Mechanical Engineering Commons^™

Nanoporous Bi2te3 Thermoelectric Based Knudsen Gas Pump., Abderrazzak Faiz

Electronic Theses and Dissertations

This dissertation reports on the fabrication of a bi-directional Knudsen gas pump using a multifunctional nanoporous thermoelectric material. The integration of the channels into the thermoelectric material has the advantages of reducing heat losses and power consumption, improving the pump efficiency, and reducing the overall pump size. The Knudsen pump operates on the thermal transpiration principle, the phenomenon that gas molecules drift from the cold end to the hot end of a narrow channel. The gas pumping is realized in the transition or free molecular regime. The Knudsen pump is needed in a great number of applications such as gas …

Photomechanical Actuation Of Liquid Crystal Nanotube Elastomers., Xiaoming Fan

Electronic Theses and Dissertations

Elastomeric composites based on nanotube liquid crystals (LCs) that preserve the internal orientation of nanotubes could lead to anisotropic physical properties and flexible energy conversion. Using simple vacuum filtration technique of fabricating nanotube LCs films and utilizing a transfer process to poly (dimethyl) siloxane wherein the LCs arrangement is preserved, in this thesis we demonstrate unique and reversible photomechanical response of this layered composite to excitation by near infra-red (NIR) light at ultra-low nanotube mass fractions. Schlieren textures were noted in these LCs composites confirming long range macroscopic nematic order of nanotubes within the composites. Maximum photomechanical stress of ~23kPa, …

Cost Effectiveness Of 2015 Iecc Compliance Using The Hers Index, Florida Solar Energy Center, Philip W. Fairey

FSEC Energy Research Center®

The EnergyGauge HERS software tool is used to examine the 2012 IECC Standard Reference Design (IECC SRD) configuration for three-bedroom, one-story 2000 ft² and three-bedroom, two-story 2,400 ft² single-family homes in sixteen representative U.S. cities. The energy use of the 2012 SRD homes is compared against the energy use of homes complying with the 2015 IECC using the ERI compliance method. HERS simulations for each home are conducted for both a best case home orientation and a worst case home orientation. Improvements to the 2012 IECC SRD homes are made such that the HERS Index for the homes …

Fluid Powered Miniature In Vivo Robots For Minimally Invasive Surgery (Mis), Abolfazl Pourghodrat

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Minimizing the invasiveness of surgery is believed to improve patient outcomes. Bleeding, infection, and pain are major concerns in surgery afflicting patients for decades. Minimally invasive techniques have come into play to reduce these concerns and smooth the evolution of abdominal surgery to a scarless process where nearly all surgeries can be performed without a skin incision. Technology continually advances the frontier of development of novel surgical devices to implement less invasive surgical techniques.

Fusion of robotics and Minimally Invasive Surgery (MIS) has created new opportunities to develop diagnostic and therapeutic tools. Surgical robotics is advancing from externally actuated systems …

Electrokinetic Instabilities In Ferrofluid Microflows, Dhileep Thanjavur Kumar

All Theses

Lab-on-a-chip devices have been increasingly used in the past two decades for chemical and biomedical analysis. These devices employ the concepts of microfluidics and offer the promise of incorporating multiple laboratory processes onto a single portable chip. Electric field has been often employed in microfluidic devices for the ease of fluid and sample control as well as the convenience of chip integration and interfacing. Flow instabilities can take place when two fluids of unequal electrical properties are pumped through a microchannel under the application of an adequately strong electric field. The study of these electrokinetic instabilities in microfluidic devices is …

Modeling And Design Strategy Of Online Advertising Ecosystem, Qiuchen Wang

All Theses

Internet has undoubtedly become a major and effective medium for advertising, and it will soon replace traditional advertising media. Online advertising ecosystem is consisted of thousands of agents, which can be divided into three types: users, advertisers and publishers. Each type of the agents plays an important role in the ecosystem. However, it is generally very difficult to model such a complex and large-scale system, not to mention the design of suitable strategies for the ecosystem. On the other side, replicator-mutator (RM) dynamics combine tools from evolutionary dynamics of populations, complex networks, and control theory to study evolution of behavior …

