studiot

The starange message appeared again just now as I logged in tonight. I really would appreciate a reply from a moderator or administrator as to whethere thi notice could be generated by the site software.

+1 Or you can do my sheet of paper an peperpot (ink sander) experiment. Another variation to play with is Buffons needle. https://en.wikipedia.org/wiki/Buffon's_needle_problem

I'm sure we've had this thread, been there got the teashirt before.

I'm sure you actually meant something else.

Campfire electric generators and EMP questions. Are you a survivalist preparing for a nuclear war ? I remember discussion after TSR2 was cancelled, because it was thought that the russian military electronic hardware was still way behind the West and all driven on valve technology, as was that of TSR2. Because of this it was thought that they would survive an EMP much more than the West which was going wholesale semiconductor. Swansont's point about voltage spike is the relevant parameter because semiconductors have quite low thresholds of overvoltage. I have seen significant damage cause to semiconductor equipment by lightning strikes, which produce more localised EMPs. There is no protection from this because it is atmouspherically borne. Also protection devices are nearly all 'one-shot', which means that they are sacrificially damaged/destroyed in preference to the protected equipment and should be replaced after every active operation. So one EMP or many ?

Very interesting proposition and well worth discussing. +1 Compact ? Efficient ? Simple ? You missed one - Safe ? I don't think steam is the way to go but it is certainly possible. Let us say that your power requirements are up to a couple of hundred watts and work with that. This is available from Hero's steam engine in Ancient Greece a couple of thousand years ago. Modern estimates, base on available model engineering place the efficiency as between less than 0.1% and up to 1%. But there are many practical and safety drawbacks to steam since you loose the working fluid by expansion and have to keep topping up the water supply. Speed regulation would also be required as the output would otherwise vary over a very wide range, as the device spin speed is heavily temperature dependant and a camp fire is not a steady temperature. From a safety point of view, the exhaust steam would need safe dissipation. Topping up the water is not only a chore, but also a safety matter since any boiler could explode with too little water. So a closed system should be devised. By using hot water rather than steam this could be achieved. Any electric moter can be run as a generator so thinking about central heating pumps, with come in a 20 to 200 watt range their technology could be employed. Such pumps are available with an impellor rotor sealed in a chamber and driven magnetically by the mains supply. Reversing the idea could produce wattage in the desired range, So a sealed chamber heater with some tubing could provide a ciculating system which drives a gravity hot water flow, safely and more controllably than with steam. However other modern technology, as described by exchemist (+1) also fall within this wattage range. In this case the device would be indirectly heated by the campfire to keep within its operating temperature range. So these are practical points for thought and discussion.

English is descended from AngloSaxon not Old Norse. Out of interest I borrowed my wifes's copy of Sweet's AnglosSaxon Reader, 5th Ed, 1895. When she was at Londondon university all students of English were required to be competent in Old English. The interesting thing is that I could not find your letters in Sweet, although there is some similarity. Modern English please, because it may be that you have something interesting and worthwhile to discuss. Ed I have just corrected my spelling mistakes. I think that is more than enough to lay onto other members, without adding alphabetic ones as well.

An Infinity can be bounded below or bounded above yet unbounded in the other.

