Engineering Commons^™

Symbolically Aided Model Development For An Induction Machine In Virtual Test Bed, Wenzhong Gao, Eugene V. Slovodnik, Roger A. Dougal

Faculty Publications

A new phase-domain induction machine model for use in power system dynamic simulation is developed with the aid of a symbolic tool. The symbolic tool can automatically construct a time-domain power system component model in the resistive companion form (RCF) that is widely used in time-domain simulators. The automatic differentiation technique (aDT) is utilized within the context of a symbolic modeling language, and the tool has been implemented for the virtual test bed (VTB) simulation environment. The new induction machine model was used to study start-up transients of an induction motor. The new model was verified by comparing the simulation …

Making Learning Visible: Peer Review And The Scholarship Of Teaching, Paul Savory

Department of Industrial and Management Systems Engineering: Presentations

This is the conference program from the March 2004 national conference, Making Learning Visible: Peer Review and the Scholarship of Teaching. This conference was hosted by the UNL Peer Review of Teaching project and the University of Nebraska-Lincoln.

Making Learning Visible: Peer Review And The Scholarship Of Teaching, Paul Savory

Department of Industrial and Management Systems Engineering: Presentations

This is the promotional brochure from the March 2004 national conference, Making Learning Visible: Peer Review and the Scholarship of Teaching. This conference was hosted by the UNL Peer Review of Teaching project and the University of Nebraska-Lincoln.

Nanotube Magnetism, Yucheng Sui, Ralph Skomski, Kory D. Sorge, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

FePt and Fe3O4 nanotubes are produced by hydrogen reduction in nanochannels of porous alumina templates and investigated by electron microscopy, x-ray diffraction analysis, and magnetic measurements. Loading the templates with a Fe chloride and Pt chloride mixture followed by hydrogen reduction at 560 °C leads to the formation of ferromagnetic FePt nanotubes in the alumina pores. Using a Fe nitrate solution, thermally decomposed at 250 °C and reduced in hydrogen for 2.5 h at the same temperature, yields Fe3O4 tubes. The length of the nanotubes is about 50 mm and their diameters range from about 150 to 220 nm, depending …

Humidity Effects On The Determination Of Elastic Properties By Atomic Force Acoustic Microscopy, D.C. Hurley, Joseph A. Turner

Nebraska Center for Materials and Nanoscience: Faculty Publications

We have investigated how ambient humidity can affect quantitative measurements of elastic properties on the nanoscale. Using an emerging technique called atomic force acoustic microscopy (AFAM), two samples were examined: a thin film of fluorosilicate glass and a section of borosilicate glass. When experimental results were analyzed using a simple model of the atomic force microscope cantilever dynamics, values of the tip–sample contact stiffness k* increased approximately linearly with relative humidity. The effect is believed to be due to the presence of a humidity-dependent layer of water on the sample. To account for this, the data analysis model was …

Isomer Energy Source For Space Propulsion Systems, Benjamin L. Johnson

Theses and Dissertations

Presented in this work are the results of an investigation of alternative means for powering spacecraft and launch vehicles with energy sources other than chemical combustion. Nuclear thermal propulsion and the energy release of a nuclear spin isomer present potential for increased rocket performance with compact, high-energy fuel sources replacing the combustion engines of the Delta IV-H 1st and 2nd stage vehicles. Analysis of historical fission designs along with the isomer hafnium-178-m2 in a particle bed configuration was conducted. Energy storage levels of 1.3 GJ/g are possible with this material, though the successful triggering and maintenance of a chain reaction …

Design Of A Space Borne Autonomous Infrared Tracking System, Matthew B. Kimsal

Theses and Dissertations

Complete characterization of the space environment in support of the United States goal of space Situational Awareness is not currently achievable. When confronted with recent increases in the deployment and miniaturization of microsatellites by numerous nations, the questions of foreign space capabilities are magnified. This study sought to determine the feasibility of and experimentally demonstrate a microsatellite capability to autonomously loiter about and track a target satellite. Various methods of passive remote sensing were investigated to determine the best means of detecting and tracking a target in space. Microbolometer-based infrared sensors were identified as the best alternative. A representative system …

Modeling And Analysis Of Post-Conflict Reconstruction, Damon B. Richardson

Theses and Dissertations

The forces at play in reconstruction operations are a complex system of time phased interlocking cause and effect relationships that are not thoroughly understood. A model capable of capturing the general dynamics involved in post-conflict reconstruction would provide insight to decision makers regarding potential policy alternatives. This research effort demonstrates the viability of using systems dynamics modeling techniques to simulate the establishment of public order and safety in a post-conflict reconstruction operation (Phase IV operations). A high level generic framework is developed that can be used as a general template for modeling post-conflict reconstruction. It is then demonstrated with a …

