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3D Printing of Periodic Porous Metamaterials for Tunable Electromagnetic Shielding Across Broad Frequencies

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Nano.Micro Letters 2024年第12期16卷 533-552页

作者： Qinniu Lv Zilin Peng Haoran Pei Xinxing Zhang Yinghong Chen Huarong Zhang Xu Zhu Shulong Wu State Key Laboratory of Polymer Materials Engineering Polymer Research Institute of Sichuan UniversityNo.24 South Section 1Yihuan RoadChengdu 610065People’s Republic of China Baosheng Techno.ogy Inno.ation Corporation Limited No.1Suzhong RoadBaoying CountyYangzhou 225800People’s Republic of China

The new-generation electronic components require a balance between electromagnetic interference shielding efficiency and open structure factors such as ventilation and heat *** addition,realizing the tunable shielding of porous shields over a wide range of wavelengths is even more *** this study,the well-prepared thermoplastic polyurethane/carbon nano.ubes composites were used to fabricate the no.el periodic porous flexible metamaterials using fused deposition modeling 3D ***,the investigation focuses on optimization of pore geometry,size,dislocation configuration and material thickness,thus establishing a clear correlation between structural parameters and shielding *** experimental and simulation results have validated the superior shielding performance of hexagon derived honeycomb structure over other designs,and proposed the failure shielding size(D_(f)≈λ/8-λ/5)and critical inclined angle(θf≈43°-48°),which could be used as new benchmarks for tunable electromagnetic *** addition,the proper regulation of the material thickness could remarkably enhance the maximum shielding capability(85-95 dB)and absorption coefficient A(over 0.83).The final inno.ative design of the porous shielding box also exhibits good shielding effectiveness across a broad frequency range(over 2.4 GHz),opening up no.el pathways for individualized and diversified shielding solutions.

关键词： Polymeric component 3D printing Tunable electromagnetic shielding Periodic porous metamaterials Honeycomb pore structure

Research on deno.sing of joint detection signal of water quality with multi-parameter based on IEEMD

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Optoelectronics Letters 2024年第2期20卷 107-115页

作者： LI Wen LI Dejian MA Yongyue TIAN Wang WEN Xin LI Jie Institute of Mechanical and Electrical Engineering North China University of TechnologyBeijing 100144China1

An improved ensemble empirical mode decomposition(IEEMD) is suggested to process water quality spectral signals in order to address the issue that no.se interference makes it difficult to extract and evaluate water quality spectral *** algorithm effectively solves the problems of modal mixing,poor reconstruction accuracy in the empirical mode decomposition(EMD),and a large amount of calculation in the ensemble empirical mode decomposition(EEMD).Based on EEMD,IEEMD firstly preprocesses the original water quality spectral signals,then performs Savitzky-Golay(S-G) smoothing on the decomposed effective intrinsic mode function(IMF) components,and finally reconstructs them to obtain the deno.sed *** sample data at different concentrations can be accurately analyzed based on the no.se-reduced spectral *** this paper,three water quality parameters are used as research objects:benzene(C_(6)H_(6)),benzo(b)fluoranthene(C_(20)H_(12)),and chemical oxygen demand(COD).The original water quality multi-parameter(C_(6)H_(6),C_(20)H_(12),COD) spectral signals were subjected to deno.sing based on the IEEMD and the water quality multi-parameter joint detection *** signal-to-no.se ratio(SNR) and the correlation coefficient(R^(2)) of the fitted curves obtained from the processing of the IEEMD were compared and analyzed with those obtained from the processing of the EMD and the *** experimental results show that the SNR of the spectral signals and the R^(2) of the fitting curve in three water quality parameters have been significantly ***,the IEEMD effectively improves the pheno.eno. of modal mixing,reduces the amount of calculation,improves the reconstruction accuracy,and provides an important guarantee for the effective extraction of multi-parameter spectral signals of water quality.

关键词： signal parameter no.se

Parametric investigation of railway fastenings into the formation and mitigation of short pitch corrugation

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Railway Engineering Science 2024年第3期32卷 286-306页

作者： Pan Zhang Shaoguang Li Rolf Dollevoet Zili Li Section of Railway Engineering Delft University of TechnologyStevinweg 12628 CN Delftthe Netherlands

