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arXiv 2024年

作者： McDevitt, Christopher J. Arnaud, Jonathan Tang, Xian-Zhu Nuclear Engineering Program Department of Materials Science and Engineering University of Florida GainesvilleFL32611 United States Theoretical Division Los Alamos National Laboratory Los AlamosNM87545 United States

This work extends the adjoint-deep learning framework for runaway electron (RE) evolution developed in Ref. [1] to account for large-angle collisions. By incorporating large-angle collisions the framework allows the avalanche of REs to be captured, an essential component to RE dynamics. This extension is accomplished by using a Rosenbluth-Putvinski approximation to estimate the distribution of secondary electrons generated by large-angle collisions. By evolving both the primary and multiple generations of secondary electrons, the present formulation is able to capture both the detailed temporal evolution of a RE population beginning from an arbitrary initial momentum space distribution, along with providing approximations to the saturated growth and decay rates of the RE population. Predictions of the adjoint-deep learning framework are verified against a traditional RE solver, with good agreement present across a broad range of parameters. © 2024, CC BY.

关键词： Electrons

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Estimate of the Driving Force for Creep Crack Growth

SSRN

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SSRN 2024年

作者： Kolednik, Otmar Kegl, Marko Gubeljak, Nenad Predan, Jozef Erich Schmid Institute of Materials Science Austrian Academy of Sciences LeobenA-8700 Austria Faculty of Mechanical Engineering University of Maribor MariborSI-2000 Slovenia

The paper presents a numerical study on the crack driving force (CDF) of growing cracks in elastic−plastic, creeping materials, applying the concept of configurational forces. Crack propagation is modelled by alternating creep and crack extension steps in C(t)-specimens made of a nickel-base superalloy Waspaloy at a temperature of 700°C. The prescribed load is varied so that small-scale creep (ssc-), transition creep (tc-) or extensive creep (ec-) conditions prevail. It is shown that the CDF is given by the J-integral for elastic−plastic, creeping materials [[EQUATION]], which has been introduced in a preceding paper, evaluated for a contour around the active creep zone. A procedure for evaluating the CDF is presented, which is applicable for ssc-, tc- and moderate ec- conditions, but not for "pronounced" ec-conditions where high creep strains occur near the upper boundary of the specimens. The conventional creep crack growth parameters based on the C*-integral are also determined. It is found that the experimental C*-integral, C*exp, and the experimental Ct-integral, Ct,ssc, do not reflect the crack driving force for ec- and ssc-conditions, but that they coincide with the rate of the CDF, taken at the end of each creep stage before the next crack extension step. © 2024, The Authors. All rights reserved.

关键词： Creep

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Computational Study of Rarefied Gas Flow and Heat Transfer in Lid-driven Cylindrical Cavities

arXiv

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arXiv 2023年

作者： Zhu, Mengbo Roohi, Ehsan Ebrahimi, Amin Xianning West Road Beilin District Xi'an710049 China Department of Materials Science and Engineering Faculty of Mechanical Maritime and Materials Engineering Delft University of Technology Mekelweg 2 Delft2628 CD Netherlands

The gas flow characteristics in lid-driven cavities are influenced by several factors, such as cavity geometry, gas properties, and boundary conditions. In this study, the physics of heat and gas flow in cylindrical lid-driven cavities with various cross-sections, including fully or partially rounded edges, is investigated through numerical simulations using the direct simulation Monte Carlo (DSMC) and the discrete unified gas kinetic scheme (DUGKS) methods. The thermal and fluid flow fields are systematically studied for both constant and oscillatory lid velocities, for various degrees of gas rarefaction ranging from the slip to the free-molecular regimes. The impact of expansion cooling and viscous dissipation on the thermal and flow fields, as well as the occurrence of counter-gradient heat transfer (also known as anti-Fourier heat transfer) under non-equilibrium conditions, are explained based on the results obtained from numerical simulations. Furthermore, the influence of the incomplete tangential accommodation coefficient on the thermal and fluid flow fields is discussed. A comparison is made between the thermal and fluid flow fields predicted in cylindrical cavities and those in square-shaped cavities. The present work contributes to the advancement of micro/nano-electromechanical systems (MEMS/NEMS) by providing valuable insights into rarefied gas flow and heat transfer in lid-driven cavities. © 2023, CC BY.

