Did the Salon article have the nerve to point out that the real problem here is the academic critics' unwillingness to ever admit that reading a story is just fun? That's the basic reason SF is not even on most critics' radar. Of course, half of what they do talk up is worse than decent SF, and Homer and Shakespeare are worse than most _bad_ SF -- but they're old so they're OK...
Anyone here welded titanium? I wasn't a welder in the Air Force, and it was a long, long time ago, but IIRC the metal shop had to drag out all sorts of gear if welding Ti was necessary. I think you have to flood the weld area with nitrogen because its ignition temperature in air is lower than the melting temperature. Of course, you need something much hotter than the normal welding torch. Then you get the weld done and need to grind down the excess bead -- and as hard as Ti is, that's going to take some time.
But it's mighty durable once it's together.
Re:Not Really A Concern
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Space Wars
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read what they are working on/testing before you make a knee-jerk reaction to a success or failure. I'd agree, IF the starwarites had been honest about what their success meant. Namely that their guidance system works, and they haven't even started the detection system tests. Yes, to hit a bullet with a bullet is a hell of a good guidance system, even when the target bullet is broadcasting it's location. But this rather points up how far they have to go yet -- do you think detection systems are going to be easier?
Re:Space Defense Initiative (SDI)
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Space Wars
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A "kinetic kill vehicle" could be designed to be quite effective against ground targets. That is, a chunk of tungsten big enough to re-enter without burning much metal off, with a guidance system that will work all the way to the ground. (Jerry Pournelle calls such a weapon a "crowbar", see Footfall for instance. It really isn't much more than a crowbar with fins, once you work out how to shield the video camera or radar and CPU so they'll survive re-entry and guide it into the target.) This is quite a lot different from a KKV for space, where most targets would be destroyed simply by colliding with an unshielded guidance system and empty rocket motor; if you need a "payload" at all, its probably just a few ounces of hard metal to punch through no more than 1/4" of armor. OTOH, the space-space KKV needs high-velocity propulsion to intercept its target, while the crowbar needs only enough rocket power to drop out of orbit, or possibly will be launched by catapult with no retrorockets.) A dense object dropping from orbit is going to be going a few thousand meters per second at impact, so its kinetic energy probably exceeds the energy in an equal mass of TNT. I expect a fifty-pounder (25 kilo) would leave a house-sized crater; a considerably smaller one could punch through the top armor of a tank, if the terminal guidance is good enough to hit a moving and possibly camoflauged target. And the guidance issue is just electronics and programming -- if you can't do it now, wait a few years and Moore's law will make it possible.
Of course, right now putting that 50 pound crowbar into orbit costs something like half a million dollars. You can fly a lot of airstrikes for that much. OTOH, to drop a bomb on Saddam Hussein we would have to fight his Air Force, and even if we didn't lose any people we'd almost certainly get several multimillion dollar fighters bunged up. Maybe instead, we crowbar Saddam's limo, crowbar his successor, and so on until we get someone reasonable... That's if Bush doesn't mind setting a for precedent for everyone who has a beef with the US sending assassins after the US president. (I certainly wouldn't mind that, considering the sort of people we've had running for president the last 50 years, but I'm not sitting in the hot seat.;-)
If Lucas claimed he based StarWars on westerns and war movies, he was already lying then. He's compounding it now by letting this university idiot draw a direct line between the ancient mythic sources and StarWars, ignoring the many SF authors that explored mythic themes, whose work Lucas "sampled". The Jedi Knights are Lensmen, not Gary Cooper or John Wayne lawmen and soldiers, and certainly not Greek heroes. Tatooine is more like Dune than the American Southwest, or even the Sahara desert. Coruscant is like nothing at all in myth or non-futuristic fiction, but it certainly resembles Trantor.
I doubt that anyone with more than a passing acquaintance with written science fiction would want to over-analyze Star Wars. It's bloody obvious. Tatooine = Dune. Coruscant = Trantor = Rome. Jedi Knights = Lensmen. Luke = the callow kid starring in 90% of SF...
The thing is, somehow this Joseph Campbell (not to be mistaken for the great magazine editor of the "Golden Age") won't admit to ever reading anything just for fun in his whole life, and so is unaware of all the SF stories Lucas "sampled". Instead, he goes back to the ancient myths -- which are the same sort of stories as bad SF writing, but age has made them academically respectable. And Lucas suddenly discovers his work becoming respectable among the snooty crowd, and is lapping it up...
No, what he needs (and no doubt he is aware of it), is a better pump. Also proper tubing fittings, hose clamps, baffles inside the waterblock to direct the flow so all of it gets cooled, ears on the block to attach spring-clip heatsink holders, and so on. But the cheap 10-minute pump is good enough for checking out whether he's on the right track -- and he claims his budget was 77 pence, which I think is about $1 US. Aquarium pumps run continuously and aren't too expensive, but on that budget you use what you already have...
