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arXiv 2020年

作者： Jakobs, F. Ostler, T.A. Lambert, C.-H. Yang, Y. Salahuddin, S. Wilson, R.B. Gorchon, J. Bokor, J. Atxitia, U. Dahlem Center for Complex Quantum Systems and Fachbereich Physik Freie Universität Berlin Berlin14195 Germany LiégeB-4000 Belgium College of Business Technology and Engineering Sheffield Hallam University Howard Street SheffieldS1 1WB United Kingdom Department of Electrical Engineering and Computer Sciences University of California BerkeleyCA94720 United States Department of Materials Science and Engineering University of California BerkeleyCA94720 United States Lawrence Berkeley National Laboratory 1 Cyclotron Road BerkeleyCA94720 United States Department of Mechanical Engineering and Materials Science and Engineering Program University of California RiversideCA92521 United States ETH Zurich Hönggerbergring 64 Zürich8093 Switzerland Portland Technology Development Department Intel Corp. HillsboroOR97006 United States Universite de Lorraine CNRS IJL NancyF-54000 France

Many questions are still open regarding the physical mechanisms behind the magnetic switching in GdFeCo alloys by single optical pulses. Phenomenological models suggest a femtosecond scale exchange relaxation between sublattice magnetization as the driving mechanism for switching. The recent observation of thermally induced switching in GdFeCo by using both several picosecond optical laser pulse as well as electric current pulses has questioned this previous understanding. This has raised the question of whether or not the same switching mechanics are acting at the femoand picosecond scales. In this work, we aim at filling this gap in the understanding of the switching mechanisms behind thermal single-pulse switching. To that end, we have studied experimentally thermal single-pulse switching in GdFeCo alloys, for a wide range of system parameters, such as composition, laser power and pulse duration. We provide a quantitative description of the switching dynamics using atomistic spin dynamics methods with excellent agreement between the model and our experiments across a wide range of parameters and timescales, ranging from femtoseconds to picoseconds. Furthermore, we find distinct element-specific damping parameters as a key ingredient for switching with long picosecond pulses and argue, that switching with pulse durations as long as 15 picoseconds is possible due to a low damping constant of Gd. Our findings can be easily extended to speed up dynamics in other contexts where ferrimagnetic GdFeCo alloys have been already demonstrated to show fast and energy-efficient processes, e.g. domain-wall motion in a track and spin-orbit torque switching in spintronics devices. Copyright © 2020, The Authors. All rights reserved.

关键词： Ternary alloys

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Optimising phase change materials for ventilated building components in sustainable building design: a comprehensive review

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Energy and Buildings 2025年

作者： Farhan Lafta Rashid Mudhar A. Al-Obaidi Wadhah Amer Hatem Najah M.L. Al Maimuri Arman Ameen Shabbir Ahmad Ephraim Bonah Agyekum Saif Ali Kadhim Karrar A. Hammoodi Petroleum Engineering Department College of Engineering University of Kerbala Karbala 56001 Iraq Technical Instructor Training Institute Middle Technical University Baghdad 10074 Iraq Middle Technical University Technical Institute of Baquba Baquba Diyala 32001 Iraq Building and Construction Techniques Engineering Department College of Engineering and Engineering Techniques Al-Mustaqbal University Hillah Babylon 51001 Iraq Department of Building Engineering Energy Systems and Sustainability Science University of Gävle 801 76 Gävle Sweden Graduate Program of Ocean Engineering School of Engineering Universidade Federal do Rio Grande Rio Grande Italia Avenue km 8 96201-900 Brazil Institute of Geophysics and Geomatics China University of Geosciences Wuhan 430074 China Department of Nuclear and Renewable Energy Ural Federal University Named after the First President of Russia Boris Yeltsin 19 Mira Street Ekaterinburg 620002 Russia Western Caspian University 31 Istiglaliyyat Street AZ1001 Baku Azerbaijan Istanbul Okan University Tuzla Campus 34959 Tuzla Istanbul Turkey Mechanical Engineering Department University of Technology – Iraq Baghdad Iraq College of Engineering University of Al Maarif Al Anbar Iraq

