Stage 1: Starting with Births

Mdule 2C Building the Mdel Presenter s Guide Stage 1: Starting with Births Presenter Ntes are in text bxes thrughut the dcument. File Mdel Hand Variable Bx Arrw Rate Pacman Y=x 2 Run Run AutSim Input/Output Object Cntrl Panel Open Vensim. If a previus mdel appears, under the File menu, select New Mdel. If the Mdel Settings windw pens, enter these values, then click OK. INITIAL TIME = 0 FINAL TIME = 50 TIME STEP = 1 Units fr Time Year Integratin Type Euler If the Mdel Settings windw des nt appear, direct participants t click n the Mdel drpdwn menu and select Settings. There are tw very imprtant icns n the menu bar the hand and the pacman. The hand is the icn t use when yu want t brwse, mve r resize the mdel. The pacman is used t delete a mistake. The pacman desn t ask fr cnfirmatin f the delete it assumes that yu mean what yu say. T build the mdel shwn belw Births Ppulatin births per mse Click and release n the Bx icn, click in the white space, type Ppulatin in the rectangle that appears, hit Enter. Use the tiny circle in the lwer right hand crner f the bx t adjust the bx size s the wrds are easy t read. CAST---Mdule 2C: Presenter s Guide Pittsburgh Supercmputing Center Page 1

Click and release n the Rate icn. Mve t the left f the Ppulatin bx, click and release, mve the muse int the Ppulatin bx, click and release again. In the rectangle that appears, type Births and hit Enter. Click and release n the Variable icn. Mve under the Births rate, click and release, and type births per mse in the rectangle that appears. Hit Enter. Click and release n the Arrw icn. Mve the muse ver the wrds births per mse and click and release. Then mve the muse ver the wrds Births, and click and release. A blue arrw shuld appear. The head f the arrw shuld be pinting t Births. Using the same actin, cnnect Ppulatin t Births with a blue arrw. Yu can make the blue arrws curve by pulling n the tiny circle attached t each arrw. Putting the math in the mdel Click n the Y=x 2 buttn. Ntice that all variables are shaded in black. That means we haven t given Vensim any numbers yet. Click n the bx called Ppulatin. Enter 100 in the Initial Value bx and yur windw shuld lk like the ne belw. Nte that Vensim has filled in fr yu that Ppulatin is the Integral f Births. If yur students are taking calculus, yu can tell them Vensim is slving differential equatins numerically. Fr the rest f the wrld, yu can simply say that Vensim will be adding Births t the Ppulatin t get next year s Ppulatin. Nte that there is a Units bx where yu can type the apprpriate units fr the variable being measured. Nte the Cmment bx fr dcumentatin. We will g ver the ther bxes when we d ther variables. Click OK t clse the windw. Click n births per mse and enter 0.5. Als enter the values seen belw fr Minimum Value, Maximum Value, and Increment. These will be used fr the slider bars yu will see later. Click OK t clse the windw. CAST---Mdule 2C: Presenter s Guide Pittsburgh Supercmputing Center Page 2

Click n Births and enter births per mse* Ppulatin by clicking n the names in the Variables bx and the symbl * n the keypad r n yur keybard. Running the Mdel Run the mdel by clicking n the green running man next t the white bx that says Current. If a dialgue bx appears saying Dataset Current already exists. D yu want t verwrite it?, click n Yes. T see the utput, click n Ppulatin, then click n the Graph icn n the left sidebar. A graph will appear shwing that there are ver 60 billin mse at the end f 50 years. T see a table f values, click n the Table Time Dwn icn n the left sidebar. Reflectin Questins 1. Lk carefully at the first fur values under Ppulatin n the table. D they agree with the numbers calculated by the class and recrded n the chart earlier? The first fur mse ppulatin numbers generated by the mdel shuld be 100, 150, 225, 337.5. This is a gd time t pint ut that the mdel has n knwledge that fractinal mse dn t exist. It s just ding the math. CAST---Mdule 2C: Presenter s Guide Pittsburgh Supercmputing Center Page 3

Run AutSim the mdel by clicking n the green running man with hrizntal bars t the right f the ther green man. Nte the mini-graphs that appear in Ppulatin and Births. Use the slider bars t vary the births per mse. Reflectin Questin 2. What kind f grwth des this mdel illustrate? Expnential grwth is illustrated. 3. Hw wuld yu simulate zer ppulatin grwth with this mdel? A births per mse f 0 gives zer ppulatin grwth. Click the Stp Sign t return the mdel t its riginal state. CAST---Mdule 2C: Presenter s Guide Pittsburgh Supercmputing Center Page 4

