creating an expression
Hello everybody!
I have to model the absorption coefficient of the air and gas mixture and this is: a = 0.01 if T< 323 K a=0.01 +(3/49/377)(T/-323) if 323<=T<700 K a=3.5 +(3.5/700)(T-700) if T>700 How can I set this? I tried to set it the in the expression editor but I don't know how to set the "if" argument... Can you give me a suggestion? Ioana |
Re: creating an expression
Hi Ioana, the only way using CEL that comes into mind is using nested step functions. If your picewise function a is a=a1 for T<T1 a=a2 for T between T1 and T2 a=a3 for T>T2, then try:
f1=step(T-T1) f2=step(T-T2) A(T)=a1+(a2-a1)*f1 so then your desired function is a(T)=A+(a3-A)f2 regards pi |
Re: creating an expression
Hi Pi!
There is no other way to do it? I don't know CEL and unfortunately I do not understand of word of your explanation. I saw that the help doesn't provide more suggestions in this direction, so I guess I have to look for another way. ioana |
Re: creating an expression
Hi Ioana, the typing in my message yesterday was not very clear. sorry. Type the right units for the absortion coef where is indicated below and load it into pre as a CCL:
LIBRARY:LIBRARY CEL:CEL EXPRESSIONS:EXPRESSIONS T1=323 [K] T2=700[K] f1=step((T-T1)/1 [K]) f2=step((T-T2)/1 [K]) a1 = 0.01 [units?] a2=0.01 +(3/49/377)(T-323[K]) [units?] a3=3.5 +(3.5/700)(T-700[K]) [units?] A=a1+(a2-a1)*f1 a=A+(a3-A)*f2 END END END hope it is more clear. regards |
Re: creating an expression
Dear Pi,
Thank you very much for your help. I will load the file in pre. Have a nice day, Ioana |
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