Search results for "Linear system"

showing 10 items of 1558 documents

Linear and nonlinear fractional hereditary constitutive laws of asphalt mixtures

2016

The aim of this paper is to propose a fractional viscoelastic and viscoplastic model of asphalt mixtures using experimental data of several tests such as creep and creep recovery performed at different temperatures and at different stress levels. From a best fitting procedure it is shown that both the creep one and recovery curve follow a power law model. It is shown that the suitable model for asphalt mixtures is a dashpot and a fractional element arranged in series. The proposed model is also available outside of the linear domain but in this case the parameters of the model depend on the stress level.

Materials scienceasphalt mixtureStrategy and Managementcreep test0211 other engineering and technologies02 engineering and technologyfractional calculusPower lawcreep test.ViscoelasticityDashpot0203 mechanical engineering021105 building & constructionSettore ICAR/04 - Strade Ferrovie Ed AeroportiComposite materialviscoplasticityviscoelasticityCivil and Structural EngineeringBuilding constructionmechanical modelsViscoplasticityMechanicsmechanical modelFractional calculusfractional calculus asphalt mixture viscoelasticity viscoplasticity rheology mechanical models creep testfractional calculuNonlinear system020303 mechanical engineering & transportsCreepAsphaltrheologyTH1-9745
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Simple equations for strength and deformability verification of tubular steel wind turbine towers

2021

Abstract Simple analytical expressions for a preliminary design of tubular steel wind turbine towers under flexure and shear are proposed. Expressions derived included local buckling effects, shear to moment interaction, ovalization of cross-section and inelastic rotation of foundation. A finite-element analysis with ABAQUS program was also conducted for examination of the ovalization effects and for the whole response of steel tube in flexure. Numerical and analytical results were compared with the experimental results of recent studies available in the literature, showing good agreement. The range of variable investigated refers to medium and large size steel wind tower with cylindrical s…

Materials sciencebusiness.industry0211 other engineering and technologiesFoundation (engineering)020101 civil engineering02 engineering and technologyStructural engineeringTurbineFinite element method0201 civil engineeringShear (sheet metal)Moment (mathematics)Nonlinear systemBuckling021105 building & constructionbusinessTowerCivil and Structural EngineeringEngineering Structures
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Enhanced Nonlinear Optical Coefficients of MAPbI3 Thin Films by Bismuth Doping

2020

The poor photostability under ambient conditions of hybrid halide perovskites has hindered their recently explored promising nonlinear optical properties. Here, we show how Bi3+ can partially substitute Pb2+ homogeneously in the commonly studied MAPbI3, improving both environmental stability and photostability under high laser irradiation. Bi content around 2 atom % produces thin films where the nonlinear refractive (n2) and absorptive coefficients (β), which modify the refractive index (Δn) of the material with light fluence (I), increase up to factors of 4 and 3.5, respectively, compared to undoped MAPbI3. Higher doping inhibits the nonlinear parameters; however, the samples show higher f…

Materials sciencebusiness.industryDopingHalideLaserFluencelaw.inventionNonlinear systemlawOptoelectronicsGeneral Materials ScienceIrradiationPhysical and Theoretical ChemistryThin filmbusinessRefractive indexThe Journal of Physical Chemistry Letters
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Proton exchanged waveguides in LiNbO<inline-formula><sub>3</sub></inline-formula> and LiTaO<inline-formula><sub>3…

1998

Materials sciencebusiness.industryGeneral Engineeringchemistry.chemical_elementNonlinear opticsNonlinear crystalsConvertersLaserNeodymiumAtomic and Molecular Physics and Opticslaw.inventionNonlinear systemOpticschemistrylawbusinessOptical Engineering
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An Improved Thermal Lamination Model for Analysis of Heat Transfer in Composite Structures

2002

A new thermal lamination model and its associated finite element model are presented for analysis of heat transfer in laminated composite structures. The form of the present model closely resembles that of recent zig-zag sublaminate structural laminate theories. The through-thickness distribution of temperature is assumed to vary linearly within each ply, and continuity of transverse flux at ply interfaces is enforced analytically. Thus, the number of computational degrees-offreedom (DOFs) is made independent of the number of plies in the sublaminate. In its present form, the model contains only two computational DOFs in each sublaminate–the temperature at the top and bottom surface of the…

