Search found 46 matches
- Sat Jun 16, 2018 5:11 am
- Forum: Vensim
- Topic: how to convert the units from "person" to "kit/person"
- Replies: 3
- Views: 2657
Re: how to convert the units from "person" to "kit/person"
Yes, I want to have correct units in my model. attached is the revised version of the model. could you please check and confirm if the units are correct now. how about the formulation for the rate "leaving the shelter", is the formulation correct? (Population in shelter*Fraction of populat...
- Fri Jun 15, 2018 10:38 am
- Forum: Vensim
- Topic: how to convert the units from "person" to "kit/person"
- Replies: 3
- Views: 2657
how to convert the units from "person" to "kit/person"
Hi, I want to model the required amount of consumable relief items (such as water, medicine,etc..) for an evacuation scenario. I developed a simple model based on the following formula: p(t)=1/(1+EXP(-α*(Time-H))^2) where Pt is the percentage of the evacuees who have departed by time t and α and H a...
- Tue Jun 05, 2018 5:08 am
- Forum: Vensim
- Topic: help in modeling demand in disasters
- Replies: 5
- Views: 3518
Re: help in modeling demand in disasters
I revised the demand model in the previous post and attached the new version to this post. it looks like parameter "n" actually refers to "time". so previous formulation was wrong. the new formulation for G(n) is: G 0*Time*exp(-k*Time)+"(G r)" it shows an overshoot and ...
- Tue Jun 05, 2018 4:54 am
- Forum: Vensim
- Topic: help in modeling demand in disasters
- Replies: 5
- Views: 3518
Re: help in modeling demand in disasters
Yes, calibrating parameters will not generate the graph that I want. The descriptions are the authors response to my email regarding how to model a disaster demand. Graph that I want to match shows the solution of his model and I realized that it’s actually “wrong” to match the model output to this ...
- Mon Jun 04, 2018 2:36 am
- Forum: Vensim
- Topic: help in modeling demand in disasters
- Replies: 5
- Views: 3518
Re: help in modeling demand in disasters
for some reason, I cant upload two pictures in one post. I add the result that I want to get to this post.
- Sun Jun 03, 2018 6:09 am
- Forum: Vensim
- Topic: help in modeling demand in disasters
- Replies: 5
- Views: 3518
Re: help in modeling demand in disasters
I forgot to add the graphs. I add them to this post.
- Sun Jun 03, 2018 5:41 am
- Forum: Vensim
- Topic: help in modeling demand in disasters
- Replies: 5
- Views: 3518
help in modeling demand in disasters
Hi, I want to model disaster demand and I have the following description for modeling it using Vensim: The easiest way to model the disaster-generated demand is as an instantaneous constant G at the beginning (time step n=0). So you would have D(0)=G. It is also often realistic to use a disaster-gen...
- Tue May 22, 2018 3:01 am
- Forum: Vensim
- Topic: problem in initializing my model in equilibrium “Simultaneous initial value equation involving…”
- Replies: 4
- Views: 3209
Re: problem in initializing my model in equilibrium “Simultaneous initial value equation involving…”
Hi, I simplified my model to only one layer of a supply chain. the model has only 4 stocks. as suggested the formulation for the initial value of "in transit = shipment*lead time" works. But there are other stocks that not sure how what could be the initial value formulation. specifically ...
- Sun May 20, 2018 5:32 am
- Forum: Vensim
- Topic: problem in initializing my model in equilibrium “Simultaneous initial value equation involving…”
- Replies: 4
- Views: 3209
problem in initializing my model in equilibrium “Simultaneous initial value equation involving…”
Hello, I am facing a problem in initializing my model in equilibrium. I receive the following error: “Simultaneous initial value equation involving…” Can anyone help to resolve this problem? thank you. Model is attached to this post. The parametric value of the “InTansit” stock for equilibrium is “6...
- Tue Sep 19, 2017 2:10 am
- Forum: System Dynamics Discussion
- Topic: How to allocate budget to different rates?
- Replies: 6
- Views: 7702
Re: How to allocate budget to different rates?
HI Thanks for the corrections the units are now A.O.k.., but I have a few questions about your changes to the model: - What “TIME STEP” does in the formulation of the rate “deliveries to beneficiaries”? Why do we need to divide “Relief inventory” to “TIME STEP” in this rate formula? - Why do you kee...
- Mon Sep 18, 2017 3:29 am
- Forum: System Dynamics Discussion
- Topic: How to allocate budget to different rates?
- Replies: 6
- Views: 7702
Re: How to allocate budget to different rates?
Hi everyone, many thanks for the comments and input. I'm trying to do an experiment based on my knowledge of the real world. so here is the experiment: a non-governmental organization (NGO) receives money from the donors and spends this money for buying inventory or training of its staff. The NGO se...
- Sat Sep 16, 2017 4:42 am
- Forum: System Dynamics Discussion
- Topic: How to allocate budget to different rates?
- Replies: 6
- Views: 7702
How to allocate budget to different rates?
Hi everyone, what is the best way to allocate a certain amount of a "stock" to different inflow rates? I am trying to allocate a stock called "total available budget" to two other stocks: 1- total inventory budget 2- total training budget I am not sure that the formulation of my ...
- Sun May 29, 2016 5:57 am
- Forum: System Dynamics Discussion
- Topic: How to model order quantity?
- Replies: 0
- Views: 8228
How to model order quantity?
Hi,
I want to model order quantity, considering demand during lead time and safety stock. How to model this in system dynamics? any suggestions?
I want to model order quantity, considering demand during lead time and safety stock. How to model this in system dynamics? any suggestions?