Fatigue-Induced Failure In Horizontal-Axis Wind-Turbine (Hawt) Blades And Hawt Drivetrain Gears, Varun Chenna

All Theses

Wind energy is one of the most promising and the fastest growing installed alternative-energy production technologies. In fact, it is anticipated that by 2030, at least 20% of the U.S. energy needs will be met by various onshore and offshore wind-farms [a collection of wind-turbines (converters of wind energy into electrical energy) at the same location]. A majority of wind turbines nowadays fall into the class of the so-called Horizontal Axis Wind Turbines (HAWTs). Turbine blades and the gearbox are perhaps the most critical components/subsystems in the present designs of HAWTs. The combination of high failure rates (particularly those associated …

Development Of An In Vitro System For Evaluation Of Prosthetic Vein Valves, Ross Gorman

All Theses

Chronic venous insufficiency is a chronic disorder where venous pressure is not reduced during exercise. In a healthy individual, the vein valves and muscle pumps of the extremities combine to allow for a reduction in venous pressure during exercise. Consistent high pressure in the leg can lead to disability, pain, and ulcer formation. Typical causes of chronic venous insufficiency are venous reflux and acute venous obstruction. Research is under way to develop a prosthetic vein valve that can easily be implanted with a minimally invasive catheter procedure which addresses chronic venous insufficiency. This thesis discusses development of an in vitro …

Theoretical And Computational Design Analysis Of A Harmonica Type Aeroelastic Energy Harvester, Songkai Wang

All Theses

A wind energy harvester inspired by music playing harmonicas was proposed for micro-power generation. The energy harvester utilizes flow-excited self-sustained oscillations of a piezoelectric cantilever beam mounted in a wind pipe to generate electric power. The dependence of the energy harvester's power generation performance on a set of the design parameters such as the chamber volume, aperture width and beam dimensions has been studied previously. However, the performance of the nonlinear multi-physics system with two-way fluid structure coupling also depends on other design parameters such as the geometry of the oscillatory beam, the beam mounting configuration and the geometry of …

Finite Element Beam Model For Piezoelectric Energy Harvesting Using Higher Order Shear Deformation Theory, Akhilesh Surabhi

All Theses

Piezoelectric energy harvesting devices convert mechanical energy to usable electrical energy, which can be used to power other electronic devices and sensors. Typical piezoelectric harvesters are unimorph cantilever composite beams, which have a single active piezoceramic layer and a passive substrate or a bimorph that has a passive substrate sandwiched between two piezoceramic layers. Power is captured across a coupled load resistor circuit in either a series or parallel connection. The mathematical modeling approaches for piezoelectric beam harvesters present in literature range from analytical distributed parameter modeling, to approximate distributed parameter, Rayleigh- Ritz global discretization or finite element local discretization. …

Acoustic Scattering And Radiation Response Of Circular Hexagonal And Auxetic Honeycomb Shell Structures, Vaibhav Iyer

All Theses

Sandwich panels with honeycomb cores are used in many engineering applications because of their high strength to weight ratio, vibration isolation and sound transmission loss characteristics. Previous studies indicate that such sandwich structures with auxetic honeycomb cores (negative in-plane Poisson's ratio) can have a higher sound transmission loss compared to a regular hexagonal honeycomb core structure. In this study, sound scattering and acoustic radiation characteristics of sandwich structures with hexagonal and auxetic cores arranged in a circular pattern interacting with exterior acoustic domains of both air and water have been investigated using finite element analysis. A novel in-plane honeycomb geometry …

Electroencephalography(Eeg) Data Collection And Processing Through Machine Learning, Jayshree Desai

Graduate Theses and Dissertations

Machine learning methods are an excellent way for understanding the neural basis of human decision making. Some machine learning systems try to eradicate the need for human intuition in data analysis whereas others embrace a collective approach between humans and machines. The objective of this project is to collect Electroencephalography (EEG) signals through wireless sensors, and the process the collected signals through machine learning methods. The EEG data is collected using three EEG electrodes, each being the positive, negative and ground terminals respectively. Since the signal measures in the unit of micro-volts it needs to be amplified using amplifier circuit. …

