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Investigation of Power Density Amplification in Stacked Triboelectric Nanogenerators

Energy & Environmental Materials 2024年第5期7卷 368-375页

作者： Fan Shen Qin Zhang Hengyu Guo Chen Cao Ying Gong Junlei Wang Yan Peng Zhongjie Li School of Mechatronic Engineering and Automation Shanghai UniversityShanghai 200444China Department of Applied Physics Chongqing UniversityChongqing 400044China Institute of Artificial Intelligence School of Future TechnologyShanghai UniversityShanghai 200444China School of Mechanical and Power Engineering Zhengzhou UniversityZhengzhou 450000China Shanghai Artificial Intelligence Laboratory Shanghai 200232China

In engineering practice,the output performance of contact separation TENGs(CS-TENGs)increases with the increase of tribo-pair area,which includes increasing the size of single layer CS-TENGs(SCS-TENGs)or the number of units(zigzag TENGs).However,such two strategies show significant differences in output power and power *** this study,to seek a universal CS-TENG design solution,the output performance of a SCS-TENG and a zigzag TENG(Z-TENG)is systematically compared,including voltage,current,transferred charge,instantaneous power density,and charging power *** relationship between contact area and output voltages is explored,and the output voltage equation is *** experimental results reveal that SCS-TENGs yield better performance than Z-TENGs in terms of voltage,power,and power density under the same total contact area.Z-TENGs show energy loss during the transfer of mechanical energy,and such loss is aggravated by the increasing number of *** instantaneous peak power of the SCS-TENG is up to 22 times that of the Z-TENG(45 cm^(2)).Furthermore,the power density of capacitor charging of SCS-TENGs is 131%of that of Z-TENGs,which are relatively close.Z-TENG is a feasible alternative when the working space is limited.

关键词： contact separation power density triboelectric nanogenerators zigzag

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Variational solution to the lattice Boltzmann method for Couette flow

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Physical Review E 2024年第5期109卷 055305-055305页

作者： Joseph T. Johnson Mahyar Madadi Daniel R. Ladiges Yong Shi Barry D. Hughes John E. Sader School of Mathematics and Statistics Department of Materials Physics Research School of Physics Center for Computational Sciences and Engineering Department of Mechanical Materials and Manufacturing Engineering Graduate Aerospace Laboratories and Department of Applied Physics

Literature studies of the lattice Boltzmann method (LBM) demonstrate hydrodynamics beyond the continuum limit. This includes exact analytical solutions to the LBM, for the bulk velocity and shear stress of Couette flow under diffuse reflection at the walls through the solution of equivalent moment equations. We prove that the bulk velocity and shear stress of Couette flow with Maxwell-type boundary conditions at the walls, as specified by two-dimensional isothermal lattice Boltzmann models, are inherently linear in Mach number. Our finding enables a systematic variational approach to be formulated that exhibits superior computational efficiency than the previously reported moment method. Specifically, the number of partial differential equations (PDEs) in the variational method grows linearly with quadrature order while the number of moment method PDEs grows quadratically. The variational method directly yields a system of linear PDEs that provide exact analytical solutions to the LBM bulk velocity field and shear stress for Couette flow with Maxwell-type boundary conditions. It is anticipated that this variational approach will find utility in calculating analytical solutions for novel lattice Boltzmann quadrature schemes and other flows.

关键词： Rarefied flows Boltzmann theory Lattice-Boltzmann methods

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Magnetoelastic coupling driven magnon gap in a honeycomb antiferromagnet

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Physical Review B 2024年第10期110卷 104419页

作者： Jeongheon Choe Andrey Baydin Gaihua Ye Bowen Ma Cynthia Nnokwe Martin Rodriguez-Vega David Lujan Swati Chaudhary Fuyang Tay Jiaming He Hiroyuki Nojiri Jianshi Zhou Gregory A. Fiete Junichiro Kono Rui He Xiaoqin Li Department of Physics Center of Complex Quantum Systems Center for Dynamics and Control of Materials Department of Electrical and Computer Engineering Smalley–Curl Institute Department of Physics Applied Physics Graduate Program Smalley–Curl Institute Department of Mechanical Engineering Institute for Materials Research Department of Physics and Astronomy Department of Materials Science and NanoEngineering

