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Search Results: 1 - 10 of 145250 matches for " Mel F; "
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Effect of Disinfectants on Elastic Modulus, Flexural Strength and Color Stability of Denture Base Resins  [PDF]
Tobias Bensel, Jens J. Bock, Lisa Zumpe, Sonia Mansour, Nadine Blümel, Julia Seeliger, Arne F. Boeckler
Open Journal of Stomatology (OJST) , 2018, DOI: 10.4236/ojst.2018.84013
Abstract: Objective: Infection control protocols dictate the disinfection of dentures. There are no products available which are designed for the specific use of disinfecting dentures. The objective of this study was to investigate the impact of chemical disinfectants on elastic modulus, flexural strength and color stability of denture base resins. Methods: 256 specimens from four acrylic denture base resins were manufactured. Two cold-curing denture base resins: PalaXpress (Heraeus Kulzer, Hanau, Germany), Futura Gen (Schuetz Dental, Roßbach, Germany) and two heat-curing denture base resins: Paladon 65 (Heraeus Kulzer, Hanau, Germany), FuturAcryl 2000 (Schuetz Dental, Roßbach, Germany) were used. Three chemical disinfecting agents were tested: Impresept, D050 Instru-Gen, Stammopur DR. Specimens were stored in distilled water and in chemical disinfecting agents. They were divided randomly into groups. E-Modulus and flexural strength were measured using the three-point bending test. Color changes (ΔE) were determined spectrophotometrically. Results: The disinfection agents showed no significant influence on the E-modulus compared to distilled water (Acrylic vs. distilled water from (Futura Gen) 2688.80 ± 230.78 vs. 2766.60 ± 91.22 MPa to (PalaXpress) 3004.20 ± 26.40 vs. 2851.00 ± 95.23 MPa). Flexural strength after storage in distilled water and disinfection did not differ significantly (Acrylic vs. distilled water from (Paladon65) 27.28 ± 1.30 vs. 28.42 ± 0.84 N/mm2, (p > 0.05) to (PalaXpress) 30.88 ± 0.25 vs. 29.68 ± 0.79 N/mm2, p < 0.001). Disinfection caused a significant color change with Impresept of Paladon 65 (p ≤ 0.001), FuturaAcryl 2000 with Stammopur DR and D 050 Instru-Gen (p ≤ 0.001). Conclusions: The investigated disinfection agents did not influence elastic modulus and flexural strength of denture base resins negatively. ΔE-values were in a range of 1 to 2. Thus, the detected color changes may be marginal. Clinical relevance: Single use disinfections are feasible for acrylic dentures regarding to elastic modulus and flexural strength.
Simulación de Convertidores de Potencia en Sistemas Eólicos
Melício,Rui; Mendes,Victor M.F;
Información tecnológica , 2007, DOI: 10.4067/S0718-07642007000400005
Abstract: this paper presents an analysis of the present installed electric power capacity of renewable energy power systems in portugal, and analyzes the present state of power converters applied to wind farms. also, this paper presents a simulation of a wind energy system with the usual topology for power converters, a two-levels converter, a multi-level converter and a matrix converter, using pulse modulation by space vector modulation. the simulation allows concluding that the waves for the electric voltage and the current in the converters ac/dc/ac have better performance than in the matrix converter ac/ac.
Modelling nitrogen and phosphorus loads in a Mediterranean river catchment (La Tordera, NE Spain)
F. Caille, J. L. Riera,A. Rosell-Melé
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2012,
Abstract: Human activities have resulted in increased nutrient levels in many rivers all over Europe. Sustainable management of river basins demands an assessment of the causes and consequences of human alteration of nutrient flows, together with an evaluation of management options. In the context of an integrated and interdisciplinary environmental assessment (IEA) of nutrient flows, we present and discuss the application of the nutrient emission model MONERIS (MOdelling Nutrient Emissions into River Systems) to the Catalan river basin, La Tordera (north-east Spain), for the period 1996–2002. After a successful calibration and verification process (Nash-Sutcliffe efficiencies E=0.85 for phosphorus and E=0.86 for nitrogen), the application of the model MONERIS proved to be useful in estimating nutrient loads. Crucial for model calibration, in-stream retention was estimated to be about 50 % of nutrient emissions on an annual basis. Through this process, we identified the importance of point sources for phosphorus emissions (about 94% for 1996–2002), and diffuse sources, especially inputs via groundwater, for nitrogen emissions (about 31% for 1996–2002). Despite hurdles related to model structure, observed loads, and input data encountered during the modelling process, MONERIS provided a good representation of the major interannual and spatial patterns in nutrient emissions. An analysis of the model uncertainty and sensitivity to input data indicates that the model MONERIS, even in data-starved Mediterranean catchments, may be profitably used by water managers for evaluating quantitative nutrient emission scenarios for the purpose of managing river basins. As an example of scenario modelling, an analysis of the changes in nutrient emissions through two different future scenarios allowed the identification of a set of relevant measures to reduce nutrient loads.
