| Nonlinear Thomson Scattering of Intense Laser Pulse from Beams and Plasmas |
23 AUG 93 |
55 pages |
| Authors:
Eric Esarey; Sally K. Ride; Phillip Sprangle; NAVAL RESEARCH LAB WASHINGTON DC
|
 | A Comprehensive theory is developed to describe the nonlinear Thomson scattering of intense laser fields from beams and plasmas. This theory is valid for linearly or circularly polarized incident laser fields of arbitrary intensities and for electrons of arbitrary energies. Explicit expressions for the intensity distributions of the scattered radiation are calculated and numerically evaluated. The space-charge electrostatic potential, which is important in high density plasmas and prevents the axial ... |
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| Collisonless Dynamics of the Magnetosphere |
AUG 93 |
41 pages |
| Authors:
Amitava Bhattacharjee; COLUMBIA UNIV NEW YORK DEPT OF APPLIED PHYSICS
|
| Experiment: An energetic electron belt has been created in a laboratory terrella for the first time. Measurements indicate the trapped- electron belt to be localized in radius and have a non-Maxwellian energy distribution ranging from 10 to 40 keV. Using multiple probes, we have clearly identified drift-resonant instabilities leading to rapid radial transport. Transport in a dipole appears to require multiple modes, and its bursty nature suggests a profile relaxation ... |
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| A Study of High Field Transport in Wide Band Gap Electronic Materials Using a Picosecond Transient Charge Technique |
02 JUL 93 |
9 pages |
| Authors:
Craig J. Scott; MORGAN STATE UNIV BALTIMORE MD
|
| We propose a study of electron and hole traps and carrier drift velocity for high electric field strengths using the transient charge technique (TCT) with a picosecond electron beam probe. The uniqueness in the proposed approach lies in the use of a photocathode SEM to generate picosecond electron pulses with high lateral resolution to generate electron hole pairs. Ultrafast electron beam pulses allow narrow drift regions to be characterized and ... |
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| Evaluation of Habitat Suitability Index Models for Riverine Life Stages of American Shad, with Proposed Models for Premigratory Juveniles |
JUL 93 |
32 pages |
| Authors:
Robert M. Ross; Thomas W. Backman; Randy M. Bennett; FISH AND WILDLIFE SERVICE WASHINGTON DC
|
| Field evaluations of existing habitat suitability index (HSI) models for spawning adults, eggs, and larvae of American shad (Alosa sapidissima) were conducted in 1990-92; initial models for juveniles in nursery habitats were developed. Fish abundance in various habitats of the upper Delaware River was quantified by (1) observation of adult spawning activity, (2) collection of eggs and larvae with metered plankton and drift nets, and (8) enumeration of juveniles by ... |
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| A Theory for Optical Wavelength Control in Short Pulse Free Electron Laser Oscillators |
JUN 93 |
110 pages |
| Authors:
Wade F. Wilkenson; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The future safety of the U.S. Navy warship depends on the development of a directed energy self-defense system to keep pace with the ever-improving technology of anti-ship missiles. Two candidates are reviewed. The free electron laser (FEL) has the most advantages, but a chemical laser proposed by TRW is ready for installation on existing ships. Initial testing of issues related to directed energy use at sea can be conducted with ... |
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| Analysis of Simulated Drift Patterns of a High Altitude Balloon Surveillance System |
JUN 93 |
71 pages |
| Authors:
Kurt C. Reitinger; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| This study evaluates the potential of high altitude balloons as surveillance platforms. It begins with the mobile Theater Ballistic Missile (TBM) detection problem encountered during the Persian Gulf War of 1990-1991 and it describes a possible scenario using high altitude balloon surveillance systems to locate TBM's accurately enough for effective engagement by strike assets. It presents the history and military use of balloons, and it describes the current state of ... |
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| VLF Source Localization with a Freely Drifting Acoustic Sensor Array |