I do hope that he used thermal grease -- the article doesn't say one way or the other, but even a perfect heat sink can't cool well if the heat has trouble getting _to_ it.
One thing that did kind of bother me: "Although it seems that copper would be best suited for making a water block, I'm not entirely convinced without physical proof." It scares me that anyone who has to ask would be doing this! Copper is indeed the best material, unless you are on a NASA cost plus 10% contract, then use gold and increase your profit.;-) Copper is resistant to corrosion and has the second highest heat transfer rate (by volume) of any material available in bulk. Gold is better and aluminum is worse on both counts. When aluminum is used instead of copper, they are trading off a little effectiveness for considerable savings in cost and weight; if you are using water, weight better not be an issue, and for a do-it-yourself project you'd spend a lot more trying to solder aluminum than copper will cost...
Water is the optimal coolant, when only physical properties are considered. It's reasonably low viscosity (easy to pump), and has an extremely high heat capacity. The only problems are that it is rather corrosive and electrically conductive, so leaks are really bad news, but the heat capacity is so much higher than most non-conductive fluids that engineers will often pick it anyhow. Other choices: Oil will take a stronger pump, thicker tubing, and bigger radiator, because you have to move more fluid at higher viscosity. Certain chloroflourocarbons are good enough at cooling and entirely safe to spill on live electronics, but they're also pretty much illegal nowadays. And distilled water is much cheaper than any alternative fluid...
Unless, possibly, said books were found open, and highlighted, on the table of said drug lab... One book was still in it's wrapper and the police lab determined that neither had been read.
OTOH, the books were found in the bedroom where methamphetamine had been manufactured. One reason the police wanted the records was to get additional evidence as to which of the four people living in the trailer house were sleeping in that bed.
And on the gripping hand, the appellate court noted a number of curious gaps in the evidence, according to the records. There may have been more books in that room, but only two were seized -- and that choice was obviously content based. (The books were about synthesizing drugs.) The books and the laboratory glassware had been dusted for prints, but the court record did not show the results. The justices seem inclined to assume that the police hadn't put the results in the record for the subpoena case because they would have shown who was running the lab clearly enough to make the book purchase records unnecessary...
The simulation is reasonably accurate because they are staying with areas that are already well described by current theories, confirmed by all the real nukes we've detonated. They are not trying out new reactions. Probably they are not even trying out new bomb designs. Mostly, they are just looking at how 20 or 30 years of aging (allowing a small part of the fissionable U235 or Plutonium to decay) will affect the nuclear reaction, to determine the point at which existing bombs will _have_ to be recycled.
The only real option for actual explosions now is to set off undersized bombs deep underground. That gives valuable data too, but it's hardly better at predicting actual weapons performance than the simulations. (Of course, Saddam may yet "volunteer" a part of Iraq for a live aboveground test...)
"People dye" means they change color. Although being near ground zero would be apt to cause various color changes (probably ending in black & crispy), perhaps you meant "die"?
Sorry, but there is very broad class of simulations where distributed computing across the internet is not going to help, called Finite Element Analysis. I don't know the specifics of nuclear explosion simulations, but the basic setup is similar to simulations of electromagnetic fields, mechanical stress and strain, heat transfer, the weather, etc. You divide the volume of interest up into lots of little cells (the "finite elements"). For a cell, you determine how conditions in a cell are influenced by influenced by neighboring cells, as well as the pre-existing condition of the cell. You code those equations into a program, and it cycles through all the cells to calculate the next state (one time tick later), then repeats until done.
For instance, in a heat transfer simulation, the temperature of a cell changes from the initial temperature towards the average temperature of neighboring cells at a rate determined by the thermal conductivity of the material: T1(x,y,z) = (1-k)*T0(x,y,z) + k*(T0(x-1,y,z)+T0(x+1,y,z)+T0(x,y-1,z)+T0(x,y+1,z) +T0(x,y,z-1)+T0(x,y,z+1))/6. You need special forms of this equation for cells at the edges. You write _for_ loops to cycle through all the cells and an outside _for_ loop to step through the time ticks -- or you might use a pre-written simulation program where you just have to plug in the cell geometry and the equations. Nuclear simulations must be considerably more complicated: it would require several variables tracking temperature, local concentrations of reacted and unreacted materials, radiation density, etc., and equations tracking how materials, flow in and out of the cells, among other things.
