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Thermal transport in semiconductor nanostructures, graphene,and related two-dimensional materials

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Chinese Physics B 2018年第5期27卷 74-82页

作者： Alexandr i.Cocemasov Calina i.isacova Denis L.Nika E.Pokatilov Laboratory of Physics and Engineering of Nanomaterials Department of Physics and EngineeringMoldova State University

We review experimental and theoretical results on thermal transport in semiconductor nanostructures（multilayer thin films, core/shell and segmented nanowires）, single-and few-layer graphene, hexagonal boron nitride, molybdenum disulfide, and black phosphorus. Different possibilities of phonon engineering for optimization of electrical and heat conductions are discussed. The role of the phonon energy spectra modification on the thermal conductivity in semiconductor nanostructures is revealed. The dependence of thermal conductivity in graphene and related two-dimensional（2 D） materials on temperature, flake size, defect concentration, edge roughness, and strain is analyzed.

关键词： phonons thermal conductivity nanowire graphene two-dimensional (2D) materials

Hardness-Lattice Parameter Correlation for Aged Al-Zn-Mg Alloys

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Journal of Materials Science & Technology 2010年第12期26卷 1083-1088页

作者： P.Fernandez G.Gonzalez i.Alfonso i.A.Figueroa instituto de investigaciones en Materiales Universidad Nacional Aut'onoma de M'exicoCircuito ExteriorCd.UniversitariaDel.Coyoac'anM'exicoDF.04510Mexico

Two ternary Al-2.2Zn-0.95Mg and ***-2.1Mg （in wt pct） alloys, with Zn：Mg ratios close to 2.5 were produced by conventional ingot casting metallurgy. The ingots were solution heat treated at 500℃ for 0.5 h and aged at 180℃ for times between 0.5 and 80 h. The structural characterization was carried out by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, selected area electron diffraction （SAED） and Vickers mierohardness measurements （HV）. The study was focused on the investigation of the precipitates formation and the relationship between hardness and lattice parameter for α-Al. The results showed that there was an inverse correlation for all the experimental conditions, and the aged peaks coincided with lattice parameter minima. Significant precipitates formation only occurred for the alloy containing 5.5 wt pct Zn and 2.1 wt pct Mg, provoking an important strengthening and variations in the lattice parameter, however, this was not observed for the alloy containing 2.2 wt pct Zn and 0.95 wt pct Mg. A plausible explanation of the increment of hardness values could be the presence of a well distributed η phase （MgZn2）. At initial stages of the precipitation process, η′ was the most abundant precipitate while the phase τ- was observed at overaged conditions. These results showed that the aging response of the conventionally cast Al-Zn-Mg alloys could be obtained using the lattice parameter of the α-Al matrix, even for alloy systems with low precipitates formation.

关键词： Aluminum alloy X-ray diffraction Precipitation Lattice parameter Hardness

Nonlinear dynamics of two degree of freedom systems with linear and nonlinear stiffnesses

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Earthquake Engineering and Engineering Vibration 2013年第3期12卷 411-420页

作者： Bayat Mahmoud i.Pakar Department of Civil Engineering Mashhad Branch Islamic Azad UniversityMashhad Iran

in this study, a new analytical approach is developed to analyze the free nonlinear vibration of conservative two-degree-of-freedom （TDOF） systems. The mathematical models of these systems are governed by second--order nonlinear partial differential equations. Nonlinear differential equations were transferred into a single equation by using some intermediate variables. The single nonlinear differential equations are solved by using the first order of the Hamiltonian approach （HA）. Different parameters, which have a significant impact on the response of the systems, are considered and discussed. Some comparisons are presented to verify the results between the Hamiltonian approach and the exact solution. The maximum relative error is less than 2.2124 % for large amplitudes of vibration. it has been established that the first iteration of the Hamiltonian approach achieves very accurate results, does not require any small perturbations, and can be used for a wide range of nonlinear problems.

