Engineering Commons^™

Laminar-Turbulent Transition For Attached And Separated Flow, Qian Zhang

University of Kentucky Doctoral Dissertations

A major challenge in the design of turbomachinery components for aircraft gas turbine engines is high cycle fatigue failures due to flutter. Of particular concern is the subsonic/transonic stall flutter boundary which occurs at part speed near the stall line. At these operating conditions the incidence angle is large and the relative Mach number is high subsonic or transonic. Viscous effects dominate for high incidence angles.

In order to predict the flutter phenomena, accurate calculation of the steady and unsteady aerodynamic loading on the turbomachinery airfoils is necessary. The development of unsteady aerodynamic models to predict the unsteady forces and …

Engineering Sport Safety: A Study Of Equestrian Cross Country Eventing, Katherine M. Kahmann

University of Kentucky Master's Theses

The sport of equestrian cross country eventing has seen many serious and even fatal injuries due to rotational horse falls in recent years. The sport originally consisted of horse and rider teams jumping stationary, wood fences. However, in a move towards increasing safety for horses and riders, frangible and deformable safety devices have been emerging in the field. This thesis provides an overview of safety designs that are currently available and those that are on the horizon. Also, a path-finder method of evaluating and developing safety fence designs was outlined and applied to two distinct designs, a hinged gate and …

Sustainable Resource Utilization In Manufacturing Of Printed Circuit Board Assembly: Exergy Analysis Of The Process, Subramaniam Saiganesh

University of Kentucky Master's Theses

Engineering for sustainable development requires prudent utilization of resources under economic, environmental and societal constraints. Resource utilization must follow a holistic approach. This brings in a need for comprehensive metrics which are simple, standard and universal. Thermodynamics may offer a metric that focuses on both quality and quantity of energy resources which may carry information to be combined with other metrics. This metric may be a thermodynamic property called exergy or available energy, which provides a better insight into resource use in both energy and non-energy producing systems. This thesis is devoted to a study of the exergy concept in …

Solid Oxide Fuel Cell Electrode Characterization And Improvement For Fuel Flexibility And Supplemental Power Production, Isaiah D. Kellogg

Doctoral Dissertations

"Solid oxide fuel cells (SOFC) were fabricated and the electrodes tested for their individual catalytic effectiveness in various fuels by exposing each electrode to mixed gas while the opposite electrode was exposed to its respective pure gas. Mixed hydrogen and oxygen gas was successfully utilized as fuel in a single chamber SOFC (SC-SOFC). The conditions at which the porous nickel-yttria-stabilized zirconia (Ni-YSZ) cermet anode performed well did not significantly overlap the conditions at which the La₀.₈Sr₀.₂Fe₀.₈Co₀.₂ oxide (LSCF) cathode performed well, but there was significant catalytic activity at both electrodes which increased the open circuit voltage (OCV) beyond that predicted …

Analysis Of Laminated Architectural Glazing Subjected To Combined Wind And Debris Impact Loading, Mahesh Shibarooru Shetty

Doctoral Dissertations

"Laminated glazing has been a popular form of window glazing in recent years and is found to be effective during extreme weather conditions like hurricane. Laminated glass is composed of two glass layers with a polymer as an interlayer. The main objective of this work involves studying the stress response, failure and damage analysis of rectangular laminated architectural glazing against combined wind and windborne debris impact. Here both small-hard (like roof gravel) and large-soft (like timber) windborne debris are considered. The stress response of the rectangular laminated architectural glazing was modeled using the finite element code ABAQUS. The effect of …

Implementation Of Integrated Function Structure And Object-Oriented Design Framework, Qiong Gao

Masters Theses

"The function structure method is commonly used in mechanical product design. Although a function structure allows defining all the functions of the components of a product and their interactions, it does not have an effective architecture for the software design of a mechatronic product. An integrated function structure and object-oriented design framework was recently developed to overcome this disadvantage. In this thesis, the implementation of this framework to design several products in different categories, including an inkjet printer, and electric screwdriver and a vacuum cleaner, is discussed. The design results obtained using the new framework are compared to the design …

Enhancement Of Single-Lap Joint Strength Under Tension Using Piezoelectric Actuation, Ryan Michael Meyer

LSU Master's Theses

Composite adhesively bonded joint structures have seen increased use over conventional riveted due to their ease of manufacturing and quality strength-to-weight ratios. However, adhesively bonded joints lack the rigidity and failure strength of riveted assemblies, due to high stress concentrations which develop in the adhesive layer, which makes them prone to undesirable deformation and failure. Piezoelectric materials feature the ability to produce mechanical strain when subjected to an applied voltage and vice-versa. Therefore, it is proposed to use piezoelectric actuators to transmit counterbalancing forces to increase the rigidity and strength of composite joints. Existing studies have been limited in that …

A Portable Phonatory Feedback Device For Patients With Speech Disorders, Richie Sajan

LSU Master's Theses

Vocal intensity-related speech disorders such as dysarthria and vocal nodules can limit quality of life and reduce the patient’s ability to interact with family, socialize, or pursue employment. Behavioral speech therapies exist to address these issues but have limited effectiveness because they are expensive and clinic-based. The ability to monitor vocal intensity outside of the clinical setting will greatly aid in the treatment of these speech disorders, enabling patients to make quicker progress by reinforcing techniques learned in the clinic. The Voice Volume Monitor (VVM) is a portable and cost-effective therapeutic aid designed for this purpose, providing real-time feedback regarding …

