One of the main customers for satellite launchs is the military. Something as simple as google search should be able to pick this up (e.g., search for "ariane military")...
Military percentages of various orbit profiles Low-earth-orbit ~15% (rest is mostly comm stuff) Medium-earth-orbit ~65% (bulk of military stuff) Geosync-orbit ~10% (rest is tv/telephone/dbs)
Things might be skew a bit when the ESA starts launching Galileo (the GPS competitor), but the direction depends on your view of dual-use technology. However, they don't call it the military-industrial complex for nuthin' (military contracting is just as popular in europe as it is in the US)...
Listening to antecdotal stuff like this is why people get hurt.
Although if you apply ordinary common sense about regular personal tax law, this would appear to be the case (you don't pay until you sell and your basis is the original price paid). However, this was considered a loophole where the rich could get deferred compensation without paying taxes (and thus getting the time-value of the money for free).
To address this loophole, the government created something called the Alternative Minimum Tax (AMT) which is a lower flat tax rate, but in addition to loosing a bunch of tax deductions you normally get, you also have to include the difference between the option price and the market price of exercised incentive stock options (ISOs) as ORDINARY INCOME. The rule is that you have to pay whichever tax (AMT or regular) is MORE!
The reason most people don't know about AMT is that they think it doesn't apply to them, but it certainly does. It used to only affect rich folks, but stock trickling down to the lower ranks wasn't forseen when the AMT code was adopted, so now it is affecting more and more people who don't even expect it (although turbo tax does this correctly most of the time)...
The non-qualified option is slightly different in that your estimated tax liability is always due immediatly (not just if AMT calculations turn out to be MORE) so the IRS code requires actual withholding (just like your W-2 exemptions), except it's at a fixed rate (to avoid people claiming too many exemptions).
Disclaimer, your tax situation may be different. Consult a tax expert to keep you out of bankruptcy due to AMT if you ever get into ISOs.
Think of it as the bubble patterns is one member of a very-very large set (the "bubble" set) and the laser is a projection or mapping function of this member of the bubble set on to a much smaller "diffraction pattern" set. Since the different laser angles can be used, that's like using different mapping functions.
A verification agency isn't gonna store which member of the bubble set each token is and do a diffraction simulaton with computers everytime the token is scanned, but more likely they will store the one or two projections on to the diffraction pattern set which are created by the one or two reader devices that are marketed. Also the whole diffraction pattern isn't gonna be stored, but just the part of the pattern sampled by the device.
This seems like a much easier problem to solve for the token forgers. All they have to do is make a token that when projected to the one or two sampled diffraction sets stored by the verification agency instead the the infinite possible diffraction patterns of arbitrary precision.
Then you have the uniqueness problem. Since the verification agencies are likely only storing sub-space projections which are finitely sampled, there's the possibility of collisions between two cards. At least with a non-one-way function, you can detect collisions beforehand, now you have to make the card with bubbles and project them to you subspaces and only then discover there's a collision and you have to throw the token away. This also defeats the feature alluded to that you can always use another projection. If you don't check for collisions ahead of time, they will inevitably occur (think of the birthday paradox).
There are fundamental mathematics working against any scheme that depends on low probability of collision. You don't have to duplicate a specific thing, but you hope for a collision (which is duplicating any one of a large set). This of course is much easier to do and is the known as the birthday paradox in probability theory. This has been used as theoretical fodder to break many encryption systems (meets in the middle attacks).
Here's another way to think of it. You have a zillion digit credit card number (token) and you apply a few different hash functions (laser angles) to the number to get a "signature" (diffraction pattern). The only advantage of this technology is that it's hard to duplicate this zillion digit number where most things electronic are easily duplicated. But some of the other "features" don't seem easy to take advantage of.
It's like the phreakers of yesteryear where they just guessed long-distance calling card codes if the set is large enough, collisions are inevitable. That's when companies invented PIN numbers. What it probably means that these tokens will probably end up being only as secure as your 4 digit ATM PIN... Something to think about...
Sometimes when you think outside the box, you realize that the box was green and the grass is really dead out there too...
ahem, professional equipment largely betaCAM
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Sony Kills Betamax
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· Score: 2
Although pro-equipment could play betamax and could use betamax tape (albeit the higher quality stuff and filling the tape after 20min), most people confuse betaMAX (the consumer format) with betaCAM (the pro format).
Consumer BetaMAX players could not play betaCAM tapes so I doubt many pros bought them...
Although I don't doubt some garage shops uses betaMAX along the way, I think this categorization only serves to confuse the issue.
Before widespread DNS and the MX tag, email addresses looked like...
myneighbor!herfriend!uunet!yahoo!slew
No kidding, email addresses used to be the other way with rmail/uucp! (and for a small time when internet email was just starting to be popular it was both ways with % signs, not to mention other nasty hpmail/vaxmail/x.400/x.500 hybrids)
You had to source route your email explicitly although uunet was pretty good about knowing about big sites and was pretty reasonable about relaying a small amount of email for a small fee. Setting up email w/o DNS (and root servers) might be like gnutella without much bandwidth. Think of DNS root server as the virtual site that can automatically tell you where to find out how to route everything.
The only reason email is as popular as it is today is that interoperability is pretty common (except for the spam-sources). Imagine if say 1/2 the email addresses uses a proprietary postoffice maintained "dns-like" service... It would sort of be like if the post office didn't license zip-codes to be used by their competitors (sort of how they don't let fedex/ups send to p.o.boxes)... You could set up a separate internet email, but there would be no interop...
