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Articles 31 - 60 of 88
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Planar Organic Photovoltaic Devices, Feras Alzubi
Planar Organic Photovoltaic Devices, Feras Alzubi
Electronic Theses and Dissertations
Organic Photovoltaic devices (OPV) are considered to be attractive candidates for clean and renewable energy source because of their potential for low cost of fabrication, easy processing, and their mechanical flexibility. The device efficiency of OPV cells are limited by several factors. Among them are: (i) donor-acceptor interface, (ii) morphology of the materials, (iii) electrode-organic semiconductor (OSC) interface and (iv) device architecture such as active material thickness and electrode separation. Although, the donor-acceptor interface has been studied in detail, the commonly prevalent vertical OPV device structure does not allow a good understanding of the other key issues as the vertical …
Computational Methods For Comparative Non-Coding Rna Analysis: From Structural Motif Identification To Genome-Wide Functional Classification, Cuncong Zhong
Electronic Theses and Dissertations
Recent advances in biological research point out that many ribonucleic acids (RNAs) are transcribed from the genome to perform a variety of cellular functions, rather than merely acting as information carriers for protein synthesis. These RNAs are usually referred to as the non-coding RNAs (ncRNAs). The versatile regulation mechanisms and functionalities of the ncRNAs contribute to the amazing complexity of the biological system. The ncRNAs perform their biological functions by folding into specific structures. In this case, the comparative study of the ncRNA structures is key to the inference of their molecular and cellular functions. We are especially interested in …
Chemometric Applications To A Complex Classification Problem: Forensic Fire Debris Analysis, Erin Waddell
Chemometric Applications To A Complex Classification Problem: Forensic Fire Debris Analysis, Erin Waddell
Electronic Theses and Dissertations
Fire debris analysis currently relies on visual pattern recognition of the total ion chromatograms, extracted ion profiles, and target compound chromatograms to identify the presence of an ignitable liquid. This procedure is described in the ASTM International E1618-10 standard method. For large data sets, this methodology can be time consuming and is a subjective method, the accuracy of which is dependent upon the skill and experience of the analyst. This research aimed to develop an automated classification method for large data sets and investigated the use of the total ion spectrum (TIS). The TIS is calculated by taking an average …
Electrical, Optical And Chemical Properties Of Organic Photo Sensitve Materials, Zheng Shi
Electrical, Optical And Chemical Properties Of Organic Photo Sensitve Materials, Zheng Shi
Electronic Theses and Dissertations
Light as a “green” source of energy has become increasingly attractive throughout the past century and has shown versatility for the application of activating chemical reactions. Compared with traditional energy sources, it provides a more direct, selective and controllable method. My PhD study was focused on the study of photochemistry of organic materials in two different systems. The first system is regarding reversible photoacids which generate protons on irradiation. With the aim of systematically studying these novel types of long lived photoacids, a series of photoacids was designed, synthesized and whose chemical mechanism was thoroughly investigated. This type of photoacid …
Fabrication Of Metallic Antenna Arrays Using Nanoimprint Lithography, Yu-Wei Lin
Fabrication Of Metallic Antenna Arrays Using Nanoimprint Lithography, Yu-Wei Lin
Electronic Theses and Dissertations
This Thesis describes the development of a cost-effective process for patterning nanoscale metal antenna arrays. Soft ultraviolet (UV) Nanoimprint Lithography (NIL) into bilayer resist was chosen since it enables repeatable large-scale replication of nanoscale patterns with good lift-off properties using a simple low-cost process. Nanofabrication often involves the use of Electron Beam Lithography (EBL) which enables the definition of nanoscale patterns on small sample regions, typically < 1 mm 2 . However its sequential nature makes the large scale production of nanostructured substrates using EBL cost-prohibitive. NIL is a pattern replication method that can reproduce nanoscale patterns in a parallel fashion, allowing the low-cost and rapid production of a large number of nanopatterned samples based on a single nanostructured master mold. Standard NIL replicates patterns by pressing a nanostructured hard mold into a soft resist layer on a substrate resulting in exposed substrate regions, followed by an optional Reactive Ion Etching (RIE) step and the subsequent deposition