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## Full-Text Articles in Engineering

#### Surface And Sub-Surface Ablation Cell Design For Remote (Robotic) Radioactive Soil Analysis Using Laser Ablation-Inductively Coupled-Atomic Emission Spectrometry/Mass Spectrometry La-Icp-Aes/Ms , Reza Bashirzadeh

*Retrospective Theses and Dissertations*

There are approximately 1800 uncontrollable hazardous waste sites across the United States. The Department of Energy (DOE) is responsible for cleaning up several of these sites that were contaminated as a result of producing weapon-grade nuclear fuels in different states since the 1940s. Site characterization is the first and a very critical step in the remediation program of a radioactive contaminated site. During this process, all the necessary information about location, level, and chemical composition of the contaminated sites must be collected for the clean up planning. Ames Laboratory, one of the U.S. Department of Energy sites, has adopted ...

Unstructured Grid Algorithms For Two- And Three-Dimensional Flows On Parallel Computers , Thomas Hans Ramin

#### Unstructured Grid Algorithms For Two- And Three-Dimensional Flows On Parallel Computers , Thomas Hans Ramin

*Retrospective Theses and Dissertations*

The Navier-Stokes equations are solved numerically for two-and three-dimensional viscous laminar flows. The domain is discretized using triangular control volumes in two dimensions and tetrahedra in three dimensions, using existing grid generators. The flow solvers are implemented on a variety of computers, including distributed memory parallel computers;A finite-volume approach is used to discretize the governing flow equations in conservation law form using conserved variables. A cell centered approach is used where the unknowns are computed at the center of each control volume. Both explicit and implicit solution strategies are pursued. In the two-dimensional version of the algorithm an explicit ...

Unstructured Surface And Volume Decimation Of Tessellated Domains , Kevin Joseph Renze

#### Unstructured Surface And Volume Decimation Of Tessellated Domains , Kevin Joseph Renze

*Retrospective Theses and Dissertations*

A general algorithm for decimating unstructured discretized data sets is presented. The discretized space may be a planar triangulation, a general 3D surface triangulation, or a 3D tetrahedrization. The decimation algorithm enforces Dirichlet boundary conditions, uses only existing vertices, and assumes manifold geometry. Local dynamic vertex removal is performed without history information while preserving the initial topology and boundary geometry. The tessellation at each step of the algorithm is preserved and, in the pathological case, every interior vertex is a candidate for removal. The research focuses on how to remove a vertex from an existing unstructured n-dimensional tessellation, not on ...

A Compliant Model For Estimation And Optimization Of Damping In Vibrating Structures , Thomas Jeffrey Thompson

#### A Compliant Model For Estimation And Optimization Of Damping In Vibrating Structures , Thomas Jeffrey Thompson

*Retrospective Theses and Dissertations*

Proposed future space missions involve large structures which must maintain precise dimensional tolerances even during dynamic maneuvers. In order to attenuate disturbances in the many modes of vibration of such a structure, active and passive vibration control are proposed. The passive control is to be achieved by placing viscous or viscoelastic members or materials within a structure in order to absorb energy. Ascertaining the best combination of locations for such treatments is difficult due to the large number of cases, each of which requires computationally expensive complex eigenvalue analyses of a finite element model to compute modal damping values;In ...

Bubble And Elutriation Control In Fluidized Beds With Electric Fields , Jiun-Shen Wang

#### Bubble And Elutriation Control In Fluidized Beds With Electric Fields , Jiun-Shen Wang

*Retrospective Theses and Dissertations*

The mechanisms for controlling elutriation and bubbling effect in a fluidized bed are largely unexplored. Increased understanding of these hydrodynamic effects will help to improve both fluidized bed design and operation;In the present study, an electric field was used as an independent parameter to control the formation of bubbles and the elutriation of fines in a fluidized bed. Various forces which acted on the particles were compared. It was concluded that both the current constriction force and hydrodynamic force dominated the behavior of the bed;The bed expansion increased as much as 15% of the bed height at the ...

Dynamic Balance And Walking Control Of Biped Mechanisms , James J. Troy

#### Dynamic Balance And Walking Control Of Biped Mechanisms , James J. Troy

*Retrospective Theses and Dissertations*

The research presented here focuses on the development of a feedback control systems for locomotion of two and three dimensional, dynamically balanced, biped mechanisms. The main areas to be discussed are: development of equations of motion for multibody systems, balancing control, walking cycle generation, and interactive computer graphics. Additional topics include: optimization, interface devices, manual control methods, and ground contact force generation;Planar (2D) and spatial (3D) multibody system models are developed in this thesis to handle all allowable ground support conditions without system reconfiguration. All models consist of lower body segments only; head and arm segments are not included ...

