Modular Machining Line Design and Reconfiguration: Some Optimization Methods

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Comparison of energy transfer between Terbium and Ytterbium ions in glass and glass ceramic: Application in photovoltaic

The structural and optical properties of thin layers based on 70%SiO 2 –30%HfO 2 doped with different concentra- tion of rare earth ions (terbium and ytterbium) have been studied with a view to integrating them in a photovoltaic cell as a spectral conversion layer in order to improve its efficiency, by using down-conversion process. These thin films were synthesized by using sol gel technique and deposited on the pure silica substrate by dip-coating method. The DC layer can be placed on the front side of a solar cell and can enhance the current by converting ultraviolet (UV) photons into a large number of visible photons. In present study two series of samples are compared, the first series corresponds to samples treated at 900 °C (glass- S) while the second series concerns samples treated at 1000 °C (glass-ceramic- SC). These series are based on 70SiO 2 –30HfO 2 activated by different molar concentrations of rare earths [Tb + Yb]/[Si + Hf] = 7%, 9%, 12%, 15%, 17%, 19% and 21%. Photoluminescence results of reference samples (without Yb 3 + ) showed an emission from 5 D 4 to 7 F J ( J = 3, 4, 5, 6) level characteristic transitions of Tb 3 + , with a maximum peak in the green centered at 543.5 nm cor- responding to the 5 D 4 →7 F 5 transition. For the co-doped samples a clear NIR PL emission around 980 nm was detected, due to the 2 F 5/2 →2 F 7/2 transition of Yb 3 + ions. From luminescence decay curves of Tb 3 + maximum emission peak ( 7 F 5 →5 D 4 transition at 543.5 nm) we have identified the energy transfer efficiency. The quantum efficiency increases by increasing the total [Tb + Yb] concentration. The most significant yield was achieved with [Tb + Yb] = 19%, the maximum quantum transfer efficiency obtained was 190% for glass-ceramic samples and 161% for glassy one

Silver doping of silica-hafnia waveguides containing Tb3+/Yb3+ rare earths for downconversion in PV solar cells

The aim of this paper is to study the possibility to obtain an efficient downconverting waveguide which combines the quantum cutting properties of Tb3+/Yb3+ codoped materials with the optical sensitizing effects provided by silver doping. The preparation of 70SiO(2)-30HfO(2) glass and glass-ceramic waveguides by sol-gel route, followed by Ag doping by immersion in molten salt bath is reported. The films were subsequently annealed in air to induce the migration and/or aggregation of the metal ions. Results of compositional and optical characterization are given, providing evidence for the successful introduction of Ag in the films, while the photoluminescence emission is strongly dependent on the annealing conditions. These films could find potential applications as downshifting layers to increase the efficiency of PV solar cells. (C) 2016 Elsevier B.V. All rights reserved

Comparative study of back-stepping controller and super twisting sliding mode controller for indirect power control of wind generator

© 2021 Springer. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1007/s13198-019-00905-7This paper presents the application nonlinear control to regulate the rotor currents and control the active and reactive powers generated by the Doubly Fed Induction Generator used in the Wind Energy Conversion System (WECS). The proposed control strategies are based on Lyapunov stability theory and include back-stepping control (BSC) and super-twisting sliding mode control. The overall WECS model and control scheme are developed in MATLAB/Simulink and the simulation results have shown that the BSC leads to superior performance and improved transient response as compared to the STSMC controller.Peer reviewe

Tb3+/Yb3+ codoped silica-hafnia glass and glass-ceramic waveguides to improve the efficiency of photovoltaic solar cells

In this paper we present the investigation of the energy transfer efficiency between Tb3+ and Yb3+ ions in silica-hafnia waveguides. Cooperative energy transfer between these two ions allows to cut one 488 nm photon in two 980 nm photons and could have important applications in improving the performance of photovoltaic solar cells. Previous works revealed that for a given concentration of donors (Tb3+, increasing the number of acceptors (Yb3+) located near to the Tb3+ ion can increase the Tb-Yb transfer probability. However, when increasing the density of active ions, some detrimental effects due to cross-relaxation mechanisms become relevant. On the basis of this observation the sample doping was chosen keeping constant the molar ratio [Yb]/[Tb] = 4 and the total rare earths contents were [Tb + Yb]/[Si + Hf] = 5%, 7%, 9%. The choice of the matrix is another crucial point to obtain an efficient down conversion processes with rare earth ions. To this respect a 70SiO(2)-30HfO(2) waveguide composition was chosen. The comparison between the glass and the glass-ceramic structures demonstrated that the latter is more efficient since it combines the good optical properties of glasses with the optimal spectroscopic properties of crystals activated by luminescent species. A maximum transfer efficiency of 55% was found for the highest rare earth doping concentration

Artesunate induces necrotic cell death in schwannoma cells

Established as a potent anti-malaria medicine, artemisinin-based drugs have been suggested to have anti-tumour activity in some cancers. Although the mechanism is poorly understood, it has been suggested that artemisinin induces apoptotic cell death. Here, we show that the artemisinin analogue artesunate (ART) effectively induces cell death in RT4 schwannoma cells and human primary schwannoma cells. Interestingly, our data indicate for first time that the cell death induced by ART is largely dependent on necroptosis. ART appears to inhibit autophagy, which may also contribute to the cell death. Our data in human schwannoma cells show that ART can be combined with the autophagy inhibitor chloroquine (CQ) to potentiate the cell death. Thus, this study suggests that artemisinin-based drugs may be used in certain tumours where cells are necroptosis competent, and the drugs may act in synergy with apoptosis inducers or autophagy inhibitors to enhance their anti-tumour activity

Novel Regulatory Mechanisms for Generation of the Soluble Leptin Receptor: Implications for Leptin Action

The adipokine leptin realizes signal transduction via four different membrane-anchored leptin receptor (Ob-R) isoforms in humans. However, the amount of functionally active Ob-R is affected by constitutive shedding of the extracellular domain via a so far unknown mechanism. The product of the cleavage process the so-called soluble leptin receptor (sOb-R) is the main binding protein for leptin in human blood and modulates its bioavailability. sOb-R levels are differentially regulated in metabolic disorders like type 1 diabetes mellitus or obesity and can, therefore, enhance or reduce leptin sensitivity.To describe mechanisms of Ob-R cleavage and to investigate the functional significance of differential sOb-R levels we established a model of HEK293 cells transiently transfected with different human Ob-R isoforms. Using siRNA knockdown experiments we identified ADAM10 (A Disintegrin And Metalloproteinase 10) as a major protease for constitutive and activated Ob-R cleavage. Additionally, the induction of lipotoxicity and apoptosis led to enhanced shedding shown by increased levels of the soluble leptin receptor (sOb-R) in cell supernatants. Conversely, high leptin concentrations and ER stress reduced sOb-R levels. Decreased amounts of sOb-R due to ER stress were accompanied by impaired leptin signaling and reduced leptin binding.Lipotoxicity and apoptosis increased Ob-R cleavage via ADAM10-dependent mechanisms. In contrast high leptin levels and ER stress led to reduced sOb-R levels. While increased sOb-R concentrations seem to directly block leptin action, reduced amounts of sOb-R may reflect decreased membrane expression of Ob-R. These findings could explain changes of leptin sensitivity which are associated with variations of serum sOb-R levels in metabolic diseases

Modélisation de la configuration des lignes d'usinage avec équipements standard

Universitaires de Grenoble, p. 65-66. Livre des résumés. ISBN 978-2-7061-1398-7, Presse