Digital Commons Network^™

An Examination Of The Relationship Between Mental Resources And Performance Strategies, Douglas L. Miller

Psychology Theses & Dissertations

Based on the work of Klapp, Marshburn, and Lester (1983) and more generally on principles of the Multiple Resource Theory, it was proposed that human short-term memory consists of two mental resource channels, one that is tapped by span memory tasks and one tapped by immediate working memory tasks. It was further hypothesized that dual-task performance would be better under conditions where one of the component tasks tapped the proposed span memory channel and one tapped the proposed working memory channel, than when both tasks tapped the same channel. In addition, it was hypothesized that dual-tasks tapping the same memory …

Calibration Of Old Dominion University Low-Speed Wind Tunnel, Nicolaos P. Sargianos

Mechanical & Aerospace Engineering Theses & Dissertations

No Abstract.

An Investigation Of Overvoltage Effects On A Gas-Blown Spark Gap, Michael Steven Mazzola

Electrical & Computer Engineering Theses & Dissertations

This experimental investigation addresses the anomalous overvoltage breakdown and subsequent recovery characteristics observed in gas-blown spark gaps. Previous investigations have reported a two-stage recovery process in self-break, pulse-charged, gas-blown spark gape in which the spark gap recovers first to an intermediate breakdown strength before recovering to the undisturbed breakdown voltage. The recovery process has been explained in terms of two different characteristic times. The first is that required to obtain initial recovery in which the spark gap regains its intrinsic breakdown strength. The second time is that required to obtain final recovery in which the pulse-charged spark gap regains the …

A Frequency Domain Digital Signal Processor For Laser Velocimeter Systems, Andreas Evangelos Savvakis

Electrical & Computer Engineering Theses & Dissertations

A new signal processor for laser velocimeter systems is proposed. The proposed processor incorporates automatic initialization, real time operation, and can efficiently process input signals comprised of as low as 150 photons, with mean oscillation frequency up to 100 MHZ, and input turbulence from 0 to 20%. A bank of digital bandpass filters is employed for the energy spectrum estimation of the input signal. A deterministic model is developed to describe the relationship between the filter output energies and the input signal parameters. The input frequency is estimated by linearly weighting the filter output energies. A spline function approximation approach …

Wind Streamline Ambiguity Removal Of Microwave Scatterometer Data, Hans W. Zaepfel

Electrical & Computer Engineering Theses & Dissertations

There is a class of satellite microwave scatterometers that return oceanographic information which includes wind vectors with directional ambiguity. The first part of the ambiguity removal process is to reduce the data to a directional ambiguity of 180°. This thesis shows that wind direction change contains the information required for streamline ambiguity removal and that syntactic pattern recognition techniques can be used to locate the areas of wind direction change. Spreading the information along the areas of wind direction change results in the removal of the streamline ambiguity. The algorithm is implemented and the results are presented showing that it …

Chemoviscosity Modeling Of Thermosetting Resins, Jia-Mo Bai

Mechanical & Aerospace Engineering Theses & Dissertations

A new analytical model for simulating chemoviscosity of thermosetting resin has been formulated. The model is developed by modifying the well-established Williams-Landel-Ferry (WLF) theory in polymer rheology for thermoplastic materials. By introducing a relationship between the glass transition temperature Tg (t) and the degree of cure a(t) of the resin system under cure, the WLF theory can be modified to account for the factor of reaction time. Temperature-dependent functions of the modified WLF theory constants C₁(T) and C₂(T) were determined from the isothermal cure data. Theoretical predictions of the model for the resin under dynamic …

The Effect Of Grinding On The Sorption Capacity Of Activated Carbon, John Garrett Dempsey

Civil & Environmental Engineering Theses & Dissertations

The current procedure employed to design full scale activated carbon contacting systems is presented in detail and followed by a review of the more important process controls and operating parameters. Inherent limitations of the design procedure are identified, with the need to be able to accurately predict carbon sorption capacity from bench scale analysis determined to be the most important. Some of the more recent models developed to predict activated carbon sorption capacity were analyzed leading to the realization that even the most sophisticated dynamic models were based upon sorption capacities determined from classical isotherm procedures. The validity of the …

