| Construction and Analysis of Multi-Rate Partitioned Runge-Kutta Methods |
Jun 2012 |
107 pages |
| Authors:
Patrick R Mugg; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
 | Adaptive mesh refinement (AMR) of hyperbolic systems allows us to refine the spatial grid of an initial value problem (IVP), in order to obtain better accuracy and improved efficiency of the numerical method being used. However, the solutions obtained are still limited to the local Courant-Friedrichs-Lewy (CFL) time-step restrictions of the smallest element within the spatial domain. Therefore, we look to construct a multi-rate time-integration scheme capable of solving an ... |
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| Development of Nonuniformities in Swirling, Rocket Injectors |
May 2012 |
14 pages |
| Authors:
Malissa D Lightfoot; Vinod Narayanan; Alan L Kastengren; S A Schumaker; Stephen A Danczyk; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIR
|
| A high-performing, stable rocket engine requires injectors which produce predictable, uniform, temporally stable sprays. The use of high-velocity gas to atomize a liquid, such as in an ox-rich engine cycle, can produce complex, unsteady behavior. Two types of unsteady behavior, pulsing and changes in the spray s centerline, were observed in a specific type of prefilming rocket injector a Gas-Centered Swirl Coaxial (GCSC) injector. The reason for this unsteadiness is ... |
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| Nonuniform High-Gamma (60-500 Hz) Power Changes Dissociate Cognitive Task and Anatomy in Human Cortex |
09 Feb 2011 |
12 pages |
| Authors:
Charles M Gaona; Mohit Sharma; Zachary V Freudenburg; Jonathan D Breshears; David T Bundy; Jarod Roland; Dennis L Barbour; Gerwin Schalk; Eric C Leuthardt; NEW YORK STATE DEPT OF HEALTH ALBANY
|
| High-gamma-band (60 Hz) power changes in cortical electrophysiology are a reliable indicator of focal, event-related cortical activity. Despite discoveries of oscillatory subthreshold and synchronous suprathreshold activity at the cellular level, there is an increasingly popular view that high-gamma-band amplitude changes recorded from cellular ensembles are the result of asynchronous firing activity that yields wideband and uniform power increases. Others have demonstrated independence of power changes in the low- and high-gamma ... |
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| On the Number of Segments Needed in a Piecewise Linear Approximation |
MAY 2010 |
14 pages |
| Authors:
Christopher L. Frenzen; Tsutomu Sasao; Jon T. Butler; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF APPLIED MATHEMATICS
|
| The introduction of high-speed circuits to realize an arithmetic function f as a piecewise linear approximation has created a need to understand how the number of segments depends on the interval a less or equal to x less than b and the desired approximation error epsilon. |
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| On Providing Non-uniform Scheduling Guarantees in a Wireless Network |
Jan 2010 |
13 pages |
| Authors:
Vartika Bhandari; Nitin H Vaidya; ILLINOIS UNIV AT URBANA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| Significant research effort has been directed towards the design and performance analysis of imperfect scheduling policies for wireless networks. These imperfect schedulers are of interest despite being sub-optimal, as they allow for more tractable implementation at the expense of some loss in performance. However much of this prior work takes a uniform scaling approach to analyzing scheduling performance, whereby the performance of a scheduling policy is characterized in terms of ... |
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| Development of Commercially Useable Codes to Simulate Aluminized Propellant Combustion and Related Issues |
03 Nov 2009 |
194 pages |
| Authors:
John Buckmaster; BUCKMASTER RESEARCH URBANA IL
|
| We have modified and developed a large number of codes relevant to the task including: a packing code to generate propellant morphology models; a homogenization code to predict homogenized properties of a heterogeneous propellant; a combustion code that predicts fluctuations in the hot gases coming off the propellant surface; and fluids codes that describe the rocket chamber flow, the rocket nozzle flow, aluminum transport, and nozzle erosion. The packing code ... |
