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Behavior of the collective rotor in nuclear chiral motion

Physical Review C 2019年第6期99卷 064326-064326页

作者： Q. B. Chen N. Kaiser Ulf-G. Meißner J. Meng Physik-Department Technische Universität München D-85747 Garching Germany Helmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics Universität Bonn D-53115 Bonn Germany Institute for Advanced Simulation Institut für Kernphysik and Jülich Center for Hadron Physics Forschungszentrum Jülich D-52425 Jülich Germany Ivane Javakhishvili Tbilisi State University 0186 Tbilisi Georgia State Key Laboratory of Nuclear Physics and Technology School of Physics Peking University Beijing 100871 China Yukawa Institute for Theoretical Physics Kyoto University Kyoto 606-8502 Japan

The behavior of the collective rotor in the chiral motion of triaxially deformed nuclei is investigated using the particle rotor model by transforming the wave functions from the K representation to the R representation. The energy spectra of the doublet bands and their energy differences as functions of the triaxial deformation are first examined and then the angular momentum components of the rotor, proton, neutron, and the total system are investigated. Moreover, the probability distributions of the rotor angular momentum (R plots) and their projections onto the three principal axes (KR plots) are analyzed. The evolution of the chiral mode from a chiral vibration at the low spins to a chiral rotation at high spins is illustrated at triaxial deformations γ=20∘ and 30∘.

关键词： Collective models Nuclear structure & decays

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Fast Parallel Algorithm for Slicing STL Based on Pipeline

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Chinese Journal of Mechanical Engineering 2016年第3期29卷 549-555页

作者： MA Xulong LIN Feng YAO Bo Key Laboratory for Advanced Materials Processing Technology Ministry of Education of China Tsinghua University Department of Mechanical Engineering Army Aviation Institute of PLA

In Additive Manufacturing field, the current researches of data processing mainly focus on a slicing process of large STL files or complicated CAD models. To improve the efficiency and reduce the slicing time, a parallel algorithm has great advantages. However, traditional algorithms can＇t make full use of multi-core CPU hardware resources. In the paper, a fast parallel algorithm is presented to speed up data processing. A pipeline mode is adopted to design the parallel algorithm. And the complexity of the pipeline algorithm is analyzed theoretically. To evaluate the performance of the new algorithm, effects of threads number and layers number are investigated by a serial of experiments. The experimental results show that the threads number and layers number are two remarkable factors to the speedup ratio. The tendency of speedup versus threads number reveals a positive relationship which greatly agrees with the Amdahl＇s law, and the tendency of speedup versus layers number also keeps a positive relationship agreeing with Gustafson＇s law. The new algorithm uses topological information to compute contours with a parallel method of speedup. Another parallel algorithm based on data parallel is used in experiments to show that pipeline parallel mode is more efficient. A case study at last shows a suspending performance of the new parallel algorithm. Compared with the serial slicing algorithm, the new pipeline parallel algorithm can make full use of the multi-core CPU hardware, accelerate the slicing process, and compared with the data parallel slicing algorithm, the new slicing algorithm in this paper adopts a pipeline parallel model, and a much higher speedup ratio and efficiency is achieved.

关键词： additive manufacturing STL model slicing algorithm data parallel pipeline parallel

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Enhanced rejection of cations by low-level cationic surfactant during ultrafiltration of low-level radioactive wastewater

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Separation and Purification technology 2017年 175卷 314-320页

作者： Zhang, Xue Niu, Lixia Li, Fuzhi Zhao, Xuan Hu, Hongying Collaborative Innovation Center for Advanced Nuclear Energy Technology Institute of Nuclear and New Energy Technology Tsinghua University Beijing 100084 China State Environmental Protection Key Laboratory of Microorganism Application and Risk Control (MARC) Graduate School at Shenzhen Tsinghua University Shenzhen 518055 China Environmental Simulation and Pollution Control State Key Joint Laboratory School of Environment Tsinghua University Beijing 100084 China

The influence of cationic surfactant hexadecyl trimethyl ammonium bromide (CTAB) on the rejection of metal salts was investigated during ultrafiltration of low-level radioactive wastewater (LLRW). In the presence of CTAB below the critical micelle concentration (CMC), the rejection of nuclides significantly increased from 24%–33% to 50% for Cs(I) and above 90% for Sr(II), Co(II), and Ag(I). These increased rejections are attributed to CTAB fouling layer, which led to a more hydrophilicity and more positively-charged membrane surface. The nuclide content on the fouling layer increased with increasing CTAB concentration, and 55–80% of Co(II), Sr(II), and Ag(I) were adsorbed on the membrane at 400 mg/L CTAB. The high deposition of Ag(I) is partially due to the formation of AgBr. Based on these results, low-levels of cationic surfactant can significantly enhance the UF rejections of cations, but membrane fouling and nuclide deposition should not be ignored. © 2016

