Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 7 of 7
Full-Text Articles in Physics
Determining The Gasb/Gaas-(2 × 8) Reconstruction, Jessica E. Bickel, Normand A. Modine, Joanna Mirecki Millunchick
Determining The Gasb/Gaas-(2 × 8) Reconstruction, Jessica E. Bickel, Normand A. Modine, Joanna Mirecki Millunchick
Physics Faculty Publications
Highly strained thin layers of GaSb/GaAs possess a (2 × 4) reconstruction at low Sb overpressures, and a (2 × 8) reconstruction at high Sb overpressures. While the atomic details of the Sb/GaAs-(2 × 4) are well known, the details of the (2 × 8) are not understood. In this paper, we use density functional theory to analyze possible (2 × 8) structures. Comparing scanning tunneling microscope images from both simulation and experiment and examining the relative energies of possible (2 × 8) structures, we show the α(2 × 8) and β(2 × 8) are the thermodynamically stable surface reconstructions …
Extended Defects In The Potts-Percolation Model Of A Solid: Renormalization Group And Monte Carlo Analysis, H. T. Diep, Miron Kaufman
Extended Defects In The Potts-Percolation Model Of A Solid: Renormalization Group And Monte Carlo Analysis, H. T. Diep, Miron Kaufman
Physics Faculty Publications
We extend the model of a 2d solid to include a line of defects. Neighboring atoms on the defect line are connected by springs of different strength and different cohesive energy with respect to the rest of the system. Using the Migdal-Kadanoff renormalization group we show that the elastic energy is an irrelevant field at the bulk critical point. For zero elastic energy this model reduces to the Potts model. By using Monte Carlo simulations of the three- and four-state Potts model on a square lattice with a line of defects, we confirm the renormalization-group prediction that for a defect …
Assessment Of Mixing In Passive Microchannels With Fractal Surface Patterning, Petru S. Fodor, M. Itomlenskis, Miron Kaufman
Assessment Of Mixing In Passive Microchannels With Fractal Surface Patterning, Petru S. Fodor, M. Itomlenskis, Miron Kaufman
Physics Faculty Publications
We explore numerically the feasibility of enhancing the mixing capability of microchannels by employing the Weierstrass fractal function to generate a pattern of V-shaped ridges on the channel floor. Motivated by experimental limitations such as the finite resolution (similar to 10 mu m) associated with rapid prototyping through soft lithography techniques, we study the influence on the quality of mixing of having finite width ridges. The mixing capability of the designs studied is evaluated using an entropic measure and the designs are optimized with respect to: the distances between the ridges and the position range of their tip along the …
Destruction, Amorphization And Reactivity Of Nano-Bn Under Ball Milling, A. N. Streletskii, D. G. Permenov, B. B. Bokhonov, I. V. Kolbanev, A. V. Leonov, I. V. Berestetskaya, Kiril A. Streletzky
Destruction, Amorphization And Reactivity Of Nano-Bn Under Ball Milling, A. N. Streletskii, D. G. Permenov, B. B. Bokhonov, I. V. Kolbanev, A. V. Leonov, I. V. Berestetskaya, Kiril A. Streletzky
Physics Faculty Publications
The processes of mechanical activation of a hexagonal boron nitride (h-BN) and its reactivity upon interaction with hydrogen and water were investigated using X-ray, TEM, Microdiffraction, Dynamic Light Scattering, FTIR-spectroscopy, adsorption (BET). Initial h-BN samples were monocrystalline plates 70–80 nm thick. Mechanical treatment of h-BN is accompanied by plate splitting and formation of crystallographically oriented “rods.” The rod thickness gradually diminishes to less than 5 nm. Specific surface area of the rods (400 m2/g), is found to be equal to the outer geometrical surface of rods. As nanocrystallites form “c” parameter of h-BN increases. When nanocrystallites are less than several …
Optical Stress On The Surface Of A Particle: Homogeneous Sphere, Feng Xu, James A. Lock, Gérard Gouesbet, Cameron Tropea
Optical Stress On The Surface Of A Particle: Homogeneous Sphere, Feng Xu, James A. Lock, Gérard Gouesbet, Cameron Tropea
Physics Faculty Publications
A rigorous solution (generalized Lorenz-Mie theory) and an approximate solution (geometrical optics) are developed for the optical stress distribution on the surface of a homogeneous sphere. Demonstration calculations are made for plane-wave and Gaussian-beam illuminations. The influence of diffracted waves, surface waves, interference effects, caustic points, beam width, and refractive index on the stress is analyzed. The Debye series is used to evaluate the validity of geometrical optics and provides a quantitative analysis of the contribution of rays of different orders.
A Statistical Approach To The Life Cycle Analysis Of Cumulus Clouds Selected In A Virtual Reality Environment, Thijs Heus, Harmen J.J. Jonker, Harry E.A. Van Den Akker, Eric J. Griffith, Michal Koutek, Frits H. Post
A Statistical Approach To The Life Cycle Analysis Of Cumulus Clouds Selected In A Virtual Reality Environment, Thijs Heus, Harmen J.J. Jonker, Harry E.A. Van Den Akker, Eric J. Griffith, Michal Koutek, Frits H. Post
Physics Faculty Publications
In this study, a new method is developed to investigate the entire life cycle of shallow cumuli in large eddy simulations. Although trained observers have no problem in distinguishing the different life stages of a cloud, this process proves difficult to automate, because cloud-splitting and cloud-merging events complicate the distinction between a single system divided in several cloudy parts and two independent systems that collided. Because the human perception is well equipped to capture and to make sense of these time-dependent three-dimensional features, a combination of automated constraints and human inspection in a three-dimensional virtual reality environment is used to …
Observational Validation Of The Compensating Mass Flux Through The Shell Around Cumulus Clouds, Thijs Heus, C. Freek J. Pols, Harmen J.J. Jonker, Harry E.A. Van Den Akker, Donald H. Lenschow
Observational Validation Of The Compensating Mass Flux Through The Shell Around Cumulus Clouds, Thijs Heus, C. Freek J. Pols, Harmen J.J. Jonker, Harry E.A. Van Den Akker, Donald H. Lenschow
Physics Faculty Publications
The existence of a subsiding shell around cumulus clouds has been observed before in several aircraft measurement campaigns. Recent results from large-eddy simulations (LES) showed that the downward mass flux through the shell compensates for a significant fraction of the upward mass flux through the cloud. In this study, aeroplane measurements from the Rain In Cumulus over the Ocean (RICO) field campaign are used to verify the existence of this compensating mass flux. Just as in the LES results, the in-shell downward mass flux is found to be significant. However, a few differences were found in comparison with the LES …