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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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[en] CONSTRUCTION OF A SCANNING MAGNETIC MICROSCOPE USING HALL EFFECT SENSORS MODEL HG-362A / [pt] CONSTRUÇÃO DE UM MICROSCÓPIO MAGNÉTICO DE VARREDURA USANDO SENSORES DE EFEITO HALL MODELO HG-362A

CHRISTIAN DAVID MEDINA GARCIA 22 June 2020 (has links)
[pt] A microscopia magnética de varredura tem sido um importante campo de pesquisa destinado à obtenção das propriedades magnéticas de diferentes materiais e suas aplicações em áreas como geologia, medicina, ciências e tecnologia. No Laboratório de Instrumentação do Departamento de Física da PUC-Rio construímos e calibramos um microscópio magnético de varredura capaz de medir e mapear amostras com massas na ordem de microgramas. O microscópio foi construído utilizando um sistema de leitura baseado em uma configuração gradiométrica que utiliza dois elementos sensores de efeito Hall com tamanho de 300 um (micrômetro) e está separado da superfície da amostra por uma distância de 143 um (micrômetro). Os mapeamentos podem ser realizados sob um campo magnético aplicado de até 500 mT. Aperfeiçoamos o microscópio Hall utilizando uma plataforma feita de acrílico capaz de diminuir o ruído mecânico gerado durante o mapeamento usando um sistema de molas ligada à atuadores lineares responsáveis pela varredura bidimensional. Também foi construído um sistema de leitura composto por três placas de circuito impresso de baixo custo. O microscópio Hall possui uma sensibilidade em torno de 300 nTrms/ (Hz) 1/2 e foi calibrado usando uma esfera de níquel com 99 porcento de pureza. A sensibilidade em momento magnético alcançada foi da ordem de 10 −12Am2. Todos os equipamentos envolvidos na operação do microscópio são controlados utilizando a linguagem LabVIEW. Como exemplo de aplicação, fabricamos cubos feitos de micropartículas de óxido de ferro e nanopartículas magnéticas de magnetita usando o método de coprecipitação em meio alcalino. As propriedades magnéticas destes materiais foram obtidas utilizando o microscópio construído. / [en] Scanning magnetic microscopy has been an important field of research for obtaining magnetic properties of different materials and their applications in areas such as geology, medicine, science, and technology. In this study, a scanning magnetic microscope, capable of measuring and mapping samples with masses in the microgram range, was developed and calibrated at the Instrumentation Laboratory of the Physics Department of the PUC-Rio. This device was developed using a reading system based on a gradiometric configuration with two 300 um Hall-effect sensor elements. The microscope was separated from the sample surface by a distance of 143 um. The mappings can be performed under an applied magnetic field of up to 500 mT. The Hall microscope was improved by using a platform made of acrylic capable of reducing mechanical noise generated during the mapping, through a system of springs connected to linear actuators responsible for twodimensional scanning. A reading system with three low-cost printed circuit boards was also developed. The Hall microscope has a sensitivity of around 300 nTrms/(Hz)1/2 and was calibrated using a nickel sphere (99 percent pure). The magnetic moment sensitivity achieved was of the order of 10 −12Am2. All devices used for operating the microscope were controlled using the LabVIEW language. As an application example, cubes of iron oxide microparticles and magnetite magnetic nanoparticles were made using the alkaline coprecipitation method. The magnetic properties of these materials were obtained using the microscope developed in this study.
12

[pt] MICROSCOPIA MAGNÉTICA DE VARREDURA UTILIZANDO SENSORES DE EFEITO HALL COM POLARIZAÇÃO DE CORRENTE PULSADA / [en] SCANNING MAGNETIC MICROSCOPY USING HALL EFFECT SENSORS BIASED WITH PULSED CURRENT

