微纳米气泡形成羟基自由基的研究进展

从微纳米气泡溶液中是否可以产生·OH、·OH的鉴别方法、·OH的生成机理以及强化·OH的生成等几个方面论述了微纳米气泡溶液中生成·OH的研究进展.电子自旋共振技术和荧光分光光度法作为检测·OH的2种技术,均存在一定的误导性,对于荧光分光光度法,最重要的就是排除H2 O2的干扰.此外,目前要获得含有高浓度·OH的微纳米气...     

可反应性纳米二氧化硅对聚乳酸结晶行为的影响

通过熔融共混法制备了聚乳酸（PLLA）／可反应性纳米二氧化硅（RNS）复合材料,用透射电子显微镜观察RNS在PLLA基体中的分散情况,用差示扫描量热仪（DSC）和X射线衍射仪（XRD）对复合材料的非等温结晶行为进行了研究,并利用Jeziomy法和Mo法对复合材料的非等温结晶动力学进行分析。结果表明,RNS在PLLA中分散均匀,RNS的加入虽不会改变PLLA的晶型,但RNS与PLLA之间的相互作用及其异相成核能力会对聚乳酸基体的结晶速率和结晶度产生影响,导致材料结晶过程发生变化。     

极压抗磨添加剂对高温复合锂基润滑脂性能影响的研究

将3种极压抗磨添加剂（T 304、T 321和T 404）分别加入到4种不同组分的高温复合锂基润滑脂中，考察其对润滑脂性能的影响。研究发现，加入不同的添加剂使润滑脂的油膜强度、锥入度和滴点产生不同的变化，并对其产生的原因作了机理分析。     

A method to fabricate hydroxyapatite/poly(lactic acid) microspheres intended for biomedical application

The interaction between organic and inorganic materials enables one to fabricate inorganic/organic microsphere composites. In a novel microemulsion method, we have prepared surfactant-free poly(lactic acid) (PLA)/hydroxyapatite (HAp) microspheres by using the interfacial interaction between inorganic and organic materials, because surfactants are undesireble materials for biomedical applications due to their non-biodegradability. The studies that varied the ion concentrations in oil/water microemulsions revealed that HAp was nucleated at the end group PLA, COOH, and the array of the PLA end groups determined the crystal phase of the calcium phosphate as HAp under the low ion concentration condition. PLA induced the nucleation and precipitation of HAp at the oil/water interface, simultaneously, the precipitated HAp stabilized the microemulsion without surfactants. This novel process made surfactants unnecessary for organic/inorganic microsphere fabrications.     

基于辨识模型集的无人半潜水下机器人系统深度动态滑模控制切换策略研究

BQ-01无人半潜水下机器人深度运动模型参数未知,无法为基于模型的控制策略提供控制参数,导致该系统不易快速达到预期的性能指标要求,为此提出一种多辨识模型动态滑模控制方法。该控制方法采用平均拟合偏差方法,减少了系统辨识过程中出现过多冗余辨识模型参数组,以切换的方式为动态滑模控制方法选取最佳模型参数;同时采用状态反馈方法实现滑模面抖动指数衰减,从而解决了系统深度运动调节问题。BQ-01系统湖泊试验结果表明,所提辨识方法能够为滑模控制策略提供最佳控制参数,且提高了系统运动控制品质。     

内能源转管武器曲柄连杆机构优化设计

曲柄连杆机构是内能源转管武器的重要驱动机构。为了提高内能源转管自动机运动的平稳性,运用动力学分析理论,以曲柄连杆机构参数为优化变量建立了优化设计数学模型。经过优化计算求得的曲柄连杆机构参数,可以使内能源转管武器较快达到稳定射速且射速波动和后坐阻力也有较大改善。该方法对研究曲柄连杆机构的结构参数设计具有较普遍的适用性。     

