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arXiv 2024年

作者： Vazquez, Guillermo Sauceda, Daniel Arróyave, Raymundo Department of Materials Science and Engineering Texas A&M University College StationTX77843 United States J. Mike Walker’66 Department of Mechanical Engineering Texas A&M University College StationTX77843 United States Wm Michael Barnes’64 Department of Industrial and Systems Engineering Texas A&M University College StationTX77843 United States

The Cluster Expansion (CE) Method encounters significant computational challenges in multicomponent systems due to the computational expense of generating training data through density functional theory (DFT) calculations. This work aims to refine the cluster and structure selection processes to mitigate these challenges. We introduce a novel method that significantly reduces the computational load associated with the calculation of fitting parameters. This method employs a Graph Neural Network (GNN) model, leveraging the M3GNet network, which is trained using a select subset of DFT calculations at each ionic step. The trained surrogate model excels in predicting the volume and energy of the final structure for a relaxation run. By employing this model, we sample thousands of structures and fit a CE model to the energies of these GNN-relaxed structures. This approach, utilizing a large training dataset, effectively reduces the risk of overfitting, yielding a CE model with a root-mean-square error (RMSE) below 10 meV/atom. We validate our method’s effectiveness in two test cases: the (Cr,Hf,Mo,Ta,Ti,Zr)B2 diboride system and the Refractory High-Entropy Alloy (HEA) AlHfNbTaTiZr system. Our findings demonstrate the significant advantages of integrating a GNN model, specifically the M3GNet network, with CE methods for the efficient predictive analysis of chemical ordering in High Entropy materials. The accelerating capabilities of the hybrid ML-CE approach to investigate the evolution of Short Range Ordering (SRO) in a large number of stoichiometric systems. Finally, we show how it is possible to correlate the strength of chemical ordering to easily accessible alloy parameters. © 2024, CC BY-NC-ND.

关键词： Density functional theory

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Transferable screened range-separated hybrid functionals for electronic and optical properties of van der Waals materials

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Physical Review materials 2023年第10期7卷 104001-104001页

作者： María Camarasa-Gómez Ashwin Ramasubramaniam Jeffrey B. Neaton Leeor Kronik Department of Molecular Chemistry and Materials Science Weizmann Institute of Science Rehovoth 7610001 Israel Department of Mechanical and Industrial Engineering University of Massachusetts Amherst Amherst Massachusetts 01003 USA Materials Science and Engineering Graduate Program University of Massachusetts Amherst Amherst Massachusetts 01003 USA Department of Physics University of California Berkeley California 94720 USA Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA Kavli Energy NanoSciences Institute at Berkeley University of California Berkeley California 94720 USA

The accurate description of electronic properties and optical absorption spectra is a long-standing challenge for density functional theory. Recently, the introduction of screened range-separated hybrid (SRSH) functionals for solid-state materials has allowed for the calculation of fundamental band gaps and optical absorption spectra that are in very good agreement with many-body perturbation theory. However, since solid-state SRSH functionals are typically tuned to reproduce the properties of bulk phases, their transferability to low-dimensional structures, which experience substantially different screening than in the bulk, remains an open question. In this work, we explore the transferability of SRSH functionals to several prototypical van der Waals materials, including transition-metal sulfides and selenides, indium selenide, black phosphorus, and hexagonal boron nitride. Considering the bulk and a monolayer of these materials as limiting cases, we show that the parameters of the SRSH functional can be determined systematically, using only the band-edge quasiparticle energies of these extremal structural phases as fitting targets. The resulting SRSH functionals can describe both electronic band structures and optical absorption spectra with accuracy comparable to more demanding ab initio many-body perturbation theory (GW and Bethe-Salpeter equation) approaches. Selected examples also demonstrate that the SRSH parameters, obtained from the bulk and monolayer reference structures, display good accuracy for band structures and optical spectra of bilayers, indicating a degree of transferability that is independent of the fitting procedure.

