it is easy to replace the first stage with out-of-car hydrogen generation, if and when clean hydrogen becomes cheap and easy to transport.
That is of course the whole issue with the hydrogen cars. Manufactures can build small runs of hydrogen (be it ICE, ECE or fuel cell) cars as a technology showcase and to buy political/marketing points without having to worry the cars will actually be able to be fueled. Nocera at MIT and other have done great work to make certain non-fossil hydrogen production more viable, but this has not solved the practical aspect of hydrogen handling, storage and transportation. The construction of high temperature nuclear reactors will also enable thermal cracking of water.
Hydrocarbons are easy to store and transport and have a much higher energy density. Continuing development of biomass (especially algae based) and synthetic liquid fuels offers the ability to reuse most of the current national fueling infrastructure and still close the carbon cycle. There are other benefits as well. Algae reactors connected to smoke stacks absorb not only the CO2 but also nitrogen oxides. The pressed algae can be used as a non-fossil fuel based fertilizer.
Obviously hydrogen energy transport and fuel-cell vehicles hold some promise. But I am very concerned with the hype and almost religious defense of all things hydrogen "the ocean is full of hydrogen" especially when there are many other technologies that are closer or even in deployment that we can use right now.
Actually, If I remember correctly, the A4 line of VW cars uses 430nm deep blue LEDs for back lighting in the instrument cluster. I don't know if it has helped keep me awake for long drives (740 miles, continuous no stops, 10 hours, one tank of diesel), but it is pretty. I had to look up the wavelength because it is difficult to match and the deep blue LEDs are somewhat more rare. The standard blue LED is at 470nm.
I cannot comment directly to the article as I haven't read it. From the summary I does seem like pop-psychology. However, I can see it taken another way.
As a nerdy electrical engineer, I spend a great deal of time performing thought experiments. The subject of a thought experiment could be work, school or hobby related or it could be based on an experience of mine. I absolutely abhor the behavior of terrorists and violent criminals. My personal philosophy is to cause no harm to others except in direct cases of self-defense. Thus I will never work on weapons systems (as an aside I have one exception to this rule; I'd work on the LightSaber if I could keep one). But a thought experiment hurts no one and can be a fun mental challenge. Thought experiments can be making new designs, refining old ones, finding clever hacks, or circumventing some standard.
When I see or experience security theater (pick your favorite example), I try to deconstruct the faulty reasoning behind that particular practice. I then play a game to figure out easy ways to circumvent the faux security or perhaps make it actually safer. Obviously it is just a mental game, but it both saddens and angers me when there is no difficulty in finding the flaws that keep people in constant fear and willing to play the security theater game. It further frustrates me that if I were to point out the flaws, it would cause me great harm as I would be immediately suspect, despite my intentions. I'm certainly not the smartest person, so if I can play these games, so can people who are willing to be violent. Thus security theater is also a failed attempt at security through obscurity.
It is likely, someone will troll this post and accuse me of being a 'turrist'.
Yes, there is some good science on Youtube. I'm a fan of music played over Tesla coils personally.
But the Brainiac clip of alkali metals in a bathtub was admitted to be fraudulent. The producers didn't think the real reaction had enough bang, so they actually used explosives. You can catch more information about this from Bad Science or from a guy that actually did the reactions. The second link has a decent explanation too.
Since I can't mod the parent any higher, I must reinforce "Saying that Nyquist's theorem is wrong is equivalent to stating that the value of pi is really 6."
I also like the way LWATCDR puts in in another post:
Damm right my ears are so good that I can toss out the cornerstone of DSP!
Vinyl doesn't have an infinite resolution anymore than a photograph does. You can not keep blowing up a photograph even though it is an analog recording medium. Vinyl does have a finite resolution just like digital methods.
Let's look at both of these. The Nyquist criteria is that to sample any band-limited signal, you must sample at or greater than twice the maximum bandwidth. So for audio at 20-20kHz (round up to 20kHz bandwidth), one must sample at least at 40kHz. Sampling means to take a continuous time waveform and take a measure of it's amplitude periodically. It the classical sense, Nyquist assumes infinite precision; the amplitude is measured and reproduced exactly with no error. The basis of the Nyquist criteria is purely mathematical.
