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Fuel Efficiency Numbers Overstate MPG More For Cars With Small Engines

serbanp Re:Overstated or misrepresented? (402 comments)

My 17yo Civic has a complete mileage log for all of the 205k miles it traveled, i.e. how many gallons to full (I never do partial refueling) and how many miles traveled. If anything, the mileage is consistently better than what was on the windshield when I bought it new.

In fact, looking at the numbers I can see the seasonal patterns (2MPG lower in winter), probably caused by my state switching to the winter blend (more Ethanol).

about two weeks ago
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The Great Lightbulb Conspiracy

serbanp Re: I dunno about LEDs, but CFLs don't last (602 comments)

No LED-based lighting fixture uses a voltage regulator and a series resistor to limit the current through the LED.

The LED is driven by a current regulator; yes, it usually has a small sense resistor to measure and adjust the driving current, but that's something totally different from a resistor used to limit the current.

Remember, the 'D' in LED stands for (semiconductor) "Diode", which means that in forward conduction it has an exponential relationship between current and voltage. The only way to control the brightness is to control the current, you can't rely on the equivalent "resistance" (i.e. Vd/Id).

The premature failure of the LED bulb is caused exclusively by the embedded electronics degrading at high temperature. Since the LED is still dumping a lot of heat when working, the heat must be dissipated (hence puny LEDs and bulky, machined Al heatsinks) or the electronics get fried.

Guess what the drive to reduce the manufacturing cost will do to the quality of the LED bulbs?

about three weeks ago
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In Maryland, a Soviet-Style Punishment For a Novelist

serbanp OTOH (441 comments)

the Idiocracy syndrome cuts both ways. Yeah, the official reaction was a little over the top. However, I pity the young lad for having no imagination whatsoever. Nothing in the wide world to write about but more gore in a school setting? Right.

about a month and a half ago
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Limiting the Teaching of the Scientific Process In Ohio

serbanp Re:The US slides back to the caves (528 comments)

The number 12 is involved only in the foot/inch ratio. Other stuff (lb/oz = 16, yd/ft=3, mi/yd=1760 - wtf!) is even whackier.

Although I agree that woodworking is much better in inches than in millimeters.

about 2 months ago
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Entire South Korean Space Programme Shuts Down As Sole Astronaut Quits

serbanp Re:reminds me of the old joke (186 comments)

You're actually talking about today's Albania, isn't it? Wikipedia does mention that all fixed-wing aircraft have been retired from their Air Force in the last couple of years.

about 2 months ago
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Entire South Korean Space Programme Shuts Down As Sole Astronaut Quits

serbanp reminds me of the old joke (186 comments)

Q: Why did Albanian airforce not participate in WW2? A: The pilot was sick.

Sounds similar to SK's Space Program issue.

about 2 months ago
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Nokia Buys a Chunk of Panasonic

serbanp Re:Nokia still has products? (54 comments)

Repeat slowly after me: Elop, Stephen Elop. Elon Musk is a different (way different!) person...

about 3 months ago
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Google Offers a Million Bucks For a Better Inverter

serbanp Re:so... (260 comments)

The input is DC so there is no need for low frequency input decoupling

Unfortunately, that's not true. The output is AC and the input-referred current will reflect it, i.e. will be quite high when the output reaches its highest (340V). Since the input source has an equivalent internal resistance of 10Ohm and would droop too much, some bulk capacitance is needed to provide these 120Hz current surges.

I agree with you that the design revolves around the placement of power components (capacitors, inductor, power switches and some sort of heatsinking), then the control circuitry be crammed in the spaces between them.

about 3 months ago
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Google Offers a Million Bucks For a Better Inverter

serbanp Re:so... (260 comments)

Having read the actual spec, I realized that my question was stupid. Input voltage is 450V, therefore the inverter is just a full-bridge DC/DC converter

The challenge is actually perfectly doable, with the only difficult points being the size of the switching inductor and the input bulk (most likely tantalum) and output filtering (must be ceramic) capacitors. IOW, the winner will be the one with the best connections to component manufacturers.

about 3 months ago
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Google Offers a Million Bucks For a Better Inverter

serbanp Re:Why? (260 comments)

Having read the actual Spec Document, the input voltage is 450V DC, with an equivalent series resistance of 10Ohm. Definitely not 12V DC.

about 3 months ago
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Google Offers a Million Bucks For a Better Inverter

serbanp so... (260 comments)

what is the state of the art w.r.t. the 12VDC->110VAC/60Hz 1kW inverters?

about 3 months ago
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No Shortage In Tech Workers, Advocacy Groups Say

serbanp Re:it depends on what "skilled worker" means. (401 comments)

However, there are about 600,000 H1B workers in the USA. How many of these do you believe have the skills only found in comp-sci grad programs, or more to the point, how many of those don't have and don't need grad school comp-sci skills?

One thing I never understood is why so many posters on /. believe that Comp-Sci is the only highly technical field that matters. H1B visa holders are many times technically-educated people who have nothing to do with programming (i.e. Chemistry, Materials Physics, EE etc).

The Sun does not revolve around IT, so why are we suggesting it does?

about 3 months ago
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Nathan Myhrvold's Recipe For a Better Oven

serbanp Re:Hacking ovens? (228 comments)

I have half-bricks on the bottom of my gas-fired oven. It bakes much more evenly and keeps the temperature very steady.

Yes, thermal mass is the ticket, not just-in-time heat control gimmicks.

about 4 months ago
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Nathan Myhrvold's Recipe For a Better Oven

serbanp this guy is out of his mind (228 comments)

Not only it's not obvious what "better" means when baking is involved, but he's showing his Microsoft roots here, stupid "improvements" that make the whole system break so much easier.

It's a known fact that most "modern" residential ovens, the ones with displays, lots of buttons to set baking programs etc, should never use the self-clean cycle. The thermal insulation is not good enough to protect the electronics (a.k.a. control board) and the oven fails, typically after a high-heat cycle (the self-clean reaches 700-800*F). This is equally true for GE and Whirlpool as well as for Viking and Ilve.

Adding more electronics to a hot environment is asking for more and expensive trouble.

Commercial appliances are better built though, are they Myhrvold's target? In any case, his post is just a petulant rant showing overkill application of technology, just because "he can". Zapping mosquitoes with laser beams sounds more realistic...

about 4 months ago
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DNA Study: First Farmers Were Also Sailors

serbanp Re:Why not also Egypt? (40 comments)

However, the general consensus is that Egypt borrowed the agriculture invention, and rather late at that (~5000BC), not the other way around.

The Egypt's ancient culture has been focused on the Nile *exclusively*, they did not care about the delta and sea-faring until they started meddling in Middle East affairs (1200BC or so). The first major sea port has been founded in Classic Antiquity only!

about 4 months ago
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Fasting Triggers Stem Cell Regeneration of Damaged, Old Immune System

serbanp Re:My friends don't fart... (148 comments)

My apologies, I was thinking of the colon. EFL (English as a fourth language).

Thanks for the correction.

about 4 months ago

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