Please do because that thread introduced several utterly fundamental ideas in Mathematics, some of them so simple that people tend to pass over them too quickly. In the mathematical world we have abstract idealisations. These are often models of the material world. We can pretend that the material world follows our mathematical model for some limited extent of the mathematical model. (just like with the linear model of the curve) So in that thread I introduced 'the world of shapes' These are idealisations or perfect implementations of a mathematical idea for instance of a square. The material world cannot match squares (or any other shape) perfectly at all scales. If we make the square small enough the gaps between the atoms stop the square being complete. But we can get pretty good squares from a block of concrete. So nothing in the material world is truly scale invariant. It is a good match just for a range of scales. So we come to self similarity. Two figures in mathematics are called 'similar' if their shape are the same, except for a scale factor. For instance a triangle with angles 45, 45, 90 is similar to any other and all other triangles with these three angles. But when we look at squares there is a difficulty. For a square, not only do all the angles have to be 90, but all the sides have to be the same length for a figure to be a square ! We have just introduced a second parameter -- Length, which was not needed for the triangle. There is a no problem if we scale the side lengths by the same factor. So a square with all sides twice as long as another square is similar to the other square. But now the area of the figure is scaled by a different factor as the larger square has four times the area of the smaller. But since the two squares are still similar we observe that the similarity property can involve more than one scale factor being applied appropriately. So when we talk about self similarity between two shapes we need to specify what property is being scaled and therefore self similar. It gets yet more complicated as we could apply different scales along two or more of the coordinate axes. This will change the spae of the similarity so it is not called a similarity but an affinity. Fractals can also be made from self affinities. Fractals that have nothing to do with shape in the material world can also be made by Self organisation, though not all such organisation leads to fractal geometry. Self replication probabilistic trees, though not all such trees are fractal. Fractals are so named because their apparent 'dimension' is not a whole number. Our material world is firmly 3 dimensional plus time so nothing material can actually be fractal. So when we say that a coastline length is fractal, we are saying that there is a fractal abstract model which is self similar down to infinitesimal sizes that matches the given coastline to some finite limiting size. Coastlines are interesting because this limiting size of self similar is actually very large. Yes there are smaller and smaller bays and inlets and peninsulas, but the smaller ones are not an exact shape copy of the larger ones. This is the difference between a material world fractal and a mathematical world one like the Koch snowflake, where every reduction of scale brings an exact copy of shape.

Merry Christmas to all members.

+1

Where did universal processes creep into the discussion ? And what are universal processes ? I wish to talk about invariance of scale. Then we need to go back to school and do some geometry to separate out some fundamentals. Self similarity is not the same as scale invariance. the two concepts may concide (and often do) but they are separate geometric concepts. In preparation for more detail, please go and review our discussion about linear mathematics. The point to revise is that over a short interval we can always pretend (and usually do) that a curved line is linear. The more curved the line the shorter that interval has to be. You don't need to defend yourself, no one is attacking you or blaming you. This is a friendly discussion. 😀 Exchemist is talking about the science of mineralogy, and yes he certainly knows more than most.

Although Ball does not go into the rather complicated mathematics of chemical kinetics he does outline the Activator - Inhibitor nature of the origin of zebra stripes. This outline shows clearly that the biochemical reactions are what a pair of intertwined multistep reactions. Each has its own differential equation and the set of equations are linked by something akin to a feedback system. Such systems can be pretty complicated and we are only just at the beginning of being able to solve them. Exchemist is quite right to push this. When I have time I will read your article. Meanwhile you need to make a clear distinction between individual crystals and crystal systems and their growth. They are not the same or subject to the same laws. Perfect individual crystals always have regular non fractal geometry. But there are several different effects that apply to the growth of crystal systems. I wonder if the articles are thinking of snowflakes or other dendritic structures ? Dendrites occur when a crystal can basically grow freely. That is it is not restricted in the space around it. They occur because of self interaction between growing parts of of the structure and result in the structural branching so characteristic of snowflakes. But the flakes are made of lots of individual perfect small crystals and do not exhibit this branching at the scale of individual cystals or smaller. The 'Koch Snowflake' models this, but as a mathematical construct it is truly scale independent and therefore fractal. Geologists are well used to ordering the sequence of solidifying minerals from a magma melt because the solidifying minerals are often intruded into cracks and other confined spaces so the mineral that solidifies first out of the magma will have all the space available and form the most nearly perfect crystals. The next mineral to solidify would have to fill the gaps and so on, resulting in malformed crystals, truncated at rock boundaries. It can also be a way of distinguishing whether volcanic rocks are intrusive or extrusive. In this case there is no fractal aspect to the process at all.

I don't know whom you are referring to but it could be taken to be insulting. Nothing to do with me, but I see you are accumulating negative rep points, be warned about the story of the dog. There is actually quite a bit of truth in the rest of your post, pity there were so amny points each too short and without support. Nevertheless Yes Murray did the work on the Zebras, as was acknowledged in my reference. I assume by Dr Falsi you mean Dr Fauci ? I also assume you think isolation was wrong ? I would be interested to see you apply the very simple Laplace equation to obtain the kind of chemical and biochemical phenomena we are talking about. What function are you connecting in space and time ? You are correct in that there is a substantial probability element in epidemic modelling. This link was proven and started more than a century before Covid By Ross.

