Table of Content

28 February 2020, Volume 26 Issue 1

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Invited Review

Electromagnetic effect of pulsed electromagnetic field in molten metals and its applications

Yanyi XU, Qijie ZHAI

2020, 26(1):  1-20.  doi:10.12066/j.issn.1007-2861.2206

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Owing to the development of human society, higher quality metal materials are demanded. Cleanliness and homogenisation are typical goals of high-quality metal products. New opportunities for advances in material preparation technology are afforded by the development of physical science and technology. Recently, electric current pulses and pulsed magnetic fields have attracted significant attention in metal preparation owing to the high instantaneous energy and low circuit load afforded. Herein, the basic theory of electromagnetic effects in molten metals is first introduced. Subsequently, research status regarding the distributions of magnetic field, current, electromagnetic force, and corresponding flow fields in molten metals under applied electric current pulses and pulsed magnetic fields are presented and reviewed. Finally, studies and industrial applications of pulsed electromagnetic fields in metal cleaning and homogenisation are introduced.

Research Articles

(k,n) visual cryptography scheme based on XOR decryption

Songge GUO, Donghui LYU, Yujing DAI, Yanli REN

2020, 26(1):  21-32.  doi:10.12066/j.issn.1007-2861.1997

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Traditional visual cryptography schemes recover secret images by stacking shares directly. Since the stacking operation can be denoted by logical OR operation and since white pixels can't be fully recovered with these schemes, the decryption effect is not satisfactory. This paper proposes a (k,n) random grid-based visual cryptography scheme based on exclusive OR (XOR) decryption by using reflexivity of XOR for encryption and by applying the same color representation method as digital images. The secret images can be recovered in two situations: when computational devices are not available, the secret images can be recovered by stacking shares directly; when computational devices are available, the secret images can be recovered by XOR operation. With better visual quality, the secret images recovered this way can be lossless since all shares are collected. Compared with existing visual cryptography schemes, better visual quality is obtained with this new scheme.

Research on compression and denoising of speech signal based on the Takenaka-Malmquist system

Ya LEI, Yong FANG, Liming ZHANG

2020, 26(1):  33-46.  doi:10.12066/j.issn.1007-2861.1996

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The sparse representation of speech signal is one of the important research directions in speech compression, denoising and other speech processing. On the basis of matching pursuit (MP), orthogonal matching pursuit (OMP) and other greedy algorithms, this paper proposes a greedy weight algorithm based on Takenaka-Malmquist system (TMGW) for the compression of speech signal. This algorithm has the advantage of requiring only fewer decomposition numbers when reconstructing the speech signal, and it does well for achieving the goal of speech compression. Besides, in view of the fact that energy distribution between the signal and noise at time-frequency surface after sparse decomposition is different, this algorithm can realize the purpose of denoising. The experiment results show that the TMGW algorithm is more effective for the sparse representation of speech signal than the matching pursuit algorithm based on the adaptive Gabor sub-dictionary (GMP).

Energy efficiency of OOK transmitters with distinct battery utilization factor models

Tingting SHEN, Tao WANG, Yanzan SUN, Yating WU

2020, 26(1):  47-57.  doi:10.12066/j.issn.1007-2861.2019

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The average battery energy consumption per bit is now used as performance metric for research on energy constraint in wireless sensor networks (WSNs). This paper proposes an on-off keying (OOK) transmitter with an instaneous discharge current (IDC) based battery utilization factor (BUF) model or an average discharge current (MDC) based BUF model, and derives the analytical expression of the battery energy consumption per bit for the two models under Rayleigh channel with specified symbol error rate (SER). On this basis,the impact of the battery parameter and distance on the energy consumption per bit is analyzed through a theoretical approach. Simulation results indicate that the energy consumption per bit for both models increases as battery parameter and distance increase and that theIDCbased BUF model corresponds to larger battery energy consumption per bit. When the battery parameter and distance are large, the energy consumption per bit of the two models is significantly higher than that of the ideal battery. When $\gamma $=0.015 and $d$=90 m, the energy consumption per bit for theIDCbased BUF model is nearly 60% higher than that of ideal battery, while the energy consumption per bit forMDCbased BUF model is about 25% higher.

