Class Diffusion

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Container
              |
              +--java.awt.Panel
                    |
                    +--java.applet.Applet
                          |
                          +--BaseApplet
                                |
                                +--BaseApplet2
                                      |
                                      +--Diffusion

public class Diffusion

extends BaseApplet2

implements java.lang.Runnable

Applet to model diffusion. Displays electrons moving in a rectangular area, plus a temperature slider and momentum histograms.

See Also:

Serialized Form

Inner Class Summary

class	Diffusion.Electron Class to simulate a single electron
protected class	Diffusion.TemperatureListener Listener to detect changes in the position of the temperature slider.

Inner classes inherited from class BaseApplet2

BaseApplet2.FixedButton, BaseApplet2.FixedCheckbox, BaseApplet2.GraphClickListener

Inner classes inherited from class BaseApplet

BaseApplet.MozillaWorkaround, BaseApplet.ResizeListener

Inner classes inherited from class java.awt.Component

java.awt.Component.AWTTreeLock

Field Summary

protected java.awt.Button	animButton
protected java.awt.TextField	countField
protected double	dt The time step to use (default 0.001)
protected int	electronCount The number of electrons
protected java.util.Vector	electrons A Vector containing all electrons present in the simulation.
protected int	electronSize The size (in pixels) of circle to draw for an electron
protected int	h Local copy of the height of the display area
protected int	hSpace
protected boolean	killed true if the animation should terminate at the next available opportunity, otherwise false.
protected double	maxT The maximum temperature permitted
protected double	minT The minimum temperature permitted
protected java.awt.Button	resetButton
protected double	simH Width of the box, in simulation units
protected double	simW Width of the box, in simulation units
protected int	sliderW
protected int	sliderX
protected double	temp The temperature
protected java.awt.TextField	tempField
protected Diffusion.TemperatureListener	tempListener
protected java.lang.Thread	thr The animation thread, or null if no animation is in progress.
protected Plotter	tPlotter
protected double	vMultiplier The velocity multiplier.
protected int	vSpace
protected int	w Local copy of the width of this applet
protected Histogram	xHist
protected Plotter	xvPlotter
protected Histogram	yHist
protected Plotter	yvPlotter

Fields inherited from class BaseApplet2

boxes, buttons, enablePrompt, fields, focus, panel, statusLabel, useSwing, V_MARGIN

Fields inherited from class BaseApplet

buffer, GRAPH_MARGIN, refresh, resizeListener, safetyLimit, useBuffer

Fields inherited from class java.applet.Applet

serialVersionUID, stub

Fields inherited from class java.awt.Panel

base, nameCounter, serialVersionUID

Fields inherited from class java.awt.Container

component, containerListener, containerSerializedDataVersion, dispatcher, layoutMgr, maxSize, ncomponents, serialVersionUID

Fields inherited from class java.awt.Component

actionListenerK, adjustmentListenerK, appContext, assert, background, BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, changeSupport, componentListener, componentListenerK, componentOrientation, componentSerializedDataVersion, containerListenerK, cursor, dropTarget, enabled, eventMask, focusListener, focusListenerK, font, foreground, hasFocus, height, incRate, inputMethodListener, inputMethodListenerK, isInc, isPacked, itemListenerK, keyListener, keyListenerK, LEFT_ALIGNMENT, locale, LOCK, minSize, mouseListener, mouseListenerK, mouseMotionListener, mouseMotionListenerK, name, nameExplicitlySet, newEventsOnly, ownedWindowK, parent, peer, peerFont, popups, prefSize, RIGHT_ALIGNMENT, serialVersionUID, textListenerK, TOP_ALIGNMENT, valid, visible, width, windowListenerK, x, y

Constructor Summary

Diffusion()

Method Summary

void	actionPerformed(java.awt.event.ActionEvent ae) Subclasses should at least provide an empty implementation of this method.
void	animate() Toggles the animation.
void	doPaint(java.awt.Graphics g) Called by forcePaint() to actually perform the painting.
protected double	gaussian() Returns a gaussian-distributed random number, using the Box-Muller transform.
int	getCount() Returns the number of electrons
double	getT() Returns the selected temperature
void	init() Performs extra initialisation, including adding a panel to the bottom of the applet.
void	reset() Stops any running animation, and generates a new set of electrons with random momentum.
void	run() This method loops through an update/repaint cycle.
void	setCount(int i) Sets the number of electrons, resetting the simulation if necessary.
void	setT(double t) Sets the selected temperature
void	spawnElectrons(int count) Destroys any electrons present in the simulation, and replaces them with a new set of electrons, arranged in a square, and with (approximately) gaussian momentum distribution.
void	spawnElectrons(int w, int n, double space) Adds electrons to the simulation, arranged in a rectangle.
void	start() Applets should use this method to perform any final initialisation necessary to "activate" the applet
void	startAnim() Starts the animation.
void	stop() When this method is called, the applet should cease any user interaction.
void	stopAnim() Stops the animation.
void	updateInput() Reads in (and validates) input from the text fields.
void	updateSimulation(double dt) Steps through the simulation logic by a specified time step.

