Electrical and Electronics Commons^™

Pressure-Dependent Nanoheteroepitaxy Of Cdte On Si(100) And Soi(100) Substrates Using The Close-Spaced Sublimation Technique, Hoong Yan See Tao

Open Access Theses & Dissertations

CdTe is an ideal II-VI semiconductor compound with a direct bandgap energy of 1.53 eV used in solar cells and infrared detector applications [8]. The National Renewable Energy Laboratory (NREL) reported that cadmium telluride (CdTe) thin films solar cells have achieved efficiency of 16.5% and with potential for improvement up to the theoretical value of 29% [14]. The close-spaced sublimation (CSS) method used for solar cell CdTe growth is being tested for selective CdTe nanoheteroepitaxial growth because the CSS method is cost efficient compared to the molecular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE) methods. High quality films …

An Ultra Low Power Subthreshold Delta Sigma Digital To Analog Converter, Ricardo Baca

Open Access Theses & Dissertations

Abstract

In the last four decades the incorporation of analog, digital and mixed-signal integrated circuits (IC) using Complementary Metal Oxide Semiconductor (CMOS) technology has been dramatically increasing and is improving almost every aspect of modern life. Furthermore, the continuous advances in CMOS Very Large System Integration (VLSI) technology allow higher integration densities and the increasing number of subsystems in a single chip results in higher speed execution and lower power consumption. Therefore, the increasing digitalization in electronic circuits across a wide range of battery-operated applications where reliability and power dissipation are critical requires Digital to Analog Converters (DACs) with higher …

Collaborative And Distributed Algorithms For Localization In Wireless Sensor Networks Based On The Solution Of Spatially Constrained Local And Sub-Local Problems, Juan De Dios Cota

Open Access Theses & Dissertations

In this research we present algorithms for the distributed and collaborative localization of nodes for applications in wireless sensor networks. The algorithms are distributed in the sense that each node can estimate its own position using only range information and position estimates from neighboring nodes. The algorithms aim at achieving good accuracy with low computational complexity and low energy consumption. We consider the full localization process consisting of an initialization stage followed by a refinement stage.

For initialization, we propose a \emph{bilateration} algorithm where each node uses a set of anchors and their respective ranges to solve a set of …

Conformal Electronics Packaging Through Additive Manufacturing And Micro-Dispensing, Richard I. Olivas

Open Access Theses & Dissertations

Realizing electronic systems that are conformal with curved or complex surfaces is difficult if not impossible with conventional fabrication techniques, which require rigid, two dimensional, printed circuit boards (PCB). Flexible copper based fabrication is widely available commercially providing conformance, but not simultaneously stiffness. As a result, these systems are susceptible to reliability problems if repeatedly bent or stretched. The integration of Additive Manufacturing (AM) combined with Direct Print (DP) micro-dispensing can produce shapes of arbitrary and complex form that also allows for 1) miniature cavities for insetting electronic components and 2) conductive traces for electrical interconnect between components. The fabrication …

Algorithms For Training Large-Scale Linear Programming Support Vector Regression And Classification, Pablo Rivas Perea

Open Access Theses & Dissertations

The main contribution of this dissertation is the development of a method to train a Support Vector Regression (SVR) model for the large-scale case where the number of training samples supersedes the computational resources. The proposed scheme consists of posing the SVR problem entirely as a Linear Programming (LP) problem and on the development of a sequential optimization method based on variables decomposition, constraints decomposition, and the use of primal-dual interior point methods. Experimental results demonstrate that the proposed approach has comparable performance with other SV-based classifiers. Particularly, experiments demonstrate that as the problem size increases, the sparser the solution …

Slow Complexity Wavelet Packet Compression Of Bayer Images For Communication Over Wireless Sensor Networks, Ivan Calzada