of e.g. metal onto the exposed substrate area. However, non-vertical sidewalls of the features in the resist layer resulting from an imperfect hard mold, from reflow of the resist layer, or from isotropic etching in the RIE step iii may cause imperfect lift-off. To overcome this problem, a bilayer resist method can be used. Using stacked resist layers with different etch rates, undercut structures can be obtained after the RIE step, allowing for easy lift-off even when using a mold with non-vertical sidewalls. Experiments were carried out using a nanostructured negative SiO2 master mold. Various material combinations and processing methods were explored. The negative master mold was transferred to a positive soft mold, leaving the original master mold unaltered. The soft mold consisted of a 5 m thick top Poly(methyl methacrylate) (PMMA), or Polyvinyl alcohol (PVA) layer, a 1.5 mm thick Polydimethylsiloxane (PDMS) buffer layer, and a glass supporting substrate. The soft mold was pressed into a bilayer of 300 nm PMMA and 350 nm of silicon based UV-curable resist that was spin-coated onto a glass slide, and cured using UV radiation. The imprinted patterns were etched using RIE, exposing the substrate, followed by metal deposition and lift-off. The experiments show that the use of soft molds enables successful pattern transfer even in the presence of small dust particles between the mold and the resist layer. Feature sizes down to 280 nm were replicated successfully
Can One Hear...? An Exploration Into Inverse Eigenvalue Problems Related To Musical Instruments, Christine Adams
Can One Hear...? An Exploration Into Inverse Eigenvalue Problems Related To Musical Instruments, Christine Adams
Electronic Theses and Dissertations
The central theme of this thesis deals with problems related to the question, “Can one hear the shape of a drum?” first posed formally by Mark Kac in 1966. More precisely, can one determine the shape of a membrane with fixed boundary from the spectrum of the associated differential operator? For this paper, Kac received both the Lester Ford Award and the Chauvant Prize of the Mathematical Association of America. This problem has received a great deal of attention in the past forty years and has led to similar questions in completely different contexts such as “Can one hear the …
External Cavity Mode-Locked Semiconductor Lasers For The Generation Of Ultra-Low Noise Multi-Gigahertz Frequency Combs And Applications In Multi-Heterodyne Detection Of Arbitrary Optical Waveforms, Josue Davila-Rodriguez
External Cavity Mode-Locked Semiconductor Lasers For The Generation Of Ultra-Low Noise Multi-Gigahertz Frequency Combs And Applications In Multi-Heterodyne Detection Of Arbitrary Optical Waveforms, Josue Davila-Rodriguez
Electronic Theses and Dissertations
The construction and characterization of ultra-low noise semiconductor-based mode-locked lasers as frequency comb sources with multi-gigahertz combline-to-combline spacing is studied in this dissertation. Several different systems were built and characterized. The first of these systems includes a novel mode-locking mechanism based on phase modulation and periodic spectral filtering. This mode-locked laser design uses the same intra-cavity elements for both mode-locking and frequency stabilization to an intra-cavity, 1,000 Finesse, Fabry-Pérot Etalon (FPE). On a separate effort, a mode-locked laser based on a Slab-Coupled Optical Waveguide Amplifier (SCOWA) was built. This system generates a pulse-train with residual timing jitter of
Curvelets And The Radon Transform, Jill Dickerson
Curvelets And The Radon Transform, Jill Dickerson
Electronic Theses and Dissertations
Computed Tomography (CT) is the standard in medical imaging field. In this study, we look at the curvelet transform in an attempt to use it as a basis for representing a function. In doing so, we seek a way to reconstruct a function from the Radon data that may produce clearer results. Using curvelet decomposition, any known function can be represented as a sum of curvelets with corresponding coefficients. It can be shown that these corresponding coefficients can be found using the Radon data, even if the function is unknown. The use of curvelets has the potential to solve partial …
Optimization Problem In Single Period Markets, Tian Jiang
Optimization Problem In Single Period Markets, Tian Jiang
Electronic Theses and Dissertations
There had been a number of researches that investigated on the security market without transaction costs. The focus of this research is in the area that when the security market with transaction costs is fair and in such fair market how one chooses a suitable portfolio to optimize the financial goal. The research approach adopted in this thesis includes linear algebra and elementary probability. The thesis provides evidence that we can maximize expected utility function to achieve our goal (maximize expected return under certain risk tolerance). The main conclusions drawn from this study are under certain conditions the security market …