Methods inherited from class BaseApplet2

add, add, addButton, addCheckbox, addField, addField, addField, addListeners, focusGained, focusLost, getDouble, getGraphHeight, getInt, lockControls, makeButton, makePanel, paintDashedLineH, paintDashedLineV, register, removeListeners, setComponentsEnabled, setLayout, setPromptEnabled, textValueChanged, toString, unlockControls

Methods inherited from class BaseApplet

changeFont, forcePaint, getAppletInfo, getParameterInfo, itemStateChanged, paint, refresh, update

Methods inherited from class java.applet.Applet

destroy, getAppletContext, getAudioClip, getAudioClip, getCodeBase, getDocumentBase, getImage, getImage, getLocale, getParameter, isActive, newAudioClip, play, play, resize, resize, setStub, showStatus

Methods inherited from class java.awt.Panel

, addNotify, constructComponentName

Methods inherited from class java.awt.Container

add, add, add, add, addContainerListener, addImpl, applyOrientation, countComponents, deliverEvent, dispatchEventImpl, dispatchEventToSelf, doLayout, eventEnabled, findComponentAt, findComponentAt, getAlignmentX, getAlignmentY, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents_NoClientCode, getComponents, getCursorTarget, getInsets, getLayout, getMaximumSize, getMinimumSize, getMouseEventTarget, getPreferredSize, getWindow, initIDs, insets, invalidate, invalidateTree, isAncestorOf, layout, lightweightPrint, list, list, locate, minimumSize, nextFocus, paintComponents, paramString, postProcessKeyEvent, postsOldMouseEvents, preferredSize, preProcessKeyEvent, print, printComponents, printOneComponent, processContainerEvent, processEvent, proxyEnableEvents, proxyRequestFocus, readObject, remove, remove, removeAll, removeContainerListener, removeNotify, setCursor, setFocusOwner, setFont, transferFocus, updateCursor, validate, validateTree, writeObject

Methods inherited from class java.awt.Component

action, add, addComponentListener, addFocusListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addPropertyChangeListener, addPropertyChangeListener, areInputMethodsEnabled, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, disable, disableEvents, dispatchEvent, enable, enable, enableEvents, enableInputMethods, firePropertyChange, getBackground, getBounds, getBounds, getColorModel, getComponentOrientation, getCursor, getDropTarget, getFont_NoClientCode, getFont, getFontMetrics, getForeground, getGraphics, getHeight, getInputContext, getInputMethodRequests, getIntrinsicCursor, getLocation, getLocation, getLocationOnScreen, getName, getNativeContainer, getParent_NoClientCode, getParent, getPeer, getSize, getSize, getToolkit, getToolkitImpl, getTreeLock, getWidth, getWindowForObject, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, isDisplayable, isDoubleBuffered, isEnabled, isEnabledImpl, isFocusTraversable, isLightweight, isOpaque, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, printAll, processComponentEvent, processFocusEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, remove, removeComponentListener, removeFocusListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, reshape, setBackground, setBounds, setBounds, setComponentOrientation, setDropTarget, setEnabled, setForeground, setLocale, setLocation, setLocation, setName, setSize, setSize, setVisible, show, show, size, toString, transferFocus

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, registerNatives, wait, wait, wait

Field Detail

sliderW

protected int sliderW

sliderX

protected int sliderX

hSpace

protected int hSpace

vSpace

protected int vSpace

electronCount

protected int electronCount

The number of electrons

thr

protected java.lang.Thread thr

The animation thread, or null if no animation is in progress.

killed

protected boolean killed

true if the animation should terminate at the next available opportunity, otherwise false.

electrons

protected java.util.Vector electrons

A Vector containing all electrons present in the simulation.

