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Study Of Electronic Characteristics Of Heterojunction With Intrinsic Thin-Layer Devices And Defect Density Profile Of Nanocrystalline Silicon Germanium Devices, Watson Paul Mulder Jan 2015

Study Of Electronic Characteristics Of Heterojunction With Intrinsic Thin-Layer Devices And Defect Density Profile Of Nanocrystalline Silicon Germanium Devices, Watson Paul Mulder

Graduate Theses and Dissertations

Heterojunction with Intrinsic Thin-layer (HIT) solar cells are an important photovoltaic technology, recently reaching record power conversion efficiencies. HIT cells hold advantages over the conventional crystalline Si solar cells, such as their fabrication at lower temperatures and their shorter fabrication time. It is important to understand the electronic characteristics and transport properties of HIT cells to continue to improve their efficiencies. The fundamental measurements of a HIT solar cell with an innovative n+/p/p+ structure are presented. We also report on a series of these HIT cells fabricated on wafers with different doping concentrations, observing the relationship between doping ...


Power Conversion Techniques In Nanometer Cmos For Low-Power Applications, Wei Fu Jan 2015

Power Conversion Techniques In Nanometer Cmos For Low-Power Applications, Wei Fu

Graduate Theses and Dissertations

As System-on-Chip (SoCs) in nanometer CMOS technologies grow larger, the power management process within these SoCs becomes very challenging. In the heart of this process lies the challenge of implementing energy-efficient and cost-effective DC-DC power converters. To address this challenge, this thesis studies in details three different aspects of DC-DC power converters and proposes potential solutions. First, to maximize power conversion efficiency, loss mechanisms must be studied and quantified. For that purpose, we provide comprehensive analysis and modeling of the various switching and conduction losses in low-power synchronous DC-DC buck converters in both Continuous Conduction Mode (CCM) and Discontinuous Conduction ...


Uncertainty In Power System Planning, Oluwaseyi Ayorinde Olatujoye Jan 2015

Uncertainty In Power System Planning, Oluwaseyi Ayorinde Olatujoye

Graduate Theses and Dissertations

Deterministic transmission planning is based on deterministic assumptions, by planning for a single forecasted set of conditions. The issue of adaptability in transmission and generation expansion planning has become important for planners in order to deal with future uncertainties. Adaptability is "the ability to change (or be changed) to fit changed circumstances" [ ]. Adaptability planning helps mitigate losses in unforeseen situations and exploit opportunities in expected situations. Adaptability also provides the opportunities to take alternative actions after events unfold. Adaptable plans can help reduce future costs and time, and it also reduces complexity associated with possible future changes to the existing ...


Methods Of Magnetic Field Switching For Biomedical And Power Applications, Narimdinda Robert Bouda Jan 2015

Methods Of Magnetic Field Switching For Biomedical And Power Applications, Narimdinda Robert Bouda

Graduate Theses and Dissertations

Surrounded by electromagnetic (EM) fields humans continuously interact and utilize EM fields for domestic devices, telecom systems, power systems and different medical applications including MRI (Magnetic Resonance Imaging) and TMS (Transcranial Magnetic Stimulation). During the last century, numerous new electronic devices and technologies have been developed leading to an exponential increase in exposure to Electromagnetic Fields. Although all of these applications are byproducts of Maxwell' experimentation, there are considerable differences in the way they interact with us.

In the treatment of noninvasive treatment of the human brain, the majority of the research has been mainly focused on realizing systems that ...


Slew-Rate Enhancement And Trojan State Avoiding For Fully-Differential Operational Amplifier, Chongli Cai Jan 2015

Slew-Rate Enhancement And Trojan State Avoiding For Fully-Differential Operational Amplifier, Chongli Cai

Graduate Theses and Dissertations

Operational amplifiers are fundamental building blocks in modern analog and mixed-signal systems such as data converters, switched-capacitor circuits, and filters. The fully-differential structure is extensively used in these applications because of its improved dynamic performance with respect to such aspects as signal-to-noise ratio (SNR) and total harmonic distortion (THD) when compared to its single-ended counterpart. In some of these applications, the fully-differential amplifier is required to have fast transient settling time without slew-rate limitations. Power consumption also must be taken into consideration because low power consumption can significantly reduce a battery's weight and size, and extend its life-time. A ...


