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Thermal activation of Ti_((1-x))Au_((x))thin films with enhanced hardness and biocompatibility

Bioactive Materials 2022年第9期7卷 426-445页

作者： Cecil Cherian Lukose Ioannis Anestopoulos Theodora Mantso Leon Bowen Mihalis I.Panayiotidis Martin Birkett Department of Mechanical and Construction Engineering Northumbria UniversityNewcastle Upon TyneUK Department of Cancer Genetics Therapeutics&Ultrastructural PathologyThe Cyprus Institute of Neurology and GeneticsNicosiaCyprus The Cyprus School of Molecular Medicine The Cyprus Institute of Neurology and GeneticsNicosiaCyprus Department of Applied Sciences Northumbria UniversityNewcastle Upon TyneUK Department of Physics G.J.Russell Microscopy FacilityDurham UniversityDurhamUK

The lifetime of orthopaedic implants can be extended by coating the softer Ti6Al4V alloy with harder biocompatible thin *** this work,thin films of Ti_((1-x))Au_((x))are grown on Ti_(6)Al_(4)V and glass substrates by magnetron sputtering in the entire x=0-1 range,before their key biomechanical properties are performance tuned by thermal *** the first time,we explore the effect of in-situ substrate heating versus ex-situ post-deposition heat-treatment,on development of mechanical and biocompatibility performance in Ti-Au films.A~250% increase in hardness is achieved for Ti-Au films compared to bulk Ti6Al4V and a~40%improvement from 8.8 GPa as-grown to 11.9 and 12.3 GPa with in-situ and ex-situ heat-treatment respectively,is corelated to changes in structural,morphological and chemical properties,providing insights into the origins of super-hardness in the Ti rich regions of these materials.X-ray diffraction reveals that as-grown films are in nanocrystalline states of Ti-Au intermetallic phases and thermal activation leads to emergence of mechanically hard Ti-Au intermetallics,with films prepared by in-situ substrate heating having enhanced crystalline *** morphology images show clear changes in grain size,shape and surface roughness following thermal activation,while elemental analysis reveals that in-situ substrate heating is better for development of oxide free Ti3Auβ-*** tested Ti-Au films are non-cytotoxic against L929 mouse fibroblast cells,while extremely low leached ion concentrations confirm their *** peak hardness performance tuned to>12 GPa and excellent biocompatibility,Ti-Au films have potential as a future coating technology for load bearing medical implants.

关键词： Ti-Au thin film coating Hardness Biocompatible L929 mouse fibroblast Implants

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Challenges and Opportunities of Machine Learning on Neutron and X-ray Scattering

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Synchrotron Radiation News 2022年第4期35卷 16-20页

作者： Drucker, Nathan C. Liu, Tongtong Chen, Zhantao Okabe, Ryotaro Chotrattanapituk, Abhijatmedhi Nguyen, Thanh Wang, Yao Li, Mingda Quantum Measurement Group MIT Cambridge MA United States School of Engineering and Applied Sciences Harvard University Cambridge MA United States Department of Physics MIT Cambridge MA United States Department of Mechanical Engineering MIT Cambridge MA United States Department of Chemistry MIT Cambridge MA United States Department of Electrical Engineering and Computer Science MIT Cambridge MA United States Department of Nuclear Science and Engineering MIT Cambridge MA United States Department of Physics and Astronomy Clemson University Clemson SC United States

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AI Aided GPR Data Multipath Summation Using x-t Stacking Weights

AI Aided GPR Data Multipath Summation Using x-t Stacking Wei...

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International Conference on Telecommunications and Signal Processing (TSP)

作者： Economou Nikos Nasir Sobhi Al Abri Said Bader Al Shaqsi Hamdan Hamdan Applied Geophysics Lab School of Mineral Resources Engineering Technical University of Crete Chania Greece Department of Earth Sciences Sultan Qaboos University College of Science Muscat Oman Department of Applied Physics and Astronomy Petroleum Geosciences and Remote Sensing Program Sharjah University UAE

