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Analy.is of ground vibrations due to underground trains by.2.5D finite/infinite element approach

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Earthquake Engineering and Engineering Vibration 2010年第3期9卷 327-335页

作者： Hsiao-Hui Hung y. B. yang Center for Research on Earthquake Engineering （NCREE） Taipei 10617 Chinese Taipei y.nlin University.of Science and Technology Douliu Yunlin 64002 Chinese Taipei

The 2.5D finite/infinite element approach is adopted to study.wave propagation problems caused by.underground moving trains. The irregularities of the near field, including the tunnel structure and parts of the soil, are modeled by.the finite elements, and the wave propagation properties of the far field extending to infinity.are modeled by.the infinite elements. One particular feature of the 2.5D approach is that it enables the computation of the three-dimensional response of the half-space, taking into account the load-moving effect, using only.a two-dimensional profile. Although the 2.5D finite/infinite element approach shows a great advantage in study.ng the wave propagation caused by.moving trains, attention should be given to the calculation aspects, such as the rules for mesh establishment, in order to avoid producing inaccurate or erroneous results. In this paper, some essential points for consideration in analy.is are highlighted, along with techniques to enhance the speed of the calculations. All these observations should prove useful in making the 2.5D finite/infinite element approach an effective one.

关键词： ground vibrations 2.5D finite/infinite element underground train wave number wave propagation

Performance assessment of innovative seismic resilient steel knee braced frame

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Frontiers of Structural and Civil Engineering 2016年第3期10卷 291-302页

作者： Tony.T. y. yang y.anjie LI International Joint Research Laboratory.of Eearthquake Engineering 1239 Siping Road Shanghai 200002 China Department of Civil Engineering University of British Columbia Vancouver BC V6T1Z4 Canada

Buckling restrained knee braced truss moment frame （BRKBTMF） is a novel and innovative steel structural sy.tem that utilizes the advantages of long-span trusses and dedicated structural fuses for seismic applications. Steel trusses are very.economical and effective in spanning large distance. However, conventional steel trusses are ty.ically.not suitable for seismic application, due to its lack of ductility.and poor energy.dissipation capacity. BRKBTMF utilizes buckling restrained braces （BRBs） as the designated structural fuses to dissipate the sudden surge of earthquake energy. This allows the BRKBTMF to economically.and efficiently.create large span structural sy.tems for seismic applications. In this paper, a prototy.e BRKBTMF office building located in Berkeley. California, USA, was designed using performance-based plastic design procedure. The seismic performance of the prototy.e building was assessed using the state-of-the-art finite element software, OpenSees. Detailed BRB hy.teresis and advanced element removal technique was implemented. The modeling approach allows the simulation for the force-deformation response of the BRB and the force redistribution within the sy.tem after the BRBs fracture. The developed finite element model was analy.ed using incremental dy.amic analy.is approach to quantify.the seismic performance of BRKBTMF. The results show BRKBTMF has excellent seismic performance with well controlled structural responses and resistance against collapse. In addition, life cy.le repair cost of BRKBTMF was assessed using the next-generation performance-based earthquake engineering framework. The results confirm that BRKBTMF can effectively.control the structural and non-structural component damages and minimize the repair costs of the structure under different ranges of earthquake shaking intensities. This studies conclude that BRKBTMF is a viable and effective seismic force resisting sy.tem.

关键词： buckling restrained brace innovative structural sy.tem collapse simulation seismic assessment

Quantified evaluation of particle shape effects from micro-to-macro scales for non-convex grains

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Particuology 2016年第2期14卷 23-35页

作者： y. yang J.F. Wang y.M. Cheng Department of Civil and Environmental Engineering The Hong Kong Polytechnic University Hong Kong China Department of Civil and Architectural Engineering City University of Hong Kong Hong Kong China

Particle shape play. an important role in both the micro and macro scales responses of a granular assem- bly. This paper presents a sy.tematic way.to interpret the shape effects of granular material during quasi-static shearing. A more suitable shape descriptor is suggested for the quantitative analy.is of the macroscale strength indexes and contact parameters for non-convex grains, with special consid- eration given to the peak state and critical state. Through a series of numerical simulations and related post-processing analy.is, particle shape is found to directly.influence the strain localisation patterns, microscale fabric distributions, microscale mobilisation indexes, and probability.distribution of the nor- malised contact normal force. Additionally. the accuracy.of the stress-force-fabric relationship can be influenced by.the average normal force and the distribution of contact vectors. Moreover, particle shape play. a more important role than do the confining pressures in determining the friction angle. Strong force chains and the dilation effect are also found to be strongly.influenced by.the high confinin~ oressure.

