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Applied Mathematics and Mechanics(English Edition) 2019年第8期40卷 1135-1154页

作者： s.M.ABO-DAHAB A.M.ABD-ALLA A.A.KILANY Department of Mathematics Faculty of SciencesTaif UniversityTaif 888Saudi Arabia Department of Mathematics Faculty of ScienceSouth Valley UniversityQena 83523Egypt Department of Mathematics Faculty of ScienceSohag UniversitySohag 82524Egypt

The effects of rotation and gravity on an electro-magneto-thermoelastic medium with diffusion and voids in a generalized thermoplastic half-space are studied by using the Lord-shulman (L-s) model and the dual-phase-lag (DPL) model. The analytical solutions for the displacements, stresses, temperature, diffusion concentration, and volume fraction field with different values of the magnetic field, the rotation, the gravity, and the initial stress are obtained and portrayed graphically. The results indicate that the effects of gravity, rotation, voids, diffusion, initial stress, and electromagnetic field are very pronounced on the physical properties of the material.

关键词： electromagnetic field gravity field rotation initial stress voids diffusion normal mode analysis Lord-shulman (L-s) model dual-phase-lag (DPL) model

Localized Corrosion Characteristics of Nickel Alloys： A Review

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Acta Metallurgica sinica(English Letters) 2017年第4期30卷 296-305页

作者： Helmuth sarmiento Klapper Natalia s. Zadorozne Raul B. Rebak Center for Materials Research Baker Hughes 29221 CelleGermany Instituto de Materiales de Misiones (IMAM) UNaMCONICET 3300 Posadas Argentina GE Global Research Schenectady NY 12309 USA

There are a great variety of commercial nickel alloys mainly because nickel is able to dissolve a large amount of alloying elements while maintaining a single ductile austenitic phase. Nickel alloys are generally designed for and used in highly aggressive environments, for example, those where stainless steels may experience pitting corrosion or environmentally assisted cracking. While nickel alloys are generally resistant to pitting corrosion in chloride-containing environments, they may be prone to crevice corrosion attack. Addition of chromium, molybdenum and tungsten increases the localized corrosion resistance of nickel alloys. This review on the resistance to localized corrosion of nickel alloys includes specific environments such as those present in oil and gas upstream operations, in the chemical process industry and in seawater service.

关键词： Nickel alloys Localized corrosion Oil and gas seawater Chemical process industry

A review of ferroelectric materials for high power devices

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Journal of Materiomics 2022年第4期8卷 739-752页

作者： sergey I.shkuratov Christopher s.Lynch Loki Incorporated 1334 Royal RoadNorwoodMO65717USA Bourns College of Engineering University of California at RiversideCA92521USA

Compact autonomous ultrahigh power density energy storage and power generation devices that exploitthe spontaneous polarization of ferroelectric materials are capable of producing hundreds of kilovoltvoltages,multi-kiloampere currents,and megawatt power levels for brief interval of *** storagelife of these devices is four orders of magnitude longer than that for electrochemical batteries andelectrochemical *** is an up to date survey of ferroelectric materials used for these highpower *** types of ferroelectric ceramics possess the ability to be depolarized under adia-batic compression and can be successfully used for high power *** addition to bulk ferro-electric ceramics,multilayer ferroelectric films are very efficient materials for high power *** importance is the ability of relaxor ferroelectric single crystals to produce significantly higherelectric charge density and energy density than ceramics,making them promising materials for highpower *** provided is a brief survey of recent developments of ferroelectric materials forhigh energy density and power density dielectric *** ceramics have been developed,including antiferroelectric and relaxor antiferroelectric solid solutions,providing high energy densityand efficiency simultaneously.

关键词： Energy storage Ferroelectric Antiferroelectric Relaxor High power density

Complex variable approach in studying modified polarization saturation model in two-dimensional semipermeable piezoelectric media

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Applied Mathematics and Mechanics(English Edition) 2017年第11期38卷 1517-1532页

作者： s. sINGH K. sHARMA R. R. BHARGAVA Department of sciences and Humanities National Institute of Technology UttarakhandSrinagar(Garhwal)246174India Department of Mathematics Indian Institute of Technology RoorkeeRoorkee 247667India

