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Dissertations / Theses on the topic 'Spiral array'

Author: Grafiati

Published: 10 March 2023

Last updated: 31 July 2025

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1

Tweedie, Andrew. "Spiral 2D array designs for volumetric imaging." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23167.

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The use of linear phased arrays in NDE inspections has recently grown, resulting in faster inspection of components. Phased arrays are also used in underwater sonar and biomedical imaging. All applications require 2 dimensional (2D) arrays, capable of volumetric imaging, to further increase scan speed, and to allow tighter focussing on targets. However, 2D arrays have not found widespread use, mainly due to the large number of elements required to implement standard periodic designs. Alternative array configurations that feature a much lower element count offer a more pragmatic solution. This

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2

Zhang, Piyou. "Slotted Spiral Antennas and Widebandwidth Array Systems." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1222311888.

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3

Jiwani, Aziz Mohamed Husein. "Conical spiral antennas for the Square Kilometre Array - a feasibility study." Thesis, Curtin University, 2013. http://hdl.handle.net/20.500.11937/200.

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The Square Kilometre Array is a next-generation radio telescope originally slated to operate at 70 – 450 MHz frequency in its lowest band (SKA-low). This thesis examines aspects of SKA-low station design and finds that two-stage beamforming produces acceptable performance. Additionally, single- and dual-polarised conical spirals are evaluated as candidate SKA-low elements. Though neither versions are strong candidates for SKA, the single-polarised spiral is an excellent antenna for use in Global Epoch of Reionisation experiments.

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4

Hinostroza, Israel. "Design of wideband arrays of spiral antennas." Phd thesis, Supélec, 2013. http://tel.archives-ouvertes.fr/tel-00830469.

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This work focuses on the design of wideband dual polarized arrays using spiral antennas. These antennas are known for having wideband properties. But, due to the presence of the grating lobes, the bandwidth is decreased when using an array instead of a single antenna. In order to obtain a dual polarized array, it is needed to use elements of opposite polarization, which creates great distances between same polarization elements, meaning an earlier presence of the grating lobes. In this work, an analytic method was developed to estimate the bandwidth of the spiral arrays. This method showed tha

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5

Wu, Ya-Lin, Kazushi Sakamoto, and Hsi-An Pan. "Submillimeter Array 12CO (2-1) Imaging of the NGC 6946 Giant Molecular Clouds." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623951.

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We present a (CO)-C-12 (2-1) mosaic map of the spiral galaxy NGC 6946 by combining data from the Submillimeter Array and the IRAM 30m telescope. We identify 390 giant molecular clouds (GMCs) from the nucleus to 4.5 kpc in the disk. GMCs in the inner 1 kpc are generally more luminous and turbulent, some of which have luminosities > 10(6)K. km. s(-1) pc(2) and velocity dispersions > 10. km s(-1). Large-scale bar-driven dynamics likely regulate GMC properties in the nuclear region. Similar to the MilkyWay and other disk galaxies, GMC mass function of NGC 6946 has a shallower slope (index > -2) in

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6

Caswell, Eric D. "Design and Analysis of Star Spiral with Application to Wideband Arrays with Variable Element Sizes." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/25963.

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This dissertation details the development of the star spiral antenna and demonstrates the advantages of the star spiral when used in a wideband array with variable element sizes. The wideband array with variable element sizes (WAVES) is a multi-octave array that uses different sized circular Archimedean spirals for each octave of frequency coverage. A two-octave WAVES array has been presented in the literature, but a gap in the two-octave frequency coverage exists along the principal axes. The star spiral antenna was developed to eliminate the performance gap in the WAVES array. The star sp

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7

Asif, Rameez. "Design and Implementation of System Components for Radio Frequency Based Asset Tracking Devices to Enhance Location Based Services. Study of angle of arrival techniques, effects of mutual coupling, design of an angle of arrival algorithm, design of a novel miniature reconfigurable antenna optimised for wireless communication systems." Thesis, University of Bradford, 2017. http://hdl.handle.net/10454/17143.

