Engineering Commons^™

Fabrication And Characterization Of Electrospun Cactus Mucilage Nanofibers, Yanay Pais

USF Tampa Graduate Theses and Dissertations

This work seeks to fabricate, optimize, and characterize nanofibers of cactus Opuntia ficus-indica mucilage and Poly (vinyl alcohol) (PVA) by electrospinning. Mucilage is a neutral mixture of sugars produced by cactus and PVA is a non-toxic, water-soluble, synthetic polymer, which is widely used as a co-spinning agent for polymers. Mucilage was extracted from the cactus pad and prepared for electrospinning by mixing with acetic acid. Two types of PVA were used differentiating in high and low molecular weights. Concentrations of PVA were varied to find an adequate threshold for fiber formation. Changing the ratio of PVA to cactus mucilage produced …

Molybdenum Nitride Films In The Back Contact Structure Of Flexible Substrate Cdte Solar Cells, Vasudha Guntur

USF Tampa Graduate Theses and Dissertations

CdTe solar cells in the superstrate configuration have achieved record efficiencies of 16% but those in the substrate configuration have reached efficiencies of only 7.8%. A major reason for the lower efficiency of substrate CdTe solar cells is the poor back contact. In this work, CdTe solar cells of the substrate configuration have been fabricated on flexible metallic substrates. For this type of devices, impurity diffusion out of stainless-steel substrates due to high temperature processing can be a cause for poor cell performance. It is necessary to investigate ways of improving the back contact by trying to mitigate the above …

An Ofdm Based Aeronautical Communication System, Jamal Haque

USF Tampa Graduate Theses and Dissertations

Wireless connectivity is becoming an integral part of our society. A new paradigm for aeronautical data services is beginning to take shape. The advances in signal processing, rapid prototyping, an insatiable consumer demand for Internet services, increase in aircraft traffic, aircraft safety, etc., are driving the demand for high speed data services. Programs led by the National Aeronautics and Space Administration (NASA), the Federal Aviation Administration (FAA), EUROCONTROL and Networking the Sky for Civil Aeronautical Communications (NEWSKY) are all looking into aeronautical platforms as part of their Aeronautical Data Network (ADN). The desire is to provide low delay, cost effective …

Fabrication And Characterization Of Novel 2sss Cigs Thin Film Solar Cells For Large-Scale Manufacturing, Keshavanand Jayadevan

USF Tampa Graduate Theses and Dissertations

A novel 2SSS (2 Step Solid Selenization) CIGS (Cu, In, Ga, Se) thin film solar cell recipe was developed which can be a replacement to the conventional co-deposition process usually employed for large-scale manufacturing. The co-deposition procedure is faced with multiple problems such as selenium incorporation, effective gallium incorporation in the absorber. It is a 2-step proprietary procedure with better control over growth mechanisms and material utilization for the absorber layer for the CIGS thin film solar cells. It makes use of solid selenium source as preferred by manufacturers. Each step of the 2-step procedure was dealt with separately for …

Decision Support Models For Design Of Fortified Distribution Networks, Qingwei Li

USF Tampa Graduate Theses and Dissertations

Lean distribution networks have been facing an increased exposure to the risk of unpredicted disruptions causing significant economic forfeitures. At the same time, the existing literature contains very few studies that examine the impact of fortification of facilities for improving network reliability. This dissertation presents three related classes of models that support the design of reliable distribution networks. The models extend the uncapacitated P-median and fixed-charge location models by considering heterogeneous facility failure probabilities, supplier backups, and facility fortification within a finite budget. The first class of models considers binary fortification via linear fortification functions. The second class of models …

Resource Allocation Methodologies With Fractional Reuse Partitioning In Cellular Networks, Hazar Aki

USF Tampa Graduate Theses and Dissertations

Conventional cellular systems have not taken full advantage of fractional frequency reuse and adaptive allocation due to the fixed cluster size and uniformed channel assignment procedures. This problem may cause more fatal consequences considering the cutting-edge 4G standards which have higher data rate requirements such as 3GPP-LTE and IEEE 802.16m (WiMAX). In this thesis, three different partitioning schemes for adaptive clustering with fractional frequency reuse were proposed and investigated. An overlaid cellular clustering scheme which uses adaptive fractional frequency reuse factors would provide a better end-user experience by exploiting the high level of signal to interference ratio (SIR). The proposed …

The Impact Of Pharmacy Work Design On Pharmacist Productivity, Nicholas Allen Coblio

USF Tampa Graduate Theses and Dissertations

Healthcare costs in the United States continue to grow at an alarming rate. Concerning the cost of medications, there are a number of factors that drive these costs. While personnel costs are not the largest of these, they do contribute a significant portion. The cost of the cognitive component of order processing by pharmacists can range from three dollars to over six dollars per prescription depending on the production throughput of the pharmacist.

