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Cross-focusing of two chirped Gaussian laser beams and THz wave generation in plasmas of multi-ion species under a weakly relativistic and ponderomotive regime

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Plasma Science and Technology 2022年第10期24卷 1-11页

作者： M r jafari MILANI S rEZAEI M J jafari Photonics and Quantum Technologies research School Nuclear Science and Technology Research InstituteTehran 14665-678Iran Plasma and Fusion research School Nuclear Science and Technology Research InstituteTehran 14399-51113Iran

The generation of terahertz(THz)waves via the beating of two high-intensity chirped Gaussian lasers in a multi-ion-species plasma is numerically studied by taking into account the weak relativistic and ponderomotive regime of *** coupled differential equations for beamwidth parameters are extracted by introducing the dielectric function of such plasma and using WKB and paraxial ray *** amplitude of THz radiation at beat frequency resulting from the nonlinear current density induced by the beat ponderomotive force of the cross-focusing of beams was *** impacts of the chirp frequency parameter,initial laser intensity and initial ionic species density(specifically,the presence of singly and doubly charged ions)in the plasma on THz generation were *** numerical results reveal that THz radiation generation strongly depends on the chirp frequency parameter.A specific range of chirp frequencies exists for self-focusing as well as THz generation with a'turning point',where the THz emission reaches its maximum *** results show that the strength of self-focusing and consequently the generated THz radiation are reduced by increasing the density of doubly charged ionic species in the plasma due to the suppression of the nonlinear effects.

关键词： laser–plasma interaction THz generation chirped Gaussian laser beams

Intermetallic growth behavior during post deformation annealing in multilayer Ti/Al/Nb composite interfaces

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International Journal of Minerals,Metallurgy and Materials 2022年第8期29卷 1608-1617页

作者： r.jafari B.Eghbali Department of Materials Engineering Faculty of EngineeringUrmia UniversityP.O.Box 57561-165UrmiaIran Faculty of Materials Engineering Sahand University of TechnologyP.O.Box 51335-1996TabrizIran

The tri-metal Ti-Al-Nb composites were processed through three procedures:hot pressing,rolling,and hot pressing,followed by subsequent *** fabricated composites were then subjected to annealing at 600,625,and 650℃ temperatures at different *** observation at the interfaces reveals that the increase in plastic deformation strain significantly affects TiAl_(3) intermetallic layers’evolution and accelerates the layers’*** the contrary,the amount of applied strain does not significantly affect the evolution of the NbAl_(3) intermetallic layer *** was also found that Al and Ti atoms’diffusion has occurred throughout the TiAl_(3) layer,but only Al atoms diffuse through the NbAl_(3) *** slow growth rate of the NbAl_(3) intermetallic layer is due to the lack of diffusion of Nb atoms and the high activation energy of Al atoms’reaction with Nb atoms.

关键词： intermetallic compounds diffusion Ti/Al/Nb composite deformation annealing

Non-harmonic resonance of viscoelastic structures subjected to time-dependent exponentially decreasing transverse distributed loads

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Earthquake Engineering and Engineering Vibration 2023年第3期22卷 825-840页

作者： Nasrin jafari Department of Civil Engineering Isfahan University of TechnologyIsfahan 84156-83111Iran

In this paper,the non-harmonic resonance of Bernoulli viscoelastic beams,Kirchhoff viscoelastic plates,Timoshenko viscoelastic beams,and Mindlin viscoelastic plates subjected to time-dependent exponentially decreasing transverse distributed load is investigated for the first *** constitutive equations are expressed utilizing Boltzmann integral law with a constant bulk *** displacement vector is approximated by employing the separation of variables *** Laplace transformation is used to transfer equations from the time domain to the Laplace domain and vice *** novel point of the proposed method is to express,prove and calculate the critical time in which the displacement will be several times the displacement at time *** addition,this new method calculates the maximum deflection at the critical time,explicitly and exactly,without any need to follow the time-displacement curve with a low computational ***,the proposed method introduces the critical range of time so that the responses are greater than the responses at time zero.

