Enthalpy

The 3kHz pinger works within a narrow resonance (Q=1000) which drifts more than the bandwidth: Ti-Al6V4 is 0.3% stiffer at +5°C than +20°C, and water pressure tilts the beams more, which raises the resonance by one half (tilting initially more would improve, as well as putting the extra elasticity elsewhere). To drive the electromechanical aggregate at its resonance, the oscillator must include it in the loop. Here the coils have a few extra turns to provide a feedback voltage resulting from the speed gained by resonance. The coils' inductance happens to make a voltage about as strong as the one resulting from the speed relative to the magnet. This helps the amplifier's output, which can saturate for efficiency. But to guarantee oscillation driven by the mechanical resonance, I suggest to have two feedback windings per voice coil, at two different positions, where the mutual inductance from the power winding differs. The induction by the magnet will differ as well, but by an other amount, so that some weighed difference between the voltages at both feedback windings results essentially from the speed and not from the mutual inductance. The adjustment can be made outside the mechanical resonance frequency. Driving only one power winding still permits a decent degraded operation. If an open circuit is the more probable failure at these power and voltage, the windings from both sides can be paralleled. Separate amplifier outputs improve probably nothing. Cycles of 0% to 100% power can make the start less easy. Keeping 1% power for permanent oscillation during the cycle can be done by a reduced voltage to feed the amplifier's output(s). Marc Schaefer, aka Enthalpy

That's an example of a (safe) 100Wh Li-MnO2 primary battery. It delivers 3V from one cell, compared with 6 cells for 12V at a car battery - and lithium is much better than lead. 22Wh would take some 8Ah, or 1/4 the drawn size. Alas, the pressure vessel around it triples the mass. A magnesium battery working in the open seawater would save this vessel.

NO, I am not. I speak about a military attack on nuclear power plants by armed forces, that can use conventional weapons to quickly make a country uninhabitable. That's so remarkable, there's always someone who tries to shift the discussion to terrorism on this topic.

Excimers and rare gas fluorides demonstrate that chemical bonds can be made with a rare gas that has a full shell. Some are stable, and of technological importance. I suppose it's of interest to chemists as well, including if it doesn't fit simpler theories. Could you detail what you call double bond and leaving group here?

So you see that sound is no faster in stainless steel. Your two authors should have stated what kind of stainless. In martensitic and ferritic stainless, sound is minimally faster than in carbon steel. In the common austenitic, it's slower. Anyway, you mixed up the material with the wave. "Bulk waves" is when the material can't change its lateral dimension because the the thickness is much bigger than half a wavelength in the metal, and then the stiffness isn't Young's modulus E any more, but it divided by 1-2*µ2, Poisson's coefficient. Obviously not the case in a bell. And from 1st of January to 31st of December, the modes of a bell are flexural. But you won't find a table of their speed because it depends on the frequency and thickness. The sound of a bell isn't harmonic, that's perfectly known. The frequency of the perceived note is even absent from the spectrum. But no, these spectrum lines are not emitted by small nor by distinct areas of the bell. Each is emitted by the whole bell, which superposes many modes.

Depending on what we want to call non-valence bonds, this can be less new than it seems. In excimer lasers and lamps, exotic molecules are created, which can be extremely unstable, or stable enough to be stored for many minutes: Xe2, XeF2, ArCl2 and many more. The rare gas used have no valence electron at all. Transition elements show a fuzzy limit between valence and deep shells. I vaguely suppose that metastable molecules, possible antibinding, form in the imploding bubbles during sonoluminescence. Then, should we call it a chemical bond, if only pressure keep the atoms together? Squeezing atoms will necessarily modify the orbitals, and creating also molecular orbitals is rather natural under such conditions. Easier to experiment than lithium trifluoride? Just take metallic lithium (very compressible), put pressure around it, observe if it shares more than one electron. Or try with rubidium instead. For instance the optical properties can be observed in a diamond anvil, and these will change, especially the optical frequency at which absorption augments.

