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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.
11

Theory of symmetry and asymmetry in two-dimensional magnetic recording heads

Edress Mohamed, Ammar Isam January 2016 (has links)
As part of the natural evolution and continued optimisation of their designs, current and future magnetic recording heads, used and proposed in technologies such as perpendicular recording, shingled magnetic recording and two-dimensional magnetic recording, often exhibit asymmetry in their structure. They consist of two semi-infinite poles separated by a gap (where the recording field is produced), with an inner gap faces inclined at an angle. Modelling of the fields from asymmetrical structures is complex, and no explicit solutions are currently available (only implicit conformal mapping solutions are available for rational inclination angles). Moreover, there is limited understanding on the correlation between the gap corner angle and the magnitude, distribution and wavelength response of these head structures. This research was therefore set out to investigate approximate analytical and semi-analytical methods for modelling the magnetic potentials and fields of two-dimensional symmetrical and asymmetrical magnetic recording heads, and deliver a quantitative understanding of the behaviour of the potentials and fields as functions of gap corner angles. The accuracy of the derived expressions (written in terms of the normalised root-mean-square deviation) was assessed by comparison to exact available solutions for limited cases, and to finite-element calculations on Comsol Multiphysics. Two analytical methods were derived to approximately model the fields from two-dimensional heads with tilted gap corners in the presence and absence of a soft magnetic underlayer (SUL): in the first method, the potential near a single, two-dimensional corner held at a constant potential is derived exactly through solution of Laplace's equation for the scalar potential in polar coordinates. Then through appropriate choice of enclosing boundary conditions, the potentials and fields of two corners at equal and opposite potentials and displaced from each other by a distance equal to the gap length were superposed to map the potential and field for asymmetrical and symmetrical heads. For asymmetrical heads, the superposition approximation provided good agreement to finite-element calculations for the limited range of exterior corner angles 0 from 0 (right-angled corner) to 45, due to the mismatch of surface charge densities on both poles for this geometry. For symmetrical head structures, the superposition approximation was found to yield remarkable agreement to exact solutions for all gap corner orientations from 0 (right-angled head) to 90 ("thin" gap head). In the second method derived in this research for modelling asymmetrical heads involved using a rational function approximation with free parameters to model the surface potential of asymmetrical heads. The free parameters and their functional dependence on corner angle were determined through fitting to finite-element calculations, enabling the derivation of analytical expressions for the magnetic fields that are in good agreement with exact solutions for all corner angels (0 to 90). To complement the two approximate methods for modelling the fields from asymmetrical and symmetrical heads, a new general approach based on the sine integral transform was derived to model the reaction of soft underlayers on the surface potential or field of any two-dimensional head structure, for sufficiently close head-to-underlayer separations. This method produces an infinite series of correction terms whose coefficients are functions of the head-to-underlayer separation and gap corner angle, that are added to the surface potential or field in the absence of an underlayer. This new approach demonstrated good agreement with finite-element calculations for sufficiently close head-to-underlayer separations, and with the classical Green's functions solutions for increasing separations. Using the derived analytical method and explicit expressions in this work, an understanding of the nature of the magnetic fields and their spectra as functions of the gap corner angles is gained. This understanding and analytical theory will benefit the modelling, design and optimisation of high performance magnetic recording heads.
12

Globalization of Clinical Research and Assessment of Global Access to Treatments Approved between 2006-2015

Escandon, Rafael Duncan 01 January 2019 (has links)
Globalization in clinical research and development has increased since the 1990s. Products approved in the United States (U.S.) and European Union (EU) include increasing numbers of research participants from low- and middle-income countries. The purposes of this quantitative correlational study were to investigate the lag time, or drug lag, between U.S. approval and the approval of selected drugs in all countries that hosted their pivotal clinical trials. The study population was limited to products approved first in the U.S. between 2006 and 2015. The health capability model and research for health justice framework were the theoretical frameworks for the study. Data were collected from public reports and websites of the U.S. Food and Drug Administration (FDA), European Medicines Agency, National Institutes of Health, local ministries of health, National Association of Securities Dealers Automated Quotations, New York Stock Exchange, the World Bank, and a subscription-based report from Springer Publications. Data were analyzed descriptively, with inferential statistics performed via Wilcoxon and chi-square tests. Independent variables were FDA approval year, drug indication, FDA review type, orphan indication, host country World Bank income category, sponsor market capitalization, and sponsor headquarters country. The dependent variable was drug lag, in months. The U.S. to EU drug lag was significantly shorter than U.S. to last host country drug lag. Lower host country income was also associated with longer drug lag. Reducing drug lag may create justice for research participants, improve health outcomes, and yield positive social changes.
13

