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Comment: Low voltage DC for distribution is silly (Score 1) 582

by craighansen (#49792667) Attached to: How Tesla Batteries Will Force Home Wiring To Go Low Voltage

Low-voltage DC needs 10x more copper for the same power, and extending power runs to "home run" makes the wires even longer. Unless you pay for that extra copper, wiring losses will eat your savings. The big issue with ACDC conversion is that the AC is 60/50 Hz, which means energy storage of 8-10ms x wattage for efficient conversion is required. Better efficiency and lower wiring costs would come from using higher voltage DC and/or higher frequency AC. Aviation, submarines, spacecraft, trains and some industrial tools use 400 Hz AC - which allows for smaller transformers and motors. DCDC converters essentially have internal oscillators to perform the voltage conversion, and can choose an even higher frequency to minimize energy storage time. The reason we're still using 60/50 Hz is because it's the way things always were, just like train gauges are a good match to two horses side-to-side, and perhaps because 60/50Hz hum is less annoying than 400Hz hum - but hum just means that you're losing power to the environment, so it's power efficient to eliminate that anyway.

That being said, when retrofitting incandescent lighting systems with lower-power lighting, it could make sense to use existing wiring at a lower voltage AND LOWER POWER LEVEL. That way the power/voltage conversion could be grouped together in one or a few places so that higher-efficiency converters can be used, but still kept close to the points of use to minimize wiring loss. Unfortunately, the retrofit market is going for power conversion in individual lighting fixtures so one fixture at a time can be changed out.

Comment: Re:Let me get this straight... (Score 1) 293

by craighansen (#49778743) Attached to: Amtrak Installing Cameras To Watch Train Engineers

Plain old walking isn't very safe (>6000 deaths per year average [includes bicyclists]), and much less safe than passengers on a train (7 deaths per year average).
Of course, it's because of those other forms of transportation that walking isn't safe.

http://journalistsresource.org...

Comment: The public wants that false sense of security (Score 1) 293

by craighansen (#49778667) Attached to: Amtrak Installing Cameras To Watch Train Engineers

That false sense of security is just what the public wants. The TSA is doing exactly that for airplanes.

Seriously, consider the recent derailment that has triggered this announcement. They already know the train was accelerating into the curve, and travelling faster than any permanent speed limit would allow. A GPS-based system (including accelerometers to assist the GPS when going through tunnels) would have been able to advise the engineer that the train was travelling at nearly twice the permanent posted speed, perhaps with a loud, audible warning that could alert an engineer that may have been distracted by idiots throwing rocks at the train, (with a time-limited shut-off to handle the case when the GPS is showing the wrong speed or location). It could even, be allowed to stop acceleration and apply brakes if not overridden within a few seconds of its warning by an alert engineer. It could even have a little video camera in it, and store the last 30 minutes of movement. It could even be made as an Android or iPhone app with no hardware development (save the USB-connection to slow the train), so it could be deployed in a matter of months instead of decades, at a cost that wouldn't need an Act of Congress to fund.

But sure, go ahead and give the public what it wants.

Comment: Re:How about speed arrestors, instead? (Score 2) 293

by craighansen (#49778389) Attached to: Amtrak Installing Cameras To Watch Train Engineers

So, yes, it's important that safety overrides be designed with a lick or two of sense - such as a override that automatically resets after a limited time, and/or only permits very low-speed operations, and an override that permits operation only if the doors are open less than a few millimeters, and only operates until the next stop. Was that too hard?

Comment: Re:30 years ago.... (Score 1) 293

by craighansen (#49778339) Attached to: Amtrak Installing Cameras To Watch Train Engineers

Yes, all that may be true, but enforcing permanent speed limits via a self-contained system would have prevented several major accidents and could have been implemented in minimum time and money so it could actually have been deployed. All that fancy-ass consideration has driven up the price and delayed the implementation of anything at all except the sharp wits of a tired old train engineer, who probably doesn't know how worn the wheels are and only remembers a few of the thousands of regulations that some desk jockey put in place without knowing how it was going to affect train operations.

Here's prime example of the perfect being the enemy of the good, and you're failing to see it in front your face. Trains are crashing, dude.

Comment: Re:Meh (Score 5, Informative) 372

by craighansen (#49634605) Attached to: Global Carbon Dioxide Levels Reach New Monthly Record

This was predictable based upon the Keeling curve, which has a seasonal oscillation based upon northern hemisphere plant growth. http://www.climatecentral.org/... About two years ago, the peaks of the CO2 concentration measured at Mauna Kea exceeded 400 ppm. Now the average is 400ppm, and in about two years, the trough of the CO2 concentration will exceed 400ppm.

The way things are going that'll be the last point we see 400ppm until the next extinction event.

Comment: Re:A story for those who (Score 1) 128

by craighansen (#49608819) Attached to: 4.0 Earthquake Near Concord, California

It was barely noticeable - that's why I went to the USGS site to see what it was. Didn't know we had to edumacate Slashdot on the Richter/Mercalli scale, particularly the editors who choose what random notes to put on the front page. Still, a magnitude 4.0 is a release of more energy than a MOAB http://en.wikipedia.org/wiki/G... , so I felt it even though 100km away. Those living in Concord would've felt a little more.

Comment: Re:A story for those who (Score 2) 128

by craighansen (#49608765) Attached to: 4.0 Earthquake Near Concord, California

An expression of caution following a quake "predicts" many more quakes than will really occur, as the probability is still less than 50%. Knowing of increased probability merely opens considerations of what to do during a "cautionary" period - minor adjustments such as lowering speed on the Transbay tunnel, or postponing crane lifts or tower climbs might be the kinds of things to do, but people may well tire of making these adjustments when nothing happens repeatedly. Bringing all life to a screaming halt or evacuating the cities isn't an appropriate response, but expressing relief at small shocks is what got those Italian scientists/bureaucrats convicted (all but one overturned on appeal). http://www.dailymail.co.uk/new...

I earned some ridicule today because a 4.0 quake wasn't followed by a larger quake - was even adjusted to a 3.6 magnitude. I was surprised when it posted to the front page - I thought it was just a note that might get combined into some other posting - slow news day, I guess. A few thousand people posted to the "I felt it" links on the USGS and similar sites, and enough people pressed "+" on the firehose to outweigh my own personal "-".

Comment: Re:A story for those who (Score 1) 128

by craighansen (#49608059) Attached to: 4.0 Earthquake Near Concord, California

I didn't put it on the front page. I did follow up with a comment that this was a group of 4 quakes, the first of which, magnitude 2.5 was about 10 minutes before the largest at magnitude 4.0. Slashdot's editors must have chosen to ignore the followup. There was another smaller one about an hour later. Yes, 4.0 is a small quake and I wasn't upset about it. Perhaps it would be interesting to note that quakes do follow each other in statistical groupings, so a small quake can indicate another following quake with increased probability - a ten minute warning is arguably more meaningful than the tens of seconds we can get by outrunning the p- and s- waves with electromagnetic waves.

Comment: Re:the real traitors (Score 1) 200

by craighansen (#49423837) Attached to: Snowden Demystified: Can the Government See My Junk?

++this. The "Three hops" rule, using a connection factor of 190 (the average number of friends on facebook), you're not a target of surveillance if none of the 5 million people that are friends of friends of friends of you are foreign nationals. http://www.theguardian.com/wor...

(You'll have to drag the slider to 190 to get the 5 million figure.)

If a 6600 used paper tape instead of core memory, it would use up tape at about 30 miles/second. -- Grishman, Assembly Language Programming

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