Wikipedia:Reference desk/Archives/Science/2015 July 9

= July 9 =

Steel mill
In a fully-integrated steel mill (one that has its own blast furnaces, coke ovens, ore concentration plant, forming operations and so on), what is the noisiest piece of equipment (besides the forging press, of course)? 2601:646:8E01:9089:F88D:DE34:7772:8E5B (talk) 04:32, 9 July 2015 (UTC)
 * I've been next to a Trip_hammer and ear protection is a must. 196.213.35.146 (talk) 06:58, 9 July 2015 (UTC)
 * See also Stamp_mill and Ball_mill. 196.213.35.146 (talk) 07:03, 9 July 2015 (UTC)
 * OK, so the noisiest is the power hammer/forging press (just like I thought), and then the stamp mill/ball mill for the raw ore? Thanks!  Any other particularly noisy machines in a steel mill? 2601:646:8E01:9089:F88D:DE34:7772:8E5B (talk) 03:44, 10 July 2015 (UTC)

Control and communications engineering
This is often advertised by colleges and companies as the design of systems such as ventilation, fire management etc but what does the engineering discipline involve specifically? Does it involve a lot of certain types of calculations? Programming? Building a network map? 94.10.240.191 (talk) 09:59, 9 July 2015 (UTC)


 * I worked in communications and control in the Marines, schooling at 29 Palms. I also took multiple classes in communications and electronics controllers. The areas of study were mostly electronics. It was memorization of a lot of protocols. For example, if you want to connect a TPS-32 radar to an opsat, you need to know how the data is formatted and transmitted on both ends and, as needed, convert it. You will need to understand analog vs digital signals. It isn't what I consider to be a difficult field. The entire school from "these are what we call numbers" to "now you can create your own communications interface" in the Marine Corps was just 13 weeks. 209.149.114.69 (talk) 12:35, 9 July 2015 (UTC)
 * I am curious if the Marine Corps calls this occupational specialization "engineer", "technician", "operator," "rifleman," or if they use some other terminology. I have no doubt that you worked with advanced technology, but I am not sure that this is "engineering."  I have been led to understand that most Engineers in the Marine Corps are warrant officers or commissioned officers who have  (typically) completed a four-year degree in engineering.  Nimur (talk) 17:25, 9 July 2015 (UTC)
 * My MOS was 5963 (which is retired). My job entailed troubleshooting electronic circuits in radar and communication equipment, be it in communications, processing, power, or interface. I had to identify the defective part, which could be an IC, but was more likely a blown transistor or capacitor. Then, replace it. On deployment, when interfacing with foreign equipment, I had to customize electronic circuits to simply "make it work". We regularly made analog-digital converters and "elbows" which converted serial-parallel communications and, in my latter years, I did a lot of copper-fiber converters. We did have a warrant officer. He was a good guy, but he was just a paper pusher. Nobody above E5 (sgt) did real work. There wasn't much reason for an officer to ever walk away from a desk. As a joke, we replaced many officer's desk chairs with toilets so they wouldn't have to ever leave. 209.149.114.69 (talk) 18:10, 9 July 2015 (UTC)
 * With respect, it sounds like you had a pathological relationship between your enlisted ranks and your officers. This is unfortunate, and it doesn't reflect my experience with Marines: it is important to have mutual respect between enlisted Marines, officers, and civilian employees, with recognition that we all fulfill different roles in the organization.  At the same time, surely you know that some important work is done at a desk.  "Officer" and "office" have the same etymology for a reason, and it's no surprise that many members of these ranks sit at a desk while performing duty.  For example, who made sure that you had the resources you required to conduct your duties?  ICs don't occur naturally: an organization must communicate its needs, interact with a contractor, facilitate the design of these specialized parts, ensure that replacements are available in whatever country your deployment might take you... all so that you can repair it when it breaks!  The work you saw was surely difficult, but it was only a small part - perhaps the most tangible part - of the entire scope of the operation of a technologically-equipped military.  One difference between a technician and an engineer (or, an enlistee and an officer) is that the less tangible work is not typically assigned to the enlistee or the technician; and the direct, tangible work (like soldering wires, lifting heavy objects, and shooting powerful rifles) is work that is rarely assigned to the engineer or the officer.  I bring this up because it may serve to help the OP formulate their idea about what an engineer does.  Surely an engineer can learn to do the work that a technician may do; and even a Marine General is capable of firing a rifle; reciprocally, I believe that a smart technician or an ambitious Marine could serve well in the reciprocal roles... but that would probably entail a change of "title."
