So, I decided to take pictures of part of someone else's life at MIT: 6.131 Lab.

6.131 Lab, or Power Electronics is one of those classes that reminds students why they came to MIT in the first place. At this time of year in many other classes, students are cramming as much into their heads as possible for midterms. At this time of the year in 6.131, students have just finished working late nights to create a system that lets them drive a go-cart. Now they're working on controlling fluorescent lights.

Breadboard by Noah S. '10

Why, you might ask, does a fluorescent light need to be controlled? You have likely seen a demonstration of how easy it is to wire up an incandescent bulb; you basically just connect it to a battery. In these more traditional bulbs, the filament is a resistive unit, so the more voltage you put across it, the more current will flow through, and the brighter it will shine. The filament is made out of metal (these days, usually Tungsten), so even though there is some resistance there, it is not very high.

In a fluorescent light, instead of a wire filament, there is a tube filled with low-pressure mercury vapor. When the light is turned off, this gas provides a very high resistance. Even though mercury is metal just like Tungsten is, it's spread out as a gas. For electric current to flow through the bulb, it needs to be able to jump from one atom of metal to the next, all the way to the end of the bulb.

Signal Generator in Power Electronics Lab at MIT

So that's the first difference: to get the light going in the first place, you need to provide a HUGE voltage. So why aren't fluorescent bulbs just like incandescents with bigger batteries? Well, as soon as you have started the flow of electrons through the tube, the vapor ionizes! This means that its resistance drops very suddenly. If you continued to use the same amount of voltage you used to start the lamp to run it, it would explode!

Noah S. '10 -- Hard at work. See the giant green donut-thing with red wire? That's a huge inductor.

And then the final kicker: The V-I characteristics, or relationships between voltage and current, for the lamp, are really weird. Even if you put a high amount of voltage in to start the lamp, then bring it down to the perfect level, it is a very fragile system. If some tiny little variable changes, like the temperature, it could become unstable, the current could run away, and it would still break! *For 6.131 Professor Leeb's explanation of why this happens, see note at the end.

The answer to all of our problems!

So, the answer, clearly, is to use the circuity represented above. All clear? Just in case it's not, let's explain...

So, the goal is to provide a big initial voltage, then turn it down and set up some sort of self-policing system.
Most of the things in the picture above are just made to generate a huge square wave (40 Volts). There's a part where you can adjust the Duty Cycle, or what part of the time the square wave is high or low. The other really important parts are right next to the part labeled 'Fluorescent Lamp.' They are 'L' and 'C.' The huge square wave comes in through L (an inductor) and then chooses whether to go through the C (capacitor) or lamp. If the lamp is off, it goes through the C, since there's so much resistance in the lamp. If the lamp is on, it goes through the lamp and mostly avoids the capacitor.

When the lamp is off, the inductor and capacitor form a resonant circuit. If the frequency of the square wave going in is right, the voltage in the capacitor voltage builds up until it is high enough that the lamp starts. Once the lamp starts, the inductor helps to keep the amount of current in the lamp steady.

Other cool things about the lab are winding the big inductors yourself, doing all your own soldering, and working with chips that are getting hot enough that they need huge heat sinks (the big black metal things in the photo below.) Let me know if you have any questions about 6.131 or lab classes in general. And thanks to Noah S. '10 for showing me his circuitry and giving me a refresher course on building a lamp ballast :)

Totem board, Noah S. '10

*I'm going to quote Professor Leeb himself here, because he explains it so clearly.

In the lit fluorescent lamp, "an increase in terminal voltage corresponds to a decrease in terminal current, and vice-versa. This happens because, roughly, as the current decreases in the tube, the number of charged carriers in the tube also decreases, decreasing the conductivity of the plasma column in the tube. So a higher voltage is needed to maintain the lower current! Increasing the current on the other hand, increases the conductivity of the plasma. A lower voltage is required in this case to sustain the higher current.

