Search found 73 matches

by Bill Braun
Fri Jan 02, 2004 9:23 am
Forum: 2004
Topic: Models for Winning Business
Replies: 7
Views: 5654

Models for Winning Business

>1. establishing and maintaining a preferred supplier position >2. developing a relationship of trust with the customer >3. the offering itself >4. price Congratulations on the contract. All of the above impress me as attractiveness multipliers in their own right in which each of their respective co...
by Bill Braun
Sat Nov 29, 2003 2:27 pm
Forum: 2003
Topic: Manufacturing Control Systems
Replies: 30
Views: 32327

Manufacturing Control Systems

9 At 12:10 PM 11/27/2003 -0500, you wrote: >The important thing to me is to have a **single** name that contrasts >with the term "discrete event". Calling that other thing "a series of >discrete events" in one case and a "process" in another case doesnt do >it for me. Yaman, can you find a single na...
by Bill Braun
Sun Nov 23, 2003 9:35 am
Forum: 2003
Topic: What do you mean by the term mental model?
Replies: 5
Views: 8469

What do you mean by the term mental model?

6 At 09:02 AM 11/20/2003 -0500, you wrote: >I would be interested to learn what practitioners of system dynamics mean by >the term mental model. If you refer to a written authority, I would >appreciate learning what your reference source is. Jim, I most commonly refer to information that is filtered...
by Bill Braun
Sun Nov 23, 2003 9:29 am
Forum: 2003
Topic: Discrete Event vs. DiffEq Models
Replies: 4
Views: 7990

Discrete Event vs. DiffEq Models

5 >My discrete event model took a schedule template as input, replicated every >week for as long as the simulation time horizon. Patients would arrive >according to a Poisson process. Tim, Do you mean the patients actually arrive at the clinic according to a Poisson distribution, or their request fo...
by Bill Braun
Wed Jun 11, 2003 5:42 pm
Forum: 2003
Topic: Community Forum
Replies: 10
Views: 10036

Community Forum

The original genesis of Rutgers inquiry stemmed from the desire to search through list archives for past posts. What is the overall demand for such searching capabilities? With what frequency is the demand for such searches real? Have you found this a drawback to this list with enough fequency to th...
by Bill Braun
Wed May 28, 2003 8:34 am
Forum: 2003
Topic: Traffic jams and congestion
Replies: 8
Views: 6541

Traffic jams and congestion

Jim, how would the inventory model play out at an intersection (assume fourway, a crossroads) where the spacing must change in an anticipatory way. For example, in heavy traffic, even though the light is still green, I wait until the car in front of me clears the intersection before entering it (tem...
by Bill Braun
Wed May 21, 2003 8:12 am
Forum: 2003
Topic: Community Forum
Replies: 10
Views: 10036

Community Forum

Web based discussion boards are relatively inexpensive to operate (scripts can be found in a variety of places for free) and may be the only option for people who do not have direct access to a server where list serv software is running. I suspect those factors mostly explain their proliferation. Fo...
by Bill Braun
Fri Apr 25, 2003 7:57 am
Forum: 2003
Topic: Can system dynamics models "learn"
Replies: 46
Views: 15330

Can system dynamics models "learn"

I read and understood the original message to ask if the the model itself could learn (and thus change). With that as a reference point, I asked if a model that learns/changes could lose its problem focus. I think what you describe in your example below, Jim, is the learning that emerges from variou...
by Bill Braun
Fri Feb 21, 2003 5:09 pm
Forum: 2003
Topic: attractivenss multiplier
Replies: 6
Views: 8331

attractivenss multiplier

The best example in practice that I know of is Urban Dynamics, by Jay W. Forrester. It is priceless in its application of the attractiveness multiplier, and quite useful for a host of other reasons as well. A good addition to your library. I consider it a staple in mine. Bill Braun From: Bill Braun ...
by Bill Braun
Wed Jul 17, 2002 9:38 am
Forum: 2002
Topic: Negative Stocks
Replies: 4
Views: 5182

Negative Stocks

I am starting a model of a large watershed. The question has arisen regarding ponds that go dry (inches of water at pond beds low point = 0) and then become parched below the physical pond bed (e.g., the typical cracking of completely dried mud). Rainfall in this case will not instantly add water to...
by Bill Braun
Mon Apr 15, 2002 11:49 am
Forum: 2002
Topic: Modeling Anticipation
Replies: 8
Views: 8635

Modeling Anticipation

Assumption: In an SD model (within the context of a policy) past decisions are "made present" through feedback from stocks. The stocks capture the diffusion of decisions over time. The mess that results is the accumulation of the effects of a stream of decisions, i.e., iterations of Decision > Flow ...
by Bill Braun
Sun Mar 10, 2002 9:00 am
Forum: 2002
Topic: System Dynamics Society Membership
Replies: 9
Views: 5611

System Dynamics Society Membership

Arguing For: This could be done quite easily and as a matter of Society policy. Populate the list membership from the Society membership and be done with it. The argument may have merit though I question whether it is here (on the list) that it should be explored. Arguing Against: Delays. Different ...
by Bill Braun
Mon Dec 10, 2001 8:09 am
Forum: 2001
Topic: A causes B
Replies: 14
Views: 17776

A causes B

I have no training in physics, just an avid interest, reading as much as I can. My (untrained) understanding is that at the particle level there is a tremendous amount of interdependent, interactive causal influence going on, but none of it is "simple" cause and effect (of the A causes B variety). T...
by Bill Braun
Sun Dec 09, 2001 9:17 am
Forum: 2001
Topic: Text Based SD software
Replies: 15
Views: 12792

Text Based SD software

As Geoff guessed, when one drops an SD object on the desktop using Powersim, it is an "empty vessel". In fact, right at creation time the object contains a question mark to indicate that it does not contain an equation. Further, the model cannot be run with any object that has a question mark (i.e.,...
by Bill Braun
Tue Nov 20, 2001 9:01 am
Forum: 2001
Topic: Attractiveness Multiplier, who cares?
Replies: 1
Views: 6588

Attractiveness Multiplier, who cares?

