[Date Index] [Thread Index] [Author Index]

Re: Substitutions

• To: mathgroup at smc.vnet.net
• Subject: [mg77896] Re: Substitutions
• From: "Shahriar Khushrushahi" <shahriar at mit.edu>
• Date: Tue, 19 Jun 2007 06:40:13 -0400 (EDT)
• References: <1181833391.078257.209380@x35g2000prf.googlegroups.com>

Hi

>
>  Ive had this problem come up quite often and I was wondering if
>  someone could help me. I have expressions that are quite complex and
>  what I would like to do is define a new non-dimensional parameter that
>  would have many of the variables of the expression clumped in it and
>  that would reduce the complexity of my expression. I have used /. but
>  Ive realized that unless what I want to replace is of the exact
>  fractional form it wont substitute.
>
>  This is my problem


http://mit.edu/shahriar/Public/1.bmp


>  and say I want to rewrite this equation using new non-dimensional
> parameters such


http://mit.edu/shahriar/Public/2.bmp

 Another example of this is I have an equation (
> http://mit.edu/shahriar/Public/3.bmp ) and I want to replace Bx/ì0 with a
> new variable say B_x Mathematica wont do it unless it is exactly like the
> form Bx/ì0 so a rule like Bx/ì0 ->B_x is useless in dealing with this.




 If someone would help, i would be very grateful. Thanks
>
>