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arXiv 2023年

作者： Kobayashi, Kazuho Ueno, Seiya Higuchi, Takehiro Department of Mechanical Engineering Materials Science and Ocean Engineering Graduate School of Engineering Science Yokohama National University Kanagawa Yokohama-city Japan Faculty of Environment and Information Sciences Yokohama National University Japan

Multi-robot patrolling represents a potential application for robotic systems to survey wide areas efficiently. However, such systems have seen few examples of real-world applications due to their lack of human predictability. This paper proposes the Local Reactive (LR) algorithm for multirobot patrolling, aiming to satisfy two primary needs: (i) efficient patrolling and (ii)providing humans with enhanced situation awareness to improve system predictability. Each robot selects its patrol target from the local areas around its current location based on two requirements: (i)patrolling locations with greater need and (ii)reporting its achievements to the base station. The algorithm is distributed and coordinates the robots without centralized control, enabling them to share their patrol achievements and the degree of need to report to the base station. The proposed algorithm outperformed existing algorithms in both patrolling effectiveness and the base station’s situation awareness. Copyright © 2023, The Authors. All rights reserved.

关键词： Base stations

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A Griffith Description of Fracture for Non-Monotonic Loading with Application to Fatigue

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SSRN 2024年

作者： Saha, Subhrangsu Dolbow, John E. Lopez-Pamies, Oscar Department of Civil and Environmental Engineering The University of Illinois Urbana–ChampaignIL61801 United States Department of Mechanical Engineering and Materials Science Duke University DurhamNC27708 United States

With the fundamental objective of establishing the universality of the Griffith energy competition to describe the growth of large cracks in solids \emph{not} just under monotonic but under general loading conditions, this paper puts forth a generalization of the classical Griffith energy competition in nominally elastic brittle materials to arbitrary \emph{non-monotonic} quasistatic loading conditions, which include monotonic and cyclic loadings as special cases. Centered around experimental observations, the idea consists in: $i$) viewing the critical energy release rate $\mathcal{G}_c$ \emph{not} as a material constant but rather as a material function of both space $\bfX$ and time $t$, $ii$) one that decreases in value as the loading progresses, this solely within a small region $\Omega_\ell(t)$ around crack fronts, with the characteristic size $\ell$ of such a region being material specific, and $iii$) with the decrease in value of $\mathcal{G}_c$ being dependent on the history of the elastic fields in $\Omega_\ell(t)$. By construction, the proposed Griffith formulation is able to describe any Paris-law behavior of the growth of large cracks in nominally elastic brittle materials for the limiting case when the loading is cyclic. For the opposite limiting case when the loading is monotonic, the formulation reduces to the classical Griffith formulation. Additional properties of the proposed formulation are illustrated via a parametric analysis and direct comparisons with representative fatigue fracture experiments on a ceramic, mortar, and PMMA. © 2024, The Authors. All rights reserved.

关键词： Brittleness

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Study on Thermal Deformation Constitutive Model and Microstructure of Forged N06625 Nickel-Based Alloy

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SSRN 2024年

作者： Lu, Yibo Li, Yugui Song, Yaohui Yao, Lu Huang, Zizhou Wang, Jiayao Zou, Zhijie School of Mechanical Engineering Taiyuan University of Science and Technology Shanxi Taiyuan030024 China Engineering Research Center Heavy Machinery Ministry of Education Taiyuan University of Science and Technology Shanxi Taiyuan030024 China School of Materials Science and Engineering Taiyuan University of Science and Technology Shanxi Taiyuan030024 China

The thermal deformation behavior of N06625 nickel-based alloy at 950~1200℃, strain rate of 0.1~10s-1, and deformation amount of 60% was studied by single pass compression experiment. The flow stress first increases to the peak value in the work hardening process, then slowly decreases in dynamic softening, and finally becomes stable. The strain-compensated Arrhenius (SCA) model, BP artificial neural network (BP) model, and piecewise function (PF) model are constructed based on the stress-strain curve. It is found that the best constitutive model of N06625 nickel-based alloy is the piecewise function model. The power dissipation diagrams under different strains are constructed and combined with EBSD analysis;the results show that the area of the high power dissipation zone and the power dissipation value (η) increase with the increase of strain, and the peak η under each strain appears in the range of 1200℃-0.1s-1. The dynamic recrystallization process will affect η. The lower the strain rate and the higher the deformation temperature, the more dynamic recrystallization occurs, and the higher the η. © 2024, The Authors. All rights reserved.

