Highly Efficient Spectral Calibration Methods for Swept-Source Optical Coherence Tomography

Recent techniques in optical coherence tomography (OCT) make use of specialized light sources that sweep across a broad optical bandwidth, allowing for longer depth ranges at higher resolutions. The produced light source signal can be described as a gaussian damped sinusoid that non-uniformly sweeps across a narrow frequency band. When sampling this interferometric signal uniformly, the generated images present considerable distortion, because the spectral information is a function of wavenumber "k", not time. To solve this problem a "calibration" step needs to be performed; in this process, the acquired interferogram signal is linearized into k-space. The process usually involves estimating the phase-frequency change profile of the SS-OCT system via Hilbert transformation, inverse tangent and phase unwrapping. In this thesis, a multitude of low complexity, computationally efficient methods for the real-time calibration of Swept Source Optical Coherence Tomography (SS-OCT) systems are implemented and results are evaluated against commonly performed calibration techniques such as Hilbert transformation. Simulation shows execution times decisively improved by up to a factor of ten, depending on the used technique. Axial resolution was also slightly improved across all the tested techniques. Moreover, the inverse tangent and phase unwrapping steps necessary for Hilbert transform calibration techniques are eliminated, vastly reducing circuit implementation complexity and making the system suitable for future inexpensive, power efficient, on-chip solutions in SS-OCT post-processing

Reliable Navigation for SUAS in Complex Indoor Environments

Indoor environments are a particular challenge for Unmanned Aerial Vehicles (UAVs). Effective navigation through these GPS-denied environments require alternative localization systems, as well as methods of sensing and avoiding obstacles while remaining on-task. Additionally, the relatively small clearances and human presence characteristic of indoor spaces necessitates a higher level of precision and adaptability than is common in traditional UAV flight planning and execution. This research blends the optimization of individual technologies, such as state estimation and environmental sensing, with system integration and high-level operational planning. The combination of AprilTag visual markers, multi-camera Visual Odometry, and IMU data can be used to create a robust state estimator that describes position, velocity, and rotation of a multicopter within an indoor environment. However these data sources have unique, nonlinear characteristics that should be understood to effectively plan for their usage in an automated environment. The research described herein begins by analyzing the unique characteristics of these data streams in order to create a highly-accurate, fault-tolerant state estimator. Upon this foundation, the system built, tested, and described herein uses Visual Markers as navigation anchors, visual odometry for motion estimation and control, and then uses depth sensors to maintain an up-to-date map of the UAV\u27s immediate surroundings. It develops and continually refines navigable routes through a novel combination of pre-defined and sensory environmental data. Emphasis is put on the real-world development and testing of the system, through discussion of computational resource management and risk reduction

Optical Network Design, Modelling and Performance Evaluation for the Upgraded LHC at CERN

This thesis considers how advances in optical network and optoelectronic technologies may be utilised in particle physics applications. The research is carried out within a certain framework; CERN's Large Hadron Collider (LHC) upgrade. The focus is on the upgrade of the "last-tier" data links, those residing between the last information-processing stage and the accelerator. For that purpose, different network architectures, based on the Passive Optical Network (PON) architectural paradigm, are designed and evaluated. Firstly, a Time-Division Multiplexed (TDM) PON targeting timing, trigger and control applications is designed. The bi-directional, point-to-multipoint nature of the architecture leads to infrastructure efficiency increase. A custom protocol is developed and implemented using FPGAs. It is experimentally verified that the network design can deliver significantly higher data rate than the current infrastructure and meet the stringent latency requirements of the targeted application. Consequently, the design of a network that can be utilised to transmit all types of information at the upgraded LHC, the High-Luminosity LHC (HL-LHC) is discussed. The most challenging requirement is that of the high upstream data rate. As WDM offers virtual point-to-point connectivity, the possibility of using a Wavelength-Division Multiplexed (WDM) PON is theoretically investigated. The shortcomings of this solution are identified; these include high cost and complexity, therefore a simpler architecture is designed. This is also based on the PON paradigm and features the use of Reflective Electroabsorption Modulators (REAM) at the front-end (close to the particle collision point). Its performance is experimentally investigated and shown to meet the requirements of a unified architecture at the HL-LHC from a networking perspective. Finally, since the radiation resistance of optoelectronic components used at the front-end is of major importance, the REAM radiation hardness is experimentally investigated. Their radiation resistance limits are established, while new insights into the radiation damage mechanism are gained

