Search Results (1 - 25 of 12229 Results)

Sort By  
Sort Dir
 
Results per page  

Balagurunathan, JayakishanInvestigation of Ignition Delay Times of Conventional (JP-8) and Synthetic (S-8) Jet Fuels: A Shock Tube Study
Master of Science (M.S.), University of Dayton, 2012, Mechanical Engineering
The global depletion of petroleum-based fuels has led the world to more closely examine alternate fuels. Therefore, alternate fuels produced from feedstocks such as coal, soybeans, palm oil or switch grass through methods such as coal liquefaction, biomass gasification, and Fischer-Tropsch synthesis have been tested. Among these techniques, fuels generated using Fischer-Tropsch technologies are of interest because they produce clean burning hydrocarbons similar to those found in commercial fuels. Therefore, in this study the Fischer-Tropsch derived S-8 fuel was evaluated as a drop-in replacement for the jet fuel JP-8. The jet fuel JP-8 is comprised of n-, iso- and cyclo- alkanes as well as aromatics while the S-8 fuel is primarily comprised of n- and iso- alkanes. The composition of the fuel affects its ignition characteristics chemically and physically by either advancement or delay of time to ignition. Since this study focused on the chemical effects, the fuels were completely pre-vaporized and pre-mixed. A high pressure, high temperature heated single pulse shock tube was used for this study. The shock tube is an established experimental tool used to obtain ignition delay data behind reflected shock waves under operating conditions relevant to modern engines. The experiments were conducted over a temperature range of 1000-1600 K, a pressure of 19±2 atm, equivalence ratios of 0.5, 1 and 3, within a dwell time of 7.6±0.2 ms and an argon dilution of 93% (v/v). Ignition delay times were measured using the signal from the pressure transducer on the end plate with guidance from the optical diagnostic signal. Along with JP-8 and S-8, the ignition delay of n-heptane was also studied. N-heptane was chosen to represent the n-alkanes in the fuels for this study since it was present in both fuels and also to prove the fact that the n-alkanes were rate controlling. The results indicate that both S-8 and JP-8 fuels have similar ignition delays at corresponding equivalence ratios. The fuel-rich mixtures ignited faster at lower temperatures (<1150 K) and the fuel-lean mixtures ignited faster at higher temperatures (>1150 K). In the transition period between lower to higher temperatures (~1100-1200 K), the equivalence ratio had no significant effect on the ignition delay time. The results also show that the ignition delay time measurements of S-8 and JP-8 fuels are similar to the ignition delay of n-heptane at the equivalence ratio of Φ=0.5 and thereby indicate that the n-alkanes present in these fuels controlled the ignition under these conditions. The ignition delay results of S-8 and JP-8 at Φ=3.0 from this study were also compared to prior work (Kahandawala et al., 2008) on 2-methylheptane and n-heptane/toluene (80/20 liquid vol.%), respectively and found to be indistinguishable. This data serves to extend the gas phase ignition delay database for both JP-8 and S-8 and is the first known data taken for both these fuels at higher temperatures (>1000 K) for an equivalence ratio of 3.0 with argon as the diluent gas.

Committee:

Sukh Sidhu, Dr (Committee Chair); Philip Taylor, Dr (Committee Member); Moshan Kahandawala, Dr (Committee Member)

Subjects:

Aerospace Engineering; Aerospace Materials; Alternative Energy; Automotive Engineering; Automotive Materials; Chemical Engineering; Chemistry; Energy; Engineering; Environmental Engineering; Mechanical Engineering; Petroleum Engineering; Technology

Keywords:

Ignition delay; shock tube; S-8; JP-8; Jet fuels; Fuel characteristics; heated shock tube; Fischer-Tropsch; Alternate fuels; alkanes; synthetic fuel; fuel; iso-alkanes; jayakishan balagurunathan

Kondaveeti, RajivImpact of Halogenated Aliphatic and Aromatic Additives on Soot and Polycyclic Aromatic Hydrocarbons -- An Ethylene-air Laminar Co-flow Diffusion Flame Study
Master of Science (M.S.), University of Dayton, 2012, Mechanical Engineering

The objective of this study is to investigate the effects of aliphatic and aromatic halogenated additives on soot and PAH formation (polycyclic aromatic hydrocarbon) using a laminar co-flow ethylene-air diffusion flame. Both aliphatic surrogates (bromobutane, chlorobutane and bromo/chlorobutane mix) and aromatic surrogates (benzene, bromobenzene, chlorobenzene and bromo/chlorobenzene mix) were added to the base fuel for investigation. The soot particles were collected on quartz filters and their mass was determined using a Leco carbon burn-off method. The gaseous effluents were collected in an Amberlite XAD-2 sorbent trap and extracted using the Soxhlet technique. Gas chromatography / mass spectrometry (GC/MS) was used to identify and quantify the extracted gaseous effluents. Significant amounts of enols were detected along with PAHs, indicating that enols are also important intermediate species in hydrocarbon combustion.

The results showed that all the halogenated additives reduced the temperature of the sampling system, indicating flame suppression properties. All the additives gave increased soot yields when compared to the baseline experiment. The brominated fuel additives displayed a higher propensity to soot than the corresponding chlorinated fuel additives. The aromatic additives showed a greater tendency to soot than their aliphatic counterparts. All the additives increased the total PAH and enol yields, with benzene yielding the highest. The halogenated form of benzene decreased the total PAH and enol yields when compared to benzene, suggesting that halogens accelerate the conversion of PAHs to soot. The effect of bromine in increasing the total PAH and enol yields is more than that of chlorine.

Committee:

Dr. Sukh Sidhu (Committee Chair); Dr. Philip Taylor (Committee Member); Dr. Moshan Kahandawala (Committee Member)

Subjects:

Aerospace Engineering; Analytical Chemistry; Automotive Engineering; Chemical Engineering; Chemistry; Engineering; Environmental Engineering; Mechanical Engineering; Organic Chemistry; Petroleum Engineering

Keywords:

Co-Flow Ethylene-Air Diffusion Flame; Flame retardants; Halogenated additives; Brominated; Chlorinated; Benzene; Chlorobenzene; Bromobenzene; Chlorobutane; Bromobutane; Bromochloro mixtures; Emissions; Soot; PAHs; Polycyclic Aromatic Hydrocarbons; Enols

Briggs, Maxwell H.Improving Free-Piston Stirling Engine Power Density
Doctor of Philosophy, Case Western Reserve University, 2015, EMC - Mechanical Engineering
Analyses and experiments demonstrate the potential benefits of optimizing piston and displacer motion in a free piston Stirling Engine. Isothermal analysis shows the theoretical limits of power density improvement due to ideal motion in ideal Stirling engines. More realistic models based on nodal analysis show that ideal piston and displacer waveforms are not optimal, often producing less power than engines that use sinusoidal piston and displacer motion. Constrained optimization using nodal analysis predicts that Stirling engine power density can be increased by as much as 58% using optimized higher harmonic piston and displacer motion. An experiment is conducted in which an engine designed for sinusoidal motion is forced to operate with both second and third harmonics, resulting in a maximum piston power increase of 14%. Analytical predictions are compared to experimental data showing close agreement with indirect thermodynamic power calculations, but poor agreement with direct electrical power measurements.

Committee:

Joseph Prahl (Advisor)

Subjects:

Aerospace Engineering; Alternative Energy; Applied Mathematics; Conservation; Design; Electrical Engineering; Energy; Engineering; Mechanical Engineering; Mechanics; Naval Engineering; Nuclear Engineering; Technology

Keywords:

Stirling, Engine, Power Density, Energy, Free-Piston, Nodal Analysis, Isothermal Analysis, Analysis, Experimental Validation,

Thummalapalli, Vimal KumarBiomimetic Composite T-Joints
Master of Science (M.S.), University of Dayton, 2011, Materials Engineering

Composite structural joints, as observed throughout the natural world, have been systematically altered and proven via lengthy evolutionary processes. Biological fixed joints tend to exhibit unique attributes, including highly optimized fiber paths to minimize stress concentrations. In addition, since the joints consist of continuous, uncut fiber flow patterns, the joint does not inhibit the biological organism in the transportation of information, chemicals and food from one part of the body to the other. To the contrary, large sections of man-made composite material structures are often joined using bolted or bonded joints, which involve low strength and high stress concentrations. These methods are also expensive to achieve. Additional functions such as fluid transport, electrical signal delivery, and electrical and thermal conductivity across the joints typically require parasitic tubes, wires, and clips. By using the biomimetic methods, we seek to overcome the limitations which are present in the conventional methods. In the present work, biomimetic co-cured composite sandwich T-joints were constructed using unidirectional glass fiber, epoxy resin, and structural foam. The joints were fabricated using the wet lay-up vacuum bag resin infusion method. Foam sandwich T-joints with multiple continuous fiber architectures and sandwich foam thickness were prepared. The various joint designs were tested quasi-statically in bending of the T in a calibrated screw-driven load frame. Custom, purpose-designed fixtures were required to support the base of the joint during the bending load. The weight savings using the biomimetic approaches is discussed, as well as a comparison of failure modes versus fiber/core architectures is given.

