检索结果-南通市图书馆

free vibration and transient response of double curved beams connected by intermediate straight beams

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2025年第1期46卷 37-62页

作者： r.A.JAfArI-TALOOKOLAEI H.GHANDVAr E.JUMAEV S.KHATIr T.CUONG-LE School of Mechanical Engineering Babol Noshirvani University of Technology Department of Mechanical Engineering Faculty of Engineering New Uzbekistan University University of Business and Science Center for Engineering Application and Technology Solutions Ho Chi Minh City Open University

This paper investigates the free vibration and transient response of interconnected structures including double curved beams and intermediate straight beams,which are all constructed from functionally graded porous(fGP) materials. The strain potential and kinetic energies of each beam along with the work done by the external force are calculated. Additionally, a higher-order beam element is introduced to derive stiffness and mass matrices, along with the force vector. The curved and straight beams are discretized, and their assembled stiffness, mass matrices, and force vectors, are *** conditions at the joints are used to derive the total matrices of the entire structure. Subsequently, the natural frequencies and transient response of the system are determined. The accuracy of the mathematical model and the self-developed computer program is validated through the comparison of the obtained results with those of the existing literature and commercial software ANSYS, demonstrating excellent ***, a comprehensive study is conducted to investigate the effects of various parameters on the free vibration and transient response of the considered structure.

关键词：

Nonlinear vibration analysis of fractional viscoelastic Euler–Bernoulli nanobeams based on the surface stress theory

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2017年第4期30卷 416-424页

作者： M.faraji Oskouie r.Ansari f.Sadeghi Department of Mechanical Engineering University of Guilan

The nonlinear vibrations of viscoelastic Euler-Bernoulli nanobeams are studied using the fractional calculus and the Gurtin-Murdoch theory. Employing Hamilton＇s principle, the governing equation considering surface effects is derived. The fractional integro-partial differential governing equation is first converted into a fractional-ordinary differential equation in the time domain using the Galerkin scheme. Thereafter, the set of nonlinear fractional time-dependent equations expressed in a state-space form is solved using the predictorcorrector method. finally, the effects of initial displacement, fractional derivative order, viscoelasticity coefficient, surface parameters and thickness-to-length ratio on the nonlinear time response of simply-supported and clamped-free silicon viscoelastic nanobeams are investigated.

关键词： fractional calculus Viscoelastic nanobeam Nonlinear vibrations

N-methyl-D-aspartate receptor functions altered by neuronal PTP1B activation in Alzheimer’s disease and schizophrenia models

在线全文

学校读者我要写书评

暂无评论

Neural regeneration research 2022年第10期17卷 2208-2210页

作者： Alexandre f.r.Stewart Hsiao-Huei Chen Department of Biochemistry Microbiology and ImmunologyUniversity of Ottawaand University of Ottawa Heart InstituteOttawaONCanada Centre for Infection Immunity and InflammationOttawaONCanada Medicine Cellular and Molecular MedicineUniversity of Ottawa Brain and Mind InstituteOttawa Hospital Research InstituteOttawaONCanada

Glutamate is the main exc i tatory neurotransmitter in the brain and binds to two major classes of receptors,theα-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid(AMPA)and the N-methyl-D-aspartate(NMDA)*** AMPA receptors that are immediately activated by glutamate release,NMDA receptors are blocked by magnesium and can only be activated by glutamate after membrane ***,NMDA receptors are only activated after repeated AMPA receptor activation by *** receptors are,for the most part,calcium-permeable *** influx through NMDA receptors modulates synaptic transmission in neurons based on prior history of excitation,and provides a means of scaling the strength of synapses required for Hebbian plasticity.

