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LES investigation of cavitating flows around a sphere with special emphasis on the cavitation–vortex interactions

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Acta Mechanica Sinica 2020年第6期36卷 1238-1257,I0002页

作者： yun Long Xinping Long Bin ji State Key Lab of Water Resources and Hydropower Engineering Science School of Power and Mechanical EngineeringWuhan UniversityWuhan430072China Key Lab of Jet Theory and New Technology of Hubei Province Wuhan UniversityWuhan430072China

Large eddy simulation(LES)was coupled with a homogeneous cavitation model to study turbulent cavitating flows around a *** simulations are in good agreement with available experimental data and the simulated accuracy has been evaluated using the LES verification and validation *** cavitation numbers are simulated to study important flow characteristics in the sphere wake,*** cavity growth/contraction,interactions between the cloud and sheet cavitations and the vortex structure *** spectral characteristics of the wake for typical cloud cavitation conditions were classified as the periodic cavitation mode,high Strouhal number mode and low Strouhal number *** frequency distributions in the wake were analyzed and different dominant flow structures were identified for each of the three ***,the cavitation and vortex relationship was also studied,which is an important issue associated with complex cavitating sphere *** types of cavitating vortex structures alternate,which indicates that three different cavity shedding regimes may exist in the *** of vorticity transport equation shows a significant vorticity increase at the cavitation closure region and in the vortex cavitation *** study provides a physical perspective to further understand the flow mechanisms in cavitating sphere wakes.

关键词： Cavitation Cavitating flow Sphere Large eddy simulation(LES) Vortex structure

Enhancing oxygen reduction reaction of Pt-Co/C nanocatalysts via synergetic effect between Pt and Co prepared by one-pot synthesis

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Rare Metals 2023年第1期42卷 146-154页

作者： yun-Feng Wu ji-Wei Ma yun-Hui Huang School of Materials Science and Engineering Tongji UniversityShanghai201804China School of Materials Science and Engineering Huazhong University of Science and TechnologyWuhan430074China

Designing highly active and durable electrocatalysts towards oxygen reduction reaction(ORR)plays a paramount importance for proton exchange membrane fuel ***-based binary alloys Pt-M(M=3d-transition metals)possessing excellent electronic and geometric properties have received increasing interests as highly active ***,we report a series of Pt_(x)Co/C(x=1,2,3)catalysts by a facile one-pot soft-chemistry *** the acidic conditions,the mass activities of PtCo/C,Pt_(2)Co/C and Pt_(3)Co/C are 0.526,0.462 and 0.441 A·mgPt^(-1),which are 2.60,2.31 and 2.22 times higher than that of Pt/C(0.200 A·mgPt^(-1)),*** specific activities of PtCo/C,Pt_(2)Co/C and Pt_(3)Co/C are 706.59,679.41 and 801.83μA·cm^(-2),which are accordingly 2.89,2.76 and 3.28 times higher than that of Pt/C(244.75μA·cm^(-2)).Notably,Pt_(3)Co/C shows a remarkable *** 5000 cycles of the accelerated durability testing,the mass activity and specific activity of Pt_(3)Co/C catalyst are 2.47 and 3.80 times higher than that of the commercial Pt/C,*** improved ORR activity and durability can be ascribed to the synergistic interaction between Pt and Co.

关键词： Proton exchange membrane fuel cells(PEMFCs) Pt_(x)Co/C catalysts Synergetic effect Oxygen reduction reaction(ORR) One-pot synthesis

Topological r-entropy and Measure Theoretic r-entropy of Flows

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Acta Mathematica Sinica,English Series 2022年第4期38卷 761-769页

作者： Yong ji yun Ping WANG Department of Mathematics Ningbo UniversityNingbo 315211P.R.China School of Science Ningbo University of TechnologyNingbo 315211P.R.China School of Mathematical Sciences and Institute of Mathematics Nanjing Normal UniversityNanjing 210023P.R.China

The topological r-entropy and measure theoretic r-entropy of a flow are *** a flow(X,φ),it is shown that topological(measure theoretic)r-entropy is equal to the topological(measure theoretic)entropy of the time one ... 详细信息

关键词： Topological r-entropy measure theoretic r-entropy flow

Experimental investigation of vortex generator influences on propeller cavitation and hull pressure fluctuations

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Journal of Hydrodynamics 2020年第1期32卷 82-92页

作者： Hong-bo Huang yun Long Bin ji National Key Laboratory on Ship Vibration and Noise China Ship Scientific Research CenterWiuxi 214082China State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan 430072China

In this paper,the transient turbulent cavitating flow around a marine propeller behind a ship was investigated experimentally with emphasis on how vortex generator(VG)influences propeller cavitation and hull pressure *** experiments were carried out in China Large Cavitation Channel with the closed test section covering 10.5 m in length and cross-section of 2.2 m^2×2.0m^*** experiment recorded instantaneous cavitation photos of the propeller and pressure fluctuations on the hull *** results demonstrate that without vortex generator,the sheet cavitation inception begins at-50°(310°),and then from-50°(310°)to 30°,the extent and area of sheet cavitation *** vortex generator installed on the hull,the sheet cavitation inception occurs in advance at-60°(300°),and the sheet cavitation expands to larger rotation range due to the vortex *** is shown that the vortex generator with proper geometry and installed location may contribute the highly nonuniform wake to be more uniform,and can make the change of propeller cavitation to be milder,which decrease the pressure fluctuations in this *** analysis indicates that the vortex generator may promote the energy distribution to be more uniform in physical and spectral space in some degree.

