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#1100 by OnlyMe on 01 Jan, 2016 15:32
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http://www.popularmechanics.com/science/a18801/3d-printed-wonder-ceramics-wont-shatter/
I want a FRUSTUM from this!
Shell
A poor man's alternative would be to cast and then plate parts, or cast over conventional parts, with something like this,
http://www.hightemptools.com/castablerefractory.html
You would not get the same clear picture of how heat transfers through the frustum, but as long as the frustum temperature does not exceed the limits the plating or metal frustum wall can handle, the ridged casting should limit distortion and any associated resonance shift.
If you want heat disspation, there are other casting materials that conduct heat, instead of acting as insulators. -
#1101 by Mulletron on 01 Jan, 2016 15:34
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It would certainly be useful if (a much more rigorous) integration of total energy content could be done at each step of the time marching simulation, so as to have a smooth E(t) plot to summarize how fast the electromagnetic energy builds up, and then compare to what would be expected from Q value, assuming a constant rate of effective power P delivery to the cavity :
E(t)=τ2×P×(1-e-t/τ2) with τ2=Q/ω
http://forum.nasaspaceflight.com/index.php?topic=39004.msg1466547#msg1466547
The rate of power delivery to the frustum is not constant. Far from it.
Initially a resonant cavity being filled looks like a short and almost all the power is rejected with Forward power being almost zero and Reflected power being almost all that was generated.
Ok, get that, so instant constant power delivery from t=0 would need (almost) infinite amplitude initially...
But I can't wrap my head around the distinction between "external Q" and "ohmic Q" and the corresponding β ratio, I'll leave that to the experts...QuoteOk some of the discussion is accelerator cavity related but it still works.
I feel if MEEP is to reflect cavity reality, this 5 x TC fill time, due to Reflected power starting out at almost 100% and dropping to almost 0%, needs to be shown to occur.
Well I don't know what TC we are talking about if there is 2 different Qs involved. Seems like the flattish energy buildup in the initial ~100 time slices (in the long run by Aero) could relate to this initial "refractory" period with almost 100% power reflected, then when we'd have an effective constant power delivery against losses (ohmic + reflected) proportional to energy, that'd give the 1st order (1-e-t/τ2) ...
I somehow get that the cavity is driven by a given amplitude, not by a given forward power, but at some point (as shown on your linked plots) P_forward reaches a plateau. Isn't the corresponding τ1 possibly much below the τ2 of the ensuing charge at (almost) constant P against losses proportional to E ? Sorry for the speculations, not my domain really.
Hi Frobnicat. I found some info about external Q on the last page of this ref:
http://uspas.fnal.gov/materials/10MIT/Lecture6.pdf -
#1102 by glennfish on 01 Jan, 2016 16:10
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You're right, Traveller, buoyancy wouldn't happen that quick. More importantly, it wouldn't decline that quick.
I would expect buoyancy to propagate at just under 340 m/s. What propagation delay would you expect?
If you are talking balloon like buoyancy, I have no idea how fast any air inside the frustum will heat.., other than by contact with the thermal heating of the frustum itself.
As far as the frustum heating and any internal ballooning or external convection, don't you have to account for how long it take the frustum's heat capacity to be filled before it begins to transfer heat?
Unless you expect that microwave heating of the frustum is uniform, not consistent with Shell's unrecorded observations, any heating of the interior surface of the metal frustum will not be transferred out with 100% efficiency until the frustum is uniformly heated to its full heat capacity.
Shell observed that her side walls felt cool while the endplates felt warm.
Until the whole frustum reaches a stable and uniform temperature, you cannot assume heat will be conducted or dissipated, inside or outside the frustum, in an ideal manner. Some of the initial dissipation will be into the metal frustum itself.
It might be helpful to find a thermal transfer simulator.
We have conduction, convection and radiation, with conduction dominating the others. Air is a pretty good insulator and will heat a few orders of magnitude slower than copper. However, once a given volume of air is at a higher temperature than ambient, your choice of ideal gas laws will equalize the pressure and cause the "lift" effects very very fast, I would expect the pressure differential to reach equilibrium at something slightly less than the speed of sound. I wouldn't expect it to linger around looking for Elvis before reaching equilibrium with it's environment. While the speed of sound is about 340 m/s the rms speed of air molecules is about 500 m/s at 20 C.
