nanocomposites in a water−isopropanol system. Generally the depositing agent (OH−) and some reducing agents (such as HS− and H2S) could be produced from the hydrolyzation of Na2S in aqueous solution. Therefore utilizing Na2S as a precursor could enable the occurrence of the deposition of Co2+ and the deoxygenation of graphite oxide (GO) at the same time. Remarkably the electrochemical specific capacitance of the graphene−Co(OH)2 nanocomposite reaches a value as high as 972.5 F·g−1, leading to a significant improvement in relation to each individual counterpart (137.6 and 726.1 F·g−1 for graphene and Co(OH)2, respectively). The feeding ratios between Co(OH)2 and graphene oxide have a pronounced effect on their electrochemical activities.
300 citations
TL;DR: In this article, the thermal conductivities of the composites reached maxima that were respectively 2.9 and 20.7 times that of the epoxy alone, and a method that partially replaces microfiller with nanofiller was used to further improve the thermal performance.
257 citations
04 Nov 2010
TL;DR: A fast method to detect image copy-move forgery is proposed based on the SURF (Speed up Robust Features) descriptors, which are invariant to rotation, scaling etc.
Abstract: As the advent and growing popularity of image editing software, digital images can be manipulated easily without leaving obvious visual clues. If the tampered images are abused, it may lead to potential social, legal or private consequences. To this end, it’s very necessary and also challenging to find effective methods to detect digital image forgeries. In this paper, a fast method to detect image copy-move forgery is proposed based on the SURF (Speed up Robust Features) descriptors, which are invariant to rotation, scaling etc. Results of experiments indicate that the proposed method is valid in detecting the image region duplication and quite robust to additive noise and blurring.
244 citations
TL;DR: The results demonstrate that it is much more efficient than representative image feature descriptors, such as the edge orientation auto-correlogram and the texton co-occurrence matrix and has good discrimination power of color, texture and shape features.
TL;DR: In this article, a new approach to the fabrication of GNS by ethylenediamine reduction in N,N-dimethylformamide (DMF) was reported. But this method requires the use of a large number of dispersing agents.
Abstract: The direct dispersion of graphene nanosheets (GNS) in an organic medium, without assistance of dispersing agents, has been considered to be an insurmountable challenge. Herein we report a new approach to the fabrication of GNS by ethylenediamine (EDA) reduction in N,N-dimethylformamide (DMF). By this method, chemical reduction as well as dispersion of GNS can be carried out in one step. Characterization indicated that the bulk of oxygen-containing functional groups were removed from graphene oxide, and stable DMF colloidal suspensions containing homogeneously dispersed GNS were successfully obtained. Our findings make it possible to prepare graphene-based nanocomposites using a quick and low-cost solution processing technique.
TL;DR: A system framework is presented to recognize multiple kinds of activities from videos by an SVM multi-class classifier with a binary tree architecture and the thought of hierarchical classification is introduced and multiple SVMs are aggregated to accomplish the recognition of actions.
15 Apr 2010-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: A composite plate of Mg alloy (AZ31B) and an Al alloy (7075) was fabricated by explosive welding and the microstructure and properties of the bonding interface after explosive cladding were investigated as mentioned in this paper.
Abstract: A composite plate of Mg alloy (AZ31B) and an Al alloy (7075) was fabricated by explosive welding. The microstructure and properties of the bonding interface after explosive cladding were investigated. The results show that the bonding interface had a wavy appearance with solidified melts in a regularly spaced pattern of discrete regions. Adiabatic shear bands and twin structure were found on the AZ31B Mg alloy side. “Metallurgical bonding” of the explosive welding interface was achieved by local diffusion with an approximate 3.5 μm thick diffusion layer. No intermetallics were formed. Shear strength across the bonding interface of AZ31B/7075 composite was ca. 70 MPa. The maximum bending stress reached 670 MPa.
TL;DR: The obtained nanocomposites exhibit a high catalytic activity for the thermal decomposition of ammonium perchlorate (AP), due to the concerted effect of CuO and GO.
