Search found 44 matches

by Yaman Barlas
Fri Nov 17, 2006 12:41 pm
Forum: SD Mailing List Archive
Topic: QUERY Beer Game Simulation Model
Replies: 3
Views: 21871

QUERY Beer Game Simulation Model

Posted by yaman barlas <ybarlas@boun.edu.tr> Dear Abhijit; Short answer to your question is 'yes' there are such simulation models. More specifically, a couple of years ago we created a model that EXACTLY replicates the physical beer game. The related article is in the proceedings of ISDC 2005, Bost...
by Yaman Barlas
Thu Nov 04, 2004 5:48 pm
Forum: SD Mailing List Archive
Topic: Discrete-flow modelling for business simulation
Replies: 7
Views: 7180

Discrete-flow modelling for business simulation

Dear Magne; I see your points and agree that integer and/or logical variables are sometimes needed for better, more compact formulations. I think this little debate is about 'degree', not 'kind'. So although I have no problem with your arguments in general, I am also adding the following caution: In...
by Yaman Barlas
Mon Oct 25, 2004 8:12 am
Forum: SD Mailing List Archive
Topic: Discrete-flow modelling for business simulation
Replies: 7
Views: 7180

Discrete-flow modelling for business simulation

Hello Magne; I now understand what it is you try to do and why you would need a stock. Thanks for detailed explanation. You are right, you do need a stock in this case. Having said this, let me add that I personally do not think a 'special' stock-flow definition and technology is needed to achieve i...
by Yaman Barlas
Wed Oct 20, 2004 6:10 pm
Forum: SD Mailing List Archive
Topic: Discrete-flow modelling for business simulation
Replies: 7
Views: 7180

Discrete-flow modelling for business simulation

Dear Magne; There is one part in your message that I do not understand. (Below). Although you are technically solving an integer flow and stock problem, WHY would one use such a stock? A stock means, your 'logical flows' would accumulate. You correctly state that a non integer 'true' is meaningless....
by Yaman Barlas
Tue Oct 12, 2004 5:16 pm
Forum: SD Mailing List Archive
Topic: Dynamical Systems and System Dynamics ??
Replies: 12
Views: 19138

Dynamical Systems and System Dynamics ??

Hello Esteban; Here is one way of characterizing the relations between dynamical systems and system dynamics: system dynamics is the name adopted by a community who does work on dynamical systems of certain type (policy problems of socio-economic or strategic management nature) with a special focus ...
by Yaman Barlas
Wed Sep 08, 2004 5:21 pm
Forum: SD Mailing List Archive
Topic: Project Management Flight simulator
Replies: 2
Views: 5156

Project Management Flight simulator

Hello all; This is in response to Ilir Rodiqi's inquiry about a week ago. We indeed have a PM flight simulator.(SOFTSIM). Its essential structure is Tarek Abdel Hamid's software project management structure. We simplified some parts and added some structures so that it can be used as a more general ...
by Yaman Barlas
Mon Jul 05, 2004 10:43 am
Forum: SD Mailing List Archive
Topic: Modelling ERP/MRP and Common Inventory Policies
Replies: 3
Views: 5233

Modelling ERP/MRP and Common Inventory Policies

You may find this useful -albeit indirectly and partially related to your question: We have done some work on testing the standard inventory control rules (such as (s, Q), (s,S), (S, R), (s, S, R)) in a dynamic feedback context. We modeled and replicated them in stock-flow jargon. Results are summar...
by Yaman Barlas
Sat Jan 10, 2004 6:53 pm
Forum: SD Mailing List Archive
Topic: Can SD models be validated without being run?
Replies: 38
Views: 27368

Can SD models be validated without being run?

