At least 47 U.S.-traded Chinese companies have received buyout offers totaling $42.6 billion since the start of last year, lured by the prospect of relisting at a higher valuation in Shanghai or Shenzhen, data compiled by Bloomberg show. Any new regulations could affect companies like U.S.-listed security software maker Qihoo 360 Technology Co., whose $9.3 billion buyout is still pending after it signed a definitive deal agreement in December.