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High-temperature mechanical properties of aluminium alloys reinforced with titanium diboride (TiB_2) particles

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Rare Metals 2011年第2期30卷 200-205页

作者： J.ooro Ingeniería y Ciencia de los Materiales ETSI IndustrialesUniversidad Politécnica de Madridc/José Gutiérrez Abascal2.28006 MadridSpain

The physical and mechanical properties of metal matrix composites were improved by the addition of reinforcements. The mechanical properties of particulate-reinforced metal-matrix composites based on aluminium alloys （6061 and 7015） at high temperatures were studied. Titanium diboride （TiB2） particles were used as the reinforcement. All the composites were produced by hot extrusion. The tensile properties and fracture characteristics of these materials were investigated at room temperature and at high temperatures to determine their ultimate strength and strain to failure. The fracture surface was analysed by scanning electron microscopy. TiB2 particles provide high stability of the alumin- ium alloys （6061 and 7015） in the fabrication process. An improvement in the mechanical behaviour was achieved by adding TiB2 particles as reinforcement in both the aluminium alloys. Adding TiB2 particles reduces the ductility of the aluminium alloys but does not change the microscopic mode of failure, and the fracture surface exhibits a ductile appearance with dimples formed by coalescence.

关键词： metal-matrix composites aluminium high-temperature properties titanium diboride

Cracking Susceptibility After Post-Weld Heat Treatment in Haynes 282 Nickel Based Superalloy

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Acta Metallurgica Sinica(English Letters) 2013年第6期26卷 747-753页

作者： L.o.osoba A.K.Khan S.o.Adeosun Department of Metallurgical and Materials Engineering University of Lagos Department of Mechanical and Manufacturing Engineering University of Manitoba

This paper presents a study of the standard post-weld heat treatment （PWHT） behaviour of autogenous laser welded γ＇ age-hardenable precipitation strengthened nickel based superalloy Haynes 282 （HY 282）. The study involves a careful and detailed microstructural characterisation as well as an analysis of the weld cracking susceptibility during welding and Gleeble thermo-mechanical physical simulation. Various factors that could influence post-weld cracking in superalloys weld were experimentally examined. our microstructural exami- nation of the as-solution heat treated （SHTed） material and the thermo-mechanically refined grain material shows that intergranular heat affected zone （HAZ） cracking is observable in only the as-welded SHTed material. There was no indication of post-weld heat treatment cracking in all welded materials. our conclusion, in this study, is that the chemistry of superalloy HY 282 which aids the preclusion/formation of deleterious so- lidification microconstituents during welding as well as its relatively slow aging kinetics enhances its resistance to PWHT cracking.

关键词： Cracking Microstructure Analysis Nickel based Superalloy

Results from a comprehensive GPS Network: natural gas pipeline GPS Network

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International Journal of Digital Earth 2013年第S02期6卷 67-80页

作者： o.Yildirim Faculty of Engineering and Natural Sciences Gaziosmanpas¸a UniversityTokatTurkey

Developing the Nabucco engineering infrastructure was the most challenging task imaginable and required state-of-the-art *** this purpose,a NabuccoGlobal Positioning System(GPS)Network was *** is 762 km ***-hundred and two ground control unit points were *** order to provide the relationship with ITRF96 datum,it was surrounded by TFNGN(Turkish Fundamental National GPS Network)and TNVCN(Turkish National Vertical Control Network)*** observations were evaluated in the form of a unique *** being reduced to projection segments,coordinates in ED50 datum were provided between datums by 2D-Helmert *** heights related to the GPS Network were obtained by the improvement of TG-03 data based on a GPS/leveling *** objective of the study is to present the results of a comprehensive engineering project which involved many geodetic considerations including GPS,orthometric heights,and geoid undulations and gives insight into the accuracy and precision of such large projects in terms of recent geodetic *** this study,a Global Navigation Satellite System(GNSS)-based geodetic infrastructure is presented,methods to obtain the necessary precision requirements are provided,and experience is shared in order to provide an example of a large-scale pipeline project,and to provide insight into the planning necessary for future similar engineering projects.