ISBN: (数字)9798350365597

ISBN: (纸本)9798350365603

Migration velocity of Ground Penetrating Radar (GPR) data is a low wavenumber attribute crucial for migration. Obtaining a migration velocity model, which is considered closer to a Root Mean Square (RMS) model, from zero-offset (ZO) data requires analysis of the available diffractions whose density and (x, t) coverage is random. Thus, accuracy and efficiency of such a velocity model either for migration or its usage for interval velocity model estimation is not guaranteed. Here, with the aid of an Artificiaal Intelligence (AI) algorithm, which detects diffractions and usage of their kinematic information, we generate a diffraction velocity model used for the assignment of 2D weights for weighted multipath summation. The scope is to efficiently focus the scattered energy within a GPR section. We describe this methodology and demonstrate its application in enhancing the lateral continuity of reflections. We compare it with the multipath summation using lD weights with simulated data and present its application on marble assessment GPR data for imaging cracks in the subsurface structure.

关键词： Analytical models Diffraction Stacking Estimation Kinematics Data models Reflection

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Nonlinear bubble behaviours of compressible Rayleigh–Taylor instability with isothermal stratification in cylindrical geometry

arXiv

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arXiv 2025年

作者： Yuan, Ming Zhao, Zhiye Liu, Luoqin Wang, Pei Liu, Nan-Sheng Lu, Xi-Yun Department of Modern Mechanics University of Science and Technology of China Anhui Hefei230026 China Department of Mechanical and Aerospace Engineering The Hong Kong University of Science and Technology Hong Kong Institute of Applied Physics and Computational Mathematics Beijing100094 China

Nonlinear evolutions of two-dimensional single-mode compressible Rayleigh–Taylor instability (RTI) with isothermal stratification are investigated in cylindrical geometry via direct numerical simulation for different Atwood numbers (AT = 0.1 − 0.9) and Mach numbers (Ma = 0.1 − 0.9). It is found that the nonlinear bubble growth involves the effects of density stratification, vorticity accumulation and flow compressibility and shows considerable differences between convergent (acceleration acting radially inward) and divergent (acceleration acting radially outward) cases. Specifically, the density stratification leads to non-acceleration at low AT and high Ma. The accelerations in convergent cases are dominated by vorticity accumulation at low AT and low Ma and by flow compressibility at high AT and high Ma whereas the accelerations in divergent cases are purely induced by flow compressibility at high AT and high Ma. Based on the nonlinear theory of incompressible cylindrical RTI with uniform-density background (Zhao et al., J. Fluid Mech., vol. 900, 2020, A24), an improved model is proposed by taking the density variation, vorticity accumulation and flow compressibility into consideration. This model is verified by numerical results and well reproduces the bubble evolution for different AT and Ma from linear to highly nonlinear regimes. © 2025, CC BY.

关键词： Vorticity

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Topology of three-dimensional Dirac semimetals and quantum spin Hall systems without gapless edge modes

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Physical Review Research 2023年第1期5卷 L012019-L012019页

作者： Alexander C. Tyner Shouvik Sur Danilo Puggioni James M. Rondinelli Pallab Goswami Graduate Program in Applied Physics Northwestern University Evanston Illinois 60208USA Department of Physics and Astronomy Northwestern University Evanston Illinois 60208 USA Department of Materials Science and Engineering Northwestern University Illinois 60208 USA Northwestern Argonne Institute for Science and Engineering Evanston Illinois 60208 USA

The quantum spin Hall states are usually expected to possess gapless, helical edge modes. We show that the generic, n-fold-symmetric, momentum planes of three-dimensional, stable Dirac semimetals, which are orthogonal to the direction of nodal separation are examples of generalized quantum spin Hall systems, that possess quantized, spin or relative Chern numbers as bulk topological invariants, and gapped edge modes. We demonstrate these planes and the celebrated Bernevig-Zhang-Hughes model support identical quantized, non-Abelian Berry flux of magnitude 2π. Hence, they display identical quantized, topological response such as spin-charge separation and pumping of one Kramers-pair or SU(2) doublet, when probed with a magnetic flux tube. The Dirac points are identified as unit-strength, monopoles of SO(5) Berry connection, describing topological phase transitions between generalized quantum spin Hall and trivial insulators. Our work identifies precise bulk invariant and quantized response of Dirac semimetals, which are not diagnosed by nested Wilson loops and filling anomaly of corner-localized-states, and shows that many two-dimensional higher-order topological insulators can be understood as generalized quantum spin Hall systems.

