A robust inversion method for quantitative 3D shape reconstruction from coaxial eddy-current measurements

This work is motivated by the monitoring of conductive clogging deposits in steam generator at the level of support plates. One would like to use monoaxial coils measurements to obtain estimates on the clogging volume. We propose a 3D shape optimization technique based on simplified parametrization of the geometry adapted to the measurement nature and resolution. The direct problem is modeled by the eddy current approximation of time-harmonic Maxwell's equations in the low frequency regime. A potential formulation is adopted in order to easily handle the complex topology of the industrial problem setting. We first characterize the shape derivatives of the deposit impedance signal using an adjoint field technique. For the inversion procedure, the direct and adjoint problems have to be solved for each coil vertical position which is excessively time and memory consuming. To overcome this difficulty, we propose and discuss a steepest descent method based on a fixed and invariant triangulation. Numerical experiments are presented to illustrate the convergence and the efficiency of the method

Have Your Cake and Eat It? Productive Parallel Programming via Chapel’s High-level Constructs

Explicit parallel programming is required to utilize the growing parallelism in computer hardware. However, current mainstream parallel notations, such as OpenMP and MPI, lack in programmability. Chapel tries to tackle this problem by providing high-level constructs. However, the performance implication of such constructs is not clear, and needs to be evaluated. The key contributions of this work are: 1. An evaluation of data parallelism and global-view programming in Chapel through the reduce and transpose benchmarks. 2. Identification of bugs in Chapel runtime code with proposed fixes. 3. A benchmarking framework that aids in conducting systematic and rigorous performance evaluation. Through examples, I show that data parallelism and global-view programming lead to clean and succinct code in Chapel. In the reduce benchmark, I found that data parallelism makes Chapel outperform the baseline. However, in the transpose benchmark, I found that global-view programming causes performance degradation in Chapel due to frequent implicit communication. I argue that this is not an inherent problem with Chapel, and can be solved by compiler optimizations. The results suggest that it is possible to use high-level abstraction in parallel languages to improve the productivity of programmers, while still delivering competitive performance. Furthermore, the benchmarking framework I developed can aid the wider research community in performance evaluations

Power Consumption of Instruction Encodings on Cortex-M4

Energy efficiency is increasingly important with wider use of batterypowered devices. There are many factors involved in the power consumption of instructions, such as encodings. The energy implication of these factors is not clear, and needs to be evaluated. The main contribution of this work is the characterization of power consumption of some instruction encodings of ARM v7-M on Cortex-M4 MCU STM32L476VGT6. I also designed and implemented a self-contained power measurement infrastructure on 32L476GDISCOVERY. I found that the encodings of instructions could affect the energy consumption of the MCU. The results of this work can make application programmers and hardware vendors be aware of the energy characteristics of programs and devices. Future work of a more detailed model could allow us to predict the energy consumption when designing new systems.A report submitted for the course COMP2300 (Advanced Studies Extension

Air quality analysis of nitrogen oxides and relationships with ozone pollution

Master of ScienceDepartment of Chemical EngineeringJennifer L. AnthonyLarry E. EricksonAir pollution can harm us when it accumulates in the air in high enough concentrations. Nitrogen oxides (NOx), especially nitrogen dioxide (NO₂), are increasingly of concern due to the environmental and health problems they cause. This reviews the recent literature on the reasons and impacts of NOx pollution as well as ozone pollution related to NOx emissions. A review of the impacts of transportation is provided as it pertains to various types of NOx pollution. To improve the air quality, the recent research focuses on how suitable monitoring methods can be used to more economically and precisely collect data on pollution concentrations. Multiple researchers have explored low-cost monitors. Other research explores more convenient ways to eliminate NOx pollution to improve air quality. Regarding the impact of transportation on NOx emissions, vehicle emission technologies are of concern to an increasing number of people, such as using urea to reduce NOx emission for diesel vehicles and developing all-electrical vehicles and plug-in hybrid electric vehicles. This research focused on the data analysis of NO₂ and ozone concentrations in Chicago from the SASA project. Other analyses also provided some data for states and cities in the U.S. to show the relationship between NOx and ozone with transportation. Variations of NOx and ozone emissions were explored. First, the hourly variations in NOx and ozone emissions each day were studied. Second, the seasonal variation in NOx and ozone pollution was analyzed. Third, the differences in NOx emissions on working days and weekends were found. The impacts of NOx emissions on the variation in the ozone concentration in the air were discussed. The purpose of this research is to help more people, especially residents in the communities of Chicago, related to the SASA project to realize the hazard of NOx pollutants to humans and the environment, become aware of the importance and urgency of reducing NOx emissions, and provide feasible methods to solve this problem