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1999

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Articles 781 - 810 of 1307

Full-Text Articles in Engineering

Integrated Ups/Ins Precision Approach Landing With M3ae Interference Avoidance, Stephan H. Chastain Mar 1999

Integrated Ups/Ins Precision Approach Landing With M3ae Interference Avoidance, Stephan H. Chastain

Theses and Dissertations

Several past research efforts have developed methods to take advantage of Global Positioning System (UPS) positioning and apply it to a precision landing system (PLS). There have been proposals to phase out the current Instrument Landing System (ILS) in favor of a more cost-efficient and effective system. Accomplishments have been made in detailing a system implementing an INS aided with differential UPS, a UPS pseudolite, and a radar altimeter to handle the critical PLS requirements. This research applies the newly developed Modified Multiple Model Adaptive Estimation (M3AE) architecture in an attempt to enhance the performance of a PLS in an …

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Incorporating Scene Mosaics As Visual Indexes Into Uav Video Imagery Databases, Timothy I. Page Mar 1999

Incorporating Scene Mosaics As Visual Indexes Into Uav Video Imagery Databases, Timothy I. Page

Theses and Dissertations

The rise of large digital video archives has strengthened the need for more efficient ways of indexing video files an accessing the information contained in them. Reconnaissance platforms, such as the Predator UAV, are contributing thousands of hours of video footage that require analysis, storage, and retrieval. A process is proposed for converting a video stream into a series of mosaic and selected still images that provide complete coverage of the original video. The video mosaic images can be utilized as visual indexes into a video database. In addition, mosaic images contain information from an entire sequence of video frames …

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An Empirical Prediction Model Of The Performance Impacts Of Material Tolerances In Frequency Selective Surfaces Using The Monte Carlo Method, Matthew D. Craig Mar 1999

An Empirical Prediction Model Of The Performance Impacts Of Material Tolerances In Frequency Selective Surfaces Using The Monte Carlo Method, Matthew D. Craig

Theses and Dissertations

Standard computational tools predicting frequency selective surface (FSS) performance model periodic structures as an infinite-by-infinite array of perfectly placed elements with perfect, identical dimensions, and with dielectric layers of uniform thickness and material composition. These models do not address perturbations caused by manufacturing tolerances of elements and dielectric layers, nor do they address edge effects caused by finite-by-finite dimensional arrays. The Monte Carlo Method was used to determine the effects of random variations in element dimension, placement, dielectric thickness, and dielectric material on FSS performance. A full-factorial experimental design was applied, and eight hundred twenty-five unique finite arrays of elements …

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Asymmetric Load Balancing On A Heterogeneous Cluster Of Pcs, Christopher A. Bohn Mar 1999

Asymmetric Load Balancing On A Heterogeneous Cluster Of Pcs, Christopher A. Bohn

Theses and Dissertations

In recent years, high performance computing with commodity clusters of personal computers has become an active area of research. Many organizations build them because they need the computational speedup provided by parallel processing but cannot afford to purchase a supercomputer. With commercial supercomputers and homogenous clusters of PCs, applications that can be statically load balanced are done so by assigning equal tasks to each processor. With heterogeneous clusters, the system designers have the option of quickly adding newer hardware that is more powerful than the existing hardware. When this is done, the assignment of equal tasks to each processor results …

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Non Co-Operative Detection Of Lpi/Lpd Signals Via Cyclic Spectral Analysis, Andrew M. Gillman Mar 1999

Non Co-Operative Detection Of Lpi/Lpd Signals Via Cyclic Spectral Analysis, Andrew M. Gillman

Theses and Dissertations

This research proposes and evaluates a novel technique for detecting LPI/LPD communication signals using a digital receiver primarily designed to detect radar signals, such as a Radar Warning Receiver (RWR) or an Electronic Support Measures (ESM) receiver. The proposed Cyclic Spectrum Analysis (CSA) receiver is a robust detector that takes advantage of the spectral correlation properties of second-order cyclostationary signals. A computationally efficient algorithm is used to estimate the Spectral Correlation Function (SCF). Using state-of-the-art FFT processing, it is expected that the proposed CSA receiver architecture could estimate the entire cyclic spectrum m approximately 0.6 ms. The estimate is then …