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The angle of arrival estimation of multiple sources plays a vital role in the field of array signal processing as MIMO systems can be employed at both the transmitter and the receiver end and the system capacity, reliability and throughput can be significantly increased by using array signal processing. Almost all applications require accurate direction of arrival (DOA) estimation to localize the sources of the signals. Another important parameter of localization systems is the array geometry and sensor design which can be application specific and is used to estimate the DOA. In this wo

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8

Giagka, V. "Flexible active electrode arrays for epidural spinal cord stimulation." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1460520/.

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In spinal cord injured (SCI) individuals the neural pathway between the brain and the extremities is damaged. However, there is still the capacity to elicit muscle activation despite the absence of any supraspinal input. Recent studies have proposed epidural spinal cord electrical stimulation (ESCS) as a means to facilitate locomotor recovery in SCI humans. In epidural stimulation a number of electrodes are placed in the spine, outside the dura, and stimulus current pulses are used to ‘tune’ the spinal circuitries. Some rat studies have supported this concept, but further testing is required t

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9

Yang, Calvin Tseng. "Recording locomotor neural ensemble activity using 3-D microprobe arrays and the development of a flexible planar array for recording spinal small-field cord-dorsum potentials." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1666917911&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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10

Greenspon, Charles. "Linear multi-electrode arrays for recording population data from the spinal dorsal horn." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/52849/.

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The dorsal horn of the spinal cord is a complex laminar structure integrating exteroceptive signals from the primary afferent fibers into the central nervous system. The laminae of the spinal cord exhibit specialised roles and distinct processes occur across the axes of the dorsal horn. One of the most common in vivo approaches to recording spinal activity is single unit electrophysiology of cells that are believed to be representative of the subjects perception of stimuli. This approach has produced invaluable data but has not progressed in over half a century and fails to account for the spe

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11

Mendes, ruiz Pedro. "Réseaux multi-octave d'antennes spirales connectées." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC075/document.

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Une des problématiques qui est souvent associée aux réseaux large bande est l’apparition des lobes de réseaux, liée à la périodicité de l’espacement entre les éléments du réseau. Un autre problème dans les réseaux large bande est la fréquence de fonctionnement de l’élément du réseau. La plus basse fréquence d’opération est généralement liée à la taille de l’élément. Dans cette thèse un réseau d’anneaux concentriques a été développé. Les connections entre les spirales de polarisation opposée diminuent le coefficient de réflexion dans les fréquences basses. La topologie des anneaux concentriques

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12

Roschier, Ulla M. A. "Studies on neuronal network activity of olfactory bulb, spinal cord and frontal cortex grown on microelectrode arrays in vitro : the role of gap junctions in network integration." Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/28291/.

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This project focused on understanding the mechanisms involved in CNS integration. The anatomy and physiology of mammalian olfactory system was investigated in order to develop an organotypic in vitro sensory system to increase our understanding of sensory processing at a neural network level. The olfactory network cultures grown on multielectrode arrays (MEAs) were found to only rarely exhibit electrical activity and it was decided this was an unsuitable preparation for the purposes of this study. The spinal cord was chosen as a secondary sensory system, initially in co-culture with dorsal roo

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13

Xu, Binbin. "Étude de la Dynamique des Ondes Spirales à l'Échelle Cellulaire par Modèles Expérimental et Numérique." Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00955873.

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Parmi les causes de décès d'origine cardiaque, les troubles du rythme occupent une place majeure, particulièrement les troubles auriculaires. Cette situation alarmante a motivé une recherche intense, mais qui est limitée par la disponibilité de modèles expérimentaux permettant de reproduire les mécanismes cellulaires de déclenchement et d'extensions de ces anomalies. Qu'ils surviennent sur un cœur sain ou pathologique, qu'ils soient bénins ou potentiellement dangereux (risque de mort subite), les troubles du rythme constituent un chapitre important de la cardiologie. Ils posent d'importants pr

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14

Abdoun, Oussama. "Analyse spatiotemporelle de données MEA pour l'étude de la dynamique de l'activité de la moelle épinière et du tronc cérébral immatures chez la souris." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR15266/document.

