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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.
61

AVALIAÇÃO DE TRATAMENTOS DE SUPERFÍCIE DA CERÂMICA YTZP SOBRE A RESISTÊNCIA DE UNIÃO A UM CIMENTO RESINOSO / EVALUATION OF Y-TZP SURFACE TREATMENTS ON BOND STRENGTH TO A RESIN CEMENT

May, Michele Mirian 03 August 2015 (has links)
This in vitro study was conducted to evaluate the influence of surface treatments on the bond strength between an yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic and resin cement. For this purpose, 120 Y-TZP blocks (IPS e.max® ZirCAD in inLab®) were randomly distributed into 12 experimental groups (n = 10), according to six surface treatment strategies and two storage conditions (24 hours post cementation and after 60 days in water and 10,000 thermocicles): AS (as sintered, no treatment); TBS (tribochemical silica coating followed by silanization); AAP (particle abrasion with 50 μm aluminum oxide followed by application of Monobond®Plus); FS (fusion sputtering); SN (5 nm SiO2 nanofilm deposition and silanization) and FSSN (FS + SN). The Y-TZP blocks were embedded in acrylic resin and cylinders of resin cement (Ø=0.96 mm x 1 mm in height) (RelyX ARC) were built up on the ceramic surface. After the storage, the specimens were submitted to microshear test (μSBS) (1 mm/min) in a universal testing machine. After testing, the surfaces were analyzed with a stereomicroscope and scanning electron microscope (SEM) in order to categorize the failure modes. One additional specimen per surface treatment strategy was analyzed by X-ray diffraction, for phases content, and by SEM for micromorphology observation. Bond strength values were statistically analyzed by Kruskal-Wallis and Mann Whitney tests for surface treatments (p <0.001) and aging factor (p <0.05). In both storage conditions, TBS and AAP provided higher bond strength values, followed by FSSN, FS and SN groups. The aging negatively influenced the results, with one exception for the FS. An increase in the amount of monoclinic phase was observed in the abraded groups. Sandblasting of alumina particles followed by application of a primer with MPA is as effective as the tribochemical treatment combined with silane for pretreatment of the Y-TZP surface, with respect to the bond strength to the composite. / No presente trabalho objetivou-se avaliar, in vitro, o efeito de diferentes tratamentos de superfície na resistência de união de uma cerâmica à base de zircônia policristalina tetragonal estabilizada por ítria (Y-TZP) a um cimento resinoso. Para tanto, 120 blocos de Y-TZP (IPS e.max® ZirCAD for inLab®, Ivoclar-Vivadent, Schaan, Liechtenstein) foram distribuídos randomicamente em 12 grupos experimentais (n=10), conforme 6 estratégias de tratamento de superfície e 2 condições de envelhecimento (24 horas e após o envelhecimento em água e termociclagem): AS (sem tratamento); TBS (jateamento de partículas de alumina revestidas por sílica e silanização); AAP (abrasão com partículas de alumina seguida da aplicação de primer universal); FS (pulverização de micropartículas de zircônia na superfície livre da Y-TZP e após, fusão por sinterização); SN (deposição de nanofilme de sílica com 5 nm) e FSSN (FS seguido de SN). Os blocos de Y-TZP foram embutidos em resina acrílica e microcilindros de cimento resinoso (0,96 mm de diâmetro; 1 mm de altura) (RelyX ARC) foram confeccionados na superfície cerâmica. Após o armazenamento, os testes de microcisalhamento foram conduzidos a uma velocidade de 1 mm/min, em máquina de ensaios universal. Após o teste, as superfícies foram analisadas com estereomicroscópio e microscópio eletrônico de varredura (MEV) para caracterização das falhas. Em um espécime adicional, também foi conduzida análise de fases do material por difração de raios-X e caracterização da micromorfologia de superfície em MEV. Os valores de resistência de união foram submetidos aos testes estatísticos Kruskal-Wallis e Mann Whitney para os tratamentos testados (p<0.001) e para o fator envelhecimento (p<0.05). Em ambas as condições de envelhecimento, TBS e AAP proporcionaram os maiores valores de resistência adesiva, seguidos dos grupos FSSN, FS e SN. O envelhecimento influenciou negativamente os resultados, com única exceção para o FS. A difractometria revelou aumento de conteúdo monoclínico nos grupos jateados. FS não alterou a percentagem de fase monoclínica. O jateamento de partículas de alumina seguido da aplicação de um primer com MPA apresentou-se tão efetivo quanto o tratamento triboquímico aliado ao silano, para o pré-tratamento da superfície da Y-TZP, no que diz respeito à resistência de união ao compósito.
62

Contribuição ao estudo da deformação permanente de misturas asfálticas densas à luz de ensaios de fluência por compressão uniaxial estática e dinâmica / Contribution for the rutting study on hot mixture asphalt by means of static and dynamic creep tests

