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A VSC-based Model for Power Flow Assessment of Multi-terminal VSC-HVDC Transmission Systems

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Journal of Modern Power Systems and Clean Energy 2021年第6期9卷 1363-1374页

作者： Ricardo Martínez-Parrales Claudio R.Fuerte-Esquivel boris A.Alcaide-Moreno Enrique Acha Faculty of Electrical Engineering Universidad Michoacana de San Nicolás de Hidalgo(UMSNH) National Center for Energy Control Secretary of Energy Department of Electrical Engineering Tampere University(TU)

This paper puts forward a new practical voltage source converter(VSC)based AC-DC converter model suitable for conducting power flow assessment of multi-terminal VSCbased high-voltage direct current(VSC-MTDC)*** model uses an advanced method to handle the operational limits and control modes of VSCs into the power flow *** new model is incorporated into a unified framework encompassing AC and DC power grids and is solved by using the Newton-Raphson method to enable quadratically convergent iterative *** use of complementarity constraints,together with the Fischer-Burmeister function,is proposed to enable the seamless incorporation of operational control modes of VSC and automatic enforcement of any converter’s operational limits that become violated during the iterative solution ***,a dedicated process for checking limits is no longer ***,all existing relationships between the VSC control laws and their operational limits are considered directly during the solution of the power flow *** applicability of the new model is demonstrated with numerical examples using various multi-terminal AC-DC transmission networks,one of which is a utility-sized power system.

关键词： Complementarity constraint current limit high-voltage direct current(HVDC) voltage source converter(VSC) multi-terminal VSC-HVDC(VSC-MTDC)system power flow

Analysis of sea level changes in the Caspian Sea related to Cosmo-geophysical processes based on satellite and terrestrial data

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Geodesy and Geodynamics 2018年第6期9卷 449-455页

作者： Vladimir Kaftan boris Komitov Sergey Lebedev Geophysical Center Russian Academy of Sciences Moscow Russia Peoples' Friendship University of Russia Moscow Russia Institute of Astronomy and NAO “Rozhen” of Bulgarian Academy of Science Sofia Bulgaria Space Research Institute Russian Academy of Sciences Moscow Russia

Analysis results of the average annual sea levels in the Caspian Sea obtained from ground and satellite observations, corresponding to solar activity characteristics, magnetic field data, and length of day are presented. Spectra of the indicated processes were investigated and their approximation models were also built. Previously assumed statistical relationships between space-geophysical processes and Caspian Sea level(CSL) changes were confirmed. A close connection was revealed between the low-frequency models of the solar and geomagnetic activity parameters and the CSL changes. Predictions extending into the next decades showed a high probability of an increase in the CSL and a decrease of the compared space-geophysical parameters.

关键词： CSL Analysis of sea level changes in the Caspian Sea related to Cosmo-geophysical processes based on satellite and terrestrial data LOD SSN

Holography with high-power CW coherent terahertz source: optical components, imaging, and applications

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Light(Advanced Manufacturing) 2022年第3期3卷 103-119页

作者： Yulia Choporova boris Knyazev Vladimir Pavelyev Novosibirsk State University 630090 NovosibirskRussia Budker Institute of Nuclear Physics 630090 NovosibirskRussia Samara National Research University 443086 SamaraRussia Image Processing Systems Institute of the RAS-Branch of the FSRC“Crystallography and Photonics”RAS 443001 SamaraRussia

This paper presents the results of 15 years of studies in the field of terahertz holography at the Novosibirsk free electron *** cover two areas:research on obtaining holographic images in the terahertz range and the use of diffractive optical elements to form high-power terahertz radiation fields with specified characteristics(intensity,phase,and polarization),using well-studied and widely applied in the optical range methods of optical(analog),digital,and computer-generated *** experiments were performed with the application of high-power coherent monochromatic frequency-tunable radiation from the Novosibirsk free electron *** features of hologram registration in the terahertz range are ***,technologies,and optical materials for terahertz holographic elements are discussed.A wide range of promising applications of high-power terahertz fields with a given spatial structure is *** results of the study of terahertz holograms recorded as digital holograms,as well as radiation-resistive optical elements realized as computer-synthesized holograms,are presented.

