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Achieving room-temperature M_(2)-phase VO_(2) nanowires for superior thermal actuation

Nano Research 2021年第11期14卷 4146-4153页

作者： Yong-Qiang Zhang Kai Chen Hao Shen Yue-Cun Wang Mohamed Nejib Hedhili Xixiang Zhang Ju Li Zhi-Wei Shan Center for Advancing Materials Performance from the Nanoscale State Key Laboratory for Mechanical Behavior of MaterialsXi’an Jiaotong UniversityXi’an710049China Physical Science and Engineering Division King Abdullah University of Science and Technology(KAUST)Thuwal23955-6900Saudi Arabia Departments of Nuclear Science and Engineering and Materials Science and Engineering Massachusetts Institute of TechnologyCambridgeMA02139USA

Vanadium dioxide (VO_(2)) has emerged as a promising micro-actuator material for its large amplitude and high work density across the transition between the insulating (M_(1) and M_(2)) and metallic (R) phase. Even though M_(2)–R transition offers about 70% higher transformation stress than M_(1)–R structural phase transition, the application of the M_(2) phase in the micro-actuators is hindered by the fact that previously, M_(2) phase can only stay stable under tensile stress. In this work, we propose and verify that by synthesizing the VO_(2) nanowires under optimized oxygen-rich conditions, stoichiometry change can be introduced into the nanowires (NWs) which in turn yield a large number free-standing single-crystalline M_(2)-phase NWs stable at room temperature. In addition, we demonstrate that the output stress of the M_(2)-phase NWs is about 65% higher than that of the M_(1)-phase NWs during their transition to R phase, quite close to the theoretical prediction. Our findings open new avenues towards enhancing the performance of VO_(2)-based actuators by using M_(2)–R transition.

关键词： single crystalline vanadium dioxide(VO_(2))nanowires metal-insulator transition room-temperature M_(2)phase micro-actuator martensitic transformation transformation strain

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Degradation behaviour and damage mechanisms of carbon fibre reinforced polymer composite laminates subjected to laser irradiation

Composites Part C: Open Access

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Composites Part C: Open Access 2025年 17卷

作者： Kamlade, Patrick K. Panta, Jojibabu Mammone, Max Yang, Richard Mildren, Richard P. Wang, John Ibrahim, Matthew Thomson, Rodney Zhang, Y.X. Centre for Advanced Manufacturing Technology School of Engineering Design and Built Environment Western Sydney University Locked Bag 1797 Penrith 2751 NSW Australia MQ Photonics Research Centre School of Mathematical and Physical Sciences Macquarie University Macquarie Park 2109 NSW Australia Platforms Division Defence Science and Technology Group Melbourne 3207 VIC Australia Advanced Composite Structures Australia Pty Ltd 19 Rocklea Drive Port Melbourne 3207 Australia School of Mechanical and Mechatronic Engineering University of Technology Sydney Ultimo 2007 NSW Australia

This study presents a comprehensive and insightful investigation into the thermal degradation and damage mechanisms of carbon fibre reinforced polymer (CFRP) composite laminates exposed to continuous wave laser irradiation with a Gaussian beam profile. The effects of laser power, beam diameter, and exposure time were explored to reflect practical scenarios such as material processing, maintenance, and damage assessment. Thermogravimetric analysis (TGA) was first carried out in both nitrogen and air environments to understand the thermal stability and degradation behaviour of the CFRP material. Initial laser tests were conducted at 30 W and 40 W using a beam diameter of 3.46 mm to assess early-stage damage. These results informed a more intensive study using a higher laser power of 98 W with beam diameters of 3.18 mm and 5.70 mm, where specimens were irradiated until complete perforation. Thermal imaging was used to monitor surface temperature evolution on both front and back sides during irradiation. For the 98 W cases, the larger beam diameter required a 53 % longer exposure time to achieve perforation, highlighting the role of power density in damage progression. Post-irradiation analysis using scanning electron microscopy (SEM), ultrasonic C-scans, and micro-focused X-ray computed tomography (micro-CT) revealed fibre sublimation, matrix decomposition, cone-shaped perforations, and interlaminar cracking. The results provide valuable insights into how CFRP materials respond to high-intensity laser exposure and can support the development of strategies to mitigate damage and improve structural performance in real-world applications. © 2025 The Authors

关键词： Carbon fibre reinforced polymer (CFRP) Damage Degradation behaviour Laser irradiation Material characterisation Thermal stability

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Ergodic capacity of cognitive radio under imperfect channel-state information

Ergodic capacity of cognitive radio under imperfect channel-...