Andressa Ka Yan NG 17 January 2013 (has links)
Esta dissertação apresenta um estudo da deformação permanente de misturas asfálticas à luz dos resultados de ensaios de fluência por compressão uniaxial estática e dinâmica. Para isso, um programa experimental completo foi desenvolvido combinando fatores relacionados às misturas asfálticas e às condições de ensaio. Foram produzidos corpos de prova de misturas asfálticas densas tipo CAUQ com asfalto convencional (CAP 50/70) e com asfalto modificado com polímero SBS (CAP 50/70+SBS), variando o volume de vazios em dois níveis, 4 e 7%, e a presença de aditivo em dois níveis, sem e com cal hidratada. Os corpos de prova foram submetidos a ensaios de fluência com carregamentos estático e dinâmico em dois níveis de tensões, 0,1 MPa e 0,4 MPa, e em duas temperaturas diferentes, 40 e 50ºC. Essas condições do programa experimental permitiram observar o efeito do modificador SBS, da presença da cal e do volume de vazios nas misturas asfálticas, e entender o efeito da temperatura, do nível de tensão e do tipo de carregamento no comportamento de cada tipo de mistura asfáltica. Os resultados indicam que (i) a adição da cal promoveu redução de deformação acumulada somente nas misturas com ligante convencional (CAP 50/70); (ii) as misturas com volume de vazios de 7% apresentam maiores acúmulos de deformação permanente independente da presença de cal, do tipo de carregamento e da temperatura do ensaio, sendo maiores para a mistura asfáltica com CAP 50/70; (iii) as misturas com ligante modificado se mostraram menos sensíveis às variações da temperatura e do nível de tensão; (iv) e a melhora das características das misturas com asfalto modificado com polímero é detectada somente a partir de ensaios dinâmicos. / This paper presents a study of rutting on hot mixture asphalt (HMA) by means of static and dynamic creep tests. A full factorial experiment was developed considering factors related to HMA and to the test conditions. It was produced HMA (unmodified (CAP 50/70) and SBS modified binders) specimens at two different air voids (4 and 7%) and with or without hydrated lime. The specimens were submitted to static and dynamic creep tests at two stress levels, 0,1 MPa e 0,4 MPa, and two temperatures, 40 e 50ºC. These conditions of the experimental program allowed to observe the effects of the modifier SBS, the presence of the lime and the air voids in HMA, and to understand the effects of the temperature, stress and the type of loading on the behavior of each type of asphalt mix. The results indicate that (i) the addition of lime promoted reduction of accumulative deformation only in mixtures with conventional binder (CAP 50/70), (ii) mixtures with 7% air voids showed greater accumulation of permanent deformation regardless of presence of lime, the type of load and temperature of the test, mainly for the conventional HMA, (iii) the Polymer Modified Asphalt Hot Mix Asphalt (PMA-HMA) were less sensitive to temperature and the stress variation (iv) the improvement of the polymer modified asphalt mixture characteristics (PMA-HMA) were detected only on dynamic load conditions.
63

A shear bond strength, microleakage and laser microscopic study of two dental compomers.

Moodley, Desi January 1999 (has links)
Magister Chirurgiae Dentium (MChD) / Purpose: To evaluate and compare the in-vitro shear bond strength and micro leakage of two compomers with their adhesive systems and to examine the dentine-restorative interface under confocal scanning laser microscopy (CSLM). Matoiats and Methods: For shear bond strength (SBS) testing thirty non-carious human molars were used of which fifteen molars were restored with Dyract AP using Non-Rinse Conditioner (NRC) and Prime&Bond NT (PBNT) and fifteen were restored with F2000 and Scotchbond Multi-Purpose Plus (SBMP). For the microleakage evaluation cavity preparations were made on the facial surfaces of thirty non-carious premolars. These were then restored with the respective compomer system. The specimens were thermocycled, sectioned and examined for dye penetration. The dentine-restorative interface was examined through a confocal scanning laser microscope. The primers of the bonding agents were labelled with rhodamine B and the adhesive resins were labelled with fluorescein and examined under CSLM in fluorescent mode. Results: The mean SBS for PBNT and SBMP were 12.8 and 18.1 MPa, respectively. The microleakage scores showed Dyract with PBNT leaked on the dentine side in 13 of the 15 specimens examined. On the enamel side 2 of the 15 specimens showed microleakage. With F2000 and SBMP no micro leakage was observed on either enamel or dentine sides. The CSLM images show clear resin tag and hybrid layer formation for both the materials examined, although SBMP showed deeper penetration into the dentine with longer resin tags. The length of the resin tags and thickness of the hybrid layer for PBNT was found to be approximately 10 um and 2 um respectively. SBMP showed resin tags measuring about 100 um while the hybrid layer measured about 5 um. Conclusion: This study demonstrates that the acid-etch technique ofSBMP with F2000 produces higher bond strength and no micro leakage when compared to the self-etching/self-priming "non-rinse technique" of NRC with PBNT and Dyract.
64

