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Articles 991 - 1020 of 4566

Full-Text Articles in Engineering

The Effect Of Martensite-Fractions Assumptions In Shape Memory Alloy Springs, Christian Vazquez Jan 2018

The Effect Of Martensite-Fractions Assumptions In Shape Memory Alloy Springs, Christian Vazquez

Electronic Theses and Dissertations

This research addresses various models of a spring-mass system that uses a spring made of a shape memory alloy (SMA). The system model describes the martensite fractions, which are values that describe an SMA's crystalline phases, via differential equations. The model admits and this thesis contrasts two commonly used but distinct assumptions: a homogeneous case where the martensite fractions are constant throughout the spring's cross section, and a bilinear case where the evolution of the martensite fractions only occurs beyond some critical radius. While previous literature has developed a model of the system dynamics under the homogeneous assumption using the …

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Flow Control Of Tandem Cylinders Using Plasma Actuators, Jonah Larsen Jan 2018

Flow Control Of Tandem Cylinders Using Plasma Actuators, Jonah Larsen

Honors Undergraduate Theses

The flow over a set of tandem cylinders at a moderate Reynolds numbers (Re), and with different separation lengths has been studied. Two dimensional (2D) and three-dimensional (3D) plasma actuators were used to control the flow over the leading cylinder to change the vortex shedding, and subsequently the flow on the second cylinder. The 3D plasma actuator was segmented along the length of the cylinder with a spacing of λ = 4 while the 2D actuator simply ran straight down the span of the cylinder. Particle image velocimetry (PIV) measurements were used to investigate the flow along the central plane …

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Mechanical Properties Of The Skeleton Of Acropora Cervicornis, Bridget Masa Jan 2018

Mechanical Properties Of The Skeleton Of Acropora Cervicornis, Bridget Masa

Honors Undergraduate Theses

This research explores the instantaneous mechanical behavior of the skeleton of the critically endangered staghorn coral Acropora cervicornis. Both bleached and sanded skeletons were used in this experiment. The Raman spectroscopy test showed that there was no significant change in the Raman shift between the three branches tested. The shifts were nearly identical to Raman shifts of calcium carbonate. Vickers hardness test found that 1 Bleached had the average hardness of 3.44 GPa with a standard deviation of 0.12 GPa. The sanded sample also had a similar value of 3.54 GPa with a standard deviation of 0.13 GPa. Samples from …

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Surfactant Driven Assembly Of Freeze-Casted, Polymer-Derived Ceramic Nanoparticles On Grapehene Oxide Sheets For Lithium-Ion Battery Anodes, Ali Zein Khater Jan 2018

Surfactant Driven Assembly Of Freeze-Casted, Polymer-Derived Ceramic Nanoparticles On Grapehene Oxide Sheets For Lithium-Ion Battery Anodes, Ali Zein Khater

Honors Undergraduate Theses

Traditional Lithium-Ion Batteries (LIBs) are a reliable and cost-efficient choice for energy storage. LIBs offer high energy density and low self-discharge. Recent developments in electric-based technologies push for replacing historically used Lead-Acid batteries with LIBs. However, LIBs do not yet meet the demands of modern technology. Silicon and graphene oxide (GO) have been identified as promising replacements to improve anode materials. Graphene oxide has a unique sheet-like structure that provides a mechanically stable, light weight material for LIB anodes. Due to its structure, reduced graphene oxide (rGO) is efficiently conductive and resistive to environmental changes. On the other hand, silicon-based …

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A Machine Learning Approach To Assess The Separation Of Seismocardiographic Signals By Respiration, Brian Solar Jan 2018

A Machine Learning Approach To Assess The Separation Of Seismocardiographic Signals By Respiration, Brian Solar

Honors Undergraduate Theses

The clinical usage of Seismocardiography (SCG) is increasing as it is being shown to be an effective non-invasive measurement for heart monitoring. SCG measures the vibrational activity at the chest surface and applications include non-invasive assessment of myocardial contractility and systolic time intervals. Respiratory activity can also affect the SCG signal by changing the hemodynamic characteristics of cardiac activity and displacing the position of the heart. Other clinically significant information, such as systolic time intervals, can thus manifest themselves differently in an SCG signal during inspiration and expiration. Grouping SCG signals into their respective respiratory cycle can mitigate this issue. …

