New Open Source Physics collection resources

NVT-Molecular Dynamics Model

Sun, 19 May 2013 18:33:32 EST

The NVT-Molecular Dynamics Model performs molecular dynamics simulations at constant temperature of 32, 108, 256 or 500 molecules interacting through the Lennard-Jones potential, in a wide range of densities and temperatures covering liquid, vapor and solid states. Thermodynamic properties, radial and speed distribution functions, velocity autocorrelation functions (vcf's) and their Fourier spectra, and mean square displacements (msd's) are calculated and displayed. Self-diffusion coefficients are worked out from the vcf's and msd's. Self space-time correlation functions (sstcf's) are estimated and compared with the Gaussian approximation. The 3D molecular motions can also be visualized. The motion equations are integrated by two methods, at user's choice: the damped-force with leap-frog Verlet's algorithm, and the "ad-hoc" rescaling with the velocity Verlet algorithm. The model allows to assess the role of the potential cut-off distance, the number of steps in equilibration runs, the time-step and the gap between time origins for vcf's, msd's and sstcf's. The NVT-Molecular Dynamics Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Instantaneous Frequency Stock Market Model

Fri, 17 May 2013 09:42:02 EST

The Instantaneous Frequency Stock Model estimates a stock's cyclical fluctuations over a three-day period to determine how fast the market is moving. The instantaneous frequency of an input signal is calculated by modeling an input function's most recent data points as a sin wave and performing a Fourier transform to derive the function's frequency. This model implements different velocity indicators on daily closing prices of a few common companies, and allows the user to compare values of the indicators at different times. The Instantaneous Frequency model was developed by Matt Mohorn using the Easy Java Simulations (EJS) modeling tool. You can examine and modify the physical model for this simulation if you have Ejs installed by right-clicking within the plot and selecting "Open Ejs Model" from the pop-up menu.

Teaching with Moodle and OSP Plugins

Fri, 19 Apr 2013 15:16:15 EST

This talk describes Moodle courseware created at Davidson College for introductory physics and astronomy courses that, in addition to standard Moodle content, incorporate in-class polling and simulations using open source Moodle plugins. We will show how we use the In-class Polling for All Learners (IPAL) plugin developed by Bill Junkin to download questions from a databank in the ComPADRE digital library. We will also show how to use the EJSApp plugin developed by Rubén Heradio and Luis de la Torre Cubillo at the National Distance Education University (UNED) in Madrid to embed Easy Java Simulations (EJS) applications (such as simulations, virtual and remote laboratories) into a Moodle course. These tools allow teachers to easily incorporate computer-based modeling into their curriculum by providing an open and extensible solution for incorporating interactive engagement pedagogies into their Moodle courses.

Stock Market Momentum Model

Tue, 16 Apr 2013 08:58:04 EST

The Stock Market Momentum Model uses the change in price to predict a future change. In trading jargon, this change in price is referred to as momentum. Mathematically, the model can be considered to be a causal high pass filter of degree 1. In this model, the user can analyze the momentum indicator response as it relates to the daily closing price of a few popular stock indices. The upper plot shows the closing price and a smoothed price (in blue) if the filter is turned on. The lower panel is the momentum indicator. Users can drag a cursor left and right to compare values on these two graphs. Below, the cursor is dropped at a point where the momentum shifts from negative to positive values, which happens to be the beginning of a bull market. A trader would want to buy at these opportunities and sell when the momentum becomes negative. Time is measured in years and in each year there are approximately 253 business days.

Stock Market Causal High Pass Filter Model

Mon, 15 Apr 2013 08:56:32 EST

One application of econophysics is the use of high pass filters to analyze stock market data. To determine how fast the market is moving, the Stock Market Causal High Pass Filter Model uses a technique known as causal high pass filters to estimate market velocity and acceleration. Different order indicators are presented in this model, and the user can study the sensitivity and accuracy of the various indicators.

HS-WCA-LJ Monte Carlo Model

Tue, 12 Mar 2013 07:38:53 EST

The HS-WCA-LJ Monte Carlo Model performs simultaneous canonical Monte Carlo (MC) simulations of 108, 256 or 500 particles interacting through the hard sphere (HS), the Weeks, Chandler and Andersen (WCA) and the Lennard-Jones (LJ) pair potentials. It was inspired by the review of Chandler, Weeks and Anderson on WCA theory, illustrating that "the attractive interactions help fix the volume of the system, but the arrangements and motions of molecules within that volume are determined primarily by the local packing and steric effects produced by the repulsive forces". The radial distribution functions for the three systems are plotted after every MC cycle, at densities and temperatures chosen by the user, and the data Tables display thermodynamic results from the LJ and WCA potentials. The thermodynamics of the HS system was addressed to another application cataloged at Open Source Physics. The objective of this application is: (i) to illustrate the canonical MC method with three different systems;(ii) to probe the densities and temperatures at which the HS and WCA potentials approach the structure(defined by the radial distribution functions) of the LJ system, regarding their use in perturbation theory. The HS-WCA-LJ Monte Carlo Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Airborne Infection SEIR Model

