If you were to take your calories from asparagus (which has a big carbon footprint), riding a bike actually has a bigger carbon footprint than a city bus
Correction: asparagus only has a large carbon footprint if you import it from Chile to North America at whatever-time-of-year. If you are instead purchasing it from a farmer in the same area as you, in season, then its carbon footprint is hardly larger than any of other foodstuff. Don't malign the food itself, malign the source and the method of consumption. People simply have to accept that it is thoroughly unnatural to have tender asparagus tips in September. I'm not an eco-absolutist, but people need to be mindful of their food: what is it, where does it comes from, how is it grown, when is it in season, etc.
Pushing it requires propellant, but pulling it doesn't
If you propose that, to push the asteroid, you first stop most of its spinning, then the pushing scenario requires huge amounts of additional fuel before you even begin talking about changing its trajectory. Landing and firmly attaching a rocket to an asteroid or comet is not a trivial undertaking - what works for some bodies may not work for others.
The big benefit of the gravitational tether is that it matters not a whit if the asteroid is tumbling wildly, or off-gassing (i.e., a comet), or is held together too loosely to attach to - you are simply applying force to this civilization-threatening mass by using another mass: action at a distance. The "at a distance" part circumvents a lot of thorny challenges.
There's a company in Europe (don't recall the name) who are also developing an "enclosed motorcycle" type of vehicle, but they don't use gyros... below a certain speed or at too great an agle, there are two large "training wheels" which flip down and right the bike
That's either the Ecomobile or Monotracer. I first saw that on an ooooold show called Beyond 2000, which aired back when the year 2000 still seemed in the future.
Lit Motors has developed an enclosed motorcycle that uses an active gyro assembly under the driver to keep the thing upright when at a standstill and during sudden accelerations (i.e., during an accident). The gyro mechanism can also be used to assist in cornering.
And I can see now: a whole generation of planetary scientists suddenly dying en masse. First the rapture of witnessing such an event and being given the chance to study its aftermath. But then comes the crushing notion that they've wasted their careers trying to figure out the past and present of Mars: a past that is about to be completely obscured by the cometary effects, and a present that is about to be completely obliterated.
Meh, from what I hear plutonium isn't all that hard to work. It machines well enough (the bomb industry can machine it into interesting revolved ellipsoids to fit into MIRV warheads). It is usually found and used as a pure metal. Pure metals tend to be pretty soft and ductile - it is only once you start alloying things that they gain their mechanically useful properties. The main downside is that you can't work it in the open air: the chips will burn, and because plutonium is a fantastically toxic metal, not to mention its radioactivity, you practically have to live in a hazmat suit to handle it.
Do you know what the "depleted" in depleted uranium means? Depleted uranium is what's left over from uranium enrichment. Naturally occurring uranium is a mixture of U-238 and U-235 (plus some other stuff). Enrichment separates the fissile U-235 for use in power plants and bombs, leaving the U-238 behind. The U-238 is slightly radioactive, but isn't considered a nuclear fuel. This is why it's called depleted uranium - all its usefulness as a nuclear fuel has been separated out. Depleted uranium gets used in armor-piecing weapons because it is impressively dense (2/3 denser than lead), is harder than lots of other dense metals, is an abundant leftover of the nuclear industry, and spalls in just the right way. No one considers it a nuclear weapon, because there is nothing "nuclear" about its mechanics as a weapon. Ballistics aside, depleted uranium's greatest problem is that it is still a really toxic metal.
Even if a 9/11 happened every year, it wouldn't be serious, in terms of economic damage and loss of life
Did you even slow down to consider the full magnitude of a statement like that? A 9/11 happening each year would be a 20% increase in the homocide rate. Air travel would plummet. Air travel did stop for a few days immediately afterward. NYC suffered tremendous economic losses - the loss of a couple billion dollars of prime real estate, the disruption of business for weeks and months, the suspension of trading and subsequent drop in stock markets, the strain on emergency services, the long term costs of cleanup and rebuilding, long-term disability for those that were there, the loss of tourism, the psychological trauma, the erosion of freedom... need I go on? Yeah, maybe we would get used to it, and the next 9/11 would not be as bad as the last, but there are costs associated with that kind of normalization, too. You think that these are inconsequential or "not serious"?
