检索结果-南通市图书馆

Growth of skyrmionic MnSi nanowires on Si： Critical importance of the SiO2 layer

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

Nano Research 2014年第12期7卷 1788-1796页

作者： Siwei Tang ivan kravchenko Jieyu Yi Guixin cao Jane Howe David Mandrus Zheng Gai Department of Materials Science and Engineering University of Tennessee Knoxville TN 37996 USA Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge TN 37831 USA Hitachi High Technologies inc. Rexdale ON M9W 6A4 Canada

MnSi in the B20 structure is a prototypical helimagnet that forms a skyrmion lattice, a vortex-like spin texture under applied magnetic field. We have systematically explored the synthesis of single crystal MnSi nanowires via controlled oxide-assisted chemical vapor deposition and observed a characteristic signature of skyrmion magnetic ordering in the MnSi nanowires. The thickness of the SiO2 layer on the Si substrate plays the key role in obtaining a high yield of B20 MnSi skyrmion nanowires. A growth mechanism was proposed that is consistent with the existence of an optimum SiO2 thickness. A growth phase diagram was constructed based on the extensive studies of various growth conditions for various MnSi nanostructures. The persistence of both the helicoidal and skyrmion magnetic ordering in the one-dimensional wires was directly revealed by ac and dc magnetic measurements.

关键词： skyrmion spintronics oxide-assisted growth nanowires magnetic materials

ON THE EXPERiMENTAL iNVESTiGATiON OF AiR—BREATHiNG ENGiNE OF NEW SCHEMES

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

Chinese Journal of Aeronautics 1992年第1期 1-4页

作者： Bakulev V i.kravchenko i V Moscow Aviation institute

The use of hydrogen as the fuel of hybrid engine has a high value of specificparameters and wide prospect in the future in aerospace field. Three schemes of this kindof engine are proposed in this paper: （1）《The First-borne》 turbo-rocket engine withgasified and pre—heated （in heat exchanger） hydrogen as a working fluid of turbine. （2）The gas generator hydrogen bypass turbo-jet engine with an afterburner. （3） The enginewith the same above scheme but having an additional heat exchanger behind *** throttle characteristic of 《First-borne》 scheme of engine has been tested by usinga small-size engine on a special test rig and equipment. The investigation results showthat the performance of this engine under F= const, Tc（?）ch= Const, FThroat= Var programeof regulation is most *** addition, the variation of specific thrust Pspec, specific fuel consumption Cspecandthrust P are shown and explained.

关键词： area BREATHiNG ENGiNE OF NEW SCHEMES ON THE EXPERiMENTAL iNVESTiGATiON OF AiR line

Dusty Sheaths in Magnetized Plasmas

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Plasma Science and Technology 2004年第4期6卷 2377-2382页

作者： Yu.i.Chutov O.Yu.kravchenko S.Masuzaki A.Sagara R.D.Smirnov Yu.Tomita Taras Shevchenko Kiev University KievUkraineTaras Shevchenko Kiev UniversityKievUkraineNational Institute for Fusion ScienceJapanNational Institute for Fusion ScienceJapanThe Graduate University for Advanced StudiesJapanNational Institute for Fusion ScienceJapan

Parameters of self-consistent magnetized dusty sheaths are investigated usingcomputer simulations of a temporal evolution of one-dimensional slab plasma with dust *** evolution is caused by a collection of electrons and ions by both a wall (electrode) and dustparticles, which are initially immersed into plasma and distributed in front of the *** results show the existence of oscillations of a self-consistent potential in magnetizeddusty sheaths including boundary potentials. Dust particles weaken magnetized sheaths and createadditional sheaths close to a boundary of dust particles. The magnetic field does not influence onthe dust particle charge.

