Gas station without pumps

2017 February 5

Units matter

Filed under: Circuits course — gasstationwithoutpumps @ 11:37
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I was a little surprised by how many students had trouble with the following homework question, which was intended to be an easy point for them:

Estimate C2(touching) − C2(not touching), the capacitance of a finger touch on the packing-tape and foil sensor, by estimating the area of your finger that comes in contact with the tape, and assume that the tape is 2mil tape (0.002” thick) made of polypropylene (look up the dielectric constant of polypropylene on line). Warning: an inch is not a meter, and the area of your finger tip touching a plate is not a square meter—watch your units in your calculations!

Remember that capacitance can be computed with the formula C = \frac{\epsilon_r\epsilon_0 A}{d}~,
where \epsilon_r is the dielectric constant,  \epsilon_0=8.854187817E-12 F/m is the permittivity of free space, A is the area, and d is the distance between the plates.

The problem is part of their preparation for making a capacitance touch sensor in lab—estimating about how much capacitance they are trying to sense.

There is a fairly wide range of different correct answers to this question, depending on how large an area is estimated for a finger touch. I considered any area from 0.5 (cm)2 to 4 (cm)2 reasonable, and might have accepted numbers outside that range with written justification from the students.  Some students have no notion of area, apparently, trying to use something like the length of their finger times the thickness of the tape for A.

People did not have trouble looking up the relative dielectric constant of polypropylene (about 2.2)—it might have helped that I mentioned that plastics were generally around 2.2 when we discussed capacitors a week or so ago.

What people had trouble with was the arithmetic with units, a subject that is supposed to have been covered repeatedly since pre-algebra in 7th grade. Students wanted to give me area in meters or cm (not square meters), or thought that inches, cm, and m could all be mixed in the same formula without any conversions.  Many students didn’t bother writing down the units in their formula, and just used raw numbers—this was a good way to forget to do the conversions into consistent units.  This despite the warning in the question to watch out for units!

A lot of students thought that 1 (cm)2 was 0.01 m2, rather than 1E-4 m2. Others made conversion errors from inches to meters (getting the thickness of the tape wrong by factors of 10 to 1000).

A number of students either left units entirely off their answer (no credit) or had the units way off (some students reported capacitances in the farad range, rather than a few tens of picofarads).

A couple of students forgot what the floating-point notation 8.854187817E-12 meant, even though we had covered that earlier in the quarter, and they could easily have looked up the constant on the web to figure out the meaning if they forgot.  I wish high-school teachers would cover this standard way of writing numbers, as most engineering and science faculty assume students already know how to read floating-point notation.

Many students left their answers in “scientific” notation (numbers like 3.3 10-11 F) instead of using more readable engineering notation (33pF). I didn’t take off anything for that, if the answer was correct, but I think that many students need a lot more practice with metric prefixes, so that they get in the habit of using them.

On the plus side, it seems that about a third of the class did get this question right, so there is some hope that students helping each other will spread the understanding to more students.  (Unfortunately, the collaborations that are naturally forming seem to be good students together and clueless students together, which doesn’t help the bottom half of the class much.)

2016 November 13

BioTreks—a specialized research journal for high-school students

Filed under: Uncategorized — gasstationwithoutpumps @ 18:09
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Five and half years ago, I published a blog post, Journals for high school researchers, which listed the tiny number of venues I knew of that were open to high-school researchers.

At iGem this year, I heard about a new peer-reviewed journal for high-school students: BioTreks.  Currently the journal is planning on one issue a year, and solely on the subject of synthetic biology, which seems a bit narrow to me:

In 2016, BioTreks will begin publishing open access, peer-reviewed articles related to the implementation and outcome of high school student-driven synthetic biology research. We’re currently accepting original articles that present perspectives, methodologies, and outcomes related to the study and practice of synthetic biology in high schools. Students, educators, and biologists from around the world are invited to contribute content that promotes and describes synthetic biology education and research at the high school level. Authors who are interested in contributing original research articles, methods papers, literature reviews, editorial perspectives to the journal are encouraged to contact us for more information. We look forward to hearing more about your experiences in synthetic biology and discussing ways in which you can share your insights in our journal. Please contact us to learn more about publishing in the journal.