Estudo de caso sobre a aquicultura no brasil e os impactos da desoneração tributária da cadeia produtiva do pescado nacional

Quintella, Fernando Luiz de Vasconcellos 30 April 2014 (has links)
Submitted by Fernando Luiz de Vasconcellos Quintella (fquintella290@gmail.com) on 2014-12-19T18:03:40Z No. of bitstreams: 1 Dissertação Mestrado - Final FQ.pdf: 2930502 bytes, checksum: c1930d59919d847b584f24e3105bd6d4 (MD5) / Approved for entry into archive by ÁUREA CORRÊA DA FONSECA CORRÊA DA FONSECA (aurea.fonseca@fgv.br) on 2014-12-22T11:56:08Z (GMT) No. of bitstreams: 1 Dissertação Mestrado - Final FQ.pdf: 2930502 bytes, checksum: c1930d59919d847b584f24e3105bd6d4 (MD5) / Approved for entry into archive by Marcia Bacha (marcia.bacha@fgv.br) on 2015-01-13T12:07:13Z (GMT) No. of bitstreams: 1 Dissertação Mestrado - Final FQ.pdf: 2930502 bytes, checksum: c1930d59919d847b584f24e3105bd6d4 (MD5) / Made available in DSpace on 2015-01-13T12:07:50Z (GMT). No. of bitstreams: 1 Dissertação Mestrado - Final FQ.pdf: 2930502 bytes, checksum: c1930d59919d847b584f24e3105bd6d4 (MD5) Previous issue date: 2014-04-30 / As questões ligadas às desonerações tributárias como fomento ao desenvolvimento do país vêm ganhando muita importância e destaque no cenário político e econômico brasileiro. Sendo assim, este estudo de caso fictício tem como objetivo promover uma reflexão acerca dos fatores que sejam relevantes para a desoneração da cadeia produtiva do pescado e atingir objetivos educacionais expondo aos estudantes às interdependências e consequências ao longo do processo. O caso também pretende promover uma discussão sobre as ações gerenciais apropriadas, com utilização de ferramentas de planejamento para orientar tomadas de decisões e, para tanto, apresenta alguns fatores facilitadores e obstáculos, bem como benefícios alcançados, que são impactados por múltiplos fatores. Dentro dos parâmetros estabelecidos, as conclusões levam ao entendimento de que a solução mais indicada seria a de trabalhar na desoneração e mais especificamente nas rações do pescado, que, com a redução dos custos, proporcionaria mais demanda, maior produção, mais investimentos em tecnologia, mais formalização da economia e tantos outros benefícios econômicos e sociais.
14

Konzeption einer fachlichen Facette für einen Bibliothekskatalog am Beispiel der Universitätsbibliothek Mannheim

Frick, Julian 20 January 2012 (has links)
Eine in vielen Bibliothekskatalogen bislang nicht verwirklichte Recherchefunktion ist die gezielte Suche nach Literatur aus bestimmten Fachgebieten. Recherchen mit Notationen der im Katalog verwendeten Klassifikation oder mit Schlagwörtern können den Anspruch an eine fachgebietsumfassende Suche meist nicht erfüllen. Eine mögliche Lösung ist die Entwicklung einer bibliotheksspezifischen fachlichen Facette, in der jeder Titel über seine sachlichen Erschließungsdaten einem oder mehreren Fächern zugeordnet wird. Im Vortrag wird nach einem Überblick über bereits vorhandene fachliche Facettierungsmöglichkeiten in verschiedenen Bibliothekskatalogen die Konzeption einer fachlichen Facette für den Bibliothekskatalog der Universitätsbibliothek Mannheim erläutert. Hierbei wurden im Besonderen die vorliegenden Sacherschließungsdaten sowie die fachlichen Schwerpunkte der Medienbestände der Universitätsbibliothek Mannheim berücksichtigt. Das Ziel war die Definition und die Zusammenstellung von Fächern, die im Bibliothekskatalog in unterschiedlichen Varianten umgesetzt und verwendet werden können.

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