Wikipedia:Reference desk/Archives/Science/2015 March 31

= March 31 =

Thesis layout
Are academics likely to penalise Students for minor things such as the page numbering one page being unaligned compared to the header by a few centimetres? Will they get a ruler and check? — Preceding unsigned comment added by 176.251.144.101 (talk) 13:07, 31 March 2015 (UTC)
 * If the thesis is going to be published by your university, yes, they might very well check and be quite rigorous about the format rules. Academics usually don't care about things like that, but it is generally not just academics who have to sign off on a thesis.  (If it's an undergraduate thesis this might not apply, but you should check in any case.) Looie496 (talk) 13:53, 31 March 2015 (UTC)


 * If your institution does care then normally they will provide a style file. That way you can just include it and your thesis will be correctly formatted with little work.Dja1979 (talk) 14:23, 31 March 2015 (UTC)


 * When I submitted by PhD thesis, it took two tries to get the content accepted. It took three months to get the formatting accepted. I actually had to rewrite paragraphs because they didn't like how they wrapped from one page to another. I had to call the author of a paper because they disagreed with the title of his paper and wanted clarification. As for the ruler check - I had a hell of a time with tables. If a table began at the top of a page, it was 1/8th of an inch lower than the pages that began with words. I had to write a special rule into Latex to detect tables starting out a page and then add a -1/8 inch top margin to them. All in all, your advisors will likely care very little for formatting. The university itself may care a lot. 209.149.113.207 (talk) 14:29, 31 March 2015 (UTC)

Justification of Math of AC Circuit Analysis
If two variables are uncorrelated or orthogonal can they be treated as an ordered pair say complex number like AC voltage phasor or impedance phasor is there any mathematical theoremm to justify this claim — Preceding unsigned comment added by 103.24.110.221 (talk) 15:09, 31 March 2015 (UTC)
 * Well ... if the two variables are normalized so they have zero mean and equal standard deviation then the standard deviation of the pair is the square root of the sum of squares like a complex number norm. But overall I don't see the point. For AC analysis hte complex numbers are meaningful and useful rather than just being numbers cobbled together as a pair. Dmcq (talk) 16:34, 31 March 2015 (UTC)
 * Not sure what Dmcq is talking about and how it relates to your question. But short answer: Yes. Take the complex number a+ib. a and b are orthogonal and do not influence each other and therfore can be treated seperately. --109.146.20.31 (talk) 17:18, 2 April 2015 (UTC)

Exercise intensity
Since low-intensity, long-duration exercises can make the body consume more fat, I am wondering how this may be applicable on a bike ride. As a cyclist, I have encountered varying slopes along the bike path. Sometimes, the bike path may be approximately horizontal, and the ride would be a breeze. Sometimes, the bike path may descend more steeply, making the cyclist less likely to input more force on the pedals and more likely to input more force on the brakes. Sometimes, the bike path may ascend more steeply, making the cyclist go against gravity. Some people say that " Exercise is a subset of physical activity that is planned, structured, and repetitive and has as a final or an intermediate objective the improvement or maintenance of physical fitness." If the bike path is incredibly unpredictable, and the cyclist has a preference to change bike paths because it feels more exciting and pleasurable to see new sights, is that considered "exercise" or just "physical activity"? Also, is there a way to classify the intensity of a physical activity, given the unpredictability of the road? 140.254.136.154 (talk) 16:12, 31 March 2015 (UTC)
 * I'd say cycling for fitness is an exercise. Yes, you can classify the intensity - just wear a heart rate monitor. Most models will not only determine current heart rate, but will also allow you to integrate over time, giving a (somewhat vaguely defined) calorie count for a given period. Or use a classification scheme for routes. --Stephan Schulz (talk) 16:20, 31 March 2015 (UTC)
 * How do you use a classification scheme for routes? Maybe use Google to help you determine the sea level height of the terrain and the distance to get from Point A to Point B, and then use physics and mathematics to calculate the average velocity. What about the resistance of the pedals or the ground? Sometimes, the ground can be concrete (sidewalk), grass (no sidewalk), or asphalt (car roads). 140.254.136.154 (talk) 16:41, 31 March 2015 (UTC)
 * But then, if you want to calculate the average velocity of the bicycle to get from Point A to Point B, assuming that you are riding at a constant velocity, then you'd have to do some field research and get on the road. And that assumes that you enjoy traveling on the same road all the time. Maybe it'd be just easier to ditch the low-intensity, long-duration advice, and just have fun! 140.254.136.154 (talk) 17:11, 31 March 2015 (UTC)
 * Jeeez...what an awful definition. I guess by that only those who go along to a gym and do monotonous exercises watching some mindless thing on a screen are actually doing exercise. Doing something social and fun that has a physical activity component will keep people doing it far longer than all those people who pay for joining a gym and give up from sheer boredom after a few weeks. And I don't blame them giving up - it looks to me like it would move the fat from the arms and legs to the brain. If you want to make bicycling harder pull on the brake ;-) but yes I'd advise making cycling interesting as you're more likely to keep it up. Dmcq (talk) 16:24, 31 March 2015 (UTC)
 * The definition comes from a 1985 scientific publication. Perhaps, definitions have changed since then. 140.254.136.154 (talk) 16:52, 31 March 2015 (UTC)
 * As you said, "Some people say ...", and the paper itself "proposes definitions to distinguish ["Physical activity," "exercise," and "physical fitness"]". Their definitions are not universally accepted.  Your latter question regarding "classify the intensity of a physical activity" should be answerable, but the former one is simply a matter of semantics. -- ToE 12:40, 1 April 2015 (UTC)


