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arXiv 2022年

作者： Ramezankhani, Milad Nazemi, Amir Narayan, Apurva Voggenreiter, Heinz Harandi, Mehrtash Seethaler, Rudolf Milani, Abbas S. Materials And Manufacturing Research Institute University Of British Columbia Kelowna Canada Department Of Computer Science University Of British Columbia Kelowna Canada Stuttgart Germany Department Of Electrical And Computer Systems Engineering Monash University Clayton Australia

Despite the successful implementations of physics-informed neural networks in different scientific domains, it has been shown that for complex nonlinear systems, achieving an accurate model requires extensive hyperparameter tuning, network architecture design, and costly and exhaustive training processes. To avoid such obstacles and make the training of physics-informed models less precarious, in this paper, a data-driven multi-fidelity physics-informed framework is proposed based on transfer learning principles. The framework incorporates the knowledge from low-fidelity (auxiliary) systems and limited labeled data from target (actual) system to significantly improve the performance of conventional physics-informed models. While minimizing the efforts of designing a complex task-specific network for the problem at hand, the proposed settings guide the physics-informed model towards a fast and efficient convergence to a global optimum. An adaptive weighting method is utilized to further enhance the optimization of the model's composite loss function during the training process. A data-driven strategy is also introduced for maintaining high performance in subdomains with significant divergence between low- and high-fidelity behaviours. The heat transfer of composite materials undergoing a cure cycle is investigated as a case study to demonstrate the proposed framework's superior performance compared to conventional physics-informed models. © 2022, CC BY-NC-ND.

关键词： Flow control

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Design and Manufacture of Periodic Metastructure materials with Broadband EM Absorption

Design and Manufacture of Periodic Metastructure Materials w...

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IEEE International Symposium on Electromagnetic Compatibility (EMC)

作者： Dandan Zhang Steven Mamolo Kanat Anurakparaorn Yiheng Xiao Eric Michielssen Alan I. Taub Department of Materials Science and Engineering University of Michigan Ann Arbor MI USA Department of Aerospace Engineering University of Michigan Ann Arbor MI USA Department of Industrial Engineering King Mongkut’s Institute of Technology Ladkrabang Bangkok Thailand Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA Department of Mechanical Engineering University of Michigan Ann Arbor MI USA

ISBN: (数字)9798350360394

ISBN: (纸本)9798350360400

Computational modeling and optimization were utilized to design the metastructure of a polymer nanocomposite system. The goal is to minimize the reflection loss (RL) and broaden the absorption bandwidth. Truncated cones with a perfect electric conductor on the top surface were chosen. With this innovative metastructure, the absorption bandwidth of RL at -20dB has been increased from 0, as observed in non-porous materials, to 1.83 GHz. The samples with optimized metastructures were manufactured using hot pressing and computer numerical control (CNC) machining techniques. This approach provided an efficient way to design and precisely manufacture materials with targeted EM absorption.

关键词： Absorption Computational modeling Bandwidth Pressing Machining Conductors Reflection Polymers computer numerical control Optimization

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Additive Manufacturing of Magnetic Components for Heterogeneous Integration

Additive Manufacturing of Magnetic Components for Heterogene...

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Electronic Components and Technology Conference (ECTC)

作者： Yi Yan Lanbing Liu Chao Ding Luu Nguyen Jim Moss Yunhui Mei Guo-Quan Lu Center for Power Electronics Systems Virginia Tech Blacksburg VA USA Department of Materials Science and Engineering Virginia Tech Blacksburg VA USA Texas Instruments Inc. Santa Clara CA USA School of Materials Science and Engineering Tianjin University Tianjin China The Bradley Department of Electrical and Computer Engineering Virginia Tech Blacksburg VA USA

In an effort to simplify the process of integrating magnetic components to power electronics circuits, an additive manufacturing (AM) process, or commonly known as 3D-printing, for fabricating magnetic components is studied in this work. A commercial multi-extruder paste-extrusion 3D printer was evaluated for making magnetic components. We developed two material systems for printing magnetic cores: (1) curable powdered iron paste system, and (2) sinterable ferrite system. We used commercial nanosilver paste for the conductive winding. A half piece of constant-flux inductor (CFI) and a planar inductor were fabricated in this study. For the half piece CFI, 3D-printing was used with nanosilver paste and low-temperature curable powdered iron paste. The printed winding was sintered at 250 deg C for 30 minutes firstly and then magnetic paste was printed to cover the sintered winding. The magnetic paste was cured at 230 deg C for one hour without any external pressure to form the structure. Two printed pieces were connected to form the full size CFI. Inductance of the CFI was measured to be about 3.5 μH. The DC resistance of the winding was 59 m. For the planar inductor, 3D printing was used with nanosilver paste and high-temperature sinterable ferrite paste. It was sintered at 920oC for 14 hours without any external pressure to form the structure. The inductance of the planar inductor was measured to be about 792 nH. The DC resistance of the winding was 15 m. Microstructures of the printed inductors were examined by scanning electron microscopy (SEM). Both the winding and core magnetic properties can be improved by adjusting the feed paste formulations and their flow characteristics and fine-tuning the printer parameters.

