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How to translate compartmentalized liver to analog computer? I Just want to learn to translate the figure to equations. 

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Highly reputed source(International)-:





The compartmental analysis figure is the diagram that I want to translate to differential equations and eventually analog computer.


This is from


This book. IDK about the author, but I bet that this is extremely reliable compared to the materials locally available and written by local authors. But it doesn't tell which equation it is modeling, so I am not 100% sure about it.

It has problems as well-:


It doesn't use negative for K12 And idk why is it using negative for K23.


Less reputed source-:


This is pretty ambiguous, their equation and figure don't even match.


Highly reputed source(LOCAL)-:




If this source is correct, I don't understand how is it correct?


My thoughts about sign what they should be-:


 If the arrows are coming towards the block in consideration, add + sign else add - sign.

For eg-: consider x1 block, then we find x1', for that + will be what comes inside i.e K21*x2, and - will be what goes outside ie.K12*x1. 

My Teacher(He hasn't written any pdfs that I know of)-:

He says "some books have written plus(in K21) while some minus I am not sure what it is actually." He is not the one who will check my final exam paper.




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The honest answer from Digilent's end of things is that this question (a real life application of a process control problem) is beyond the scope of our Forum.

When I glance through the diagrams, it seems that the equations associated with the second set of diagrams are correct with the negative sign (though I have never studied this particular biological process so I cannot verify which source is correct). All of the triangles are an amplifier/adder of some kind; there are a number of different resources online that describe how different types of amplifiers work and are calculated in electronic hardware.


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