Discriminative Dictionary Learning With Spatial Constraints, Muhammad Nazar Khan
Discriminative Dictionary Learning With Spatial Constraints, Muhammad Nazar Khan
Electronic Theses and Dissertations
In this thesis, we investigate the use of dictionary learning for discriminative tasks on natural images. Our contributions can be summarized as follows: • We introduce discriminative deviation based learning to achieve principled handling of the reconstruction-discrimination tradeoff that is inherent to discriminative dictionary learning. • Since natural images obey a strong smoothness prior, we show how spatial smoothness constraints can be incorporated into the learning formulation by embedding dictionary learning into Conditional Random Field (CRF) learning. We demonstrate that such smoothness constraints can lead to state-of-the-art performance for pixel-classification tasks. • Finally, we lay down the foundations of super-latent …
Absorptive And Refractive Optical Nonlinearities In Organic Molecules And Semiconductors, Davorin Peceli
Absorptive And Refractive Optical Nonlinearities In Organic Molecules And Semiconductors, Davorin Peceli
Electronic Theses and Dissertations
The main purpose of this dissertation to investigate photophysical properties, third order nonlinearity and free carrier absorption and refraction in organic materials and semiconductors. Special emphasis of this dissertation is on characterization techniques of molecules with enhanced intersystem crossing rate and study of different approaches of increasing triplet quantum yield in organic molecules. Both linear and nonlinear characterization methods are described. Linear spectroscopic characterization includes absorption, fluorescence, quantum yield, anisotropy, and singletoxygen generation measurements. Nonlinear characterization, performed by picosecond and femtosecond laser systems (single and double pump-probe and Z-scan measurements), includes measurements of the triplet quantum yields, excited-state absorption, two-photon …
Development Of An Efficient Molecular Single-Electron Transport Spectroscopy, Alvar Garrigues
Development Of An Efficient Molecular Single-Electron Transport Spectroscopy, Alvar Garrigues
Electronic Theses and Dissertations
In this thesis I present a complete and detailed guide for the development process and fabrication of efficient single-electron transistors (SETs) and a better single-molecule magnets (SMMs) deposition yield. Starting from a commercial Si/SiO2 wafer I show the steps for the deposition of different layers to fabricate a SET as well as the improvements achieved in those for a completely functional SET device. The development process is based on a combination of optical lithography and e-beam lithography with metal deposition in ultra-high vacuum. The improvements involve a better conductance in the Al gate component, with a controlled formation of the …
A Compiler-Based Framework For Automatic Extraction Of Program Skeletons For Exascale Hardware/Software Co-Design, Amruth Rudraiah Dakshinamurthy
A Compiler-Based Framework For Automatic Extraction Of Program Skeletons For Exascale Hardware/Software Co-Design, Amruth Rudraiah Dakshinamurthy
Electronic Theses and Dissertations
The design of high-performance computing architectures requires performance analysis of largescale parallel applications to derive various parameters concerning hardware design and software development. The process of performance analysis and benchmarking an application can be done in several ways with varying degrees of fidelity. One of the most cost-effective ways is to do a coarse-grained study of large-scale parallel applications through the use of program skeletons. The concept of a “program skeleton” that we discuss in this paper is an abstracted program that is derived from a larger program where source code that is determined to be irrelevant is removed for …
Automatically Acquiring A Semantic Network Of Related Concepts, Sean Szumlanski
Automatically Acquiring A Semantic Network Of Related Concepts, Sean Szumlanski
Electronic Theses and Dissertations
We describe the automatic acquisition of a semantic network in which over 7,500 of the most frequently occurring nouns in the English language are linked to their semantically related concepts in the WordNet noun ontology. Relatedness between nouns is discovered automatically from lexical co-occurrence in Wikipedia texts using a novel adaptation of an information theoretic inspired measure. Our algorithm then capitalizes on salient sense clustering among these semantic associates to automatically disambiguate them to their corresponding WordNet noun senses (i.e., concepts). The resultant concept-to-concept associations, stemming from 7,593 target nouns, with 17,104 distinct senses among them, constitute a large-scale semantic …