Quantization is then taking a time-sampled waveform and assigning a coded value to each amplitude from a fixed set. So 8-bit audio has 256 possible values the amplitude can take and 16-bit audio has 65536 values. The difference between the original sample amplitude and the quantized sample is the quantization error and this causes errors in the reproduced waveform.
But does this quantization error actually hurt us? First in in modern digital audio (and DSP in general), we use oversampling and dither to reduce the errors in sampling and quantization. The errors in reproduction can be modeled as an additive noise (error component) at a receiver. Now comes into play Shannon-Hartley theorem. It basically states that given a certain signal power and a certain noise power, one can never communicate more information than the channel capacity (a rate of information transfer). The numbers in Shannon are not wishy-washy but hard limits. In this case we can model our ear as the receiver of information, and the noise is additive including (noise in the recording, CD or record errors, background noise in the listening room, the listeners heartbeat, etc.).
Now we can compare the quantization errors in the CD to the scratch noise and limited analog resolution of the record with a more apples-to-apples comparison. The "pure analoginess" of the vinyl record cannot overcome it's own inherent noise content (even the most pristine) or the fact that each playing degrades it. And the quantization error in the CD is rendered sub-audible (far below the noise floor). One cannot get around Nyquist or Shannon-Hartley without upsetting the past 80 years of development of communication and information theory. One would have to have extraordinary and incredible proof of this basic but important mathematical theories being wrong, which would overturn pretty much half of the entire electrical engineering world. If it is digital and deals with the real world, Nyquist applies. And even if not, Shannon applies; Shannon always applies.
That said, I love tube amplifiers. I think they are beautiful and the vintage electronics of yesteryear are amazing. It's the same way that I love the UNIVAC and the Difference Engine. But please, let's not continue to repeat pseudoscience. It's certainly gotten tiring debating people who thing the moon landing was a hoax, let's not let vinyl audio get pulled into such a state.
Did this line "The ADS shoots a beam of millimeters waves, which are longer in wavelength than x-rays but shorter than microwaves" hurt anyone else's brain? A better line would be "longer wavelength than infrared and light, but shorter than microwaves". A microwave oven at 2.45GHz has a 12.2cm wavelength in free space. One could consider the long IR band to start at around 30um, or about 10 THz. The spectrum continues to shorter and shorter wavelengths with visible light around 500THz (600nm yellow-orange), then ultraviolet up to about 30PHz (30,000THz at 10nm) before the x-ray band.
Was the statement true? Yes. But it doesn't really provide the reader with any useful information. Instead it leaves open a spectral window of about 7 orders of magnitude. Similar misunderstandings of this type are the same reasons why many people think that microwave radiation, such as that from cell phones, are the same as ionizing radiation such as hard x-rays and gamma radiation. Yes, it is all electromagnetic radiation, but someone is seriously missing the point.
Actually, I just got the strangest mental image. Let's work on that analogy a little. (Slightly OT)
If McDonalds fell under the DMCA, you can choose to buy a Big Mac or not (see exceptions below). Regardless, you still have the option of finding food elsewhere. However, if you purchase the Big Mac, you will be bound by a very specific set of rules found on the inside of the wrapper: You are the only person authorized to consume the Big Mac, you may not sell it or offer it to others. You may not examine, disassemble or modify the Big Mac (e.g. you cannot take the pickles off, or add more mustard, cut the burger in half). You may not tell others how to perform these actions, or possess or traffic in tools to assist with these actions (e.g. a knife). You must consume the Big Mac from the original wrapper; it may not be placed on a plate, in a lunchbox, or in a fridge. The Big Mac must be purchased and consumed within the US, and the right to consume may be revoked at any time without warning. Violation of any of these conditions will make you subject to civil fines (upwards of $150,000US per instance) and possibly criminal penalties.
