Wright-Patterson Air Force Base

About: Wright-Patterson Air Force Base is a other organization based out in Wright-Patterson AFB, Ohio, United States. It is known for research contribution in the topics: Laser & Microstructure. The organization has 5817 authors who have published 9157 publications receiving 292559 citations. The organization is also known as: Wright-Patterson AFB & FFO.

Magnetocrystalline anisotropy of Sm Co 5 and its interpretation on a crystal-field model

Abstract: Results of magnetization measurements on carefully prepared single crystals of Sm${\mathrm{Co}}_{5}$ are presented over the temperature range 4-970 K. The contribution of the rare-earth sublattice magnetocrystalline anisotropy was evaluated using the data on Y${\mathrm{Co}}_{5}$ as "a blank." These results are interpreted on the basis of a singleion model. The following Hamiltonians were employed to obtain eigenvalues: $\mathcal{H}(\mathrm{parallel}\mathrm{to} c \mathrm{axis})=\ensuremath{\lambda}\stackrel{\ensuremath{\rightarrow}}{\mathrm{L}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{S}}+{\mathcal{H}}_{\mathrm{CF}}+2{\ensuremath{\mu}}_{B}{S}_{z}{H}_{\mathrm{ex}}$, $\mathcal{H}(\mathrm{perpendicular}\mathrm{to} c \mathrm{axis})=\ensuremath{\lambda}\stackrel{\ensuremath{\rightarrow}}{\mathrm{L}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{S}}+{\mathcal{H}}_{\mathrm{CF}}+2{\ensuremath{\mu}}_{B}{S}_{x}{H}_{\mathrm{ex}}$. ${H}_{\mathrm{ex}}$ was regarded as arising mainly from the cobalt sublattice. Contributions arising from the multiplets $^{6}H_{\frac{7}{2}}$ and $^{6}H_{\frac{9}{2}}$ to the ground multiplet $^{6}H_{\frac{5}{2}}$ were included. The crystal field was evaluated in terms of Racah's tensor-operator technique employing $3\ensuremath{-}j$ and $6\ensuremath{-}j$ symbols. With the two sets of eigenvalues obtained from the above expressions, the anisotropy energy to rotate the magnetization direction from the axis to the plane was calculated and compared with experimental results on single crystals of Sm${\mathrm{Co}}_{5}$. It is shown that the sign of the crystal-field parameter predicts the correct easy direction of magnetization and that the free-energy values calculated from 4 to 970 K are in reasonable agreement with experiment.

Behavior of linear reconstruction techniques on unstructured meshes

Abstract: : This report presents an assessment of a variety of reconstruction schemes on meshes with both quadrilateral and triangular tessellations. The investigations measure the order of accuracy, absolute error and convergence properties associated with each method. Linear reconstruction approaches using both Green-Gauss and least squares gradient estimation are evaluated against a structured MUSCL scheme wherever possible. In addition to examining the influence of polygon degree and reconstruction strategy, results with three limiters are examined and compared against unlimited results when feasible. The methods are applied on quadrilateral, right triangular, and equilateral triangular elements in order to facilitate an examination of the scheme behavior on a variety of element shapes. The numerical test cases include well known internal and external inviscid examples and also a supersonic vortex problem for which there exists a closed form solution to the 2-D compressible Euler equations. Such investigations indicate that the least squares gradient estimation provides significantly more reliable results on poor quality meshes. Furthermore, limiting only the face normal component of the gradient can significantly increase both accuracy and convergence while still preserving the integral cell average, and maintaining monoticity. The first order method performs poorly on stretched triangular meshes, and analysis shows that such meshes result in poorly aligned left and right states for the Riemann problem. The higher average valence of a vertex in the triangular tessellations does not appear to enhance the wave propagation, accuracy, or convergence properties of the method. Unstructured, Upwind, Inviscid, Reconstruction, Limiters, Riemann problems.

A review of the neurotoxicity risk of selected hydrocarbon fuels.

Abstract: Over 1.3 million civilian and military personnel are occupationally exposed to hydrocarbon fuels, emphasizing gasoline, jet fuel, diesel fuel, or kerosene. These exposures may occur acutely or chronically to raw fuel, vapor, aerosol, or fuel combustion exhaust by dermal, respiratory inhalation, or oral ingestion routes, and commonly occur concurrently with exposure to other chemicals and stressors. Hydrocarbon fuels are complex mixtures of 150-260+ aliphatic and aromatic hydrocarbon compounds containing varying concentrations of potential neurotoxicants including benzene, n-hexane, toluene, xylenes, naphthalene, and certain n-C9-C12 fractions (n-propylbenzene, trimethylbenzene isomers). Due to their natural petroleum base, the chemical composition of different hydrocarbon fuels is not defined, and the fuels are classified according to broad performance criteria such as flash and boiling points, complicating toxicological comparisons. While hydrocarbon fuel exposures occur typically at concentrations below...

Multiple Timescale Flight Control Using Reconfigurable Sliding Modes

Abstract: Adual-timescaleaircrafte ight-controlproblemisaddressedviacontinuoussliding-modecontrol.Sliding-surface boundary-layer recone guration is used to account for actuator dynamics, dee ection limits, and rate limits. A recone gurable sliding-mode e ight controller is designed that achieves robust, high-accuracy tracking of outerloop command angles before and after damage to an aircraft. Angular rate commands are robustly tracked in an inner loop. The recone gurable e ight-control strategy is based on a continuous sliding-mode controller with direct boundary-layer adaptation for recone guration. On-line explicit system or damage identie cation is not required. Therecone gurablesliding-modee ight-controltechniqueisapplied to anonlineare ight-dynamicsmodelofan F-16 aircraft. Computer simulations demonstrate stability and high-accuracy tracking performance without violation of actuator limits.

Immobilization of histidine-tagged proteins on nickel by electrochemical dip pen nanolithography.

Abstract: Dip-pen nanolithography (DPN) is becoming a popular technique to “write” molecules on a surface by using the tip of an atomic force microscope (AFM) coated with the desired molecular “ink”. In this work, we demonstrate that poly-histidine-tagged peptides and proteins, and free-base porphyrins coated on AFM probes, can be chelated to ionized regions on a metallic nickel surface by applying an electric potential to the AFM tip in the DPN process. DPN has been accomplished in the Tapping Mode of AFM, which creates many possible applications of positioning and subsequently imaging biomolecules, especially on soft surfaces.