"Pessimist by policy, optimist by temperament--it is possible to be both. How? By never taking an unnecessary chance and by minimizing risks you can't avoid. This permits you to play out the game happily, untroubled by the certainty of the outcome." -- Robert Heinlein, Time Enough For Love.
I think it's especially important for engineers to be pessimistic by policy; I like to think, while crossing a bridge, that the engineers involved thought through all the worst-case scenarios and didn't just assume that everything was going to work out right.
1. Selectable analog notch filtering. My receiver is blocked--no signal is reaching the ADC, let alone the processing software. Which analog notch filter do I select? Some guy downloads a movie from a train station kiosk with his SDR PDA while a policeman is standing next to him listening to the dispatcher on his SDR radio, transmitting from the tower on the hill. At the antenna of the policeman's radio, the signal from the kiosk is 80 dB stronger than the signal from the dispatcher. How does selectable analog notch filtering help the policeman's receiver?
2. Your sensibly coded signal only needs 20dB of coding gain. You're assuming that the two stations are equidistant, and have equivalent antenna gains--two factors almost certainly not true. Since power goes as the square of the distance (and more like the cube, indoors) it's more frequently the case that one signal is 40, 60, or 80 dB stronger--and perhaps more!--than the other. Your coding solution becomes wildly impractical under these very real-world conditions. The absolute power transmitted is irrelevant to your argument in an environment where the channel path loss can exceed 150 dB--on useable links!
3. Nodes will need to do stochastic meshing and automatic power regulation. This is demonstrably false: You're requiring a mesh network in which each node transmits at a power level such that the signals received by each node are of substantially the same strength. Try that with, say, five randomly-placed nodes and show me how it works. Or, better, go to a shift change at your local police station, and ensure that each of the officers' radios receives the repeater on the hill when thirty of them are standing next to each other and one transmits. If they don't, explain that the radios on which their lives may depend will work, once they get away from all the other policemen, and that it's really not that important that they work in the station. Hint: Get paid in advance of product delivery.
4. Convert [emergency] services to spread-spectrum also. If you mean simple spread-spectrum, I have no disagreement. However, if you mean to imply the conversion of emergency services to cognitive radio, I disagree. A typical duty cycle for a policeman's radio is the so-called 5-5-90 usage pattern, meaning 5% actively transmitting, 5% actively receiving, and 90% standby (meaning the radio is monitoring the dispatcher but there is no traffic for the particular officer, so the radio remains silent). So 95% of the time, the radio transmits nothing. In a cognitive system, how is everything else in the cognitive radio system going to know that the policeman's radio is there, and to modify its transmissions so that the policeman can hear the dispatcher as he walks down the street?
5. There will be far fewer [interference] disputes. Why would this be? Interference complaints hardly clog the courts as it is, and the ones of which I am aware, like the BPL vs. amateur radio situation, involve unintentional radiators causing interference much stronger than can be overcome by processing gain.
Oh, and don't complain about the "really vile politics" that created the standards we have today. Anyone with experience in, say, the IEEE 802 wireless standards organization lately--especially in the cognitive radio groups--creating the standards of tomorrow can't really complain about the vile politics of the past. I think what the GP was trying to point out is that you'll make a better cognitive radio system if you learn why the existing protocols and hardware are as they are--and, contrary to popular belief, it isn't all politics and ignorance. Often the reasons are subtle yet important, and nobody, especially the hapless user, benefits if the SDR/cognitive radio industry has to relearn nearly a century of radio protocol design experience one error at a time.
