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High-voltage direct current fault current interruption:A technology review

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High Voltage 2021年第2期6卷 171-192页

作者： Rene p.p.Smeets Nadew A.Belda Innovation KEMA LabsArnhemNetherlands

This review paper describes fault current interruption principles and various high-voltage direct currrent(HVDC)circuit breaker ***,fundamentals of HVDC fault current interruption and a generic set of requirements of HVDC circuit breakers are *** critical parameters during fault current interruption are assessed using a simplified mathematical ***,the state-of-the-art of HVDC circuit breaker technologies and their application in actual HVDC multi-terminal projects is *** sub-components of HVDC circuit breakers are standard components used in a non-standard application and,hence,have to face non-standard *** of today's HVDC circuit breaker technologies consist of mechanical switching devices and metal-oxide surge arresters,which are used in an unconventional way.A critical analysis of these stresses compared to the stresses in a conventional application is ***-mendations on testing supported with examples of actual full-power‘complete’demonstration of HVDC circuit breakers up to 350 kV/20 kA are ***,the actual status of standardisation activities is presented.

关键词： fault critical hence

Finite-time stabilization of uncertain non-autonomous chaoticgyroscopes with nonlinear inputs

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Applied Mathematics and Mechanics(English Edition) 2012年第2期33卷 155-164页

作者： M.p.AGHABABA H.p.AGHABABA Electrical Engineering Department Urmia University of Technology Urmia Iran Department of Mathematics University of Tabriz Tabriz Iran Research Center for Industrial Mathematics University of Tabriz Tabriz Iran

Gyroscopes are one of the most interesting and everlasting nonlinear nonautonomous dynamical systems that exhibit very complex dynamical behavior such as chaos. In this paper, the problem of robust stabilization of the nonlinear non-autonomous gyroscopes in a given finite time is studied. It is assumed that the gyroscope system is perturbed by model uncertainties, external disturbances, and unknown parameters. Besides, the effects of input nonlinearities are taken into account. Appropriate adaptive laws are proposed to tackle the unknown parameters. Based on the adaptive laws and the finite-time control theory, discontinuous finite-time control laws are proposed to ensure the finite-time stability of the system. The finite-time stability and convergence of the closed-loop system are analytically proved. Some numerical simulations are presented to show the efficiency of the proposed finite-time control scheme and to validate the theoretical results.

关键词： non-autonomous chaotic gyroscope finite-time control nonlinear input,uncertainty unknown parameter

Reducing the anisotropy of a Brazilian disc generated in a bonded-particle model

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Acta Mechanica Sinica 2018年第4期34卷 716-727页

作者： Q.Zhang X.p.Zhang p.Q.Ji The Key Laboratory of Safety for Geotechnical and Structural Engineering of Hubei province School of Civil EngineeringWuhan University

The Brazilian test is a widely used method for determining the tensile strength of rocks and for calibrating parameters in bondedparticle models（BpMs）. In previous studies, the Brazilian disc has typically been trimmed from a compacted rectangular specimen. The present study shows that different tensile strength values are obtained depending on the compressive loading direction. Several measures are proposed to reduce the anisotropy of the disc. The results reveal that the anisotropy of the disc is significantly influenced by the compactibility of the specimen from which it is trimmed. A new method is proposed in which the Brazilian disc is directly generated with a particle boundary, effectively reducing the anisotropy. The stiffness（particle and bond） and strength（bond） of the boundary are set at less than and greater than those of the disc assembly, respectively,which significantly decreases the stress concentration at the boundary contacts and prevents breakage of the boundary particle bonds. This leads to a significant reduction in the anisotropy of the disc and the discreteness of the tensile strength. This method is more suitable for carrying out a realistic Brazilian test for homogeneous rock-like material in the BpM.