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| Fokker-Planck Model for Thermal Smoothing in Inhomogeneous Laser-Matter Interactions |
24-Jul-2009 |
16 pages |
| Authors:
Michael J Keskinen; NAVAL RESEARCH LAB WASHINGTON DC
|
| Using a fully kinetic 2D Fokker-Planck model, the generation and evolution of ion density perturbations from nonuniform laser deposition in a plasma slab have been studied. It is found that significant smoothing of the ion density perturbations from nonuniform optically smoothed single beam laser deposition can be achieved on hydrodynamic time scales over a long range of scale sizes. In addition, it is observed that the Fokker-Planck model predicts more ... |
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| Spray Nonuniformities in Gas-Centered Swirl-Coaxial Injectors (Preprint) |
Jul-2009 |
7 pages |
| Authors:
Malissa D Lightfoot; Stephen A Danczyk; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
|
| Experimental studies of gas-centered swirl-coaxial (GCSC) injectors have revealed five basic types of nonuniformities in the spray. These nonuniformities can be classified as either affecting the centerline of the spray, with respect to the centerline of the injector, or affecting the temporal mass-distribution. The details of these behaviors are discussed as are possible driving factors and design criteria for avoidance. In general, high momentum flux operations are suggested for minimizing ... |
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| Evaluation of a High Resolution Wind Model Over a Complex Terrain Surface |
Apr-2009 |
45 pages |
| Authors:
Sam S Chang; Dennis M Garvey; chatt C Williamson; Giap Huynh; ARMY RESEARCH LAB ADELPHI MD
|
| A complete and comprehensive description of the high resolution wind (HRW) model is presented. The HRW model has been in development at the U.S. Army Research Laboratory, formerly U.S. Army Atmospheric Sciences Laboratory, since 1978. This model is a two-dimensional, diagnostic atmospheric surface-layer wind model with a horizontal grid spacing of the order of 100 m over a domain of about 5 by 5 km. It uses Gauss? principle of ... |
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| The Effects of Terrain on a System of Systems |
Dec-2008 |
135 pages |
| Authors:
Cher H Ong; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Modern combat operations are predominantly joint or combined arms, in which different forces and weapon systems come together to fight as a single entity as a system composed of many different systems. For land forces, system of systems typically exists at battalion and above-sized forces. This thesis investigates the effects of two types of terrain (urban and rivers) on combat operations. Using a synthesis of various simulation techniques (rapid scenario ... |
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| Turbulent Mixing in Stably Stratified Flows |
01-Mar-2008 |
101 pages |
| Authors:
MASSACHUSETTS UNIV AMHERST
|
| High resolution direct numerical simulations are used to investigate the dynamics of turbulence in flows subject to strong stable stratification, which are common in natural settings. Results are presented for two categories of simulations, uniform and non-uniform density stratification. For all simulated flows, the density stratification was held constant in time, and there was no ambient shear. Flows with uniform density stratification are first analyzed to help provide clear insight ... |
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| Analysis of Non-Uniform Gain for Control of a Deformable Mirror in an Adaptive-Optics System |
MAR 2008 |
131 pages |
| Authors:
Kevin P. Vitayaudom; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
|
| The objective of this research was to develop and experimentally verify the use of spatially varying gain maps on the servo-loop controller of a deformable mirror for improvements in the performance of an adaptive optics system and the mitigation of instabilities that can occur over edge actuators of a deformable mirror. The edge subapertures of a Shack-Hartmann wavefront sensor have lower signal-to-noise ratios and are more susceptible to measurement errors ... |
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| On the Non-Uniform Complexity of Brain Connectivity (PREPRINT) |
DEC 2007 |
6 pages |
| Authors:
Gloria Haro; Christophe Lenglet; Guillermo Sapiro; Paul Thompson; MINNESOTA UNIV MINNEAPOLIS INST FOR MATHEMATICS AND ITS APPLICATIONS
|