关键词： PTP1B aspartate NMDA

Damage detection on framed structures: modal curvature evaluation using Stockwell Transform under seismic excitation

在线全文

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2015年第2期14卷 265-274页

作者： r.Ditommaso f.C.Ponzo G.Auletta Department of Structures Geotechnics Engineering Geology University of Basilicata School of Engineering University of Basilicata

The key parameters for damage detection and localization are eigenfrequencies, related equivalent viscous damping factors and mode shapes. The classical approach is based on the evaluation of these structural parameters before and after a seismic event, but by using a modern approach based on time-frequency transformations it is possible to quantify these parameters throughout the ground shaking phase. In particular with the use of the S-Transform, it is possible to follow the temporal evolution of the structural dynamics parameters before, during and after an earthquake. In this paper, a methodology for damage localization on framed structures subjected to strong motion earthquakes is proposed based on monitoring the modal curvature variation in the natural frequency of a structure. Two examples of application are described to illustrate the technique: Computer simulation of the nonlinear response of a model, and several laboratory(shaking table) tests performed at the University of Basilicata(Italy). Damage detected using the proposed approach and damage revealed via visual inspections in the tests are compared.

关键词： damage detection S-transform band-variable fi lter

Band structure,fermi surface,elastic,thermodynamic,and optical properties of AlZr3,AlCu3,and AlCu2Zr:first-principles study

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2016年第8期25卷 103-112页

作者： Parvin r Parvin f Ali M S Islam A K M A Department of Physics Rajshahi University Rajshahi-6205 Bangladesh Department of Physics Pabna University of Science and Technology Pabna 6600 Bangladesh International Islamic University Chittagong 154/A College Road Chittagong-4203 Bangladesh

The electronic properties（fermi surface,band structure,and density of states（DOS）） of Al-based alloys AlM3（M=Zr and Cu） and AlCu2Zr are investigated using the first-principles pseudopotential plane wave method within the generalized gradient approximation（GGA）.The structural parameters and elastic constants are evaluated and compared with other available ***,the pressure dependences of mechanical properties of the compounds are *** temperature dependence of adiabatic bulk modulus,Debye temperature,specific heat,thermal expansion coefficient,entropy,and internal energy are all obtained for the first time through quasi-harmonic Debye model with phononic effects for T = 0 K-100 *** parameters of optical properties（dielectric functions,refractive index,extinction coefficient,absorption spectrum,conductivity,energy-loss spectrum,and reflectivity） of the compounds are calculated and discussed for the first *** reflectivities of the materials are quite high in the Ir-visible-UV region up to ~ 15 eV,showing that they promise to be good coating materials to avoid solar *** of the properties are also compared with those of the Al-based Ni3 Al compound.

关键词： first principle calculations fermi surface elastic moduli entropy and internal energy optical properties

field-induced phase transitions in chiral smectic liquid crystals studied by the constant current method

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2016年第5期25卷 373-379页

作者： H Dhaouadi r Zgueb O riahi f Trabelsi T Othman Departement de physiqu Faculte des Sciences de Tunis Laboratoire de physique de la matiere molle et de modelisation electromagnetique (LP3ME) Universite Tunis Elmanar Campus universitaire 2092 Tunis Tunisia

In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the（E, T） phase diagram of the studied product can be *** this work, we make a slight modification to the measurement principles based on this method. This modification allows the characteristic parameters of ferroelectric liquid crystal to be quantitatively measured. The use of a current square signal highlights a phenomenon of ferroelectric hysteresis with remnant polarization at null field, which points out an effect of memory in this compound.

关键词： chiral smectic liquid crystal constant current method ferroelectric polarization dielectric permittivity

Effects of Strain rate and Deformation Temperature on Microstructures and Hardness in Plastically Deformed Pure Aluminum

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2011年第1期27卷 1-7页

作者： f. Huang N.r. Taot K. Lu Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang110016 China

The microstructures and hardness of pure Al samples subjected to plastic deformation with different tem- peratures and strain rates were investigated. The results showed that the strain-induced grain refinement is significantly benefited by increasing strain rate and reducing deformation temperature. The saturated size of refined subgrains in Al can be as small as about 240 nm in cryogenic dynamic plastic deformation （DPD）. Grain boundaries of the DPD Al samples are low-angle boundaries due to suppression of dynamic recovery during deformation. Agreement of the measured hardness with the empirical Hall-Petch relation extrapolated from the coarse-grained Al implies that the low-angle boundaries can contribute to strengthening as effective as the conventional grain boundaries.