But the point is, even at the most complicated, the calculations for one cell at one time tick are only going to take a few microseconds on a decent CPU. If you parallelize it by assigning one CPU to a cell, the CPU will do the calculations, then it will have to exchange data with all the other CPU's. The communications requirements can be met only by providing lots of direct dedicated CPU-CPU, or CPU-memory-CPU links. That is, it takes custom hardware. Try to do it through any kind of shared bus, and the comm bandwidth will severely limit the number of CPU's that can be actually used. Don't even think of trying to use the internet with latencies of seconds, and bandwidths of 56KHz to a few MHz.
This is bad news, not for DOE who have the money to build that custom hardware (and would have to keep their bomb secrets in-house anyhow), but for all the engineers and scientists who would love to have thousands of computers crunching their data for free, but their equations aren't suitable for it. For SETI@home, I think each computer gets a module consisting of one piece of recorded data and a batch of tests to be run against it; the modules do not have to communicate in between setup and completion, so little bandwidth is needed. It's great when it works, but we only know how to divide up big computing jobs completely like that for a few special cases.
The basic issue is changing requirements. A contractor building high-rise apartments does not have to worry about the customer coming around when it's half built to look at it and say, "You know, I think I want a hospital instead." Programmers quite often have to deal with customers that are just about that confused -- they can't begin figuring out what they really want until they see what they asked for on the screen.
More than that, software vendors routinely write a program, release it, then add features so they can sell it again. It's as if the builder has finished the apartment building, and now they want a factory tacked onto the north side and a Wendy's onto the east. Next year, add a hospital wing to the west. Repeat once a year for 10 years and you get one hell of a mess, but how else would M$ keep a continuing revenue stream from the same OS and Office programs?
OS/360 was actually heading over a cliff. The various pieces of software did not work when they were put together. The OS was delivered years late and massively over budget. Many IBM 360's (costing six figures back when $1 was worth something) were delivered and then spent years simply running emulators for the old machines they replaced, because the native software wasn't ready.
Yes, there were lots of things they could have done -- like define a subset of the original committee-designed bloated specification, get that working, then start adding features. But the manager (Fred Brooks) didn't know that, yet, and didn't even know the project was in trouble until it was impossible to deliver anything at all on deadline. Afterwards, he wrote a book, The Mythical Man-Month, which has become a standard text for large-project management. But he learned how by doing it wrong, more massively than anyone ever had before...
If you've got the requirements well enough defined in terms of previous work that you can estimate accurately, then most likely all you've got to do is cut and paste the old code anyhow...
proofs are as much a social event as a mathematical cedrtainty.
You are going a bit too far. Proofs do require a social activity before they are accepted, namely rigorous checking by a number of other mathematicians. But most proofs have survived such checking as to be mathematical certainties -- within a given system of axioms.
For instance, the Pythagorean theorem has a simple one page proof that has been reviewed by every mathematics student for over 2,000 years, and no flaw has been found. It's certain -- within Euclidean geometry. It also is known to have limited real-world applicability: it won't be exact for right triangles drawn on the curved surface of the earth, nor (according to General Relativity theory) will it be exact for large triangles in space. But it's close enough for most surveying work, and more than close enough for machine shop work.
On the other extreme, there is the computer-generated proof of the 4-color theorem. IIRC, one mathematician could not read the whole proof in a lifetime. Merely understanding how they formulated the problem into a computer program will take up more of your life than most people want to spend on a single abstract problem. Certain computer bugs can be ruled out by re-compiling the program for different computers and comparing results, but the real question is whether the program is correct -- and apparently mathematicians who have reviewed it think it is correct, with a lot higher probability than is needed to execute a man in Texas, but not everyone agrees it is _proven_.
And what's the real-world applicability? In theory a mapmaker could get along with just 4 colors, but it's easier and clearer to use more...
The Bering Strait is ice-covered, but IIRC it's never really solid. The currents are too strong, so the ice keeps moving, in the form of lots of solid slabs grinding together. The trick is not to fall into the cracks between floes and not to get tipped over by the ridges, etc., raised by collisions between floes. A really big "snowmobile" would help with the first two problems, but it can't be too big or you'll run the risk of smaller floes sinking under the weight.
Also, there's the problem of navigating on floes that are drifting at several mph. Does GPS work well up there? The worst navigation error would be to wind up on a floe drifting away from the rest.
From the article (2nd page): "To vary the transmission of light through color filters, LCDs use magnetic fields to twist particles floating in a liquid--an inherently less precise process."
No, LCD's use electric fields. CRT's use magnetic fields to focus and scan the beams. Why do tech-oriented mags hire technical idiots?
If a community decides that it wants its libraries to use filtering software
1. Communities are one thing, Congress is something different. Constitutionally, Congress's regulatory power is _supposed_ to be very much more limited than states and localities. If that Red/Green map bandied about after the 2000 election means anything, it's that different parts of the USA have quite different community standards... If you want to put filtering software into your local library, run for the library board on that platform, don't try to impose your desires everywhere.