 * Addressing the concerns about officers and desk-work: Engineers also usually perform their work while seated. I used to joke about the liberal arts students at university who could conduct class outside: they just needed a pleasant novel and a quiet grassy spot in the sun!  The engineering students could never do this!  To conduct class outside, we'd need to bring a computer, a table of integrals, two textbooks, scratch paper, a digital multimeter, a bench power supply, at least two oscilloscopes, so we'd need to take a desk with us... !
 * Nimur (talk) 01:23, 10 July 2015 (UTC)
 * At university level, control and communication engineering are concerned with the mathematical/applied concepts of control theory/control systems and communication theory//communication systems respectively, and are often (though not always) taught as part of the electrical engineering curriculum. Abecedare (talk) 15:16, 9 July 2015 (UTC)
 * So there's not much maths involved? 94.10.240.191 (talk) 16:42, 9 July 2015 (UTC)
 * Did you read the articles linked above? Most people consider dynamical systems and assessing Lyapunov_stability to be fairly mathy. That said, I don't know if e.g. 209...69's experience required a strong background in differential equations, but as an academic topic, there is certainly lots of math involved. Perhaps we could give you more specific explanations if you linked to a specific course program you are interested in. As Nimur points out, there will be a lot of variation in terminology. Perhaps one can be trained to hookup certain hardware bits without doing much math, but serious design and analysis of control systems definitely requires some serious mathematical background. However perhaps you could install or service one without being able to solve differential equations. It all depends on the course programs and job requirements. SemanticMantis (talk) 17:33, 9 July 2015 (UTC)
 * Along the same lines - even if you are involved in civilian work - you can learn technologies, operate sophisticated machinery, and generally immerse yourself in engineered systems without actually being an engineer: rather, without practicing the very rigorous disciplined mathematical approaches that engineers use. However, to actually conduct engineering, you will need math, and lots of math.
 * The Occupational Outlook Handbook does not define "Communications Engineer" but describes several types of communications and telecommunications technicians. To practice as an engineer, you would probably take a four-year degree in electrical engineering or computer engineering, described in the OOH.  "Electrical engineers design, develop, test, and supervise the manufacturing of electrical equipment, such as electric motors, radar and navigation systems, communications systems, and power generation equipment. Electronics engineers design and develop electronic equipment, such as broadcast and communications systems—from portable music players to global positioning systems (GPS)."  The critical difference is in the design: engineers build new systems, while technicians use systems that have been previously built by engineers.  Both are complicated disciplines, but one of them requires loads and loads and loads more math.  Nimur (talk) 17:40, 9 July 2015 (UTC)
 * So if for example you graduated from a course in control and communications engineering and did a lot of maths then for example got a job with a company that specialises in designing such systems for buildings, structures or transport infrastructure, would the job involve a lot of maths? Sorry if the questions seem very amateur. 94.10.240.191 (talk) 17:48, 9 July 2015 (UTC)
 * 94.110: At a 4 year college level and any professional job following it, both fields will certainly involve considerable math. To get an idea of the subject and type of material involved, here are the first courses a student will typically take for these fields: Signal and systems and Systems and control (you can brose through the lecture material online). However we will be better able to answer your questions, if you can tell us what kind of course you are specifically interested in (4 year undergrad, 2 year college, vocational etc). Abecedare (talk) 17:57, 9 July 2015 (UTC)
 * Indeed. I would categorize these areas of signal theory and control theory as some of the most intense, difficult, heaviest applications of mathematics out of any subject area in any branch of modern mathematics, science, or engineering.  If you don't already love logarithms, we might be able to help you learn to feel differently about them; but you will need to love math if you intend to survive the Transforms.  You will never see the world the same way afterward.  Nimur (talk) 01:23, 10 July 2015 (UTC)

Smoking before the invention of the match

 * Match
 * Cigar
 * Tobacco pipe
 * Snuff (tobacco)

Christopher Columbus brought tobacco to Europe from the Americas. The chemical match was invented in the 19th century. Snuff has been popular in the 17th century.

Before the invention of the chemical match, how did a smoker light his/her cigar or pipe during daytime or outdoors? There are lamps indoors at night. Probably a cooking fire indoors. How did they light their tobacco when a fire source is not around? -- Toytoy (talk) 15:09, 9 July 2015 (UTC)


 * With a spill (a thin piece of wood, which you would light in the fire and use like a match). I've also read of people taking a coal from the fire (using tongs) and using that to light a pipe. DuncanHill (talk) 15:13, 9 July 2015 (UTC)
 * Sorry, misread your question! DuncanHill (talk) 15:18, 9 July 2015 (UTC)

I am not a smoker. I have very little idea about smoking.

