阶段性变动:乡村土改运动中积极分子生成与淘汰机制研究——以河南商水县为例(1947-1953)

通过对商水县土改运动的过程——急性土改、剿匪反霸清算、土改、土改复查与民主建政等几个阶段的考察,可以发现在不同的革命阶段,具有不同行为特点的积极分子相继出现,同时部分旧积极分子遭到淘汰。积极分子之所以有阶段性的变动,与其在群众运动中的生成与淘汰方式密切相关,进而可以发现,积极分子的涌现在于工作队与积极分子对革命运动推动中形成的双向合力互动,积极分子淘汰的深层次原因在于革命与乡村的内在紧张。这种积极分子在革命进程的阶段性变动虽然给党——国家塑造的运动型社会运行机制提供了动力,但也不可避免的带来了一定的负面影响,即对社会生活常规化的冲击、造成积极分子代际冲突以及部分人过分积极、热衷斗争,使其他基层群众不安等。总之,以积极分子的阶段性变动表现出来的这种社会底层的选择、选拔、录用方式,一方面强化了贫雇农、中农与党——国家的联系,有助于社会的总体性整合,另一方面也反映了外生条件下产生的积极行为转化为一种内生性的主动、自觉积极的艰难。

Compliant landing of a trotting quadruped robot based on hybrid motion/force robust control

A compliant landing strategy for a trotting quadruped robot on unknown rough terrains based on contact force control is presented. Firstly, in order to lower the disturbance caused by the landing impact force, a landing phase is added between the swing phase and the stance phase, where the desired contact force is set as a small positive constant. Secondly, the joint torque optimization of the stance legs is formulated as a quadratic programming(QP) problem subject to equality and inequality/bound constraints. And a primal-dual dynamical system solver based on linear variational inequalities(LVI) is applied to solve this QP problem. Furthermore, based on the optimization results, a hybrid motion/force robust controller is designed to realize the tracking of the contact force, while the constraints of the stance feet landing angles are fulfilled simultaneously. Finally, the experiments are performed to validate the proposed methods.