Recent content by anuttarasammyak

  1. anuttarasammyak

    POTW Sum of an Alternating Series

    Excellent. Let me follow you. T(x):=\sum_{n=1}^{\infty}\frac{\sin(n(\pi-x))}{n^3} for ##-\pi < x < \pi## Regarding this as Fourier series, ##n^{3}## in denominator shows that T(x) is tertial function of x from integration by parts in the calculation of components. We can write T(x) with...
  2. anuttarasammyak

    POTW Sum of an Alternating Series

    I would try another transformation S=Re(-i\sum_{n=1}^\infty \frac{e^{\frac{\pi n i}{2}}}{n^3}) =\lim_{x\rightarrow 1} Re(-i (\frac{\pi i}{2})^3 \int dx \int dx \int dx \sum_{n=1}^\infty e^{\frac{\pi nx i}{2}}) with convention that all the integral constants are zero. S=\frac{\pi^3}{8}Re( -...
  3. anuttarasammyak

    Why don't hydrogen ions have osmotic activity in living organisms?

    Then have you known osmotic behaviour of H3O+ ion, which could cease your question ?
  4. anuttarasammyak

    Why don't hydrogen ions have osmotic activity in living organisms?

    So your question seems why only neutral atoms and molecules pass the membrane ? I say it in logic. I do not know the facts.
  5. anuttarasammyak

    Why don't hydrogen ions have osmotic activity in living organisms?

    Do you mean any postive charged ions cannot pass membrane or hydrogen ion only ?
  6. anuttarasammyak

    Why don't hydrogen ions have osmotic activity in living organisms?

    Though I am not good at chemistry, I think hydrogen ion, i.e. proton and proton-neutron core, pass the semipermeable membrane including ones in living organism. Why not ?
  7. anuttarasammyak

    Particle confined in 3D box - quantum states

    In a narrow sense of mathematics, you are right. But in physics almost all the numbers in calculation is approximate. I am afraid that thinking of integer 583 just is not practical.
  8. anuttarasammyak

    Particle confined in 3D box - quantum states

    I asked Wolfram as shown There seems no integers to satisfy the relation. In neighbor, (2,3,27) satisfies a^2+b^2+c^2=582 and (2,2,24),(6,8,22) satisfies a^2+b^2+c^2=584 where I excluded (0,10,22) which includes physically prohibited 0.
  9. anuttarasammyak

    POTW Sum of an Alternating Series

    Thanks for pointing out the difficulty. From my last line \frac{8}{\pi^3}S=\frac{1}{2}\int_{0}^{\infty} p^2 dp \ (\sum_{n=1}^\infty \sin \frac{n\pi} {2}\sin \frac{pn\pi} {2} ) In here \sum_{n=1}^\infty \sin \frac{n\pi} {2}\sin \frac{pn\pi} {2}=\frac{1}{2}\sum_{n=1}^\infty [\cos...
  10. anuttarasammyak

    Solve the equation : ##x^4+12x^3+2x^2+25=0##

    I am afraid that in this way we would not succed to reduce the effort than solving the equation itself.
  11. anuttarasammyak

    POTW Sum of an Alternating Series

    Inspired by answer of julian, let me show my sketch using Fourier transform and distribution.
  12. anuttarasammyak

    Engineering Why does my integrator pole disappear when I simplify this?

    The result of attempt 2 would be written as \frac{A}{s}+\frac{B}{s+c} where c=R_\rho^{-1}(C_\rho^{-1}+C_2^{-1}) You can get constants A and B by calculation. You find it sum of simple pole functions. You do not have to do this reduction in applying residue theorem. The result of attempt 2...
  13. anuttarasammyak

    Engineering Why does my integrator pole disappear when I simplify this?

    BLUE BOX should be R_\rho C_\rho +1/s which makes attempts 1 and 2 have same result.
  14. anuttarasammyak

    Classic Incline problem with cylinder

    Axes are x and y as I wrote x- y- directions of velocity in my post #2. In xy coordinate, ##P(x_p,0)##. The contact point on the slope ##C(x_C,y_C)## in xy axes coordinate is x_C=x_P+R\phi \cos \beta+x_{C0} y_C=-R\phi \sin \beta+y_{C0} where ##(x_{C0}, y_{C0})## is initial position of C when...
  15. anuttarasammyak

    Classic Incline problem with cylinder

    Does your "x" or "time derivative of x" have something to do with the Lagrangian of ? I do not find it in parameter of the Lagrangian.
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