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Relationship between space charge and nonlinear characteristics of ZnO varistor

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Science China(Technological Sciences) 2011年第7期54卷 1771-1778页

作者： WANG qian TU YouPing ding LiJian JU ZeLi Beijing Key Laboratory of High Voltage & EMC North China Electric Power University Beijing 102206 China

In order to reveal the conduction mechanism of ZnO varistor, the pulsed electroacoustic (PEA) measurement is employed to investigate the space charge distribution characteristics of ZnO varistors under different current densities in this paper. Experimental results show that the relationship between the space charge and the current density is consistent with the voltage-current characteristics, and can reflect the nonlinear characteristics of ZnO varistor. The space charge increases linearly with the increase of the electric field strength and the current density in the small current region, this reflects the decrease of the surface states of the grain boundary and changes of the Schottky barrier. There exists a transition region between the small current and middle current regions, where the current is composed of the current by the emission of thermally activated electrons and the tunneling current. In the middle current region, the space charge will decrease as the current increases, and will disappear with the depletion layer decreasing to zero.

关键词： ZnO varistors pulsed electroacoustic (PEA) measurement space charge double Schottky barrier

Corrosion mechanism of Zn-Al-Mg-coated steel in simulated polluted marine atmosphere

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Journal of Iron and Steel Research International 2024年第9期31卷 2294-2307页

作者： Pei-dong Ning Li-yuan Xiao Jin Wang qian-qian Liu Kui Xiao Research Institute JISCO Hongxing Iron and Steel Co.Ltd.Jiayuguan735100GansuChina Institute for Advanced Materials and Technology University of Science and Technology BeijingBeijing100083China

The corrosion behaviour of zinc–aluminium–magnesium-coated steel in a simulated polluted marine atmospheric environment was ***,an indoor ageing acceleration test was carefully designed by simulating a polluted marine *** objective was to in-depth investigate the corrosion mechanism of Zn–Al–Mg-coated steel exposed to a simulated polluted marine *** experiments were carried out by scanning electron microscopy for micro-morphological characterization,X-ray diffraction,electrochemical impedance spectroscopy and electrodynamic polarization curves for the aged *** analysis of the results obtained after an indoor accelerated ageing test shows that Zn–Al–Mg coatings generate insoluble Zn_(5)Cl_(2)(OH)_(8)·H_(2)O and Zn_(4)SO_(4)(OH)_(6)during the corrosion process,which hinders the diffusion of corrosive substances into the substrate,and the insoluble substances are structurally dense and thus inhibit further ***,this effectively inhibits the occurrence of further corrosion,and thus,Zn–Al–Mg coating can significantly extend the service life of Zn–Al–Mg-coated steel.

关键词： Zn-Al-Mg-coated steel Electrochemical impedance spectroscopy Polarization curve Atmospheric corrosion Marine atmosphere

Effects of Corridor Networks on Plant Species Composition and Diversity in an Intensive Agriculture Landscape

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维普期刊数据库

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Chinese Geographical Science 2014年第1期24卷 93-103页

作者： TANG qian LIANG Guofu LU Xunling ding Shengyan Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions Ministry of Education College of Environment and Planning Henan University College of Life Science Henan University

The development of modern agriculture has resulted in much homogenization of the landscape consisting of large patches of farmland,so small remnant non-crop habitats especially linear corridors play an important role in the conservation of species and the maintenance of ecosystem ***,little attention has been paid to the effects of corridors structural characteristics on the plant species restricted to such *** this study,we selected three types of corridors including ditch,hedgerow and road,and analyzed their structural *** plant species presented in these corridors were investigated,and the species diversity,abundance and frequency were ***,spatial arrangements of corridors were classified into different types to discuss whether there were significant effects of corridor network on plant *** results show that three types of corridors have different effects on plant species composition and *** one-one combined corridor networks and total network associated by three corridors have more complex structural features than each single type of ***,there is no strong correlation between the corridor networks with their plant *** suggest that carrying out a pointed vegetation survey at corridor intersections to further test the relationships between structural features of corridor and plants is necessary.

关键词： habitat corridor spatial arrangement plant diversity connectivity intensive agriculture landscape

Axial control for nonlinear resonances of electrostatically actuated nanobeam with graphene sensor

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Applied Mathematics and Mechanics(English Edition) 2017年第4期38卷 527-542页

作者： Canchang LIU qian ding Qingmei GONG Chicheng MA Shuchang YUE School of Transportation and Vehicle Engineering Shandong University of Technology School of Mechanical Engineering Tianjin University

The nonlinear resonance response of an electrostatically actuated nanobeam is studied over the near-half natural frequency with an axial capacitor controller. A graphene sensor deformed by the vibrations of the nanobeam is used to produce the voltage signal. The voltage of the vibration graphene sensor is used as a control signal input to a closed- loop circuit to mitigate the nonlinear vibration of the nanobeam. An axial control force produced by the axial capacitor controller can transform the frequency-amplitude curves from nonlinear to linear. The necessary and sufficient conditions for guaranteeing the system stability and a saddle-node bifurcation are studied. The numerical simulations are conducted for uniform nanobeams. The nonlinear terms of the vibration system can be transformed into linear ones by applying the critical control voltage to the system. The nonlinear vibration phenomena can be avoided, and the vibration amplitude is mitigated evidently with the axial capacitor controller.

