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A LS-SVM （Least Squares Support Vector Machines） Approach for Predicting Critical Flashover Voltage of Polluted Insulators

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Journal of Energy and Power Engineering 2013年第2期7卷 355-360页

作者： Abdelhalim Mahdjoubi Boubakeur Zegnini Mohammed Belkheiri studies and development of semiconductors and dielectrics materials laboratory LeDMaScD Amar Telidji University ofLaghouat Laghouat 03000 Algeria Telecommunications Signals and Systems Laboratory LTSS Amar Telidji University of Laghouat Laghouat 03000 Algeria

LS-SVM （least squares support vector machines） are a class of kemel machines emphasizing on primal-dual aspects in a constrained optimization framework. LS-SVMs aim at extending methodologies typical of classical support vector machines for problems beyond classification and regression. This paper describes a methodology that was developed for the prediction of the critical flashover voltage of polluted insulators by using a LS-SVM. The methodology uses as input variables characteristics of the insulator such as diameter, height, creepage distance, form factor and equivalent salt deposit density. The estimation offlashover performance of polluted insulators is based on field experience and laboratory tests are invaluable as they significantly reduce the time and labour involved in insulators design and selection. The majority of the variables to be predicted are dependent upon several independent variables. The results from this work are useful to predict the contamination severity, critical flashover voltage as a function of contamination severity, arc length, and especially to predict the flashover voltage. The validity of the approach was examined by testing several insulators with different geometries. Moreover, the performance of the proposed approach with other intelligence method based on ANN （artificial neural networks） is compared. It can be concluded that the LS-SVM approach has better generalization ability that assist the measurement and monitoring of contamination severity, flashover voltage and leakage current.

关键词： LS-SVM flashover modeling polluted insulator equivalent salt deposit density.

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Photodetectors based on junctions of two-dimensional transition metal dichalcogenides

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Chinese Physics B 2017年第3期26卷 174-188页

作者：魏侠闫法光申超吕全山王开友 State Key laboratory of Superlattices and Microstructures Institute of Semiconductors Chinese Academy of Sciences College of materials Science and Opto-Electronic Technology University of Chinese Academy of Science

Transition metal dichalcogenides （TMDCs） have gained considerable attention because of their novel properties and great potential applications. The flakes of TMDCs not only have great light absorption from visible to near infrared, but also can be stacked together regardless of lattice mismatch like other two-dimensional （2D） materials. Along with the studies on intrinsic properties of TMDCs, the junctions based on TMDCs become more and more important in applications of photodetection. The junctions have shown many exciting possibilities to fully combine the advantages of TMDCs, other 2D materials, conventional and organic semiconductors together. Early studies have greatly enriched the application of TMDCs in photodetection. In this review, we investigate the efforts in photodetectors based on the junctions of TMDCs and analyze the properties of those photodetectors. Homojunctions based on TMDCs can be made by surface chemical doping, elemental doping and electrostatic gating. Heterojunction formed between TMDCs/2D materials, TMDCs/conventional semiconductors and TMDCs/organic semiconductor also deserve more attentions. We also compare the advantages and disadvantages of different junctions, and then give the prospects for the development of junctions based on TMDCs.

关键词： transition metal dichalcogenides homojunction heterojunction photodetector

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Graphene-driving strain engineering to enable strain-free epitaxy of AlN film for deep ultraviolet light-emitting diode

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Light(Science & Applications) 2022年第5期11卷 808-819页

作者： Hongliang Chang Zhetong Liu Shenyuan Yang Yaqi Gao Jingyuan Shan Bingyao Liu Jingyu Sun Zhaolong Chen Jianchang Yan Zhiqiang Liu Junxi Wang Peng Gao Jinmin Li Zhongfan Liu Tongbo Wei Research and development Center for Semiconductor Lighting Technology Institute of SemiconductorsChinese Academy of Sciences100083 BeijingChina Center of materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences100049 BeijingChina Center for Nanochemistry(CNC) Beijing Science and Engineering Center for NanocarbonsBeijing National Laboratory for Molecular SciencesCollege of Chemistry and Molecular EngineeringPeking University100871 BeijingChina Electron Microscopy laboratory and International Center for Quantum MaterialsSchool of PhysicsPeking University100871 BeijingChina Beijing graphene institute(BGI) 100095 BeijingChina Academy for Advanced Interdisciplinary studies Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced MaterialsPeking University100871 BeijingChina State Key laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of Sciences100083 BeijingChina

