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A review of friction stir welding of steels： Tool, material flow, microstructure, and properties

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Journal of Materials science & Technology 2018年第1期34卷 39-57页

作者： F.C. Liu Y. Hovanski M.P. Miles C.D. Sorensen T.W. Nelson Department of Mechanical engineering Brigham Young University Provo UT 84602. USA Manufacturing engineering Technology Brigham Young University Provo UT 84602 USA

Considerable progress has been achieved in friction stir welding （FSW） of steels in every aspect of tool fab- rication, microstructure control and properties evaluation in the past two decades. With the development of reliable welding tools and precise control systems, FSW of steels has reached a new level of technical maturity. High-quality, long welds can be produced in many engineering steels. Compared to traditional fusion welding, FSW exhibits unique advantages producing joints with better properties. As a result of active control of the welding temperature and/or cooling rate, FSW has the capability of fabricating steel joints with excellent toughness and strength. For example, unfavorable phase transformations that usu- ally occur during traditional welding can be avoided and favorable phase fractions in advanced steels can be maintained in the weld zone thus avoiding the typical property degradations associated with fusion welding. If phase transformations do occur during FSW of thick steels, optimization of microstructure and properties can be attained by controlling the heat input and post-weld cooling rate.

关键词： Joining Stainless steels Carbon steels High strength low alloy (HSLA) steels Advanced high strength steels (AHSS) Oxide dispersion strengthened (ODS) steels

Breakup of spherical vesicles caused by spontaneous curvature change

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Acta Mechanica Sinica 2012年第6期28卷 1545-1550页

作者： Ping Liu Ju Li Yong-Wei Zhang Institute of High Performance Computing Department of Nuclear science and engineering Massachusetts Institute of Technology

We present our theoretical analysis and coarse- grained molecular dynamics （CGMD） simulation results to describe the mechanics of breakup of spherical vesi- cles driven by changes in spontaneous curvature. System- atic CGMD simulations reveal the phase diagrams for the breakup and show richness in breakup morphologies. A the- oretical model based on Griffith fracture mechanics is devel- oped and used to predict the breakup condition.

关键词： Molecular dynamics Bending modulus Phasediagram. Fracture

Insights to the formation of secondary inorganic PM_(2.5):Current knowledge and future needs

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International Journal of Agricultural and Biological engineering 2015年第2期8卷 1-13页

作者： Lingjuan Wang-Li Department of Biological and Agricultural engineering North Carolina State UniversityRaleighNC 27695USA

As a criteria pollutant,fine particulate matter(fine PM,***_(2.5))adversely affects public health and environment,contributes to visibility degradation and regional *** fine PM includes primary and secondary PM_(2.5).While the primary PM_(2.5) is from direct emissions,the secondary PM_(2.5) is formed in the atmosphere through photochemical reaction,condensation and other atmospheric *** it is well known that ammonia(NH3)may react with acidic gas species to form secondary inorganic PM_(2.5)(iPM_(2.5))as ammonium salts,limited research has been done to quantify the impacts of NH_(3) emissions of animal feeding operations(AFOs)on the dynamics of such chemical reactions and gas-particle phases *** paper is to provide comprehensive review of existing research on AFO PM chemical speciation and on the formation of secondary iPM_(2.5) as impacted by AFO air *** gaps and future studies in characterizing AFO PM and assessing impacts of AFO air emissions on atmospheric PM are discussed.

关键词： environmental pollution particulate matter inorganic PM_(2.5) animal feeding operations ammonia formation of secondary PM_(2.5)

Experimental study of bed-load transport using particle motion tracking

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International Journal of Sediment Research 2017年第1期32卷 73-81页

作者： Jaeho Shim Jennifer G.Duan Department of Civil engineering and engineering Mechanics University of Arizona

A series of experiments were conducted in a flume to study bed-load *** motion of bed-load particles was captured by a series of images taken by a high-speed camera.A novelparticle motion tracking method was developed to automatically detect all the moving particles and calculate the instantaneous particle *** instantaneous bed load transport rate was calculated based on particle velocity and the volume of moving *** verify this method,bed load transport rate based on the image processing technique was compared to the manually measured ones as well as data from other *** showed that the new technique made it possible to quantify the spatial and temporal variations of bed load transport rate at the individual particle scale.

关键词： Bed-load transport Particle tracking Particle velocity

Electroactive shape-memory polymer nanocomposites incorporating carbon nanofiber paper

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International Journal of Smart and Nano Materials 2010年第1期1卷 2-12页

作者： Haibao Lu Yanju Liu Jihua Gou Jinsong Leng Shanyi Du Center for Composite Materials and Structures Harbin Institute of TechnologyHarbin 150001China Department of Aerospace science and Mechanics No.92 West Dazhi StreetHarbin Institute of Technology(HIT)HarbinChina Department of Mechanical Materials&Aerospace EngineeringUniversity of Central FloridaOrlandoFL 32816USA

A conductive carbon nanofiber(CNF)paper is described for the actuation of shape recovery of a shape-memory polymer(SMP)by electrically resistive Joule *** CNF paper was manufactured using a traditional physical vapor deposition process and the microscale morphology and structure of the CNF paper were observed using a scanning electron *** CNF paper was found to be porous,with the pore size determined by the weight concentration of *** excellent electrical properties of pure CNF papers and their SMP composites were characterized by the four-point probe *** recovery actuation of this type of SMP composite induced by electrically resistive heating was achieved with a 12 V ***,the thermomechanical properties of the SMP composite were studied with respect to the volume fraction of CNF paper.

