检索结果-南通市图书馆

Thermal state calculation of chamber in small thrust liquid rocket engine for steady state pulsed mode

Chinese Journal of Aeronautics 2019年第2期32卷 253-262页

作者： alexey Gennadievich VOROBYEV Svatlana Sergeevna VOROBYEVA Lihui ZHANG Evgeniy Nikolaevich BELIAEV Department of Rocket Engines Moscow Aviation Institute School of Astronautics Beihang University

This paper presents a method of thermal state calculation of combustion chamber in small thrust liquid rocket engine. The goal is to predict the thermal state of chamber wall by using basic parameters of engine: thrust level, propellants, chamber pressure, injection pattern, film cooling parameters, material of wall and their coating, etc. The difficulties in modeling the startup and shutdown processes of thrusters lie in the fact that there are the conjugated physical processes occurring at various parameters for non-design conditions. A mathematical model to predict the thermal state of the combustion chamber for different engine operation modes is developed. To simulate the startup and shutdown processes, a quasi-steady approach is applied by replacing the transient process with time-variant operating parameters of steady-state processes. The mathematical model is based on several principles and data commonly used for heat transfer modeling: geometry of flow part, gas dynamics of flow, thermodynamics of propellants and combustion spices, convective and radiation heat flows, conjugated heat transfer between hot gas and wall, and transient approach for calculation of thermal state of construction. Calculations of the thermal state of the combustion chamber in single-turn-on mode show good convergence with the experimental results. The results of pulsed modes indicate a large temperature gradient on the internal wall surface of the chamber between pulses and the thermal state of the wall strongly depends on the pulse duration and the interval.

关键词： Combustion chamber Film cooling Mathematical model Nonstationary thermal mode Small thrust liquid rocket engine Steady pulse mode Thermal state

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

Exploiting the quantum mechanically derived force field for functional materials simulations

引用

npj Computational Materials 2021年第1期7卷 1405-1413页

作者： alexey Odinokov Alexander Yakubovich Won-Joon Son Yongsik Jung Hyeonho Choi Samsung R&D Institute Russia(SRR) Samsung Electronics12 Dvintsev StreetMoscow 127018Russia Data and Information Technology Center Samsung ElectronicsHwaseong 18448Korea Samsung Advanced Institute of Technology(SAIT) Samsung Electronics130 Samsung-roYeongtong-guSuwon 16678Korea

The computational design of functional materials relies heavily on large-scale atomistic *** simulations are often problematic for conventional classical force fields,which require tedious and time-consuming parameterization of interaction *** problem can be solved using a quantum mechanically derived force field(QMDFF)—a system-specific force field derived directly from the first-principles *** present a computational approach for atomistic simulations of complex molecular systems,which include the treatment of chemical reactions with the empirical valence bond *** accuracy of the QMDFF is verified by comparison with the experimental properties of liquid *** illustrate the capabilities of our methodology to simulate functional materials in several case studies:chemical degradation of material in organic light-emitting diode(OLED),polymer chain packing,material morphology of organometallic *** presented methodology is fast,accurate,and highly automated,which allows its application in diverse areas of materials science.

关键词： functional field quantum

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

Asymmetry ratio as a parameter of Eu^3＋ local environment in phosphors

引用

Journal of Rare Earths 2018年第5期36卷 474-481页

作者： Ilya E. Kolesnikov alexey V. Povolotskiy Daria V. Mamonova Evgeny Yu. Kolesnikov alexey V. Kurochkin Erkki Lahderanta Mikhail D. Mikhailov Saint Petersburg State University 7/9 Universitetskaya nab. 199034 St.petersburg.Russia Lappeenranta University of Technology LUT Skinnarilankatu 34 53850 Lappeenranta Finland Scientific and Technological Institute of Optical Material Science VNTs S. I. Vavilov State Optical Institute Babushkina 36-1 192171 St. Petersburg Russia Volga State University of Technology Lenin Sq. 3 424000 Yoshkar-Ola Russia

Study of the local environment of certain ion is quite a complex problem. Due to the unique luminescent properties, Eu^3＋ ions can be used as a structural probe. In this paper, effect of doping concentration,excitation wavelength and excitation mechanism on asymmetry ratio was systematically studied using Y3Al5O12：Eu^3＋, YVO4：Eu^3＋ and Y2O3：Eu^3＋nanophosphors. The asymmetry ratio gives information about the local surrounding and environmental changes around the Eu^3＋ ions. Asymmetry ratios of YAG：Eu^3＋and YVO4：Eu^3＋ nanopowders were calculated using standard technique and the obtained average values were found to be 0.75 and 8.2, respectively. However, it is found that standard method of asymmetry ratio calculation is suitable only for samples where all Eu^3＋ ions occupy one site. The ＂multisite model＂ of asymmetry ratio calculation was developed and used for Y2O3：Eu^3＋ nanocrystalline powders. Average value of asymmetry ratio for Eu^3＋ ions occupied ＂normal＂ sites is 6.0 and for Eu^3＋ ions occupied ＂defect＂sites is 2.3.

