Engineering Commons^™

Radiative Heat Transfer Analysis Of Railroad Bearings For Wayside Thermal Detector Optimization, James Alexandro Aranda

Theses and Dissertations

Wayside hot-box detectors (HBDs) are devices that are currently used to evaluate the health of railcar components including bearings, axles, and brakes by monitoring their temperatures. While HBDs have been instrumental in reducing some train derailments in the past few decades, the number of non-verified bearing removals has increased significantly. In general, HBDs tend to underestimate bearing temperatures in both field service and in laboratory testing, which is not surprising considering the simple two-point calibration method that is used to calibrate these devices. Because of this, different calibrations were compared and analyzed including two-point, three-point, and multi-point calibrations. Analysis of …

Synthesis And Design Of Metals Sulfide/Carbon Composite-Fibers Anodes For Lithium Ion Batteries, Jorge Lopez

Theses and Dissertations

In this study, Forcespinning is used to produce Titanium sulfide (TiS2)/carbon composite fibers for use as lithium-ion battery anodes. The high surface area to volume ratio of the composite fibers can have a high impact on the ionic and electronic conductivity of the active materials leading to improved electrochemical performance of the battery. TiS2 nanoparticles were chosen as the active materials to produce Metal-Li-alloys/C composite fibers due to their high theoretical capacity and low volume change during charge/discharge cycles. The use of a 2-D layered structure of TiS2 nanoparticles in the carbon fiber matrix can greatly accommodate more Li-ions between …

Boron Nitride Thin-Film Deposited By Rf Magnetron Sputtering, Jesus A. Valladares Gonzalez

Theses and Dissertations

Cubic Boron Nitride is considered a superhard material, its thermochemical stability makes it suitable for applications with corrosive environments and high temperatures. C-BN is grown by PDV on Si substrates. The plasma is energized via an RF source to sputter the target. The ion species in the plasma can be described by the classic electrodynamic expression . Plasma temperature is given by T = (6.2836*E/8*k). The sputter is given by the ratio of the heat transfer to the enthalpy of formation , of the target. The Hall Measurement is performed as recommended by NIST. The measurement was performed on a …

Improving Thermal-Hydraulic Performance Of Flat-Tube Louver-Fin Heat Exchangers By Eliminating Louver Gap Condensate Bridges, Alan L. Jones

Theses and Dissertations

The air side performance of heat exchangers is a well studied subject. Flat-tube louver-fin heat exchangers experience a decrease in performance when operating in dehumidifying conditions. As water vapor is pulled from the air, water condensate may create blockages between louvers. Flat-tube louver-fin heat exchanger may experience a drop in thermal-hydraulic performance by up to 50% due to blockages. The aim of this study is to make macro scale geometric changes to louver dimensions and eliminate louver condensate bridges. By eliminating louver condensate blockages, the heat exchanger should see an overall gain in thermal performance when compared to current fin …

Aligning Anatomical Knee Model With Kinematic Experimental Data To Investigate Squat Exercise, Jose Mario Salinas

Theses and Dissertations

A two-dimensional inverse dynamics anatomical model of the human knee was developed by aligning anatomical structures of the knee (taken from x-rays) with kinematic experimental data (collected from motion capture cameras). The mathematical model was used to study the forces related to the tibiofemoral and patellofemoral joints during the squat and knee extension exercises. Forces calculated by the model included: tibiofemoral contact force, patellofemoral contact force, forces generated by cruciate ligaments, quadriceps force, and patellar tendon force. Bone alignment consisted of superimposing the geometric center of the lateral femoral condyle (from x-rays) with the relative instantaneous center of rotation of …

A Systematic Approach To High Blood Pressure Risk Analysis And Healthcare Cost Reduction In Young Adults [Metodología Sistemática Para El Análisis De Riesgo Y Reducción De Costos De Servicios Médicos De Hipertensión En Adultos Jóvenes], Francisco Rafael Torres Diaz

Theses and Dissertations

The purpose of this research is to utilize publicly available data to estimate the current rate of occurrence of undiagnosed High Blood Pressure (HBP) in young adults (18 to 24 years old) and the out-of-pocket healthcare expenses associated with complications of HBP, to provide feasible alternatives to mitigate the effects on a region's economy. This has been done by building a Risk Factor Simulation Model that utilizes known HBP risk factors’ correlation to HBP, insurance coverage data, and rate of diagnosis to formulate the average Risk Factor Value for a region, which through an Annual Expected Cost Function estimates the …

