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Wright-Patterson Air Force Base

OtherWright-Patterson AFB, Ohio, United States
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 & Mach number. The organization has 5817 authors who have published 9157 publications receiving 292559 citations. The organization is also known as: Wright-Patterson AFB & FFO.


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Journal ArticleDOI
08 Feb 2012-ACS Nano
TL;DR: The results suggest that peptide-based approaches may be able to achieve control over the structure/function relationship of nanomaterials where the peptide sequence could be used to selectivity tune such capabilities.
Abstract: The ability to tune the size, shape, and composition of nanomaterials at length scales <10 nm remains a challenging task. Such capabilities are required to fully realize the application of nanotechnology for catalysis, energy storage, and biomedical technologies. Conversely, nature employs biomacromolecules such as proteins and peptides as highly specific nanoparticle ligands that demonstrate exacting precision over the particle morphology through controlling the biotic/abiotic interface. Here we demonstrate the ability to finely tune the size, surface structure, and functionality of single-crystal Pd nanoparticles between 2 and 3 nm using materials directing peptides. This was achieved by selectively altering the peptide sequence to change the binding motif, which in turn modifies the surface structure of the particles. The materials were fully characterized before and after reduction using atomically resolved spectroscopic and microscopic analyses, which indicated that the coordination environment prior...

81 citations

Journal ArticleDOI
TL;DR: In this article, the reaction kinetics between α-Ti alloys and single crystal sapphire, the phase composition and morphology of the reaction-zone, and the phase compatibility in the system Ti-Al-O were investigated as part of a study to determine the feasibility of fabricating useful Al2O3-reinforced titanium matrix composites.
Abstract: The reaction kinetics between α-Ti alloys and single crystal sapphire, the phase composition and morphology of the reaction-zone, and the phase compatibility in the system Ti-Al-O were investigated as part of a study to determine the feasibility of fabricating useful Al2O3-reinforced titanium matrix composites. In the temperature range 650 to 1000° C titanium reduces Al2O3 to form a complex reaction layer consisting of two distinct zones; an inner zone adjacent to the Al2O3 of a TiO phase containing isolated particles of (Ti, Al)2O3, presumably, and an outer zone of a Ti3Al phase adjacent to the Ti matrix. The isothermal growth of the reaction layer follows a parabolic rate law. The temperature dependence of the rate constants fits an Arrhenius equation yielding activation energies of 50 to 52 kcal/mol. The high Al alloys, except Ti-6Al-2Sn-4Mo-2Zr, reacted more rapidly than pure Ti indicating that Al diffusion through the reaction zone may be the rate-limiting step.

81 citations

Journal ArticleDOI
TL;DR: In this paper, a modified eddy viscosity model is incorporated into the compressible Navier-Stokes equations to reproduce the response of turbulence to a severe pressure gradient in the flowfield.
Abstract: A modified eddy viscosity model is incorporated into the compressible Navier-Stokes equations. The modification attempts to reproduce the response of turbulence to a severe pressure gradient in the flowfield. This relaxation phenomenon is described by an exponential decay of the unperturbed eddy viscosity coefficient downstream of the perturbation in terms of a prescribed length scale. The system of equations is solved by MacCormack's time-splitting explicit numerical scheme for a series of compression corner configurations. Computations are performed for ramp angles varying from 15 to 25° at a Mach number of 2.96 and a Reynolds number of 10 7. Calculations utilizing the modified eddy viscosity for the interacting turbulent flow compare very well with experimental measurements, particularly in the prediction of the upstream pressure propagation and location of the separation and the reattachment points. Good agreement is also attained between the measured and calculated density profiles in the viscous-inviscid interaction region.