Open Access Theses & Dissertations

The purpose of this thesis was to develop a low complexity image compression algorithm for Wireless Sensor Networks (WSN). The main constraints in a WSN node are limited processing power, memory allocation, and battery life. The goal of this thesis was to develop an image compression algorithm that would thrive under this constraint environment. The main focus was to minimize the complexity of the algorithm by taking advantage of the spatial correlation found in Bayer images. The algorithm employs line based 1-D Discrete Wavelet Packets Transform of Bayer images. In addition the image compression method includes the application of a …

Generation Of High Resolution Radar Signals Using Three Dimensional Chaotic Flows, Chandra Sekhar Pappu

Open Access Theses & Dissertations

The purpose of this project is to investigate the system parameter and certain signal processing techniques to achieve wide bandwidth and frequency agility in order to build a high resolution radar. The technique relies on the output of an n-dimensional (n>2) non-linear system that exhibits chaotic behavior.

Firstly, the compressed Lorenz attractor is considered which has a set of three state variables x, y and z and three control parameters &rho, &beta, and &sigma. By varying &rho and &beta as function of time highly chaotic parameter space region is simulated such that chaotic signal behaves optimally.

For comparison purpose …

A Subthreshold Reconfigurable Architecture For Harsh Environments, Ameet O. Chavan

Open Access Theses & Dissertations

Energy harvesting and functional reconfigurability are necessary features in order to simultaneously achieve longer operating lifetimes and versatility in application for many next generation electronic systems. The presented research incorporates capabilities that not only enable applications to self-power from ambience but also permit change in functionality based on real-time application requirements. Currently, many applications are battery powered with custom hardware, which severely confines the application platform. Moreover, maintenance and upgrades are prohibitively expensive, particularly in the case of remote locations with limited accessibility. For harsh environments like Space or the battlefield, apart from features such as low power and econfigurability, …

Categorization Of Functional Impairments In Human Locomotion Using The Methods Of The Fusion Of Multiple Sensors And Computational Intelligence, Huiying Yu

Open Access Theses & Dissertations

The main aim of this dissertation work was to develop an intelligent system to monitor, quantify and differentiate variances in human gait with high reliability and efficiency using the fusion of multiple sensor data and the methods of fuzzy inferential logic.

Gait disorders are heterogeneous and produce disabilities that vary substantially from individual to individual. The recognition, quantification and analysis of gait dysfunction is complex and, requires the integration of large amounts of data across multiple domains (kinetic, kinematic and electromyographic). Current systems for gait analysis generally require space and complex imaging equipment, as well as prolonged processing time, rendering …

Investigation Of Selective Nanohetero-Epitaxy Growth On Si(100) Substrates For Hgcdte Infrared Detector Applications, Aryzbe Diaz

Open Access Theses & Dissertations

The selective CdTe Nanohetero-Epitaxy growth on Si(100) substrates has been achieved without the use of a mask in an attempt to reduce the dislocation density at the CdTe/Si interface to 10⁵/cm³ using the Close-Space Sublimation (CSS) technique, which is a low-cost effective technique for the deposition of polycrystalline CdTe films. Furthermore, CdTe is a compound semiconductor with a direct bandgap of 1.5 eV, which makes it an ideal material for the applications of infrared detectors and solar cells. It has been demonstrated that the selective growth of CdTe on patterned Si(100) substrates results in CdTe grains with …

12 Bit Charge Redistribution Digital To Analog Converter For The Residence Time Fluxgate Magnetometer, Miguel Angel Alamillo

Open Access Theses & Dissertations

The continuous advances in CMOS VLSI technology have culminated in high speed, low voltage CMOS digital circuits with gate delays below 50 ps at 1.5 V supply. At the same time, high voltage analog signal processing has fallen behind to the high flexibility and high reliability of DSP. However, the main drawback of DSP is the need for high accuracy low distortion data converters and as a consequence of the persistent efforts of reducing size, cost and power of solid-state components the field of CMOS Mixed-Signal circuit design has become of the utmost importance.

