Engineering Commons^™

Implementation Of Gy-Eq For Deterministic Effects Limitation In Shield Design, John W. Wilson, Myung-Hee Y. Kim, Giovanni De Angelis, Francis A. Cucinotta, Nobuaki Yoshizawa, Francis F. Badavi

Mathematics & Statistics Faculty Publications

The NCRP has recently defined RBE values and a new quantity (Gy-Eq) for use in estimation of deterministic effects in space shielding and operations. The NCRP's RBE for neutrons is left ambiguous and not fully defined. In the present report we will suggest a complete definition of neutron RBE consistent with the NCRP recommendations and evaluate attenuation properties of deterministic effects (Gy-Eq) in comparison with other dosimetric quantities.

Lunar Lava Tube Radiation Safety Analysis, Giovanni De Angelis, J. W. Wilson, M. S. Clowdsley, J. E. Nealy, D. H. Humes, J. M. Clem

Mathematics & Statistics Faculty Publications

For many years it has been suggested that lava tubes on the Moon could provide an ideal location for a manned lunar base, by providing shelter from various natural hazards, such as cosmic radiation, meteorites, micrometeoroids, and impact crater ejecta, and also providing a natural environmental control, with a nearly constant temperature, unlike that of the lunar surface showing extreme variation in its diurnal cycle. An analysis of radiation safety issues on lunar lava tubes has been performed by considering radiation from galactic cosmic rays (GCR) and Solar Particle Events (SPE) interacting with the lunar surface, modeled as a regolith …

Nato Code Of Best Practice For C2 Assessment, Dave Alberts, Tim Bailey, Paul Choinard, Andreas Tolk, Gary Wheatley, John Wilder

Computational Modeling & Simulation Engineering Books

This major revision to the Code of Best Practice (COBP) for C² Assessment is the product of a NATO Research and Technology Organisation (RTO) sponsored Research Group (SAS-026). It represents over a decade of work by many of the best analysts from the NATO countries. A symposium (SAS-039) was hosted by the NATO Consultation Command Control Agency (NC3A) that provided the venue for a rigorous peer review of the code. This new version of the COBP for C² assessment builds upon the initial version of the COBP produced by SAS-002. The earlier version focused on the analysis of …

Study Of Non-Equilibrium Electron Dynamics In Metals, Wael Mohamed Gomaa Ibrahim

Electrical & Computer Engineering Theses & Dissertations

Thermal phenomena, such as heat propagation, lattice melting, and ablation, are the result of energy deposition in metals. A fundamental understanding of the electron dynamics leading to these thermal phenomena would benefit many laser applications, such as laser deposition of thin films and laser processing.

In this work, thin metal films were prepared using the resistive heating evaporation technique. High dynamic range autocorrelators were constructed to characterize the different laser systems used in this study. The nonequilibrium electron dynamics in single layer gold films, multi-layer gold-vanadium, and gold-titanium films were studied. The time evolution of the electron temperature was monitored …

Investigation Of Port Fuel Injector Spray Mass Distribution By Laser Induced Fluorescence, Tuba Bayraktar

Mechanical & Aerospace Engineering Theses & Dissertations

Modern internal combustion engines have stringent requirements for performance and reduced toxic emissions. The fuel delivery system, and particularly the fuel injectors, have a vital role in reducing unburned hydrocarbons (HC) and carbon monoxide (CO) in exhaust emission.

The main goal of this study is to map the spatial and temporal distribution of the spray from a low-pressure gasoline fuel injector. To attain this goal, three tasks were performed: (1) the experimental investigation of the spray oscillation as functions of operating pressure and injector timing, (2) the determination of the appropriate dye/fuel combinations for one particular experimental technique, and (3) …

Aligning Hierarchical Goals In An Organization: The Path From Training To Performance, Jeanette Denise Selby-Lucas

Engineering Management & Systems Engineering Theses & Dissertations

Training is a multi-billion-dollar industry, and with the advent of the training technology revolution and the possibilities it provides to business and government, as well as to the academic community, it is important to determine if the money invested in training by these communities is providing the expected performance on the part of those who are trained. This can be done by quantitatively evaluating the relationship between training and performance.

