Visualizing and Understanding Tectonism and Volcanism on Earth and Other Terrestrial Bodies

This dissertation presents new methods of visualizing, teaching, assessing, modeling, and understanding tectonics on Earth and other celestial bodies. Tectonics is the study of planetary lithospheres and includes impact, plate, plume, cryo- and gravitational mechanisms. This dissertation is concerned with plate tectonics and plate/mantle plume interactions. Plate tectonics describes the mainly horizontal motion of lithospheric plates over the asthenosphere. Lithosphere is created at ridges and consumed at subduction zones. In addition to the plate tectonic system, mantle plumes also contribute to mass motions in the subsurface Earth. Both plate tectonics and plume upwelling processes help shape the present form of the planetary surface, including long volcanic island chains, deep ocean basins, and plate boundary triple junctions. Better understanding of these processes by visualization and numerical modeling is one of the primary goals of this study. In the geospatial analysis lab at ODU, our research methodology starts with the creation of visualizations for teaching. These include Google Earth-based virtual field explorations enhanced with digitized specimens and emergent geological and geophysical cross sections. We test these in classes with IRB compliance and sometimes this leads to the discovery of tectonic research questions which we then explore. Settings studied in this investigation are Tonga Trench in the western Pacific Ocean, Artemis on Venus, the Hawaiian-Emperor seamount chain, and the Azores triple junction. Some of these cases pose specific geophysical problems that were selected for further study. The Tonga Trench is a subduction zone that includes trench rollback and opening of a marginal basin—the Lau Basin. The rollback process is difficult to imagine, and therefore we created a set of instructional resources using COLLADA models and the Google Earth Application Programming Interface (API). Animated models for the assessments tests and exploration of different initiations of the subduction process led to a new alternative hypothesis for rollback. Virtual field explorations required the development of new interface features for the Google Earth API. All these instructional materials were combined into modular multi-user virtual field trip experiences and were subject to IRB-compliant evaluation of learning outcomes. Animated COLLADA models for the Hawaii Islands and Emperor Seamounts helped explain the origin and time progression of the island chain. From seismic data, a three-dimensional reconstruction of the Hawaiian mantle plume was created raising the question of the horizontal advection of the plume conduit in the mantle and its correlation with the change in trend of the islands. The Hawaiian–Emperor chain on Earth is spread out as the Pacific plate is moving over the Hawaiian mantle plume. On Venus, however, the Artemis structure was able to grow to super-plume size due to the absence of plate motion. For Venus, visualization was done on a much larger scale, including cross sections of the whole plate showing large plume structures, and Magellan SARS imagery of surface features. In the Azores triple junction, dispersion of plume material is influenced by plate boundary geometry, creating anomalies in seafloor geophysical data for several hundred kilometers away from the plume center. To explore the interaction between a mantle plume and a plate boundary triple junction, a series of three dimensional finite element numerical models was calculated. A parameter space investigation changed the location of the plume conduit and its volume flux, as well as the treatment of viscosity. Flow patterns, dynamical topography, relative crustal thickness variations and waist width scaling relationships resulting from these calculations give valuable insight into the importance of triple junction configuration in the dispersion of plume material

Identifying Fake News from the Variables that Governs the Spread of Fake News

Several researchers have attempted to investigate the processes that govern and support the spread of fake news. This paper collates and identifies these variables. This paper then categorises these variables based on three key players that are involved in the process: Users, Content, and Social Networks. The authors conducted an extensive review of the literature and a reflection on the key variables that are involved in the process. The paper has identified a total of twenty-seven variables. Then the paper presents a series of tasks to mitigate or eliminate these variables in a holistic process that could be automated to reduce or eliminate fake news propagation. Finally, the paper suggests further research into testing the method in lab conditions

Facebook Fake Profile Identification: Technical and Ethical Considerations

March 2019, Facebook updated its security procedures requesting ID verification for people who wish to advertise or promote political posts of adverts. The announcement received little media coverage even though it is an interesting development in the battle against Fake News. This paper reviews the current literature on different approaches in the battle against the spread of fake news, including the use of computer algorithms, A.I, and introduction of ID checks. Critical to the evaluation is consideration into ID checks as a means to combat the spread of Fake News. To understand the process and how it works, the team undertook a social experiment combined with reflective analysis to better understand the impact of ID check policies when combined with other standards policies of a typical platform. The analysis identifies grave concerns. In a wider context, standardising such policy will leave political activists in countries vulnerable to reprisal from authoritarian regimes. Other impacts include people who use fake names to protect the identity of adopted children or to protect anonymity from abusive partners. The analysis also points to the fact that troll arms could bypass these checks rendering the use of ID checks less effective in the battle to combat fake news. The analysis also points to the fact that troll arms could bypass these checks rendering the use of ID checks less effective in the battle to combat fake news

OPTIMIZATION OF EXAM DISTRIBUTION

Academic research findings report level of cheating in exams involving students studying from each other. Several publications have examined means for preventing cheating by means of exam versions, rotations of questions, and addressing social factors. Yet one preventative aspect of exam cheating seems to be neglected and that is exam distribution. In this paper, the authors introduce the Exam Distribution Problem (EDP).  Defining a given k versions of an exam in a classroom with n × m chairs, the paper attempts to find the optimal distribution of exam papers such that every two exams of the same version are at maximal distance from each other. Relevant works in Graph-Theory are examined with simulation of Naïve Algorithm (random) and Sequential Release Algorithm (common) for EDP are reviewed. A cost is assigned for instances where two papers of the same version appear in direct proximity thus associated with higher opportunity for cheating. The results showed that the Sequential Release Algorithm did on average no better than the Random Algorithm. Using Optimization Algorithm, the team presents a new approach, the Dichotomous Interleaved Pairing Algorithm (DIP) that achieves minimal adjacency between two identical exam papers and minimal risk of cheating.  Article visualizations