关键词： Constitutive models

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Kinetic and Equilibrium Shapes of Cylindrical Grain Boundaries

arXiv

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arXiv 2024年

作者： Qiu, Anqi Qiu, Caihao Chesser, Ian Han, Jian Srolovitz, David J. Holm, Elizabeth A. Department of Materials Science and Engineering Carnegie Mellon University PittsburghPA15213 United States Department of Materials Science and Engineering City University of Hong Kong Hong Kong XCP-5 Los Alamos National Laboratory Los AlamosNM87545 United States Department of Mechanical Engineering The University of Hong Kong Hong Kong Department of Materials Science and Engineering University of Michigan Ann ArborMI48109 United States

In this work, we investigate the shape evolution of rotated, embedded, initially cylindrical grains (with [001] cylinder axis) in Ni under an applied synthetic driving force via molecular dynamics simulations and a continuum, disconnection-based grain boundary migration model. For some initial misorientations, the expanding grains form well-defined, faceted shapes, while for others the shapes remain cylindrical. The embedded grains tend to rotate during grain boundary migration, with the direction of rotation dependent on initial misorientation and direction of growth (expand/shrink). The kinetic shapes, which are bounded by low mobility grain boundary planes, differ from equilibrium shapes (bounded by low energy grain boundaries). The multi-mode disconnection model-based predictions are consistent with the molecular dynamics results for faceting tendency, kinetic grain shape, and grain rotation as a function of misorientation and whether the grains are expanding or contracting. This demonstrates that grain boundary migration and associated grain rotation are mediated by disconnection flow along grain boundaries. © 2024, CC BY.

关键词： Molecular dynamics

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Challenges for and Pathways toward Li-MetalBased All-Solid-State Batteries

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ACS ENERGY LETTERS 2021年第4期6卷 1399-1404页

作者： Albertus, Paul Anandan, Venkataramani Ban, Chunmei Balsara, Nitash Belharouak, Ilias Buettner-Garrett, Josh Chen, Zonghai Daniel, Claus Doeff, Marca Dudney, Nancy J. Dunn, Bruce Harris, Stephen J. Herle, Subramanya Herbert, Eric Kalnaus, Sergiy Libera, Joesph A. Lu, Dongping Martin, Steve McCloskey, Bryan D. McDowell, Matthew T. Meng, Y. Shirley Nanda, Jagjit Sakamoto, Jeff Self, Ethan C. Tepavcevic, Sanja Wachsman, Eric Wang, Chunsheng Westover, Andrew S. Xiao, Jie Yersak, Thomas Department of Chemical and Biomolecular Engineering University of Maryland College Park Maryland 20742 United States Ford Motor Company Dearborn Michigan 48121 United States Mechanical Engineering Department University of Colorado Boulder Colorado 80309 United States Department of Chemical and Biomolecular Engineering and Lawrence Berkeley National Laboratory Materials Sciences Division University of California Berkeley California 94720 United States Energy and Transportation Science Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 United States Solid Power Inc. Louisville Colorado 80027 United States Chemical Sciences and Engineering Division Argonne National Laboratory 9700 South Cass Avenue Argonne Illinois 60439 United States Lawrence Berkeley National Laboratory Energy Storage and Distributed Resources Division University of California Berkeley California 94720 United States Department of Materials Science and Engineering University of California Los Angeles California 90095 United States Applied Materials Inc. 3225 Oakmead Village Drive B12_2F6 Santa Clara California 95054 United States Department of Materials Science and Engineering Michigan Technological University Houghton Michigan 49931 United States Energy and Environmental Directorate Pacific Northwest National Laboratory Richland Washington 99352 United States Department of Materials Science & Engineering Iowa State University of Science & Technology Ames Iowa 50011 United States Woodruff School of Mechanical Engineering and School of Materials Science and Engineering Georgia Institute of Technology Atlanta Georgia 30332 United States Department of NanoEngineering and Materials Science and Engineering Program University of California San Diego La Jolla California 92093 United States Department of Materials Science and Engineering and Department of Mechanical Engineering University of Michigan Ann Arbor Michigan 48109 United States Chemical and Materials Systems Laborat

