264 results found
Bennetts LG, Peter MA, Craster R, 2018, Graded resonator arrays for spatial frequency separation and amplification of water waves, Publisher: CAMBRIDGE UNIV PRESS
Choi W, Shi F, Lowe MJS, et al., 2018, Rough surface reconstruction of real surfaces for numerical simulations of ultrasonic wave scattering, NDT & E INTERNATIONAL, Vol: 98, Pages: 27-36, ISSN: 0963-8695
© 2018 SIAM. Published by SIAM under the terms. This paper explores the concept of near-cloaking in the context of time-dependent heat propagation. We show that after the lapse of a certain threshold time, the boundary measurements for the homogeneous heat equation are close to the cloaked heat problem in a certain Sobolev space norm irrespective of the density-conductivity pair in the cloaked region. A regularized transformation media theory is employed to arrive at our results. Our proof relies on the study of the long time behavior of solutions to the parabolic problems with high contrast in density and conductivity coefficients. It further relies on the study of boundary measurement estimates in the presence of small defects in the context of steady conduction problems. We then present some numerical examples to illustrate our theoretical results.
© 2018, The Author(s). In this paper, we present an asymptotic model describing localised flexural vibrations along a structured ring containing point masses or spring–mass resonators in an elastic plate. The values for the required masses and stiffnesses of resonators are derived in a closed analytical form. It is shown that spring–mass resonators can be tuned to produce a “negative inertia” input, which is used to enhance localisation of waveforms around the structured ring. Theoretical findings are accompanied by numerical simulations, which show exponentially localised and leaky modes for different frequency regimes.
Puvirajesinghe TM, Zhi ZL, Craster RV, et al., 2018, Tailoring drug release rates in hydrogel-based therapeutic delivery applications using graphene oxide, JOURNAL OF THE ROYAL SOCIETY INTERFACE, Vol: 15, ISSN: 1742-5689
Shi F, Lowe MJS, Skelton EA, et al., 2018, A time-domain finite element boundary integral approach for elastic wave scattering, COMPUTATIONAL MECHANICS, Vol: 61, Pages: 471-483, ISSN: 0178-7675
Shin S, Chergui J, Juric D, et al., 2018, A hybrid interface tracking - level set technique for multiphase flow with soluble surfactant, JOURNAL OF COMPUTATIONAL PHYSICS, Vol: 359, Pages: 409-435, ISSN: 0021-9991
Skelton EA, Craster RV, Colombi A, et al., 2018, The multi-physics metawedge: graded arrays on fluid-loaded elastic plates and the mechanical analogues of rainbow trapping and mode conversion, NEW JOURNAL OF PHYSICS, Vol: 20, ISSN: 1367-2630
Smith ER, Theodorakis PE, Craster RV, et al., 2018, Moving Contact Lines: Linking Molecular Dynamics and Continuum-Scale Modeling., Langmuir
Despite decades of research, the modeling of moving contact lines has remained a formidable challenge in fluid dynamics whose resolution will impact numerous industrial, biological, and daily life applications. On the one hand, molecular dynamics (MD) simulation has the ability to provide unique insight into the microscopic details that determine the dynamic behavior of the contact line, which is not possible with either continuum-scale simulations or experiments. On the other hand, continuum-based models provide a link to the macroscopic description of the system. In this Feature Article, we explore the complex range of physical factors, including the presence of surfactants, which governs the contact line motion through MD simulations. We also discuss links between continuum- and molecular-scale modeling and highlight the opportunities for future developments in this area.