This is an interesting discovery since it's not obvious that the minimum energy trajectories between lagrange points follows a strange attractor (and aren't simply random or divergent). This means that if the trajectories are truly chaotic (i.e., follow tube-like strange attractors), once you get near the attractors (matching position/velocity vectors), maybe you can't predict exactly how you are going to get there, but you can be pretty sure that you will stay near the attractor so you needn't waste all your manuvering fuel trying to make minor course adjustments to try and stay on a specific trajectory. If it all pans out, this would probably turn out to be a pretty important discovery for inter-planetary minimum energy trajectories...
Nowhere did Mr. Lo describe in his paper that the gravity cancels out on these paths (only that they were minimum energy and connected the Lagrange points).
The whole idea of a minimum energy paths through the solar system is that it's a dynamical systems of greater than 2 dimensions. The weird thing about dynamical systems of 3 dimensions is that trajectories in some of these systems exhibit a type of predictability called a "strange" attractor.
Strange attractors for trajectories are different than the attractors you normally see in 2 dimensions (like local minima or orbits that retrace themselves) in that small pertubations can cause greatly divergent behavior. Even though the behavior appears chaotic, in some systems, the behavior can still be described as nearby a "strange" attractor. This is effect is often called chaos, and the study of strange attractors is called chaos theory.
Apparently Mr. Lo has worked out a theory where the minimum energy trajectories under this complicated dynamical system (planetary gravitational attraction) exhibits attractors that looks like "tubes" that exhibit the chaos-like behavior of strange attractors.
At first glance, these tubes appear to have the dynamical structure similar to n-body orbits (this factoid about orbits was first discovered by Michel Henon in the 60's). "orbits" in n-body systems don't actually retrace themselves, but sort of looks like a coiled up extension cord. The envelope or attractor of the orbits look sort of like a mis-shaped torus (squished donut), where the orbits can pretty much be anywhere on the surface of the donut (the attractor), but the path it takes is somewhat unpredictable (chaos) and highly dependent on initial conditions. There are more complicated attractors (some involving little islands of stability inside the donut) depending on the energy level, but this is the basic idea. This discovery seems to extend this known factoid about orbits to the structure of minimum energy trajectories in n-body gravitational fields.
All this will be moot, however, when in the 2004 election, Al Gore wins the presidency by taking credit for inventing the Interplanetary Super-Highway while giving a campaign speech for an increased budget for Nasa leading all the l337 geek-crackers to rig the newly approved, non-tamperproof election computers... I boldly predict this will be henceforth called the "butterfly-ballot" effect... But I digress...;^)
Asynchronous logic always appears to be better than synchronous at first glance, but when you do the math, sometimes it isn't so clear...
Have you wondered why when traffic gets heavy on a freeway, it slows down? This is sort of like an asynchronous processor where every instruction is trying to get processed as quickly as they can (every driver is independent) but they need micro-synchronization to prevent collisions (brake lights, gas pedals). When the freeway is mostly empty, micro-synchronization works fine. However, as you approach the capacity limit, sometimes a global clock helps, sometimes it doesn't...
If you have a pipeline, you get back pressure waves as you approach the capacity which can make things slower than a synchronous system. If the processing topology is more complicated, it becomes even more difficult to analyze...
This effect is well known and affects things like processors and networks. Lookup articles on slotted ALOHA (a packet radio protocol) for some of the math if you are interested in some of the math behind this...
Note: this goes quite a long ways to showing that conventional wisdom about pi being random digits isn't actually true... Pseudo random is more like it...
However, it isn't really applicable to this multidimensional compression nonsense since the counting argument still applies.
Suspiciously, this looks to be similar to what the fractal folks were pushing in the '80s if you replace gems with iterators... Every once in a while you have to change the color of your snake oil label to confuse the masses...
One of the first common "thinking-out-of-the-box" techniques used to crack smart cards was the sw was written to take different amounts of time to compute legal and illegal keys. By measuring the battery consumption, the smart card crackers could only search the space of legal keys.
No doubt this was a sw path put in by a well intentioned programmer trying to save battery life, but now all respected encryption systems reccomend a "veil" strategy, where all encryption/decryption operations take the same amount of time and power regardless of the key.
In practice this means that you find out the max time and power (plus some margin) and if you are done early and without using enough power, you waste time and power to pad out the the veil...
Nice thought, but this just goes to show that cryptographic systems really need to be designed by experts...
real compression uses frame-to-frame correlation for compression. The dct is merely to
transform the residual difference into something simpler to code. It's also used in mpeg
for key frames, but those only are usually inserted once every 1/2 second and are
generally coded at resonably high quality.
During the mpeg4 competition, people proposed wavelets for the key frames, but in practice
it didn't look much better since most of compression came from inter-frame motion
compensated prediction, the difference wasn't high enough to justify changing things...
In jpeg2000, you generally don't have multiple frames to compress, so using wavelets makes
a bunch of sense. Wavelets didn't perform very well on coding the residuals so it isn't
used for that... (residual is mostly noise)
if I were setting up a posting scheme, I'd hash the IP address using a cryptographic
hash and post it so I could tell anonymous posters apart...
Or at least if a poster with a real name was using anonymous posting to try to make a
not-so-clever post that bombed so bad they didn't want it attributed to them...;^)
Since probably many people on/. probably don't know how this works, I'll post a brief summary.
The aperature equation determines the resolution of a satellite (or any other imaging instrument).
X = h*lambda/(L*cos(A))
where h is the height, lambda is the wavelength of the electromagnetic signal (light, radio, etc),
L*cos(A) is the projected length of the receiver (antenna, lens aperature)...