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Model Experiment on Deep Rock Fragmentation Induced by Blasting with Different Coupling Mediums

SSRN

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SSRN 2023年

作者： Yang, Jiacai Liu, Zhixiang Liu, Kewei Li, Xudong Guo, Can Zou, Liansong School of Resources and Safety Engineering Central South University Changsha China Department of Mechanical and Structural Engineering and Materials Science University of Stavanger Stavanger Norway

In this study, 26 blasting experiments were carried out on single-hole cubic specimens (100 mm side length) with different coupling mediums (air, water and Oobleck), decoupling ratios (1.67, 2.00 and 2.33) and various uniaxial static stresses (0-10 MPa). After each test, the blast-induced rock fragments were carefully collected, sieved and weighed. The results show that: (1) Under non-stress loading conditions, the coupling mediums were ranked according to the fragmentation size (worse-to-better): air, water and Oobleck. Under uniaxial static stress, the rock fragmentation induced by blasting with Oobleck contains less fine particles and the maximum fragments with a smaller size compared to water-coupling blasting. (2) The crack initiation and propagation patterns in blasting using various coupling mediums are different, which results in distinct fragmentation in each blasting. The main reason is the different ability of the coupling mediums in propagating explosion stress waves and its mechanical response to the blasting load. © 2023, The Authors. All rights reserved.

关键词： Blasting

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Capacitive Origami Sensing Modules for Measuring Force in a Neurosurgical, Soft Robotic Retractor

Capacitive Origami Sensing Modules for Measuring Force in a ...

引用

IEEE International Conference on Robotics and Automation (ICRA)

作者： Daniel Van Lewen Catherine Wang Hun Chan Lee Anand Devaiah Urvashi Upadhyay Sheila Russo Department of Mechanical Engineering Boston University Boston MA USA Division of Materials Science and Engineering Boston University Boston MA USA School of Medicine Boston University Boston MA USA

ISBN: (数字)9798350384574

ISBN: (纸本)9798350384581

In neurosurgery, soft robots have the potential to introduce significant benefits over traditional metal tools for their ability to safely interact with delicate tissues. In this paper, we introduce a proof-of-concept soft, capacitive origami sensing module (OSM) that can measure forces during neurosurgical retraction. Using origami-inspired design and fabrication principles, the OSM is easily folded and integrated within a soft robotic retractor that interacts with brain tissue to generate a surgical workspace upon actuation. We demonstrate the individual OSM signal response to forces and folding. We further characterize the OSM response within a fully-assembled soft robotic retractor to both folding and the application of forces over 0-5 N showing a 0.38 N average prediction error and resolution of 0.25 N. The sensing capability of the retractor is validated on an in-vitro model to demonstrate prediction errors of 0.06 N and the proposed operation during neurosurgery.

关键词： Fabrication Force measurement Force Soft robotics Predictive models Robot sensing systems Capacitance

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Comparison of Coherent and Incoherent Donut Beams for Deep Tissue STED Microscopy

Comparison of Coherent and Incoherent Donut Beams for Deep T...

