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Laser additive manufacturing for infrastructure repair:A case study of a deteriorated steel bridge beam

Journal of Materials Science & Technology 2023年第23期154卷 149-158页

作者： Shengbiao Zhang Peijun Hou Jiyun Kang Tianyi Li Shahryar Mooraj Yang Ren Catherine H.Chen A.John hart Simos Gerasimidis Wen Chen Department of Mechanical and Industrial Engineering University of Massachusetts Amherst MA 01003 USA Department of Civil and Environmental Engineering University of Massachusetts Amherst MA 01003 SA Department of Materials Science and Engineering Massachusetts Institute of Technology Cambridge MA 02139 USA X-ray Science Division Argonne National Laboratory Lemont IL 60439 USA Massachusetts Department of Transportation Boston MA 02116 USA Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge MA 02139 USA Department of Physics City University of Hong Kong Kowloon Hong Kong China

As our transportation infrastructure ages,its deterioration is becoming a growing *** and effective methods for repair can reduce the need for time-and cost-intensive replacement of structures such as roadway *** this work,laser-based additive manufacturing(AM)was developed for the repair of damaged beams in steel bridges.A corroded structural beam of low-carbon A36 steel was selected for this case study and 316L stainless steel was used for repair due to its excellent mechanical properties and corrosion *** repair experiments were performed on specimens extracted from the beam,and prepared with various groove shapes(Rectangular,Trapezoidal,and U-shaped).More in-depth parametric and microstructural studies were carried out with a series of U-shaped specimens repaired with the linear laser input energy varied from 19.5 to 30.0 J mm–*** tensile properties of the repaired specimens and interface structures were also investigated in *** was found that the repaired specimens had a slightly higher tensile strength despite a reduction in tensile elongation compared to the A36 steel base *** influence of interfacial microstructure and heterogeneity on the mechanical properties of the repaired specimens was *** work suggests the promising potential to employ AM for structural repair and provides fundamental insights into processing-structure-property relationships in laser AM-repaired materials.

关键词： Additive manufacturing Structural repair Mechanical properties Transportation infrastructure Dissimilar joint

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A General Algorithm for Calculating Irreducible Brillouin Zones

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Communications in Computational Physics 2022年第2期31卷 495-515页

作者： Jeremy J.Jorgensen John E.Christensen Tyler J.Jarvis Gus L.W.hart Department of Physics and Astronomy Brigham Young UniversityProvoUtah84602USA Department ofMathematics BrighamYoungUniversityProvoUtah84602USA

Calculations of properties of materials require performing numerical integrals over the Brillouin zone(BZ).Integration points in density functional theory codes are uniformly spread over the BZ(despite integration error being concentrated in small regions of the BZ)and preserve symmetry to improve computational *** points over an irreducible Brillouin zone(IBZ),a rotationally distinct region of the BZ,do not have to preserve crystal symmetry for greater *** freedom allows the use of adaptive meshes with higher concentrations of points at locations of large error,resulting in improved algorithmic *** have created an algorithm for constructing an IBZ of any crystal structure in 2D and *** algorithmuses convex hull and half-space representations for the BZ and IBZ to make many aspects of construction and symmetry reduction of the BZ *** algorithm is simple,general,and available as open-source software.

关键词： Brillouin zone irreducible Brillouin zone

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球磨介质及尺寸对铜锌矿矿浆化学性质及矿物表面化学性质的影响

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中国有色金属学报 2017年第8期27卷 1701-1707页

作者：陈哲夏柳荫 Brian hart 池汝安余军霞武汉工程大学化学与环境工程学院武汉430073 西安大略大学表面化学研究所

采用飞行时间二次离子质谱仪和改良球磨机研究了磨矿环境对铜锌矿矿浆的化学性质和闪锌矿的表面化学性质的影响。通过采用改良后的球磨机实现磨矿过程中溶液p H、矿浆电位、电导率、溶解氧含量及离子浓度等矿浆化学性质的实时监测。随... 详细信息

