Doctor of Philosophy, Case Western Reserve University, 2008, Mechanical Engineering

The scope of this dissertation is to develop and apply a non-intrusive molecular Rayleigh scattering diagnostic that is capable of providing time-resolved simultaneous measurements of gas temperature, velocity, and density in unseeded turbulent flows at sampling rates up to 32 kHz. Molecular Rayleigh scattering is elastic light scattering from molecules; the spectrum of Rayleigh scattered light contains information about the gas temperature and velocity of the flow. Additionally, the scattered signal is directly proportional to the molecular number density. These characteristics are utilized in the development of the measurement technique. This dissertation results in the following: 1. Development of a point-based Rayleigh scattering measurement system that provides time-resolved simultaneous measurement of temperature, velocity, and density at sampling rates up to 32 kHz. 2. Numerical modeling of the light scattering and detection process to evaluate uncertainty levels and capabilities of the measurement technique. 3. Validation of the developed measurement system in benchmark flow experiments in which velocity and temperature fluctuations were decoupled and independently forced at various amplitudes and frequencies. 4. Demonstration of simultaneous measurement of all three quantities in an electrically-heated free jet facility at NASA Glenn Research Center. 5. Comparison of Rayleigh scattering measurements in all experiment phases with thermal anemometry measurements. The experimental measurements are presented in terms of first-order time-series results that are measured directly by the technique, and second-order statistics, such as power spectral density and rms fluctuations, which are calculated from the direct time-resolved quasi-instantaneous measurements. Temperature fluctuation results are compared with constant current anemometry measurements and velocity fluctuation results are compared with constant temperature anemometry measurements. Experiments were (open full item for complete abstract)

Committee: Chih-Jen Sung (Advisor) Subjects: Engineering, Mechanical

Doctor of Philosophy, The Ohio State University, 2020, Electrical and Computer Engineering

Inertial sensors became wearable with the advances in sensing and computing technologies in the last two decades. Captured motion data can be used to build a pedestrian inertial navigation system (INS); however, time-variant bias and noise characteristics of low-cost sensors cause severe errors in positioning. To overcome the quickly growing errors of so-called dead-reckoning (DR) solution, this research adopts a pedestrian INS based on a Kalman Filter (KF) with zero-velocity update (ZUPT) aid. Despite accurate traveled distance estimates, obtained trajectories diverge from actual paths because of the heading estimation errors. In the absence of external corrections (e.g., GPS, UWB), map information is commonly employed to eliminate position drift; therefore, INS solution is fed into a higher level map-matching filter for further corrections. Unlike common Particle Filter (PF) map-matching, map constraints are implicitly modeled by generating rasterized maps that function as a constant spatial prior in the designed filter, which makes the Bayesian estimation cycle non-recursive. Eventually, proposed map-matching algorithm does not require computationally expensive Monte Carlo simulation and wall crossing check steps of PF. Second major usage of the rasterized maps is to provide probabilities for a self-initialization method referred to as the Multiple Hypothesis Testing (MHT). Extracted scores update hypothesis probabilities in a dynamic manner and the hypothesis with the maximum probability gives the correct initial position and heading. Realistic pedestrian walks include room visits where map-matching is de-activated (as rasterized maps do not model the rooms) and consequently excessive positioning drifts occur. Another MHT approach exploiting the introduced maps further is designed to re-activate the map filter at strides that the pedestrian returns the hallways after room traversals. Subsequently, trajectories left behind inside the rooms are heuristically adjus (open full item for complete abstract)

Committee: Alper Yilmaz Prof (Advisor); Keith Redmill Prof (Committee Member); Charles Toth Prof (Committee Member); Janet Best Prof (Other) Subjects: Electrical Engineering; Engineering

MS, University of Cincinnati, 2002, Arts and Sciences : Geology

This paper describes the development of a testing technique to determine groundwater flow direction and velocity in a single well. A series of experiments were performed using a device designed specifically to fit into a 152.4 mm (6 inch) diameter well casing. A test apparatus was assembled of polyvinyl chloride (PVC) pipes using porous stones to simulate groundwater flow conditions in an aquifer. The measurement device released fluorescein dye into the center of the simulated well using a dye release mechanism consisting of a glass vial with a salt plug suspended in modeling clay at its base. A small hole in exposed the top and bottom of the salt plug allowed the exchange of dye with the groundwater flowing past the dye outlet hole. The dye released into the well was subsequently adsorbed onto the surface of carbon rods located at eight equally spaced points around the perimeter of the well. The relative amount of the fluorescein dye remaining in the dye release vial, as well as the amount adsorbed on the carbon rods, was measured by the intensity of fluorescence detected by a fluorometer. The amount of the dye adsorbed onto the rods was shown to indicate the direction of groundwater flow with low directional dispersion. Groundwater flow velocity measurements were attempted using two methods. The first method correlated the fluorometer reading for the fluorescein dye/groundwater mixture remaining in the vial after a measured period of time with the flow velocity. The second method correlated the root-mean-square of the fluorometer readings for the fluorescein dye adsorbed onto and extracted from the carbon rods for an individual experiment with the groundwater flow velocity. The results of the first method's groundwater flow velocity experiments were a set of linear equations based on a multiple linear regression analysis relating discharge, measurement time, and fluorometer readings. The second method resulted in a linear relationship between the groundwater flow (open full item for complete abstract)

Committee: Dr. David Nash (Advisor) Subjects: Geology

Doctor of Philosophy, The Ohio State University, 2009, Biomedical Engineering

Velocity measurement based on phase-contrast magnetic resonance imaging (PC-MRI) is firmly recognized as a valuable and accurate technique to assess hemodynamics in a variety of clinical applications. However, conventional PC-MRI requires the acquisition of two separate and complete k-space dataset with different flow sensitivities. Real-time MR velocity measurement experiences limited success due to the insufficient temporal sampling rate to depict hemodynamic prosperities within each cardiac cycle. Accelerated data acquisition strategies described by this dissertation were developed to reduce the reference data requirements. Time-efficient PC-MRI methods accelerate the acquisition of phase-reference data in the spatial and temporal domain with minimum loss of velocity accuracy. Root-Mean-Square error estimation demonstrates the accuracy of the proposed accelerated velocity measurement methods as compared to the conventional PC-MRI reconstruction. As an alternative accelerated PC-MRI, shared velocity encoding (SVE) method was developed to achieve the same temporal sampling rate comparing to standard MR cine scans. In SVE method, phase-difference images from alternative polarity pairs (+ -), (- +), (+ -), etc. can be reconstructed and resulted in a factor of 2 increase in the effective temporal resolution. With the SVE method implementation, the local pulse wave velocity (PWV) measurement becomes practical and useful in the common carotid arteries in current clinical 1.5T MRI scanners. Echo-planar imaging (EPI) is an ultra-high-speed MRI method that is capable of producing snap-shot MR images in the ranges of 10-100 msec. Recently, EPI sequence has been used in attempts to acquire real-time cardiac cine images in a standard MR scan. Consequently, we propose to utilize the advantage of high acquisition speed of EPI combining with PC-MRI to achieve real-time velocity measurement in the major vessels. However, chemical shift artifacts resulting from the off-resonanc (open full item for complete abstract)

Committee: Orlando Simonetti PhD (Committee Chair); Subha Raman MD (Committee Member); Petra Schmalbrock PhD (Committee Member); Yiucho Chung PhD (Committee Member) Subjects: Biomedical Research