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Mauk, Rachel GrantPrediction of Intensity Change Subsequent to Concentric Eyewall Events
Doctor of Philosophy, The Ohio State University, 2016, Atmospheric Sciences
Concentric eyewall events have been documented numerous times in intense tropical cyclones over the last two decades. During a concentric eyewall event, an outer (secondary) eyewall forms around the inner (primary) eyewall. Improved instrumentation on aircraft and satellites greatly increases the likelihood of detecting an event. Despite the increased ability to detect such events, forecasts of intensity changes during and after these events remain poor. When concentric eyewall events occur near land, accurate intensity change predictions are especially critical to ensure proper emergency preparations and staging of recovery assets. A nineteen-year (1997-2015) database of concentric eyewall events is developed by analyzing microwave satellite imagery, aircraft- and land-based radar, and other published documents. Events are identified in both the North Atlantic and eastern North Pacific basins. TCs are categorized as single (1 event), serial (>= 2 events) and super-serial (>= 3 events). Key findings here include distinct spatial patterns for single and serial Atlantic TCs, a broad seasonal distribution for eastern North Pacific TCs, and apparent ENSO-related variability in both basins. The intensity change subsequent to the concentric eyewall event is calculated from the HURDAT2 database at time points relative to the start and to the end of the event. Intensity change is then categorized as Weaken (<= -10 kt), Maintain (+/- 5 kt), and Strengthen (>= 10 kt). Environmental conditions in which each event occurred are analyzed based on the SHIPS diagnostic files. Oceanic, dynamic, thermodynamic, and TC status predictors are selected for testing in a multiple discriminant analysis procedure to determine which variables successfully discriminate the intensity change category and the occurrence of additional concentric eyewall events. Intensity models are created for 12 h, 24 h, 36 h, and 48 h after the concentric eyewall event’s end. Leave-one-out cross validation is performed on each set of discriminators to generate classifications, which are then compared to observations. For each model, the top combinations achieve 80-95% overall accuracy in classifying TCs based on the environmental characteristics, although Maintain systems are frequently misclassified. The third part of this dissertation employs the Weather Research and Forecasting model to further investigate concentric eyewall events. Two serial Atlantic concentric eyewall cases (Katrina 2005 and Wilma 2005) are selected from the original study set, and WRF simulations performed using several model designs. Despite strong evidence from multiple sources that serial concentric eyewalls formed in both hurricanes, the WRF simulations did not produce identifiable concentric eyewall structures for Katrina, and only transient structures for Wilma. Possible reasons for the lack of concentric eyewall formation are discussed, including model resolution, microphysics, and data sources.

Committee:

Jay Hobgood (Advisor); Jeffery Rogers (Committee Member); David Bromwich (Committee Member); Jialin Lin (Committee Member)

Subjects:

Atmospheric Sciences; Earth; Meteorology

Keywords:

tropical cyclones; hurricanes; concentric eyewalls; multiple linear discriminant analysis; WRF

Fischer, Stephen MichaelMETABOLIC DIFFERENCES BETWEEN A BOUT OF ECCENTRIC, CONCENTRIC, AND TRADITIONAL RESISTANCE EXERCISE
MS, Kent State University, 2016, College and Graduate School of Education, Health and Human Services / School of Health Sciences
PURPOSE: To determine the extent to which metabolic variables such as VO2(ml/kg/min), percentage of energy derived from carbohydrates (%CHO) and heart rate (HR) as well as blood glucose and lactate vary between resistance workouts comprised of solely eccentric, concentric or traditional muscle contractions. METHODS: N=12 men and women completed a traditional (TRAD), concentric (CONC), and eccentric (ECC) full-body resistance workout at 65% of a measured 1 repetition max with each condition matched for work. During each condition, the subject was fitted to a metabolic cart and metabolic variables were recorded through indirect calorimetry and heart rate monitor. Blood glucose and blood lactate were taken at five different stages. RESULTS: Both the TRAD and CONC conditions resulted in significantly (p < 0.001, and p < 0.001 respectively) greater VO2 values when compared to the ECC condition. Accumulation of lactate Post Ex. was also significantly (both p < 0.001) greater in the TRAD and CONC compared to the ECC. CONCLUSION: Results indicate a much greater metabolic demand from concentric and traditional contractions compared to eccentric muscle contractions on a whole body level.