Využití rychle reagujícího SBS polymeru při výrobě asfaltových směsí / Usage of fast-reacting SBS polymer in the production of asphalt mixtures

Dohnálek, Jakub January 2022 (has links)
The subject of this diploma thesis is a research of bituminous binder modification by fast react-ing polymer SBS. The theoretical part covers an introduction to bituminous binders, their pro-duction, chemical and physical-mechanical properties. The identification of bituminous binders and their use in bituminous mixtures is briefly described. To conclude, current modification methods are described in detail and important modifiers are introduced. In the practical part, three applied tests (softening point, elastic recovery and penetration) are described in detail. The bituminous binders tested (20/30, 30/45, 70/100, PMB 25/55-55 and PMB 45/80-50) and the fast-reacting polymer SBS are introduced. Samples with two weight percentages of SBS, 7,5% and 10%, are produced. Two mixing times, 60 seconds and 600 seconds were used to mix the bituminous binder and SBS. In conclusion, the results are evaluated and commented. Further research suggestions regarding this field are recommended.
65

Design and Fabrication of Suspended Waveguides With Photonic Grating Structures

Lombardo, David 29 June 2020 (has links)
No description available.
66

DRESDYN - Entwicklung der Forschungsanlage für große Experimente mit flüssigem Natrium

Melnikov, Anton 22 July 2016 (has links)
Die Anlage DRESDYN dient in erster Linie der Erforschung des planetaren Dynamo-Effektes. Für die Untersuchungen wird ein zylindrischer Behälter mit 2 Meter Innendurchmesser und 2 Meter Länge vollständig mit flüssigem Natrium gefüllt. Zur Erzielung des Dynamoeffektes vollführt der Behälter eine Rotation bis zu 10 Hz und eine Präzession bis zu 1 Hz, wobei der Winkel zwischen den jeweiligen Achsen zwischen 45 und 90° liegt. Während der Versuche entsteht im Behälter ein komplexes dynamisches Druckfeld, sowie Temperaturgradienten, was zu komplexen überlagerten Spannungszuständen führt. Desweiteren entstehen während der Rotation des Behälters und der massiven Rahmenkonstruktionen große Massenkräfte, welche z.B. in Form vom gyroskopischen Moment beschrieben werden können. Die Strukturzuverlässigkeit der Anlage muss gewährleistet sein, was vielerlei Nachweise nach sich zieht. Es wird erläutert wie die Knotenlasten mittels MKS (MBSim) berechnet wurden und wie mittels FEM (ANSYS) an linearen und nichtlinearen Modellen verschiedene Analysen durchgeführt wurden. Zusätzlich wird eine Möglichkeit der Anwendung der FKM-Richtlinie auf die Ergebnisse von ANSYS mit Hilfe von MathCad Prime kurz erklärt, wobei durch die Rückführung die Auslastungsgrade direkt im ANSYS Modell angezeigt werden können. Zusätzlich werden Untersuchungen und Modellabgleiche (Nichtlinearitäten z.B. reibungsbehaftete Kontakte) an einem skalierten Prototyp der Verriegelungseinrichtung geplant, was ebenfalls vorgestellt wird. Der Vortrag soll einen Aufschluss über die für die Entwicklung der Anlage angewendeten Methoden geben, sowie einige interessante mittels MKS und FEM gelöste Aufgaben vorstellen.
67

Acciones supervisoras realizadas en respuesta a las medidas aplicadas por la crisis de la COVID-19

Reyes Godinez, Flor Reynalda 17 January 2023 (has links)
En el presente documento se expone las principales acciones de supervisión empleadas en materia de riesgo de crédito y solvencia a partir de la experiencia adquirida como Supervisora del Sistema Financiero en la Superintendencia Adjunta de Banca y Microfinanzas durante el 2020-2021, las cuales se realizaron en torno a las medidas emitidas por la Superintendencia de Banca Seguros y AFP (SBS), en respuesta a la crisis provocada por la COVID-19. Sobre el particular, las acciones de supervisión estuvieron orientadas a abordar los problemas inmediatos y desplegar actividades de monitoreo de la crisis de acuerdo al tamaño y complejidad de cada entidad financiera con el fin de verificar el adecuado cumplimiento de las medidas emitidas e identificar oportunamente las necesidades o riesgos que afecten su continuidad. En esa línea, las acciones de supervisión desplegadas por el equipo técnico de la SBS, aplicadas bajo el enfoque de supervisión basada en riesgos y alineada a los principios básicos para una supervisión eficaz - normas internacionales mínimas sobre mejores prácticas de supervisión - resultan relevantes para que las medidas emitidas contribuyan en fortalecer los principales objetivos de este organismo que son preservar la
68

