Open Access. Powered by Scholars. Published by Universities.®

Engineering Commons

Open Access. Powered by Scholars. Published by Universities.®

2019

Portland State University

Theses/Dissertations

Discipline
Keyword
Publication

Articles 31 - 39 of 39

Full-Text Articles in Engineering

Design And Performance Evaluation Of Linear And Axial-Flux Magnetic Gears, Mojtaba Bahrami Kouhshahi Apr 2019

Design And Performance Evaluation Of Linear And Axial-Flux Magnetic Gears, Mojtaba Bahrami Kouhshahi

Dissertations and Theses

The conversion from low speed to high speed and vice versa in various forms, including rotary and linear motion, is a requirement for a wide range of applications. For example, wind power generation requires a conversion of low speed rotation of turbine blades to high speed generator rotation, and ocean wave power generation is achievable by conversion of low speed linear motion to either high speed rotation or high speed linear motion. Mechanical gearboxes, hydraulic and pneumatic actuators are commonly used to achieve these conversions. However, these systems suffer from reliability issues, high maintenance requirements, noise, and lack of overload ...


A Study Of Thermal Energy Storage Of Phase Change Materials: Thermophysical Properties And Numerical Simulations, Kyung-Eun Min Apr 2019

A Study Of Thermal Energy Storage Of Phase Change Materials: Thermophysical Properties And Numerical Simulations, Kyung-Eun Min

Dissertations and Theses

A Thermal Energy Storage (TES) system is meant for holding thermal energy in the form of hot or cold materials for later utilization. A TES system is an important technological system in providing energy savings as well as efficient and optimum energy use. The main types of a TES system are sensible heat and latent heat. A latent heat storage is a very efficient method for storing or releasing thermal energy due to its high energy storage density at constant temperatures, and a latent heat storage material can store 5-14 times more heat per unit volume than a sensible heat ...


Investigation Of Electronic And Optical Properties Of 2-Dimensional Semiconductor Tin Selenide (Snse) Thin Films, Shakila Afrin Mar 2019

Investigation Of Electronic And Optical Properties Of 2-Dimensional Semiconductor Tin Selenide (Snse) Thin Films, Shakila Afrin

Dissertations and Theses

Over the last 5 decades, the semiconductor industry has been well served by Si based technology due to its abundant availability, lower manufacturing cost, large wafer sizes and less complexity in fabrication. Over this period, electronic devices and integrated systems have been miniaturized by downscaling of the transistors. The miniaturization has been guided by the Moore's law where the numbers of transistors have doubled over every two years. However, the trend of transistor miniaturization is fast approaching its limit. Hence, alternate and innovative solutions are necessary to tackle this problem and this propels the research for finding novel materials ...


On The Drought Recovery And Resiliency: How Terrestrial And Riverine Ecosystems Recover From Agricultural And Hydrological Droughts, Behzad Ahmadi Mar 2019

On The Drought Recovery And Resiliency: How Terrestrial And Riverine Ecosystems Recover From Agricultural And Hydrological Droughts, Behzad Ahmadi

Dissertations and Theses

Climate extremes, in particular droughts are significant driving forces towards riverine and terrestrial ecosystems disturbance. Drought impacts on stream ecosystems include losses that can either be direct (e.g. destruction of habitat for aquatic species) or indirect (e.g. deterioration of water quality, soil quality, and increased chance of wildfires). This study investigates hydrological and agricultural droughts and their recovery durations. For the riverine ecosystems, this study combines hydrologic drought and water quality changes during droughts and represents a multi-stage framework to detect and characterize hydrological droughts, while considering water quality parameters. Hydrological droughts are categorized into three stages of ...