关键词： Dynamic plastic deformation Microstructure Hardness Strain rate Temperature

Social interactivity in pigeon courtship behavior

在线全文

学校读者我要写书评

暂无评论

Current Zoology 2017年第1期63卷 85-95页

作者： Emma L.r. WArE Daniel r. SAUNDErS Nikolaus f, TrOJE Department of Psychology Queen's University Kingston Ontario K7L 3N6 Canada Centre for Neuroscience Studies Queen's University Kingston Ontario K7L 3N6 Canada Wellesley Institute Toronto Ontario M4V 3B Canada Centre for Brain/Mind Sciences University of Trento Trento Italy Department of Biology Queen's University Kingston K7L 3N6 Canada

A closed-loop teleprompter system was used to isolate and manipulate social interactivity in thenatural courtship interactions of pigeons Columbia livia. In Experiment 1, a live face-to-face real-time interaction between 2 courting pigeons （Live） was compared to a played back version of thevideo stimulus recorded during the pairs Live interaction. We found that pigeons were behavinginteractively; their behavior depended on the relationships between their own signals and those oftheir partner. In Experiment 2, we tested whether social interactivity relies on spatial cues presentin the facing direction of a partner＇s display. By moving the teleprompter camera 90~ away from itsoriginal location, the partner＇s display was manipulated to appear as if it is directed 90~ away fromthe subject. We found no effect of spatial offset on the pigeon＇s behavioral response. In Experiment3, 3 time delays, 1 s, 3s, and 9s, a Live condition, and a playback condition were chosen to investi-gate the importance of temporal contiguity in social interactivity. furthermore, both opposite-sex（courtship） and same-sex （rivalry） pairs were studied to investigate whether social-context affectssocial interactivity sensitivity. Our results showed that pigeon courtship behavior is sensitive totemporal contiguity. Behavior declined in the 9 s and Playback conditions as compared to Live con-dition and the shorter time delays. for males only, courtship behavior also increased in the 3-sdelay condition. The effect of social interactivity and time delay was not observed in rivalry inter-actions, suggesting that social interactivity may be specific to courtship.

关键词： courtship behavior, pigeons, social interactivity, spatial offset, time delay, video playback.

A strategy for designing stable nanocrystalline alloys by thermo-kinetic synergy

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2020年第8期36卷 21-31页

作者： H.r.Peng B.S Liu f.Liu State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an710072China School of Materials and Chemical Engineering Xi’an Technological UniversityXi’an710021China Analytical and Testing Center Northwestern Polytechnical UniversityXi’an710072China

Aiming to design stable nanocrystalline(NC)materials,so far,it has been proposed to construct nanostructure stability maps in terms of thermodynamic parameters,while kinetic stabilization has seldom been considered,despite the synergy of thermodynamics and ***,the thermodynamically stabilized NC materials may be easily subjected to grain growth at high temperatures due to the weakly kinetic *** from the thermo-kinetic synergy,a stabilization criterion is proposed as a function of intrinsic solute parameters(*** activation energy for bulk diffusion and the segregation enthalpy),intrinsic solvent parameters(*** intrinsic activation energy for GB migration and the GB energy)and processing parameters(*** grain size,the temperature and the solute concentration).Using first-principles calculations for a series of combinations between fifty-one substitutional alloying atoms as solute atoms and fe atom as fixed solvent atom,it is shown that the thermal stability neither simply increases with increasing the segregation enthalpy as expected by thermodynamic stabilization,nor monotonically increases with increasing the activation energy for bulk diffusion as described by kinetic *** combination of thermodynamic and kinetic contributions,the current stabilization criterion evaluates quantitatively the thermal stability,thus permitting convenient comparisons among NC materials involved by various combinations of the solute atoms,the solvent atoms,or the processing *** of this thermo-kinetic stabilization criterion has been tested by current experiment results of fe-Y alloy and previously published data of fe-Ni,fe-Cr,fe-Zr and fe-Ag alloys,etc.,which opens a new window for designing NC materials with sufficiently high thermal stability and sufficiently small grain size.

关键词： Thermo-kinetic Synergy Criterion Thermal stability Nanocrystalline materials