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Simulation of thermal processes in metamaterial millimeter-wave to infrared converter for millimeter-wave imager

International Journal of Modeling, Simulation, and Scientific Computing 2014年第S01期5卷 120-128页

作者： Peter S.Zagubisalo Andrey G.Paulish sergey a.kuznetsov Novosibirsk Branch of the Institute of Semiconductor Physics Siberian Branch of Russian Academy of Sciences 2/1 pr.Akademika LavrentyevaNovosibirsk 630090Russian Federation Novosibirsk State University 2 ul.PirogovaNovosibirsk 630090Russian Federation

The main characteristics of millimeter-wave(MM-wave)image detector were simulated by means of accurate numerical modeling of thermophysical processes in a metamaterial MM-to-IR *** converter represents a multilayer structure consisting of an ultra thin resonant metamaterial absorber and a perfect emissive *** absorber consists of a dielectric self-supporting film that is metallized from both sides.A micropattern is fabricated from one *** absorption of the MM waves induces the converter heating that yields enhancement of IR emission from the emissive *** emission is detected by IR *** this contribution an accurate numerical model for simulation of the thermal processes in the converter structure was created by using COMSOL Multiphysics *** simulation results are in a good agreement with experimental results that validates the *** simulation shows that the real-time operation is provided for the converter thickness less than 3µm and time response can be improved by decreasing of the converter *** energy conversion efficiency of MM waves into IR radiation is over 80%.The converter temperature increase is a linear function of a MM-wave radiation power within three orders of the dynamic *** blooming effect and ways of its reducing are also *** model allows us to choose the ways of converter structure optimization and improvement of image detector parameters.

关键词： Metamaterials subterahertz waves terahertz waves millimeter waves highimpedance surface ultra-thin absorber focal plane array detector bolometric detectors thermodynamic modeling optical readout system

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Stabilization of Hyperbolic Chaos by the Pyragas Method

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Journal of Mathematics and System Science 2014年第12期4卷 755-762页

作者： sergey Belyakin Arsen Dzanoev sergey kuznetsov Physics Faculty Moscow State University Moscow 119992 Russia

For a long time it was a common opinion that hyperbolic attractors are artificial mathematical constructions. However, in the recent papers there were proposed physically realizable systems that possess, in their phase space, the set with features that are very similar to hyperbolic type of attractors. As is known, invariant sets are called hyperbolic attractors of the dynamical system if they are closed, topologically transitive subsets, and every their trajectory possesses uniform hyperbolicity. Very familiar types of the hyperbolic attractors are Smale-Williams＇ solenoid and Plykin＇s attractor. Further, it is well known that chaotic systems are very sensitive to the external perturbations. This property is used for controlling nonlinear systems and chaos suppression. Thus, an important question arises： Is it possible to suppress chaos in systems with hyperbolic attractors because these attractors are structurally stable subsets？ In the present contribution we study the possibility of stabilization of chaotic oscillations in systems with the Smale-Williams hyperbolic attractors by means of the Pyragas method with a delay. It is shown that by means of external perturbation the dynamical system could be controllable： the hyperbolic attractor degenerates into a periodic one.

关键词： Dynamical system hyperbolic attractors Pyragas method

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Radiation of a TM mode from an open end of a three-layer dielectric capillary

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Chinese Physics B 2024年第7期33卷 311-318页

作者： sergey NGalyamin Alexandr MAltmark St.Petersburg State University 7/9Universitetskayanab.St.Petersburg 199034Russia St.Petersburg Electrotechnical University“LETI” 5ProfessoraPopovaSt.Petersburg 197022Russia

Modern trends in beam-driven radiation sources include the interaction of Cherenkov wakefields in open-ended circular waveguides with complicated dielectric linings, with a three-layer dielectric capillary recently proposed to reduce radiation divergence being a representative example [Opt. Lett. 45 5416(2020)]. We present a rigorous approach that allows for an analytical description of the electromagnetic processes that occur when the structure is excited by a single waveguide TM mode. In other words, the corresponding canonical waveguide diffraction problem is solved in a rigorous formulation. This is a continuation of our previous papers which considered simpler cases with a homogeneous or two-layer dielectric filling. Here we use the same analytical approach based on the Wiener–Hopf–Fock technique and deal with the more complicated case of a three-layer dielectric lining. Using the obtained rigorous solution, we discuss the possibility of manipulating the far-field radiation pattern using a third layer made of a low permittivity material.