2. The actual standards used in commercial filtering software are not set by community standards, or even by Congress, but rather by the software vendors. AND THEIR BLOCK LISTS ARE SECRET, AS ARE THE METHODS THEY USE TO CREATE THE LISTS!!!
3. Similar filtering software has actually blocked political speech in the past, even the Democratic party web site, and probably still is now. It's hard to tell, because simply probing a filter to determine what it blocks and publishing the results is apt to bring a lawsuit for "revealing trade secrets." OTOH, the filter vendors assume no responsibility for improperly blocking a site -- since they won't even reveal their blocking criteria, it's hard to prove they f'd up...
So what would be acceptable filtering? I can see two approaches:
--Open source filtering: your block list is open to public inspection. Of course, you'll have a hard time making money off of selling that list, since anyone can just download it and feed it into their server themselves, so it might be hard to get the staff needed to keep up with thousands of new porn sites an hour. (Not that the commercial vendors seem to be doing much better.) And you'll have teenagers downloading the list and trying to visit every site on it. (Keeps them off the streets. 8-)
Government certification: The filter software will be checked out by bureaucrats, who will do just as thorough a job as the Aussie patent officials that approved a patent for the wheel, or the INS officials who rubberstamped Mohammed Atta's application for a student visa so he could learn to fly airliners into buildings. And, in the everchanging world of the internet, the job will be done with the promptness of that gov't contractor who mailed out the approval five months after Atta became the world's most famous dead terrorist...
Private Certification: Congress _could_ write the law so vendors would certify themselves as complying with the law and the Constitution, notify each blocked site that they were doing so, and stand exposed to lawsuits from anyone they blocked wrongly. "Blocked wrongly" meaning that the blockage violates either the 1st Amendment or standards published by the vendor. Let's set the penalty at a minimum of $10,000/day + legal fees and court costs, or actual damages if higher.
I don't think it would be a good idea to allow lawsuits for mistakes the other way, because it seems to be utterly beyond anyone's capability to even come close to identifying all the porn sites. Well, maybe there could be a suit if redhotsluts.xxx stayed unblocked for over six months... I'd suggest just putting in a truth in advertising provision; if the vendor's sales materials clearly say the filter will allow much but not all porn through, and it does block _some_ porn, then you can't sue because it didn't block everything, but if their ads claim the filter is effective, then they get sued for every bare tittie that gets through the PG setting...
Don't you just love giving businessmen a choice like that: tell the truth ("this don't work") and get no sales, or lie and get sued into bankruptcy. 8-)
And finally, of course the libraries cannot be required to install a filter until at least three competing companies have self-certified their filters as both non-infringing on free speech and effective, and are selling them low enough to be within the library budgets. Maybe in 50 years, AI will have advanced to the point that someone can actually make that certification and not lose about a $million per copy sold to lawsuits. (HAL can visit 9,000 sites a second, and if he gets a virtual erection, on the list it goes...)
No no, if it's down, it could simply be Slashdot affecting it. But notice that slashdot itself must be getting at least one hit for every hit on a slashdotted site, so it's certainly possible to handle the traffic -- with the right setup. Do you mean to say that M$/Unisys didn't provide for their site becoming "popular"? Or that you just can't make use Windoze servers take the traffic?
Write software that coexists well with open-source free software, and is enough better to be worth paying for. (end joke for the day)
But if you are a multi-billion company that finds just writing software that _works_ to be a major challenge nowadays, you have to find a more, errrrr, creative solution, such as:
1. Lie a lot. Spread the FUD widely and deeply with massive advertising campaigns. Hope no court ever holds you accountable for advertising high reliability in your server software, when your "server" software is actually barely reliable enough for the corporate desktop...
2. Send lots of b^r^i^b^e^s campaign contributions to Congress and try to get laws passed making it difficult to legally write open source. Form an alliance with Disney, which appears to own at least two senators...
3. Cash in your stock before the Wall Street morons figure out that your company is doomed. (Well, not really doomed. Worst case MSFT will still sell some $billions/year to businesses that have locked themselves into MS proprietary data formats so it takes 10 years to convert -- it's just that it takes some $hundred billions/year of sales to justify the present stock price. I'm not a stock analyst, but IMO the present price seems to assume that next year every starving Chinese peasant will somehow come up with enough money to buy a genuine Windows CD as a wall ornament -- they don't have power and can't afford batteries so what else would they do with it?)
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And 19th century royalty dined off of aluminum plates. It was more expensive than gold...
