Electrical and Computer Engineering Commons^™

Femtosecond Laser Micromachining Of Low-Temperature Co-Fired Ceramic And Glass Fiber Reinforced Polymer Printed Circuit Boards Materials, Raif Farkouh

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Low-temperature co-fired ceramic (LTCC), and glass fiber reinforced polymer (GFRP) printed circuit boards (PCBs) are two materials used for the packaging of electronics. The excellent mechanical and electrical properties of LTCC, combined with the ability to embed passive components offer superior radio frequency (RF) performance and device miniaturization for high-frequency applications. Due to its unique properties, LTCC provides superior performance in applications as diverse as military radar, imaging systems, advanced automotive sensing, telecommunications, and satellites. The use of LTCC in these applications has created a demand for the micromachining of holes, channels, and cavities with specific geometries and structures. Likewise, …

Generalized Ellipsometry On Complex Nanostructures And Low-Symmetry Materials, Alyssa Mock

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

In this thesis, complex anisotropic materials are investigated and characterized by generalized ellipsometry. In recent years, anisotropic materials have gained considerable interest for novel applications in electronic and optoelectronic devices, mostly due to unique properties that originate from reduced crystal symmetry. Examples include white solid-state lighting devices which have become ubiquitous just recently, and the emergence of high-power, high-voltage electronic transistors and switches in all-electric vehicles. The incorporation of single crystalline material with low crystal symmetry into novel device structures requires reconsideration of existing optical characterization approaches. Here, the generalized ellipsometry concept is extended to include applications for materials with …

Condensation And Subsequent Freezing Delays As A Result Of Using A Femtosecond Laser Functionalized Surface, Chongji Huang

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Femtosecond laser surface processing (FLSP) enhances the anti-icing properties of a commonly used aircraft alloy, Al 7075-O Clad. The wettability of Al 7075-O Clad was altered by changing the surface morphology through FLSP and the surface chemistry through siloxane vapor deposition. Tall mound and short mound FLSP functionalized surfaces were created through two sets of laser parameters. Atmospheric condensation and subsequent freezing of condensates on FLSP Al 7075-O Clad was studied. Results indicate that both structure height and surface wettability play a role in the delay of freezing. Freezing occurred on the FLSP superhydrophilic surface faster than on a unprocessed …

Anti-Icing Properties Of Femtosecond Laser Surface Processed Material, Ryan James Bell

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

In this thesis, the use of femtosecond laser surface processing (FLSP) to enhance the anti-icing properties of a commonly used aircraft alloy, Al 7075-O Clad is described. By changing the surface morphology through FLSP and the surface chemistry through siloxane vapor deposition, the wettability of Al 7075-O Clad was altered.

Condensation and the subsequent freezing of condensates on FLSP Al 7075-O Clad was studied. Both structure height and surface wettability were shown to play a role in the delay of freezing. Freezing occurred on the FLSP superhydrophilic surface faster than on the unprocessed Al 7075-O Clad surface, however, freezing was …

Application-Aware Cognitive Multi-Hop Wireless Networking Testbed And Experiments, Trenton T. Evans

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

In this thesis, we present a new architecture for application-aware cognitive multihop wireless networks (AC-MWN) with testbed implementations and experiments. Cognitive radio is a technique to adaptively use the spectrum so that the resource can be used more efficiently in a low cost way. Multihop wireless networks can be deployed quickly and flexibly without a fixed infrastructure. In presented new architecture, we study backbone routing schemes with network cognition, routing scheme with network coding and spectrum adaptation. A testbed is implemented to test the schemes for AC-MWN. In addition to basic measurements, we implement a video streaming application based on …

Laser-Assisted Metal Organic Chemical Vapor Deposition Of Gallium Nitride, Hossein Rabiee Golgir

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Due to its unique properties, gallium nitride is of great interest in industry applications including optoelectronics (LEDs, diode laser, detector), high power electronics, and RF and wirelss communication devices. The inherent shortcomings of current conventional deposition methods and the ever-increasing demand for gallium nitride urge extended efforts for further enhancement of gallium nitride deposition. The processes of conventional methods for gallium nitride deposition, which rely on thermal heating, are inefficient energy coupling routes to drive gas reactions. A high deposition temperature (1000-1100 °C) is generally required to overcome the energy barriers to precursor adsorption and surface adatom migration. However, there …

Smart Feedback Control For Fiber-Optics Acoustic Emission Sensor System, Xiangyu Luo