关键词： Fractionalization Geometric & topological phases Spintronics Topological insulators Topological phase transition Topological phases of matter

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Simulation-Free Determination of Microstructure Representative Volume Element Size via Fisher Scores

arXiv

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arXiv 2024年

作者： Liu, Wei Mojumder, Satyajit Liu, Wing Kam Chen, Wei Apley, Daniel W. Department of Industrial Engineering and Management Sciences Northwestern University EvanstonIL60208 United States Theoretical and Applied Mechanics Program Northwestern University EvanstonIL60208 United States Department of Mechanical Engineering Northwestern University EvanstonIL60208 United States

A representative volume element (RVE) is a reasonably small unit of microstructure that can be simulated to obtain the same effective properties as the entire microstructure sample. Finite element (FE) simulation of RVEs, as opposed to much larger samples, saves computational expense, especially in multiscale modeling. Therefore, it is desirable to have a framework that determines RVE size prior to FE simulations. Existing methods select the RVE size based on when the FE-simulated properties of samples of increasing size converge with insignificant statistical variations, with the drawback that many samples must be simulated. We propose a simulation-free alternative that determines RVE size based only on a micrograph. The approach utilizes a machine learning model trained to implicitly characterize the stochastic nature of the input micrograph. The underlying rationale is to view RVE size as the smallest moving window size for which the stochastic nature of the microstructure within the window is stationary as the window moves across a large micrograph. For this purpose, we adapt a recently developed Fisher score-based framework for microstructure nonstationarity monitoring. Because the resulting RVE size is based solely on the micrograph and does not involve any FE simulation of specific properties, it constitutes an RVE for any property of interest that solely depends on the microstructure characteristics. Through numerical experiments of simple and complex microstructures, we validate our approach and show that our selected RVE sizes are consistent with when the chosen FE-simulated properties converge. Copyright © 2024, The Authors. All rights reserved.

关键词： Microstructure

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In-plane Wilson loop for measurement of quantized non-Abelian Berry flux

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Physical Review B 2024年第19期109卷 195149-195149页

作者： Alexander C. Tyner Shouvik Sur Qunfei Zhou Danilo Puggioni Pierre Darancet James M. Rondinelli Pallab Goswami Graduate Program in Applied Physics Northwestern University Evanston Illinois 60208 USA Department of Physics and Astronomy Northwestern University Evanston Illinois 60208 USA Materials Research Science and Engineering Center Northwestern University Evanston Illinois 60208 USA Center for Nanoscale Materials Argonne National Laboratory Argonne Illinois 60439 USA Department of Materials Science and Engineering Northwestern University Evanston Illinois 60208 USA Northwestern Argonne Institute for Science and Engineering Evanston Illinois 60208 USA

Band topology of anomalous quantum Hall insulators can be precisely addressed by computing the Chern numbers of constituent nondegenerate bands, describing the presence of quantized, Abelian Berry flux through the two-dimensional Brillouin zone. Can Berry flux be captured for the SU(2) Berry connection of two-fold degenerate bands in spinful materials preserving space-inversion (P) and time-reversal (T) symmetries without detailed knowledge of underlying basis? We address this question by investigating the correspondence between a non-Abelian generalization of Stokes' theorem and the manifestly gauge-invariant eigenvalues of Wilson loops computed along in-plane contours which preserve the underlying crystalline symmetry. The importance of this correspondence is elucidated by performing natural number resolved classification of ab initio band structures of three-dimensional, Dirac materials. Our work underscores how identification of quantized Berry flux, both Abelian and non-Abelian, offers a unified framework for addressing first-order and higher-order topology of insulators and semimetals.

