Tuesday, February 26, 2013

Using Energy2D to simulate Trombe walls

A Trombe wall is a sun-facing wall separated from the outdoors by glass and an air space. It consists a solar absorber (such as a dark surface) and two vents for air in the house to circulate through the space and carry the solar heat to warm the house up. In a way, a Trombe wall is like a machine that uses air as a convey belt of thermal energy harvested from the sun. Trombe walls are very simple and easy to make and are sometimes used in passive solar green buildings.

Hiding sophisticated power of computational fluid dynamics behind a simple graphical user interface, our Energy2D software can easily simulate how a Trombe wall works. The two images in this blog post show screenshots of a Trombe wall simulation and its closeup version. You can play the simulation on this page and download the models there. If you open the models using Energy2D, you should be able to see how easy it is to tweak the models and create realistic heat flow simulations.

Solar chimneys operate based on similar principles. Energy2D should be able to simulate solar chimneys as well. Perhaps this would be a good challenge to you. (I will post a solar chimney simulation later if I figure out how to do it.)

Tuesday, February 12, 2013

A mixed-reality gas lab

In his Critique of Pure Reason, the Enlightenment philosopher Immanuel Kant asserted that “conception without perception is empty, perception without conception is blind. The understanding can intuit nothing, the senses can think nothing. Only through their unison can knowledge arise.” More than 200 years later, his wisdom is still enlightening our NSF-funded Mixed-Reality Labs project.

Mixed reality (more commonly known as augmented reality) refers to the blending of real and virtual worlds to create new environments where physical and digital objects co-exist and interact in real time to provide user experiences that are impossible in only real or virtual world. Mixed reality provides a perfect technology to promote the unison of perception and conception. Perception happens in the real world, whereas conception can be enhanced by the virtual world. Knitting the real and virtual worlds together, we can build a pathway that leads perceptual experiences to conceptual development.

We have developed and perfected a prototype of mixed reality for teaching the Kinetic Molecular Theory and the gas laws using our Frame technology. This Gas Frame uses three different types of sensors to translate user inputs into changes of variables in a molecular simulation on the computer: A temperature sensor is used to detect thermal changes in the real world and then change the temperature of the gas molecules in the virtual world; a gas pressure sensor is used to detect gas compression or decompression in the real world and then change the density of the gas molecules in the virtual world; a force sensor is used to detect force changes in the real world and then change the force on a piston in the virtual world. Because of this underlying linkage with the real world through the sensors, the simulation appears to be "smart" enough to detect user actions and react in meaningful ways accordingly.

Each sensor is attached to a physical object installed along the edge of the computer screen (see the illustration above). The temperature sensor is attached to a thermal contact area made of highly conductive material, the gas pressure sensor is attached to a syringe, and the force sensor is attached to a spring that provides some kind of force feedback. These three physical objects provide the real-world contextualization of the interactions. In this way, the Gas Frame not only produces an illusion as if students could directly manipulate tiny gas molecules, but also creates a natural association between microscopic concepts and macroscopic perception. Uniting the actions of students in the real world and the reactions of the molecules in the virtual world, the Gas Frame provides an unprecedented way of learning a set of important concepts in physical science.

Pilot tests of the Gas Frame will begin at Concord-Carlisle High School this week and, collaborating with our project partners Drs. Jennie Chiu and Jie Chao at the University of Virginia, unfold at several middle schools in Virginia shortly. Through the planned sequence of studies, we hope to understand the cognitive aspects of mixed reality, especially on whether perceptual changes can lead to conceptual changes in this particular kind of setup.

Acknowledgements: My colleague Ed Hazzard made a beautiful wood prototype of the Frame (in which we can hide the messy wires and sensor parts). The current version of the Gas Frame uses Vernier's sensors and a Java API to their sensors developed primarily by Scott Cytacki. This work is made possible by the National Science Foundation.

Saturday, February 2, 2013

A petition for Java to Oracle from more than 15,000 people

Java is a programming language used by millions of developers and a software platform used by hundreds of millions of users. It has been one of the top three computer languages since it was born. More recently, it has become the sole language for creating Android apps and its adoption is exploding in mobile computing as the Android market grows: As of October 2012, there have been over 700,000 apps in the Android Market, rivaling (and expected to surpass) the number of apps in the Apple Store (see a Financial Times report in December 2012).

Java has become a community asset, not a tool for making money to pay for someone's islands and yachts. Unfortunately, its original creator, Sun Microsystems, has gone out of business. Its current owner, Oracle Corporation, decided that it can make a few pennies from each user by turning the Java installer into a piece of foistware that gives users unwanted software such as the Ask Toolbar. This action effectively jeopardizes an excellent computer technology like Java by lowering it to the same level of notorious adware that nobody wants.

My colleague Saeid Nourian has started a change.org petition to ask Oracle to stop this bundling. In about a week, more than 10,000 people from all over the world have signed the petition. The goal of the petition, however, is to collect 250,000 signatures.