Hence, why would there be an expectation that thermal effects wouldn't happen fast? I think we'd see thermal effect changes in milliseconds. -
#1103 by glennfish on 01 Jan, 2016 16:12
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You're right, Traveller, buoyancy wouldn't happen that quick. More importantly, it wouldn't decline that quick.
I would expect buoyancy to propagate at just under 340 m/s. What propagation delay would you expect?
Glenn,
You need to understand that when Iulian pointed the small end down, he measured weight increase on his scale, so the downward force that was generated was greater than the upward buoyancy force.
When you say propagate at 340 m/sec, hey man that is a fast energy wave propagation in air from a internally heated frustum from maggie generated Rf. Bit hard to understand the logic behind that statement. Also you need to quality your statement with the amount of the upward Force that would be generated and in what time frame and response time.
Maybe generate a Glenn upward force overlay as against the measured data that can also explain the very rapid drop in upward force being generated when the maggie was switched off?
Maybe I'm missing something here but how can the upward Force that was being thermally generated (as you suggest) drop so rapidly when the maggie was switched off? This is not a small variation in Force generation.
I'm not proposing thermal or not for these results.
I'm just suggesting that a thermal effect will have virtually no delay that a human could observe without instruments.
The suggestion that thermal's couldn't happen that fast was what I was objecting to. -
#1104 by Rodal on 01 Jan, 2016 16:33
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There are several computer programs that can model all these coupling effects. One such program is ANSYS, for example, that could simulate the multi-physics involved: electromagnetics, thermoelastic thermal expansion, conduction, radiation, and convection (including fluid mechanics with ANSYS/FLUENT or ANSYS/CFD).You're right, Traveller, buoyancy wouldn't happen that quick. More importantly, it wouldn't decline that quick.
I would expect buoyancy to propagate at just under 340 m/s. What propagation delay would you expect?
If you are talking balloon like buoyancy, I have no idea how fast any air inside the frustum will heat.., other than by contact with the thermal heating of the frustum itself.
As far as the frustum heating and any internal ballooning or external convection, don't you have to account for how long it take the frustum's heat capacity to be filled before it begins to transfer heat?
Unless you expect that microwave heating of the frustum is uniform, not consistent with Shell's unrecorded observations, any heating of the interior surface of the metal frustum will not be transferred out with 100% efficiency until the frustum is uniformly heated to its full heat capacity.
Shell observed that her side walls felt cool while the endplates felt warm.
Until the whole frustum reaches a stable and uniform temperature, you cannot assume heat will be conducted or dissipated, inside or outside the frustum, in an ideal manner. Some of the initial dissipation will be into the metal frustum itself.
It might be helpful to find a thermal transfer simulator.
We have conduction, convection and radiation, with conduction dominating the others. Air is a pretty good insulator and will heat a few orders of magnitude slower than copper. However, once a given volume of air is at a higher temperature than ambient, your choice of ideal gas laws will equalize the pressure and cause the "lift" effects very very fast, I would expect the pressure differential to reach equilibrium at something slightly less than the speed of sound. I wouldn't expect it to linger around looking for Elvis before reaching equilibrium with it's environment. While the speed of sound is about 340 m/s the rms speed of air molecules is about 500 m/s at 20 C.
Hence, why would there be an expectation that thermal effects wouldn't happen fast? I think we'd see thermal effect changes in milliseconds.
The roadblocks are multiple: many people do not have the background and experience using programs like ANSYS, they lack the multi-disciplinary background (electromagnetism, thermoelasticity and fluid mechanics), many lack the financial resources to afford programs like ANSYS, and lack access to the computational resources to conduct such a fully coupled, multi-physics analysis.
