scholarly journals Experimental characterisation of the bound acoustic surface modes supported by honeycomb and hexagonal hole arrays

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Timothy A. Starkey ◽  
Vicky Kyrimi ◽  
Gareth P. Ward ◽  
J. Roy Sambles ◽  
Alastair P. Hibbins
Keyword(s):  
Band Structure ◽  
Field Measurements ◽  
Sample Surface ◽  
Honeycomb Lattice ◽  
Local Pressure ◽  
Linear Dispersion ◽  
Surface Modes ◽  
Hexagonal Hole ◽  
Hole Arrays ◽  
Full Band Structure

Abstract The Dirac point and associated linear dispersion exhibited in the band structure of bound (non-radiative) acoustic surface modes supported on a honeycomb array of holes is explored. An aluminium plate with a honeycomb lattice of periodic sub-wavelength perforations is characterised by local pressure field measurements above the sample surface to obtain the full band-structure of bound modes. The local pressure fields of the bound modes at the K and M symmetry points are imaged, and the losses at frequencies near the Dirac frequency are shown to increase monotonically as the mode travels through the K point at the Dirac frequency on the honeycomb lattice. Results are contrasted with those from a simple hexagonal array of similar holes, and both experimentally obtained dispersion relations are shown to agree well with the predictions of a numerical model.

A Probabilistic High-Pressure Zone Model for Local and Global Loads During Ice-Structure Interactions

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Rocky S. Taylor ◽  
Martin Richard ◽  
Ridwan Hossain
Keyword(s):  
High Pressure ◽  
Field Measurements ◽  
Zone Model ◽  
Probabilistic Framework ◽  
Local Pressure ◽  
Pressure Zone ◽  
Current Design ◽  
Ice Loads ◽  
High Pressure Zone ◽  
Ice Failure

For temperate ice regions, guidance provided by current design codes regarding ice load estimation for thin ice is unclear, particularly for local pressure estimation. This is in part due to the broader issue of having different recommended approaches for estimating local, global, and dynamic ice loads during level ice interactions with a given structure based on region, scenario type, and a variety of other conditions. It is essential from a design perspective that these three scenarios each be evaluated using appropriate definitions for local design areas, global interaction area, and other structural details. However, the need for use of different modeling approaches for ice loads associated with each of these scenarios is not based on ice mechanics but rather has largely evolved as a result of complexities in developing physics-based models of ice failure in combination with the need to achieve safe designs in the face of limited full-scale data and the need for implementation in a probabilistic framework that can be used for risk-based design assessments. During a given interaction, the ice is the same regardless of the design task at hand. In this paper, a new approach is proposed based on a probabilistic framework for modeling loads from individual high-pressure zones acting on local and global areas. The analysis presented herein considers the case of thin, first-year sea ice interacting with a bottom-founded structure based on an empirical high-pressure zone model derived from field measurements. Initial results indicate that this approach is promising for modeling local and global pressures.

An Infrared Interferometer for Elastoplastic Crack-Tip Field Investigation of Homogeneous and Bimaterial Beams: A Study of Three-Dimensional Effects and J-Dominance

1998 ◽  
Vol 65 (4) ◽  
pp. 1032-1041
Author(s):  
J. K. Sinha ◽  
H. V. Tippur
Keyword(s):  
Plane Deformation ◽  
Three Dimensional ◽  
Surface Preparation ◽  
Field Measurements ◽  
Sample Surface ◽  
Field Investigation ◽  
Crack Tip Field ◽  
Full Field ◽  
Infrared Wavelength ◽  
Dimensional Effects

An infrared interferometer capable of performing real-time full-field noncontacting deformation field measurements on optically rough surfaces is proposed as a tool for elastoplastic fracture mechanics investigations. The choice of the infrared wavelength allows interferometric measurements on fracture samples with little or no surface preparation and is more tolerant of the damage accumulation near the crack. The interferometer also bridges a sensitivity gap among existing techniques for out-of-plane deformation measurement. First, a rigorous Fourier optics analysis is provided for the interferometer and the range of surface roughness that can be studied using this interferometer is examined. The interferometer is then used for mapping deformations near elastoplastically deformed cracks in aluminum beams and solder-copper bimaterials. The regions of dominant three-dimensional effects and J-dominance are examined on the sample surface by evaluating measurements along with companion finite element analyses and the HRR fields.

scholarly journals Photonic band structure evolution of a honeycomb lattice in the presence of an external magnetic field

2009 ◽  
Vol 105 (3) ◽  
pp. 034303 ◽  
Author(s):  
C. A. Duque ◽  
N. Porras-Montenegro ◽  
S. B. Cavalcanti ◽  
L. E. Oliveira
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Band Structure ◽  
Structure Evolution ◽  
Honeycomb Lattice ◽  
Photonic Band Structure ◽  
Photonic Band

scholarly journals Monte Carlo Simulations of High Field Transport in Electroluminescent Devices

VLSI Design ◽  
1998 ◽  
Vol 8 (1-4) ◽  
pp. 401-405
Author(s):  
Manfred Dür ◽  
Stephen M. Goodnick ◽  
Martin Reigrotzki ◽  
Ronald Redmer
Keyword(s):  
Band Structure ◽  
High Field ◽  
Light Emission ◽  
Essential Element ◽  
Impact Excitation ◽  
Field Energy ◽  
Pseudopotential Calculations ◽  
Full Band ◽  
Full Band Structure

High field transport in phosphor materials is an essential element of thin film electroluminescent device performance. Due to the high accelerating fields in these structures (1–3 MV/cm), a complete description of transport under high field conditions utilizing information on the full band structure of the material is critical to understand the light emission process due to impact excitation of luminescent impurities. Here we investigate the role of band structure for ZnS, GaN, and SrS based on empirical pseudopotential calculations to study its effect on the high field energy distribution of conduction band electrons.

First Principles Calculations of Graphene Doped with Al, P and Si Heteroatoms

2017 ◽  
Vol 16 ◽  
pp. 52-55 ◽  
Author(s):  
Maria Teresa Romero ◽  
Yuliana Avila Alvarado ◽  
Reyes Garcia-Diaz ◽  
Carlos Rodriguez Garcia ◽  
Raul Ochoa Valiente ◽  
...  
Keyword(s):  
Band Structure ◽  
Fermi Level ◽  
Density Functional ◽  
Pristine Graphene ◽  
High Symmetry ◽  
Linear Dispersion ◽  
Graphene Layers ◽  
Doping Effects ◽  
Semiconductor Behavior ◽  
Quantum Espresso

In this work, studies of the doping effects on the electronic and structural properties of graphene were performed. Calculations have been done within the periodic density functional theory (DFT) as implemented in PWscf code of the Quantum Espresso Package. Graphene layers have been modeled using the 4x4 periodic supercells. The doping is explored considering phosphorus (P), aluminum (Al) and silicon (Si) heteroatoms. One heteroatom per supercell was considered. Electronic structure results show that the pristine graphene has a linear dispersion at high symmetry K point and zero gap. Band structure of graphene doped with Al atoms exhibit a metal behavior since a valence band crosses the Fermi level. Graphene doped with P also presents a metal behavior but in this case a conduction band crosses the Fermi level. In addition, when the dopant is Si the band structure shows a semiconductor behavior with a 0.3 eV gap. In all cases, the zero gap energy characteristic of graphene was changed by dopant heteroatom. The Dirac lineal dispersion relation is preserved only in the pristine graphene.

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