关键词： Flow of gases

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Enhancing Supercapacitor Performance with Innovative Nanocomposite: Electrochemical Investigation of Reduced Graphene Oxide-Supported Copper Manganese Dual- Metal Organic Frameworks

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SSRN 2024年

作者： Tan, Shangrong Yao, Zhuo Huang, Hong Lv, Ziqiang Liu, Zechen Guo, Shiqi University of Science and Technology Liaoning Liaoning Anshan114051 China Department of Mechanical and Materials Engineering Wright State University DaytonOH45435 United States

Supercapacitors have attracted considerable attention because of their benefits in terms of high power density, rapid charge-discharge rates, and extended cycle life. Metal-organic framework materials (MOFs), known for their exceptionally high surface area and adjustable pore architectures, are extensively employed in the realm of energy conversion and storage. Nevertheless, the inadequate conductivity of MOF materials impedes their desirable electrochemical performance when employed as electrode materials in supercapacitors. We utilized a straightforward solvothermal technique to produce graphene-supported Cu/Mn-BTC metal-organic framework materials. These materials were then used as electrode materials for supercapacitors. Mn-BTC was effectively incorporated onto the surface and into the pores of Cu-BTC via solvothermal treatment. The incorporation of reduced graphene oxide (rGO) greatly increased the conductivity of MOF materials. In a three-electrode system, the graphene-supported Cu/Mn-BTC electrode material exhibited a specific capacitance of 362.2 C g-1 at a current density of 1 A g-1. Assembled into a symmetric supercapacitor, the material achieved a specific capacitance of 141.46 F g-1 at a current density of 1 A g-1, with a maximum energy density of 12.6 Wh kg-1 at a power density of 111.1 W kg-1. After 1000 charge-discharge cycles, the capacitance retention rate was 83.55%. © 2024, The Authors. All rights reserved.

关键词： Graphene

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Biomimetic surfaces with patterned wettability for improved dehumidification/air condition efficiency

Biomimetic surfaces with patterned wettability for improved ...

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作者： Mingjia Fang Haoyang Tang Gege Ke Guanying Li School of Metal Materials Engineering Jiangsu University of Science and Technology of Materials science and Engineering School of Environmental Science Chemistry Duke Kunshan University School of Mechanical and Mining Engineering The University of Queensland Material Science and Engineering University of North Texas

Dehumidification has a massive impact on the energy efficiency of the air condition system. Condensation is a common way to achieve dehumidification. However, a certain amount of energy is required for harvesting water from the air through condensation. A hybrid hollow fiber membrane system proves to be effective in lowering the consumption of ***, the surfaces with patterned wettability receives inadequate attention despite its potential to achieve energyefficient dehumidification. This review casts a view on the mechanism of condensation via patterned surfaces, which are normally originated from natural biomimetic surfaces. Then, three kinds of surfaces, including the completely hydrophobic surface, completely hydrophilic surface, and the hybrid surface, is employed to explain the working principles of dehumidification via condensation. Besides, the connection between air conditioning and dehumidification and an application that involves a membrane dehumidification and water harvest system for condensation are introduced. It can be concluded that the patterned surfaces do have potentials that can be adopted to air conditioning, considering its exceptional condensation capability.

关键词： patterned wettability condensation dehumidification air conditioning

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Template Preparation of Porous Pt-Modified Sno2 Microflowers for Vocs with High Response

SSRN

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SSRN 2023年

作者： Ren, Haibo Tao, Siqi Pan, Hui Huang, Jiarui Joo, Sang Woo School of Materials Science and Engineering Anhui Polytechnic University Wuhu241000 China School of Chemistry and Materials Science Anhui Normal University Wuhu241002 China School of Mechanical Engineering Yeungnam University Gyeongbuk Gyeongsan38541 Korea Republic of

Porous SnO2 microflowers consisting of uniform nanosheets modified by Pt NPs were synthesized using a self-sacrificing template followed by a reduction strategy. The Pt@SnO2, SnO2–Se, and SnO2–S samples were characterized using a series of techniques. The gas-sensing behaviors of the samples toward volatile organic gases (VOCs) were studied. The Pt@SnO2 sensors exhibited superior gas-sensing performance for formaldehyde gas. The Pt@SnO2 sensors presented a stronger response (100.2), shorter response–recovery times (14 s/23 s), and lower working temperature (200 °C) for 100 ppm formaldehyde gas. The Pt@SnO2 sensors also showed excellent responses toward other VOCs, such as 100 ppm ethanol (82.5), acetone (73.9), and isopropanol (62.1). The gas-sensing mechanism of the Pt@SnO2 sensors was examined. The larger available surface area, favorable hierarchical flower-like nanostructure assembled by nanosheets, larger pore size, and larger proportion of oxygen vacancies and adsorption-state oxygen species, smaller crystallite size, and spillover effect of Pt catalysts contributed to the enhanced gas-sensing behaviors of Pt@SnO2 sensors. Overall, the synthetic strategy for flower-like SnO2 nanostructures can be applied widely. © 2023, The Authors. All rights reserved.

