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Articles 3601 - 3630 of 4194

Full-Text Articles in Physical Sciences and Mathematics

High Gain / Broadband Oxide Glasses For Next Generation Raman Amplifiers, Clara Rivero Jan 2005

High Gain / Broadband Oxide Glasses For Next Generation Raman Amplifiers, Clara Rivero

Electronic Theses and Dissertations

Interest in Raman amplification has undergone a revival due to the rapidly increasing bandwidth requirements for communications transmission, both for long haul and local area networks, and recent developments in the telecom fiber industry and diode laser technology. In contrast to rare earth doped fiber amplifiers, for which the range of wavelengths is fixed and limited, Raman gain bandwidths are larger and the operating wavelength is fixed only by the pump wavelength and the bandwidth of the Raman active medium. In this context, glasses are the material of choice for this application due to their relatively broad spectral response, and …

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Measurement And Characterization Of Microwave Transient Electromagnetic Fields Generated From Laser/Matter Interaction, Nicholas Barbieri Jan 2005

Measurement And Characterization Of Microwave Transient Electromagnetic Fields Generated From Laser/Matter Interaction, Nicholas Barbieri

Electronic Theses and Dissertations

From past experiments conducted with high intensity lasers, it has been known for some time that laser matter interactions result in the emission of short, transient electromagnetic pulses. Previous investigations into laser generated electromagnetic pulses provide basic information regarding frequencies where such pulses may be present, along with the time duration of the pulses. Such investigations have also demonstrated a number of measurement techniques in which basic information on the pulses may be obtained. The purpose of this current investigation is to obtain a more thorough description and understands of electromagnetic pulses generated for laser matter interaction. To this end, …

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Synthesis Of Alkylthiol-Containing Fluorene Derivatives For Gold Nanoparticle Functionalization, Sriram Mukundarajan Jan 2005

Synthesis Of Alkylthiol-Containing Fluorene Derivatives For Gold Nanoparticle Functionalization, Sriram Mukundarajan

Electronic Theses and Dissertations

A novel synthetic methodology has been developed for attaching fluorene derivatives, containing different types of electron donating and accepting groups at the 2 and 7 positions, to gold nanoparticles of different sizes by exploiting the affinity of the thiol functional group for gold. The distance between the dye and nanoparticles was varied by introducing two alkyl chains containing different number of carbon atoms at the 9 position on the fluorene ring system. The methodology that was developed gave enough scope for performing Radiative Decay Engineering (RDE) studies, in order to investigate the impact of gold nanoparticles on the singlet oxygen …

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Design Of A Dynamic Focusing Microscope Objective For Oct Imaging, Supraja Murali Jan 2005

Design Of A Dynamic Focusing Microscope Objective For Oct Imaging, Supraja Murali

Electronic Theses and Dissertations

Optical Coherence Tomography (OCT) is a novel optical imaging technique that has assumed significant importance in bio-medical imaging in the last two decades because it is non-invasive and provides accurate, high resolution images of three dimensional cross-sections of body tissue, exceeding the capabilities of the current predominant imaging technique –ultrasound. In this thesis, high resolution OCT is investigated for in vivo detection of abnormal skin pathology for the early diagnosis of cancer. The technology presented is based on a dynamic focusing microscopic imaging probe conceived for skin imaging and the detection of abnormalities in the epithelium. A novel method for …

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Qos In Cognitive Packet Networks: Adaptive Routing, Flow And Congestion Control, Pu Su Jan 2005

Qos In Cognitive Packet Networks: Adaptive Routing, Flow And Congestion Control, Pu Su

Electronic Theses and Dissertations

With the emergence of various applications that have different Quality of Service (QoS) requirements, the capability of a network to support QoS becomes more and more important and necessary. This dissertation explores QoS in Cognitive Packet Networks (CPN) by using adaptive routing, flow and congestion control. We present a detailed description and analysis of our proposed routing algorithms based on single and multiple QoS constraints. An online estimation of packet loss rate over a path is introduced. We implement and evaluate the adaptive routing scheme in an experimental CPN test-bed. Our experiments support our claims that the users can achieve …

