Department: Computational Science and Engineering ![[clear]](close-x.png "Remove this limiter")
13 matches in the database.
These are records: 1 - 13.
1.
Bufler, Travis Dale.
Automatic Target Detection Via Multispectral UWB OFDM Radar Imaging.
Degree: MS, Computational Science and Engineering, 2012, Miami University
► This research proposes using the multispectral radar imaging methodology for target detection…
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▼ This research proposes using the multispectral radar imaging methodology for target detection in complicated scenarios. The investigation proposes to extend this concept to ultrawideband radar by means of employing multi-carrier waveforms based upon Orthogonal Frequency Division Multiplexing (OFDM) modulation. Individual sub-bands of an OFDM waveform can be processed separately to yield range and cross-range reconstruction of a target scene containing both useful targets and clutter. An image based automatic target recognition algorithm has been developed to provide decision making within each sub-band. Target detection in resultant images will be performed and contrasted with the detection performance of a traditional xed-waveform Synthetic Aperture Radar system. The adaptive removal of clutter from these selected images will result in a system that looks to improve detection performance.
Advisors/Committee Members: Garmatyuk, Dmitriy.
Subjects: Electrical Engineering; Engineering
Keywords: SAR; gradient; divergence; target detection; vector fields; clutter; radar
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2.
Gong, Yun.
Incoherent Scatter Study of Dynamics in the Ionosphere E- and F-Region at Arecibo.
Degree: MS, Computational Science and Engineering, 2012, Miami University
► This thesis reports the investigation of the dynamics and associated phenomena occurring…
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▼ This thesis reports the investigation of the dynamics and associated phenomena occurring in the ionospheric E- and F-region heights above Arecibo. The observational data was derived with an incoherent scatter radar (ISR) from Arecibo Observatory, Puerto Rico. The thesis focuses primarily on two aspects. One is to study the atmospheric tidal and planetary waves. This is the first time that dual-beam ISR has been used for E- and F-region tidal and planetary wave studies. The vertical structures of the observed tidal and planetary waves are analyzed rigorously. This study is the first to report the existence and possible excitation mechanism of a terdiurnal tide in the F-region at low latitude. The second aspect is to give a more complete explanation of the midnight collapse phenomenon. The F-region electric field, ambipolar diffusion, and tidal components in the meridional wind all play a role in causing the midnight collapse at Arecibo.
Advisors/Committee Members: Zhou, Qihou.
Subjects: Aeronomy; Engineering
Keywords: incoherent scatter radar; the ionosphere; tidal and planetary waves; midnight collapse
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3.
Gossard, Justin.
Numerical Simulation of the Steady-State, Thermal-Hydraulic Performance of Microchannel and Minichannel Evaporators with Headers and Louvered Fins.
Degree: MS, Computational Science and Engineering, 2011, Miami University
► In this study, a finite volume, steady-state evaporator model that includes rectangular…
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▼ In this study, a finite volume, steady-state evaporator model that includes rectangular minichannel and microchannel tubes with louvered fins and headers was developed and validated. The model provides the user with the option of selecting from several published correlations when calculating the air-side and refrigerant-side heat transfer and pressure drop within the control volume. The model was then used to compare the thermal-hydraulic performance of experimental ternary refrigerant mixtures to more traditional refrigerants—namely, R-125/R-32/R-161 (34%/15%/51%) versus R-22 and R-125/R-143a/R-161(45%/40%/15%) versus R-404a. The numerical model was also used to study the effects of header-induced maldistribution on evaporator performance by comparing the predicted cooling capacity and refrigerant-side pressure drop to a distribution rating parameter (Φ) defined by Bowers et al. (2010). It was shown that as the distribution of quality between tubes becomes more uniform (i.e. Φ → 1), the cooling capacity and refrigerant-side pressure drop both approach their maximum values.
Advisors/Committee Members: Sommers, Andrew.
Subjects: Mechanical Engineering
Keywords: evaporator; microchannel; refrigerant mixtures; numerical simulation; maldistribution
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4.
