Topic

# Aspect ratio

About: Aspect ratio is a research topic. Over the lifetime, 5152 publications have been published within this topic receiving 60682 citations.

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TL;DR: Using a seed-mediated growth approach in a rod-like micellar media, silver nanorods of varied aspect ratio were prepared from nearly spherical 4 nm silver nanoparticles as mentioned in this paper.

1,127 citations

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TL;DR: In this article, the influence of aspect ratio α, from zero to infinity, on the effective elastic moduli of a transversely isotropic composite was examined, where the reinforcing inclusions, which could be flakes or short fibers, are assumed to be spheroidal and unidirectionally aligned.

Abstract: This paper examines the influence of aspect ratio α, from zero to infinity, on the effective elastic moduli of a transversely isotropic composite. The reinforcing inclusions, which could be flakes or short fibers, are assumed to be spheroidal and unidirectionally aligned. Of the five independent elastic constants, the longitudinal Young's modulus E11 and in-plane shear modulus μ12 appear to increase with increasing aspect ratio, while the transverse Young's modulus E22, out-plane shear modulus μ23, and plane-strain bulk modulus K23, generally decrease. It is further noted that E11 is more sensitive to α when α > 1 but the others are more so when α < 1. The present analysis was carried out by the combination of Eshelby's and Mori-Tanaka's theories of inclusions.

636 citations

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TL;DR: There exist two competing key factors: a weighting factor assigned to the shape parameter and the dielectric function of the metal particle, which control the relative enhancement in the scattering and absorption as well as the linearity of resonance wavelength with regard to the aspect ratio.

Abstract: The current intense interest in the properties of plasmonic nanostructures for their applications in chemical and biochemical sensors, medical diagnostics and therapeutics, and biological imaging is fundamentally based on their enhanced optical absorption and scattering properties. In this study, the optical extinction, absorption, and scattering efficiencies were calculated as a function of shape definition, aspect ratio, surrounding medium, and material selection. The discrete dipole approximation method was used, which is known to be a very useful and versatile computational tool for particles with any arbitrary shape. Relative contribution of scattering to the total extinction for the longitudinal mode was found to be significantly dependent on the aspect ratio of the nanorod in a somewhat complex manner, different from a typical linear relationship for the resonance wavelength. A slight elongation of Au nanosphere gives rise to a drastic increase in the relative scattering efficiency, which eventually reaches a maximum and begins to decrease with further increase in the aspect ratio. This is ascribed to the increasing absorptive contribution from the larger imaginary dielectric function of the metal particle in the longer wavelength region where the red-shifted excitation of the longitudinal resonance mode occurs. For transverse mode exhibiting the blue-shift in the resonance peak, on the contrary, the absorption efficiency is relatively enhanced compared to the scattering efficiency with increasing aspect ratio. This is thought to result from the dominant effect of the interband transition present in this wavelength region. Besides the dependence of plasmonic characteristics on the aspect ratio of nanorod, the DDA results for a small change of the end-cap shape and the index of the surrounding medium lead us to conclude that there exist two competing key factors: a weighting factor assigned to the shape parameter and the dielectric function of the metal particle, which control the relative enhancement in the scattering and absorption as well as the linearity of resonance wavelength with regard to the aspect ratio.

594 citations

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TL;DR: In this article, the authors considered the problem of transient natural convection in a cavity of aspect ratio A [les ] 1 with differentially heated end walls and used scale analysis to show that a number of initial flow types are possible, collapsing ultimately onto two basic types of steady flow, determined by the relative value of the non-dimensional parameters describing the flow.

Abstract: The problem of transient natural convection in a cavity of aspect ratio A [les ] 1 with differentially heated end walls is considered. Scale analysis is used to show that a number of initial flow types are possible, collapsing ultimately onto two basic types of steady flow, determined by the relative value of the non-dimensional parameters describing the flow. A number of numerical solutions which encompass both flow types are obtained, and their relationship to the scale analysis is discussed.

532 citations

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TL;DR: In this article, a wide range of pore shapes, including oblate spheroids, tubes, cracks, and an equilibrium geometry controlled by a dihedral angle, are studied.

Abstract: Seismic wave velocities of melt or aqueous fluid containing systems are studied over a wide range of pore shapes, including oblate spheroids, tubes, cracks, and an equilibrium geometry controlled by a dihedral angle. The relative role of liquid compressibility and pore geometry on the V P /V S velocity ratio is clarified. The result clearly indicates that P and S velocity structures determined by seismic tomography can be used to verify whether interfacial energy-controlled melt or fluid geometry (equilibrium geometry) is achieved. Relationships between the diverse models are clearly established by relating each model to the oblate spheroid model in terms of the equivalent aspect ratio. As a function of the aspect ratio, a significant effect of pore geometry on d In V S /d In V P , the ratio of the fractional changes in V S and V P , is shown. Equilibrium geometry of the partially molten rocks, characterized by a dihedral angle of 20°-40°, corresponds to an aspect ratio of 0.1-0.15. The value of d In V S /d In V P expected for the texturally equilibrated partially molten rocks is shown to be 1-1.5, which is much smaller than that expected for cracks and dikes with an aspect ratio of <10 -2 -10 -3 . In the upper mantle low-velocity regions the seismologically obtained value of d In V S /d In V P is within this range beneath the Bolivian Andes (1.1-1.4) but is as high as 2 beneath Iceland (1.7-2.3) and beneath northeastern Japan (2.0). The former region can be regarded as a region where equilibrium geometry is achieved, and the latter regions can be regarded as regions where dikes and veins typical of a system far from the textural equilibrium dominate.

495 citations