Sunday, February 21, 2016

Bed-ridden reading

When you're flat on your back after (e.g. shoulder) surgery and you'd like to do something more than watch the boob tube, it is frustrating to realize you can't hold a book in position. E-books might change that.

There are several possibilities. You can mount a flatscreen monitor on the ceiling, and use a tablet at your hand with some kind of bluetooth interface to the monitor pickup, which would then control the monitor. This would allow other things besides just books, of course. You could fumble through your email, browse the web, or setup your own boob tube feed. However, room lighting might make it less than ideal. Room lighting (and the greater expense!) make projection on a screen on the ceiling even less attractive.

It would be easier to mount swing-arm type of holder (with stiff springs!) to the headboard for your e-reader or tablet. If you can lift your arm, it should be fairly easy to control. If you can't, a tablet should be within easy bluetooth range of a corresponding device you could have at your side.

Available on Amazon, turns out.


Saturday, January 04, 2014

Antenna charging

I've been at conferences in which the series of meetings lasted long enough to have participants scrambling for power outlets to keep their laptops running. Typically there aren't enough.

Suppose one were to attach an antenna that served as a charger, matched with a large broadcast antenna grid on the ceiling. The broadcast antenna measures backscatter and dynamically adjusts its broadcast distribution to focus as much power as possible on the receiving antennas. Starting with pulses, and dropping back to pulse mode from time to time, might make this easier.

In an auditorium a floppy charging antenna is likely to hang vertically, which isn't exactly ideal. So the antenna should be stiff like the old radio antennas, but even so I've been in crowded auditoriums where there such a thing would be parting the remaining hair of the fellow in the row in front, so this might not work very well.

There will be some wastage, which may not be acceptable in crowded rooms. If everybody is flopping antennas into the middle of a desk the level of wastage is probably safe.

The size and grid density of the broadcast antenna will determine the number of simultaneous beams (unless you want to cycle among them).


Wednesday, July 24, 2013

New cell phone state

Caller ID is great--I can often identify who is calling by the ring tone. In some cases I ignore the call and settle for voice mail later; especially when driving or in a meeting.

My phone is either receiving or not receiving a call. Maybe it is busy, or off, or I just haven't answered it yet, but no information can reach me until I pick up.

Suppose I specified that for some phone number, I was willing to accept additional data to be communicated during the ring. I could turn this feature on when driving. (I tried a bluetooth headset but the battery ran down quickly.)

  1. This could be a simple flag that turned on a "whoop" to indicate that this is an emergency call (e.g. please pull over and take this call).
  2. It could be a text message that text-to-voice turns into an additional spoken message during the ring (e.g. "You left your passport on the table!").
  3. It could be a chunk of speech sent as data that gets appended to the ring tone.

This isn't something to turn on during a business meeting, and there are opportunities for mischief if somebody gets hold of your phone and resets permissions for you. And the police would probably want to be able to override preferences ("Please pull over now and wait in your car").

There are times it would be handy, and it doesn't seem as though it should be hard to implement.


Thursday, October 25, 2012

Parallelism in disk readout?

Suppose you have a high performance RAID array; just for laughs say RAID6+1. The read speed is significantly faster than the read speed for a single disk, and the mirroring helps preserve the data from loss when one drive dies. Seems cool, though pricy; and people use them all the time.

But how easy is it to back up? Don't ask. Unless you get the full bandwidth it takes a long time to back up 80TB or so, and even with full bandwidth it takes a while.

Suppose your chassis was designed for a particular RAID configuration (instead of being customer-selectable). Let it be, instead of Nx2, Nx3. Instead of having a single mirror, you have 2, one of which is read/write and the other of which is "write only" for the main controller.

However, each of the drives in that third "write-only" row have their own independent controller. (For the moment forget about spares. They add some complexity but nothing overwhelming.) Each controller is linked to a multiplexer that manages 2 or 3 drives and communicates over a fibre-channel connection.

Now suppose you have a second chassis with N drives, each of which has its own controller similarly linked to a multiplexer. A bundle of fibre-channel cables connects one chassis to the other.

  1. The chassis is told that a backup is at hand, and senses the presence and health of the other chassis
  2. The chassis pauses all pending reads and writes
  3. When all active reads and writes have completed, the controller takes a snapshot, and releases the pending reads and writes
  4. The controller releases all drives in the third (write-only) row and instructs the sub-controllers to begin
  5. Each sub-controller communicates with its companion in the backup chassis, and writes the blocks on its disk to the other.
  6. When the last copy is done, the sub-controllers relinquish their disks back to the main controller.
  7. When the main controller has full control again, it pauses pending reads and writes again.
  8. When all active reads and writes have completed, the controller takes another snapshot, and releases the pending reads and writes
  9. The controller uses the incremental change between snapshots to update the disks in the third row.
  10. When the update is complete, another pause and snapshot is required to take into account the changes that happened while the update was happening
  11. A few iterations may be needed until the incremental is small enough that the system may be acceptably frozen long enough to make the final update.
  12. The three rows are now again in sync, and the backup chassis holds a consistent backup of the system. It can be removed and stored, or whatever is desired.