An Analytical And Experimental Study Of Clearance And Bearing-Bypass Load Effects In Composite Bolted Joints, Rajiv Vikas Arun Naik

Mechanical & Aerospace Engineering Theses & Dissertations

A combined analytical and experimental study is conducted to determine the effects of clearance and bearing-bypass loading for mechanically fastened joints in composites. A simple method of analysis is developed to account for the nonlinear effects of bolt-hole clearance. The nonlinear load-contact variations for clearance-fit fasteners are also measured using specially instrumented fasteners. For a quasi-isotropic graphite/epoxy laminate, results show that the contact arc as well as the peak stresses around the hole and their locations are strongly influenced by the clearance. After a slight initial nonlinearity, the peak stresses vary linearly with applied load. The typical clearance levels are …

The Effect Of The Revolution On Norfolk Politics, Mary C. Chrysostomides

History Theses & Dissertations

This study sought to determine whether the Revolution had a revolutionary effect on Norfolk as measured by changes in the wealth and occupation of common councilmen, the nature of politics, and the formal structure of the government of the borough. The politics, politicians, and governmental structure of Norfolk twenty years before the Revolution were compared to the politics, politicians, and governmental structure twenty years after the Revolution. The data for the study were drawn from damage claims, newspapers, wills, probate records, tax records, personal papers, travel accounts, petitions submitted to the General Assembly, statutes and ordinances, and other public records. …

Optimal Cure Cycle Design Of A Resin-Fiber Composite Laminate, Jeenson Sheen

Mechanical & Aerospace Engineering Theses & Dissertations

High performance polymeric composites have been experiencing increasing usage in the aerospace and automobile industries. Such materials are commonly composed of long or chopped fibers embedded in the thermosetting resin matrix. Changes in physical and chemical properties of such composite materials during the cure process are rather complex. Thus, it is not a trivial task to properly design a cure cycle (temperature and pressure profiles) for a cure process. The material should be cured uniformly and completely with the lowest void content; the temperature inside the laminate must not exceed some maximum value; and the cure process should be completed …

An Experimental And Analytical Investigation Of Incompressible Fluid Flow Through A Distensible Tube System, Steven C. Wells

Mechanical & Aerospace Engineering Theses & Dissertations

An analysis was made of pressure and flow in a novel elastic tube system which has been used to theorize certain aspects of renal hemodynamic cs. Validation of the theory could alter the treatment of certain heart and kidney disorders. In an attempt to better understand a system flow anomaly under steady driving head conditions, experiments were performed, and a mathematical model was developed. The development of the model incorporated a set of nonlinear differential and algebraic equations. Using a finite-difference analysis as the method for obtaining a numerical solution, various pressures and flows were obtained. Results for the steady-state …

A Quantitative Approach To Simulation And Analysis Of Storm Water Systems, John Nathan Paine

Civil & Environmental Engineering Theses & Dissertations

A generalized package of hydrologic and hydraulic models and programs is developed for the quantitative analysis of watersheds and drainage networks. The package is microcomputer based and is available to interested parties. Full documentation is included in the Appendix. The approach applies a lengthy historical rainfall record to the system in continuous simulation. One of the most powerful operational hydraulic routing models available is adopted into the package. Output takes the form of statistical predictions of flood stages, discharges, storage requirements, and rainfall analyses for various return-periods. Computer runs are completely summarized. The package was applied to a 969-acre watershed …

Effects Of Air Polishing And Rubber Cup Polishing On Enamel Abrasion, April Kee

Dental Hygiene Theses & Dissertations

An investigation was conducted to determine if statistically significant differences in enamel abrasion occurred when molar specimens were air polished (AP) and rubber cup polished (RCP). Thirty human molars were randomly divided into two groups. Molar buccal surfaces were masked longitudinally to provide control surfaces. Each polishing technique was applied for two minutes and thirty seconds on fifteen exposed enamel surfaces. Buccal enamel surfaces were divided into coronal and cervical sections for microscopic review. Six enamel thickness measurements were determined for each coronal and cervical enamel section using the scanning electron microscope. Measurements of AP and RCP coronal and cervical …

