蝙蝠喉部发声组织建模及发声机理*

建立蝙蝠发声组织模型对超声机理研究及在智能设备的应用具有重要意义。根据蝙蝠喉部发声组织结构特点,通过有限元方法构建了蝙蝠的3种不同发声组织模型,分析了尺寸、材料力学参数、组织结构和张力4个因素对发声组织特征频率的影响。结果表明,如果用人类声带,按比例缩小构建蝙蝠喉部组织模型,蝙蝠无法发出超声波。构建组织结构含甲状软骨和声带的半鼓状模型和只含声带的条状模型,两种模型的特征频率相近且在合理的参数域内均无法达到超声范围。而含膜条状模型的特征频率可以通过张力进行超声频率的调节,这与文献的实验结果一致。因此,可基于含膜条状模型对蝙蝠喉管发声组织进行建模及其发声机理研究。     

Al/AlN多层膜的摩擦磨损性能研究

采用柱状靶磁控溅射系统制备Al/AlN纳米多层膜,采用纳米压痕仪测量Al/AlN纳米多层膜的纳米硬度,在UMT-2M型摩擦磨损试验机上评价其摩擦磨损性能.结果表明:当AlN层较厚时,薄膜在很短时间内被磨穿;调节Al/AlN层厚比为2.9/1.1时,薄膜的摩擦磨损性能明显提高;当保持Al/AlN层厚比为2.9/1.1、变化多层膜的调制周期时,薄膜的摩擦系数较低,但硬度较低的薄膜由于承载能力不够,不能够保持优良的摩擦磨损性能.     

Isolation of a carbon nanohoop with M(o)bius topology

Carbon nanohoop,a class of constrained molecular architecture consisting of linked arene units,has attracted considerable interest from both experimental and th...     

Carbene-catalyzed activation of cyclopropylcarbaldehydes for mannich reaction and δ-lactam formation: remote enantioselecitvity control and dynamic kinetic asymmetric transformation

An N-heterocyclic carbene(NHC)-catalyzed enantioselective Mannich reaction of the remote γ-carbon of cyclopropylcarbaldehydes is disclosed for the first time. Diastereo-and enantiomerically enriched multicyclic δ-lactam compound is afforded as the main product from 8 possible stereo-specific isomers through dynamic kinetic asymmetric transformation(DYKAT) processes. Multiple chiral functional molecules can be afforded from the lactam products through simple protocols with retentions of the optical purities.     

马尔可夫域变模型在我国季度GDP增长率序列建模中的应用

本文建立了我国季度GDP同比增长率序列的马尔可夫域变模型,通过与线性AR(X)、LSTAR和ARCH等模型的比较,结果表明它更好地刻画了研究对象的均值、波动性和动态结构存在域变行为的非线性特征.     

结构方程模型应用陷阱分析

结构方程模型近几年在我国心理学、管理学应用研究领域得到越来越多的应用,但部分应用者因其对其基本原理理解不够透彻导致误用或错用这种重要统计手段。本文通过结合实证研究实例对一些常见应用错误(问题)的分析揭示结构方程模型的原理,以期帮助应用者避免应用陷阱、提高实证研究水平。     

The Antibacterial Activity Mode of Action of Plantaricin YKX against Staphylococcus aureus

We aimed to evaluate the inhibitory effect and mechanism of plantaricin YKX on S. aureus. The mode of action of plantaricin YKX against the cells of S. aureus indicated that plantaricin YKX was able to cause the leakage of cellular content and damage the structure of the cell membranes. Additionally, plantaricin YKX was also able to inhibit the formation of S. aureus biofilms. As the concentration of plantaricin YKX reached 3/4 MIC, the percentage of biofilm formation inhibition was over 50%. Fluorescent dye labeling combined with fluorescence microscopy confirmed the results. Finally, the effect of plantaricin YKX on the AI-2/LuxS QS system was investigated. Molecular docking predicted that the binding energy of AI-2 and plantaricin YKX was −4.7 kcal/mol and the binding energy of bacteriocin and luxS protein was −183.701 kcal/mol. The expression of the luxS gene increased significantly after being cocultured with plantaricin YKX, suggesting that plantaricin YKX can affect the QS system of S. aureus.     

关于Young-Laplace公式的吉布斯自由能证明

对于为论证球形液滴附加压强的Young-Laplace公式而设计的一个理想实验,有文献试图借助吉布斯自由能函数进行证明,本文给出符合这一条件的证明方法.     

自呼吸式DMFC电堆构建与电池性能研究

本文报道了一种能驱动风扇工作的自呼吸式DMFC小型电堆,电堆主要南燃料储罐、膜电极(MEA)、集流体等组成.文中针对影响该电池性能的主要参数,如电堆的活化过程、甲醇浓度等因素进行了研究.同时,本文还对电堆的恒电流放电时的电流曲线特点以及阴极水的生成规律进行了初步考察和探讨.     

三维跨音速叶栅自动气动优化设计

应用三维叶栅自动设计参数化方法,选择E3约束的条件下进行了自动气动优化设计.优化后,最优叶栅的总压恢复系数比参考叶栅提高了0.8%,流量和出口气流角都在约束范围内.对优化结果的详细气动分析表明,叶栅性能有显著的改善,表明该算法具有良好的优化性能.