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361.
A novel Daphyniphyllum alkaloid, Daphlongeramine A (1) with a unique fused octacyclic skeleton, together with a quite recently reported alkaloid Paxdaphnine A (2), were isolated from the fruits of Daphniphyllum longeracemosum. The structures were elucidated on the basis of spectroscopic data. 相似文献
362.
Hongping Li Lin Chen Yi Zhang Xiaorui Ji Shuai Chen Haojie Song Changsheng Li Hua Tang 《Crystal Research and Technology》2014,49(4):204-211
In this work, we developed a facile and effective hydrothermal method synthesis of MoSe2 nanoflowers on reduced graphene oxide (RGO) sheets. The as‐prepared MoSe2/reduced graphene oxide (MoSe2/RGO) composites are characterized by X‐ray diffractometer (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicated that MoSe2 nanoflowers were successfully deposited on RGO nanosheets to form a well interconnected hybrid structure. The tribological properties of MoSe2/RGO composites as lubricating oil additive were investigated by a UMT‐2 ball‐on‐plate friction and wear tester. By the addition of MoSe2/RGO composites in paraffin oil, the antiwear ability was improved and the friction coefficient was decreased. The based oil with MoSe2/RGO composites showed better tribological properties than the oil with MoSe2 and pure oil. The good friction and wear properties of MoSe2/RGO composites as additives were attributed to the formation of a thin physical tribofilm on the substrate. 相似文献
363.
Shuhui Lv Hongping Li Deming HanZhijian Wu Xiaojuan Liu Jian Meng 《Journal of magnetism and magnetic materials》2011,323(5):416-421
Electronic structure calculations based on density functional theory (DFT) within the generalized gradient approximation (GGA) and GGA+U for manganite cuprate compound LuCu3Mn4O12 have been performed, using the full-potential linearized augmented plane wave method. The calculated results indicate that LuCu3Mn4O12 is ferrimagnetic and half-metallic in both GGA and GGA+U calculations. The minority-spin band gap is 0.7 eV within GGA, which is larger than that of LaCu3Mn4O12 (0.3 eV), indicating its better half-metallicity. Further, the minority-spin gap enlarges from 0.7 to 2.8 eV with U taken into account, and simultaneously the Fermi level being shifted to the middle of the gap, making the half-metallic energy gap to be 1.21 eV. These results demonstrate that electronic correlation effect enhances the stability of half-metallic property. These facts make this system interesting candidates for applications in spintronic devices. 相似文献
364.
基于非结构网格,给出模拟两相流的统一间断有限元框架.其中,不可压Navier-Stokes方程采用IPDG(Interior penalty discontinuous Galerkin)方法求解;Level Set方程采用RKDG(Runge-Kutta discontinuous Galerkin)方法求解.方腔驱动流在不同Re数时的数值结果验证了该方法在单相流动中的有效性.气泡上升过程的模拟结果表明:该方法避免了重新初始化,且计算量小、实施简单,可有效求解具有运动界面的不可压两相流问题. 相似文献
365.
366.
Zhou Q Lu X Liu X Zhang L He H Zhu J Yuan P 《Journal of colloid and interface science》2011,355(1):237-242
Molecular dynamic simulations have been carried out to investigate the behavior of methane hydration in Na-smectite interlayers with different layer-charge distributions and water contents under certain pressure-temperature (P-T) conditions, which is analogous to the methane hydrate-bearing marine sediments. It was found that sufficient interlayer water is necessary for coordinating with methane and forming hydrate-like structures. Methane molecules are solvated by nearly 12-13 water molecules and coordinated with six oxygen atoms from the clay surface in the interlayer of nontronite as well as in montmorillonite. The mobility of the interlayer water of smectite, which is determined by the layer-charge amount and distribution of smectite, also influences the stability of hydrate methane complexes. The tetrahedral negative charge site is closer to the surface than the octahedral charge site and is more effective in confining water than methane water molecules. 相似文献
367.
离子的极化和形变是无机化学教学中的一对重要概念,这对概念可以用于解释化合物的结构及许多物理和化学性质。然而一些教科书在介绍这对概念时,大都把极化作用限于阳离子,把形变作用限于阴离子,而忽略了阴离子的极化作用和阳离子的形变作用。同时,在应用这对概念解释化合物结构和性质时,条理上也不十分清晰,甚至还出现自相矛盾的情况,使得学生在学习这对概念时感到困惑。本文介绍了离子的极化和形变这对概念的基本含义,讨论了影响极化能力和形变程度的因素,分析了一些化合物的结构以及溶解度、颜色和热稳定性等物理和化学性质。特别是对一些教学中有争议的问题给出了合理解释。在分析小分子结构时,极化和形变概念的运用可以弥补杂化轨道理论和价层电子对互斥理论的不足。 相似文献
368.
369.
Single crystals of the title compounds are prepared by solid state reactions of M2CO3 (M: K, Rb, Cs), PbO, PbF2, H3BO3, and (NH4)H2PO4 in a molar ratio of 2:5:5:4:3 (Pt crucible, 700 °C, 10 h). 相似文献
370.
近年来,通过仿生生命体自我修复损伤这一现象而研制的自修复材料,可有效延长材料的使用寿命、提高材料的使用安全性、降低资源浪费,具有巨大的发展潜力。其中,自修复有机硅材料因兼具自我修复的功能和有机硅材料的优异性能,已成为当下的研究热点。由于外界刺激条件如紫外光、温度等是材料实现损伤自我修复的外在驱动力,在很大程度上影响着材料的修复效能,且不同的刺激条件具有不同的优缺点和应用领域。因此,本文将基于自修复过程中外界刺激因素的不同,对自修复有机硅材料尤其是近五年来的最新研究成果进行综述,从外援型和本征型自修复有机硅材料两方面入手,以本征型自修复有机硅材料为重点,并对自修复有机硅材料今后的发展进行了分析展望。 相似文献