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Impact of Roughness Spanwise Wavelength on Secondary Flow Rearrangement

Journal of Fluids engineering 2025年第8期147卷 081302页

作者： Yang, Jianzhi Yang, Xiang Liu, Luoqin Zhu, Jian Zhu, Xiaowei Department of Built Environment Hefei University of Technology Hefei ANHUI230009 China Department of Mechanical Engineering The Pennsylvania State University University ParkPA16802 United States Department of Modern Mechanics University of Science and Technology of China Hefei ANHUI230027 China Department of Mechanical and Materials Engineering Portland State University PortlandOR97207 United States

Spanwise heterogeneity in surface roughness generates secondary mean flows in a rough-wall turbulent boundary layer. This study investigates the influence of roughness spanwise wavelength on the arrangement of these secondary flows using direct numerical simulation (DNS). We systematically vary the spanwise wavelength, S/δ, from π/16 to 2π, while maintaining constant roughness height and surface coverage density. Here, S represents the roughness spanwise wavelength, and δdenotes the outer length scale, which in this case is the half-channel height. Secondary flows are observed in all DNS cases, but their configurations depend on the spanwise wavelength. Specifically, small wavelengths result in low-momentum pathways (LMPs) above the roughness elements, whereas large wavelengths lead to high-momentum pathways (HMPs) at these locations. To elucidate the mechanisms behind this rearrangement, we analyze the mean streamwise vorticity transport equation. The findings indicate that shear stress anisotropy induces another pair of secondary vortices above the roughness elements as the spanwise wavelength increases. Given that secondary flows are features of the mean flow, we further examine the budgets of the dispersive kinetic energy (DKE). The analyses reveal that at small spanwise wavelengths, shear production primarily generates DKE, while at large wavelengths, wake production becomes the dominant energy source. Building on these insights, we propose a refined classification for surfaces with spanwise heterogeneity. Copyright © 2025 by ASME.

关键词： Kinetic energy

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Continuous Lithium-Ion Extraction From Seawater and Mine Water With a Fuel Cell System and Ceramic Membranes

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Energy & Environmental materials 2024年第6期 258-265页

作者： Cansu K?k Lei Wang Jean Gustavo A.Ruthes Antje Quade Matthew E.Suss Volker Presser INM-Leibniz Institute for New Materials Department of Materials Science & Engineering Saarland University Leibniz Institute for Plasma Science and Technology Faculty of Mechanical Engineering Technion-Israel Institute of Technology Wolfson Department of Chemical Engineering Technion-Israel Institute of Technology Grand Technion Energy Program Technion-Israel Institute of Technology Saarene-Saarland Center for Energy Materials and Sustainability

The demand for electronic devices that utilize lithium is steadily increasing in this rapidly advancing technological *** high-purity lithium in an environmentally friendly way is challenging by using commercialized ***,we propose the first fuel cell system for continuous lithium-ion extraction using a lithium superionic conductor membrane and advanced *** fuel cell system for extracting lithium-ion has demonstrated a twofold increase in the selectivity of Li+/Na+while producing electricity.

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Multi-objective parametric modelling during minimum quantity lubrication machining of Incoloy 800H 6

Multi-objective parametric modelling during minimum quantity...

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6th International Conference on Advancements in materials and Manufacturing, ICAAMM 2024

作者： Reddy Paturi, Uma Maheshwera Nandan, Konidhala Vamshi, Nudurupati Achintya Sahasra Bhojane, Omkar Sunil Reddy, Goturi Sheshank Reddy, N.S. Department of Mechanical Engineering CVR College of Engineering Telangana Hyderabad501510 India School of Materials Science and Engineering Gyeongsang National University Jinju52828 Korea Republic of

This study utilizes multi-objective optimization to minimize surface roughness and maximize material removal rate (MRR) during minimum quantity lubrication (MQL) turning of Incoloy 800H under different cutting conditions. The correlations among process conditions are examined using response surface methodology (RSM) and the desirability function. The obtained optimal values for the cutting parameters are as follows: 125 m/min cutting speed, 0.1 mm/rev feed rate, and 0.05 mm depth of cut. The predicted surface roughness and MRR were 0.585 μm and 4377.932 mm3/min, respectively. A correlation coefficient of 0.9006 for surface roughness and 0.9979 for MRR indicates a significant degree of agreement between experimental data and model predictions. The results show that the application of RSM can help in identifying optimal cutting conditions and minimize the need for extensive experimental trials in machining. © Published under licence by IOP Publishing Ltd.

