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Concurrent generation and amplification of longitudinal and bending waves using defective phononic crystals

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Applied Mathematics and Mechanics(English Edition) 2025年第2期46卷 269-288页

作者： s.h.JO Department of Mechanical Robotics and Energy Engineering Dongguk University

Defective phononic crystals (PnCs) have enabled spatial localization and quantitative amplification of elastic wave energy. Most previous research has focused on applications such as narrow-bandpass filters, ultrasonic sensors, and piezoelectric energy harvesters, typically operating under the assumption of an external elastic wave incidence. Recently, a novel approach that uses defective PnCs as ultrasonic actuators to generate amplified waves.has emerged. however, the existing studies are limited to the generation of either longitudinal or bending waves, with no research addressing the concurrent generation of both. hence, this paper proposes a straightforward methodology for the concurrent generation and amplification of both wave types utilizing defect modes at independent defect-band frequencies. Bimorph piezoelectric elements are attached to the defect, with each element connected to independent external voltage sources. By precisely adjusting the magnitude and temporal phase differences between the voltage sources, concurrently amplified wave generation is achieved. The paper highlights the advantages of the proposed analytical model. This model is both computationally timeefficient and accurate, in comparison with the COMsOL simulation results. For instance,in case studies, the analytical model reduces the computational time from one hour to mere seconds, while maintaining acceptable error rates of 1%in peak frequencies. This concurrent wave-generation methodology opens new avenues for applications in rotating machinery fault diagnosis, structural health monitoring, and medical imaging.

关键词： phononic crystal (PnC) defect concurrent generation piezoelectric ultrasonic actuator O328 O346

Automatic Mesh Generation on a Regular Background Grid

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Journal of Computer science & Technology 2002年第6期17卷 882-887页

作者： LO s.h 刘剑飞 Department of Civil Engineering The University of Hong Kong Hong Kong P.R. China Department of Mechanics Peking University Beijing 100871 P.R. China

This paper presents an automatic mesh generation procedure on a 2D domain based on a regular background grid. The idea is to devise a robust mesh generation s.heme with equal emphasis on quality and efficiency. Instead of using a traditional regular rectangular grid, a mesh of equilateral triangles is employed to ensure triangular element of the best quality will be preserved in the interior of the domain. As for the boundary, it is to be generated by a node/segment insertion process. Nodes are inserted into the background mesh one by one following the sequence of the domain boundary. The local structure of the mesh is modified based on the Delaunay criterion with the introduction of each node. Those boundary segments, which are not produced in the phase of node insertion, will be recovered through a systematic element swap process. Two theorems will be presented and proved to set up the theoretical basic of the boundary recovery part. Examples will be presented to demonstrate the robustness and the quality of the mesh generated by the proposed technique.

关键词： mesh generation background grid triangular mesh boundary recovery

Free vibration and transient response of double curved beams connected by intermediate straight beams

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Applied Mathematics and Mechanics(English Edition) 2025年第1期46卷 37-62页

作者： R.A.JAFARI-TALOOKOLAEI h.GhANDVAR E.JUMAEV s.KhATIR T.CUONG-LE s.hool of Mechanical Engineering Babol Noshirvani University of Technology Department of Mechanical Engineering Faculty of Engineering New Uzbekistan University University of Business and science Center for Engineering Application and Technology solutions Ho Chi Minh City Open University

This paper investigates the free vibration and transient response of interconnected structures including double curved beams and intermediate straight beams,which are all constructed from functionally graded porous(FGP) materials. The strain potential and kinetic energies of each beam along with the work done by the external force are calculated. Additionally, a higher-order beam element is introduced to derive stiffness and mass matrices, along with the force vector. The curved and straight beams are discretized, and their assembled stiffness, mass matrices, and force vectors, are *** conditions at the joints are used to derive the total matrices of the entire structure. subsequently, the natural frequencies and transient response of the system are determined. The accuracy of the mathematical model and the self-developed computer program is validated through the comparison of the obtained results with those of the existing literature and commercial software ANsYs, demonstrating excellent ***, a comprehensive study is conducted to investigate the effects of various parameters on the free vibration and transient response of the considered structure.

