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Klinische Untersuchungen verschiedener Versiegelungsmaterialien zur kariesprophylaktischen Versiegelung von Fissuren und Verhinderung undichter Füllungsränder unter besonderer Berücksichtigung des Zeit- und KostenfaktorsIhlow, Dankmar, January 1980 (has links)
Thesis (doctoral)--Freie Universität Berlin, 1980.
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A new polygonal-winding permanent magnet brushless DC motor drive for electric vehicles /Wang Yong, January 2004 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2005.
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Essays in consumptionFernandez-Corugedo, Emilio January 2000 (has links)
No description available.
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IMPLEMENTATION OF A PLANAR MAGNETIC MANIPULATOR WITH ROTATABLE PERMANENT MAGNETSTituana, Luis Rodrigo 01 May 2020 (has links)
The development of new techniques for control of magnetic objects by external magnetic fields has been in constant improvement. These advancements range from the design and fabrication of magnetic nanoparticles to design and control of actuators that enable their manipulation. The ability to guide such magnetic objects at a distance without any direct mechanical contact is an attractive feature with great potential in medical applications. Magnetic fields are not distorted by their interaction with nonmagnetic materials, like those in the human body; and pose no harm to living tissues, which make them convenient tools for minimally invasive techniques and treatments. Moreover, several actuator configurations have been proposed to achieve the remote motion of a magnetic particle or magnetic fluids. Arrays of electromagnets have been widely utilized due to their lack of mechanical parts and flexibility to accurately and rapidly change their magnetic field by controlling the current through their coils. However, they are relatively weak for their size and electrical power, making them inefficient for medical applications which need large magnetic forces at relatively long distances. On the other hand, permanent magnets have a much higher strength-to-size ratio than electromagnets and allow for control from larger distances. The disadvantage is that their magnetic fields cannot be turned off and a mechanical actuator is needed to modify their position and orientation to change their field. In this work, a magnetic manipulator used as a testbed to manipulate a magnetic bead is designed. It consists of an array of six diametrically magnetized cylindrical permanent magnets evenly spaced around a petri dish, following the work in [11]. Servomotors are utilized to precisely adjust the direction of the magnets according to a control law developed by other researchers in the past. A monochromatic camera located above the petri dish provides the feedback on the position of the bead and a set of hall-effect sensors provides the location of the poles of the magnets. The dynamics of the system is modeled by a linearized set of state-space equations where the magnetic field is estimated with an analytical expression for the geometry of the magnets. The testbed has been designed with the CAD software SolidWorks and its structure has been completely 3D printed with polylactic acid (PLA) filament. The design is tested under different speeds of the servomotors and initial orientations of the magnets. Some recommendations are presented at the end for improvement and considerations for future designs.
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Permanent-magnet models in finite element analysisBui, QuocViet January 1977 (has links)
No description available.
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A clinical investigation of the general disintegration and strength characteristics of four temporary filling materialsBastawi, Aly Eloui A., 1928- January 1963 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / The purpose of this study was to evaluate clinically, the general
disintegration, gross fracture, marginal breakdown, and surface texture
in Class I and Class II restorations of four temporary filling materials
having widely varying physical properties. They were zinc oxide-eugenol
(Temrex), zinc oxide-rosin eugenol (Caulk’s), zinc phosphate
cement (Tenacin), and silico-phosphate cement (Kryptex). Powder-liquid
ratios and all manipulative procedures for each of the four materials
were standardized. Compressive strength, solubility and abrasion resistance
tests were carried out in the laboratory on the same standardized
mixes used in the clinical part. A total of 137 standardized cavities were
prepared in deciduous and permanent teeth of 37 children and restored
with the four materials in an effort to equalize the distribution between
the four quadrants. Rubber base impressions were taken as permanent
records for evaluation at the one week, one month and three months
observation visits. Zinc oxide-rosin eugenol (Caulk) exhibited the
least resistance to disintegration and the roughest surface while the
zinc oxide eugenol (Temrex) exhibited considerably more resistance and
the smoothest surface. Zinc phosphate showed the greatest resistance to
disintegration. Silico-phosphate cement exhibited the same behavior in
Class I restorations but showed higher failure in Class II restorations
due to fractures. Zinc phosphate exhibited smoother surface than the
silico-phosphate cement. There was no correlation between in vitro
solubility and clinical disintegration. Compressive strength seemed to
be related to the general durability of the materials.
