Hydrodynamic and Ballistic Transport over Large Length Scales in 
GaAs/AlGaAs

ABSTRACTInterfaces can be considered at a variety of length scales. All interfaces except grain boundaries are dielectric interfaces. In many cases, the geometric constraints of matching two lattices must be considered, together with the misfit strains that are often present. Continuum mechanics is useful for tackling such problems. In many cases, however, the local ordering of ions must also be considered. Atomistic simulation is therefore necessary, together with the problems associated with large length scales and long time scales. We discuss a number of examples to illustrate the issues involved and the compromises between different approaches that must be made.

Download Full-text

Hydrophobicity at Small and Large Length Scales

The Journal of Physical Chemistry B ◽

10.1021/jp984327m ◽

1999 ◽

Vol 103 (22) ◽

pp. 4570-4577 ◽

Cited By ~ 1072

Author(s):

Ka Lum ◽

David Chandler ◽

John D. Weeks

Keyword(s):

Length Scales ◽

Large Length

Download Full-text

Monte Carlo Modeling of Phonon Transport Using Scattering Phase Functions

ASME 2008 3rd Energy Nanotechnology International Conference ◽

10.1115/enic2008-53022 ◽

2008 ◽

Cited By ~ 1

Author(s):

Neil Zuckerman ◽

Jennifer R. Lukes

Keyword(s):

Thermal Conductivity ◽

Monte Carlo ◽

Numerical Methods ◽

Ballistic Transport ◽

Simulation Method ◽

Phonon Transport ◽

Nanometer Scale ◽

Boltzmann Transport ◽

Length Scales ◽

Scale Structures

The calculation of heat transport in nonmetallic materials at small length scales is important in the design of thermoelectric and electronic materials. New designs with quantum dot superlattices (QDS) and other nanometer-scale structures can change the thermal conductivity in ways that are difficult to model and predict. The Boltzmann Transport Equation can describe the propagation of energy via mechanical vibrations in an analytical fashion but remains difficult to solve for the problems of interest. Numerical methods for simulation of propagation and scattering of high frequency vibrational quanta (phonons) in nanometer-scale structures have been developed but are either impractical at micron length scales, or cannot truly capture the details of interactions with nanometer-scale inclusions. Monte Carlo (MC) models of phonon transport have been developed and demonstrated based on similar numerical methods used for description of electron transport [1-4]. This simulation method allows computation of thermal conductivity in materials with length scales LX in the range of 10 nm to 10 μm. At low temperatures the model approaches a ballistic transport simulation and may function for even larger length scales.

Download Full-text

Collective behaviour

10.1093/oso/9780192846839.003.0008 ◽

2021 ◽

pp. 94-101

Author(s):

Adrian P Sutton

Keyword(s):

Plastic Deformation ◽

Ballistic Transport ◽

Theory Of Elasticity ◽

Atomic Scale ◽

Length Scales ◽

New Science ◽

Large Numbers ◽

Deformation And Fracture ◽

Long Range Interactions ◽

Reductionist Approach

At each change of length-sale in a material new science emerges. The reductionist approach focuses on the atomic and electronic length scales in the belief that a fundamental understanding can be achieved only at this smallest scale. It is blind to the emergence of science no less fundamental at larger length scales resulting from interactions between very large numbers of atoms and defects. While the atomic scale always remains important, a complete understanding of plastic deformation and fracture involves long-range interactions between defects described by the theory of elasticity. Even the mechanism of electronic conduction in a metal changes from ballistic transport at the nanoscale to the diffusive transport of Ohm’s law at the macroscale.

Download Full-text

Attenuation of the wake of a sphere in an intense incident turbulence with large length scales

Physics of Fluids ◽

10.1063/1.3425628 ◽

2010 ◽

Vol 22 (5) ◽

pp. 055105 ◽

Cited By ~ 30

Author(s):

Zouhir Amoura ◽

Véronique Roig ◽

Frédéric Risso ◽

Anne-Marie Billet

Keyword(s):

Length Scales ◽

Large Length

Download Full-text

Modifying the structure and flow behaviour of aqueous montmorillonite suspensions with surfactant

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2012.0262 ◽

2013 ◽

Vol 371 (1988) ◽

pp. 20120262 ◽

Cited By ~ 11

Author(s):

Yannan Cui ◽

Claire L. Pizzey ◽

Jeroen S. van Duijneveldt

Keyword(s):

Light Scattering ◽

Sol Gel ◽

Colloidal Suspensions ◽

Scattering Data ◽

Length Scales ◽

Number Of Factors ◽

Concentric Cylinders ◽

Large Length ◽

Sol Gel Transition ◽

Gel Transition

Colloidal suspensions of plate-like particles undergo a variety of phase transitions. The predicted isotropic/nematic transition is often pre-empted by a sol/gel transition, especially in suspensions of the most commonly used natural swelling clay montmorillonite (MMT). A number of factors, including charge interactions, flexibility and salt concentration, may contribute to this competition. In this study, the effect of surfactant adsorption on suspensions of MMT was studied using rheology, small-angle X-ray scattering, static light scattering and optical microscopy. The addition of a polyetheramine surfactant reduced the moduli of the system and shifted the sol/gel transition to a much higher clay concentration, compared with suspensions of bare clay particles. Yet, scattering data revealed no change in suspension structure on length scales up to around a micrometre. Primary aggregates remain at this length scale and no nematic phase is formed. There is, however, a change in structure at large length scales (of order 20 μm) where light scattering indicates the presence of string-like aggregates that disappear on addition of surfactant. Microscope images of dried suspensions also revealed a string-like structure. The dried strings show strong birefringence and may consist of concentric cylinders, self-assembled from clay sheets.

Download Full-text