I think for pretty much any system running on wired electricity, regenerative braking is used to dump the power back into the grid
That assumes that the infrastructure has been designed to accept a "backwards" flow of electricity. Designing a system that has power flow in only one direction is easier and cheaper than one that has bidirectional flow. Historically, and particularly in the United States, the cost of electricity has been a relatively small slice of a subway's total lifetime cost. The capital investment and the other operating costs are pretty big by comparison. Much easier to just dump all that kinetic energy into a resistor bank somewhere. I'm not saying that's the right way to do it, but that has historically been the thought process
It may not necessarily be batteries, but some sort of localized storage may be useful for subway and light rail. The size of the train system's electrical infrastructure needs to be sized to the peak electrical demand, which is greatest when the train is accelerating. Being able to have some storage on the train would allow for regenerative braking. Right now, all the kinetic energy of the train's motion, which is an awful lot, is lost every time the train slows or stops. It's lost as heat and wear in the brakes, and as a tremendous amount of acoustic energy (the terribly shrieking of the train's approach). Boosting the on-board storage with some power fed in when the train is stationary allows the fixed infrastructure to be sized to the average power demand, which is a different beast. Finally, some localized storage would allow the train to operate for short distances where there is no electrical infrastructure. This would allow the electrical system to be broken up into smaller, isolated, more manageable parts. If one zone goes down due to accident, disaster, or just for maintenance, the train system can continue to function. It is redundancy through distribution.
The article is missing some details, so I'll fill in a bit based on what I know of conventional and research-level prosthetics.
What it appears they are going to do is implant some wires into the man's residuum. These wires - electrodes - will have two purposes:
1. To pick up muscle contractions or muscle-control firings in the nerves
2. To stimulate the sensory nerves in the same general viscinity
In conventional motor-driven, upper-limb prostheses, particularly below-the-elbow, the control signals are measured using surface EMGs (ElectroMyoGraphic sensors). These aren't measuring nerve firings, per se, but rather the electrical activity of actual muscle contractions (in the forearm). This is done because the actual motor nerves are pretty tiny, and the signal in them is fairly small. The muscle, on the other hand, is much easier to locate, and it acts as a natural amplifier of what the nerve tells it to do. It's the difference between probing a tiny signal wire coming out of your MP3 player and picking up the sound that is resonating in the speaker housing.
The downside of using surface EMGs is that, by measuring electrical potentials across several cm of skin and muscle, it is hard to pick up on individual muscle contractions. So, it is generally not possible to pick up on just the muscle that flexed/extended the index finger. The best you can usually do is pick up on the flexion/extension signals for all finger muscles or the wrist. Another downside is that the EMGs are usually mounted to the socket - the molded plastic or composite structure that mechanically interfaces the prosthesis to the residuum. As the wearer moves around and sweats, the EMGs can shift over the skin surface, which degrades the signal strength and specificity.
By implanting EMG electrodes under the skin, you can mostly eliminate the problems of the having the electrodes shifting, because they'll move with the tissue they are measuring. You may also be able to get more localized measurements (crosstalk is a difficult problem), and so get more than 1-2 channels of control input. This approach is not exactly new, but neither is it widespread. Amputees are, naturally, a bit wary of invasive procedures - they don't want to risk screwing up what they have left. The other downside is that, at least in this case, they are opting for transdermal electrodes - wires poking through the skin, which could have long-term drawbacks. Some work is being done with fully implanted EMGs that can be probed using near field technologies - RFID in your muscles - but that is still a work in progress.
Stimulating nerves to provide sensory feedback is, likewise, not exactly new, but hasn't made it into clinical practice. There have been anecdotes about patients who have undergone targeted nerve reinnervation who, when you poke them in a certain place on their pectoral muscle, report "feeling" a sensation in their lost hand. Again, going to implanted electrodes allows you the chance to have must greater specificity.
Aside from the invasive nature of the procedure, my main concern with this project is its longevity. How long can the electrodes exist within the body? Will you still be able to get or produce a worthwhile signal after 1 month, 6 months, 10 years? The prosthesis can be repaired and replaced over time, but tinkering around with the electrodes may not be feasible. I also have some concerns about the durability of the sensing elements in the prosthetic hand, but that is more straightforward engineering than anything else.
The "law against unlocking cellphones" isn't a law - it is a regulation, a rule set by the Librarian of Congress. This is good, because it is probably easier to change than a law, which requires an act of (a very hostile and deadlocked) congress.
True, perhaps, but is that a problem? For instance, I've been very impressed with the programming from Revision3 - an online-only "TV" studio whose lineup is heavily aligned with the/. crowd. They even have their own "channel" on Roku devices.
That was one of my reactions to the article as well. This line from the end of page 1:
...other companies will make the decision to recruit and, if needed, train a new generation of programmers
We've seen for quite a few years that many companies expect new employees to "hit the ground running", with nothing more than a cursory new employee orientation. Training, especially on-the-job training and formal mentorship/apprenticeship models, have largely fallen by the wayside. In other words, hiring managers want employees who have all the skills to do exactly the job the company needs, in exactly the way they think they need it done. Then they are surprised when they can't find someone who exactly matches that profile.
