A SCALE-BASED MODEL OF REFLECTIVITY

Fractals ◽  
1994 ◽  
Vol 02 (03) ◽  
pp. 413-416 ◽  
Author(s):  
E. MICHAEL SHIPULSKI ◽  
CHRISTOPHER A. BROWN
Keyword(s):  
Computer Simulation ◽  
Patch Size ◽  
Specular Reflection ◽  
Incident Angle ◽  
Incident Light ◽  
Design Evaluation ◽  
Patch Area ◽  
Interaction Models ◽  
Specular Reflectance ◽  
Reflectance Measurements

A computer simulation is described that models reflectivity as a set of discrete interactions, represented by perfectly reflecting, triangular mirrors fit to the surface using the patchwork method.1 The model is based on a premise that topographically dependent phenomena, such as reflectivity, interact with surfaces over certain scales and that these interaction scales can be used to characterize the interactions for use in the design evaluation of reflective topographies. The simulation is performed on a reflective topography and the results are discussed. Results from the simulation, plots of degree of specular reflection versus patch area, or scale, show that modeling the surface as a collection of mirrors of decreasing size results in less light reflected in the specular direction, or more scattering. Increased scattering from a reduction in patch size, or size of the interaction, models the increased scattering due to a reduction in wavelength of the incident light and reduced scattering due to an increase in incident angle, both shown experimentally in specular reflectance measurements.

Versatile thin layer spectroelectrochemical cell employing specular reflectance

1987 ◽  
Vol 65 (5) ◽  
pp. 919-923 ◽  
Author(s):  
A. Scott Hinman ◽  
Brad J. Pavelich
Keyword(s):  
Thin Layer ◽  
Specular Reflection ◽  
Incident Light ◽  
Tetrabutylammonium Perchlorate ◽  
Specular Reflectance ◽  
Advantages And Disadvantages ◽  
Ftir Characterization ◽  
Sandwich Type

A versatile thin layer spectroelectrochemical cell employing specular reflection of the incident light beam from the electrode surface is described. Its application to in-situ uv–vis and FTIR characterization of the products of electrochemical reactions and to thin layer voltammetry and coulometry as well as conventional cyclic voltammetry is demonstrated for the oxidation of tetraphenylporphinatozinc in dichloroethane/tetrabutylammonium perchlorate solution. The advantages and disadvantages of this type of cell as compared to more conventional sandwich type optically transparent thin layer electrodes are discussed.

scholarly journals Strong Modulations of Optical Reflectance in Tapered Core–Shell Nanowires

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3572 ◽  
Author(s):  
Francesco Floris ◽  
Lucia Fornasari ◽  
Vittorio Bellani ◽  
Andrea Marini ◽  
Francesco Banfi ◽  
...  
Keyword(s):  
Incident Angle ◽  
Core Shell ◽  
Specular Reflectance ◽  
Sensing Applications ◽  
Reflected Light ◽  
Geometrical Features ◽  
Wide Range ◽  
Vertically Aligned ◽  
Reflectance Measurements ◽  
Shell Nanowires

Random assemblies of vertically aligned core–shell GaAs–AlGaAs nanowires displayed an optical response dominated by strong oscillations of the reflected light as a function of the incident angle. In particular, angle-resolved specular reflectance measurements showed the occurrence of periodic modulations in the polarization-resolved spectra of reflected light for a surprisingly wide range of incident angles. Numerical simulations allowed for identifying the geometrical features of the core–shell nanowires leading to the observed oscillatory effects in terms of core and shell thickness as well as the tapering of the nanostructure. The present results indicate that randomly displaced ensembles of nanoscale heterostructures made of III–V semiconductors can operate as optical metamirrors, with potential for sensing applications.

Angular Color Prediction Model for Anisotropic Halftone Prints on a Metallic Substrate

2019 ◽  
Vol 2019 (1) ◽  
pp. 159-169
Author(s):  
P. Pjanic ◽  
L. Yang ◽  
A. Teleman ◽  
R. D. Hersch
Keyword(s):  
Prediction Model ◽  
Rotation Angle ◽  
Color Change ◽  
Specular Reflection ◽  
Incident Angle ◽  
Incident Light ◽  
Plastic Layer ◽  
Dot Gain ◽  
Yellow Line ◽  
Color Prediction

Under specular reflection, non-isotropic halftones such as line halftones printed on an ink-receiving plastic layer superposed with a metallic layer change their colors upon in-plane rotation of the print. This color change is due to the orientation-dependent optical dot gain of the halftone. A strong dot gain occurs when the incident light is perpendicular to the halftone line structure. A color prediction model is proposed which predicts under specular reflection the color of cyan, magenta and yellow line halftones as a function of the azimuthal rotation angle, the incident angle and the line frequency. The model is calibrated by measuring 17 reflectances at the (25° : 25°) measurement geometry, with the incident light parallel to the halftone lines. The model has been tested for several azimuthal rotation and incident viewing angles, each time for 125 different cyan, magenta and yellow ink surface coverages. The obtained prediction accuracies are between ΔE94 = 3.5 and ΔE94 = 7.

