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Atef, Ali HadiANALYSES OF URSEIS MOHO REFLECTIONS BENEATH THE PREURALIAN FOREDEEP OF THE URAL MOUNTAINS, RUSSIA
Master of Science, University of Akron, 2007, Geology-Geophysics
Reprocessing of the western-most portion of the Urals Seismic Experiment and Integrated Studies (URSEIS) survey across the southern Urals in Russia provided enhanced images of the crust and crust-mantle boundary (Moho). Shallow (less than 6 km deep), continuous subhorizontal reflections were associated with the base of the foreland basin. Those reflections appeared to shallow to the east. The middle and lower crust were generally reflective across the study area. The crust-mantle boundary (Moho) was imaged as high amplitude, continuous, subhorizontal reflections across the entire profile in the stacked section. The Moho reflections were dominated by low frequency arrivals that appeared as single and multi-cycle wavelets. Amplitude, frequency content and velocity analyses of those Moho reflections revealed that the Moho varied laterally on the kilometer-scale and vertically at the 100-meter scale. Power spectrum analyses appeared to indicate that the Moho represented a change from granulite to eclogite in a layer located at 43.8 km depth that varied in thickness from 125-200 m. Other reflections observed below Moho depths were determined to be crustal shear wave reflections based on their low stacking velocities.

Committee:

David Steer (Advisor)

Subjects:

Geology; Geophysics

Keywords:

Amplitude Versus Offset (AVO); Frequency Versus Offset (FVO); Amplitude Versus Shot Point (AVSP); Frequency versus Shot Point (FVSP); Model of Moho boundary; Frequency-Wave number analyses

Bishop, Daniel W.GMSK Demodulation Methods and Comparisons
Master of Science, University of Akron, 2008, Electrical Engineering
Modern phase modulated communication systems, such as GSM cellular phones,require the transmitters to meet a number of performance parameters so that robust links can be achieved. A few of these parameters include: well tuned carrier frequency, low peak phase offset, and low RMS phase error. These parameters must be tested on all new cellular phones coming off the manufacturing line. The mass quantities of cellular phones being produced require that the tests be done quickly and accurately. The method for determining the frequency and phase performance of a GMSK transmitter requires a receiver to generate an ideal reference signal that contains the same symbols as the measured signal. The measured signal is subtracted from the ideal signal so that the errors generated from the transmitter can be easily determined. This work has two goals. First, it surveys methods of building robust GMSK receivers for testing the transmitter. Second, it proposes a new algorithm to improve performance. Building a GMSK receiver to test the transmitter requires three major components. These components are: the timing recovery mechanism, the carrier recovery mechanism, and the demodulator. The purpose of the timing recovery is to align the sampled data to symbols. This work surveys some previously derived methods such as cross correlation and autocorrelation methods. It then presents a new method that is an extension of the cross correlation method by adding a multiple linear regression technique. The purpose of the carrier recovery is to determine the carrier offset from the nominal frequency. Among previously derived methods we survey methods such as squaring the IQ data and using data aided carrier recovery. A new method derived from the multiple linear regression method is then presented. A maximum likelihood demodulator is essential for a robust receiver and this work discusses two methods. The integrate and dump method is by itself not a maximum likelihood detector, but with the proposed extension of the mini trellis it then becomes a pseudo-maximum likelihood detector. The Viterbi demodulator is a maximum likelihood detector and this work presents some optimizations for state reduction to decrease the number of computations and the amount of memory needed. We then compare the performance and accuracy of each of the component methods with simulations.

Committee:

Nathan Ida, PhD (Advisor)

Keywords:

Frequency Offset; GSM; Training Sequences; phase error; offset; bits; Viterbi

Butterfield, AndreiCharacterization of a Utica Shale Reflector Package Using Well Log Data and Amplitude Variation with Offset Analysis
Master of Science (MS), Wright State University, 2014, Earth and Environmental Sciences
Using well logs and AVO gradient analysis, I identify and characterize a package of reflectors associated with the Utica Shale from vibroseis data collected by Wright State University at the Gabor Gas Storage field near Canton, Ohio. I also correlate TOC measurements from wells to densities and velocities at the same depths. On the seismic data, I interpret prominent reflections from the top and bottom of the Utica Shale and an intra-Utica reflector of varying frequency content associated with a velocity/density low in well log data. I investigate the possibility that the lateral variation in frequency content and change in wavelet character of these reflections is influenced by velocity gradients, termed Wolf Ramps. A Matlab software script was written in order to approximate this behavior using synthetic wavelets, and the resulting model matched well with the seismic data. Additionally, I note a possible reverse fault within the Utica that could create fracture porosity and a migration pathway. To model the AVO response, an AVA volume was created from prestack data and reflection coefficients up to 30 degrees of incidence were calculated using the two-term Aki-Richards approximation. Large negative normal incidence reflection coefficients attenuated at higher angles of incidence (Class IV anomalies) were observed at the top of Utica reflector, a response consistent with a change from silica-rich nonsource shale to black source shale. Large positive normal incidence reflection coefficients decreasing at higher angles of incidence (Class I anomalies) were noted at the bottom of Utica reflector, consistent with a shift from low impedance source shale to higher impedance calcareous shale. To perform forward modeling, I used geophysical well logs and NS-EW vibroseis line data. Using Hampson Russell commercial software, acoustic impedance and reflectivity were computed from sonic and density logs. An average wavelet at the Utica two-way travel time was extracted using Promax software and convolved with the reflectivity to create a synthetic seismogram for each well. Lastly, the Utica Shale and underlying formations were correlated in Petrel software using well logs in the vicinity of the seismic lines. The results of the correlation allowed me to make connections between the depositional processes that led to the formation of the Ohio Utica from the New York Utica, for which outcrops and a large number of well logs are available.

Committee:

Doyle Watts, Ph.D. (Advisor); Ernest Hauser, Ph.D. (Committee Member); David Dominic, Ph.D. (Committee Member)

Subjects:

Geology; Geophysics

Keywords:

AVO; shale; Utica; Point Pleasant; Trenton; Wolf Ramp; seismic interpretation; crossplot; shale petrophysics; well log; amplitude versus offset; amplitude variation with offset

Hu, GuoningMonaural speech organization and segregation
Doctor of Philosophy, The Ohio State University, 2006, Biophysics

In a natural environment, speech often occurs simultaneously with acoustic interference. Many applications, such as automatic speech recognition and telecommunication, require an effective system that segregates speech from interference in the monaural (one-microphone) situation. While this task of monaural speech segregation has proven to be very challenging, human listeners show a remarkable ability to segregate an acoustic mixture and attend to a target sound, even with one ear. This perceptual process is called auditory scene analysis (ASA). Research in ASA has inspired considerable effort in constructing computational ASA (CASA) based on ASA principles. Current CASA systems, however, face a number of challenges in monaural speech segregation.

This dissertation presents a systematic and extensive effort in developing a CASA system for monaural speech segregation that addresses several major challenges. The proposed system consists of four stages: Peripheral analysis, feature extraction, segmentation, and grouping. In the first stage, the system decomposes the auditory scene into a time-frequency representation via bandpass filtering and time windowing. The second stage extracts auditory features corresponding to ASA cues, such as periodicity, amplitude modulation, onset and offset. In the third stage, the system segments an auditory scene based on a multiscale analysis of onset and offset. The last stage includes an iterative algorithm that simultaneously estimates the pitch of a target utterance and segregates the voiced target based on a pitch estimate. Finally, our system sequentially groups voiced and unvoiced portions of the target speech for non-speech interference, and this grouping task is performed using feature-based classification.

Systematic evaluation shows that the proposed system extracts a majority of target speech without including much interference. Extensive comparisons demonstrate that the system has substantially advanced the state-of-the-art performance in voiced speech segregation, and represents the first systematic study of unvoiced speech segregation.