Cross Range Smear Characterization In Xpatch Isar Images, Peter E. Muend

Theses and Dissertations

This thesis investigates a cross range smear phenomenon seen in far field, frequency domain Xpatch calculations. The phenomenon is very subtle, manifesting itself in 2-D ISAR images as a low-level scatterer response smeared in the cross range direction. This cross range smear occurs only using complex target models with certain characteristics. It is also a mathematical construct, not occurring in physical SAR systems. Using a carefully constructed scattering target set, Xpatch-generated ISAR images are used to characterize cross range smear in terms of its input parameters. The characterization is done as a DOE-based polynomial approximation to the observed smear levels. …

Evaluation Of Current Automated Civil Engineer System Non-Appropriated Funds Project Programming Procedures, Joshua C. Ligday

Theses and Dissertations

It is essential that businesses continually improve their automated information systems (AIS) to support the changing needs of the organization. The Air Force civil engineering organization is no exception since they have drastically improved their Automated Civil Engineer System (ACES) through end user support since its implementation in 2000. However, there are many problems associated with the non-appropriated funds (NAF) project programming business rules within ACES. These problem areas were not addressed until recently when an integrated process team met and proposed numerous changes to how NAF programming is accomplished in ACES. This research effort, through a web-based survey, focuses …

An Electromagnetic Tool For Damping And Fatigue Analysis, Todd M. Hoover

Theses and Dissertations

An automated test system was developed by the USAF Turbine Engine Fatigue Facility (TEFF). This system was initially designed to reduce the time and manpower required to characterize damping treatments. It is based on a digitally controlled environmental chamber with automated data acquisition and processing. Several outputs are available including identification of natural frequencies, modal damping ratios from the acquired frequency responses, and changes in damping with response amplitude; however, the TEFF additionally desires the capability to study fatigue under a free boundary condition. The system consists of a test specimen suspended by a pendulum to closely simulate free boundary …

Afci Quarterly Input – Unlv January Through March, 2004, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division

Transmutation Research Program Reports (TRP)

Quarterly report highlighting research projects and objectives of the Transmutation Research Program at the Nuclear Science & Technology Division, Harry Reid Research Center.

The University of Nevada, Las Vegas supports the AFCI through research and development of technologies for economic and environmentally sound refinement of spent nuclear fuel. The UNLV program has four components: infrastructure, international collaboration, student-based research, and management and program support.

Inside Unlv, Gian Galassi, Carol C. Harter, Kenneth E. Marks

Inside UNLV

No abstract provided.

Stress Corrosion Cracking Studies, K. S. Raja, S. Namjoshi, Amy J. Smiecinski

Publications (YM)

This document reports on the activities for Task 17 of the U.S. DOE/UCCSN Cooperative Agreement Number DE-FC28-98NV12081. There are three subtasks in this Task, the experimental results, discussions, and conclusions of which are presented in the following sections. Data Sources and Electronic Data Control The Data Identification numbers for the data, graphs, and tables in this report, as submitted to the Data Management Database, are tabulated below. The table also includes the source files for the said data as well as the corresponding scientific notebooks where the data can be found. All data in the Q section of the report …

Optimal Design Of Generalized Multiple Model Adaptive Controllers, Thomas E. Brehm

Theses and Dissertations

Advanced analysis and optimal design techniques that achieve performance improvement for multiple model adaptive control (MMAC) and multiple model adaptive estimation (MMAE) based control are developed and tested for this dissertation research. An adjunct area of research yielded modified linear quadratic Gaussian (LQG) control design techniques that also can be applied to nonadaptive control. For the Modified LQG (MLQG) controller, the proposed designs remove the assumption that the Kalman filter as the observer and the controller gain matrix design are necessarily based on the same model as the best system model. The filter and controller gain matrices are both determined …

A Rapidly-Converging Alternative To Source Iteration For Solving The Discrete Ordinates Radiation Transport Equations In Slab Geometry, Nicholas J. Wager

Theses and Dissertations

I present a numerical technique to solve the time independent Boltzmann Transport Equation for the transport of neutrons and photons. The technique efficiently solves the discrete ordinates equations with a new iteration scheme. I call this new scheme the angle space distribution iteration method because it combines a non-linear, high angular-resolution flux approximation within individual spatial cells with a coarse angular-resolution flux approximation that couples all cells in a spatial mesh. This shown to be an efficient alternative to source iteration. The new method is implemented using the step characteristic and exponential characteristic spatial quadrature schemes. The latter was introduced …

