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Air Force Institute of Technology

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Articles 2671 - 2678 of 2678

Full-Text Articles in Physical Sciences and Mathematics

Low Temperature Photoluminescence Study Of Silicon-Germanium Alloy Superlattices, Maxwell M. Chi Dec 1991

Low Temperature Photoluminescence Study Of Silicon-Germanium Alloy Superlattices, Maxwell M. Chi

Theses and Dissertations

Low temperature photoluminescence studies were performed on nine silicon germanium alloy superlattice samples. The luminescence spectra showed sharp peaks in the 0.95 to 1.05 eV energy range, and a broad band located 0.05 to 0.12 eV below the alloy bandgap. The sharp peaks were identified as transitions associated with impurity bound excitons. The linewidth was about 10 times that in pure silicon; in addition, the peaks shifted to lower energy as the sample temperature was raised from 1.4 to 15 K. These features were attributed to effects of random distribution of atoms in the alloy. The broad band shifted to …

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An Algorithm For Robust Eigenstructure Assignment Using The Linear Quadratic Regulator, Thomas C. Huckabone Dec 1991

An Algorithm For Robust Eigenstructure Assignment Using The Linear Quadratic Regulator, Thomas C. Huckabone

Theses and Dissertations

The Linear Quadratic Regulator (LQR) can guarantee a robust closed loop eigenstructure for full state feedback. The algorithm developed here takes advantage of the stability guarantees of LQR to achieve an eigenstructure close to desired but within the allowable region of LQR. The algorithm selects the LQR weighting matrices, Q and R, that minimize the distance between the elements of the desired and LQR achievable eigenstructures. The minimization is accomplished by using a simplex based optimization routine. Specific weightings placed on the elements of the desired eigenstructure define the relative importance of each element. The algorithm is programmed in FORTRAN …

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Synthetic Aperture Multi-Telescope Tracker Apparatus, Richard A. Carreras, Salvatore J. Cusumano, Morton B. Jenks, Robert I. Suizu May 1987

Synthetic Aperture Multi-Telescope Tracker Apparatus, Richard A. Carreras, Salvatore J. Cusumano, Morton B. Jenks, Robert I. Suizu

AFIT Patents

A plurality of telescopes provide output return signals which are applied both directly and in sampled form to a photo-detector cell. The detected signals from the photo-detector will represent the constant and transient errors of the telescope system. A low pass filter insures that the tracker provides only the constant or D.C. component of the error, while a high pass filter insures that the existing measuring devices for each telescope beam provide only the transient or A.C. component of the error. The A.C. and D.C. error signals are summed together with the appropriate applied gains on each channel such that …

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Optically Phased Laser Transmitter, Janet S. Fender, Salvatore J. Cusumano, Robert R. Butts, Christopher R. Dehainaut Jan 1987

Optically Phased Laser Transmitter, Janet S. Fender, Salvatore J. Cusumano, Robert R. Butts, Christopher R. Dehainaut

AFIT Patents

An apparatus and technique are described for phasing the outputs of a multiplier telescope array used as a laser transmitter. The technique uses samples of the transmitted beams to control optical path lengths through the separate telescopes so that the beams add coherently at the receiver. The phasing concept is applicable both to systems which provide inputs to the multiple telescopes by dividing a single laser beam and to systems in which the inputs to the telescopes and multiple, phase-locked laser beams. The approach is also compatible with single line and multi-line lasers, and it does not entail stringent alignment …

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Stochastic Estimation Applied To The Land Speed Of Sound Record Attempt By A Rocket Car, David A. Reinholz Dec 1983

Stochastic Estimation Applied To The Land Speed Of Sound Record Attempt By A Rocket Car, David A. Reinholz

Theses and Dissertations

Optimal linear smoothing theory is applied to the data from the Speed of Sound record attempt of a three-wheeled rocket car on 17 December 1979. A forward-backward estimation method is used which employs a seven state forward-running extended Kalman filter and a Meditch-form backward recursive 'fixed-interval' smoothing algorithm. Data for this analysis is supplied by a longitudinal accelerometer mounted on the vehicle and tracking radar measurements of range, azimuth, and elevation. States of interest include two components of vehicle position and velocity, accelerometer time-correlated error, and radar range and azimuth bias errors. Two iterations of the forward-backward smoothing algorithm provide …

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Lasing Conditions Of Elemental Sulfur In A Gas Discharge, David E. Egbert Sep 1972

Lasing Conditions Of Elemental Sulfur In A Gas Discharge, David E. Egbert

Theses and Dissertations

The partial pressures from heated sulfur crystals and helium, and sulfur and nitrogen required for ionic sulfur laser action in a gas discharge were determined. Previous work with sulfur lasers is reviewed and population inversion mechanisms are presented for the ionic sulfur laser lines. Possible excitation mechanisms are presented for both electron and ion or atomic collision excitation. Transition diagrams for all the known ionic sulfur laser transitions and an approximate potential energy curve for the diatomic sulfur molecule are presented. Laser action was achieved only when a spark gap pulser was used with a laser tube especially designed to …

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Software Simulation Of The D17b Computer, Bruce Chatterton Mar 1972

Software Simulation Of The D17b Computer, Bruce Chatterton

Theses and Dissertations

A software program has been written which simulates the functions of the Minuteman D17B computer at the register transfer level. The simulation program is written in the FORTRAN Extended language to be used on the Intercom System (teletype) of a CDC 6600 computer system. The simulation program consists of a main program and eight subroutines. A programming language for the D17B simulation was formed which contains numbers and load codes, switches, and miscellaneous commands. Example programs run on the simulated computer have been included to show the types of output available.

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Investigation Of The Platinum-Rich Portion Of The Platinum-Tantalum Phase Diagram, Bob Dean Browning Aug 1961

Investigation Of The Platinum-Rich Portion Of The Platinum-Tantalum Phase Diagram, Bob Dean Browning

Theses and Dissertations

The Pt-Ta binary system was investigated at two isotherms;1000°C and 1500°C, and at eleven alloy compositions in the range of 50 to 100 atomic percent platinum. The alloys were examined by x-ray diffraction and metallography. Three intermetallic compounds, Pt2Ta, Pt3Ta, and Pt4Ta were found to exist in this composition range. The Pt4Ta intermetallic appeared only at the 1500°C isotherm. Platinum dissolved tantalum substitutionally to 90 atomic percent at 1500 °C and to approximately 80 atomic percent at 1000 °C.

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