[For the record, I am not one of the bitter long-term unemployed who have been stung by this. I was schooled in engineering, got hired as an engineer right out of school, and am happily employed as such today. But I am cognizant of the largely artificial obstacles that many of my peers face]
A Commodore 64 with an old inefficient linear regulator based power supply still only drew up to 15W from the wall.
Perhaps, but that C64 can be duplicated/emulated with a low-end ARM processor - with appropriate connections to a keyboard, tape drive, disk drive, monitor, etc. - on a PCB that draws maybe 1 W. The inefficiencies in the wall wart may well be greater than the power consumed by the computer.
Alternately, there are c64 emulators for iOS, Android, etc. that, in effect, give you the keyboard (albeit, usually an onscreen keyboard, though bluetooth is available, too) instant access to the entire c64 library, and a screen in a package that only draws about 2 W.
For one thing, it is very easy to write them down. For another, they lend themselves very easily to computation using binary math. Any number of the form 2^n - 1 is just a string of n 1's. E.g., 2^5 - 1 = 31 = 11111b.
As to your other question, regarding 2^n + 1, those would be of the form of a '1', followed by (n-1) '0's, followed by another '1'. E.g., 2^5 + 1 = 33 = 1000001b. I don't know if these are any more or less likely to be prime. I suspect less likely, otherwise those would be what are studied so much.
The new prime number, 2 multiplied by itself 57,885,161 times, less one, has 17,425,170 digits
"There are 10 kinds of people in the world. Those who understand binary, and those that don't."
This new number is 2^57,885,161 - 1, so naturally it has 57,885,161 digits, all of them 1. A simpler example: 2^5 - 1 is a Mersenne prime. Written in binary it's 100000 - 1 = 11111.
Oh! You meant that it has 17,425,170 decimal digits. Booooooooring!
Meh - I've replaced the battery in four separate iPhones in a total of five occassions. The 1st-gen, 3G, and 3GS were tricky to get into, but the 4 and higher are trivial, even if they have pentalobular screws. I wouldn't plan on doing it on a daily basis, but the vast, overwhelming majority of phone users don't burn through a single charge in a day. For the outliers there are external batteries. Yes, the slashdot crowd is different: your mileage may vary. But isn't the slashdot crowd all about consumer choice? Don't like Apple's implementation, take your cash elsewhere. I won't fuss, throw anything, or flame.
Slashdot Mirror
One simple reason: all that EPA and other regulatory testing needs to be done before the car hits the market.
Correction: asparagus only has a large carbon footprint if you import it from Chile to North America at whatever-time-of-year. If you are instead purchasing it from a farmer in the same area as you, in season, then its carbon footprint is hardly larger than any of other foodstuff. Don't malign the food itself, malign the source and the method of consumption. People simply have to accept that it is thoroughly unnatural to have tender asparagus tips in September. I'm not an eco-absolutist, but people need to be mindful of their food: what is it, where does it comes from, how is it grown, when is it in season, etc.
If you propose that, to push the asteroid, you first stop most of its spinning, then the pushing scenario requires huge amounts of additional fuel before you even begin talking about changing its trajectory. Landing and firmly attaching a rocket to an asteroid or comet is not a trivial undertaking - what works for some bodies may not work for others.
The big benefit of the gravitational tether is that it matters not a whit if the asteroid is tumbling wildly, or off-gassing (i.e., a comet), or is held together too loosely to attach to - you are simply applying force to this civilization-threatening mass by using another mass: action at a distance. The "at a distance" part circumvents a lot of thorny challenges.
That's either the Ecomobile or Monotracer. I first saw that on an ooooold show called Beyond 2000, which aired back when the year 2000 still seemed in the future.
Lit Motors has developed an enclosed motorcycle that uses an active gyro assembly under the driver to keep the thing upright when at a standstill and during sudden accelerations (i.e., during an accident). The gyro mechanism can also be used to assist in cornering.
And I can see now: a whole generation of planetary scientists suddenly dying en masse. First the rapture of witnessing such an event and being given the chance to study its aftermath. But then comes the crushing notion that they've wasted their careers trying to figure out the past and present of Mars: a past that is about to be completely obscured by the cometary effects, and a present that is about to be completely obliterated.