Cobalt titanate, CoTiO3, is a honeycomb antiferromagnet recently confirmed experimentally to host Dirac magnons, topological spin-orbit excitons, and chiral phonons. Here, we investigate a magnon gap at the zone center which calls for a refined spin Hamiltonian. We propose a microscopic model for the magnon gap and attribute it to a lattice-distortion (phonon)-induced higher-order spin interaction. Strong magnetoelastic coupling in CoTiO3 is also evident in Raman spectra, in which the magnetic order exerts a stronger influence on phonons corresponding to in-plane ionic motions than those with out-of-plane motions. We further examine the evolution of the zone-center magnons in a high magnetic field up to 18.5 T via THz absorption spectroscopy measurements. Based on this field dependence, we propose a spin Hamiltonian that not only agrees with magnon dispersion measured by inelastic neutron scattering but also includes fewer exchange constants and a realistic anisotropy term. Our work highlights the broad implications of magnetoelastic coupling in the study of topologically protected bosonic excitations.

关键词： Magnetism Magnons Topological materials Raman spectroscopy Terahertz spectroscopy

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EXPLOITING A TRANSFORMER ARCHITECTURE FOR SIMULTANEOUS DEVELOPMENT OF TRANSITION AND TURBULENCE MODELS FOR TURBINE FLOW PREDICTIONS 69

EXPLOITING A TRANSFORMER ARCHITECTURE FOR SIMULTANEOUS DEVEL...

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69th ASME Turbo Expo 2024: Turbomachinery Technical Conference and Exposition, GT 2024

作者： Fang, Yuan Reissmann, Maximilian Pacciani, Roberto Zhao, Yaomin Ooi, Andrew S.H. Marconcini, Michele Akolekar, Harshal D. Sandberg, Richard D. Department of Mechanical Engineering University of Melbourne VIC3010 Australia Department of Industrial Engineering University of Florence Florence50139 Italy Center for Applied Physics and Technology HEDPS College of Engineering Peking University Beijing100871 China Department of Mechanical Engineering School of AI & Data Science Indian Institute of Technology Jodhpur324030 India

ISBN: (纸本)9780791888070

Previous studies have shown the potential of using a multi-objective CFD (computational fluid dynamics) - driven machine-learning approach to train both transition and turbulence models in RANS (Reynolds averaged Navier-Stokes) calculations for improved turbine flow predictions (Akolekar et al., GT2022-81091;Fang et al., GT2023-102902). However, conducting CFD-driven training incurs a high computational cost as thousands of RANS calculations are required if the starting guesses are taken from an initial population of randomly generated models. This paper, for the first time, adopts a transformer technique, belonging to the class of natural language processing models, in gene expression programming (GEP), to expedite the training process for transition and turbulence models. The efficacy of utilizing the transformer is investigated for two scenarios. In one, we introduce previously trained models to randomly generated ones in the initial population of candidate models, facilitating the generation of models with a higher likelihood of achieving lower cost function values from the outset. In the other scenario, assuming that no suitable information is available from pre-training, a dynamic approach is employed at certain training iterations, where models exhibiting significant errors are excluded and replaced by those trained on the fly by the transformer and demonstrating smaller errors. Additionally, we incorporate mathematical operators such as minimum, maximum, and exponential functions, along with a technique called a rolling window, to avoid nested functions in the trained models. This enhances the flexibility in constructing trained models while still allowing us to delve into the underlying physics and provide recommendations for developing physical models. Finally, we also introduce two additional physical features that serve as training inputs for the turbulence model that contribute to smaller errors. With these enhancements to the previous GEP framework, mo

关键词： Exponential functions

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Light control with Weyl semimetals

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eLight 2023年第1期3卷 268-296页

作者： Cheng Guo Viktar S.Asadchy Bo Zhao Shanhui Fan Department of Applied Physics Stanford UniversityStanfordCA 94305USA Ginzton Laboratory and Department of Electrical Engineering Stanford UniversityStanfordCA 94305USA Department of Electronics and Nanoengineering Aalto University02150 EspooFinland Department of Mechanical Engineering University of HoustonHoustonTX 77204USA

Weyl semimetals are topological materials whose electron quasiparticles obey the Weyl *** possess many unusual properties that may lead to new *** is a tutorial review of the optical properties and applications of Weyl *** review the basic concepts and optical responses of Weyl semimetals,and survey their applications in optics and thermal *** hope this pedagogical text will motivate further research on this emerging topic.

关键词： Weyl semimetal Topological materials Axion electrodynamics Nanophotonics Thermal photonics Optical nonreciprocity

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Review of Nano-Composite PCM AlN/EG and Heat Pipe as a Hybrid Battery Thermal Management System 4

Review of Nano-Composite PCM AlN/EG and Heat Pipe as a Hybri...