The obvious functionality of data converters …

Computer-Aided Detection Of Sleep Apnea And Sleep Stage Classification Using Hrv And Eeg Signals, Edson F. Estrada

Open Access Theses & Dissertations

Sleep is a circadian rhythm essential for human life. Many events occur in the body during this state. In the past, significant efforts have been made to provide clinicians with reliable and less intrusive tools to automatically classify the sleep stages and detect apnea events. A few systems are available in the market to accomplish this task. However, sleep specialists may not have full confidence and trust in such systems due to issues related to their accuracy, sensitivity and specificity. The main objective of this work is to explore possible relationships among sleep stages and apneic events and improve on …

Design And Simulation Of A Position Sensitive Device With Gaussian Response, Debra Erin Medina

Open Access Theses & Dissertations

Not Required

Sensor Interpolation And Super Resolution Image Reconstruction Using The Optimal Recovery Framework, Veenarai Moram

Open Access Theses & Dissertations

Wireless sensor networks have the potential to benefit society in a myriad of ways, but due to constraints of sensor placement, obtaining the desired signals is not an easy problem. Retrieving the information accurately from sensors placed randomly is a challenging problem of sensor communication and signal interpolation. In this research the optimal recovery (OR) method, a deterministic framework that can use a priori bandwidth or spectral shape information, is used to interpolate from the given samples produced by sensors. In the reconstruction formulation, a worst case error signal occurs. To minimize this error, the OR method uses a norm …

Dynamic Modeling Of Human Gait And Motor, Chad Everett Joshua Macdonald

Open Access Theses & Dissertations

The simulation of gait, impairments and the outcomes of rehabilitation strategies is an important area of research. The ability to study the efficacy of treatment options before applying them to patients has the potential to improve the efficiency of the rehabilitation process. Any such simulations must incorporate some model of the motor learning process to properly anticipate the responses of patients.This dissertation presents initial work on the modeling of gait and the study of motor adaptation with a view towards simulating the motor adaptation process during gait.

Specifically, an inverse dynamic model of gait incorporating sagittal plane limb and torso …

Novel Control Technique For Cadmium Sulfide, Rafael Ordonez

Open Access Theses & Dissertations

Cadmium sulfide Chemical-Bath-Deposition parameters are modified to allow, for the first time, real time monitoring of cadmium ion molarity using a commercially available cadmium ion Ion-Selective-Electreode at 60°C. This modification involves alterations to typical deposition parameters that eliminate the formation of cadmium hydroxide and keep cadmium ion molarity above 10-7M. The new or atypical parameters developed are pH values below 8.9 and lower moralities for all chemicals. In order to have complexation of cadmium ion driven mainly by ammonia, parameters that minimized complexation by other chemicals are found. Cadmium acetate concentration below 2mM and ammonium acetate concentration below 10mM minimize …

Acoustic Reflectometry Using Gaussian-Modulated Sinusoidal Waves And The Ware-Aki Algorithm, Ernesto Rodrigo Vazquez Ceron

Open Access Theses & Dissertations

Acoustic reflectometry, a non invasive technique, consists of solving, the inverse problem of estimating the cross sectional area as function of the distance of a cylindrical cavity by impacting an audible acoustic pulse of high amplitude and short duration, and analyzing the reflected wave. The technique has been applied in Biomedical Engineering to estimate both the area of a human upper airway and the patency of endotracheal tubes as a function of distance. Several ways have been tested to improve the quality of an acoustic pulse and different algorithms have been tested to reduce the losses. However, an acoustic pulse …

Resistive Switching Of Tin Dioxide (Sno2) For Memristor Applications, Sergio Fabian Almeida

Open Access Theses & Dissertations

In the last decades new electrical devices have been investigated in order to overcome problems caused by integrated circuit shrinking. Within these devices there is one that has attracted much attention due to its high scalability and simple structure. This device was proposed theoretically by Leon Chua in 1971 who gave it the name of "Memristor". In the recent years thin films structures composed of a metal/oxide/metal (MOM) stack have been linked to this new device, also known as "Resistive switching". There are several applications for the memristor; one of the most important is for resistive random access memory (ReRAM) …

Simulation And Optimization Of Ultra Thin Photovoltaics, Jose Luis Cruz-Campa

Open Access Theses & Dissertations

Sandia National Laboratories (SNL) conducts pioneering research and development in Micro-Electro-Mechanical Systems (MEMS) and solar cell research. This dissertation project combines these two areas to create ultra-thin small-form-factor crystalline silicon (c-Si) solar cells. These miniature solar cells create a new class of photovoltaics with potentially novel applications and benefits such as dramatic reductions in cost, weight and material usage.