With these properties, "imagine a slight, inevitable disturbance that momentarily increases the current in the bulb. This disturbance could be a slight change in exterior temperature, for example. The voltage across the tube remains fixed, but now we are "off" the equilibrium curve, with a larger number of charge carriers in the tube compared to before the disturbance. Off the equilibrium curve, this voltage will push yet more current into the bulb, further increasing the conductivity. If the voltage remains unchanged, the bulb enters a "runaway" condition, where the current increases until something breaks."

So far, I've met a *ton* of companies. I can tell, thanks to previous internships and projects, that there are some that I am not a match for, some which would be alright, and only one (so far) that I would love. I think my interview with them went well, but they're also incredibly selective.

I'm beginning to be a little more polished in interviews, now that I've experienced enough of them to have an idea of what's coming. Some companies will rephrase their questions, but in the end they want to know the same things: who you are as a person, and how that will fit in with the company. (It's actually pretty similar to college admissions, once you get past the surface differences.) One thing that has been paying off for me is the time I spent in UPOP (MIT's Undergraduate Practice Opportunities Program) two years ago. They do an outstanding job teaching MIT students how to interact effectively with companies. My title comes from a motivating example they gave us at the beginning of their program. A company representative at a career fair came to MIT and reported that the students lacked social graces. A student had actually come up to them and asked, "Do you have jobs? Can I have one?"

Speaking of uncomfortable situations: I was waiting for an interview lately, just before 9:00 am. (That's not the uncomfortable part; I like mornings.) There were over a dozen other students waiting with me to interview with various companies. A recruiter stuck her head into our waiting room and called a name. There was no response. "Strike one!" she announced, and left. Ouch. You know, I looked at the clock when she came in. It was 8:59 and 30 seconds. So in my book, the student was not yet late. And if they had been on an MIT schedule, with classes and meetings tending to start at 5 minutes after the hour, the student would still have over 5 minutes to arrive. I guess my high school band teacher had it right after all, "If you're early, you're on time; if you're on time you're late; if you're late you're left. "

As high school seniors work on their applications to MIT, they should make sure to submit materials in a timely fashion. You should also take the appropriate tests and let MIT know how you scored. But the main focus of your attention should be on showing the Admissions Office who you are as a person. I get emails regularly from applicants who are nervous about the other aspects. They want to know my SAT score and my fr iends' SAT scores and my mom's SAT score. But that's not the point! Don't let yourself get too wrapped up in having the right numbers. Just in case anyone has missed it thus far, I'll bold it. Tell MIT what motivates and excites you. They want to admit real people, not academic robots MIT wants to admit people who, besides being intelligent, will contribute to our amazing community. It's one of those things I like about MIT.

Good luck, applicants! And wish me luck, as another type of applicant!

I graduated in June, but I'm not gone yet! Due to a great program in Course 6 (Electrical Engineering and Computer Science) at MIT, I am able to stay on to complete a Master's Degree. The M.Eng program in Course 6 is something students can apply for in their junior year. They then start to integrate graduate-level courses with their regular courseload. This puts them in position to finish all of the requirements for the Master's degree as well as the Bachelor's in only 5 years. (If the two degrees were completed sequentially, they would generally take a total of 6 years.) Besides the time-savings, I am excited about this program because it offers a way to cap off a lot of theoretical learning with one big project that requires actual application of the ideas. I also happen to have absolutely *amazing* advisers. We're working understanding how humans produce speech -- more on that in a later post.

Number 2: Learning to Teach

I've joined the Scheller Teacher Education Program (STEP) this fall. It's basically a crash-course series of classes on education in theory and practice. The theory side covers issues such as, 'Should we be developing students' creative thinking skills or giving them practical lessons and vocational training?' The practice side teaches us the nitty gritty of discipline, lesson planning, and how to get students' attention. STEP also includes classroom observation, and eventually teaching in nearby schools!