Achaoui Y, Antonakakis T, Brule S, et al., 2017, Clamped seismic metamaterials: ultra-low frequency stop bands, NEW JOURNAL OF PHYSICS, Vol: 19, ISSN: 1367-2630
Colombi A, Ageeva V, Smith RJ, et al., 2017, Enhanced sensing and conversion of ultrasonic Rayleigh waves by elastic metasurfaces, SCIENTIFIC REPORTS, Vol: 7, ISSN: 2045-2322
Colombi A, Craster R, Clark M, et al., 2017, Slow waves, elastic rainbow and dynamic anisotropy with a cluster of resonant rods on an elastic halfspace, 2017 11th International Congress on Engineered Material Platforms for Novel Wave Phenomena (METAMATERIALS), Publisher: IEEE, Pages: 409-410
Colombi A, Roux P, Miniaci M, et al., 2017, The role of large scale computing behind the development of seismic (and elastic) metamaterials., 2017 11th International Congress on Engineered Material Platforms for Novel Wave Phenomena (METAMATERIALS), Publisher: IEEE, Pages: 406-408
Colquitt DJ, Colombi A, Craster RV, et al., 2017, Seismic metasurfaces: Sub-wavelength resonators and Rayleigh wave interaction, JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, Vol: 99, Pages: 379-393, ISSN: 0022-5096
Craster R, Guenneau S, Hutridurga H, et al., 2017, Regularized transformation optics for transient heat transfer, 2017 11th International Congress on Engineered Material Platforms for Novel Wave Phenomena (METAMATERIALS), Publisher: IEEE, Pages: 127-129
Dubrovina E, Craster RV, Papageorgiou DT, 2017, Two-layer electrified pressure-driven flow in topographically structured channels, JOURNAL OF FLUID MECHANICS, Vol: 814, Pages: 222-248, ISSN: 0022-1120
Haslinger SG, Movchan NV, Movchan AB, et al., 2017, CONTROLLING FLEXURAL WAVES IN SEMI-INFINITE PLATONIC CRYSTALS WITH RESONATOR-TYPE SCATTERERS, QUARTERLY JOURNAL OF MECHANICS AND APPLIED MATHEMATICS, Vol: 70, Pages: 215-247, ISSN: 0033-5614
Lefebvre G, Antonakakis T, Achaoui Y, et al., 2017, Unveiling extreme anisotropy in elastic structured media, Physical Review Letters, Vol: 118, ISSN: 0031-9007
Periodic structures can be engineered to exhibit unique properties observed at symmetry points, such as zero group velocity, Dirac cones, and saddle points; identifying these and the nature of the associated modes from a direct reading of the dispersion surfaces is not straightforward, especially in three dimensions or at high frequencies when several dispersion surfaces fold back in the Brillouin zone. A recently proposed asymptotic high-frequency homogenization theory is applied to a challenging time-domain experiment with elastic waves in a pinned metallic plate. The prediction of a narrow high-frequency spectral region where the effective medium tensor dramatically switches from positive definite to indefinite is confirmed experimentally; a small frequency shift of the pulse carrier results in two distinct types of highly anisotropic modes. The underlying effective equation mirrors this behavior with a change in form from elliptic to hyperbolic exemplifying the high degree of wave control available and the importance of a simple and effective predictive model.
Maling B, Colquitt DJ, Craster RV, 2017, Dynamic homogenisation of Maxwell's equations with applications to photonic crystals and localised waveforms on gratings, WAVE MOTION, Vol: 69, Pages: 35-49, ISSN: 0165-2125
Maling B, Schnitzer O, Craster RV, 2017, RADIATION FROM STRUCTURED-RING RESONATORS, SIAM JOURNAL ON APPLIED MATHEMATICS, Vol: 77, Pages: 1047-1067, ISSN: 0036-1399
O'Neill J, Selsil Ö, Haslinger SG, et al., 2017, Active cloaking for flexural waves in a pinned kirchhoff plate
O'Neill J, Selsil O, Haslinger SG, et al., 2017, ACTIVE CLOAKING FOR FINITE CLUSTERS OF PINS IN KIRCHHOFF PLATES, SIAM Journal on Applied Mathematics, Vol: 77, Pages: 1115-1135, ISSN: 0036-1399
This paper considers active cloaking of a square array of evenly spaced pins in a Kirchhoff plate in the presence of flexural waves. Active sources, modeled as ideal point sources, are represented by the nonsingular Green's function for the two-dimensional biharmonic operator and have an arbitrary complex amplitude. These sources are distributed exterior to the cluster, and their complex amplitudes are found by solving an algebraic system of equations. This procedure ensures that selected multipole orders of the scattered field are successfully annulled. For frequencies in the zero-frequency stop band, we find that a small number of active sources located on a grid is sufficient for cloaking. For higher frequencies, we achieve efficient cloaking with the active sources positioned on a circle surrounding the cluster. We demonstrate the cloaking efficiency with several numerical illustrations, considering key frequencies from band diagrams and dispersion surfaces for a Kirchhoff plate pinned in a doubly periodic fashion.