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Analysis Of The Applicability Of Video Segmentation To Unmanned Aerial Vehicle Surveillance Video, Bradley L. Pyburn Mar 1999

Analysis Of The Applicability Of Video Segmentation To Unmanned Aerial Vehicle Surveillance Video, Bradley L. Pyburn

Theses and Dissertations

The focus of this research is to determine if applying edge detection segmentation (proposed by Ramin Zabih, Justin Miller, and Kevin Mai) to Unmanned Aerial Vehicle (UAV) video footage can provide meaningful segments for database storage and retrieval. The edge detection segmentation algorithm is applied to fifty-four UAV video sequences containing visual effects such as abrupt camera changes, camera zooms, motion (rapid and gradual), and cloud cover while varying the frame rate from 5 fps to 30 fps. An analysis of the results is performed to compare actual versus expected outcomes, similar sequences, and scenes with motion, along with explaining …

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Graphical User Interface And Microprocessor Control Enhancement Of A Pseudorandom Code Generator, John M. Kos Mar 1999

Graphical User Interface And Microprocessor Control Enhancement Of A Pseudorandom Code Generator, John M. Kos

Theses and Dissertations

Modern digital communication techniques often require the generation of pseudorandom numbers or sequences. The ability to quickly and easily produce various codes such as maximal length codes, Gold codes, Jet Propulsion Laboratory ranging codes, syncopated codes, and non-linear codes in a laboratory environment is essential. This thesis addresses the issue of providing automated computer control to previously built, manually controlled hardware incorporating the Stanford Telecom STEL-1032 Pseudo-Random Number (PRN) Coder. By incorporating a microcontroller into existing hardware, the STEL-1032 can now be conveniently controlled from a MATLAB Graphical User Interface (GUI). The user can quickly create, save, and recall various …

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Low Grazing Angle Terrain Backscattering Coefficient Generator, William N. O'Connor Mar 1999

Low Grazing Angle Terrain Backscattering Coefficient Generator, William N. O'Connor

Theses and Dissertations

A near-horizon probabilistic terrain backscatter coefficient generator is introduced, combining modified sea-state curves with Weibull-type probability density functions. A total of nine terrain type classifications (soils & rocks, trees, grasses, shrubs, short vegetation, roads, urban areas, dry snow, and wet snow) are supported, for seven radar bands (L, S, C, X, Ku, Ka, and W), and both linear (HH, VV) and cross (HV, VH) polarizations. The Weibull functions are based on measured sigma and match the published data. The functions also provide a probabilistic nature to the generator. Modified sea state curves are used in place of the Weibull functions …

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Terrain Backscattering Coefficient Generator, Ricardo Mediavilla Mar 1999

Terrain Backscattering Coefficient Generator, Ricardo Mediavilla

Theses and Dissertations

Using already available data, a backscattering coefficient generator (BCG) for several types of terrain and measurement conditions is developed. The types of terrain are: (1) soils and rocks, (2) trees, (3) grasses, (4) shrubs, (5) short vegetation, (6) roads, (7) urban areas, (8) dry snow, and (9) wet snow. These data sets typically cover incidence angles ranging between 0 and 80 degrees where 0 is normal to the terrain. Measurement conditions are defined by: (1) incidence angle, (2) wave polarizations configuration (HH, HV, or VV), and (3) radar band (L, C, S, X, Ku, Ka, or W). The BCG output …

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Modulation Of Electrostatic Microelectromechanical Mirrors Using A Cmos Controller, Paul C. Rounsavall Mar 1999

Modulation Of Electrostatic Microelectromechanical Mirrors Using A Cmos Controller, Paul C. Rounsavall

