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Comment: Re: How do I refill it? (Score 3, Informative) 192

by jo_ham (#48409751) Attached to: Toyota Names Upcoming Hydrogen Fuel Cell Car

Isn't the temperature a result of high pressure? As in, if you jam enough atoms into a space eventually they have less room to move and get colder? I'm sort of basing this off observation of my air compressor relief valve and not science. Air duster canisters can generate frost. That kind of thing.

So pressurizing a bunch of hydrogen would mean if it ruptures and someone touches the canister, instant frostbite.

What about the "destroying everything it touches" part?

ps: I am a different AC than OP.

The Ideal Gas Law determines what happens to a gas under pressure: PV = nRT

Pressure is proportional to volume, so if you compress a gas it shrinks in volume until eventually it liquefies - but the point at which it does depends on the phase diagram for that particular gas. The properties change depending on the molecules.

If you release pressure quickly then it expands very rapidly and cools down. This is a function of thermodynamics. Similarly, if you compress a gas it will heat up for the same reason. This is common to all gases. Jamming the molecules in ever tighter will increase the temperature. Your air compressor heats up when it is compressing air because of this. When you let the pressure out, the temperature of the air drops rapidly.

Where things like hydrogen are special is that you can't liquefy them by simply pressurising it. You need to cool it down too - the triple point of hydrogen is about 22 K and the critical point is about 32 K - hydrogen simply can not be a liquid at any pressure unless the temperature is between these two values (22 K is -251 C or -420 F - cryogenically cold temperatures).

Any gas under pressure is a hazard - cylinders of nitrogen are pressurised to 300 bar and if one of those ruptures you're in a world of hurt, despite the fact that nitrogen itself is inert, but we routinely handle high pressure gasses in industrial and commercial environments. You take more precautions with a hydrogen cylinder (or any cylinder of flammable gas), but the handling procedures for flammables overlap a lot with the non-flammables like nitrogen and argon.

Comment: Re:enable trim on yosemite (Score 1) 326

by jo_ham (#48399021) Attached to: Apple Disables Trim Support On 3rd Party SSDs In OS X

It's the same as reducing charging speed with non-Apple iPhone cables. The only reason is to make you buy expensive Apple parts.

Ah, yes, that pesky problem with conforming to the USB specification for safety reasons.

If you know your charger, cable and device have been tested to be safe to pull multiple amps then the device will do so (but be technically out of spec).

Charger reporting as a standard USB port? Drop back to the published spec for maximum current draw.

Sorry, you were in the middle of an Apple bash, I didn't mean to interrupt. Carry on.

Let's also ignore the fact that adding driver signing to the kernel is not somehow "solely to stop third party SSDs".

 

Comment: Re:Also - couldn't you actually just sign the driv (Score 1) 326

by jo_ham (#48399005) Attached to: Apple Disables Trim Support On 3rd Party SSDs In OS X

No, you couldn't, since they are Apple's drivers not yours. Apple's driver takes over handling of external drives, but it refuses to TRIM them. Previously, people worked around that by patching the driver, but signing prevents that.

Right, but drive vendors could sign a driver and supply it with the hardware, they just choose not to do so because the vast majority of bare SSDs are sold for Windows boxes where Microsoft's driver is not picky about TRIM support.

Comment: Re:Stupid, trucks cause the problem (Score 1) 554

by jo_ham (#48395157) Attached to: The Downside to Low Gas Prices

In the UK, cars are taxed on the amount of CO2 emissions generated.

Why not just tax petrol? Petrol burned is directly proportional to the amount of CO2 actually (not theoretically) emitted. This band system for efficiency is unnecessarily complicated.

Petrol is taxed, and taxed very, very heavily (the price at the pump in the UK is about 75% tax). CO2 emissions are also taxed. Driving is expensive in the UK, but it does wholly pay for the upkeep of our roads.

Comment: Re:Great! Now how about... (Score 1) 136

by jo_ham (#48356009) Attached to: Apple Releases iMessage Deregistration Utility

A utility for getting all my photos out of iPhoto, and all my data out of Time Machine?

You mean something that reads the HFS+ filesystem?

Time Machine backups are copies of your files. If you have software that can read your original files then that very same software can also open the copy of the file that Time Machine made. You do not need Time Machine's interface to read these files.

If you use Time Machine on a network drive then there's an additional step of mounting the disk image it creates, which is left as an exercise to the reader.

Comment: Re:An Obscenity (Score 1) 253

by jo_ham (#48170751) Attached to: Facebook and Apple Now Pay For Female Employees To Freeze Their Eggs

I'll pick one you missed off: life experience. Although from your comments so far, it seems you believe that all you do at work is make money, get a big office and get a title. I can see why, given your limited experience with this, that you might think it is a "new fangled" idea.

Yes, yes, we'll get off your lawn.

Comment: Re:5K display (and computer) for $2500 (Score 1) 355

by jo_ham (#48167193) Attached to: Apple Announces iPad Air 2, iPad mini 3, OS X Yosemite and More

No. This is what I hate about these iMacs. And especially more since this high-res display. You get a good, expensive display, which you could easily keep for 10-15 years, but are forced to throw it away when you want to upgrade the computer, after say 2-8 years. A Mac mini duck-taped on the back of a monitor takes about the same space anyways.

Are you sure about that? The current generation of iMacs can act as a standard monitor when connected to another machine. Up until a few weeks ago, I was using one that had a failed hard drive in it as a monitor for a desktop PC via a simple mini Displayport to Displayport cable connected to the PC's graphics card.

Probably not at this time - the display sharing feature has been dropped from the spec sheet, probably because the new iMac only has Thunderbolt 2 and thus doesn't quite have the bandwidth to drive a 5k display over that interface.

I think it will probably return when this model hits revision 2 and gains Thunderbolt 3 running the new display port spec that has adequate bandwidth to run a display of that resolution.

I believe this is also why we haven't seen an update to the standalone thunderbolt display yet - Apple will want it to retain the Thunderbolt connectivity and there's no specification available right now to run such a large panel over that interface (or any external interface I believe) without doing things like multiplexing two TB2 busses together.

Those wanting to use this thing as a monitor are going to be out of luck until TB3 arrives I fear.

There is a good possibility that the new iMacs can also be used as a monitor as well.

Comment: Re: Apple Pay (Score 2) 355

by jo_ham (#48167155) Attached to: Apple Announces iPad Air 2, iPad mini 3, OS X Yosemite and More

They absolutely did, and they talked about it specifically when Apple Pay was announced during the iPhone 6 keynote.

The design of the system is that your credit card number is hashed together with the unique device ID of your phone to create a signing key (the card number itself is then never stored anywhere). You then activate apple pay with your bank so they have a way to verify your purchases. When you then use your device to buy something a transaction-specific token is generated from your signing key that is passed to your bank, who then verify it, and send back a yay/nay to the vendor. The bank then debits the money. Each transaction you make generates a new token that is passed via the vendor to your bank.

The key things that Apple pointed out were that a) Apple doesn't know what you bought or how much it was, b) the vendor you are buying from doesn't know what your credit card number is and c) your credit card number is not stored on your phone. If you lose your phone you can log into iCloud and invalidate the signing key.

If you want to hear that from the horse's mouth, Tim Cook spent several minutes on it during the iPhone 6 keynote.

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