La evaluación de las incorrecciones identificadas durante la realización de la auditoria (NIA 450) y su impacto en el sistema de control interno en el sector de cooperativas de ahorro y crédito asociadas a la FENACREP en los distritos de Jesús María y Pueblo Libre, 2017 / The evaluation of the inaccuracies identified during the audit (NIA 450) and its impact on the internal control system in the credit union sector associated to the FENACREP in the districts of Jesús María and Pueblo Libre, 2017

Aranda Veramendi, Jackeline Shane, Gómez Prado, Devy 10 November 2018 (has links)
La presente investigación tiene como objetivo demostrar la importancia de la evaluación de las incorrecciones identificadas durante la realización de la auditoria (NIA 450) y su impacto en el sistema de control interno en el sector de las cooperativas de ahorro y crédito asociadas a la FENACREP en los distritos de Jesús maría y pueblo libre. Para el desarrollo del presente trabajo, hemos realizado una investigación cualitativa y cuantitativa. Por ello, se utilizó encuestas aplicadas a los Gerentes Financieros o auditores internos de las cooperativas de ahorro y crédito que se encuentran ubicadas en el área de nuestro punto de investigación y entrevistas para recopilar las opiniones de los Auditores Financieros de las principales firmas de gran reconocimiento en el país. Asimismo, desarrollamos un caso integrador donde se evaluó el efecto de las incorrecciones identificadas y su impacto en el sistema de control interno de las cooperativas de ahorro y crédito. Los resultados de la investigación demuestran que las cooperativas de ahorro y crédito si tienen un impacto significativo después de realizada la auditoría externa, debido a los cambios positivos que se generan en la obtención de mejores procedimientos y controles. Todo ello, nos ha permitido concluir que la evaluación de las incorrecciones identificadas durante la auditoria tiene influencia en el sistema de control interno, ya que, después de pasar por un proceso de auditoría externa e identificar las falencias, estos han generado un impacto significativo positivo sobre el control interno, debido a que, las áreas en las que se identificaron los errores pudieron ser analizadas y evaluadas, tanto la reestructuración como la implantación de mejores controles internos para la compañía. / This research aims to demonstrate the importance of the evaluation of the improprieties identified during the completion of the audit (ISA 450) and their impact on the system of internal control in the field of savings and credit cooperatives associated with FENACREP district of Jesus Maria and Pueblo Libre. For this reason, then for the development of this work, we conducted a qualitative and quantitative research. For this reason, we used surveys applied to the financial managers of cooperatives such as credit unions, which are located in the area of our point of research and interviews to collect the views of the financial auditors of the major auditing firms of the world. In addition, we develop a case Integrator where evaluated the effect of the improprieties identified and its impact on the system of internal control of savings and credit cooperatives. The results of the investigation show that the cooperatives of savings and credit if they have a significant impact after the external audit, due to the positive changes they generate in obtaining better procedures and controls. All, has allowed us to conclude that the assessment of the improprieties identified during the audit has influence in the internal control system, because after going through an audit process and identify the flaws, these have generated a Significant impact on internal control because areas identified with errors were able to analyze and evaluate the restructuring and implementation of better internal controls for the company. / Tesis
69

Spolupráce rodiny a školy na počátku vzdělávání / Cooperation of family and school at the beginning of schooling

Dušková, Tereza January 2011 (has links)
Name: Cooperation of family and school at the beginning of schooling Author: Dušková, T. Supervisor: Mgr. Kargerová, J., Ph.D. The diploma thesis is focused on the cooperation of family and school at the beginning of schooling. The theoretical part describes the school and the family as the institutions that have an irreplaceable position in a life of child. It offers a view into the history and its forms of cooperation and aims which were reached in compare with today's understanding of the child and childhood. It deals with 1989 and its events which influenced the politic, economic and pedagogic situation - the child is in the middle of the family a school attention. The education is innovated, reformatted and new laws together with some new school programmes are issued. The theoretical background is finished by a description of Začít spolu program, its brief characteristic and concrete forms of cooperation with families. The empiric part surveys the situation in an ordinary school and the school worked according to the Začít spolu program. It compares their elementary and secondary levels and it offers some recommendations for better family-school cooperation.
70

Istanalyse C-Bindung Sachsen: Ermittlung der Kohlenstoffbindung von Treibhausgasspeichern und -senken in Sachsen

Grünwald, Thomas 28 August 2019 (has links)
Die Konzentrationen der Treibhausgase (THG) Kohlendioxid (CO2), Methan (CH4) und Lachgas (N2O) haben ein Niveau erreicht, welches mit sehr hoher Wahrscheinlichkeit seit 800.000 Jahren nicht vorgekommen ist (Stocker et al. 2013).

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