Search found 63 matches

by "Jay W. Forrester"
Mon Dec 01, 2003 7:34 pm
Forum: SD Mailing List Archive
Topic: Discrete vs. continuous (or aggregated) representation
Replies: 1
Views: 7008

Discrete vs. continuous (or aggregated) representation

It seems to me that much of the discussion of discrete vs. continuous (or perhaps described as aggregated) representation in a model has been carried on in the abstract without defining the essential context and purpose of the representation. Regarding whether or not detailed information must accomp...
by "Jay W. Forrester"
Tue Nov 18, 2003 7:31 pm
Forum: SD Mailing List Archive
Topic: Urban dynamics follow through
Replies: 2
Views: 4001

Urban dynamics follow through

In message (SD4480) Peter Sanders gave obsolete publisher information for the following books that are now available from Pegasus Communications, Waltham, MA, USA. >2) Alfeld, Louis E., and Alan K. Graham. 1976. Introduction to Urban Dynamics. > >3) Forrester, Jay W. 1969. Urban Dynamics. > >5) Grah...
by "Jay W. Forrester"
Fri Nov 14, 2003 10:12 am
Forum: SD Mailing List Archive
Topic: Manufacturing Control Systems
Replies: 30
Views: 51642

Manufacturing Control Systems

Perhaps the information below will be useful. Information on System Dynamics Jay W. Forrester Information revised October 6, 2001 System Dynamics Bibliography: To order the system dynamics bibliography of over 4100 entries, specify IBM type PC, or Macintosh Send $35 in US$ drawn on a US bank to: Sys...
by "Jay W. Forrester"
Tue Sep 16, 2003 10:20 am
Forum: SD Mailing List Archive
Topic: Sustainability of Transport
Replies: 1
Views: 3257

Sustainability of Transport

Perhaps the information below will be useful. Information on System Dynamics Jay W. Forrester Information revised October 6, 2001 System Dynamics Bibliography: To order the system dynamics bibliography of over 4100 entries, specify IBM type PC, or Macintosh Send $35 in US$ drawn on a US bank to: Sys...
by "Jay W. Forrester"
Sun Sep 08, 2002 3:50 pm
Forum: SD Mailing List Archive
Topic: Using Systems Thinking to Teach Basic Math
Replies: 6
Views: 7689

Using Systems Thinking to Teach Basic Math

You should obtain: Fisher, D. M. (2001). Lessons in High School Mathematics: A Dynamic Approach. Hanover, NH, High Performance Systems, Inc. From a system dynamics viewpoint, Fisher treats Algebra I, Algebra II, Pre-calculus, and Calculus. -- ---------------------------------------------------------...
by "Jay W. Forrester"
Mon Aug 05, 2002 10:24 am
Forum: SD Mailing List Archive
Topic: Barry Richmond
Replies: 0
Views: 3120

Barry Richmond

Unfortunate news to all: Yesterday, Sunday, August 4, I received a sad and distressing phone call from Nancy Maville, vice president of High Performance. She said that Barry Richmond suffered a heart attack and did not survive. I assume it was Saturday. She said he had gone running with his daughter...
by "Jay W. Forrester"
Wed Jul 17, 2002 9:14 pm
Forum: SD Mailing List Archive
Topic: Differential equations
Replies: 25
Views: 39542

Differential equations

Several writers have recently implied that differential equations are a more fundamentally correct way of representing dynamic systems than the integrations in a system dynamics formulation. As examples, Christopher Barker wrote: > Standard SD approaches use stock formulae that attempt to >approxima...
by "Jay W. Forrester"
Tue Apr 16, 2002 9:55 pm
Forum: SD Mailing List Archive
Topic: Modeling Anticipation
Replies: 8
Views: 14073

Modeling Anticipation

Bill Braun asks how forecasts of he future can be incorporated in a model: >Can forecasts of the future be dynamically modeled, with information from >stocks (that represent a future state) feeding back into current decisions? > On must start by realizing that there is no information truly coming to...
by "Jay W. Forrester"
Sun Mar 17, 2002 9:05 pm
Forum: SD Mailing List Archive
Topic: SD Models from Written Text???
Replies: 2
Views: 3172

SD Models from Written Text???

