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Articles 1 - 30 of 40
Full-Text Articles in Engineering
A Systems Approach To Design And Plan Sustainable Antifragile Infrastructure Based On Aggregate Footprint And Satisfaction, Farboud Khatami
A Systems Approach To Design And Plan Sustainable Antifragile Infrastructure Based On Aggregate Footprint And Satisfaction, Farboud Khatami
Theses and Dissertations
The concepts of robustness and sustainability in planning and design of water and energy infrastructures have been extensively explored in previous research, primarily focusing on system reliability, environmental considerations, and economic aspects. This study aims to broaden the understanding of these concepts by offering comprehensive frameworks that capture the essence of robustness and sustainability at two distinct levels.
The first level of investigation focuses on the performance of infrastructure networks during natural disasters. Traditionally, this has been addressed using reliability, resilience, and vulnerability metrics. However, these methods rely on static, deterministic, and non-stationary data, which is inadequate when dealing with …
Effect Of Stimulus Waveform On Transcranial Magnetic Stimulation Metrics In Proximal And Distal Arm Muscles, Christopher Lynch
Effect Of Stimulus Waveform On Transcranial Magnetic Stimulation Metrics In Proximal And Distal Arm Muscles, Christopher Lynch
Theses and Dissertations
Objectives: The purpose of this study was to determine the effect of common transcranial magnetic stimulation (TMS) waveforms (monophasic and biphasic) on resting motor threshold (RMT), active motor threshold (AMT), and motor evoked potential (MEP) amplitudes in the biceps and first dorsal interosseous (FDI) because waveforms may affect motor targets differently. Additionally, we determined the test-retest reliability of TMS metrics for each stimulation type and muscle.
Methods: Ten individuals participated in two sessions of single-pulse TMS delivered to the motor cortex perpendicular to the central sulcus. MEPs were normalized to the maximum EMG signal during contraction and were recorded at …
Root Cause Analysis And Classification Of Single Point Failures In Designs Applying Triple Modular Redundancy In Sram Fpgas, James D. Swift
Root Cause Analysis And Classification Of Single Point Failures In Designs Applying Triple Modular Redundancy In Sram Fpgas, James D. Swift
Theses and Dissertations
Radiation effects encountered in space or aviation environments can affect the configuration bits in Field Programmable Gate Arrays (FPGA) causing errors in FPGA output. One method of increasing FPGA reliability in radiation environments includes adding redundant logic to mask errors and allow time for repair. Despite the redundancy added with triple modular redundancy (TMR) and configuration scrubbing there exist some configuration bits that individually affect multiple TMR domains causing errors in FPGA output. A new tool called DeBit is introduced that identifies hardware resources associated with a single bit failure. This tool identifies a novel failure mode involving global routing …
Evaluating And Improving The Seu Reliability Of Artificial Neural Networks Implemented In Sram-Based Fpgas With Tmr, Brittany Michelle Wilson
Evaluating And Improving The Seu Reliability Of Artificial Neural Networks Implemented In Sram-Based Fpgas With Tmr, Brittany Michelle Wilson
Theses and Dissertations
Artificial neural networks (ANNs) are used in many types of computing applications. Traditionally, ANNs have been implemented in software, executing on CPUs and even GPUs, which capitalize on the parallelizable nature of ANNs. More recently, FPGAs have become a target platform for ANN implementations due to their relatively low cost, low power, and flexibility. Some safety-critical applications could benefit from ANNs, but these applications require a certain level of reliability. SRAM-based FPGAs are sensitive to single-event upsets (SEUs), which can lead to faults and errors in execution. However there are techniques that can mask such SEUs and thereby improve the …
Impacts Of Changing The Transit Signal Priority Requesting Threshold On Bus Performance And General Traffic: A Sensitivity Analysis, Michael Harmon Sheffield
Impacts Of Changing The Transit Signal Priority Requesting Threshold On Bus Performance And General Traffic: A Sensitivity Analysis, Michael Harmon Sheffield
Theses and Dissertations