Achieving Universal Liaisons And Healthcare Contact Center Centralization Through The Use Of Decision Support Tools, Jared S. Fiacco

Graduate Dissertations and Theses

Healthcare contact centers often experience a large volume of calls and traditional standardized guidelines can be difficult to follow during an active call. While more common workflows can be memorized, they change often because Healthcare is a dynamic field. Constant updates to workflows, an abundance of different processes and provider preferences, and a fast paced environment can lead Customer Service Liaisons (CSLs) to handle patient inquiries incorrectly. Active decision support tools enable a CSL to follow an updated workflow without needing to navigate through complex guidelines and emails. This research shows that contact center centralization through the use of decision …

Analysis Of Flash In Injection Molding Using Flow Simulation And Design Of Experiments, Claudia Lizette Lopez

Theses and Dissertations

This study presents a method of detecting flash by using flow simulation along with the mold processing conditions and the DOE analysis values from all input and output parameters that will be calculated. All of this would be completed in order to compare and verify the DOE and simulation results and find out if it can be applied to an actual live production molded part, in this case, the Leap char ribbon. This paper will also describe the scrap issue that is presently happening on this molded part, and what are the options that there is in order to find …

Design And Qualification Of A Robust Polyurethane Based Conformal Coating Process For Sodimms, Rajat Dhiman

Graduate Dissertations and Theses

Conformal coatings protect printed circuit board assemblies, including the electronic components that the assemblies are populated with. A variety of materials and application methods can be used to conformally coat assemblies. The process setup is crucial to repeatable process reliability. The manual spray based conformal coating is widely used. This method of application was selected due to its compatibility, affordability, and efficiency with the required application. Polyurethanes, one of the families of conformal coatings, provide resistance against abrasion, heat, and chemicals while reducing the risk of tin whiskers. In order to minimize the need for rework and create an efficient, …

Using Multifactor Inputs Bp Neural Network To Make Power Consumption Prediction, Hao Song

Graduate Dissertations and Theses

With the development of modern information and technology (IT), smart grids became one of the major components of smart cities, to take full advantage of the smart grid, the capability of intelligent scheduling and planning of electricity delivery is essential. For this purpose, researchers have investigated methodologies for power consumption prediction and demand side management (DSM). In addition, conducting a comprehensive analysis and obtaining an accurate evaluation of power consumption are the premise and basis for a more robust and efficient power grid design and transformation. Therefore, it is meaningful to explore forecasting models that are able to reflect the …

Forcespinning Of Metal Oxides And Metal Sulfides And Their Applications As Alternative Anode Materials For Lithium-Ion And Sodium-Ion Batteries, Alejandra Valdez

Theses and Dissertations

Molybdenum-Oxide/Carbon (MoO2/C) composite nanofibers were synthesized using Forcespinning method and subsequent heat treatment, for use as anode materials for lithium-ion batteries. Due to the layered structure of MoO2, the composite nanofibers are very promising for use as anode material for LIBs. The MoO2/C composite fiber anodes exhibit good electrochemical performance and cycling stability.

Multi-Objective Design Optimization Of Reverse Total Shoulder Arthroplasty To Maximize Range Of Motion And Joint Stability, Josie A. Elwell

Graduate Dissertations and Theses

Reverse total shoulder arthroplasty was developed to restore range of motion (ROM) and joint stability to patients with pre-operative conditions that are not addressed by conventional replacements. Although reverse total shoulder arthroplasty is the current gold standard for treating a range of indications, the effects of varying its design on functional outcomes of the procedure are still not well understood.

