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Articles 31 - 48 of 48
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A One-Dimensional Model For Storm Breaching Of Barrier Islands, Cheol Shik Shin
A One-Dimensional Model For Storm Breaching Of Barrier Islands, Cheol Shik Shin
Civil & Environmental Engineering Theses & Dissertations
A set of numerical models is developed for simulating the four stages of barrier breaching characterized by one horizontal spatial dimension.
The SBEACH model is employed for the first stage of dune/beach erosion. The Lax-Wendroff two-step explicit scheme for Stage II is developed to simulate initiation of ocean flood propagation on initially dry barrier islands and the method of characteristics (MOC), is employed to compute additional boundary data. The development of the Preissmann implicit scheme for water motion and a forward time centered space explicit scheme for sediment motion in Stages III and IV provide a tool to study the …
Sensitivity Analysis And Optimization Of Aerodynamic Configurations With Blend Surfaces, Almuttil Mathew Thomas
Sensitivity Analysis And Optimization Of Aerodynamic Configurations With Blend Surfaces, Almuttil Mathew Thomas
Mechanical & Aerospace Engineering Theses & Dissertations
A novel (geometrical) parametrization procedure using solutions to a suitably chosen fourth order partial differential equation is used to define a class of airplane configurations. Inclusive in this definition are surface grids, volume grids, and grid sensitivity. The general airplane configuration has wing, fuselage, vertical tail and horizontal tail. The design variables are incorporated into the boundary conditions, and the solution is expressed as a Fourier series. The fuselage has circular cross section, and the radius is an algebraic function of four design parameters and an independent computational variable. Volume grids are obtained through an application of the Control Point …
Exact Solutions For Orthogonal And Non-Orthogonal Magnetohydrodynamic Stagnation-Point Flow, Shahrooz Moosavizadeh
Exact Solutions For Orthogonal And Non-Orthogonal Magnetohydrodynamic Stagnation-Point Flow, Shahrooz Moosavizadeh
Mathematics & Statistics Theses & Dissertations
The viscous plane flow of an electrically conducting fluid towards an infinite wall is solved in the presence of a magnetic field which is aligned with the flow far from the wall. The problem has two dimensionless parameters-- ε, the magnetic Prandtl number, and β, the square of the ratio of Alfven velocity to fluid velocity far from the wall. The problem has a similarity solution which reduces the governing equations to a system of coupled ordinary differential equations which can be solved numerically. For extreme values of ε, both large and small, singular perturbation techniques are used to derive …
Variational Methods In Sensitivity Analysis And Optimization For Aerodynamic Applications, Adem Ibrahim Hussen
Variational Methods In Sensitivity Analysis And Optimization For Aerodynamic Applications, Adem Ibrahim Hussen
Mechanical & Aerospace Engineering Theses & Dissertations
Variational methods (VM) sensitivity analysis, which is the continuous alternative to the discrete sensitivity analysis, is employed to derive the costate (adjoint) equations, the transversality conditions, and the functional sensitivity derivatives. In the derivation of the sensitivity equations, the variational methods use the generalized calculus of variations, in which the variable boundary is considered as the design function. The converged solution of the state equations together with the converged solution of the costate equations are integrated along the domain boundary to uniquely determine the functional sensitivity derivatives with respect to the design function.
The determination of the sensitivity derivatives of …
Unsteady, Transonic Flow Around Delta Wings Undergoing Coupled And Natural Modes Response: A Multidisciplinary Problem, Margaret Anne Menzies
Unsteady, Transonic Flow Around Delta Wings Undergoing Coupled And Natural Modes Response: A Multidisciplinary Problem, Margaret Anne Menzies
Mechanical & Aerospace Engineering Theses & Dissertations
The unsteady, three-dimensional Navier-Stokes equations coupled with the Euler equations of rigid-body dynamics are sequentially solved to simulate and analyze the aerodynamic response of a high angle of attack delta wing undergoing oscillatory motion. The governing equations of fluid flow and dynamics of the multidisciplinary problem are solved using a time-accurate solution of the laminar, unsteady, compressible, full Navier-Stokes equations with the implicit, upwind, Roe flux-difference splitting, finite-volume scheme and a four-state Runge-Kutta scheme, respectively. The primary model under consideration consists of a 65° swept, sharp-edged, cropped delta wing of zero thickness at 20° angle of attack. In a freestream …
Real Time Control Of Nonlinear Dynamic Systems Using Neuro-Fuzzy Controllers, Amitava Jana
Real Time Control Of Nonlinear Dynamic Systems Using Neuro-Fuzzy Controllers, Amitava Jana
Dissertations
The problem of real time control of a nonlinear dynamic system using intelligent control techniques is considered. The current trend is to incorporate neural networks and fuzzy logic into adaptive control strategies. The focus of this work is to investigate the current neuro-fuzzy approaches from literature and adapt them for a specific application. In order to achieve this objective, an experimental nonlinear dynamic system is considered. The motivation for this comes from the desire to solve practical problems and to create a test-bed which can be used to test various control strategies. The nonlinear dynamic system considered here is an …
