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Comment Re:Yes more reliable (Score 1) 101

The idea is that your device runs a calendar app and syncs with Google Calendar. You then get notifications regardless if you are online or outside a coverage area,

And through what magic does that sync occur if you are offline or outside a coverage area?

I'm not foolisbn enough to give an advertizing company my callendar, but I'm pretty sure that Google Clendar uses TCP/IP to sync. Which means you have to have data reception. Which is much less avaiable than SMS.

Comment Re:Tesla enables Edison to win the endgame? (Score 1) 597

I said as much above.

In an AC system, that current is continuously changing, so those transmission lines are continuously radiating away some amount energy. But that's not all. If there are any conductors nearby, those E-M waves can induce a current in those conductors, and the resulting E-M waves from that induced current can drag on the AC line further. This mutual induction is how transformers work. But, along an AC transmission line, unwanted coupling results in transmission losses. So, an AC system has a built in, inherent source of losses in the alternating current itself.

...and...

In a DC system, with a fixed, perfectly resistive load, the current doesn't change, so there's no radiative losses. In the real world, though, the loading on the system is continually changing, so the actual current demand on the DC system will vary over time, and some energy will be radiated away. To some extent that can be filtered, but that's limited by the amount of storage you can put near the ends of the transmission.

Comment Re:Availability (Score 1) 692

Because it's cheaper to have an immortal serf class than it is to have to train up larval serfs for 20 years at a net negative value before they're useful? Young people are generally a resource sink with no return on investment for a couple decades.

Historically speaking, a young person began to earn an income much earlier than age 20. It's only our modern laws and policies that have been pushing this later and later. Even today this continues as more and more young people start their careers laden with high college debt.

Comment Re:capacitance loss (Score 1) 597

Capacitors store energy, they don't dissipate it. Likewise with inductors.

Transmission lines represent both capacitive and inductive loads simultaneously. The capacitance, inductance, resistance of the transmission line together combine to form the characteristic impedance of the line. (Ok, there's one additional term: the conductance of the dielectric between the conductors. But, for high voltage transmission lines that are widely separated, this term is effectively 0.)

The characteristic impedance of a transmission line is of primary importance for determining the ideal load impedance for the line. In an impedance matched system, the maximum power will be transmitted to the load with no reflections.

Reflections can cause a phase shift between voltage and current, making a transmission line effectively look reactive or inductive. (See surge impedance loading.) This can be corrected for in the same ways as reactive or inductive loads by adding capacitance or inductance elsewhere.

If the load itself is reactive or inductive then you can get reactive power transfer. Reactive vs. inductive is in some sense a matter of sign; in one, current leads voltage, in the other current lags voltage. In both cases, current is out of phase with voltage and that's the problem to be solved.

Reactive power doesn't transmit any actual power to the load, but it still sends current through the system. Current is subject to ohmic losses (thanks to our friend I*I*R). Sending current without delivering real power subjects you to losses without any benefits.

In general, the capacitance of the transmission line itself isn't the culprit on its own. Rather, if you have a reactive load (either capacitive or inductive), or you have imperfect impedance matching between the load and the transmission line, you can get current flowing through your wires that isn't driving a load. That excess current incurs plain ol' resistive losses.

There is one way high capacitance can cause real problems for transmission line management, though. The rate of propagation of waves through a conductor slows in proportion to the square root of the product of the inductance and the capacitance. So, for a highly capacitive line, reflections move slowly through the system, and it becomes more difficult to compensate for transients. That seems to be the real bugbear for buried high-capacitance lines. Again, you're not losing to the capacitance directly, but rather to the knock on effects that lead to poorly compensated reflections and reactive power transfer in the system.

(Dr. Jetton, if you're reading this... EE305 may have been 20 years ago for me, but I haven't completely forgotten it. And Dr. Schertz... I didn't completely forget my T-line theory either. I wouldn't be surprised if either of you would point out flaws in my summary above.)

Comment Re:Premature (Score 1) 597

I used 5v as an example as the linked article spoke specifically of running 5V and 12V everywhere. I agree that you really want a higher voltage for distribution. 48V goes a long way, although it still requires quite a lot more copper than 110V or 240V for the same power carrying capacity. (About 5x if I did my math correctly.)

Now, if those in-wall adaptors could store some charge locally (small capacitor bank), and you didn't have to wire for peak current, only sustained current, maybe you could get away with smaller wiring that way. I'm skeptical.

Comment Google's Useless About Updates (Score 2) 83

Well, thank you very much, telling me that I'd get better battery life if I installed the new Android version. As far as I can tell (at least with all previous Android versions), Google's instructions for installing the new software are "What? You don't have one of these three Google-brand phones? Then wait for your carrier!".

That's bad enough for my phone (which has a carrier, and Samsung's a reasonably major brand, though my previous HTC phone never got upgraded), but my tablet's Wifi-only, so there's no carrier, just a manufacturer who sold that model 2 years ago and doesn't have that tablet easily located on their website, and as far as I can tell, if I were to dump IceCreamSandwich for Cyanogen (who at least tell you what hardware resources you need for each version), I'd lose access to the Google Play Store?

Comment Re:Premature (Score 1) 597

I see what you mean. Let's put some numbers to that for everyone's benefit.

According to the table I linked previously, the OOOO gauge wire is 0.16072 ohms per 1000m. So, for a 20m run, that's about 0.00321 ohms. The voltage drop incurred by 330A across that resistance would be just over 1.06 volts.

For a 5V run, that's pretty significant, really. And you'd be dissipating over 350W in that wire alone. Yow! At 330A, you'd be burning 20% of your power just in that cable if you used OOOO gauge cabling.

Now the same numbers for 10 gauge wire, 15A, 110V, 20m. That's 3.276392 ohms per 1000m, or 0.0655 ohms for 20m. Voltage drop at 15A is 0.983V. Peak power dissipated in the wire is 15A * 0.983V = 14.7W. (RMS power is only ~10W.)

Submission + - Sourceforge staff takes over a user's account and wraps their software installer (arstechnica.com) 11

An anonymous reader writes: Sourceforge staff took over the account of the GIMP-for-Windows maintainer claiming it was abandoned and used this opportunity to wrap the installer in crapware. Quoting Ars:

SourceForge, the code repository site owned by Slashdot Media, has apparently seized control of the account hosting GIMP for Windows on the service, according to e-mails and discussions amongst members of the GIMP community—locking out GIMP's lead Windows developer. And now anyone downloading the Windows version of the open source image editing tool from SourceForge gets the software wrapped in an installer replete with advertisements.


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