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Hi

you can use bolean equations such as (x<1) in an expression which means that the results of the () is either 1 if x is strictly smaller than 1, or is equal to 0 otherwise. In your case you have two bolean operatins so you have different cases on each side of the limit "X" .

Such expressions have the danger that the abrupt changes in values might give some headaches to the solver, and you might not converge, it all depends ...

Furthermore, if you have an uppercase "X" its probably that you are in the "spatial frame" (see the doc 4.1 about the frames)

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Good luck
Ivar

Hi,

There is something weird in this logical function:
Generally, the logical expression can be written as :

F=(M value or expression)*(condition1 && condition2)
This means that the value of F is equal to M if condition 1 AND 2 are fulfilled!

F=(N value or expression)*(condition3 | condition4)
This means that the value of F is equal to N if condition 3 OR 4 is fulfilled!

You can combine both of them as:
F=(M value or expression)*(condition1&&condition2) + (N value or expression)*(condition3 | condition4) which covers the whole range.

But in your expression Z=A*exp(-D)*((X<P)+(X>=P)*exp(D))
You are saying that the value of Z is equal to A*exp(-D) if (X<P)+(X>=P)*exp(D) !!! The condition is wrong

I guess you are trying to express it as: Z=A*exp(-D)*(X<P)+exp(D)*(X>=P) ?? This is correct!

I hope it helps!!

Cheers

Hi

I missed that one ;)

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Good luck
Ivar

thanks for your suggestion and I Double checked the form of expression I want to express, (as given in the Diode model)
Z=A*exp(-D)*((X<P)+(X>=P)*exp(D))
as I have just started to explore comsol, I cant say for sure but,
I guess the final expression would be Z= A*exp(-D) for X<P

and A*exp(-D)*exp(D) for X>= P
maybe because only one of the condition could be true at a time,
Is it correct....??


Regards,
E

Hi,

Yes, you are right. The expression exists in the diode model!!

To understand it, I just used equivalent expression
F=A*((x<5)+(x>=5)*b)
If you plot this expression in Comsol functions you will observe that:
When x<5 F= A
When x>=5 F=A*b

The A is a common factor for the two logical conditions. A*(condition1+condition2*expression)
It is just a compacted writing of this logical function (something which is absent in the doc!!)
You can even re-write it in a simple manner as I have described above.

At least I learned something new today ;-)

I hope it helps

Cheers