81 citations

Journal ArticleDOI
TL;DR: In this article, a novel orthogonal lithography process is reported to pattern all-inorganic perovskite CsPbX3 (X = Cl, Br, I) arrays which cannot be patterned with traditional approaches.
Abstract: DOI: 10.1002/adom.201800474 passivation to achieve high quantum yield due to the self-passivation effect of halogen,[5,6] enabling a facile synthesis of highly fluorescent emitters without the need of careful design of core/shell interface.[7,8] In addition, the absorption and emission spectra of QDs can be altered not only by size but also by the facile composition tuning via anion (i.e., X) exchange, thereby providing more freedom to achieve superior optical properties.[9] Moreover, high net optical gain value of 450 cm−1 and low pump threshold down to 5 μJ cm−2 have been reported, demonstrating that these QDs can be readily used for light amplification and lasing at very low excitation intensity.[10] These properties have been extensively studied for use in spectrochemical probes, light-emitting diodes, and vertical cavity surface emitting lasers. Clearly, these show that CsPbX3 QDs have potential for a variety of optoelectronic applications.[11–13] In recent years, patterning techniques for single crystal and polycrystalline perovskite materials have been extensively developed including electron beam lithography, controlled crystallization via molding, inkjet printing, and template-assisted patterning with intriguing photonic properties.[14–19] In contrast, nearly all studies of perovskite nanoparticles such as QDs to date have focused on the synthesis, photophysics, and optoelectronic applications while the development of patterning techniques has been comparatively few and limited in scope.[20,21] This approach contrasts sharply to the Cd-based QDs where high-resolution lithographic methods such as electron-beam lithography and photolithography have been adopted widely to integrate Cd-based QDs into microand nanoscale devices.[22,23] The difference is essentially understandable, when considering the ionic nature of CsPbX3 QDs, which makes them prone to dissolution in common polar solvents that are required in these high-resolution lithographic methods.[19,24] The chemical instability to polar solvents severely hinders the integration of these QDs into patterned photonic structures. Moreover, unlike counterpart of the bulk perovskite materials that can be patterned by dissolving polymer spheres or templates with nonpolar solvent such as toluene,[19] the ligand-capped perovskite QDs are unfortunately well dispersed in nonpolar solvents. The solvent constraint in both polar and nonpolar solvents indeed places the development of CsPbX3 QD patterning for miniaturized optical arrays in a dilemma. Clearly, a novel lithographic Herein, a novel orthogonal lithography process is reported to pattern all-inorganic perovskite CsPbX3 (X = Cl, Br, I) quantum dot (QD) arrays which cannot be patterned with traditional approaches. This approach involves a combination of fluorinated polymer and solvent to resolve issues of polar–nonpolar solvent constraints thus enabling the fabrication of complex patterns with high optical gain and multicolor emission. This approach is utilized to fabricate high-resolution large-area arrays of microdisk lasers and multicolor (binary and ternary emission) pixels. The optical cavity modes of CsPbBr3 QD microdisk lasers are readily controlled by tuning the disk size, where the mode spacing decreases while the number of modes increases with increasing disk diameter. Finally, the versatility of this approach for the integration of environmentally sensitive QDs with different emission signatures and composition on the same chip, while achieving high-density, high-resolution large-area QD arrays with multicolor pixels, is demonstrated.

81 citations

Journal ArticleDOI
TL;DR: In this article, the role of each parameter in the acceleration of crack tip damage is governed mainly by their relative influence on the nature of the corresponding plastic deformation and associated slip line density.
Abstract: — In this paper observations concerning the effects of mechanical variables on the crack growth process in alloy 718 are reviewed and analyzed on the basis of the related deformation characteristics in the crack tip region. The variables included temperature, frequency, wave shape, hold time, load ratio and load interaction. These analyses have suggested that the role of each parameter in the acceleration of crack tip damage is governed mainly by their relative influence on the nature of the corresponding plastic deformation and associated slip line density. On the basis of this view (which assumes crack growth damage covers the range from cyclic- to fully time-dependent processes), the interactive effects of loading parameters are discussed when considering the corresponding fracture mode. Conflicting experimental observations under different operating conditions are examined.

81 citations


Authors

Showing all 5825 results

NameH-indexPapersCitations
John A. Rogers1771341127390
Liming Dai14178182937
Mark C. Hersam10765946813
Gareth H. McKinley9746734624
Robert E. Cohen9141232494
Michael F. Rubner8730129369
Howard E. Katz8747527991
Melvin E. Andersen8351726856
Eric A. Stach8156542589
Harry L. Anderson8039622221
Christopher K. Ober8063129517
Vladimir V. Tsukruk7948128151
David C. Look7852628666
Richard A. Vaia7632425387
Kirk S. Schanze7351219118
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20234
202211
2021279
2020298
2019290
2018272