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User: K-Man

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  1. Re:Beside the point. on Better Sniper Detection · · Score: 2

    The question is whether they can hit the round in the air. That would be something. I don't know much about military tech, but it seems like an artillery-interception system would be comparatively easy, given the systems that are being developed for missile interception. A ground-based laser would certainly be easier to build and deploy than a flying one.

  2. This comes up every few years. on Space-Time-Gravity and Magnetism · · Score: 2

    Electromagnetic forces are, IIRC, 10^42 times stronger than gravitational ones, so every once in a while someone comes up with a theory that galaxies repel each other due to static buildup, or form giant magnets, etc. Since any effect theorists come up with is 10^42 times more powerful than any similar gravitational effect, it doesn't take much to get these arguments going.

    However giant supercluster-moving charge and current distributions have yet to be discovered in any shape or form, to put it bluntly.

  3. Hot glue gun and toothpicks on Lego Vs. Meccano & Engineering Knowledge · · Score: 2

    I've been keeping this a secret, but you can built just about anything in a few minutes with hot glue and toothpicks. Towers, bridges, cantilevers, I've done it all.

    Start with a board as the base, put drops of glue on the corners of a square one toothpick wide, put in 4 toothpicks as verticals, and connect them horizontally to form a cube. Repeat to build box girders, etc. You can add diagonal braces as needed.

    Hot glue is about the best thing every made for connecting small wooden structural members - strong, flexible, and it sets almost instantaneously. You can also melt the glue with the point of the glue gun to add additional 'picks to a joint, or to disassemble it.

    It can be a little bit too flexible for some things, but if the point is to get some experience with structural design, it's ideal.

  4. Re:Beside the point. on Better Sniper Detection · · Score: 2

    Optical and radar-based systems, which this one is not, pick up the bullet before it gets 50 feet out of the barrel (or the muzzle flash, using an infrared CCD camera). Since the speed of a bullet is about 2500 feet/sec., the target may have more than a second of warning to duck out of the way, depending on the range.

    Acoustic systems are obviously handicapped by the lower speed of sound ( 1000 ft/sec), but it may be possible to pick up the sound sooner if a sensor is closer to the shooter than the target is. Presumably that's the basis of this system.

  5. Re:Decommutator on Can Anyone Identify this (Cold War?) Stuff? · · Score: 2

    My first job after college used a "Remote Multiplexer/Demultiplexer" from Teledyne(?). Is this the same thing? IIRC this box was solid state (and large) and had additional capabilities, like sending out control signals during the cycle. Unfortunately it tended to overcycle by one instruction, meaning it would latch on things that were supposed to be latched off at the end of a sampling run. Many nights of fun with the oscilloscope.

    And yes, by the time I worked on this box it was obsolete, in the mid-80's.

  6. DB2 is still my favorite on dB Choices - Oracle, DB2 or Something Else? · · Score: 2

    ...after using Oracle and Sybase/SQL Server.

    A few reasons (I'm not even going to try to cover all the bases):

    1. SQL3: This is probably the last attempt at a standard SQL, but it still seems to have a few more brains behind it than PL/SQL or T-SQL. My apps have a strong need for recursive SQL, which is present only in SQL3.

    2. ODBC: This is, or at least was, an open standard API. DB2's API is essentially ODBC, while Oracle continues to push OCI, and ODBC drivers for it are hit or miss. I'm not sure about now, but a few years ago one could write an ODBC app and link it to the DB2 CLI directly, without an ODBC driver or driver manager.

    3. Price.

  7. Wait, I see the problem on The Ultimate Limits Of Computers · · Score: 2
    The readers are getting confused by this paragraph:


    The maximum energy an ultimate laptop can contain is given by Einstein's famous formula relating mass and energy: E = m c2. Plugging in the laptop's mass, the speed of light, and combining the result with Eq. 2 tells us that the maximum number of operations per second a 1 kg lump of matter can be made to perform is 5.4258 * 10 50. This means that the speed of a computer is ultimately limited by the energy that is available to it.