Committee:

John McDaniel, Ph.D. (Advisor)

Subjects:

Kinesiology

Keywords:

Eccentric Concentric Metabolism

Katragadda, MaheshDesign and Simulation of a Planar Crossed-Dipole Global Navigation Satellite System (GNSS) Antenna in the L1 Frequency Band
Master of Science (MS), Ohio University, 2012, Electrical Engineering (Engineering and Technology)
The purpose of this research was to design and investigate the performance of a planar cross-dipole Global Navigation Satellite System (GNSS) receiver antenna to operate in GNSS L1 frequency band with multipath mitigation performance. First, a crossed-half-wavelength dipole antenna was designed to resonate centered at 1.6 GHz, and then various configurations were investigated and simulated. In an attempt to improve the antenna’s multipath mitigation performance, these various configurations included the addition of concentric rings in various numbers and sizes with the inclusion of cavity banking. Roger’s dual copper clad RO3010¿¿ material was used as a substrate for the design. The simulated cavity backing consisted of a thin block of Styrofoam¿¿ and Cumming’s RGDS-124 (microwave absorbing material) placed between the substrate and the ground plane (finite and infinite), simulated to increase the antenna performance. The prototype crossed-dipole antenna configurations were tuned and optimized based on the simulated results obtained from the Agilent’s Advanced Design System Momentum 2009U1 software. The S-parameters and radiation pattern results obtained from these simulations were compared and analyzed in MATLAB¿¿. The simulated antenna prototype performance is expected to meet the performance requirements for L1 GNSS receiver antenna.

Committee:

Chris Bartone, PhD (Committee Chair); Sanjeev Gunawardena, PhD (Committee Member); Simbo Odunaiya, PhD (Committee Member); David Ingram, PhD (Committee Member)

Subjects:

Electrical Engineering

Keywords:

Multipath Mitigation; VSWR 2:1; ADS Momentum; GNSS L1 Frequency Band Antenna; Printed Dipole; Concentric Rings; 1.6 GHz; S-parameters

Mustafa, MansoorInvestigation into Offset Streams for Jet Noise Reduction
Master of Science, The Ohio State University, 2015, Aero/Astro Engineering
This effort investigates the near field behavior of two ideally-expanded subsonic dual-stream jets. One case implements a traditional symmetric, concentric dual-stream nozzle configuration while the other imposes an asymmetric, eccentric layout to model the behavior of an offset stream. The essence of an offset stream is to force an uneven azimuthal distribution of the secondary coflow and create an outside stream that varies in thickness. Past studies have shown a benefit in acoustic propagation in the direction of the thickest coflow and the present work further analyzes this phenomenon. A LES (Large Eddy Simulation) approach is implemented to run the simulations for both cases and a number of qualitative and quantitative analyses tools are used for post-processing. A reduction in the noise levels for the lower, thicker side of the eccentric nozzle is observed in comparison to the baseline concentric case. Examination of the mean flow behavior shows a shorter, thinner primary potential core for the offset case and a faster axial velocity decay rate. The asymmetric distribution of the coflow causes varying velocity profiles in the radial direction for the top and bottom regions and consequently produces unique flow features on either side. Lower levels of shear stress and slower decay rates lead to less turbulence production on the lower side of the eccentric nozzle. An investigation into the flow structures reveals lower vorticity and weaker convective structures on the bottom which influences propagation in that direction. Two-point correlation analysis reveals the presence of smaller turbulence scales in the lower, thicker portion of the eccentric case. This is further confirmed by an Empirical Mode Decomposition (EMD) study that shows lower frequency ranges dominate the concentric near field in comparison to the eccentric. The combination of these unique features demonstrate the principles behind the acoustic benefit of implementing offset stream flows in dual-stream nozzle configurations.

Committee:

Datta Gaitonde (Advisor); Mei Zhuang (Committee Member)

Subjects:

Aerospace Engineering

Keywords:

offset; noise reduction; jets; aerospace; aerodynamics; LES; computational simulation; jet noise; eccentric; concentric; dual-stream; nozzle