Ventana software support forum

Dear JJ, Thanks so much for your comments. To answer your first question: I am a student. So the model discussed over past few days is for my own interest, only. By using the co-flow, I want to track how the dynamics of scrappage and retrofit would affect the average efficiency of those plants in us...

Dear JJ, Thank you so much for your comments. I agree with you that Tom's model is elegant and serves the purpose much better. For the original aging chain model that you corrected, I thought it would still be of value to further explore it by adding a co-flow of efficiency. So I did it. The efficie...

Hi Tom, Thank you so much for sharing this interesting model. The treatment of "Cohort Start" and "Cohort Age" appears to be important. Still trying to understand the INITIAL equations for Cohort Start - appreciate if you could elaborate a bit. If I understand it correctly, this ...

Hi JJ, Thank you so much for making corrections and explaining your thoughts. Subtracting the scrap from the level in order to calculate the reinjection helps solve the problem of negative values. The logic behind it, as you explained, makes sense. I am expanding this model by putting up co-flows to...

Hi JJ, Many thanks for sharing your thoughts. I do not fully understand your suggestion that "build an ageing chain of 5 cohorts of plants based on their life time expectancy and not on their real age". However, I built a simplified model, to highlight the fundamental issue of concern. In ...

Hi Tom, many thanks for your further comments. I totally agree with you on the need of using aging chain and also co-flow, which are what I have already used. The headache is the retrofit - more specifically, the extra lifetime due to each retrofit. Regarding the reinjection: for a cohort of plants ...

Hi JJ, thanks for your comments. The purpose of the modelling is to study the trend of average efficiency of the power plants ( measured in the unit of gram coal consumed per kWh generated). There is a natural improvement of the efficiency over time, as a result of technological advancement. Moreove...

Hi Tom, thanks for your comments. Yes, that bothers me, too. Reinjection would mean that a certain plant is likely to be renovated again sometime soon, which does not make sense in real life. One way round it is to perhaps set a certain time period (e.g. 5 years, 10 years, or so) during which the al...

Hi Administrator, thanks for further explanation. So, for those plants aged between 1 and 10, their extra lifetime years gained through a retrofit are less than 10 years? For example, for a plant aged 7, after retrofit, its age will drop to 1, which means the extra lifetime gained is 6 years. Is thi...

Hi Administrator, Many thanks for the model and your explanation. It provides an interesting perspective other than mapping subscripts. For the "retrofitted plants rate", why does "plants to retrofit [age]" need to be summed over age? Also, after including all subscript elements ...

Hi, Suppose a model is about age cohorts of a population. The age cohorts are from 0 to 100. If subrange A is from 0 to 90, subrange B is from 10 to 60, is possible to somehow "map" subrange B onto the subrange 0 to 50 of subrange A, without having to create a new subrange specifically fro...

Hi Tom, Thank you so much. In fact, I did use an aging chain for the plants. The aging chain is based on subscripting. Each cohort of plants has a duration of 1 year. The solution interval is also 1 year. This is to prevent blending. So, there are a total of 100 cohorts of plants. Mapping of subscri...

Hi Tomfid, I am not sure if I fully understand your question. No, it is not required that the plants must be discrete, because the total number is very big. Fraction is okay. Could you please offer some advice on how to solve it? Many thanks. Do you need discrete plants, or can you have fractional r...

Thanks. However I feel that the issue is different from re-work. I have attached a simple example for review and discussion. For simplicity, I did not use subscript. Some comments are written in the model for explaining the issue. Many thanks. I'm finding it hard to follow what you are asking withou...

Hi, I am trying to model a situation where X% of every year's elements of an aging chain undergo renovation and therefore have increased lifetime (and as a result, will be scrapped at times later than originally expected). More specifically, suppose I have a stock of 1000 newly developed power gener...

Sorry I did not make myself clear enough. The fraction per year is a subscripted variable. Each subscript correspond to one year (one time step). So, for example, for year 10, fraction per year [year 10] should have only one single data point, something like 0.001; for year 10, fraction per year [ye...

Thanks. I want to get the fraction per year, i.e. those horizontal lines in the first graph shall all disappear. For each single year, it is a pulse, i.e. just one data point. The peripheral of these pulse is like the curve shown in the third graph (profile). I don't understand what you want to do. ...

Hi, I have a model with a data variable called profile, which is taken from an Excel using GET XLS DATA function. I want to get data point from this profile for each single year, which will be passed to another variable in the same model. In other words, for any single year, only 1 data point taken ...

Thanks a lot. I missed the function of "->" in the sample model, which is the key to make possible the mapping.

Administrator wrote:It's all in the help system,
http://www.vensim.com/documentation/ind ... apping.htm

Thanks a lot. The example given by you is clear, and explains the issue. However, in the above-mentioned AGE model, I cannot see where the subscript mapping has been done. Please could you enlighten me a bit further? Thanks. The age model is not against the rule, it uses subscript mapping. It's not ...

Hi, I am struggling with the ERROR message saying Subscript Range - XXX - appears on the right, but not left . Vensim Help does say that " The most important subscript rule is that a subscript appearing on the right hand side of an equation must also appear on the left hand side. " However...

Yes, I did. I can open those sample functions by finding them here C:\Users\Public\Vensim\Models\FunctionExamples. However this is troublesome. Is there any solution? Thanks.

Administrator wrote:Did you install using admin permissions?

It sounds like the file associations have been messed up.

Hi, I have just upgraded my Vensim Pro 6.4 to Vensim Pro 7.1. However, when clicking sample models provided in Vensim Help, nothing happens. Previously when using Vensim Pro 6.4, clicking a sample model (usually in the form of a hyperlink given at the bottom of the explanation of a function) will im...

Well, it is simply because the cohorts are just a small part of my model and I am reluctant to make any changes to the other parts. That being said, to be honest I know nothing about Ventity and have not got time to explore it. Just a general question please - would it be possible to "import&qu...

Hi Tomfid, thanks a lot for quick reply. But cohort related items are only part of my model, so I have to use Vensim. In that case, if I still want to use COHORT CONTROL, will upgrading from Vensim Pro to Vensim DSS be the only option? Thanks. That's a DSS feature. You may find that Ventity is a bet...