关键词： shape-memory polymer resistive heating electroactive carbon nanofiber

Recent progress in hydrocarbon biofuel synthesis:Pathways and enzymes

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Chinese Chemical Letters 2015年第4期26卷 431-434页

作者： Feng-Ming Lin E.Neil G.Marsh Xiaoxia Nina Lin State Key Laboratory of Bioelectronics School of Biological Science and Medical EngineeringSoutheast University Department of Chemistry University of Michigan Department of Chemical engineering University of Michigan Department of Biological Chemistry University of Michigan

Biofuels derived from hydrocarbon biosynthetic pathways have attracted increasing attention. Routes to hydrocarbon biofuels are emerging and mainly fall into two categories based on the metabolic pathways utilized： Fatty acid pathway-based alkanes/alkenes and isoprenoid biosynthetic pathway based terpenes. The primary focus of this review is on recent progress in the application of hydrocarbon biosynthetic pathways for hydrocarbon biofuel production, together with studies on enzymes, including efforts to engineering them for improved performance.

关键词： BiofuelFatty acid biosynthesis pathwaylsoprenoid biosynthesis pathwayMetabolic engineering

Substrates for clinical applicability of stem cells

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World Journal of Stem Cells 2015年第2期7卷 243-252页

作者： Sanjar Enam Sha Jin Department of Biomedical engineering Thomas J Watson School of Engineering and Applied SciencesState University of New York in Binghamton

The capability of human pluripotent stem cells(h PSCs) to differentiate into a variety of cells in the human body holds great promise for regenerative medicine. Many substrates exist on which h PSCs can be self-renewed, maintained and expanded to further the goal of clinical application of stem cells. In this review, we highlight numerous extracellular matrix proteins, peptide and polymer based substrates, scaffolds and hydrogels that have been pioneered. We discuss their benefits and shortcomings and offer future directions as well as emphasize commercially available synthetic peptidesas a type of substrate that can bring the benefits of regenerative medicine to clinical settings.

关键词： Human pluripotent stem cells Extracellularmatrix protein Synthetic substrate Peptide Polymer Scaffold Hydrogel

Numerical analysis of modal tomography for solar multi-conjugate adaptive optics

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Research in Astronomy and Astrophysics 2012年第4期12卷 465-471页

作者： Bing Dong De-Qing Ren Xi Zhang Physics ＆ Astronomy Department California State University Northridge CA 91330-8268 USA national Astronomical Observatories/Nanjing Institute of Astronomical Optics ＆ Technology Chinese Academy of Sciences Nanjing 210042 China

Multi-conjugate adaptive optics （MCAO） can considerably extend the cor- rected field of view with respect to classical adaptive optics, which will benefit solar observation in many aspects. In solar MCAO, the Sun structure is utilized to provide multiple guide stars and a modal tomography approach is adopted to implement three- dimensional wavefront restorations. The principle of modal tomography is briefly re- viewed and a numerical simulation model is built with three equivalent turbulent lay- ers and a different number of guide stars. Our simulation results show that at least six guide stars are required for an accurate wavefront reconstruction in the case of three layers, and only three guide stars are needed in the two layer case. Finally, eigen- mode analysis results are given to reveal the singular modes that cannot be precisely retrieved in the tomography process.

关键词： instrumentation: multi-conjugate adaptive optics -- tomography

TECHNICAL RESEARCH NEEDS FOR SUSTAINABLE BUILDINGS: Results from a Multidisciplinary NSF Workshop

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Journal of Green Building 2009年第4期4卷 101-112页

作者： Leidy Klotz Vivien Loftness Gregor Henze David Sailor David Riley Department of Civil engineering Clemson University School of Architecture Carnegie Mellon University Department of Civil Environmentaland Architectural EngineeringUniversity of Colorado at Boulder Department of Mechanical and Materials engineering Portland State University Department of Architectural engineering Penn State

This article describes research needs for sustainable buildings as defi ned in a July 2009 national science foundationsponsored *** workshop brought together building researchers with researchers in the areas of distributed renewable energy and multifunctional materials to engage their expertise and identify overlapping research needs and *** overview of sustainable building design provided the broad context for *** overview was followed by focused presentations in building control systems,advanced building envelopes,and systems and process *** addition,presentations on distributed renewable energy and multi-functional materials supported the participants in outlining and generating research needs that connect the topic *** primary outcome from this part of the workshop was the identifi cation of key sustainable building research needs in:transformative measurements;passive strategies;regional solutions and living labs;systems integration;storage and cascades;adoption of international advances;and implementation and market *** needs,along with associated technical challenges and potential impacts,are described in this paper to guide sustainable building research.

关键词： research needs measurement passive strategies regional solutions systems integration implementation market transformation