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Unpinning the spiral waves by using parameter waves

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Chinese Physics B 2021年第5期30卷 682-686页

作者： lu peng Jun Tang School of Materials and Physics China University of Mining and TechnologyXuzhou 221116China

The spiral waves anchored to heterogeneous areas are more difficult to control and eliminate than freely rotating ones in homogenous *** eliminate pinned spiral waves,the resistant force should be provided to resist the pinning *** than advection field,we introduce parametric wave to play the role of providing resistant *** is found that the parametric wave with large enough amplitude and proper frequency can unpin and eliminate the spiral wave *** capability of parametric wave in providing resistant force is dependent on its amplitude and frequency *** the basis of parametric wave,the dependence of pinning force on the size and level of heterogeneity is further confirmed.

关键词： pinned spiral wave heterogeneity pinning force

Packing properties of binary mixtures in disordered sphere systems

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Particuology 2014年第5期12卷 155-166页

作者： Lingyi Meng peng lu Shuixiang Li Department of Mechanics & Aerospace Engineering College of EngineeringPeking University

Mixtures of binary spheres are numerically simulated using a relaxation algorithm to investigate the effects of volume fraction and size ratio, A complete profile of the packing properties of binary spheres is given. The density curve with respect to the volume fraction has a triangular shape with a peak at 70% large spheres. The density of the mixture increases with the size ratio, but the growth becomes slow in the case of a large size disparity, The volume fraction and size ratio effects are reflected in the height and movement, respectively, of specific peaks in the radial distribution functions. The structure of the mixture is further analyzed in terms of contact types, and the mean coordination number is demonstrated to be primarily affected by ＂large-small＂ contacts. A novel method for estimating the average relative excluded volume for binary spheres by weighting the percentages of contact types is proposed and extended to polydisperse packings of certain size distributions. The method can be applied to explain the density trends of polydisperse mixtures in disordered sphere systems,

关键词： Disordered packing Binary spheres Volume fraction Size ratio

History dynamics of unified empire in China(770 BC to 476 BC)

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CAAI Transactions on Intelligence Technology 2023年第3期8卷 880-892页

作者： peng lu Mengdi Li Jiawen lu Zhuo Zhang Department of Sociology Central South UniversityChangshaChina School of Automation Central South UniversityChangshaChina Social System Center Beijing Institute for General Artificial IntelligenceBeijingChina Depart of Economics Graduate School of Arts&SciencesColumbia UniversityNew YorkNew YorkUSA

The laws and regulations in human history can be revealed by computational *** 221 before Christ(BC)to 1912 Anno Domini(AD),the unification pattern has dominated the main part of Chinese history for 2132 *** the emergence of the first unified empire,the Qin Empire in 221 BC,there existed the Eastern Zhou dynasty(770 BC to 221 BC).This long dynasty has two stages,and here we focus on the first *** Spring-Autumn stage was from 770 BC(with 148 states)to 476 BC(with 32 states).The whole country(China)is modelled as a multi‐agent system,which contains multiple local *** behave autonomously under certain action rules(wars and conflicts),which forms the main reason for the annexations and disappearance of most *** factors(power,loyalty,bellicosity and alliance)have been considered in our model settings,and simulation outcomes will be monitored and ***,an optimal solution is obtained,which well unveils the internal mechanism and statistical features of real big ***,counterfactuals are used to explore the non‐linear effects of the key factors,which deepens the authors’understanding of civilisa-tion evolutions in human history.

