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Summary: It was repeatedly shown that the locomotion evoked by epidural-induced electrical stimulation can last for a certain amount of time after stimulation cessation in decerebrated and spinal animals. This so-called after-stepping reflects the maintenance level for the activation of locomotor neuronal circuitry, but only scarce information exists about after-stepping peculiarities. We provide a comparative investigation of after-stepping and stepping under epidural stimulation using electromyographic and kinematic signals as well as ground reaction forces in 16 decerebrated cats. Our principal findings are as follows: (1) the ground reaction forces decrease more after epidural stimulation cessation compared to anterior–posterior limb movements; (2) the step cycle duration is longer for after-steps; (3) the electromyographic signal of the extensor gastrocnemius lateralis muscle during after-stepping decreases faster compared to the signal from the flexors iliopsoas and tibialis anterior and to the extensor soleus muscle; and (4) electromyographic stability is reduced after epidural stimulation cessation. We suppose that different levels of the spinal central pattern generator can be differently attenuated after external trigger cessation. These data could be important for the elaboration of locomotor models and for rehabilitation techniques. New Findings: Our new findings come from comparative investigations of the so-called after-stepping (locomotion after electrical stimulation cessation) and locomotion observed during epidural-induced electrical stimulation. Our new findings are as follows: after epidural stimulation cessation, (1) the ground reaction forces decrease faster compared to anterior–posterior limb movements; (2) the electromyographic signal of the extensor gastrocnemius lateralis muscle decreases faster compared to the signals from the flexors iliopsoas and tibialis anterior and to the extensor soleus muscle; and (3) electromyographic stability is reduced. Full article

In the current hydrodynamic research relating to planing hulls, the stern flap and steps are generally considered to be two independent resistance reduction measures. Limited research has focused on the coupled effects of flaps and steps. Therefore, experimental and numerical simulation methods are carried out in this paper to explore the influence of the flap mounting angle coupled with the steps. A series of model towing tests were implemented for a double-stepped planing hull with 2°, 3° and 4.5° flap angles. The test results show that, as the mounting angle increased, the low speed resistance performance was improved and the porpoising critical speed was delayed, with a slight resistance cost. Based on the tests, a numerical simulation method was established with volume Froude numbers ranging from 0.88 to 5.20. The simulated hull flow field showed good agreement with the testing data. The simulation results suggest a cavity induces the negative pressure after the steps; the cavity core region is the air phase, and this expands with the air–water mixture flow. The cavity also causes wetted surface reduction and pressure distribution changes. Finally, comparisons of cavities after-steps and load coefficients of different planing surfaces among models were considered. Numerical results analysis gave distinct interpretations for the experimental phenomenon of porpoising critical speed increasing with a slight resistance increment. Full article