关键词： Cationic surfactant Fouling Low-level radioactive wastewater Nuclide rejection Ultrafiltration

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New method for calculating electromagnetic effects in semileptonic beta-decays of mesons

arXiv

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arXiv 2020年

作者： Seng, Chien-Yeah Feng, Xu Gorchtein, Mikhail Jin, Lu-Chang Meißner, Ulf-G Helmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics Universität Bonn Bonn53115 Germany School of Physics Peking University Beijing100871 China Collaborative Innovation Center of Quantum Matter Beijing100871 China Center for High Energy Physics Peking University Beijing100871 China State Key Laboratory of Nuclear Physics and Technology Peking University Beijing100871 China Helmholtz Institute Mainz MainzD-55099 Germany GSI Helmholtzzentrum für Schwerionenforschung Darmstadt64291 Germany Johannes Gutenberg University MainzD-55099 Germany RIKEN-BNL Research Center Brookhaven National Lab UptonNY11973 United States Physics Department University of Connecticut StorrsCT06269-3046 United States Institute for Advanced Simulation Institut für Kernphysik Jülich Center for Hadron Physics Forschungszentrum Jülich Jülich52425 Germany Tbilisi State University Tbilisi0186 Georgia

We construct several classes of hadronic matrix elements and relate them to the low-energy constants in Chiral Perturbation Theory that describe the electromagnetic effects in the semileptonic beta decay of the pion and the kaon. We propose to calculate them using lattice QCD, and argue that such a calculation will make an immediate impact to a number of interesting topics at the precision frontier, including the outstanding anomalies in |Vus| and the top-row Cabibbo-Kobayashi-Maskawa matrix unitarity. Copyright © 2020, The Authors. All rights reserved.

关键词： Hadrons

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Interaction of Individual Skyrmions in a Nanostructured Cubic Chiral Magnet

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Physical Review Letters 2018年第19期120卷 197203-197203页

作者： Haifeng Du Xuebing Zhao Filipp N. Rybakov Aleksandr B. Borisov Shasha Wang Jin Tang Chiming Jin Chao Wang Wensheng Wei Nikolai S. Kiselev Yuheng Zhang Renchao Che Stefan Blügel Mingliang Tian The Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field Laboratory Chinese Academy of Sciences and University of Science and Technology of China Hefei 230026 China Department of Physics School of Physics and Materials Science Anhui University Hefei 230601 China Laboratory of Advanced Materials Department of Materials Science Collaborative Innovation Center of Chemistry for Energy Materials Fudan University Shanghai 200438 China Department of Physics KTH-Royal Institute of Technology Stockholm SE-10691 Sweden M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences Ekaterinburg 620990 Russia Peter Grünberg Institute and Institute for Advanced Simulation Forschungszentrum Jülich and JARA 52425 Jülich Germany Department of Physics University of Science and Technology of China Hefei 230031 China Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China

We report direct evidence of the field-dependent character of the interaction between individual magnetic skyrmions as well as between skyrmions and edges in B20-type FeGe nanostripes observed by means of high-resolution Lorentz transmission electron microscopy. It is shown that above certain critical values of an external magnetic field the character of such long-range skyrmion interactions changes from attraction to repulsion. Experimentally measured equilibrium inter-skyrmion and skyrmion-edge distances as a function of the applied magnetic field shows quantitative agreement with the results of micromagnetic simulations. The important role of demagnetizing fields and the internal symmetry of three-dimensional magnetic skyrmions are discussed in detail.