Ling, Yu.
Nonlinear Response of a Skin Panel under Combined Thermal and Structural Loading.
Degree: MS, Computational Science and Engineering, 2012, Miami University
► Future hypersonic vehicle will operate in an extreme environment, which involves extreme…
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▼ Future hypersonic vehicle will operate in an extreme environment, which involves extreme aerodynamic heating, fluctuating pressure and acoustic loading. Hypersonic vehicle must be reusable, lightweight and affordable in such environment. For hypersonic flight, the structure experiences complex aeroacoustic loads. The design of the structure depends on the ability to predict the response and the life of structure in extreme environment. This research presents a detailed investigation of the interactions and interplay among these parameters as evidenced by the nonlinear (static and dynamic) response of the panel. A representative panel was selected as part of a ramp skin panel on a blend wing body hypersonic vehicle concept. This project focuses on the nonlinear response of the skin panel under combined thermal and structural loading. Thermal buckling, snap-through, and snap-buckling behaviors have been investigated by using different structural boundary condition. The long term goal of this research includes capturing fluid structure interaction as well as developing design curves for nonlinear response of the panel.
Advisors/Committee Members: Shukla, Amit.
Subjects: Mechanical Engineering
Keywords: hypersonic aircraft; skin panel; nonlinear response; thermal buckling; snap-through
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5.
Mao, Xiaolei.
GPS CARRIER SIGNAL PARAMETERS ESTIMATION UNDER IONOSPHERE SCINTILLATION.
Degree: MS, Computational Science and Engineering, 2011, Miami University
► Ionosphere scintillation can induce large GPS carrier phase tracking error, and may…
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▼ Ionosphere scintillation can induce large GPS carrier phase tracking error, and may cause the carrier tracking loop to lose lock under a strong scintillation scenario. This thesis proposes the inverse adaptive phase lock loop (PLL) method to estimate the GPS carrier signal parameters more precisely. Simulated signals with different scintillation levels are used to evaluate this tracking method. The results demonstrated the effectiveness of the inverse adaptive PLL method in improving GPS signal carrier parameter estimations especially for signals with low de-correlation time or higher phase fluctuation rate. Real scintillation data collected during the last solar max at the Ascension Island are also used in the performance evaluations. The results show that while the real scintillation signals exhibited deep signal fading, its phase fluctuations rate is relatively low, indicating relatively mild signal dynamics. The inverse adaptive phase lock loop has limited performance improvement against this type of scintillations.
Advisors/Committee Members: Morton, Yu.
Subjects: Electrical Engineering
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6.
McDonough, Laura.
Receptance Based Control of Aeroelastic Systems for Flutter Suppression.
Degree: MS, Computational Science and Engineering, 2012, Miami University
► The field of aeroelasticity deals with mutual interaction between inertial, elastic, and…
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▼ The field of aeroelasticity deals with mutual interaction between inertial, elastic, and aerodynamic properties of a flexible system. Aeroelastic instabilities, such as flutter, can lead to fatigue and potential failure of an aerospace structure. Active control strategies may be needed to avoid such instabilities to achieve increased flight performance. In this research, receptance based active control schemes are developed for flutter suppression and flutter-boundary extension. In principle, this method utilizes receptance frequency response functions extracted from embedded sensors and actuators of the aircraft, representing the true aeroelastic interaction, for control force computations. Hence, it circumvents potential modeling errors associated with structural and aerodynamic parameters, which are used in traditional state-space based aeroelastic control. In this study, receptance based single input, multiple input and output state feedback control is developed. Several aspects of control design including actuator dynamics, optimization and robustness are demonstrated through numerical simulations and computational studies.
Advisors/Committee Members: Singh, Kumar.
Subjects: Aerospace Engineering; Mechanical Engineering
Keywords: Aeroelasticity; control; aircraft; active control; receptance method; single input; multiple input; output; control design
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7.
Niu, Fei.
PERFORMANCES OF GPS SIGNAL OBSERVABLES DETRENDING METHODS FOR IONOSPHERE SCINTILLATION STUDIES.