Hi Kim, I am not sure I understood all of your questions, but I will reply anyway with few things I know: I- A good (and important) part of model validation is done WITHOUT simulation: I call this direct structure testing. This means establishing confidence in the validity of each equation one by on...
by Yaman Barlas
Tue Dec 02, 2003 12:04 pm
Forum: SD Mailing List Archive
Topic: Manufacturing Control Systems
Replies: 30
Views: 51665

Manufacturing Control Systems

Jim, If our purpose is to choose a single term and If I had freedom to choose from scratch, I would get rid of the term event because it is this term that would cause problem in the continuous worldview. But since the term event is so established in the discrete community, I have no such freedom. An...
by Yaman Barlas
Thu Nov 27, 2003 1:38 pm
Forum: SD Mailing List Archive
Topic: Manufacturing Control Systems
Replies: 30
Views: 51665

Manufacturing Control Systems

2 I mostly agree with Jim Hines explanation of events vs. time. The only part I have diffculty adopting is a continuous event. I would either call it a series of discrete events ( in the discrete-time case) or something like a process in the continuous-time. ----- In any case, the other part of the ...
by Yaman Barlas
Thu Jun 05, 2003 12:09 pm
Forum: SD Mailing List Archive
Topic: Systems Dynamics Models for Higher Education
Replies: 6
Views: 11183

Systems Dynamics Models for Higher Education

Michael J Schwandt wrote: > ... What models exist that cross institution boundaries and consider > broader systems? We have a model that models the National higher education system of Turkey, starting with high school graduation, the central placement exam, placement, enrollment and finally graduati...
by Yaman Barlas
Thu Jun 05, 2003 10:23 am
Forum: SD Mailing List Archive
Topic: Systems Dynamics Models for Higher Education
Replies: 6
Views: 11183

Systems Dynamics Models for Higher Education

Hello, There has been similar queries in the past. I am pasting our typical reply (apologies to those who have read this before): We have an interactive simulation game for university management (UNIGAME) here at Bogazici. We can send it free for personal educational esearch use. Please contact us i...
by Yaman Barlas
Wed Jun 04, 2003 8:41 pm
Forum: SD Mailing List Archive
Topic: Traffic jams and congestion
Replies: 8
Views: 11909

Traffic jams and congestion

This is a delayed reply to the "traffic congestion" query and a couple of related notes. A couple of students in our group did a nice modeling project of the dynamics of bottlenecks/gridlocks caused by *feedback effects* at intersections. (I believe Bill Braun referrred to this phenomenan)...
by Yaman Barlas
Fri May 02, 2003 7:05 pm
Forum: SD Mailing List Archive
Topic: Can system dynamics models "learn"
Replies: 46
Views: 33412

Can system dynamics models "learn"

Part of this discussion (on learning) has dealt with "Models which add, delete, or edit its own equations..." as a definition of learning(1). Most comments on this topic went on to state that "such self-altering models are not achievable in Stella, Vensim of Powersim"(2). I would...
by Yaman Barlas
Wed Apr 30, 2003 7:59 pm
Forum: SD Mailing List Archive
Topic: Channel Systems
Replies: 5
Views: 5216

Channel Systems

We did a research a few years ago on strategies of insurance management. In this problem, policies are sold thru two different channels: a- agencies, b- direct marketing salesforce. The problem can be very interesting, because the two channels have different structures, needs, motivations and contro...
by Yaman Barlas
Sun Apr 20, 2003 3:27 pm
Forum: SD Mailing List Archive
Topic: Can system dynamics models "learn"
Replies: 46
Views: 33412

Can system dynamics models "learn"

Depending on what is exactly meant by "learning", this question may have different answers: - A simple negative (goal-seeking feedback) loop involves learning: An action is taken, the result is measured and evaluated, and it is "learned" that the action was either insufficient/in...
by Yaman Barlas
Fri Apr 19, 2002 4:46 pm
Forum: SD Mailing List Archive
Topic: SD and University Management
Replies: 1
Views: 2693

SD and University Management

We have an interactive simulation game for university management (UNIGAME) here at Bogazici. We can send it free for personal educational esearch use. The primary author of the product is Vedat Diker, now at Albany. And here is the basic reference: ÒA Dynamic Simulation Game for Strategic University...
by Yaman Barlas
Thu Apr 18, 2002 6:22 pm
Forum: SD Mailing List Archive
Topic: System Dynamics for Agriculture and Business
Replies: 2
Views: 3653

