Wikipedia:Reference desk/Archives/Science/2016 January 1

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January 1

Process capability index

How come the Process capability index is abbreviated as $C_{pk}$ instead of $C_{pc}$? Where did the "k" come from? 731Butai (talk) 05:19, 1 January 2016 (UTC)

This article[1] says that the k stands for "centralizing facteur" [sic]. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:40, 1 January 2016 (UTC)

One guy claims it stands for a Japanese word.[2] ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:44, 1 January 2016 (UTC)

On here, someone makes the same claim, but someone else says that that's wrong and it actually comes from the "k-statistic", which she says is an old name for the z-statistic (otherwise called the standard score or z-score). She says this in an authoritative manner, but I would not know. For what it's worth, k-statistic apparently has a different meaning today. --76.69.45.64 (talk) 07:41, 1 January 2016 (UTC)

Other compounds of Krypton not included

A quick web-search turns up: Krypton Tetrachloride KrCl4; Krypton Difluoride KrF2; Krypton Hexabromide KrBr6; Krypton Dichromate Kr2Cr2O7; Krypton Chromate KrCrO4; Krypton Tetrafluoride KrF4; and Krypton Dioxide KrO2. Is there any reason none of these are included? There may be, but it's not obvious what it is. Eldin raigmore (talk) 06:44, 1 January 2016 (UTC)

Because you didn't add them to the article?--Jayron32 06:51, 1 January 2016 (UTC)

Any content to be added would need a WP:RS citation. Careful..."a quick web search" can turn up lots of material that does not meet the verifiability requirement for encyclopedia content. For example, all I see in google for "krypton dichromate" is its use as a distracter in a multiple-choice problem-set that is solely about chemical nomenclature. DMacks (talk) 22:41, 1 January 2016 (UTC)

References

Wedge-Tailed Eagle eyesight

Recently I read that wedge-tailed eagles can see in both the infra-red and ultra-violet spectrums as well as in the normal range of human sight. What I'm wondering is how do people know this? The only idea that I could think of is that dissection of the eye has led to people thinking this. If so, what differs from the eagle's eye to our own? 1.136.96.24 (talk) 09:15, 1 January 2016 (UTC)

so where did you read this, and why didn't you ask the author? Greglocock (talk) 10:10, 1 January 2016 (UTC)

Sorry here is the link to the page: Wedge-tailed eagle#Behaviour and diet, and that paragraph has not been sourced. 1.136.96.24 (talk) 10:28, 1 January 2016 (UTC)

If it hasn't been sourced it quite possibly is incorrect. It says here "birds do not see above about 700 nanometers. While some birds range into UV, IR light is as invisible to them as it is to us" and, although it's a blog, it's well sourced. From that, one way to tell is to see if the birds react to IR or UV illumination. Richerman (talk) 16:13, 1 January 2016 (UTC)

You should also read the following:

• http://skeptics.stackexchange.com/questions/30796/is-this-comparison-of-wedge-tailed-eagles-and-bald-eagles-accurate

• http://physics.stackexchange.com/questions/147746/why-human-and-most-of-vertebrates-cannot-see-near-infrared-light-720nm-1500nm

I've deleted the assertion about IR from the article. Richerman (talk) 16:31, 1 January 2016 (UTC)

Okay, thanks. 1.136.96.238 (talk) 19:58, 1 January 2016 (UTC)

Chess computer calculations

When it's stated that chess engines evaluate millions moves per second, do they include Tal-styled sacrifices of heavy pieces that superficially look losing? Or the calculations stop whenever they see a heavy piece sacrifice due to famous materialistic computer approach? I know that computers can sac light figures, but what about heavy pieces in exchange for unstoppable attack? Brandmeister^talk 09:37, 1 January 2016 (UTC)

Our article Computer_chess states:

Chess programs differ in terms of how and what types of pruning and extension rules are included as well as in the evaluation function. Some programs are believed to be more selective than others (for example Deep Blue was known to be less selective than most commercial programs because they could afford to do more complete full width searches), but all have a base full width search as a foundation and all have some selective components (Q-search, pruning/extensions).

It goes on to say that "In addition to points for pieces, most evaluation functions take many factors into account, such as pawn structure, the fact that a pair of bishops are usually worth more, centralized pieces are worth more, and so on." So it sounds like some engines might exclude heavy sacrifices outright, while others might just highly penalize them in the evaluation function. OldTimeNESter (talk) 10:29, 1 January 2016 (UTC)

The cost of searching is an exponential function of depth, with quite a large multiplier. Shallow searches are so cheap that it is worth performing them even for moves that look very bad. In other words, no serious program is going to miss a sacrifice on the next move that pays off three moves later, regardless of how large the sacrifice. The possible difference comes in a situation where the computer is exploring, say, the possibility of a large sacrifice five moves in the future, which doesn't pay off until five moves after the sacrifice. Looie496 (talk) 18:07, 1 January 2016 (UTC)

With a fixed availability of compute power, you have a choice:

1. to do a 'shallow' search - just a handful of moves ahead - then use a lot of horsepower to evaluate the resulting board positions by looking at a bunch of heuristics (less lost pieces is good, strong pawn structure is good...etc). You hope that the resulting scores are accurate estimations of the 'goodness' of the board position.
2. to do a 'deep' search - looking as far into the future as possible - then doing a very rapid scan of the gazillions of resulting positions. Because you're examining many more possible future board positions, you don't have as much time to do a really detailed analysis of each position - but hopefully, by looking further into the future, you don't have to.

