One space blanket should be enough provided that the correct side is facing outward: the one with the high infrared reflectivity and low emissivity.
That emissivity is around 0.04, which means that the apparent infrared temperature is 0.96*Te+0.04*Ts, withTe the environmental temperature and Ts your surface temperature. Example: Te=20 C, Ts=35 C: apparent temperature 20.6 C, which will drown in the noise.
Unfortunately it's difficult to tell which side is the reflective one by eye. Of the few ones that I've tested, the other side can be close to a black body radiator. The instructions "put this side inwards to reflect body heat back" are not always correct.
A typical 8 Mpix sensor would be much better as a 2 Mpix sensor of the same total detector size and sensitivity... So if you have a crappy electron well that can hold 10^4 photoelectrons...
That's all fine, but what really matters how many more electrons the well will hold if you make the sensor pixel 4 times larger in area and how many more photoelectrons you can generate at the same exposure settings. If both of them are scaled by a factor 4, you can just as well average four adjacent small pixels to create a lower-resolution image.
Of course this averaging should be done in the camera/phone firmware before the JPEG compression step.
Does that also apply to SD and micro-SD cards? Nowadays these Raspberry Pi and comparable devices use micro-SD cards to run the operating system. I have the impression that typical flash cards and USB sticks nowadays use 4 MB erase blocks and the wear leveling on these is probably not very smart, so just a/var/log/syslog on a 4 GB card that gets a line every minute will wear itself out in about 2 years.
Actually I have had a couple of sd cards fail on me (one Nokia 2 GB dead on arrival (2008), later on an 8 GB and 2 GB card on other phones in the last two years within a two years after purchase).
On a related note: I wished that manufacturers of those thumb drives and sd cards specified not only sequential read/write throughput but also write throughput for random 4 kB blocks. With many drives, throughput will drop to 20 kB/s. (Source: http://forum.micromart.co.uk/Topic413730.aspx )
I usually begin a session by telling my student that it's only gonna take 10 minutes.
Instead of the success stories, I would be more interested in how many students are like me and the guy I replied to: hours and hours of practicing to get anywhere.
Mind you, people like me are also behind the rest in dance classes, car driving (with stick shift and Dutch bicyclists everywhere) and everything else that requires motoric coordination skills.
It took an hour a day for a solid month before I could juggle three balls at all.
Sounds familiar. Then I met a woman (who ended up becoming my wife) and explained her the basics and within twenty minutes she was able to keep three balls in the air for ten throws or so.
That day, I decided to restrict myself to practicing skils that I actually have some talent for.:-)
"From TFA, the changing cross srction reduces resistance as it stretches.... they could be designed for no change when stretched"
Well, that's not quite what TFA writes: "As expected, electrical measurements show that the fibers increase resistance as the fiber elongates and the cross sectional area narrows. Fibers with large diameters (~600 [micrometers]) change from a triangular to a more circular cross-section during stretching, which has the appeal of lowering the resistance below that predicted by theory."
The abstract doesn't mention how the circular/triangular transition would affect the resistance - with conservation of volume it shouldn't matter. But I don't read here in any way that this effect would be able to cancel the resistance increase due to stretching.
Note that in first approximation, resistance would scale as L^2 for a wire with length L (both diameter decrease and length increase affect the resistance). With stretching up to a factor 10, i.e. 100x increase in resistance, a small effect due to the shape of the cross section would be negligible.
"Coal spews more radiation than a nuclear meltdown"
I'd like to see a source for that. More radiation than a properly functioning nuclear plant, maybe. But accidents like Chernobyl or Fukushima: no way!
Plus: the radioactivity released by coal plants is mostly in the fly ash, which is filtered out in modern plants. So it's essentially comparing near zero amounts of radioactivity.
Rough translation of section VIII: The publisher is not allowed to [generate artificial traffic]. In case of a violation, the publisher is instantaneously and without warning subject to a fine of EUR 50,000 plus EUR 500 for every additional day of violation.
a website could put in T&Cs... terms for $1,000,000 per day penalty for late payment on an account worth $10,000 in it's total life.
In 2008, I got an email inviting me to participate in an affiliate network. I was curious, but the T&C indeed had a statement along the lines of "if you generate invalid clicks, as judged solely by us, you will be obliged to pay EUR 50,000 fine". I wonder what would have happened if I had done business with them. As a business-to-business deal, consumer protection laws would probably not have applied there.
The website still exists: http://www.cleafs.com/ ; they are still fishy: there is a form to apply as a publisher, with a checkbox for accepting the T&C, but no link to the T&C.
An analog filter doesn't peek ahead either, and is therefore limited in what it can do. But such a limited analog filter should be trivial to simulate as a digital no-peak-ahead filter.
Give me one example of something that can be done with an analog filter which is not trivial to simulate in a zero-delay streaming digital filter.
"all of the cheap ways to do digital signal processing add intolerable amounts of latency, so hearing aids are stuck with hybrid analog+digital designs"
I don't see what kind of analog filter circuits would would be so difficult to simulate digitally with more than 1 sample of latency. An analog filter is essentially a network of components that subtract, add, multiply, and accumulate voltages. That's trivial to do with a low end dsp which acts on a digital stream and has a couple of bytes storage.
