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Experimental and numerical characterization of 3D‑printed scaffolds under monotonic compression with the aid of micro‑Ct volume reconstruction

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Bio-Design and Manufacturing 2021年第2期4卷 222-242页

作者： R.Baptista M.F.C.Pereira A.Maurício D.Rechena V.Infante M.Guedes CDP2t Departamento de Engenharia MecanicaEscola Superior de Tecnologia de SetúbalInstituto Politécnico de Setúbal2910‑761 SetúbalPortugal CERENA DECivilInstituto Superior TécnicoUniversidade de LisboaAv.Rovisco Pais11049‑001 LisbonPortugal IDMEC Instituto Superior TécnicoUniversidade de LisboaAv.Rovisco Pais11049‑001 LisbonPortugal IPFN Instituto Superior TécnicoUniversidade de Lisboa1049‑001 LisbonPortugal CeFEMA Instituto Superior TécnicoUniversidade de LisboaAv.Rovisco Pais11049‑001 LisbonPortugal

Even when damaged by injury or disease bone tissue has the remarkable ability to *** this process is limited by large size bone defects,tissue engineering is responsible for restoring,maintaining or improving tissue *** are support structures,designed to be implanted in the damaged site,supporting mechanical loads and protecting the regenerating bone *** this paper,3D-printed PLA scaffolds with three different porosity values and two different geometries were experimentally and numerically ***-Ct analysis showed that fused filament fabrication can be used to produce scaffolds with the desired porosity and 100%of interconnected *** monotonical compression,scaffolds apparent compressive modulus increased from 89 to 918 MPa,while yield stress increased from 2.9 to 27.5 MPa as porosity decreased from 70 to 30%.Open porosity decreased up to 8%on aligned scaffolds and 14%on staggered scaffolds,after compression,while scaffold’s surface-to-volume ratio highest reduction(7.48 to 4.55 mm−1)was obtained with aligned low porosity ***-Ct volume reconstruction allowed for scaffold simplified numerical models to be built and *** agreement was found when predicting scaffold’s apparent compressive ***,it can be concluded that 3D printing is a viable scaffold manufacturing technique for trabecular bone replacement.

关键词： Scaffold Pore design Mechanical behavior Micro-Ct analysis Finite element method

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Improving Linked-Lists Using tree Search Algorithms for Neighbor Finding in Variable-Resolution Smoothed Particle Hydrodynamics

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Communications in Computational Physics 2019年第6期26卷 57-86页

作者： Shahab Khorasanizade J.M.M.Sousa IDMEC Instituto Superior T́ecnicoUniversidade de LisboaAv.Rovisco Pais1049-001 LisboaPortugal

Improving linked-lists for neighbor finding with the use of tree search algorithms is proposed here,aiming to cope with highly non-uniform resolution simulations employing a meshless *** new procedure,coined Quadtree Cells Grid,has been implemented in Smoothed Particle Hydrodynamics(SPH).the SPH scheme employed is adaptive,thus allowing for particle refinement in desired regions of the *** to the wide range of coexisting particle mass levels,standard linked-list neighbor search algorithms become ***,an alternative is found based on the use of hierarchical data structures,using quadtrees(in 2D problems).the present algorithm exploits the advantages of both linked-lists and quadtree meth-ods with the goal of increasing computational efficiency,when dealing with highly non-uniform particle *** cases involving two distinct flow problems have demonstrated that the computational cost of the current adaptive neighbor finding algorithm scales linearly with the total number of particles,thus retrieving this characteristic of linkedlists in uniform grid ***,the memory usage increased as a result of the more complex data structure.

关键词： Smoothed particle hydrodynamics linked-list quadtree neighbor finding variable resolution

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Experimental and numerical analysis of multi-chamber oscillating water column devices

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Journal of Hydrodynamics 2024年第3期36卷 492-503页

作者： Jorge Gadelho Kourosh Rezanejad C.Guedes Soares Centre for Marine technology and Ocean Engineering(CENtEC) Instituto Superior TécnicoUniversidade de LisboaAvenida Rovisco PaisLisboaPortugal

