4,686 Works

Minimal Norm Constrained Interpolation

Larry Dean Irvine
In computational fluid dynamics and in CAD/CAM a physical boundary, usually known only discreetly (say, from a set of measurements), must often be approximated. An acceptable approximation must, of course, preserve the salient features of the data (convexity, concavity, etc.) In this dissertation we compute a smooth interpolant which is locally convex where the data are locally convex and is locally concave where the data are locally concave. Such an interpolant is found by posing...

Ring Dynamics in the Western Gulf of Mexico

Adolphe W. Indest
The interaction of a recently-formed Loop Current ring and a fossil ring is studied using observations and a two-layered eddy-resolving general circulation model of the Gulf of Mexico. This interaction is investigated by following the evolution of volume, energy, potential vorticity, angular momentum and enstrophy within a model ring as it moves westward and encounters a fossil ring along the continental slope of the Gulf of Mexico. By comparing the model results with drifter and...

An Experimental Study of an Axisymmetric Turbulent Boundary Layer Disturbed By a Periodic Freestream

Chithrabhanu Koodalattupuram
Behavior of an axisymmetric equilibrium turbulent boundary layer disturbed by a propeller wake in the freestream was investigated experimentally. Tests were conducted in a low speed wind tunnel and measurements of turbulence quantities were made using an X wire probe and a constant temperature anemometer. The boundary layer flow on a cylindrical body was characterized by measuring its gross parameters and comparing them with classical values. Propeller speed was measured using an electronic circuit whose...

Factors Affecting the Kinetics of Light Intensity Adaptation in Marine Phytoplankton

Chunzhi Guo
It has been suggested that the recent light history of phytoplankton and the kinetics of photoadaptation can be used to provide information about the vertical mixing processes in the upper mixed layer. To be useful as a parameter in a model of photoadaptation and vertical mixing, the response of a photoadaptive variable to changes in growth irradiance must be monotonic, significant, and comparable in time rate scale to mixing processes. Previous studies of photoadaptation kinetics...

On a Moving Boundary Problem of Transitional Ballistics

Jen-Ing G. Hwang
A major problem which arises in computer simulation of the firing of a gun weapon is the development of numerical schemes which effectively account for the physics of projectile motion. The chief difficulty is that away from the projectile the calculation is ordinarily accomplished on a fixed numerical grid, whereas due to projectile movement some cells of the grid near the projectile undergo volume changes as the calculation proceeds. A local finite volume scheme is...

Integrated System Identification and Adaptive State Estimation for Control of Flexible Space Structures

Chung-Wen Chen
Accurate state information is crucial for control of flexible space structures in which the state feedback strategy is used. The performance of a state estimator relies on accurate knowledge about both the system and its disturbances, which are represented by system model and noise covariances respectively. For flexible space structures, due to their great flexibility, obtaining good models from ground testing is not possible. In addition, the characteristics of the systems in operation may vary...

Low Speed Flowfield Characterization by Infrared Measurements of Surface Temperatures

Ehud Gartenberg
An experimental program was aimed at identifying areas in low speed aerodynamic research where infrared imaging systems can make significant contributions. Implementing a new technique, a long electrically heated wire was placed across a laminar jet. By measuring the temperature distribution along the wire with the IR imaging camera, the flow behavior was identified. Furthermore, using Nusselt number correlations, the velocity distribution could be deduced. The same approach was used to survey wakes behind cylinders...

Nonlinear Response and Fatigue Estimation of Surface Panels to White and Non-White Gaussian Random Excitations

Jean-Michel Dhainaut
In stochastic structural dynamics, the majority of analyses have dealt with linear structures under stationary, Gaussian, and band-limited white noise excitations. Although these simplifying assumptions may be justified, in many processes experimental data have shown quite frequently the non-stationary and non-Gaussian characteristics of the loads. An efficient finite element modal formulation has recently been developed to extend the analysis to nonlinear structural responses. Laminated plate theory and von Karman large displacement relations are used to...

