What did they do, release an aerosol? I hate imprecise reporting.
Anyway, the primary source (the safety report from the NRC) is available from the union local web site. (I confirmed that the same document is available directly from the NRC, but couldn't find a URL that didn't include my personal information.)
Some of one's success in Jeopardy has to do with timing the button push, so that it's after the question has been asked, but before one's competitors. (If you press too soon, you get locked out for a period of time.) A machine, especially an electronic machine, has an obvious advantage here. How was this handled?
The myth that free-space propagation loss is frequency-dependent is probably the most pervasive misunderstanding in wireless. Read the "Physical Explanation" in your own link:
The FSPL [Free-Space Path Loss] expression above often leads to the erroneous belief that free space attenuates an electromagnetic wave according to its frequency. This is not the case, as there is no physical mechanism that could cause this. [Emphasis added.]
Think about it: If free-space path loss increased as the square of frequency, there would be so much loss at light frequencies that we'd never see the sun!
Free-space path loss is actually just the result of the transmitted energy density decreasing on a sphere centered on the source as the radius (and, therefore, the sphere's surface area) increases. A second effect, which causes all the confusion, is often added into the definition: The type of antenna used at the receiver.
To match the isotropic source at the center of the sphere, people (including the Wikipedia author) typically, and quite reasonably, make the assumption that the receiving antenna (on the surface of the sphere) is an isotropic antenna, too. The problem is, the effective area of an isotropic antenna is inversely proportional to the square of the operating wavelength. This gives the free-space path loss equation a frequency dependency that "free-space path loss" actually doesn't have.
This belief is compounded by the types of antennas typically used in simple wireless devices. Dipole antennas, like isotropic antennas, have an effective area that is inversely proportional to the square of the operating wavelength. Think about it: A dipole resonant at 60 MHz is 40 times longer than a dipole resonant at 2400 MHz, so its effective area is 1600 times greater. If one just swaps antennas it's going to look like the received 2400 MHz signal is 1/1600 that of the 60 MHz signal, due to "increased path loss" at the higher frequency, when really it's just that the 2400 MHz antenna is smaller.
Pleasantly, not all antennas have an effective area that is inversely proportional to the square of the operating wavelength. Parabolic dishes, for example, have an effective area that constant as the frequency is varied. If one assumes that the receiving antenna in the free-space path loss model were a parabolic dish, one would conclude that there is no frequency dependence of the loss, since there would be only the inverse 4*pi*d^2 term present. This could be "experimentally verified" by having a link with a dipole antenna on one end and a parabolic dish on the other, which (quite correctly) would show no frequency dependence in its path loss -- it would be the same at all frequencies.
Interestingly, if parabolic dishes (or other constant-area antennas) were used at both ends of the link, the "path loss" would appear to decrease with increasing frequency -- the opposite of what appears to happen if two dipoles are used.
One can vary the antennas used and get whatever frequency response one desires -- but the intrinsic path loss itself is always the same. (Frequencies for broadcast were selected for entirely different reasons.)
VHF TV frequencies can refract, diffuse and (to a small extent) skip off the ionosphere. I reckon that 2.4GHz would be easier to pick up on Alpha Centauri than in China.
I suspect the GP was engaging in a bit of hyperbole with the "China" reference, but reception of Chinese VHF TV signals in Australia is in fact possible on rare occasionsvia the ionosphere. The propagation modes usually involve simple refraction from the E layer or F layer, although occasionally more exotic types of propagation, such as trans-equatorial propagation ("TEP"), occur. However, these all fall into the category of anomalous propagation, occurring for a few hours per month or year and, while interesting phenomena in their own right, aren't suitable on which to base one's daily Internet service.
It is also true that ionospheric propagation of 2.4 GHz signals is unknown. However...