关键词： Bernoulli and Timoshenko viscoelastic beams critical time non-harmonic resonance time-dependent decreasing exponential load Kirchhoff and Mindlin viscoelastic plates

A non-fluorinated mechanochemically robust volumetric superhydrophobic nanocomposite

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Journal of Materials Science & Technology 2021年第7期66卷 213-225页

作者： E.Vazirinasab G.Momen r.jafari Department of Applied Sciences University of Quebec in Chicoutimi(UQAC)555boul.de I'universiteChicoutimiQuebecG7H 2B1Canada

The widespread use of water-repellent superhydrophobic surfaces is limited by the inherent fragility of their micro-and nanoscale roughness, which is prone to damage and degradation. Here, we report a non-fluorinated volumetric superhydrophobic nanocomposites that demonstrate mechanochemical robustness. The nanocomposites are produced through the addition of microscale diatomaceous earth and nanoscale fumed silica particles to high-temperature vulcanized silicone rubber. The water-repellency of the surface and bulk of nanocomposites having 120 phr of filler was determined based on the water contact angle and contact angle hysteresis. We compared the water-repellency of nanocomposites of differing diatomaceous earth to fumed silica mass ratios. Increasing the amount of diatomaceous earth enhanced the water-repellency of the nanocomposite surface, whereas an increased amount of fumed silica improved the water-repellency of the bulk material. Moreover, increasing the diatomaceous earth/fumed silica mass ratio improved the cross-linking density and hardness values of the *** being subjected to a range of mechanical durability tests, including sandpaper abrasion,knife scratching, tape peeling, water jet impact, and sandblasting, the nanocomposite maintained a water contact angle of 163. and contact angle hysteresis of 2°. When the water-repellency of the prepared nanocomposites eventually deteriorated, we restored their superhydrophobicity by removing the upper surface of the nanocomposite. This extraordinary robustness stems from the embedded low surface energy micro/nanostructures distributed throughout the nanocomposite. We also demonstrated the chemical stability, UV resistance, and self-cleaning abilities of the nanocomposite to illustrate the potential for real-life applications of this material.

关键词： Volumetric superhydrophobic Nanocomposite Diatomaceous earth Hierarchical micro/nanostructure Mechanical robustness Chemical stability Self-cleaning

Corrosion Behaviors of Two Types of Commercial Stainless Steel after Plastic Deformation

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Journal of Materials Science & Technology 2010年第9期26卷 833-838页

作者： Esmaeil jafari Materials Science and Engineering Department Islamic Azad University Shiraz Branch

The influence of deformation temperature,strain rate and alloying elements such as chromium,nickel,copper,on corrosion resistance of a 304 stainless steel after plastic deformation was *** techniques employed were tensile test at room and elevated temperature,deep drawing tests at various strain rates,X-ray diffraction test and potentiodynamic and cyclic polarization,metallography by optical and scanning electron *** showed that chromium,nickel and copper had a significant effect on corrosion resistance of steel after plastic *** was observed that corrosion resistance after plastic deformation was a function of deformation temperature and alloying elements.

关键词： Corrosion resistance Plastic deformation Stainless steel Phase transformation Polarization test

Introducing the general condition for an operator in curved space to be unitary

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Chinese Physics B 2021年第8期30卷 220-223页

作者： jafari Matehkolaee Mehdi Faculty of Physics Semnan UniversitySemnan35131-19111Iran

We investigate the general condition for an operator to be *** condition is introduced according to the definition of the position operator in curved *** a particular case,we discuss the concept of translation operator in curved space followed by its relation with an anti-Hermitian *** we introduce a universal formula for adjoint of an arbitrary linear *** procedure in this paper is totally different from others,as we explore a general approach based only on the algebra of the *** approach is only discussed for the translation operators in one-dimensional space and not for general operators.

