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 & 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.

Intermetallic alloys based on gamma titanium aluminide

Abstract: Titanium-aluminide alloys based on TiAl have an excellent potential to become one of the most important aerospace materials because of their low density, high melting temperature, good elevated-temperature strength and modulus retention, high resistance to oxidation and hydrogen absorption, and excellent creep properties. The chief roadblock to their application is poor ductility at low to intermediate temperatures that results in low fracture toughness and a fast fatigue-crack growth rate. During the last several years, a great deal of effort has been made to improve these ductile properties. These endeavors have met with some success through chemistry modification and microstructure control.

Valence-band ordering in ZnO

Abstract: The emission and reflection spectra of ZnO have been investigated in the intrinsic region and the data have been interpreted in terms of the wurtzite crystal band structure. Free-exciton emission is observed for the first time. Both the ${\ensuremath{\Gamma}}_{5}$ and ${\ensuremath{\Gamma}}_{6}$ state excitons associated with top valence band have been identified. This identification has established the valence-band symmetry ordering in ZnO.

Adaptive sequential estimation with unknown noise statistics

Abstract: Sequential estimators are derived for suboptimal adaptive estimation of the unknown a priori state and observation noise statistics simultaneously with the system state. First- and second-order moments of the noise processes are estimated based on state and observation noise samples generated in the Kalman filter algorithm. A limited memory algorithm is developed for adaptive correction of the a priori statistics which are intended to compensate for time-varying model errors. The algorithm provides improved state estimates at little computational expense when applied to an orbit determination problem for a near-earth satellite with significant modeling errors.

Adhesion of Graphite Fibers to Epoxy Matrices: I. The Role of Fiber Surface Treatment

Abstract: Adhesion between graphite fibers and epoxy matrices is a necessary and sometimes controlling factor in achieving optimum performance. Manufacturers′ proprietary fiber surface treatments promote adhesion without providing a basic understanding of the fiber surface properties altered through their use. This study has combined fiber surface chemistry, morphology, interfacial strength measurements and fracture characterization in order to elucidate the role of surface treatments. The results of this investigation lead to the conclusion that surface treatments designed to promote adhesion to epoxy matrix materials operate through a two-part mechanism. First, the treatments remove a weak outer fiber layer initially present on the fiber. Second surface chemical groups are added which increase the interaction with the matrix. Increases in fiber surface area are not an important factor in promoting fiber-matrix adhesion. In some cases the upper limit to fiber-matrix interfacial shear strength is the intri...

Liquid Fuels and Propellants for Aerospace Propulsion: 1903-2003

Abstract: Introduction M AJOR increases in liquid-fueled propulsion performance have occurred in the past 100 years.TheWright brothersŽ rst  ew on 14 December 1903 with an engine that generated slightly more than 130 lb of thrust for  ights that ranged from 120 to 850 ft (Ref. 1). Contrast that with current aircraft such as the Boeing 777, which can  y 8000 n miles, equipped with engines from the GE90 and PW4000 series that generate over 100,000 lb of thrust. The Wright brothers probably consumed less than a gallon of gasoline in that Ž rst day of  ight tests. In 1997, airlines consumedan average of 177 million gal/day of jet fuel worldwide.2¤ Robert Goddard’s Ž rst  ight of a liquid rocket on 16March 1926 reachedan altitudeof 41 ft and landed184 ft from the launchpoint (seeRef. 3). Again, the contrast with current vehicles such as the space shuttle, which can lift over 50,000 lb to 200C miles into low Earth orbit, is dramatic. The intent of this paper is to describe the evolution of liquid fuels for aircraft and rockets as the engines and vehicles they fuel have undergone these signiŽ cant increases in performance.