Unconventional Elastomeric Microsystems: Fabrication And Application, Jungwook Paek Jan 2015

Unconventional Elastomeric Microsystems: Fabrication And Application, Jungwook Paek

Graduate Theses and Dissertations

Elastomer-based microsystems hold great promise for a diverse range of applications such as rapid prototyping of lab-on-a-chip device, soft-MEMS, and soft-robotics. For better performance in such applications, unconventional elastomeric structures in terms of size, shape, and patterning trajectory, have been intensely sought after in microtechnology but their realization has been a continuous challenge. Here, as my dissertation work, I present new microfabrication schemes which enable the realizations of unconventional PDMS structures, and their applications, which will enrich the field of soft-microsystems.

First, I present a new fabrication scheme for the realization of cylindrical microfluidic (MF) channels with 3D trajectories based ...


Correctness Results For On-Line Robust Principal Components Analysis, Brian Thomas Lois Jan 2015

Correctness Results For On-Line Robust Principal Components Analysis, Brian Thomas Lois

Graduate Theses and Dissertations

This work studies two interrelated problems - online robust PCA (RPCA) and online low-rank matrix completion (MC). In recent work by Candes et al., RPCA has been defined as a problem of separating a low-rank matrix (true data), L:=[ℓ₁, ℓ₂, ... ℓt, ... , ℓtmax and a sparse matrix (outliers), S:=[x₁, x₂, ... xt, ..., xtmax] from their sum, M:=L+S. Our work uses this definition of RPCA. An important application where both these problems occur is in video analytics in trying to separate sparse foregrounds (e.g., moving objects) and slowly changing backgrounds.

While there has been a large amount of recent ...


Radio Frequency And Capacitive Sensors For Dielectric Characterization Of Low-Conductivity Media, Robert Thomas Sheldon Jan 2015

Radio Frequency And Capacitive Sensors For Dielectric Characterization Of Low-Conductivity Media, Robert Thomas Sheldon

Graduate Theses and Dissertations

Low-conductivity media are found in a vast number of applications, for example as electrical insulation or as the matrix polymer in high strength-to-weight ratio structural composites. In some applications, these materials are subjected to extreme environmental, thermal, and mechanical conditions that can affect the material's desired performance. In a more general sense, a medium may be comprised of one or more layers with unknown material properties that may affect the desired performance of the entire structure. It is often, therefore, of great import to be able to characterize the material properties of these media for the purpose of estimating ...


A Broadband Bistable Piezoelectric Cantilever-Based Vibration Energy Harvester With Nonlinear High Power Extraction, Kanishka Aman Singh Jan 2015

A Broadband Bistable Piezoelectric Cantilever-Based Vibration Energy Harvester With Nonlinear High Power Extraction, Kanishka Aman Singh

Graduate Theses and Dissertations

This work presents a nonlinear vibration energy harvester, which combines a nonlinear bistable broadband piezoelectric cantilever used to transduce ambient vibration energy, with synchronized capture for efficient harvesting over broadband sources. An accurate model of the bistable transducer, that augments the Butterworth van Dyke piezoelectric model to capture the external magnetic force added as a bias to the external vibrations, is presented. Its validity has been demonstrated through physical implementation and experimental validation against simulation of the mathematical model. For efficient extraction of the transduced energy, nonlinear extraction circuits, namely synchronous charge extraction (SCE) and parallel synchronized switch harvesting on ...


Dynamic Optimization Based Reactive Power Planning For Improving Short-Term Voltage Performance, Magesh Kumar Paramasivam Jan 2015

Dynamic Optimization Based Reactive Power Planning For Improving Short-Term Voltage Performance, Magesh Kumar Paramasivam

Graduate Theses and Dissertations

Short term voltage stability in the form of delayed voltage recovery (FIDVR) poses a significant threat to system stability and reliability. This work examines the voltage instability issue in a power system with dense concentration of induction motor loads and applies dynamic VAR injection as a counter-measure to ensure short term voltage stability following a large disturbance. The dynamic behavior of motor loads, such as decelerating and stalling, is considered as the major cause of FIDVR incidents especially during summer peak load conditions in areas where low inertia single-phase air conditioning (A/C) motors comprise a significant portion of the ...