07 MAY 1993 |
17 pages |
| Authors:
G. Chen; W. Hodgkiss; NAVAL COMMAND CONTROL AND OCEAN SURVEILLANCE CENTER RDT AND E DIV SAN DIEGO CA
|
| Source localization and tracking capability of the freely drifting Swallow float volumetric array is demonstrated with matched-field processing (MFP) technique using the 14-Hz cw data collected during the 1989 Swallow float experiment conducted in the northeast Pacific by Marine Physical Laboratory. Initial MFP of the experimental data revealed difficulties in estimating the source depth and range while the source azimuth estimate was quite successful. The main cause of the MFP ... |
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| Mobilities and Interaction Potentials for the O(+)-He and O(-)-He Systems |
15 APR 1993 |
6 pages |
| Authors:
A. A. Viggiano; Robert A. Morris; E. A. Mason; PHILLIPS LAB HANSCOM AFB MA
|
| Mobilities of O(+) and O(-) ions in He gas have been measured as a function of electric field strength at temperatures from 93 to 568 K. The results are compared with previous work, and analyzed in terms of a temperature- field strength scaling rule and the O(+)-He and O(-)-He potentials. Emphasis is placed on how much information on the potentials can be obtained from simple features of the mobility curve ... |
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| Numerical Studies of Low Temperature Gallium Arsenide Buffer Layers and Their Influence on Device Operation |
14 APR 93 |
18 pages |
| Authors:
H. L. Grubin; J. P. Kreskovsky; SCIENTIFIC RESEARCH ASSOCIATES INC GLASTONBURY CT
|
| The focus of the program is the development and application of an algorithm for studying charge transport in low temperature gallium arsenide (LT GaAs) buffer layers and the influence of such layers on device operation. During this reporting period the drift and diffusion equations were modified to include the contributions of clusters in one and two dimensions. In addition, the effects of high resistance material on the operation of FETs ... |
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| Method for Extracting Tidal and Inertial Motion from ARGOS Ice Buoys Applied to the Barents Sea during CEAREX |
APR 93 |
68 pages |
| Authors:
P. Turet; C. H. Pease; R. S. Pritchard; J. E. Overland; NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION SEATTLE WA PACIFIC MARINE ENV IRONMENTAL LABS
|
| A harmonic analysis of tidal and inertial action was applied to observations of position of ARGOS buoys deployed on drifting multiyear sea ice in the Eastern Arctic-Barents Sea during CEAREX (1988-89). An ARGOS positioning- data screening protocol was developed and constructed using a constrained least squares algorithm for separate estimation of tidal and inertial currents. The analysis provided estimates of individual tidal components at 15-day intervals along the sea ice ... |
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| Study of Gain in C-Band Deflection Cavities for a Frequency-Doubling Magnicon Amplifier |
26 MAR 93 |
20 pages |
| Authors:
S. H. Gold; C. A. Sullivan; B. Hafizi; W. M. Manheimer; NAVAL RESEARCH LAB WASHINGTON DC
|
| We report an experimental study of the gain between two half- wavelength, 5.7 GHz TM 110 pillbox cavities, separated by a quarter-wavelength drift space, and powered by a 170A, 500 keV electron beam immersed in an 8.1 kG magnetic field. These cavities constitute the first section of a planned multicavity detection system, whose purpose is to spin up an electron beam to high transverse momentum for injection into the output ... |
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| Profiling ALACE Instruments |
20 MAR 93 |
28 pages |
| Authors:
Jeff Sherman; SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA
|
| The Autonomous Lagrangian Circulation Explorer (ALACE) is a free drifting oceanographic float which drifts at a level of neutral buoyancy and periodically rises to the surface where it transmits data to System Argos satellites and is located by them. The basic float was intended to observe ocean currents but recent developments, described in this report, have led to three new versions with expanded capabilities. One model reports temperature profiles from ... |
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| Thermal Expansion, Modulus, and Muzzle Drift |
MAR 93 |
18 pages |
| Authors:
