Saturday, January 30, 2010

Laser fusion milestone

What better way to mark the 50th anniversary year of the laser than by producing a 669 kJ laser pulse (reported in Science), and then following that up with a 1 MJ pulse? (See BBC News article.)

Maybe getting it over the 1.2 MJ threshold and observing ignition of controlled thermonuclear fusion? This year?

They claim that it can be done this year, even though they did these initial experiments without the neutron shielding in place that is needed before doing that experiment because of the energetic neutrons that are produced by the d-t fusion reaction.


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An algebra problem

A story from the tutoring room, where I encountered a student taking first semester chemistry for science majors who was struggling with a simple density problem.

(Why they teach complicated algebra problems before they teach any chemistry is a mystery to me, but I no longer remember what pedagogy my chemistry classes followed.)

Given that our chemistry class has college algebra as a prerequisite, I think the problem itself is instructive.

After a significant amount of prompting on an easier problem, the student was able to get all of the given data for this problem into the appropriate chem-SI units of g and cm. This left something like the following problem, except written as a fraction:

2.705 = 276/(30.48 * 1219.2 * X)
Solve for X.

The student was,it appeared, utterly helpless when faced with all of those numbers.

My suggestion that he cross multiply the X and 2.705 met the sort of look I would expect if I had said it in Japanese. OK, clear fractions? Still no luck. I don't think he saw this as a fraction. Multiply both sides by X? Ah, progress. Now he could compute the right side and solve 2.705*X = Number. Just to check, I asked him about
5 = 7/(3*X)
No problem there, although slow as molasses doing it.

When I started telling this story to a chemistry colleague, she starting laughing so hard that she almost fell out of her chair before I was halfway through it. She regularly sees this at the start of every semester. Now I know why she says my students aren't like hers. Many (but not all) of the kids who make that kind of mistake are weeded out by pre-calc and trig before they get to me.

When I asked a couple of math colleagues about this problem, I learned that they include problems with "messy" numbers on pre-calc exams, but not in college algebra. They also said they suspect that not all pre-calc classes give messy application problems. So that is why I was not surprised that a student in Becky Hirta's Calculus Circus had trouble with a graph where the answer was not obviously going to come out in simple integer steps.

Footnote:

Two of my physics students messed up a problem essentially as follows:
2.66 = 7.79+3.47*X
2.66/7.79 = 7.79/7.79 + 3.47*X
0.3415 = 3.47*X
To save you the effort, 2.66/7.79 is about 0.3415. Bet you didn't know that 7.79/7.79 was zero!

Yep, that is how at least two of them "canceled" that number that was added on the right. Again, my math colleagues tell me that this sort of error is not uncommon among students entering calculus 1, and that they are more likely to make it with numbers rather than symbols. I have to wonder if they would have subtracted 7.79 if it had been at the end
2.66 = 3.47*X + 7.79
instead of at the beginning....


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Sunday, January 17, 2010

Engaged Learners

I don't have a label for students? Well, I do now. (I'm not going to file it under peeves because it doesn't peeve me.)

Regular readers know that Rudbeckia Hirta is the wind beneath my wings at the start of most semesters. Like today, where she tells me her university has FOUR different kinds of "undecided" majors, going all the way down to "completely undecided". I smile just thinking of that student wandering aimlessly through academia.

But I digress. This post is about starting your homework, well, a bit late.

You see, I have some quasi-administrative duties that put me in charge of dealing with student problems with a homework system during times our college doesn't have anyone handling user support. So what do I see in my inbox this weekend, which is the second weekend of the semester, but 3 (count them, three) problems getting into the system. Haven't gotten one of those for days, and now three of them.

Does this sound like either this problem or this one from RH? Well, it would if we had started class this week, but we didn't. We started the week before, so it takes a special level of engagement to wait until the Sunday before the homework is due to see if you know how to get in.

Disengaged engagement, I would say.

Reading those e-mails after reading RH's blog was like deja vu all over again.

My students, of course, have homework due right away (like RH, on the Friday of the first week of class for a Wednesday start). I find that if you coddle them with a late start, they don't start. And I make sure the slackers know that the vast majority of their fellow students have done the problems the day before they are due. The instructor for one of the classes involved takes the opposite approach. Not a good idea, but it was useful to see the flaw in that plan confirmed once again. But I do need to talk to him about that.

Like I said up above, I'm not peeved. I'm just an amused spectator like when I read RYS. I'm gambling that these students will never make it to my physics class, but they will get quite a wake-up call on the first day if they do make it there.

Or on the third day, but that is a different story.


