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Articles 1 - 23 of 23
Full-Text Articles in Engineering
Eit, Slow Light, And Sealing Methods For Embedding Rubidium Into The Arrow System, Katherine Barnett Hurd
Eit, Slow Light, And Sealing Methods For Embedding Rubidium Into The Arrow System, Katherine Barnett Hurd
Theses and Dissertations
Light-matter interactions are fundamentally based on the quantum mechanical principles that govern photons, electrons and other fundamental particles. One very interesting phenomenon within all of light-matter interactions is Electromagnetically Induced Transparency(EIT). This phenomenon causes an otherwise absorbing atomic transition to stop absorbing through quantum mechanical interference of probability wave functions. Corresponding to that change in absorption, will be a sudden, large change in the index of refraction. This change in the index of refraction leads to another phenomenon in which the group velocity of light can be slowed down dramatically. In the past, many researchers have been able to achieve …
An Onboard Vision System For Unmanned Aerial Vehicle Guidance, Barrett Bruce Edwards
An Onboard Vision System For Unmanned Aerial Vehicle Guidance, Barrett Bruce Edwards
Theses and Dissertations
The viability of small Unmanned Aerial Vehicles (UAVs) as a stable platform for specific application use has been significantly advanced in recent years. Initial focus of lightweight UAV development was to create a craft capable of stable and controllable flight. This is largely a solved problem. Currently, the field has progressed to the point that unmanned aircraft can be carried in a backpack, launched by hand, weigh only a few pounds and be capable of navigating through unrestricted airspace. The most basic use of a UAV is to visually observe the environment and use that information to influence decision making. …
Nonlinear Observability Analysis Of Bearing-Only Cooperative Localization Using Graph Theory, Rajnikant Sharma
Nonlinear Observability Analysis Of Bearing-Only Cooperative Localization Using Graph Theory, Rajnikant Sharma
Faculty Publications
In this report we investigate the nonlinear observability properties of bearing-only cooperative localization. We establish a link between observability and a graph representing measurements and communication between the robots.
Observability Analysis Of Bearing-Only Cooperative Localization, Rajnikant Sharma
Observability Analysis Of Bearing-Only Cooperative Localization, Rajnikant Sharma
Faculty Publications
In this report we investigate the nonlinear observability properties of bearing-only cooperative localization. We establish a link between observability and a graph representing measurements and communication between the robots. It is shown that graph theoretic properties like the connectivity and the existence of a path between two nodes can be used to explain the observability of the system.
Mimo Channel Spatial Covariance Estimation: Analysis Using A Closed-Form Model, Yanling Yang
Mimo Channel Spatial Covariance Estimation: Analysis Using A Closed-Form Model, Yanling Yang
Theses and Dissertations
Multiple-input Multiple-output (MIMO) wireless communication systems allow increased spectral efficiency and therefore promise significant improvement in performance. However, because of the rapid variation in channel state information (CSI) in networks with mobile nodes or scatterers, it is difficult both to maintain high communication performance and to create channel models that effectively represent the time-varying behavior of the channels. The spatial covariance of the MIMO channel describes the average power gain on each transmit-receive antenna pair as well as the correlation between the complex link gains and thus provides critical information for understanding the performance of the system and for creating …
Scatterometer Contamination Mitigation, Michael Paul Owen
Scatterometer Contamination Mitigation, Michael Paul Owen
Theses and Dissertations
Microwave scatterometers, which use radar backscatter measurements to infer the near-surface wind vector, are unique in their ability to monitor global wind vectors at high resolutions. However, scatterometer observations which are contaminated by land proximity or rain events produce wind estimates which have increased bias and variability, making them unreliable for many applications. Fortunately, the effects of these sources of contamination can be mitigated. Land contamination of backscatter measurements occurs when land partially fills the antenna illumination area. This reduces and masks the wind-induced backscatter signal. Land contamination is mitigated by quantifying the amount of contamination in a single observation …
Qpsk And Oqpsk In Frequency Nonselective Fading, Michael D. Rice
Qpsk And Oqpsk In Frequency Nonselective Fading, Michael D. Rice
Faculty Publications
The maximum likelihood estimator for the fading gain in a frequency non-selective fading channel is derived and analyzed for offset QPSK (OQPSK). The corresponding impact of estimator errors on the bit error probability performance for OQPSK is also derived.