Abstract: A facile chemical procedure capable of aligning CuO nanoparticles on graphene oxide (GO) in a water–isopropanol system has been described. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations indicate that the exfoliated GO sheets are decorated randomly by spindly or spherical CuO nanoparticle aggregates, forming well-ordered CuO:GO nanocomposites. A formation mechanism of these interesting nanocomposites is proposed as intercalation and adsorption of Cu2+ ions onto the GO sheets, followed by the nucleation and growth of the CuO crystallites, which in return resulted in the exfoliation of GO sheets. Moreover, the obtained nanocomposites exhibit a high catalytic activity for the thermal decomposition of ammonium perchlorate (AP), due to the concerted effect of CuO and GO.
TL;DR: In order to improve the corrosion resistance, a fluoride coating was prepared on the surface of AZ31B magnesium alloy as discussed by the authors, which showed a dense coating with some irregular pores was formed, and the TF-XRD analysis indicated that the coating was mainly composed of MgO and MgF(2).
TL;DR: Experimental results show that the proposed LPP solution scheme is able to classify much more accurately than conventional LPP and to obtain a classification performance that is only little influenced by the definition of neighbor samples.
TL;DR: In this paper, a memristor based oscillator is presented, which generates a steady periodic orbit and has a transition from transient chaotic to steady periodic behaviour, but the complicated dynamical behaviour is extremely dependent on the initial condition of the Memristor.
Abstract: By replacing Chua's diode in the canonical Chua's oscillator with a smooth flux-controlled memristor, a memristor based oscillator is presented. The memristor oscillator generates a steady periodic orbit and has a transition from transient chaotic to steady periodic behaviour. The complicated dynamical behaviour is extremely dependent on the initial condition of the memristor.
TL;DR: An in situ method of nucleating gold or palladium nanoparticles in the presence of ethylene glycol as a reducing agent, while simultaneously reducing GO to graphene is described, enabling insight into the electronic pathways available to the graphene-nanoparticle system.
Abstract: Understanding energy transfer mechanisms in graphene derivatives is strongly motivated by the unusually interesting electronic properties of graphene, which can provide a template for the creation of novel nanostructured derivatives. From a synthetic point of view, it is highly attractive to envision being able to synthesize pristine graphene from precursors such as graphene oxide (GO). While this goal may be challenging over large length-scales, it is possible to generate regions of graphene at the nanoscale, confirmed by Raman spectroscopy or other methods. We describe an in situ method of nucleating gold or palladium nanoparticles in the presence of ethylene glycol as a reducing agent, while simultaneously reducing GO to graphene. The Au nanoparticles aid in spectroscopic characterization by both quenching fluorescence, allowing the graphene D and G bands to be quantified, and yielding a surface enhancement of about two orders of magnitude. We observe the excitation profile (488–785 nm) of the surface enhanced Raman spectrum (SERS) of graphene with Au nanoparticles adsorbed on the surface. Both the D and G bands display a resonance at approximately 593 nm (2.09 eV). This resonance may be interpreted as a combination of the plasmon resonance at 548 nm and a likely contribution from charge transfer as well. In addition, we observe a stiffening of the G band compared with that of graphene. The mechanism of the SERS, whether plasmonic or charge transfer-based, enables insight into the electronic pathways available to the graphene–nanoparticle system. We discuss our results in the context of several existing studies of graphene-based nanostructure derivatives.
TL;DR: Comparative results demonstrate that the new adaptive total variation method based on a new edge indicator, named difference curvature, can avoid the staircase effect and better preserve fine details.
TL;DR: It is found that the complex atomic configuration in metallic glasses can be interpreted globally as a combination of the spherical-periodic order and local translational symmetry.
Abstract: In this Letter, we have revealed the common structural behavior of metallic glasses through scrutinizing the evolution of pair distribution functions from metallic liquids to glasses and statistically analyzing pair distribution functions of 64 metallic glasses It is found that the complex atomic configuration in metallic glasses can be interpreted globally as a combination of the spherical-periodic order and local translational symmetry The implications of our study suggest that the glass transition could be visualized mainly as a process involving in local translational symmetry increased from the liquid to glassy states
TL;DR: In this paper, a first-principles band gap criterion is founded to measure impact sensitivity for a series of energetic crystals with similar structure or with similar thermal decomposition mechanism, the smaller the band gap is, the easier the electron transfers from the valence band to the conduction band and the more they becomes decomposed and exploded.