The rise in energy-efficient, sustainable building operations necessitates the development of advanced innovations that reduce heating and cooling demands while maintaining comfortable indoor thermal conditions. Phase change materials (PCMs) demonstrate significant potential as a stabilization mechanism through latent heat storage for managing residential indoor temperatures; however, their integration into systems requires further optimisation. This review examines PCM-assisted ventilation technologies—specifically ventilated façades, roofs, and windows—highlighting their energy performance, which ranges from 7.7 % to 32.8 %, and their capacity to reduce peak temperatures by 2.5 °C to 7.02 °C. These improvements are influenced by PCM thickness of 15–35  mm and melting temperatures of 15–37 °C. The combination of PCM-enhanced hybrid systems with natural or mechanical ventilation has shown greater operational effectiveness, particularly in hot climates and when integrated with adaptive control systems to achieve optimal performance. Despite their benefits, widespread adoption of PCM technologies is hindered by high material costs, hysteresis effects, and limited discharge cycle efficiency. Nevertheless, PCM-enhanced ventilation systems have proven capable of supporting sustainable, low-energy buildings. Continued research is needed to develop cost-effective design strategies, automated control mechanisms, and climate-responsive optimisations to fully realize their potential.

关键词： Energy-efficient ventilation systems Phase change materials (PCMs) Residential buildings Sustainable thermal management

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Considering discrepancy when calibrating a mechanistic electrophysiology model

arXiv

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arXiv 2020年

作者： Lei, Chon Lok Ghosh, Sanmitra Whittaker, Dominic G. Aboelkassem, Yasser Beattie, Kylie A. Cantwell, Chris D. Delhaas, Tammo Houston, Charles Novaes, Gustavo Montes Panfilov, Alexander V. Pathmanathan, Pras Riabiz, Marina Weber dos Santos, Rodrigo Worden, Keith Mirams, Gary R. Wilkinson, Richard D. Computational Biology & Health Informatics Dept. of Computer Science University of Oxford United Kingdom MRC Biostatistics Unit University of Cambridge United Kingdom Centre for Mathematical Medicine & Biology School of Mathematical Sciences University of Nottingham United Kingdom Department of Bioengineering University of California San Diego United States Systems Modeling and Translational Biology GlaxoSmithKline R&D Stevenage United Kingdom ElectroCardioMaths Programme Centre for Cardiac Engineering Imperial College London United Kingdom CARIM School for Cardiovascular Diseases Maastricht University Netherlands Graduate Program in Computational Modeling Universidade Federal de Juiz de Fora Brazil Department of Physics and Astronomy Ghent University Belgium Laboratory of Computational Biology and Medicine Ural Federal University Ekaterinburg Russia U.S. Food and Drug Administration Center for Devices and Radiological Health Office of Science and Engineering Laboratories United States Department of Biomedical Engineering King’s College London Alan Turing Institute United Kingdom Dynamics Research Group Department of Mechanical Engineering University of Sheffield United Kingdom School of Mathematics and Statistics University of Sheffield United Kingdom

Uncertainty quantification (UQ) is a vital step in using mathematical models and simulations to take decisions. The field of cardiac simulation has begun to explore and adopt UQ methods to characterise uncertainty in model inputs and how that propagates through to outputs or predictions. In this perspective piece we draw attention to an important and under-addressed source of uncertainty in our predictions — that of uncertainty in the model structure or the equations themselves. The difference between imperfect models and reality is termed model discrepancy, and we are often uncertain as to the size and consequences of this discrepancy. Here we provide two examples of the consequences of discrepancy when calibrating models at the ion channel and action potential scales. Furthermore, we attempt to account for this discrepancy when calibrating and validating an ion channel model using different methods, based on modelling the discrepancy using Gaussian processes (GPs) and autoregressive-moving-average (ARMA) models, then highlight the advantages and shortcomings of each approach. Finally, suggestions and lines of enquiry for future work are provided. Copyright © 2020, The Authors. All rights reserved.

