Recognition of vertical vowel graphemes of Korean characters based on combination of vowel graphemes

Korean characters consist of 2 dimensional distributed consonantal and vowel graphemes. The purpose of reducing the 2 dimensional characteristics of Korean characters to linear arrangements at early stage of character recognition is to decrease the complexity of following recognition task. By defining the identification codes for the vowel graphemes of Korean characters, the rules for combination of vowel graphemes are established, and a recognition algorithm based on the rules for combination of vowel graphemes, is therefore proposed for vertical vowel graphemes. The algorithm has been proved feasilbe through demonstrating simulations.

Research Progress of Carbon-Silicone Composite Materials

Silicone is a kind of polymer material with high cross-linked structure,which is com-posed by Si-O-Si main chain.Due to the special molecular chain structure,silicone mate-rials are characterized by oxidation resistance,aging resistance,high and low temperature resistance and chemical corrosion resistance.Moreover,silicone materials have process-able properties,simple forming process,good mechanical property,non-toxic and pollution-free.Therefore,silicone has been widely concerned by researchers at home and abroad.In this paper,the main research progress and application directions of carbon-silicone composite at home and abroad in recent years are reviewed.

Theoretical study on absorption of formaldehyde in graphene

Density functional theory（DFT）based ab-initio calculations were used to study formaldehyde（CH_2O）adsorptive behavior on graphene sheet.The results indicate that formaldehyde molecule is weakly bound to graphene with small adsorption values（approximately-0.064eV）,but the interaction between CH_2O and graphene sheets can be greatly strengthened by means of doped atoms,which can provide a basis for the development of CH_2O storage materials.

超声辅助法合成的石墨烯-TiO_2复合材料声催化降解罗丹明B(英文)

A series of graphene-TiO2 composites was fabricated from graphene oxide and titanium n-butoxide(TNB) by an ultrasonic-assisted method.The structure and composition of the nanocomposites were characterized by Raman spectroscopy,BET surface area measurements,X-ray diffraction,transmission electron microscopy,and ultraviolet-visible absorption spectroscopy.The average size of the TiO2 nanoparticles on the graphene nanosheets was controlled at around 10-15 nm without using surfactant,which is attributed to the pyrolysis and condensation of dissolved TNB into TiO2 by ultrasonic irradiation.The catalytic activity of the composites under ultrasonic irradiation was determined using a rhodamine B(RhB) solution.The graphene-TiO2 composites possessed a high specific surface area,which increased the decolorization rate for RhB solution.This is because the graphene and TiO2 nanoparticles in the composites interact strongly,which enhances the photoelectric conversion of TiO2 by reducing the recombination of photogenerated electron-hole pairs.

RhB Adsorption Performance of Magnetic Adsorbent Fe_3O_4/RGO Composite and Its Regeneration through A Fenton-like Reaction

Adsorption is one of the most effective technologies in the treatment of colored matter containing wastewater. Graphene related composites display potential to be an effective adsorbent. However, the adsorption mechanism and their regeneration approach are still demanding more efforts. An effective magnetically separable absorbent, Fe3O4 and reduced graphene oxide(RGO) composite has been prepared by an in situ coprecipitation and reduction method. According to the characterizations of TEM, XRD, XPS, Raman spectra and BET analyses, Fe3O4 nanoparticles in sizes of 10-20 nm are well dispersed over the RGO nanosheets, resulting in a highest specific area of 296.2 m2/g. The rhodamine B adsorption mechanism on the composites was investigated by the adsorption kinetics and isotherms. The isotherms are fitting better by Langmuir model, and the adsorption kinetic rates depend much on the chemical components of RGO. Compared to active carbon, the composite shows 3.7 times higher adsorption capacity and thirty times faster adsorption rates. Furthermore,with Fe3O4 nanoparticles as the in situ catalysts, the adsorption performance of composites can be restored by carrying out a Fenton-like reaction, which could be a promising regeneration way for the adsorbents in the organic pollutant removal of wastewater.

Enhanced Cu/graphene adhesion by doping with Cr and Ti:A first principles prediction

We presented a density functional theory study on doping effects of transition metals(Cr and Ti)on the Cu/graphene interface adhesion.Various undoped Cu/graphene interface structures were constructed using both the sandwich and the surface models.Energetics calculations showed that the interface binding strength only weakly depends on interface coordination.Both interface models predicted the top-fcc coordination type as the most energy-favored,with a low binding energy value.Segregated Cr prefers to substituting for Cu, while Ti occupies a hollow site at the interface.Although the segregation tendencies are both very weak,once present on the interface,both dopants can greatly increase the interface binding energy and improve the adhesion.

