To see the other types of publications on this topic, follow the link: SQUID.
Dissertations / Theses on the topic 'SQUID'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'SQUID.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Atkin, Ian L. "Dynamics of SQUIDs and multiple SQUID arrays." Thesis, Heriot-Watt University, 1997. http://hdl.handle.net/10399/666.
Full text
2
Collot, Romain. "Etude d’une tête de réception hyperfréquence en technologie supraconductrice." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT043.
Full textAbstract:
Les systèmes de télécommunication de type radio logicielle ou "Software Defined Radio" (SDR) exploitent les techniques numériques qui permettent leur reconfigurabilité, que ce soit en termes de fréquence, de bande passante utilisée, ou de méthode de modulation/démodulation des signaux. Ceux-ci nécessitent des architectures permettant la numérisation des signaux analogiques RF à des fréquences d'échantillonnage de plusieurs dizaines de GHz, avec des bandes passantes de plusieurs dizaines de MHz et une résolution supérieure à 10 bits. Ces objectifs sont très difficiles à atteindre avec la technologie actuelle des semi-conducteurs. La logique à quantum de flux magnétique ou logique "Rapid Single-Flux-Quantum" (RSFQ) se présente comme un candidat séduisant pour la conception de tels systèmes.En effet, celle-ci permet d'atteindre des fréquences d'horloge de plusieurs centaines de GHz pour une consommation d'environ 100 nW par porte logique. Le travail de thèse a consisté en la réalisation d'un prototype de chaîne de réception RF analogique-numérique en technologie RSFQ. L'étude et la conception des différents blocs la constituant comme le convertisseur analogique-numérique et ceux de traitement du signal numérisé en aval a été réalisée. Les premiers résultats expérimentaux confirment la fonctionnalité des cellules RSFQ de base constituant le bloc de traitement numérique. La difficulté à faire fonctionner expérimentalement les blocs plus complexes a soulevé la question de la sensibilité des cellules RSFQ aux perturbations magnétiques extérieures. Cette problématique a été étudiée sur des circuits RSFQ simples et a permis de conclure qu'un champ magnétique externe de quelques dizaines de $mu$T était suffisant pour dégrader le fonctionnement de tels circuits. Une solution de prise en compte des effets d'un champ magnétique externe dans le simulateur utilisé a été développée pour anticiper ces problèmes dès la conception. Celle-ci a été validée expérimentalement avec un Superconducting Quantum Interference Device (SQUID)Information and telecommunication Software Defined Radio (SDR) systems are mainly based on digital techniques, which enable to easily reconfigure them, in terms of frequency, bandwidth and modulation techniques. They can process the information entirely in a digital way, by directly sampling the input RF signal and require analog-to-digital converters with strong performances. Indeed, SDR systems have to work at sampling frequencies of several tens of GHz, with large bandwidths and a suitable resolution ($geq$ 10 bits). Rapid-Single-Flux-Quantum logic (RSFQ) seems to be an interesting solution to design such systems. This technology can reach clock frequencies of several hundreds of GHz with a power consumption of only 100 nW per logic gate. This work deals with the design of a superconductive RF front-end receiver based on RSFQ technology. The study of the different parts of the chain was done, such as the analog-to-digital converter and the signal processing part of the digital signal. Experimental results confirm that all simple RSFQ cells work with correct margins. Complex circuits work with more difficulty, raising the issue of the sensitivity of RSFQ cells to external magnetic disturbances. This point was studied on basic RSFQ cicuits and shows that a magnetic field of about 10 $mu$T is sufficient to spoil the operation of the circuit. Moreover, a solution to take into account magnetic effects in the simulation of the circuits was developed and experimentally validated on a Superconducting Quantum Interference Device (SQUID)
3
Burger, Willem Adriaan. "The design and analysis of a DC SQUID for a SQUID microscope." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/2239.
Full textAbstract:
Thesis (MScEng (Electrical and Electronic Engineering))--Stellenbosch University, 2008.This thesis relates to the analysis and design of a SQUID microscope. Superconductor theory is discussed in depth to provide a thorough understanding of Josephson junctions and of dc SQUID magnetometers. The behaviour and suitability of different types of single-layer dc SQUIDs are looked at. The quality of the superconducting material patterned onto a substrate and the Josephson junction design used affect the behaviour of a practical dc SQUID. Noise and cooling play an integral part in the design and operation of a dc SQUID. The source of noise is looked at in an effort to minimize its effect. Cryocooling is essential to real world operation so different cooling strategies and their consequences are analyzed. This thesis focuses on modeling the behaviour of the dc SQUID to creating a practical system for use inside a SQUID microscope. Operating the dc SQUID with the appropriate electronics will linearize the device, reduce the effect of noise, and create a device with wide bandwidth. Each step in creating a practical system is discussed in detail. Simulations are used to create models predicting the behaviour of the dc SQUID and the electronics. They are then used to design and create practical electronic systems. Measurements are performed on Josephson junctions and dc SQUID magnetometers using the designed electronics. The Josephson junctions behave as predicted and were successfully tested. The dc SQUIDs did not behave as predicted and were not successfully tested. The SQUIDs were damaged, either by a malfunction in the cryocooler or through age related deterioration. A full test of the flux-locked loop was not possible and the dc SQUID was not linearized.
4
Lang, Gillian. "SQUID gradiometers fo biomagnetism." Thesis, University of Strathclyde, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366811.
Full text
5
Palomaki, Tauno A. "Dc SQUID phase qubit." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8575.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
6
Maluleke, Vutlhari Absalom. "The effects of boat mooring systems on squid egg beds during squid fishing." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2528.
Full textAbstract:
Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2017.In South Africa, squid fishing vessels need to find and then anchor above benthic squid egg beds to effect viable catches. However, waves acting on the vessel produce a dynamic response on the anchor line. These oscillatory motions produce impact forces of the chain striking the seabed. It is hypothesised that this causes damage to the squid egg bed beneath the vessels. Different mooring systems may cause more or less damage and this is what is investigated in this research. The effect of vessel mooring lines impact on the seabed during squid fishing is investigated using a specialised hydrodynamic tool commercial package ANSYS AQWA models. This study analysed the single-point versus the two-point mooring system’s impact on the seabed. The ANSYS AQWA models were developed for both mooring systems under the influence of the wave and current loads using the 14 and 22 m vessels anchored with various chain sizes. The effect of various wave conditions was investigated as well as the analysis of three mooring line configurations. The mooring chain contact pressure on the seabed is investigated beyond what is output from ANSYS AQWA using ABAQUS finite element analysis. The real-world velocity of the mooring chain underwater was obtained using video analysis. The ABAQUS model was built by varying chain sizes at different impact velocities. The impact pressure and force due to this velocity was related to mooring line impact velocity on the seabed in ANSYS AQWA. Results show the maximum impact pressure of 191 MPa when the 20 mm diameter chain impacts the seabed at the velocity of 8 m/s from video analysis. It was found that the mooring chain impact pressure on the seabed increased with an increase in the velocity of impact and chain size. The ANSYS AQWA impact pressure on the seabed was found to be 170.86 MPa at the impact velocity of 6.4 m/s. The two-point mooring system was found to double the seabed mooring chain contact length compared to the single-point mooring system. Both mooring systems showed that the 14 m vessel mooring line causes the least seabed footprint compared to the 22 m vessel.