Low-Loss Hollow Waveguide Platforms For Optical Sensing And Manipulation, Evan J. Lunt
Low-Loss Hollow Waveguide Platforms For Optical Sensing And Manipulation, Evan J. Lunt
Theses and Dissertations
This dissertation presents a method for fabricating integrated hollow and solid optical waveguides on planar substrates. These waveguides are antiresonant reflecting optical waveguides (ARROWs), where high-index cladding layers confine light to hollow cores through optical interference. Hollow waveguides that can be filled with liquids or gases are an important new building block for creating highly-integrated optical sensors. The method developed for fabricating these integrated waveguides employs standard processes and materials used in the microelectronics industry, allowing for parallel, low-cost fabrication. Dielectric cladding layers are deposited on a silicon wafer using plasma-enhanced chemical vapor deposition (PECVD). After the lower cladding layers …
Thin Film Microfluidic And Nanofluidic Devices, Mark Noble Hamblin
Thin Film Microfluidic And Nanofluidic Devices, Mark Noble Hamblin
Theses and Dissertations
Lab-on-a-chip devices, also known as micro total analysis systems (μTAS), are implementations of chemical analysis systems on microchips. These systems can be fabricated using standard thin film processing techniques. Microfluidic and nanofluidic channels are fabricated in this work through sacrificial etching. Microchannels are fabricated utilizing cores made from AZ3330 and SU8 photoresist. Multi-channel electroosmotic (EO) pumps are evaluated and the accompanying channel zeta potentials are calculated. Capillary flow is studied as an effective filling mechanism for nanochannels. Experimental departure from the Washburn model is considered, where capillary flow rates lie within 10% to 70% of theoretical values. Nanochannels are fabricated …
Impedance Imaging And Measurements By Micro Probes In Aqueous Environments, Tao Shang
Impedance Imaging And Measurements By Micro Probes In Aqueous Environments, Tao Shang
Theses and Dissertations
The dissertation presented here describes two research projects that may, at first glance, seem unrelated. Their unifying principle is the measurement of electrical impedance for the detection and analysis of biological materials. Impedance measurements have long been employed and studied in scientific fields, and the dissertation begins with a summary of historical methodology, applications, and terminology. Utilizing impedance measurements for microscopic imaging is the driving motivation for Scanning Impedance Imaging (SII). This technique manifests the distribution of electrical impedance inside biological tissues and is described after the dissertation's introduction. SII can provide micron-scale imaging resolution by scanning a shielded microprobe …
Wireless Sensor Network Approach To Aeronautical Telemetry, Oluwasegun Babatunde Tinubi
Wireless Sensor Network Approach To Aeronautical Telemetry, Oluwasegun Babatunde Tinubi
Theses and Dissertations
Wireless sensor networks have become a rapidly growing research field in recent years. They are envisioned to have a wide range of applications in military, environmental and many other fields. We examine the performance of wireless sensor network applications to aeronautical telemetry. To date, test ranges have relied on a single telemetry ground station for the reception of packets from all air borne transmitters. We researched an alternate means of achieving this same goal with fewer resources. It is a well known fact that communication power and bandwidth are the most expensive commodities in wireless communications. The telemetry world is …
Scatterometer Image Reconstruction Tuning And Aperture Function Estimation For Advanced Microwave Scanning Radiometer On The Earth Observing System, Brian Adam Gunn
Scatterometer Image Reconstruction Tuning And Aperture Function Estimation For Advanced Microwave Scanning Radiometer On The Earth Observing System, Brian Adam Gunn
Theses and Dissertations
AMSR-E is a space-borne radiometer which measures Earth microwave emissions or brightness temperatures (Tb) over a wide swath. AMSR-E data and images are useful in mapping valuable Earth-surface and atmospheric phenomena. A modified version of the Scatterometer Image Reconstruction (SIR) algorithm creates Tb images from the collected data. SIR is an iterative algorithm with tuning parameters to optimize the reconstruction for the instrument and channel. It requires an approximate aperture function for each channel to be effective. This thesis presents a simulator-based optimization of SIR iteration and aperture function threshold parameters for each AMSR-E channel. A comparison of actual Tb …
Design And Feasibility Testing For A Ground-Based, Three-Dimensional, Ultra-High-Resolution, Synthetic Aperture Radar To Image Snowpacks, Stephen Joseph Preston
