1. Reactors don't explode. :
See SL-1, Chernobyl, and the one the AEC blew in Idaho just for fun.
2. A Chernobyl style accident is impossible with a light water reactor.
True, but there are still about 843 other failure modes that don't involve the many bad design features of RBMK-style reactors.
3. Even with a Chernobyl style reactor and even if they had the exact same accident the problem would have been manageable if they had a freaking containment building.
Not feasible if you're a poor country that needs a RBMK style reactor that can be refueled while running.
4. Reactors all go critical. What you don't want is for them to go super critical.
Duh. And I think you're confusing super-critical to with prompt-critical. Very different beasts.
5. No modern reactor can go super critical the fuel they use isn't enriched enough to go super critical and they all need a moderator like water to work.
Nope. Enrichment has nothing to do with it. AT least three reactors have gone boom with low enrichment uranium.
(1) OLED Breakthrough Yields 75% More Efficient Light (2)...reducing the ultra-thin lightsâ(TM) energy consumption by 75% (3) increases photoluminescence emission rates by 1.75 times (4) increases light intensity twofold.
*Four* numerical figures, and no two of them compatible in any way.
(1): "a 75% more efficient light" would mean an increase to 175% or original, a factor of 1.75 times better. (2): "reducing by 75%" means a factor of 4 better. (3): "increases photoluminescence emission rates by 1.75 times" means a 2.75 time increase, a factor of 2.75 (4): "increases light intensity twofold" is a factor of 2.
All incompatible. Wonder what the real numbers are?
It would seem to violate Kirchoff's and Ohm's laws to expect that a milliamp of current looping from keyboard to motherboard is somehow going to jump out to earth ground, somehow. And that signal will somehow be detectable among the many AMPS of other quasi-random signals running along the motherboard, and many amps of ambient noise on the power line.
And filtering is of very limited help. The spectrum of keyboard signals is overlaid by dozens of power line harmonics of much greater amplitude.
What does work is to pick up the direct radiation from some of the cheaper unshielded keyboards. You have to be within a few feet of the keyboard but even a cheap transistor radio can pick up the keyboard signals.
This "Story" is a bogus rehashing of old, old methods. Old as in 60 to 80 years old. The NSA has been grabbing serial teletype signals off adjacent signal and power wires for at least that long.
It's old and in this case quantitatively bogus. The keyboard signals are milliamps. The leakage to chassis ground will be at least 40dB down, or under a microamp. The leakage from there to earth ground will be at least another 20dB down so we're down in the nanoamp range. By comparison the background ground currents from the PC's switching power supply and other devices will be several thousand times greater. If there's a light dimmer on the same circuit the noise will be nearly a million times greater. You can't combat that kind of background noise.
Same problem with the keyboard vibrations-laser scheme. They got the idea from a 1930's detective story where the secretary put her gold cigarette case under the phone receiver so her typing could be heard on the other end. Old!
But that only had a chance of working because each typewriter key row has a specific length of lever and spring, plus the typefaces are arrayed in a curve, so each one strikes the paper from a different angle, giving the listener an opportunity to guess the letter from the combination of X info from the length of the lever and spring, and Y info from the typeface strike angle.
But that is completely inapplicable to a modern keyboard, where THE KEYS ARE ALL IDENTICAL. No differing row and arc info at all. Maybe a teensy difference if the keyboard base is flimsy and has a slight change in resonance across the board. But unlikely.
Uh, no. You can't get any energy out of the pressure difference in the atmosphere or ocean. The pressure difference is there because the medium has already adjusted to the lowest energy state. You cant milk any more energy out of a system that is already at lowest equilibrium.
These well-meaning schemes still founder on the basic problems of working in a salt-water environment and the issue of a very dilute energy source. You can't make a generator that works directly off ocean-swells-- the swells come by so slowly you'd need a coil inductance of about ten thousand Henries.
A simple loop of wire, as postulated, has about a millionth of that.
