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Comment Implementation is questionable (Score 1) 75

Here in Boston, cabbies would say that the machine was broken because they wanted you to pay cash and not have to send the card company 5% or whatever. So the city raised rates to compensate for that fee. Guess what? "The machine is broken" is what you will hear most of the time if you offer a card at the end of the ride.

Comment Another useful vacuum tube: Thermionic converter. (Score 1) 95

Another vacuum tube technology with current applications and substantial advantages over semiconductor approaches to the same problems is the Thermionic Converter. This is a vacuum-tube technology heat engine that turns temperature differences into electric power - by boiling electrons off a hot electrode and collecting them, at a somewhat more negative voltage (like 0.5 to 1 volt), at a cooler electrode.

Semiconductor approaches such as the Peltier Cell tend to be limited in operating temperature due to the materials involved, and lose a major fraction of the available power to non-power-producing heat conduction from the hot to the cold side of the device. Thermionic converters, by contrast are vacuum devices, and inherently insulating (with the heat conducted almost entirely by the working electrons, where it is doing the generation, or parasitic infrared radiation, which can be reflected rater than absorbed at the cold side.) They work very well at temperatures of a couple thousand degrees, a good match to combustion, point-focused solar, and nuclear thermal sources.

Thermionic converters have been the subject to recent improvements, such as graphine electrodes. The power density limitation of space charge has been solved, by using a "control grid" to encourage to charge to move along from the emitter to the collector and magnetic fields to guide it (so it doesn't discharge the control grid and waste the power used to charge it).

Current thermionic technology can convert better than 30% of the available thermal energy to electrical power and achieves power densities in the ballpark of a kilowatt per 100 square cm (i.e. a disk about 4 1/2 inches in diameter). That's a reasonably respectable carnot engine. This makes it very useful for things like topping cycles in steam plants: You run it with the flame against the hot side so it is at the combustion temperature, and the "cold" side at the temperature of the superheated steam for your steam cycle. Rather than wasting the energy of that temperature drop (as you would with a pure steam cycle) you collect about a third of it as electricity.

It also beats the efficiency of currently available solar cell technology (and the 33.4% Shockleyâ"Queisser theoretical limit for single-junction cells), if you don't mind mounting it on a sun-tracker. Not only that, but you can capture the "waste heat" at a useful temperature without substantial impairment to the electrical generation or heat collection, and thus use the same surface area for both generation and solar heating. (Doing this with semiconductor solar cells doesn't work well, because they become far less efficient when running a couple tens of degrees above room temparature.)

Comment Re:Again: Big Dumb Co (Score 1) 145

It might surprise you to know I've wanted to do the EXACT SAME THING -- start a company to make dead-simple appliances. I can't tell you how many 20-30 year old appliances from the 80s I've replaced in the last 2 decades, and the replacements are good for 5-10 years. I'd pay $1,000 for a washing machine TOMORROW if it had quality components (switches, motors, hinges, etc.), user-serviceable parts, and if it would last 50-100 years. No reason it couldn't. I don't care if it's a bit heavier and has thicker parts and is a bit less efficient, as long as it lasts. You know what's inefficient? BUYING NEW DAMN APPLIANCES EVERY 8 YEARS.

Comment Easy answer (Score 2) 398

"What are you doing to make selling electric cars as profitable and painless for your dealers as selling gasoline or diesel vehicles?"

What am I doing? That's easy: I'm NOT GIVING A SHIT HOW THEY FEEL. If I want to buy one, I'll walk into a dealer, and they can take my money, or not. Salesman's not making enough money? Wah wah wah, go get a real fucking job and do something USEFUL for a living.

Comment Re:Many a young engineer.... (Score 2) 95

... every schematic drawn by every semiconductor engineer got the arrow backwards.

As I heard it, The arrow is "backward" because Benjamin Franklin, when doing his work unifying "vitreous" and "resinous" electricity as surplus and deficit of a single charge carrier (and identifying the "electrical pressure" later named "voltage"), took a guess at which corresponded to a surplus of a movable charge carrier. He had a 50% chance to assign "positive" to the TYPICAL moving charge carrier in the situations being experimented with (charge transfer by friction between different substances, currents in metallic conductors, and high voltage discharges in air and water-in-air aerosols) and happened to guess "wrong".

