| Analysis of Blending Algorithms in Computer Graphics |
17 OCT 88 |
110 pages |
| Authors:
Ronald J. Leach; HOWARD UNIV WASHINGTON D C
|
 | The research on this project centered around the analysis, development, and implementation of fast algorithms for representing a surface which blends together two or more intersecting surfaces. The blending surface should provide a smoother transition than is available when simply considering the intersection of the surfaces. The algorithms developed must be efficient because the major portion of computing time in a solid modeling system should be devoted to the important ... |
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| Noise and Sonic Boom Impact Technology. PCBOOM Computer Program for Sonic Boom Research. Volume 1. Technical Report |
OCT 88 |
56 pages |
| Authors:
Dwight E. Bishop; BBN LABS INC CANOGA PARK CA
|
| The PCBOOM computer program, described in this technical report, calculates the location and magnitude of sonic boom overpressures on the ground due to supersonic flight under standard atmosphere and no wind propagation conditions. The program is intended for environmental planners and engineers who may need to estimate the noise impact from individual flights of supersonic military aircraft. The program runs on a Zenith Z-248 personal computer and also should run ... |
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| Downstream Ray Tracing in Beam Optics Codes |
OCT 88 |
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| Authors:
Wilfredo B. Reyes; UTAH UNIV SALT LAKE CITY DEPT OF ELECTRICAL ENGINEERING
|
 | Tunnel emittance growth in beams is a subtle phenomenon which requires the use of highly accurate simulation codes and methods to achieve reliable results. This report discusses use of self-consistent beam optics codes in studies of emittance growth in very long PPM focused electron beams. A novel method by which a given problem can be accurately solved in a stairstep series downstream is presented. The deformable mesh code is used ... |
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| Monterey Bay Acoustic Tomography: Ray Tracing and Environmental Assessment |
SEP 88 |
92 pages |
| Authors:
Theresa M. Rowan; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| This thesis recommends the locations for placement of five sonobuoys which are to be used in the 12-16 December 1988 acoustic tomography experiment in Monterey Bay. The experiment will test a low-cost tomographic system for studying internal waves and surface waves. The five sites were determined to be the most optimal locations for acoustic signal acquisition, based on predicted eigenray simulation and oceanic environment assessment. The Multiple Profile Ray-Tracing Program ... |
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| Improvement of Three Dimensional Acoustic Field Estimation Using Tomographic Reconstructions of the Ocean |
AUG 88 |
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| Authors:
Elizabeth A. Rowe; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
|
| To determine the efficacy of tomographic reconstructions of the ocean sound speed structure in improving acoustic field predictions for source localization, a 150 km by 350 km volume of ocean 3000 meters deep was synthetically modeled to be similar to the Gulf Stream system, including an eddy and a front. The features were Gaussian, with the eddy's maximum sound speed perturbation being 10m/s and the front's maximum perturbation 15m/s. Two ... |
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| Noise and Sonic Boom Impact Technology. BOOMAP2 Computer Program for Sonic Boom Research. Volume 3. Program Maintenance Manual |
AUG 88 |
412 pages |
| Authors:
Philip J. Day; Thomas M. Reilly; Harry Seidman; BBN LABS INC CANOGA PARK CA
|
| Air Combat Maneuvering Instrumentation/Tactical Air Combat Training Systems (ACMI/TACTS) are used at several Military Operating Areas (MOA) in the U.S. and abroad as postflight pilot debriefing aids in training for air-to-air combat. Engineering flight data are acquired and recorded from several radar facilities simultaneously during flights in appropriately instrumented MOAs. These data are used to generate the information required for subsequent graphical replays of the aircraft position, airspeed, g-value, altitude ... |
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| The Temporal and Spatial Variability of the Marine Atmospheric BoundaryLayer and Its Effect on Electromagnetic Propagation in and Around the GreenlandSea Marginal Zone |
JUN 88 |
122 pages |
| Authors:
Douglas J. Groters; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Variability of the MABL and its effect on the electromagnetic (EM) refractive structure around the Greenland Sea marginal ice zone were examined. Rawinsonde profiles and surface observations collected from 3 ships during MIZEX-87(20 March-11 April) served as the data set. A program, developed to calculate the refractivity at each vertical level of the rawinsonde profiles, also identified the levels at which trapping, superrefraction and subrefraction occurred. Temporal studies ... |
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| Optimization of Microwave Magnetoelastic Delay Lines |
MAY 88 |
129 pages |
| Authors:
Bruce F. Feldman; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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| A new ray tracing computer program which optimizes the design of linearly dispersive, two-port magnetoelastic delay lines operating at microwave frequencies has been developed. The simulation shows that delay line line bandwidth and dynamic range can be separately optimized for the value of a wave focussing parameter within a limited range. Whereas previous work had demonstrated that there are a potentially infinite number of synthesized magnetic fields which produce the ... |
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| Sources of Asthenopia in Navy Flight Simulators |
25 APR 88 |
14 pages |
| Authors:
Sheldon M. Ebenholtz; BATTELLE MEMORIAL INST COLUMBUS OH
|
| Asthenopia was defined and the oculomotor systems responsible for eye strain were identified. The oculomotor systems functional during flight simulator training also were described and the conditions under which Navy flight simulators could produce asthenopia were pointed out. Asthenopic symptoms are closely related to those of simulator sickness. In order to lower the incidence of asthenopic symptoms the verification of the proper calibration of virtual-image optics by application of computerized ... |
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| A Theoretical Investigation of Laser-Sustained Plasma Thruster |
21 APR 88 |
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| Authors:
San-Mou Jeng; Dennis Keefer; TENNESSEE UNIV SPACE INST TULLAHOMA CENTER FOR LASER APPLICATIONS
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| A numerical code has been successfully developed for the investigation of thruster performance using a laser-sustained hydrogen plasma as the propellant. The plasma was sustained using a 10.6 micrometer CO2 laser beam which is focused at different positions within the thruster. The physical model assumed that plasma is in thermodynamically equilibrium (LTE), and geometric ray tracing was adopted to describe the laser beam. The steady-state, axisymmetric, Navier-Stokes equations coupled with ... |
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| A Theoretical Evaluation of Laser Sustained Plasma Thruster Performance |
21 APR 88 |
|
| Authors:
San-Mou Jeng; Dennis Keefer; TENNESSEE UNIV SPACE INST TULLAHOMA CENTER FOR LASER APPLICATIONS
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| An extensive numerical experiment has been conducted to evaluate rocket thruster performance using a laser-sustained hydrogen plasma as the propellant. The plasma was sustained using a 30 kW CO2 laser beam operated at 10.6 micrometers focused inside the thruster. The steady-state Navier-Stokes equations coupled with the laser power absorption process have been solved numerically. A pressure based Navier-Stokes solver using body-fitted coordinate was used to calculate the laser-supported rocket flow ... |
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| A Probabilistic Model of the Apparent Radiance of a Rough Sea |
04 MAR 88 |
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| Authors:
R. G. Priest; I. B. Schwartz; NAVAL RESEARCH LAB WASHINGTON DC
|
| A widely used approach to the specification of the background statistics of wind driven sea states is the power spectral method. Coupled with a ray trace of the sky radiance, one can create deterministic images of a rough sea in the infrared. In this paper a probabilistic model of a rough sea is presented as an alternative to the power spectral approach. The model takes into account self-shadowing of the ... |
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| Methodologies for Resolving Anomalous Position Information in Torpedo Range Tracking Using Simulation |
MAR 88 |
|
| Authors:
William M. Kroshl; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| This thesis investigates the problem of resolving dual path records of torpedoes being tracked on an acoustic range using short baseline arrays. An acoustic signal is sent out by a torpedo at short intervals. This signal is then received by the four hydrophones of a short baseline array. Arrival time differences in the signal are used to determine an estimated position for the torpedo at the time the signal was ... |
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| Ionosonde Studies of Field-Aligned Irregularities during High-Power HF Heating at Arecibo |
FEB 88 |
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| Authors:
Leo F. McNamara; Bodo W. Reinisch; Jurgen Buchau; LOWELL UNIV MA CENTER FOR ATMOSPHERIC RESEARCH
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| Backscatter ionograms recorded by an airborne digital ionosonde during the September 1981 ionospheric HF heating campaign at Arecibo have been simulated using simplified ionospheric models and analytic raytracing techniques. The simulations indicate that irregularities were created at all altitudes from the interaction height (where the plasma frequency was equal to the heater frequency down to the base of the F layer, but with a preferred altitude near the interaction height. ... |
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| Computer Programs for High-Current Beam Transport in Accelerators |
DEC 87 |
|
| Authors:
Brendan B. Godfrey; MISSION RESEARCH CORP ALBUQUERQUE NM
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| Numerical techniques exist for modeling particle beam dynamics in high current accelerators at several levels of fidelity. Equilibria can be determined with beam envelope codes, particle ray-tracing, Vlasov equilibrium solvers, and single-disk particle codes. The linear stability of these equilibria is addressed with dispersion relations solved numerically, linearized PIC codes, and single- and multi-component beam centroid programs. Beam nonlinear dynamics are investigated with multidimensional PIC codes employing either the complete ... |
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| A Fortran Code for the Calculation of Probe Volume Geometry Changes in a Laser Anemometry System Caused by Window Refraction |
NOV 87 |
|
| Authors:
Albert K. Owen; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER
|
| A computer code has been written which utilizes ray tracing techniques to predict the changes in position and geometry of a laser doppler velocimeter probe volume resulting from refraction effects. The code predicts the position change, changes in beam crossing angle, and the amount of uncrossing that occur when the beams traverse a region general axisymmetric and general surface windows and is currently operational on a VAX 8600 computer system. ... |
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| Analysis of Environmental Assessment Procedures during OTH Emulator Test Flights. |
NOV 1987 |
22 pages |
| Authors:
Gary S. Sales; Jurgen Buchau; LOWELL UNIV MA CENTER FOR ATMOSPHERIC RESEARCH
|
| HP propagation ionograms made between the OTH radar in Maine and the AFGL Airborne Ionospheric Observatory were analyzed. MOF values for the various modes identified were compared with MUF values derived from a quasi-mid-point ionospheric sounder (Argentia, Newfoundland). Discrepancies between MUFF1 and MOFF1 values were resolved by ray tracing through a realistic ionosphere (derived from the Argentia ionograms) and identified was due to difficulties in mode identification, when the E ... |
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| Comparison with Oblique Sounder Data of High-Latitude HF Propagation Predictions from 'Radar C' and 'AMBSCOM' Computer Programs |
NOV 87 |
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| Authors:
Nikhil Dave; NAVAL OCEAN SYSTEMS CENTER SAN DIEGO CA
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| A study is done using two HF propagation prediction programs - Radar C and AMBCOM - to determine how well they predict median values of oblique sounder data of maximum observed frequencies (MOF) at high latitudes. The main differences between RADAR C and AMBCOM are the inclusion in the latter of high- latitude ionosphere and auroral absorption models, as well as a more sophisticated and accurate ray-tracing scheme. The data ... |
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| Correcting Ray Field Failures Caused by Focusing in an Inhomogeneous Duct: A Critical Look at the Gaussian Beam Method, |
NOV 1987 |
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| Authors:
E. Niver; M. S. Vogas; C. J. Ruiz; L. B. Felsen; NEW JERSEY INST OF TECH NEWARK DEPT OF ELECTRICAL ENGINEERING