I guess that before invention of cheap and fast-ignition safety matches, it was still difficult to light anything using earlier chemical matches. That's why people used to smoke cigars instead of cigarettes. Cigars last longer so you don't need to light cigar very often. -- Toytoy (talk) 15:33, 9 July 2015 (UTC)


 * The humanities reference desk might be a better place for this question. Bus stop (talk) 15:40, 9 July 2015 (UTC)


 * They would use one of these, which combined flint, steel and a small reservoir of tinder and fulfilled the same function as a modern butane lighter. There's a short section in Tinderbox about them (the paragraph beginning "When away from home…"). – iridescent  15:51, 9 July 2015 (UTC)


 * I also suspect that people smoked less then. Tobacco was more expensive then, so maybe smoking a pipe once a day, sitting by the fire in the evening, would have to suffice for most.   To smoke during the day would have been more of an inconvenience, too, not only because they would have had to start a fire, but also pouring tobacco into either a pipe or rolling papers, etc.  So, not something so easy to do while working.  Then there's the safe disposal of the embers.  A fireplace is also handy for that (there wasn't nearly so much concrete around then in sidewalks and streets, allowing the embers to be conveniently quashed with a shoe).  StuRat (talk) 16:24, 9 July 2015 (UTC)


 * For the record, it only takes about 5-10 seconds to roll a cigarette, provided one has some practice. Not exactly going to get in the way of a work day - I've known people who roll over 20 per day. SemanticMantis (talk) 19:57, 9 July 2015 (UTC)


 * Don't forget to include the time to put down whatever he was working on, get the rolling papers and tobacco out, open up the packages, remove one rolling paper, reseal the packages, then put it all back away again after and pick up whatever he was working on, etc. (I've been amazed that it takes me something like 5 minutes to put something in the trunk of my car from my house, even though the garage is right next to the house.  Once I include opening and closing the house door, garage door, trunk, and putting on and removing my shoes and maybe a jacket, a 30 second task is up to 5 minutes.) StuRat (talk) 23:00, 9 July 2015 (UTC)


 * From thinking "I'd like a fag" to having it lit takes me no more than 30 seconds, and that's hand-rolling. Cunningly, instead of keeping my tobacco and papers outside in the car I have things called "pockets" and "a desk", in or on which I keep my pouch. DuncanHill (talk) 23:05, 9 July 2015 (UTC)


 * My garage example was just to show how things can take far longer that you would think. And even something as simple as multiple pockets might not have been widespread if you go back far enough (women's clothes still seem to often lack those today).  If you had to root around in a sack containing your lunch, etc., to find the relevant items, it could take quite a bit longer. StuRat (talk) 23:10, 9 July 2015 (UTC)


 * You may like to read History_of_commercial_tobacco_in_the_United_States and History_of_tobacco. Match says that a chemical match was on the market in 1805 - cigarrettes weren't very popular until after the war of 1812, and weren't widespread until after 1830. So for cigarettes at least, matches have been available for most of their popular history. SemanticMantis (talk) 19:57, 9 July 2015 (UTC)


 * I'm sure this was solved by people that needed to fire cannons much earlier than tobacco. I think it was a called a Slow match and soldiers carried it around, lit.  --DHeyward (talk) 23:19, 9 July 2015 (UTC)

How long for water droplets to evaporate.
I asked my question a few days ago. I asked a work colleague to ask his brother (who teaches physics at a university), and I got his reply today:

"If he stays in the bathroom and doesn't open any windows it could easily take him more than an hour to get dry, maybe longer if he leaves the shower running. If he goes to a dry, well-ventilated room he should be dry in 20 minutes. If he walks around while drying, it will take about 10 minutes. If he wants more information please let me know."

Thank you to "Sturat" for being the only person to attempt a sensible answer.

— Preceding unsigned comment added by 212.225.93.0 (talk) 18:16, 9 July 2015 (UTC)


 * Thank goodness this was put to rest. It was keeping me awake at night. Cheers, Justin15w (talk) 19:24, 9 July 2015 (UTC)


 * Given this is a reference desk, can you ask him to cite his references? ;) Vespine (talk) 22:39, 9 July 2015 (UTC)


 * He was just guessing, like the rest of us, but he had the advantage of having some experience of typical local humidity levels. The OP could have obtained the same answer by a simple experiment.    D b f i r s   13:28, 11 July 2015 (UTC)


 * You're quite welcome ! I will mark this Q resolved. StuRat (talk) 21:18, 12 July 2015 (UTC)