7
Kwon, Soun Pil. "Design of a large bandwidth scanning SQUID microscope using a cryocooled hysteretic dc SQUID." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3361.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
8
Lee, Su-Young. "Multi-channel scanning SQUID microscopy." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1490.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2004.Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
9
Balestro, Franck. "Dynamique quantique d'un SQUID-DC." Phd thesis, Université Joseph Fourier (Grenoble), 2003. http://tel.archives-ouvertes.fr/tel-00004224.
Full textAbstract:
Une étude théorique que nous avons menée prédit qu'un SQUID-DC, ayant un facteur de qualité égal à 100 dans son régime d'effet tunnel macroscopique, permet une mesure quantique en un coup l'état de charge d'un qubit avec une erreur de l'ordre de 2%. Ce travail de thèse s'inscrit donc dans l'étude et le développement expérimental d'un système de mesure quantIque d'un SQUID. Nous avons étudié la dynamique d'échappement de l'état de tension nulle d'un SQUID-DC inductif en fonction du flux et de la température. Nous avons mis en évidence le régime d'effet tunnel macroscopique et d'activation thermique, dans le cadre de l'échappement d'une particule fictive métastable d'un potentiel bi-dimensionnel. Le temps de vie de l'état de tension nulle d'un SQUID dans son régime d'activation thermique a été mesuré dans la gamme des nano-secondes grâce à une technique d'impulsions en flux. L'utilisation d'impulsions micro-ondes a également permis de mesurer la fréquence plasma d'un SQUID par une technique d'activation résonante, et de mesurer un facteur de qualité de l'ordre de 100.
10
Patel, Trupti. "Nanomechanical resonators for SQUID readout." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10043534/.
Full textAbstract:
Nano-electromechanical systems (NEMS) are an important new class of device, with a growing range of applications, from tests of quantum mechanics through to nanoscale metrology and a vast number of different sensors. Cryogenic operation is also possible, and at low temperatures, nanoscale resonators exhibit quantum behaviour. NEMS resonators require readout of ultra-small, atomic scale displacements. To achieve this at low temperatures we have developed an ultrasensitive nanoSQUID readout of a coupled current-carrying NEMS resonator. The NanoSQUIDs are fabricated by gallium focussed ion beam milling and are based on niobium nanobridge weak links (Dayem bridges). The nanoSQUIDs have low loop inductance and low junction capacitance resulting in high flux and energy sensitivity. This work focusses on the characterisation of the resonator and nanoSQUID after they have been incorporated onto one chip. This is done through nanoindentation to characterise resonators and electronic measurements of the SQUID using a low-temperature preamplifier. It is found that the model used based upon an Euler-Bernoilli beam is correct close the centre of the sample but does not fit data points well close to the contacts. It is found the resonators have Young’s modulus in the range of 3GPa-241GPa. Both beam and paddle-shaped resonators are investigated and the models are made based upon the two different shapes. That for the paddle is based upon the same as the beam but uses a rectangular function to describe the changing area moment of inertia along the length of the resonator. The SQUID devices are characterised and found to have a typical noise floor of 0.2μ 0/pHz. Problems which have arisen due to the orientation of the two magnetic fields and their effect on the SQUID performance are discussed. We consider the geometry and optimum coupling of rectangular and square Si3N4 resonators to matching similar shaped nanoSQUID loops. We also discuss simulations of the nanoSQUID response versus resonator position for both symmetric and asymmetric configurations. It is found that optimal coupling is achieved in the asymmetric case due to the cancelling of the change in flux in the symmetric case. The use of a normal conducting or superconducting resonator is compared. It is found that a superconducting resonator provides a much larger SQUID response when actuated towards the device but cannot be used in the regime due to limitations of the superconducting transition temperature of Al (the resonator) being lower than the non-hysteretic operable temperature of the SQUID. Preliminary measurements are conducted on the coupled devices. It is noted that the signal from the device in the conducting case may be read out at 2! due to the sinusoidal change in flux through the SQUID loop and position of the resonator. The possibility of measuring such a signal is first investigated using a spectrum analyser but it is found the SQUID is pushed to nonlinear regions of its transfer curve. This results in a component of the signal at 2! due to the nonlinearity of the SQUID response. Conditions under which the SQUID is still operating in small signal mode (to preserve linearity of the SQUID response) are considered and from this we conclude there is a need to use phase sensitive detection to achieve optimum sensitivity. This technique is used to conduct the final measurement of the motion of the resonator by the SQUID and a preliminary result is found.
11
Ouanani, Saphia. "Étude de réseaux de jonctions Josephson à haute température critique." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS208.
Full textAbstract:
La jonction Josephson (JJ) est le composé de base de nombreux circuits électroniques supraconducteurs (SQUID, détecteurs d’ondes millimétriques, logique RSFQ). Avec la découverte des supraconducteurs HTc (à haute température critique), d’intenses recherches ont été entreprises pour réaliser des JJ fonctionnant à la température de l’azote liquide (77 K) permettant l’utilisation d’une cryogénie compacte. Toutefois, la complexité de ces matériaux a longtemps rendu difficile le développement d’une technologie viable et simple à mettre en œuvre. Parmi les méthodes de fabrication de jonctions, celle utilisant l’irradiation par faisceau d’ions a atteint un niveau de maturité suffisamment important pour pouvoir envisager la production de circuits comportant plusieurs milliers de JJ à HTc.Le but de ma thèse repose sur la fabrication, la caractérisation et l’étude des propriétés électromagnétiques de réseaux de jonctions Josephson réalisés dans des films minces d’YBa2Cu3O7-d. par la méthode d’irradiation ioniqueThe Josephson junction (JJ) is the basis of many compound superconducting electronic circuits (SQUID detectors millimeter wave RSFQ logic). With the discovery of HTS superconductors (high critical temperature), intensive research has been undertaken to make JJ operating at the temperature of liquid nitrogen (77 K) allowing the use of a compact cryogenics. However, the complexity of these materials has long hampered the development of a viable technology and simple to implement. Among the junctions manufacturing methods, one using the ion beam irradiation has reached a sufficiently high degree of maturity to be able to envisage the production of circuits having thousands of JJ to HTS.The aim of my thesis is based on the fabrication, characterization and study of the electromagnetic properties of Josephson arrays achieved in thin films of YBa2Cu3O7-d. by the ion irradiation method
12
Schön, Pieter-Jan. "An investigation into the influence of the environment on spawning aggregations and jig catches of chokka squid Loligo Vulgaris reynaudii off the south coast of South Africa." Thesis, Rhodes University, 2000. http://hdl.handle.net/10962/d1016369.