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Friday, January 15, 2010

Jobs - Redux

There have been quite a few jobs-related articles on IHE and in the blogs lately that deserve linkage and comment. I'll put those below, after pointing to the jobs category where I group articles I have written in the past. The series started with a pair of articles that looked at the supply side (focus on the cycles we have seen over the past 50 years) and demand side (focus on where the jobs and will be) for physics, but much of what I describe is being lived today by folks in history and humanities.

The biggest difference between physics and the liberal arts area is probably that 2/3 of Physics PhDs have always ended up working in industry, with only a short (but very significant) period when the vast majority went into academia. Significant because it resulted in a faculty that remains woefully ignorant of where most of their students will get jobs.

Now, on to the articles.

1) There is a fantastic article in IHE this week about hiring at two year colleges by an English professor. It is the perfect complement to what I wrote some time ago about getting a job at a CC, and pretty much proves my thesis that science and humanities are looking for the same thing at the CC level. There is a huge overlap between the suggestions in that article and the ones in mine, and both emphasize the difference between applying at a CC and what is expected at other types of colleges and universities.

As he said, you must know what we do and what kind of students we have (particularly if you are going to teach composition or algebra or general education classes) if you hope to have any chance of getting a job at a CC. And I will add that I think one of the comments in that article is from someone totally ignorant of what we look for. Having been an adjunct at a CC is NOT the kiss of death. Quite the opposite. Just as med schools want students who have seen the pukey side of a hospital so they don't quit two years in when they discover they have to spend all of their time with sick people, CCs want to hire people who know exactly what they are going to be dealing with for the next 20 years.

2) There was also an earlier article (Part One on 'The Two-Year Option') where Hurley (an English prof at Diablo Valley College) goes into some detail about why he finds the CC environment such a good fit. Like him, I think I have a terrific job that is quite different from what I thought might be my career goal, and like him I find my students an interesting group.

3) For the back story about the job situation in the humanities, history, etc, check out these articles from IHE: History and English and links therein. To me, this is all deja-vu of the situation my older friends and colleagues faced about 40 years ago, as detailed here. Only they had it worse, because their job odds went from 90% to 1% in just a few years, and stayed very low for a decade. And if you read that article you will know why I find comments about Boomers offensive: that pipeline got blocked by the generation that earned a PhD when the first Boomers graduated from high school and stayed in those R1 faculty jobs for 40 years or more.

I think I left something out, but that will do for now.

UPDATED 16 January:

Thanks to Dr. Crazy's blog about bleak job prospects (which contains links to two other articles on that topic), I know remember that I left out Dean Dad's blog about why undergrads go on to graduate school when the job prospects are so poor.

4) Dean Dad wrote a great analysis saying that it is the loss of a clearly legible path to other careers that leads high achievers to pursue the mostly dead-end path to a PhD in the humanities. I can see that, because there is quite a bit of truth to it even in physics, and physics is a field where there are jobs that clearly use physics even if faculty and career advisers don't know about them. It is much less clear how you would get a job in industry with a history degree than with a physics degree.

5) And read what Dr. Crazy wrote from the English end of the world (linked above, as well as what it looked like to Tenured Radical and Historiann from the history side.

6) Sort of unrelated, sort of related, I just read Malcolm Gladwell's article in the January 18 issue of The New Yorker about entrepreneurs. (Only the abstract is available on-line, but it gives a really good summary of the article.) The thesis (drawn from descriptions of some very successful businessmen that, like Ted Turner, have usually been described as gamblers) is that SUCCESSFUL entrepreneurs go after the sure thing. The unsuccessful ones are the gamblers. Gambling on a faculty position in the humanities at an R1 or Ivy where you teach one small class a year for a six figure salary might fall into the latter category, because even a job at a CC or at a regional comprehensive (what Dr. Crazy describes) is far from a sure thing and FAR from the "life of the mind" those students are gambling on.

I'm really glad my niece did not go to graduate school.


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Friday, January 1, 2010

Happy New Year!

I Got It!
see more deMotivational Posters

Or see the original ones: from Despair, Inc.

I like the one that's new for 2010: Bailouts

But let's not overlook this one or the T shirts for social media and the big bank bailouts.


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Friday, December 25, 2009

Uncertain Christmas Gift

At first, this gift was in a mixed state.


It was clearly a book, and the odds favored it being a particular book, but could we know for sure without opening it?


Ah, now we know for sure ...

It is a GREAT book!

Notes added to correct a major oversight -

Link to the How to teach physics to your dog book web site. (Chad gets an extra cut if orders go through there.)

Here are the two semi-famous blogs that started it all:

Those stories are the basis for two of the chapters. Each chapter starts with a dialog with Emmy, followed by an elaboration on the science behind that idea.

Chad deserves major kudos in my view for including a final chapter that debunks much of the junk that has been written based on pseudo-quantum non-science.