MULTIFUNCTIONAL BEHAVIORS OF TWO-DIMENSIONAL MATERIALS AND THEIR COMPOSITES

Two-dimensional (2D) materials, including graphene, transition metal carbides or nitrides (TMC/Ns), have rich surface chemistry, superb electrical and mechanical properties. These unique properties make them ideal for multifunctional devices. Among them, we focused on graphene and TMC/Ns (i.e., MXenes), as well as their composites. Unlike the well-known graphene, MXenes, are relatively new and typically synthesized by the selective etching of the “A” layers from the layered carbides and /or nitrides known as MAX phases, which introduce MXenes with rich terminal groups (e.g. -O-, -OH, -F). During my Ph.D. study, firstly, the adhesive and frictional behaviors, which are related to successful film transfer and shear force transmission of 2D materials, respectively, were studied. Secondly, in-plane mechanical behaviors of 2D materials, were characterized using in situ experimental tools for micro-scale samples. At last, the high surface affinity and versatile chemical binding capabilities for 2D materials were applied in virus sensing. Results show that the increase of AgNWs reduces the adhesion of AgNWs-GN. Long-range interaction, high adhesion and friction forces were observed for MXene/MXene interface, which is due to interactions between MXene terminating groups. The dependence of Young’s modulus and strength on the number of stacked MXene monolayers is much weaker than multilayer graphene and MoS2 stacks due to -O- atom bridging. Highly nonlinear responses and large residual deformations were observed under cyclic compression of MXene microparticles. At last, a wireless, flexible on-mask immunosensing-based COVID-19 breath sensor was developed to detect air-borne viruses --Abstract, p. ii

Air Force Institute of Technology Research Report 2012

This report summarizes the research activities of the Air Force Institute of Technology’s Graduate School of Engineering and Management. It describes research interests and faculty expertise; lists student theses/dissertations; identifies research sponsors and contributions; and outlines the procedures for contacting the school. Included in the report are: faculty publications, conference presentations, consultations, and funded research projects. Research was conducted in the areas of Aeronautical and Astronautical Engineering, Electrical Engineering and Electro-Optics, Computer Engineering and Computer Science, Systems and Engineering Management, Operational Sciences, Mathematics, Statistics and Engineering Physics

Smart Technologies for Precision Assembly

This open access book constitutes the refereed post-conference proceedings of the 9th IFIP WG 5.5 International Precision Assembly Seminar, IPAS 2020, held virtually in December 2020. The 16 revised full papers and 10 revised short papers presented together with 1 keynote paper were carefully reviewed and selected from numerous submissions. The papers address topics such as assembly design and planning; assembly operations; assembly cells and systems; human centred assembly; and assistance methods in assembly

Symmetry in Electromagnetism

Electromagnetism plays a crucial role in basic and applied physics research. The discovery of electromagnetism as the unifying theory for electricity and magnetism represents a cornerstone in modern physics. Symmetry was crucial to the concept of unification: electromagnetism was soon formulated as a gauge theory in which local phase symmetry explained its mathematical formulation. This early connection between symmetry and electromagnetism shows that a symmetry-based approach to many electromagnetic phenomena is recurrent, even today. Moreover, many recent technological advances are based on the control of electromagnetic radiation in nearly all its spectra and scales, the manipulation of matter–radiation interactions with unprecedented levels of sophistication, or new generations of electromagnetic materials. This is a fertile field for applications and for basic understanding in which symmetry, as in the past, bridges apparently unrelated phenomena―from condensed matter to high-energy physics. In this book, we present modern contributions in which symmetry proves its value as a key tool. From dual-symmetry electrodynamics to applications to sustainable smart buildings, or magnetocardiography, we can find a plentiful crop, full of exciting examples of modern approaches to electromagnetism. In all cases, symmetry sheds light on the theoretical and applied works presented in this book

Air Force Institute of Technology Research Report 2016

This Research Report presents the FY16 research statistics and contributions of the Graduate School of Engineering and Management (EN) at AFIT. AFIT research interests and faculty expertise cover a broad spectrum of technical areas related to USAF needs, as reflected by the range of topics addressed in the faculty and student publications listed in this report. In most cases, the research work reported herein is directly sponsored by one or more USAF or DOD agencies. AFIT welcomes the opportunity to conduct research on additional topics of interest to the USAF, DOD, and other federal organizations when adequate manpower and financial resources are available and/or provided by a sponsor. In addition, AFIT provides research collaboration and technology transfer benefits to the public through Cooperative Research and Development Agreements (CRADAs)