Full textAbstract:
Erratic and highly variable catches in the South African chokka squid Loligo vulgaris reynaudii fishery, cause socio-economic hardship for the industry and uncertainty for resource managers. Catch forecasting can reduce this problem as it is believed that catch variability is strongly influenced by environmental factors. In this study, data were collected at varying temporal and spatial scales. Data for the hourly time-scale study were collected from 1996-1998, aboard commercial vessels, whilst for the longer time-scales, data were extracted for Kromme Bay (a single fishing area) from existing databases (1991-1998) that were comprised of compulsory catch returns and oceanographic data. The environment-catch relationship for chokka squid on the inshore spawning grounds was then investigated using multiple correlation and regression analysis, analysis of variance, contingency table analysis and cross-correlation statistical techniques. This simple, direct, 'black box' statistical approach was relatively successful in developing a predictive capability. On a short time-scale (hourly), the regression model accounted for 32% of the variability in catch, with turbidity the main determinant (13%). On a daily monthly time-scale, the best prediction model was on a monthly scale, accounting for 40% of the variability in catch. The principal determinant, bottom temperature anomaly (11 %), was found to lag one month forward. Seasonal and diel catch variations induced changes in the relative importance of turbidity, water temperature and wind direction on catches. A strong, positive relationship was found between easterly winds (which cause upwelling) and catch, particularly in summer. Catch rates, however, decreased with an increase in turbidity. The correlation between temperature and catch was generally negative, however, higher catches were associated with a temperature range of 13-18°C. Highest catch rates were associated with easterly winds, zero turbidity conditions and sea surface temperatures from 15.0-16.9°C. Selected case studies (in situ observations) suggested that upwelling and turbidity events act as environmental triggers for the initiation or termination of the spawning process, respectively. A holistic approach is required to improve predictive capability of chokka squid abundance. Although short-term predictability remains essential (i.e. hourly-scale), future research should concentrate on long-term prediction models (e.g., monthly time-scales) involving greater spatial variation, which are the most important for management.
13
Paik, Han-hee. "Coherence in dc SQUID phase qubits." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/7469.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
14
Barker, Michael Jonathan. "Development of a scanning SQUID microscope." Thesis, University of Birmingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343851.
Full text
15
Robinson, Adam Philip. "SQUID magnetometry of magnetic nanoparticle systems." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420916.
Full text
16
Weiss, Benjamin Paul Ingersoll Andrew P. "Martian paleomagnetism with the SQUID microscope /." Diss., Pasadena, Calif. : California Institute of Technology, 2003. http://resolver.caltech.edu/CaltechETD:etd-02032003-104251.
Full text
17
Bruno, Antonio Carlos Oliveira. "Gradiômetros supercondutores acoplados a SQUIDs e sua aplicação em biomagnetismo." Universidade de São Paulo, 1990. http://www.teses.usp.br/teses/disponiveis/54/54132/tde-19052009-095436/.
Full textAbstract:
O objetivo desta tese foi o estudo da detecção de campos magnéticos fracos através da utilização de gradiômetros supercondutores acoplados à SQUIDs e sua aplicação ao biomagnetismo. Um novo modelo teórico para descrição do gradiômetro foi desenvolvido com a obtenção da sua função de transferência espacial. Através desta função de transferência a atuação do gradiômetro sobre os sinais detectados pode ser quantificada. Além disso, foi desenvolvido para a medida experimental da função de transferência, onde as imperfeições no processo de construção do sensor podem ser medidas e avaliadas. Foi proposta uma nova terminologia para descrição do gradiômetro ao invés de sua descrição física. Nesta terminologia, o gradiômetro ficará especificado pelo seu roll off, freqüência de corte espacial e ganho máximo. Também foi generalizado o método para projeto de gradiômetros onde novas configurações podem ser construídas e testadas. A partir da obtenção desta função de transferência um método para calibração tesla /volt do sistema foi desenvolvido, com uma precisão até então não alcançada por outros métodos e perfeitamente apropriado para utilização em sistemas multicanais. Finalmente foi desenvolvido um algorítimo de desconvolução para, a partir de sinais detectados com gradiômetros planares, recuperar o sinal original como ele tivesse sido detectado somente por uma bobina. Este algorítmo também pode ser utilizado para auxílio no projeto de arrays destes gradiômetros.The objective of this thesis was to study the detection of weak magnetic fields through the use of superconducting gradiometers coupled to SQUIDs and its application to biomagnetism. A new theoretical model for the specification of the gradiometer was developed by obtaining its spatial transfer function. Through the transfer function the signal detected by the gradiometer can be quantified. Besides, a procedure was developed to experimentally measure the spatial transfer, where the imperfections in the construction process of the sensor can be measured and evaluated. A new terminology was proposed for specification of the gradiometer instead of his physical description. Using this terminology, the gradiometer will be specified by its roll off, spatial cutoff frequency and maximum gain. Also the method was generalized for design of gradiometers where new configurations can be built and tested. From the transfer function a method for tesla/volt calibration of the system was developed. Finally a deconvolution algorithm was developed, that from signals detected by the gradiometer the original signal can be recovered. This algorithm also can be used in the design of gradiometer arrays.
18
Wong, Ying-yee. "The squid jigging industry in Hong Kong /." View the Table of Contents & Abstract, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37563324.
Full text
19
Baverstock, Jenny. "Biochemistry of visual transduction in squid photoreceptors." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302983.
Full text
20
Langmack, Keith Antony. "Structure and biochemistry of squid photoreceptor microvilli." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253282.
Full text
21
Fardy, J. S. "Magnetopneumographic studies using a squid-based system." Thesis, Swansea University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636954.
Full textAbstract:
Magnetopneumography (MPG) is a non-invasive technique of measuring occupationally acquired pulmonary dust. Most industrially generated dusts and fumes contain ferro- or ferrimagnetic particles which, after being exposed to a magnetising field, exhibit some degree of remanent magnetisation. By magnetising the thorax of an occupationally exposed subject in an external magnetising field and measuring the thoracic remanent magnetic fields using a SQUID (Superconducting QUantum Interference Device) magnetometer, information on the total lung dust burden and lung dust distribution may be obtained. The work described here concentrates on subjects who have been occupationally exposed to asbestos over extended periods as laggers at a local power station. Initial calibration of the response of the SQUID system was carried out using phantom measurements. Qualitative information regarding a subject's pulmonary dust burden and distribution is described and a comparison of the measured dust distributions with diseased tissue locations as shown by established medical imaging techniques such as Computerised Tomography (CT) and x-radiography is performed. The phenomenon of relaxation, which describes the variation in thoracic remanent magnetic field with time is also investigated. A physical interpretation of the phenomenon is given and the characteristic parameters relating to the severity of disease, and to gross localised pathological tissue changes are discussed. A mathematical model of the problem is described and computational simulations of both the whole lung phantoms, and human subjects are carried out. In this manner, a direct comparison between measurement and theory can be made. Finally, using post mortem lung samples known to contain asbestos fibres, a direct comparison between information derived from electron microscopy and MPG is made in order to assess the sensitivity and reliability of measurements made using the magnetometric technique.
22
Wong, Ying-yee, and 黃影怡. "The squid jigging industry in Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B45013640.
Full text
23
Al-Khawaja, Sameer. "Time dependent phenomena in squid ring circuits." Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298105.
Full text
24
Meng, Kevin Dehan. "Designing a microhydraulically-driven mini-robotic squid." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104264.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 90-93).