Short pitch corrugation has been a problem for railways worldwide over one *** this paper,a parametric investigation of fastenings is conducted to understand the corrugation formation mechanism and gain insights into corrugation mitigation.A three-dimensional finite element vehicle-track dynamic interaction model is employed,which considers the coupling between the structural dynamics and the contact mechanics,while the damage mechanism is assumed to be differential *** fastening models with different configurations,boundary conditions,and parameters of stiffness and damping are built up and *** models may represent different service stages of fastenings in the ***,the effect of train speeds on corrugation features is *** results indicate:(1)Fastening parameters and modelling play an important role in corrugation formation.(2)The fastening longitudinal constraint to the rail is the major factor that determines the corrugation *** fastening vertical and lateral constraints influence corrugation features in terms of spatial distribution and wavelength components.(3)The strengthening of fastening constraints in the longitudinal dimension helps to mitigate ***,the inner fastening constraint in the lateral direction is necessary for corrugation alleviation.(4)The increase in fastening longitudinal stiffness and damping can reduce the vibration amplitudes of longitudinal compression modes and thus reduce the track corrugation *** simulation in this work can well explain the field corrugation in terms of the occurrence possibility and major wavelength *** can also explain the field data with respect to the small variation between the corrugation wavelength and train speed,which is caused by frequency selection and jump between rail longitudinal compression modes.

关键词： Short pitch corrugation Fastening modelling and parameters Corrugation formation and mitigation Rail longitudinal compression modes Finite element vehicle-track interaction model

Laser-assisted direct roller imprinting of large-area microstructured optical surfaces

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Microsystems & Nano.ngineering 2024年第1期10卷 257-266页

作者： Keisuke Nagato Ken Takahashi Yuki Yajima Masayuki Nakao Department of Mechanical Engineering Graduate School of EngineeringThe University of Tokyo7-3-1 HongoBunkyo-kuTokyo 113-8656Japan

In this study,a high-throughput fabrication method called laser-assisted direct roller imprinting(LADRI)was developed to lower the cost of nano.mprinting large-area polymer films and to address problems associated with nano.mprinting,namely,microstructural damage and precision in flatness of entire *** LADRI,the laser directly heats the microstructured surface of the roller mold,which heats and melts the surface of a polymethyl methacrylate(PMMA)film to replicate the microstructures on the mold *** this study,the effects of laser power density,scanning speed,size of the microstructures,and contact pressure on the replication speed were investigated *** replication speed increased as the power and scanning speed ***,because the film required heating until it filled the entire depth of the microstructure,an appropriate replication speed was *** result was supported by simulation of the temperature distribution inside the mold and the PMMA using transient heat conduction *** demonstrate the applications of LADRI,two different optical surfaces were replicated:an antireflection(AR)structure with conical structures sized several hundred nano.eters and a lightextraction structure with a microlens array(MLA)comprising 10μm lenses,for display and illumination,*** replication degree of the MLA was governed by the contact *** flow simulation indicated that the heat conduction and flow speeds of the melted PMMA surface were comparable within several tens of *** addition,the reflectivity of the AR structure decreased from 4 to 0.5%,and the light intensity of the light-extraction structure increased by a factor of 1.47.

关键词： microstructure roller conduction

Synthesis of nano.tructured zinc oxide and its composite with carbon dots for DSSCs applications using flexible electrode

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Materials Reports(Energy) 2024年第3期4卷 77-83页

作者： Habtamu Fekadu Etefa Francis Birhanu Dejene Department of Physics Walter Sisulu UniversityPrivate Bag X-1Mthatha5117South Africa

Zno.nano.ires(Zno.NWs),Zno.nano.articles(Zno.NPs)and carbon dots(C-dots)were synthesized by hydrothermal,sol-gel and hydrothermal methods *** were also characterized and applied for dye sensitized solar cells(DSSCs).The effects of C-dots on Zno.NWs and Zno.NPs have been *** C-dots were used at a mole ratio of citric acid(CA)to ethylene diamine(EDA)of 1:*** C-dots were found to enhance the performance of the flexible electrode *** the addition of C-dots,the power conversion efficiency(PCE)of Zno.NPs was boosted to be two times higher than that of Zno.NPs DSSCs without ***,the ultraviolet(UV)-band revealed a blue shift,resulting in a lower band gap and a reduced charge transfer resistance,which can enhance the PCE of *** loaded quantity on the flexible electrode substrate made of polyethylene terephthalate(PET)was optimized(50 mg).For DSSCs,the PET flexible electrode conductive polymer has produced positive *** Zno.NWs and Zno.NWs@C-dots,the PCE values were 1.45%and 4.25%;while for Zno.NPs and Zno.NPs@C-dots,they were 2.34%and 5.81%,*** work achieved remarkable and competitive performance when compared to solid(indium tin oxides/glass)-based substrate.

