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Stragglers-Robust First-Order Distributed Optimization Algorithms Over Networks Utilizing Gradient Coding, Elie Atallah
Stragglers-Robust First-Order Distributed Optimization Algorithms Over Networks Utilizing Gradient Coding, Elie Atallah
Electronic Theses and Dissertations
This dissertation considers distributed algorithms for centralized and decentralized networks that solve general convex optimization problems. First, a centralized algorithm is explored for parameter server networks robust to the straggler problem. It is proved that the server nodes' estimates converge to the minimizer of the global objective function with connections vulnerable to an allowed number of stragglers. We then show that convergence is also attained in other different cases: Either by using only the received local gradients scenario or the scenario of using delayed local gradients for the non received gradients. Concurrently, the convergence rates for the above aforementioned scenarios …
Dynamics Of A Perfectly Premixed Jet Flame Exhibiting Self-Excited High-Frequency, Transverse Thermoacoustic Instabilities, Lucky Tran
Electronic Theses and Dissertations
This work is an investigation of the behavior of a premixed turbulent jet flame in a cylindrical dump combustor. The degeneracy of the simple configuration in this study lends itself for a detailed study of inherent mechanisms of a self-excited thermoacoustic instability in isolation from system coupling effects, enabling detailed numerical simulations to be carried out to supplement experimental findings. Tests were done at a nominal pressure of 8 bar and inlet temperature around 450 ˚C. Self-excited large eddy simulations were also carried out in OpenFOAM, using a b-Ξ flame-wrinkling model to model the combustion process. Eigenfrequency analysis in COMSOL …
Compressible Turbulent Reactions For Hypersonic Propulsion Applications, Jonathan Sosa
Compressible Turbulent Reactions For Hypersonic Propulsion Applications, Jonathan Sosa
Electronic Theses and Dissertations
This work presents the first measurement of turbulent burning velocities of a highly-turbulent compressible standing flame induced by shock-driven turbulence in a Turbulent Shock Tube. High-speed schlieren, chemiluminescence, PIV, and dynamic pressure measurements are made to quantify flame-turbulence interaction for high levels of turbulence at elevated temperatures and pressure. Distributions of turbulent velocities, vorticity and turbulent strain are provided for regions ahead and behind the standing flame. The turbulent flame speed is directly measured for the high-Mach standing turbulent flame. From measurements of the flame turbulent speed and turbulent Mach number, transition into a non-linear compressibility regime at turbulent Mach …
Frequency-Reconfigurable Microstrip Patch And Cavity-Backed Slot Espars, Wei Ouyang
Frequency-Reconfigurable Microstrip Patch And Cavity-Backed Slot Espars, Wei Ouyang
Electronic Theses and Dissertations
Wireless communication systems have rapidly evolved over the past decade which has led to an explosion of mobile data traffic. Since more and more wireless devices and sensors are being connected, the transition from the current 4G/LTE mobile network to 5G is expected to happen within the next decade. In order to improve signal-to-noise ratio (SNR), system capacity, and link budget, beam steerable antenna arrays are desirable due to their advantage in spatial selectivity and high directivity. Electronically steerable parasitic array radiator (ESPAR) that can achieve low-cost continuously beamsteering using varactor diodes have attracted a lot of attention. This dissertation …
A Smart Uav Platform For Railroad Inspection, Ryan Debevec
A Smart Uav Platform For Railroad Inspection, Ryan Debevec
Electronic Theses and Dissertations
Using quadcopters for analysis of an environment has been an intriguing subject of study recently. The purpose of this work is to develop a fully autonomous UAV platform for Railroad inspection The dynamics of the quadrotor is derived using Euler's and Newton's laws and then linearized around the hover position. A PID controller is designed to control the states of the quadrotor in a manner to effectively follow a vision-based path, using the down facing camera on a Parrot Mambo quadrotor. Using computer vision the distance from the position of the quadrotor to the position of the center of the …
Cavitation And Heat Transfer Over Micro Pin Fins, Arash Nayebzadeh
Cavitation And Heat Transfer Over Micro Pin Fins, Arash Nayebzadeh
Electronic Theses and Dissertations
With the dramatic increase in the usage of compact yet more powerful electronic devices, advanced cooling technologies are required to maintain delicate electronic components below their maximum allowable temperatures and prevent them from failure. One solution is to use innovative pin finned heat sinks. This research is centered on the evaluation of hydrodynamic cavitation properties downstream pin fins and extended toward single-phase heat transfer enhancement of array of pin fins in microchannel. In this work, transparent micro-devices capable of local wall temperature measurements were micro fabricated and tested. Various experimental methods, numerical modeling and advanced data processing techniques are presented. …