Forensic applications of IR infrared microscopic internal reflection spectroscopy

1992 ◽  
Vol 50 (2) ◽  
pp. 1528-1529
Author(s):  
Edward G. Bartick ◽  
John A. Reffner
Keyword(s):  
Specular Reflection ◽  
Forensic Analysis ◽  
Attenuated Total Reflection ◽  
Internal Reflection ◽  
Standard Size ◽  
Ir Microscopy ◽  
Ir Analysis ◽  
Plastic Explosives ◽  
Internal Reflection Spectroscopy ◽  
Reflectance Measurements

Since the introduction of commercial Fourier transform infrared (FTIR) microscopic systems in 1983, IR microscopy has developed as an important analytical tool in research, industry and forensic analysis. Because of the frequent encounter of small quantities of physical evidence found at crime scenes, spectroscopic IR microscopes have proven particularly valuable for forensic applications. Transmittance and reflectance measurements have proven very useful. Reflection-absorption, specular reflection, and diffuse reflection have all been applied. However, it has been only very recently that an internal reflection (IRS) objective has been commercially introduced.The IRS method, also known as attenuated total reflection (ATR), has proven very useful for IR analysis of standard size samples. The method has been applied to adhesive tapes, plastic explosives, and general applications in the analysis of opaque materials found as evidence. The small quantities or uncontaminated areas of specimens frequently found requiring forensic analysis will often be directly applicable to microscopic IRS analysis.

Heat/mass transport in shear flow over a heterogeneous surface with first-order surface-reactive domains

2015 ◽  
Vol 782 ◽  
pp. 260-299 ◽  
Author(s):  
Preyas N. Shah ◽  
Eric S. G. Shaqfeh
Keyword(s):  
Mass Transfer ◽  
Shear Rate ◽  
Shear Flow ◽  
Reaction Rate ◽  
Patch Size ◽  
Patch Area ◽  
First Order ◽  
Effective Boundary ◽  
Order Surface ◽  
Slip Distance

Surfaces that include heterogeneous mass transfer at the microscale are ubiquitous in nature and engineering. Many such media are modelled via an effective surface reaction rate or mass transfer coefficient employing the conventional ansatz of kinetically limited transport at the microscale. However, this assumption is not always valid, particularly when there is strong flow. We are interested in modelling reactive and/or porous surfaces that occur in systems where the effective Damköhler number at the microscale can be $O(1)$ and the local Péclet number may be large. In order to expand the range of the effective mass transfer surface coefficient, we study transport from a uniform bath of species in an unbounded shear flow over a flat surface. This surface has a heterogeneous distribution of first-order surface-reactive circular patches (or pores). To understand the physics at the length scale of the patch size, we first analyse the flux to a single reactive patch. We use both analytic and boundary element simulations for this purpose. The shear flow induces a 3-D concentration wake structure downstream of the patch. When two patches are aligned in the shear direction, the wakes interact to reduce the per patch flux compared with the single-patch case. Having determined the length scale of the interaction between two patches, we study the transport to a periodic and disordered distribution of patches again using analytic and boundary integral techniques. We obtain, up to non-dilute patch area fraction, an effective boundary condition for the transport to the patches that depends on the local mass transfer coefficient (or reaction rate) and shear rate. We demonstrate that this boundary condition replaces the details of the heterogeneous surfaces at a wall-normal effective slip distance also determined for non-dilute patch area fractions. The slip distance again depends on the shear rate, and weakly on the reaction rate, and scales with the patch size. These effective boundary conditions can be used directly in large-scale physics simulations as long as the local shear rate, reaction rate and patch area fraction are known.

Optical Analysis of Hole Patterned Ag Nanoparticle Structure

2021 ◽  
Vol 21 (8) ◽  
pp. 4192-4199
Author(s):  
Hyun-Ji Jeon ◽  
Ji-Yeon Kim ◽  
Jinnil Choi
Keyword(s):  
Metal Nanoparticles ◽  
Optical Transmission ◽  
Incident Angle ◽  
Incident Light ◽  
Localized Surface Plasmon ◽  
Optical Analysis ◽  
Optical Noise ◽  
Hole Configuration ◽  
Nanoparticle Structure ◽  
Sub Wavelength

A structure with periodic sub-wavelength nanohole patterns interacts with incident light and causes extraordinary optical transmission (EOT), with metal nanoparticles leading to localized surface plasmon resonance (LSPR) phenomena. To explore the effects of metal nanoparticles (NPs), optical analysis is performed for metal NP layers with periodic hole patterns. Investigation of Ag NP arrangements and comparisons with metal film structures are presented. Ag NP structures with different hole configuration are explored. Also, the effects of increasing light incident angle are investigated for metal NP structures where EOT peak at 460 nm wavelength is observed. Moreover, electric field distributions at each transmittance peak wavelengths and optical noise are analyzed. As a result, optical characteristics of metal NP structures are obtained and differences in resonance at each wavelength are highlighted.