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Phase Synchronization In Three-Dimensional Lattices And Globally Coupled Populations Of Nonidentical Rossler Oscillators, Limin Qi Jan 2005

Phase Synchronization In Three-Dimensional Lattices And Globally Coupled Populations Of Nonidentical Rossler Oscillators, Limin Qi

Electronic Theses and Dissertations

A study on phase synchronization in large populations of nonlinear dynamical systems is presented in this thesis. Using the well-known Rossler system as a prototypical model, phase synchronization in one oscillator with periodic external forcing and in two-coupled nonidentical oscillators was explored at first. The study was further extended to consider three-dimensional lattices and globally coupled populations of nonidentical oscillators, in which the mathematical formulation that represents phase synchronization in the generalized N-coupled Rossler system was derived and several computer programs that perform numerical simulations were developed. The results show the effects of coupling dimension, coupling strength, population size, and …

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System Design And Optimization Of Optical Coherence Tomography, Avni Ceyhun Akcay Jan 2005

System Design And Optimization Of Optical Coherence Tomography, Avni Ceyhun Akcay

Electronic Theses and Dissertations

Optical coherence imaging, including tomography (OCT) and microscopy (OCM), has been a growing research field in biomedical optical imaging in the last decade. In this imaging modality, a broadband light source, thus of short temporal coherence length, is used to perform imaging via interferometry. A challenge in optical coherence imaging, as in any imaging system towards biomedical diagnosis, is the quantification of image quality and optimization of the system components, both a primary focus of this research. We concentrated our efforts on the optimization of the imaging system from two main standpoints: axial point spread function (PSF) and practical steps …

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Compressed Pattern Matching For Text And Images, Tao Tao Jan 2005

Compressed Pattern Matching For Text And Images, Tao Tao

Electronic Theses and Dissertations

The amount of information that we are dealing with today is being generated at an ever-increasing rate. On one hand, data compression is needed to efficiently store, organize the data and transport the data over the limited-bandwidth network. On the other hand, efficient information retrieval is needed to speedily find the relevant information from this huge mass of data using available resources. The compressed pattern matching problem can be stated as: given the compressed format of a text or an image and a pattern string or a pattern image, report the occurrence(s) of the pattern in the text or image …

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Formalization Of Input And Output In Modern Operating Systems: The Hadley Model, Matthew Gerber Jan 2005

Formalization Of Input And Output In Modern Operating Systems: The Hadley Model, Matthew Gerber

Electronic Theses and Dissertations

We present the Hadley model, a formal descriptive model of input and output for modern computer operating systems. Our model is intentionally inspired by the Open Systems Interconnection model of networking; I/O as a process is defined as a set of translations between a set of computer-sensible forms, or layers, of information. To illustrate an initial application domain, we discuss the utility of the Hadley model and a potential associated I/O system as a tool for digital forensic investigators. To illustrate practical uses of the Hadley model we present the Hadley Specification Language, an essentially functional language designed to allow …

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Network Intrusion Detection: Monitoring, Simulation And Visualization, Mian Zhou Jan 2005

Network Intrusion Detection: Monitoring, Simulation And Visualization, Mian Zhou

Electronic Theses and Dissertations

This dissertation presents our work on network intrusion detection and intrusion sim- ulation. The work in intrusion detection consists of two different network anomaly-based approaches. The work in intrusion simulation introduces a model using explicit traffic gen- eration for the packet level traffic simulation. The process of anomaly detection is to first build profiles for the normal network activity and then mark any events or activities that deviate from the normal profiles as suspicious. Based on the different schemes of creating the normal activity profiles, we introduce two approaches for intrusion detection. The first one is a frequency-based approach which …

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Analyzing The Community Structure Of Web-Like Networks: Models And Algorithms, Aurel Cami Jan 2005

Analyzing The Community Structure Of Web-Like Networks: Models And Algorithms, Aurel Cami