This study extends the scholarly literature by developing the concept of organizational alignment through a combination of Human Performance Technology literature and traditional engineering methodologies. Organizational training and performance is …

Excimer Emission From Pulsed Microhollow Cathode Discharges, Mohamed Moselhy

Electrical & Computer Engineering Theses & Dissertations

Microhollow cathode discharges (MHCDs) are direct current, high-pressure, non-equilibrium gas discharges. Direct current MHCDs in xenon and argon have shown to emit excimer radiation at 172 and 127 nm, respectively. Internal efficiency of excimer emission in DC MHCD was measured to be 6–9% in xenon, and 1–6%, depending on the gas flow rate in argon. This high efficiency is due to the high rate of rare gas excitation by electrons accelerated in the cathode fall and to subsequent three-body collisions in the high-pressure gas. The excimer power scales linearly with current; however, due to the increasing size of the source …

A Conceptual Design Tool For Engineers: An Amalgamation Of Theory Of Constraints, Theory Of Inventive Problem Solving And Logic, Stephen R. Luke

Mechanical & Aerospace Engineering Theses & Dissertations

This research creates a design methodology by synthesizing three different design tools, the Theory of Inventive Problem Solving (TRIZ), the Theory of Constraints (TOC) and Logic. The basic approach of this design method is to: (1) Reduce a design problem to a logic diagram, (2) Code the inputs and outputs to determine desirability and degree of control, (3) Identify the best inputs to manipulate in order to obtain the desired outputs and (4) Exploit innovative algorithms developed in TRIZ to find the best ways to manipulate the chosen inputs.

This research integrates and expands the methods of TRIZ and TOC. …

Development Of An Efficient Ti:Sapphire Laser Transmitter For Atmospheric Ozone Lidar Measurements, Khaled A. Elsayed

Electrical & Computer Engineering Theses & Dissertations

The impetus of this work was to develop an all solid-state Ti:sapphire laser transmitter to replace the current dye lasers that could provide a potentially compact, robust, and highly reliable laser transmitter for differential absorption lidar measurements of atmospheric ozone. Two compact, high-energy pulsed, and injection-seeded Ti:sapphire lasers operating at a pulse repetition frequency of 30 Hz and wavelengths of 867 nm and 900 nm, with M² of 1.3, have been experimentally demonstrated and compared to model results. The Ti:sapphire lasers have shown the required output beam quality at maximum output pulse energy, 115 mJ at 867 nm and …

Cuin1-Xalxse2 Thin Films And Solar Cells, P. D. Paulson, M. W. Haimbodi, S. Marsillac, R. W. Birkmire, W. N. Shafarman

Electrical & Computer Engineering Faculty Publications

CuIn[sub 1-x]Al[sub x]Se[sub 2] thin films are investigated for their application as the absorber layer material for high efficiency solar cells. Single-phase CuIn[sub 1-x]Al[sub x]Se[sub 2] films were deposited by four source elemental evaporation with a composition range of 0≤x≤0.6. All these films demonstrate a normalized subband gap transmission >85% with 2 µm film thickness. Band gaps obtained from spectroscopic ellipsometry show an increase with the Al content in the CuIn[sub 1-x]Al[sub x]Se[sub 2] film with a bowing parameter of 0.62. The structural properties investigated using x-ray diffraction measurements show a decrease in lattice spacing as the Al content increases. …

Robust Face Representation And Recognition Under Low Resolution And Difficult Lighting Conditions, Mohammad Moinul Islam

Electrical & Computer Engineering Theses & Dissertations

This dissertation focuses on different aspects of face image analysis for accurate face recognition under low resolution and poor lighting conditions. A novel resolution enhancement technique is proposed for enhancing a low resolution face image into a high resolution image for better visualization and improved feature extraction, especially in a video surveillance environment. This method performs kernel regression and component feature learning in local neighborhood of the face images. It uses directional Fourier phase feature component to adaptively lean the regression kernel based on local covariance to estimate the high resolution image. For each patch in the neighborhood, four directional …

Generic Cost Estimation Framework For Design And Manufacturing Evaluation, Uday A. Kilkami

Mechanical & Aerospace Engineering Theses & Dissertations

A major drawback of current cost estimation models is their incapability of embracing effectively complete product development stage. Parametric estimation works well in early stages of design, but in detail design stage, a more complete estimation is provided by process model based and detail estimation techniques. A major paradigm shift is proposed in this work whereby ‘Cost’ is to be considered as a design parameter from scientific perspective, and it is to be treated as a design consequence rather than as an operational outcome. A comprehensive framework using System Analysis fundamentals is designed to study ‘Process Cost’ aspects of part …

