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Charge disproportionation and site-selective local magnetic moments in the post-perovskite-type Fe_(2)O_(3) under ultra-high pressures

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npj Computational Materials 2019年第1期5卷 345-351页

作者： ivan Leonov Gregory Kh.Rozenberg igor A.abrikosov M.N.Miheev institute of Metal Physics Russian Academy of Sciences620137 YekaterinburgRussia Materials Modeling and Development Laboratory National University of Science and Technology‘MISIS’119049 MoscowRussia School of Physics and Astronomy Tel Aviv University69978 Tel AvivIsrael Department of Physics Chemistry and Biology(IFM)Linköping UniversitySE-58183 LinköpingSweden

The archetypal 3d Mott insulator hematite,Fe_(2)O_(3),is one of the basic oxide components playing an important role in mineralogy of Earth’s lower mantle.its high pressure-temperature behavior,such as the electronic properties,equation of state,and phase stability is of fundamental importance for understanding the properties and evolution of the Earth’s interior.Here,we study the electronic structure,magnetic state,and lattice stability of Fe_(2)O_(3)at ultra-high pressures using the density functional plus dynamical mean-field theory(DFT+DMFT)approach.in the vicinity of a Mott transition,Fe_(2)O_(3) is found to exhibit a series of complex electronic,magnetic,and structural transformations.in particular,it makes a phase transition to a metal with a post-perovskite crystal structure and site-selective local moments upon compression above 75 GPa.We show that the site-selective phase transition is accompanied by a charge disproportionation of Fe ions,with Fe^(3±δ)and δ~0.05–0.09,implying a complex interplay between electronic correlations and the lattice.Our results suggest that site-selective local moments in Fe_(2)O_(3) persist up to ultra-high pressures of~200–250 GPa,i.e.,sufficiently above the core-mantle boundary.The latter can have important consequences for understanding of the velocity and density anomalies in the Earth’s lower mantle.

关键词： magnetic local high

Dipolar spin relaxation of divacancy qubits in silicon carbide

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npj Computational Materials 2021年第1期7卷 1974-1984页

作者： Oscar Bulancea-Lindvall Nguyen T.Son igor A.abrikosov Viktor ivády Department of Physics Chemistry and BiologyLinköping UniversitySE-58183 LinköpingSweden Wigner Research Centre for Physics Hungarian Academy of SciencesPO Box 49H-1525 BudapestHungary Max-Planck-institut für Physik komplexer Systeme Nöthnitzer Straße 38D-01187 DresdenGermany

Divacancy spins implement qubits with outstanding characteristics and capabilities in an industrial semiconductor host On the other hand,there are still numerous open questions about the physics of these important defects,for instance,spin relaxation has not been thoroughly studied yet.Here,we carry out a theoretical study on environmental spin-induced spin relaxation processes of divacancy qubits in the 4H polytype of silicon carbide(4H-SiC).We reveal all the relevant magnetic field values where the longitudinal spin relaxation time T,drops resonantly due to the coupling to either nuclear spins or electron spins.We quantitatively analyze the dependence of the T,time on the concentration of point defect spins and the applied magnetic field and provide ananalytical expression.We demonstrate that dipolar spin relaxation plays a significant role both in as-grown and ion-implanted samples and it often limits the coherence time of divacancy qubits in 4H-SiC.

关键词： relaxation vacancy resonant

First principles calculation of spin-related quantities for point defect qubit research

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npj Computational Materials 2018年第1期4卷 32-44页

作者： Viktor ivády igor A.abrikosov Adam Gali Department of Physics Chemistry and BiologyLinköping UniversitySE-58183 LinköpingSweden Wigner Research Centre for Physics Hungarian Academy of SciencesPO Box 49Budapest H-1525Hungary Materials Modeling and Development Laboratory National University of Science and Technology‘MISIS’119049 MoscowRussia Department of Atomic Physics Budapest University of Technology and EconomicsBudafokiút 8Budapest H-1111Hungary