Three-Dimensional Elastic-Plastic Finite Element Analysis Of Fatique Crack Growth And Closure, Rahmatollah G. Chermahini

Mechanical & Aerospace Engineering Theses & Dissertations

The purpose of this study was to develop a three-dimensional, elastic-plastic, finite element analysis to investigate crack extension and closure under cyclic loading. The initial study concentrated on the behavior of a straight through crack in a finite-thickness plate subjected to tensile loading (middle-crack tension specimen). The finite element model was composed of 8-noded (linear-strain) isoparametric elements. In the analysis, the material was assumed to be elastic-perfectly plastic. Zienkiewicz's "initial-stress" method, von Mises' yield criterion, and Drucker's normality condition, under small-strain assumptions, were used to account for plasticity. The three-dimensional analysis is capable of extending the crack and changing boundary …

Generic Specifications In Lil And In Ada Via Analogies, George Chester Harrison

Computer Science Theses & Dissertations

We address the problem of .making verifiable specifications in generic program units in the Ada Programming Language*. We illustrate the methodologies of LIL proposed by Joseph Goguen and Justify the use of such a specification languages using analogy programming originally proposed by Nachum Dershowitz. The work in these areas is new and noticeably incomplete. We address our concern about the reusability of Ada software in a programming environment that includes a specification language like LIL. * Ada is a registered trademark of the U.S. Government (Ada Joint Program Office)

Deterministic Linear Predictors For Bit Rate Improvement, Dhanvant H. Goradia

Electrical & Computer Engineering Theses & Dissertations

This thesis addresses the application of deterministic linear predictor s for telemetry based systems. Deterministic linear predictors are considered as a viable alternative to block transform coding in order to achieve bit rate reduction. A method of calculating the predictor coefficients of a deterministic linear predictor is presented. The system model is developed parametrically with respect to the bandwidth, polynomial order, signal class and predictor length. Two classes of signals, deterministic and random are analyzed and bounds on the performance of the deterministic linear predictor are established. A family of six pole Butterworth filters are used as presample filters in …

The Fleet Landing Exercises And The Development Of Modern American Amphibious Doctrine, W. Howard Meissel Jr.

History Theses & Dissertations

The Fleet Landing Exercises conducted by the United States Marine Corps in conjunction with the Navy and Army were some of the most significant military exercises conducted in American history. This thesis analyzes the seven exercises conducted between 1935 and 1941 to see how field testing affected amphibious doctrine, organization, and equipment development. This study summarizes the successes and failures of each exercise in regard to the evolution of a strong tactical doctrine, the training of a cadre of officers and men, and the development of the equipment vital to perform the amphibious mission. Primary information is largely drawn from …

The Remarkable John Bigelow, Jr.: An Examination Of Professionalism In The United States Army, 1877-91, Howard K. Hansen Jr.

History Theses & Dissertations

This thesis describes the military career of John Bigelow, Jr. , with emphasis on the professional development of United States Army officers. It questions the role Bigelow played in the formation of army professionalism, a sense of corporate responsibility to exercise military expertise correctly. A focus on Bigelow to delineate professionalism in the army provides a fresh perspective of a pivotal period in American military history in the aftermath of the Civil War and before the United States started to build a colonial empire. Bigelow articulated a comprehensive concept of total^ar as he perceived its development in the United States. …

An Evaluation Of A Taylor-Galerkin Algorithm For High Speed Inviscid Flows Using Quadrilateral And Triangular Elements, Kim S. Bey

Mechanical & Aerospace Engineering Theses & Dissertations

The Taylor-Galerkin finite element algorithm is used to obtain solutions to the two-dimensional compressible Euler equations. The mathematical formulation of the algorithm is presented for a typical scalar equation. The derivation results in element equations which are assembled over the entire solution domain to obtain the system of equations that are solved explicitly. The algorithm has the unique feature that the finite element matrices can be evaluated in closed form, avoiding expensive numerical integration. Aspects of vector programming strategies and mesh generation important to an effective analysis procedure are also described. Solutions to supersonic flow problems with exact solutions are …