Thus we say electrons have a negative charge, "classical current" corresponds to the sum of the flow of moving positive charge minus the flow of negative charge (i.e. the negative of the electron current, which is all there is in normal-matter metallic conductors), the arrowhead on diodes (and junction transistors) points in the direction of classical current across a junction, and so on.

But though it's the charge carrier in metallic conduction and (hard) vacuum tubes, the electron ISN'T the only charge carrier. Even in the above list of phenomena, positive ion flow is a substantial part of electrical discharge currents in air - static sparks and lightning. Positive moving charge carriers are substantial contributors to current as you get to other plasma phenomena and technologies - gas-filled "vacuum" tubes (such as thyratons), gas an LIQUID filled "vacuum" tubes (ignatrons), gas discharge lighting, arc lighting, arc welding, prototype nuclear fusion reactors, ...

Move on to electrochemistry and ALL the charge carriers are ions - atoms or molecular groups with an unequal electron and proton count, and thus a net charge - which may be either positive or negative (and you're usually working wit a mix of both).

And then there's semiconductors, where you have both electrons and "holes" participating in metallic conduction. Yes, you can argue that hole propagation is actually electron movement. But holes act like a coherent physical entity in SO many ways that it's easier to treat them as charge carriers in their own right, with their own properties, than to drill down to the electron hops that underlie them. For starters, they're the only entity in "hole current" that maintains a long-term association with the movement of a bit of charge - any given electron is only involved in a single hop, while the hole exists from its creation (by an electron being ejected from a place in the semiconductor that an electron should be, by doping or excitation, leaving a hole) to their destruction (by a free electron falling into them and releasing the energy of electron-hole-pair separation). They move around - like a charge carrier with a very short (like usually just to the next atom of the solid material) mean free path.

For me the big tell is that they participate in the Hall Effect just as if they were a positive charge carrier being deflected by a magnetic field. The hall voltage tells you the difference between the fraction of the current carried by electrons excited into a conduction band and that carried by holes - whether you think of them as actual moving positive charge carriers or a coordinated hopping phenomenon among electrons that are still in a lower energy state. Further, much of interesting semiconductor behavior is mediated by whether electrons or holes are the "majority carrier" in a given region - exactly what the hall effect tells you about it.

So, as with many engineering phenomena, the sign for charge and current is arbitrary, and there are both real and virtual current carriers with positive charge. Saying "they got it wrong" when classical current is the reverse of electron current is just metallic/thermionic conduction chauvinism. B

Comment ...or the difference may be totally insignificant. (Score 1) 469

The marginal increase in the probability of an someone being a terrorist given that you know he's an engineer may be startling in relative terms, but in absolute terms it's insignificant.

Estimates of total active membership in terror groups worldwide is under 200,000, but let's assume there's even million active terrorists just for the sake of having round numbers and not having to quibble over where to put the decimal point. There are seven billion people in the world, so the rate of terrorist participation in the general population is 14 thousandths of a percent; let's call that p(T), and call the probability that someone is a terrorist given that they're an engineer p(T|E). Let's look at the absolute marginal difference being an engineer makes, i.e.:P(T|E) - P(T)

i. p(T) = 0.0001428
i. p(T|E) = 9 * P(T) = 0.001286
iii. P(T|E) - P(T) = 0.001143

So being an engineer increases your chance of being a terrorist by at most about 1/10 of 1% under wildly pessimistic assumptions. In fact the marginal difference is really more like 1/50 of 1%. Now it's interesting that the rates of terrorism are so much larger among engineers than other people, but it has little practical significance and being an engineer myself that's what I'm most concerned with. If you were designing a surveillance program and were picking out groups that need keeping tabs on, 1/10 % is a grasping-at-straws number

Comment Re:Vacuum tubes handle EMP's better (Score 1) 95

"No point progressing since the bombs are gonna fall any day now. Then where will your fancy silicon highways and databases be?"

Given that the Internet Protocol and much of the rest of the networking technology that still underpins the Internet were developed as part of a cold-war program to create a communication system that could survive a nuclear attack that destroyed most of it, and still reorganize itself to pass messages quickly, efficiently, and automatically among any nodes that still had SOME path between them, your post seems to come from some alternate universe to the one I inhabit.

"When it comes to humility, I'm the greatest." -- Bullwinkle Moose