Mechanical Engineering Commons^™

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 …

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 …

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 …

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, …

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 …

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 …

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 …

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 …

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 …

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 …

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 …

Investigation Of Concurrent Energy Harvesting From Ambient Vibrations And Wind, Amin Bibo

All Dissertations

In recent years, many new concepts for micro-power generation have been introduced to harness wasted energy from the environment and maintain low-power electronics including wireless sensors, data transmitters, controllers, and medical implants. Generally, such systems aim to provide a cheap and compact alternative energy source for applications where battery charging or replacement is expensive, time consuming, and/or cumbersome. Within the vast field of micro-power generation, utilizing the piezoelectric effect to generate an electric potential in response to mechanical stimuli has recently flourished as a major thrust area. Based on the nature of the ambient excitation, piezoelectric energy harvesters are divided …

Advanced Bulk Processing Of Lightweight Materials For Utilization In The Transportation Sector, Justin Milner

All Dissertations

The overall objective of this research is to develop the microstructure of metallic lightweight materials via multiple advanced processing techniques with potentials for industrial utilization on a large scale to meet the demands of the aerospace and automotive sectors. This work focused on (i) refining the grain structure to increase the strength, (ii) controlling the texture to increase formability and (iii) directly reducing processing/production cost of lightweight material components. Advanced processing is conducted on a bulk scale by several severe plastic deformation techniques including: accumulative roll bonding, isolated shear rolling and friction stir processing to achieve the multiple targets of …

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 …

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 …

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 …

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 …

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. …

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 …

Increased Span Length For The Mgs Long-Span Guardrail System, Nicholas A. Weiland

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

Long-span guardrail systems have been recognized as an effective means of shielding low-fill culverts while minimizing construction efforts and limiting culvert damage and repair. The current MGS long-span design provided the capability to span unsupported lengths up to 25 ft (7.6 m) without the use of nested guardrail. The excellent performance of the MGS long-span system in full-scale crash tests suggested that longer span lengths may be possible with the current design.

A detailed analysis of the MGS long-span guardrail system was performed using the finite element software program LS-DYNA^®. It was shown that the MGS long-span design …

Understanding The Effects Of Blast Wave On The Intracranial Pressure And Traumatic Brain Injury In Rodents And Humans Using Experimental Shock Tube And Numerical Simulations, Aravind Sundaramurthy

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

Blast induced neurotrauma (BINT) has been designated as the “signature injury” to warfighters in the recent military conflicts. In the past decade, conflicts in Iraq (operation Iraqi freedom) and Afghanistan (operation enduring freedom) as well as the increasing burden of the terrorism around the world resulted in an increased number of cases with blast Traumatic Brain Injury (bTBI). Recently, a lot of research has been done to study the neurological and neurochemical degenerations resulting from BINT using animal models especially rat models. However, it is not clear how and whether the biological outcomes from animal models can be translated to …

Reinterpretation Of Velocity-Dependent Atomic Friction: Influence Of The Inherent Instrumental Noise In Friction Force Microscopes, Yalin Dong, Hongyu Gao, Ashlie Martini, Philip Egberts

Mechanical Engineering Faculty Research

We have applied both the master equation method and harmonic transition state theory to interpret the velocity-dependent friction behavior observed in atomic friction experiments. To understand the discrepancy between attempt frequencies measured in atomic force microscopy experiments and those estimated by theoretical models, both thermal noise and instrumental noise are introduced into the model. It is found that the experimentally observed low attempt frequency and the transition point at low velocity regimes can be interpreted in terms of the instrumental noise inherent in atomic force microscopy. In contrast to previous models, this model also predicts (1) the existence of a …

Panel I: Connecting 2nd Law Analysis With Economics, Ecology And Energy Policy, Richard Gaggioli, Mauro Reini

Mechanical Engineering Faculty Research and Publications

The present paper is a review of several papers from the Proceedings of the Joint European Thermodynamics Conference, held in Brescia, Italy, 1–5 July 2013, namely papers introduced by their authors at Panel I of the conference. Panel I was devoted to applications of the Second Law of Thermodynamics to social issues—economics, ecology, sustainability, and energy policy. The concept called Available Energy which goes back to mid-nineteenth century work of Kelvin, Rankine, Maxwell and Gibbs, is relevant to all of the papers. Various names have been applied to the concept when interactions between the system of interest and an environment …

