Recent Advances in Ceramic Materials for Dentistry

Dental ceramics constitute a heterogeneous group of materials with desirable optical and mechanical proprieties combined with chemical stability. They are inorganic non-metallic materials used in several applications. These materials are biocompatible to tissue, highly esthetic, with satisfying resistance to tensile and shear stress. Over the past years, several developments in new ceramic materials in dental restoration were achieved, including processing techniques and high mechanical properties. Thus, concepts on the structure and strengthening mechanisms of dental ceramic materials are also discussed. The dental practitioner requires best knowledge concerning indications, limitations, and correct use of started materials. The purpose of this book chapter is to overview advances in new ceramic materials and processes, which are used in dentistry. The properties of these materials are also discussed

Residual selection in HDR video compression

International audienceHigh Dynamic Range (HDR) videos are commonly compressed using existing Low Dynamic Range (LDR) coding standards. This necessarily implies a Tone Mapping (TM) stage which aims at reducing the input video range while preserving the most significant scene details. In most cases, a residual sequence is encoded and used in the decoder side to recover the HDR content. The challenge is thus to efficiently encode both LDR sequences (TM and residual) without compromising the quality of the reconstructed video. The choice of the residual sequence can have a deep impact on the HDRvideo coder performances. In this work, we analyze the residual streams in terms of entropy and we discuss HDR video coding performances based on different residuals. Subjective and objective assessments show that differential residual presents much higher efficiency than ratio residuals in terms of bandwidth saving and HDR reconstruction quality

Revertible tone mapping of high dynamic range imagery: Integration to JPEG 2000

International audienceThis paper presents a revertible tone mapping approach based on subband architecture where the dynamic range of the HDR (High Dynamic Range) image is decreased to LDR (Low Dynamic Range) to fit several types of applications. The LDR image can be later expanded to get back the original HDR content. One important benefit of the proposed approach is its backward compatibility with low dynamic (LDR) image applications since no extra information is needed to perform a very efficient HDR reconstruction. In order to improve the efficiency of our TM (Tone Mapping), we couple it with an optimisation procedure to minimize the reconstruction error. Subjective and objective comparisons with state-of-the-art methods have shown superior quality results of both tone mapped and reconstructed images. As a potential application, the integration of the proposed tone mapping to JPEG 2000 encoder achieved competitive performance compared to reference HDR image encoders

Synthesis and Characterization of MgO Thin Films Obtained by Spray Technique for Optoelectronic Applications

Magnesium oxide (MgO) thin films with different magnesium concentrations ([Mg2+] = 0.05, 0.1, 0.15 and 0.2 mol·L−1) in a spray solution have been successfully grown using a spray pyrolysis technique. X-ray diffraction (XRD), Maud software, FTIR spectroscopy, a confocal microscope, Wien2k software, spectrophotometry and a Photoluminescence spectrometer were used to investigate the structural, morphological and optical properties. XRD analysis revealed a better crystalline quality of the MgO thin layer synthesized with [Mg2+] = 0.15 mol·L−1, which crystallized into a face-centered cubic structure along the preferred orientation (200) lattice plan. The enhancement of the crystalline quality for the MgO thin film ([Mg2+] = 0.15 mol·L−1) was obtained, which was accompanied by an increment of 94.3 nm of the crystallite size. No secondary phase was detected and the purity phase of the MgO thin film was confirmed using Maud software. From the transmission spectra results, high transparent and antireflective properties of the MgO thin film were observed, with an average transmission value of about 91.48% in the visible range, which can be used as an optical window or buffer layer in solar cell applications. The films also have a high reflectance value in the IR range, which indicates that the highly reflective surface will prevent an increase in surface temperature under solar irradiation, which could be beneficial in solar cell applications. A direct band gap type was estimated using the Tauc relation which is close to the experimental value of 4.0 eV for optimal growth. The MgO material was tested for the degradation of methylene blue (MB), which reached a high photodegradation rate of about 83% after 180 min under sunlight illumination. These experimental trends open a new door for promising the removal of water contaminants for photocatalysis application

Effect of Al and Mg Doping on Reducing Gases Detection of ZnO Nanoparticles

In this work, the main objective is to enhance the gas sensing capability through investigating the effect of Al and Mg doping on ZnO based sensors. ZnO, Mg1% doped ZnO, Al5% doped ZnO and (Al5%, Mg1%) co-doped ZnO nanoparticles (NPs) were synthesized by a modified sol-gel method. The structural characterization showed the hexagonal crystalline structure of the prepared samples. Morphological characterizations confirmed the nanometric sizes of the NPs (27–57 nm) and elemental composition investigation proved the existence of Al and Mg with low concentrations. The optical characterization showed the high absorbance of the synthesized samples in the UV range. The gas sensing performances of the synthesized samples, prepared in the form of thick films, were investigated. Sensing tests demonstrated the high influence of the Al and Mg on the sensing performances towards H2 and CO gas, respectively. The 5A1MZO-based sensor exhibits high sensitivity and low detection limits to H2 (<2 ppm) and CO (<1 ppm). It showed a response around 70 (at 250 °C) towards 2000 ppm H2 and 2 (at 250 °C) towards CO