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Towards multiple hazard resilient bridges:a methodology for modeling frequent and infrequent time-varying loads Part I,Comprehensive reliability and partial failure probabilities

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Earthquake Engineering and Engineering Vibration 2012年第3期11卷 293-301页

作者： Zach Liang George C.Lee department of mechanical and Aerospace Engineering University at Buffalo department of Civil Structural and Environmental EngineeringUniversity at Buffalo

The current AASHTO load and resistance factor design （LRFD） guidelines are formulated based on bridge reliability, which interprets traditional design safety factors into more rigorously deduced factors based on the theory of probability. This is a major advancement in bridge design specifications. However, LRFD is only calibrated for dead and live loads. In cases when extreme loads are significant, they need to be individually assessed. Combining regular loads with extreme loads has been a major challenge, mainly because the extreme loads are time variables and cannot be directly combined with time invariant loads to formulate the probability of structural failure. To overcome these difficulties, this paper suggests a methodology of comprehensive reliability, by introducing the concept of partial failure probability to separate the loads so that each individual load combination under a certain condition can be approximated as time invariant. Based on these conditions, the extreme loads （also referred to as multiple hazard or MH loads） can be broken down into single effects. In Part II of this paper, a further breakdown of these conditional occurrence probabilities into pure conditions is discussed by using a live truck and earthquake loads on a bridge as an example. There are three major steps in establishing load factors from MH load distributions：（1） formulate the failure probabilities; （2） normalize various load distributions; and （3） establish design limit state equations. This paper describes the formulation of the failure probabilities of single and combined loads.

关键词： multiple hazards bridge probability-based design comprehensive reliability partial failure probability

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Study on the dynamic characteristics of flow over building cluster at high Reynolds number by large eddy simulation

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Science China(Physics,Mechanics & Astronomy) 2014年第6期57卷 1144-1159页

作者： WANG BoBin WANG ZhiShi CUI GuiXiang ZHANG ZhaoShun department of mechanical engineering Tsinghua University department of Civil and environmental Engineering University of Macao

In this paper,the dynamic characteristics of building clusters are simulated by large eddy simulation at high Reynolds number for both homogeneous and heterogeneous building *** save the computational cost a channel-like flow model is applied to the urban canopy with free slip condition at the upper *** results show that the domain height is an important parameter for correct evaluation of the dynamic *** domain height must be greater than 8h(h is the average building height)in order to obtain correct roughness height while displacement height and roughness sublayer are less sensitive to the domain *** Reynolds number effects on the dynamic characteristics and flow patterns are *** turbulence intensity is stronger inside building cluster at high Reynolds number while turbulence intensity is almost unchanged with Reynolds number above the building *** height increases monotonously with Reynolds number by 20%from Re*=103 to Re*=105 but displacement height is almost *** the canopy layer of heterogeneous building clusters,flow structures vary between buildings and turbulence is more active at high Reynolds number.

关键词： building array high Reynolds number large eddy simulation

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Lattice Boltzmann simulation of natural convection in open end cavity with inclined hot wall

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Applied Mathematics and Mechanics(English Edition) 2015年第4期36卷 523-540页

作者： M.NAZARI H.SHOKRI A.A.MOHAMAD department of mechanical Engineering Shahrood University of Technology department of mechanical Engineering Schulich School of EngineeringCentre for Environmental Engineering for Research and EducationUniversity of Calgary

Natural convection in an open end cavity with a hot inclined wall is simulated based on the lattice Boltzmann method （LBM）. The physics of flow and energy transfer in open end cavities are addressed when the hot wall is inclined. The combination of the two topics （open cavity and inclined walls） is the main novelty of the present study. The effects of the angle of the hot inclined wall on the flow field and heat transfer are thoroughly investigated. The Prandtl number is fixed to 0.71 （air）. The Rayleigh number and the angle of the hot inclined wall are varied in the range of 10^4 to 10^6 and 60° to 85°, respectively. The results are presented for two different aspect ratios, i.e., A = 1 and 2. The results obtained with the LBM are also compared with those of the finite volume method （FVM）. The predicted results of the LBM conform to those of the FVM. The results show that by increasing the angle of the hot inclined wall and the aspect ratio of the cavity, the average Nusselt number decreases. The trend of the local Nusselt number on the inclined wall is also discussed.