Deep blue mostly does the latter. Calling it a "computer" is slightly misleading because most of the computational power came from custom circuitry that did nothing but search and score positions - they were not programmable in the normal sense of a computer - just dedicated circuitry. This super-fast hardware allowed it to look deeper into the future than other chess systems - but that inherently limited the complexity of the board position scoring system.

Both approaches will tend to "prune" the rapidly exploding "tree" of possible board positions by rejecting the obviously bad ones and looking deeper into the more promising-looking ones.

These approaches mean that sometimes a deliberate sacrifice of a high-value piece will be noticed as a "good move" for the computer because the search is deep enough to "see" the ultimate payoff...but other times, if the payoff is too far into the future, the benefit will be missed. Shallow search plus complex scoring systems result in chess programs that aren't good at seeing long-term benefits of sacrifices - deep searchers do much better at that. But deep search software can't easily make use of the many 'rules of thumb' that human chess players know about board position strength - such as measuring how blocked or unblocked various pieces are - so they may fail completely to 'understand' the value of things like pawn centrality, having to 'deduce' the value only by searching future board positions that result from having good versus bad pawn positioning has on other simpler metrics such as the value of captured pieces.

Both approaches can produce great chess computers - but the deep search approach is superior when custom hardware is involved because you can use a large quantity of identical chips that are individually very fast - but very stupid devices.

SteveBaker (talk) 04:44, 3 January 2016 (UTC)

U.K. ceng

Does the UK Engineering Councils Chartered Engineer (UK) status count as a level 7 qualification in the National Qualifications Framework if you get it without a masters degree? 90.201.187.44 (talk) 17:12, 1 January 2016 (UTC)

No. A CEng on its own is not an educational qualification, and therefore doesn't count on the Qualifications and Credit Framework scale. This is the official register from Ofqual - the Engineering Council is not listed as an accredited organization (although McDonalds and the Worshipful Company of Spectacle Makers are). Tevildo (talk) 19:53, 1 January 2016 (UTC)

It seems you need to reach level 7 qualification to obtain UK Chartered Engineer status. I don't see how you can obtain it without being at this level, independent of the route to it. --Llaanngg (talk) 21:49, 1 January 2016 (UTC)

Yes, the CEng requires an MEng degree, but it isn't itself an academic qualification. Someone interested in your qualifications will want to know the details of the underlying MEng, not the resulting CEng. Tevildo (talk) 23:12, 1 January 2016 (UTC)

You can get CEng if you can demonstrate you've met the learning objectives equivalent to an MEng. 2A02:C7D:B91D:CC00:4DD8:2342:2A48:E95F (talk) 00:30, 2 January 2016 (UTC)

Indeed, and you can get grandfathered in if you met the academic qualifications at the time you graduated. Somewhere in a box I have a letter confirming that my BA was sufficient. Greglocock (talk) 02:22, 2 January 2016 (UTC)

Humid desert climate?

I've noticed that Dubai is pretty humid, but it's still classified as a desert, and based on vegetation coverage of the surrounding area the classification is warranted. So, two questions.

1. Why is Dubai not fertile? Why doesn't the humidity provide moisture for many plants?
2. Why is Dubai sandy? I thought that hot deserts were sandy from temperature extremes (day vs night) breaking the rocks from contraction and expansion. And the humidity of Dubai means that the day–night extremes are not very severe.--Leon (talk) 21:29, 1 January 2016 (UTC)

It's probably like the difference between drinking champagne and breathing the vapors. Sagittarian Milky Way (talk) 22:30, 1 January 2016 (UTC)

It's possible that the humidity rarely reaches the level where precipitation occurs. In that case, not much of it gets into the soil, apparently not enough to support crops. StuRat (talk) 04:39, 2 January 2016 (UTC)

Sulfuric acid spill

The recent sulfuric acid spill in Australia has taught me something new -- I didn't know the corrosive liquid is transported in such a vast quantity. I suppose it is for industrial uses. I'd like to know if it is common to transport it in such a massive quantity? --BorgQueen (talk) 21:35, 1 January 2016 (UTC)

I can't cite any sources, but I remember reading somewhere that it is among the most common industrial chemicals, and, yes, produced and transported on a massive scale. —Steve Summit (talk) 21:40, 1 January 2016 (UTC)

According to sulfuric acid, 180 million tonnes were produced in 2004. It is among the most commonly produced chemicals [3] and has many uses. I'm sure it is pretty common to transport it in large quantities, though I don't have an immediate reference. Dragons flight (talk) 21:47, 1 January 2016 (UTC)

