This is a well studied problem. I work on (time homogeneous) Maxwell's equations and we use finite elements successfully with variable coefficients. Peter Monk's book, "Finite Elements for Maxwell's Equations" has some good details. However, this is probably a more complicated problem that you want.
I don't have any good references to hand, but for the plain old wave equation (time inhomogeneous and homogeneous) you could try looking at discontinuous Galerkin methods. Depending on the inhomogeneity in your coefficients, you might be able to use a Godunov scheme. Your local friendly applied mathematics professor specialising in numerical methods for PDEs should be able to tell you more.
If you're interested in contemporary research, there are plenty of conferences on this kind of stuff. Here's a recent one.
Such a theorem does exist and is proven! Arrow's Theorem states that it's impossible to design a voting system that satisfies three really basic conditions:
a) The removal of one candidate from the race would not affect the rank of the others;
b) If everyone prefers candidate A to candidate B then the algorithm should rank A above B;
c) There is no dictator (i.e. there's more than one person voting).
The same criteria should also apply to a perfect search engine - the removal of one page from the web should not affect the relative ranking of the others, if everyone thinks page A is better than page B, page A should come first and, to be practical, the engine should take as input the priorities of more than just one person (it's not feasible to build a customized search engine that knows exactly the priorities of each individual user).
Therefore, a perfect search algorithm does not exist
Deaf kids can learn to read and write a (version of a spoken) language. Generally, they learn it slower than hearing kids. There is a big debate in deaf education about whether you teach kids a spoken language first (so that they can integrate with hearing society) or whether you teach them in sign language (because it's a more natural language when you can't hear and so kids learn other things faster). My own view is that there's no reason not to use both - there are plenty of children in bilingual families that demonstrate that learning two languages when you're young doesn't really inhibit your ability to learn either of them.
But, I think that's all a little irrelevant to the value of this technology. When it comes down to it, a lot of deaf people find that the most natural type of communication for them to use is a sign language. I think this makes sense: it's visual, it's fast, it's full-duplex (with no lag) and it allows for expressiveness that you don't get in text (or at least that you don't get so easily) - interruptions, hesitations, quizicallity. Think of all the different sentiments that the word "yeah" can take on in spoken language and how you'd express them in text.
So sign languages are here to stay (even when they're not taught in schools, they often emerge spontaneously among communities of deaf people) and they will continue to be the first language for many people. It's great that this technology might allow people to communicate using it over long distances with the convenience that we can communicate using spoken languages.
With the appropriate authority, the police can do things that your everyday hacker on the street might find very difficult, e.g. gain physical entry to Downing Street, so there's no reason that there would be a gaping hole waiting for black-hats to enter through.
There are several organisations in the UK that regularly do IT security work for the ministry of defence, the police and the security services and have staff who are cleared to high security levels. I worked for Detica about 10 years ago and I think that they would have had the capability to assist in this kind of thing then, don't know if they still do. Qinetiq might be another firm that would have people with relevant expertise.
... and, now that I've read the article more carefully, it seems like what Cringely's talking about solves that problem in a novel way. Rather than fighting the fluid dynamics (by making the arm stiffer), it seems that they exploit it:
"...the flexible metal foil yields to the head, pushed away by a layer of compressed air, rather than being struck by it."
My guess is that, at least for data centre applications, the power saving he claims for this design does not come from the lower mass of the platters (which would only matter if you're spinning up and down a lot), but from the decreased drag due to smaller arms.
Turbulence isn't created by dust, it's a feature of the non-linearity of the Navier Stokes equations.
The arm holding the read/write head sits in the middle of what would otherwise be a nicely rotating flow between the platters. The Reynolds number for flow between platters in a disk drive is going to be something like 30 m/s * 0.001 m / 2E-5 m^2/s = 1500 >> 1, so vortices will be shed off the back of the arm. Which basically means turbulence.
Incidentally, this is currently one of the limits to increasing disk drive performance per watt. The arm also creates drag, which you'd like to minimise. To do that, you make the arm as thin as possible. However, the thinner you make it, the less stiff it is. Too thin and it will deform too much because of the vortex shedding and get too close to the platters.
Maybe it would help if you actually saw a calendar. In England, September 15 1752 (2 days after the change) was a Friday. If you failed to take into account the calendar change then you'd expect that September 1 was also a Friday. But it wasn't. It was a Tuesday. So the calendar change changed which day of the month the Fridays fall on.
It depends on the frame of reference, i.e. if by "when the Fridays are" I meant periods of seconds before or after epoch then you're right. If by "when the Fridays are", I meant "which days of the month Fridays fall on", then I'm right. Since the context clearly points to the second interpretation, I'm right:-).
No it wasn't. Read your documentation: "the current Gregorian calendar indefinitely extended in both directions". So your code is invalid pre-1582 (and even later if you consider that not every country adopted it immediately).
Never ask a computer scientist to do the job of an historian?
nanotechnology, the emerging science of harnessing sub-microscopic organisms for everyday use
And I should pay any attention to the rest of the article because...?