To that end, it is not yet clear which configurations, in terms of both design and surgical placement parameters, maximize range of motion and stability of the joint. It was hypothesized that there is trade-off between the two. These types …

Computational Fluid Dynamics Modeling And In Situ Physics-Based Monitoring Of Aerosol Jet Printing Toward Functional Assurance Of Additively-Manufactured, Flexible And Hybrid Electronics, Roozbeh (Ross) Salary

Graduate Dissertations and Theses

Aerosol jet printing (AJP)—a direct-write, additive manufacturing technique—has emerged as the process of choice particularly for the fabrication of flexible and hybrid electronics. AJP has paved the way for high-resolution device fabrication with high placement accuracy, edge definition, and adhesion. In addition, AJP accommodates a broad range of ink viscosity, and allows for printing on non-planer surfaces. Despite the unique advantages and host of strategic applications, AJP is a highly unstable and complex process, prone to gradual drifts in machine behavior and deposited material. Hence, real-time monitoring and control of AJP process is a burgeoning need. In pursuit of this …

Development Of Collagen-Based Scaffolds For Differentiation Of Induced Pluripotent Stem Cells, Siteng Fang

Graduate Dissertations and Theses

Collagen hydrogel has been broadly studied and applied in engineering 3D scaffold materials in tissue engineering. A collagen hydrogel can provide cells with a porous and soft environment to proliferate and differentiate. However, lacking mechanical stiffness and shrinkage resistance made it a challenge to sustain shape and size during a long stem cell differentiation process. In addition, a cytocompatible scaffold for human induced pluripotent stem cell (iPSC)-laden culture has not been fully investigated. The goal of this study is to develop stable and biocompatible collagen-based scaffolds that are suitable for direct seeding and lineage progression of iPSCs. In this work, …

Assessing The Tensile And Fatigue Behavior Of Aerosol Jet Printed Nano Silver Particle Traces On Polyimide Substrates, Roshan Muralidharan

Graduate Dissertations and Theses

Flexible interconnects are integral to flexible hybrid electronics. Aerosol jet, inkjet or screen printing offer various advantages and disadvantages compared to electroplating, but the behavior of printed metal traces under various types of loading is very different and not yet well understood. This thesis presents an assessment of the electromechanical behavior of aerosol jet printed Nano silver particles on two common polyimide substrates, Upilex and Kapton.

There are many different aspects to electromechanical testing of flexible interconnects, but this work focuses on the effects of tension and cyclic loading. In comparison to the much more widely researched electroplated copper or …

Use Of A Triboelectric Generator For A Tunable Wideband Energy Harvester And A Threshold Shock Sensor, Daniel S. Nelson

Graduate Dissertations and Theses

The prevalence of triboelectricity as a transduction mechanism has increased rapidly in recent years. We will discuss two uses for triboelectric generators. One design is a tunable wideband energy harvester. An axial force and amplitude limiter work together to create an energy harvester that can accommodate various frequency sources and have a large operating bandwidth. The addition of the compressive axial force also softens the system, which allows for higher voltage outputs. A proof of concept of a threshold shock sensor is proposed that incorporates bi-stability along with the triboelectric effect. A clamped-clamped buckled beam will switch stable states when …

Antimicrobial Properties And Characterization Of Polymer/Composite Nanofibers, David De La Garza

Theses and Dissertations

Pathogenic bacteria have been the cause of many illnesses worldwide due to their rapid growth and reproduction in food and water. Bacteria-resistant antibiotics and kidney complications due to overuse of antibiotics has remained a large public health concern. The goal of this research project was to find an alternative by producing nanofibers that inhibit microbial growth utilizing Forcespinning technology. The Forcespinning of poly(acrylic acid) (PAA) with Single Wall Carbon Nanotubes functionalized with OH (SWCNT-OH) and Ag + flakes were carried out on solutions with different concentrations. Scanning electron microscopy was used to view fiber morphology and investigate the average nanofiber …

Design And Synthesis Of Novel Nanometallic Catalysts And Electrode Materials For Green Fuel Cells, Jing Zhang

Graduate Dissertations and Theses

The United Nations formally adopted 17 sustainable development goals (SDGs) at its 2015 summit. Many of these goals addressed issues such poverty, hunger, health, education, climate-change, gender equality, water, sanitation, energy, urbanization, environment and social justice. The seventh SDG seeks to ensure access to affordable, reliable, sustainable and modern energy for all. So among all renewable forms of energy, fuel cells with high efficiency have attracted a lot of attention recently. In particular, the direct ethanol fuel cells (DEFCs) and microbial fuel cells (MFCs) are significant due to their green fuel, less waste generated and environmental friendliness. Hence the overall …

Mechanical Reinforcement Of Polyacrylamide Hydrogels Using Pristine Single-Walled Carbon Nanotubes, Wuxiang Feng