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作者： Rezki, Zouheir Alouini, Mohamed-Slim Electrical Engineering Program Physical Science and Engineering Division King Abdullah University of Science and Technology Thuwal 23955-6900 Saudi Arabia

A spectrum-sharing communication system where the secondary user is aware of the instantaneous channel-state information (CSI) of the secondary link but knows only the statistics and an estimated version of the secondary transmitter-primary receiver link is investigated. The optimum power profile and the ergodic capacity of the secondary link are derived for general fading channels [with a continuous probability density function (pdf)] under the average and peak transmit power constraints and with respect to the following two different interference constraints: 1) an interference outage constraint and 2) a signal-to-interference outage constraint. When applied to Rayleigh fading channels, our results show, for example, that the interference constraint is harmful at the high-power regime, because the capacity does not increase with the power, whereas at the low-power regime, it has a marginal impact and no-interference performance, which corresponds to the ergodic capacity under average or peak transmit power constraint in the absence of the primary user, may be achieved. © 2012 IEEE.

关键词： Outages

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Vortex dynamics on a 2D curved surface using discrete exterior calculus 21

Vortex dynamics on a 2D curved surface using discrete exteri...

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21st Australasian Fluid Mechanics Conference, AFMC 2018

作者： Jagad, Pankaj Mohamed, Mamdouh S. Samtaney, Ravi Mechanical Engineering Physical Science and Engineering Division King Abdullah University of Science and Technology Jeddah Saudi Arabia Department of Mechanical Design and Production Faculty of Engineering Cairo University Giza Egypt

ISBN: (纸本)9780646597843

We present examples of vortex dynamics on a curved 2D surface using simulations based on the approach of discrete exterior calculus (DEC) developed by Mohamed et al. [8]. The DEC method allows a coordinate independent implementation and preserves vector calculus identities discretely. In addition, it has been demonstrated to exhibit good conservation of secondary flow quantities such as kinetic energy (for inviscid flows) and discretely satisfies vorticity conservation both locally and globally. These structure-preserving properties of DEC make it a suitable tool to investigate vortex and vorticity dynamics on 2D curved surfaces. In particular, we focus on the flow past a stationary cylinder (a canonical problem in fluid dynamics) embedded on a sphere (positive Gaussian curvature) or another cylinder (zero Gaussian curvature). We compute quantities of dynamical importance such as the drag coefficient, lift coefficient and Strouhal number. Another example presented is the evolution of initially randomly distributed vortices on a unit sphere in to a quadrupolar vortical structure similar to reported in Dritschel et al. [4]. © 2018 Australasian Fluid Mechanics Society. All rights reserved.

关键词： Kinetics

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A two-stage biological gas to liquid transfer process to convert carbon dioxide into bioplastic

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Bioresource Technology Reports 2018年 1卷 61-68页

作者： Al Rowaihi, Israa S. Kick, Benjamin Grötzinger, Stefan W. Burger, Christian Karan, Ram Weuster-Botz, Dirk Eppinger, Jörg Arold, Stefan T. King Abdullah University of Science and Technology KAUST Catalysis Center Physical Sciences and Engineering Division Thuwal Saudi Arabia Technical University of Munich Department of Mechanical Engineering Institute of Biochemical Engineering Garching Germany King Abdullah University of Science and Technology Computational Bioscience Research Center Biological and Environmental Sciences and Engineering Division Thuwal Saudi Arabia

The fermentation of carbon dioxide (CO2) with hydrogen (H2) uses available low-cost gases to synthesis acetic acid. Here, we present a two-stage biological process that allows the gas to liquid transfer (Bio-GTL) of CO2 into the biopolymer polyhydroxybutyrate (PHB). Using the same medium in both stages, first, acetic acid is produced (3.2 g L−1) by Acetobacterium woodii from 5.2 L gas-mixture of CO2:H2 (15:85 v/v) under elevated pressure (≥2.0 bar) to increase H2-solubility in water. Second, acetic acid is converted to PHB (3 g L−1 acetate into 0.5 g L−1 PHB) by Ralstonia eutropha H16. The efficiencies and space-time yields were evaluated, and our data show the conversion of CO2 into PHB with a 33.3% microbial cell content (percentage of the ratio of PHB concentration to cell concentration) after 217 h. Collectively, our results provide a resourceful platform for future optimization and commercialization of a Bio-GTL for PHB production. © 2018

关键词： Carbon dioxide

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Application of phase-field method in rechargeable batteries

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npj Computational Materials 2020年第1期6卷 206-213页