A modified polarization saturation model is proposed and addressed math- ematically using a complex variable approach in two-dimensional （2D） semipermeable piezoelectric media. In this model, an existing polarization saturation （Ps） model in 2D piezoelectric media is modified by considering a linearly varying saturated normal electric displacement load in place of a constant normal electric displacement load, applied on a saturated electric zone. A centre cracked infinite 2D piezoelectric domain subject to an arbitrary poling direction and in-plane electromechanical loadings is considered for the analytical and numerical studies. Here, the problem is mathematically modeled as a non-homogeneous Riemann-Hilbert problem in terms of unknown complex potential functions representing electric displacement and stress components. Having solved the Hilbert problem, the solutions to the saturated zone length, the crack opening displace- ment （COD）, the crack opening potential （COP）, and the local stress intensity factors （sIFs） are obtained in explicit forms. A numerical study is also presented for the proposed modified model, showing the effects of the saturation condition on the applied electrical loading, the saturation zone length, and the COP. The results of fracture parameters obtained from the proposed model are compared with the existing Ps model subject to electrical loading, crack face conditions, and polarization angles.

关键词： complex variable fracture parameter local stress intensity factor (sIF),piezoelectric polarization saturation (Ps) model

Low-temperature oxidation behavior of Mosi_2 powders

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Journal of University of science and Technology Beijing 2007年第6期14卷 558-561页

作者： Peizhong Feng Xuanhui Qu Islam s. Humail Xueli Du state Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China school of Materials science and Engineering China University of Mining and Technology Xuzhou 221116 China

The oxidation behavior of molybdenum disilicide （Mosi2） powders at 400, 500, and 600℃ for 12 h in air were investigated by using X-ray diffraction （XRD） and transmission electron microscopic （TEM） techniques. significant changes were observed in volume, mass, and color. Especially at 500℃, the volume expansion was found to be as high as 7-8 times, the color changed from black to yellow-white, and the mass gain was about 169.34% after 8 h, with siO2 and MoO3 as main reaction products. The gains in volume and mass were less at 400 and 600℃ compared with those at 500℃, probably due to the less reaction rate at 400℃ and the formation of silica glass scale at 600℃, which would protect the matrix and restrain the diffusion of oxygen and molybdenum. Thus, the accelerated oxidation behavior of Mosi2 powder appeared at 500℃ and the volume expansion was the sign of accelerated oxidation.

关键词： molybdenum disilicide low-temperature oxidation accelerated oxidation volume expansion

Review of deployment technology for tethered satellite systems

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Acta Mechanica sinica 2018年第4期34卷 754-768页

作者： B.s.Yu H.Wen D.P.Jin state Key Laboratory of Mechanics and Control of Mechanical structures Nanjing University of Aeronautics and Astronautics

Tethered satellite systems（Tsss） have attracted significant attention due to their potential and valuable applications for scientific research. With the development of various launched on-orbit missions, the deployment of tethers is considered a crucial technology for operation of a Tss. Both past orbiting experiments and numerical results have shown that oscillations of the deployed tether due to the Coriolis force and environmental perturbations are inevitable and that the impact between the space tether and end-body at the end of the deployment process leads to complicated nonlinear phenomena. Hence, a set of suitable control methods plays a fundamental role in tether deployment. This review article summarizes previous work on aspects of the dynamics, control, and ground-based experiments of tether deployment. The relevant basic principles, analytical expressions, simulation cases, and experimental results are presented as well.

关键词： Tethered satellite Deployment Dynamics Control Experiment

Asymptotic and numerical study of a surface breaking crack subject to a transient thermal loading

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Acta Mechanica sinica 2006年第1期22卷 22-27页

作者： A.B. Movchan I.s. Jones ljmu.ac.uk Department of Mathematical sciencesUniversity of Liverpoo UK L69 3BX school of EngineeringJames Parsons BuildingJohn Moores UniversityByrom st.Liverpool UK. L3 3AF E-mail: i.s.jones

An asymptotic algorithm is applied to the problem of a finite, thermo-elastic solid containing a surface breaking crack, when the exterior surface is subjected to oscillatory thermal loading. This algorithm involves the study of a model problem. An analytical and numerical study of this model problem of a thermo-elastic half space containing a surface breaking crack and subjected to oscillatory thermal loading is presented. The crack surface is traction free. In particular, the amplitude of the stress intensity factor at the crack vertex is found as a function of the crack depth and the frequency of thermal oscillation.