| A stratification and manifold learning approach for analyzing High Angular Resolution Diffusion Imaging "HARDI" data is introduced in this paper. HARDI data provides high-dimensional signals measuring the complex microstructure of biological tissues, such as the cerebral white matter. We show that these high-dimensional spaces may be understood as unions of manifolds of varying dimensions/complexity and densities. With such analysis, we use clustering to characterize the structural complexity of the white ... |
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| Exploring Naval Tactics with UAVs in an Island Complex Using Agent-Based Simulation |
JUN 2007 |
87 pages |
| Authors:
Vasileios Lalis; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The benefits of Unmanned Aerial Vehicles (UAV) at sea are undisputed. The amount and speed of the incoming information from a UAV, combined with its maneuverability and time-on-task capability, are assets to any navy. For the Greek Navy, the main local operation area is the Aegean and Ionian Sea. As Greece lies between three continents (Europe, Asia, Africa), there is a great deal of sea traffic and potential illegal activities, ... |
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| Communication Aspects in Urban Terrain |
DEC 2006 |
99 pages |
| Authors:
Volker Pfeiffer; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The nature of warfare has changed dramatically during the last decade. Western armies are increasingly required to conduct complex operations in urban terrain against asymmetric threats. These opponents use cities and their inhabitants for cover and concealment. In such situations, modern equipped armies often cannot fully utilize many of their most powerful weapons. To overcome this situation, modern communication systems are being acquired and deployed to provide real-time reconnaissance; thereby, ... |
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| Estimating Mass Discharge From Dense Nonaqueous Phase Liquid Source Zones Using Upscaled Mass Transfer Coefficients: An Evaluation Using Multiphase Numerical Simulations |
28 NOV 2006 |
14 pages |
| Authors:
John A. Christ; C. A. Ramsburg; Kurt D. Pennell; Linda M. Abriola; AIR FORCE ACADEMY COLORADO SPRINGS CO
|
| Difficulties associated with identifying the dense nonaqueous phase liquid (DNAPL) source zone architecture at the field scale, combined with the computational costs of field-scale DNAPL dissolution simulations, have motivated the development of a number of simplified models that rely upon upscaled (i.e., domain-averaged) mass transfer coefficients to approximate field-scale dissolution processes. While conceptually attractive, these upscaled models have yet to be fully evaluated for prediction of mass recovery from a ... |
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| Multilevel Multipole-Free Fast Algorithm For Electromagnetic Scattering Problems In Layered Media |
29 SEP 2006 |
161 pages |
| Authors:
Michael A. Saville; ILLINOIS UNIV AT URBANA-CHAMAPIGN
|
| A multilevel multipole-free algorithm is presented for solving electromagnetic scattering problems in the vicinity of a half space or layered medium. By replacing the multipole expansion in the fast inhomogeneous plane wave algorithm (FIPWA) with a multipole-free expansion, this new algorithm is simpler to derive and retains O(N log N) scaling in memory and processing time. To develop this new algorithm, known as the multipole-free fast inhomogeneous plane wave algorithm ... |
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| Alpha/Beta Heat Treatment of a Titanium Alloy with a Non-Uniform Microstructure (Preprint) |
AUG 2006 |
42 pages |
| Authors:
S. L. Semiatin; T. M. Lehner; J. D. Miller; R. D. Doherty; D. U. Furrer; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
|
| The effect of alpha/beta solution temperature and cooling rate on the evolution of microstructure during the heat treatment of Ti-6Al-2Sn-4Zr-2Mo-0.1Si (Ti6242Si) with a partially-spheroidized starting microstructure of equiaxed + remnant lamellar alpha was established. Experiments comprising induction heating to a peak temperature of 971 or 982 degrees C followed by cooling at a rate of 11 or 42 degrees C/min revealed that the volume fraction of the equiaxed alpha grew ... |
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| A Comparison of Main Rotor Smoothing Adjustments Using Linear and Neural Network Algorithms |
MAR 2006 |
