6,368 research outputs found

    UMSL Bulletin 2023-2024

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    The 2023-2024 Bulletin and Course Catalog for the University of Missouri St. Louis.https://irl.umsl.edu/bulletin/1088/thumbnail.jp

    Integrated Optical Fiber Sensor for Simultaneous Monitoring of Temperature, Vibration, and Strain in High Temperature Environment

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    Important high-temperature parts of an aero-engine, especially the power-related fuel system and rotor system, are directly related to the reliability and service life of the engine. The working environment of these parts is extremely harsh, usually overloaded with high temperature, vibration and strain which are the main factors leading to their failure. Therefore, the simultaneous measurement of high temperature, vibration, and strain is essential to monitor and ensure the safe operation of an aero-engine. In my thesis work, I have focused on the research and development of two new sensors for fuel and rotor systems of an aero-engine that need to withstand the same high temperature condition, typically at 900 °C or above, but with different requirements for vibration and strain measurement. Firstly, to meet the demand for high temperature operation, high vibration sensitivity, and high strain resolution in fuel systems, an integrated sensor based on two fiber Bragg gratings in series (Bi-FBG sensor) to simultaneously measure temperature, strain, and vibration is proposed and demonstrated. In this sensor, an L-shaped cantilever is introduced to improve the vibration sensitivity. By converting its free end displacement into a stress effect on the FBG, the sensitivity of the L-shaped cantilever is improved by about 400% compared with that of straight cantilevers. To compensate for the strain sensitivity of FBGs, a spring-beam strain sensitization structure is designed and the sensitivity is increased to 5.44 pm/με by concentrating strain deformation. A novel decoupling method ‘Steps Decoupling and Temperature Compensation (SDTC)’ is proposed to address the interference between temperature, vibration, and strain. A model of sensing characteristics and interference of different parameters is established to achieve accurate signal decoupling. Experimental tests have been performed and demonstrated the good performance of the sensor. Secondly, a sensor based on cascaded three fiber Fabry-Pérot interferometers in series (Tri-FFPI sensor) for multiparameter measurement is designed and demonstrated for engine rotor systems that require higher vibration frequencies and greater strain measurement requirements. In this sensor, the cascaded-FFPI structure is introduced to ensure high temperature and large strain simultaneous measurement. An FFPI with a cantilever for high vibration frequency measurement is designed with a miniaturized size and its geometric parameters optimization model is established to investigate the influencing factors of sensing characteristics. A cascaded-FFPI preparation method with chemical etching and offset fusion is proposed to maintain the flatness and high reflectivity of FFPIs’ surface, which contributes to the improvement of measurement accuracy. A new high-precision cavity length demodulation method is developed based on vector matching and clustering-competition particle swarm optimization (CCPSO) to improve the demodulation accuracy of cascaded-FFPI cavity lengths. By investigating the correlation relationship between the cascaded-FFPI spectral and multidimensional space, the cavity length demodulation is transformed into a search for the highest correlation value in space, solving the problem that the cavity length demodulation accuracy is limited by the resolution of spectral wavelengths. Different clustering and competition characteristics are designed in CCPSO to reduce the demodulation error by 87.2% compared with the commonly used particle swarm optimization method. Good performance and multiparameter decoupling have been successfully demonstrated in experimental tests

    Beam scanning by liquid-crystal biasing in a modified SIW structure

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    A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

    Evaluation of different segmentation-based approaches for skin disorders from dermoscopic images

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    Treballs Finals de Grau d'Enginyeria Biomèdica. Facultat de Medicina i Ciències de la Salut. Universitat de Barcelona. Curs: 2022-2023. Tutor/Director: Sala Llonch, Roser, Mata Miquel, Christian, Munuera, JosepSkin disorders are the most common type of cancer in the world and the incident has been lately increasing over the past decades. Even with the most complex and advanced technologies, current image acquisition systems do not permit a reliable identification of the skin lesion by visual examination due to the challenging structure of the malignancy. This promotes the need for the implementation of automatic skin lesion segmentation methods in order to assist in physicians’ diagnostic when determining the lesion's region and to serve as a preliminary step for the classification of the skin lesion. Accurate and precise segmentation is crucial for a rigorous screening and monitoring of the disease's progression. For the purpose of the commented concern, the present project aims to accomplish a state-of-the-art review about the most predominant conventional segmentation models for skin lesion segmentation, alongside with a market analysis examination. With the rise of automatic segmentation tools, a wide number of algorithms are currently being used, but many are the drawbacks when employing them for dermatological disorders due to the high-level presence of artefacts in the image acquired. In light of the above, three segmentation techniques have been selected for the completion of the work: level set method, an algorithm combining GrabCut and k-means methods and an intensity automatic algorithm developed by Hospital Sant Joan de Déu de Barcelona research group. In addition, a validation of their performance is conducted for a further implementation of them in clinical training. The proposals, together with the got outcomes, have been accomplished by means of a publicly available skin lesion image database

