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Full-Text Articles in Engineering

Application Aware For Byzantine Fault Tolerance, Hua Chai Jan 2014

Application Aware For Byzantine Fault Tolerance, Hua Chai

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Driven by the need for higher reliability of many distributed systems, various replication-based fault tolerance technologies have been widely studied. A prominent technology is Byzantine fault tolerance (BFT). BFT can help achieve high availability and trustworthiness by ensuring replica consistency despite the presence of hardware failures and malicious faults on a small portion of the replicas. However, most state-of-the-art BFT algorithms are designed for generic stateful applications that require the total ordering of all incoming requests and the sequential execution of such requests. In this dissertation research, we recognize that a straightforward application of existing BFT algorithms is often inappropriate …


Biogeography-Based Optimization For Combinatorial Problems And Complex Systems, Dawei Du Jan 2014

Biogeography-Based Optimization For Combinatorial Problems And Complex Systems, Dawei Du

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Biogeography-based optimization (BBO) is a heuristic evolutionary algorithm that has shown good performance on many problems. In this dissertation, three problem1s 1 are researched for BBO: convergence speed and optimal solution convergence of BBO,1 1BBO application to combinatorial problems, and BBO application to complex systems. The first problem is to analyze BBO from two perspectives: how the components of BBO affect its convergence speed and the reason that BBO converges to the optimal solution. For the first perspective, which is convergence speed, we analyze the two essential components of BBO -- population construction and information sharing. For the second perspective, …


Oppositional Biogeography-Based Optimization, Mehmet Ergezer Jan 2014

Oppositional Biogeography-Based Optimization, Mehmet Ergezer

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This dissertation outlines a novel variation of biogeography-based optimization (BBO), which is an evolutionary algorithm (EA) developed for global optimization. The new algorithm employs opposition-based learning (OBL) alongside BBO migration to create oppositional BBO (OB BO). Additionally, a new opposition method named quasi-reflection is introduced. Quasireflection is based on opposite numbers theory and we mathematically prove that it has the highest expected probability of being closer to the problem solution among all OBL methods that we explore. Performance of quasi-opposition is validated by mathematical analysis for a single-dimensional problem and by simulations for higher dimensions. Experiments are performed on benchmark …


Byzantine Fault Tolerance For Distributed Systems, Honglei Zhang Jan 2014

Byzantine Fault Tolerance For Distributed Systems, Honglei Zhang

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The growing reliance on online services imposes a high dependability requirement on the computer systems that provide these services. Byzantine fault tolerance (BFT) is a promising technology to solidify such systems for the much needed high dependability. BFT employs redundant copies of the servers and ensures that a replicated system continues providing correct services despite the attacks on a small portion of the system. In this dissertation research, I developed novel algorithms and mechanisms to control various types of application nondeterminism and to ensure the long-term reliability of BFT systems via a migration-based proactive recovery scheme. I also investigated a …


Biogeography-Based Optimization Of A Variable Camshaft Timing System, George L. Thomas Jan 2014

Biogeography-Based Optimization Of A Variable Camshaft Timing System, George L. Thomas

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Automotive system optimization problems are difficult to solve with traditional optimization techniques because the optimization problems are complex, and the simulations are computationally expensive. These two characteristics motivate the use of evolutionary algorithms and meta-modeling techniques respectively. In this work, we apply biogeography-based optimization (BBO) to radial basis function (RBF)-based lookup table controls of a variable camshaft timing system for fuel economy optimization. Also, we reduce computational search effort by finding an effective parameterization of the problem, optimizing the parameters of the BBO algorithm for the problem, and estimating the cost of a portion of the candidate solutions in BBO …


Laboratory Measurements Of The Deep Venusian Atmosphere, Timothy J. Palinski Jan 2014

Laboratory Measurements Of The Deep Venusian Atmosphere, Timothy J. Palinski

ETD Archive

NASA Glenn Research Center has designed and built a test chamber that can recreate the hot, dense atmospheric conditions of the deep Venusian atmosphere, where pressures range as high as 92 atmospheres and temperatures as high as 740 K. The majority of this thesis lies in experimentally measuring and quantifying the infrared absorption of CO2 at Venus-like conditions in this laboratory setting. In particular, we describe the challenges and solutions involved in achieving repeatable laboratory test conditions, as well as the iterative process of modifying/optimizing our experimental test setup, including proposed future improvements. We discuss our measured CO2 absorption spectra, …


Tcp Ftat (Fast Transmit Adaptive Transmission): A New End-To-End Congestion Control Algorithm, Mohammed Ahmed Melegy Mohammed Afifi Jan 2014

Tcp Ftat (Fast Transmit Adaptive Transmission): A New End-To-End Congestion Control Algorithm, Mohammed Ahmed Melegy Mohammed Afifi

ETD Archive

Congestion Control in TCP is the algorithm that controls allocation of network resources for a number of competing users sharing a network. The nature of computer networks, which can be described from the TCP protocol perspective as unknown resources for unknown traffic of users, means that the functionality of the congestion control algorithm in TCP requires explicit feedback from the network on which it operates. Unfortunately this is not the way it works with TCP, as one of the fundamental principles of the TCP protocol is to be end-to-end, in order to be able to operate on any network, which …


Electrostatically Controlled Enzymatic Reaction, Metabolic Processes And Microbial Generation Of Electric Power, Yang Song Jan 2014

Electrostatically Controlled Enzymatic Reaction, Metabolic Processes And Microbial Generation Of Electric Power, Yang Song

ETD Archive

This thesis shows that electric fields can be used to control electron transport in biological systems and improve the performance of biological devices using an external gating voltage. It has recently been shown that an ultrasensitive detection method based on electric field effect can be used to control the kinetics of enzymatic conversion of glucose. The first part of the thesis is a mechanistic study of the enzyme catalyzed conversion of glucose to gluconolactone using the field effect enzymatic detection (FEED) technique. Use of a voltage controlled enzymatic system decreased electrons tunnel between electrode and active center of glucose oxidase …


Program Verification Of Freertos Using Microsoft Dafny, Matthew J. Matias Jan 2014

Program Verification Of Freertos Using Microsoft Dafny, Matthew J. Matias

ETD Archive

FreeRTOS is a popular real-time and embedded operating system. Real-time software requires code reviews, software tests, and other various quality assurance activities to ensure minimal defects. This free and open-source operating system has claims of robustness and quality [26]. Real-time and embedded software is found commonly in systems directly impacting human life and require a low defect rate. In such critical software, traditional quality assurance may not suce in minimizing software defects. When traditional software quality assurance is not enough for defect removal, software engineering formal methods may help minimize defects. A formal method such as program verication is useful …


Bio-Inspired Optimization Of Ultra-Wideband Patch Antennas Using Graphics Processing Unit Acceleration, Brian Vyhnalek Jan 2014

Bio-Inspired Optimization Of Ultra-Wideband Patch Antennas Using Graphics Processing Unit Acceleration, Brian Vyhnalek

ETD Archive

Ultra-wideband (UWB) wireless systems have recently gained considerable attention as effective communications platforms with the properties of low power and high data rates. Applications of UWB such as wireless USB put size constraints on the antenna, however, which can be very dicult to meet using typical narrow band antenna designs. The aim of this thesis is to show how bio-inspired evolutionary optimization algorithms, in particular genetic algorithm (GA), particle swarm optimization (PSO) and biogeography-based optimization (BBO) can produce novel UWB planar patch antenna designs that meet a size constraint of a 10 mm 10 mm patch. Each potential antenna design …