If you want to find out more, get hold of a copy og this book from Oxford university. It deals with all sorts of organic and inorganic self organisation (pattern forming) including fractal and cellular automata. There are pages of good references in the back. Here is the excerpt about the zebras.

If it is valid why are the stripes of Equus grevyi different from the stripes of Equus burchelli ?

Excellent question +1 I did read the article and I'm sorry but I think find it to be a load of wishful thinking without proper scientific scrutiny. Befor the quote phi selected we have this peach it suffers from the same lack of scrutinity of conservation of mechanical energy as The temperature of protoearth is estimated at 2300oK (NOAA) Are whatever 'minerals' that are stable at 2300oK also stable esp magnetically at 230oK ? As a matter of interest I did see a much more plausible 'evolution' of mineral structures into natural radio transmitters as a basis for a scifi story in the mid 1960s.

Excellent summary. +1

That's nowhere near the standard of silly mistakes I make. +1

Simplest way is to go to a Ford dealer (parts dept) and measure the hinge from a transit 150. I found plenty of drawings without dimensions on the web. You mkay also find another van and be able to measure the ground distances if they are relevant. Trying to use a photo as evidence of measurement is likely to tie anyone up in legal arguments about photgrammetry. This is because the actual point of the road vertically below the hing is difficult to locate on the photo and capable of significant argument, depending upon who is measuring it.

That article was all journalism and not enough substance (for me) to figure out what they were doing , let alone how they did it. Please also remember that a standing wave can also be modelled as two travelling waves going in opposite directions.

Yes of course there is, but direction of travel has quantum implications only sometimes. By this I mean that there is a quantum solution for a particle freely travelling in space in any direction the solution is the same unless of course the travel medium is not homogeneous and istropic. Normally we do not employ this solution because the quantum levels are so closely spaced that it is effectively a continuum. The direction of travel becomes important in the band theory of metals and semiconductors. As regards your question in time, Genady is correct that some solutions are time independent, such as the particle in the box or the potential well models of an electron in an atom or a crystal. But I don't see this has any relevence to travelling. Does this help ?

I think it is worth pointing out the difference between absorbtion and adsorbtion. Adsorbtion is the interaction at the surface or interface only. Absorbtion molecules of one material are incorporated into the body mass of the other. The distinction may bit a bit blurred with 'solids' such as sponges which have a very large internal surface area.

Good morning and welcome, Rao. Good first post. +1 One way to view the equations of mathematical physics or engineering systems is to dvide them into The equations of constitution or the constitutive equations, for a continuum also called 'the material description'. For example the equations of motion of the particles. The equations of compatibility. These are usually geometric constraints for example the continuity equation in incompressible flow. These are then solved as a set of simultaneous equations. It is not necessary to discretise or digitise all these equations, a mixed set will also do. If you would like to give us more details of you intended application we may be able to be more specific. There are also discrete phenomena which appear in the continuum model, such as water hammer, hydraulic jumps, vortices, sonic booms, water bores, etc. For example, fluid flows are often modelled by using finite element techniques. The mesh is calibrated against known values at the nodes and the actual equations set is replaced by simplere ones for the internodal spaces. So called hat functions (similar to dirac delta functions) are popular for this. the give 'pulses' which match the change of measured variable from one node to the next. There is not enough computing power on our whole planet to track the constitutive equations at the molecular level. For example there are about 1028 molecules in the fuel tank of for a Saturn V rocket.

Many thanks for trying to help. +1 Notes. The black notifications indicated only appear sometimes. They only appear when logging into Science Forums and remain for about 20 seconds then disappear. I have never found an actual message anywhere, either on the forums or in my email or on the pc. I have no idea who or what c-19 might be. I only get a notification that there is a new pm by email, not the text of the meessage. The last pm I received was on nov 5 and I read it so it is not new. The screenshot was taken on Dec 14 so more than amonth later.