In addition to developing structurally optimized, weight-efficient joints, a tremendous ancillary benefit to the approach is the ability to easily embed wires and micro tubes contiguous across the joined elements. This approach is key to achieving true robust structural multi-functionality.

Committee:

Steven Donaldson (Committee Chair); Thomas Whitney (Committee Member); Elias Toubia (Committee Chair)

Subjects:

Aerospace Engineering; Aerospace Materials; Automotive Engineering; Automotive Materials; Biology; Civil Engineering; Engineering; Materials Science; Mechanical Engineering; Mechanics; Naval Engineering; Plant Sciences; Polymers; Textile Research

Keywords:

Composites; Composite T-Joints; Sandwitch Structures; Biomimetics; Bionic

Howenstine, Julie AnneRecruitment Strategies Aiming to Attract Females into Undergraduate Engineering Programs: Examining Their Role and Use
Doctor of Philosophy, University of Toledo, 2013, Higher Education
By 2009, the percentage of women who graduated with general undergraduate degrees had increased to almost 58% of all students who completed 4-year degree programs (National Center for Education Statistics, 2009a). These percentages, however, have not been reflected in the enrollment rates of females into undergraduate engineering programs. In 2009, the percentage of females enrolled in undergraduate engineering degrees was only 13% (National Center for Education Statistics, 2009b). Education is a lifelong decision and individuals are becoming more psychologically involved in their college choice (Maringe & Gibbs, 2009). Recruitment activities are only one factor in the college choice decision but are an important one. Recruitment strategies to attract under-represented groups to the field of engineering had in general lacked success. Recruitment is a way to represent and promote a college or a university truthfully to those who are seeking information about it (National Association for College Admission Counseling, 2009). Recruiting consists of initiatives and materials which serve to persuade prospective students to enroll in schools and specific degree programs. Understanding the specific types of recruitment strategies created for women and the way recruitment impacts enrollment trends of women will help institutions become more effective at attracting female students into engineering programs. While research on recruitment has identified some recruitment strategies effective in attracting women to engineering, such as mentoring to prospective students (Ocif & Marshall-Goodell, 1996; Wilkins et al., 2006), marketing learning and living communities (Jaschik, 2010; Kuh et al., 2006; Stinson, 1990; Trenor, 2007; Washington Center website, 2011), as well as offering female-focused financial aid programs (Astin 1997; Cech et al., 2008) to prospective students, we still do not fully understand the whole array of recruitment strategies geared towards women. This study explored, for the first time, the array of recruitment strategies used by institutions to recruit women into undergraduate engineering degree programs. Its purpose was to map what institutions do to recruit women into undergraduate engineering programs, and shed light on why and how these institutions use the recruitment strategies they use. In addition this study aimed to analyze a potential relationship of strategies geared specifically for women with enrollment trends of female undergraduates in engineering programs. Although the study identified a host of traditional and specialized recruitment strategies geared for women, it also confirmed that many institutions have not yet initiated activities to recruit women to their engineering programs. Amongst those women-specific recruitment initiatives that the study identified, mentoring programs, female-focused financial aid, and female campus visits emerged as the prevalent ones. In addition, institutions often included female students and faculty as recruiters and role models, emphasized the need to build relationships with university representatives and the institution in general, and utilized existing programs designed for women as part of their recruitment message.

Committee:

Snejana Slantcheva-Durst, Ph.D. (Advisor); Anthony Koh, Ph.D. (Committee Member); Marek Kolar, Ph.D. (Committee Member); Vickie Kuntz, Ph.D. (Committee Member)

Subjects:

Civil Engineering; Education; Electrical Engineering; Engineering; Gender Studies; Higher Education; Industrial Engineering; Marketing; Mass Communications; Mechanical Engineering; Personal Relationships; Womens Studies

Keywords:

Chilly climate; learning & living communities; promotional mix; advertising; personal selling; sales promotion; public relations; direct marketing; recruitment; recruitment initiatives; recruitment materials; specialized & traditional recruitment

Aliev, RuslanCFD Investigation of Heat Exchangers with Circular and Elliptic Cross-Sectional Channels
Master of Science in Mechanical Engineering, Cleveland State University, 2015, Washkewicz College of Engineering
Design of the fluid flow and heat transfer components utilizing the Computational Fluid Dynamics (CFD) is relatively new yet cheaper and accurate method that becomes popular and reliable today. In this thesis, design of a heat exchanger using CFD analysis technique is considered. A key investigation of this devise is the selection of the tubes and connection them to inlet and outlet manifolds. Correctly selected tube size and tube cross section impacts the heat exchanger performance. Thermal and hydrodynamic performance of the flow in circular and elliptic tubes connected to the inlet and outlet manifolds have been computationally investigated for maximum Figure of Merit. The tube with high Figure of Merit is the one with high heat transfer rate and low pressure drop. The tube has four different configurations of the cross section: a circular tube and three elliptic tubes with aspect ratios = 0.75, 0.50, and 0.25. All tubes are constrained to have the same wetted perimeter and the length, thus have the same heat transfer area. The tube is a smooth straight tube that has the length of 0.3048 m (12 in.) and wetted perimeter of 0.0798 m (3.1416 in.). The tube wall thickness is negligible. The contribution of the inlet and outlet manifolds is examined. A wide range of Reynolds numbers is covered, Re =100 (laminar flow), 10,000 (transitional flow), and 20,000 (turbulent flow). ANSYS FLUENT commercial code has been utilized in this investigation. The code was validated matching with experimental correlations (for developing hydrodynamic and thermal flow) available in the literature. The CFD simulation results were in agreement with the experimental correlation within 5%. This investigation started with simulating 12 different flow conditions inside the tubes without manifolds: three sets with four different tube options (as stated above) in each set. Each set represents the different flow regime: laminar transitional and turbulent with set Reynold number value, as noted earlier. All CFD simulation results were evaluated for their Figure of Merit (“Goodness” factor). The elliptic tube with aspect ratio = 0.25 showed the highest figure of merit for all cases of Re. In the following stage of this research the results of selected tube (aspect ratio = 0.25) was integrated with inlet and outlet manifolds. In this scenario only laminar and turbulent flow regimes were examined. The contribution of the inlet and outlet manifolds overall resulted a negative effect. The reasons of that impact are the following: (1) the inlet flow condition into the tube is no longer uniform (as was assumed in the earlier study), (2) the pressure drop in the manifolds are significantly higher than that in the tube. and (3) the tube length investigated is short. Despite significantly improved thermal characteristics of the tube flow after adding the manifolds, the magnitude of increased friction factor influenced the value of Figure of Merit.