|
| Ducting due to an inhomogeneous refractive index profile affects the propagation of electromagnetic signals in various regions of the earth's environments. At high frequencies ray methods afford a versatile, and numerically easily implementable, method for predicting the field at the receiver. However, when ducting occurs, multiple refractions of the confined rays cause field enhancement due to focusing, and when there is an abrupt change in the ducting profile, critically incident ... |
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| Bathymetric Hazard Survey Test |
20 AUG 87 |
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| Authors:
F. T. Erskine; G. M. Bernstein; S. M. Brylow; W. T. Newbold; R. C. Gauss; NAVAL RESEARCH LAB WASHINGTON DC
|
| NRL is developing a long range active acoustics technique for estimating seamount heights and mapping undersea topography over an entire ocean basin region. A concept demonstration, the BHST, was conducted in the eastern Atlantic in 1980. The technique uses explosive shot acoustic sources and a large aperture, towed acoustic receiver array. Reverberation data are output to an imaging system to study the spatial distribution of acoustic backscatter. These images are ... |
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| The Application of Coupled-Mode Theory to Propagation in Shallow Water with Randomly Varying Sound Speed |
JUN 87 |
35 pages |
| Authors:
Rolf Thiele; SACLANT ASW RESEARCH CENTRE LA SPEZIA (ITALY)
|
| Sound propagation in the Baltic Sea cannot be described correctly by range independent propagation models, even for areas with more or less constant water depths. The reason is the inability of such models to take account of the effect of forward scattering of sound produced by horizontal variations in the speed of the sound. Schneider and Sellschopp have simulated the forward- scattering effect by applying a parabolic equation method in ... |
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| Coupled Acoustic and Ocean Thermodynamic Model |
JUN 87 |
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| Authors:
Jacques M. Fourniol; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| An acoustic ray tracing algorithm is developed and coupled with a thermodynamic upper ocean mixed layer model. For a test case, the coupled mixed layer-acoustic model is applied to a specific area in the western Mediterranean Sea. Climatological atmospheric forcing is used time during different seasons. The response of the acoustic model to the predicted changes in the sound-speed profile is analyzed to show dependence of acoustic propagation upon the ... |
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| Global Model for Sound Absorption in Sea Water. Part 3. Arctic Regions |
14 MAY 87 |
43 pages |
| Authors:
R. H. Mellen; P. M. Scheifele; D. G. Browning; NAVAL UNDERWATER SYSTEMS CENTER NEW LONDON CT NEW LONDON LAB
|
| Sound absorption in sea water is known to be caused by ionic relaxations involving magnesium sulfate, boric acid and magnesium carbonate. Absorption is regionally dependent, due mainly to the pH-dependence of the boric acid relaxation. In the nominal sea-water pH range 7.7-8.3, the magnitude increases by roughly a factor of four at the lower frequencies. Since pH varies with depth as well as location, absorption also depends on the ray ... |
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| Global Model for Sound Absorption in Sea Water. Part 2. GEOSECS pH Data Analysis |
14 MAY 87 |
68 pages |
| Authors:
R. H. Mellen; P. M. Schiefele; D. G. Browning; NAVAL UNDERWATER SYSTEMS CENTER NEW LONDON CT NEW LONDON LAB
|
| Ionic relaxations involving magnesium sulfate, boric acid and magnesium, carbonate are known to account for sound absorption in sea water. Regional dependence of sound absorption has been shown to be caused mainly by the pH-dependence of the boric acid relaxation. In the nominal sea water pH range 7.7-8.3, the magnitude can be expected to vary over neatly a factor of four at lower frequencies. Since pH varies with depth as ... |
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| Global Model for Sound Absorption in Sea Water |
14 MAY 87 |
58 pages |
| Authors:
R. H. Mellen; P. M. Scheifele; D. G. Browning; NAVAL UNDERWATER SYSTEMS CENTER NEW LONDON CT NEW LONDON LAB
|
| The attenuation term in the sonar equation for propagation loss can be taken to include all losses that are proportional to range. Absorption in the medium is usually the dominant mechanism; however, interface scattering, volume scattering and diffraction can also become important components under certain conditions. Sound absorption in sea water is an order of magnitude greater than in fresh water at sonar frequencies. Resonator experiments in the 1950's identified ... |