Plus you need considerable iron to channel the magnetic flux. No way around it.
Regarding the kites, figure out what the very lightest generator weighs, per watt. Hint: not under 30 kilos per KW. Now assume you want to power 100 houses, say 50 KW.
Figure out the size of the kite needed to lift than many tons. Now at a 30 degree kitestring angle, the pull on the string will be twice the weight of the kite. Figure out how much 60,000 feet of kite string that will take that kind of stress weighs. Now you need another large kite just to hold up the kite string.
And BTW, the "high speed" winds up there are not a panacea. They're high speed but low in density. The energy is, again, very dilute. You need to at least double the size of the kite to get the same amount of lift and pull as you can get at low altitudes. .
IIRC the DeLorean company got almost as much cash from the Brits to build a factory in Northern Ireland.
Turned out with all the lack of infrastructure and suppliers, it would have been cheaper to build the factory in Beverly Hills.
Looks like Tesla is going one step further and actually building the factory right away in a high-cost area..... And aren't there dozens of GM car factories just sitting idle?
It's unlikely that a plywood plane would show up on England's chain-home or chain-home-low radars.
The technology at the time forced them to use frequencies in the 10-meter range. An object has to be at least 1/4 the wavelength in order to give a sizeable reflection.
So a plane with just two smallish metal engines would likely be invisible among the usual sea and ground clutter.
Do any of these kite-engineers know how much a wind turbine and generator WEIGH? We're talking hundreds of tons. Please point to a kite that can lift 1% of that. Now go play with your kites and leave us alone.
It's amazing what you can do with a spreadsheet. Fudge things just right, and you can overcome a wall of facts, even a 8 times disadvantage. Awesome.
But back in the real world, trains and ships can move stuff for pennies a ton-mile, at useful and quiet speeds, with very low emissions, and requiring relatively low-energy infrastructure of wood and iron. While air transport moves stuff at a cost of almost a dollar a ton-mile, while emitting a whole lot more noise near the endpoints, and requiring a lot more ecological modification, including many square miles of flat and clearcut land for airports. Not to mention the use of huge amounts of electricity to refine the aluminum for the airframes.
Next up, these guys should prove how the optimum diet is one of steak and cherry pie. It can be done.
You know you'd think so but the article does not mention that, and other scientists (think cold fusion) have failed to make the simple in/out measurements.
I hope these guys are correct, but there are a few things to look into:
* A small segment of blasted filament would look brighter if the laser simply thinned out the filament or raised its resistance. Tungsten has a strong negative temperature coefficient of resistance so the total power draw might not change much. I hope they were not misled in this way.
* Light bulb filaments are very tightly curled so a significant part of the light intersects nearby loops of the filament. A better, blacker emissive surface will also be a much better absorber, making the whole thing a wash.
The claim of "invisibility" sounds like exactly what one would write in a grant proposal to the Naval Research Lab.
Never mind it's very very unlikely.
Any practical cloaking device is almost certainly going to work in only one linear direction and at one temperature and frequency.
And imperfectly at best.
And probably be larger than what it's trying to cloak.
But sonar pulses are spread in frequency and can arrive from any direction, making such a cloaking device useless.
This just sounds like the perfect phrase to put in a grant proposal to get some Admiral to sign off on it.
Pulsars have been used for geodesic measurements for about 30 years. The nice short regular pulses make it possible to track the movement of continental plates down to the miliionth of a LOC length.
(1) Encode the data as the packet length. (2) Encode the data as the packet checksum (3) Encode the data as the fragment offset. (4) Encode the data as the number of extra ACKS. (5) Encode the data as the starting connection sequence number. (6) Encode the data as the window size. (7) Encode the data as the inter-packet delay.
Steganography has the fatal flaw that the method has to remain secret. One basic rule of encryption is to assume the method is discernible and the security must be all in some secret key.
