scholarly journals Travelling Surface Plasmons with Interference Envelope and A Vision for Time Crystals

2018 ◽  
Author(s):  
Amir Djalalian-Assl
Keyword(s):  
Film Thickness ◽  
Surface Waves ◽  
Skin Depth ◽  
Incident Field ◽  
Propagation Mechanism ◽  
Surface Mode ◽  
Thin Metallic Film ◽  
Volume Charge Density ◽  
The Impact ◽  
Sub Wavelength

The influence of the film thickness and the substrate’s refractive index on the surface mode at the superstrate is an important study step that may help clearing some of the misunderstandings surrounding their propagation mechanism. A single sub-wavelength slit perforating a thin metallic film is among the simplest nanostructure capable of launching Surface Plasmon Polaritons on its surrounding surface when excited by an incident field. Here, the impact of the substrate and the film thickness on surface waves is investigated. When the thickness of the film is comparable to its skin depth, SPP waves from the substrate penetrate the film and emerge from the superstrate, creating a superposition of two SPP waves, that leads to a beat interference envelope with well defined loci which are the function of both the drive frequency and the dielectric constant of the substrate/superstrate. As the film thickness is reduced to the SPP’s penetration depth, surface waves from optically denser dielectric/metal interface would dominate, leading to volume plasmons that propagate inside the film at optical frequencies. Interference of periodic volume charge density with the incident field over the film creates charge bundles that are periodic in space and time.

scholarly journals Travelling Surface Plasmons with Interference Envelope and A Vision for Time Crystals

2018 ◽  
Author(s):  
Amir Djalalian-Assl
Keyword(s):  
Film Thickness ◽  
Surface Waves ◽  
Skin Depth ◽  
Incident Field ◽  
Propagation Mechanism ◽  
Surface Mode ◽  
Thin Metallic Film ◽  
Volume Charge Density ◽  
The Impact ◽  
Sub Wavelength

The influence of the film thickness and the substrate’s refractive index on the surface mode at the superstrate is an important study step that may help clearing some of the misunderstandings surrounding their propagation mechanism. A single sub-wavelength slit perforating a thin metallic film is among the simplest nanostructure capable of launching Surface Plasmon Polaritons on its surrounding surface when excited by an incident field. Here, the impact of the substrate and the film thickness on surface waves is investigated. When the thickness of the film is comparable to its skin depth, SPP waves from the substrate penetrate the film and emerge from the superstrate, creating a superposition of two SPP waves, that leads to a beat interference envelope with well defined loci which are the function of both the drive frequency and the dielectric constant of the substrate/superstrate. As the film thickness is reduced to the SPP’s penetration depth, surface waves from optically denser dielectric/metal interface would dominate, leading to volume plasmons that propagate inside the film at optical frequencies. Interference of periodic volume charge density with the incident field over the film creates charge bundles that are periodic in space and time.

scholarly journals Travelling Surface Plasmons with Interference Envelope and A Vision for Time Crystals

2018 ◽  
Author(s):  
Amir Djalalian-Assl
Keyword(s):  
Film Thickness ◽  
Surface Waves ◽  
Skin Depth ◽  
Incident Field ◽  
Propagation Mechanism ◽  
Surface Mode ◽  
Thin Metallic Film ◽  
Volume Charge Density ◽  
The Impact ◽  
Sub Wavelength

The influence of the film thickness and the substrate’s refractive index on the surface mode at the superstrate is an important study step that may help clearing some of the misunderstandings surrounding their propagation mechanism. A single sub-wavelength slit perforating a thin metallic film is among the simplest nanostructure capable of launching Surface Plasmon Polaritons on its surrounding surface when excited by an incident field. Here, the impact of the substrate and the film thickness on surface waves is investigated. When the thickness of the film is comparable to its skin depth, SPP waves from the substrate penetrate the film and emerge from the superstrate, creating a superposition of two SPP waves, that leads to a beat interference envelope with well-defined loci which are the function of both the drive frequency and the dielectric constant of the substrate/superstrate. As the film thickness is reduced to the SPP’s penetration depth, surface waves from optically denser dielectric/metal interface would dominate, leading to volume plasmons that propagate inside the film at optical frequencies. Interference of periodic volume charge density with the incident field over the film creates charge bundles that are periodic in space and time.