The realization of a standalone microrobotic platform has thus far been elusive due to size, weight, and power constraints. Recently, a novel microhydraulic electrowetting actuator (MEA) has been developed at MIT Lincoln Laboratory, enabling powerful, efficient, and scalable actuation. The MEA's use of efficient (17 > 65%), low-voltage electrowetting (<25 V) and high power density favorably positions the actuator for applications in microrobotics, which includes systems on the centimeter-scale and below. In this thesis, I present the design of a miniature robotic "squid" which features the MEA as the driving component. The system was inspired by cephalopod paralarvae, which predominantly rely on jet propulsion in their early stages of development. The squid robot can produce thrust by diaphragm pump-like operation, in either single-acting or double-acting modes. Since the actuator is a critical component, further modeling and analysis on the MEA is first presented and confirmed by experiments. After demonstrating actuator reliability, the design and fabrication of the squid are presented, from component-level considerations to system assembly procedures. High-resolution 3D printing methods are exploited to fabricate monolithic, multi-material structures and to develop passive flap check valves for gauging the pumping capability of MEA. The pump characteristics are modeled and tested, achieving flow rates of up to 1.79 mL/min. A finalized robotic squid design is predicted to swim at a velocity of 3 cm/s, which is comparable to that of young squid. Suggestions are made for the continued development of the mini-robotic squid. It is hoped that the squid design presented herein will serve as a precursor to more advanced, standalone microrobotic systems, which may find use in medicine and defense-related applications.
by Kevin Dehan Meng.
S.M.
25
Muller, Benjamin John Frederick. "The development of a SQUID-based gradiometer." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4378.
Full textAbstract:
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: This thesis presents an attempt at creating a fully functional SQUID for the purposes of a predefined application. The goal of the work is to provide a method of development, primarily utilising the facilities of the Engineering Faculty of the University of Stellenbosch, with minimal assistance from other departments. This method is then analysed and the successes and failures discussed in order to provide guidelines and recommendations for future research. The device consists of a gradiometric SQUID, as well as electronics which provide the SQUID bias current, output linearisation and output signal filtering. YBCO is used for the superconducting material, allowing the use of liquid nitrogen as coolant which eases the operation and portability of the device. Various methods of creating Josephson junctions are tested, such as constriction bridges using AFM lithography and step-edge junctions, with and without different buffer layers. Proof of concept simulations demonstrate the viability of the device. Unfortunately, a functional device could not be constructed, mostly due to the design requiring higher levels of resolution and process control than some of the available facilities can provide. Recommendations are provided for future researchers.
AFRIKAANSE OPSOMMING: Hierdie tesis beskryf ’n poging om ’n volledige funksionele SQUID te vervaardig vir die doeleindes van ’n vasgestelde toepassing. Die doel van die werk is om ’n metode te voorsien wat hoofsaaklik gebruik maak van die fasiliteite van die Ingenieurswese Fakulteit van die Universiteit van Stellenbosch, met minimale hulp van ander departemente. Hierdie metode word dan ondersoek en die suksesse en mislukkings bespreek om riglyne en voorstellings te voorsien vir toekomstige navorsing. Die toestel bestaan uit ’n gradiometriese SQUID, sowel as elektronika wat voorsiening maak vir voorspanning, uittree-linearisering en ’n uittree-filter. YBCO is as supergeleidende materiaal gebruik, wat die gebruik van vloeibare stikstof as verkoeler moontlik maak en dus die hantering en draagbaarheid van die toestel vergemaklik. Verskillende metodes om Josephson-vlakke te vervaardig is getoets, onder andere vernouingsbrugvlakke deur middel van AFM litografie en stapvlakke met en sonder bufferlae. Bewys van konsep simulasies demonstreer die lewensvatbaarheid van die toestel. Ongelukkig kon ’n funksionele weergawe van die toestel nie vervaardig word nie, hoofsaaklik as gevolg van die ontwerp wat hoër resolusievlakke en beter prosesbeheer benodig as wat sekere van die beskikbare fasiliteite kan voorsien. Aanbevelings word voorsien vir toekomstige navorsers.
26
Digby, Megan Elizabeth. "Broadband DC SQUID NMR spectrometry on metals." Thesis, Royal Holloway, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322702.
Full textAbstract:
This Thesis describes the development of a broadband pulsed NMR spectrometer, based on a sensitive DC SQUID amplifier with wideband electronics, to observe directly the free precession of nuclear spins in bulk metallic samples (with broad NMR linewidths) at Larmor frequencies cß/2 ,r below 1 MHz. The sample is located inside a pickup coil, which forms a superconducting flux transformer with the input coil of the SQUID. The SQUID amplifier operates in a flux-locked-loop (FLL), hence it is sensitive to signals from DC up to the bandwidth of the FLL electronics. A modified commercial DC SQUID amplifier, with modulated feedback electronics, observed NMR signals from bulk platinum samples (T2 - 1.1 ms), at 1.5 K. The SQUID amplifier had a 50 kHz bandwidth, a dead-time - 50 μs, and a coupled energy sensitivity cc - 500h. The measurements showed that it is important to minimise the time-constant of eddy current decay in the sample, which scales with r2, as expected, where r is the sample dimension. A DC SQUID amplifier with additional positive feedback and wideband electronics configured using the direct offset integration technique, observed NMR signals from a bulk aluminium sample (T2 - 30 μs) at 20 mK. This SQUID amplifier had a 7.5 MHz bandwidth, the dead-time was 55 μs for small transmitter pulses and e,; - 600h. The use of a strongly coupled input coil with the SQUID necessitated damping across the coil to smooth out the SQUID flux-voltage characteristicThe NMR measurements showed that eddy current decay is less important if the NMR signal size is enhanced by cooling the sample. Measurements also confirmed that the NMR signal from bulk metal is proportional to 4c0, and that a reasonable estimate of the signal size is made by assuming the signal is due to spins within half the skin-depth of the surface
27
Mercado, Vanessa Tais Cruz. "Análise socioambiental dos pescadores de lulas (Mollusca: Cephalopoda) na região de São Sebastião, Estado de São Paulo." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/21/21134/tde-03082017-095947/.
