I have a MacBook Pro that is less than a year old. It took a 3 foot drop on to padded carpet and the bottom case corner by the optical drive got bent.
This happened to me with a 12" Powerbook G4 a number of years ago. Rather than accept that I couldn't use the optical drive, or get a replacement case, or get my discs scratched up, I just bent the corner back until the case was flat again.
The sensitivity they are referring to is the amount of electrons released by the incident light - Amps of current per Watt of sunlight. Sunlight has a broad spectrum, and this technique allows more of the infrared portion of the spectrum (which is a lot) to cause electrons to flow.
However, and this is important, they achieved this by lowering the bandgap energy of the silicon. Why is that important? Remember that power, when it comes to electronics, is current times voltage. The voltage of a solar cell (open circuit voltage) is more or less the bandgap energy (divided by one electron charge). So, yeah, they get more electrons to flow for the same amount of incident sunlight, but the cell's voltage has also been lowered. Do you end up with more or less power as a result? Does the greater current overcome the lowered voltage? Since they haven't actually published data on a solar cell made from this technique, there isn't really a way to tell for certain.
My guess is that they won't be able to get vast power gains - possibly lower ones. The reason for this is that, right now, one photon with energy greater than the bandgap energy has a chance to create one electron-hole pair. If the photon has more energy than the bandgap energy, it doesn't make a correspondingly more energetic electron-hole pair. Even if the photon had twice the bandgap energy, it can't make two electron-hole pairs. So, a blue photon creates as much useful electrical energy as a red photon, despite the fact that the blue photon has more energy in it. One can play around with the bandgap energy of the PV cell to make better use of the high energy photons, but at the cost of excluding lower energy photons like infrared and red. More info here. This is why the solar cells with greatest efficiency are actually multi-junction cells - several solar cells with different bandgap energies stacked on top of each other, each tuned to a different portion of the solar spectrum.
The article mentions how these guys should be able to use their black silicon to create multiple electron-hole pairs from a single photon. In order to do that, however, they have to provide a bias voltage. In that case, the solar cell is sucking power, not producing it. That's fine if what you want is a very sensitive photo sensor - it's basically a solid-state photomultiplier tube. It's not a way to generate electrical power.
Some people turn up their music so that it really is loud in their ears. Most people, however, turn it up so damn loud to get the desired signal (music) above the background noise: car traffic, car interiors, subways, crowds, airplane cabins. When the noise floor is already pretty loud (50-80 dB), you have to pump up the volume on that music player ever higher to be able to "hear" it. There's psychoacoustics involved beyond just the overlapping audio sources. Music played that loud, even if it doesn't seem loud (because it's only, say, 10-20 dB above the noise floor) is actually well above the NIOSH limits on what can be a safe prolonged exposure. Result: hearing loss.
The only real solution that will allow you to hear your music (or cellphone, for that matter) without having to crank it up to damage-inducing volumes, is to reduce the noise floor. This can be done pretty easily with passive noise attenuation - padded headphones can give you a few dB of attenuation of low frequencies, and tens of dBs at higher frequencies. Earbuds offer almost no passive noise attenuation, although they could do a little bit if they sealed off the ear canal. Unfortunately, big padded headphones are a lot more conspicuous than little white earbuds, and they didn't come with your iPod, and you can't easily stow them in your pocket.
The other alternative is active noise reduction, like the Bose QuietComfort. You can even find noise-cancelling earbuds, although they tend to not work as well. Unfortunately, ANR doesn't come cheap if you want something that actually works and doesn't ruin your listening experience. Still, digital signal processing with low-power components will probably make this more widely-available in the future....if you can still hear anything by then.
This place will be making a killing, if anyone uses it. The cost of consumables for 3D printing tends to not actually be all that bad. I routinely use a Stratasys machine that does FDM (fused deposition modeling - extruding hot plastic layer by layer), and the consumable cost is something like $5/in^3. Compare that to the quoted price of these guys: $3/cm^3. Do a units conversion (16.4 cm^3 = 1 in^3), and you'll find these guys are charging about 10x the consumable cost. This, of course, assumes that they are using some sort of FDM process. It could be adhered powders, stereolithography, polyjet, etc., in which case the consumable cost is somewhat different, but still not exhorbitant. They must be rapidly depreciating their printers and/or incurring huge software and bandwidth costs to think that $50/in^3 is a bargain price.
There are tons of places you can upload models and get them printed, certainly for less than this.
It sounds funny. 500x the light absorption of 2D cells? Come on.
That line puzzled me, too. Current (silicon) photovoltaic cells are 10%-20% efficient. The barriers to higher efficiency aren't light absorbtion - just look at how dark a solar panel it, not much light is escaping it - but from the semiconductor fundamentals at work.
Still, 10%-20% ain't bad. But how can you improve that 500-fold?
I don't want to drag on the kid's accomplishments, because there is probably something real there. If anything, I blame shoddy science journalism that has a lot of quotes from bystanders but essentially no real information.
The main reason, I am thinking, is that the solar array would be in shadow, and therefore useless, for about 14 continuous days a month. Yes, they could bring up a fuel cell or batteries for energy storage, but those have cycle efficiencies to worry about, and probably weigh a lot more than the dishwasher-sized nuclear generator.
There's a difference in scale here. The generator that NASA wants would be rated for about 40 kW, enough for a couple dozen typical homes. A nuclear generating station here on Earth is about 1 GW, 25,000 times larger, and there are a few hundred of those. The article states that the generator for the moon could be quite compact, about the size of a large trashcan, or a small dishwasher, and only a tiny portion of that is the nuclear fuel. The nuclear fuel, I am guessing, would probably be bound up in some ceramic substrate, much like how they construct RTGs for deep space probes like Voyager and Cassini. An RTG is designed to survive a catastrophic rocket accident, and reentry, without spreading significant radioactive material.
So, yes, NASA can pretty safely get a few kg of radioactive ceramics to the surface of the moon, and still decline to think about launching thousands of tons of existingnuclear waste.
I'd stay away from titanium for a fusion reactor - it is susceptible to embrittlement by hydrogen, which is just what they happen to fill the reactor with.
One thing that's in steel's favor, however, is that not only is it widely available, but can be made with very tight process control, and everyone knows how to work with it. Other, more exotic materials are harder to come by in large quantities (not just expensive - sometimes you can't get large amounts at any price), there will be significant batch-to-batch variations in composition and mechanical properties, and you'll have to develop a lot of specialized knowledge on how to work it. It is just one more project risk in a program riddled with them.
But, I agree with your main point - that there are plenty of other things you could build with. If they are going to be spending a lot of time to develop "supersteel," then they may as well spend that effort working on a more suitable material.
Don't you realize that, by exposing them to such strenuous conditions that kill off the weak, you are only working to select a superbreed of tardigrades? I'm sure all that radiation have caused mutations to make them stronger, bigger, with voracious appetites and mind-control powers.
Pretty soon they'll be strong enough to challenge us! I say we launch a preemptive strike to eliminate all tardigrades immediately!
[I'm not actually crazy, this is all tongue-in-cheek alarmism, which is all the rage these days]
When China first got into space flight, their pilots were referred to as taikonauts ("taiko" meaning "space" in Chinese I presume) by Western media. What happened to that?
Yes, but in uncontrolled media markets, there is an incentive to keep that delay as short as possible. If you don't have it as close to live as possible, the next guy will, or some blogger. When the President comes on to give a live address, it has maybe a 5-second delay, not an hour. This is, in part, how some live shows occasionally get into trouble - remember the infamous "wardrobe malfunction" as the SuperBowl a few years back?
When Armstrong stepped onto the Moon, he was live to the entire world.
There are some people who think their girlfriends are pretty, their children are smart, their opinions matter and that they are significant in the light of 60 years on a planet of 6.6 billion people.
My beef with (most) creationists is that they also think:
* That my girlfriend (wife, now) should really not be so uppity to believe she should have a career and exercise her mind and opinion Instead, she should be barefoot in the kitchen, continually pregnant, and look to me as head of the household as Christ is head of the church.
* That my children should not be taught to think, but rather think exactly like they do, and ignore most things that science and reasoned investigation have revealed.
* That 90% of those 6.6 billion people (i.e., the ones not like them), not to mention nearly everyone who has lived before, are going straight to hell and damnation, whether they are moral or not.
So I don't think I'll apologize and respect their diverse opinions.
I get your joke, but it presents an opening to state the following little known fact:
Diamonds are not, in fact, forever
Under normal temperature and pressure conditions, diamond is not the most stable form of carbon - graphite is. Using thermodynamic arguments and building a free energy curve, one can show that some fraction of a diamond must decay to graphite in order to achieve a minimum energy state. It does take a very long time for this to happen - geologic time - but even a "long time" is not forever. If you aren't that patient, heat the diamond up to, say, 1500 C to speed things up. Oh, but be sure to do that in the absence of oxygen, because diamond burns just like other forms of carbon.
If you had read TFA, you would have learned that the first prototype disc was placed on the Rosetta space probe, which will land on comet Comet 67P/Churyumov-Gerasimenko in 2014. It is likely that the disc will survive a very long time there.
This sounds like more than the shock absorbers found in your car and other mechanical systems. Those are passive spring-mass-damper systems. These sound like active vibration control systems, that try to cancel out one shaking by producing an equal and opposite shaking. It's fairly straightforward, the sort of thing you can learn in an undergraduate control theory class, but getting it to work robustly, even on a test stand, takes a fair bit of tuning. Getting it to work on a complex system like Ares seems to be asking for trouble.
If nothing else, it's certainly a very heavy fix. My rocket science is a little rusty, but the 1600 lbs of active weight in the first stage probably doesn't translate into 1600 lbs of lost payload (if it were in the crew capsule, then yes, but the first stage doesn't go all the way to orbit). Even so, it's some lost payload capacity, and does nothing to tackle the root cause of the problem. Back to the drawing board, guys!
On the iPhone it takes two taps to purchase and install an application. The first tap is on the price itself. Usually you need to provide the password to your iTunes account, too.
So, yes, this person was an idiot. Did he think that the $999.99 price he tapped was not actually the price?
I'm pretty sure that iTunes can be configured for one-click purchasing, but I don't think that applies to iPhone apps. I myself have it set up to use a shopping cart, so that I don't purchase something accidentally. It cuts back on impulse buys, too.
Like in chess, tournament players in Go are allowed only so much time in a game (not on a per turn basis, but on a per game basis). So, yes, a slower computer could just continue to think and think, but runs the risk of running out of playing time before the game is finished (a forfeit).
Computers that play chess, go, and similar games can't hope to make the best possible move during each turn - there isn't nearly enough time to run through all possible combinations. Instead, they run through many possible moves, propagating it through many additional turns, and eventually pick the best move from that subset that they have considered. Getting the computer to decide on a good move in a reasonable amount of time is a tricky part of tuning the algorithm.
A faster computer, suggested by Moore's Law, would be able to run more iterations or branches of the algorithm per second, which suggests it will be able to come up with better moves that it would otherwise not have time to think up.
If you've got a small, agile car that can be agile in a controlled manner on ice, I think you'd have quite the market in regions that experience actual weather.
Dude, get a Subaru and some snow tires. They're the national car of the Republic of Vermont.
Slashdot Mirror
This happened to me with a 12" Powerbook G4 a number of years ago. Rather than accept that I couldn't use the optical drive, or get a replacement case, or get my discs scratched up, I just bent the corner back until the case was flat again.
The sensitivity they are referring to is the amount of electrons released by the incident light - Amps of current per Watt of sunlight. Sunlight has a broad spectrum, and this technique allows more of the infrared portion of the spectrum (which is a lot) to cause electrons to flow.
However, and this is important, they achieved this by lowering the bandgap energy of the silicon. Why is that important? Remember that power, when it comes to electronics, is current times voltage. The voltage of a solar cell (open circuit voltage) is more or less the bandgap energy (divided by one electron charge). So, yeah, they get more electrons to flow for the same amount of incident sunlight, but the cell's voltage has also been lowered. Do you end up with more or less power as a result? Does the greater current overcome the lowered voltage? Since they haven't actually published data on a solar cell made from this technique, there isn't really a way to tell for certain.
My guess is that they won't be able to get vast power gains - possibly lower ones. The reason for this is that, right now, one photon with energy greater than the bandgap energy has a chance to create one electron-hole pair. If the photon has more energy than the bandgap energy, it doesn't make a correspondingly more energetic electron-hole pair. Even if the photon had twice the bandgap energy, it can't make two electron-hole pairs. So, a blue photon creates as much useful electrical energy as a red photon, despite the fact that the blue photon has more energy in it. One can play around with the bandgap energy of the PV cell to make better use of the high energy photons, but at the cost of excluding lower energy photons like infrared and red. More info here. This is why the solar cells with greatest efficiency are actually multi-junction cells - several solar cells with different bandgap energies stacked on top of each other, each tuned to a different portion of the solar spectrum.
The article mentions how these guys should be able to use their black silicon to create multiple electron-hole pairs from a single photon. In order to do that, however, they have to provide a bias voltage. In that case, the solar cell is sucking power, not producing it. That's fine if what you want is a very sensitive photo sensor - it's basically a solid-state photomultiplier tube. It's not a way to generate electrical power.
Some people turn up their music so that it really is loud in their ears. Most people, however, turn it up so damn loud to get the desired signal (music) above the background noise: car traffic, car interiors, subways, crowds, airplane cabins. When the noise floor is already pretty loud (50-80 dB), you have to pump up the volume on that music player ever higher to be able to "hear" it. There's psychoacoustics involved beyond just the overlapping audio sources. Music played that loud, even if it doesn't seem loud (because it's only, say, 10-20 dB above the noise floor) is actually well above the NIOSH limits on what can be a safe prolonged exposure. Result: hearing loss.
The only real solution that will allow you to hear your music (or cellphone, for that matter) without having to crank it up to damage-inducing volumes, is to reduce the noise floor. This can be done pretty easily with passive noise attenuation - padded headphones can give you a few dB of attenuation of low frequencies, and tens of dBs at higher frequencies. Earbuds offer almost no passive noise attenuation, although they could do a little bit if they sealed off the ear canal. Unfortunately, big padded headphones are a lot more conspicuous than little white earbuds, and they didn't come with your iPod, and you can't easily stow them in your pocket.
The other alternative is active noise reduction, like the Bose QuietComfort. You can even find noise-cancelling earbuds, although they tend to not work as well. Unfortunately, ANR doesn't come cheap if you want something that actually works and doesn't ruin your listening experience. Still, digital signal processing with low-power components will probably make this more widely-available in the future....if you can still hear anything by then.
This place will be making a killing, if anyone uses it. The cost of consumables for 3D printing tends to not actually be all that bad. I routinely use a Stratasys machine that does FDM (fused deposition modeling - extruding hot plastic layer by layer), and the consumable cost is something like $5/in^3. Compare that to the quoted price of these guys: $3/cm^3. Do a units conversion (16.4 cm^3 = 1 in^3), and you'll find these guys are charging about 10x the consumable cost. This, of course, assumes that they are using some sort of FDM process. It could be adhered powders, stereolithography, polyjet, etc., in which case the consumable cost is somewhat different, but still not exhorbitant. They must be rapidly depreciating their printers and/or incurring huge software and bandwidth costs to think that $50/in^3 is a bargain price.
There are tons of places you can upload models and get them printed, certainly for less than this.
Well, of course online gaming is going to be lively. You wouldn't expect Google Bore (beta) to be a force here.
A clarification: the cost of replacement equipment was £1,000, not $1,000.
A ton of helium! What's the big deal? That's, like, way lighter than a ton of air!
[I'm being facetious about the weights, but in terms of cost, losing a ton of helium is freakin' expensive]
He raps with a British accent - therefore he must be smart.
That line puzzled me, too. Current (silicon) photovoltaic cells are 10%-20% efficient. The barriers to higher efficiency aren't light absorbtion - just look at how dark a solar panel it, not much light is escaping it - but from the semiconductor fundamentals at work.
Still, 10%-20% ain't bad. But how can you improve that 500-fold?
I don't want to drag on the kid's accomplishments, because there is probably something real there. If anything, I blame shoddy science journalism that has a lot of quotes from bystanders but essentially no real information.
Tell me when I can get a PCI card with a one or more Cell co-processors to do the heavy lifting.
The main reason, I am thinking, is that the solar array would be in shadow, and therefore useless, for about 14 continuous days a month. Yes, they could bring up a fuel cell or batteries for energy storage, but those have cycle efficiencies to worry about, and probably weigh a lot more than the dishwasher-sized nuclear generator.
There's a difference in scale here. The generator that NASA wants would be rated for about 40 kW, enough for a couple dozen typical homes. A nuclear generating station here on Earth is about 1 GW, 25,000 times larger, and there are a few hundred of those. The article states that the generator for the moon could be quite compact, about the size of a large trashcan, or a small dishwasher, and only a tiny portion of that is the nuclear fuel. The nuclear fuel, I am guessing, would probably be bound up in some ceramic substrate, much like how they construct RTGs for deep space probes like Voyager and Cassini. An RTG is designed to survive a catastrophic rocket accident, and reentry, without spreading significant radioactive material.
So, yes, NASA can pretty safely get a few kg of radioactive ceramics to the surface of the moon, and still decline to think about launching thousands of tons of existingnuclear waste.
I'd stay away from titanium for a fusion reactor - it is susceptible to embrittlement by hydrogen, which is just what they happen to fill the reactor with.
One thing that's in steel's favor, however, is that not only is it widely available, but can be made with very tight process control, and everyone knows how to work with it. Other, more exotic materials are harder to come by in large quantities (not just expensive - sometimes you can't get large amounts at any price), there will be significant batch-to-batch variations in composition and mechanical properties, and you'll have to develop a lot of specialized knowledge on how to work it. It is just one more project risk in a program riddled with them.
