69 research outputs found
Plasmon Resonances in Nanoparticles, Their Applications to Magnetics and Relation to the Riemann Hypothesis
The review of the mathematical treatment of plasmon resonances as an
eigenvalue problem for specific boundary integral equations is presented and
general properties of plasmon spectrum are outlined. Promising applications of
plasmon resonances to magnetics are described. Interesting relation of
eigenvalue treatment of plasmon resonances to the Riemann hypothesis is
discussed.Comment: 10 pages; misprints corrected, some explanations added. Physica B
(2011
Improved Crank-Nicolson method for modelling diffusion of electromagnetic fields in hysteretic soft magnetic laminations
Mathematical analysis of plasmonic nanoparticles: the scalar case
Localized surface plasmons are charge density oscillations confined to metallic nanoparticles. Excitation of localized surface plasmons by an electromagnetic field at an incident wavelength where resonance occurs results in a strong light scattering and an enhancement of the local electromagnetic fields. This paper is devoted to the mathematical modeling of plasmonic nanoparticles. Its aim is threefold: (i) to mathematically define the notion of plasmonic resonance and to analyze the shift and broadening of the plasmon resonance with changes in size and shape of the nanoparticles; (ii) to study the scattering and absorption enhancements by plasmon resonant nanoparticles and express them in terms of the polarization tensor of the nanoparticle. Optimal bounds on the enhancement factors are also derived; (iii) to show, by analyzing the imaginary part of the Green function, that one can achieve super-resolution and super-focusing using plasmonic nanoparticles. For simplicity, the Helmholtz equation is used to model electromagnetic wave propagation
Meshfree finite differences for vector Poisson and pressure Poisson equations with electric boundary conditions
We demonstrate how meshfree finite difference methods can be applied to solve
vector Poisson problems with electric boundary conditions. In these, the
tangential velocity and the incompressibility of the vector field are
prescribed at the boundary. Even on irregular domains with only convex corners,
canonical nodal-based finite elements may converge to the wrong solution due to
a version of the Babuska paradox. In turn, straightforward meshfree finite
differences converge to the true solution, and even high-order accuracy can be
achieved in a simple fashion. The methodology is then extended to a specific
pressure Poisson equation reformulation of the Navier-Stokes equations that
possesses the same type of boundary conditions. The resulting numerical
approach is second order accurate and allows for a simple switching between an
explicit and implicit treatment of the viscosity terms.Comment: 19 pages, 7 figure
Nondestructive monitoring of ageing of Alkali resistant Glass fiber reinforced cement (GRC)
Glass fiber reinforced cement (GRC) is a composite material made of portland cement mortar and alkali resistant (AR) fibers. AR fibers are added to portland cement to give the material additional flexural strength and toughness. However, ageing deteriorates the fibers and as a result the improvement in the mechanical properties resulted from the fiber addition disappears as the structure becomes
old. The aim of this paper is monitoring GRC ageing by nondestructive evaluation (NDE) techniques. Two different NDE techniques (1) nonlinear impact resonant acoustic spectroscopy analysis and (2) propagating ultrasonic guided waves are used for this purpose. Both techniques revealed a reduction of the nonlinear behavior in the GRC material with ageing. Specimens are then loaded to failure to obtain their strength and stiffness. Compared to the un-aged specimens,
the aged specimens are found to exhibit more linear behavior, have more stiffness but less toughness. Finally, undisturbed fragments on the fracture surface from mechanical tests are inspected under the electron microscope, to understand the fundamental mechanisms that cause the change in the GRC behavior with ageing.The authors want to acknowledge the financial support of the Ministerio de Ciencia e Innovacion MICINN, Spain, and FEDER funding (Ondacem Project: BIA 2010-19933) and BES-2011-044624. Also thanks to PAID-02-11 Program from Universitat Politecnica de Valencia.Eiras Fernández, JN.; Kundu, T.; Bonilla Salvador, MM.; Paya Bernabeu, JJ. (2013). Nondestructive monitoring of ageing of Alkali resistant Glass fiber reinforced cement (GRC). Journal of Nondestructive Evaluation - NDT and E International. 32:300-314. https://doi.org/10.1007/s10921-013-0183-yS30031432Bentur, A., Fibre, M.S.: Reinforced Cementitious Composites, 2nd edn. 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Academic Press, New York (2003)Van Den Abeele, K.E.A., Carmeliet, J., Ten Cate, J.A., Johnson, P.A.: Nonlinear elastic wave spectroscopy (NEWS) techniques to discern material damage, part II: single-mode nonlinear resonance acoustic spectroscopy. Res. Nondestruct. Eval. 12(1), 31–42 (2000)Chen, J., Jayapalan, A.R., Kim, J.Y., Kurtis, K.E., Jacobs, L.J.: Rapid evaluation of alkali–silica reactivity of aggregates using a nonlinear resonance spectroscopy technique. Cem. Concr. Res. 40(6), 914–923 (2010)Leśnicki, K.J., Kim, J.Y., Kurtis, K.E., Jacobs, L.J.: Characterization of ASR damage in concrete using nonlinear impact resonance acoustic spectroscopy technique. Nondestruct. Test. Eval. Int. 44(8), 721–727 (2011)Bouchaala, F., Payan, C., Garnier, V., Balayssac, J.P.: Carbonation assessment in concrete by nonlinear ultrasound. Cem. Concr. Res. 41(5), 557–559 (2011)Eiras, J.N., Popovics, J.S., Borrachero, M.V., Monzó, J., Payá, J.: Nonlinear impact resonant acoustic spectroscopy to discern mechanical damage in cement based materials. In: 15th International Conference on Experimental Mechanics, Porto, Portugal (2012)Kundu, T.: Ultrasonic Nondestructive Evaluation: Engineering and Biological Material Characterization. CRC Press, Boca Raton (2004)Kundu, T.: Ultrasonic and Electromagnetic NDE for Structure and Material Characterization—Engineering and Biomedical Applications. CRC Press, Boca Raton (2012)Dutta, D., Sohn, H., Harries, K.A., Rizzo, P.: A nonlinear acoustic technique for crack detection in metallic structures. Struct. Health Monit. 8(3), 251–262 (2009)Aymerich, F., Staszewski, W.J.: Impact damage detection in composite laminates using nonlinear acoustics. Composites, Part A, Appl. Sci. Manuf. 41(9), 1084–1092 (2010)EN 1170-1:1998. Precast concrete products. Test method for glass-fibre reinforced cement. 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