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Synthesis of Graphene Oxide Nanosheets via Modified Hummers’ Method and Its Physicochemical Properties
摘要： The efficient synthesis of exfoliated graphene oxide nanosheets (GO) via modified Hummers’ method was successfully carried out. The physicochemical properties of GO were determined by Fourier transform infrared spectroscopy (FTIR), UV-visible spectrophotometry (UV-vis), x-ray diffraction analysis (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). The graphite was fully oxidized by strong oxidizing agent caused the oxygen-containing functional groups such as C-O-C, C=O, and COOH were introduced into the graphite layers as analyzed by Raman and FTIR. XRD pattern of GO showed 2θ of 12.0o with interlayer spacing ~ 7.37A which describe non uniform crystal structure with the addition of oxygen containing functional groups. UV-vis spectrum of GO exhibit maximum absorption peak at ~ 234 nm corresponding to the aromatic C=C bond with π-π* transition. The morphology of GO was observed to have flake-like shape and less transparent layers by TEM. The properties of synthesized GO suggest high potential in producing the high quality of graphene which is can be applied as the electrocatalyst support for direct methanol fuel cell application.
关键词： Graphene oxide nanosheets,characterization,Hummers’ method,graphite,chemical oxidation
更新于2025-09-23 15:22:29
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XCT image reconstruction by a modified superiorized iteration and theoretical analysis
摘要： In this paper, we propose an improved iteration superiorization method for X-ray computed tomography image reconstruction. We simplify the classic superiorized iteration by removing two constraints imposed on the perturbation. A novel method is proposed to determine the perturbation amount and direction for the superiorized iteration simultaneously. Some theoretical properties (convergence for instance) of the superiorized iteration sequence with the proposed perturbation are analysed. We present a general proof for the convergence of ART-like iterations with summable perturbations. In addition, we prove the convergence of simultaneous iterations without the summable perturbation assumption. Experiments on simulated and real data not only verify the theoretical result but also show that the proposed algorithm is superior to the classic superiorized iteration and can reconstruct desirable images.
关键词： XCT image reconstruction,superiorization of iteration,proximity perturbation,algebraic method
更新于2025-09-23 15:22:29
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Cu(OH)2 Nanostructures for Dynamic Photodegradation of Methyl Orange under Visible Light
摘要： A new material of Cu(OH)2 nanostructures was prepared using cupric nitrate and sodium hydroxide as raw materials by the chemical precipitation method. The Cu(OH)2 nanostructures were characterized by scanning electron microscope, transmission electron microscopy, infrared spectrometer, and X-ray diffractometer. The results showed that the Cu(OH)2 nanostructures exhibited excellent uniform and dispersion at 40°C. A series of factors was investigated to effect the photocatalytic efficiency of methyl orange (MO), such as the concentration of Cu(OH)2 nanostructures, the reaction time of the Cu(OH)2 nanostructures, the initial concentration of MO, and so on. As a result, the Cu(OH)2 nanostructures exhibited excellent photocatalytic efficiency with the concentration of 20 mg L–1 Cu(OH)2 nanostructures, the initial concentration of MO was 15 mg L–1 and the stirring time was 70 min.
关键词： photocatalytic efficiency,chemical precipitation method,Cu(OH)2 nanostructures
更新于2025-09-23 15:22:29
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A Coefficient Inverse Problem with a Single Measurement of Phaseless Scattering Data
摘要： We present a reconstruction method for solving a 3D coefficient inverse problem with a single measurement of phaseless scattering data. These are multifrequency data generated by a single direction of the incident plane wave. Our method consists of two stages, each of which is challenging in its own right. The first stage is the problem of the reconstruction of the wave field itself on the measurement plane from the measured intensity. In this stage, we prove a uniqueness result and study a numerical method for this reconstruction. After obtaining the approximate scattered field on the measurement plane, in the second stage, we exploit our newly developed globally convergent numerical method to solve the coefficient inverse problem with the phased scattering data. Our two-stage method does not require any advanced information about the true solution of the phaseless coefficient inverse problem. Numerical examples are presented to demonstrate the performance of the method.
关键词： phaseless inverse scattering,reconstruction method,one measurement,uniqueness theorems,coefficient inverse problem
更新于2025-09-23 15:22:29
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[IEEE 2018 2nd IEEE Conference on Energy Internet and Energy System Integration (EI2) - Beijing, China (2018.10.20-2018.10.22)] 2018 2nd IEEE Conference on Energy Internet and Energy System Integration (EI2) - Design of PFC in Wireless Charging System for Electric Vehicle
摘要： A power factor correction (PFC) circuit is constructed, based on average period compensation method(APCM) in this paper. The cut-off frequency 2kHz and 10Hz are closed for current loop and voltage loop, and the phase margin of each loop is 80 degrees. By contrasting the THD of fundamental wave calculated to the 40th and the peak value of voltage ripple wave, PI values and transfer functions of both current loop and voltage loop are got. Then the input current and output voltage in PFC steady operation are simulated, and results are in accord with the small-signal model. In Simulink, the output capacitance is charged in advance and saturation controller is adopted, by which the overshoot of output voltage decreases by 6.3%, and the THD of input current is only 3.76%, which meet the demands for power-factor correction in wireless charging system for EV.