作者： Qiao Wang Geng Zhang Yajie Li Zijian Hong Da Wang Siqi Shi Materials Genome Institute Shanghai UniversityShanghai 200444China School of Materials Science and Engineering Shanghai UniversityShanghai 200444China Physical Science and Engineering Division(PSE) King Abdullah University of Science and Technology(KAUST)Thuwal 23955-6900Saudi Arabia Department of Mechanical Engineering Carnegie Mellon UniversityPittsburghPennsylvania 15213USA

Rechargeable batteries have a profound impact on our daily life so that it is urgent to capture the physical and chemical fundamentals affecting the operation and *** phase-field method is a powerful computational approach to describe and predict the evolution of mesoscale microstructures,which can help to understand the dynamic behavior of the material *** this review,we briefly introduce the theoretical framework of the phase-field model and its application in electrochemical systems,summarize the existing phase-field simulations in rechargeable batteries,and provide improvement,development,and problems to be considered of the future phase-field simulation in rechargeable batteries.

关键词： field phase method

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Route-Based Emissions Inventory and Energy Consumption of Passenger Vehicles: Case of Addis Ababa, Ethiopia

Innovation and Green Development

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Innovation and Green Development 2025年第3期4卷

作者： Amanuel Gebisa Aga Girma Gebresenbet Rajendiran Gopal Ramesh Babu Nallamothu Mechanical Engineering Department Adama Science and Technology University Adama P.O. Box 1888 Ethiopia Division of Automation and Logistics Department of Energy and Technology Swedish University of Agricultural Science P.O. Box 7032 750 07 Uppsala Sweden Automotive Engineering Program Department of Mechanical and Industrial Engineering Bahir Dar Institute of Technology Bahir Dar University P.O.Box 79 Ethiopia

Emission inventories play a crucial role in identifying the primary sources of atmospheric pollution. In urban environments, including Addis Ababa, elevated concentrations of vehicle emissions pose significant environmental risks. Consequently, measuring vehicle emissions becomes imperative for estimating the impact of passenger vehicles on urban air quality. In 2022, a drive cycle specific to Addis Ababa was developed for the first time; however, it was not utilized for determining both fuel consumption and vehicle emissions. Previous studies on emission inventories primarily focused on vehicle classification, neglecting variations in emissions on different types of roads. This study introduces routes-based emissions inventories and fuel consumption estimates for passenger cars based on the Addis Ababa drive cycle and the Worldwide Harmonized Light Vehicles Test Cycle. To validate the model, an experimental chassis dynamometer setup was employed. The findings of this study revealed that driving in the congested urban areas of Addis Ababa contributes to 56.25 % carbon monoxide, 37.28 % carbon dioxide, 38.19 % nitrogen oxides, 58.25 % volatile organic compound, 29 % particulate matter emissions, along with 37.29 % fuel consumption. Furthermore, congested urban and rural areas in Addis Ababa account for 60 %–73 % of all emissions and fuel consumption from passenger vehicles. The Addis Ababa city administration shall adopt cleaner technologies, improve public transportation access, and implement stricter emissions standards to mitigate vehicular pollution in the city.

关键词： Addis Ababa Fuel consumption Passenger vehicle Vehicle emissions Emission inventory

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Application of neutron grating interferometry and tomography to the nineteenth century Korean copper coins

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Scientific Reports 2025年第1期15卷 1-11页

作者： Kim, Youngju Daugherty, M. Cyrus Hussey, Daniel S. LaManna, Jacob M. Jacobson, David L. Kim, Jongyul Wolf, Caitlyn M. Kienzle, Paul A. Kim, Daeseung Han, Minsu Choo, Hahn Lee, Seung Wook Kim, TaeJoo Neutron Science Division Korea Atomic Energy Research Institute Daejeon South Korea Physical Measurement Laboratory National Institute of Standards and Technology Gaithersburg 20899 MD United States Department of Chemistry and Biochemistry University of Maryland College Park 20742 MD United States Information Technology Laboratory National Institute of Standards and Technology Gaithersburg 20899 MD United States NIST Center for Neutron Research National Institute of Standards and Technology Gaithersburg 20899 MD United States School of Mechanical Engineering Pusan National University Busan South Korea Department of Heritage Science and Technology Studies Korea National University of Heritage Buyeo South Korea Department of Materials Science and Engineering University of Tennessee Knoxville 37996 TN United States