At the beginning of the project, unusually low efficiencies were obtained in the research group. The intention of this research was thus to investigate the main causes of the low efficiencies through simulation, design, fabrication, and characterization.

Commercial simulation tools were …

Compressive Sensing With Prior Information Applied To Magnetic Resonance Imaging, Cristiano Jacques Miosso

Open Access Theses & Dissertations

This dissertation introduces the theory of compressive sensing with prior information about a signal's sparse representation. We show, mathematically and in numerical simulations, that prior information improves signal reconstruction, in terms of number of required measurements, computation time and signal-to-noise ratios. Following, we present a set of methods for enhanced magnetic resonance imaging and tomography that can be combined with prior information, for enhanced image quality.

In developing the theory of compressive sensing with prior information, we provide a mathematical proof of the required condition (in terms of number of linear measurements) for reconstruction using the ideal approach of l0-minimization, …

Novel Control Technique For Cadmium Sulfide Chemical Bath Deposition Using Real Time Monitoring Of Cadmium Ion Molarity, Rafael Ordonez

Open Access Theses & Dissertations

Cadmium sulfide Chemical-Bath-Deposition parameters are modified to allow, for the first time, real time monitoring of cadmium ion molarity using a commercially available cadmium ion Ion-Selective-Electreode at 60°C. This modification involves alterations to typical deposition parameters that eliminate the formation of cadmium hydroxide and keep cadmium ion molarity above 10-7M. The new or atypical parameters developed are pH values below 8.9 and lower moralities for all chemicals. In order to have complexation of cadmium ion driven mainly by ammonia, parameters that minimized complexation by other chemicals are found. Cadmium acetate concentration below 2mM and ammonium acetate concentration below 10mM minimize …

Application Of Sensor Fusion To Human Locomotor System, John Kweku Avor

Open Access Theses & Dissertations

This research study proposes a multi-sensor data fusion technique to determine the complex interactions between the sensory, muscular and mechanical components of the human locomotor systems (neuromechanics). The object in this work is to demonstrate the viability in using inertial sensors for accurate gait phase determination and to present the acceleration effect specific body segment contributes in order to establish a functional gait. The current method used in determining gait phases consist of combining ground reaction force and angular data, this method is time consuming and cannot be totally reliable. We found out that gait phases can be determined distinctively …

Detection Of Gas/Odor Based On Quartz Crystal Microbalance Sensors And Fuzzy Similarity Measure, Yi-Chen Lo

Open Access Theses & Dissertations

In this research, an array of six Quartz Crystal Microbalance sensors (QCM) using fuzzy similar measurement is proposed to recognize different gases and the percentage of those gases in a mixed gas. The experiment suggests three different gases, oxygen, helium, and argon as test gases and the nitrogen as the reference gas. Six QCMs in this array are coated respectively with six different specific polymers that are selected based on Linear Solvation Energy Relationship (LSER) method, in order to absorb gas molecules so as to recognize responses of resonant frequency changes from QCMs. Testing with different gases results in different …

Assessment Of Super-Resolution For Face Recognition From Very-Low Resoution Images, James Roger Roeder

Open Access Theses & Dissertations

Super-Resolution (SR) involves the registration of multiple images/frames and reconstruction of a single higher resolution image. The goal of this research is to use multiple, very-low resolution images, such as those produced from a video sequence in a wireless sensor network system, as input to the super-resolution process in a face recognition system. The algorithm used for face recognition is the Fisherfaces method with a nearest neighbor classifier used for the recognition decision. Super-resolution consists of two stages, a registration stage and a reconstruction stage.

