Search found 73 matches

by Bill Braun
Fri Feb 23, 2001 7:41 am
Forum: SD Mailing List Archive
Topic: The time scale regarding when to use system dynamics
Replies: 8
Views: 6461

The time scale regarding when to use system dynamics

In our desire to extend the utility of SD is it possible we are trying to combine the hammer, the saw and the screwdriver into a single tool? When the tool is finally designed, will it be so cumbersome that it wont be used for much of anything? If analysis and synthesis are different ways of viewing...
by Bill Braun
Tue Jan 30, 2001 8:26 am
Forum: SD Mailing List Archive
Topic: Military Human Resources
Replies: 2
Views: 3417

Military Human Resources

The Air National Guard in St. Louis constructed a model several years ago that addressed retention in the Guard. It may be helpful. I cannot find the name of the contact person, although at the time he was a member of this list. [Hosts note: I looked into this a little and it was Robert Glitz who po...
by Bill Braun
Tue Nov 14, 2000 7:56 am
Forum: SD Mailing List Archive
Topic: Building your own models
Replies: 18
Views: 60253

Building your own models

At 10:48 AM 11/13/00 -0500, Jim Hines wrote: >I like your comment about the desirability of building your own model. What >do you (and others) make of the many queries in this list asking for models >on this or that topic? They may not be seeking them just to cannibalize. They are also a wonderful w...
by Bill Braun
Thu Nov 09, 2000 7:47 am
Forum: SD Mailing List Archive
Topic: Delays in SD modeling!!
Replies: 15
Views: 54853

Delays in SD modeling!!

A pipeline delay (infinite order material delay) might be what you are
looking for if you are modeling specific, time defined stages that people
go through (such as a training period before any productivity starts).

Bill Braun
From: Bill Braun <medprac@hlthsys.com>
by Bill Braun
Wed Sep 20, 2000 6:00 pm
Forum: SD Mailing List Archive
Topic: Translation of Urban Dynamics Model
Replies: 0
Views: 5572

Translation of Urban Dynamics Model

Ive "translated" Jay Forresters Urban Dynamics model (Appendix A from Urban Dynamics) into Powersim. The output of the model is close to the tables in Chapter 3 (Growth and Stagnation, which I have taken to be outputs from the baseline model). However, the output values are not exact. I su...
by Bill Braun
Tue Jul 25, 2000 10:12 am
Forum: SD Mailing List Archive
Topic: Tracking purchase prices on past transactions
Replies: 6
Views: 10124

Tracking purchase prices on past transactions

Hi Bill, This may be a wild leap, completely untested nor very well thought out for that matter. In Powersim there is a sample population molecule that accounts for age (young, middle, old, etc.) buckets and region (north and south) buckets. Could you treat the region bucket as "hold" and ...
by Bill Braun
Mon Jun 26, 2000 8:30 am
Forum: SD Mailing List Archive
Topic: linking flow to flow directly?
Replies: 9
Views: 35885

linking flow to flow directly?

At 10:13 AM 6/24/00 +0100, Geoff Coyle: >Id really be careful about making the model more detailed as a substitute >for making it smart. At my stage of learning modeling this embodies the challenge I face. How to intuit the variables that best describe the structure of the system without adding vari...
by Bill Braun
Mon Jun 19, 2000 7:17 am
Forum: SD Mailing List Archive
Topic: Health Care Model
Replies: 6
Views: 5352

Health Care Model

X-UIDL: 10442-938505322 Status: O X-Status: The Healthcare EMBA class at Baldwin Wallace College is working on an Idealized Health System Design Project. Community health is a large component of the model. We are largely in the conceptualization stages for the second generation of the model. The fir...
by Bill Braun
Mon Jun 19, 2000 7:17 am
Forum: SD Mailing List Archive
Topic: Health Care Model
Replies: 6
Views: 5352

Health Care Model

The Healthcare EMBA class at Baldwin Wallace College is working on an Idealized Health System Design Project. Community health is a large component of the model. We are largely in the conceptualization stages for the second generation of the model. The first model (by the class that graduated last D...
by Bill Braun
Mon Jun 19, 2000 7:03 am
Forum: SD Mailing List Archive
Topic: linking flow to flow directly?
Replies: 9
Views: 35885

linking flow to flow directly?

X-UIDL: 10441-938505322 Status: O X-Status: > Bill Braun wrote: > > "Try linking the inflow > directly to the outflow > (bypassing the stock) and use > the delay as such: > > flow: shrimp entering lagoon = > some input > flow: shrimp leaving lagoon = > delay(shrimp entering lagoon, > time in la...
by Bill Braun
Mon Jun 19, 2000 7:03 am
Forum: SD Mailing List Archive
Topic: linking flow to flow directly?
Replies: 9
Views: 35885

linking flow to flow directly?

> Bill Braun wrote: > > "Try linking the inflow > directly to the outflow > (bypassing the stock) and use > the delay as such: > > flow: shrimp entering lagoon = > some input > flow: shrimp leaving lagoon = > delay(shrimp entering lagoon, > time in lagoon)" > >Ford Stone wrote: > > Perhaps...
by Bill Braun
Tue May 30, 2000 11:42 am
Forum: SD Mailing List Archive
Topic: Levels in Abstract Models
Replies: 4
Views: 3820

Levels in Abstract Models

In March I asked for some direction on how to approach and treat levels that are abstract (e.g., attitudes) rather than tangible (e.g., inventory). I received a number of replies. This is a compiled list of what I eventually found and studied. Many thanks to Paul Newton and Tom Fiddaman for their su...
by Bill Braun
Fri Mar 31, 2000 10:39 am
Forum: SD Mailing List Archive
Topic: Levels in Abstract Models
Replies: 4
Views: 3820

Levels in Abstract Models

I am looking for guidance and/or references for identifying levels, rates and auxiliaries in models that deal with largely abstract concepts. This could be mental models or changes in organizational culture or norms. In particular, I am exploring the dynamics of population based health (not health c...
by Bill Braun
Mon Feb 14, 2000 2:58 pm
Forum: SD Mailing List Archive
Topic: SD: Simply another tool for public policy development?
Replies: 14
Views: 8656

SD: Simply another tool for public policy development?

