Abating exhaust noises in jet engines

A noise abating improvement for jet engines including turbojets, turbofans, turboprops, ramjets, scramjets, and hybrid jets is introduced. A provision is made for an apparatus in the primary and/or secondary flow streams of the engines; the apparatus imparts to the exhaust gases a component rotation or swirl about the engine's longitudinal axis. The rotary component in the exhaust gases causes a substantial suppression of sound energy build up normally produced by an axial flow exhaust system

Minimization of jet and core noise by rotation of flow

Jet and core noise can be reduced and flame lengths may be significantly decreased when exhaust gases are caused to rotate or swirl about longitudinal axis of exhaust. Combustion in rotating flows is steady and quiet, and is not accompanied by pulsations or violent fluctuations

Planetary film reconnaissance system

Design, fabrication, assembly of planetary film reconnaissance syste

Third Conference on Sonic Boom Research

Prediction methods for sonic boom generation and propagation with overpressure minimization in supersonic transport design and operatio

All-Optical Depletion of Dark Excitons from a Semiconductor Quantum Dot

Semiconductor quantum dots are considered to be the leading venue for fabricating on-demand sources of single photons. However, the generation of long-lived dark excitons imposes significant limits on the efficiency of these sources. We demonstrate a technique that optically pumps the dark exciton population and converts it to a bright exciton population, using intermediate excited biexciton states. We show experimentally that our method considerably reduces the DE population while doubling the triggered bright exciton emission, approaching thereby near-unit fidelity of quantum dot depletion.Comment: 5 pages, 3 figure

Katrina\u27s Continuing Impact on Procurement - Emergency Procurement Powers in H.R. 3766

As Hurricane Katrina relief efforts grow into the billions of dollars, the U.S. Congress is considering additional legislation to liberalize procurement, including H.R. 3766, co-sponsored by Representatives Kenny Marchant and Tom Davis. In these comments on the proposed legislation, Professors Christopher Yukins and Joshua Schwartz asked whether the proposed changes, which would eviscerate competition for most procurement related to disaster relief, are truly necessary. Professor Yukins suggests that, though it might in some circumstances be necessary to dismantle the federal regulatory regime to accommodate a wave of new firms in the federal market, there is too little evidence yet to support such radical measures. Professor Schwartz argues that there is no basis, empirically or analytically, for any effort to undo the careful protections afforded by the federal procurement system

Large rare fluctuations in systems with delayed dissipation

We study the probability distribution and the escape rate in systems with delayed dissipation that comes from the coupling to a thermal bath. To logarithmic accuracy in the fluctuation intensity, the problem is reduced to a variational problem. It describes the most probable fluctuational paths, which are given by acausal equations due to the delay. In thermal equilibrium, the most probable path passing through a remote state has time reversal symmetry, even though one cannot uniquely define a path that starts from a state with given system coordinate and momentum. The corrections to the distribution and the escape activation energy for small delay and small noise correlation time are obtained in the explicit form.Comment: 9 page