A sensitivity analysis was performed on the transit signal priority (TSP) requesting threshold to evaluate its impact on bus performance and general traffic. Two distinct bus routes were evaluated to determine the optimal requesting threshold that would balance the positive impacts on bus performance with the negative impacts on general traffic. Route 217, a conventional bus route, and the Utah Valley Express (UVX), a bus rapid transit line, utilize a dedicated short-range communication (DSRC)-based TSP system as part of their normal, day-to-day operations. Using field-generated data exclusively, bus performance and general traffic were evaluated over a 7-month period from February …
Application Of Survival Analysis Techniques To Probabilistic Assessment Of Fatigue In Steel Bridges, Azam Nabizadehdarabi
Application Of Survival Analysis Techniques To Probabilistic Assessment Of Fatigue In Steel Bridges, Azam Nabizadehdarabi
Theses and Dissertations
The fatigue of engineering materials under repetitive loading is a significant issue affecting the design and durability of components and systems in a variety of engineering-related applications including civil, mechanical, aerospace, automotive, and electronics. Many factors can affect the service life of a component or system under repetitive loading, such as the type of structure, loading, connection details, stress state, peak stress or stress range, surface condition, temperature, and environmental exposure. Currently, there is no comprehensive probabilistic approach that can systematically address all the factors that contribute to fatigue on a single mathematical platform. However, advanced analysis techniques developed for …
Targeted Germanium Ion Irradiation Of Aluminum Gallium Nitride/Gallium Nitride High Electron Mobility Transistors, Melanie E. Mace
Targeted Germanium Ion Irradiation Of Aluminum Gallium Nitride/Gallium Nitride High Electron Mobility Transistors, Melanie E. Mace
Theses and Dissertations
Microscale beams of germanium ions were used to target different locations of aluminum galliumnitride/gallium nitride (AlGaN/GaN) high electron mobility transistors (HEMTs) to determine location dependent radiation effects. 1.7 MeV Ge ions were targeted at the gap between the gate and the drain to observe displacement damage effects while 47 MeV Ge ions were targeted at the gate to observe ionization damage effects. Electrical data was taken pre, during, and post irradiation. To separate transient from permanent degradation, the devices were characterized after a room temperature anneal for at least 30 days. Optical images were also analyzed pre and post irradiation. …
Improving The Single Event Effect Response Of Triple Modular Redundancy On Sram Fpgas Through Placement And Routing, Matthew Joel Cannon
Improving The Single Event Effect Response Of Triple Modular Redundancy On Sram Fpgas Through Placement And Routing, Matthew Joel Cannon
Theses and Dissertations
Triple modular redundancy (TMR) with repair is commonly used to improve the reliability of systems. TMR is often employed for circuits implemented on field programmable gate arrays (FPGAs) to mitigate the radiation effects of single event upsets (SEUs). This has proven to be an effective technique by improving a circuit's sensitive cross-section by up to 100x. However, testing has shown that the improvement offered by TMR is limited by upsets in single configuration bits that cause TMR to fail.This work proposes a variety of mitigation techniques that improve the effectiveness of TMR on FPGAs. These mitigation techniques can alter the …
Product Development Process For Small Unmanned Aerial Systems, Jonathan D. Poole
Product Development Process For Small Unmanned Aerial Systems, Jonathan D. Poole
Theses and Dissertations
The DoD has recognized the need for persistent Intelligence, Surveillance and Reconnaissance (ISR) over the last two decades. Recent developments with commercial drones have changed the market structure; there is now a thriving and extensive market base for drone based remote sensing. This research provides system engineering methods to support the DoD use of this burgeoning market to meet operational ISR needs. The three contributions of this research are: a process to support Small Unmanned Aerial Systems (SUAS) design, tools to support the design process, and tools to support risk assessment and reduction for both design and operations. The process …
Optimization For Integration Of Plug-In Hybrid Electric Vehicles Into Distribution Grid, Shuaiyu Bu
Optimization For Integration Of Plug-In Hybrid Electric Vehicles Into Distribution Grid, Shuaiyu Bu
Theses and Dissertations
Plug-in hybrid electric vehicles (PHEVs) feature combined electric and gasoline powertrains with internal combustion engine and electric motors powered by battery packs. The battery packs of PHEVs are mostly charged during off-peaks hours at lower prices and meanwhile absorb the excess power from the grid. Similarly, the power stored in the batteries can also flow back to the electric grid in response to ease the peak load demands.
