Gas station without pumps

2020 March 31

Forty-third weight progress report

Filed under: Uncategorized — gasstationwithoutpumps @ 14:55
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This post is yet another weight progress report, continuing the previous one, part of a long series since I started in January 2015.

This year is not going as well as last year.

I’m about 5 pounds heavier than the same time last year.

I’ve been doing a lot of stress snacking lately, and staying home to do grading really resulted in my weight going up.  Without the discipline of bicycling up to campus every day (and skipping lunch most days), my weight has not only stopped going down, but started up again.

I  averaged only 2.8 miles/day of bicycling in March, down from 4.83 miles/day in February, and 5.13 miles/day in January.  My walking is also down: my Verily study watch from Project Baseline reports 117k steps for March (3900/day) down from 190k steps for February (about 6600/day) and 240k steps for January (about 7700/day).

I’m going to take a walk today (wearing my COVID-19 mask) to get in a little exercise. I’m also going to have to come up with some way to motivate myself to exercise more—not just for this cower-in-place period, but longer term, so that I can continue even after retirement.

COVID-19 mask

Filed under: Uncategorized — gasstationwithoutpumps @ 14:40
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On Sunday, I sewed myself a mask for when I need to go out to the store.  I used a pattern from Tiana’s Closet, which seemed to me almost the same as many others on the web.  I modified it in one major way—replacing the elastic with ties that go behind the head (using some 30-year-old bias tape that my wife had).

The results look a bit sinister:

I think I’ll make the next one out of a more cheerful fabric.

Flattening and reinforcing the curved seam was a little harder than I expected (it has been a long time since I sewed anything curved), but not too bad.

There was one problem with the mask design—the part that covers the nose does not fit tightly to the nose, leaving a gap between the nose and the cheek. This means that exhaled breath goes up through the gap and fogs my glasses.

Here is a closeup of the gap under my eye.

I’m not sure how to redesign the mask to avoid that gap. Commercial N95 masks (of which I have a handful from last year’s fire season) use a strip of soft metal to pinch the mask tight around the nose. I tried using some soft 12-gauge copper wire to make a nose clip, but I was not able to make one that helped.

Does anyone have a pattern that works well for big European noses? Or suggestions for ways to avoid or close the gap?

2020 March 29

Recycled writing

Filed under: Uncategorized — gasstationwithoutpumps @ 08:32
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I’ve been reading a lot of coronavirus coverage on the Associated Press, and I’m getting very tired of seeing the same paragraph buried somewhere in every article:

For most people, the coronavirus causes mild or moderate symptoms, such as fever and cough that clear up in two to three weeks. But for others, especially older adults and people with existing health problems, the virus can cause more severe illness, including pneumonia, and lead to death.

This must have been a mandate from the AP administrators—surely the reporters themselves would have been more varied in how they presented the information, even if they were plagiarizing each other.

Perhaps the AP administrators could loosen the reins a little and let their reporters and editors determine the content?

2020 March 28

Exponential and logistic growth

Filed under: Uncategorized — gasstationwithoutpumps @ 16:37
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I was just thinking that the current COVID-19 crisis provides a teachable moment for showing the advantage of semilogy plots (log scale on the y axis, linear on the x axis) for showing exponential data.  So I grabbed information from one of the many sources reporting the number of cases and number of deaths due to COVID-19 [] and plotted them in different ways.

Here is what the data looks like on a linear graph:

This shows the rapid growth of the cases, but is hard to project into the future. It is also hard to see whether the growth rate is changing or how the deaths are related to the cases.

My next step was to use a log scale and to fit exponential curves to the data (actually fitting the log of the model to the log of the data, to avoid being biased by just the most recent data). I fit the data from March 2 on, since there were small-number effects before then.

The doubling time is alarmingly short for both the number of cases and for the number of deaths. Of course, exponential growth models don’t work well when projected indefinitely far into the future—at some point the infection rate predicted by the model exceeds 100%, which makes no sense. A better model is a logistic model: A \frac{2^{(t-t_c)/\lambda}}{1+2^{(t-t_c)/\lambda}}, which has three parameters:
A, the eventual fraction of the population affected
t_c, the time at which half of A is affected
\lambda, the doubling time.

I did fits of the logistic-growth model with three different assumptions about the eventual fraction affected: everyone, 10%, and 1% of the population, then fit the other parameters.

Right now, we can’t distinguish between any of these models, but by April 15 we may be able to see which curve we are on. I’ve added data points for Santa Cruz County and for California, which are both about five days behind the national curve.

I made no attempt to make projections for the deaths. That number seems to be growing at a slower rate than the total number of cases, which probably indicates that recent testing has been uncovering a larger fraction of the actual cases than earlier testing, and that the growth rate for the actual number of cases is doubling about every 3.2 days, not every 2.4 days. If that is correct, we may see a slow-down of the number of cases that does not indicate saturation of the logistic model, but just testing catching up with the backlog of cases.

2020 March 27

Day off today, planning sabbatical

Filed under: Circuits course — gasstationwithoutpumps @ 22:47
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Today was a day off for University of California, celebrating Cesar Chavez Day, though the official day for that is next Tuesday March 31.  I did a little undergraduate director work via e-mail, but mostly took it easy today.

