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Conference rusure::math

Title:Mathematics at DEC
Moderator:RUSURE::EDP
Created:Mon Feb 03 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2083
Total number of notes:14613

978.0. "Inverse Laplace Transforms" by AUSSIE::BENHAM (Lewis, CSS Engineering, Australia) Wed Nov 23 1988 18:15

	I have a Laplace transform problem which is a bit tricky.
	There are two possible approaches. Perhaps there might be some
	suggestions forthcoming as to how this particular problem can be
	solved.

	I would like to know if there is an inverse Laplace tranform of
	either of the following two general functions.

	         -1
       		L   {  f(g(s))  }  =  ???


	         -1 {		� }
       		L   {   a [f(s)]  }  =  ???
		    {  e          }

	Thanks,
	Lewis.

T.RTitleUserPersonal
Name
DateLines
978.1don't know of anyAITG::DERAMODaniel V. {AITG,ZFC}:: D'EramoSun Dec 04 1988 12:349
     I assume you want the results expressed in terms of
      -1              -1
     L  { f(s) } and L  { g(s) }.  I don't recall any such
     general formula for Laplace transforms and doubt that one
     exists.  I only vaguely recall a connection between
     multiplying by x on one side and differentiating on the
     other.
     
     Dan
978.2Try a different tackAUSSIE::BENHAMLewis, CSS NSG-S EngineeringMon Dec 12 1988 17:4229
	OK, seems like no go on those ones in .0. Let's try a different
	approach. How about the following.

						�
		       [                       ]         �
		f(s) = [ ( a + bs ) ( c + ds ) ]  =  g( s  )
                       [                       ]

		Find g(s) ?


	Also I have managed to find a couple of Laplace tranform tables.
	One result in particular is:

                {     � }
                {  -as  }
	     -1	{ e     }        (  a  )
	    L	{ ----- } =  erfc(-----)
		{   s   }        (   � )
				 ( 2t  )

                                        
	Could anyone provide a proof of this result and thus in combination
	with the result for the top expression, find a solution to my problem.

	Thanks,
	Lewis.