Slashdot is powered by your submissions, so send in your scoop

 



Forgot your password?
typodupeerror

Comment Re:couldn't that be done with books, too? (Score 1) 126

I learned a ton on my own as a kid by reading random articles out of an encyclopedia, and some of those "How Things Work" series of books. I imagine kids in India could do so, too— except that they don't have access to such books. So it seems overall more a matter of access to knowledge, in any form, than of something new and magical about technology-based learning as a specific form.

I am a kid from India and did exactly the same things. I wasn't dirt poor or anything but I used to buy books for a couple of rupees (old books that were destined to be recycled). In India, people will pay you money for old newspapers and books that they will recycle later and many of them will sell these old books and magazines to others as a side business.

I used to buy tons of business magazines and stray volumes of encyclopaedia, mainly because I was bored and loved knowing anything about anything.

Children will figure out a way to learn if they want to. Access to information is sometimes the least of the problems, most often it is inspiring them with that sense of awe and wonder.

Space

Spinning Black Hole's Edge Rotates At Nearly the Speed of Light 227

astroengine writes "Astronomers have directly measured the spin of a black hole for the first time by detecting the mind-bending relativistic effects that warp space-time at the very edge of its event horizon. By monitoring X-ray emissions from iron ions (iron atoms with some electrons missing) trapped in the black hole's accretion disk, the rapidly-rotating inner edge of the disk of hot material has provided direct information about how fast the black hole is spinning. Astronomers used NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) — that was launched into Earth orbit in June 2012 — and the European observatory XMM-Newton measured X-ray radiation as a tool to directly infer the spin of NGC 1365's black hole. 'What excites me is the fact that we are able to do this for the very massive black holes at the centers of galaxies but we can also make the same measurement for black holes in our galaxy ... black holes that resulted from the explosion of a star ... The fact we can extend this from billions of solar masses to 10 solar masses is pretty cool,' Fiona Harrison, professor of physics and astronomy at the California Institute of Technology, Pasadena, Calif., and principal investigator of the NuSTAR mission, told Discovery News."

Comment Re:Can't Go Backwards (Score 5, Insightful) 736

To put it another way, it is impossible to make an accurate progress bar because it is impossible to predict the future. That's all.

You can make assumptions, extrapolation, use past performance,etc but you are never going to get it accurate.

This is like getting pissed at your GPS because it told you you will reach in 22 mins when it actually took you 35.

It is either a dumbass expectation from the user or a dumbass design decision. You might have as well used an hourglass so the user could spend their time shaking it trying to get the sand to fall faster.

Comment Re:CMOS (Score 1) 126

Sure, very little current flows through the transistor's gate. But, the transistors themselves are imperfect switches, and so you get some current flowing from Vdd to Vss all the time anyway. For the products I tend to work on, around half or more of the power consumption comes from leakage, amazingly.

For the uninitiated: CMOS gates consist of a pair of complementary switches. One set connects Vdd (the positive voltage indicating a logic '1') to the output node, and the other set connects Vss or GND (the zero voltage indicating a logic '0') to the output node. The way CMOS works, there should only be one path from either Vdd or Vss to the output node. All other paths must be open.

The simplest example is an inverter. It has two switches. The switch from Vdd to output opens with the input is 1 and closes when the input is 0. The switch from Vss to output does the opposite: Closes when the input is 1 and opens when the input is 0.

CMOS burns power two main ways. The first and most obvious way is through switching, also called dynamic power. When the output goes to '1', the gate outputs a high voltage. This voltage then charges all of the gates connected to that output. Even if the gates don't leak, they still end up taking on a certain amount of charge due to their capacitance. The total charge taken on is V*C, where V is the voltage and C is the total capacitance of all the inputs this gate drives. Later, when the gate's output switches to 0, all that charge flows back out to ground. The more often you switch an output from 1 to 0, the more charge you ratchet from Vdd to Vss. Furthermore, while you're switching, there's often a very brief period when the two switches are both slightly closed. You can get some current racing directly from Vdd to Vss at this time.

The second, perhaps less obvious way CMOS burns power is through leakage. Modern transistors are far from perfect switches. When they're closed, they conduct, and when they're open they also conduct, just not as well. This leads to a phenomenon known as leakage. That is, even when the gates aren't switching, there's a constant current from Vdd to Vss, because the transistors haven't completely cut off the current flow. You can sometimes address this by lowering the input voltage or using transistors with different threshold voltages, but that trades off speed for leakage.

So, while the promise of CMOS is that no current flows when gates don't switch, the actuality is that tiny transistors in modern processes aren't as good at holding up to that ideal.

Comment Re:Black white or grey (Score 1) 242

How about some data? 3Q11 saw around 750K units world wide for plasma and LCD public displays according to this link., whereas the North American and Chinese LCD and plasma TV market for 3Q12 was closer to 54M units, according to this link from the same source.

