56,130 research outputs found
Film study for a star correlator Final report
Photographic recording film evaluation for star field image processing in spacecraft environment and use in star correlato
Performance of a spin-based insulated gate field effect transistor
Fundamental physical properties limiting the performance of spin field effect
transistors are compared to those of ordinary (charge-based) field effect
transistors. Instead of raising and lowering a barrier to current flow these
spin transistors use static spin-selective barriers and gate control of spin
relaxation. The different origins of transistor action lead to distinct size
dependences of the power dissipation in these transistors and permit
sufficiently small spin-based transistors to surpass the performance of
charge-based transistors at room temperature or above. This includes lower
threshold voltages, smaller gate capacitances, reduced gate switching energies
and smaller source-drain leakage currents.Comment: 4 pages including 3 figures, APL in pres
Measurement-Device-Independent Approach to Entanglement Measures
Within the context of semiquantum nonlocal games, the trust can be removed
from the measurement devices in an entanglement-detection procedure. Here we
show that a similar approach can be taken to quantify the amount of
entanglement. To be specific, first, we show that in this context a small
subset of semiquantum nonlocal games is necessary and sufficient for
entanglement detection in the LOCC paradigm. Second, we prove that the maximum
pay-off for these games is a universal measure of entanglement which is convex
and continuous. Third, we show that for the quantification of
negative-partial-transpose entanglement, this subset can be further reduced
down to a single arbitrary element. Importantly, our measure is operationally
accessible in a measurement-device-independent way by construction. Finally,
our approach is simply extended to quantify the entanglement within any
partitioning of multipartite quantum states.Comment: 8 pages, 2 figures, the main result is split into two theorems with
slight modifications, extended proof
Sun-Like Magnetic Cycles in the Rapidly-Rotating Young Solar Analog HD 30495
A growing body of evidence suggests that multiple dynamo mechanisms can drive
magnetic variability on different timescales, not only in the Sun but also in
other stars. Many solar activity proxies exhibit a quasi-biennial (2
year) variation, which is superimposed upon the dominant 11 year cycle. A
well-characterized stellar sample suggests at least two different relationships
between rotation period and cycle period, with some stars exhibiting long and
short cycles simultaneously. Within this sample, the solar cycle periods are
typical of a more rapidly rotating star, implying that the Sun might be in a
transitional state or that it has an unusual evolutionary history. In this
work, we present new and archival observations of dual magnetic cycles in the
young solar analog HD 30495, an 1 Gyr-old G1.5V star with a rotation
period near 11 days. This star falls squarely on the relationships established
by the broader stellar sample, with short-period variations at 1.7 years
and a long cycle of 12 years. We measure three individual long-period
cycles and find durations ranging from 9.6-15.5 years. We find the short-term
variability to be intermittent, but present throughout the majority of the time
series, though its occurrence and amplitude are uncorrelated with the longer
cycle. These essentially solar-like variations occur in a Sun-like star with
more rapid rotation, though surface differential rotation measurements leave
open the possibility of a solar equivalence.Comment: 12 pages, 6 figures. Submitted to Ap
Application of ERTS-1 imagery and underflight photography in the detection and monitoring of forest insect infections in the Sierra Nevada Mountains of California
The author has identified the following significant results. Analysis of ERTS-1 imagery with underflight aerial photo support including U-2, in the Sierra Nevada Mountains of California, indicates promising possibilities of detecting and monitoring forest insect outbreaks visually with some mechanical support utilizing the VP-8 image analyzer. Visually, it is possible at a scale of 1:1,000,000 to discriminate between large areas of damaged and undamaged forests; timbered and non-timbered areas; pasture land and cultivated fields; desert and riparian vegetation. At a scale of 1:80,000 it is possible to distinguish among three classes of tree mortality; defoliated and undefoliated areas; non-host mixed conifers; and mountain meadows, rock domes, lakes and glaciers. Machine tests showed significant differences in image densities among various bands and mortality areas
A Preliminary Study of Solar Powered Aircraft and Associated Power Trains
The feasibility of regeneratively powered solar high altitude powered platform (HAPP) remotely piloted vehicles was assessed. Those technologies which must be pursued to make long duration solar HAPPs feasible are recommended. A methodology which involved characterization and parametric analysis of roughly two dozen variables to determine vehicles capable of fulfilling the primary mission are defined. One of these vehicles was then conceptually designed. Variations of each major design parameter were investigated along with state-of-the-art changes in power train component capabilities. The midlatitude mission studied would be attainable by a solar HAPP if fuel cell, electrolyzer and photovoltaic technologies are pursued. Vehicles will be very large and have very lightweight structures in order to attain the combinations of altitude and duration required by the primary mission
The use of computer-generated color graphic images for transient thermal analysis
Color computer graphics techniques were investigated as a means of rapidly scanning and interpreting large sets of transient heating data. The data presented were generated to support the conceptual design of a heat-sink thermal protection system (TPS) for a hypersonic research airplane. Color-coded vector and raster displays of the numerical geometry used in the heating calculations were employed to analyze skin thicknesses and surface temperatures of the heat-sink TPS under a variety of trajectory flight profiles. Both vector and raster displays proved to be effective means for rapidly identifying heat-sink mass concentrations, regions of high heating, and potentially adverse thermal gradients. The color-coded (raster) surface displays are a very efficient means for displaying surface-temperature and heating histories, and thereby the more stringent design requirements can quickly be identified. The related hardware and software developments required to implement both the vector and the raster displays for this application are also discussed
Asymptotic iteration method for eigenvalue problems
An asymptotic interation method for solving second-order homogeneous linear
differential equations of the form y'' = lambda(x) y' + s(x) y is introduced,
where lambda(x) \neq 0 and s(x) are C-infinity functions. Applications to
Schroedinger type problems, including some with highly singular potentials, are
presented.Comment: 14 page
Characteristics of Separated Flow Regions Within Altitude Compensating Nozzles Final Report
Characteristics of separated flow regions within altitude compensating nozzle
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