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\author "" |
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\end_header |
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|
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\begin_body |
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|
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\begin_layout Chapter |
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Vessel Model for Beginners |
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\begin_inset LatexCommand label |
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name "cha:model1" |
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|
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\end_inset |
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|
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|
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\end_layout |
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|
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\begin_layout Standard |
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You read our propaganda about the ASCEND system in which we said it was |
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to help technical people create hard models. |
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We said you can tackle really large models -- 100,000 equations, compiling |
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and solving them in minutes on a PC. |
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We also pointed out that you can readily solve the small problems many |
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currently solve using a spreadsheet, only once posed you can solve them |
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inside out, upside down and backwards. |
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|
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\end_layout |
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|
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\begin_layout Standard |
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This sounded intriguing so you downloaded the system and installed it. |
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Hopefully, this proved quite straight forward. |
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You double-clicked the ASCEND icon on your desktop and started it up for |
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the first time. |
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Four windows opened up. |
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You panicked. |
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|
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\end_layout |
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|
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\begin_layout Standard |
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Who wouldn't? |
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\end_layout |
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|
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\begin_layout Standard |
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To use this system properly requires that you learn how to use it. |
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If you pay the price to do so - and we hope it is not a large price, then |
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we believe you will find the tools we have provided to help you create |
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and debug models will pay you back handsomely. |
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|
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\end_layout |
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|
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\begin_layout Standard |
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This chapter |
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\noun off |
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and the next two chapters ( |
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\noun default |
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Chapter |
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\noun off |
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|
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\begin_inset LatexCommand ref |
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reference "cha:model2" |
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|
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\end_inset |
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|
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and |
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\noun default |
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Chapter |
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\noun off |
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|
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\begin_inset LatexCommand ref |
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reference "cha:model3" |
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|
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\end_inset |
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|
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) |
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\noun default |
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|
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\noun off |
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are meant to be a good first step along the path to learning how to use |
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ASCEND. |
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We |
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\noun default |
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will |
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\noun off |
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lead you through the steps for creating and testing a simple model. |
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You will also learn how to improve this model so it may be more readily |
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shared with others. |
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We will present our reasons for the steps we take. |
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We |
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\noun default |
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will |
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\noun off |
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show you all the buttons you should push as you proceed. |
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\end_layout |
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|
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\begin_layout Standard |
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We strongly suggest you put time aside and go through all three of these |
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early chapters to introduce yourself to ASCEND. |
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It should take you about two to three hours. |
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The second chapter is particularly important if you wish to understand |
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our approach to good modeling practices. |
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\end_layout |
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|
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\begin_layout Standard |
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\begin_inset Marginal |
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status collapsed |
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|
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\begin_layout Standard |
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the problem |
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\end_layout |
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|
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\end_inset |
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|
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Step 1: |
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\emph on |
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We are going to create and test an ASCEND model to compute, the mass of |
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the metal in the sides and ends of the thin-walled cylindrical vessel |
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\emph default |
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|
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\begin_inset LatexCommand index |
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name "vessel" |
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|
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\end_inset |
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|
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|
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\emph on |
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shown in Figure |
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\begin_inset LatexCommand ref |
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reference "fig:model1.thinWalledVessel" |
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|
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\end_inset |
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|
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. |
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|
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\end_layout |
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|
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\begin_layout Standard |
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\begin_inset Float figure |
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wide false |
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sideways false |
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status open |
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\begin_layout Standard |
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\noun off |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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\InsetSpace ~ |
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|
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\begin_inset Graphics |
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filename howto-model1Fig1.eps |
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BoundingBox 0bp 0bp 280bp 260bp |
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|
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\end_inset |
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|
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|
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\end_layout |
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|
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\begin_layout Standard |
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\begin_inset Caption |
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|
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\begin_layout Standard |
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A thin-walled cylindrical vessel with flat ends |
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\begin_inset LatexCommand label |
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name "fig:model1.thinWalledVessel" |
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|
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\end_inset |
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|
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|
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\end_layout |
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|
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\end_inset |
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|
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|
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\end_layout |
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|
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\end_inset |
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|
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|
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\end_layout |
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|
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\begin_layout Standard |
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Step 2: |
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\emph on |
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This model is to become a part of a library of models which others can use |
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in the future. |
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You must document it. |
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You must add methods to it to make it easy for others to make it well-posed. |
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You should probably parameterize it, and finally you must create a script |
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which anyone can easily run that solves an example problem to illustrate |
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its use. |
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\end_layout |
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|
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\begin_layout Standard |
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\begin_inset Marginal |
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status collapsed |
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|
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\begin_layout Standard |
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topics covered |
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\end_layout |
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|
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\end_inset |
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|
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Topics covered in this and the following two chapters are: |
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\end_layout |
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|
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\begin_layout Itemize |
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\begin_inset Marginal |
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status collapsed |
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|
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\begin_layout Standard |
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T |
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\noun off |
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his chapter) |
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\end_layout |
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|
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\end_inset |
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|
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Converting the word description to an ASCEND model. |
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\end_layout |
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|
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\begin_layout Itemize |
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Loading the model into ASCEND, dealing with the error messages. |
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\end_layout |
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|
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\begin_layout Itemize |
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Compiling the model. |
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\end_layout |
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|
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\begin_layout Itemize |
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Browsing the model to see if it looks right |
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\end_layout |
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|