There are propagation modes that favor the higher frequencies over the lower ones. Tropospheric propagation, for example, is much more effective at 2.4 GHz than it is at VHF, and can occur at all parts of the sunspot cycle, since it depends on weather conditions instead of the ionosphere. For example, Table 2.1 in this article shows propagation from California to Hawaii on 2304, 3456, and even 5760 MHz via a well-known tropospheric duct. (See also this discussion on the relevance to trans-Australia propagation.) Paths in excess of 6000 km (Western Australia to Reunion Island, off the east coast of Africa) have been reported. But again, this is anomalous propagation, unsuitable for daily Internet service.
The GP has a point about transmitted power. VHF TV broadcast stations have effective radiated powers ("ERPs", defined as their transmitted powers multiplied by their antenna gains) measured in the hundreds of thousands to millions of watts, as well as high antenna sites (on towers), so it's a bit unfair to compare VHF TV reception ranges to those of 2.4 GHz Wi-Fi systems.
The main advantage of the proposed system is that the users, in remote sheep stations, won't have to replace their existing VHF TV antennas, which would otherwise be a significant financial investment (and that the system would be point-to-point, rather than point-to-multipoint, which enables frequency reuse without loss of bandwidth). Were this not the case, it would be clear to most RF system designers that a microwave system would be superior to the VHF system. Not only is more bandwidth typically available (remember, there are no competing services in the outback), but a 2.4-GHz antenna the same physical size (strictly speaking, having the same effective area) as the VHF TV antenna would have substantially more gain: The gain of a parabolic dish goes up as the square of the operating frequency. Operating an antenna at 2.4 GHz instead of, say, 60 MHz (in the VHF TV band) would result in a gain increase of 1600, or 32 dB. If it had 18 dB of gain at VHF (a pretty decent TV antenna), it would now be 50 dB at 2.4 GHz. (This is why point-to-point microwave systems were used before they were overtaken in the bandwidth race by optical fiber.) This additional 32 dB of gain would greatly increase the range of the 2.4 GHz system over the VHF system, and would be available all the time -- making for a suitable Internet connection. In fact,
To be sure; I wasn't taking a position in the discussion, only correcting a factual error.
I guess while I'm at it (in for a penny, in for a pound...), the Volt isn't "full electric until it drains the batteries completely." The state-of-charge software in the car limits the discharge to 25% of capacity (and the charge to 90% of capacity) to optimize the life of the battery. All battery-driven cars of which I am aware, including the Prius, control the battery state-of-charge in a similar way, for a similar reason.
But your overall point is valid -- the differing requirements on pure-EV and hybrid batteries make for very different battery designs. There are many, many differences between the Volt and Prius batteries -- starting with chemistry: The Volt's is Li-ion while the Prius' is NiMH.
The Prius battery state of charge is controlled by a dedicated MCU -- dedicated largely to maximize the life of the battery. (It's located in the battery compartment.) It keeps the battery between 45 and 75 percent charged under nearly all circumstances. It's about as far removed from the charging system of a hand power tool as it is possible to get.
Of course, a pure EV is likely to make larger demands on its battery than the Prius, but the point remains that intelligent control of the battery's state of charge greatly extends battery life.
The ICE of the Prius is required only when speeds exceed 42 mph. Below that, it will maintain a constant speed using only electric power until the battery discharges (at which time the ICE restarts, the battery recharges, and the cycle repeats -- especially if the driver uses an off throttle shift to put it back into electric mode). At 40 mph one can go a mile or so on level ground without using the ICE, solely on electric power.
... so if the eel is in sight of the tree, and is photophobic (or -philic), can one set up an oscillation in which eel movement causes light which causes more movement, making the tree lights flash at a substantially constant rate?
It's also not true that ships are "utterly uncontrolled, free to emit whatever they like." See, for example, these regulations. Note the MARPOL, the International Convention for the Prevention of Pollution From Ships, treaty conventions.
Hatch and Bennett are the two US Senators from Utah, while Bishop represents Utah's 1st District (most of northern Utah) and Matheson represents Utah's 2nd District (most of Southern and Southeastern Utah), the latter two in the US House of Representatives. (The western portion of Utah forms the 3rd House District, represented by Jason Chaffetz. No word on why he didn't sign on with everyone else.)
