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christriddle@googlemail.c science forum beginner
Joined: 10 Jul 2006
Posts: 12

Posted: Thu Jul 13, 2006 8:42 am Post subject:
Logistic timestep problem



Hi,
First of all I'm not sure if this belongs here, if not, could you
suggest a more appropriate group.
I'm having some problems researching the possibility of explicit
solutions to military logistics problems.
Although, I think the actual problem is more general. I have a
timestep simulation tool that simulates strategiclift (aircraft,
ships, etc...) moving "stuff" from a start port to an end port.
Obviously aircraft make many flights back and forth.
While a timestep simulation suits this problem, it is quite expensive
in time.
The question I need answering is whether there exists an explicit
solution to such a problem. I'm pretty sure it's not linear, and
perhaps chaotic behaviour prevents such a solution.
By the way, when I say solution I mean things like finding:
a) How long it takes to move everything with various amounts of
startlift, port infrastructure (#berths, #AC handlers, etc...) and so
on;
b) The optimum number of the above to produce the quickest time; etc...
I would be very grateful if you could point me in a direction to find
if such a thing is possible and if so, whether the complexity of such a
solution would make it impractical.
Many many thanks. Sorry the question is so long (and most probably
confusing!)
Chris Riddle 

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Peter Spellucci science forum Guru
Joined: 29 Apr 2005
Posts: 702

Posted: Thu Jul 13, 2006 11:19 am Post subject:
Re: Logistic timestep problem



In article <1152780168.218894.94870@m79g2000cwm.googlegroups.com>,
christriddle@googlemail.com writes:
Quote:  Hi,
First of all I'm not sure if this belongs here, if not, could you
suggest a more appropriate group.
I'm having some problems researching the possibility of explicit
solutions to military logistics problems.
Although, I think the actual problem is more general. I have a
timestep simulation tool that simulates strategiclift (aircraft,
ships, etc...) moving "stuff" from a start port to an end port.
Obviously aircraft make many flights back and forth.
While a timestep simulation suits this problem, it is quite expensive
in time.
The question I need answering is whether there exists an explicit
solution to such a problem. I'm pretty sure it's not linear, and
perhaps chaotic behaviour prevents such a solution.
By the way, when I say solution I mean things like finding:
a) How long it takes to move everything with various amounts of
startlift, port infrastructure (#berths, #AC handlers, etc...) and so
on;
b) The optimum number of the above to produce the quickest time; etc...
I would be very grateful if you could point me in a direction to find
if such a thing is possible and if so, whether the complexity of such a
solution would make it impractical.
Many many thanks. Sorry the question is so long (and most probably
confusing!)
Chris Riddle

with all the side considerations you mention, this is a mixed problem with
integer (#...) variables nad continuous variables, nonlinear and hence
there is no hope for an analytical solution. the problem generally fits
into "optimal control". especially minimum time otpimal control,
and even a simple looking problem like
minimal time take up and capture in two aircrafts combat
results in a hard mathematical
problem.
transportation problems with no time constraints on the other side can be solved
routinely, but also not via closed formulae
hth
peter 

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