I'm not entirely sure you understand the concept of coding gain.
ooooh, yes, he does. This isn't a "noise" issue where, you're right, coding gain would help. This is a "nonlinearity" (e.g., blocking and intermodulation) issue, where coding gain is irrelevant or inadequate, and the "obvious workarounds" typically don't work well in practice. A digression:
Blocking occurs when you're trying to receive some desired signal, at some reasonable signal strength, and at least one strong, undesired signal, on an arbitrary frequency, also reaches an active stage of the receiver. If the undesired signal is strong enough, it can corrupt the dc bias of the active stage. The small-signal gain of the receiver drops, often by 80 dB or more, so the desired signal (and all others, often including the undesired signal that caused the problem in the first place) simply disappears. It's an impressive thing to see in action. Essentially no signal reaches the backend of the receiver, where the correlators are that produce the coding gain. You can experience blocking for yourself by listening to a station on a car AM radio and then driving close by (~200 m) the antennas of a second AM radio station. The signal from the first station fades out as you approach the second, leaving you with no signal at all. Just...silence.
Blocking is most easily prevented in conventional receivers by providing passive filters before the active circuits (i.e., the LNA), filtering out the strong signals elsewhere in the spectrum before they have a chance to affect the active circuits. (The filters are why the AM radio test above doesn't affect your car FM radio.) However, this produces a narrowband radio (unless one is willing to make really complicated tracking and switching RF filters, as seen in early shortwave receivers), which is not suitable for SDR. Less efficiently, one can increase the dc bias power of the active circuits, so that stronger undesired signals are needed to produce blocking, but the tradeoff is dB-for-dB, so a 10 dB improvement in blocking performance is achieved by a 10x increase in receiver power consumption. Not a pleasant trade, in most applications.
In the GP's discussion of intermodulation, the P is right, coding gain will help overcome intermodulation distortion--but he's wrong in saying "as long as I can get a few dB of coding gain." The difficulty is that intermodulation products frequently are very much stronger (~30 dB or more) than the desired signal. A simple definition of direct sequence coding gain is the ratio of the chip rate to the bit rate; to get 30 dB of coding gain the chip rate has to be a thousand times the bit rate, so your moderate-performance 1 Mb/s system requires a chip rate of 1 Gc/s--nice, if you have an open channel wide enough to put it in (along with the power to code and decode it); a bit of a bother otherwise. And that's for only 30 dB of protection.
Analog stage / ADC overloading is still a problem, but there are some obvious workarounds.
Let's discuss workarounds.
One "obvious" workaround to avoid intermodulation is to reduce the gain of the receiver front end when strong signals are detected by the receiver via some kind of AGC (and assuming this can be done without reducing the overall receiver intercept point). This has the attraction that the receiver bandwidth must be wide to ensure that the undesired signals reach the AGC detector, something compatible with the SDR concept. The receiver gain is set high when no or weak signals reach the AGC detector, and low when strong signals reach it.
What happens in a blocking environment, though? In a blocking environment, the receiver's "analog stages" are "overloaded", so that no signal reaches the AGC detector. The AGC system responds as designed, and attemps to maximize the gain of said analog stages. This ensures that they remain overloaded! Note that it's difficult for the SDR algorithms to figure out what's going on, be
I saw the accident from my office building. The windows on the correct side were in the accounting department, so a bunch of us engineers invaded some poor accountant's office, displacing piles of beans (and accountants) already there.
The weather was clear, so we had a great view of the exhaust trail as it went up. When the accident occurred, the solid-rocket boosters went their separate ways, forming a "Y" in the exaust trail. The accountants said, "Oooh, isn't that neat looking!" The engineers said, "Uh-oh...that's not supposed to happen...."
(a)...so what keeps the rider from flapping behind the handlebars like a flag (best case) or immediately turning into a somewhat crispy spectator, as his now-riderless bike rockets off without him?
The slingshot technique works because Jupiter is also moving--it's in orbit around the Sun, at about 30,000 mph (48,000 km/hr). When the probe approaches Jupiter from behind, the probe is gravitationally attracted to something (Jupiter) traveling at 30,000 mph, so it speeds up. Relative to Jupiter, you're right, it's a zero-sum game (i.e., the probe does seem to speed up and then slow down again, relative to the planet) but the velocity of concern is the so-called heliocentric velocity, or the velocity relative to the Sun, and that is greatly increased.
