Preparation and microstructural analysis of poly(ethylene oxide) comb‐type grafted poly(N‐isopropyl acrylamide) hydrogels crosslinked by poly(ϵ‐caprolactone)

Poly(N‐isopropyl acrylamide) (PNIPAAm)‐graft‐poly(ethylene oxide) (PEO) hydrogels crosslinked by poly(?‐caprolactone) diacrylate were prepared, and their microstructures were investigated. The swelling/deswelling kinetics and compression strength were measured. The relationship between the structure and properties of hydrogel are discussed. It was found that the PEO comb‐type grafted structure reduced the thermosensitivity and increased the compression strength. The addition of poly(?‐caprolactone) (PCL) accelerated the deswelling rate of the hydrogels. Meanwhile, the entanglement of PCL chains restrained the further swelling of the network of gels. The PCL crosslinking agent and PEO comb‐type grafted structure made the behavior of the hydrogels deviate from the rubber elasticity equations. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Li2CO3和TiO2合成Li4Ti5O12的工艺优化

为了优化碳酸锂和二氧化钛合成尖晶石Li4Ti5O12的工艺,实验采用TG、XRD、SEM等手段研究了该工艺的等温动力学。测试结果表明,在400℃时碳酸锂和二氧化钛的反应过程由扩散控制,在450℃时的反应过程由界面化学反应控制,在500~600℃时属于随机成核和随后生长机理,积分动力学方程为G(α)=[-ln(1-α)]2,表观活化能为191.35 kJ/mol。在动力学研究基础上,优化了合成工艺,其中850℃下反应8 h的产物的放电比容量为167 mA·h/g,循环25次后容量基本不变,表现出良好的循环性能。     

Treatment of carbon cloth anodes for improving power generation in a dual‐chamber microbial fuel cell

BACKGROUND: For a microbial fuel cell (MFC), the anode material plays a crucial role in power output. RESULTS: A dual‐chamber MFC was constructed using carbon cloth (CC) anodes treated by concentrated nitric acid (CC‐A) and heated in a muffle furnace (CC‐H), respectively. The experiment results showed that the stable maximum voltages were 0.42–0.46 V for CC, 0.52–0.58 V for CC‐A and 0.80 V for CC‐H under the condition of a 1000 Ω external resistance, which were much higher than those reported in the literature so far. Moreover, the maximum power density of the CC‐H anode (687 mW m^?2) was larger than for the CC‐A anode (480 mW m^?2) and the CC anode (333 mW m^?2). Electrochemical impedance spectroscopy (EIS) results revealed that the internal resistance was 251 Ω for CC anode, 202 Ω for CC‐A anode and 162 Ω for CC‐H anode. Scanning electron microscopy (SEM) results indicated that the increase of power generation was attributed to the increase of bacteria counts attached to anodes. The power output of the MFC increased along with the increase of the N1s/C1s ratio, which was proved by X‐ray photoelectron spectroscopy (XPS) analysis. CONCLUSIONS: Carbon cloth anodes treated by concentrated nitric acid and high temperature resulted in improved power generation by a microbiol fuel cell. © 2012 Society of Chemical Industry     

电动汽车PMSM MTPA控制系统 抗积分饱和速度控制

电动汽车电机驱动系统大多采用传统PI控制,存在积分饱和现象,系统易产生超调和振荡问题,因此将抗积分饱和控制策略引入永磁同步电机最大转矩电流比控制调速系统中,以提升系统的稳定性。采用反馈算法求解转矩电流高次方程,解决了高次方程求解困难的问题,实现了最大转矩电流比控制;速度环和电流环均采用抗积分饱和PI控制,有效地抑制了积分饱和,减小了系统的超调量,提高了电机控制精度。基于Matlab/Simulink搭建了系统模型并进行仿真,仿真结果表明,所设计的系统有效地抑制了积分饱和现象,减少了速度的超调,具有良好的动态和稳态性能,可以较好地满足电动汽车电机驱动系统的要求。     

