Hello everyone, I have started to use this program from just a couple of days and I have some problems with the model that I'm trying to implement.

So basically I have two ODE with into them some parameters that changing in time...Obviously, nothing work and I would like to have a little bit of help.

Ok, I'm not the best at explaining this, so I attach the file and I hope that someone can give me some good advice to make this thing work!

Prova modello permeabilita.sm (128 KiB) downloaded 35 time(s).

You need to be more careful about the variables and their order in the document.

Wrote

You need to be more careful about the variables and their order in the document.

:d This seems to me a great advice!

Now I try to fix it and, in general, to be more ordered.

Wrote

Now I try to fix it and, in general, to be more ordered.

If you describe the original system, it becomes clearer what you want to get.

Wrote

Wrote

Now I try to fix it and, in general, to be more ordered.

If you describe the original system, it becomes clearer what you want to get.

Basically, this set of equations should describe the evolution of the atmosphere inside a packaging.

So we have O2i which is the evolution of oxygen inside the packaging, which decreases because inside there is a fruit that breathes.
Co2i is the evolution of CO2, which increases because the fruit emits it.
ro2 and rco2 would be the breathing of the fruit, which also changes according to the atmosphere of the packaging.

Is a model that you can find in the article:
Modeling respiration–transpiration in a modified atmosphere packaging system containing blueberry
Yoonseok Song a, Nick Vorsa b, Kit L. Yam a,*


And yes...probably isn't the best choices for a first try but unfortunately its what I need

Now I try to fix a little bit better the file and we will see what other problem come out :d

Wrote

Wrote

So we have O2i which is the evolution of oxygen inside the packaging,
which decreases because inside there is a fruit that breathes.

Most interesting/waiting to taste the fruit from your project !
Cheers ... Jean

hoping they are not poisoned! :d

Ok, seems that I was able to do some progress here but, obviously, there is something that I think doesn't work



In your opinion this way the value of rco2 change with the new value of Co2i or it remains the initial value that I have set?

Prova modello permeabilita.sm (129 KiB) downloaded 27 time(s).

...

Wrote

...

Really thank you for this correction, seems great!

g Ok, definitely I have to study hard and better how to use smath and repay the community.

I think you need something like this.

Modeling respiration-transpiration in a modified atmosphere packaging system containing blueberry (uni).sm (15 KiB) downloaded 35 time(s).
Modeling respiration-transpiration in a modified atmosphere packaging system containing blueberry (uni).pdf (61 KiB) downloaded 42 time(s).
Modeling respiration-transpiration in a modified atmosphere packaging system containing blueberry (2002).pdf (349 KiB) downloaded 37 time(s).

Thank you a lot for all this advice.

Now I work a little on this thing and we will see what progress I'm able to do.

I'm sure that in the end, it will work!

Wrote

Now I work a little on this thing and we will see what progress I'm able to do.

AbsTol, RelTol is very specific w/o project application(s)
The attached is suggestive of exploring more.

ODE GearsBDF Undocumented.sm (18 KiB) downloaded 31 time(s).

Wrote

From the web visit, if 9 out of 10 same link are "404",
the originator is negligent, not to say "not trustable"
Paying $ to Elswier ... my ass !
No need for all that jargon, just give what you want to control,
I will close a control loop to optimum degree of accuracy !

Sorry, for sure is for my bad english, I'm missing the meaning.

What I want to obtain is the evolution of the atmospheric concentration and respiration in the packaging.

So something like



That is more or less what uni has done

Wrote

... blue berries that have been hyper-frozen are much better
than fresh blue berries. I get my fresh blue berries from next farmer,
enjoy fresh and don't freeze. Never purchase blue berries from California
in winter Quebec. Just leave them for the naive shoppers.

Lol..actually I will have to use this for things related to strawberries...I don't even like strawberries...end at the end of the day the thing that I have a real interest to see is how damn big must be the pore in the film for avoid to reach the 0% of O2

You can set breakpoint on line in D(t,oco) and you will see how values changed.

Wrote

You can set breakpoint on line in D(t,oco) and you will see how values changed.

Yes, I have to study a little bit about this function of smath...to be honest, all the functions!

In general, there is something that doesn't work properly, because the chart describes the depleting and the increment almost linear until the O2 don't reach 0. After that point the CO2 increment start to being described in a "realistic way


I mean, I'm expecting to see something like that (the thick blue lines)

You need to set real values for all variables. It is not entirely clear from the article what values to use. I can't help here, because I'm not familiar with this task.
I have demonstrated how you can solve this problem. Now you just need to correctly describe it in terms of the program. I wish you success.

Wrote

You need to set real values for all variables. It is not entirely clear from the article what values to use. I can't help here, because I'm not familiar with this task.
I have demonstrated how you can solve this problem. Now you just need to correctly describe it in terms of the program. I wish you success.

Thank you a lot my friend, I really appreciate the help.

When all will be done I will post here the program, so that it can be useful for everyone.

Wrote

I mean, I'm expecting to see something like that (the thick blue lines)

Like this ??? ... freak parameters at will .

... up to You the expert !
Cheers ... Jean

Prova modello permeabilita.sm (129 KiB) downloaded 35 time(s).