Mon, 11 Mar 2013 09:01:05 EST

The Airborne Infection SEIR Model examines the time evolution of four populations in an epidemic: those who are susceptible to infection, those who have been exposed but do not yet exhibit symptoms, those who are infected and contagious, and those who have recovered from the infection. The SUSCEPTIBLE-EXPOSED-INFECTED-REMOVED (SEIR) Model shows that infection can spread throughout a population in just a matter of days. Infections and viruses can be transmitted relatively easily, or can be prevented all together if certain conditions are satisfied. This model examines the spread of infection in indoor environments and the parameters that shape its transmission. The Airborne Infection SEIR Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Hard Spheres Monte Carlo Model

Wed, 20 Feb 2013 18:48:59 EST

The Hard Sphere Monte Carlo Model performs canonical Monte Carlo simulations of 256 or 500 hard spheres covering the fluid and solid states. The results are analysed through the radial distributions functions from which the equation of state (EOS) is estimated. This is done by fitting a polynomial to the radial distribution functions in order to exrapolate them to the hard spheres distance of contact. The consistency of the simulations is assessed by the errors of the predicted compressibility factors relatively to the accurate EOS reported by Wu and Sadus. The Hard Sphere Monte Carlo Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Exponential Moving Average Stock Model

Wed, 13 Feb 2013 20:09:46 EST

A primary application of econophysics is using digital signal processing techniques to filter and predict market data, which is theorized to exhibit random walk motion. An exponential moving average is one tool that physicists use to smooth data from an input signal to identify its trends. The Exponential Moving Average Stock Model implements three types of exponential moving averages and allows the user to change the parameters of each. The model allows the user to view the results of exponential moving averages computed on the New York Stock Exchange daily closing price of six familiar companies. It demonstrates one way that traders use causal filters to smooth market data and forecast the next day's price.

Poisson Distribution Model

Wed, 13 Feb 2013 19:30:38 EST

The Poisson Distribution Model shows how to use the Apache Commons Math library (included in EJS) to generate random numbers that follow the Poisson distribution. A histogram of the numbers is displayed. This simple teaching example illustrates the use of the Histogram view element and how to speed up a simulation by running the model several time before updating the view.

Optimization with the Apache Library Model

Wed, 23 Jan 2013 07:24:05 EST

The Optimization with the Apache Library model demonstrates how the Apache Optimization library can be used within EJS to fit experimental data. In this simulation, six different optimization algorithms have been implemented, and three different types of (pre-measured) experimental data are included: nuclear decay, a falling ball, and a damped oscillator. In the description pages, exercises are provided that encourage the user to explore the efficiency and effectiveness of different algorithms (applied to different types of data), and the process of implementing code from the Apache Optimization library is described. In this simulation, the sum of squared deviations is minimized, but if you have estimates for the uncertainties in your experimental data, the implementation can easily be modified to instead minimize the value of the chi-squared or reduced chi-squared deviation. For maximization problems, simply follow the example code provided here, but replace the word MINIMIZE with MAXIMIZE. The EJS “Optimization with the Apache library” model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_Optimization_Apache.jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the plot and selecting "Open Ejs Model" from the pop-up menu item.

Sharing Video Experiments with Tracker Digital Libraries

Sun, 13 Jan 2013 13:19:14 EST

Sharing is an important component of learning. This talk will show how to access and create shared collections of videos and video experiments using the free Tracker video analysis and modeling tool. Tracker's Digital Library (DL) browser makes it easy to browse and open high-quality videos and experiments in online collections from ComPADRE, LivePhoto, physics departments and teacher workshops. And your students can now share their own experiments with their peers, instructors or the world by zipping and cataloging them for the DL browser using Tracker itself. Tracker is available for the Windows, Mac and Linux platforms from Cabrillo College at http://www.cabrillo.edu/~dbrown/tracker/ or from the ComPADRE Open Source Physics collection at http://www.compadre.org/OSP/. Partial funding was provided by NSF grant DUE-0442581.

EasyJavaSimulations meets Moodle, Arduino and (walks towards) the iPad

Sun, 13 Jan 2013 13:09:56 EST

This talk describes recent additions to Easy Java Simulations (EJS). EJS is a modeling and authoring tool that helps teachers and students create interactive simulations of physics processes. We show additions that help integrate EJS applets with on-line courses and laboratory activities. In particular, we show how to embed EJS generated applets into Moodle courses, including communication of the applet with the Moodle file repository and collaborative learning. We also show how EJS simulations can send and receive data to/from a number of laboratory equipment such as Arduino and Phidgets (and others to come). Finally, we show work in progress that reuses EJS architecture for tablets. This work will eventually help us quickly port existing EJS simulations at ComPADRE into tablets supporting Javascript and HTML5, such as the iPad and Android tablets.

Conference Presentation: Tracking the Coriolis Force

Sat, 12 Jan 2013 18:12:09 EST

This conference presentation describes a ready-to-use laboratory activity using Tracker for both video analysis and video modeling of the "fictional" Coriolis force. Students use video analysis to track the motion of a ball in a rotating reference frame. Then, they build a model of the motion using Tracker's modeling tools and compare the experiment to theory.

