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Just wanted to chime in with some notes on conditional execution:

First of all, if all you care about is single-issue non-superscalar with a relatively deep pipeline, conditional execution is probably a good idea in my experience due to the very low implementation cost. Especially if your branch prediction is lousy. However, if you are aiming for high-end systems conditional move may not be that big of a deal. See for example the following analysis from Linus Torvalds regarding cmov: http://yarchive.net/comp/linux... where it can be seen that cmov is basically a win only if you have situations where a branch predictor wouldn't do a good job. However, it may still be a good idea to keep some sort of conditional instruction around since it is likely to be useful if you are dealing with for example lossless compression/decompressions since you are typically dealing with unpredictable data in this case.

I could also chime in with an interesting tidbit from ARM1. Conditional execution was probably a really big deal here since the ARM1 didn't have any caches. It did however have support for burst reads from memory. As long as it was fetching instructions sequentially it could basically sustain a very high instruction throughput. A branch would however reduce the performance significantly since the burst had to be aborted. Conditional execution could be done while maintaining the burst however. This is one of the reasons why ARM1 with about 30000 transistors was competitive in performance with for example the 68020 which had close to 200000 transistors. If the ARM instruction set was designed today however it is likely that the designers would not go crazy with conditional execution since the bits could be better used for something else.

They can publish the modifications (and I believe they already do)

OP claimed they did not need to release the modifications source at all

but they do not have to release source code of the binary blob that is embedded in the code.

Not neciscarily according to the guy whos name is on the kernel.
http://yarchive.net/comp/linux/gpl_modules.html/
http://linuxmafia.com/faq/Kernel/proprietary-kernel-modules.html/

A bit like Nvidia has a part open code that is perfectly readable, and a part that contains the binary blob (that is completely unreadable).

Nvidia releases a driver, not a modified kernel. Said binary blob has to be very careful which parts of hte kernel it twiddles

http://yarchive.net/comp/ibm_p...

Let's see what Linus said in 1999:

- Microkernels are as fast or faster.

Bzzt! Dishonest. Usually the argument goes that in theory, you can spend a lot of time speeding up a microkernel to the point where the speed difference is megligible, and then the other so-called "advantages" of microkernels will make up for the rest.

The even more dishonest answer is that you can optimize your microkernel so that it is faster than some other (productized) monolithic kernel.

Dishonest: it assumes that nothing can be done on the monolithic kernel. That's like saying "if I ate steroids for 15 years, I would be stronger than my neigbour who doesn't eat steroids, so I must be stronger".

In fact, all of the arguments about microkernels in the '90s, even L4, were that if we work hard enough, they can be almost as fast as a monokernel. Those context switches are a real killer and a monokernel needs a lot less of them.

Of course, the funny thing is, the more you argue that the kernel is doing it wrong, the more you are arguing that systemd is doing it wrong.

On modern hardware, context switching is much less costly than it was on a '386. It may be time to revisit microkernels now. Systemd would still be wrong.

Why is there a problem using drivers in a kernal, and not a problem running any non-GPL code on Linux? It aint explicitly in the license. And that is deliberate, because it is designed to be a lose as possible.

From the horse's mouth, although some might call him an ass instead ;-)
http://yarchive.net/comp/linux...

Historically, there's been things like the original Andrew filesystem
module: a standard filesystem that really wasn't written for Linux in the
first place, and just implements a UNIX filesystem. Is that derived just
because it got ported to Linux that had a reasonably similar VFS interface
to what other UNIXes did? Personally, I didn't feel that I could make that
judgment call. Maybe it was, maybe it wasn't, but it clearly is a gray
area.

Personally, I think that case wasn't a derived work, and I was willing to
tell the AFS guys so.

http://yarchive.net/comp/linux...

ZFS was clearly developed for a different operating system, and I don't think Linus would care. If he does, I'd like to see something he has written on the subject.

Unless there is a copyright holder with reason and "standing" to sue, there is no violation.

Don't let the licensing FUD scare you. Linus has publicly stated that licensing in a case that's a very near equivalent to ZFS' licensing is fine.

The anticipated problem with the license has always been on the Linux side. The license ZFS is released under doesn't in any way prohibit the ZFS code from being used in other places with other licenses (like the *BSD's). There has never been a concern that using ZFS with Linux violates the ZFS license (and thus could bring Oracle's well-fed lawyers down upon you). The contention has been that combing CDDL code with GPL-2 in a derivative work violates the GPL and thus places you in trouble with Linux's license. The core problem is that CDDL places additional restrictions on binary code resulting from derivative works, which GPL-2 prohibits.