If a tuning fork is alone in air, it's a bipolar souce. Though, its bottom is commonly put on a wood part that radiates more strongly for being bigger - and sometimes at a resonator. The bottom (middle of the U shape) vibrates with a small displaceent that fits the wood part better. This movement can result in a monopole source if a resonator is used, often a quarterwave box. It is perfectly known that flexural waves become shear waves at higher frequencies, at about the frequency where both propagation speeds get equal. You almost got away from compression waves, go on, that's the right direction. Sound is slower in usual austenitic stainless steel, and by less than 20%. Wrong figures somehow. 6000m/s would be very much. Anyway, compression waves are irrelevant in a bell. 5000m/s would give a resonance outside ear's range, so it's about time to change your opinion. No compression wave. At very high pressure swing, acoustics get nonlinear because P*V is a product. It stays nonlinear whatever the gamma. Anyway, sound is linear at the sound pressure levels produced by a bell. Nonlinearities are observed at pressure swings near one atm, which is the case in brass instruments. Musicians can blow air with 0.3atm overpressure in the lungs (3m water depth). The first research paper investigated a trombone and wanted to explain that way why the sound gets harder at fortissimo. They did see the nonlinear propagation of a strong pressure front, similar to an explosion pressure front. Though, whether this causes the harder sound, or rather the hard beat of the lips at fortissimo, is discussed.

Something is wrong in the 50° because perpendicular to the surface at one side remains perpendicular at the other. Probably the reference of the angle. Instead of learning whether it's a sine or cosine and what sign it has and from where the angle is measured, and so on, it's better to remember simple ideas, like "the speed component parallel to the interface matches on both sides", and deduce the formula each time you need it. You'd make fewer mistakes. ----- I don't quite understand "the depth at which one sees the fish". If looking vertically, one sees the fish below, and nothing more. Shall the observer have lidar eyes that measure a propagation speed to deduce a distance?

I'm not interested about how other people supposedly got to right or wrong conclusions, what their supposed hidden motivations may be, and so on. Such pseudo-reasonings have nothing to do with science. Hard fact is that bunker busters are much stronger than needed to pierce any buclear reactor, present or even future, as a target of that size cannot be hardened economically. The other hard fact is that power plants are among the very first targets in any war.

Where did you pick 20Ah? (Ah, not aH, amp/hour even less so). Watt=amp*volt. Lithium is not lead. 22Wh / 50mW = 440h. 20% duty cycle make 2200h or 92 days.

Here's my black box pinger design (click for full size), meant to radiate isotropic 40mW at 3kHz for long range, and from 8km water depth to include all Ocean floor. The hull and resonators are of Ti-Al6V4 treated for 1030MPa yield, 3mm thick at the caps, 4mm at the cylinder. A long cylinder would need 5.5mm to resist oval buckling, and a short cylinder as well may need a few azimuthal stiffening rings - theory fails, so check Nasa's Sp-8007 instead: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19690013955.pdf (thanks!) Vibration is small at the seals; if these damp too much, one may try rings of unalloyed titanium, squeezed at assembly and used once, or reduce the vibration by a longer cylinder and sturdy stiffening rings separated from the flange. Air at 1atm inside is fine for the function, but if altitude moves the seals which leak then in deep water, a low pressure and greased rings would help - or grooves narrow in both directions if possible. The pre-stress at the flanges shouldn't have to exceed the force of an external pressure. Stainless screws in titanium seize horribly (material pairing theories are wrong), but the Bulten company claims to have the proper coating. An variant at smaller pre-stress might be a spring wire, pre-formed in zig-zag, bent elastically for assembly, that passes many times at each part alternately. -------------------- Materials and shapes that resist the water pressure hardly change their volume to radiate as a monopole, but resonance helps us. Here 0.68µm peak radius oscillation over equivalent 39mm length shall provide 40mWrms acoustic power and need radial 2.7kN peak, essentially as reactive power. Poisson's coefficient (µ=0.31 for Ti-Al6V4) loses volume only as 1-µ/2 if we act at the radius. The radial amplitude decreases with axial distance as exp(-x/x0) with (x0/R)2=G/E=39GPa/104GPa if the walls only shear; add lengthwise stiffeners if the walls bend. I computed no azimuthal stiffener, but added the wave reflected at the flanges for the force and subtracted it for the displacement. The radiation resistance (Pa*s/m3) of a small source is 0.5*pi*rho*F2/c: at 3kHz in water 9.4Mohm - and in air 50kohm, which still radiates 210µW or 52dBa at 10m, ouch. Inertia of the resonator provides the big reactive power that deforms the hull, and the actuator the small active power for radiation and losses. Mass at the walls would be too heavy for 3kHz, so I use instead 2*50g connected by beams tilted to tg=0.14. Speed makes voice coil motors efficient. To claim peak 0.19N from each at 0.21m/s peak, I added compliance at the tilted beams (two sets of eight, each 16mm 30mm2) from 41MN/m by the hull to 18MN/m. This necessarily increases the reactive energy and raises Q=440 to 1000. The thinner beam ends must bend easily. Ti-Al6V4 dissipates little. The walls, beams and masses are better turned from one piece, and the beams then separated, say by laser cutting. The weld seam must be perfect; consider laser or electron beam. Ageing needs thin sections and is best done after welding, but dissipation may need to de-scale the surfaces. A cage should protect the hull against damping objects. Unsymmetric masses or stiffnesses keep a single resonance but introduce a lengthwise vibration of the hull. If its fastenings create any damping then, symmetrize. -------------------- The coils must be stiff; glass fiber between the copper layers should help - check as well the printed coils I describe there http://www.scienceforums.net/topic/74606-blinds-stick-with-laser-tactile/#entry743275 The neodymium magnets could be hold and wrapped in thin aramide strands and create 0.53T at the D=29mm W=6mm L=5mm gap. The coils drift by 1.6mm through outer 80MPa. For peak 5.6A*turn, they dissipate 2mW rms each. Laminar viscous losses are P=S*F*pi*rho*V2*e where e2=eta/(pi*F*rho) with eta in Pa*s. At 3kHz, 1m2 and 1m/s, this amounts to 39W for water and 0.12W for air. They are around 200µW in air here and tiny in water. The design is flexible, and piezoelectric or magnetostrictive actuators would find a matching impedance at some position of the beams. A clapper can also ring the masses, beams and hull like a bell; the compressive and flexural stiffnesses and the masses are easily tweaked for increased Q then; consider vacuum. 100g of Li-MnO2 would provide 22Wh, enough for 3 months of 50mWe pulses with 0.4+1.6s cycles. The powered pinger weighs ~1kg. As the hull for 100g batteries adds 200g, a magnesium-seawater battery is even more advantageous. Marc Schaefer, aka Enthalpy