关键词： Gas detectors

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Data-Driven Models for Predicting Solar Radiation in Semi-Arid Regions

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Computers, materials & Continua 2023年第1期74卷 1625-1640页

作者： Mehdi Jamei Nadjem Bailek Kada Bouchouicha Muhammed A.Hassan Ahmed Elbeltagi Alban Kuriqi Nadhir Al-Ansar Javier Almorox El-Sayed M.El-kenawy Engineering Faculty Shohadaye Hoveizeh Campus of TechnologyShahid Chamran University of AhvazDashte AzadeganIran Energies and Materials Research Laboratory Department of Matter SciencesFaculty of Sciences and TechnologyUniversity of TamanghassetTamanghassetAlgeria Unitéde Recherche en Energies Renouvelables en Milieu Saharien(URERMS) Centre de Développement des Energies Renouvelables(CDER)01000AdrarAlgeria Mechanical Power Engineering Department Faculty of EngineeringCairo UniversityGiza12613GizaEgypt Agricultural Engineering Department Faculty of AgricultureMansoura UniversityMansoura35516Egypt CERIS Instituto Superior TécnicoUniversidade de LisboaLisbonPortugal Department of Civil Environmental and Natural Resources EngineeringLulea University of Technology97187LuleaSweden Universidad Politécnica de Madrid UPMAvd.Puerta de Hierro28040MadridSpain Department of Communications and Electronics Delta Higher Institute of Engineering and TechnologyMansoura35111Egypt Faculty of Artificial Intelligence Delta University for Science and TechnologyMansoura35712Egypt

Solar energy represents one of themost important renewable energy sources contributing to the energy transition *** that the observation of daily global solar radiation(GSR)is not affordable in some parts of the globe,there is an imperative need to develop alternative ways to predict ***,the main objective of this study is to evaluate the performance of different hybrid data-driven techniques in predicting daily GSR in semi-arid regions,such as the majority of Spanish ***,four ensemble-based hybrid models were developed by hybridizing Additive Regression(AR)with Random Forest(RF),Locally Weighted Linear Regression(LWLR),Random Subspace(RS),and *** base algorithms of the developed models are scarcely applied in previous studies to predict solar *** testing phase outcomes demonstrated that the ARRF models outperform all other hybrid *** provided models were validated by statisticalmetrics,such as the correlation coefficient(R)and root mean square error(RMSE).The results proved that Scenario#6,utilizing extraterrestrial solar radiation,relative humidity,wind speed,and mean,maximum,and minimum ambient air temperatures as the model inputs,leads to the most accurate predictions among all scenarios(R=0.968–0.988 and RMSE=1.274–1.403 MJ/m^(2)・d).Also,Scenario#3 stood in the next rank of accuracy for predicting the solar radiation in both validating *** AD-RF model was the best predictive,followed by AD-RS and ***,this study recommends new effective methods to predict GSR in semiarid regions.

关键词： Solar radiation prediction random forest locally-weighted linear regression additive regression

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Nano-Ceramic Coating's Critical Contribution to Protect Centrifugal Pump Under Difficult Operating Conditions

Nano-Ceramic Coating's Critical Contribution to Protect Cent...

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Advances in science and engineering Technology International Conferences (ASET)

作者： Ahmed Albtoush Mohammed Almajali Hesham Almomani Aziz Almahadin Mechanical Engineering Department Mutah University Karak Jordan Defence and Security program Rabdan Academy Abu Dhabi UAE Industrial Engineering Department Hashmite University Zarqa Jordan Faculty of Engineering Technology & Science Higher Colleges of Technology Dubai UAE