And before you cry foul because I picked different years, please note I picked the same quarter, and the peak quarter for the year for both years. You can also look at the Y/Y growth and extrapolate the 2011 numbers from 2012. The Y/Y growth numbers were negative, meaning it fell slightly, and yet TVs are about 2 orders of magnitude larger than public displays.

So, yeah, I was off a bit. It's 2 orders of magnitude. Still, that drives a lot more economies of scale in the TV market.

That's the total market for public displays. Now what proportion of these public displays are actually appropriate for e-Ink? And how does that compare to consumer uses, such as e-readers for volume?

Comment Re:Honesty (Score 1) 709

I don't think I have ever heard of horse milk being consumed.

I think you can buy it in Belgium. And while I've never seen ewe's milk, there's plenty of cheeses made from it.

I once had a goat milk yoghurt. It didn't taste too bad but it smelled awful. As, in fact, do goats.

You mean it smelt ewe?

Comment Re:Language is hardly relevant (Score 4, Interesting) 437

No, that's not fine tuned enough. Standard practice here is to program an FPGA to do the less important work, with wire wrapped transistors doing anything that needs to perform well.

Anything less is, well, lazy.

From what (little) I know, that's exactly what data warehouse appliances like Netezza and Teradata do. They have custom built FPGAs to do the SQL execution significantly faster than what a CPU can do.

Comment Re:NOVA did a show on ancient blacksmithing recent (Score 1) 201

Not that it matters, but just to set the record straight, "damascus" steel, just like the "Arabic" numeral system, was neither invented in Damascus nor in Arabia nor in Spain.

You are talking about Damascus steel, I'm talking about the Damascus sword. The Damascus sword indeed used wootz high quality steel (at least originally) but it also had a secret manufacturing process which was equally important.

I don't know enough about sword history, but I do know that the Indian swords or "talwars" during that time period were also damascus pattern swords. I also know that they were commonly made in India at that time. However, I'm not contradicting your point per se, I'm only adding to it. Sword making in itself is a highly evolved and nuanced art form.

To my knowledge, the real tricky part was in making the steel ingots which were made exclusively in India, and were exported by Arabian traders to the rest of the world. It is worth noting that the mystery behind wootz steel has been a topic of constant research for hundreds of years and has remained a mystery until a few years ago despite constant and repeated attempts to crack the puzzle. The first microscopic analysis of steel was done on wootz steel.

Comment Re:NOVA did a show on ancient blacksmithing recent (Score 2) 201

Quote from the show:

ALAN WILLIAMS: The swords were far better than any other swords made, before or since, in Europe. And these must have been extraordinarily valuable to their contemporaries, because of their properties.

Except for the Damascus sword, which was fabricated in several places in the Muslim empire, including, famously, in Toledo, Spain, where to this date there is a blade making industry.

Not only that, but the Viking sword was merely an attempt to duplicate the quality of the Saracen sword.

Not that it matters, but just to set the record straight, "damascus" steel, just like the "Arabic" numeral system, was neither invented in Damascus nor in Arabia nor in Spain. Both the numeral system and the steel was invented in India. It should be more accurately called Wootz steel. This steel making technique technique was mastered and perfected by ironsmiths in South India around 300BC. The original technique also died with the ironsmiths over time, and has was only recently replicated with success some years ago.

References:
http://www.tms.org/pubs/journals/jom/9809/verhoeven-9809.html
http://archaeology.about.com/od/wterms/g/wootz.htm
http://www.britannica.com/EBchecked/topic/647868/wootz-steel

The first article is the most informative and comprehensive of all.

To quote from the articles linked above,
"Wootz is the name given to an exceptional grade of iron ore steel first made in southern and south central India and Sri Lanka perhaps as early as 300 BC. Wootz is formed using a crucible to melt, burn away impurities and add important ingredients, and it contains a high carbon content (nearly 1.5%).

Although iron making was part of Indian culture by as early as 1100 BC (at sites such as Hallur), the earliest evidence for the processing of iron in a crucible has been identified at the site of Kodumanal in Tamil Nadu province, and possibly also at Andhra Pradesh. The term 'wootz' appears in English in the late 18th century, and is probably derived from ukku, the word for crucible steel in the Indian language Kannada, and possibly from 'ekku' in old Tamil.

Wootz steel is the primary component of Damascan steel. Syrian blacksmiths used wootz ingots to produce extraordinary steel weaponry throughout the middle ages. "

For the record, I'm not a steel expert by any stretch, but I do love Japanese cooking knives, especially AS sandwitched core ones, and was really disappointed to learn that my first flashy "Damascus" pattern knife was only chemically etched and not a true damascus pattern.

Slashdot Top Deals

Reference the NULL within NULL, it is the gateway to all wizardry.

Working...