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Histerisímetro de Entreferro Variável HEV : uma proposta alternativa para a caracterização de ímãs permanentesAnocibar, Héctor Rolando January 2007 (has links)
A determinação das principais propriedades magnéticas de um ímã permanente geralmente requer sistemas de medição sofisticados e custosos. Este trabalho analisa e propõe um sistema de caracterização de ímãs permanentes de Terras Raras à temperatura ambiente de baixo custo e de implementação mais simples e rápida. Ele consiste de um circuito magnético formado pelo ímã permanente sob caracterização, uma culatra de aço, um entreferro variável e uma sonda de efeito Hall com seu respectivo gaussímetro para a medição da intensidade do campo magnético no entreferro. Como introdução se apresenta o estado da arte da caracterização dos ímãs permanentes, conceitos básicos de magnetismo e em relação aos ímãs permanentes, sua história, os principais tipos, sua importância e suas aplicações principais. Os resultados teóricos e experimentais são comparados a resultados certificados, validando o método como proposto. / Determining the main magnetic properties of a permanent magnet usually requires sophisticated and expensive measurement setups. This work analyses and proposes a low-cost system to characterize Rare Earth permanent magnets at ambient temperature with easy and fast implementation. It consists of a magnetic circuit with the permanent magnet under test, appropriate pole pieces, a variable air gap and a Hall Effect probe with its respective Gaussmeter. As an introduction, it is presented the state of the art of permanent magnets characterization, basic concepts of magnetism and its history, the main types of permanent magnets, their importance and applications. The theoretical and experimental results are compared to certified ones, validating so the method as proposed.
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Histerisímetro de Entreferro Variável HEV : uma proposta alternativa para a caracterização de ímãs permanentesAnocibar, Héctor Rolando January 2007 (has links)
A determinação das principais propriedades magnéticas de um ímã permanente geralmente requer sistemas de medição sofisticados e custosos. Este trabalho analisa e propõe um sistema de caracterização de ímãs permanentes de Terras Raras à temperatura ambiente de baixo custo e de implementação mais simples e rápida. Ele consiste de um circuito magnético formado pelo ímã permanente sob caracterização, uma culatra de aço, um entreferro variável e uma sonda de efeito Hall com seu respectivo gaussímetro para a medição da intensidade do campo magnético no entreferro. Como introdução se apresenta o estado da arte da caracterização dos ímãs permanentes, conceitos básicos de magnetismo e em relação aos ímãs permanentes, sua história, os principais tipos, sua importância e suas aplicações principais. Os resultados teóricos e experimentais são comparados a resultados certificados, validando o método como proposto. / Determining the main magnetic properties of a permanent magnet usually requires sophisticated and expensive measurement setups. This work analyses and proposes a low-cost system to characterize Rare Earth permanent magnets at ambient temperature with easy and fast implementation. It consists of a magnetic circuit with the permanent magnet under test, appropriate pole pieces, a variable air gap and a Hall Effect probe with its respective Gaussmeter. As an introduction, it is presented the state of the art of permanent magnets characterization, basic concepts of magnetism and its history, the main types of permanent magnets, their importance and applications. The theoretical and experimental results are compared to certified ones, validating so the method as proposed.