Please take a look into Nyquist, oversampling and dither for A/D and D/A conversion. You'll find that the frequencies above 20kHz don't make a difference to our ear, but the process of digitization and playback have a number of real world limitations that make practical conversion difficult to achieve both frequency range and dynamic range. Through oversampling and dither (and therefore noise-shaping), it is possible to "convert" one to the other. These techinques are used to overcome the limitations of real world analog anti-aliasing and anti-imaging filters.
Now where high frequencies (>20kHz) can make a difference is if they non-linearly interact with the audible portion of the frequency spectrum. This usually takes place in electronics as it is difficult to find standard speakers that have a response much above 20kHz.
Of course there is the issue of marketing. It is always good to have a new format (at least for the manufactures). For the record: CD's are recorded at 16bit/44.1kHz, DVDs are usually 16bit/48kHz, DVD-Audio can be upwards of 24bit/196kHz, and SACD is 1-bit/2.8MHz but for most people and most systems, the CD standard will be good enough.
It is true that many FPGA's are SRAM based and therefore require configuration upon startup. However, a number of FPGA's by various vendors are anti-fuse based and/or Flash based.
An anti-fuse FPGA is programmed once and is forever locked to that configuration. This works really well for high-volume or high-reliability applications at the expense of future configuration. Flash devices are like a mix between SRAM based and anti-fuse based FPGAs. But as other posters have mentioned, there are some very cheap SRAM based FPGAs and start-up configuration time is usually under a second for the small ones.
A few questions for you, ApharmdB. I'm just curious.
Your radiometer was ground based correct? Were you looking directly at down-welling radiation where a drop in your signal output corresponded with an increase in water vapor density?
In order to use one antenna, it sounds like you had two tuned RF Front ends, one for each frequency. Did you use a standard heterodyne receiver architecture? What was your base-band bandwidth prior to your power detector or did you digitize? Polarization?
Sorry for all the questions. I've built a few radiometer systems before and I've always been curious about the different architectures and relative performance of them.
Related to the article, it is vital that we maintain an interference free spectrum around important atmospheric and astronomical bands. This could very easily become of greater importance than even BPL interference.
Relativity will affect the clock, and will manifest as a phase delay (all frequency shifts can be modeled as a moving phase delay). However, the basic Doppler shift from all the various celestial motions is dominant. We have a very cool system to detect and measure minute phase shifts and adjust the frequency of our earth-side oscillators to correct for any phase shifts.
And yes, sometimes the jargon in the lab sounds like something out of Star Trek.
It is an amazing day to have a project you are working on get posted to the front page of Slashdot. I am actually working on the distributed ground receivers for the MLCD laser signal.
Believe me when I tell you this is an ambitious project, but after months of continuous progress, I am completely confident that we'll achieve full rate comm, in the daytime, with the sun out, with Mars on the other side of the solar system.
To give you an idea of how hard this is, think about this. Each telescope receiver must have a perfectly accurate clock that can track the transmitter within much less than one clock cycle at near GHz rates. That means the clocks, completely unconnected must match (in our case) to better than 0.0000000001% (yes that is the right number of zeros) across the distance. We need an optical system that can filter out all light other than the laser signal and a detector that actually counts individual photons and time tags them to that very precise clock. The whole system must take into account the Doppler shift of the clock and the laser wavelength and then we must aggregate all this photon data.
A year ago, I would have been very skeptical of such a claim. But seeing as how I am about to give a presentation on our success with just such a system, sitting on a lab bench next door to my office, I am a believer.
One PC, one BenQ PB6200 DLP projector, and a smattering of amplifiers and and speakers. Why convert to NTSC or anything else when VGA does just fine. For the richer of us, one could even use a DVI projector.
No kidding on that soldering iron. I'm surprised he didn't just destroy the whole board immediately. He should have had a proper chisel tip in the thing at least.
Now if he wanted to do an actual good job, he should have had a nice Metcal solder station like this MX500. I've used these things for years and it is impossible for me to ever touch a normal soldering iron again. Just make sure to keep the tips nice and clean.
1) No, the reason why people don't have enough food is because the distrabution system wastes is and the large international agribiz companies don't allow it (there isn't enough profit in feeding the world)
2) Since Monsanto and the others have already legalized massive monoculture genetically modified food-stuffs and are over producing in such mass quantities as to require governmental price regulation (see as proof to reply 1 above), it make sense to just let them use this over abundance to make fuel too. I mean, we're already screwed anyway right.