关键词： Terahertz range Holography Diffractive optical elements Imaging,Free electron laser

Uncertainty-aware molecular dynamics from Bayesian active learning for phase transformations and thermal transport in SiC

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npj Computational Materials 2023年第1期9卷 2000-2007页

作者： Yu Xie Jonathan Vandermause Senja Ramakers Nakib H.Protik Anders Johansson boris Kozinsky John A.Paulson School of Engineering and Applied Sciences Harvard UniversityCambridgeMAUSA Department of Physics Harvard UniversityCambridgeMAUSA Corporate Sector Research and Advance Engineering Robert Bosch GmbHRenningenUSA Interdisciplinary Centre for Advanced Materials Simulation Ruhr-Universität BochumBochumGermany Robert Bosch LLC Research and Technology CenterWatertownMAUSA

Machine learning interatomic force fields are promising for combining high computational efficiency and accuracy in modeling quantum interactions and simulating atomistic *** learning methods have been recently developed to train force fields efficiently and *** them,Bayesian active learning utilizes principled uncertainty quantification to make data acquisition *** this work,we present a general Bayesian active learning workflow,where the force field is constructed from a sparse Gaussian process regression model based on atomic cluster expansion *** circumvent the high computational cost of the sparse Gaussian process uncertainty calculation,we formulate a high-performance approximate mapping of the uncertainty and demonstrate a speedup of several orders of *** demonstrate the autonomous active learning workflow by training a Bayesian force field model for silicon carbide(SiC)polymorphs in only a few days of computer time and show that pressure-induced phase transformations are accurately *** resulting model exhibits close agreement with both ab initio calculations and experimental measurements,and outperforms existing empirical models on vibrational and thermal *** active learning workflow readily generalizes to a wide range of material systems and accelerates their computational understanding.

关键词： computer thermal utilize

LOW-RANK TENSOR STRUCTURE OF SOLUTIONS TO ELLIPTIC PROBLEMS WITH JUMPING COEFFICIENTS

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Journal of Computational Mathematics 2012年第1期30卷 14-23页

作者： Sergey Dolgov boris N.Khoromskij Ivan Oseledets Eugene E.Tyrtyshnikov Moscow Institute of Physics and Technology Russia Max-Planck-Institute for Mathematics in Sciences Inselstr.22-26D-04103 LeipzigGermany Institute of Numerical Mathematics Russian Academy of SciencesGubkina 8119991 MoscowRussia Lomonosov Moscow State University Russia University of Siedlce Poland(visiting professor)

We study the separability properties of solutions to elliptic equations with piecewise constant coefficients in Rd, d ≥ 2. The separation rank of the solution to diffusion equation with variable coefficients is prese... 详细信息

关键词： Structured matrices Elliptic operators Poisson equation Matrix approxima-tions Lowrank matrices Tensors Canonical decomposition.

Interface-induced warping in hybrid two-dimensional materials

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Nano Research 2015年第6期8卷 2015-2023页

作者： John M. Aired Zhuhua Zhang Zhili Hu boris I. Yakobson Department of Material Science and Nanoengineering Rice University Houston Texas 77005 USA

Two-dimensional hybrid materials consisting of heterogeneous domains have been of great interest. Using empirical molecular dynamical simulation, we show that the morphology of such hybrid 2D materials can extend into the third dimension via strong warping intrinsic to the interfaces between the domains. The interface warping stems from the compressive stress in the domain with a larger lattice constant and even penetrates into the stretched domain. Based on classic plate theory, we analytically quantify the amplitude, wave length and penetration depth of the interface warping as functions of the lattice mismatch, achieving good agreement with the simulations. Moreover, we propose that periodically placing pentagon-heptagon dislocations along the interface can eliminate the warping in the 2D material and such defective interface can be more favorable than the warped one over a critical domain size, which is consistent with recent experimental observations. Our results suggest that the interface warping in 2D hybrid materials should be considered in further exploring their promising properties.

关键词： graphene interface rippling mechanical property hybrid 2D materials

A new form of liquid matter:Quantum droplets

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Frontiers of physics 2021年第3期16卷 11-31页

作者： Zhi-Huan Luo Wei Pang Bin Liu Yong-Yao Li boris A.Malomed Department of Applied Physics South China Agricultural UniversityGuangzhou510642China Department of Experiment Teaching Guangdong University of TechnologyGuangzhou510006China School of Physics and Optoelectronic Engineering Foshan UniversityFoshan528000China Department of Physical Electronics School of Electrical EngineeringFaculty of Engineeringand Center for Light-Matter InteractionTel Aviv UniversityTel Aviv69978Israel Instituto de Alta Investigación Universidad de TarapacáCasilla 7DAricaChile