P. J. Cote; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
|
| Drifts in gun muzzle orientation are commonly observed during firing and are generally attributed to thermal stresses generated by temperature differences in different parts of the tube. Thermal shrouds are used to reduce the amplitude of such drifts. The present report addresses drifts that may originate from overall tube temperature rather than temperature differences. In these cases, the original muzzle orientation is recovered only when the tube returns to its ... |
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| High-Latitude Electric Field Studies Using DMSP Data |
18 FEB 93 |
50 pages |
| Authors:
M. R. Hairston; R. A. Heelis; TEXAS UNIV AT DALLAS RICHARDSON CENTER FOR SPACE SCIENCES
|
| Analysis using data from the ion drift meter in the SSIES instrument package on the DMSP series of satellites is used to calculate the electrostatic potential distribution in the polar ionosphere. Numerous geophysical parameters such as the location and magnitude of the potential extreme and the classification of the potential distribution as one of the three Heppner-Maynard models can be derived from this data analysis. An earlier version of this ... |
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| Monthly Mean Sea Ice Data from the Polar Ice Prediction System (PIPS), the Regional Polar Ice Prediction System - Barents Sea (RPIPS-B), the Regional Polar Ice Prediction System - Greenland Sea (RPIPS-G), and the Polar Ice Prediction System 2.0 (PIPS2.0) |
FEB 93 |
126 pages |
| Authors:
P. G. Posey; R. H. Preller; NAVAL RESEARCH LAB DETACHMENT STENNIS SPACE CENTER MS
|
| The Polar Ice Prediction System (PIPS), the Regional Polar Ice Prediction System-Barents Sea (RPIPS-B) and the Regional Polar Ice Prediction System-Greenland Sea (RPIPS-G) are all operational sea ice forecasting systems which have been run daily at the Fleet Numerical Oceanography Center (FNOC) since September 1987, June 1989, and October 1991, respectively. The basis for all three models is the Hibler ice model. The Hibler ice model calculates ice drift, ice ... |
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| PDE, Differential Geometric and Algebraic Methods in Nonlinear Filtering |
07 JAN 93 |
11 pages |
| Authors:
Stephen S. Yau; ILLINOIS UNIV AT CHICAGO CIRCLE DEPT OF MATHEMATICS STATISTICS AND COMPUTER SC IENCE
|
| We have constructed explicitly the most general class of finite dimensional filters which include both Kalman-Bucy filters and Benes filters as special cases. We also proved that if the state space dimension is less than three, then generically all finite dimensional filters must be those constructed by us from the Lie algebraic point of view. Without making any assumption on the drift term of the filtering system, we can write ... |
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| Performance Evaluation of the Honeywell GG1308 Miniature Ring Laser Gyroscope |
JAN 93 |
|
| Authors:
M. F. Vinnins; L. D. Gallop; DEFENCE RESEARCH ESTABLISHMENT OTTAWA (ONTARIO)
|
 | This report describes the results of the performance evaluation of a Honeywell GG1308 miniature Ring Laser Gyroscope (RLG). The tests include turn-on and cold start, bias drift, scale factor, scale factor linearity, thermal transients and effects of dither compensation. The gyroscope demonstrated excellent high-rate performance although significant scale factor deviations were noted during temperature variations. Instrument design characteristics and areas of potential future investigation are also discussed.... Ring Laser Gyroscope(RLG), ... |
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| On Predicting the Person-in-Water Drift for Search and Rescue |
93 |
83 pages |
| Authors:
Tsung-Chow Su; FLORIDA ATLANTIC UNIV BOCA RATON CENTER FOR APPLIED STOCHASTICS RESEARCH
|
| Search and rescue of persons in distress on the high seas requires the capability to accurately predict the position of the survivors. The current approaches on drift prediction are based on an empirical correlation between wind speed and person motion from limited field data. There is also no drift data available for person wearing survival suit. Consequently, there is not sufficient data for accurate prediction and thus have complicated the ... |
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| Eastern-Western Arctic Sea Ice Analysis, 1993 |
