Sedimentation and bioturbation at Caiwei Guyot in the western North Pacific

本研究以中国第27次大洋科学考察航次在西北太平洋采薇海山附近海域采集的沉积物岩芯为研究对象，利用230Thex和230Thex/232Th法测定了沉积物的质量累积速率和线性沉积速率，结合有机碳、氮含量的分析，获得沉积物中有机碳、氮的累积速率，同时利用210Pbex示踪法研究了采薇海山沉积物的生物扰动作用，探讨了生物扰动作用与沉积速率、有机物累积速率等因素之间的关系。 采薇海山区沉积物质量累积速率和无压实线性沉积速率的变化范围分别为0.06~1.14kg/m2/ka和0.12~2.50mm/ka，平均值分别为0.45±0.35kg/m2/ka和1.080.83mm/ka。采薇海...Sediment cores at Caiwei guyot in the western North Pacific were analysed for determining the sediment mass accumulation rate and linear sedimentation rate via 230Thex and 230Thex/232Th methods. The accumulation rate of organic carbon and nitrogen was further calculated based on the organic carbon and nitrogen content in surface sediments. Besides, bioturbation was evaluated by 210Pbex tracer. The...学位：理学硕士院系专业：海洋与地球学院_海洋化学学号：2232013115138

Mechanical behavior and micro-mechanism of carbon nanotube networks under friction

Friction behavior of carbon nanotube networks (CNNs) is ubiquitous in applications, however, is poorly inves-tigated. Here, we employ coarse-grained molecular dynamics (CGMD) simulations to investigate friction be-haviors and microscopic mechanism of CNNs. We first give a phase diagram to determine the initial contacting state of supported or trapped for an indenter in CNNs. In a supported state, friction force is mainly orig-inated from the local surface adhesion of CNNs which experience stable elastic deformation in friction process. In contrast, in a trapped state, friction force is mainly activated by nonlocal reconstitution of carbon nanotubes (CNTs) accompanied with irreversible bond breaking. Furthermore, with an increased normal pressure, the friction force keeps nearly constant for a supported indenter while it increases linearly for a trapped one; the friction force is linearly or nonlinearly related to the sliding velocity of an indenter in a supported or trapped state. Importantly, there is a critical crosslink density, above which, the coefficient of friction is greatly decreased due to enhanced integrity of CNNs. These results provide a profound understanding of friction deformation behavior of CNNs, which is of great significance for optimal design in practical applications