The present invention provides a positioning device for positioning a table, including a base, a motor that drives the table in the driving area on the base, a position sensor that detects the position of the table, and a control unit that controls the motor. In a preferred embodiment, the invention is a method of grafting polar groups onto biodegradable polymers and modified biodegradable polymer compositions produced by the method. The relationship is affected by the source-observer or observer-observer distance but the correction is small for large distances. The method includes logging into the account via the computing device based on receipt of the user verification. The cellulose fibers include about 40% to about 80% of cellulose fibers from post-consumer waste.