Re: Engineering requests

*To*: mathgroup at smc.vnet.net*Subject*: [mg125265] Re: Engineering requests*From*: danl at wolfram.com*Date*: Sat, 3 Mar 2012 06:52:54 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <jiqflj$3o$1@smc.vnet.net>

On Friday, March 2, 2012 6:49:55 AM UTC-6, McHale, Paul wrote: > So, here are some problems we face, but don't have great answers for in Mathematica. > > 1. Dimensional analysis. To do this, we must have unit support. The best description of this is the ability to calculate (V/R)^2 R and have it return a unit of watts. Other programs handily support this (though they are sorely lacking in other places :)) Probably not exactly what you want, but you might have a look here. http://library.wolfram.com/infocenter/Conferences/7513/ In[40]:= minimalUnits[(v/o)^2*o] Out[40]= {Watts} > 2. Tolerances support. One difficulty we have is determining the min/max at a certain point in a circuit even if the circuit is not complicated to model. I use lists {Rmax,Rmin} and Table. Works, but is a little clumsy. > [...] Have you tried using Interval[...] to specify value ranges? For basic arithmetic this should offer some possibilities. If you are computing, say, solutions to differential equations with toleranced input values, that will be more of a challenge. In effect what one wants is some sensitivity analysis. Can be done (using NDSolve), but is not so simple. That is to say, I do not recall the details of the setup. Daniel Lichtblau Wolfram Research

**Follow-Ups**:**Re: Engineering requests***From:*"McHale, Paul" <Paul.McHale@excelitas.com>