>Cell phones don't transmit with many watts of power, and they still work in rural areas.
Power needed is proportional to the bandwidth. If you want to send Morse code, you only need like a 1Hz bandwidth and it only takes milliwatts to overcome the noise in a 1Hz bandwidth. To send voice, you only need a few KHz of bandwidth, so the power required is modest. But if you want cable modem amounts of thruput, you need Megahertz of bandwidth and it takes correspondingly more power to fill that bandwidth.
I'm sorry if I gave the impression that "majority wins" in Science. The truth is what wins.
It doesn't matter if a million people claim something is true, one opposing and truthful fact outweighs any number of claims or beliefs.
But in this case there are HUNDREDS of peer-reviewed papers on one side, and now this one yahoo's claim.
Now it's POSSIBLE that this guy's claims are correct. Even so, I suspect at least 80% of the other papers did not rely on this allegedly flawed data.
So just on probability we'd be remiss to draw any conclusions from this one new data point.
Putting wireless internet on the freed-up TV channels is a particularly poor use of the spectrum. Each TV channel is only about 6 MHz wide (4.5 plus some guard space). That would accomodate maybe 50 million bits per second of service, across the propagation range of VHF and UHF, which depending on power and weather, can range from a few hundred meters to several hundred miles. If you use a few hundred watts you could cover a few square miles, but so can the current Wifi channels. Covering a large rural are is impractical as you'd need many watts of power transmitted at the user's end, and only a limited number of users could be handled.
Um, isn't this as sucky solution, as at each city the reflections are going to jack up the background noise level? Even with a good match, you're unlikely to get less than 10% reflection and crosstalk at each junction. After just a FEW hops the reflection noise is going to mask any desired signal.
Also I don't see (from the abstract) how they're going to extract the desired shortest answer from all the wrong answers and reflections.
Isn't it well known that you should not validate some data that the user might still be able to modify? That's security 101.
What's the problem with copying parameters to some memory space that the user can't reach, like the system heap? Surely moving a few bytes isn't going to be a big performance hit, compared to the time it takes to validate parameters.
90% CO2 reduction? Where is the other 10% coming from?
And exactly how do they store the liquid hydrogen? Did they use up all the luxury trunk space with a vacuum-lined flask? That would explain why they chose a luxury car-- the other ones didn't have the room.
BTW how many miles can one go on a tankful of that stuff? It's mighty light,e ven in liquid form, so there's not a whole lot of energy in a standard car tankful.
Hmm, I seem to recall:
The Macintosh had a "keycaps" desk accessory, circa 1984
Good ol PLATO had a touchscreen keybaord, circa 1973.
Some judges might consider this Prior Art.
Having any Govt investigate efficiency is about as practical as the Madonna Commission On Chastity and Modesty.
Computers are doing just fine at reducing their power consumption by many percent a year without the govt's "help".
ahem, nice try, but we don't live in Utopia, where all your cherry-picked numbers and wishes come true:
Sun of 6 hours per day average or 5.5KwH/ m^2 / day.
That's cherry-picking. At Talahassee it's about 4.5, lower in most other states.
And that's at right-angles to the Sun, but you've already set on a fixed collector, which isn't going to catch the full insolation. Subtract another 30%.
... 30 yr mortgage.... Go ask your banker if you can get a 30-year loan on a solar panel.
... with subsidies... Subsidies only work when very few people ask for them. If everybody qualified, then of course the subsidies are pointless... everybody gets them means everybody has to pay for them too. No benefit to anybody.
.. i pay retail electric prices I was assuming like TFA a solar concentrator, which would be unlikely for home use. A utility would only benefit the avoided cost of unreliable wholesale power, which is much much less than your retail cost of reliable delivered power.
I'd like solar power to take off too, but IMHO it's not helpful to spin wildly optimistic projections and end up with pissed off early-adopters.
>3 cents per kWh? Sign me up. Electricity in NY is several times more expensive than that.
That's the wholesale price that utilities are willing to pay for unreliable power.
Here's a page that runs the numbers...
yeah. Very creative.
First of all, in the long run you have to triple the cost, as the 2/3 subsidy will only work if very few people make use of it.
Obviously, if EVERYBODY asked for the subsidy, it evaporates.
And if you look at the bottom line, you have to pay out $12K ($36K actually), and maybe if you're lucky, get $1,200 a year back.
Which isnt going to even pay for interest and maintenance, much less make a dent in the principal.
I wish at least someone would run the numbers on these things once and for all.
Solar collectors are expensive.
You need a mirror, a support, maybe a steering system, periodic cleaning and maintenance.
If the support is going to last more than one year, it needs to be rather sturdy in order to survive wind, rain, maybe snow and hail.
So we're talking an installed cost of lets say $500 per square meter, more if it's steerable. Plus yearly cleaning and maintenance.
