下游塔架对水平轴风力机叶片气动负荷的作用

为了研究水平轴风力机叶轮与下游塔架之间的动静干涉作用,并将二者的相互作用简化为二维翼型与后置圆柱之间的气动干涉,通过数值模拟的方法分析了在翼型尾缘下游不同位置处放置的圆柱对叶片载荷的影响.研究结果表明,下游塔架对叶片载荷的影响主要与塔架直径和二者的相对位置有关.当叶片掠过圆柱塔架时,翼型上下表面的流速分布产生了明显的改变,进而造成气动载荷发生显著的变化,其变化幅度可以达到定常计算情况下的50%.该工作对风力机叶片的周期气动力疲劳寿命的评估提供了参考.     

用矩阵实现模糊本体映射

当前的本体映射技术主要是针对明确概念集合的本体,这些技术无法处理语义网上的不确定信息。文中提出了扩展现有本体映射方法来支持不确定信息的本体映射。这种扩展称为模糊本体映射(FOM),它主要是基于模糊理论和图理论。FOM主要是计算本体的概念之间的相似度所形成的矩阵,并定义了一系列算法来推理模糊本体概念之间的模糊关系。     

一种用于电织针的超薄直线电机磁路与结构设计方案的有限元分析

针对一种超薄永磁直线同步电机,在苛刻的尺寸约束条件下重点针对初级导线的布置、永磁的体积确定及布置方式进行研究,最后借助有限元分析软件ANSYS进行仿真,仿真结果能较好的满足电机的约束条件.分析计算表明,设计方案可行,为进一步开展电机的实际试制工作打下了良好的理论基础.     

全球变暖与中国极端气候事件变化

极端天气气候事件(以下简称极端气候事件),是指一个地点或地区发生概率较小的天气气候现象,又称异常天气气候事件.极端气候事件往往可以造成很大的危害.其中,高温(热浪)、低温(寒潮)、暴雨洪涝、少雨干旱、台风和沙尘暴等常能造成严重的自然灾害,引起人员伤亡和经济损失.     

实验教学在电工学教学中的作用及应用

在电工学教学中,采用实验教学法,使教学内容由难化易、由繁化简,从而激发学生的学习兴趣,培养学生的思维品质.     

基于有限体积法的螺旋槽气体推力轴承润滑计算

为避免螺旋槽边界曲线对计算造成的不便,利用坐标变换将螺旋区域变为扇形单元,采用有限体积法得到气体雷诺方程的离散计算式,并将计算结果与已发表的有限差分法、有限元方法及解析算法的计算结果进行对照,验证了本文计算模型和数值方法的正确性.结果表明:当螺旋角在10°到15°之间取值时,承载力可获得最大值;槽深减小,压力增大,摩擦转矩也有一定的增加;压力分布的明显特点是:槽台交界处压力取极值;压缩数高,压力增大,压力梯度大.     

RF磁控溅射法制备PbTe纳米薄膜

利用RF磁控溅射和真空退火方法制备了PbTe纳米薄膜.利用SEM、XRD、AFM和FTIR分别对制备的样品的表面形貌和颗粒大小、结构以及带隙宽度进行了测试.结果显示,在10 W溅射功率下制备的PbTe纳米薄膜为纳米颗粒镶嵌薄膜,在20 W功率下为PbTe颗粒膜.10 W制备的纳米颗粒的平均直径为40 nm左右,平均高度为5 nm; 20 W制备的颗粒直径为100 -400 nm,平均高度为65 nm;两个条件下制备的样品均表现出明显的<100>方向的择优取向性,并且20 W的结晶质量比10 W的好.FTIR分析显示10 W和20 W制备的薄膜的带隙宽度分别为0.340 eV和0.343 eV,都比块体带隙宽度大.     

Solvothermal synthesis and ferromagnetic property of bamboo-shoot-like oriented carbon micromaterials

Bamboo-shoot-like oriented carbon micromaterials (BOCMs) were synthesized by a solvothermal method at 450°C for 4 h using deoiled asphalt (DOA) as carbon source, toluene as solvent, ferrocene as catalyst precursor and amphiphilic triblock copolymer P123 as surfactant. The morphology and structure of the products were characterized by X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy and Fourier transform infrared spectroscopy. The results reveal that the obtained products have good distribution with uniform diameters of about 0.5 μm and the lengths of 1–1.5μm, and hydrogen-carbon bonds are observed on the surface of BOCMs. The growth mechanism of BOCMs is discussed, in which that the catalysis of ferrocene and the dispersion and assembly of the aromatic molecules of DOA directed by P123 are critical to the formation of the BOCMs. The coercivity value (231.91 Oe) from the measurement of a vibrating sample magnetometer shows that the BOCMs have an obvious ferromagnetic behavior.     

U-Pb dating of detrital zircons from the Wudangshan Group in the South Qinling and its geological significance

U-Pb dating was made by the LA-ICP-MS method for detrital zircons from the Wudangshan volcanic-sedimentary succession in the South Qinling. Samples comprise quartz sandstones of the Wudangshan Group collected from the base of the Yangping Formation and an upper layer of the Shuangtai Formation overlain its volcanic sequence, and two river-sand collections from the drainage systems cutting across the two formations, respectively. The results show that the Yangping detrital zircons are dominated by 830–780 Ma grains with a minor population of ~1.0–0.84 Ga and sporadic grains of ~2.6, ~2.4 and 2.0 Ga, whereas the Shuangtai zircons yield an upper intercept age of 763±33 Ma, identical to the timing of the Wudangshan volcanism within error, with few concordant grains of 1.9 and 0.86 Ga. Age spectra for the two river-sand samples are similar to those of the Yangping and Shuangtai Formations, respectively. It thus suggests that the Wudangshan strata are less than 780 Ma, whereas their major detrital zircon populations of 1.0–0.85 Ga and 830–780 Ma are consistent with timing of the Hannan magmatic activities along the northwestern margin of the South China Block. This suggests a Hannan or adjacent area provenance for the Wudangshan strata. The Wudang area is characterized by rift-related igneous events at ~755 and ~680 Ma, respectively, pointing to a tectono- magmatic history different from the Hannan area. It is inferred that the ~755 Ma magmatism is likely to indicate a separation of the South China Block from the supercontinent Rodinia, while the ~680 Ma event suggests a further split between the South Qinling and some unknown continent.     

炼油装置加热炉节能存在的问题及解决措施

分析目前炼油装置加热炉运行过程中存在的主要问题,并针对这些问题进行探讨;提出通过优化换热流程、联合回收余热、提高加热炉效率等来解决这些问题,从而优化加热炉运行,达到节能的目的。