关键词： nonlinear vibration two-degree-of-freedom (TDOF) analytical approach Hamitonian approach (HA)

Design and Analysis of Hybrid Systems for Scooters

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Chinese Journal of Mechanical Engineering 2011年第5期24卷 752-759页

作者： CHEN i-Ming LiU Tyng Department of Mechanical Engineering Taiwan University

Hybrid technology has been widely developed for various vehicles in recent ***,due to the limitation of size and space,it is difficult to apply the technology in the small two-wheeled vehicles,especially *** scooters,the hybrid system could be with small capacity,and must be simple and *** Purpose of this study is to analyze and develop the conceptual designs of fuel-electric hybrid systems especially for ***,the graph called ＂function power graph（FPG）＂ is defined,which transforms traditional mechanical schematic diagrams into simplified graphs,and makes the characteristics of hybrid systems can be identified *** on the FPG,a systematic method for synthesizing all possible arrangements of hybrid systems,then,is developed,and the hybrid system arrangements with one internal combustion engine（iCE）,one electric machine（M/G）,and some mechanical clutch units are all *** order to evaluate the applicability of these design concepts for Scooters,twelve system functions and three system complexities are defined,and this evaluation process can be automated numerically by using a computer program,which is Matlab in this *** the systematic design and analysis methods developed,the function capability and characteristics of current hybrid systems can be easily identified,and also,new and useful hybrid systems are found for future possible applications.

关键词： hybrid-system conceptual design automated synthesis scooter

Determination of a suitable set of loss models for centrifugal compressor performance prediction

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Chinese Journal of Aeronautics 2017年第5期30卷 1644-1650页

作者： Elkin i.GUTiERREZ VELASQUEZ Faculty of Mechanical Engineering Universidad Antonio Narino Medellln 050012 Colombia

Performance prediction in preliminary design stages of several turbomachinery components is a critical task in order to bring the design processes of these devices to a successful conclusion. in this paper, a review and analysis of the major loss mechanisms and loss models, used to determine the efficiency of a single stage centrifugal compressor, and a subsequent examination to determine an appropriate loss correlation set for estimating the isentropic efficiency in preliminary design stages of centrifugal compressors, were developed. Several semi-empirical correlations,commonly used to predict the efficiency of centrifugal compressors, were implemented in FORTRAN code and then were compared with experimental results in order to establish a loss correlation set to determine, with good approximation, the isentropic efficiency of single stage *** aim of this study is to provide a suitable loss correlation set for determining the isentropic efficiency of a single stage centrifugal compressor, because, with a large amount of loss mechanisms and correlations available in the literature, it is difficult to ascertain how many and which correlations to employ for the correct prediction of the efficiency in the preliminary stage design of a centrifugal compressor. As a result of this study, a set of correlations composed by nine loss mechanisms for single stage centrifugal compressors, conformed by a rotor and a diffuser, are specified.

关键词： Centrifugal compressor Efficiency loss Performance prediction Preliminary design Turbomachinery

influence of high-temperature convective flow on viability of Scots pine needles(Pinus sylvestris L.)

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Journal of Forestry Research 2020年第5期31卷 1489-1497页

作者： i.G.Gette N.V.Pakharkova i.V.Kosov i.N.Bezkorovaynaya Siberian Federal University 79 SvobodnyKrasnoyarskRussia 660041 Sukachev institute of Forest SB RAS Federal Research Center “Krasnoyarsk Science Center of SB RAS”50 AkademgorodokKrasnoyarsk 660036Russia

During a forest fire,plants are affected by high temperatures causing *** the time of burning,it is difficult to record temperature changes in tree crowns and the associated effects on *** paper presents the results of modelling a high-temperature effect simulating a convective flow from a ground *** of the response was carried out by the parameters of rapid fluorescence(Fv/Fm,ETR),the state of the pigment complex,and the relative water content in the *** characterize the degree of heat endurance and short-term effects concerning thermal damage,saplings of Scots pine(Pinus sylvestris L.)were used at different times during the growing season(June,July,August,September).Experimental heating at 55℃ lasted for 5 and 10 *** were different levels of heat resistance by the *** in June show that heating of the saplings significantly suppressed *** July,August,and September,the photochemical quantum yield(Fv/Fm)was restored to 75%and 60%from the initial level after 5-and 10-min heating,*** electron transport rate(ETR)for saplings in September was restored to their initial level within 3 days after a short heat *** of the photosynthetic activity in needles was observed after a 5-min impact,but by the end of the study period,restoration had not reached control values.A longer heating of 10 min resulted in an irreversible suppression of photosynthesis and destruction of the photosynthetic apparatus,as evidenced by the decrease in the number of photosynthetic pigments.