Multidirectional Power Flow Control among Double Winding Six-Phase Induction Machine Winding Sets

This paper presents an indirect rotor-field oriented control (IRFOC) algorithm for symmetrical six-phase double-winding induction machines with four three-phase sub-winding sets. The presented algorithm introduces the ability to control the power flow between different sub-winding sets. Multiple three-phase induction machines are utilised for critical applications such as more-electric aircrafts, due to their high reliability and fault tolerant capabilities. In this paper, the proposed control scheme is utilising the auxiliary currents of each six-phase sub-motor to achieve full control of the sub-winding sets current amplitudes and consequently the power flow direction for each sub-winding set. A six-phase induction machine with double winding is utilised to validate the proposed control scheme. Four isolated voltage source inverters (VSIs) are used to supply each winding set of the machine. The double-winding six-phase induction machine controlled by the proposed IRFOC algorithm is simulated using Matlab/Simulink. Presented simulation results validate the ability of the algorithm to appropriately control the power flow of each sub-winding set

Signatures of electron-boson coupling in half-metallic ferromagnet Mn5_5Ge3_3: study of electron self-energy Σ(ω)\Sigma(\omega) obtained from infrared spectroscopy

We report results of our infrared and optical spectroscopy study of a half-metallic ferromagnet Mn$_5$Ge$_3$. This compound is currently being investigated as a potential injector of spin polarized currents into germanium. Infrared measurements have been performed over a broad frequency (50 - 50000 cm$^{-1}$) and temperature (10 - 300 K) range. From the complex optical conductivity $\sigma(\omega)$ we extract the electron self-energy $\Sigma(\omega)$. The calculation of $\Sigma(\omega)$ is based on novel numerical algorithms for solution of systems of non-linear equations. The obtained self-energy provides a new insight into electron correlations in Mn$_5$Ge$_3$. In particular, it reveals that charge carriers may be coupled to bosonic modes, possibly of magnetic origin

Analytical formula for leg voltage THD of a PWM multilevel inverter

In this paper derivation of an analytical formula for the leg voltage THD is presented. The considered system is a leg of a multilevel pulse width modulated (PWM) voltage source inverter (VSI). The solution is based on the Parseval's theorem. The assumption throughout the derivations is that the ratio of the switching to the fundamental frequency is high. Derivations are based on the integration of the power of the PWM signal in a single switching period over the fundamental period of the signal. Only an ideal sinusoidal reference leg voltage is analysed. Analytical expression for the leg voltage THD is given for any number of levels. Validity of the derived analytical equations is confirmed by simulations and experiments

Evaluation of DC-link voltage ripple in five-phase PWM voltage source inverters

This paper presents the analysis of the DC-link voltage switching ripple in five-phase PWM voltage source inverters with balanced load. The analysis is particularly important for the design and selection of a DC-link capacitor making it possible to meet desired electrical performance of the inverter system. Simple and practical equation for designing the DC-link capacitor is proposed relating the value of capacitance to the maximum value (peak-to-peak) of the DC-link voltage ripple. The amplitude of the DC-link voltage switching ripple is analytically derived as a function of modulation index, and the amplitude of the output current and phase angle. In order to show peak-to-peak voltage ripple distribution, different diagrams are introduced. Reference is made to continuous symmetric centred PWM modulation (i.e., space vector modulation SVM). In order to verify proposed developments, simulations have been carried out by Matlab/Simulink considering full range of modulation index and output phase angle

Charge order, metallic behavior and superconductivity in La_{2-x}Ba_xCuO_4 with x=1/8

The ab-plane optical properties of a cleaved single crystal of La_{2-x}Ba_xCuO_4 for x=1/8 (T_c ~ 2.4 K) have been measured over a wide frequency and temperature range. The low-frequency conductivity is Drude-like and shows a metallic response with decreasing temperature. However, below ~ 60 K, corresponding to the onset of charge-stripe order, there is a rapid loss of spectral weight below about 40 meV. The gapping of single-particle excitations looks surprisingly similar to that observed in superconducting La_{2-x}Sr_{x}CuO_4, including the presence of a residual Drude peak with reduced weight; the main difference is that the lost spectral weight moves to high, rather than zero, frequency, reflecting the absence of a bulk superconducting condensate.Comment: 4 pages, with 1 table and 3 figure

Analytical Formulas for Phase Voltage RMS Squared and THD in PWM Multiphase Systems

The analysis and assessment of the pulsewidth modulation (PWM) techniques is commonly based on the comparison of the total harmonic distortion (THD) results. THD is usually calculated by application of the Fourier transformation and by taking a limited number of harmonics into the consideration. In this paper, derivation of analytical formulas for the phase voltage THD is presented. The considered system is a symmetrical multiphase starconnected load, supplied from a multilevel pulsewidth-modulated voltage-source inverter (VSI, three-phase case is also covered). The solution is based on the Parseval’s theorem, which links frequency spectrum and time domain through the average power (i.e., rootmean- square (rms) squared value) of the signal. The assumption throughout the derivations is that the ratio of the switching to fundamental frequency is high. Derivations are based on the integration of the power of the PWM signal in a single switching period over the fundamental period of the signal. Only ideal sinusoidal reference voltages are analyzed, and no injection of any type is considered. Formulas for phase voltage THD for any number of phases are derived for two- and three-level cases, for themost commonly used carrier-based methods. Comparison of the analytically obtained curves with simulation and experimental results shows a high level of agreement and validates the analysis and derivations