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Air Force Institute of Technology

1997

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Articles 1 - 30 of 144

Full-Text Articles in Engineering

Experimental Investigation Of The Influence Of Molecular Weight On Mixing And Penetration In Supersonic Dissimilar Gaseous Injection Into A Supersonic Cross-Flow, Troy A. Giese Dec 1997

Experimental Investigation Of The Influence Of Molecular Weight On Mixing And Penetration In Supersonic Dissimilar Gaseous Injection Into A Supersonic Cross-Flow, Troy A. Giese

Theses and Dissertations

In pursuit of a more efficient and effective fuel-air mixing for a SCRAMjet combustor, this study investigated relative near field effects of molecular weight on mixing and penetration of different gaseous injection into a supersonic (M=2.9) cross flow. Helium and argon gas were chosen as injectants because of the large differences in molecular weights. Also, mixing enhancement was observed by injecting the traverse gas jet parallel to the compression face of a ramp. Color schlieren photography was used to identify the shock structures and interactions in the flow field. Measurements of mean flow properties were used to establish the jet …

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Pollution Prevention Process Influences In The Weapon System Acquisition Life Cycle, Tedmond B. Grady Dec 1997

Pollution Prevention Process Influences In The Weapon System Acquisition Life Cycle, Tedmond B. Grady

Theses and Dissertations

This research develops a system structure for the pollution prevention acquisition process and uses system dynamics modeling to develop management strategies that optimize life cycle cost. The structure of the pollution prevention acquisition process is developed by identifying primary influences and mechanisms and determining how they interact within the acquisition process. The model structure is based on the premise that rising total projected Life Cycle Cost (LCC) would provide an incentive to perform pollution prevention changes to reduce the overall LCC cost. The model successfully produces the expected reasonable behavior and confidence in the model structure is achieved using standard …

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Secondary Data Support And Non-Homogeneities In Space-Time Adaptive Processing, Todd B. Hale Dec 1997

Secondary Data Support And Non-Homogeneities In Space-Time Adaptive Processing, Todd B. Hale

Theses and Dissertations

One of the primary problems with the application of Space-Time Adaptive Processing (STAP) techniques is secondary data support for the interference plus noise covariance matrix estimate. Reed has shown the required secondary data support to achieve performance within 3 dB of optimal SINR is approximately equal to twice the degrees of freedom (DOF) used in the algorithm. Reed proved this rule for Sample Matrix Inversion (SMI) techniques. A concern arises when applying this rule to a newer class of reduced dimension STAP algorithms that do not fall under the SMI umbrella. This thesis focuses on the Cross Spectral Metric (CSM) …

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Micro-Electromechanical Switches For Micro-Satellite Power Transfer, Glen A. Kading Dec 1997

Micro-Electromechanical Switches For Micro-Satellite Power Transfer, Glen A. Kading

Theses and Dissertations

In the past few years, microelectromechanical systems (MEMS) have emerged as a promising new technology with tremendous application potential. One of the possible implementations of MEMS technology is in the development of micro-satellites. It should be possible to mass-produce micro-satellites at a fraction of the cost of one conventional satellite. In order for satellites to be robust, a method of transferring power to systems must be addressed. As micro-satellites are made with conventional integrated circuit technologies at a very small scale, a means of transferring power on a similar scale will be investigated. This research addresses the issue of the …

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Atmospheric Induced Errors In Space-Time Adaptive Processing, Vinod D. Naga Dec 1997

Atmospheric Induced Errors In Space-Time Adaptive Processing, Vinod D. Naga

Theses and Dissertations

This thesis examines the effects of atmospheric turbulence-induced phase perturbations on the performance of ground-based Space-Time Adaptive Processing (STAP) systems. Both Fully Adaptive Joint Domain Optimum and Partially Adaptive Factored-Time Space processing methods are examined. This thesis concentrates on the turbulence effects on STAP applied to ground-based arrays. This thesis further focuses on the capability of STAP to resolve targets at low elevation angles in the presence of turbulence. Only clutter interference and receiver noise are considered. Turbulence effects on the EM phase-front are calculated for turbulence strength Cn(2) values ranging from 5.0 x 10(exp -14) m-2/3 to 5.0 x …