Committee:

DeLiang Wang (Advisor); William Masters (Other); Eric Fosler-Lussier (Other)

Keywords:

unvoiced; SPEECH; pitch; SNR; voiced; onset and offset

Soong, Chi-LiFast time-domain-based GPS acquisition
Master of Science (MS), Ohio University, 1996, Electrical Engineering & Computer Science (Engineering and Technology)
Fast time-domain-based GPS acquisition

Committee:

Michael Braasch (Advisor)

Keywords:

Global Positioning System; Quartz Oscillator; Doppler-Based Frequency Offset

Kota, BhargavAnalyzing Spread Spectrum Channel Sounder Performance using Static Channel Measurements
Master of Science (MS), Ohio University, 2010, Electrical Engineering (Engineering and Technology)
Performing channel sounding experiments is often considered a first step towards statistical channel modeling. The data obtained for a particular wireless channel environment is then analyzed and the channel is modeled by comparing it to known statistical models. Hence the authenticity of the experimental data is a most critical part in the process of channel modeling. We use channel sounding equipment called Sounder for statistical channel modeling. For synchronizing the transmitter and receiver local oscillators, the sounder manufacturer, Berkeley Varitronics Systems Inc., recommends calibrating the sounder, called “training”. But, there is an uncertainty about the time for which the sounder should be trained before taking measurements for a particular duration of time. After training, the allowed measurement time is estimated from parameters like current count and last count obtained during training, but it is not absolute. How the measurement data varies when the sounder is operated in measurement mode beyond the estimated measurement time is unknown. For this reason, the validity of data obtained during some field measurements is highly uncertain. This thesis work tries to understand the behavior of sounder when operated in measurement mode up to six times the allowed measurement time and succeeds at it. The conclusions drawn from this thesis work are very useful during field measurements to understand the measurement data logged for longer measurement times when the allowed measurement time is very less. This thesis work will also serve as a guide to the operation and understanding of our sounder for future students.

Committee:

David Matolak (Advisor)

Subjects:

Engineering

Keywords:

Sounder; wireless channel characterization; frequency offset

Lewis, Kristin N.Pain Modulation in Tension-Type and Migraine Headaches: The Offset Analgesia Effect
Doctor of Philosophy (PhD), Ohio University, 2014, Clinical Psychology (Arts and Sciences)
Objective: Migraine and Tension-type headaches are common and disabling disorders, but their pathophysiologies are poorly understood. Dysfunctional pain inhibition is postulated to contribute to the development and/or maintenance of these disorders. Offset analgesia, a temporal contrast effect which activates brain structures involved in pain modulation, has never been assessed in headache sufferers. The object of the study was to compare the offset analgesia effect in a group of headache sufferers to a group of healthy controls. Methods: Undergraduate college students (N=111) were recruited through a research participant pool, and were compensated for their participation with research credit. Participants provided demographic and inclusion/exclusion information, and completed a diagnostic interview for headache disorders. Next, participants established their pain threshold for a temperature stimulus. This temperature was used in the offset analgesia procedure in which participants were asked to continuously rate a series of 3 temperatures: 5 seconds at pain threshold, 5 seconds at 1 degree Celsius above pain threshold, and 15 seconds at pain threshold. Results: Participants with headaches reported an average of 41 headaches a year, with the most common diagnosis being Frequent Episodic Tension-type (30%), followed by Migraine (26%), Infrequent Episodic Tension-type (9%), and Mixed (7%). Although offset analgesia was observed, t (99) = 3.54, p < .01, there was no significant difference in the degree of offset analgesia when healthy controls were compared to those with migraine or tension-type headache, F (2, 88) = 1.17, p = .31. Degree of offset analgesia also did not differ as a function of headache frequency, r < 0.04, n=76, p=.96. Conclusions: The current study demonstrated offset analgesia in a sample of young adults, and provides the first evidence that this form of pain modulation is not associated with headache symptoms. It should be noted, however, that differences may yet be observed in a clinical population with more severe and/or prolonged headache history.

Committee:

Christopher France, PhD (Committee Chair)

Subjects:

Health; Psychology

Keywords:

headache; pain modulation; offset analagesia

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

Flanders, Justin M.Thermal Transport and Heat Exchanger Design for the Space Molten Salt Reactor Concept
Master of Science, The Ohio State University, 2012, Nuclear Engineering
Surface power and nuclear electric propulsion in space necessitate the development of high energy density, long term continuous power sources. Research at The Ohio State University under the NASA Ralph Steckler Space Grant Colonization Research and Technology Development Opportunity has identified molten salt reactors (MSRs) as a potentially appealing technology for high power, high temperature space fission systems. This thesis examines component specific design related to thermal transport in an attempt to further establish the feasibility of MSRs in space. Specifically, the optimization of the associated heat exchangers for a Brayton power cycle is discussed in detail. In addition, power cycle and secondary coolant selection, material selection, and general MSR design considerations are discussed. The primary heat exchanger was optimized to maximize the margin to super prompt critical (MSPC), with a final MSPC equal to 513 pcm. The secondary and tertiary heat exchangers were optimized to minimize helium pressure drop, with a combined pressure loss of 2.62 kPa obtained.