关键词： Average Period Compensation Method,Active PFC Circuit,Wireless Charging Technology
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Automatic Forest Extraction Method Based on Self-Organizing Map Algorithm Using Gf-2 Images
摘要： With more and more high-spatial-resolution images being applied to interpret objects and to extract information, machine learning methods have emerged as solutions for the large amount image data’s processing and analyzing. But how to improve the efficiency and accuracy of interpretation and extraction becomes a problem. For China Geological Survey’s national forest survey project, we proposed an automatic extraction method to extract forest area from high resolution images of GF-2 satellite based on self-organization map (SOM) which is an artificial neural network (ANN) method using unsupervised learning to produce a low-dimensional, discretized representation of the input space of the training samples. Also, the proposed method was applied to three different areas to verify its accuracy. Compared with those of human-computer interactive interpretation, the results of the proposed method had high classification accuracy for extracting forest information.
关键词： GF-2 satellite,self-organization map,extraction method,Forest,automatic
更新于2025-09-23 15:22:29
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Synthesis and Characterization of ZnO-ZrO <sub/>2</sub> Nanocomposites for Photocatalytic Degradation and Mineralization of Phenol
摘要： ZnO-ZrO2 nanocomposites using zinc (II) acetylacetonate and different ZnO contents (13, 25, 50, and 75% mol) were synthesized through sol-gel method. The synthesis process was strongly related to nanocomposite properties especially on their structural composition. The obtained ZnO-ZrO2 nanomaterials presented tetragonal crystalline structure for zirconia whereas hexagonal one was formed in ZnO. Raman spectroscopy and XRD patterns confirmed the formation of tetragonal zirconia whereas inhibition of monoclinic structure was observed. Addition of ZnO affected the pore size distribution of the composite, and the measured specific surface areas were from 10 m2/g (for pure ZnO) to 46 m2/g (pristine ZrO2). Eg values of ZrO2 were modified by ZnO addition, since calculated values using Kubelka-Munk's function varied from 4.73 to 3.76 eV. The morphology and size of the nanomaterials investigated by electron microscopy showed formation of nanorods for ZnO with sizes ranging from 50 nm to 300 nm while zirconia was formed by smaller particles (less than 50 nm). The main advantage of using the nanocomposite for photocatalytic degradation of phenol was the mineralization degree, since 75ZnO-ZrO2 nanocomposite surpassed mineralization reached by pure ZnO and also inhibited formation of undesirable intermediates.
关键词： sol-gel method,UV-A irradiation,phenol mineralization,photocatalytic degradation,ZnO-ZrO2 nanocomposites
更新于2025-09-23 15:22:29
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A Quantum Chemical Study of Germanium-Substituent Bonding in Complex Compounds of Germanium
摘要： Spatial and electronic structures of six-coordinated germanium compounds are calculated within МР2 and AIM methods using PC GAMESS-Firefly, MORPHY, and AIMALL software packages. Main topological characteristics of germanium-substituent bonds are determined in these molecules.
关键词： AIM method,quantum chemistry
更新于2025-09-23 15:22:29
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Effects of Heat-Treatment on Photoluminescence Spectra and Photocatalytic Properties of Solution-Combusted ZnO Nanopowders
摘要： ZnO nanopowders were prepared by a solution combustion method (SCM). The SCM ZnO nanopowders were heat-treated at 200, 400, 500, or 700 °C for 30 min in air and the photoluminescence (PL) of the nanopowders was evaluated. Two strong PL emission peaks are generally recognized as the unique PL signature of ZnO, one is from the band-edge emission and the other corresponds to green emission. The green emission is derived from crystalline defects, and is a critical obstacle for the electrooptical applications of ZnO. Surprisingly, the PL spectra of the SCM ZnO powders showed a single sharp peak near 390 nm. Furthermore, the intensity of this blue emission doubled when the synthesized ZnO powder was heat-treated at 400 °C. The green emission appeared for the sample treated at 500 °C, and was the highest for that treated at 700 °C. To confirm the photocatalytic activity of the ZnO powder heat-treated at 400 °C, the removal of Ag ions from a used photofilm developer was evaluated, with complete removal within 10 min. The removal of the Ag ions by the ZnO powder heat-treated at 400 °C was more than two orders of magnitude faster than that achieved with the SCM ZnO powder. The relation between PL and photocatalytic activity was explained in terms of recombination of the photogenerated electrons. These results might be very useful for highly efficient photocatalyst applications.
关键词： Heat-Treatment,ZnO Nanopowder,PL Spectra,Solution Combustion Method
更新于2025-09-23 15:22:29
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Enhanced UV emission of TiO <sub/>2</sub> –ZnO nanocomposite films synthesized by simplified sol–gel dip-coating method
摘要： TiO2–ZnO composite film was regarded as a promising candidate for UV emitter devices. For exploring a lower cost and convenient preparation method for highly efficient UV-emission TiO2–ZnO composite film, we used a simplified method in which mixing ZnO sol and TiO2 sol directly to prepare TiO2–ZnO nanocomposite films with a varied atomic ratio of Zn/(Ti + Zn) (TiO2, Z20, Z40, Z60, Z80, ZnO) on glass substrates and discussed its optical properties for the first time in this study. The photoluminescence (PL) spectra indicated that the UV emission of the composite films was greatly enhanced compared with that showed by single-phase TiO2 or ZnO film. In particular, the UV emission intensity of Z60 composite film was enhanced by a factor of 10 compared to that of single-phase ZnO or TiO2. The enhanced PL intensity of the composite films could be attributed to fluorescence resonance energy transfer (FRET).
关键词： TiO2–ZnO Nanocomposite Films,Optical Property,Simplified Sol–Gel Method,FRET
更新于2025-09-23 15:22:29