There is disclosed a wireless access system in which subscriber registration, deletion, and the like are set in a pertinent wireless base station in accordance with a request from a management center, and remote maintenance is realized. The material is produced by the photopolymerization of reactants having thiol and olefin moieties. In another embodiment, a nonvolatile memory device may include a cell array having two groups of memory cells, and the memory cells in different groups may be simultaneously driven with erase voltages having different levels during an erase operation. The optical sending apparatus having such a construction can generate high-density WDM optical signals, the dispersion of which is compensated in advance, by a polarization crossing method. A method for inspecting the specimen may include directing light from a light source toward a surface of the specimen and detecting light returned from the surface using a linear sensor array. The macrophytes can include floating aquatic plants, such as water hyacinths, submerged aquatic plants, and terrestrial or aquatic plants caused to float artificially.