关键词： Windings Magnetic cores Inductors Ferrites Resistance Toroidal magnetic fields Permeability

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Dynamical scattering in coherent hard X-ray nanobeam bragg diffraction

arXiv

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arXiv 2020年

作者： Pateras, A. Park, J. Ahn, Y. Tilka, J.A. Holt, M.V. Kim, H. Mawst, L.J. Evans, P.G. Department of Materials Science & Engineering University of Wisconsin-Madison MadisonWI53706 United States Center for Nanoscale Materials Argonne National Laboratory ArgonneIL60439 United States Department of Electrical and Computer Engineering University of Wisconsin-Madison MadisonWI53706 United States

Unique intensity features arising from dynamical diffraction arise in coherent x-ray nanobeam diffraction patterns of crystals having thicknesses larger than the x-ray extinction depth or exhibiting combinations of nanoscale and mesoscale features. We demonstrate that dynamical scattering effects can be accurately predicted using an optical model combined with the Darwin theory of dynamical x-ray diffraction. The model includes the highly divergent coherent x-ray nanobeams produced by Fresnel zone plate focusing optics and accounts for primary extinction, multiple scattering, and absorption. The simulation accurately reproduces the dynamical scattering features of experimental diffraction patterns acquired from a GaAs/AlGaAs epitaxial heterostructure on a GaAs (001) substrate. Copyright © 2020, The Authors. All rights reserved.

关键词： Nanowires

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Characterizing Battery Behavior for Time Dependent Currents

Characterizing Battery Behavior for Time Dependent Currents

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IEEE Energy Conversion Congress and Exposition

作者： Thuwaragan Sritharan David Yan Francis Dawson Keryn Liany Department of Electrical and Computer Engineering University of Toronto Department of Materials Science and Engineering University of Toronto

ISBN: (纸本)9781467308021

Batteries connected to the DC grid are exposed to a variety of currents. This paper presents measurements on a Ni-MH battery under different loading conditions and shows how a small signal circuit model can be used to explain the observations, establishing links between physical processes within the battery and elements in the model. At DC currents over 2 C, the impedance of the battery is not influenced by the ripple frequency, but rather by the higher temperatures. Results also show that the impact of the ripple frequency on modulation of the double layer charge is negligible at ripple frequencies exceeding 5 kHz. The amplitude of pulses that can be applied are shown to be governed by diffusion limits and the battery’s state of charge.

关键词： Characterizing Battery Behavior Time Dependent Currents observations

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(INVITED) On the evolution of nanoparticles in nanoparticle-doped optical fibers

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Optical materials: X 2022年 16卷

作者： Cahoon, Mary Ann Meehan, Bailey Hawkins, Thomas W. McMillen, Colin Antonick, Paul Riman, Richard E. Dragic, Peter D. Digonnet, Michel J.F. Ballato, John Department of Materials Science and Engineering Clemson University ClemsonSC29634 United States Department of Chemistry Clemson University ClemsonSC29634 United States Department of Materials Science and Engineering Rutgers The State University of New Jersey Piscataway NJ08855 United States Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign UrbanaIL61801 United States Edward L. Ginzton Laboratory Stanford University Stanford CA94305 United States

The doping of dielectric nanoparticles (NPs) into the cores of silica fibers doped with a rare earth (RE) has proven to be an effective approach for controlling the spectroscopic performance of the rare earth. However, little is understood about the chemical and structural evolution of the NPs during fiber preform fabrication, or how any process-induced changes in the NPs affect the optical properties of the resultant fiber. In this work, rare-earth-doped alkaline-earth (AE) fluoride [RE:(AE)F2, RE = Yb, Eu;AE = Ca, Sr, Ba] nanoparticles were synthesized, suspension-doped in a silica preform fabricated using modified chemical vapor deposition (MCVD), and their evolution from as-synthesized to processed into a final preform were thoroughly studied. A thermal profile of the preform during fabrication was developed based on optical-pyrometer temperature measurements and used for time/temperature/structural correlations. A series of characterization methods, including x-ray diffraction, electron microscopy, optical spectroscopy, and thermochemical analyses were employed to study the NP phase and structure evolution. The fluoride NPs are shown to react with the core-glass soot, eventually oxidizing and amorphizing under the thermal treatment associated with the preform fabrication. This work sets the foundation for understanding the composition and structure of RE:(AE)F2 NPs in silica optical fiber cores, and aids in the understanding and tailoring of the optical properties of the resultant fiber. © 2022 The Author(s)

关键词： Nanoparticles

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Analysis of product codes for frequency-hopped spread-spectrum with partial band interference

Analysis of product codes for frequency-hopped spread-spectr...