Now a square meter of sunlight is about 1 kilowatt of light.
Going into a 17% efficient solar cell, allowing for clouds and "night", is going to average about 60 watts of DC.
At electricity going for the wholesale rate of 3 cents a KwH, which is, that's.2 cents per hour.
But wait, this is undependable power, going away at every passing cloud, so it either is going to have to go into a storage device, (more $$$, more losses), or the utility is not going to pay you the going rate for dependable power, instead maybe half that at best, if they'll take it at all (you see to take it they'll have to build more gas-turbine peaking plants to make up for the cloudy times).
So taking that into account, it nets out to about $9 per year. Probably closer to $7 if you include time down for maintenance and cleaning.
For an investment of $500.
So you can't even pay the cost of interest on the loan, much less the cost of cleaning and maintenance, much less making any headway on the principal.
There's a place I know. Where Xerox copiers glow. And ever dang millisec another sheet gets flecked Slathered with toner, the particulate kind So in the air it should be easy to find All kinds of glop, by the bucket and pail for all bystanders to strongly inhale.
>I don't trust your first two assumptions. Given that nobody here seems sure how much of our normal "walking energy" is going to waste already, capping the extractable energy at 10% seems totally arbitrary.
Maybe not so arbitrary. How much of your physical effort are you willing to give away?
The figures provided to me by the notoriously inaccurate Internet say that a reasonably fit cyclist generates 1/3 HP
yes...
>and walking can't be too much less than that.
Wanna think that over again? When I walk I'm probably not using more than 1/5 of my max output. Either you're *very* weak or you walk very fast.
>I also found a couple of sites that claim we burn around 150 food calories per hour while walking, which translates into 627kJ/h, or 174W, or 1/4 HP.
That would be if your leg muscles were the only thing using energy in your body, AND the muscles were 100% efficient.
So if instead of 1/10 of 1/20 of a horsepower from each person, we imagine getting 1/5 of 1/4 of a horsepower, suddenly the numbers start looking ten times better.
We're not getting 1/5 or 1/4, or 1/20. And even if the numbers were 1000 times better, you couldnt even pay the interest on the money, much less pay for maintenance, or paying down the principal.
Oh come on. Define "system". They only had ten years to develop the Saturn V, the LEM, the launchpad, and train everybody.
Actually, the Saturn V was flying in 1966 IIRC, so that's six years. That's 166,666 "systems" developed per year.
With only 250 days per year, that's nearly 700 systems RFQ, bid, contractor chosen, staff gathered, system designed, prototyped, debugged, documented and tested every working day.
There weren't enough typewriters on the planet to even begin doing that much paperwork every day. Pleez.
Nobody's going to build a Saturn V for "terrorist" applications.
You can't build a Saturn V from a poster. Or a blueprint. Or even 100 blueprints. Every detail, from the metallurgy of the rivets, to the welding techniques for the heat exchangers, to the construction of the tools, dies, jigs, test fixtures, processing chemicals, dips, platings, surface treatments, case-hardenings, ball peening, test plans, processing timelines, and much more, each encompasses a whole thick book of technology, most of which has been lost. Or is available on microfiche from any good Univerity or Govt documents repository library. Plus the Saturn V had about 130,000 subcontractors that supplied everything from gold-plated lockwashers to platinum-skinned servomotors. The technology for those was not captured in the basic Saturn V documents. For instance the specs for a small servomotor might have read "35 ft-lbs torque, 0.1% resolution, 77 to 800 degrees C. and how they did it was a trade secret of some now defunct subcontractor. And the making of the motor's teflon-coated wires was a trade secret of the wire manufacturer. And so on. Multiply that by 130,000 times.
So you not only would not want to, you could not even begin to build a Saturn V from the "blueprints".
Hmmm, well the numbers still don't work out too well.
To get the 6 million candellas of a $7 flash-bang grenade, assuming your typical super-bright LEDS of 10 candelas,
and a beamwidth of 36 degrees you'd need 6,000 LEDS. That's a lot of bux.
"ARGGGHHH! Light just slightly brighter than what we're accustomed to!"
No, seriously, this sounds really lame. SWAT teams already do this, successfully, with "flash-bang" grenades. Or you could use a big-ol' magnesium flashbulb. No need for new yet wimpy LED's.
The numbers don't look good-- You have to precisely track the shell in flight with extreme accuracy.
>Radar. You know, komputurs and stuff.
Yes, I know. But radar is far from accurate enough. Radar waves are slowed down by air density, bent and refracted by thermal layers, and slowed even more by humidity. For best accuracy you need short wavelength radar waves, which are strongly absorbed by moisture in the air. If the shell is a mile away, you need better than 0.02% accuracy in range, elevation, and azimuth, which is WAAY more accuracy than you're going to be able to get in the field.