With the increasing penetration and integration of PHEVs, the reliability of PHEVs is essential to overall power system reliability since the charging mechanisms of PHEVs can influence the reliability of power system. …
Assessing The Reliability Of The B-1b Lancer Using Survival Analysis, Francisco J. Rodriguez
Assessing The Reliability Of The B-1b Lancer Using Survival Analysis, Francisco J. Rodriguez
Theses and Dissertations
During the 2017 posture statement to the US Senate Armed Services Committee, the Secretary of the Air Force and Chief of Staff of the Air Force stated the Air Force suffers from shrinking aircraft inventory, aging aircraft fleets, and flying beyond the expected service life. These trends are not an exception to the B-1B Lancer, which has been in service since 1986. Recently, the B-1B Lancer has maintained the lowest mission capable (MC) rates of 47.7 percent. The purpose of this research is to explore the failure rates of the B-1B Lancer using survival analysis that investigates the failure behavior …
Hvdc Transmission System Reliability Evaluation Based On Condition-Dependent Failure Models Of Converters And Transformers, Zibo Wang
Theses and Dissertations
Wind energy, especially offshore wind energy, is the focus of policy for countries that want to make significant use of renewable energy. With the development of semiconductor technology, high voltage direct current (HVDC) technology is being widely used for the transmission of wind power from offshore windfarms to onshore power grids. The application of HVDC technology can benefit the power system in many ways, such as operation security, reliability performance and economy. With the increasing number of applications of HVDC, the reliability performance of HVDC plays an important role in the overall power system reliability. Although the reliability of HVDC …
Large Scale Integration Of Electric Vehicles Into The Power Grid And Its Potential Effects On Power System Reliability, Mingzhi Zhang
Large Scale Integration Of Electric Vehicles Into The Power Grid And Its Potential Effects On Power System Reliability, Mingzhi Zhang
Theses and Dissertations
In this thesis, the potential effects of large scale integration of electric vehicles into the power grid are discussed in both the beneficial and detrimental aspects. The literature review gives a comprehensive introduction about the existing smart charging algorithms. According to the system structure and market mechanism, the smart charging algorithms can be divided into centralized and distributed method. With the knowledge of driving patterns and charging characteristics of electric vehicles, both the centralized and decentralized smart charging algorithms are studied in this research.
Based on the smart charging pricing and sequential price update mechanism, a multi-agent based distributed smart …
Using On-Chip Error Detection To Estimate Fpga Design Sensitivity To Configuration Upsets, Andrew Mark Keller
Using On-Chip Error Detection To Estimate Fpga Design Sensitivity To Configuration Upsets, Andrew Mark Keller
Theses and Dissertations
SRAM-based FPGAs provide valuable computation resources and reconfigurability; however, ionizing radiation can cause designs operating on these devices to fail. The sensitivity of an FPGA design to configuration upsets, or its SEU sensitivity, is an indication of a design's failure rate. SEU mitigation techniques can reduce the SEU sensitivity of FPGA designs in harsh radiation environments. The reliability benefits of these techniques must be determined before they can be used in mission-critical applications and can be determined by comparing the SEU sensitivity of an FPGA design with and without these techniques applied to it. Many approaches can be taken to …
High-Speed Programmable Fpga Configuration Memory Access Using Jtag, Ammon Bradley Gruwell
High-Speed Programmable Fpga Configuration Memory Access Using Jtag, Ammon Bradley Gruwell
Theses and Dissertations
Over the past couple of decades Field Programmable Gate Arrays (FPGAs) have become increasingly useful in a variety of domains. This is due to their low cost and flexibility compared to custom ASICs. This increasing interest in FPGAs has driven the need for tools that both qualify and improve the reliability of FPGAs for applications where the reconfigurability of FPGAs makes them vulnerable to radiation upsets such as in aerospace environments. Such tools ideally work with a wide variety of devices, are highly programmable but simple to use, and perform tasks at relatively high speeds. Of the various FPGA configuration …
Reliability And Cost Impacts For Attritable Systems, Bryan R. Bentz
Reliability And Cost Impacts For Attritable Systems, Bryan R. Bentz
Theses and Dissertations