Distinguishing differences between authentic artifacts and replicas is a significant challenge in the field of cultural heritage. In this study, we explore the application of neutron grating interferometry and tomography techniques to identify Korean copper coins in the nineteenth century of Joseon period by investigating structural differences between genuine objects and replicas. Neutron grating interferometry provides the microstructural information of coins, including features such as pores and precipitates, through a dark field image derived from small-angle neutron scattering. Additionally, neutron transmission tomography examines the three-dimensional internal structures and potentially hidden features of coins. Both neutron imaging techniques highlight regions that contain lead precipitates in the copper alloy, showing consistent agreement with optical imaging and with the quantitative lead content measured by energy dispersive X-ray spectroscopy. The distinct corrosion patterns observed in the authentic coin and replica provide empirical explanations for the general corrosion mechanism of copper alloy. This interpretation finds support in the moderate contribution of dark field contrast from cuprite, which underlies the signal of lead precipitates. © The Author(s) 2025.

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Design,simulation,and testing of a tunable MEMS multi-threshold inertial switch

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Microsystems & Nanoengineering 2024年第2期10卷 37-46页

作者： Qiu Xu Rodrigo T.Rocha Yousef Algoos Eric Feron Mohammad I.Younis Faculty of Electronic Information Engineering Huaiyin Institute of TechnologyHuai’an223003PR China Computer Electrical and Mathematical Science and Engineering DivisionKing Abdullah University of Science and TechnologyThuwal23955-6900Saudi Arabia Piezoelectric Microsystem Technologies Silicon Austria LabsVillach9524Austria Physical Sciences and Engineering Division King Abdullah University of Science and TechnologyThuwal23955Saudi Arabia Mechanical Engineering Department State University of New YorkBinghamtonNY13902USA

This paper presents a tunable multi-threshold micro-electromechanical inertial switch with adjustable threshold *** demonstrated device combines the advantages of accelerometers in providing quantitative acceleration measurements and g-threshold switches in saving power when in the inactive state upon experiencing acceleration below the *** designed proof-of-concept device with two thresholds consists of a cantilever microbeam and two stationary electrodes placed at different positions in the sensing *** adjustable threshold capability and the effect of the shock duration on the threshold acceleration are analytically investigated using a nonlinear beam *** are shown for the relationships among the applied bias voltage,the duration of shock impact,and the tunable *** fabricated prototypes are tested using a shock-table *** analytical results agree with the experimental *** designed device concept is very promising for the classification of the shock and impact loads in transportation and healthcare applications.

关键词： tunable acceleration testing

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engineering of dendritic dopant-free hole transport molecules:enabling ultrahigh fill factor in perovskite solar cells with optimized dendron construction

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science China Chemistry 2021年第1期64卷 41-51页

作者： Wei Chen Yang Wang Bin Liu Yajun Gao Ziang Wu Yongqiang Shi Yumin Tang Kun Yang Yujie Zhang Weipeng Sun Xiyuan Feng Frédéric Laquai Han Young Woo Aleksandra B.Djurisic Xugang Guo Zhubing He Department of Materials Science and Engineering Southern University of Science and TechnologyShenzhen 518055China Department of Physics The University of Hong KongPokfulamHong KongChina King Abdullah University of Science and Technology KAUST Solar CenterPhysical Sciences and Engineering DivisionMaterial Science and Engineering ProgramThuwal 23955-6900Kingdom of Saudi Arabia Department of Chemistry Korea UniversitySeoul 02841South Korea

Developing dopant-free hole-transporting materials(HTMs)for high-performance perovskite solar cells(PVSCs)has been a very active research topic in recent years since HTMs play a critical role in optimizing interfacial charge carrier kinetics and in turn determining device ***,a novel dendritic engineering strategy is first utilized to design HTMs with a D-A type molecular framework,and diphenylamine and/or carbazole is selected as the building block for constructing *** HTMs show good thermal stability and excellent film morphology,and the key optoelectronic properties could be fine-tuned by varying the dendron *** them,MPA-Cz-BTI and MCz-Cz-BTI exhibit an improved interfacial contact with the perovskite active layer,and non-radiative recombination loss and charge transport loss can be effectively ***,high power conversion efficiencies(PCEs)of 20.8%and 21.35%are achieved for MPA-Cz-BTI and MCz-Cz-BTI based devices,respectively,accompanied by excellent long-term storage *** encouragingly,ultrahigh fill factors of 85.2%and 83.5%are recorded for both devices,which are among the highest values reported to *** work demonstrates the great potential of dendritic materials as a new type of dopant-free HTMs for high-performance PVSCs with excellent FF.

关键词： dendritic molecules hole-transporting materials dopant-free ultrahigh fill factor perovskite solar cells

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