There has been an interesting discussion exchange on formal methods to derive models from written text. The effort is probably worth pursuing for the insights it will yield about process. However, in any rather complicated modeling project, only a very minor fraction of the relevant information is t...
by "Jay W. Forrester"
Fri Mar 15, 2002 8:34 pm
Forum: SD Mailing List Archive
Topic: On information quality and appropriateness
Replies: 3
Views: 7661

On information quality and appropriateness

On June 23, 2001, in (SD2234), Elaine Lovitt asked about modeling the "effects of data quality on the work we perform.... if any work has been done on value of information or data quality modelling" I regret being so late in responding. There are two issues here--first, the appropriateness...
by "Jay W. Forrester"
Thu Nov 22, 2001 9:46 am
Forum: SD Mailing List Archive
Topic: models for urban systems
Replies: 2
Views: 7062

models for urban systems

The information below may be useful. =============================================== =============================================== Information on System Dynamics Jay W. Forrester Information revised October 6, 2001 System Dynamics Bibliography: To order the system dynamics bibliography of over 410...
by "Jay W. Forrester"
Sat Nov 17, 2001 10:14 am
Forum: SD Mailing List Archive
Topic: Attractiveness Multiplier, does it matter?
Replies: 0
Views: 5460

Attractiveness Multiplier, does it matter?

George Richardson wrote, regarding the formulation of multipliers in "Urban Dynamics." >My bet would be the more multipliers in the formulation, the LESS >volatile it (the value of the product) becomes. There would be >myriad feedback effects that would actively compensate for extreme >val...
by "Jay W. Forrester"
Sat Nov 10, 2001 8:14 pm
Forum: SD Mailing List Archive
Topic: Attractiveness Multiplier
Replies: 12
Views: 32670

Attractiveness Multiplier

In Attractiveness Multiplier (SD3448), Bill Braun wrote: >With three variables, if each produces a value of 0.9 (through their >respective table functions), overall attractiveness is 0.729. ...... >This suggests that the greater the >number of variables determining attractiveness, the more "con...
by "Jay W. Forrester"
Mon Oct 15, 2001 8:48 pm
Forum: SD Mailing List Archive
Topic: Is it possible to omit soft variables?
Replies: 8
Views: 16650

Is it possible to omit soft variables?

At various times in this discussion forum, people have suggested that one should not include in models soft variables that lack quantitatively measured values. I suggest that such omission of soft variables is not possible. If one "omits" a variable, it has a very specific assumed value in...
by "Jay W. Forrester"
Fri Aug 10, 2001 9:51 am
Forum: SD Mailing List Archive
Topic: Inventory Management System
Replies: 1
Views: 3805

Inventory Management System

You do not indicate how much study and experience that you have had with system dynamics. However, perhaps the material below will be useful. If you have not already studied it carefully, I suggest that you start with my "Industrial Dynamics" book that is available as given below; especial...
by "Jay W. Forrester"
Wed Aug 01, 2001 9:43 pm
Forum: SD Mailing List Archive
Topic: Thoughts for future conferences
Replies: 5
Views: 5738

Thoughts for future conferences

I agree with George Richardson when when he wrote: >I am convinced we are strongest when we realize we are four or five >constituencies which need each other: academics, consultants, >practitioners in public and private sector employ, and k-12 >teachers. Each group grows in numbers and sophisticatio...
by "Jay W. Forrester"
Wed Jul 18, 2001 9:08 pm
Forum: SD Mailing List Archive
Topic: Human Behavior in System Dynamics Models
Replies: 9
Views: 11101