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\begin_layout Itemize |
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Solving the model. |
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\end_layout |
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|
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\begin_layout Itemize |
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Examining the results. |
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\end_layout |
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|
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\begin_layout Itemize |
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More thoroughly testing the model. |
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\end_layout |
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|
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\begin_layout Itemize |
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\begin_inset Marginal |
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status collapsed |
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|
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\begin_layout Standard |
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Chapter\InsetSpace ~ |
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|
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\begin_inset LatexCommand vref |
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reference "cha:model2" |
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|
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\end_inset |
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|
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|
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\end_layout |
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|
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\end_inset |
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|
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Converting the model to a more reusable form by adding methods to it and |
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by parameterizing it. |
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\end_layout |
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|
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\begin_layout Itemize |
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Creating a script to load and execute an instance of the model. |
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\end_layout |
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|
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\begin_layout Itemize |
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\begin_inset Marginal |
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status collapsed |
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|
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\begin_layout Standard |
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Chapter\InsetSpace ~ |
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|
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\begin_inset LatexCommand vref |
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reference "cha:model3" |
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|
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\end_inset |
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|
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|
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\end_layout |
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|
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\end_inset |
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|
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Creating an array of models. |
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\end_layout |
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|
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\begin_layout Itemize |
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Using an existing library model for plotting. |
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\end_layout |
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|
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\begin_layout Itemize |
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Creating a case study using the model. |
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\end_layout |
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|
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\begin_layout Standard |
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We shall introduce many of the features of the modeling language as well |
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as the use of the interactive interface you use when compiling, debugging, |
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solving and exploring your model. |
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Language features include units conversion, arrays and sets. |
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\end_layout |
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|
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\begin_layout Section |
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Converting the word description into an ASCEND model |
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\begin_inset LatexCommand label |
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name "sec:model1.converting-the-word" |
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|
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\end_inset |
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|
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|
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\end_layout |
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|
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\begin_layout Standard |
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\begin_inset Marginal |
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status collapsed |
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|
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\begin_layout Standard |
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an ASCEND model is a type |
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\begin_inset LatexCommand index |
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name "type" |
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|
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\end_inset |
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|
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definition |
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\end_layout |
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|
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\end_inset |
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|
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Every ASCEND model is, in fact, a type definition. |
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To "solve a model," we make an instance |
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\begin_inset LatexCommand index |
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name "instance" |
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|
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\end_inset |
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|
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of a type and solve the instance. |
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So we shall start by creating a vessel type definition. |
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We will have to create our type definition as a text file using a text |
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editor. |
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(Some simple text editors |
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\begin_inset LatexCommand index |
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name "text editors" |
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|
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\end_inset |
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|
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include |
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\family typewriter |
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emacs |
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\family default |
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|
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\begin_inset LatexCommand index |
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name "emacs" |
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|
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\end_inset |
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|
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and |
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\family typewriter |
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gedit |
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\begin_inset LatexCommand index |
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name "gedit" |
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|
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\end_inset |
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|
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|
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\family default |
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on Linux, and Notepad |
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\begin_inset LatexCommand index |
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name "Notepad" |
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|
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\end_inset |
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|
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and TextPad |
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\begin_inset LatexCommand index |
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name "TextPad" |
485 |
|
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\end_inset |
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|
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on Windows. |
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We shall discuss editors shortly.) |
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\end_layout |
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|
492 |
\begin_layout Standard |
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We need first to decide the parts to our model. |
494 |
In this case we know that we need the variables |
495 |
\begin_inset LatexCommand index |
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name "variables, vessel" |
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|
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\end_inset |
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|
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listed in Table |
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\begin_inset LatexCommand ref |
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reference "tab:model1.variablesVesselModel" |
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|
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\end_inset |
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|
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|
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\noun off |
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. |
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We readily fill in the first three columns in this table. |
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We shall discuss the entry in the last column in a moment. |
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\end_layout |
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|
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\begin_layout Standard |
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\begin_inset Float table |
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wide false |
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sideways false |
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status open |
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|
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\begin_layout Standard |
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\begin_inset Caption |
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|
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\begin_layout Standard |
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Variables required for model |
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\begin_inset LatexCommand label |
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name "tab:model1.variablesVesselModel" |
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|
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\end_inset |
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|
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\end_layout |
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\end_inset |
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\end_layout |
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|
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\begin_layout Standard |
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\begin_inset Tabular |
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<lyxtabular version="3" rows="5" columns="4"> |
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<features> |
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<column alignment="center" valignment="top" leftline="true" width="0"> |
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<column alignment="center" valignment="top" leftline="true" width="0"> |
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<column alignment="center" valignment="top" leftline="true" width="0"> |
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<column alignment="center" valignment="top" leftline="true" rightline="true" width="1in"> |
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<row topline="true" bottomline="true"> |
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Symbol |
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
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\begin_inset Text |
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|
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\begin_layout Standard |
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Meaning |
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\end_layout |
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|
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\end_inset |
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</cell> |
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
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\begin_inset Text |
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|
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\begin_layout Standard |
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Typical Units |
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\end_layout |
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|
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\end_inset |
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</cell> |
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
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\begin_inset Text |
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|
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ASCEND variable type |
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\end_layout |
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|
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</cell> |
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</row> |
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<row topline="true"> |
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D |
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\end_layout |
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</cell> |
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
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\begin_inset Text |
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|
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\begin_layout Standard |
