Search results

  1. Hemmer

    Intuition about Stokes flow beween solid walls

    Hi there, I have a question about incompressible Stokes flow in a channel between solid walls (with no-slip boundary conditions at ##y = 0, L_y##). It is my intuition that, if the flow direction is ##x## (periodic), and the direction normal to the walls is ##y##, then there cannot be a net...
  2. Hemmer

    Parallel FORTRAN output varies with addition of arbitrary WRITE statement

    Hi there, I've been puzzling over the following code (which works in serial). It produces radically different answers if the (blank) WRITE(*,*) is included or not. Any help greatly appreciated! eps = 0.0 !$omp parallel do default(none) private(i, j, current_angle, current_energy) &...
  3. Hemmer

    Geodesic Sphere

    As the choice of axis is arbitrary, you can choose one such that \theta is zero. Then varying \phi (which as you point out should have no \theta dependence) is just tracing out a great circle.
  4. Hemmer

    Relationship between Debye Temperature and Speed of Sound in Metals

    Thanks yes this makes sense. I had funnily enough just worked it out 5 mins ago, I forgot that k could be found fairly easily by estimating a.
  5. Hemmer

    Relationship between Debye Temperature and Speed of Sound in Metals

    Homework Statement I'm struggling to understand the relationship between the Debye temperature and the speed of sound in a substance. An example problem given is: Estimate the Debye Temperature of Silicon and Lead, given that their respective speeds of sound are 9150 m/s and 1320 m/s. (not...
  6. Hemmer

    Finding angles in a four sided room

    Thanks for clearing that up. It does make sense to me now. Thanks for your time!
  7. Hemmer

    Finding angles in a four sided room

    I can see why this would be the case for a square or similarly symmetrical shape, as by squashing the square you can mirror the change in angles on each side of the diagonal. I'm not convinced that this is the case for irregular/asymmetric shapes though? Try it with some different lengths of...
  8. Hemmer

    Finding angles in a four sided room

    This is a little problem that I encountered while trying to measure the floor plan of an irregularly shaped reverberation chamber. I have measured the length of the four walls (all of different lengths). However I didn't measure the angles at the corners (which are in general not 90°), thinking...
  9. Hemmer

    Structure factor

    Because you simply have list of atoms I don't think you need to break it down into S = S_{basis} \times S_{fcc} (although I suppose it is possible to do it that way?). Using the sum and substituting in the list of vectors you should get: \sum_j = n_j exp(iK.r_j) = n_{Na}( 1 + e^{i\pi(h + k)} +...
  10. Hemmer

    Capacitance of Concentric Shells (different charges)

    Homework Statement A thin conducting shell of radius a has charge q. Concentric to this is another shell of radius b (b > a) with a different charge Q. How is the charge distributed and what is the capacitance of the two shells. No hint to the relative polarity of the charges is given...
  11. Hemmer

    Quick Differentiation Qu.

    Never mind I managed to solve it (i think!). B \propto \frac{-3}{s^{3}} \frac{dv}{dt} using substitution of s for v.
  12. Hemmer

    Developing a website

    Well yeah the images would require some design software, but the code is largely based on vBulletin, with tweaks that could be made by hand. Yeah sure I'd also recommend something like Dreamweaver but it's expensive, and you can become lazy and too dependpent on just dragging and dropping. If...
  13. Hemmer

    Quick Differentiation Qu.

    Yes the velocity is constant. The rest of the question isn't relevant to my problem, but I can post if you want. And yes by rate of change I mean: \frac{dB(s)}{dt}
  14. Hemmer

    What if Gmail had been Designed by Microsoft?

    So true. I'm looking forward to seeing the new gmail too.
  15. Hemmer

    Developing a website

    I'd recommend coding by hand using notepad or something similar. Try a few firefox extensions like code view to help learn how html works.
  16. Hemmer

    Quick Differentiation Qu.

    Homework Statement I have nearly finished a problem. I am at the stage where I have: B(s)\propto\frac{1}{s^{3}} v=\frac{ds}{dt} I want to find the rate of change of B(s), but expressed in terms of a velocity, rather than a displacement. Homework Equations So for displacement: B'(s)...
  17. Hemmer

    Det(A^n) = det(A)^n

    Question. Prove det(A^n) = det(A) ^ n I have: det(AB) = det(A)det(B) (holds for any number of factors) set A=B det(AA) = det(A)det(A) det(A^2) = det(A)^2 ? Is this enough for a proof?
Top