Theses and Dissertations

Microelectromechanical Systems (MEMS) is a rapidly growing technology that lends itself particularly well to optical applications. An example of an optical MEMS device is the piston-action mirror that modulates the phase of reflected light. The phase of reflected light can be varied using thermal or electrostatic actuation to control the position of the mirror. In previous research, a modulation method to control thermally actuated mirrors was developed. This thesis presents the development, implementation, fabrication, and testing of a complimentary metal oxide semiconductor (CMOS) controller capable of directly interfacing between a digital system, such as a computer, and an electrostatically actuated …

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Antenna Gain Enhancement Using A Photonic Band Gap Reflector, Karl C. Schloer Mar 1999

Antenna Gain Enhancement Using A Photonic Band Gap Reflector, Karl C. Schloer

Theses and Dissertations

Scientists have long known that periodic structures can filter electromagnetic (EM) waves. In the last decade, extension of one- and two-dimensionally periodic structures into a third periodic dimension has produced photonic band gap (PBG) structures. A PBG structure is characterized by its omnidirectional stop band at a set of frequencies determined by the structure's periodicity and permittivity. In the present research, we investigate such a structure as an antenna reflector. We aim to develop a modeling approach that provides accurate computations of PBG behavior without relying on massively parallel processing. We also construct and measure the bulk reflection and transmission …

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Exploring The Management Of Outsourcing And The Determination Of Civil Engineering Minimum Manning Numbers In Order To Optimize Air Force Benefits, David J. Anason Mar 1999

Exploring The Management Of Outsourcing And The Determination Of Civil Engineering Minimum Manning Numbers In Order To Optimize Air Force Benefits, David J. Anason

Theses and Dissertations

This thesis investigates the relationship between peacetime and wartime tasks for Air Force Civil Engineering career fields in regard to outsourcing. Relevant literature in civilian sector outsourcing techniques is then studied to determine how they decide on what to outsource and what to keep insourced. Peacetime tasks performed by individual career fields are correlated with the wartime tasks to determine if there is any valuable wartime training gained from the completion of peacetime work orders. Several interviews completed with Air Force Civil Engineer readiness experts to evaluate an importance factor for each career field wartime mission. This importance factor and …

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Application Of The Finite Element Method To The Scattering Of A Two-Dimensional, Semi-Infinite Periodic Structure, Perry N. Villanueva Mar 1999

Application Of The Finite Element Method To The Scattering Of A Two-Dimensional, Semi-Infinite Periodic Structure, Perry N. Villanueva

Theses and Dissertations

Infinite periodic structures have been studied heavily because of their efficient filtering capabilities. They generally exhibit sharp frequency roll-offs at the frequency band of interest. In the RF region of the electromagnetic spectrum, periodic structures find applications such as radomes and photonic bandgap materials. Most studies have been done with infinitely periodic arrays because it is convenient to collapse an infinite array into one representative period using Floquet Analysis. Truncating an infinite array introduces an edge and invalidates Floquet analysis over the entire array. This thesis formulates a Finite Element Method (FEM) solution of a semi-infinite periodic array consisting of …

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Te Scattering From Bubbles In Ram, John G. Cochran Mar 1999

Te Scattering From Bubbles In Ram, John G. Cochran

Theses and Dissertations

This research looks at various bubble sizes in one particular magnetic RAM (MAURAM) type, from grazing incidence (00) to 450 and at a frequency range from 2-18 GHz, TE polarization. The results from the absolute RCS measurement of the various sized RAM bubbles are discussed in terms of a frequency dependent increase in RCS. In the frequency band of interest, 2-18GHz, a RAM bubble increases the RCS at all angles, from grazing incidence (00) to 450. From 10-18GHz the RAM bubble does not cause an increase in RCS. In general the highest RCS is at 2GHz and tapers down as …

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Substrate Availability In Solid Waste Landfills, Brian D. Benter Mar 1999

