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2014 May 12

Lecture for pulse monitor

Filed under: Circuits course — gasstationwithoutpumps @ 19:27
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Today’s class started with handing back the audio-amp lab reports, which spanned a much wider range than usual. Everyone had an ok design, but some students explained it well, while others had numbers that appeared by magic or with completely incoherent explanations. Although I could have predicted a couple of the worst reports, the group that did the best was not the one I expected.  I’m quite pleased that they did such a good job, as I was not sure I was getting through to them—it made up for my disappointment at the relatively poor performance of a couple of the groups I had expected better of.

I pointed out to the students that there was no “correct” answer to most design problems, and that being able to explain how they came up with the design was at least as important as the design they came up with.  If some spec changed, an engineer would want to be able to modify the design without having to do the whole thing over from scratch.  (I didn’t say it, but I think that some of the groups that couldn’t explain their work would not be able to redo their designs from scratch, even if none of the specs changed.)

The multistep problems in last week’s lab and this week’s are difficult just because they have so many chained steps, though each individual step is pretty easy. I suspect that many of the students have never worked multistep problems before and are shutting down the moment they don’t have a predefined protocol to follow.

I asked how many people had done the prelab for tomorrow’s lab (as I had requested they do over the weekend). As expected, no one. I asked how many had attempted it—only about a third of the class. I asked where they were getting stuck—on the first step, figuring out how much light came out of the LED. Rather than going on and doing the rest of the chain of computations symbolically, they just gave up, so that they had nothing done, rather than an almost complete problem solved, with just one hole in it to be filled.

My lecture for most of the remaining hour consisted of explaining to them almost exactly the same thing that was in their lab handout. Luckily, I was expecting this inability or unwillingness of students to learn from written material, because I saw it last year also (though not on this lab, since this lab is all new).  I would really love it if students would read things and at least try to do the assigned homework before class and come in with specific questions, rather than expecting to get everything in lectures for the first time. But I’ve resigned myself to students having less than zero initiative about learning new things.

Today had been scheduled for photodiodes and phototransistors, but we only got to those topics for the last 15 minutes of class, as I spent the first 55 minutes patiently going over what they needed to do to convert candelas to lumens to watts for the LEDs, to estimate how much light is absorbed or scattered in a finger, to estimate how much of the remaining light makes it to the sensor, and to compute how much current one would then see in the sensor. I didn’t do the computations for them (which seems to be what they expect—too much scaffolding in their other classes?), but I’m hoping that they can now read the homework assignment.

Despite my warnings that they would need to have the prelab done before lab starts tomorrow, or they are likely to run out of time for this lab, I’m betting that only one group will have gotten as far as a schematic, and that most of the class will again waste most of the lab time doing their prelab homework.  I’ve not figured out a way to break them of this, but I’ll need to get better at getting students to work outside lab, or I won’t be able to handle  two lab sections next year.

I am going to suggest that they write up half their lab report before Wednesday’s class, so that they can uncover the places where they can’t reconstruct their thinking before the final report is due on Friday, while there is still time to ask questions and modify the design.

On Wednesday, I plan to talk about the second stage of the amplifier for the pulse monitor, adding gain for 0.2Hz–30Hz but blocking DC.  But figuring out how much gain they need requires them to have completed the first stage of the amplifier on Tuesday, and looking at the output with an AC-coupled oscilloscope, to see and measure the small fluctuation caused by opacity changes in the finger. I’m not sure that all groups will get that far, having not started on the design over the weekend as I told them to.

The class ended after a very brief and informal presentation of how a diode works, what causes photocurrent, and why the phototransistor has 100–1000× the current of a photodiode.

Sorry if I seem to be too much of a curmudgeon today—I’m very tired and even entirely expected behavior from the students was depressing.  This isn’t even a “students-nowadays” complaint, as I remember having the same sort of disappointment about students being unwilling or unable to read assignments when I started as a professor 32 years ago. Perhaps there is some Shangri-La somewhere, where most students do the assigned reading and struggle to understand it before class rather than waiting to be spoonfed, but I’ve never taught there.


2013 May 1

Senior thesis reading leads to learning

Filed under: Uncategorized — gasstationwithoutpumps @ 17:00
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Reading senior theses has lead me to learning a bunch of new things—not so much from the theses themselves, which are often rather light on background information, but in trying to help students debug their problems and fill in their missing background.