Studies at the organization which was the focus of the research, as well as reports in the literature, indicated that work disruption and other environmental factors could …

Analytical Methods To Support Risk Identification And Analysis In Healthcare Systems, Laila Nadime Cure Vellojin

USF Tampa Graduate Theses and Dissertations

Healthcare systems require continuous monitoring of risk to prevent adverse events. Risk analysis is a time consuming activity that depends on the background of analysts and available data. Patient safety data is often incomplete and biased. This research proposes systematic approaches to monitor risk in healthcare using available patient safety data. The methodologies combine traditional healthcare risk analysis methods with safety theory concepts, in an innovative manner, to allocate available evidence to potential risk sources throughout the system. We propose the use of data mining to analyze near-miss reports and guide the identification of risk sources. In addition, we propose …

Thermal Response Of Lithium Tantalate For Temperature Measurement, Ardit Agastra

USF Tampa Graduate Theses and Dissertations

This thesis describes the study of the thermal response of the pyroelectric material named lithium tantalate or LT (LiTaO3) in aid of this material’s possible use for temperature measurement. The temperature range studied was between 5-99 oC. The sensor was excited using a silicon rubber heater. The lithium tantalate sensor and the rubber heater were enclosed such that the temperature would reach steady state faster. The enclosure was a small insulated box in order to reduce any extraneous effects on the sensor. The output signal of the lithium tantalate sensor was then amplified by using four different amplifying circuits and …

Regulation Of Cell Adhesion Strength By Spatial Organization Of Focal Adhesions, Kranthi Kumar Elineni

USF Tampa Graduate Theses and Dissertations

Cell adhesion to extracellular matrix (ECM) is critical to various cellular processes like cell spreading, migration, growth and apoptosis. At the tissue level, cell adhesion is important in the pathological and physiological processes that regulate the tissue morphogenesis. Cell adhesion to the ECM is primarily mediated by the integrin family of receptors. The receptors that are recruited to the surface are reinforced by structural and signaling proteins at the adhesive sites forming focal adhesions that connect the cytoskeleton to further stabilize the adhesions. The functional roles of these focal adhesions extend beyond stabilizing adhesions and transduce mechanical signals at the …

Numerical Simulations Of Heat Transfer Processes In A Dehumidifying Wavy Fin And A Confined Liquid Jet Impingement On Various Surfaces, Mutasim Mohamed Sarour Elsheikh

USF Tampa Graduate Theses and Dissertations

This thesis consists of two different research problems. In the first one, the heat transfer characteristic of wavy fin assembly with dehumidification is carried out. In general, fin tube heat exchangers are employed in a wide variety of engineering applications, such as cooling coils for air conditioning, air pre-heaters in power plants and for heat dissipation from engine coolants in automobile radiators. In these heat exchangers, a heat transfer fluid such as water, oil, or refrigerant, flows through a parallel tube bank, while a second heat transfer fluid, such as air, is directed across the tubes. Since the principal resistance …

Stress Corrosion Cracking Evaluation Of Candidate High Strength Stainless Steels For Prestressed Concrete, Joseph Rogelio Fernandez

USF Tampa Graduate Theses and Dissertations

Prestressed concrete piles are commonly used to support over-water highway bridges in marine environments. The reinforcing steel within will ultimately be degraded via corrosion damage due to the penetration of chloride ions from sea water. The service life of these structures is, in part, dictated by the time required to diffuse chloride ions through the concrete cover and subsequently corrode the steel. Therefore, by slowing the rate of diffusion or increasing the chloride threshold of the steel (or both) an increased service life can be expected. This thesis focuses on the latter whereby stainless steel reinforcing alternatives were investigated to …

In Situ Biofiltration Of Dissolved Organic Carbon In Reverse Osmosis Membrane Filtration, Russell Rosario Ferlita

