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气象科技进展 2019年第2期 94-94页

作者： grant ritchie

Predicting surface deformation during mechanical attrition of metallic alloys

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npj Computational Materials 2019年第1期5卷 843-857页

作者： Shan Cecilia Cao Xiaochun Zhang Jian Lu Yongli Wang San-Qiang Shi Robert O.ritchie Department of Materials Science&Engineering University of CaliforniaBerkeleyCA 94720USA Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China Department of Mechanical Engineering City University of Hong KongHong KongChina Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHung HomHong Kong Materials Sciences Division Lawrence Berkeley National LaboratoryBerkeleyCA 94720USA

Extensive efforts have been devoted in both the engineering and scientific domains to seek new designs and processing techniques capable of making stronger and tougher *** such method for enhancing such damage-tolerance in metallic alloys is a surface nano-crystallization technology that involves the use of hundreds of small hard balls which are vibrated using high-power ultrasound so that they impact onto the surface of a material at high speed(termed Surface Mechanical Attrition Treatment or SMAT).However,few studies have been devoted to the precise underlying mechanical mechanisms associated with this technology and the effect of processing *** SMAT is dynamic plastic deformation process,here we use random impact deformation as a means to investigate the relationship between impact deformation and the parameters involved in the processing,specifically ball size,impact velocity,ball density and kinetic *** analytical and numerical solutions,we examine the size of the indents and the depths of the associated plastic zones induced by random impacts,with results verified by experiment in austenitic stainless *** addition,global random impact and local impact frequency models are developed to analyze the statistical characteristics of random impact coverage,together with a description of the effect of random multiple impacts,which are more reflective of *** believe that these models will serve as a necessary foundation for further,and more energy-efficient,development of such surface nano-crystalline processing technologies for the strengthening of metallic materials.

关键词： deformation alloys metallic

Highly efficient surface-emitting semiconductor lasers exploiting quasi-crystalline distributed feedback photonic patterns

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Light(Science & Applications) 2020年第1期9卷 1498-1508页

作者： Simone Biasco Andrea Ciavatti Lianhe Li AGiles Davies Edmund H.Linfield Harvey Beere David ritchie Miriam S.Vitiello NEST CNR-Istituto Nanoscienze and Scuola Normale SuperiorePiazza San Silvestro 1256127 PisaItaly School of Electronic and Electrical Engineering University of LeedsLeeds LS29JTUK Cavendish Laboratory University of CambridgeCambridge CB30HEUK

Quasi-crystal distributed feedback lasers do not require any form of mirror cavity to amplify and extract *** implemented on the top surface of a semiconductor laser,a quasi-crystal pattern can be used to tune both the radiation feedback and the extraction of highly radiative and high-quality-factor optical modes that do not have a defined symmetric or anti-symmetric ***,this methodology offers the possibility to achieve efficient emission,combined with tailored spectra and controlled beam ***,we apply this concept to a onedimensional quantum cascade wire *** lithographically patterning a series of air slits with different widths,following the Octonacci sequence,on the top metal layer of a double-metal quantum cascade laser operating at THz frequencies,we can vary the emission from single-frequency-mode to multimode over a 530-GHz bandwidth,achieving a maximum peak optical power of 240mW(190 mW)in multimode(single-frequency-mode)lasers,with record slope efficiencies for multimode surface-emitting disordered THz lasers up to ≈570 mW/A at 78 K and ≈720 mW/A at 20 K and wall-plug efficiencies of η≈1%.