关键词： operator theory algebraic methods unitary operator translation operator

Evaluation of the efficiency of irrigation methods on the growth and survival of tree seedlings in an arid climate

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Journal of Arid Land 2020年第3期12卷 495-507页

作者： Zahra jafari SayedHamid MATINKHAH Mohammad r MOSADDEGHI Mostafa TArKESH Department of Natural resources Isfahan University of TechnologyIsfahan ***Iran Department of Soil Science Department of AgricultureIsfahan University of TechnologyIsfahan ***Iran

Scarce and scattered precipitation in arid regions is detrimental for newly planted *** is essential to provide required water storage for seedlings in restoration projects in the first year of their *** subsurface irrigation can be much more effective than the surface irrigation because of the regulation of water availability and reduction in water *** studied the effect of surface and subsurface irrigation methods on the growth and survival of four common tree species including heaven tree(Ailanthus altissima(Mill.)Swingle),China berry(Melia azedarach L.),white mulberry(Morus alba L.),and black locust(robinia pseudoacacia L.)by installing underground clay reservoirs with different permeabilities in Isfahan City,*** amounts of animal manure and wheat straw were mixed with clay fraction and cooked in a pottery kiln at 900°C to produce reservoirs with different *** experimental treatments consisting of irrigation and tree species were considered with a factorial arrangement in a completely randomized design with three replications in 2016 and *** water potential of seedlings,which is indirectly related to drought resistance,was measured by a portable pressure *** results showed that saplings height,basal diameter,number of leaves,chlorophyll content and stomatal conductance were significantly(Pr in the subsurface irrigation with low permeability than in the surface irrigation,but the number of branches of the studied species were not significantly(P>0.05)affected by the irrigation methods and different permeabilities of clay *** clay reservoirs with low and medium permeabilities constantly provide better conditions for plant growth,and water with lower pressure and longer time intervals to the plant roots as compared with the reservoirs with high *** of variance of the data showed that year and interaction between year and permeability of reservoir had si

关键词： subsurface irrigation clay reservoirs permeability restoration arid area

Data driven models for compressive strength prediction of concrete at high temperatures

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Frontiers of Structural and Civil Engineering 2020年第2期14卷 311-321页

作者： Mahmood AKBArI Vahid jafari DELIGANI Department of Civil Engineering Faculty of EngineeringUniversity of KashanKashan ***Iran

The use of data driven models has been shown to be useful for simulating complex engineering processes,when the only information available consists of the data of the *** this study,four data-driven models,namely multiple linear regression,artificial neural network,adaptive neural fuzzy inference system,and K nearest neighbor models based on collection of 207 laboratory tests,are investigated for compressive strength prediction of concrete at high *** addition for each model,two different sets of input variables are examined:a complete set and a parsimonious set of involved *** results obtained are compared with each other and also to the equations of NIST Technical Note standard and demonstrate the suitability of using the data driven models to predict the compressive strength at high *** addition,the results show employing the parsimonious set of input variables is sufficient for the data driven models to make satisfactory results.

关键词： data driven model compressive strength oncrete high temperature

Investigation of parameters influencing erosive wear using DEM

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Friction 2020年第1期8卷 136-150页

作者： Akbar jafari reza ABBASI HATTANI Department of Mechanical Engineering Sirjan University of TechnologySirjan ***Iran

The effects of several parameters on the erosive wear were studied using the discrete element method(DEM).The Finnie model was implemented using an open‐source *** the time integration,the Gear algorithm was used,and to ensure the accuracy of the DEM results,a time‐step sensitivity analysis was *** problem was modeled in two parts:first,the impact of a single particle on a surface was modeled,and then a more general model was prepared to examine the wear of surfaces under the flow of *** effects of the surface area,impact angle,speed,particle size,particle density,Young’s modulus,Poisson’s ratio,and restitution coefficient on the wear were studied numerically,and the results are discussed herein.

关键词： wear erosion Finnie discrete element