Abstract: In this article, we review some recent studies in predicting impact sensitivity for different classes of energetic crystals based on first-principles band gap. Based on these investigations on metal azides, a first-principles band gap criterion is founded to measure impact sensitivity for a series of energetic crystals. For energetic crystals with similar structure or with similar thermal decomposition mechanism, the smaller the band gap is, the easier the electron transfers from the valence band to the conduction band, and the more they becomes decomposed and exploded. Applications of this criterion on other series of energetic crystals show that the first-principles band gap criterion is applicable to different series of energetic crystals with similar structure or with similar thermal decomposition mechanism. This criterion may be useful for molecular design of high-energy density materials.
04 Oct 2010
TL;DR: An innovative IRC called Cortcha is proposed that is scalable to meet the requirements of large-scale applications and relies on recognizing objects by exploiting the surrounding context, a task that humans can perform well but computers cannot.
Abstract: We systematically study the design of image recognition CAPTCHAs (IRCs) in this paper. We first review and examine all existing IRCs schemes and evaluate each scheme against the practical requirements in CAPTCHA applications, particularly in large-scale real-life applications such as Gmail and Hotmail. Then we present a security analysis of the representative schemes we have identified. For the schemes that remain unbroken, we present our novel attacks. For the schemes for which known attacks are available, we propose a theoretical explanation why those schemes have failed. Next, we provide a simple but novel framework for guiding the design of robust IRCs. Then we propose an innovative IRC called Cortcha that is scalable to meet the requirements of large-scale applications. It relies on recognizing objects by exploiting the surrounding context, a task that humans can perform well but computers cannot. An infinite number of types of objects can be used to generate challenges, which can effectively disable the learning process in machine learning attacks. Cortcha does not require the images in its image database to be labeled. Image collection and CAPTCHA generation can be fully automated. Our usability studies indicate that, compared with Google's text CAPTCHA, Cortcha allows a slightly higher human accuracy rate but on average takes more time to solve a challenge.
TL;DR: In this article, Fe-doped ZnO thin films were prepared by sol-gel method on Si and glass substrates and influence of Fe doping concentration on the structural and optical properties of the films was studied.
TL;DR: Bacterial cellulose nanofibers were biosynthesized by Acetobacter xylinum NUST5.2, and displayed a remarkable capability for orienting TiO(2) nanoparticle arrays, and showed higher efficiency than that of the commercial photocatalyst P25.2.
Abstract: Bacterial cellulose (BC) nanofibers were biosynthesized by Acetobacter xylinum NUST5.2, and displayed a remarkable capability for orienting TiO2 nanoparticle arrays. Large quantities of uniform BC nanofibers coated with TiO2 nanoparticles can be easily prepared by surface hydrolysis with molecular precision, resulting in the formation of uniform and well-defined hybrid nanofiber structures. The mechanism of arraying spherical TiO2 nanoparticles on BC nanofibers and forming well-defined, narrow mesopores are discussed in this paper. The BC/TiO2 hybrid nanofibers were used as photocatalyst for methyl orange degradation under UV irradiation, and they showed higher efficiency than that of the commercial photocatalyst P25.
TL;DR: The experiments show that the proposed matrix-based complex PCA, a feature level fusion method for bimodal biometrics that uses a complex matrix to denote two biometric traits from one subject, can achieve a higher classification accuracy than the 2DPCA and PCA techniques.
TL;DR: In this paper, a dual acidic ionic liquid catalyst was prepared via anchoring 3-sulfobutyl-1-(3-propyltriethoxysilane) imidazolium hydrogen sulfate onto silica gel by covalent bonds.
TL;DR: In this article, the authors presented new correlations for calculating the elemental composition based on proximate analysis of biomass using 66 data points, and validated by using 20 data points selected from different categories of biomass than that for correlations derivation.
TL;DR: In this article, the effect of aging time of ZnO sol on the structural and optical properties of the films was studied and it was shown that appropriate aging of the sol is very important for the improvement of structural and the optical quality of the thin films derived from sol-gel method.
TL;DR: Nitrospira was dominant being better adapted to the low DO and shorter sludge retention times (SRT) of this plant, while Nitrobacter increased in abundance during the winter months, when temperatures were lower and DO concentrations higher.