Attritable systems trade system attributes like reliability and reparability to achieve lower acquisition cost and decrease cost risk. Ultimately, it is hoped that by trading these attributes the amount of systems able to be acquired will be increased. However, the effect of trading these attributes on system-level reliability and cost risk is difficult to express complicated reparable systems like an air vehicle. Failure-time and cost data from a baseline limited-life air vehicle is analyzed for this reliability and reparability trade study. The appropriateness of various reliability and cost estimation techniques are examined for these data. This research employs the cumulative …
Towards Design And Analysis For High-Performance And Reliable Ssds, Qianbin Xia
Towards Design And Analysis For High-Performance And Reliable Ssds, Qianbin Xia
Theses and Dissertations
NAND Flash-based Solid State Disks have many attractive technical merits, such as low power consumption, light weight, shock resistance, sustainability of hotter operation regimes, and extraordinarily high performance for random read access, which makes SSDs immensely popular and be widely employed in different types of environments including portable devices, personal computers, large data centers, and distributed data systems.
However, current SSDs still suffer from several critical inherent limitations, such as the inability of in-place-update, asymmetric read and write performance, slow garbage collection processes, limited endurance, and degraded write performance with the adoption of MLC and TLC techniques. To alleviate these …
A Secure, Reliable And Performance-Enhancing Storage Architecture Integrating Local And Cloud-Based Storage, Christopher Glenn Hansen
A Secure, Reliable And Performance-Enhancing Storage Architecture Integrating Local And Cloud-Based Storage, Christopher Glenn Hansen
Theses and Dissertations
The constant evolution of new varieties of computing systems - cloud computing, mobile devices, and Internet of Things, to name a few - have necessitated a growing need for highly reliable, available, secure, and high-performing storage systems. While CPU performance has typically scaled with Moore's Law, data storage is much less consistent in how quickly performance increases over time. One method of improving storage performance is through the use of special storage architectures. Such architectures often include redundant arrays of independent disks (RAID). RAID provides a meaningful way to increase storage performance on a variety of levels, some higher-performing than …
Duplicate With Choose: Using Statistics For Fault Mitigation, Jon-Paul Anderson
Duplicate With Choose: Using Statistics For Fault Mitigation, Jon-Paul Anderson
Theses and Dissertations
This dissertation presents a novel technique called duplicate with choose (DWCh) which is a modification of the fault detection technique duplicate with compare (DWC). DWCh adds a smart decider block to DWC that monitors the duplicated circuits and decides which circuit is fault free when a fault occurs. If chosen correctly, DWCh is able to mask faults at a lower cost than conventional techniques like TMR.This dissertation derives reliability expressions for DWCh showing that under ideal conditions its reliability exceeds the most commonly used fault masking technique for spacecraft, triple modular redundancy. For non-ideal conditions, DWCh provides a lower cost …
Measuring Soft Error Sensitivity Of Fpga Soft Processor Designs Using Fault Injection, Nathan Arthur Harward
Measuring Soft Error Sensitivity Of Fpga Soft Processor Designs Using Fault Injection, Nathan Arthur Harward
Theses and Dissertations
Increasingly, soft processors are being considered for use within FPGA-based reliable computing systems. In an environment in which radiation is a concern, such as space, the logic and routing (configuration memory) of soft processors are sensitive to radiation effects, including single event upsets (SEUs). Thus, effective tools are needed to evaluate and estimate how sensitive the configuration memories of soft processors are in high-radiation environments. A high-speed FPGA fault injection system and methodology were created using the Xilinx Radiation Test Consortium's (XRTC's) Virtex-5 radiation test hardware to conduct exhaustive tests of the SEU sensitivity of a design within an FPGA's …
Exploration Of Erasure-Coded Storage Systems For High Performance, Reliability, And Inter-Operability, Pradeep Subedi
Exploration Of Erasure-Coded Storage Systems For High Performance, Reliability, And Inter-Operability, Pradeep Subedi
Theses and Dissertations
With the unprecedented growth of data and the use of low commodity drives in local disk-based storage systems and remote cloud-based servers has increased the risk of data loss and an overall increase in the user perceived system latency. To guarantee high reliability, replication has been the most popular choice for decades, because of simplicity in data management. With the high volume of data being generated every day, the storage cost of replication is very high and is no longer a viable approach.