Note that there is conservation of energy, of course; Jupiter also slows down in its orbit slightly in response to the energy it adds to the probe, but the amount is unmeasurable due to the mass ratio between Jupiter and the probe. The speedup is therefore considered "free."
Regarding your second question, the probe doesn't slow down again, and does do a very fast flyby. However, we know so close to nothing about Pluto that we don't have to get very close to get new information--for example, the resolution of the New Horizons cameras will exceed that of the best Earth telescopes (including Hubble) for 150 days. (Of course, it will take 4-9 months, depending on which estimate you like, to transmit the data back to the earth at the probe's minimum data rate--which it likely will use at that distance--of 800 bits/s.)
Trust me, everyone that experiences both (a) a hurricane and (b) a Florida tropical thunderstorm--which is to say, most of the population of the state--is immediately aware of absence of thunder and lightning in hurricanes. You don't need scientific instruments to identify the presence or absence of a phenomenon that causes the family dog (and the occasional owner) to run and hide under the bed almost every summer afternoon, quivering from the sound of thunderclaps.
It's well known folk wisdom that hurricanes usually don't produce lightning. The fact that these three did is what makes it interesting.
This is an ultrawideband through-wall imaging system, and is an old technology that has been around for many years. Two of the many manufacturers are Time Domain [Flash!] and Camero.
Note that, while military radio emissions are regulated in the U.S. by the NTIA, U.S. civilian use of ultrawideband through-wall imaging systems is controlled by the FCC (by regulations established in April 2002 [pdf!]). 47 U.S.C. 15.510(5)(e) [pdf!] states that
Through-wall imaging systems operating under the provisions of this section shall bear thefollowing or similar statement in a conspicuous location on the device:
"Operation of this device is restricted to law enforcement, emergency rescue and firefighter personnel. Operation by any other party is a violation of 47 U.S.C. 301 and could subject the operator to serious legal penalties."
Basically, and as defined by rules elsewhere, it's illegal even to possess one in the U.S. if you're not a first-responder type.
Knowledge of history is important. The world is not a memoryless system. How can you understand the present state of the system if you do not understand the past?
Jacques D'Arsonval (1851-1940) is far better known for designing the analog electrical meter movement (galvanometer) that bears his name. Nearly all DC voltmeters (and ammeters) you are likely to see (well, okay, largely--but not entirely--relegated to museums nowadays) are of the D'Arsonval type.
No problem--not writing what you mean to say happens to us all. Just look at my comment--"The superfluidity of helium-3, a fermion, was shown to be a superfluid in the 1970s," indeed. And that after previewing and editing a half-dozen times! I feel responsible for the loss of several English teachers, whose heads I have just caused to explode.
Although the conditions set for this experiment are very unlikely to be able to exist outside of a laboratory, we now know that superfluidity is a concept that can exist.
Superfluid materials are well-known; the first example, the boson helium-4, was discovered in 1937. The superfluidity of helium-3, a fermion, was shown to be a superfluid in the 1970s.
Superfluidity occurs when particles pair up (half spin-up and half spin-down) to produce a material without viscosity, in a manner analogous to that of the electron Cooper pairs of superconductivity. The novelty here is that superfluidity has been shown to occur in particle populations in which there is an unequal number of spin-up and spin-down particles, and the discovery of a phase change in which "when unpaired spin-up atoms rose above 10 percent of the total sample, the unpaired loners were suddenly expelled, leaving a core of superfluid pairs surrounded by a shell of excess spin-up atoms" (from TFA).
The New Horizons probe to Pluto launches next month. The latest news has the probe launching between January 17 (a six-day delay from the original plan, due to a fuel tank problem) and February 14.