Substrate Availability In Solid Waste Landfills, Brian D. Benter

Theses and Dissertations

Numerous models exist to both predict and represent the many biological activities that occur in the modern landfill. These different models use varying methods of characterizing what is happening, what is thought to happen, or what should be happening based on both empirical data and theoretical reasoning. The model presented here is an extension of the system dynamics model originally presented by Colborn in 1997. The revamped model presents a different perspective on what happens as solid organic waste is transformed to simpler substances. This new view involves a bacterial population performing hydrolysis whose growth is limited by the amount …

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An Integrated Synthetic Aperture Radar/Global Positioning System/Inertial Navigation System For Target Geolocation Improvement, Brian J. Young Mar 1999

An Integrated Synthetic Aperture Radar/Global Positioning System/Inertial Navigation System For Target Geolocation Improvement, Brian J. Young

Theses and Dissertations

This thesis explores a potential integration technique to fuse information from an inertial navigation system (INS) and global positioning system (GPS) with synthetic aperture radar target measurements. Using Kalman filtering techniques, an INSIGPS/SAR integrated system was simulated in a single Kalman filter to analyze the SAR target geolocation accuracy benefits. Three different GPS receiver models were used in the integrated system: stand-alone (SGPS), differential (DGPS), and carrier-phase differential GPS (CPGPS). Each of these GPS models were integrated with a common INSISAR combination to determine the target geolocation accuarcy improvements due only to GPS receiver type. Thesis results show that SAR …

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The Determinants Of Locational Choice For Air Force Military Renters: Implications For Policy, Eldrick L. Hill Mar 1999

The Determinants Of Locational Choice For Air Force Military Renters: Implications For Policy, Eldrick L. Hill

Theses and Dissertations

Housing allowances and military family housing make up approximately $7 billion dollars of the budget for the Department of Defense (DoD). The military uses a Housing Market Analysis (HMA) to determine rental housing availability around its installations. This thesis describes and analyzes the locational choices of military renters. This thesis examines 16 bases in the continental U.S. using military and census data. It is concluded that the locational preferences of military renters vary inversely with distance from their duty location and this needs to be accounted for when assessing the availability of military rental housing. The implications of military renter …

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Optimal Wavelet Denoising For High Range Resolution Radar Classification, Brian M. Huether Mar 1999

Optimal Wavelet Denoising For High Range Resolution Radar Classification, Brian M. Huether

Theses and Dissertations

Noncooperative identification (NCTI) of airborne targets is a top priority for the Air Force and this thesis makes a significant contribution to that area. High range resolution radar (HRR) provides an attractive means to perform NCTI. When measured HRR data is used, classification performance is excellent. However, it is often not feasible to acquire measured HRR signatures for a wide set of targets, thus necessitating the use of synthetically generated HRR data. Classification performance suffers severe degradation when using synthetic data. This thesis suggests that a large portion of HRR signature content is non-discriminatory and that this content is a …

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Development Of Site Characterization Simulator, Neil W. Kassel Mar 1999

Development Of Site Characterization Simulator, Neil W. Kassel

Theses and Dissertations

The purpose of this study was to develop a tool for Remedial Project Managers (RPMs) to learn and practice the site characterization process. One of the key difficulties encountered by RPMs during site characterization is the need to develop a model of the site based on limited data. These limited data are used to determine parameters that describe hydrogeologic and contaminant properties (aquifer hydraulic conductivity, contaminant concentration, etc.) and are obtained using sampling techniques that interrogate a very small volume, usually much smaller than node spacing of the computer model used to simulate site conditions. The value of the parameter …

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Optimal Pulsed Pumping Schedule Using Calculus Of Variation Methodology, Tay W. Johannes Mar 1999

Optimal Pulsed Pumping Schedule Using Calculus Of Variation Methodology, Tay W. Johannes

Theses and Dissertations

Application of a variational optimization technique has demonstrated the potential strength of pulsed pumping operations for use at existing pump-and-treat aquifer remediation sites. The optimized pulsed pumping technique has exhibited notable improvements in operational effectiveness over continuous pumping. The optimized pulsed pumping technique has also exhibited an advantage over uniform time intervals for pumping and resting cycles. The most important finding supports the potential for managing and improving pumping operations in the absence of complete knowledge of plume characteristics. An objective functional was selected to minimize mass of water removed and minimize the non-essential mass of contaminant removed. General forms …