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| Geometrical Theory of Diffraction for High-Frequency Coherence Functions in a Weakly Ramdom Media with Inhomogeneous Background Profile, |
MAY 1987 |
|
| Authors:
R. Mazar; L. B. Felsen; POLYTECHNIC UNIV FARMINGDALE NY WEBER RESEARCH INST
|
| The localization of high-frequency wave propagation around ray trajectories, and the reflection and (or) diffraction of these local plane wave fields by boundaries, inhomogeneities and (or) scattering centers has been combined via the Geometrical Theory of Diffraction (GTD) into one of the most effective means of analyzing high-frequency wave phenomena in complex deterministic environments. These constructs are here incorporated into a stochastic propagation and diffraction theory for statistical moments of ... |
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| Specular Scatter: A New Mechanism for Ionospheric Backscatter, |
MAY 1987 |
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| Authors:
Gary S. Sales; LOWELL UNIV MA CENTER FOR ATMOSPHERIC RESEARCH
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| Recent investigation into backscatter from ionospheric irregularities at high frequency (3 to 30 MHz) has indicated that the usual scatter mechanism requiring orthogonality with the field-aligned irregularities in the E and F region of the ionosphere is not sufficient to explain all the observations. Particularly the range dependence of ionospheric clutter as seen by an OTH radar system looking into or near the auroral region poses a major problem. Assuming ... |
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| Final Report of the Selected Research Program of the Office of Naval Research |
31 JAN 87 |
|
| Authors:
Norman Bleistein; Jack K. Cohen; John A. DeSanto; Frank G. Hagim; COLORADO SCHOOL OF MINES GOLDEN CENTER FOR WAVE PHENOMENA
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| This is a final report for the project, The Application of Inverse Methods to the Ocean Environment, supported by the Selected Opportunities Research Program of the Office of Naval Research at the Colorado School of Mines. During the three years spanned by the SRO, we have made major progress in the theory and application of inversion methods. At the start of the SRO, our inversion techniques were restricted to idealized ... |
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| Teleseismic Waveform Modeling Incorporating the Effects of Known Three- Dimensional Structure Beneath the Nevada Test Site |
02 JAN 87 |
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| Authors:
Vernon F. Cormier; MASSACHUSETTS INST OF TECH CAMBRIDGE EARTH RESOURCES LAB
|
| The focusing and defocusing of telemseismic P waves predicted by a known (Taylor, 1983) three-dimensional structure beneath the Nevada Test Site is calculated by dynamic ray tracing and superposition of Gaussian beams. The 20 to 100 km scale lengths of this model, having velocity fluctuations of several per cent, account for a factor of three fluctuations in the azimuthal pattern of P amplitudes. Since similar sized scale lengths and intensities ... |
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| An Altitude-Error Display for Height-Finder Radar |
JAN 87 |
50 pages |
| Authors:
A. E. Barrios; NAVAL OCEAN SYSTEMS CENTER SAN DIEGO CA
|
| Strong ducting conditions occur over many ocean areas. These conditions affect height-finder radars (such as the SPS-48) in giving accurate target positions. Most height-finder radars calculate altitude based on a standard atmosphere. When ducting conditions are present, large errors can occur between the calculated and the true target height, depending on the transmitter height and the target range. In many cases, these errors are greater than 50 percent. A height-finder ... |
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| Displaying Three-Dimensional Data |
87 |
|
| Authors:
Letitia Korbly; Peter V. O'Neil; ALABAMA UNIV IN BIRMINGHAM DEPT OF MATHEMATICS
|
| The objective of the project was to graphically represent data obtained in the course of solving equations of fluid dynamics. Studies of three- dimensional data were done with data arising from a fluid dynamics problem involving high temperatures and velocities. Three representational methods were used: (1) particle tracings showing vectors pointing in the direction of flow at a point, 2) representation of contours, and 3) ray tracing, with color values ... |