关键词： graphene sensor nanobeam nonlinear vibration electrostatic force

Lock-up function of fluorine enhances photovoltaic performance of polythiophene

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Science China Chemistry 2017年第2期60卷 251-256页

作者： Na Jiao Dan He Liu qian Zhongli Lei Liming ding Key Laboratory of Applied Surface and Colloid Chemistry Ministry of EducationShaanxi Normal UniversityXi'an 710062China National Center for Nanoscience and Technology Beijing 100190China

Three model polythiophenes,PTCBT,PTCFBT and PFTCBT,have been synthesized to investigate the effect of fluorination on photovoltaic performance of *** with PTCBT,PFTCBT with F atom on TC unit shows a narrower optical bandgap(1.79 eV),higher crystallinity,and ideal morphology in the active layer,leading to a higher short-circuit current density(J_(SC))of 11.84 mA/cm^2 and a power conversion efficiency(PCE)of 5.93%.The lock-up function of fluorine enhances polythiophene backbone planarity and molecular packing.

关键词： polythiophene fluorination planarity photovoltaic performance

A Hardware Trojan Detection Method Based on the Electromagnetic Leakage

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China Communications 2019年第12期16卷 100-110页

作者： Lei Zhang Youheng dong Jianxin Wang Chaoen Xiao ding ding Beijing Electronic Science and Technology Institute

Hardware Trojan(HT) refers to a special module intentionally implanted into a chip or an electronic system. The module can be exploited by the attacker to achieve destructive functions. Unfortunately the HT is difficult to detecte due to its minimal resource occupation. In order to achieve an accurate detection with high efficiency, a HT detection method based on the electromagnetic leakage of the chip is proposed in this paper. At first, the dimensionality reduction and the feature extraction of the electromagnetic leakage signals in each group(template chip, Trojan-free chip and target chip) were realized by principal component analysis(PCA). Then, the Mahalanobis distances between the template group and the other groups were calculated. Finally, the differences between the Mahalanobis distances and the threshold were compared to determine whether the HT had been implanted into the target chip. In addition, the concept of the HT Detection Quality(HTDQ) was proposed to analyze and compare the performance of different detection methods. Our experiment results indicate that the accuracy of this detection method is 91.93%, and the time consumption is 0.042s in average, which shows a high HTDQ compared with three other methods.

关键词： hardware trojan detection side channel analysis electromagnetic leakage principal component analysis Mahalanobis distance detection quality

EFFECT OF FRACTIONAL ORDER PARAMETER ON THERMOELASTIC BEHAVIORS OF ELASTIC MEDIUM WITH VARIABLE PROPERTIES

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Acta Mechanica Solida Sinica 2015年第6期28卷 682-692页

作者： Yingze Wang dong Liu qian Wang Jianzhong Zhou Department of Energy and Power Engineering Jiangsu University Department of Mechanical Engineering Jiangsu University

This paper is concerned with the thermoelastic behaviors of an elastic medium with variable thermal material properties. The problem is in the context of fractional order heat conduction. The governing equations with variable thermal properties were established by means of the fractional order calculus. The problem of a half-space formed of an elastic medium with variable thermal material properties was solved, and asymptotic solutions induced by a sudden temperature rise on the boundary were obtained by applying an asymptotic approach. The propagations of thermoelastic wave and thermal wave, as well as the distributions of displacement, temperature and stresses were obtained and plotted. Variations in the distributions with different values of fractional order parameter were discussed. The results were compared with those obtained from the case of constant material properties to evaluate the effects of variable material properties on thermoelastic behaviors.

关键词： generalized thermoelasticity fractional order heat conduction variable thermal material properties asymptotic solution thermal shock

Simulation of wind-driven circulation and temperature in the near-shore region of southern Lake Michigan by using a channelized model

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Journal of Hydrodynamics 2013年第1期25卷 97-111页

作者： LIU Lubo FU Xu-dong WANG Guang-qian Department of Civil and Geomatics Engineering Lyles College of Engineering California State University State Key Laboratory of Hydroscience and Engineering Tsinghua University

To enhance the efficiency of a pathogen forecasting model in the beach areas of southern Lake Michigan and to reduce the computation time, the near-shore current is approximated as a channelized flow parallel to the shorelines in clockwise or anti-clock- wise direction within the accuracy tolerance range. A channelized model with a curvilinear boundary can significantly reduce the computation effort, and at the same time achieve a good agreement between the predicted and measured water surface elevations, currents, and water temperatures. The sensitivity analysis results show that the suitable channel width for the near-shore region of southern Lake Michigan should be no less than 10 kin. The modeling results of the water temperature are much less sensitive to the channel width than those of the current velocity and the water surface elevation. The modeling results also show a close correlation between the speeds of the wind and the near-shore current. The current may fully respond the wind stress with a time lag of several hours. The correlation may provide an approximate estimation of the lake circulation under some wind conditions for a practical fore- casting purpose. More complex wind-current relationships need to be described with a more sophisticated hydrodynamic model. This verified model can be used for the pathogen forecasting in the near-shore regions of southern Lake Michigan in the future.

关键词： near-shore channelized wind hydrodynamic model

Effects of the precipitation of stabilizers on the mechanism of grain fracturing in a zirconia metering nozzle

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International Journal of Minerals,Metallurgy and Materials 2016年第9期23卷 1041-1047页

作者： Liang Zhao Qun-hu Xue dong-hai ding College of Materials and Mineral Resources Xi'an University of Architecture and TechnologyXi'an 710055China Shaanxi Techno-institute of Recycling Economy Xi'an 710055China

The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied using an X-ray fluorescence analyzer, scanning electron microscope, and electron probe. Results revealed that the composition, structure, and mineral phase of the original layer, transition layer, and affected layer of the metering nozzle differed because of stabilizer precipitation and steel slag permeation. The stabilizer MgO formed low-melting phases with steel slag and impure SiO2 on the boundaries（pores） of zirconia grains; consequently, grain fracturing occurred and accelerated damage to the metering nozzle was observed.

关键词： continuous casting metering nozzle partially stabilized zirconia grains fracture mechanisms electron probe microanalysis