Committee:

Mounir Ibrahim, PhD (Committee Chair); Majid Rashidi, PhD (Committee Member); Asuquo Ebiana, PhD (Committee Member)

Subjects:

Aerospace Engineering; Automotive Engineering; Mechanical Engineering; Nuclear Engineering; Petroleum Engineering

Keywords:

CFD analysis; circular and elliptic tube flow; heat exchanger; internal fluid flow; heat transfer; internal forced convection; figure of merit

Almansour, Amjad Saleh AliUSE OF SINGLE TOW CERAMIC MATRIX MINICOMPOSITES TO DETERMINE FUNDAMENTAL ROOM AND ELEVATED TEMPERATURE PROPERTIES
Doctor of Philosophy, University of Akron, 2017, Mechanical Engineering
The room and high temperature mechanical properties of continuous ceramic fiber reinforced matrix composites makes them attractive for implementation in aerospace and nuclear applications. However, the effect of fiber content has not been addressed in previous work. Therefore, single tow composites with fiber content ranging from 3 to 47 % was studied. Single fiber tow minicomposite is the basic architectural feature of woven and laminate ceramic matrix composites (CMCs). An in depth understanding of the initiation and evolution of damage in various ceramic fiber reinforced minicomposites with different fiber volume fractions and interphases was investigated employing several non-destructive evaluation techniques. A new technique is used to determine matrix crack content based on a damage parameter derived from speed of sound measurements which is compared with the established method using cumulative energy of Acoustic Emission (AE) events. Also, a modified theoretical model was implemented to obtain matrix stress at the onset of matrix cracking. Room temperature tensile, high temperature creep rupture and high temperature oxidation degradation loading conditions were all considered and composites’ constituents were characterized. Moreover, fibers/matrix load sharing was modeled in creep and fiber volume fraction effect on load transfer was investigated using derived theoretical models. Fibers and matrix creep parameters, load transfer model results and numerical model methodology were used to construct minicomposites’ creep strain model to predict creep damage of the different fiber type and content minicomposites. Furthermore, different fiber volume fractions ceramic matrix minicomposites’ electrical resistivity temperature dependence isn’t well understood. Therefore, the influence of fiber content, heat treatment cycles and creep on electrical resistivity measurements of SiC/SiC minicomposites were also studied here. Next, minicomposites’ testing and characterization methodology was used to screen and characterize slurry-derived mullite bond coated minicomposites for enhanced oxidation and creep resistance. Finally, this study shows valuable testing methodologies and models approach for use in screening, developing and improving new generation ceramic matrix composites.

Committee:

Gregory Morscher, Dr (Advisor); Tirumalai Srivatsan, Dr (Committee Member); Craig Menzemer, Dr (Committee Member); Alper Buldum, Dr (Committee Member); Kwek Tze Tan, Dr (Committee Member); Robert Goldberg, Dr (Committee Member); Manigandan Kannan, Dr (Committee Member)

Subjects:

Acoustics; Aerospace Engineering; Aerospace Materials; Chemical Engineering; Chemistry; Electrical Engineering; Engineering; Experiments; High Temperature Physics; Materials Science; Mathematics; Mechanical Engineering; Mechanics; Metallurgy; Theoretical Mathematics; Theoretical Physics

Keywords:

Minicomposites,CMCs,Velocity of Sound, Creep, Creep Modelling, Creep Damage Characterization, Failure Analysis, Acoustic Emission, Electrical Resistance, Environmental Barrier Coating, EBC, CVI-SiC Creep, SiC Fibers Creep, Stress Dependent Matrix Cracking

Aksu, AlperBENCH-TOP VALIDATION OF INTELLIGENT MOUTH GUARD
Master of Science in Biomedical Engineering, Cleveland State University, 2013, Fenn College of Engineering
Concussion is the signature athletics injury of the 21st Century. Scientists are hard at work monitoring effects of hard impacts on the human brain. However, existing tools and devices are inadequate to screen the effects. Hence, a new approach is required to accurately quantify peak values of head impacts or concussions and relate these values to clinical brain health outcomes. A new head impact dosimeter, the Intelligent Mouth Guard (IMG) has been developed and can be conveniently located inside the mouth. In this study, the IMG printed circuit board (PCB) including four (4) high-quality shock resistant sensors has been developed and implemented as a tri-axial impact analyzer in a mouthpiece. The bench-top validation process of the IMG was divided into theoretical uncertainty analysis of linear accelerometers, theoretical uncertainty analysis of angular rate sensors, bench-top uniaxial impact testing of linear accelerometers and bench-top uniaxial static testing of angular rate sensors. More specifically, this study also presents a method based on National Bureau of Standards (NBS) of analyzing measurement error for any components of a specialized electrical circuit and any types of data acquisition system. In the current application of an IMG printed circuit board (PCB), utilized for linear acceleration, angular acceleration and angular velocity measurements, has sensor uncertainties quantified. The uncertainty model is branched into two parts: The bias error (B) and the random error (R). In this paper, expected measurement error types for PCB components (ADXL001 linear accelerometer, L3G4200D gyroscope) are quantified and their effects on the IMG system are computed. The uncertainty analysis presented here can be a guide in future in vitro and in vivo IMG validation tests. During bench-top testing, IMG linear accelerometers quantified peak linear acceleration with 98.2% accuracy and 98.0% precision. The IMG gyroscope quantified peak angular velocity with 97.0% accuracy and 99.7% precision. In summary, the results showed that the IMG may possess adequate sensors to fulfill the expectations relevant to head concussion diagnosis with a known uncertainty. Future work should involve improvement for optimum data analysis and filtering methods, further validation testing, including in vitro and in vivo tests.

Committee:

Adam Bartsch, Ph.D. (Advisor); Murad Hizlan, Ph.D. (Committee Member); Sridhar Ungarala, Ph.D. (Committee Member); Majid Rashidi, Ph.D. (Committee Member)

Subjects:

Automotive Engineering; Biomedical Engineering; Electrical Engineering; Engineering; Mechanical Engineering

Keywords:

Head Impact, Concussion, Statistical Uncertainty Analysis, Validation, Mouth Guard, Bench-Top Testing, Sensor Uncertainty Analysis

Ghanbarian-Alavijeh, BehzadModeling Physical and Hydraulic Properties of Disordered Porous Media: Applications from Percolation Theory and Fractal Geometry
Doctor of Philosophy (PhD), Wright State University, 2014, Environmental Sciences PhD
A fundamental component of the hydrologic cycle is the movement of fluids in the pore space of geological formations and soils. Prediction of the motion of fluids in such porous materials requires first modeling the physical properties of the medium itself, and second, invoking a capable theory to describe fluid transport in tortuous interconnected pathways. In this dissertation, for the former we use fractal geometry since most phenomena in nature are fractal, and for the latter percolation theory is applied because it has successfully described flow and transport in disordered networks and media. We propose models for the soil water retention curve and tortuosity. We also focus on modeling different kinds of transport, such as air permeability, gas and solute diffusion, unsaturated hydraulic conductivity, and dispersion. Applications of critical path based analyses of flow and conduction properties reveals asymmetry between the saturation dependence of the air and water permeabilities as well as distinctions between the electrical and hydraulic conductivities. In particular, the saturation dependence of the hydraulic conductivity is strongly dependent on the pore size distribution, but that of the electrical conductivity is only weakly so, and the air permeability is not dependent. Gas diffusion relates more closely to the air permeability, while solute diffusion is, under a wide range of circumstances, tied directly to the electrical conductivity. Comparisons with experiment confirmed this. Applying critical path analysis and universal scaling from percolation theory to media that could be treated within the pore-solid fractal (PSF) approach, we developed unimodal and bimodal models for unsaturated hydraulic conductivity in porous media. Predictions were developed for unsaturated hydraulic conductivity using the soil water retention curve. To evaluate our unimodal model we used 104 experiments from the UNSODA database and compared with two other models. The results obtained indicated that our non-universal percolation based model predicted unsaturated hydraulic conductivity better than the other two models. In order to evaluate the bimodal models for soil water retention and unsaturated hydraulic conductivity curves, we compared them with 8 measured experiments collected from the UNSODA database. Although the bimodal unsaturated hydraulic conductivity model was fitted well to the experiments, we found discrepancy between measurements and predictions. We found that the predictions were relatively more successful for the first regime at large water contents than the second regime at low water contents. The universal scaling law from percolation theory was confirmed for the saturation dependence of the air permeability. Analyzing two independent databases including 39 experiments showed that the experimental exponent was 2.028 ± 0.028 and 1.814 ± 0.386 for the first and second databases, respectively. We found the extracted exponent in the power law fit is most sensitive to the measured values of the air permeability at low values of the air-filled porosity, and in cases where these experimental values are missing, the data can yield values significantly different from 2. We also found that the threshold value of the air-filled porosity could be predicted reasonably from the wet end of the soil water retention curve. Diffusion modeling in percolation clusters provided a theoretical framework to address gas and solute transport in porous media. Theoretically, above the percolation threshold, the saturation dependence of gas and solute diffusion should follow universal scaling from percolation theory with an exponent of 2.0. In order to evaluate our hypothesis, we used 71 and 106 gas and solute experiments, respectively, including different types of porous media available in the literature. Although our results conclusively confirmed the universality of gas diffusion, we found scatter in solute diffusion data. Nonetheless, the experimental exponent of solute diffusion was very close to 2 (1.842). We found that combining percolation and effective medium theories resulted in an accurate numerical prefactor for both gas and solute diffusion. We also developed a saturation dependence model for dispersion. Based on concepts from critical path analysis, cluster statistics of percolation, and fractal scaling of percolation clusters we derived an expression for the characteristic velocities along different pathways through the network. We compared our theoretical framework for solute transport with two experimental databases. Our model evaluation with experiments indicated excellent results. In the first dataset, we fitted our model to the arrival time distribution calculated from the measured breakthrough curve at saturation and determined the model parameters. Then those parameters were used to predict the arrival time distribution at two other saturations, giving an excellent match with the measurements. In the second dataset, the arrival time distribution was predicted from the measured soil water retention curve. Our results indicated that we predicted the arrival time distribution very well for 5 unsaturated experiments.