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| A Data Structure for a Multi-Illumination Model Renderer |
DEC 86 |
|
| Authors:
Michael J. Zyda; C. T. Wu; John S. Falby; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The rendering of realistic computer images is important for many scientific, technical and commercial and endeavors. Available literature provides the mathematical models to be utilized by a renderer. Lacking from the literature though are implementation details. This study examines some of the existing illumination and shading models and present a data structure and initial design for a multi-illumination model renderer. Keywords: light rays; ray tracing; computer graphics; computer generated images. ... |
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| A Comparison of Radiation Transport Methods in Axisymmetric Geometries |
06 OCT 1986 |
|
| Authors:
John L. Giuliani Jr; NAVAL RESEARCH LAB WASHINGTON DC
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| The radiative transfer equation with a fixed source and fixed absorption is studied in axisymmetric geometries. A comparison of solutions for several model problems is presented using two different numerical schemes. The first scheme uses the radiation diffusion approximation with flux-limiting; the second, a multi-directional ray trace. The underlying spatial grid over which the solutions are calculated is a distorted set of quadrilaterals for application to two dimensional, Lagrangian, radiation-hydrodynamic ... |
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| Proton Beam Deposition, Heating, and Radiation from an Iron Plasma |
19 SEP 86 |
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| Authors:
J. E. Rogerson; R. W. Clark; NAVAL RESEARCH LAB WASHINGTON DC
|
| A fully self consistent one dimensional ion beam slab interaction model has been applied to the investigation of the interaction of an energetic proton beam with an iron slab target. This model describes the slowing down of the beam, the hydrodynamic response and ionization dynamics of the slab, and detailed radiation emission and transport. An extensive atomic level structure with collisional radiative ionization dynamics is employed. A hybrid radiation transport ... |
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| Measurement and Calculation of the Stokes or Mueller Matrix for the Scattering of Electromagnetic Radiation from Irregular Particles |
14 SEP 86 |
|
| Authors:
Edward S. Fry; George W. Kattawar; Chia-Ren Hu; TEXAS A AND M UNIV COLLEGE STATION DEPT OF PHYSICS
|
| This work significantly advances the understanding of electromagnetic interactions with small particles whose dimensions are of the order of a wavelength. A joint theoretical experimental approach is used so that theoretical predictions could be provided with experimental back up and vice versa. Extensive results on electromagnetic interactions with cubes and sphere multiplets have been onbtained. Beautiful symmetry theorems for forward and backward scattering have been discovered. A major theoretical bonus ... |
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| Water Mass and Acoustic Analysis of the East Greenland Current |
SEP 86 |
|
| Authors:
James M. Clipson; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| Two cluster analysis techniques, one heuristic and one iterative, are used to investigate the spatial coherence of the water masses of the East Greenland Current (EGC), in the vicinity of the East Greenland Polar Front (EGPF). Both techniques are shown to be generally reliable, although the iterative technique is more consistent with classical oceanographic analyses. The techniques are applied to data to explore the grouping behavior of the water masses. ... |
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| Nonlinear Effects in Long Range Underwater Propagation |
14 JUL 86 |
|
| Authors:
David T. Blackstock; TEXAS UNIV AT AUSTIN APPLIED RESEARCH LABS
|
| Research was carried out to determine the extent to which nonlinearity affects long range underwater propagation. The research was divided into three tasks. Task I. Shock pulse propagation in a homogeneous ocean. A numerical propagation program based on weak shock theory, with account taken of real ocean absorption and dispersion, was developed. Refraction(due to inhomogeneity of the medium) was neglected. Task II. Nonlinear propagation in a depth dependent ocean. The ... |
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| Preliminary Investigation of Optimum Frequency for Sound Propagation in Shallow Sound Channels |