146 pages |
| Authors:
Nathan A. Miller; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH DEPT OF AERONAUTICS AND ASTRONAUTICS
|
| Helicopter main rotor smoothing is a maintenance procedure that is routinely performed to minimize airframe vibrations induced by non-uniform mass and/or aerodynamic distributions in the main rotor system. This important task is both time consuming and expensive, so improvements to the process have long been sought. Traditionally, vibrations have been minimized by calculating adjustments based on an assumed linear relationship between adjustments and vibration response. In recent years, artificial neural ... |
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| An Airborne Radar Model For Non-Uniformly Spaced Antenna Arrays |
MAR 2006 |
101 pages |
| Authors:
Matthew V. Young; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
|
| This thesis presents an airborne radar model for non-uniformly spaced antenna arrays. Non-uniform arrays potentially possess advantages unobtainable by uniformly spaced arrays. An element position matrix is defined to accommodate arbitrary element locations. The new element position matrix affects the time/phase delay to each element, spatial frequencies, steering vectors, space-time snapshots, and covariance matrices. The joint domain localized and factored time-space-time adaptive processing algorithms are also updated so they are ... |
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| Prostate Dose Escalation by Innovative Inverse Planning-Driven IMRT |
NOV 2005 |
114 pages |
| Authors:
Lei Xing; STANFORD UNIV CA
|
| With the development of computer controlled MLC, IMRT now provides unprecedented means to deliver 3D-dose distributions with sub-centimeter resolution. Inverse planning is at the foundation of IMRT and critically determines its success. As practiced now, however, the capacity of IMRT is greatly underutilized because of the inferior performance of the inverse planning systems. Because of the tacit ignorance of intra-structural tradeoff, the IMRT plans generated by these systems for prostate ... |
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| Comparison of a Distributed Operations Force to a Traditional Force in Urban Combat |
SEP 2005 |
188 pages |
| Authors:
Michael Babilot; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Two motivations drove this study of the Distributed Operations Platoon (DO) in urban combat: (1) the Marine Corps Warfighting Lab (MCWL) is developing the concepts to apply to a DO in the Sea Viking 2006 experiment and (2) Marines are engaged daily in urban combat in support of the Iraq reconstruction efforts. This thesis explores whether a DO is suitable for urban combat operations by analyzing the results of simulations ... |
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| Utilization of Web Services to Improve Communication of Operational Information |
SEP 2004 |
133 pages |
| Authors:
David Lowery; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF COMPUTER SCIENCE
|
| Currently under development, the Global Information Grid (GIG) enterprise Services (ES) is a suite of capabilities intended to provide improved user access to mission-critical data via Web-based and network technologies. Some of the problems of implementing such capabilities include non-uniform data formats, incompatible run-time environments and nonstandard proprietary applications, all of which block operational interoperability. Web services are specifically designed to address the interoperability challenges of a service- oriented architecture ... |
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| Using Agent-Based Distillations to Explore Logistics Support to Urban, Humanitarian Assistance/Disaster Relief Operations |
SEP 2003 |
170 pages |
| Authors:
Eric Wolf; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| There are two motivations for studying Humanitarian Assistance/ Disaster Relief (HA/DR) operations. First, the Marine Corps will be a first- responder in the future. Second, logistics support takes on a primary role. This thesis identifies the potential for using agent-based models to support logistical decision-making in an urban, HA/DR environment. We develop a simulation using Map Aware Non-uniform Automata (MANA). Our scenario depicts a relief convoy with security attachment, operating ... |
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| Single-Mode Wavelength Division Demultiplexer for Bit-Parallel Fiber Optic Networks |
