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Institution

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.


Papers
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Journal ArticleDOI
06 Feb 2009-Science
TL;DR: It is reported that vertically aligned nitrogen-containing carbon nanotubes (VA-NCNTs) can act as a metal-free electrode with a much better electrocatalytic activity, long-term operation stability, and tolerance to crossover effect than platinum for oxygen reduction in alkaline fuel cells.
Abstract: The large-scale practical application of fuel cells will be difficult to realize if the expensive platinum-based electrocatalysts for oxygen reduction reactions (ORRs) cannot be replaced by other efficient, low-cost, and stable electrodes. Here, we report that vertically aligned nitrogen-containing carbon nanotubes (VA-NCNTs) can act as a metal-free electrode with a much better electrocatalytic activity, long-term operation stability, and tolerance to crossover effect than platinum for oxygen reduction in alkaline fuel cells. In air-saturated 0.1 molar potassium hydroxide, we observed a steady-state output potential of –80 millivolts and a current density of 4.1 milliamps per square centimeter at –0.22 volts, compared with –85 millivolts and 1.1 milliamps per square centimeter at –0.20 volts for a platinum-carbon electrode. The incorporation of electron-accepting nitrogen atoms in the conjugated nanotube carbon plane appears to impart a relatively high positive charge density on adjacent carbon atoms. This effect, coupled with aligning the NCNTs, provides a four-electron pathway for the ORR on VA-NCNTs with a superb performance.

6,370 citations

Journal ArticleDOI
TL;DR: In this article, an operationally simple strength criterion for anisotropic materials is developed from a scalar function of two strength tensors, which satisfies the invariant requirements of coordinate transforma tion, takes into account the difference in strengths due to positive and negative stresses, and can be specialized to account for different material symmetries, multi-dimensional space, and multi-axial stresses.
Abstract: An operationally simple strength criterion for anisotropic materials is developed from a scalar function of two strength tensors. Differing from existing quadratic approximations of failure surfaces, the present theory satisfies the invariant requirements of coordinate transforma tion, treats interaction terms as independent components, takes into account the difference in strengths due to positive and negative stresses, and can be specialized to account for different material symmetries, multi-dimensional space, and multi-axial stresses. The measured off-axis uniaxial and pure shear data are shown to be in good agreement with the predicted values based on the present theory.

3,030 citations

Journal ArticleDOI
TL;DR: The Halpin-Tsai equations are based upon the self-consistent micromechanics method developed by Hill as discussed by the authors. But they are not suitable for semi-crystalline polymers.
Abstract: The Halpin-Tsai equations are based upon the “self-consistent micromechanics method” developed by Hill. Hermans employed this model to obtain a solution in terms of Hill's “reduced moduli”. Halpin and Tsai have reduced Hermans' solution to a simpler analytical form and extended its use for a variety of filament geometries. The development of these micromechanic's relationships, which form the operational bases for the coniposite analogy of Halpin and Kardos for semi-crystalline polymers, are reviewed herein.

2,609 citations

Journal ArticleDOI
13 Aug 2004-Science
TL;DR: Measurements of plastic yielding for single crystals of micrometer-sized dimensions for three different types of metals find that within the tests, the overall sample dimensions artificially limit the length scales available for plastic processes.
Abstract: When a crystal deforms plastically, phenomena such as dislocation storage, multiplication, motion, pinning, and nucleation occur over the submicron-to-nanometer scale. Here we report measurements of plastic yielding for single crystals of micrometer-sized dimensions for three different types of metals. We find that within the tests, the overall sample dimensions artificially limit the length scales available for plastic processes. The results show dramatic size effects at surprisingly large sample dimensions. These results emphasize that at the micrometer scale, one must define both the external geometry and internal structure to characterize the strength of a material.

2,113 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