Thermal sensors based on ytterbium-erbium doped nano-glassceramics
Lead-fluoride nano-glassceramics doped with ytterbium and erbium have been developed and synthesized. The influence of heating on the green up-conversion luminescence of erbium has been experimentally investigated. Nano-glassceramics are promising candidates for temperature sensors.
Fabrication and characterization of nanoscale, Er3+-doped, ultratransparent oxy-fluoride glass ceramics
We show that oxy-fluoride glass ceramics, with typical composition, 32(SiO2):9(AlO1.5):31.5(CdF2):18.5(PbF2):5.5(ZnF2): 3.5(ErF3) mol % have potential applications in telecommunications. Upon heat treatment, Er3+ nucleates the growth of the nanocrystalline β-PbF2, which acts as its host. Heat treatment at 440 °C for 5 h and at 390 °C for 3 h gave rise to ∼12 and ∼2.5 nm diameter crystals, respectively. The emission band of Er3+ in the 1.54 μm telecommunications window (4I13/2→4I15/2 transition, at the half-height width) was 75 nm in the former and 90 nm in the latter case, while 4I13/2↔4I15/2 absorption and emission bands became wavelength divergent in both cases. Also in the latter case, the spectrum was flat from 1.53 to 1.56 μm. The evolution of spectral behavior is explained by changes in average site geometry of the Er3+ dopant, related to the α→β phase transition of PbF2, which is stimulated by heat treatment.
Transient nonlinear thermal stability analysis of metro cable under pulse power
The load of metro cable system varies a lot from morning rush hours to the evening closure time. With many trains hopping in the rush hours, the long term and economical short term thermal stability become a big issue as a result of the large difference between thermal time constant and the electrical time constant of cable. Based on a 10kV three-core XLPE metro power cable model, the theoretical thermal capacity was calculated according IEC standard. Then, a Finite Element Method (FEM) was employed to analyze the transient electro-thermal phenomena, taking into account various types of power loss in cable system and the non-linear electrical conductivity of the conductor. Finally, the thermal distribution inside the cable was presented as a function of time, and the maximum thermal capacity was predicted in metro cable.