管线钢管局部屈曲应变分析与计算

针对基于应变的管线设计所使用的管线钢管进行变形能力评价,为基于应变设计地区用的钢管产品标准的指标制订提供技术基础。本文以精确建模的数值仿真计算作为钢管全尺寸弯曲变形试验的有效补充,对钢管进行了屈曲变形行为的研究;针对钢管产品试制中不同的材料性能进行了仿真计算,最终提出:两个与钢管临界屈曲应变相关的应力比指标Rt5.0/Rt1.0和Rt2.0/Rt1.0分别为1.04和1.08。该研究结果为基于应变设计地区使用的钢管标准的制订提供了技术支持。     

Spreading fully at the ice-water interface is required for high ice recrystallization inhibition activity

Although materials for ice recrystallization inhibition(IRI) are essential for the cryopreservation of cells and tissues, there exists no guiding mechanism for the design of such materials. Therefore, the construction of materials for IRI relies on the try-and-error strategy. Herein, through changing the tacticity of hydroxyl groups on poly(vinyl alcohol)(PVA) backbones with the affinities of PVAs to ice unchanged, we experimentally find IRI activity decreases significantly for isotactic PVA in comparison to that of atactic PVA. Molecular dynamics simulation shows atactic PVA spreads fully at the ice-water interface due to its much stronger interaction with water. This indicates atactic PVA can cover more ice surface and possess a higher IRI activity when the same amount of PVAs are used, which is consistent with the results that PVA can cover the same amount of ice surface more efficiently through experimentally measuring the adsorption of PVAs on the ice surface. A guiding mechanism of high active IRI materials can be obtained: only having affinity to ice is not enough to obtain high IRI activity(i.e., only small amount of materials is required to reduce the size of ice crystals to ca.(35±10) μm), IRI agents must also have high affinity to water, i.e., low interfacial energies, to both ice and water. The former is to guarantee the adsorption of the IRI agent on the ice surface, and the latter is required for the IRI agent to spread sufficiently at the ice-water interface. Therefore, each IRI molecule can effectively block the diffusion of water onto the ice surface, and consequently inhibits the growth of ice. A spreading coefficient of IRI agents is therefore introduced to quantitatively assess the capability of IRI agents to spread at the ice-water interface.     

赣南离子吸附型稀土矿床成矿特征概述

赣南是我国离子型稀土资源的主产区之一,其成矿母岩分布广,成矿条件优越,稀土配分类型多样。本文从成矿背景和矿床分布规律,成矿母岩和矿体赋存特征,以及矿石中稀土的赋存状态和配分类型等方面较为详细地总结了赣南稀土矿床成矿地质特征。     

Free vibration of thermo-elastic microplate based on spatiotemporal fractional-order derivatives with nonlocal characteristic length and time

A fractional-order thermo-elastic model taking into account the small-scale effects of the thermo-elastic coupled behavior is developed to study the free vibration of a higher-order shear microplate. The nonlocal strain gradient theory is modified with the introduction of the fractional-order derivatives and the nonlocal characteristic length. The Fourier heat conduction is replaced by the non-Fourier heat conduction with the introduction of the fractional order and the memory characteristic tim...