A review of multi-chamber oscillating water column(OWC)device designs is *** significant variations of these devices are discussed,onshore OWC(OOWC)and a floating OWC(FOWC).the efficiency results of several theoretical studies based on low-and high-fidelity numerical models are presented and compared with the model scale ***,low-fidelity numerical models are very fast to run,but their accuracy is limited compared with high-fidelity numerical *** model experiments usually give results much more accurate than numerical models,but they need adequate facilities and are very *** the case of the OOWC,all models show a similar trend of total efficiency,but while the analytical model shows a maximum value of around 90%efficiency,the CFD model shows 60%,and the experiments only go up to 40%.the main reason is connected with the mathematical simplifications and assumptions that do not represent all the hydrodynamic and aerodynamic processes between the water,air,and *** the case of the FOWC,interestingly,the experimental results show a maximum efficiency of almost 100%,while the analytical model only predicts a maximum of 80%.the efficiency seems highly dependent on the heave motion resonance of the entire device,where the analytical model fails to predict this natural frequency.

关键词： Wave energy converters oscillating water column(OWC) multi-chambers experimental modelling numerical modelling

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Eliminating the Unruh effect of relativistic Dirac fields by partial measurements

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Communications in theoretical Physics 2020年第12期72卷 130-136页

作者： N A Khan Syed tahir Amin Munsif Jan Centro de Física das Universidades do Minho e Porto Departamento de Física e AstronomiaFaculdade de CiênciasUniversidade do Porto4169-007 PortoPortugal Departamento de Física Instituto Superior TécnicoUniversidade de LisboaAv.Rovisco Pais1049-001 LisboaPortugal CeFEMA Instituto Superior TécnicoUniversidade de LisboaAv.Rovisco Pais1049-001 LisboaPortugal instituto de telecomunicacoes LAv.Rovisco Pais1049-001 LisboaPortugal CAS Key Laboratory of Quantum Information University of Science and Technology of ChinaHefei 230026China

the retrieval of lost entanglement for relatively accelerated fermionic observers of a tripartite system by a partial measurement technique has been *** the prospective of the negativities of one-tangles and theπ-tangle,we show that the degraded entanglement in noninertial frames with single-mode approximation is completely retrieved by an optimal strength of the partial measurement or the partial measurement *** addition,we find that the optimal one-tangle with respect to inertial and noninertial observers turns out to be the same for an optimal strength of partial measurements at q0=0 when two accelerated observers move with infinite acceleration.

关键词： entanglement retrieval π-tangle Unruh decoherence

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Functional traits:the pathways to riverine plant resistance in times of hydropeaking

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Ecological Processes 2023年第1期12卷 884-915页

作者： Alejandro Baladrón María Dolores Bejarano Isabel Boavida CERIS Civil Engineering Research and Innovation for SustainabilityInstituto Superior TécnicoUniversidade de LisboaAv.Rovisco Pais1049-001 LisbonPortugal Natural Resources Department Universidad Politécnica de Madrid(UPM)Calle JoséAntonio Novais1028040 MadridSpain

Hydropeaking,which refers to rising or falling discharges caused by the turning on or off of hydro-turbines to generate electricity,is a topic of growing interest due to its impact on fluvial *** date,most hydropeaking studies have focused on the impact of peak fluctuations on invertebrate and fish communities,but little attention has been paid to its impact on riverine plants and how functional traits may make them resistant to *** performed a review to assess how a set of 32 plant functional traits can be expressed in riverine plant species,and found evidence of how such expression affects their capacity to cope with common sources of hydropeaking disturbance(i.e.,inundation,fast water drawdown,and rapid water fluctuations linked to up-ramping and down-ramping hydropeaking operations).the information here presented can simplify the evaluation of impacts on riverine plant communities worldwide,as well as to detect suitable species to successfully restore rivers affected by hydropower production.