So, although if there would be enough interest and funding involved I can very well see how that this would be the approach to follow to analyze such coupling effects, and that doing so would be achievable for an organization with the required funding (I do have such background and experience to make this statement: take a look at my profile in LinkedIN) the fact is that at present there is no such interest or funding for the EM Drive effort. Even at NASA the funding is paltry: Paul March reported fabricating the tested truncated cone in his own family room (as shown in previous threads)
So I would suggest, that the most effective approach is to conduct clean, well thought-out experiments that eliminate as much as possible these effects (that contaminate the measurement and interpretation of what has been called "anomalous force").
For example, the effect of air convection can be practically eliminated by conducting experiments in a partial vacuum, as done by NASA and by TU Dresden (who measured forces orders of magnitude smaller than those claimed by Yang and Shawyer who never reported a single experiment in partial vacuum). That still leaves Lorentz forces, thermal expansion and thermal radiation effects which need to be properly addressed in partial vacuum experiments.
____
PS: You are correct that thermal effects can take place much faster than other people discuss (it is just that they are not calculating and not contemplating how fast thermal effects are possible) -
#1105 by OnlyMe on 01 Jan, 2016 16:53
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You're right, Traveller, buoyancy wouldn't happen that quick. More importantly, it wouldn't decline that quick.
I would expect buoyancy to propagate at just under 340 m/s. What propagation delay would you expect?
If you are talking balloon like buoyancy, I have no idea how fast any air inside the frustum will heat.., other than by contact with the thermal heating of the frustum itself.
As far as the frustum heating and any internal ballooning or external convection, don't you have to account for how long it take the frustum's heat capacity to be filled before it begins to transfer heat?
Unless you expect that microwave heating of the frustum is uniform, not consistent with Shell's unrecorded observations, any heating of the interior surface of the metal frustum will not be transferred out with 100% efficiency until the frustum is uniformly heated to its full heat capacity.
Shell observed that her side walls felt cool while the endplates felt warm.
Until the whole frustum reaches a stable and uniform temperature, you cannot assume heat will be conducted or dissipated, inside or outside the frustum, in an ideal manner. Some of the initial dissipation will be into the metal frustum itself.
It might be helpful to find a thermal transfer simulator.
We have conduction, convection and radiation, with conduction dominating the others. Air is a pretty good insulator and will heat a few orders of magnitude slower than copper. However, once a given volume of air is at a higher temperature than ambient, your choice of ideal gas laws will equalize the pressure and cause the "lift" effects very very fast, I would expect the pressure differential to reach equilibrium at something slightly less than the speed of sound. I wouldn't expect it to linger around looking for Elvis before reaching equilibrium with it's environment. While the speed of sound is about 340 m/s the rms speed of air molecules is about 500 m/s at 20 C.
Hence, why would there be an expectation that thermal effects wouldn't happen fast? I think we'd see thermal effect changes in milliseconds.
A metal surface will not heat up and transfer heat in milliseconds. I can heat cooking oil to a couple hundred degrees C on a stove top burner. Take an empty pan at 24 degrees C, place it over a burner and measure the temperature on the inside surface of the pan... Even using a pan composed of a single layer of stainless steal it takes around 10 seconds to raise the temperature by 20 degrees C... And the temperature of the side wall of the pan, Rises even slower inside or out.
That is why I am saying that thermal effects would be delayed, or more gradual.., even more so on the declining side, since unless you have heated the entire pan or frustum to a uniform temperature, the temperature of the whole will still be trying to equalized.
Ballooning for a frustum depends on either out gassing which results in a lower pressure inside than outside or if sealed that the frustum actually expands enough, to alter its displacement... Either one again would be far slower than thermal conductivity.
External convection very much depends on how fast, in reality heat is transferred through the frustum walls... And as demonstrated by the final conclusions re: The Pioneer Anomaly, exactly how and where heat is dissipated will affect radiating thermal thrust and should affect any convection currents.
The thermal issues are anything but simple or ideal. -
#1106 by Flyby on 01 Jan, 2016 16:59
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http://www.popularmechanics.com/science/a18801/3d-printed-wonder-ceramics-wont-shatter/
hmmmm.. interesting... and it gives me an idea...
I want a FRUSTUM from this!
