检索结果-南通市图书馆

Assessment of buckling-restrained braced frame reliability using an experimental limit-state model and stochastic dynamic analysis

引用

Earthquake Engineering and Engineering Vibration 2009年第3期8卷 373-385页

作者： Blake m.Andrews Junho Song Larry A.Fahnestock Wiss JanneyElstner AssociatesIncNorthbrookIllinoisUSA Department of Civil and Environmental Engineering University of Illinois at Urbana-ChampaignUrbanaIllinoisUSA

Buckling-restrained braces （BRBs） have recently become popular in the United States for use as primary members of seismic lateral-force-resisting systems. A BRB is a steel brace that does not buckle in compression but instead yields in both tension and compression. Although design guidelines for BRB applications have been developed, systematic procedures for assessing performance and quantifying reliability are still needed. This paper presents an analytical framework for assessing buckling-restrained braced frame （BRBF） reliability when subjected to seismic loads. This framework efficiently quantifies the risk of BRB failure due to low-cycle fatigue fracture of the BRB core. The procedure includes a series of components that：（1） quantify BRB demand in terms of BRB core deformation histories generated through stochastic dynamic analyses; （2） quantify the limit-state of a BRB in terms of its remaining cumulative plastic ductility capacity based on an experimental database; and （3） evaluate the probability of BRB failure, given the quantified demand and capacity, through structural reliability analyses. Parametric studies were conducted to investigate the effects of the seismic load, and characteristics of the BRB and BRBF on the probability of brace failure. In addition, fragility curves （i.e., conditional probabilities of brace failure given ground shaking intensity parameters） were created by the proposed framework. While the framework presented in this paper is applied to the assessment of BRBFs, the modular nature of the framework components allows for application to other structural components and systems.

关键词： risk and reliability analysis buckling-restrained brace stochastic dynamic analysis first-order reliability method cumulative plastic ductility capacity

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Development of a rarefaction wave at discharge initiation in a storage silo--DEm simulations

引用

Particuology 2018年第1期16卷 37-49页

作者： R. Kobylka J. Horabik m. molenda Institute of Agrophysics Polish Academy of Sciences ul. Doswiadczalna 4 20-290 Lublin Poland

The generation of a rarefaction wave at the initiation of discharge from a storage silo is a phenomenon of scientific and practical interest. The effect, sometimes termed the dynamic pressure switch, may create dangerous pulsations of the storage structure. Owing to the nonlinearity, discontinuity, and heterogeneity of granular systems, the mechanism of generation and propagation of stress waves is complex and not yet completely understood. The present study conducted discrete element simulations to model the formation and propagation of a rarefaction wave in a granular material contained in a silo. modeling was performed for a flat-bottom cylindrical container with diameter of 0.1 or 0.12 m and height of 0.5 m. The effects of the orifice size and the shape of the initial discharging impulse on the shape and extent of the rarefaction wave were examined. Positions, velocities, and forces of particles were recorded every 10-5 s and used to infer the location of the front of the rarefaction wave and loads on construction members. Discharge through the entire bottom of the bin generates a plane rarefaction wave that may be followed by a compaction wave, depending on the discharge rate. Discharge through the orifice generates a spherical rarefaction wave that, after reflection from the silo wall, travels up the silo as a sequence of rarefaction-compaction cycles with constant wavelength equal to the silo diameter, During the travel of the wave along the bin height, the wave amplitude increases with the distance traveled. Simulations confirmed earlier findings of laboratory and numerical （finite element method） experiments and a theoretical approach, estimating the speed of the front of the rarefaction wave to range from 70 to 80 m/s and the speed of the tail to range from 20 to 60 m/s.

关键词： Granular flow Dynamic pressure switch Discrete element method Silo discharge Stress wave Rarefaction wave

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Fabrication of an r-Al_2Ti intermetallic matrix composite reinforced with α-Al_2O_3 ceramic by discontinuous mechanical milling for thermite reaction

引用

International Journal of minerals,metallurgy and materials 2014年第10期21卷 1037-1043页

作者： A.mosleh m.Ehteshamzadeh R.Taherzadeh mousavian Department of materials Science and Engineering Shahid Bahonar University of Kerman Department of metallurgy Zanjan Branch Islamic Azad University

In this study, a powder mixture with an Al/TiO2 molar ratio of 10/3 was used to form an r-Al2Ti intermetallic matrix composite （ImC） reinforced with α-Al2O3 ceramic by a novel milling technique, called discontinuous mechanical milling （Dmm） instead of milling and ignition of the produced thermite. The results of energy dispersive X-ray spectroscopy （EDX） and X-ray diffraction （XRD） of samples with varying milling time indicate that this fabrication process requires considerable mechanical energy. It is shown that Al2Ti-α-Al2O3 ImC with small grain size was produced by Dmm after 15 h of ball milling. Peaks for γ-TLA1 as well as Al2Ti and Al2O3 are observed in XRD patterns after Dmm followed by heat treatment. The microhardness of the Dmm-treated composite produced after heat treatment was higher than Hv 700.

