Mechanical Engineering Commons^™

Supramolecular Nanolayer Reconfiguration After Molecular Intercalation, Alexandre Dhôtel, Hui Li, Lucia Fernandez-Ballester, Laurent Delbreilh, Boulos Youssef, Xiao Cheng Zeng, Li Tan

Department of Engineering Mechanics: Faculty Publications

We examined the structural reconfiguration after intercalating foreign additives, that is, tetramethoxysilane (TMOS), within already formed supramolecular nanolayers of hexadecyltrimethoxysilane (HDTMS). Our experiments indicated that the newly formed interdigitated structure is a thermodynamically more stable configuration. Even after the HDTMS formed initial bilayer-by-bilayer structures, mixing of these aggregates with foreign additives at room temperature can change the original structure to a more compact configuration (i.e., interdigitated). Our MD simulations further revealed that the most favorable organization for this interdigitated stacking appears to be a formation of relatively small domains of HDTMS and TMOS molecules, supporting our proposal of a heterogeneous …

Analysis Of A Monolithic Crystal Plate Acoustic Wave Filter, Huijing He

Department of Mechanical and Materials Engineering: Faculty Publications

We study thickness–shear and thickness–twist vibrations of a finite, monolithic, AT-cut quartz plate crystal filter with two pairs of electrodes. The equations of anisotropic elasticity are used with the omission of the small elastic constant c56 . An analytical solution is obtained using Fourier series from which the res-onant frequencies, mode shapes, and the vibration confinement due to the electrode inertia are calculated and examined.

Heat Transfer Through A Rotating Ball Bearing At Low Angular Velocities, Sarah Isert

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

Bearings are commonly used in mechanical systems when there are rotating parts in the system. For bearings that run at speeds above about 1000 revolutions per minute, such as those used in aircraft turbines, machining tools, and automotive engines, it is important to take into account the heat transfer through the bearing system due to friction. Heat transfer is generally not considered for applications where the bearing is rotating at low speeds, such as clocks and bicycles. However, for certain aerospace applications, such as precision instruments or wind turbines, the heat transfer through the bearing becomes relevant. The case where …

Computational Study Of Passive Neutron Albedo Reactivity (Pnar) Measurement With Fission Chambers, Sandra De La Cruz

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Passive Neutron Albedo Reactivity technique (PNAR) was used to assay used nuclear fuel as a potential method for the measurement of fissionable material in fuel assemblies. A Monte Carlo transport code (MCNPX 2.6) was used to develop simulation models to evaluate the PNAR technique. The MCNPX simulated models consisted of two 17x17 Pressurized Water Reactor (PWR) used fuel assemblies; one with an initial 3 wt% uranium-235*, cooled for 20 years and second with an initial 4 wt% uranium-235*, cooled for 5 years. Each used fuel assembly was simulated at four different burn up rates of 15, 30, 45, and …

Characteristics Of Combustion Flame Sprayed Nickel Aluminum Using A Coanda Assisted Spray Manipulation Collar For Off-Normal Deposits, Reid S. Archibald

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A novel flame spray collar called the Coanda Assisted Spray Manipulation collar (CSM) has been tested for use on the Sulzer Metco 5P II combustion flame spray gun. A comparison study of the stock nozzle and the CSM has been performed by evaluating the porosity, surface roughness, microhardness, tensile strength and microscopy of normal and off-normal sprayed NiAl deposits. The use of the CSM collar resulted in the need to position the sprayed coupons closer to the gun, which in turn affected the particle impact energy and particle temperatures of the NiAl powder. For the CSM, porosities had a larger …

Investigation Of The Design And Static Behavior Of Cylindrical Tubular Composite Adhesive Joints Utilizing The Finite Element Method And Stress-Based Failure Theories, Michael D. Lambert

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The stress and strength behavior of cylindrical tubular adhesive joints composed of dissimilar materials was explored. This was accomplished with the finite element method (FEM) and stress-based failure theories. Also, it was shown how a design of experiments (DOE) based method can be used to objectively organize the process of optimizing joint strength by using stress-based failure criteria.

The finite element program used in this work was written in-house from scratch to implement the FEM for the purpose of solving both axisymmetric and three-dimensional linear elastic governing equations of static equilibrium. The formulation of the three-dimensional model is presented, and …

Automatic Particle Image Velocimetry Uncertainty Quantification, Benjamin H. Timmins

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The uncertainty of any measurement is the interval in which one believes the actual error lies. Particle Image Velocimetry (PIV) measurement error depends on the PIV algorithm used, a wide range of user inputs, flow characteristics, and the experimental setup. Since these factors vary in time and space, they lead to nonuniform error throughout the flow field. As such, a universal PIV uncertainty estimate is not adequate and can be misleading. This is of particular interest when PIV data are used for comparison with computational or experimental data.