LFTR have never worked. And once again, thorium reactors need plutonium, so they demand uranium reactors, and the amount of available 235U limits how much thorium can be exploited. By the way, about every criticality accident happened with liquid nuclear fuels. The claim of a molten salt reactor being safer is extremely doubtful.

As the Bluefin is a mapping sonar, it knows very accurately its speed versus the Ocean floor. This gives it the displacement precisely. Acoustic references are used to retrieve heads of oil wells on the Ocean floor for instance, or to position actively oil rigs. It's uncommon when exploring a new area. Bigger military submarines have other means, some being known. Rather common presently are gravity gradients, created by geographic features like subaquatic mountains, and measured by sensitive gradiometers. This gives an absolute position. Maybe the many gravity-mapping satellites are meant to produce navigation maps for submarines, not just for pure science. http://en.wikipedia.org/wiki/Gravity_gradiometer Magnetometers and magnetic gradiometers have been used as well for navigation, but mainly in an attempt to detect submarines. In principle, one could compare the measured field with a map to know the absolute position.

What I read about (without understanding anything more) is that it could be two faintly coupled mesons or four quarks with bonds of similar strength between each pair. As QCD makes nearly no prediction presently, observing something new shouldn't weaken it that much, would it?

Electron into orbit is still a widespread concept, but it's superseded, and misleading. That was Bohr's model of the atom, at a time people still imagined particles as points on definite paths like planets. This model explained much, but not why the orbits were stable, and is abandoned now. Since Quantum Mechanics and Schrödinger, particles are waves. Electrons bound to a nucleus are orbitals or weighed sums of orbitals. The orbitals are immobile, or time-independent, or steady-states; for being immobile, they don't radiate light. The other bound electrons, or weighed sums of several orbitals, do move. They wobble at a frequency proportional to the difference of energy between the orbitals. As the charged electron wobbles, it emits or absorbs light. So you don't have to search for a detailed process where the point electron would "jump" from one orbital to an other. When the electron changes its shape from one orbital to an other, the intermediate shapes wobble and absorb or emit light. Other events can change the shape of an electron, like a collision with an other atom, an interaction with a nearby electron... "Completely dark" is subtle. On Earth without cooling, the surroundings wouldn't be much colder than 300K, so the atom receives permanently photons around 10µm wavelength. These aren't energetic enough for most orbital changes, but enough to change the rotation of molecules. In cold places you still have the 3K background radiation. Artificial cooling achieves colder temperatures. Then you have photons filling vacuum, which make the link between stimulated emission (laser) and spontaneous emission, which is numerically an emission stimulated by these minimum photons. The rate (or rather the mean delay) at which an atom absorbs a well-tuned photon is proportional to the power density of the light, which is the number of hotons per area and time units. The emission rate increases when well-tuned photons are already present (laser), but not only. A reflecting cavity accelerates the emission even if the emitting atom is alone; as opposed, a detuned cavity can slow down the emission. And yes, a change of state means that the atom changes its energy, or angular momentum, or magnetic momentum (often several of them), or other quantities that are conserved, so this means that an other object (for instance a photon) takes the difference with it.

