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Comment: Yes and no (Score 3, Informative) 43

by Okian Warrior (#49803059) Attached to: First Ultraviolet Quantum Dots Shine In an LED

Generally speaking, yes... so long as you are still within the effect range.

The germicidal effect comes from an absorption band in DNA. This is (like everything else) a bell curve, where the effect drops off either side of the peak.

This diagram is a good visual.

Note that commonly available UV emitters (including UV lasers and LEDs and the quantum dots mentioned in the article) are so far out of the effective range to be completely ineffective.

And anything that is effective is pretty dangerous to use, so be careful taking one apart.

Comment: About 264 nanometers (Score 4, Informative) 43

by Okian Warrior (#49803023) Attached to: First Ultraviolet Quantum Dots Shine In an LED

Peak effectiveness for sterilization is around 264 nanometers. DNA has a specific absorption at that wavelength, so light at this frequency destroys DNA.

This wavelength is in the UV-C band, which is the radiation blocked by the ozone layer, which is one reason people are concerned about ozone: it protects us from DNA-damaging radiation.

Mercury emits UV at around 254, which is close enough to the DNA absorption peak to have good effect. A fluorescent bulb without phosphor and UV-transparent glass will work.

The wavelengths cited in the post, 377nm, are too long for germicidal effect. If the work can be extended, it would result in much more efficient germicidal bulbs by generating wavelengths closer to optimal, and because quantum dots are generally very efficient.

You can get UV bulbs for your furnace that stick into the plenum and disinfect the air as it blows past. You might be able to run one of these from an inverter while hiking. Be sure to cover the bulb and be *very* careful not to look at it when it's on.

Comment: Re:Russian rocket motors (Score 1) 62

by Bruce Perens (#49787045) Attached to: SpaceX Cleared For US Military Launches

Russia would like for us to continue gifting them with cash for 40-year-old missle motors, it's our own government that doesn't want them any longer. For good reason. That did not cause SpaceX to enter the competitive process, they want the U.S. military as a customer. But it probably did make it go faster.

Also, ULA is flying 1960 technology, stuff that Mercury astronauts used, and only recently came up with concept drawings for something new due to competitive pressure from SpaceX. So, I am sure that folks within the Air Force wished for a better vendor but had no choice.

Comment: Context (Score 3, Informative) 62

by Bruce Perens (#49782349) Attached to: SpaceX Cleared For US Military Launches

This ends a situation in which two companies that would otherwise have been competitive bidders decided that it would cost them less to be a monopoly, and created their own cartel. Since they were a sole provider, they persuaded the government to pay them a Billion dollars a year simply so that they would retain the capability to manufacture rockets to government requirements.

Yes, there will be at least that Billion in savings and SpaceX so far seems more than competitive with the prices United Launch Alliance was charging. There will be other bidders eventually, as well.

Comment: Soverign debt (Score -1, Troll) 742

I'd like to hear what the economists here think should be done about Greece.

"Soverign debt is not like personal debt!"

That's what the economists on this very blog say, when discussing US debt. It doesn't matter how far into debt the US is, anyone can see this by comparing our debt to our GDP: the latter number is really big, while the debt is really small.

See? You can't just say getting into debt is bad, because the two are entirely different.

I'd like to hear what the Slashdot economists think should be done about Greece.

Comment: Re:32MB? (Score 1) 227

by Okian Warrior (#49760509) Attached to: Google Developing 'Brillo' OS For Internet of Things

32MB? Bah. I remember the days when you could fit a whole OS in a hundred K! And 640K was enough for anyone!

Pfft, I remember running 40 users on terminals on a machine with 16K that probably had less than 1/10,000th of the cpu power a laptop has today.

Luxury!

I remember putting the boot card at the front of my deck, placing it in the card reader, and pressing the "load" button on a system with 4K of core memory(*).

Who'd have thought 40 years ago, we'd all be sitting here drinking chateau de chatillon.

(*) That part's actually true. I started on an IBM-1130, predecessor to the IBM-360.

Comment: Proctored voting (Score 3, Insightful) 103

A lot of people think online voting is the next big thing, but the problem is actually very hard to do online.

To do it right requires a "proctored" setting where the person is guaranteed to be alone, and unobserved (including video recording).

If you can't guarantee that the person is alone, then they can be coerced into voting a specific way. If you can't guarantee that the person isn't observed, then the person can sell their vote.

Video recording hasn't been addressed yet, but with the current system a voter can record their vote as proof of how they voted, and so vote selling is possible. It's functionally the same as being observed, just time shifted.