I chatted with one of the originators of the idea for a while at the iGEM Jamboree, and they may be open to expanding the journal to be “synthetic biology and bioengineering”, which is a considerably wider scope, and which may open up opportunities for a lot more high school students.

I don’t know whether this would require them to rewrite their description of their goals:

Ars Biotechnica is a 501(c)3 public charity whose mission is to support science education by introducing high school students to the emerging field of synthetic biology. We do so by awarding grants for schools to use in obtaining laboratory supplies, coordinating local and regional symposia on synthetic biology, and administering a peer-reviewed journal. Our organization has been providing financial and technical support to iGEM-bound synthetic biology teams since 2013 and supporting high school focused synthetic biology symposia since late last year. We’re now excited to announce the launch of BioTreks, a peer-reviewed journal just for high school synthetic biology.

The organization has a very small budget and relies mainly on volunteers:

BioTreks is maintained by a volunteer staff of dedicated biologists, students, and educators. If you have a background in biology, education, peer-reviewed publication, or graphics design and would like to help us develop and maintain the journal, then we would like to hear from you. Volunteers can work remotely and on their own time to coach students on writing scientific papers, serve as section editors, copy editors, and peer-reviewers, and contribute to the journal’s overall presentation and design. Please contact us to learn more about volunteer opportunities at the journal.

They don’t charge anything to students for publication—they aren’t a vanity press that makes money off of selling overpriced printing to suckers students.

If anyone knows of other journals interested in high-school submissions (not vanity presses), let me know, and I’ll blog about them!

2016 November 11

Overvaluing innovation

Filed under: Uncategorized — gasstationwithoutpumps @ 10:43
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Mark Guzdial, in We overvalue innovation and entrepreneurship: Shifting the focus to Maintenance over Fads, points out

We increasingly teach computer science to prepare students to be innovators and create new things (e.g., join startups), when the reality is that most computer science graduates are going to spend the majority of their time maintaining existing systems. (See the papers by Beth Simon and Andy Begel tracking new hires at Microsoft.)  Few who do enter the startup world will create successful software and successful companies, so it’s unlikely that those students who aim to create startups will have a lifelong career in startups. In terms of impact and importance, keeping large, legacy systems running is a much greater social contribution than creating yet another app or game, when so few of those startup efforts are successful.

His post was triggered by a Freakonomics podcast In Praise of Maintenance, which includes Lee Vinsel (of Stevens Institute of Technology) saying

VINSEL: The value of engineering is much, much more than just innovation and new things.  Focusing on taking care of the world rather than just creating the new nifty thing that’s going to solve all of our problems.  If you look at what engineers do, out in the world, like 70–80 percent of them spend most of their time just keeping things going. And so, this comes down to engineering education too, when we’re forcing entrepreneurship and innovation as the message, is that we’re just kind of skewing reality for young people and we’re not giving them a real picture and we’re also not valuing the work that they’re probably going to do in their life. That just seems to me to be kind of a bad idea.

It also includes Martin Casado, a general partner with the venture capital firm Andreessen Horowitz, saying

CASADO: Large public companies in mature markets tend to invest primarily on maintenance. And often they don’t have the additional capital you need to do large innovation. So for example between say 2011 and 2015 growth companies, companies that are in fast-growing areas, spent two times more than legacy companies on research and development. So as companies mature , the majority of their investment and their spend is kind of maintaining existing technologies and so forth. And this is largely because of the pressure from the public markets.

The idea is that well-established companies don’t innovate—they maintain.  When they need innovation, they buy a startup company that looks promising.  Venture capitalists invest in highly speculative innovations, while the stock market invests in stable companies that mainly do maintenance rather than innovation.

Steven Dubner, the podcast author, says

Not often, but once in awhile, I take the time to marvel at the fact that so many people do so much work behind the scenes to keep the world humming. Whether it’s the internet, the roads, the electricity grid, you name it. Of course it’s easy to point out the failures—they’re visible, whereas the bulk of maintenance is practically invisible. But, in praise of maintenance, let me just say this: it’s necessary work; it’s hard work; and for people like me, who are always in a hurry to make the next new thing, it can be really unappealing work.

Although the podcast was talking mainly about infrastructure maintenance (both civil engineering and cyber infrastructure), I like Mark Guzdial’s approach of looking at engineering education, which has started stressing entrepreneurship.