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Different Facial Recognition Techniques In Transform Domains, Taif Al Obaidi Jan 2018

Different Facial Recognition Techniques In Transform Domains, Taif Al Obaidi

Electronic Theses and Dissertations

The human face is frequently used as the biometric signal presented to a machine for identification purposes. Several challenges are encountered while designing face identification systems. The challenges are either caused by the process of capturing the face image itself, or occur while processing the face poses. Since the face image not only contains the face, this adds to the data dimensionality, and thus degrades the performance of the recognition system. Face Recognition (FR) has been a major signal processing topic of interest in the last few decades. Most common applications of the FR include, forensics, access authorization to facilities, …

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Pressure Image Based Attitude Controller For Small Unmanned Aerial Vehicles, Kenneth Thompson Jan 2018

Pressure Image Based Attitude Controller For Small Unmanned Aerial Vehicles, Kenneth Thompson

Electronic Theses and Dissertations

As technology improves, small unmanned aerial vehicles (SUAV) have been identified for their utility in a variety of applications in which larger unmanned craft may be incapable of accomplishing mission objectives. These aircraft with their small size and long flight durations are ideal for hazardous inspection and long duration surveillance missions. One challenge preventing the widespread adoption of these systems is their instability to abrupt changes in the flow field around them due to wind gusts or flow separation. Currently, traditional rigid body based sensors are implemented in their flight control systems, which are sufficient in higher inertia aircraft for …

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Performance Predication Model For Advance Traffic Control System (Atcs) Using Field Data, Masood Mirza Jan 2018

Performance Predication Model For Advance Traffic Control System (Atcs) Using Field Data, Masood Mirza

Electronic Theses and Dissertations

Reductions in capital expenditure revenues have created greater demands from users for quality service from existing facilities at lower costs forcing agencies to evaluate the performance of projects in more comprehensive and "greener" ways. The use of Adaptive Traffic Controls Systems (ATCS) is a step in the right direction by enabling practitioners and engineers to develop and implement traffic optimization strategies to achieve greater capacity out of the existing systems by optimizing traffic signal based on real time traffic demands and flow pattern. However, the industry is lagging in developing modeling tools for the ATCS which can predict the changes …

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Theoretical Paschen's Law Model For Aerospace Vehicles: Validation Experiment, Jaysen Mulligan Aroche Jan 2018

Theoretical Paschen's Law Model For Aerospace Vehicles: Validation Experiment, Jaysen Mulligan Aroche

Electronic Theses and Dissertations

Aerospace vehicles often experience triboelectric charging while traversing the atmosphere. Triboelectric charging occurs when a material come into frictional contact with a different material. Aerospace vehicles triboelectrically charge due to frictional contact with dust and ice crystals suspended in the atmosphere. Launch vehicles traversing ice clouds in low-pressure atmosphere are especially prone to electrostatic discharge events (i.e. sparks). These conditions are hazardous and affect the vehicle's launch commit criteria. In 2010, engineers from an ARES-I rocket launch reported concerns with triboelectric charging over their self-destruct system antenna. This concern was addressed by putting the antenna through harsh conditions in a …

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Investigation Of Factors Contributing To Fog-Related Single Vehicle Crashes, Jiazheng Zhu Jan 2018

Investigation Of Factors Contributing To Fog-Related Single Vehicle Crashes, Jiazheng Zhu

Electronic Theses and Dissertations

Fog-related crashes continue to be one of the most serious traffic safety problems in Florida. Based on the historical crash data, we found that single-vehicle crashes have the highest severity among all types of crashes under fog conditions. This study first analyzed the contributing factors of the fog-related single-vehicle crashes' (i.e., off road/rollover/other) severity in Florida from 2011 to 2014 using association rules mining. The results show that lane departure distracted driving, wet road surface, and dark without road light are the main contributing factors to severe fog-related single vehicle crashes. Some suggested countermeasures were also provided to reduce the …

