Follow Slashdot stories on Twitter


Forgot your password?

Japanese Scientists Fire the Most Powerful Laser On the Planet 114 114

Sepa Blackforesta writes: Scientist from University of Osaka claim have fired the world's most powerful laser. The beam was intact for 2-petawatt, pulse lasted just one picosecond. While it produced a huge amount of power, the energy required for the beam itself is equivalent to that needed to power a microwave for two seconds. An associate professor of electrical engineering at Osaka University Junji Kawanaka says “With heated competition in the world to improve the performance of lasers, our goal now is to increase our output to 10 petawatts.”

Comment Re:Buy an rf jammer, become a drone collector (Score 1) 1167 1167

The whole 'water absorption' thing is mostly a myth. There is not a large absorption band at 2.4 GHz - that frequency was chosen specifically since it's in an ISM band where devices that generate and use RF for non-communications purposes are meant to live.

Comment Re:Buy an rf jammer, become a drone collector (Score 1) 1167 1167

... illegally transmitting in restricted spectrum.

2.4 GHz is some of the _least_ restricted RF spectrum, FWIW.

Too bad I can't charge for using Amateur radio - I can legally transmit up to 1500W into the antenna on that band (2300-2450 MHz) with no restriction on Effective Isotropic Radiated Power. Here's a 1.0x0.6 m somewhat paraboloid antenna that has 24 dB gain in a 10x14 degree pattern, making the EIRP 377kW. I bet that would pop the radios in that drone.

(Naturally I'd never do this - according to RF exposure limits, that setup would exceed the limits for uncontrolled human exposure out to 180 feet or so).

Comment Re:Safety (Score 1) 63 63

They may be, given the horrendous loss involved and the use of directional coupling. That 50 Watt limit is not absolute, it's more of a guideline for Amateur radio stations specifically, not all emitters. Your cell phone at < 4W is also closely regulated due to its proximity to human tissue. Please refer to the FCC RF exposure site for the full regs.

RF exposure is a function of frequency, duty cycle, distance, transmitter power, and antenna gain. I have a tiny 10mW 10GHz transmitter that couples its power via WR-90 waveguide. If my math is correct, that's 3.1 mW/cm^2 at the mouth of the waveguide - WAY over the exposure limit of 1.0 mW/cm^2 at 10 GHz for uncontrolled access.

Remember, sunburns are actually RF burns.

Comment I've had issues with the Win10 NVIDIA drivers... (Score 3, Insightful) 316 316

Usually the problem is something like, "it isn't giving me the newest driver" or simply the poor quality of the drivers in the first place. (For awhile there, if I clicked on the start button, it would cause my screen to reset!) And a lot of "your driver stopped responding so we turned it off, then back on again."

In some ways, I like that the drivers are being pushed to me automatically, but at the same time, if I'm doing multiple reinstalls in a single day, I've already downloaded the drivers... I don't need them to be downloaded YET AGAIN, every install...

Comment Depends who you ask... (Score 4, Interesting) 217 217

At Facebook, it's memcached, with an HDD backup, eventually put onto tape...

At Google, it's a ramdisk, backed up to SSD/HDD, eventually put onto tape...

For anyone who can't afford half a petabyte of RAM with the commensurate number of computers? I have no good ideas... except maybe RAM cache of SSD, cache of HDD, backed up on tape...

Using something like HDFS to store your data in a Hadoop cluster of file requests, is likely the best F/OSS solution you're going to get for that...

Comment Re:Safety (Score 1) 63 63

Magnetic fields don't hurt you

STATIC magnetic fields don't seem to hurt you. Time-varying magnetic fields most certainly can hurt you. In addition to ionizing radiation (x-rays, gamma rays) which can obviously hurt you, plain old radio waves can too:

Radiation burns can also occur with high power radio transmitters at any frequency where the body absorbs radio frequency energy and converts it to heat.[1] The U.S. Federal Communications Commission (FCC) considers 50 watts to be the lowest power above which radio stations must evaluate emission safety. Frequencies considered especially dangerous occur where the human body can become resonant, at 35 MHz, 70 MHz, 80-100 MHz, 400 MHz, and 1 GHz.[2] Exposure to microwaves of too high intensity can cause microwave burns.

Comment Re:Does indeed happen. (Score 1) 634 634

Yeah, I don't normally get feed back either. But it is kind of suspicious when I do get feedback...

I think it's a lot related to the xkcd comic:

If I spend a bunch of time rewriting code (which everyone does), as a man they might think "oh, well, he's just refactoring, or having a bad day." But when I do it, they think "wow, women can't code..." and then reject me out of hand without attempting to rationalize an explanation for why it should be overlooked...

Not that I'm particularly complaining here... this is just life as a woman in the tech industry... that and "oh wow, what does your boyfriend do at Google?" Actually, he's a literature teacher, I'm the genius programmer troubleshooter who knows almost everything about computers...

Comment Re:Not acupuncture (Score 2) 159 159

Sticking needles in people at random locations around the body does not...

Actually, that's precisely the problem with acupuncture working better than placebo. Acupuncture works whether you're following their "rules" or just randomly sticking needles into people...

Basically, it turns out, that forcing a person to lay still for a long time has the same benefits of destressing as just laying on a sofa and chilling... or a massage, or any other relaxing activity...

Comment Re:Does indeed happen. (Score 1) 634 634

We don't really know what the facts of the case are, but I wonder what it is about people that lead them to believe they're being discriminated against based on a particular factor, like age, race, etc?

Because I've worked for Microsoft, Amazon (as consultant, i.e. well-paid "contractor) and Google, and I have been recognized by SourceForge in a Project of the Month.

And then they return answers like "we want someone with more experience programming". To which my 7 year friend at Google laughed and said, "are they looking for someone who's on the verge of retiring?!"

Seriously, when the answer they tell you doesn't make sense... it doesn't make sense.

If at first you don't succeed, you must be a programmer.