As Paul Marsh did here detecting the MRO on its way to Mars, one of the benefits of setting up the receiving system while the probe is outbound is that the signal starts out strong, so your first-generation system can be somewhat crude. As the signal weakens (over the years in the New Horizons case), you can gradually refine your setup (and perhaps count on new technology to be developed in the meantime).
BTW, for those interested in the technical details of telecommunications with NASA deep space probes, a good place to start is the Future Missions Planning Office site. It contains communication link design tools, HTML links to applicable CCSDS standards, etc.
The leakage path relevant to tunneling is through the gate oxide, from the gate to the channel below it. In this case, the width of the barrier is the gate oxide thickness, not the gate length. So the ways to decrease tunneling include having a thicker gate oxide, but of course it'll still be slower (less capacitive coupling of the gate to the charge in the channel). A representative paper reviewing gate tunneling and its effects on logic gate performance is this one (in pdf).
Also, the height of the barrier is determined by the material properties, not the gate voltage. With that said, I still don't understand how the authors can do what the press release says they say they do. How does RTA affect the material properies enough to affect tunneling significantly? MOS gate oxides are one of the most studied materials known to man, with uncounted man-millenia devoted to eliminating any defects therein. What did they miss?
A final thought--if this was such a fundamental breakthrough one would think it would be presented at the International Electron Devices Meeting itself, rather than at the small conference associated with it held later in the week. But maybe not.
My vote is for the "The People" series of short stories by Zenna Henderson. It's usually regarded as fantasy, but I've always considered it firmly in the sci-fi camp.
The backdrop of the stories is a spaceship of human-looking aliens ("The People") that crash-lands in the American Southwest, scattering individuals and groups over a large area. The aliens have certain abilities not usually seen in the Southwest (telekinesis, etc.), but have to try to blend in with the local population nevertheless. Not only are the stories largely concerned with interpersonal relationships (the loneliness of feeling different from everyone else and the desire to fit in with the group is a strong theme, something I expect will resonate with early teenage girls), the protagonists are often teenage girls as well.
The stories were collected in a 1995 book, "Ingathering: The Complete People Stories of Zenna Henderson" (also available at Amazon et al.), and it's a great read. I've always felt that the best introduction to the series is the short story "Ararat," but YMMV.
Many comments to this post have pointed out the importance of a reliable power source for the electronic doorknob. I note that it's possible to use the energy of the motion of the knob itself to power the lock (and whatever other security feature one may reasonably desire). There may be earlier references to to this technique, but the one with which I am familiar is by Gerald F. Ross et al. Their paper, "Batteryless Sensor for Intrusion Detection and Assessment of Threats. - Technical rept. 7 Jul 94-12 Feb 95" is available as Defense Nuclear Agency Technical Report DNA-TR-95-21 from the National Technical Information Service; their design was also patented as US patent 5,317,303, available from the USPTO (although their usually reliable search engine seems to be down as I write this).
Basically, the technique uses a wireless sensor network to monitor door openings and closings. When someone turns the knob, a generator powers a wireless transmitter, which sends a request to some central authority, which determines whether the door should be opened or not.
The general term for these types of batteryless techniques is energy scavenging (or energy harvesting); there are many other examples of these techniques available on the web, and a book, "Energy Scavenging for Wireless Sensor Networks : with Special Focus on Vibrations," is also available. There is at least one company, Enocean, dedicated to the production of such systems.
The biggest advantage for the designer of battery-powered portable devices is that an eink display need only be driven when the display contents change, while an LCD must be constantly driven (by rail-to-rail signals driving the display capacitance) even if the display contents do not change. This means that, for applications requiring infrequent updates (e.g., status displays on cell phones, pagers, Apple Nanos, etc.), the eink display driver can be turned off, saving power. Further, eink has the legibility of conventional paper, so under conditions in which ordinary paper is readable the LCD backlight is not needed, saving considerably more power.
This must be a record. Two hours and only five comments? [Insert witty comment here. Subject may be the character of the original poster, the quality of Slashcode, or one of your own choosing.]
