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


Forgot your password?

Comment some of the challenges (Score 4, Informative) 218 218

IEEE Spectrum had an article last year describing some of the challenges we'll need to overcome in order to achieve exascale computing.

Here's another, somewhat pessimistic piece they posted in 2008 - a digest of a DARPA report that went into significant technical detail.

The biggest hurdle is power, and the biggest driver of that isn't the actual computation (i.e., the energy to perform some number of FLOPS), but rather moving that data around (between cores, to/from RAM, across a PCB, and among servers). Other hurdles include how to manage so many cores, ensure they are working (nearly) concurrently, how to handle hardware failures (which will be frequent given the amount of hardware), and writing software that can even make use of such technology in anything approaching optimal fashion.

Not to say its impossible, merely hard given the present state of things and projecting a bit into the future. But as we know, "it is difficult to make predictions, especially about the future." [source?]

Comment Re:Make the stuff (Score 2) 91 91

The purpose of the investigation was really the atomic-level computer simulation. Specifically, they were investigating whether they could properly simulate the entropy levels of an alloy in the solid and liquid phases, and the heat of fusion required to melt the substance, then extrapolate the melting point from that data. Ultimately, finding a material with a record-high melting point was the challenge used to develop the computation, not an end to itself.

That said, now that they've identified the alloy, the article mentions they are will be collaborating with another institution to synthesize and characterize it, hopefully verifying their calculations and predictions.

Comment Re:Very nifty, but... (Score 1) 62 62

Because scaling supersonic aerodynamics up to a spacecraft with twice the size is nontrivial

I'll grant you it is a nontrivial problem, and being able to make it work on a larger vehicle is a slick piece of engineering. On the other hand, the video presents nothing new about those aerodynamics, nor any of the challenges they needed to solve to maintain the concept in SpaceShipTwo. Instead, to use a car analogy, the video goes something like "motorcycles have two wheels, cars have four. Ours product is cool because it has three, something we first developed over a decade ago. The latest version is cooler because it also has three." When you come to that last sentence I hope you will conclude, as I did, that the creation of this video was not at all worth posting on Slashdot.

Comment Very nifty, but... (Score 4, Informative) 62 62

The feathering mechanism is very clever and effective, and I'm sure that Richard Branson and Virgin Galactic love getting free advertising on Slashdot. But this concept - the mechanism, the shuttlecock behavior, the passive stabilization - was successfully demonstrated when SpaceShipOne won the X-Prize ... in 2004.

So please explain, Oh submitter and editors, why are you cluttering up our lives with old news?

Comment Re:wtf people (Score 1) 66 66

It's a developing story. By linking to a Google News search, readers will be able to see (what google's algorithms think are) the most important and relevant news articles related to the topic.

Bonus: if it turns out to all be a hoax, the linked-to Google search will, months or years from now, reflect that.

Submission + - James Horner, Movie Composer, Dies in Plane Crash

necro81 writes: James Horner, the Oscar-winning composer for the soundtracks of dozens of movies, died Monday while piloting his aircraft in California. Horner, who had a long collaboration with directors James Cameron and Ron Howard, was behind the music for major blockbusters like Avatar, Titanic, Braveheart, Apollo 13, and A Beautiful Mind. Other scores notable to the /. crowd include Star Trek II, Sneakers, Deep Impact, Aliens, Searching for Bobby Fischer, Willow, and *Batteries Not Included.

Comment Re:Comparing apples to miniature oranges (Score 1) 409 409

The linked-to article from the CDC accounts for that. In Figure 3, you'll see the heavily skewed distribution of sugar-drink consumption. About 50% of the population (myself included), consumes zero on any given day, but it goes waaaaay up from there. The 178/103 cal value I used is the average, reported by the authors, across the entire population.

I would argue, however, that this does not change my math, since I'm talking averages. If half of the population isn't drinking any, the way to cut the average consumption in half is for those that are doing the drinking to have a commensurate decrease in their consumption. The ones most affected by drinking would also be most affected by cutting back. (As you have said.) While the half that isn't consuming these drinks would see no weight loss because of others' cutting back (although there's evidence to suggest that your own weight is influenced by the weight of your friends), the ones that are drinking would see more substantial weight loss (and boy do they need it).

Again, on average, the math works out in the way that I have described

Comment Re:Comparing apples to miniature oranges (Score 1) 409 409

which would be a poor investment, because then pepsi would just completely replace coca-cola.. And if you bought them out then some other third party would rise.

Which is why I added "It's total fantasy." I was not making a policy prescription - I was making a scale comparison.

Comment Re:Comparing apples to miniature oranges (Score 1) 409 409

Consumption of Sugar Drinks in the United States, 2005–2008

"Overall, males consume an average of 178 kcal from sugar drinks on any given day, while females consume 103 kcal."

(Nutritional calories (the kind listed on food labels) are equivalent to kilocalories (of the thermodynamic type). I'll use the more coloquial "cal" for the nutritional measure rather than the thermodynamic measure.)