Opening Band Gap of Graphene by Chemical Doping: a First Principles Study

Single atom chemically doped graphene has been theoretically studied by density functional theory. The largest band gap, 0.62 eV, appears in arsenic atom doped graphene, then 0.60 eV comes by the tin atom, whose deformations can neither be ignored. It is also found that oxygen and iron single atom embedded graphene can open band gap by 0.52 and 0.54 eV, respectively. Moreover, doping O atom shows little distortion and high stability by charge redistribution. The band gap of Fe doped graphene is opened by orbital hybridization. The other heteroatom doped results are a little inferior to them.

Preparation and Application of Manganese Dioxide/Graphene Composite in Lithium Sulfur Batteries

Graphene/manganese dioxide composites and grapheme/manganese dioxide/sulfur(G/MnO2/S) composite cathode were prepared by hydrothermal method and by vapor permeation, respectively. Their structure, morphology and specific surface area were characterized by X-ray diffraction, electron microanalysis and nitrogen adsorption analysis. The composites show morphology of nanosheets, high specific surface area and even distribution of sulfur. The sulfur accounts for 75% in the G/MnO2/S composite by thermogravimetric analysis. The electrochemical performance of G/S and G/MnO2/S cathode were investigated. The G/MnO2/S composite cathodes show excellent rate performance and cycle stability. At a 0.2C current density, initial discharge specific capacity is 1 061 m A·h·g^-1 and maintains 698 m A·h·g^-1 after 100 cycles;At a 1C current density, maximum discharge capacity reaches 816 m A·h·g^-1 and average capacity decreasing rate is only 0.073%/cycle after running over 400 cycles. Electrochemical mechanism of the composites cathodes was analyzed. The sulfur adsorption of Mn O2 inhibited the loss of active material sulfur, so, the electrochemical performance of the complex was improved.

Loading direction-dependent shear behavior at different temperatures of single-layer chiral graphene sheets

The loading direction-dependent shear behavior of single-layer chiral graphene sheets at different temperatures is studied by molecular dynamics （MD） simulations. Our results show that the shear properties （such as shear stress-strain curves, buckling strains, and failure strains） of chiral graphene sheets strongly depend on the loading direction due to the structural asymmetry. The maximum values of both the critical buckling shear strain and the failure strain under positive shear deformation can be around 1.4 times higher than those under negative shear deformation. For a given chiral graphene sheet, both its failure strain and failure stress decrease with increasing temperature. In particular, the amplitude to wavelength ratio of wrinkles for different chiral graphene sheets under shear deformation using present MD simulations agrees well with that from the existing theory. These findings provide physical insights into the origins of the loading direction-dependent shear behavior of chiral graphene sheets and their potential applications in nanodevices.

Theoretical investigation on the Raman spectroscopy on graphene-based materials

Graphene, the thinnest and hardest nano-material in the world, is non-toxic, sustainable and with minimal environmental footprint. As one of the most important carbon materials, it is composed of a monolayer of carbon atoms with a honeycomb structure. Nowadays, scientists have tried to use it in the biomedicine subject because of its superior physical and chemical properties and excellent biocompatibility.

Development of high quality Fe_3O_4/rGO composited electrode for low energy water treatment

Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for water treatment. Graphene(rGO) has been intensively studied for CDI electrode because of its advantages such as excellent electrical conductivity and high specific surface area. However, its 2D dimensional structure with small specific capacitance, high resistance between layers and hydrophobicity degrades ion adsorption efficiency. In this work, we successfully prepared uniformly dispersed Fe3O4/rGO nanocomposite by simple thermal reactions and applied it as effective electrodes for CDI. Iron oxides play a role in uniting graphene sheets, and specific capacitance and wettability of electrodes are improved significantly;hence CDI performances are enhanced. The hardness removal of Fe3O4/rGO nanocomposite electrodes can reach 4.3 mg/g at applied voltage of 1.5V, which is 3 times higher than that of separate r GO electrodes.Thus this material is a promising candidate for water softening technology.