Erasure coding is another approach of adding redundancy in storage systems, which provides high reliability at a …
Configuration Scrubbing Architectures For High-Reliability Fpga Systems, Aaron Gerald Stoddard
Configuration Scrubbing Architectures For High-Reliability Fpga Systems, Aaron Gerald Stoddard
Theses and Dissertations
Field Programmable Gate Arrays (FPGAs) are being used more frequently in space applications because of their reconfigurability and intensive processing capabilities. FPGAs in environments like space are susceptible to ionizing radiation which can cause Single Event Upsets (SEUs) in the FPGA's configuration memory. These upsets may cause the programmed user design on the FPGA to deviate from its normal behavior. Space missions cannot afford to allow important data processing applications to become corrupted due to these radiation upsets.Configuration scrubbing is an upset mitigation technique that detects and corrects upsets in an FPGA's configuration memory. Configuration scrubbing periodically monitors an FPGA's …
Reliability Of Bridge Superstructures In Wisconsin, Azam Nabizadehdarabi
Reliability Of Bridge Superstructures In Wisconsin, Azam Nabizadehdarabi
Theses and Dissertations
ABSTRACT
RELIABILITY OF BRIDGE SUPERSTRUCTURES IN WISCONSIN
by
Azam Nabizadehdarabi
The University of Wisconsin-Milwaukee, 2015
Under the Supervision of Professor Habib Tabatabai
Bridge reliability analyses form the basis of modern bridge design provisions. Such analyses are also used to evaluate bridge condition and assess future maintenance needs. The majority of these reliability assessments are based on evaluating risks associated with the various load effects exceeding their corresponding resistance. However, bridge components such as decks and superstructures typically do not reach the end of their service lives by exceeding the strength limit states (structural failure). Survival analyses, which are commonly used …
Temperature And Stress Effect Modeling In Fatigue Of H13 Tool Steel At Elevated Temperatures With Applications In Friction Stir Welding, Bradley Valiant Jones
Temperature And Stress Effect Modeling In Fatigue Of H13 Tool Steel At Elevated Temperatures With Applications In Friction Stir Welding, Bradley Valiant Jones
Theses and Dissertations
Tooling reliability is critical to welding success in friction stir welding, but tooling fatigue is not well understood because it occurs in conditions that are often unique to friction stir welding. A fatigue study was conducted on a commonly used tooling material, H13 tool steel, using constant stress loading at temperatures between 300°C and 600°C, and the results are presented. A model is proposed accounting for temperature and stress effects on fatigue life, utilizing a two-region Arrhenius temperature model. A transition in temperature effect on fatigue life is identified. Implications of the temperature effect for friction stir welding suggest that …
Single Event Mitigation For Aurora Protocol Based Mgt Fpga Designs In Space Environments, Alexander Stanley Harding
Single Event Mitigation For Aurora Protocol Based Mgt Fpga Designs In Space Environments, Alexander Stanley Harding
Theses and Dissertations
This work has extended an existing Aurora protocol for high-speed serial I/O between FPGAs to provide greater fault recovery in the presence of high-energy radiation. To improve on the Aurora protocol, additional resets that affect larger portions of the system were used. Detection for additional error modes that occurred but were not detected by the Aurora protocol was designed. Radiation testing was performed on the Aurora protocol with the additional mitigation hardware. The test gathered large amounts of data on the various error modes of the Aurora protocol and how the additional mitigation circuitry affected the system. The test results …
Development Of A Chloride Concentration Sampling Protocol For Concrete Bridge Decks, Sharlan Renae Montgomery
Development Of A Chloride Concentration Sampling Protocol For Concrete Bridge Decks, Sharlan Renae Montgomery
Theses and Dissertations