And since when is essay writing all that valuable in say the techie world?
Are you kidding? It's especially valuable in the techie world -- a world that incessantly suffers from misunderstanding by the general public. Ask yourself how popular Linux would be today, if Linus had published a well-written series of introductory articles about it in the popular press, 20 years ago. Ask any small company: The technical writer is key to the success of the organization, because he/she introduces the product to the customer -- either directly, in the company documentation, or indirectly, by ghostwriting articles in the trade and popular press.
If you don't believe me, try the following. Take a collection of your peers. Ask them each to write a four-page article for the trade press presenting and explaining Moore's Law. Now compare their papers with Gordon Moore's original. Which one is easier to understand, and more persuasive? Which one do you think would still be remembered 45 years later?
Yeah, I used it only after some consideration. How else to describe a culture largely composed of individuals that are monolingual, but do not speak the same language? -- especially in comparison to Japan, where everyone one meets can be assumed fluent in Japanese? I considered "heterolingual," but that seems even more inventive, and I'm not going near "homolingual" in this forum...
Seriously, the vending machines are one of my favourite things about Japan.
Indeed. When I returned the two biggest culture shocks were (a) returning to US vending machines, and (b) returning to the US passenger rail system.
Come to think of it, there were several other shocks, too -- returning to the US cell phone system; returning to impolite retail salespeople; returning to inexpensive fruits, meats, and vegetables; returning to a multi-ethnic and multi-monolingual culture, etc. It took a while to re-adapt.
Slashdot Mirror
What did they do, release an aerosol? I hate imprecise reporting.
Anyway, the primary source (the safety report from the NRC) is available from the union local web site. (I confirmed that the same document is available directly from the NRC, but couldn't find a URL that didn't include my personal information.)
... through an incredibly long chain of butterfly effects ...
It's not that long. Who wouldn't go faster if chased by amorous crocodiles?
Breaking how? Transmission failure? Frame fracture?
Did TFA mean, by chance, "the sound a vehicle braking"?
Some of one's success in Jeopardy has to do with timing the button push, so that it's after the question has been asked, but before one's competitors. (If you press too soon, you get locked out for a period of time.) A machine, especially an electronic machine, has an obvious advantage here. How was this handled?
Also,
Pleasantly, not all antennas have an effective area that is inversely proportional to the square of the operating wavelength.
should be
Pleasantly, not all antennas have an effective area that is proportional to the square of the operating wavelength.
This is why independent review of technical articles is so useful. You can lead a writer to "Preview", but you can't make him think.
The problem is, the effective area of an isotropic antenna is inversely proportional to the square of the operating wavelength.
should be,
The problem is, the effective area of an isotropic antenna is proportional to the square of the operating wavelength.
and
Dipole antennas, like isotropic antennas, have an effective area that is inversely proportional to the square of the operating wavelength.
should be
Dipole antennas, like isotropic antennas, have an effective area that is proportional to the square of the operating wavelength.
Sorry about that.
The myth that free-space propagation loss is frequency-dependent is probably the most pervasive misunderstanding in wireless. Read the "Physical Explanation" in your own link:
Think about it: If free-space path loss increased as the square of frequency, there would be so much loss at light frequencies that we'd never see the sun!
Free-space path loss is actually just the result of the transmitted energy density decreasing on a sphere centered on the source as the radius (and, therefore, the sphere's surface area) increases. A second effect, which causes all the confusion, is often added into the definition: The type of antenna used at the receiver.
To match the isotropic source at the center of the sphere, people (including the Wikipedia author) typically, and quite reasonably, make the assumption that the receiving antenna (on the surface of the sphere) is an isotropic antenna, too. The problem is, the effective area of an isotropic antenna is inversely proportional to the square of the operating wavelength. This gives the free-space path loss equation a frequency dependency that "free-space path loss" actually doesn't have.