14 MAR 2003 |
54 pages |
| Authors:
Jie Qiao; Bipin Bihari; Ray T. Chen; OMEGA OPTICS INC AUSTIN TX
|
| In summary, this SBIR program was highly successful, and a few modules were completely packaged for delivery to the JPL labs for further testing. We contacted the JPL team at a later stage. However, it appears that JPL team was not interested in taking delivery of these modules. However, a set of 32-channel WDM/WDDM modules were successfully used to demonstrate a high throughput bit-serial data transfers between two computers for ... |
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| Refinements in a DCT Based non-Uniform Embedding Watermarking Scheme |
MAR 2003 |
143 pages |
| Authors:
Michail D. Giakoumakis; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Perceptual watermarking is a promising technique towards the goal of producing invisible watermarks. It involves the integration of formal perceptual models in the watermarking process, with the purpose of determining those portions of an image that can better tolerate the distortion imposed by the embedding and ensuring that the watermarking will inflict the least possible degradation on the original image. In a previous study the Discrete Cosine Transform was used, ... |
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| Superresolution of Passive Millimeter-Wave Imaging |
2003 |
4 pages |
| Authors:
Stanley J. Reeves; AUBURN UNIV AL DEPT OF COMPUTER AND ELECTRICAL ENGINEERING
|
| This project develops a new method for image acquisition to improve resolution. Ordinarily, a focal plane sensor array is arranged in a rectangular grid at sub-Nyquist spacing, and the array must be dithered to sample the image plane at the Nyquist rate in each dimension. However, the Nyquist rate oversamples the image due to the usually circular support of the diffraction- limited image spectrum. We develop efficient algorithms for optimizing ... |
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| Modes in a Nonneutral Plasma Column of Finite Length |
24 JUN 2002 |
6 pages |
| Authors:
S. N. Rasband; Ross L. Spencer; BRIGHAM YOUNG UNIV PROVO UT DEPT OF PHYSICS AND ASTRONOMY
|
| A Galerkin, finite-element, nonuniform mesh computation of the mode equation for waves in a non-neutral plasma of finite length in a Cold-Fluid model gives an accurate calculation of the mode eigenfrequencies and eigenfunctions. We report on studies of the following: (1)finite-length Trivelpiece-Gould modes with flat-top and realistic density profiles, (2)finite-length diocotron nodes with flat density profiles. We compare with the frequency equation of Fine and Driscoll Phys Plasmas 5, 601 ... |
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| Eigensolution Analysis of the Discontinuous Galerkin Method with Non- uniform Grids, Part I: One Space Dimension |
DEC 2001 |
33 pages |
| Authors:
Fang Q. Hu; INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING HAMPTON VA
|
| We present a detailed study of spatially propagating waves in a discontinuous Galerkin scheme applied to a system of linear hyperbolic equations. We start with an eigensolution analysis of the semi-discrete system in one space dimension with uniform grids. It is found that, for any given order of the basis functions, there are at most two spatially propagating numerical wave modes for each physical wave of the Partial Differential Equations ... |
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| High Temperature Superconductor RF Probes for Breast Cancer Research |
OCT 2001 |
38 pages |
| Authors:
Paul C. Wang; HOWARD UNIV WASHINGTON DC
|
| Nuclear magnetic resonance imaging and spectroscopy techniques have been used to study the breast cancer cells and tumor grown on animal. The goal of this study is to gain knowledge, which could be useful to improve the specificity of diagnosis and staging of breast cancer in clinic. Intrinsically, NMR techniques have weak signals, which limit the ultimate spatial resolution in image and sensitivity in spectrum. A high temperature superconductor RF ... |
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| A Unified Joint Probabilistic Data Association with Multiple Models |
JUL 2001 |
|
| Authors:
S. J. Davey; S. B. Colegrove; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION SALISBURY (AUSTRALIA) ELECTRONICS AND SURVEILLANCE RESEARCH
|