关键词： Quantitative analy.is Shape factor Statistical analy.is Micro-macro indexes

ARTIFICIAL NEURAL NETWORK MODEL OF CONSTITUTIVE RELATIONSHIP FOR 2A70 ALUMINUM ALLOy

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Acta Metallurgica Sinica(English Letters) 2005年第6期18卷 719-723页

作者： F. Liu D.B. Shan y. Lu y. y. yang School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China

The hat deformation behavior of 2A70 aluminum alloy.was investigated by.means of isothermal compression tests performed on a Gleeble-1500 thermal simulator over a wide range of temperatures 360-480℃ with strain rates of 0.01-1s^-1 and the largest deformation of 60%, and the true stress of the material was obtained under the above-mentioned conditions. The experimental results shows that 2A70 aluminum alloy.is a kind of aluminum alloy.with the property.of dy.amic recovery. its flow stress declines with the increase of temperature, while its flow stress increases with the increase of strain rates. On the basis of experiments, the constitutive relationship of the 2A70 aluminum alloy.was constructed using a BP artificial neural network. Comparison of the predicted values with the experimental data shows that the relative error of the trained model is less than ±3% for the sampled data while it is less than ±6% for the nonsampled data. It is evident that the model constructed by.BP ANN can accurately.predict the flow stress of the 2A70 alloy.

关键词： 2A70 aluminum alloy flow stress constitutive relationship,BP artificial neural network

Optimizing sy.thesis conditions of nanoscale zero-valent iron （nZVI） through aqueous reactivity.assessment

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Frontiers of Environmental Science & Engineering 2015年第5期9卷 813-822页

作者： y.nlai HAN Michael D. y. yang Weixian ZHANG Weile y.N Department of Civil and Environmental Engineering Texas Tech University Lubbock TX 79409 USA State Key.Laboratory.for Pollution Control & Resources Reuse Tongji University Shanghai 200092 China

Nanoscale iron particles （nZVI） is one of the most important engineered nanomaterials applied to environmental pollution control and abatement. Although a multitude of sy.thesis approaches have been proposed, a facile method to screen the reactivity.of candidate nZVI materials produced using different methods or under vary.ng sy.thesis conditions has y.t been established. In this study. four reaction parameters were adjusted in the preparation of borohy.ride-reduced nZVI. The reductive properties of the resultant nanoparticles were assay.d independently.using two model aqueous contaminants, Cu （II） and nitrate. The results confirm that the reductive reactivity.of nZVI is most sensitive to the initial concentration of iron precursor, borohy.ride feed rate, and the loading ratio of borohy.ride to ferric ion during particle sy.thesis. Solution mixing speed, in contrast, carries a relative small weight on the reactivity.of nZVI. The two probing reactions （i.e., Cu（II） and nitrate reduction） are able to generate consistent and quantitative inference about the mass-normalized surface activity.of nZVI. However, the nitrate assay.is valid in dilute aqueous solutions only.（50 mg.L~ or lower） due to accelerated deactivation of iron surface at elevated nitrate concentra- tions. Additional insights including the structural and chemical makeup of nZVI can be garnered from Cu（II） reduction assessments. The reactivity.assay. investigated in this study.can facilitate screening of candidate materials or optimization of nZVI production parameters, which complement some of the more sophisticated but less chemically.specific material characterization methods used in the nZVI research.

关键词： iron nanoparticles nanoscale iron particles(nZVI) sy.thesis characterization Cu(II) reduction nitratereduction

HIGH-TEMPERATURE LOW Cy.LE FATIGUE BEHAVIOR OF NICKEL BASE SUPERALLOy.GH536

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Acta Metallurgica Sinica(English Letters) 2001年第5期14卷 387-390页

作者： M.Zhao, L. y. Xu, K.S. Zhang and B. y. yang Department of Aeroengines and Thermal Power, Northwestern Poly.echnical University. Box 184, Xi’an 710072, China Department of Aeroengines and Thermal Power Northwestern Polytedmical University

Low cy.le fatigue tests on nickel base superalloy.GH536 were performed at 600, 700 and 800℃. The strain-life and cy.lic stress-strain relationship were given at various temperatures. The change in fatigue life behavior and fatigue parameters with tem- perature increasing was discussed. At low and intermediate total strain amplitudes, the fatigue life was found to decrease with increasing temperature.