关键词： Uncertainty analysis

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Modelling and reducing fuel flow pulsation of a fuel-metering system during pump mode switching in a turbofan engine

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IOP Conference Series: Earth and Environmental science 2019年第5期240卷

作者： S Masuda F Shimizu M Fuchiwaki K Tanaka Control Systems Engineering Department Research & Engineering Division Aero Engines Space & Defense Business Area IHI Corporation 229 Tonogaya Mizuho-machi Nishitama-gun Tokyo 190-1297 Japan Department of Computer Science and Systems Engineering Doctoral Program Graduate School of Computer Science and Systems Engineering Kyushu Institute of Technology 680-4 kawazu Iizuka-shi Fukuoka 820-8502 Japan Department of Mechanical Information Science and Technology School of Computer Science and Systems Engineering Kyushu Institute of Technology 680-4 kawazu Iizuka-shi Fukuoka 820-8502 Japan

In this research, the transient characteristics of a new type fuel metering system for aircraft turbofan engines using two types of pumps, a gear pump and a centrifugal pump, were studied by modelling and simulation. This new fuel metering system is capable of hydraulically unloading the operating state of each pump by the pump mode switching mechanism within the permissible range of the pump rotation speed and the fuel flow rate and it is possible to reduce the fuel temperature rise due to the pressure loss in the circuit in the operation region of the entire fuel system. In addition to this, by using a small centrifugal pump that can realize high discharge flow rate, it is possible to reduce weight compared to the conventional fuel system. However, when the pump mode is switched, unexpected fluctuation in the fuel flow rate can occur when a large change in the inlet pressure of the system occurs, the pressure control unit cannot follow the change, and the transient phenomenon cannot be suppressed. At this time, the pressure waveform generated at the time of changing the pump mode includes a high frequency component such that the pressure control unit, which plays a role of keeping the metering valve differential pressure constant, cannot follow up. Therefore, in this paper, we focused on the frequency of the pressure change waveform when the pump mode was changed and studied the model of the fuel system inlet pressure in the gear pump mode. Based on that model, we propose a method to reduce the frequency characteristics of the pressure change occurring at the time of pump mode change.

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The control of brain network dynamics across diverse scales of space and time

arXiv

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arXiv 2019年

作者： Tang, Evelyn Baum, Graham L. Roalf, David R. Satterthwaite, Theodore D. Pasqualetti, Fabio Bassett, Danielle S. Department of Bioengineering School of Engineering & Applied Science University of Pennsylvania PA19104 United States Max Planck Institute for Dynamics and Self-Organization Göttingen37079 Germany Neuroscience Graduate Program Perelman School of Medicine University of Pennsylvania PA19104 United States Department of Psychiatry Perelman School of Medicine University of Pennsylvania PA19104 United States Department of Mechanical Engineering University of California Riverside RiversideCA92521 United States Department of Physics & Astronomy College of Arts & Sciences University of Pennsylvania PA19104 United States Department of Electrical & Systems Engineering School of Engineering & Applied Science University of Pennsylvania PA19104 United States Department of Neurology Perelman School of Medicine University of Pennsylvania PA19104 United States

The human brain is composed of distinct regions that are each associated with particular functions and distinct propensities for the control of neural dynamics. However, the relation between these functions and control profiles is poorly understood, as is the variation in this relation across diverse scales of space and time. Here we probe the relation between control and dynamics in brain networks constructed from diffusion tensor imaging data in a large community based sample of young adults. Specifically, we probe the control properties of each brain region and investigate their relationship with dynamics across various spatial scales using the Laplacian eigenspectrum. In addition, through analysis of regional modal controllability and partitioning of modes, we determine whether the associated dynamics are fast or slow, as well as whether they are alternating or monotone. We find that brain regions that facilitate the control of energetically easy transitions are associated with activity on short length scales and slow time scales. Conversely, brain regions that facilitate control of difficult transitions are associated with activity on long length scales and fast time scales. Built on linear dynamical models, our results offer parsimonious explanations for the activity propagation and network control profiles supported by regions of differing neuroanatomical structure. Copyright © 2019, The Authors. All rights reserved.