The energy-efficient deep ultraviolet(DUV)optoelectronic devices suffer from critical issues associated with the poor quality and large strain of nitride material system caused by the inherent mismatch of *** this work,we have prepared the strain-free AlN film with low dislocation density(DD)by graphene(Gr)-driving strain-pre-store engineering and a unique mechanism of strain-relaxation in quasi-van der Waals(QvdW)epitaxy is *** DD in AlN epilayer with Gr exhibits an anomalous sawtooth-like evolution during the whole epitaxy *** can help to enable the annihilation of the dislocations originated from the interface between AlN and Gr/sapphire by impelling a lateral two-dimensional growth ***,it can induce AlN epilayer to pre-store sufficient tensile strain during the early growth stage and thus compensate the compressive strain caused by ***,the low-strain state of the DUV light-emitting diode(DUV-LED)epitaxial structure is realized on the strain-free AlN template with ***,the DUV-LED with Gr demonstrate 2.1 times enhancement of light output power and a better stability of luminous wavelength compared to that on bare *** in-depth understanding of this work reveals diverse beneficial impacts of Gr on nitride growth and provides a novel strategy of relaxing the vital requirements of hetero-mismatch in conventional heteroepitaxy.

关键词： sapphire diode strain

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Characteristics of InGaN multiple quantum well blue-violet laser diodes

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Science China(Technological Sciences) 2006年第6期49卷 727-732页

作者： LI Deyao1, ZHANG Shuming1, WANG Jianfeng1, CHEN Jun1, CHEN Lianghui2, CHONG Ming2, ZHU Jianjun1, ZHAO Degang1, LIU Zongshun1, YANG Hui1 & LIANG Junwu1 1. State Key laboratory of Integrated Optoelectronics, Institute of semiconductors, Chinese Academy of Sciences, Beijing 100083, China 2. Nano-Optoelectronics laboratory, Institute of semiconductors, Chinese Academy of Sciences, Beijing 100083, China State Key laboratory of Integrated Optoelectronics Institute of Semiconductors Chinese Academy of Sciences Beijing China Nano-Optoelectronics laboratory Institute of Semiconductors Chinese Academy of Sciences Beijing China

studies on InGaN multiple quantum well blue-violet laser diodes have been reported. Laser structures with long-period multiple quantum wells were grown by metal-organic chemical vapor deposition. Triple-axis X-ray diffraction (TAXRD) measurements show that the multiple quantum wells were high quality. Ridge waveguide laser diodes were fabricated with cleaved facet mirrors. The laser diodes lase at room temperature under a pulsed current. A threshold current density of 3.3 kA/cm[2]; a characteristic temperature T 0 of 145 K were observed for the laser diode.

关键词： metalorganic chemical vapor deposition (MOCVD), GaN-based laser diodes, multiple quantum well, ridge waveguide, threshold current.

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A crosstalk-free dual-mode sweat sensing system for naked-eye sweat loss quantification via changes in structural reflectance

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Bio-Design and Manufacturing 2024年第4期7卷 428-438页

作者： Bowen Zhong Hao Xu Xiaokun Qin Lingchen Liu Hailong Wang Lili Wang State Key laboratory for Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China Center of materials Science and Optoelectronic Engineering University of Chinese Academy of SciencesBeijing 100049China

Sweat loss monitoring is important for understanding the body’s thermoregulation and hydration status,as well as for comprehensive sweat *** recent advances,developing a low-cost,scalable,and universal method for the fabrication of colorimetric microfluidics designed for sweat loss monitoring remains *** this study,we propose a novel laserengraved surface roughening strategy for various flexible *** process permits the construction of microchannels that show distinct structural reflectance changes before and after sweat *** leveraging these unique optical properties,we have developed a fully laser-engraved microfluidic device for the quantification of naked-eye sweat *** sweat loss sensor is capable of a volume resolution of 0.5µL and a total volume capacity of 11µL,and can be customized to meet different performance ***,we report the development of a crosstalk-free dual-mode sweat microfluidic system that integrates an Ag/AgCl chloride sensor and a matching wireless measurement flexible printed circuit *** integrated system enables the real-time monitoring of colorimetric sweat loss signals and potential ion concentration signals without ***,we demonstrate the potential practical use of this microfluidic sweat loss sensor and its integrated system for sports medicine via on-body studies.

