Neutrally reinforced holes in symmetrically laminated plates

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76616/1/AIAA-46360-396.pd

Investigation of Reynolds Stresses in a 3D Idealized Urban Area Using Large Eddy Simulation

High resolution, large eddy simulation (LES) of neutral flow through an array of cubes has been conducted with periodic boundary conditions in lateral and longitudinal directions. In this paper, we first describe the model formulation and validate the simulation by comparing the mean flow and turbulence statistics with wind-tunnel experimental data from a cube array of buildings. The LES model is then used to investigate the physical mechanisms that lead to the low turbulent stresses that have been reported in the lower half of the urban canopy layer. To do this, the urban boundary layer is conceptually broken down into three distinct regions: (a) the urban roughness sub-layer, (b) street channels (roads with axis aligned with mean wind direction aloft) and (c) street canyons (roads with axis normal to the mean wind direction aloft). The distribution of the Reynolds stresses differ significantly amongst these regions and we hypothesize that the low stresses in the lower half of the canopy can been attributed to the temporary unstable of the above mentioned regions at different periods of time. In a complex urban area, these regions can be observed intermittently at the same physical location, thus, stresses with opposite signs have the potential to cancel each other and on average yield a low magnitude. In this paper, mean turbulence statistics and spectra from high resolution LES have been analyzed for these scenarios and the results have been interpreted within the context of the proposed idealized flow regions

Generalized conductance sum rule in atomic break junctions

When an atomic-size break junction is mechanically stretched, the total conductance of the contact remains approximately constant over a wide range of elongations, although at the same time the transmissions of the individual channels (valence orbitals of the junction atom) undergo strong variations. We propose a microscopic explanation of this phenomenon, based on Coulomb correlation effects between electrons in valence orbitals of the junction atom. The resulting approximate conductance quantization is closely related to the Friedel sum rule.Comment: 4 pages, 1 figure, appears in Proceedings of the NATO Advanced Research Workshop ``Size dependent magnetic scattering'', Pecs, Hungary, May 28 - June 1, 200

Large-eddy simulation of spectral coherence in a wind turbine wake

This work is mainly dedicated to the study of the characteristics of spectral coherence of turbulence fluctuations in wind turbine wakes. A computational fluid dynamics (CFD) code has been implemented using a large-eddy simulation (LES) approach, which is thought to be conceptually more suitable for studying the turbulence evolution in a wind turbine wake. Comparisons with experimental data from the Nørrekær Enge II Windfarm, in Denmark, and with an analytical model proposed by Panofsky and Dutton have been performed, and the results are found to be in reasonable agreement with both

Interobserver reliability of articular examination in juvenile idiopathic arthritis.

Diagnosis, treatment and follow-up of children with juvenile idiopathic arthritis are based upon the articular examination. The objective of the current study was to assess the interobserver agreement in grading the joint with arthritis and limited range of motion, and to detect the sources of disagreement. Twenty children with juvenile idiopathic arthritis were included. Assessment parameters were a) Physician Global Assessment, b) number of joints with active arthritis, and c) number of joints with limited range of motion. A total number of 1,320 joints were examined by both observers, blinded to each other. Each observer marked the involved joints as active arthritis, as limited range of motion, or as both. Interobserver agreement was determined by using Kappa statistics and, Wilcoxon signed rank test. The statistical analysis was performed by SPSS 10.0. There was no statistical difference in the comparison of Physician Global Assessment of the two observers. There was substantial agreement in both arthritis and limited range of motion scores. Chance corrected agreement for the interobserver reliability was also performed for frequently involved joint such as. neck, wrist, hip and knee. A substantial agreement was found. The close agreement between the observers could be attributed to standardization of examination techniques and to using objective variables