Modelling nitrogen and phosphorus loads in a Mediterranean river catchment (La Tordera, NE Spain)
F. Caille,J. L. Riera,A. Rosell-Melé
Hydrology and Earth System Sciences Discussions , 2011, DOI: 10.5194/hessd-8-7555-2011
Abstract: Human activities have resulted in increased nutrient levels in many rivers all over Europe. Sustainable management of river basins demands an assessment of the causes and consequences of human alteration of nutrient flows, together with an evaluation of management options. In the context of an integrated and interdisciplinary environmental assessment (IEA) of nutrient flows, we present and discuss the application of the nutrient emission model MONERIS (MOdelling Nutrient Emissions into River Systems) to the Catalan river basin, La Tordera (North-East of Spain), for the period 1996-2002. After a successful calibration and verification process (Nash-Sutcliffe efficiencies E = 0.85 for phosphorus, and E = 0.86 for nitrogen), the application of the model MONERIS proved to be useful to estimate nutrient loads. Crucial for model calibration, in-stream retention (mainly affected by variability in precipitation) was estimated to be about 50 % of nutrient emissions on an annual basis. Through this process, we identified the importance of point sources for phosphorus emissions (about 94 % for 1996–2002), and diffuse sources, especially inputs via groundwater, for nitrogen emissions (about 31 % for 1996–2002). Despite potential hurdles related to model structure, observed loads, and input data encountered during the modelling process, MONERIS provided a good representation of the major interannual and spatial patterns in nutrient emissions. An analysis of the model uncertainty and sensitivity to input data indicates that the model MONERIS, even in data-starved Mediterranean catchments, may be profitably used for evaluating quantitative nutrient emission scenarios that may help catchment managers and planners to develop effective policy and management measures to reduce nutrient loads.
Evaluación numérica y experimental de las transformaciones mecánicas y microestructurales en aceros recocidos Batch
Monsalve, A.,Artigas, A.,Celentano, D.,Meléndez, F.
Revista de Metalurgia , 2004,
Abstract: The heating and cooling curves during "batch" annealing process of low carbon steels have been modeled using the finite element technique. This has allowed to predict the transient thermal profile for every point of the annealed coils, particularly for the hottest and coldest ones. Through experimental measurements, the results have been adequately validated since a good agreement has been found between experimental values and those predicted by the model. Moreover, an Avrami recristalization model has been coupled to this thermal balance computation. Interrupted annealing experiments have been made by measuring the recristalized fraction on the extreme points of the coil for different times. These data gave the possibility to validate the developed recristalization model through a reasonably good numerical-experimental fitting. Se modelizaron las curvas de calentamiento y de enfriamiento durante el proceso de recocido batch de aceros de bajo contenido en carbono, utilizando la técnica de elementos finitos. Esto, ha permitido conocer, para cada punto de las bobinas recocidas, el perfil térmico desarrollado, particularmente para el punto más caliente y para el más frío. A través de mediciones experimentales, se validaron estos resultados, encontrándose un buen ajuste entre los valores experimentales y los predichos por el modelo empleado. A su vez, se acopló al modelo térmico, un modelo de recristalización del tipo Avrami, con lo cual se ha podido predecir la fracción recristalizada en cada momento y en cada punto. Se realizaron experimentos de recocidos interrumpidos, midiéndose la fracción recristalizada en los puntos extremos de la bobina a distintos tiempos, lo cual permitió validar el modelo de recristalización planteado, encontrándose una buena correspondencia entre los valores predichos por el modelo y aquellos encontrados experimentalmente.
Simulación de Convertidores de Potencia en Sistemas Eólicos Simulation of Power Converters for Wind Energy Systems
Rui Melício,Victor M.F Mendes
Información Tecnológica , 2007,
Abstract: En el presente trabajo se hace un análisis actual de la capacidad instalada de producción de energía eléctrica utilizando fuentes de energía renovable en Portugal y se analiza la situación actual relacionada con convertidores electrónicos de potencia. Además el trabajo aporta información sobre la simulación de topologías de convertidores de potencia en los sistemas de energía eólica, los convertidores usuales de dos niveles, el convertidor multinivel y el convertidor matricial. Se usa el método de la modulación de los pulsos de disparo mediante vectores espaciales de tensión y el control por modo de deslizamiento. Esta simulación permite concluir que las ondas de tensión y corriente en los convertidores de dos etapas AC/DC/AC se presentan con mejor comportamiento armónico que en el convertidor de una etapa AC/AC. This paper presents an analysis of the present installed electric power capacity of renewable energy power systems in Portugal, and analyzes the present state of power converters applied to wind farms. Also, this paper presents a simulation of a wind energy system with the usual topology for power converters, a two-levels converter, a multi-level converter and a matrix converter, using pulse modulation by space vector modulation. The simulation allows concluding that the waves for the electric voltage and the current in the converters AC/DC/AC have better performance than in the matrix converter AC/AC.
