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Thermal characteristics in the cutting of Inconel 718 Superalloy Using cw Nd:YAG Laser

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Journal of Materials Science & Technology 2010年第4期26卷 362-366页

作者： D.G. Ahn K.w. Byun M.c. Kang Department of Mechanical Engineering Chosun University 375 Seosuk-dong Dong-gu Gwang-ju 501-759 Korea Hybrid Materials Solution National core Research (NcRc) Pusan National University San 30 Changjeon-dong Keumjeong-gu Busan 609-735 Korea

The objective of the this study is to investigate the effects of cutting parameters on thermal characteristics, including practical cutting regions, the formation of the kerfwidth and the heat transfer phenomenon, in the cutting of Inconel 718 super-alloy sheets using a cw Nd：YAG laser. From the results of the experiments, the influence of process parameters on both the practical cutting region and the kerfwidth has been examined. In addition, it has been shown that the kerfwidth of the specimen lies in the range of 0.53-0.61 mm. In order to examine characteristics of the heat transfer during the laser cutting process, a three-dimensional quasi-steady heat transfer analysis has been performed using the commercial code SYSwELD V9.0. From the results of the analysis, the influence of cutting parameters on the temperature distribution in the vicinity of the cut section has been quantitatively evaluated. Based on these results, optimal cutting conditions have been estimated.

关键词： cw Nd:YAG laser Inconel 718 Kerfwidth Quasi-steady heat transfer analysis

PREcIPITATION BEHAVIOR IN A cu-Sn-Ni-Zn-P LEAD FRAME MATERIAL

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Acta Metallurgica Sinica(English Letters) 2003年第3期16卷 155-160页

作者： w.H.Tian c.K.Yan M.Nemoto Department of Materials Physics and chemistry University of Science and Technology BeijiingBeijing 100083ChinaInstitute of Metal ResearchThe Chinese Academy of SciencesShenyang 110016ChinaSasebo National College of Technology Okishin 1-1 Sasebo 857-1193 Japan

Transmission electron microscopy (TEM) observations were carried out for examining the precipitation behavior in a cu-Sn-Ni-Zn-P lead frame material. TEM observations revealed that the precipitate is hexagonal Ni5P2 and the orientation relationship between the cu matrix and Ni$Pi precipitate is (111)fcc//(0001)hcp, [101]fcc//[1120]hcp, where the suffix fcc denotes the cu matrix and hep denotes the hexagonal Ni5P2 precipitate. The Ni5P2 precipitate is ovoidal in shape at the beginning of aging at lower temperature. By prolonging the aging time or increasing the aging temperature, Ni5P2 precipitate grows and shows a rod-like shape. The Ni added cu based lead frame material has a comparative mechanical properties with that of TAMAc15 which has been developed and used in electrical industry.

关键词： lead frame materials mechanical properties atom diffusion precipitate transmission electron microscopy

Longwall automation: Delivering enabling technology to achieve safer and more productive underground mining

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International Journal of Mining Science and Technology 2015年第6期25卷 865-876页

作者： Ralston Jonathon c. Reid David c. Dunn Mark T. Hainsworth David w. coal Mining Research Program CSIRO Energy

The ongoing need to deliver improved safety, productivity and environmental benefit in coal mining presents an open challenge as well as a powerful incentive to develop new and improved solutions. This paper assesses the critical role that enabling technologies have played in the delivery of remote and automated capability for longwall mining. A brief historical account is given to highlight key technical contributions which have influenced the direction and development of present-day longwall technology. The current state of longwall automation is discussed with particular attention drawn to the technologies that enable automated capability. Outcomes are presented from an independently conducted case study that assessed the impact that cSIRO＇s LASc longwall automation research has made to the longwall mining industry in Australia. Importantly, this study reveals how uptake of this innova- tive technology has significantly benefitted coal mine productivity, improved working conditions for personnel and enhanced environmental outcomes. These benefits have been widely adopted with cSIRO automation technology being used in 60 per cent of all Australian underground operations. International deployment of the technology is also emerging. The paper concludes with future challenges and opportunities to highfight the ongoing scope for longwall automation research and development.