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Tous les réseaux de neurones immatures génèrent une activité dite « spontanée »qui persiste même en l’absence de toute afférence et est impliquée dans de nombreux processus développementaux. Cette activité apparaît in vitro sous formes de vagues calciques ou électriques pouvant se propager sur de grandes distances et embraser toute la préparation. Toutefois, sa dynamique a été assez peu étudiée jusqu’à présent. En vue de combler quelque peu cette lacune, nous avons utilisé des matrices de microélectrodes (MEA) pour caractériser l’activité rythmique spontanée dans la moelle épinière embryonnair

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15

Andrade, Fernanda Gonçalves de. "Estudo das alterações na expressão gênica dos ependimomas." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/5/5138/tde-01092014-154140/.

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Ependimomas são tumores gliais raros. Podem ser encontrados em qualquer localização do sistema nervoso central e, apesar de histologia similar, parecem apresentar alterações genômicas distintas. As variáveis clínicas são intercorrelacionadas e, geralmente, incapazes de predizer o curso da doença. O objetivo do presente estudo foi analisar a expressão aumentada de genes e proteínas em ependimomas e correlacionar com dados clínicos dos pacientes. Foram estudados casos de pacientes com ependimoma submetidos à ressecção cirúrgica no Hospital das Clínicas, Universidade de São Paulo, no período entr

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16

Johansson, Martin M. "The Human Y chromosome and its role in the developing male nervous system." Doctoral thesis, Uppsala universitet, Institutionen för organismbiologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-261789.

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Recent research demonstrated that besides a role in sex determination and male fertility, the Y chromosome is involved in additional functions including prostate cancer, sex-specific effects on the brain and behaviour, graft-versus-host disease, nociception, aggression and autoimmune diseases. The results presented in this thesis include an analysis of sex-biased genes encoded on the X and Y chromosomes of rodents. Expression data from six different somatic tissues was analyzed and we found that the X chromosome is enriched in female biased genes and depleted of male biased ones. The second st

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17

Lind, Anne-Li. "Biomarkers for Better Understanding of the Pathophysiology and Treatment of Chronic Pain : Investigations of Human Biofluids." Doctoral thesis, Uppsala universitet, Anestesiologi och intensivvård, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-326180.

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Chronic pain affects 20 % of the global population, causes suffering, is difficult to treat, and constitutes a large economic burden for society. So far, the characterization of molecular mechanisms of chronic pain-like behaviors in animal models has not translated into effective treatments. In this thesis, consisting of five studies, pain patient biofluids were analyzed with modern proteomic methods to identify biomarker candidates that can be used to improve our understanding of the pathophysiology chronic pain and lead to more effective treatments. Paper I is a proof of concept study, where

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18

MOORE, Moore Thomas Allen. "Alternating Current Electroosmotic Micropumping Using A Square Spiral Microelectrode Array." Thesis, 2011. http://hdl.handle.net/1974/6350.

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An alternating current electroosmotic micro pumping device has been designed, experimentally tested and theoretically analyzed using an electrohydrodynamic theoretical model applied to a computer simulation model. The device SP-1 is a microelectrode array which uses the principal of AC electroosmosis (EO), ions driven along microelectrode surfaces by coulomb forces produced by tangential electric fields. These ions, when driven, induce a net fluid motion due to viscous drag forces. Three submerged microelectrode wires were deposited on a substrate using microfabrication techniques such that a

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19

Chiou, Shyr-Fuu, and 邱時甫. "Heat Transfers Of Reciprocating Spiral Tube and Impingement Jet-Array in Compound Piston Cooling System." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/17966275701546296328.

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碩士<br>國立高雄海洋科技大學<br>輪機工程研究所<br>92<br>As a result of ever-mounting power-to-weight ratio of a marine diesel engine, the thermal loads of a piston （involving the thermal stress and material temperatures）increased accordingly. To cope with this particular developing trend, heat transfer augmentation for the internal cooling system of piston is essential in order to assure the reliability of piston. This research program examined the heat transfer performances of a spiral cooling passage and an impingement jets array with piston cooling application. The research focused on the influences of recipr

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20

Stegenburgs, Edgars. "Generation of Orbital Angular Momentum (OAM) Modes with a Spiral Phase Plate Integrated Laser Source." Diss., 2021. http://hdl.handle.net/10754/668819.