采用飞行时间二次离子质谱仪和改良球磨机研究了磨矿环境对铜锌矿矿浆的化学性质和闪锌矿的表面化学性质的影响。通过采用改良后的球磨机实现磨矿过程中溶液p H、矿浆电位、电导率、溶解氧含量及离子浓度等矿浆化学性质的实时监测。随着磨矿时间的延长,矿浆p H值缓慢升高,矿浆电位和溶解氧含量迅速下降。结果表明:球形磨矿介质的直径越小,矿浆中溶解氧消耗越快,磨矿后矿浆静电位越低,矿浆的离子浓度也越低。飞行时间二次离子质谱仪对磨矿后闪锌矿的表面化学分析表明,磨矿后铁氧化物和氢氧化物会附着于闪锌矿表面,球磨介质的材料与尺寸大小对矿物表面存在的二次离子有较大影响。分别与不锈钢球或者2.54 cm的大球相比,铸铁球或1.27 cm的小球可为矿浆提供更多的铁离子,促进磨矿环境下的电化学反应,从而在闪锌矿表面累积更多的铁氧化物或氢氧化物,降低铜离子的吸附。因此,矿浆化学性质和闪锌矿的表面化学性质受磨矿介质的材料与介质的尺寸控制。

关键词：闪锌矿磨矿溶液化学表面化学飞行时间二次离子质谱

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Use of BayesSim and Smoothing to Enhance Simulation Studies

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Open Journal of Statistics 2017年第1期7卷 153-172页

作者： Jeffrey D. hart Department of Statistics Texas A&M University College Station TX USA

The conventional form of statistical simulation proceeds by selecting a few models and generating hundreds or thousands of data sets from each model. This article investigates a different approach, called BayesSim, that generates hundreds or thousands of models from a prior distribution, but only one (or a few) data sets from each model. Suppose that the performance of estimators in a parametric model is of interest. Smoothing methods can be applied to BayesSim output to investigate how estimation error varies as a function of the parameters. In this way inferences about the relative merits of the estimators can be made over essentially the entire parameter space, as opposed to a few parameter configurations as in the conventional approach. Two examples illustrate the methodology: One involving the skew-normal distribution and the other nonparametric goodness-of-fit tests.

关键词： Loss Function Bayes Risk Prior Distribution Regression Simulation Skew-Normal Distribution Goodness of Fit

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The Medical Home Transformation

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Journal of Health Science 2017年第3期5卷 128-134页

作者： Namita Azad Emily hart Montefiore Medical Group 200 Corporate Blvd. South Suite 175 Yonkers NY 10701 USA

To maintain productivity in today＇s healthcare market, it is important for institutions to have a delivery system that allows for transformation and adaptation. This paper introduces the Medical Home Transformation Model which demonstrates the effectiveness of employing a team of embedded coaches within a five-step capacity building program in conjunction with learning collaboratives, the adaptation medium. This model demonstrates the effectiveness of concurrently employing the coaching lifecycle and a five-step capacity building program. Moreover, the model details the formation of multidisciplinary teams at each clinical site, meaningful data reporting at site and physician levels and best practice sharing at collaboratives and seminars. A discussion then demonstrates the success of MMG （Montefiore Medical Group） as it applies the model to its ambulatory care network of 22 health centers in effort to achieve PCMH （Patient Centered Medical Home） recognition, improve clinical outcomes, and document financial benefits. While PCMH is currently the sought after delivery system framework, this paper will also demonstrate the adaptability of the model to any prescribed framework which continues advancement toward the ＂Triple Aim＂. Such a model has enabled MMG to surpass national standards of clinical care within a conf＇wmed vulnerable population and has placed MMG at the forefront for primary care delivery system reform.

关键词： Transformation PCMH primary care quality improvement innovation coaching.

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Current evidence on potential of adipose derived stem cells to enhance bone regeneration and future projection

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World Journal of Stem Cells 2021年第9期13卷 1248-1277页

作者： Quang Le Vedavathi Madhu Joseph M hart Charles R Farber Eli R Zunder Abhijit S Dighe Quanjun Cui Department of Orthopaedic Surgery University of Virginia School of MedicineCharlottesvilleVA 22908United States Orthopaedic Surgery Research Thomas Jefferson UniversityPhiladelphiaPA 19107United States Center for Public Health Genomics University of VirginiaCharlottesvilleVA 22908United States Departments of Public Health Sciences and Biochemistry and Molecular Genetics University of VirginiaCharlottesvilleVA 22908United States Department of Biomedical Engineering University of VirginiaCharlottesvilleVA 22908United States