93 |
109 pages |
| Authors:
NAVAL ICE CENTER WASHINGTON DC
|
| This publication is the 20th edition of the annual Arctic sea-ice atlases prepared by the JIC. The atlas contains weekly charts depicting Northern Hemisphere ice conditions and extent. The significant use of high resolution satellite imagery, combined with valuable ice reconnaissance data from various sources, has greatly improved the accuracy of these analyses. The purpose of this atlas is to provide the user with reliable weekly hemispheric ice analyses. These ... |
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| Ionospheric Structure Specifications and Systems Effects |
31 DEC 92 |
35 pages |
| Authors:
Sunanda Basu; BOSTON COLL CHESTNUT HILL MA INST FOR SPACE RESEARCH
|
| Ionospheric scintillation measurements are examined in relation to the satellite in-situ measurements of electron density structures in the ionosphere and the plasma processes responsible for the generation of these structures. Radio waves from satellites are scattered and ionospheric scintillation is recorded on the ground in the presence of a relative motion between the satellite, the ionosphere and the observer. The electron density irregularity spectrum of extended equatorial spread F structures, ... |
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| Theoretical Investigations of Ultrafast Phenomena in Condensed Matter |
DEC 92 |
14 pages |
| Authors:
Thomas F. George; WASHINGTON STATE UNIV PULLMAN
|
| Theoretical models and computational codes have been developed to describe chemical and physical phenomena associated with solids, microstructure clusters and polymers, with special attention given to nonlinear optical effects and ultrafast processes. The following topics have been investigated: light- induced drift of electrons in semiconductor heterostructures; photoinduced electron transfer in coupled quantum wells; quantum beats in time-resolved luminescence spectra; scale-invariant theory of optical properties of fractals; optical properties of small ... |
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| Confidence on the Three-Point Estimator of Frequency Drift |
Dec-1992 |
10 pages |
| Authors:
Christine Hackman; Marc A Weiss; NATIONAL INST OF STANDARDS AND TECHNOLOGY BOULDER CO TIME AND FREQUENCY DIV
|
| It has been shown that a three-point second difference estimator is nearly optimal for estimating frequency drift in many common atomic oscillators. We derive a formula for the uncertainly of this estimate as a function of the integration time and of the Allan variance associated with this inkegration time. |
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| Enhanced Higher Order Parametric X-Radiation Production |
DEC 92 |
120 pages |
| Authors:
Kay L. DiNova; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| This thesis examines parametric x-radiation (PXR) which is the Bragg scattering of the virtual photons associated with the Coulomb field of relativistic charged particle from the atomic planes of a crystal. Higher order parametric x-radiation from the (002) planes of a thick mosaic graphite crystal have been observed. The raw PXR data was collected using a SiLi detector and a Pulse Height Analyzer (PHA) software program. The data was corrected ... |
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| Diagnostics of Magnetic Substorms Using Satellite Observations of Magnetic Pulsations |
26 OCT 92 |
65 pages |
| Authors:
Chin S. Lin; SOUTHWEST RESEARCH INST SAN ANTONIO TX
|
| This project has demonstrated that one class of magnetic pulsations known as stormtime Pc 5 waves is correlated with substorm onsets. Stormtime Pc 5 waves observed by geostationary satellites in the afternoon sector is characterized by oscillations of magnetic field with a period from 2 to 10 minutes, easily detected by magnetometers on communication or weather satellites. The estimated substorm onset times are found to be within 20 minutes of ... |
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| Force-Free Time-Harmonic Plasmoids |
OCT 92 |
62 pages |
| Authors:
Jack Nachamkin; DAYTON UNIV OH RESEARCH INST
|
| A heretofore unexplored solution of Maxwell's equations is investigated for time-harmonic waves in a partially ionized gas. The analysis is focused on the spherically symmetric cases that behave like electromagnetic energy trapped in the form of a plasmoid . It will be shown that a critical frequency exists, below which the current cannot be carried by electrons and the plasmoid remains stable. Resonant sizes will be shown to exist such ... |