Committee:

Allen Hunt, Ph.D. (Advisor); Thomas Skinner, Ph.D. (Advisor); Muhammad Sahimi, Ph.D. (Committee Member); Robert Ritzi, Ph.D. (Committee Member); Chao Chen Huang, Ph.D. (Committee Member)

Subjects:

Agricultural Engineering; Agriculture; Chemical Engineering; Civil Engineering; Environmental Engineering; Environmental Science; Fluid Dynamics; Geological; Geology; Geophysical; Geophysics; Hydrologic Sciences; Hydrology; Petroleum Engineering; Physics; Soil Sciences; Theoretical Mathematics

Keywords:

Percolation theory, Fractals, Porous media, Dispersion, Unsaturated hydraulic conductivity, Air permeability, Diffusion, Tortuosity, Saturation dependence, Pore-size distribution

Roth, Nicholas DanielEnergy Assessment at a Health Care Facility
Master of Science, University of Toledo, 2010, Industrial Engineering

With the recent volatility in prices for coal and natural gas, energy conservation has become not only essential for environmental sustainability, but many organizations are finding it necessary to reduce their energy consumption for financial reasons. One of the most important initial steps that organizations must participate in before starting an energy reduction program is for them to conduct a full scale energy assessment.

While much of the focus of recent energy conservation efforts has been in the manufacturing and transportation industries, the healthcare industry is one that has often been neglected. What has made energy conservation even more of a necessity in healthcare has been the rise in costs associated with medical procedures and medical insurance.

One organization that is currently researching processes for conducting robust energy assessments is the Environmentally Conscious Design and Manufacturing Laboratory, funded by the University of Toledo College of Engineering and the Lucas County Solid Waste Management District. This lab, which has been in existence since 1996, has performed a number of solid waste assessments and has only recently been performing energy assessments. Following the 2006 merger between the University of Toledo and the Medical University of Ohio, the research lab has taken much more of an interest in researching medical facilities.

The purpose of this is to examine how an energy assessment process can be adopted for use in a medical facility. Included in this study is a case study of an energy assessment that was performed on a 292 bed hospital in Northwest Ohio.

Committee:

Matthew Franchetti, Ph.D. (Committee Chair); Abdollah Afjeh, Ph.D. (Committee Member); Steven Kramer, Ph.D. (Committee Member)

Subjects:

Electrical Engineering; Energy; Engineering; Environmental Engineering; Health Care; Industrial Engineering; Mechanical Engineering

Keywords:

energy assessment; health care; lighting; electricity; hospital

Lipkin, IlyaTesting Software Development Project Productivity Model
Doctor of Philosophy in Manufacturing and Technology Management, University of Toledo, 2011, Manufacturing and Technology Management

Software development is an increasingly influential factor in today’s business environment, and a major issue affecting software development is how an organization estimates projects. If the organization underestimates cost, schedule, and quality requirements, the end results will not meet customer needs. On the other hand, if the organization overestimates these criteria, resources that could have been used more profitably will be wasted.

There is no accurate model or measure available that can guide an organization in a quest for software development, with existing estimation models often underestimating software development efforts as much as 500 to 600 percent. To address this issue, existing models usually are calibrated using local data with a small sample size, with resulting estimates not offering improved cost analysis.

This study presents a conceptual model for accurately estimating software development, based on an extensive literature review and theoretical analysis based on Sociotechnical Systems (STS) theory. The conceptual model serves as a solution to bridge organizational and technological factors and is validated using an empirical dataset provided by the DoD.

Practical implications of this study allow for practitioners to concentrate on specific constructs of interest that provide the best value for the least amount of time. This study outlines key contributing constructs that are unique for Software Size E-SLOC, Man-hours Spent, and Quality of the Product, those constructs having the largest contribution to project productivity. This study discusses customer characteristics and provides a framework for a simplified project analysis for source selection evaluation and audit task reviews for the customers and suppliers.

Theoretical contributions of this study provide an initial theory-based hypothesized project productivity model that can be used as a generic overall model across several application domains such as IT, Command and Control, Simulation and etc¿¿¿ This research validates findings from previous work concerning software project productivity and leverages said results in this study. The hypothesized project productivity model provides statistical support and validation of expert opinions used by practitioners in the field of software project estimation.

Committee:

Jeen Su Lim (Committee Chair); James Pope (Committee Member); Michael Mallin (Committee Member); Michael Jakobson (Committee Member); Wilson Rosa (Advisor)

Subjects:

Aerospace Engineering; Armed Forces; Artificial Intelligence; Business Administration; Business Costs; Computer Engineering; Computer Science; Economic Theory; Economics; Electrical Engineering; Engineering; Industrial Engineering; Information Science; Information Systems; Information Technology; Management; Marketing; Mathematics

Keywords:

"Software Estimation"; "Software Cost Model"; "Department of Defense Data"; COCOMO; "Software Project Productivity Model"

Sander, Zachary HugoHeat Transfer, Fluid Dynamics, and Autoxidation Studies in the Jet Fuel Thermal Oxidation Tester (JFTOT)
Master of Science (M.S.), University of Dayton, 2012, Mechanical Engineering
Modern military aircraft use jet fuel as a coolant before it is burned in the combustor. Prior to combustion, dissolved O2 and other heteroatomic species react with the heated fuel to form insoluble particles and surface deposits that can impair engine performance. For safe aircraft operation, it is important to minimize jet fuel oxidation and resultant surface deposition in critical aircraft components. The Jet Fuel Thermal Oxidation Tester (JFTOT) is a thermal stability test that measures the tendency for fuel to form such deposits and delivers a pass/fail grade for each fuel tested. However, the extent of oxidation and the corresponding deposition occurring in the JFTOT is not fully understood. A JFTOT Model Mark II was modified to include a bulk outlet thermocouple measurement and a downstream oxygen sensor to measure bulk oxygen consumption. Experimental results show a direct relationship between the bulk outlet temperature and JFTOT setpoint temperature with the bulk outlet less than the setpoint temperature. Several fuels were also tested at varying setpoint temperatures with complete oxygen consumption by 320°C and a wide range of oxygen consumption from 10-85% at 260°C. Due to the complex fluid flows in the JFTOT, computational fluid dynamics (CFD) was used to model the heat transfer and fluid flow. A three-dimensional simulation showed considerable recirculation within the JFTOT due to buoyancy effects from gravity and resulted in complex residence time behavior. In addition, CFD simulations performed with a pseudo-detailed chemical kinematic mechanism showed an under prediction in both oxidation and deposition for similar fuels tested experimentally but yielded bulk outlet temperature predictions of less than 2% error. Simulations of deposition were of the right order of magnitude and matched the deposit profile of comparable experimental ellipsometry data.

Committee:

Steven S. Zabarnick, PhD (Committee Co-Chair); Jamie S. Ervin, PhD (Committee Co-Chair); James T. Edwards, PhD (Committee Member)

Subjects:

Aerospace Engineering; Chemical Engineering; Chemistry; Energy; Engineering; Fluid Dynamics; Mechanical Engineering; Petroleum Engineering

Keywords:

JFTOT;CFD; heat transfer; oxidation; autoxidation; deposition; ellipsometry; jet fuel thermal oxidation tester; oxygen consumption; FT; fischer tropsh; hrj; jp-8; jet a-1; thermal stability; fluid mechanics; astm d3241; flir; interferometry; udri

Gunbatar, YakupNonlinear Adaptive Control and Guidance for Unstart Recovery for a Generic Hypersonic Vehicle
Doctor of Philosophy, The Ohio State University, 2014, Electrical and Computer Engineering
This work presents the development of an integrated flight controller for a generic model of a hypersonic air-breathing vehicle. The flight control architecture comprises a guidance and trajectory planning module and a nonlinear inner-loop adaptive controller. The emphasis of the controller design is on achieving stable tracking of suitable reference trajectories in the presence of a specific engine fault (inlet unstart), in which sudden and drastic changes in the vehicle aerodynamics and engine performance occur. First, the equations of motion of the vehicle for a rigid body model, taking the rotation of the Earth into account, is provided. Aerodynamic forces and moments and engine data are provided in lookup-table format. This comprehensive model is used for simulations and verification of the control strategies. Then, a simplified control-oriented model is developed for the purpose of control design and stability analysis. The design of the guidance and nonlinear adaptive control algorithms is first carried out on a longitudinal version of the vehicle dynamics. The design is verified in a simulation study aiming at testing the robustness of the inner-loop controller under significant model uncertainty and engine failures. At the same time, the guidance system provides reference trajectories to maximize the vehicle's endurance, which is cast as an optimal control problem. The design is then extended to tackle the significantly more challenging case of the 6-degree-of-freedom (6-DOF) vehicle dynamics. For the full 6-DOF case, the adaptive nonlinear flight controller is tested on more challenging maneuvers, where values of the flight path and bank angles exceed the nominal range defined for the vehicle. Simulation studies show stable operation of the closed-loop system in nominal operating conditions, unstart conditions, and during transition from sustained scramjet propulsion to engine failure mode.