Energy Efficiency In Cognitive Radio Network: Study Of Cooperative Sensing Using Different Channel Sensing Methods, Chenxuan Cui Jan 2015

Energy Efficiency In Cognitive Radio Network: Study Of Cooperative Sensing Using Different Channel Sensing Methods, Chenxuan Cui

Graduate Theses and Dissertations

When cognitive radio (CR) operates, it starts by sensing spectrum and looking for idle bandwidth. There are several methods for CR to make a decision on either the channel is occupied or idle, for example, energy detection scheme, cyclostationary detection scheme and matching filtering detection scheme [1]. Among them, the most common method is energy detection scheme because of its algorithm and implementation simplicities [2]. There are two major methods for sensing, the first one is to sense single channel slot with varying bandwidth, whereas the second one is to sense multiple channels and each with same bandwidth. After sensing ...


Development Of Smartphone-Based Spectroscopy Instruments For Diagnostic Test Analysis, Benjamin Jin Seong Ch'ng Jan 2015

Development Of Smartphone-Based Spectroscopy Instruments For Diagnostic Test Analysis, Benjamin Jin Seong Ch'ng

Graduate Theses and Dissertations

The latest generation of smartphones are more powerful than the first computer that sent the man to the moon. These smartphones are increasingly seen as handheld computers due to the capabilities that can be done with smartphones. Therefore, in this thesis, we will demonstrate the utilization of a smartphone-based spectrometer using the CMOS CCD chip of the camera. The characterization and integration between the smartphone and spectrometer is done to ensure robust and reliable results. The smartphone-based spectrometer is able to measure accurately and made to be comparable to industrial spectrometers. This research was done in order to attempt to ...


Spectral Diffusion Map Approach For Structural Health Monitoring Of Wind Turbine Blades Using Distributed Sensors, Venkatesh Chinde Jan 2015

Spectral Diffusion Map Approach For Structural Health Monitoring Of Wind Turbine Blades Using Distributed Sensors, Venkatesh Chinde

Graduate Theses and Dissertations

Distributed Sensor Networks (DSN) has emerged as a sensing paradigms in the structural engineering field due to the application of Structural Health Monitoring (SHM) for large-scale structures which results in accurately diagnosing the health of structures and enhancing the reliability and robustness of monitoring systems. The multisensor network greatly enhances the feasibility of applying SHM and also provides awareness of structural damage. In this work, we develop data-driven method for the diagnosis of damage in mechanical structures using an array of distributed sensors. The proposed approach relies on comparing intrinsic geometry of data sets corresponding to the undamage and damage ...


Study Of Transport Properties And Defect Density Profile In Nanocrystalline Silicon Germanium Devices, Siva Konduri Jan 2015

Study Of Transport Properties And Defect Density Profile In Nanocrystalline Silicon Germanium Devices, Siva Konduri

Graduate Theses and Dissertations

Nanocrystalline Silicon-Germanium (nc-SiGe:H) is a useful material for photovoltaic devices and photo-detectors. Its bandgap can be tuned between Si (~1.1 eV) and Ge (~0.7 eV) by changing the alloy composition during growth. The material exhibits a good absorption extending to the infrared region even with thin layers. However previous work has shown that devices with higher Ge content have poor device performance. Also, very little work has been done previously to measure and understand the defect spectrum of nanocrystalline (Si,Ge). Defects control recombination, and hence, the performance of solar cell devices.

This work deals with studying ...