Chiral Current in a Graphene Battery

We review the formulation of graphene’s massless Dirac equation, under the chiral electromagnetism approach, hopefully demystifying the material’s unusual chiral, relativistic, effective theory. In Dirac’s theory, many authors replace the speed of light by the Fermi velocity, in this paper we deduce that in graphene the Fermi velocity is obtained from the connection between the electromagnetic chirality and the fine structure constant when the electric wave E is quasi parallel to the magnetic wave H. With this approach we can consider the properties of electric circuits involving graphene or Weyl semimetals. The existence of the induced chiral magnetic current in a graphene subjected to magnetic field causes an interesting and unusual behavior of such circuits. We discuss an explicit example of a circuit involving the current generation in a “chiral battery”. The special properties of this circuit may be utilized for creating “chiral electronic” devices.

Switching effects in superconductor/ferromagnet/superconductor graphene junctions

The Josephson effect in the superconductor/ferromagnet/superconductor （SFS） graphene Josephson junction is studied using the Dirac Bogoliubov-de Gennes （DBdG） formalism. It is shown that the SFS graphene junction drives 0–π transition with the increasing of p=h0L/vF？, which captures the effects of both the exchange field and the length of the junction; the spin-down current is dominant. The 0 state is stable for p 〈 pc （critical value pc ≈ 0.80） and the π state is stable for p 〉 pc, where the free energy minima are at φg=0 and φg=π, respectively. The coexistence of the 0 and π states appears in the vicinity of pc.

The inelastic electron tunneling spectroscopy of edge-modified graphene nanoribbon-based molecular devices

The inelastic electron tunneling spectroscopy（IETS） of four edge-modified finite-size grapheme nanoribbon（GNR）-based molecular devices has been studied by using the density functional theory and Green＇s function method. The effects of atomic structures and connection types on inelastic transport properties of the junctions have been studied. The IETS is sensitive to the electrode connection types and modification types. Comparing with the pure hydrogen edge passivation systems, we conclude that the IETS for the lower energy region increases obviously when using donor–acceptor functional groups as the edge modification types of the central scattering area. When using donor–acceptor as the electrode connection groups, the intensity of IETS increases several orders of magnitude than that of the pure ones. The effects of temperature on the inelastic electron tunneling spectroscopy also have been discussed. The IETS curves show significant fine structures at lower temperatures. With the increasing of temperature, peak broadening covers many fine structures of the IETS curves.The changes of IETS in the low-frequency region are caused by the introduction of the donor–acceptor groups and the population distribution of thermal particles. The effect of Fermi distribution on the tunneling current is persistent.

非平衡压缩实现高灵敏度、线性响应协同的离电压力传感器

Flexible pressure sensors with high sensitivity and linearity are highly desirable for robot sensing and human physiological signal detection.However,the current strategies for stabilizing axial microstructures(e.g.,micro-pyramids)are mainly susceptible to structural stiffening during compression,thereby limiting the realization of high sensitivity and linearity.Here,we report a bending-induced nonequilibrium compression process that effectively enhances the compressibility of microstructures,thereby crucially improving the efficiency of interfacial area growth of electric double layer(EDL).Based on this principle,we fabricate an iontronic flexible pressure sensor with vertical graphene(VG)array electrodes.Ultra-high sensitivity(185.09 kPa^(-1))and linearity(R^(2)=0.9999)are realized over a wide pressure range(0.49 Pa–66.67 k Pa).It also exhibits remarkable mechanical stability during compression and bending.The sensor is successfully employed in a robotic gripping task to recognize the targets of different materials and shapes based on a multilayer perception(MLP)neural network.It opens the door to realizing haptic sensing capabilities for robotic hands and prosthetic limbs.

SnSb@carbon nanocable anchored on graphene sheets for sodium ion batteries

The development of materials with unique nanostructures is an effective strategy for the improvement of sodium storage in sodium ion batteries to achieve stable cycling performance and good rate capability. In this work, SnSb- core/carbon-shell nanocables directly anchored on graphene sheets （GS） were synthesized by the hydrothermal technique and chemical vapor deposition. The simultaneous carbon coating and the encapsulation of SnSb alloy is effective for alleviating the volume-change problem in sodium ion batteries. After optimizing the electrolyte for SnSb in the sodium ion batteries, the optimized coaxial SnSb/carbon nanocable/GS （SnSb/CNT@GS） nanostructure demonstrated stable cycling capability and rate performance in 1 M NaClO4 with propylene carbonate （PC） ＋ 5% fluoroethylene carbonate （FEC）. The SnSb/CNT@GS electrode can retain a capacity of 360 mAh/g for up to 100 cycles, which is 71% of the theoretical capacity. This is higher than in the other three electrolytes tested （1 M NaClO4 in PC, 1 M NaC104 in PC/FEC （1：1 v/v） and 1 M NaPF6 ＋ PC）, and higher than that of the sample without the addition of graphene. The good electrochemical performance can be attributed to the efficient buffering provided by the outer carbon nanocable layer and the graphene inhibiting the agglomeration of SnSb particles, as well as its high conductivity.