Electronic Theses and Dissertations

This dissertation investigates the community structure of web-like networks (i.e., large, random, real-life networks such as the World Wide Web and the Internet). Recently, it has been shown that many such networks have a locally dense and globally sparse structure with certain small, dense subgraphs occurring much more frequently than they do in the classical Erdös-Rényi random graphs. This peculiarity--which is commonly referred to as community structure--has been observed in seemingly unrelated networks such as the Web, email networks, citation networks, biological networks, etc. The pervasiveness of this phenomenon has led many researchers to believe that such cohesive groups of …

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Ramanujan's Formula For The Riemann Zeta Function Extended To L-Functions, Katherine J. Merrill Jan 2005

Ramanujan's Formula For The Riemann Zeta Function Extended To L-Functions, Katherine J. Merrill

Electronic Theses and Dissertations

Ramanujan's formula for the Riemann-zeta function is one of his most celebrated. Beginning with M. Lerch in 1900, there have been many mathematicians who have worked with this formula. Many proofs of this formula have been given over the last 100 years utilizing many techniques and extending the formula. This thesis provides a proof of this formula by the Mittag-Leffler partial fraction expansion technique. In comparison to the most recent proof by utilizing contour integration, the proof in this thesis is based on a more natural growth hypothesis. In addition to a less artificial approach, the partial fraction expansion technique …

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Grassland And Woodland Bird Occurrence And Habitat Selection In The Prairie-Forest Transition Zone Of Minnesota, Thomas Robert Cooper Jan 2005

Grassland And Woodland Bird Occurrence And Habitat Selection In The Prairie-Forest Transition Zone Of Minnesota, Thomas Robert Cooper

Electronic Theses and Dissertations

Numerous species of woodland and grassland nesting birds have experienced population declines in the midwestern United States. Habitat loss and habitat fragmentation are suspected to be two of the underlying causes for the population declines of woodland and grassland birds. The Minnesota Valley Wetland Management District (WMD) covers 14 counties in southeastern Minnesota in the transition zone between forested and prairie ecoregions. Little information is available relative to which birds are using grassland or woodland habitat within the WMD and how their presence or absence is related to the available habitat conditions. Therefore, my study objectives were to: 1) determine …

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Early Paleozoic Orogenesis In The Maine-Quebec Appalachians, Christopher Charles Gerbi Jan 2005

Early Paleozoic Orogenesis In The Maine-Quebec Appalachians, Christopher Charles Gerbi

Electronic Theses and Dissertations

Accretionary orogens, such as the Appalachian orogen, form by episodic docking of oceanic and continental fragments. Two factors that exert significant control on the development of an accretionary orogen are: (1) the nature and source of the accreting fragments, and (2) the thermal and deformational structure of the crust. This study addresses aspects of both of these controls. In the Northern Appalachians, a long-lived but untested hypothesis suggested that Early Paleozoic accretion in western Maine, which marked the initiation of Appalachian development, involved the docking of an island arc. My goal was to test this hypothesis for the Maine-Qukbec segment …

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Porphyroblast Kinematics And Crenulation Cleavage Development In The Aureole Of The Mooselookmeguntic Pluton, Western Maine, Matthew E. Dupee Jan 2005

Porphyroblast Kinematics And Crenulation Cleavage Development In The Aureole Of The Mooselookmeguntic Pluton, Western Maine, Matthew E. Dupee

Electronic Theses and Dissertations

The porphyroblastic pelitic schists of western Maine are ideal for studying the deformation and metamorphism that accompanies pluton emplacement. A regional lowpressure, high-temperature metamorphic event affected the areally extensive Silurian sediments with the thermal peak occuning ca. 404 Ma. This metamorphism produced the widespread assemblage staurolite + andalusite + biotite +I- garnet, and occurred during the late stages of development of a northeast-trending, steeply-dipping axial-surface foliation. A period of extensive plutonism accompanied and followed this Acadian-aged deformation and metamorphism. This study focuses specifically on the contact aureole of the Mooselookmeguntic pluton emplaced ca. 370 Ma. Contact metamorphism accompanied the development …

