Substitutions

*To*: mathgroup at smc.vnet.net*Subject*: [mg77898] Substitutions*From*: SK <skhushrushahi at gmail.com>*Date*: Tue, 19 Jun 2007 06:41:15 -0400 (EDT)

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/=CE=BC0 with a new variable say B_x Mathematica wont do it unless it is exactly like the form Bx/=CE=BC0 so a rule like Bx/=CE=BC0 ->B_x is useless in dealing with = this. If someone would help, i would be very grateful. Thanks