Growth by the heat exchanger method of NaBiW2O8 and Na5B2P3O13 crystals

In this paper, we present the results of our attempt to grow NaBiW2O8 (NBW) and Na5B2P3O13 (NBP) crystals by the heat exchanger method (HEM). This method is slightly different from the Bridgman technique: the crucible is kept fixed in the setup and the center of the crucible bottom is cooled by a variable helium gas flow. It allows very good control of the growth rate and minimizes parasitic crystallization at the crucible walls. First experiments for growing these two materials by the HEM technique have shown very promising results with single-crystal sizes of few cubic centimetres.

Half-Symmetric Lens Based Localization Algorithm for Wireless Sensor Networks

International audienc

Anisotropy of the spectroscopic, optical and thermo-mechanical properties of Li6Eu1-xGdx(BO3)3 crystals optimized for heat-scintillation cryogenic bolometers

International audienceOptical, spectroscopic and thermo-mechanical properties of monoclinic Li6Eu1-xGdx(BO3)3 (x = 0,0.25,0.35) bulk single crystals, grown to be used in the design of heat-scintillation cryogenic bolometers (HSCBs), were investigated. The linear thermal expansion was determined along the a, b, c and c* directions over the temperature range 303–873 K, and its tensor principal coefficients were calculated for both x = 0.25 and x = 0. In addition, the anisotropic thermal conductivity was measured over the temperature range 20-400 K in Li6Eu0.75Gd0.25(BO3)3 (LGEB7, x = 0.25), and the principal components of its tensor at 300 K were established. Spectroscopic properties such as polarized absorption, polarized emission, Raman spectroscopy and optical refractive indices are also reported for the first time. Based on the polarized emission spectra, the line and oscillator strengths, the radiative lifetimes and fluorescent branching ratios were obtained. The intensity parameters Ωλ (λ = 2,4) were obtained and then predicted via the Judd–Ofelt theory. The crystal field parameters and the 7F1 level splitting were discussed using the simple overlap model (SOM) and the method of equivalent nearest neighbours (MENN). The 613 nm emission originates from the 5D0→7F2 transition and the associated stimulated emission peak cross section reaches its maximum value in π-polarization, ≈1.07 × 10−20 cm2 in LGEB7. The thermo-mechanical characterizations and spectroscopic analysis in LGEB7 suggest that this crystal has better optical properties than the Eu3+-doped Li6Y(BO3)3 crystals. However, its potential for solid-state laser applications is still quite speculative, unless a clever thermo-mechanical management of the crystal under laser operation is designed

Anisotropy of the spectroscopic, optical and thermo-mechanical properties of Li6Eu1-xGdx(BO3)3 crystals optimized for heat-scintillation cryogenic bolometers

Optical, spectroscopic and thermo-mechanical properties of monoclinic Li6Eu1-xGdx(BO3)3 (x = 0,0.25,0.35) bulk single crystals, grown to be used in the design of heat-scintillation cryogenic bolometers (HSCBs), were investigated. The linear thermal expansion was determined along the a, b, c and c* directions over the temperature range 303–873 K, and its tensor principal coefficients were calculated for both x = 0.25 and x = 0. In addition, the anisotropic thermal conductivity was measured over the temperature range 20-400 K in Li6Eu0.75Gd0.25(BO3)3 (LGEB7, x = 0.25), and the principal components of its tensor at 300 K were established. Spectroscopic properties such as polarized absorption, polarized emission, Raman spectroscopy and optical refractive indices are also reported for the first time. Based on the polarized emission spectra, the line and oscillator strengths, the radiative lifetimes and fluorescent branching ratios were obtained. The intensity parameters Ωλ (λ = 2,4) were obtained and then predicted via the Judd–Ofelt theory. The crystal field parameters and the 7F1 level splitting were discussed using the simple overlap model (SOM) and the method of equivalent nearest neighbours (MENN). The 613 nm emission originates from the 5D0→7F2 transition and the associated stimulated emission peak cross section reaches its maximum value in π-polarization, ≈1.07 × 10−20 cm2 in LGEB7. The thermo-mechanical characterizations and spectroscopic analysis in LGEB7 suggest that this crystal has better optical properties than the Eu3+-doped Li6Y(BO3)3 crystals. However, its potential for solid-state laser applications is still quite speculative, unless a clever thermo-mechanical management of the crystal under laser operation is designed

Optimal number of routing paths in multi-path routing to minimize energy consumption in wireless sensor networks

In wireless sensor networks, multi-path routing is proposed for energy balancing which prolongs the network lifetime as compared to single-path routing where utilization of a single route between a source node and the base station results in imbalanced energy dissipation. While it is evident that increasing the number of routing paths mitigates the problem of energy over-utilization in a subset of nodes acting as relays, the net effect of the proliferation of multiple routing paths on energy balancing remains unclear. It is imperative to keep the number of routing paths as low as possible without significantly deteriorating the network lifetime; therefore, determination of the optimal number of routing paths in multi-path routing by considering the tradeoff in routing complexity and network lifetime extension is an interesting research problem. In this study, to investigate the impact of the number of routing paths in multi-path routing on network-wide energy balancing under optimal operating conditions, we build a novel mixed integer programming framework. We explore the parameter space consisting of a number of paths, number of nodes, maximum transmission range, network area, and network topology. The results of the analysis show that by utilizing the optimization scheme proposed, it is possible to achieve near-optimal energy consumption (within 1.0% neighborhood of the case where no restrictions are imposed on the number of routing paths in multi-path routing) using at most two paths for each node.Publisher's Versio