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Histerisímetro de Entreferro Variável HEV : uma proposta alternativa para a caracterização de ímãs permanentesAnocibar, Héctor Rolando January 2007 (has links)
A determinação das principais propriedades magnéticas de um ímã permanente geralmente requer sistemas de medição sofisticados e custosos. Este trabalho analisa e propõe um sistema de caracterização de ímãs permanentes de Terras Raras à temperatura ambiente de baixo custo e de implementação mais simples e rápida. Ele consiste de um circuito magnético formado pelo ímã permanente sob caracterização, uma culatra de aço, um entreferro variável e uma sonda de efeito Hall com seu respectivo gaussímetro para a medição da intensidade do campo magnético no entreferro. Como introdução se apresenta o estado da arte da caracterização dos ímãs permanentes, conceitos básicos de magnetismo e em relação aos ímãs permanentes, sua história, os principais tipos, sua importância e suas aplicações principais. Os resultados teóricos e experimentais são comparados a resultados certificados, validando o método como proposto. / Determining the main magnetic properties of a permanent magnet usually requires sophisticated and expensive measurement setups. This work analyses and proposes a low-cost system to characterize Rare Earth permanent magnets at ambient temperature with easy and fast implementation. It consists of a magnetic circuit with the permanent magnet under test, appropriate pole pieces, a variable air gap and a Hall Effect probe with its respective Gaussmeter. As an introduction, it is presented the state of the art of permanent magnets characterization, basic concepts of magnetism and its history, the main types of permanent magnets, their importance and applications. The theoretical and experimental results are compared to certified ones, validating so the method as proposed.
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Thermal management of an axial flux permanent magnet machine considering heat pipesScowby, Seath 03 1900 (has links)
Thesis (MScEng) -- Stellenbosch University, 2003. / ENGLISH ABSTRACT: Axial Flux Permanent Magnet (AFPM) machines have become attractive because of significant
improvements in permanent magnets over the past decade, improvements in power electronic
devices, and the ever increasing need for more efficient machines in electric vehicle systems. In
comparison with the cylindrical radial flux motor, the AFPM machine is better in a number of
aspects: short frame; compact construction; high efficiency; brush less construction; good starting
torque and high-power density. The common modes of failure and typical operating conditions
of AFPM machines are discussed further. The focus of this research project is a prototype AFPM
machine developed by the Electrical Engineering Department of The University of Stellenbosch.
The machine considered has a power rating of 300 kW and an operating efficiency of 95 % at a
speed of 2300 rpm. This specific machine is used as an example to illustrate the thermal
characteristics of geometrically similar AFPM machines.
The thermal characterization was achieved with the use of two numerical computer models.
Firstly a fluid model was specially developed and experimentally verified. The objective of the
fluid model was to calculate the mass flow rate of air through any geometrically similar AFPM
machine. The fluid model was further used to investigate the effects of different magnet
thickness and axial gaps between the stator and the rotor plates on the mass flow rate of air
through the machine. The fluid model was verified with experimental testing that was done on a
half-scale Perspex model. During the experimental testing the magnet thickness was varied
between 2.5 mm, 5.0 mm, and 7.5 mm along with axial gaps of 6.5 mm, 7.5 mm, 8.5 mm, and
9.5 mm. The fluid model showed a correlation to within 10 % of the experimental mass flow
rates. The results of these tests showed that the magnet thickness and axial gap between the
stator and the rotor plates had no significant effect on the mass flow rate of air. The fluid model
was based on one-dimensional, steady-state, and incompressible flow.
The second numerical computer model was a thermal model. This model was used to calculate
the transient temperature response of the AFPM machine. The model was based on a twodimensional
transient finite difference solution technique. Experimental temperatures taken from
the prototype AFPM machine were used to verify the thermal model. Correlations between the
experimental and theoretical temperatures were within 5.8 % of each other. The thermal model
was used to investigate the effect of geometrical changes on the temperatures in the AFPM
machine. It was found that these geometrical changes had no significant effect on the
temperatures in the AFPM machine. It was also established that increasing the air mass flow rate over about I kg/s had no further effect on lowering the temperatures. The stator was also
identified as being the most critical component as it reached its maximum temperature limit
before any other component. Heat pipes were considered as an alternative thermal management
technique. The location of the heat pipe was limited to the stator. Further simulations were done
to investigate the effect of the heat pipe properties on the amount of heat removed from the
stator.