For the purposes of estimating, let's call is 140 (nutrional) cal/person/day.

From a weight loss standpoint, you generally need a caloric deficit of 2500 cal to burn off one pound of fat (approx 500 g). If the consumption of sugar drinks (their definition includes sports drinks, sweetened juices, Kool-Aid, etc.) were cut in half, that would be 70 fewer calories per day per person, or about 25000 cal/year. That represents a weight loss of about 10 pounds per person in the first year.

As for the other aspect of it, soda consumption today versus the 1960s, here at least is one datapoint (Fig. 1): in the 1967, soda production was about 200 12-oz can equivalents per person per year; in 2004, it was about 400.

I stand by my earlier point: if soda consumption today were more like the 1960s, a lot of people would lose a lot of weight, and about as much as I estimated. So, yes, unlike many Slashdotters, I am not merely speaking hyperbolically out of my ass because I want the world to be that way.

Comment Re:This is evil! (Score 1) 90 90

Assuming a five year note, average household size of four, and the costs paid entirely by the locals, that should about double the $65/month that is the nominal cost of the system. They'll get that back with taxes eventually, but it's not clear whether the taxes will be on the locals or Statewide. Assuming a five year note, average household size of four, and the costs paid entirely by the locals, that should about double the $65/month that is the nominal cost of the system.

And in the meantime, they'll get an awful lot of value out of it. Plus, the useful life of the fiber is measured in decades, during which it will continue to provide value. Even at a cost of $1900/person, it's a valuable investment.

Heck, I borrowed orders of magnitude more per person for the house I live in! I still considered that a worthwhile expenditure, even though I'll be spending a lot more than five years paying that off.

Comment Re:Comparing apples to miniature oranges (Score 1) 409 409

So in your world view , Sodas are the great satan? It's not uncommon to have the belief.

Sodas are not exactly the great Satan - it is difficult to ascribe morality or cunning evil to a beverage - but they are the single most easily identified and avoidable cause of the problem.

If soda consumption returned to 1960s levels (i.e., 8-12 oz per serving (250-350 mL)), the collective weight of the U.S. population would immediately begin to drop. As a conservative estimate, the weight loss would be 1.5-3.0 million metric tons (5-10 kg per capita, but with a very uneven distribution). I would also hazard that a few million people in the U.S. would avoid Type II diabetes and all the morbidity that comes with that, ultimately saving some hundreds of billions in unnecessary medical costs. In that sense, soda contributes heavily to shortening peoples lives and throttling our economy. Killing us and robbing us; maybe soda really is evil?

Come to think of it... the market capitalization of Coca-Cola is about $175 billion. For that price, the U.S. government should buy them out and shut them down - an investment that would easily pay for itself via reduced Medicare/Medicaid costs over the next generation. It's total fantasy - neither markets nor politics play that way - but that is the scope of the problem and solution.

Comment Re:CUBEsat? (Score 1) 22 22

I expect someone may have worked out the numbers, but for a Mars relay you have more-or-less no attitude control and need a fair bit of power for at least several hours

The article mentions that the MarCO sats will have cold-gas thrusters for course correction and attitude adjustment. There are also a set of three reaction wheels for fine attitude adjustment. I expect the attitude adjustment is for optimal solar panel alignment during the cruise, then for radio alignment during the InSight landing.

(On the other hand, the article says that the MarCO satellites will communicate via X-Band radio to the 70-m receivers in the deep space network. From the picture I don't see anything like a convention "dish" high-gain antenna, so perhaps the radio alignment needs are not terribly stringent)

Comment Re:We'll talk when (Score 1) 639 639

Why wish for a good wine from Orkney when you can drown your sorrows in some of the best scotch in the world? Each location has its agronomic strengths.

Much as I would like to, I don't live in a climate that can support avocado trees. On the other hand, I don't think there are many sugar maples in Mexico and California, but we have them on every hillside 'round here.

Comment Solar Panel Voltage (Score 1) 597 597

Is it still the case that solar panels are wired to produce 12-V output? As I understand it, this was done historically for the convenience of interfacing with 12-V lead-acid batteries. This historical quirk has made almost everything else about solar more difficult and expensive, because it's a low-voltage, high-current architecture.

If, on the other hand, solar panels were wired to produce, say, 120 V DC output (i.e., the cells or panels wired more in series than parallel), then lots of things get easier and less expensive. All the wiring can be of much lighter gauge due to the lower current. The losses in the inverter would be lower because of lower resistive losses and more of 1:1 voltage ratio. Some components (capacitors, FETs and IGBTs) may be more expensive because of the higher voltage rating, but that is a relatively small incremental cost compared to the cost of copper.

It seems to me that a lot, if not the majority, of new residential solar installations are grid-tied with no battery attached. It seems that the system should be designed to make that easier and more efficient, rather than tie ourselves to historical off-the-grid designs. Plus, if Tesla and others are designing new style batteries for this market, they can design them for higher voltage.

Time-sharing is the junk-mail part of the computer business. -- H.R.J. Grosch (attributed)