 | This paper presents the theory and examples of performance for a new algorithm that tracks targets using a Multiple Model Unified Joint Probabilistic Data Association (MM-UJPDA) filter. The models in the MM-UJPDA can be set to the ambiguity velocities encountered when initiating tracks on a sensor that has ambiguous velocities in its measurements. Alternately, the models can be set for tracking manoeuvring targets. Thus each parallel filter in the MM-UJPDAF ... |
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| Improved Thermal Barrier Coating System Based on a Cathodically Deposited Alpha Alumina Sublayer |
APR 2001 |
31 pages |
| Authors:
Rabi S. Bhattacharya; Bhaskar S. Majumdar; UES INC DAYTON OH
|
| This report was developed under a SBIR contract for Topic AF00-146. The primary objective of this Phase I research was to evaluate the feasibility of using an alpha alumina sublayer to reduce oxidation damage and improve the life of advanced thermal barrier coatings (TBC). A patented filtered cathodic arc deposition technique was used to deposit a 0.5-micrometers-thick alumina sublayer at 1000 deg C on a Pt-Al bond-coat deposited on a ... |
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| Improved Thermal Barrier Coating System Based on a Cathodically Deposited Alpha Alumina Sublayer |
APR 2001 |
|
| Authors:
Rabi S. Bhattacharya; Baskar Majumdar; UES INC DAYTON OH
|
| This report has been developed under a SBIR contract for Topic AF00- 146. The primary objective of this Phase I research was to evaluate the feasibility of using an alpha alumina sublayer to reduce oxidation damage and improve life of advanced thermal barrier coatings (TBC). A patented filtered cathodic arc deposition technique was used to deposit a 0.5 um thick alumina sublayer at 10000C on a Pt-Al bond-coat deposited on ... |
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| Optimal Rate of Convergence of Monotone Empirical Bayes Tests for a Normal Mean |
MAR 2001 |
16 pages |
| Authors:
Shanti S. Gupta; Jianjun Li; PURDUE UNIV LAFAYETTE IN DEPT OF STATISTICS
|
| This paper studies monotone empirical Bayes tests for a normal mean under a linear loss. The optimal rate of convergence of the monotone empirical Bayes tests is obtained. Applying a few techniques and using the non-uniform estimate of the remainder in the central limit theorem, we are able to construct a monotone empirical Bayes test and show that it achieves the best possible rate over a broad class of prior ... |
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| A Computational-Experimental Approach to Hierarchical Modeling of Damage and Failure in Non-Uniform Composite Materials |
2001 |
145 pages |
| Authors:
Somnath Ghosh; OHIO STATE UNIV COLUMBUS DEPT OF MECHANICAL ENGINEERING
|
| Progress has been made in advancing the state of the art in multiple- scale modeling of damage in composite materials, as delineated below. Interfacial Debonding Analysis in Multiple Fiber Reinforced Composites: Decohesion at multiple fiber interfaces of elastic fiber reinforced composites is modeled by the Voronoi cell finite element model (VCFEM). Interfacial debonding is accommodated by cohesive zone models and simulations are compared with results from experiments, performed using cruciform ... |
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| Experiments With an Adapative Multigrid Shallow-Water Tropical Cyclone Model |
MAY 2000 |
2 pages |
| Authors:
Brittany L. Mitchell; Scott R. Fulton; CLARKSON UNIV POTSDAM NY
|
| Accurate modeling of tropical cyclone motion and in. tensity change requires resolving the flow both within and around the storm. Since the spatial scales in these two regions differ substantially, uniform resolution is inherently inefficient: the grid should be refined only near the storm. This idea motivates conventional nested-grid methods such as used in VlCBAR (DeMaria et al., 1992) and the GFDL model (Kurihara et ... |
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| Nonuniform Quantization for Diffractive Optical Elements Design |
2000 |
7 pages |
| Authors:
Chung J. Kuo; Hung C. Chien; Ni Y. Chang; Chia H. Yeh; NATIONAL CHUNG CHENG UNIV CHIAYI (TAIWAN) GRADUATE INST OF COMMUNICATIONS
|
| Recently, the applications of diffractive optical element (DOE) for commerce and research have become more and more popular. DOE itself has a lot of advantages like small volume, low weight, ease of reproduce and low cost. A DOE actually can be considered as a wavefront modulator, and its performance can also be described as a complex amplitude transmittance. In the past, we usually design a DOE by quantizing the phase ... |