关键词： double curved beam finite element method functionally graded porous (FGP) material intermediate straight beam O313 vibration analysis

Dynamic stress concentration in an infinitely long cylindrical cavity due to a point s.herical source embedded within a fluid-saturated poroelastic formation of infinite extent

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Applied Mathematics and Mechanics(English Edition) 2025年第1期46卷 139-156页

作者： h.hOssEINI O.BALILAshAKI Department of Mechanical Engineering Faculty of EngineeringGolestan University

The effects of a harmonically exciting monopole source on an infinitely long cylindrical cavity embedded entirely within a fluid-saturated poroelastic formation of infinite extent are examined theoretically. It is assumed that the source is located outside the cavity at a specified distance from the borehole axis. The magnitudes of the hoop and radial stresses beside the pore pressures exerted on the interface and inside the porous medium surrounding the borehole are calculated and discussed. Biot's poroelastic modeling along with three types of boundary conditions for the cylindrical interface including the ideal fluid, empty borehole, and rigid inclusion with a hard boundary is employed for the analysis. Utilizing a proper translational addition theorem for expressing the incident s.herical wave in terms of cylindrical wave expansions, the proposed boundary conditions at the interface are satisfied. stresses are formulated by means of wave potential functions in a three-dimensional(3D) manner. The effects of the frequency and the radial distance between the source and borehole on the induced stresses are examined for the first cylindrical modes over frequency spectra. Two permeability conditions for the interface and three types of soils for the porous formation are considered throughout the analysis. To give an overall outline of the study, a numerical example is presented. The results clearly indicate that the distance is a key parameter and has considerable effects on the induced stress values. In addition, the interface permeability condition and soil characteristics play an important role in determining the dynamic response of the borehole. Finally,the obtained results are compared with the relevant analyses existing in the literature for some limit cases, and good agreement is achieved.

关键词： cylindrical cavity O353.4 point source porous medium stress concentration wave-field transformation

Multi-Objective optimization for stable and efficient cargo transportation of partial space elevator

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Defence Technology(防务技术) 2025年第2期44卷 17-29页

作者： Gefei shi Zheng h.Zhu s.hool of Aeronautics and Astronautics Sun Yat-sen UniversityGuangzhou 510275China shenzhen Key Laboratory of Intelligent Microsatellite Constellation Shenzhen 518107China Department of Mechanical Engineering York University4700 Keele StreetTorontoCanada

This paper proposed a new libration decoupling analytical speed function(LD-AsF)in lieu of the classic analytical speed function to control the climber's speed along a partial space elevator to improve libration stability in cargo *** LD-AsF is further optimized for payload transportation efficiency by a novel coordinate game theory to balance competing control objectives among payload transport speed,stable end body's libration,and overall control input via model predictive *** transfer period is divided into several sections to reduce computational *** validity and efficacy of the proposed LD-AsF and coordinate game-based model predictive control are demonstrated by computer *** results reveal that the optimized LD-AsF results in higher transportation speed,stable end body's libration,lower thrust fuel consumption,and more flexible optimization space than the classic analytical speed function.

关键词： Partial space elevator stable transportation Libration decoupling analytical speed function Coordinate game Model predictive control Pareto optimization

A mild, configurable, flexible CoNi-LDh(v)/Zn battery based on h-vacancy-induced reversible Zn^(2+) intercalation

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Journal of Energy Chemistry 2025年第1期100卷 498-508页

作者： Xinyue Cheng Dingsheng Wu hao Gao Qingqing Wang Pengfei Lv sam s.Yoon Qufu Wei Key Laboratory of Eco–textiles Ministry of EducationJiangnan UniversityWuxi 214122JiangsuChina School of Mechanical EngineeringKorea UniversitySeoul 136–713Republic of Korea Received 12 August 2024Revis