But, I agree with your main point - that there are plenty of other things you could build with. If they are going to be spending a lot of time to develop "supersteel," then they may as well spend that effort working on a more suitable material.
Don't you realize that, by exposing them to such strenuous conditions that kill off the weak, you are only working to select a superbreed of tardigrades? I'm sure all that radiation have caused mutations to make them stronger, bigger, with voracious appetites and mind-control powers.
Pretty soon they'll be strong enough to challenge us! I say we launch a preemptive strike to eliminate all tardigrades immediately!
[I'm not actually crazy, this is all tongue-in-cheek alarmism, which is all the rage these days]
When China first got into space flight, their pilots were referred to as taikonauts ("taiko" meaning "space" in Chinese I presume) by Western media. What happened to that?
Yes, but in uncontrolled media markets, there is an incentive to keep that delay as short as possible. If you don't have it as close to live as possible, the next guy will, or some blogger. When the President comes on to give a live address, it has maybe a 5-second delay, not an hour. This is, in part, how some live shows occasionally get into trouble - remember the infamous "wardrobe malfunction" as the SuperBowl a few years back?
When Armstrong stepped onto the Moon, he was live to the entire world.
My beef with (most) creationists is that they also think:
* That my girlfriend (wife, now) should really not be so uppity to believe she should have a career and exercise her mind and opinion Instead, she should be barefoot in the kitchen, continually pregnant, and look to me as head of the household as Christ is head of the church.
* That my children should not be taught to think, but rather think exactly like they do, and ignore most things that science and reasoned investigation have revealed.
* That 90% of those 6.6 billion people (i.e., the ones not like them), not to mention nearly everyone who has lived before, are going straight to hell and damnation, whether they are moral or not.
So I don't think I'll apologize and respect their diverse opinions.
I get your joke, but it presents an opening to state the following little known fact:
Diamonds are not, in fact, forever
Under normal temperature and pressure conditions, diamond is not the most stable form of carbon - graphite is. Using thermodynamic arguments and building a free energy curve, one can show that some fraction of a diamond must decay to graphite in order to achieve a minimum energy state. It does take a very long time for this to happen - geologic time - but even a "long time" is not forever. If you aren't that patient, heat the diamond up to, say, 1500 C to speed things up. Oh, but be sure to do that in the absence of oxygen, because diamond burns just like other forms of carbon.
Some references: [1], [2], [3]
Fluorinert
If you had read TFA, you would have learned that the first prototype disc was placed on the Rosetta space probe, which will land on comet Comet 67P/Churyumov-Gerasimenko in 2014. It is likely that the disc will survive a very long time there.
This sounds like more than the shock absorbers found in your car and other mechanical systems. Those are passive spring-mass-damper systems. These sound like active vibration control systems, that try to cancel out one shaking by producing an equal and opposite shaking. It's fairly straightforward, the sort of thing you can learn in an undergraduate control theory class, but getting it to work robustly, even on a test stand, takes a fair bit of tuning. Getting it to work on a complex system like Ares seems to be asking for trouble.
If nothing else, it's certainly a very heavy fix. My rocket science is a little rusty, but the 1600 lbs of active weight in the first stage probably doesn't translate into 1600 lbs of lost payload (if it were in the crew capsule, then yes, but the first stage doesn't go all the way to orbit). Even so, it's some lost payload capacity, and does nothing to tackle the root cause of the problem. Back to the drawing board, guys!
On the iPhone it takes two taps to purchase and install an application. The first tap is on the price itself. Usually you need to provide the password to your iTunes account, too.
So, yes, this person was an idiot. Did he think that the $999.99 price he tapped was not actually the price?
I'm pretty sure that iTunes can be configured for one-click purchasing, but I don't think that applies to iPhone apps. I myself have it set up to use a shopping cart, so that I don't purchase something accidentally. It cuts back on impulse buys, too.
Examples, please?
Like in chess, tournament players in Go are allowed only so much time in a game (not on a per turn basis, but on a per game basis). So, yes, a slower computer could just continue to think and think, but runs the risk of running out of playing time before the game is finished (a forfeit).
Computers that play chess, go, and similar games can't hope to make the best possible move during each turn - there isn't nearly enough time to run through all possible combinations. Instead, they run through many possible moves, propagating it through many additional turns, and eventually pick the best move from that subset that they have considered. Getting the computer to decide on a good move in a reasonable amount of time is a tricky part of tuning the algorithm.
A faster computer, suggested by Moore's Law, would be able to run more iterations or branches of the algorithm per second, which suggests it will be able to come up with better moves that it would otherwise not have time to think up.
Dude, get a Subaru and some snow tires. They're the national car of the Republic of Vermont.