Any dust, fog or clouds and it's useless.
>Useless? No. Reduced range? Perhaps.
Useless, probably. Battlefields get mighty dusty after a few artillery barrages.
And you're a very fragile sitting duck, with your beam revealing your position.
>I believe in most cases the wavelengths used are out of the visual spectrum.
Doesnt matter, every army with $40 has bought infrared scopes.
>Anyway, most of the time these systems will be deployed to protect high value assets whose position is already known to the enemy (like an airbase or something).
I was referring to the laser cannon being a sitting duck. A very high value target that gives away its exact position with megawatts of emission. It doesnt get much better than that.
>have you seen a teleprinter? A piezo inkjet printer? a hard disk drive?... poor examples for your thesis.... all those devices have error rates much
higher than tolerable in a computer. You need parts with error rates well below 10^-12, it's hard to make mechanical gadgets that will operate a billion times without failure. The technology is over 1000 times too unreliable in the best case.
Ahem, perhaps these pencil-pushers should talk to actual chip makers and bakers first before speculating on the applications of graphene. Anything that's only one atom thick isn't compatible with current or any forseeable IC process. Chips have to undergo many heating, cooling, deposition, and diffusion steps before they're done. Anything one-atom thick is going to diffuse away in the process. You also have the reliability problem-- you need reliable connections, millions of them. Anything one-atom thick is going to have too many defects.
Moving parts do not scale down at all! Even at the micro-meter level, effects like friction, surface tension, dust, and gas make moving parts impractical to impossible. Even in a good vacuum there are too many gas molecules to make nano-scale mechanics work.
Your typical moving parts are good for maybe ten million operations before they wear out. Figure out how long your computer would last at that rate.
Error and assembly error rates for mechanical devices are much too high for computer applications.
The numbers don't look good-- You have to precisely track the shell in flight with extreme accuracy. Any dust, fog or clouds and it's useless. Countermeasures are simple and cheap-- smoke, dust, chaff.
And you're a very fragile sitting duck, with your beam revealing your position.
Sounds like a typical Pentagon money-blowing project.
Slashdot Mirror
Power needed is proportional to the bandwidth. If you want to send Morse code, you only need like a 1Hz bandwidth and it only takes milliwatts to overcome the noise in a 1Hz bandwidth. To send voice, you only need a few KHz of bandwidth, so the power required is modest. But if you want cable modem amounts of thruput, you need Megahertz of bandwidth and it takes correspondingly more power to fill that bandwidth.
But in this case there are HUNDREDS of peer-reviewed papers on one side, and now this one yahoo's claim.
Now it's POSSIBLE that this guy's claims are correct. Even so, I suspect at least 80% of the other papers did not rely on this allegedly flawed data.
So just on probability we'd be remiss to draw any conclusions from this one new data point.
There are hundreds to thousands of scientists writing hundreds to thousands of studies based on several million observations.
Now here comes along ONE yahoo who supposedly points out ONE alleged flaw.
Ergo we can draw the conclusion that global warming isn't happening. ?
Go buy yourself a sense of proportion.
Putting wireless internet on the freed-up TV channels is a particularly poor use of the spectrum. Each TV channel is only about 6 MHz wide (4.5 plus some guard space). That would accomodate maybe 50 million bits per second of service, across the propagation range of VHF and UHF, which depending on power and weather, can range from a few hundred meters to several hundred miles. If you use a few hundred watts you could cover a few square miles, but so can the current Wifi channels. Covering a large rural are is impractical as you'd need many watts of power transmitted at the user's end, and only a limited number of users could be handled.
Also I don't see (from the abstract) how they're going to extract the desired shortest answer from all the wrong answers and reflections.
Isn't it well known that you should not validate some data that the user might still be able to modify? That's security 101.
What's the problem with copying parameters to some memory space that the user can't reach, like the system heap? Surely moving a few bytes isn't going to be a big performance hit, compared to the time it takes to validate parameters.
And exactly how do they store the liquid hydrogen? Did they use up all the luxury trunk space with a vacuum-lined flask? That would explain why they chose a luxury car-- the other ones didn't have the room.
BTW how many miles can one go on a tankful of that stuff? It's mighty light,e ven in liquid form, so there's not a whole lot of energy in a standard car tankful.
Hmm, I seem to recall: The Macintosh had a "keycaps" desk accessory, circa 1984 Good ol PLATO had a touchscreen keybaord, circa 1973. Some judges might consider this Prior Art.
Having any Govt investigate efficiency is about as practical as the Madonna Commission On Chastity and Modesty. Computers are doing just fine at reducing their power consumption by many percent a year without the govt's "help".
That's the wholesale price that utilities are willing to pay for unreliable power.
