We call this phenomenon substitution with lowercases.
in order to approximate the practical coverage of our method, we classified unknown words that occur more than two times in the Kyoto University and NTT Blog (KNB) corpus 5 into four types: words that are covered by the lexicon created by Murawaki and Kurohashi (2008) (Murawaki's Lexicon), words that are not covered by Murawaki's Lexicon but have entries in Wikipedia, words that are covered only by our method, and the others.