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Comment Re:I don't see much point in this (Score 1) 64

I think Twitter is a bit faster than that. Twitter users in Japan seem to respond really fast when they feel any moderate level of shaking; at times, if you follow enough Japanese people on Twitter, your entire timeline gets filled with people saying "oh hey, something's shaking" or "it's rocking" or "boobs!". So yes, you will get advanced warning if there are people closer to the epicentre than you posting on Twitter (and as long as they are not using a certain phone provider which got overloaded during the big earthquake/tsunami last year while all the other providers were fine). And yes, this obviously doesn't work if the earthquake knocks out all the cell phone infrastructure in the areas between you and the epicentre.

Amusingly enough, I was watching a UStream broadcast run by some Japanese guy and people from a different area of Japan told him that they just had an earthquake, and he replied saying he didn't get any info here. Then, several seconds later, the earthquake alarm went off in the broadcast. So, I think Twitter isn't going to be very far off in terms of speed and definitely should be able to inform you about an ongoing earthquake as long as it's not a super short one and you're like next to the epicentre.

Comment Re:For those who still don't get it (Score 1) 98

The analogy kind of works and kind of doesn't. A parallax barrier has an image layer and a fixed mask layer. What these guys did was to allow for multiple layers with time-varying patterns and optimize the pattern on each layer so as to create a better image. So it's more like "this is to integral what parallax on crack is to lenticular."

Comment (Score 2) 98

The company website is scant on details of their technology, but it's obvious that a different implementation is used and my guess from what they do say is that it's a lenticular device that only generates horizontal parallax. In that case, try tilting your head 90 degrees to the side and you'll lose depth perception, whereas this wouldn't be the case for the tensor display mentioned in the article. It might not be that important of an issue, until you want to lie down on a couch and watch a 3D program on TV...

Comment Re:It's a tensor display. (Score 4, Informative) 98

Oh interesting, so they finally gave it a name. I remember coming across the 2-layer version of the display sometime ago. Looks like they also have an interesting theoretical foundation to go with it; the abstract of the first paper from Gordon Wetzstein's page gives a nice overview.

What essentially is going on is that you can model (at least when talking about things much larger than the wavelength of light) light as a four-dimensional function (i.e. intensity of light along all the possible rays that fill space), which is referred to in this research area as a "light field." Putting a mask somewhere in space will mask out a 2D-extrusion of the mask shape in 4D space. Putting multiple masks at different planes will mask out the product of this 2D-extrusions (and the extrusion angle varies as a function of depth). Hence, what they are doing is attempting to piece together the original 4D function by piecing together unmasked portions at each time frame.

For a more simplified view, you can think of this as trying to create a 2D picture through a sequence of special single-color 2D pictures created by placing stripe patterns oriented at a fixed set of angles on top of a light panel.

If you've taken linear algebra, it is somewhat like decomposing a matrix into a sum of rank-one matrices, except here each component needs to be positive (masks cannot create "negative" light).

Comment Re:Bad system design? (Score 2) 88

There's plenty of other stuff in there making up the total system weight: structural framework, power supplies, and of course the mercury delay line memories, which were basically big sealed tanks of mercury. It also seems to have had magnetic drum storage, another heavy component. And I doubt weight of the system was a major concern anyway, as long as the floor could support it.

Comment Re:Why did these require so much power? (Score 2) 88

Perhaps because the low-power tubes were considered unsuitable for computing applications? Vacuum tubes in digital switching circuits have quite a different workload from those used in radios as amplifiers. The low-power tubes may not have provided fast switching performance, or they may have been unreliable in switching circuits. I'd think that power usage was a secondary concern for the designers of these computers; reducing it would be nice, but not at the cost of speed or reliability.

Comment Re:Help Me Out Here (Score 3, Interesting) 532

They're Iranian Air Force roundels: the outer ring is green instead of the blue used by the Royal Air Force. Although the Iranian Air Force's officer corps was purged after the Islamic revolution, its markings are only slightly modified from those of the old Imperial Iranian Air Force, which dates back to 1920, two decades before the occupation by the British during World War II. So it's not surprising that they were modeled after the British ones--or perhaps the French ones, since the French were actually the first to use the roundel. The French one is almost identical to the British, except that it has red on the outside and blue in the center. Anyway, the three-ring roundel is a very popular insignia for military aircraft, and lots of countries use it.

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