I had read something similar few years ago, that astronomers believe to observe the effect of a great concentration of mass beyond the horizon that limits our present observations, as inferred from the speed of the matter near this horizon, which seems to be attracted. That would be an indirect observation of something beyond the horizon.

Letting the bullet spin doesn't suffice to deflect it. And from asymmetric force perpedicular to the initial speed, I'd rather expect a small deflection towrds the air. Head-on against a wall, the bullet or the wall is squeezed, or both. The rebound, if any, is weak. The best materials achieve a head-on elastic rebound at 40m/s or little more, while rifle bullets can have 300-800m/s and aren't hard neither. Computer simulations of a bullet impact, or a kinetic impactor (often >800m/s), use to neglect completely the strength of the bullet, and model it as a liquid with inertia.

If you compute the probabilty density per volume unit, all S orbitals have the maximum at the nucleus. If you compute the probability density per radius unit, the maximum is not at the nucleus.

Accidents do happen, and not in the way we imagined them, because then we would have avoided them (often). So instead of "safe because on the tertiary circuit" is say "unsafe because of pipes between a reactor and homes". The toxicity of a nuclear reactor is so immensely huge that any connecting tube is too much. [Airbrush: dig 6 miles deep anywhere to have geothermal power] It doesn't even need an active volcano. Geothermal energy works in the Rhine valley or in Bavaria, because people want so. The next active volcano is 1,000km away, the next geyser 2,000km. Volcanos quiet since millenia are nearer, like 300km. These are only especially favourable places. Geothermal heat is available everywhere - but the investment and returns differ, sure.

Good insulators comprise much gas (like air) and little solid materials, because solids conduce heat more. Dust would be less favourable. Though, you might perhaps compensate that by thicker wall, provided the net result is cheaper.

When the arguments fail, try style? Dams have already been rust by weapons, and nuclear reactors have already exploded, so we can compare. The dam inundates a valley for some weeks, the nuclear reactor renders a region unuseable for centuries. It is my opinion that the proposed travelling wave reactor doesn't work. I don't need other sources for that. And yes, the community does agree. An no, checking who says what and supposedly why does not make a scientific opinion; these are a most propaganda methods. Terra Power proposed starting the travelling wave reactor, which would be a breeder with unfavourable geometry, using 235U. This proves definitely that TerraPower doesn't know the job. Only plutonium provides enough neutrons per fission to make a breeder, because a breeder needs not only on neutron for the next fission, but also one neutron to breed the next fissile nucleus. That's common knowledge about breeders, perfectly agreed by "the community". So well known that I wonder why you challenge this but put my knowledge in question. The other claims by Terra Power are just wrong, including the consumption of nuclear waste. The question is instead: why do you, why should anyone, believe a group of crooks?

It's not only the walls. Tritium regeneration itself would need to multiply the neutrons (on tritium fusion makes one neutron, one neutron is needed to convert a lithium into one tritium). The neutron multiplicator would let 14MeV neutrons hit a heavy atom like lead, and this makes radioactivity, including with medium life (I just checked by hand, software would find more nuclides). http://www.scienceforums.net/topic/82015-nuclear-fusion-when-do-we-get-the-energy-of-the-future/#entry794721 http://www.scienceforums.net/topic/69318-is-fusion-power-the-way-forward/#entry704591 I understand better how reactors work than the crooks who proposed the travelling-wave reactor and wanted to ignite it with uranium instead of plutonium. I cited no opinion, because I make mine by myself. I don't insist, and actually never suggested, to build coal-fired power plants. You do, as nuclear proponents who suggest it's the only choice. I don't. I dislike your method of attributing me things I didn't write. The alternative to both nuclear and carbon dioxide emissions is renewable energy, it works already, and wind electricity is already cheaper than nuclear one. 92.50£/MWh for nuclear energy http://www.world-nuclear-news.org/NN_Strike_price_deal_for_Hinkley_Point_C_2110131.html 82.00€/MWh for wind energy http://www.developpement-durable.gouv.fr/Les-tarifs-d-achat-de-l,12195.html nuclear electricity is unaffordable.

