检索结果-南通市图书馆

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

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

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

引用

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

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

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

引用

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

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

New WA-system of kravchenko functions in digital signal processing

引用

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)

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

kravchenko probabilityweight functions in problems of radar signals correlation processing

引用

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

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Highly transparent ytterbium doped yttrium lanthanum oxide ceramics

引用

Journal of Rare Earths 2014年第3期32卷 254-258页

作者： M.Ivanov Yu.Kopylov V.kravchenko 李江 A.Medvedev 潘裕柏 Institute of Electrophysics UrB of RAS 106Amundsena 620016 Ekaterinburg Russia Institute of Radioengineering and Electronics named after V.A. Kotelnikov RAS Vvedensky Sq. 1 Fryazino Moscow region 141120 Russia Shanghai Institute of Ceramics Chinese Academy of Science Ural Federal University 19 Mira 620002 Ekaterinburg Russia

To prepare ytterbium doped lanthania yttria nanopowder a method of laser evaporation of mixed oxides was used. After calcinations of the powder at 1200 ℃ a pure single-phase solid solution yb3＋：（LaxY1-x）2O3 was formed in the nanoparticles. Influence of lanthanum oxide as an isovalent additive on the yttria structure was investigated. The lanthanium ions were proved to be a good aid to sinter yttria ceramics doped with Yb3＋ at moderate temperatures about 1650 ℃. The ceramics with relative density higher than 99.99% and grain size about 40 μm were fabricated. Full transmittance of 1.8 mm thick Yb0.11 La0.23Y1.66O3 ceramics reached 82.5% at 800 nm. This material could be a good gain medium for ytterbium high power pulse lasers.

关键词： RE-doped ceramics nanopowders ytterbium oxide transparency

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Multifunctional metaoptics based on bilayer metasurfaces

引用

Light(Science & Applications) 2019年第1期8卷 466-474页

作者： You Zhou Ivan I.kravchenko Hao Wang Hanyu Zheng Gong Gu Jason Valentine Interdisciplinary Materials Science program Vanderbilt UniversityNashvilleTN 37212USA Center for Nanophase Materials Sciences Oak Ridge National LaboratoryOak RidgeTN 37831USA Min H.Kao Department of Electrical Engineering and Computer Science University of TennesseeKnoxvilleTN 37996USA Department of Electric Engineering and Computer Science Vanderbilt UniversityNashvilleTN 37212USA Department of Mechanical Engineering Vanderbilt UniversityNashvilleTN 37212USA

Optical metasurfaces have become versatile platforms for manipulating the phase,amplitude,and polarization of light.A platform for achieving independent control over each of these properties,however,remains elusive due to the limited engineering space available when using a single-layer *** instance,multiwavelength metasurfaces suffer from performance limitations due to space filling constraints,while control over phase and amplitude can be achieved,but only for a single ***,we explore bilayer dielectric metasurfaces to expand the design space for *** ability to independently control the geometry and function of each layer enables the development of multifunctional metaoptics in which two or more optical properties are independently *** a proof of concept,we demonstrate multiwavelength holograms,multiwavelength waveplates,and polarization-insensitive 3D holograms based on phase and amplitude *** proposed architecture opens a new avenue for designing complex flat optics with a wide variety of functionalities.

关键词： surface. optics independently

来源：

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

kravchenko atomic transforms in digital signal processing

引用

Journal of Measurement Science and Instrumentation 2012年第3期3卷 228-234页

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

The modified atomic transformations are constructed and proved. On their basis the new complex analytic wavelets are obtained. The proof of the Fourier transforms existence in L~ and L2 on the basis of the theory of atomic functions （AF） are presented. The numerical experiments of digital time series processing and physical analysis of the results confirm the efficiency of the proposed transforms.

关键词： atomic functions(AF) Fourier series space-time transforms digital signal processing(DSp)

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Mollisols properties and Changes in Ukraine and China

引用

Chinese Geographical Science 2011年第3期21卷 257-266页

作者： Yuri S kravchenko ZHANG Xingyi LIU Xiaobing SONG Chunyu Richard M CRUSE Key Laboratory of Mollisols Agroecology Northeast Institute of Geography and Agroecology Chinese Academy of Sciences Harbin 150081 China National University of Life and Environmental Sciences of Ukraine Kyiv 03041 Ukraine Department of Agronomy Iowa State University Ames 500011 IA USA

Soils are the foundation of civilizations and the basis for human food *** in Ukraine and Northeast China are two out of the four major Mollisol regions in the *** natural areas from which Mollisols developed are the prairies and steppes that experience temperate and freezing *** review paper introduces the general climate,vegetation,and topography of Mollisols regions in Ukraine and Northeast China,analyzes their properties,including soil texture,soil organic matter content,soil bulk density,pH,cation exchange capacity and other chemical properties,and compares the property changes and management practices of Mollisols in relation to sustainable grain production.

关键词： Mollisols soil properties soil organic matter tillage Mollisols management

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

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

引用

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

来源：

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

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：