Full textAbstract:
O objetivo deste estudo foi obter um diagnóstico socioambiental incluindo aspectos do etnoconhecimento dos pescadores de São Sebastião e Ilhabela (litoral norte de SP) associado à pesca de lula. Para o estudo, foram selecionados sete pontos no município de São Sebastião e dois pontos em Ilhabela. Para obtenção de dados, foi aplicado um questionário semiestruturado, contendo perguntas sobre condições socioeconômicas, infraestrutura comunitária e individual, etnoconhecimento, custos da pesca e primeira comercialização, assim como a origem da arte de pesca. As respostas foram divididas em dados qualitativos e quantitativos. Posteriormente, os dados qualitativos foram pontuados como dados quantitativos para a análise de correlação não paramétrica e de agrupamento. Aspectos históricos sobre o surgimento do zangarilho foram também explorados. Os resultados apontaram que: 1) a pesca da lula tem importância econômica, pois representa um aumento na renda do pescador; 2) não houve nenhuma correlação entre o rendimento com a pesca de lula e condições sociais ou infraestruturais; 3) a maioria dos pescadores tem idade entre 41-50 anos e, quanto ao nível escolar, a maioria possui o 10 grau incompleto e a maior parte tem emprego para complementar a renda; 4) a maior parte dos pescadores obtém em média entre R$800,00 e R$4000,00, com um ganho significativo nos meses de verão; 5) em relação à infraestrutura comunitária, foi verificada carência de acesso a escolas e hospitais; 6) a maioria dos entrevistados possui residência em São Sebastião, sendo a maior parte delas de alvenaria e com fornecimento de energia elétrica deficiente em praias mais afastadas; 7) a maioria dos pescadores considera a pesca da lula lucrativa; 8) quanto à comercialização, os melhores rendimentos são obtidos quando a venda é feita diretamente para o consumidor; 9) em termos históricos, a pesca da lula não é somente passada de pai para filho, mas também passada entre eles e amigos, tornando possível dizer que constitui um processo cultural; 10) o etnoconhecimento em relação à lula demonstrou ser significativo no que diz respeito à época de ocorrência, locais onde há fêmeas com ovas, conhecimento sobre a reprodução, sobre seus hábitos alimentares e teia alimentar. Os resultados obtidos a partir dessa pesquisa podem servir para um futuro plano de manejo.The aim of this study was to carry out a socio environmental diagnosis which included the ethnoknowledge aspects of the fishermen from San Sebastian and Ilhabela regarding the squid fishery. We selected seven points in San Sebastian and two in Ilhabela. To obtain the data, we applied a semi-structured questionnaire covering the socioeconomic, regional infrastructure, squid sales and values, origin of the fishing skills and ethnoknowledge. The responses were initially split in qualitative and quantitative data. Afterwards, the qualitative data were scored as in quantitative parameters for cluster and non parametric correlation analysis. Historical aspects regarding the emergence of the squid jig (zangarilho) were also explored. The results showed that: 1) the squid fishery is economically important because it represents an increase to the fisherman\'s income; 2) there was no correlation between the squid fishery income and social and local infrastructure conditions 3) the majority of the fishermen community is composed of: men who are 41-50 years old; have incomplete high school degree; and work to supplement income; 4) most of the fishermen earning is about R$ 800 and R$ 4,000 with a major income in the summer; 5) the community infrastructure shows a significant lack of schools and hospitals facilities; 6) most of the fishermen live in San Sebastian, in masonry houses, and have problems regarding the electricity supply in remote beaches; 7) most of the fishermen consider squid fishing a lucrative activity; 8) the best yields are obtained when the squid is sold directly to the consumer; 9) historically, the squid fishing is handed down from father to son and among friends, which characterizes a cultural process; 10) the squid fishery ethnoknowledge shown to be significant concerning the occurrence period, places where females can be found, knowledge about feeding habits, reproduction and food web. The results obtained from this research may be useful for a future management plan.
28
Waluda, Claire Marie. "Oceanographic influences on the Illex argentinus (Cephalopoda: Ommastrephidae) fishery, Southwest Atlantic." Thesis, University of Aberdeen, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368533.
Full textAbstract:
In this study, environmental and fishery data are used to examine links between the oceanography of the Southwest Atlantic, and the distribution and abundance of the ommastrephid squid Illex argentinus. Spatial and temporal patterns in squid distribution and abundance are examined using Geographic Information Systems (GIS), remotely-sensed satellite-derived environmental data and statistical techniques. Inter-annual variability in the recruitment of I. argentinus was shown to be influenced by both large and mesoscale oceanographic processes operating during the early life history stages at the Brazil-Falkland (Malvinas) confluence. During the fishery period, in Falkland Islands (Malvinas) waters, variability in large scale sea surface temperature (SST) was not found to influence the abundance of I. argentinus, but the distribution of squid within the fishery was found to be associated with mesoscale oceanographic features occurring in this region. Indices describing oceanographic variability during the early life-stages were found to be of value in predicting the recruitment of squid to the fishery in Falkland Islands (Malvinas) waters. Teleconnections were shown to exist between SST anomalies in the Pacific (related to El Nino-Southern Oscillation (ENSO) events) and the Atlantic, and it is possible that environmentally-driven recruitment variability in squid populations such as I. argentinus may prove to be a useful biological indicator of global phenomena such as ENSO. Oceanographic variability was found to be an important factor in influencing both the distribution and abundance of I. argentinus in the Southwest Atlantic. The techniques used in this study are readily transferable to the study of other ommastrephid squid species.
29
Martins, Maria Clara Prata Ribeiro. "Biology of pre- and post-hatching stages of Loligo vulgaris Lamarck, 1798 and Loligo forbesi Steenstrup, 1856 (Mollusca, Cephalopoda)." Thesis, University of Aberdeen, 1997. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU483279.
Full textAbstract:
Loligo vulgaris and Loligo forbesi (Cephalopoda, Myopsida) are sympatric in geographical distribution. Samples of Loligo vulgaris and Loligo forbesi eggs were collected in the two geographical areas where each species occurs predominantly, southern coast of Portugal and northwestern coast of Scotland, respectively. The embryos and hatchlings were reared in the laboratory at several experimental temperatures. This study presents new information on various aspects of the early life stages of Loligo sp. The spawned egg clusters of both species had similar external appearance. The egg strings of Loligo vulgaris are smaller and contain more eggs of smaller volume than those of Loligo forbesi. Temperature appears to be the factor limiting the distribution of these species. The percentage of deformed embryos was higher in Loligo vulgaris acclimated to lower temperature levels (13°C). The duration of the embryonic development was shortened with increasing temperature, and at similar temperature level the difference in the embryonic phase of Loligo vulgaris and Loligo forbesi was approximately 200 day-degrees. The normal hatching period from one egg string was 3 to 4 hours for both species at all experimental temperature levels. Starved Loligo vulgaris hatchlings survived longer than starved Loligo forbesi hatchlings. Maximum survival rates in Loligo vulgaris fed ad libitum were associated to the presence of live zooplankton and lower hatchling density in rearing tanks. At late embryonic stages the activity of the chorionated embryos increases in response to mechanical disturbance and to changes of light intensity. In undisturbed embryos the rate of mantle contractions increases towards pre-hatching stages. In artificial rearing condition, Loligo forbesi and Loligo vulgaris hatchlings exhibit positive phototaxis, swim at 2-3 mantle contractions per second and at relative velocities varying between 20-130 dorsal mantle lengths per second. The cost of sustained swimming was estimated between 0.02-0.06 J h-1, and the cost of transport for 7 mg hatchling was 4-12 J g-1 m-1.
30
Cabanellas, Reboredo Miguel. "Socio-ecological approach of the recreational squid shery." Doctoral thesis, Universitat de les Illes Balears, 2014. http://hdl.handle.net/10803/145976.
Full textAbstract:
El creciente impacto de la pesca recreativa sobre el declive de los stocks, hace necesario considerar el role que este sector desempeña sobre la dinámica poblacional de los recursos explotados. Uno de los recursos que sufre una fuerte explotación, tanto por el sector comercial como por el sector recreativo, es el calamar Europeo Loligo vulgaris. Esta Tesis afronta el reto de poner en relieve el potencial impacto que este sector ejerce sobre esta especie. Para ello, aspectos clave de la vida del calamar, la dinámica de la pesquería recreativa y sus interacciones han sido abordadas. Con esta tesis ofrecemos información clave para la comprensión de los patrones de esfuerzo desarrollados por la pesca de recreo, lo cuales guardan una estrecha relación con las agregaciones reproductoras en costa de esta especie. Esta Tesis demuestra el importante papel de la pesca recreativa en la explotación y dinámica poblacional de este valorado recurso.
31
Troeman, Aico Giardano Paul. "Nanosquid magnetometers and high resolution scanning squid microscopy." Enschede : University of Twente [Host], 2007. http://doc.utwente.nl/58110.
Full text
32
Perry, A. R. "Magnetisation measurements of superconductors with a SQUID magnetometer." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240048.
Full text
33
Dyball, Helen Catherine Jane. "A study of 3He films using SQUID NMR." Thesis, Royal Holloway, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252057.