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| Improved Visual Aid for VLF MSK Signals. |
01 SEP 1992 |
|
| Authors:
Lynn K. Thomas; Paul A. Singer; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| A visual display system provides patterns for visually aiding an operator in determining the nature and noise environment of the incoming signal. A conventional signal receiver and an oscilloscope are coupled to a phase detector, a clock circuit and a frequency synthesizer. The clock circuit synchronizes the operation of the receiver, phase detector and frequency synthesizer. The phase detector includes a digital delay means for imparting a digital time delay ... |
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| VLF Source Localization with a Freely Drifting Sensor Array |
SEP 92 |
155 pages |
| Authors:
George C. Chen; SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA MARINE PHYSICAL LAB
|
| Source localization and tracking capability of the freely drifting Swallow float volumetric array is demonstrated with matched-field processing (MFP) technique using data collected during the 1989 Swallow float experiment conducted in the Northwest Pacific, Marine Physical Laboratory's set of nine freely drifting, infrasonic sensors, capable of recording ocean ambient noise in the 1- to 25-Hz range, was deployed to span the water column of 4100-m depth, with horizontal aperture on ... |
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| VLF Source Localization with a Freely Drifting Acoustic Sensor Array |
SEP 1992 |
157 pages |
| Authors:
G. C. Chen; NAVAL COMMAND CONTROL AND OCEAN SURVEILLANCE CENTER RDT AND E DIV SAN DIEGO CA
|
| The objective of this study is to demonstrate the source localization and tracking capability of the freely drifting Swallow float volumetric array with the matched-field processing (MFP) technique using data collected during the 1989 Swallow float experiment conducted in the Northeast Pacific. A set of nine freely drifting, infrasonic sensors, capable of recording ocean ambient noise in the 1- to 25-Hz range, was deployed to span the water column of ... |
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| Environmental Measurements in the Beaufort Sea, Spring 1991 |
SEP 1992 |
101 pages |
| Authors:
T. Wen; F. Karig; W. Felton; WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB
|
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| SOFAR Float Trajectories from an Experiment to Measure the Atlantic Cross Equatorial Flow (1989-1990) |
AUG 92 |
|
| Authors:
Philip L. Richardson; Marguerite E. Zemanovic; Christine M. Wooding; William J. Schmitz Jr; James F. Price; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
| Neutrally buoyant SOFAR floats at nominal depths of 800, 1800, and 3300 m were tracked for 21 months in the vicinity of western boundary currents near 6N and at several sites in the Atlantic near 11N and along the equator. Trajectories at 1800 m show a swift (> 50 cm.sec), narrow (100 km wide) southward-flowing deep western boundary current (DWBC) extending from 7N to the equator. At times (February-March 1989) ... |
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| Theory of Light-Induced Drift of Electrons in Coupled Quantum Wells |
JUL 92 |
24 pages |
| Authors:
Mark I. Stockman; Leonid S. Muratov; Thomas F. George; WASHINGTON STATE UNIV PULLMAN
|
| A theory of the new effect of light-induced drift (LID) in coupled potential wells is developed on the basis of the density-matrix method. The effect appears when light excites intersubband electronic transitions. LID manifests itself as the photocurrent of the 2-d electron gas in the well plane, which depends on coherent electron tunneling between the coupled wells. The theory shows the effect to possess distinctive features such as a characteristic ... |
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| Real-Time Tomography Mooring |
JUN 92 |
|
| Authors:
James Lynch; Daniel Frye; Kenneth Peal; Stephen Liberatore; Sean Kery; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
