Surfacing

PVL MSc Student Elisabeth Smith had a bit of a split personality over the summer months, interning at MDA and directing her research back here at the lab with the help of Undergraduate Research Assistant Keagan Lee. Now that she has returned to the lab full time, she is working on writing up the results and finishing up her Thesis.

By Elisabeth Smith

After a summer full of exciting robot testing, customer demos and Excel Macro writing, it was time for me to leave behind my internship and return to the lab and classroom. Having an undergraduate assistant to run experiments over the summer was a great boon, as he was able to collect large amounts of data and come up with an improved method for mixing the particles into my system during the experiment. This greatly improved the data collected for the experiment.

As a brief recap, my research is to develop a method for the determination of the turbidity (that is, the extinction or blocking of light in a liquid due to the presence of particles) by processing images of a laser. The experiment is conducted by shining a laser into an aquarium full of water, taking pictures of said laser, then adding a fixed amount of particles to the system and taking more images, repeating this until the laser is barely visible with the camera. Previously, I was running into issues with the particles simply falling to the bottom of the aquarium instead of being well mixed, resulting in a non-homogenous system. My undergraduate assistant, Keagan, and I came up with a few possible methods to resolve this – such as improved circulation systems, or allowing more time between image series to let the particles better mix. Eventually Keagan came up with a glaringly simple and effective method: remove some water from the system with a beaker, add the particles into that beaker, then mix well and return it to the system. The system would homogenize far quicker than previously, and there were little to no issues with particles settling at the bottom of the aquarium.

 There was a brief learning curve getting back into running the experiment – Keagan had developed a new, sturdier rig for holding the camera and laser above the aquarium. Figuring out how to use this and the improved circulation system took some time, but it was a well thought-out set up, so picking it back up was not very difficult. My biggest challenge was having to switch the positions of two of the tubes that are at the corners of the aquarium, as they were in the wrong place, and I had already filled the aquarium with water. But, I learned a fun fact: you can apply duct tape underwater! Another fun fact: it becomes increasingly difficult to do so the longer your arm is submerged in ice-cold water. It seems as though York sources their water directly from the Arctic circle.

Once these small issues were addressed, I ran into another problem where I discovered my laser was incorrectly positioned in my aquarium. Due to this, I had to stop my experiment part way, pump out all the water and particles I had already added, and repeat it all over again with the laser properly positioned. I conducted this experiment by swapping in the three different lasers we were using for each addition of particles – so after I added particles, I would take images of each of the lasers before adding the next batch of particles. This is a very time efficient method, though it makes a single session quite long. 

I only have a few more experiments to run and analyze, and then I will be focusing my efforts on beginning to write my thesis. So far, the data I have collected and analyzed is very promising – there are clear relations between the amount of particles in the system and the visibility of the laser, and I will be fitting the resulting curves to an equation that will allow us to predict these curves. It also appears (pending further analysis!) that the wavelength (which accounts for the different colors of light) does not appear to make a significant difference in the extinction curves for these experiments – this is a very interesting and unexpected observation.  Very soon I will have more interesting observations to share!