    You're misstating the definition of E in equations 1 and 2. E is not "maximum energy", it is defined as the exact mass-energy of the physical system, in this case 1kg. The speed of a computer is not limited by the energy available to it, it is limited by the mass-energy that is in it.

    You might rephrase it by something like "Since E is the total mass-energy of the laptop, a simple unit conversion shows that the maximum number of operations per second ...etc."
  8. Re:Not good science on The Ultimate Limits Of Computers · · Score: 2

    The upper bound is on the number of measurable physical states that any physical system with mass 1kg can attain in a certain time period.

    The verbiage about E=mc^2 is redundant, the author is simply restating the fact that E in equations 1 and 2 is, and has always been, relativistic mass-energy, not what appears on your PG&E bill.

  9. Re:Is it just me or did the author make a mistake? on The Ultimate Limits Of Computers · · Score: 2

    Equations 1 and 2, etc. do not require conversion to kinetic energy of any kind; they're just restatements of the fundamental de Broglie wavelength:

    E = h-bar * nu

    from high school physics. This gives the light wavelength if the object is a photon (zero rest mass), otherwise this wave effect is called the "probability wave" and is reputed to have connections to alternate universes, etc.

    It doesn't matter if E is rest mass or kinetic energy; the wavelength effect is the same, and in fact originally derives from special relativity. Heisenberg's principle is essentially a statement of the resolving power of these waves, for instance in electron microscopes, or in any measuring instrument. Equations 1 and 2 say that one can't measure much more often than delta t, which is fairly straightforward since one is working with waves whose period is at least delta t.

  10. Re:[ot]Google's data structure? on Interview With Google's Director of Research · · Score: 3

    That's true if the data is changing. However most search engines do web crawls in large chunks, and index the data once in one large block. Under such conditions dynamic management of hit lists and other data structures is not necessary. Basically, the bytes are packed as tight as they can get them so that it all fits into memory.

    As far as I can tell from their paper, Google manages its web crawls the same way. It partitions the data into "barrels" and indexes each separately. Once the indices are built, they aren't updated. They also extend the hit lists to include word position and some other attributes for each hit.

  11. Re:[ot]Google's data structure? on Interview With Google's Director of Research · · Score: 2

    The documents are assigned id's 1..n and, for each word, an ordered list of id's of documents containing the word is constructed. When a search asks for, say, "cheese fondue" the array for "cheese" and the array for "fondue" are retrieved and merged using a sorted list merge (fast, since the arrays are already ordered). The result is a list of document id's that were in both lists, i.e. documents containing both words.

    There are various ways to speed this up by compressing the arrays, hash joins, etc., but the basic idea is the same.

  12. If they can read your files... on Multi-User Websites and Lack of Security? · · Score: 2

    Can't they read your MySQL datafiles? Seems like protecting passwords would be moot.

  13. Re:Love my TIVO! on Buying a PVR that Doesn't Require a Subscription? · · Score: 3

    Tivo requires one initial dial-in, with no service activation required, to download who-knows-what (like the software).

    After that it's manually programmable with no phone link, or subscription.

  14. Correct, also see link on Why Unicode Won't Work on the Internet · · Score: 2

    Yes, the author was overbroad with that statement. All languages work on a restricted set of phonemes; there are some 200+ identified, but no one language uses near that number. Hangul covers all the Korean phonemes, but not much else.

    Here's a good description of Hangul. If you check this page, you'll notice I was wrong about the vowels; they don't seem to describe their own pronunciations at all, but rather the yin and yang elements of their sounds :-P.

  15. Re:All Character sets simultaneously?? on Why Unicode Won't Work on the Internet · · Score: 2
    I got all sorts of spurious matches from the Latin words, which wouldn't happen if the Greek and Roman letters weren't sharing a single character space.


    However, in Unicode, Chinese, Korean, and Japanese all share the same codepoints and glyphs, so you can't grep for one language or another.

    For instance, if you were searching in Korean for "Kim Il Sung", this string in Unicode would be the same as the Chinese characters for "gold" (jin), "one" (yi), and "star" (sheng), so your search would get hits from other sino-based languages in addition to Korean.