Linus has weighed in specifically on the AFS filesystem module here: http://yarchive.net/comp/linux...

But one gray area in particular is something like a driver that was originally written for another operating system (ie clearly not a derived work of Linux in origin). At exactly what point does it become a derived work of the kernel (and thus fall under the GPL)?
[...]
Historically, there's been things like the original Andrew filesystem module: a standard filesystem that really wasn't written for Linux in the first place, and just implements a UNIX filesystem. Is that derived just because it got ported to Linux that had a reasonably similar VFS interface to what other UNIXes did? Personally, I didn't feel that I could make that judgment call. Maybe it was, maybe it wasn't, but it clearly is a gray area.

Personally, I think that case wasn't a derived work, and I was willing to tell the AFS guys so. [Emphasis added]

- Linus Torvalds on the fa.linux.kernel group, Thu, 4 Dec 2003

Given that ZFS was originally written for Solaris and the core code works essentially unmodified (with a porting layer in some cases) on Solaris, *BSD, Linux, possibly other systems, there are lots of indications that it should fall into the same category as the AFS code: The ZFS modules are not derivative works of Linux and thus may be used with Linux even though their license prevents them from being incorporated into Linux.

You've over-simplified what is & isn't a derivative work. Linus himself has written about the distinction specifically as it applied to the Andrew Filesystem:

http://yarchive.net/comp/linux...

According to Linus, a driver that was originally written independently of Linux for another system and simply ported *to* Linux is not a derivative work. That's exactly the case for what ZoL is.

You've also misrepresented what the ZFS modules do in terms of their contact with kernel internals:

touches unexported APIs of the kernel

Neither ZoL or the SPL layer that it depends on touch any non-public or GPL-only symbols of the kernel. If they did, you'd be correct in there being an issue. They don't, and there isn't.

Actually, I believe the claim is that it was which is why Nvidia ended up using a two part driver module in the early days with one being licensed under the LGPL.

I'm not sure how they do it now but I don't think they use the two part modules any more. I believe Travolds has made statements that binary only blobs in the kernel violate the GPL too as they are derivative. Actually, here is an interesting discussion concerning the linux kernel and derived works the confusion possibilities.

It can. Here is a more in-depth discussion.

The deciding factor is whether or not it is using the defined API. If so, it is mere use and not derivation.

You are wrong; if you care to understand why, Linus explains in more depth.

"Insisting on absolute safety is for people who don't have the balls to live in the real world."

One of my favorite quotes, from Mary Shafer, SR-71 Flying Qualities Lead Engineer at NASA Dryden Flight Research Center.

They probably continue to apply lessons learned long ago. Unfortunately technology screw-ups are often easier to fix than policy screw-ups, or "you have to pass the bill to see what's in it," and we can only guess what will happen.

The message to take away here is "Even a million jobs are not worth 1 human life." If you understand and live by that, you will be a better person.

If that were true no significant civil engineering project would ever be done. It is statistically normal for people to die accidentally on large projects in the real world. More generally one of the statistical disadvantages of being a man instead of a woman is a much higher likelihood of dying or being seriously injured in an industrial (i.e. job) accident.

Of course, just like your quote, "Failure is not an option" is also just something to aspire to, not reality.

Insisting on absolute safety is for people who don't have the balls to live in the real world. -- Mary Shafer, NASA

You do not just get to handwave away the threats.

And you do not get to just hand wave in threats. The numbers affected by terrorism in this country are close to non-existent compared to a hundred other more important threats.

The self serving "the sky is falling" chicken little media circus that the security agencies are running isn't helping either. The reality is that for a country of 300,000,000+ people the terrorism that is occurring or threatening to occur is in the noise. You're numerically illiterate if you think otherwise.

"Insisting on absolute safety is for people who don't have the balls to live in the real world." -- Mary Shafer, NASA risks researcher.

Well then good thing the Linux kernel isn't licensed under the GPL. It's licensed under a modified GPL allowing for binary drivers.

That's not true at all. The license is clarified to indicate that user-land programs aren't licensed under the GPL. The license modification is to make it GPL 2.0 only, not 2.0 or greater.

See here for more info. The only question is whether the driver is a derivative work or not, which is a complicated legal term which didn't have software in consideration when it was (poorly) defined.

As Henry Spencer said long ago, Skylon & every other hyperspace plane suffer from the problem where they accelerate slowly & are incapable of performing the last steps in attaining orbit without a rocket motor.

