Enthalpy

The inner and outer faces of the wall have essentially the same speed. I also expect a significant intensity at the inner face, but only near to it, which is difficult to observe... As soon as the observation point goes near the center, the zero sum reduces the intensity. Near the rim, you hear the difference between the inner and outer faces, or very little. At the outer face, you have the possibility to be farther from the rim, and near one of the four (for the lowest mode) antinodes, where the destructive effect of the out-of-phase antinodes is small.

It's just a liquid solution. Not a reaction in terms of oxidation or reduction or anything similar. That's why potentials aren't expected to help pick a metal. Each metal keeps its electron count, and the solid one diffuses in the liquid. Generally, liquid metals are good solvents for other metals. For instance mercury, sodium-potassium eutectic and the like use to dissolve many metals. So if handling any liquid metal, including gallium (which is forbidden in airliners for that very reason), one should have a warning lamp go on in his mind, and remember that few metals don't dissolve. In semiconductor processes, we used tungsten and sometimes platinum as a barrier between silicon and gold (yes, some time ago!) because warm solid gold woud dissolve other materials, even silicon. Such choice would be a weak hint that refractory metals resist dissolution better - but nothing more than a weak hint. And our gold wasn't even liquid. Could that possibly be a cultural difference ? As a plain boring old European, it surprises me every time too.

This exceeds by far my knowledge. Being aware that I don't understand Relativity hence have no possibility to grasp these waves, I just assume nothing at all and stick to what I read. Beware about moving objects and retarded potential, though. At least for charged particles and electric fieds, the observed electric field results from the particle's position at the time of observation, not one propagation time prior to it. I've also read that this holds for gravitational waves, too. This being necessary to keep stable planet orbits.

The destructive inetrference is more effective inside because of short distance and direct sight. The mathematical aanlysis of a ring would be simple, with modes frequencies like N2 but with integer N starting at N. A bell is more complicated because the dome adds stiffness. This raises the lowest modes more than the higher ones.

A quick electric motor-alternator, hopefully wounded with graphite fibres as I suggested, would be nice at the turbocharger of a piston engine. Rotating that fast, the motor-alternator is tiny. Coupled with a battery or supercapacitor, it permits to accelerate the turbocharger quickly when the driver requests power, and bring more air to the piston engine than the exhaust turbine permits. When braking, it regenerates energy from the turbine. A similar function exists with pressured air, but electricity is more flexible, and a battery uses to be lighter than an air tank. Splitting the turbine and compressor on two shafts, with an alternator and a distinct motor to transfer power, may bring some more flexibility. This is foreseen at Formula 1 race cars in 2014, if I interpret properly newspaper articles. Useable on any turbocharger car, and the fibre-wounded magnets reduce the mass and magnet costs over a steel sleeve, through higher azimutal speed. Marc Schaefer, aka Enthalpy

It's a lubricant. It bring the proper viscosity, plus several desired properties more. In PEG hydraulic oils, they have to add surfactants. That's why I'm not enthusiastic about "reproducing" the water lube. The analysis has missed all additives, which are vital for a lubricant: - Anticorrosion agents - Wetting agents - Antifoaming agents ... and more! Putting only some PEG-PPG in water will achieve the viscosity and the viscosity index (good with PEG), only. The engine is likely to fail within few weeks, say by corrosion. I feel safer to use a PEG-based hydraulic oil with the same viscosity. Some brake fluids are of this type. At least, it will have the additives to work as a lubricant. Things like "hydrolub".

The frequency of a bell depends on the dimensions squared. It can be very different from 440Hz! This is a bending mode! It doesn"t equal a size divided by a compression wave velocity! You apply a factor-of-20 from the compression wave's speed, but this would increase the frequency, not decrease! Anyway, /20 and *20 are obviously both false. The frequency results from a flexural wave. The waves propagate to the entire bell, and much more quickly so than the sound lasts.

Gold is known for that behaviour, silver as well. Tin wets it very easily because gold doesn't form an oxide layer, but thereafter, bye-bye gold. You need a different metal that forms no oxide layer but resists corrosion. One choice is palladium, used on the caps of microwaves components for being nonmagnetic. Nickel is an other, much cheaper. In case nickel isn't expensive enough for you, you may try cobalt, molybdenum and few more. Beware nickel layers can be electrolytic or electroless, and in one case, it contains phosphorus up to 13% - then I doubt tin wets it easily.

What about graphite? Could that work? Though, if copper works, it's of course the best choice.

That's my (very limited) understanding. A movement along the object-to-observer line won't make a transverse wave, as these are said to be. Though, I had nearly the same interrogation as you, asking why a pair of stars shouldn't create a dipolar wave resulting from the difference of propagation time. That would make a longitudinal dipolar wave. Gravitational ones are said to be transverse and quadripolar.