关键词： 2-dimensional systems Density functional theory First-principles calculations GW method

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Porous Mesh Manifold for Enhanced Pool Boiling Performance

SSRN

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SSRN 2024年

作者： Giglio, Roman Shattique, Muhammad Rubaiet Dede, Ercan M. Narumanchi, Sreekant Asheghi, Mehdi Goodson, Kenneth E. Palko, James W. Department of Mechanical Engineering University of California MercedCA United States Materials and Biomaterials Science and Engineering Graduate Program University of California MercedCA United States Toyota Research Institute of North America Ann ArborMI United States National Renewable Energy Laboratory GoldenCO United States Department of Mechanical Engineering Stanford University StanfordCA United States

High performance electronics are continuously demanding cooling of higher heat fluxes. Phase change cooling, including pool boiling, is a useful approach to address this challenge, however competition between liquid and vapor flows generally limit the heat fluxes that can be dissipated. Here a manifold structure formed from metallic mesh is introduced to control the disposition of liquid and vapor phases above a boiling surface enhanced with a porous structure. Copper mesh forms defined liquid flow paths using capillary action to guide and distribute liquid evenly over the heated surface and open channels to facilitate vapor escape. The manifold performance is characterized in pool boiling with water above a laser textured aluminum nitride heat dissipation surface with pin fin structures having heights of 110 µm and spacing of 30 µm with a heated area of 5 mm x 5 mm. Maximum heat flux of 490W/cm is reached with the manifold in the pool boiling configuration, representing a 64% increase over the porous surface alone. Maximum superheat found for the manifold is 36 K, which is 14 K higher than the porous surface without manifold. Factors limiting performance of the manifold are analyzed. Based on variation of manifold geometry and numerical simulation, the primary limitation to heat flux is found to be viscous resistance to liquid flow in the manifold mesh. The increased superheat is attributed to partial flooding of the boiling surface as indicated by reduction in superheat using external suction. Similar systems and structures for enhanced two-phase cooling are compared. © 2024, The Authors. All rights reserved.

关键词： Heat flux

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Laser Processed Aluminum Nitride Structures for Enhanced Two-Phase Cooling

SSRN

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SSRN 2024年

作者： Giglio, Roman Shattique, Muhammad Rubaiet Md. Dede, Ercan M. Narumanchi, Sreekant Asheghi, Mehdi Goodson, Kenneth E. Palko, James W. Department of Mechanical Engineering University of California MercedCA United States Materials and Biomaterials Science and Engineering Graduate Program University of California MercedCA United States Toyota Research Institute of North America Ann ArborMI United States National Renewable Energy Laboratory GoldenCO United States Department of Mechanical Engineering Stanford University StanfordCA United States

The demand for higher heat flux cooling is increasing as the use of power electronics continues to expand. Two-phase cooling approaches that are tightly integrated into electronic packages offer potential for high performance. Here we describe a method to produce microscale pillars directly in aluminum nitride using UV laser ablation that is compatible with existing substrates for power electronics packaging and offers high precision and short production time. The resulting structures show significantly enhanced performance in pool boiling compared to unmodified surfaces. Effectiveness in two-phase cooling is investigated in terms of critical heat flux, heat transfer coefficient, and thermal resistance. The micropillar structures achieve a maximum critical heat flux of 299 W/cm2 and heat transfer coefficients up to 20 W/cm2 K for cooled areas of 0.25 cm2 in deionized water. Performance is attributed to the effective capillary rewetting of the surface during boiling and increased surface area. Corrosion of the aluminum nitride surface by the water working fluid is observed and contributes to a slow degradation of the measured heat transfer coefficient. The potential for simple processing routes to allow tight integration of two-phase cooling of electronics more generally is considered. © 2024, The Authors. All rights reserved.