This belief is compounded by the types of antennas typically used in simple wireless devices. Dipole antennas, like isotropic antennas, have an effective area that is inversely proportional to the square of the operating wavelength. Think about it: A dipole resonant at 60 MHz is 40 times longer than a dipole resonant at 2400 MHz, so its effective area is 1600 times greater. If one just swaps antennas it's going to look like the received 2400 MHz signal is 1/1600 that of the 60 MHz signal, due to "increased path loss" at the higher frequency, when really it's just that the 2400 MHz antenna is smaller.
Pleasantly, not all antennas have an effective area that is inversely proportional to the square of the operating wavelength. Parabolic dishes, for example, have an effective area that constant as the frequency is varied. If one assumes that the receiving antenna in the free-space path loss model were a parabolic dish, one would conclude that there is no frequency dependence of the loss, since there would be only the inverse 4*pi*d^2 term present. This could be "experimentally verified" by having a link with a dipole antenna on one end and a parabolic dish on the other, which (quite correctly) would show no frequency dependence in its path loss -- it would be the same at all frequencies.
Interestingly, if parabolic dishes (or other constant-area antennas) were used at both ends of the link, the "path loss" would appear to decrease with increasing frequency -- the opposite of what appears to happen if two dipoles are used.
One can vary the antennas used and get whatever frequency response one desires -- but the intrinsic path loss itself is always the same. (Frequencies for broadcast were selected for entirely different reasons.)
When one stopped getting paid for lunch hour.
I suspect the GP was engaging in a bit of hyperbole with the "China" reference, but reception of Chinese VHF TV signals in Australia is in fact possible on rare occasions via the ionosphere. The propagation modes usually involve simple refraction from the E layer or F layer, although occasionally more exotic types of propagation, such as trans-equatorial propagation ("TEP"), occur. However, these all fall into the category of anomalous propagation, occurring for a few hours per month or year and, while interesting phenomena in their own right, aren't suitable on which to base one's daily Internet service.
It is also true that ionospheric propagation of 2.4 GHz signals is unknown. However...
There are propagation modes that favor the higher frequencies over the lower ones. Tropospheric propagation, for example, is much more effective at 2.4 GHz than it is at VHF, and can occur at all parts of the sunspot cycle, since it depends on weather conditions instead of the ionosphere. For example, Table 2.1 in this article shows propagation from California to Hawaii on 2304, 3456, and even 5760 MHz via a well-known tropospheric duct. (See also this discussion on the relevance to trans-Australia propagation.) Paths in excess of 6000 km (Western Australia to Reunion Island, off the east coast of Africa) have been reported. But again, this is anomalous propagation, unsuitable for daily Internet service.
The GP has a point about transmitted power. VHF TV broadcast stations have effective radiated powers ("ERPs", defined as their transmitted powers multiplied by their antenna gains) measured in the hundreds of thousands to millions of watts, as well as high antenna sites (on towers), so it's a bit unfair to compare VHF TV reception ranges to those of 2.4 GHz Wi-Fi systems.
The main advantage of the proposed system is that the users, in remote sheep stations, won't have to replace their existing VHF TV antennas, which would otherwise be a significant financial investment (and that the system would be point-to-point, rather than point-to-multipoint, which enables frequency reuse without loss of bandwidth). Were this not the case, it would be clear to most RF system designers that a microwave system would be superior to the VHF system. Not only is more bandwidth typically available (remember, there are no competing services in the outback), but a 2.4-GHz antenna the same physical size (strictly speaking, having the same effective area) as the VHF TV antenna would have substantially more gain: The gain of a parabolic dish goes up as the square of the operating frequency. Operating an antenna at 2.4 GHz instead of, say, 60 MHz (in the VHF TV band) would result in a gain increase of 1600, or 32 dB. If it had 18 dB of gain at VHF (a pretty decent TV antenna), it would now be 50 dB at 2.4 GHz. (This is why point-to-point microwave systems were used before they were overtaken in the bandwidth race by optical fiber.) This additional 32 dB of gain would greatly increase the range of the 2.4 GHz system over the VHF system, and would be available all the time -- making for a suitable Internet connection. In fact,
To be sure; I wasn't taking a position in the discussion, only correcting a factual error.
