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Stiefel–Whitney classes and topological phases in band theory

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Chinese Physics B 2019年第11期28卷 1-17页

作者： Junyeong Ahn Sungjoon Park Dongwook Kim Youngkuk Kim bohm-Jung Yang Department of Physics and Astronomy Seoul National UniversitySeoul 08826Korea Center for Correlated Electron Systems Institute for Basic Science(IBS)Seoul 08826Korea Center for Theoretical Physics(CTP) Seoul National UniversitySeoul 08826Korea

We review the recent progress in the study of topological phases in systems with space–time inversion symmetry *** an anti-unitary symmetry which is local in momentum space and satisfies I2 ST= 1 such as PT in two dimensions(2 D)and three dimensions(3 D) without spin–orbit coupling and C2 T in 2 D with or without spin–orbit coupling, where P, T, C2 indicate the inversion, time-reversal, and two-fold rotation symmetries, respectively. Under IST, the Hamiltonian and the periodic part of the Bloch wave function can be constrained to be real-valued, which makes the Berry curvature and the Chern number vanish. In this class of systems, gapped band structures of real wave functions can be topologically distinguished by the Stiefel–Whitney numbers instead. The first and second Stiefel–Whitney numbers w1 and w2, respectively,are the corresponding invariants in 1 D and 2 D, which are equivalent to the quantized Berry phase and the Z2 monopole charge, respectively. We first describe the topological phases characterized by the first Stiefel–Whitney number, including1 D topological insulators with quantized charge polarization, 2 D Dirac semimetals, and 3 D nodal line semimetals. Next we review how the second Stiefel–Whitney class characterizes the 3 D nodal line semimetals carrying a Z2 monopole *** particular, we explain how the second Stiefel–Whitney number w2, the Z2 monopole charge, and the linking number between nodal lines are related. Finally, we review the properties of 2 D and 3 D topological insulators characterized by the nontrivial second Stiefel Whitney class.

关键词： topological semimetal

Modeling and analysis of the ocean dynamic with Gaussian complex network

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Chinese Physics B 2020年第10期29卷 588-597页

作者： Xin Sun Yongbo Yu Yuting Yang Junyu Dong Christian bohm Xueen Chen Department of Computer Science and Technology Ocean University of ChinaQingdao 266000China Frontiers Science Center for Deep Ocean Multispheres and Earth System Qingdao 266000China Institut für Informatik Ludwig Maximilian University of MunichMunich 80331-81929Germany College of Physical and Environmental Oceanography Ocean University of ChinaQingdao 266000China

The techniques for oceanographic observation have made great progress in both space-time coverage and quality, which make the observation data present some characteristics of big data. We explore the essence of global ocean dynamic via constructing a complex network with regard to sea surface temperature. The global ocean is divided into discrete regions to represent the nodes of the network. To understand the ocean dynamic behavior, we introduce the Gaussian mixture models to describe the nodes as limit-cycle oscillators. The interacting dynamical oscillators form the complex network that simulates the ocean as a stochastic system. Gaussian probability matching is suggested to measure the behavior similarity of regions. Complex network statistical characteristics of the network are analyzed in terms of degree distribution, clustering coefficient and betweenness. Experimental results show a pronounced sensitivity of network characteristics to the climatic anomaly in the oceanic circulation. Particularly, the betweenness reveals the main pathways to transfer thermal energy of El Niño–Southern oscillation. Our works provide new insights into the physical processes of ocean dynamic, as well as climate changes and ocean anomalies.

关键词： complex networks ocean dynamic Gaussian mixture model physical processes

Interface evolution of TiAl/Ti6242 transient liquid phase joint using Ti, Cu foils as insert metals

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中国有色金属学会会刊：英文版 2005年第2期15卷 375-378页

作者：段辉平 K.H.bohm V.Ventzke M.Koak School of Materials Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100083 China Institute for Materials Research GKSS Research Center Geesthacht Geesthacht D-21502 Germany

The interface evolution of TiAl/Ti6242 joint produced by transient liquid phase(TLP) bonding with Ti, Cu foils as insert metals was investigated. The results show that the surface oxide layer on TiAl plays a very important role in the formation process of the joint. A ‘bridge’ effect is observed because of the presence of the oxide layer on the surface of TiAl. The diffusion behavior of Cu atoms in TiAl is strongly controlled by the vacancies beneath the surface of TiAl. Based on the interface diffusion and interface wettability, a mechanism for the effect of bonding pressure, bonding temperature, holding time and stacking sequence of the insert foils on the joint formation process were proposed.

