Joule Heating

Hi Guys Salaam I am doing simulation of IC pins On Comsol. My Objective is to evaluate the joule heating effect on the IC Pins due to the injection of electirc current pulse.

While simulation, I have encountered a problem given. If someone guides me what does this error means.

ERROR

Undefined variable. - Variable: PortName - Global scope Failed to evaluate operator. - Operator: if - Global scope Failed to evaluate expression. - Expression: if(PortName==1,if((comp1.ec.term1.int(comp1.ec.I0)/comp1.ec.term1.int(1))!=0,comp1.ec.term1.int(comp1.ec.I0)/comp1.ec.term1.int(1),1),0) Failed to evaluate variable. - Variable: comp1.ec.I0_1 - Defined as: if(PortName==1,if((comp1.ec.term1.int(comp1.ec.I0)/comp1.ec.term1.int(1))!=0,comp1.ec.term1.int(comp1.ec.I0)/comp1.ec.term1.int(1),1),0) Failed to evaluate expression. - Expression: d(comp1.ec.I0_1test(comp1.ec.term1.V0_ode),{test@1}) Failed to evaluate Jacobian of expression. - Expression: comp1.ec.I0_1test(comp1.ec.term1.V0_ode) error in COMSOL