Full text
34
Diggins, Jonathan. "Computational modelling of weak link SQUID ring circuits." Thesis, University of Sussex, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386508.
Full text
35
RIBEIRO, EDUARDO PARENTE. "MAGNETIC SUSCEPTIBILITY TOMOGRAPHY USING A SUPERCONDUCTOR SQUID MAGNETOMETER." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1996. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8650@1.
Full textAbstract:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORVárias modalidades de tomografia já foram desenvolvidas para aplicações na área médica. São exemplos a tomografia de raio-x, tomografia de ressonância magnética, que são técnicas usadas rotineiramente no ambiente clínico, e a tomografia de impedância elétrica ainda considerada como uma técnica em pesquisa. Com a utilização do dispositivo de detecção magnética SQUID (Superconducting Quantum Interference Device) a partir da década de setenta tornou- se possível realizar medida dos fracos campos magnéticos produzidos pelo corpo humano com uma razão sinal/ruído antes não alcançada. A susceptibilidade magnética é uma propriedade física da matéria, incluindo os tecidos biológicos, de interagir com o campo magnético aplicado. Uma técnica para reconstruir a distribuição tridimensional de susceptibilidade magnética de um corpo a partir da medida da perturbação magnética foi estudada e aprimorada. Foram realizadas simulações para avaliar a qualidade da reconstrução a partir das projeções em diferentes arranjos geométricos na presença de ruído e foi efetuada a reconstrução tomográfica a partir de medidas experimentais com amostras de acrílico. Esta modalidade de tomografia embora apresente severa limitação de resolução espacial representa uma nova fonte de informação sobre o interior do corpo com promissoras aplicações na área biomédica e de ensaios não destrutivos.
Several modalities of tomography have been developed for medical applications. Some example are x-ray tomography, positron emission tomography and magnetic resonance imaging which are used routinely in the clinical enviroment and electricall impedance tomography, still considered a research technique. During the seventies, measurements of the weak fields produced by the human body with unprecendet signal to noise ratio were made possible with the use of SQUIDs (Superconducting Quantum Interference Device). Magnetic susceptibility is a physical property of the matter including biological tissues to interact with an applied magnetic field. A technique to reconstruct three-dimensional susceptibity distribuition from measurements of the pertubartion of the magnetic field was studied and improved. Simulations to reconstruct the three-dimensional susceptibility distribution of a body from the measurement in the presence of noise were carried out and the tomographic reconstruction from the measurement in the presence of noise were carried out and the tomographic reconstruction from experimental measurement in the presence of noise were carried out and the tomographic reconstruction from experimental measurements with acrylic samples performed. Although this new modality of tomography presents severe spatial resolution limitation, it represents a new source of informatio from the interior of body with promising applications in the biomedical field and nondestrutive evaluations.
36
Holzer, Jenny Rebecca. "Scanning SQUID Microscope Measurements on Josephson Junction Arrays." University of Cincinnati / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ucin973710069.
Full text
37
Veauvy, Cécile. "Imagerie magnétique par micro-SQUID à basse température." Université Joseph Fourier (Grenoble), 2002. http://www.theses.fr/2002GRE10011.
Full text
38
Botha, Gerald. "A business plan for an international squid business." Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/21604.
Full textAbstract:
Talhado Fishing Enterprises (Pty) Ltd is a squid fishing company founded in 1988, with sea and land based freezing facilities. Operating from the East coast situated in the Port Elizabeth harbour, the company processes and packages its caught and bought out product for sales to its export customers situated in Spain and Italy. The company is privately owned, 38.8 percent owned by previously disadvantaged persons. This study examines the whether it would be feasible to expand its operations into the USA, namely into the California area where a squid fishery exists. The study further centres around the company’s existing markets, namely Spain and Italy, to establish whether demand exists to purchase this Californian squid specie. The reason for the study is that due to legislative and political issues growth in the squid industry in South Africa is limited. It is therefore considered pertinent to source further supply of product in order to expand its business. The aim of the study is establish whether it is feasible to expand the company’s operations internationally and does the outcome of this initial study warrant the development of an in depth business plan. In order to achieve these objectives the following approach was followed: A comprehensive literature study was conducted with regard to the industry internationally and locally; Interviews was conducted with independent experts such as attorneys and industry role players situated in California; Potential sellers of businesses were sourced in the California and interviews were arranged with these role players; The response to the interviews was measured against the literature study conducted and financial statements supplied.
39
Madan, Jeannie Jamshed. "Oxygen uptake by the gills and skin of cephalopods." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243198.
Full text
40
Barthelmess, Henry-Jobes. "YBa2Cu3O7dc-SQUID-Magnetometer für biomagnetische Messungen in magnetischen Störfeldern." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965212238.
Full text
41
Alaniz, Flores Monica. "Experiment Control Electronics for Spinning Quad Ionospheric Deployer SQUID." Thesis, KTH, Rymd- och plasmafysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91730.
Full textAbstract:
The Spinning QUad Ionospheric Deployer (SQUID) is a soundingcrocket experiment developed to test and verify a novel mechanism to deploy wire booms. The SQUID consists of the Rocket Mounted Unit (RMU) and the Free Flying Unit (FFU), the former is attached to the rocket and the latter is ejected. The FFU carries the electronics box (eBox) that controls the system and the boom deployment system known as SCALE. The FFU needs to be independent when has been ejected from the rocket. This thesis work covers the design and manufacture of the SQUID electronics system to control the functionality of the experiment. The control is implemented in a Field Programmable Gate Array (FPGA) using the VHDL language. The integration, testing and validation of software and hardware also is presented here. The SQUID experiment was launched onboard the REXUS-10 rocket from ESRANGE the 23rd February 2011.
42
Brierley, Andrew Stuart. "Aspects of genetic diversity and population structure of squid." Thesis, Bangor University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316589.
Full text
43
LIMA, EDUARDO ANDRADE. "SPATIAL FILTER MODELS FOR SUPERCONDUCTING GRADIOMETERS COUPLED TO SQUID." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2001. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1729@1.
Full textAbstract:
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOOs sensores SQUID(Superconducting Quantum Interference Device)são os detentores mais sensíveis de fluxo magnético conhecidos atualmente.Devido à sua elevada sensibilidade, os Squids frequentemente necessitam ser acoplados aos chamados gradiômetros (conjunto de bobinas supercondutoras conectadas entre si de forma substrativa ) de modo a reduzir a contaminação do sinal por ruídos ambientais. A resposta do sensor ao campo magnético é fortemente dependente da geometria do gradiômetro, sendo portanto de grande relevância o desenvolvimento de um modelo analítico que permita a reprodução acurada dos efeitos do gradiômetro sobre o sinal de saída, e que também seja uma ferramenta auxiliar no projeto destes dispositivos, nas suas diversas configurações. Nesta Tese,propõe-se um novo modelo que tem como base métodos de processamento de sinais, considerando os gradiômetros como filtros espaciais multidimensionais, com campo magnético como entrada e o fluxo líquido como saída. São discutidas e comparadas as principais configurações gradiométricas encontradas na literatura e são realizados projetos para a detecção de campos magnéticos em uma aplicação usual de sensores SQUIDS. Também é estudada uma técnica de desconvulação, que permite obter o campo magnético ( o que se deseja medir ) a partir do conhecimento do fluxo líquido ( o que efetivamente é medido pelo Squid).