关键词：铝钛合金瞬态液相压焊表面蒸气机械性能

Magnetic wallpaper Dirac fermions and topological magnetic Dirac insulators

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npj Computational Materials 2023年第1期9卷 1695-1702页

作者： Yoonseok Hwang Yuting Qian Junha Kang Jehyun Lee Dongchoon Ryu Hong Chul Choi bohm-Jung Yang Center for Correlated Electron Systems Institute for Basic Science(IBS)Seoul 08826Korea Department of Physics and Astronomy Seoul National UniversitySeoul 08826Korea Center for Theoretical Physics(CTP) Seoul National UniversitySeoul 08826Korea

Topological crystalline insulators(TCIs)can host anomalous surface states which inherits the characteristics of crystalline symmetry that protects the bulk ***,the diversity of magnetic crystalline symmetries indicates the potential for novel magnetic TCIs with distinct surface ***,we propose a topological magnetic Dirac insulator(TMDI),whose two-dimensional surface hosts fourfold-degenerate Dirac fermions protected by either the p'_(c)4mm or p40 g0 m magnetic wallpaper *** bulk topology of TMDIs is protected by diagonal mirror symmetries,which give chiral dispersion of surface Dirac fermions and mirror-protected hinge *** propose candidate materials for TMDIs including Nd_(4)Te_(8)Cl_(4)O_(2)0 and DyB_(4) based on first-principles calculations,and construct a general scheme for searching TMDIs using the space group of paramagnetic parent *** theoretical discovery of TMDIs will facilitate future research on magnetic TCIs and illustrate a distinct way to achieve anomalous surface states in magnetic crystals.

关键词： Dirac topological protected

Diversity, Cohesion and the Development of the European Integration

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Economics World 2014年第6期2卷 395-408页

作者： Amost bohm Lenka Stibranyiova Technical University of Liberec Liberec Czech Republic

The European Union （EU） this year has entered into the next phase of its existence, not only in terms of new economic conditions of the unwinding of the financial and economic crisis, but also on the basis of the results of European Parliament elections and the adoption of the EU financial fi＇amework for the period from 2014 to 2020. These indisputable facts does not change our view of the situation in which the EU is, or at major tasks whose managing can be considered as condition of its continued existence as an important part of the global economy. As the fundamental problem of the EU, persisting differences in economic level of the member states is considered. The aim of this paper is not to formulate and even to propose how the EU should look like in the future, but to assess criteria of decision making about concept of its future direction. In this context, the verification of argument will be performed, that only the integration of the countries that have common interests and objectives respectively are able to make the same efforts to meet them, is in certain stages of integration possible and functional. Conversely, a broader territorial structured integration of countries with significantly different economic parameters is feasible and functional only at lower stages of integration. This paper starts from that the process of economic convergence among member states as a condition for integration can be realized at the lower stage of the integration process, in terms of economic and monetary union, then only the expense of reducing the dynamics of economic development of integration group as a whole. Some degree of equilibrium of economic levels represents an important condition for the success of the integration project. To meet this goal, current differences in economic level of individual EU member states （comparative analysis using indicators of growth rate and development of GDP/capita） will be analyzed, including the assessment of the cost of the EU f

关键词： European Union (EU) enlargement and performance stages of economic integration financial framework 2014-2020 cohesion programs economic convergence rescue systems and mechanisms of the EU

The Crisis, Responsibility and Regulation

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Chinese Business Review 2012年第4期11卷 343-354页

作者： bohm Amost, Fujerova Irena Technical University ofLiberec Liberec Czech Republic

