Triggered earthquakes and tremor: Their characteristics and physical mechanisms

Dynamic triggering of earthquakes is investigated and compared among three geothermal/volcanic regions of California, and dynamic triggering of tremor is investigated and compared among several strike-slip faults in the Western Hemisphere. The characteristics of the triggering waves - amplitude, frequency, and incidence of the triggering waves on faults – are explored. Results indicate that for earthquake triggering, peak dynamic stress (amplitude) appears to be the primary controlling factor. On the other hand, tremor triggering is controlled by amplitude, frequency, and incidence of the seismic waves on the fault. In addition, earthquake triggering primarily occurs in geothermal regions with extensional tectonics, while tremor triggering occurs predominately in compressional or transpressional tectonic environments. A geothermal region’s susceptibility to triggering by external stressing is found to be proportional to its background activity rate. However, tremor triggering appears to occur more often than earthquake triggering. The observation that tremor is triggered more often than earthquakes could be a reflection of a fault being weaker at depth (where tremor occurs) than in the shallower crust (where earthquakes occur). That is, tremor may be more easily triggered due to a fault having low effective stress, pressurized fluids, and/or a perpetual state of near-criticality at depths where tremor occurs. Potential research directions that further explore dynamic triggering of earthquakes and tremor are discussed.Ph.D

Theoretical studies of electronically adiabatic and non-adiabatic chemical reaction

Part I presents several sets of comparisons of semi-classical, quasi-classical and exact quantum reactive scattering calculations for collinear chemical reactions. The possibility of modifying the standard quasi-classical method according to a quantum criterion is investigated. The systems studied are H + H_2, F + H_2, and F + D_2. In addition, a theoretical investigation of the semi-classical S matrix is made. Details of a quasi-classical current density analysis of the H + H_2 reaction are presented and a comparison with exact quantum results is made. A direct test of two versions of the vibrationally adiabatic theory of chemical reactions is made in Part II for the H + H_2 reaction. The adiabaticity of the symmetric stretch motion of the H_3 transition state is focussed upon. In addition, a determination of the completeness of adiabatic basis sets for scattering calculations is made. The theory of electronically non-adiabatic chemical reactions is presented in Part III. Quantum calculations of the collinear H^+ + H_2 → H_2 + H^+ reaction are described. A model and a realistic potential energy surface are employed in these calculations. A fictitious electronically non-adiabatic H + H_2 collinear chemical reaction is treated quantum mechanically. Two potential energy surfaces and a coupling surface are developed for this purpose. The reaction Ba(^1S) + ON_2(X^1Σ) → BaO(X^1Σ) + N_2(X^1Σ^+_g), BaO(a^3II) + N_2(X^1Σ^+_g) is studied quantum mechanically. The singlet and triplet potential energy surfaces are devised as is a spin-orbit coupling surface. Electronically adiabatic and non-adiabatic transition probabilities are calculated as a function of the initial translational energy of the reagents.</p

Game-theoretic approaches for smart prosumer communities

Global warming is endangering the Earth’s ecosystem. It is imperative for humanity to limit greenhouse gas emissions in order to combat rising global average temperatures. Demand-side management (DSM) schemes have widely been analysed in the context of the future smart grid. Often they are based on game-theoretic approaches to schedule the electricity consumption of its participants such that it results in small peak-to-average ratios (PAR) of the aggregated load. In order to guarantee high comfort levels for the consumer, we investigate DSM schemes on the basis of individually owned energy storage systems. The scheduling of these batteries is incentivised by a specific pricing function offered to the users. Within this thesis we cover various aspects for these type of management schemes. Firstly, we design a simple game-theoretic scheduling mechanism and analyse how the battery model, more specifically the round-trip efficiency, affects the outcome. From the simulations we find the importance of highly efficient energy storage systems for the engagement of participants. Secondly, the simple scheduling mechanism is replaced with a more advanced dynamic game, that models fine-grained control over the battery. For this novel game, we derive an analytical solution for the best response of a user, considerably speeding up the solution algorithm for the game. Furthermore, a comparison between the two games also shows the improvements in reducing the PAR of the aggregated load. Based on the augmented game, we investigate the resilience of the equilibrium solution with respect to inevitable real-world forecasting errors. One of the main findings of this thesis is reflected in the results showing the robustness of the schedules for a large number of simulated scenarios and even in the worst-case. Thirdly, we explicitly deal with the finite horizon effect that occurs due to the fixed time frame of the game mechanism. This eventually leads to a DSM system which results in a mean PAR of the aggregated load close to the optimum. Further studies show that these outcomes can be achieved due to the interaction of the households. Individual scheduling of batteries reduces the potential reduction of PAR and is especially detrimental for the robustness against forecasting errors. Fourthly, the developed model is analysed with respect to cyber-physical attacks. We develop a novel type of data-injection attack on the forecasted data and show their impact. After suggesting suitable monitoring strategies to the utility company, a game-theoretic model is employed to understand their decision making process. Finally, we investigate which battery size is optimal for such a DSM scheme. The respective experiments give insight into the different factors that determine the sizing of the battery. From the results we can infer that certain types of users only require a small scale battery system to achieve considerable gains. Overall, this thesis provides an in-depth analysis of a demand-side management scheme that can be employed by prosumers all around the world in the nearest future. Furthermore, the experiments give insights to utility companies to focus on community approaches and how they can mitigate potential cyber attacks

