# alan2here

Senior Members

641

1. ## A spinning disc top speed

At slow speeds at least if this occurs it is very low. @swansont Yes. The idea is influenced by the crookes radiometer, but in this case it dosn't have nearly so much friction. I recorn that it has less resistance in air than the crookes radiometer does in a vacume. If I understand you correctly then for example a 200 Mw laser could cause about 1 newton of force. This is force required to accelerate 1KG by 1MPS? This sounds like a lot. I presume a good way to measure the decay in speed is by how long it takes to half in speed. I can't test it now but lets presume it is 1 minute in air and an hour in a vacume. The magnet weighs 0.21g for near optimum size. I don't know how much the disc and fins would weigh.
2. ## computing, with cogs on

Thanks. Although it didn't answer many of my questions.
3. ## flat pack brick house

Does Pex plumbing suport high presure and other such problems associated with real life plumbing situations? If so that looks fantastic as well.
4. ## A spinning disc top speed

Set up diamagnetic levitation like this. goo.gl/owIJo, goo.gl/1efGV. Above or below the magnet place a disc of materal, the materal must be thin and light, it will probbably be light enough if it can be made thin enough. Put fins along the top or bottom of the disc from the center to the edge that are black on one side and white on the other, they can't extend far from the disc. Put the experiment into a vacuum such as that found inside a light bulb and shine a laser onto the end of one of the fins. Would this test the materal to destruction? How long would this be likely to take with for example steel?
5. ## computing, with cogs on

I was thinking about differential gears having discovered them in Lego Technic recently and been impressed by there working. Using only simple cogs that turn along the conventional axis. Shafts that are cylindrical, connect the gears together, don't move around except rotation along their usual axis, the usual three input\output differential gears and rigid parts that hold things in place what sort of logic could one construct? When two gears are connected the 2nd turns at the same speed as the first but in the other direction, like a multiplication by -1. A trivial setup with differential gears allows two inputs and one output where the speed of the output is the average of the input speeds. Thus we could imagine doing mathamatics with such systems. Below are examples that should be possible with the design constraints described above. ✔s show ones that I have confirmed work. i or i1, i2, i3 etc... represents inputs. o or o1, o2, o3 etc... represents outputs. n or n1, n2, n3 etc... represents constants, in a programming languege you might think of thease as literals, they would usually be defined here as for example the number of teeth on a cog. ✔ o = i ✔ o1, o2, o3 etc... = i ✔ o = i * -1 ✔ o = i * n ✔ o = average(i1, i2) = (i1 + i2) * 0.5, this uses a differential gear ✔ o = i1 + i2 = average(i1, i2) * 2 ✔ o = i1 - i2 = i1 + (i2 * -1) The following use speed 0 as false and 1 as true o = not(i) = ((i - 0.5) * -1) + 0.5 ✔ o = i1 uxor i2 = i1 - i2 o = i1 uxnor i2 = not(i1 uxor i2) etc... uxor (uneven xor) truth table: i1 i2 o 0 0 0 1 0 1 0 1 -1 - uneven 1 1 1 Conditions such as the 'if' used in programming requires for example the a logic gate 'implies'. I don't know how this could be done. There couldn't at this point be flow controll, recursion, storing of state etc... or could there? If the ouptut to a differential was optionally scaled and then connected to it's input then the mechanism locks up. Why this occurs is more apparent when it is built.
6. ## moving on a map

I have now solved this problem with help from http://mathforum.org/dr.math/
7. ## moving on a map

Given the 4 inputs I have can the 2 outputs I require be determined using the great circle method? p.s. Please could somone look at the spreadsheet I posted.
8. ## moving on a map

Thanks. I don't need to do the "divide your journey distance by radius of earth" part as I want to input distance as an angle difference between the start and end points, not as a distance, so it's quite convenient. Thanks for the verification that this distance (angle difference) is measured in radians, so presumably pi*0.5 = quarter of the way round the sphere. http://en.wikipedia.org/wiki/Spherical_law_of_cosines There dosn't seem to be any one equation with all the parts I need that I can get Wolfram Alpha (I'm not being lazy I'm just not verry good) to rearrange. If this isn't relevent as Rick's equation works and I'm just using it wrongly or you can't do it like this and so this is a dead end anyway then I don't want to spend too much time on it, however if it is usefull does this look right? Set 'u' lat and long to be on the starting point Set 'w' lat and long to be on the north pole Set 'C' as the angle facing Set 'a' as the distance to travel. Find 'v' lat and long.
9. ## moving on a map