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4th International Symposium on Advances and Innovation in mechanical engineering, ISAIME 2023

作者： Kadek Ervan Hadi Wiryanta, I. Nindhia, Tjokorda Gde Tirta Septiadi, Wayan Nata Made Joni, I. Study Program of Mechanical Engineering Faculty of Engineering Udayana University Bali Bukit Jimbaran80361 Indonesia Mechanical Engineering Department Politeknik Negeri Bali Bali Badung Indonesia Department of Physics Padjadjaran University Jl. Raya Bandung Sumedang KM 21 Jatinangor Jawa Barat45363 Indonesia

The battery thermal management system (BTMS) is essential for maintaining the battery's temperature and hence its performance. BTMS is classified into three types: active cooling, passive cooling, and hybrid approaches. Because of its simple design, lack of additional power, and even temperature distribution, PCM is extensively used as a BTMS as a passive cooling technique. PCM also has drawbacks like leak sensitivity and limited heat conductivity. This stimulates PCM performance enhancement attempts. Adding reinforcing material to PCM is a standard way to increase its performance. Aluminum nitride (AlN) and expanded graphite (EG) are commonly employed as fillers. The addition of EG and nano-AlN materials can improve the performance of PCM composites compared to pure PCM. Chemical interactions between these materials do not take place either. It is undeniably advantageous that these two materials may be combined into pure paraffin-based PCM for energy storage applications. The combined or hybrid system of BTMS is the optimum alternative for increasing heat transmission from the battery modules into the surrounding environment. The battery temperature will at good maintained well with the combination of 2 (two) and 3 (three) passive cooling methods or even combined with active cooling methods such as air-forced convection. In BTMS, the heat pipe is widely employed as a heat transfer improvement. © 2025 Institute of physics Publishing. All rights reserved.

关键词： Heat pipes

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Acquisition and Synchronisation of Cardiography Signals from a Clinical Patient Monitor with Facial Video Recordings 1

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5th International Conference on Biomedical and Health Informatics, ICBHI 2022

作者： Meher, Jagmohan Wang, Chien-Chih Nordling, Torbjörn E. M. Department of Mechanical Engineering National Cheng Kung University No. 1 University Rd. Tainan701 Taiwan Department of Applied Physics and Electronics Umeå University Umeå90187 Sweden

ISBN: (数字)9783031592164

ISBN: (纸本)9783031592157

A far too frequent practical challenge in clinical informatics research and method development for acquiring vital signs is the extraction and synchronisation of signals from proprietary devices for the clinical monitoring of patients. In an ongoing study evaluating methods for video-based remote photoplethysmography (rPPG), we needed to extract ground truth values of electrocardiogram (ECG) and pulse oximetry (SpO2) signals from the Philips vitals monitor while recording the facial video of the subject, simultaneously. This ground truth data will be used to train the model that will perform rPPG. Various software can extract data from the Philips vitals monitor with features like data acquisition, parsing, and visualisation, but they lack synchronisation with the facial video. Therefore, we developed the Patient Monitor Data Extractor (PMDE), which collects data from the Philips IntelliVue monitors following the Data export interface programming guide provided by Philips. We set up a DHCP server on a Windows 7 computer with a webcam and interfaced with the monitor through LAN with UDP/IP. We used C++ and Windows Sockets API to develop our software and communicate over UDP. For synchronisation with the video cameras, we turned off the light in the room and used this sudden brightness drop as a trigger. The timestamp of the monitor was recorded when the webcam detected the trigger. The PMDE software records ECG at 500 Hz and SpO2 at 125 Hz with a synchronisation error of less than two sampling periods, which is about 40 ms for a 50 fps video. We conclude that PMDE is uniquely suited for recording data for rPPG evaluation because of its synchronisation feature. We have used PMDE to collect a dataset of facial videos with ground truth ECG and SpO2 signals. We intend to make PMDE available as open source to save other researchers time. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.

