113,410 research outputs found
Dual band combiner for horn antenna
A corrugated horn antenna, adapted to be coupled to a waveguide at its apex for X-band excitation is further adapted to be connected to waveguides through a circumferential slot for S-band excitation at four distinct phases selected for the desired S-band polarization. The circumferential slot is positioned along the axial length of the horn for good impedance matching and is provided with an X-band choke in the form of two concentric choke slots. For further improvement in impedance matching, the second (outer) choke slot is divided by plugs into four segments that coincide with waveguide ports for the four distinct phases of the S-band
Comments on the Aharonov-Casher effect
We study the basic requirements for neutron confinement in the framework of
some 3-D Aharonov-Casher configurations.Comment: To appear in Physica Scripta (2001
Direct observation of voids in the vacancy excess region of ion bombarded silicon
The results reported in this letter indicate that the spatial separation of the vacancy and interstitial excesses which result from ion bombardment gives rise to stable voids upon annealing at 850 °C even for implants where the projected ion range is only of the order of a few thousand Ångstrom. Such voids have been observed directly by transmission electron microscopy. Furthermore, in cases where both voids and interstitial-based defects are present at different depths, it is found that Au has a strong preference for decorating void surfaces and hence Au can, indeed, be used as a selective detector of open volume defects in Si.One of the authors ~J.W.-L.!
acknowledges the Australian Research Council for financial
support
User's guide for CCT2WA (converting CCT's to work-addressable file)
The CCT2WA program, developed to convert the shuttle post-flight computer compatible tape data to a word addressable mass storage file, is described. The use of utility processors that can be used to copy word addressable files from mass storage to mass storage is also described
The administration of research. An interpretive summary of the Proceedings of the National Conference on the Administration of Research, 1947-1964
Research management and administration - summary of conference proceeding
Non-universal Casimir Effect in Saturated Superfluid He Films at T
Measurements of Casimir effects in He films in the vicinity of the bulk
superfluid transition temperature have been carried out, where
changes in the film thickness and the superfluid density are both monitored as
a function of temperature. The Kosterlitz-Thouless superfluid onset temperature
in the film is found to occur just as the Casimir dip in the film thickness
from critical fluctuations becomes evident. Additionally, a new film-thickening
effect is observed precisely at when the temperature is swept
extremely slowly. We propose that this is a non-universal Casimir effect
arising from the viscous suppression of second sound modes in the film.Comment: 5 pages, 6 figures, corrected an equation, small change to fit valu
Analysis of radar images of the active volcanic zone at Krafla, Iceland: The effects of look azimuth biasing
The geomorphic expression of Mid-Ocean-Ridge (MOR) volcanism in a subaerial setting occurs uniquely on Earth in Iceland, and the most recent MOR eruptive activity has been concentrated in the Northeastern Volcanic Zone in an area known as Krafla. Within the Krafla region are many of the key morphologic elements of MOR-related basaltic volcanism, as well as volcanic explosion craters, subglacial lava shields, tectonic fissure swarms known as gjar, and basaltic-andesite flows with well developed ogives (pressure-ridges). The objective was to quantify the degree to which the basic volcanic and structural features can be mapped from directional SAR imagery as a function of the look azimuth. To accomplish this, the current expression of volcanic and tectonic constructs was independently mapped within the Krafla region on the E, W, and N-looking SAR images, as well as from SPOT Panchromatic imagery acquired in 1987. The initial observations of the E, W, and N images indicates that fresh a'a lava surfaces are extremely radar bright (rough at 3 cm to meter scales) independent of look direction; this suggests that these flows do not have strong flow direction related structures at meter and cm scales, which is consistent with typical Icelandic a'a lava surfaces in general. The basic impression from a preliminary analysis of the effects of look azimuth biasing on interpretation of the geology of an active MOR volcanic zone is that up to 30 percent of the diagnostic features can be missed at any given look direction, but that having two orthogonal look direction images is probably sufficient to prevent gross misinterpretation
Bosonic stringlike behavior and the Ultraviolet filtering of QCD
The gluonic action density is calculated in static mesons at finite
temperature just below the deconfinement point. Our focus is to elucidate the
role of vacuum ultraviolet fluctuations which are filtered using an improved
smearing algorithm. In the intermediate source separation distance, where the
free string picture poorly describes the flux tube width profile, we find upon
reducing the vacuum action towards the classical instanton vacuum, the
characteristics of the flux tube converge and compare favorably with the
predictions of the free bosonic string. This result establishes a connection
between the free string action and vacuum gauge fields and reveals the
important role of ultraviolet physics in understanding the lattice data at this
temperature scale. As a by-product of these calculations, we find the
broadening of the QCD flux tube to be independent of the ultraviolet filtering
at large distances. Our results exhibit a linearly divergent pattern in
agreement with the string picture predictions.Comment: 8 pages, 8 Figures, 1 Tabl
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