关键词： Electronic structure of atoms & molecules First-principles calculations Topological insulators

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Understanding complex crowd dynamics with generative neural simulators

arXiv

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arXiv 2024年

作者： Minartz, Koen Hendriks, Fleur Koop, Simon Martinus Corbetta, Alessandro Menkovski, Vlado Department of Mathematics and Computer Science Eindhoven University of Technology Netherlands Department of Mechanical Engineering Eindhoven University of Technology Netherlands Department of Applied Physics and Science Education Eindhoven University of Technology Netherlands Eindhoven Artificial Intelligence Systems Institute Netherlands

Understanding the dynamics of pedestrian crowds is an outstanding challenge crucial for designing efficient urban infrastructure and ensuring safe crowd management. To this end, both small-scale laboratory and large-scale real-world measurements have been used. However, these approaches respectively lack statistical resolution and parametric controllability, both essential to discovering physical relationships underlying the complex stochastic dynamics of crowds. Here, we establish an investigation paradigm that offers laboratory-like controllability, while ensuring the statistical resolution of large-scale real-world datasets. Using our data-driven Neural Crowd Simulator (NeCS), which we train on largescale data and validate against key statistical features of crowd dynamics, we show that we can perform effective surrogate crowd dynamics experiments without training on specific scenarios. We not only reproduce known experimental results on pairwise avoidance, but also uncover the vision-guided and topological nature of N-body interactions. These findings show how virtual experiments based on neural simulation enable data-driven scientific discovery. Copyright © 2024, The Authors. All rights reserved.

关键词： Stochastic systems

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Designing Lotus-Like Superhydrophobic Self-Cleaning Surface Using Carbon Nanotubes

SSRN

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SSRN 2024年

作者： Agnihotri, Prabhat K. Rahal, Shubham Choudhury, Moutushi Dutta Samanta, Devranjan Das, Sarit K. Department of Mechanical Engineering Indian Institute of Technology Ropar Nangal Road Punjab Rupnagar140001 India Department of Physics Amity Institute of Applied Sciences Amity University Major Arterial Road AA II Newtown West Bengal Kolkata700135 India Department of Mechanical Engineering Indian Institute of Technology Madras Chennai600 036 India Department of Mechanical and Industrial Engineering Indian Institute of Technology Roorkee Uttarakhand Roorkee247667 India

Artificial superhydrophobic and self-cleaning surfaces are desirable in many engineering applications. Lotus leaves have long been the benchmark for the design and fabrication of artificial non-wetting surfaces. Here, we report the design and fabrication of superhydrophobic surfaces that mimic the behaviour of lotus leaves. Akin to the microstructure of lotus leaves, an intrinsically hierarchical microstructure is created using carbon nanotubes (CNTs). The conventional CNT growth protocol is modified to induce multiscale features with lower diameter CNTs on the top of thicker CNTs. Together they form a dandelion seed head type structure with thicker CNTs as "beak" and thinner CNTs as "pappus". The wetting and self-cleaning behaviour of CNT coated surface is compared with the lotus leaves. The wetting behaviour of never-wet commercial spray and Cu and Ni foils are also recorded for comparison. The contact angle (CA), contact angle hysteresis (CAH) and sliding angle of water drops on CNT coated surface are comparable with the lotus leaves. The wobbling motion of water drops on the CNT coated surface is similar to that on the lotus leaves and spray coated surface with varying contact line length with time. It also induces the self-cleaning characteristics to CNT coated surfaces similar to lotus leaves. Finally, the present study demonstrates a feasible strategy to design and fabricate lotus leaves like artificial superhydrophobic surfaces with hierarchical CNT structures. © 2024, The Authors. All rights reserved.

关键词： Carbon nanotubes

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Updates to the DScribe Library: New Descriptors and Derivatives

arXiv

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arXiv 2023年

作者： Laakso, Jarno Himanen, Lauri Homm, Henrietta Morooka, Eiaki V. Jäger, Marc O.J. Todorović, Milica Rinke, Patrick Department of Applied Physics Aalto University P.O. Box 11100 Aalto00076 Finland Department of Mechanical and Materials Engineering University of Turku TurkuFI-20014 Finland

We present an update of the DScribe package, a Python library for atomistic descriptors. The update extends DScribe’s descriptor selection with the Valle-Oganov materials fingerprint and provides descriptor derivatives to enable more advanced machine learning tasks, such as force prediction and structure optimization. For all descriptors, numeric derivatives are now available in DSribe. For the many-body tensor representation (MBTR) and the Smooth Overlap of Atomic Positions (SOAP), we have also implemented analytic derivatives. We demonstrate the effectiveness of the descriptor derivatives for machine learning models of Cu clusters and perovskite alloys. Copyright © 2023, The Authors. All rights reserved.

关键词： Machine learning

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