At 02:50 PM 11/19/2001 -0000, Richard Stevenson wrote, in part: >You may formulate variables like attractiveness in different ways, the >ultimate validity test being that it makes sense to the manager who is going I work with physicians routinely. They have a very healthy respect for data and eviden...
by Bill Braun
Tue Nov 20, 2001 8:48 am
Forum: 2001
Topic: A causes B
Replies: 14
Views: 17776

A causes B

If A (and only A) does indeed cause B, then every time B occurs, A will be present or will have occurred sometime prior. The longer the delay between A and B, the more tenuous the causal link. There may also be other contributing or non-obvious links. Fire [A] causes Heat . Fire [A] also heats Stone...
by Bill Braun
Fri Nov 09, 2001 8:51 am
Forum: 2001
Topic: Attractiveness Multiplier
Replies: 12
Views: 21760

Attractiveness Multiplier

For the attractiveness multiplier, are the following valid equations? If there are three variables that determine overall attractiveness, V[1], V[2], and V[3], the attractiveness multiplier equation is V[1] * V[2] * V[3]. Similarly, ten variables would be V[1] * V[2] *...* V[10]. With three variable...
by Bill Braun
Thu Nov 01, 2001 8:08 am
Forum: 2001
Topic: Attractiveness Multiplier
Replies: 12
Views: 21760

Attractiveness Multiplier

There have been a number of comments about Urban Dynamics (e.g., Sterman, SD3408) and the debated merits and flaws of the model. Is the use of multipliers (UD, Productivity Press, pp. 23-25) still considered a valid approach to represent the dynamics of attractiveness (actual and, with delays, perce...
by Bill Braun
Mon Sep 17, 2001 4:04 pm
Forum: 2001
Topic: Evaluating an organizations structure
Replies: 1
Views: 11920

Evaluating an organizations structure

If you are looking for resources in addition to SD models, I recommend Richard Dafts book, Organization Theory and Design. It contains a number of models that rely on dependent and independent variables and which are largely oriented to fitting the organization to its external environment as well as...
by Bill Braun
Tue Jul 24, 2001 8:26 am
Forum: 2001
Topic: Human Behavior in System Dynamics Models
Replies: 9
Views: 5934

Human Behavior in System Dynamics Models

Jacks request for example models prompts me to wonder if weve lost the notion of boundaries. If we are attempting to model the deep roots of human feeling and emotion in the belief that they are the ultimate drivers of behavior, it would seem to be a good time to propose we construct a model of ever...
by Bill Braun
Mon Jun 04, 2001 7:58 am
Forum: 2001
Topic: ST & SD in real life
Replies: 13
Views: 6731

ST & SD in real life

At 10:08 AM 6/1/01 -0400, Jim Hines wrote, in part: >A more promising route, suggested a few years ago by David Andersen, might >be to certify educational programs, rather than individuals. This seems >MUCH easier to me, and might accomplish 70% or more of the objectives. I concur at the same time I...
by Bill Braun
Wed May 23, 2001 7:52 am
Forum: 2001
Topic: Models of Medical Risk / Misadventure
Replies: 3
Views: 5138

Models of Medical Risk / Misadventure

While not directly SD related, the November, 1998 (Volume 76) issue of the Milbank Quarterly had a number of articles on quality. The articles are written by some of the authors of the Institute of Medicine report, although I believe this volume predates the IOMs report. Bill Braun From: Bill Braun ...
by Bill Braun
Tue May 08, 2001 7:25 am
Forum: 2001
Topic: Discrete Event Simulation (DES) and System Dynamics
Replies: 1
Views: 4545

Discrete Event Simulation (DES) and System Dynamics

I offered to post Goeffs paper on my page at school so anyone could
retrieve it direct. If anyone else wants to make a document available this
way send it to me and Ill add it to the page.

The page is at http://www.bw.edu/~wbraun/sysdyn

Bill Braun
From: Bill Braun <medprac@hlthsys.com>
by Bill Braun
Tue May 01, 2001 8:06 am
Forum: 2001
Topic: Fast demonstrations of complex behaviour
Replies: 14
Views: 11768

Fast demonstrations of complex behaviour

At 10:33 AM 4/30/01 -0400, George Richardson wrote: >Is that the "IT" people are supposed to get from this exercise? And >if thats it, then what do we do with it? Perhaps the value varies with the experience and knowledge of the people engaged in the exercise. I have not tried this exercise yet but ...
by Bill Braun
Tue Apr 10, 2001 8:39 am
Forum: 2001
Topic: Fast Demonstration of Complex Behavior
Replies: 6
Views: 17316

Fast Demonstration of Complex Behavior

The group exercise aimed at positioning everyone to be equidistant from two other people in a group is reminiscent of the "boids" program. The hypothesis of the program was that cohesion in flocks could be explained by three rules: 1) match speed with birds in your neighborhood, 2) maintain equal di...