Did the Salon article have the nerve to point out that the real problem here is the academic critics' unwillingness to ever admit that reading a story is just fun? That's the basic reason SF is not even on most critics' radar. Of course, half of what they do talk up is worse than decent SF, and Homer and Shakespeare are worse than most _bad_ SF -- but they're old so they're OK...
Anyone here welded titanium? I wasn't a welder in the Air Force, and it was a long, long time ago, but IIRC the metal shop had to drag out all sorts of gear if welding Ti was necessary. I think you have to flood the weld area with nitrogen because its ignition temperature in air is lower than the melting temperature. Of course, you need something much hotter than the normal welding torch. Then you get the weld done and need to grind down the excess bead -- and as hard as Ti is, that's going to take some time.
But it's mighty durable once it's together.
read what they are working on/testing before you make a knee-jerk reaction to a success or failure. I'd agree, IF the starwarites had been honest about what their success meant. Namely that their guidance system works, and they haven't even started the detection system tests. Yes, to hit a bullet with a bullet is a hell of a good guidance system, even when the target bullet is broadcasting it's location. But this rather points up how far they have to go yet -- do you think detection systems are going to be easier?
A "kinetic kill vehicle" could be designed to be quite effective against ground targets. That is, a chunk of tungsten big enough to re-enter without burning much metal off, with a guidance system that will work all the way to the ground. (Jerry Pournelle calls such a weapon a "crowbar", see Footfall for instance. It really isn't much more than a crowbar with fins, once you work out how to shield the video camera or radar and CPU so they'll survive re-entry and guide it into the target.) This is quite a lot different from a KKV for space, where most targets would be destroyed simply by colliding with an unshielded guidance system and empty rocket motor; if you need a "payload" at all, its probably just a few ounces of hard metal to punch through no more than 1/4" of armor. OTOH, the space-space KKV needs high-velocity propulsion to intercept its target, while the crowbar needs only enough rocket power to drop out of orbit, or possibly will be launched by catapult with no retrorockets.) A dense object dropping from orbit is going to be going a few thousand meters per second at impact, so its kinetic energy probably exceeds the energy in an equal mass of TNT. I expect a fifty-pounder (25 kilo) would leave a house-sized crater; a considerably smaller one could punch through the top armor of a tank, if the terminal guidance is good enough to hit a moving and possibly camoflauged target. And the guidance issue is just electronics and programming -- if you can't do it now, wait a few years and Moore's law will make it possible.
;-)
Of course, right now putting that 50 pound crowbar into orbit costs something like half a million dollars. You can fly a lot of airstrikes for that much. OTOH, to drop a bomb on Saddam Hussein we would have to fight his Air Force, and even if we didn't lose any people we'd almost certainly get several multimillion dollar fighters bunged up. Maybe instead, we crowbar Saddam's limo, crowbar his successor, and so on until we get someone reasonable... That's if Bush doesn't mind setting a for precedent for everyone who has a beef with the US sending assassins after the US president. (I certainly wouldn't mind that, considering the sort of people we've had running for president the last 50 years, but I'm not sitting in the hot seat.
If Lucas claimed he based StarWars on westerns and war movies, he was already lying then. He's compounding it now by letting this university idiot draw a direct line between the ancient mythic sources and StarWars, ignoring the many SF authors that explored mythic themes, whose work Lucas "sampled". The Jedi Knights are Lensmen, not Gary Cooper or John Wayne lawmen and soldiers, and certainly not Greek heroes. Tatooine is more like Dune than the American Southwest, or even the Sahara desert. Coruscant is like nothing at all in myth or non-futuristic fiction, but it certainly resembles Trantor.
Why overanalyze it? It just ruins it.
I doubt that anyone with more than a passing acquaintance with written science fiction would want to over-analyze Star Wars. It's bloody obvious. Tatooine = Dune. Coruscant = Trantor = Rome. Jedi Knights = Lensmen. Luke = the callow kid starring in 90% of SF...
The thing is, somehow this Joseph Campbell (not to be mistaken for the great magazine editor of the "Golden Age") won't admit to ever reading anything just for fun in his whole life, and so is unaware of all the SF stories Lucas "sampled". Instead, he goes back to the ancient myths -- which are the same sort of stories as bad SF writing, but age has made them academically respectable. And Lucas suddenly discovers his work becoming respectable among the snooty crowd, and is lapping it up...
No, what he needs (and no doubt he is aware of it), is a better pump. Also proper tubing fittings, hose clamps, baffles inside the waterblock to direct the flow so all of it gets cooled, ears on the block to attach spring-clip heatsink holders, and so on. But the cheap 10-minute pump is good enough for checking out whether he's on the right track -- and he claims his budget was 77 pence, which I think is about $1 US. Aquarium pumps run continuously and aren't too expensive, but on that budget you use what you already have...