Committee:

Andrea Serrani, Prof. (Advisor); Umit Ozguner, Prof. (Committee Member); Zhang Wei, Prof. (Committee Member)

Subjects:

Aerospace Engineering; Computer Engineering; Electrical Engineering; Engineering

Keywords:

Hypersonic; unstart; adaptive control; nonlinear control; adaptive backstepping; trajectory optimization; optimal; tuning functions; longitudinal; 6-DOF; 3-DOF; Earth rotation; Control design model; coordinated turn; endurance; Equations of motion

Lee, Jin WooMulti-level Decoupled Optimization of Wind Turbine Structures Using Coefficients of Approximating Functions as Design Variables
Doctor of Philosophy, University of Toledo, 2017, Mechanical Engineering
This dissertation proposes a multi-level optimization method for slender structures such as blades or towers of wind turbine structures. This method is suited performing structural optimizations of slender structures with a large number of design variables (DVs). The proposed method uses a two-level optimization process: a high-level for a global optimization of a structure and a low-level for optimizations of sectioned computational stations of the structure. The high-level optimization uses approximating functions to define target structural properties along the length of a structure, such as stiffness. The approximating functions are functions of the distance from the root of the structure that are defined using basis functions such as polynomials or exponential functions. The high-level DVs are the coefficients of the functions. Thus, the number of the high-level DVs is independent of the number of sections. Moreover, selecting smooth approximating functions help to obtain alternative designs with smooth shapes. The low-level optimization finds an optimum parametric design, such as laminate layups, that matches with the target structural properties defined at the high-level optimization. At the low-level optimization, the proposed method uses an optimizer in each section. Each optimizer is independent of the optimizers in the other sections, thereby decomposing a large optimization problem into several small ones. This approach reduces the number of DVs per optimizer at the low-level optimization which reduces the design space of each section and eliminates the design space of coupling between sections. Once optimum designs are found from all sections at the low-level, the high-level solvers evaluate them for the entire structure. The advantage of the proposed method is that it reduces the number of iterations of the high-level optimization because it considers a small number of high-level DVs. Computational efficiency increases because the computationally extensive high-level solvers need to be run less frequently to obtain an optimum solution. An additional advantage of the proposed method is that it produces many feasible alternatives. Using example problems, the paper demonstrates that the proposed method converges faster in the early iterations, and generates more alternative designs with smooth geometry than traditional single-level methods.

Committee:

Efstratios Nikolaidis, Ph.D. (Committee Chair); Vijay Devabhaktuni, Ph.D. (Committee Co-Chair); Abdollah Afjeh, Ph.D. (Committee Co-Chair); Sorin Cioc, Ph.D. (Committee Member); Douglas Nims, Ph.D. (Committee Member); Larry Viterna, Ph.D. (Committee Member)

Subjects:

Aerospace Engineering; Energy; Engineering; Environmental Economics; Environmental Engineering; Mechanical Engineering; Operations Research

Keywords:

optimization; multi-level; decoupled; structural; design; analysis; approximating function; design variable; computational cost; composite material; renewable energy; wind turbine; blade; tower; modeFRONTIER; FAST; Department of Energy

Shohel, Muhammad Shah NewazPanting Fatigue of Welded Steel Tee Details
Doctor of Philosophy, University of Akron, 2015, Civil Engineering
A total of thirty samples of A36 structural “T” were tested under fatigue loading. Of the thirty, ten samples were tested under panting fatigue conditions. At a constant amplitude of stress ratio 0.01, fatigue tests were conducted under axial, combined axial and bending and pure bending conditions. Test data for a predefined stress range (Sre) and number of cycles to failure from the specimens were used to construct the stress range vs. life (S-N) curves for these structural welded “T”s. Differences were observed and noted in the individual S-N curves as well as in the combined S-N curves. Comparison of the S-N curves provided an indication of a suitable design resistance for these welded details. Fatigue design classification systems need to implement this classification for panting conditions, and design provisions are recommended. After testing, fatigue cracks were exposed and examined in a scanning electron microscope (SEM) to study the crack initiation and crack growth kinetics as well as the characteristics features that governed the observed fatigue behavior. The use of stress range as the primary fatigue strength parameter is a direct consequence of the role of residual stresses in the welded details and affects the S-N curves and is reflected in the use of the stress range and influences the slope as compared to typical design S-N curves. In order to understand the residual stresses and the effect on welded “T” fatigue behavior, two specimens were tested by the hole-drilling technique. Both the Power Series and the Integral Methods were employed for reducing the data. Resulting stress profiles and the general data trends were examined and compared for both cases and its effect on the S-N curves were discussed. Experiments were enriched with a Finite Element (FEA) study for axial, axial plus bending and pure bending specimens to numerically calculate the stress intensity factor (KI) in two dimensions as well as three dimensions. Stress intensity factors found in 2D and 3D finite element analysis were verified by widely accepted analytical solutions available in the literature. Three-dimensional opening mode stress intensity factors (3D-SIF) for structural steel welded “T” details study showed that a two-dimensional shape dependent correction factor can be introduced for a semi-elliptical surface crack for evaluating the three dimensional stress intensity factor. The minor axis (a) to major axis (c) i.e. the aspect ratio (a/c) of a semi-elliptical crack plays a key role in the approximation of 3D-SIF values, and in the present study were estimated for a three-dimensional crack analysis. The estimated three dimensional stress intensity factor (3D-SIF) was determined by a correlation between a/c and the two dimensional stress intensity (2D-SIF) factor for semi-elliptical cracks in the thickness direction of a welded “T”. Resulting equations may be used to estimate the 3D-SIF values from the 2D-SIF without much ambiguity. Recommendations regarding the analytical solutions and the design of S-N curves are provided when secondary bending effects are present

Committee:

Craig Menzemer, Dr. (Advisor); Anil Patnaik, Dr. (Committee Member); David Roke, Dr. (Committee Member); T.S. Srivatsan, Dr. (Committee Member); Dmitry Golovaty, Dr. (Committee Member)

Subjects:

Aerospace Engineering; Civil Engineering; Engineering; Materials Science; Mathematics; Mechanical Engineering

Keywords:

Panting fatigue; welded steel T details; S-N curves; 2D and 3D stress intensity factor; ANSYS

McNeilly, Ryan J.Nanostructured Microcantilever for the Detection of Volatile Compounds
Master of Science (M.S.), University of Dayton, 2017, Bioengineering
In this study, nanostructured, functionalized microcantilevers have been designed, fabricated, and characterized for the sensing of volatile organic compounds. Sensing devices were fabricated with either four or eight hammerhead-shaped cantilevers. These cantilevers vibrate laterally in-plane making them highly suitable for sensing in both air and liquid. Silicon oxide nanostructure was deposited on the cantilevers to increase the surface area and sensitivity of the devices. Molecular recognition peptides were chemically tethered to the surfaces to create a selective response for the analytes of interest. When the analytes have bound to the surface of the cantilever, a shift in resonance frequency is produced and detected by piezoresistive sensors. This frequency shift can be used to determine the mass of analyte bound to the surface. The cantilever sensors are expected to provide fast and highly sensitive detection, and can be fabricated in an array format for sensing multiple compounds in complex samples. The nanostructured cantilever sensors show strong potential for applications in medical, environmental, food safety, and hazardous gas monitoring applications.