LANNA ISABELY MORAIS SINIMBU 19 October 2023 (has links)
[pt] A pesquisa de caracterização de materiais é fundamental para o desenvolvimento de diversas tecnologias. No campo de estudo de amostras anisotrópicas como o caso encontrado no paleomagnetismo, é importante estudar a caracterização magnética de minerais rochosos para compreender o campo geomagnético. A caracterização de amostras anisotrópicas, como rochas, tem aplicações na datação do tempo geológico e na caracterização de minérios que sofrem mudanças magnéticas em temperaturas superiores à de Curie. Assim, é necessário conhecer as propriedades físicas desses materiais em relação ao comportamento magnético. Existem várias instrumentações usados neste estudo, como magnetômetro utilizando sensores Superconducting Quantum Interference Device (SQUID), magnetômetro de Amostra Vibrante (VSM), Magnetic Property Measurement System (MPMS) e os Microscópios Magnéticos de Varreduras (MMV) entre outros. Entretanto, o MMV permite mapear o comportamento magnético do material realizando desta forma uma caracterização magnética local da amostra. Nesse contexto, foi proposta uma alternativa de leitura usando a técnica Delta Mode da empresa Keithley no MMV. O objetivo é eliminar os efeitos termoelétricos, realizar medições com baixo ruído de tensão e obter uma alternativa para a leitura do campo magnético induzido no MMV. No desenvolvimento do trabalho, foram utilizados sensores de efeito Hall do modelo HQ-811 em uma configuração gradiométrica, juntamente com uma fonte de corrente (Keithley, modelo 6220) e um Nanovoltímetro (Keithley, modelo 2182A). Os resultados iniciais da calibração revelaram um desvio de cerca de 6 por cento nas medições. Com base nessa calibração, nosso objetivo final é empregar a técnica Delta Mode no MMV para obter as curvas de magnetização das amostras, mesmo em situações desafiadoras de sobreposição de sinais de campo magnético induzido. A metodologia adotada envolve o uso de partículas magnéticas de óxido de ferro em escala nano e micro, posicionadas em três cavidades cilíndricas (A1, A2 e A3) de aproximadamente 800 micrômetros de diâmetro com 800 micrômetros de profundidade, dentro do mesmo porta-amostra. Durante o experimento, um dos desafios foi lidar com a sobreposição de sinais quando aplicado um campo magnético perpendicular ao plano do porta-amostra. Para determinar o valor de magnetização de cada amostra, utilizamos um modelo teórico de um cilindro de corrente devido ao formato das cavidades onde as amostras foram depositadas. Os valores de magnetizações encontrados para diferentes espaçamentos de posicionamento das amostras foram em média de AM1= 62,59 Am(2) /kg, AM2= 13,14 Am(2) /kg e AM3= 10,13 Am(2) /kg para um campo de 0,5 T, onde apresentaram reprodutividade para diferentes situações. / [en] Materials characterization research is fundamental for the development of various technologies. In the field of anisotropic sample studies, such as in paleomagnetism, it is important to investigate the magnetic characterization of rock minerals to understand the geomagnetic field. Characterizing anisotropic samples, such as rocks, has applications in geological time dating and the characterization of ores that undergo magnetic changes at temperatures higher than the Curie temperature. Therefore, it is necessary to understand the physical properties of these materials in relation to their magnetic behavior. Various instrumentation techniques are used in this study, including magnetometers using Superconducting Quantum Interference Device (SQUID) sensors, Vibrating Sample Magnetometer (VSM), Magnetic Property Measurement System (MPMS), and Magnetic Scanning Microscopes (MMV), among others. However, MMV allows for mapping the magnetic behavior of the material, thus providing a local magnetic characterization of the sample. In this context, an alternative reading technique using the Delta Mode of the Keithley company was proposed for MMV. The objective is to eliminate thermoelectric effects, perform low-noise voltage measurements, and provide an alternative for reading the induced magnetic field in MMV. In the course of this work, Hall effect sensors of the HQ-811 model in a gradiometric configuration, along with a current source (Keithley, model 6220), and a Nanovoltmeter (Keithley, model 2182A) were used. The initial calibration results revealed a deviation of about 6 percent in the measurements. Based on this calibration, our ultimate goal is to employ the Delta Mode technique in the MMV to obtain the magnetization curves of the samples, even in challenging situations of overlapping induced magnetic field signals. The adopted methodology involves the use of nano- and micro-scale iron oxide magnetic particles positioned in three cylindrical cavities (A1, A2, and A3) of approximately 800 micrometers in diameter with 800 micrometers in depth, within the same sample holder. During the experiment, one of the challenges was dealing with signal overlap when a magnetic field was applied perpendicular to the plane of the sample holder. To determine the magnetization value of each sample, a theoretical model of a current cylinder was used due to the shape of the cavities where the samples were deposited. The magnetization values found for different sample positioning spacings were on average AM1 = 62.59 Am(2)/kg, A(2) = 13.14 Am(2)/kg, and A3 = 10.13 Am(2)/kg for a magnetic field of 0.5 T, which showed reproducibility for different situations.
13

Development of a multimodal port freight transportation model for estimating container throughput