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Evaluation Of The Natural Biodegradation Of Aircraft Deicing Fluid Components In Soils, Laura M. Johnson Dec 1997

Evaluation Of The Natural Biodegradation Of Aircraft Deicing Fluid Components In Soils, Laura M. Johnson

Theses and Dissertations

This research effort was conducted to analyze the biodegradation of propylene glycol (PG) and tolyltriazole in two different soil types; a sandy soil and a high clay soil. Both an automated respirometer and a high performance liquid chromatograph (H PLO) were used in the analysis. Two separate experiments were conducted. In the first experiment, one level of tolyltriazole was added to the soils to determine whether or not there was a difference in the biodegradation rates of tolyltriazole in the two soils. The respirometer results indicated that there was a significant difference between the respiration rates of the microorganisms in …

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User Location Determination Strategy In A Low Earth Orbit Satellite Network, Jaehee Lee Dec 1997

User Location Determination Strategy In A Low Earth Orbit Satellite Network, Jaehee Lee

Theses and Dissertations

Recently, many Low Earth Orbit (LEO) satellite systems have been proposed for the purpose of global communication and one of those systems is planned to start the commercial service in 1998. These LEO satellite systems are providing most of current communication services (voice, fax, data, paging, and even real time video service) without any limitation on place and time. However, little is published about their detail system methodology on user tracking and managing schemes. This thesis presents two user location tracking algorithms in a LEO environment. One (Gateway Approach) is the most likely approach under present system proposals, while the …

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Optimal Pulsed Pumping For Remediation Of Aquifers When Sorption Is Rate-Limited, Lawrence J. Schmitt Dec 1997

Optimal Pulsed Pumping For Remediation Of Aquifers When Sorption Is Rate-Limited, Lawrence J. Schmitt

Theses and Dissertations

A variational optimization technique is developed to acquire an optimal schedule of pulsed pumping operations for use at existing pump-and-treat aquifer remediation sites. The optimization problem is stated as a minimization of a generic management objective functional, constrained by the contaminant transport equations in two-dimensional or three-dimensional flow models which account for rate-limited sorption. The two-dimensional case is fully developed and a first-order rate equation is used to describe the transport of sorbing contaminant. The first variation provides necessary optimality conditions that must be met by any optimal solution, in turn leading to a pulsed pumping schedule of operation. The …

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Self-Assembly Of Microstructures, Paul E. Kladitis Dec 1997

Self-Assembly Of Microstructures, Paul E. Kladitis

Theses and Dissertations

Four areas are investigated in this research: erecting microstructures normal to the substrate plane without direct human intervention (self-assembled), providing low resistance electrical connections to the erected microstructure, realizing circular motion normal to the substrate plane, and implementing a micro-robot. The designs in this research concentrate on erecting and providing power to a leg designed for use with the micro-robot. The leg and the attached low resistance electrical connectors were not self-assembled because the accompanying actuators were not powerful enough. However, the novel connectors provide the most practical, versatile, and lowest possible resistance connections for the MUMPs fabrication process. The …

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Applying Flywheel Energy Storage To Solar Electric Orbital Transfers, Mark W. Marasch Dec 1997

Applying Flywheel Energy Storage To Solar Electric Orbital Transfers, Mark W. Marasch

Theses and Dissertations

This study investigated the application of flywheel energy storage to minimum time, constant thrust orbital maneuvers using electric propulsion. The advantages of using stored energy to continue electric thruster operations while in eclipse were explored. The boundary value problems for several schemes of energy use were examined, and numerical solutions were found. Results of simulations utilizing energy storage were compared to results without energy storage. Schemes incorporating energy storage were found to have advantages in terms of propellant mass used, time spent in transit, and deliverable payload.