Iv'e just tried it in Excell. It dosn't work, for example moving a distance of 0 causes you to end in a very different place than you started. My question is either whats up with Doctor Rick's equation or more likely how I have written it wrongly? This Excell file shows a position and the intention to move north east, the simple method of moving it that only works neer the equator and ricks method. It plots thease onto a graph. http://with-logic.co.uk/a/moving.xlsx
10. ## moving on a map

TonyMcC an excellent observation, thanks. However the distances are relative to revolutions, so we go for example "quarter way round the sphere north east" not "10 miles round the sphere north east", therefore it dosn't matter how big the sphere is for this part of the calculation, going a quarter of the way round a small sphere from an existing latitude and longitude will produce the same final latitude and longitude as going quarter of the way round a large sphere in the same direction. The equation came from the link and I can't understand why it works, but it does seem to take the correct inputs and the text in the link describes it's process as producing the answer I need. Do you have doubts that it works imatfaal? I'd love to go though them now before trying to implement this equation.
11. ## moving on a map

Fantastic :¬) Have I understood this correctly? http://mathforum.org/library/drmath/view/51816.html d is the distance to travel tc is the angle at which to face at the start lat1 is the latitude at the start lon1 is the longitude at the start lat = asin(sin(lat1)*cos(d)+cos(lat1)*sin(d)*cos(tc)) dlon = atan2(sin(tc)*sin(d)*cos(lat1),cos(d)-sin(lat1)*sin(lat)) lon = mod(lon1-dlon +pi,2*pi)-pi Shadow. To move on a plane. x' = x + sin(a) y' = y + cos(a) As in 'x' after youv'e moved = x + sin(a) and y' = y + cos(a) where 'a' is a number representing the angle your moving at, so the next 'x' is one unit in 'a' direction from the previous. However this dosn't work between latitudes and longitudes on a sphere except neer the equator. Also TobyMaC i'm specifically trying to avoid using that method for now. Id rather use the equation above if possible to continue to deal in latitude and longitude instead of trying to calculate the normal of a vector, measure an intersecting sphere and a plane amoung various other things I would have to do to implement it that way. It would involve rewriting a lot of existing stuff as well, putting it into a form that would require me to make a trip back here if I ever needed to change anything.
12. ## moving on a map

Thanks. Based on the information in the article. Seems to sumerise my problem nicely. I don't entirly understand the equations in the article but I think it's saying: A. distances on an X\Y plane = sqrt(x^2 + y^2) B. distances on a lat\long sphere = sqrt(latitude^2 + (cos(?) * longitude^2)) Also: moving on an X\Y plane: C. x' = x + sin(a) y' = y + cos(a) moving on a lat\long sphere: D. latitude' = ? longitude' = ? C is to A as D is to B. I'm not sure that it's possible to determine D from just this information though.
13. ## moving on a map

For moving about on a sphere in a "straight" line in a given direction. final_latitude = latitude + (sin(angle) * distance) final_longitude = longitude + (cos(angle) * distance) Except it only works well in the tropics, neer the equator. The closer to the poles you go the more inaccurate it becomes tending to be attracted towards them, does anyone know how to correct it?
14. ## flat pack brick house

Thanks Externet, it looks good. It's nice to see a combination of efficent space, nice looking, cheap, folding etc... but also with curves. I was in London for the day recently and saw in that day amoung many other things the container city. It really is verry nice.
15. ## Is this Steorn info correct

Regardless of if Steron are right in general, does this information seem accurate? http://www.steorn.com/images/asymmetry-and-energy-in-magnetic-systems.pdf
16. ## flat pack brick house

I saw this as well recently, which I love.
17. ## flat pack brick house

I just worked out the cost for a container city to add one unit (for most people thats for one house). I included the bare bones and some stuff to make it feel homely as well, it came to about £6500.
18. ## what angle range prevents a crash?

yes. I imagined that would be the case.
19. ## Representing RGB colour in 3-space