Gbologah, Franklin Ekoue 08 July 2010 (has links)
Computer based simulation models have often been used to study the multimodal freight transportation system. But these studies have not been able to dynamically couple the various modes into one model; therefore, they are limited in their ability to inform on dynamic system level interactions. This research thesis is motivated by the need to dynamically couple the multimodal freight transportation system to operate at multiple spatial and temporal scales. It is part of a larger research program to develop a systems modeling framework applicable to freight transportation. This larger research program attempts to dynamically couple railroad, seaport, and highway freight transportation models. The focus of this thesis is the development of the coupled railroad and seaport models. A separate volume (Wall 2010) on the development of the highway model has been completed. The model railroad and seaport was developed using Arena® simulation software and it comprises of the Ports of Savannah, GA, Charleston, NC, Jacksonville, FL, their adjacent CSX rail terminal, and connecting CSX railroads in the southeastern U.S. However, only the simulation outputs for the Port of Savannah are discussed in this paper. It should be mentioned that the modeled port layout is only conceptual; therefore, any inferences drawn from the model's outputs do not represent actual port performance. The model was run for 26 continuous simulation days, generating 141 containership calls, 147 highway truck deliveries of containers, 900 trains, and a throughput of 28,738 containers at the Port of Savannah, GA. An analysis of each train's trajectory from origin to destination shows that trains spend between 24 - 67 percent of their travel time idle on the tracks waiting for permission to move. Train parking demand analysis on the adjacent shunting area at the multimodal terminal seems to indicate that there aren't enough containers coming from the port because the demand is due to only trains waiting to load. The simulation also shows that on average it takes containerships calling at the Port of Savannah about 3.2 days to find an available dock to berth and unload containers. The observed mean turnaround time for containerships was 4.5 days. This experiment also shows that container residence time within the port and adjacent multimodal rail terminal varies widely. Residence times within the port range from about 0.2 hours to 9 hours with a mean of 1 hour. The average residence time inside the rail terminal is about 20 minutes but observations varied from as little as 2 minutes to a high of 2.5 hours. In addition, about 85 percent of container residence time in the port is spent idle. This research thesis demonstrates that it is possible to dynamically couple the different sub-models of the multimodal freight transportation system. However, there are challenges that need to be addressed by future research. The principal challenge is the development of a more efficient train movement algorithm that can incorporate the actual Direct Traffic Control (DTC) and / or Automatic Block Signal (ABS) track segmentation. Such an algorithm would likely improve the capacity estimates of the railroad network. In addition, future research should seek to reduce the high computational cost imposed by a discrete process modeling methodology and the adoption of single container resolution level for terminal operations. A methodology combining both discrete and continuous process modeling as proposed in this study could lessen computational costs and lower computer system requirements at a cost of some of the feedback capabilities of the model This tradeoff must be carefully examined.
14

Model klienta veřejné správy z pohledu Unified Foundational Ontology / Model of public administration client from the perspective of Unified Foundational Ontology

Marek, Jan January 2017 (has links)
The thesis deals with possibilities of using Unified Foundational Ontology in modeling the onto-logical model of the public administration client, which was created as a result of the Optimiza-tion of life situations in relation to the Register of Rights and Obligations project. The main aim of this thesis is to extend and propose a modification of the current methodology of modeling the ontological model of the public administration client corresponding to the UFO-A ontology. By analyzing the current methodology and ontological model, it proposes the incorporation of OntoUML, which is based on UFO-A ontology. Its key benefit is the methodology of modeling the ontological model of the public administration client corresponding to the UFO-A ontology. The proposed methodology is presented in a case study.
15

Zlepšování výkonnosti procesů organizace na bázi potenciálu zlepšení / Improving of process performance of organization based on improvement potential

Hemala, David January 2011 (has links)
The theme of the thesis is the area of process management. In the theoretical part of the thesis the basic terms are explained, so as the other areas, which relate to area of processes and proces management. This section also describes the essential terms used in the methodology of the real potential for improvement. The whole theoretical part concludes description of selected ISO standards, which the analyzed company disposes. The practical part of the thesis is aimed to describtion and application of the methodology to achieve the potential improvement in the environment of manufacturing company. This methodology is also accompanied by several activities that contribute to the complexity of the methodology. The following describes the operation of manufacturing companies in order to analyze the maturity of individual processes and also describe the selected processes,which were based on analysis of the processes identified as the highest priority for this company. After completing the necessary steps of analysis, individual potentials, that can contribute to increase the efficiency of the process areas in the analyzed company, have been identified. What could affect the achievement of the real potential is expressed by means of hard and soft effects. The last part of the thesis consist of specific procedures, which serves to remove the internal limits of the company, respectively to achieve the identified potential.
16

Entwicklung eines neuen digitalen Menschmodells für den Einsatz in kleinen und mittleren Unternehmen

