1,265,305 research outputs found
Apparatus for measuring an aircraft's speed and height
An apparatus for measuring aircraft horizontal speed and height above ground without the need for airborne cooperative devices is presented. Two ground level TV cameras separated by a measured distance and pointed at zenith are placed in line with the projection of the expected path of the aircraft. Speed is determined by measuring the time that it takes the aircraft to travel between the fields of view of the two TV cameras using zenith crossings as the reference points. Height is determined by correlating the speed with the time required to cross the field of view of either of the two cameras
Coupled Mode Theory of Electron‐Beam Parametric Amplification
A theory of parametric amplification in a filamentary electron beam by transverse fields is developed in coupled mode form. Space charge effects are neglected. In addition to beam modes at the signal frequency, beam modes at frequencies ωn=ω+ω_p, n=0, ±1, ±2…, where ω_p is the pump frequency, are coupled together. A discussion of the general form of the equations is given and reveals the circumstances under which exponential gain or periodic energy transfer between various modes can occur. When applied to quadrupole electric pump fields, a description of the quadrupole amplifiers of Adler, Wade, and Gordon is obtained. This theory is then used to evaluate the noise contribution from synchronous beam modes and higher cyclotron idler modes. Coupling by axially symmetric electric fields and by axially symmetric magnetic fields is discussed, and other amplification schemes suggested. The theory of coupling by axially symmetric fields can also be used to study lens effects on noise in the gun region
Traffic control system and method
Frequency of carrier received by aircraft is measured and compared with reference to indicate magnitude of Doppler shift. One Doppler frequency range is selected and indicated by digital signal. Difference between frequency is offset of apparent carrier frequency transmitted by aircraft
The X-ray transient XTE J1118+480: Multiwavelength observations of a low-state mini-outburst
We present multiwavelength observations of the newly discovered X-ray
transient XTE J1118+480 obtained in the rising phase of the 2000 April
outburst. This source is located at unusually high Galactic latitude and in a
very low absorption line of sight. This made the first EUVE spectroscopy of an
X-ray transient outburst possible. Together with our HST, RXTE, and UKIRT data
this gives unprecedented spectral coverage. We find the source in the low hard
state. The flat IR-UV spectrum appears to be a combination of optically thick
disk emission and flat spectrum emission, possibly synchrotron, while at higher
energies, including EUV, a typical low hard state power-law is seen. EUVE
observations reveal no periodic modulation, suggesting an inclination low
enough that no obscuration by the disk rim occurs. We discuss the nature of the
source and this outburst and conclude that it may be more akin to
mini-outbursts seen in GRO J0422+32 than to a normal X-ray transient outburst.Comment: 4 pages, 3 figures, replaced with accepted version. Uses
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A system of regional agricultural land use mapping tested against small scale Apollo 9 color infrared photography of the Imperial Valley (California)
System of regional agricultural land use mapping tested against Apollo 9 color infrared photography of Imperial Valley, Calif
A cusp electron gun for millimeter wave gyrodevices
The experimental results of a thermionic cusp electron gun, to drive millimeter and submillimeter wave harmonic gyrodevices, are reported in this paper. Using a "smooth" magnetic field reversal formed by two coils this gun generated an annular-shaped, axis-encircling electron beam with 1.5 A current, and an adjustable velocity ratio alpha of up to 1.56 at a beam voltage of 40 kV. The beam cross-sectional shape and transported beam current were measured by a witness plate technique and Faraday cup, respectively. These measured results were found to be in excellent agreement with the simulated results using the three-dimensional code MAGIC
Optical gyroscope system
Light beams pass in opposite directions through a single mode fiber optic wave guide that extends in a circle or coil in an optical gyroscope system which measures the rotation rate of the coil by measuring the relative phase shifts of the beams by interferometric techniques. Beam splitting and phase shifting of the light are facilitated by utilizing brief pulses of light and by using light-controlling devices which are operated for a brief time only when the light pulse passes in one direction through the device but not at a different time when the pulse is passing in the opposite direction through the device. High accuracy in rotation measurement is achieved at both very slow and very fast rotation rates, by alternately operating the system so that at zero rotation the interfering waves are alternately 90 out of phase and in phase. Linear polarization of the light beams is maintained by coiling the full length of the optic fiber in a single plane
Radiofrequency spectroscopy of Li p-wave molecules: towards photoemission spectroscopy of a p-wave superfluid
Understanding superfluidity with higher order partial waves is crucial for
the understanding of high- superconductivity. For the realization of a
superfluid with anisotropic order parameter, spin-polarized fermionic lithium
atoms with strong p-wave interaction are the most promising candidates to date.
We apply rf-spectroscopy techniques that do not suffer from severe final-state
effects \cite{Perali08} with the goal to perform photoemission spectroscopy on
a strongly interacting p-wave Fermi gas similar to that recently applied for
s-wave interactions \cite{Stewart08}. Radiofrequency spectra of both quasibound
p-wave molecules and free atoms in the vicinity of the p-wave Feshbach
resonance located at 159.15\,G \cite{Schunck05} are presented. The observed
relative tunings of the molecular and atomic signals in the spectra with
magnetic field confirm earlier measurements realized with direct rf-association
\cite{Fuchs08}. Furthermore, evidence of bound molecule production using
adiabatic ramps is shown. A scheme to observe anisotropic superfluid gaps, the
most direct proof of p-wave superfluidity, with 1d-optical lattices is
proposed.Comment: 5 pages, 3 figure
Traffic control system and method Patent
Traffic control system for supersonic transports using synchronous satellite for data relay between vehicles and ground statio
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