Become a fan of Slashdot on Facebook

 



Forgot your password?
typodupeerror

Comment: Declaratory judgment (Score 3, Informative) 30 30

There's a mechanism in US law to deal with this kind of thing. It's called a "declaratory judgment," where a plaintiff who has reason to be afraid that the law will be enforced to land him in prison or bankruptcy sues for a judgment that either the law doesn't forbid his (in this case) publication of his research or that the Constitution forbids a law that would. Yeah, such suits ain't cheap. Fortunately there are several nonprofits that exist to fight exactly that kind of battle.

Comment: Re:ABC Anywhere But China (Score 5, Informative) 236 236

Key difference: the Chinese don't, generally speaking, have the power to kick in my door here in the USA (or for that matter in most places outside of China). The USA has, on the other hand, demonstrated both the ability and willingness to vanish people to "black sites" without any regard for what most people would recognize as due process.

Comment: Re:Tesla enables Edison to win the endgame? (Score 1) 597 597

http://www.hvswitch.com/

Forward voltage at rated current is 450 volts. Even at 30 KV that's some serious loss. The specified risetime of 10 ns into a resistive load isn't bad, but the falltime isn't specified and the interesting loads are all inductive -- falltime into those is tricky because of snubbing losses and Miller capacitance.

Others rather less precisely specified but generally similar.

Rather more to the point, though, is that they don't get you usable voltage conversion. You still need a transformer, so the semiconductor losses are in addition to the transformer losses. And all of that lovely high-frequency switching causes problems when you're dealing with transformer cores weighing tons. Which you need to keep the Q of the transformer up (inductive loss is pretty much a pure function of how much copper you're willing to pay for.)

The loss of efficiency is acceptable for applications like PC power supplies or lighting ballasts because the added functionality such as flexible regulation makes up for it. But when you're looking to handle the output of gigawatt power plants, you really don't want to be dissipating several percent of your output (pure loss) into a solid-state system that has to be kept below 70 degrees under peak load, which around here means an ambient temperature of close to 50 degrees. That is, for one, a big direct cost for the inefficiency. Also a honking enormous cooling system prone to catastrophic failure due to thermal runaway. And, finally, a maintenance nightmare. What is the service MTBF of one of those switches? Now, figure it for an array capable of handling a gigawatt. Don't forget that you can't just take the system down for safe maintenance.

Much as I love transistors, this isn't happening in my lifetime.

Comment: Re:Tesla enables Edison to win the endgame? (Score 2) 597 597

The main advantage of AC, is that it was easier to step from one voltage to another using transformers, a technology from the 1800s. With modern solid state DC to DC converters, that is no longer an issue.

Do you know what the most efficient switch is for voltages over a kilovolt? I'll give you a hint: it's not based on semiconductors. Especially for high power. There's this little matter of "breakdown voltage," for one. Also "channel resistance." When someone comes up with a transistor [1] that can do three-nines [2] voltage conversion, we can talk.

[1] And bear in mind that I spent forty years making a good living from the little darlin's. I just don't hold illusions about 'em.
[2] Check the losses that power-station transformers tolerate while doing conversions on megawatts. Those suckers get effficient.

Comment: Here we go again (Score 1) 64 64

KDE 4 broke a lot of the functions I used on 3 (like, for instance, email. KMail was great, now I'm stuck with the inferior but functional Thunderbird). And they never did fix them. Still broken and worse with every revision.

So I'm dreading the day when the only supported KDE will be the still-not-fully-functional version 5. What have they broken now, never to fix?

Comment: This could be loads of fun (Score 3, Interesting) 113 113

I have a new Subaru with their collision-avoidance system and by and large it's very nice, but its lane-boundary warning system can get ... confused by tar-patched road cracks and especially by rutted snow. Which is OK by me when it's just a warning but if the car decides to actually act on that it's going to be a wee bit exciting.

Comment: Re:It depends (Score 1) 486 486

"Was their paper peer reviewed?"

I think all the other students were too busy writing exams, so no...

Okay, that's mean. To be fair, one author is a Project Manager. However, another is an Associate Professor who teaches "W2014 - SENG 533 - Software Performance Evaluation"... this is a concern for his students.

Comment: Data mining (Score 2) 179 179

If you search all possible cancers for a connection with some chemical (e.g. sucrose) you will come up with several positives with a 95% confidence. Which is why you have to use statistical tests that account for all of the different targets.

Thus, at the very least the WHO needs to explain the stats rather than just the raw "probably causes cancer."

Comment: The fix (Score 1) 56 56

I'm surprised that the blurb didn't emphasize that the microbe in question is also a nitrogen fixer. Which means that it not only produces fuels but also fertilizer without needing additional energy input (bear in mind that a large chunk of Koch Industries income is from the sale of fossil-fuel based ammonia.)

Hacking's just another word for nothing left to kludge.

Working...