1,720,992 research outputs found
Numerical Modeling for the Analysis of Plasmon Oscillations in Metallic Nanoparticles
No full textThis work is focused on the numerical modeling, in the frequency domain, of the plasmon oscillations induced in metallic nanoparticles of arbitrary shapes by an external electromagnetic field. The electromagnetic response of the nanoparticles is modeled through a proper frequency dependent dielectric constant. The electromagnetic field scattered by the nanoparticles is evaluated by a full-wave integral formulation where the unknown is the induced current density. The integral equations are solved numerically by the finite element method, by decomposing the current density in the solenoidal and non-solenoidal components and using the edge-elements. Particular care has been devoted to treat, within such numerical method, arbitrary topologies. A detailed analysis is carried out to understand the limit of applicability of the electro-quasi-stationary model and a characteristic length lm of the metal, together with the wavelength of the electromagnetic field, are found to provide a constraint on the maximum nanoparticle size that can be treated within such approximation
Simulated Inspection of Wavy Planar Pieces with an Eddy Current Technique: Application Cases of the Simposium Project
No full textSIMPOSIUM is a research collaborative project funded in the Seventh Framework Programme of the European Commission. SIMPOSIUM gathers industrial end-users in various fields (aeronautics, automotive, energy, steel), software solutions providers, academic and RTOs, aiming at providing interoperable simulation tools for non destructive evaluation and materials characterization usable at any stage of the product lifecycle (from conception to manufacturing and maintenance). Those simulation codes are focused on electromagnetic and ultrasonic techniques, widely used both for defect detection and materials characterization, and include numerical (Finite Elements Method, Finite Differences in Time Domain, Finite Integration Technique), analytical or semi-analytical (pencil techniques for beam propagation, scattering coefficients) and hybrid formulations (coupling method based on combination of semi-analytical and numerical techniques to perform numerical techniques in very limited domains while handling large application cases) to deal with complex geometries and material properties (hysteretic materials, grain scattering...) . Those simulation tools have been exploited to simulate 11 application cases provided by the industrial partners and cover a large range of industrial fields: evaluation of complex structures (ultrasonic evaluation of composites, structural noise for steel application), complex geometries (eddy current inspections of boreholes and uneven surfaces), complex flaws (solid inclusions, stress corrosion cracks...), materials characterization of complex parts with varying and hysteretical properties(evaluation of forged shafts, electrical steel, bearing parts). Developments carried out within SIMPOSIUM are briefly presented and some experimental and simulated results among the industrial application cases are illustrated which show the benefits of non destructive evaluation and materials characterization simulation for conceiving and optimizing methods, interpreting results, for improved manufacturing processes and evaluation of semi-final or final products. The research leading to these results has received funding from the European Community’s Seventh Framework Program (FP7/2007-2013) under Grant Agreement No.285549: SIMPOSIUM project
Three-Dimensional Computation of Magnetic Fields in Hysteretic Media With Time-Periodic Sources
No full textThe Simposium Project: Numerical Simulation of Rotating Probe for Eddy Current Testing of Metallic Bore Holes
No full textSurface integral formulations for the design of plasmonic nanostructures
No full textNumerical formulations based on surface integral equations (SIEs) provide an accurate and efficient framework for the solution of the electromagnetic scattering problem by three-dimensional plasmonic nanostructures in the frequency domain. In this paper, we present a unified description of SIE formulations with both singular and nonsingular kernel and we study their accuracy in solving the scattering problem by metallic nanoparticles with spherical and nonspherical shape. In fact, the accuracy of the numerical solution, especially in the near zone, is of great importance in the analysis and design of plasmonic nanostructures, whose operation critically depends on the manipulation of electromagnetic hot spots. Four formulation types are considered: the N-combined region integral equations, the T-combined region integral equations, the combined field integral equations and the null field integral equations. A detailed comparison between their numerical solutions obtained for several nanoparticle shapes is performed by examining convergence rate and accuracy in both the far and near zone of the scatterer as a function of the number of degrees of freedom. A rigorous analysis of SIE formulations and their limitations can have a high impact on the engineering of numerous nano-scale optical devices such as plasmon-enhanced light emitters, biosensors, photodetectors, and nanoantennas
The moisture issue affecting the historical buildings in the Alps region
No full textThis paper deals with the climate-related risks associated with the conservation of historical buildings in the Alps region. The aim of the paper is to build the microclimatic curve of the T°C (temperature) and RH% (Relative Humidity) daily average in different locations (at a similar altitude in the same valleys), compare them against each other and also to the microclimatic curves obtained in the Po valley [3]. The case studies in Valtellina and Val Poschiavo Valley were identified to monitor and analyse the thermo-hydrometrical variation of air T°C and RH%, followed by a thorough assessment and documentation of the buildings (state of conservation, materials and building techniques, presence of rising damp and intervention for its reduction). The analysis is composed of visual inspections, microclimate monitoring using psychrometry and monitoring probes, Infra-Red (IR) Thermography. The result of the study explores the correlation with factors pertaining to building materials and construction techniques, the climatic and microclimatic characteristics. Curves describing the daily mean values of T°C and RH% for a period of one year have been defined by the authors for each of the historical buildings
A fast procedure for the assessment of historical floor timber beams in presence of pictorial decoration
No full textWith the aim of defining a procedure for the rapid and easily reproducible investigation of timber structures, such as historical wooden floors with pictorial decorations, it is intended to present the methodology applied during a test campaign on floor timbers, with some limitations on the investigation. The floors analysed belong to a Baroque aristocratic palace open to the public and used as a museum: the space and time available for the investigation were therefore very limited. Diagnostic instrumental investigations (ambient humidity and resistance drilling) were carried out at selected points, following visual observations of the state of preservation of the wood and paint, wood species identification, construction technique, type of support and geometry, possibly deformed and/or damaged (maximum deflection along the profile), in order to minimise interaction with the historic timberwork. It was possible to take a sample of material from the damaged areas to check for the possible presence of pathogenic micro-organisms.
The intention is to be able to calibrate an operational method that allows the comparison of as many similar structures as possible, knowing that, for various reasons, it will not always be possible to carry out exhaustive and extensive surveys on all of them, as would be preferable. However, these investigations must be able to provide sufficient data for structural evaluation, but also for their correct maintenance and conservation, both within the same building and in similar timber structure
The microclimates unbalance of subterrain historic spaces in Italy
No full textOne of the primary challenges in conserving a historic site or building in use is determining the optimal threshold for safe and comfortable usage, as well as quantifying and qualifying the risks associated with this usage. To establish a standardised monitoring procedure that effectively collects the necessary information and data, it is crucial to have robust data management procedures focused on capturing essential information for maintenance planning. Additionally, gathering information to support information exchange among key stakeholders involved in the conservation of historical buildings and surfaces, particularly regarding microclimate evaluation and management, is imperative.
To achieve these goals, the paper presents microclimatic curves obtained from monitoring buildings in Milan and Sardinia (Cagliari), two regions with distinct geographical and climatic characteristics. The analysis of these curves allows researchers to identify similarities between different locations, similarities within the same location, and the range of days where exterior climate conditions are more stable. This stability enables frequent exchange between the interior and exterior with minimal risk to the conservation of historical materials. These findings are particularly important when a new usage requires the placement, substitution, resetting, or implementation of HVAC systems, including the use of dehumidifiers, to monitor and reduce rising damp [1-2]
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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