Gas station without pumps

2016 August 3

Missing comma

Filed under: Uncategorized — gasstationwithoutpumps @ 20:42
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Our local paper had a headline: “4 dead identified as cause of California bus crash probed“.  I couldn’t help but wonder how they were identified as the cause of the crash, and what they were probed with.

2016 May 22

Disappointing class-D amplifier reports

Filed under: Circuits course — gasstationwithoutpumps @ 15:59
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I have a huge stack of grading to do this weekend (about 20 new design reports and about 30 redone reports from earlier labs). I was rather disappointed with the reports for the class-D amplifiers, not because the amplifiers didn’t work (they mostly did), but because about 80% of the class is getting a REDO for errors in their schematics, which means I’ll be having to grade the reports again.  I consider 20% REDO an acceptable level, but not 80%.

The most common error in the schematics was one that I had seen a fair amount in previous years: getting the source and drain of the pFETs swapped.  It is a fairly serious error, as putting the transistors in backwards would cause a lot of shoot-through current from the body diode conducting.  Students were wiring their transistors correctly (after some false starts), but documenting their designs wrong.  A number of students also used the depletion-mode instead of enhancement-mode FET symbol, but I consider this a much less serious error (as long as they included the right part number), and would not have triggered an automatic redo for that mistake.

I warned the students about the source and drain orientation repeatedly, both as a class and (in many cases) individually.  I was very careful to point out the convention for the source and drain notation in class and in the book, and they had it on their data sheets as well.  I don’t know what else I can do, other than instituting in-class quizzes, which I may have to do next year.

There were a number of other documentation problems in the reports this week:

  • Using their loudspeaker models, but not including the model in the report.  In many cases, it was clear from their plots that they had screwed up the model somehow, but without any formulas or parameter values, it was impossible to figure out what they had screwed up.
  • Oscilloscope pictures that did not say what the probes were connected to, or had incorrect labeling of the probes. This was mainly really bad lab technique, where they failed to write down what they were doing, and couldn’t reconstruct it from their memories.  That is one aspect of the labs that I’ve not put much emphasis on this year—writing down what they are doing as they do it.  I may have to emphasize that more next year, especially since the labs will be broken up into 4 95-minute sections instead of 2 3-hour sections, which will make memory even more unreliable.
  • Not reporting the PWM frequency.
  • Not remembering to include their bypass capacitors in their schematics. Some students may not have had bypass capacitors, though it was very difficult to get the amplifiers to work without them, as the H-bridge dumps a lot of high-frequency energy into the power lines, which gets coupled back to the comparator and the preamp.
  • Generally bad copy editing.  The spelling and grammar problems in some reports are just common non-native problems with articles, plurals, and verb tense, but a lot of the reports had huge numbers of spelling errors, duplicate words, missing words, comma problems, and incomplete sentences.  I’ll be addressing this problem next year by giving students a bit more time to complete the reports (though that didn’t seem to help on the one report that students had more time on this year).

2013 May 10

Avoid passive voice

Filed under: Uncategorized — gasstationwithoutpumps @ 20:45
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I’ve been reading 13 different senior theses this quarter (5 drafts of each—we’re currently on the 3rd drafts).  One of the biggest writing problems that I’ve been trying to fix is the gross overuse of passive voice. Passive voice is often overused in scientific writing, partly out of a misguided attempt to sound formal and partly to remove the people who did the experiment from the description of the experiment.  The result often sounds like the authors are trying very hard to disassociate themselves from the project.

Nick Falkner describes this use of passive well in The Blame Game: Things were done, mistakes were made:

The error is regretted? By whom? This is a delightful example of the passive voice, frequently used because people wish to avoid associating the problem with themselves.

But the whole point of a senior thesis is to show what a particular individual knows and has done (and presumably can do again).  The author must attribute every concept and action in the thesis to the right person: those ideas that come from the literature need to be properly cited, work done by others in the lab needs to be properly credited, and work done by the author of the thesis needs to be explicitly claimed.  (I’m aware of all the passive in the last sentence—see below for explanations of some acceptable uses of passive voice.)