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vessel diameter |
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\end_layout |
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|
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\end_inset |
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</cell> |
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
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\begin_inset Text |
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\begin_layout Standard |
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m, ft |
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\end_layout |
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|
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\end_inset |
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</cell> |
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<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
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length |
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H |
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\end_layout |
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</cell> |
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<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
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vessel height |
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|
682 |
\begin_layout Standard |
683 |
wall thickness |
684 |
\end_layout |
685 |
|
686 |
\end_inset |
687 |
</cell> |
688 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
689 |
\begin_inset Text |
690 |
|
691 |
\begin_layout Standard |
692 |
mm, in |
693 |
\end_layout |
694 |
|
695 |
\end_inset |
696 |
</cell> |
697 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
698 |
\begin_inset Text |
699 |
|
700 |
\begin_layout Standard |
701 |
|
702 |
\family typewriter |
703 |
length |
704 |
\end_layout |
705 |
|
706 |
\end_inset |
707 |
</cell> |
708 |
</row> |
709 |
<row topline="true" bottomline="true"> |
710 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
711 |
\begin_inset Text |
712 |
|
713 |
\begin_layout Standard |
714 |
|
715 |
\family typewriter |
716 |
metal_density |
717 |
\end_layout |
718 |
|
719 |
\end_inset |
720 |
</cell> |
721 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
722 |
\begin_inset Text |
723 |
|
724 |
\begin_layout Standard |
725 |
metal density |
726 |
\end_layout |
727 |
|
728 |
\end_inset |
729 |
</cell> |
730 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
731 |
\begin_inset Text |
732 |
|
733 |
\begin_layout Standard |
734 |
kg/m |
735 |
\begin_inset Formula $^{\textrm{3}}$ |
736 |
\end_inset |
737 |
|
738 |
, lbm/ft |
739 |
\begin_inset Formula $^{\textrm{3}}$ |
740 |
\end_inset |
741 |
|
742 |
|
743 |
\end_layout |
744 |
|
745 |
\end_inset |
746 |
</cell> |
747 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
748 |
\begin_inset Text |
749 |
|
750 |
\begin_layout Standard |
751 |
|
752 |
\family typewriter |
753 |
mass_density |
754 |
\end_layout |
755 |
|
756 |
\end_inset |
757 |
</cell> |
758 |
</row> |
759 |
</lyxtabular> |
760 |
|
761 |
\end_inset |
762 |
|
763 |
|
764 |
\end_layout |
765 |
|
766 |
\end_inset |
767 |
|
768 |
|
769 |
\end_layout |
770 |
|
771 |
\begin_layout Standard |
772 |
We will be computing the masses for the metal in the side wall and in the |
773 |
ends for this vessel. |
774 |
As this is a thin-walled vessel, we shall compute the volume of metal as |
775 |
the area of the walls times the wall thickness. |
776 |
The following equations allow us to compute the required areas |
777 |
\end_layout |
778 |
|
779 |
\begin_layout Standard |
780 |
\begin_inset Formula \begin{equation} |
781 |
\mathrm{side\, wall\, area}=\pi DH\label{eq:model1.side-wall-area}\end{equation} |
782 |
|
783 |
\end_inset |
784 |
|
785 |
|
786 |
\end_layout |
787 |
|
788 |
\begin_layout Standard |
789 |
\begin_inset Formula \begin{equation} |
790 |
\mathrm{single\, end\, area}=\frac{\pi D^{2}}{4}\label{eq:model1.single-end-area}\end{equation} |
791 |
|
792 |
\end_inset |
793 |
|
794 |
|
795 |
\end_layout |
796 |
|
797 |
\begin_layout Standard |
798 |
We should be interested in the volume of the vessel, which we compute as: |
799 |
\end_layout |
800 |
|
801 |
\begin_layout Standard |
802 |
\begin_inset Formula \begin{equation} |
803 |
\mathrm{vessel\, volume}=\mathrm{single\, end\, area}\times H\label{eq:model1.vessel-volume}\end{equation} |
804 |
|
805 |
\end_inset |
806 |
|
807 |
|
808 |
\end_layout |
809 |
|
810 |
\begin_layout Standard |
811 |
We add the variables in Table |
812 |
\begin_inset LatexCommand ref |
813 |
reference "tab:model1.moreVariablesVessel" |
814 |
|
815 |
\end_inset |
816 |
|
817 |
|
818 |
\noun off |
819 |
to our list. |
820 |
\end_layout |
821 |
|
822 |
\begin_layout Standard |
823 |
\begin_inset Float table |
824 |
wide false |
825 |
sideways false |
826 |
status open |
827 |
|
828 |
\begin_layout Standard |
829 |
\begin_inset Caption |
830 |
|
831 |
\begin_layout Standard |
832 |
Some more variables |
833 |
\begin_inset LatexCommand index |
834 |
name "variables, vessel" |
835 |
|
836 |
\end_inset |
837 |
|
838 |
required for vessel model |
839 |
\begin_inset LatexCommand label |
840 |
name "tab:model1.moreVariablesVessel" |
841 |
|
842 |
\end_inset |
843 |
|
844 |
|
845 |
\end_layout |
846 |
|
847 |
\end_inset |
848 |
|
849 |
|
850 |
\end_layout |
851 |
|
852 |
\begin_layout Standard |
853 |
\begin_inset Tabular |
854 |
<lyxtabular version="3" rows="6" columns="4"> |
855 |
<features> |
856 |
<column alignment="center" valignment="top" leftline="true" width="0"> |
857 |
<column alignment="center" valignment="top" leftline="true" width="1.5in"> |
858 |
<column alignment="center" valignment="top" leftline="true" width="0"> |
859 |
<column alignment="center" valignment="top" leftline="true" rightline="true" width="1in"> |
860 |
<row topline="true" bottomline="true"> |
861 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
862 |
\begin_inset Text |
863 |
|
864 |
\begin_layout Standard |
865 |
Symbol |
866 |
\end_layout |
867 |
|
868 |
\end_inset |
869 |
</cell> |
870 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
871 |
\begin_inset Text |
872 |
|
873 |
\begin_layout Standard |
874 |
Meaning |
875 |
\end_layout |
876 |
|
877 |
\end_inset |
878 |
</cell> |
879 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
880 |
\begin_inset Text |
881 |
|
882 |
\begin_layout Standard |
883 |
Typical Units |
884 |
\end_layout |
885 |
|
886 |
\end_inset |
887 |
</cell> |
888 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
889 |
\begin_inset Text |
890 |
|
891 |
\begin_layout Standard |
892 |
ASCEND variable type |
893 |
\end_layout |
894 |
|
895 |
\end_inset |
896 |
</cell> |
897 |
</row> |
898 |
<row topline="true"> |
899 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
900 |
\begin_inset Text |
901 |
|
902 |
\begin_layout Standard |
903 |
|
904 |
\family typewriter |
905 |
side_area |
906 |
\end_layout |
907 |
|
908 |
\end_inset |
909 |
</cell> |
910 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
911 |
\begin_inset Text |
912 |
|
913 |
\begin_layout Standard |
914 |
area in the sidewall of the vessel |
915 |
\end_layout |
916 |
|
917 |
\end_inset |
918 |
</cell> |
919 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
920 |
\begin_inset Text |
921 |
|
922 |
\begin_layout Standard |
923 |
m |
924 |
\begin_inset Formula $^{\textrm{2}}$ |
925 |
\end_inset |
926 |
|
927 |
, ft |
928 |
\begin_inset Formula $^{\textrm{2}}$ |
929 |
\end_inset |
930 |
|
931 |
|
932 |
\end_layout |
933 |
|
934 |
\end_inset |
935 |
</cell> |
936 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
937 |
\begin_inset Text |
938 |
|
939 |
\begin_layout Standard |
940 |
|
941 |
\family typewriter |
942 |
area |
943 |
\end_layout |
944 |
|
945 |
\end_inset |
946 |
</cell> |
947 |
</row> |
948 |
<row topline="true"> |
949 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
950 |
\begin_inset Text |
951 |
|
952 |
\begin_layout Standard |
953 |
|
954 |
\family typewriter |
955 |
end_area |
956 |
\end_layout |
957 |
|
958 |
\end_inset |
959 |
</cell> |
960 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
961 |
\begin_inset Text |
962 |
|
963 |
\begin_layout Standard |
964 |
total area iin the ends of the vessel |
965 |
\end_layout |
966 |
|
967 |
\end_inset |
968 |
</cell> |
969 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
970 |
\begin_inset Text |
971 |
|
972 |
\begin_layout Standard |
973 |
m |
974 |
\begin_inset Formula $^{\textrm{2}}$ |
975 |
\end_inset |
976 |
|
977 |
, ft |
978 |
\begin_inset Formula $^{\textrm{2}}$ |
979 |
\end_inset |
980 |
|
981 |
|
982 |
\end_layout |
983 |
|
984 |
\end_inset |
985 |
</cell> |
986 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
987 |
\begin_inset Text |
988 |
|
989 |
\begin_layout Standard |
990 |
|
991 |
\family typewriter |
992 |
area |
993 |
\end_layout |
994 |
|
995 |
\end_inset |
996 |
</cell> |
997 |
</row> |
998 |
<row topline="true"> |
999 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
1000 |
\begin_inset Text |
1001 |
|
1002 |
\begin_layout Standard |
1003 |
|
1004 |
\family typewriter |
1005 |
vessel_volume |
1006 |
\end_layout |
1007 |
|
1008 |
\end_inset |
1009 |
</cell> |
1010 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
1011 |
\begin_inset Text |
1012 |
|
1013 |
\begin_layout Standard |
1014 |
volume of the vessel |
1015 |
\end_layout |
1016 |
|
1017 |
\end_inset |
1018 |
</cell> |
1019 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
1020 |
\begin_inset Text |
1021 |
|
1022 |
\begin_layout Standard |
1023 |
m |
1024 |
\begin_inset Formula $^{3}$ |
1025 |
\end_inset |
1026 |
|
1027 |
, ft |
1028 |
\begin_inset Formula $^{\textrm{3}}$ |
1029 |
\end_inset |
1030 |
|
1031 |
|
1032 |
\end_layout |
1033 |
|
1034 |
\end_inset |
1035 |
</cell> |
1036 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
1037 |
\begin_inset Text |
1038 |
|
1039 |
\begin_layout Standard |
1040 |
|
1041 |
\family typewriter |
1042 |
volume |
1043 |
\end_layout |
1044 |
|
1045 |
\end_inset |
1046 |
</cell> |
1047 |
</row> |
1048 |
<row topline="true"> |
1049 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
1050 |
\begin_inset Text |
1051 |
|
1052 |
\begin_layout Standard |
1053 |
|
1054 |
\family typewriter |
1055 |
metal_volume |
1056 |
\end_layout |
1057 |
|
1058 |
\end_inset |
1059 |
</cell> |
1060 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
1061 |
\begin_inset Text |
1062 |
|
1063 |
\begin_layout Standard |
1064 |
total volume of metal in the walls |
1065 |
\end_layout |
1066 |
|
1067 |
\end_inset |
1068 |
</cell> |
1069 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
1070 |
\begin_inset Text |
1071 |
|
1072 |
\begin_layout Standard |
1073 |
m |
1074 |
\begin_inset Formula $^{3}$ |
1075 |
\end_inset |
1076 |
|
1077 |
, ft |
1078 |
\begin_inset Formula $^{\textrm{3}}$ |
1079 |
\end_inset |
1080 |
|
1081 |
|
1082 |
\end_layout |
1083 |
|
1084 |
\end_inset |
1085 |
</cell> |
1086 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
1087 |
\begin_inset Text |
1088 |
|
1089 |
\begin_layout Standard |
1090 |
|
1091 |
\family typewriter |
1092 |
volume |
1093 |
\end_layout |
1094 |
|
1095 |
\end_inset |
1096 |
</cell> |
1097 |
</row> |
1098 |
<row topline="true" bottomline="true"> |
1099 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
1100 |
\begin_inset Text |
1101 |
|
1102 |
\begin_layout Standard |
1103 |
|
1104 |
\family typewriter |
1105 |
metal_mass |
1106 |
\end_layout |
1107 |
|
1108 |
\end_inset |
1109 |
</cell> |
1110 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
1111 |
\begin_inset Text |
1112 |
|
1113 |
\begin_layout Standard |
1114 |
total mass of the metal in the walls of the vessel |
1115 |
\end_layout |
1116 |
|
1117 |
\end_inset |
1118 |
</cell> |
1119 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
1120 |
\begin_inset Text |
1121 |
|
1122 |
\begin_layout Standard |
1123 |
kg, lbm |
1124 |
\end_layout |
1125 |
|
1126 |
\end_inset |
1127 |
</cell> |
1128 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
1129 |
\begin_inset Text |
1130 |
|
1131 |
\begin_layout Standard |
1132 |
|
1133 |
\family typewriter |
1134 |
mass |
1135 |
\end_layout |
1136 |
|
1137 |
\end_inset |
1138 |
</cell> |
1139 |
</row> |
1140 |
</lyxtabular> |
1141 |
|
1142 |
\end_inset |
1143 |
|
1144 |
|
1145 |
\end_layout |
1146 |
|
1147 |
\end_inset |
1148 |
|
1149 |
|
1150 |
\end_layout |
1151 |
|
1152 |
\begin_layout Standard |
1153 |
We believe that no one should create a model of any consequence without |
1154 |
worrying about the units for expressing the variables within it. |
1155 |
We consider that to be a commandment handed down from somewhere on high; |
1156 |
however, we know that others do not believe as we do. |
1157 |
Grant us our beliefs. |
1158 |
We have created in the ASCEND system a library of variable and constant |
1159 |
types called atoms.a4l |
1160 |
\begin_inset LatexCommand index |
1161 |
name "atoms.a4l" |
1162 |
|
1163 |
\end_inset |
1164 |
|
1165 |
. |
1166 |
\end_layout |
1167 |
|
1168 |
\begin_layout Standard |
1169 |
The file type " |
1170 |
\family typewriter |
1171 |
.a4l |
1172 |
\begin_inset LatexCommand index |
1173 |
name "a4l" |
1174 |
|
1175 |
\end_inset |
1176 |
|
1177 |
|
1178 |
\family default |
1179 |
" designates it to be an ASCEND IV library file |
1180 |
\begin_inset LatexCommand index |
1181 |
name "library file" |
1182 |
|
1183 |
\end_inset |
1184 |
|
1185 |
. |
1186 |
Double-click on this link to see the approximately 150 different types |
1187 |
ranging from universal constants |
1188 |
\begin_inset LatexCommand index |
1189 |
name "universal constants" |
1190 |
|
1191 |
\end_inset |
1192 |
|
1193 |
such as |
1194 |
\begin_inset Formula $\pi$ |
1195 |
\end_inset |
1196 |
|
1197 |
(=3.14159...) and |
1198 |
\begin_inset Formula $e$ |
1199 |
\end_inset |
1200 |
|
1201 |
(=2.718...) to |
1202 |
\family typewriter |
1203 |
length |
1204 |
\family default |
1205 |
, |
1206 |
\family typewriter |
1207 |
mass |
1208 |
\family default |
1209 |
and |
1210 |
\family typewriter |
1211 |
angle |
1212 |
\family default |
1213 |
. |
1214 |
If we have not created one that you need, you can use this library of types |
1215 |
to see how to construct one for yourself and add it to your file of type |
1216 |
definitions. |
1217 |
You will find detailed instructions for how to make your own variable type |
1218 |
library in Chapter\InsetSpace ~ |
1219 |
|
1220 |
\begin_inset LatexCommand vref |
1221 |
reference "cha:atoms" |
1222 |
|
1223 |
\end_inset |
1224 |
|
1225 |
. |
1226 |
\end_layout |
1227 |
|
1228 |
\begin_layout Standard |
1229 |
\begin_inset Marginal |
1230 |
status collapsed |
1231 |
|
1232 |
\begin_layout Standard |
1233 |
type definition library for variables and constants |
1234 |
\end_layout |
1235 |
|
1236 |
\end_inset |
1237 |
|
1238 |
ASCEND considers variable and constant types to be elementary or "atomic" |
1239 |
to the system. |
1240 |
These type definitions can contain only attributes for variables and constants. |
1241 |
They cannot contain equations, for example. |
1242 |
Thus ASCEND calls such a type definition an atom rather than a model. |
1243 |
Figure |
1244 |
\begin_inset LatexCommand ref |
1245 |
reference "fig:model1.atomVolume" |
1246 |
|
1247 |
\end_inset |
1248 |
|
1249 |
|
1250 |
\noun off |
1251 |
illustrates the definition for the type volume. |
1252 |
|
1253 |
\end_layout |
1254 |
|
1255 |
\begin_layout Standard |
1256 |
\begin_inset Float figure |
1257 |
wide false |
1258 |
sideways false |
1259 |
status open |
1260 |
|
1261 |
\begin_layout Standard |
1262 |
\begin_inset LatexCommand index |
1263 |
name "ATOM" |
1264 |
|
1265 |
\end_inset |
1266 |
|
1267 |
|
1268 |
\begin_inset ERT |
1269 |
status open |
1270 |
|
1271 |
\begin_layout Standard |
1272 |
|
1273 |
|
1274 |
\backslash |
1275 |
lstset{language=ASCEND} |
1276 |
\end_layout |
1277 |
|
1278 |
\begin_layout Standard |
1279 |
|
1280 |
|
1281 |
\backslash |
1282 |
begin{lstlisting} |
1283 |
\end_layout |
1284 |
|
1285 |
\begin_layout Standard |
1286 |
|
1287 |
ATOM volume REFINES solver_var |
1288 |
\end_layout |
1289 |
|
1290 |
\begin_layout Standard |
1291 |
|
1292 |
DIMENSION L^3 |
1293 |
\end_layout |
1294 |
|
1295 |
\begin_layout Standard |
1296 |
|
1297 |
DEFAULT 100.0{ft^3}; |
1298 |
\end_layout |
1299 |
|
1300 |
\begin_layout Standard |
1301 |
|
1302 |
lower_bound := 0.0{ft^3}; |
1303 |
\end_layout |
1304 |
|
1305 |
\begin_layout Standard |
1306 |
|
1307 |
upper_bound := 1e50{ft^3}; |
1308 |
\end_layout |
1309 |
|
1310 |
\begin_layout Standard |
1311 |
|
1312 |
nominal := 100.0{ft^3}; |
1313 |
\end_layout |
1314 |
|
1315 |
