Improved synergetic excitation control for transient stability enhancement and voltage regulation of power systems

This paper proposes decentralized improved synergetic excitation controllers (ISEC) for synchronous generators to enhance transient stability and obtain satisfactory voltage regulation performance of power systems. Each generator is considered as a subsystem, for which an ISEC is designed. According to the control objectives, a manifold, which is a linear combination of the deviation of generator terminal voltage, rotor speed and active power, is chosen for the design of ISEC. Compared with the conventional synergetic excitation controller (CSEC), a parameter adaptation scheme is proposed for updating the controller parameter online in order to improve the transient stability and voltage regulation performance simultaneously under various operating conditions. Case studies are undertaken on a single-machine infinite-bus power system and a two-area four-machine power system, respectively. Simulation results show the ISEC can provide better damping and voltage regulation performance, compared with the CSEC without parameter adaptation scheme and the conventional power system stabilizer.     

Optimised phase compositions and improved microwave dielectric properties based on calcium tin silicates

The Ca_(1+2y)Sn_(1-x)Si_(1+y)O_(5-2x+4y) low-permittivity microwave dielectric ceramics were prepared through solid-state reaction at 1350–1450 °C for 5 h. The relations between microwave dielectric properties and phase compositions for non-stoichiometric Ca_(1+2y)Sn_(1-x)Si_(1+y)O_(5-2x+4y) ceramics have been investigated. A single CaSnSiO₅ phase with abnormally positive temperature coefficient of resonant frequency (τ_f = + 62.5 ppm/°C) was synthesised at 1450 °C. This composition was an effective τ_f compensator of CaSiO₃ and Ca₃SnSi₂O₉ phases with typically negative τ_f value. The CaSiO₃ second phase was related to the Sn deficiency in the CaSn_(1-x)SiO_(5-2x) (0 < x < 1.0) composition, whereas the Ca₃SnSi₂O₉ second phase was obtained by controlling the Ca:Sn:Si ratios on the basis of the Ca_(1+2y)SnSi_(1+y)O_(5+4y) (0 < y < 1.0) composition. A promising low-permittivity millimetre-wave ceramic with most excellent microwave dielectric properties (ε_r = 10.2, Q×f = 81,000 GHz and τ_f = −4.8 ppm/°C) was produced from the Ca_(1+2y)SnSi_(1+y)O_(5+4y) (y = 0.4) ceramic.     

Nanostructured titanium nitride for highly sensitive localized surface plasmon resonance biosensing

Titanium nitride (TiN) as an alternative plasmonic ceramic material with superb properties including high hardness, outstanding corrosion resistance and excellent biocompatibility, has exhibited great potential for optical biochemical sensing applications. By sputtering about 35 nm–50 nm TiN on glass (f-TiN), the surface was found to provide sensing capability toward NaCl solution through the phenomenon of surface plasmon resonance. When the TiN film of about 27 nm–50 nm in thickness was sputtered onto a roughened glass surface (R–TiN), the sensing capability was improved. This was further improved when holes at nanoscale were created in the TiN film of about 19 nm–27 nm in thickness (NH–TiN). The roughened surface and nanohole patterns provided confinement of surface plasmons and significantly improved the sensitivity toward the local refractive index changes. In detail, the calculated refractive index resolution (RIR) of the optimal NH–TiN sensors for NaCl was found to be 9.5 × 10⁻⁸ refractive index unit (RIU), which had outperformed the f-TiN and R–TiN sensors. For biosensing, the optimized NH–TiN sensor was found to be capable to detect both small and large biomolecules, i.e. biotin (molecular weight of 244.3 g/mol) and human IgG (160,000 g/mol), in a label-free manner. Especially, the NH–TiN sensor significantly improved sensitivity in detecting small molecules due to the localized plasmonic confinement of electromagnetic field. Combining with the excellent mechanical and durability properties of TiN, the proposed NH–TiN can be a strong candidate for plasmonic biosensing applications.     