Shell
for 2016, I'm planning to test a ceramic powder which is compatible with my 3dpowder printer as I'd like to expand into consumer ceramics. It is certainly not an as hightech product as you've showed. It is indeed rather brittle and porous (as mentioned in the video), it needs a surface sealer and glazing for a good finish.
But...if I could find a way to copper plate it, it might be a path to take and test... will need a few months to test the product, and equip my shop (ceramic oven, etc) though...
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#1107 by Rodal on 01 Jan, 2016 17:20
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...
A metal surface will not heat up and transfer heat in milliseconds. I can heat cooking oil to a couple hundred degrees C on a stove top burner. Take an empty pan at 24 degrees C, place it over a burner and measure the temperature on the inside surface of the pan... Even using a pan composed of a single layer of stainless steal it takes around 10 seconds to raise the temperature by 20 degrees C... And the temperature of the side wall of the pan, Rises even slower inside or out.
That is why I am saying that thermal effects would be delayed, or more gradual.., even more so on the declining side, since unless you have heated the entire pan or frustum to a uniform temperature, the temperature of the whole will still be trying to equalized.
Ballooning for a frustum depends on either out gassing which results in a lower pressure inside than outside or if sealed that the frustum actually expands enough, to alter its displacement... Either one again would be far slower than thermal conductivity.
External convection very much depends on how fast, in reality heat is transferred through the frustum walls... And as demonstrated by the final conclusions re: The Pioneer Anomaly, exactly how and where heat is dissipated will affect radiating thermal thrust and should affect any convection currents.
The thermal issues are anything but simple or ideal.
https://www.researchgate.net/publication/268804028_NASA%27S_MICROWAVE_PROPELLANT-LESS_THRUSTER_ANOMALOUS_RESULTS_CONSIDERATION_OF_A_THERMO-MECHANICAL_EFFECTQuote from: RodalIt has been argued that the anomalous results found by NASA's Brady et.al for microwave cavities (that supposedly act as a propellant-less thruster) cannot be due to thermal effects because a) the temperature increase would need to amply exceed several degrees C to be explained by thermal effects and b) thermal effects take place too slowly (minutes) and cannot explain the impulsive response of the thrust pendulum exhibiting a rise to full amplitude in half the pendulum's period (rise to full amplitude in little over 2 seconds). These (analytically unsupported) arguments are invalidated here: a thermo-mechanical effect (thermal buckling) is shown that occurs in less than 1 second (for the copper thickness that has been argued as employed for the microwave cavity), with a temperature increase of a degree C or less and that results in forces of the same magnitude (microNewtons) as reportedly measured by NASA.
The above, is just one among several thermoelastic mechanisms that have been examined to produce anomalous forces. It has been recognized since then that the most important mechanism affecting NASA's pendulum results is the effect on displacement of the center of mass due to thermal expansion (which also occurs in a vacuum).
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#1108 by Mulletron on 01 Jan, 2016 17:37
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http://arxiv.org/abs/hep-ph/0408006
Using asymmetric resonators to search for Lorentz violations. Lol see figure 8.
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#1109 by rfmwguy on 01 Jan, 2016 20:10
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OK, homework time. Like to summarize test stands across some experimenters and I need help. I noticed this was not a column on the EmDrive.wiki page
Experimenter/type of test
rfmwguy/balance beam
shawyer/rotary table and balance beam?
Aachen/torsion
Nasa/torsion?
OK, you see where I'm going with this, I want to summarize the testing into a few groups, balance beam, torsion, pendulum, spring loaded arm (Iulian), air table...etc.
Anyone want to take a crack at it?
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#1110 by Rodal on 01 Jan, 2016 21:46
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what does LENR mean ?
The problem with acronyms. LENR apparently can stand for Low Energy Nuclear Reaction or for Low Energy Nano Reaction (or even for Long Exposure Noise Reduction ).
Does the NR in LENR mean "Nuclear Reaction" or "Nano Reaction" ? (If Nano Reaction, do they mean that the reaction is not nuclear ? -in which case it would be preferable to spell out LENR...)
