Ultrasonic synthesis, characterization and formation mechanism of aggregated nanorings of EuF3

The aggregated nanorings of EuF3 were synthesized via ultrasonic irritation in aqueous solution. The products were characterized by X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. XRD pattern proved that the crystalline phase of the EuF3 rings was hexagonal. The SEM and TEM images indicated that the as-prepared EuF3 nanocrystals had ring-like morphology and were aggregated by numerous small crystallites （about 10-15 nm in diameter）; the outer diameter of the rings was in the range of 200--300 nm, while the inner diameter was in the range of 50-80 nm with a thickness of 30-40 nm. Moreover, the time-depend experiments were carried out to disclose the formation mechanism of the as-prepared ring-like nanostructures.     

pH值调节剂对微表处混合料性能影响的研究

利用磷酸作为微表处沥青乳液的pH值调节剂,并对微表处混合料进行路用性能测试,分析磷酸对微表处混合料性能的影响.结果表明,相比传统的盐酸pH值调节方式,基于磷酸的pH值调节方式使得沥青乳化剂分子在微表处混合料拌合过程中能够始终保持活性,可以改善微表处混合料的粘聚力,有效提高微表处混合料的成型速度和强度,并且能够提高微表处混合料的抗磨耗能力和抗水损害性能.     

次同步谐振的暂态扭矩放大问题研究

分析串补引起的暂态扭矩放大(transient torque amplification,TA)的危害和发生条件,提出影响电厂机组TA问题严重程度的因素主要包括暂态故障清除时间和机组轴系的自然扭振频率.暂态故障清除时间为轴系主导扭振频率的半波长的奇数倍时,TA问题最严重;系统的电气谐振频率与机组轴系频率吻合得越好,串补...