Resonance applet by Prof. Wolfgang Christian

[lookang]

Harmonic Oscillator Resonance from F:\EasyJavaSimulation\EJS_4.1_081216\EJS_4.1\workspace\source\users\davidson\wochristian\osc\SHOResonance.xml

wochristian@davidson.edu

Plots the energy and phase of the simple harmonic oscillator after transients have decayed.

This is an applet that i tried to make a while back but didn't figure out how to.

i aim to allow b = 0 , 0.1 , 1 to show no damping, light damping , heavy damping on a single plot.

work in progress still.

Any help is appreciated


source code
download the *.jar for using the applet on standalone without internet connection.

[lookang]

i can't figure out the codes in the xml, therefore not able to modify much.

any help ?

[Fu-Kwun Hwang]

Please post the code which you are in trouble. I will try to help!

[lookang]

i am puzzled by this code in the evolution
Record Data.

Code:

transientCounter--;  //  does this line do this? transientCounter = 0 ?
if(transientCounter<=0){
  double energy = 0.5*(m*v*v + k*x*x);  // assign TOTAL energy = 0.5*(m*v*v + k*x*x)
  double maxX = Math.sqrt(2*energy/k);  // maxX = maximum amplitude
  _view.resonanceTrace.addPoint(freq, maxX);//  what is this  _view.resonanceTrace.addPoint  command? where can i read about this line or where is the reference made to this resonanceTrace ?
  double phase= Math.atan2(x*omegaD,v);
  _view.phaseTrace.addPoint(freq, phase);
  freq += df;  // freq = freq +df;
  omegaD = 2*Math.PI*freq;  // formula
  dt=1.0/freq;  // dt = 1/ freq;
  transientCounter=transientCycles;  // not sure what this do
  t=x=v=0;  //  set to zero v = 0, x = 0. t = 0 guess to solve another resonance problem ?
  _resetSolvers();  // where did this come from? looks like it is to reset the ODE solvers but i don't see any codes about it, is it one of those command lines like _initialise(); etc
}

[Fu-Kwun Hwang]

Where is the above code coming from?
I guest it was not written by you.

_view.resonanceTrace.addPoint(freq, maxX);

it means that there is a GUI element in the view, it's name is resonanceTrace
and that element support build in function: addPoint.
I would guest it is a trace element.
There are web pages about all the  function for GUI elements.
Please check out http://fem.um.es/EjsWiki/index.php/Main/Elements

[lookang]

From
F:\EasyJavaSimulation\EJS_4.1_081216\EJS_4.1\workspace\source\users\davidson\wochristian\osc\SHOResonance.xml
wochristian@davidson.edu


One day i hope to be able to write codes like this, but not today.

If Davidson use normal EJS function of trace, i will be able to follow how the trace was drawn.

[Fu-Kwun Hwang]

transientCounter--; 　is equal to transientCounter=transientCounter-1;
The actual value determined by initial value when the variable was defined (1000).

_view.phaseTrace.addPoint(freq, phase);
I will not use the above code. It is easier to set (Input X, Input Y) to (freq , phase).
That is the way EJS was designed to do.
Prof. Wolfgang Christian is a very good programmer, so he like to use build in function directly.
But I will use the normal way.


if(transientCounter<=0){
...
}

The above part was used to reset everything to time t=0 when the evolution page has been run 1000 times.
It is similar to add those code (inside if) to initialization page and issue _initialize() in EJS.

I have never used "_resetSolvers(); " so I do not know what it is.
I did not find any difference when I comment out the above line (did not execute it).

[lookang]

thanks for reading the source xml file.

i will KIV this, until i can redesign the resonance modeling using EJS default functions.

i will work on this soon:)