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Access Games: A Game Theoretic Framework For Fair Bandwidth Sharing In Distributed Systems, Sudipta Rakshit Jan 2005

Access Games: A Game Theoretic Framework For Fair Bandwidth Sharing In Distributed Systems, Sudipta Rakshit

Electronic Theses and Dissertations

In this dissertation, the central objective is to achieve fairness in bandwidth sharing amongst selfish users in a distributed system. Because of the inherent contention-based nature of the distributed medium access and the selfishness of the users, the distributed medium access is modeled as a non-cooperative game; designated as the Access Game. A p-CSMA type medium access scenario is proposed for all the users. Therefore, in the Access Game, each user has two actions to choose from: "transmit" and "wait". The outcome of the Access Game and payoffs to each user depends on the actions taken by all the users. …

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Creating Models Of Internet Background Traffic Suitable For Use In Evaluating Network Intrusion Detection Systems, Song Luo Jan 2005

Creating Models Of Internet Background Traffic Suitable For Use In Evaluating Network Intrusion Detection Systems, Song Luo

Electronic Theses and Dissertations

This dissertation addresses Internet background traffic generation and network intrusion detection. It is organized in two parts. Part one introduces a method to model realistic Internet background traffic and demonstrates how the models are used both in a simulation environment and in a lab environment. Part two introduces two different NID (Network Intrusion Detection) techniques and evaluates them using the modeled background traffic. To demonstrate the approach we modeled five major application layer protocols: HTTP, FTP, SSH, SMTP and POP3. The model of each protocol includes an empirical probability distribution plus estimates of application-specific parameters. Due to the complexity of …

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Optical Wave Propagation In Discrete Waveguide Arrays, Jared Hudock Jan 2005

Optical Wave Propagation In Discrete Waveguide Arrays, Jared Hudock

Electronic Theses and Dissertations

The propagation dynamics of light in optical waveguide arrays is characteristic of that encountered in discrete systems. As a result, it is possible to engineer the diffraction properties of such structures, which leads to the ability to control the flow of light in ways that are impossible in continuous media. In this work, a detailed theoretical investigation of both linear and nonlinear optical wave propagation in one- and two-dimensional waveguide lattices is presented. The ability to completely overcome the effects of discrete diffraction through the mutual trapping of two orthogonally polarized coherent beams interacting in Kerr nonlinear arrays of birefringent …

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Liquid Crystal Optics For Communications, Signal Processing And 3-D Microscopic Imaging, Sajjad Khan Jan 2005

Liquid Crystal Optics For Communications, Signal Processing And 3-D Microscopic Imaging, Sajjad Khan

Electronic Theses and Dissertations

This dissertation proposes, studies and experimentally demonstrates novel liquid crystal (LC) optics to solve challenging problems in RF and photonic signal processing, freespace and fiber optic communications and microscopic imaging. These include free-space optical scanners for military and optical wireless applications, variable fiber-optic attenuators for optical communications, photonic control techniques for phased array antennas and radar, and 3-D microscopic imaging. At the heart of the applications demonstrated in this thesis are LC devices that are non-pixelated and can be controlled either electrically or optically. Instead of the typical pixel-by-pixel control as is custom in LC devices, the phase profile across …

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Coherence Properties Of Optical Near-Fields, Adela Apostol Jan 2005

Coherence Properties Of Optical Near-Fields, Adela Apostol

Electronic Theses and Dissertations

Next generation photonics-based technologies will ultimately rely on novel materials and devices. For this purpose, phenomena at subwavelength scales are being studied to advance both fundamental knowledge and experimental capabilities. In this dissertation, concepts specific to near-field optics and experimental capabilities specific to near-field microscopy are used to investigate various aspects of the statistical properties of random electromagnetic fields in the vicinity of optically inhomogeneous media which emit or scatter radiation. The properties of such fields are being characterized within the frame of the coherence theory. While successful in describing the far-field properties of optical fields, the fundamental results of …

