## Featured Modeling Archive
The Zeeman Heartbeat Model uses work in Catastrophe Theory to create a simulation of the heartbeat cycle. The heart is represented as a blue circle in phase space and travels from diastole to systole which are represented as the green circles. Cardiac muscle fiber length (x) is represented on the y-axis and electrochemical activity (b) is represented on the x-axis. The model calculates the heart rate (in beats per minute) and a variable called gamma which is intrinsic to the pacemaker.
The Gray-Scott Reaction Diffusion Model displays the spatial concentration of chemical species U and V under the influence of the reaction U+2V->3V and V->P. The simulation models this reaction in an open system with a constant addition of U and removal of V due to a flow. Combining this autocatalytic process with diffusion results in pattern formation that has a surprising variety of spatiotemporal patterns when starting in the initial state U=1 and V=0 except for a square grid at the center where U=1/2 and V=1/4.
The Boltzmann Distribution From A Microcanonical Ensemble Model allows students and instructors to explore why the Boltzmann distribution has its characteristic exponential shape. In this model, particles have only one degree of freedom–the energy to move in one dimension.
The Simulated Annealing Method for the Traveling Salesman Model demonstrates the use of the "simulated annealing algorithm" to attempt to solve the "travelling salesman" problem. A text file containing longitude and latitude data for 120 cities in the US and southern Canada is loaded when this program begins.
The 3-D Hydrogen Atom Probability Densitites model simulates the probability density of the first few (n = 1, 2, and 3, and associated l and m values) energy eigenstates for the Hydrogen atom (the Coulomb potential). The main window shows the energy level diagram for the solutions to the Coulomb potential in 3D.
The Ejs QM Eigenstate Superposition Demo model displays the time dependence of a variety of superpositions of energy eigenfunctions for the infinite square well and harmonic oscillator potentials. One of the eleven pre-set superpositions can be selected via a drop-down menu with the resulting wave function shown in phase-as-color representation.
The EJS Phases of Moon model displays the the appearance of Moon and how it changes depending on the position of Moon relative to Earth and Sun. The main window shows Earth (at the center). By using the Options Menu the Moon View window shows the appearance of Moon as seen from Earth when Moon is in the position shown in the main window.
The Exoplanet Detection: Transit Method model simulates the detection of exoplanets by using the transit method. In this method, the light curve from a star, and how it changes over time due to exoplanet transits, is observed and then analyzed. When the exoplanet passes in front of the star (transits), it blocks part of the starlight. This decrease in starlight is shown on the graph.
The EJS Newton's Mountain model illustrates the motion of a projectile launched from the top of a VERY tall mountain on Earth. The diagram shown in the simulation is taken from Newton's A Treatise on the System of the World, which he wrote after the Principia. Newton concluded that a projectile launched horizontally with sufficient speed would orbit Earth rather than crashing to Earth's surface.
The Ejs Great Circles model displays the frictionless motion of a particle that is constrained to follow the surface of a perfect sphere. The sphere rotates underneath the particle, but since there is no friction, and the sphere is perfectly spherical, the motion of the particle is not influenced by the sphere. Next 10 » |