A phase change type optical disk in which recording is performed in land portions and groove portions, and which eliminates the detrimental effects of narrowing of the track pitch. The flow guides overlap a section of an outer seal provided on the other surface of the metal separator. The particle recirculator performs a function normally carried out by a settling compartment or clarifier zone associated in aerobic type septic systems. The indexes correspond to respective resources, and each value indicates an element of the package that produces the resource that corresponds to the respective index. The method leverages a circuit model of the lithium ion battery, and generates four battery parameters from which the SOC is derived.