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Digital Vertical Aerial Camera System For High-Resolution Site Inspections In Conservation Easment Monitoring, Kenton Williams Jan 2005

Digital Vertical Aerial Camera System For High-Resolution Site Inspections In Conservation Easment Monitoring, Kenton Williams

Electronic Theses and Dissertations

A three-level satellite to ground monitoring scheme for conservation easement monitoring has been implemented in which high-resolution imagery serves as an intermediate step for inspecting high priority sites. A digital vertical aerial camera system was developed to fulfill the need for an economical source of imagery for this intermediate step. A method for attaching the camera system to small aircraft was designed, and the camera system was calibrated and tested. To ensure that the images obtained were of suitable quality for use in Level 2 inspections, rectified imagery was required to provide positional accuracy of 5 meters or less to …

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A New Hybrid Diffractive Photo-Mask Technology, Jin Won Sung Jan 2005

A New Hybrid Diffractive Photo-Mask Technology, Jin Won Sung

Electronic Theses and Dissertations

In the field of photolithography for micro-chip manufacturing, the photo-mask is used to print desired patterns on a proper photo-resist on wafer. The most common type of photo-mask is binary amplitude mask made an opaque layer of chrome. The principle and potential application of hybrid photo-mask with diffractive phase element and binary amplitude is presented in this dissertation paper from both numerical modeling and experimental research. The first important application is the characterization of aberration in the stepper system using hybrid diffractive photo-mask. By utilizing multiple diffractive illumination conditions, it is possible to characterize Zernike wave front aberration coefficients up …

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Transform Based And Search Aware Text Compression Schemes And Compressed Domain Text Retrieval, Nan Zhang Jan 2005

Transform Based And Search Aware Text Compression Schemes And Compressed Domain Text Retrieval, Nan Zhang

Electronic Theses and Dissertations

In recent times, we have witnessed an unprecedented growth of textual information via the Internet, digital libraries and archival text in many applications. While a good fraction of this information is of transient interest, useful information of archival value will continue to accumulate. We need ways to manage, organize and transport this data from one point to the other on data communications links with limited bandwidth. We must also have means to speedily find the information we need from this huge mass of data. Sometimes, a single site may also contain large collections of data such as a library database, …

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An Interactive Distributed Simulation Framework With Application To Wireless Networks And Intrusion Detection, Oleg Kachirski Jan 2005

An Interactive Distributed Simulation Framework With Application To Wireless Networks And Intrusion Detection, Oleg Kachirski

Electronic Theses and Dissertations

In this dissertation, we describe the portable, open-source distributed simulation framework (WINDS) targeting simulations of wireless network infrastructures that we have developed. We present the simulation framework which uses modular architecture and apply the framework to studies of mobility pattern effects, routing and intrusion detection mechanisms in simulations of large-scale wireless ad hoc, infrastructure, and totally mobile networks. The distributed simulations within the framework execute seamlessly and transparently to the user on a symmetric multiprocessor cluster computer or a network of computers with no modifications to the code or user objects. A visual graphical interface precisely depicts simulation object states …

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Recovery Of Hydrogen And Helium From Their Mixtures Using Metal Hydrides, Muzaffer Tonguc Oztek Jan 2005

Recovery Of Hydrogen And Helium From Their Mixtures Using Metal Hydrides, Muzaffer Tonguc Oztek

Electronic Theses and Dissertations

Waste streams of hydrogen and helium mixtures are produced at the Kennedy Space Center during purging of the hydrogen systems and supply lines. This process is done prior to and after hydrogen servicing. The purged waste gases are lost to the atmosphere, resulting in an annual loss of 2 million and 0.1 million standard cubic meters of helium and hydrogen, respectively. Recovery of these gases will have an economic benefit. Metals, alloys, and intermetallics are known to react with hydrogen in favorable conditions; therefore, they have the possibility of serving as separating and recovery agents. In this study, Mg2Ni, VTiNi …