关键词： Cavitating flow pressure fluctuations propeller and ship hull vortex generator

Three-Terminal Thermionic Heat Engine Based on Semiconductor Heterostructures

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Chinese Physics Letters 2020年第12期37卷 11-16页

作者： yun-yun Yang Shuai Xu ji-Zhou He Department of Physics Nanchang UniversityNanchang 330031China

We propose a model for three-terminal thermionic heat engines based on semiconductor *** to electron transport theory,we drive the formulas for the charge current and energy current flowing from the electron reservoir and we then obtain the power output and efficiency in the linear and nonlinear ***,we analyze the performance characteristic of the thermionic heat engine and get the maximum power output by optimizing the performance ***,we optimize the thermodynamic performance of the thermionic heat engine by maximizing the product of the power output and efficiency.

关键词： parameters. reservoir Engine

A mechanical model for the adhesive contact with local sliding induced by a tangential force

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Acta Mechanica Solida Sinica 2017年第4期30卷 369-373页

作者： Gan-yun Huang ji-Feng Yan Department of Mechanics School of Mechanical EngineeringTianjin University

Adhesion has been demonstrated to play an important role in contact and friction between objects at small scales. While various models have been established for adhesive contact under normal forces, studies on the adhesive contact under tangential force have been far fewer, which if any, are mostly confined to the non-slipping situations. In the present work, a model has been proposed for adhesive contact with local sliding under tangential forces. Herein, the onset of local sliding in adhesive contact has been addressed by assuming the nucleation of dislocations. By analogy with the emission of dislocations at a crack tip, the critical tangential force for the onset of sliding has been determined, and its effect on the evolution of contact size has also been studied. Comparison with relevant experiments has verified the validity of the present model.

关键词： Adhesive contact Tangential force Local sliding Dislocation Contact size

Chromatin-remodeling complexes:Conserved and plant-specific subunits in Arabidopsis

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Journal of Integrative Plant Biology 2022年第2期64卷 499-515页

作者： ji-yun Shang Xin-jian He National Institute of Biological Sciences Beijing102206 China Tsinghua Institute of Multidisciplinary Biomedical Research Tsinghua UniversityBeijing100084 China

Adenosine triphosphate-dependent chromatin remodeling complexes are important for the regulation of transcription,DNA replication,and genome stability in *** genetic studies have illustrated various biological functions of core and accessory subunits of chromatin-remodeling complexes in plants,the identification and characterization of chromatin-remodeling complexes in plants is lagging behind that in yeast and *** studies determined whether and how the Arabidopsis SWI/SNF,ISWI,INO80,SWR1,and CHD chromatin remodelers function in multi-subunit complexes in *** conserved and plant-specific subunits of chromatin-remodeling complexes have been identified and *** findings provide a basis for further studies of the molecular mechanisms by which the chromatinremodeling complexes function in plants.

关键词： ATPase chromatin remodeling complex INO80 ISWI SWI/SNF SWR1 transcription

Damage Spreading in Neural Network with Local Connection and Cycle Stored Patterns

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Chinese Physics Letters 1996年第9期13卷 644-647页

作者： ji Dao-yun CHEN Tian-lun Department of Physics Nankai UniversityTianjin 300071

The simulation results of damage spreading show the happening of dynamical chaotic-frozen phase transition in a one-dimensional system,a neural network with cycle stored patterns and local *** chaotic phase,the averag... 详细信息

关键词： behavior chaotic dynamical

A New Sufficient Degree Condition for a Graphic Sequence to Be Forcibly k-Edge-Connected

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Acta Mathematicae Applicatae Sinica 2022年第1期38卷 223-228页

作者： jian-hua YIN ji-yun GUO School of Science Hainan UniversityHaikou 570228China

A graphic sequence π =(d1, d2,..., dn) is said to be forcibly k-edge-connected if every realization of π is k-edge-connected. In this paper, we obtain a new sufficient degree condition for π to be forcibly k-edgeconnected. We also show that this new sufficient degree condition implies a strongest monotone degree condition for π to be forcibly 2-edge-connected and a conjecture about a strongest monotone degree condition for π to be forcibly 3-edge-connected due to Bauer et al.(Networks, 54(2)(2009) 95-98), and also implies a strongest monotone degree condition for π to be forcibly 4-edge-connected.

关键词： graphic sequence forcibly k-edge-connected graphic sequence a strongest monotone degree condition