Committee:

Thomas Blue, PhD (Advisor); Xiaodong Sun, PhD (Committee Member)

Subjects:

Nuclear Engineering

Keywords:

molten salt; molten salt reactors; NASA; space nuclear; Brayton; heat exchanger; offset strip fin

Feng, CongProjection Algorithm for Improved Corridor Signal Coordination
Master of Science in Engineering, University of Akron, 2009, Civil Engineering

With ever-increasing travel demands on current urban roadway networks and limited financial resources, it has become increasingly challenging for traffic engineers to improve the roadway level of service efficiently and economically (1). Compared with an infrastructure reconstruction project, optimizing the current traffic facilities, especially the traffic signal control systems, is favored by most of traffic engineers. In many cases, advanced traffic control devices and well designed traffic operation strategies can provide effectively relief from congestion with considerably low investment.

In recent years, more and more state-of-the-art traffic control systems have been developed to reduce travel delay, smooth traffic flow, monitor traffic incident, and reduce fuel consumption. Many advanced technologies have been integrated in modern traffic control systems, including new vehicle detection devices, video processing hardware, short-range communication equipment, GPS, GIS, etc. In those systems, signal coordination is one of the most important concepts, especially when the system is designed for the entire signalized urban corridor rather than isolated intersection.

A corridor signal optimization method called projection algorithm (PA) was developed and tested in this thesis. By using green splits at each intersection and the link length as well as speed limit between intersections as input, PA calculates the offset for each intersection to maximize the green bandwidth along the corridor and it further improves the method by considering the residual queue, start-up delay, unbalanced directional volume in signal optimization. The signal timing plan from this algorithm has been evaluated in VISSIM simulation platform and the effectiveness is discussed. Preliminary results show that PA is able to produce effective signal coordination plans, especially in low and medium volume conditions with competitive output in comparison with plans from other methods. Built on the findings, a comprehensive evaluation of the green bandwidth method has also been conducted for future research and field implementation.

Committee:

Ping Yi, PhD (Advisor)

Subjects:

Civil Engineering

Keywords:

Green Bandwidth; Signal Coordination; Linear Programming; Offset Optimization; VISSIM Simulation

Bhandari, Khagendra PCharacterization and Application of Colloidal Nanocrystalline Materials for Advanced Photovoltaics
Doctor of Philosophy, University of Toledo, 2015, Physics
Solar energy is Earth’s primary source of renewable energy and photovoltaic solar cells enable the direct conversion of sunlight into electricity. Crystalline silicon solar cells and modules have dominated photovoltaic technology from the beginning and they now constitute more than 90% of the PV market. Thin film (CdTe and CIGS) solar cells and modules come in second position in market share. Some organic, dye-sensitized and perovskite solar cells are emerging in the market but are not yet in full commercial scale. Solar cells made from colloidal nanocrystalline materials may eventually provide both low cost and high efficiency because of their promising properties such as high absorption coefficient, size tunable band gap, and quantum confinement effect. It is also expected that the greenhouse gas emission and energy payback time from nanocrystalline solar PV systems will also be least compared to all other types of PV systems mainly due to the least embodied energy throughout their life time. The two well-known junction architectures for the fabrication of quantum dot based photovoltaic devices are the Schottky junction and heterojunction. In Schottky junction cells, a heteropartner semiconducting material is not required. A low work function metal is used as the back contact, a transparent conducting layer is used as the front contact, and the layer of electronically-coupled quantum dots is placed between these two materials. Schottky junction solar cells explain the usefulness of nanocrystalline materials for high efficiency heterojunction solar cells. For heterojunction devices, n-type semiconducting materials such as ZnO , CdS or TiO2 have been used as suitable heteropartners. Here, PbS quantum dot solar cells were fabricated using ZnO and CdS semiconductor films as window layers. Both of the heteropartners are sputter-deposited onto TCO coated glass substrates; ZnO was deposited with the substrate held at room temperature and for CdS the substrate was at 250 C. Within this work, CdS was demonstrated for the first time as the heteropartner for a quantum dot absorber layer. Iron pyrite nanocrystal (NC) could not be used as an absorber layer in thin film solar cells because the material’s very high free hole density rendered it nearly metallic in nature. However, the author discovered and demonstrated that an iron pyrite nanocrystal film functions well as a back contact buffer layer for CdTe solar cells. Performance of CdTe devices when using FeS2/Au as back contact approaches that of a laboratory standard Cu/Au back contact.