\begin_layout Standard |
1316 |
|
1317 |
END volume; |
1318 |
\end_layout |
1319 |
|
1320 |
\begin_layout Standard |
1321 |
|
1322 |
|
1323 |
\backslash |
1324 |
end{lstlisting} |
1325 |
\end_layout |
1326 |
|
1327 |
\begin_layout Standard |
1328 |
|
1329 |
\end_layout |
1330 |
|
1331 |
\end_inset |
1332 |
|
1333 |
|
1334 |
\end_layout |
1335 |
|
1336 |
\begin_layout Standard |
1337 |
\begin_inset Caption |
1338 |
|
1339 |
\begin_layout Standard |
1340 |
A typical type definition, called an atom, used to define variable and constant |
1341 |
types |
1342 |
\begin_inset LatexCommand label |
1343 |
name "fig:model1.atomVolume" |
1344 |
|
1345 |
\end_inset |
1346 |
|
1347 |
|
1348 |
\end_layout |
1349 |
|
1350 |
\end_inset |
1351 |
|
1352 |
|
1353 |
\end_layout |
1354 |
|
1355 |
\end_inset |
1356 |
|
1357 |
|
1358 |
\end_layout |
1359 |
|
1360 |
\begin_layout Standard |
1361 |
The definition starts by stating that volume is a specialization of |
1362 |
\begin_inset LatexCommand index |
1363 |
name "solver\\_var" |
1364 |
|
1365 |
\end_inset |
1366 |
|
1367 |
|
1368 |
\family typewriter |
1369 |
solver_var |
1370 |
\family default |
1371 |
. |
1372 |
The type |
1373 |
\family typewriter |
1374 |
solver_var |
1375 |
\family default |
1376 |
refines a base type in the system known as |
1377 |
\family typewriter |
1378 |
real |
1379 |
\family default |
1380 |
|
1381 |
\begin_inset LatexCommand index |
1382 |
name "real" |
1383 |
|
1384 |
\end_inset |
1385 |
|
1386 |
and adds several attributes to it that a nonlinear equation solver may |
1387 |
need, such as a lower and upper bounds, a 'fixed' flag, and so forth. |
1388 |
|
1389 |
\end_layout |
1390 |
|
1391 |
\begin_layout Standard |
1392 |
\begin_inset Marginal |
1393 |
status collapsed |
1394 |
|
1395 |
\begin_layout Standard |
1396 |
dimensions |
1397 |
\begin_inset LatexCommand index |
1398 |
name "dimensions" |
1399 |
|
1400 |
\end_inset |
1401 |
|
1402 |
and units |
1403 |
\begin_inset LatexCommand index |
1404 |
name "units" |
1405 |
|
1406 |
\end_inset |
1407 |
|
1408 |
in ASCEND. |
1409 |
|
1410 |
\end_layout |
1411 |
|
1412 |
\end_inset |
1413 |
|
1414 |
The type definition for volume states that volume has dimensionality of |
1415 |
length to the power 3 ( |
1416 |
\family typewriter |
1417 |
L^3 |
1418 |
\family default |
1419 |
) where L is one of the 10 dimensions supported by ASCEND (see |
1420 |
\noun off |
1421 |
in ASCEND Syntax document for the 10 dimensions defined within the ASCEND |
1422 |
language). |
1423 |
\end_layout |
1424 |
|
1425 |
\begin_layout Standard |
1426 |
One may express the value for a volume using any units which are consistent |
1427 |
with the dimensionality of |
1428 |
\family typewriter |
1429 |
L^3 |
1430 |
\family default |
1431 |
, such as |
1432 |
\family typewriter |
1433 |
{ft^3} |
1434 |
\family default |
1435 |
, |
1436 |
\family typewriter |
1437 |
{m^3} |
1438 |
\family default |
1439 |
, |
1440 |
\family typewriter |
1441 |
{gal} |
1442 |
\family default |
1443 |
, or even |
1444 |
\family typewriter |
1445 |
{mile^4/mm} |
1446 |
\family default |
1447 |
. |
1448 |
Setting the lower bound to |
1449 |
\family typewriter |
1450 |
0 {ft^3} |
1451 |
\family default |
1452 |
says volume must be a nonnegative number. |
1453 |
ASCEND used the nominal value for scaling a variable of type volume when |
1454 |
solving, here |
1455 |
\begin_inset Formula $100\,\mathrm{ft}^{3}$ |
1456 |
\end_inset |
1457 |
|
1458 |
. |
1459 |
\end_layout |
1460 |
|
1461 |
\begin_layout Standard |
1462 |
One may change the values for the bounds, default and nominal values at |
1463 |
any time. |
1464 |
\end_layout |
1465 |
|
1466 |
\begin_layout Standard |
1467 |
We now can understand the last column in Table |
1468 |
\begin_inset LatexCommand ref |
1469 |
reference "tab:model1.variablesVesselModel" |
1470 |
|
1471 |
\end_inset |
1472 |
|
1473 |
|
1474 |
\noun off |
1475 |
and |
1476 |
\noun default |
1477 |
Table |
1478 |
\noun off |
1479 |
|
1480 |
\begin_inset LatexCommand ref |
1481 |
reference "tab:model1.moreVariablesVessel" |
1482 |
|
1483 |
\end_inset |
1484 |
|
1485 |
. |
1486 |
For each variable or constant in the system, we have identified its type |
1487 |
in the file |
1488 |
\family typewriter |
1489 |
\noun default |
1490 |
atoms.a4l |
1491 |
\family default |
1492 |
\noun off |
1493 |
. |
1494 |
That is, we looked in this file for the type definition that corresponded |
1495 |
to the variable we were defining and listed that type here. |
1496 |
This task is not as onerous as it seems. |
1497 |
As we shall see later, we provide a tool to find for you all atom types |
1498 |
that correspond to a particular set of units, e.g, |
1499 |
\family typewriter |
1500 |
\noun default |
1501 |
ft^3 |
1502 |
\family default |
1503 |
\noun off |
1504 |
-- i.e., the computer will do the searching for you. |
1505 |
\end_layout |
1506 |
|
1507 |
\begin_layout Standard |
1508 |
In Figure |
1509 |
\begin_inset LatexCommand ref |
1510 |
reference "fig:model1.universalConstant" |
1511 |
|
1512 |
\end_inset |
1513 |
|
1514 |
|
1515 |
\noun off |
1516 |
we see the definition of one of the universal constants contained in |
1517 |
\family typewriter |
1518 |
\noun default |
1519 |
atoms.a4l |
1520 |
\family default |
1521 |
\noun off |
1522 |
. |
1523 |
This definition is very short; it gives the name of the type |
1524 |
\family typewriter |
1525 |
\noun default |
1526 |
circle_constant |
1527 |
\family default |
1528 |
\noun off |
1529 |
|
1530 |
\begin_inset LatexCommand index |
1531 |
name "circle\\_constant" |
1532 |
|
1533 |
\end_inset |
1534 |
|
1535 |
, that it refines |
1536 |
\family typewriter |
1537 |
\noun default |
1538 |
real_constant |
1539 |
\family default |
1540 |
\noun off |
1541 |
|
1542 |
\begin_inset LatexCommand index |
1543 |
name "real\\_constant" |
1544 |
|
1545 |
\end_inset |
1546 |
|
1547 |
and that it has the value |
1548 |
\family typewriter |
1549 |
\noun default |
1550 |
1 {PI |
1551 |
\begin_inset LatexCommand index |
1552 |
name "PI" |
1553 |
|
1554 |
\end_inset |
1555 |
|
1556 |
} |
1557 |
\family default |
1558 |
\noun off |
1559 |
|
1560 |
\begin_inset LatexCommand index |
1561 |
name "\\{PI\\}" |
1562 |
|
1563 |
\end_inset |
1564 |
|
1565 |
where the internal conversion needed for |
1566 |
\family typewriter |
1567 |
\noun default |
1568 |
{PI} |
1569 |
\family default |
1570 |
\noun off |
1571 |
is defined in the file defining the built-in units in ASCEND. |
1572 |
One can add more units if desired at any time to ASCEND by defining one |
1573 |
or more personal units files ( |
1574 |
\noun default |
1575 |
Chapter |
1576 |
\noun off |
1577 |
|
1578 |
\begin_inset LatexCommand vref |
1579 |
reference "cha:units" |
1580 |
|
1581 |
\end_inset |
1582 |
|
1583 |
|
1584 |
\noun default |
1585 |
|
1586 |
\noun off |
1587 |
tells you how to do this). |
1588 |
\end_layout |
1589 |
|
1590 |
\begin_layout Standard |
1591 |
\begin_inset Marginal |
1592 |
status collapsed |
1593 |
|
1594 |
\begin_layout Standard |
1595 |
universal constant |
1596 |
\begin_inset LatexCommand index |
1597 |
name "universal constant" |
1598 |
|
1599 |
\end_inset |
1600 |
|
1601 |
definition |
1602 |
\end_layout |
1603 |
|
1604 |
\end_inset |
1605 |
|
1606 |
|
1607 |
\begin_inset Float figure |
1608 |
wide false |
1609 |
sideways false |
1610 |
status open |
1611 |
|
1612 |
\begin_layout LyX-Code |
1613 |
\begin_inset ERT |
1614 |
status open |
1615 |
|
1616 |
\begin_layout Standard |
1617 |
|
1618 |
|
1619 |
\backslash |
1620 |
begin{ascend} |
1621 |
\end_layout |
1622 |
|
1623 |
\begin_layout Standard |
1624 |
|
1625 |
UNIVERSAL CONSTANT circle_constant |
1626 |
\end_layout |
1627 |
|
1628 |
\begin_layout Standard |
1629 |
|
1630 |
REFINES real_constant :== 1{PI}; |
1631 |
\end_layout |
1632 |
|
1633 |
\begin_layout Standard |
1634 |
|
1635 |
|
1636 |
\backslash |
1637 |
end{ascend} |
1638 |
\end_layout |
1639 |
|
1640 |
\end_inset |
1641 |
|
1642 |
|
1643 |
\end_layout |
1644 |
|
1645 |
\begin_layout Standard |
1646 |
\begin_inset Caption |
1647 |
|
1648 |
\begin_layout Standard |
1649 |
\begin_inset LatexCommand label |
1650 |
name "fig:model1.universalConstant" |
1651 |
|
1652 |
\end_inset |
1653 |
|
1654 |
Type definition for |
1655 |
\family typewriter |
1656 |
circle_constant; |
1657 |
\family default |
1658 |
has value of |
1659 |
\family typewriter |
1660 |
1 {PI} |
1661 |
\family default |
1662 |
or 3.1415927 |
1663 |
\end_layout |
1664 |
|
1665 |
\end_inset |
1666 |
|
1667 |
|
1668 |
\end_layout |
1669 |
|
1670 |
\end_inset |
1671 |
|
1672 |
|
1673 |
\end_layout |
1674 |
|
1675 |
\begin_layout Standard |
1676 |
We shall in fact find this constant useful in our program, and we can either |
1677 |
introduce a constant with this value or simply use the value |
1678 |
\family typewriter |
1679 |
1{PI} |
1680 |
\family default |
1681 |
in our program. |
1682 |
We shall choose to do the latter. |
1683 |
\end_layout |
1684 |
|
1685 |
\begin_layout Standard |
1686 |
It is time to write our first version for the model, which we do in Figure |
1687 |
|
1688 |
\begin_inset LatexCommand ref |
1689 |
reference "fig:model1.modelVessel" |
1690 |
|
1691 |
\end_inset |
1692 |
|
1693 |
|
1694 |
\noun off |
1695 |
( |
1696 |
\noun default |
1697 |
available as |
1698 |
\begin_inset LatexCommand index |
1699 |
name "vesselPlain.a4c" |
1700 |
|
1701 |
\end_inset |
1702 |
|
1703 |
|
1704 |
\family typewriter |
1705 |
vesselPlain.a4c |
1706 |
\family default |
1707 |
in the ASCEND model library). |
1708 |
|
1709 |
\noun off |
1710 |
We first list any other files containing type definitions which this model |
1711 |
will use; here we list |
1712 |
\family typewriter |
1713 |
\noun default |
1714 |
"atoms.a4l" |
1715 |
\family default |
1716 |
\noun off |
1717 |
following the keyword |
1718 |
\family typewriter |
1719 |
\noun default |
1720 |
REQUIRE |
1721 |
\family default |
1722 |
\noun off |
1723 |
|
1724 |
\begin_inset LatexCommand index |
1725 |
name "REQUIRE" |
1726 |
|
1727 |
\end_inset |
1728 |
|
1729 |
. |
1730 |
ASCEND is sensitive to case so pay attention to where we use and do not |
1731 |
use capital letters. |
1732 |
Keywords are always capitalized. |
1733 |
Often for clarification we use capital letters in a name we use for a variable |
1734 |
or label (e.g., we use |
1735 |
\family typewriter |
1736 |
\noun default |
1737 |
D |
1738 |
\family default |
1739 |
\noun off |
1740 |
for diameter rather than |
1741 |
\family typewriter |
1742 |
\noun default |
1743 |
d |
1744 |
\family default |
1745 |
\noun off |
1746 |
). |
1747 |
Note that all ASCEND statements end with a semicolon (i.e., with |
1748 |
\noun default |
1749 |
' |
1750 |
\family typewriter |
1751 |
; |
1752 |
\family default |
1753 |
' |
1754 |
\noun off |
1755 |
) and not at the end of a line and that blank lines have no impact. |
1756 |
Comments are between opening and closing parenthesis/asterisk pairs, i.e., |
1757 |
' |
1758 |
\family typewriter |
1759 |
\noun default |
1760 |
(* |
1761 |
\family default |
1762 |
\noun off |
1763 |
' and ' |
1764 |
\family typewriter |
1765 |
\noun default |
1766 |
*) |
1767 |
\family default |
1768 |
\noun off |
1769 |
'. |
1770 |
\end_layout |
1771 |
|
1772 |
\begin_layout Standard |
1773 |
\begin_inset Marginal |
1774 |
status collapsed |
1775 |
|
1776 |
\begin_layout Standard |
1777 |
the first version of the code for vessel |
1778 |
\end_layout |
1779 |
|
1780 |
\end_inset |
1781 |
|
1782 |
|
1783 |
\begin_inset Float figure |
1784 |
wide false |
1785 |
sideways false |
1786 |
status open |
1787 |
|
1788 |
\begin_layout LyX-Code |
1789 |
\begin_inset ERT |
1790 |
status open |
1791 |
|
1792 |
\begin_layout Standard |
1793 |
|
1794 |
|
1795 |
\backslash |
1796 |
begin{ascend} |
1797 |
\end_layout |
1798 |
|
1799 |
\begin_layout Standard |
1800 |
|
1801 |
REQUIRE "atoms.a4l"; |
1802 |
\end_layout |
1803 |
|
1804 |
\begin_layout Standard |
1805 |
|
1806 |
MODEL vessel; |
1807 |
\end_layout |
1808 |
|
1809 |
\begin_layout Standard |
1810 |
|
1811 |
(* variables *) |
1812 |
\end_layout |
1813 |
|
1814 |
\begin_layout Standard |
1815 |
|
1816 |
side_area, end_area IS_A area; |
1817 |
\end_layout |
1818 |
|
1819 |
\begin_layout Standard |
1820 |
|
1821 |
vessel_vol, wall_vol IS_A volume; |
1822 |
\end_layout |
1823 |
|
1824 |
\begin_layout Standard |
1825 |
|
1826 |
wall_thickness, H, D IS_A distance; |
1827 |
\end_layout |
1828 |
|
1829 |
\begin_layout Standard |
1830 |
|
1831 |
H_to_D_ratio IS_A factor; |
1832 |
\end_layout |
1833 |
|
1834 |
\begin_layout Standard |
1835 |
|
1836 |
metal_density IS_A mass_density; |
1837 |
\end_layout |
1838 |
|
1839 |
\begin_layout Standard |
1840 |
|
1841 |
metal_mass IS_A mass; |
1842 |
\end_layout |
1843 |
|
1844 |
\begin_layout Standard |
1845 |
|
1846 |
\end_layout |
1847 |
|
1848 |
\begin_layout Standard |
1849 |
|
1850 |
(* equations *) |
1851 |
\end_layout |
1852 |
|
1853 |
\begin_layout Standard |
1854 |
|
1855 |
FlatEnds:end_area = 1{PI} * D^2 / 4; |
1856 |
\end_layout |
1857 |
|
1858 |
\begin_layout Standard |
1859 |
|
1860 |
Sides:side_area = 1{PI} * D * H; |
1861 |
\end_layout |
1862 |
|
1863 |
\begin_layout Standard |
1864 |
|
1865 |
Cylinder:vessel_vol = end_area * H; |
1866 |
\end_layout |
1867 |
|
1868 |
\begin_layout Standard |
1869 |
|
1870 |
Metal_volume:(side_area + 2 * end_area) * |
1871 |
\end_layout |
1872 |
|
1873 |
\begin_layout Standard |
1874 |
|
1875 |
wall_thickness = wall_vol; |
1876 |
\end_layout |
1877 |
|
1878 |
\begin_layout Standard |
1879 |
|
1880 |
HD_definition:D * H_to_D_ratio = H; |
1881 |
\end_layout |
1882 |
|
1883 |
\begin_layout Standard |
1884 |
|
1885 |
VesselMass:metal_mass = metal_density * wall_vol; |
1886 |
\end_layout |
1887 |
|
1888 |
\begin_layout Standard |
1889 |
|
1890 |
END vessel; |
1891 |
\end_layout |
1892 |
|
1893 |
\begin_layout Standard |
1894 |
|
1895 |
|
1896 |
\backslash |
1897 |
end{ascend} |
1898 |
\end_layout |
1899 |
|
1900 |
\end_inset |
1901 |
|
1902 |
|
1903 |
\end_layout |
1904 |
|
1905 |
\begin_layout Standard |
1906 |
\begin_inset Caption |
1907 |
|
1908 |
\begin_layout Standard |
1909 |
\begin_inset LatexCommand label |
1910 |
name "fig:model1.modelVessel" |
1911 |
|
1912 |
\end_inset |
1913 |
|
1914 |
First version of the type definition for |
1915 |
\family typewriter |
1916 |
vessel |
1917 |
\family default |
1918 |
. |
1919 |
|
1920 |
\end_layout |
1921 |
|
1922 |
\end_inset |
1923 |
|
1924 |
|
1925 |
\end_layout |
1926 |
|
1927 |
\end_inset |
1928 |
|
1929 |
|
1930 |
\end_layout |
1931 |
|
1932 |
\begin_layout Standard |
1933 |
Our model definition has the following structure for it so far: |
1934 |
\end_layout |
1935 |
|
1936 |
\begin_layout Itemize |
1937 |
|
1938 |
\family typewriter |
1939 |
MODEL |
1940 |
\family default |
1941 |
|
1942 |
\begin_inset LatexCommand index |
1943 |
name "MODEL" |
1944 |
|
1945 |
\end_inset |
1946 |
|
1947 |
statement |
1948 |
\end_layout |
1949 |
|
1950 |
\begin_layout Itemize |
1951 |
list of variable we intend to use in the type definition |
1952 |
\end_layout |
1953 |
|
1954 |
\begin_layout Itemize |
1955 |
equations |
1956 |
\end_layout |
1957 |
|
1958 |
\begin_layout Itemize |
1959 |
|
1960 |
\family typewriter |
1961 |
END |
1962 |
\family default |
1963 |
|
1964 |
\begin_inset LatexCommand index |
1965 |
name "END" |
1966 |
|
1967 |
\end_inset |
1968 |
|
1969 |
statement |
1970 |
\end_layout |
1971 |
|
1972 |
\begin_layout Standard |
1973 |
While we have put the statements in this order, we could mix up and intermix |
1974 |
the middle two types of statements, even going to the extreme of defining |
1975 |
the variables after we first use them. |
1976 |
The |
1977 |
\family typewriter |
1978 |
MODEL |
1979 |
\family default |
1980 |
and |
1981 |
\family typewriter |
1982 |
END |
1983 |
\family default |
1984 |
statements begin and end the type definition. |
1985 |
\end_layout |
1986 |
|
1987 |
\begin_layout Standard |
1988 |
You should see little that surprises you in the syntax here. |
1989 |
However, you may have noted that we have created a definition that says |
1990 |
absolutely nothing about how to use the variables and equations listed. |
1991 |
There is no solution procedure buried in this type definition. |
1992 |
In ASCEND the idea of solving is separate from saying what we intend to |
1993 |
solve. |
1994 |
Also note that we have not said anything about the values for any of the |
1995 |
variables nor what we intend to calculate and what variables we intend |
1996 |
to treat as fixed input. |
1997 |
\end_layout |
1998 |
|
1999 |
\begin_layout Section |
2000 |
Editing, compiling and browsing an ASCEND model |
2001 |
\end_layout |
2002 |
|
2003 |
\begin_layout Standard |
