Optimal design and analysis of a high-speed, low-voltage polymer Mach-Zehnder interferometer electro-optic switch

Detailed model, analysis and design technique are presented for simulating a high-speed polymer Mach-Zehnder interferometer (MZI) electro-optic switch with push-pull dual driving electrodes and rib waveguides. The novel formulas of the time-domain response are derived. Thorough optimization and simulation for the designed device are performed. The total length of the basic function unit of the switch is about 5049 μm, the push-pull switching voltage is 2.23 V, the switching time is 18.1 ps, and the insertion loss and crosstalk are less than 2.64 and −30 dB, respectively, within the range of the operation wavelength from 1534 to 1566 nm. These results are in good agreement with those obtained from the beam propagation method (BPM).     

Thermally Driven Structure and Performance Evolution of Atomically Dispersed FeN4 Sites for Oxygen Reduction

FeN₄ moieties embedded in partially graphitized carbon are the most efficient platinum group metal free active sites for the oxygen reduction reaction in acidic proton‐exchange membrane fuel cells. However, their formation mechanisms have remained elusive for decades because the Fe?N bond formation process always convolutes with uncontrolled carbonization and nitrogen doping during high‐temperature treatment. Here, we elucidate the FeN₄ site formation mechanisms through hosting Fe ions into a nitrogen‐doped carbon followed by a controlled thermal activation. Among the studied hosts, the ZIF‐8‐derived nitrogen‐doped carbon is an ideal model with well‐defined nitrogen doping and porosity. This approach is able to deconvolute Fe?N bond formation from complex carbonization and nitrogen doping, which correlates Fe?N bond properties with the activity and stability of FeN₄ sites as a function of the thermal activation temperature.     

Investigation of formation,recognition, stabilization,and conversion of dimeric G-quadruplexes of HIV-1 integrase inhibitors by electrospray ionization mass spectrometry

The dimeric G-quadruplex structures of d(GGGTGGGTGGGTGGGT) (S1) and d(GTGGTGGGTGGGTGGGT) (S2), the potent nanomolar HIV-1 integrase inhibitors, were detected by electrospray ionization mass spectrometry (ESI-MS) for the first time. The formation and conversion of the dimers were induced by NH(4)(+), DNA concentration, pH, and the binding molecules. We directly observed the specific binding of a perylene derivative (Tel03) and ImImImbetaDp in one system consisting of the intramolecular and the dimeric G-quadruplexes of the HIV-1 integrase inhibitor, which suggested that Tel03 could shift the equilibrium to the dimeric G-quadruplex formation, while ImImImbetaDp induces preferentially a structural change from the dimer to the intramolecular G-quadruplex. The results of this study indicated that Tel03 and ImImImbetaDp favor the stabilization of the dimeric G-quadruplex structures.     

Effect of AlSiFe on the anodizing process of 6063 aluminum

AlSiFe phase can form microscopic galvanic couples that decrease corrosion resistance of 6063 aluminum which may influence the anodizing process. Two samples of 6063 aluminum were prepared. One sample was cut along the extrusion direction of the billet, and the other was cut perpendicular to the extrusion direction. Both samples exhibited the same characteristics, except for the distribution of the second phase AlSiFe. Both samples were subjected to anodizing treatments. Comparison between anodic oxide films was performed. The microstructure of Al substrates and anodic oxide films were examined using a scanning electron microscope, an optical microscope, and a glow discharge optical emission spectrometer. Results indicated that the thicknesses and elemental distributions of the anodic oxide films were almost the same. Moreover, the second phase AlSiFe influenced the anodic oxidation process, resulting in cavities in the anodic oxide film that affected its brightness. Copyright © 2016 John Wiley & Sons, Ltd.     

Separation distance dependent fluorescence enhancement of fluorescein isothiocyanate by silver nanoparticles

Nanocomposites consisting of a metal core, a silica-spacer shell with controlled thickness, and a dye-labelled shell were synthesized and separation distance dependent fluorescence enhancement of fluorescein isothiocyanate by silver nanoparticles was studied; the results indicated an optimum enhancement of 4.8 times with a spacer shell thickness of 21 nm.     

固体酸对醇酸树脂聚酯反应的催化作用

本文研究了固体酸对醇酸树脂缩聚酯反应的催化作用,讨论了催化剂的表面酸度、制备条件及反应物分子构型等对催化聚酯反应的影响。在接近生产条件下研究了醇酸树脂聚酯反应动力学,发现多相酸催化聚酯反应与均相酸催化聚酯反应具有相似的动力学规律。     

聚合物微环谐振器电光开关阵列的优化与模拟

利用耦合模理论、电光调制理论和微环谐振理论,提出了一个聚合物微环谐振器电光开关阵列的模型.该器件由N-1个微环和N条平行信道构成,在微环上施加不同方式的驱动电压,可以实现N条信道的开关功能.以7微环8信道结构为例,在1550 nm谐振波长下对该器件进行了优化和模拟.结果表明,微环波导芯的截面尺寸为1.7μm×1.7μm,波导芯与电极间的缓冲层厚度为2.5 μm,电极厚度为0.2μm,微环半径为13.76 μm,微环与信道间的耦合间距为0.14μm,输出光谱的3 dB带宽约为0.05 nm,开关电压约为8.1 V左右,插入损耗约为0.23～4.6 dB,串扰小于-20 dB.     

有理三角Bézier曲线曲面光滑融合的构造

为了使自由曲线曲面在较为简单的条件下能够达到相对高阶的光滑拼接,并在不改变控制顶点的情况下自由调整曲线曲面的形状,构造了含多个形状参数的有理三角函数.基于该组基函数,定义了含多个形状参数的有理三角曲线曲面,并讨论了曲线曲面的光滑拼接条件.根据拼接条件,分别定义了由含多个形状参数的有理三角曲线曲面构成的分段组合曲线、分片组合曲面.这种新的曲线曲面能够自动保证组合曲线、曲面的连续性.数值实例的结果显示了该方法的有效性.     

基于可信基站和HASH函数的WSN密钥管理方案

针对现有的基于二元多项式或q-composite的密钥管理方案存在的被捕获率高和网络连通率低的缺点,提出了一种基于可信基站产生三元多项式密钥和HASH函数的WSN密钥管理方案;首先,采用层次型分簇路由协议将整个WSN监测区域划分为簇,然后,由可信基站产生三元多项式密钥,并将其分配给簇头,当任意两簇头之间共享的多项式密钥超过q时可以进行通信,并通过HASH函数来生成对应的通信密钥,有效地隐藏了节点的部分密钥信息;理论研究和仿真试验结果表明:文中方法能有效地实现网络的密钥管理,较其他方法相比,具有网络连通率高和抗捕获能力强的优点,具有一定的优越性。