The Impact of State Equity Standards on Leaders' Espoused Beliefs About Social Justice

Amanda Hadgraft
School leaders are tasked with greater responsibilities than ever before. Today’s school leaders are expected to act as social justice leaders, ensuring all students have an equitable environment to learn in. State departments of education hold leaders accountable by comparing standardized test scores of students in majority and minority groups. The problem is these assessments measure the outcome of learning, but fail to measure the environments learning occurs in. The purpose of this study was...

Quaternary Seismic Stratigraphy of the Inner Shelf and Coastal Zone, Southern Delmarva Peninsula, Virginia

Anthony M. Foyle
The Pleistocene stratigraphic record beneath the Virginia inner shelf is largely unknown. On the adjacent lower Atlantic Coastal Plain of southeastern Virginia, the Pleistocene record consists of seven stacked transgressive sequences, while on the southern Delmarva Peninsula, a series of three transgressive to highstand sequences are developed. Reconstruction of the mid-Atlantic basin margin response to high-frequency Quaternary glacioeustasy is limited by this sparse record of late transgressive through early regressive deposition. Knowledge of high-frequency depositional...

Three-Dimensional Elastic-Plastic Finite Element Analysis of Fatique Crack Growth and Closure

Rahmatollah G. Chermahini
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,...

The Solution of a Singular Integral Equation Arising From a Lifting Surface Theory for Rotating Blades

Mark H. Dunn
A technique is presented for the solution of a linear, two dimensional, singular, Volterra integral equation of the first kind. The integral equation, originally developed by Farassat and Myers, is derived from the basic equations of linearized acoustics and models the lifting force experienced by an infinitesimally thin surface moving tangent to itself. As a particular application, the motion of modern high speed aircraft propellers (Advanced Technology Propellers) is considered. The unknown propeller blade surface...

A Preliminary Study of a Job Analytic Inventory Derived From a Behavioral Consistency Method for Assessing Intrinsic Motivation

William John Banis
The research question for this study asked if the Job Specifications Inventory (JSI) had acceptable internal reliability and an ability to differentiate among occupational groups. The JSI was designed to have subject matter experts rate the importance of skill, content, context, relationship and work focus requirements of jobs or occupations. The JSI used a taxonomy of 268 behavioral elements derived from the content analyses of satisfying achievements reported by a large, diverse clientele. A clinical-type...

Productivity Measurement for Home Health Care Registered Nurses

Lazelle Emminizer Benefield
The purpose of this study is to develop a productivity measurement applicable to home health registered nurses (RNs) by identifying and quantifying the knowledge and ability variables that define productive nurse practice. A preliminary set of knowledge and ability variables was identified based on content analysis of interviews with local nurse managers and round I of a three round Delphi procedure, using a purposive sample of nurse managers from nationally preeminent agencies. A randomized national...

Measurement of the gπNN(t) Form Factor

Kelly Gene Vansyoc
Cross sections were measured for the reaction 1H(e, e′π+) n at the energy W = 1.95 GeV and momentum transfer Q2 = 0.6 (GeV/c)2. At this W and Q2, the longitudinal cross section is dominated by t-channel production, giving a unique opportunity to examine the strong coupling form factor gπNN(t). The measured cross sections were separated using a method similar to a Rosenbluth separation. For the extraction of gπNN(t), the Actor and Körner model [42]...

Measurement of Hyperfine Coupling Constants of the 5d²D₃/₂ and 5d²D₅/₂ Levels in Atomic Cesium Using Polarization Quantum Beat Spectroscopy

Wo Yei
Accurate measurements of hyperfine constants have revealed effects that can not be explained by a simple hydrogenic picture of the alkali atoms such as cesium [1-3]. More precise experimental results and theoretical treatments are in demand for the alkali elements, especially for atomic cesium because of its wide range of applications. Therefore, it is essential to understand its atomic and nuclear structure. Precision measurement of its excited-states properties such as hyperfine structure provides global information...

Urban Terrorism: Strategies for Mitigating Terrorist Attacks Against the Domestic Urban Environment

John J. Kiefer
This study identifies strategies to mitigate the impact of terrorist attacks against the domestic urban environment. It uses multiple qualitative research methods to identify patterns of attack used by terrorists against urban targets in the United States and suggest ways for policymakers to mitigate the effects of a terrorist attack through not only physical, but also organizational, political, legal, and social strategies. It uses case analysis, literature review, and interviews with experts in domestic terrorism...