    It's difficult even to sort Unicode correctly without choosing some language or another, due to this overlap of characters. "Alphabetical order" is different for the different Asian languages, even though they use the same characters.
  16. Re:You bring up a good point on Why Unicode Won't Work on the Internet · · Score: 3

    If you read the article, you'll find a decent description of Korean Hangul, which has around the same number of characters as English (IIRC, it has 24).

    Hangul outdoes the latin alphabet in several ways. For one, as you mention, pronunciation in English is difficult, while in Hangul it is almost completely unambiguous. Each phoneme maps to one character, and vice-versa. There is no confusion over whether to write "cat" or "kat", for example. Only one letter has the "k" sound.

    Each Hangul character is a pictogram describing the position of the tongue, palate, and lips to use when pronouncing it. Whereas most phonetic alphabets consist of ideograms recycled as phonetic symbols, Hangul seems to be the only one to consist of symbols constructed purely for phonetic meaning.

    Since the job of a phonetic alphabet is only to represent phonemes, I would say that this alphabet does the job better than latin.

  17. Re:Korean Police and the Internet on Taking Games Seriously In Korea · · Score: 2

    ...and Korea has not, despite submissions.

  18. Korean Police and the Internet on Taking Games Seriously In Korea · · Score: 2

    While the article makes it seem that the game has become a major threat to societal order, I would interject a bit of skepticism due to recent history with respect to Korean authorities and the Internet.

    The rest of the world has decried net censorship, but the Korean government has embraced it wholeheartedly. Police have acted on the theory that free speech and communication are causes of crime. Websites advocating suicide have been shut down, their user logs have been confiscated, and users have been investigated by the police, based on claims, made by the same police, that people have committed suicide after visiting the sites. More broadly, the government recently issued a secret list hundreds of thousands of "forbidden" web sites, which are to be blocked by ISPs.

    While in the West we have become accustomed to tabloid journalists and cheap political hacks attacking the Internet, we should realize that Korea already has an institutionalized FUD network, and any claims should be taken with a dose of salt.

  19. Re:Behold the blind eye of US journalism on Taking Games Seriously In Korea · · Score: 2

    Also, if you meet a Korean person, you'll often be asked your age. This question arises due to the necessity of fitting each person into the Confucian hierarchy.

    Other languages also reflect social structure, but Confucius formalized these tendencies, and the language has more terms describing social and family relationships. For instance, "aunt" is broken into "aunt on the father's side" (como) and "aunt on the mother's side" (yimo). It gets complicated, but most cultures have some traces of this practice.

    There's also a polite informal tense which gets around much of the status-checking.

  20. Re:Using Light on Light-Based Computers Using Quantum Principles · · Score: 2

    I'm about at the same stage of understanding. I suspect that wave mechanics (as the opticists used) may underly a lot of the claims. QC relies heavily on Bennett's work in reversible computing. The idea is that information, and its underlying physical representation, can flow both ways through the logic gates, just as light can propagate or resonate both ways in an optical system. If the system is stable (that's something I'm not convinced of), then the observed wave function should reflect the proper relationship between the "input" and "output" (even if we, say, put in a known output and want to reverse to an input). Measurements against such a system should yield statistics that reflect the wavefunction at different parts of the system, and the wavefunction will represent something about the information we're seeking.

    I don't see anything so mysterious about this. QM brings on a lot of handwaving (eg Deutsch's claim that QC "proves" that the many-worlds interpretation is correct), but I believe the opticists are on the right track when they say a lot of the logic can be done in non-quantum systems. QM at best provides a good source of waveforms to put through our interferometers.

  21. Re:When a scientist misspeaks? on Light-Based Computers Using Quantum Principles · · Score: 2
    I would like to think that our enlightment grows with time, but every new article I read about quantum computing research seems to be filled with more and more hyperbole.


    Yes, I think the field is incredibly strange and wonderful, but not for the physics. The ignorance and mutual misdirection are entertaining. What other field has physicists, philosophers, and computer scientists, all misunderstanding each other in fundamental ways? Now we have the optics community involved. Maybe at least we can separate the wave mechanics from the rest of it all, if there is any remainder.