- Sun May 22, 2016 1:19 pm
- Forum: System Dynamics Discussion
- Topic: is the formulation of this model correct?
- Replies: 0
- Views: 5139
is the formulation of this model correct?
Hi, I developed a model for "population evacuation behavior". I want to relate this model to a "operations staff" model. Basically, what I want to model is the following scenario; population evacuate a place due to disaster, an organization is responsible in providing relief to t...
- Sun May 08, 2016 3:49 am
- Forum: System Dynamics Discussion
- Topic: Optimisation of a variable based on resource allocation
- Replies: 2
- Views: 3284
Re: Optimisation of a variable based on resource allocation
Administrator wrote:I don;t see why you couldn't do it. Why do you think it's a problem?
I have not seen a similar work, please advice me where I can find some readings on this issue.
- Sun May 01, 2016 8:57 am
- Forum: System Dynamics Discussion
- Topic: Optimisation of a variable based on resource allocation
- Replies: 2
- Views: 3284
Optimisation of a variable based on resource allocation
Hi,
Can anyone advise whether this is possible in Vensim;
In a model that utilizes allocation to many function, is it possible to optimise a variable (Let's say service level), based on the given priorities to the resources ?
Thanks in advance
Can anyone advise whether this is possible in Vensim;
In a model that utilizes allocation to many function, is it possible to optimise a variable (Let's say service level), based on the given priorities to the resources ?
Thanks in advance
- Wed Mar 23, 2016 1:20 pm
- Forum: System Dynamics Discussion
- Topic: what "quant" means? QUEUE AGE AVERAGE(queue,quant)
- Replies: 1
- Views: 2951
what "quant" means? QUEUE AGE AVERAGE(queue,quant)
Hi, I am trying to understand the QUEUE AGE AVERAGE(queue,quant) function. I am not sure what is the interpretation of "quant". anyone knows? also, I am not clear with the meaning of this statement; "Returns the average age of the oldest quant elements in queue. This is useful for tra...
- Wed Mar 16, 2016 2:34 am
- Forum: System Dynamics Discussion
- Topic: Problem in linking two variables
- Replies: 2
- Views: 3506
Re: Problem in linking two variables
is the link looks reasonable and How about the effect of skills on productivity?Administrator wrote:You already have "staff capacity" that is calculated using "productivity" and "operations staff". Why not link that to the "Deliveries to Beneficiaries" rate?
- Sun Mar 13, 2016 4:47 am
- Forum: System Dynamics Discussion
- Topic: Problem in linking two variables
- Replies: 2
- Views: 3506
Problem in linking two variables
Hi all, I am developing a model that considers delivering goods to the beneficiaries in case of a disaster. I have trouble in linking two variables. what I want to do is that to link "operation staff" to a rate " deliveries to beneficiaries". how to do this? additionally is the f...
- Tue Mar 01, 2016 8:29 am
- Forum: System Dynamics Discussion
- Topic: modeling organization image (reputation)
- Replies: 9
- Views: 6885
Re: modeling organization image to stakeholders
So I tried to restrict the value of stock to be between 0 and 1, but I am not really sure that the model is now correct, primarily because of the equation that I used for rate. is this model correct? (attached to this post) here is the equation for rate; MIN(Average Service Level,1-Image)/delay Rega...
- Sun Feb 28, 2016 5:37 am
- Forum: System Dynamics Discussion
- Topic: Different between Stella , Vensim and Powersim, need help
- Replies: 19
- Views: 27750
Re: Different between Stella , Vensim and Powersim, need hel
I've been working with Vensim, Stella professional, Stella 10.1, AnyLogic university edition. I would definitely recommend you to go with Vensim, primarily because of the software interface that makes modeling easy to understand with analysis tools. in addition to this, the support that you get from...
- Tue Feb 16, 2016 2:58 am
- Forum: System Dynamics Discussion
- Topic: modeling organization image (reputation)
- Replies: 9
- Views: 6885
Re: modeling organization image to stakeholders
The "image" level, what are the bounds for this? Does it go from 0-1 or 0-100? The warnings you are getting are because "Image" goes above 1, and the lookup only goes to 1. They are only warnings, the model will still run. But it would be better to make sure the lookup bounds ma...
- Mon Feb 15, 2016 11:30 am
- Forum: System Dynamics Discussion
- Topic: Problem in Reconstructing System Dynamics Models
- Replies: 10
- Views: 8099
Re: Problem in Reconstructing System Dynamics Models
Administrator wrote:Yes, I think the model is wrong (I've edited my last post to give you an example using time step).
Maybe I am just not using it correctly.
Thank you for your comments. They are really helpful. Let me read them carefully and I try to find out what's going on in this model.
Best,
- Mon Feb 15, 2016 9:41 am
- Forum: System Dynamics Discussion
- Topic: Problem in Reconstructing System Dynamics Models
- Replies: 10
- Views: 8099
Re: Problem in Reconstructing System Dynamics Models
I want to run this model because it probably helps me in my own research.Yes, I've contacted the author and I didn't receive any response. So do you think the model is wrong?!
- Mon Feb 15, 2016 9:16 am
- Forum: System Dynamics Discussion
- Topic: Problem in Reconstructing System Dynamics Models
- Replies: 10
- Views: 8099
Re: Problem in Reconstructing System Dynamics Models
I cannot help on this, I don't know. Where did you get the model? The author hasn't bothered with units, or any documentation. And a very quick look shows up obvious errors (the equation for "supplies consumed" is incorrect). The model is from a published paper (attached to this post (Fil...