2004 |
Could we compile an instance of a vessel given this definition? If there |
2005 |
had been some arrays in our definition for which we did not say how many |
2006 |
items were in the arrays, we could not. |
2007 |
However, here we could compile an instance, putting aside storage space |
2008 |
for each of the variables and somehow capturing the equations relating |
2009 |
them. |
2010 |
\end_layout |
2011 |
|
2012 |
\begin_layout Standard |
2013 |
\begin_inset Marginal |
2014 |
status open |
2015 |
|
2016 |
\begin_layout Standard |
2017 |
Do not alter the models subdirectory |
2018 |
\end_layout |
2019 |
|
2020 |
\end_inset |
2021 |
|
2022 |
When we compile new models, we need a place to store them. |
2023 |
One possibility would be to put them into the |
2024 |
\family typewriter |
2025 |
models |
2026 |
\family default |
2027 |
|
2028 |
\begin_inset LatexCommand index |
2029 |
name "models" |
2030 |
|
2031 |
\end_inset |
2032 |
|
2033 |
subdirectory of the ASCEND installation |
2034 |
\begin_inset Foot |
2035 |
status collapsed |
2036 |
|
2037 |
\begin_layout Standard |
2038 |
On windows this might be |
2039 |
\family typewriter |
2040 |
c: |
2041 |
\backslash |
2042 |
Program File |
2043 |
\backslash |
2044 |
ASCEND |
2045 |
\backslash |
2046 |
models |
2047 |
\family default |
2048 |
. |
2049 |
On Linux, this might be |
2050 |
\family typewriter |
2051 |
/usr/share/ascend/models |
2052 |
\family default |
2053 |
. |
2054 |
The location can vary depending on how you went about installing ASCEND. |
2055 |
\end_layout |
2056 |
|
2057 |
\end_inset |
2058 |
|
2059 |
. |
2060 |
However, you really should leave the contents of this subdirectory untouched |
2061 |
-- always. |
2062 |
Hopefully the files will be read-only from your user account. |
2063 |
We count on being able to replace the model library totally every time |
2064 |
you install a new version of ASCEND. |
2065 |
Whenever we add new model libraries or corrected versions of previously |
2066 |
existing model libraries, we put them in this subdirectory. |
2067 |
This subdirectory belongs to us (the developers of the system): hands off, |
2068 |
please. |
2069 |
\end_layout |
2070 |
|
2071 |
\begin_layout Standard |
2072 |
\begin_inset Marginal |
2073 |
status open |
2074 |
|
2075 |
\begin_layout Standard |
2076 |
rather put your things into the ascdata |
2077 |
\begin_inset LatexCommand index |
2078 |
name "ascdata" |
2079 |
|
2080 |
\end_inset |
2081 |
|
2082 |
subdirectory (you own it) |
2083 |
\end_layout |
2084 |
|
2085 |
\end_inset |
2086 |
|
2087 |
To avoid this problem, ASCEND also creates a subdirectory called |
2088 |
\family typewriter |
2089 |
ascdata |
2090 |
\family default |
2091 |
that it will not touch when you install a new version of ASCEND. |
2092 |
It will look in this subdirectory first when looking for a file to load |
2093 |
when you have not given a full path name for finding that file. |
2094 |
The install process for ASCEND will place |
2095 |
\family typewriter |
2096 |
ascdata |
2097 |
\family default |
2098 |
into your home directory |
2099 |
\begin_inset LatexCommand ref |
2100 |
reference "id:#id(pgfId-1007944)" |
2101 |
|
2102 |
\end_inset |
2103 |
|
2104 |
|
2105 |
\begin_inset Foot |
2106 |
status collapsed |
2107 |
|
2108 |
\begin_layout Standard |
2109 |
On Windows, your home directory will normally be the My Documents folder. |
2110 |
On Linux, it will normally be |
2111 |
\family typewriter |
2112 |
/home/ |
2113 |
\emph on |
2114 |
username |
2115 |
\family default |
2116 |
\emph default |
2117 |
. |
2118 |
Note that in both systems, you can set an |
2119 |
\begin_inset Quotes eld |
2120 |
\end_inset |
2121 |
|
2122 |
environment |
2123 |
\begin_inset Quotes erd |
2124 |
\end_inset |
2125 |
|
2126 |
variable to designate your home directory. |
2127 |
\end_layout |
2128 |
|
2129 |
\end_inset |
2130 |
|
2131 |
|
2132 |
\noun off |
2133 |
. |
2134 |
ASCEND tells you where it has placed this subdirectory when you install |
2135 |
it. |
2136 |
However, if you did not note where that was, then you will have to search |
2137 |
for it (using a tool like "FIND file or folder"). |
2138 |
\end_layout |
2139 |
|
2140 |
\begin_layout Standard |
2141 |
It is within the folder |
2142 |
\family typewriter |
2143 |
ascdata |
2144 |
\family default |
2145 |
that you should place any ASCEND models you create. |
2146 |
When running a script (which we shall talk about later), ASCEND first looks |
2147 |
in this subdirectory for files, and then it looks in the models subdirectory. |
2148 |
It stops looking when it finds the first available version of the file. |
2149 |
\end_layout |
2150 |
|
2151 |
\begin_layout Standard |
2152 |
\begin_inset Marginal |
2153 |
status collapsed |
2154 |
|
2155 |
\begin_layout Standard |
2156 |
create a text file containing the model definition |
2157 |
\end_layout |
2158 |
|
2159 |
\end_inset |
2160 |
|
2161 |
Next open an editor |
2162 |
\begin_inset LatexCommand index |
2163 |
name "text editors" |
2164 |
|
2165 |
\end_inset |
2166 |
|
2167 |
, such as |
2168 |
\family typewriter |
2169 |
emacs |
2170 |
\family default |
2171 |
|
2172 |
\begin_inset LatexCommand index |
2173 |
name "emacs" |
2174 |
|
2175 |
\end_inset |
2176 |
|
2177 |
, |
2178 |
\family typewriter |
2179 |
gedit |
2180 |
\family default |
2181 |
|
2182 |
\begin_inset LatexCommand index |
2183 |
name "gedit" |
2184 |
|
2185 |
\end_inset |
2186 |
|
2187 |
, |
2188 |
\family typewriter |
2189 |
vi |
2190 |
\family default |
2191 |
|
2192 |
\begin_inset LatexCommand index |
2193 |
name "vi" |
2194 |
|
2195 |
\end_inset |
2196 |
|
2197 |
, |
2198 |
\family typewriter |
2199 |
vim |
2200 |
\family default |
2201 |
|
2202 |
\begin_inset LatexCommand index |
2203 |
name "vim" |
2204 |
|
2205 |
\end_inset |
2206 |
|
2207 |
, Notepad |
2208 |
\begin_inset LatexCommand index |
2209 |
name "Notepad" |
2210 |
|
2211 |
\end_inset |
2212 |
|
2213 |
or TextPad |
2214 |
\begin_inset LatexCommand index |
2215 |
name "TextPad" |
2216 |
|
2217 |
\end_inset |
2218 |
|
2219 |
. |
2220 |
Now type in or, better yet, cut-and-paste the statements in Figure |
2221 |
\begin_inset LatexCommand ref |
2222 |
reference "fig:model1.modelVessel" |
2223 |
|
2224 |
\end_inset |
2225 |
|
2226 |
|
2227 |
\noun off |
2228 |
. |
2229 |
Be very careful to match the use of capital and small letters. |
2230 |
Do not worry about blanks between symbols but do not embed blanks within |
2231 |
symbols. |
2232 |
In other words, do not put a blank in the middle of the symbol |
2233 |
\family typewriter |
2234 |
\noun default |
2235 |
side_wall |
2236 |
\family default |
2237 |
\noun off |
2238 |
but do not worry about putting zero or more blanks between |
2239 |
\family typewriter |
2240 |
\noun default |
2241 |
side_wall |
2242 |
\family default |
2243 |
\noun off |
2244 |
and |
2245 |
\family typewriter |
2246 |
\noun default |
2247 |
= |
2248 |
\family default |
2249 |
\noun off |
2250 |
in an equation. |
2251 |
\end_layout |
2252 |
|
2253 |
\begin_layout Standard |
2254 |
When you are finished, be sure to save the file as a text file. |
2255 |
Call it |
2256 |
\family typewriter |
2257 |
vesselPlain.a4c |
2258 |
\family default |
2259 |
. |
2260 |
The " |
2261 |
\family typewriter |
2262 |
.a4c |
2263 |
\family default |
2264 |
" stands for "ASCEND 4 Code". |
2265 |
Many Windows editors will append " |
2266 |
\family typewriter |
2267 |
.txt |
2268 |
\family default |
2269 |
" to the file name. |
2270 |
Remove the |
2271 |
\family typewriter |
2272 |
.txt |
2273 |
\family default |
2274 |
ending off the file name -- do not let Microsoft bully you into thinking |
2275 |
you should not -- and change it to " |
2276 |
\family typewriter |
2277 |
.a4c |
2278 |
\begin_inset LatexCommand index |
2279 |
name "a4c" |
2280 |
|
2281 |
\end_inset |
2282 |
|
2283 |
|
2284 |
\family default |
2285 |
". |
2286 |
|
2287 |
\end_layout |
2288 |
|
2289 |
\begin_layout Standard |
2290 |
(This model is also available as |
2291 |
\family typewriter |
2292 |
vesselPlain.a4c |
2293 |
\family default |
2294 |
in the ASCEND models library, but we suggest it would be better for you |
2295 |
to go through the exercise of creating your own version here. |
2296 |
At the least copy the library file to your ASCEND space so you can play |
2297 |
with your own version at this time.) |
2298 |
\end_layout |
2299 |
|
2300 |
\begin_layout Standard |
2301 |
When you are done, you should have a text file called |
2302 |
\family typewriter |
2303 |
vesselPlain.a4c |
2304 |
\family default |
2305 |
stored in your ASCEND/models/vessel subdirectory. |
2306 |
It should contain precisely the statements in Figure |
2307 |
\begin_inset LatexCommand ref |
2308 |
reference "fig:model1.modelVessel" |
2309 |
|
2310 |
\end_inset |
2311 |
|
2312 |
|
2313 |
\noun off |
2314 |
with care having been taken to match capital and lower case letters as |
2315 |
shown there. |
2316 |
\end_layout |
2317 |
|
2318 |
\begin_layout Standard |
2319 |
\begin_inset Marginal |
2320 |
status collapsed |
2321 |
|
2322 |
\begin_layout Standard |
2323 |
start the ASCEND system. |
2324 |
Move and resize the windows to make yourself comfortable. |
2325 |
\end_layout |
2326 |
|
2327 |
\end_inset |
2328 |
|
2329 |
Start the ASCEND system by double clicking on the ASCEND icon if you are |
2330 |
on Windows or typing |
2331 |
\family typewriter |
2332 |
ascend |
2333 |
\family default |
2334 |
at the command line if you are using a Linux machine |
2335 |
\begin_inset Foot |
2336 |
status collapsed |
2337 |
|
2338 |
\begin_layout Standard |
2339 |
Depending on the Linux version you have installed, you might find that the |
2340 |
command is |
2341 |
\family typewriter |
2342 |
ascend4 |
2343 |
\family default |
2344 |
or that you have an ASCEND option in your GNOME 'Applications' menu. |
2345 |
\end_layout |
2346 |
|
2347 |
\end_inset |
2348 |
|
2349 |
. |
2350 |
Four windows will appear, three smaller ones and one larger one that will, |
2351 |
if left unattended, disappear by itself in a few seconds. |
2352 |
Move the three smaller ones around on your screen so they do not overlap |
2353 |
or so they overlap very little. |
2354 |
Resize them if you want to. |
2355 |
You might start by putting the one called Script |
2356 |
\begin_inset LatexCommand index |
2357 |
name "Script window" |
2358 |
|
2359 |
\end_inset |
2360 |
|
2361 |
in the upper left, the one called Library |
2362 |
\begin_inset LatexCommand index |
2363 |
name "Library window" |
2364 |
|
2365 |
\end_inset |
2366 |
|
2367 |
in the upper right and the one called Console |
2368 |
\begin_inset LatexCommand index |
2369 |
name "Console" |
2370 |
|
2371 |
\end_inset |
2372 |
|
2373 |
in the lower right. |
2374 |
We shall assume you have placed them in these positions in the following |
2375 |
so, even if that is not your favorite placement, it might be useful to |
2376 |
use it for now. |
2377 |
\end_layout |
2378 |
|
2379 |
\begin_layout Standard |
2380 |
\begin_inset Marginal |
2381 |
status collapsed |
2382 |
|
2383 |
\begin_layout Standard |
2384 |
note that each window by itself looks pretty nonthreatening |
2385 |
\end_layout |
2386 |
|
2387 |
\end_inset |
2388 |
|
2389 |
As you can see, each window by itself looks like a pretty normal window. |
2390 |
Each has buttons across the top under which one will find different tools |
2391 |
to run. |
2392 |
Each also has one to three sub-windows for displaying things. |
2393 |
Each has a Help button that you can push at any time that you want to read |
2394 |
all kinds of detailed things about the window |
2395 |
\begin_inset Foot |
2396 |
status collapsed |
2397 |
|
2398 |
\begin_layout Standard |
2399 |
assuming you have got the help files installed on your system, which you |
2400 |
may not find you have. |
2401 |
\end_layout |
2402 |
|
2403 |
\end_inset |
2404 |
|
2405 |
. |
2406 |
For the moment we will provide you with the "just-in-time" details here |
2407 |
so you do not need to be sidetracked just yet by pushing these Help buttons. |
2408 |
\end_layout |
2409 |
|
2410 |
\begin_layout Standard |
2411 |
\begin_inset Marginal |
2412 |
status collapsed |
2413 |
|
2414 |
\begin_layout Standard |
2415 |
hey, where did that window go? I want it back NOW! |
2416 |
\end_layout |
2417 |
|
2418 |
\end_inset |
2419 |
|
2420 |
If you ever lose a window, open the Script window and under the Tools |
2421 |
\begin_inset LatexCommand index |
2422 |
name "Tools" |
2423 |
|
2424 |
\end_inset |
2425 |
|
2426 |
button, select the window you wish to open. |
2427 |
You cannot lose the Script window unless you shut down ASCEND. |
2428 |
For other windows in ASCEND, you can close them and re-open them as required. |
2429 |
Any window that you closed can usually be restored by going back to the |
2430 |
Script window and selected it from the Tools menu there. |
2431 |
\end_layout |
2432 |
|
2433 |
\begin_layout Standard |
2434 |
\begin_inset Marginal |
2435 |
status collapsed |
2436 |
|
2437 |
\begin_layout Standard |
2438 |
How do I quit |
2439 |
\begin_inset LatexCommand index |
2440 |
name "quit ASCEND" |
2441 |
|
2442 |
\end_inset |
2443 |
|
2444 |
ASCEND? |
2445 |
\end_layout |
2446 |
|
2447 |
\end_inset |
2448 |
|
2449 |
To exit |
2450 |
\begin_inset LatexCommand index |
2451 |
name "exit ASCEND" |
2452 |
|
2453 |
\end_inset |
2454 |
|
2455 |
ASCEND, close the Script window. |
2456 |
You will be asked to confirm that you want to exit ASCEND. |
2457 |
If you have simulations in memory this will stop you from losing your results. |
2458 |
\end_layout |
2459 |
|
2460 |
\begin_layout Standard |
2461 |
\begin_inset Marginal |
2462 |
status collapsed |
2463 |
|
2464 |
\begin_layout Standard |
2465 |
saving |
2466 |
\begin_inset LatexCommand index |
2467 |
name "saving window position" |
2468 |
|
2469 |
\end_inset |
2470 |
|
2471 |
window positions |
2472 |
\begin_inset LatexCommand index |
2473 |
name "window position" |
2474 |
|
2475 |
\end_inset |
2476 |
|
2477 |
|
2478 |
\end_layout |
2479 |
|
2480 |
\end_inset |
2481 |
|
2482 |
ASCEND will not remember your window locations automatically. |
2483 |
If you like where you have placed the windows for ASCEND on your display, |
2484 |
go to the Script window and select 'Save all appearances |
2485 |
\begin_inset LatexCommand index |
2486 |
name "window locations, save" |
2487 |
|
2488 |
\end_inset |
2489 |
|
2490 |
|
2491 |
\begin_inset LatexCommand index |
2492 |
name "appearances, save all" |
2493 |
|
2494 |
\end_inset |
2495 |
|
2496 |
' under the View |
2497 |
\begin_inset LatexCommand index |
2498 |
name "View" |
2499 |
|
2500 |
\end_inset |
2501 |
|
2502 |
menu. |
2503 |
A similar tool exists for each window for saving only its position. |
2504 |
\end_layout |
2505 |
|
2506 |
\begin_layout Standard |
2507 |
\begin_inset Marginal |
2508 |
status collapsed |
2509 |
|
2510 |
\begin_layout Standard |
2511 |
start by loading and compiling using tools in the Library window |
2512 |
\end_layout |
2513 |
|
2514 |
\end_inset |
2515 |
|
2516 |
We shall start with the Library window in the upper right. |
2517 |
This window provides you with the tools to load and compile files containing |
2518 |
type definitions. |
2519 |
You can also display |
2520 |
\begin_inset LatexCommand index |
2521 |
name "display" |
2522 |
|
2523 |
\end_inset |
2524 |
|
2525 |
the code for the different types you have loaded. |
2526 |
\end_layout |
2527 |
|
2528 |
\begin_layout Standard |
2529 |
\begin_inset Marginal |
2530 |
status collapsed |
2531 |
|
2532 |
\begin_layout Standard |
2533 |
use the left mouse button unless we tell you otherwise (however, on you |
2534 |
own explore using the right mouse button in any of the windows) |
2535 |
\end_layout |
2536 |
|
2537 |
\end_inset |
2538 |
|
2539 |
Let's load your file. |
2540 |
Under the File button select the 'Read types from File |
2541 |
\begin_inset LatexCommand index |
2542 |
name "Read Types from File" |
2543 |
|
2544 |
\end_inset |
2545 |
|
2546 |
' tool. |
2547 |
You select this tool by clicking on it using the left mouse button - i.e., |
2548 |
the button you should have expected to use. |
2549 |
A window will appear asking you to find the file you want to read into |
2550 |
ASCEND. |
2551 |
Navigate to where you stored |
2552 |
\family typewriter |
2553 |
vesselPlain.a4c |
2554 |
\family default |
2555 |
(in the subdirectory |
2556 |
\family typewriter |
2557 |
ascdata |
2558 |
\family default |
2559 |
) and select that file. |
2560 |
If you have the wrong ending on the file (you left |
2561 |
\family typewriter |
2562 |
.txt |
2563 |
\family default |
2564 |
or you forgot to put |
2565 |
\family typewriter |
2566 |
.a4c |
2567 |
\family default |
2568 |