关键词： Dipolar interaction Exchange interaction Ferromagnetism Magnetic phase transitions Micromagnetism Spin relaxation

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Influence of Temperature on Stacking Fault Energy and Creep Mechanism of a Single Crystal Nickel-based Superalloy

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Journal of Materials Science & technology 2016年第8期32卷 790-798页

作者： Sugui Tian Xinjie Zhu Jing Wu Huichen Yu Delong Shu Benjiang Qian Shenyang University of Technology Shenyang 110870 China Aviation Key Laboratory of Science and Technology on Materials Testing and Evaluation Science and Technology on Advanced High TemperatureStructural Materials Laboratory Beijing Institute of Aeronautical Materials Beijing 100095 China

The influence of temperatures on the stacking fault energies and deformation mechanism of a Re- containing single crystal nickel-based superalloy during creep at elevated temperatures was investigated by means of calculating the stacking fault energy of alloy, measuring creep properties and performing contrast analysis of dislocation configuration. The results show that the alloy at 760 ℃ possesses lower stacking fault energy, and the stacking fault of alloy increases with increasing temperature. The defor- mation mechanism of alloy during creep at 760 ℃ is 7＇ phase sheared by 〈110〉 super-dislocations, which may be decomposed to form the configuration of Shockley partials plus super-lattice intrinsic stacking fault, while the deformation mechanism of alloy during creep at 1070 ℃ is the screw or edge super- dislocations shearing into the rafted 7＇ phase. But during creep at 7（50 and 980 ℃, some super- dislocations shearing into 7＇ phase may cross-slip from the {111} to {100} planes to form the K-W locks with non-plane core structure, which may restrain the dislocations slipping to enhance the creep resis- tance of alloy at high temperature. The interaction between the Re and other elements may decrease the diffusion rate of atoms to improve the microstructure stability, which is thought to be the main reason why the K-W locks are to be kept in the Re-containing superalloy during creep at 980 ℃.

关键词： Single crystal nickel-based superalloy Stacking fault energy Creep Contrast analysis Deformation mechanism

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Experimental Evaluation of Fatigue Behaviors and Tensile Properties of Selective Laser Melted K536 Alloy at Elevated Temperatures

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Procedia Structural Integrity 2017年 7卷 84-91页

作者： R.D. Xu Z.H. Jiao H.C. Yu Aviation Key Laboratory of Science and Technology on Materials Testing and Evaluation Science and Technology on Advanced High Temperature Structrual Materials Laboratory Beijing Key Laborotory of Aeronautical Materials Testing and Evaluation Beijing Institute of Aeronautical Materials Beijing 100095 China

Additive-manufacturing techniques show more and more utilization potentialities in today’s aviation industry. In order to ensure safe operation of additive-manufactured parts, it is important to have their mechanical properties well-characterized and assessed. In this study, elevated temperature fatigue behaviours and tensile properties of a selective laser melting (SLM) fabricated K536 alloy are investigated for horizontal and vertical building orientation, respectively. A series of tensile tests at 20 ºC ~700 ºC temperature range and stress-controlled fatigue tests at 400ºC and 600ºC are conducted. Effects of building orientation and temperature on tensile and fatigue behaviours are analysed. Scanning Electron Microscopy (SEM) is used to examine the fracture surfaces of fatigue specimens to qualify the failure mechanism and crack initiation sites. K536 parts manufactured via SLM are shown to exhibit anisotropic tensile properties at different testing temperatures. Anisotropy of fatigue properties is not obvious at 400ºC and 600ºC. Cracks are likely to initiate at the surface sliding or subsurface crystallographic plane of fatigue specimens in middle life regime and at subsurface or central zone crystallographic plane in longer life regime. In shorter life regime, cracks are easy to initiate at un-melted zones of fatigue specimens.

关键词： Additive manufacturing Selective Laser Melting K536 fatigue behavior tensile

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Evaluation on Tensile and Fatigue Crack Growth Performances of Ti6Al4V Alloy Produced by Selective Laser Melting

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Procedia Structural Integrity 2017年 7卷 124-132页

作者： Z.H. Jiao R.D. Xu H.C. Yu X.R. Wu Aviation Key Laboratory of Science and Technology on Materials Testing and Evaluation Science and Technology on Advanced High Temperature Structrual Materials Laboratory Beijing Key Laborotory of Aeronautical Materials Testing and Evaluation Beijing Institute of Aeronautical Materials Beijing 100095 China