The Superconducting Quantum Interference Device (squid) sensor is the most sensitive device available to detect magnetic flux.Due to its high sensitivity, SQUIDs are often coupled to gradiometers - a set superconducting coils connect in a subtractive way - in order to reduce environmental noise. Because the response of the sensor depends on the gradiometer geometry it is of great importance the development of an analytical model that accurately reproduces the gradiometer effects over the output signal and also helps in the design of such devices. A novel model based on signal processing methods is proposed in this Thesis, which considers gradiometers as multi-dimensional spatial filters with the magnetic field as input and the net magnetic flux as output. The main configurations found in the literature are compared and commented, and gradiometers are designed to detect magnetic field in a typical application of SQUID sensors.Moreover,it is studie the decovolution issue, which allows the obtainment of the magnetic field( what is to be measured in most cases )from flux measuresmentes (what is actully measured by SQUID sensors.
Los sensores SQUID(Superconducting Quantum Interference Device)son los detentores más sensibles de flujo magnético conocidos actualmente. Por su elevada sensibilidad, los Squids necesitan ser frecuentemente acoplados a los llamados gradiómetros (conjunto de bobinas supercondutoras conectadas entre sí de forma substrativa) para reducir la contaminación de la señal por ruídos ambientales. La respuesta del sensor al campo magnético depende fuertemente de la geometría del gradiómetro. Es por ello que resulta de gran relevancia el desarrollo de un modelo analítico que permita la reprodución precisa de los efectos del gradiómetro sobre la señal de salida, y que también sea una herramienta auxiliar en el proyecto de estos dispositivos, en sus diversas configuraciones. En esta tesis se propone un nuevo modelo que tiene como base los métodos de procesamiento de señales, considerando los gradiómetros como filtros espaciales multidimensionales, con campo magnético como entrada y el flujo líquido como salida. Se discuten y comparan las principales configuraciones gradiométricas encontradas en la literatura así como proyectos para la detección de campos magnéticos en una aplicación usual de sensores SQUIDS. Tambiém se estudia una técnica de desconvulación, que permite obter el campo magnético (que se desea medir) a partir del conocimiento del flujo líquido (que efectivamente es medido por el Squid).
44
Bennington-Gray, Suzanne. "Magnetic characterisation of nanostructured magnetic systems using SQUID magnetometry." Thesis, Queen's University Belfast, 2019. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.766289.
Full text
45
Graser, Ferdl Wolfgang. "A reproducible design and manufacturing process for SQUID magnetometers." Thesis, Stellenbosch : University of Stellenbosch, 2005. http://hdl.handle.net/10019.1/1865.
Full textAbstract:
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005.A process was developed to design and manufacture a dc SQUID magnetometer. Superconductor theory is given as a foundation to explain the Josephson junction. This knowledge is applied to explain the ideal and practical dc SQUID. The design of the dc SQUID is done with inductance calculation formulas. Each step of the manufacturing process is discussed in detail. Many improvements have been made to the process to make each step reproducible. The steps in the manufacturing process that were done in-house are: manufacturing an YBa2Cu3O7−d pellet, depositing the thin film with the pulsed laser deposition process, creating a mask with the UV lithography process, wet etching the circuit and depositing silver contact pads with thermal evaporation. The device is packaged on a printed circuit board device holder and shielded with a mu-metal shield. A test setup is developed to test the final device. Each step in the manufacturing process was successful. The final device did not work, due to oxidisation of the YBa2Cu3O7−d thin film.
46
Roel, Beatriz Adelaida. "Stock assessment of the Chokka Squid : Loligo vulgaris reynaudii." Doctoral thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/19576.
Full textAbstract:
Summary in English.Bibliography: p. [199]-210.
The primary aim of the study was to assess the status and productivity of chokka squid. Main hypotheses examined are the following: that the sharp decline in the trawl fishery catch per unit effort (CPUE) data in the early 1980s, reflects a real decline in the trawlers catch rate; that the decline in the trawl CPUE index is caused by the jig fishery removing the biomass that otherwise would be available to the trawl fishery; that the jig fishery "disturbs" the spawning process and causes a decline in subsequent recruitment. Catch and effort data from the two fisheries, as well as biomass estimates from spring and autumn research surveys, were used. The two main fisheries and the catch and effort data are described. General Linear Modelling (GLM) was performed on the CPUE data from the trawl fishery in order to obtain annual indices of abundance. Further, results from a GLM analysis on two years of monthly jig CPUE data are presented. The dynamics of the stock biomass on the spawning grounds were modelled in order to assess the effects of current levels of effort and the existing closed season on the resource. The dynamics of the stock and the fishery were captured by a simple biomass-based model. Two dynamic methods were used to estimate model parameters: 1. a process-error estimator; 2. an observation-error estimator. All model parameter were estimated by maximum likelihood, and the corresponding confidence intervals were estimated by bootstrapping.
47
Koshnick, Nicholas C. "Nano-squid susceptometry and fluctuation effects in superconducting rings /." May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Full text
48
Martin, Lindsay. "Fisheries management, fishing rights and redistribution within the commercial chokka squid fishery of South Africa." Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1007500.
Full textAbstract:
The objective of this thesis is to analyse the management and redistribution policies implemented in the South African squid industry. This is done within the broader context of fisheries policies that have been implemented within the South African fishing industry as the squid industry has developed. The study therefore has an institutional basis, which reviews the development of institutional mechanisms as they have evolved to deal fisheries management problems. These mechanisms (which can either be formal or informal) consist of committees, laws and constitutions that have developed as society has progressed. Probably the most prominent of these, in terms of current fisheries policy, is the Marine Living Resources Act (MLRA) of 1998. The broad policy prescription of the MLRA basically advocates the sustainable utilisation of marine resources while outlining the need to restructure the fishing industry to address historical imbalances and to achieve equity. It is this broad objective that this thesis applies to the squid fishery. The primary means of achieving the above objective, within the squid industry, has been through the reallocation of permit rights. These rights also provide the primary means by which effort is managed. A disruption in the rights allocation process therefore has implications for resource management as well. Permits rights can be described as a form of use right or propertY right. These rights are structured according to their operational-level characteristics, or rules. Changing these rules can thus affect the efficiency or flexibility of a rights based system. This is important because initial reallocation of rights, by the Department of Environmental Affairs and Tourism (DEAT), was based on an incomplete set of rights. This partly led to the failure of early redistribution attempts resulting in a "paper permit" market. Nevertheless, this thesis argues that redistribution attempts were based on ill-defined criteria that contributed to the failure described above. In addition to this the method through which redistribution was attempted is also questionable. This can be described as a weak redistribution strategy that did not account for all equity criteria (i.e. factors like capital ownership, employment or relative income levels). This thesis thus recommends, among other things, that an incentive based rights system be adopted and that the design of this system correctly caters of the operational-level rules mentioned above. In addition to this a strong redistribution, based on fishing capital, ownership, income and the transfer of skills, should be implemented.KMBT_363
Adobe Acrobat 9.54 Paper Capture Plug-in
49
Lochner, Emile Tobias. "Towards a global SQUID network through optimal monitoring station design." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96817.
