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Seismic responses and resilience of novel SMA-based self-centring eccentrically braced frames under near-fault ground motions

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Frontiers of Structural and Civil Engineering 2022年第8期16卷 962-975页

作者： zhi-peng CHEN Songye ZHU Department of Civil and Environmental Engineering The Hong Kong Polytechnic UniversityHong Kong 999077China

In this paper,the seismic responses and resilience of a novel K-type superelastic shape memory alloy(SMA)self-centring(SC)eccentrically braced frame(EBF)are *** simulation models of the SMA-based SC-EBF and a corresponding equal-stiffness traditional EBF counterpart are first established based on some existing *** twenty-four near-fault ground motions are used to examine the seismic responses of both EBFs under design basis earthquake(DBE)and maximum considered earthquake(MCE)*** fragility and loss analyses are subsequently conducted through incremental dynamic analyses(IDA),and the resilience of the two EBFs are eventually *** resilience assessment basically follows the framework proposed by Federal Emergency and Management Agency(FEMA)with the additional consideration of the maximum residual inter-storey drift ratio(MRIDR).The novel SMA-based SC-EBF shows a much better resilience in the study and represents a promising attractive alternative for future applications.

关键词： shape memory alloy eccentrically braced frame self-centring fragility loss function resilience

Effect of relaxation time on the squeezed correlations of bosons for evolving sources in relativistic heavy-ion collisions

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Nuclear Science and Techniques 2022年第2期33卷 87-92页

作者： Wei-Ning Zhang peng-zhi Xu School of Physics Dalian University of TechnologyDalian 116024China College of Computer Science and Technology Jilin Normal UniversitySiping 136000China

The squeezed back-to-back correlation(SBBC)of a boson-antiboson pair is sensitive to the time distribution of the particle-emitting source,and the SBBC function for an evolving source is expected to be affected by the relaxation time of the *** this study,we investigated the effect of relaxation time on the SBBC *** propose a method for calculating the SBBC function with relaxation-time approximation for evolving *** functions of D^(0)D^(-0)in relativistic heavy-ion collisions were investigated using a hydrodynamic *** found that the relaxation time reduces the amplitudes of the SBBC *** becomes apparent for long relaxation times and large initial relative deviations of the chaotic and squeezed amplitudes from their equilibrium values in the temporal steps.

关键词： Relaxation time Squeezed back-to-back correlation Evolving source Relativistic heavy-ion collisions

NUMERICAL SIMULATION OF PROPAGATION AND BREAKING PROCESSES OF A FOCUSED WAVES GROUP

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Journal of Hydrodynamics 2012年第3期24卷 399-409页

作者： HUANG Zong-liu LIN peng-zhi State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University Chengdu 610065China

A two-dimensional numerical wave flume is developed to study the focused waves group propagation and the consequent breaking processes. The numerical model is based on the Reynolds-Averaged Navier-Stokes （PANS） equations, with the standard k - c turbulence model to simulate the turbulence effects. To track the complicated and broken free-surface, the Volume Of Fluid （VOF） method is employed. The numerical model combines the ＂Partial Cell Treatment （PCT）＂ method with the ＂Locally Relative Stationary （LRS）＂ concept to treat the moving wave paddle so that various waves can be generated directly in a fixed Cartesian grid system. The theoretical results of the linear and nonlinear waves are used to validate the numerical wave flume firstly, and then a plunging breaking wave created by a focused waves group is simulated. The numerical results are compared to the experimental data and other simulation results, with very good agreements. The turbulence intensity, the flow field and the energy dissipation in the breaking processes are analyzed based on the numerical results. It is shown that the present numerical model is efficient and accurate for studying the waves group generation, the waves packet propagation, and the wave breaking processes.