Effects Of Relaxed Assumptions On The State Switching Technique, Stephen Ilardi

HIM 1990-2015

This thesis explores the effects of two assumptions commonly used in mathematical models related to a piezoelectric damping method known as State Switching. The technique relies on changing the stiffness state of a piezoelectric patch through control of the electrical boundary conditions. The transition between stiffness states is assumed to occur instantaneously and in concurrence with the switch event. In actuality, the transition will occur over a finite time and will trail behind the switch event by a finite time. For these assumptions to be valid, the effects of switch duration and delay on the performance of the State Switching …

Modeling Financial Markets Using Concepts From Mechanical Vibrations And Mass-Spring Systems, Michael Gandia

HIM 1990-2015

This thesis describes a method of modeling financial markets by utilizing concepts from mechanical vibration. The models developed represent multi-degree of freedom, mass-spring systems. The economic principles that drive the design are supply and demand, which act as springs, and shareholders, which act as masses. The primary assumption of this research is that events cannot be predicted but the responses to those events can be. In other words, economic stimuli create responses to a stock’s price that is predictable, repeatable and scientific. The approach to determining the behavior of various financial markets encompassed techniques such as Fast Fourier Transform and …

Effects Of Local Ph On The Formation And Regulation Of Cristae Morphologies, Dong Hoon Song, Jonghyun Park, Martin A. Philbert, Ann Marie Sastry, Wei Lu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Cristae, folded subcompartments of the inner mitochondrial membrane (IMM), have complex and dynamic morphologies. Since cristae are the major site of adenosine triphosphate synthesis, morphological changes of cristae have been studied in relation to functional states of mitochondria. In this sense, investigating the functional and structural significance of cristae may be critical for understanding progressive mitochondrial dysfunction. However, the detailed mechanisms of the formation and regulation of these cristae structures have not been fully elucidated. Among the hypotheses concerning the regulation of cristae morphologies, we exclusively investigate the effects of the local pH gradient on the cristae morphologies by using …

Conflict Management And Model Consistency In Multi-User Cad, Ammon Ikaika Hepworth

Theses and Dissertations

The NSF Center for e-Design, Brigham Young University (BYU) site has re-architected Computer Aided Design (CAD) tools, enabling multiple users to concurrently create, modify and view the same CAD part or assembly. This technology allows engineers, designers and manufacturing personnel to simultaneously contribute to the design of a part or assembly in real time,enabling parallel work environments within the CAD system. Multi-user systems are only as robust and efficient as their methods for managing conflicts and preserving model consistency. Conflicts occur in multi-user CAD when multiple users interoperate with the same or dependent geometry. Some conflicts can lead to model …

A Study Comparing The Pedagogical Effectiveness Of Virtual Worlds And Of Traditional Training Methods, Benjamin Peters

Theses and Dissertations - UTB/UTPA

This experiment tests whether a virtual world is a more suitable alternative to classical paper and pen case studies for teaching people how to disarm improvised explosive devices (IED). Following preliminary training, the subjects are separated into a group of 32 and one of 33. The odd-numbered subjects receive case studies while the even-numbered subjects receive training in the virtual world, Second Life. After their training, each subject is put into a simulated test where they attempt to properly disarm a mock IED attached to a victim played by an actor/actress. The results of the experiment show no significant difference …

Development And Applications Of The Expanded Equivalent Fluid Method, Bharath Kumar Kandula

Dissertations

Ocean acoustics is the study of sound in the oceans. Electromagnetic waves attenuate rapidly in the water medium. Sound is the best means to transmit information underwater. Computational numerical simulations play an important role in ocean acoustics. Simulations of acoustic propagation in the oceans are challenging due to the complexities involved in the ocean environment. Different methods have been developed to simulate underwater sound propagation. The Parabolic-Equation (PE) method is the best choice in several ocean acoustic problems. In shallow water acoustic experiments, sound loses some of its energy when it interacts with the bottom. An equivalent fluid technique was …