We live in a universe permeated by cosmic rays of very high energies. The flux is about 0.2 ray per square centimeter per second. Each ray can easily ionize a track a billion atoms long.
In a billion years that's about 6 x 10^21 bits damaged per square cm. Not exactly legible.
I wish somebody with a lick of sense would vet these ideas before they got out there.
All that's going to happen with IR spectrometers checking the water supply is a constant din of false positives, which will at first cause panic, then lethargy. Even a 0.001% false positive rate is way too high when you're trying to find a 0.0000001% signal.
If you go down to your local 24-hour CVS MegaStore, peer at the hearing-aid battery end cap display, you'll see about 24 different kinds of "hearing air-cells". Cells where you remove a little cover over some breathing air holes to activate them.
Thanks for the backup. A few more things I noticed:
(1) At some bias settings that transistor and its stray lead inductances is likely to act like a VHF oscillator. Don't use this thing to measure noise on a plane! ( Aircraft nav aids and voice comms are in the VHF range.)
(2) Those buzzers seem to be spec'd to operate at particular frequencies, which strongly suggests they're resonant. That will make the frequency response particularly peaked and non-optimal.
(3) Using a device in a way it's not designed is not only likely to give poor performance, it's also risky. The manufacturer may make changes which improve its efficiency for its intended application, but may wreck its alternate use. For example they might change the buzzer to have a higher resonant Q, which would give it a purer tone, but make its frequency response useless as microphone. They might even make these changes from batch to batch, frustrating those users that get the "wrong" batch.
---
Then again it's an ill wind that blows no good. This would be an excellent learning experience IF you presented it as:
"Here's a working design. Find at least TEN major things wrong with it that would doom it as an actual usable product. Suggest remedies."
It's neither "fun" nor "interesting" when your design is 8 times as complicated and expensive as one that works, and yours is neither stable, accurate, hi-fi, or immune to temperature changes, power supply noise or electrical interference.
Yes it's fun to mess around with parts and get them to do something, anything. But this is not an example of any kind of sane engineering. I assume most people going into $95,000 debt to attend MIT intend to try to be useful engineers. This item on your resume is a quick ticket to Palookaville.
This project is an excellent example of how having a little theoretical knowledge is a bad thing.
They have just enough knowledge to get into complicated and pointless gain calculations, but they miss most of the really important things. Here's a few:
(1) A piezo buzzer is not designed for any kind of flat frequency response. Which is a basic requirement for a sound-level meter. Major fail from the get-go.
(2) We're going on 60 years of having a spec for sound meter weighing curves and envelope filtering characteristics. Yet no mention of that in the article. A randomly designed meter is useless.
(3) They go on and on about calculating the gain of the amplifier stage, and they do it incorrectly. We care not one whit about the DC gain. The AC gain is dependent on the AC impedance of the source and load. Even the DC gain they calculate is useless as those transistors have a huge range of gains. And no analysis of the DC stability, which is harder to get right. Gain just happens, stability has to be designed in.
(4) Biasing the base from a pot in that fashion is never done in practice. A better design would use two resistors and avoid the cost and impedance variations of the one pot "design".
(5) A real design would have the +5 volt line decoupled and filtered to keep microprocessor switching noise out.
----
In summary these designers should wait until they get past the first chapter of their transistor class before going out and trying to design anything. Good design requires more than slavish focusing on one small area. An engineer has to have a broad view.
If memcpy() is hazardous, that means they also need to ban any operations that can mimic its effects, such as for loops, array indexing, ++ and --. And any call to read() or fread(). That sure would tighten things up!
Why does anyone care about these numbers besides movie studio producers? I've not seen any correlation between movies that I enjoy versus their box office. Often quite the opposite.
Slashdot Mirror
All wrong:
1. Reactors don't explode. :
See SL-1, Chernobyl, and the one the AEC blew in Idaho just for fun.
2. A Chernobyl style accident is impossible with a light water reactor.
True, but there are still about 843 other failure modes that don't involve the many bad
design features of RBMK-style reactors.