关键词： Drought Flooding Waterlogging Hydropeaking Plant trait Riverine vegetation

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Characterization of the topography and Wettability of English Weed Leaves and Biomimetic Replicas

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Journal of Bionic Engineering 2014年第3期11卷 346-359页

作者： Pedro Miguel Matos Pereira Ana Sofia Moita Gabriel Amaro Monteiro Duarte Miguel Franca Prazeres IBB - Institute for Biotechnology and Bioengineering Centre for Biological and Chemical Engineering Department of Bioengineering Instituto Superior Tecnico Universidade de Lisboa Av. Rovisco Pals 1049-001 Lisboa Portugal IN+ - Center for Innovation Technology and Policy Research Instituto Superior T~cnico Universidade de Lisboa Av. Rovisco Pais 1049-001 Lisboa Portugal

the topography and wettability of the underside of English weed （Oxalis pes-caprae） leaves and of their biomimetic replicas are investigated. Polyvinyl siloxane molds were cast from the leaves and then filled with an epoxy pre-polymer to produce replicas. the particular topographical structures of leaves and replicas were evaluated by optical microscopy and Scanning Electron Microscopy （SEM） analysis. the static wettability of leaves and replicas was assessed by contact angle measurements, while the dynamic wettability was characterized by estimating contact angle hysteresis and studying the dynamic behavior of impacting water droplets. A smooth glass slip and its replica were used as control surfaces. the replica moulding method used was able to transfer the characteristic pattern of irregular 100 μm - 200 μm × 60 μm convex papillae interspersed with stomata of the original leaf to the epoxy replicas. the static contact angle of 143°± 3° and the contact angle hysteresis of 2~ indicate that the underside of the English weed leaf is close to superhydrophobic. the lower contact angles （130° ± 4°） and higher hysteresis （31°） observed for the replica when compared with the original leaves were associated to an inaccurate replication of the chemistry and structures of the three-dimensional wax projections covering the plant surface. Also, trichomes in the original leaves could not be accurately reproduced due to their flexibility and fragility. Differences in wetting behavior were also evident from droplet impact experiments, with rebound regimes prevailing in the original leaves and regimes characterized by higher adhesion and larger dissipation predominating in the replicas. Nevertheless, the morphological features of the leaf transferred to the replica were sufficient to promote a clear hydrophobic behavior of the replica when compared with the smooth epoxy reference surface.

关键词： biomimetic surfaces oxalis pes-caprae English weed replica molding wettability micro-topography

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Analysis of foundation sliding of an arch dam considering the hydromechanical behavior

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Frontiers of Structural and Civil Engineering 2012年第1期6卷 35-43页

作者： Maria Luísa Braga FARINHA JoséVieira de LEMOS Emanuel MARANHA DAS NEVES LNEC-National Laboratory for Civil Engineering Av.Brasil 101Lisboa 1700-066Portugal ISt-instituto superior técnico Av.Rovisco Pais 1Lisboa 1049-001Portugal

this paper presents the application of a methodology which can be used to assess arch dam foundation stability,using the discrete element method(DEM)and the code 3DEC.A global three-dimensional model of a dam foundation was developed,in which some discontinuities were simulated and both the grout and drainage curtains were *** model,calibrated taking into account recorded data,was used to carry out nonlinear mechanical *** same model was employed to perform a hydraulic analysis,based on equivalent continuum concepts,which allowed the water pressure pattern within the foundation to be *** water pressures were applied on discontinuities involved in the possible sliding mechanism along the dam/foundation interface,and the safety of the dam/foundation system was evaluated using a process of reduction of strength characteristics,with the aim of calculating the minimum safety factors that ensure *** were compared with those obtained with the usual bi-linear uplift pressure distribution at the base of the dam,commonly used in concrete dam *** relevance of carrying out hydraulic analysis in arch dam foundation failure studies is highlighted.

关键词： concrete dams rock foundations hydromechanical behavior failure analysis

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Non-destructive corrosion study on a magnesium alloy with mechanical properties tailored for biodegradable cardiovascular stent applications

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Journal of Materials Science & technology 2021年第7期66卷 128-138页

作者： Changhong Cai Marta M.Alves Renbo Song Yongjin Wang Jingyuan Li School of Materials Science and Engineering University of Science and Technology BeijingBeijing100083China Centro de Qufmica Estrutural Instituto Superior TecnicoUniversidade de LisboaAv.Rovisco Pais1049-001LisboaPortugal

