Slashdot is powered by your submissions, so send in your scoop


Forgot your password?

Comment Re:kind of like a small town fireworks show? (Score 1) 200

??? I don't see that all. The links are just google image searches on "reykjavík fireworks", "brenna gamlárskvöldið", and "jóðhátíð í eyjum". Oh, hmm.... I'm betting that because I'm searching from Iceland I get differently biased results. I know that my regular google searches at least bias towards Icelandic sites. Okay, well, basically picture this for an hour while several dozen of these are ongoing, or summer festivals like this.

We kinda like fire.

Comment Re:kind of like a small town fireworks show? (Score 1) 200

Hmm, interesting, they actually limit how many can be shot off?

Yes, your description of size, wind, etc are accurate. Also it's a rather moist climate, not much fire risk. And most buildings are concrete. And the city is half surrounded by ocean. And since the money goes to support the rescue services, the incentive is to encourage people to shoot off as many as possible, rather than the other way around.

Comment Re:Tech likely to disrupt: (Score 1) 247

Irrelevant. You're still limited by supply rates and feed wire heating.

LOL. No, you most certainly are not. Supply for the vehicle is from local storage, charged slowly over time, ready for fast discharge when needed

LOL yourself. You were crediting ultracapacitors with fast charging. Now your "counter" is saying that no, you're talking about slow charging. Well, make up your damned mind.

As for feed wire heating, that's absurd. At these lengths, and these voltages, it's simply not a problem.

At the *thousands of amps* needed to surpass the charge rate capacity of li-ions, yes, you bloody well are talking about wire heating problems.

I know that with multiple high energy motors, motor peak current demands can be very high, particularly in the case of high power motors that batteries aren't good for, and that semiconductors can be arranged for very high parallelism.

Oh, please, get real. The supercar-performance Tesla Roadster uses a 215kW motor peak, max 100kW sustained. To drain the whole pack with the pedal to the floor constantly (which, as noted, the car doesn't support) would take over 15 minutes. The fastest you can actually drain it without overheating the car is about 45 minutes. And this is for a car that does 0-100 in 3,7 seconds.

Learn to admit when you make a mistake and move on. The concept that there's sort of car performance limitation from not being able to instantly discharge the whole pack is utterly absurd.

Oh heck no, not even close.

Then follow the instructions in the very next sentence that you ignored. But given that few car parts last longer than 10 years, and most ultracapacitors don't last that long, I think that's an unreasonable demand.

Montana's not a great environment for batteries at times. I'd have to rig a cover for it all, probably lose 6 inches of depth in the bed. Hmmm. :)

Montana? You did see that one of the supercap info sheets linked showed that they're only rated down to -25C, right? Why would you choose that over good li-ions which go down to -40C (some varieties go even lower)? Are you fond of getting stuck out in the cold?

It's only when they are unused for long periods of times that they don't.

In fantasyland, perhaps. Check the specsheets for actual real-world ultracaps, like the ones I linked. They explicitly state that capacity declines from having energy stored in them. So unless your plan is to fully discharge your car after every use, yeah, good luck with that.

The idea that their lifespan in use is ten years is a complete myth.

Yeah, what do those stupid nuthead supercap manufacturers know about their own products? fyngyrz, you tell them what's what!

Yes, yes, of course you can break them if you misuse them

You can break them by precisely the same method you said that you can't, as per the spec sheets of the manufacturers.

UC won't overcharge if a continuous supply is applied to them that is under their rated voltage.

The spec sheets explicitly contradict that.

Show me one in continuous, low cycle rate use that needs to be.

The spec sheets all explicitly describe the exact same internal resistance rise with time. There's tons and tons of peer-reviewed research on it. But no, no, we have fyngyrz here to correct all those stupid boffins!

According to all manufacturer information out there, the primary loss mechanism is not cycling but energy storage. You can cycle them tons without problem, but each second you leave them charged raises their internal resistance. The higher you charge them and the further the ambient temperature is from the optimal, the faster they die.

Look on EBay. Search for them. Look at all the used ones pulled from equipment. Why do you think that is?

For the exact same reason I can do that for batteries?

All of mine are; my initial curiosity resulted in a buying spree, and that eventually turned into the DC supply for my radio station, which requires about a kilowatt and a half when fully dialed up. I get a solid hour of runtime there, more without the linear running. Not a battery in sight. That's been working flawlessly since it was put into service just before 2000.

Whoopee. Because I'm sure you're storing full power in them continuously when you're not using your station, right, and they're operating and being stored at outdoor temperatures? Surely that's the case, because otherwise you'd be making a stupid analogy, and I know you wouldn't do that!

