碎屑石榴石地球化学物源分析与解释:粒度的影响

单矿物地球化学分析是沉积物源分析研究的重要手段,运用广泛。沉积物中碎屑矿物的粒度组成,即水动力分选作用,是否影响到基于这种方法的物源解释,目前尚不清楚且受到的关注不多。通过研究柴达木盆地北缘地区第三系沉积物中的680颗碎屑石榴石（0.068～0.557 mm）的主量元素地球化学组成数据,解释了不同粒度的碎屑石榴石物源。结果显示,0.063～0.125 mm的碎屑石榴石的地球化学结果中Fe2+与Mn2+含量更高,表明其母岩的变质结晶程度较弱,故物源解释结果更可能为中—低级角闪岩相变沉积岩,而其他粒径的碎屑石榴石Ca2+与Mg2+含量更高,这说明其物源区的温压条件较前者高,因而物源解释结果为低级变质相,中酸性火成岩,榴辉岩等宽泛结果。这种碎屑石榴石粒度差异导致的地球化学组成的不同,说明碎屑石榴石的颗粒大小在一定程度上会影响物源解释结果。因此,在进行单矿物地球化学物源研究时,选取特定粒径（0.063～0.125 mm或0.125～0.25 mm）组成的碎屑矿物进行分析,可以消除水动力分选作用的影响,有助于获得更为准确的物源解释结果。国家自然科学基金项目(41806052);;\n福建省自然科学基金项目(2017J05067);;\n厦门大学校长基金项目(20720160114);厦门大学大学生创新创业训练计划项目(2017X0642)~

Learning peg-in-hole assembly using Cartesian DMPs with feedback mechanism

Purpose: This paper aims to enable the robot to obtain human-like compliant manipulation skills for the peg-in-hole (PiH) assembly task by learning from demonstration. Design/methodology/approach: A modified dynamic movement primitives (DMPs) model with a novel hybrid force/position feedback in Cartesian space for the robotic PiH problem is proposed by learning from demonstration. To ensure a compliant interaction during the PiH insertion process, a Cartesian impedance control approach is used to track the trajectory generated by the modified DMPs. Findings: The modified DMPs allow the robot to imitate the trajectory of demonstration efficiently and to generate a smoother trajectory. By taking advantage of force feedback, the robot shows compliant behavior and could adjust its pose actively to avoid a jam. This feedback mechanism significantly improves the dynamic performance of the interactive process. Both the simulation and the PiH experimental results show the feasibility and effectiveness of the proposed model. Originality/value: The trajectory and the compliant manipulation skill of the human operator can be learned simultaneously by the new model. This method adopted a modified DMPs model in Cartesian space to generate a trajectory with a lower speed at the beginning of the motion, which can reduce the magnitude of the contact force.</p