AnMg-2Zn-0.6Zr-0.6Nd alloy for biodegradable cardiovascular stent applications was prepared through indirect extrusion. the alloy exhibited a superior combination of tensile yield strength(tYS), ultimate tensile strength(UtS) and elongation(EL) of about 269 MPa, 298 MPa and 25.6 %, respectively. In addition,the non-destructive electrochemical frequency modulation(EFM) technique was used for the first time to investigate the corrosion behavior of Mg alloys combined with electrochemical impedance spectroscopy(EIS) in Dulbecco’s Modified Eagle’s Medium(DMEM) and in Hank’s solution. Compared with the corrosion rate of 0.07 mm/year in Hank’s solution, lower corrosion rate of 0.03 mm/year was achieved in DMEM. the significant differences between the corrosion rate trends were discussed and related with the composition of the corrosion layer formed. Depending on the biomimetic fluids tested, different corrosion products were precipitated on the alloy’s surface: a compact and homogeneous layer of Mg_(x)Ca_(y)(PO_(4))_(z) and Zn(OH)_(2) and organic compounds was formed in DMEM, whereas a partial coverage of Mg_(x)Ca_(y)(PO_(4))_(z) and Zn(OH)_(2) was formed in Hank’s solution.

关键词： Mg-Zn-Zr-Nd alloy Mechanical property Corrosion EIS EFM

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Fatigue Reliability Assessment of Correlated Welded Web-frame Joints

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Journal of Marine Science and Application 2014年第1期13卷 23-31页

作者： W.Huang Y.Garbatov C.Guedes Soares Centre for Marine technology and Engineering (CENtEC) Instituto Superior Técnico Universidade de Lisboa Av. Rovisco Pais 1049-001 Lisboa Portugal Centre for Marine technology and Engineering (CENtEC) Instituto Superior Técnico Universidade de Lisboa Av. Rovisco Pais 1049-001 Lisboa Portuga

the objective of this work is to analyze the fatigue reliability of complex welded structures composed of multiple web-frame joints, accounting for correlation effects. A three-dimensional finite element model using the 20-node solid elements is generated. A linear elastic finite element analysis was performed, hotspot stresses in a web-frame joint were analyzed and fatigue damage was quantified employing the S-N approach. the statistical descriptors of the fatigue life of a non-correlated web-frame joint containing several critical hotspots were estimated. the fatigue reliability of a web-frame joint wasmodeled as a series system of correlated components using the Ditlevsen bounds. the fatigue reliability of the entire welded structure with multiple web-frame joints, modeled as a parallel system of non-correlated web-frame joints was also calculated.

关键词： fatigue reliability hotspot stress S-N approach finite element analysis web-frame joints

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Dynamics of Droplets of Biological Fluids on Smooth Superhydrophobic Surfaces under Electrostatic Actuation

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Journal of Bionic Engineering 2016年第2期13卷 220-234页

作者： Ana Sofia Moita Catarina Laurencia Joana Anastacio Ramos Duarte Miguel Franca Prazeres Antonio Luis Nobre Moreira IN+ - Center for Innovation Technology and Policy Research Instituto Superior Tecnico Universidade de Lisboa Av. Rovisco Pais 1049-001 Lisboa Portugal iBB - Institute for Bioengineering and Biosciences Department of Bioengineering Instituto Superior Tecnico Universidade de Lisboa Av. Rovisco Pais 1049-001 Lisboa Portugal

this study describes the dynamic behaviour of droplets of biological liquids on hydrophobic surfaces under electrostatic actuation, to devise sample handling in lab-on-chip diagnostic tools. Bovine Serum Albumin （BSA） is taken as a representative biomolecule, since it is often used in adsorption studies. Green Fluorescence Protein （GFP） is also considered, given its natural fluorescence. Several effects such as sample concentration and pH are discussed. the results show negligible effects of proteins concentration in electrowetting, although increased concentrations endorse passive adsorption mechanisms, which alter the local wettability of the substrates precluding droplet motion. Bioinspired surfaces promote the largest spreading diameter, which is beneficial for droplet motion. However, surface roughness promotes energy dissipation limiting the receding droplet motion. Hence, the most effective approach is altering the surface chemistry. the coating is applied to a surface with a mean roughness smaller than 20 nm and does not alter significantly the topography, thus leading to the so-called smooth superhydrophobic surface. this coating also reduces passive proteins adsorption, as confirmed by Confocal Microscopy （CM）, which is beneficial for droplet motion. Evaluating absorption spectra of protein solutions evidences an increase in protein concentration ascribed to droplet evaporation as confirmed by theoretical analysis and time resolved infrared visualization.

关键词： bioinspired surfaces biofluids electrostatic actuation hydrophobicity adsorption evaporation

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