Design And Feasibility Testing For A Ground-Based, Three-Dimensional, Ultra-High-Resolution, Synthetic Aperture Radar To Image Snowpacks, Stephen Joseph Preston
Theses and Dissertations
This thesis works through the design of a radar-based system for imaging snowpacks remotely and over large areas to assist in avalanche prediction. The key to such a system is the ability to image volumes of snow at shallow, spatially-varying angles of incidence. To achieve this prerequisite, the design calls for a ground-based Synthetic Aperture Radar (SAR) capable of generating three-dimensional, ultra-high-resolution images of a snowpack. To arrive at design parameters for this SAR, the thesis works through relevant principles in avalanche mechanics, alpine-snowpack geophysics, and electromagnetic scattering theory. The thesis also works through principles of radar, SAR, antenna, and …
Summary Of Feedback Edge Set Papers, Jonathan Johnson
Summary Of Feedback Edge Set Papers, Jonathan Johnson
Faculty Publications
The problem of finding a set of edges F from a directed graph G = (V,E) such that the graph G0 = (V,E − F) contains no cycles is known as the feedback edge set (FES) problem or the feedback arc set problem. A related problem is the minimum feedback edge set problem, in which the feedback edge set F must be minimal. The feedback edge set problem has application in applying a common reliability technique called triple modular redundancy to FPGA circuit designs where configuration memory scrubbing is employed [1].
Secret Key Establishment Using Wireless Channels As Common Randomness In Time-Variant Mimo Systems, Chan Chen
Secret Key Establishment Using Wireless Channels As Common Randomness In Time-Variant Mimo Systems, Chan Chen
Theses and Dissertations
Encryption of confidential data with a secret key has become a widespread technique for securing wireless transmissions. However, existing key distribution methods that either deliver the secret key with a key distribution center or exchange the secret key using public-key cryptosystems are unable to establish perfect secret keys necessary for symmetric encryption techniques. This research considers secret key establishment, under the broad research area of information theoretic security, using the reciprocal wireless channel as common randomness for the extraction of perfect secret keys in multiple-input multiple-output (MIMO)communication systems. The presentation discusses the fundamental characteristics of the time-variant MIMO wireless channel …
Signal Processing Methods For Ultra-High Resolution Scatterometry, Brent A. Williams
Signal Processing Methods For Ultra-High Resolution Scatterometry, Brent A. Williams
Theses and Dissertations
This dissertation approaches high resolution scatterometry from a new perspective. Three related general topics are addressed: high resolution σ^0 imaging, wind estimation from high resolution σ^0 images over the ocean, and high resolution wind estimation directly from the scatterometer measurements. Theories of each topic are developed, and previous approaches are generalized and formalized. Improved processing algorithms for these theories are developed, implemented for particular scatterometers, and analyzed. Specific results and contributions are noted below. The σ^0 imaging problem is approached as the inversion of a noisy aperture-filtered sampling operation-extending the current theory to deal explicitly with noise. A maximum aposteriori …
Investigation Of Rf Curing Parameters In Resin Infusion Molding, Christopher K. Love
Investigation Of Rf Curing Parameters In Resin Infusion Molding, Christopher K. Love
Theses and Dissertations
The purpose of this study is to investigate RF or Radio Frequency energy as a viable alternative to traditional heating methods for the purpose of curing resins used in resin infusion molding, a molding system for polymeric composites. Traditional heating/curing methods include technologies such as room temperature, oven, microwave, infrared, and ultraviolet. Although RF curing provides far more advantages than disadvantages, its implementation into a manufacturing process can be challenging. Specifically, three critical elements must be present in order for RF to function in a manner that is profitable to the manufacturer. Those elements are: (1) the proper generator (voltage …
Automatic Identification And Tracking Of Retraction Fibers In Time-Lapse Microscopy, Meher Talat Shaikh
Automatic Identification And Tracking Of Retraction Fibers In Time-Lapse Microscopy, Meher Talat Shaikh
Theses and Dissertations
Digital image processing is widely used in the field of time-lapse microscopy and biological research to provide statistical data of cellular dynamics. The data can provide more comprehensive understanding of the molecular phenomenon. Further, digital image processing enables rapid and consistent quantification of qualitative observations. The image processing model examined here provides a study to identify structures called retraction fibers (RFs) that are formed during epithelial-mesenchymal transition (EMT) [1], an important developmental process which also occurs during cancer metastasis. Quantifying RF formation is an important task for biologists studying cellular regulation of EMT. This thesis work uses digital image processing …