System Identification Of An Unmanned Tailsitter Aircraft, Nathan W. Edwards

Theses and Dissertations

The motivation for this research is the need to improve performance of the autonomous flight of a tailsitter UAV. Tailsitter aircraft combine the hovering and vertical take-off and landing capability of a rotorcraft with the long endurance flight capability of a fixed-wing aircraft. The particular aircraft used in this research is the V-Bat, a tailsitter UAV with a conventional wing and the propeller and control surfaces located within a ducted-fan tail assembly. This research focuses on identifying the models and parameters of the V-Bat in hover and level flight as a basis for the design of the control systems for …

Equilibrium And Dynamic Charge Storage In Nanopores With Room Temperature Ionic Liquids, Peng Wu

All Dissertations

Electrochemical capacitors store electrical energy physically in the electrical double layers at the electrode/electrolyte interfaces. In spite of their high power density and extraordinary cyclability, the widespread deployment of electrochemical capacitors is limited by their moderate energy density. The current surge in interest in electrochemical capacitors is driven by recent breakthroughs in developing novel electrode and electrolyte materials. In particular, electrodes featuring sub-nanometer pores and room-temperature ionic liquids are promising materials for next-generation electrochemical capacitors. To realize the full potential of these materials, a basic understanding of the charge storage mechanisms in them is essential. In this Dissertation, using atomistic …

Microfluidic Particle And Cell Manipulation Using Reservoir-Based Dielectrophoresis, Saurin Patel

All Dissertations

Controlled manipulation of synthetic particles and biological cells from a complex mixture is important to a wide range of applications in biology, environmental monitoring, and pharmaceutical industry. In the past two decades microfluidics has evolved to be a very useful tool for particle and cell manipulations in miniaturized devices. A variety of force fields have been demonstrated to control particle and cell motions in microfluidic devices, among which electrokinetic techniques are most often used. However, to date, studies of electrokinetic transport phenomena have been primarily confined within the area of microchannels. Very few works have addressed the electrokinetic particle motion …

Hydraulic Switch For Dishwashers With Bottle Blaster System., Lazaro Galban

Electronic Theses and Dissertations

A dishwasher works by using water pressure to operate the Spray Arms. There are different types of wash systems with the most common being two spray arms, a lower and middle arm. These two spray arms operate independently from each other and can be powered individually. In this particular wash system, the subsystem of interest is the Mid Spray Arm which is connected with the Bottle Blaster where both operate simultaneously. The Mid Spray Arm is used to clean the upper dishwasher rack while the Bottle Blaster is used to clean bottles, also in the upper rack. In order to …

A Decision Support Model For Process Planning In Remanufacturing Using Fuzzy Set Theory And Genetic Algorithm, Juan C. Martinez

Theses and Dissertations - UTB/UTPA

The environmental awareness and resources preservation has boosted the use of remanufacturing processes. Many important studies have been made in this area, but there are still pitfalls and opportunities that have not been explored yet. Specifically, the cleaning processes play a critical role in remanufacturing. It is among the top of most costly processes and it plays a key step in remanufacturing because delivers a free of contaminant product ready for reprocessing. Understanding and selecting the best processes to meet the need and goals of remanufacturers are important for effective and efficient remanufacturing. Due to variables and high uncertainty associated …

Development Of A Black-Box Transient Thermal Model For Residential Buildings, Andrew Cross

UNLV Theses, Dissertations, Professional Papers, and Capstones

Heavily populated metropolitan areas located in cooling-dominated climates, as are found in the Desert Southwest, pose a challenge to electrical utilities that service these areas. During the late afternoons of the summer months, residents of these metropolitan areas require larger than normal amounts of power to run their homes' air conditioning systems, at significant expense to the utilities. In the study reported here, interior temperature and power consumption data, accumulated over the course of a year and a half from seven houses within a Las Vegas neighborhood, are used to develop a predictive black-box statistical model for residential thermal transience. …

Feedback Speed Control Of A Small Two-Stroke Internal Combustion Engine That Propels An Unmanned Aerial Vehicle, Paul D. Fjare