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| Test Specimen Design Incorporating Multiple Fracture Sites and Multiple Strain Material Fractures. |
18 MAY 1999 |
|
| Authors:
Virginia G. DeGlorgi; Andrew B. Geltmucher; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| A material test specimen design is taught for the determination of critical strain and stress states for multiaxial fracture. The objective of the specimen is to increase the amount of data obtained per specimen while retaining simplicity in testing procedure by using standard tension testing machines to generate the primary deformation of the specimen. The specimen, in conjunction with analytical or computational simulation, uses nonuniform deformation fields produced by secondary ... |
|
| Acoustic Localization and Decay of the Incoherent Impulse Response |
02 NOV 1998 |
6 pages |
| Authors:
Eric Smith; TEXAS UNIV AT AUSTIN APPLIED RESEARCH LABS
|
| Applied Research Laboratories, The University of Texas at Austin (ARL:UT) was tasked to study the effects of strong random scattering in acoustic media with macroscopically non-uniform scattering strengths. A statistical, field- theoretic method, previously applied in condensed matter physics and seismology, was introduced to study these effects analytically. Non-uniform random scattering was found to produce phenomena closely related to acoustic localization, which results from uniform ... |
|
| Fiber Optic Bragg Gratings |
NOV 1998 |
73 pages |
| Authors:
James M. Battiato; Kent E. Hulick; AIR FORCE RESEARCH LAB ROME NY
|
| Coupled mode theory was used to model reflection fiber gratings. The effects of experimental parameters on grating characteristics were modeled for both uniform and non-uniform grating profiles using this approach. Fabrication of gratings in standard communication single mode fiber required an enhancement of the fiber's photosensitivity by way of high-pressure hydrogen treatment. The theory behind this technique as well as the experimental system used to treat the fibers was discussed. ... |
|
| A Performance Analysis of the IRIDIUM Low Earth Orbit Satellite System |
01 JUN 1998 |
113 pages |
| Authors:
Carl E. Fossa Jr.; AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH SCHOOL OF ENGINEERING
|
| This thesis provides a performance evaluation of the IRIDIUM Low Earth Orbit Satellite system. It examine's the system's ability to meet real time communications constraints with a degraded satellite constellation. The analysis is conducted via computer simulation. The simulation is run at low, medium, and high loading levels with both uniform and non-uniform traffic distributions. An algorithmic approach is used to select critical satellites to remove from the constellation. Each ... |
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| Strength Evolution in the Sintering of Bronze Powder Metal Compacts and Application to Thermal Cycle Design |
15 MAY 1998 |
|
| Authors:
Gregory A. Shoales; PENNSYLVANIA STATE UNIV UNIVERSITY PARK
|
| Powder metallurgy allows fabrication of complex net-shape components. Accurate design specification of these components requires precise prediction of their response to sintering process parameters. Nonuniform sintering responses, such as strain gradients, can result in process failures such as distortion and cracking. To avoid these types of process failures without costly trial and error design, the most important response to understand is the compact's strength as it evolves during the sintering ... |
|
| An Evaluation of Frequency Domain Ensemble Averging to Improve Aircraft Stability Derivative Estimation |
MAR 1998 |
184 pages |
| Authors:
Lawrence M. Hoffman; AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH SCHOOL OF ENGINEERING
|
| This research evaluated a process to improve aircraft stability derivative estimation results. The Have Derivatives process used overlap ensemble averaging in the frequency domain to minimize noise on the original time domain signals. The process estimated average complex frequency response functions that were then transformed back into the time domain as a set of discrete pulse responses with far less noise than the original signals. These clean signals were used ... |
|
| Correcting Radiance Data for Randomly Occurring Nonuniform Illumination of the IFOV of Individual Detectors in Arrays |