关键词： diffraction radiation open-ended waveguide Wiener–Hopf technique Cherenkov radiation

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Analytical solution of axisymmetric contact problem about indentation of a circular indenter into a soft functionally graded elastic layer

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Acta Mechanica Sinica 2013年第2期29卷 196-201页

作者： sergey Volkov sergey Aizikovich Yue-Sheng Wang Igor Fedotov Research and Education Center "Materials" Don State Technical University South Federal University Research Institute of Mechanics and Applied Mathematics Institute of Engineering Mechanics Beijing Jiaotong University Department of Mathematical Technology Tshwane University of Technology

The paper addresses a contact problem of the theory of elasticity,i.e.,the penetration of a circular indenter with a flat base into a soft functionally graded elastic *** elastic properties of a functionally graded layer arbitrarily vary with depth,and the foundation is assumed to be elastic,yet much harder than a *** analytical solution is constructed,and it is shown that the solutions are asymptotically exact both for large and small values of characteristic dimensionless geometrical parameter of the *** examples are analyzed for the cases of monotonic and nonmonotonic variations of elastic *** results for the case of homogeneous layer are compared with the results for nondeformable foundation.

关键词： Contact problems·Indentation·Functionally graded layer

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Updated Kimura-Takemoto classification of atrophic gastritis

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World Journal of Clinical Cases 2021年第13期9卷 3014-3023页

作者： sergey M Kotelevets sergey A Chekh sergey Z Chukov Department of Therapy Medical InstituteNorth Caucasus State Academy for Humanities and TechnologiesCherkessk 369000Russia Department of Software Development Institute of Applied Mathematics and Information TechnologyNorth Caucasus State Academy of Humanities and TechnologiesCherkessk 369000Russia Department of Mathematics Institute of Applied Mathematics and Information TechnologyNorth Caucasus State Academy of Humanities and TechnologiesCherkessk 369000Russia Department of Pathological Anatomy Stavropol State Medical UniversityStavropol 355017Russia

BACKGROUND The Updated Sydney system for visual evaluation of gastric mucosal atrophy viaendoscopic observation is subject to sampling error and interobserver *** Kimura-Takemoto classification system was developed to overcome *** compare the morphological classification of atrophic gastritis between theKimura-Takemoto system and the Updated Sydney *** total of 169 patients with atrophic gastritis were selected according to diagnosisby the visual endoscopic Kimura-Takemoto method. Following the UpdatedKimura-Takemoto classification system, one antrum biopsy and five gastriccorpus biopsies were taken according to the visual stages of the Kimura-Takemoto system. The Updated Kimura-Takemoto classification system was thenapplied to each and showed 165 to have histological mucosal atrophy;theremaining 4 patients had no histological evidence of atrophy in any biopsy. The Updated Kimura-Takemoto classification was verified as a referencemorphological method and applied for the diagnosis of atrophic gastritis. Addingone more biopsy from the antrum to the six biopsies according to the Updated Kimura-Takemoto classification, constitutes the updated combined Kimura-Takemoto classification and Sydney *** sensitivity for degree of mucosal atrophy assessed by the Updated Sydneysystem was 25% for mild, 36% for moderate, and 42% for severe, when comparedwith the Updated Kimura-Takemoto classification of atrophic gastritis formorphological diagnosis. Four types of multifocal atrophic gastritis wereidentified: sequential uniform (type 1;in 28%), sequential non-uniform (type 2;in7%), diffuse uniform (type 3;in 23%), diffuse non-uniform (type 4;in 24%), and"alternating atrophic – non-atrophic" (type 5;in 18%). The pattern of the spread ofatrophy, sequentially from the antrum to the cardiac segment of the stomach,which was described by the Updated Kimura-Takemoto system, washistologically confirmed in 82% of cases ***

关键词： Updated Sydney system Kimura-Takemoto classification Prevention Gastric cancer Atrophic gastritis Morphology

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Reactivation of hepatitis B virus infection – an important aspect of multifaceted problem

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World Journal of Gastroenterology 2024年第26期30卷 3193-3197页

作者： sergey Morozov sergey Batskikh Department of Gastroenterology Hepatology and NutritionFederal Research Center of NutritionBiotechnology and Food SafetyMoscow 115446Russia Department of Hepatology Moscow Clinical Scientific Center N.A.A.S.LoginovMoscow 111123Russia

In this editorial we comment on the article published in the recent issue of the W orld Journal of *** focus specifically on the problem of occult hepatitis B virus(HBV)infection,that is a result of previous hepatitis B(PHB)and a source for reactivation of *** prevalence of PHB is underestimated due to the lack of population testing ***,this condition not only com-plicate anticancer treatment,but may be responsible for the development of other diseases,like cancer or autoimmune *** we unveil possible mecha-nisms responsible for realization of these processes and suggest practical approa-ches for diagnosis and treatment.

