贵金属Ag中光学和磁光性质的研究实验

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铌酸钾锂晶体的生长和缺陷

用电阻加热提拉法生长了一系列较大尺寸,组分离子均匀性较好的铌酸钾锂晶体.利用X射线荧光光谱法测量了不同配比的熔体中生长出的晶体组成,用同步辐射X射线测量了晶体结构,结果表明随晶体组成变化,晶体的晶格常数发生了变化.根据晶体组分离子浓度与折射率的关系研究了晶体折射率变化情况,结果表明用本方法生长的大尺寸KLN晶体,寻常折射率no在测量误差范围内没有变化,非寻常折射率ne的变化率在820nm仅为1.22×10-4/mm,在410nm仅为1.93×10-4/mm.晶体的干涉条纹证明了晶体有良好的光学均匀性.结合晶体生长实验,探讨了改进晶体组分离子浓度分布均匀性的方法,结果表明采用籽晶和坩锅向相同方向旋转可以改善晶体生长界面处组分离子浓度的波动,提高晶体组分离子均匀性.晶体的缺陷研究表明晶体结构完整性较好,位错形状与晶体结构相一致,密度为7.5×104,[001]轴是晶体的极化轴.晶体对890～960nm波长范围的cw-Ti:sapphire激光倍频结果表明晶体有良好的倍频性能.     

立足基础 推陈出新 综合应用——2004年高考理科综合能力测试化学试题评析

2004年全国高考理科综合能力测试(以下简称理综)中,涉及化学学科的试题在第Ⅰ卷(选择题)中有9道,在第Ⅱ卷(非选择题)中有5道,分值为118分。其中第Ⅰ卷的第6、16题及第Ⅱ卷的第31题的(1)(2)小题是分属于生化、物化和生化综合的学科间综合试题。     

Theory study on a photonic-assisted radio frequency phase shifter with direct current voltage control

A photonic-assisted radio frequency phase shifter with direct current voltage control is proposed using a polymer- based integrated Mach-Zehnder modulator. A closed-form expression of radio frequency （RF） signal power and phase is given. Theoretical calculation reveals that by carefully setting the bias voltages, RF signal power variation lower than 1-dB and phase accuracy less than 3° can be achieved and are not degraded by perturbation of modulation index once the bias voltage drift is kept within -3% -- 3%.     

刚柔耦合约束多体系统的动力分析

本文提出了描述柔性多体系统的牵连坐标系统。该系统由惯性参考系,牵连坐标系,物体坐标系及单元坐标系组成,实现了对刚体平动,刚体转动及弹性运动的连续分解,最大限度地消除了由于刚体大角度转动导致的非线性特性。以有限元法为基础,应用拉格朗日方程建立了在该坐标下的刚柔耦合约束多体系统的动力学控制方程。该方程具有耦合程度小、易于推导、编程及求解等优点,为大规模约束多体系统的动力分析提供了新的途径。本文还讨论了平面铰链约束的约束形式及约束方程,最后给出了一个典型多体系统的数值算例。     

妙用Origin求实验极值

以光电效应中"光电管伏安特性曲线的测定"为例,介绍了Origin软件在确定实验极值方面的一些特殊应用。结果表明利用该软件处理物理实验数据能大大减轻学生繁杂的数据计算及绘图步骤,有效避免了手工处理所带来的误差,并且能准确直观地获取手工方法难以得到的实验极值。     

Simulation study on an improved frequency-doubled triangular-shaped pulse train generator with reduced harmonic distortion

An approach to reducing the harmonic distortion in frequency-doubled triangular-shaped pulse train generation is proposed. It requires a dual-parallel Mach Zehnder modulator followed by a section of dispersive fiber, as the key component. The basic principle is to make the expression of optical intensity approximately equal to the Fourier expansion of idea triangular-shaped waveform. A detailed expression of the final optical intensity is given by theory and then verified by simulation. It is found that the impact of the undesired harmonic distortion is greatlv reduced.     

Density functional theory study of Mg_2Ni_n(n= 1–8) clusters

The density functional theory B3PW91 with LANL2DZ basis sets has been used to study the possible geometries of Mg2Nin(n = 1–8) clusters. For the lowest energy structures of the clusters, stabilities, electronic properties, and natural bond orbital(NBO) are calculated and discussed. The results show that the doped Mg atoms reduce the stabilities of pure Ni clusters. The Mg2Ni2, Mg2Ni4, and Mg2Ni6clusters are more stable than neighboring clusters. The system appears magic number characteristics. In addition, the hybridization phenomenon occurs, owing to the interaction of Mg and Ni. The result of charge transfer is that Ni atom is negative and the Mg atom is positive. We also conclude that the 3p and 4d orbitals of the Ni atom have an effect on the stabilities of the clusters.     

基于谐波拟合产生周期性三角形光脉冲串的实验研究

实验研究了一种基于谐波拟合产生周期性三角形光脉冲串的方法,方案首先利用马赫曾德调制器的载波抑制调制,获得具有周期性起伏的连续光强度信号,然后利用光纤色散所致的射频功率衰落效应,对光强度表达式中四次谐波分量进行抑制,调节调制深度后,光强度表达式将向理想三角形傅里叶展开式的前三项进行逼近,最后以谐波拟合的方式获得重复频率为射频调制频率二倍的周期性三角形光脉冲串.结合实验,在9.862 GHz和7.678 GHz射频调制频率下,获得了脉冲重复频率19.724 Gb/s(脉冲全宽约50.7 ps)和15.356Gb/s(脉冲全宽约65.1 ps)的稳定三角形光脉冲串输出,改变色散量并反向调节调制频率,可进一步改变脉冲的重复频率,所获得的实验结果与理论预期基本符合.     

超高效液相色谱-串联质谱法测定小麦和土壤中抗倒酯及其代谢物残留量

建立了小麦植株、籽粒和土壤中抗倒酯及其代谢物残留量的超高效液相色谱-串联质谱检测方法。样品中残留的农药用乙腈-0.1mol/L H3PO4提取,提取液加NaCl盐析除水后,取乙腈层直接进样分析,采用电喷雾串联质谱仪在多反应监测扫描模式下进行测定,基质外标法定量。抗倒酯及其代谢物抗倒酸在各自的线性范围内,线性关系良好,相关系数均为0.999。对小麦植株、籽粒和土壤中抗倒酯和抗倒酸在3个添加浓度水平的回收率进行测定,其平均回收率在73.8%~98.2%之间,相对标准偏差在0.5%~4.8%之间。抗倒酯和抗倒酸的检出限分别为0.05 mg/kg和0.5 mg/kg。