Effect Of Size Parameters Research Articles

Enhanced absorption based on gap-plasmon resonance and Fabry–Perot resonance in a refractory metasurface

In this paper, we report a polarization-independent broadband metasurface perfect absorber based on tunable gap magnetic resonance and Fabry–Perot (FP) resonance in a structure with consecutive size variation. By using the finite-difference time-domain method, the effects of size parameters are investigated. Due to the coexistence of the FP-like resonance and gap magnetic resonance, the near-unit absorption reaches as high as 99.46% with nanocone morphology throughout the visible-to-near infrared regime where most solar radiation is located. The structure raised in this paper is less complex and more thermally stable due to abandoning the spacer layer in traditional tri-layer structures. This method can be developed for other refractory materials and has great potential in solar energy related optoelectronics applications.

Optical Properties of Porous Alumina Ceramics with Micron Open Cells

Porous ceramic material is widely used in a great deal of fields. In this work, porous alumina ceramics with micron open cells are modeled by applying the inverse opal structure. The considered porous alumina ceramics are periodic with different size parameters. The diameters of spherical pores are 200, 400, 600, and 800 nm, while the ratios of height to diameter range from 0.1 to 0.9. The absorptivity, transmissivity, and reflectivity for the wavelength range from 0.2 to 2 μm are calculated using the finite difference time domain (FDTD) method. Then the effects of size parameters and incident angle on the optical properties are discussed. The results show that the absorptivity is usually very small. For the transmissivity, a wide dip in the transmission spectrum appears when the diameter and height exceed the critical values, and a red shift of the transmission spectrum's wide dip with increasing height is observed. When the incident wavelength is longer than the critical wavelength, the spectral transmissivities of porous ceramics with a certain diameter reach a stable domain. Moreover, the red shift of the wide dip, the critical incident wavelength, and the critical ratio of height to diameter are visibly affected by the size parameters and the incident angle.

Angular scattering of an Airy beam light sheet by a concentric sphere

Angular distribution of scattered light by a particle reveals information of its topology and refractive index, which has been proved to be an effective method to identify and characterize the particle. In this paper, numerical study on angular scattering of a polarized one-dimensional Airy beam light sheet by concentric spheres is presented. Plane-wave spectrum method is adopted to simplify the problem into classic Mie scattering problem, which significantly improves computational efficiency. The effects of size parameters, refractive index and position of concentric spheres and Airy beam radius on the angular distribution of scattered light are investigated. This paper provides theoretical results for light scattering measurement where Airy beam light sheet is employed for reducing effects of multiple scattering.

Torsional Vibration and Static Analysis of the Cylindrical Shell Based on Strain Gradient Theory

In this paper, the free vibration and torsional static analysis of cylindrical shell are developed using modified strain gradient theory. In doing this, the governing equations and classical and non-classical boundary conditions are derived using Hamilton’s principle. After obtaining equations governing the problem, the differential quadrature method is used to discretize the equations of motion of the vibration problem and to examine the single-walled carbon nanotube (SWCNT) with two clamped-free and clamped–clamped supports as a special application of this formulation. Also, torsional static analysis is carried out for the clamped–clamped SWCNT. Results reveal that SWCNT rigidity in strain gradient theory is higher than that in couple stress theory or the classical theory, which leads to increase in torsional frequencies and decrease in torsion of SWCNT. Results also demonstrate that the effect of size parameter and SWCNT torsion in different lengths and diameters is considerable.

FREE VIBRATION OF MICROTUBULES AS ELASTIC SHELL MODEL BASED ON MODIFIED COUPLE STRESS THEORY

In this study, first, the thin cylindrical shell theory was derived from the modified couple stress theory and, afterwards, the vibration of protein microtubules (MTs) was investigated using the developed model. In order to model protein MTs more precisely, the cylindrical micro-shell model was used. Also, to take account of small size effects, equations of motion were obtained on the basis of the modified couple stress theory. For this purpose, first, using Hamilton's principle, vibration equations of cylindrical shell with boundary conditions were derived from the modified couple stress theory. Finally, the effects of size parameters, MT dimensions, and the medium surrounding on the axial and circumferential vibration frequency of the MT were examined. It should be noted that the results obtained from the cylindrical micro-shell model, unlike those from the beam model, have lower dependency on MT length, but they have extreme dependency on MT thickness and radius. In the end, it is worth noting that the model developed in this study can predict experimental results with greater precision compared to classic models. In other words, this model narrows the gap existing between experimental results and previous models and theories.

Analysis of conical shells in the framework of coupled stresses theory

In this paper, the thin conical shell model is developed by using the modified couple stress theory. This non-classical formulation can incorporate size effects in nano/micro scales. For this purpose, the thin shell model is used along with the modified couple stress theory, and the equations of motion with partial differentials and classical and non-classical boundary conditions are derived by using Hamilton’s principle. Finally, the free vibrations of the single-walled carbon nanocone (SWCNC) are examined as a special case. The SWCNC is modeled as simply supported, and the Galerkin method is used to solve the vibrational problem. Results of the new formulation are compared to the classical theory. The results show that nanoshell rigidity is greater in the modified couple stress theory than in the classical theory, which leads to an increase in the natural frequencies. Also, the effect of size parameter on the vibration frequency of SWCNC in different lengths and apex angles is examined.

Numerical Simulation and Analysis of Low Hysteresis Brush Seals

To better understand the bristle behavior and leakage performance in brush seals, a Computational Fluid Dynamics (CFD) model has been developed, in which the brush is treated as an anisotropic porous region with nonlinear resistance coefficients. With the calculated pressure distribution and the cantilever beam theory, aerodynamic and contact forces on bristles are calculated utilizing the Finite Element Method; and bristle deflections in the axial direction and in the orthogonal plane are obtained. Subsequently their influences on friction force and torque are evaluated. Computed different kinds of low hysteresis brush seals, discuss the effect of size parameters of front plate and back plate on low hysteresis brush seals.