LD抽运腔内和频571.6nm连续波黄光激光器

报道了全固态连续波571.6nm黄光激光器.黄激光是分别由两片Nd∶YAG的1444nm和946nm谱线非线性和频产生,两条谱线在各自晶体对应能级跃迁分别为4F3/2-4I15/2和4F3/2-4I9/2.实验中采用复合腔结构,利用RTP晶体II类临界相位进行内腔和频,当注入到两片Nd∶YAG晶体的抽运功率分别为25W和14.8W时,获得562mW的连续波571.6nm黄激光输出,4h功率稳定度优于±2.9%.     

氢同位素转动跃迁拉曼频移的理论计算

激光拉曼光谱作为一种非侵入式的物质结构和成分分析的测试手段特别适合于核工业中含氚放射性同位素气体的定性和定量分析。将经典物理学方法和量子力学理论相结合,采用非刚性转子校正模型,计算获得了H2、HD、HT、D2、DT、T26种氢同位素气体分子的转动跃迁拉曼频移,为氢同位素气体拉曼光谱谱峰的辨识提供理论数据。通过实验测定H2和D2的转动拉曼光谱,得到这2种分子的转动拉曼图谱和拉曼频移,并将测定结果与计算结果进行比较,验证了理论计算方法的可行性和正确性。     

Long-reach 60-GHz radio-over-fiber system based on turbo-coded OFDM

Turbo-coded 1.25-Gb/s orthogonal frequency-division multiplexing （OFDM） signals in 60-GHz radio-over-fiber system are demonstrated.It can overcome impairments in fibers and extend transmission distance.Experimental results show that the transmission distance of turbo-coded OFDM signals at 1.25 Gb/s with coding （pure bit rate of 830 Mb/s） can be extended by over 30%.     

Blind frequency offset estimation based on cyclic prefix and virtual subcarriers in CO-OFDM system

A new blind frequency offset estimation method based on cyclic prefix and virtual subcarriers in coherent optical orthogonal frequency division multiplexing （CO-OFDM） system is presented. It is able to estimate the fractional part and integral part of frequency offset at the same time. Its estimation range is about [-3.5 GHz, 3.5 GHz]. The influence of the integral frequency offset is comprehensively analyzed in COOFDM system. Its performances in the additive white Gaussian noise （AWGN） channel and the dispersive channel are investigated, respectively. Simulation results indicate that even in the dispersive channel, when the optical signal-to-noise ratio （OSNR） is low, it can still work very well.     

A novel OFDM-CPM modulation scheme and its application in WDM-PON

A novel scheme to generate, transmit, and receive an optical orthogonal frequency division multiplexing (OFDM) continuous phase modulation (CPM) signal, which is combining minimum shift keying (MSK) coding with OFDM optical modulation, for downlink application in a 4×2.5-Gb/s wavelength division multiplexing (WDM) passive optical access network, is proposed and experimentally validated. We also realize wavelength remodulation for carrying upstream on-off keying (OOK) data to reduce the cost budget at the optical network unit. The experimental results show that the power penalties for the downlink and the uplink data after transmission over 25-km SMF-28 fiber are 0.1 dB and smaller than 0.4 dB, respectively.     

究竟哪儿错了

“含参不等式恒成立问题”是高中数学中一类很重要的问题．近几年的高考在这方面的考查比较频繁,是高考命题中的一个热点．这类问题往往覆盖知识点多、综合性强、解法灵活,是同学们学习的一个难点．由于高考考查频繁,各种复习资料、报刊杂志研究透彻,     

约束条件下的运动直线问题

约束条件下的运动直线问题是一类应用较为广泛又较为流行的数学问题,它与一些特定函数的最值(或值域)、线性规划的图解法、含参方程有解以及不等式恒成立问题都密切相关.在一般情况下,人们比较习惯用纯代数的方法解决这类问题,过程和步骤显得较为烦琐复杂.笔者最近对这类问题做     

对一道数学高考题的探讨

三个同学对2006年上海高考理科第12题:"关于x的不等式x2+25+|x3-5x2|≥ax在[1,12]上恒成立,求实数a的取值范围"提出各自的解题思路.……     

竹炭固相萃取-恒能量同步荧光法测定河水中多环芳烃

建立了竹炭固相萃取-恒能量同步荧光法检测河水中多环芳烃(PAHs)的方法。优化了实验条件。选定正己烷为洗脱溶剂,洗脱溶剂体积为15mL,上样速率为5mL/min,上样体积为500mL。采用恒能量同步荧光法对流出液中PAHs进行测定,其相关系数r≥0.9976,检出限在0.025～1.5ng/mL之间,相对标准偏差为0.72%～1.68%。该法用于龙岩市省控断面九龙江河水中PAHs的测定,水样的加标回收率为76.8%～104.4%。     

Adaptive Wavelet Solution to the Stokes Problem

This paper deals with the design and analysis of adaptive wavelet method for the Stokes problem. First, the limitation of Richardson iteration is explained and the multiplied matrix M0 in the paper of Bramble and Pasciak is proved to be the simplest possible in an appropiate sense. Similar to the divergence operator, an exact application of its dual is shown; Second, based on these above observations, an adaptive wavelet algorithm for the Stokes problem is designed. Error analysis and computational complexity are given; Finally, since our algorithm is mainly to deal with an elliptic and positive definite operator equation, the last section is devoted to the Galerkin solution of an elliptic and positive definite equation. It turns out that the upper bound for error estimation may be improved.