 * What matters is the power to weight ratio. A reasonable fit person should be at at 3 Watt/kg or higher. To maintain this level of fitness he/she should exercise at about 80% of this ratio. But if you are fitter than that, say you are at 5 Watt/kg, then you need to exercise a lot harder to maintain your fitness. So, what is hard exercise for someone may to a fitter person be such light physical exertion that it doesn't even qualify as exercise.


 * What is very important is that you expend a significant amount of energy compared to your resting metabolic rate. E.g. I will typically burn 1000 Kcal per day and I eat 4000 Kcal per day, so quarter of the total is due to exercise. This is a healthy ratio and also the 1000 Kcal is in absolute terms quite a lot, it is almost half my dinner. If I were to do less running (say half an hour instead of one hour) and I would do that every other day instead of every day, then the 1000 Kcal per day would become 250 kcal per day which is totally insignificant, both compared to the total amount of food that I need to eat and also in absolute terms. The 1000 Kcal extra eaten in the form of whole grain pasta, whole grain bread, olive oil will bring in a significant amount of extra nutrients that will make you a lot fitter. Count Iblis (talk) 20:32, 31 March 2015 (UTC)
 * So, how do you figure out the power-to-weight ratio? The weight can probably derived from a scale, but how would you be able to determine the amount of power that you exert during a physical activity? 140.254.136.178 (talk) 20:52, 31 March 2015 (UTC)
 * The easiest way is to do a test on a home trainer, then you can directly read off the power. Alternatively, you can use formulas that estimate this from your weight and running speed. Take e.g. this online tool. If I enter my weight of 55 kg, the distance I ran of 15 km, the time it took of 1 hour and 10 minutes, then it says that I burned 855 calories, which is actually 855 Kcal. To convert this into the power, you first need to divide this energy by 4 because only a quarter of the burned energy is the useful work done by the muscles. Then to convert to kilo Joules, you must multiply by about 4.18, and because the previous factor of 4 has some error margin, you can assume that both these factors will approximately cancel. So, the total amount of useful work my muscles have performed will have been approximately 855 KJ. If we divide this by the time in seconds we get the power which is 855 kJ/(70*60 seconds) = approximately 200 Watt. So, I've been exercising today at a power to weight ratio of about 3.6 Watt/kg, which is a good ratio.
 * What if you are a cyclist? How do you derive the power formula and adapt it to cycling? 140.254.70.33 (talk) 21:24, 31 March 2015 (UTC)
 * See here. Count Iblis (talk) 01:08, 1 April 2015 (UTC)
 * I disagree that it's wasted time to excercise less. Virtually everyone burns most of their calories while at rest.  Excercise that retains muscle mass that needs to be fed even while sleeping is useful.  Exercise is often a very small percentage of food taken in but the overhead in maintaining muscle is still there.  Even overweight people have to be careful with exercise to avoid catabolizing muscle to support the activity.  --DHeyward (talk) 06:33, 4 April 2015 (UTC)

The latest Boeing and the latest Airbus
How many buttons, switches, and knobs are there in the cockpits of the most-recently released airplanes from Boeing and Airbus? 20.137.2.50 (talk) 17:05, 31 March 2015 (UTC)


 * Many! There are many variants of both the Boeing 787 and the Airbus A380; the flight decks can be configured for each customer (e.g. each airline may work with the manufacturer to customize the flight deck).  They also both use glass cockpits, so there are software buttons on the touchscreen panels.  You might enjoy reading the Flight Deck promotional material from Boeing, and the A380 3D Cockpit Tour from Airbus.  Nimur (talk) 17:15, 31 March 2015 (UTC)
 * Thanks! 20.137.2.50 (talk) 17:20, 31 March 2015 (UTC)