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arXiv 2023年

作者： Woodward, Michael Tian, Yifeng Lin, Yen Ting Hader, Christoph Fasel, Hermann Livescu, Daniel Graduate Interdisciplinary Program in Applied Mathematics Department of Mathematics University of Arizona TucsonAZ85721 United States Computer Computational and Statistical Sciences Division Los Alamos National Laboratory Los AlamosNM87544 United States Department of Aerospace and Mechanical Engineering University of Arizona TucsonAZ85721 United States

We introduce the Mori-Zwanzig (MZ) Modal Decomposition (MZMD), a novel technique for performing modal analysis of large scale spatio-temporal structures in complex dynamical systems, and show that it represents an efficient generalization of Dynamic Mode Decomposition (DMD). The MZ formalism provides a mathematical framework for constructing non-Markovian reduced-order models of resolved variables from high-dimensional dynamical systems, incorporating the effects of unresolved dynamics through the memory kernel and orthogonal dynamics. We present a formulation and analysis of the modes and spectrum from MZMD and compare it to DMD when applied to a complex flow: a Direct Numerical Simulation (DNS) data-set of laminar-turbulent boundary-layer transition flow over a flared cone at Mach 6. We show that the addition of memory terms by MZMD improves the resolution of spatio-temporal structures within the transitional/turbulent regime, which contains features that arise due to nonlinear mechanisms, such as the generation of the so-called "hot" streaks on the surface of the flared cone. As a result, compared to DMD, MZMD improves future state prediction accuracy, while requiring nearly the same computational cost. Copyright © 2023, The Authors. All rights reserved.

关键词： Dynamic mode decomposition

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The connection between polymer collapse and the onset of jamming

arXiv

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arXiv 2023年

作者： Grigas, Alex T. Fisher, Aliza Shattuck, Mark D. O’Hern, Corey S. Graduate Program in Computational Biology and Bioinformatics Yale University New HavenCT06520 United States Integrated Graduate Program in Physical and Engineering Biology Yale University New HavenCT06520 United States Department of Mechanical Engineering and Materials Science Yale University New HavenCT06520 United States Benjamin Levich Institute and Physics Department The City College of New York New YorkNY10031 United States Department of Physics Yale University New HavenCT06520 United States Department of Applied Physics Yale University New HavenCT06520 United States

Previous studies have shown that the interiors of proteins are densely packed, reaching packing fractions that are as large as those found for static packings of individual amino-acid-shaped particles. How can the interiors of proteins take on such high packing fractions given that amino acids are connected by peptide bonds and many amino acids are hydrophobic with attractive interactions? We investigate this question by comparing the structural and mechanical properties of collapsed attractive disk-shaped bead-spring polymers to those of three reference systems: static packings of repulsive disks, of attractive disks, and of repulsive disk-shaped bead-spring polymers. We show that attractive systems quenched to temperatures below the glass transition T Tg and static packings of both repulsive disks and bead-spring polymers possess similar interior packing fractions. Previous studies have shown that static packings of repulsive disks are isostatic at jamming onset, i.e. the number of contacts Nc matches the number of degrees of freedom, which strongly influences their mechanical properties. We find that repulsive polymers are hypostatic at jamming onset, but effectively isostatic when including quartic modes. While attractive disk and polymer packings are hyperstatic, we identify a definition for interparticle contacts for which they can also be considered as effectively isostatic. As a result, we show that the mechanical properties (e.g. scaling of the potential energy with excess contact number and low-frequency contribution to the density of vibrational modes) of weakly attractive disk and polymer packings are similar to those of isostatic repulsive disk and polymer packings. Our results demonstrate that static packings generated via attractive collapse or compression of repulsive particles possess similar structural and mechanical properties. © 2023, CC BY.