Effect Of Equivalence Ratio And G-Loading On In-Situ Measurements Of Chemiluminescence In An Ultra Compact Combustor, Jason M. Armstrong

Theses and Dissertations

Using a spectrometer and high temperature fiber optics the relative intensities of the near-infrared, visible, and ultraviolet radiation emitted from the C2*, CH*, and OH* radicals were measured at eight discrete locations within the Ultra Compact Combustor test rig. Blackbody radiation in the near infrared also was observed. The tests were conducted at various g-loadings and overall equivalence ratios and with various air hole configurations. These measurements were compared to determine the effect of these changes on the radiation emitted. Local C2* intensities were used to estimate the flame location within the combustor and the local CH*/OH* ratio was used …

Maneuver Design For Fast Satellite Circumnavigation, Stanley D. Straight

Theses and Dissertations

The feasibility of satellite operations in close proximity to a reference satellite is of interest for both civilian and military applications. One such operation is circular circumnavigation in a time period less than the orbital period of the reference satellite. This thesis investigates a guidance scheme for such maneuvers involving impulsive burns at specific points within a specified toroidal region centered on the circular-orbiting reference satellite. Two analytical methods for determining the magnitude and direction of the impulses are demonstrated. These methods are then used as initial estimates in an optimization scheme to produce the minimum total required impulse.

Effect Of A Variable Contact Load On Fretting Fatigue Behavior Of Ti-6al-4v, Andrew J. Jutte

Theses and Dissertations

Effects of a variable contact load on the high cycle fretting fatigue behavior of Ti-6AL-4V were investigated. Experimental tests were performed using a new test setup capable of applying a contact load varying in amplitude, frequency, and phase and independently measuring shear forces on opposite sides of a specimen. Finite element analysis (FEA) of experimental and idealized loading conditions was performed and local mechanistic parameters and the Modified Shear Stress Range (MSSR) fatigue parameter were determined. Correlations between contact width, slip amplitude, fatigue life and a variable contact load were established with variable contact loading shown to have a damaging …

Investigation Of Atmospheric Reentry For The Space Maneuver Vehicle, Dennis J. Mcnabb

Theses and Dissertations

This study investigated the atmospheric reentry of the Space Maneuver Vehicle from low-earth orbit using an entry guidance concept similar to the Space Shuttle. The Space Maneuver Vehicle was modeled as a point mass with aerodynamic properties as determined using Newtonian impact theory. For the rarefied-flow transition regime bridging formulae are used to capture the effects of both hypersonic continuum flow and free molecular flow. Constraints to the reentry are developed and a reentry corridor is defined in the drag-velocity plane. Bank angle modulation is established as the primary means for controlling drag and range. The guidance concept is applied …

Geometric Approach To Orbital Formation Mission Design, Matthew J. Press

Theses and Dissertations

For distributed remote sensing architectures to be useful for collecting data, it is essential to have a methodology for relating orbital formation parameters to remote sensing requirements. Utilizing the characteristics of formation parameters, an orbital design approach is developed that establishes a satellite formation from a desired instantaneous spatial distribution as viewed from a target ground site. To maintain a conceptually basic representation, a geometric approach is used to develop the correlating algorithm. This tool will enable mission planning for orbital formations as well as future concept exploration.

The Evaluation Of The Damping Characteristics Of A Hard Coating On Titanium, Christopher M. Blackwell

Theses and Dissertations

Engine failures due to fatigue have cost the Air Force an estimated $400 million dollars per year over the past two decades (Garrison, 2001). Damping treatments capable of reducing the internal stresses of fan and turbine blades to levels where fatigue is less likely to occur have the potential for reducing cost while enhancing reliability. This research evaluates the damping characteristics of magnesium aluminate spinel, MgO+Al₂O₃, (mag spinel) on titanium plates. The material and aspect ratio were chosen to approximate the low aspect ratio blades found in military gas turbine fans. The plates were tested with …

Creating Cost Growth Models For The Engineering And Manufacturing Development Phase Of Acquisition Using Logistic And Multiple Regression, Brandon M. Lucas

Theses and Dissertations

Cost growth remains a concern for cost analysts, program managers, senior DoD decision-makers, Congress, and even the American public. All of these people have a vested interest in the cost of DoD programs and most would like to see those costs decrease; as such, we need additional tools to help combat cost growth. Previous research creates the foundation for the use of a two-step methodology to help predict cost growth, which we follow closely. First, utilizing logistic regression we analyze whether specific program characteristics predict cost growth within the Engineering and Manufacturing Development (EMD) phase for combined RDT&E and procurement …

Estimating Cost Growth In Engineering And Schedule Cost Categories Using A Two-Pronged Regression Approach, Chris J. Mcdaniel