Restoration uses the backup chassis as a source and a high-performance one as a target.

How long will such a backup take? A 3TB disk being read at 250GB/hour will take about 6 hours. That's better than a full backup any other way I know of (I'm not counting synthetic full backups. If you lose one of the "deltas" you're up the creek.)

I shudder to think how much this would cost. But I wish we had a few at work.


Sunday, October 02, 2011

Which type of stroke?

The blood supply to the brain is a web encased in a rigid box. I'd not expect the blood vessels to be able to expand much--between brain tissue and other fluid around them, there's not much to compress and no room to go thanks to the skull. But there should be a little elasticity to the blood vessels, and there are so many that the effect should add up.

With each heart beat we have a more or less predictable pressure wave going into the network, and so there should be a consistent pressure wave coming out. It can't be exactly the same shape, because in different parts of the network blood travels different distances facing different impedances, but it should be consistent.

Now suppose some major vessel has broken and there is bleeding in the brain. If the blood loss is significant I'd expect there to be a change in the wave shape. In particular, blood would leak out of the broken vessel and slowly reenter, giving the output pulse a longer tail.

So the obvious questions are:

  1. Are the output pulse shapes (maybe convoluted with the input pulse if need be) consistent enough between people that we can use differences for diagnosis?
  2. Is the tail from a leaky vessel discernible in the output pulse, and if so at what level?
  3. Are there other things that would mimic this?

You have to measure the input also, since a long tail on the input is quite possible, and you'd need to correct for that.

If it is possible to distinguish a leaky vessel-brain from a normal one, it would be possible to distinguish a broken blood vessel stroke from a clot blockage stroke. (The instrumentation shouldn't be very expensive--transducers and some ADCs and a small processor to compare the results--a display if you want to get some human input.) Since you don't want to use blood thinners to treat someone with a broken blood vessel stroke, and since getting treatment fast is vital, this might be useful in an ER.

I don't think it would be possible to positively ID a blockage this way, since that would merely appear as larger impedance, and without some prior measurements you wouldn't know if this was normal or not--brains are different.

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Tuesday, January 11, 2011

Font Directories

Eldest Son told me that the printing programs he is learning lock out most fonts so that the user isn't swamped with pages upon pages of fonts. The "book" classifies them as text, dingbats, symbols, script, and a few other things.

That doesn't make any sense. I don't know enough about fonts to devise a scheme myself, but just from inspection you can make general categories. My untutored eye says there are blocky fonts, and shaded fonts, and fonts that are good for tiny print, and such like things. A given font may wind up in several different categories--which seems harmless.

Suppose one imposes a directory structure on the fonts, and uses links to insert them in multiple places as needed. For example, if you want to search alphabetically, there's a "B" directory that contains links to all the fonts with names that start with "B". If you want German Black Letter, there's a directory for German fonts, as a subdirectory of the NonEnglish directory. The icon for the directory has not one (as Windows uses now) but multiple images of the letter A illustrating some of the directory's contents: or from subdirectories if the directory contains nothing but subdirectories.

It'd take some work to devise the scheme and implement it, but searching that would be a lot easier than scrolling down a few hundred options.

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Friday, October 01, 2010

Aspergers and theater revisited

A few years ago I mused about the possibility of teaching roles and how to detect them using theater. We were not able to schedule any kind of formal therapy along these lines. There was a local person who was interested in this sort of thing, but unfortunately she/he had some personal issues and went transsexual--and, though she had been given no introduction or description, our daughter was weirded out just meeting him/her/whatever. That did not seem a good match. It was encouraging to think that even with Aspergers our daughter could instantly detect that something was seriously different, and probably wrong. But that group wasn't going to work for her. We encouraged our youngest daughter to join a theater group in high school, partly to help her with finding a role in the chaotic mess and partly to help with learning about role-playing and detecting roles as described earlier. She found it frustrating at times, but learned to enjoy it. It is nice to have clear-cut lines and roles, and she did well at that. She loves opera and the great romantic/tragic characters, but opera doesn't always have the most realistic dialog and roles... I wish I could say there were breakthroughs, but this has been and still is an incremental process.

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