Number 3: Randomites

Though I'm living in an apartment now, I still take time to go back to Random Hall. One must-experience event at Random is their fall rush, designed to introduce freshmen to their unique culture. I attended a great new event this year, led by ch3cooh '11. There were three parts to the event: building MIT out of candy, rolling it up into katamari, and eating it! Here are some pictures of the process shot by Zev '08, M.Eng '09:

Step 1: Building MIT out of candy.
The big peanutbuttery gob with the Hershey's kisses on it is labeled 'Stata'. Nearby are graham cracker representations of the two parallel buildings of East Campus and the Green building (the tallest building in Cambridge!) You can see the blue jello version of the Charles River flowing through the center. I'm not sure whose idea the snow-capped mountains or volcano were... I haven't seen them around campus.

Step 2: Rolling it up into katamari.
We started with a small glob of chocolate and marshmallow mixture, and rolled our katamari around the board while listening to remixes of the song (the song can be heard on this Youtube video.

Step 3: Eating it!
This was harder for some people than for others...

My family came into town on Wednesday for graduation. Classes were over, and the most stressful thing I had to deal with was cleaning my room. It was pretty relaxing. I didn't even have to rush around Boston saying goodbye to people and places that I've known, because I'm staying for another year to finish my Master's degree (through the MEng/VI-A programs).

Since I am going to around for another year, I saw the graduation ceremony as more of a check-point than a finish line. I also think that attending MIT has had a side-effect of keeping me from getting too excited about ceremonies in general. After four years of urgent deadlines (Test! Lab of Doom! 4 PSETS! 2 Tests!), I seem to have adjusted some internal excit-o-meter. So in the days leading up to graduation I was glad, but not super-excited.

The big day came. Every senior gets four tickets to give to friends or family for graduation, and I was using my four for my family. This meant that my boyfriend (who is class of '08) couldn't come see me graduate in person. I did the next best thing to bringing him, and brought Roary instead.

Photo Credit: Tiffany Tseng

Roary is the stuffed tiger that my boyfriend gave me on our first Valentine's Day together. I attached him to my mortarboard using a strip of cloth and a couple of alligator clips. I used the alligator clips because they were the first thing to come to hand, but after I was finished I realized that it was also a nice nod to Course 6. Tiffany '09 took the picture above for me. The first picture in this post and the rest to follow are courtesy of the Tech photographers (who have more similar pics here.)

All the graduates-to-be congregated in the Johnson Athletic Center and sorted out who they would walk next to. Then we processed to Killian Court where our friends and families waited for us.

Photo Credit: David Templeton

Once we were actually all together walking towards Killian, it started to sink in that we were really graduating and I started getting excited about it. As we passed some of the buildings, I saw a sign hanging from a window and half a dozen people leaning out and waving at us. The sign said, "Congratulations Course 1 Grads!" and the people waving seemed to be their professors.

Photo Credit: William Yee

The ceremony itself was nice. There were a lot of people graduating though, and I eventually found myself looking around for other decorated mortarboards. I didn't have my camera on me, but I've pulled some pictures from The Tech of interesting ones. I think the aero-astro majors had the highest percentage of grads with decorated caps.

Photo Credit: William Yee

Some people wore stoles with the colors of their country or region.

Photo Credit: William Yee

A friend of mine actually substituted the cap out entirely for a black cowboy hat (he attached the tassel to the brim.)
I'm not sure about the significance of this next one...

Photo Credit: Eric Schmiedl

Brains...

Photo Credit: David Templeton

And a crab.

Photo Credit: William Yee

We heard speeches by the Governor of Massachusetts and MIT's President. After the speech by our Class President, we got to turn our "Brass Rats" (class rings) in the opposite direction. Before graduating, we wear the rings so that we can see an image of the Boston skyline when we look at them. This is supposed to remind us that we'll get through MIT eventually and go out into the world. Once we've graduated, we wear the rings so that we see an image of the MIT skyline. This is so that we can look back on the good times we had at MIT.

Photo Credit: Ricardo Ramirez

Part way through the ceremony, some people broke out half a dozen beach balls and started them bouncing around the student section. The reappeared later, presumably when people were bored.