Full textAbstract:
Thesis (MEng)--Stellenbosch University, 2015.ENGLISH ABSTRACT: The Superconducting Quantum Interference Device (SQUID) is one of the most sensitive magnetic field sensors in the world. These instruments can only be used optimally for geomagnetic research if placed far from man-made magnetic signals. Moving the SQUID to a remote site leads to several infrastructure-related problems including construction, power, data connectivity, and cryogenic cooling. This thesis investigates possible solutions to these problems and develops guidelines for designing future remote SQUID stations. A remote SQUID observatory typically consists of three structures placed approximately 40 m apart. These include: the control room, which houses all computers and supporting electronics, the power hut, which contains a regulated battery bank charged from a solar array that delivers DC power to the rest of the system, and the SQUID hut itself, which is thermally insulated by cavity walls. The SQUID is placed on an isolation pillar that decouples it from structural vibrations due to wind and outside temperature uctuations. The temperature inside the SQUID hut is also monitored as changes in temperature can result in small deformations of the SQUID mounting system which lead to changes in the SQUID's orientation. The changes in the orientation will appear as slow varying magnetic signals on the SQUID output. In principle, it is possible to compensate for these variations through post-processing. The SQUID needs to be cryogenically cooled to function. The SANSA SQUID is a High Temperature Superconductor (HTS) and operates using liquid nitrogen. Immersion cooling is used, as it is the simplest method, and produces the least amount of mechanical and electrical noise. Over time the liquid nitrogen will evaporate and needs to be replaced without significantly disrupting SQUID operations. A simple yet effective pumping scheme was developed that can transfer approximately 1.8 litres of liquid nitrogen every minute from a refill dewar. Monitoring of the liquid nitrogen level is an important management tool for a remote station, as refilling will be the primary reason for technicians to visit the site. The monitoring is achieved by placing the SQUID dewar on a specially designed non-magnetic load cell scale. The scale has been designed to limit the amount of tilting as the weight changes since this would also change the SQUID orientation. When a HTS SQUID is cooled in a large magnetic field, such as the Earth's field, Abrikosov vortices are likely to form in the superconducting material. As these vortices jump between pinning sites in the material, they increase the 1/f noise of the device and have been found to reduce the stability of the SQUID. Metal shields can be used to reduce the magnetic field, but are awkward to use and also reduce the magnitude of the signals of interest. In this thesis, a shielding method using Helmholtz coils is investigated. These coils are relatively simple and inexpensive to construct and do not attenuate the signals of interest. It was found that by cooling the SQUID in the reduced magnetic field, generated by the Helmholtz coils, the stability of the SQUID can be improved significantly.
AFRIKAANSE OPSOMMING: Die SQUID is die mees sensitiewe magneetveld sensors in die wêreld. Hierdie instrument kan slegs optimaal vir geometriese navorsing gebruik word indien dit ver van mensgemaakte magneetvelde opgestel word. Om die SQUID in 'n afgesonderde area op te stel veroorsaak verskeie probleme met betrekking tot infrastruktuur sover dit konstruksie, kragvoorsiening, en kriogeniese afkoeling aangaan. Hierdie tesis ondersoek moontlike oplossings vir die probleme en riglyne te ontwikkel vir die oprigting van toekomstige SQUID stasies. 'n Tipiese afgele SQUID observatorium bestaan gewoonlik uit 3 strukture wat 40m van mekaar opgestel is. Die beheerkamer bevat al die elektroniese apperaat, die kragkamer bevat 'n stel gereguleerde batterye wat deur sonpanele helaai word en DS krag verskaf aan die stasie en die SQUID-kamer wat deur middel van spoumure teen hitte gensoleer is. Die SQUID word op 'n gesoleerde pilaar geplaas om die invloed van vibrasies a.g.v. wind en wisselende buite temperature te verminder. Die temperatuur binne die SQUID kamer word ook noukeurig gemonitor aangesien wisseling in temperatuur geringe vervorming van die SQUID se montering kan veroorsaak wat 'n verandering van die SQUID se orintasie veroorsaak. Hierdie veranderings sal waargeneem word as stadige varirende sein in die SQUID se lesings. In beginsel is dit moontlik om vir dit te kompenseer deur middel van naprosessering. Die SQUID moet kriogenies afgekoel word om te funksioneer. Die SANSA SQUID is 'n Ho Temperatuur Supergeleier (HTS) en vloeibare stikstof word gebruik vir verkoeling. Afkoeling deur middel van indompeling word gebruik omdat dit die kleinste hoeveelheid meganiese en elektroniese versteuring veroorsaak. Die vloeibare stikstof verdamp mettertyd em moet vervang word sonder om die werking van die SQUID merkbaar te onderbreek. 'n Eenvoudige tog effektiewe oorpompstelsel is ontwikkel wat ongeveer 1.8 liter/minuut vloeibare stikstof vanuit 'n hervullings vakuum es kan oorpomp. Die meting van die vloeibare stikstof vlak is 'n belangrike aspek van die instandhouding van 'n afgele stasie aangesien dit die hoof rede sal wees vir tegnici om die perseel te besoek. Die meting word bewerkstellig deur die plasing van die SQUID se vakuum es op 'n spesiale ontwerpte, nie-magnetiese vrag sel skaal. Hierdie skaal is ontwerp om die mate van kanteling te beperk aangesien dit die orentasie van die SQUID kan benvloed. Wanneer 'n HTS SQUID binne in 'n groot magnetiese veld afgekoel word, is dit waarskynlik dat Abrikosov vortekse in die supergeleidende materiaal sal ontstaan. Soos hierdie vortekse rondspring in die materiaal vermeerder dit die 1/f ruis en daar is gevind dat die stabiliteit van die SQUID nadelig benvloed word. Metaal skilde kan gebruik word om die invloed van die magneetveld te verminder, maar is ongerie ik om te gebruik en verminder ook die sterkte van die seine wat waarneem wil word. In hierdie tesis word Helmholtz spoele ondersoek as 'n afskermings metode. Hierdie spoele is eenvoudig om te vervaardig en verminder nie die sterkte van waarneembare seine nie. Daar is gevind dat die stabiliteit van die SQUID merkbaar verbeter word deur afkoeling in 'n lae magnetiese veld soos bewerkstellig deur die Helmholtz spoele.
50
Van, der Vyver Johan Samuel Frederik. "The geographic stock structure of chokka squid, Loligo Reynaudi, and its implications for management of the fishery." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1012973.
Full textAbstract:
It is currently hypothesised that the chokka squid (Loligo reynaudi) consist of a single stock. This was tested through a spatial comparison of the morphology of this species. Forty three morphometric characters were measured from 1079 chokka squid collected from three regions: the south coast of South Africa, the west coast of South Africa, and southern Angola. While no significant differences were found for the hard body parts, results from discriminant function analyses showed the soft body morphometric characters from each of the three regions differed, with an overall correct classification rate of 100% for males and 99% for females in all three regions. Due to the existing model being used to assess the resource currently being updated it was not feasible to apply this model to the area-disaggregated data from this study. Rather, the CPUE trends and catches from the area-disaggregated data were compared against those of the area-aggregated data, as a first attempt to discern any appreciable differences which would suggest the use of disaggregated data in future assessments. Both the trawl and jig CPUE trends from the area-disaggregated analysis differed only slightly from those of the area-aggregated data. Similarly, the spring and autumn biomass trends for the main spawning area (east of 22°E) followed the same trends as for the full area. It is therefore concluded that there is currently no need to assess the resource on an area-disaggregated basis.