Committee:

Randy Ellingson (Advisor); Victor Karpov (Committee Member); Michael Heben (Committee Member); Rupali Chandar (Committee Member); Terry Bigioni (Committee Member)

Subjects:

Energy; Engineering; Materials Science; Nanoscience; Nanotechnology; Physics

Keywords:

Quantum Dots, Nanocrystals, Synthesis, Characterization, PbS, Iron bromide, Iron pyrite, Solar Cell, Schottky junction, Heterojunction, Back contact, UPS, XPS, Work function, Band offset, LCA, Meta-analysis, Embedded energy, EPBT, EROI

Bhave, Chittatosh CA Computational Study of the Heat Transfer Characteristics of Offset-Strip Fin Cores
MS, University of Cincinnati, 2017, Engineering and Applied Science: Mechanical Engineering
Enhanced extended surfaces such as offset-strip fins (OSF) are effective in increasing the area density as well as altering the convective flow behavior to provide higher heat transfer coefficient in compact heat exchangers. This is achieved by periodic disruption and reattachment of the new thin boundary layer on the fin plate of each offset-strip fin module. The heat transfer characteristics and the flow physics inside the OSF cores is revisited in this computational analysis for laminar air flows (Pr = 0.7) and their performance is compared with plain fins. A simplified model of thin fins is used to study the effect of fin geometric parameters, viz., offset-fin length l, fin separation s and fin thickness t. The parametric variation is restricted to the practical range of fin density (8 fpi to 22.6 fpi) and low blockage ratio to the flow (<20%) while systematically increasing the offset-fin length (1 < l/s < 35). The results show that the short offset-fin length provides higher heat transfer enhancement compared to the plain rectangular fins, while the fin thickness and fin separation show negligible improvement in heat transfer rate for a constant offset-fin length ratio (l/s). The offset-fin effect diminishes as Reynolds number decreases or the offset-fin length becomes very large, as the OSF performance asymptotically approaches towards that of a plain rectangular fin. The OSF cores are shown to reduce the heat transfer surface area by 30% - 50% while keeping a constant pressure drop as that for a plain rectangular fin. A practical case with short offset-fin length (~ 3mm) having a squarer cross-section fins (s/h > 0.5) with intermediate to low fin density (8 fpi to 12 fpi) provides smaller pressure drop gradients as well as larger heat transfer enhancement capacity for a constant heat duty application.

Committee:

Milind Jog, Ph.D. (Committee Chair); Je-Hyeong Bahk, Ph.D. (Committee Member); Raj Manglik, Ph.D. (Committee Member)

Subjects:

Mechanics

Keywords:

Heat Transfer;Offset-Strip Fin

Li, HongxiangPerformance of Multitone Direct Sequence Spread Spectrum in the Presence of Imperfect Carrier Synchronization
Master of Science (MS), Ohio University, 2004, Electrical Engineering & Computer Science (Engineering and Technology)

We provide new analytical and computer simulation results for the performance of multitone direct-sequence spread spectrum (MT-DS-SS) signaling in the presence of imperfect synchronization, modeled as frequency offset and phase noise. We investigate performance as a function of frequency offset/phase noise standard deviation, number of subcarriers and the per-subcarrier processing gain. We assume coherent detection with BPSK modulation. Comparisons between simulations and analysis show excellent agreement. Our approach offers a realistic analytical/numerical method for performance evaluation when the target error probability values are of the order of 10 −6 or lower. In addition, our method can also be easily applied to any multicarrier system with other frequency offset/phase noise models.

Committee:

David Matolak (Advisor)

Keywords:

Multitone direct-sequence spread spectrum (MT-DS-SS); Imperfect Carrier Synchronization; Frequency Offset; Phase Noise; Multicarrier