关键词： lattice Boltzmann method (LBM) natural convection open end cavity,inclined wall

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A Fully Coupled Thermomechanical Model of Friction Stir Welding(FSW) and Numerical Studies on Process Parameters of Lightweight Aluminum Alloy Joints

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Acta Metallurgica Sinica(English Letters) 2018年第1期31卷 1-18页

作者： Saad B.Aziz Mohammad W.Dewan Daniel J.Huggett Muhammad A.Wahab Ayman M.Okeil T.Warren Liao department of mechanical and Industrial Engineering Louisiana State University department of Civil and environmental Engineering Louisiana State University

This paper presents a new thermomechanical model of friction stir welding which is capable of simulating the three major steps of friction stir welding （FSW） process, i.e., plunge, dwell, and travel stages. A rate-dependent Johnson- Cook constitutive model is chosen to capture elasto-plastic work deformations during FSW. Two different weld schedules （i.e., plunge rate, rotational speed, and weld speed） are validated by comparing simulated temperature profiles with experimental results. Based on this model, the influences of various welding parameters on temperatures and energy generation during the welding process are investigated. Numerical results show that maximum temperature in FSW process increases with the decrease in plunge rate, and the frictional energy increases almost linearly with respect to time for different rotational speeds. Furthermore, low rotational speeds cause inadequate temperature distribution due to low frictional and plastic dissipation energy which eventually results in weld defects. When both the weld speed and rotational speed are increased, the contribution of plastic dissipation energy increases significantly and improved weld quality can be expected.

关键词： Aluminum alloy Friction stir welding Temperature distribution Plastic energy Frictional energy Rate-dependent model Friction modeling

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Impact of Friction Stir Welding (FSW) Process Parameters on Thermal Modeling and Heat Generation of Aluminum Alloy Joints

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Acta Metallurgica Sinica(English Letters) 2016年第9期29卷 869-883页

Friction stir welding （FSW） is a solid-state joining process, where joint properties largely depend on the amount of heat generation during the welding process. The objective of this paper was to develop a numerical thermomechanical model for FSW of aluminum--copper alloy AA2219 and analyze heat generation during the welding process. The thermomechanical model has been developed utilizing ANSYS APDL. The model was verified by comparing simulated temperature profile of three different weld schedules （i.e., different combinations of weld parameters in real weld situations） from simulation with experimental results. Furthermore, the verified model was used to analyze the effect of different weld parameters on heat generation. Among all the weld parameters, the effect of rotational speed on heat generation is the highest.

关键词： Friction stir welding Frictional dissipation energy Temperature distribution Friction modeling Aluminum alloy

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Catalyst–Support Interaction in Polyaniline‑Supported Ni_(3)Fe Oxide to Boost Oxygen Evolution Activities for Rechargeable Zn‑Air Batteries

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Nano-Micro Letters 2025年第1期17卷 176-190页

作者： Xiaohong Zou Qian Lu Mingcong Tang Jie Wu Kouer Zhang Wenzhi Li Yunxia Hu Xiaomin Xu Xiao Zhang Zongping Shao Liang An department of mechanical Engineering The Hong Kong Polytechnic UniversityHung HomKowloonHong Kong SARPeople’s Republic of China Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment TechnologySchool of Environmental Science and TechnologyNanjing University of Information Science and TechnologyNanjing 210044People’s Republic of China department of Chemistry The Chinese University of Hong KongMa Lin BuildingShatinHong Kong SAR 999077People’s Republic of China WA School of Mines:Minerals Energy and Chemical Engineering(WASM‑MECE)Curtin UniversityPerthWA 6102Australia Research Institute for Advanced Manufacturing The Hong Kong Polytechnic UniversityHung HomKowloonHong Kong SARPeople’s Republic of China Research Institute for Smart Energy The Hong Kong Polytechnic UniversityHung HomKowloonHong Kong SARPeople’s Republic of China