At the 98th Annual Meeting of the Cordilleran Section of the Geological Society of America (May 13-15, 2002), in Corvallis, Oregon, there were several papers on this bulge in the "Hazards and Risks from Cascade Volcanoes" session. Apparently it was discovered in April 2001; the GSA even sent out a press release about the bulge in May 2002.
Slashdot Mirror
Better pictures.
Let's take 'em one at a time...
1. Selectable analog notch filtering. My receiver is blocked--no signal is reaching the ADC, let alone the processing software. Which analog notch filter do I select? Some guy downloads a movie from a train station kiosk with his SDR PDA while a policeman is standing next to him listening to the dispatcher on his SDR radio, transmitting from the tower on the hill. At the antenna of the policeman's radio, the signal from the kiosk is 80 dB stronger than the signal from the dispatcher. How does selectable analog notch filtering help the policeman's receiver?
2. Your sensibly coded signal only needs 20dB of coding gain. You're assuming that the two stations are equidistant, and have equivalent antenna gains--two factors almost certainly not true. Since power goes as the square of the distance (and more like the cube, indoors) it's more frequently the case that one signal is 40, 60, or 80 dB stronger--and perhaps more!--than the other. Your coding solution becomes wildly impractical under these very real-world conditions. The absolute power transmitted is irrelevant to your argument in an environment where the channel path loss can exceed 150 dB--on useable links!
3. Nodes will need to do stochastic meshing and automatic power regulation. This is demonstrably false: You're requiring a mesh network in which each node transmits at a power level such that the signals received by each node are of substantially the same strength. Try that with, say, five randomly-placed nodes and show me how it works. Or, better, go to a shift change at your local police station, and ensure that each of the officers' radios receives the repeater on the hill when thirty of them are standing next to each other and one transmits. If they don't, explain that the radios on which their lives may depend will work, once they get away from all the other policemen, and that it's really not that important that they work in the station. Hint: Get paid in advance of product delivery.
4. Convert [emergency] services to spread-spectrum also. If you mean simple spread-spectrum, I have no disagreement. However, if you mean to imply the conversion of emergency services to cognitive radio, I disagree. A typical duty cycle for a policeman's radio is the so-called 5-5-90 usage pattern, meaning 5% actively transmitting, 5% actively receiving, and 90% standby (meaning the radio is monitoring the dispatcher but there is no traffic for the particular officer, so the radio remains silent). So 95% of the time, the radio transmits nothing. In a cognitive system, how is everything else in the cognitive radio system going to know that the policeman's radio is there, and to modify its transmissions so that the policeman can hear the dispatcher as he walks down the street?
5. There will be far fewer [interference] disputes. Why would this be? Interference complaints hardly clog the courts as it is, and the ones of which I am aware, like the BPL vs. amateur radio situation, involve unintentional radiators causing interference much stronger than can be overcome by processing gain.
Oh, and don't complain about the "really vile politics" that created the standards we have today. Anyone with experience in, say, the IEEE 802 wireless standards organization lately--especially in the cognitive radio groups--creating the standards of tomorrow can't really complain about the vile politics of the past. I think what the GP was trying to point out is that you'll make a better cognitive radio system if you learn why the existing protocols and hardware are as they are--and, contrary to popular belief, it isn't all politics and ignorance. Often the reasons are subtle yet important, and nobody, especially the hapless user, benefits if the SDR/cognitive radio industry has to relearn nearly a century of radio protocol design experience one error at a time.
ooooh, yes, he does. This isn't a "noise" issue where, you're right, coding gain would help. This is a "nonlinearity" (e.g., blocking and intermodulation) issue, where coding gain is irrelevant or inadequate, and the "obvious workarounds" typically don't work well in practice. A digression:
Blocking occurs when you're trying to receive some desired signal, at some reasonable signal strength, and at least one strong, undesired signal, on an arbitrary frequency, also reaches an active stage of the receiver. If the undesired signal is strong enough, it can corrupt the dc bias of the active stage. The small-signal gain of the receiver drops, often by 80 dB or more, so the desired signal (and all others, often including the undesired signal that caused the problem in the first place) simply disappears. It's an impressive thing to see in action. Essentially no signal reaches the backend of the receiver, where the correlators are that produce the coding gain. You can experience blocking for yourself by listening to a station on a car AM radio and then driving close by (~200 m) the antennas of a second AM radio station. The signal from the first station fades out as you approach the second, leaving you with no signal at all. Just...silence.