Add in the requirements for recounts and verification, and physical ballots in a proctored environment is the simple solution.

I've seen mathematical solutions that make tampering statistically impossible. The system injects a large portion of non-human votes in a cryptographically secure way such that it doesn't change the actual outcome, but it's impossible for a hacker to change votes due to the statistical likelihood that he'll change one of the non-human votes and be detected.

Even with these systems, you still need a proctored environment that guarantees anonymous and unobserved voting.

Comment: My response to Elon Musk (Score 1) 495

by Okian Warrior (#49740555) Attached to: The Brainteaser Elon Musk Asks New SpaceX Engineers

And on the subject of interviewing companies, here's my response to Elon Musk:

The North Pole.

You lay a rifle on the surface of a [perfectly] spherical planet with no atmosphere. Firing the rifle, due to the curvature of the planet the bullet goes some distance and then falls to the ground. As you increase the muzzle velocity of the bullet, the point if impact gets further and further from the rifle.

If the planet has an acceleration of 10m/(s^2), what velocity must the bullet have to go around the planet and hit the gun in the stock?

(NB: This is a trick question, but Elon Musk is an actual rocket scientist.)

Comment: And for the record (Score 1) 495

by Okian Warrior (#49740393) Attached to: The Brainteaser Elon Musk Asks New SpaceX Engineers

Oh, and for the record, the puzzle that Elon Musk asks is:

1) Older than dirt
2) The answer is common knowledge (hence, not a good puzzle to ask)
3) Has more than one correct answer
4) Is being asked wrong.

The actual full text of the puzzle should read something like: "A hunter walks [South... West... North... ends up in the same spot] and sees a bear. What color was the bear? (This version has only one answer.)

Here's one that *you* can ask during an interview.

You need to order weights for a 2-pan balance to weigh objects. The objects all weigh integral ounces (ie - no fractions), and the weights are all integral ounces.

What is the minimum *number of weights* you can use that lets you weigh anything up to 100 ounces?

(NB: the answer isn't 7.)

Comment: I hate puzzles in interviews (Score 1) 495

by Okian Warrior (#49740303) Attached to: The Brainteaser Elon Musk Asks New SpaceX Engineers

I really, *really* dislike hearing brain teasers in an interview.

Not because I don't like puzzles (I do), not because it's not a good way to judge the candidate (it is, in a sense), but because it shows up the deficiencies of the interviewer and the company.

Most of the time, the interviewer isn't into puzzles. They just looked something up on the internet, got a list of "here's a puzzle to ask the candidate", and mindlessly ask the question(*).

And when this happens, I answer the puzzle and then ask the interviewer my own puzzle, and see how they react.

Invariably, the answer is "I don't know. What's the answer?" within 3 seconds.

I don't want to work for someone like that, I don't want to work for a *company* that would hire someone like that, life's too short to spend time working amid thinkless drones.

A really bad company is when the VP or someone sticks his head in the door with a "hey, just wanted to see how it's going. Can you answer this question for me?" thing. I keep a chinese block puzzle in my pocket (that I invented) for this exact situation: I write down his answer on the whiteboard, hand him the puzzle, and say "if you can't disassemble this and reassemble it before the day is over, I don't want to work here".

Polite and reasonable interviews don't get this level of response, but turnabout is fair play. Ask me about my experience, ask me to solve a typical problem from the job description, get a feel for how well I work with others... these are reasonable.

But ask me why sewer caps are round, and you'll have to prove why you're company is good enough for me to work there. While you're interviewing me, I'm also interviewing *you*.

If everyone was more aggressively responsive to these types of games, companies wouldn't play them.

(*) Once, just once, I got into a real discussion of puzzles with the interviewer, I've got no problem with that. So long as it's not mindless bingo-card checkmarking, it's OK.

Comment: Re:Energy underlies all economic activity (Score 1) 256

So, in a world where the best EROEI available is 20, only 4% of all that societies efforts need to be devoted to obtaining energy. In a world where the best EROEI is 5, 20% of all the work is devoted to getting the energy to power civilization. At EROEI of 2, fully half of all our efforts as a civilization are devoted to energy extraction/production and everything else (agriculture, industry, medicine, art) has to fit into the remaining half of our time and resources.

So as EROEI drops, sometime before you hit 1, you're left with a nation of nothing but farmers and people working in solar panel factories, and any further decrease in EROEI means choosing between food on the table and power when you hit a light switch. At that point (if not before) civilization collapses.

That's an insightful answer, and is probably what people are talking about when they describe EROEI issues.

