Jump to content

Enthalpy

Senior Members
  • Content Count

    3860
  • Joined

  • Last visited

Community Reputation

249 Beacon of Hope

5 Followers

About Enthalpy

  • Rank
    Scientist

Recent Profile Visitors

The recent visitors block is disabled and is not being shown to other users.

  1. To reduce losses at woodwinds and brass instruments, I have suggested walls and stiffeners of damping materials. It's not that clear. Depending in the frequency mismatch between a mechanical resonance and the fundamental or overtone to be preserved, material losses can increase or decrease the power picked from the air column. Here's a graph of the conductance G = Re(Y) of a series RLC circuit representing the absorption by a wall, around a mechanical resonance and for different Q. The black dips indicate semitone spacing, the mechanical resonance falls randomly among them, I displayed th
  2. Some brass luthiers allege the flare's material matters especially. Here are some physics arguments. The acoustic pressure acts axially on the wall where the section changes. This creates mechanical movements that produce a volume oscillation where the section changes. Mechanical resonances amplify the movements and shift its phase, so the volume oscillation acts as a loss and dampens the resonance of the air column, as already explained for other wall effects. The force at the flare can also produce a volume oscillation at a bend and reciprocally, as they are mechanically coupled.
  3. How to reduce the losses at the bends? Difficult and unsure: determine the mechanical resonant frequencies, check where the air pressure nodes are at these frequencies, locate the bends where the air column excites the mechanical resonances less. Though, the instrument has many mechanical resonances and it emits many notes containing many overtones. Choose bend radii that couple little with the air column at the mechanical resonant frequencies. Could this explain the quest for very big radii at the slide trombone and others? The difference of path length doesn't explain it well, the
  4. As usual, you revert to rhetorics when your misconceptions are disproven. Rhetorics is not a part of physics. And please read the topic before re-asking information already given.
  5. Rest mass is unaffected. Inertia depends on rest mass + kinetic energy. This is the basic and historically first reason to build accelerators bigger, as the bending magnets can't keep a small radius as kinetic energy increases despite the speed remains nearly constant. If you didn't grasp this, why do you troll threads about Relativity? And for your information: every single form of energy contributes to the mass, without exception. This is why you were asked during your studies to compute reaction energies by comparing the masses of reactants and products. A uranium atom c
  6. Figures about the effect of a bend at a trumpet. The trumpet is (the photo of) a YTR3335, the bend is the last before the flare. From counting pixels, the outer diameter at mid-bend is already Do=13.2mm. I take 0.4mm thickness (matters little) hence Di=12.4mm. These are uniform in my model. CuZn30 (8530kg/m3 and E=115GPa) gives the section, in SI units, EI=37.9, µ=0.137kg/m and sqrt(EI/µ)=16.6. The bend has mean D=74mm R=37mm, is 2*58mm long, and the straight sections to the pistons are 93mm long. I model the resonance modes by zero movement at the pistons and no rotation at the
  7. Wow, so much interest for this topic! Here a few answers - I probably forget some interrogations. Much is also in the early messages. My preferred particles are (since the beginning) protons at the LHC, as they give an easier wavelength. Other particles are interesting too: Pb ions at the LHC, electrons at the future CLIC. I had also thought at alphas at the LHC. My central idea is that horizontal near-light speed lets the falling particle emit more light than if dropped from zero speed, just as the synchrotron radiation increases sharply with the particle energy. This gives a chance
  8. Nearly all brass instruments have bodies of thin tube, where the dispersion relation of bending waves simplifies. mu*w2 = EI*k4 where mu is the mass per length unit, w=2pi*F and k is the wave number: k*lambda=2pi. For a thin tube, mu ~ 2pi*R*e*rho and I ~ pi*R3*e where R is the radius, e the thickness and rho the density, so EI/mu ~ R2*0.5*E/rho w ~ sqrt(0.5*E/rho)*R*k2 with: Sqrt(0.5*E/rho) ~ ============================================ 860 Polypropylene 940 Ebonite 1000 ABS 2300 Vectra LCP, isotropic 2020 Sterling Ag 2596 CuZn30 2620 CuZn20 2753 CuNi18Zn27 2640 Ni (Co?
  9. This illustrates how the distribution of air pressure pushes on the bends of a tube of constant section. Less pedantic, more visual than the former message. The standing wave has, at some instant, the locations of its maximum pressure (antinode) indicated in red, of its pressure nodes and maximum speed in orange, and of its minimum pressure (antinode) in blue. In the left case, the pressure distribution component Pc*cos(k*R*phi) matters. The higher pressure in the right-hand bend pushes it outwards because the outer curve has a bigger area than the inner curve (the previous mes
  10. At bends, a wave in an air column creates net forces on the wall even if the section is uniform. This applies to woodwinds too. Imagine the small angle element is physically closed at its entrance and exit. The acoustic pressure inside won't let the closed volume element accelerate, so the sum of the forces on the entrance and exit sections compensate the net force on the wall, hence the two initial formulas. They tell already that where and when the acoustic pressure is positive, a bend is pushed outwards the curve, and where and when negative, inwards. For instance the ends o
  11. Friction welding, as in the last lessage, saves raw material and keeps the full tube strength. Big series, as in architecture, justify the special machine. Smaller amounts, as for a launcher or a satellite, can more classically use the big outer or inner surface of a tube to exploit the full section's strength. Top left on the sketch, smooth tube heads fit in or on the tube ends over enough length. Or the tubes can fit at the truss nodes directly, without tube heads. Low-temp filler exists to braze aluminium. A nickel layer on aluminium lets solder wet and adhere. Glue could be cons
  12. Kinetic energy creates gravity. You can measure on scales its contribution to the mass. The kinetic energy of baryons in an atom is easily measured. Relativistic particles too fall with 9.8m/s2 on Earth. This results directly from the relativity principle, as explained in the first message. It's 12 orders of magnitude less than the proton's kinetic energy. Where would you suppose the energy of the synchrotron light comes from, when a magnetic field deflects the relativistic particle?
  13. More of the magnificent tárogató, by Erdő Zoltán now Remembering - Remembering II - Folk song Wow!
  14. As seen from the lab, the particle falls at 9.8m/s2 despite being heavier. As seen from the particle, it accelerates much more than 9.8m/s2 to drop by the same height in a shorter time, and this happens because the Earth moving quickly is heavier. Frequency: the wavelength for a free fall over 30m horizontal distance is around 540nm. It's a benefit from the synchrotron effect, and the reason to make the experiment at an accelerator, as I propose. Without this effect, the radiation would be impossible to measure practically, as the other people noted before my proposal.
  15. Ni serves to make multilayer ceramic capacitors (MLCC). Depending on the manufacturer and the model hence the use (radiofrequencies), it can constitute the stacked electrodes and the barrier against diffusion and dissolution against solder at the terminals. The stack of electrodes and dielectric is sintered at once from nanopowder, while the barrier is electrodeposited on the sintered metallic terminals. TDK - Murata - Johanson Ni is ferromagnetic, which badly increases its losses by Kelvin effect (skin effect) at radiofrequencies. Pd was an answer for the terminals of radiofrequency ca
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.