Point defect research in semiconductors has gained remarkable new momentum due to the identification of special point defects that can implement qubits and single photon emitters with unique characteristics.indeed,these implementations are among the few alternatives for quantum technologies that may operate even at room temperature,and therefore discoveries and characterization of novel point defects may highly facilitate future solid state quantum technologies.First principles calculations play an important role in point defect research,since they provide a direct,extended insight into the formation of the defect states.in the last decades,considerable efforts have been made to calculate spin-dependent properties of point defects from first principles.The developed methods have already demonstrated their essential role in quantitative understanding of the physics and application of point defect qubits.Here,we review and discuss accuracy aspects of these novel ab initio methods and report on their most relevant applications for existing point defect qubits in semiconductors.We pay attention to the advantages and limitations of the methodological solutions and highlight additional developments that are expected in the near future.Moreover,we discuss the opportunity of a systematic search for potential point defect qubits,as well as the possible development of predictive spin dynamic simulations facilitated by ab initio calculations of spin-dependent quantities.

关键词： defect quantities principles

The genetics of race differentiation——should it be studied?

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National Science Review 2023年第4期10卷 6-7页

作者： Chung-i Wu NSR School of Life Sciences Sun Yat-sen University

in this issue, NSR publishes an article entitled ‘Expression profiles of east-west highly differentiated genes in Uyghur genomes’ by Ning et al.(2023) [1]. Briefly, it is about the regulation of gene expression in Uyghur genomes, which are admixed between Asian and European genomes. in evolutionary terms, this is a case of post-isolation secondary contact over a time span of thousands of years. in most other cases, such as African Americans, the admixture has a time span of <300 years. Furthermore,

关键词： DROSOPHiLA-MELANOGASTER iNCiPiENT SPECiATiON SEXUAL iSOLATiON

Applications and theoretical perspectives of artificial intelligence in the rate of penetration

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Petroleum 2022年第2期8卷 237-251页

作者： Chinedu i.Ossai Ugochukwu i.Duru Faculty of Health Arts and DesignSwinburne UniversityJohn Street HawthornVictoria3122Australia Federal University of Technology Owerri Nigeria

Artificial intelligence(Ai)is becoming popular for the Rate of Penetration(ROP)estimation,hence,the need to study the best techniques and their advantages over empirical models.Various literatures were analysed to determine the prevalence of Ai in ROP computation and compare the computation accuracies with empirical models.Artificial Neural Network(ANN)accounted for over 92%of the Ai techniques used for ROP computation and Weight on Bit(WOB)mostly influenced the computation accuracy.The accuracy of Ai algorithms is better than the empirical models thus,will improve the drilling efficiency,reduce cost and enhance the development of pad wells.

关键词： Artificial intelligence Drilling operations Rate of penetration optimization Artificial neural network Weight on bit

Corporate governance in generating companies of the Russian electric power industry in the context of ESG agenda

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Global Energy interconnection 2022年第5期5卷 512-523页

作者： Galina i.Sheveleva Melentiev Energy Systems institute of Siberian Branch of the Russian Academy of Sciences 130 Lermontov St.Irkutsk 664033Russia

To address the issues of investment appeal in the Russian electric power industry,this study analyzes the dynamics of corporate governance,including permanent redistribution of property and compliance with the Russian Corporate Governance Code,in wholesale and territorial-generating companies.The increasing concentration of property in the hands of the state and its implications for investors are also noted.This study reveals the violations of essential principles,and the substantial differences in corporate governance practices,in the best-and worst-performing companies.Additional standards for better corporate governance practices to benefit the investors in the context of the current Environmental,Social,and corporate Governance(ESG)agenda are proposed.This study provides a new insight at the development of corporate governance in Russian power generating companies through property redistribution and compliance with corporate governance principles.

