In-plane response of a rotating annular disk under fixed concentrated edge loads

This paper investigates the in-plane response of a rotating annular disk under concentrated edge loads with both the radial and tangential components. Lame's potentials are used to simplify the highly coupled equilibrium equations. It is demonstrated that the problem of fixed disk-rotating load differs from the problem of rotating disk-fixed load not only by the centrifugal effect, but also by additional terms arising from Coriolis effect. While the effect of these Coriolis terms may be negligible when the rotational speed is small or the concentrated edge load is in the radial direction, they are important in the high rotational speed range when the concentrated edge load is in the tangential direction. Numerical results of the natural frequencies and steady-state response are presented for a radius ratio of 0.3 with emphasis on the difference between the responses of fixed disk-rotating load and rotating disk-fixed load systems.     

等离子喷涂ZrO2涂层显微结构表征和热导率分析（英文）

利用大气等离子喷涂制备了ZrO2涂层,采用扫描电子显微镜结合图像分析的方法对涂层的显微结构特征(总气孔率和大气率)进行了量化表征.同时利用扫描电子显微镜附带X射线扫描成像对涂层内部的微裂纹和大的分隔裂纹的三维分布进行了表征.据此建立了ZrO2涂层显微结构与热导率之间的关系.室温下,涂层N2的热导率较N1的低,因为涂层N2内气孔和微裂纹数较多;在1000℃,由于微裂纹的烧结作用导致热导率增大,所以涂层N2的热导率较N1反而高.高温下,涂层内由微裂纹汇聚而形成的大的分隔裂纹的存在则可以有效地抑制烧结,降低涂层的热导率.     

Discovering Functional Organized Point of Interest Groups for Spatial Keyword Recommendation

A point of interest (POI) is a specific point location that someone may find useful. With the development of urban modernization, a large number of functional organized POI groups (FOPGs), such as shopping malls, electronic malls, and snacks streets, are springing up in the city. They have a great influence on people’s lives. We aim to discover functional organized POI groups for spatial keyword recommendation because FOPGs-based recommendation is superior to POIs-based recommendation in efficiency and flexibility. To discover FOPGs, we design clustering algorithms to obtain organized POI groups (OPGs) and utilize OPGs-LDA (Latent Dirichlet Allocation) model to reveal functions of OPGs for further recommendation. To the best of our knowledge, we are the first to study functional organized POI groups which have important applications in urban planning and social marketing.     

透射模式电子背散射衍射技术在纳米材料研究中的应用

为了提高电子背散射衍射技术的空间分辨率, 使之能够对纳米尺度的晶粒或超细粉末进行相鉴定和取向分析, 本研究通过自主设计的透射模式电子背散射衍射技术的样品台, 及调整EBSD探头位置及角度, 收集到清晰、完整的透射电子菊池衍射花样。研究了减薄块体样品厚度对透射电子菊池衍射花样的影响, 对减薄氧化锆涂层样品进行了t-EBSD面分布分析, 其结果的平均角度偏差(MAD)值仅为0.38, 成功鉴定出小于30 nm尺度的纳米氧化锆涂层立方相; 将超声分散后的纳米TiO₂粉体滴在铜网上, 采用t-EBSD对纳米颗粒进行点分析, 成功鉴定了锐钛矿相和金红石相TiO₂, 其中纳米锐钛矿TiO₂粉体的最小尺寸为20 nm左右, 使得扫描电镜中相鉴定的最小分辨率从目前的约100 nm提高到小于30 nm, 大大拓展了电子背散射衍射技术在纳米材料研究中的应用范围。     

Thermal explosion hazards on 18650 lithium ion batteries with a VSP2 adiabatic calorimeter

Thermal abuse behaviors relating to adiabatic runaway reactions in commercial 18650 lithium ion batteries (LiCoO₂) are being studied in an adiabatic calorimeter, vent sizing package 2 (VSP2). We select four worldwide battery producers, Sony, Sanyo, Samsung and LG, and tested their Li-ion batteries, which have LiCoO₂ cathodes, to determine their thermal instabilities and adiabatic runaway features. The charged (4.2 V) and uncharged (3.7 V) 18650 Li-ion batteries are tested using a VSP2 with a customized stainless steel test can to evaluate their thermal hazard characteristics, such as the initial exothermic temperature (T₀), the self-heating rate (dT/dt), the pressure rise rate (dP/dt), the pressure-temperature profiles and the maximum temperature (T_max) and pressure (P_max). The T_max and P_max of the charged Li-ion battery during the runaway reaction reach 903.0 °C and 1565.9 psig (pound-force per square inch gauge), respectively. This result leads to a thermal explosion, and the heat of reaction is 26.2 kJ. The thermokinetic parameters of the reaction of LiCoO₂ batteries are also determined using the Arrhenius model. The thermal reaction mechanism of the Li-ion battery (pack) proved to be an important safety concern for energy storage. Additionally, use of the VSP2 to classify the self-reactive ratings of the various Li-ion batteries demonstrates a new application of the adiabatic calorimetric methodology.