关键词： lasers surface quantum

Variation in sexual dimorphism and assortative mating do not predict genetic divergence in the sexually dimorphic Goodeid fish Girardinichthys multiradiatus

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Current Zoology 2012年第3期58卷 440-452页

作者： C. MACIAS GARCIA G SMITH C. GONZALEZ ZUARTH J. A. GRAVES M. G. ritchie Departamento de Ecologia Evolutiva Instituto de Ecologia UNAM A. E 70-275 C. E 04510 M6xico DE M6xico School of Biology University of St Andrews St Andrews Fife KY16 9TH Scotland UK

Sexual dimorphism is often used as a proxy for the intensity of sexual selection in comparative studies of sexual selection and diversification. The Mexican Goodeinae are a group of livebearing freshwater fishes with large variation between species in sexual dimorphism in body shape. Previously we found an association between variation in morphological sexual dimorphism between species and the amount of gene flow within populations in the Goodeinae. Here we have examined if mor- phological differentiation within a single dimorphic species is related to assortative mating or gene flow between populations. In the Amarillo fish Girardinichthys multiradiatus studies have shown that exaggerated male fins are targets of female preferences. We find that populations of the species differ in the level of sexual dimorphism displayed due to faster evolution of differences in male than female morphology. However, this does not predict variation in assortative mating tests in the laboratory; in fact dif- ferences in male morphology are negatively correlated with assortative mating. Microsatellite markers reveal significant genetic differences between populations. However, gene flow is not predicted by either morphological differences or assortative mating. Rather, it demonstrates a pattern of isolation by distance with greater differentiation between watersheds. We discuss the caveats of predicting behavioural and genetic divergence from so-called proxies of sexual selection [Current Zoology 58 （3）： 440-452, 2012].

关键词： Sexual dimorphism Assortative mating Genetic distance Speciation Viviparous fish

Bioinspired fish-scale-like magnesium composites strengthened by contextures of continuous titanium fibers:Lessons from nature

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Journal of Magnesium and Alloys 2023年第3期11卷 869-881页

作者： Yanyan Liu Qin Yu Guoqi Tan Mingyang Zhang Enling Tang Shaogang Wang Zengqian Liu Qiang Wang Zhefeng Zhang Robert O.ritchie Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China Department of Materials Science and Engineering University of California BerkeleyBerkeleyCA 94720USA Key Laboratory of Transient Physical Mechanics and Energy Conversion Materials of Liaoning Province Shenyang Ligong UniversityShenyang 110159China Liaoning Provincial Key Laboratory of Oral Diseases School and Hospital of StomatologyChina Medical UniversityShenyang 110001China

Natural fish scales demonstrate outstanding mechanical efficiency owing to their elaborate architectures and thereby may serve as ideal prototypes for the architectural design of man-made *** bioinspired magnesium composites with fish-scale-like orthogonal plywood and double-Bouligand architectures were developed by pressureless infiltration of a magnesium melt into the woven contextures of continuous titanium *** composites exhibit enhanced strength and work-hardening ability compared to those estimated from a simple mixture of their constituents at ambient to elevated *** particular,the double-Bouligand architecture can effectively deflect cracking paths,alleviate strain localization,and adaptively reorient titanium fibers within the magnesium matrix during the deformation of the composite,representing a successful implementation of the property-optimizing mechanisms in fish *** strength of the composites,specifically the effect of their bioinspired architectures,was interpreted based on the adaptation of classical laminate *** study may offer a feasible approach for developing new bioinspired metal-matrix composites with improved performance and provide theoretical guidance for their architectural designs.

关键词： Magnesium composites Bioinspired materials Fish scales Bouligand-type architecture Structural reorientation

Ice-templated porous tungsten and tungsten carbide inspired by natural wood

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Journal of Materials Science & Technology 2020年第10期42卷 187-197页

作者： Yuan Zhang Guoqi Tan Da Jiao Jian Zhang Shaogang Wang Feng Liu Zengqian Liu Longchao Zhuo Zhefeng Zhang Sylvain Deville Robert O.ritchie Laboratory of Fatigue and Fracture for Materials Institute of Metal Research.Chinese Academy of SciencesShenyang 110016China School of Mechanical Engineering Liaoning Shihua UniversityFushun 113001China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China School of Materials Science and Engineering Xi'an University of TechnologyXi'an710048China Laboratoire De Synthese Et Fonctionnalisation Des Ceramiques UMR3080 CNRS/Saint-Gobain CREESaint-Gobain Research ProvenceCavaillon 84306France Department ofMateriab Science and Engineering University of California BerkeleyBerkeleyCA 94720USA