关键词： Corporate governance Russian power generating companies ESG agenda

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Vertical seismic absorber utilizing inertance and negative stiffness implemented with gas springs

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Earthquake Engineering and Engineering Vibration 2023年第1期22卷 225-241页

作者： Kalogerakou M Paradeisiotis A Antoniadis i Dynamics and Structures Laboratory School of Mechanical EngineeringNational Technical University of Athens15780 AthensGreece

A novel implementation of negative stiffness elements(NSEs)is proposed,utilizing industrial grade nitrogen gas springs as pre-stressed stiffness elements in a configuration with lever arms.This NSE is combined with an inerter to form a stiff dynamic absorber(SDA)for vertical seismic protection of structures with base isolation.The SDA is optimized to minimize vertical accelerations while ensuring static structural integrity,excellent damping performance and containment of relative displacements.The introduction of gas springs in place of conventional linear springs addresses important practical limitations through features of non-linearity and industrial grade manufacturing.The proposed implementation is dimensioned for a 50-ton structure and evaluated numerically for 25 actual earthquake records,in comparison with a linear SDA model and an equivalent conventional damper(CD).individual and averaged results of acceleration and displacement time histories demonstrate vastly superior response compared to CD regarding induced accelerations for similar displacements.Performance equivalency with the linear SDA model indicates the stability of the gas spring implementation while guaranteeing predictability,tested endurance,proper tolerances,and off-axis motion resistance without requiring additional guiding components,as opposed to conventional springs.These features render the proposed implementation a promising solution for the realization of NSEs in seismic protection.

关键词： negative stiffness gas springs vertical seismic protection KDamper inerter

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Taxonomy,distribution,and contemporary exposure of terrestrial mammals to floods and human pressure across different areas for biodiversity conservation in China

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integrative Zoology 2024年第3期19卷 458-467页

作者： Roman SHARNUUD Eric i.AMECA MOE Key Laboratory for Biodiversity Science&Ecological Engineering College of Life SciencesBeijing Normal UniversityBeijingChina Climate Change Specialist Group Species Survival CommissionInternational Union for Conservation of NatureGlandSwitzerland

A significant research focus is placed on identifying animal species and areas at future risk to human-induced alterations of the environment and long-term changes in climatic conditions.Yet,the extent to which exposure to extreme climatic events and intense human pressure can increase the risk of harmful impacts on species remains poorly investigated.Focusing on terrestrial mammals in China,one of the world’s megadiverse countries,we investigated patterns of contemporary exposure to floods and human pressures and determined their taxonomic representation and distribution across three major area-based conservation schemes,namely,national nature reserves(NNRs),priority areas for biodiversity conservation(PABCs),and key biodiversity areas(KBAs).Among the 440 species assessed with moderate or high exposure to floods,327(∼75%)also qualified as moderate or high in exposure to intense human pressure.These species mainly belong to the orders Chiroptera,Eulipotyphla,and Rodentia.Likewise,there were 305,311,and 311 species with moderate or high exposure to flood and intense human pressure represented across NNRs,PABCs,and KBAs,respectively.Our findings support the prioritization of KBAs for expansion of site-based protection efforts such as NNRs in China,considering threats to species from exposure to adverse effects from both extreme climate and human pressure.

关键词： conservation floods human pressure mammals taxonomy

Simulation of detection and scattering of sound waves by the lateral line of a fish

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Chinese Physics B 2022年第2期31卷 398-404页

作者： V M Adamyan i Y Popov i V Blinova V V Zavalniuk Odessa i.i.Mechnikov National University Dvoryanskaya Str.2Odesa65082Ukraine iTMO University Kronverkskiy49Saint Petersburg197101Russia Odessa Military Academy 10 Fontanska RoadOdesa 65009Ukraine

A solvable model of lateral line of a fish based on a wave equation with additional boundary conditions on a set of isolated points is proposed.Within the framework of this model it is shown that the ratio of pressures on lateral lines on different fish flanks,as well as the cross section of sound scattering on both the lines,strongly depends on angles of incidence of incoming sound waves.The strong angular dependence of the pressure ratio seems to be sufficient for the fish to determine the directions from which the sound is coming.

关键词： acoustic equation point self-adjoint perturbations of Laplace operator scattering lateral line

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