Fantastic explanations btw. If you like you can think of full brightness of for example 255 per channel as being 1, so for example if your color has 128 green at a color depth that gives 255 as being the full brightness you could think of it as half green or 0.5. Some OpenGL\DirectX things work like this. A perfect black keeps it's same number of 0. You could then immagine 2 as being twice as much green light as your monitor is capable of, if you wanted to imagine the ammount of green required to be between 0 of 255 and 1 of 255 (a verry dark green that appears as good as black), it would be roughly 0.001953125 in this model reguardless of color depth. If you got a bright monitor and sat in a dark room you could make full brightness unpleasent and turn the brightness of your interface down giving everything more muted colors. Then it would be easyer to reprent verry bright things but harder to differentiate subtle differences in dark things. HDR photography plays with ideas like thease often to great effect.
20. ## what angle range prevents a crash?

Take a 2D enviroment that contains a straight line where the x and y coordanates of the two ends of the line are known and also the position of a car and the angle it is facing (7 values). The car moves forward in a straight line. Is there a simple, reasonably computationally fast way to work out if the car ever intersects (crashes into) the line? Would it become much more complicated if one of thease additional pieces of information was needed? either where did the intersection occur or given multiple lines which one was intersected first.
21. ## flat pack brick house

Reguarding land ownership costs with the containers it's a bit easyer as it's a bit like a caravan park but where the caravans are stacked in a pattern, it can all be moved easily, one could for example rent the ground it was on then move it to some ground they owned later. reguarding foundations, there may need exist sometimes. Building on a hard surface is cirtainly no problem, no foundations required, a single unit could even be put on a soft surface and alloud to sink in a little and there should be no subsidence problems, would just need to make sure it didn't become slanted, not that I'm sugesting building one on mud without any foundations would be a good idea but it shows how flexable it is. I don't know for sure if the zigsaw bricks would work. I didn't imagine there would be any gaps but with no cerment I guess there could be. See the inside of thease http://www.youtube.com/watch?v=65C9OLvmjpI Was there something you had in mind which was different than this and that would work differntly than if it were in a brick house, you could replace the laminate flooring with fluffy carpets or my preferance which is to add a rug on top, add more skirting boards, huge comfy sofa, mount more modern lights into the ceiling and walls as they appear to be added inside the container, devide up the inside with interiour wooden, glass-brick, cloth walls etc... Hell, marble pillars and stained diamond sections in the windows with all the money you save over a conventional house if it was all done reasonably efficently.
22. ## flat pack brick house

I don't like the idea of something that only poor countries might like. However, wow :¬) that looks fantastic. http://www.containercity.com/ I bet containers are really cheep and they could look like nice, upmarket expensive houses inside, you could even buy a room at a time to expand your home! but it's all probbably dirt cheap. Rain could be quite noisy but it should be ok. You could combine thease with easy pipes and the such as well. Would rust be a problem?
23. ## Bore+Argon+Gallium+Indium= Real?

Is bargain cheap to produce. </joke>
24. ## Wikileaks releases 92,000 classified documents on Afghanistan

I love Wikileaks. Just wanted to state my support for anti-secrecy, on a sliding scale of organisation size. The government, being verry big and important can't keep secrets, because Wikileaks keeps them in check.
25. ## public transport, solved at last, possibly

I got this idea after waiting ages and having to walk quite a way to travel home in an empty a decaying and otherwise empty UK buss. Of course having a nice bus is more expensive and more of them is obviously a problem as well, but with a bit of technoligy there could be a solution. How about a system whereby people messege a central controll there current and intended destinations, the system sends them a neerby place to walk to and the time untill they need to be there. A bus then turnes up, much better condition than any current UK public busses, which should be almost full of people after the current people have got off and people waiting have got on. People can't just turn up to get on, they much connect to the system and tell it what they want to do. When you get off at the destination specified you are then messeged what to do next, which may involve another bus or taxi etc... The system would need to perform a complicated task, more than a little pathfinding and scheduling. It needs to find the most efficent routes to send the busses, the most efficent times for people to get on and off and where they can sensibly walk given an ever changing set of reqests. There may in extreme cases even need to be smaller taxi like vehicles deployed.
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