    A physics-based model of swarming jellyfish

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    We propose a model for the structure formation of jellyfish swimming based on active Brownian particles. We address the phenomena of counter-current swimming, avoidance of turbulent flow regions and foraging. We motivate corresponding mechanisms from observations of jellyfish swarming reported in the literature and incorporate them into the generic modelling framework. The model characteristics is tested in three paradigmatic flow environments.Comment: 35 pages, 14 figure

    Modelling the folding pathway of DNA nanostructures

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    DNA origami is a robust technique for bottom-up nano-fabrication. It encodes a target shape into uniquely addressable interactions between a set of short 'staple' strands and a long 'scaffold' strand. The mechanisms of self-assembly, particularly regarding kinetics, need to be better understood. Origami design usually relies on optimising the thermodynamic stability of the target structure, and thermal annealing remains the most fool-proof assembly protocol. This work focuses on studying the folding pathway of three types of origami through simulations: a reconfigurable T-junction origami, several traditional origami, and origami with coated scaffolds. The T-junction origami is intended as an economically feasible method of changing the uniqueness of interactions. My contribution to this work is to characterise the basic structural motif through oxDNA, a nucleotide-resolution model of DNA. The thesis then focuses on extending a domain-level model of DNA origami to study several experimental origami designs. We reveal design-dependent free energy barriers using biased simulations and relate this to the observed hysteresis in experiments. We also highlight the role of specific design elements in determining the folding pathway. A novel method of lowering the temperature of error-free assembly using coated scaffolds is then presented, with simulations indicating the existence of an activation barrier. By exposing particular regions of the scaffold, we can lower assembly time and temperature

    Magnetic control of Single 123Sb and 31P Implanted Donors in Silicon

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    Nuclear spins – such as the spin-1/2 of 31^{31}Ph or spin-7/2 of 123^{123}Sb - implanted in a silicon nano-device provide a compelling platform for advancing donor spin quantum architectures as well as investigating fundamental physics. The hyperfine interaction and electric quadrupole in group-V donors offer a natural way to control the nuclear spins using electric fields, which are easier to confine in a nanometric device, as opposed to magnetic fields. Modulating the isotropic hyperfine interaction with oscillating electric fields allows for control of nuclear spins via electric dipole spin resonance (EDSR). The quadrupolar interaction of high nuclear spins allows for direct drive of the nucleus with electric fields via nuclear electric resonance (NER). This thesis explores two avenues for quantum information encoding in implanted donors with all-electrical control: The first involves encoding a qubit in the antiparallel electron-nuclear spin states of the donor (flip-flop qubit), where one qubit gates are realised by EDSR. The second leverages the d-dimensional Hilbert space of the ionized (d = 8) or neutral (d = 16) 123^{123}Sb donor for multiqubit and qudit encoding. To that end, we first demonstrate full magnetic and electric coherent control on 123^{123}Sb and 31^{31}P. Expanding on previous work in \Sb, we show that we can navigate the whole Hilbert space of the neutral and ionized donor coherently, reconstruct the full spectrum, and characterize the quadrupolar interaction. We compare the performance of hyperfine-mediated drive (EDSR) for \Sb and \Ph, as well as the hyperfine-enhanced drive of their nuclear spins. Up to ten times faster EDSR drive is measured for 123^{123}Sb, due to a higher tunability of the hyperfine interaction. Five times faster hyperfine-enhanced drive is obtained for the neutral 123^{123}Sb nucleus due to the higher ratio between the hyperfine coupling constant and nuclear Zeeman splitting. We investigate the sources of relaxation (T1T_1) and decoherence (T2T_2) for a 123^{123}Sb and 31^{31}P measured in the same device and relate their coherence times to the sensitivity of each atom to electric and magnetic noise. Lastly, we benchmark magnetic and electric drive on the ionized nucleus with gate set tomography, and show comparable one-qubit gate fidelities above 99\% for both driving mechanisms. These results lay the foundations for leveraging high-spin donor nuclei in experiments on logical qubit encoding, quantum sensing and high-dimensional quantum information processing

    OCM 2023 - Optical Characterization of Materials : Conference Proceedings

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    The state of the art in the optical characterization of materials is advancing rapidly. New insights have been gained into the theoretical foundations of this research and exciting developments have been made in practice, driven by new applications and innovative sensor technologies that are constantly evolving. The great success of past conferences proves the necessity of a platform for presentation, discussion and evaluation of the latest research results in this interdisciplinary field

    Graduate Catalog of Studies, 2022-2023

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