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MathGroup Archive 2005

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Reduce bug report

  • To: mathgroup at smc.vnet.net
  • Subject: [mg56273] Reduce bug report
  • From: Chris Chiasson <chris.chiasson at gmail.com>
  • Date: Wed, 20 Apr 2005 05:32:48 -0400 (EDT)
  • Reply-to: Chris Chiasson <chris.chiasson at gmail.com>
  • Sender: owner-wri-mathgroup at wolfram.com

I am sending this to MathGroup first in the hope that I am wrong.

In the code below, I give two sets of equations. On Mathematica 5.0
for Windows, the Reduce command does not finish evaluation if Most@ is
removed from the second equation set.

I have done my best to make sure the problem is well posed by making
sure there are exactly as many equations as unknowns (less unit
variables) and by telling Mathematica that all units are nonzero.

Reduce can easily handle it if the last equation of the "defining
equations" (prob2[defineqns]) is separate system from the rest of the
equations, but this should be unnecessary.

I realize that it is possible I have made a mistake in posing the
problem to Mathematica; if so, please enlighten me.

prob2[given]={\[ScriptCapitalN][3600]\[Equal](3600*Circle)/Minute,
    BT[max,3600]\[Equal](236*Meter*Newton)/Radian,\[ScriptCapitalN][
        5500]\[Equal](5500*Circle)/Minute,BP[max,5500]\[Equal]100*Kilo*Watt,
    z\[Equal](2*Circle)/Cycle,Vd\[Equal]3*Liter,\[Eta][mech]\[Equal]9/10,
    sfc\[Equal](9*Kilogram)/(100*Joule*Mega),
    LHV\[Equal](44*Joule*Mega)/Kilogram,CR\[Equal]89/10,k\[Equal]7/5}

prob2[defineqns]=
  Most@{BP[max,3600]\[Equal]BT[max,3600]*\[ScriptCapitalN][3600],
      BP[max,5500]\[Equal]BT[max,5500]*\[ScriptCapitalN][5500],
      BMEP[max,3600]\[Equal](2*Pi*Radian*z*BT[max,3600])/(Circle*Vd),
      BMEP[max,3600]/IMEP[max,3600]\[Equal]\[Eta][mech],
      BMEP[max,5500]\[Equal](2*Pi*Radian*z*BT[max,5500])/(Circle*Vd),
      BMEP[max,5500]/IMEP[max,5500]\[Equal]\[Eta][mech],\[Eta][
          ind]\[Equal]1/(LHV*sfc),\[Eta][otto]\[Equal]1-(CR^(-1))^(-1+k)}

prob2[units]={Circle,Cycle,Joule,Kilo,Kilogram,Liter,Mega,Meter,Minute,Newton,
    Radian,Watt}

prob2[redvars]={CR,k,LHV,sfc,Vd,z,BMEP[max,3600],BMEP[max,5500],BP[max,3600],
    BP[max,5500],BT[max,3600],BT[max,5500],IMEP[max,3600],
    IMEP[max,5500],\[ScriptCapitalN][3600],\[ScriptCapitalN][5500],\[Eta][
      ind],\[Eta][mech],\[Eta][otto]}

prob2[numsoln]=
  Refine[Reduce[Flatten@{prob2[given],prob2[defineqns]},prob2[redvars],
      Backsubstitution->True],#!=0&/@prob2[units]]

Regards,
-- 
Chris Chiasson
Kettering University
Mechanical Engineering
Graduate Student
1 810 265 3161


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