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Hierarchical Corridor Safety Analysis Using Multiple Approaches, Saif Alarifi Jan 2018

Hierarchical Corridor Safety Analysis Using Multiple Approaches, Saif Alarifi

Electronic Theses and Dissertations

Traffic crashes are a major cause of concern globally. Extensive efforts from transportation professionals have been made to investigate new methods to identify the contributing factors to crashes at various locations on the road network. Corridors, among other road network's components, play a vital role in moving people and goods between primary zones in different areas, and the safety and operational improvements of them have been the focus of many studies since they carry the most traffic on the road network. Corridors contain mainly intersections and segments, and previous corridor studies have focused on a sole type of road entity. …

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Investigating And Facilitating The Transferability Of Safety Performance Functions, Ahmed Tarek Ahmed Farid Jan 2018

Investigating And Facilitating The Transferability Of Safety Performance Functions, Ahmed Tarek Ahmed Farid

Electronic Theses and Dissertations

Safety performance functions (SPFs) are essential analytical tools in the road safety field. The SPFs are statistical regression models used to predict crash counts by roadway facility type, crash type and severity. The national Highway Safety Manual (HSM) is a generic guidebook used for road safety evaluation and enhancement. In it, default SPFs, developed using negative binomial (NB) regression, are provided for multiple facility types and crash categories. Roadway agencies, whether public or private, may opt to not invest their resources in data collection and processing to develop own localized SPFs. Instead, the agencies may adopt the HSM's. However, the …

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A Modeling Framework Of Brittle And Ductile Fractures Coexistence In Composites, Yangyang Qiao Jan 2018

A Modeling Framework Of Brittle And Ductile Fractures Coexistence In Composites, Yangyang Qiao

Electronic Theses and Dissertations

In order to reduce the weight of automobiles and aircrafts, lightweight materials, such as aluminum alloy, advanced high strength steel, composite materials, are widely used to replace the traditional materials like mild steel. Composite materials are complicated in material mechanical properties and less investigated compared to metallic materials. Engineering composites can be categorized into polymer matrix composites (PMCs), metal matrix composites (MMCs) and ceramic matrix composites (CMCs) according to their matrix materials. A set of mechanical experiments ranging from micro scale (single fiber composite and thin film composite) to macro scale (PMCs and MMCs) were conducted to fully understand the …

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Security Of Autonomous Systems Under Physical Attacks: With Application To Self-Driving Cars, Raj Gautam Dutta Jan 2018

Security Of Autonomous Systems Under Physical Attacks: With Application To Self-Driving Cars, Raj Gautam Dutta

Electronic Theses and Dissertations

The drive to achieve trustworthy autonomous cyber-physical systems (CPS), which can attain goals independently in the presence of significant uncertainties and for long periods of time without any human intervention, has always been enticing. Significant progress has been made in the avenues of both software and hardware for fulfilling these objectives. However, technological challenges still exist and particularly in terms of decision making under uncertainty. In an autonomous system, uncertainties can arise from the operating environment, adversarial attacks, and from within the system. As a result of these concerns, human-beings lack trust in these systems and hesitate to use them …

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A Decision Support Model For Autonomous Trucks Strategies, Ahmad Mohamed Jan 2018

A Decision Support Model For Autonomous Trucks Strategies, Ahmad Mohamed

Electronic Theses and Dissertations

We examined the potential to improve the movement of freight using Truck Platooning Lane strategies on limited access highways in the State of Florida. In the First part of this research, we investigated the potential benefits from dedicating one lane from existing lanes for autonomous trucks only. In this regard, a general framework tool was developed to evaluate and compare different measurements (e.g., travel tim and emissions) to better assist decision makers to determine the most effective freight transportation strategy. Additionally, the travel time, level of service and emissions on Florida Strategic Intermodal System (SIS) were systematically analyzed using a …

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Excellent Surface Passivation For High Efficiency C_Si Solar Cells, Sara Bakhshi Jan 2018