Plugging in some numbers say...
h=1000km, (too high for a survellance satellite, but easier math)
lambda=1um (near infra-red)
L=1m (a small satellite)
With this you get 1 meter resolution (yikes), although it doesn't account for distortion, etc...
Of course one way to increase the resolution is to get closer (reduce h), use higher frequencies
(reduce wavelengths), or increase the receiving aperature (big satellites are hard to fly).
Then there's this trick to increase the resolution of satellites that combine multiple "looks" of
the same object from different positions to simulate a large aperature. This technique is
called synthetic aperature imaging.
Non-geo-stationary satellites can combine multiple "looks" at a point while they fly by to
improve the resoltion. Of course there are problems like dopper shift, atmospheric distortion,
range shifts, etc that have to get accounted for, but this is the basic idea.
The problem with a geo-stationary satellite looking at you is that they fly very high
(very large h) and the don't move relative to the point target.
Of course a more realistic account would be in Tom Clancy's Patriot games where the real-time
image could only be obtained for a short time until the low-flying fast-moving spy satellite
couldn't see the target any more over the horizon...
As people have already mentioned, the numbers are probably not pseudo-random as they were
retrieved from random.org...
However, if someone decides to be cute and repeat this challenge with a pseudorandom sequence,
you don't need to be a good mathmetician, you just need to know how to read a paper written
by a good mathmetician... Look for the paper...
Massey, J. 1969. Shift-Register Synthesis and BCH Decoding. IEEE Transactions on Information Theory.
IT-15(1): 122-127.
Abstract -- It is shown in this paper that the iterative algorithm introduced by Berlekamp
for decoding BCH codes actually provides a general solution to the problem of synthesizing the
shortest linear feedback shift register capable of generating the prescribed finite sequence of
digits. The equivalence of the decoding problem for BCH codes to a shift-register synthesis
problem is demonstrated...
This is probably in most textbooks on linear codes for encryption and/or error detection and
allows you to recreate the shortest LFSR (linear feedback shift register, a common component
of pseudo random number generators), given a sequence of digits. Of course nobody would
use a non-cryptographically secure PRNG like random() would they?
So you take the number, pass it through this algorithm, find the shortest LFSR, and the
decompressor just takes the LFSR initial state and reproduces the sequence according to the LFSR.
Then again, the shortest LFSR can be thought of as the linear complexity of the number and who
knows it might just accidentally compress the sequence the challenger gives you (not likely,
but who knows?)...
Always remember... "stand on the backs of giants" whenever possible;^)
The Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer
Space, Including the Moon and Other Celestial Bodies of 27 January 1967 effectively said that
none of the signatory nations could claim the moon
You are just buying the name...
on
Paper Phones
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· Score: 2
As for the DSP, the Lucent DSP1609 was specifically designed for cell phone applications.
For the RF front-end for cell phones, fujitsu makes one for $2...
You can even put in the RF discretes in a
package...
Cell phone batteries are made to be rechargable which isn't necessarily the case here...
A cell phone draws about 200 milliwatts when running which isn't very much. The watt density
of a watch battery is good enough to power a disposable cell phone for quite a while...
If you do the research, it's amazing how little presumably expensive things cost in volume.
Retail and wholesale finished goods carry substantial markups from unfinished goods...
I know it's pretty depressing to see that you paid really good money for your plastic cell phone made by erikson, nokia, qualcomm, motorola, samsung, etc., but really, that stuff doesn't cost much at all...
You are just buying the name!
Re:And there was stupid old me ...
on
Paper Phones
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· Score: 2
After searching for 1 minute on the internet...
- $4.96 DSP (and this is a way overkill in performance)
I can imagine that people who deal with computers all the time think that silicon chips have to be
packaged, but in many "cheap" consumer devices, silicon die are generally wirebonded to cheap
circuit boards and then simply epoxied over. No leads, sockets, connectors, or other stuff...
Given this "cell phone" would probably just 4x4 button cross sense lines, power, ground, antenna,
speaker out, mic in, maybe 24 wires, this is more than what's in your wrist watch, but not by much.
If you have a chance, tear apart one of those greeting cards that can record and playback your
voice... That whole thing cost about $2 to manufacture... The total card cost is dwarfed
by the cost of the battery at about $1... (oh yeah, they have to pay for the paper and
printing too...), doesn't leave much for the electronics (including mic and speaker)...
Admittedly, RF cell phone logic is more advanced than the analog flash memory cells that make up
most of the greeting card, but hey for a few bucks more, you get something better... Right now, 10
million transistor chips cost about $5/die, I'm pretty sure a bare bones cell-phone is on the
order of ~1M transistors... (to put things in perspective, a 6502 had 4,000 transistors)
I don't think there's a claim that it's thin film technology (it's called super thin technology).
Ahh, those marketing folks pulled a fast one on you, just imagine what they do to non-chemists;^)
Of course those greeting cards that record your voice have a silicon chip in them and it wouldn't
surprize me if that if this turns out to be real, there's a silicon chip in there as well attached
by epoxy to a thin film flexible circuit board which has an embedded antenna and a voltage
regulator in thin film technology.
And the state-of-the art allows for low cost microphone and speaker tranducers (they already
come with those greeting cards), although it looks like from the pictures that it requires a cheap
hands-free cell phone adaptor...
I've seen similar thin film circuit boards with a package-less silicon chip be manufactured for 20
to 30 cents so this isn't really out of the realm of possibility (although I'm guessing a cell phone
chip is more complicated than the ones I've seen).
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intelligence investigation, information furnished by a confidential source, (E) would disclose techniques and procedures for law
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The reason that pranks worked as well as they did in the past is that the people who did them took a chance. I doubt the legal climate is that much worse today than it was when the pranks were done...