A Non-Linear Vortex Panel Method For Wings With Edge Separation, Vijay Kalburgi

Mechanical & Aerospace Engineering Theses & Dissertations

A global nodal vortex panel method is developed to predict steady aerodynamic loads on rectangular lifting surfaces with side edge separation. The lifting surface and free shear layers are modeled by bound and free vortex sheets respectively, which are then discretized into triangular bound and free vortex panels respectively. On each triangular panel, a linear distribution of vorticity is defined in terms of the global components of vorticity at its nodes. The velocity field induced by any triangular vortex panel is obtained in closed form. The vortex core of the side edge vortex is modeled by a concentrated core of …

Disease Incidence Of Demersal Finfishes From The Southern And Western Branches Of The Elizabeth River, Virginia, Randal D. Owen

Biological Sciences Theses & Dissertations

Fishes from the industrialized environs of the Elizabeth River, Virginia were surveyed for external evidence of disease during June through October 1984. A highly significant (p < 0.001) incidence of disease was found in demersal fishes collected by otter trawl from a site in the industrially contaminated Southern Branch compared to a less contaminated Western Branch site. Cataracts, fin erosion and dermal lesions were the most commonly occurring anomalies in the Southern Branch finfish.

Static, solid-phase toxicity tests employing sediment collected from the Southern Branch site resulted in an immediate toxic stress in the spot, Leiostomus xanthurus, which resulted in 100% mortality within 24 hours, compared with no mortalities in control systems. Spot exposed to control, i.e., pollution free, and diluted Southern Branch sediments innoculated with the pathogenic bacterial species, Vibrio anguillarium, developed significant (p ≤ 0.020) cases of fin erosion at a mean total bacterial community density …

Dynamic Analysis Of An Earth-Orbiting Satellite Deploying Hinged Appendages, Kevin Fielding Oakes

Mechanical & Aerospace Engineering Theses & Dissertations

The planar liberational dynamics of an arbitrary spacecraft with deployable hinged appendages is presented here both analytically and numerically. The system model consists of a central rigid satellite moving about the earth in a circular orbit at a uniform orbital rate. Attached to the satellite are two unfolding rigid booms with specified mass and length. Tip masses are included at the ends of each boom and deployment is driven by torsional springs at both frictionless hinge points. The equations of motion are developed for both a single- and double-appendage model through the use of Lagrange's equations. The formulation accounts for …

Erosion Of Yellow Brass And Type 304 Stainless Steel In A Gas Blown Spark Gap, Rakasi Madhava Reddy

Mechanical & Aerospace Engineering Theses & Dissertations

Erosion rates of yellow brass and type 304 stainless steel electrodes were studied in air under pulse discharge conditions at a voltage of 100 kV, a current of 20 kA, and pulse durations of 70 ns. Anodes and cathodes, configured vertically, were fitted with removable hemispherical tips having a diameter of 0.95 cm and a mass of 3 gm. Tests were conducted inside a low speed, high pressure wind tunnel at pressures of 30 and 50 psig and air velocities ranging from 0 to 36 nm/s.

Erosion was studied gravimetrically for several flow velocities. As many as 60,000 discharges were …

Laser Pump And Probe Excited State Absorption Measurements, Shawpin Jong

Electrical & Computer Engineering Theses & Dissertations

A pump and probe technique was used to investigate triplet-triplet excited state absorption in solutions of the scintillators 2,5 diphenyloxazole (PPO) and 2,1 naphthyl,5 phenylzole (a-NPO) in several solvents.

KrF excimer radiation (248 nm) was used to pump the samples under investigation as well as a tunable dye laser which was used as the probe. Time-resolution was obtained by changing the optical path difference between the pump and probe beams.