关键词： Amino acids

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Data-Driven Mori-Zwanzig: Approaching a Reduced Order Model for Hypersonic Boundary Layer Transition

arXiv

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arXiv 2023年

作者： Woodward, Michael Tian, Yifeng Mohan, Arvind Lin, Yen Ting Hader, Christoph Fasel, Hermann Chertkov, Misha Livescu, Daniel Graduate Interdisciplinary Program in Applied Mathematics Department of Mathematics University of Arizona TucsonAZ85721 United States Computer Computational and Statistical Sciences Division Los Alamos National Laboratory Los AlamosNM87544 United States Department of Aerospace and Mechanical Engineering University of Arizona TucsonAZ85721 United States

In this work, we apply, for the first time to spatially inhomogeneous flows, a recently developed data-driven learning algorithm of Mori-Zwanzig (MZ) operators, which is based on a generalized Koopman’s description of dynamical systems. The MZ formalism provides a mathematically exact procedure for constructing non-Markovian reduced-order models of resolved variables from high-dimensional dynamical systems, where the effects due to the unresolved dynamics are captured in the memory kernel and orthogonal dynamics. The algorithm developed in this work applies Mori’s linear projection operator and an SVD based compression to the selection of the resolved variables (equivalently, a low rank approximation of the two time covariance matrices). We show that this MZ decomposition not only identifies the same spatio-temporal structures found by DMD, but it can also be used to extract spatio-temporal structures of the hysteresis effects present in the memory kernels. We perform an analysis of these structures in the context of a laminar-turbulent boundary-layer transition flow over a flared cone at Mach 6, and show the dynamical relevance of the memory kernels. Additionally, by including these memory terms learned in our data-driven MZ approach, we show improvement in prediction accuracy over DMD at the same level of truncation and at a similar computational cost. Furthermore, an analysis of the spatio-temporal structures of the MZ operators shows identifiable structures associated with the nonlinear generation of the so-called "hot" streaks on the surface of the flared cone, which have previously been observed in experiments and direct numerical simulations. Copyright © 2023, The Authors. All rights reserved.

关键词： Dynamic mode decomposition

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Current scenario and potential of waste cooking oil as a feedstock for biodiesel production in Indonesia: Life cycle sustainability assessment (LCSA) review

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Case Studies in Chemical and Environmental engineering 2025年 11卷

作者： Rahman, Arif Oktaufik, M.A.M. Sasongko, Triyono Widi Guntoro, Iwan Soedjati, Dadi Abbas, Najmi Rahman, Abdul Ulfah, Fathiah Widiarto, Ari Siswanto Dharmawan Trihadi, Sudarwaji Edi Yuwono Kusrestuwardani Prihatin, Anggara Lomak Hadi, Adim Indrijarso, Surat Rahardjo, Priyambodo Barkah, Arief Febijanto, Irhan Sasongko, Nugroho Adi Research Center for Sustainable Production System and Life Cycle Assessment National Research and Innovation Agency – BRIN Indonesia Department of Mechanical Engineering Faculty of Engineering Universitas Esa Unggul Jakarta Indonesia Principal Expert of the Steering Board National Research and Innovation Agency - BRIN Indonesia Energy Security Graduate Program Republic of Indonesia Defense University (UNHAN RI) IPSC Sentul Area West Java Bogor 16810 Indonesia

WCO is a second-generation biofuel made up of accumulated free fatty acids, which can be used as feedstock for biodiesel production. The review aims to: (a) evaluate the sustainability of waste cooking oil (WCO) for biodiesel production in Indonesia using life cycle sustainability assessment (LCSA) methods;(b) explain the challenges, development, recommendation, and industrial potential of WCO for biodiesel production in Indonesia;and (c) determine the sustainability concept of WCO for biodiesel production. This study was carried out by reviewing papers related to LCSA which include Life Cycle Assessment (LCA), Life Cycle Cost Analysis (LCCA), and Social Life Cycle Assessment (SLCA). The review found that the WCO collection, pretreatment, and transesterification processes have the biggest environmental impact caused by the use of chemicals, catalysts, and electrical energy from fossil fuels. According to the LCCA results, WCO-based biodiesel production has a high economic potential and is more practicable due to lower raw material and production costs than biodiesel from edible and non-edible plants. Meanwhile, the SLCA aspect emphasizes that the WCO-based biodiesel industry must consider social indicators such as employment provision, human rights, human health impact, working conditions, local community impact, cultural heritage, socio-economic repercussions, governance, and large accident risk. There are several recommendations that can be made to develop WCO-based biodiesel, namely the government must demonstrate political commitment by promoting WCO as a national energy source feedstock. The sustainable concept has three pillars: environmental, economic, and social. These pillars must simultaneously direct every stage of the WCO production process. To produce high-quality biodiesel, the government must support all of these stages, establish regulations and governance for WCO supply and the WCO processing industry, and provide implementable R&D, adequate funding