IMO, the problem with pranks today are really a function of two issues...
The first issue is that the current crop of pranksters are far more destructive than their historical counterparts...
For example, the original rose bowl prank (the card flipping prank) was entertaining. The second rose bowl prank (the scoreboard) was educational (the original software didn't have lowercase letters). The hollywood sign was at least promotional...
Dropping pianos, stealing statues, doing DOS attacks on ebay and etrade are a bit more destructive than the typical prank of yore...
The second issue (this is somewhat of a cheap shot), but I think the average college student of today is a bit more fearful of having a police record and spending a night in jail than the students of previous generations... Witness the massive decline in student rallies/protests from the 60's 70's 80's to the nearly non-existant activism of the 90's up to today...
I'm not saying pranks are akin to protests, but I think the aversion of today's student to legal troubles is a growth trend of the last few decades. Today it seems the limit of testing the boundaries of the law is restricted to downloading a few MP3s...
All sweepstakes after the McDonald's prank have restricted entries to "hand-written", but that didn't stop Caltech-ers from trying it again with a KROC contests between southland (LA area) schools for a private oingo-boingo concert.
Supposedly, the college that submitted the most entries won a free concert (oingo-boingo was supposed to give a free concert for the school). So a bunch of us got together and filled in a whole bunch of hand written 3x5 note-card entries and beat out UCLA, USC, CSNR, CSLA...
However, even having beat the other schools by more than 2x entries, oingo-boingo refused to give caltech a concert... So the caltech law dept helped the students write a few nasty letters, but to no avail... no concert for us...;^(
Moral of the story, having the administration on your side sometimes doesn't help (although if potential jail time is involved, it certainly helps, but that is another story....)
Giving $100,000 to United Way isn't the same as... giving $100,000 to the ACLU which isn't the same as... giving $100,000 to PETA which isn't the same as... giving $100,000 to GreenPeace which isn't the same as... giving $100,000 to the Sisters of Charity... giving $100,000 to the Sierra Club...
I doubt people can come to an agreement on a valid comparison as to the social-environmental benefits vs the dollars contributed...
I'd rather see companies spend less on charity so that we can spend more (and get the results we want instead of what the sleazy charity fundraisers can trick a company into giving)...
Personally I think most of these "charties" spend too much of thier money on themselves rather than the causes they champion. United way for example, is one of the lower-return-per-dollar charaties.
Environmental contributions aren't much better...
One of the current hot debate topics is the issue of destroying dams in the columbia basin (NW united states) to restore the original river flow...
The destroy/restore side:
http://www.removedams.org/index.cfm
One would think this is a no-brainer, but more in-depth analysis indicates there's another side to this debate:
http://www.buchal.com/links/links.htm
Which is right? I won't give my opinion here, but suffice it to say, I don't want any company that delegates the task of figuring out which one is right to somebody who "unfortunatly, doesn't have any time to do the legwork today" (to quote a poor unfortuante soul) attempting to figure this one out for me...
Means the object is listed in the Henry Draper Catalog of celestial objects. Another common catalog is the Durchmusterung id number which start with letters like BD, CD, CP, etc.
The catalog naming is slightly arbitrary, but at least it makes it easy to look up. More common names that you might have heard of before are things like NGC-xxxx...
P.S. actually this isn't much different than the whole DNS naming system if you think about it... There are "top level" names like slashdot.org and stuff underneath like www.slashdot.org...
Although proofs and such can be very comforting to know about, engineers (and some scientists) routinely used "unproven results" before the mathematical machinery is totally developed...
For example, Heaviside algebraic operator theory was used for solving linear differential equations before the mathematicians finished proving the domain of applicability (Laplace et al)...
Newton's fluxions were used long before integral calculus formalized the operation of integration. Not to mention infinite series, asymptotic analysis and the list goes on and on...
The quest for "truth" in mathematics has been a long, unexpected journey... If you haven't studied up on it, read about Hilbert and his program to formalize math... then read about Godel and how he showed that sometimes this mathematical foundation is really a mirage.
Sometimes practical use is more satisfying than theoretical comfort... So think about how the "truth" of the FLT really affects things. I imagine it's a lot less effect than you might think...
Slashdot Mirror
One of the main customers for satellite launchs is the military. Something as simple as google search should be able to pick this up (e.g., search for "ariane military")...
Military percentages of various orbit profiles
Low-earth-orbit ~15% (rest is mostly comm stuff)
Medium-earth-orbit ~65% (bulk of military stuff)
Geosync-orbit ~10% (rest is tv/telephone/dbs)
Things might be skew a bit when the ESA starts launching Galileo (the GPS competitor), but the direction depends on your view of dual-use technology. However, they don't call it the military-industrial complex for nuthin' (military contracting is just as popular in europe as it is in the US)...
Listening to antecdotal stuff like this is why people get hurt.
Although if you apply ordinary common sense about regular personal tax law, this would appear to be the case (you don't pay until you sell and your basis is the original price paid). However, this was considered a loophole where the rich could get deferred compensation without paying taxes (and thus getting the time-value of the money for free).
To address this loophole, the government created something called the Alternative Minimum Tax (AMT) which is a lower flat tax rate, but in addition to loosing a bunch of tax deductions you normally get, you also have to include the difference between the option price and the market price of exercised incentive stock options (ISOs) as ORDINARY INCOME. The rule is that you have to pay whichever tax (AMT or regular) is MORE!