Efficient Methods For Robust Circuit Design And Performance Optimization For Carbon Nanotube Field Effect Transistors, Muhammad Ali Mar 2019

Efficient Methods For Robust Circuit Design And Performance Optimization For Carbon Nanotube Field Effect Transistors, Muhammad Ali

Dissertations and Theses

Carbon nanotube field-effect transistors (CNFETs) are considered to be promising candidate beyond the conventional CMOSFET due to their higher current drive capability, ballistic transport, lesser power delay product and higher thermal stability. CNFETs show great potential to build digital systems on advanced technology nodes with big benefits in terms of power, performance and area (PPA). Hence, there is a great need to develop proven models and CAD tools for performance evaluation of CNFET-based circuits. CNFETs specific parameters, such as number of tubes, pitch (spacing between the tubes) and diameter of CNTs determine current driving capability, speed, power consumption and area ...


Behavior Of Non-Ductile Slender Reinforced Concrete Columns Retrofit By Cfrp Under Cyclic Loading, Wisam Amer Aules Mar 2019

Behavior Of Non-Ductile Slender Reinforced Concrete Columns Retrofit By Cfrp Under Cyclic Loading, Wisam Amer Aules

Dissertations and Theses

In the Middle East region and many countries in the world, older reinforced concrete (RC) columns are deemed to be weak in seismic resistance because of their low amount of reinforcement, low grades of concrete, and large spacing between the transverse reinforcement. The capacity of older RC columns that are also slender is further reduced due to the secondary moments. Appropriate retrofit techniques can improve the capacity and behavior of concrete members. In this study, externally bonded Carbon Fiber Reinforced Polymer (CFRP) retrofit technique was implemented to improve the behavior of RC columns tested under constant axial load and cyclic ...


Spectral Clustering For Electrical Phase Identification Using Advanced Metering Infrastructure Voltage Time Series, Logan Blakely Jan 2019

Spectral Clustering For Electrical Phase Identification Using Advanced Metering Infrastructure Voltage Time Series, Logan Blakely

Dissertations and Theses

The increasing demand for and prevalence of distributed energy resources (DER) such as solar power, electric vehicles, and energy storage, present a unique set of challenges for integration into a legacy power grid, and accurate models of the low-voltage distribution systems are critical for accurate simulations of DER. Accurate labeling of the phase connections for each customer in a utility model is one area of grid topology that is known to have errors and has implications for the safety, efficiency, and hosting capacity of a distribution system. This research presents a methodology for the phase identification of customers solely using ...


Application Of Improved Feature Selection Algorithm In Svm Based Market Trend Prediction Model, Qi Li Jan 2019

Application Of Improved Feature Selection Algorithm In Svm Based Market Trend Prediction Model, Qi Li

Dissertations and Theses

In this study, a Prediction Accuracy Based Hill Climbing Feature Selection Algorithm (AHCFS) is created and compared with an Error Rate Based Sequential Feature Selection Algorithm (ERFS) which is an existing Matlab algorithm. The goal of the study is to create a new piece of an algorithm that has potential to outperform the existing Matlab sequential feature selection algorithm in predicting the movement of S&P 500 (^GSPC) prices under certain circumstances. The two algorithms are tested based on historical data of ^GSPC, and Support Vector Machine (SVM) is employed by both as the classifier. A prediction without feature selection ...


From Drought To Food-Energy-Water-Security Nexus: An Assessment Of Food Insecurity In The Middle East, Maysoun Ayad Hameed Jan 2019

From Drought To Food-Energy-Water-Security Nexus: An Assessment Of Food Insecurity In The Middle East, Maysoun Ayad Hameed

Dissertations and Theses

Drought is an extreme climate phenomenon that happens slowly and periodically threatens the environmental and socio-economic sectors. Developing countries have experienced crucial conditions in meeting the needs for food, energy, and water security. Natural disasters contribute as risky sources of food insecurity and vulnerability in the Middle East. This dissertation presents a country-level review and quantitative assessment of the current issues associated with the Food-Energy-Water-Security (FEWS) Nexus in the Middle East. In this study, sixteen countries in the Middle East are chosen, namely, Arabian Peninsula, Iran, Syria, Lebanon, Israel, Palestine, Egypt, and Turkey. The most recent datasets are used to ...