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Individual Housing Choices Among Air Force Members, Michael J. Johnson Mar 1999

Individual Housing Choices Among Air Force Members, Michael J. Johnson

Theses and Dissertations

Air Force members have three different housing choices: live in MFH, rent in the local community, or buy a house in the local community. A set of six constructs (Housing Attributes, Safety, Pet Importance, Location, Military Housing Perception, and Community) that encompass members' considerations is developed and analyzed. The data was extracted from a survey that was specifically designed to illicit the relative importance of each construct during the housing decision making process. Each construct was measured using a Likert scale score. Statistical analysis was performed to determine the overall Likert mean score for each construct. Using the Likert mean …

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Natural Attenuation Of Chlorinated Ethenes By Anaerobic Reductive Dechlorination Coupled With Aerobic Cometabolism, Derek D. Veerkamp Mar 1999

Natural Attenuation Of Chlorinated Ethenes By Anaerobic Reductive Dechlorination Coupled With Aerobic Cometabolism, Derek D. Veerkamp

Theses and Dissertations

Chlorinated solvents and their daughter products are the most common contaminants of groundwater at industrial and military facilities in the United States. Limitations of conventional technologies have intensified efforts to find alternative methods to remediate contaminated sites to regulatory goals set by CERCLA. Natural attenuation of chlorinated solvents is a promising alternative to traditional pump and treat methods but has not been well understood or widely accepted. This modeling study investigated the ability of TCE to completely degrade under various aquifer conditions and rate order constants. It also examined a case study of a former landfill site at Moody AFB. …

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Textual Analysis Of Environmental Compliance Assessment Program Findings, Arthur L. Gepner Jr. Mar 1999

Textual Analysis Of Environmental Compliance Assessment Program Findings, Arthur L. Gepner Jr.

Theses and Dissertations

The United States Air Force (USAF) is committed to assessing environmental compliance; this is achieved in the USAF through the Environmental Compliance Assessment Management Program (ECAMP). These ECAMP audits are designed strictly to assess compliance performance at one point-in-time. They are not intended to assess underlying environmental management systems. This study provides insight into the USAF Environmental Management System (EMS) through a textual analysis of ECAMP data. The analysis discovers eleven categories that emerged from the data: performance, communication, documentation, coordination, training, guidance, notification, resource, human resource, material resource, and financial resource. These categories display a hierarchical relationship. This hierarchical …

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Environmental Management Strategies In Public Sector Organizations, Charles P. Roberts Mar 1999

Environmental Management Strategies In Public Sector Organizations, Charles P. Roberts

Theses and Dissertations

Environmental management research investigates environmental and ecological practices in organizations. Environmental strategy models or typologies are developed to classify organizations according to their environmental and ecological practices. Past research for environmental management strategy has focused on the profit sector versus the public sector. Drivers such as market and financial forces may not be as evident in the public sector as they are in the profit sector. This research explored environmental management strategies in public sector organizations. An environmental management strategy typology was developed to investigate the structural aspects of organizations. The typology and respective instruments were used in a case …

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Decision Analysis Methodology To Evaluate Organization, Shawn C. Thompson Mar 1999

Decision Analysis Methodology To Evaluate Organization, Shawn C. Thompson

Theses and Dissertations

The organizational structure of the civil engineer squadron's operations flight has undergone numerous changes over the last fifty years. Today the structure of the flight to the element level is mandated by Air Force Instructions; however, each unit is given the flexibility to organize below the element level. Most civil engineer units are struggling through the decision of how to organize their flights without a sound methodology to guide their efforts. Providing such a methodology is the objective of this thesis. To accomplish the objective, the history behind the operations flight structure was researched. In addition to this historical research, …