I haven't been able to find Henry's post but here's another one:
http://yarchive.net/space/launchers/space_plane.html

I think this is quite interesting.

http://yarchive.net/comp/linux/drive_caches.html

While I've often gotten the impression that the write cache opens up a large "write hole", Linus says that data is cached only for milliseconds, not held in the cache for several seconds. Still, I'd like to see battery backed caches in regular drives and/or controllers.

Would be nice to hear from some drive firmware writers.

I did a quick search, but couldn't find it. It had little details, but lacked some of the overarching story (it assumed knowledge of things that would not be obvious to an outside viewer). The story followed this line however: http://yarchive.net/mil/japanese_surrender.html

Call me a cynic, but I think everyone wised up to the fact that they weren't really buying solid gold toilet seats, so they had to find something else in the budget to fund all that black ops stuff...

The toilet seat thing was blown way out of proportion. It was a custom-molded plastic assembly for military aircraft use, and as most people here know, when you do injection molding, the initial tooling costs are very high. High setup costs + low volume = seemingly outrageous per-unit price. It's not as if they were paying $700 for the same type of toilet seat you can buy at the local Home Depot.

Clearly, whomever thought this was a Pretty Neat Idea hasn't read this:

http://yarchive.net/car/rv/generator_synchronization.html

and doesn't understand what happens when you're even a bunch of *degrees* out of sync, much less a few decihertz. We don't have *near* enough HVDC intertie to make this not matter, and I can't imaging how they think this is gonna work -- nothing at all on NERC's website to say what's *really* gonna happen, either.

Love all the warning, too.

I think the organization that's responsible for the reliability of the entire USA power grid has some idea of the need for frequency stabilization when connecting new power sources to the grid. Not that it's relevant for what they are proposing - power plants already know how to sync up their generators to the grid and they don't care if it's 60.001 Hz or 60.002 Hz, they'll take that into account.

The magnitude of this frequency deviation is tiny, 20 minutes/year is about .003% - the power grid can fluctuate much more than than on a daily basis, but until now, it's always been corrected to keep the overall frequency at 60 Hz.

Clearly, whomever thought this was a Pretty Neat Idea hasn't read this:

http://yarchive.net/car/rv/generator_synchronization.html

and doesn't understand what happens when you're even a bunch of *degrees* out of sync, much less a few decihertz. We don't have *near* enough HVDC intertie to make this not matter, and I can't imaging how they think this is gonna work -- nothing at all on NERC's website to say what's *really* gonna happen, either.

Love all the warning, too.

In terms of scale it seems like we might just be able to get away with blasting our refuse into the sun and not see any significant consequences.

Scale-wise, the Sun could probably swallow the whole Earth and get only mild indigestion. However, launching anything into the Sun is a waste of energy; it's cheaper to punt it into interstellar space, as discussed here.

Can you have a read of this first http://yarchive.net/space/exotic/tower_launch.html

Few km of height is largely insignificant,

11km of height is quite significant, I assure you.

else you would see spaceports on major highlands; a launcher works primarily horizontally, for speed - and tower could provide very little of that (remember there's a square in kinetic energy...)

The tower doesn't need to point straight up. Do take a look at this http://yarchive.net/space/exotic/tower_launch.html

In fact, we already have a launcher which does more than your fantasy could ever accomplish - Pegasus rocket (check it out). It is one the least cost efficient launchers around. Please, drop the wishful thinking.

Please learn the difference between realism and dogmatism. ;)

By the rocket equation, mass fraction is determined by velocity and exhaust velocity is driven two things; the mass of the molecules being put out and the pressure/temperature of the combustion chamber.

A rocket goes up because of the asymmetry between molecules being flung against the top of the reaction chamber while passing out the bottom. I know that the chaos in the chamber means that the best way to think about this is a pressure parameter rather than the direction of individual molecules. But I've always wanted to know whether you could make a rocket engine more efficient by using electromagnetic fields to orient the molecules in such a way that the chemical reactions are biased to have more reaction products being flung up and down rather than side to side.

Taking the H2+O2 reaction as an example: The reaction proceeds in a complex way, however magnetic fields are able to affect similar reactions.

"The UV band in general is absolutely considered to be ionizing."

No, it is not "in general".

See http://www.hps.org/publicinformation/ate/q2111.html.

and http://ehs.uky.edu/biosafety/uv_radiation.html

and http://yarchive.net/env/ultraviolet_dna_damage.html

and http://www.osha.gov/SLTC/radiation_nonionizing/index.html#ultraviolet

and http://www.icnirp.de/PubOptical.htm

Again, vacuum ultraviolet is something people will never come into contact with since you'd literally have to be in a vacuum to do so.
So in terms of the UV that anyone cares about from a health standpoint, it is not ionizing.