关键词： composite materials intermetallics alumina titanium aluminide ball milling thermite reaction process

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Crystal Growth of[Ca3Al(OH)6·12H2O]2·(SO4)3·2H2O (Ettringite) Studied Under microgravity Conditions

引用

Journal of Wuhan University of Technology(materials Science) 2020年第5期35卷 893-899页

作者： meier m R LEI L Rinkenburger A Plank J Technische Universitat miinchen Chair for Construction Chemistry85747 GarchingLichtenbergstrafie 4Germany

On parabolic flights,the growth of ettringite,[Ca3Al(OH)6·12H2O]2·(SO4)3·2H2O,a major reaction product of cement with water which forms instantaneously,was crystallized under microgravity conditions and *** the experiments,Ca(OH)2/Al2(SO4)3 solutions were combined and reacted for 10?s,followed by immediate filtration of the suspension and subsequent quenching with *** the ettringite crystals,the size,aspect ratios,quantity and morphology were determined and the results were compared with those from identical experiments performed under terrestric *** microgravity,generally smaller crystals (l-2.9 μm) precipitated in larger amount than under normal gravity (l-3.5 μm).The aspect ratios of the crystals grown under terrestric or microgravity condition were comparable at about *** is assumed that the reason for the smaller ettringite crystals is the absence of convection leading to more initial nuclei,but slower crystal growth which is diffusion ***,no preference relative to the ion transport to the different faces of the crystals *** results contribute to the understanding of the mineralization of inorganic salts under microgravity conditions for which hitherto only a handful of examples were reported.

关键词： crystallization ettringite microgravity morphology nucleation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Wash Waves Generated by High Speed Displacement Ships

引用

China Ocean Engineering 2015年第5期29卷 757-770页

作者：周利兰高高 R.H.m.Huijsmans Key Laboratory of High Performance Ship Technology ministry of Education Wuhan University of Technology School of Transportation Wuhan University of Technology Delft University of Technology

It is difficult to compute far-field waves in a relative large area by using one wave generation model when a large calculation domain is needed because of large dimensions of the waterway and long distance of the required computing points. Variation of waterway bathymetry and nonlinearity in the far field cannot be included in a ship fixed process either. A coupled method combining a wave generation model and wave propagation model is then used in this paper to simulate the wash waves generated by the passing ship. A NURBS-based higher order panel method is adopted as the stationary wave generation model; a wave spectrum method and Boussinesq-type equation wave model are used as the wave propagation model for the constant water depth condition and variable water depth condition, respectively. The waves calculated by the NURBS-based higher order panel method in the near field are used as the input for the wave spectrum method and the Boussinesq-type equation wave model to obtain the far-field waves. With this approach it is possible to simulate the ship wash waves including the effects of water depth and waterway bathymetry. Parts of the calculated results are validated experimentally, and the agreement is demonstrated. The effects of ship wash waves on the moored ship are discussed by using a diffraction theory method. The results indicate that the prediction of the ship induced waves by coupling models is feasible.

关键词： wash waves wave generation model wave spectrum method Boussinesq type equation wave model motions of moored ship

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Fabrication and Characterization of Undoped and Cobalt-doped ZnO Based UV Photodetector Prepared by RF-sputtering

引用

Journal of materials Science & Technology 2013年第12期29卷 1139-1145页

作者： Husam S.Al-Salman m.J.Abdullah School of Physics University Sains Malaysia Department of Physics College of ScienceUniversity of Basrah

Undoped and 1 at.% Co-doped ZnO nanostructure based UV photodetectors were successfully fabricated by RF- magnetron sputtering technique with comb like Pt electrodes. Cobalt ions were successfully incorporated into the lattice of the ZnO nanostructure without changing its wurtzite structure. It was indicated that Co-doping can effectively adjust the luminescence properties of the ZnO nanostructure. The undoped and Co-doped ZnO photodetectors were observed to have photosensitivities of 1.44 x 104 % and 8.57 x 102 % and low dark currents of 9.74 x 10-8 A and 1.18 x 10-7 A, respectively.

关键词： Characterization Co-doped ZnO UV photodetector

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Static and dynamic responses of a microcantilever with a T-shaped tip mass to an electrostatic actuation

引用

Acta mechanica Sinica 2016年第6期32卷 1104-1122页

作者： B.Firouzi m.Zamanian S.A.A.Hosseini Department of mechanical Engineering Faculty of Engineering Kharazmi University