as the ending), tell the system to list all files and pick the one you |
2569 |
want. |
2570 |
The |
2571 |
\family typewriter |
2572 |
.a4c |
2573 |
\family default |
2574 |
is used by the system to list only the files it thinks you might want to |
2575 |
load, but ASCEND isn't fussy. |
2576 |
It will attempt to load any file you pick. |
2577 |
\end_layout |
2578 |
|
2579 |
\begin_layout Standard |
2580 |
Look in the Console window at the lower right, and, if the file loads without |
2581 |
any errors being listed there, you can skip past the next bit to where |
2582 |
you should start to compile an instance. |
2583 |
The next bit has some useful hints on how to debug your models. |
2584 |
If you want some debugging experience, put a known error into your |
2585 |
\family typewriter |
2586 |
vesselPlain.a4c |
2587 |
\family default |
2588 |
file and see what happens. |
2589 |
This move will give you a reason to read the following section. |
2590 |
\end_layout |
2591 |
|
2592 |
\begin_layout Standard |
2593 |
\begin_inset Marginal |
2594 |
status open |
2595 |
|
2596 |
\begin_layout Standard |
2597 |
Do not ignore the diagnostics |
2598 |
\begin_inset LatexCommand index |
2599 |
name "diagnostics" |
2600 |
|
2601 |
\end_inset |
2602 |
|
2603 |
that might appear in the Console window |
2604 |
\end_layout |
2605 |
|
2606 |
\end_inset |
2607 |
|
2608 |
If the Console window in the lower right starts filling with several tens |
2609 |
of lines of diagnostics, look to see if you included the |
2610 |
\family typewriter |
2611 |
REQUIRE |
2612 |
\family default |
2613 |
|
2614 |
\begin_inset LatexCommand index |
2615 |
name "REQUIRE" |
2616 |
|
2617 |
\end_inset |
2618 |
|
2619 |
statement at the beginning of your model file. |
2620 |
Without that statement, ASCEND is missing all the definitions for the types |
2621 |
of variables in your model, and it will go wild telling you so |
2622 |
\begin_inset Foot |
2623 |
status collapsed |
2624 |
|
2625 |
\begin_layout Standard |
2626 |
It might also be choking on a Word document because you forgot to save |
2627 |
it as a text file. |
2628 |
\end_layout |
2629 |
|
2630 |
\end_inset |
2631 |
|
2632 |
. |
2633 |
\end_layout |
2634 |
|
2635 |
\begin_layout Standard |
2636 |
While loading the files containing these types, ASCEND will look very closely |
2637 |
at the syntax and will give you all kinds of diagnostic messages in the |
2638 |
Console window (lower right) if you have done something wrong. |
2639 |
It will also at times spew out some warning messages |
2640 |
\begin_inset LatexCommand index |
2641 |
name "warning messages" |
2642 |
|
2643 |
\end_inset |
2644 |
|
2645 |
if you have done something thought to be poor modeling style. |
2646 |
You must heed the error messages as the file will not load if there are |
2647 |
any. |
2648 |
ASCEND will tell you if it did not load the file. |
2649 |
|
2650 |
\end_layout |
2651 |
|
2652 |
\begin_layout Standard |
2653 |
You should consider heeding the warnings if you get any. |
2654 |
If you ignore them now, they may come back and haunt you later. |
2655 |
However, there are times when we issue a warning but everything will work, |
2656 |
and you will think we were not too clever. |
2657 |
Our response: better modeling style |
2658 |
\begin_inset LatexCommand index |
2659 |
name "modeling style" |
2660 |
|
2661 |
\end_inset |
2662 |
|
2663 |
can eliminate these warnings. |
2664 |
(It's been our system so we get to have the last word.) |
2665 |
\end_layout |
2666 |
|
2667 |
\begin_layout Standard |
2668 |
\begin_inset Marginal |
2669 |
status collapsed |
2670 |
|
2671 |
\begin_layout Standard |
2672 |
how do I jump |
2673 |
\begin_inset LatexCommand index |
2674 |
name "jump to line" |
2675 |
|
2676 |
\end_inset |
2677 |
|
2678 |
|
2679 |
\begin_inset LatexCommand index |
2680 |
name "line numbers" |
2681 |
|
2682 |
\end_inset |
2683 |
|
2684 |
to line 100 of a file when using some of the standard editors? |
2685 |
\end_layout |
2686 |
|
2687 |
\end_inset |
2688 |
|
2689 |
The error and warning messages will contain a line number in the file where |
2690 |
the error has occurred. |
2691 |
This will be the line number as counted by an editor with the first line |
2692 |
being line 1 in the file. |
2693 |
Editors always provide you with a means to get directly to a line number |
2694 |
in a file. |
2695 |
Find out how to do that or you will not be too happy with debugging a large |
2696 |
file. |
2697 |
\end_layout |
2698 |
|
2699 |
\begin_layout Standard |
2700 |
You will be in the debug mode for a new system so do not expect it to be |
2701 |
totally obvious the first few times you make an error. |
2702 |
We have tried to use language that should be meaningful, but we may have |
2703 |
failed or the error may be pretty subtle and not possible for us to anticipate |
2704 |
how to describe it in your terms. |
2705 |
(Send us a bug report if you have any good ideas on language.) |
2706 |
\end_layout |
2707 |
|
2708 |
\begin_layout Standard |
2709 |
\begin_inset Marginal |
2710 |
status collapsed |
2711 |
|
2712 |
\begin_layout Standard |
2713 |
reloading a file |
2714 |
\begin_inset LatexCommand index |
2715 |
name "reloading a file" |
2716 |
|
2717 |
\end_inset |
2718 |
|
2719 |
|
2720 |
\begin_inset LatexCommand index |
2721 |
name "file, reloading" |
2722 |
|
2723 |
\end_inset |
2724 |
|
2725 |
overwrites the previous version |
2726 |
\end_layout |
2727 |
|
2728 |
\end_inset |
2729 |
|
2730 |
You can reload any file your have corrected using the Read types from file |
2731 |
tool under the File menu. |
2732 |
It will overwrite the previous version of the file only if the file has |
2733 |
changed since it was last loaded (note that we do not reload those big |
2734 |
files unless you make a change even if you tell us to). |
2735 |
\end_layout |
2736 |
|
2737 |
\begin_layout Standard |
2738 |
\begin_inset Marginal |
2739 |
status collapsed |
2740 |
|
2741 |
\begin_layout Standard |
2742 |
displaying the code |
2743 |
\end_layout |
2744 |
|
2745 |
\end_inset |
2746 |
|
2747 |
You can display the code you have written. |
2748 |
Select the model vessel in the right window of the Library. |
2749 |
Then under the Display |
2750 |
\begin_inset LatexCommand index |
2751 |
name "Display window" |
2752 |
|
2753 |
\end_inset |
2754 |
|
2755 |
menu at the top, select the tool Code. |
2756 |
The Display window will open displaying the code for this model. |
2757 |
\end_layout |
2758 |
|
2759 |
\begin_layout Standard |
2760 |
\begin_inset Marginal |
2761 |
status collapsed |
2762 |
|
2763 |
\begin_layout Standard |
2764 |
now compile as " |
2765 |
\family typewriter |
2766 |
v |
2767 |
\family default |
2768 |
" |
2769 |
\end_layout |
2770 |
|
2771 |
\end_inset |
2772 |
|
2773 |
Okay, you have your file loaded without getting any diagnostics. |
2774 |
You are ready to compile |
2775 |
\begin_inset LatexCommand index |
2776 |
name "compile" |
2777 |
|
2778 |
\end_inset |
2779 |
|
2780 |
. |
2781 |
In the Library window, look in the left window and select the file |
2782 |
\family typewriter |
2783 |
vesselPlain.a4c |
2784 |
\family default |
2785 |
. |
2786 |
It contains the type definition you wish to compile. |
2787 |
You should see the type vessel appear in the right window. |
2788 |
Select vessel. |
2789 |
Under the Edit button, select Create simulation. |
2790 |
A small window opens and asks you to name the simulation. |
2791 |
Call it |
2792 |
\family typewriter |
2793 |
v |
2794 |
\family default |
2795 |
-- yes, just the letter "v", and select "OK". |
2796 |
Short names for instances often seem to be preferable. |
2797 |
|
2798 |
\end_layout |
2799 |
|
2800 |
\begin_layout Standard |
2801 |
Look again in the Console window for diagnostics. |
2802 |
If everything worked without error, you will see some statistics telling |
2803 |
you how many models, relations and so forth you have created during the |
2804 |
compile step. |
2805 |
\end_layout |
2806 |
|
2807 |
\begin_layout Standard |
2808 |
\begin_inset Marginal |
2809 |
status collapsed |
2810 |
|
2811 |
\begin_layout Standard |
2812 |
and pass the instance |
2813 |
\begin_inset LatexCommand index |
2814 |
name "instance" |
2815 |
|
2816 |
\end_inset |
2817 |
|
2818 |
to the Browser |
2819 |
\begin_inset LatexCommand index |
2820 |
name "Browser" |
2821 |
|
2822 |
\end_inset |
2823 |
|
2824 |
|
2825 |
\end_layout |
2826 |
|
2827 |
\end_inset |
2828 |
|
2829 |
Select |
2830 |
\family typewriter |
2831 |
v IS A vessel |
2832 |
\family default |
2833 |
in the bottom of the Library window. |
2834 |
Then under the Export |
2835 |
\begin_inset LatexCommand index |
2836 |
name "Export" |
2837 |
|
2838 |
\end_inset |
2839 |
|
2840 |
button, select 'Simulation to Browser |
2841 |
\begin_inset LatexCommand index |
2842 |
name "Export Simulation to Browser" |
2843 |
|
2844 |
\end_inset |
2845 |
|
2846 |
' to export |
2847 |
\family typewriter |
2848 |
v |
2849 |
\family default |
2850 |
to the Browser tool set. |
2851 |
The Browser window will open and contain |
2852 |
\family typewriter |
2853 |
v |
2854 |
\family default |
2855 |
. |
2856 |
It might be useful to enlarge this window and move it down a bit, placing |
2857 |
it a bit to the right of the center of your screen. |
2858 |
(Remember you can save this positioning and sizing of the Browser window |
2859 |
by going under the View menu and picking 'Save appearance'.) |
2860 |
\end_layout |
2861 |
|
2862 |
\begin_layout Standard |
2863 |
\begin_inset Marginal |
2864 |
status collapsed |
2865 |
|
2866 |
\begin_layout Standard |
2867 |
examine |
2868 |
\family typewriter |
2869 |
v |
2870 |
\family default |
2871 |
by playing with it in the Browser |
2872 |
\end_layout |
2873 |
|
2874 |
\end_inset |
2875 |
|
2876 |
In the left upper window of the Browser, you will find |
2877 |
\family typewriter |
2878 |
v |
2879 |
\family default |
2880 |
to be the current object. |
2881 |
Listed in the right window are all the parts of the current object. |
2882 |
You will see the variables listed here along with an indication of their |
2883 |
type. |
2884 |
For example, you will find |
2885 |
\family typewriter |
2886 |
Cylinder IS A relation |
2887 |
\family default |
2888 |
and |
2889 |
\family typewriter |
2890 |
D IS A distance |
2891 |
\family default |
2892 |
listed, among many others. |
2893 |
|
2894 |
\family typewriter |
2895 |
Cylinder |
2896 |
\family default |
2897 |
is one of the equations you wrote describing the model while |
2898 |
\family typewriter |
2899 |
D |
2900 |
\family default |
2901 |
was the diameter of the vessel. |
2902 |
|
2903 |
\end_layout |
2904 |
|
2905 |
\begin_layout Standard |
2906 |
\begin_inset Marginal |
2907 |
status collapsed |
2908 |
|
2909 |
\begin_layout Standard |
2910 |
included flags |
2911 |
\begin_inset LatexCommand index |
2912 |
name "included flags" |
2913 |
|
2914 |
\end_inset |
2915 |
|
2916 |
|
2917 |
\begin_inset LatexCommand index |
2918 |
name "flag, included" |
2919 |
|
2920 |
\end_inset |
2921 |
|
2922 |
for relations |
2923 |
\end_layout |
2924 |
|
2925 |
\end_inset |
2926 |
|
2927 |
If you pick any of the parts in the right or bottom windows, it becomes |
2928 |
the current object; its parts then show in the right window. |
2929 |
For example, a relation has a boolean part (a flag that takes the value |
2930 |
|
2931 |
\family typewriter |
2932 |
TRUE |
2933 |
\family default |
2934 |
or |
2935 |
\family typewriter |
2936 |
FALSE |
2937 |
\family default |
2938 |
) indicating whether or not it is to be included when ASCEND solves the |
2939 |
equations you defined for the model. |
2940 |
\end_layout |
2941 |
|
2942 |
\begin_layout Standard |
2943 |
If you wish to display the current value for this flag, pick 'Display Atom |
2944 |
Values |
2945 |
\begin_inset LatexCommand index |
2946 |
name "Display Atom Values" |
2947 |
|
2948 |
\end_inset |
2949 |
|
2950 |
' under the View menu. |
2951 |
This tool toggles a switch that causes either the value or the type to |
2952 |
show for a variable, a constant or a relation in the upper right window |
2953 |
of the Browser. |
2954 |
Try toggling it back and forth and looking at different things in the Browser. |
2955 |
\end_layout |
2956 |
|
2957 |
\begin_layout Standard |
2958 |
Pick each of the tools under View and note what happens to the displaying |
2959 |
of things in the Browser. |
2960 |
\end_layout |
2961 |
|
2962 |
\begin_layout Standard |
2963 |
Across the bottom of the Browser window note the buttons you can select |
2964 |
labeled |
2965 |
\family typewriter |
2966 |
RV |
2967 |
\family default |
2968 |
, |
2969 |
\family typewriter |
2970 |
DV |
2971 |
\family default |
2972 |
and so forth. |
2973 |
If you have made the Browser window large enough, you will see to the right |
2974 |
of these buttons the type of objects whose value you want to appear or |
2975 |
not in the lower Browser window as you toggle each button. |
2976 |
Toggle each of these buttons and see if the lower display changes. |
2977 |
If it does not, then this type of part is not in the current object. |
2978 |
\end_layout |
2979 |
|
2980 |
\begin_layout Section |
2981 |
Solving |
2982 |
\begin_inset LatexCommand index |
2983 |
name "Solving" |
2984 |
|
2985 |
\end_inset |
2986 |
|
2987 |
an ASCEND instance |
2988 |
\end_layout |
2989 |
|
2990 |
\begin_layout Standard |
2991 |
Well, you have been patient. |
2992 |
While there are lots of interesting tools left to explore in the Browser, |
2993 |
perhaps it is time to try to solve this model. |
2994 |
To solve |
2995 |
\family typewriter |
2996 |
v |
2997 |
\family default |
2998 |
, make it the current object (it alone should be listed in the upper left |
2999 |
window of the Browser). |
3000 |
Then, under the Export |
3001 |
\begin_inset LatexCommand index |
3002 |
name "Export to Solver" |
3003 |
|
3004 |
\end_inset |
3005 |
|
3006 |
menu, select 'to Solver'. |
3007 |
The Solver window will open, along with a smaller window labeled Eligible |
3008 |
\begin_inset LatexCommand index |
3009 |
name "window, Eligible" |
3010 |
|
3011 |
\end_inset |
3012 |
|
3013 |
|
3014 |
\begin_inset LatexCommand index |
3015 |
name "Eligible window" |
3016 |
|
3017 |
\end_inset |
3018 |
|
3019 |
. |
3020 |
Move the Eligible window up a bit so it does not cover any or very little |
3021 |
of the Solver window. |
3022 |
Move the Solver window to the lower left and enlarge it so you can see |
3023 |
all of its contents. |
3024 |
|
3025 |
\end_layout |
3026 |
|
3027 |
\begin_layout Standard |
3028 |
\begin_inset Marginal |
3029 |
status collapsed |
3030 |
|
3031 |
\begin_layout Standard |
3032 |
if ASCEND stops responding |
3033 |
\begin_inset LatexCommand index |
3034 |
name "responding, ASCEND stops" |
3035 |
|
3036 |
\end_inset |
3037 |
|
3038 |
, hunt down one of those "nasty" windows with a "yellow lock |
3039 |
\begin_inset LatexCommand index |
3040 |
name "yellow lock" |
3041 |
|
3042 |
\end_inset |
3043 |
|
3044 |
" and close it properly |
3045 |
\end_layout |
3046 |
|
3047 |
\end_inset |
3048 |
|
3049 |
This Eligible window is 'modal': if it is open and you do not do something |
3050 |
to make it happy and go away, it will stop you from doing anything else |
3051 |
in the ASCEND system. |
3052 |
Such windows appear with a black lock icon in a yellow field -- we shall |
3053 |
call it a "yellow lock." They demand you attend to them |
3054 |
\emph on |
3055 |
now |
3056 |
\emph default |
3057 |
. |
3058 |
A good solution would be for such a window to stay open and on top of all |
3059 |
the other open windows. |
3060 |
Unfortunately we have not been able under all window managers to stop it |
3061 |
from ducking under another window. |
3062 |
If you ever find ASCEND unwilling to respond, iconify the other windows |
3063 |
to get them out of the way, until you find one of these windows. |
3064 |
On the PC you can go to the icon bar at the bottom of your screen and, |
3065 |
by clicking on the window, bring it to the top. |
3066 |
Then do whatever it takes to make it happy and close properly -- such as |
3067 |
cancel it. |
3068 |
If you are not careful here, for example, this window will hide under the |
3069 |
Solver window before you are through with it. |
3070 |
\end_layout |
3071 |
|
3072 |
\begin_layout Standard |
3073 |
\begin_inset Marginal |
3074 |
status open |
3075 |
|
3076 |
\begin_layout Standard |
3077 |
is our problem well-posed |
3078 |
\begin_inset LatexCommand index |
3079 |
name "well-posed" |
3080 |
|
3081 |
\end_inset |
3082 |
|
3083 |
? |
3084 |
\end_layout |
3085 |
|
3086 |
\end_inset |
3087 |
|
3088 |
The Solver window contains the information we need to see to explain why |
3089 |
the Eligible window opened in the first place. |