Catalyst–support interaction plays a crucial role in improving the catalytic activity of oxygen evolution reaction(OER).Here we modulate the catalyst–support interaction in polyaniline-supported Ni_(3)Fe oxide(Ni_(3)Fe oxide/PANI)with a robust hetero-interface,which significantly improves oxygen evolution activities with an overpotential of 270 mV at 10 mA cm^(-2)and specific activity of 2.08 mA cm_(ECSA)^(-2)at overpotential of 300 mV,3.84-fold that of Ni_(3)Fe *** is revealed that the catalyst–support interaction between Ni_(3)Fe oxide and PANI support enhances the Ni–O covalency via the interfacial Ni–N bond,thus promoting the charge and mass transfer on Ni_(3)Fe *** the excellent activity and stability,rechargeable Zn-air batteries with optimum Ni_(3)Fe oxide/PANI are assembled,delivering a low charge voltage of 1.95 V to cycle for 400 h at 10 mA cm^(-2).The regulation of the effect of catalyst–support interaction on catalytic activity provides new possibilities for the future design of highly efficient OER catalysts.

关键词： Catalyst-support interaction Supported catalysts Heterointerface Oxygen evolution reaction Zn-air batteries

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Effect of forest fire on tree diversity and regeneration potential in a tropical dry deciduous forest of Mudumalai Tiger Reserve, Western Ghats, India

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Ecological Processes 2017年第1期6卷 331-338页

作者： Satyam Verma Dharmatma Singh Sathya Mani Shanmuganathan Jayakumar environmental informatics and Spatial Modeling Lab Department of Ecology and Environmental SciencesSchool of Life SciencesPondicherry UniversityPuducherry 605014India

Introduction:The study was conducted in Mudumalai Tiger Reserve,in the Western Ghats to understand the effect of a single fire event on tree diversity and regeneration *** forest patches were selected which were unburned,2-year-old burn,5-year-old burn,and 15-year-old *** 0.1 ha square plots were laid randomly in all four patches and analyzed for tree diversity,stand structure,and regeneration of tree ***:A total of 4129 individuals of tree species were recorded in field surveys,comprising 3474 seedlings,121 saplings,and 534 ***,40 tree species were recorded in study plots,from which 28 species were seedlings,16 species were saplings,and 37 species were at tree ***:Tree diversity decreased in 2-year-old and 5-year-old burnt plots and was reached to the level of unburnt plots in 15 years of *** of small size classes started increasing after the *** density increased linearly in subsequent years after fire but sapling and tree density recorded less than control in B2 but was higher in B5 and *** overall fire affected diversity,but regeneration showed a positive trend.

关键词： Dry deciduous forest Forest fire Fire mapping Regeneration Western Ghats

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Stand structure, phenology and litterfall dynamics of a subtropical mangrove Bruguiera gymnorrhiza

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Journal of Forestry Research 2016年第3期27卷 513-523页

作者： Md.Kamruzzaman Mouctar Kamara Sahadev Sharma Akio Hagihara Forestry and Wood Technology Discipline Khulna University Laboratory of Forest Utilization Graduate School of Global Environmental Studies Kyoto University department of mechanical & environmental informatics Tokyo Institute of Technology Laboratory of Ecology and Systematics Faculty of ScienceUniversity of the Ryukyus