A method to estimate the uncertainty due to the PIV calculation of …

Turbulence Modeling Of Strongly Heated Internal Pipe Flow Using Large Eddy Simulation, Michal Hradisky

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The main objective of this study was to evaluate the performance of three Large Eddy Simulation (LES) subgrid scale (SGS) models on a strongly heated, low Mach number upward gas flow in a vertical pipe with forced convection. The models chosen for this study were the Smagorinsky-Lilly Dynamic model (SLD), the Kinetic Energy Transport model (KET), and the Wall-Adaptive Local-Eddy viscosity model (WALE). The used heating rate was sufficiently large to cause properties to vary significantly in both the radial and streamwise directions. All simulations were carried out using the commercial software FLUENT.

The effect of inlet turbulence generation techniques …

Peripheral Soldering Of Flip Chip Joints On Passive Rfid Tags, Md Syful Islam

UNLV Theses, Dissertations, Professional Papers, and Capstones

Flip chip is the main component of a RFID tag. It is used in billions each year in electronic packaging industries because of its small size, high performance and reliability as well as low cost. They are used in microprocessors, cell phones, watches and automobiles. RFID tags are applied to or incorporated into a product, animal, or person for identification and tracking using radio waves. Some tags can be read from several meters away or even beyond the line of sight of the reader. Passive RFID tags are the most common type in use that employ external power source to …

Requirements Determination Of A Novel Non-Pneumatic Wheel Shear Beam For Low Rolling Resistance, Niranjan Thyagaraja

All Theses

The hysteretic loss associated with cyclic shear in the elastomeric shear layer is one of the prevailing concerns for the development of a low rolling loss non-pneumatic wheel. We propose to eliminate the hysteretic losses associated with the elastomeric shear layer and thus, reduce the corresponding rolling resistance by using linear elastic materials which are inherently non-hysteretic. Since the shear modulus of a viscoelastic shear layer is less than that of an elastic material by several orders of magnitude, the challenge to achieve a low effective shear modulus shear layer with linear elastic materials directs towards the development of a …

Agent-Based Under Hood Packing, Karthik Ravindranath

All Theses

Improving vehicle performance and passenger comfort has been a prime engineering concern and focus of research for many years in automotive design. Turning to high-performance components in an effort to improve vehicle performance alone is often not enough and their placement and interactions with other components should also be an integral part of the improvement process. With the advancement in hybrid electric vehicle technology, the packing of components under the hood is ever more essential and challenging. Under hood packing is a multi-objective optimization problem with many, and mostly conflicting objectives. A non-deterministic multi-objective evolutionary algorithm needs to be integrated …

Evaluation Of Biomass And Coal Briquettes For A Spreader Stoker Boiler Using An Experimental Furnace - Modeling And Test, Gavin Wiggins

All Theses

The compliance of coal-fired boilers with emissions regulations is a concern for many facilities. The introduction of biomass briquettes in industrial boilers can help to reduce greenhouse gas emissions and coal usage. In this research project, a thermodynamic chemical equilibrium model was derived and analytical simulations performed for a coal boiler system for several types of biomass fuels such as beech, hickory, maple, poplar, white oak, willow, sawdust, torrefied willow, and switchgrass. The biomass emissions were compared to coal and charcoal emissions. The chemical equilibrium analysis numerically estimated the emissions of CO, CO2, NO, NO2, N2O, SO2, and SO3. When …

Implementation Of Delayed-Feedback Controllers On Continuous Systems And Analysis Of Their Response Under Primary Resonance Excitations, Yousef Qaroush

All Dissertations

During the last three decades, a considerable amount of research has been directed toward understanding the influence of time delays on the stability and stabilization
of dynamical systems. From a control perspective, these delays can either have a compounding and destabilizing effect, or can actually improve controllers'
performance. In the latter case, additional time delay is carefully and deliberately introduced into the feedback loop so as to augment inherent system delays and
produce larger damping for smaller control efforts. While delayed-feedback algorithms have been successfully implemented on discrete dynamical systems with
limited degrees of freedom, a critical issue appears in …

A Methodology For The Analysis Of In-Vehicle Operating Data And Design Of Intelligent Vehicle Systems For Improved Automotive Safety, Matthew Jensen

All Dissertations

Every year global motorization increases as more motor vehicles are manufactured, and the total number of vehicle miles traveled rises. These increased travel opportunities result in higher numbers of injuries, fatalities, and monetary losses associated with traffic-related crashes. In the last decade, hundreds of thousands of people were killed by vehicle collisions in the United States. The World Health Organization has labeled traffic crashes as the ninth leading cause of global disease; by the year 2020, traffic crashes are expected to rise to number three. An opportunity exists to improve global human safety through research and innovation in driver training …

High Resolution Vision-Based Servomechanism Using A Dynamic Target With Application To Cnc Machines, Carlos Montes-Solano

All Dissertations

This dissertation introduces a novel three dimensional vision-based servomechanism with application to real time position control for manufacturing equipment, such as Computer Numerical Control (CNC) machine tools. The proposed system directly observes the multi-dimensional position of a point on the moving tool relative to a fixed ground, thus bypassing the inaccurate kinematic model normally used to convert axis sensor-readings into an estimate of the tool position.