关键词： Synchronization

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Strategies to enhance hydrogen storage performances in bulk Mg-based hydrides

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Journal of Materials Science & Technology 2023年第22期153卷 139-158页

作者： Xin F.Tan Manjin Kim Kazuhiro Yasuda Kazuhiro Nogita School of Mechanical and Mining Engineering The University of QueenslandSt.LuciaQLD 4072Australia Department of Applied Quantum Physics and Nuclear Engineering Kyushu UniversityFukuoka 819-0395Japan John de Laeter Centre Curtin UniversityGPO Box U1987PerthWA 6845Australia

Bulk Mg-based hydrogen storage materials have the potential to provide a low-cost solution to diversify energy storage and *** to nano powders which require handling and processing under hydrogen or an inert gas atmosphere,bulk Mg-based alloys are safer and are more oxidation *** methods and existing infrastructures can be used to process and handle these ***,bulk Mg alloys have smaller specific surface areas,resulting in slower hydrogen sorp-tion kinetics,higher equilibrium temperatures,and enthalpies of hydride *** work reviews the effects of the additions of a list of alloying elements and the use of innovative processing meth-ods,e.g.,rapid solidification and severe plastic deformation processes,to overcome these *** challenges,advantages,and weaknesses of each method and future perspectives for the development of Mg-based hydrogen storage materials are discussed.

关键词： Hydrogen storage Metal hydrides Mg alloys Mg hydrides

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Cold Glow Discharge Nitrogen Plasma Pretreatment of Banana Fibre for Improving the mechanical Characterisation of Banana/Epoxy Composites

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Journal of The Institution of Engineers (India): Series D 2022年第2期103卷 417-429页

作者： Gupta, Upendra Sharan Tiwari, Sudhir Sharma, Uttam Viliya, Kundan Mechanical Engineering Department Shri Vaishnav Vidyapeeth Vishwavidyalaya Indore453111 India Mechanical Engineering Department Shri Govindram Seksaria Institute of Technology and Science Indore452002 India Applied Physics Department Shri Vaishnav Vidyapeeth Vishwavidyalaya Indore453111 India

Natural fibers are naturally supple and have various properties depending upon their chemical composition and physical aspects. Banana fiber is a derivative of the processing of the "banana plant’s pseudostem" (Musasepientum) the current research on the application of natural fiber composites has shown that the physical treatment of fibers improves their adherence to matrices. This works aims to investigate the effect of Cold glow discharge nitrogen plasma treatment on Musa sapientum (banana) fiber to modify the interfacial bonding of fiber-matrix, with cold glow discharge nitrogen plasma treatment 80 W (30 min) and 120 W (30 min) was being utilized. To improve the interfacial strength of banana fibers, induce a sufficient transfer of stress between the matrix and fiber. The cold glow discharge nitrogen plasma treatment 80 W (30 min.) of banana fiber provided the banana fiber reinforced epoxy composite(BFREC) has been found to have improved nearly 81.79% higher interlaminar shear strength, 66.16% higher flexural strength, and 57.54% higher tensile strength. To estimate the morphological characteristics for cold glow discharge nitrogen plasma treated banana fiber and untreated banana fibers performed by FT-IR spectroscopy and (XRD), which showed the improved fiber surface structure, better mechanical and tribological properties can be obtained, broaden the scope of green materials for industrial applications. © 2022, The Institution of Engineers (India).

关键词： Glow discharges

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TiZrHfNb refractory high-entropy alloys with twinning-induced plasticity

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Journal of Materials Science & Technology 2024年第20期187卷 72-85页

作者： Shubin Wang Da Shu Peiying Shi Xianbing Zhang Bo Mao Donghong Wang Peter.K.Liaw Baode Sun Shanghai Key Lab of Advanced High-temperature Materials and Precision Forming and State Key Lab of Metal Matrix Composites School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China Department of Mechanical and Energy Engineering Southern University of Science and TechnologyShenzhen 518055China Department of Materials Science and Engineering The University of TennesseeKnoxvilleTN37996USA

The twinning-induced plasticity(TWIP)effect has been widely utilized in austenite steels,β-Ti alloys,and recently developed face-centered-cubic(FCC)high-entropy alloys(HEAs)to simultaneously enhance the tensile strength and *** this study,for the first time,the TWIP effect through hierarchical{332}<113>mechanical twinning has been successfully engineered into the TiZrHfNb refractory HEAs by decreasing temperature and tailoring the content of Nb to destabilize the BCC *** cryogenic tem-perature,the comprehensive hierarchical{332}<113>mechanical twins are activated in TiZrHfNb_(0.5) alloy from micro-to nanoscale and progressively segment the BCC grains into nano-scale islands during de-formation,ensuring sustainable strain hardening capability and eventually achieving a substantial 35%uniform tensile *** addition,at 77 K,the tensile strength and uniform elongation of TiZrHfNbx alloys can further be adjusted by a moderate increase of *** results above shed new light on the de-velopment of high-performance refractory HEAs with a high and adjustable strength and ductility com-bination down to the cryogenic temperature.

关键词： Refractory high-entropy alloys Cryogenic temperature Twinning induced plasticity Hierarchical twins Tensile properties

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