关键词： dusty sheaths magnetized plasmas computer simulations

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

在线全文

学校读者我要写书评

暂无评论

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

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

在线全文

学校读者我要写书评

暂无评论

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

Dynamic changes in microbial activity and community structure during biodegradation of petroleum compounds:A laboratory experiment

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2007年第8期19卷 1003-1013页

作者： Li Hui ZHANG Ying kravchenko irina XU Hui ZHANG Cheng-gang Key Laboratory of Terrestrial Ecological Processes Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China. Winogradsky institute of Microbiology Russian Academy of Sciences Moscow 117312 Russia

With 110-d incubation experiment in laboratory, the responses of microbial quantity, soil enzymatic activity, and bacterial community structure to different amounts of diesel fuel amendments were studied to reveal whether certain biological and biochemical characteristics could serve as reliable indicators of petroleum hydrocarbon contamination in meadow-brown soil, and use these indicators to evaluate the actual ecological impacts of 50-year petroleum-refining wastewater irrigation on soil function in Shenfu irrigation area. Results showed that amendments of ~ 1000 mg/kg diesel fuel stimulated the growth of aerobic heterotrophic bacteria, and increased the activity of soil dehydrogenase, hydrogenperoxidase, polyphenol oxidase and substrate-induced respiration. Soil bacterial diversity decreased slightly during the first 15 d of incubation and recovered to the control level on day 30. The significant decrease of the colony forming units of soil actinomyces and filamentous fungi can be taken as the sensitive biological indicators of petroleum contamination when soil was amended with 〉15000 mg/kg diesel fuel. The sharp decrease in urease activity was recommended as the most sensitive biochemical indicator of heavy diesel fuel contamination. The shifts in community structure to a community documented by Sphingomonadaceae within a-subgroup of Proteobacteria could be served as a sensitive and precise indicator of diesel fuel contamination. Based on the results described in this paper, the soil function in Shenfu irrigation area was disturbed to some extent.

关键词： petroleum hydrocarbons enzymatic activity bacterial diversity microbial community structure DGGE

New WA-system of kravchenko functions in digital signal processing

在线全文

学校读者我要写书评

暂无评论

Journal of Measurement Science and instrumentation 2012年第4期3卷 345-351页

作者： V F kravchenko D V Churikov Kotel'nikov institute of Radio Engineering and Electronics Russian Academy of Sciences

On the basis of modified atomic transformations the new WA-systems of kravchenko functions are *** an example the digital processing of time series of the various physical nature processing is *** numerical experiment... 详细信息

关键词： atomic functions WA-systems of functions wavelets digital signal processing(DSP)

Topology-empowered membrane devices for terahertz photonics

在线全文

学校读者我要写书评

暂无评论

Advanced Photonics 2022年第4期4卷 29-37页

作者： Quanlong Yang Dongyang Wang Sergey Kruk Mingkai Liu ivan kravchenko Jiaguang Han Yuri Kivshar ilya Shadrivov Australian National University Nonlinear Physics CentreResearch School of PhysicsCanberra ActonAustralia Central South University School of Physics and ElectronicsChangshaChina The Hong Kong University of Science and Technology Department of PhysicsHong KongChina Center for Nanophase Materials Sciences Oak Ridge National LaboratoryOak RidgeTennesseeUnited States Tianjin University Center for Terahertz Waves and College of Precision Instrument and Optoelectronics EngineeringTianjinChina

Control of terahertz waves offers a profound platform for next-generation sensing,imaging,and information ***,all conventional terahertz components and systems suffer from bulky design,sensitivity to imperfections,and transmission *** propose and experimentally demonstrate onchip integration and miniaturization of topological devices,which may address many existing drawbacks of the terahertz *** design and fabricate topological devices based on valley-Hall photonic structures that can be employed for various integrated components of on-chip terahertz *** demonstrate valleylocked asymmetric energy flow and mode conversion with topological waveguide,multiport couplers,wave division,and whispering gallery mode *** devices are based on topological membrane metasurfaces,which are of great importance for developing on-chip photonics and bring many features into terahertz technology.

关键词： topological devices terahertz photonics membrane on-chip

kravchenko probabilityweight functions in problems of radar signals correlation processing

在线全文

学校读者我要写书评

暂无评论

Journal of Measurement Science and instrumentation 2013年第3期4卷 231-237页

作者： V F kravchenko D V Churikov Kotel'nikov institute of Radio Engineering and Electronics of Russian Academy of Sciences

in this report the combined method of correlation radar signal(RS)processing based on the theory of atomic functions(AF)is *** of using of new kravchenko probability weight functions(WF)designs are *** functional to estimate accuracy and efficiency of RS processing for concrete physical models is *** is shown that the proposed approach significantly improves the quality of the coherent analysis of RS.

关键词： radar signal (RS) atomic funtions (AF) weight functions (WF)CLC number:TN911.7 Document code:AArticle iD:1674-8042(2013)03-0231-07