Electronic transport through a quantum ring coupled to ferromagnetic leads

We study the spin-dependent transport through a one-dimensional quantum ring with taking both the Rashba spin--orbit coupling (RSOC) and ferromagnetic leads into consideration. The linear conductance is obtained by the Green's function method. We find that due to the quantum interference effect arising from the RSOC-induced spin precession phase and the difference in travelling phase between the two arms of the ring, the conductance becomes spin-polarized even in the antiparallel magnetic configuration of the two leads, which is different from the case in single conduction channel system. The linear conductance, the spin polarization and the tunnel magnetoresistance are periodic functions of the two phases, and can be efficiently tuned by the structure parameters.     

基于不同碱基含量的[FeFe]-氢化酶模型化合物功能化聚合物的合成与表征

将含二炔基的[2Fe2S]模型化合物[Fe2(μ-SCH2C≡CH)2(CO)6](A)和双叠氮单体2,6-(N3CH2)Py(B,Py=吡啶)与含碱性基团的双炔单体(2-Py CH2)N(CH2C≡CH)2(C,Py=吡啶)通过"点击反应"以不同比例进行共聚,得到了6种含不同碱基量的[FeFe]-氢化酶模型化合物功能聚合物Polymer-1~Polymer-6。通过红外光谱、硫元素分析、热重、扫描电镜和电化学对这些聚合物进行了表征。红外光谱和电化学研究表明二铁六羰基单元A以二铁五羰基的形式存在于聚合物中。在共聚过程中,增加单体C的含量能显著改变聚合物的形貌和增加其在有机溶剂中的溶解度,同时热稳定性也有所增加。这些聚合物在含有醋酸的DMF介质中催化质子还原的行为表明,通过单体C引入的碱性基团所形成的次级配位环境对二铁中心的催化性能有显著影响。     

BY分子筛的合成、表征及其裂化性能考察

采用水热晶化法合成了含杂原子硼的Y型分子筛，利用MAS NMR、XRD、IR等表征方法，证明了硼进入Y型分子筛的骨架中。利用吡啶吸附红外光谱、轻油微反装置分别测定了Y和BY分子筛的表面酸性及其裂化性能。结果表明，硼的引入增加了Y分子筛的B酸中心数目以及裂化和氢转移反应活性，导致裂化汽油中的烯烃明显降低，芳烃随之增加。     

阳极缓冲层修饰对聚合物太阳能电池性能的影响

为提高聚合物太阳能电池的能量转换效率,将聚乙二醇(PEG)掺入PEDOT∶PSS阳极缓冲层,研究了阳极缓冲层修饰对聚合物太阳能电池性能的影响。首先研究了聚乙二醇对PEDOT∶PSS薄膜电导率的影响,发现PEG会与PEDOT和PSS相互作用,使得PEDOT链重新排布,有利于电荷载流子的传输,从而显著改善了PEDOT∶PSS薄膜的电导率,当PEDOT∶PSS中掺入体积分数为2%~4%的PEG时,可得到较大的电导率。然后,以PEG修饰的PEDOT∶PSS薄膜作为阳极缓冲层制备了聚合物太阳能电池,研究了PEG的掺入对聚合物太阳能电池性能的影响。实验发现,PEG改善的PEDOT∶PSS电导率有利于提高电池的短路电流密度和填充因子,从而改善了器件光伏性能。当PEDOT∶PSS中掺入体积分数为2%的PEG时,聚合物太阳能电池的能量转换效率最高,比未掺杂的器件提高了24.4%。     

An analytical model for the polarization of synchrotron radiation in a soft X-ray region

Conventionally, the polarization of a synchrotron soft X-ray beam is measured through a polarimeter based on multilayer optical elements. The major drawback of the traditional approach is the difficulty in comparing different configurations due to the misalignment of each incident angle. In this paper, a new analytical model, based on the variation of reflectivity for different incident angles, is established to facilitate the extraction of important polarization-related information, i.e. angular distribution of polarization components, a tiny change of the direction of azimuth rotation axis of polarizer, etc.     

点击化学法制备含有肉桂酸酯基团的线性聚合物的研究

利用点击化学方法合成了一种侧链上含有肉桂酸酯基团的线性聚合物,利用核磁共振(1H NMR)、红外光谱(FTIR)、凝胶渗透色谱(GPC)和示差扫描量热分析(DSC)等方法对该聚合物的结构和性能进行了表征。DSC谱图显示,在170℃附近出现一个明显的放热峰,通过进一步的实验证明,该放热峰是由聚合物侧链上残余的叠氮基团与肉桂酸酯基团上的碳碳双键发生反应引起的。另外,实验证明,通过稀盐酸处理,可以消除聚合物中残余的叠氮基团。     

基于石墨烯纳米带的齿形表面等离激元滤波器的研究

提出了一种基于石墨烯纳米带的齿形表面等离激元波导滤波器, 并且用时域有限差分法研究了这种结构. 单个齿形的滤波器可以实现带阻滤波, 其滤波特性可以用基于散射矩阵的解析模型解释. 滤波器的透射谱特性可以通过调节齿的长度、宽度以及石墨烯的化学势来改变. 由于石墨烯的化学势可以用门电路来调节, 这种结构的滤波器可以在器件加工完成后灵活地调节其工作波长. 同时研究了多齿滤波器, 这种结构可以实现宽带滤波, 文中对具有不同齿数、周期的滤波器的透射谱进行了细致的研究. 研究结果对实现基于石墨烯的大规模集成光电子器件提供了重要的理论参考.     

北京同步辐射装置3B3光束线传输效率及输出特性的计算

从北京正负电子对撞机储存环弯转磁铁光源的辐射特性入手, 分析了BSRF-3B3光源及其光束线光学系统的输出特性, 分别给出各光学元件的传输效率和采用不同单色器晶体在样品处的计算结果. 为光束线设计、调试及诊断提供了理论依据. 同时也为弯转磁铁光源光束线的输出特性的计算, 提供了一个模式.     

计算机仿真实验在物理实验教学中的作用

计算机仿真实验是近年来在多媒体教学中开辟的新领域,在物理实验中开设计算机仿真实验,可以缓解硬件资源不足,起到增强学生实验技能、提高实验教学效果的作用,并实现教学模式多样化.     

Creation of multi-frequency terahertz waves by optimized cascaded difference frequency generation

A new scheme which generates multi-frequency terahertz (THz) waves from planar waveguide by the optimized cascaded difference frequency generation (OCDFG) is proposed. A THz wave with frequency ω_T1 is generated by the OCDFG with two infrared pump waves, and simultaneously a series of cascaded optical waves with a frequency interval ω_T1 is generated. The THz wave with a frequency of M-times ω_T1 is generated by mixing the m-th-order and the (m+M)-th-order cascaded optical wave. The phase mismatch distributions of cascaded difference frequency generation (CDFG) are modulated by changing the thickness of planar waveguide step by step, thereby satisfying the phase-matching condition from first-order to high-order cascaded Stokes process step by step. As a result, the intensity of THz wave can be enhanced and modulated by controlling the cascading order of OCDFG.