Anomalous Dielectric Variability in the central peak of Tycho crater on the Moon: New insights from Mini-RF S-band Observations

2021 ◽  
Author(s):  
Shashwat Shukla ◽  
Gerald Wesley Patterson
Keyword(s):  
Dielectric Constant ◽  
Hyperspectral Image ◽  
Central Peak ◽  
Skin Depth ◽  
The Moon ◽  
Near Surface ◽  
Low Dielectric ◽  
Crater Morphology ◽  
High Dielectric ◽  
The Impact

<p>One of the unique candidates to explore the evolution of physical surface processes on the Moon is Tycho, a dark haloed impact crater representing well-preserved bright ray pattern and intact crater morphology. Sampling of the central peak in such complex crater formation proves significant in terms of unraveling intriguing science of the lunar interior. With the current state-of-the-art radar technology, it is possible to evaluate the response of the geologic features constrained in the near surface and subsurface regolith environments. This can be achieved by modelling the dielectric constant of media, which is a physical parameter crucial for furthering our knowledge about the distribution of materials within different stratigraphic layers at multiple depths. Here, we used the applicability of Mini-RF S-band data augmented with a deep learning based inversion model to retrieve the dielectric variations over the central peak of the Tycho crater. A striking observation is made in certain regions of the central peak, wherein we observe anomalously high dielectric constant, not at all differentiated in the hyperspectral image and first Stokes parameter image, which usually is a representation of retrieved backscatter of the target. The results are also supported by comparing the variations in the scattering mechanisms. We found those particular regions to be associated with high degree of depolarization, thereby attributing to the presence of cm- to m- scale scatterers buried within a low dielectric layer that are not big enough to produce even-bounce geometry for the radar wave. Moreover, we also observe high rock concentration in the central peak slopes from DIVINER data and NAC images, indicating the exposure of clasts ranging in size from 10 meter to 100s of meter. Furthermore, from surface temperature data, these distinctive outcrops sense warmer temperature at night than the surrounding, which suggests the existence of thermal skin depth in such vicinities. Interestingly, we are able to quantify the pessimistic dielectric constant limit of the large boulder in the middle of the central peak, observable at the Mini-RF radar wavelength, as 4.54 + j0.077. Compared to the expected dielectric constant of rocks, this value is lowered significantly. One probable reason could be the emergence of small radar shadows due to the rugged surface of the boulder on the radar illuminated portion. From our analysis, we showcase the anomalous dielectric variability of Tycho central peak, thereby providing new insights into the evolution of the impact cratering process that could be important for both science and necessary for framing human or robotic exploration strategies.  </p>

Magnetic modulation of Fano resonances in optically thin terahertz superlattice metasurfaces

2021 ◽  
Author(s):  
Subhajit Karmakar ◽  
Ravi Varshney ◽  
Dibakar Roy Chowdhury
Keyword(s):  
Magnetic Field ◽  
Free Space ◽  
Skin Depth ◽  
Electromagnetic Energy ◽  
Magnetic Control ◽  
Fano Resonances ◽  
Electromagnetic Responses ◽  
On Chip ◽  
Magneto Resistance ◽  
Sub Wavelength

Abstract Optically thin metasurfaces operating at sub-skin depth thicknesses are intriguing because of its associated low plasmonic losses (compared to optically thick, beyond skin-depth metasurfaces). However, their applicability has been restricted largely because of reduced free space coupling with incident radiations resulting in limited electromagnetic responses. To overcome such limitations, we propose enhancement of effective responses (resonances) in sub-skin depth metasurfaces through incorporation of magneto-transport (Giant Magneto Resistance, GMR) concept. Here, we experimentally demonstrate dynamic magnetic modulation of structurally asymmetric metasurfaces (consisting of superlattice arrangement of thin (~ 10 nm each) magnetic (Ni)/ nonmagnetic (Al) layers) operating at terahertz (THz) domain. With increasing magnetic field (applied from 0 to 30 mT approximately, implies increasing superlattice conductivity), we observe stronger confinement of electromagnetic energy at the resonances (both in dipole and Fano modes). Therefore, this study introduces unique magnetically reconfigurable ability in Fano resonant THz metamaterials, which directly improves its performances operating in the sub-skin depth regime. Our study can be explained by spin-dependent terahertz magneto-transport phenomena in metals and can stimulate the paradigm for on-chip spin-based photonic technology enabling dynamic magnetic control over compact, sub-wavelength, sub-skin depth metadevices.

Coupled processes in an ocean-sea ice-wave configuration

2021 ◽  
Author(s):  
Stefanie Rynders ◽  
Yevgeny Aksenov ◽  
Andrew Coward
Keyword(s):  
Sea Ice ◽  
Surface Waves ◽  
Wave Attenuation ◽  
Computational Cost ◽  
Breaking Waves ◽  
Coupled Processes ◽  
Computational Power ◽  
Marine Systems ◽  
Ocean Surface Waves ◽  
The Impact