关键词： Biodiesel Life cycle assessment Life cycle cost analysis Life cycle sustainability assessment Social life cycle assessment Waste cooking oil

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Lightweight equivariant model for efficient machine learning interatomic potentials

arXiv

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arXiv 2023年

作者： Yang, Ziduo Wang, Xian Li, Yifan Lv, Qiujie Chen, Calvin Yu-Chian Shen, Lei Department of Mechanical Engineering National University of Singapore Singapore117575 Singapore Artificial Intelligence Medical Research Center School of Intelligent Systems Engineering Shenzhen Campus of Sun Yat-sen University Shenzhen518107 China Department of Physics National University of Singapore Singapore117551 Singapore -Preferred Program School of Electronic and Computer Engineering Peking University Shenzhen Graduate School Shenzhen518055 China State Key Laboratory of Chemical Oncogenomics School of Chemical Biology and Biotechnology Peking University Shenzhen Graduate School Shenzhen518055 China Guangdong L-Med Biotechnology Co. Ltd Guangdong Meizhou514699 China Research Institute Chongqing401123 China

In modern computational materials science, deep learning has shown the capability to predict interatomic potentials, thereby supporting and accelerating conventional simulations. However, existing models typically sacrifice either accuracy or efficiency. Moreover, lightweight models are highly demanded for offering simulating systems on a considerably larger scale at reduced computational costs. Here, we introduce a lightweight equivariant interaction graph neural network (LEIGNN) that can enable accurate and efficient interatomic potential and force predictions for molecules and crystals. Rather than relying on higher-order representations, LEIGNN employs a scalar-vector dual representation to encode equivariant features. By learning geometric symmetry information, our model remains lightweight while ensuring prediction accuracy and robustness through the equivariance. Our results show that LEIGNN consistently outperforms the prediction performance of the representative baselines and achieves significant efficiency across diverse datasets, which include catalysts, molecules, and organic isomers. Furthermore, we conduct molecular dynamics (MD) simulations using the LEIGNN force field across solid, liquid, and gas systems. It is found that LEIGNN can achieve the accuracy of ab initio MD across all examined systems. Copyright © 2023, The Authors. All rights reserved.

关键词： Prediction models

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Structural, optical, and thermal properties of BN thin films grown on diamond via pulsed laser deposition

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Physical Review Materials 2023年第9期7卷 094602-094602页

作者： Abhijit Biswas Gustavo A. Alvarez Tao Li Joyce Christiansen-Salameh Eugene Jeong Anand B. Puthirath Sathvik Ajay Iyengar Chenxi Li Tia Gray Xiang Zhang Tymofii S. Pieshkov Harikishan Kannan Jacob Elkins Robert Vajtai A. Glen Birdwell Mahesh R. Neupane Elias J. Garratt Bradford B. Pate Tony G. Ivanov Yuji Zhao Zhiting Tian Pulickel M. Ajayan Department of Materials Science and Nanoengineering Rice University Houston Texas 77005 USA Sibley School of Mechanical and Aerospace Engineering Cornell University Ithaca New York 14853 USA Department of Electrical and Computer Engineering Rice University Houston Texas 77005 USA Applied Physics Graduate Program Smalley-Curl Institute Rice University Houston Texas 77005 USA DEVCOM Army Research Laboratory RF Devices and Circuits Adelphi Maryland 20783 USA Naval Research Laboratory Chemistry Division Washington District of Columbia 20375 USA

Heterostructures based on ultrawide-bandgap (UWBG) semiconductors (bandgap>4.0eV), such as BN and diamond, hold significant importance for the development of high-power electronics in the next generation. However, achieving in situ heteroepitaxy of BN/diamond or vice versa remains exceptionally challenging due to the complex growth kinetics involved. In this work, we grew BN thin film on (100) single-crystal diamonds using pulsed laser deposition and investigated its structural, magnetic, optical, and thermal properties. The structural analyses confirmed the growth of BN films, which exhibited diamagnetic behavior at room temperature. Notably, the film demonstrated anisotropic refractive index characteristics within the visible-to-near-infrared wavelength range. The room-temperature cross-plane thermal conductivity of BN is 1.53 ± 0.77 W/mK, while the thermal conductance of the BN/diamond interface is 20±2MW/m2K. These findings have significant implications for a range of device applications based on UWBG BN/diamond heterostructures.