由2自由度并联髋关节构成的脊柱式四足步行机器人步态规划和稳定性分析

针对四足机器人研究中的承载能力低、行走平稳性差问题,设计了一种由2自由度并联髋关节构成的脊柱式四足步行机器人。采用解析几何法和坐标变换法对机器人站立腿和摆动腿进行运动学建模,根据足端位置逆解求得了髋关节变量,进而提出一种无膝关节四足机器人的直行步态、定点转向步态和爬楼梯步态规划方法。基于运动学模型和步态规划方法,通过数值仿真分别得到步态周期内瞬时稳定裕度数据和重心高度变化数据,结果表明四足机器人有较好的稳定性。机器人步态试验验证了该步态规划方法的合理性和有效性。     

An effective approach to reinforced closed-cell Al-alloy foams with multiwalled carbon nanotubes

Exploring the reinforcing role of carbon nanotubes to obtain materials (polymers, metals, ceramics) with enhanced properties has been often attempted, but the success is strongly limited by the dispersing degree of carbon nanotubes. Here we report on an innovative colloidal approach to disperse the carbon nanotubes in the powders mixture of the precursor materials in order to profit from their reinforcing potential and obtain a new class of closed-cell metal foams. The feasibility of the proposed approach was demonstrated for aluminium foams reinforced with multi-walled carbon nanotubes. These nanocomposite metal foams synergistically combine the remarkable properties of both metal foams and carbon nanotubes. The results indicate that the tubular structure of carbon nanotubes is preserved throughout the entire the process. The carbon nanotubes are individually dispersed, stretched and randomly aligned in the aluminium-matrix of these closed-cell foams, thus potentiating their homogeneous 3D reinforcing role. Accordingly, the Vickers micro-hardness of the closed-cell foams was greatly enhanced.     

Y2-xLaxMo3O12陶瓷的制备及其热膨胀性能

以分析纯Y2O3、La2O3和MoO3为原料,采用固相反应法制备Y2–xLaxMo3O12(0≤x≤2.00)系列陶瓷。利用X射线衍射仪、场发射扫描电子显微镜、能谱仪、热重分析仪和热机械分析仪对样品的物相组成、微观结构、吸湿性和热膨胀特性进行了表征。结果表明:在750℃烧结10 h可制备得到Y2–xLaxMo3O12(0≤x≤2.00)系列陶瓷;Y2–xLaxMo3O12(0≤x≤2.00)陶瓷断面晶粒呈不规则多边形,为多孔结构。热重分析发现:Y2Mo3O12陶瓷易吸湿,掺入La后吸湿现象消失。在178～600℃测试温度范围内,随La掺入量增加,Y2–xLaxMo3O12(0≤x≤2.00)系列陶瓷样品的热膨胀系数呈增大趋势。     

Synthesis and thermal expansion properties of Y2−xLaxMo3O12 (x=0, 0.5, 2)

Y_2−xLa_xMo₃O₁₂ (x=0, 0.5, 2) ceramics were successfully synthesized by the solid state reaction method. The microstructure, composition and thermal expansion property of the resulting samples were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and dilatometry. Results indicate that the Y_1.5La_0.5Mo₃O₁₂ crystallizes in monoclinic Tb₂Mo₃O₁₂-type structure and it is non-hygroscopic. The Y_1.5La_0.5Mo₃O₁₂ ceramic is denser than the Y₂Mo₃O₁₂ and La₂Mo₃O₁₂ ceramics, and its relative density can reach 94.12% of the theoretical value. Most importantly, it shows almost zero thermal expansion and its thermal coefficient is 0.87×10⁻⁶ K⁻¹ from 178 °C to 600 °C. Y₂Mo₃O₁₂ ceramic shows negative thermal expansion whereas La₂Mo₃O₁₂ ceramic shows positive thermal expansion, their thermal expansion coefficients being−12.06×10⁻⁶ K⁻¹ and 8.88×10⁻⁶×10⁻⁶ K⁻¹, respectively.