USF Tampa Graduate Theses and Dissertations

Biofouling, or the formation of biofilm on membrane surfaces, can decrease the performance (decreased flux and/or increased operating pressure) of a reverse osmosis (RO) membrane system in a water treatment plant. However, biofilms have been used in water treatment systems to remove organic carbon from water via biofilters and successfully reduce biofilm growth downstream. This research investigates the possibility that the heterotrophic biofilm present on membrane surfaces removes nutrients from the treatment water, thereby making it nutrient deprived as it travels along the treatment train. This may potentially be exploited as an in situ biofilter to actively remove dissolved organic …

Cactus Mucilage-Assisted Heavy Metal Separation: Design And Implementation, Dawn Iona Fox

USF Tampa Graduate Theses and Dissertations

Natural contamination of groundwater by arsenic (As) has become a critical public health threat in many parts of the world. The well-known regions associated with As contamination of groundwater are Bangladesh and West Bengal, India where approximately 100 million people are exposed to high levels of arsenic by drinking arsenic-contaminated groundwater and about 35 million are already affected. Long-term drinking of arsenic-contaminated water leads to arsenicosis, which is characterized by cancers of the skin, organ disease and certain other types of cancer. Affected developing communities are at higher risk because they may not have access to conventional water treatment facilities. …

Feasibility Of Wastewater Reuse For Fish Production In Small Communities In A Developing World Setting, Joshua James Girard

USF Tampa Graduate Theses and Dissertations

Eradicating poverty, malnutrition, and the burden of disease have been included as three of the major issues facing the world. The United Nation member countries, having set forth the Millennium Development Goals, have committed themselves to solving these problems. Two major factors which affect solutions to these problems are increasing water stress and implementing improved sanitation. Integration of tilapia aquaculture and reuse of wastewater has been suggested as a solution which addresses both of these factors. The objective of this study is to examine the feasibility, and explore the benefits and drawbacks, to implementing small community wastewater fed (WWF) aquaculture …

Safety Evaluation Of Roadway Lighting Illuminance Levels And Its Relationship With Nighttime Crash Injury Severity For West Central Florida Region, Enrique Gonzalez-Velez

USF Tampa Graduate Theses and Dissertations

The main role of roadway lighting is to produce quick, accurate and comfortable visibility during nighttime conditions. It is commonly known that good lighting levels enable motorists, pedestrians and bicyclists to obtain necessary visual information in an effective and efficient manner. Many previous studies also proved that roadway lighting minimizes the likelihood of crashes by providing better visibility for roadway users.

Appropriate and adequate roadway lighting illuminance levels for each roadway classification and pedestrian areas are essential to provide safe and comfortable usage. These levels are usually provided by national, or local standards and guidelines. The Florida Department of Transportation …

Interface Engineered Diamond Coatings For Dry Machining Applications, Humberto Arturo Gomez Vega

USF Tampa Graduate Theses and Dissertations

Several studies have been propose to improve the adhesion of diamond films on cemented carbide tool materials, however a systematic study in identifying the role of the factors that affect the final diamond adhesion and the resulting machining performance of the tool under real manufacturing conditions is still unexplored. CVD diamond film's extraordinary qualities bring little benefit if the film fails to adhere sufficiently to the substrate. Inadequate adhesion undermines tool performance and longevity, causing unpredictable behavior under load and possibly leading to unexpected failure of the tool in the production line. This dissertation investigates the effects of different surface …

Embodied Energy Assessment Of Rainwater Harvesting Systems In Primary School Settings On La Peninsula Valiente, Comarca Ngobe Bugle, Republic Of Panama, Kaitlin Elinor Green

USF Tampa Graduate Theses and Dissertations

The United Nations Millennium Development goals aim to make improvements in access to potable water. In the Bocas del Toro region of Panama, rainwater harvesting systems are making that goal more attainable. Rainwater harvesting, especially in rural, difficult access areas, may be a viable water source improvement that will allow a greater population to access improved water. This study uses the Carnegie Mellon University Economic Input-output Life Cycle Assessment tool to assess the embodied energy of plastic and ferrocement rainwater harvesting systems in rural Panama. Rainwater harvesting systems are assessed as source improvement technologies that increase access to potable water. …

Energy Recovery Devices In Seawater Reverse Osmosis Desalination Plants With Emphasis On Efficiency And Economical Analysis Of Isobaric Versus Centrifugal Devices, Mageed Jean Guirguis