Trader Joe’s

I started the day by bicycling to Trader Joe’s to take advantage of their first hour for seniors (I’m over 65 now, so I qualify, though I don’t think I’m at particularly high risk). The setup was that they had two lines—one for seniors and one for others, allowing people to self-identify to choose which line to join.  The cart handles were being cleaned between uses and customers were getting their hands sprayed before being let in.  They were regulating the number of people at a time in the store, but the line moved fairly quickly, as people were not lingering in the store.

Trader Joe’s has always had super-wide aisles, so social distancing in the store was easy.  I quickly grabbed the stuff I had come for (most of my TJ staples: beer, cider, port, chocolate, paper towels, and soap) and checked out quickly so that others could enter the store.  I don’t think I need to go back to TJs for a couple of weeks, as I have at least a 2-week supply now of just about everything that I ever buy there (we got laundry detergent, cereal, and toilet paper a week or two before shopping got crazy).

Mowing lawn

After I got home from shopping (and scrubbing my hands and the doorknobs I’d touched), I got out the electric lawn mower and mowed both the front yard and the back yard.  The grass (and oxalis and wild onions and all the many other plants that make up my “lawn”) had gotten pretty long, but the plants were still soft, young plants, so the mowing went fairly quickly.  I even managed to fill my 40-gallon green-waste container with blackberry vines, ivy, and chunks of the dead rosemary bush.

Having sabbatical  this spring does mean that I’ll probably be able to keep the grass cut this year, for the first time in about a decade.  No 4′-high meadow with 8′ thistles this year!  Removing all the ivy and blackberries, though, is probably beyond me—filling the 40-gallon green-waste container weekly will probably be just enough to keep the current overgrowth from getting bigger, without making an appreciable dent in the 500 square feet covered with with them.

Preparing for sabbatical

I’m going to take this weekend off (sleeping, re-reading fantasy or science fiction books) and on Monday I’ll start working on creating video tutorials for sections of my book. I’m still debating how to do the visuals for the videos: prepared slides, pen on paper with a document camera, white board in front of the computer, or tablet and stylus.

I am not fond of prepared slides as a presentation style, though I know it has become the most common style for STEM lectures, so having a set of slides to bundle with the book might make it more attractive for instructors to adopt.  My lecture style has been more of an improvisational performance, triggered by questions from the students—that will not translate well to videos with no audience, so I’m going to have to develop a whole new teaching style for myself.

I’m looking at a few document cameras on Amazon ($100–$150), though I briefly considered making a stand for my cellphone (which has a 12MP camera) instead.  I think that having a USB-attached camera with a reasonably designed arm will work better with the various software I might use for making the video than trying to jury-rig something with my cellphone, so I’d be willing to invest in the document camera—if writing on paper works for me as a lecturing style.

The closest I’ve come to using that style in the past was in Spring 2000, after I had the bike accident that necessitated removing my spleen.  I had to lecture sitting down with an overhead projector until my ribs healed—I found it much more limiting than my usual large-whiteboard lecture style, as I could not build up an information-rich surface to point back to previous items on, as I had to keep changing pages.  Whatever I do for the videos is going to have the same problem, though, as the screen is a tiny, little window that can only hold one thing at a time.

I’ll probably also have to invest in colored markers if I lecture on paper—I write somewhat more legibly with a broad chisel-tip calligraphy marker.  I’ve only used black calligraphy markers in the past (the Itoya double-header), but I see that the same company makes colored ones in the same style.

I tried a whiteboard in front of my desktop for the last (optional) lecture of BME 51A.  It was not technically very successful—lighting and contrast were problems, as well as the size of the writing on the screen being too small.  I could try a small whiteboard with a document camera, but I suspect that it will not work as well as paper and calligraphy markers.

One big advantage of the document camera is that I can put small objects (like components or breadboards) on the screen easily—I even do that in some of my live lectures.

The most expensive option is to get a tablet computer (e.g., iPad or Surface) and pressure-sensitive stylus.  I’m not convinced that I’ll be able to write all that well on them, and interfacing them to software that let’s me switch easily back and forth between a head-shot camera, a small-parts camera, preprepared images, and the stuff-drawn-on-the-tablet may be difficult.

Of course, if I’m putting together a video, I don’t have the same time constraints that a live remote lecture would have, as I can film each scene separately and edit them together.  Editing takes up a lot of time though, so I’m not sure I want to go that route, rather than recording in one continuous stretch.  (Yes, I know the quality would be better if I spent a lot of time editing, but I’m not sure I have the time to do even quick-and-dirty tutorials on all the topics.)

Another big change for me is that I’ll probably have to work from a script, rather than doing an improv lecture.  That’s because I’ll need to do closed-captioning on the videos if I post them on YouTube, as the automatic YouTube closed captioning is ludicrously bad (see YouTube closed captions are awful), and it takes forever to put in the captioning unless you have a script already prepared.

Going from big whiteboard real estate and an improv style to tiny screens and tight scripting is going to be a big change for me.  It’s a good thing I have six months to experiment with different approaches and don’t have to go live on Monday  like most of my colleagues.

Unexpected consequences

One good consequence of the sudden forced switch to remote teaching is that there has been more discussion of pedagogical tools (Canvas quizzes, document cameras, tablets, zoom, take-home exams, …) among the faculty in the past week than there has been in the previous 5 years.

Unfortunately, all the discussion has been about lecturing and high-volume remote testing, with none about teaching writing, engineering design, or hands-on lab skills, which are the topics that really need attention (but which are probably going to be sacrificed in this quarter’s remote teaching).

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