Oscillatory Motion of Viscoelastic Drops on Slippery Lubricated Surfaces

The introduction of slippery lubricated surfaces allows the investigation of the flow of highly viscous solutions which otherwise will hardly move on standard solid surfaces. Here we present the study of the gravity induced motion of small viscoelastic drops deposited on inclined lubricated surfaces. The viscoelastic fluids exhibit shear thinning and, more importantly, a significant first normal stress difference N1. Despite the homogeneity of the surface and of the fluids, drops of sufficiently high N1 move down with an oscillating instantaneous speed whose frequency is found to be directly proportional to the average speed and inversely to the drop volume. The oscillatory motion is caused by the formation of a bulge at the drop rear that starts rolling around the moving drop.

Delta Based Non-Anthropomorphic Hand

The paper reports design and implementation of a Delta Robot based non-anthropomorphic hand. A set of three constant orientation Delta robots are shown to be useful to perform manipulation maneuvers on the object. Voice coil arc actuators are deployed to improve the backdrivability of the robot. The hand consists of three constant orientation fingers which are deployed to grasp an object. The fingers are programmed to behave as a set of springs to generate stable object acquisition. The capability of the robotic hand to perform different maneuvers is demonstrated. The dynamic feedback linearisation method is shown to be useful both for controlling the robotic hand and also to ensure passive grasp of the robotic system. It is shown that the hand can be used to catch an object, improve the grasp forces on the surface of the object, impart oscillatory motion, and also to throw the object in a prescribed direction. Standalone examples are described to suggest the same. The backdrivability of the voice coil arc actuators are demonstrated to be of purpose in improving the passive grasp behaviour of the robot. The swift motion of the actuators are shown to be useful while performing quick oscillations and also to throw the object.

The Vendian–Cambrian Cyclometric Stratigraphic Scale for the Southern and Central Siberian Platform

—The general Vendian stratigraphic scale of Siberia, with the uncertain age of the Vendian base ranging from 600 to 630– 640 Ma in most of recent publications, remains worse constrained than the Cambrian scale, in which the boundaries of epochs and stages have been well defined. However, the imperfect classical stratigraphic division has been compensated by data on the cyclicity of the Vendian–Cambrian sedimentary section. The Vendian stratigraphy of the Siberian Platform and the related deposition history with cycles of sedimentation and gaps, as well as the hierarchy of sedimentation processes, can be inferred from the succession of alternating clastic, carbonate, and salt units. The cyclicity of geologic processes and their recurrence are attributed to periodic oscillatory motions of the crust. The ranks of these motions correlate with the cyclicity of sedimentary strata, including regocyclites, nexocyclites, and halcyclites separated by gaps. Each Vendian long-period oscillatory motion begins with a regocyclite and ends with a regional-scale gap. The Cambrian section includes one pre-Mayan regional gap at the end of the early Cambrian long-period cycle. Cambrian regocyclites are composed of carbonate subformations and formations in the lower part and alternating salt and carbonate beds in the upper part.