Microphotometry of Underwater Shadowing by a Moss from a Niagara Escarpment Waterfall

2010 ◽  
Vol 17 (1) ◽  
pp. 125-131
Author(s):  
Howard J. Swatland
Keyword(s):  
Point Source ◽  
Single Cells ◽  
Incident Light ◽  
Polarized Light ◽  
Specular Reflectance ◽  
Light Spectra ◽  
Niagara Escarpment ◽  
Single Leaf ◽  
Diffuse Illumination ◽  
Air Water Interface

AbstractMicroscope and fiber-optic spectrophotometry of transmittance and backscattering both showed moss leaves to be capable of casting strong shadows, with a single leaf blocking approximately 90% of incident light from a point source. In leaves with only one layer of cells, the transmittance through the cytoplasm of single cells was similar to that for whole leaves. Analysis of cell wall birefringence by polarized-light interferometry indicated that cell walls might normally scatter rather than transmit light. Spectra transmitted through, or backscattered from, the upper green layers of moss were dominated by selective absorbance from chlorophyll, but there was also evidence of wavelength-dependent scattering, as detected in the lower layers of brown, dead moss. Specular reflectance from moss leaves was detected by polarimetry and may have contributed to the relatively high macroscopic transmittance of stationary moss in water. Shadowing by moss leaves was confirmed by dynamic measurements of mosses in turbulent water without bubbles. Flicker patterns from leaves were superimposed on the underwater flicker pattern created at the air-water interface, thus flecks of light were reduced in intensity, increased in frequency, and decreased in duration. This was detected with both point source and diffuse illumination of samples.

INVERSE PATCHWORK TRANSFORM

Fractals ◽  
1994 ◽  
Vol 02 (03) ◽  
pp. 429-431
Author(s):  
P. D. CHARLES ◽  
C. A. BROWN ◽  
W. A. JOHNSEN
Keyword(s):  
Surface Topography ◽  
Surface Area ◽  
Patch Size ◽  
Basis Functions ◽  
Patch Area ◽  
Mathematical Basis ◽  
Surface Design ◽  
Surface Data ◽  
Design And Manufacture

The patchwork method uses triangular patches to estimate surface area as a function of patch size. The patch area can be interpreted as a scale of observation. Using the patchwork method, one can identify crossover scales, or thresholds, which distinguish scales where a surface is best described by Euclidean or fractal geometries. An inverse patchwork transform is proposed by which a set of relative areas and crossover data can be transformed to derive topographical data. The inverse patchwork transform and patchwork method provide mathematical basis functions for conversion between two domains-scales of observation and surface topography, providing a system for synthesizing surface data with desired characteristics. This method can also serve as a tool for aiding in surface design and manufacture.

Calculation of Spectral Optical Constants Using Combined Ellipsometric and Reflectance Methods for Smooth and Rough Bulk Samples

2021 ◽  
pp. 000370282110478
Author(s):  
Gilles Fortin
Keyword(s):  
Rough Surface ◽  
Optical Constants ◽  
Sample Surface ◽  
Infrared Region ◽  
Homogeneous Sample ◽  
Specular Reflectance ◽  
Scattering Effects ◽  
Spectral Ranges ◽  
Reflectance Measurements ◽  
Polarized Reflectance

Spectra of the optical constants n and k of a substance are often deduced from spectroscopic measurements, performed on a thick and homogeneous sample, and from a model used to simulate these measurements. Spectra obtained for n and k using the ellipsometric method generally produce polarized reflectance simulations in strong agreement with the experimental measurements, but they sometimes introduce significant discrepancies over limited spectral ranges, whereas spectra of n and k obtained with the single-angle reflectance method require a perfectly smooth sample surface to be viable. This paper presents an alternative method to calculate n and k. The method exploits both ellipsometric measurements and s-polarized specular reflectance measurements, and compensates for potential surface scattering effects with the introduction of a specularity factor. It is applicable to bulk samples having either a smooth or a rough surface. It provides spectral optical constants that are consistent with s-polarized reflectance measurements. Demonstrations are performed in the infrared region using a glass slide (smooth surface) and a pellet of compressed ammonium sulfate powder (rough surface).

scholarly journals Surface plasmon-polaritons in deformed graphene excited by attenuated total internal reflection

2019 ◽  
Vol 5 (1) ◽  
pp. 7-11
Author(s):  
Maksim O. Usik ◽  
Igor V. Bychkov ◽  
Vladimir G. Shavrov ◽  
Dmitry A. Kuzmin
Keyword(s):  
Surface Plasmon ◽  
Surface Plasmon Polaritons ◽  
Total Internal Reflection ◽  
Incident Angle ◽  
Incident Light ◽  
Attenuated Total Reflection ◽  
Reflection Method ◽  
Molding Flow ◽  
Plasmon Polaritons ◽  
Effective Excitation

Abstract In the present work we theoretically investigated the excitation of surface plasmon-polaritons (SPPs) in deformed graphene by attenuated total reflection method. We considered the Otto geometry for SPPs excitation in graphene. Efficiency of SPPs excitation strongly depends on the SPPs propagation direction. The frequency and the incident angle of the most effective excitation of SPPs strongly depend on the polarization of the incident light. Our results may open up the new possibilities for strain-induced molding flow of light at nanoscales.

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