关键词： Lubrication

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Safe pipelines for hydrogen transport

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International Journal of Hydrogen Energy 2025年 136卷 672-685页

作者： Jemblie, Lise Hagen, Anette Brocks Hagen, Catalina H.Musinoi Nyhus, Bård Alvaro, Antonio Wang, Dong Koren, Erik Aas Johnsen, Roy Zhang, Zhiliang Yamabe, Junichiro Matsunaga, Hisao Olden, Vigdis SINTEF Department of Materials and Nanotechnology SINTEF Industry Trondheim7034 Norway NTNU Department of Mechanical and Industrial Engineering Norwegian University of Science and Technology Richard Birkelands Vei 2B Trondheim7034 Norway NTNU Department of Structural Engineering Norwegian University of Science and Technology Richard Birkelands Vei 2B Trondheim7034 Norway Fukuoka University Department of Mechanical Engineering 8-19-1 Nanakuma Jonan-ku Fukuoka814-0180 Japan Kyushu University Department of Mechanical Engineering 744 Motooka Nishi-ku Fukuoka819-0395 Japan

The hydrogen compatibility of two X65 pipeline steels for transport of hydrogen gas is investigated through microstructural characterization, hydrogen permeation measurements and fracture mechanical testing. The investigated materials are a quenched and tempered pipeline steel with a fine-grained homogeneously distributed ferrite-bainite microstructure, and hot rolled pipeline steel with a ferrite-pearlite banded microstructure. All tests are performed both under electrochemical and gaseous hydrogen charging conditions. A correlation between electrochemical hydrogen charging and gaseous charging is determined. The results point to inherent differences in the interaction between hydrogen and the two material microstructures. Further research is needed to unveil the influence of material microstructure on hydrogen embrittlement. © 2024 The Authors

关键词： Hydrogen embrittlement

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Nitrogen-induced optimization of corrosion resistance for nanocrystalline soft magnetic Fe-Zr-B alloys

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Journal of materials science & Technology 2024年第19期186卷 15-27页

作者： Haoran Ma Wenquan Wang Yanxin Liu Xiahe Liu Aina He Yaqiang Dong Yong Wang Jiawei Li CAS Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application TechnologyNingbo Institute of Materials Technology&EngineeringChinese Academy of SciencesNingbo 315201China Department of Mechanical Science and Engineering Northeast Petroleum UniversityDaqing 163318China Shenyang National Laboratory for Materials Science Northeastern UniversityShenyang 110819China School of Metallurgy Northeastern UniversityShenyang 110819China University of Chinese Academy of Sciences Beijing 100049China

The poor corrosion resistance restricts the industrial applications of nanocrystalline soft magnetic Fe-Zr-B *** reported a facile plasma-nitriding surface process to enhance the corrosion resistance of a nanocrystalline Fe90 Zr7 B3 alloy without deteriorating its soft magnetic *** po-larization and electrochemical impedance spectroscopy were performed to investigate the corrosion *** nitrided alloy shows higher corrosion resistance than the untreated alloy,as evidenced by a nobler corrosion potential,lower corrosion current and higher polarization resistance of surface corrosion film,while their magnetic properties are *** microstructures of both nanocrystalline alloys were examined by high-resolution transmission electron microscopy(HRTEM)and the compositions of their corrosion films analyzed by X-ray photoelectron spectroscopy(XPS).For the nitrided alloy,a more homo-geneous nanocrystalline structure developed in the surface nitrided layer containing corrosion-resistant nitride phases(Fe3 N and ZrN)provides a higher resistance against chloride ***,the ni-trided layer facilitates the formation of a more protective corrosion film with the increased ratios of Fe2+/Fe3+and O2−/OH−as well as higher enrichment of Zr-and B-oxides,while the N-species(NH4+and NO3−)formed in the corrosion film behave as good corrosion inhibitors and further enhance the film *** findings provide a simple strategy for the preparation of corrosion-resistant nanocrystalline soft magnetic alloys to satisfy a variety of engineering requirements.