Refinement And Characterization Of Synthetic Vocal Fold Models, Shelby Charisse Ward

Theses and Dissertations

Understanding vocal fold mechanics is an integral part of voice research and synthetic vocal fold models are an essential tool in characterizing vocal fold mechanics. These models contain multiple layers with varying stiffness, much like human vocal folds. The purpose of this thesis is to improve the current models and modeling techniques, as well as investigate the impact of asymmetry on model vibration. A new design for an MRI-based model is detailed. This model has a more realistic geometry than the simplified models and mimics some of the vibratory characteristics observed in human vocal folds. The MRI-based model was used …

Variable Viscosity Condition In The Modeling Of A Slider Bearing, Kedar Nath Uprety, S.C. Mancas

Publications

To reduce tear and wear of machinery lubrication is essential. Lubricants form a layer between two surfaces preventing direct contact and reduce friction between moving parts and hence reduce wear. In this short letter the lubrication of two slider bearings with parallel and nonparallel is studied. First, we show that bearings with parallel plates cannot support any load. For bearings with nonparallel plates we are interested on how constant and temperature dependent viscosity affects the properties of the bearings. Also, a critical temperature for which the bearings would fail due to excess in temperature is found for both latter cases. …

Easily Implantable And Stable Nail-Fastener For Skeletal Fixation And Method, David Lecronier, Patrick Atkinson

Mechanical Engineering Patents

An intramedullary nail (20) defining a bore (34) is inserted into a medullary canal (26) of a bone (24). A threaded fastener (22) has a compression portion (48) presenting a compression portion diameter (DCP) and a threaded portion (50) presenting a threaded portion diameter (DTP). The fastener (22) extends through a near cortex hole (40) and/or a far cortex hole (42), and the threaded portion (22) threadedly engages the bore (34). A compression transmission device (54) is disposed between a head (44) of the fastener (22) and the intramedullary nail (20) for transmitting the compressional load of the threaded fastener …

Thermal Resistance At An Interface Between A Crystal And Its Melt, Zhi Liang, William J. Evans, Pawel Keblinski

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Non-Equilibrium Molecular Dynamics Simulations Are Used to Determine Interfacial Thermal Resistance (Kapitza Resistance) between a Crystal and its Melt for Three Materials Including Ar, H2O, and C8H 18 (Octane). the Simulation Results Show that the Kapitza Resistance at a Crystal-Melt Interface is Very Small and Thus Has a Negligible Effect on Thermal Transport Across the Crystal-Melt Interface. the Underlying Origins of This Behavior Are the Very Good Vibrational Property Match between the Two Materials Forming the Interface and Good Interfacial Bonding. the Result Also Indicates that the Commonly-Used Assumption that Temperature Profile is Continuous at the Crystal-Melt Interface is Valid …

Analysis And Application Of Passive Gait Rehabilitation Methods, Ismet Handzic

USF Tampa Graduate Theses and Dissertations

Human gait is elegant and efficient in propelling the body forward. While a healthy human gait is symmetric, any deviation from symmetry can cause inefficiencies to the entire body. Such asymmetries may present themselves in hemiplegic patients, prosthetic users, lower limb injuries, limb height and weight discrepancies, or abnormal overground foot rolling. In this dissertation, practical passive methods to alleviate such asymmetric walking dynamics are presented. The novel concepts presented in this manuscript can all be related and applied to passive gait rehabilitation, that is, the rehabilitation of a person's gait through methods that do not require external power. One …

Acoustic Testing Of Generator/Alternator Fans, Jacob Kriesel

Culminating Projects in Electrical Engineering

The intent of this project was to fill in a gap of the testing knowledge possessed for acoustics of an alternator within a generator set. The objective was to build a test fixture that would allow the user to test the acoustics of alternators without the driving force of an engine, which is a high acoustic source during testing. Eliminating the engine from the equation would allow for more accurate data of the product line, allowing for better utilization of acoustic tools when implementing sound source dampening. At the end of the project, it was found that the test fixture …