re = /(numberPinyin":\s*".*)(v)(.*)"/m
str = '[\'{"russian": "женщина", "english": "woman, v","numberPinyin": "nv3","typeOfChar":"character","typeOfTranslating":"original"}\',
\'{"chinese": "弯竖左钩", "russian": "вогнутая с крюком влево", "english": "concave with left hook","numberPinyin": "eav","typeOfChar":"stroke","typeOfTranslating":"byStrokes"}\',
\'{"chinese": "弯竖右钩", "russian": "вогнутая с крюком вправо", "english": "concave with right hook","numberPinyin": "vm2","typeOfChar":"stroke","typeOfTranslating":"byStrokes"}\']'
subst = '\\1ü\\3'
result = str.gsub(re, subst)
# Print the result of the substitution
puts result
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html