"I have three spare batteries (ie 4 batteries) to make damn sure I can use it!"
I used to carry a spare with my previous phone, but I found it a pain to keep track of which one needs charging. Plus, you need to power cycle the phone both to switch batteries and to recharge the spare, which is annoyingly slow on a smartphone.
Nowadays I carry a usb cable to charge my phone from my laptop, and a Duracell portable recharger in case I don't have a laptop around. The portable charger is good for about 2/3 recharge of the built in battery of my htc Desire S.
According to TFA they didn't account for Coriolis effects. The overall rotation causes 60 pixels of shift per hour, whereas the differences in rotation speed are only good for 3 pixels per hour.
I don't know much about hydrodynamics of gas giants, but I suppose that there is a mechanism that prevents the formation of hurricane-like structures that are big enough and rotating fast enough to show up on photos of this resolution. Typical photos of Jupiter show only small scale eddies. Except for Jupiter's big spot, but even that one doesn't change shape on a timescale of a few hours.
"make your router and computers with directional antennas so your gear can just ignore interference. using a phased array antenna"
I've built improvised directional antennas for wifi routers out of cardboard, paper, and aluminum foil. Bend a sheet of aluminum foil on paper (25x15 cm will do) into a curved shape and mount it on the router antenna. Convenient if placing the router in the center of the house is impractical. Because the wavelength is 12 cm at 2.4 GHz it won't generate a tighly focused beam, but it will help reducing interference with transmitters behind the reflector and boost the signal in front.
"...many data centers use gycol as it caries more heat than pure water."
No it doesn't. The heat capacity of ethylene glycol is only half that of water. But mixed with water it acts as anti-freeze, which is convenient since the evaporator that cools the water may reach freezing temperatures occasionally.
A friend of me lost his phone that way, so it does happen. (busy station in Amsterdam at 9 am).
I once received such a request. I let him tell me the phone number and the message and I made the actual call. (in the train)
I once made such a request myself (flat battery, on the platform at 6 pm, needed to tell that my train was 2 hours late). Fortunately the other one didn't make a big deal out of lending me his 40 euro feature phone. Composing an sms on a phone with a different UI is tough, though...
I'm fiddling with my phone most of the time when I'm waiting for something in public (often reading slashdot, see signature). I might be an easy target for someone who just sneaks up on me, grabs it, and runs away with it.
it seems at first glance that a bit too many of the entries relied in part on turning code into ascii art.
If you have been hacking for a week to squeeze a complex program into 2 kB (excluding whitespace), which by itself will lead to hard-to-read code, then spending another half hour on creative formatting is just the icing on the cake. Actually, the contest rules state that ascii obfuscation doesn't count towards the scoring; the jury will run it through a C beautifier anyway.
That said, the program endoh2 generates an ascii-art obfuscated program. The program 'deckmyn' uses the white space in the source code as data.
I find it pretty impressive what the authors manage to squeeze in tiny programs. Notable things in previous years that I remember include a C compiler and an x86 virtual machine, if I recall correctly. This year, the 'tromp' program is an interpreter - although I don't fully get what it does.:-)
Too bad that this slashdot story draws so few comments.
"we need two levels of driver's license. A higher level... which brings privileges like... exceed speed limits on certain roads like divided highways."
Surely you believe that you will pass the test, since you know that you are an above-average driver?
You are probably right about the risk of no-lights at night. Besides the Orlando study, I have read, somewhere, that the most-vigorously enforced cycling safety law in the Netherlands is that one.
Well, "vigorously enforced"... Typically, about 30% of the cyclists in the cities don't have a light. In practice the enforcement means that the police sets up a trap when it's dark during rush hour and fines everyone cycling through without light. That would happen a couple of times at various locations in the bigger cities every winter. I think a car driver has a far greater chance of being caught speeding than a cyclist cycling being caught without lights.
A soft compound, knobby tire results in a smaller area, higher pressure and thus melting snow.
The freezing-point depression of ice induced by pressure is 13 MPa/K. If you concentrate 100 kg (1 kN) on 1 cm2 of ice, the freezing point will go down from 0 C to -0.8 C. So that won't make much of a difference. And even if it would, it's not clear to me why this would help you while cycling in the snow.
bicycles don't damage the road, they are far too light for that.
That argument of course becomes less valid once L.A. (from TFA) has built those 1600 mi of bike lanes, supposedly with maintenance costs for special traffic lights, road markings, and damage from weather and tree roots.
Slashdot Mirror
One space blanket should be enough provided that the correct side is facing outward: the one with the high infrared reflectivity and low emissivity.
That emissivity is around 0.04, which means that the apparent infrared temperature is 0.96*Te+0.04*Ts, withTe the environmental temperature and Ts your surface temperature. Example: Te=20 C, Ts=35 C: apparent temperature 20.6 C, which will drown in the noise.
Unfortunately it's difficult to tell which side is the reflective one by eye. Of the few ones that I've tested, the other side can be close to a black body radiator. The instructions "put this side inwards to reflect body heat back" are not always correct.