A charge-coupled device (CCD camera) is used as the position transducer, which directly measures the current position error of the tool referenced to an absolute coordinate system. Due to the direct-sensing nature of the …

Aerodynamic Thrust Vectoring For Attitude Control Of A Vertically Thrusting Jet Engine, M. Ryan Schaefermeyer

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

NASA’s long range vision for space exploration includes human and robotic missions to extraterrestrial bodies including the moon, asteroids and the martian surface. All feasible extraterrestrial landing sites in the solar system are smaller and have gravitational fields of lesser strength than Earth’s gravity field. Thus, a need exists for evaluating autonomous and human-piloted landing techniques in these reduced-gravity situations. A small-scale, free-flying, reduced-gravity simulation vehicle was designed by a group of senior mechanical engineering students with the help of faculty and graduate student advisors at Utah State University during the 2009-2010 academic year. The design reproduces many of the …

Synthesis And Characterization Of Poly(Butylene Oxide) Grafted Carbon Nanofibers, Carlos Ramos, Ram Thapa, Karen Lozano, Mircea Chipara, Domingo Ferrer, Jose J. Gutierrez

Mechanical Engineering Faculty Publications

The grafting of polybutylene oxide onto purified and functionalized carbon nanofibers is reported. Grafting was possible after the insertion of 2-(formyloxy)ethyl 2-bromo-2-methylpropanoate onto the carbon nanofibers. The polymerization of tetrahydrofuran was mediated by copper(I) bromide and 1,1,4,7-pentamethyl diethylenetriamine. The polymer-grafted carbon nanofibers were characterized by Raman spectrsocopy, Transmission Electron Microscopy, and Thermogravimetric Analysis. TEM images of CNF-COOH (A), CNF-PBO (B), completely open tip of CNF-COOH, and coated tip of CNF-PBO (D) are shown in the left panel. The right panel depicts the distribution of bromine (blue), and carbon (red) atoms inside and in the vicinity of CNF-Br (as obtained by …

Anisotropic Compressive Pressure-Dependent Effective Thermal Conductivity Of Granular Beds, R. Daniel Garrett

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

In situ planetary effective thermal conductivity measurements are typically made using a long needle-like probe, which measures effective thermal conductivity in the probe's radial (horizontal) direction. The desired effective vertical thermal conductivity for heat flow calculations is assumed to be the same as the measured effective horizontal thermal conductivity. However, it is known that effective thermal conductivity increases with increasing compressive pressure on granular beds and horizontal stress in a granular bed under gravity is related to the vertical stress through Jaky's at-rest earth pressure coefficient. No research has been performed previously on determining the anisotropic effective thermal conductivity of …

Coanda-Assisted Spray Manipulation Implementation To Plasma Spray, Katie E. Mabey

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Co and a-assisted Spray Manipulation (CSM) is a means of modifying the direction of a jet. Previous isothermal static vectoring research is expanded to plasma spray. Two- dimensional Particle Image Velocimetry (PIV) was used to determine the vectoring results for small angles between 5-10°. Suitable parameters were determined for use on a plasma spray gun for small angle vectoring. Three-dimensional PIV was used to determine the elect of high speed rotation on a vectored jet. A 2-piece CSM collar was retrofitted to a Praxair SG-100 plasma spray gun that replaced the standard faceplate. Two separate collars were tested: one designed …

Evaluation Of The Aerodynamic Differences Of A Balloon Shape And A Sphere Using Computational Fluid Dynamic Modeling In Fluent, Daniel Burton Scholes

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

While tracking balloons for wind characterization, there was a question about the theoretical rise rate and corresponding coefficient of drag of a balloon shape as compared to a sphere. Since there are many studies published detailing the drag on spherical shapes, the question of whether or not a balloon can be treated as a sphere begged to be answered.

In this study we apply Computational Fluid Dynamic (CFD) modeling to compare the aerodynamic behavior and drag of a sphere to that of a balloon as it moves through fluid at Reynolds numbers from 10,000 to 100,000.

Fluent CFD models are …