Recommendations were made concerning the thermal management of the current and possible
future prototype AFPM machines. It was recommended that a further more detailed investigation
into the use of heat pipes be considered. This recommendation is substantiated by the fact that in
this research project only one type of heat pipe was considered and its location was limited to
within the stator. / AFRIKAANSE OPSOMMING: AFPM masjiene het meer aantreklik geword weens betekenisvolle verbeteringe in permanente
magnete gedurende die laaste dekade, verbeteringe in elektroniese toestelle en die vraag na meer
effektiewe masjiene in elekriese voertuigstelsels. Die AFPM masjien is beter as die Silindriese
Radiale Fluksie Motor wat die volgende aspekte betref: die kort raamwerk; kompakte
konstruksie; hoe effektiwiteit; borsellose konstruksie; goeie aanvangsdraaimoment; en hoe-krag
digtheid. Die algemene vorms van faling en ook die tipiese werkstoestande van die AFPM word
verder bespreek. Hierdie navorsingsprojek fokus op die prototipe AFPM masjien wat ontwikkel
is deur die Elektriese Ingenieurs Departement van die Universiteit van Stellenbosch. Die
masjien onder bespreking wek 300 kW per uur op en is 95% effektief teen 'n spoed van 2300
rpm. Hierdie masjien word gebruik om die termiese kenmerke van geometries-gelyksoortige
masjiene te illustreer.
Die termiese eienskappe is bepaal deur die gebruik van twee numeriese rekenaarmodelle.
Eerstens is 'n vloeistofmodel spesiaal ontwerp en eksperimenteel geverifieer. Die doel van die
vloeistofmodel was om die massa vloeitempo van lug deur enige geometries-gelyksoortige
AFPM masjien te bereken. Die vloeistofmodel is verder gebruik om die uitwerking van
verskillende magneetdiktes en aksiale gapings tussen die stator en die rotorplate op die massa
vloeitempo van lug deur die masjien te ondersoek. Die vloeistofmodel is geverifieer deur
eksperimentele toetsing wat gedoen is op 'n halfskaal Perspex model. Tydens die toetsing het
magneetdiktes gewissel tussen 2.5 mm, 5.0 mm en 7.5 mm en die aksiale gapings tussen 6.5 mm,
7.5 mm en 9.5 mm. Die vloeistof model het 'n korrelasie van binne 10 % van die eksperimentele
massa vloeistempo getoon. Die resultate van hierdie toetse het getoon dat die magneetdiktes en
die aksiale gapings tussen die stator en die rotorplate geen noemenswaardige uiterking op die
massa vloeitempo van lug gehad het nie. Die vloeistofmodel is gebaseer op een-dimensionele,
gestadigde, onsamedrukbare vloei.
Die tweede numeriese model was 'n termiese model. Hierdie model is gebruik om die transiente
temperatuur respons van die AFPM masjien te bereken. Die model is gebaseer op 'n tweedimensionele,
transiente eindige-verskil oplossingstegniek.
Eksperimentele temperature gemeet op die prototipe AFPM masjien is gebruik om die termiese
model te verifeer. Die eksperimentele en teoretiese temperature het binne 5.8% met mekaar
gekorrelleer. Die termiese model is gebruik om die uitwerking van geometriese veranderinge op
die temperatuur in die AFPM masjien te ondersoek. Daar is gevind dat hierdie geometriese veranderinge geen noemenswaardige uitwerking op die temperature van die AFPM masjien
gehad het nie. Daar is ook vasgestel dat 'n vermeerdering in die lug massa vloeitempo yerby I
kg/s geen verdere uitwerking het op die verlaging van die temperatuur gehaad het nie. Die stator
is ge-identifiseer as die mees kritiese komponent aangesien dit sy maksimum temperatuur limiet
bereik het voor enige ander komponent, Hittepype is oorweeg as 'n alternatiewe termiese
bestuurstegniek. Die plasing van die pype is tot die stator beperk. Verdere simulasies is
uitgevoer om die uitwerking van die hittepyp eienskappe op die hoeveelheid hitte wat verwyder
word van die stator te ondersoek.
Aanbevelings is gemaak m.b.t die termiese bestuur van die huidige en moontlike toekomstige
prototipes van AFPM masjiene. Daar is aanbeveel dat daar in meer besonderhede ondersoek
ingestel word na die gebruik van hittepype. Die rede hiervoor is dat daar in hierdie studie net
gebruik gemaak is van een tipe hittepyp en dat die plasing daarvan beperk is tot binne die stator.
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