Sure, that's an extreme example, but you get the idea.

There are standard techniques for dealing with such things. e.g. ramp up the compiler warnings and see what they're complaining about or replace a type with a deliberate dud to see where it's used and inspect it. It's not magic or hard, it just requires routine developer expertise. Usually in modular code the side effects of new code (e.g. device driver) are minimal, even more so for a beginner engaged in an introductory project. The large kernel code can actually be a benefit in that it provides enormous numbers of examples to learn from with some examples likely to be very close to what you want to do.

It is true that there are many developers who think they're expert but aren't that would find this impossible (see dailywtffor many examples) however nobody wants those people anywhere near the kernel code. Or any code for that matter.

---

Insisting on absolute safety is for people who don't have the balls to live in the real world.

-- Mary Shafer, risks researcher, NASA

I suppose to be pedantic I'm protecting against the financial impact of loss, not the loss itself, but that's really splitting hairs.

I guess I wasn't clear as I think you misunderstand what I said. Insurance pays for nothing - it's merely a bet with the insurance company. You betting with the insurance company that you will be robbed, they're betting that you won't and they price that bet to cover their overheads.

Either you pay when you're robbed or you pay the insurance company a regular sum who in turn pay when you're robbed. The insurance company is in it for a profit so they're never going to price the bet so they make a loss, meaning you come out ahead. Because of their overheads you should never buy insurance for anything you can cover with your own cash flow unless you are confident the insurance company is underpricing the bet for you which is unlikely given their experience.

The only time you should voluntarily buy insurance is for large items where they have much deeper pockets than you and can cover things you can't. That's rarer than you might think though; even with insurance there's going to be catastrophes which aren't covered because of a loophole, act of god or because the insurance company has gone bust, so you can never have complete peace of mind.

I agree about everything being tradeoffs, intangible or tangible. There's no such thing as perfect security.

---

Insisting on absolute safety is for people who don't have the balls to live in the real world.

-- Mary Shafer, risks researcher, NASA

The thorough investigation by the Apollo 204 Review Board of the Apollo accident determined that the test conditions at the time of the accident were "extremely hazardous." However, the test was not recognized as being hazardous by either NASA or the contractor prior to the accident. Consequently, adequate safety precautions were neither established nor observed for this test. The amount and location of combustibles in the command module were not closely restricted and controlled, and there was no way for the crew to egress rapidly from the command module during this type of emergency nor had procedures been established for ground support personnel outside the spacecraft to assist the crew. Proper emergency equipment was not located in the "white room" surrounding the Apollo command module nor were emergency fire and medical rescue teams in attendance.

There appears to be no adequate explanation for the failure to recognize the test being conducted at the time of the accident as hazardous. The only explanation offered the committee is that NASA officials believed they had eliminated all sources of ignition and since to have a fire requires an ignition source, combustible material, and oxygen, NASA believed that necessary and sufficient action had been taken to prevent a fire.

Of course, all ignition sources had not been eliminated.

The Apollo 204 Review Board reported that it took approximately 5 minutes to open all hatches and remove the two outer hatches after the fire was reported; that the first firemen arrived about 8 to 9 minutes after the fire was reported and that the first medical doctors did not arrive until about 12 minutes or more after the fire was reported. Thus there was not expert medical opinion available on opening the hatch to determine the condition of the three astronauts although medical opinion based on autopsy reports concluded that chances for resuscitation decresed rapidly once consciousness was lost and that resuscitation was impossible by the time the hatch was opened.

It is clear from the Board's report and the testimony before the committee that this kind of accident was completely unexpected; that both NASA and the contractor were completely unprepared for it despite the amount of documentation of fire hazards in pure oxygen environments. The committee can only conclude that NASA's long history of successes in testing and launching space vehicles with pure oxygen environments at 16.7 p.s.i. and lower pressures led to overconfidence and complacency.

Excerpts from The Apollo 204 Report: Summary

However, it is a common misconception that low-pressure pure oxygen does not increase the fire hazard. Not true. It doesn't increase it to nearly the horrible level of 14.7psi oxygen, but it does increase it quite a bit.