Along with passive voice, students misuse the first-person plural, which has little role in a single-author work like a thesis. Almost the only time that “we” should appear in a thesis is shortly after a listing of who “we” are. It is ok to say, for example, “Alpha Beta and I ran alternating shifts for the 48-hour data collection period.  We collected samples every hour …”, but it is not ok to say “We collected samples every hour … “, if you did it alone, or (worse) if someone else in the lab did it and not you.  Saying “Samples were collected every hour …” sounds like you don’t know or are not willing to say who collected the samples (perhaps because it was done illegally?).

I am not going to prohibit students all use of the passive (as some writing instructors do, or used to do)—passive voice is sometimes useful. For example, passive can be used for improving the flow of a paragraph, since it allows flipping a sentence, which can strengthen the old infonew info flow heuristic.  This flipping of sentences is best shown with some schematic sentences: we start with

A creates B. C modifies B. D controls C.

and we can improve the flow by modifying to

A creates B. B is then modified by C, which is controlled by D.

Note that the second sentence of the above paragraph uses passive (“passive can be used …”) in order to connect better to the topic sentence.

Aside: The “we” in the middle of the paragraph above is not the multi-author “we”, which is as wrong for this single-author blog post as it would be in a thesis, but the “you-and-I” version of “we”, which is also acceptable in theses.

Students worry that if they avoid passive, then they’ll end up starting every sentence with “I”.  Certainly, starting every sentence identically would be a problem, but avoiding that problem is fairly easy, particularly if students talk about the goals and purposes of experiments, rather than just giving technician-level protocol dumps of what they did. Note that I did not use passive at all in this paragraph, and only this last sentence has “I” as a subject—forming gerunds is one good way to create alternative subjects for sentences.

Although my writing instructor’s despair about overuse of passive voice has been the theme of this post, that was not the point of Nick’s blog post—it was a plea to students (and others!) to take responsibility for their actions.  He wants people to be aware that actions have actors:

Responsibility doesn’t have to be a burden but it does give you a reason to exercise your agency, your capacity to act and to make change in the world. If all of your problems are in the passive voice, then “assignments are handed in late”, “the money ran out”, “mistakes were made” rather than “I didn’t start early enough or put enough time in or I was horribly ill and thought I could just push through”, “I spent all of my money too quickly” and “I made a mistake”.

His point is a good one (go read the whole article), but his equating passive voice with refusal of responsibility is the message I want to get to the thesis writers.  The whole goal of a thesis is to establish agency—that the writer of the thesis knows and has done certain things, so the writer should avoid using passive voice.  (I initially had written “passive voice should be avoided as much as possible”, but I didn’t trust that all my readers would get the joke—my apologies to those who would have.)

2012 June 8

Dangling modifiers

Filed under: Uncategorized — gasstationwithoutpumps @ 20:30
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While awkwardly written and somewhat dated, AAUP and the academy pay homage to the seminal 1940 Statement of Principles on Academic Freedom and Tenure.

via The Tenure Denial of Norman Finkelstein (By Peter Kirstein).

Although I have little interest in the details of other people’s tenure cases, I do read the AAUP (American Association of University Professors) blog to know what the union I belong to does.  It seems that they believe in dangling modifiers. Or is “awkwardly written” intended to be a clever self-referential remark?

2012 April 1

Dangling modifier

Filed under: Uncategorized — gasstationwithoutpumps @ 16:39
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This morning I was reading an old fantasy book (copyright 1998) that had some really purple prose, and I came across an excellent example of a dangling modifier:

A goblet of dark, potent wine clutched in a hand that trembled ever so slightly from fatigue, he sat pensively at the long desk.

That’s not quite bad enough for the Bulwer-Lytton contest, and it is the second sentence of Chapter 10, not the opening sentence anyway.  Changing the first noun phrase to a participle would fix dangling modifier: Clutching a goblet of dark, potent wine in a hand that trembled ever so slightly from fatigue, he sat pensively at the long desk.  That doesn’t fix the problem of purple prose, of course.

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