Flexible Zn-based batteries.have attracted increasing research interest as essential components of wearable energy storage ***,the advancement of flexible aqueous Zn-based batteries based on Co-Ni layered double hydroxide (CoNi-LDh) as the cathode material is.hampered by their poor cycling stability and the corrosiveness of alkaline ***,CoNi-LDh nanosheets enriched with h vacancies (CoNi-LDh(v)) were constructed on a flexible carbon cloth (CC) substrate via electrochemical deposition and *** Zn-based battery comprising CoNi-LDh(v)@CC as the cathode exhibited highly reversible conversion reactions and stable operation in 3 M ZnsO4electrolyte (ph=4).The battery delivered an excellent specific capacity (225 mA h g^(-1),0.26 mA h cm^(-2)),acceptable cycling stability(53.9%,900 cycles),and high dis.harging *** abundant h vacancies served as active sites for the reversible intercalation of Zn^(2+)and the extravasation of NO_(3)-generated channels and space for Zn^(2+)transport and storage,together enabling an excellent Zn^(2+)storage ***,a sandwich-structured solid-state CoNi-LDh(v)@CC//Zn@CC battery was fabricated and was found to exhibit a noteworthy electrochemical performance and mechanical *** a proof of concept,the unencapsulated battery powered a digital watch under various deformation conditions and operated stably for 80 ***,the flexible battery displayed outstanding customizability,maintaining an open-circuit voltage of 1.42 V even after being cut *** proposed engineering strategy contributes to the realization of textiles with truly wearable energy-storage devices.

关键词： CoNi/Zn battery h vacancies Mild aqueous electrolyte Tailorable battery Wearable energy storage device

Effect of ECAP temperature on microstructure and mechanical properties of Al–Zn–Mg–Cu alloy

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Progress in Natural science:Materials International 2016年第2期26卷 182-191页

作者： M.h.shaeri M.shaeri M.Ebrahimi M.T.salehi s.h seyyedein Department of Metallurgy and Materials Engineering Engineering Faculty Imam Khomeini International University Department of Materials science and Engineering Sharif University of Technology Department of Mechanical Engineering University of Maragheh Department of Metallurgy and Materials Engineering Iran University of Science and Technology

The effect of equal channel angular pressing(ECAP) at different temperatures(room temperature, 120,150 and 180 °C) on microstructure and mechanical properties of Al-7075 solid solution alloy was investigated. Microstructure of the specimens was examined using orientation imaging microscopy,transmission electron microscopy as well as X-ray diffractometer, and mechanical properties were measured by Vickers microhardness and tensile tests. Microstructural investigations showed that after3 or 4 passes of ECAP, fi ne grains with average grain sizes in range of 300–1000 nm could be obtained at different ECAP temperatures. Increasing ECAP temperature from 120 to 180 °C caused a decrease in mechanical properties as a result of increasing grains and precipitates sizes, decreasing fraction of high angle boundaries and also transformation of η′ into η phase, while increasing ECAP temperature from RT to 120 °C leads to an increase in mechanical properties due to the formation of small η′ precipitates. so it can be concluded that ECAP process at 120 °C is the optimum process for attaining maximum mechanical properties. Quantitative estimates of various strengthening mechanisms revealed that the improvement of mechanical properties was mainly attributed to grain re fi nement strengthening, precipitation strengthening and dislocation strengthening.

关键词： Equal channel angular pressing Microstructure strengthening mechanisms Mechanical properties

Iron-promoted zirconia-alumina supported Ni catalyst for highly efficient and cost-effective hydrogen production via dry reforming of methane

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Journal of Environmental sciences 2025年第2期148卷 274-282页

作者： Ahmed s.Al-Fatesh Naitik Patel Vijay Kumar srivastava Ahmed I.Osman David W.Rooney Anis.h.Fakeeha Ahmed E.Abasaeed Mohammed F.Alotibi Rawesh Kumar Chemical Engineering Department College of EngineeringKing Saud UniversityP.O.Box 800Riyadh 11421Saudi Arabia Department of Chemistry Indus UniversityAhmedabadGujarat 382115India s.hool of Chemistry and Chemical Engineering Queen’s University BelfastBelfast BT95AGNorthern IrelandUK Institute of Refining and Petrochemicals Technologies King Abdulaziz City for Science and Technology(KACST)P.O.Box 6086Riyadh 11442Kingdom of Saudi Arabia