关键词： focused waves group plunging breaking Volume Of Fluid (VOF) k - ε turbulence model irregular wave maker

Numerical Simulation of the Vortex-Induced Vibration of A Curved Flexible Riser in Shear Flow

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China Ocean Engineering 2018年第3期32卷 301-311页

作者： ZHU Hong-jun LIN peng-zhi State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum University State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University

A series of fully three-dimensional(3 D) numerical simulations of flow past a free-to-oscillate curved flexible riser in shear flow were conducted at Reynolds number of 185–1015. The numerical results obtained by the two-way fluid–structure interaction(FSI) simulations are in good agreement with the experimental results reported in the earlier study. It is further found that the frequency transition is out of phase not only in the inline(IL) and crossflow(CF) directions but also along the span direction. The mode competition leads to the non-zero nodes of the rootmean-square(RMS) amplitude and the relatively chaotic trajectories. The fluid–structure interaction is to some extent reflected by the transverse velocity of the ambient fluid, which reaches the maximum value when the riser reaches the equilibrium position. Moreover, the local maximum transverse velocities occur at the peak CF amplitudes, and the values are relatively large when the vibration is in the resonance regions. The 3 D vortex columns are shed nearly parallel to the axis of the curved flexible riser. As the local Reynolds number increases from 0 at the bottom of the riser to the maximum value at the top, the wake undergoes a transition from a two-dimensional structure to a 3 D one. More irregular small-scale vortices appeared at the wake region of the riser, undergoing large amplitude responses.

关键词： vortex-induced vibration flexible riser shear flow fluid–structure interaction computational fluid dynamics

Depth-resolved numerical model of dam break mud flows with Herschel-Bulkley rheology

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Journal of Mountain Science 2022年第4期19卷 1001-1017页

作者： TANG Jin-bo LIN peng-zhi CUI peng State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan UniversityChengdu 610065China Key Laboratory of Mountain Hazards and Earth Surface Processes Chinese Academy of SciencesInstitute of Mountain Hazards and EnvironmentChinese Academy of Sciences and Ministry of Water ConservancyChengdu 610041China Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing 100101China

Mud flows are common phenomena in mountainous areas,which can threaten human safety and cause property losses under certain extreme *** the dynamic characteristics of mud flows,especially in the vertical direction,is helpful for risk reduction and hazard *** this study,a 2D depth-resolved numerical model based on Herschel-Bulkley rheology was developed to study the vertical structures of unsteady mud flows with a *** numerical model was solved by the projection method,and the free surface of mud flows was captured through the VOF *** fully validate this new model,a series of laboratory experiments involving dam break mud flows were conducted,and the mud flow heights,bottom pressures and envelopes of mud residuum were *** numerical model proposed in this study was first validated by the steady-state solution for uniform flows of Herschel-Bulkley fluid on an inclined ***,the simulated and measured mud flow heights,bottom pressures at different x locations and envelopes with different bed slopes showed good ***,the numerical results for a Herschel-Bulkley fluid dam break flow were used to validate the proposed model,which further revealed good *** that,the scenarios in which mud flows impact on a structure were numerically studied,and the vertical profiles of the front velocity and impact pressure on the structure were analyzed and *** results show that a plug layer was formed in the mud flow under unsteady and nonuniform flow conditions,and the impact pressure on the structure was dominated by the dynamic *** addition,the vertical position with the maximum impact pressure acting on the structure was not at the bottom or the surface of the mud flows,and the normalized vertical position rose as the yield stress and consistency coefficient increase for Herschel-Bulkley fluids.

关键词： Mud flows Herschel-Bulkley rheology Depth-resolved model Numerical simulation Vertical profiles

Effects of time-varying liquid bridge forces on rheological properties,and resulting extrudability and constructability of three-dimensional printing mortar

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Frontiers of Structural and Civil Engineering 2023年第9期17卷 1295-1309页

作者： peng zhi Yu-Ching WU Timon RABCZUK Department of Structural Engineering Tongji UniversityShanghai 200092China Institute of Structural Mechanics Bauhaus University of WeimarWeimar 99423Germany

Extrudability and constructability are two important,yet contradictory issues pertaining to the construction of three-dimensional(3D)printing *** is easily achieved when 3D printing cement mortar has a high water content and low cohesion,but the printed structure is easily ***,a 3D printing cement mortar with a low water content and high cohesion has a relatively stable printed structure although the cement mortar might not be *** study proposes a particle-based method to simulate 3D printing mortar extrusion and construction as an overall planning tool for building ***,a discrete element model with time-varying liquid bridge forces is developed to investigate the microscopic effects of these forces on global rheological ***,a series of numerical simulations relevant to 3D printable mortar extrudability and constructability are carried *** study demonstrates that the effects of time-varying liquid bridge forces on rheological properties and the resulting extrudability and constructability of 3D printing mortar are ***,an optimized region that satisfies both the extrusion and construction requirements is provided for 3D printing industry as a reference.