The electron is considered elemental so it wouldn't have a shape. What do you call the size of an electron? If you try to locate it precisely, it is smaller than any method humans have found up to now to measure it, so it's qualified by "point-like". In that sense, one couldn't compare it with a basket ball of a bee if zooming in the atom - it would remain a point at any magnification. Though, I see no reason to attribute to the electron any other size than the wave, which can be small or big depending on the context. I just say (and I'm not alone) that in an atom, the electron (pair) is the orbital, so inner electrons are a bit smaller than the atom, outer electrons as big as the atom - or a few atoms in a molecule. Some electrons, the S orbitals, have their maximum probability density right on the nucleus, so they need no tunnelling. These are the ones absorbed in a radioactive decay mode called electron capture. Strings are one theory which predicted new particles that have not been observed, especially not at the LHC yet. As such, this theory deserves full language caution. Orbitals, which I don't distinguish from electrons, are immobile. One calls them "stationary". That's why they don't radiate - only transitions between them do. Being immobile (but having an extension, or being "fuzzy" if you prefer) they could lead to some definition of a fixed distance - but said distance will depend on how one defines it. The electrostatic energy would make one such definition. Saying that the electron (pairs) are orbitals, I see no vacuum at all in the atom. The atom is completely filled with the electrons. Though, if one tries to locate more finely the electrons, he will find one only from time to time. Virtual particles have the size of the wave, which depends on the particle's (missing) energy and rest mass. One can define better the size of a particle if it's composite like an atom nucleus, but these are highly unlikely as virtual particles: only the lightest ones have significance. One fundamental choice in the representation of particles is whether you want to imagine them as permanent points whose position is uncertain and determined by a wavefunction, or as being the wave, which carries some undivisible properties (charge, spin...) which are accounted for through an integer number of particles, and which can change its shape and size depending on the context.

You're getting forward, congrats in this misleading context. If you have a flexible narrow tube and put one end in your ear, you can explore deeper in the bell and observe that the sound is weaker at the rim. Or use a small microphone. Yes, you have heard the nodes and antinodes, because a bell has a multipolar pattern, instead of being an isotropic source. The first mode is a quadripole, consistent with the animated picture. Maybe this discussion reaches flexural waves some day, who knows. Because, well, a compression wave at 6,000m/s would let a 0.1m diameter bell resonate at 20kHz which wouldn't be audible. By the way, an acoustic resonance does not need a resonator bigger than half a wavelength. A Helmholtz resonator, like a glass bottle, is much smaller. The two modes on the animated picture you linked correspond to nearly-degenerated modes. The first pair of modes of a bell are quadripolar, they look the same but are 45° apart from an other. If the bell has no perfect cylindrical symmetry, then these two modes have different frequencies and produce a beat, which sounds badly: it's a "broken bell". I believe that higher pairs of modes are always detuned in a bell, and that this is a condition to sound like a bell.

The primary source is for free, so efficiency doesn't make the cost directly. It's more a question of investment versus production. Like 1M$ for one hole. That can be a reasonable investment to provide heat and electricity to a town. Geothermal energy would need more holes than oil and gas, sinking the unit cost. Extinguishing rig fires was also considered mature technology, but when all Koweit rigs burned, people found methods to extinguish them hundred times faster and cheaper than before. Think at co-generation. Produce electricity with a limited conversion efficiency, heat the homes with the unconverted energy. Operational with fossile fuels, just transfer the technology 1:1 to geothermal. No. Nuclear electricity is expensive, much more than fossile fuels, and more than wind power. Britain has just guaranteed a MWh price for its future EPR more expensive than for wind electricity. Please don't suggest (I know you haven't) heating homes from reactors without conversion to electricity. Reactors are concentrated poison. Connecting cities to them through a shisha would be insane. That's absolutely right in principle, though I didn't check the figures again. The total flux is comparable with Mankind's energy consumption. So strictly speaking, it isn't a renewable energy. It remains very interesting nevertheless, because the heat stored in Earth's accessible rocks is immense, and covers our consumption for millenia. Call it an abundent fossile clean energy if you wish, I won't argue about the words - but it's there and advantageous.