关键词： Sweat loss sensor Microfluidic design Structural reflectance Dual-mode integration Crosstalk-free

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Nanoscale cathodoluminescence spectroscopy probing the nitride quantum wells in an electron microscope

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Chinese Physics B 2024年第3期33卷 144-149页

作者：刘哲彤刘秉尧梁冬冬李晓梅李晓敏陈莉朱瑞徐军魏同波白雪冬高鹏 Electron Microscopy laboratory School of PhysicsPeking UniversityBeijing 100871China Academy for Advanced Interdisciplinary studies Peking UniversityBeijing 100871China Research and development Center for Semiconductor Lighting Technology Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China Center of materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China Beijing National laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China International Center for Quantum materials Peking UniversityBeijing 100871China

To gain further understanding of the luminescence properties of multiquantum wells and the factors affecting them on a microscopic level,cathodoluminescence combined with scanning transmission electron microscopy and spectroscopy was used to measure the luminescence of In_(0.15)Ga_(0.85)N five-period multiquantum *** lattice-composition-energy relationship was established with the help of energy-dispersive x-ray spectroscopy,and the bandgaps of In_(0.15)Ga_(0.85)N and GaN in multiple quantum wells were extracted by electron energy loss spectroscopy to understand the features of cathodoluminescence *** luminescence differences between different periods of multiquantum wells and the effects of defects such as composition fluctuation and dislocations on the luminescence of multiple quantum wells were *** study establishing the direct relationship between the atomic structure of In_(x)Ga_(1-x)N multiquantum wells and photoelectric properties provides useful information for nitride applications.

关键词： nitride multiquantum wells defect cathodoluminescence scanning transmission electron microscopy

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Synthesis and optical properties of high-quality ultrathin homogeneous GaAs_(1-x)Sb_(x) nanowires

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Science China(Physics,Mechanics & Astronomy) 2024年第12期67卷 148-156页

作者： Ran Zhuo Lianjun Wen Jian Wang Xiuming Dou Lei Liu Xiyu Hou Dunyuan Liao Baoquan Sun Dong Pan Jianhua Zhao State Key laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing100083China College of materials Science and Opto-Electronic Technology University of Chinese Academy of SciencesBeijing100049China

Ternary GaAs_(1-x)Sb_(x) nanowires with designable bandgaps and lattice constants show important potential applications in band structure engineering as well as optical and optoelectronic ***,large diameters,low aspect ratios and even spontaneous core-shell structures are always found in GaAs_(1-x)Sb_(x) nanowires,which are hindering their optical and optoelectronic ***,we report the controlled synthesis of ultrathin GaAs_(1-x)Sb_(x) nanowires on Si(111)substrates by molecular-beam *** is found that ultrathin GaAs_(1-x)Sb_(x) nanowires with a diameter less than 40 nm and an aspect ratio exceeding 35 can be obtained by precisely tuning the Ga flux and the growth *** growth of the ultrathin GaAs_(1-x)Sb_(x) nanowires with a large-composition-range(0≤x≤0.4)are also achieved by directly tuning the antimony *** structural studies confirm that these ultrathin nanowires exhibit high crystal-quality,and no spontaneous core-shell nanostructures are observed along the axial and radial directions of the *** far as we known,it is the first time that homogeneous GaAs_(1-x)Sb_(x) nanowires are grown by molecular-beam *** measurements prove that the ultrathin GaAs_(1-x)Sb_(x) nanowires have a narrower full width at half maximum of the photoluminescence peak compared with those results reported in the literatures,and their emission wavelengths can be tuned from 850 nm(GaAs)to 1271 nm(GaAs_(0.6)Sb_(0.4)).In addition,the optical properties of the ultrathin GaAs_(1-x)Sb_(x) nanowires can be further improved by using the Al_(0.5)Ga_(0.5)As shell as a passivation *** work lays a foundation for the development of high-performance GaAs_(1-x)Sb_(x) nanowire-based optical and optoelectronic devices.

关键词： GaAs_(1−x)Sb_(x) nanowire molecular-beam epitaxy optical property

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Negative-to-Positive Tunnel Magnetoresistance in van der Waals Fe_(3)GeTe_(2)/Cr_(2)Ge_(2)Te_(6)/Fe_(3)GeTe_(2)Junctions

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Chinese Physics Letters 2023年第7期40卷 51-55页

作者：王子奥张晓敏朱文凯闫法光刘鹏飞袁喆王开友 State Key laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China Center of materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China Center for Advanced Quantum studies and Department of Physics Beijing Normal UniversityBeijing 100875China