electronSize

protected int electronSize

The size (in pixels) of circle to draw for an electron

w

protected int w

Local copy of the width of this applet

h

protected int h

Local copy of the height of the display area

simW

protected double simW

Width of the box, in simulation units

simH

protected double simH

Width of the box, in simulation units

dt

protected double dt

The time step to use (default 0.001)

temp

protected double temp

The temperature

vMultiplier

protected double vMultiplier

The velocity multiplier. Rather than adjusting the momentum of every electron whenever the temperature is changed, a constant multiplier is applied to all velocities. If the velocities were modified directly, inaccuracies would creep in quite rapidly (temperature changes every time slider is "seen" in a different position).

minT

protected double minT

The minimum temperature permitted

maxT

protected double maxT

The maximum temperature permitted

animButton

protected java.awt.Button animButton

resetButton

protected java.awt.Button resetButton

tempField

protected java.awt.TextField tempField

countField

protected java.awt.TextField countField

tempListener

protected Diffusion.TemperatureListener tempListener

tPlotter

protected Plotter tPlotter

xvPlotter

protected Plotter xvPlotter

yvPlotter

protected Plotter yvPlotter

xHist

protected Histogram xHist

yHist

protected Histogram yHist

Constructor Detail

Diffusion

public Diffusion()

Method Detail

init

public void init()

Description copied from class: BaseApplet2

Performs extra initialisation, including adding a panel to the bottom of the applet.

Overrides:

init in class BaseApplet2

start

public void start()

Description copied from class: BaseApplet

Applets should use this method to perform any final initialisation necessary to "activate" the applet

Overrides:

start in class BaseApplet2

stop

public void stop()

Description copied from class: BaseApplet

When this method is called, the applet should cease any user interaction. In particular, any threads explicitly started should be stopped, any external resources should be closed. This method should negate the action of start().

Overrides:

stop in class BaseApplet2

startAnim

public void startAnim()

Starts the animation. This method will have no effect if the animation is already in progress.

stopAnim

public void stopAnim()

Stops the animation. This method will have no effect if the animation is not in progress.

run

public void run()

This method loops through an update/repaint cycle. It is intended to execute in a separate thread, so should not be invoked directly. Instead, the startAnim() method should be used, which will start this method in a new thread.

Specified by:

run in interface java.lang.Runnable

actionPerformed

public void actionPerformed(java.awt.event.ActionEvent ae)

Description copied from class: BaseApplet

Subclasses should at least provide an empty implementation of this method.

Overrides:

actionPerformed in class BaseApplet

updateInput

public void updateInput()

Reads in (and validates) input from the text fields.

Throws:

java.lang.IllegalArgumentException - if any input fields are invalid

animate

public void animate()

Toggles the animation. If the animation is running, it will be stopped, otherwise a new animation will be started.

reset

public void reset()

Stops any running animation, and generates a new set of electrons with random momentum. The momentum components of the electrons will follow an approximate gaussian distribution; the positions will be so as to arrange the particles in an approximate square.

doPaint

public void doPaint(java.awt.Graphics g)

Description copied from class: BaseApplet

Called by forcePaint() to actually perform the painting. Subclasses should implement this method as if it were the standard paint() method; buffering will then take place transparently.

Overrides:

doPaint in class BaseApplet

Tags copied from class: BaseApplet

Parameters:

g - The Graphics object on which to paint

updateSimulation

public void updateSimulation(double dt)

Steps through the simulation logic by a specified time step. Any size of step can be chosen, with the proviso that it should be sufficiently small that no particle can travel the entire distance between two opposite walls within that time.

Parameters:

dt - the size of the time interval to consider

spawnElectrons

public void spawnElectrons(int count)

Destroys any electrons present in the simulation, and replaces them with a new set of electrons, arranged in a square, and with (approximately) gaussian momentum distribution.

Parameters:

count - the number of electrons to create

spawnElectrons

public void spawnElectrons(int w,
                           int n,
                           double space)

Adds electrons to the simulation, arranged in a rectangle.

Parameters:

n - The number of electrons to add

w - The number of electrons per row

space - The spacing (simulation units) between electrons

gaussian

protected double gaussian()

Returns a gaussian-distributed random number, using the Box-Muller transform.

getT

public double getT()

Returns the selected temperature

setT

public void setT(double t)

Sets the selected temperature

getCount

public int getCount()

Returns the number of electrons

setCount

public void setCount(int i)

Sets the number of electrons, resetting the simulation if necessary.