Spitzhirn, Michael, Bullinger, Angelika C. January 2013 (has links)
Der Einsatz von digitalen Menschmodellen erlaubt neben einer frühzeitigen ergonomischen Analyse die Gestaltung von Arbeitsprozessen und stellt ein hilfreiches Werkzeug in der Produkt- und Prozessgestaltung dar. Im Rahmen dieses Beitrages soll auf ausgewählte Schwerpunkte der Entwicklung des digitalen Menschmodells „The Smart Virtual Worker“ eingegangen werden. Das Forschungsprojekt soll einen Beitrag zur Lösung, der mit dem demografischen Wandel der Gesellschaft einhergehenden Herausforderungen leisten. Die daraus resultierenden Forschungsschwerpunkte liegen insbesondere in der Einbeziehung von Alterungs- und psychischen Faktoren in die Bewegungsgenerierung des Menschmodells und der Modellierung von Umweltbedingungen. In Umsetzung des Projektes wurde ein erstes Arbeitsszenario erarbeitet, auf dessen Basis die vorgenannten Forschungsaufgaben interdisziplinär gelöst werden sollen.
17

A process model of Transactive Memory System Shared Knowledge Structure emergence: A computational model in R

Samipour-Biel, Sabina Pakdehi 05 August 2022 (has links)
No description available.
18

Developing an Instrument to Assess Teachers’ Knowledge of the Nature of Mathematical Modeling and Their Attitude toward Such Modeling

Asempapa, Reuben S. 08 July 2016 (has links)
No description available.
19

Modellbildung und Simulation des Plasma-Schweißens zur Entwicklung innovativer Schweißbrenner

Alaluss, Khaled Ahmed 21 February 2017 (has links)
In der vorliegenden Habilitationsarbeit wurden technisch-konstruktive Lösungsansätze basierend auf einem entwickelten strömungs-thermomechanischen/magneto-hydro-dynamischen Simulationsmodell zur Entwicklung/Charakterisierung eines physikalischen Prozesswirkprinzips des betrachteten Mikro- und Hochleistungs- sowie Orbital-Plasma-Schweißprozesses und dessen physikalischer Effekte entwickelt. Dabei wurden die differenten Einflussgrößen beim Plasmaschweißprozess erfasst, analysiert und ihre Wirkung auf Schweißprozessverhalten und Brennerkonstruktion charakterisiert. Die damit gewonnenen Ergebnisse wurden zur werkstofflichen, technisch-konstruktiven Entwicklung der Brennerkopfmodelle hinsichtlich der Ausführungsgeometrien des Prozessgaszuführungs- und Brennerkühlsystems genutzt. Im Rahmen des erarbeiteten thermomechanischen Simulationsmodells wurden die beim Plasma-Auftragschweißen von Verbundbauteilen auftretenden Temperaturfelder, Verformungen und Eigenspannungen vorausbestimmt, untersucht und analysiert. Mittels des erarbeiteten Simulationsmodells wurden werkstoffliche, konstruktive und fertigungstechnische Maßnahmen zur Minimierung/Beeinflussung schweißbedingter Verformungen und Eigenspannungen simulativ untersucht und bewertet. / In this work, technical and constructive solutions were developed based on simulation models (process and structural) for fluid mechanical, thermomechanical and magneto-hydrodynamic effects. The simulation process included improving and characterising the physical operating principles for micro plasma welding, high performance plasma welding and orbital plasma welding. Also, the physical effects for the above plasma welding processes were studied and analysed. From these different physical properties of the parameters for the plasma welding processes, and their effects on plasma welding process behaviour and torch design were analysed and characterised. The results were used for the development and construction of plasma welding torch models, which included material selection and geometrical design such as, process gas supply design, torch cooling system design, and other related torch designs. By developing the thermomechanical simulation model, deformations and residual stresses that were generated by heating during the plasma welding process were investigated and analysed. The developed thermomechanical model included material, structural and welding specifications such as buffering and preheating. Simulations utilizing this model were used in order to reduce the residual stresses and deformations of the welded components.
20

Modellierung - Simulation des Plasma-Schweißens zur Entwicklung innovativer Schweißbrenner

Alaluss, Khaled, Mayr, Peter 06 June 2017 (has links)
- An Plasmaschweißbrennern treten starke thermomechanische Beanspruchungen aufgrund der ablaufenden thermophysikalischen Teilprozesse auf. Diese können durch funktionsgerechte werkstoffliche, konstruktive und fertigungstechnische Brennergestaltung bewerkstelligt und die Thermobilanz und Lebensdauer der Brenner verbessert werden. - Anhand des entwickelten strömungs-thermomechanischen/magneto-hydro-dynamischen Simulationsmodells wurden werkstofflich-konstruktive Lösungsansätze für Entwicklung von physikalischen Prozesswirkprinzipien der betrachteten Plasma-Schweißprozessvarianten erarbeitet. - Differente Einflussgrößen des Plasmaschweißprozesses wurden erfasst, analysiert und ihre Wirkung auf Prozessverhalten und Brennerkonstruktion ermittelt. - Die damit gewonnenen Erkenntnisse wurden für werkstoffliche, technisch-konstruktive Brennerentwicklung bzgl. der Ausführungsgeometrien, Prozessgaszuführung und Brennerkühlung genutzt.

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