关键词： Brain

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Electromagnetic Optimization Based on Gaussian Crow Search Approach

Electromagnetic Optimization Based on Gaussian Crow Search A...

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2018 International Symposium on Power Electronics, Electrical Drives, Automation and Motion, SPEEDAM 2018

作者： Dos Santos Coelho, Leandro Klein, Carlos Eduardo Mariani, Viviana Cocco Do Nascimento, Carlos Augusto Richter Askarzadeh, Alireza PUCPR Industrial and Systems Eng. Graduate Program PPGEPS Federal University of Parana UFPR Department of Electrical Engineering DEE/PPGEE Pontifical Catholic University of Parana Curitiba PR Brazil PUCPR Mechanical Engineering Graduate Program PPGEM Curitiba Pontifical Catholic University of Parana PR Brazil Department of Energy Management and Optimization Institute of Science and High Technology and Environmental Sciences Graduate University of Advanced Technology Kerman Iran

ISBN: (纸本)9781538649411

Metaheuristic algorithms have provided efficient tools to designers by which it became possible to determine the optimum solutions of optimization problems encountered in several fields such as engineering, finance and computation. Generally metaheuristics are based on metaphors that are taken from nature or some other processes. Recently, an optimization metaheuristic paradigm based on the social behavior of the crows, called crow search algorithm (CSA), has been proposed. The idea of CSA is motivated from the storing process of the excess food in hiding places then restoring it in the necessary time. The CSA has many favorable characteristics, such as ease of implementation, the need to adjust only a few parameters, a favorable balance between search diversification and intensification, and fast convergence and high sensitivity. However, to enhance the performance of the standard CSA approach, this paper proposes to tune the control parameters using population diversity information and normal (Gaussian) probability distribution function. Loney's solenoid benchmark and circular antenna array design problems are used to evaluate the effectiveness of the conventional CSA and the proposed variant. Simulation results and comparisons with the CSA demonstrated that the performance of the proposed MCSA approach is promising in electromagnetics optimization. © 2018 IEEE.

关键词： Optimization

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Analyses of protein cores reveal fundamental differences between solution and crystal structures

arXiv

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arXiv 2019年

作者： Mei, Zhe Treado, John D. Grigas, Alex T. Levine, Zachary A. Regan, Lynne O'Hern, Corey S. Integrated Graduate Program in Physical & Engineering Biology Yale University New HavenCT06520 United States Department of Chemistry Yale University New HavenCT06520 United States Department of Mechanical Engineering & Materials Science Yale University New HavenCT06520 United States Graduate Program in Computational Biology & Bioinformatics Yale University New HavenCT06520 United States Department of Pathology Yale University New HavenCT06520 United States Department of Molecular Biophysics and Biochemistry Yale University New HavenCT06520 United States Institute of Quantitative Biology Biochemistry and Biotechnology Center for Synthetic and Systems Biology School of Biological Sciences University of Edinburgh Department of Physics Yale University New HavenCT06520 United States Department of Applied Physics Yale University New HavenCT06520 United States

There have been several studies suggesting that protein structures solved by NMR spectroscopy and x-ray crystallography show significant differences. To understand the origin of these differences, we assembled a database of high-quality protein structures solved by both methods. We also find significant differences between NMR and crystal structures|in the root-mean-square deviations of the Cα atomic positions, identities of core amino acids, backbone and sidechain dihedral angles, and packing fraction of core residues. In contrast to prior studies, we identify the physical basis for these differences by modelling protein cores as jammed packings of amino-acid-shaped particles. We find that we can tune the jammed packing fraction by varying the degree of thermalization used to generate the packings. For an athermal protocol, we find that the average jammed packing fraction is identical to that observed in the cores of protein structures solved by x-ray crystallography. In contrast, highly thermalized packing-generation protocols yield jammed packing fractions that are even higher than those observed in NMR structures. These results indicate that thermalized systems can pack more densely than athermal systems, which suggests a physical basis for the structural differences between protein structures solved by NMR and x-ray crystallography. Copyright © 2019, The Authors. All rights reserved.