Two decades ago, entrepreneurship was a minor add-on to engineering education.  A few engineers were expected to form startups, but they were mostly on their own—it was a path only for highly motivated individuals, not seen as a dominant form of employment. Now every engineering school seems to push entrepreneurship at its students, as if working for someone else is some sort of failure.

For faculty, this push is often a “do-as-I-say-not-as-I-do” admonition:

The fraction of start-up owners among recent graduates is 6.4% for all universities and colleges and 5.2% for top-rated schools. These fractions are several times higher than the fraction of start-up owners among faculty, which is 1.3% for all schools and 1.6% for top-rated schools. Indeed, start-ups by recent graduates outnumber start-ups by faculty by a factor of 24.3 among all colleges and universities and by a factor of 11.7 when looking only at “top-rated schools”. [http://docplayer.net/2732929-Startups-by-recent-university-graduates-versus-their-faculty-implications-for-university-entrepreneurship-policy.html]
Now 6.4% of graduates owning start-ups is a pretty large number of students, so there is reason to make entrepreneurship instruction widely available, but apparently 94.6% of students are not going to be owners of start-ups, so there needs to be more emphasis on the sort of maintenance work that is the bread-and-butter of any industry.
(Before someone calls me on it, I’m aware that my 94.6% figure is bogus—the 6.4% figure was based on current owners of start-ups, not eventual owners of start-ups.  I suspect that the number of eventual entrepreneurs may be double or even triple the reported figure, which still leaves over 80% of the students never owning start-ups.)
So the traditional engineering education, which prepared students about equally for new design and for maintenance of existing systems, is still much needed.  How should we be shaping our curricula to meet both sets of needs? How do we get the message to students that innovation is only a small part of the real job, particularly when the media is putting so much emphasis on “innovation” and “disruption”?

2016 September 20

Trick for encouraging cooperation

Filed under: Uncategorized — gasstationwithoutpumps @ 15:26
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Adam Grant, a professor at the Wharton School of the University of Pennsylvania, provided an interesting technique for encouraging cooperation in his business-school classes (a culture noted for cut-throat competition between students):

How could I get students to help one another?

Four years ago, I found a way. The most difficult section of my final exam was multiple choice. I told the students that they could pick the one question about which they were most unsure, and write down the name of a classmate who might know the answer — the equivalent of a lifeline on the game show “Who Wants to Be a Millionaire?” If the classmate got it right, they would both earn the points.

Essentially, I was trying to build a collaborative culture with a reward system where one person’s success benefited someone else. It was a small offering — two points on a 120-point exam — but it made a big difference. More students started studying together in small groups, then the groups started pooling their knowledge.

You can read more about his attempts to encourage student cooperation in Why We Should Stop Grading Students on a Curve, published in the New York Times.

I don’t think I can use this exact technique, as none of the courses I teach involve exams—all are graded on the written reports that students write.  I could use it for homework, I suppose, but the overhead of checking other student’s responses might increase the turnaround time for homework grading.  I’m also already seeing more cooperation on the homework than I really want.

Furthermore, students quickly learn who the best student in the class is, and would just point to him or her, with no increase in useful cooperation.  So I think this technique would only work in student cultures that currently have a high degree of secretiveness and competition, not in already collaborative cultures.

2016 September 15

Research Report | Siemens Competition

Filed under: Uncategorized — gasstationwithoutpumps @ 12:23
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I was reading the guidelines for a research report for the Siemens competition for high-school science projects.  Overall, the guidelines are good, but I have one quibble with their description of the first section:

Introduction: the “why” section (2-3 pages)

  • Start with a broad picture of the problem you have chosen to study and why it is interesting. Provide a brief review of pertinent scientific literature, describe what information is missing and how your work addresses this gap in the literature. Previous relevant publications and patents must be properly cited in the text of the Research Report and included in the Reference section of your report.
  • Describe the specific problem to be solved, the research question to be answered, the hypothesis(es) to be tested, or the product to be developed (if any). Provide a brief rationale for the research and why the work is important.

I believe that they are encouraging a common mistake: burying the lede. Theses, grant proposals, student projects, and papers should start with a direct statement of the research question or design goal of the project, then provide the “broad picture” and “why it is interesting”. I’m very tired of wading through a page or more of mush trying to find out what a student project (or published research paper) is.

Swapping the two points that they put in the first section would improve the quality immensely.

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