The reason most people don't know about AMT is that they think it doesn't apply to them, but it certainly does. It used to only affect rich folks, but stock trickling down to the lower ranks wasn't forseen when the AMT code was adopted, so now it is affecting more and more people who don't even expect it (although turbo tax does this correctly most of the time)...
The non-qualified option is slightly different in that your estimated tax liability is always due immediatly (not just if AMT calculations turn out to be MORE) so the IRS code requires actual withholding (just like your W-2 exemptions), except it's at a fixed rate (to avoid people claiming too many exemptions).
Disclaimer, your tax situation may be different. Consult a tax expert to keep you out of bankruptcy due to AMT if you ever get into ISOs.
1. sub-space projection
2. uniqueness
Think of it as the bubble patterns is one member of a very-very large set (the "bubble" set) and the laser is a projection or mapping function of this member of the bubble set on to a much smaller "diffraction pattern" set. Since the different laser angles can be used, that's like using different mapping functions.
A verification agency isn't gonna store which member of the bubble set each token is and do a diffraction simulaton with computers everytime the token is scanned, but more likely they will store the one or two projections on to the diffraction pattern set which are created by the one or two reader devices that are marketed. Also the whole diffraction pattern isn't gonna be stored, but just the part of the pattern sampled by the device.
This seems like a much easier problem to solve for the token forgers. All they have to do is make a token that when projected to the one or two sampled diffraction sets stored by the verification agency instead the the infinite possible diffraction patterns of arbitrary precision.
Then you have the uniqueness problem. Since the verification agencies are likely only storing sub-space projections which are finitely sampled, there's the possibility of collisions between two cards. At least with a non-one-way function, you can detect collisions beforehand, now you have to make the card with bubbles and project them to you subspaces and only then discover there's a collision and you have to throw the token away. This also defeats the feature alluded to that you can always use another projection. If you don't check for collisions ahead of time, they will inevitably occur (think of the birthday paradox).
There are fundamental mathematics working against any scheme that depends on low probability of collision. You don't have to duplicate a specific thing, but you hope for a collision (which is duplicating any one of a large set). This of course is much easier to do and is the known as the birthday paradox in probability theory. This has been used as theoretical fodder to break many encryption systems (meets in the middle attacks).
Here's another way to think of it. You have a zillion digit credit card number (token) and you apply a few different hash functions (laser angles) to the number to get a "signature" (diffraction pattern). The only advantage of this technology is that it's hard to duplicate this zillion digit number where most things electronic are easily duplicated. But some of the other "features" don't seem easy to take advantage of.
It's like the phreakers of yesteryear where they just guessed long-distance calling card codes if the set is large enough, collisions are inevitable. That's when companies invented PIN numbers. What it probably means that these tokens will probably end up being only as secure as your 4 digit ATM PIN... Something to think about...
Sometimes when you think outside the box, you realize that the box was green and the grass is really dead out there too...
Although pro-equipment could play betamax and could use betamax tape (albeit the higher quality stuff and filling the tape after 20min), most people confuse betaMAX (the consumer format) with betaCAM (the pro format).
Consumer BetaMAX players could not play betaCAM tapes so I doubt many pros bought them...
Although I don't doubt some garage shops uses betaMAX along the way, I think this categorization only serves to confuse the issue.
Before widespread DNS and the MX tag, email addresses looked like...
myneighbor!herfriend!uunet!yahoo!slew
No kidding, email addresses used to be the other way with rmail/uucp! (and for a small time when internet email was just starting to be popular it was both ways with % signs, not to mention other nasty hpmail/vaxmail/x.400/x.500 hybrids)
You had to source route your email explicitly although uunet was pretty good about knowing about big sites and was pretty reasonable about relaying a small amount of email for a small fee. Setting up email w/o DNS (and root servers) might be like gnutella without much bandwidth. Think of DNS root server as the virtual site that can automatically tell you where to find out how to route everything.
The only reason email is as popular as it is today is that interoperability is pretty common (except for the spam-sources). Imagine if say 1/2 the email addresses uses a proprietary postoffice maintained "dns-like" service... It would sort of be like if the post office didn't license zip-codes to be used by their competitors (sort of how they don't let fedex/ups send to p.o.boxes)... You could set up a separate internet email, but there would be no interop...
Just food for thought...
Oh yeah, one other thing...
This is an interesting discovery since it's not obvious that the minimum energy trajectories between lagrange points follows a strange attractor (and aren't simply random or divergent). This means that if the trajectories are truly chaotic (i.e., follow tube-like strange attractors), once you get near the attractors (matching position/velocity vectors), maybe you can't predict exactly how you are going to get there, but you can be pretty sure that you will stay near the attractor so you needn't waste all your manuvering fuel trying to make minor course adjustments to try and stay on a specific trajectory. If it all pans out, this would probably turn out to be a pretty important discovery for inter-planetary minimum energy trajectories...
Nowhere did Mr. Lo describe in his paper that the gravity cancels out on these paths (only that they were minimum energy and connected the Lagrange points).
;^)
The whole idea of a minimum energy paths through the solar system is that it's a dynamical systems of greater than 2 dimensions. The weird thing about dynamical systems of 3 dimensions is that trajectories in some of these systems exhibit a type of predictability called a "strange" attractor.
Strange attractors for trajectories are different than the attractors you normally see in 2 dimensions (like local minima or orbits that retrace themselves) in that small pertubations can cause greatly divergent behavior. Even though the behavior appears chaotic, in some systems, the behavior can still be described as nearby a "strange" attractor. This is effect is often called chaos, and the study of strange attractors is called chaos theory.