关键词： Safety Productivity Environment Mining automation Longwall mining Remote mining

Stem cells for cardiac repair: an introduction

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Journal of Geriatric cardiology 2013年第2期10卷 186-197页

作者： Bastiaan c du Pr(e) Pieter A Doevendans Linda w van Laake Departments of cardiology and Medical Physiology Division of Heart and Lungs University Medical Center Utrecht P.O. box 85500 3508 GA Utrecht the Netherlands Departments of cardiology and Medical Physiology Division of Heart and Lungs University Medical Center Utrecht P.O. box 85500 3508 GA Utrecht the Netherlands Inter university Cardiology Institute of the Netherlands P.O. box 19258 2501 DG Utrecht the Netherlands Departments of cardiology and Medical Physiology Division of Heart and Lungs University Medical Center Utrecht P.O. box 85500 3508 GA Utrecht the Netherlands Hubrecht Institute P.O box 85164 3508 AD Utrecht the Netherlands

cardiovascular disease is a major cause of morbidity and mortality throughout the world. Most cardiovascular diseases, such as ischemic heart disease and cardiomyopathy, are associated with loss of functional cardiomyocytes. Unfortunately, the heart has a limited regenerative capacity and is not able to replace these cardiomyocytes once lost. In recent years, stem cells have been put forward as a potential source for cardiac regeneration. Pre-clinical studies that use stem cell-derived cardiac cells show promising results. The mechanisms,though, are not well understood, results have been variable, sometimes transient in the long term, and often without a mechanistic *** are still severalmajor hurdles to be taken. Stem cell-derived cardiac cells should resemble original cardiac cell types and be able to integrate in the damaged heart. Integration requires administration of stem cell-derived cardiac cells at the right time using the right mode of delivery. Once delivered, transplanted cells need vascularization, electrophysiological coupling with the injured heart, and prevention of immunological rejection. Finally, stem cell therapy needs to be safe, reproducible, and affordable. In this review, we will give an introduction to the principles of stem cell based cardiac repair.

关键词： Stem cell Regeneration Heart cardiomyocytes

Transverse vibration of pre-tensioned nonlocal nanobeams with precise internal axial loads

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Science china(Technological Sciences) 2011年第8期54卷 2007-2013页

作者： LI cheng LIM c. w. YU JiLin ZENG Qingchuan Department of Modern Mechanics University of Science and Technology of China Hefei 230026 China Department of Building and construction City University ofHong Kong Tat Chee Avenue Kowloon Hong Kong SAR China china and USTc-cityU Joint Advanced Research centre Suzhou 215123 China college of water conservancy and tlydropower Engineering Hohai University Nanjing 210098 China

This paper investigates the transverse vibration of a simply supported nanobeam with an initial axial tension based on the nonlocal stress field theory with a nonlocal size parameter. considering an axial elongation due to transverse vibration, the internal axial tension is not precisely equal to the external initial tension. A sixth-order nonlinear partial differential equation that governs the transverse vibration for such nonlocal nanobeam is derived. Using a perturbation method, the relation between natural frequency and nonlocal nanoscale parameter is derived and the transverse vibration mode is solved. The external axial tension and nonlocal nanoscale parameter are proven to play significant roles in the nonlinear vibration behavior of nonlocal nanobeams. Such effects enhance the natural frequency and stiffness as compared to the predictions of the classical continuum mechanics models. Additionally, the frequency is higher if the precise internal axial load is considered with respect to that when only the approximate internal axial tension is assumed.