As one datapoint, estimated total 200,875 railcarloads of sulfuric acid in the US for 1998 through 2001.Surface Transportation Security, vol. 20, Transportation Research Board (NCHRP Report 525), 2006, p. A-8 DMacks (talk) 22:24, 1 January 2016 (UTC)

Sulphuric acid is far from the worst chemical transported at scale. There used to be whole trainloads of liquid chlorine passing near my home town. Caused some concern, as you may imagine. Fgf10 (talk) 23:49, 1 January 2016 (UTC)

Just hope they don't transport the liquid chlorine in the same train as something that might explode in an accident. --76.69.45.64 (talk) 01:16, 2 January 2016 (UTC)

See also Graniteville train disaster. No explosives necessary. Tevildo (talk) 01:46, 2 January 2016 (UTC)

That's also very bad, but it's a different problem from the one in Mississauga. --76.69.45.64 (talk) 11:09, 2 January 2016 (UTC)

Senior scientist

How comes that a common term such as senior scientist doesn't have an article (or a redirect)? --Leyo 22:52, 1 January 2016 (UTC)

It is listed in List of academic ranks. I am not sure a redirect is needed.--Llaanngg (talk) 23:28, 1 January 2016 (UTC)

Thanks. If the redirect in Adiunkt is fine, it would be fine here, too, I guess. --Leyo 23:43, 1 January 2016 (UTC)

I think common is a relative term here. I'm guessing it may be common in some countries (Canada and translated from Bulgarian, according to our table?), but I've never heard it here in the UK as an academic 'rank'. It seems a rather non specific term. We prefer more descriptive terms (for instance, I am a research associate) Fgf10 (talk) 23:47, 1 January 2016 (UTC)

"senior scientist" site:ac.uk gives ~7500 Google hits ("senior scientist" site:.ca ~44000). I would say, it's common enough. ;-) --Leyo 00:41, 2 January 2016 (UTC)

True, but "research associate" site:ac.uk gives 154,000 Google hits, "research fellow" site:ac.uk 326,000 and "principal investigator" site:ac.uk 236,000. Still say it's not particularly common. Fgf10 (talk) 11:56, 2 January 2016 (UTC)

How many of these pages use the phrase as a formal title, and how many use it as a vague description (like "celebrity")? —Tamfang (talk) 09:30, 2 January 2016 (UTC)

I cannot count them, but many are used like titles: Associate Professor & Senior Scientist, Emeritus Professor and Senior Scientist, Senior Scientist and Director, Name, Senior Scientist, Organization etc. --Leyo 12:40, 2 January 2016 (UTC)

Note that several of those don't seem to be academic ranks but positions or titles outside academia and in fact not all of them are in the UK (although I'm fairly sure the position/title is used in the UK particularly outside academia, the job search for example seem to find some in the UK). Notably, all the senior scientists listed in the last ref are listed under industry, even those at UCB. (Well there is only one, the other is a senior principal scientist.) The second last one seems to be at the at the Museum of Natural Sciences although the person is also at a university albeit with what I assume is a non-teaching position (Research Professor). So while you could say the person is an academic, it's not so clear if the senior scientist position should be considered an academic rank. The other two seem to be clearly academics albeit the senior scientist positions are at a research unit in the university and over clinical trials respectively. Still you could perhaps say these are academic ranks.

Of course this is complicated by the fact that there's no simple definition of an academic, you're likely to get disagreements.

A research associate or fellow at a university is often included even though they have no real teaching (at most they may assist research students in some capacity) with the traditional assumption that they are either going to advance to a teaching position or move away from academia. However someone with a senior research position at an independent institute or particularly a private company is generally not going to be considered an academic, even if they are co-supervising a student. Research professors or similar more terminal research-level positions at universities may also be considered an academic even though their role and job may be fairly similar to someone at an independent institute. (At the very least, it makes sense to list them with other academic ranks.)

Nil Einne (talk) 04:52, 3 January 2016 (UTC)

(EC, written but unsaved a while ago) I'm not sure if just concentrating on it being an academic rank is correct anyway. While some senior scientists may be in academia and in some places it may even be a common academic rank, since it seems to imply a research only role it may be it's not common in certain places like the UK where such roles are uncommon in academia at such a senior level. However there may still be senior scientists outside academia, for example in independent research institutions (private or public) and in private companies. The searches in the UK sort of support the idea this may be where the position is most common in the UK. Nil Einne (talk) 13:27, 2 January 2016 (UTC)

What about a disambiguation then? --Leyo 17:04, 3 January 2016 (UTC)

Disambiguation is to help a reader select among relevant articles. Many medium to large companies with a research and development department have senior scientists, and each company has its own definition of what a senior scientist is, so the term is too diffuse to have a clear meaning that we could write an article about. Thus, there isn't any article to which the proposed disambiguation page could refer the reader. Bear in mind that Wikipedia is not a dictionary, so a one-sentence explanation of what a senior scientist is belongs in a dictionary, not Wikipedia. Jc3s5h (talk) 17:15, 3 January 2016 (UTC)

There actually is at least one article, List of academic ranks, where Senior scientist is listed. --Leyo 20:37, 3 January 2016 (UTC)