Apparently Mr. Lo has worked out a theory where the minimum energy trajectories under this complicated dynamical system (planetary gravitational attraction) exhibits attractors that looks like "tubes" that exhibit the chaos-like behavior of strange attractors.
At first glance, these tubes appear to have the dynamical structure similar to n-body orbits (this factoid about orbits was first discovered by Michel Henon in the 60's). "orbits" in n-body systems don't actually retrace themselves, but sort of looks like a coiled up extension cord. The envelope or attractor of the orbits look sort of like a mis-shaped torus (squished donut), where the orbits can pretty much be anywhere on the surface of the donut (the attractor), but the path it takes is somewhat unpredictable (chaos) and highly dependent on initial conditions. There are more complicated attractors (some involving little islands of stability inside the donut) depending on the energy level, but this is the basic idea. This discovery seems to extend this known factoid about orbits to the structure of minimum energy trajectories in n-body gravitational fields.
All this will be moot, however, when in the 2004 election, Al Gore wins the presidency by taking credit for inventing the Interplanetary Super-Highway while giving a campaign speech for an increased budget for Nasa leading all the l337 geek-crackers to rig the newly approved, non-tamperproof election computers... I boldly predict this will be henceforth called the "butterfly-ballot" effect... But I digress...
Asynchronous logic always appears to be better than synchronous at first glance, but when you do the math, sometimes it isn't so clear...
Have you wondered why when traffic gets heavy on a freeway, it slows down? This is sort of like an asynchronous processor where every instruction is trying to get processed as quickly as they can (every driver is independent) but they need micro-synchronization to prevent collisions (brake lights, gas pedals). When the freeway is mostly empty, micro-synchronization works fine. However, as you approach the capacity limit, sometimes a global clock helps, sometimes it doesn't...
If you have a pipeline, you get back pressure waves as you approach the capacity which can make things slower than a synchronous system. If the processing topology is more complicated, it becomes even more difficult to analyze...
This effect is well known and affects things like processors and networks. Lookup articles on slotted ALOHA (a packet radio protocol) for some of the math if you are interested in some of the math behind this...
It's called PSLQ lattice reduction...
h tm l
i .h tml
You can get the details here...
http://www.mathsoft.com/asolve/plouffe/plouffe.
http://www.lacim.uqam.ca/plouffe/Simon/articlep
Note: this goes quite a long ways to showing that conventional wisdom about pi being random digits isn't actually true... Pseudo random is more like it...
However, it isn't really applicable to this multidimensional compression nonsense since the counting argument still applies.
Suspiciously, this looks to be similar to what the fractal folks were pushing in the '80s if you replace gems with iterators... Every once in a while you have to change the color of your snake oil label to confuse the masses...
-slew
One of the first common "thinking-out-of-the-box" techniques used to crack smart cards was the sw was written to take different amounts of time to compute legal and illegal keys. By measuring the battery consumption, the smart card crackers could only search the space of legal keys.
No doubt this was a sw path put in by a well intentioned programmer trying to save battery life, but now all respected encryption systems reccomend a "veil" strategy, where all encryption/decryption operations take the same amount of time and power regardless of the key.
In practice this means that you find out the max time and power (plus some margin) and if you are done early and without using enough power, you waste time and power to pad out the the veil...
Nice thought, but this just goes to show that cryptographic systems really need to be designed by experts...
real compression uses frame-to-frame correlation for compression. The dct is merely to
transform the residual difference into something simpler to code. It's also used in mpeg
for key frames, but those only are usually inserted once every 1/2 second and are
generally coded at resonably high quality.
During the mpeg4 competition, people proposed wavelets for the key frames, but in practice
it didn't look much better since most of compression came from inter-frame motion
compensated prediction, the difference wasn't high enough to justify changing things...
In jpeg2000, you generally don't have multiple frames to compress, so using wavelets makes
a bunch of sense. Wavelets didn't perform very well on coding the residuals so it isn't
used for that... (residual is mostly noise)
if I were setting up a posting scheme, I'd hash the IP address using a cryptographic
;^)
;^)
hash and post it so I could tell anonymous posters apart...
Or at least if a poster with a real name was using anonymous posting to try to make a
not-so-clever post that bombed so bad they didn't want it attributed to them...
Oh wait, sorry
Since probably many people on /. probably don't know how this works, I'll post a brief summary.
;^)
The aperature equation determines the resolution of a satellite (or any other imaging instrument).
X = h*lambda/(L*cos(A))
where h is the height, lambda is the wavelength of the electromagnetic signal (light, radio, etc),
L*cos(A) is the projected length of the receiver (antenna, lens aperature)...
Plugging in some numbers say...
h=1000km, (too high for a survellance satellite, but easier math)
lambda=1um (near infra-red)
L=1m (a small satellite)
With this you get 1 meter resolution (yikes), although it doesn't account for distortion, etc...
Of course one way to increase the resolution is to get closer (reduce h), use higher frequencies
(reduce wavelengths), or increase the receiving aperature (big satellites are hard to fly).
Then there's this trick to increase the resolution of satellites that combine multiple "looks" of
the same object from different positions to simulate a large aperature. This technique is
called synthetic aperature imaging.
Non-geo-stationary satellites can combine multiple "looks" at a point while they fly by to
improve the resoltion. Of course there are problems like dopper shift, atmospheric distortion,
range shifts, etc that have to get accounted for, but this is the basic idea.
The problem with a geo-stationary satellite looking at you is that they fly very high
(very large h) and the don't move relative to the point target.
Of course a more realistic account would be in Tom Clancy's Patriot games where the real-time
image could only be obtained for a short time until the low-flying fast-moving spy satellite
couldn't see the target any more over the horizon...