Well, you can say anything you want, but I don't think you've demonstrated any of this

Yeah, damn the manufacturer spec sheets!

Yes, that's exactly what I was talking about. Are you actually ignorant of the rate of technological disruptions we've seen pop up in tech after tech?

And your reason for presuming that they'll apply to supercaps but not to batteries, when the trend is precisely the opposite, is...?

Comment Re:kind of like a small town fireworks show? (Score 3, Interesting) 200

I don't get why American fireworks displays are so small. I'd love to see this copter fly through fireworks in Reykjavík on New Years Eve. The Macy's 4th of july fireworks display in New York shoots off about 10 tons of fireworks. Iceland (most of the population being in Reykjavík and its adjacent municipalities, about 250k people) shoots off about 600 tons of fireworks on New Years, the weight of about 5 adult blue whales. The whole city looks like this for literally about an hour. It's not organized, it's just everyone shooting off an average of about 9 kilograms / 20 pounds per family - some more, some less. You see fireworks like the stuff that copter flew through in little towns of 1-2 thousand people. Even if you only count organized displays, it just seems to be so disproportionately little in the US. Pretty much every festival that does fireworks here shoots off several tons. Or otherwise just burns pretty much everything that's not nailed down. Or as more often is the case, both at the same time.

Comment Popularity != Quality (Score 1) 197

There should have been modifiers for typical bugs per kloc and security holes per kloc.

Also, there are many more layers to the industry. Scientific computing? Avionics? Publishing?

The subdivisions between languages are also a bit... strange. Java/Oak isn't truly uniform, whatever anyone claims. C and C++ have standards that aren't always backwards-compatible - if you ignore such changes, why bother listing C# or D as distinct? Lump the lot, together with B and BCPL under a single header.

My guess is that accurate representation of languages isn't possible (when does a dialect become a distinct language?) but that if it was, none of the so-called "big three" languages would be in the top 10. Computer languages are as bad as natural languages when it comes to classifiers.

Last, but by no means least, people rarely directly code any more. They code within engines, usually using some weird fringe language nobody has ever heard of that turns out to be Lua or Visual Basic with the keywords words renamed for the theme. Real programmers (as opposed to integer or complex programmers) tend to be in the minority, have become rarer after Qualcomm outlawed them, and are mostly in mourning for Freshmeat. But as a lot are Goths anyway, it's hard to tell.

Comment Re:Not Aluminum? Not a good sign. (Score 1) 247

I've never seen any studies of aluminum or titanium rebar. That'd be pretty darned costly, though, especially titanium.

Carbon fiber rebar seems to outperform bassalt rebar, though it's a lot more expensive. They're both very similar in form and how you work with them.

More common than either of them is fiberglass rebar. But the performance benefit of basalt rebar is a lot better than glass rebar, and it's not that much more expensive. Also, fiberglass can suffer slow degradation from moisture - not as fast as steel-rebar concrete degrades, but it's a known issue. Both carbon and basalt fiber are very resistant to this, and experience little to no degradation with time.

Two attempts to deal with rebar rust have been plastic coated rebar and stainless steel rebar. By and large, plastic coated rebar has proven to be a failure - in some places it's even shortened the concrete's lifespan. Stainless rebar usually offers some increased lifespan, but not as much as you might expect, and it's really expensive.

I mentioned earlier that how you work with composites versus metals is different. With metals, they're very heavy; the composites are light and easy to transport. Metals need tools to bend; the composites you can bend by hand. However, composites can't do sharp corners like metals can; you have to cut them and then bind the cut pieces together, or purchase premade corner pieces. But thankfully composites are much easier to cut than metals. The metals handle much higher temperatures than composites, due to the plastic binding. However in practice it doesn't affect fire resistance much, the huge thermal mass of the concrete and the fact that it outgasses generally prevents excessive fiber delamination. The biggest problem is experience. Few construction crews have experience working with non-ferrous rebar. Fiberglass has been researched the longest, nearly half a century, and while it's proven itself, the construction industry is generally very slow to take up new technology. Basalt fiber rebar has only been in pilot projects for a 20-30 years. While by all standards it appears to be more long-term durable than fiberglass (in addition to being stronger to begin with), it'll probably be even longer before you start seeing it in widespread use.

Not only do I like the stats it presents, especially versus its price point, but I also like helping promote new technology that I like. Also, there just seems to be something fitting about a home built in Iceland being with basalt rebar, basalt dust pozzolan, with basalt sand and gravel, and built on basalt bedrock ;)

Slashdot Top Deals

I judge a religion as being good or bad based on whether its adherents become better people as a result of practicing it. - Joe Mullally, computer salesman