Organic-inorganic hybrid materials from a new octa(2,3-epoxypropyl)silsesquioxane with diamines

Hybrid materials based on a new polyhedral oligomeric silsesquioxane, octa(2,3-epoxypropyl)silsesquioxane (OE) with diamines of 4,4′-methylenedianiline (DDM) and 5-trifluoromethyl-1,3-phenylenediamine (FPA) were prepared and characterized. OE was synthesized from cage-structured octaallylsilsesquioxane (OA) with m-chloroperbenzoicacid. The FTIR studies suggested that the N-H bond in diamines was not completely reacted with epoxy group due to steric hindrance and also extensive hydrogen bonding existed in the hybrid materials. The retention of the cage structure in the prepared hybrid materials was suggested by the FTIR and ²⁹Si NMR studies. The OE/FPA hybrid materials had superior thermal/mechanical characteristics than the OE/DDM due to the higher rigidity of the FPA than that of DDM or the silicon-fluorine interaction enhancing crosslinking reaction or hydrogen bonding. The prepared OE/FPA had a T_g of 170 °C, which was higher than diglycidyl ether of bisphenyl A (DGEBA)/DDM at the same stoichiometric ratio. It also had excellent thermal, mechanical, and dielectric characteristics with high storage modulus of 1.8 GPa (30 °C) and 0.3 GPa (250 °C), low coefficient of thermal expansion of 86 μm/m °C, and dielectric constant of 2.19. Thus, it can be high performance materials with potential applications for electronic packaging.     

Multiple model-based event-triggered adaptive control of a class of discrete-time nonlinear systems

In this study, the problem of event-triggered-based adaptive control (ETAC) for a class of discrete-time nonlinear systems with unknown parameters and nonlinear uncertainties is considered. Both neural network (NN) based and linear identifiers are used to approximate the unknown system dynamics. The feedback output signals are transmitted, and the parameters and the NN weights of the identifiers are tuned in an aperiodic manner at the event sample instants. A switching mechanism is provided to evaluate the approximate performance of each identifier and decide which estimated output is utilised for the event-triggered controller design, during any two events. The linear identifier with an auxiliary output and an improved adaptive law is introduced so that the nonlinear uncertainties are no longer assumed to be Lipschitz. The number of transmission times are significantly reduced by incorporating multiple model schemes into ETAC. The boundedness of both the parameters of identifiers and the system outputs is demonstrated though the Lyapunov approach. Simulation results demonstrate the effectiveness of the proposed method.     

VQ codebook design using modified K-means algorithm with feature classification and grouping based initialization

Multimedia Tools and Applications - Vector quantization (VQ) has been successfully used in data compression and feature extraction areas. Codebook design is the essential step of VQ. The K-means...     

矿用组合开关主控单元的设计

根据矿井生产的需要,文章设计了一种基于AVR单片机的组合开关,概括地介绍了其主要功能及控制方式,简述了上位机控制单元硬件构成及软件设计思想。实际应用表明:该开关有助于提高矿井生产安全性,可靠性高,使用灵活。     

基于随机过程的PSO收敛性分析

分析了粒子群优化算法 (PSO) 的全局收敛性. 在已有文献的假设前提下和随机系统理论基础上, 对 PSO 进行算法分析推导, 给出了其动力学系统依均方收敛的一个充分条件, 从而有效地避免了已有文献基于线性时变离散系统研究 PSO 收敛性的不足. 通过对所得的粒子运行轨迹图和已有文献相比较, 得到了更好的结果和判据. 通过仿真实验分析研究, 验证了该结论的有效性.     