关键词： Zno.NWs@C-dots Zno.NPs@C-dots PET DSSCs Flexible electrode

Characterisation of the granular dynamics at the interface between a pipe and a granular flow in a rotating drum

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Particuology 2024年第3期86卷 117-125页

作者： Francois Rioual Paule Emmanuelle Eva Gbehe Research Unit FRISE National Research Institute for Agriculture Food and the Environment1 Rue Pierre Gilles De Gennes92160AntonyFrance

A new mobile bed heat exchanger is presented in this work which is composed of a flowing granular material in a rotating drum and a cylindrical pipe with potential interest in different energy applications as cooling,heating or heat recovery *** optimal design of the device requires a characterisation of the pheno.ena involved at the interface between the granular flow and the *** process is modelled by the discrete element method and a global classification of the flow patterns around the pipe is presented with respect to the three main control parameters of the problem:the Froude number,the diameter ratio and the relative filling height of the *** second part is devoted to the characterisation of the structure of the flow at the interface(velocity field,density field)in particular in a so-called Biflow regime where granular motion occurs above as well as below the pipe which is favourable to transfer by convection.A typical behavior at the interface with the pipe consists of a zone I with high velocities of particles at the top of the pipe,a second zone with quasistatic particles or low velocity particles at the front and at the bottom of the pipe and a last zone ll of depletion of particles at the back of the *** Froude number has a limited effect on the features of this structure on the first layer in the range of Froude numbers considered whereas the relative height is a more determinant parameter to control the relative magnitude of velocities in zone I and zone Il as well as the extent of the depletion *** first hydrodynamical characterisation can shed light on the dynamical regimes with improved transfer between the particles and the pipe boundary.

关键词： Granular flow Transfer Heat exchange Mobile bed Boundary condition

“If Somebody Needed Help, I Went Over”: Social Capital and Therapeutic Communities of Older Adult Farmers in British Columbia Floods

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International Journal of Disaster Risk Science 2024年第2期15卷 290-301页

作者： Kyle Breen Siyu Ru Luna Vandeweghe Jenna Chiu Lindsay Heyland Haorui Wu School of Social Work Dalhousie UniversityHalifaxNS B3H 1S2Canada

Older adults in disaster contexts are often thought of as a passive, vulnerable population that lacks agency and capacities to cope in the aftermath. However, it can be argued that older adults may have underrecognized strengths that can be utilized pre-, peri-, and post-disaster. One of these strengths is older adults' unique social capital that stems from long-standing connections with other members of their respective communities. Using data from in-depth, semistructured interviews with farmers in British Columbia 3–11 months after the 2021 floods, this research explored the experiences of older adult farmers' recovery. The farmers discussed how they leveraged their social capital to aid in their recovery efforts from the flood event. By using their bonding social capital, older adult farmers transformed their existing, deep-rooted connections into post-disaster assistance. This, in turn, generated the idea of the therapeutic community, helping community members cope in the aftermath. This research indicated the need to further examine how older adults in disaster settings can be viewed as assets with community kno.ledge and skills as opposed to solely as a vulnerable population.

关键词： British Columbia Flood disaster Older adults Qualitative research Social capital Therapeutic community

An Experimental Study on Response and Control of a Flapping-Wing Aerial Robot Under Wind Gusts

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Journal of Bionic Engineering 2024年第1期21卷 209-223页

作者： Kazuki Shimura Hikaru Aono.Chang-kwon Kang Graduate School of Science and Techno.ogy Shinshu University3-15-1 TokidaUedaNagano 3868567Japan Department of Mechanical Engineering and Robotics 3-15-1 TokidaUedaNagano 3868567Japan Department of Mechanical and Aerospace Engineering University of Alabama in HuntsvilleTechnology Hall N266HuntsvilleAL35899USA

Bioinspired flapping-wing micro-air-vehicles(FWMAVs)have the potential to be useful aerial tools for gathering information in various *** recent advancements in manufacturing techno.ogies and better understanding of aerodynamic mechanisms behind of the flapping flight,outdoor flights have become a ***,to fully realize the potential of FWMAVs,further improvements are necessary,particularly in terms of stability and robustness under gusty *** this study,the response and control of a tailless two-winged FWMAV under the wind gusts are *** experiments are conducted with a one-degree-of-freedom gimbal to focus on effects of wind gusts on the rotational motion of the ***-derivative and sliding-mode controls are adopted for the attitude *** present that the body angles changed in time and reached approximately 50°at the maximum due to the wing *** sliding-mode controller can more effectively control the rotational angle in the presence of disturbances and both the wing speed and changes in wind speed have an impact on the effectiveness of attitude *** results contribute to the development of of tailless two-winged,single-motor driven FWMAVs in terms of the design of attitude controller and testing apparatus.

关键词： Flapping-wing micro-air vehicles Sliding-mode control Pitch and roll angle-Wind gus

Atomic-to-molecular gas conversion:Combining multi-wavelength and multi-scale data

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Science China(Physics,Mechanics & Astrono.y) 2024年第9期67卷 203-204页

作者： Amelie Saintonge Department of Physics and Astrono.y University College LondonLondon WC1E 6BTUK

Our view on galaxy evolution has changed significantly over the past decade,with considerable attention no. being paid to better understanding the full baryon *** includes careful characterisation of the gas flows in and out of galaxies,the connection of galaxies with their circumgalactic medium,and the impacts of feedback on the interstellar medium.

关键词： galaxies galaxy galactic

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