关键词： nonlocal stress natural frequency free vibration nonlocal nanoscale

NUMERIcAL SIMULATION OF MAcRO-SEGREGATION IN STEEL INGOT DURING SOLIDIFIcATION

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Acta Metallurgica Sinica(English Letters) 2004年第3期17卷 288-294页

作者： c.w.Ma H.F.Shen T.Y.Huang B.c.Liu Department of Mechanical Engineering Tsinghua University Beijing 100084 ChinaDepartment of Mechanical Engineering Tsinghua University Beijing 100084 ChinaDepartment of Mechanical Engineering Tsinghua University Beijing 100084 ChinaDepartment of Mechanical Engineering Tsinghua University Beijing 100084 China

A mathematical model coupling the momentum, energy and species conservation equa-tions was proposed to calculate the macro--segregation of Fe--c alloy ingot during solid-ification. The corresponding simulation software which concurrently solves the macro-scopic mass, momentum, energy and species conservation equations has been developedby applying the SIMPLE algorithm.The thermo--solutal convection in a NH_4 cl--H_2O ingot is verified and the result showsgood agreement with that reported. Then macro--segregation in a steel ingot is simu-lated by using the developed program. The steel ingot is in a rectangular mold with ariser. The fluid flow is mainly induced by the temperature field and the solid fraction.The macro--segregation pattern is mainly affected by the thermo--induced convectionin the mushy zone. The negative segregation forms along the walls of the casting.The positive segregation forms at the top center of the casting into the riser. Thespecies concentration reaches the peak in the center of the ingot where solidificationends lastly.

关键词： macro-segregation thermo-solutal convection steel ingot numerical simulation

Quantifying local fire regimes using the Landsat data-archive:a conceptual framework to derive detailed fire pattern metrics from pixel-level information

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International Journal of Digital Earth 2019年第5期12卷 544-565页

作者： Ignacio San-Miguel David w.Andison Nicholas c.coops Integrated Remote Sensing Studio Department of Forest Resources ManagementUniversity of British ColumbiaVancouverBCCanada Bandaloop Landscape-Ecosystem Services North VancouverBCCanada

Free and open access to the Landsat archive has enabled the detection and delineation of an unprecedented number of fire events across the *** the availability and potential of these data,few studies have analysed residual vegetation patterns and/or partial mortality of fire across the canadian boreal forest,and those available,are either incomplete or ***,they all differ in the methods and spatial language,which makes it difficult for managers to interpret fire patterns over large *** is an urgent need for methods to help unify fire pattern observations across the canadian boreal *** study explores the capacity of the Landsat data archive when coupled with a recently developed fire mapping approach and a robust spatial language to characterize and compare tree mortality patterns across the boreal plains ecozone,*** 507 fires 2.5 Mha mapped,this study represents the most comprehensive analysis of mortality patterns for study *** from this demonstration generated an accurate characterization of the fire patterns the various ecoregions based on seven key fire *** comparison between ecoregions revealed differences in the amount of residual vegetation,which in turn suggested various climate,topography and/or vegetation ecosystem drivers.

关键词： Fire emulation historical range of variability landscape metrics fire patterns disturbance-based management

Assessing the thermal stability of toolmarks casting materials through optical comparison microscopy,virtual comparison microscopy and quantitative similarity scores

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Forensic Sciences Research 2022年第4期7卷 782-789页

作者： Alaric c.w.Koh Kai Yuan Yeoh Forensic chemistry and Physics Laboratory Health Sciences AuthoritySingapore

Toolmarks,particularly those found on bulky,inaccessible or immovable items,can be recovered by *** allow for subsequent comparative examinations,the casting material,typically polysiloxanes or silicones,must be able to capture and preserve fine details within a toolmark *** study the stability of such details after exposure to heat,toolmark casts were heated at either 60°c for 2 h,or 90°c for 1 *** casts were subsequently compared to casts that had not been exposed to heat,using traditional optical comparison microscopy,as well as virtual comparison *** toolmark signatures were also extracted from the casts and compared pairwise to obtain quantitative similarity scores based on cross-correlation,consecutive matching striae and Mann-whitney *** results show that the fine surface details captured on all four commercial toolmark casting materials tested herein remained stable after exposure to *** study shows that the above heating protocols are viable viral inactivation methods for toolmark casts that are potentially contaminated with human coronaviruses,such as *** findings also apply to other scenarios,such as for casts that were left in a vehicle parked under the sun.

关键词： Forensic sciences casts coronavirus comparison microscopy polysiloxane thermal stability toolmarks

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