关键词： particle-based simulation liquid bridge force rheological property 3D printing mortar extrudability constructability

Structures and energetics of semicoherent interfaces of precipitates in hcp/bcc systems:A molecular dynamics study

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Journal of Materials Science & Technology 2021年第8期67卷 50-60页

作者： Jin-Yu Zhang Fu-zhi Dai zhi-peng Sun Wen-Zheng Zhang Key Laboratory of Advanced Materials(MOE) School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China Science and Technology of Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of ChinaChengdu 610041China

α/β(hcp/bcc)interfaces are of great importance in the microstructure development and the mechanical properties of titanium and zirconium *** work contributes to the study of interface energetics and interfacial structures of the precipitate in the hcp/bcc system based on a simulation study using molecular statics(MS)and molecular dynamics(MD).The input orientation relationship(OR)was calculated based on the O-line *** on the energy of the interfaces containing the invariant line(IL),two preferred facets were determined by the Wulff construction,which explained the observed orientations of the habit plane(HP)and the side facet(SF).The deviation of the observed precipitate morphology from the equilibrium shape was discussed in terms of interface *** structures of the interfaces surrounding a three-dimensional(3 D)precipitate,including the preferred facets and the end face,were obtained at the atomic *** simulated dislocation structures and atomic structures in these interfaces are in good agreement with those of the experimental observations for Ti-Cr alloys.A method was suggested for modifying the O-cell structure with the guidance of the relaxed structure,yielding consistency between the calculated dislocation structure based on the generalized O-element approach and the simulation results.

关键词： Interface Misfit dislocation Precipitate

Optical Properties of *** and Nanosaws Synthesized by Thermal Evaporation Method

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Chinese Journal of Chemical Physics 2012年第2期25卷 226-230,I0004页

作者： zhi-wei peng Bing-suo Zou School of Physics and Electronic Engineering Guangzhou UniversityGuangzhou 510006China Key Lab for Micro-Nano Optoeletronic Devices of MOE Hunan UniversityChangsha 410082China

By a simple one-step H2-assisted thermal evaporation method, high quality CdS nanos- tructures have been successfully fabricated on Au coated Si substrates in large scale. The as-synthesized CdS nanostructures consisted of sword-like nanobelts and toothed nanosaws with a single-crystal hexagonal wurtzite structure. The deposition temperature played an important role in determining the size and morphology of the CdS nanostruetures. A combination of vapor-liquid-solid and vapor-solid growth mechanisms were proposed to interpret the formation of CdS nanostructures. Photoluminescence measurement indicated that the nanobelts and nanosaws have a prominent green emission at about 512 nm, which is the band-to-band emission of CdS. The waveguide characteristics of both types of CdS nanos-truetures were observed and discussed.

关键词： CdS nanostructures Thermal evaporation Photoluminescence Optical waveguide

Identifiability of intermediate variables on causal paths

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Frontiers of Mathematics in China 2013年第3期8卷 517-539页

作者： Wanlu DENG zhi GENG peng LUO School of Mathematical Sciences Peking University Beijing 100871 China

We discuss the discovery of causal mechanisms and identifiability of intermediate variables on a causal path. Different from variable selection, we try to distinguish intermediate variables on the causal path from other variables. It is also different from ordinary model selection approaches which do not concern the causal relationships and do not contain unobserved variables. We propose an approach for selecting a causal mechanism depicted by a directed acyclic graph （DAG） with an unobserved variable. We consider several causal networks, and discuss their identifiability by observed data. We show that causal mechanisms of linear structural equation models are not identifiable. Furthermore, we present that causal mechanisms of nonlinear models are identifiable, and we demonstrate the identifiability of causal mechanisms of quadratic equation models. Sensitivity analysis is conducted for the identifiability.

关键词： Causal network directed acyclic graph (DAC) identifiability intermediate variable structural equation model