Injuries to the postnatal skeleton are naturally repaired through successive stepsinvolving specific cell types in a process collectively termed “bone regeneration”.Although complex, bone regeneration occurs through a series of well-orchestratedstages wherein endogenous bone stem cells play a central role. In most situations,bone regeneration is successful;however, there are instances when it fails andcreates non-healing injuries or fracture nonunion requiring surgical or therapeuticinterventions. Transplantation of adult or mesenchymal stem cells (MSCs) definedby the International Society for Cell and Gene Therapy (ISCT) as CD105+-CD90+CD73+CD45-CD34-CD14orCD11b-CD79αorCD19-HLA-DR- is beinginvestigated as an attractive therapy for bone regeneration throughout the *** isolated from adipose tissue, adipose-derived stem cells (ADSCs), aregaining increasing attention since this is the most abundant source of adult stemcells and the isolation process for ADSCs is straightforward. Currently, there isnot a single Food and Drug Administration (FDA) approved ADSCs product forbone regeneration. Although the safety of ADSCs is established from their usagein numerous clinical trials, the bone-forming potential of ADSCs and MSCs, ingeneral, is highly controversial. Growing evidence suggests that the ISCT definedphenotype may not represent bona fide osteoprogenitors. Transplantation of bothADSCs and the CD105- sub-population of ADSCs has been reported to induce bone regeneration. Most notably, cells expressing other markers such as CD146,AlphaV, CD200, PDPN, CD164, CXCR4, and PDGFRα have been shown torepresent osteogenic sub-population within ADSCs. Amongst other strategies toimprove the bone-forming ability of ADSCs, modulation of VEGF, TGF-β1 andBMP signaling pathways of ADSCs has shown promising results. The U.S. FDAreveals that 73% of Investigational New Drug applications for stem cell-basedproducts rely on CD105 expression as the “positive” marker for adult stem cell

关键词： Mesenchymal stem cells Adipose-derived stem cells Endogenous stem cells Skeletal stem cells Bone regeneration

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Machine-learned interatomic potentials for alloys and alloy phase diagrams

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npj Computational Materials 2021年第1期7卷 139-147页

作者： Conrad W.Rosenbrock Konstantin Gubaev Alexander VShapeev Livia B.Pártay Noam Bernstein Gábor Csányi Gus L.W.hart Department of Physics and Astronomy Brigham Young UniversityProvoUTUSA84602 Skolkovo Institute of Science and Technology Skolkovo Innovation CenterNobel Str.3Moscow 143026Russia Department of Chemistry University of ReadingWhiteknightsReading RG66ADUK Department of Chemistry University of WarwickCoventry CV47ALUK US Naval Research Laboratory Center for Computational Materials ScienceWashingtonDC 20375USA Department of Engineering University of CambridgeTrumpington StreetCambridge CB21PZUK

We introduce machine-learned potentials for Ag-Pd to describe the energy of alloy configurations over a wide range of *** compare two different *** tensor potentials(MTPs)are polynomial-like functions of interatomic distances and *** Gaussian approximation potential(GAP)framework uses kernel regression,and we use the smooth overlap of atomic position(SOAP)representation of atomic neighborhoods that consist of a complete set of rotational and permutational invariants provided by the power spectrum of the spherical Fourier transform of the neighbor *** types of potentials give excellent accuracy for a wide range of compositions,competitive with the accuracy of cluster expansion,a benchmark for this *** both models are able to describe small deformations away from the lattice positions,SOAP-GAP excels at transferability as shown by sensible transformation paths between configurations,and MTP allows,due to its lower computational cost,the calculation of compositional phase *** the fact that both methods perform nearly as well as cluster expansion but yield off-lattice models,we expect them to open new avenues in computational materials modeling for alloys.

关键词： alloy alloys phase

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California Simulation of Evapotranspiration of Applied Water and Agricultural Energy Use in California

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Journal of Integrative Agriculture 2013年第8期12卷 1371-1388页

作者： Morteza N Orang Richard L Snyder Shu Geng Quinn J hart Sara Sarreshteh Matthias Falk Dylan Beaudette Scott Hayes Simon Eching California Department of Water Resources Department of Land Air and Water ResourcesUniversity of California School of Environment and Energy Shenzhen Graduate SchoolPeking University