Apollo 1 Fire: Henry Spencer About Yarchieve.net [and Henry Spencer]

The thorough investigation by the Apollo 204 Review Board of the Apollo accident determined that the test conditions at the time of the accident were "extremely hazardous." However, the test was not recognized as being hazardous by either NASA or the contractor prior to the accident. Consequently, adequate safety precautions were neither established nor observed for this test. The amount and location of combustibles in the command module were not closely restricted and controlled, and there was no way for the crew to egress rapidly from the command module during this type of emergency nor had procedures been established for ground support personnel outside the spacecraft to assist the crew. Proper emergency equipment was not located in the "white room" surrounding the Apollo command module nor were emergency fire and medical rescue teams in attendance.

There appears to be no adequate explanation for the failure to recognize the test being conducted at the time of the accident as hazardous. The only explanation offered the committee is that NASA officials believed they had eliminated all sources of ignition and since to have a fire requires an ignition source, combustible material, and oxygen, NASA believed that necessary and sufficient action had been taken to prevent a fire.

Of course, all ignition sources had not been eliminated.

The Apollo 204 Review Board reported that it took approximately 5 minutes to open all hatches and remove the two outer hatches after the fire was reported; that the first firemen arrived about 8 to 9 minutes after the fire was reported and that the first medical doctors did not arrive until about 12 minutes or more after the fire was reported. Thus there was not expert medical opinion available on opening the hatch to determine the condition of the three astronauts although medical opinion based on autopsy reports concluded that chances for resuscitation decresed rapidly once consciousness was lost and that resuscitation was impossible by the time the hatch was opened.

It is clear from the Board's report and the testimony before the committee that this kind of accident was completely unexpected; that both NASA and the contractor were completely unprepared for it despite the amount of documentation of fire hazards in pure oxygen environments. The committee can only conclude that NASA's long history of successes in testing and launching space vehicles with pure oxygen environments at 16.7 p.s.i. and lower pressures led to overconfidence and complacency.

Excerpts from The Apollo 204 Report: Summary

However, it is a common misconception that low-pressure pure oxygen does not increase the fire hazard. Not true. It doesn't increase it to nearly the horrible level of 14.7psi oxygen, but it does increase it quite a bit.

Apollo 1 Fire: Henry Spencer About Yarchieve.net [and Henry Spencer]

The vibrations that are commonly called 'pogo' in big rockets are caused by a feedback / resonance of thrust oscillations with inlet pressure of the turbopumps, see this extensive discussion. Pogo is fixed by adding dampers to the propellant lines. Ares I, like every big solid, has combustion instabilities that cause thrust oscillations, but there's no feedback like in a liquid rocket. Only danger is hitting one of the structural resonances and ringing the rocket like a bell (and possibly causing the structure to 'diverge').

As someone who used to commute via bike, I say it's pretty freaky having a hybrid come whooshing by, even if it's in a different lane. Almost as bad as a city bus, which has it's engine in the back so you don't hear it until the bus is practically on top of you. A little audible warning would be nice. It doesn't need to sound like a Harley to be effective.

May be better for you to start using a rear view mirror. Just like trucks, cars, motorbikes and mopeds. Or a rear view camera if you want to be high tech. Perhaps with an education campaign. It's crazy to deliberately make noise when cities are already too loud as it is. Particularly in traffic jams or late at night. I'm really looking forward to the day when cities have minimal air pollution and minimal sound pollution.

---

Insisting on absolute safety is for people who don't have the balls to live in the real world.

-- Mary Shafer, risks researcher, NASA

"We want to legalise non-commercial file sharing"

ie. We want to reduce copyright to meaninglessness. It's abolishment in all but name.

Does anyone actually respect copyright laws anymore? Or, for that matter, any laws? I know I'm seeing them more and more as hindrances, rather than protections.

*that* is why they'll get nowhere.

Well, my local Pirate Party will sure get my vote in all future elections, simply because they're against surveillance. Getting rid of copyright, which is the biggest hindrance to preserving our increasingly electronic culture, is a nice plus.

I'm all in favour of changing the balance of power, but extremists like that should really just shut up.. they make things worse.