Materials sciencebusiness.industryMechanical EngineeringNumerical analysisComposite number02 engineering and technologyStructural engineeringLamination (topology)021001 nanoscience & nanotechnologyFinite element methodSettore ING-IND/14 - Progettazione Meccanica E Costruzione Di MacchineNonlinear system020303 mechanical engineering & transports0203 mechanical engineeringMechanics of MaterialsThermalHeat transferMaterials ChemistryCeramics and CompositesDevelopment (differential geometry)composite numerical model0210 nano-technologybusinessJournal of Composite Materials
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Phase-matching measurements and Sellmeier equations over the complete transparency range of KTiOAsO_4, RbTiOAsO_4, and CsTiOAsO_4

2000

The sphere method is used for the direct measurement of sum- and difference-frequency generation phase matched in the principal planes of KTiOAsO4, RbTiOAsO4, and CsTiOAsO4, including the tuning curves of 1.064-µm-pumped OPO’s emitting between 3 and 5 µm. The nonlinear least-squares fitting of our experimental data leads to refined dispersion equations of the principal refractive indices; the resulting dual-oscillator form equations are valid over the complete transparency range of the three studied materials.

Materials sciencebusiness.industryPhase (waves)Statistical and Nonlinear PhysicsNonlinear optical crystalAtomic and Molecular Physics and OpticsNonlinear systemOpticsDispersion (optics)Range (statistics)Transparency (data compression)businessRefractive indexPhase matchingJournal of the Optical Society of America B
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Toward Metal Halide Perovskite Nonlinear Photonics.

2018

The possibility of controlling light using the nonlinear optical properties of photonic devices opens new points of view in information and communications technology applications. In this Perspective, we review and analyze the potential role of metal halide perovskites in a framework different from their usual one in photovoltaic and light-emitting devices, namely, the one where they can play as nonlinear photonic materials. We contextualize this new role by comparing the few extant results on their nonlinear optical properties to those of other known nonlinear materials. As a result of this analysis, we provide a vision of future developments in photonics that can be expected from this new…

Materials sciencebusiness.industryPhotovoltaic systemPhysics::OpticsHalide02 engineering and technology021001 nanoscience & nanotechnology01 natural sciencesEngineering physicsPhotonic metamaterial010309 opticsNonlinear systemNonlinear opticalExtant taxon0103 physical sciencesGeneral Materials SciencePhysical and Theoretical ChemistryPhotonics0210 nano-technologybusinessPerovskite (structure)The journal of physical chemistry letters
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Effect of structure relaxation on the holographic recording in amorphous As2S3 films

1997

Abstract Results of the experimental studies of holographic recording in a-As 2 S 3 films, such as exposure and intensity dependences, spatial frequency dependence, are reported. Several peculiarities are found including recording intensity threshold, nonmonotonical intensity dependences, nonlinear exposure curves, the change of the spatial frequency response due to film aging. These peculiarities are explained in terms of the phenomenological model which is based on the simultaneous action of the photostructural changes and the relaxational structural changes.

Materials sciencebusiness.industryRelaxation (NMR)Atomic and Molecular Physics and OpticsElectronic Optical and Magnetic MaterialsAmorphous solidNonlinear systemOpticsPhenomenological modelsense organsSpatial frequencyElectrical and Electronic EngineeringPhysical and Theoretical Chemistryskin and connective tissue diseasesbusinessHolographic recordingIntensity (heat transfer)Optics Communications
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Multimodal nonlinear imaging of suspended carbon nanotubes using circular polarizations

2013

In this work, multimodal nonlinear microscopy of suspended CNTs using circular polarizations (CP) was reported. Significant variations in the SHG and THG signals of the CNTs between left hand circular polarization (LHCP) and right hand circular polarization (RHCP) were observed. The variations in the nonlinear signals can be associated to the unique properties of the CNTs such as chirality.

Materials sciencebusiness.industryScanning electron microscopePhysics::Medical PhysicsNanophotonicsSecond-harmonic generationCarbon nanotubeChirality (electromagnetism)law.inventionCondensed Matter::Materials ScienceNonlinear systemOpticsOptical microscopelawOptoelectronicsbusinessCircular polarization2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE/IQEC
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Thermal imaging in artificial nonlinear media

1997

A method has been developed to determine the temperature distribution of ferroelectric surfaces and volumes. Based on the nonlinear optical effect of second harmonic generation (SHG) in highly nonlinear ferroelectric coating, demonstration of 2D thermosensing has been performed in the wide temperature range (77 K - 600 K). Physical concept of SHG thermal imaging, design of thermosensitive coating and experimental verification of the method has been discussed.

Materials sciencebusiness.industrySecond-harmonic generationengineering.materialAtmospheric temperature rangeFerroelectricityNonlinear systemOpticsCoatingThermographyThermalengineeringbusinessRefractive indexSPIE Proceedings
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