Low power circuits and systems for wireless neural stimulation

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 155-161).Electrical stimulation of tissues is an increasingly valuable tool for treating a variety of disorders, with applications including cardiac pacemakers, cochlear implants, visual prostheses, deep brain stimulators, spinal cord stimulators, and muscle stimulators. Brain implants for paralysis treatments are increasingly providing sensory feedback via neural stimulation. Within the field of neuroscience, the perturbation of neuronal circuits wirelessly in untethered, freely-behaving animals is of particular importance. In implantable systems, power consumption is often the limiting factor in determining battery or power coil size, cost, and level of tissue heating, with stimulation circuitry typically dominating the power budget of the entire implant. Thus, there is strong motivation to improve the energy efficiency of implantable electrical stimulators. In this thesis, I present two examples of low-power tissue stimulators. The first type is a wireless, low-power neural stimulation system for use in freely behaving animals. The system consists of an external transmitter and a miniature, implantable wireless receiver-and-stimulator utilizing a custom integrated chip built in a standard 0.5 ptm CMOS process. Low power design permits 12 days of continuous experimentation from a 5 mAh battery, extended by an automatic sleep mode that reduces standby power consumption by 2.5x. To test this device, bipolar stimulating electrodes were implanted into the songbird motor nucleus HVC of zebra finches. Single-neuron recordings revealed that wireless stimulation of HVC led to a strong increase of spiking activity in its downstream target, the robust nucleus of the arcopallium (RA). When this device was used to deliver biphasic pulses of current randomly during singing, singing activity was prematurely terminated in all birds tested. The second stimulator I present is a novel, energy-efficient electrode stimulator with feedback current regulation. This stimulator uses inductive storage and recycling of energy based on a dynamic power supply to drive an electrode in an adiabatic fashion such that energy consumption is minimized. Since there are no explicit current sources or current limiters, wasteful energy dissipation across such elements is naturally avoided. The stimulator also utilizes a shunt current-sensor to monitor and regulate the current through the electrode via feedback, thus enabling flexible and safe stimulation. The dynamic power supply allows efficient transfer of energy both to and from the electrode, and is based on a DC-DC converter topology that is used in a bidirectional fashion. In an exemplary electrode implementation, I show how the stimulator combines the efficiency of voltage control and the safety and accuracy of current control in a single low-power integrated-circuit built in a standard 0.35 pm CMOS process. I also perform a theoretical analysis of the energy efficiency that is in accord with experimental measurements. In its current proof-of-concept implementation, this stimulator achieves a 2x-3x reduction in energy consumption as compared to a conventional current-source-based stimulator operating from a fixed power supply.by Scott Kenneth Arfin.Ph.D

Leadership within the context of school equality policy

My thesis examines leadership within the context of school equality policy. I define leadership as the interaction of leaders, followers and situation. There were two research aims. To clarify, illustrate and evaluate the distinction between leadership and management; both theoretically and practically in relation to school policy. A second aim was to collect and examine the views of teaching staff from Head teachers to Teaching Assistants in three primary schools. These aims produced three research questions: • Where does power and control lay in primary schools? Is power and control similar to leadership and management? • What leadership characteristics come out of a primary school equality policy context? • How and why are schools using leadership within the context of primary school equality policy? Questions were addressed through a qualitative research design using a focused, in-depth case study approach. I collected and analysed semi-structured interviews from teaching staff and documentary evidence from Ofsted reports. Research conclusions were: that leadership/power and control/management are similar when discussing school organisations. This view is supported by academic specialists (Crawford 2014). Analysis suggested that leadership and management can be seen as a continuum from wicked to tame complicated problems (Grint 2010; Western 2008) when developing school policy. Finally, this continuum seems to work at the micro school, meso schools and macro government levels. I found 8 major characteristics of school leadership including team, experience and respect which involved formal and informal leadership; however, interviewees saw formal leadership as central. Finally, the how and why of equality policy involved solo and distributed leadership; for the schools, shared leadership of Equality policy was seen as an important element in ensuring access and opportunity according to their ethos and vision and meeting internal and external accountability requirements. This research raised an issue concerning the paucity of Teaching Assistant voice in Ofsted reports and academic literature