关键词： Growth Thermal conductivity Boron nitride Thin films Wide band gap systems Film deposition Laser ablation Thermoreflectance

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Comparative operational carbon footprints of a vehicle in Brazil: Electric, ethanol, and gasoline

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Cleaner Energy systems 2025年 12卷

作者： João Marcelo Fernandes Gualberto Galiza Silvia Guillén-Lambea Monica Carvalho Graduate Program in Mechanical Engineering Federal University of Paraiba Brazil Aragón Institute for Engineering Research (I3A) University of Zaragoza Spain Department of Renewable Energy Engineering Federal University of Paraiba Brazil

This study quantifies the operational carbon footprint of the Renault Kwid E-Tech (electric vehicle) and Renault Kwid Intense flex (gasoline and ethanol internal combustion engine vehicle) under a Well-to-Wheel approach within the Brazilian context. With a functional unit of 100,000 km, this analysis evaluates greenhouse gas (GHG) emissions associated with fuel consumption and considers different electric mixes across Brazilian regions, along with the periodic maintenance of each vehicle type. The results reveal significant environmental benefits in regions such as the Northeast, where renewable energy sources predominate, reducing the carbon footprint of the electric model, with a carbon footprint of 0.071 kg CO 2 -eq/kWh. By contrast, the higher carbon intensity of the South’s electricity mix reliant on coal, with a carbon footprint of 0.281 kg CO 2 -eq/kWh, presents limitations in achieving emissions reductions with electric vehicles. Ethanol, a renewable biofuel in the Brazilian market, demonstrated a 46 % reduction in GHG emissions compared to gasoline. This study contributes to the sustainable mobility discourse, highlighting the critical role of regional energy sources, fuel choices, and sustainable production practices in emissions outcome. These insights support the development of policies encouraging cleaner energy matrices and biofuel use, contributing to Brazil's emissions reduction goals.

关键词： Life cycle assessment Greenhouse gas emissions Automobiles Electric vehicle

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Surface Roughness-Induced Changes in Important Physical Features of CoFeSm Thin Films on Glass Substrates during Annealing

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Materials 2023年第21期16卷 6989-6989页

作者： Fern, Chi-Lon Liu, Wen-Jen Chang, Yung-Huang Chiang, Chia-Chin Chen, Yuan-Tsung Lu, Pei-Xin Su, Xuan-Ming Lin, Shih-Hung Lin, Ko-Wei Department of Materials Science and Engineering National Chung Hsing University Taichung40227 Taiwan Department of Materials Science and Engineering I-Shou University Kaohsiung84001 Taiwan Bachelor Program in Industrial Technology National Yunlin University of Science and Technology 123 University Road Section 3 Yunlin Douliou64002 Taiwan Department of Mechanical Engineering National Kaohsiung University of Science and Technology Kaohsiung80778 Taiwan Graduate School of Materials Science National Yunlin University of Science and Technology 123 University Road Section 3 Yunlin Douliou64002 Taiwan Department of Electronic Engineering National Yunlin University of Science and Technology 123 University Road Section 3 Yunlin Douliou64002 Taiwan