Simulation of Active Control of Asymmetric Flows Around Slender Pointed Forebodies

Hazem Sharaf El-Din
At high angles of attack, the flowfield over slender forebodies becomes asymmetric with substantial side force, which may exceed the available control capability. The unsteady compressible Navier-Stokes equations are used to investigate the effectiveness of different active control methods to alleviate and possibly eliminate the flow asymmetry and the subsequent side force. Although the research work focuses on active control methods, a passive control method has been investigated. The implicit, Roe flux-difference splitting, finite volume...

Building a Consensus for the Development of National Standards in History

Mary Vassilikou Bicouvaris
This research project examines the process used by the National History Standards Project to build consensus for the development of national standards for teaching history in America's schools. Since the publication of A Nation At Risk: The Imperative for Educational Reform by the National Commission of Excellence in Education in 1983, the American educational community has been in the grips of a reform movement. The aim of this movement is to examine where we have...

Distribution of Foraminifera and Pollen in Coastal Depositional Environments of the Southern Delmarva Peninsula, Virginia, U.S.A.

Han Jun Woo
The coastal zone of the southern Delmarva Peninsula exhibits a wide variety of barrier island system subenvironments. This study investigates whether 20 a priori subenvironments can be distinguished from each other on the basis of abiotic environmental variables, pollen assemblages, living foraminiferal populations, and total (living plus dead) foraminiferal assemblages. The physical data collected from the coastal zone were subjected to canonical variate analysis which discriminated 83% of the stations in 19 groups. These groups...

Diapycnal Mixing and Mass Transfer in Western Boundary Currents

Jose Luis Pelegri Llopart
The distribution of nutrient flux in five sections across the Gulf Stream (from the Florida Straits of 35°W) is characterized by an intense core, centered at the depth of the 26.8 σt isopycnal surface. This 'Nutrient Stream' transports nutrients of O(103 kmol s-1} of nitrate and proportional amounts of other nutrients. Water mass and nutrient balances of nine isopycnal layers reveal significant diapycnal mixing between upper-thermocline and surface waters in the sector of the Stream...

Some Solutions to a Lens Model With Applications to Warm-Core Eddies

Juping Liu
A model of lens-shaped anticyclonic eddies based on nonlinear shallow water equations is developed. The model is a three-layer fluid and allows for one asymmetric mode as well as specified environmental flows. The solution scheme is a polynomial expansion of the field variables. When inserted into the hydrographic equations, the expansion yields eight first-order differential equations for the time dependent amplitudes. This system of ordinary differential equations is numerically tractable. As long as the initial...

The Marine Geochemistry of Selenium

Kazufumi Takayanagi
A fluorometric method for the determination of Se (IV) and total selenium in natural waters has been developed and optimized. The detection limit is about 20 pM for both analyses using a one liter sample. The precisions were about 2 % at 338 pM for Se (IV) and at 234 pM for total selenium. The concentrations of both total selenium and Se (IV) decreased with increasing salinity in the surface waters of the James River...

In Situ Regulation of Cytosolic Phospolipase A2

Beverly A. Rzigalinski
The 85 kDa cytosolic phospholipase A2 (cPLA2) is an agonist-responsive effector for intracellular signal transduction through the arachidonate cascade. In vitro studies have demonstrated that this enzyme is regulated by sub-micromolar calcium and is specific for arachidonate as the sn-2 fatty acyl group of phospholipid substrates. However, very little data is available regarding in situ mechanisms which govern the activity of cPLA2. The primarily objective of these studies was to develop an in situ system...

Phytoplankton Dynamics in the Very Low Salinity Region of the James River Estuary, Virginia, U.S.A.

Changho Moon
During summer and autumn discharge from the James River estuary, Virginia, was less than 120 m3sec-1. There was a peak phytoplankton biomass in the very low salinity region (defined as the location where surface salinity measured less than 0.5$ 0/00) and this peak represented five to ten times greater biomass than adjacent waters. The peak biomass occurred independent of the tidal state and the location of nutrient inputs. It disappeared during winter and spring, and...

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