Abstract During shale gas exploration, natural fractures in reservoirs may be induced by cyclic loads frequently encountered different geological processes, including tectonic movements, seismic actions, and artificial construction interference (vertical horizontal wells drilling hydraulic fracturing). In this paper, experiments PFC 2D simulations are conducted to investigate the mechanical res...

Universalities and intriguing analogies in the statistics of avalanches are revealed for three physical systems defined on largely different length energy scales. Earthquakes induced by tectonic scale dynamics, micro-scale level quakes observed from slipping crystallographic planes metals a one-dimensional, room-scale spring-block type Burridge-Knopoff model is studied similar statistical viewp...

At present, most precast shear walls are implemented in accordance with the method equivalent to a cast-in-place structure, where joint is complicated, and construction difficult. According characteristics of wall structures, design “strong horizontal joints, weak vertical joints” for structure proposed. The existing was used form strong damper connect joints joints. It can reduce pouring concr...

Is the common folklore, that oars are less efficient at propulsion than propellers, correct? Here we examine the propulsive efficiency of the oars used in competitive rowing. We take the propulsive efficiency η of rowing to be the ratio of the energetic benefit, the energy Db dissipated by boat drag, to the energetic cost, the work Wr performed by the rower. Air drag is neglected as is the ener...

Optimal control of dampers has been proposed to mitigate vibration effects in mechanical systems. In many cases, systems are subject to periodic forcing and the goal is to maximize the energy dissipated by the damper. In contrast to prior work utilizing instantaneous or infinite-time−horizon optimization, this paper employs periodic optimal control to maximize the energy dissipated per cycle. F...