Ultrasonic Measurement Of Drawability (R-Values) Of Low Carbon Steel Sheets , Kaveh Forouraghi

#### Ultrasonic Measurement Of Drawability (R-Values) Of Low Carbon Steel Sheets , Kaveh Forouraghi

*Retrospective Theses and Dissertations*

The present research was designed to evaluate an ultrasonic technique for measuring the drawability of low carbon steel sheets nondestructively. This technique, which uses electro magnetic acoustic transducers (EMAT's) is embodied in a fully automatic ultrasonic device called Ultra-Form, which was developed by Iowa State University in 1990. EMAT transducers generate the ultrasonic pulses in the sheet (without any need for a coupling medium) whose velocities are then related to the microstructural factors (crystallographic texture) that control drawability in rolled sheets. Drawability (usually interpreted by measuring r-values of low carbon steels) is an important property indicative of the formability ...

Numerical Modeling Of Reactive Gas Assisted Laser Cutting Of Metals , Chin Kooi Lim

#### Numerical Modeling Of Reactive Gas Assisted Laser Cutting Of Metals , Chin Kooi Lim

*Retrospective Theses and Dissertations*

A two-dimensional finite difference model for reactive gas assisted laser cutting of metals is presented. The effects due to heat transfer and fluid dynamics are taken into consideration in the present model by simultaneously solving the conservation equations in the molten metal and gas jet regions. The solutions in the two regions are coupled at the erosion front where a free surface model is assumed. The erosion front is allowed to deform so that laser-material coupling can be determined based on the local incident angle. Oxidation reactions are considered only at the erosion front and the heat flux due to ...

An Investigation Of The Mechanics Of Rollover For Cars And Light Trucks , Yvonne Irene Katherine Lund

#### An Investigation Of The Mechanics Of Rollover For Cars And Light Trucks , Yvonne Irene Katherine Lund

*Retrospective Theses and Dissertations*

Rollover of cars and light trucks in single vehicle accidents is of great interest to designers in the automotive industry and to regulators in government agencies. This thesis addresses metrics--the static stability factor, the tilt table ratio, the side pull test, and the critical sliding velocity--which are proposed measures of vehicle resistance to rollover;A notable finding is that the critical sliding velocity, CSV, is independent of the vehicle mass and roll moment of inertia and depends only on the track width and center of gravity height. Furthermore, while side pull testing and tilt table testing are mainly dependent on ...

Laser Machining And Its Thermal Effects On Silicon Nitride And Steel , Aloke K. Ray

#### Laser Machining And Its Thermal Effects On Silicon Nitride And Steel , Aloke K. Ray

*Retrospective Theses and Dissertations*

An investigation was undertaken to examine the physical and thermal processes involved in laser machining of ceramics and metals. Two types laser machining viz. milling and cutting were studied. The objective is to provide a better understanding of laser machining that in turn facilitate achieving tighter tolerances, excellent surface integrity and improved properties of the parts;A 1500 W continuous wave CO2 laser was used for this purpose to groove and mill reaction bonded silicon nitride (RBSN) and hot-isostically pressed silicon nitride (HIPSN). Experimental results showed that the material removal mechanism was essentially chemical decomposition at 2150 K leading to ...

Propagation Of Uncertainty In A Knowledge-Based System To Assess Energy Management Strategies For New Technologies , Chun-Yen Hsu

#### Propagation Of Uncertainty In A Knowledge-Based System To Assess Energy Management Strategies For New Technologies , Chun-Yen Hsu

*Retrospective Theses and Dissertations*

The goal of this project is to investigate the propagation of uncertainty in a knowledge-based system that assesses energy management strategies for new gas and electric technologies that can help reduce energy consumption and demand. The new technologies that have been investigated include lighting, electric heat pumps, motors, refrigerators, microwave clothes dryers, freeze concentration, electric vehicles, gas furnaces, gas heat pumps, engine-driven chillers, absorption chillers, and natural gas vehicles distributed throughout the residential, commercial, industrial, and transportation sectors;The description of a complex assessment system may be simplified by allowing some degree of uncertainty. A number of uncertainty-representing mechanisms, such ...