Graduate Dissertations and Theses

Hydrogels have great promise as an innovative biomedical material possessing many advantages such as high water content, porous structure, and excellent biocompatibility. Although hydrogels have been used to develop some successful applications, they commonly do not have sufficient mechanical strength required for artificial soft tissues. Here, the author fabricated reinforced PAAm hydrogels using single-walled carbon nanotubes as reinforcing materials. The fusion of SWCNTs and the PAAm matrix successfully generated SWCNTs/PAAm hybrid gels with improved mechanical strength. Moreover, the aqueous dispersion of SWCNTs used for engineering the hybrid gels remained excellent stability after two months. SEM images from previous research and …

Lead Doped Carbon Nanofibers In Li-Ion Batteries, Omar Torres

Theses and Dissertations

Lead acid batteries have been a very reliable rechargeable battery since its inception in the mid-1800s. Lithium-Ion batteries have been sought out for their light-weight and capacity of holding large amounts of energy in a small amount of space. Few studies have been conducted in the use of lead in lithium-ion batteries.

In this thesis, lead-doped carbon nanofibers were produced by using the Forcespinning® method and used as an anode on a lithium-ion battery. The morphology, material characterization and thermal properties of the anode material were analyzed using the Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Thermogravimetric Analysis …

Fibers For Skin Regeneration, Astrid Michelle Rodriguez Negron

Theses and Dissertations

This thesis presents the successful development of biocompatible Polyvinyl Butyral (PVB), PVB/Polylysine and PVB/Tannic Acid (TA)/Polylysine fibers from an ethanol solution, Polyhydroxybutyrate (PHB), PHB/Polylysine, PHB/TA/Polylysine fibers from a chloroform solution and Chitosan (CH)/Pullulan (PL)/TA and CH/PL/TA/Polylysine fibers from an aqueous solution. The fibers were mass produced utilizing the Forcespinning® (FS) technology. The morphology of the fibers was characterized using a scanning electron microscope (SEM) and the fibers average diameter was calculated. The thermal properties of the fibers were characterized using a thermogravimetric analyzer (TGA) and a differential scanning calorimeter (DSC). The antibacterial activity of the fibers was assessed using against …

Design Of A Multidirectional Wear Testing Device For Simulating Wear Of Biocompatible Materials Used In Joint Implants, Carlos A. Rodriguez Betancourth

Theses and Dissertations

In the present work, a novel multidirectional pin-on-disc wear testing device designated CNC-POD (computer-numerical-control pin-on-disc) capable of replicating the cross-shear motions experienced by a prosthesis in vivo was designed and developed in the UTRGV in order to evaluate the wear resistance of new biomaterials. The CNC-POD consists of six temperature-controlled pin-on-disc stations mounted on a two-axis CNC table (X-Y). Each pin-on-disc station is load-programmable up to 510 Newtons (115 pounds). The CNC table allows the machine to reproduce a wide range of 2D patterns in millimeter scale on the six stations under a specific load. Friction force is measured during …

The Effect Of Heat Generation In The Railroad Bearing Thermoplastic Elastomer Suspension Element On The Thermal Behavior Of Railroad Bearing Assembly, Oscar Osvaldo Rodriguez

Theses and Dissertations

Understanding the internal heat generation of the railroad bearing elastomer suspension element during operation is essential to predict its dynamic response and structural integrity, as well as to predict the thermal behavior of the complete railroad bearing assembly including the bearing adapter. The latter is essential for sensor selection and placement within the adapter (e.g., typical temperature sensors have operating ranges of up to 125°C or 257°F). The internal heat generation is a function of the loss modulus, strain, and frequency. Based on experimental studies, estimations of internally generated heat within the thermoplastic elastomer pad were obtained. The calculations show …

The Use Of Mixed Organic/Ionic Liquid Electrolytes With Forcespun Metal Oxides/Carbon Microfiber Electrodes In Lithium Ion Batteries, Jahaziel Villarreal

Theses and Dissertations

Conventional Lithium-Ion Battery (LIB) electrolytes have serious safety concerns because of highly flammability. In order to mitigate this drawback, alternative electrolytes with low volatility and non-flammable need to be synthesis. Ionic liquids (ILs) and mixed organic ionic liquid electrolytes (MOILEs) are the most suitable replacement for the highly flammable commercial organic electrolytes. In this academic investigation, a new perspective on the electrochemical performance of the ionic liquid EMI-TFSI as an alternate non-flammable electrolyte. In parallel, the use of Forcespun nanofibers as binder-free anodes will be analyzed to further improve overall electrochemical performance.