Comportamiento gregario aparente de dinosaurios condicionado por una deformación sinsedimentaria. (Igea, La Rioja. Espa a)
Meléndez, A.,Pérez-Lorente, F.
Estudios Geologicos , 1996, DOI: 10.3989/egeol.96521-2255
Abstract: During the sedimentation of the Era del Peladillo strata, there are sorne movements of tectonic inestability that produced their deformation. Deformation rubbed former structures (prints), created new others (steps, nodes, etc.) and allowed long ponds to formo In these ponds a group of small teropodes dinosaurs left their prints. There are criteria enough in the outcrop to state a sequence of events. These events will allow to establish the sedimentation environment, the step sequence sucession of sorne dinosaurs groups, the relative age of the sedimentary deformation, the appearance of a structural barrier and the gregarious behaviour of these vertebrates. Durante la etapa de sedimentación que produjo las rocas que afloran en el yacimiento de la Era del Peladillo, hubo momentos de inestabilidad tectónica que deformaron capas de materiales todavía no enterrados. La deformación borró algunas estructuras anteriores (icnitas) y creó otras nuevas (escalones, nodos, etc.) y permitió que se formaran charcas alargadas en las que un grupo de dinosaurios terópodos peque os dejaron sus huellas. Existen en el afloramiento suficientes criterios para postular una secuencia de acontecimientos que permiten establecer el ambiente sedimentario, la sucesión de paso de grupos de dinosaurios, la edad relativa de la deformación sinsedimentaria, el establecimiento de una peque a barrera natural y el comportamiento gregario de los vertebrados que dejaron aquí sus pisadas.
Generalization of the Second Order Vector Potential Formulation for Arbitrary Non-Orthogonal Curvilinear Coordinates Systems from the Covariant Form of Maxwell's Equations  [PDF]
Denis Prémel
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2012, DOI: 10.4236/jemaa.2012.410055
Abstract: A great number of semi-analytical models, notably the representation of electromagnetic fields by integral equations are based on the second order vector potential (SOVP) formalism which introduces two scalar potentials in order to obtain analytical expressions of the electromagnetic fields from the two potentials. However, the scalar decomposition is often known for canonical coordinate systems. This paper aims in introducing a specific SOVP formulation dedicated to arbitrary non-orthogonal curvilinear coordinates systems. The electromagnetic field representation which is derived in this paper constitutes the key stone for the development of semi-analytical models for solving some eddy currents moelling problems and electromagnetic radiation problems considering at least two homogeneous media separated by a rough interface. This SOVP formulation is derived from the tensor formalism and Maxwell’s equations written in a non-orthogonal coordinates system adapted to a surface characterized by a 2D arbitrary aperiodic profile.
A Note on Factor Prices and Technical Progress  [PDF]
Carl-Gustav Melén
Technology and Investment (TI) , 2011, DOI: 10.4236/ti.2011.23021
Abstract: Changes in the factor prices have important impacts on characteristics of investments, such as the expected lifetime, the factor intensity and the factor productivity of new capital goods. Considering both changes in factor prices as well as technical progress, different effects arise at either high substitutability or low substitutability in production. It can be shown that for a production function close to the Cobb-Douglas case, higher interest rates and technical progress will decrease the expected lifetime, the capital intensity and productivity, while the reversed outcome occurs at lower substitutability between factor inputs.
The Elasticity of Substitution and Characteristics of New Investments  [PDF]
Carl-Gustav Melén
Modern Economy (ME) , 2012, DOI: 10.4236/me.2012.32021
Abstract: Changes in the interest rate and the capital cost will influence important characteristics of investments, such as the expected life time, the factor intensity and the factor productivity of new capital goods. When Harrod-neutral technical progress is endogenous and variable, an increased interest rate will lower the lifetime as well as the factor intensity of the capital good in the Cobb-Douglas case, while there will be a reversed outcome when the substitutability between factor inputs is low. The latter outcome can be interpreted in terms of a reswitching process, that is, one identical factor intensity can arise at two different factor price ratios.
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