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unit syntax error,and the expression is in orange.

Posted 2010年10月7日 GMT-4 00:39 7 Replies

youf Blue
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Hi, everyone

The expression of " 2*x^0.5 " is in orange and cued with "unit syntax error". However, " 2*x^2 " is correct. what's wrong with the expression?

thanks!

youf.

7 Replies Last Post 2014年11月24日 GMT-5 11:01
Chris McCorquodale
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Posted: 1 decade ago 2010年10月7日 GMT-4 03:38
Hi,

At a guess i'd say its to do with the power...instead of x^0.5, try sqrt(x). If not, what expression are you trying to enter it as because It could be to do with the units becoming messed up.

Let me know how you get on.

Regards,

Chris
Hi, At a guess i'd say its to do with the power...instead of x^0.5, try sqrt(x). If not, what expression are you trying to enter it as because It could be to do with the units becoming messed up. Let me know how you get on. Regards, Chris
Magnus Ringh COMSOL Employee

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Posted: 1 decade ago 2010年10月7日 GMT-4 03:56
No, sqrt(x) is the same as x^0.5.

The problem is that the unit syntax in COMSOL Multiphysics only accepts integer exponents, so there is no unit for "square root of meter," but if this is not what you want, you can de-dimensionalize x using COMSOL unit syntax:

2*(x[1/m])^0.5

does not produce an error.

Magnus Ringh, COMSOL
No, sqrt(x) is the same as x^0.5. The problem is that the unit syntax in COMSOL Multiphysics only accepts integer exponents, so there is no unit for "square root of meter," but if this is not what you want, you can de-dimensionalize x using COMSOL unit syntax: 2*(x[1/m])^0.5 does not produce an error. Magnus Ringh, COMSOL
youf Blue
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Posted: 1 decade ago 2010年10月7日 GMT-4 05:22
Hi,Chris

Thanks for your answer!

The problem still occur when "x^0.5" is instead by "sqrt(x)". However, it disappears when instead by "(x[1/m])^0.5". So Magnus' method is valid. The units is important sometimes in Comsol.

I guess it is only a warning message of unstandard when a expression is in orange. Because the result is not changed when "x^0.5" is instead by "sqrt(x)" or "(x[1/m])^0.5".

youf.
Hi,Chris Thanks for your answer! The problem still occur when "x^0.5" is instead by "sqrt(x)". However, it disappears when instead by "(x[1/m])^0.5". So Magnus' method is valid. The units is important sometimes in Comsol. I guess it is only a warning message of unstandard when a expression is in orange. Because the result is not changed when "x^0.5" is instead by "sqrt(x)" or "(x[1/m])^0.5". youf.
youf Blue
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Posted: 1 decade ago 2010年10月7日 GMT-4 05:26
Hi, Magnus

Thanks for your help very much!

Your method is valid. The units is important sometimes in Comsol.I guess it is only a warning message of unstandard when a expression is in orange. Because the result is not changed when "x^0.5" is instead by "sqrt(x)" or "(x[1/m])^0.5".


youf.
Hi, Magnus Thanks for your help very much! Your method is valid. The units is important sometimes in Comsol.I guess it is only a warning message of unstandard when a expression is in orange. Because the result is not changed when "x^0.5" is instead by "sqrt(x)" or "(x[1/m])^0.5". youf.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 2010年10月7日 GMT-4 05:39
Hi

orange is a warning, it seems that V4.0a has an issue with sqrt and fractional power and how to handle units, probably repaired in V4.1, that I suspect will come out today, isnt it the Boston conf day today ?

--
Good luck
Ivar
Hi orange is a warning, it seems that V4.0a has an issue with sqrt and fractional power and how to handle units, probably repaired in V4.1, that I suspect will come out today, isnt it the Boston conf day today ? -- Good luck Ivar
youf Blue
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Posted: 1 decade ago 2010年10月7日 GMT-4 06:56
Hi, Ivar

Thanks for your answer!

I could not found the help issue in Comsol V4.0a documentation. However, it is not important. At least it has be proved that Comsol can handle these the kinds of trouble automatically now.

Yeah, it is "COMSOL Conference 2010 Boston" today! (www.comsol.com/conference2010/usa/)

I wish Comsol get better and strongger!

youf.
Hi, Ivar Thanks for your answer! I could not found the help issue in Comsol V4.0a documentation. However, it is not important. At least it has be proved that Comsol can handle these the kinds of trouble automatically now. Yeah, it is "COMSOL Conference 2010 Boston" today! (http://www.comsol.com/conference2010/usa/) I wish Comsol get better and strongger! youf.
Prakash Gurudev
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Posted: 1 decade ago 2014年11月24日 GMT-5 11:01
In continuation with this, how would someone enter, x^0.7.
Am not being able to do it following above comments..
In continuation with this, how would someone enter, x^0.7. Am not being able to do it following above comments..

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