关键词： Eu3+ Oxide powders Luminescence Asymmetry ratio Structural probe Rare earths

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

Interactions of sulfuric acid with common atmospheric bases and organic acids: Thermodynamics and implications to new particle formation

引用

Journal of Environmental Sciences 2020年第9期32卷 130-140页

作者： Yunfeng Li Haijie Zhang Qingzhu Zhang Yisheng Xu alexey B.Nadykto Environment Research Institute Shandong UniversityQingdao 266237China State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental ScienceBeijing 100012China Department of Applied Mathematics Moscow State University of Technology“Stankin”Moscow 127994Russia

Interactions of the three common atmospheric bases,dimethylamine((CH3)2 NH),methylamine(CH3 NH2),ammonia(NH3),all considered to be efficient stabilizers of binary clusters in the Earth’s atmosphere,with H2 SO4,the key atmospheric precursor,and 14 common atmospheric organic acids(COAs)(formic,acetic,oxalic,malonic,succinic,glutaric acid,adipic,benzoic,phenylacetic,pyruvic,maleic acid,malic,tartaric and pinonic acids)have been studied using the density functional theory(DFT)and composite high-accuracy G3 MP2 *** thermodynamic stability of mixed(COA)(H2 SO4),(COA)(B1),(COA)(B2)and(COA)(B3)dimers and(COA)(H2 SO4)(B1),(COA)(H2 SO4)(B2)and(COA)(H2 SO4)(B3)trimers,where B1,B2 and B3 refer to(CH3)2 NH,CH3 NH2 and NH3,respectively,have been investigated and their impacts on the thermodynamic stability of clusters containing H2 SO4 have been *** investigation shows that interactions of H2 SO4 with GOA,(CH3)2 NH,CH3 NH2 and NH3 lead to the formation of more stable mixed dimers and trimers than(H2 SO4)2 and(H2 SO4)2(base),respectively,and emphasize the importance of common organic species for early stages of atmospheric *** also show that although amines are generally confirmed to be more active than NH3 as stabilizers of binary clusters,in some cases mixed trimers containing NH3 are more stable thermodynamically than those containing CH3 *** study indicates an important role of COA,which coexist and interact with that H2 SO4 and common atmospheric bases in the Earth atmosphere,in formation of stable prenucleation clusters and suggests that the impacts of COA on new particle formation(NPF)should be studied in further details.

关键词： bases particle atmospheric

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

Restored oligodendrogenesis by fibroblast growth factor 17:molecular mechanism for rejuvenating ageing-related memory deficit

引用

Signal Transduction and Targeted Therapy 2022年第8期7卷 2652-2654页

作者： Xiao-Yi Xiong alexey Semyanov Yong Tang School of Acupuncture and Tuina Chengdu University of Traditional Chinese MedicineAcupuncture&Chronobiology Key Laboratory of Sichuan Province610075 ChengduChina Department of Molecular Neurobiology Shemyakin-Ovchinnikov Institute of Bioorganic ChemistryRussian Academy of SciencesMiklukho-Maklaya Street 16/10Moscow 117997Russia Sechenov First Moscow State Medical University Bolshaya Pirogovskaya Str 19с1Moscow 119146Russia International Collaborative Centre on Big Science Plan for Purinergic Signalling Chengdu University of Traditional Chinese MedicineSchool of Health and RehabilitationChengdu University of Traditional Chinese Medicine610075 ChengduChina

Correspondence:Yong Tang(tangyong@***)In a recent article published in Nature,1 Iram et *** the first to identify fibroblast growth factor 17(Fgf17)from the young mice cerebrospinal fluid(YM-CSF)as a key molecule to improve cognitive functions in aged mice by driving the proliferation and differentiation of oligodendrocyte progenitor cells(OPCs),indicating that effective remyelination induced by young CSF factors may provide a novel and promising therapeutic strategy to rejuvenate the ageing brain,which again confirms that factors present in the young tissue can serve as therapies in ameliorating ageing-related symptoms.

关键词： driving young mechanism

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

Open-data-driven embeddable quality management services for map-based web applications

引用

Big Earth Data 2018年第4期2卷 395-422页

作者： alexey Noskov Alexander Zipf Institute of Geography Heidelberg UniversityHeidelbergGermany

Various map-centered web services facilitate citizens’*** applications exist for many years *** to simplification and improvement of technologies supporting WebGIS,mapbased services become more popular and important *** quality assurance for such services is a significant *** many of such applications intensively use open data,approaches focused on open solutions are *** work proposes a data-quality concept,which is based on intrinsic and comparable ***(OSM)allows intrinsic data ***,it is used as a reference dataset for quality assessment of public-sector-information Open Data *** point(EDP)-based statistics enables to filter out lowquality Open Data features.A data-type model carries out the inventory of OSM *** comparison of raster web-map tile file sizes and calculation of a simplified data quality indicator make it possible to specify acceptable data quality *** instances of quality assurance web services incorporate data features with acceptable *** work provides all required software and data for the deployment of such services under liberal *** instructions allow users to adopt the proposed solutions for their *** generic use cases illustrate the advantages of the introduced shared web services.