Additive manufacturing (AM) technologies are increasing in importance for aerospace application, where the demand for a fundamental understanding and predictability of static and dynamic material properties are high. As the most widely used and studied alloy for this technology, Selective laser melting (SLM) produced Ti6Al4V alloy is evaluated on tensile and fatigue crack growth (FCG) performances at RT and 400℃. Conventionally manufactured Ti6Al4V alloys are concerned for comparison. Different orientations are considered to investigate the anisotropy of tensile and FCG behavior. The results show that, the tensile properties at RT and 400℃ are highly dependent on the specimen orientation relative to build direction. The FCG resistance is related to specimen orientation in the near threshold region but no relationship with specimen orientation in the steady growth stage at RT. The FCG resistance is much less influenced by specimen orientation at 400℃. The tensile strength at RT and 400℃ of SLM alloy reaches even exceeds the strength level of conventionally manufactured alloys such as forging, bar and casting. The steady stage FCG resistance under stress ratio of 0.1 of SLM alloy is also comparable to conventionally manufactured alloys. The SLM alloy shows higher FCG resistance under stress ratio of 0.1 than 0.5, but the d a /d N -△ K curves of the two stress ratios are very close to each other. The steady stage FCG rate at RT is slower than 400℃ in the lower △ K region and faster in the higher △ K region.

关键词： SLM tensile properties fatigur crack growth anisotropy elevated temperature

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Deciphering the mechanism of near-threshold J/ψ photoproduction

arXiv

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arXiv 2020年

作者： Du, Meng-Lin Baru, Vadim Guo, Feng-Kun Hanhart, Christoph Meißner, Ulf G. Nefediev, Alexey Strakovsky, Igor Helmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics Universität Bonn BonnD-53115 Germany Institute for Theoretical and Experimental Physics NRC "Kurchatov Institute" Moscow117218 Russia P.N. Lebedev Physical Institute of the Russian Academy of Sciences Leninskiy Prospect 53 Moscow119991 Russia CAS Key Laboratory of Theoretical Physics Institute of Theoretical Physics Chinese Academy of Sciences Zhong Guan Cun East Street 55 Beijing100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing100049 China Institute for Advanced Simulation Institut für Kernphysik Jülich Center for Hadron Physics Forschungszentrum Jülich JülichD-52425 Germany Tbilisi State University Tbilisi0186 Georgia Moscow Institute of Physics and Technology 141700 Institutsky lane 9 Dolgoprudny Moscow Region Russia National Research Nuclear University MEPhI 115409 Kashirskoe highway 31 Moscow Russia Institute for Nuclear Studies Department of Physics George Washington University WashingtonDC20052 United States

The photoproduction of the J/ψ off the proton is believed to deepen our understanding of various physics issues. On the one hand, it is proposed to provide access to the origin of the proton mass, based on the QCD multipole expansion. On the other hand, it can be employed in a study of pentaquark states. The process is usually assumed to proceed through vector-meson dominance, that is the photon couples to a J/ψ which rescatters with the proton to give the J/ψp final state. In this Letter, we provide a compelling hint for and propose measurements necessary to confirm a novel production mechanism via the ΛcD¯ (∗) intermediate states. In particular, there must be cusp structures at the ΛcD¯ (∗) thresholds in the energy dependence of the J/ψ photoproduction cross section. The same mechanism also implies the J/ψ-nucleon scattering lengths of order 1 mfm. Given this, one expects only a minor contribution of charm quarks to the nucleon mass. Copyright © 2020, The Authors. All rights reserved.

关键词： Hadrons

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Behavior of the collective rotor in nuclear chiral motion

arXiv

引用

arXiv 2019年

作者： Chen, Q.B. Kaiser, N. Meißner, Ulf-G Meng, J. Physik-Department Technische Universität München GarchingD-85747 Germany Helmholtz-Institut für Strahlen- und Kernphysik and Bethe Center for Theoretical Physics Universität Bonn BonnD-53115 Germany Institute for Advanced Simulation Institut für Kernphysik Jülich Center for Hadron Physics Forschungszentrum Jülich JülichD-52425 Germany Ivane Javakhishvili Tbilisi State University Tbilisi0186 Georgia State Key Laboratory of Nuclear Physics and Technology School of Physics Peking University Beijing100871 China Yukawa Institute for Theoretical Physics Kyoto University Kyoto606-8502 Japan

The behavior of the collective rotor in the chiral motion of triaxially deformed nuclei is investigated using the particle rotor model by transforming the wave functions from the K-representation to the R-representation. After examining the energy spectra of the doublet bands and their energy differences as functions of the triaxial deformation, the angular momentum components of the rotor, proton, neutron, and the total system are investigated. Moreover, the probability distributions of the rotor angular momentum (R-plots) and their projections onto the three principal axes (KR-plots) are analyzed. The evolution of the chiral mode from a chiral vibration at the low spins to a chiral rotation at high spins is illustrated at triaxial deformations γ = 20◦ and 30◦. Copyright © 2019, The Authors. All rights reserved.

关键词： Angular momentum

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