3090 |
Examine the information the Solver displays. |
3091 |
It tells you that |
3092 |
\family typewriter |
3093 |
v |
3094 |
\family default |
3095 |
has 6 relations defining it and that all are equalities and included. |
3096 |
It has no inequalities. |
3097 |
On the right side we see there are 10 variables and all are 'free |
3098 |
\begin_inset LatexCommand index |
3099 |
name "free variables" |
3100 |
|
3101 |
\end_inset |
3102 |
|
3103 |
.' A free variable is one for which you want the system to compute a value. |
3104 |
Hmm, 6 equations in 10 variables. |
3105 |
Something is wrong here. |
3106 |
For a well-posed problem, you want 6 equations in 6 variables (i.e., square |
3107 |
\begin_inset LatexCommand index |
3108 |
name "square" |
3109 |
|
3110 |
\end_inset |
3111 |
|
3112 |
). |
3113 |
ASCEND reports that the system is underspecified |
3114 |
\begin_inset LatexCommand index |
3115 |
name "underspecified" |
3116 |
|
3117 |
\end_inset |
3118 |
|
3119 |
by 4. |
3120 |
This means you need to pick four of the variables and declare them to be |
3121 |
fixed |
3122 |
\begin_inset LatexCommand index |
3123 |
name "fixed" |
3124 |
|
3125 |
\end_inset |
3126 |
|
3127 |
. |
3128 |
You will also have to pick values for these fixed variables before you |
3129 |
can solve for the remaining 6. |
3130 |
For such a small problem as this one, this task is not formidable. |
3131 |
For a model with 50,000 equations and 60,000 variables, one would quit |
3132 |
and go home. |
3133 |
We have exposed a need here. |
3134 |
We certainly would like ASCEND to help us here for this small problem. |
3135 |
But we insist that it help us in major ways to make the 50,000 equation, |
3136 |
60,000 variable problem possible. |
3137 |
\end_layout |
3138 |
|
3139 |
\begin_layout Standard |
3140 |
\begin_inset Marginal |
3141 |
status collapsed |
3142 |
|
3143 |
\begin_layout Standard |
3144 |
picking variables we are going to fix |
3145 |
\end_layout |
3146 |
|
3147 |
\end_inset |
3148 |
|
3149 |
Okay, the small help such as needed here is why the Eligible window opened. |
3150 |
Let's return to it. |
3151 |
It lists all the variables of those not yet fixed that are eligible to |
3152 |
be fixed and still leave us a calculation that has a chance to solve. |
3153 |
The algorithm to find eligible variables does an quick analysis of the |
3154 |
structure of the equations. |
3155 |
The variables it lists are those that can be fixed |
3156 |
\emph on |
3157 |
without |
3158 |
\emph default |
3159 |
the system becoming numerically singular. |
3160 |
So any variables that are not shown |
3161 |
\emph on |
3162 |
cannot possibly |
3163 |
\emph default |
3164 |
help you. |
3165 |
\end_layout |
3166 |
|
3167 |
\begin_layout Standard |
3168 |
So look at the list and decide what you would like to fix for your first |
3169 |
calculation with this model. |
3170 |
Diameter ( |
3171 |
\family typewriter |
3172 |
v.D |
3173 |
\family default |
3174 |
) seems a good choice. |
3175 |
Now you can see why we called the instance just plain old |
3176 |
\family typewriter |
3177 |
v |
3178 |
\family default |
3179 |
. |
3180 |
A longer name would get tiring here. |
3181 |
Anyway, pick |
3182 |
\family typewriter |
3183 |
v.D |
3184 |
\family default |
3185 |
. |
3186 |
Immediately the list reappears with |
3187 |
\family typewriter |
3188 |
v.D |
3189 |
\family default |
3190 |
no longer on it. |
3191 |
ASCEND has just repeated the eligibility analysis, and found that more |
3192 |
variables still need to be fixed. |
3193 |
\end_layout |
3194 |
|
3195 |
\begin_layout Standard |
3196 |
We have three more to pick. |
3197 |
On the list are both vessel height, |
3198 |
\family typewriter |
3199 |
v.H |
3200 |
\family default |
3201 |
, and |
3202 |
\family typewriter |
3203 |
v.H_to_D_ratio |
3204 |
\family default |
3205 |
. |
3206 |
We certainly cannot pick both of these. |
3207 |
One implies the other if we know a value for |
3208 |
\family typewriter |
3209 |
v.D |
3210 |
\family default |
3211 |
. |
3212 |
Pick |
3213 |
\family typewriter |
3214 |
v.H_to_D_ratio |
3215 |
\family default |
3216 |
. |
3217 |
Note that |
3218 |
\family typewriter |
3219 |
v.H |
3220 |
\family default |
3221 |
is no longer eligible. |
3222 |
Good. |
3223 |
We would be worried if it were still there. |
3224 |
\end_layout |
3225 |
|
3226 |
\begin_layout Standard |
3227 |
We see |
3228 |
\family typewriter |
3229 |
v.metal_density |
3230 |
\emph on |
3231 |
. |
3232 |
|
3233 |
\family default |
3234 |
\emph default |
3235 |
Pick it. |
3236 |
Strange. |
3237 |
Metal mass and volume stayed eligible. |
3238 |
Why? If we pick metal mass, wall thickness is implied, and the same is |
3239 |
true if we were to pick metal volume. |
3240 |
However, as it seems much more natural to pick |
3241 |
\family typewriter |
3242 |
wall_thickness |
3243 |
\family default |
3244 |
, make that the last variable you choose. |
3245 |
The Solver window now says this problem is square (i.e., it has 6 equations |
3246 |
in the same number of unknowns). |
3247 |
Table |
3248 |
\begin_inset LatexCommand ref |
3249 |
reference "tab:model1.variableFixed" |
3250 |
|
3251 |
\end_inset |
3252 |
|
3253 |
|
3254 |
\noun off |
3255 |
summarizes the four variables we have elected here to fix. |
3256 |
\end_layout |
3257 |
|
3258 |
\begin_layout Standard |
3259 |
\begin_inset Float table |
3260 |
wide false |
3261 |
sideways false |
3262 |
status open |
3263 |
|
3264 |
\begin_layout Standard |
3265 |
\begin_inset Caption |
3266 |
|
3267 |
\begin_layout Standard |
3268 |
\begin_inset LatexCommand label |
3269 |
name "tab:model1.variableFixed" |
3270 |
|
3271 |
\end_inset |
3272 |
|
3273 |
Variables we have fixed |
3274 |
\begin_inset LatexCommand index |
3275 |
name "fixed variables" |
3276 |
|
3277 |
\end_inset |
3278 |
|
3279 |
|
3280 |
\end_layout |
3281 |
|
3282 |
\end_inset |
3283 |
|
3284 |
|
3285 |
\end_layout |
3286 |
|
3287 |
\begin_layout Standard |
3288 |
\begin_inset Tabular |
3289 |
<lyxtabular version="3" rows="5" columns="1"> |
3290 |
<features> |
3291 |
<column alignment="center" valignment="top" leftline="true" rightline="true" width="0"> |
3292 |
<row topline="true" bottomline="true"> |
3293 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
3294 |
\begin_inset Text |
3295 |
|
3296 |
\begin_layout Standard |
3297 |
variable |
3298 |
\end_layout |
3299 |
|
3300 |
\end_inset |
3301 |
</cell> |
3302 |
</row> |
3303 |
<row topline="true"> |
3304 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
3305 |
\begin_inset Text |
3306 |
|
3307 |
\begin_layout Standard |
3308 |
|
3309 |
\family typewriter |
3310 |
D |
3311 |
\end_layout |
3312 |
|
3313 |
\end_inset |
3314 |
</cell> |
3315 |
</row> |
3316 |
<row topline="true"> |
3317 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
3318 |
\begin_inset Text |
3319 |
|
3320 |
\begin_layout Standard |
3321 |
|
3322 |
\family typewriter |
3323 |
H_to_D_ratio |
3324 |
\end_layout |
3325 |
|
3326 |
\end_inset |
3327 |
</cell> |
3328 |
</row> |
3329 |
<row topline="true"> |
3330 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
3331 |
\begin_inset Text |
3332 |
|
3333 |
\begin_layout Standard |
3334 |
|
3335 |
\family typewriter |
3336 |
meta_density |
3337 |
\end_layout |
3338 |
|
3339 |
\end_inset |
3340 |
</cell> |
3341 |
</row> |
3342 |
<row topline="true" bottomline="true"> |
3343 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
3344 |
\begin_inset Text |
3345 |
|
3346 |
\begin_layout Standard |
3347 |
|
3348 |
\family typewriter |
3349 |
wall_thickness |
3350 |
\end_layout |
3351 |
|
3352 |
\end_inset |
3353 |
</cell> |
3354 |
</row> |
3355 |
</lyxtabular> |
3356 |
|
3357 |
\end_inset |
3358 |
|
3359 |
|
3360 |
\end_layout |
3361 |
|
3362 |
\end_inset |
3363 |
|
3364 |
|
3365 |
\end_layout |
3366 |
|
3367 |
\begin_layout Standard |
3368 |
\begin_inset Marginal |
3369 |
status collapsed |
3370 |
|
3371 |
\begin_layout Standard |
3372 |
ASCEND partitions the problem into smaller problems for solving |
3373 |
\end_layout |
3374 |
|
3375 |
\end_inset |
3376 |
|
3377 |
Toward the bottom right of the |
3378 |
\series bold |
3379 |
Solver |
3380 |
\series default |
3381 |
window, we see there are 6 "blocks |
3382 |
\begin_inset LatexCommand index |
3383 |
name "blocks" |
3384 |
|
3385 |
\end_inset |
3386 |
|
3387 |
." What are blocks? ASCEND has examined the equations and, in this case, |
3388 |
has discovered that not all the equations have to be solved simultaneously. |
3389 |
There are 6 blocks of equations which it can solve in sequence. |
3390 |
6 blocks and 6 equations means that ASCEND has found a way to solve the |
3391 |
model by solving 6 individual equations in sequence -- i.e., one at a time. |
3392 |
This is a good thing: it usually means that the solver will have less problems |
3393 |
with locating the overall solution. |
3394 |
\end_layout |
3395 |
|
3396 |
\begin_layout Standard |
3397 |
As well as breaking down the system into blocks, ASCEND has the ability |
3398 |
to rearrange some simple algebraic equations so that unknown variables |
3399 |
can be evaluated directly from the known values, with no need for iterative |
3400 |
numerical methods. |
3401 |
This is only possible if there is just one equation in the block. |
3402 |
In fact, this problem, with the 4 variables we selected to be fixed, can |
3403 |
be solved entirely without iteration. |
3404 |
\end_layout |
3405 |
|
3406 |
\begin_layout Standard |
3407 |
\begin_inset Marginal |
3408 |
status open |
3409 |
|
3410 |
\begin_layout Standard |
3411 |
displaying the incidence matrix |
3412 |
\begin_inset LatexCommand index |
3413 |
name "incidence matrix" |
3414 |
|
3415 |
\end_inset |
3416 |
|
3417 |
|
3418 |
\end_layout |
3419 |
|
3420 |
\end_inset |
3421 |
|
3422 |
Can we see what ASCEND has just discovered? It turns out we can (we would |
3423 |
not have asked if we could not). |
3424 |
Under the Display menu on the Solver, select the 'Incidence matrix tool |
3425 |
\begin_inset LatexCommand index |
3426 |
name "incidence matrix tool" |
3427 |
|
3428 |
\end_inset |
3429 |
|
3430 |
'. |
3431 |
A window pops open showing us the incidence of variables in the equations |
3432 |
and display them in the order that ASCEND has found to solve them, also |
3433 |
known as a sparsity matrix |
3434 |
\begin_inset LatexCommand index |
3435 |
name "sparsity matrix" |
3436 |
|
3437 |
\end_inset |
3438 |
|
3439 |
or sparsity pattern |
3440 |
\begin_inset LatexCommand index |
3441 |
name "sparsity pattern" |
3442 |
|
3443 |
\end_inset |
3444 |
|
3445 |
. |
3446 |
The dark squares are incidences under the variables for which we are solving; |
3447 |
the lighter looking 'X' symbols to the right side are incidences for the |
3448 |
fixed (known) variables. |
3449 |
Click on the incidence in the upper left corner. |
3450 |
ASCEND immediately identifies it for us as the |
3451 |
\family typewriter |
3452 |
end_area |
3453 |
\family default |
3454 |
. |
3455 |
It identifies the equation as the one we labeled |
3456 |
\family typewriter |
3457 |
FlatEnds |
3458 |
\family default |
3459 |
. |
3460 |
We can go back to our model and find the equation ASCEND will solve first. |
3461 |
The other variable in this equation is in the set we fixed; pick it and |
3462 |
discover it is |
3463 |
\family typewriter |
3464 |
D |
3465 |
\family default |
3466 |
, the vessel diameter. |
3467 |
Of course we can compute the area of the ends given the diameter. |
3468 |
The |
3469 |
\emph on |
3470 |
end_area |
3471 |
\emph default |
3472 |
is |
3473 |
\begin_inset Formula $\pi D^{2}/4$ |
3474 |
\end_inset |
3475 |
|
3476 |
. |
3477 |
\end_layout |
3478 |
|
3479 |
\begin_layout Standard |
3480 |
Play with the other incidences here. |
3481 |
See what the other equations are and the order ASCEND will use to solve |
3482 |
them. |
3483 |
\end_layout |
3484 |
|
3485 |
\begin_layout Standard |
3486 |
Okay, we return to our task of solving. |
3487 |
We need next to supply values for the variables we have selected to be |
3488 |
fixed. |
3489 |
Again, the approach we are going to take is acceptable for this small problem, |
3490 |
but we would not want to have to do what we are about to do for a large |
3491 |
problem. |
3492 |
Fortunately, we really have thought about these issues and have some nice |
3493 |
approaches that work even for extremely large problem -- like 100,000 equations. |
3494 |
\end_layout |
3495 |
|
3496 |
\begin_layout Standard |
3497 |
\begin_inset Marginal |
3498 |
status collapsed |
3499 |
|
3500 |
\begin_layout Standard |
3501 |
which variables are currently fixed for this problem? |
3502 |
\end_layout |
3503 |
|
3504 |
\end_inset |
3505 |
|
3506 |
Let's see. |
3507 |
Do you remember the variables we fixed? What if you do not? Well, we go |
3508 |
back to the Browser. |
3509 |
Be sure |
3510 |
\family typewriter |
3511 |
v |
3512 |
\family default |
3513 |
remains the current object (it alone is in the upper left window). |
3514 |
Under the Find menu select 'by Type |
3515 |
\begin_inset LatexCommand index |
3516 |
name "Find by Type" |
3517 |
|
3518 |
\end_inset |
3519 |
|
3520 |
.' A small window opens with default information in it saying it will find |
3521 |
for us all objects contained in the current object |
3522 |
\family typewriter |
3523 |
v |
3524 |
\family default |
3525 |
of type |
3526 |
\family typewriter |
3527 |
solver_var |
3528 |
\family default |
3529 |
whose |
3530 |
\family typewriter |
3531 |
fixed |
3532 |
\family default |
3533 |
flags are set to |
3534 |
\family typewriter |
3535 |
TRUE |
3536 |
\family default |
3537 |
. |
3538 |
These are precisely the attributes for the variables we have fixed. |
3539 |
Select OK and a list of the four variables we fixed earlier appears. |
3540 |
\end_layout |
3541 |
|
3542 |
\begin_layout Standard |
3543 |
\begin_inset Marginal |
3544 |
status collapsed |
3545 |
|
3546 |
\begin_layout Standard |
3547 |
specifying values for the fixed variables - this approach is useful for |
3548 |
small problems |
3549 |
\end_layout |
3550 |
|
3551 |
\end_inset |
3552 |
|
3553 |
For each variable on this list, we should supply a value. |
3554 |
Select |
3555 |
\family typewriter |
3556 |
D |
3557 |
\family default |
3558 |
in the lower window of the Browser using the right (the right, not the |
3559 |
left -- make |
3560 |
\family typewriter |
3561 |
v |
3562 |
\family default |
3563 |
the current object and do it again) mouse button. |
3564 |
A window opens in which we input a value for |
3565 |
\family typewriter |
3566 |
D |
3567 |
\family default |
3568 |
. |
3569 |
Put in the value 4 in the left window and ft in the right. |
3570 |
Continue by putting in the values for the variables as listed in Table |
3571 |
|
3572 |
\begin_inset LatexCommand ref |
3573 |
reference "tab:model1.valuesFixedVars" |
3574 |
|
3575 |
\end_inset |
3576 |
|
3577 |
|
3578 |
\noun off |
3579 |
. |
3580 |
These values immediately appear in the Browser window as you enter them. |
3581 |
If you did not fully appreciate the proper handling of dimension and units |
3582 |
before, you just got a taste of its advantages. |
3583 |
|
3584 |
\noun default |
3585 |
You |
3586 |
\noun off |
3587 |
did not have to worry about specifying these things in consistent preselected |
3588 |
units |
3589 |
\noun default |
3590 |
-- ASCEND did this for you. |
3591 |
\end_layout |
3592 |
|
3593 |
\begin_layout Standard |
3594 |
\begin_inset Float table |
3595 |
wide false |
3596 |
sideways false |
3597 |
status open |
3598 |
|
3599 |
\begin_layout Standard |
3600 |
\begin_inset Caption |
3601 |
|
3602 |
\begin_layout Standard |
3603 |
\begin_inset LatexCommand label |
3604 |
name "tab:model1.valuesFixedVars" |
3605 |
|
3606 |
\end_inset |
3607 |
|
3608 |
Values to use for fixed variables |
3609 |
\end_layout |
3610 |
|
3611 |
\end_inset |
3612 |
|
3613 |
|
3614 |
\end_layout |
3615 |
|
3616 |
\begin_layout Standard |
3617 |
\begin_inset Tabular |
3618 |
<lyxtabular version="3" rows="5" columns="3"> |
3619 |
<features> |
3620 |
<column alignment="center" valignment="top" leftline="true" width="0"> |
3621 |
<column alignment="center" valignment="top" leftline="true" width="0"> |
3622 |
<column alignment="center" valignment="top" leftline="true" rightline="true" width="0"> |
3623 |
<row topline="true" bottomline="true"> |
3624 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
3625 |
\begin_inset Text |
3626 |
|
3627 |
\begin_layout Standard |
3628 |
variable |
3629 |
\end_layout |
3630 |
|
3631 |
\end_inset |
3632 |
</cell> |
3633 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
3634 |
\begin_inset Text |
3635 |
|
3636 |
\begin_layout Standard |
3637 |
