Phase difference mapping of two-dimensional metallic nanohole arrays

2012 ◽  
Vol 100 (23) ◽  
pp. 233102 ◽  
Author(s):  
S. L. Wong ◽  
H. C. Ong
Keyword(s):  
Phase Difference ◽  
Two Dimensional ◽  
Nanohole Arrays

FABRICATION OF TWO-DIMENSIONAL PHOTONIC CRYSTALS WITH GE2SB2TE5 NANOHOLE ARRAYS BY NANOSPHERE LITHOGRAPHY

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1300-1305
Author(s):  
KI-HO SONG ◽  
HYUN-YONG LEE ◽  
HOE-YOUNG YANG ◽  
SUNG-WON KIM ◽  
JAE-HEE SEO ◽  
...  
Keyword(s):  
Photonic Crystals ◽  
Plasma Treatment ◽  
Treatment Time ◽  
Reduction Rate ◽  
Nanosphere Lithography ◽  
Two Dimensional ◽  
Photonic Bandgaps ◽  
Nanohole Arrays ◽  
Plasma Treatment Time ◽  
Lift Off

Two-dimensional photonic crystals (2D-PCs) with Ge 2 Sb 2 Te 5 ( GST ) nanohole arrays were prepared by the nanosphere lithography (NSL) process. A primary factor of PCs is that the refractive index (n) and the n-modulation can be realized by using the GST films, which exhibit a reversible phase transformation between amorphous and crystalline states by laser illumination. The polystyrene (PS) spheres with a diameter of 500 nm were spin-coated on Si substrate and subsequently reduced by O 2-plasma treatment. The reduced spheres were utilized as a lift-off mask of the NSL process and their size and separation could be precisely controlled. Amorphous GST films were thermally evaporated and then the reduced PS spheres were removed. The fabricated GST nanohole arrays were observed by SEM and AFM. The nanohole diameters are nearly linearly reduced with increasing plasma-treatment time (t). The reduction rate (δ) for the conditions of this work was evaluated to be ~ 0.92 nm/s. The period (Λ) and filling factor (η) of PCs are structure parameters that determine their photonic bandgaps (PBGs). η-modulation can be easily achieved via a control of t and the Λ can be also modulated by the use of PS spheres with specific diameter. In addition, the PBGs for the fabricated GST 2 D PC were calculated by considering the amorphous and crystalline states of GST .

Two-dimensional multispectral imager based on tiled arrangement of metallic nanohole arrays

2014 ◽  
Author(s):  
Mohamadreza Najiminaini ◽  
Bozena Kaminska ◽  
Jeffrey J. L. Carson
Keyword(s):  
Two Dimensional ◽  
Nanohole Arrays ◽  
Multispectral Imager

On the Conditions under which Energy can be Extracted from an Air Stream by an Oscillating Aerofoil

1954 ◽  
Vol 4 (1) ◽  
pp. 54-68 ◽  
Author(s):  
N. C. Lambourne
Keyword(s):  
Phase Difference ◽  
Amplitude Ratio ◽  
Vortex Sheet ◽  
Frequency Parameter ◽  
The Other ◽  
Positive Energy ◽  
Two Dimensional ◽  
Zero Energy ◽  
Upper Limit ◽  
Air Stream

SummaryA simple system is considered in which a two-dimensional aerofoil in an air stream performs a coupled oscillation in pitching and vertical translation. An expression for the energy transferred from stream to aerofoil is derived as a function of the frequency parameter, amplitude ratio and phase difference, and the conditions under which positive energy can be extracted from the stream are investigated. The connection between the case of zero energy transfer, and the critical flutter state is noted.Attention is confined to the incompressible case and diagrams show the results obtained when the air loads are obtained from (i) vortex sheet theory and (ii) the classical set of constant derivatives.Vortex sheet theory leads to the conclusion that, provided that the amplitude ratio and phase difference satisfy certain conditions, energy can be extracted from the stream for all values of the frequency parameter. On the other hand, the use of a set of constant derivatives places an upper limit on the values of the frequency parameter for the extraction of energy.

Numerical Investigation of the Effects of Core Heterogeneities on Waterflood Relative Permeabilities

1970 ◽  
Vol 10 (04) ◽  
pp. 381-392 ◽  
Author(s):  
John D. Huppler
Keyword(s):  
Numerical Simulation ◽  
Porous Medium ◽  
Pressure Drop ◽  
Difference Equation ◽  
Relative Permeability ◽  
Phase Difference ◽  
Two Dimensional ◽  
Relative Permeabilities ◽  
Two Phase ◽  
Relative Permeability Curves

Abstract Numerical simulation techniques were used to investigate the effects of common core heterogeneities upon apparent waterflood relative-permeability results. Effects of parallel and series stratification, distributed high and low permeability lenses, and vugs were considered. permeability lenses, and vugs were considered. Well distributed heterogeneities have little effect on waterflood results, but as the heterogeneities become channel-like, their influence on flooding behavior becomes pronounced. Waterflooding tests at different injection rates are suggested as the best means of assessing whether heterogeneities are important. Techniques for testing stratified or lensed cores are recommended. Introduction Since best results from waterflood tests performed on core plugs are obtained with homogeneous cores, plugs selected for testing are chosen for their plugs selected for testing are chosen for their apparent uniformity. We know, however, that uniform appearance can be misleading. For example, flushing concentrated hydrochloric acid through an apparently homogeneous core plug often produces "wormholes" in higher permeability regions. Also, we sometimes find that all core plugs from a region of interest have obvious heterogeneities, so any flooding tests must be run on nonhomogeneous core plugs. plugs. Nevertheless, relative permeabilities, as obtained routinely from core waterflood data, are calculated using the assumption that the core is a homogeneous porous medium. While it is obvious that porous medium. While it is obvious that heterogeneties mill affect these apparent relative permeabilities, there appear to be no experimental permeabilities, there appear to be no experimental results reported in the literature to indicate just how serious the problem is. Accordingly, a computer simulation study of core waterfloods was conducted to systematically examine the effects of different sizes and types of core heterogeneities on flood results. The study was performed by numerical simulation using two-dimensional, two-phase difference equation approximations to describe the immiscible water-oil displacement. For each simulation the permeability and porosity distribution of the heterogeneous core to be studied was specified; fluid flow characteristics of the system, including a single set of input relative-permeabilities curves, were stipulated The system was set in capillary pressure equilibrium at the reducible water saturation. Then a waterflood simulation was performed. From the resulting fluid production and pressure-drop data a set of production and pressure-drop data a set of relative-permeability curves was calculated using the standard computational procedure applicable to homogeneous cores. In this paper these calculated relative-permeability curves are denoted as "waterflood" curves to distinguish them from the specified input curves. The waterflood relative-permeability curves should closely match the input curves for homogeneous systems. Since the same set of input relative-permeability curves was used for all rock sections, deviations of the waterflood from the input relative-permeability curves gave an indication of the effects of heterogeneities. When the system was heterogeneous and there was good agreement between waterflood and input relative-permeability curves, then the heterogeneities did not strongly influence the flow behavior and the system responded homogeneously. MATHEMATICAL MODEL AND METHOD The waterflood simulations were carried out using two-dimensional, two-phase difference equation approximations to the incompressible-flow differential equations:* .....................(1) ....................(2) SPEJ P. 381

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