Blocking is most easily prevented in conventional receivers by providing passive filters before the active circuits (i.e., the LNA), filtering out the strong signals elsewhere in the spectrum before they have a chance to affect the active circuits. (The filters are why the AM radio test above doesn't affect your car FM radio.) However, this produces a narrowband radio (unless one is willing to make really complicated tracking and switching RF filters, as seen in early shortwave receivers), which is not suitable for SDR. Less efficiently, one can increase the dc bias power of the active circuits, so that stronger undesired signals are needed to produce blocking, but the tradeoff is dB-for-dB, so a 10 dB improvement in blocking performance is achieved by a 10x increase in receiver power consumption. Not a pleasant trade, in most applications.
In the GP's discussion of intermodulation, the P is right, coding gain will help overcome intermodulation distortion--but he's wrong in saying "as long as I can get a few dB of coding gain." The difficulty is that intermodulation products frequently are very much stronger (~30 dB or more) than the desired signal. A simple definition of direct sequence coding gain is the ratio of the chip rate to the bit rate; to get 30 dB of coding gain the chip rate has to be a thousand times the bit rate, so your moderate-performance 1 Mb/s system requires a chip rate of 1 Gc/s--nice, if you have an open channel wide enough to put it in (along with the power to code and decode it); a bit of a bother otherwise. And that's for only 30 dB of protection.
Let's discuss workarounds.
One "obvious" workaround to avoid intermodulation is to reduce the gain of the receiver front end when strong signals are detected by the receiver via some kind of AGC (and assuming this can be done without reducing the overall receiver intercept point). This has the attraction that the receiver bandwidth must be wide to ensure that the undesired signals reach the AGC detector, something compatible with the SDR concept. The receiver gain is set high when no or weak signals reach the AGC detector, and low when strong signals reach it.
What happens in a blocking environment, though? In a blocking environment, the receiver's "analog stages" are "overloaded", so that no signal reaches the AGC detector. The AGC system responds as designed, and attemps to maximize the gain of said analog stages. This ensures that they remain overloaded! Note that it's difficult for the SDR algorithms to figure out what's going on, be
I saw the accident from my office building. The windows on the correct side were in the accounting department, so a bunch of us engineers invaded some poor accountant's office, displacing piles of beans (and accountants) already there.
The weather was clear, so we had a great view of the exhaust trail as it went up. When the accident occurred, the solid-rocket boosters went their separate ways, forming a "Y" in the exaust trail. The accountants said, "Oooh, isn't that neat looking!" The engineers said, "Uh-oh...that's not supposed to happen...."
(a) ...so what keeps the rider from flapping behind the handlebars like a flag (best case) or immediately turning into a somewhat crispy spectator, as his now-riderless bike rockets off without him?
(b) Rocket: $1k.
Optional backrest: $2k
Attorneys' fees for traffic citation collection: priceless
c) Lessee...how long until someone makes a reference to the Darwin Award?
The slingshot technique works because Jupiter is also moving--it's in orbit around the Sun, at about 30,000 mph (48,000 km/hr). When the probe approaches Jupiter from behind, the probe is gravitationally attracted to something (Jupiter) traveling at 30,000 mph, so it speeds up. Relative to Jupiter, you're right, it's a zero-sum game (i.e., the probe does seem to speed up and then slow down again, relative to the planet) but the velocity of concern is the so-called heliocentric velocity, or the velocity relative to the Sun, and that is greatly increased.