But there's a logical flaw in that argument, which is that it assumes that the energy needs of civilization must exactly fit the leftover energy. It does not take into account the magnitudes involved, it does not count leftover "unused" energy, and it compares a linear system with an exponential.

Take a concrete example from your numbers. Suppose EROEI is 2 as described. One half of our energy goes into making more energy, one half of the remainder (1/4 of the total) lets us live comfortably, and the remainder can be invested in even more energy production.

Or to put it another way, suppose a solar panel will produce the energy equivalent of 4x it's energy investment over 20 years (which is about right with today's technology). This is an exponential rise in energy output which triples every 20 years! At some point in the future, the solar panels produce enough energy to replace themselves as they get worn out, and have enough leftover energy to power our civilization.

Or a counter example, on a distant planet suppose EROEI for fossil fuels is 100 but the maximum flow is limited by geology. How much civilization can there be when EROEI is high, but the total energy is only enough to power [the equivalent of] a small U.S. state?

So far as I can tell, no one has addressed this logical flaw in the EROEI argument.

From a mathematical perspective, EROEI appears to makes no sense.

Comment: Re:Can I turn features off? (Score 1) 441

by Okian Warrior (#49731911) Attached to: Choosing the Right IDE

And for the record, turning off electric-mode in emacs is wildly difficult to actually do.

Can you follow along?

- click on the "C" menu
- mouse over the "Toggle" item
- click on the "Electric Mode" item

Is this really so wildly difficult?

Was I complaining about manual control, or talking about setting this in the profile file?

Comment: Question on EROEI (Score 3, Interesting) 256

Can someone help me understand EROEI ("Energy Return on Energy Input").

All the research on future sources of energy (that I can find) say that we're doomed as a civilization because the EROEI for renewables isn't as large as that of fossil fuels.

Okay, EROEI is the energy you get out minus (or divided by) the energy you put in, I get that. Fossil fuels take relatively little energy to gather, and generate lots of energy so their EROEI is rather large.

Wind and solar require a larger energy input per energy out, so it's EROEI is smaller but still greater than 1, even after accounting for mining the raw materials.

I'm not clear how the economic conclusion is reached that solar and wind cannot power our civilization. If we have enough rooftop solar and wind farms to generate all the energy we need as a civilization, and if there's enough left over to make *more* solar and wind installations over time (to replace the warn out bits), then why does EROEI matter?

Assuming that EROEI is a net energy positive (with a reasonable margin of error), why does it even matter at all?

(Also note: world population growth is slowing, and is steady or decreasing in all industrialized nations (including the US if you deduct immigration). The standard economic model assumes infinite consumption, but is that assumption correct? Is there be an upper limit to personal comfort in terms of energy use? Or at least diminishing returns? Would finite population and finite consumption invalidate the standard economic model?)

Comment: Can I turn features off? (Score 4, Interesting) 441

by Okian Warrior (#49730609) Attached to: Choosing the Right IDE

One question I always ask when evaluating a new whizz-bang high sparkle product is: can I turn the features off?

If you use more than one application in your development, you're always bumping into interface inconsistencies. Having to stop and look at the result of what you typed is annoying, time consuming and distracting.

I can type <tab> really, *really* fast, so it makes absolutely no sense to try to overcomplicate things by having the editor try to do some sort of indentation for me - it only means that I have to stop and look every time, and I can't get used to the feature because no other application does it the same way.

For emacs in particular, all the various "electric $LANG" modes have different ideas of which characters are electric, what their behaviour is, and what coding style I should be using. Selecting a coding style to use is about 2 hours of internet search, editing the profile, restarting, and testing. (And that's if you're using one of the approved styles, otherwise you're either stuck or forced to learn lisp. *shudder*)

(And for the record, turning off electric-mode in emacs is wildly difficult to actually do. One pitfall example: having "save state" turned on will override the profile file, leaving you wondering why the profile command from the online tutorial didn't work.)

You can't get used to it, you can't develop muscle memory or take your eyes off the screen because the minute you switch to something else (the browser, E-mail client, putty terminal, LibreOffice or anything else), muscle memory results in errors.

Lots of applications have these inconsistencies. Clicking in a text editor will place the cursor where the mouse is, while clicking on the address bar in the browser *selects* the line and places the cursor at the end. It takes 1 click to insert text normally, it takes 3 clicks to insert into the address bar. Muscles don't remember that.

People spend an inordinate amount of time fumbling the interface without actually thinking about it. Your "rich, user experience" isn't warranted and reduces efficiency.

Just give me a simple, direct interface.

Top Ten Things Overheard At The ANSI C Draft Committee Meetings: (9) Dammit, little-endian systems *are* more consistent!

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