Degree: MS, Computational Science and Engineering, 2012, Miami University
► Ionosphere scintillation impacts GNSS receiver performance. The scintillation effects are measured by…
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▼ Ionosphere scintillation impacts GNSS receiver performance. The scintillation effects are measured by two scintillation indices, the amplitude scintillation index S4 and the phase scintillation index sigma_phi. These indices are computed from detrended signal power and carrier phase obtained from the receiver tracking loop outputs, respectively. Recent studies show that the values of these indices depend on the detrending method used to remove the non-scintillation effects. This thesis presents our investigation of the error sources in the scintillation detrending methods. For amplitude scintillation, the main error source is the detrending filter group delay. For phase scintillation, inappropriate detrending filter cutoff frequency selection is the dominant error contributing factor. The paper presents the error assessment and correction techniques for both detrending methods, and the resulting correlations between amplitude and phase scintillations.
Advisors/Committee Members: Morton, Jade.
Subjects: Electrical Engineering
Keywords: Ionosphere Scintillation; Detrending; GNSS Tracking Measurements
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8.
Pennington, Jason R.
Radar Signal Characteristic Extraction with FFT-Based Techniques.
Degree: MS, Computational Science and Engineering, 2011, Miami University
► This research project develops computationally efficient digital signal processing algorithms for digital…
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▼ This research project develops computationally efficient digital signal processing algorithms for digital wideband receivers to determine the existence of radar signals and, if radar signal(s) are present, extract in real time, pertinent signal characteristics such as frequency, signal power, modulation type, and pulse width. Unlike a conventional communication receiver, the digital wideband receiver algorithms considered in this project assume no a priori knowledge about the number of radar signals and their characteristics. Two types of radar signals, namely, pulsed continuous-wave (CW) and chirping signals, are considered in this thesis. Different techniques are exploited to optimize receiver performance. The receiver algorithms developed in this project can successfully detect multiple signals with different characteristics.
Advisors/Committee Members: Cheng, Chi-Hao.
Subjects: Electrical Engineering; Engineering
Keywords: FFT; DSP; autocorrelation; EW receiver; communication system
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9.
Praveen, Vikram.
Event Driven GPS Data Collection System for Studying Ionospheric Scintillation.
Degree: MS, Computational Science and Engineering, 2011, Miami University
► Scintillation in the ionosphere is a highly stochastic phenomenon that occurs due…
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▼ Scintillation in the ionosphere is a highly stochastic phenomenon that occurs due to random electron density fluctuations affecting trans-ionospheric communication channels like Global Positioning System, satellite radio, etc. To study this phenomenon and its effects on electro-magnetic radio waves, we need to capture the affected radio signals. Since scintillation events are short-lived, spatially and temporally sporadic phenomena, capturing scintillation-corrupted data is a difficult task. The diagnostic for scintillation events is called the scintillation indices. The most common scintillation indices currently used are the S4 index and σφ index. The S4 index relates to the amplitude distortion and the σφ index provides a measure of phase variation induced by the ionosphere in the radio frequency signal due to scintillation. This thesis presents a triggering system that senses scintillation events and triggers data acquisition and recording utilizing the Carrier to Noise Ratio, S4 and σφ parameters. Data collected over five months is analyzed and presented.
Advisors/Committee Members: Morton, Yu Tong.
Subjects: Engineering; Physics; Systems Design
Keywords: GPS; Ionospheric Scintillation; Data Collection System
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10.
Santana, Julio III.
Investigating Ionospheric Parameters Using the Plasma Line Measurements From Incoherent Scatter Radar.
Degree: MS, Computational Science and Engineering, 2012, Miami University
► Because of deficiencies in sampling resolution and storage space, the plasma line…
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▼ Because of deficiencies in sampling resolution and storage space, the plasma line frequency component of the incoherent scatter radar (ISR) spectrum has been neglected in experimentally verifying ionospheric parameters. Several incoherent scatter theories were independently developed with confirmation from low resolution data in the 1960s that used the plasma line resonant frequency and plasma line peak intensity to derive ionospheric parameters. Now that higher resolution measurement techniques exist, this thesis investigates three methods for obtaining plasma line resonant frequency, peak intensity, and spectral width. Following this study, several salient features endemic to the ISR experiment performed on January 15-17th, and January 22nd of 2010 are presented and analyzed.