关键词： Thermo-elasticity surface breaking crack Wiener-Hopf solution Weight function method

Creep Behavior and Microstructure Evolution of sand–Cast Mg–4Y–2.3Nd–1Gd–0.6Zr Alloy Crept at 523–573 K

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Journal of Materials science & Technology 2017年第1期33卷 79-89页

作者： Y.H.Kang H.Yan R.s.Chen The Group of Magnesium Alloys and Their Applications Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China University of the Chinese Academy of sciences Beijing 100049China

High temperature tensile-creep behavior of Mg-4Y-2.3Nd-IGd-O.6Zr （wt%, WE43（T6）） alloy at 523- 573 K was investigated. The creep stress exponent is equal to 4.6, suggesting the underlying dislocation creep mechanism. The activation energy is （199 _＋ 23） kJ/mol, which is higher than that for self- diffusion in Mg and is believed to be associated with precipitates coarsening or cross slip. The creep mechanism is further suggested to be dislocation climb at 523 K, while a cross slip at 573 K is possible. The metastable 13＇ and ~]1 phases in the WE43（T6） alloy were relatively thermal stable at 523 K and could be effective to hinder the dislocation climb, which contributed to its excellent creep resistance. However, at 573 K it readily transforms into equilibrium/3e phase and coarsens within two hours, thereby causing a decrease of creep resistance. In addition, precipitate free zones approximately normal to applied stress direction （directional PFZs） developed during the creep deformation, especially at 573 K. Those zones became preferential sites to nucleate, extend and connect microcracks and cavities, which lead to the intergranular creep fracture. Improving the thermal stability of precipitates or introducing thermally stable fine plate-shaped precipitates on the basal planes of Mg matrix could enhance the high temperature creep resistance.

关键词： WE43 alloy Creep PFZs Precipitate Fracture

Conversion of an atomic to a molecular argon ion and low pressure argon relaxation

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Chinese Physics B 2016年第1期25卷 697-705页

作者： M N stankov A P Jovanovie V Lj Markovic s N stamenkovic Department of Physics Faculty of Sciences and MathematicsUniversity of Ni Viegradska 33Ni 18001Serbia

The dominant process in relaxation of DC glow discharge between two plane parallel electrodes in argon at pressure 200 Pa is analyzed by measuring the breakdown time delay and by analytical and numerical models. By using the approx- imate analytical model it is found that the relaxation in a range from 20 to 60 ms in afterglow is dominated by Ar＋ ions, produced by atomic-to-molecular conversion of Ar＋ ions in the first several milliseconds after the cessation of the discharge. This conversion is confirmed by the presence of double-Gaussian distribution for the formative time delay, as well as con- version maxima in a set of memory curves measured in different conditions. Finally, the numerical one-dimensional （1D） model for determining the number densities of dominant particles in stationary DC glow discharge and two-dimensional （2D） model for the relaxation are used to confirm the previous assumptions and to determine the corresponding collision and transport coefficients of dominant species and processes.

关键词： argon discharge afterglow relaxation fluid model plasma reactions

synthesis of ZnO Nanoparticles onto sepiolite Needles and Determination of Their sensitivity toward Humidity, NO_2 and H_2

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Journal of Materials science & Technology 2016年第6期32卷 573-582页

作者： M.Hassan Ahmed s.Afify J.M.Tulliani Department of Applied science and Technology Politecnico di Torino

This work investigated the sensitivity toward humidity, NO2 and H2 of ZnO modified sepiolite （si12Mg8O30（OH）4.（H2O）4.8H2O）. To this aim, sepiolite powder was first modified by leaching magnesium ions in HCI then by precipitating nano-sized Zn-based compounds under basic conditions. A subse- quent thermal treatment at 550 ℃ for 1 h was performed. The powders were characterized by X-ray diffraction （XRD）, specific surface area measurements, thermogravimetric and differential thermal anal- ysis and field emission scanning electron microscopy, as well as high resolution transmission electron microscopy. The XRD patterns showed that all leached heat treated samples were made of anhydrous sepiolite and of ZnO. sensors were then obtained by screen printing these materials onto commercial alumina substrates with Pt electrodes. All the investigated compositions were capable of detecting NO2 down to ppm level and 20 ppm H2, at an optimal working temperature of 300°C. These detection limits are in line with the current best results reported in literature.

关键词： Clay minerals Gas sensor sensitivity Hydrogen sensor Nitrogen Oxide