Catch up on stories from the past week (and beyond) at the Slashdot story archive


Forgot your password?

Slashdot videos: Now with more Slashdot!

  • View

  • Discuss

  • Share

We've improved Slashdot's video section; now you can view our video interviews, product close-ups and site visits with all the usual Slashdot options to comment, share, etc. No more walled garden! It's a work in progress -- we hope you'll check it out (Learn more about the recent updates).


Comment: Re:QuikClot and Celox (Score 1) 69

If this technology becomes common place, I expect those with crustacean allergies will be required to wear a red tag same as those with pencilin allergies.

It might even become practice to use it anyway and follow up with a treatment for the anaphylaxis, if the bleeding is severe enough. People can survive shellfish reactions with management - severe internal bleeding, not so much.

Comment: Re:The value of technology investment (Score 1) 82

by bill_mcgonigle (#49365579) Attached to: SpaceX's New Combustion Technologies

This is the first article I've seen that explains well how GPUs can/are being used for practical applications along with what can be achieved and some of the issues.

GPU's have been used for all sorts of "practical" computations for half a decade now, but the really interesting part here is that CFD has been particularly GPU-resistant using existing algorithms. See the Xeon Phi processor, etc. for non-GPU approaches to throwing dedicated hardware at the problem. It's easy to underestimate the enormity of this quote, but "starting from scratch" when necessary is something SpaceX excels at:

I am grateful to SpaceX for allowing us to basically start from scratch on CFD and in many ways reinventing the wheel.

It's hard to gain sufficient insight from TFA but it sounds like this is as big as hidden-line-removal in computer graphics and that they've moved CFD to the boundary conditions and made that GPU-computable, which is like solving two or three orders of magnitude at once.

Comment: Re:Wrong Focus (Score 4, Informative) 82

by jcr (#49365325) Attached to: SpaceX's New Combustion Technologies

As it happens, back in the '80s I worked at a company (Commonwealth Scientific) that built ion-beam guns based on the Kaufman duoplasmatron, which was the basis of the mercury-vapor thrusters that NASA had developed in the 1960s. The company was trying to make the aperture of the guns as wide as possible, and the difficulties included neutralizing the ion beam on the way out, keeping the plasma inside the gun stable, and keeping the beam density even. Basically, the bigger the gun, the harder it was to make it run steadily. When I was there, they had 8" apertures and were working on scaling them up to 12" apertures.


Comment: Re:Cut energy use by WHAT? (Score 1) 150

by AnotherBlackHat (#49365125) Attached to: Graphene Light Bulbs Coming To Stores Soon

Err - no.

That number on the Digikey page isn't lumens per watt (I've no idea what unit mw/W is supposed to be).

If you look at the datasheet that LED is a max of 139 lumens with a forward voltage drop of 2.9 at 350 mA, or slightly less than 140 lumens per watt (under ideal conditions).

By definition there are 683 lumens per watt of radiant power at a wavelength of 555 nm.

The highest announced efficiency LED to date is "only" 303 lumens per watt -
303/683 = 0.44 or 44%

The best LED I can actually buy is still under 200 lumens per watt, less than 30%

The 4flow, which is pretty close to the best consumer LED light bulb you can get is only 85 lumens per watt.

All much better (efficacy) than a CFL or incandescent, but no where near 48%

Comment: :( Can you help the world? Re:Cumbered (Score 1) 290

by davidwr (#49356847) Attached to: Ask Slashdot: What Makes Some Code Particularly Good?

Take all work you've written and entrust it with someone who will publish it a few years after you die and after your estate is settled or a few years after the last company that would have any claim to it ceases to exist, or after any copyrights or patents other than yours that apply can reasonably be presumed to have expired (probably 95 years after you wrote the code), whichever comes later.

"You're a creature of the night, Michael. Wait'll Mom hears about this." -- from the movie "The Lost Boys"