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Tuning of frictional properties in torsional contact by means of disk grading

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Friction 2022年第5期10卷 787-802页

作者： Gianluca COSTAGLIOLA Federico BOSIA nicola m.pugno Civil Engineering Institute Ecole Polytechmique Federale de LausamneLausanne 1015Switzerland Department ofApplied Science and Technology Politecnico di TorinoCorso Duca degli Abruzzi 24Torino 10129Italy Laboratory for BioinspiredBionicNanoMeta Materials&MechanicsDepartment of CivilEnvironmental and Mechanical EngineeringUniversity of TrentoTrento 38123Italy School of Engineering and materials Science Queen Mary University of LondonLondon EI 4NSUK

The contact of two surfaces in relative rotating motion occurs in many practical applications,from mechanical devices to human joints,displaying an intriguing interplay of effects at the onset of sliding due to the axisymmetric stress *** and numerical models have been developed for some typical configurations,but work remains to be done to understand how to modify the emergent friction properties in this *** this paper,we extend the two-dimensional(2D)spring-block model to investigate friction between surfaces in torsional *** investigate how the model describes the behavior of an elastic surface slowly rotating over a rigid substrate,comparing results with analytical calculations based on energy *** show that an appropriate grading of the tribological properties of the surface can be used to avoid a non-uniform transition to sliding due to the axisymmetric configuration.

关键词： friction torsion numerical simulations grading

mECHANICS OF CARBON NANOSCROLLS: A REVIEW

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Acta mechanica Solida Sinica 2010年第6期23卷 484-497页

作者： Xinghua Shi nicola m. pugno Huajian Gao School of Engineering Brown University 610 Barus & Holley 182 Hope Street Providence RI 02912 USA Laboratory of Bio-inspired Nanomechanics 'Giuseppe maria pugno ' Department of Structural Engineering Politecnico di Torino Corso Duca degli Abruzzi 24 10129 Torino Italy

Carbon nanoscrolls （CNSs） belong to the same class of carbon-based nanomaterials as carbon nanotubes but are much less studied in spite of their great potential for applications in nanotechnology and bioengineering. Fundamental description, understanding and regulation of such materials will ultimately lead to a new generation of integrated systems that utilize their unique properties. In this review, we describe some of the recent advances in theoretical investi- gation on structural and dynamical behavior of CNS, as well as relevant simulation techniques. Theoretically it has been found that a stable equilibrium core size of CNS can be uniquely determined or tuned from the basal graphene length, the interlayer spacing, the interaction energy between layers of CNS and the bending stiffness of graphene. Perturbations of the surface energy, which can be controlled by an electric field, will cause a CNS to undergo breathing oscillatory motion as well as translational rolling motion on a substrate. The tunable core size of CNS also enables it to serve potentially as transmembrane water channels in biological systems.

关键词： Graphene

The effect of pyrazine odor on avoidance learning and memory in wild robins Erithacus rubecula

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Current Zoology 2011年第2期57卷 208-214页

作者： Emma C. SIDDALL nicola m. mARPLES School of Natural Sciences Trinity College Dublin Dublin 2 Ireland

Toxic insects advertise their defended state to potential predators using warning displays. Frequently these displays use cues through more than one sensory modality, and combine color, smell and sound to produce a multimodal warning display. Signalling through more than one sensory pathway may enhance the rate of avoidance learning, and the memorability of the learned avoidance. A common insect warning odor, pyrazine, has previously been shown to increase the rate of learned avoidance of unpalatable yellow prey by domestic chicks （GaUus gallus domesticus）, and the odor also improved memory of this learned avoidance. However, to date no research has examined this response to pyrazine odor using wild birds under natural conditions. This study used wild robins （Erithacus rubecula） to investigate whether wild birds avoided yellow baits that smelled of pyrazine more strongly than those presented with no odor. The results provide some evidence that pyrazine odor does increase the level of protection an aposematic insect gains from a wild avian predator, but that the effect of pyrazine on learned avoidance was much weaker than was found with domestic chicks .

关键词： Aposematism Learned avoidance memory multimodal warning display Pyrazine Robins

Hear no evil： The effect of auditory warning signals on avian innate avoidance, learned avoidance and memory

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Current Zoology 2011年第2期57卷 197-207页

作者： Emma C. SIDDALL nicola m. mARPLES School of Natural Sciences Trinity College Dublin Dublin 2 Ireland

many aposematic insect species advertise their toxicity to potential predators using olfactory and auditory signals, in addition to visual signals, to produce a multimodal warning display. The olfactory signals in these displays may have interesting effects, such as eliciting innate avoidance against novel colored prey, or improving learning and memory of defended prey. However, little is known about the effects of such ancillary signals when they are auditory rather than olfactory. The few studies that have investigated this question have provided conflicting results. The current study sought to clarify and extend understanding of the effects of prey auditory signals on avian predator responses. The domestic chick Gallus gallus domesticus was used as a model avian predator to examine how the defensive buzzing sound of a bumblebee Bombus terrestris affected the chick＇s innate avoidance behavior, and the learning and memory of prey avoidance. The results demonstrate that the buzzing sound had no effect on the predator＇s responses to unpalatable aposematically colored crumbs, suggesting that the agitated buzzing of B. terrestris may provide no additional protection from avian predators .