For example, today I found out a little about how nitrogenases (which usually fix nitrogen N2 to make ammonia NH3) produce H2—I did a search with the student to try to find the stochiometry of the reaction, and we found a paper that explained not just the reactions but what mutations had been needed to turn off the normal control of the nitrogenase, so that it would continue to be active (and producing lots of hydrogen) even when there was no nitrogen to fix.  I couldn’t see any reason for the nitrogenase to be active when it wasn’t producing ammonia, and indeed it isn’t in the wild-type bacterium.

I also helped another student look at pitch detection algorithms (for finding pulse rate from video feeds), using cepstral analysis. He’d been using FFTs, which are not bad, but which can be confusing to interpret when there are higher harmonics present.  The cepstrum is often easier to find the fundamental from, and I’m curious whether it will help with the rather noisy data he has to work from.

A third student was having trouble with non-expression of a viral protein in an archaeal host system, and I suggested looking for the viral sequence in the CRISPR repeats of the archaeal genome, to see if the strain had been previously infected by this virus and so was chopping up the DNA or mRNA they were trying to express. I didn’t know before looking whether CRISPR systems would attack RNA or just viral DNA—the article I looked at suggested that it would attack RNA as well as DNA.  I also suggested that they look to see whether the desired mRNA was actually being expressed (using cDNA and PCR), to see whether the problem was a translation problem or a transcription/RNA-processing problem.

A fourth student had questions about whether he should include an electron micrograph from the literature to show the structure of the virus he was trying to express a protein from, so we brought up the paper on my computer (with a bit of a detour, since he had mis-spelled one of the author names).  The picture was worth including for the purposes of his thesis.  We also talked about whether a particular part of his thesis writing should be given more prominence and more generally about his paragraph and section structure.


2011 November 6

NPR SF/fantasy list as a decision tree

Filed under: Uncategorized — gasstationwithoutpumps @ 00:30
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On August 11, 2011, NPR released the results of the online vote they had for the top 100 science fiction and fantasy books.  While I’m sure that there are many quibbles about which books did and didn’t get on the list (it is clearly biased toward recently published books), it is a fairly good selection of books, and most of the books on the list will reward a reader looking for something they haven’t read before.  (I think I’ve read 42 of the first 50 on the list—I got distracted and lost count after that.)

If you are having trouble making up your mind what to read next, try the flowchart posted by T.N. Tobias on the SF Signal blog:

The blog post has links to an interactive version and a (huge) poster-printable version, so go there if you want more!

2011 June 6

Teaching technical reading

Filed under: Uncategorized — gasstationwithoutpumps @ 16:33
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I have often taught technical writing, but it never occurred to me that I might need to teach “technical reading” skills as well.  There has been an excellent series of blog posts on Mylène’s blog “shifting phases” on teaching reading comprehension to engineering techs.I particularly liked the techniques in How Reading Comprehension Led To Formal Logic, in which students had a design task (making an assessment plan) that required close reading of rather dry technical material.  Having a clear goal for the reading (to minimize the amount of work they would have to do in the assessment, while still meeting the standard) motivated the students to tackle material that they would otherwise have found too difficult and to dry to cope with.

It might be difficult to incorporate some of the methods Mylène uses in my grad classes, but I can see them being very useful in undergrad and high-school classes.  The problem is not that the grad students are necessarily better readers, but they certainly think that they are, and so would resist attempts to micromanage their learning.  I need to think about ways I could get them to improve their reading skills without insulting their ability or motivation.

I’ve already been using the grad-school classic—the journal club, where students read a published paper and present it to the class, filling in with background material from other papers and critiquing the research as they present it. This works well with some students, but those who have reading weaknesses generally do a poor job and are unaware of how much more they should be doing.  Even seeing good examples from other students does not seem to be enough for some, though that is a big part of the pedagogic justification for doing journal club.

2011 May 23

Reading Comprehension: Identifying Confusion

Filed under: Uncategorized — gasstationwithoutpumps @ 20:05
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I recently posted about Mylène’s attempts to teach “technical reading.” Now she has another post on a different exercise she used: Reading Comprehension: Identifying Confusion.  Once more, good stuff that would be very useful in beginning engineering classes.

I have a hard time justifying 20 minutes in my grad classes on this sort of vocabulary-based reading (though there are probably students who need it).  It might be a good exercise to get into the TA training course though, on the off chance that they would accept the instruction if disguised as a technique they could teach, rather than one they need to use themselves.

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