Meh, from what I hear plutonium isn't all that hard to work. It machines well enough (the bomb industry can machine it into interesting revolved ellipsoids to fit into MIRV warheads). It is usually found and used as a pure metal. Pure metals tend to be pretty soft and ductile - it is only once you start alloying things that they gain their mechanically useful properties. The main downside is that you can't work it in the open air: the chips will burn, and because plutonium is a fantastically toxic metal, not to mention its radioactivity, you practically have to live in a hazmat suit to handle it.
Do you know what the "depleted" in depleted uranium means? Depleted uranium is what's left over from uranium enrichment. Naturally occurring uranium is a mixture of U-238 and U-235 (plus some other stuff). Enrichment separates the fissile U-235 for use in power plants and bombs, leaving the U-238 behind. The U-238 is slightly radioactive, but isn't considered a nuclear fuel. This is why it's called depleted uranium - all its usefulness as a nuclear fuel has been separated out. Depleted uranium gets used in armor-piecing weapons because it is impressively dense (2/3 denser than lead), is harder than lots of other dense metals, is an abundant leftover of the nuclear industry, and spalls in just the right way. No one considers it a nuclear weapon, because there is nothing "nuclear" about its mechanics as a weapon. Ballistics aside, depleted uranium's greatest problem is that it is still a really toxic metal.
Did you even slow down to consider the full magnitude of a statement like that? A 9/11 happening each year would be a 20% increase in the homocide rate. Air travel would plummet. Air travel did stop for a few days immediately afterward. NYC suffered tremendous economic losses - the loss of a couple billion dollars of prime real estate, the disruption of business for weeks and months, the suspension of trading and subsequent drop in stock markets, the strain on emergency services, the long term costs of cleanup and rebuilding, long-term disability for those that were there, the loss of tourism, the psychological trauma, the erosion of freedom... need I go on? Yeah, maybe we would get used to it, and the next 9/11 would not be as bad as the last, but there are costs associated with that kind of normalization, too. You think that these are inconsequential or "not serious"?
That assumes that the infrastructure has been designed to accept a "backwards" flow of electricity. Designing a system that has power flow in only one direction is easier and cheaper than one that has bidirectional flow. Historically, and particularly in the United States, the cost of electricity has been a relatively small slice of a subway's total lifetime cost. The capital investment and the other operating costs are pretty big by comparison. Much easier to just dump all that kinetic energy into a resistor bank somewhere. I'm not saying that's the right way to do it, but that has historically been the thought process
It may not necessarily be batteries, but some sort of localized storage may be useful for subway and light rail. The size of the train system's electrical infrastructure needs to be sized to the peak electrical demand, which is greatest when the train is accelerating. Being able to have some storage on the train would allow for regenerative braking. Right now, all the kinetic energy of the train's motion, which is an awful lot, is lost every time the train slows or stops. It's lost as heat and wear in the brakes, and as a tremendous amount of acoustic energy (the terribly shrieking of the train's approach). Boosting the on-board storage with some power fed in when the train is stationary allows the fixed infrastructure to be sized to the average power demand, which is a different beast. Finally, some localized storage would allow the train to operate for short distances where there is no electrical infrastructure. This would allow the electrical system to be broken up into smaller, isolated, more manageable parts. If one zone goes down due to accident, disaster, or just for maintenance, the train system can continue to function. It is redundancy through distribution.
I personally prefer to siphon my power from the third rail of the subway. But, if you want to try to get all inductive and not get your hands dirty...
What it appears they are going to do is implant some wires into the man's residuum. These wires - electrodes - will have two purposes:
In conventional motor-driven, upper-limb prostheses, particularly below-the-elbow, the control signals are measured using surface EMGs (ElectroMyoGraphic sensors). These aren't measuring nerve firings, per se, but rather the electrical activity of actual muscle contractions (in the forearm). This is done because the actual motor nerves are pretty tiny, and the signal in them is fairly small. The muscle, on the other hand, is much easier to locate, and it acts as a natural amplifier of what the nerve tells it to do. It's the difference between probing a tiny signal wire coming out of your MP3 player and picking up the sound that is resonating in the speaker housing.
The downside of using surface EMGs is that, by measuring electrical potentials across several cm of skin and muscle, it is hard to pick up on individual muscle contractions. So, it is generally not possible to pick up on just the muscle that flexed/extended the index finger. The best you can usually do is pick up on the flexion/extension signals for all finger muscles or the wrist. Another downside is that the EMGs are usually mounted to the socket - the molded plastic or composite structure that mechanically interfaces the prosthesis to the residuum. As the wearer moves around and sweats, the EMGs can shift over the skin surface, which degrades the signal strength and specificity.