I would like to point out that we have had some amazing nuclear technology ready for primetime since the mid 80's known as Pebble-bed. I know many of the/.'rs know about this, but to some it is quite new.
The pebble bed reactor design is intrinsically safe both while operating and during dismantling. The fuel (which can be uranium or mixed with plutonium) is encased in small high strength ceramic beads. The encapsulation serves to prevent the release of radioactive material even if the reactor vessel is breached as well as separate the fuel and prevent it from melting into a large mass.
The reactor is then cooled with high temperature helium gas, which also acts as a moderator. Here is the second line of safety; should the reactor get too hot or the helium is released, no moderation occurs. This means that the fast neutrons stay fast and are unable to cause a chain reaction. Hence, a catastrophic failure of both the containment vessel and cooling system would cause the reactor to physically shut itself down.
But the best part about the high-temperature gas-cooled pebble-bed reactors (long name) is that they burn up over 90% of the primary fuel and the waste products are still encapsulated by the pebbles. This is radically different from the water-cooled reactors which usually are only capable of 10% fuel efficiency and generate (instead of eliminate) plutonium.
Because of the efficiency, these reactors can be fueled by the waste of our current light water reactors, which between 1968 and 1998 generated 38400 metric tons of waste containing mostly uranium and plutonium (which if not eliminated could be used by to build bombs).
Although it is a pipe dream to think that the oil industry and the US government might actually support these newer nuclear technologies, let us take one step farther in waste disposal. Today, we are all set to bury those 40ktons of waste in Yucca Mountain for 10,000 years... but this is useless. Who knows if there will even be a United States in 10,000 years? By putting the spent pebbles from the reactors into a particle accelerator, we can use neutron transmutation (fun word huh?) to cut the dangerous half-life of waste to less than 100 years and about break even on power consumption. 100 years is far more manageable than 10,000.
Of course, these ideas aren't my own, just compiled from many other well respected scientists and others. If any one is interested in some this material, including a little more history and comparison of other fossil and renewable energy sources, please take a look at this proposal on energy policy.
Of course the hydrogen-centric system won't happen for quite some time for numerous reasons. But there is something that we could do now that would make the road to hydrogen later much, much easier.
What is needed is a stable, clean national electricity supply that is independent of fossil fuels. I am talking about nuclear power. New reactors, such as high temperature gas cooled pebble-bed reactors, can compete with fossil fuels while creating far less waste and no risk of meltdown. They can even be used to burn off the 38 thousand tones of nuclear waste we have (including plutonium that could be used to make bombs).
Of course, this needs to be coupled with other technologies as well to provide a complete end-to-end energy production solution. We need to use fuel reprocessing in order to extend our fuel supply and eliminate wastes. We can use neutron transmutation to decrease the life of radioactive wastes from tens of millennia to tens of years.
There is no way that we can implement even a limited hydrogen energy storage and transport system until we have a stable and abundant source of electricity. Currently, Bush wants to build 2000 more coal fired power plants over the next 20 years (check http://www.energy.gov/). Even if hydrogen goes through 100%, we'll just be burning that much more coal.
P.S. - The Wired article also makes reference to hydrogen as an abundant supply of energy. If we don't eliminate this notion, we will be in sore trouble. Hydrogen can only be a transport of energy.
I was given a very high quality stereo receiver (Denon AVR-3000) a number of years ago that had been damaged by lightning. The receiver was off at the time, and after some checking I determined only the microcontroller sections were fried.
The problem was that replacing the uC was difficult and ultimately a failure. So instead, I decided to use it as just a main amplifier. Although it no longer has any "features" it's been a great amplifier for the past five years. Take a look at the amplifier (JPEG - 60.5KB). All the empty space is from the six removed controller and switching boards. All the control functions are bypassed and hardwired in now.