The Development Of An Enterprise Supply Chain Model For Naval Warship Construction, Rex A. Wallen

Computational Modeling & Simulation Engineering Theses & Dissertations

The utilization of computer simulation in the shipbuilding industry is not a new concept and many shipyards in the US and around the world are using simulation tools in a variety of ways with various levels of success. In other industries, computer simulation has proven itself as a powerful tool for reducing non-value added activities and promises to become more prominent in its use as a resource management tool. Its use in the manufacturing of outfitting components in the construction of Naval warships has had limited success due mainly to the inherent nature of ship construction, especially shipyards engaged in …

External Aerodynamics Of Heavy Ground Vehicles: Computations And Wind Tunnel Testing, Ilhan Bayraktar

Mechanical & Aerospace Engineering Theses & Dissertations

Aerodynamic characteristics of a ground vehicle affect vehicle operation in many ways. Aerodynamic drag, lift and side forces have influence on fuel efficiency, vehicle top speed and acceleration performance. In addition, engine cooling, air conditioning, wind noise, visibility, stability and crosswind sensitivity are some other tasks for vehicle aerodynamics. All of these areas benefit from drag reduction and changing the lift force in favor of the operating conditions. This can be achieved by optimization of external body geometry and flow modification devices. Considering the latter, a thorough understanding of the airflow is a prerequisite.

The present study aims to simulate …

A Formal Object Model For Layered Networks To Support Verification And Simulation, Rasha M. B. E. Morsi

Electrical & Computer Engineering Theses & Dissertations

This work presents an abstract formal model of the interconnection structure of the Open Systems Interconnection Reference Model (OSI-RM) developed using Object-Oriented modeling principles permitting it to serve as a re-usable platform in supporting the development of simulations and formal methods applied to layered network protocols. A simulation of the object model using MODSIM III was developed and Prototype Verification System (PVS) was used to show the applicability of the object model to formal methods by formally specifying and verifying a Global Systems for Mobile communications (GSM) protocol. This application has proved to be successful in two aspects. The first …

Modeling Aspects Of Magnetic Actuators And Magnetic Suspension Systems, V. Dale Bloodgood Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

This dissertation is a study of new modeling techniques developed for magnetic suspension systems. The techniques discussed are modifications of magnetic circuit theory and fundamental eddy current models. The techniques are compared against experimental test results and finite element data. The information gained from the experimental testing is used to provide insight into magnetic bearing design.

A small-gap modeling technique called extended circuit theory is developed that incorporates information about the system gained from finite element data, or experimental data, to be included in the analytic model. The variations between the classical magnetic circuit model and the finite element model …

The Effect Of Model Formulation On The Comparative Performance Of Artificial Neural Networks And Regression, Michael F. Cochrane

Engineering Management & Systems Engineering Theses & Dissertations

Multiple linear regression techniques have been traditionally used to construct predictive statistical models, relating one or more independent variables (inputs) to a dependent variable (output). Artificial neural networks can also be constructed and trained to learn these complex relationships, and have been shown to perform at least as well as linear regression on the same data sets. Research on the use of neural network models as alternatives to multivariate linear regression has focused predominantly on the effects of sample size, noise, and input vector size on the comparative performance of these two modeling techniques. However, research has also shown that …

Major Factors That Influence The Employment Decisions Of Generation X Consulting Engineers, Robert William Mayfield

Engineering Management & Systems Engineering Theses & Dissertations

The purpose of this research was to study Generation X consulting engineers (those born between the years 1964 and 1980) in Lynchburg, Virginia, to determine the major factors that influence their employment decisions. Engineering consulting firms throughout the United States, particularly those in Lynchburg, have struggled to recruit young engineers in recent years. The recruiting of young engineers has been regarded by managers and executives as the single greatest challenge to the consulting profession. Despite the consensus within the profession that the problem existed, recommended solutions have been mostly speculative in nature and unsubstantiated by supportive data. This study focused …

Systemic Issues In Asynchronous Delivery Of Graduate Engineering Management Programs, Charles Keating, David Dryer, Andres Sousa-Poza, William Peterson, Robert Safford