关键词： Occult hepatitis B virus infection Hepatitis B virus reactivation Previous hepatitis B Cancer Autoimmune disorders

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A Note on Transition Kernels for the Most UnfavourableMixed Strategies of the Market

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Journal of the Operations Research Society of China 2024年第1期12卷 35-50页

作者： sergey N.Smirnov Faculty of Computational Mathematics and Cybernetics Lomonosov Moscow State UniversityMoscowRussian Federation 119991

We consider a deterministic model of market evolution with trading constraints andapply a game-theoretic approach to the superhedging *** obtain sufﬁcientconditions for the game equilibrium and prove under these conditions the existenceof a Borel-measurable transition kernel describing dependence on price prehistory ofthe most unfavourable mixed strategy of the market.

关键词： Superhedging Guaranteed deterministic approach Optimal mixedstrategies of the market Borel-measurable transition kernel Game equilibrium

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Structural Stability of the Financial Market Model: Continuity of Superhedging Price and Model Approximation

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Journal of the Operations Research Society of China 2024年第1期12卷 215-241页

作者： sergey N.Smirnov Faculty of Computational Mathematics and Cybernetics Lomonosov Moscow State UniversityMoscow119991Russian Federation

The present paper continues the topic of our recent paper in the same journal,aiming to show the role of structural stability in financial *** the context of financial market modeling,structural stability means that a specific“no-arbitrage”property is unaffected by small(with respect to the Pompeiu–Hausdorff metric)perturbations of the model’s *** formulate,based on our economic interpretation,a new requirement concerning“no arbitrage”properties,which we call the“uncertainty principle”.This principle in the case of no-trading constraints is equivalent to structural *** demonstrate that structural stability is essential for a correct model approximation(which is used in our numerical method for superhedging price computation).We also show that structural stability is important for the continuity of superhedging prices and discuss the sufficient conditions for this continuity.

关键词： Uncertainty Structural stability No arbitrage Continuity of superhedging price Compact-valued multifunction Financial market model approximation Trading constraints

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Analysis of NIR spectroscopic data using decision trees and their ensembles

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Journal of Analysis and Testing 2018年第3期2卷 274-289页

作者： sergey Kucheryavskiy Department of Chemistry and Bioscience Aalborg UniversityNiels Bohrs vej8EsbjergDenmark

Decision trees and their ensembles became quite popular for data analysis during the past *** of the main reasons for that is current boom in big data,where traditional statistical methods(such as,e.g.,multiple linear regression)are not very ***,in chemometrics these methods are still not very widespread,first of all because of several limitations related to the ratio between number of variables and *** paper presents several examples on how decision trees and their ensembles can be used in analysis of NIR spectroscopic data both for regression and *** will try to consider all important aspects including optimization and validation of models,evaluation of results,treating missing data and selection of most important *** performance and outcome of the decision tree-based methods are compared with more traditional approach based on partial least squares.

关键词： NIR spectroscopy Decision trees Classification and regression trees Random forests

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Experimental and Numerical Assessment of the Influence of Bottomhole Pressure Drawdown on Terrigenous Reservoir Permeability and Well Productivity

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Fluid Dynamics & Materials Processing 2023年第3期19卷 619-634页

作者： sergey Popov sergey Chernyshov Evgeniy Gladkikh Oil and Gas Research Institute of Russian Academy of Science Moscow119333Russian Perm National Research Polytechnic University Perm614990Russian

During oil and gas fields development,a decrease in reservoir and bottomhole pressure has often a detrimental effect on reservoir properties,especially *** study presents the results of laboratory tests conducted to determine the response of terrigenous reservoir core-sample permeability to changes in the effective stresses and a decrease in the reservoir *** considered samples were exposed for a long time to a constant high effective stress for a more reliable assessment of the viscoplastic *** to these experiments,the decrease of the core samples permeability may reach 21%with a decrease in pressure by 9.5 MPa from the initial reservoir *** simulations have been also *** have been based on the finite element modeling of the near-wellbore zone of the terrigenous reservoir using poroelasticity *** simulation results show a limited decrease in reservoir permeability in the near-wellbore zone(by 17%,which can lead to a decrease in the well productivity by 13%).

关键词： Terrigenous reservoir permeability core sample reservoir pressure bottomhole pressure drawdown effective stress well productivity

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