Search found 1162 matches

by LAUJJL
Tue Feb 20, 2018 6:11 pm
Forum: Vensim
Topic: Optimization - VECTOR LOOKUP and other approaches ?)
Replies: 13
Views: 149

Re: Optimization - VECTOR LOOKUP and other approaches ?)

Hi

Sounds strange.

It is no more possible to edit previous posts!

I then add this remark.

One interest of starting with one category of vehicle, is that when you go to 2 categories etc.., you may use a subscript for the category. this will simplify the sketch of the model.

Regards.

JJ
by LAUJJL
Tue Feb 20, 2018 5:55 pm
Forum: Vensim
Topic: Optimization - VECTOR LOOKUP and other approaches ?)
Replies: 13
Views: 149

Re: Optimization - VECTOR LOOKUP and other approaches ?)

Hi I join this discussion a bit late. I start again with the purpose of the model. It is to determine the right amount of cars of each category to buy each year, that depends on each category characteristics and the objective: minimizing the buying costs and the gap between the observed and real pet...
by LAUJJL
Thu Feb 15, 2018 9:39 am
Forum: Vensim
Topic: Problem using NORMAL RANDOM
Replies: 5
Views: 71

Re: Problem using NORMAL RANDOM

In fact, the random normal function does not work, if both the minimum and the maximum are equal to the mean. a second solution to this limitation, is if this happens, to force the minimum and maximum to extreme indetermined values and the standard deviation to 0, to make the function work. See the ...
by LAUJJL
Thu Feb 15, 2018 8:19 am
Forum: Vensim
Topic: Problem using NORMAL RANDOM
Replies: 5
Views: 71

Re: Problem using NORMAL RANDOM

joined a model.
Use the synthesim and the sliders Under the constants to experiment how it works.

Regards.

JJ
by LAUJJL
Thu Nov 23, 2017 1:21 pm
Forum: Vensim
Topic: Model changing lifetime due to renovation
Replies: 30
Views: 675

Re: Model changing lifetime due to renovation

Hi Your calculation of efficiency is biased: your forget the cost of building new plants and the cost of retrofitting them. If you introduce these costs, you will see a difference of 'efficiency' depending on the retrofitting policy even if the coal consumption is the same. What you want to calculat...
by LAUJJL
Wed Nov 22, 2017 9:29 am
Forum: Vensim
Topic: Model changing lifetime due to renovation
Replies: 30
Views: 675

Re: Model changing lifetime due to renovation

Hi One first question. What is your job? Working for an organisation, consultant, student? What is the purpose of the model? The purpose is to find policies that will be implemented, or is it a simple student work whose purpose is learning? One must not forget that a model must be understood to be c...
by LAUJJL
Tue Nov 21, 2017 8:44 am
Forum: Vensim
Topic: Model changing lifetime due to renovation
Replies: 30
Views: 675

Re: Model changing lifetime due to renovation

Hi After studying Tom's model, it looks better adapted to the problem. It is based on real age cohorts, which is more natural and calculates for each cohort, how much additional age or capacity is added, that is enough to understand the behaviour and further needs. It is probably easier to implement...
by LAUJJL
Mon Nov 20, 2017 3:45 pm
Forum: Vensim
Topic: Model changing lifetime due to renovation
Replies: 30
Views: 675

Re: Model changing lifetime due to renovation

Hi I have made some corrections to your model. First correction, error units, I have changed some parameters from DMNL to 1/year. Another problem is the capacity to draw more from a level that its value and the level becomes negative. This becomes from the formulation of the reinjection that does no...
by LAUJJL
Sun Nov 19, 2017 10:38 am
Forum: Vensim
Topic: Model changing lifetime due to renovation
Replies: 30
Views: 675

Re: Model changing lifetime due to renovation

Hi To solve that problem, I would start with a very simple model that I have understood fully by using it. This problem needs an ageing chain with multiple co-flows to trace different attributes as Tom mentioned. I would then build an ageing chain of 5 cohorts of plants based on their life time expe...
by LAUJJL
Fri Nov 17, 2017 8:13 pm
Forum: Vensim
Topic: 64 bit beta release
Replies: 13
Views: 4495

Re: 64 bit beta release

Hi Tom I would like a 64 bits version at the condition that it is not bugged, has the same features and runs as quickly as the 32 bits version. For some runs i am obliged to build a save list or reduce the save period, Something that is meanwhile cumbersome but manageable. Something that is probably...
by LAUJJL
Fri Nov 17, 2017 3:46 pm
Forum: Vensim
Topic: Model changing lifetime due to renovation
Replies: 30
Views: 675

Re: Model changing lifetime due to renovation

Hi

This problem is difficult to solve partly because the purpose of modelling this problem is not known. What do you expect from this model?

Reading the thread I could not find the purpose.

To resume what will be the model useful for?

Regards.

