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  1. U

    MATLAB Matlab - can't even do a simple arithmatic

    Every system has its limits. If you want to use it at its limits then you should understand what they are. Expecting 20 significant figures of accuracy from double precision floating point is asking it to go beyond its limits. Those errors are inherent in how floating point numbers in...
  2. U

    MATLAB Matlab, Three Dimensional plot of three charges

    What approach would you take in C++? This looks like something that could be done with the finite element or finite difference (?) method. But I guess there's an easier or analytic way you have in mind. Conceptually Matlab isn't much different from C++, just without the objects (I think?)...
  3. U

    MATLAB MATLAb creating variables from ascii document

    I'm pretty sure there's an easier way. A command that does it in one hit. But I forget.
  4. U

    MATLAB Matlab error message needs help

    This is a complete stab in the dark. But my wild guess is that the software is creating a temporary batch file (Nov20....bat) and then trying to run it. When it tries to run it, the file isn't there. It could be not there because some unreported error ocurred while trying to create it. or it...
  5. U

    DOUBT in numerical integration

    Oops I didn't see the title of you message. In that case there must be something wrong with your Matlab code since it should be able to integrate anything it can evaluate. Could you paste the code, including the limits of the integration? Seems like a function that can easily be numerically...
  6. U

    Find mappings between two surface meshes (for morphing)

    No. I don't want to interpolate. Actually I already have linear interpolation working fine. I want to find out which points to interpolate between. Most sets of pairs of points will produce a random tangle. I want to find, for example only those 6 sets shown in the picture. Currently I...
  7. U

    Can anyone solve my PDE equation?

    I don't really know. But if you categorize it by order, linearity, homogeneity, etc. then you can look up techniques for solving that particular type of equation. Oh, solve2? Are you using some software? Which software?
  8. U

    IF loop within a FOR loop problem

    You want to update cpto each iteration, and use that updated value in the next iteration? Why is cpto an array? Why not a single value that changes every iteration? Do you need to keep track of all the previous values? Either way, you can update cpto at the end of the loop and the new value...
  9. U

    DOUBT in numerical integration

    Are you trying to do numerical or symbolic integration? Maybe that's a function which has no analytic integral? If numerical, what are the limits?
  10. U

    Find mappings between two surface meshes (for morphing)

    Thanks chiro However, interpolation isn't my problem. I intend to simply use linear interpolation despite its problems. It's the stage before interpolation that I'm stuck on. How can I find the pairs of vertices to interpolate between? In my example there are 6 possible sets of...
  11. U

    Find mappings between two surface meshes (for morphing)

    I want to morph two surface meshes made from triangles and quadrilaterals. They are already "compatible" so that one can be converted to the other simply by changing the coordinates of the vertices. No vertices, gaps, edges, etc. are created or destroyed. Not sure of the terminology. I think...
  12. U

    Programming for Engineers!

    I want to have a little rant about this and hope you don't go down the dark path so many have gone before. If you want to write software that anybody else might use, or if anybody else might want to read/modify the source code, then you should look at software engineering too. UIs are also...
  13. U

    Force transmitted by engine

    You mean torque? power = torque * angular velocity. There may be peaks above that because of the non-constant torque produced by an engine.
  14. U

    Would open or flanged ball bearings be better for this application?

    You need to work out the thrust (axial) load as well as the radial load, and find bearings that can support them. Also consider misalignment and speed. Try SKF's site, it has pretty comprehensive tools to select a bearing. The ones with the covers can have grease retained in them. If it's open...
  15. U

    Trying to design a robotic joint.

    Because of the limited range of motion, you could also use a big pulley with a steel wire or chain fixed to it. Wind the other end of the loop around a drum on the servo/motor. If you're not worried about speed you could also put a counterweight on the arm and that eliminates the torque...
  16. U

    Motor for robotic therapeutic suit for the legs

    For an electric motor you could use a controller/etc to make sure it doesn't get overloaded. If overloading is only a rare accident, then you could use something like an MCB or other over-current cut-out.
  17. U

    Trying to design a robotic joint.