Engineering Management & Systems Engineering Faculty Publications

The purpose of this paper is to examine systemic issues that impact the design, delivery, and maintenance of asynchronous engineering management educational products. Asynchronous education continues to rapidly evolve as an alternative to traditional classroom delivery. An asynchronous educational system requires the effective integration of technology, supporting processes, and infrastructure design to prepare, deliver, and maintain asynchronous educational products. Currently, the technological capabilities for delivery of asynchronous education have outstripped the ability to maximize those advanced technologies. To help understand this rift between technology and our ability to deploy that technology this paper examines three critical areas. First, the distinctions …

Engineering Management- The Minor Of Choice, William Peterson, Paul Kauffmann, Charles Keating, Resit Unal

Engineering Management & Systems Engineering Faculty Publications

The minor in engineering management provides several real benefits to undergraduate engineering and engineering technology students, not the least of which can be a substantially larger starting salary. The other benefits it offers students are in the skill sets developed (project management, engineering economics, organization behavior / principles of management, and either statistical concepts or decision techniques), the preparation to start an engineering management graduate degree, and the bridging of the competency gaps identified in several national surveys. This paper addresses the benefits of the minor to engineering management programs.

Atomic Hydrogen Cleaning Of Inp(100): Electron Yield And Surface Morphology Of Negative Electron Affinity Activated Surfaces, M. A. Hafez, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Atomic hydrogen cleaning of the InP(100) surface has been investigated using quantitative reflection high-energy electron diffraction. The quantum efficiency of the surface when activated to negative electron affinity was correlated with surface morphology. The electron diffraction patterns showed that hydrogen cleaning is effective in removing surface contaminants, leaving a clean, ordered, and (2×4)-reconstructed surface. After activation to negative electron affinity, a quantum efficiency of ∼6% was produced in response to photoactivation at 632 nm. Secondary electron emission from the hydrogen-cleaned InP(100)-(2×4) surface was measured and correlated to the quantum efficiency. The morphology of the vicinal InP(100) surface was investigated using …

An Instrument For Assessing Knowledge Gain In A First Course In Circuit Theory, Vishnu K. Lakdawala, Stephen A. Zahorian, Oscar R. González, Amit Kumar H., James Leathrum

Electrical & Computer Engineering Faculty Publications

Although there has been considerable research on the development and use of assessment instruments to measure the effectiveness of various pedagogical approaches to teaching introductory physics classes (Hestenes et al. 1, Hestenes et al 2, Hake 3, Saul et al. 4) and other science courses (for example, see Vosniadou 5), there is relatively little similar work that has been done to develop assessment instruments for the first circuit theory course that is taught in electrical and computer engineering. Given the large numbers of students nationwide who take such a course, the challenge this course presents to beginning engineering students, and …

High-Efficiency Solar Cells Based On Cu(Inal)Se[Sub 2] Thin Films, S. Marsillac, P. D. Paulson, M. W. Haimbodi, R. W. Birkmire, W. N. Shafarman

Electrical & Computer Engineering Faculty Publications

A Cu(InAl)Se₂solar cell with 16.9% efficiency is demonstrated using a Cu(InAl)Se₂thin film deposited by four-source elemental evaporation and a device structure of glass/Mo/Cu(InAl)Se₂/CdS/ZnO/indium tin oxide/(Ni/Algrid)/MgF₂. A key to high efficiency is improved adhesion between the Cu(InAl)Se₂ and the Mo back contact layer, provided by a 5-nm-thick Ga interlayer, which enabled the Cu(InAl)Se₂ to be deposited at a 530 °C substrate temperature. Film and device properties are compared to Cu(InGa)Se₂ with the same band gap of 1.16 eV. The solar cells have similar behavior, with performance limited by recombination through …

121.6 Nm Radiation Source For Advanced Lithography, Jianxun Yan, Ashraf El-Dakrouri, Mounir Laroussi, Mool C. Gupta

Electrical & Computer Engineering Faculty Publications

A vacuum ultraviolet (VUV) light source based on a high-pressure cylindrical dielectric barrier discharge (DBD) has been developed. Intense and spectrally clean Lyman-α line at 121.6 nm was obtained by operating a DBD discharge in neon with a small admixture of hydrogen. The spectrum, optical power, stability, and efficiency of the source were measured. The influence of the gas mixture and total gas pressure on the VUV intensity has been investigated. Maximum optical power of 3.2 W and spectral width 0.03 nm was achieved. Power stability of 2% for 100 h of operation has also been obtained. The newly developed …