We evaluated the phenology and litterfall dynamics of the mangrove Bruguiera gymnorrhiza（L.）Lamk along the Okukubi River, Okinawa Island, *** 3 years, this species showed the highest litterfall of leaves and stipules in summer and the lowest litterfall in winter. From Kendall＇s coefficient of concordance, the monthly changes in leaf, stipule, and branch were strongly and significantly concordant among years. Leaf and stipule litterfall could be governed by monthly maximum wind speed, monthly day length, and monthly mean air temperature. Branch litterfall depended on monthly maximum wind speed and monthly rainfall, and increased exponentially with increasing monthly maximum wind speed. Mean total litterfall was 11.8 Mg ha^（-1）yr^（-1）, with the largest component being leaf litterfall（65.8 %）. Annual leaf litterfall per plot was almost constant regardless of the tree density of the plot. Mean leaf longevity was 18 *** and mature propagule litterfall might be influenced by monthly mean air temperature, monthly day length and monthly mean air temperature. The average development periods from flower buds to flowers and flower buds to mature propagules were 1 and 8 months, *** for leaf and branch, all vegetative and reproductive organ litterfall had clear annual cycles. B. gymnorrhiza showed a positive correlation between leaf production and reproductive organ production.

关键词： Constant leaf mass Conversion rate Development phase environmental factors Monthlypattern

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State of the art and computational aspects of time-dependent waiting models for non-signalised intersections

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Journal of Traffic and Transportation Engineering(English Edition) 2020年第6期7卷 808-831页

作者： Raffaele Mauro Andrea Pompigna department of Civil Environmental and Mechanical EngineeringUniversity of TrentoTrento 38123Italy

Time-dependent models are of great importance in highway engineering as they are appropriate for evaluating waiting times and queue lengths at intersections,which are integral parts of various activities in planning,verification and decision support for *** reviewing the literature of the main time-dependent models based on the coordinate transformation method and a discussion about some computational issues in time-evolution profiles for non-signalised intersections,the paper identifies the requirements these models have to satisfy in order to be used as"basic"cases for analysing complex evolutionary ***"basic"cases are presented with their timedependent equations for vehicle waiting times and vehicle number;they have been completed and dimensionally homogenised in this *** they are recursive,these formulas can be applied for sequential intervals in the time domain in both vehicles and passenger car *** closed-form expressions for state variables show to be mutually equivalent in comparison with discrete event simulation models and imbedded Markov chain *** all the three models the paper presents a common deterministic simplification for average waiting time,with good approximation results in the tested *** proposed time-dependent formulas will contribute to a better adherence to the real phenomena,compared to the extremely simplified and unrealistic methods suggested by the international manuals for level of service *** proposed formulas will be useful for current applications and possible future development in order to meet the emerging needs of road and transport engineering.

关键词： Traffic engineering Priority system Non-signalised intersections Time-dependent queue model Shared queue delay Coordinate transformation method

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A multi-class time-dependent model for the analysis of waiting phenomena at a motorway tollgate

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Journal of Traffic and Transportation Engineering(English Edition) 2021年第2期8卷 237-256页

作者： Andrea Pompigna Raffaele Mauro department of Civil Environmental and Mechanical EngineeringUniversity of TrentoTrento 38123Italy

The planning, design and operational management of motorway toll booths are of great interest in traffic engineering, as these facilities directly influence the quality of the service offered to users. This paper focuses on a time-dependent queue model based on the coordinates transformation criterion for operations assessment at a motorway tollgate. This model allows to face the whole spectrum of situations that may characterize a toll booth,some of which often fall outside the boundaries of the probabilistic theory for stationary *** paper proposes an M=G=1 multi-class queue model for the evaluation of evolutionary profiles of waiting times and queue lengths by closed-form equations. The results obtained for three numerical test cases show a good approximation level, compared with the mean values of queue parameters obtained reiterating a discrete-state simulation *** proposed time-dependent equations will be useful in technical cases, allowing to operate quickly and compactly even when probabilistic queue theory is not applicable or produce unrealistic results, and the burden of complexity of the simulation approach is not conveniently absorbable. The discussion highlights a significant flexibility of the model proposed in addressing situations with conventional vehicles, i.e., with total human control and proposes some considerations for application in future scenarios with the presence of connected vehicles(CVs).

关键词： Traffic engineering Time-dependent queue model Shared queue Coordinate transformation method Tollgate

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