Human Behavior in System Dynamics Models

Are there any management or social system models that do not at least implicitly include human behavior? "Jack Ring" <jring@amug.org> in SD3313 wrote >Although the Sterman model to which you refer is quite interesting it is >largely an economics model and includes no obvious variables for ...
by "Jay W. Forrester"
Wed Jul 18, 2001 10:11 am
Forum: SD Mailing List Archive
Topic: The order of a system
Replies: 16
Views: 10656

The order of a system

I believe that the "order" of a system is determined by the number of integrations (stocks or levels). An exponential decay or growth system with one stock is a first order system. The system with two stocks in a single loop, which generates a sine wave, is a second order system. The order...
by "Jay W. Forrester"
Tue May 29, 2001 2:45 pm
Forum: SD Mailing List Archive
Topic: ST & SD in real life
Replies: 13
Views: 13143

ST & SD in real life

In (SD3256), Eric Melse wrote: > >Is ST/SD a product that can be sold/implemented/used by business people >for make (operational?) decisions? > Such comments, which have run through much of this discussion about using system dynamics, focuses on decisions and seems to miss the real power of system d...
by "Jay W. Forrester"
Tue Mar 20, 2001 10:41 am
Forum: SD Mailing List Archive
Topic: Scaling Up & Modelling Human Decision-Making
Replies: 1
Views: 2913

Scaling Up & Modelling Human Decision-Making

The information below may be useful. =============================================== =============================================== Information on System Dynamics Jay W. Forrester Information revised March 18, 2001 System Dynamics Bibliography: To order the system dynamics bibliography of over 4100...
by "Jay W. Forrester"
Sun Feb 18, 2001 11:48 am
Forum: SD Mailing List Archive
Topic: The time scale regarding when to use system dynamics
Replies: 8
Views: 6459

The time scale regarding when to use system dynamics

Two recent communications on this email list have suggested that system dynamics is useful when the time scale of interest in months or years, but that discrete simulation should be used if the time scale of interest is in the range of hours or days. I believe that the time scale of interest is not ...
by "Jay W. Forrester"
Tue Jan 02, 2001 10:59 am
Forum: SD Mailing List Archive
Topic: Diabetics SD models
Replies: 3
Views: 12455

Diabetics SD models

Jack Fisher wrote: >I am interested in reviewing any models that refer to the regulation of >blood-sugar in normal and diabetic conditions. The following may be useful: Foster, R. O. (1970). The Dynamics of Blood-Sugar Regulation, M. I. T. M.Sc. Thesis, Electrical Engineering department, For a repro...
by "Jay W. Forrester"
Sun Dec 03, 2000 1:58 pm
Forum: SD Mailing List Archive
Topic: Sampling Theory -
Replies: 0
Views: 5374

Sampling Theory -

>Im currently modeling organisational behaviour and Im looking for the >connection of sampling time (delta T) and systems stability. >What is the impact of increasing delta T on the systems stability. Im >using Routh Stability test but Im afraid it would not work in my case >because my delta T can b...
by "Jay W. Forrester"
Wed Nov 29, 2000 3:53 pm
Forum: SD Mailing List Archive
Topic: Building your own models
Replies: 18
Views: 60245

Building your own models

>... (there is an article by JF somewhere to >the effect "Counter Intuitive Behavior of social systems" in this regard). I >agree. The Counterintuitive paper is available at: http://sysdyn.mit.edu oad-maps m-toc.html --------------------------------------------------------- Jay W. Forreste...
by "Jay W. Forrester"
Fri Sep 22, 2000 3:40 pm
Forum: SD Mailing List Archive
Topic: Limitations of SD!
Replies: 2
Views: 6763

Limitations of SD!

Perhaps the information below will be useful. =============================================== =============================================== Information on System Dynamics Jay W. Forrester August 25, 1999 System Dynamics Bibliography: To order the system dynamics bibliography of over 4100 entries, ...