In this study, nonlinear static and dynamic responses of a microcantilever with a T-shaped tip mass excited by electrostatic actuations are investigated. The electrostatic force is generated by applying an electric voltage between the horizontal part of T-shaped tip mass and an opposite electrode plate. The cantilever microbeam is modeled as an Euler-Bernoulli beam. The T-shaped tip mass is assumed to be a rigid body and the nonlinear effect of electrostatic force is considered. An equation of motion and its associated boundary conditions are derived by the aid of combining the Hamilton principle and Newton’s method. An exact solution is obtained for static deflection and mode shape of vibration around the static position. The differential equation of nonlinear vibration around the static position is discretized using the Galerkin method. The system mode shapes are used as its related comparison functions. The discretized equations are solved by the perturbation theory in the neighborhood of primary and subharmonic resonances. In addition, effects of mass inertia, mass moment of inertia as well as rotation of the T-shaped mass, which were ignored in previous works, are considered in the analysis. It is shown that by increasing the length of the horizontal part of the T-shaped mass, the amount of static deflection increases, natural frequency decreases and nonlinear shift of the resonance frequency increases. It is concluded that attaching an electrode plate with a T-shaped configuration to the end of the cantilever microbeam results in a configuration with larger pull-in voltage and smaller nonlinear shift of the resonance frequency compared to the configuration in which the electrode plate is directly attached to it.

关键词： mEmS Electrostatic Static deflection Natural frequency Pull-in voltage Perturbation theory T-shaped mass Primary and subharmonic resonances

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Fabrication of chitosan/silica hybrid coating on AZ31 mg alloy for orthopaedic applications

引用

Journal of magnesium and Alloys 2023年第2期11卷 614-628页

作者： m.Kalaiyarasan S.Pugalmani N.Rajendran Department of Chemistry CEG CampusAnna UniversityChennai600025Tamil NaduIndia Department of Orthodontics Saveetha Dental College and HospitalsSaveetha Institute of Medical and Technical ScienceSaveetha UniversityChennai-600077India

Biocompatible conversion of chitosan and chitosan/silica hybrid coating were prepared to enhance the biocompatibility and corrosion resistance of biodegradable AZ31 mg alloy. The coatings were optimized and analysed with potentiodynamic polarization, SEm, ATR-IR and XPS studies. Potentiodynamic polarization studies, revealed that the coatings exhibited high corrosion resistance. The surface morphology of the Ch-3/Si coating showed small globular rough structure. The presence of functional groups was confirmed by ATR-IR. For a better understanding of chitosan/silica hybrid coating, the chemical states were examined by XPS studies. The in-vitro bioactivity of the coated samples was evaluated in Earle’s solution, which formed a dense layer of coral-like structure and calcium-deficient apatite with less stoichiometric ratio than the hydroxyapatite. In-vitro cell culture studies exhibited a good cell proliferation rate and the fabricated Ch-3/Si coating was found to be non-hemolytic. The bacterial studies proved that Ch-3/Si coating possessed inherent antibacterial activity.

关键词： AZ31 mg alloy Chitosan/silica Hemocompatibility mTT assay and antibacterial Studies

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Simulation of buoyancy-induced turbulent flow from a hot horizontal jet

引用

Journal of Hydrodynamics 2014年第1期26卷 104-113页

作者： El-AmIN m.F. SUN Shuyu SALAm Amgad Computational Transport Phenomena Laboratory (CTPL) Division of Physical Sciences and EngineeringKing Abdullah University of Science and Technology

Experimental visualizations and numerical simulations of a horizontal hot water jet entering cold water into a rectangular storage tank are described. Three different temperature differences and their corresponding Reynolds numbers are considered. Both experimental visualization and numerical computations are carried out for the same flow and thermal conditions. The realizable k-e model is used for modeling the turbulent flow while the buoyancy is modeled using the Boussinesq approximation. Polynomial approximations of the water properties are used to compare with the Boussinesq approximation. Numerical solutions are obtained for unsteady flow while pressure, velocity, temperature and turbulence distributions inside the water tank as well as the Froude number are analyzed. The experimental visualizations are performed at intervals of five seconds for all different cases. The simulated results are compared with the visualized results, and both of them show the stratification phenomena and buoyancy force effects due to temperature difference and density variation. After certain times, depending on the case condition, the flow tends to reach a steady state.

关键词： turbulent flow realizablc k - e turbulence model heat transfer jet heat storage

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Slip effects on shearing flows in a porous medium

引用

Acta mechanica Sinica 2008年第1期24卷 51-59页

作者： m.Khan T.Hayat Y.Wang Department of mathematics Quaid-i-Azam University Islamabad 44000 Pakistan Chair of Fluid Dynamics Department of Mechanical Engineering Darmstadt University of TechnologyHochschulstrasse 164289 Darmstadt Germany

This paper deals with the magnetohydrodynamic （mHD） flow of an Oldroyd 8-constant fluid in a porous medium when no-slip condition is no longer valid. modified Darcy＇s law is used in the flow modelling. The non-linear differential equation with non-linear boundary conditions is solved numerically using finite difference scheme in combination with an iterative technique. Numerical results are obtained for the Couette, Poiseuille and generalized Couette flows. The effects of slip parameters on the velocity profile are discussed.

关键词： Porous medium. magnetohydrodynamic flow Slip effect

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：