关键词： ITRF96 ED50 datum GPS/leveling accuracy

operations on 3-Dimensional Small Covers

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Chinese Annals of Mathematics,Series B 2010年第3期31卷 393-410页

作者： Shintaro KURoKI Department of Mathematical Science KAIST 335 Gwahangno (373-1 Guseong-dong) Yuseong-gu Daejeon 305-701 Korea School of Mathematical Sciences Fudan University

The purpose of this paper is to study relations among equivariant operations on 3-dimensional small covers. The author gets three formulas for these operations. As an application, the Nishimura＇s theorem on the construction of oriented 3-dimensional small covers and the Lu-Yu＇s theorem on the construction of all 3-dimensional small covers are improved. Moreover, for a construction of 3-dimensional 2-torus manifolds, it is shown that all operations can be obtained by using the equivariant surgeries.

关键词： Equivariant surgery Finite group action Small cover 3-dimensional manifold 3-dimensional simple polytope

Male obesity and subfertility, is it really about increased adiposity？

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Asian Journal of Andrology 2015年第3期17卷 450-458页

作者： Nicole o McPherson Discipline of obstetrics and Gynaecology School of Paediatrics and Reproductive Health The Robinson Institute The University of Adelaide South Australia 5005 Australia Freemasons Foundation Center for Mens Health The University of Adelaide South Australia 5005 Monash IVF Group Melbourne Victoria 3168 Australia

The prevalence of overweight and obesity in reproductive-aged men is increasing worldwide, with 〉70% of men 〉18 years classified as overweight or obese in some western nations. Male obesity is associated with male subfertility, impairing sex hormones, reducing sperm counts, increasing oxidative sperm DNA damage and changing the epigenetic status of sperm. These changes to sperm function as a result of obesity, are further associated with impaired embryo development, reduced live birth rates and increased miscarriage rates in humans. Animal models have suggested that these adverse reproductive effects can be transmitted to the offspring; suggesting that men＇s health at conception may affect the health of their children, in addition to higher adiposity, male obesity is associated with comorbidities, including metabolic syndrome, hypercholesterolemia, hyperleptinemia and a pro-inflammatory state, all which have independently been linked with male subfertility. Taken together, these findings suggest that the effects of male obesity on fertility are likely multifactorial, with associated comorbidities also influencing sperm, pregnancy and subsequent child health.

关键词： embryo fertility infertility inflammation metabolic syndrome sperm

optical properties of GaAs

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Journal of Semiconductors 2013年第3期34卷 7-11页

作者： J.o.Akinlami A.o.Ashamu Department of Physics Federal University of AgricultureP.M.B 2240AbeokutaOgun StateNigeria

We have investigated the optical properties of gallium arsenide(GaAs) in the photon energy range 0.6- 6.0 *** obtained a refractive index which has a maximum value of 5.0 at a photon energy of 3.1 eV;an extinction coefficient which has a maximum value of 4.2 at a photon energy of 5.0 eV;the dielectric constant,the real part of the complex dielectric constant has a maximum value of 24 at a photon energy of 2.8 eV and the imaginary part of the complex dielectric constant has a maximum value of 26.0 at a photon energy of 4.8 eV;the transmittance which has a maximum value of 0.22 at a photon energy of 4.0 eV;the absorption coefficient which has a maximum value of 0.22×10~8 m^(-1) at a photon energy of 4.8 eV,the reflectance which has a maximum value of 0.68 at 5.2eV; the reflection coefficient which has a maximum value of 0.82 at a photon energy of 5.2 eV;the real part of optical conductivity has a maximum value of 14.2×10^(15) at 4.8 eV and the imaginary part of the optical conductivity has a maximum value of 6.8×10^(15) at 5.0 *** values obtained for the optical properties of GaAs are in good agreement with other results.