Slashdot Mirror
That is of course the whole issue with the hydrogen cars. Manufactures can build small runs of hydrogen (be it ICE, ECE or fuel cell) cars as a technology showcase and to buy political/marketing points without having to worry the cars will actually be able to be fueled. Nocera at MIT and other have done great work to make certain non-fossil hydrogen production more viable, but this has not solved the practical aspect of hydrogen handling, storage and transportation. The construction of high temperature nuclear reactors will also enable thermal cracking of water.
Hydrocarbons are easy to store and transport and have a much higher energy density. Continuing development of biomass (especially algae based) and synthetic liquid fuels offers the ability to reuse most of the current national fueling infrastructure and still close the carbon cycle. There are other benefits as well. Algae reactors connected to smoke stacks absorb not only the CO2 but also nitrogen oxides. The pressed algae can be used as a non-fossil fuel based fertilizer.
Obviously hydrogen energy transport and fuel-cell vehicles hold some promise. But I am very concerned with the hype and almost religious defense of all things hydrogen "the ocean is full of hydrogen" especially when there are many other technologies that are closer or even in deployment that we can use right now.
Actually, If I remember correctly, the A4 line of VW cars uses 430nm deep blue LEDs for back lighting in the instrument cluster. I don't know if it has helped keep me awake for long drives (740 miles, continuous no stops, 10 hours, one tank of diesel), but it is pretty. I had to look up the wavelength because it is difficult to match and the deep blue LEDs are somewhat more rare. The standard blue LED is at 470nm.
I cannot comment directly to the article as I haven't read it. From the summary I does seem like pop-psychology. However, I can see it taken another way.
As a nerdy electrical engineer, I spend a great deal of time performing thought experiments. The subject of a thought experiment could be work, school or hobby related or it could be based on an experience of mine. I absolutely abhor the behavior of terrorists and violent criminals. My personal philosophy is to cause no harm to others except in direct cases of self-defense. Thus I will never work on weapons systems (as an aside I have one exception to this rule; I'd work on the LightSaber if I could keep one). But a thought experiment hurts no one and can be a fun mental challenge. Thought experiments can be making new designs, refining old ones, finding clever hacks, or circumventing some standard.
When I see or experience security theater (pick your favorite example), I try to deconstruct the faulty reasoning behind that particular practice. I then play a game to figure out easy ways to circumvent the faux security or perhaps make it actually safer. Obviously it is just a mental game, but it both saddens and angers me when there is no difficulty in finding the flaws that keep people in constant fear and willing to play the security theater game. It further frustrates me that if I were to point out the flaws, it would cause me great harm as I would be immediately suspect, despite my intentions. I'm certainly not the smartest person, so if I can play these games, so can people who are willing to be violent. Thus security theater is also a failed attempt at security through obscurity.
It is likely, someone will troll this post and accuse me of being a 'turrist'.
Yes, there is some good science on Youtube. I'm a fan of music played over Tesla coils personally.
But the Brainiac clip of alkali metals in a bathtub was admitted to be fraudulent. The producers didn't think the real reaction had enough bang, so they actually used explosives. You can catch more information about this from Bad Science or from a guy that actually did the reactions. The second link has a decent explanation too.
Since I can't mod the parent any higher, I must reinforce "Saying that Nyquist's theorem is wrong is equivalent to stating that the value of pi is really 6."
I also like the way LWATCDR puts in in another post:
Damm right my ears are so good that I can toss out the cornerstone of DSP! Vinyl doesn't have an infinite resolution anymore than a photograph does. You can not keep blowing up a photograph even though it is an analog recording medium. Vinyl does have a finite resolution just like digital methods.Let's look at both of these. The Nyquist criteria is that to sample any band-limited signal, you must sample at or greater than twice the maximum bandwidth. So for audio at 20-20kHz (round up to 20kHz bandwidth), one must sample at least at 40kHz. Sampling means to take a continuous time waveform and take a measure of it's amplitude periodically. It the classical sense, Nyquist assumes infinite precision; the amplitude is measured and reproduced exactly with no error. The basis of the Nyquist criteria is purely mathematical.
Quantization is then taking a time-sampled waveform and assigning a coded value to each amplitude from a fixed set. So 8-bit audio has 256 possible values the amplitude can take and 16-bit audio has 65536 values. The difference between the original sample amplitude and the quantized sample is the quantization error and this causes errors in the reproduced waveform.