基于iOS的高速存储电路设计与实现

为了解决iOS移动设备外部存储器件传输速度及存储容量的问题,设计了一套适用iOS的外设高速存储电路。通过采用兼容USB2.0的数据高速传输和处理技术USB3.1标准,以提高传输速度;使用Flash Raid技术进行读写管理,将NAND和eMMC Flash芯片的数据并行传输和管理技术进行集成,实现双Flash芯片同步读写的双通道数据高速传输与存储,并内置多种容错机制。实验结果表明,重新设计的高速存储电路可适应和扩展外设存储容量,还可提升读写速度,其在iOS端的读写速度达到25, 16 MB/s,实现了iOS移动设备外部存储高速传输与存储目的。     

Molecular dynamics simulation of thermal conductivities of superlattice nanowires

Materials with low thermal conductivity, high electric conductivity and high Seebeck coeffi-cient are desirable for high performance solid-state thermoelectric devices. The performance of thermoelectric devices depends on the figure of merit ZT, given by 2(/),ZTSTsl= where , , , STsl are the Seebeck coefficient, absolute temperature, electrical conductivity and thermal conductivity, respectively. To compete with the phase change based energy conversion devices economically, materials with …     

基于无线传感网络的道路照明系统

实现道路科学照明、绿色照明的关键问题是能够测量和控制到每一盏路灯,无线传感网络是解决这一问题最好的技术之一。选择Freescale公司MC13213芯片,设计了一种嵌入式无线通信模块,使整条道路的每一盏路灯自主联网,接受控制中心的指令,反馈路灯的各种状态,根据环境光强度和时段自动调节照明亮度,在保证道路照明质量和视觉舒适的情况下,节约电能20%~30%。     

Research on visual object tracking by fusing dynamic and static features

Traditionally, most tracking algorithms only use the single static feature or single dynamic feature to model the object. The static feature based model can not describe the object's dynamic characteristics and is difficult to adapt to the changing object with a background cluster, abrupt movement and rotations. While the classical optical flow is able to describe local dynamic characteristics, it has aperture issues. Therefore, we present a new tracking method based on fusing the dynamic and static features adaptively: the dynamic feature is extracted by the bidirectional optical flow and error metric adaptively, and is fused with the static feature by the fusion weight efficiently. The fusion weight based covariance is constructed to evaluate error ellipse which describes the object's scale and orientation exactly; the weight assignment parameter is updated by an on-line parameter updating mechanism, which balances the dynamic feature and static feature and ensures the tracking adaptation to the object's velocity and scene changes. Experiments show that the proposed algorithm can achieve better tracking results compared with the related algorithms, on the occasions when the object moves abruptly and rotates with a background cluster.     

环境敏感型虚拟植物的设计与实现

环境敏感型植物模拟是当今虚拟现实技术发展的一个重要分支,吸引了众多科学家参与其中,并提出了多种模拟方法和模型,其中L系统是应用最为广泛的方法之一.针对L系统生成效率低的问题,通过改变底层的存储方式,为其设计了二又树式的存储结构,简化了上下文搜索过程,提高了生成效率;并通过引入环境因子,模拟了自然界中环境对植物生长过程和外形的影响.     

混凝土细观层次损伤数值模拟——随机骨料结构的生成

目的在细观层次上对混凝土进行数值模拟,进而对混凝土的力学性能分析.方法应用蒙特卡罗方法,使用C＋＋语言编程开发二维三相混凝土随机骨料结构（RAS）模型.结果提出了避免产生不合常规骨料颗粒的控制措施,引入向量理论分析并去除凹点,弥补了现有方法中确定骨料多边形延伸率的缺陷;并在Visual C＋＋上模拟实现、生成了具有概率和统计意义的RAS.最后,通过一个数值算例验证了所提方法的有效性.结论笔者提出的RAS产生方法为进一步开发混凝土细观有限元模型打下了坚实的基础.