Upon looking for the meaning of LENR one encounters:Quote from: WikipediaA small community of researchers continues to investigate cold fusion, now often preferring the designation low-energy nuclear reactions (LENR)...Since cold fusion articles are rarely published in peer-reviewed mainstream scientific journals, they do not attract the level of scrutiny expected for mainstream scientific publications.
Wonder why using LENR (instead of cold fusion) became fashionable... it reminds me of https://en.wikipedia.org/wiki/Rebranding . -
#1111 by birchoff on 01 Jan, 2016 22:59
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Can we please keep the LENR out of here? We already have enough critics.
LENR is very real as is EmDrive.
2016 is going to be a very interesting year as a lot of folks duck for cover as 2 techs are proven to be very real and game changing.
For EmDrives to make a really serious dent in space, the tech needs a lot of electrical energy. Really more than any existing space power tech can deliver. Do the math. Check it out. When you replace chem propulsive energy with EmDrive kinetic energy from electricity you need a lot electrical power to make it work. EmDrive electrical energy to kinetic energy conversion efficiency is VERY LOW. In the process of generating the kinetic a LOT OF HEAT will be generated.
So no LENR direct electrical energy generation in space and the EmDrive in space may die a slow death as chem energy can do the job at a better efficiency.
And LENR is outside of the scope of this forum.
Do the efficiency maths. Without the high energy density direct LENR to electricity generation efficiency that can deliver, there is little chance of EmDrive delivering space.
Anyway well past my bed time. Night all.
While I know I should just let this die... I have to respond.
While I am open to LENR hopefully delivering on its promise. It isnt neccessary. If EmDrive pans out. We will start powering them with Fuel Cells, and solar since our initial scope will be Earth LEO/GEO, Moon, Mars, Venus. So whatever we can do with just those energy sources will be done. At the same time. Nuclear Fission reactors will finally gain yet another reason to be fast tracked to the front of the deep space energy generation line. Since heat management is bound to be something we will have to deal with anyway. We might as well build a heat rejection system that can handle fission/fusion reactors that generate electricity from thermal conversion.
So no LENR isnt the only way we get the solar system or stars in our galaxy. Even though it would be a pretty sweet solution if it materialized as promised.
Recall fuel cells are energy storage systems (like batteries) not long-term energy production systems (like solar/nuclear systems).
Yes I am aware of that. however, If one were to assume a high thrust EmDrive would be available in the near term. We would not be in a position to imediately power it with a fission reactor. We also do not have everything we need to begin immediately tooling about the inner and outer solar system. So I suspect the first use cases for a working EmDrive would be to replace existing ion/chemincal rocket use. That could be done with fuel cells. sure you wouldnt get unlimited range. But assuming all you needed to do in the immediate term once an EmDrive is available is get between LEO and GEO and the Moon a fuel cell should work just fine. Solar should work as well, but its always nice to have a few backups if possible when your in space. -
#1112 by RFPlumber on 01 Jan, 2016 23:54
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This is a very custom design job. A very rough sketch of my design is attached.
This design needs no circulator and Rf dummy load as the real time Rf environment is monitored at least 100 times a second and will never allow the Rf amp to be over stressed. Rf power is programmed from approx 200mW to 100W with real time Forward and Reflected power feedback. If reflected power exceeds programmed limits, power output levels are dropped back in real time.
I am envy of your RF amp. What is it? Who makes them?
Also, what are you using the 3 way splitter for? Just to excite 3 separate loops at the same time? -
#1113 by RFPlumber on 02 Jan, 2016 00:28
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https://www.researchgate.net/publication/268804028_NASA%27S_MICROWAVE_PROPELLANT-LESS_THRUSTER_ANOMALOUS_RESULTS_CONSIDERATION_OF_A_THERMO-MECHANICAL_EFFECTQuote from: RodalIt has been argued that the anomalous results found by NASA's Brady et.al for microwave cavities (that supposedly act as a propellant-less thruster) cannot be due to thermal effects because a) the temperature increase would need to amply exceed several degrees C to be explained by thermal effects and b) thermal effects take place too slowly (minutes) and cannot explain the impulsive response of the thrust pendulum exhibiting a rise to full amplitude in half the pendulum's period (rise to full amplitude in little over 2 seconds). These (analytically unsupported) arguments are invalidated here: a thermo-mechanical effect (thermal buckling) is shown that occurs in less than 1 second (for the copper thickness that has been argued as employed for the microwave cavity), with a temperature increase of a degree C or less and that results in forces of the same magnitude (microNewtons) as reportedly measured by NASA.