Quintanilla FH, Lowe MJS, Craster RV, 2017, The symmetry and coupling properties of solutions in general anisotropic multilayer waveguides, JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, Vol: 141, Pages: 406-418, ISSN: 0001-4966
Sasihithlu K, Pendry JB, Craster RV, 2017, Van der Waals Force Assisted Heat Transfer, Zeitschrift für Naturforschung - Section A Journal of Physical Sciences, Vol: 72, Pages: 181-188, ISSN: 0932-0784
Phonons (collective atomic vibrations in solids) are more effective in transporting heat than photons. This is the reason why the conduction mode of heat transport in nonmetals (mediated by phonons) is dominant compared to the radiation mode of heat transport (mediated by photons). However, since phonons are unable to traverse a vacuum gap (unlike photons), it is commonly believed that two bodies separated by a gap cannot exchange heat via phonons. Recently, a mechanism was proposed [J. B. Pendry, K. Sasihithlu, and R. V. Craster, Phys. Rev. B 94, 075414 (2016)] by which phonons can transport heat across a vacuum gap – through the Van der Waals interaction between two bodies with gap less than the wavelength of light. Such heat transfer mechanisms are highly relevant for heating (and cooling) of nanostructures; the heating of the flying heads in magnetic storage disks is a case in point. Here, the theoretical derivation for modelling phonon transmission is revisited and extended to the case of two bodies made of different materials separated by a vacuum gap. Magnitudes of phonon transmission, and hence the heat transfer, for commonly used materials in the micro- and nano-electromechanical industry are calculated and compared with the calculation of conduction heat transfer through air for small gaps as well as the heat transfer calculation due to photon exchange.
Schnitzer O, Craster RV, 2017, BLOCH WAVES IN AN ARBITRARY TWO-DIMENSIONAL LATTICE OF SUBWAVELENGTH DIRICHLET SCATTERERS, SIAM JOURNAL ON APPLIED MATHEMATICS, Vol: 77, Pages: 2119-2135, ISSN: 0036-1399
Shi F, Lowe M, Craster R, 2017, Diffusely scattered and transmitted elastic waves by random rough solid-solid interfaces using an elastodynamic Kirchhoff approximation, PHYSICAL REVIEW B, Vol: 95, ISSN: 2469-9950
Theodorakis PE, Muller EA, Craster RV, et al., 2017, Physical insights into the blood-brain barrier translocation mechanisms, Physical Biology, Vol: 14, ISSN: 1478-3975
The number of individuals suffering from diseases of the central nervous system (CNS) is growing with an aging population. While candidate drugs for many of these diseases are available, most of these pharmaceutical agents cannot reach the brain rendering most of the drug therapies that target the CNS inefficient. The reason is the blood–brain barrier (BBB), a complex and dynamic interface that controls the influx and efflux of substances through a number of different translocation mechanisms. Here, we present these mechanisms providing, also, the necessary background related to the morphology and various characteristics of the BBB. Moreover, we discuss various numerical and simulation approaches used to study the BBB, and possible future directions based on multi-scale methods. We anticipate that this review will motivate multi-disciplinary research on the BBB aiming at the design of effective drug therapies.
Uppal AS, Craster RV, Matar OK, 2017, Dynamics of spreading thixotropic droplets, JOURNAL OF NON-NEWTONIAN FLUID MECHANICS, Vol: 240, Pages: 1-14, ISSN: 0377-0257
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