Investigation Of Dynamic Friction In Lubricated Surfaces, Hanuman Rachoor
Investigation Of Dynamic Friction In Lubricated Surfaces, Hanuman Rachoor
Dissertations
The research reported in this dissertation is concerned with the development of friction models for lubricated contacts. A few analytical models have been developed to investigate the friction under dynamic velocity conditions. In this study, two different tribological situations such as conformal and non-conformal contacts have been chosen. Friction modeling covers boundary, mixed and full fluid film friction regions. A new theory based on the elastic properties of the surface materials, and fluid film properties of the lubricant at the contact has been developed to determine the dynamic friction in boundary, mixed and full hydrodynamic lubrication regions. In the full …
Design For Quality Manufacturability Analysis Of Total Nonconformity Damaged Parts, Samir R. Gami
Design For Quality Manufacturability Analysis Of Total Nonconformity Damaged Parts, Samir R. Gami
Theses
The competitive nature of modern manufacturing, demands that innovative approaches be applied in order to have a competitive edge. Shortening the product development cycle, the period from initial design to full production, is a priority for most manufacturers today. The DFQM methodology addresses the issue of quality manufacturability (QM) - the likelihood that defects will occur during manufacture of a product in a standard plant. As a consequence, DFQM helps to shorten the design cycle time. The DFQM architecture identifies a variety of design factors and variables that influence specific defects. This process of influencing defects can be described by …
Design And Analysis Of Environmentally Safe Cooling Systems For Machine Tools, Haiping Xu
Design And Analysis Of Environmentally Safe Cooling Systems For Machine Tools, Haiping Xu
Theses
Many cooling systems of metal cutting and both their advantages and disadvantages have been reviewed. The cutting forces' relationships, stress distribution, energy consumption and heat generation of orthogonal processes are discussed. A two-dimensional finite element model has been developed to design and analyze a new proposed cooling device, which comes from the idea of "A Novel Cooling Device" proposed by Billatos et al. First, a thermal calculation is completed to compare the temperature difference between two different shapes of coiled pipe. Then, three different cutting conditions, which were considered in the experiments by Childs et al, are conducted under three …
Implementation Of A Three-Dimensional Non-Intrusive Particle Tracking System, Vivek Gupta
Implementation Of A Three-Dimensional Non-Intrusive Particle Tracking System, Vivek Gupta
Theses
A Three-Dimensional Non-Intrusive Particle Tracking System has been developed at NJIT's Particle Technology Center to provide experimental results for validating theories being developed in the field of Particle Technology. The system utilizes the principle of magnetic induction between several high-frequency miniature transmitters mounted inside a sphere and a set of receiving loop antennae mounted outside the experimental apparatus. Basic theories and algorithms for the tracking system have already been developed. The focus of this thesis is to make the tracking system more accurate, reliable and user-friendly and to apply it to the study of vibrated beds and chute flows. Various …
Propagation Of Guided Acoustic Waves In Composite Media, Michael David Seale
Propagation Of Guided Acoustic Waves In Composite Media, Michael David Seale
Dissertations, Theses, and Masters Projects
Composite materials are being more widely used today by aerospace, automotive, and a number of other commercial industries because of their advantages over conventional metals. Composites are finding applications ranging from bicycle frames to the proposed High-Speed Civil Transport (HSCT). Determining the response to a variety of damage mechanisms is necessary for a complete understanding of the total use environment of composite structures. The objective of the research presented here is to provide a method of quantifying the amount of damage in composite materials for a number of different damage scenarios. Components which have non-visible damage, but have degraded performance, …
Gaseous Flux And Distribution Of Polycyclic Aromatic Hydrocarbons Across The Air-Water Interface Of Southern Chesapeake Bay, Kurt E. Gustafson
Gaseous Flux And Distribution Of Polycyclic Aromatic Hydrocarbons Across The Air-Water Interface Of Southern Chesapeake Bay, Kurt E. Gustafson
Dissertations, Theses, and Masters Projects
Gaseous fluxes of polycyclic aromatic hydrocarbons (PAHs) across the air-water interface of Southern Chesapeake Bay were calculated for the period January 1994 through May 1995 using a modified two-film model. Additionally, the distributions of PAHs between the vapor and aerosol phase in the atmosphere, and between the freely dissolved and suspended particulate phase in the water column were investigated. Net instantaneous gaseous fluxes of PAHs were determined to vary in direction and magnitude both spatially and temporally across the air-water interface of Southern Chesapeake Bay at four sites ranging from remote to urban and highly industrialized. The magnitude of gas …