...
Very plausible. Now, my humble understanding is that in order to test for this theory one would need to measure the abnormal force at 2 different Q values. Since the dissipated power would remain the same, one would then expect the same force regardless of Q.
...Of course, this requires observing some abnormal force to begin with. -
#1114 by rfmwguy on 02 Jan, 2016 00:35
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Old news from a couple of months ago, but Digital Trends produced a couple of videos targeted for gradeschoolers. If you look carefully, you'll see our long lost friend Iulian's video snippet. Hope he is doing well:
http://www.digitaltrends.com/cool-tech/emdrive-news-rumors/ -
#1115 by R.W. Keyes on 02 Jan, 2016 01:16
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http://www.popularmechanics.com/science/a18801/3d-printed-wonder-ceramics-wont-shatter/
I want a FRUSTUM from this!
Shell
Yes, let's see if this process can be adapted for YBCO! But for now, I am going to keep my eyes on MgB2. For the time being, it's only my eyes, as I can't get my hands on any until my money arrives...which should be soon! -
#1116 by oyzw on 02 Jan, 2016 01:41
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I have a friend who is a high temperature superconducting engineer, has been promoting his design of YBCO thin film resonatorhttp://www.popularmechanics.com/science/a18801/3d-printed-wonder-ceramics-wont-shatter/
I want a FRUSTUM from this!
Shell
Yes, let's see if this process can be adapted for YBCO! But for now, I am going to keep my eyes on MgB2. For the time being, it's only my eyes, as I can't get my hands on any until my money arrives...which should be soon! -
#1117 by oyzw on 02 Jan, 2016 02:04
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http://www.popularmechanics.com/science/a18801/3d-printed-wonder-ceramics-wont-shatter/
I want a FRUSTUM from this!
Shell
Yes, let's see if this process can be adapted for YBCO! But for now, I am going to keep my eyes on MgB2. For the time being, it's only my eyes, as I can't get my hands on any until my money arrives...which should be soon!
[/quote。 Cooling MgB2 cavity is very difficult -
#1118 by DnA915 on 02 Jan, 2016 03:18
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MEEP and EM Sim people,
So I decided to go ahead and get GSVit (GPU accelerated simulations) working on the AWS cloud, partially just because of my own curiosity. It took a bit more work than I anticipated, but I did finally get their benchmarks done and I thought it would be worth sharing:
The machine I was using was a very powerful 8 Core Xenon with a very high end NVIDIA GPU. The benchmark compared all cores of the processors vs the GPU. What I found was that with a processor of this speed and cores, the GPU acceleration was not as extreme as I had hoped. The benchmarks went through a variety of materials, but for most, it was in the 5x to 10x range when comparing GPU to all cores. There were a few materials where the speedup was drastic, but for the most part, it disappointed me some. Also, just for the record, when comparing to a single core, it did give about a 40x speed bump, so their quoted numbers were not deceptive. If anyone is interested, I'd be happy to share the exact numbers or the VirtualBox image for the non-GPU version. I also have a public AMI up on AWS at the moment if you search for GSVit.
- David
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#1119 by R.W. Keyes on 02 Jan, 2016 06:06
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Can you tell us more? YBCO looks very difficult to fabricate with the dimensions and smoothness we require.
I have a friend who is a high temperature superconducting engineer, has been promoting his design of YBCO thin film resonatorhttp://www.popularmechanics.com/science/a18801/3d-printed-wonder-ceramics-wont-shatter/
I want a FRUSTUM from this!
Shell
Yes, let's see if this process can be adapted for YBCO! But for now, I am going to keep my eyes on MgB2. For the time being, it's only my eyes, as I can't get my hands on any until my money arrives...which should be soon!