I guess while I'm at it (in for a penny, in for a pound...), the Volt isn't "full electric until it drains the batteries completely." The state-of-charge software in the car limits the discharge to 25% of capacity (and the charge to 90% of capacity) to optimize the life of the battery. All battery-driven cars of which I am aware, including the Prius, control the battery state-of-charge in a similar way, for a similar reason.
But your overall point is valid -- the differing requirements on pure-EV and hybrid batteries make for very different battery designs. There are many, many differences between the Volt and Prius batteries -- starting with chemistry: The Volt's is Li-ion while the Prius' is NiMH.
The Prius battery state of charge is controlled by a dedicated MCU -- dedicated largely to maximize the life of the battery. (It's located in the battery compartment.) It keeps the battery between 45 and 75 percent charged under nearly all circumstances. It's about as far removed from the charging system of a hand power tool as it is possible to get.
Of course, a pure EV is likely to make larger demands on its battery than the Prius, but the point remains that intelligent control of the battery's state of charge greatly extends battery life.
The ICE of the Prius is required only when speeds exceed 42 mph. Below that, it will maintain a constant speed using only electric power until the battery discharges (at which time the ICE restarts, the battery recharges, and the cycle repeats -- especially if the driver uses an off throttle shift to put it back into electric mode). At 40 mph one can go a mile or so on level ground without using the ICE, solely on electric power.
Yes.
... so if the eel is in sight of the tree, and is photophobic (or -philic), can one set up an oscillation in which eel movement causes light which causes more movement, making the tree lights flash at a substantially constant rate?
Piezoelectric Eels for Energy Harvesting in the Ocean.
Here I sit, fresh out of mod points ... my compliments, sir!
At what point does this move out of the "relevation" category?
When it moves into the "revelation" category?
I flew the concorde to England a few times in the 90s. I really miss it.
This. I fear we'll not see its like again in my lifetime.
Surprisingly enough, "gas cylinders."
Yours in anglophilia,
dtmos
I'm still struggling to figure out what either of you is talking about. Rational what?
Or do you mean rationale?
It's also not true that ships are "utterly uncontrolled, free to emit whatever they like." See, for example, these regulations. Note the MARPOL, the International Convention for the Prevention of Pollution From Ships, treaty conventions.
Hatch and Bennett are the two US Senators from Utah, while Bishop represents Utah's 1st District (most of northern Utah) and Matheson represents Utah's 2nd District (most of Southern and Southeastern Utah), the latter two in the US House of Representatives. (The western portion of Utah forms the 3rd House District, represented by Jason Chaffetz. No word on why he didn't sign on with everyone else.)
Are you kidding? It's especially valuable in the techie world -- a world that incessantly suffers from misunderstanding by the general public. Ask yourself how popular Linux would be today, if Linus had published a well-written series of introductory articles about it in the popular press, 20 years ago. Ask any small company: The technical writer is key to the success of the organization, because he/she introduces the product to the customer -- either directly, in the company documentation, or indirectly, by ghostwriting articles in the trade and popular press.
If you don't believe me, try the following. Take a collection of your peers. Ask them each to write a four-page article for the trade press presenting and explaining Moore's Law. Now compare their papers with Gordon Moore's original. Which one is easier to understand, and more persuasive? Which one do you think would still be remembered 45 years later?
Words matter.
Yeah, I used it only after some consideration. How else to describe a culture largely composed of individuals that are monolingual, but do not speak the same language? -- especially in comparison to Japan, where everyone one meets can be assumed fluent in Japanese? I considered "heterolingual," but that seems even more inventive, and I'm not going near "homolingual" in this forum...
Indeed. When I returned the two biggest culture shocks were (a) returning to US vending machines, and (b) returning to the US passenger rail system.
Come to think of it, there were several other shocks, too -- returning to the US cell phone system; returning to impolite retail salespeople; returning to inexpensive fruits, meats, and vegetables; returning to a multi-ethnic and multi-monolingual culture, etc. It took a while to re-adapt.