Master of Science (MS), Ohio University, 2018, Biological Sciences (Arts and Sciences)

Currently, there is a dearth of information regarding the status and ecology of bat populations in the Rocky Mountain region of North America due to the scarcity of known hibernacula, which are the primary location for performing population counts in eastern North America. The lack of knowledge and traditional tools required to monitor these populations presents barriers for biologists and land managers tasked with conserving bat species believed to be at risk of extinction or extirpation. Unfortunately, there are no estimates of abundance available for many populations of bats and the absence of locations to monitor populations leaves biologists in many regions without the techniques required to create such estimates. To provide much-needed population ecology data, we designed and built a long-term passive monitoring system capable of continuously monitoring the abundance of little brown myotis (Myotis lucifugus) residing in distinct populations within Yellowstone National Park. To advance our understanding of bat ecology for this region, our monitoring system also assessed roost fidelity, connectivity, and seasonal movements. We subcutaneously implanted high-frequency passive integrated transponders (HF-PIT) into 297 female little brown myotis and installed 8 continuously scanning readers and 45 antennas inside 3 maternity roosts used by distinct populations in the Lamar Valley, Tower Junction, and Mammoth Hot Springs regions of Yellowstone National Park. We recorded 2,929,742 detections of 196 HF-PIT tagged bats (66.0%) between June 2017 and August 2018. We used a mark-resight analysis to quantify abundance based on detections of individually marked bats recorded by high-frequency radio-frequency identification (RFID) readers and counts of bats exiting monitored roosts. From these mark-resight analyses, we estimated the pre-parturition size of the Mammoth population to be 847 (95% CI = 749-987; SE 59.8) in 2017, and 836 (95% CI = 722-989; SE 67.3) in 2018. The La (open full item for complete abstract)

Committee: Joseph Johnson (Advisor); Viorel Popescu (Committee Member); Willem Roosenburg (Committee Member) Subjects: Animal Diseases; Animals; Biology; Ecology; Wildlife Conservation; Wildlife Management

Master of Science in Engineering, Youngstown State University, 2016, Department of Electrical and Computer Engineering

Radio frequency birdcage coils are widely used in clinical magnetic resonance imaging. In order to effectively design a birdcage coil, optimum capacitance calculation on the rungs or end rings is critical. Several methods are discussed in this thesis to calculate the capacitance. The first method is called lumped circuit element method, which is a commonly used technique to calculate the capacitance and resonant modes. However, the RF coil design begins to fail under quasi-static assumption as the frequency increases. Therefore, to accurately determine the capacitance, we use frequency domain analysis method for both the low-pass and high-pass birdcage coils in COMSOL Multiphysics. Modeling the birdcage coil in a 3D simulation environment helps to analyze the electromagnetic field and absorbed power in the volume of interest, such as field homogeneity, circularity, and specific absorption rate (SAR). In order to verify the optimal capacitance value, a computer program (Birdcage Builder) is used based on the model designed. Four frequencies are considered for the simulation, 64 MHz, 127.5 MHz, 170 MHz and 200 MHz corresponding to 1.5 T, 3 T, 4 T and 4.7 T MRI systems respectively.

Committee: Lin Sun PhD (Advisor); Philip Munro PhD (Committee Member); Frank Li PhD (Committee Member) Subjects: Electrical Engineering

MS, University of Cincinnati, 2004, Engineering : Computer Engineering

This thesis presents automated techniques for synthesis of high performance RF circuits. The top-down methodology developed encompasses all stages of RF design from circuit sizing, layout generation to parasitic extraction and performance analysis. The objective of this methodology is to minimize the design time and generate efficient, correct and re-usable design solutions. In the proposed methodology, given a circuit netlist and a set of performance goals, a ready-to-tapeout layout is generated which meets the specified performance constraints. A sizing tool is integrated to perform design space exploration. A parameterized layout generator generates the layout based on the input sizes. An RF-Performance Analysis system (PAS-RF) comprising of a set of C++ functions is also developed for measuring the performance of the RF circuit. The proposed methodology is successfully tested by synthesizing variants of RF receiver circuits (LNA, Mixers, VCO etc.) for different performance criterion.

Committee: Dr. Ranga Vemuri (Advisor) Subjects:

Doctor of Philosophy, The Ohio State University, 2007, Electrical Engineering

Nowadays there has been increasing demand for radio frequency (RF) power amplifiers (PAs) to have high efficiency so as to extend wireless terminal's battery/talk time and achieve low form-factor in mobile, as well as reduce the cooling and electrical power cost in base stations. The classical design equations of efficient switching-mode class E PAs have been challenged by non-ideal issues which can lead the analysis of class E PAs to be enormously complex and intractable. In this work, the design of class E pHEMT PA has been improved based on the ADS load-pull simulation, which permits an iterative search for the nominal impedance values that maximize efficiency and output power under various bias/load conditions of the active transistor. An important contribution of this dissertation is the proposed multi-harmonic real-time active load-pull (RT-ALP) based on the large signal network analyzer (LSNA), for designing high efficiency non-linear PAs. It applies real-time tunings at the second and third harmonic frequencies, which enable to quickly synthesize a wide range of harmonic load reflection coefficients without stability issue due to open-loop structure. Fast acquisition of reliable large-signal data generates the RF dynamic loadlines, PAE and power contour plots for guiding the design of non-linear PAs. A GaN HEMT demonstrats a PAE of 81% (class F) at 2 GHz by tuning up to the third harmonic. Based on the predicted optimal impedances, a pHEMT PA is designed and constructed with matching networks achieving 68.5% PAE at 2 GHz, further demonstrating the efficacy and reliability of the proposed multi-harmonic RT-ALP for the interactive design of power efficient PAs. An integrated CMOS Doherty PA for 3.5 GHz WiMAX is designed using the 0.18µm TSMC CMOS. Cascode transistors are chosen to achieve high efficiency and address the low breakdown voltage issue. Lumped components replace the λ/4 transmission line for circuitry miniature. The layout passes all the DRC/LVS ch (open full item for complete abstract)

Committee: Patrick Roblin (Advisor) Subjects:

Master of Science (MS), Ohio University, 1998, Electrical Engineering & Computer Science (Engineering and Technology)

An implementation of acquisition using transform domain/cycle code shift keying system on a multipath channel

Committee: Jeffrey Dill (Advisor) Subjects: