TLDR: Molten salt has zero benefit as a nighttime storage system. Ordinary boiling water is a better choice by a factor of >500.
I can't find good data on the heat capacity of the particular salt used in this system, but heat capacities for salts in general are around 1 J/kg-K.. If you're dealing with a temperature change of 700 K, that means each kg of salt can store around 700 J of heat. To store enough heat to power a typical American household overnight (1 kw x 12 hours), you'd need 61 tonnes of salt.
Now, most power plants use water as the working fluid. The latent heat of vaporization of water means that steam stores *at least* 330,000 J per kg of water in the phase change alone, plus additional specific heat if the steam is stored above the boiling point, which I'm too lazy to calculate.
That means that plain old ordinary water, already used in every thermodynamic power plant ever made, is at least 500 times better at storing heat than salt is.
First: if you're not reading The Oil Drum, you should be.
But on to my point. The controlling factor for building nuclear power plants is not money or power, but fear. Fear of contamination controls the decade-long permitting process. Fear of terrorist attack or accident controls the number of guards, monitoring personnel, and operators who work at the plant on a daily basis. The majority of the expense of actually building the plant goes into safety and security systems.
Now, some of these fears are reasonable. But that's not the point: the point is that a small power plant is just as scary as a large one.
The best power plant is not the most energy efficient one, or even the one that's strictly speaking the safest. It's the one that produces the least amount of fear per gigawatt. And that means building gigantic plants.
Either form of polarization can be used to implement an LCD
I'm not gonna come out and say you're wrong here, but since liquid crystals work by rotating the orientation of linearly polarized light, and since that rotation shouldn't have any effect on circularly polarized light, I don't see how you can make an LCD that uses circular polarization.
Now, you can always add a quarter-wave plate to the front of the screen to convert the linearly polarized light to circular as it exits, but that's not the same thing.
LCDs are moving to the circular polarization form for that reason.
I can't find any info on the Net to suggest this is true, and I haven't ever seen an LCD screen that didn't respond to polarizing glasses.
I'm not Windows expert, but isn't this exactly the way the certificate system is supposed to operate? This sounds like a security success story, not a failure.
Driver needs certificate to work with OS. Driver is found to contain security flaw. Certificate is revoked, OS refuses to recognize driver, security hole is closed. Now driver manufacturer has to clean up their act before their drivers are allowed back in the house.
The headline reads "Microsoft has no plans to patch new flaw", but isn't the certificate revocation at least as good as a patch? More so, because it seals off any *other* undiscovered bugs in the driver? Or am I missing something?
There was also some blog discussion of delivering a lifeboat Dragon in the Shuttle cargo bay. But since then, the Shuttle life has shortened and SpaceX's schedule has stretched to the point where that's probably impossible.
Finally, it will costs a great deal of money for NASA to get to the moon. So, why not offer up an X-Prize
Do all the cars in question have drive-by-wire electronic throttles? If so, you're right. But if not, sensor / software failure cannot cause uncontrolled acceleration, because the mechanical link, not the computer, sets the throttle. The worst that can happen from a faulty throttle position sensor is that the computer floods the engine, causing a stall.
Somebody with some lawyer skills, fill me in here: If I'm walking down the street not suspected of any crime and I spit on a public sidewalk, can the police scoop it up and DNA fingerprint me? I'm assuming not, that my discarded DNA has an expectation of privacy which they need probable cause to collect.
Does a DNA match with the suspect's son constitute probable cause to gather DNA evidence on the father? Does a judge need to sign off on it? If it *is* probable cause, why do they need a stakeout? Why can't they just wave a subpoena in his face, frogmarch him into the police station and jam a swab in his mouth?
Yes, but often the defendant and *his brother* are both potential suspects.
This actually came up in a case I served on a jury for. The defense argued that the *other* brother could well have committed the crime, and given the poor quality of DNA evidence, we couldn't disprove that beyond a reasonable doubt.
DNA collision among close-knit racial groups is worth thinking about; collision within families is a serious problem.
Where do we get to the part where the status quo is restored to a rocket system that doesn't work, and probably will never work, which has so far achieved ten times less with ten times the money as a commercial system (SpaceX)? A status quo that's designed for a lunar mission which we can never afford, and which would be a stupid idea in the first place?
I don't care about which state is getting which money to support which political agenda, democrat or republican. What I care about is space missions that *work*. Robotic missions to the solar system, plus a manned orbital and/or Mars mission supported by either the Shuttle or a COTS program, will work. Going to the Moon in a pork-powered megarocket won't.
I'm drawing a distinction between American government and American culture and technology. The US government has, of course, supported some oppressive governments, but it's done so in *spite* of our cultural power, not because of it.
You basically have all of that rolled into one with Saudi Arabia, and they do not fear us.
Yes they do. They don't see our government as a threat, but if you showed your average Saudi sheikh or mullah a Facebook page showing his daughter in blue jeans and a T-shirt attending a Lady Gaga concert, he'd probably have a heart attack. And if he survived, we'd probably have to grant the daughter political asylum.
We only spread freedom for businesses; individual freedom never plays into the equation.
I share a lot of your cynicism, but you're looking at too short a timeframe. Iraq, sure. But we didn't have a real economic interest in launching airstrikes in Yugoslavia, for example, and until very recently we had very little corporate incentive to defend South Korea. The U.S. government does act to defend corporate freedom, yes, but that's not its *only* motivation.
And besides, U.S. corporate interests aren't necessarily in opposition to the creeping free-speech hegemony I'm talking about. After all, what do we *make* here in the U.S.? Music, movies, TV shows and software.
(Protests against Iranian election results) http://mashable.com/2009/06/20/iran-youtube/...and that's just a start. We as geeks may have buzzwords like "semantic web" that we like to trot out, but the fact is that whenever you give people new tools to talk openly to one another on a mass scale, whether that's text, audio, or video, oppressive governments tremble.
And the great thing about the Internet is that it's designed from the ground up to reject authority. Cracking down on free speech on the Internet, no matter what form that speech takes, is like wrestling a greased pig.
This goes to something I've been saying for years now. The U.S. has some pretty impressive military power, but that's not what scares the world's dictators, religious zealots, and oppressive regimes. What do they fear about us? Rock 'n' roll, short skirts, blue jeans, and *especially* cell phones, e-mail, and Facebook.
The U.S. does a lot of things poorly, including, lately, waging ground wars. But one thing we're still very very good at: coming up with new ways for the world's young people to mock and ridicule authority figures, and for adults to talk to each other freely without government interference.
The cell phone, the 18" satellite dish, and the Internet are the most terrifying weapons against autocratic states the world has ever known. Is Facebook a threat to oppressive regimes? HELL YES, and we should be proud of that.
U.S. foreign policy should recognize this fact, and use it to its advantage. Rather than planning air strikes against Iranian and North Korean nuclear sites, we should be flying over and dropping cell phones, laptops, and MP3 players loaded with Rage Against the Machine and Ani diFranco.
Actually no! Check Figure 2 in the original article. Hydrogen and oxygen isotopes are linearly related to each other in natural waters, following the "Global Meteoric Water Line". If you measure delta-2H, you know delta-18O or vice versa.
and put most of the [grading] emphasis on exams where the subject is not known before hand.
I'll tell you from first-hand experience that students, even honest ones, HATE it when you do this. Well "tough titties", right? But even worse, many honest students do well in a normal assignment setting, but if you put them in an exam situation, they freak out and do very poorly. Exam anxiety is a very real problem, and grading by exams alone is unfair to these students.
Good point re the use of hair to provide a timeline, but if you figure the average human consumes about 1.5 kg of water a day, and contains about 60 kg of water, that means the water has a residence time of about a month and a half. It'll take that long to "flush out" your system.
And the "one degree of freedom" problem still limits the location accuracy of this. Check the map in the original article. The isotopic ratio of water is the same in Florida as in Texas; the same in Boston as in San Francisco. This data can narrow down a person's location, but it'll never provide a unique unambiguous location.
This may be forensically useful, but don't think of it like a fingerprint or a DNA match. There's only one degree of freedom here -- whether the water is isotopically "heavy" or "light". All of a person's water co9nsumption history is mixed up into one number.
So you won't be able to tell the difference between, say, a person who lived all year in Illinois (with a moderate isotope ratio) and a person who flies back and forth between Montana and Florida (who'd have a mix of "heavy" and "light" water in their system.)
if students were evaluated in a meaningful and practical way, this service would be useful to maybe a handful of smart but lazy students.
Okay, smart guy, now you're on the hook. What's your concrete proposal for evaluating students in, say, an English class in a "meaningful and practical way" that is impervious to ghostwriting and plagiarism?
As a college professor who tries to come up with unplagiarizeable assignments on a daily basis, I can tell you that this is easier said than done.
Why bother *sending* them to anyone? Just post some family shots on Picasa and make the album public. Hell, one of the spies worked as a real estate agent: posting photos on the net is a big part of her job.
People post millions of public pictures on the Net every day, it's not the least bit suspicious.
Yes, this is apparently what happened. Read pages 8-13 of the criminal complaint. After years of covert surveillance, three days ago the FBI arranged a meeting between an undercover agent posing as a Russian intelligence official and one of the alleged spies.
The undercover agent knew the right code phrases, but asked a lot of nosy questions. He/she actually convinced the Russian agent to give him/her the laptop she used for secret communications so it could be repaired, which has got to be one of the ballsiest counterespionage moves ever. But the Russian agent apparently got suspicious, bought a disposable cell phone, called for confirmation, and never showed up for a followup meeting.
At this point, the FBI decided to haul in the net.
Slashdot Mirror
TLDR: Molten salt has zero benefit as a nighttime storage system. Ordinary boiling water is a better choice by a factor of >500.
I can't find good data on the heat capacity of the particular salt used in this system, but heat capacities for salts in general are around 1 J/kg-K.. If you're dealing with a temperature change of 700 K, that means each kg of salt can store around 700 J of heat. To store enough heat to power a typical American household overnight (1 kw x 12 hours), you'd need 61 tonnes of salt.
Now, most power plants use water as the working fluid. The latent heat of vaporization of water means that steam stores *at least* 330,000 J per kg of water in the phase change alone, plus additional specific heat if the steam is stored above the boiling point, which I'm too lazy to calculate.
That means that plain old ordinary water, already used in every thermodynamic power plant ever made, is at least 500 times better at storing heat than salt is.
This plant has one key advantage over your pet "LFTR": it actually exists.
Actual power plants beat fictitious power plants any day of the week.
First: if you're not reading The Oil Drum, you should be.
But on to my point. The controlling factor for building nuclear power plants is not money or power, but fear. Fear of contamination controls the decade-long permitting process. Fear of terrorist attack or accident controls the number of guards, monitoring personnel, and operators who work at the plant on a daily basis. The majority of the expense of actually building the plant goes into safety and security systems.
Now, some of these fears are reasonable. But that's not the point: the point is that a small power plant is just as scary as a large one.
The best power plant is not the most energy efficient one, or even the one that's strictly speaking the safest. It's the one that produces the least amount of fear per gigawatt. And that means building gigantic plants.
Either form of polarization can be used to implement an LCD
I'm not gonna come out and say you're wrong here, but since liquid crystals work by rotating the orientation of linearly polarized light, and since that rotation shouldn't have any effect on circularly polarized light, I don't see how you can make an LCD that uses circular polarization.
Now, you can always add a quarter-wave plate to the front of the screen to convert the linearly polarized light to circular as it exits, but that's not the same thing.
LCDs are moving to the circular polarization form for that reason.
I can't find any info on the Net to suggest this is true, and I haven't ever seen an LCD screen that didn't respond to polarizing glasses.
I'm not Windows expert, but isn't this exactly the way the certificate system is supposed to operate? This sounds like a security success story, not a failure.
Driver needs certificate to work with OS. Driver is found to contain security flaw. Certificate is revoked, OS refuses to recognize driver, security hole is closed. Now driver manufacturer has to clean up their act before their drivers are allowed back in the house.
The headline reads "Microsoft has no plans to patch new flaw", but isn't the certificate revocation at least as good as a patch? More so, because it seals off any *other* undiscovered bugs in the driver? Or am I missing something?
I'm not saying the idea of a Dragon in the shuttle bay makes any sense at all: personally it baffles me too. But the idea is out there.
Re "Lifeboat Dragon", see the first two "back up" slides here:
http://www.spacex.com/20090617_Elon_Musk_Augustine_Commission.pdf
There was also some blog discussion of delivering a lifeboat Dragon in the Shuttle cargo bay. But since then, the Shuttle life has shortened and SpaceX's schedule has stretched to the point where that's probably impossible.
Finally, it will costs a great deal of money for NASA to get to the moon. So, why not offer up an X-Prize
Finally, screw the moon. The moon is a trap.
+1, flamebait.
Do all the cars in question have drive-by-wire electronic throttles? If so, you're right. But if not, sensor / software failure cannot cause uncontrolled acceleration, because the mechanical link, not the computer, sets the throttle. The worst that can happen from a faulty throttle position sensor is that the computer floods the engine, causing a stall.
Somebody with some lawyer skills, fill me in here: If I'm walking down the street not suspected of any crime and I spit on a public sidewalk, can the police scoop it up and DNA fingerprint me? I'm assuming not, that my discarded DNA has an expectation of privacy which they need probable cause to collect.
Does a DNA match with the suspect's son constitute probable cause to gather DNA evidence on the father? Does a judge need to sign off on it? If it *is* probable cause, why do they need a stakeout? Why can't they just wave a subpoena in his face, frogmarch him into the police station and jam a swab in his mouth?
Yes, but often the defendant and *his brother* are both potential suspects.
This actually came up in a case I served on a jury for. The defense argued that the *other* brother could well have committed the crime, and given the poor quality of DNA evidence, we couldn't disprove that beyond a reasonable doubt.
DNA collision among close-knit racial groups is worth thinking about; collision within families is a serious problem.
Where do we get to the part where the status quo is restored to a rocket system that doesn't work, and probably will never work, which has so far achieved ten times less with ten times the money as a commercial system (SpaceX)? A status quo that's designed for a lunar mission which we can never afford, and which would be a stupid idea in the first place?
I don't care about which state is getting which money to support which political agenda, democrat or republican. What I care about is space missions that *work*. Robotic missions to the solar system, plus a manned orbital and/or Mars mission supported by either the Shuttle or a COTS program, will work. Going to the Moon in a pork-powered megarocket won't.
Last I checked, Time Warner was higher on the Fortune 500 list than Lockheed Martin.
This is the most brazen act of pork barrel politics since the Bridge to Nowhere. Actually, it *is* a bridge to nowhere.
I'm drawing a distinction between American government and American culture and technology. The US government has, of course, supported some oppressive governments, but it's done so in *spite* of our cultural power, not because of it.
You basically have all of that rolled into one with Saudi Arabia, and they do not fear us.
Yes they do. They don't see our government as a threat, but if you showed your average Saudi sheikh or mullah a Facebook page showing his daughter in blue jeans and a T-shirt attending a Lady Gaga concert, he'd probably have a heart attack. And if he survived, we'd probably have to grant the daughter political asylum.
We only spread freedom for businesses; individual freedom never plays into the equation.
I share a lot of your cynicism, but you're looking at too short a timeframe. Iraq, sure. But we didn't have a real economic interest in launching airstrikes in Yugoslavia, for example, and until very recently we had very little corporate incentive to defend South Korea. The U.S. government does act to defend corporate freedom, yes, but that's not its *only* motivation.
And besides, U.S. corporate interests aren't necessarily in opposition to the creeping free-speech hegemony I'm talking about. After all, what do we *make* here in the U.S.? Music, movies, TV shows and software.
A web that gives you only pretty pictures won't help the world, and likewise won't hurt a government.
No? How about these pretty pictures?
(Wikileaks video of US military killing civilians)
http://www.youtube.com/watch?v=5rXPrfnU3G0&has_verified=1
(Tienanmen Square)
http://en.wikipedia.org/wiki/Tank_Man
(Protests against Iranian election results) ...and that's just a start. We as geeks may have buzzwords like "semantic web" that we like to
http://mashable.com/2009/06/20/iran-youtube/
trot out, but the fact is that whenever you give people new tools to talk openly to one another on a mass scale, whether that's text, audio, or video, oppressive governments tremble.