Excellent Surface Passivation For High Efficiency C_Si Solar Cells, Sara Bakhshi

Electronic Theses and Dissertations

Semiconductor surface clean is sometimes perceived as costly but long recognized as pivotal in determining the final semiconductor device performance and yield. In this contribution, we investigated the effectiveness of crystalline silicon surface cleaning by a simple UV-ozone process in comparison to the industry standard RCA clean for silicon photovoltaic applications. We present a unique method of processing the silicon surface effectively by UV-ozone cleaning. Despite being simple, UV-ozone cleaning results in a superior surface passivation quality that is comparable to high-quality RCA clean. When used as a stack dielectric—UV-ozone oxide overlaid by aluminum oxide—the thickness of UV-ozone oxide plays …

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Cost And Environmental Impacts Of Leachate Nitrogen/Phosphorus Management Approaches, Alaa Alanezi Jan 2018

Cost And Environmental Impacts Of Leachate Nitrogen/Phosphorus Management Approaches, Alaa Alanezi

Electronic Theses and Dissertations

Landfill leachate is a challenging wastewater to discharge into municipal wastewater treatment plants (WWTPs), the most common approach for leachate management, due to the presence of contaminants that may affect the performance of the treatment plant. Treatment, disposal, and transportation of leachate are expensive and therefore a concern. Currently, sidestream treatment is becoming increasingly common in WWTPs prior to returning the liquid to the plant influent. For this research, a new treatment scheme is introduced combining centrate and leachate to reduce contaminants, recover phosphorous and nitrogen through struvite precipitation, and reduce energy requirements through anaerobic ammonium oxidation (Anammox). By combining …

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Equivalency Analysis Of Sidestick Controller Modes During Manual Flight, Alex Rummel Jan 2018

Equivalency Analysis Of Sidestick Controller Modes During Manual Flight, Alex Rummel

Electronic Theses and Dissertations

Equivalency analysis is a statistical procedure that can enhance the findings of an analysis of variance in the case when non-significant differences are identified. The demonstration of functional equivalence or the absence of practical differences is useful to designers introducing new technologies to the flight deck. Proving functional equivalence is an effective means to justify the implementation of new technologies that must be "the same or better" than previous technology. This study examines the functional equivalency of three operational modes of a new active control sidestick during normal operations while performing manual piloting tasks. Data from a between-subjects, repeated-measures simulator …

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Investigation Into The Feasibility Of Adding Turbulators To Rocket Combustion Chamber Cooling Channels Using A Conjugate Heat Transfer Analysis, Tyler Buchanan Jan 2018

Investigation Into The Feasibility Of Adding Turbulators To Rocket Combustion Chamber Cooling Channels Using A Conjugate Heat Transfer Analysis, Tyler Buchanan

Electronic Theses and Dissertations

A conjugate heat transfer analysis will be carried out to simulate an 89 kN thrust chamber hydrogen cooling channel, to determine the feasibility of adding turbulators to the combustion chamber cooling channels at various parameters such as angle, pitch, and height of the turbulator. An existing regeneratively cooled chamber environment is simulated and used as a baseline case to be compared against. The new design includes using ribbed turbulators or delta wedges in the cooling channels to increase the heat transfer on the channel hot wall (wall adjacent to the hot gas wall) and on the two channel sidewalls. With …

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Nondestructive Testing Methods Aided Via Numerical Computation Models For Various Critical Aerospace Power Generation Systems, Peter Warren Jan 2018

Nondestructive Testing Methods Aided Via Numerical Computation Models For Various Critical Aerospace Power Generation Systems, Peter Warren

Electronic Theses and Dissertations

A current critical necessity for all industries which utilize various equipment that operates in high temperature and extreme environments, is the ability to collect and analyze data via non destructive testing (NDT) methods. Operational conditions and material health must be constantly monitored if components are to be implemented precisely to increase the overall performance and efficiency of the process. Currently in both aerospace and power generation systems there are many methods that are being employed to gather several necessary properties and parameters of a given system. This work will focus primarly on two of these NDT methods, with the ultimate …

