Magneto optical rib waveguide with low refractive index

The phase matching condition is an important requirement for magneto-optical waveguide devices. In this work, the design rules that must be imposed on the geometry and the index of magneto optical rib waveguides to make them behave as phase matched rib waveguides have been simulated. Using film mode matching method, the results show that operation in phase matching is possible under certain circumstances with selected index and geometries. We simulated the performance of such devices and we determined the waveguide dimensions (height, width, and etching depth) and the index that satisfy the phase matching conditions

Preservation of York Minster historic limestone by hydrophobic surface coatings

Magnesian limestone is a key construction component of many historic buildings that is under constant attack from environmental pollutants notably by oxides of sulfur via acid rain, particulate matter sulfate and gaseous SO 2 emissions. Hydrophobic surface coatings offer a potential route to protect existing stonework in cultural heritage sites, however, many available coatings act by blocking the stone microstructure, preventing it from 'breathing' and promoting mould growth and salt efflorescence. Here we report on a conformal surface modification method using self-assembled monolayers of naturally sourced free fatty acids combined with sub-monolayer fluorinated alkyl silanes to generate hydrophobic (HP) and super hydrophobic (SHP) coatings on calcite. We demonstrate the efficacy of these HP and SHP surface coatings for increasing limestone resistance to sulfation, and thus retarding gypsum formation under SO/H O and model acid rain environments. SHP treatment of 19th century stone from York Minster suppresses sulfuric acid permeation

Scale effect on hydraulic conductivity and solute transport: Small and large-scale laboratory experiments and field experiments

[EN] Hydraulic conductivity (K), dispersivity (alpha) and partition coefficient (K-d) can change according to the measurement support (scale) and that is referred to as scale effect. However, there is no clear consensus about the behavior of these parameters with the change in the scale. Comparison between results obtained in different support of measurements in the field and in the laboratory can promote the discussion about scale effects on K, alpha, and K-d, and contribute to understanding how these parameters behave with the change in the scale of measurement, the main objectives of the present paper. Small and large-scale laboratory tests using undisturbed soil samples and field experiments at different scales were performed. Results show that for the same measurement condition, K, alpha, and K-d increase with scale in all studied magnitudes. Caution should be taken when using K, alpha, and K-d values in numerical models with no concern about the scale effect. The lack of consideration of the difference of scale between field and laboratory measurements and numerical model may compromise the reliability of the predictions and misrepresent the responses.The authors thank the financial support by the Brazilian National Council for Scientific and Technological Development (CNPq) (Project 401441/2014-8). The doctoral fellowship awarded to the first author by the Coordination of Improvement of Higher Level Personnel (CAPES) is gratefully acknowledged. The first author also thanks the international mobility grant awarded by CNPq, through the Science Without Borders program (grant number: 200597/2015-9), and the international mobility grant awarded by Santander Mobility in cooperation with the University of Sao Paulo.Almeida De-Godoy, V.; Zuquette, L.; Gómez-Hernández, JJ. (2018). Scale effect on hydraulic conductivity and solute transport: Small and large-scale laboratory experiments and field experiments. Engineering Geology. 243:196-205. https://doi.org/10.1016/j.enggeo.2018.06.020S19620524

Behavior of pre-cracked deep beams with composite materials repairs

International audienceThe study covers the behavior of reinforced concrete deep beams loaded under 4-point bending, failed by shear and repaired using bonding glass fiber reinforced plastics fabrics (GFRP) patches. Two rehabilitation methods have been used to highlight the influence of the composite on the ultimate strength of the beams and their failure modes. In the first series of trials the work has been focused on the reinforcement/rehabilitation of the beam by following the continuous configuration of the FRP fabric. The patch with a U-shape did not provide satisfactory results because this reinforcement strategy does not allow to increase the ultimate strength or to avoid the abrupt shear failure mode. A second methodology of rehabilitation/reinforcement has been developed in the form of SCR (Strips of Critical Region), in which the composite materials reinforcements are positioned to band the inclined cracks (shear) caused by the shear force. The results obtained by using this method lead a superior out come in terms of ultimate strength and change of the failure mode from abrupt shearing to ductile bending

Statistical Analysis of 3-Point Bending Properties of Polymer Concretes Made From Marble Powder Waste, Sand Grains, and Polyester Resin

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Temperature dependence of the electrical resistivity and absolute thermoelectric power of amorphous metallic glass Ni33.3Zr66.7

International audienceElectron transport properties and thermal stability of Ni33.3Zr66.7 metallic glass (MG) have been studied using an original device for simultaneous measurements of electrical resistivity and absolute thermoelectric power (ATP) controlled by a LabView software written by one of us. The electrical resistivity and absolute thermoelectric power were measured simultaneously and very accurately over a temperature range from 25 to 400 °C with a nominal heating rate of 0.5 K min− 1. The electronic thermal conductivity was also determined using the Wiedemann–Franz law in the same temperature range. Due to its high efficiency, this technique is more and more used because it is characterized by a high sensitivity to detection of the phase transitions related to electronic transport, which is the aim of this study. Analysis of the temperature dependence of the resistivity and ATP of the Ni33.3Zr66.7 glassy ribbons proves the potential of this characterization method to study the thermal behavior of metallic glasses. The crystal structure and the morphology of Ni33.3Zr66.7 metallic glass in the as-quenched state and after heat treatments were studied using X-ray diffraction (XRD), and scanning electron microscope (SEM)