Note that there is conservation of energy, of course; Jupiter also slows down in its orbit slightly in response to the energy it adds to the probe, but the amount is unmeasurable due to the mass ratio between Jupiter and the probe. The speedup is therefore considered "free."
Google is your friend; see this page, this page, this page for more information.
Regarding your second question, the probe doesn't slow down again, and does do a very fast flyby. However, we know so close to nothing about Pluto that we don't have to get very close to get new information--for example, the resolution of the New Horizons cameras will exceed that of the best Earth telescopes (including Hubble) for 150 days. (Of course, it will take 4-9 months, depending on which estimate you like, to transmit the data back to the earth at the probe's minimum data rate--which it likely will use at that distance--of 800 bits/s.)
Trust me, everyone that experiences both (a) a hurricane and (b) a Florida tropical thunderstorm--which is to say, most of the population of the state--is immediately aware of absence of thunder and lightning in hurricanes. You don't need scientific instruments to identify the presence or absence of a phenomenon that causes the family dog (and the occasional owner) to run and hide under the bed almost every summer afternoon, quivering from the sound of thunderclaps.
It's well known folk wisdom that hurricanes usually don't produce lightning. The fact that these three did is what makes it interesting.
(c.f. the rarity of lightning in snowstorms--a.k.a. thundersnow.)
This is an ultrawideband through-wall imaging system, and is an old technology that has been around for many years. Two of the many manufacturers are Time Domain [Flash!] and Camero.
Note that, while military radio emissions are regulated in the U.S. by the NTIA, U.S. civilian use of ultrawideband through-wall imaging systems is controlled by the FCC (by regulations established in April 2002 [pdf!]). 47 U.S.C. 15.510(5)(e) [pdf!] states that
Basically, and as defined by rules elsewhere, it's illegal even to possess one in the U.S. if you're not a first-responder type.Try again.
Knowledge of history is important. The world is not a memoryless system. How can you understand the present state of the system if you do not understand the past?
Jacques D'Arsonval (1851-1940) is far better known for designing the analog electrical meter movement (galvanometer) that bears his name. Nearly all DC voltmeters (and ammeters) you are likely to see (well, okay, largely--but not entirely--relegated to museums nowadays) are of the D'Arsonval type.
ah, make that, "...the heads of whom I have just caused to explode." Sheesh.
No problem--not writing what you mean to say happens to us all. Just look at my comment--"The superfluidity of helium-3, a fermion, was shown to be a superfluid in the 1970s," indeed. And that after previewing and editing a half-dozen times! I feel responsible for the loss of several English teachers, whose heads I have just caused to explode.
Superfluid materials are well-known; the first example, the boson helium-4, was discovered in 1937. The superfluidity of helium-3, a fermion, was shown to be a superfluid in the 1970s.
Superfluidity occurs when particles pair up (half spin-up and half spin-down) to produce a material without viscosity, in a manner analogous to that of the electron Cooper pairs of superconductivity. The novelty here is that superfluidity has been shown to occur in particle populations in which there is an unequal number of spin-up and spin-down particles, and the discovery of a phase change in which "when unpaired spin-up atoms rose above 10 percent of the total sample, the unpaired loners were suddenly expelled, leaving a core of superfluid pairs surrounded by a shell of excess spin-up atoms" (from TFA).
It's called "quantum entanglement of research labs," and is impressive because of the incredible mass of such objects :)
The New Horizons probe to Pluto launches next month. The latest news has the probe launching between January 17 (a six-day delay from the original plan, due to a fuel tank problem) and February 14.
As Paul Marsh did here detecting the MRO on its way to Mars, one of the benefits of setting up the receiving system while the probe is outbound is that the signal starts out strong, so your first-generation system can be somewhat crude. As the signal weakens (over the years in the New Horizons case), you can gradually refine your setup (and perhaps count on new technology to be developed in the meantime).