JJ
by LAUJJL
Fri Oct 13, 2017 1:47 pm
Forum: System Dynamics Discussion
Topic: Asymmetrical Smooth
Replies: 3
Views: 179

Re: Asymmetrical Smooth

Hi Be careful using an if then else nested within the smooth, and verify how it works. The smooth function hides the previous smooth and may generate strange results. With the level formulation you see exactly what Vensim is doing, but it is maybe possible too to visualize how the smooth function is...
by LAUJJL
Fri Oct 13, 2017 10:20 am
Forum: System Dynamics Discussion
Topic: Asymmetrical Smooth
Replies: 3
Views: 179

Re: Asymmetrical Smooth

Hi joined a possible way. It uses preferably the formulation of smooth with a level (see the documentation of smooth) . One must use the synthesim and vary the different parameters to see if the formulation makes sense. The demand is sometimes positive or sometimes nul depending on the mini and maxi...
by LAUJJL
Thu Sep 28, 2017 6:57 am
Forum: Vensim
Topic: Help with model calibration
Replies: 359
Views: 12180

Re: Help with model calibration

Hi Leon As your deadline is Saturday, it is time to accept the fact that by this time you will not have the model finished and to act in consequence. You are not an expert in SD. Then nobody expects a prefessional work from you At your place, I would change this negative situation into a positive on...
by LAUJJL
Tue Sep 19, 2017 8:18 am
Forum: System Dynamics Discussion
Topic: How to allocate budget to different rates?
Replies: 6
Views: 378

Re: How to allocate budget to different rates?

Hi - 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? It is to prevent the level going negative. At each time step, you can only deliver the amount of kits in the level and this amount...
by LAUJJL
Mon Sep 18, 2017 4:35 pm
Forum: System Dynamics Discussion
Topic: How to allocate budget to different rates?
Replies: 6
Views: 378

Re: How to allocate budget to different rates?

HI

As your purpose is to help spending the money, you should concentrate on your purpose and not on how to increase the number of donors.

Joined a simple model on only the spending.

Your donor part does not make sense anyhow.

Look at the units in the model joined.

Regards.

JJ
by LAUJJL
Sat Sep 16, 2017 6:05 pm
Forum: System Dynamics Discussion
Topic: How to allocate budget to different rates?
Replies: 6
Views: 378

Re: How to allocate budget to different rates?

Hi

You should try to study the Vensim user guide seriously before wanting to model even very simple problems!

It is for instance a good practice to put units in the equations!

Joined a simplified model.

Regards.

JJ
by LAUJJL
Mon Aug 14, 2017 4:15 pm
Forum: System Dynamics Discussion
Topic: Need Assistance to ensure model equations are correct
Replies: 1
Views: 173

Re: Need Assistance to ensure model equations are correct

HI

Two remarks.

There are no units in your model which makes your model difficult to understand.

There is no dynamic in your model: no feedback loops anywhere.

Regards.

JJ
by LAUJJL
Sat Aug 05, 2017 4:51 pm
Forum: Vensim
Topic: Help with model calibration
Replies: 359
Views: 12180

Re: Help with model calibration

Hi Leon. I prefer to stop my remarks because they may be inappropriate. You have a continuous deterministic model and seem to have discreet data. This is why you use a small time step to be able to introduce your discreet data. I have no experience of that. I have too a lot of exogenous discreet dat...
by LAUJJL
Fri Aug 04, 2017 3:37 pm
Forum: Vensim
Topic: Help with model calibration
Replies: 359
Views: 12180

Re: Help with model calibration

Hi Leon. I have made deep changes to the model. I have added again the cumulative miles driven as I had not understood its long term effect on the driving quality and of course there is no reason to smooth it. I have first replaced memories by forgotten events which is the same and avoids the cumber...
by LAUJJL
Thu Aug 03, 2017 4:08 pm
Forum: Vensim
Topic: Help with model calibration
Replies: 359
Views: 12180

Re: Help with model calibration

Hi Leon I have experienced with the time that it is not easy and sometimes misleading to comment other works. I have no idea of your problem, of your environment, your constraints etc.. When modeling one must take into account all these factors. I work on my own problems and my ideas about what shou...
by LAUJJL
Wed Aug 02, 2017 8:15 am
Forum: Vensim
Topic: Help with model calibration
Replies: 359
Views: 12180

Re: Help with model calibration

Hi Leon 4 remarks concerning your last model joined teen-driver-model. 1. Why one unit error and why not zero? 2. Adding subscripts has no utility at least at this level as each subscript result is independent from the others. It adds a complexity without any utility. It is always possible to add su...
by LAUJJL
Mon Apr 03, 2017 7:26 am
Forum: Vensim
Topic: protecting a model while making it possible to be run
Replies: 5
Views: 450

Re: protecting a model while making it possible to be run

Hi

Thank you for the information.

I did not think about protecting the VBA code.

Regards.

JJ
by LAUJJL
Sun Apr 02, 2017 3:32 pm
Forum: Vensim
Topic: protecting a model while making it possible to be run
Replies: 5
Views: 450

Re: protecting a model while making it possible to be run

Hi I want that the user may not read the open whatever the version he uses, unless having a password. But he may use the published model via Excel VBA with or without a password. But if it needs a password, it is only to run the model, and not to read it. To resume, I want to keep the source code se...
by LAUJJL
Fri Mar 31, 2017 9:41 am
Forum: Vensim
Topic: protecting a model while making it possible to be run
Replies: 5
Views: 450

protecting a model while making it possible to be run

Hi I want to protect my model against being read, while still making it possible to be run from Excel VBA DLL without the password that protects the model or eventually with another one. If I protect the model and make a published model from the binary file protected, it asks in Excel the password. ...

Go to advanced search