Worse for whom? Who suffers if surveillance is reduced? Who suffers if copyright is abolished or limited to a reasonable term? Why, the people who brought it upon themselves. They were warned:

"Pass this law: and that feeling is at an end. Men very different from the present race of piratical booksellers will soon infringe this intolerable monopoly. Great masses of capital will be constantly employed in the violation of the law. Every art will be employed to evade legal pursuit; and the whole nation will be in the plot. On which side indeed should the public sympathy be when the question is whether some book as popular as Robinson Crusoe, or the Pilgrim's Progress, shall be in every cottage, or whether it shall be confined to the libraries of the rich for the advantage of the great-grandson of a bookseller who, a hundred years before, drove a hard bargain for the copyright with the author when in great distress? Remember too that, when once it ceases to be considered as wrong and discreditable to invade literary property, no person can say where the invasion will stop. The public seldom makes nice distinctions. The wholesome copyright which now exists will share in the disgrace and danger of the new copyright which you are about to create. And you will find that, in attempting to impose unreasonable restraints on the reprinting of the works of the dead, you have, to a great extent, annulled those restraints which now prevent men from pillaging and defrauding the living." -Thomas Babington Macaulay, in a speech delivered in the house of commons on the 5th of February 1841

There is a new type of flu, a fair number of people *have* died from it.

A hundred people in a Mexican population of millions. That's far lower than practically any other cause of death. Those reporters really need to get a sense of proportion.

Sure the appropriate authorities need to monitor it for the very small possibility it turns out to be something serious but the general hysteria is just ridiculous.

For all the reporters know those people who died were vulnerable due to poor nutrition and other factors. It's not a first world country after all. I wonder why we haven't see any news stories detailing those deaths.

This is a gross media beat up by the drug companies (e.g. The bird flu "epidemic" and Tamiflu probably made Roche hundreds of millions of dollars - probably well worth spending a few million on astroturf), not to mention other vested interests. Just look at the media reports - it's all about suspected cases, not actual cases, and ridiculousness like making a fuss about a few suspected cases leaving one country's population of millions and entering another country's millions. Well, duh.

I repeat, they really need to get a sense of proportion. If they're so mathematically illiterate that they're not capable of getting a sense of proportion then they should shut up and go back to school - they're not qualified to say a damn thing.

---

Insisting on absolute safety is for people who don't have the balls to live in the real world.

-- Mary Shafer, risks researcher, NASA

CO2 isn't toxic...

Really? I'll assume you're just messing around.

http://yarchive.net/explosives/nitrates.html

A more efficient method would be to covertly dig a chamber
under a public urinal and pipe the fluid into a drum filled
with earth and provided with holes in the bottom to let the
bacterially processed nitrate solution drop into an evaporating
pan. Late at night you could then use the hot-air hand dryer
in the unoccupied men's or ladies room to quickly remove the
water.

You mean accidentally reaching a circular orbit again after the orbit had already become elliptical? I think that'd be extremely unlikely. When various objects act on one another (as they invariably do), they're most likely to become more elliptical, not less.

Is that right? You might want to tell that to Henry Spencer, since he's been saying the opposite for years.

People should receive due process, no matter what they appear to be doing.

Problem is, we live in an imperfect world. The police aren't mind readers, they have to believe what they see and make reasonable decisions based on what they see and currently if they see a "shooter" on a rooftop the balance of probabilities is that they're dangerous and need to be controlled before an innocent gets hurt (including themselves if they're mentally ill). Like many real world situations there's no time for due process but making an incomplete decision on incomplete information in limited time is better than making no decision at all and possibly allowing an innocent getting hurt. If your game ever became popular then the balance of probabilities would change and maybe what the police would do would change too.

However, there's also the added problem that police are only human and some are in dangerous situations every day. That means if they personally want survive for any length of time statistically they have to assume the worst every day. Even though they will be wrong more often than not, they will be right when it matters to them, when they really are personally in danger.

A bit like the distinction between type I and type II errors in statistics. Not sure what can be done about it other than giving police non-lethal options and protecting them as much as possible so they don't feel the need to assume/do the worst all the time.

---

Insisting on absolute safety is for people who don't have the balls to live in the real world.

-- Mary Shafer, risks researcher, NASA

just to be nit picky I wondered whether he could feel the pain of scooping out the brain.

If the following is right

http://yarchive.net/med/brain_pain.html

then only if some large blood vessels are extended. So theoretically if you have a splitting headache from a glass of red wine or a migraine you can always tell yourself your brain is not directly involved.

There are actually brain operations where the patient is awake and probably doesn't feel much pain.

Hope that helps.

Oh really?

Funny that you mention Japan later on, after spouting the above line of nonsense. Contrary to that the gun nuts would have you believe, guns are NOT actually illegal in Japan. They are simply well regulated. Hmmmm... "well regulated". That sounds strangely familiar; like maybe I've heard or read it somewhere, specifically relating to bearing arms, before.

