Naval Surface Warfare Center

About: Naval Surface Warfare Center is a facility organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Radar & Sonar. The organization has 2855 authors who have published 3697 publications receiving 83518 citations. The organization is also known as: NSWC.

Electronic structure of Ni 3 Al and NiAl 3 alloys:mX-ray-absorption fine-structure analysis

Abstract: X-ray-absorption fine structure (XAFS) above the Ni K edge in Ni{sub 3}Al and NiAl{sub 3} alloys has been measured and theoretical full multiple-scattering analysis of these data have been done. The theoretical XAFS are found to be in agreement with experimental data. The XAFS of Ni{sub 3}Al and NiAl{sub 3} alloys are rather different. Since the dipole transition matrix element is not a very sharp function of the energy the experimental XAFS reflects the averaged in space partial Ni p unoccupied states in the conduction bands of the Ni{sub 3}Al and NiAl{sub 3} alloys, showing changes in the electronic structure going from Ni{sub 3}Al to NiAl{sub 3} alloy. Theoretical partial density of states curves calculated along the axis parallel to the c vector differ from the partial density of states curves calculated in the {ital ab} plane for both alloys. {copyright} {ital 1997} {ital The American Physical Society}

On Multipath Propagation in Electrically Large Reflective Spaces

Abstract: A simple model for predicting the characteristic energy decay time of wireless RF emissions in confined, reflective spaces is presented. Based on this cavity decay time, accurate estimates of room quality factor, diffuse (multipath propagation) insertion loss, and statistical electric field coverage can be easily obtained. Spaces of interest for model applications include aircraft cabins, below-deck compartments in ships, metallic storage buildings and reflective room enclosures. Decay time predictions are shown to be in excellent agreement with measured data in a reverberant test chamber over the 110 GHz frequency range.

Relating deformation to hot spots in shock-loaded crystals of ammonium perchlorate

Abstract: The purpose of this work is to perform a microscopic-scale study of the role that crystal defects have in forming hot spots during shock loading of large, optical quality, pure single crystals of ammonium perchlorate (AP). The crystals were immersed in mineral oil at various distances from a detonator that provided the shock. The small explosive donor permitted recovery of the crystals for quantitative chemical analysis of decomposition and microindentation hardness testing. Hardness testing was also performed on an unshocked crystal to determine 1) the slip systems associated with primary and secondary deformation in accommodating the indenter and 2) the crack propagation directions at the surface as well as into the crystal. High-speed photographs of the shock-loaded crystals showed slip and cracking systems identified by hardness testing. Some of the systems were luminous. In addition, when a crystal with a large indentation was shocked near its reaction threshold, significant light appeared in the vicinity of the identation following shock passage. As such, preferred chemical reactivity in AP has been associated with its deformation systems and the presence of large strain centers.

Aluminum Hydride as a Fuel Supplement to Nanothermites

Abstract: PressurizationratesincreasebyafactorofabouttwowiththeadditionofAlH3,whereasburntubevelocitiesincrease by about 25%. The enhancement in pressurization rate appears to primarily be a result of the increased pressure associated with the AlH3 decomposition in the nanocomposite thermite system and an enhancement in convective heat transfer. Similar experiments were conducted with micron-scale aluminum in place of the aluminum hydride, whichresultedinareductionofallthepreviouslymentionedparameterswithrespecttothebaselinenanoaluminum– copper-oxide thermite. The addition of any amount of alane to iron oxide based thermite resulted in a reduction in performance in pressure cell testing. The performanceofBi2O3 basedthermite was largelyunaffected by alaneuntil alanebecamethemajorityfuelcomponent.Theseresultshavebeenfoundtocorrelatewithchangesinthecombustion mechanism through equilibrium calculations.