铁位掺杂对磷酸铁锂电化学性能的影响

采用球磨法制备了铁位掺杂的磷酸铁锂（LiFePO4）正极材料。使用X射线衍射（XRD）、环境扫描电子显微镜（ESEM）对制备的材料进行表征,并将材料组装成扣式电池,使用蓝电系统和电化学工作站对其进行电化学性能测试和分析。结果表明,LiM0.05Fe0.95PO4和LiFePO4结构几乎一样,在0.1 C倍率下LiFePO4的首次放电比容量为125 mA·h/g,掺杂M（M=Mg,Cu,Zn）后首次放电比容量为145、141、139 mA·h/g,材料的电化学性能明显提高,其交流阻抗减小,循环50次后容量保持率为87%左右。     

Low-Cost Embedded Controller for Complex Control Systems

Because of limited resource of embedded platforms, the computational complexity of advanced control algorithms raises significant challenges for the use of embedded systems in complex control field. A Scilab/Scicos based embedded controller is developed on which various control software can be easily modeled, simulated, implemented, and evaluated to meet the ever-expanding requirements of industrial control applications. Built on the Cirrus Logic EP9315 ARM systems-on-chip board, this embedded controller is possible to develop complex embedded control systems that employ advanced control strategies in a rapid and cost-efficient fashion. Due to the free and open source nature of the software packages used, the cost of the embedded controller is minimized.     

基于ZIF-8/Au@f-CNF增敏型双酚A电化学传感器的构建及性能研究

摘 要：目的 设计制备了金属有机框架ZIF-8掺杂、负载金纳米粒子的碳纳米纤维复合材料（ZIF-8-doped gold nanoparticles-loaded carbon nanofibers, ZIF-8/Au@f-CNF）,用于玻碳电极（glassy carbon electrode, GCE)表面功能化修饰,以构建食品中双酚A污染物的增敏型电化学传感,并探索对双酚A的增敏检测机制。方法 将利用室温溶剂法制备的ZIF-8与原位还原法制备的负载金纳米粒子的碳纳米纤维（gold nanoparticles-loaded carbon nanofibers, Au@f-CNF）超声混合,滴注在GCE电极表面,构建ZIF-8/Au@f-CNF电化学传感器。运用X-射线光电子能谱仪（X-ray Photoelectron Spectroscopy, XPS）和透射电子显微镜（transmission electron microscopy, TEM）、循环伏安法（cyclic voltammetry, CV）和电化学阻抗法（electrochemical impedance spectroscopy, EIS）对材料表面形貌和电化学性能进行表征,考察了扫速和pH值等参数对双酚A电化学传感行为的影响。结果 ZIF-8/Au@f-CNF复合材料显示较为均匀的掺杂状态,经ZIF-8/Au@f-CN修饰后的GCE电极（ZIF-8/Au@f-CNF/GCE）电活性面积明显提升,是未经修饰裸GCE面积的1.62倍,对双酚A的氧化峰电流峰值显著提升至原来的2.84倍。结论 将ZIF-8的多孔特性和Au@f-CNF的电催化性能相结合,赋予ZIF-8/Au@f-CNF/GCE对目标物良好的吸附性能和电化学反应活性,基于纳米材料的协同效应可实现对双酚A的增敏传感检测,该研究为新型复合材料的开发及增敏传感器构建提供了研究思路和方法借鉴。     

水平井压裂裂缝形成机理初探与应用

水平井储层水力压裂改造是近几年国内外发展起来的一项新技术,还存在一些技术问题.为此,初步研究了水平井水力压裂机理,建立了水平井眼的应力分布模型,给出了水平井眼地层破裂压力的计算公式.该模型在现场试验中应用效果良好.     

New scheme for braiding Majorana fermions

Non-Abelian statistics can be achieved by exchanging two vortices in topological superconductors with each grabbing a Majorana fermion (MF) as zero-energy quasi-particle at the cores. However, in experiments it is difficult to manipulate vortices. In the present work, we propose a way to braid MFs without moving vortices. The only operation required in the present scheme is to turn on and off local gate voltages, which liberates a MF from its original host vortex and transports it along the prepared track. We solve the time-dependent Bogoliubov–de Gennes equation numerically, and confirm that the MFs are protected provided the switching of gate voltages for exchanging MFs are adiabatic, which takes only several nano seconds given reasonable material parameters. By monitoring the time evolution of MF wave-functions, we show that non-Abelian statistics is achieved.