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Disinfection By-Product Reduction Study Of A Small Central Florida Public Water System, Paul Staubus Jan 2018

Disinfection By-Product Reduction Study Of A Small Central Florida Public Water System, Paul Staubus

Electronic Theses and Dissertations

The disinfection of water for potabilization has proven to be one of the most significant public achievements of the 20th century. Although chemical disinfectants are successfully utilized to inactivate acute pathogenic organisms, they may react with natural organic matter (NOM) to produce potentially-harmful disinfection by-products (DBPs). As a result, the United States Environmental Protection Agency regulates DBPs such as total trihalomethanes (TTHMs) and haloacetic acids (HAAs). The research herein is focused on the formation, removal, and control of TTHMs and HAAs in a small public water system (PWS) in Polk County, Florida (County). Pilot-scale tests were implemented to determine the …

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Explore Contributing Geometric Factors And Built-Environment On Bicycle Activity And Safety At Intersections, Scott Castro Jan 2018

Explore Contributing Geometric Factors And Built-Environment On Bicycle Activity And Safety At Intersections, Scott Castro

Electronic Theses and Dissertations

This study attempts to explore all factors associated with bicycle motor-vehicle crashes at intersections in order to improve bicycle safety and bicycle activity. Factors such as exposure (bicycle and vehicle volumes), existing facilities (bike lanes, sidewalks, shared-use paths), geometric design (# of lanes, speed limit, medians, legs, roadway conditions), and land-use were collected and evaluated using Poisson, Zero-Inflated Poisson, and Negative Binomial models in SAS 9.4 software. Increasing the bicycle travel mode can have positive lasting effects on personal health, the environment, and improve traffic conditions. Deterrents that keep users from riding bicycles more are the lack of facilities and …

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Accommodating Exogenous Variable And Decision Rule Heterogeneity In Discrete Choice Models: Application To Bicyclist Route Choice, Bibhas Dey Jan 2018

Accommodating Exogenous Variable And Decision Rule Heterogeneity In Discrete Choice Models: Application To Bicyclist Route Choice, Bibhas Dey

Electronic Theses and Dissertations

The thesis contributes to our understanding of incorporating heterogeneity in discrete choice models with respect to exogenous variables and decision rules. Specifically, we evaluate latent segmentation based mixed models that allow for segmenting population based on decision rules while also incorporating unobserved heterogeneity within the segment level decision rule models. In our analysis, we choose to consider the random utility framework along with random regret minimization approach. Further, instead of assuming the number of segments (as 2), we conduct an exhaustive exploration with multiple segments across the two decision rules. Within each segment we also allow for unobserved heterogeneity. The …

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The Relationship Between Agile Project Management And Project Success Outcomes, Thomas Bergmann Jan 2018

The Relationship Between Agile Project Management And Project Success Outcomes, Thomas Bergmann

Electronic Theses and Dissertations

Agile project management (APM) has recently emerged as a new approach to managing complex projects. Some experts believe that APM will become the standard project management approach used in the 21st century. However, thus far, the role of agility in project management has not been widely investigated. In the recent past, the concept of agility has mainly been applied to software development projects. The literature on agility is still in its early stages, and further research needs to be conducted in new project management domains. This study is intended to determine the impact of the adoption of APM on project …

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Customizable Phased Array Antenna Using Reconfigurable Antenna Elements, Mahmoud Shirazi Jan 2018

Customizable Phased Array Antenna Using Reconfigurable Antenna Elements, Mahmoud Shirazi

Electronic Theses and Dissertations

A shared-aperture reconfigurable slot-ring antenna array switching between different frequency bands and polarizations is presented for phased array applications. PIN diode switches are incorporated into the slots of the antenna to change the state of the reconfigurable slot-ring antenna array. Each frequency band has its own feeding lines which allows for the use of high-performance narrow-band transmit/receive (T/R) modules instead of ultra wideband (UWB) T/R modules. Furthermore, the spacing between the elements in each frequency band is less than half free-space wavelength (λ0) over the frequency band of operation which enables grating-lobe-free beam scanning. This is the first shared-aperture reconfigurable …

