Arduino's are cheap, infinitely useful microcontrollers. Log and react to temperatures, humidity, sound, movement, light, air pollution and on and on and on. Unfortunately, for continuous data collection you either need to write data to an SD card (not the greatest solution because eventually you'll need a physical connection to get the data), have a dedicated PC (obviously expensive although with a Raspberry Pi it's an option) or use a network connectivity shield.
Instead of replacing the batteries in my garage door opener, I decided to rig up a system that would allow me (and my wife) to open our garage door from our cell phones. This made sense to me instead of replacing the batteries, and my wife eventually came around to the idea as well.
OpenFOAM is an open source C++ library for running CFD simulations using the finite volume method. It's hard to install and even harder to use, but at least we can make the installation easier!
If you use a version of Mac OS X (probably >= 10.6), all you need to do is download a pre-compiled image of OpenFOAM. They aren't too easy to come by, so I've decided to make the one I use available for everybody's enjoyment. I've also compiled swak4foam with it which is an added bonus.
Ever since I needed a simple thermocouple data logger at work and found that they cost at least $600, it's been a little bit of a hobby of mine to get small, cheap computers to do useful things. After all, they used the equivalent of about 3 Commodore 64s to fly to the moon, and these things have about the same computing power as a modern day calculator, so why is it so hard/expensive to set up something with similar computing power to simply record data?
This is one of the best explanations that I've seen on the process of getting a PhD:
To survive this period, you have to be willing to fail from the moment you wake to the moment your head hits the pillow. You must be willing to fail for days on end, for months on end and maybe even for years on end. The skill you accrete during this trauma is the ability to imagine plausible solutions, and to estimate the likelihood that an approach will work.
Lately I found myself needing to solve the 1D spherical diffusion equation using the Python programming language. To make sure that I can remember how to do this in the far future (because I will forget), this post goes over a few examples of how it can be done.
Diffusion in a sphere happens all the time, mostly when chemical reactions are involved and a reactant or a product has to make its way to or from the reaction site. In my case, the application is lithium-ion batteries where lithium diffuses into and out-of a particle of the active material.
For anybody who needs to connect to the Unversity of Ottawa or Queen's University proxy servers to read journal articles etc.., here's the "easy button" way to do it. (but you still need your user id/password)
To easily connect to the University of Ottawa proxy so that you can read journal articles, drag the following link to your bookmarks bar:
PVDF is polymer and acts as a binder that is mixed with the lithium storing active material and electron conducting carbon so that the mixture maintains good contact with all the components in a lithium-ion battery. Because of the the earthquake/tsunami in Japan, a major producer of PVDF (Kureha Corp with ~70% of production) is struggling and this has already begun to affect the battery supply for some Apple products.
This is a rough calculation of the amount of PVDF binder used in a lithium-ion "laptop" battery (ie. 18650 cell).