    Can you explain a bit more clearly? If it's rotating about a vertical axis then it may only need a very low torque. That also depends on the acceleration. If it's a horizontal axis, calculate the torque required to overcome gravity. Once you have some estimated numbers you can compare to...
  18. U

    What do you call a more general boundary condition?

    OK, and you can't have an IC like "The temperature everywhere at all times from 0 to 1 is some T(x,y,z). ? If you impose that, then (except for special cases) you have to change the equation (or make it coupled equations?) so the rate of heat generation within the domain is no longer fixed, but...
  19. U

    What do you call a more general boundary condition?

    Excuse me if I'm a bit mixed up here. I don't work directly with DEs... Maybe what counts as "a term in the PDE" depends what you say the equation is? Suppose it's: k d2T/dx2 + q. = 0 If we fix q.=0 then we can apply two T=constant BCs and determine the T field. But what if we fix T...
  20. U

    What do you call a more general boundary condition?

    Is there a term to describe something like a boundary condition but which can be applied within the domain, not just on the boundaries? For example in a heat transfer problem you might specify a constant rate of heat generation in some region. Is that still called a boundary condition...
  21. U

    Plastic combustion engines and why aren't they used

    Yes I think that's the reason a lot of wonderful sounding ideas never end up in production. There are a million and one novel ideas for engines. Even the original Diesel engine was a complete failure. The inventor thought it would revolutionize engines, but it turned out blowing coal dust into...
  22. U

    Plastic combustion engines and why aren't they used

    It's not clear that there would be much benefit. Car buyers don't want light-weight cars and they don't want fuel efficient cars. This is demonstrated by all the over-sized and over-powered cars that people choose to buy. When was the last time you saw a 3-wheeled covered motorcycle? Many people...
  23. U

    Crankcase Supercharging Question

    If the crankcase is sealed there wouldn't be much loss compressing and expanding the air quickly. Pumping it through a valve like your engine would be a different story though.
  24. U

    ANSYS Mechanical- Shell and Link

    Is any of the deflection in the axial direction of the link element? That element has no stiffness to bending, so it will freely move in other directions. It has no rotational DOFs so they can't be constrained.
  25. U

    ANSYS Mechanical- Shell and Link

    If the link is just sharing a node with some elements on the pipe, then it'll be a non-physical point constraint, which might be causing too much deflection in the pipe wall. Are you seeing excessive deflection around that point, and in the pipe wall, rather than the link?
  26. U

    How to Read CAD Drawings?

    This is something that some people seem to be able to do automatically while others never stop finding it difficult. You kind of have to first know what 3D things look like in 2D. Eg a cylinder may be a rectangle in two of the views and a circle in the other view. Then when you see circles you...
  27. U

    Heating using convection

    Considering only convection, I doubt it would do much. Sure it'd force some hot air horizontally around the reflector, but then it'll start rising again before getting far. You call it a reflector, so if it's reflective you might want to orient it to reflect the radiant heat towards the...
  28. U

    Increasing Heat Transfer Area

    It's a pity you can't know the mass flow rate. With that and your existing measurements you can confidently estimate the losses and predict what wattage heater is required. I probably know no more than you about using wet air. My guess is it would have a higher heat capacity, but I don't think...
  29. U

    Electricity from steam at home?

    These guys already have one on the market, so that at least proves something. The basic idea may be relevant to you Leejay - use the high temperature heat to run a generator, then use the low temperature exhaust to heat the hot water for central heating/showers. You...
  30. U

    Increasing Heat Transfer Area

    Which heat transfer is much less? Heat flux into the reactor? Does that matter if it heats more slowly? Did you see the air temperature (or heater temperature) increase with a low flow rate? I'd really like some idea of the flow rate to quantify it. However it's hard to imagine anything else...