Developing cost-effective and high-performance catalyst systems for dry reforming of methane(DRM)is crucial for producing hydrogen(h_(2))***,we investigate using iron(Fe)as a promoter and major alumina support in Ni-based catalysts to improve their DRM *** addition of iron as a promotor was found to add reducible iron species along with reducible NiO species,enhance the basicity and induce the deposition of oxidizable *** incorporating 1 wt.%Fe into a 5Ni/10ZrAl catalyst,a higher CO_(2) interaction and formation of reducible"NiO-species.having strong interaction with support"was observed,which led to an∼80%h_(2) yield in 420 min of Time on stream(TOs).Further increasing the Fe content to 2 wt.%led to the formation of additional reducible iron oxide species and a noticeable rise in h_(2) yield up to 84%.Despite the severe weight loss on Fe-promoted catalysts.high h_(2) yield was maintained due to the proper balance between the rate of Ch_(4) decomposition and the rate of carbon deposit ***,incorporating 3 wt.%Fe into the 5Ni/10ZrAl catalyst resulted in the highest CO_(2) interaction,wide presence of reducible NiO-species,minimumgraphitic deposit and an 87%h_(2) *** findings suggest that ironpromoted zirconia-alumina-supported Ni catalysts can be a cheap and excellent catalytic system for h_(2) production via DRM.

关键词： Dry reforming of methane Coke resistant hydrogen production Cheap catalyst Fe-promoted catalyst

La3+ substitution-adjusted magnetic and optical properties with enhanced photocatalytic activity and stability of copper zinc nickel ferrites for wastewater treatment applications

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Journal of Rare Earths 2025年第2期43卷 319-328页

作者： N.s.Al-Bassami General studies Department Jubail Industrial College

Copper-zinc-nickel（Cu-Zn-Ni） ferrite nanoparticles are used for wastewater treatment ***,low degradation efficiency and stability are two main issues that make them unsuitable for actual production *** this paper,the citrate-nitrate auto-combustion method was applied for the formation of Cu0.5Zn0.25Ni0.25LaxFe2-xO4;（0≤x≤0.1;step 0.02）(CZNL) *** the substitution process entails the replacement of a small ion with a larger one,the lattice constant and crystallite size does not exhibit a consistent incremental *** behavior is justified and *** size of all the CZNL ferrite nanoparticles is in the range of 8-12 nm,and the lattice constant is in the range of 8.6230 to 8.4865 *** morphological analysis conducted using field emission-scanning electron microscopy（FE-sEM） reveals that the CZNL exhibits agglomerated s.herical *** energy dispersive X-ray spectrameter（EDAX） analysis was employed to confirm the elemental composition of CZNL *** the process entails the substitution of Fe3+magnetic ions with nonmagnetic ions La3+,the magnetic parameters of CZNL nanoferrites show a general decreasing trend as *** 20 K,saturation magnetization Ms shows an overall drop in its values from 59.302 emu/g at x=0.0-41.295 emu/g at x=0.1,the smallest value of 37.87 emu/g is recorded at x=*** highest coercivity（hc=125.9 Oe） and remanence（Mr=13.32 emu/g） are recorded for x=0.08 and x=0.04 nanoferrite,*** band gap of all the CZNL nanoferrites was determined using the Kubelka-Munk function and Tauc plot for direct permitted *** doping modifies the band gap（within 1.86-1.75 eV）,increases light absorption,induces efficient e/h separation and charge migration to *** nanoferrite Cu0.5Zn0.25Ni0.25La0.06Fe1.94O4achieves a degradation efficiency of 97.3% for methylene blue（MB） dye removal after just 60 *** five recycling processes,the nanoc

关键词： Copper-zinc-nickel Ferrite Photocatalytic properties Rare earths Wastewater treatment