Fast Estimation Of Nonlinearities In Atomic Force Microscopy, Wenyu Wang Jan 2015

Fast Estimation Of Nonlinearities In Atomic Force Microscopy, Wenyu Wang

Graduate Theses and Dissertations

We propose a fast method to reconstruct the curve of tip-surface force v.s. distance

in Atomic Force Microscopy (AFM). A precise and fast force curve reconstruction can

help improve research in material science, biological science, chemistry, etc. Existing

techniques require multiple sinusoids at the input to introduce intermodulation terms,

i.e., exponential components at equally spaced frequencies, and the estimation is done

by balancing those terms. Instead of using intermodulation terms, our method tries to

balance time domain samples. The method is based on the assumption that a discrete

model approximates the continuous AFM model well when sampled at ...


Novel Acceleration Approaches Of Accurate And Efficient Modeling Of High Speed Interconnects In Layered Media, Hongsheng Xu Jan 2015

Novel Acceleration Approaches Of Accurate And Efficient Modeling Of High Speed Interconnects In Layered Media, Hongsheng Xu

Graduate Theses and Dissertations

Accurate modeling of interconnect structures is an important issue in modern high frequency circuit and chip design; such as the accurate computation of the frequency dependent internal impedance of interconnect structures, like wires and conducting

strips, and the accurate and efficient electromagnetic (EM) modeling for shielded microstrip structures, especially in multilayered medium.

In the first part of this dissertation, a rigorous volume integral equation (VIE) is developed for the current distributions over two-dimensional conducting cylinders.

For very low frequencies, it can be reduced to the widely-used quasi-static approximation. The different VIEs, surface integral equation (SIE), and partial differential equation (PDE ...


Network Topology Identification Based On Measured Data, Mahdi Zamanighomi Jan 2015

Network Topology Identification Based On Measured Data, Mahdi Zamanighomi

Graduate Theses and Dissertations

We consider the problem of modeling of systems and learning of models from a limited number of measurements. We also contribute to the development of inference algorithms that require high-dimensional data processing. As an inspiring example, a growing interest in biology is to determine dependencies among genes. Such problem, known as gene regulatory network inference, often leads to identifying of large networks through relatively small gene expression data.

The main purpose of the thesis is to develop models and learning methods for data based applications. In particular, we first build a dynamical model for gene-gene interactions to learn the topology ...


Effective Medium Modeling And Experimental Characterization Of Multilayer Dielectric With Periodic Inclusion, Teng Zhao Jan 2015

Effective Medium Modeling And Experimental Characterization Of Multilayer Dielectric With Periodic Inclusion, Teng Zhao

Graduate Theses and Dissertations

Multi-layered dielectric structures are widely seen in modern semiconductor industry. Their applications cover multi-scaled areas such as in chips, packagings and printed circuit boards. Effective medium modeling for these structures enables fast yet accurate analysis so that the computational cost are reduced dramatically. In this dissertation, the numerical modeling techniques and experimental validations are explored for a general multilayer dielectric with periodic inclusions structure.

The effective medium model based on the same reflection and transmission coefficients is introduced. The extraction procedure for effective constitutive parameters is described in detail. The branch cut issue in extraction procedure is examined and the ...


The Crypto-Aided Physical Layer Integrity Check In Cooperative Relaying Communication, Xudong Liu Jan 2015

The Crypto-Aided Physical Layer Integrity Check In Cooperative Relaying Communication, Xudong Liu

Graduate Theses and Dissertations

In the cooperative relaying communication, the system has to defend itself against the eavesdropper which may undermines the message integrity by sending the modified messages. We propose a physical layer integrity check scheme for cooperative relaying communication, where a source broadcast the signals to both destination target and an untrustworthy relay node. The approach exploits physical layer signals in detecting the modified messages conducted by the relay. We develop a scheme that utilizes a few cryptography information in the initial message packets to estimate the optimal detecting threshold. By applying the optimal detecting method, the proposed approach achieves almost same ...


Cellular Level Studies And Coil System Design For Transcranial Magnetic Stimulation, Yiwen Meng Jan 2015

Cellular Level Studies And Coil System Design For Transcranial Magnetic Stimulation, Yiwen Meng

Graduate Theses and Dissertations

Transcranial Magnetic Stimulation is a novel non-invasive neuromodulation technique to treat human brain disorders such as depression, Parkinson's disease and PTSD. It uses pulsed currents in the coils to generate time varying magnetic field which induce eddy currents in the conductive tissues of human brain. Recently, there are several research publications in the field of TMS, specifically on coil designs, clinical trials and some in-vivo animal studies.