JUL 86 |
|
| Authors:
Suk W. Yoon; Calvin R. Dunlap; Wendy L. Bradfield-Smith; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Optimum frequency for propagation of sound in shallow sound channels was studied using two acoustic transmission loss models. The split step Parabolic Equation model (a full wave model) and the Fast Asympotic Coherent Transmission loss model, version 9H (a ray tracing model) were tested against experimental data collected in the northeast Pacific Ocean. The models were found to be valid predictors of optimum frequency for the shallow sound channel. Both ... |
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| Effects of Strong Diffraction on the Focusing and Scattering of Acoustic Waves |
JUN 86 |
|
| Authors:
T. B. Gabrielson; S. T. McDaniel; D. W. Thomson; PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
|
| In many wave propagation problems, diffraction is considered to be a second order effect that diffuses the sharp shadows and focal surfaces predicted by ray theory. However, if the frequency is low enough so that the wavelength is comparable to the size of the focusing region, structured fields of significant level can be found in classical shadows and smooth, featureless enhancement can replace the sharp, multiple convergences common at higher ... |
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| Random-Bottom Structural and Topographical Effects on Sound Transmission in a Shallow Channel |
31 MAY 86 |
|
| Authors:
W. L. Siegmann; M. J. Jacobson; C. E. Ashley; RENSSELAER POLYTECHNIC INST TROY NY DEPT OF MATHEMATICAL SCIENCES
|
| Effects of horizontal stochastic bottom structure on acoustic intensity in an isospeed ocean have been studied. The bottom density and sound speed were taken to be random and ray theory was used. In this study we add a rough water bottom interface, consisting of large scale, two dimensional random facets upon which small scale roughness may be superimposed. Each facet is assumed to possess small random depth deviation, slope, and ... |
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| Ray-Tracing in Three Dimensions for Calculation of Radiation Dose Calculations |
27 MAY 86 |
|
| Authors:
Dennis R. Kennedy; ARMY MILITARY PERSONNEL CENTER ALEXANDRIA VA PROGRAM ANALYSIS OFFICE
|
| This thesis addresses several methods of calculating the radiation dose distribution for use by technicians or clinicians in radiation therapy treatment planning. It specifically covers the calculation of the effective pathlength of the radiation beam for use in beam models representing the dose distribution. A two-dimensional method by Bentley and Milan is compared to the method of Strip Trees developed by Duda and Hart and then a three-dimensional algorithm built ... |
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| A Numerical Model for Shoaling and Refraction of Second-Order Cnoidal Waves Over an Irregular Bottom |
MAY 86 |
|
| Authors:
Thomas A. Hardy; Nicholas C. Kraus; COASTAL ENGINEERING RESEARCH CENTER VICKSBURG MS
|
| A numerical model for calculating shoaling and refraction of finite- amplitude waves in shallow water is presented. The model is designed to employ second-order cnoidal wave theory, can be used also. A brief review of water-wave theory is given, followed by an outline of a second-order cnoidal wave theory derivation. A description is provided of the basic similarities and differences between cnoidal wave theory and the more commonly used small-amplitude ... |
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| Teleseismic Waveform Modeling Incorporating the Effects of Known Three- Dimensional Structure Beneath the Nevada Test Site |
14 APR 86 |
|
| Authors:
Vernon F. Cormier; MASSACHUSETTS INST OF TECH CAMBRIDGE EARTH RESOURCES LAB
|
| Calculations were performed in 3-D models of the upper 75 - 100 km. of the crust ad mantle beneath the NORSAR array, a model for a region in the northerm California (Zandt, 1981), and a model generated by random perturbations to a 1-D velocity structure. In both the NORSAR and Zandt models, azimuthal variations in travel time were found to be on the order of a factor of 2 and ... |
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| Nonlinear Internal Gravity Wave Propagation, Saturation, and Absorption in the Atmosphere |
09 APR 86 |
|
| Authors:
Timothy J. Dunkerton; PHYSICAL DYNAMICS INC BELLEVUE WA
|