3. Even with a Chernobyl style reactor and even if they had the exact same accident the problem would have been manageable if they had a freaking containment building.
Not feasible if you're a poor country that needs a RBMK style reactor that can be refueled while running.
4. Reactors all go critical. What you don't want is for them to go super critical.
Duh. And I think you're confusing super-critical to with prompt-critical. Very different beasts.
5. No modern reactor can go super critical the fuel they use isn't enriched enough to go super critical and they all need a moderator like water to work.
Nope. Enrichment has nothing to do with it. AT least three reactors have gone boom with low enrichment uranium.
(1) OLED Breakthrough Yields 75% More Efficient Light ...reducing the ultra-thin lightsâ(TM) energy consumption by 75%
(2)
(3) increases photoluminescence emission rates by 1.75 times
(4) increases light intensity twofold.
*Four* numerical figures, and no two of them compatible in any way.
(1): "a 75% more efficient light" would mean an increase to 175% or original, a factor of 1.75 times better.
(2): "reducing by 75%" means a factor of 4 better.
(3): "increases photoluminescence emission rates by 1.75 times" means a 2.75 time increase, a factor of 2.75
(4): "increases light intensity twofold" is a factor of 2.
All incompatible. Wonder what the real numbers are?
It would seem to violate Kirchoff's and Ohm's laws to expect that a milliamp of current looping from keyboard to motherboard is somehow going to jump out to earth ground, somehow. And that signal will somehow be detectable among the many AMPS of other quasi-random signals running along the motherboard, and many amps of ambient noise on the power line.
And filtering is of very limited help. The spectrum of keyboard signals is overlaid by dozens of power line harmonics of much greater amplitude.
What does work is to pick up the direct radiation from some of the cheaper unshielded keyboards. You have to be within a few feet of the keyboard but even a cheap transistor radio can pick up the keyboard signals.
This "Story" is a bogus rehashing of old, old methods. Old as in 60 to 80 years old. The NSA has been grabbing serial teletype signals off adjacent signal and power wires for at least that long.
It's old and in this case quantitatively bogus. The keyboard signals are milliamps. The leakage to chassis ground will be at least 40dB down, or under a microamp. The leakage from there to earth ground will be at least another 20dB down so we're down in the nanoamp range. By comparison the background ground currents from the PC's switching power supply and other devices will be several thousand times greater. If there's a light dimmer on the same circuit the noise will be nearly a million times greater. You can't combat that kind of background noise.
Same problem with the keyboard vibrations-laser scheme. They got the idea from a 1930's detective story where the secretary put her gold cigarette case under the phone receiver so her typing could be heard on the other end. Old!
But that only had a chance of working because each typewriter key row has a specific length of lever and spring, plus the typefaces are arrayed in a curve, so each one strikes the paper from a different angle, giving the listener an opportunity to guess the letter from the combination of X info from the length of the lever and spring, and Y info from the typeface strike angle.
But that is completely inapplicable to a modern keyboard, where THE KEYS ARE ALL IDENTICAL. No differing row and arc info at all. Maybe a teensy difference if the keyboard base is flimsy and has a slight change in resonance across the board. But unlikely.
I call bogus.
Uh, no. You can't get any energy out of the pressure difference in the atmosphere or ocean. The pressure difference is there because the medium has already adjusted to the lowest energy state. You cant milk any more energy out of a system that is already at lowest equilibrium.
These well-meaning schemes still founder on the basic problems of working in a salt-water environment and the issue of a very dilute energy source.
You can't make a generator that works directly off ocean-swells-- the swells come by so slowly you'd need a coil inductance of about ten thousand Henries.
A simple loop of wire, as postulated, has about a millionth of that.
Plus you need considerable iron to channel the magnetic flux. No way around it.
Regarding the kites, figure out what the very lightest generator weighs, per watt. Hint: not under 30 kilos per KW. Now assume you want to power 100 houses, say 50 KW.