| A real-time tomography system has been developed which combines ocean acoustic tomography with satellite-based time keeping and satellite telemetry. The basis of the system is the acoustic tomography transceiver and its associated acoustic navigation grid. To this basic system, a link to the surface has been added to provide a pathway for telemetry of the tomographic data to shore and a downlink for satellite-derived time which is used to correct ... |
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| Probing Trapped Ion Energies Via Ion-Molecule Reaction Kinetics: Fourier Transform Ion Cyclotron Resonance Mass Spectrometry |
28 MAY 92 |
22 pages |
| Authors:
James E. Bruce; John R. Eyler; FLORIDA UNIV GAINESVILLE DEPT OF CHEMISTRY
|
| The kinetic energy-dependent Ar+N2 ion-molecule reaction has been used as a chemical thermometer to determine the kinetic energy of ions produced by electron ionization and trapped using a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. The rate constant for this reaction obtained on the FTICR mass spectrometer was compared to previous work, which allowed a kinetic energy estimate to be made. In addition, the effects of varying parameters such ... |
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| Charge Transport in High-Resistivity Photorefractive Crystals (Bi sub 12 Sio sub 20 ZnSE GaAs), |
22 MAY 1992 |
|
| Authors:
A. V. IIinskii; AKADEMIYA NAUK SSSR LENINGRAD FIZIKO-TEKHNICHESKII INSTITUT
|
| Introduction. The paper reviews our studies(l-7 concerned) of photoinduced charge dynamics and electric field evolution in the case of external field screening. The experimental methods providing possibility of electric field distribution direct measurements are considered. It is found that there are two different regimes of electric field screening which depend on experimental conditions (kind of crystal, temperature): narrowing of major carriers depletion region and stratification effect (numerous space charge layers ... |
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| Conduction Band and Trap Limited Mobilities in Bi sub 12 Sio sub 20, |
22 MAY 1992 |
|
| Authors:
P. Nouchi; J. P. Partanen; R. W. Hellwarth; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES
|
| The mobility of photoexcited charge carriers in photorefractive insulators can be measured with a holographic time-of-flight technique. By illuminating the crystal with two interfering 30 ps laser pulses at the wavelength of 532 nm, we create an instantaneous sinusoidal pattern of photoexcited charge carriers. A strong electric field E sub 0 is applied across the crystal causing the sinusoidal pattern of charge carriers to drift with a velocity muE sub ... |
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| Nanosecond Photorefractive Effects in KNbO sub 3, |
22 MAY 1992 |
|
| Authors:
I. Biaggio; M. Zgonik; P. Gunter; EIDGENOESSISCHE TECHNISCHE HOCHSCHULE ZURICH (SWITZERLAND)
|
| Two laser beams interfering in a photorefractive crystal ionize light absorbing impurities and produce two initially overlapping concentration gratings. These two gratings consist of ionized donors that are immobile and of free charges that can move due to diffusion in a concentration gradient and drift in an external or internal electric field. Spatial separation between the two gratings produces a space-charge field which modulates the refractive indices of the crystal ... |
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| Phase-Locked Detection of Running Interference Pattern in Photorefractive SBN, |
22 MAY 1992 |
|
| Authors:
O. P. Nestiorkin; Ye. P. Shershakov; B. Ya. Zel'Dovich; N. V. Bogodaev; L. I. Ivleva; CHELYABINSK POLYTECHNIC INST (USSR)
|
| Holographic grating in a photorefractive crystal may be recorded due to the diffusion of electrons or their drift in external or Intrinsic photovoltaic dc field as a result of illumination by a static interference pattern. Those traditional mechanisms are well studied. Running interference pattern may be registered by the phase-locked detection in the externally applied ac field. That mechanism was realized in the paraelectric crystal Bi12TiO20 (BTO). In this work ... |
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| Effect of Light-Induced Drift in Confined Semiconductors Heterostructures, |
22 MAY 1992 |
|
| Authors:
Mark I. Stockman; Lakshmi N. Pandey; Thomas F. George; STATE UNIV OF NEW YORK AT BUFFALO AMHERST
|