Other material can be found in Chad's general category of Physics with Emmy, but that is mostly about writing (including the story of how he got the book contract) and promoting the book. So you don't have to dig through all of that for the best bits, here is the link to one that includes the slides from a talk he gave, and two movies that deserve special mention: The Bohr-Einstein Debate (with puppets) should not be watched while drinking coffee. The choice of character actors is, shall we say, priceless. But it is not just whimsy. As a long-time student of those discussions and owner of a personal library of some of the key books, I think Chad did a very good job selecting what belongs in his little play.


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Thursday, December 24, 2009

It is almost Christmas ...

... and it's not really Christmas until we hear dogs barking "Jingle Bells".




It was a sure sign of the approaching holiday when J. P. McCarthy would play that song on WJR.


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Tuesday, December 22, 2009

Merry Christmas and a Happy New Bank!

Bank failures continue. Every week (usually on Friday), the FDIC moves in and takes over a few more failing banks. Most are in trouble because of bad commercial loans. There was one striking example locally where an investor group led by a Realtor bought a 5 million dollar property and couldn't even pay the taxes on it from the rents. It sold for less than half that in foreclosure. Although the bank that lost about three million dollars on that one loan was not in this state, some local banks have made similarly bad decisions.

[Memo to the right wingnuts: There has been no change in the law regarding loans to poor people to encourage home ownership, yet the banks have tightened up their lending practices. That is what mathematicians call a counterexample to the claim that politics rather than greed caused lenders to loan money without checking anything. Another counter example would be where a Swiss bank nagged an owner into refinancing a now-bankrupt resort so they could earn the origination fee.]

So how can you tell if your bank is over extended? How can you find out how many toxic loans it has, or how many bank-owned properties it owns? Easy:

An MSNBC story provided a nice, color coded map showing the extent of the problem on a state-by-state basis with links to a separate "bank tracker" site. The main article only does banks, but if you go to the main site you can choose (top of the left column) to look for banks or credit unions as well as their methodology and who has obtained TARP funding.

It is worth a look, although you do have to know where your bank has its headquarters.

What I like is that they show the time dependence of the bad assest ratio in a bar graph, so you can see the trend as well as the raw numbers in a table. For perspective, the reason their bar graphs don't max out when a bank gets to a 100% ratio between troubled assets and capital plus reserves is that the ones that have been taken over can be in the 300% to 600% territory. However, that is not the only metric. I saw one bank where the ratio was just over 100% but they had been losing over a hundred million dollars a quarter for a year.

I was glad to see that our banks and our credit union are in reasonable shape. One has a ratio around 40%, but it has been stable for most of the year and they are still making a profit. Not so for another local bank, which has advertised how helpful it is to local businesses. Their ratio has been going up by leaps and bounds, hitting 100% last quarter along with a large negative profit. I wouldn't buy any stock in that one!

And always remember: the cap on FDIC insurance applies to the sum of all of the accounts in your name, not each account.


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Lazy American Students?

There is an interesting "quick take" in IHE today asking the rhetorical question Do American Students Bring Down the Curve? based on an opinion column in The Boston Globe that answers it in the affirmative.

First, it is important to realize that this is the opinion of one instructor, and even she does not claim that all low grades go to Americans (which make up 80% of the undergrad population at her private business college) or that none of the A grades go to Americans. But, from where I teach (at a CC), I think she has it all wrong. She has a problem with Snowflakes, not Americans. Let us start with where she teaches, then look at what she might not be doing where she teaches.

The college:

She teaches at Babson College. Yeah, I had to look it up, although I suspect Bostonians would be aware of it. This is a small (the entire freshman class of 471 would fit easily in one half of the dorm I lived in at Enormous State University, with space enough for half to have private rooms) expensive private college ($37,824 for tuition plus $12,500 for room and board) that is basically devoted to business majors. [Aside: that room and board rate is almost twice what it is at Enormous State, so they probably do all have private rooms.]

They look selective (471 enroll out of 4100 applications), but their middle-50 on the SAT (1830 to 2070, meaning 610 to 690 on each part) puts about a quarter of their freshman class below the "aptitude" of most of my 2nd year CC students and in a range where we would likely be requiring remedial math or english classes. A bit over 20% are international students.

(These details are from their official facts page. Purely by accident, I saw an article in a November "Business Week" that ranked them highly for custom executive business education programs.)

Definitely "snowflake" territory. Many of the American students are probably Wannabe Trumps with well off (if not wealthy) parents and got by with minimal effort in suburban schools where you get a bonus point toward your GPA just for taking what is called an honors class. [Schools where a 4.0 is the new 3.0 average.] In that environment, the mere fact that the college gives out C, D, and F grades in a freshman composition or history class is probably a shock. I'll admit that I am shocked that grades like that are tolerated by a student-centered retention program where one mid-year drop out costs the college $25,000!