N-doped graphene and TiO_2 supported manganese and cerium oxides on low-temperature selective catalytic reduction of NO_x with NH_3

A series of N-doped graphene(NG)and TiO_2 supported MnO_x–CeO_2 catalysts were prepared prepared by a hydrothermal method.The catalysts with different molar ratios of Mn/Ce(6:1,10:1,15:1)were investigated for the low-temperature selective catalytic reduction(SCR)of NO_x with NH_3.The synthesized catalysts were characterized by HRTEM,SEM,XRD,BET,XPS,and NH_3-TPD technologies.The characterization results indicated that manganese and cerium oxide particles dispersed on the surface of the TiO_2–NG support uniformly,and that manganese and cerium oxides existed in different valences on the surface of the TiO_2–NG support.At Mn element loading of 8 wt%,MnO_x–CeO_2(10:1)/TiO_2–1%NG displayed superior activity and improved SO_(2 )resistance.On the basis of the catalyst characterization,excellent catalytic performance and SO_2 tolerance at low temperature were attributed to the high content of manganese with high oxidation valence,extensive oxidation of NO into NO_2 by CeO_2 and strong NO adsorption capacity,and electron transfer of N-doped graphene.

Liquid-phase Exfoliated WS2-Graphene Composite Anodes for Potassium-ion Batteries

Tungsten disulfide(WS2) has been recognized as a promising anode material for rechargeable potassium-ion batteries(PIBs). However, its K-ion intercalation capacity is limited to ~60 mAh·g^(-1). Here, we report a WS2-graphene composite anode which is fabricated through simple filtration of liquid-phase exfoliated WS2 and graphene nanosheet delivers a significantly improved specific capacity of 137 mAh·g^(-1) at a current density of 10 mA·g^(-1). The composite anodes also exhibit remarkable rate capability and long-term cyclability over 500 cycles. These results highlight the WS2-graphene composite structure as a promising anode material for long lifespan rechargeable potassium-ion batteries.

First-principles study of lithium intercalated bilayer graphene

Litbium intercalated bilayer graphene has been investigated using first-principles density functional theory calculations. Re- sults show that there exist AB and AA stacking sequences for bilayer graphene in which the latter is more favorable for the Li storage and the former will evolve into the latter with the intercalation of Li ions. The relationship between the interlayer dis- tance of two graphene sheets and the intercalated capacity of Li ions is discussed, It is found that structural defect is identified to store Li ions more favorably than pristine bilayer graphene and an isolated C atom vacancy in bilayer graphene can capture three Li ions between two graphene sheets.

Sulfur–nitrogen co-doped graphene supported cobalt–nickel sulfide rGO@SN-CoNi_(2)S_(4) as highly efficient bifunctional catalysts for hydrogen/oxygen evolution reactions

Designing highly active and stable electrocata-lysts for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)is a challenge for energy con-version and storage technology.In this work,a S and N co-doped graphene supported cobalt–nickel sulfide composite catalyst(rGO@SN-CoNi_(2)S_(4))was synthesized simply via a one-step hydrothermal method.The as-synthesized CoNi_(2)S_(4)particles grew in a mosaic manner inside GO lamellae and were encapsulated with graphene.As a bifunctional catalyst,the r GO@SN-CoNi_(2)S_(4)exhibits excellent electrocatalytic performance under alkaline con-ditions,which only required the overpotential of 142.6 mV(vs.RHE)and 310 m V(vs.RHE)to deliver a current density of 10 mA·cm^(-2) for HER and OER,respectively.The good hydrophilicity of the r GO@SN,the pure phase of bimetallic structure,and the chemical coupling/interaction between the CoNi_(2)S_(4)and the rGO@SN are attributable to be the possible reasons responsible for the higher HER and OER catalytic activities.Additionally,the rGO@SN-CoNi_(2)S_(4)also shows a great potential for serving as an excellent cathode and anode electrolyzer during the water splitting process.