;-) Copper is resistant to corrosion and has the second highest heat transfer rate (by volume) of any material available in bulk. Gold is better and aluminum is worse on both counts. When aluminum is used instead of copper, they are trading off a little effectiveness for considerable savings in cost and weight; if you are using water, weight better not be an issue, and for a do-it-yourself project you'd spend a lot more trying to solder aluminum than copper will cost...
I do hope that he used thermal grease -- the article doesn't say one way or the other, but even a perfect heat sink can't cool well if the heat has trouble getting _to_ it.
One thing that did kind of bother me: "Although it seems that copper would be best suited for making a water block, I'm not entirely convinced without physical proof." It scares me that anyone who has to ask would be doing this! Copper is indeed the best material, unless you are on a NASA cost plus 10% contract, then use gold and increase your profit.
Water is the optimal coolant, when only physical properties are considered. It's reasonably low viscosity (easy to pump), and has an extremely high heat capacity. The only problems are that it is rather corrosive and electrically conductive, so leaks are really bad news, but the heat capacity is so much higher than most non-conductive fluids that engineers will often pick it anyhow. Other choices: Oil will take a stronger pump, thicker tubing, and bigger radiator, because you have to move more fluid at higher viscosity. Certain chloroflourocarbons are good enough at cooling and entirely safe to spill on live electronics, but they're also pretty much illegal nowadays. And distilled water is much cheaper than any alternative fluid...
Although I appreciate one moderator's recognition of my attempt to be funny, IMO sien's post was much funnier...
Unless, possibly, said books were found open, and highlighted, on the table of said drug lab... One book was still in it's wrapper and the police lab determined that neither had been read.
OTOH, the books were found in the bedroom where methamphetamine had been manufactured. One reason the police wanted the records was to get additional evidence as to which of the four people living in the trailer house were sleeping in that bed.
And on the gripping hand, the appellate court noted a number of curious gaps in the evidence, according to the records. There may have been more books in that room, but only two were seized -- and that choice was obviously content based. (The books were about synthesizing drugs.) The books and the laboratory glassware had been dusted for prints, but the court record did not show the results. The justices seem inclined to assume that the police hadn't put the results in the record for the subpoena case because they would have shown who was running the lab clearly enough to make the book purchase records unnecessary...
The simulation is reasonably accurate because they are staying with areas that are already well described by current theories, confirmed by all the real nukes we've detonated. They are not trying out new reactions. Probably they are not even trying out new bomb designs. Mostly, they are just looking at how 20 or 30 years of aging (allowing a small part of the fissionable U235 or Plutonium to decay) will affect the nuclear reaction, to determine the point at which existing bombs will _have_ to be recycled.
The only real option for actual explosions now is to set off undersized bombs deep underground. That gives valuable data too, but it's hardly better at predicting actual weapons performance than the simulations. (Of course, Saddam may yet "volunteer" a part of Iraq for a live aboveground test...)
"People dye" means they change color. Although being near ground zero would be apt to cause various color changes (probably ending in black & crispy), perhaps you meant "die"?
Sorry, but there is very broad class of simulations where distributed computing across the internet is not going to help, called Finite Element Analysis. I don't know the specifics of nuclear explosion simulations, but the basic setup is similar to simulations of electromagnetic fields, mechanical stress and strain, heat transfer, the weather, etc. You divide the volume of interest up into lots of little cells (the "finite elements"). For a cell, you determine how conditions in a cell are influenced by influenced by neighboring cells, as well as the pre-existing condition of the cell. You code those equations into a program, and it cycles through all the cells to calculate the next state (one time tick later), then repeats until done.
) +T0(x,y,z-1)+T0(x,y,z+1))/6. You need special forms of this equation for cells at the edges. You write _for_ loops to cycle through all the cells and an outside _for_ loop to step through the time ticks -- or you might use a pre-written simulation program where you just have to plug in the cell geometry and the equations. Nuclear simulations must be considerably more complicated: it would require several variables tracking temperature, local concentrations of reacted and unreacted materials, radiation density, etc., and equations tracking how materials, flow in and out of the cells, among other things.
For instance, in a heat transfer simulation, the temperature of a cell changes from the initial temperature towards the average temperature of neighboring cells at a rate determined by the thermal conductivity of the material: T1(x,y,z) = (1-k)*T0(x,y,z) + k*(T0(x-1,y,z)+T0(x+1,y,z)+T0(x,y-1,z)+T0(x,y+1,z
But the point is, even at the most complicated, the calculations for one cell at one time tick are only going to take a few microseconds on a decent CPU. If you parallelize it by assigning one CPU to a cell, the CPU will do the calculations, then it will have to exchange data with all the other CPU's. The communications requirements can be met only by providing lots of direct dedicated CPU-CPU, or CPU-memory-CPU links. That is, it takes custom hardware. Try to do it through any kind of shared bus, and the comm bandwidth will severely limit the number of CPU's that can be actually used. Don't even think of trying to use the internet with latencies of seconds, and bandwidths of 56KHz to a few MHz.