USF Tampa Graduate Theses and Dissertations

With huge demands for potable water in regions lacking fresh water sources such as surface or ground water, various potential technologies have been explored for eliminating water shortage. Seawater emerged as a potential source and a major lifeline for such water-deprived areas. The development of seawater reverse osmosis (SWRO) technology proved to be a groundbreaking innovation, making it easier to extract pure water from seawater. Ever since its inception, SWRO technology has taken many leaps towards the development of energy efficient and high yielding systems. The reduction in energy consumption of desalination plants that were based on the SWRO technology …

Design And Testing Of A Motion Controlled Gait Enhancing Mobile Shoe (Gems) For Rehabilitation, Ismet Handzic

USF Tampa Graduate Theses and Dissertations

Persons suffering central nervous system damage, such as a stroke, coma patients, or individuals that have suffered damage to the spinal cord, brainstem, cerebellum, and motor cortex, sometimes develop an asymmetric walking pattern where one leg does not fully swing backward. This uneven gait hinders these individuals in properly and efficiently moving through everyday life.

Previous research in humans and various animals has introduced a split belt treadmill to analyze possible rehabilitation, which can recreate a correct gait pattern by altering the speed of each track. Gait adaptation was achieved by having the split belt treadmill move each leg at …

Utilizing A Computational Model For The Design Of A Passive Dynamic Walker, Craig Alan Honeycutt

USF Tampa Graduate Theses and Dissertations

Recent interest in using passive dynamic walkers (PDWs) for gait rehabilitation studies has presented a need for a robust, easily built mechanism. Unfortunately, these passive robots are hypersensitive to many variables outside of the usual design considerations that are studied when constructing them. By accentuating previous failures instead of suppressing them, this thesis presents a number of problematic situations commonly experienced when testing and tuning a PDW.

Further, through a complete design of a 4-legged PDW with knees, simple design axioms brought about by myself and others are put into a practical context and applied directly to design. This thesis …

Diamond Based-Materials: Synthesis, Characterization And Applications, Qiang Hu

USF Tampa Graduate Theses and Dissertations

The studies covered in this dissertation concentrate on the various forms of diamond films synthesized by chemical vapor deposition (CVD) method, including microwave CVD and hot filament CVD. According to crystallinity and grain size, a variety of diamond forms primarily including microcrystalline (most commonly referred to as polycrystalline) and nanocrystalline diamond films, diamond-like carbon (DLC) films were successfully synthesized. The as-grown diamond films were optimized by changing deposition pressure, volume of reactant gas hydrogen (H2) and carrier gas argon (Ar) in order to get high-quality diamond films with a smooth surface, low roughness, preferred growth orientation and high sp3 bond …

Growth And Characterization Of Thermoelectric Ba8Ga16Ge30 Type-I Clathrate Thin-Films Deposited By Pulsed Dual-Laser Ablation, Robert Harry Hyde

USF Tampa Graduate Theses and Dissertations

The on-going interest in thermoelectric (TE) materials, in the form of bulk and films, motivates investigation of materials that exhibit low thermal conductivity and good electrical conductivity. Such materials are phonon-glass electron-crystals (PGEC), and the multi-component type-I clathrate Ba₈Ga₁₆Ge₃₀ is in this category. This work reports the first investigation of Ba₈Ga₁₆Ge₃₀ films grown by pulsed laser deposition (PLD).

This dissertation details the in-situ growth of polycrystalline type-I clathrate Ba₈Ga₁₆Ge₃₀ thin-films by pulsed laser ablation. Films deposited using conventional laser ablation produced films that contained a …

Techniques For Enhancing Reliability In Vlsi Circuits, Ransford Morel Hyman Jr

USF Tampa Graduate Theses and Dissertations

Reliability is an important issue in very large scale integration(VLSI) circuits. In the absence of a focus on reliability in the design process, a circuit’s functionality can be compromised. Since chips are fabricated in bulk, if reliability issues are diagnosed during the manufacturing of the design, the faulty chips must be tossed, which reduces product yield and increases cost. Being aware of this situation, chip designers attempt to resolve as many issues dealing with reliability on the front-end of the design phase (architecture or systemlevel modeling) to minimize the cost of errors in the design which increases as the design …

Oxygen Diffusion Characterization Of Frp Composites Used In Concrete Repair And Rehabilitation, Chandra K. Khoe

USF Tampa Graduate Theses and Dissertations

Many independent studies have conclusively demonstrated that fiber reinforced polymers (FRP) slow down chloride-induced corrosion of steel in concrete. The mechanism for this slow down is not well understood but it has been hypothesized that FRP serves as a barrier to the ingress of chloride, moisture, and oxygen that sustain electrochemical corrosion of steel.