UNLV Theses, Dissertations, Professional Papers, and Capstones

Unmanned aerial vehicles (UAV) require intelligent control of their power source. Small UAV are typically powered by electric motors or small two-stroke internal combustion (IC) engines. Small IC engines allow for longer flight times but are more difficult to control and cause significant ground noise. A hybrid operation that uses the engine at high altitudes and the electric motors at low altitudes is desired. This would allow for extended flight with acceptable ground noise levels. Since the engine can not be restarted in the air it must be able to remain at idle for an extended time without stalling. A …

The Second Generation Of The Cccm System For In-Vitro Cardiac Tissue Engineering., Mai-Dung Thi Nguyen

Electronic Theses and Dissertations

Cardiovascular disease is the leading cause of death worldwide. When a myocardial infarction occurs, scar tissue compensates the damaged myocardial tissue. This scar tissue increases the stiffness of the heart tissue, reduces the heart’s function, and finally leads to the heart failure (HF) disease. To have the tissue engraftment, in-vitro cardiac tissue should have the same properties as the native mature cardiac tissue. However, current in-vitro cell culture technologies fail to accurately recreate the in-vivo like mechanically physiological environment for in-vitro cardiac tissue culture, and therefore, fail to regenerate the in-vivo like mature cardiac tissue. Hence, a microfluidic cardiac cell …

Numerical Investigation Of Hydrodynamic Focusing And Coulter Principle In A Microfluidic Device, Muheng Zhang

Electronic Theses and Dissertations

Particle information such as particle size and amount is significant to many fields such as chemical engineering, biological research, medical analysis, and environment detection. Microfluidic Coulter counter is suitable for this task because it can get fast and accurate analysis. However, the fundamental principle and several design strategies details are still needed to be analyzed and modeled in order to improve its performance. This dissertation focused on several challenges from the numerical simulation aspects. First one is the analysis for the hydrodynamic focusing in microfluidic Coulter Counter. In recent years, many microfluidic Coulter Counter designs have utilized a technique termed …

Numerical Study Of Leading Edge Vortex Circulation Development On Finite Aspect Ratio Perching Wings., Kyle Hord

Electronic Theses and Dissertations

The perching maneuver of natural fliers is a complex motion involving fast change of angle of attack, complicated wing kinematics, large wing deformation and agile body motion control, but the prominent aerodynamic features can be revealed using a simple pitch-up wing motion coupled with a stream wise deceleration. In this dissertation the aerodynamic forces, the leading edge vorterx (LEV) development, and LEV circulation of pitch-up and perching wings are extensively studied at low Reynolds number conditions. 2D and 3D wings of different aspect ratios were linearly pitched up from 0 to 90 at three reduced pitch rates. The numerical investigation …

Investigation Of Traditional And Alternate Living Hinge Designs For Fused Deposition Modeling Additive Manufacturing Process, Cassandra Sue Gribbins

Doctoral Dissertations and Master's Theses

A manuscript-style thesis composed of three studies covered the application of living hinge designs in the additive manufacturing process of fused deposition modeling. Initial research included comparing numerical and analytical linear analyses on a traditional living hinge design. The second research consisted of tensile testing for the material properties of the Acrylonitrile Butadiene Styrene (ABS) used in fused deposition modeling (FDM) process by the MakerBot 2X as well as adjusting the traditional design to be printed. The third study explored alternate living hinge designs that utilize the geometric freedom provided by additive manufacturing to more evenly distribute stress across the …

Cfd Simulation Of The Thermal Performance Of A Parallel Counter-Parallel Flow Heat Exchanger For The Treatment Of Hypothermia, Alex Heller

UNLV Theses, Dissertations, Professional Papers, and Capstones

Hypothermia is a life-threatening condition. Currently, active warming methods are the most effective treatment for dysthermic patients. The aim of this study is to investigate the use of computational fluid dynamics (CFD) in evaluating the thermal performance of a parallel/counter-parallel flow heat exchanger used as part of a fluid warmer to treat Hypothermia. The 3D model of the heat exchanger is divided into three regions; Infusate (fluid to be heated), Hot Water (heating fluid), and a Solid Region (wall). At the end of the heat exchanger, an elbow section is used to create the counter-parallel flow arrangement specific to this …