Theses and Dissertations

This research confirms the usefulness of the logistic and multiple regression two-step procedure for assessing cost growth in major DoD weapon systems. We compile programmatic data from the Selected Acquisition Reports (SARs) between 1990 and 2002 for programs covering all defense departments. Our analysis concentrates on cost growth in the procurement appropriations of the Engineering and Manufacturing Development phase of acquisitions. We investigate the use of logistic regression in cost growth analysis to predict whether or not cost growth will occur in a program. If applicable, multiple regression is implemented to predict how much cost growth will occur. Our study …

Analysis And Forecasting Of Army Operating And Support Cost For Rotary Aircraft, John C. Hawkins

Theses and Dissertations

This research explores forecasting techniques to estimate the Cost per Flying Hour (CPFH) for Army Helicopters. Specifically, three separate forecasting techniques were evaluated to better predict the CPFH for better estimating and budgeting by the U.S. Army. For forecasting purposes, actual CPFH figures were compiled from 1995 to 2003 for all MACOMs flying the AH-64A, the CH-47D, and the UH-60A helicopters. The number of MACOMs was then reduced to the top three with regard to total CPFH expenditure. The use of a 3-year moving average, the single exponential smoothing method, and Holt's linear method were explored for each helicopter's data. …

Analysis And Forecasting Of Air Force Operating And Support Cost For Rotary Aircraft, Matthew E. Laubacher

Theses and Dissertations

This research explores forecasting techniques to estimate the Cost per Flying Hour (CPFH) for Air Force Helicopters. Specifically, this research evaluates three separate forecasting techniques to predict the CPFH for better estimating and budgeting by the U.S. Air Force. It starts by empirically analyzing the Operating and Support cost by CAIG categories for each helicopter. For forecasting purposes, the actual CPFH figures were compiled from FY96 to FY03 for a total of eight MAJCOMs flying the MH-53J/M, the HH-60G, or the UH-1N helicopters. The research explores the use of a 3-year moving average, the single exponential smoothing method, and Holt's …

Reusable Space Vehicle Ground Operations Baseline Conceptual Model, Dennis R. Maynard, Patricia Pettit

Theses and Dissertations

Modeling efforts for future space operation vehicles at the United States Air Force Research Labs Air Vehicles Directorate have been focused towards the in-flight mission. To better serve the research and development effort, a simulation of the ground operations is required allowing for trade-offs within turnaround operations and between the components that drive those procedures. However, before a simulation can be developed a conceptual model must be generated to guide the model building process. This research provides a baseline conceptual model for reusable space vehicles based on the space shuttle as the only operational vehicle of its kind. The model …

Effects Of Duty Schedule Variance And Overtime On The Job Satisfaction And Turnover Intentions Of Usaf F-16 Crew Chiefs, Michael J. Shellhamer

Theses and Dissertations

This thesis empirically assessed how duty schedule variance and overtime affect the job satisfaction and turnover intentions of USAF F-16 crew chiefs. A survey was completed by 346 active duty USAF F-16 crew chiefs regarding their perceptions of duty schedule variance, overtime, job satisfaction and intent to leave the Air Force. Theory suggests that turnover behavior is a multistage process that involves organizational, individual, and attitudinal components. Using multivariate correlation and regression analyses, plausible evidence was found to support the idea that duty schedule variance and overtime plays a role in USAF F-16 crew chief turnover intentions via job satisfaction. …

Age Replacement And Service Rate Control Of Stochastically Degrading Queues, Patrick S. Chapin

Theses and Dissertations

This thesis considers the problem of optimally selecting a periodic replacement time for a multiserver queueing system in which each server is subject to degradation as a function of the mean service rate and a stochastic and dynamic environment. Also considered is the problem of optimal service rate selection for such a system. In both cases, the performance metric is the long-run average cost rate. Analytical expressions are obtained, in terms of Laplace transforms, for the nonlinear objective functions, necessitating the use of numerical Laplace transform inversion to evaluate candidate solutions in conjunction with standard numerical algorithms. Due to the …

Effects Of Uncertainty On Real World Aerospace Mission Data, Steven J. Barosko

Theses and Dissertations

Uncertainty is an age old element of warfare. How does one measure success or failure on the battlefield? This thesis explores the effect of uncertainty on real world aerospace mission data from Operation Iraqi Freedom (OIF). Sources of uncertainty are identified during data preparation and the effects of uncertainty are investigated using multivariate analysis techniques. Two distinct cases are analyzed: one case with a low level of uncertainty in predicting whether or not a mission is pre-planned or alert generated, and another case with a high level of uncertainty in predicting whether or not a mission is a success or …