2.0SIR2.0SIR2.02.02.0SIR2.0SIRingSIRSIRingSIRingSIRSIR2.02.02.0SIR2.0SIRSIR+=SIR2.02.0SIR2.0SIR2.0SIRSIRSIR2.02.0SIRSIR2.0SIRSIRSIRSIR2.02.02.02.0SIRSIR2.02.0SIR2.0SIR（）