Double Pendulum With Elastic Rods Model

Sat, 12 Jan 2013 10:42:14 EST

The Double Pendulum With Elastic Rods Model shows two massless rods each with a different length. At the end of each rod is mass, m1; and m2. The user can vary the lengths of the rods and values of the masses within the simulation. A velocity dependent resistance can also be added by adjusting a drag variable in the simulation. In this simulation, the rods are modeled as very stiff springs. If the rod gets longer or shorter than its rest length, a very strong force drives it back to its rest length. The spring constant for each rod is 1.0E+7 N/m. In a sense, this is what happens in a real double pendulum. A real physical rod pulls or pushes back to its rest length under tension or compression. There is also a drag force that is linearly dependent on the velocity vector. The drag constant determines the strength of the drag force. Initially the drag is set to zero. The Double Pendulum With Elastic Rods Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Modeling the History of Astronomy: Ptolemy, Copernicus and Tycho

Fri, 11 Jan 2013 19:26:37 EST

This paper, submitted to Astronomy Education Review, describes a series of activities in which students investigate and use the models of planetary motion introduced by the Hellenistic astronomer Claudius Ptolemy in the 2nd Century, by the Polish astronomer Nicolaus Copernicus in the mid-16th Century, and by the Danish astronomer Tycho Brahe in the late16th Century. The activities involve the use of open source software to help students discover important observational facts, learn the necessary vocabulary, understand the fundamental properties of different theoretical models, and relate the theoretical models to observational data. Once they understand the observations and models, students complete a series of projects in which they observe a fictitious solar system with four planets orbiting in circles around a central star and construct both Ptolemaic and Copernican models for that system. The computer simulations, activity handouts, and project assignments discussed in the paper are all available in a ComPADRE shared file folder: http://www.compadre.org/OSP/filingcabinet/share.cfm?UID=12250&FID=33000&code=A816D1F75A.

Interesting Projects With Tracker Video Analysis

Thu, 10 Jan 2013 19:08:34 EST

Abstract: Video analysis makes any project more exciting and interesting. In this talk, I will go over my favorite examples of video analysis including (but not limited to): video analysis of Angry Birds, using video analysis to spot faked videos, determining the height of a space balloon, and examining the download progress bar on your computer.

Simple Fictitious Solar Systems

Fri, 04 Jan 2013 11:28:17 EST

The Simple Artificial Solar Systems package is a zip archive containing a set of thirty different Java programs (created using Easy Java Simulations) that simulate the night sky for fictitious solar systems. Each simulation illustrates the motion of a "Sun" and some "planets" relative to a fixed background of stars. Students can use these simulations to make qualitative and quantitative observations of the solar and planetary motions. These observations can then be used to construct models (Ptolemaic, Copernican, Tychonic, etc) for that solar system. Handouts for these projects are provided as supplementary documents. All of the solar systems were constructed such that all planets orbit in a common plane around the central "Sun". All orbits are circular, and thus the planets move uniformly on their orbits. This makes the geometry of the models much simpler. Included in the zip archive is a spreadsheet giving the required data for each system. Instructors who want their students to complete the projects individually should assign the 30 solar systems at random and privately document which solar system (by number) each student receives. Change the name of the solar system file from "ejs_YourSolarSystem01.jar" to "StudentNameSolarSystem.jar" (using the actual names of your students, of course) and then distribute the files to your students. That way your students will not know which system they have, so even if they get a copy of the solar system data file they will not be able to determine the data for their solar system without doing the necessary work (unless they want to rely on a 1 in 30 chance of guessing correctly).

Computational Neuroscience Package

Thu, 27 Dec 2012 10:13:33 EST

The Computational Neuroscience Launcher Package contains read-to-run computer models that describe the biophysics of the action potential. Contained within the launcher are nine models in four sections; each of the sections illustrates a different aspect of neural dynamics. Section one has models with variables corresponding to specific biological properties, section two models have analytically-determinable firing rates based on input, section three emphasizes phase-plane analysis, and section four shows the dynamics of neural networks. Each model represents just one approach to the still-developing field of neuroscience. The Computational Neuroscience Launcher Package was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify the simulations in this package if you have EJS installed by right-clicking within a running stimulation and selecting "Open Ejs Model" from the pop-up menu item.

Wilson-Cowan Delayed Neuron Network Model

Sat, 22 Dec 2012 09:13:14 EST

The Wilson-Cowan Delayed Neuron Network Model compares the Wilson-Cowan equations for network dynamics with a network of excitatory and inhibitory neurons. In this version of the Wilson-Cowan model, the differential equations have two different delays to represent the interaction between the excitatory and inhibitory populations of neurons. The neurons fire based on a weighted random number generator, and the activity of each population can be compared directly to the activity levels predicted by the Wilson-Cowan model. The Wilson-Cowan Delayed Neuron Network Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.