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  • Users: mechj
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  1. mechj

    On Nonlinear Conductive Heat Transfer Equation

    I see the difference b/w analytic solution and analytic function. Wasn't trying to ruffle any feathers, just help out. jdm "Education is what remains after one has forgotten everything he learned in school." Albert Einstein
  2. mechj

    On Nonlinear Conductive Heat Transfer Equation

    quote: "If one of you is aware of a possible existance of an analytical solution (even if approxinate)." From MathWorld: A real function is said to be analytic if it possesses derivatives of all orders and agrees with its Taylor series in a neighborhood of every point. By this definition if...
  3. mechj

    On Nonlinear Conductive Heat Transfer Equation

    You can formulate your finite element equations using Galerkin expansion (some finite element formulations are based on this). A Galerkin expansion is basically just minimizing the residual wrt to a weight function. The weight function is basically a shape function, and it can be anything that...
  4. mechj

    On Nonlinear Conductive Heat Transfer Equation

    Could you use a Galerkin expansion? Regards, jdm "Education is what remains after one has forgotten everything he learned in school." Albert Einstein
  5. mechj

    Turning Thin Walled Stainless Steel

    Thanks for your replies. I think on the first run I am going to try and use a plug. My only concern is the operator having difficulties taking it in and out of each part (400 pcs). I would consider a mandrel type set up, but I am not sure if this would be most cost effective. Regards, jdm...
  6. mechj

    Turning Thin Walled Stainless Steel

    I have a problem and am not sure what to do. I have a part and it is to be made from stainless steel round bar stock. The wall thickness that is called out is .030" and the length is 1.00". The id tolerance is +/- .001. Any ideas on how this can be machined without crushing the part? The...
  7. mechj

    Using fnval in for loop SLOW

    I figured it out. You can use fnval in the manner which I said could not be done. ie.. m(1:n) = fnval(t(1:n),f1) + fnval(t(1:n),f2) not sure what I was doing wrong before, but this does work, and my time to compute on cycle went from 2.4sec to .35sec. Regards, jason m. "Education is what...
  8. mechj

    Using fnval in for loop SLOW

    Hello all, I am writing a code for some data analysis, and I have to fit a spline to the local max and min points in data. To fit the spline I am using fun1 = csape(x1,y1) fun2 = csape(x2,y2) I then have to find the mean of the two splines. For that I use the following code. (I did not want...
  9. mechj

    Signal Extraction

    Greg, Thanks for the info. I will experiment with the methods you outlined. I have been reading some papers on time series analysis and found a good paper outlining a method for decomposing signals into there intrinsic modal frequencies or "IMF". This shows some promise. It can be used to...
  10. mechj

    Signal Extraction

    Hello all, I am working a problem, and am not sure how to proceed. Hoping someone can point me in the right direction. I have a system response that is made up of many modes of vibration. The system is nonlinear (Modal Analysis Fails!), due to the inclussion of of a series of coulomb...
  11. mechj

    Upgrade from 7.3 to a higher version of Red-hat

    I have updated from fedora 2 to fedora 3 and had no loss of data. I believe fedora and red hat are basically the same operating system. Just you get the tech support with red hat and fedora gets none. Anyways you should be fine. I believe it will ask you if you are upgrading during...
  12. mechj

    Need formula for deflection

    If everything is linear and you know the stress from the impact load could not back out the strain from this as a first order approximation? Regards, jm "Education is what remains after one has forgotten everything he learned in school." Albert Einstein
  13. mechj

    Gas Meter Fittings 45LT, 30LT, 10LT

    Does anyone know where I can find any information on the threas sizes of gas meter fittings. Specifically the 45LT, 30LT, and 10LT fittings? I have searched google and looked in the machinist hand book but have found very little. Only info so far is the pitch 11 1/2. If anyone has any...
  14. mechj

    Anyone using Maple?

    Maple is and excellent program, I use it regulary to simplify long expressions, solve system of equations, and some calculus. I use specifically for symbolic math, not sure how well it works for numerics, for that I use MATLab. There is a program that is very similar to Maple called XMaxima...
  15. mechj

    Beam Natural Frequencies

    Thank you all for your insight. I have a much better understanding. Here is how I take it: Ralieghs Quotient R is the ratio of the potential to the kinetic energy. So if the forcing does not show up in the boundary conditions it will not affect the Natural Frequency. A force in the boundary...
  16. mechj

    Beam Natural Frequencies

    I have a question regarding natural frequencies of cantilever beams. Under what conditions does loading affect the natural frequencies of the beam? Does this happen when the loading shows up in the boundary condition (ie an axial load applied to the free end)? What about when the beam is...
  17. mechj

    help :how to implement do while loop in matlab

    In the MATLab command window type help for The information you want should be there. jdm "Education is what remains after one has forgotten everything he learned in school." Albert Einstein
  18. mechj

    Math in word processors

    If you are running a Linux machine, LaTeX is an excellent tool to display equations in text. "Education is what remains after one has forgotten everything he learned in school." Albert Einstein
  19. mechj

    MS Letters of Rec From Employer

    I was always under the impression that goverment agencies were very willing to pay for continuing education. I have even heard of people working for goverment research institutions getting there PhD. at a school away from were they work while still recieving there salary. I did several...
  20. mechj

    Greatest physical misconceptions

    I heard somebody today refer the "speed" of gravity. In the context of interstellar space travel. It was stated that, and I am quoting this, that "When we have computers that can conquer the speed of gravity we can travel anywhere in the universe because time stops." Anyone no what the...

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