Figure out the size of the kite needed to lift than many tons. Now at a 30 degree kitestring angle, the pull on the string will be twice the weight of the kite. Figure out how
much 60,000 feet of kite string that will take that kind of stress weighs. Now you need another large kite just to hold up the kite string.
And BTW, the "high speed" winds up there are not a panacea. They're high speed but low in density. The energy is, again, very dilute. You need to at least double the size of the kite to get the same amount of lift and pull as you can get at low altitudes.
.
IIRC the DeLorean company got almost as much cash from the Brits to build a factory in Northern Ireland.
Turned out with all the lack of infrastructure and suppliers, it would have been cheaper to build the factory in Beverly Hills.
Looks like Tesla is going one step further and actually building the factory right away in a high-cost area. .... And aren't there dozens of GM car factories just sitting idle?
It's unlikely that a plywood plane would show up on England's chain-home or chain-home-low radars.
The technology at the time forced them to use frequencies in the 10-meter range.
An object has to be at least 1/4 the wavelength in order to give a sizeable reflection.
So a plane with just two smallish metal engines would likely be invisible among the usual sea and ground clutter.
Do any of these kite-engineers know how much a wind turbine and generator WEIGH? We're talking hundreds of tons. Please point to a kite that can lift 1% of that. Now go play with your kites and leave us alone.
It's amazing what you can do with a spreadsheet. Fudge things just right, and you can overcome a wall of facts, even a 8 times disadvantage.
Awesome.
But back in the real world, trains and ships can move stuff for pennies a ton-mile, at useful and quiet speeds, with very low emissions, and requiring relatively low-energy infrastructure of wood and iron.
While air transport moves stuff at a cost of almost a dollar a ton-mile, while emitting a whole lot more noise near the endpoints, and requiring a lot more ecological modification, including many square miles of flat and clearcut land for airports. Not to mention the use of huge amounts of electricity to refine the aluminum for the airframes.
Next up, these guys should prove how the optimum diet is one of steak and cherry pie. It can be done.
You know you'd think so but the article does not mention that, and other scientists (think cold fusion) have failed to make the simple in/out measurements.
I hope these guys are correct, but there are a few things to look into:
* A small segment of blasted filament would look brighter if the laser simply thinned out the filament or raised its resistance.
Tungsten has a strong negative temperature coefficient of resistance so the total power draw might not change much. I hope
they were not misled in this way.
* Light bulb filaments are very tightly curled so a significant part of the light intersects nearby loops of the filament. A better, blacker emissive surface will also be a much better absorber, making the whole thing a wash.
The claim of "invisibility" sounds like exactly what one would write in a grant proposal to the Naval Research Lab.
Never mind it's very very unlikely.
Any practical cloaking device is almost certainly going to work in only one linear direction and at one temperature and frequency.
And imperfectly at best.
And probably be larger than what it's trying to cloak.
But sonar pulses are spread in frequency and can arrive from any direction, making such a cloaking device useless.
This just sounds like the perfect phrase to put in a grant proposal to get some Admiral to sign off on it.
Pulsars have been used for geodesic measurements for about 30 years. The nice short regular pulses make it possible to track the movement of continental plates down to the miliionth of a LOC length.
Heh, I can think up a half dozen better stegas:
(1) Encode the data as the packet length.
(2) Encode the data as the packet checksum
(3) Encode the data as the fragment offset.
(4) Encode the data as the number of extra ACKS.
(5) Encode the data as the starting connection sequence number.
(6) Encode the data as the window size.
(7) Encode the data as the inter-packet delay.
Steganography has the fatal flaw that the method has to remain secret. One basic rule of encryption is to assume the method is discernible and
the security must be all in some secret key.
Sorry, can't tell if you're kidding.
( Cosmic rays can go through several feet of lead. )
We live in a universe permeated by cosmic rays of very high energies. The flux is about 0.2 ray per square centimeter per second. Each ray can easily ionize a track a billion atoms long.