Analysis and modeling of piezoelectric laminated smart structures with both geometric and electroelastic material nonlinearities

Shunqi ZHANG, Shuyang ZHANG, Min CHEN, Guozhong ZHAO

2020, 26(1):  58-68.  doi:10.12066/j.issn.1007-2861.2014

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Piezoelectric smart structures under strong driving voltages will result in large displacements and rotations, in which electroelastic material and geometric nonlinearities affect simultaneously the structural response. In order to provide a precise model for design and application of piezoelectric smart structures, geometrically nonlinear finite element (FE) models with strong driving voltages are developed based on the first-order shear deformation hypothesis. The proposed models consider both geometric and material nonlinearities, in which the geometrically nonlinear effects include von Kármán type nonlinear, moderate rotation nonlinear and large rotation nonlinear. The present models are validated effectively and accurately through comparison with the experimental data from the literature. Finally, simulations and validations have been conducted through a plate structure and a cantilevered semicircular cylindrical piezoelectric shell structure in terms of the proposed different models to verify the necessity and precision.

Three-waveguide couplers designed by shortcut to adiabaticity

Zhiyong HAN, Jielong SHI, Zixuan LAN, Xi CHEN

2020, 26(1):  69-75.  doi:10.12066/j.issn.1007-2861.2192

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A shortcut-to-adiabaticity protocol is proposed to design short light directional couplers by combining adiabatic elimination and counter-diabatic driving for three-level systems. For more practical implementations, we consider unitary transformation to design the waveguide width and adjacent waveguide pitch. In our example, a three-waveguide coupler is simulated by beam propagation method. Compared with adiabatic couplers, the designed coupler is shorter by four times. This approach is applicable to quantum information processing and integrated optics.

Compression properties of 3D dual-pyramid lattice materials

Li DING, Xiaoying MAN, Weihua XIE, Yumin ZHANG, Hailin CAO, Xiaolin LIANG

2020, 26(1):  76-84.  doi:10.12066/j.issn.1007-2861.1983

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The compression properties of the dual-pyramid lattice materials consisting of resin hollow tubes were studied and compared with those of the homogeneous materials. Specimens of lattice materials and homogeneous materials were fabricated using multi nozzle plastic additive manufacturing technology. The compression properties of homogeneous materials and lattice materials of two cellular sizes were tested. The compression stress-strain curves of different strain rates were obtained. The effects of geometry size of unit cell and strain rate were researched. The equations for predicting the stress-strain relations before material failures were obtained by fitting experimental data. The stress prediction results agree with the experimental results. The research results show that the cellular size significantly affects the compressive properties of lattice materials. The yield strain changed little under different strain rates, and the yield strength difference is relatively large. The yield strain of the presented lattice materials is greater than that of the homogeneous resin materials, and the yield strength is not greater than that of the homogeneous resin materials.

Effect of Fe content on the crystal structure and mechanical properties of ordered Ni₄Mo alloy

Teng WANG, Yexin CHEN, Yaxi XIE

2020, 26(1):  85-94.  doi:10.12066/j.issn.1007-2861.2022

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The effect of iron content on the crystal structure and mechanical properties of ordered Ni₄Mo alloy has been studied in this paper. The results show that the crystal structure of the alloys is still single-phase with D1$_{\rm a}$ structure when the content of iron is less than 10% in the ordered Ni₄Mo alloy. However, the crystal structure of the ordered Ni$_{70}$Mo$_{20}$Fe$_{10 }$ alloy is single phase with the face-centered cubic structure when the content of iron is 10% in the alloy. When the content of iron is increased continuously, there is a second phase with close-packed hexagonal structure precipitated in alloy. The elongation of the ordered Ni$_{70}$Mo$_{20}$Fe$_{10 }$ alloys reaches 30.9%, which is 12 times of the elongation of the ordered Ni₄Mo alloys when tested in vacuum. Additionally, the hydrogen embrittlement susceptibility of the ordered Ni₄Mo alloy in gaseous hydrogen is also effectively reduced by iron alloying.