This is bad news, not for DOE who have the money to build that custom hardware (and would have to keep their bomb secrets in-house anyhow), but for all the engineers and scientists who would love to have thousands of computers crunching their data for free, but their equations aren't suitable for it. For SETI@home, I think each computer gets a module consisting of one piece of recorded data and a batch of tests to be run against it; the modules do not have to communicate in between setup and completion, so little bandwidth is needed. It's great when it works, but we only know how to divide up big computing jobs completely like that for a few special cases.
The basic issue is changing requirements. A contractor building high-rise apartments does not have to worry about the customer coming around when it's half built to look at it and say, "You know, I think I want a hospital instead." Programmers quite often have to deal with customers that are just about that confused -- they can't begin figuring out what they really want until they see what they asked for on the screen.
More than that, software vendors routinely write a program, release it, then add features so they can sell it again. It's as if the builder has finished the apartment building, and now they want a factory tacked onto the north side and a Wendy's onto the east. Next year, add a hospital wing to the west. Repeat once a year for 10 years and you get one hell of a mess, but how else would M$ keep a continuing revenue stream from the same OS and Office programs?
OS/360 was actually heading over a cliff. The various pieces of software did not work when they were put together. The OS was delivered years late and massively over budget. Many IBM 360's (costing six figures back when $1 was worth something) were delivered and then spent years simply running emulators for the old machines they replaced, because the native software wasn't ready.
Yes, there were lots of things they could have done -- like define a subset of the original committee-designed bloated specification, get that working, then start adding features. But the manager (Fred Brooks) didn't know that, yet, and didn't even know the project was in trouble until it was impossible to deliver anything at all on deadline. Afterwards, he wrote a book, The Mythical Man-Month, which has become a standard text for large-project management. But he learned how by doing it wrong, more massively than anyone ever had before...
If you've got the requirements well enough defined in terms of previous work that you can estimate accurately, then most likely all you've got to do is cut and paste the old code anyhow...
proofs are as much a social event as a mathematical cedrtainty.
You are going a bit too far. Proofs do require a social activity before they are accepted, namely rigorous checking by a number of other mathematicians. But most proofs have survived such checking as to be mathematical certainties -- within a given system of axioms.
For instance, the Pythagorean theorem has a simple one page proof that has been reviewed by every mathematics student for over 2,000 years, and no flaw has been found. It's certain -- within Euclidean geometry. It also is known to have limited real-world applicability: it won't be exact for right triangles drawn on the curved surface of the earth, nor (according to General Relativity theory) will it be exact for large triangles in space. But it's close enough for most surveying work, and more than close enough for machine shop work.
On the other extreme, there is the computer-generated proof of the 4-color theorem. IIRC, one mathematician could not read the whole proof in a lifetime. Merely understanding how they formulated the problem into a computer program will take up more of your life than most people want to spend on a single abstract problem. Certain computer bugs can be ruled out by re-compiling the program for different computers and comparing results, but the real question is whether the program is correct -- and apparently mathematicians who have reviewed it think it is correct, with a lot higher probability than is needed to execute a man in Texas, but not everyone agrees it is _proven_.
And what's the real-world applicability? In theory a mapmaker could get along with just 4 colors, but it's easier and clearer to use more...
The Bering Strait is ice-covered, but IIRC it's never really solid. The currents are too strong, so the ice keeps moving, in the form of lots of solid slabs grinding together. The trick is not to fall into the cracks between floes and not to get tipped over by the ridges, etc., raised by collisions between floes. A really big "snowmobile" would help with the first two problems, but it can't be too big or you'll run the risk of smaller floes sinking under the weight.
Also, there's the problem of navigating on floes that are drifting at several mph. Does GPS work well up there? The worst navigation error would be to wind up on a floe drifting away from the rest.
You mean "thinner", not "flatter".
From the article (2nd page): "To vary the transmission of light through color filters, LCDs use magnetic fields to twist particles floating in a liquid--an inherently less precise process."
No, LCD's use electric fields. CRT's use magnetic fields to focus and scan the beams. Why do tech-oriented mags hire technical idiots?