| Numerical and theoretical studies of internal gravity waves have been performed to understand the role of convective instabilities in nonlinear, large amplitude gravity waves; the effects of saturation and self acceleration on transient gravity wave, mean flow interaction; the role of local convective instabilities in producing turbulent modifications of potential temperature and trace constituents in breaking gravity waves; and the propagation and refraction of inertial and non inertial gravity waves ... |
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| Acoustic Description of South Atlantic Ocean Warm Core Eddy |
10 MAR 86 |
|
| Authors:
Linda S. Petitpas; David G. Browning; NAVAL UNDERWATER SYSTEMS CENTER NEWPORT RI
|
| This document contains the viewgraph presentation which investigates the thermohaline/baroclinic scales of the meso-scale eddies associated within the Brazil Malvinas (Falkland) Confluence. One of the eddies investigated was a warm core anti-cyclonic eddy centered about 43 deg 50 min S and 54 deg 15 min W (18-19 October) with a diameter of 125 km. The XBT's and CTD's taken through the eddy were used with a range dependent acoustic prediction ... |
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| Master Oscillator and Diagnostic Unit Design |
JAN 86 |
|
| Authors:
F. C. Way; D. F. Schaack; SPECTRON DEVELOPMENT LABS INC ALBUQUERQUE NM
|
| This report describes the design and development of a Dye Laser operating at 353 nm and an associated beam diagnostics unit capable of measuring UV phase, intensity and energy. The dye laser consists of a flashlamp pumped oscillator, including spatial and temporal mode selectors and a wavelength tuning device. The output of the oscillator at 706 nm is amplified by a flashlamp pumped dye amplifier. The resulting output is frequency ... |
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| Laser-Generated Beam Array for Commutation of Spatially Modulated Optical Signals |
86 |
|
| Authors:
J. Taboada; SCHOOL OF AEROSPACE MEDICINE BROOKS AFB TX
|
| A coherent optical method and concept are presented for the generation of an intense, very precisely spaced 2-D array of laser beams which maintain their relative position over significant distances. The array is achieved through the use of a recently invented quadriprism. A signal pattern encoded on a 128x128 array has been precisely transported over several meters. An attractive feature of the system is the low optical energy in the ... |
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| Meteorological Measurements on Line-of-Sight Microwave Radio Links |
22 NOV 85 |
|
| Authors:
James F. Morrissey; Yutaka Izumi; Owen Cote; AIR FORCE GEOPHYSICS LAB HANSCOM AFB MA
|
| Meteorological measurements on two experimental microwave radio links in New England are presented. The links were from Pack Monadnock in N.H. to Prospect Hill in Waltham, Mass., in 1983, and from Saddleback Mountain in N.H. to Prospect Hill in 1984. These data are then used in ray-trace programs to determine multipath delays and variations in the angle of arrival at the receiver. Several cases of low-level ducts due to inversions ... |
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| Nonlinear Acoustics: Long Range Underwater Propagation, Air-Filled Porous Materials, and Noncollinear Interaction in a Waveguide |
28 OCT 85 |
|
| Authors:
David T. Blackstock; TEXAS UNIV AT AUSTIN APPLIED RESEARCH LABS
|
| Research on three topics in nonlinear acoustics is described. (1) Nonlinear effects in long range underwater propagation. The equations of nonlinear geometrical acoustics have been derived from the general equations of fluid mechanics for and inhomogeneous fluid. And analytical solution for the waveform of an arbitrary pressure signal traveling along a ray path has been implemented by a computer program. Not included in the program are effects of reflection and ... |
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| Teleseismic Waveform Modeling Incorporating the Effects of Known Three- Dimensional Structure Beneath the Nevada Test Site |
22 OCT 85 |
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| Authors:
Vernon F. Cormier; MASSACHUSETTS INST OF TECH CAMBRIDGE EARTH RESOURCES LAB
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| Seismograms were synthesized by the Gaussian beam method and ray trajectories were plotted for a plane wave incident on a 3-D structure obtained from block inversion of teleseismic travel times observed at a local array in central California. The amplitude variations for the given profile are smaller than the order of magnitude variations typically observed. Since amplitudes are sensitive to smaller scale velocity features than travel times, this may indicate ... |
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Reports by Keyword(s)
RAY TRACING