Investigation on the thermoelectric properties of beta -Zn₄Sb₃ graphene composites

Fengcai LIU, Pengfei GAO, Qingfei MENG, Juan QIN, Weimin SHI, Linjun WANG

2020, 26(1):  95-101.  doi:10.12066/j.issn.1007-2861.2011

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beta-Zn₄Sb₃/graphene composite material was prepared by mixing graphene powder and beta -Zn₄Sb₃ powder through hot pressing, and its structure and thermoelectric properties were checked. The results of X-ray diffraction show that the main component of the composite samples is still beta -Zn₄Sb₃ phase,and that the average grain size decreases slightly with the increase of graphene concentration, indicating that there is no significant effect on the phase formation of the composite sample when the graphene concentration is within 5.0%. In addition, the Seebeck coefficient of the composites containing graphene varies only slightly, but the electrical conductivity decreases and the thermal conductivity increases, which contributes to the lowering of the ZT value. The main reason might be the reduction of hole concentration due to the electron compensation effect accompanied by the incorporation of graphene, thereby reducing the sample carrier concentration, and the changes to the Zn atom disorder of beta -Zn₄Sb₃ as well.

Optimization parameter of the graphene dispersion and the wettability of graphene/ZrO$_2$ ceramic composites

Hongrong ZOU, Lei SHI, Chenghui LIN, Yaping ZHANG, Liqi LIU

2020, 26(1):  102-112.  doi:10.12066/j.issn.1007-2861.2021

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The wettability of ZrO₂ ceramic was improved in the graphene/ZrO₂ ceramic composites fabricated by impregnating graphene dispersion into ZrO₂ ceramic sintered by micro wave. Firstly, the graphene dispersion was fabricated by ball milling, and the size of graphene with 200.3 nm was obtained after optimizing the process parameter of the ratio of ball, speed, time. Then, the structure of graphene was analyzed through X-ray diffraction (XRD), Raman spectrometer and transmission electron microscope (TEM), and the wettability of ceramic was also investigated. The results showed that the graphene dispersion remained steady for a long time with keeping a few layers. When adding the graphene to the ZrO₂ ceramic, the wettability of ZrO₂ ceramic was obviously improved because of its lower contact angle and higher surface energy.

Occurrence, sources and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from Xin'anjiang River-reservoir system

Ye LIU, Yujie WANG, Fushun WANG, Xia LIANG, Xueping CHEN, Ming YANG, Jing MA

2020, 26(1):  113-122.  doi:10.12066/j.issn.1007-2861.2017

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The gas chromatography coupled with a mass selective detector was used to separate and quantify the 16 polycyclic aromatic hydrocarbons (PAHs) in surface sediments from Xin'anjiang River-reservoir system in southeast China. Sixteen PAHs were detected in all sediment samples and the total concentrations of 16 PAHs ranged from 260 to 1 652 ng/g dw (dry weight) with an average of 973 ng/g dw. The high molecular weight PAHs were the dominant compounds. The highest concentration was found at Lanjiang River (1 530 ng/g dw), while the lowest was found at the central area of Xin'anjiang reservoir (600 ng/g dw). The diagnostic parameters showed that the wood and coal combustion might be the main source of PAHs. Based on the classification of existing research, the sediments from upstream of Xin'anjiang River, central area of Xin'anjiang reservoir and Fuchunjiang River were slightly polluted, but the sediments from the backwater region of Xin'anjiang reservoir and Lanjiang River were severely contaminated. As the result of the ecological risk assessment shows, there will be occasional adverse effect, but no frequent adverse effect.

One-step hydrothermal synthesis of Ni₃S₂ nano hollow sphere for high-performance supercapacitors

Xiaomeng JIANG, Yiyang HU, Chenghui LIN, Lingli CHENG, Zongxin PI, Zheng JIAO

2020, 26(1):  123-131.  doi:10.12066/j.issn.1007-2861.2008

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Ni₃S₂ nano hollow sphere was successfully synthesized with one-step hydrothermal method, in which nickel acetate and L-cysteine were used as nickel source and sulfur source, respectively. The morphology, composition, and phase structure of the as-prepared material were characterized by X-ray diffraction (XRD) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that the as-prepared Ni₃S₂ was uniform hollow sphere with an average diameter of about 300 nm, and it has good dispersion. The Ni₃S₂ was pressed on the foam nickel to be a work electrode, and its performance of supercapacitor was investigated. The results suggested that the as-prepared Ni₃S₂ nano hollow sphere has excellent rate capability and cycle performance. This is due to its good stability and specific hollow spherical structure, which not only provides abundant active sites for electrode reaction, but also effectively shortens the transmission path of electrons and ions.