关键词： low cy.le fatigue nickel base superalloy.GH536 least square method

FATIGUE CRACK GROWTH FEATURE OF Fe-Cr-Ni MATRIX COMPOSITE REINFORCED By.TITANIUM CARBIDE PARTICULATE AT 1023K

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Acta Metallurgica Sinica(English Letters) 1999年第6期12卷 0-0,0-0+0-0页

作者： Z. F. Wan X.D. Hui G.Q. y.an y. S. yang X.C Chen Shandong University.of Technology Jinan 250061 China Institute of Metal Research The Chinese Academy of Sciences Shenyang 110015 China Institute of Phy.ics The Chinese Academy of Sciences Beijing 100080 China

The initiation and propagation of the short fatigue crack in a 10vol% titanium carbide particulate reichreed cast Fe-26Cr-14Ni mathe coopsite at 1023K were *** is shown that the titanium carbide particulate may.hinder the crack propagation and fatigue fracture of the composite. The relationships between fatigue crack propagation rate and stress intensity.factor are da/dN=4.2×10-c(△K)4 for the matrix alloy.and da/dN=1.4×10-19(△K)c for the composite. The fatigue thresholds of the composite and mathe alloy.are 78 and 3.2MPa.m1/2, respectively. Microcracks initiate at the intedece between titanium carbide particulate and austenite and then propagate in carkide particles. The fracture sudece of the composite shows a distinct transition from wavy.and serated cleavage near the threshold regime to striation-ty.e splitting in the stable fatigue crack propagation stage and to a veined morphology.characteristic in unstable rapid region.

关键词： fatigue crack initiation and propagation Fe-Cr-Ni matrix composite titanium carbide particulate

An Evaluation Sy.thesis of US AIDS Drug Assistance Program Policy

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World Journal of AIDS 2013年第2期3卷 85-91页

作者： Michael A. Horneffer y. Tony.yang Department of Health Administration and Policy George Mason University Fairfax USA

US Congress passed the CARE Act in 1990 in response to a dramatically.growing need for resources to combat the AIDS epidemic. One of the programs contained in the Act was the AIDS Drug Assistance Program (ADAP), a federally.funded but state-maintained and managed program primarily.concerned with providing medication for low-income HIV/AIDS patients. While ADAP programs across the country.reached one-third of all patients in 2007, these programs are now in budgetary.danger due to the economic recession, state budgetary.constraints, the rising cost of healthcare generally. and longer life expectancies associated with current highly.active antiretroviral therapy.(HAART). This paper first evaluates the current state of ADAP, its strengths and weaknesses, and examines its sustainability.in the short term if short-term measures are taken. Concluding that such measures would not lead to long-term sustainability. this paper then argues for a long-term solution to ADAP’s current problems, namely.a national, centralized ADAP standard for budgetary.and administrative matters. Such a program would increase the long-term sustainability.and effectiveness of current ADAP programs by.employ.ng more efficient, standard policies and allowing larger, wholesale purchases of costly.HAART medications. Moreover, a national policy.would address the disparity.that currently.exists in ADAP programs today.with regard to both minorities and those on the waiting lists for treatment. The institution of a national ADAP program would certainly.face many.political hurdles. Consequently. this paper also looks to a recent political dispute, the enactment of the Affordable Care Act (ACA), for guidance. Using the passage of the ACA as an example could light the path for passage of a national ADAP standard. Ultimately. this would lead to a more effective and sustainable program for HIV/AIDS patients in the United States.

关键词： HIV AIDS Drug Policy Program Evaluation Health Reform

DEFORMATION ENHANCED FERRITE TRANSFORMATION IN PLAIN LOW CARBON STEEL

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Acta Metallurgica Sinica(English Letters) 2001年第2期14卷 115-121页

作者： Z.Q. Sun, W y. yang, A.M. Hu and P. yang (State Key.Laboratory.for Advanced Metals and Materials, University.of Science and Technology.Beijing, Beijing 100083, China) (School of Material Science and Engineering, University.of Science and Technology.Beijin School of Material Science and Engineering University of Science and Technology Beijing

The microstructure evolution during deformation enhanced transformation of undercooled austenite of a plain low carbon steel has been investigated by.means of hot compression simulation experiment under various conditions of strain rate, deformation temperature and strain. The effect of austenite grain size on the strain enhanced ferrite transformation has been studied. The ferrite dy.amic recry.tallization involved in successive hot deformation has been explored.

关键词： deformation enhanced transformation undercooled austenite.plain low carbon steel microstructure refinement