Any antenna or coil emits both. It's just a matter of how much. That is, an efficient antenna must be big enough, in terms of wavelength. Shorter than 1/20 wavelength, it's getting frankly difficult to radiate well. Such an antenna creates an important electromagnetic field, which propagates far. The field also accepts power from the transmitter even if no receiver is near, and sends it to the rest of the Universe. A short dipole or loop creates essentially an electric respectively magnetic field, which drops very quickly over the distance, like R-3. Such a field stores energy but does not radiate power; it accepts power from the transmitter only if a receiver is near enough. Though, the dipole or loop can (and does!) have its own power losses. Imperfect life makes that short dipoles and loops also radiate a small electromagnetic field. A loop would make a magnetic near-field, but as this field diminishes over distance, from the point where it gets the amplitude corresponding to the electric field, you get a honest far-field, which is electromagnetic, and decreases as R-1. Small but present. This relates directly with the way a loop radiates. Imagine the current flowing in it, in phase everywhere, and along a closed path. - Near the loop, one side is nearer to the observer, and this side's effect predominates. This is the near field. It's magnetic mainly. - Farther, the amplitude difference would give only the R-3 decrease hence vanish. But an other effect is less affected by distance hence predominates: the field emitted from the nearer side arrives earlier than from the farther side. Because the alternating current changes meanwhile (over the propagation time difference), the effects don't cancel out. That's the far field. You see that: - The far field needs loop dimensions not too small, as compared with the wavelength - It is less sensitive to the distance, since it's not an imperfect amplitude cancellation. The phase difference doesn't reduce with the distance. The far field doesn't relate simply with the self-inductance. It's more the near field, or in fact, the very near field, since the inductance is just the magnetic flux divided by the current. A toroidal coil for instance would have a flux, a self-inductance, but no significant far field. Sometimes, small antennas are necessary. That's the case with long waves, medium waves, which are kilometric and hectometric. Antennas are small hence inefficient, but they work. They can be coils, preferably on a ferrite core, but air coils are just bigger. Formulas, including the radiation resistance of a small loop, which lets compute the electromagnetic power and fields radiated by the loop, are for instance in "Antennas", from Kraus.

Hearing the sound much louder at less than 2cm distance is a clear indication of a near-field situation, where the emitting object is smaller than, say half a wavelength. Similar to a mosquito, whose noise vanishes quickly with distance. Under these conditions, the inner interference is very efficient - and it is destructive, because the vibration pattern of a bell is symmetric. The first mode is just an ellipse deformation, the second has three pairs of antinodes where three move outwards when the other three move inwards, and so on for higher modes. The opposite speeds sum to zero sound effect.

Reverse sound, as well as sub-wavelength focussing, demand very accurate sounds. Microphones use to be accurate, but your may need to first identify the response of your loudspeakers. Of course, you can't move the loudspeakers. Or even, I'd use a loudspeaker as the microphone, then swap the functions but keep all transducers as they are and where they are. Time-reversing the signal would make more sense then, while keeping the whole transmission chain. EVen, I'd keep the (very small, not 4 nor 8 ohm) load impedance while using the loudspeaker as a microphone. I'm very surprised about resonances lasting for 1s. That would demand very low flow loss through the opening, possibly made long and smooth. Even a beer bottle resonates shorter. The picture is unclear about the distance of the microphone - it's probably no that far from the array. "Far" would then refer to the sound source, not to the array. The Physorg paper doesn't tell neither if all cans resonate at the same frequency, or are rather tuned individually.

Pulling a piston or a liquid from a cylinder will make an extremely bad vacuum, full of gas. First, you have the residual volume of gas in the cylinder. Then, you have all walls outgassing. And if applying, vapour pressure. Vacuum needs seals, and there are residual volumes around seals. Getting a vaccum as good as interplanetary space is damned difficult on Earth, and needs to bake all walls, use a cascade of special pumps and so on, and even then, there are still plenty of molecules.

No. Gravitational waves are traditionally described as transverse and quadripolar. Simple outwards acceleration should not produce any. Hence my query, if the step reaching us when light does is called a gravitational wave or not. Change of the centre of mass: if considerig the whole mass, including the ejected one, it won't happen - consistently with the quadripolar nature of these waves. Waves are produced when massive objects get closer or farther apart as seen from our position, which must happen if an unsymmetric explosion ejects more matter to one side.

One Soyuz crew had to escape the launcher by firing the emergency rocket that pulls the capsule away. In their optimum position, they survived some 20g unharmed. The limited speed difference must have helped as well.

What kind of relationship do you imagine between virtual particles, which are well understood, and dark energy?

It would be a perpetual motion. Because, from the 500kWh, you could use 180kWh to run the motor, and get the remaining 320kWh without any power input.

