Hello CHO,
The Mayr block is not a standard block available in the Simulink library. You will typically need to implement the Mayr equation using basic Simulink blocks, such as Gain, Sum, Integrator, etc. The Mayr equation is typically expressed as: 
where 
is the conductance, 
is the power loss in the arc, and 
is the arc time constant. Use the following blocks to implement this:
where is the conductance, is the power loss in the arc, and is the arc time constant. Use the following blocks to implement this:- Gain: For the
factor. - Divide: To compute
. - Sum: To implement the subtraction
. - Integrator: To integrate the rate of change of conductance.
I hope this helps!