An Investigation Of Diameter Measurement Repeatability Using A Coordinate Measuring Machine And A Multi-Baseline Repeatability Assessment Methodology, Bruce Marsh
Dissertations and Theses @ UNI
The need for reliable and consistent measurement has become more acute with the use of statistical process control (SPC), gage repeatability and reproducibility (Gage R&R) assessment, and high precision, computer-controlled gaging systems. Although it is often overlooked, the inspection methodology under which various features are inspected has an impact on Gage R&R results. This notion was confirmed when a 1993 thesis study substantiated inspection methodology as a source of measurement variability in direct computer-controlled, coordinate measuring machines (DCC/CMMs). Although this study explored a methodology to bring measurement variability under statistical control, the tested assessment methodology--single baseline repeatability assessment--was not validated. …
Plastic Fiber Rolling For Concrete Reinforcement, Jeffery S. Thomas
Plastic Fiber Rolling For Concrete Reinforcement, Jeffery S. Thomas
Masters Theses
"Fiber reinforced concrete is gaining in acceptance and usage as its strength and toughness benefits are realized. Polypropylene fibers are currently the most commonly used fibers. However, the cost of virgin plastics limits the percent content that can be economically added to concrete. One would first believe that recycled plastics could offer a viable alternative to virgin-plastic fibers, but at present time extra selection and cleaning steps required to reprocess the recycled plastic into fibers makes it more expensive than virgin-plastic fibers. A fiber rolling process conceived and developed at the University of Missouri-Rolla has the potential of making recycled …
Investigation Of Electrotribological And Arc Erosion Behavior Of Cu-15vol.%Cr In Situ Composite, Zhongyu Chen
Investigation Of Electrotribological And Arc Erosion Behavior Of Cu-15vol.%Cr In Situ Composite, Zhongyu Chen
Masters Theses
Electrotribological and arc erosion behavior of Cu-15vol.%Cr in situ composite was investigated in terms of coefficient of friction, interfacial resistance, bulk temperature, and wear rate as a function of normal pressure, sliding speed, and electrical current. Microstructural change due to electrical sliding was studied to understand wear mechanisms. Cu-15vol.%Cr in situ composite was selected in this research because it exhibits an excellent combination of mechanical strength and electrical/thermal conductivity.
It was found that the average coefficient of friction decreased with increasing electrical current under dry electrical sliding. The average coefficient of friction was lower under lubricated electrical sliding than that …
Application Of Reanalysis Techniques For Pattern Design Of Spot Welds, Young San Kim
Application Of Reanalysis Techniques For Pattern Design Of Spot Welds, Young San Kim
Mechanical & Aerospace Engineering Theses & Dissertations
Extensive benchmarking on competitive cars has shown that the durability of vehicles, assembly-induced variations, and assembly cost are directly related to the quality and number of spot welds. On most luxury cars, approximately 4,500 to 5,000 spot welds are found. On less expensive cars, the range is from 3,500 to 4,500. These cars usually inherit more noise, rattles, squeaks, and other quality-related problems. These problems have motivated the search for a new capability to systematically place welds in the most critical areas, with a minimum number of welds for car bodies, while satisfying all performance requirements (e.g., stiffness, stress distribution, …
Numerical Simulation Of Complex, Three-Dimensional, Turbulent-Free Jets, Robert V. Wilson
Numerical Simulation Of Complex, Three-Dimensional, Turbulent-Free Jets, Robert V. Wilson
Mechanical & Aerospace Engineering Theses & Dissertations
Three-dimensional, incompressible turbulent jets with rectangular and elliptical cross-section are simulated with a finite-difference numerical method. The full Navier-Stokes equations are solved at low Reynoids numbers, whereas at high Reynolds numbers filtered forms of the equations are solved along with a sub-grid scale model to approximate the effects of the unresolved scales. A 2-N storage, third-order Runge-Kutta scheme is used for temporal discretization and a fourth-order compact scheme is used for spatial discretization. Although such methods are widely used in the simulation of compressible flows, the lack of an evolution equation for pressure or density presents particular difficulty in incompressible …
The Modeling Of Structural-Acoustic Interaction Using Coupled Fe/Be Method And Control Of Interior Acoustic Pressure Using Piezoelectric Actuators, Yucheng Shi
Mechanical & Aerospace Engineering Theses & Dissertations
A coupled finite element (FE) and boundary element (BE) approach is presented to model full coupled structural/acoustic/piezoelectric systems. The dual reciprocity boundary element method is used so that the natural frequencies and mode shapes of the coupled system can be obtained, and to extend this approach to time dependent problems. The boundary element method is applied to interior acoustic domains, and the results are very accurate when compared with limited exact solutions. Structural--acoustic problems are then analyzed with the coupled finite element/boundary element method, where the finite element method models the structural domain and the boundary element method models the …