If a community decides that it wants its libraries to use filtering software
1. Communities are one thing, Congress is something different. Constitutionally, Congress's regulatory power is _supposed_ to be very much more limited than states and localities. If that Red/Green map bandied about after the 2000 election means anything, it's that different parts of the USA have quite different community standards... If you want to put filtering software into your local library, run for the library board on that platform, don't try to impose your desires everywhere.
2. The actual standards used in commercial filtering software are not set by community standards, or even by Congress, but rather by the software vendors. AND THEIR BLOCK LISTS ARE SECRET, AS ARE THE METHODS THEY USE TO CREATE THE LISTS!!!
3. Similar filtering software has actually blocked political speech in the past, even the Democratic party web site, and probably still is now. It's hard to tell, because simply probing a filter to determine what it blocks and publishing the results is apt to bring a lawsuit for "revealing trade secrets." OTOH, the filter vendors assume no responsibility for improperly blocking a site -- since they won't even reveal their blocking criteria, it's hard to prove they f'd up...
So what would be acceptable filtering? I can see two approaches:
--Open source filtering: your block list is open to public inspection. Of course, you'll have a hard time making money off of selling that list, since anyone can just download it and feed it into their server themselves, so it might be hard to get the staff needed to keep up with thousands of new porn sites an hour. (Not that the commercial vendors seem to be doing much better.) And you'll have teenagers downloading the list and trying to visit every site on it. (Keeps them off the streets. 8-)
Government certification: The filter software will be checked out by bureaucrats, who will do just as thorough a job as the Aussie patent officials that approved a patent for the wheel, or the INS officials who rubberstamped Mohammed Atta's application for a student visa so he could learn to fly airliners into buildings. And, in the everchanging world of the internet, the job will be done with the promptness of that gov't contractor who mailed out the approval five months after Atta became the world's most famous dead terrorist...
Private Certification: Congress _could_ write the law so vendors would certify themselves as complying with the law and the Constitution, notify each blocked site that they were doing so, and stand exposed to lawsuits from anyone they blocked wrongly. "Blocked wrongly" meaning that the blockage violates either the 1st Amendment or standards published by the vendor. Let's set the penalty at a minimum of $10,000/day + legal fees and court costs, or actual damages if higher.
I don't think it would be a good idea to allow lawsuits for mistakes the other way, because it seems to be utterly beyond anyone's capability to even come close to identifying all the porn sites. Well, maybe there could be a suit if redhotsluts.xxx stayed unblocked for over six months... I'd suggest just putting in a truth in advertising provision; if the vendor's sales materials clearly say the filter will allow much but not all porn through, and it does block _some_ porn, then you can't sue because it didn't block everything, but if their ads claim the filter is effective, then they get sued for every bare tittie that gets through the PG setting...
Don't you just love giving businessmen a choice like that: tell the truth ("this don't work") and get no sales, or lie and get sued into bankruptcy. 8-)
And finally, of course the libraries cannot be required to install a filter until at least three competing companies have self-certified their filters as both non-infringing on free speech and effective, and are selling them low enough to be within the library budgets. Maybe in 50 years, AI will have advanced to the point that someone can actually make that certification and not lose about a $million per copy sold to lawsuits. (HAL can visit 9,000 sites a second, and if he gets a virtual erection, on the list it goes...)
I think he means that techs are Einsteins "relative" to the management.
My dog is an Einstein relative to the management...
No no, if it's down, it could simply be Slashdot affecting it. But notice that slashdot itself must be getting at least one hit for every hit on a slashdotted site, so it's certainly possible to handle the traffic -- with the right setup. Do you mean to say that M$/Unisys didn't provide for their site becoming "popular"? Or that you just can't make use Windoze servers take the traffic?
Write software that coexists well with open-source free software, and is enough better to be worth paying for.
(end joke for the day)
But if you are a multi-billion company that finds just writing software that _works_ to be a major challenge nowadays, you have to find a more, errrrr, creative solution, such as:
1. Lie a lot. Spread the FUD widely and deeply with massive advertising campaigns. Hope no court ever holds you accountable for advertising high reliability in your server software, when your "server" software is actually barely reliable enough for the corporate desktop...
2. Send lots of b^r^i^b^e^s campaign contributions to Congress and try to get laws passed making it difficult to legally write open source. Form an alliance with Disney, which appears to own at least two senators...
3. Cash in your stock before the Wall Street morons figure out that your company is doomed. (Well, not really doomed. Worst case MSFT will still sell some $billions/year to businesses that have locked themselves into MS proprietary data formats so it takes 10 years to convert -- it's just that it takes some $hundred billions/year of sales to justify the present stock price. I'm not a stock analyst, but IMO the present price seems to assume that next year every starving Chinese peasant will somehow come up with enough money to buy a genuine Windows CD as a wall ornament -- they don't have power and can't afford batteries so what else would they do with it?)