Transient excited state absorption was measured in a wide spectral region between 330 nm and 600 nm, showing a peak at 400 nm for PPO solutions, and two …

Convective Heat Transfer From Circular Cylinders Located Within Perforated Cylindrical Shrouds, Kamran Daryabeigi

Mechanical & Aerospace Engineering Theses & Dissertations

The influence of perforated cylindrical shrouds on the convective heat transfer to circular cylinders in transverse flow has been studied experimentally. Geometries studied were similar to those used in industrial platinum resistance thermometers. The influence of Reynolds number, ventilation factor (ratio of the open area to the total surface area of shroud), radius ratio (ratio of shroud's inside radius to bare cylinder's radius), and shroud orientation with respect to flow were studied.

The experiments showed that perforated shrouds with ventilation factors in the range 0.1 to 0.4 and radius ratios in the range 1.1 to 2.1 could enhance the convective …

An Investigation Of High Strength To Weight Corrugated Compression Panels With Non-Load Carrying Webs, Charles Thomas Lee Mills

Mechanical & Aerospace Engineering Theses & Dissertations

An investigation of the weight saving potential of corrugated compression panel concepts using curved elements and non-load carrying webs was performed. The concepts investigated were corrugated panels with flat and curved caps with beaded webs. These concepts utilize a beaded web that carries negligible axial load but is very stiff in the transverse direction. Therefore the web substantially stabilizes the load carrying caps to produce a high weight-strength efficient structure.

The optimum geometry parameters were determined using an iterative solution method employing simplified buckling assumptions. The results were checked with a non-linear optimization program coupled to a rigorous buckling analysis. …

Patterns Of Diurnal Vertical Distribution And Dispersal-Recruitment Mechanisms Of Decapod Crustacean Larvae And Postlarvae In The Chesapeake Bay, Virginia And Adjacent Offshore Waters, Robert Copeland Maris

OES Theses and Dissertations

Larval dispersal and subsequent postlarval recruitment are extremely significant processes affecting the maintenance of ecologically and economically important populations of decapod crustaceans. Vertical positioning in the water column plays a major role in the particular strategies of retention or expulsion with immigration.

The present study was undertaken to investigate variations in vertical distribution according to temporal (diurnal), spatial (estuarine, transition, oceanic), ontogenetic (larval stages, postlarvae) and various environmental factors (especially light, temperature, salinity and tides). Also, effects of vertical positioning on dispersal-recruitment were examined.

Three stations were established for the present study: York River mouth (estuarine) (37°12'N, 76°16'W); Chesapeake Bay …

On The Existence Of Periodic And Eventually Periodic Solutions Of A Fluid Dynamic Forced Harmonic Oscillator, Charlie H. Cooke

Mathematics & Statistics Faculty Publications

For certain flow regimes, the nonlinear differential equation Y¨=F(Y)−G, Y≥0, G>0 and constant, models qualitatively the behaviour of a forced, fluid dynamic, harmonic oscillator which has been a popular department store attraction. The device consists of a ball oscillating suspended in the vertical jet from a household fan. From the postulated form of the model, we determine sets of attraction and exploit symmetry properties of the system to show that all solutions are either initially periodic, with the ball never striking the fan, or else eventually approach a periodic limit cycle, after a sufficient number of bounces away from …

A Study Of The Word Processing Field In The Tidewater Area, Patricia G. Powell

OTS Master's Level Projects & Papers

To study word processing, one must gain information on these specific areas: 1. To determine what jobs would be available in the word processing field in the Tidewater region in the next five years; 2. To determine the entry skill levels that would be required by employers in the word processing field; 3. to suggest curricular changes needed in Tidewater area word processing training programs.

An Assessment Of Current Procedures And Practices For Placement Of Handicapped Students In Vocational Programs In Chesapeake, Virginia, Linda Denise Britt

OTS Master's Level Projects & Papers

The questions related to this study were: 1. What major pieces of legislation shaped and promoted new cooperation between special education and vocational education in serving the handicapped? 2. How can administrators, special educators, vocational educators, guidance counselors, and parents augment cooperation, support, and communication between each other? 3. What are some of the considerations that effect decisions for placement of handicapped students in a vocational program?