Maybe, but I won't. All these claims and questions are nothing that can decide whether one thesis is right or wrong. One tries to argue about intentions or behaviour of people, the other about my desire or not. I don't go in such sterile debates.

X-rays and photons with the energy of gamma rays have been observed from the ground as well, which I trust more because the rays can be linked definitely with one bolt there. I fully agree with a population of electrons with high energy, since over 100eV, they loose less energy per unit length than a low energy, hence continue to accelerate. Ahead of the main bolt is a good place to first attain this energy. We had the discussion there: http://www.scienceforums.net/topic/68307-lightning-and-gamma-rays/ especially the rationale about linear energy transfer, post #4 on 25 August 2012

The mass throughput multiplied by the (vector) speed change gives you the force at each angle. The force is along the bisector, and if the angle of the speed change is a and the liquid's speed V, the speed change is 2*sin(a/2)*V.

ITER, and more fusion reactor attempts, are a huge disappointment to me. They need tritium to work - a tokamak like ITER cannot use anything else, even within the usual next 50 years - but tritium isn't available in significant amounts on Earth. Only deuterium. Presently, tritium is made by uranium reactors, in tiny amounts. Uranium reactors produce 200MeV energy as they make <1 neutron available to make one tritium, and this tritium produces only 20MeV in a fusion reactor. Instead of obtaining 90% electricity from uranium and 10% from fusion, 100% from uranium is better. So the fusion reactor must breed the tritium it uses, but that's difficult. One deuterium-tritium fusion gives one neutron. One neutron makes one tritium from one lithium. Because of the losses, this scheme can't work. The proposed method is a neutron multiplier. The neutron from fusion breaks a lead atom (there is too little beryllium on Earth) to release more neutrons, which react with lithium to make tritium. Such an experiment is planned on ITER: search for tritium breeding blanket But even if regeneration did work (more tritium produced than consumed, which is far from certain now), breaking lead atoms (or any heavy one) produces radioactivity the big way: only a fraction of the neutron and lead reaction make nasty products, but because fusing one tritium makes only 25MeV, eight times more lead atoms must react than uranium atoms are fissioned for the same heat. Quick hand estimates tell that the nasty radioisotopes are as abundent as by uranium fission. I put some hand estimates there: http://saposjoint.net/Forum/viewtopic.php?f=66&t=2450&start=10#p32310 this should be done by software, which would probably find more undesireable radioisotopes. Note that many links to data I put there are broken. I understand ITER looks like a nice toy, but from the radioactivity issue, I consider it the wrong direction. Worse: other energy sources are working better and better while fusion isn't ready by far. So working on a tokamak may be fun, but useless. One's time is better invested in finding cheap and efficient ways to store electricity, since wind for instance already produces cheaper energy than uranium.

Inconel and other nickel alloys serve at temperatures where steel stops, including stainless steel. The reasons: - Corrosion - Creep. Nickel alloys typically serve to +700°C or little more, depending on the stress. A combustion chamber may have walls at +800°C while turbine blades prefer +700°C. Long and expensive research develops better alloys, because this is the fundamental limit to gas turbines. Single-crystal nickel alloy is present-day tech, and turbine blades are actively cooled, with air passing through their hollow centre. Steel would stop much earlier, like +500°C in favourable cases. Creeping starts far before the melting temperature. Titanium stops before temperatures where nickel serves. Already soft, and worse, it can catch fire. But Al-Ti, about 50/50, has been studied. Molybdenum would be the next step beyond nickel; cobalt is uncommon; then youd have niobium, possibly tantalum and hafnium, and tungsten. Ceramics as much as possible, like ZrO2 stabilized with Y2O3, and carbon-carbon. Nickel alloys can be somewhat brittle at cold, but not at the service temperature. It's a worry when machining, and during temperature cycles. I'd suspect that the environment, like coking, embrittles the nickel parts in a Diesel engine.

Thanks!

A. Very near to speed light, that's already done, but just with electrons, protons, lead ions. To propel a human body near speed light, we have no technology, not even a guess of it. A bis. If the traveller survives permanent 30m/s2, he achieves speeds similar to light within four months. At least that would go. B. Yes, time would slow down without limit as he approaches light speed, so that the traveller could reach any distance (which looks smaller to him) within a limited time - if only technology could achieve the speed. Notice that time doesn't slow down for his family that stayed on Earth. C. None. Nuclear fission and fusion are not concentrated enough to achieve anything near light speed. Antimatter would, but is out of our technological reach. D. Ignoring all about the propulsion, how to answer about the materials? E. I'm too old to say "never", for having seen things realize that were doomed "impossible" before: detecting and even imaging exoplanets, imaging individual atoms... But I'm old enough to say "not with the current technology", even wildly extrapolated.