Sure, every now and again, someone simply flips their lid and kills a bunch of people. But that happens pretty much EVERYWHERE. Meanwhile, on average, Japan has a MUCH lower crime rate than many, if not most other countries (At least the ones on which we bother keeping the stats.) Also note, that those graphs show crime rates in absolute numbers. Click the "per capita" tab (Japan has about half the population of the US.), and their place in those lists drops down to about the level of your floor.

cya,
john

the system needed in a car could be significantly smaller

It could be, but you have to remember that there is next to zero insulation in your car. The metal and glass frame is sucking in heat from the outside quite fast, if a unit is too weak, it'd never keep up.

Google isn't helping a lot here (I've been looking for 15 minutes or so) but I found this posting (ignore the guy who wants "colder freon") from 1995 stating that car ACs are 3 to 4 tons http://www.yarchive.net/ac/humidity_removal.html which is in line with what my father told me when I was a little kid. Ebay says "The average factory installed auto A/C unit is rated at 1-3/4 ton." http://reviews.ebay.com/Frequently-Asked-Auto-A-C-Questions-Part-2_W0QQugidZ10000000000932442

"One ton" of air conditioning power is 12,000 BTU/hr, which wiki (sorry, too lazy to do the math myself) claims is 3517 watts (not counting the inefficiency in converting electrical watts to actual heat transfer, meaning actual power required to get one ton of AC is higher). Central AC seems to average about 3 tons, based on the prevalence of that number in example calculations like this one.

Based on these numbers, your window unit is significantly weaker than a car AC system.

As far as reactivity with atmospheric Ozone (O3), Halogens (big electronegative atoms) Chlorine and/or Bromine in refrigerant = BAD. Fluorine only in refrigerant = GOOD. We are talking about a class of chemicals that are modified Natural Gases like Methane, Ethane, etc.. that have had one or more of their Hydrogens replaced with CL, Br, or F to make them "less flammable" and to engineer their properties making them superior refrigerants. See the ~Montreal Protocol~ http://en.wikipedia.org/wiki/Montreal_Protocol "At present, 191 nations have become party to the Montreal Protocol (see external link below). Those 5 that are not as of September 2007 are Andorra, Iraq, San Marino, Timor-Leste and Vatican City." A single 12 ounce can of R-12 Automotive Freon was only ~$.99 in the 1980's? [You could recharge your car AC Cheaply and ON YOUR OWN.] The current price on the R134A replacement is over $10 per 12 ounce can! ( http://en.wikipedia.org/wiki/R-134a ) And if you are lucky enough to have some stock of the old banned R12, is it selling over $25 per 12oz can now!! http://search.ebay.com/search/search.dll?sofocus=1&catref=m37&satitle=R12+can+refrigerant In addition, you MUST now be Professionally Licensed to even tap into an R12 air conditioning system's coolant loop using only special expensive approved refrigerant recycling/vapor recovery equipment which costs many hundreds of dollars per unit. Not to mention, R134a refrigerant REQUIRES a new class of synthetic lubricant oils, special compatible plumbing/hoses, and new compressor designs. R134a and its oils are corrosive to many metals (R12 was not) and R134a is NOT as good of a refrigerant compared to R12 (therefore AC systems in vehicles today are a bit larger and a bit less efficient to yield the same cooling needs, after all; cars are really just greenhouses with wheels) So a chemical that is virtually as inexpensive to manufacture (comparing R12 to its "replacement" R134a) now costs over 10x as much to purchase, yields complete incompatibility with older R12 systems, and creates a very lucrative "gray market" and "black market" for R12 refrigerant. R12 refrigerant manufacturers created as much R12 as was humanly possible before the Montreal Protocol manufacturer's ban date. Realize that this is and has been an artificially controlled market and now the profits are crazy. (Think like the cost of manufacture of a CD compared to the sale price) The politics of this were simple: making fortunes and claiming positive environmental action. There are R12 "blends" that are mixtures of various things that sort of work ok, but there is not a good replacement even to date and stockpiles of R12 only get more expensive. But hey, Yay for the environment! More references: http://yarchive.net/ac/politics.html

Frankly, I don't think $30 million is enough.

Some people may aim for the prize simply because it's fun. No other reason is needed.

Why climb a mountain? Why live? It's a pretty sad life that's only interested in putting extra zeros on a bank account.

---

Insisting on absolute safety is for people who don't have the balls to live in the real world.