Environmental impact of passenger ships in port

The environmental impact of ships can be of different types. This thesis covers air pollution due to chemicals and concentrates on local effects due to compounds emitted in the exhaust gases of internal combustion engines and acoustic pollution. The attention has been focused on the consequences of the presence of many ships in ports located close to inhabited zones. For port-scale analyzes, the case study is the port of Naples for which traffics, geographic conformation, meteorological conditions, results of experimental campaigns both in the field of acoustic and environmental impact are available. In the field of polluting emissions, the case study for the simulations is a catamaran in service at the port of Naples for which experimental measurements at sea and bench tests are available. For the simulation of acoustic emissions, the case study is a passenger ship for which experimental measurements and forecast data are available. Experimental campaigns and simulations have been carried out on the port of Naples and most of the applications concern passenger ships, but methods and procedures can be applied to a general case. The thesis consists of six chapters, briefly introduced here. Each chapter contains a first subsection named "aims and scope" precisely to describe its main purposes in a more extended way than the summary presented here. The theme is first framed in the more general context of the environmental impact of anthropogenic activities and of marine transportation in particular assessment studies and documents issued by international bodies reporting targets for limiting the global environmental impact of the shipping sector are briefly summarized. Recalls on the main mechanisms of formation and reduction of pollutants are exposed. The second chapter describes the bottom-up method aimed at estimating the emissions of passenger ships in port. To obtain an estimation of all the emissions a series of very specific steps are necessary. The main information to be collected and produced concerns: traffic, routes, arrival and departure schedules, engine loads, emissions, heights, and diameters of the funnels. The technique of data collection and its use was gradually deepened (from simple cruise calendar to AIS data). The main application on the entire port sees the use of AIS data. The starting AIS data have been processed through an "ad hoc" MATLAB code capable of managing a relevant amount of data and returning a complete calendar of all the movements of every ship arriving and operating in the port. The use of AIS data has brought about improvements in the calculation methodology for emissions as well, allowing for example a more accurate analysis of average speeds in port and idle times. The port of Naples, where all the analysis were developed, is presented next. The traffics for the years and reference periods chosen in the subsequent analyzes are presented (2012, 2016, and 2018). A comprehensive study of the environmental impact of ships cannot be separated from the creation of atmospheric dispersion models. These models require the flow of pollutants emitted in the main operational phases in port (navigation, maneuvering, and mooring) as the main inputs. The results allow to estimate the weight that the passenger branch has on air quality also thanks to cross-comparisons with port measurements and ARPAC (Regional Agency for Environmental Protection in Campania) data. After the analysis of the environmen0tal impact on a port scale, the problem of emissions has been approached by applying a designated simulation, with the aim to overcome the use of emission factors. The first part of the chapter describes a state of the art of simulation model and an in-depth analysis of the main emission simulation methodologies. An engine model has been created in RICARDO WAVE environment; this engine model was validated and calibrated on an engine installed onboard a passenger ship operating in the port of Naples. Bench test results in terms of power, torque, consumption, and rpm have been used to calibrate the model while experimental measurements validated it. In the dissertation, a description of the case study (ship, engine, bench tests, and sea trials), a description of the model, and an interpretation of the results are presented. The validation on sea trials shows the effectiveness of the model both in terms of main engine parameters and emissions. At the end of the chapter, a comparison between the three emission estimation methodologies (EMEP-EEA, with AIS data, simulations, and experimental campaign) has been carried out. The next chapter of the thesis concerns the assessment of the acoustic impact of passenger ships in port. The structure of the research is typically the same: simulation and experimental results. The first part shows some experimental surveys made on a passenger ship in port that served as validation of a simulation model built in the TERRAIN OLIVE TREE LAB SUITE environment. The second and last part presents the methodology and results obtained in the context of a collaborative research project between the Universities of Naples, Genoa, and Trieste. The project aimed at characterizing the acoustic impact of a ship in light of the new additional class notation published by the Lloyds Register "Procedure for the Determination of Airborne Noise Emissions from Marine Vessels Airborne Noise Emissions from Marine Vessels". The last chapter sets out three applications in order to keep the problem set in a global scale context. The first presents an analysis of the possible countermeasures that can be applied to the cruise ship fleet aimed at environmental safeguarding (DNV Appraisal Tool), in the wake of the EEOI and EEDI. Furthermore, in the context of the environmental impact on a port scale, preliminary measurements of polluting emissions using remote measurement instruments (LIDAR) were carried out with the aim of allowing an indirect estimate of the concentrations of pollutants in the exhausts of ships, thus significantly reducing the uncertainties related to ground-level measurements with active or passive samplers. The last application, on the other hand, concerns the ports and the possible activities and initiatives to be implemented in order to host fleet of increasingly green and eco-sustainable ships (Environmental Ship Index)