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Comment Re:Huffman alternative (Score 4, Insightful) 135

Look, they clearly state that the operate at the level of JPEG-files. So, where is the confusion coming from? They are analyzing JPEG files and using features of that format to compress the already compressed files further.

Which I, honestly, find very impressive.

The reproduce JPEG files in a bit-by-bit faithful fashion. And the have tested in on 16 million (or was it billion) files where it worked without problems plus they don't replace user files unless they have checked that it decodes correctly. I presume that the process is actually transparent to the Dropbox user.

I don't see the problem that you have with this, sorry.

Good work lads!

Comment Re: It's what they say (Score 1) 112

The use of "y" at the end of a word and "i" in its place in the middle of a word was a convention by printers which made it easier to deal with the "y" descender in a stylish way.

I would not say this in many forums, but this is slashdot....

*I* find it convincing and interesting though a reference would be nice. And this is /. so it is appropriate to learn something new and slightly odd.

A pet hate of mine is faux archaic signs like "Ye olde cheese shoppe". The "ye" is just a misunderstanding AFAIK of "the" written with a slightly open, regional form of the letter thorn which vaguely looks like a "y" though it just means "th".

Comment Re:How about fixing the systems? (Score 1) 143

Leap seconds are announced months in advance

i.e. with less warning than the revalidation time for a lot of safety-critical systems.

Hmm., hopefully safety-critical systems are implemented so that they have provisions for leap seconds built in already. What should be needed is organizational procedures for setting the appropriate flag in time.

Further, I would expect that many safety-critical systems are more concerned with elapsed time from some epoch (switch on, last firing of engine, last heart-beat) and less about civic(?) calender time (we meet on January 2nd, 2016 11:01:14 EST).

Finally, in really hairy cases things should be referred to a simpler, monotonous scale (TAI or, yuck some domain specific scheme).


Comment How about fixing the systems? (Score 1) 143

As I see it, this is a question about standardizing and implementing systems properly. Leap seconds are announced months in advance.

It can't be such a big problem systems that handle this correctly.

But then, daylight savings time still seems to give problems. Sheesh!


PS. Anybody who knows about problems with leap days?

Comment Doubt that I would be able (Score 2) 258

I don't remember my passwords as something I can write down on paper or recite.

I can type them in normal circumstances but if I am under any kind of stress (such as having just mistyped once), then I can't. In fact, I need the visual clues from being at my usual desk/terminal/cave in order to type one correctly. That's how I type the right password depending on the situation.

If I were to be detained at an airport then it is *highly* unlikely that I would be able to give them up.


How about you guys?

Comment Self-serving -- meh! (Score 1) 839

A shift in taxation towards consumption is blatantly self-serving as the ultra-rich consume a disproportionate small fraction of their income and (especially) wealth.

Strangely, I have the impression that income taxes are comparatively low in the US whereas the corporate taxes are exceptionally high. Anyone who can comment meaningfully on this?


Comment Success for me; depends on definition (Score 1) 182

I've followed three online courses. One I completed and did all the assignments. Two where I watched all the material but did not attempt the assignments (one required I rigged up a video camera to submit; could not be bothered).

Quite frankly, I got what I wanted out of these courses. So how is this a failure?

I have to balance effort with other commitments. I trust I am not the only one. Signing up is cheap. I've signed up for a few more but other real life took precedent. No big deal.

On the other hand, I don't see online courses replacing traditional educational settings but that was pretty naive to being with.

So: nothing to see here. Yawn!

Comment Not news at all (Score 1) 275

That stealth technology is vulnerable to long-wave radar is old, old news. I believe that the Aussies' Jindalee (JORN) radar has shown this a long time. Also, back in the 90s, the Russians claimed that there is no stealth for wavelengths longer than 30 cm (1 GHz) AFAIR.

Now the obvious problem is that it's not easy to make a compact radar for a long wavelength but if you can steer a missile close enough with a cumbersome radar then other sensors on the missile might finish the job off. Other sensor technologies are not exactly standing still.