| The effect of light-induced drift (LID) in gases, predicted by Gel'mukhanov and Shalagin and observed later, is manifested in mechanical drift of the absorbing atoms (molecules) in response to optical excitation. The effect of LID takes place if the atom interaction with light is velocity-dependent (due to the Doppler effect), the spectrum of the exciting radiation is asymmetric with respect to the the absorption line, and the absorbing molecules experience ... |
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| The Soliton Frequency Stabilization and Raman Self Frequency Shift Suppression in Fibers Doped Er and Tm IONS, |
22 MAY 1992 |
|
| Authors:
E. M. Dianov; K. K. Konstantinov; A. N. Pilipetskii; A. N. Starodumov; AKADEMIYA NAUK SSSR MOSCOW
|
| The possibility of the Raman self-frequency shift suppression is of great interest for both the high bit rate communication lines and the lasers with fiber cavities. In the communication lines for picosecond pulses the frequency shifts are small. Frequency drift toward a maximum of the gain profile in an active fibers can compensate to some extent the effect of self-frequency shift. |
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| Femtosecond Time-Resolved Studies of High-Field Parallel Transport in GaAs Quantum Wells, |
22 MAY 1992 |
|
| Authors:
W. Sha; T. B. Norris; W. J. Schaff; MICHIGAN UNIV ANN ARBOR ULTRAFAST SCIENCE LAB
|
| Ballistic transport of electrons in semiconductors has recently been a topic of great interest. These studies are important because ballistic transport is expected to play a role in the operation of a number of state-of-the-art semiconductor devices. Ballistic drift in a field-free region of electrons launched across a heterojunction has been observed. In this paper we describe experiments that apply optical spectroscopy to time-resolve the distribution functions of electrons in ... |
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| Experimental Comparison of the 'AC Field'and 'Moving Grating' Techniques for BTO and BSO Crystals, |
22 MAY 1992 |
|
| Authors:
E. V. Mokrushina; V. V. Prokof'ev; S. L. Sochava; S. I. Stepanov; AKADEMIYA NAUK SSSR LENINGRAD FIZIKO-TEKHNICHESKII INSTITUT
|
| There are two techniques of nonstationary holographic recording which are widely used for PRCs with long drift lengths of photocarriers. There are recording of a moving interference pattern in an external DC electric field and recording of a fixed pattern in an AC field. Both of them allow the efficiency of the drift mechanism of recording in the external electric field to be increased and the recorded hologram to be ... |
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| Studies of Optical Beam Phase-Conjugation and Electromagnetic Scattering Process |
05 MAY 92 |
64 pages |
| Authors:
Robert W. Hellwarth; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES
|
| In this project we have performed both experimental and theoretical studies of optical beam phase-conjugation and of electromagnetic scattering and propagation with intense optical fields. We have: (1) made measurements of high- power four-wave mixing in many new polymers synthesized at USC to characterize their nonlinear optical properties; (2) made what we believe is the first observation of nonexponential attenuation of a weak optical beam in a homogeneous (highly scattering) ... |
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| Numerical Studies of Low Temperature Gallium Arsenide Buffer Layers and Their Influence on Device Operation |
APR 92 |
12 pages |
| Authors:
H. L. Grubin; J. P. Kreskovsky; SCIENTIFIC RESEARCH ASSOCIATES INC GLASTONBURY CT
|
| This report summarizes recent work on the development and application of an algorithm for studying charge transport in low temperature gallium arsenide (LT GaAs) buffer layers and their influence on device operation. During this reporting period the drift and diffusion equations were modified to include the transient dependence of electrons and holes for gallium arsenide. Calculations were performed for two-terminal, one and two-dimensional structures. Studies with the one-dimensional structures focussed ... |
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| Stress Relief: Proof of the Mechanism of Photo-Induced Index Change, |
APR 1992 |
|
| Authors:
D. Wong; S. B. Poole; M. G. Sceats; SYDNEY UNIV (AUSTRALIA)
|
