Easy-B
I finally seem to have time to catch up on the projects I've been collecting for years. I would always pick things up for 'when I have the time' and now I no longer have an excuse. A few years ago I found a collection of rubber band powered micro planes at a thrift store and I snatched up two models.
I've been covetous of these model airplanes ever since I saw a video of one flying lazy circles in an auditorium at a couple miles per hour. Here's an example:
I opened the boxes and saw the instructions were in Japanese and English and all the pieces were there, the strips of balsa wood, the gossamer plastic and the rubber band. The planes use a few pieces of piano wire for the propeller shaft and tail hook and two of the tiniest teflon bearings I've ever seen. After this quick inspection the boxes went on a shelf. I pulled them out a few weeks ago.
I decided to construct the larger plane first, reasoning that working with larger pieces of wood might be easier (I don't know if this is true) and followed the single page of instructions. The instructions were sparse but got the message across if you read everything carefully.
There were a couple errors in the instructions and I took the drawing illustrating how to stretch the plastic film over the wing too literally. From the picture it seemed like I would have plenty of plastic to cover both the top and bottom of both the wing and the stabilizers but when I measured the remaining plastic after gluing the first piece, I discovered I was already a couple millimeters too short to cover the bottom of the primary wing. I'm not sure how much of a difference it makes to the aerodynamics of the ultra-light wing but it was irritating. I could have partially covered the bottom of the primary wing but I thought it might be better to leave it entirely uncovered.
Handling the plastic was a nightmare. It was so thin and light I could barely see it and I couldn't feel it between my fingers. It would also static cling to everything. Despite it's thinness when i tried to cut the excess with a hobby knife it just snagged and tore. I had to resort to using scissors to cut the remainder and it was very difficult to hold the wing and the scissors perfectly parallel, close together, and still as I closed the jaws on something I couldn't feel and barely see. The result was a horrible jagged mess which I trimmed as best I could before gluing down the edges.
Throughout the whole project it felt like I was one distracted moment away from smashing the whole thing to bits. The resulting plane is so light any small pressure causes the wood to bend alarmingly. While taking these pictures some fuzz on my sleeve caught on the tail and I nearly broke the whole wing in half before I realized. I'm still not sure if it will survive until I can find a large enough indoor space to fly it properly.
Building the next one has moved to the bottom of my queue of projects but I'm still happy with the result.
Radiation units
I've been confused about radiation units forever and finally decided to settle the question. I'm sharing this so you can become just as confused as I was and then, hopefully, enlightened.
We describe radiation with rads, roentgens, rutherfords, sieverts, rems, curies, becquerels, and grays - why so many units?. Most of these are were abandoned/deprecated as we learned more about what radiation is and how it works. Last years fashion of roentgens, rems, rutherfords, and rads are old news girl, the new hotness this season are becquerels, grays, and sieverts.
These units are used to measure both the energy and rate of ionizing radiation (radiation strong enough to knock electrons off of atoms) and to the immediate and eventual harm this causes to human tissue. To measure the amount of radioactive decay in a substance you should use Becquerels but it took us a while to get there:
- Curies (Ci) (1910) - defined to measure the quantity of radium emanating in equilibrium with 1 gram of radium.
- Roentgen (R) (1928) - Used to describe the electric charge freed in a volume of air.
- Rutherfords (Rd) (1946) - defined as the activity of a quantity of radioactive material is which one million nuculei decay per second.
- Becquerels (Bq) (1975) - defined as 1 nuclear decay per second.
There are 36996 rutherfords and 37 billion becquerels in a curie.
To measure the probability of developing a fatal cancer after exposure to radiation use sieverts. They replaced roentgens which were established in 1976. These units are often described as stochastic units because they represent a probablity you will get sick. Again we had a different unit for a while:
- Roentgen equivalent man (rem) (1976)
- Sievert (Sv) (19??)
One sievert represents a 5.5% chance of developing a fatal cancer. My little radiation meter measures everything in sieverts.
To calculate the odds of getting sick from radiation exposure you need to quantify the amount absorbed by your tissue. This is currently measured in grays:
- Rad (rad) (1953) - the dose causing 100 ergs of energy to be absorbed in one gram
- Gray - the absorption of one joule of radiation energy per kilogram
There are 100 gray in one rad.
Grays are also used as units describing kerma - the sum of the initial kinetic energy of all charged particles liberated by ionizing radiation.
There's a bunch of terms used to describe how well radiation is absorbed by tissue including:
- Absorbed dose (measured in grays) - the energy absorbed in matter
- Equivalent dose (measured in sieverts) - the stochastic health effect of radiation taking into consideration how much a particular biological tissue absorbs the radiation
- Effective dose (measured in sieverts) - same as equivalent dose but the sum total of all biological tissues
- Committed dose - The risk if an effective dose was applied uniformly to the whole body(?)
I'm still unclear about the difference between the terms for different doses and it seems orthagonal to the intent of this post so I'm dropping it.
One interesting note I came across while wading through the wikipedia.
The typical human body contains roughly 0.1 μCi (14 mg) of naturally occurring potassium-40. A human body containing 16 kg (35 lb) of carbon would also have about 24 nanograms or 0.1 μCi of carbon-14. Together, these would result in a total of approximately 0.2 μCi or 7400 decays per second inside the person's body (mostly from beta decay but some from gamma decay).
British Airways Flight 5390
His feet got caught in the flight controls, jamming the stick forward, turning off the autopilot, and forcing the plane into a dive and the sudden decompression pulled the cockpit door off it's hinges and onto the throttle controls so the copilot had no way of controlling the plane. Also the noise of the 550mph wind made it impossible to radio for help.
A flight attendant saw the captain hanging out the window and grabbed his legs. Eventually they got the debris off the controls and untangled his legs and the copilot brought the plane down to 12000 feet where they could breath but he cautioned the attendant to continue to hold on to the captain's legs because he didn't want him to release the body and have to fly into an engine.
At the lower altitude captains body slide down over the side and his face was smacking into the side windows leaving a smear of blood over everything.
The attendant holding his legs eventually had to switch places with another because all the skin on his arm was burned off from the cold and high wind shear. They flew another 30 minutes before the copilot could land the plane.
When they reached the ground they discovered the captain was somehow still alive.
You can skip through a terrible re-enacted documentary here (or here). Some of these pictures are re-created and some are real.
Beyond the Infinite Two Minutes
I can recommend this Japanese movie by Junta Yamaguchi. It's about a man who lives above a small cafe and discovers a computer monitor in his room and the monitor in the cafe downstairs are connected like a video call except the one upstairs shows events from 2 minutes in the future and the one downstairs shows 2 minutes in the past. He spends some time running up and down the stairs asking and answering his own questions and then his friends come over and one has the bright idea to point the monitors at each other. This generates an infinite number of images extending farther into the future and hijinks ensue.
I dislike most time travel movies but unlike every other dystopic plot this one keeps it lighthearted and didn't leave me feeling irritated.
Also the entire movie is filmed in a single shot.
dotfiles
I posted about my version controlled dotfiles setup before but the scripts I used have evolved and I was going to rebuild the repo to host it on this site anyway. The main difference is I now use a python script instead of bash to pull dotfiles into the repository. The code also has a command line argument that could be used to re-configure a system with the given dotfiles but I wouldn't recommend using it because it's under tested. When setting up a new system I generally like to do things manually so I can see exactly what has changed.
The infrequently updated blog.