Acceleration Element For Femtosecond Electron Pulse Compression, Bao-Liang Qian, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

An acceleration element is proposed for compressing the electron pulse duration in a femtosecond photoelectron gun. The element is a compact metal cavity with curved-shaped walls. An external voltage is applied to the cavity where a special electric field forms in such a way that the slow electrons in the electron pulse front are accelerated more than the fast electrons, and consequently the electron pulse duration will be compressed. The distribution of the electric field inside the acceleration cavity is analyzed for the geometry of the cavity. The electron dynamics in this acceleration cavity is also investigated numerically. Numerical results …

Electron Pulse Broadening Due To Space Charge Effects In A Photoelectron Gun For Electron Diffraction And Streak Camera Systems, Bao-Liang Qian, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The electron pulse broadening and energy spread, caused by space charge effects, in a photoelectron gun are studied analytically using a fluid model. The model is applicable in both the photocathode-to-mesh region and the postanode electron drift region. It is found that space charge effects in the photocathode-to-mesh region are generally unimportant even for subpicosecond pulses. However, because of the long drift distance, electron pulse broadening due to space charge effects in the drift region is usually significant and could be much larger than the initial electron pulse duration for a subpicosecond electron pulse. Space charge effects can also lead …

Using Spreadsheet Programs In Teaching Machine Design, Cheng Y. Lin, Gary R. Crossman

Engineering Technology Faculty Publications

This paper presents an approach on using spreadsheets to teach machine design. It also lists detailed procedures on how to implement the teaching scheme. Results show that spreadsheet programs can help students organize their design procedures. By using the characteristics of spreadsheet programs, students do not have to repeat the same calculation and can get the alternate solution of a design almost instantly when given different values on the inputs. When compared to the method taught by using calculators, students can significantly improve their performance on homework problems and tests. From teaching evaluations, their interest in taking such a course …

Active And Adaptive Flow Control Of Twin-Tail Buffet And Applications, Zhi Yang

Mechanical & Aerospace Engineering Theses & Dissertations

Modern fighter aircraft with dual vertical tails are operated at high angles of attack. The vortex generated by leading edge extension (LEX) breaks down before reaching the two vertical tails. The wake of highly unsteady, turbulent flow causes unbalanced broadband aerodynamic loading on the tails and may produce severe buffet on the tails and lead to tail fatigue failure.

Flow suction along the vortex cores (FSVC) is investigated as an active control method for tail-buffet alleviation. Suction tubes have been tilted at different angles to study the control effectiveness of suction tubes orientation. Flow field response, aerodynamic loading and aeroelastic …

Electrical Network-Based Time-Dependent Model Of Electrical Breakdown In Water, R. P. Joshi, J. Qian, K. H. Schoenbach

Bioelectrics Publications

A time-dependent, two-dimensional, percolative approach to model dielectric breakdown based on a network of parallel resistor–capacitor elements having random values, has been developed. The breakdown criteria rely on a threshold electric field and on energy dissipation exceeding the heat of vaporization. By carrying out this time-dependent analysis, the development and propagation of streamers and prebreakdown dynamical evolution have been obtained directly. These model simulations also provide the streamer shape, characteristics such as streamer velocity, the prebreakdown delay time, time-dependent current, and relationship between breakdown times, and applied electric fields for a given geometry. The results agree well with experimental data …

A Task Process Pre-Experimental Model, Holly A. H. Handley, Alexander H. Lewis

Engineering Management & Systems Engineering Faculty Publications

The Adaptive Architectures for Command and Control (A2C2) program is a multidisciplinary program that employs a scientific basis for designing and analyzing adaptive and reconfigurable organizational structures at the Joint Task Force level. As part of its unique model-driven experimentation method, a pre-experimental model is created to support the formulation of hypotheses, the determination of key variables and parameter values, and the prediction of organizational performance. The pre-experimental model is used to explore the parameters of the experimental design in order to determine the appropriate region to conduct officer-in-the-loop experiments at the Naval Postgraduate School. A pre-experimental model based on …