1998 |
8 pages |
| Authors:
H. Berger; E. H. Bosch; E. Simental; ARMY TOPOGRAPHIC ENGINEERING CENTER FORT BELVOIR VA
|
| This paper discusses the nonuniform illumination of individual pixels in an array that is intrinsic to the scene viewed, as opposed to turbulence or platform motion as an error source in quantitative imagery. It describes two classes of algorithms to treat this type of problem. It points out that this problem can be viewed as a type of inverse problem with a corresponding integral equation unlike those ... |
|
| Thermal Residual Stress Relaxation and Distortion in Surface Enhanced Gas Turbine Engine Components |
1998 |
12 pages |
| Authors:
P. Prevey; D. Hombach; P. Mason; LAMBDA RESEARCH CINCINNATI OH
|
| Compressive residual stresses are often de{deliberately induced in the surfaces of turbine engine components using a variety of surface enhancement methods to improve fatigue life. Thermal stress relaxation can occur in both the Ti and Ni alloys used in compressor and turbine stages Nonuniform relaxation of the compressive layer can cause distortion of the critical aerodynamics shapes of thin blades potentially effecting engine performance. |
|
| Review of Recent Results on Optimal Orthonormal Subband Coders |
JUL 1997 |
12 pages |
| Authors:
P. P. Vaidyanathan; CALIFORNIA INST OF TECH PASADENA
|
| The conditions for optimality of uniform orthonormal subband coders are reviewed. A number of properties of optimal filter banks are then summarized. The case of nonuniform orthonormal filter banks is also considered, and it is shown that the well known connection between optimal coding gain, energy compaction, and principal component property does not extend to the nonuniform case. |
|
| Processing Irradiance Measurement Data in the Field-of-View Domain |
1997 |
11 pages |
| Authors:
H. Berger; E. H. Bosch; ARMY TOPOGRAPHIC ENGINEERING CENTER ALEXANDRIA VA TOPOGRAPHIC SYSTEMS LAB
|
| The sensing of spatial imagery and spectral signatures involves the measurement of radiance. However detectors measure irradiance and the radiance must be inferred from that. This paper reports a method of processing irradiance measurement data to obtain radiance in a manner so as to reduce the errors caused by the unknown nonuniform illumination of the instantaneous-field-of-view (IFOV) of the individual optical detectors in an array of such ... |
|
| Modeling of Crack Initiation and Growth in Solid Rocket Propellants Using Macromechanics and Micromechanics Theories |
SEP 96 |
96 pages |
| Authors:
James H. Lee; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Modeling and simulation of crack initiation and propagation in solid rocket propellant materials were conducted using both the macromechanics approach and the micro/macromechanics approach. Due to their composition, the solid rocket propellant can be construed as particle reinforced composites. The macromechanics approach entailed a numerical simulation of a finite element model to predict the crack behavior based on the damage initiation, growth, and local saturation. Its results were then compared ... |
|
| Selected Articles |
03 JUN 96 |
44 pages |
| Authors:
NATIONAL AIR INTELLIGENCE CENTER WRIGHT-PATTERSON AFB OH
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| Partial contents: Calibration of the optical quality of a large telescope system; Measurement of water vapor content in singlet oxygen generator by spectrometric methods; Effect of atmospheric turbulence on precision of laser tracking system; Effects of coating thickness nonuniformity on far-field performance of beam indicator. |
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| Microstructural Development in AL-LI-CU-MG Alloys and Metal Matrix Composites |
DEC 95 |
204 pages |
| Authors:
Xiaoli Tang; PENNSYLVANIA STATE UNIV UNIVERSITY PARK COLL OF EARTH AND MINERAL SCIENCES
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| The aging responses of both an 8090 alloy and a SiC reinforced 8090 alloy matrix composite, at 190 deg C, have been fully characterized for the first time using various analytical techniques. Two stage hardening was observed in both materials and somewhat unexpectedly, the aging response of the composite was unchanged as compared to the unreinforced 8090 alloy. Microstructural development during the aging of both materials was studied using electron ... |
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