An Adhesive Vinyl-Acrylic Electrolyte And Electrode Binder For Lithium Batteries, Binh Tran
An Adhesive Vinyl-Acrylic Electrolyte And Electrode Binder For Lithium Batteries, Binh Tran
Electronic Theses and Dissertations
This dissertation describes a new vinyl-acrylic copolymer that displays great potential for applications in lithium ion batteries by enabling processes that are novel, faster, safer, and less costly than existing manufacturing methods. Overall, the works presented are based on tailored chemical synthesis directly applied to lithium ion battery manufacturing. Current manufacturing methods still have many flaws such as toxic processes and other time consuming if not costly steps. Understanding the chemistry of materials and processes related to battery manufacturing allows the design of techniques and methods that can ultimately improve the performance of existing batteries while reducing the cost. Chapter …
Injection Locking Of Semiconductor Mode-Locked Lasers For Long-Term Stability Of Widely Tunable Frequency Combs, Charles Williams
Injection Locking Of Semiconductor Mode-Locked Lasers For Long-Term Stability Of Widely Tunable Frequency Combs, Charles Williams
Electronic Theses and Dissertations
Harmonically mode-locked semiconductor lasers with external ring cavities offer high repetition rate pulse trains while maintaining low optical linewidth via long cavity storage times. Single frequency injection locking generates widely-spaced and tunable frequency combs from these harmonically mode-locked lasers, while stabilizing the optical frequencies. The output is stabilized long-term with the help of a feedback loop utilizing either a novel technique based on Pound-Drever-Hall stabilization or by polarization spectroscopy. Error signals of both techniques are simulated and compared to experimentally obtained signals. Frequency combs spaced by 2.5 GHz and ~10 GHz are generated, with demonstrated optical sidemode suppression of unwanted …
Exchange Coupling In Molecular Magnets: Zero, One And Three Dimensions, Asma Amjad
Exchange Coupling In Molecular Magnets: Zero, One And Three Dimensions, Asma Amjad
Electronic Theses and Dissertations
Molecular magnets with different dimensionality, whether they are zero-dimensional singlemolecule magnets (SMM) or one-dimensional single-chain magnets (SCM) are very interesting, since they allow probing the fundamental aspects bordering quantum and classical physics at the nanoscale level. This dissertation covers experimental studies of two Mn-based exchangecoupled molecule-based magnets and two Co-based single-chain magnets, using both dc Halleffect magnetometry and electron paramagnet resonance (EPR) techniques. In these multidimensional systems, the spin of the molecule exhibits quantum mechanical behavior at low temperature. It is quite interesting to observe the effect of magnetic exchange interactions on the magnetic properties of various complexes; hence they …
Nonparametric And Empirical Bayes Estimation Methods, Rida Benhaddou
Nonparametric And Empirical Bayes Estimation Methods, Rida Benhaddou
Electronic Theses and Dissertations
In the present dissertation, we investigate two different nonparametric models; empirical Bayes model and functional deconvolution model. In the case of the nonparametric empirical Bayes estimation, we carried out a complete minimax study. In particular, we derive minimax lower bounds for the risk of the nonparametric empirical Bayes estimator for a general conditional distribution. This result has never been obtained previously. In order to attain optimal convergence rates, we use a wavelet series based empirical Bayes estimator constructed in Pensky and Alotaibi (2005). We propose an adaptive version of this estimator using Lepski’s method and show that the estimator attains …
Non-Destructive Analysis Of Trace Textile Fiber Evidence Via Room-Temperature Fluorescence Spectrocopy, Krishnaveni Appalaneni
Non-Destructive Analysis Of Trace Textile Fiber Evidence Via Room-Temperature Fluorescence Spectrocopy, Krishnaveni Appalaneni
Electronic Theses and Dissertations
Forensic fiber evidence plays an important role in many criminal investigations. Nondestructive techniques that preserve the physical integrity of the fibers for further court examination are highly valuable in forensic science. Non-destructive techniques that can either discriminate between similar fibers or match a known to a questioned fiber - and still preserve the physical integrity of the fibers for further court examination - are highly valuable in forensic science. When fibers cannot be discriminated by non-destructive tests, the next reasonable step is to extract the questioned and known fibers for dye analysis with a more selective technique such as high-performance …
Mode-Division Multiplexed Transmission In Few-Mode Fibers, Neng Bai