Photo Credit: William Yee

Eventually it was my turn to walk. I was slightly worried about walking with the tiger on my head (since it had a high center of mass) but all went well. President Hockfield even complimented me on it as she shook my hand!

After the ceremony, I met up with my family and we went to a couple of receptions for graduating students, complete with delicious food.

And that's it. I'm graduated. Weird.

My main activities for the past two weeks have been working during the day, working at night, and squeezing in doctor’s appointments wherever they fit. Helpful tip: don’t get sick while at MIT.

So when my friend Roxana '09 suggested biking to see the Battle of Lexington, I was THRILLED!

We woke at 3:30 on Patriot's Day Morning and rode off into a quiet, misty land. Massachusetts Avenue, so often clogged with cars, was transformed. It belonged to just we cyclists, and we soared over the pavement, thrilled to use muscles which had begun to rust in place...

We arrived at Lexington just before 6 am, and a huge crowd had already gathered. There were three tiers of people: those standing in front, those perching on ladders/ladder constructions, and those in the trees.

Niki '09 and I grabbed a bench. She stood on the bench and I stood on the bench's back, using her shoulder to steady myself. We traded off for the better vantage point a couple of times.

The Redcoats and the Patriots met and exchanged harsh words. Both sides postured a bit. A shot was fired, and battle broke out.

When it was all over, women and children tended the fallen.

The British marched off, to loud boos from the present-day audience.

And then we fraternized with the enemy.

This guy turned out to be an MIT alum. He also told us about the first time he was part of the reenactment, in 2001. He had never watched the reenactment before being in it, and didn't know the guys planing patriots. So, he was really unsure how the battle would unfold, if he could trust them not to really stab him, etc. He also told us an amusing story about how he was scared out of course 12 and into course 22.

We grabbed some hot sustenance from a Dunkin' Donuts and biked back to Boston as the sun rose.

And we all lived happily ever after (at least, until the next set of deadlines arrives).

This break I'm going to get to know my new camera better! I've started using it already around Cambridge. Can you identify all the locations? (Eternal Fame and Glory to whoever sends me the complete list first.)

I'm working on designing something that makes Interlocking Stabilized Soil Bricks. Basically, it's a machine that applies some sort of pressure to some mixture of dirt and concrete. It has to be able to make a strong brick using pressure instead of heat. Also, the bricks should have a shape that lets them interlock, so that they don't need mortar to hold together.

And of course the machine should be fast and cheap and easy to use and produce strong, perfect bricks.

My group is throwing around all sorts of ideas to apply pressure right now; screws, levers, pulleys, impacts, vibration, the soul-crushing weight of all the work at MIT ... But what we could use are facts.

Do you know how Zambian/Malawian/Ghanaian dirt compares to dirt commonly found in, say... Massachusetts? Or what sort of building materials are just laying around in these countries? What sort of skills people have? Have you used one of the existing machines, like in the picture? How was it? What sort of buildings do local people usually build (round? square? tall?)?

Did you play with mud as a child? I'll take any leads...

I included this picture in a previous blog. I was tired of working, and it reminded me of the good times at MIT. Well, in Honduras, but related to MIT.

Going to Honduras was a sort of Grand Finale to a class I took in the Fall of 2007 about Development. It's also known as D-Lab I. Right now, I have the chance to take D-Lab II. This class focuses less on the big picture of Development and more on Design; every group of four students chooses one project and follow it through over the course of a semester.

I'm not sure if I have the time for D-Lab this semester or not... I might take it even if I don't, because these projects are pretty awesome. We have 15 to choose from, but here are my favorite 6:

1) Turning Plastic Bags into Rope and Netting -- The world uses a trillion plastic bags every year, and many of them end of dotting the countrysides. There are so many hanging around in South Africa that people joke that they are the National Flower. What people could use more of is netting, to catch fish with and to put over beds to keep malaria-carrying mosquitoes off. Can we use plastic bags to do this?