关键词： Data quality big spatial data WebGIS REST API computer vision

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

PARTIAL STABILITY ANALYSIS OF SOME CLASSES OF NONLINEAR SYSTEMS

引用

Acta Mathematica Scientia 2017年第2期37卷 329-341页

作者： Alexander ALEKSANDROV Elena ALEKSANDRO VA alexey ZHABKO 陈阳舟 Saint Petersburg State University Saint Petersburg 199034Russia Beijing Key Laboratory of Transportation Engineering College of Metropolitan TransportationBeijing University of TechnologyBeijing 100124China

A nonlinear differential equation system with nonlinearities of a sector type is studied. Using the Lyapunov direct method and the comparison method, conditions are derived under which the zero solution of the system is stable with respect to all variables and asymptotically stable with respect to a part of variables. Moreover, the impact of nonstationary perturbations with zero mean values on the stability of the zero solution is investigated. In addition, the corresponding time-delay system is considered for which delay-independent partial asymptotic stability conditions are found. Three examples are presented to demonstrate effectiveness of the obtained results.

关键词： Nonlinear systems partial asymptotic stability LyaPunov function sector nonlinearities time-delay

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 Application for Prediction of Sapphire Crystals Defects

引用

电子科技学刊：英文版 2020年第1期18卷 1-9页

作者： Yulia Vladimirovna Klunnikova Maxim Vladimirovich Anikeev alexey Vladimirovich Filimonov Ravi Kumar Institute of Nanotechnology Electronics and Engineering EquipmentSouthern Federal UniversityTaganrog 347928 Institute of Computer Technology and Information Security Southern Federal UniversityTaganrog347928 Department of Physical Electronics Peter the Great St.Petersburg Polytechnic UniversitySt.Petersburg 195251 the Department of Metallurgical and Materials Engineering Indian Institute of Technology MadrasChennai600036

We investigate the impact of different numbers of positive and negative examples on machine learning for sapphire crystals defects prediction. We obtain the models of crystal growth parameters influence on the sapphire crystal growth. For example, these models allow predicting the defects that occur due to local overcooling of crucible walls in the thermal node leading to the accelerated crystal growth. We also develop the prediction models for obtaining the crystal weight, blocks, cracks, bubbles formation, and total defect characteristics. The models were trained on all data sets and later tested for generalization on testing sets, which did not overlap the training *** training and testing, we find the recall and precision of prediction, and analyze the correlation among the features. The results have shown that the precision of the neural network method for predicting defects formed by local overcooling of the crucible reached 0.94.

关键词： Defects machine learning sapphire crystals

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

Observation of Zitterbewegung in photonic microcavities

引用

Light(Science & Applications) 2023年第6期12卷 1084-1090页

作者： Seth Lovett Paul M.Walker alexey Osipov alexey Yulin Pooja Uday Naik Charles E.Whittaker Ivan A.Shelykh Maurice S.Skolnick Dmitry N.Krizhanovskii Department of Physics and Astronomy University of SheffieldS37RH SheffieldUK Department of Physics and Technology ITMO UniversitySt.Petersburg 197101Russia Science Institute University of IcelandDunhagi 3IS-107 ReykjavikIceland

We present and experimentally study the effects of the photonic spin–orbit coupling on the real space propagation of polariton wavepackets in planar semiconductor microcavities and polaritonic analogues of *** particular,we demonstrate the appearance of an analogue Zitterbewegung effect,a term which translates as‘trembling motion’in English,which was originally proposed for relativistic Dirac electrons and consisted of the oscillations of the centre of mass of a wavepacket in the direction perpendicular to its *** a planar microcavity,we observe regular Zitterbewegung oscillations whose amplitude and period depend on the wavevector of the *** then extend these results to a honeycomb lattice of coupled microcavity *** to the planar cavity,such lattices are inherently more tuneable and versatile,allowing simulation of the Hamiltonians of a wide range of important physical *** observe an oscillation pattern related to the presence of the spin-split Dirac cones in the *** both cases,the experimentally observed oscillations are in good agreement with theoretical modelling and independently measured bandstructure parameters,providing strong evidence for the observation of Zitterbewegung.

关键词： planar versatile analogues

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

A Neural Circuit for Gut-Induced Sugar Preference

引用

Neuroscience Bulletin 2021年第5期37卷 754-756页

作者： Xin Cao Hai-Yan Yin Henning Ulrich alexey Semyanov Yong Tang International Collaborative Centre on Big Science Plan for Purinergic Signalling Chengdu University of Traditional Chinese MedicineChengdu 610075China Acupuncture&Chronobiology Key Laboratory of Sichuan Province Chengdu 610075China Department of Biochemistry Institute of ChemistryUniversity of Sao PauloSao Paulo 05508Brazil Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry Russian Academy of SciencesMoscowRussia 117997 Sechenov First Moscow State Medical University MoscowRussia 119146

Glucose is an essential source of energy in humans. Over the past decades, consumption of sugar has increased greatly and constitutes a large part of the global energy intake [1]. Currently, overconsumption of sugar is a serious problem around the world and contributes to the high incidence of obesity, type 2 diabetes mellitus, hypertension, and all-cause mortality [1].

关键词： intake mortality sugar

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

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：