value |
3638 |
\end_layout |
3639 |
|
3640 |
\end_inset |
3641 |
</cell> |
3642 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
3643 |
\begin_inset Text |
3644 |
|
3645 |
\begin_layout Standard |
3646 |
units |
3647 |
\end_layout |
3648 |
|
3649 |
\end_inset |
3650 |
</cell> |
3651 |
</row> |
3652 |
<row topline="true"> |
3653 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
3654 |
\begin_inset Text |
3655 |
|
3656 |
\begin_layout Standard |
3657 |
|
3658 |
\family typewriter |
3659 |
D |
3660 |
\end_layout |
3661 |
|
3662 |
\end_inset |
3663 |
</cell> |
3664 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
3665 |
\begin_inset Text |
3666 |
|
3667 |
\begin_layout Standard |
3668 |
4 |
3669 |
\end_layout |
3670 |
|
3671 |
\end_inset |
3672 |
</cell> |
3673 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
3674 |
\begin_inset Text |
3675 |
|
3676 |
\begin_layout Standard |
3677 |
|
3678 |
\family typewriter |
3679 |
ft |
3680 |
\end_layout |
3681 |
|
3682 |
\end_inset |
3683 |
</cell> |
3684 |
</row> |
3685 |
<row topline="true"> |
3686 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
3687 |
\begin_inset Text |
3688 |
|
3689 |
\begin_layout Standard |
3690 |
|
3691 |
\family typewriter |
3692 |
H_to_D_ratio |
3693 |
\end_layout |
3694 |
|
3695 |
\end_inset |
3696 |
</cell> |
3697 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
3698 |
\begin_inset Text |
3699 |
|
3700 |
\begin_layout Standard |
3701 |
3 |
3702 |
\end_layout |
3703 |
|
3704 |
\end_inset |
3705 |
</cell> |
3706 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
3707 |
\begin_inset Text |
3708 |
|
3709 |
\begin_layout Standard |
3710 |
|
3711 |
\end_layout |
3712 |
|
3713 |
\end_inset |
3714 |
</cell> |
3715 |
</row> |
3716 |
<row topline="true"> |
3717 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
3718 |
\begin_inset Text |
3719 |
|
3720 |
\begin_layout Standard |
3721 |
|
3722 |
\family typewriter |
3723 |
meta_density |
3724 |
\end_layout |
3725 |
|
3726 |
\end_inset |
3727 |
</cell> |
3728 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
3729 |
\begin_inset Text |
3730 |
|
3731 |
\begin_layout Standard |
3732 |
5000 |
3733 |
\end_layout |
3734 |
|
3735 |
\end_inset |
3736 |
</cell> |
3737 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
3738 |
\begin_inset Text |
3739 |
|
3740 |
\begin_layout Standard |
3741 |
|
3742 |
\family typewriter |
3743 |
kg/m^3 |
3744 |
\end_layout |
3745 |
|
3746 |
\end_inset |
3747 |
</cell> |
3748 |
</row> |
3749 |
<row topline="true" bottomline="true"> |
3750 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
3751 |
\begin_inset Text |
3752 |
|
3753 |
\begin_layout Standard |
3754 |
|
3755 |
\family typewriter |
3756 |
wall_thickness |
3757 |
\end_layout |
3758 |
|
3759 |
\end_inset |
3760 |
</cell> |
3761 |
<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none"> |
3762 |
\begin_inset Text |
3763 |
|
3764 |
\begin_layout Standard |
3765 |
5 |
3766 |
\end_layout |
3767 |
|
3768 |
\end_inset |
3769 |
</cell> |
3770 |
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none"> |
3771 |
\begin_inset Text |
3772 |
|
3773 |
\begin_layout Standard |
3774 |
|
3775 |
\family typewriter |
3776 |
mm |
3777 |
\end_layout |
3778 |
|
3779 |
\end_inset |
3780 |
</cell> |
3781 |
</row> |
3782 |
</lyxtabular> |
3783 |
|
3784 |
\end_inset |
3785 |
|
3786 |
|
3787 |
\end_layout |
3788 |
|
3789 |
\end_inset |
3790 |
|
3791 |
|
3792 |
\end_layout |
3793 |
|
3794 |
\begin_layout Standard |
3795 |
You can now solve this model. |
3796 |
Go the Solver window and, under the Execute menu, select Solve. |
3797 |
You will get a message telling you the model solved. |
3798 |
Dismiss that message and return to the Browser window to examine the results. |
3799 |
You should see the following results: |
3800 |
\end_layout |
3801 |
|
3802 |
\begin_layout LyX-Code |
3803 |
\begin_inset ERT |
3804 |
status open |
3805 |
|
3806 |
\begin_layout Standard |
3807 |
|
3808 |
|
3809 |
\backslash |
3810 |
begin{ascend} |
3811 |
\end_layout |
3812 |
|
3813 |
\begin_layout Standard |
3814 |
|
3815 |
D = 1.21922 meter |
3816 |
\end_layout |
3817 |
|
3818 |
\begin_layout Standard |
3819 |
|
3820 |
H = 3.65765 meter |
3821 |
\end_layout |
3822 |
|
3823 |
\begin_layout Standard |
3824 |
|
3825 |
H_to_D_ratio = 3 |
3826 |
\end_layout |
3827 |
|
3828 |
\begin_layout Standard |
3829 |
|
3830 |
end_area = 1.16748 meter^2 |
3831 |
\end_layout |
3832 |
|
3833 |
\begin_layout Standard |
3834 |
|
3835 |
metal_density = 5000 kilogram/meter^3 |
3836 |
\end_layout |
3837 |
|
3838 |
\begin_layout Standard |
3839 |
|
3840 |
metal_mass = 408.62 kilogram |
3841 |
\end_layout |
3842 |
|
3843 |
\begin_layout Standard |
3844 |
|
3845 |
side_area = 14.0098 meter^2 |
3846 |
\end_layout |
3847 |
|
3848 |
\begin_layout Standard |
3849 |
|
3850 |
vessel_vol = 4.27025 meter^3 |
3851 |
\end_layout |
3852 |
|
3853 |
\begin_layout Standard |
3854 |
|
3855 |
wall_thickness = 0.005 meter |
3856 |
\end_layout |
3857 |
|
3858 |
\begin_layout Standard |
3859 |
|
3860 |
wall_vol = 0.0817239 meter^3 |
3861 |
\end_layout |
3862 |
|
3863 |
\begin_layout Standard |
3864 |
|
3865 |
|
3866 |
\backslash |
3867 |
end{ascend} |
3868 |
\end_layout |
3869 |
|
3870 |
\end_inset |
3871 |
|
3872 |
|
3873 |
\end_layout |
3874 |
|
3875 |
\begin_layout LyX-Code |
3876 |
|
3877 |
\end_layout |
3878 |
|
3879 |
\begin_layout Standard |
3880 |
\begin_inset Note Note |
3881 |
status collapsed |
3882 |
|
3883 |
\begin_layout Standard |
3884 |
Some of this stuff appears to have changed in the PDF.... |
3885 |
\end_layout |
3886 |
|
3887 |
\end_inset |
3888 |
|
3889 |
|
3890 |
\end_layout |
3891 |
|
3892 |
\begin_layout Standard |
3893 |
\begin_inset Marginal |
3894 |
status collapsed |
3895 |
|
3896 |
\begin_layout Standard |
3897 |
alter the units used for displaying values |
3898 |
\end_layout |
3899 |
|
3900 |
\end_inset |
3901 |
|
3902 |
You may wish to alter the units used to display these results. |
3903 |
For example, you enter the diameter |
3904 |
\emph on |
3905 |
D |
3906 |
\emph default |
3907 |
in ft. |
3908 |
You may wish to reassure yourself the |
3909 |
\family typewriter |
3910 |
1.21922 meter |
3911 |
\family default |
3912 |
is 4 ft. |
3913 |
Go to the Script window and under the Tools menu select |
3914 |
\emph on |
3915 |
' |
3916 |
\emph default |
3917 |
Measuring units'. |
3918 |
The |
3919 |
\series bold |
3920 |
Units |
3921 |
\series default |
3922 |
window |
3923 |
\begin_inset LatexCommand index |
3924 |
name "Units window" |
3925 |
|
3926 |
\end_inset |
3927 |
|
3928 |
|
3929 |
\begin_inset LatexCommand index |
3930 |
name "window, Units" |
3931 |
|
3932 |
\end_inset |
3933 |
|
3934 |
will open. |
3935 |
Enlarge it appropriately and then place it to the top and far right of |
3936 |
your display. |
3937 |
\end_layout |
3938 |
|
3939 |
\begin_layout Standard |
3940 |
There are two ways you can reset the units for displaying length. |
3941 |
\end_layout |
3942 |
|
3943 |
\begin_layout Enumerate |
3944 |
Length is a basic dimension in ASCEND so under the |
3945 |
\emph on |
3946 |
Display |
3947 |
\emph default |
3948 |
button select Length. |
3949 |
A side window will open with all the alternate units supported in ASCEND |
3950 |
for length. |
3951 |
Select ft. |
3952 |
\end_layout |
3953 |
|
3954 |
\begin_layout Enumerate |
3955 |
Or, in the lower part of the Units window is a frame labeled 'Set units'. |
3956 |
Clear and then type |
3957 |
\family typewriter |
3958 |
ft |
3959 |
\family default |
3960 |
then hit Enter. |
3961 |
\end_layout |
3962 |
|
3963 |
\begin_layout Standard |
3964 |
In either way, the units for all length variables will switch to ft. |
3965 |
Look at the values in the Browser window. |
3966 |
\end_layout |
3967 |
|
3968 |
\begin_layout Standard |
3969 |
The left upper window of the Units window contains many variable types that |
3970 |
have composite dimensions. |
3971 |
For example, you will find volume there. |
3972 |
Pick it and the right window fills with all the alternative units in which |
3973 |
you can express volume. |
3974 |
\end_layout |
3975 |
|
3976 |
\begin_layout Standard |
3977 |
Play with changing the units for displaying the various variables in the |
3978 |
vessel instance v. |
3979 |
|
3980 |
\end_layout |
3981 |
|
3982 |
\begin_layout Standard |
3983 |
One point - the left window displaying types having composite dimensions |
3984 |
will display only one type for each composite dimension. |
3985 |
If the atom types you have loaded were to include volume_difference as |
3986 |
well as volume, then only one of the two types, volume or volume_difference, |
3987 |
will be listed here. |
3988 |
Changing the units to express either changes the units for both. |
3989 |
\end_layout |
3990 |
|
3991 |
\begin_layout Standard |
3992 |
\begin_inset Marginal |
3993 |
status collapsed |
3994 |
|
3995 |
\begin_layout Standard |
3996 |
returning to a consistent set of units |
3997 |
\end_layout |
3998 |
|
3999 |
\end_inset |
4000 |
|
4001 |
When you are done, you may wish to return to a consistent set, such as SI |
4002 |
\begin_inset LatexCommand index |
4003 |
name "SI" |
4004 |
|
4005 |
\end_inset |
4006 |
|
4007 |
. |
4008 |
Under the Display button are different sets; pick |
4009 |
\emph on |
4010 |
SI (MKS) set |
4011 |
\emph default |
4012 |
. |
4013 |
\end_layout |
4014 |
|
4015 |
\begin_layout Standard |
4016 |
\begin_inset Marginal |
4017 |
status collapsed |
4018 |
|
4019 |
\begin_layout Standard |
4020 |
now we can solve the model in other ways |
4021 |
\end_layout |
4022 |
|
4023 |
\end_inset |
4024 |
|
4025 |
We can now resolve our vessel instance in any number of different ways. |
4026 |
For example we can ask what the diameter would be if we had a volume of |
4027 |
|
4028 |
\emph on |
4029 |
250 ft3 |
4030 |
\emph default |
4031 |
. |
4032 |
To accomplish this calculation, we need first to make |
4033 |
\emph on |
4034 |
vessel_volume |
4035 |
\emph default |
4036 |
a variable whose value we wish to fix. |
4037 |
When we do this the model will be overspecified. |
4038 |
ASCEND will indicate this problem to us and offer us a list of variables |
4039 |
- including the vessel diameter |
4040 |
\emph on |
4041 |
D |
4042 |
\emph default |
4043 |
, one of which we will have to "unfix |
4044 |
\begin_inset LatexCommand index |
4045 |
name "unfix" |
4046 |
|
4047 |
\end_inset |
4048 |
|
4049 |
." Finally we need to alter the value of |
4050 |
\emph on |
4051 |
vessel_volume |
4052 |
\emph default |
4053 |
to the desired value and solve. |
4054 |
Explicit instructions to accomplish these steps are as follows. |
4055 |
\end_layout |
4056 |
|
4057 |
\begin_layout Itemize |
4058 |
In the |
4059 |
\series bold |
4060 |
Browser |
4061 |
\series default |
4062 |
window, make |
4063 |
\emph on |
4064 |
vessel_volume |
4065 |
\emph default |
4066 |
the current object (select it using the left mouse button). |
4067 |
The right window of the |
4068 |
\series bold |
4069 |
Browser |
4070 |
\series default |
4071 |
display the parts of the |
4072 |
\emph on |
4073 |
vessel_volume |
4074 |
\emph default |
4075 |
, among them is the fixed flag with a value of |
4076 |
\emph on |
4077 |
FALSE |
4078 |
\emph default |
4079 |
. |
4080 |
|
4081 |
\end_layout |
4082 |
|
4083 |
\begin_layout Itemize |
4084 |
(If you do not see the value for fixed but rather its type as a boolean, |
4085 |
under the |
4086 |
\emph on |
4087 |
View |
4088 |
\emph default |
4089 |
button at the top, select |
4090 |
\emph on |
4091 |
Display Atom Values. |
4092 |
\emph default |
4093 |
) |
4094 |
\end_layout |
4095 |
|
4096 |
\begin_layout Itemize |
4097 |
Pick fixed with the right mouse button, and, in the small window that opens, |
4098 |
delete the value |
4099 |
\emph on |
4100 |
FALSE |
4101 |
\emph default |
4102 |
, enter the value |
4103 |
\emph on |
4104 |
TRUE |
4105 |
\emph default |
4106 |
and select |
4107 |
\emph on |
4108 |
OK |
4109 |
\emph default |
4110 |
. |
4111 |
\end_layout |
4112 |
|
4113 |
\begin_layout Itemize |
4114 |
Now make v the current object by picking it in the left window of the |
4115 |
\series bold |
4116 |
Browser |
4117 |
\series default |
4118 |
. |
4119 |
\end_layout |
4120 |
|
4121 |
\begin_layout Itemize |
4122 |
Export v to the Solver again by selecting to Solver under the Export button. |
4123 |
A window entitled Overspecified |
4124 |
\begin_inset LatexCommand index |
4125 |
name "Overspecified" |
4126 |
|
4127 |
\end_inset |
4128 |
|
4129 |
will appear listing the variables v.D, v.H_to_D_ratio and v.vessel_volume. |
4130 |
Pick v.D and hit the OK button; ASCEND will reset its fixed flag to FALSE. |
4131 |
\end_layout |
4132 |
|
4133 |
\begin_layout Itemize |
4134 |
Finally, return to the |
4135 |
\series bold |
4136 |
Browser |
4137 |
\series default |
4138 |
window and select |
4139 |
\emph on |
4140 |
vessel_volume |
4141 |
\emph default |
4142 |
with the right mouse button. |
4143 |
In the small window that appears type |
4144 |
\emph on |
4145 |
250 |
4146 |
\emph default |
4147 |
in the left window, |
4148 |
\emph on |
4149 |
ft^3 |
4150 |
\emph default |
4151 |
in the right, and hit the |
4152 |
\emph on |
4153 |
OK |
4154 |
\emph default |
4155 |
button. |
4156 |
\end_layout |
4157 |
|
4158 |
\begin_layout Itemize |
4159 |
Under the |
4160 |
\emph on |
4161 |
Execute |
4162 |
\emph default |
4163 |
button in the |
4164 |
\series bold |
4165 |
Solver |
4166 |
\series default |
4167 |
window, select |
4168 |
\emph on |
4169 |
Solve |
4170 |
\emph default |
4171 |
. |
4172 |
\end_layout |
4173 |
|
4174 |
\begin_layout Standard |
4175 |
Note the |
4176 |
\series bold |
4177 |
Solver |
4178 |
\series default |
4179 |
reports only 4 blocks for 6 equations. |
4180 |
This time it has to solve some equations simultaneously. |
4181 |
In the |
4182 |
\series bold |
4183 |
Solver |
4184 |
\series default |
4185 |
window, under the |
4186 |
\emph on |
4187 |
Display |
4188 |
\emph default |
4189 |
button, select the |
4190 |
\emph on |
4191 |
Incidence matrix |
4192 |
\emph default |
4193 |
tool. |
4194 |
You will see that the first three equations must be solved together as |
4195 |
a single block of equations. |
4196 |
\end_layout |
4197 |
|
4198 |
\begin_layout Standard |
4199 |
\begin_inset Marginal |
4200 |
status collapsed |
4201 |
|
4202 |
\begin_layout Standard |
4203 |
clearing all the fixed flags |
4204 |
\end_layout |
4205 |
|
4206 |
\end_inset |
4207 |
|
4208 |
For a more complicated model you may wish to start over on the process of |
4209 |
selecting which variables are fixed. |
4210 |
You can set the fixed flags for all the variables in a problem to FALSE |
4211 |
all at once -- without knowing which are currently set to TRUE. |
4212 |
In the Browser window, under the Edit button, select the Run method tool. |
4213 |
A window will open that displays a list of default methods that are automatical |
4214 |
ly attached to every model in ASCEND. |
4215 |
One is called ClearAll. |
4216 |
Pick it and hit OK. |
4217 |
All the fixed flags for the entire model will now be reset to FALSE. |
4218 |
Can you think of a way to check if this is true? (Do you remember how to |
4219 |
check which variables are currently fixed? Repeat that check and you should |
4220 |
find no variables are on the list.) |
4221 |
\end_layout |
4222 |
|
4223 |
\begin_layout Standard |
4224 |
You might now want to play by changing what you calculate and fix. |
4225 |
\end_layout |
4226 |
|
4227 |
\begin_layout Section |
4228 |
Discussion |
4229 |
\end_layout |
4230 |
|
4231 |
\begin_layout Standard |
4232 |
You have just completed the creation and solving of a very small model in |
4233 |
ASCEND. |
4234 |
In doing so, you have been exposed to some interesting issues. |
4235 |
How can we separate the concept of the model from how we intend to solve |
4236 |
it? How do we make a model to be well-posed -- i.e., a model involving n |
4237 |
equations in n unknowns -- so we can solve it? How should one handle the |
4238 |
units for the variables in a modeling system? What we have shown you here |
4239 |
is for a small model. |
4240 |
We still need to show you how one can make a large model well-posed, for |
4241 |
example. |
4242 |
You will start to understand how one can do this in the next chapter. |
4243 |
\end_layout |
4244 |
|
4245 |
\begin_layout Standard |
4246 |
The next chapter is crucial for you to understand if you want to begin to |
4247 |
understand how we approach good modeling practice. |
4248 |
Please do continue with it. |
4249 |
As it uses the vessel model, it would, of course, be best to continue with |
4250 |
that chapter now. |
4251 |
\end_layout |
4252 |
|
4253 |
\end_body |
4254 |
\end_document |