    (We all learned that quantum mechanics destroyed the computer-like determinism of Newtonian mechanics, but now we think that, while the universe is not a big classical computer, the universe may be a big quantum computer!)


    I'm not trying to start a flamewar, but the claim that QM implies nondeterminism also falls into the unfounded hyperbole category. As someone wrote in Physical Review Letters a while ago, the stuff about trajectories not existing, and instantaneous quantum jumps, many worlds, etc., is a good way to keep from presuming too much information about a system, but it's not a proof of any deeper reality.
  22. Re:No link to quantum computers on Light-Based Computers Using Quantum Principles · · Score: 2

    Yes, they seem to be ignoring spatial complexity here. That was my reaction to the quantum paper on the same thing.

  23. Scientists discover content-addressable memory on Light-Based Computers Using Quantum Principles · · Score: 2
    So in the case of Walmsley's device, 50 different frequencies of light shine through the modulator, and if the 20th frequency is the altered one, then Walmsley knows that the bit of information he was searching for is located at position 20 in the database. A conventional computer would have had to check 20 times to find the location.


    I kind of like the mudslinging here between the quantum and optics camps, but has anybody else been troubled by the glossing over of spatial complexity here? Anybody can build a device that will solve a problem in one step. The spoiler is that the device will grow in size (or in this case, frequencies) proportional to the complexity of the problem. The QC paper on database searches did this: they claimed that a "conventional computer" could only search n items in O(n) time. But "conventional" devices have been built which find an item in O(1) time, eg by indexing the items by value. It seems like we have a mutually interfering group of entangled misconceptions here.

    Heck, you could probably shoot radar at the surface of a hard disk and tune it to find a particular bit pattern, "billions of times faster". Would that violate "classical computing limits"? Not at all.

    Overall, I would say that this is a step in the right direction. If you read the article you'll find that the stumbling block was that the optical crowd thought that the particles had to be entangled for a device to work. I suspect that this misunderstanding arose from Deutsch when he used the term incorrectly to describe a QC.

    Maybe next they'll discover that a DRAM can fetch a value from any location *in one step*. My gosh, that's amazing. (OK, I'm sarcastic, but I think the physicists have to be a bit clearer in proving that their whizbang devices are not spatially complex...and yes, I am reading the papers to try to clear this up).
  24. Re:Example of counterfactuals in QM on Computers That Solve Problems Without Being On · · Score: 2

    The point is that this beam splitter arrangement is a simple interferometer. When the bomb is a dud, its mirror does not "measure" (interact destructively with) the photon wavetrain, so the interference pattern persists. If the bomb is set up to measure the photon, the interference pattern disappears. This is about the first thing people tried with the two-slit experiment.

    Hence my question: is this configuration considered publishable? It's a no-brainer. It has no new physics, and adds nothing to the interpretation. It's a simple retelling of the old two-slit experiment, and it coins a new obfuscatory word to boot.

    Here's my "counterfactual" experiment:

    Set up two slits. Put a bomb with a (transparent) electron detector trigger over one of the slits. Do the two-slit experiment. If the bomb is a dud, the detector will not interact with the particles' de Broglie waves, and an interference pattern will appear. If the bomb is not a dud, the interference pattern will disappear (or the bomb will go off).

    For each electron going through the apparatus, you have the same 50/50 chance of detonation if the detector is working. It's harder to measure the interference pattern, since you need more than one electron, but the mechanics are the same. You still have a non-zero chance of finding that the detector is working without activating it (if all the electrons go through the other slit, and you get enough to see that the interference pattern isn't there).

  25. Re:Example of counterfactuals in QM on Computers That Solve Problems Without Being On · · Score: 2

    Big deal. Take Ye Olde Quantum Two slit experiment. Cover one slit. The interference pattern disappears. Is that "counterfactual" or simple wave mechanics? Of course the particle doesn't need to hit the bomb; its wavetrain will, and create the interference whether the particle goes one way or another.

    The obfuscation just kills me. It seems the more contorted the interpretation, the more likely it is to be published.