Search found 15 matches
- Wed Dec 15, 2004 7:43 pm
- Forum: SD Mailing List Archive
- Topic: Fuzzy logic, SD, and Business Policies
- Replies: 3
- Views: 8961
Fuzzy logic, SD, and Business Policies
A fuzzy relation between two variables can be de-fuzzified to make a LOOKUP function Vensim (formerly TABLE function in DYNAMO) and a LOOKUP function can represent a fuzzy relation between two variables. The whole argument rests on a representation theorem for fuzzy relations that says, essentially,...
- Tue Nov 09, 2004 4:07 pm
- Forum: SD Mailing List Archive
- Topic: The study of hurricanes
- Replies: 8
- Views: 11698
The study of hurricanes
In reply to George Simpson's REPLY: A large model is anything but transparent. I was not thinking of using a neural network to replace an SD model. I just thought that the parameters of the network model might say something about where the important loops are i.e. the loops that dominate a certain b...
- Sun Nov 07, 2004 3:24 pm
- Forum: SD Mailing List Archive
- Topic: The study of hurricanes
- Replies: 8
- Views: 11698
The study of hurricanes
Perhaps the question we should be asking ourselves on this list is whether a neural network model of an SD model could tell us something about the important causes of the model's behaviour, and if so, is it more efficient to use a neural network instead of the dominant-loop or dominant-mode approach...
- Sun Nov 07, 2004 3:18 pm
- Forum: SD Mailing List Archive
- Topic: The study of hurricanes
- Replies: 8
- Views: 11698
The study of hurricanes
Wolfram's approach exploits the properties of cellular automata first made famous (early 70s) by Conway's Game of Life in which local rules for creating/destroying cells give rise to intriguing patterns on a monitor when the cells are represented as pixels that are lit or dark according to the state...
- Thu Oct 28, 2004 11:55 am
- Forum: SD Mailing List Archive
- Topic: SD vs System Design Engineering
- Replies: 2
- Views: 7144
SD vs System Design Engineering
At a presentation of the SD approach to resource management (human,
equipment, financial resources), someone asked how SD compares with
System Design Engineering. Any enlightenment from this list would be
welcome. Thanks
Joel Rahn
jrahn@sympatico.ca
equipment, financial resources), someone asked how SD compares with
System Design Engineering. Any enlightenment from this list would be
welcome. Thanks
Joel Rahn
jrahn@sympatico.ca
- Mon Oct 18, 2004 12:36 pm
- Forum: SD Mailing List Archive
- Topic: Dynamical Systems and System Dynamics ??
- Replies: 12
- Views: 19238
Dynamical Systems and System Dynamics ??
I hesitate to stir up this sort of hornet's nest but field theories (electro-magnetic, acoustic,...) do not use material stocks and flows and they can represent such phenomena as the Doppler effect. However quantized versions (photons, phonons,...) use flows and densities (i.e. numbers per unit volu...
- Fri Jun 11, 2004 10:15 pm
- Forum: SD Mailing List Archive
- Topic: AnyLogic Software
- Replies: 7
- Views: 9697
AnyLogic Software
Gord Kubanek (and I to a lesser extent) is looking at Anylogic as an
alternative to SD for HR problems. Should have something to say in about
a month.
Joel Rahn
jrahn@sympatico.ca
alternative to SD for HR problems. Should have something to say in about
a month.
Joel Rahn
jrahn@sympatico.ca
- Tue Feb 03, 2004 11:39 am
- Forum: SD Mailing List Archive
- Topic: Using Statistics in Dynamics Models
- Replies: 28
- Views: 21039
Using Statistics in Dynamics Models
Jim Hines wrote: >J.J. Laubles is extremely clear (and concise!) in providing the principle >that must guide much (but maybe not all?) statistical testing: If you can >prove A implies B with only a 5% chance of error. And, if you can prove that >B is not true, then youve proved that A is not true wi...
- Thu Jan 29, 2004 8:23 am
- Forum: SD Mailing List Archive
- Topic: Using Statistics in Dynamics Models
- Replies: 28
- Views: 21039
Using Statistics in Dynamics Models
John Sterman wrote: > My good friend Jim Hines "question[s] whether statistical estimates > have any rational claim on our attention other than widespread use and > anecdotal evidence of usefulness." Jim wants rigorous demonstrations > of the value of statistical reasoning and estimation m...
- Tue Dec 02, 2003 1:53 pm
- Forum: SD Mailing List Archive
- Topic: Manufacturing Control Systems
- Replies: 30
- Views: 52290
Manufacturing Control Systems
Jim Hines wrote: >Ray says " Lets make sure we are talking about the same thing. " > >So just to be clear, were talking about two separate dimensions of a >model: A time dimension and an event dimension. Time can be either >discrete or continuous. Events can either be discrete or [insert a...
- Tue Dec 02, 2003 12:55 pm
- Forum: SD Mailing List Archive
- Topic: Manufacturing Control Systems
- Replies: 30
- Views: 52290
Manufacturing Control Systems
Now that I know what we are talking about, and inspired by Jims diagrams, I suggested that "repeated event" describes Jims "extended event" when it occurs in discrete time and "interval event" describes a Hinesian "extended event" in continuous time. Sorry it ...
- Sat May 10, 2003 10:34 am
- Forum: SD Mailing List Archive
- Topic: Number of replications
- Replies: 5
- Views: 5178
Number of replications
You are dealing with confidence intervals. A good simulation text like Law & Kelton will give you an answer with the usual caveats about using such intervals. A quick answer is: no. of replications = Variance* (z(alpha/2)/half-interval of confidence)^2 where: z(alpha/2) is the appropriate Normal...
- Tue May 06, 2003 11:54 am
- Forum: SD Mailing List Archive
- Topic: SD Models applied to logistics
- Replies: 3
- Views: 4013
SD Models applied to logistics
This seems to be a model about recycling. If so, the classic reference is Jorgen Randers chapter in Dynamics of Growth in a Finite World. Another source of inspiration may be an issue of Interfaces published by The ORMS Society (or INFORMS as it is now) in 2001 I believe. There was an article about ...
- Tue May 06, 2003 11:34 am
- Forum: SD Mailing List Archive
- Topic: Model to link engineering, markets, finance
- Replies: 1
- Views: 2392
Model to link engineering, markets, finance
The classic reference, as many will no doubt reply, is Jim Lyneis book: Lyneis, J. M., Corporate Planning and Policy Design, MIT Press, 1980. Check with Pegasus Communications for current availability. Jims book does not deal in _great_ detail with the engineering/operations sector but it has the es...
- Tue Apr 29, 2003 3:20 pm
- Forum: SD Mailing List Archive
- Topic: Work on the Spread of SARS
- Replies: 2
- Views: 3162
Work on the Spread of SARS
A short answer to Daniel Janoschs question is: The SARS epidemic is worthy of caution but not yet panic. Media hysteria has not been abated by the way public health authorities have handled the ever-changing information about the disease and its spread. From my vantage point here in Quebec City, I w...