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studiot last won the day on January 5

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2114 Glorious Leader

About studiot

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    Somerset, England
  • Favorite Area of Science
    applications of physical sciences
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    Semi Retired Technical Consultant

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  1. To emphasise this, the degree of 'protection' depends upon the nature and quality of the grounding. Inadequate or wrongly placed grounding can lead to damage in its own right.
  2. Hello Col and welcome. +1 for a good start, I look forward to further worthwhile contributions. I've been a member since 2012 and in that time I have seen many threads started discussing the question, "What is space ?" So it is indeed apressing question. So pressing that in fact we now need to separate what is meant by a physical space and what is meant by a mathematical space. Defining a mathematical space is easy. You need a set containing at least three (perhaps four) sets of objects. 1) A set of mathematical objects you wish to work with. 2) A set of coefficients you wish to apply 3) A set of axiomatic relations between these objects 4) Perhaps if you want to be complete then a set of results (theorems lemmas etc) you can deduce from these. Hi Markus, I think you have this the wrong way round. Mathenmatical structures are models of physical reality, rather than physical reality being a model of mathematics.
  3. Anyone wish to own up ? https://www.bbc.co.uk/news/business-55738540
  4. This claim is not meaningless it is just plain wrong and arises from a basic misunderstanding of celestial navigation with a sextant, where the term 'arc of the sun or arc of other celestial body arises' It is not the altitude (which is the arc measured in degrees) but the plane from which is it is reckoned that changes with altitude and with altitude and other factors which have to be corrected for. This plane is called the true horizon and is not directly available to the observer so various 'observable horizons' are employed - marine navigators use the water horizon, aerial navigators use an 'artificial horizon' (yes aircraft still carry sextants for emergency navigation when the more modern electronic systems are broken). Clearly these calculations are correct since navigators do arrive at their destinations using them. The calculations and sight corrections can be quite complicated, here is a simple explanation. https://knowledgeofsea.com/correction-to-sextant-altitudes/
  5. Generally an excellent explanation, +1, but your examples need updating somewhat. Both these examples were used in 1930's electrical equipment but have long since been abandoned as wasteful of power and potentially dangerous as they result in the excessive generation of heat. https://electronics.stackexchange.com/questions/252352/setting-heat-on-electric-stove Electronerd, are you sure you meant a bridge rectifier ? There are many sorts of bridges, but a simple bridge rectifier is not directly comparable to a rheostat. A bridge is a particular sort of circuit configuration containing four circuit components arranged in a 'diamond pattern. Some bridges are used for power control. This application would be comparable to using a rheostat for this purpose, but much more efficient. Such a bridge would be called a 'controlled bridge rectifier' and contain at least one, probably two or four silicon controlled rectifiers (SCR) or TRIACs If you have been reading about bridges for power control are you sure you don't mean this sort of bridge rectifier ?
  6. Several countries have tried using Bluetooth to measure soical distancing distances. None (to my knowledge) have found a successful method. So what are the problems they are facing ?
  7. OK so I will try to discuss communication of Mathematics, rather than principle of Mathematics. I can't see where you have mentioned any basic Maths, computer code is hardly basic if it is indeed Maths at all. However I beg to disagree with your outright rejection of History. Perhaps your experience of History at school was of the sort "History is a list of dates of battles, deaths and treaties to be learned by heart and regurgitated for the examiner". History actually offers many lessons for those that care to peer into them. Not the least being concerning computer code. Coding languages have a very short lifetime; I have seen them come and go and stopped bothering to learn the new fashion decades ago now so I have little idea of the meaning of your example. The last serious program I wrote was PFortran TRIP (Trigonometric Intersection Program). British schools went through a phase of demanding that every child learn 'programming'. This mean resources were wasted on teaching first, different versions of BASIC, then PASCAL, then some early scripting. None of which are current today. History also tells us that the basic mathematical operation of counting is at least as old as writing, probably much older. Now schools used to teach using the old fashioned balance scales. Good schools would actually get the pupils to set up pretend shops acting as customers and shoperkeeps. They would weigh out amounts of materials, say potatoes or sand and also practice with pretend money. This allowed a method of counting by the custemr presenting say a half crown coin and the shopkeeper saying That's one and fivepence and then making up the one and fivepence to half a crown with coins to provide the change. Instant communication of arithmetic and fractions. For those who were a dunce at school arithmetic there was the joke, you say you can't do maths but you can still instantly recognise that you need a treble eighteen, double top and single nineteen to finish in a darts match when you are on 113! Would these be the sorts of examples you are looking for ?
  8. studiot

    Frozen chips

    Well thought out and presented answer +1
  9. Is it? I wasn't aware of this. A detailed explanation of what I mean would be off topic in this thread so I will start another one for that purpose. I will let you know when I have posted it.
  10. Swedish scientists use slowmo videography in a wind tunnel to confirm 1970s hypothesis of the aerodynamics of butterfly flight. https://www.bbc.co.uk/news/science-environment-55719955
  11. To add to this. Mathematical continuity is defined in terms of the inverse functions, not the functions themselves. This has implications for any calculus you choose to adopt.
  12. Ok. As a little tip - conventionally, writing (t,x,y,z) will imply Cartesian coordinates to most readers; if you want to indicate a general coordinate basis, it is better to use the notation x0,x1,x2,x3 , as it is less ambiguous. @Anamitra Palit I would like to add to this my comment to the OP. "(t,x,y,z) could represent coordinates of four dimensional space in a general manner" No they couldn't. t has the wrong physical dimensions to make this a physical space of four dimensions. You can only make an abstract 'space' (in the mathematical sense) with mixed dimensions on the coordinate axes. It is important to always keep this distinction in mind.
  13. Reviewing your opening post I see that I did not give enough prominence to your actual question in my answer. Which is just how much of our NHS resources are being diverted by C-19 because of how long those patients who need hospital spend there All this week the BBC news cameras are following events in the Royal London Hospital, where they also went at the start of the pandemic. The RLH is a small 500 bed distict hospital in the middle of the East End of London. In normal times they have 40 odd intensive care beds, counted into the 500. Yesterday (Monday) it was reported that of the 500 beds over 490 were occupied by a 'high dependency' covid patient. Some of these will still be there months later. So what about the other 450 odd displaced would be patients ? This phenomenon also affects your interpretation of figures. The figures I was quoting were the daily new infections set against the daily deathis within 28 days of testing positive for C-19. This gives a good estimate of your chance of dying from C-19 if you caught it today. It would be false accounting to count in the number or % in the population with C-19 at any one time since the condition lasts a long time and you do not catch it every day. Here are some figures on that just released by the Office for National Statistics. https://www.bbc.co.uk/news/health-55718213
  14. I wasn't and the OP stated You misunderstand although you posted a fair description of the partial working of a condensing boiler, it is a pity you have to always contradict me. The situation is much more complicated, for instance there may be no 'return' flow to a boiler running in DHW mode. But certainly if the inlet water is 100oC or greater then the output water would scald you. In fact it would scald you at a much lower temperature. The point is that the inlet water temperature is not fixed. But the output temperature will be set (there are often adjustable controls in a boiler for this) for both DHW and CH mode for efficiency purposes.
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