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Everything posted by exchemist

  1. Adam and Eve set the original precedent, I suppose. I can't see it's a big deal in Christianity. To be honest, the issue in practice is not disturbing other people or drawing attention to oneself. That's very much a matter of where you are and what the expectations are in that situation. For instance it is quite normal to wear very little on the beach, but if one were to dress like that on the London Underground*, it would be a big distraction. So if you are nudists, in a place set aside for that, the person who would draw attention to himself would the one dressed in a double-breasted suit. * However when my late wife worked in Rio de Janeiro, it was perfectly normal to see a guy in speedos on the bus, with a surfboard under his arm, next to all the people dressed for the office.
  2. Here is the best reply I got on the other forum: "They are vortex generators. They generate tiny vortexes very close to the wing surfaces, thereby disrupting the laminar flow near the wing. One of their most important functions is to make the stall break more gradual. If one wing of the aircraft stalls suddenly while the other wing is generating lift, the aircraft will roll violently towards the stalled wing. Using ailerons to try to counter this will just make it worse since ailerons increase the (effective) angle of attack of the wings when deflected downward, and thereby deepen the stall. They also slightly reduce stall speed by ensuring laminar flow is NOT maintained. This is somewhat counterintuitive since laminar flow is a very efficient regime for an airfoil to work in. But in a laminar flow airfoil, again the stall break happens very suddenly. The turbulence created by the vortex generators ensures that any stall occurs gradually by disrupting the (primarily) laminar flow over the wing, and allows the wing to keep flying while partially stalled. They also increase drag and reduce cruise speed at a given power setting. They are still seen as worth the tradeoff because they increase maximum takeoff weight by providing more margin against violent stalls at low airspeed, and the slowest airspeed that an airplane can get off the ground is one of the primary determinants in both runway length needed and maximum safe takeoff weight for a given runway." So my guess is they may look like lights at night, due to being illuminated by the rotating beam of a fuselage navigation beacon, but in fact they are vortex generators.
  3. I suppose you might get some help from Fick's Second Law of Diffusion for gases: https://en.wikipedia.org/wiki/Fick's_laws_of_diffusion But I can't help thinking it is a bit artificial to assume two parallel, laminar flows down the pipe, which mix solely by diffusion from each into the other. I's have thought that introducing some turbulence would shorten the length of pipe needed considerably.
  4. No. Move to Europe, where these silly antiquated measures are not used.😁 More seriously, I went to school in the UK during the transition to metric units and had to learn both at school. If you live in a benighted country with these ancient systems, you just have to learn them, I'm afraid. P.S. I never knew a "cup" was an actual measure. We had to learn gills, quarts and gallons. It seems there are 2 gills in a cup. So I've learnt something today.
  5. Yes I agree. However it is normal in most western countries for illustrations in children's books to show a mixture of sexes and ethnicities, simply to make sure all the children see the book, and the subject, as being "for them". Especially perhaps with maths, as this has some baggage of -ve stereotyping, viz. a history of being seen as "nerdy", or "for boys" and so forth. So if that's all it is, then it's disgraceful that books are withdrawn for it.
  6. The integral, with respect to t, of 1/t is: ln t +C, surely?
  7. A winglet is to reduce wasted energy from wingtip vortices. That is a different thing.
  8. No reply yet from the person I was hoping might respond, but someone else reckons they are vortex generators to improve the air flow towards the wing tip, where, due to the flexing of the wing, it is (so I'm being told) the part likely to stall first as the angle of attack increases.
  9. Yes. The problem is fracking may be sold by our idiotic government as short term, but it isn't at all. The best short term options are renewables. Regarding education, that's a different topic but I've just listened to an episode on "The Briefing Room" on Radio 4 about Britain's poor economic productivity, which (among other things) laments our rigid education system. This fails to turn out the sort of mid-skilled people one needs to provide the bulk of the workforce in a higher productivity economy, like that of Germany or France. Our record is very poor compared to theirs. We are fixated on A levels, which are extraordinarily narrow (my son chose the IB instead), and on going to university to study more narrow disciplines, often of questionable value. Different governments try different gimmicks, like the apprenticeship scheme, but there is no consistency and so it never takes root and starts to show results.