This dissertation presents results from an experimental study that determined the oxygen permeation rates of materials used in infrastructure repair. In the study, the oxygen permeation constants for epoxy, carbon and glass fiber laminates, concrete, epoxy-concrete and FRP-concrete systems were determined and a method developed to …

A Remotely Operated Multi-Tracked Vehicle For Subterranean Exploration Of Gopher Tortoise Burrows, William Keese

USF Tampa Graduate Theses and Dissertations

The gopher tortoise is a land tortoise living in the southeastern United States. It is a species in decline and is listed as threatened or endangered in six different states. The gopher (as commonly referred) digs burrows that it uses for many reasons and spends most of its time underground. Problems occur when trying to estimate a population because a gopher tortoise digs more than one burrow. This thesis demonstrates an innovative way to survey and investigate a gopher tortoise burrow hole by using a multi-tracked remotely operated vehicle. The vehicle carried two cameras (fore and aft) and was equipped …

Biodegradation Of Bisphenol-A And 17b-Estradiol In Soil Mesocosms Under Alternating Aerobic/Anoxic/Anaerobic Conditions, Won-Seok Kim

USF Tampa Graduate Theses and Dissertations

Soil-aquifer treatment (SAT) has been proposed as a method for reusing treated municipal wastewater. SAT is characterized by alternating cycles of aerobic and anaerobic conditions in the subsurface, in response to alternating cycles of flooding and drainage of a surface impoundment. It is not yet known how these alternating redox conditions affect the removal of potentially harmful endocrine-disrupting compounds (EDCs) from treated effluent.

The overall objective of my doctoral research is to determine the fate of EDCs in alternating aerobic/anoxic/anaerobic conditions under simulated SAT conditions. To assess the fate of EDCs in simulated SAT conditions, I first had to develop …

Minimal And Symmetric Global Partition Polynomials For Reproducing Kernel Elements, Mario Jesus Juha

USF Tampa Graduate Theses and Dissertations

The Reproducing Kernel Element Method is a numerical technique that combines finite element and meshless methods to construct shape functions of arbitrary order and continuity, yet retains the Kronecker-δ property. Central to constructing these shape functions is the construction of global partition polynomials on an element. This dissertation shows that asymmetric interpolations may arise due to such things as changes in the local to global node numbering and that may adversely affect the interpolation capability of the method. This issue arises due to the use in previous formulations of incomplete polynomials that are subsequently non-affine invariant. This dissertation lays out …

Self-Alignment Of Silicon Microparts On A Hexadecane-Water Interface By Surface Tension, Caroline Elizabeth Liberti

USF Tampa Graduate Theses and Dissertations

Mechanical assembly of systems and structures on the micro-scale can be inefficient as particles of sub-millimeter dimensions are difficult to manipulate. Cutting edge manufacturing methods implement self-assembly as an approach to ordering micro and nano-sized parts into a desired arrangement. This thesis studies a technique utilizing surface tension as a method of actuating microparts on a liquid-liquid interface via lateral capillary interactions. Preliminary experimentation is conducted to investigate the feasibility of developing a new method for self-alignment of microparts by observing the influence of interfacial geometry on the movement of silicon tiles along a hexadecanewater interface. Different surface geometries are …

Operational Performance Evaluation Of Four Types Of Exit Ramps On Florida's Freeways, Linjun Lu

USF Tampa Graduate Theses and Dissertations

This research focuses primarily on the analysis of exit ramp performance related to safety and operations. The safety analysis focuses on the impacts of different exit ramp types for freeway diverge areas and different factors contributing to the crashes that occur on the exit ramp sections. The operational analysis is based mainly on simulations by TSIS-CORSIM. Different ramp effects and guidance for selecting optimal exit ramp type are concluded. Issues related to ramp sections and crossroad sections are also demonstrated. Minimum ramp length and minimum distance between ramp terminal and downstream or upstream intersections are calculated. The operational analysis was …