Buffer Controlled Cache For Low Power Multicore Processors, Marven Calagos

Theses and Dissertations

This thesis proposes a buffered dual access mode cache to reduce power consumption in multicore caches for embedded systems. This cache is called Buffer Controlled Cache (BCC cache). The proposed scheme introduces a pre-cache buffer to determine how to access the cache. The proposed cache shows better prediction rates and lower power consumption than conventional caches, such as Phased cache and Way-prediction cache. For single core implementation, Simplescalar and Cacti simulators have been used for these simulations using SPEC2000 benchmark programs. The experimental results show that the proposed cache improves the power consumption by 37%-42% over the conventional caches. Multi2Sim …

Superharmonic Resonance Of Second Order For Electrostatically Actuated Mems Cantilevers, Martin Amador Botello

Theses and Dissertations

The nonlinear dynamics of electrostatically actuated micro-electro-mechanical system (MEMS) cantilever resonators are investigated. The applied Alternating Current (AC) voltage is in the realm of superharmonic resonance of the second order (near one-fourth of the natural frequency of the resonator) and hard excitations. Method of Multiple Scales (MMS) and Reduced Order Models (ROMs) are used to solve the dimensionless partial differential equation (PDE) of motion along with boundary and initial conditions. MMS transforms the PDE of motion into zero-order and first-order problems. ROMs uses mode shapes of vibration for undamped cantilever resonator as a basis of functions. ROM is …

Multifunctional Carbon Systems (Interlaminated Carbon Nanofiber Mats/ Carbon Nanotubes Polymer Composites), Homero Gonzalez Guardiola

Theses and Dissertations

Carbon nanomaterials have been an attractive topic within diverse industrial sectors given their outstanding properties for decades. One of the properties that has been calling attention is it’s shielding effectiveness (SE) for electromagnetic interference (EMI), because of the constant race of improving portable electronic and wireless communication devices among other applications. The present study, analyzes the properties of interlaminated Carbon Nanofiber (CNF) mats/Carbon Nanotubes (CNT) polymer composites, emphasizing in its capability to shield EMI. The CNF mats were developed with Polyvinyl alcohol (PVA) as a precursor and by means of the Forcespinning® technology which uses centrifugal force to create fibers …

Ensemble Machine Learning To Predict Family Consent For Organ Donation, Md Ehsan Khan

Graduate Dissertations and Theses

There is ever increasing disparity between number of organs needed for transplantation and numbers available for donation to save lives. As a result, thousands of people die every year waiting for organs. Therefore, it is now more important than ever before to take serious actions to decrease this disparity. One way to bridge gap between organ demand and supply is to increase family consent for organ donation. This research studied the factors associated with family consent. Machine Learning approach had been used in very few literature to understand factors related to family consent. This study uses six Ensemble Machine Learning …

Side-Information For Steganography Design And Detection, Tomas Denemark

Graduate Dissertations and Theses

Today, the most secure steganographic schemes for digital images embed secret messages while minimizing a distortion function that describes the local complexity of the content. Distortion functions are heuristically designed to predict the modeling error, or in other words, how difficult it would be to detect a single change to the original image in any given area. This dissertation investigates how both the design and detection of such content-adaptive schemes can be improved with the use of side-information.

We distinguish two types of side-information, public and private: Public side-information is available to the sender and at least in part also …

Cyber-Physical Embedded Systems With Transient Supervisory Command And Control: A Framework For Validating Safety Response In Automated Collision Avoidance Systems, Daniel K. Trembley

Graduate Dissertations and Theses

The ability to design and engineer complex and dynamical Cyber-Physical Systems (CPS) requires a systematic view that requires a definition of level of automation intent for the system. Since CPS covers a diverse range of systemized implementations of smart and intelligent technologies networked within a system of systems (SoS), the terms “smart” and “intelligent” is frequently used in describing systems that perform complex operations with a reduced need of a human-agent. The difference between this research and most papers in publication on CPS is that most other research focuses on the performance of the CPS rather than on the correctness …