The structures of tungsten and tungsten carbide scaffolds play a key role in determining the properties of their infiltrated composites for multifunctional ***,it is challenging to construct and control the architectures by means of self-assembly in W/WC systems because of their large *** we present the development of unidirectionally porous architectures,with high porosities exceeding 65 vol.%,for W and WC scaffolds which in many respects reproduce the design motif of natural wood using a direct ice-templating *** was achieved by adjusting the viscosities of suspensions to retard sedimentation during *** processing,structural characteristics and mechanical properties of the resulting scaffolds were investigated with the correlations between them *** relationships were established to describe their strengths based on the mechanics of cellular solids by taking into account both inter-and intra-lamellar *** fracture mechanisms were also identified,especially in light of the *** study extends the effectiveness of the ice-templating technique for systems with large densities or particle *** further provides preforms for developing new natureinspired multifunctional materials,as represented by W/WC-Cu composites.

关键词： Ice-templating Tungsten Scaffolds Fracture mechanisms Bioinspired materials

Bioinspired tungsten-copper composites with Bouligand-type architectures mimicking fish scales

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Journal of Materials Science & Technology 2022年第1期96卷 21-30页

作者： Yuan Zhang Guoqi Tan Mingyang Zhang Qin Yu Zengqian Liu Yanyan Liu Jian Zhang Da Jiao Faheng Wang Longchao Zhuo Zhefeng Zhang Robert O.ritchie Shi-Changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China Department of Materials Science and Engineering University of California BerkeleyBerkeleyCA94720USA Jihua Laboratory Foshan 528200China School of Materials Science and Engineering Xi’an University of TechnologyXi’an 710048China

The microscopic Bouligand-type architectures of fish scales demonstrate a notable efficiency in enhancing the damage tolerance of materials;nevertheless,it is challenging to reproduce in *** bioinspired tungsten-copper composites with different Bouligand-type architectures mimicking fish scales were fabricated by infiltrating a copper melt into woven contextures of tungsten *** composites exhibit a synergetic enhancement in both strength and ductility at room temperature along with an improved resistance to high-temperature *** strengths were interpreted by adapting the classical laminate theory to incorporate the characteristics of Bouligand-type *** particular,under load the tungsten fibers can reorient adaptively within the copper matrix by their straightening,stretching,interfacial sliding with the matrix,and the cooperative kinking deformation of fiber grids,representing a successful implementation of the optimizing mechanisms of the Bouligand-type architectures to enhance strength and *** study may serve to promote the development of new high-performance tungsten-copper composites for applications,e.g.,as electrical contacts or heat sinks,and offer a viable approach for constructing bioinspired architectures in metallic materials.

关键词： Bouligand structure Tungsten-copper composites Fish scales Structural reorientation Bioinspired designs

The innate interfacial elastic strain field of a transformable B2 precipitate embedded in an amorphous matrix

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npj Computational Materials 2023年第1期9卷 41-48页

作者： Xiaoling Fu Yujun Lin Mixun Zhu Kai Wang Jiaqing Wu Xing Tong Wenli Song Ming Jen Tan Yuanzheng Yang Jun Shen Gang Wang Chan Hung Shek Robert O.ritchie School of Materials and Energy Guangdong University of TechnologyGuangzhou 510006China Songshan Lake Materials Laboratory Dongguan 523808China Institute of High Energy Physics Chinese Academy of Sciences(CAS)Beijing 100049China Spallation Neutron Source Science Center Dongguan 523803China Singapore Centre for 3D Printing School of Mechanical and Aerospace EngineeringNanyang Technological UniversitySingapore 639798Singapore School of Materials Science and Engineering Fujian University of TechnologyFuzhou 350118China Institute of Materials Shanghai UniversityShanghai 200444China Department of Materials Science and Engineering City University of Hong KongKowloon TongHong Kong SARChina Department of Materials Science&Engineering University of CaliforniaBerkeleyCA 94720USA

