The present invention provides an improved orthopedic system for the modification of the distance between the maxilla and zygoma. The fuel cell assembly has opposite first and second ends with a length therebetween. The composition shows a synergistic tanning effect. Consequently, an apparatus can be constructed at low cost. The calculation expression can be defined based on fields of the records, as well as other information, for example, various state variables of the database The calculation expression can, in turn, be evaluated with respect to each record to determine whether a request to perform an operation on that particular record should be granted or denied. Accordingly, the packet can be transmitted in an optimal speed suitable for the multi-channel environment, without requiring pre-communication for multi-channel adaptation among the nodes of the PLC system and a stable communication between the nodes connected to the power line can be performed.