Co60Fe20Sm20 thin films were deposited onto glass substrates in a high vacuum setting. The films varied in thickness from 10 to 50 nm and underwent annealing processes at different temperatures: room temperature (RT), 100, 200, and 300 °C. Our analysis encompassed structural, magnetic, electrical, nanomechanical, adhesive, and optical properties in relation to film thickness and annealing temperature. X-ray diffraction (XRD) analysis did not reveal characteristic peaks in Co60Fe20Sm20 thin films due to insufficient growth-driving forces. Electrical measurements indicated reduced resistivity and sheet resistance with increasing film thickness and higher annealing temperatures, owing to hindered current-carrier transport resulting from the amorphous structure. Atomic force microscope (AFM) analysis showed a decrease in surface roughness with increased thickness and annealing temperature. The low-frequency alternating current magnetic susceptibility (χac) values increased with film thickness and annealing temperature. Nanoindentation analysis demonstrated reduced film hardness and Young’s modulus with thicker films. Contact angle measurements suggested a hydrophilic film. Surface energy increased with greater film thickness, particularly in annealed films, indicating a decrease in contact angle contributing to this increase. Transmittance measurements have revealed intensified absorption and reduced transmittance with thicker films. In summary, the surface roughness of CoFeSm films at different annealing temperatures significantly influenced their magnetic, electrical, adhesive, and optical properties. A smoother surface reduced the pinning effect on the domain walls, enhancing the χac value. Additionally, diminished surface roughness led to a lower contact angle and higher surface energy. Additionally, smoother surfaces exhibited higher carrier conductivity, resulting in reduced electrical resistance. The optical transparency decreased due to the smoother surface of C

关键词： Thin films

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On Algebraically Invariant Control for Tropical Dynamical systems:Pseudo-polynomial Methods and Robustness Considerations

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IFAC-PapersOnLine 2024年第1期58卷 48-53页

作者： André E. de Morais Carlos Andrey Maia Graduate Program in Electrical Engineering Universidade Federal de Minas Gerais (UFMG) Av. Ant. Carlos 6627 31270-901 Belo Horizonte MG Brasil Control and Industrial Processes area Instituto Federal de Minas Gerais IFMG campus Sabará - Rodovia MGC 262 Km 10 34564-070 Sabará MG Brasil Dpto. Engenharia Elétrica UFMG Av. Ant. Carlos 6627 31270-901 Belo Horizonte MG Brasil

Designing an invariant controller for a Tropical Linear Dynamical System involves formulating a tropical control law to ensure that the system state remains within a tropical subspace whenever the initial condition is situated within that subspace. In this paper, we explore a controller design approach that not only takes into account the invariance property but also optimizes the closed-loop system performance. Also, a preliminary discussion on control robustness is presented along with a new proposition.

关键词： Tropical Algebra Discrete Event systems Invariant Control Modeling and Simulation

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Bolt preload loss due to modal excitation of a c-beam structure 38th

Bolt preload loss due to modal excitation of a c-beam struct...

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38th IMAC, A Conference and Exposition on Structural Dynamics, 2020

作者： Miller, Max Johnson, Chris Sonne, Noah Mersch, John Kuether, Robert J. Smith, Jeff Ortiz, Jonel Castelluccio, Gustavo Moore, Keegan J. Graduate Program in Architectural Acoustics Rensselaer Polytechnic Institute – Troy New YorkNY United States Department of Mechanical Engineering University of Illinois – Urbana ChampaignIL United States Department of Aerospace Engineering University of Colorado – Boulder BoulderCO United States Sandia National Laboratories AlbuquerqueNM United States School of Aerospace Transport and Manufacturing Cranfield University – Cranfield Bedfordshire United Kingdom Department of Mechanical and Materials Engineering University of Nebraska-Lincoln LincolnNE United States

ISBN: (纸本)9783030476250

Bolted joints often risk failure due to the loss of fastener preload when subjected to dynamic, multiaxial loads. This process is a complex problem that depends on multiple attributes such as loading direction, rate, contact within the threads and the interface, material properties, and many others. Current literature suggests that oscillatory shearing loads appear to be most detrimental to the loss of preload in threaded fasteners. To investigate the effect of less idealized loading conditions, an experimental setup employing a bolted c-beam structure is used to study loss of preload from various initial preloads during harmonic excitation near specific resonant frequencies of the structure. The preload force is measured using bolts equipped with internal strain gauges and the structure is excited at specific modes via sine dwell excitation with an electrodynamic shaker. The experiments were designed to measure loss of preload as a function of excitation duration and strength. A finite element model incorporating a fully-threaded joint is developed in parallel to investigate the effectiveness of each at measuring and predicting bolt loosening. © The Society for Experimental Mechanics, Inc 2021.

关键词： Modal analysis

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