When a transformable B2 precipitate is embedded in an amorphous matrix,it is often experimentally observed that the crystalline-amorphous interface not only serves as an initiation site for the martensitic transformation due to local stress concentrations,but also as an inhibitor to stabilize the transformation,the latter being attributed to the“confinement effect”exerted by the amorphous matrix,according to the Eshelby *** two seemingly incongruous factors are examined in this study using molecular dynamics simulations from an atomic interaction *** innate strain gradient in the vicinity of the crystalline-amorphous interface is *** actual interface,the compressive/dilatative transition,and the interfacial maximum strain are investigated to differentiate from the conventional“interface”located within a distance of a few *** innate interfacial elastic strain field model is applicable for the design of materials with a higher degree of martensitic transformation and controllable stress concentration,even in cryogenic environments.

关键词： strain transformation martensitic

Amnion epithelial cells——a novel therapy for ischemic stroke?

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Neural Regeneration Research 2018年第8期13卷 1346-1349页

作者： Megan A.Evans Brad R.S.Broughton grant R.Drummond Henry Ma Thanh G.Phan Euan M.Wallace Rebecca Lim Christopher G.Sobey Department of Physiology Anatomy & Microbiology La Trobe University Cardiovascular Disease Program Department of Pharmacology Biomedicine Discovery Institute Monash University Department of Medicine Monash University The ritchie Centre Hudson Institute of Medical Research Department of Obstetrics and Gynaecology Monash University

Stroke is a leading cause of death and disability and new therapies are desperately needed. Given the complex nature of ischemic brain injury, it has been postulated that cell-based therapies may be useful. However, cell resources, invasive extraction procedures, immunological rejection, tumorigenesis and ethical challenges make it unlikely that many stem cell types could serve as a practical source for therapy. By contrast, these issues do not pertain to human amnion epithelial cells（h AECs）, which are placenta-derived stem cells. We recently assessed the effects of systemically delivered hAECs on stroke outcome using four animal models of stroke. We demonstrated that when injected intravenously after ischemia onset, hAECs migrate preferentially to the spleen and injured brain to limit apoptosis and inflammation, and attenuate early brain infiltration of immune cells, progression of infarction and systemic immunosuppression and to ultimately ameliorate functional deficits. When administration of hAECs is delayed by 1-3 days poststroke, long-term functional recovery can still be enhanced in young and aged mice of either sex. Moreover, our proof-of-principle findings suggest that h AECs are effective at limiting post-stroke infarct development in non-human primates. Overall, the results suggest that hAECs could be a viable clinical stroke therapy.

关键词： ischemic stroke cerebral infarction stem cells human amnion epithelial cells inflammation immunosuppression brain repair mouse non-human primate

Frequency-tunable continuous-wave random lasers at terahertz frequencies

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Light(Science & Applications) 2019年第1期8卷 828-840页

作者： Simone Biasco Harvey E.Beere David A.ritchie Lianhe Li AGiles Davies Edmund H.Linfield Miriam S.Vitiello NEST CNR-Istituto Nanoscienze and Scuola Normale SuperiorePiazza San Silvestro 1256127 PisaItaly Cavendish Laboratory University of CambridgeCambridge CB30HEUK School of Electronic and Electrical Engineering University of LeedsLeeds LS29JTUK

Random lasers are a class of devices in which feedback arises from multiple elastic scattering in a highly disordered structure,providing an almost ideal light source for artefact-free imaging due to achievable low spatial ***,for many applications ranging from sensing and spectroscopy to speckle-free imaging,it is essential to have high-radiance sources operating in continuous-wave(CW).In this paper,we demonstrate CW operation of a random laser using an electrically pumped quantum-cascade laser gain medium in which a bi-dimensional(2D)random distribution of air holes is patterned into the top metal *** obtain a highly collimated vertical emission at ~3 THz,with a 430 GHz bandwidth,device operation up to 110 K,peak(pulsed)power of 21 mW,and CW emission of 1.7 ***,we show that an external cavity formed with a movable mirror can be used to tune a random laser,obtaining continuous frequency tuning over 11 GHz.

关键词： tunable tuning pumped