But I digress...
As people have already mentioned, the numbers are probably not pseudo-random as they were
;^)
retrieved from random.org...
However, if someone decides to be cute and repeat this challenge with a pseudorandom sequence,
you don't need to be a good mathmetician, you just need to know how to read a paper written
by a good mathmetician... Look for the paper...
Massey, J. 1969. Shift-Register Synthesis and BCH Decoding. IEEE Transactions on Information Theory.
IT-15(1): 122-127.
Abstract -- It is shown in this paper that the iterative algorithm introduced by Berlekamp
for decoding BCH codes actually provides a general solution to the problem of synthesizing the
shortest linear feedback shift register capable of generating the prescribed finite sequence of
digits. The equivalence of the decoding problem for BCH codes to a shift-register synthesis
problem is demonstrated...
This is probably in most textbooks on linear codes for encryption and/or error detection and
allows you to recreate the shortest LFSR (linear feedback shift register, a common component
of pseudo random number generators), given a sequence of digits. Of course nobody would
use a non-cryptographically secure PRNG like random() would they?
So you take the number, pass it through this algorithm, find the shortest LFSR, and the
decompressor just takes the LFSR initial state and reproduces the sequence according to the LFSR.
Then again, the shortest LFSR can be thought of as the linear complexity of the number and who
knows it might just accidentally compress the sequence the challenger gives you (not likely,
but who knows?)...
Always remember... "stand on the backs of giants" whenever possible
Check out NASA's version of the story.
As for the DSP, the Lucent DSP1609 was specifically designed for cell phone applications.
For the RF front-end for cell phones, fujitsu makes one for $2...
You can even put in the RF discretes in a
package...
Cell phone batteries are made to be rechargable which isn't necessarily the case here...
A cell phone draws about 200 milliwatts when running which isn't very much. The watt density
of a watch battery is good enough to power a disposable cell phone for quite a while...
If you do the research, it's amazing how little presumably expensive things cost in volume.
Retail and wholesale finished goods carry substantial markups from unfinished goods...
I know it's pretty depressing to see that you paid really good money for your plastic cell phone made by erikson, nokia, qualcomm, motorola, samsung, etc., but really, that stuff doesn't cost much at all...
You are just buying the name!
- $4.96 DSP (and this is a way overkill in performance)
- $2.60 battery
And there's no LCD in this phone...
I imagine a purchasing agent could do a bit better if they spent some more time...
This just goes to show how much people pay for distribution and advertizing...
I can imagine that people who deal with computers all the time think that silicon chips have to be
packaged, but in many "cheap" consumer devices, silicon die are generally wirebonded to cheap
circuit boards and then simply epoxied over. No leads, sockets, connectors, or other stuff...
Given this "cell phone" would probably just 4x4 button cross sense lines, power, ground, antenna,
speaker out, mic in, maybe 24 wires, this is more than what's in your wrist watch, but not by much.
If you have a chance, tear apart one of those greeting cards that can record and playback your
voice... That whole thing cost about $2 to manufacture... The total card cost is dwarfed
by the cost of the battery at about $1... (oh yeah, they have to pay for the paper and
printing too...), doesn't leave much for the electronics (including mic and speaker)...
Admittedly, RF cell phone logic is more advanced than the analog flash memory cells that make up
most of the greeting card, but hey for a few bucks more, you get something better... Right now, 10
million transistor chips cost about $5/die, I'm pretty sure a bare bones cell-phone is on the
order of ~1M transistors... (to put things in perspective, a 6502 had 4,000 transistors)
I don't think there's a claim that it's thin film technology (it's called super thin technology). ;^)
Ahh, those marketing folks pulled a fast one on you, just imagine what they do to non-chemists
Of course those greeting cards that record your voice have a silicon chip in them and it wouldn't
surprize me if that if this turns out to be real, there's a silicon chip in there as well attached
by epoxy to a thin film flexible circuit board which has an embedded antenna and a voltage
regulator in thin film technology.
And the state-of-the art allows for low cost microphone and speaker tranducers (they already
come with those greeting cards), although it looks like from the pictures that it requires a cheap
hands-free cell phone adaptor...
I've seen similar thin film circuit boards with a package-less silicon chip be manufactured for 20
to 30 cents so this isn't really out of the realm of possibility (although I'm guessing a cell phone
chip is more complicated than the ones I've seen).
Just some food for thought...
My guess is that they are squeamish about the medical stuff in exception #6...
(find the text of the FOIA here)
(b) This section does not apply to matters that are--
(1)(A) specifically authorized under criteria established by an Executive order to be kept secret in the interest of national defense or foreign policy and (B) are in fact properly classified pursuant to such Executive order;
(2) related solely to the internal personnel rules and practices of an agency;
(3) specifically exempted from disclosure by statute (other than section 552b of this title), provided that such statute (A) requires that the matters be withheld from the public in such a manner as to leave no discretion on the issue, or (B) establishes particular criteria for withholding or refers to particular types of matters to be withheld;
(4) trade secrets and commercial or financial information obtained from a person and privileged or confidential;
(5) inter-agency or intra-agency memorandums or letters which would not be available by law to a party other than an agency in litigation with the agency;
(6) personnel and medical files and similar files the disclosure of which would constitute a clearly unwarranted invasion of personal privacy;
(7) records or information compiled for law enforcement purposes, but only to the extent that the production of such law enforcement records or information (A) could reasonably be expected to interfere with enforcement proceedings, (B) would deprive a person of a right to a fair trial or an impartial adjudication, (C) could reasonably be expected to constitute an unwarranted invasion of personal privacy, (D) could reasonably be expected to disclose the identity of a confidential source, including a State, local, or foreign agency or authority or any private institution which furnished information on a confidential basis, and, in the case of a record or information compiled by a criminal law enforcement authority in the course of a criminal investigation or by an agency conducting a lawful national security intelligence investigation, information furnished by a confidential source, (E) would disclose techniques and procedures for law enforcement investigations or prosecutions, or would disclose guidelines for law enforcement investigations or prosecutions if such disclosure could reasonably be expected to risk circumvention of the law, or (F) could reasonably be expected to endanger the life or physical safety of any individual;
(8) contained in or related to examination, operating, or condition reports prepared by, on behalf of, or for the use of an agency responsible for the regulation or supervision of financial institutions; or
(9) geological and geophysical information and data, including maps, concerning wells.
