A method for processing an image signal includes evaluating an edge factor based on a characteristic of an original image signal. In one implementation, a system may receive a request for information over a voice channel from a mobile terminal and respond to the request with text transmitted to the mobile terminal over a text channel. The non-metal-ion aliphatic polyester is not only applicable to common use, but is also suitable as high value-added medical material and packing material which contacts with food directly than other metal-containing polyester. In another embodiment, feed to a multi-stage reactor is split between different compartments of reactor.