关键词： civilization dynamics empire dynamics the great unity

Scaling law of resolved-scale isotropic turbulence and its application in large-eddy simulation

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Acta Mechanica Sinica 2014年第3期30卷 339-350页

作者： Le Fang Bo Li Li-peng lu cole Centrale de Pe'kin Beihang University The State Key Laboratory of Nonlinear Mechanics Chinese Academy of Science Laboratoire de M canique des Fluides et d’Acoustique Universit de Lyoncole centrale de Lyon69134 EcullyFrance School of Energy and Power Engineering Beihang University

Eddy-damping quasinormal Markovian （EDQNM） theory is employed to calculate the resolved-scale spectrum and transfer spectrum, based on which we investigate the resolved-scale scaling law. Results show that the scaling law of the resolved-scale turbulence, which is affected by several factors, is far from that of the full-scale turbulence and should be corrected. These results are then applied to an existing subgrid model to improve its performance. A series of simulations are performed to verify the necessity of a fixed scaling law in the subgrid modeling.

关键词： Scaling law Large-eddy simulation CZZSmodel

Heat transport mechanisms of low Mach number turbulent channel flow with spanwise wall oscillation

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Acta Mechanica Sinica 2010年第3期26卷 391-399页

作者： Jian Fang Li-peng lu Liang Shao National Key Laboratory of Science and Technology on Aero-Engines School of Jet Propulsion Beihang University 100191 Beijing China Laboratory of Fluid Mechanics and Acoustics Ecole Centrale de Lyon Lyon France

Large eddy simulation （LES） of low Mach num- ber compressible turbulent channel flow with spanwise wall oscillation （SWO） is carried out. The flow field is analyzed with emphases laid on the heat transport as well as its rela- tion with momentum transport. When turbulent coherent structures are suppressed by SWO, the turbulent transports are significantly changed, however the momentum and heat transports change in the same manner, which gives the evi- dence of inherently consistent transport mechanisms between momentum and heat in turbulent boundary layers. The Reynolds analogies of all the flow cases are quite good, which confirms again the fact that the transport mechanisms of momentum and heat are consistent, which gives theoreti- cal support for controlling the wall heat flux control by using the drag reducing techniques.

关键词： Large eddy simulation Turbulent heat transport Wall heat fluxSpanwise wall oscillation

Acoustic emission study of the plastic deformation of quenched and partitioned 35CrMnSiA steel

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International Journal of Minerals,Metallurgy and Materials 2014年第12期21卷 1196-1204页

作者： Yang Li Gui-yong Xiao lu-bin Chen Yu-peng lu Key Laboratory for Liquid–Solid Structural Evolution and Processing of Materials Ministry of Education of Chin Shandong University School of Materials Science and Engineering Shandong University

Acoustic emission （AE） monitored tensile tests were performed on 35CrMnSiA steel subjected to different heat treatments. The results showed that quenching and partitioning （Q-P） heat treatments enhanced the combined mechanical properties of high strength and high ductility for commercial 35CrMnSiA steel, as compared with traditional heat treatments such as quenching and tempering （Q-T） and austempering （AT）. AE signals with high amplitude and high energy were produced during the tensile deformation of 35CrMnSiA steel with retained austenite （RA） in the microstructure （obtained via Q-P and AT heat treatments） due to an austenite-to-martensite phase transformation. Moreover, additional AE signals would not appear again and the mechanical properties would degenerate to a lower level once RA degenerated by tempering for the Q-P treated steel.

关键词： low alloy steels plastic deformation heat treatment acoustic emissions martensitic transformations

Conformal Ricci flow on asymptotically hyperbolic manifolds

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Science China Mathematics 2019年第1期62卷 157-170页

作者： peng lu Jie Qing Yu Zheng Department of Mathematics University of Oregon Department of Mathematics University of California at Santa Cruz School of Mathematical Sciences East China Normal University

In this article, we study the short-time existence of conformal Ricci flow on asymptotically hyperbolic manifolds. We also prove a local Shi's type curvature derivative estimate for conformal Ricci flow.