Here's a page that runs the numbers...
yeah. Very creative.
First of all, in the long run you have to triple the cost, as the 2/3 subsidy will only work if very few people make use of it. Obviously, if EVERYBODY asked for the subsidy, it evaporates.
And if you look at the bottom line, you have to pay out $12K ($36K actually), and maybe if you're lucky, get $1,200 a year back. Which isnt going to even pay for interest and maintenance, much less make a dent in the principal.
There's a place I know.
Where Xerox copiers glow.
And ever dang millisec
another sheet gets flecked
Slathered with toner, the particulate kind
So in the air it should be easy to find
All kinds of glop, by the bucket and pail
for all bystanders to strongly inhale.
So everybody at Kinko's is dead.
So everybody at Kinko's is dead.
Maybe not so arbitrary. How much of your physical effort are you willing to give away?
The figures provided to me by the notoriously inaccurate Internet say that a reasonably fit cyclist generates 1/3 HP
yes...
>and walking can't be too much less than that.
Wanna think that over again? When I walk I'm probably not using more than 1/5 of my max output. Either you're *very* weak or you walk very fast.
>I also found a couple of sites that claim we burn around 150 food calories per hour while walking, which translates into 627kJ/h, or 174W, or 1/4 HP.
That would be if your leg muscles were the only thing using energy in your body, AND the muscles were 100% efficient.
So if instead of 1/10 of 1/20 of a horsepower from each person, we imagine getting 1/5 of 1/4 of a horsepower, suddenly the numbers start looking ten times better.
We're not getting 1/5 or 1/4, or 1/20. And even if the numbers were 1000 times better, you couldnt even pay the interest on the money, much less pay for maintenance, or paying down the principal.
Oh come on. Define "system". They only had ten years to develop the Saturn V, the LEM, the launchpad, and train everybody. Actually, the Saturn V was flying in 1966 IIRC, so that's six years. That's 166,666 "systems" developed per year. With only 250 days per year, that's nearly 700 systems RFQ, bid, contractor chosen, staff gathered, system designed, prototyped, debugged, documented and tested every working day. There weren't enough typewriters on the planet to even begin doing that much paperwork every day. Pleez.
To get the 6 million candellas of a $7 flash-bang grenade, assuming your typical super-bright LEDS of 10 candelas, and a beamwidth of 36 degrees you'd need 6,000 LEDS. That's a lot of bux.
"ARGGGHHH! Light just slightly brighter than what we're accustomed to!"
No, seriously, this sounds really lame. SWAT teams already do this, successfully, with "flash-bang" grenades. Or you could use a big-ol' magnesium flashbulb. No need for new yet wimpy LED's.
>Radar. You know, komputurs and stuff.
Yes, I know. But radar is far from accurate enough. Radar waves are slowed down by air density, bent and refracted by thermal layers, and slowed even more by humidity. For best accuracy you need short wavelength radar waves, which are strongly absorbed by moisture in the air. If the shell is a mile away, you need better than 0.02% accuracy in range, elevation, and azimuth, which is WAAY more accuracy than you're going to be able to get in the field.
Any dust, fog or clouds and it's useless. >Useless? No. Reduced range? Perhaps.
Useless, probably. Battlefields get mighty dusty after a few artillery barrages.
And you're a very fragile sitting duck, with your beam revealing your position. >I believe in most cases the wavelengths used are out of the visual spectrum.
Doesnt matter, every army with $40 has bought infrared scopes. >Anyway, most of the time these systems will be deployed to protect high value assets whose position is already known to the enemy (like an airbase or something).
I was referring to the laser cannon being a sitting duck. A very high value target that gives away its exact position with megawatts of emission. It doesnt get much better than that.
>have you seen a teleprinter? A piezo inkjet printer? a hard disk drive? ... poor examples for your thesis.... all those devices have error rates much
higher than tolerable in a computer. You need parts with error rates well below 10^-12, it's hard to make mechanical gadgets that will operate a billion times without failure. The technology is over 1000 times too unreliable in the best case.
Ahem, perhaps these pencil-pushers should talk to actual chip makers and bakers first before speculating on the applications of graphene. Anything that's only one atom thick isn't compatible with current or any forseeable IC process. Chips have to undergo many heating, cooling, deposition, and diffusion steps before they're done. Anything one-atom thick is going to diffuse away in the process. You also have the reliability problem-- you need reliable connections, millions of them. Anything one-atom thick is going to have too many defects.
Anti-artillery shell cannon??
The numbers don't look good-- You have to precisely track the shell in flight
with extreme accuracy. Any dust, fog or clouds and it's useless.
Countermeasures are simple and cheap-- smoke, dust, chaff.
And you're a very fragile sitting duck, with your beam revealing your position.
Sounds like a typical Pentagon money-blowing project.