2) A Bicycle Trailer -- A previous D-Lab student created a bicycle ambulance for use in rural areas. Can we modify this design so that the ambulances can also be used to carry vegetables to market or bricks to a building site?

3) Bamboo Matchsticks -- Bamboo plants grow quickly and their roots stabilize the soil. If we created the right machine, people in rural villages could mass-produce matchsticks. It would provide income for them, and also prevent the deforestation that currently occurs because of matchstick-making.

4) Interlocking Stabilized Soil Block Maker -- Making bricks takes a lot of heat energy, which usually means burning a lot of fossil fuels. We can trade pressure for heat. We can also change the shape of bricks; if they are made to interlock, we won't need mortar. This could revolutionize construction in the developing world.

5) Liquid Chlorine Dispenser -- Deliver the correct amount of chlorine to personal containers as people get their water from a community source. This purifies the water right before the people drink it, so you don't have to worry about re-contamination in transit. There's already a device that does this, but it's much too expensive.

6) Charcoal Briquette Press -- Take bits of charcoal (created from sugar cane or corn cobs or any number of things by a process D-Lab already loves using). Form them into lots of little square briquettes. Make it fast and easy.

Of course, these are just my favorites... the other 9 are pretty awesome as well. Some of them involve using cell phones as a tool, or Braille, or solar heating. This is the definitely the class to take if you want to invent something people really want.

So, what do you think? Should I try to squeeze the class into my schedule? If I do, what project should I work on? Any suggestions for cool projects for future D-Lab classes?

My Good Sir,

Have you ever ridden on an airplane? During the Holiday Season? Without your Super-Sparkly-Platinum member's benefits? Incognito, so that your employees don't know that they need to behave around you? Might I make a small suggestion? DO. Then go back to your interviews and repeat, "We need to take excellent care of our customer," and MEAN it this time.

I could tell you a story about a traveler who arrived at the wrong airport after a trip four times longer than the one purchased. Or they could. To paraphrase: "We'll arrive in time for your delayed connection." "Though you sprinted through the airport and made the connection, we decided to give your seat away... Oops, I miscounted, you could have been on that one." "You definitely have a seat on the next flight." "The next flight has been canceled. Since before you spoke with the last agent. There is no hope for you." "Oh, you can standby on another airline. Let me transfer that ticket." "What? They say we haven't transferred the ticket? Well, that's because we aren't allowed to. No, it's not possible. I don't care if they say it needs to be done. I don't care if the other employee told you she did it. You have issues with communication." "Huh. Yeah, sometimes transferring tickets gets messed up when they do it at the airport. Let me put you on a flight to another city." "We're leaving at 8. 9. 9:40. 10. 10:30. 10:50. 11:30. We'll get you out sometime, we swear. Unless the pilots' hours roll over before they get here. Then they need to rest."

Have you noticed that this ALWAYS happens? At least seen it in the movies? Random guess: This will happen to masses of people next year, too.

I'm sick of airlines who tell me I am not communicating correctly when they won't share gate information with the the next terminal. When each employee I speak to contradicts the previous one.

I'm sick of being offered a limited-offer discounted hotel room when this whole mess is your fault. (And don't blame the weather. You chose your hub. An idiot could have told you it has lousy weather EVERY year exactly when everyone wants to get home.)

I'm sick of limited blanket and cot supplies and nearly nonexistent power outlets.

I'm walking home next year.

Yours sincerely,

Kimberly F. Dietz

Except it was originally going to be longer and angrier. And delivered by a hit man. A hit man who smelling like rotting fish, adding that extra epsilon of unpleasantness to the situation. But of course I calmed down eventually, and I do realize the futility of this approach. So I started trying to think constructively.

Ideas For Improved Holiday Travel On Airlines

• I was delayed for several hours because the crew assigned to my plane was stranded elsewhere, and there was no one to fly it, though it sat at the gate gathering ice. I see that your retired pilots' club has over 900 dues-paying members. While many of them have surely let their pilots' licenses lapse, I can't believe they all have, if only because some must have retired recently. Hire them on again for the holidays! Pay them handsomely to be "on call" at busy airports.
  