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2023 Conference on Lasers and Electro-Optics, CLEO 2023

作者： Shanavas, Thariq McLeod, Robert R. Siemens, Mark E. Gopinath, Juliet T. Department of Physics University of Colorado BoulderCO80309 United States Department of Electrical Computer and Energy Engineering University of Colorado BoulderCO80309 United States Department of Physics University of Denver DenverCO80204 United States Materials Science Engineering Program University of Colorado BoulderCO80309 United States

We numerically compare the null quality for STED microscopy generated by Laguerre-Gaussian beams with orbital angular momentum and donut beams generated by incoherent addition of orthogonal Hermite Gaussian beams when... 详细信息

ISBN: (纸本)9781957171258

关键词： Tissue

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Improving Constant Power Flux Weakening in MnBi Interior Permanent Magnet Traction Motors

Improving Constant Power Flux Weakening in MnBi Interior Per...

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IEEE Energy Conversion Congress and Exposition, ECCE

作者： Ryan Brody Paul Ohodnicki Mohendro K. Ghosh Brandon Grainger Department of Electrical and Computer Engineering University of Pittsburgh Pittsburgh PA USA Department of Mechanical Engineering and Materials Science University of Pittsburgh Pittsburgh PA USA

Interior permanent magnet synchronous motors (IPMSMs) using Neodymium Iron Boron (NdFeB) permanent magnets (PMs) dominate in applications, like in electric vehicles (EVs), which require high torque density, high power density, and high efficiency while maintaining reasonable cost and manufacturability. However, extraordinary price volatility of rare-earth (RE) elements in NdFeB PMs has led to an effort to develop low cost, RE-free PMs that outperform ferrites (the best existing alternative). Because of its high coercivity (Hc) at high temperatures and relatively low cost with reduced price volatility, manganese bismuth (MnBi) based PMs have attracted attention despite a remanent flux density (B r ) closer to those of ferrites. Lower Br reduces short circuit current thus reducing constant power speed ratio (CPSR) when directly replacing NdFeB in reference designs with MnBi. This paper reviews why CPSR lowers when doing so but then shows that redesigning the rotor using a segmented PM-assisted synchronous reluctance motor (PMASynRM) topology with MnBi can improve CPSR.

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Novel ruthenium-based catalysts with atomic dispersion for oxygen evolution reaction in water electrolysis

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materials Today Chemistry 2024年 35卷

作者： Liao, Kuo-Wei Chen, Hsueh-Yu Wei, Wen-Hui Chen, Guan-Cheng Yamanaka, Ichiro Liu, Bo-Tau Hong, Ting-Fu Chiang, Tai-Chin Huang, Hsin-Chih Wang, Chen-Hao Department of Materials Science and Engineering National Taiwan University of Science and Technology Taipei106335 Taiwan Department of Chemical Science and Engineering School of Materials and Chemical Technology Tokyo Institute of Technology Meguro-ku Tokyo152-8552 Japan Department of Chemical and Materials Engineering National Yunlin University of Science and Technology Yunlin640301 Taiwan Department of Materials Engineering National Pingtung University of Science and Technology Pingtung912301 Taiwan Global Development Engineering Program National Taiwan University of Science and Technology Taipei106335 Taiwan Advanced Manufacturing Research Center National Taiwan University of Science and Technology Taipei106335 Taiwan

This study introduces a method for fabricating ultra-high-performance catalysts designed for the oxygen evolution reaction (OER), employing a combination of ball-milling, autoclave heat treatment procedures, and a two-step heat treatment approach. This method produces catalysts characterized by an atomic dispersion of ruthenium on nitrogen-doped carbon sheets (Ru–O/N–C–NH3). The Ru–O/N–C–NH3 catalyst exhibits exceptional OER activity in alkaline conditions, achieving a mass activity of 16842 A g−1Ru at 1.52 V, and a minimal overpotential of 290 mV at a current density of 10 mA cm−2. Moreover, this catalyst demonstrates enduring stability, showing no significant decay after a 100-h stability test in anion exchange membrane water electrolysis (AEMWE), with a mass activity approximating 62000 A g−1PGM. This is nearly three orders of magnitude greater than the AEMWE that utilizes commercial IrO2 as an anode. The atomic dispersion and the Ru–O/N bonding of the catalyst are substantiated to contribute to the notable enhancement in OER activity. © 2023 Elsevier Ltd

关键词： Ruthenium

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