Committee:

Karolyn Hansen, Ph.D. (Advisor); Kristen Comfort, Ph.D. (Committee Member); Matthew Lopper, Ph.D. (Committee Member)

Subjects:

Biochemistry; Biomedical Engineering; Chemical Engineering; Electrical Engineering; Mechanical Engineering

Keywords:

biosensor; sensor; microcantilever; volatile organic compound; nanostructure; glancing angle deposition

Keerthi, SandeepLow Velocity Impact and RF Response of 3D Printed Heterogeneous Structures
Master of Science in Mechanical Engineering (MSME), Wright State University, 2017, Mechanical Engineering
Three-dimensional (3D) printing, a form of Additive manufacturing (AM), is currently being explored to design materials or structures with required Electro-Mechanical-Physical properties. Microstrip patch antennas with a tunable radio-frequency (RF) response are a great candidate for 3D printing process. Due to the nature of extrusion based layered fabrication; the processed parts are of three-layer construction having inherent heterogeneity that affects structural and functional response. The purpose of this study is to identify the relationship between the anisotropy in dielectric properties of AM fabricated acrylonitrile butadiene styrene (ABS) substrates in the RF domain and resonant frequencies of associated patch antennas and also to identify the response of the antenna before and after a low velocity impact. In this study, ANSYS high frequency structure simulator (HFSS) is utilized to analyze RF response of patch antenna and compared with the experimental work. First, a model with dimensions of 50 mm x 50 mm x 5 mm is designed in Solidworks and three separate sets of samples are fabricated at three different machine preset fill densities using an extrusion based 3D printer LulzBot TAZ 5. The actual solid volume fraction of each set of samples is measured using a 3D X-ray computed tomography microscope. The printed materials appeared to exhibit anisotropy such that the thickness direction dielectric properties are different from the planar properties. The experimental resonant frequency for one fill-density is combined with ANSYS-HFSS simulation results to estimate the bulk dielectric constant of ABS and the equivalent dielectric properties in planar and thickness directions. The bulk dielectric properties are then used in HFSS models for other two fill densities and the simulated results appear to match reasonably well with experimental findings. The similar HFSS modeling scheme was adopted to understand the effect of material heterogeneity on RF response. In addition, a hybrid structure with dimensions of 50 mm x 50 mm x 20 mm is designed with the first 15 mm thickness being a cellular BCC structure and the other 5 mm being a solid cuboid. These samples are printed on an extrusion based 3D printer Stratasys uPrint using ABS. A patch antenna is embedded at the interface of the solid and the cellular structure. Both ABAQUS finite element modeling and experimental methods are used to understand the load-displacement and the energy absorption behavior of the hybrid structure under low velocity impact loadings. The hybrid structure is impacted on both sides to investigate the damage tolerance capabilities of embedded electronic components.

Committee:

Ahsan Mian, Ph.D. (Advisor); Raghavan Srinivasan, Ph.D. (Committee Member); Joy Gockel, Ph.D. (Committee Member)

Subjects:

Aerospace Engineering; Automotive Engineering; Design; Electrical Engineering; Mechanical Engineering; Mechanics; Plastics; Technology

Keywords:

Additive Manufacturing; AM; 3D Printing; Acrylonitrile Butadiene Styrene; ABS; Microstrip Patch Antenna; Porous; ANSYS-HFSS; ABAQUS-Explicit Dynamics; Hybrid Structure; Lattice Structure; BCC; RF applications; Low Velocity Impact; Dielectric material

Lee, Jung JuRemoval of Microcystin-LR from Drinking Water Using Adsorption and Membrane Processes
Doctor of Philosophy, The Ohio State University, 2009, Civil Engineering

The presence of cyanobacteria and associated cyanotoxins in surface water is of increasing concern. Microcystins are one of the most dangerous and commonly occurring classes of cyanotoxins. Ingestion of microcystin-LR can lead to liver damage and the promotion of liver tumors. Due to adverse health effects, the World Health Organization set a guideline level of 1 part per billion (ppb) for microcystin-LR in drinking water. However, current water treatment facilities may not specifically treat drinking water for microcystins.

The overall goal of this research was to develop an advanced and effective process for the removal of microcystins from drinking water. To achieve this goal, powdered activated carbon (PAC), iron oxide nanoparticles, and ultrafiltration (UF) membranes were explored as promising treatment technologies.

The use of ultrafiltration was investigated for the rejection of microcystin-LR from drinking water. Adsorption dominated rejection for most UF membranes, at least at early filtration times, while both size exclusion and adsorption were important in removing microcystin-LR by the tight thin-film membranes. The extent of membrane adsorption was generally related to membrane hydrophobicity.

The application of ultrafiltration coupled with powdered activated carbon (PAC-UF) was also investigated. Of the two different PAC materials, wood-based activated carbon was more effective at removing microcystin-LR than coconut-based carbon due to greater mesopore volume. The PAC-UF system had the highest removal efficiency among the three processes (i.e., PAC adsorption, ultrafiltration, and PAC-UF) for both hydrophobic polyethersulfone (PES) and hydrophilic cellulose acetate (CA) membranes. When PAC was coupled to UF using PES membranes, greater removal of microcystin-LR occurred compared to when CA membranes were used, due to sorption of the toxin to the PES membrane surface.

In further studies, Suwannee River Fulvic Acid (SRFA) was used to examine the effect of natural organic matter on the removal of microcystin-LR during UF or PAC-UF. When PES membranes were previously fouled by SRFA, increased size exclusion and reduced adsorption of microcystin-LR were observed, probably due to pore blockage and fewer available adsorption sites as a result of SRFA sorption. However, simultaneous addition of both microcystin and SRFA resulted in no change in microcystin-LR adsorption. The presence of SRFA reduced microcystin-LR removal by PAC-UF, primarily due to competition between SRFA and microcystin-LR for adsorption sites on the PAC surface.

Finally, an adsorption study was performed on microcystin-LR using iron oxide (maghemite) nanoparticles. Adsorption was primarily attributed to electrostatic interactions, although hydrophobic interactions may also play a role. The adsorption of microcystin-LR decreased with increasing pH. The ionic strength affected microcystin adsorption by screening the electrostatic interactions. Adsorption decreased at higher SRFA concentrations (above 2.5 mg/L) due to competitive adsorption between SRFA and microcystin-LR for limited sorption sites.

This laboratory-scale work is an initial step in developing an advanced treatment system that could be easily incorporated into drinking water treatment facilities. It is expected that this research can provide both practical and fundamental information for more efficient process design, leading to effective removal of harmful cyanotoxins and improved water quality and safety.

Committee:

Harold Walker (Advisor); Linda Weavers (Committee Member); John Lenhart (Committee Member); Yu-Ping Chin (Committee Member)

Subjects:

Chemical Engineering; Chemistry; Civil Engineering; Engineering; Environmental Engineering; Environmental Science; Geochemistry

Keywords:

Cyanobacteria; Microcystin-LR; Removal, Adsorption, Powdered Activated Carbon, Ultrafiltration, PAC-UF, Iron Oxide Nanoparticles, Natural Organic Matter

Kosmerl, Paul F.Water Balance of Retrofit, Right-of-way Rain Gardens
Master of Science, The Ohio State University, 2012, Food, Agricultural and Biological Engineering
Increased storm runoff results from urbanization and development. Rain gardens can reduce runoff in a cost-effective manner as compared to expensive infrastructure construction, but more knowledge of their behavior and performance are required to increase their applications. This research demonstrates that rain gardens can reduce storm runoff from developments built without stormwater retention infrastructure to mitigate increases in storm runoff. Retrofit rain gardens were installed in a residential neighborhood in Westerville, Ohio, in July 2010. Between spring of 2011 and 2012, inflow and outflow volumes and soil water content were monitored for 20 simulated rainfall events. The change in water storage within the rain garden was calculated from the initial and final soil water content of 15 cm layers for the 60 cm depth of the rain gardens. A water balance equation was used to estimate the volume of water exfiltrating to the surrounding in situ soil. Overall, the rain gardens provided a 44% volume reduction from inflow to outflow with 15% of the inflow exfiltrating to the surrounding soil. Three inlet designs for right-of-way rain gardens were also evaluated. The original construction allowed for vegetative growth at the inlet, which accumulated debris and inhibited inflow during natural storm events. Replacing the vegetation and soil at the entrance with stones reduced hydrologic performance, but underlining the stones with bentonite clay provided a statistically significant increase in volume reduction during simulated rainfall events. This study finds that retrofit, right-of-way rain gardens can substantially reduce storm runoff in a residential development despite their proximity to curb underdrains and their small garden to impervious area ratios.

