Simulation of iced wing aerodynamics

The sectional and total aerodynamic load characteristics of moderate aspect ratio wings with and without simulated glaze leading edge ice were studied both computationally, using a three dimensional, compressible Navier-Stokes solver, and experimentally. The wing has an untwisted, untapered planform shape with NACA 0012 airfoil section. The wing has an unswept and swept configuration with aspect ratios of 4.06 and 5.0. Comparisons of computed surface pressures and sectional loads with experimental data for identical configurations are given. The abrupt decrease in stall angle of attack for the wing, as a result of the leading edge ice formation, was demonstrated numerically and experimentally

Spin-Polarization transition in the two dimensional electron gas

We present a numerical study of magnetic phases of the 2D electron gas near freezing. The calculations are performed by diffusion Monte Carlo in the fixed node approximation. At variance with the 3D case we find no evidence for the stability of a partially polarized phase. With plane wave nodes in the trial function, the polarization transition takes place at Rs=20, whereas the best available estimates locate Wigner crystallization around Rs=35. Using an improved nodal structure, featuring optimized backflow correlations, we confirm the existence of a stability range for the polarized phase, although somewhat shrunk, at densities achievable nowadays in 2 dimensional hole gases in semiconductor heterostructures . The spin susceptibility of the unpolarized phase at the magnetic transition is approximately 30 times the Pauli susceptibility.Comment: 7 pages, 4 figure

Effects of Backflow Correlation in the Three-Dimensional Electron Gas: Quantum Monte Carlo Study

The correlation energy of the homogeneous three-dimensional interacting electron gas is calculated using the variational and fixed-node diffusion Monte Carlo methods, with trial functions that include backflow and three-body correlations. In the high density regime the effects of backflow dominate over those due to three-body correlations, but the relative importance of the latter increases as the density decreases. Since the backflow correlations vary the nodes of the trial function, this leads to improved energies in the fixed-node diffusion Monte Carlo calculations. The effects are comparable to those found for the two-dimensional electron gas, leading to much improved variational energies and fixed-node diffusion energies equal to the release-node energies of Ceperley and Alder within statistical and systematic errors.Comment: 14 pages, 5 figures, submitted to Physical Review

Near-infrared Imaging Polarimetry of GGD 27: Circular Polarization and Magnetic Field Structures

Jungmi Kwon, et al, 'NEAR-INFRARED IMAGING POLARIMETRY OF GGD 27: CIRCULAR POLARIZATION AND MAGNETIC FIELD STRUCTURES', The Astrophysical Journal, 824:95 (14pp), June 2016. doi:10.3847/0004-637X/824/2/95. © 2016. The American Astronomical Society. All rights reserved.Near-infrared imaging polarimetry in the J, H, and K s bands was carried out for GGD 27 in the dark cloud Lynds 291. Details of an infrared reflection nebula associated with the optical nebulosity GGD 27 and the infrared nebula GGD 27 IRS are presented. Aperture photometry of 1263 point-like sources, detected in all three bands, was used to classify them based on a color-color diagram, and the linear polarization of several hundred sources was determined, with the latter used to map the magnetic field structure around GGD 27. This field, around GGD 27 IRS, appears to be associated with the extended CO outflow of IRAS 18162-2048 however, there are partly distorted or bent components in the field. The Chandrasekhar-Fermi method gives an estimate of the magnetic field strength as ˜90 μG. A region associated with GGD 27 IRS is discovered to have a circular polarization in the range of ˜2%-11% in the K s band. The circular polarization has an asymmetric positive/negative pattern and extends out to ˜ 120″ or 1.0 pc. The circular and linear polarization patterns are explained as resulting from a combination of dense inner and fainter outer lobes, suggesting episodic outflowPeer reviewedFinal Published versio

Similar zone-center gaps in the low-energy spin-wave spectra of NaFeAs and BaFe2As2

We report results of inelastic-neutron-scattering measurements of low-energy spin-wave excitations in two structurally distinct families of iron-pnictide parent compounds: Na(1-{\delta})FeAs and BaFe2As2. Despite their very different values of the ordered magnetic moment and N\'eel temperatures, T_N, in the antiferromagnetic state both compounds exhibit similar spin gaps of the order of 10 meV at the magnetic Brillouin-zone center. The gap opens sharply below T_N, with no signatures of a precursor gap at temperatures between the orthorhombic and magnetic phase transitions in Na(1-{\delta})FeAs. We also find a relatively weak dispersion of the spin-wave gap in BaFe2As2 along the out-of-plane momentum component, q_z. At the magnetic zone boundary (q_z = 0), spin excitations in the ordered state persist down to 20 meV, which implies a much smaller value of the effective out-of-plane exchange interaction, J_c, as compared to previous estimates based on fitting the high-energy spin-wave dispersion to a Heisenberg-type model.Comment: 5 pages, 4 figures, 1 tabl

Effects of Supplemental Beta-mannanase on Digestible Energy and Metabolizable Energy Contents of Copra Expellers and Palm Kernel Expellers Fed to Pigs

The purpose of this study was to determine the effect of β-mannanase supplementation on digestible energy (DE) and metabolizable energy (ME) contents of copra expellers (CE) and palm kernel expellers (PKE) fed to pigs. Six barrows with an initial body weight of 38.0 kg (standard deviation = 1.5) were randomly allotted to a 6×6 Latin square design with 6 dietary treatments and 6 periods. Six experimental diets were prepared in a 3×2 factorial treatment arrangement with 3 diets of a corn-soybean meal-based diet, a CE 30% diet, and a PKE 30% diet and with 2 concentrations of supplemental β-mannanase at 0 or 2,400 U/kg. All diets had the same proportion of corn:soybean meal ratio at 2.88:1. The marker-to-marker procedure was used for fecal and urine collection with 4-d adaptation and 5-d collection periods. No interactive effects were observed between diet and β-mannanase on energy digestibility and DE and ME contents of experimental diets. However, diets containing CE or PKE had less (p<0.05) DE and ME contents compared with the corn-soybean meal-based diet. The DE and ME contents in CE and PKE were not affected by supplemental β-mannanase. Taken together, we failed to find the effect of β-mannanase supplementation on energy utilization in CE and PKE fed to pigs

Design Principles for High-Capacity Mn-Based Cation-Disordered Rocksalt Cathodes

Mn-based Li-excess cation-disordered rocksalt (DRX) oxyfluorides are promising candidates for next-generation rechargeable battery cathodes owing to their large energy densities, the earth abundance, and low cost of Mn. In this work, we synthesized and electrochemically tested four representative compositions in the Li-Mn-O-F DRX chemical space with various Li and F content. While all compositions achieve higher than 200 mAh g−1 initial capacity and good cyclability, we show that the Li-site distribution plays a more important role than the metal-redox capacity in determining the initial capacity, whereas the metal-redox capacity is more closely related to the cyclability of the materials. We apply these insights and generate a capacity map of the Li-Mn-O-F chemical space, LixMn2-xO2-yFy (1.167 ≤ x ≤ 1.333, 0 ≤ y ≤ 0.667), which predicts both accessible Li capacity and Mn-redox capacity. This map allows the design of compounds that balance high capacity with good cyclability