Wear behavior of the abrasive grains used in optical glass polishing

In this work the wear behavior of cerium oxide abrasive grains during the glass polishing was studied. Polishing tests have been done by different types of cerium oxide abrasive grains. The grains have been recovered and examined during the operation. The morphology, the granulometric distribution, the chemical composition and the agglomeration phenomenon of recovered grains have been studied.     

Coloration and structure behavior after silver and copper nanoparticles formation in soda lime glass

In this work, an ion exchange non‐conventional process commonly called ancient painting process without using molten salts is used as a method for glass coloring. In this process of coloration, a mixture of metallic particles with kaolin and arabic adhesive is applied on the soda lime glass surface. Afterwards, the painted glass is submitted to the heat treatment to obtain the color. A comparative study is carried out in order to investigate the diffusion of metallic nanoparticles (silver and copper) in soda lime glasses depending on several parameters as the concentration and composition of stain spread on glass, and the heat treatment temperature. Characterization of the composition and structure of the painted glasses is performed by UV‐visible spectroscopy. In addition, nanoindentation and scanning electron microscopy (SEM) with energy dispersive X‐ray analysis (EDS) techniques are used to determine the penetration of metallic nanoparticles into glass. The obtained result shows that the coloration of painted glass differs and depends on the concentration and the kind of the mixture of the paw. Moreover, it was found that the effect of the heat treatment temperature is primordial on the formation and diffusion of metallic nanoparticles.     

Determination of the Friction Coefficient During Glass Polishing

In this paper, the friction coefficient was measured using a computer-controlled electrical system. The obtained results of the friction behavior during the polishing process indicate that the friction coefficient increases in the first minutes of polishing and then tends to be stable. The effect of some polishing parameters such as velocity and polishing pad nature was studied. It was found that these parameters have an important influence on the friction behavior. Indeed, it was found that the increase of the velocity reduces the friction coefficient. However, the nature of the polishing pads produces enormous variation of the friction coefficient.     

Sucrose supplementation during traditional carob syrup processing affected its chemical characteristics and biological activities

The addition of sucrose is optional during carob syrups traditional processing. In this work, the polyphenolic profiles of carob syrups supplemented (CSS) or not with sugar (CS) were analyzed using RP-HPLC–ESI-MS. Quantitative data showed that adding of sucrose significantly (p < 0.05) decreased the polyphenolic amounts of about 58.6%, from 4.5 ± 0.32 to 1.86 ± 0.26 mg/g of CS and CSS, respectively. Gallic acid was the most abundant compound in both syrups representing 60.93% (CS) and 69.26% (CSS) of the total phenolics. Moreover, the adding of sugar decreased (p < 0.05) the antiradical potentials of 28% and 74%, as determined, respectively, by the ABTS and DPPH assays. CS was found to exhibit stronger antibacterial and antifungal activities than CSS. Bacillus cereus was the most sensitive strain to the extracts with CMI ≈500 (CS) and 622 (CSS) μg/ml. Both syrup extracts were cytotoxic to human neuroblastoma (SH-SY5Y) and fibroblast (3T3) cell lines as well as to mouse embryonic stem cells (D3). Tumoral SH-SY5Y cells were the most susceptible to the extracts with IC50 = 311.7 ± 23.65 (CS) and 390.6 ± 34.97 μg/ml (CSS). This study provides, for the first time, new analytical insights into traditionally made carob syrups and highlights the negative effect of sugar supplementation during processing.     

阿尔及利亚新第三纪Tafna盆地地震构造研究

通过对阿尔及利亚东北部Tafna盆地区域地质资料、地震活动规律、震源分布和震源机制分析,详细研究了该盆地的地震构造模式。由地震震源机制分析可知Tafna盆主要受到NE—SE的挤压,显示该盆地应力场主要受到欧亚板块和非洲板块的碰撞影响。这一研究结果与目前Tafna盆地区域构造格架具有很好的一致性。     

The instructional benefits of dynamic visualizations in the acquisition of basketball tactical actions

Recent studies exploring the effects of dynamic visualizations on learning compared with static visualizations have yielded mixed results. Procedural motor learning is one of the few fields in which dynamic representations have shown to be effective. Many of the studies have suggested that this advantage is mainly due to the activation of the “mirror‐neuron system.” This study explores this explanation in physical education domain and analysed the effects of instructional media (video vs. photographs), showing tactical actions in basketball, on learning outcomes (i.e., game understanding and game performance), cognitive load (i.e., mental effort invested and estimated difficulty), and attitudes (i.e., attention, enjoyment, engagement, and challenge) in secondary school students. For all of the indicators, the results show that learning from video was more effective than learning from photographs. These findings have implications for the effective design of instructional media and provide confirmation of the superiority of video for teaching tactical actions involving the entire body.     

Detailed study of silver metallic film diffusion in a soda-lime glass substrate for optical waveguide fabrication

We present the study of multimode glass waveguides fabricated by a silver-ion electromigration process followed by a diffusion process. The study is concerned mainly with the diffusion process, which occurs by variation of the diffusion time. The obtained guides are analyzed by the prism-coupling technique, which determines their effective refractive indices that are treated by the inverse WKB method,assumed to be proportional to the silver ions' concentration profiles, for which a Gaussian model is attributed. Diffusion coefficients then are determined from these Gaussian profiles experimentally by both methods. These diffusion coefficients show a concentration dependence related to the variation of the diffusion time. A mathematical model representing the best fit to this dependence is also presented. Finally, our results are compared with other research results, with which we find good agreement.     

First-principles elastic constants and electronic structure of beryllium chalcogenides BeS, BeSe and BeTe

A theoretical study of structural, elastic and electronic properties of BeS, BeSe and BeTe is presented using the full-potential augmented plane-waves plus local orbitals (APW + lo) within density-functional theory (DFT). Results are obtained using both the local-density approximation (LDA) and the generalized gradient approximation (GGA) for the exchange-correlation potentials. The ground-state properties, like lattice constant, bulk modulus and its first derivative obtained from our calculations agree very well with experimental and other theoretical calculations. Band structures, and total valence charge densities including spin–orbit interaction are analyzed in great detail. The calculated values of the energy gaps, bandwidths, and spin–orbit splittings and the correct band degeneracies are compared to experimental and/or ab initio results. The calculated energy gap for the series of beryllium chalcogenides BeS, BeSe and BeTe is found to be indirect (Γ–X) and underestimated by about 40% for both LDA and PBE-GGA compared to experiment. We have also reported the elastic constants of these materials; the elastic constants have been derived by the stress–strain relation.     

Simulation of species transport and water management in PEM fuel cells

A single phase computational fuel cells model is presented to elucidate three-dimensional interactions between mass transport and electrochemical kinetics in proton exchange membrane (PEM) fuel cells with straight gas channels. The governing differential equations are solved over a single computational domain, which consists of a gas channel, gas diffusion layer, and catalyst layer for both the anode and cathode sides of the cell as well as the solid polymer membrane. Emphasis is placed on obtaining a basic understanding of how three-dimensional flow and transport phenomena in the air cathode impact the electrochemical process in the flow field. The complete cell model has been validated against experimentally measured polarization curve, showing good accuracy in reproducing cell performance over moderate current density interval. Fully three-dimensional results of the flow structure and species profiles are presented for cathode flow field. The effects of pressure on oxygen transport and water removal are illustrated through main axis of the flow structure. The model results indicate that oxygen concentration in reaction sites is significantly affected by pressure increase which leads to rising fuel cells power.