Even though FDA has approved TMS technique to treat depression , the basic mechanism or how does the neural tissue react to TMS is still not well understood. Therefore, conducting in-vitro study on ...


Mems Graphene Strain Sensor, Clinton Wen-Chieh Young Jan 2015

Mems Graphene Strain Sensor, Clinton Wen-Chieh Young

Graduate Theses and Dissertations

Graphene is a two dimensional honeycomb structure of sp^2 hybridized carbon atoms that has possibilities in many applications due to its excellent mechanical and electrical properties. One application for Graphene is in the field of sensors. Graphene’s electronic properties do not degrade when it undergoes mechanical strain which is advantageous for strain sensors. In this thesis, certain properties, such as the piezo-resistivity and flexibility, of graphene will be explored to show how they can be utilized to make a strain sensing device. Our original fabrication process of patterning graphene and the transfer process of graphene onto a flexible ...


Sparse And Low Rank Signal Recovery With Partial Knowledge, Jinchun Zhan Jan 2015

Sparse And Low Rank Signal Recovery With Partial Knowledge, Jinchun Zhan

Graduate Theses and Dissertations

In the first part of this work, we study sparse recovery problem in the presence of bounded noise. We obtain performance guarantees for modified-CS and for its improved version, modified-CS-Add-LS-Del, for recursive reconstruction of a time sequence of sparse signals from a reduced set of noisy measurements available at each time. Under mild assumptions, we show that the support recovery error and reconstruction error of both algorithms are bounded by a time-invariant and small value at all times.

In the second part of this work, we study batch sparse recovery problem in the presence of large and low rank noise ...


Device Physics Of Organic And Perovskite Solar Cells, Mehran Samiee Esfahani Jan 2015

Device Physics Of Organic And Perovskite Solar Cells, Mehran Samiee Esfahani

Graduate Theses and Dissertations

We report on fundamental electronic properties of the PTB7:PCBM70 bulk heterojunction solar cells: Sub-gap quantum efficiency measurements determine the Urbach energy of tail states (33 meV) and D/A interfacial bandgap (1.34 eV). Density of deep defects is determined by capacitance spectroscopy, and is ~1016 cm-3.eV-1. By photo-current spectroscopy, we assess surface recombination velocity at D/A interface, which translates to a capture cross-section of ~10-16 cm2 for deep defects. These properties are then used in our analytical modeling. Using a multiple-level trap model, we compute recombination rates in the cells. The model can predict dark saturation ...


Multilevel Sequence Detection For Dynamic Mode Atomic Force Microscopy, Yan Ren Jan 2015

Multilevel Sequence Detection For Dynamic Mode Atomic Force Microscopy, Yan Ren

Graduate Theses and Dissertations

The atomic force microscope is an instrument that is widely used in fields such as biology, chemistry and medicine for imaging at the atomic level. In this work, we consider a specific mode of AFM usage, known as the dynamic mode where the AFM cantilever probe is forced sinusoidally. In the absence of interaction with the sample being imaged, the cantilever follows a predictable sinusoidal trajectory. The deflection of the cantilever probe changes when it interacts with the sample being imaged and imaging is performed by interpreting these changes.

In this work, we present a sequence detection based algorithm that ...


Mems-Compatible Processes For Fabricating Nanostructures And Their Applications, Yuan He Jan 2015

Mems-Compatible Processes For Fabricating Nanostructures And Their Applications, Yuan He

Graduate Theses and Dissertations

During the past decades, many different nanostructures have been successfully synthesized and developed. Due to their nanoscale dimensions, the nanostructures (i.e., nanostructured film, nanotubes, quantum dots) usually exhibit unique optical, electronic, or mechanical properties, which differ from those of the same bulk material. This dissertation focuses on the development and applications of two types of nanostructures: high aspect ratio (HAR) silicon nanostructures and anodic aluminum oxide (AAO) nanopores.