As the primary cause of concrete bridge deck deterioration in the United States is corrosion of the steel reinforcement as a result of the application of chloride-based deicing salts, chloride concentration testing is among the most common techniques for evaluating the condition of a concrete bridge deck. The objectives of this research were to 1) compare concrete drilling and powder collection techniques to develop a sampling protocol for accurately measuring chloride concentrations and 2) determine the number of chloride concentration test locations necessary for adequately characterizing the chloride concentration of a given bridge deck. Laboratory experiments on concrete drilling and …
Electron – Phonon Interaction In Multiple Channel Gan Based Hfets: Heat Management Optimization, Romualdo A. Ferreyra
Electron – Phonon Interaction In Multiple Channel Gan Based Hfets: Heat Management Optimization, Romualdo A. Ferreyra
Theses and Dissertations
New power applications for managing increasingly higher power levels require that more heat be removed from the power transistor channel. Conventional treatments for heat dissipation do not take into account the conversion of excess electron energy into longitudinal optical (LO) phonons, whose associated heat is stored in the channel unless such LO phonons decay into longitudinal acoustic (LA) phonons via a Ridley path. A two dimensional electron gas (2DEG) density of ~5×1012cm-2 in the channel results in a strong plasmon–LO phonon coupling (resonance) and a minimum LO phonon lifetime is experimentally observed, implying fast heat removal from …
Dc, Microwave, And Noise Properties Of Gan Based Heterojunction Field Effect Transistors And Their Reliability Issues, Congyong Zhu
Dc, Microwave, And Noise Properties Of Gan Based Heterojunction Field Effect Transistors And Their Reliability Issues, Congyong Zhu
Theses and Dissertations
AlGaN/GaN and InAlN/GaN-based heterojunction field effect transistors (HFETs) have demonstrated great high power and high frequency performance. Although AlGaN/GaN HFETs are commercially available, there still remain issues regarding long-term reliability, particularly degradation and ultimately device failure due to the gate-drain region where the electric field peaks. One of the proposed degradation mechanisms is the inverse-piezoelectric effect that results from the vertical electric field and increases the tensile strain. Other proposed mechanisms include hot-electron-induced trap generation, impurity diffusion, surface oxidation, and hot-electron/phonon effects. To investigate the degradation mechanism and its impact on DC, microwave, and noise performance, comprehensive stress experiments were …
Performance And Reliability Study And Exploration Of Nand Flash-Based Solid State Drives, Guanying Wu
Performance And Reliability Study And Exploration Of Nand Flash-Based Solid State Drives, Guanying Wu
Theses and Dissertations
The research that stems from my doctoral dissertation focuses on addressing essential challenges in developing techniques that utilize solid-state memory technologies (with emphasis on NAND flash memory) from device, circuit, architecture, and system perspectives in order to exploit their true potential for improving I/O performance in high-performance computing systems. These challenges include not only the performance quirks arising from the physical nature of NAND flash memory, e.g., the inability to modify data in-place, read/write performance asymmetry, and slow and constrained erase functionality, but also the reliability drawbacks that limits solid state drives (SSDs) from widely deployed. To address these challenges, …
Reliability Techniques For Data Communication And Storage In Fpga-Based Circuits, Yubo Li
Reliability Techniques For Data Communication And Storage In Fpga-Based Circuits, Yubo Li
Theses and Dissertations
This dissertation studies the effects of radiation-induced single-event upsets (SEUs) on field-programmable gate array(FPGA)-based circuits. It analyzes and quantifies a special case in data communication, that is, the synchronization issue of signals when they are sent across clock domains in triple modular redundancy (TMR) circuits with the presence of SEUs. After demonstrating that synchronizing errors cannot be eliminated in such case, this dissertation continues to present novel synchronizer designs that can guarantee reliable synchronization of triplicated signals. Fault injection tests then show that the proposed synchronizers provide between 6 and 10 orders of magnitude longer mean time to failure (MTTF) …