Generalized Image Formation For Pulsed And Lfm-Cw Synthetic Aperture Radar, Evan C. Zaugg
Generalized Image Formation For Pulsed And Lfm-Cw Synthetic Aperture Radar, Evan C. Zaugg
Theses and Dissertations
Approximations made in the traditional signal model for synthetic aperture radar (SAR) processing cause defocusing of the radar images when the system operates under conditions where the approximations lose validity. This dissertation investigates a number of these approximations and presents algorithmic improvements based on generalizations of the approxmations of the SAR signal model. These improvements result in better focused imagery from SAR systems with varied designs and parameters. Among the advancements presented is the development of a generalized chirp-scaling algorithm and a generalized frequency scaling algorithm to address the problems caused by approximations based on a Taylor series expansion of …
Design Method For Optimized Wideband Iterative Differential Amplifier In Mos Technology, Steven L. Minch
Design Method For Optimized Wideband Iterative Differential Amplifier In Mos Technology, Steven L. Minch
Theses and Dissertations
Wideband amplifiers are an important part of analog design, and much effort has been expended in improving them. A popular implementation of a wideband amplifier is to use one or two stages with high gain in one or both stages. An alternative to this method is presented in this work, developed for Metal Oxide Semiconductor (MOS) amplifiers. The new approach, building on previous work in bipolar technology, uses multiple differential MOS stages to achieve similar gain requirements to other wideband amplifiers. It is shown that multiple stages with low gain, if implemented according to the present design method, can lead …
Synchronization Voter Insertion Algorithms For Fpga Designs Using Triple Modular Redundancy, Jonathan Mark Johnson
Synchronization Voter Insertion Algorithms For Fpga Designs Using Triple Modular Redundancy, Jonathan Mark Johnson
Theses and Dissertations
Triple Modular Redundancy (TMR) is a common reliability technique for mitigating single event upsets (SEUs) in FPGA designs operating in radiation environments. For FPGA systems that employ configuration scrubbing, majority voters are needed in all feedback paths to ensure proper synchronization between the TMR replicates. Synchronization voters, however, consume additional resources and impact system timing. This work introduces and contrasts seven algorithms for inserting synchronization voters while automatically performing TMR. The area cost and timing impact of each algorithm on a number of circuit benchmarks is reported. The work demonstrates that one of the algorithms provides the best overall timing …
Multi-Aperture Coherent Change Detection And Interferometry For Synthetic Aperture Radar, David D. Madsen
Multi-Aperture Coherent Change Detection And Interferometry For Synthetic Aperture Radar, David D. Madsen
Theses and Dissertations
Interferometry and coherent change detection (CCD) utilize phase differences between complex SAR images to find terrain height and to detect small changes between images, respectively. A new method for improving interferometry and CCD using multiple sub-apertures is proposed. Using backprojection processing, multiple sub-aperture images are created for a pair of flights. An interferogram and coherence map is made from each sub-aperture. For CCD, each sub-aperture coherence map offers an independent estimate of the coherence over the same area. By combining coherence maps, low coherence areas associated with residual motion errors are reduced, shadowed areas are minimized, and the overall coherence …
Frequency Response And Gain Enhancement Of Solid-State Impact-Ionization Multipliers (Sims), Joshua L. Beutler
Frequency Response And Gain Enhancement Of Solid-State Impact-Ionization Multipliers (Sims), Joshua L. Beutler
Theses and Dissertations
A study of the frequency response and gain of Solid-state the Impact-ionization Multiplier (SIM). The SIM generates current gain via impact ionization also known as avalanche gain. The SIM provides low noise amplification from an arbitrary current source. In the case of this study, current sources consisted of photodiodes optimized for a particular wavelength of light. The SIM is fabricated from silicon and enjoys the low noise, low carrier transit time advantages of conventional silicon impact ionization devices while amplifying current from a photodiode of a different material. This is advantageous because ideal detection and multiplication regions cannot always be …