Molecular Simulation Of The Infrared Absorption Cross Section And Thermophysical Properties Of A Polyatomic Fluid, Zhi Liang

Doctoral Dissertations

"The work presented in this dissertation aims at ab initio calculations of the infrared absorption cross section, heat capacity, self-diffusion coefficient, shear viscosity and thermal conductivity of a polyatomic fluid with the aid of statistical mechanics. The simulation is firstly focused on calculating single-molecule properties such as molecular structure, vibrational energy eigen values and transition dipole moments using an efficient method based on the density functional theory. Based on these ab initio results, the infrared absorption cross sections are determined by the Fermi's Golden rule, and the thermophysical properties are determined from molecular dynamics simulations. Using carbon dioxide as an …

Experimental And Computational Investigations Of Hydrogen Safety, Dispersion And Combustion For Transportation Applications, Shravan K. Vudumu

Doctoral Dissertations

"Hydrogen is an energy carrier that can be produced from a variety of sources, offering one of the viable solutions to the increasing demands for clean and sustainable energy. Compared to the conventional fuels, hydrogen has distinct properties that need to be properly accounted for during its safer storage and delivery as well as more efficient and cleaner utilization. The broader objective of this study is to contribute to the scientific knowledge necessary to overcome key technical barriers to the widespread implementation of hydrogen in transportation applications. Specifically, lower flammability limit of hydrogen is first measured with an enhanced experimental …

Effects Of Optimized And Sub-Optimum Two Degree Of Freedom Lining Tolerances On Modeled Inlet Acoustic Attenuation And Normal Incidence Impedance Measurement At Elevated Temperatures, David R. Burd

Doctoral Dissertations

"This work first investigates the effect of manufacturing tolerances on realized attenuation for two degree-of-freedom linings with the use of lining models and finite element duct propagation codes. Acoustic linings were created for two turbofan engines that optimize attenuation at takeoff/sideline and approach conditions. Lining physical and geometric parameters were set, which best meet the optimum impedance requirements at two target frequencies. Similar linings were created to investigate sub-optimum designs. Variations of these parameters representing realistic manufacturing tolerances were used to systematically examine the effect on installed impedance and predicted attenuation. Attenuation at sideline and approach conditions was found to …

100nm Thick Aluminum Nitride Based Piezoelectric Nano Switches Exhibiting 1mv Threshold Voltage Via Body-Biasing, Nipun Sinha, Zhijun Guo, Valeriy Felmetsger, Gianluca Piazza

Nipun Sinha

This paper reports on the first demonstration of aluminum nitride (AlN) piezoelectric logic switches that were fabricated with ultra-thin (100nm) AlN films and exhibit a 1 mV threshold voltage via the body-biasing scheme. The application of a relatively low (< 6 V) fixed potential to the body terminal of a 4-terminal switch has resulted in a repeatable threshold voltage of 1 mV. The nano-switch has been cycled to > 109 cycles and, although the contact resistance was found to be high (~ 1 MΩ), the nano-films have functioned throughout to show high piezoelectric nano-film reliability.

Super-High-Frequency Two-Port Aln Contour-Mode Resonators For Rf Applications, Matteo Rinaldi, Chiara Zuniga, Chengjie Zuo, Gianluca Piazza

Matteo Rinaldi

This paper reports on the design and experimental verification of a new class of thin-film (250 nm) super-high-frequency laterally-vibrating piezoelectric microelectromechanical (MEMS) resonators suitable for the fabrication of narrow-band MEMS filters operating at frequencies above 3 GHz. The device dimensions have been opportunely scaled both in the lateral and vertical dimensions to excite a contour-extensional mode of vibration in nanofeatures of an ultra-thin (250 nm) AlN film. In this first demonstration, 2-port resonators vibrating up to 4.5 GHz have been fabricated on the same die and attained electromechanical coupling, kt2, in excess of 1.5%. These devices are employed to synthesize …

Demonstration Of Low Voltage And Functionally Complete Logic Operations Using Body-Biased Complementary And Ultra-Thin Aln Piezoelectric Mechanical Switches, Nipun Sinha, Timothy S. Jones, Zhijun Guo, Gianluca Piazza

Nipun Sinha

This paper reports, for the first time, on the demonstration of low voltage and functionally complete logic elements (NAND and NOR) implemented by using body-biased complementary and ultra-thin (250 nm thick) Aluminum Nitride (AlN) based piezoelectric mechanical switches. This work presents, firstly, the importance of scaling AlN films for the demonstration of ultra-thin AlN switches and, secondly, the implementation of a new actuation scheme based on body biasing to lower the switch threshold voltage. Four of these ultra-thin switches were connected together to synthesize functionally complete MEMS logic gates (NAND and NOR) with a ± 2V swing and a body-bias …

Pricing Residential Water To Account For Scarcity In Cyprus, Theodoros Zachariadis

Theodoros Zachariadis

No abstract provided.