But does this quantization error actually hurt us? First in in modern digital audio (and DSP in general), we use oversampling and dither to reduce the errors in sampling and quantization. The errors in reproduction can be modeled as an additive noise (error component) at a receiver. Now comes into play Shannon-Hartley theorem. It basically states that given a certain signal power and a certain noise power, one can never communicate more information than the channel capacity (a rate of information transfer). The numbers in Shannon are not wishy-washy but hard limits. In this case we can model our ear as the receiver of information, and the noise is additive including (noise in the recording, CD or record errors, background noise in the listening room, the listeners heartbeat, etc.).
Now we can compare the quantization errors in the CD to the scratch noise and limited analog resolution of the record with a more apples-to-apples comparison. The "pure analoginess" of the vinyl record cannot overcome it's own inherent noise content (even the most pristine) or the fact that each playing degrades it. And the quantization error in the CD is rendered sub-audible (far below the noise floor). One cannot get around Nyquist or Shannon-Hartley without upsetting the past 80 years of development of communication and information theory. One would have to have extraordinary and incredible proof of this basic but important mathematical theories being wrong, which would overturn pretty much half of the entire electrical engineering world. If it is digital and deals with the real world, Nyquist applies. And even if not, Shannon applies; Shannon always applies.
That said, I love tube amplifiers. I think they are beautiful and the vintage electronics of yesteryear are amazing. It's the same way that I love the UNIVAC and the Difference Engine. But please, let's not continue to repeat pseudoscience. It's certainly gotten tiring debating people who thing the moon landing was a hoax, let's not let vinyl audio get pulled into such a state.
Did this line "The ADS shoots a beam of millimeters waves, which are longer in wavelength than x-rays but shorter than microwaves" hurt anyone else's brain? A better line would be "longer wavelength than infrared and light, but shorter than microwaves". A microwave oven at 2.45GHz has a 12.2cm wavelength in free space. One could consider the long IR band to start at around 30um, or about 10 THz. The spectrum continues to shorter and shorter wavelengths with visible light around 500THz (600nm yellow-orange), then ultraviolet up to about 30PHz (30,000THz at 10nm) before the x-ray band.
Was the statement true? Yes. But it doesn't really provide the reader with any useful information. Instead it leaves open a spectral window of about 7 orders of magnitude. Similar misunderstandings of this type are the same reasons why many people think that microwave radiation, such as that from cell phones, are the same as ionizing radiation such as hard x-rays and gamma radiation. Yes, it is all electromagnetic radiation, but someone is seriously missing the point.
/rant
... in science.
ClamIAm: Oops, I hadn't seen that. Mods, please disable voting.
Actually, I just got the strangest mental image. Let's work on that analogy a little. (Slightly OT)
If McDonalds fell under the DMCA, you can choose to buy a Big Mac or not (see exceptions below). Regardless, you still have the option of finding food elsewhere. However, if you purchase the Big Mac, you will be bound by a very specific set of rules found on the inside of the wrapper: You are the only person authorized to consume the Big Mac, you may not sell it or offer it to others. You may not examine, disassemble or modify the Big Mac (e.g. you cannot take the pickles off, or add more mustard, cut the burger in half). You may not tell others how to perform these actions, or possess or traffic in tools to assist with these actions (e.g. a knife). You must consume the Big Mac from the original wrapper; it may not be placed on a plate, in a lunchbox, or in a fridge. The Big Mac must be purchased and consumed within the US, and the right to consume may be revoked at any time without warning. Violation of any of these conditions will make you subject to civil fines (upwards of $150,000US per instance) and possibly criminal penalties.
Bechthros,
Please take a look into Nyquist, oversampling and dither for A/D and D/A conversion. You'll find that the frequencies above 20kHz don't make a difference to our ear, but the process of digitization and playback have a number of real world limitations that make practical conversion difficult to achieve both frequency range and dynamic range. Through oversampling and dither (and therefore noise-shaping), it is possible to "convert" one to the other. These techinques are used to overcome the limitations of real world analog anti-aliasing and anti-imaging filters.