This brief review summarizes recent theoretical and experimental results which predict and establish the existence of quantum droplets(QDs),i.e.,robust two-and three-dimensional(2D and 3D)self-trapped states in Bose-Einstein condensates(BECs),which are stabilized by effective self-repulsion induced by quantum fluctuations around the mean-field(MF)states[alias the Lee-Huang-Yang(LHY)effect].The basic models are presented,taking special care of the dimension crossover,2D→*** reported experimental results,which exhibit stable 3D and quasi-2D QDs in binary BECs,with the inter-component attraction slightly exceeding the MF self-repulsion in each component,and in single-component condensates of atoms carrying permanent magnetic moments,are presented in some *** summary of theoretical results is focused,chiefly,on 3D and quasi-2D QDs with embedded vorticity,as the possibility to stabilize such states is a remarkable *** vortex states are presented both for QDs in free space,and for singular but physically relevant 2D modes pulled to the center by the inverse-square potential,with the quantum collapse suppressed by the LHY effect.

关键词： quantum droplet Bose-Einstein condensate Lee-Huang-Yang correction votex state

Two-dimensional anisotropic vortex quantum droplets in dipolar Bose−Einstein condensates

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Frontiers of physics 2024年第2期19卷 205-211页

作者： Guilong Li Xunda Jiang Bin Liu Zhaopin Chen boris A.Malomed Yongyao Li School of Physics and Optoelectronic Engineering Foshan UniversityFoshan 528225China Physics Department and Solid-State Institute TechnionHaifa 32000Israel Department of Physical Electronics School of Electrical EngineeringFaculty of EngineeringTel Aviv UniversityTel Aviv 69978Israel Instituto de Alta Investigación Universidad de TarapacáCasilla 7DAricaChile Guangdong-Hong Kong-Macao Joint Laboratory for Intelligent Micro−Nano Optoelectronic Technology Foshan UniversityFoshan 528225China

Creation of stable intrinsically anisotropic self-bound states with embedded vorticity is a challenging ***,no such states in Bose−Einstein condensates(BECs)or other physical settings were *** BEC suggests a unique possibility to predict stable two dimensional anisotropic vortex quantum droplets(2D-AVQDs).We demonstrate that they can be created with the vortex axis oriented perpendicular to the polarization of *** stability area and characteristics of the 2D-AVQDs in the parameter space are revealed by means of analytical and numerical ***,the rotation of the polarizing magnetic field is considered,and the largest angular velocities,up to which spinning 2D-AVQDs can follow the rotation in clockwise and anti-clockwise directions,are *** between moving 2D-AVQDs are studied too,demonstrating formation of bound states with a vortex−antivortex−vortex structure.A stability domain for such stationary bound states is *** dipolar states,that can be readily implemented by means of phase imprinting,quickly transform into robust 2D-AVQDs,which suggests a straightforward possibility for the creation of these states in the experiment.

关键词： dipolar Bose−Einstein condensate anisotropic vortex quantum droplets

Analysis of The Impact of Microfinance on The Economic Development of CEMAC States

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Analysis of The Impact of Microfinance on The Economic Devel...

作者： NDEBISSA KORMOUGUE Romeo boris 河北大学

学位级别：硕士

Financial system has a positive impact on economic development of countries. Thus the main objective of this paper is to stress the role of financial system on economic development of Economic and Monetary Community of Central Africa, EMCCA(Communauté Economique Monétaire de l'Afrique Centrale, CEMAC) countries, mainly the role of MFIs through savings mobilization function and micro credits. To achieve this goal, we have considered that financial system consists of banking system and microfinance *** financial system of CEMAC is dominated by the formal financial system, namely the banking system. During the period before independence, the authorities have carried out the nationalization of financial institutions inherited from colonization and the establishment of new banks. They maintained control over interest rates to minimize the cost of credit to public enterprises and certain priority areas. However, the intervention of the authorities did not give good results. This led CEMAC to liberalize its financial system for the purpose of enhancing the mobilization of savings and reallocation of resources to boast economic development and microfinance *** analysis revealed that the restructuring of the banking sector has enabled banks in CEMAC countries to have excess liquidity and favor the growth of microfinance institutions(MFIs). However banks contribution to the financing of economic activities remain limited, thus MFIs have increase their activities and contribute to the financing of poor population mainly from rural areas where banks are absents. The study made some recommendations mainly the development of banking system and the improvement of microfinance services to sustain economic development in CEMAC in general and in Central African Republic in particular.

关键词： Financial System CEMAC Central African Republic Economic development