BTW, for those interested in the technical details of telecommunications with NASA deep space probes, a good place to start is the Future Missions Planning Office site. It contains communication link design tools, HTML links to applicable CCSDS standards, etc.
The leakage path relevant to tunneling is through the gate oxide, from the gate to the channel below it. In this case, the width of the barrier is the gate oxide thickness, not the gate length. So the ways to decrease tunneling include having a thicker gate oxide, but of course it'll still be slower (less capacitive coupling of the gate to the charge in the channel). A representative paper reviewing gate tunneling and its effects on logic gate performance is this one (in pdf).
Also, the height of the barrier is determined by the material properties, not the gate voltage. With that said, I still don't understand how the authors can do what the press release says they say they do. How does RTA affect the material properies enough to affect tunneling significantly? MOS gate oxides are one of the most studied materials known to man, with uncounted man-millenia devoted to eliminating any defects therein. What did they miss?
A final thought--if this was such a fundamental breakthrough one would think it would be presented at the International Electron Devices Meeting itself, rather than at the small conference associated with it held later in the week. But maybe not.
My vote is for the "The People" series of short stories by Zenna Henderson. It's usually regarded as fantasy, but I've always considered it firmly in the sci-fi camp.
The backdrop of the stories is a spaceship of human-looking aliens ("The People") that crash-lands in the American Southwest, scattering individuals and groups over a large area. The aliens have certain abilities not usually seen in the Southwest (telekinesis, etc.), but have to try to blend in with the local population nevertheless. Not only are the stories largely concerned with interpersonal relationships (the loneliness of feeling different from everyone else and the desire to fit in with the group is a strong theme, something I expect will resonate with early teenage girls), the protagonists are often teenage girls as well.
The stories were collected in a 1995 book, "Ingathering: The Complete People Stories of Zenna Henderson" (also available at Amazon et al.), and it's a great read. I've always felt that the best introduction to the series is the short story "Ararat," but YMMV.
I knew I was behind the times, but geez.
How about 0100 UTC on Wednesday, or 9 PM Eastern on Tuesday?
Basically, the technique uses a wireless sensor network to monitor door openings and closings. When someone turns the knob, a generator powers a wireless transmitter, which sends a request to some central authority, which determines whether the door should be opened or not.
The general term for these types of batteryless techniques is energy scavenging (or energy harvesting); there are many other examples of these techniques available on the web, and a book, "Energy Scavenging for Wireless Sensor Networks : with Special Focus on Vibrations," is also available. There is at least one company, Enocean, dedicated to the production of such systems.
See eink's benefits page for an overview.
The biggest advantage for the designer of battery-powered portable devices is that an eink display need only be driven when the display contents change, while an LCD must be constantly driven (by rail-to-rail signals driving the display capacitance) even if the display contents do not change. This means that, for applications requiring infrequent updates (e.g., status displays on cell phones, pagers, Apple Nanos, etc.), the eink display driver can be turned off, saving power. Further, eink has the legibility of conventional paper, so under conditions in which ordinary paper is readable the LCD backlight is not needed, saving considerably more power.
I think the poster meant "principals," since it's well known that there are no "principles" in Redmond.
This must be a record. Two hours and only five comments? [Insert witty comment here. Subject may be the character of the original poster, the quality of Slashcode, or one of your own choosing.]
At the 98th Annual Meeting of the Cordilleran Section of the Geological Society of America (May 13-15, 2002), in Corvallis, Oregon, there were several papers on this bulge in the "Hazards and Risks from Cascade Volcanoes" session. Apparently it was discovered in April 2001; the GSA even sent out a press release about the bulge in May 2002.
Like a perfect vacuum, I believe nature abhors a grammar Nazi post without a grammatical error.
Make that "It's "his", her", and "its".
*sigh*
--completed grammar Nazi mode. Resuming normal operation.