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Understanding Crisis Communication And Mobility Resilience During Disasters From Social Media, Kamol Roy Jan 2018

Understanding Crisis Communication And Mobility Resilience During Disasters From Social Media, Kamol Roy

Electronic Theses and Dissertations

Rapid communication during extreme events is one of the critical aspects of successful disaster management strategies. Due to their ubiquitous nature, social media platforms offer a unique opportunity for crisis communication. Moreover, social media usage on GPS enabled devices such as smartphones allow us to collect human movement data which can help understanding mobility during a disaster. This study leverages social media (Twitter) data to understand the effectiveness of social media-based communication and the resilience of human mobility during a disaster. This thesis has two major contributions. First, about 52.5 million tweets related to hurricane Sandy are analyzed to assess …

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Design And Implementation Of Pv-Firming And Optimization Algorithms For Three-Port Microinverters, Mahmood Alharbi Jan 2018

Design And Implementation Of Pv-Firming And Optimization Algorithms For Three-Port Microinverters, Mahmood Alharbi

Electronic Theses and Dissertations

With the demand increase for electricity, the ever-increasing awareness of environmental issues, coupled with rolling blackouts, the role of renewable energy generation is increasing along with the thirst for electricity and awareness of environmental issues. This dissertation proposes the design and implementation of PV-firming and optimization algorithms for three-port microinverters. Novel strategies are proposed in Chapters 3 and 4 for harvesting stable solar power in spite of intermittent solar irradiance. PV firming is implemented using a panel-level three-port grid-tied PV microinverter system instead of the traditional high-power energy storage and management system at the utility scale. The microinverter system consists …

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The Study Of An Impinging Unsteady Jet - Fluid Mechanics And Heat Transfer Analysis, Andrea Osorio Jan 2018

The Study Of An Impinging Unsteady Jet - Fluid Mechanics And Heat Transfer Analysis, Andrea Osorio

Electronic Theses and Dissertations

The high heat transfer capabilities of impinging jets have led to their widespread use in industrial applications, such as gas turbine cooling. These impinging jets are usually manufactured on the walls of super-alloy metals and are influenced by being positioned with a confined setting. Studies have been shown to enhance the heat transfer of impinging jets by fluctuating the flow which will be analyzed in this project with two designs. The first design is a self-sustaining stationary fluidic oscillator that causes a sweeping motion jet to impinge on the surface. This is investigated using Particle Image Velocimetry (PIV) to study …

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Navigation Of An Autonomous Differential Drive Robot For Field Scouting In Semi-Structured Environments, Douglas Freese Jan 2018

Navigation Of An Autonomous Differential Drive Robot For Field Scouting In Semi-Structured Environments, Douglas Freese

Electronic Theses and Dissertations

In recent years, the interests of introducing autonomous robots by growers into agriculture fields are rejuvenated due to the ever-increasing labor cost and the recent declining numbers of seasonal workers. The utilization of customized, autonomous agricultural robots has a profound impact on future orchard operations by providing low cost, meticulous inspection. Different sensors have been proven proficient in agrarian navigation including the likes of GPS, inertial, magnetic, rotary encoding, time of flight as well as vision. To compensate for anticipated disturbances, variances and constraints contingent to the outdoor semi-structured environment, a differential style drive vehicle will be implemented as an …

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Design Of High Efficiency Brushless Permanent Magnet Machines And Driver System, Chengyuan He Jan 2018

Design Of High Efficiency Brushless Permanent Magnet Machines And Driver System, Chengyuan He

Electronic Theses and Dissertations

The dissertation is concerned with the design of high-efficiency permanent magnet synchronous machinery and the control system. The dissertation first talks about the basic concept of the permanent magnet synchronous motor (PMSM) design and the mathematics design model of the advanced design method. The advantage of the design method is that it can increase the high load capacity at no cost of increasing the total machine size. After that, the control method of the PMSM and Permanent magnet synchronous generator (PMSG) is introduced. The design, simulation, and test of a permanent magnet brushless DC (BLDC) motor for electric impact wrench …

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