关键词： Aposematism Auditory signals Dietary conservatism Avoidance learning memorability multimodal signaling

All-perfluoropolymer,nonlinear stability-assisted monolithic surface combines topology-specific superwettability with ultradurability

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The Innovation 2023年第2期4卷 60-66,59页

作者： Wanbo Li Chiu-wing Chan Zeyu Li Sin-Yung Siu Siyu Chen Han Sun Zeyu Liu Yisu Wang Chong Hu nicola maria pugno Richard N.Zare Hongkai Wu Kangning Ren Department of Chemistry Hong Kong Baptist UniversityHong Kong 999077China Department of Chemistry The Hong Kong University of Science and TechnologyHong Kong 999077China Department of Civil Environmental and Mechanical EngineeringLaboratory of Bio-InspiredBionicNanoMeta Materials and MechanicsUniversitàdi Trento38100 TrentoItaly School of Engineering and materials Science Queen Mary University of LondonLondon E14NSUK Department of Chemistry Stanford UniversityStanfordCA 94305USA School of mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Environmental and Biological Analysis Hong Kong Baptist UniversityHong Kong SAR 999077China HKBU Institute of Research and Continuing Education Shenzhen 518057China

Developing versatile and robust surfaces that mimic the skins of living beings to regulate air/liquid/solid matter is critical for many bioinspired *** notable achievements,such as in the case of developing robust superhydrophobic surfaces,it remains elusive to realize simultaneously topology-specific superwettability and multipronged durability owing to their inherent tradeoff and the lack of a scalable fabrication ***,we present a largely unexplored strategy of preparing an all-perfluoropolymer(Teflon),nonlinear stability-assisted monolithic surface for efficient regulating matters.

关键词： method durability topology

Organic petrographic and mineralogical composition of the No. 6 coal seam of the Soutpansberg Coalfield, South Africa: Insights into paleovegetation and depositional environment

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International Journal of Coal Science & Technology 2024年第3期11卷 190-207页

作者： Sanki Biswas nicola J.Wagner Ofentse m.moroeng DSI-NRF CImERA/PPm Research Group Department of GeologyUniversity of JohannesburgJohannesburgSouth Africa

This study investigates the paleodepositional conditions of the No.6 Seam of the madzaringwe Formation in makhado and Voorburg south area of the Soutpansberg Coalfield(Limpopo Province,South Africa)utilizing organic petrography and inorganic geochemical *** coals are predominantly high-volatile bituminous B-A rank with high ash yields(avg.36.1 wt%),characterized by high-vitrinite(~41.5 vol%),moderate-to-high inertinite(9.8 vol%–33.7 vol%)and low liptinite(~2.3 vol%).The distribution of inertinite varies among different coal horizons(from bottom-lower to middle-upper),suggesting differential oxidation conditions and/or paleofire ***-to-inertinite(V/I)ratio,tissue preservation–gelification index(TPI–GI),and groundwater–vegetation index(GWI–VI)plots,indicate that the peat-forming forest-swamp vegetation accumulated under mesotrophic-to-rheotrophic hydrological *** presence of structured macerals(i.e.,telinite,collotelinite,fusinite,and semifusinite)suggests well-preserved plant tissues,whereas framboidal pyrite and sulphur content(0.24 wt%–2.16 wt%)point to brackish-water influence at the peat *** coals contain quartz,kaolinite,siderite,muscovite,dolomite,calcite,and pyrite minerals,most of which were likely sourced from felsic igneous *** Al/(Al+Fe+mn)and(Fe+mn)/Ti ratios for the studied samples range between 0.24–0.97 and 0.57–70.10,*** ratios,Al–Fe–mn plot,and presence of massive botryoidal-type pyrite imply some influence of meteoric waters or fluids from hydrothermal activity ***,the chemical index of alteration(CIA:98.25–99.67),chemical index of weathering(CIW:92.04–97.66),and A–CN–K ternary diagram suggest inorganic matter suffered strong chemical weathering,indicating warm paleoclimatic conditions during the coal formation.

