A wheel slip control for DC series wound traction motor vehicles such as railway locomotives in which each traction motor drives an axle and connected wheel set. In other words, a plurality of concentric zones are provided in which the variation from far to near vision correction is continuous, i. The cone-shaped through holes located nearer the circumference of the lens have a larger inclined angle at the side near the circumference of the lens than those located in the center portion of the lens. The process receives a query input associated with a current time and a current location of a mobile computing device. The lever end of the regulator contacts a diaphragm, the diaphragm separating the outlet chamber from the external environment. The movement of the second cover can be restricted by one or more objects inserted through a partition between the first and the second compartments, such as an electronic cigarette battery andor an electronic cigarette.