Optoacoustic laser Stark spectroscopy in the ν2 band of 14NH3

Laser Stark spectroscopy of the R(5, K) transitions in the ν₂ band of ammonia was carried out using coincidences with the 9-μm band CO₂ laser lines. We observed 22 Doppler-free resonances by using an optoacoustic detector and a Lamb-dip stabilized CO₂ laser. A simultaneous analysis of sa, aa, and ss lines yields zero-field transition frequencies with an absolute accuracy of 1 ～ 2 MHz.     

Ultra high resolution of 6.2 keV 181Ta in 2H-TaSe2

The 6.2 keV γ-rays of ¹⁸¹Ta have been used to study the hyperfine interaction of ¹⁸¹Ta in the trigonal prismatic charge density wave material 2H-TaSe₂. Using a region of interest drive and an unstrained single crystal sample, we are able to resolve the splitting between the nuclear transition $\text{±}\text{5}\text{2}\text{→ ±}\text{3}\text{2}$ and $\text{±}\text{7}\text{2}\text{→ ±}\text{5}\text{2}$. Our experimental linewidth is that of the Ta metal.     

从自旋冰到自旋液态的渡越——结构与磁性质的演化

使用固相反应法得到了Ho_2-xTb_xTi₂O₇（x=0,05,1,15,2）系列多晶样品.X射线衍射（XRD）实验与2K到300K温度区间的直流磁化率测量结果显示,随着Tb即是x的增加,体系由自旋冰Ho₂Ti₂O₇向自旋液Tb₂Ti₂O_{7关键词： 自旋冰 自旋液体 自旋阻挫 晶格结构}     

铜基大块非晶合金添加微量元素对腐蚀行为的影响机理研究

通过分子动力学方法模拟了Cu-Al合金液相,然后模拟降温过程得到Cu-Al非晶合金.通过计算机编程建立了Cu-Al-M非晶基体、Cu-Al-M非晶表面及吸附O原子Cu-Al-M非晶表面原子结构模型.利用实空间连分数方法,研究了添加微量合金元素Zr,Nb,Ta,V,Y,Sc对Cu基大块非晶合金的腐蚀行为的影响机理.研究发现合金元素Zr,Nb,Ta,V,Sc不向清洁Cu基非晶表面偏聚,但除Y外向有氧吸附的表面偏聚,说明有氧吸附后Cu基非晶表面偏聚发生逆转.键级积分计算表明Zr,Nb,Ta,V,Y,Sc元素均增大与氧之间的结合力,易形成氧化膜,提高Cu基大块非晶的耐蚀性.稀土Y提高Cu基大块非晶的耐蚀性可能是由于它向合金与氧化膜界面偏聚并提高了合金与氧化膜的结合力.     

Li,N双受主共掺杂实现p型ZnO的第一性原理研究

基于密度泛函理论,采用第一性原理平面波超软赝势法,首先对六方纤锌矿结构的ZnO晶体和N,Li分别掺杂ZnO以及Li-N共掺杂ZnO晶体的几何结构分别进行了优化计算,在此基础上计算得到了未掺杂ZnO晶体和不同掺杂情况下ZnO晶体的能带结构、总体态密度、分波态密度和电荷布居数.利用计算的结果,从理论上分析了Li-N共掺杂ZnO更容易得到稳定的p型ZnO. 关键词： ZnO 电子结构 第一性原理 p型共掺杂     

发动机润滑油品质的可见-近红外光谱快速检测

研究了基于可见-近红外光谱技术的发动机润滑油品质的快速检测方法,包括粘度与含水率的预测。在获取可见-近红外光谱信息的基础上,采用广义回归神经网络分别建立了粘度与含水率的预测模型。预测集样本的确定系数分别达到了0.9818和0.9999。说明可见-近红外光谱技术能够用于发动机润滑油的含水率与粘度的预测。     

基于Matlab Simulink的物理实验——简谐振动仿真研究

以简谐振动和阻尼振动仿真为例介绍了用Simulink对物理实验进行仿真建模的方法。给出了位移、速度等振动曲线;可对振动过程中的动能、势能以及机械能进行监测。体现出Simulink仿真物理实验的优越性。     

Nearly-integrable dissipative systems and celestial mechanics

The influence of dissipative effects on classical dynamical models of Celestial Mechanics is of basic importance. We introduce the reader to the subject, giving classical examples found in the literature, like the standard map, the Hénon map, the logistic mapping. In the framework of the dissipative standard map, we investigate the existence of periodic orbits as a function of the parameters. We also provide some techniques to compute the breakdown threshold of quasi-periodic attractors. Next, we review a simple model of Celestial Mechanics, known as the spin-orbit problem which is closely linked to the dissipative standard map. In this context we present the conservative and dissipative KAM theorems to prove the existence of quasi-periodic tori and invariant attractors. We conclude by reviewing some dissipative models of Celestial Mechanics. Among the rotational dynamics we consider the Yarkovsky and YORP effects; within the three-body problem we introduce the so-called Stokes and Poynting–Robertson effects.