For what it's worth, the article also claims that the:
paint relies on the wizardry of nanotechnology to create a system that locks out unwanted cell phone signals on demand
This would be remarkable and is not true. Actually (from later on in the article), the company will:
combine this signal-blocking paint scheme with a radio-filtering device that collects phone signals from outside a shielded space, allowing certain transmissions to proceed
Which still sounds useful, but is a lot less exciting.
The occassional decent comedy (and they are VERY occasional) does NOT justify the £100+ we are expected to pay...
Lets suppose that you watch 10 hours of TV per week and half of that is spent watching BBC channels. If the BBC was commercially funded then 25% of that time would be taken up by adverts. So that's 63 hours of adverts per year that you're missing out on. How much would I have to pay you to watch 63 hours of adverts? I imagine that it would be significantly more than 100UKP.
Okay, so maybe you like some adverts or you don't watch that much BBC or you have a DVR and skip the ads anyway, but for the vast majority of television watchers in the UK, the 100UKP+ almost certainly is justified by comparing it to what the alternative is.
"It's got to be a site that's meaningful from an astrological point of view, but we don't want it to be in place that's so hostile that scientists and people won't go there," Halliday said.
And in order to make a GUI test, it's hard to think of the logistics. How exactly is it wrong if a control is one pixel down, or if it doesn't use the right layout
Kurt Vonnegut is a novelist. My top recommendation for a book to read by him would be Slaughterhouse Five. It's an account of the fire bombing of Dresden (which he witnessed, as a US soldier) near the end of World War II. Fantastic prose. So it goes.
To combat this, and see how it performed out of orbit, could it not have been launched from orbit?
RTA. It is launched from orbit. A Volna rocket (plus some other bits and pieces) places the spaceship in orbit, where it will sit for a few days before the sail is deployed.
What's more, you might want to think about what being "out of orbit" actually means. The moon is in orbit around the earth. I expect that if they got it that far (or to the same gravitational potential), they'd be very pleased with themselves. Although given that it's an experimental craft it might be more useful to them if they kept it closer.
There's the use of Hashtable; the non-thread-safe singletons; the traversal of the entire lists in ValidValuesTable.getOption; the unnecessary storing of the options and values string-arrays; the failure to pre-size the ArrayList; the fact that DropDownItems aren't immutable and, my favourite (repeated several times throughout the code):
private void loadStatusList() { Hashtable obj_Hashtable = new Hashtable(); ListValuesDAO listValuesDAO = new ListValuesDAO(); obj_Hashtable = listValuesDAO.getListValues("STATUS"); ...
I hope that IBM Global Services' QA for products is better than their QA for developerworks articles.
Re:No, that's just good compression
on
Apple Easter Egg
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· Score: 1
Oh dear.
I know I can't really complain given my GP comment, but at least I recognised that what I said made me sound like a twat.
Re:That's one big ass easter egg
on
Apple Easter Egg
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· Score: 1
shit, I guess I might be wrong, ignore me... I should have waited to download it before I commented.
Re:That's one big ass easter egg
on
Apple Easter Egg
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· Score: 0
It's the MOV file showing the easter egg that's 91Mb.
Back in 1994, Schumacher came second in Barcelona with his car stuck in fifth gear for three quarters of the race.
Undoubtably cars have improved since then, but it's a good indication of the difference a great driver can make. It doesn't matter how fast the car is, you've still got to take the right path around the corner to exit it as fast as possible.
Slashdot Mirror
I don't have any good references to hand, but for the plain old wave equation (time inhomogeneous and homogeneous) you could try looking at discontinuous Galerkin methods. Depending on the inhomogeneity in your coefficients, you might be able to use a Godunov scheme. Your local friendly applied mathematics professor specialising in numerical methods for PDEs should be able to tell you more.
If you're interested in contemporary research, there are plenty of conferences on this kind of stuff. Here's a recent one.
Talking of bad science, here are Ben Goldacre's comments. And here is also a copy of the original paper (30 double-spaced pages) so that you can judge for yourself.
Ah background checks. Yes, they clearly work really well.
a) The removal of one candidate from the race would not affect the rank of the others;
b) If everyone prefers candidate A to candidate B then the algorithm should rank A above B;
c) There is no dictator (i.e. there's more than one person voting).
The same criteria should also apply to a perfect search engine - the removal of one page from the web should not affect the relative ranking of the others, if everyone thinks page A is better than page B, page A should come first and, to be practical, the engine should take as input the priorities of more than just one person (it's not feasible to build a customized search engine that knows exactly the priorities of each individual user).
Therefore, a perfect search algorithm does not exist
But, I think that's all a little irrelevant to the value of this technology. When it comes down to it, a lot of deaf people find that the most natural type of communication for them to use is a sign language. I think this makes sense: it's visual, it's fast, it's full-duplex (with no lag) and it allows for expressiveness that you don't get in text (or at least that you don't get so easily) - interruptions, hesitations, quizicallity. Think of all the different sentiments that the word "yeah" can take on in spoken language and how you'd express them in text.
So sign languages are here to stay (even when they're not taught in schools, they often emerge spontaneously among communities of deaf people) and they will continue to be the first language for many people. It's great that this technology might allow people to communicate using it over long distances with the convenience that we can communicate using spoken languages.
