Search results for "Ceramic"
showing 10 items of 2129 documents
Céramiques diélectriques commandables pour applications micro-ondes : composites à base de titanate de baryum-strontium et d'un oxyde non ferroélectr…
2001
Since the last decades, dielectric ceramics have been considered as attractive for microwave applications as tunable dielectric resonators or phase shifters. For that, ceramic devices should be tunable – change in dielectric constant with applied voltage- with moderate to low dielectric constant (30 to 1000) and loss tangent as low as possible. To reconcile these properties, composite ceramics based on Ba0.6Sr0.4TiO3 (BSTO) and a non-ferroelectric oxide with a low dielectric constant (MgTiO3 or MgO) were synthesised. The aim of this study was to correlate the microstructure with the dielectric properties, especially the Curie temperature and the dielectric relaxation phenomena.Ceramics with…
Strengthening of Masonry Columns with BFRCM or with Steel Wires: An Experimental Study
2016
Nowadays, innovative materials are more frequently adopted for strengthening historical constructions and masonry structures. The target of these techniques is to improve the structural efficiency with retrofitting methods while having a reduced aesthetical impact. In particular, the use of basalt fiber together with a cementitious matrix emerges as a new technique. This kind of fiber is obtained by basalt rock without other components, and consequently it could be considered a natural material, compatible with masonry. Another innovative technique for strengthening masonry columns consists of applying steel wires in the correspondence of mortar joints. Both techniques have been recently pr…
Strength of cellulosic fiber/starch acetate composites with variable fiber and plasticizer content
2014
In this experimental study, the performance of injection-molded short flax and hemp fibers in plasticized starch acetate were analyzed in terms of strength. Parameters involved in the analysis are a variable fiber and plasticizer content. The measured strength of the composites varies in the range of 12–51 MPa for flax fibers and 11–42 MPa for hemp fibers, which is significantly higher than the properties of the unreinforced starch acetate matrix. The micro-structural parameters used in modeling of composite strength were obtained from optical observations and indirect measurements. Some of these parameters were qualitatively verified by X-ray microtomography.
Bis-urea macrocycles with a deep cavity.
2015
Two configurational isomers of bis-urea macrocycles have been synthesized, and their neutral molecule recognition was studied by X-ray crystallography and (1)H NMR experiments. Cooperative action between the deep cavity and the urea groups and the influence of dipole alignments on molecular recognition are discussed.
Raman and optical reflection spectra of germanate and silicate glasses
2005
Abstract Germanate and phosphosilicate glasses made in oxygen surplus conditions were studied by Raman and optical reflection methods. We found that the optical reflection spectra of the germanate glasses are quite similar to the one those of a GeO 2 crystal with the α-quartz structure. The reflection of phosphosilicate glasses is very close to silica glass-related spectra. Hence, the determining influence of the tetrahedral structure on reflection spectra is revealed. The Raman spectra of germanate samples are similar to those reported the one known in the literature. Octahedral entities, namely bands similar to stishovite vibration modes, were difficult to detect in phosphosilicate glasse…
Measuring the market power in the ceramic tile industry: An international comparison
2004
This paper measures the degree of competition faced by Spanish and Italian exporters of ceramic tiles in several European Union member states. The results indicate that Spanish producers have a substantial market power while Italian exporters face a high degree of competition. This finding is consistent with the significant gain (loss) in the world production and export shares that Spanish (Italian) producers experienced during the 1990s. The results are also consistent with accounting data. Furthermore, comparisons in the extent of market power across source countries and European destination markets reveal that most variation in the data is related to the source country. JEL no. F12, F14,…
Intraperitoneal adhesions-an ongoing challenge between biomedical engineering and the life sciences
2011
Peritoneal adhesions remain a relevant clinical problem despite the currently available prophylactic barrier materials. So far, the physical separation of traumatized serosa areas using barriers represents the most important clinical strategy for adhesion prevention. However, the optimal material has not yet been found. Further optimization or pharmacological functionalization of these barriers could give an innovative input for peritoneal adhesion prevention. Therefore, a more complete understanding of pathogenesis is required. On the basis of the pathophysiology of adhesion formation the main barriers currently in clinical practice as well as new innovations are discussed in the present r…
Finite-element simulation of residual stress induced by split-sleeve cold-expansion process of holes
2008
A three-dimensional finite-element simulation was conducted for a split-sleeve cold-expansion process in order to determine the residual stress field around an expanded hole. The commercial FEA software DEFORM-3D™, a Lagrangian implicit code designed for metal forming processes, was used to model the cold-expansion process of a fastener hole. The results show a through-thickness residual stress field in good agreement with the analytical solution developed by Guo. Moreover, the simulation has highlighted the effect of the split sleeve and the plate thickness on the residual stress field. © 2007 Elsevier B.V. All rights reserved.
Analytical bonding criteria for joint integrity prediction in friction stir welding of aluminum alloys
2014
Abstract In this study, two bonding criteria, previously used for porthole die extrusion, are applied to FSW starting from the local value of the main field variables calculated through a specifically developed 3D numerical model of the process. Their applicability and effectiveness have been assessed through an experimental and numerical campaign carried out with the main process parameters varying in a wide range. The pressure–time–flow criterion was demonstrated to be better suited for FSW processes when large welding speed is used.
Novel nanocrystalline cores for EMI suppression in cables: characterization methodology and performance study
2021
El control de las interferencias electromagnéticas (EMI) en dispositivos electrónicos es un problema cada vez mayor al que se enfrentan los diseñadores para garantizar que los dispositivos cumplan con los requisitos de compatibilidad electromagnética (EMC) para operar simultáneamente sin inferir entre sí. Este hecho se debe a la tendencia hacia una mayor integración de componentes, la reducción del tamaño y grosor de las placas de circuito impreso (PCB) y la miniaturización de las carcasas de los dispositivos. Además, otros factores como el empleo de frecuencias de conmutación más altas en los convertidores de potencia y las velocidades de datos de comunicación en los circuitos digitales. C…