关键词： conformal Ricci flow asymptotically hyperbolic manifolds short time existence local Shi's curvature derivative estimates

Introduction of parameterized sea ice drag coefficients into ice free-drift modeling

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Acta Oceanologica Sinica 2016年第1期35卷 53-59页

作者： lu peng LI Zhijun HAN Hongwei Laboratory of Coastal and Offshore Engineering Dalian University of Technology

Many interesting characteristics of sea ice drift depend on the atmospheric drag coefficient （Ca） and oceanic drag coefficient （Cw）. Parameterizations of drag coefficients rather than constant values provide us a way to look insight into the dependence of these characteristics on sea ice conditions. In the present study, the parameterized ice drag coefficients are included into a free-drift sea ice dynamic model, and the wind factor a and the deflection angle θ between sea ice drift and wind velocity as well as the ratio of Ca to Cw are studied to investigate their dependence on the impact factors such as local drag coefficients, floe and ridge geometry. The results reveal that in an idealized steady ocean, Ca/Cw increases obviously with the increasing ice concentration for small ice floes in the marginal ice zone, while it remains at a steady level （0.2-0.25） for large floes in the central ice zone. The wind factor a increases rapidly at first and approaches a steady level of 0.018 when A is greater than 20%. And the deflection angle ~ drops rapidly from an initial value of approximate 80° and decreases slowly as A is greater than 20% without a steady level like a. The values of these parameters agree well with the previously reported observations in Arctic. The ridging intensity is an important parameter to determine the dominant contribution of the ratio of skin friction drag coefficient （Cs＇/Cs） and the ratio of ridge form drag coefficient （Cr＇/Cr） to the value of Ca/Cw, a, and 8, because of the dominance of ridge form drag for large ridging intensity and skin friction for small ridging intensity among the total drag forces. Parameterization of sea ice drag coefficients has the potential to be embedded into ice dynamic models to better account for the variability of sea ice in the transient Arctic Ocean.

关键词： sea ice drag coefficient parameterization free drift modeling

Evaluation of the net CO_2 uptake in the Canada Basin in the summer of 2008

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Acta Oceanologica Sinica 2017年第8期36卷 94-100页

作者： SUN Heng GAO Zhongyong lu peng XIU peng CHEN Liqi Key Laboratory of Global Change and Marine Atmospheric Chemistry of State Oceanic Administration Third Institute of OceanographyState Oceanic Administration State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of Sciences

The third Chinese National Arctic Research Expedition （CHINARE） was conducted in the summer of 2008. During the survey, the surface seawater partial pressure of CO2 （pCO2） was measured, and sea water samples were collected for CO2 measurement in the Canada Basin. The distribution of pCO2 in the Canada Basin was determined, the influencing factors were addressed, and the air-sea CO2 flux in the Canada Basin was evaluated. The Canada Basin was divided into three regions： the ice-free zone （south of 77°N）, the partially ice-covered zone （77°-80°N）, and the heavily ice-covered zone （north of 80°N）. In the ice-free zone, pCO2 was high （320 to 368 patm, 1 patm=0.101 325 Pa）, primarily due to rapid equilibration with atmospheric CO2 over a short time. In the partially ice-covered zone, the surface pCOs was relatively low （250 to 270 patm） due to ice-edge blooms and icemelt water dilution. In the heavily ice-covered zone, the seawater pCO2 varied between 270 and 300 laatm due to biological COs removal, the transportation of low pCOs water northward, and heavy ice cover. The surface seawater pCO2 during the survey was undersaturated with respect to the atmosphere in the Canada Basin, and it was a net sink for atmospheric CO2. The summertime net CO2 uptake of the ice-free zone, the partially ice-covered zone and the heavily ice-covered zone was （4.14±1.08）, （1.79±0.19）, and （0.57±0.03） Tg/a （calculated by carbon, 1 Tg=10^12 g）, respectively. Overall, the net COs sink of the Canada Basin in the summer of 2008 was （6.5＋1.3） Tg/a, which accounted for 4%-10% of the Arctic Ocean COs sink.

关键词： Canada Basin net CO2 uptake partial pressure of CO2