The testing images were segmented using a simple skin color detection approach. After the cropping, …

Remote Control Of Multiple Robots: A Wireless Sensor Network And Virtual Reality Approach, Yingjun Zhu

Open Access Theses & Dissertations

A tele-operation system of robots based on virtual reality and WSN is established and demonstrated. Pro/E, Blender 3D and Python language are adopted to build up and carry out the virtual environment and virtual robot. Wireless Sensor Network (WSN) technology has been used to achieve the tele-operation function. The WSN enables the users to control the robots and collect the data/status from the robots as well. Robot virtual reality software has been developed and presented in the paper. The network setup and the control/communication Application Programming Interface (API) has been shown in this paper.

An Integrated Software Package For Model-Based Neuro-Fuzzy Classification Of Small Airway Dysfunction, Nazila Hafezi

Open Access Theses & Dissertations

Respiratory disorders can be difficult to differentiate, as their symptoms are sometimes similar to one another. Concerning asthma which is the major interest in this research, early detection of small airway impairment could greatly help with timely diagnosis. In this research, an integrated software package (ISP) has been developed to help clinicians in classification of asthma severities using Impulse Oscillation data.

The ISP has been developed based on object-oriented methodology. In this package, IOS "diagnostic" parameters such as AX and frequency-dependence of resistance as well as parameter estimates of extended RIC (eRIC) and augmented RIC (aRIC) models (simplified cases of …

Design Of A Low Voltage Analog To Digital Converter, Praveen Kumar Palakurthi

Open Access Theses & Dissertations

For the past 40 years, the number of transistors per chip has been increasing at an exponential rate confirming Moore's Law regarding the growth of chip complexity. Increases in transistor count have led to enhancements in functionality and made possible products with features that were unimaginable ten years ago. Consequently, the resulting increase in digitization in all electronics, across a wide range of applications, requires the Analog-to-Digital Converters (ADCs) with a higher resolution and lower power consumption. The evolution of the integrated circuit technologies and scaling methodologies partially helps in providing faster circuits and allowing complex functionalities in a given …

Vision-Based Virtual Mouse System, Tom Wanjala Watiti

Open Access Theses & Dissertations

This thesis describes a virtual mouse system that utilizes machine vision technology to enable a user to navigate through software window screens on a standard personal computer, access and control software, and/or peripheral devices attached to the personal computer. Utilizing the virtual mouse, the user can execute the standard control functions of the system mouse required to perform software application selection functions and navigation tasks without physical interface with the controlled computer. The machine vision algorithm utilizes a set of four simulated photoelectric sensors, with Gaussian filter sensitivities, to compute and track the mouse location. By utilizing Gaussian filters, instead …

Autonomous Vehicle Navigation: A Comparative Study Of Classical Logic And Neural Network Technique, Javier Alejandro Flores

Open Access Theses & Dissertations

Today is an era in which humans need the help of automated machines to facilitate their hectic lives. Over the past few decades, robotics has been one of the most researched areas in the world. One area of this research is obstacle avoidance for autonomous vehicles. In order to avoid an obstacle, the system may include two important characteristics: obstacle detection and avoidance control. In this Thesis a classical logic system and artificial neural network approach is presented. With the help of an Integrated Development Environment, a virtual robot was able to negotiate a maze and avoid obstacles according to …

An Enhanced Method For The Existing Bluetooth Pairing Protocol To Avoid Impersonation Attacks, Patricia Aidee Mendoza

Open Access Theses & Dissertations

As the use of the Bluetooth technology in wireless technologies such as computers, cell phones, personal digital assistants (PDAs), printers, digital cameras, PC peripherals, and headphones, among others, has enormously increased during this decade, it has also increased the need of employing a more secure and robust pairing protocol that protects the transfer of information between Bluetooth devices.

The existing Bluetooth pairing protocol starts when a Bluetooth device is set to be in discoverable mode and it is found by another device. After this step is completed, it initiates the pairing procedure by sharing some important device information, then by …