Now where high frequencies (>20kHz) can make a difference is if they non-linearly interact with the audible portion of the frequency spectrum. This usually takes place in electronics as it is difficult to find standard speakers that have a response much above 20kHz.
Of course there is the issue of marketing. It is always good to have a new format (at least for the manufactures). For the record: CD's are recorded at 16bit/44.1kHz, DVDs are usually 16bit/48kHz, DVD-Audio can be upwards of 24bit/196kHz, and SACD is 1-bit/2.8MHz but for most people and most systems, the CD standard will be good enough.
It is true that many FPGA's are SRAM based and therefore require configuration upon startup. However, a number of FPGA's by various vendors are anti-fuse based and/or Flash based.
An anti-fuse FPGA is programmed once and is forever locked to that configuration. This works really well for high-volume or high-reliability applications at the expense of future configuration. Flash devices are like a mix between SRAM based and anti-fuse based FPGAs. But as other posters have mentioned, there are some very cheap SRAM based FPGAs and start-up configuration time is usually under a second for the small ones.
Sorry, haven't RTFA yet.
A few questions for you, ApharmdB. I'm just curious.
Your radiometer was ground based correct? Were you looking directly at down-welling radiation where a drop in your signal output corresponded with an increase in water vapor density?
In order to use one antenna, it sounds like you had two tuned RF Front ends, one for each frequency. Did you use a standard heterodyne receiver architecture? What was your base-band bandwidth prior to your power detector or did you digitize? Polarization?
Sorry for all the questions. I've built a few radiometer systems before and I've always been curious about the different architectures and relative performance of them.
Related to the article, it is vital that we maintain an interference free spectrum around important atmospheric and astronomical bands. This could very easily become of greater importance than even BPL interference.
Sorry for the delay.
Relativity will affect the clock, and will manifest as a phase delay (all frequency shifts can be modeled as a moving phase delay). However, the basic Doppler shift from all the various celestial motions is dominant. We have a very cool system to detect and measure minute phase shifts and adjust the frequency of our earth-side oscillators to correct for any phase shifts.
And yes, sometimes the jargon in the lab sounds like something out of Star Trek.
It is an amazing day to have a project you are working on get posted to the front page of Slashdot. I am actually working on the distributed ground receivers for the MLCD laser signal.
Believe me when I tell you this is an ambitious project, but after months of continuous progress, I am completely confident that we'll achieve full rate comm, in the daytime, with the sun out, with Mars on the other side of the solar system.
To give you an idea of how hard this is, think about this. Each telescope receiver must have a perfectly accurate clock that can track the transmitter within much less than one clock cycle at near GHz rates. That means the clocks, completely unconnected must match (in our case) to better than 0.0000000001% (yes that is the right number of zeros) across the distance. We need an optical system that can filter out all light other than the laser signal and a detector that actually counts individual photons and time tags them to that very precise clock. The whole system must take into account the Doppler shift of the clock and the laser wavelength and then we must aggregate all this photon data.
A year ago, I would have been very skeptical of such a claim. But seeing as how I am about to give a presentation on our success with just such a system, sitting on a lab bench next door to my office, I am a believer.
I'd like to thank /. for making my day.
One PC, one BenQ PB6200 DLP projector, and a smattering of amplifiers and and speakers. Why convert to NTSC or anything else when VGA does just fine. For the richer of us, one could even use a DVI projector.
No kidding on that soldering iron. I'm surprised he didn't just destroy the whole board immediately. He should have had a proper chisel tip in the thing at least. Now if he wanted to do an actual good job, he should have had a nice Metcal solder station like this MX500. I've used these things for years and it is impossible for me to ever touch a normal soldering iron again. Just make sure to keep the tips nice and clean.
1) No, the reason why people don't have enough food is because the distrabution system wastes is and the large international agribiz companies don't allow it (there isn't enough profit in feeding the world)
2) Since Monsanto and the others have already legalized massive monoculture genetically modified food-stuffs and are over producing in such mass quantities as to require governmental price regulation (see as proof to reply 1 above), it make sense to just let them use this over abundance to make fuel too. I mean, we're already screwed anyway right.