Any observer of current economic development in the world and in the Europe should ask about the causes of the current crisis situation. The authors of this article perceive current situation in the European Union and many of its member states associated with long-term developmental tendencies still less respecting the objective differences in various economic situation of the member states. Establishment and further functioning of monetary union in Europe is gradually becoming a burden for many countries, which prevents full utilization of instruments of monetary and fiscal policy by daily, and in many cases qualitative differences in the problems of economies of individual member states. The fulfillment of these tendencies in particular in the Euro Area monetary policy is confronted with the dominant position of member states in fiscal policy and in the mutual differences among member states. As considerations of differences in economic level and in member states fiscal policies, both of them are based on official figures, some of them are part of the state. In addition, EU institutions face to face to crisis they are increasingly resorting to deepening statist centralization and enter more often to the processes which are usually domains of business subjects, at most of nation states. All these trends lead to a deepening asymmetry between the decision-making processes and responsibilities for economic development and they could lead to even larger failure of national economies or at European or global level. Since the accession of the Czech Republic to the European Union in 2004 our department has dealing with issues connecting to the economic management of insurance companies and in relation to the ongoing integration process research interest is extended also to other segments of financial markets.

关键词： European Union monetary and fiscal policy responsibility regulation

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Coin collecting

疯狂英语（新策略） 2019年第8期 58-59页

作者： Alan bohm 陆洪达不详

Coin collecting is one of the oldest hobbies and many people also like it in recent years,ifs become a very popular hobby for children of all *** fact,it's one of the best *** younger children,you can help them build ... 详细信息

关键词： Coin collecting oldest hobbies coin collection

Venus Flytrap HKT1-Type Channel Provides for Prey Sodium Uptake into Carnivorous Plant Without Conflicting with Electrical Excitability

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Molecular Plant 2016年第3期9卷 428-436页

作者： J. bohm S. Scherzer S. Shabala E. Krol E. Neher T.D. Mueller R. Hedrich Julius-yon-Sachs Institute Department for Molecular Plant Physiology and Biophysics University of Wurzburg Julius-von-Sachs Platz 2 97082 Wurzburg Germany School of Land and Food University of Tasmania Hobart TAS 7001 Australia Zoology Department College of Science King Saud University PO Box 2455 Riyadh 11451 Saudi Arabia Department for Membrane Biophysics Max Planck Institute for Biophysical Chemistry 37077 Goettingen Germany

The animal diet of the carnivorous Venus flytrap, Dionaea muscipula, contains a sodium load that enters the capture organ via an HKT1-type sodium channel, expressed in special epithelia cells on the inner trap lobe surface. DmHKT1 expression and sodium uptake activity is induced upon prey contact. Here, we analyzed the HKT1 properties required for prey sodium osmolyte management of carnivorous Dionaea. Analyses were based on homology modeling, generation of model-derived point mutants, and their functional testing in Xenopus oocytes. We showed that the wild-type HKT1 and its Na^＋- and K^＋-permeable mutants function as ion channels rather than K^＋ transporters driven by proton or sodium gradients. These structural and biophysical features of a high-capacity, Na^＋-selective ion channel enable Dionaea glands to manage prey-derived sodium loads without confounding the action potential-based information management of the flytrap.

关键词： sodium channel HKT1 Dionaea muscipula action potential glands sodium uptake

Correction to“Asymmetrically hypointense veins on T2*w imaging and susceptibility-weighted imaging in ischemic stroke”[World J Radiol 2013;5(4):156-165]

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World Journal of Radiology 2018年第1期10卷 7-8页

作者： Ulf Jensen-Kondering Ruwen bohm Institute of Neuroradiology University of Schleswig-HolsteinCampus KielKiel 24105Germany Institute of Experimental and Clinical Pharmacology University of Schleswig-HolsteinCampus KielKiel 24105Germany

Correction to:Jensen-Kondering U,B?hm *** hypointense veins on T2*w imaging and susceptibility-weighted imaging in ischemic *** J Radiol 2013;5(4):156-165 PMID:23671751 DOI:10.4329/wjr.v5.i4.156[1].Results Third paragraph:(1)(n=17441 patients)should read(n=441 patients)instead;(2)(n=4111 patients)should read(n=111 patients)*** paragraph:(1)(>6 h,n=15579 patients)should read(>6 h,n=579 patients)instead;(2)(≤6 h=11337 patients)should read(≤6 h=337 patients)instead;(3)(170 patients)should read(180 patients)instead.

关键词： pat