Any reasonably segregable portion of a record shall be provided to any person requesting such record after deletion of the portions which are exempt under this subsection. The amount of information deleted shall be indicated on the released portion of the record, unless including that indication would harm an interest protected by the exemption in this subsection under which the deletion is made. If technically feasible, the amount of the information deleted shall be indicated at the place in the record where such deletion is made.
The reason that pranks worked as well as they did in the past is that the people who did them
took a chance. I doubt the legal climate is that much worse today than it was when the pranks
were done...
IMO, the problem with pranks today are really a function of two issues...
The first issue is that the current crop of pranksters are far more destructive than their
historical counterparts...
For example, the original rose bowl prank (the card flipping prank) was entertaining. The second
rose bowl prank (the scoreboard) was educational (the original software didn't have lowercase
letters). The hollywood sign was at least promotional...
Dropping pianos, stealing statues, doing DOS attacks on ebay and etrade are a bit more
destructive than the typical prank of yore...
The second issue (this is somewhat of a cheap shot), but I think the average college student of
today is a bit more fearful of having a police record and spending a night in jail than the
students of previous generations... Witness the massive decline in student rallies/protests from
the 60's 70's 80's to the nearly non-existant activism of the 90's up to today...
I'm not saying pranks are akin to protests, but I think the aversion of today's student to legal
troubles is a growth trend of the last few decades. Today it seems the limit of testing the
boundaries of the law is restricted to downloading a few MP3s...
All sweepstakes after the McDonald's prank have restricted entries to "hand-written", but that
;^(
didn't stop Caltech-ers from trying it again with a KROC contests between southland (LA area)
schools for a private oingo-boingo concert.
Supposedly, the college that submitted the most entries won a free concert (oingo-boingo was
supposed to give a free concert for the school). So a bunch of us got together and filled in a
whole bunch of hand written 3x5 note-card entries and beat out UCLA, USC, CSNR, CSLA...
However, even having beat the other schools by more than 2x entries, oingo-boingo refused to
give caltech a concert... So the caltech law dept helped the students write a few nasty letters,
but to no avail... no concert for us...
Moral of the story, having the administration on your side sometimes doesn't help (although if
potential jail time is involved, it certainly helps, but that is another story....)
Giving $100,000 to United Way isn't the same as...
giving $100,000 to the ACLU which isn't the same as...
giving $100,000 to PETA which isn't the same as...
giving $100,000 to GreenPeace which isn't the same as...
giving $100,000 to the Sisters of Charity...
giving $100,000 to the Sierra Club...
I doubt people can come to an agreement on a valid comparison as to the social-environmental
benefits vs the dollars contributed...
I'd rather see companies spend less on charity so that we can spend more (and get the results we
want instead of what the sleazy charity fundraisers can trick a company into giving)...
Personally I think most of these "charties" spend too much of thier money on themselves rather than
the causes they champion. United way for example, is one of the lower-return-per-dollar charaties.
Environmental contributions aren't much better...
One of the current hot debate topics is the issue of destroying dams in the columbia basin
(NW united states) to restore the original river flow...
The destroy/restore side:
http://www.removedams.org/index.cfm
One would think this is a no-brainer, but more in-depth analysis indicates there's another side
to this debate:
http://www.buchal.com/links/links.htm
Which is right? I won't give my opinion here, but suffice it to say, I don't want any company that
delegates the task of figuring out which one is right to somebody who "unfortunatly, doesn't have
any time to do the legwork today" (to quote a poor unfortuante soul) attempting to figure this one
out for me...
HD = Henry Draper
Means the object is listed in the Henry Draper Catalog of celestial objects. Another common
catalog is the Durchmusterung id number which start with letters like BD, CD, CP, etc.
The catalog naming is slightly arbitrary, but at least it makes it easy to look up. More common
names that you might have heard of before are things like NGC-xxxx...
P.S. actually this isn't much different than the whole DNS naming system if you think about it...
There are "top level" names like slashdot.org and stuff underneath like www.slashdot.org...
Although proofs and such can be very comforting to know about, engineers (and some scientists)
routinely used "unproven results" before the mathematical machinery is totally developed...
For example, Heaviside algebraic operator theory was used for solving linear differential equations
before the mathematicians finished proving the domain of applicability (Laplace et al)...
Newton's fluxions were used long before integral calculus formalized the operation of integration.
Not to mention infinite series, asymptotic analysis and the list goes on and on...
The quest for "truth" in mathematics has been a long, unexpected journey... If you haven't studied
up on it, read about Hilbert and his program to formalize math... then read about Godel and how
he showed that sometimes this mathematical foundation is really a mirage.
Sometimes practical use is more satisfying than theoretical comfort... So think about how the
"truth" of the FLT really affects things. I imagine it's a lot less effect than you might think...