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Comment Re:Doesn't add up (Score 3, Informative) 198

As for 10KW per hour, that is huge. What is consuming that much? An industrial level hair dryer?

It's 10 kilowatt hours not kilowatts per hour. A kilowatt hour is a unit of energy which could supply a 1kW load for 10 hours, or equivalently a 10kW load for one hour, or any other load at power P [kW] for a time t [hours] where t=E/P where E is the energy in kilowatt hours. Power is the rate of consumption of energy, where a watt is 1 joule per second, and energy is what's actually needed to do a given unit of work.

kW/h is basically a nonsense unit which means 10,000 joules per second per hour. This would be a power "acceleration" unit if you actually wanted to use it. Calling kWh kilowatts per hour is a pretty common misunderstanding that you see a lot in the news so as a EE I feel compelled to clarify when possible.

Comment Re:Wrong economics? (Score 1) 457

I haven't seen the numbers, but I have heard that a big part of the cost difference between running STEM and humanities degree programs is the higher cost of the faculty. STEM professors, especially full professors at a research university, can command very high salaries outside of academia, so naturally the academic salaries have to be at least somewhat comparable in order to attract qualified candidates. Some of this salary will be payed for by grants and research contracts, endowed positions, and so on, but it is still an expense for the university.

Comment Re:hybrid A/theta modulator (Score 4, Insightful) 47

For wide bandwidth modulation formats this is a bit of a pain since you need a very wideband, high current, power supply. so they are doing an A/theta modulator but trying to simplify the bias control on the PA to avoid that.

No, they're doing something more complicated than A/theta modulation (aka envelope tracking aka envelope elimination and restorataion aka ...). They are doing an outphasing amplifier which splits the original signal into two constant amplitude variable phase signals which will reproduce the original signal when they are recombined, but they are adding some envelope tracking elements to further improve efficiency since wideband combiners will absorb the differential section of the input signals as loss.

What I'm not clear on is why they are doing this when they have a predistortion loop anyway. a pure predistortion loop should be able to achieve very similar results without any need for the PA bias adjust. you can also do it with 1 PA instead of two.

A predistorter doesn't have much of anything to do with PA efficiency (the point of this MIT research), PD's are for linearity. High efficiency PA topologies typically take a hit to linearity. Fancy techniques like outphasing and envelope tracking are better than some but they still reduce linearity. Poor linearity means increased distortion. Distortion increases error rates in digital transmissions, and it also leads to signal leaking into adjacent signal bands, which isn't allowed in the tight cellular spectral environment. So they put a PD in there to linearize things a bit further. That's probably why they are using discrete bias levels instead of continuously variable - they can optimize their PD loop to work best in these four well-characterized states which gets most of the efficiency gain while making the linearization easier.

I don't know, looks like somebody's thesis to me. Doesn't look like it's particular practical. Also, first rule of looking at schemes like this. How much of that power they saved is being used in the more complicated digital circuitry. That's the reason you don't see PD loops in cell phones. It's a wash, you spend so much power analyzing the signal to do PD that you burn up the savings . Now if you have a 10W transmitter, PD makes lots of sense.

These are not fundamental limitations. It's making more and more sense as digital processing and DSP chips get faster, cheaper, and lower power. The point of research is to try to push the state of the art and it may not be "practical" when the research paper is hot off the press. If it's good enough then it will be practical some time down the road, and if it isn't good enough then it will be left aside as a lesson learned. Apparently the researchers think its good enough to found a startup company, so they're either foolish or they understand it better than you. Time will tell.

Comment Duplicate story from Oct 31 (Score 5, Informative) 47

This is a duplicate story posted on Slashdot on Oct 31: http://hardware.slashdot.org/story/12/11/01/0021213/breakthrough-promises-smartphones-that-use-half-the-power

Luckily this time the summary includes a link to an actual technical paper. The summary and the news article make it sound like this is an Envelope Tracking amplifier, but if you read the paper this is actually something different, it is more complicated and more interesting.