Advisors/Committee Members: Zhou, Qihou.
Subjects: Aeronomy; Electrical Engineering; Plasma Physics
Keywords: Plasma line; ionosphere; incoherent scatter radar; aeronomy; Arecibo Observatory; space weather
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11.
Spalding, Scott A. Jr.
Adaptive OFDM Radar Signal Design.
Degree: MS, Computational Science and Engineering, 2012, Miami University
► This paper examines the combination of adaptive signal design and orthogonal frequency…
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▼ This paper examines the combination of adaptive signal design and orthogonal frequency division multiplexed (OFDM) pulses in order to improve their detection performance and automatic target recognition for multiple varieties of single target scenarios. This adaptive design will be performed through exploiting the target’s reflectivity function. OFDM’s performance for radar systems is discussed and analyzed, as well as its potential in adaptive design. The place of adaptive signal design in developing radar systems is examined, and methods are detailed. Estimators for determining the target’s reflectivity function (TRF) are derived and implemented. Finally, performance results for TRF identification and automatic target recognition are discussed.
Advisors/Committee Members: Garmatyuk, Dmitriy.
Subjects: Computer Engineering; Computer Science; Electrical Engineering
Keywords: radar; OFDM; signal processing; LSE; MMSE; TRF; adaptive signal design
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12.
Willey, Carson Landis.
The Nonlinear Dynamics of Quiet Standing in Humans.
Degree: MS, Computational Science and Engineering, 2011, Miami University
► Postural control has been investigated by a host of different perspectives, and…
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▼ Postural control has been investigated by a host of different perspectives, and each of them seems to develop some new insight into the process of maintaining an upright stance. It would be helpful if these processes could be used to determine a future state of balance or future patterns associated with quiet standing. This gives clinicians the ability to investigate the different plausible failure criteria for each individual patient. It would also help physical therapists to know which parameters, or muscle groups, need to be adjusted/corrected to help patients regain a reasonable state of balance. In this study, we have varied sets of parameters in order to see the trends in a proposed measure for balance assessment. This measure is compared to other previously applied balance measures and correlations are analyzed between sets.
Advisors/Committee Members: Shukla, Amit.
Subjects: Engineering
Keywords: Bifurcation, Quiet Standing, Postural Control, Controls, Computer Modeling, Nonlinear Dynamics
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13.
Yeakle, Colin.
Experimental Testing and Numerical Modeling to Capture Deformation Phenomenon in Medical Grade Polymers.
Degree: MS, Computational Science and Engineering, 2011, Miami University
► Rate-sensitivity, creep and relaxation behavior of medical grade polymers has been investigated…
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▼ Rate-sensitivity, creep and relaxation behavior of medical grade polymers has been investigated experimentally along with an assessment of different constitutive models. Two types of modified common biomedical material A and B were tested. All materials exhibited rate-sensitivity and rate-reversal behavior during creep and relaxation testing with prior loading and unloading histories for tensile and compressive tests. Numerical modeling was performed through a modified version of the Viscoplasticity Based on Overstress (VBO) model. Simulation and prediction results with good quantitative and qualitative agreement were produced for all materials in tension and compression loading. Parameter fitting using the Hybrid and Three Network Models in PolyUMod software generated material constants for ABAQUS, and the finite element results for a knee joint were verified against experimental data. The parameter fitting was unable to produce acceptable results for MATERIAL C. Implementation of VBO into the PolyUMod library is recommended to enhance modeling capability.
Advisors/Committee Members: Khan, Fazeel.
Subjects: Biomedical Engineering; Materials Science; Mechanical Engineering
Keywords: polymers; constitutive model; VBO; creep; relaxation; numerical model
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