关键词： Pinus sylvestris Heat stress Chlorophyll Fluorescence Forest fires

Heightened protein-translation activities in mammalian cells and the disease/treatment implications

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National Science Review 2020年第12期7卷 1851-1855页

作者： Chung-i Wu Haijun Wen State Key Laboratory of Biocontrol School of Life SciencesSun Yat-sen University

After cells divide,the new cells have to synthesize all the necessary cellular components in time for the next *** is a lower bound of time required for cells to double their *** mammalian cells,this lower bound may b...

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Performance enhancement of a DC-operated micropump with electroosmosis in a hybrid nanofluid:fractional Cattaneo heat flux problem

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Applied Mathematics and Mechanics(English Edition) 2022年第6期43卷 931-944页

作者： A.M.ALSHARiF A.i.ABDELLATEEF Y.A.ELMABOUD S.i.ABDELSALAM Department of Mathematics and Statistics College of ScienceTaif UniversityP.O.Box 11099Taif 21944Saudi Arabia Department of Applied Mathematics and Science Faculty of EngineeringNational University of Science and TechnologySeeb 111Sultanate of Oman Department of Mathematics College of Science and Arts at KhulisUniversity of JeddahJeddah 21589Saudi Arabia Department of Mathematics Faculty of ScienceAl-Azhar University(Assiut Branch)Assiut 71254Egypt Department of Basic Science Faculty of EngineeringThe British University in EgyptCairo 11837Egypt

The purpose of this investigation is to theoretically shed some light on the effect of the unsteady electroosmotic flow(EOF)of an incompressible fractional secondgrade fluid with low-dense mixtures of two spherical nanoparticles,copper,and *** flow of the hybrid nanofluid takes place through a vertical micro-channel.A fractional Cattaneo model with heat conduction is *** the DC-operated micropump,the Lorentz force is responsible for the pressure difference through the *** Debye-H¨ukel approximation is utilized to linearize the charge *** semianalytical solutions for the velocity and heat equations are obtained with the Laplace and finite Fourier sine transforms and their numerical *** addition to the analytical procedures,a numerical algorithm based on the finite difference method is introduced for the given domain.A comparison between the two solutions is *** variations of the velocity heat transfer against the enhancements in the pertinent parameters are thoroughly investigated *** is noticed that the fractional-order parameter provides a crucial memory effect on the fluid and temperature *** present work has theoretical implications for biofluid-based microfluidic transport systems.

关键词： hybrid nanofluid fractional Cattaneo heat flux Caputo-Fabrizio derivative

Anticorrosion properties and thin film composite deposition of ZnSiC-Cr_3C_2 coating on mild steel

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Defence Technology（防务技术） 2019年第1期15卷 106-110页

作者： A.A.Ayoola O.S.i.Fayomi A.P.i.Popoola Chemical Engineering Department Covenant University Chemical Metallurgical and Materials Engineering DepartmentTshwane University of Technology Mechanical Engineering Department Covenant University

This work considered the influence of Cr3 C2 particle loading on microstructure and mechanical properties of Zn-SiC-Cr3 C2 nanocomposite produced via electrocodeposition are investigated. The surface nature of the nanocomposite coatings were characterized using scanning electron microscope(SEM)coupled with the energy dispersive spectrometer(EDS). Abrasive wear behaviour and hardness property of Zn-SiC-Cr3 C2 nanocomposite produced were investigated using CERT UMT-2 multi-functional tribological tester and Dura Scan hardness tester. The corrosion property was evaluated through linear polarization approach. The result showed that the coatings exhibited good stability and Cr_3 C_2 nanocomposite loading significantly improved the micro structural performance, hardness property,wear resistance as well as corrosion resistance of the coatings.

关键词： Zn-SiC-Cr3C2 Electrodeposition Coatings Corrosion resistance Hardness