关键词： Heat flux

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CsPbBr3nanocrystals plasmonic distributed Bragg reflector waveguide laser

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Applied Physics Letters 2023年第7期122卷 1-6页

作者： Ahmad Kamal, Ahmad Syazwan Lin, Cheng-Chieh Wang, Zhiyu Xing, Di Lee, Yang-Chun Chen, Mu-Hsin Ho, Ya-Lun Chen, Chun-Wei Delaunay, Jean-Jacques School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-8656 Japan School of Mechanical Engineering Engineering Campus Universiti Sains Malaysia Pulau Pinang14300 Malaysia Universiti Sains Malaysia Pulau Pinang11900 Malaysia Taiwan International Graduate Program National Taiwan University and Academia Sinica No. 1 Sec. 4 Roosevelt Rd Taipei10617 Taiwan Department of Materials Science and Engineering National Taiwan University No. 1 Sec. 4 Roosevelt Rd. Taipei10617 Taiwan Academia Sinica No. 128 Sec. 2 Academia Rd. Taipei11529 Taiwan National Taiwan University No. 1 Sec. 4 Roosevelt Rd. Taipei10617 Taiwan

The recent development of perovskite-based lasers showcased the outstanding optical properties of the material such as high absorption coefficient and high quantum yield. The lasers were demonstrated in the form of nanowires and nanoplates, which are difficult to be integrated on a chip in the form of high-density arrays due to the difficulties in positioning them on the chip. The solution to this problem should be to use the well-known lithography process in the fabrication process of the lasers. In this work, we demonstrate several perovskite-based plasmonic lasers that were fabricated by using the lithographic in-mold patterning method that relies on the electron beam lithography process. The lasers utilized CsPbBr3 perovskite nanocrystals as the gain material and plasmonic distributed Bragg reflector grating structure as the optical feedback provider to achieve a low lasing threshold of 42.5 μJ/cm2 with a linewidth of 0.6 nm (FWHM) at room temperature. The use of the lithographic process in the fabrication of the lasers makes it possible to fabricate and integrate them on a chip in a relatively high-density manner, so that they can be used extensively in quantum optics and on-chip integrated photonics applications. © 2023 Author(s).

关键词： Perovskite

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Towards Scalable Automated Grading: Leveraging Large Language Models for Conceptual Question Evaluation in engineering

arXiv

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arXiv 2024年

作者： Gao, Rujun Guo, Xiaosu Li, Xiaodi Narayanan, Arun Balajiee Lekshmi Thomas, Naveen Srinivasa, Arun R. Department of Mechanical Engineering Texas A&M University J. Mike Walker '66 United States Computer Science Department University of Texas at Dallas United States Intelligent Systems Program University of Pittsburgh United States Department of Artificial Intelligence and Informatics Mayo Clinic United States

This study explores the feasibility of using large language models (LLMs), specifically GPT-4o (ChatGPT), for automated grading of conceptual questions in an undergraduate mechanical engineering course. We compared the grading performance of GPT-4o with that of human teaching assistants (TAs) on ten quiz problems from the MEEN 361 course at Texas A&M University, each answered by approximately 225 students. Both the LLM and TAs followed the same instructor-provided rubric to ensure grading consistency. We evaluated performance using Spearman's rank correlation coefficient and Root Mean Square Error (RMSE) to assess the alignment between rankings and the accuracy of scores assigned by GPT-4o and TAs under zero- and few-shot grading settings. In the zero-shot setting, GPT-4o demonstrated a strong correlation with TA grading, with Spearman's rank correlation coefficient exceeding 0.6 in seven out of ten datasets and reaching a high of 0.9387. Our analysis reveals that GPT-4o performs well when grading criteria are straightforward but struggles with nuanced answers, particularly those involving synonyms not present in the rubric. The model also tends to grade more stringently in ambiguous cases compared to human TAs. Overall, ChatGPT shows promise as a tool for grading conceptual questions, offering scalability and consistency. © 2024, CC BY-NC-ND.