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Flow Field And Loading Analysis On A Wrap-Around Fin Missile, Thomas C. Mcintyre Dec 1997

Flow Field And Loading Analysis On A Wrap-Around Fin Missile, Thomas C. Mcintyre

Theses and Dissertations

Wrap-around fin (WAF) missiles offer packaging benefits but experience rolling moments due to the curved fin design. Rolling moments stabilize unguided projectiles, but cause guidance and control problems for future guided applications. Understanding the flow field in the vicinity of the fins is critical to future missiles. Fin pressure profiles were characterized with pressure-sensitive paint. Two rectangular four-fin constructions were tested-one solid and one with a rectangular hole (slotted fin). Static pressure data were divided by free-stream total pressure for presentation. Tests were conducted at Mach numbers of 2.15, 2.28, 2.41, 2.86, 3.25, 3.50 and 3.83. Reynolds numbers based on …

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Using Cross-Eye Techniques To Counter Radio Frequency Agile Monopulse Processing, Gregory J. Meyer Dec 1997

Using Cross-Eye Techniques To Counter Radio Frequency Agile Monopulse Processing, Gregory J. Meyer

Theses and Dissertations

The purpose of this research was to evaluate how current cross-eye techniques protect an airborne platform versus a pulse-to-pulse Radio Frequency (RF) agile monopulse processing threat and, if necessary, develop a new cross-eye techniques to counter this threat. This research evaluates how both current retrodirective cross-eye techniques and an original technique, namely synchronized cross-eye, hide the true skin return in the time and frequency domain while preserving the necessary phase interferometric effects at the threat radar location. Existing retrodirective cross-eye techniques are inadequate to counter the RF agile threat due to propagation delays. Using modeling and simulation, the research shows …

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Department Of Defense Hazardous Waste Site Remediation Issues In The Republic Of Korea, Edwin H. Oshiba Dec 1997

Department Of Defense Hazardous Waste Site Remediation Issues In The Republic Of Korea, Edwin H. Oshiba

Theses and Dissertations

The purpose of this research was to provide information to DoD decision makers regarding factors influencing hazardous waste site remediation policy for South Korea. This study addressed: International agreements and U.S. and South Korean laws and policies relevant to hazardous waste sites; objectives of DoD environmental policy makers; extent and effects of soil and groundwater contamination; cleanup precedents set in other foreign countries; availability of resources and technical capabilities to investigate and remediate hazardous waste sites in South Korea; and opportunities for cooperation between the U.S. and South Korean military with regard to hazardous waste site remediation. Data were collected …

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Architecture, Design, And Implementation Of A Rapidly Prototyped Virtual Environment For A Military Spaceplane, Scott A. Rothermel Dec 1997

Architecture, Design, And Implementation Of A Rapidly Prototyped Virtual Environment For A Military Spaceplane, Scott A. Rothermel

Theses and Dissertations

The new Global Engagement vision places increased emphasis on the Air Force's ability to control and exploit space. A military spaceplane combining reliable access to space, high operational tempos, and multi-mission capabilities is in conceptual stages of development. Virtual environment technology provides an opportunity to investigate system requirements and unconventional interface paradigms for this unique vehicle. A virtual environment architecture and design based on support for a rapid prototyping development process, separation of concerns, and user interface development is presented. The rapid prototyping process allowed management of changing requirements via an evolutionary approach to implementation. Separation of the activities performed …

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A Wire Antenna Designed For Space Wave Radiation Over The Earth Using A Genetic Algorithm, Brian S. Sandlin Dec 1997

A Wire Antenna Designed For Space Wave Radiation Over The Earth Using A Genetic Algorithm, Brian S. Sandlin

Theses and Dissertations

A wire antenna is designed for optimal performance at low elevation angles in the presence of a lossy half-space. A simple genetic algorithm (GA) and GENOCOP III software are each integrated with Numerical Electromagnetics Code Version 4.1 (NEC4.1) to optimize a wire antenna geometry for multiple objectives: power gain, azimuthal symmetry, and input impedance. The performance of the two versions of the integrated GA are compared. Several of the resulting antennas are analyzed, and an antenna is proposed for use in a Remote Intrusion Monitoring System (RIMS). Simulations suggest that the proposed antenna, which is well-matched, offers a significant increase …

