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A spin-1/2 and spin-3/2 mixed Ising system in a random field is studied by the use of effective-field theory with correlations. The phase diagrams and thermal behaviours of magnetizations are investigated numerically for the honeycomb lattice (z=3) and square lattice (z=4) respectively. The tricritical behaviours for both honeycomb and square lattices, as well as the reentrant behaviour for the square lattice are found. 相似文献
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采用高效液相色谱法测定了禽蛋产品中苏丹红类染料,包括苏丹红Ⅰ,Ⅱ,Ⅲ,Ⅳ及对位红的残留量。试样中苏丹红类染料用丙酮萃取,用固相萃取法将萃取液通过MAX柱达到进一步的分离和提纯。MAX柱经过用甲醇、氢氧化钠及乙酸乙酯先后淋洗后,最终用由乙酸乙酯、甲醇及甲酸组成的淋洗剂淋洗。用氮气吹干洗出液,残渣用乙腈浸取,所得溶液经滤膜过滤后供HPLC测定。方法的检出限为0.1 mg.L-1,以咸蛋样品为基体分别加入0.25和1.0 mg.kg-1的5种苏丹红类染料的标准作了回收试验,所得回收率结果在76%~92%之间,也作了方法的精密度试验,所得相对标准偏差(n=5)均小于4.5%。 相似文献
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利用相干布居振荡技术在介质吸收光谱上产生烧孔,孔宽大约为基态粒子数恢复时间的倒数. 由增益理论分析得到不同抽运光功率对介质吸收状态的影响. 在介质的吸收区域,振荡导致光脉冲经历饱和吸收,脉冲传输延迟;在介质的增益区域,振荡又导致光脉冲经历增益饱和,脉冲传输超前. 应用此技术在掺铒光纤中实现了光速人为可控. 在掺铒光纤晶体中观测到了最慢为2.857×103m/s的光速减慢传输,相应感生群折射率为10.5×104. 根据布居振荡效应及增益理论,由速率方程出发,得到了
关键词:
光谱烧孔
相干布居振荡
饱和吸收
慢光 相似文献
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Optical Amplification and Slow Light Based on Two-Wave Mixing at Large Modulation Depth 总被引:1,自引:0,他引:1 下载免费PDF全文
Based on Kukhtarev's equations, we derive the formulae of intensity-coupling coefficient, the phase-coupling coefficient and the group velocity at large modulation depth. It is theoretically shown that the signal beam can be amplified after passing through the photorefractive crystal and the group velocity reduced to m/s, even cm/s. Meanwhile, we also analyse the influence of the thermal excitation rate and the large signal effects on optical amplification and reduction of light propagation in photorefractive two-wave mixing. 相似文献
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可分凸二次规划的不可行内点算法 总被引:1,自引:0,他引:1
给出了可分凸二次规划的不可行内点算法 ,并证明了该算法在 O(n2 L )次迭代之后 ,或者收敛到问题的一个近似最优解 ,或者说明该问题在某个较大区域内无最优解 . 相似文献
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We investigate the reduction of the group velocity propagation resulting from the steep change of the refractive index by the coherent population oscillation in erbium-doped optical fibre. The largest delay is measured to be about 8.75ms corresponding to a group index of 1.312×10^6. The time delay or advancement depends on the pump intensity. Influences of the ion density on the fractional delay and the group velocity reduction of light propagation are studied. Based on our discussion the optimization parameters should be selected in order to obtain more appropriate time delay and the slowdown of group velocity. 相似文献
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根据饱和增益理论分析可知,不同抽运光功率对应着介质不同的吸收和增益状态. 在吸收介质中,相干布居振荡效应导致光脉冲经历饱和吸收,光脉冲传输延迟;在增益介质中, 相干布居振荡效应导致光脉冲经历增益饱和,光脉冲传输超前. 本文由铒离子的亚稳态速率方程出发,建立了掺铒光纤中超光速传输的理论模型, 同时得到时间超前的数值解析表达式;讨论了低频率段超光速的饱和现象, 即超光速在低频段并不随着抽运光功率的增强而加强,而在高频率段随抽运光功率的增加而加强. 相似文献