-- Mary Shafer, risks researcher, NASA

Ha, yes, I dug out me old post on it! Here is the tower launch archive, from a few years back, which I was pointed to by Carlton Meyer, the guy responsible for the skyramp website. He and I were thinking along the same lines - how hard would it be to build a mountain to reach space? Obviously not literally, but you get the idea. Once you are past the 11km mark, you jump out of the troposphere. I'll quote one of the responses to my long ago post here:

I also went ahead and did some quick math. 1 m/s/s acceleration over 11 km is not enough:

s = s(0) + v(0)*t + 0.5*a*t^2, where s(0)=0 and v(0) = 0 so:
t = ((2*s)/a)^0.5 = 148 seconds to traverse the 11 km

v = v(0) + a*t = 0 + 1 m/s/s * 148 s = 148 m/s = 331 mph
Woefully short of escape velocity.

So then I tried 1 G and got 1040 mph, which still doesn't cut it. Next I went for 5 G's, which is on the order of what astronauts experience during a launch, and that gave me 2,326 mph. It's still not escape velocity, but surprisingly enough, it is sufficient kinetic energy to loft an object to a height of 22,000 miles, or the altitude of a geosynchronous orbit. Unfortunately, when it gets there it doesn't have sufficient tangetial velocity to stay there, so it follows a funny elliptical path 22,000 miles to the hard ground. I ran out of scratch paper before I could quantify that, however. I did have one line left to note that a 1000 kg payload accellerating at 5 G's requires 2.4 MW of power, not accounting for losses, which is one capability we do easily have.

Tack on some engines which engage after launch and you have a winner!

As for Gs, nn important question is, how fast can we accelerate? Accelerations of short duration (under perhaps 200 milliseconds) do not involve significant fluid shifts within the body, nor do they involve the various reflex responses that can affect responses to longer duration acceleration. Depending on the time that is spend under high acceleration, people can withstand extreme g-foreces. Depending on the individual's "g-tolerance" the oxygen supply to the head stops completely at 5 to 6 g resulting in unconsciousness, G-LOC. 4 is probably okay for small time periods.

The best part about it is the economy involved. Once you get past the engineering of making sure the whole thing doesn't fall down, you could probably put it all in place for around 4 to 5 billion, a quarter of NASAs annual budget.

For a given system, R134a refrigerant is less effective than R12, or other replacements. George Goble is the guy that lobbied for and lost the bid to replace R12 with a relatively inexpensive superior performing propane/iso-butane mixture. R134 performs worse, requires larger condensors, and has less heat carrying capacity. Additionally, should the condenser hit 214+F it won't work at all. The summer temps here regularly hit over 100, and in full sun on black asphalt you'll get a nice cozy 140+. Add in engine compartment heat where (surprise!!) the condenser sits....

If you've never had the pleasure of entering a dark colored car sitting out on asphalt for 8+ hours in full sun on a 115 degree day and turn on the AC and get hit with cold air, and then do the same with any R134 equipped car, you don't know what you're talking about. One last note, R134 did improve on one issue that used to be a problem with R12 systems: R134 systems don't suffer from freeze lock (that'd be where the evaporator in the dash gets so cold that water freezes onto it, blocking air flow and killing your cooling power).

So yes, R12 performs far better than R134. If you're willing to void your warranty, you can improve the performance of your R134 system by doping it with propane and iso-butane and approach the performance of an R12 system.

Ask and ye shall receive: ;)

http://www.constitution.org/cons/wellregu.htm

http://www.guncite.com/gc2ndmea.html

http://yarchive.net/gun/politics/regulate.html

http://www.thepriceofliberty.org/05/12/19/greensla de.htm

http://mason.gmu.edu/~nlund/Pubs/WklyStd2dAmd.pdf

http://www.virginiainstitute.org/publications/prim er_on_const.php#c4

To answer the posted question of "what's so special", it's the methane motor. NASA tested one, but nobody's flown with one yet.

All the major hydrocarbon fuels are within about 3% of each other in specific impulse. Methane, being readily available via natural gas, is very handy. However, it's a gas, compressed to liquid. That means its density is less than a liquid. The major liquid fuel (RP-1; pretty much JP-4/Jet A kerosene) is 22% more dense since it's a liquid. To make a methane engine worth putting into a human-rated craft will require a major step in pressure tank development. They'll need to cram a lot of gas in, and it'll have to fail safe (ie. not explode if it leaks). I suspect EADS made this part of their R&D for the project, or they'd have just gone with RP-1. For a comparison of fuels see http://yarchive.net/space/rocket/fuels/fuel_table. html

Nonsense, distilled water is perfectly safe to drink:
http://yarchive.net/med/osmotic_damage.html