Stage 2: Adding Deaths Births births per mse Ppulatin Deaths mse death fractin Add the new cmpnents t the mdel. Cautin: The rate called Deaths must be drawn s it pints away frm Ppulatin. That will tell the mdel t subtract deaths. Therefre, when yu click and release the Rate icn, yur first click in the mdel space shuld be inside the Ppulatin bx. Then mve the muse t the right and click again. Review the directins n page 1 t add the Variable mse death fractin and the tw arrws. Remind participants t use the pacman if they need t delete smething s they can redraw it. Click n the pacman, then click n the items t be deleted. Click n the Y=x 2 buttn t add data the new parts f the mdel. Nte that the Ppulatin Bx darkens, shwing that yu must click n the bx t lk at the new equatin inside. Yu shuld see Births Deaths inside the integral bx. This means that every year, births will be added and deaths will be subtracted. Click OK t clse the windw. When yu click n mse death fractin, ask yurself what fractin f mse shuld die each year. Enter that value in the text bx. Set the Minimum Value, Maximum Value, and Increment in the windw als. What bunds will yu chse fr the mse death fractin? Participants shuld use 0 and 1 as their minimum and maximum values, respectively. They may select any decimal in between fr their current mse death fractin. The Increment may be 0.1 r smaller. Nw input the equatin fr Deaths just as yu input the equatin fr Births. Yu may need t remind the participants that they can click n the variable names t enter the expressin Ppulatin * mse death fractin rather than typing in the names. Run AutSim, using the scrll bars t manipulate the mse death fractin. Reflectin Questin 4. Hw culd yu simulate a declining mse ppulatin with this mdel? If the mse death fractin is larger than the births per mse fractin, then there will be mre deaths than births and the mse ppulatin will decrease. CAST---Mdule 2C: Presenter s Guide Pittsburgh Supercmputing Center Page 5

Stage 3: Making a Custm Graph Step 1 Click n the Cntrl Panel icn at the far right end f the tp bar t pen this windw. Step 2 Click n the Graphs tab. Then click n New. Step 3 Fllw the steps belw t make the tp windw t the right lk like the windw belw it. Enter a Title this will allw yu t identify this graph. I suggest Ppulatin. Unless we say therwise, the X-Axis will represent Time and it will g frm 0 t 50 as it was set in ur mdel. T tell the mdel what t graph n the Y-Axis, click inside the first variable bx. Click n the Sel buttn, then select Ppulatin frm the list shwn. Click OK. T be sure the Y-axis starts at 0, type 0 in the Y-min bx. T be sure the graph plt is visible in a prjectin display, type 3 in the LineW bx. Yur windw shuld nw lk like the bttm windw t the right. Clse the windw by clicking n OK at the bttm f the windw. CAST---Mdule 2C: Presenter s Guide Pittsburgh Supercmputing Center Page 6

Step 4 Yu shuld see the Cntrl Panel windw pen n yur screen with Ppulatin in the white space. Click Display and yu shuld see a graph f the Ppulatin like the ne belw. Step 5 Clse the graph windw and then the cntrl panel t return t the mdel. T attach the graph t the white space, click n the Input Output Object. Click in the mdel white space t bring frth a windw. Step 6 Click in the circle by Output Custm Graph. Then use the drp-dwn menu at the bttm f the bx t select the name f the graph yu wish t display (Ppulatin). Click OK and a graph bx will appear n the screen. Yu may resize it by dragging n the small circle in the lwer right-hand crner f the bx. Run the mdel t make the graph appear. CAST---Mdule 2C: Presenter s Guide Pittsburgh Supercmputing Center Page 7

Stage 4: Making a Custm Table Step 1 Click n the Cntrl Panel icn at the far right end f the tp bar tp pen this windw. Step 2 Click n the Graphs tab. Then click n New. Step 3 In the windw shwn belw, click n the As Table buttn at the bttm center f the windw. This windw shuld appear: Step 4 In the new windw, Enter a Title different frm the ne selected fr the graph - I suggest Ppulatin Table. Click n the Variable bx. In the windw that appears, select Ppulatin and click OK. Ntice that Ppulatin nw appears in the white text bx next t Variable. Click the Add buttn n the right t mve Ppulatin int the Table Cntent bx. Click in the Running dwn bx t get a vertical display f numbers. Type 13 in bth Cell Width bxes: First and rest. The windw shuld lk like this: Clse the windw by clicking n OK at the bttm f the windw. CAST---Mdule 2C: Presenter s Guide Pittsburgh Supercmputing Center Page 8

Step 5 Yu shuld see the Cntrl Panel windw pen n yur screen with Ppulatin and Ppulatin_Table in the white space. Click n Ppulatin_Table t highlight it (if it isn t already highlighted). Then click Display. Yu shuld see a table f values like the ne belw. Step 6 Clse the graph windw and then the cntrl panel t return t the mdel. T attach the table t the white space, click n the Input Output Object. Click in the mdel white space t bring frth a windw. Step 7 Click in the circle by Output Custm Graph. Then use the drp-dwn menu at the bttm f the bx t select the bject yu wish t display (Ppulatin_Table). Click OK and a table bx will appear n the screen. Yu may resize it by dragging n the small circle in the lwer right-hand crner f the bx. Run the mdel t make the table appear. CAST---Mdule 2C: Presenter s Guide Pittsburgh Supercmputing Center Page 9