关键词： Plasma-nitriding Nanocrystalline soft magnetic Fe-based alloys Corrosion resistance Corrosion film

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Ultra-precision surface treatment of beta-titanium alloy printed using laser and electron beam melting sources

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CIRP Journal of Manufacturing science and Technology 2025年 58卷 1-19页

作者： Boban, Jibin Ahmed, Afzaal Gokcekaya, Ozkan Nakano, Takayoshi Department of Mechanical Engineering Indian Institute of Technology Palakkad Kerala 678623 India Mikrotools Private Limited Jalan Bukit Merah 159456 Singapore Division of Materials and Manufacturing Science Graduate School of Engineering Osaka University Osaka565-0871 Japan

Additive Manufacturing (AM) is a near net shape fabrication technology offering exceptional design freedom for complex part production. However, the inadequate surface quality and poorly generated micro-features adversely affect the functional performance of metal AM parts thereby restricting the direct adoption in biomedical implantation applications. Ultra-precision diamond turning (UPDT) can be regarded as a possible solution to overcome the aforementioned challenges in metal AM. However, the machinability of metal AM parts at ultra-precision level is highly sensitive to the material specific attributes and microstructure generated by the thermal characteristics of the process. In light of this, the present study follows a novel direction by investigating the dependence of distinct material characteristics imparted by two different AM powder melting sources on the ultra-precision post-treatment performance. Experiments were conducted on laser and electron beam printed beta-Ti alloy (Ti-15Mo-5Zr-3Al) which has potential importance in biomedical applications. The results demonstrate that the microstructural variations in respective samples affect the process performance and final surface integrity. The samples printed using laser powder bed fusion (LPBF) achieved a final surface finish (Sa) of ∼66.3 nm after UPDT relative to the electron beam powder bed fusion (EPBF) samples (∼104.3 nm). The cutting forces tends to exhibit sharp dip in forces in case of LPBF samples when micro-cutting was done perpendicular to the beam scanning direction. The chip morphology analysis corresponding to the LPBF and EPBF samples substantiates the generation of chips with segmentation/serrations on the free chip surface and parent material adhesion on the tool-chip contact surface. Further, precise microfeature generation was successfully accomplished on both the samples with minimal dimensional deviations on LPBF sample. Thus, the outcomes of the study establish the potential of UPDT

关键词： Titanium alloys

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Low-Voltage Graphene Interface-Engineered Organic Ferroelectric Tunnel Junction Devices

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ACS Applied materials and Interfaces 2025年第22期17卷 32773-32781页

作者： Natani, Shreyam Khajanji, Pranjali Cheng, Li Eshraghi, Kassra Zhang, Zichen Shipley, Wade Tao, Andrea R. Bandaru, Prabhakar R. Department of Mechanical Engineering University of California La Jolla San Diego 92093 CA United States Program in Materials Science University of California La Jolla San Diego 92093 CA United States

It has been indicated that the path forward for the widespread usage of ferroelectric (FE) materials may be considerably facilitated through the reduction of programming voltages to on-chip logic-compatible values of <1 V. Obstacles involve issues related to the scaling of the FEs to lower thickness as well as the presence of an interfacial layer (IL) between the high-permittivity FE and the substrate- resulting in wasted voltage across the IL. Here, we show how lower operating voltages along with a higher tunneling electroresistance (TER) could be achieved through IL engineering. We use piezoresponse force microscopy and fabricated ferroelectric tunnel junctions (FTJs) to show that ultrathin FE films deposited on single-layer graphene/Si can exhibit polarization switching at reduced voltages ∼0.8 V with significant TER as compared to directly depositing on Si. © 2025 American Chemical Society.

关键词： 2D materials ferroelectric tunnel junction (FTJ) interface engineering low voltage memory window PVDF-TrFE

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Evolution of 3d printing technology in fabrication of microfluidic devices and biological applications: a comprehensive review

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Journal of Micromanufacturing 2024年第1期7卷 110-140页

作者： Saha, Ranamay Sarkar, Moloy Choudhury, Sagnik Sarma Kumar, Hemant Bhatt, Geeta Bhattacharya, Shantanu Department of Mechanical Engineering Microsystems Fabrication Laboratory Indian Institute of Technology Kanpur Uttar Pradesh Kanpur India Department of Mechanical Engineering Laser Materials Processing Laboratory Indian Institute of Technology Kanpur Uttar Pradesh Kanpur India Department of Mechanical Engineering Birla Institute of Technology and Science Rajasthan Pilani India

Lab-on-a-chip or LOC is a term that is used to describe microfluidic devices that integrate multiple analyte detection, which are normally carried out in a laboratory, into one micro-chip unit and may have applications in diverse fields such as electronics, medicine and biomedical domains. Even though microfluidics has advanced greatly during the past decade due to increased needs for portability, reduced sample requirement and multiple analyte detection capabilities biological research has not adopted the technology at the required pace. This may be owing to the time-consuming and expensive process involved in the microfabrication of biochips, the requirement of specialised setup facilities and the extremely high cost associated with microfluidics as compared to conventional technologies. In recent years, three-dimensional (3D) printing has piqued curiosity in the scientific community. It has the potential to create complex, high-resolution structures and that too in a short timeframe depending upon device complexity. This could inspire progressive research in microfluidics, particularly finding applications in biomedical engineering and point-of-care diagnostics. This article gives an overview of how 3D printing aids in the manufacture of microfluidic devices for biological applications, as well as the existing 3D printing methods which are utilised for fabrication and the future perspective in the development of microfluidic devices. © The Author(s) 2024.