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Optical fiber sensors for ultrasonic detection have become a subject of much research in recent years. In this thesis, a fiber-optic acoustic emission (AE) sensor system that is capable of performing AE detection, even when the sensor is experiencing large quasi-static strains, is first described. The system consists of a smart selection of a wavelength notch to which a distributed feedback (DFB) laser is locked for high sensitivity AE signal demodulation. A smart feedback control unit for the DFB laser, which is the focus of this thesis, is designed and investigated. The smart control ensures that the AE signal is …

5g-Ucda Multi Antenna-To-Logical Cell Circular Fifo Mapping Strategy For High-Speed Train Wireless Communications, Subharthi Banerjee

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

2020 is the target year for the roll out of fifth generation wireless communication methodologies. The commercial vendors have characterized 5G as a collection of disruptive set of technologies to provide high throughput, low latency communication supporting a variety of services, i.e., machine to machine communication to next generation base stations and vehicle-to-vehicle communication to radio-over-fiber and high mobility channels. High-speed train wireless communication channels as a subset of high mobility channels have their clear advantages and disadvantages considering other vehicular channels. The speed of high-speed trains is going to reach 500km/hr and with Hyperloop it may reach 1000km/hr. LTE …

Project Halon: Engaging Secondary Students In High-Altitude Balooning Experiments, James M. Taylor Jr, Derrick A. Nero

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Project HALON Overview

•Fewer US STEM graduates

•Shortage of STEM educators

•Lack of engaging, high quality STEM material in the classroom

•Potentially results in lower global economic competitiveness

Experiment Constraints

•Project brings together STEM major mentors and educators

•Builds understanding of research and operational challenges

•Students get excited about more complex experiments (CubeSATs)

HALON: High Altitude Learning Over Nebraska

•High altitude balloon lift platform

•Student-designed experiments tailored to student team abilities

•NASA-inspired near-space systems engineering process for tradeoffs

•Engagement / mentoring for pre-service and in-service educators

Physiologically-Aware Communication Architecture For Transmission Of Biomedical Signals In Basns For Emerging Iot Applications, Jose Santos, Dongming Peng, Hamid Sharif

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

This research work proposes a novel physiologicallyaware communication architecture for the transmission of biomedical signals in BASNs (Body Area Sensor Networks) and wearables for emerging IoT applications. The architecture to fulfill the following objectives:

• Reduce volume of biomedical data in IoT networks and Internet infrastructure.

• Minimize the required computational load of biomedical data on the cloud side.

• Extend the lifetime of the mobile wearable/BASN through improved energy savings.

This architecture is generalizable to class of biomedical signals. It prevents large volume of biomedical data to be generated; uses patient state to control almost any system parameter; achieves …

Reducing Graphene-Metal Contact Resistance Via Laser Nano-Welding, Kamran Keramatnejad, H. Rabiee Golgir, Y. S. Zhou, D. W. Li, X. Huang, Yongfeng Lu

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

The large graphene-metal contact resistance is a major limitation for development of graphene electronics. graphene behaves as an insulator for out-of-plane carrier transport to metallic contacts.

Laser nano-welding was developed and led to RC reductions of up to 84%.

Localized laser irradiation at the edges of graphene led to the formation of chemically active point defects.

Precise structural modifications and formation of G-M bonding led to improved carrier efficiency in graphene devices.

Real-Time Internal Temperature Estimation And Health Monitoring For Igbt Modules, Ze Wang

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Field experiences have demonstrated that power semiconductor devices, such as insulated-gate bipolar transistors (IGBTs), are among the most fragile components of power electronic converters. Thermomechanical stresses produced by temperature variations during operational and environmental loads are the major causes of IGBT degradation. As the devices are often operated under complex working conditions, temperature variations and the associated damage are difficult to predict during the converter design stage. A promising approach—online health monitoring and prognosis for power semiconductor devices—that can avoid device failure and effectively schedule maintenance has attracted much interest.

This dissertation research focused on real-time accurate internal temperature estimation …

The Discrete Spring Transform: An Innovative Steganographic Attack, Aaron T. Sharp

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Digital Steganography continues to evolve today, where steganographers are constantly discovering new methodologies to hide information effectively. Despite this, steganographic attacks, which seek to defeat these techniques, have continually lagged behind. The reason for this is simple: it is exceptionally difficult to defeat the unknown. Most attacks require prior knowledge or study of existing techniques in order to defeat them, and are often highly specific to certain cover media. These constraints are impractical and unrealistic to defeat steganography in modern communication networks. It follows, an effective steganographic attack must not require prior knowledge or study of techniques, and must be …