关键词： X ray crystallography

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Molybdenum Disulfide: Scalable Fabrication of Molybdenum Disulfide Nanostructures and their Assembly (Adv. Mater. 43/2020)

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Advanced Materials 2020年第43期32卷

作者： Yun Huang Kang Yu Huaizhi Li Kai Xu Zexi Liang Debora Walker Paulo Ferreira Peer Fischer Donglei (Emma) Fan Materials Science and Engineering Program Texas Materials Institute The University of Texas at Austin Austin TX 78712 USA The Department of Advanced Electron Microscopy Imaging and Spectroscopy International Iberian Nanotechnology Laboratory Braga 4715‐330 Portugal Electrical and Computer Engineering University of Illinois at Urbana‐Champaign Urbana IL 61801 USA School of Engineering and Applied Sciences Harvard University Cambridge MA 02138 USA Mechanical Engineering Department and IDMEC Instituto Superior Técnico University of Lisbon Av. Rovisco Pais Lisboa 1049‐001 Portugal Max‐Planck‐Institute for Intelligent Systems Heisenbergstr. 3 Stuttgart 70569 Germany Institute of Physical Chemistry University of Stuttgart Pfaffenwaldring 55 Stuttgart 70569 Germany Walker Department of Mechanical Engineering The University of Texas at Austin Austin TX 78712 USA

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High-Throughput Screening: One-Step Generation of a Drug-Releasing Hydrogel Microarray-On-A-Chip for Large-Scale Sequential Drug Combination Screening (Adv. Sci. 3/2019)

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Advanced science 2019年第3期6卷 1970014-1970014页

作者： Seo Woo Song Su Deok Kim Dong Yoon Oh Yongju Lee Amos Chungwon Lee Yunjin Jeong Hyung Jong Bae Daewon Lee Sumin Lee Jiyun Kim Sunghoon Kwon Department of Electrical and Computer Engineering Seoul National University Seoul 08826 South Korea Institutes of Entrepreneurial BioConvergence Seoul National University Seoul 08826 South Korea Department of Mechanical Science and Engineering University of Illinois at Urbana-Champaign Urbana IL 61801 USA Nano Systems Institute Seoul National University Seoul 08826 South Korea Interdisciplinary Program in Bioengineering Seoul National University Seoul 08826 South Korea School of Materials Science and Engineering Ulsan National Institute of Science and Technology Ulsan 44919 South Korea

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Compact localized states and flat-band generators in one dimension

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Physical Review B 2017年第11期95卷 115135-115135页

作者： Wulayimu Maimaiti Alexei Andreanov Hee Chul Park Oleg Gendelman Sergej Flach Center for Theoretical Physics of Complex Systems Institute for Basic Science (IBS) Daejeon 34051 Republic of Korea Basic Science Program Korea University of Science and Technology (UST) Daejeon 34113 Republic of Korea Faculty of Mechanical Engineering Technion Haifa 3200003 Israel New Zealand Institute for Advanced Study Center for Theoretical Chemistry & Physics Massey University Auckland 0745 New Zealand

Flat bands (FB) are strictly dispersionless bands in the Bloch spectrum of a periodic lattice Hamiltonian, recently observed in a variety of photonic and dissipative condensate networks. FB Hamiltonians are fine-tuned networks, still lacking a comprehensive generating principle. We introduce a FB generator based on local network properties. We classify FB networks through the properties of compact localized states (CLS) which are exact FB eigenstates and occupy U unit cells. We obtain the complete two-parameter FB family of two-band d=1 networks with nearest unit cell interaction and U=2. We discover a novel high symmetry sawtooth chain with identical hoppings in a transverse dc field, easily accessible in experiments. Our results pave the way towards a complete description of FBs in networks with more bands and in higher dimensions.

关键词： Electronic structure 1-dimensional systems Electron-correlation calculations Lattice models in condensed matter

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