12,250 research outputs found
Noise removal in multichannel images
A adaptive filtering method, the Windrow-Hoff algorithm, for enhancing multichannel signals against aditive noise was investigated. It removes noise for multichannel images containing correlated signal compoments but uncorrelated noise components. Its potential application is the enhancement of multichannel microwave satellite images as a preprocessing step for the extraction of geophysical parameters
GEODYN system description, volume 1
A computer program for the estimation of orbit and geodetic parameters is presented. The areas in which the program is operational are defined. The specific uses of the program are given as: (1) determination of definitive orbits, (2) tracking instrument calibration, (3) satellite operational predictions, and (4) geodetic parameter estimation. The relationship between the various elements in the solution of the orbit and geodetic parameter estimation problem is analyzed. The solution of the problems corresponds to the orbit generation mode in the first case and to the data reduction mode in the second case
Efficient creation of molecules from a cesium Bose-Einstein condensate
We report a new scheme to create weakly bound Cs molecules from an atomic
Bose-Einstein condensate. The method is based on switching the magnetic field
to a narrow Feshbach resonance and yields a high atom-molecule conversion
efficiency of more than 30%, a factor of three higher than obtained with
conventional magnetic-field ramps. The Cs molecules are created in a single
-wave rotational quantum state. The observed dependence of the conversion
efficiency on the magnetic field and atom density shows scattering processes
beyond two-body coupling to occur in the vicinity of the Feshbach resonance.Comment: 7 pages, 4 figures, submitted to Europhysics Letter
Restoration of multichannel microwave radiometric images
A constrained iterative image restoration method is applied to multichannel diffraction-limited imagery. This method is based on the Gerchberg-Papoulis algorithm utilizing incomplete information and partial constraints. The procedure is described using the orthogonal projection operators which project onto two prescribed subspaces iteratively. Some of its properties and limitations are also presented. The selection of appropriate constraints was emphasized in a practical application. Multichannel microwave images, each having different spatial resolution, were restored to a common highest resolution to demonstrate the effectiveness of the method. Both noise-free and noisy images were used in this investigation
Resolution enhancement of multichannel microwave imagery from the Nimbus-7 SMMR for maritime rainfall analysis
A restoration of the 37, 21, 18, 10.7, and 6.6 GHz satellite imagery from the scanning multichannel microwave radiometer (SMMR) aboard Nimbus-7 to 22.2 km resolution is attempted using a deconvolution method based upon nonlinear programming. The images are deconvolved with and without the aid of prescribed constraints, which force the processed image to abide by partial a priori knowledge of the high-resolution result. The restored microwave imagery may be utilized to examined the distribution of precipitating liquid water in marine rain systems
Observation of Feshbach-like resonances in collisions between ultracold molecules
We observe magnetically tuned collision resonances for ultracold Cs2
molecules stored in a CO2-laser trap. By magnetically levitating the molecules
against gravity, we precisely measure their magnetic moment. We find an avoided
level crossing which allows us to transfer the molecules into another state. In
the new state, two Feshbach-like collision resonances show up as strong
inelastic loss features. We interpret these resonances as being induced by Cs4
bound states near the molecular scattering continuum. The tunability of the
interactions between molecules opens up novel applications such as controlled
chemical reactions and synthesis of ultracold complex molecules
GEODYN programmer's guide, volume 2, part 2
A computer program for executive control routine for orbit integration of artificial satellites is presented. At the beginning of each arc, the program initiates required constants as well as the variational partials at epoch. If epoch needs to be reset to a previous time, the program negates the stepsize, and calls for integration backward to the desired time. After backward integration is completed, the program resets the stepsize to the proper positive quantity
Tool for the Integrated Dynamic Numerical Propulsion System Simulation (NPSS)/Turbine Engine Closed-Loop Transient Analysis (TTECTrA) User's Guide
The Tool for Turbine Engine Closed-Loop Transient Analysis (TTECTrA ver2) is a control design tool thatenables preliminary estimation of transient performance for models without requiring a full nonlinear controller to bedesigned. The program is compatible with subsonic engine models implemented in the MATLAB/Simulink (TheMathworks, Inc.) environment and Numerical Propulsion System Simulation (NPSS) framework. At a specified flightcondition, TTECTrA will design a closed-loop controller meeting user-defined requirements in a semi or fully automatedfashion. Multiple specifications may be provided, in which case TTECTrA will design one controller for each, producing acollection of controllers in a single run. Each resulting controller contains a setpoint map, a schedule of setpointcontroller gains, and limiters; all contributing to transient characteristics. The goal of the program is to providesteady-state engine designers with more immediate feedback on the transient engine performance earlier in the design cycle
Off-diagonal correlations in a one-dimensional gas of dipolar bosons
We present a quantum Monte Carlo study of the one-body density matrix (OBDM)
and the momentum distribution of one-dimensional dipolar bosons, with dipole
moments polarized perpendicular to the direction of confinement. We observe
that the long-range nature of the dipole interaction has dramatic effects on
the off-diagonal correlations: although the dipoles never crystallize, the
system goes from a quasi-condensate regime at low interactions to a regime in
which quasi-condensation is discarded, in favor of quasi-solidity. For all
strengths of the dipolar interaction, the OBDM shows an oscillatory behavior
coexisting with an overall algebraic decay; and the momentum distribution shows
sharp kinks at the wavevectors of the oscillations, (where
is the atom density), beyond which it is strongly suppressed. This
\emph{momentum filtering} effect introduces a characteristic scale in the
momentum distribution, which can be arbitrarily squeezed by lowering the atom
density. This shows that one-dimensional dipolar Bose gases, realized e.g. by
trapped dipolar molecules, show strong signatures of the dipolar interaction in
time-of-flight measurements.Comment: 10 pages, 6 figures. v2: fixed a mistake in the comparison with Ref.
9, as well as several typos. Published versio
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