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Spontaneous Emission In Microcavity Lasers, Dustin Philip Ziegler Dec 1997

Spontaneous Emission In Microcavity Lasers, Dustin Philip Ziegler

Theses and Dissertations

An understanding of spontaneous emission processes within microcavities is crucial in addressing the need to make tomorrow's microlasers more efficient. One approach to improving the device efficiency is to reduce the threshold input energy at which lasing begins to occur. It has been suggested that the threshold in a microcavity laser can be decreased by increasing the fraction of spontaneous emission into the lasing mode, this can be accomplished by preferentially coupling the gain medium of the laser to the electromagnetic cavity mode of interest. It therefore becomes necessary to understand the mechanism by which this coupling takes place. This …

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Investigation Of Biodegradation Processes In Solid Waste Landfills, Philip A. Colborn Dec 1997

Investigation Of Biodegradation Processes In Solid Waste Landfills, Philip A. Colborn

Theses and Dissertations

Greater demands on landfill capacity, stricter regulations intended to minimize landfill environmental impacts, and the economic potential associated with landfill operations have shifted the emphasis of landfill disposal toward methods concerned with the long term performance and capacity of landfills. Two opposing philosophies have emerged in constructing and managing landfills: the dry tomb and the wet cell. The key to managing a landfill from the wet cell viewpoint is first understanding the biodegradation processes occurring within the landfill. This thesis attempts to determine the fundamental processes responsible for the degradation of solid waste by employing a system dynamics approach. A …

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A Dispersive Scattering Center, Parametric Model For 1-D Atr, Dane F. Fuller Dec 1997

A Dispersive Scattering Center, Parametric Model For 1-D Atr, Dane F. Fuller

Theses and Dissertations

The dispersive scattering center (DSC) model characterizes high-frequency backscatter from radar targets as a finite sum of localized scattering geometries distributed in range, these geometries, along with their relative locations, can be conveniently used as features in a one-dimensional automatic target recognition (ATR) algorithm. The DSC model's type and range parameters correspond to geometry and distance features according to the geometric theory of diffraction (GTD). Since these parameters are estimated in the phase history domain of the radar signal, the range parameter does provide superresolution in the time domain. To demonstrate the viability of feature extraction based on the DSC …

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A Comparative Analysis Of Networks Of Workstations And Massively Parallel Processors For Signal Processing, David C. Gindhart Dec 1997

A Comparative Analysis Of Networks Of Workstations And Massively Parallel Processors For Signal Processing, David C. Gindhart

Theses and Dissertations

The traditional approach to parallel processing has been to use Massively Parallel Processors (MPPs). An alternative design is commercial-off-the-shelf (COTS) workstations connected to high-speed networks. These networks of workstations (NOWs) typically have faster processors, heterogeneous environments, and most importantly, offer a lower per node cost. This thesis compares the performance of MPPs and NOWs for the two-dimensional fast Fourier transform (2-D FFT). Three original, high-performance, portable 2-D FFTs have been implemented: the vector-radix, row-column and pipeline. The performance of these algorithms was measured on the Intel Paragon, IBM SP2 and the AFIT NOW, which consists of 6 Sun Ultra workstations …

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Warning Times And Impact Predictions Of Asteroids And Comets On A Collision Course With Earth, Ahren D. Heidt Dec 1997

Warning Times And Impact Predictions Of Asteroids And Comets On A Collision Course With Earth, Ahren D. Heidt

Theses and Dissertations

This study investigates the amount of data and time necessary to accurately predict Earth impacts of Earth Crossing Objects (ECOs). Trajectories are simulated by numerically integrating in an N-Body system. Given final impact parameters, the trajectory is propagated backwards to an earlier time, creating initial conditions and simulated observation data at requested intervals to which Gaussian random noise is introduced. Utilizing a Bayes Filter to estimate position and velocity from the simulated observation data, the estimate is then propagated forward in time to determine whether or not an impact can be accurately predicted. State vectors and covariance matrices are then …