关键词： macerals Coal facies Geochemical-indices Hydrothermal madzaringwe formation Soutpansberg Coalfield

Infrared-active phonons in one-dimensional materials and their spectroscopic signatures

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npj Computational materials 2023年第1期9卷 331-337页

作者： Norma Rivano nicola marzari Thibault Sohier Theory and Simulations of materials(THEOS) École Polytechnique Fédérale de LausanneCH-1015 LausanneSwitzerland National Centre for Computational Design and Discovery of Novel materials(mARVEL) École Polytechnique Fédérale de LausanneCH-1015 LausanneSwitzerland Laboratory for materials Simulations Paul Scherrer Institut5232 Villigen PSISwitzerland Laboratoire Charles Coulomb(L2C) Universitéde MontpellierCNRSMontpellierFrance

Dimensionality provides a clear fingerprint on the dispersion of infrared-active,polar-optical *** these phonons,the local dipoles parametrized by the Born effective charges drive the LO-TO splitting of bulk materials;this splitting actually breaks down in two-dimensional ***,we develop the theory for one-dimensional(1D)systems—nanowires,nanotubes,and atomic and polymeric *** an analytical model with the implementation of density-functional perturbation theory in 1D boundary conditions,we show that the dielectric splitting in the dispersion relations collapses as x^(2) log(x)at the zone *** dielectric properties and the radius of the 1D materials are linked by the present work to these red shifts,opening infrared and Raman characterization avenues.

关键词： dimensional splitting dielectric

Solids that are also liquids: elastic tensors of superionic materials

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npj Computational materials 2023年第1期9卷 2252-2264页

作者： Giuliana materzanini Tommaso Chiarotti nicola marzari Theory and Simulations of materials(THEOS) École Polytechnique Fédérale de LausanneCH-1015 LausanneSwitzerland National Centre for Computational Design and Discovery of Novel materials(mARVEL) École Polytechnique Fédérale de LausanneCH-1015 LausanneSwitzerland Present address:Institute of Condensed matter and Nanosciences UniversitéCatholique de LouvainB-1348 Louvain-la-NeuveBelgium

Superionics are fascinating materials displaying both solid- and liquid-like characteristics: as solids, they respond elastically to shearstress;as liquids, they display fast-ion diffusion at normal conditions. In addition to such scientific interest, superionics aretechnologically relevant for energy, electronics, and sensing applications. Characterizing and understanding their elastic propertiesis, e.g., urgently needed to address their feasibility as solid-state electrolytes in all-solid-state batteries. However, static approachesto elasticity assume well-defined reference positions around which atoms vibrate, in contrast with the quasi-liquid motion of themobile ions in fast ionic conductors. Here, we derive the elastic tensors of superionics from ensemble fluctuations in the isobaric-isothermal ensemble, exploiting extensive Car-Parrinello simulations. We apply this approach to paradigmatic Li-ion conductors,and complement with a block analysis to compute statistical errors. Static approaches sampled over the trajectories oftenoverestimate the response, highlighting the importance of a dynamical treatment in determining elastic tensors in superionics.

关键词： ionic liquids ensemble

Thermal conductivity of glasses: first-principles theory and applications

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npj Computational materials 2023年第1期9卷 1253-1274页

作者： michele Simoncelli Francesco mauri nicola marzari Theory of Condensed matter Group of the Cavendish Laboratory University of CambridgeCambridgeUK Dipartimento di Fisica Universitàdi Roma La SapienzaRomaItaly Theory and Simulation of materials(THEOS)and National Centre for Computational Design and Discovery of Novel materials(mARVEL) École Polytechnique Fédérale de LausanneLausanneSwitzerland

Predicting the thermal conductivity of glasses from first principles has hitherto been a very complex *** established Allen-Feldman and Green-Kubo approaches employ approximations with limited validity—the former neglects anharmonicity,the latter misses the quantum Bose-Einstein statistics of vibrations—and require atomistic models that are very challenging for first-principles ***,we present a protocol to determine from first principles the thermal conductivityκ(T)of glasses above the plateau(i.e.,above the temperature-independent region appearing almost without exceptions in theκ(T)of all glasses at cryogenic temperatures).The protocol combines the Wigner formulation of thermal transport with convergence-acceleration techniques,and accounts comprehensively for the effects of structural disorder,anharmonicity,and Bose-Einstein *** validate this approach in vitreous silica,showing that models containing less than 200 atoms can already reproduceκ(T)in the macroscopic *** discuss the effects of anharmonicity and the mechanisms determining the trend ofκ(T)at high temperature,reproducing experiments at temperatures where radiative effects remain negligible.

关键词： glasses conductivity harmonic