Recent content by Arjan82

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    Pyramids built along dry river bed

    The latter have to be the Tau aliens, they are better!
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    Pyramids built along dry river bed

    There is a new paper in Nature saying that a now vanished branch of the Nile river (dubbed the Ahramat Branch) was much closer to where the Pyramids were build. The branch dried probably thousands of years ago. So... It wasn't aliens after all...
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    Collection of Lame Jokes

    At my work there was a special room that you could use either to relax in or for new mothers to express milk. The sign said in Dutch: "kolf ruimte / rust ruimte" ('kolven' meaning 'to express milk', 'ruimte' means 'room' and 'rust' means 'rest', i.e. 'rust ruimte' is a room to rest/relax in)...
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    B Too much energy -- thought experiment

    I think your reasoning is that the difference in density causes a larger difference in pressure if you increase the height. So (rho_hot*g*h1 - rho_cold*g*h1) < (rho_hot*g*2*h1 - rho_cold*g*2*h1), which on itself is true of course. The thing is that for equal P0 the temperature and therefore...
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    B Too much energy -- thought experiment

    The Cp for cooling is exactly equal to the Cp for heating at the same pressure and temperature, I don't know how you got two different answers....
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    B Too much energy -- thought experiment

    You cannot use the full dp due to difference in rho for the turbune power. Because the system has to overcome a small amount of friction as well. If you don't include that friction it becomes a problem where you do not need any energy at all to keep the flow going (Newton's first). In that...
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    B Too much energy -- thought experiment

    The heating of the fluid is at a higher pressure than the cooling due to hydrostatics. This means that the work done by the heating is higher than by the cooling. This is why Pcool has to be smaller than P0. A turbine will not cool down the fluid, it will convert some mechanical energy into...
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    RIP Daniel Dennett

    Yeah, he was my favorite philosopher. In fact, before I discovered him I thought philosophy was this weird thing where you asked silly questions like what the essence of existence is, what is the meaning of life or this Aristoteles stuff which was all a bit far-fetched to me. Nice to think about...
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    B Coefficient of friction in sea water

    A fluid like water is defined by its inability to sustain tangential stresses (i.e. frictional forces), or rather, a fluid will deform under even the slightest tangential stress. Thus in principle, when there is no wind or current, you can propel a boat forward with a gram of force, or even a...
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    I Fluid dynamics of sailing boat when steering

    Please also note that the moment your boat starts turning the flow into the rudder is not from straight ahead (or aft..) anymore. So this allows you to have a much greater rudder angle than what theory would suggest is possible compared to neutral. In the sailing school where I worked a long...
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    Aerodynamics: flow separation's effect on lift and drag

    Because most of the drag is 'induced drag' Wich is drag due to lift generation. Less lift thus means less drag.
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    Collection of Science Jokes P2

    Shouldn't that look more like this?
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    JavaScript How do I run an exe file on an Apple iPad?

    A lot. It is both a different operating system (Windows vs iPadOS) and a different chip set (x86 vs ARM I suppose). So, that is going to be really hard, you need some kind of framework like mono, but then for this case. I have no idea if that even exists.
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