关键词： Bonded-particle model Brazilian disc Anisotropy Compactibility particle boundary

Growth of small diameter multi-walled carbon nanotubes by arc discharge process

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Chinese physics B 2014年第3期23卷 412-417页

作者： K.T.Chaudhary J.Ali p.p.Yupapin Institute of Advanced photonics Science (ApSI) Nanotechnology Research Alliance Universiti Teknologi Malaysia 81310Johor Bahru Malaysia Nanoscale Science and Research Alliance (N’SERA) Faculty of Science King Mongkut’s Institute of Technology Ladkrabang

Multi-walled carbon nanotubes （MWCNTs） are grown by arc discharge method in a controlled methane environment. The arc discharge is produced between two graphite electrodes at the ambient pressures of 100 tort, 300 torr, and 500 torr. Arc plasma parameters such as temperature and density are estimated to investigate the influences of the ambient pressure and the contributions of the ambient pressure to the growth and the structure of the nanotubes. The plasma temperature and density are observed to increase with the increase in the methane ambient pressure. The samples of MWCNT synthesized at different ambient pressures are analyzed using transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. An increase in the growth of MWCNT and a decrease in the inner tube diameter are observed with the increase in the methane ambient pressure.

关键词： electric discharge arc plasma temperature and density carbon nanotubes

An L-band emitter with quantum memory in silicon

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npj Computational Materials 2022年第1期8卷 2498-2503页

作者： péter Udvarhelyi Anton pershin péter Deák Adam Gali Wigner Research Centre for physics P.O.Box 49H-1525BudapestHungary Budapest University of Technology and Economics Institute of PhysicsDepartment of Atomic PhysicsMűegyetem rakpart 3.1111BudapestHungary

Fluorescent centres in silicon have recently attracted great interest,owing to their remarkable properties for quantum ***,we demonstrate that the C-centre in silicon can realise an optically readable quantum register in the L-band wavelength region where the transmission losses in commercial optical fibres are *** in-depth theoretical characterisation confirms the assignment of the C-centre to the carbon-oxygen interstitial pair *** further explore its magneto-optical properties,such as hyperfine and spin-orbit coupling constants from first principles calculations,which are crucial for tight control of the quantum states of the triplet electron *** on this data,we set up quantum optics protocols to initialise and read out the quantum states of the electron spin,and realise a quantum memory by transferring quantum information from the electron spin to proximate ^(29)Si nuclear *** findings establish an optically readable long-living quantum memory in silicon where the scalability of qubits may be achieved by CMOS-compatible technology.

关键词： quantum centre optics

Mechanical Behaviors of Ti-Si-N Coatings Deposited by Bias Sputtering

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稀有金属材料与工程 2012年第S1期41卷 18-23页

作者： p W Shum Advanced Coatings Applied Research Laboratory(ACARL) Department of Mechanical and Biomedical Engineering(MBE)City University of Hong KongHong KongChina

Ti-Si-N hard coatings were deposited on steel substrates by reactive unbalanced magnetron sputtering from Ti and Si elemental targets in a mixture of Ar and N2 *** influences of negative bias voltage(in the range of-30 to-80 V)on the mechanical properties of the coatings were *** particular,the critical cycle during dynamic impact tests was employed to indicate the bonding strength of the *** was found that the Ti-Si-N coatings prepared at lower constant bias voltages could effectively improve the adhesion and the cyclic impact performance,but their hardness was dropped significantly to 13 Gpa at a bias of-30 *** bias voltage values induced greater hardness.A maximum hardness of 47 Gpa was obtained at a bias of-60 ***,the coating adhesion was worse in this case,and the number of impact cycles(～8×10 3)that the coatings could endure was much shorter than that of TiN binary coatings(～2×104).On the other hand,the bias voltage was varied linearly from-40 to-60 V during Ti-Si-N *** this circumstance,the hardness of the coatings deposited with the bias-graded configuration remained very high(42 Gpa),and the adhesion strength was improved ***,the critical impact cycle could reach as high as 1.8×***,bias-graded deposition can provide an effective processing route to prepare Ti-Si-N superhard coatings with high adhesion strength and impact resistance.