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MILCOM, Military Communications Conference

作者： T.C. Nolan W.E. Stark Department of Defense graduate fellowship program Focused Research Initiative agreement Ann Arbor MI USA Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

A jamming game is considered. A transmitter encodes the data, in a product code (PC), and transmits it in a slow frequency-hopped spread-spectrum (FHSS) system. A hostile jammer attempts to block correct packet reception by adjusting the fraction of the total band in which it distributes the jam power, /spl rho/. Two cases are considered. In the first case, the transmitter declares his strategy and the jammer uses this information to select his best jamming fraction. In the second case, the jammer declares his strategy first and the transmitter uses this information to select his best rates. Results are obtained using asymptotic analysis of a product code using singly extended Reed-Solomon (RS) row and column codes whose size grows large. This asymptotic analysis leads to good choices of the row and column rates for the PC in both cases.

关键词： Product codes Spread spectrum communication Interference Jamming Decoding Error correction codes Frequency shift keying Error correction Reed-Solomon codes Transmitters

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Quantum-Well Bound States in Graphene Heterostructure Interfaces

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Physical Review Letters 2021年第8期127卷 086805-086805页

作者： Zhongwei Dai (代中伟) Zhaoli Gao Sergey S. Pershoguba Nikhil Tiwale Ashwanth Subramanian Qicheng Zhang Calley Eads Samuel A. Tenney Richard M. Osgood Chang-Yong Nam Jiadong Zang A. T. Charlie Johnson Jerzy T. Sadowski Center for Functional Nanomaterials Brookhaven National Laboratory Upton New York 11973 USA Department of Physics and Astronomy University of Pennsylvania Philadelphia Pennsylvania 19104 USA Department of Biomedical Engineering The Chinese University of Hong Kong Hong Kong China Department of Physics and Astronomy and Materials Science Program University of New Hampshire Durham New Hampshire 03824 USA Department of Materials Science and Chemical Engineering Stony Brook University Stony Brook New York 11794 USA Department of Electrical Engineering Columbia University New York New York 10027 USA

We present experimental evidence of electronic and optical interlayer resonances in graphene van der Waals heterostructure interfaces. Using the spectroscopic mode of a low-energy electron microscope (LEEM), we characterized these interlayer resonant states up to 10 eV above the vacuum level. Compared with nontwisted, AB-stacked bilayer graphene (AB BLG), an ≈0.2 Å increase was found in the interlayer spacing of 30° twisted bilayer graphene (30°-tBLG). In addition, we used Raman spectroscopy to probe the inelastic light-matter interactions. A unique type of Fano resonance was found around the D and G modes of the graphene lattice vibrations. This anomalous, robust Fano resonance is a direct result of quantum confinement and the interplay between discrete phonon states and the excitonic continuum.

关键词： Electronic structure Graphene Heterostructures Low-energy electron microscopy Raman spectroscopy

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Multispectral Polarization-Insensitive Graphene/Silicon Guided Mode Resonance Active Metasurfaces

arXiv

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arXiv 2024年

作者： Sharma, Prateeksha Oz, Dor Lampadariou, Eleftheria Doukas, Spyros Lidorikis, Elefterios Goykhman, Ilya Faculty of Electrical and Computer Engineering Technion Haifa320000 Israel Institute of Applied Physics The Faculty of Science The Center for Nanoscience and Nanotechnology The Hebrew University of Jerusalem Jerusalem91904 Israel Department of Materials Science and Engineering University of Ioannina Ioannina45110 Greece

We investigate advanced CMOS-compatible Graphene/Silicon active metasurfaces based on guided-mode resonance filters. The simulated results show a high extinction ratio (>25 dB), narrow linewidth (~1.5 nm @1550 nm), quality factor of Q~1000, and polarization-insensitive operation. By taking advantage of graphene broadband absorption, we present a multispectral operation in the MIR using simple geometrical scaling rules. We further showcase that the same device architecture can be employed for thermo-optic tuning using graphene as an integrated microheater. Our work contributes to the development of advanced broadband silicon-based active metasurfaces for tunable spectral filters and laser mirrors, optical switches, modulators, and sensors. Copyright © 2024, The Authors. All rights reserved.

关键词： Laser mirrors

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Optimal First-Order Algorithms as a Function of Inequalities

arXiv

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arXiv 2021年

作者： Park, Chanwoo Ryu, Ernest K. Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology MA United States Department of Mathematical Sciences Interdisciplinary Program in Artificial Intelligence Seoul National University Seoul Korea Republic of

In this work, we present a novel algorithm design methodology that finds the optimal algorithm as a function of inequalities. Specifically, we restrict convergence analyses of algorithms to use a prespecified subset of inequalities, rather than utilizing all true inequalities, and find the optimal algorithm subject to this restriction. This methodology allows us to design algorithms with certain desired characteristics. As concrete demonstrations of this methodology, we find new state-of-the-art accelerated first-order gradient methods using randomized coordinate updates and backtracking line searches. © 2021, CC BY-NC-ND.

关键词： Gradient methods

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