ISBN: (数字)9798350344134

ISBN: (纸本)9798350344141

This work is done to investigate and assess the beneficial role and added value of employing a thin layer of nano-ceramic coating to protect the components of a centrifugal pump. A case study is considered, representing a centrifugal pump operating in the Arab Potash Company (APC). The ANSYS software package was used which implements numerical finite element analysis (FEA), 3D modeling, and mathematical simulations. Variables, including Von Mises stresses, deformations, and strains, were investigated associated with a number of situations related to the operation of corrosive potash salt and coating layer. Based on the numerical analysis, the research results revealed that employing a thin layer of ceramic coating protective layer could minimize the dynamic Von Mises strength's impact on the centrifugal pump's impeller and casing by 35.55%. Furthermore, it was found that utilizing a protective layer of thin-nano ceramic could alleviate the total deformations of the centrifugal pump's impeller and casing by 67.01%. It was found that using a protective layer of the thin nano-ceramic could mitigate the equivalent elastic strain on the centrifugal pump's impeller and casing by 90.14%. It was noted that maximum total deformations occur at the tip of the blades. Coating the centrifugal pump parts could improve its components' lifespan by reducing wear, corrosion, and abrasion rates.

关键词： Three-dimensional displays Deformation Corrosion Pumps Impellers Ceramics Finite element analysis Coatings Stress Strain

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FRESH-Printing of a Multi-actuator Biodegradable Robot Arm for Articulation and Grasping 12th

FRESH-Printing of a Multi-actuator Biodegradable Robot Arm f...

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Proceedings of the 12th International Conference on Biomimetic and Biohybrid Systems, Living Machines 2023

作者： Williamson, Avery S. Sun, Wenhuan Sukhnandan, Ravesh Coffin, Brian Majidi, Carmel Feinberg, Adam Yao, Lining Webster-Wood, Victoria A. Department of Mechanical Engineering Carnegie Mellon University PittsburghPA15218 United States Department of Biomedical Engineering Carnegie Mellon University PittsburghPA15218 United States Department of Materials Science and Engineering Carnegie Mellon University PittsburghPA15218 United States Human-Computer Interaction Institute School of Computer Science Carnegie Mellon University PittsburghPA15218 United States McGowan Institute for Regenerative Medicine Carnegie Mellon University PittsburghPA15218 United States

ISBN: (纸本)9783031388569

The recent popularity of soft robots for marine applications has established a need for the reliable fabrication of actuators that enable locomotion, articulation, and grasping in aquatic environments. These actuators should also reduce the negative impact on sensitive ecosystems by using biodegradable materials such as organic hydrogels. Freeform Reversible Embedding of Suspended Hydrogels (FRESH) printing can be used for additive manufacturing of small-scale biologically derived, marine-sourced hydraulic actuators by printing thin-wall structures out of sustainably sourced calcium-alginate hydrogels. However, controlling larger alginate robots with complex geometries and multiple actuation mechanisms remains challenging due to the reduced strength of such soft structures. For tethered hydrogel hydraulic robots, a direct interface with fluid lines is necessary for actuation, but the drag forces associated with tethered lines can quickly overcome the actuation force of distal and extremity structures. To overcome this challenge, in this study, we identify printing parameters and interface geometries to allow the working fluid to be channeled to distal components of FRESH-printed alginate robots and demonstrate a proof-of-concept biodegradable robotic arm for small object manipulation and grasping in marine environments. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023.

关键词： Biodegradability

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Anisotropic-Isotropic Transition of Cages at the Glass Transition

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Physical Review Letters 2024年第7期132卷 078201-078201页

作者： Huijun Zhang Qi Zhang Feng Liu Yilong Han State Key Laboratory for Mechanical Behavior of Materials Shaanxi International Research Center for Soft Matter School of Materials Science and Engineering Xi’an Jiaotong University 710049 Xi’an China Department of Physics Hong Kong University of Science and Technology Clear Water Bay Hong Kong Shenzhen Research Institute The Hong Kong University of Science and Technology Shenzhen China

Characterizing the local structural evolution is an essential step in understanding the nature of glass transition. In this work, we probe the evolution of Voronoi cell geometry in simple glass models by simulations and colloid experiments, and find that the individual particle cages deform anisotropically in supercooled liquid and isotropically in glass. We introduce an anisotropy parameter k for each Voronoi cell, whose mean value exhibits a sharp change at the mode-coupling glass transition ϕc. Moreover, a power law of packing fraction ϕ∝q1d is discovered in the supercooled liquid regime with d>D, in contrast to d=D in the glass regime, where q1 is the first peak position of structure factor, and D is the space dimension. This power law is qualitatively explained by the change of k. The active motions in supercooled liquid are spatially correlated with long axes rather than short axes of Voronoi cells. In addition, the dynamic slowing down approaching the glass transition can be well characterized through a modified free-volume model based on k. These findings reveal that the structural parameter k is effective in identifying the structure-dynamics correlations and the glass transition in these systems.

关键词： Colloidal glass Glasses

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