By implanting EMG electrodes under the skin, you can mostly eliminate the problems of the having the electrodes shifting, because they'll move with the tissue they are measuring. You may also be able to get more localized measurements (crosstalk is a difficult problem), and so get more than 1-2 channels of control input. This approach is not exactly new, but neither is it widespread. Amputees are, naturally, a bit wary of invasive procedures - they don't want to risk screwing up what they have left. The other downside is that, at least in this case, they are opting for transdermal electrodes - wires poking through the skin, which could have long-term drawbacks. Some work is being done with fully implanted EMGs that can be probed using near field technologies - RFID in your muscles - but that is still a work in progress.
Stimulating nerves to provide sensory feedback is, likewise, not exactly new, but hasn't made it into clinical practice. There have been anecdotes about patients who have undergone targeted nerve reinnervation who, when you poke them in a certain place on their pectoral muscle, report "feeling" a sensation in their lost hand. Again, going to implanted electrodes allows you the chance to have must greater specificity.
Aside from the invasive nature of the procedure, my main concern with this project is its longevity. How long can the electrodes exist within the body? Will you still be able to get or produce a worthwhile signal after 1 month, 6 months, 10 years? The prosthesis can be repaired and replaced over time, but tinkering around with the electrodes may not be feasible. I also have some concerns about the durability of the sensing elements in the prosthetic hand, but that is more straightforward engineering than anything else.
The "law against unlocking cellphones" isn't a law - it is a regulation, a rule set by the Librarian of Congress. This is good, because it is probably easier to change than a law, which requires an act of (a very hostile and deadlocked) congress.
That'd make for some hilarious jokes in a TV sitcom, if it weren't also so very sad.
True, perhaps, but is that a problem? For instance, I've been very impressed with the programming from Revision3 - an online-only "TV" studio whose lineup is heavily aligned with the /. crowd. They even have their own "channel" on Roku devices.
With shameless promotion like that, Microsoft might just send you an XBox, gratis, in exchange for a product endorsement!
We've seen for quite a few years that many companies expect new employees to "hit the ground running", with nothing more than a cursory new employee orientation. Training, especially on-the-job training and formal mentorship/apprenticeship models, have largely fallen by the wayside. In other words, hiring managers want employees who have all the skills to do exactly the job the company needs, in exactly the way they think they need it done. Then they are surprised when they can't find someone who exactly matches that profile.
[For the record, I am not one of the bitter long-term unemployed who have been stung by this. I was schooled in engineering, got hired as an engineer right out of school, and am happily employed as such today. But I am cognizant of the largely artificial obstacles that many of my peers face]
Perhaps, but that C64 can be duplicated/emulated with a low-end ARM processor - with appropriate connections to a keyboard, tape drive, disk drive, monitor, etc. - on a PCB that draws maybe 1 W. The inefficiencies in the wall wart may well be greater than the power consumed by the computer.
Alternately, there are c64 emulators for iOS, Android, etc. that, in effect, give you the keyboard (albeit, usually an onscreen keyboard, though bluetooth is available, too) instant access to the entire c64 library, and a screen in a package that only draws about 2 W.
Great news, everyone!
First thing that came into my mind.
Not a bad idea. However, it's tough to find circular LCD screens. A circular touchscreen, even more so.
For one thing, it is very easy to write them down. For another, they lend themselves very easily to computation using binary math. Any number of the form 2^n - 1 is just a string of n 1's. E.g., 2^5 - 1 = 31 = 11111b.
As to your other question, regarding 2^n + 1, those would be of the form of a '1', followed by (n-1) '0's, followed by another '1'. E.g., 2^5 + 1 = 33 = 1000001b. I don't know if these are any more or less likely to be prime. I suspect less likely, otherwise those would be what are studied so much.
"There are 10 kinds of people in the world. Those who understand binary, and those that don't."
This new number is 2^57,885,161 - 1, so naturally it has 57,885,161 digits, all of them 1. A simpler example: 2^5 - 1 is a Mersenne prime. Written in binary it's 100000 - 1 = 11111.
Oh! You meant that it has 17,425,170 decimal digits. Booooooooring!
Meh - I've replaced the battery in four separate iPhones in a total of five occassions. The 1st-gen, 3G, and 3GS were tricky to get into, but the 4 and higher are trivial, even if they have pentalobular screws. I wouldn't plan on doing it on a daily basis, but the vast, overwhelming majority of phone users don't burn through a single charge in a day. For the outliers there are external batteries. Yes, the slashdot crowd is different: your mileage may vary. But isn't the slashdot crowd all about consumer choice? Don't like Apple's implementation, take your cash elsewhere. I won't fuss, throw anything, or flame.
Groundskeeper Willie, is that you?