At the same time, it seems that a lot of aircraft performance (and ship aesthetics) are being traded-off for stealth capabilities. I hope I will not have to see how this pans out. Or pay, as a tax payer, for the dumpling aircraft: I'm looking at you, F-35.

By the way, stealth craft are apparently also vulnerable to bistatic radar geometries.

Comment Re:My daugher had 33 MBq injected last week (Score 1) 190

Before I sign off from this thread: Do you know of a good, authoritative account of the Fukushima event?

I don't, sorry. I find that there's tons of misinformation and downright falsehood about the event out there, both by tepco and anti-nuke activists,

Right, that's what I have found as well.

and I'm not gonna waste my time plowing through it and fact-checking every single line. I'm a technologist and as such much rather concern myself with the technology of newer safer and cleaner nuclear power than with politics.

Peace, man!

I just wanted to know if you had found something. You seemed very well informed.

Comment Re:My daugher had 33 MBq injected last week (Score 1) 190

Right, that's what I forgot. You're correct that Tritium originates from reactor operations, not radioactive decay after the accident had occurred, but in LWRs it appears to be a by-product of fission reactions (1 in 10000).

Well, there is a little deuterium in the water to start with but on top of that we have so many tons of water in an intense neutron flux for 40 years. Without trying to run the numbers, I am sure there is going to be a fair amount of tritium present.

Anyhow, I also just learned about the pathway to tritium in fission yesterday. Great, I learned something new.

Before I sign off from this thread: Do you know of a good, authoritative account of the Fukushima event? I heard rumours that the Tepco crew made some unfortunate choices with the operation of the isolation condensers, and that the one measuring instrument the prioritized above all else (water level) lied to them. Now, I am not going to second guess the decisions they made under extreme duress but I am curious.

Comment Re:My daugher had 33 MBq injected last week (Score 1) 190

First of all, I like your analysis.

By "a mess" I meant the fact that what was supposed to be inside the fuel rods came to the outside. That's plenty of a mess for me ;-)

I am not going to check your numbers but it sounds awfully little. Actually, I did check your number for Cs and I get 0.311 g assuming a half-life of 30 years and 6*10^23 for Avogadro's constant. Pretty impressive clean-up.

My vague understanding of this clean-up is that they have enormous amounts of cooling water that has been in direct contact with ruined fuel rods so the pollution is fairly well-defined. The waste-water is filtered and ion-exchanged (or whatever they do) leaving quite clean water with tritium in it. The tritium comes from (correct me if I am wrong) neutron capture in the reactor water over its life-time. It is already in the form of HTO. In principle, I guess, they could distil and electrolyse repeatedly to separate the tritium out. Or they could dump it into the Pacific Ocean. As I understand they chose the latter.

With tritium activation energy and auto-ignition temperature is less relevant not just because has been in the form of water for years but also because its beta-activity makes it insert itself readily into other molecules: A simple way to introduce tritium into a hydrogen containing molecule is to store the compound under tritium gas for a few days.

(Oh, I wrote Sr-99 above where I meant -90 and Cs-133 where I should have written -137. One typo and one genuine mistake :-( I have been too interested in atomic clocks lately.

Comment Re:My daugher had 33 MBq injected last week (Score 1) 190

Yeah, yeah, Tc-99m. I know. It was probably gone much earlier than that because we kept her plenty hydrated and it was chelated as the dimercapto succinicate which is eliminated in the urine. And yes, the radiation is mostly benign gamma that escapes.

Similarly, apparently what gives the Japanese the most trouble at Fukushima Daiichi (as far as I understand) is tritium which is very hard to capture in waste water but luckily decays through a very low energy beta.

Still, they have managed to make a mess with plenty of actinides, strontium-99 and caesium-133 all over the place which was emphatically *not* meant to happen.

Finally, brambus we were probably both wanting to make the point that the mere activity (as measured in becquerel) is not very informative. Dose matters. Radiation type matters. Toxicity matters.

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