  10. If they want more energy, cheaply and fast, they ought to be erecting wind turbines and encouraging farmers to put solar panels in the fields instead of trying to ban the practice. That could make a difference within 18 months, if they can bypass the planning process for an energy emergency. But they are far right fuckwits, unfortunately. (Rees-Mogg as Energy Minister? Seriously?) My understanding is that some abandoned N Sea fields - which would be economic once more at today's stratospheric prices - could be restarted a lot faster than 5 years, but I don't have chapter and verse, I'm afraid.
  11. I don't think explosives are used, are they? My understanding is it is done via hydraulic pressure. An article in yesterday's Guardian, from a former geologist for Cuadrilla, expressed the view that rocks in the UK are too heavily faulted for there to be many contiguous reserves, big enough to be economically recoverable. The current boss of Cuadrilla, interviewed today on R4, seemed more sanguine. However his estimate of recoverable reserves seemed to be 10x that of the British Geological Survey. I can't find numbers on this, unfortunately. But it seems there is no consensus on the size of the prize. What I have found is papers on the BGS report on induced seismicity: https://www.gov.uk/government/publications/review-of-the-geological-science-of-shale-gas-fracturing The other things to bear in mind, apart from induced seismicity, are the long lead time before gas from these new sources can enter the market (>5 years, typically) and the fact that when they do so, they will be priced at the global market price, so they will not make supplies any cheaper, though they can add to security of supply.
  12. I found this immediately on a web search: https://www.metric-conversions.org/weight-conversion.htm There must be lots of them.
  13. And I thought that was "Budweiser", the one made partly from rice. Real Budweiser, from Budweis,(Budweiser Budvar) is actually not bad, however. For a lager.
  14. You can also get "static mixers" to put in the pipe, to speed up the mixing and ensure it is complete: https://komax.com/the-gas-static-mixer-produce-high-quality-process-gases-for-many-application/
  15. I'm going to ask on another forum where there is an engineer who I think may have done some flying.
  16. I'm sure you are not dreaming! Since the beacon is often a rotating light, like a lighthouse beam, I imagine it would be expected to illuminate each one in sequence, though very rapidly. But we probably need comment from a pilot.
  17. Ah, I see. I wonder if it is significant that these are immediately ahead of the aileron. I think I've seen such things on other aircraft and always assumed they were not lights but small protuberances to aid airflow over the aileron. I could imagine that, if that is what they are, it's possible that at night they reflect light from a beacon on the fuselage. But I'm just speculating. I don't know if we have a pilot on the forum who can comment. Did these things seem to flash in unison or independently?
  18. By the way, didn't Geoffrey Wilkinson get his Nobel Prize for his work on organometallics, including ferrocene? If so, who better to know the unconventional (formal) oxidation states that can be involved?
  19. OK fair enough then: I don't know. But I guarantee it was not an Fe VIII compound. Maybe @John Cuthber will have a comment. He seems to be the best on inorganic chemistry that we have on this forum. I was hoping this discussion might bring him out of the woodwork, but anyway this will now ping him whenever he next logs in.
  20. Are you sure the aircraft was in clear air at the time? I've sometimes seen something similar when flying through very light cloud, which scatters light from the beacon lights on the underside so that a flashing glow becomes visible. Also could be something to do with the leading edge slat, or slot, that some aircraft extend for the approach and landing. I find it hard to think a diffuse beacon light would be helpful as a safety aid: you'd want something clear and bright, that could be seen for miles.
  21. Did you have any evidence that you made an Fe compound with an oxidation state of VIII? Or was it just a mystery reaction product that was not analysed? As far as Mellor is concerned, if he died in 1938 it seems likely that understanding of transition metal atoms and their chemistry when he was writing was less complete than today. The physics of QM only got going in the 1920s, after all, let alone its application to chemistry, and many of today's spectroscopic and other analytical techniques did not exist. I was at university about the same time as you and my Cotton & Wilkinson from that era says that for oxidation states of iron higher than III, "only for the states IV and VI are there substantiated reports of compounds." They go on to describe the tetrahedral, paramagnetic, ferrate ion.....
  22. OK, sure, all democracies are imperfect and some are worse than others. But that's not the point I was addressing, which was your apparent objection to government going to war, or taking other decisions, without a referendum to consult the people.
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