They are starting from an outphasing amplifier which divides a variable envelope signal into two constant amplitude but variable phase signals which can be amplified more efficiently since the amplifier doesn't need to output both large and small signals. But combining the signals is inefficient because the combiner must absorb some of the power when the two halves of the signal are very out of phase with each other. What the MIT researchers are doing is extending the outphasing technique to allow multiple discrete amplitudes on each amplifier to minimize the combiner inefficiency. It's more efficient than plain outphasing, I'm not sure how it compares to envelope tracking since the authors did not compare it to this in their paper.

Comment Re:Do People really pay for Porn? (Score 1) 339

Of course people really pay for porn. It costs money to create it, so somebody somewhere is paying for it to be made. Advertising doesn't add much to the industry revenue since most ads on free porn sites are for the paid porn sites and other adult sites. The free sites tend to have (in my opinion) pretty low quality in terms of the selection of content, and the display quality can be pretty bad. Some of the content there is placed by the entity who owns it, but much of it is surely pirated.

It's simply an entertainment expense and many people have no problem paying a fair price for something that they want. With a paid site you generally have a better selection of content in a genre that interests you, higher quality picture/video, and regularly added new content. In addition to people being cheap I think that there is some kind of guilt or shame that some people associate with paying for porn that they can sidestep if they only look at free porn.

Of course one problem is that many paid porn sites tend to be fairly expensive, probably because of the massive amount of marketing that they paid for on the free sites and the fact that a lot of people expect porn to be free these days, so there's a smaller number of paying customers.

Comment Re:Class C (Score 1) 110

Based on the article it sounds a lot like envelope tracking:

The new advance is essentially a blazingly fast electronic gearbox. It chooses among different voltages that can be sent across the transistor, and selects the one that minimizes power consumption, and it does this as many as 20 million times per second. The company calls the technology asymmetric multilevel outphasing.

But looking back at one of their papers: http://www-mtl.mit.edu/~jldawson/Dawson_digest2009.pdf it is not exactly envelope tracking. They are starting out with an outphasing amplifier (dividing the signal into two constant amplitude variable phase signals which can then be amplified with an efficient nonlinear amp and recombined into the original signal) and then adding a discretely variable drain bias (much like an envelope tracker) but the purpose of the variable drain voltage is actually to minimize power dissipation in the combiner's isolation resistor. Thus they compare their efficiency and linearity only to outphasing types of amplifiers. I would be curious to see how this stacks up to pure envelope tracking amplifiers.

Comment Re:Consider a pencil (Score 1) 712

I used a Graph Gear 1000 for a while. It has incredible style points, feels solidly built, and the retracting tip is a nice feature for when you keep the pencil in a bag or pocket. However after around 6 months of regular use with storage in a backpack the springiness in the clip was lost, and due to the unusual tip-retracting mechanism this mean that the tip would not stay retracted. Also I found that I was not a big fan of the narrow and hard metal grip, the heavy weight during long use, and the narrow eraser.

Nowadays my preferred pencil is the Pentel "Quicker Clicker" series, specifically the .7mm model, PD347. The wide body with a thin layer of rubber on the grip (enough to soften without being squishy) is very comfortable for me, and the large and easily accessible eraser is very handy. The non-retracting tip means I don't like to carry it around in my pocket, but since I only use it at my desk(s) and it's much cheaper than the Graph Gear I simply bought enough to cover all of the places where I'll need one.

Comment Re:Actually, (Score 3, Informative) 74

Even showing the extension you are vulnerable.
Using the unicode character U+202e one can write from right to left and hide the real extension: for example the executable "SexyL[U+202e]gpj.exe" will be shown as "SexyLexe.jpg" by the filemanager!

On linux you can create such a file with
echo > $'SexyL\342\200\256gpj.exe'

Rather than simply modding you up I decided to try this out, and it works! Which is kind of creepy.