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A System Dynamics Investigation Of Environmental Attitudes And Behaviors Influencing Solid Waste Reduction, Louis E. Lilley Dec 1997

A System Dynamics Investigation Of Environmental Attitudes And Behaviors Influencing Solid Waste Reduction, Louis E. Lilley

Theses and Dissertations

The relationship between attitudes and behavior is investigated in regard to the reduction of solid waste in a community. The theory of reasoned action, as identified by Ajzen and Fishbein in 1975, is investigated using as system dynamics approach. The closed loop system structure that would produce the expected real world response is established. The structure is then translated into a flow diagram and coded into a mathematical model. The model quantifies the values of beliefs, attitudes, intentions, behaviors, external and demographic variables, perceptions, and waste generation levels in order to illustrate how each changes over time when influenced by …

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Creating Origen Models, Gregory D. Louden Dec 1997

Creating Origen Models, Gregory D. Louden

Theses and Dissertations

The purpose of this study was to develop a methodology for creating problem dependent cross section libraries for ORIGEN (Oak Ridge Isotope Generation and Depletion Code). The Air Force Technical Applications Center (AFTAC) has a requirement to classify spent nuclear fuel. The ORIGEN codes provide generic models of commercial nuclear reactor designs that are not adequate for the detailed analysis required by AFTAC. After comparing the methods that ORIGEN2 an ORIGEN-S use to develop burnup dependent cross section libraries, the research focused on developing a methodology for creating new ORIGEN-S models. Models of the Ohio State University Research Reactor were …

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A Reconfigurable Superscalar Architecture, Christopher B. Mayer Dec 1997

A Reconfigurable Superscalar Architecture, Christopher B. Mayer

Theses and Dissertations

The invention of the Field Programmable Gate Array (FPGA) has led to a number of interesting developments. One is the idea of providing custom hardware support for applications running on a computer. These reconfigurable computers have been shown to decrease the execution time for some applications. Based on past results, attention has subsequently turned to using reconfigurable computing in general-purpose computers (e.g. desktop and workstation environments). This thesis develops a design for just such a computer. The design, FPGADLX, is based on a hypothetical superscalar computer running the DLX instruction set and is generic enough in principle to be adapted …

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Constrained Model Predictive Control Of A Nonlinear Aerospace System, Christopher M. Shearer Dec 1997

Constrained Model Predictive Control Of A Nonlinear Aerospace System, Christopher M. Shearer

Theses and Dissertations

Recent research efforts have applied the receding horizon Model Predictive Control (MPC) strategy to linearized high performance aerospace systems. The research contained in this thesis used these recent results in order to apply the MPC strategy to a nonlinear high performance aerospace system, specifically an F-16 fighter aircraft model. The model was commanded to follow dynamic trajectories of roll angle and altitude. Further, adaptive constraint techniques were used to improve system tracking. To accomplish these tasks, code and block diagrams were generated using the commercial software packages of Matlab and Simulink. Numerous simulations were conducted with the goal of achieving …

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Evaluation Of A Maximum A-Posteriori Slope Estimator For A Hartmann Wavefront Sensor, Troy B. Van Caster Dec 1997

Evaluation Of A Maximum A-Posteriori Slope Estimator For A Hartmann Wavefront Sensor, Troy B. Van Caster

Theses and Dissertations

Current methods for estimating the wavefront slope at the aperture of a telescope using a Hartmann wavefront sensor are based upon a centroid shift estimator. The centroid shift estimator determines the displacement, or shift, of the centroid off the optical axis using a moment calculation of the intensity distributions recorded in each subaperture. This centroid shift is proportional to the average slope of the wavefront in each subaperture. A maximum a-posteriori (MAP) slope estimator takes advantage of a-priori knowledge of the wavefront slope statistics and total irradiance falling on the subaperture detector arrays when determining the shift estimate. In order …