<p>Marginal ice zones are areas with many interactions between ocean, surface waves, sea ice and atmosphere. Increasing computational power makes it possible to perform increasingly complex simulations of marine systems, with more components of the climate system that are more interacting. We have produced a set of increasingly coupled simulations with NEMO, CICE and WW3, exchanging more and more variables. The configuration is global at 1 degree resolution. The focus is on wave attenuation in sea ice and the impact of using modelled wave height for ocean mixing due to breaking waves. The example simulations give an idea of the possible impact on the simulated state versus the still considerable computational cost.</p>

scholarly journals The Impact of Lubricant Film Thickness and Ball Bearings Failures

Lubricants ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 48 ◽  
Author(s):  
Matthew David Marko
Keyword(s):  
Film Thickness ◽  
Fatigue Failure ◽  
Failure Mechanisms ◽  
Roller Bearing ◽  
Lubricant Film ◽  
Theoretical Formula ◽  
Empirical Equations ◽  
Ball Bearings ◽  
Lubricant Film Thickness ◽  
The Impact

An effort was made to find a relationship between the lubricant thickness at the point of contact of rolling element ball bearings, and empirical equations to predict the life for bearings under constant motion. Two independent failure mechanisms were considered, fatigue failure and lubricant failure resulting in seizing of the roller bearing. A theoretical formula for both methods was established for the combined probability of failure using both failure mechanisms. Fatigue failure was modeled with the empirical equations of Lundberg and Palmgren and standardized in DIN/ISO281. The seizure failure, which this effort sought to investigate, was predicted using Greenwood and Williamson’s theories on surface roughness and asperities during lubricated contact. These two mechanisms were combined, and compared to predicted cycle lives of commercial roller bearing, and a clear correlation was demonstrated. This effort demonstrated that the Greenwood–Williams theories on the relative height of asperities versus lubricant film thickness can be used to predict the probability of a lubricant failure resulting in a roller bearing seizing during use.

scholarly journals Spreading and oscillation dynamics of drop impacting liquid film

2019 ◽  
Vol 881 ◽  
pp. 859-871 ◽  
Author(s):  
Xiaoyu Tang ◽  
Abhishek Saha ◽  
Chao Sun ◽  
Chung K. Law
Keyword(s):  
Film Thickness ◽  
Liquid Film ◽  
Liquid Surface ◽  
Strong Dependence ◽  
Solid Substrate ◽  
Spreading Dynamics ◽  
Viscous Loss ◽  
Shape Oscillation ◽  
Oscillation Dynamics ◽  
The Impact

We herein report an experimental study to explore the effects of impact inertia, film thickness and viscosity on the dynamics of shape deformation of a drop impacting a liquid film. We have identified that the spreading dynamics shows a weak dependence on impact inertia, but strongly depends on the film thickness. For a thick film, the liquid surface deforms and absorbs part of the impact energy, and hence inhibits spreading of the drop. For a thin film, the drop motion is restricted by the bottom solid substrate, promoting spreading. The periodicity of the capillary controlled shape oscillation, on the other hand, is found to be independent of impact inertia and film thickness. The damping of the shape oscillation shows strong dependence on the film thickness, in that the oscillation decays faster for smaller film thicknesses, due to the enhanced viscous loss.

scholarly journals Lifetime Analysis of IGBT Power Modules in Passively Cooled Tidal Turbine Converters

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1875
Author(s):  
Faisal Wani ◽  
Udai Shipurkar ◽  
Jianning Dong ◽  
Henk Polinder ◽  
Antonio Jarquin-Laguna ◽  
...  
Keyword(s):  
Thermal Cycling ◽  
Surface Waves ◽  
Stream Velocity ◽  
Insulated Gate Bipolar Transistor ◽  
Cost Of Energy ◽  
Igbt Modules ◽  
Lifetime Analysis ◽  
Tidal Turbine ◽  
Tidal Stream ◽  
The Impact

Thermal cycling is one of the major reasons for failure in power electronic converters. For submerged tidal turbine converters investigating this failure mode is critical in improving the reliability, and minimizing the cost of energy from tidal turbines. This paper considers a submerged tidal turbine converter which is passively cooled by seawater, and where the turbine has fixed-pitch blades. In this respect, this study is different from similar studies on wind turbine converters, which are mostly cooled by active methods, and where turbines are mostly pitch controlled. The main goal is to quantify the impact of surface waves and turbulence in tidal stream velocity on the lifetime of the converter IGBT (insulated gate bipolar transistor) modules. The lifetime model of the IGBT modules is based on the accumulation of fatigue due to thermal cycling. Results indicate that turbulence and surface waves can have a significant impact on the lifetime of the IGBT modules. Furthermore, to accelerate the speed of the lifetime calculation, this paper uses a modified approach by dividing the thermal models into low and high frequency models. The final calculated lifetime values suggest that relying on passive cooling could be adequate for the tidal converters as far as thermal cycling is concerned.

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