1,958 research outputs found
Thermal-structural design study of an airframe-integrated Scramjet
Design concepts are developed and evaluated for a cooled structures assembly for the Scramjet engine, for engine subsystems mass, volume, and operating requirements, and for the aircraft/engine interface. A thermal protection system was defined that makes it possible to attain a life of 100 hours and 1000 cycles. The coolant equivalence ratio at the Mach 10 maximum thermal loading condition is 0.6, indicating a capacity for airframe cooling. The mechanical design is feasible for manufacture using conventional materials. For the cooled structures in a six-module engine, the mass per unit capture area is 12.4 KN/sq m. The total weight of a six-module engine assembly including the fuel system is 14.73 KN
Reading First Impact Study: Interim Report
This report, written by Abt Associates and MDRC and published by the U.S. Department of Education's Institute of Education Sciences, finds that Reading First increased the amount of time that teachers spent on the five essential components of reading instruction, as defined by the National Reading Panel. While Reading First did not improve students' reading comprehension on average, there are some indications that some sites had impacts on both instruction and reading comprehension. An overview puts these interim findings in context
Thermal-structural design study of an airframe-integrated Scramjet
The development and evaluation of a design concept for the cooled structures assembly for the Scramjet engine is discussed. Development concepts for engine subsystems and design concepts for the aircraft/engine interface are included. A thermal protection system was defined which makes it possible to attain a life of 100 hr and 1000 cycles, the specified goal. The coolant equivalence ratio at the Mach 10 maximum thermal loading condition is 0.6, indicating a capacity for airframe cooling. The mechanical design is feasible for manufacture using conventional materials. For the cooled structures in a six module engine, the mass per unit capture area is 1256 kg/sq m. The total mass of a six module engine assembly including the fuel system is 1502 kg
Controlled lasing from active optomechanical resonators
Planar microcavities with distributed Bragg reflectors (DBRs) host, besides
confined optical modes, also mechanical resonances due to stop bands in the
phonon dispersion relation of the DBRs. These resonances have frequencies in
the sub-terahertz (10E10-10E11 Hz) range with quality factors exceeding 1000.
The interaction of photons and phonons in such optomechanical systems can be
drastically enhanced, opening a new route toward manipulation of light. Here we
implemented active semiconducting layers into the microcavity to obtain a
vertical-cavity surface-emitting laser (VCSEL). Thereby three resonant
excitations -photons, phonons, and electrons- can interact strongly with each
other providing control of the VCSEL laser emission: a picosecond strain pulse
injected into the VCSEL excites long-living mechanical resonances therein. As a
result, modulation of the lasing intensity at frequencies up to 40 GHz is
observed. From these findings prospective applications such as THz laser
control and stimulated phonon emission may emerge
Giant increase in the metal-enhanced fluorescence of organic molecules in nanoporous alumina templates and large molecule-specific red/blue shift of the fluorescence peak
The fluorescence of organic fluorophore molecules is enhanced when they are
placed in contact with certain metals (Al, Ag, Cu, Au, etc.) whose surface
plasmon waves couple into the radiative modes of the molecules and increase the
radiative efficiency. Here, we report a hitherto unknown size dependence of
this metal enhanced fluorescence (MEF) effect in the nanoscale. When the
molecules are deposited in nanoporous anodic alumina films with exposed
aluminum at the bottom of the pores, they form organic nanowires standing on
aluminum nanoparticles whose plasmon waves have much larger amplitudes. This
increases the MEF strongly, resulting in several orders of magnitude increase
in the fluorescence intensity of the organic fluorophores. The increase in
intensity shows an inverse super-linear dependence on nanowire diameter because
the nanowires also act as plasmonic 'waveguides' that concentrate the plasmons
and increase the coupling of the plasmons with the radiative modes of the
molecules. Furthermore, if the nanoporous template housing the nanowires has
built-in electric fields due to space charges, a strong molecule-specific red-
or blue-shift is induced in the fluorescence peak owing to a renormalization of
the dipole moment of the molecule. This can be exploited to detect minute
amounts of target molecules in a mixture using their optical signature
(fluorescence) despite the presence of confounding background signals. It can
result in a unique new technology for bio- and chemical-sensing
Novel early life risk factors for adult pulmonary hypertension
The role of perinatal insults in the development of adult onset pulmonary hypertension (PH) is unclear. We surveyed patients with and without PH for a history of early life risk factors, and identified prematurity, oxygen use, and respiratory illness each as risk predictors for development of adult PH
Biocatalytic Enantioselective Hydroaminations Enabling Synthesis of N-Arylalkyl-Substituted L-Aspartic Acids
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