Mode-Division Multiplexed Transmission In Few-Mode Fibers, Neng Bai
Electronic Theses and Dissertations
As a promising candidate to break the single-mode fiber capacity limit, mode-division multiplexing (MDM) explores the spatial dimension to increase transmission capacity in fiberoptic communication. Two linear impairments, namely loss and multimode interference, present fundamental challenges to implementing MDM. In this dissertation, techniques to resolve these two issues are presented. To de-multiplex signals subject to multimode interference in MDM, Multiple-InputMultiple-Output (MIMO) processing using adaptive frequency-domain equalization (FDE) is proposed and investigated. Both simulations and experiments validate that FDE can reduce the algorithmic complexity significantly in comparison with the conventional time-domain equalization (TDE) while achieving similar performance as TDE. To further …
Bridging The Gap Between Fun And Fitness: Instructional Techniques And Real-World Applications For Full-Body Dance Games, Emiko Charbonneau
Bridging The Gap Between Fun And Fitness: Instructional Techniques And Real-World Applications For Full-Body Dance Games, Emiko Charbonneau
Electronic Theses and Dissertations
Full-body controlled games offer the opportunity for not only entertainment, but education and exercise as well. Refined gameplay mechanics and content can boost intrinsic motivation and keep people playing over a long period of time, which is desirable for individuals who struggle with maintaining a regular exercise program. Within this gameplay genre, dance rhythm games have proven to be popular with game console owners. Yet, while other types of games utilize story mechanics that keep players engaged for dozens of hours, motion-controlled dance games are just beginning to incorporate these elements. In addition, this control scheme is still young, only …
Valuation Of Over-The-Counter (Otc) Derivatives With Collateralization, Leon Guerrero
Valuation Of Over-The-Counter (Otc) Derivatives With Collateralization, Leon Guerrero
Electronic Theses and Dissertations
Collateralization in over-the-counter (OTC) derivatives markets has grown rapidly over the past decade, and even faster in the past few years, due to the impact of the recent financial crisis and the particularly important attention to the counterparty credit risk in derivatives contracts. The addition of collateralization to such contracts significantly reduces the counterparty credit risk and allows to offset liabilities in case of default. We study the problem of valuation of OTC derivatives with payoff in a single currency and with single underlying asset for the cases of zero, partial, and perfect collateralization. We assume the derivative is traded …
Properties Of High Energy Laser Light Transmission Through Large Core Optical Cables, Christopher Kennedy
Properties Of High Energy Laser Light Transmission Through Large Core Optical Cables, Christopher Kennedy
Electronic Theses and Dissertations
Laser induced damage is of interest in studying the transmission of large amounts of optical energy through step-index, large core multimode fibers. Optical fibers often have to be routed around objects when laser light is being transmitted between two locations which require the fiber to bend into a curve. Depending on how tight the bend is, this can result in transmission losses or even catastrophic damage when the energy density of the laser pulse exceeds the damage threshold of silica glass. The purpose of this study is to: Establish a minimum bend radius that would allow high energy (GW/cm2 ) …
Dynamic Feedback Pulse Shaping For High Power Chirped Pulse Amplification System, Dat Nguyen
Dynamic Feedback Pulse Shaping For High Power Chirped Pulse Amplification System, Dat Nguyen
Electronic Theses and Dissertations
The topic of this proposal is the development of high peak power laser sources with a focus on linearly chirped pulse laser sources. In the past decade chirped optical pulses have found a plethora of applications such as photonic analog-to-digital conversion, optical coherence tomography, laser ranging, etc. This dissertation analyzes the aforementioned applications of linearly chirped pulses and their technical requirements, as well as the performance of previously demonstrated parabolic pulse shaping approaches. The experimental research addresses the topic of parabolic pulse generation in two distinct ways. First, pulse shaping technique involving a time domain approach is presented, that results …
Dynamical Invariants And The Fluid Impulse In Plasma Models, Martin Michalak
Dynamical Invariants And The Fluid Impulse In Plasma Models, Martin Michalak
Electronic Theses and Dissertations