关键词： complex index of refraction extinction coefficient complex dielectric constant transmittance absorption coefficient semiconductor and photon energy

optimal placement of wind turbines within a wind farm considering multi-directional wind speed using two-stage genetic algorithm

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Frontiers in Energy 2021年第1期15卷 240-255页

作者： A.S.o.oGUNJUYIGBE T.R.AYoDELE o.D.BAMGBoJE Power Energy Machines and Drives(PEMD)Research Group Department of Electrical and Electronic EngineeringUniversity of IbadanNigeria

Most wind turbines within wind farms are set up to face a pre-determined wind ***,wind directions are intermittent in nature,leading to less electricity production *** paper proposes an algorithm to solve the wind farm layout optimization problem considering multi-angular(MA)wind direction with the aim of maximizing the total power generated on wind farms and minimizing the cost of installation.A twostage genetic algorithm(GA)equipped with complementary sampling and uniform crossover is used to evolve a MA layout that will yield optimal output regardless of the wind *** the first stage,the optimal wind turbine layouts for 8 different major wind directions were determined while the second stage allows each of the previously determined layouts to compete and inter-breed so as to evolve an optimal MA wind farm *** proposed MA wind farm layout is thereafter compared to other layouts whose turbines have focused site specific wind turbine *** results reveal that the proposed wind farm layout improves wind power production capacity with minimum cost of installation compared to the layouts with site specific wind turbine *** paper will find application at the planning stage of wind farm.

关键词： optimal placement wind turbines wind direction genetic algorithm wake effect

An overview of Rationalization Theories of Non-simply Connected Spaces and Non-nilpotent Groups

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Acta Mathematica Sinica,English Series 2022年第10期38卷 1705-1721页

作者： Sergei o.IVANoV Laboratory of Modern Algebra and Applications St.Petersburg State University14th Line29bSaint Petersburg199178Russia

We give an overview of five rationalization theories for spaces(Bousfield-Kan’s Q-completion;Sullivan’s rationaliz ation;Bousifeld’s homology rationaliz ation;Casacuberta-Peschke’s Ω-rationalization;Gomez-Tato-Halperin-Tanré’s π-fiberwise rationalization)that extend the classical rationalization of simply connected *** also give an overview of the corresponding rationalization theories for groups(Q-completion;HQ-localization;Baumslag rationalization)that extend the classical Malcev completion.

关键词： Rationalisation localisation rational homotopy theory group theory

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Stability analysis of a time-delayed Van der Pol–Helmholtz–Duffing oscillator in fractal space with a non-perturbative approach

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Communications in Theoretical Physics 2024年第4期76卷 22-31页

作者： Yusry o El-Dib Department of Mathematics Faculty of EducationAin Shams UniversityRoxyCairoEgypt

The time-delayed fractal Van der Pol–Helmholtz–Duffing(VPHD)oscillator is the subject of this paper,which explores its mechanisms and highlights its stability *** time-delayed technologies are currently garnering significant attention,the focus of this research remains crucially relevant.A non-perturbative approach is employed to refine and set the stage for the system under *** innovative methodologies introduced yield an equivalent linear differential equation,mirroring the inherent nonlinearities of the ***,the incorporation of quadratic nonlinearity into the frequency formula represents a cutting-edge *** analytical solution's validity is corroborated using a numerical *** conditions are ascertained through the residual Galerkin ***,it is observed that the delay parameter,in the context of the fractal system,reverses its stabilizing influence,impacting both the amplitude of delayed velocity and the *** analytical solution's precision is underscored by its close alignment with numerical ***,the study reveals that fractal characteristics emulate damping *** its applicability across diverse nonlinear dynamical systems,this non-perturbative approach emerges as a promising avenue for future research.

关键词： Van der Pol-Helmholtz-Duffing oscillator fractal space time-delay non-perturbative approach stability analysis El-Dib's frequency formula