The emergent van der Waals magnetic material is a promising component for spintronic devices with novel ***,we report a transition of negative-to-positive magnetoresistance in Fe_(3)GeTe_(2)/Cr_(2)Ge_(2)Te_(6)/Fe_(3)GeTe_(2)van der Waals all-magnetic tunnel junctions with increasing the applied bias voltage.A negative magnetoresistance is observed first in Fe_(3)GeTe_(2)/Cr_(2)Ge_(2)Te_(6)/Fe_(3)GeTe_(2)tunnel junctions,where the resistance with antiparallel aligned magnetization of two Fe_(3)GeTe_(2)electrodes is lower than that with parallel alignment,which is due to the opposite spin polarizations of two Fe_(3)GeTe_(2)*** the bias voltage increasing,the spin polarization of the biased Fe_(3)GeTe_(2)electrode is changed so that the spin orientations of two Fe_(3)GeTe_(2)electrodes are the *** experimental observations are supported by the calculated spin-dependent density of states for Fe_(3)GeTe_(2)electrodes under a finite *** significantly bias voltage-dependent spin transport properties in van der Waals magnetic tunnel junctions open a promising route for designing electrical controllable spintronic devices based on van der Waals magnets.

关键词： (3) alignment opposite

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Enhanced High-Temperature Energy Storage Performance of All-Organic Composite Dielectric via Constructing Fiber-Re in forced Structure

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Energy & Environmental materials 2024年第2期7卷 299-307页

作者： Mengjia Feng Yu Feng Changhai Zhang Tiandong Zhang Xu Tong Qiang Gao Qingguo Chen Qingguo Chi Key laboratory of Engineering dielectrics and Its Application Ministry of EducationHarbin University of Science and TechnologyHarbin 150080China School of Electrical and Electronic Engineering Harbin University of Science and TechnologyHarbin 150080China

Optimizing the high-temperature energy storage characteristics of energy storage dielectrics is of great significance for the development of pulsed power devices and power control *** a polymer with a higher glass transition temperature(T_(g))as the matrix is one of the effective ways to increase the upper limit of the polymer operating ***,current high-T_(g)polymers have limitations,and it is difficult to meet the demand for high-temperature energy storage dielectrics with only one *** example,polyetherimide has high-energy storage efficiency,but low breakdown strength at high *** has high corona resistance,but low high-temperature energy storage *** this work,combining the advantages of two polymer,a novel high-T_(g)polymer fiber-reinforced microstructure is *** is designed as extremely fine fibers distributed in the composite dielectric,which will facilitate the reduction of high-temperature conductivity loss for *** the same time,due to the high-temperature resistance and corona resistance of polyimide,the high-temperature breakdown strength of the composite dielectric is *** the polyimide content with the best high-temperature energy storage characteristics is determined,molecular semiconductors(ITIC)are blended into the polyimide fibers to further improve the high-temperature ***,excellent high-temperature energy storage properties are *** 0.25 vol%ITIC-polyimide/polyetherimide composite exhibits high-energy density and high discharge efficiency at 150℃(2.9 J cm^(-3),90%)and 180℃(2.16 J cm^(-3),90%).This work provides a scalable design idea for high-performance all-organic high-temperature energy storage dielectrics.

关键词： all-organic energy storage density high-temperature high-temperature breakdown strength

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Polarization sensitive photodetector based on quasi-1D ZrSe_(3)

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Journal of semiconductors 2022年第10期43卷 39-49页

作者： Xingang Wang Tao Xiong Kaiyao Xin Juehan Yang Yueyang Liu Zeping Zhao Jianguo Liu and Zhongming Wei The State Key laboratory on Integrated Optoelectronics Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China State Key laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China Sino-Danish Center for Education and Research Sino-Danish College University of Chinese Academy of SciencesBeijing 100049China Center of materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

The in-plane anisotropy of transition metal trichalcogenides(MX_(3))has a significant impact on the molding of materi-als and MX_(3) is a perfect choice for polarized *** this study,the crystal structure,optical and optoelectronic aniso-tropy of one kind of quasi-one-dimensional(1D)semiconductors,ZrSe_(3),are systematically investigated through experiments and theoretical *** ZrSe_(3)-based photodetector shows impressive wide spectral response from ultraviolet(UV)to near in-frared(NIR)and exhibits great optoelectrical properties with photoresponsivity of 11.9 mA·W^(-1) and detectivity of~106 at 532 ***,the dichroic ratio of ZrSe_(3)-based polarized photodetector is around 1.1 at 808 *** study suggests that ZrSe_(3) has potential in optoelectronic applications and polarization detectors.

关键词： quasi-1D ZrSe_(3) polarization-sensitive

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