With the appropriate authority, the police can do things that your everyday hacker on the street might find very difficult, e.g. gain physical entry to Downing Street, so there's no reason that there would be a gaping hole waiting for black-hats to enter through.
There are several organisations in the UK that regularly do IT security work for the ministry of defence, the police and the security services and have staff who are cleared to high security levels. I worked for Detica about 10 years ago and I think that they would have had the capability to assist in this kind of thing then, don't know if they still do. Qinetiq might be another firm that would have people with relevant expertise.
... and, now that I've read the article more carefully, it seems like what Cringely's talking about solves that problem in a novel way. Rather than fighting the fluid dynamics (by making the arm stiffer), it seems that they exploit it:
"...the flexible metal foil yields to the head, pushed away by a layer of compressed air, rather than being struck by it."
My guess is that, at least for data centre applications, the power saving he claims for this design does not come from the lower mass of the platters (which would only matter if you're spinning up and down a lot), but from the decreased drag due to smaller arms.
Turbulence isn't created by dust, it's a feature of the non-linearity of the Navier Stokes equations.
The arm holding the read/write head sits in the middle of what would otherwise be a nicely rotating flow between the platters. The Reynolds number for flow between platters in a disk drive is going to be something like 30 m/s * 0.001 m / 2E-5 m^2/s = 1500 >> 1, so vortices will be shed off the back of the arm. Which basically means turbulence.
Incidentally, this is currently one of the limits to increasing disk drive performance per watt. The arm also creates drag, which you'd like to minimise. To do that, you make the arm as thin as possible. However, the thinner you make it, the less stiff it is. Too thin and it will deform too much because of the vortex shedding and get too close to the platters.
Maybe it would help if you actually saw a calendar. In England, September 15 1752 (2 days after the change) was a Friday. If you failed to take into account the calendar change then you'd expect that September 1 was also a Friday. But it wasn't. It was a Tuesday. So the calendar change changed which day of the month the Fridays fall on.
Your move. Fool.
It depends on the frame of reference, i.e. if by "when the Fridays are" I meant periods of seconds before or after epoch then you're right. If by "when the Fridays are", I meant "which days of the month Fridays fall on", then I'm right. Since the context clearly points to the second interpretation, I'm right :-).
Jan. 13, 1520 was a tuesday
No it wasn't. Read your documentation: "the current Gregorian calendar indefinitely extended in both directions". So your code is invalid pre-1582 (and even later if you consider that not every country adopted it immediately).
Never ask a computer scientist to do the job of an historian?
I think that the point of the GP is that it changes when the Fridays are.
And I should pay any attention to the rest of the article because ...?
For what it's worth, the article also claims that the:
paint relies on the wizardry of nanotechnology to create a system that locks out unwanted cell phone signals on demand
This would be remarkable and is not true. Actually (from later on in the article), the company will:
combine this signal-blocking paint scheme with a radio-filtering device that collects phone signals from outside a shielded space, allowing certain transmissions to proceed
Which still sounds useful, but is a lot less exciting.
Lets suppose that you watch 10 hours of TV per week and half of that is spent watching BBC channels. If the BBC was commercially funded then 25% of that time would be taken up by adverts. So that's 63 hours of adverts per year that you're missing out on. How much would I have to pay you to watch 63 hours of adverts? I imagine that it would be significantly more than 100UKP.
Okay, so maybe you like some adverts or you don't watch that much BBC or you have a DVR and skip the ads anyway, but for the vast majority of television watchers in the UK, the 100UKP+ almost certainly is justified by comparing it to what the alternative is.
You mean the Big Bang Burger Bar then.
"It's got to be a site that's meaningful from an astrological point of view, but we don't want it to be in place that's so hostile that scientists and people won't go there," Halliday said.
I expect that he didn't.
The parent is referring to a GUI to run the tests, not a test to test a GUI.
Kurt Vonnegut is a novelist. My top recommendation for a book to read by him would be Slaughterhouse Five. It's an account of the fire bombing of Dresden (which he witnessed, as a US soldier) near the end of World War II. Fantastic prose. So it goes.
RTA. It is launched from orbit. A Volna rocket (plus some other bits and pieces) places the spaceship in orbit, where it will sit for a few days before the sail is deployed.
What's more, you might want to think about what being "out of orbit" actually means. The moon is in orbit around the earth. I expect that if they got it that far (or to the same gravitational potential), they'd be very pleased with themselves. Although given that it's an experimental craft it might be more useful to them if they kept it closer.
I know I can't really complain given my GP comment, but at least I recognised that what I said made me sound like a twat.
shit, I guess I might be wrong, ignore me ... I should have waited to download it before I commented.
It's the MOV file showing the easter egg that's 91Mb.
... and quickly close again after they RTFA.
"...it's physically a regular Apple Mac, although it obviously only runs Linux..."
Undoubtably cars have improved since then, but it's a good indication of the difference a great driver can make. It doesn't matter how fast the car is, you've still got to take the right path around the corner to exit it as fast as possible.