The present invention includes methods, devices, and compositions having improved piezoelectric characteristics with high energy density. The proxy cache may be configured to cache the data blocks in a hierarchical relationship within the object. A second sensor module receives a remaining portion of the X-rays transmitted through the inspected object, and outputs a second electric signal corresponding to a second X-ray energy amount different from the first X-ray energy amount. On receiving the user information, the license server assigns a leaf of a key-managed hierarchical tree structure to the client, generates a set of node keys as a device node key, sends to the client the device node key together with a leaf ID and a private key of the client in question, and records the user information in correspondence with the leaf ID.