The invention concerns methods and devices for bending a cylindrical tube or the like so as to obtain two consecutive sections of said tube forming between them a non-null angle alpha. The cleaning liquid is selected from 2-propanol and a mixed solvent of 2-propanol and water. The turned-off sub-pixel, the sub-pixel charged with the polarity inverted data voltage, and the sub-pixel charged with the polarity maintained data voltage alternately vary on a per frame basis. If the file backup software determines that the file modification policy has been violated, the file backup software generates an alert, indicating that the modification violates the modification policy.