And the great thing about the Internet is that it's designed from the ground up to reject authority. Cracking down on free speech on the Internet, no matter what form that speech takes, is like wrestling a greased pig.
This goes to something I've been saying for years now. The U.S. has some pretty impressive military power, but that's not what scares the world's dictators, religious zealots, and oppressive regimes. What do they fear about us? Rock 'n' roll, short skirts, blue jeans, and *especially* cell phones, e-mail, and Facebook.
The U.S. does a lot of things poorly, including, lately, waging ground wars. But one thing we're still very very good at: coming up with new ways for the world's young people to mock and ridicule authority figures, and for adults to talk to each other freely without government interference.
The cell phone, the 18" satellite dish, and the Internet are the most terrifying weapons against autocratic states the world has ever known. Is Facebook a threat to oppressive regimes? HELL YES, and we should be proud of that.
U.S. foreign policy should recognize this fact, and use it to its advantage. Rather than planning air strikes against Iranian and North Korean nuclear sites, we should be flying over and dropping cell phones, laptops, and MP3 players loaded with Rage Against the Machine and Ani diFranco.
Man, this is a big deal. It's a tragedy that we haven't heard about this in the news before. It seems like the kind of thing Slashdot would have reported on years ago.
Actually no! Check Figure 2 in the original article. Hydrogen and oxygen isotopes are linearly related to each other in natural waters, following the "Global Meteoric Water Line". If you measure delta-2H, you know delta-18O or vice versa.
and put most of the [grading] emphasis on exams where the subject is not known before hand.
I'll tell you from first-hand experience that students, even honest ones, HATE it when you do this. Well "tough titties", right? But even worse, many honest students do well in a normal assignment setting, but if you put them in an exam situation, they freak out and do very poorly. Exam anxiety is a very real problem, and grading by exams alone is unfair to these students.
Good point re the use of hair to provide a timeline, but if you figure the average human consumes about 1.5 kg of water a day, and contains about 60 kg of water, that means the water has a residence time of about a month and a half. It'll take that long to "flush out" your system.
And the "one degree of freedom" problem still limits the location accuracy of this. Check the map in the original article. The isotopic ratio of water is the same in Florida as in Texas; the same in Boston as in San Francisco. This data can narrow down a person's location, but it'll never provide a unique unambiguous location.
This may be forensically useful, but don't think of it like a fingerprint or a DNA match. There's only one degree of freedom here -- whether the water is isotopically "heavy" or "light". All of a person's water co9nsumption history is mixed up into one number.
So you won't be able to tell the difference between, say, a person who lived all year in Illinois (with a moderate isotope ratio) and a person who flies back and forth between Montana and Florida (who'd have a mix of "heavy" and "light" water in their system.)
if students were evaluated in a meaningful and practical way, this service would be useful to maybe a handful of smart but lazy students.
Okay, smart guy, now you're on the hook. What's your concrete proposal for evaluating students in, say, an English class in a "meaningful and practical way" that is impervious to ghostwriting and plagiarism?
As a college professor who tries to come up with unplagiarizeable assignments on a daily basis, I can tell you that this is easier said than done.
Why bother *sending* them to anyone? Just post some family shots on Picasa and make the album public. Hell, one of the spies worked as a real estate agent: posting photos on the net is a big part of her job.
People post millions of public pictures on the Net every day, it's not the least bit suspicious.
Yes, this is apparently what happened. Read pages 8-13 of the criminal complaint. After years of covert surveillance, three days ago the FBI arranged a meeting between an undercover agent posing as a Russian intelligence official and one of the alleged spies.
The undercover agent knew the right code phrases, but asked a lot of nosy questions. He/she actually convinced the Russian agent to give him/her the laptop she used for secret communications so it could be repaired, which has got to be one of the ballsiest counterespionage moves ever. But the Russian agent apparently got suspicious, bought a disposable cell phone, called for confirmation, and never showed up for a followup meeting.
At this point, the FBI decided to haul in the net.