Much progress has been made in understanding of plasmas through the use of the MHD equations and newer models such as Hall MHD and electron MHD. As with most equations of fluid behavior, these equations are nonlinear, and no general solutions can be found. The use of invariant structures allows limited predictions of fluid behavior without requiring a full solution of the underlying equations. The use of gauge transformation can allow the creation of new invariants, while differential geometry offers useful tools for constructing additional invariants from those that are already known. Using these techniques, new geometric, integral and topological …
Femtosecond Filament Interaction As A Probe For Molecular Alignment, Erik Mckee
Femtosecond Filament Interaction As A Probe For Molecular Alignment, Erik Mckee
Electronic Theses and Dissertations
Femtosecond laser filamentation is a highly nonlinear propagation mode. When a laser pulse propagates with a peak power exceeding a critical value Pcr (5 GW at 800 nm in air), the Kerr effect tends to collapse the beam until the intensity is high enough to ionize the medium, giving rise to plasma defocusing. A dynamic competition between these two effects takes place leaving a thin and weakly ionized plasma channel in the trail of the pulse. When an ultrafast laser pulse interacts with molecules, it will align them, spinning them about their axis of polarization. As the quantum rotational wave …
On The Capillary Electrophoresis Of Monohydroxy Metabolites Of Polycyclic Aromatic Hydrocarbons And Its Application To The Analysis Of Biological Matrices, Gaston Knobel
Electronic Theses and Dissertations
Polycyclic aromatic hydrocarbons (PAH) are a class of environmental pollutants consisting of a minimum of two fused aromatics rings originating from the incomplete combustion of organic matter and/or anthropogenic sources. Numerous possible anthropogenic and natural sources make the presence of PAH ubiquitous in the environment. The carcinogenic nature of some PAH and their ubiquitous presence makes their chemical analysis a topic of environmental and toxicological importance. Although environmental monitoring of PAH is an important step to prevent exposure to contaminated sites, it provides little information on the actual uptake and subsequent risks. Parent PAH are relatively inert and need metabolic …
Climate Change Impacts On Rainfed Corn Production In Malawi, Kondwani Msowoya
Climate Change Impacts On Rainfed Corn Production In Malawi, Kondwani Msowoya
Electronic Theses and Dissertations
Agriculture is the mainstay of the economy in Malawi and accounts for 40% of the Gross Domestic Product (GDP) and 90% of the export revenues. Corn (maize) is the major cereal crop grown as staple food under rainfed conditions, covers over 92% of the total agricultural area, and contributes 54% of the caloric intake. Corn production is the principle occupation and major source of income for over 85% of the total population in Malawi. Issues of hunger and food insecurity for the entire nation are associated with corn scarcity and low production. Global warming is expected to cause climate change …
Developing A Group Decision Support System (Gdss) For Decision Making Under Uncertainty, Soroush Mokhtari
Developing A Group Decision Support System (Gdss) For Decision Making Under Uncertainty, Soroush Mokhtari
Electronic Theses and Dissertations
Multi-Criteria Decision Making (MCDM) problems are often associated with tradeoffs between performances of the available alternative solutions under decision making criteria. These problems become more complex when performances are associated with uncertainty. This study proposes a stochastic MCDM procedure that can handle uncertainty in MCDM problems. The proposed method coverts a stochastic MCDM problem into many deterministic ones through a Monte-Carlo (MC) selection. Each deterministic problem is then solved using a range of MCDM methods and the ranking order of the alternatives is established for each deterministic MCDM. The final ranking of the alternatives can be determined based on winning …
Metrology Of Volume Chirped Bragg Gratings Recorded In Photo-Thermo-Refractive Glass For Ultrashort Pulse Stretching And Compressing, Christopher Lantigua
Metrology Of Volume Chirped Bragg Gratings Recorded In Photo-Thermo-Refractive Glass For Ultrashort Pulse Stretching And Compressing, Christopher Lantigua
Electronic Theses and Dissertations
Chirped Bragg gratings (CBGs) recorded in photo-thermo-refractive (PTR) glass provide a very efficient and robust way to stretch and compress ultra-short laser pulses. These gratings offer the ability to stretch pulses from hundreds of femtoseconds, to the order of 1 ns and then recompress them. However, in order to achieve pulse stretching of this magnitude, 100 mm thick CBGs are needed. Using these CBGs to both stretch, and re-compress the pulse thus requires propagation through 200 mm of optical glass. This therefore demands perfect control of the glass homogeneity, as well as the holographic recording process of the CBG. In …