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The Rational Resolution Analysis: A Generalization Of Multi-Resolution Analyses With Application To To The Specific Emitter Identification Problem, Bruce P. Anderson Dec 1997

The Rational Resolution Analysis: A Generalization Of Multi-Resolution Analyses With Application To To The Specific Emitter Identification Problem, Bruce P. Anderson

Theses and Dissertations

The rational resolution analysis RRA is introduced and developed as a generalization of the integer, dilation multiresolution analyses MRA developed by Mallat and Meyer. Rational dilation factors are achieved by relaxing the condition on MRAs that successive approximation spaces be embedded. Conditions for perfect reconstruction are discussed and it is shown that perfect reconstruction is possible with specific constraints on the scaling function the scaling filter must have its roots on the unit circle. Furthermore, the required arrangement of the roots indicate the scaling function must be derived from a B-spline of some degree. It is proven the only compactly …

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An Analysis Of Early Software Reliability Improvement Techniques, John G. Leonard, Ric K. Nordgren Dec 1997

An Analysis Of Early Software Reliability Improvement Techniques, John G. Leonard, Ric K. Nordgren

Theses and Dissertations

This research explores early life cycle software reliability prediction models or techniques to predict the reliability of software prior to writing code, and a method for increasing or improving the reliability of software products early in the development life cycle. Five prediction models and two development techniques are examined. Each model is statically analyzed in terms of availability of data early in the life cycle, ease of data collection, and whether data is currently collected. One model and the two techniques satisfied those requirements and are further analyzed for their ability to predict or improve software reliability. While the researchers …

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A Gps Code Tracking Receiver Design For Multipath Mitigation Using Maximum Likelihood Estimation, Fred P. Baier Dec 1997

A Gps Code Tracking Receiver Design For Multipath Mitigation Using Maximum Likelihood Estimation, Fred P. Baier

Theses and Dissertations

The NAVSTAR Global Positioning System (GPS) is currently used in many applications requiring precise positioning data. Improving the precise positioning information requires the removal of errors that perturb the received signals. The errors introduced by multiple propagation channels, termed multipath, are not easily removed. These channels are caused by reflective surfaces near the receiver. As such, multipath is uncorrelated between receivers and, thus, cannot be removed through differencing techniques. This thesis investigates a GPS code tracking loop design which uses maximum likelihood (ML) estimation to determine amplitude and phase information of the multipath signal which are used to adjust code …

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Pseudorandom Code Generation For Communication And Navigation System Applications, John F. Brendle Jr. Dec 1997

Pseudorandom Code Generation For Communication And Navigation System Applications, John F. Brendle Jr.

Theses and Dissertations

This research project investigated the design, construction and evaluation of a pseudorandom code generator for communication and navigation system applications. These types of codes include spreading codes, Gold codes, Jet Propulsion Laboratory (JPL) ranging codes, syncopated codes, and nonlinear codes. Such waveforms are typically used in communication and navigation system applications. The code generator uses the Stanford Telecom STEL-1032 Pseudorandom Number (PRN) coder. A coder interface was designed and constructed for manual data entry to the registers of the PRN coder. The code generator is capable of independently clocking and generating all possible codes with lengths up to 4,294,967,295 bits. …

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Message-Bundle Converting In Intenet Protocol Multicast-Based High Level Architecture Exercises, Tracy A. Bobo Dec 1997

Message-Bundle Converting In Intenet Protocol Multicast-Based High Level Architecture Exercises, Tracy A. Bobo

Theses and Dissertations

The Department of Defense is pushing for more wide-spread and realistic interactive training simulations which increases the demand on network capacity and resources. While network bandwidth is a measurable resource, packet bandwidth, or the number of packets-per-second (Pk/s) a host can handle, is a shifting commodity. This research analyzes host performance characteristics under varying data loads. The hosts include SGI single and multi-processor systems and Intel Pentium platforms using both Windows 95 and Linux Operating Systems. The networking media covers Ethernet, ATM and FDDI. For the ATM network, both AAL5 and IP over ATM were analyzed. With the data from …

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