To continue my generalization, they have probably never had to work for a living, and might never have held a job. They know they want to be business men or women, but don't know what skills are used on the job.

I can definitely see how one tail of the distribution in her class might be made up of the 25% who combine mediocre skills from high school with poor motivation.

The teaching:

My thoughts here are driven by an observation I posted just the other day on FSP's blog in a discussion about why tenured professors should care about what is in student evaluations of teaching. My comment concerned a favorite student observation of decades past: An engineering major stated that ze hated physics and couldn't understand why ze had to take it. What did I learn? That one thing I need to teach real early in the course is why it is required for engineering majors! Turns out lots of them don't know why because they don't know what engineers actually do. This student probably would believe that something taught in an engineering class was relevant to a career, but didn't get the concept of prerequisites so everything else was just a speed bump that got in the way of what they thought they needed to study.

I'd be willing to guess that the problem is even bigger with rhetoric classes. Now Babson College knows it is relevant, but do the students?

Here is a key remark from Babson's About page that might put this in perspective:

The undergraduate curriculum integrates core competencies, key business disciplines, and the liberal arts into foundation, intermediate, and advanced-level courses. The competencies are rhetoric; quantitative and information analysis; entrepreneurial and creative thinking; ethics and social responsibility; global and multicultural perspectives; and leadership and teamwork; and critical and integrative thinking.

Notice that reference to "rhetoric", the subject taught by the author of this opinion piece?

[Side comment: I like the word FOUNDATION as a synonym for prerequisite, although I'll stick with BASIC for some of my applications. It sends the right message for engineering, in particular.]

I would hope something this basic to the learning goals of the college was part of their orientation. Of course, if those kids were busy updating Facebook (which might rival drinking as a reason for failing out of college) during orientation, they might have missed it so it needs to be said in every class, and not just on the first day. "Today we are working on the foundation for the report-writing skills refined in Business 301, skills that will get you that first big promotion." And I would hope that the teachers in their freshman business class refer to the importance of rhetoric just as I point to specific math skills they will learn later on and apply (along with physics) in more advanced engineering classes.

We all have to signal the importance of the whole of what they are learning if we expect them to retain the parts that really matter.


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Monday, December 21, 2009

Happy Solstice!

I've been pretty silent here, so should interject something.

The solstice this year was just after mid day, so the sun was at its highest point when it reached its lowest point (relatively speaking) in the southern sky.

Elsewhere ...

The topic of teaching evaluations and improving teaching at Female Science Prof's blog might be a jumping off point, but I'm not quite ready for spring semester yet. When I am, I might also pick up a few other loose threads, like math education.


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Saturday, December 5, 2009

Torque and Angular Momentum

Rhett Allain has a very nice blog post about angular momentum featuring the precession of a bicycle-wheel gyroscope that he demonstrates here:


I find wearing a long-sleeve shirt with shorts to be an interesting touch.

In addition to my comment on his blog, I'll add the following about how I introduce it in my classes:

Based on experience as a student and an instructor, I think it is usually best to present the prediction before doing the experiment. However, in this case I generally interleave the two.

As with most intro textbooks, mine packages angular momentum along with the cross product definition of torque in its own section so it is easy to omit completely. I integrate tau=rxF into my initial introduction of torque and the various ways of calculating it, but then stick with tau = I*alpha until I get to L.

As soon as I introduce L, I go into the generalized second law as tau = dL/dt (pretty much the way we jump from F = ma to F = dp/dt once momentum is defined). After connecting this to tau = I*alpha, I then ask "So don't you wonder if that cross product in the definition of torque is real? Is torque really perpendicular to the force?".

Then I do the demo, quickly, just enough to see the rotation.

WTF? At this point I do the detailed calculation, exactly as shown in Rhett's blog, and then REPEAT the demo. This time, however, I slip an "L" arrow onto the handle so they can see it precess.

What if I hold it by the opposite handle? What is tau now? Aha, it goes the other way!

What if L = 0? Ah, so "falling" is actually rotation in this case.

... and finally ...

What force keeps the center of mass from falling with L is not zero?

The string! Now if I could only measure the force on the string during the demo with L not zero and compare it to the force when L is zero ....

But to summarize: In this case I think they need to see a taste of the phenomenon to understand why I would bother with such a detailed calculation. It also means that I end up doing the demo itself several times, and I use the wheel with the L arrow on it when doing the drawings, since they are not yet experienced at getting a 3-D image out of two projective views. Few have had a drafting class or Calc III.


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Sunday, November 29, 2009

Historic papers available on line

The Royal Society has put 60 historic papers on line for free public access. It is available here.

Franklin's paper about his experiments with lightning and Newton's with color components in white light appear to be well worth a visit.


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