An apparatus including a ring oscillator and related methods are disclosed. The motion-vector detector detects, as a motion vector of the target pixel, a vector that has a starting point at a pixel on the reference frame which corresponds to the target pixel on a current frame and has an end point at the determined centroid. A hugging state between two electronic devices is assumed to be given if a first electronic device and a second electronic device are determined to undergo a specific motion pattern relative to each other while being at least in close vicinity to each other. This behavior is achieved, in part, through the use of a physical or logical clock to establish the temporal order of topological change events. The graphically printed back sheet is wound into a roll good, or an absorbent core is positioned between it and a liquid permeable topsheet to provide an absorbent disposable article. The invitation may be for inviting participation in an online social group that includes others who have sent the second query to the server system within the time window.