Committee:

Jay Martin, PhD (Advisor); Andrew Ward, PhD (Committee Member); Larry Brown, PhD (Committee Member)

Subjects:

Agricultural Engineering; Civil Engineering; Ecology; Engineering; Environmental Engineering; Hydrology

Keywords:

rain garden; bioretention; stormwater; hydrology

Wahl, Mark D.Key Influences on Hydraulic Efficiency in Treatment Wetlands
Doctor of Philosophy, The Ohio State University, 2013, Food, Agricultural and Biological Engineering
Too much of a good thing can become a problem. This is certainly the case with nutrients in surface waters. Excess nutrients are a concern in streams and lakes. While there are direct health risks related to drinking water contamination among vulnerable populations including infants, harmful algal blooms are a more prevalent concern since they manifest themselves at enrichment levels well below accepted drinking water standards. Half of the lakes in the United States have elevated nutrient levels, a condition that can ultimately lead to oxygen depletion. This problem is exported across state and national boundaries into coastal waters. Agricultural nutrient discharges are particularly difficult to address because, unlike end-of-pipe discharges, fertilizer runoff is hard to capture and treat in a cost effective manner. Appropriate technologies are needed that promote agricultural production through the sustainable management of natural resources. Treatment wetlands are a low-tech alternative to conventional water treatment. Constructed wetlands provide passive treatment of nutrient enriched runoff and other diffuse non-point sources of contamination through nutrient uptake, absorption, or chemical reduction. Hydraulic inefficiencies can substantially limit nutrient reductions when stagnant zones and preferential flow paths exist that reduce contact time. Optimally configured wetlands cost less and perform better. Unfortunately, it is not clear what constitutes an optimal configuration. Many factors, including shape, depth, and botanical structure, influence hydraulic efficiency. The various factors also influence each other, which makes it difficult to ascribe an effect to any one particular factor. Conventional investigative methods using controlled experiments focusing on a response to a single factor cannot tell the whole story. A more comprehensive approach is described here. Scaled models were used to investigate treatment wetland hydraulics. Scaling shortens the time required for a given test, making a sufficiently large number of observations more practical. Modifications were be made to the overall shape and form to achieve variation from one observation to the next. The study considered effects initially from twenty-five parameters related to the model configuration, hydraulic loading, and placement of vegetation. Eventually seven key parameters were identified. The parameters are related to (1) the alignment of the inlet and outlet, (2) a shape factor, (3) the vegetation coverage, (4) the number of wetland cells, (5) the nominal residence time, (6) stem density, and (7) the depth of water. A mathematical expression was derived relating the seven parameters to hydraulic performance. Practitioners can apply the resulting equation to evaluate wetland designs and make informed decisions with regard to tradeoffs involving hydraulic efficiency. Until now, there was no way to evaluate wetland designs in terms of hydraulic performance without invoking highly involved numerical simulations running on commercial software or else building and testing a design, at which point modifications are costly and limited. Ultimately, this tool promotes the adoption of constructed wetlands as a management practice by informing the design process with respect to hydraulic efficiency.

Committee:

Larry Brown (Advisor); Alfred Soboyejo (Committee Member); Norman Fausey (Committee Member)

Subjects:

Agricultural Engineering; Civil Engineering; Conservation; Ecology; Engineering; Environmental Engineering; Environmental Studies; Water Resource Management

Keywords:

treatment wetlands; constructed wetlands; free water surface constructed wetlands; hydraulic efficiency; hydraulic performance; stochastic model; hydraulic retention time; HRT; RTD; residence time; wetland; hydraulic model

Mirto, Clinton JamesA Sensor for Ice Monitoring on Bridge Superstructures
Master of Science, University of Toledo, 2015, Civil Engineering
In January 2015, another major icing event occurred on the Veterans’ Glass City Skyway. This event required all northbound lanes to close for a duration of 8 hours due to ice shedding. The shedding event occurred in a manner that has never been observed in field experiments or in previous icing events on the bridge. In the January 2015 event, a thin ice layer shed released in small fragments rather than the typical large sheet shedding observed in the past. The January 2015 icing event is documented thoroughly for the first time in this thesis. A weather monitoring system that provides early warning and continuous weather monitoring is only as accurate and reliable as incoming data provided by the sensors implemented on the bridge. There is data pertaining to the stay sheath condition throughout winter weather events, such as icing, that is considered invaluable and is not captured by any commercial sensor. The variables pertaining to the condition of the stay sheath that need to be captured include the presence of water and thickness of ice accumulation on the sheath itself. The University of Toledo icing research team has designed and developed two sensors to capture this information. The design, development and results from both the laboratory and field setting are presented in this thesis. This thesis will also discuss shedding observations made from the 2014-2015 ice accumulation and shedding experiments performed at the Scott Park field station. Although these particular experiments were primarily done to expose the new revised design of the University of Toledo Presence and State sensor to freeze thaw cycles, there were valuable and insightful observations made pertaining to ice shedding on stainless steel sheaths.

Committee:

Douglas Nims, Ph.D (Committee Chair); Tsun-Ming Ng, Ph.D (Committee Member); Victor Hunt, Ph.D (Committee Member)

Subjects:

Civil Engineering; Electrical Engineering; Engineering; Environmental Engineering

Keywords:

Icing; Cable-stayed bridge; anti-icing; de-icing; weather monitoring; presence and state sensor; thickness sensor

Kintz, Andrew LaneNullspace MUSIC and Improved Radio Frequency Emitter Geolocation from a Mobile Antenna Array
Doctor of Philosophy, The Ohio State University, 2016, Electrical and Computer Engineering
This work advances state-of-the-art Radio Frequency (RF) emitter geolocation from an airborne or spaceborne antenna array. With an antenna array, geolocation is based on Direction of Arrival (DOA) estimation algorithms such as MUSIC. The MUSIC algorithm applies to arbitrary arrays of polarization sensitive antennas and yields high resolution. However, MUSIC fails to obtain its theoretical resolution for simultaneous, closely spaced, co-frequency signals. We propose the novel Nullspace MUSIC algorithm, which outperforms MUSIC and its existing modifications while maintaining MUSIC's fundamental orthogonality test. Nullspace MUSIC applies a divide-and-conquer approach and estimates a single DOA at a time. Additionally, an antenna array on an aircraft cannot be perfectly calibrated. RF waves are blocked, reflected, and scattered in a time-varying fashion by the platform around the antenna array. Consequently, full-wave electromagnetics simulations or demanding measurements of the entire platform cannot eliminate the mismatch between the true, in-situ antenna patterns and the antenna patterns that are available for DOA estimation (the antenna array manifold). Platform-induced manifold mismatch severely degrades MUSIC's resolution and accuracy. We show that Nullspace MUSIC improves DOA accuracy for well separated signals that are incident on an airborne antenna array. Conventionally, geolocation from a mobile platform draws Lines of Bearing (LOB) from the antenna array along the DOAs to find the locations where the DOAs intersect with the ground. However, averaging the LOBs in the global coordinate system yields large errors due to geometric dilution of precision. Since averaging positions fails, a single emitter is typically located by finding the position on the ground that yields the Minimum Apparent Angular Error (MAAE) for the DOA estimates over a flight. We extend the MAAE approach to cluster LOBs from multiple emitters. MAAE clustering geolocates multiple simultaneous and co-frequency emitters in spite of highly erratic DOA estimates. We also mitigate manifold mismatch by applying the Direct Mapping Method (DMM). DMM averages DOA spectra on the earth's surface and estimates the emitter locations directly from the composite spectrum. In the example results presented, our goal is to geolocate four diversely polarized emitters with a seven-element antenna array. This is too challenging for MAAE and DMM. We fuse Nullspace MUSIC and DMM into the novel Nullspace DMM algorithm and demonstrate that Nullspace DMM locates all emitters. Finally, we apply the proposed geolocation algorithms to real-world experimental data. A six-element antenna array and Data Collection System (DCS) were installed on a small aircraft. The DCS recorded signals from four live transmitters during a three-hour flight over Columbus, Ohio. The four emitters were geolocated from various segments of the flight. As expected, individual DOA estimates were erratic and widespread due to the airplane's perturbations of the measured array manifold. MAAE and DMM locate at most three of the four emitters. On the other hand, Nullspace DMM yields unambiguous estimates for every emitter in every flight segment. The successful experimental trials show that Nullspace DMM could significantly enhance airborne emitter geolocation in missions such as RF spectrum enforcement, locating unknown transmitters for defense, and search and rescue operations.

