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Numerical study of viscosity and heat flux role in heavy species dynamics in Hall thruster discharge

Plasma Science and Technology 2023年第1期25卷 165-180页

作者： andrey shashkov Alexander LOVTSOV Dmitri TOMILIN Dmitrii KRAVCHENKO JSC'Keldysh Research Center' 8 Onezhskaya st.Moscow 125438Russia

A two-and three-dimensional velocity space axisymmetric hybrid-PIC model of Hall thruster discharge called Hybrid2D has been *** particle-in-cell(PIC) method was used for neutrals and ions(heavy species),and fluid dynamics on a magnetic field-aligned(MFA) mesh was used for electrons.A time-saving method for heavy species moment interpolation on a MFA mesh was *** method comprises using regular rectangle and irregular triangle meshes,connected to each other on a pre-processing *** electron fluid model takes into account neither inertia terms nor viscous terms and includes an electron temperature equation with a heat flux *** developed model was used to calculate all heavy species moments up to the third one in a stationary *** analysis of the viscosity and the heat flux impact on the force and energy balance has shown that for the calculated geometry of the Hall thruster,the viscosity and the heat flux terms have the same magnitude as the other terms and could not be ***,it was shown that the heat flux is not proportional to the temperature gradient and,consequently,the highest moments should be calculated to close the neutral fluid equation *** the same time,ions can only be modeled as a cold non-viscous fluid when the sole aim of modeling is the calculation of the operating parameters or distribution of the local parameters along the centerline of the discharge *** is because the magnitude of the viscosity and the temperature gradient terms are negligible at the ***,when a simulation’s focus is either on the radial divergence of the plume or on magnetic pole erosion,three components of the ion temperature should be taken into *** non-diagonal terms of ion pressure tensor have a lower impact than the diagonal *** to the study,a zero heat flux condition could be used to close the ion equation system in calculated geometry.

关键词： Hall thruster hybrid-PIC model moments of distribution function magnetic-field-aligned mesh

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Machine learning-based method to adjust electron anomalous conductivity profile to experimentally measured operating parameters of Hall thruster

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Plasma Science and Technology 2022年第6期24卷 148-156页

作者： andrey shashkov Mikhail TYUSHEV Alexander LOVTSOV Dmitry TOMILIN Dmitrii KRAVCHENKO JSC'Keldysh Research Center' 8 Onezhskaya St.Moscow 125438Russia

The problem of determining the electron anomalous conductivity profile in a Hall thruster,when its operating parameters are known from the experiment,is *** solve the problem,we propose varying the parametrically set anomalous conductivity profile until the calculated operating parameters match the experimentally measured ones in the best *** axial 1D3V hybrid model was used to calculate the operating parameters with parametrically set *** of the conductivity profile was performed using Bayesian optimization with a Gaussian process(machine learning method),which can resolve all local minima,even for noisy *** calculated solution corresponding to the measured operating parameters of a Hall thruster in the best way proved to be unique for the studied operating modes of *** local plasma parameters were calculated and compared to the measured ones for four different operating *** results show the qualitative *** agreement between calculated and measured local parameters can be improved with a more accurate model of plasma-wall interaction.

关键词： Hall thruster anomalous conductivity machine learning Bayesian optimization Gaussian process electric propulsion

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Surface bioactivation of PEEK by neutral atom beam technology

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Bioactive Materials 2019年第1期4卷 132-141页

作者： Joseph Khoury Irina Selezneva Sergei Pestov Vadim Tarassov Artem Ermakov andrey Mikheev Mikhail Lazov Sean R.Kirkpatrick Dmitry shashkov Alexandre Smolkov Exogenesis Corporation BillericaMAUSA Institute of Theoretical and Experimental Biophysics Russian Academy of SciencesPushchinoMoscow RegionRussia MIREA–Russian Technological University MoscowRussia OAO Technotransservice Engineering MoscowRussia

Polyetheretherketone(PEEK)is an alternative to metallic implants and a material of choice in many applications,including orthopedic,spinal,trauma,and *** titanium(Ti)and Ti-alloys are widely used in many intraosseous implants due to its biocompatibility and ability to osseointegrate,negatives include stiffness which contributes to shear stress,radio-opacity,and *** surgeons prefer to use PEEK due to its biocompatibility,similar elasticity to bone,and radiolucency,however,due to its inert properties,it fails to fully integrate with *** Neutral Atom Beam(ANAB)technology has been successfully employed to demonstrate enhanced bioactivity of PEEK both in vitro and in *** this study,we further characterize surfaces of PEEK modified by ANAB as well as elucidate attachment and genetic effects of dental pulp stem cells(DPSC)exposed to these *** modification resulted in decreased contact angle at 72.9±4.5°as compared to 92.4±8.5°for control(p<0.01)and a decreased average surface roughness,however with a nano-textured surface *** treatment also increased the ability of DPSC attachment and proliferation with considerable genetic differences showing earlier progression towards osteogenic *** surface modification is achieved without adding a coating or changing the chemical composition of the PEEK *** together,we show that ANAB processing of PEEK surface enhances the bioactivity of implantable medical devices without an additive or a coating.

关键词： PEEK neutral activation

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