In a billion years that's about 6 x 10^21 bits damaged per square cm. Not exactly legible.
I wish somebody with a lick of sense would vet these ideas before they got out there.
All that's going to happen with IR spectrometers checking the water supply is a constant din of false positives, which will at first cause panic, then lethargy. Even a 0.001% false positive rate is way too high when you're trying to find a 0.0000001% signal.
If you go down to your local 24-hour CVS MegaStore, peer at the hearing-aid battery end cap display, you'll see about 24 different kinds of "hearing air-cells". Cells where you remove a little cover over some breathing air holes to activate them.
Air-reacting cells have been around a long time.
And this is a problem, how?
Did anyone think there was NOT some nearby secure location?
Now if he'd added "and of course there are three escape tunnels surfacing at hidden helipads at X, Y, and Z," THEN maybe it would be a goof.
Thanks for the backup. A few more things I noticed:
(1) At some bias settings that transistor and its stray lead inductances is likely to act like a VHF oscillator. Don't use this thing to measure noise on a plane! ( Aircraft nav aids and voice comms are in the VHF range.)
(2) Those buzzers seem to be spec'd to operate at particular frequencies, which strongly suggests they're resonant. That will make the frequency response particularly peaked and non-optimal.
(3) Using a device in a way it's not designed is not only likely to give poor performance, it's also risky. The manufacturer may make changes which improve its efficiency for its intended application, but may wreck its alternate use.
For example they might change the buzzer to have a higher resonant Q, which would give it a purer tone, but make its frequency response useless as microphone. They might even make these changes from batch to batch, frustrating those users that get the "wrong" batch.
---
Then again it's an ill wind that blows no good. This would be an excellent learning experience IF you presented it as:
"Here's a working design. Find at least TEN major things wrong with it that would doom it as an actual usable product. Suggest remedies."
It's neither "fun" nor "interesting" when your design is 8 times as complicated and expensive as one that works, and yours is neither stable, accurate, hi-fi, or immune to temperature changes, power supply noise or electrical interference.
Yes it's fun to mess around with parts and get them to do something, anything. But this is not an example of any kind of sane engineering. I assume most people going into $95,000 debt to attend MIT intend to try to be useful engineers. This item on your resume is a quick ticket to Palookaville.
This project is an excellent example of how having a little theoretical knowledge is a bad thing.
They have just enough knowledge to get into complicated and pointless gain calculations, but they miss most of the really important things. Here's a few:
(1) A piezo buzzer is not designed for any kind of flat frequency response. Which is a basic requirement for a sound-level meter. Major fail from the get-go.
(2) We're going on 60 years of having a spec for sound meter weighing curves and envelope filtering characteristics. Yet no mention of that in the article. A randomly designed meter is useless.
(3) They go on and on about calculating the gain of the amplifier stage, and they do it incorrectly. We care not one whit about the DC gain. The AC gain is dependent on the AC impedance of the source and load. Even the DC gain they calculate is useless as those transistors have a huge range of gains. And no analysis of the DC stability, which is harder to get right. Gain just happens, stability has to be designed in.
(4) Biasing the base from a pot in that fashion is never done in practice. A better design would use two resistors and avoid the cost and impedance variations of the one pot "design".
(5) A real design would have the +5 volt line decoupled and filtered to keep microprocessor switching noise out.
----
In summary these designers should wait until they get past the first chapter of their transistor class before going out and trying to design anything. Good design requires more than slavish focusing on one small area. An engineer has to have a broad view.
If memcpy() is hazardous, that means they also need to ban any operations that can mimic its effects, such as for loops, array indexing, ++ and --. And any call to read() or fread(). That sure would tighten things up!
Why does anyone care about these numbers besides movie studio producers? I've not seen any correlation between movies that I enjoy versus their box office. Often quite the opposite.
That said I loved ST and wish it many sequels.