Committee:

Inder Gupta (Advisor); Joel Johnson (Committee Member); Fernando Teixeira (Committee Member); Can Koksal (Committee Member)

Subjects:

Aerospace Engineering; Applied Mathematics; Computer Engineering; Computer Science; Electrical Engineering; Electromagnetics; Electromagnetism; Engineering; Experiments; Mathematics; Music; Remote Sensing; Scientific Imaging; Systems Design

Keywords:

Radio Frequency Emitter Geolocation; Direction of Arrival Estimation; Antenna Array Signal Processing; Antenna Array Manifold Mismatch; Nullspace MUSIC; Polarization; Direct Mapping Method DMM; Nullspace DMM; Flight Experiment; Beamforming; Nullsteering;

Byanjankar, ManilTesting of a new Ice Presence and State Sensor on Above Deck Structure of a Bridge
Master of Science, University of Toledo, 2016, Civil Engineering
The Veterans’ Glass City Skyway (VGCS) Bridge is a large cable-stayed bridge, which crosses Maumee River in Toledo, Ohio. It is located in an area, which has a history of icing events. Since starting operation in June 2007, six major icing events have occurred. The icing events have resulted in lane and bridge closures. These icing events cause a potential hazard for motorists traveling on the bridge from the falling ice. The Ohio Department of Transportation (ODOT) chose to pursue an administrative management approach for the icing problem of the VGCS. This strategy involves the development of real-time monitoring system to detect the presence, condition, and thickness of ice on the stay which helps bridge operators to make the appropriate decisions. In order to provide the accurate data to the monitoring system, a sensor network was implemented on the bridge. This includes two new sensors developed by the UT icing research team: the UT Ice Presence and State Sensor (UT State Sensor) and the UT optical thickness sensor. These sensors were deployed on the VGCS in the summer of 2015. The UT State Sensor mounts on the stay surface to detect whether water on the stay is liquid or ice. This is critical because water beneath the ice is a precursor to ice shedding and existing sensors do not directly measure conditions on the stay. The UT State Sensor found the water beneath the ice layer during the laboratory experiments performed indoors and at UT’s outdoor field station. The UT Optical Thickness Sensor reports the thickness of ice present on the stay. The UT Optical Thickness Sensor was successfully tested in indoor laboratory. The field testing of the UT State Sensor was performed in the winter of 2015-16 on the VGCS. The data from the sensor was studied and compared to the field observation made by the ODOT personnel for several days. This winter had some days where there was a thin layers of ice formed in some places on the stays, but no ice which could cause shedding hazard was formed. The visual observations were compared with sensor output. The UT State Sensor showed ice in the same position as was observed on December 5, 2015 and December 6, 2015. The sensor output did not match the visual observation on February 24, 2016 event. The output from the UT State Sensor during the field testing on the VGCS was promising and it was concluded that more field testing was necessary. Experiments were conducted to determine the accuracy of the UT State Sensor in detecting water beneath the ice. Thirty-one freeze – thaw cycles were performed on the UT State Sensor and compared its result with visual inspection of ice. The UT State Sensor always indicated the ice to water transition and found the water beneath the ice, which is a precursor to shedding. Also, the UT State Sensor was able to detect the ice presence with significant accuracy. Overall, sensors that can make direct measurements of conditions on the stay were developed. This includes the ability to measure water beneath the ice. This layer of water is a precursor to shedding. This overcomes the inability of existing commercial sensors to directly measure conditions on the stay.

Committee:

Douglas Nims, Ph.D (Committee Chair); Victor Hunt, Ph.D (Committee Member); Cyndee Gruden, Ph.D (Committee Member)

Subjects:

Civil Engineering; Electrical Engineering; Engineering; Environmental Engineering

Keywords:

VGCS; icing event; ODOT; dashboard; UT Ice Presence and State Sensor; UT Optical Thickness Sensor

Malkoc, VeysiMicropatterning Neuronal Networks on Nanofiber Platforms
Doctor of Philosophy, The Ohio State University, 2013, Biomedical Engineering
Neuronal networks are groups of interconnected cells in the Central Nervous System (CNS) or the Peripheral Nervous System (PNS) that function in many different ways. They can provide function in the sympathetic nervous system, in a sensory circuit in the spinal column, or can be a high level processing unit in a cortex. If neuronal networks lose their ability to perform their function, this can ultimately lead to a neurological disorder in the body. Therefore it is important to conduct research on neuronal networks to better understand the underlying mechanisms of neurological disorders. Even though there has been a considerable amount of useful research conducted on neuronal networks, the connections in those neuronal networks are random. There are massive amounts of connections in a mammalian brain, so the ability to guide the connections for studying neural networks is of vital importance. In order to better understand how the brain stores and processes information, the complexity associated with neuronal networks has to be reduced. Cell patterning is a potential solution to this problem and allows simplified and organized neuronal networks. In this thesis cell patterning using microfabrication techniques is discussed and a microfabricated device that was patterned on biocompatible extracellular matrix (ECM)-like polymer electrospun nanofibers is introduced. Our device was able to pattern, organize, and simplify neuronal networks. We hypothesized that physical confinement of neural cells and limited routes of neurite extension would contribute to reduced proliferation, increased differentiation, and therefore enable the formation of more robust neural networks. The effect of cell confinement as well as the use of vacuum seeding on neural network formation was compared to cell growth on collagen-coated tissue culture polystyrene and nanofiber mats with no confining microstructures. To test the effects of the underlying nanofibers on the neural network formation, we fabricated our device on both random and aligned nanofibers. We evaluated performance of our device from a neural tissue engineering perspective. Finally, the results of various biological responses, i.e. adhesion, viability, and differentiation, of cells on our devices on random and aligned nanofibers are discussed.

Committee:

Derek Hansford (Advisor); John Lannutti (Committee Member); Yi Zhao (Committee Member)

Subjects:

Biochemistry; Biology; Biomedical Engineering; Chemical Engineering; Developmental Biology; Electrical Engineering; Engineering; Neurobiology; Neurosciences; Technology

Keywords:

Micropatterning; Neuronal Networks; PC12; Differentiation; Neurite; Vacuum Seeding; Pattern; Electrospinning; Gelatin; Polycaprolactone; Nanofibers; Photolithography; Aligned Nanofibers;Microfabrication; Cell Patterning; Nerve Growth Factor;

Zheng, DaihuaLow Velocity Impact Analysis of Composite Laminated Plates
Doctor of Philosophy, University of Akron, 2007, Civil Engineering

In the past few decades polymer composites have been utilized more in structures where high strength and light weight are major concerns. It is well known that they are susceptible to damage resulting from lateral impact by foreign objects, such as dropped tools, hail and debris thrown up from the runway. Although commercial software is capable of analyzing such impact processes, it often requires extensive expertise and rigorous training for design and analysis. Analytical models are useful as they can provide a foundation for validating the numerical results from large-scale commercial software. Therefore, it is necessary to develop analytical or semi-analytical models to better understand the behaviors of composite structures under impact and their associated failure process.

In this study, several analytical models are proposed in order to analyze the impact response of composite laminated plates. Based on Meyer’s Power Law, a semi-analytical model is obtained for small mass impact response of infinite composite laminates by the method of asymptotic expansion. The original nonlinear second-order ordinary differential equation is transformed into two linear ordinary differential equations. As a result, the semi-analytical solution of the overall impact response can be applied to contact laws with varying coefficients. Then an analytical model accounting for permanent deformation based on an elasto-plastic contact law is proposed to obtain the closed-form solutions of the wave-controlled impact responses of composite laminates.The analytical model is also used to predict the threshold velocity for delamination onset by combining with an existing quasi-static delamination criterion. The predictions are compared with experimental data and explicit finite element LS-DYNA simulation. The comparisons show reasonable agreement.

Furthermore, an analytical model is developed to evaluate the combined effects of prestresses and permanent deformation based on the linearized elasto-plastic contact law and the Laplace Transform technique. It is demonstrated that prestresses do not have noticeable effects on the time history of contact force and strains, but they have significant consequences on the plate central displacement. The combined analytical and numerical investigations provide validated models for elastic and elasto-plastic impact analysis of composite structures and shed light on the design of impact-resistant composite systems.

Committee:

Wieslaw Binienda (Advisor)

Subjects:

Engineering, Aerospace; Engineering, Civil; Engineering, Materials Science; Engineering, Mechanical

Keywords:

Low Velocity; Impact; Composites; Laminates; Delamination; Prestress; Analytical Solution

Next Page