>2 - the notion of SD as simply another tool is one that really has to be >crushed. It is an unavoidable truth of reality that things accumulate - >todays customers are the sum of all those ever won, minus all those ever >lost - todays criminal population is the sum of all those who ever took to >cr...
by Bill Braun
Thu Feb 03, 2000 8:20 am
Forum: SD Mailing List Archive
Topic: Demographic Profiles and Health Care
Replies: 11
Views: 15916

Demographic Profiles and Health Care

>normally death rate would be defined as the number of deaths/population. in >itself this is not time dependant, but a constant representing the nature of >the environment being examined (ie how good the health care is, the >environmental hazards etc). Ive struggled with this, as much a function of ...
by Bill Braun
Mon Dec 13, 1999 8:04 am
Forum: SD Mailing List Archive
Topic: Rapid SD - Practical advice sought
Replies: 4
Views: 13241

Rapid SD - Practical advice sought

There might be some utility in teaching them how to read causal loop diagrams. After you move to e-mail communication, you can upload CLD "sketches" to your web site, they can look at them and provide feedback on where to take the model. Bill Braun From: Bill Braun <medprac@hlthsys.com>
by Bill Braun
Mon Oct 25, 1999 7:39 am
Forum: SD Mailing List Archive
Topic: Negative Levels
Replies: 9
Views: 11590

Negative Levels

Hi Jim, >Your formulations are very nice. But, isnt it **usually** true that >non-negativity formulations involving "dt" are "short cuts"? In our >aggregated models, isnt a table function usually part of conceptually >better solution? A common example would be where an "effe...
by Bill Braun
Fri Sep 03, 1999 7:21 am
Forum: SD Mailing List Archive
Topic: Compartmental System
Replies: 11
Views: 8940

Compartmental System

Phil wrote: >An example (that is eluded to in the ithink Business Applications Guide): >When hospital administrators reviewed a map theyd created with nurses in >the emergency care facility, they discovered that unbeknownest to them there >was as significant flow of patients being turned away on a d...
by Bill Braun
Tue Aug 03, 1999 10:00 am
Forum: SD Mailing List Archive
Topic: Does feedback need to involve levels
Replies: 5
Views: 5971

Does feedback need to involve levels

Hi Guenther, Your example represents the challenge I had "connecting the dots" between causal loop diagrams and SD models. Your description is quite accurate if the dynamic you illustrated is represented in a CL diagram. However, the ease of CL diagrams (opinion looming on the horizon) can...
by Bill Braun
Thu Jul 29, 1999 8:27 am
Forum: SD Mailing List Archive
Topic: Where Do Babies Come From
Replies: 3
Views: 3734

Where Do Babies Come From

> for example, has babies emerging >from a "cloud", a device I find extremely counterintuitive, when its >obviously a circular flow. I had the same difficulty until someone suggested that I think of the clouds simply as a convention for indicating the boudaries of the model. As she put it,...
by Bill Braun
Mon Jun 14, 1999 9:18 am
Forum: SD Mailing List Archive
Topic: S Shaped growth followed by decline
Replies: 8
Views: 8642

S Shaped growth followed by decline

Hi John, Im not sure this fits the bill but it does produce the curve you refer to. Simple model to show the effect of marketing promotion. Run the model with promotion taking place in the first 180 days, then stop all promotion for the remaining 180 days. The "Promotional Effectiveness" v...
by Bill Braun
Thu Apr 22, 1999 10:51 am
Forum: SD Mailing List Archive
Topic: land-use and land-ownership at a regional level
Replies: 4
Views: 4314

land-use and land-ownership at a regional level

>Check on the CIFOR web site and look for references to "Flores" The direct link is http://www.cgiar.org/cifor esearch/FLORES/index.html Bill Braun From: Bill Braun <medprac@hlthsys.com> The Health Systems Group - Physician Leadership Training - Simulation Modeling for Healthcare http://ww...
by Bill Braun
Thu Nov 26, 1998 10:10 pm
Forum: SD Mailing List Archive
Topic: Strategic or tactical?
Replies: 9
Views: 6917

Strategic or tactical?

Elsewhere in their book, Ries and Trout refer to tactics as "the thing that works". I take this as meaning that an organization has discovered a/the connection with the customer. This could be, as John Gunkler says, communications oriented or operationally oriented or customer service orie...
by Bill Braun
Fri Nov 20, 1998 7:15 am
Forum: SD Mailing List Archive
Topic: Strategic or tactical?
Replies: 9
Views: 6917

Strategic or tactical?

In Bottom Up Marketing, Ries and Trout argue that "companies that set strategy first usually refuse to accept failure because they figure that all thats needed to turn a project into winner is a minor adjustment in tactices." They define tactic as a "competitive mental angle". &q...
by Bill Braun
Sat Nov 07, 1998 7:08 am
Forum: SD Mailing List Archive
Topic: Systems of problems
Replies: 5
Views: 7789

Systems of problems

Hi George, >Id ask Bill, if someone asked you to model a city (e.g., Cleveland), >would you know what to do? Id say I wouldnt, and I think you wouldnt >either. So I conclude I cant model a system, without some definition of >the dynamic problem focus of the modeling effort. Good question. I wouldnt ...