35,978 research outputs found
Use of spaceborne imaging radar in regional geomorphic studies
In the past two decades, the use of both photographic and non-photographic remote sensing from satellite platforms has provided a unique capability for the observation and study of Earth and planetary surfaces. A wide range of imaging sensors that operate in different portions of the electromagnetic spectrum have yielded images of large areas that formerly were unknown or that had not previously been observed at a simultaneous instant in time. In addition, remote sensors equipped with multispectral or multiband capabilities are capable of taking data at different wavelengths simultaneously. Notable examples include the LANDSAT series of multispectral scanners, thematic mappers, and return beam vidicons. Synthetic aperture radar and LANDSAT imagery are discussed
Fibre imaging bundles for full-field optical coherence tomography
An imaging fibre bundle is incorporated into a full-field imaging OCT system,
with the aim of eliminating the mechanical scanning currently required at the
probe tip in endoscopic systems. Each fibre within the imaging bundle addresses
a Fizeau interferometer formed between the bundle end and the sample, a
configuration which ensures down lead insensitivity of the probe fibres,
preventing variations in sensitivity due to polarization changes in the many
thousand constituent fibres. The technique allows acquisition of information
across a planar region with single-shot measurement, in the form of a 2D image
detected using a digital CCD camera. Depth scanning components are now confined
within a processing interferometer external to the completely passive endoscope
probe. The technique has been evaluated in our laboratory for test samples, and
images acquired using the bundle-based system are presented. Data are displayed
either as en-face scans, parallel to the sample surface, or as slices through
the depth of the sample, with a spatial resolution of about 30 ï Âm. The minimum
detectable reflectivity at present is estimated to be about 10-3, which is
satisfactory for many inorganic samples. Methods of improving the signal-to-
noise ratio for imaging of lower reflectivity samples are discuss
Detection of negative energy: 4-dimensional examples
We study the response of switched particle detectors to static negative
energy densities and negative energy fluxes. It is demonstrated how the
switching leads to excitation even in the vacuum and how negative energy can
lead to a suppression of this excitation. We obtain quantum inequalities on the
detection similar to those obtained for the energy density by Ford and
co-workers and in an `operational' context by Helfer. We revisit the question
`Is there a quantum equivalence principle?' in terms of our model. Finally, we
briefly address the issue of negative energy and the second law of
thermodynamics.Comment: 10 pages, 7 figure
Disentanglement and Decoherence without dissipation at non-zero temperatures
Decoherence is well understood, in contrast to disentanglement. According to
common lore, irreversible coupling to a dissipative environment is the
mechanism for loss of entanglement. Here, we show that, on the contrary,
disentanglement can in fact occur at large enough temperatures even for
vanishingly small dissipation (as we have shown previously for decoherence).
However, whereas the effect of on decoherence increases exponentially with
time, the effect of on disentanglement is constant for all times,
reflecting a fundamental difference between the two phenomena. Also, the
possibility of disentanglement at a particular increases with decreasing
initial entanglement.Comment: 3 page
Shunt voltage regulator circuit for nickel- cadmium cells with auxiliary electrodes
Shunt voltage regulator circuit for nickel- cadmium cells with auxiliary electrode
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