关键词： Ti-Si-N coatings magnetron sputtering bias voltage mechanical properties impact test

Magnetic polarization of a Mn-doped semiconductor nanostructure controlled by an external bias

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Journal of Semiconductors 2015年第7期36卷 22-28页

作者： p.paradeo Unstituto de Fisica Universidad Nacional Autonoma de Mexico

The interplay between the electric and magnetic properties in a double quantum well heterostructure doped by magnetic ions is theoretically investigated. In this material, the magnetism is mediated by the hole gas. The total magnetic polarization of the system is controllable by an external applied bias. The device has two equilibrium states （symmetric and antisymmetric configurations）. In the stable configuration （anti-ferromagnetic type）, the particle spin distribution is reversed in the adjacent wells. The stability of the system is investigated by simulating the interaction of the hole gas with the light. By using an ab initio method, we estimate the switching time of the device.

关键词： magnetic polarization quantum well stability

Experimental Investigation on Friction Welding of UNS S32205 Duplex Stainless Steel

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Acta Metallurgica Sinica(English Letters) 2014年第6期27卷 995-1007页

作者： p. M. Ajith p. Sathiya S. Aravindan Department of production Engineering National Institute of Technology Department of Mechanical Engineering Indian Institute of Technology Delhi

UNS S 32205 duplex stainless steel specimens were joined by continuous drive friction welding process. The experiments were conducted as per the Taguchi（L16 orthogonal array） method. The friction welding process parameters such as heating pressure, heating time, upsetting pressure, upsetting time, and speed of rotation were fixed with low,medium, and high levels of range based on the machine capacity, and the required knowledge was acquired from the preliminary experiments. The joint characterization studies included micro structural examination and evaluation of mechanical properties of the joints. Microhardness variation, impact toughness, and tensile strength of the joints were evaluated. Neither a crack nor an incomplete bonding zone was observed. The tensile strength of the joints was higher than the strength of the base material, and the friction and upsetting pressures were found to influence the joint strength. The tensile strength of all the welds was observed to be increasing with an increase in the rotational speed. The toughness of the friction welds was evaluated at room temperature and also at subzero（cryo） temperature conditions. The toughness for friction welds was found to be superior to the fusion welds of duplex stainless steel at room temperature and cryo conditions. Weldments exhibited better corrosion resistance than the parent material.

关键词： Duplex stainless steel Hardness Tensile strength Toughness Microstructure Corrosion

Fractals and Spatial Statistics of point patterns

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Journal of Earth Science 2013年第1期24卷 1-11页

作者： Frederik p Agterberg Geological Survey of Canada 601 Booth Street Ottawa K1A 0E8 Canada

The relationship between fractal point pattern modeling and statistical methods of pa- rameter estimation in point-process modeling is reviewed. Statistical estimation of the cluster fractal dimension by using Ripley＇s K-function has advantages in comparison with the more commonly used methods of box-counting and cluster fractal dimension estimation because it corrects for edge effects, not only for rectangular study areas but also for study areas with curved boundaries determined by re- gional geology. Application of box-counting to estimate the fractal dimension of point patterns has the disadvantage that, in general, it is subject to relatively strong ＂roll-off＂ effects for smaller boxes. point patterns used for example in this paper are mainly for gold deposits in the Abitibi volcanic belt on the Canadian Shield. Additionally, it is proposed that, worldwide, the local point patterns of podiform Cr, volcanogenic massive sulphide and porphyry copper deposits, which are spatially distributed within irregularly shaped favorable tracts, satisfy the fractal clustering model with similar fractal dimensions. The problem of deposit size （metal tonnage） is also considered. Several examples are provided of cases in which the pareto distribution provides good results for the largest deposits in metal size-frequency distribution modeling.

关键词： fractal point pattern spatial statistics roll-off effect cluster dimension pareto distribution.