Blue-to-Orange Tunable Luminescence from Europium Doped Yttrium--Silicon--Oxide--Nitride Phosphors

Europium-doped yttrium-silicon-oxide-nitride phosphors are synthesized by carbothermal reduction and nitridation method. The crystal structure of the phosphors changed gradually from oxide Y2Si2O7 to nitride YSi3N5 state with increasing dosage of Si3N4 and carbon powder. The Y2Si2O7：Eu phosphor shows a blue emission at 465 nm with 300 nm excitation and a characteristic red emission of Eu^3＋ at 612 nm with 230 nm excitation. The YSi3N5：EU phosphor shows a broad emission band centred at 595nm with some sharp peaks of Eu^3＋ with 325nm excitation. The absorption of the studied phosphors increases from 450 to 700hm with an increment in nitrogen content. Blue-to-orange tunable luminescence is observed with 390 nm excitation.     

跳扩散和随机利率模型下的欧式双向期权定价

假定股票价格的跳跃过程为一类特殊的更新跳过程,即事件发生时间间隔为相互独立且同服从Gamma分布的随机变量序列.利用鞅定价方法,用较简单的数学推导得到了在随机利率情形下跳扩散模型的欧式双向期权定价公式.