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Messenger Rna Profiling: A Prototype Method For Body Fluidand Tissue Identification, Jane Juusola Jan 2005

Messenger Rna Profiling: A Prototype Method For Body Fluidand Tissue Identification, Jane Juusola

Electronic Theses and Dissertations

Conventional methods of body fluid identification use labor-intensive, technologically diverse techniques that are performed in a series, not parallel, manner and are costly in terms of time and sample. Furthermore, for some frequently encountered body fluids, such as saliva or vaginal secretions, no confirmatory technique exists. Terminally differentiated cells, such as blood lymphocytes or epithelial cells lining the oral cavity, have a unique pattern of gene expression, which is evinced by the presence and relative abundance of specific mRNA species. If the type and abundance of mRNAs can be determined in a stain or tissue sample recovered at the crime …

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Real-Time Realistic Rendering And High Dynamic Range Image Display And Compression, Ruifeng Xu Jan 2005

Real-Time Realistic Rendering And High Dynamic Range Image Display And Compression, Ruifeng Xu

Electronic Theses and Dissertations

This dissertation focuses on the many issues that arise from the visual rendering problem. Of primary consideration is light transport simulation, which is known to be computationally expensive. Monte Carlo methods represent a simple and general class of algorithms often used for light transport computation. Unfortunately, the images resulting from Monte Carlo approaches generally suffer from visually unacceptable noise artifacts. The result of any light transport simulation is, by its very nature, an image of high dynamic range (HDR). This leads to the issues of the display of such images on conventional low dynamic range devices and the development of …

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Planning And Scheduling For Large-Scaledistributed Systems, Han Yu Jan 2005

Planning And Scheduling For Large-Scaledistributed Systems, Han Yu

Electronic Theses and Dissertations

Many applications require computing resources well beyond those available on any single system. Simulations of atomic and subatomic systems with application to material science, computations related to study of natural sciences, and computer-aided design are examples of applications that can benefit from the resource-rich environment provided by a large collection of autonomous systems interconnected by high-speed networks. To transform such a collection of systems into a user's virtual machine, we have to develop new algorithms for coordination, planning, scheduling, resource discovery, and other functions that can be automated. Then we can develop societal services based upon these algorithms, which hide …

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Resource Allocation Schemes And Performance Evaluation Models For Wavelength Division Multiplexed Optical Networks, Mounire El Houmaidi Jan 2005

Resource Allocation Schemes And Performance Evaluation Models For Wavelength Division Multiplexed Optical Networks, Mounire El Houmaidi

Electronic Theses and Dissertations

Wavelength division multiplexed (WDM) optical networks are rapidly becoming the technology of choice in network infrastructure and next-generation Internet architectures. WDM networks have the potential to provide unprecedented bandwidth, reduce processing cost, achieve protocol transparency, and enable efficient failure handling. This dissertation addresses the important issues of improving the performance and enhancing the reliability of WDM networks as well as modeling and evaluating the performance of these networks. Optical wavelength conversion is one of the emerging WDM enabling technologies that can significantly improve bandwidth utilization in optical networks. A new approach for the sparse placement of full wavelength converters based …

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Tunable Liquid Crystal Photonic Devices, Yun-Hsing Fan Jan 2005

Tunable Liquid Crystal Photonic Devices, Yun-Hsing Fan

Electronic Theses and Dissertations

Liquid crystal (LC)-based adaptive optics are important for information processing, optical interconnections, photonics, integrated optics, and optical communications due to their tunable optical properties. In this dissertation, we describe novel liquid crystal photonic devices and their fabrication methods. The devices presented include inhomogeneous polymer-dispersed liquid crystal (PDLC), polymer network liquid crystals (PNLC) and phase-separated composite film (PSCOF). Liquid crystal/polymer composites could exist in different forms depending on the fabrication conditions. In Chap. 3, we demonstrate a novel nanoscale PDLC device that has inhomogeneous droplet size distribution. In such a PDLC, the inhomogeneous droplet size distribution is obtained by exposing the …

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