• Or just teach your customers to fly while they're sitting there bored for hours on end, year after year. (Kidding.)
  
• You know how you have those little oxygen masks that pop down from the ceiling in case of an emergency? And have maybe been used once? Something less life-threatening but faaaar more common than losing cabin pressure is having a flight delayed indefinitely. Even in the rare event that the airline is giving out blankets, many people don't dare go seek them out, lest they miss their flight if/when it comes. I suggest adapting the existing technology to this situation. Imagine the commercial featuring the announcement!
  

  It begins with a shot of passengers sitting at the gate. "In the event of a change in boarding time, the comfort compartment above your seat will open automatically." Ceiling panels slide back and blankets, pillows, snacks and games pop down on the ends of bungee cords, bouncing around as they dangle just above the passengers' heads. "Assist others in need of assistance before getting too comfortable yourself." Cut to a shot of a parent carefully helping a kid open the plastic wrap on their new coloring book, then grabbing a pillow, blanket, and novel from the dangling cords, snuggling into their seat, and reading. "Name of Airline: Handling Every Emergency."

  
  
• Keep your Arrival and Departure monitors up to date, for obvious reasons.
  
• Make the process by which you update those monitors more transparent. Today a fellow passenger said to me, "You know, I've always wondered about what goes on in the little room [where someone must be predicting when the flight might leave]."
  
• Use all those idle people waiting to board planes. For instance: let them update a (probably separate) board with information they know about delays and their reasons, weather in various areas of the country, etc. Give them a small percentage off of their next flight ticket if they contribute, with a promised punishment if the information they contribute turns out to be incorrect. I'd enroll in this program immediately.
  
• Organize the inter-airline tug-of-war competition between terminals. Or a poetry jam. Or a chess tournament.
  
• Make SURE your employees are competent. Don't tolerate employees who goof off with each other while long lines wait, who give incorrect information, who don't know how to transfer tickets.
  
• Open lines of communication with other airlines. Arrange to share gate information. Arrange to trade off, covering for each other in areas where one has stronger coverage than the other. Remember Miracle on 34th Street ? Everyone loved Macy's after they started keeping track of their competitors' toys too and sending them to whatever store had what the customer really wanted. Emulate them.
  
• ...
  

Of course, this sort of suggestion list is also quite likely to go unnoticed. Then, I had one final idea.

So, last week a Facebook friend asked me to up-rate his suggestion on Change.org's Ideas For Change In America Site. The idea is that every throws in their ideas, then they consider each other's and vote on them, and the top 10 are given to the Obama team on Inauguration Day.

We could do something like this. If everyone else who had a bad travel experience puts in their ideas and also comments on which others they think are good, I'll type up a few of them and forward them to airline CEOs (or whoever the correct contact person is.) And they likely still won't listen. But here's to trying with a spirit of Audacious Hope.

p.s. To those of you still out there: Good Luck!!

And eventually looking much more reasonable, like this:

I stress eventually .

I think that if anyone understands how I feel about being stuck in an Athena cluster generating graphs all night, it is this disgruntled bull. Although the 22 other students in the cluster with me may have some idea as well.

...On an almost completely unrelated note, I recently learned a great mnemonic for the stock market types: Bulls attack by thrusting their horns up in the air and bears attack by swiping down. So a bull market is one in which the market is moving up and a bear market is one in which it's moving down!

But back to the bull in the picture. He isn't just any bull; he's from Honduras. And so he brings back some amazing memories of the trip I got to take last January with D-Lab. There have already be several blogs about how awesome D-Lab is. This one's a nice overview. I'm too sleepy to add much to them at this point, but maybe later I can tell you more about Honduras (There were all sorts of adventures, some of which involved crocodiles!). For now I'll just allow myself one more picture (of our rope pump!) and get back to work.

:) Remembering Honduras makes me happy... so does company. Let me know if you're out there working too!