(i) High aspect ratio (HAR) silicon nanostructures, including nanopillars, nanoforest and nanotubes, have attracted enormous attention in the fields of energy harvesting and storage, biomedical sensing, drug delivery, and template-based nanofabrication ...


Switched-Compensation Technique In Switched-Capacitor Circuits For Achieving Fast Settling Performance, Jiaming Liu Jan 2015

Switched-Compensation Technique In Switched-Capacitor Circuits For Achieving Fast Settling Performance, Jiaming Liu

Graduate Theses and Dissertations

Resolving stability issue is one of the major challenges in designing a perfect op-amp, the most widely used analog circuit block. Many compensation techniques have been proposed to improve the stability performance of op amps, but virtually all these techniques were developed for continuous-time applications and subsequently applied to discrete-time applications (e.g., switched-capacitor circuits). Since the early 1980s, an increasing number of op-amps have been used in switched-capacitor circuits with no special compensation method applied. Consequently, there remains a need to explore the possibility of designing a unique compensation method specifically for switched-capacitor use.

A new switched-compensation technique (SCT ...


New Developments In Magneto-Optic Interferometric Switching, John William Pritchard Jan 2015

New Developments In Magneto-Optic Interferometric Switching, John William Pritchard

Graduate Theses and Dissertations

In the next few decades, it is likely that high bandwidth wireless and optical technologies will be placed in the spotlight as the dominant avenues for communication all over the world. It is arguable that this is currently the case, and that the expectation for higher data transfer speeds, more secure and reliable transmission, and longer communication range is on an exponential rise. Thus, much effort and emphasis is being put on these technologies to advance as quickly as possible.

For optical systems, the majority of research has been focused on the realization of all-optical transmission, that is, transmission such ...


Assessment Of Vlsi Resources Requirement For A Sliced Trusted Platform Module, Hala Mohammad Hamadeh Jan 2015

Assessment Of Vlsi Resources Requirement For A Sliced Trusted Platform Module, Hala Mohammad Hamadeh

Graduate Theses and Dissertations

Recent increases in cybercrime suggest questions such as: How can one trust a secure system? How can one protect private information from being stolen and maintain security? Trust in any system requires a foundation or root of trust. A root of trust is necessary to establish confidence that a machine is clean and that a software execution environment is secure. A root of trust can be implemented using the Trusted Platform Module (TPM), which is promising for enhancing security of general-purpose computing systems.

In cloud computing, one of the proposed approaches is to use homomorphic encryption to create k program ...


Hardware Trojan Vulnerability, Xing Cao Jan 2015

Hardware Trojan Vulnerability, Xing Cao

Graduate Theses and Dissertations

Many basic analog blocks and structures, which contain positive feedback loops, are vulnerable to the presence of one or more undesired stable equilibrium points. The phenomena of multiple equilibrium points is investigated with emphasis on using a temperature-domain representation to identify equilibrium points in some circuits that have a single positive feedback loop. By example, it is shown that the presence of multiple equilibrium points can often be observed as hysteresis in a plot of an output circuit electrical variable versus temperature obtained from a bidirectional temperature sweep over a temperature interval [T_1,T_2] of interest. The hysteresis can be ...


Detection Of Sub-Surface Stresses In Ferromagnetic Materials Using A New Barkhausen Noise Method, Orfeas Kypris Jan 2015

Detection Of Sub-Surface Stresses In Ferromagnetic Materials Using A New Barkhausen Noise Method, Orfeas Kypris

Graduate Theses and Dissertations

In this work, a new, non-destructive method for obtaining stress-depth gradients in ferromagnetic structures was developed, using the information contained within magnetic Barkhausen emissions. A depth- and stress-dependent model for the frequency spectrum of Barkhausen emissions was derived and fitted to measured data obtained from steel samples with controlled stress-depth gradients. To achieve this, a library of signal processing and optimization algorithms was developed, which allowed the analysis of large datasets. To validate experimental procedures, a number of solid mechanics finite element simulations were carried out. Proof of concept is demonstrated by assuming linear stress-depth gradients and successfully calculating the ...