Preparation and electrochemical properties of MnO₂@ZnO/C composite

Zhigang LUO, Qi LI, Dayong CHEN, Shoushuang HUANG, Zhangjun HU, Zhiwen CHEN

2020, 26(1):  132-142.  doi:10.12066/j.issn.1007-2861.2012

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Metal-organic frameworks (MOFs) compounds are compounds formed by bonding metal centers and organic ligands through coordination bonds. As a new type of porous material, it has drawn much attention of researchers in various fields due to its large specific surface area, high porosity and variety of species. In this study, MnO₂@ZnO/C hybrids are rationally synthesized by using MnO₂@ZIF-8 core-shell nanowires as templates. Owing to its structural and compositional characteristics, namely, the synergistic effects between components and the conductive carbon coating, the resultant MnO₂@ZnO/C hybrids exhibit good electrochemical performance as an anode material in Li-ion batteries with a first discharge specific capacity of 1 873 mA$\cdot$h$\cdot$g^-1 and a specific capacity of 658 mA$\cdot$h$\cdot $g^-1 at a current density of 100 mA/g for 100 cycles.

Characterization and preparation of nano TiO₂/P(MMA/BMA) composite materials by bicontinuous microemulsion polymerization

Shaojin JIA, Yiyi BAO, Jiwei LI, Junyu CHEN, Wei WU, Shaohua YANG

2020, 26(1):  143-152.  doi:10.12066/j.issn.1007-2861.1998

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This paper is a study on oleic acid-modified TiO₂ nanoparticles and the incorporation of modified TiO₂ nanoparticles into polyacrylate. The oleic acid is used to modify the TiO₂ nanoparticles. From the Fourier transform-infrared spectroscopy (FT-IR) spectrum and the dispersity test, it can be seen that TiO₂ nanoparticles enhance the hydrophobic after modification. The TiO₂/poly (methyl methacrylate/butyl methacrylate) (P(MMA/BMA)) hybrid emulsion is prepared by bicontinuous microemulsion polymerization. In the FT-IR spectrum, the TiO₂ characteristic peak appears. From the scanning electron microscopy (SEM) images and energy dispersive spectrometer (EDS) analyses spectrum, it is learned that the TiO₂ nanoparticles are homogeneously dispersed in polyacrylate. The effect of addition amount of TiO₂ nanoparticles on the thermal and the ultraviolet-shielding (UV-shielding) properties is discussed. With the increase of TiO₂ content (maximum 5%), the TiO₂/P (MMA/BMA) nanocomposites are thermally stable. Besides, it can block the UV light below 400 nm.

Fabrication and electrochemical properties of nitrogen doped MOF-derived carbon electrodes

Xiang LIU, Ling CAO, Weiwei YAO, Zhen LI, Minghong WU

2020, 26(1):  153-162.  doi:10.12066/j.issn.1007-2861.2020

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The N-GQDs@cZIF-8 supercapacitor has been fabricated following a two-step process through combining N-doped graphene quantum dots (N-GQDs) with metal-organic framework-derived carbon material (cZIF-8). The N-GQDs@cZIF-8 electrode has a high specific capacitance of 246.6 F · g^-1 at a current density of 0.5 A · g^-1 in 1 mol/L H₂SO₄ electrolyte and has excellent cycle stability with 83.7% capacity retention over 8 000 cycles. At the same time, the N-GQDs@cZIF-8 supercapacitor achieves an excellent energy density of about 8.2 W · h · kg^-1 at a power density of 104.5 W · kg^-1. The outstanding electrochemical performance of the device owes much to its 3D structure with high specific surface area and high nitrogen doping level (10.13%) with high pseudo capacitive activity, which makes this electrode have potential application in the field of supercapacitors and lithium-ion batteries.