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The Quota Allocation Model: The Linear Optimization Of A Markov Decision Process, David A. Brown Mar 1999

The Quota Allocation Model: The Linear Optimization Of A Markov Decision Process, David A. Brown

Theses and Dissertations

One of the many needs of the Air Force is advanced technical degrees. These degrees can be acquired in three ways: the Air Force can directly recruit personnel with the required degrees; Air Force personnel can obtain them during off duty time from local civilian colleges near their base; or the Air Force can provide advanced academic degrees (AADs) through the Air Force Institute of Technology (AFIT) or AFIT-sponsored programs. In 1995, the AFIT Commandant initiated a re-engineering study to review the AFIT mission. One of the initiatives of that study was the Quota Allocation Model (QuAM). The QuAM model …

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Biodegradation Of Aircraft Deicing Fluid Components In Soil, Baron W. Burke Mar 1999

Biodegradation Of Aircraft Deicing Fluid Components In Soil, Baron W. Burke

Theses and Dissertations

Aircraft de-icing fluids (ADFs) are used worldwide to ensure safe aircraft operations. This research effort was conducted to analyze the biodegradation effects of two chemical components of ADFs, propylene glycol (PG) and tolyltriazole (TTA), in a high-clay soil. The research used four test methods; automated respirometry, high performance liquid chromatography (HPLC), microbial colony population counts (MCPC), and agar well diffusion tests (AWDT). The research was partitioned into two phases of investigation. Phase-one analyzed individual and combined ADF chemical components on uncontaminated soil. The presence of TTA, from 25 - 1,000 mg/kg, reduced the maximum respiration rate of 1,000 mg/kg PG …

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Implementation Of The Metaheuristic Tabu Search In Route Selection For Mobility Analysis Support System, David M. Ryer Mar 1999

Implementation Of The Metaheuristic Tabu Search In Route Selection For Mobility Analysis Support System, David M. Ryer

Theses and Dissertations

This thesis employs a reactive tabu search heuristic implemented in the Java programming language to solve a real world variation of the vehicle routing problem with the objective of providing quality routes to Mobility Analysis Support System (MASS). MASS is a stochastic simulation model used extensively by Air Mobility Command (AMC) to analyze strategic airlift capabilities and future procurement decisions. This dynamic real world problem of strategic and tactical airlift possesses a number of side constraints such as vehicle capacities, route length and time windows in a sizeable network with multiple depots and a large fleet of heterogeneous vehicles. Finding …

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An Evaluation And Comparison Of The Ace And Brace Airfield Models, David W. Wiliams Mar 1999

An Evaluation And Comparison Of The Ace And Brace Airfield Models, David W. Wiliams

Theses and Dissertations

Airfields are a critical aspect of our military's ability to project power or respond to crises throughout the world. It is crucial that mobility planners have an effective means to estimate the capacity of these airfields. The objective of this research is to examine common mobility metrics and evaluate existing means of measuring them. Currently, Air Mobility Command has two models, the Airfield Capacity Estimator (ACE) and the Base Resource and Capabilities Estimator (BRACE), that were designed to estimate the resource requirements and capacities of an airfield. This study offers a critical evaluation and comparison of the two models. Discrepancies …

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Modeling And Analysis Of Aerial Port Operations, Timothy W. Albrecht Mar 1999

Modeling And Analysis Of Aerial Port Operations, Timothy W. Albrecht

Theses and Dissertations

The focus of this thesis effort is gaining useful insight into aerial port operations by employing an animated simulation. Understanding airfield capacity, resources, and functioning allows greater accuracy and efficiency in both planning for future force structures and matching mobility assets with commanders' objectives. Two current simulations, ACE (Airfield Capacity Estimator) and BRACE (Base Resource Allocation and Capabilities Estimator), model mobility activities at the base level with some deficiencies. The model proposed by this thesis, APOM (Aerial Port Operations Model), will provide the mobility analyst an animated simulation with two, new measures of aerial port operations; a real-time estimate of …

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