An aircraft landing gear door assembly has a plurality of doors. In one embodiment, a substrate is doped by surfaced deposition of dopant followed by formation of a capping layer and thermal diffusion drive-in. A stepped portion of a nonmagnetic material having an almost vertically formed end face at a side facing an ABS surface is formed on the recording gap layer. The catalyst may be used in aromatic alkylation by contacting the catalyst with a feed of an aromatic hydrocarbon and an alkylating agent under reaction conditions suitable for aromatic alkylation. The post may insert into the opening to facilitate docking the computing device to the computing base, the first magnetic element and the second magnetic element to facilitate alignment of the post with the opening. The switches select either the field mode or the frame mode according to the notified mode.