The California Simulation of Evapotranspiration of Applied Water （CaI-SIMETAW） model is a new tool developed by the California Department of Water Resources and the University of California, Davis to perform daily soil water balance and determine crop evapotranspiration （ETo）, evapotranspiration of applied water （ETaw）, and applied water （AW） for use in California water resources planning. ETaw is a seasonal estimate of the water needed to irrigate a crop assuming 100% irrigation efficiency. The model accounts for soils, crop coefficients, rooting depths, seepage, etc. that influence crop water balance. It provides spatial soil and climate information and it uses historical crop and land-use category information to provide seasonal water balance estimates by combinations of detailed analysis unit and county （DAU/County） over Califomia. The result is a large data base of ETc and ETaw that will be used to update information in the new California Water Plan （CWP）. The application uses the daily climate data, i.e., maximum （Tx） and minimum （Tn） temperature and precipitation （Pcp）, which were derived from monthly USDA-NRCS PRISM data （PRISM Group 2011） and daily US National Climate Data Center （NCDC） climate station data to cover California on a 4 kmx4 km change grid spacing. The application uses daily weather data to determine reference evapotranspiration （ETo）, using the Hargreaves-Samani （HS） equation （Hargreaves and Samani 1982, 1985）. Because the HS equation is based on temperature only, ETo from the HS equation were compared with CIMIS ETo at the same locations using available CIMIS data to determine correction factors to estimate CIMIS ETo from the HS ETo to account for spatial climate differences. CaI-SIMETAW also employs near real-time reference evapotranspiration （ETo） information from Spatial CIMIS, which is a model that combines weather station data and remote sensing to provide a grid of ETo information. A second database containing the available soil water

关键词： soil water balance crop water requirements weather generator water resource planning crop coefficient energy use

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Physical Characteristics Explain Ball-Carrying Capability in Sub-Elite Rugby Union Players

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Journal of Science in Sport and Exercise 2023年第3期5卷 244-253页

作者： Alexander S.hart Robert M.Erskine Tom J.Mclaughlin David R.Clark School of Sport and Exercise Science Liverpool John Moores UniversityL33AF LiverpoolUK Ealing Trailfinders Rugby Club LondonUK Institute of Sport Exercise and HealthUniversity College LondonLondonUK

Purpose The aims of the present study were two-fold:(i)to investigate the relationship between physical characteristics and the game statistics associated with ball-carrying capability amongst sub-elite rugby union players,and(ii)to predict the level of change in these physical characteristics required to improve the associated game statistic via regression *** Thirty-eight senior professional players(forwards,n=22;backs,n=16)were assessed for body mass(BM),back squat(BS)single-repetition maximum(1RM)normalised to BM(1RM/BM),10 m sprint velocity(S10),10 m sprint momentum(SM10),and the game statistics from 22 games within the 2019/20 RFU Championship *** relationship between these measures and the predicted level of change in a physical measure required to improve the total number of the associated game statistic by one were assessed by Pearson’s correlation coefficient and simple regression *** In forwards,an~11.5%reduction in BM,an~11.8%improvement in BS 1RM/BM,or an~11.5%increase in S10 was required to improve the game statistics associated with ball-carrying *** backs,a~19.3%increase in BM or a~15.6%improvement in SM10 was *** These findings demonstrate that improvements in lower-body relative strength,acceleration performance,and position-specific alterations in body mass are required to maximise the ball-carrying capability and therefore match outcome of sub-elite rugby union players.

关键词： Speed Acceleration Momentum Strength Body mass

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基于预充电电容的新型混合直流断路器

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中国电机工程学报 2018年第20期38卷 5992-6000页

作者：叶晗陈武东南大学电气工程学院

混合型直流断路器技术因速度快、可靠性高,是目前直流领域断路器的重要研究方向,但现有方案存在成本高、限流效果差等缺陷。为解决上述问题,该文提出一种基于预充电电容的新型混合直流断路器,故障转移支路主要采用晶闸管代替传统的IGBT... 详细信息

混合型直流断路器技术因速度快、可靠性高,是目前直流领域断路器的重要研究方向,但现有方案存在成本高、限流效果差等缺陷。为解决上述问题,该文提出一种基于预充电电容的新型混合直流断路器,故障转移支路主要采用晶闸管代替传统的IGBT,预充电电容的投入一方面可使得晶闸管强迫关断,另一方面可有效抑制故障电流。该方案在短路线路切除过程中,较好地抑制了故障电流,同时减少了全控器件的使用,大大降低了设备成本。文中详细描述该混合直流断路器的拓扑结构、工作原理、控制策略及与现有方案的经济技术性对比,并最终通过在PLECS软件中搭建仿真模型验证其可行性和有效性。

关键词：混合直流断路器预充电电容晶闸管抑制故障电流设备成本

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