Monthly Archives: March 2009

Not too Bitter, not too Sweet

Posted on by

No bitterness rule

Advice on deciding on whether or not one should go to grad school. Striving to be realistic, without flavoring it too much in either direction.

[Y]ou should know the basic facts of grad school experience: most experiments do NOT produce useful results, but that shouldn’t stop you from trying. You are not guaranteed an academic job after your PhD – or any job in specific geographic area or any specific type of the job. You will be making minimum wage-like salaries for ~5-7 years, and even though postdocs get paid more, it is not much more. But for this time you will have the company of like-minded people who are extremely smart, you will learn a lot, and since you live only once, grad school will certainly provide a unique experience that will shape your outlook on life.

“You will make a lot of money” isn’t on the list of what happens afterward, either. (It certainly can happen, but it probably won’t). But what the PhD helps enable is the opportunity to work on interesting problems. So if the whole “hanging out with smart people” angle appeals to you, it’s certainly something to consider.

Cans in a Blanket

Posted on by

Rhett asks a straightforward question over at Dot Physics, in A blanket and cold stuff

Suppose you put take two identical cans of soda out of the fridge and place them on the floor in the middle of a room. One can you leave alone and one can you cover with a wool blanket. After an hour, you come back and check on the two cans of soda. Which will be warmer?

The reason I think it’s a great question is that it plays on a common misconception about thermodynamics, and it reminds me of a joke, and a related story.

The joke is about a person declaring that a thermos (which we often call a Dewar) is the smartest thing in the world. When it’s pointed out that all it does is keep hot things hot and cold things cold, the response is, “How does it know?”

Well, some years ago we were giving a tour of our lab to an Admiral (or Sneetch. I have taken to calling military lab visitors Sneetches, a Dr. Seuss creature. The high-ranking ones have stars upon thars) We mentioned the vacuum system, and the Admiral mentioned the lines from the joke — it keeps hot things hot and cold things cold, how does it know? My colleague was so focused in on explaining things, he didn’t recognize the joke, and started explaining the physics of heat transfer: a vacuum is a really good barrier to nonradiative heat transfer. I mentioned that it was a joke before he went in for a second round of explanation.

But the misconception — that blankets heat things up, rather than act as a barrier to heat transfer, is what is pointed out in this example.

No More Breadbox

Posted on by

I’ve mentioned before that I’m bigger than a breadbox. But that description will have to change. It’s not that I’m appreciably smaller (though I have lost some mass from running a net energy deficit the last several lunar cycles), it’s that I now have a much geekier description to use.

A colleague has been setting up a pulsed laser system, in anticipation of getting into frequency combs for optical time transfer using fibers as well as eventually doing optical clocks. And, frankly, he dropped the ball. He got the system running and announced it had a pulse, but neglected to shout “Give my creature life!” or “It … is … ALIVE!” at any stage of the work. Anyway, we were watching him tweak the system and were looking at the signal on an oscilloscope, and got to the point where we wanted a much larger bandwidth, so we started looking for the spectrum analyzer.

“Where is it?”
“I think it’s in the lab. I saw it around here somewhere.”

[Group members begin to fan out]

“Oh, there it is, behind Tom.”

I had been blocking the view of it. Ergo, I can now be described as being “bigger than a spectrum analyzer.”

Simple Toys

Posted on by

Another cheap little toy I recently acquired is a keychain containing a multicolor LED that rapidly flashes between red, blue and green. It looks white (almost) to the naked eye when it’s stationary, but when it’s moving quickly enough, persistence of vision allows you to see the different colors. My webcam frame rate is timed such that it picks this up as well.

You need to a flashplayer enabled browser to view this YouTube video

It’s been a reasonable distraction for when I’m put on hold by tech support or customer “service.”

It's What's for Dinner

Posted on by

Cooking up a Smart Nanofluid

Specialized nanoparticles floating in water make a fluid that can be switched between two states with different thermal properties, according to the 13 March Physical Review Letters. If the particles start out evenly distributed throughout the fluid volume, heat transfers more rapidly through the fluid than if they are more concentrated close to the heat source. The flow pattern is not fixed like the steady rolling produced in pure water, which suggests more complicated physics than researchers had previously predicted. But the team hopes some version of their fluid can be used to improve the regulation of heat flow in future devices.

Meat Madness

Posted on by

The meat playoff bracket champion has been crowned. Bacon fans will not be happy.

Lotta controversy. Pot roast, a 15 seed? Pepperoni and Italian sausage in the same sub-bracket? And the upsets — filet mignon losing to hanger steak? Ooh, that’s tough (not really, it was actually quite tender).

via

Doing Nothing for Fun and Profit

Posted on by

Think Negawatts, Not Megawatts

Paying big users to cut demand when capacity is strained.

10 percent of all US generating capacity exists to meet the last 1 percent of demand. Utilities paid EnerNOC $100 million last year simply to stand at the ready—insurance, in effect, against the inevitable days when every AC unit is humming.

I expect some companies who participate will install their own systems. Energy at the place of use, or distributed energy, doesn’t tax the grid because it isn’t being sent anywhere. I wonder if/when fuel cell technology matures, if this isn’t an ideal application. Generate hydrogen from cheap electricity at night, use it at peak times when electricity is expensive and/or you’re being bribed to reduce your demand.