1,024 research outputs found
Performance limitations of GaAs/AlGaAs infrared superlattices
The performance of the GaAs/AlGaAs superlattice as an infrared detecting material is modeled as a function of temperature for two cutoff wavelengths, namely, 8.3 and 10.0 µm. The results are compared with HgCdTe, the present industry standard material for infrared systems. The limiting performance of the GaAs/AlGaAs materials system is found to be orders of magnitude below that of HgCdTe for any specific cutoff wavelength and operating temperature
Low crater frequencies and low model ages in lunar maria: Recent endogenic activity or degradation effects?
Recently a number of studies have identified small lunar geologic structures
to be <100 Ma in age using standard remote sensing techniques. Here we present
new crater size frequency distributions (CSFD) and model ages using craters D>
10 m for 5 small target units: 1 Irregular Mare Patch (IMP) in Mare Nubium and
4 regions located on lunar wrinkle ridges in Mare Humorum. For comparison we
also date another IMP found in a recent study in Mare Tranquillitatis (Braden
et al., 2014). Absolute model age derivation corresponds to 465 Ma and
221 Ma for Nubium and Sosigenes IMP. We show that for IMPs and in nearby
control mare regions similar production-like cumulative log-log SFD slopes of
-3 are observed. In contrast control mare regions in Mare Humorum exhibit
shallower equilibrium slopes from -1.83 to -2. 3 out of 4 wrinkle ridges appear
to be in equilibrium but with crater life times lower than on the corresponding
maria. Low crater frequencies on one wrinkle ridge result in an age of
8.61 Ma. This study region contains 80% fresh craters which suggests that
the crater population is still in production indicative of a recent resurfacing
event
Equipment for husking macadamia nuts
Literature cited: p. 19.Mode of access: Internet
The employment of jet V-STOL aircraft at sea
The means by which the Royal Navy will continue to
operate fixed-wing aircraft at sea is by employing VTOL or·
given an aid to-take-off, STOVL aircraft. The aid being '
brought into service is -the Skijump, which permits a
large increase in payload over unassisted VTOL. The
effectiveness of skijump increases with its exit angle up
to about 40°, but other considerations of size and
ungainliness set a practical lim~tation nearer to 20°.
The endspeeds required for ballistic launch off a
skijump could be achieved or-enhanced by the use of assistance
by catapult or rocket motor. Both of these would call
for the initiation of programmes of full research and
development, while the skijump, capable of conferring.
equivalent performance if it is long enough, already exists.
The· smallest number of aircraft in an airgroup able
to keep up a useable flying task is three. A vessel big
enough to mount three aircraft together with the gear
necessary to support and arm them would be big enough to
mount a skijump as well. Its size is dictated too by the
sea conditions in which it is expected to keep operational.
The vessel in question should be a displacement ship,
either conventional (e.g. large frigate) or unconventional
(e.g. Small Waterplane Area Twin Hull). There is no role
here for either hovercraft or hydrofoil.
Commitment to the skijump.in the ship means commitment
to vectored-thrust as a means of propulsion in the
next aircraft~ When specified it must be compatible with
existing skijump decks, and it should be single-engined.
Its targets for Reliability and Maintainability mµst be
wholly related to the Availability called for, and must
be given equal prominence with performance.Ph
Educating Dental Students About Eating Disorders: Perceptions and Practice of Interprofessional Care
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153591/1/jddjde017090.pd
- …