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The objective of this work is to develop a near-infrared laser device capable of emitting orbital angular momentum (OAM) light. The prototyped device must be suitable for compact, energy-saving optical communication applications. Integrated OAM lasers will revolutionize high-capacity data transmission over any telecommuni- cation network environment, as OAM light can be guided and transmitted through kilometers of optical fibers and propagated in free space and underwater. Several methods for generating OAM light employing various complex monolithic and hybrid integration methods have been de

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21

Zhu, F., S. Gao, A. T. S. Ho, et al. "Compact-size linearly tapered slot antenna for portable ultra-wideband imaging systems." 2012. http://hdl.handle.net/10454/9771.

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No<br>A compact-size asymmetrical linearly tapered slot antenna required for portable ultra-wideband (UWB) imaging systems is presented. The total antenna size is reduced compared with the conventional linearly tapered slot antenna by using a triangular slot on the left-hand side of the tapered-shaped radiator, whereas introducing a corrugated pattern of cuts on the right side. The antenna operates over a wide bandwidth extending from 3.1 to 10.6 GHz with a maximum gain of 8.5 dBi. Stable radiation patterns are observed across the operational bandwidth, with cross-polarization levels below 20

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22

Giangrossi, Claudio. "Development and real-time implementation of novel 2-D and 3-D imaging techniques on a research scanner." Doctoral thesis, 2022. http://hdl.handle.net/2158/1272194.

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In the last decades, ultrasound imaging systems have become more and more popular thanks to their capability to investigate tissues in safe, cost effective, and non-invasive way. Their role in diagnostic imaging has become fundamental in several medical specialties, thanks also to the introduction of advanced echographic systems fostered by the efforts of several research laboratories around the world. Such efforts are more frequently based on the use of special research scanners, characterized by flexible hardware and programmable software and firmware. These features have been demonstrated i

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23

Tzuang, Lawrence Dah-Ching, and 莊大慶. "The Extraordinary Transmission through Periodic Metallic Mesh and Archimedean Spiral Hole Arrays." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/11921048832078344660.

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碩士<br>國立臺灣大學<br>電子工程學研究所<br>97<br>The extraordinary light transmission of two-dimensional rectangular metallic meshes is experimentally demonstrated. The results are explained by orthogonally superimposed one-dimensional gratings. For wavelengths that are much larger than the metal strip period, the transmission spectrum of the traditional wire-grid polarizer could be modified by interconnecting wires between the strips. It performs a special filter with a stop band from excited surface current along the additional wires that causes extra resonating modes of the individual structures. The extr

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24

Chang, Joon Young. "Implantable neural spheroid networks utilizing a concave microwell array." Thesis, 2013. https://hdl.handle.net/2144/17123.

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The goal of this study was to create pre-formed neural spheroid networks (NSN) on a polydimethyl siloxane (PDMS) concave microwell array for eventual implantation into the rat brain. Recent studies have shown that stem cells have great potential in treating various neurological insults of the central nervous system, ranging from traumatic brain and spinal cord injury, to neurodegenerative disorders. However, the use of stem cell lines in research are controversial due to the method of obtaining cells, in their formation of teratomas and degeneration into cancer cells, their non-specific differ

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25

Ghazaany, Tahereh S., Shaozhen (Sharon) Zhu, Raed A. Abd-Alhameed, et al. "Experimental Study of Coupling Compensation of Low Profile Spiral Antenna Arrays Response for Direction-finding Applications." 2016. http://hdl.handle.net/10454/8440.

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No<br>An experimental study of coupling compensation for AOA estimation using compact low profile antenna arrays with element separations of a quarter wavelength has been conducted. Two circular arrays of low profile miniaturised logarithmic spiral antennas deployed on a circular metal plate were used for data acquisition. Using the MUSIC direction-finding algorithm, the AOA estimation errors in receiving mode were observed before and after compensation: the errors were significantly decreased by coupling compensation.<br>The full text is unavailable. The publisher is unable to be contacted.

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