Comment Re:Flawed only if you redefine nutritious (Score 1) 305

Sorry, I did notice that section of the article but forgot to address it. Partly that's a bit of scientific he-said she-said that I don't have the expertise to evaluate, but the other part is I don't really trust the reporter.

The reporter has both shown a strong bias towards organics, and a willingness to bend facts (the tortured definition of nutritious) to unfairly attack the author's integrity. So I don't know if the Kirsten Brandt study was a good one, or if the excluded nutrients were important ones, or if there's any one of a dozen other reasons that those sentences could be misleading. The Standford study could be wrong, but this NY times article won't be the one to convince me, this reporter already lost my trust and I'm not going to take him at his word.

Since you dismiss the Newcastle University study only on the basis of Mark Bittman being a biased columnist (fair enough, he probably is), you may be interested to read the recent NY Times article which also explains some of the methodology differences between the studies which lead to different conclusions. In any case, I'm reserving judgement on both studies for now.


Comment Re:The basics (Score 1) 208

Only for SMD production. I've done loads of SMD for 30 years now and especially for microwave RF work doing one off I think it would take a lot longer to CAD up a solder paste mask than to just hand solder it.

I think you'll find the cost of a PnP is having to buy everything in reels, and then having reels of unused stuff sit there. Yeah no headache with 0.1 uF decoupling caps, or if you focus all your work on one exact specific model of microcontroller chip, but everything else on the board is either buy a reel and throw most of it out, or do it by hand, and if you're doing 3/4 the board by hand, may as well do the whole thing and skip the PnP...

True, a pick and place requires a large scale of operation before it becomes worth the capital and the reels. But it shouldn't take much effort to create a solderpaste mask - whenever you're defining a new pad just add the solderpaste to the pad definition and you're done, all you need to do is export the layer at the end. This is helpful even for relatively small board runs - you stencil on paste, place parts manually, and reflow in a lab toaster oven / hot plate, etc. There's very little capital and once you get above a few boards or so (depending on the board and the assembly guy) it can be faster than hand soldering.

I imagine you could even use the inverse of the soldermask layer as a paste layer, at least for non-RF boards where everything except pads is usually covered in solderpaste. It's not ideal because then a bit of misalignment puts some paste on top of the soldermask which risks bridging for fine pitches, but I know there's CAM software out there which could shrink the solderpaste layer to correct for that.

Comment Re:To quote Triumph... (Score 1) 305

I agree. What if half of the football stadiums burned down from a serial arsonist. Almost the whole, freaking country would loose their minds. And I would be sitting comfortably telling them, "It's just a game. It doesn't matter and is not really important to life in general".

There's a huge difference! What you propose involves the actual loss of billions of dollars in property investment and a major impact on the sport in the US for some years due to loss of venues. What happened on WoW will require some overtime from the admin team to fix, resecure, and restore to pristine state from backups over a fairly short period of time.

So to better respond to the WoW hack: "Who cares, it's just an online game that they can restore from backups before you know it."

Comment Re:Flawed only if you redefine nutritious (Score 4, Insightful) 305

You missed some important points when you draw your conclusion:

That's a feature, not a bug. The role of a research paper isn't to make some broad sweeping conclusion, it's to carefully explore a narrow question, were the organics more nutritious, and on that question the answer was no.

This very important section of the article (emphasis mine) is conspicuously absent from your post:
Yet even within its narrow framework it appears the Stanford study was incorrect. Last year Kirsten Brandt, a researcher from Newcastle University, published a similar analysis of existing studies and wound up with the opposite result, concluding that organic foods are actually more nutritious. In combing through the Stanford study she’s not only noticed a critical error in properly identifying a class of nutrients, a spelling error indicative of biochemical incompetence (or at least an egregious oversight) that skewed one important result, but also that the researchers curiously excluded evaluating many nutrients that she found to be considerably higher in organic foods.

At this point that given that two research institutions have published metastudies with opposite conclusions, and that errors and oversights have been identified in the Stanford study, I'd have to say that the jury is out on this topic.

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