关键词： Students

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High-value utilization of CO_(2) to synthesize sulfur-doped carbon nanofibers with excellent capacitive performance

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International Journal of Minerals,Metallurgy and materials 2020年第12期27卷 1666-1677页

作者： Meng-jun Hu Ming-zhu Yin Li-wen Hu Peng-jie Liu Shuo Wang Jian-bang Ge College of Materials Science and Engineering Chongqing UniversityChongqing 400044China Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and Advanced Materials Chongqing UniversityChongqing 400044China Nuclear Engineering Program Department of Mechanical EngineeringVirginia Polytechnic Institute and State UniversityBlacksburgVirginia 24061USA

Carbon nanofiber(CNF)is considered a promising material due to its excellent physical and chemical *** paper proposes a novel way to transform CO_(2) into heteroatom-doped CNFs,with the introduction of Fe,Co,and Ni as *** the electrolyte containing Ni O,Co2O3,and Fe_(2)O_(3) was employed,sulfur-doped CNFs in various diameters were *** the introduction of Fe catalyst,the obtained sulfur-doped CNFs showed the smallest and tightest diameter *** obtained sulfur-doped CNFs had high gravimetric capacitance(achieved by SDG-Fe)that could reach 348.5 F/g at 0.5 A/g,excellent cycling stability,and good rate *** comparison purposes,both Fe and nickel cathodes were tested,where the active metal atom at their surface could act as *** these two situations,sulfur-doped graphite sheet and sulfur-doped graphite quasi-sphere were the main products.

关键词： carbon dioxide capture electrochemical conversion carbon fiber molten salt

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Improved gas-phase infrared analysis of nitrobenzene using nanoporous silica preconcentrator

Improved gas-phase infrared analysis of nitrobenzene using n...

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Optical Sensors, Sensors 2021 - Part of OSA Optical Sensors and Sensing Congress 2021

作者： Day, Coco Hutter, Tanya Department of Chemistry University of Cambridge Lensfield Road CambridgeCB2 1EW United Kingdom Department of Mechanical Engineering Materials Science and Engineering Program Texas Materials Institute The University of Texas at Austin AustinTX78712 United States

Gas-phase infrared (IR) is often insufficiently sensitive to detect low-vapor-pressure explosives. A nanoporous silica preconcentrator was used to achieve a three-fold sensitivity enhancement of gas-phase IR for nitro... 详细信息

ISBN: (纸本)9781557528209

关键词： Nitrobenzene

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Corner cutting connects chiral colorimetry to net electric flux in lossless all-dielectric metasurfaces

arXiv

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arXiv 2024年

作者： Haddadin, Zaid Nguyen, Anna M.Y. Poulikakos, Lisa V. Department of Electrical & Computer Engineering UC San Diego La Jolla CA92093-0021 United States Department of Mechanical & Aerospace Engineering UC San Diego La Jolla CA92093-0021 United States Program of Materials Science & Engineering UC San Diego La Jolla CA92093-0021 United States

All-dielectric metasurfaces can produce structural colors, but the most advantageous design criteria are still being investigated. This work numerically studies how the two-dimensional shape of nanoparticles affects the colorimetric response under circularly polarized light (CPL) to develop a sensor distinguishing CPL orientations. Using lossless dielectric materials (silicon nitride on silicon dioxide), we achieve far-field dichroism by modifying oblong nanoparticles into L-shaped structures through corner cuts. This design suppresses one electric dipole under CPL illumination, leading to differential colorimetric responses. We link these responses to a decoupling effect in the near-field net electric flux. Our findings provide design guidelines for all-dielectric, lossless colorimetric sensors of chiral light. Copyright © 2024, The Authors. All rights reserved.

关键词： Silicon nitride

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In-situ Atomic-scale Observations of Disconnection Dynamics at the Metal/Oxide Interfaces

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Microscopy and Microanalysis 2022年第S1期28卷 150-151页

作者： Liang, Zhilu Wang, Jianyu Sun, Xianhu Chen, Xiaobo Zakharov, Dmitri N Zhou, Guangwen Department of Mechanical Engineering & Materials Science and Engineering Program State University of New York at Binghamton Binghamton NY USA Center for Functional Nanomaterials Brookhaven National Laboratory Upton NY USA

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