关键词： 3D printing additive microfabrication biosensors micro and nano system applications microfluidic devices

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Autonomous self-healing in a stretchable polybutadiene-based urethane and eutectic gallium indium conductive composite

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npj Flexible Electronics 2024年第1期8卷 74-88页

作者： Tran Duc Khanh Jinho Joo Jong-Woong Kim Department of Smart Fab Technology Sungkyunkwan UniversitySuwonSouth Korea School of Advanced Materials Science&Engineering Sungkyunkwan UniversitySuwonSouth Korea Department of Semiconductor Convergence Engineering Sungkyunkwan UniversitySuwonSouth Korea School of Mechanical Engineering Sungkyunkwan UniversitySuwonSouth Korea

In the burgeoning field of wearable electronics,flexible and durable conductors that can maintain consistent electrical properties under various conditions are critically *** research introduces a novel composite material comprising eutectic gallium-indium(EGaIn)and a polybutadiene-based urethane(PBU)specifically designed to address this ***,renowned for its superior conductivity due to its liquid state at room temperature,is strategically combined with PBU,which offers inherent flexibility and remarkable self-healing capabilities derived from reversible Diels–Alder ***,the composite maintains exceptional electrical resistance stability,withstanding mechanical strains up to 135%without compromising *** material’s self-healing capability is attributed to the autonomous mending properties of EGaIn and the reversible Diels–Alder reactions in the PBU *** result is an efficient restoration of the composite’s original properties upon incurring ***,the composite’s adaptability is showcased through its printability,allowing for precise patterning conducive to custom-designed wearable devices.

关键词： eutectic wear composite

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EXPLORING THE TECHNICAL BOUNDARIES IN UPSCALING FLOATING OFFSHORE WIND TURBINES 43

EXPLORING THE TECHNICAL BOUNDARIES IN UPSCALING FLOATING OFF...

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ASME 2024 43rd International Conference on Ocean, Offshore and Arctic engineering, OMAE 2024

作者： Janocha, Marek Jan Lee, Chern Fong Wen, Xueliang Ong, Muk Chen Raunholt, Lars Larsen, Ørjan Helgaland Søyland, Svein Department of Mechanical and Structural Engineering and Materials Science University of Stavanger Stavanger Norway Ra Wind AS Stavanger Norway

ISBN: (纸本)9780791887851

Recent advancements in offshore wind turbine technology have led to a rapid increase in the size of turbines. In the early 1980s, wind turbines had a relatively small power rating of 50 kW with rotor diameters of around 15 meters. This size grew significantly, reaching 18 MW with 260-meter rotor diameters currently under construction. The market is transitioning to even larger turbines, with a power rating expected to achieve 22 MW by 2025. This trend of increasing turbine sizes shows no signs of reaching its limit. However, it is anticipated that the cost curve will break at some point due to material limitations necessary to withstand increasing forces and moments from the environmental loads and exponentially increasing mass of the components. For floating offshore wind turbines specifically, the design complexity increases as these systems comprise of both a turbine and a floating foundation. Innovations in this area include using advanced composite materials for larger components such as blades and towers, high-fidelity numerical models for structural optimization to mitigate excessive dynamic response and employing unconventional solutions such as combined wind and wave energy conversion systems or multirotor wind turbines. Recent developments in wind turbine systems have also seen improvements in control systems and generator design, including direct-drive and multi-generator solutions. To further increase electrical energy production from wind turbines in the future, it is necessary to develop strategies that reduce costs through technological innovation, enhance performance and efficiency, and decrease maintenance, operation, and manufacturing costs. The evolution of wind turbine technology plays a pivotal role in the global wind power generation landscape, and the trend toward larger turbines is a significant aspect of this evolution. The present paper focuses on the theoretical technical limits of floating wind turbine upscaling and determining the optima

关键词： Offshore wind turbines

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