Wikipedia:Reference desk/Archives/Science/2014 October 12

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October 12

Finite State Transducers

We're learning to create FSTs for simple algorithms (drawing them by hand on paper) in class. I was wondering if we can have a string (as opposed to a single letter) as the input. The rest of the FST accepts single letters as inputs, but I need to substitute the ending "SSES" with a null character (epsilon) and I was wondering if I could do that in one step instead of having four states that accept S, S, E and S in a sequence. Is that a legit way to do things? 202.153.41.162 (talk) 06:09, 12 October 2014 (UTC)

An FSA reads not "strings" or "characters", but symbols. It's up to the programmer how he or she maps the input to the FSA's input alphabet. In this case I think defining the four-character string "sses" as a symbol on its own is a bit pointless, but it's a totally legit approach when dealing with multibyte unicode sequences, for example Asmrulz (talk) 09:30, 12 October 2014 (UTC)

Consider an FSA which matches a regexp such as "a?" (zero or one a) and looks like this. A non-UTF-8-aware regex engine, given "Щ?" as the regex (the letter Щ is represented by two bytes, 0xD0 0xA9), would construct the wrong FSA from it, one that matches "0xD0(0xA9?)" instead of "(0xD0 0xA9)?". So, yes, it can make sense to treat a mutibyte sequence as one symbol. On the contrary, a regex engine which insisted on treating multibyte sequences as single bytes, although it could handle "Щ?" by automatically parenthesizing the input (as I did in the example above) and constructing an FSA which is a sequence of states (one for each byte), would still stumble over character class expressions such as "[ЪЩ]?" (match zero or one of either Ъ or Щ) Asmrulz (talk) 10:57, 12 October 2014 (UTC)

This is just a notational shorthand, and it's obvious what it means, so there's no reason not to allow it. You should check with the instructor before using it, though. -- BenRG (talk) 18:01, 13 October 2014 (UTC)

Binomial authority for Octopus tetricus?

Hello, Reference desk/Science people. Multiple reliable sources state that a "Gould" is binomial authority for this octopus species. (Why this species? Why now? Because it is in the news.) There are many Goulds, and I've guessed that Augustus Addison Gould is the binomial authority. Am I way out of line and/or way off the mark here? Pete AU aka --Shirt58 (talk) 10:57, 12 October 2014 (UTC)

According to this paper, a similar octopus (O. ornatus) was collected by Gould (of "Gould 1852" fame) on the United States Exploring Expedition. Augustus was indeed a member of this expedition, so the identification is almost certainly correct. Tevildo (talk) 13:49, 12 October 2014 (UTC)

So... obvious octopus is octopus, amirite? (In my ill-advised BSc freshman year, it appears the professors who gave me quite a good grade in Zoology 101 might possibly have been right... but the professors that gave me record-breaking failing grades in anything to do with maths and physics were over 9,000 percent right.) Thanks Tevildo! --Shirt58 (talk) 10:52, 13 October 2014 (UTC)

Kite-powered ships and yachts

Is there a category for ocean-going vessels such as the MS Beluga Skysails that use kites? I am also interested in mass produced yachts, of perhaps more of the Chevy Volt or Plug-in Prius variety than the Tesla Model S, as I believe diesel fuel will be carbon neutral in years to decades. 76.88.167.15 (talk) 13:40, 12 October 2014 (UTC)

I'm rather skeptical that the kite will last long enough to pay for itself, then there will be the pollution of the wrecked kite to deal with. The company may get some PR benefit that still makes it a net positive, though, but that wouldn't last if everyone had one.

As opposed to fuel which is guaranteed to disappear 100% the instant you use a joule of it. Except for the part you chug back into the atmosphere as pollution, of course. But sure wind pushing at fabric can't last any appreciable amount of time. How could it last more than "an instant"? 91.120.14.30 (talk) 17:47, 13 October 2014 (UTC)

Come on, they were dealing with sail ripping with 3000 B.C. technology. I don't know how far development got in this regard by the clipper ship era (i.e. maximum mph wind before they have to be taken down and stowed), but that modern Furious Fifties yacht race (Volvo?) in the windiest waters on earth probably has them beat. Anyway they can always design the kite to fly like a flag when cables 1 and 2 are given some slack, where it should become easier to pull it in and secure for the duration of the storm. Also a kite of more expensive very strong material like Kevlar should stay during the storm and provide wicked propulsion-to-area ratios. Heck, the world's largest ship (FLNG Prelude) can survive 156 mph hurricanes. They could go ridiculous fast if they could harness that and get past the ship version of the sound barrier. Sagittarian Milky Way (talk) 21:59, 13 October 2014 (UTC)

As for the carbon-neutral diesel, I assume you mean biodiesel ? StuRat (talk) 18:45, 12 October 2014 (UTC)

No, abiotic diesel from power to gas and gas to liquids is much quicker at the same efficiencies. I am looking for something like [1] or [2] easy to park, easy to pull, easy to anchor in current and run propellers as a generator (regenerative breaking?) or a robot like [3]. 76.88.167.15 (talk) 21:20, 12 October 2014 (UTC)

Where is the energy coming from to power the gas to liquids? There's no such thing as a free lunch. You can't just burn something into a gas and convert the gas back to liquid without getting energy from something else. Why not power your ship with that something else to begin with? --OuroborosCobra (talk) 21:31, 12 October 2014 (UTC)

I don't think Wikipedia is sufficiently developed in this area, but certainly the move to kite-powered/aided water travel looks attractive. As you suggest, an auxiliary power source would be essential for manoeuvring and when wind power is inadequate. Future-oriented thinking might lead one to consider more efficient options than displacement hulls, such as a large kite with an underwater wing (foils), between them lifting the hull from the water.

Using diesel as a carbon-neutral-to-be power source is a leap of faith. Since the demand for diesel is substantial and will presumably not remotely be satisfied by carbon-neutral sources for decades (and thus small deltas in demand will have no effect on carbon-neutral supply), all extra diesel that is consumed will be sourced from non-renewable sources for decades. So unfortunately one cannot pretend that diesel consumption by anyone (even those who insist on renewable sources) will be carbon-neutral. —Quondum 23:43, 12 October 2014 (UTC)