| In some fiber sensors, temperature drift causes phase noise which degrades the sensor severely. A novel intrinsic technique is presented in which the thermal independency is built into the preform of polarimetric sensor fibers. Experiment shown that this technique offers zero temperature sensitivity over a much wider range of temperature than previously reported techniques. |
|
| Numerical Analysis of Plasma Transport in Tandem Volume Magnetic Multicusp Ion Sources |
MAR 92 |
136 pages |
| Authors:
Todd R. Vitko; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
|
| A one-dimensional fluid model of plasma transport in tandem volume magnetic multicusp ion sources is explored. The model, the positive ion source code Pos, by Glasser and Smith, calculates plasma density, drift velocity, electron temperature, and ion temperature in an ion source. The usefulness of the model is limited: (1) The plasma density trend runs opposite to experimental results, and electron temperatures are an order of magnitude higher than experimentally ... |
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| Variations in Sea Ice Thickness in the Polar Regions, |
MAR 1992 |
|
| Authors:
Peter Wadhams; CAMBRIDGE UNIV (UNITED KINGDOM)
|
| An overview paper is presented on the evidence for variations in sea ice thickness in the polar regions. Most ice thickness data in the Arctic come from upward-looking sonar profiling by submarines. The available dataset is large, but the sampling has been necessarily unsystematic, so that only very few cases exist of directly comparable profiles from different years or seasons in the same location. Comparisons made so far are reviewed. ... |
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| Variations of Extent, Area, and Open Water of the Polar Sea Ice Covers: 1978-1987, |
MAR 1992 |
|
| Authors:
Per Gloersen; William J. Campbell; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION GREENBELT MD GODDARD SPACE FLIG HT CENTER
|
| The Scanning Multichannel microwave Radiometer (SMMR) which operated onboard the Nimbus-7 satellite from October 1978 to August 1987 obtained sequential synoptic observations of the entire Arctic and Antarctic sea ice covers every 2 days through the clouds during night and day. It is a unique almost decade-long data set of the large-scale behavior of sea ice on earth. Ibis paper presents the results of an analysis of SMMR observations of ... |
|
| Data for Polar Regions Research, |
MAR 1992 |
|
| Authors:
Roy L. Jenne; NATIONAL CENTER FOR ATMOSPHERIC RESEARCH BOULDER CO
|
| Datasets available for polar research on global change topics are summarized. Emphasis is given to data that define the large, including rawinsonde data, surface meteorological observations, cloud drift winds, atmospheric analyses, sea ice, planetary radiation, and ocean forcing. Plans are discussed for making improved atmospheric analyses, using existing data. The use of CD-ROMs and DAT technologies for data distribution is discussed and selected CD-ROMs are listed. |
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| Mathematical Modeling in Studies of Arctic Ocean Circulation, |
MAR 1992 |
|
| Authors:
N. Yu Doronin; A. Yu Proshutinsky; ARCTIC AND ANTARCTIC RESEARCH INST LENINGRAD (USSR)
|
| A hierarchy of mathematical models adapted to certain physical phenomena of the Arctic Ocean has been developed. The density structure of the Arctic Ocean water is characterized by a well-marked stratification. This allows us to describe it by means of models with a discrete stratification. In this context a two dimensional model of the upper 200 m of the ocean can be considered as the lowest level of a hierarchy ... |
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| Tracing Upper Waters in the Arctic Ocean, |
MAR 1992 |
|
| Authors:
E. P. Jones; Leif G. Anderson; BEDFORD INST OF OCEANOGRAPHY DARTMOUTH (NOVA SCOTIA)
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| We report results from the 1987 F.S. Polarstern cruise to the Nansen Basin that begin to address questions regarding how global climate change might affect the Arctic. Before the effects of global change can be assessed, the sources of upper waters must be determined and their circulation patterns mapped. In surface water, total carbonate concentrations distinguish between a northern fresh water component, whose origin is river runoff, and a southern ... |
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