System Dynamics for Agriculture and Business

We have been doing a "potentially" related research: Long-term agro-socio-economic dynamics of irrigation-based regional development projects. The specific context is GAP (Southeast Turkey development project). There has been a PhD thesis and a few papers published. The work continues. If ...
by Yaman Barlas
Thu Apr 11, 2002 7:44 pm
Forum: SD Mailing List Archive
Topic: Validation of SD-models?
Replies: 2
Views: 4035

Validation of SD-models?

Hello Torsten, I have done considerable work on model validity. Here are some papers you may find useful: "A Dynamic Pattern-oriented Test for Model Validation" (with K. Kanar), Proceedings of 4th Systems Science European Congress, Valencia, Spain, Sept. 1999, pp. 269-286 ÒFormal Aspects o...
by Yaman Barlas
Tue Apr 09, 2002 4:19 pm
Forum: SD Mailing List Archive
Topic: EURO/INFORMS Conf. System dynamics cluster
Replies: 1
Views: 3085

EURO/INFORMS Conf. System dynamics cluster

Dear All, If you attended the annual SD conference in Palermo, you may recall my announcement about the "system dynamics/sytem theory CLUSTER" that I will be chairing the forthcoming EURO/INFORMS Joint Conference in Istanbul during July 6-10, 2003. Being the joint conference between Europe...
by Yaman Barlas
Mon Apr 08, 2002 8:52 pm
Forum: SD Mailing List Archive
Topic: Representing constraints
Replies: 30
Views: 43688

Representing constraints

I would submit that this whole notion of constraint is "in the eye of beholder." Any given sd model can be seen full of constraints, if one chooses to do so. - All flow and auxilary equations can be seen as constraints (assuming for the moment that we are talking about equality constraints...
by Yaman Barlas
Sat Apr 06, 2002 6:54 pm
Forum: SD Mailing List Archive
Topic: Watershed Management
Replies: 2
Views: 3783

Watershed Management

Hi Paula, We did some research on Modeling of a Wetland for Sustainable Development. Parts of it may be related to sustainable watershed mangement. It was Burak Guneralps M.S. thesis. Two references are: -" Modeling a Wetland through Sustainable Development: Uluabat Lake" (with B. Güneralp...
by Yaman Barlas
Thu Apr 04, 2002 12:09 pm
Forum: SD Mailing List Archive
Topic: EURO/INFORMS Conf. System dynamics cluster
Replies: 1
Views: 3085

EURO/INFORMS Conf. System dynamics cluster

Dear all, A couple of weeks ago I announced the system dynamics/theory cluster in the major yearly, joint EURO/INFORMS conference in Istanbul this summer. Several people contacted me with (similar) questions so I will try to make a couple of general clarifications (This will be my last message in th...
by Yaman Barlas
Tue Apr 02, 2002 6:04 pm
Forum: SD Mailing List Archive
Topic: Impacts of Intensive Agriculture and Crop Rotation on
Replies: 1
Views: 3348

Impacts of Intensive Agriculture and Crop Rotation on

We do have a related research. It is Ali Kerem Saysels doctoral thesis, completed a few years ago. It deals with the lon-term comprehensive, eco-environmental evaluation of the Southeastern Turkey Regional development project (GAP), using sd modeling. The research may help you with your more "g...
by Yaman Barlas
Mon Apr 30, 2001 7:02 pm
Forum: SD Mailing List Archive
Topic: Complex Adaptive System - Friend or Foe?
Replies: 9
Views: 31701

Complex Adaptive System - Friend or Foe?

The best answer I can come up with is "neither friend nor foe". There is nothing intrinsic in a method like CAS that would make it friend or foe of sd. The question is not very well-posed as it tends to justify the unnecessary and superficial boundaries in between different fields. (But I ...