New polychlorinated bibenzyls from Rhododendron minutiflorum

Five new polychlorinated bibenzyls(1-5)along with 3 known compounds(6-8)were isolated from the stems and leaves of Rhododendron minutiflorum.The chemical structures of all the isolates were determined by spectroscopic methods,and compounds 1 and 2 were further verified by single-crystal X-ray diffraction analyses.Compounds 1-5 were halogenated compounds which bear three to five chlorine atoms in their chemical structures.Biologi-cally,compounds 2,5 and 6 showed varying degrees of toxicity toward the Asian citrus psyllid(Diaphorina citri)with LD_(50) values 27.15,17.02 and 16.20 mg/L,respectively.These values were comparable to the positive control matrine(LD_(50)=11.86 mg/L),which were calculated using observations on day 6.Meanwhile,compound 4 hadα-glucosidase inhibitory activity with IC_(50) value of 17.87±0.74μM.

低展弦比CAES向心涡轮叶顶型线的正交设计优化（英文）

为降低叶顶泄漏损失,本文首次将NACA翼型引入向心涡轮,并采用正交试验设计和计算流体动力学(CFD)方法获得了具有最优NACA叶顶型线的向心涡轮叶片,并揭示了该叶片对叶顶泄漏损失的控制机理。结果表明,最优NACA叶顶型线具有较大的前缘内接圆半径、较小的尾缘厚度,以及更靠近前缘的最大厚度位置。其内接圆半径和最大厚度位置对向心涡轮等熵效率的影响度也随叶顶间隙增加而增大。当叶顶间隙为8%出口叶高时,最优NACA叶顶型线可使向心涡轮等熵效率提高1.47%,并使向心涡轮能够在非设计工况下具有较高效率。该型线能够降低尾缘附近的叶顶泄漏速度,减弱泄漏流与主流掺混强度,使流动损失降低。