But anyway. Drive a TDI, they're fun.
I would like to point out that we have had some amazing nuclear technology ready for primetime since the mid 80's known as Pebble-bed. I know many of the /.'rs know about this, but to some it is quite new.
The pebble bed reactor design is intrinsically safe both while operating and during dismantling. The fuel (which can be uranium or mixed with plutonium) is encased in small high strength ceramic beads. The encapsulation serves to prevent the release of radioactive material even if the reactor vessel is breached as well as separate the fuel and prevent it from melting into a large mass.
The reactor is then cooled with high temperature helium gas, which also acts as a moderator. Here is the second line of safety; should the reactor get too hot or the helium is released, no moderation occurs. This means that the fast neutrons stay fast and are unable to cause a chain reaction. Hence, a catastrophic failure of both the containment vessel and cooling system would cause the reactor to physically shut itself down.
But the best part about the high-temperature gas-cooled pebble-bed reactors (long name) is that they burn up over 90% of the primary fuel and the waste products are still encapsulated by the pebbles. This is radically different from the water-cooled reactors which usually are only capable of 10% fuel efficiency and generate (instead of eliminate) plutonium.
Because of the efficiency, these reactors can be fueled by the waste of our current light water reactors, which between 1968 and 1998 generated 38400 metric tons of waste containing mostly uranium and plutonium (which if not eliminated could be used by to build bombs).
Although it is a pipe dream to think that the oil industry and the US government might actually support these newer nuclear technologies, let us take one step farther in waste disposal. Today, we are all set to bury those 40ktons of waste in Yucca Mountain for 10,000 years... but this is useless. Who knows if there will even be a United States in 10,000 years? By putting the spent pebbles from the reactors into a particle accelerator, we can use neutron transmutation (fun word huh?) to cut the dangerous half-life of waste to less than 100 years and about break even on power consumption. 100 years is far more manageable than 10,000.
Of course, these ideas aren't my own, just compiled from many other well respected scientists and others. If any one is interested in some this material, including a little more history and comparison of other fossil and renewable energy sources, please take a look at this proposal on energy policy.
Of course the hydrogen-centric system won't happen for quite some time for numerous reasons. But there is something that we could do now that would make the road to hydrogen later much, much easier.
What is needed is a stable, clean national electricity supply that is independent of fossil fuels. I am talking about nuclear power. New reactors, such as high temperature gas cooled pebble-bed reactors, can compete with fossil fuels while creating far less waste and no risk of meltdown. They can even be used to burn off the 38 thousand tones of nuclear waste we have (including plutonium that could be used to make bombs).
Of course, this needs to be coupled with other technologies as well to provide a complete end-to-end energy production solution. We need to use fuel reprocessing in order to extend our fuel supply and eliminate wastes. We can use neutron transmutation to decrease the life of radioactive wastes from tens of millennia to tens of years.
There is no way that we can implement even a limited hydrogen energy storage and transport system until we have a stable and abundant source of electricity. Currently, Bush wants to build 2000 more coal fired power plants over the next 20 years (check http://www.energy.gov/). Even if hydrogen goes through 100%, we'll just be burning that much more coal.
There is a proposal that outlines one possible implementation of a national electrical energy policy using nuclear energy online that is worth a read. It goes over some pros and cons. United States of America: Energy Policy for the 21st Century and Beyond (PDF - 115KB)
P.S. - The Wired article also makes reference to hydrogen as an abundant supply of energy. If we don't eliminate this notion, we will be in sore trouble. Hydrogen can only be a transport of energy.
I was given a very high quality stereo receiver (Denon AVR-3000) a number of years ago that had been damaged by lightning. The receiver was off at the time, and after some checking I determined only the microcontroller sections were fried.
The problem was that replacing the uC was difficult and ultimately a failure. So instead, I decided to use it as just a main amplifier. Although it no longer has any "features" it's been a great amplifier for the past five years. Take a look at the amplifier (JPEG - 60.5KB). All the empty space is from the six removed controller and switching boards. All the control functions are bypassed and hardwired in now.