Papermaking characteristics of three Populus clones grown in the north-central United States

The papermaking properties of 22 pure and hybrid poplars are being evaluated in an on-going investigation. Twenty of the poplars were harvested after 7.5 years from three different sites in the Midwestern and North Central US. The other 2 poplars survived at only two of three sites (64 total samples). The Crandon hybrid had the highest growth rate (t ha⁻¹ y⁻¹) and wood density (both averaged across the 3 sites). This poplar had a high cellulose content (compared to the average), a low lignin content and produced bleached kraft fibers at a high yield (wt.% on wood chips). Further, this poplar responded very well to kraft pulping and oxygen delignification and bleached to the highest final brightness ever observed in our laboratory (94.5% Elrepho). It also produced an 18 kappa number unbleached pulp with <0.5% rejects in only two-thirds the time required for sugar maple (Acer saccharum).We also report on clone 220-5 that had the highest area-weighted average microfibril angle. Pulps from this poplar had excellent tensile properties and further improvements are expected with 1–2 years of additional growth that should result in a small, but significant increase in average fiber length. Some results are also presented for clone 313.55 and aspen (Populus tremuloides) to demonstrate the many substantial benefits that can be accrued from proper wood selection.     

视错觉及其应用

视觉足人类获取外部信息的最重要方式。但由于人类自身的生理、心理因素以及外界光、形、色等因素的干扰,会产生视觉误差,即视错觉。本章系统的分析了视错觉产生原因,按不同的现象和成因把视错觉分成病理视错觉、动态视错觉、几何视错觉、颜色视错觉、轮廓错觉等5类。在此基础上介绍了视错觉的应用,特别介绍了其在图像融合中的应用,并用matlab实现了图像的融合。     

污染土壤/底泥电动修复研究进展

修复污染土壤/底泥对改善生态环境质量极为重要,通过对污染土壤/底泥施加电场,可使污染物定向迁移、富集并去除。综述了电动修复的发展历程,比较了重金属、有机污染物及复合污染物的电动修复机理及其限制因素,分析了土壤预处理(加入酸、氧化剂、共溶剂、表面活性剂,搅拌,升温等)、电极优化(交换电极、阳极逼近、电极矩阵等)、多技术(EK-PRB、Fenton、IEM、ASC、超声波、电解质增强等)联用对单一电动修复的性能优化概况。总体来看,污染物分离不彻底、土壤/底泥理化性质和微观结构改变、原位规模化应用困难等制约了电动修复污染土壤/底泥的效果。针对上述技术瓶颈,提出污染原位分离-污染物处理-有价资源回收的一体化电动修复技术。该技术可解决电动修复易破坏土壤生态和污染物难以外排的问题,实现了污染处理和有价资源的回收。     

组合隔板式鱼道水力特性数值模拟研究

鱼道是为鱼类提供洄游通道的一种重要的工程措施。基于Flow-3D采用标准RNG k-ε紊流模型和Tru-VOF追踪自由液面方法,对鱼道池室内流场进行三维紊流数值模拟,研究池室内水流流速、流态空间分布,分析鱼道的水力特性对目标鱼类洄游上溯的影响。结果表明:溢流堰与竖缝组合隔板式鱼道在设计流速v=0.75 m/s条件下,竖缝处平均流速为0.83 m/s,竖缝处流速分布范围为0.76~0.89 m/s;堰上流速为0.90~1.12 m/s,回流区流速分布范围为0.09~0.25 m/s,流速大小在鱼类的克流能力范围之内,但靠竖缝隔板处存在明显的主流贴壁现象。为此开展了池室优化方案设计,使鱼道池室流态满足鱼类上溯要求。     

真三轴应力下混凝土的动态力学性能及破坏准则

为研究混凝土结构处于复杂应力状态下的静动态力学特性,进行了不同应力比及加载速率下的真三轴压缩试验。对混凝土的强度特性和变形特性展开了深入分析,并基于八面体应力空间建立了考虑应变速率效应的真三轴动态破坏准则。结果表明:真三轴受压下的混凝土极限抗压强度随着应力比的增大而增大。随着应变速率的增加,应力比较低时,混凝土的极限抗压强度逐渐增大;应力比较高时,极限抗压强度先减小后增加。随着应变速率的增加,侧向变形曲线的破坏峰值点更明显;随着应力比的增大,侧应力较大方向上的变形越来越小。基于八面体应力空间建立的真三轴动态破坏准则表达式中包含3个率效应参数,经验证与试验数据吻合较好。     

基于MapXtreme的数字校园房管系统的开发

校园规模在不断地扩大,校园房屋管理规划部门对日益更新和迅速增加的建筑物房屋信息的管理与维护愈感困难,而现有的系统对空间数据与属性数据没有很好集成,更不利于图文信息的相互查询、检索和更新等。针对如上现实问题,应用MapInfo平台中的WebGIS技术,即MapXtreme技术,以及UML统一建模技术和SQL Server数据库等技术,成功地实现了数字校园房屋管理系统设计与开发,解决了房管部门面临的查询搜索更新校园建筑房屋信息时效率低下、管理与维护困难等实际问题。