4,103 research outputs found
Electron beam instrument for measuring electric fields Patent
Electron beam deflection devices for measuring electric field
Performance improvement analysis for the Apollo unified S-band system Semiannual progress report
Performance improvement analysis for Apollo unified S band system, including computerized simulation techniques and phase lock loop studie
Simulation and study of small numbers of random events
Random events were simulated by computer and subjected to various statistical methods to extract important parameters. Various forms of curve fitting were explored, such as least squares, least distance from a line, maximum likelihood. Problems considered were dead time, exponential decay, and spectrum extraction from cosmic ray data using binned data and data from individual events. Computer programs, mostly of an iterative nature, were developed to do these simulations and extractions and are partially listed as appendices. The mathematical basis for the compuer programs is given
A Continuation Method for Nash Equilibria in Structured Games
Structured game representations have recently attracted interest as models
for multi-agent artificial intelligence scenarios, with rational behavior most
commonly characterized by Nash equilibria. This paper presents efficient, exact
algorithms for computing Nash equilibria in structured game representations,
including both graphical games and multi-agent influence diagrams (MAIDs). The
algorithms are derived from a continuation method for normal-form and
extensive-form games due to Govindan and Wilson; they follow a trajectory
through a space of perturbed games and their equilibria, exploiting game
structure through fast computation of the Jacobian of the payoff function. They
are theoretically guaranteed to find at least one equilibrium of the game, and
may find more. Our approach provides the first efficient algorithm for
computing exact equilibria in graphical games with arbitrary topology, and the
first algorithm to exploit fine-grained structural properties of MAIDs.
Experimental results are presented demonstrating the effectiveness of the
algorithms and comparing them to predecessors. The running time of the
graphical game algorithm is similar to, and often better than, the running time
of previous approximate algorithms. The algorithm for MAIDs can effectively
solve games that are much larger than those solvable by previous methods
Frequency doubling conversion efficiencies for deep space optical communications
The theory of optical frequency doubling conversion efficiency is analyzed for the small signal input case along with the strong signal depleted input case. Angle phase matching and beam focus spot size are discussed and design trades are described which maximize conversion efficiency. Experimental conversion efficiencies from the literature, which are less than theoretical results at higher input intensities due to saturation, reconversion, and higher order processes, are applied to a case study of an optical communications link from Saturn. Double pass conversion efficiencies as high as 45 percent are expected. It is believed that even higher conversion efficiencies can be obtained using multipass conversion
Advancement of the general theory of multiplexing with applications to space communications Final report, May 1966 - May 1968
Orthogonal multiplexing theory and general design criteria related to unified S band communication system
Surprisingly Little O VI Emission Arises in the Local Bubble
This paper reports the first study of the O VI resonance line emission (1032,
1038 Angstroms) originating in the Local Bubble (or Local Hot Bubble)
surrounding the solar neighborhood. In spite of the fact that O VI absorption
within the Local Bubble has been observed, no resonance line emission was
detected during our 230 ksec Far Ultraviolet Spectroscopic Explorer observation
toward a ``shadowing'' filament in the southern Galactic hemisphere. As a
result, tight 2 sigma upper limits are set on the intensities in the 1032 and
1038 Angstrom emission lines: 500 and 530 photons cm^{-2} s^{-1} sr^{-1},
respectively. These values place strict constraints on models and simulations.
They suggest that the O VI-bearing plasma and the X-ray emissive plasma reside
in distinct regions of the Local Bubble and are not mixed in a single plasma,
whether in equilibrium with T ~ 10^6 K or highly overionized with T ~ 4 to 6 x
10^4 K. If the line of sight intersects multiple cool clouds within the Local
Bubble, then the results also suggest that hot/cool transition zones differ
from those in current simulations. With these intensity upper limits, we
establish limits on the electron density, thermal pressure, pathlength, and
cooling timescale of the O VI-bearing plasma in the Local Bubble. Furthermore,
the intensity of O VI resonance line doublet photons originating in the
Galactic thick disk and halo is determined (3500 to 4300 photons cm^{-2} s^{-1}
sr^{-1}), and the electron density, thermal pressure, pathlength, and cooling
timescale of its O VI-bearing plasma are calculated. The pressure in the
Galactic halo's O VI-bearing plasma (3100 to 3800 K cm^{-3}) agrees with model
predictions for the total pressure in the thick disk/lower halo. We also report
the results of searches for other emission lines.Comment: accepted by ApJ, scheduled for May 2003, replacement astro-ph
submission corrects typos and grammatical errors in original versio
Hot Gas in the Galactic Thick Disk and Halo Near the Draco Cloud
This paper examines the ultraviolet and X-ray photons generated by hot gas in
the Galactic thick disk or halo in the Draco region of the northern hemisphere.
Our analysis uses the intensities from four ions, C IV, O VI, O VII, and O
VIII, sampling temperatures of ~100,000 to ~3,000,000 K. We measured the O VI,
O VII and O VIII intensities from FUSE and XMM-Newton data and subtracted off
the local contributions in order to deduce the thick disk/halo contributions.
These were supplemented with published C IV intensity and O VI column density
measurements. Our estimate of the thermal pressure in the O VI-rich thick
disk/halo gas, p_{th}/k = 6500^{+2500}_{-2600} K cm^{-3}, suggests that the
thick disk/halo is more highly pressurized than would be expected from
theoretical analyses. The ratios of C IV to O VI to O VII to O VIII,
intensities were compared with those predicted by theoretical models. Gas which
was heated to 3,000,000 K then allowed to cool radiatively cannot produce
enough C IV or O VI-generated photons per O VII or O VIII-generated photon.
Producing enough C IV and O VI emission requires heating additional gas to
100,000 < T < 1,000,000 K. However, shock heating, which provides heating
across this temperature range, overproduces O VI relative to the others.
Obtaining the observed mix may require a combination of several processes,
including some amount of shock heating, heat conduction, and mixing, as well as
radiative cooling of very hot gas.Comment: 10 pages, 2 figures. Accepted for publication in the Astrophysical
Journa
G65.2+5.7: A Thermal Composite Supernova Remnant With a Cool Shell
This paper presents archival ROSAT PSPC observations of the G65.2+5.7
supernova remnant (also known as G65.3+5.7). Little material obscures this
remnant and so it was well observed, even at the softest end of ROSAT's
bandpass (~0.11 to 0.28 keV). These soft X-ray images reveal the remnant's
centrally-filled morphology which, in combination with existing radio frequency
observations, places G65.2+5.7 in the thermal composite (mixed morphology)
class of supernova remnants. Not only might G65.2+5.7 be the oldest known
thermal composite supernova remnant, but owing to its optically revealed cool,
dense shell, this remnant supports the proposal that thermal composite
supernova remnants lack X-ray bright shells because they have evolved beyond
the adiabatic phase. These observations also reveal a slightly extended point
source centered on RA = 19h 36m 46s, dec = 30deg 40' 07'' and extending 6.5
arcmin in radius in the band 67 map. The source of this emission has yet to be
discovered, as there is no known pulsar at this location.Comment: In AASTEX preprint form, document is 12 pages long and includes 3
figure file
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