That's all fine, but what really matters how many more electrons the well will hold if you make the sensor pixel 4 times larger in area and how many more photoelectrons you can generate at the same exposure settings. If both of them are scaled by a factor 4, you can just as well average four adjacent small pixels to create a lower-resolution image.
Of course this averaging should be done in the camera/phone firmware before the JPEG compression step.
Yeah, much better with for example the Samsung Galaxy, Blackberry, LG, Sony... Oh wait...
Does that also apply to SD and micro-SD cards? Nowadays these Raspberry Pi and comparable devices use micro-SD cards to run the operating system. I have the impression that typical flash cards and USB sticks nowadays use 4 MB erase blocks and the wear leveling on these is probably not very smart, so just a /var/log/syslog on a 4 GB card that gets a line every minute will wear itself out in about 2 years.
Actually I have had a couple of sd cards fail on me (one Nokia 2 GB dead on arrival (2008), later on an 8 GB and 2 GB card on other phones in the last two years within a two years after purchase).
On a related note: I wished that manufacturers of those thumb drives and sd cards specified not only sequential read/write throughput but also write throughput for random 4 kB blocks. With many drives, throughput will drop to 20 kB/s. (Source: http://forum.micromart.co.uk/Topic413730.aspx )
Instead of the success stories, I would be more interested in how many students are like me and the guy I replied to: hours and hours of practicing to get anywhere.
Mind you, people like me are also behind the rest in dance classes, car driving (with stick shift and Dutch bicyclists everywhere) and everything else that requires motoric coordination skills.
Sounds familiar. Then I met a woman (who ended up becoming my wife) and explained her the basics and within twenty minutes she was able to keep three balls in the air for ten throws or so.
That day, I decided to restrict myself to practicing skils that I actually have some talent for. :-)
You don't account for the sutface tension. If you squeeze the tube thin enough, the liquid may gain energy by breaking up.
Think of water running out of a tap. The stream gets thinner and thinner as it falls and then breaks up into separate droplets.
until it gets squeezed under a chair leg or from pulling it around a corner.
"From TFA, the changing cross srction reduces resistance as it stretches. ... they could be designed for no change when stretched"
Well, that's not quite what TFA writes: "As expected, electrical measurements show that the fibers increase resistance as the fiber elongates and the cross sectional area narrows. Fibers with large diameters (~600 [micrometers]) change from a triangular to a more circular cross-section during stretching, which has the appeal of lowering the resistance below that predicted by theory."
The abstract doesn't mention how the circular/triangular transition would affect the resistance - with conservation of volume it shouldn't matter. But I don't read here in any way that this effect would be able to cancel the resistance increase due to stretching.
Note that in first approximation, resistance would scale as L^2 for a wire with length L (both diameter decrease and length increase affect the resistance). With stretching up to a factor 10, i.e. 100x increase in resistance, a small effect due to the shape of the cross section would be negligible.
Did you actually read the comments above on Alex Gabbard (the author of the link you provide) and his way of doing these calculations?
"Coal spews more radiation than a nuclear meltdown"
I'd like to see a source for that. More radiation than a properly functioning nuclear plant, maybe. But accidents like Chernobyl or Fukushima: no way!
Plus: the radioactivity released by coal plants is mostly in the fly ash, which is filtered out in modern plants. So it's essentially comparing near zero amounts of radioactivity.
Rough translation of section VIII: The publisher is not allowed to [generate artificial traffic]. In case of a violation, the publisher is instantaneously and without warning subject to a fine of EUR 50,000 plus EUR 500 for every additional day of violation.
In 2008, I got an email inviting me to participate in an affiliate network. I was curious, but the T&C indeed had a statement along the lines of "if you generate invalid clicks, as judged solely by us, you will be obliged to pay EUR 50,000 fine". I wonder what would have happened if I had done business with them. As a business-to-business deal, consumer protection laws would probably not have applied there.
The website still exists: http://www.cleafs.com/ ; they are still fishy: there is a form to apply as a publisher, with a checkbox for accepting the T&C, but no link to the T&C.
An analog filter doesn't peek ahead either, and is therefore limited in what it can do. But such a limited analog filter should be trivial to simulate as a digital no-peak-ahead filter.
Give me one example of something that can be done with an analog filter which is not trivial to simulate in a zero-delay streaming digital filter.
"all of the cheap ways to do digital signal processing add intolerable amounts of latency, so hearing aids are stuck with hybrid analog+digital designs"
I don't see what kind of analog filter circuits would would be so difficult to simulate digitally with more than 1 sample of latency. An analog filter is essentially a network of components that subtract, add, multiply, and accumulate voltages. That's trivial to do with a low end dsp which acts on a digital stream and has a couple of bytes storage.
"I have three spare batteries (ie 4 batteries) to make damn sure I can use it!"
I used to carry a spare with my previous phone, but I found it a pain to keep track of which one needs charging. Plus, you need to power cycle the phone both to switch batteries and to recharge the spare, which is annoyingly slow on a smartphone.
Nowadays I carry a usb cable to charge my phone from my laptop, and a Duracell portable recharger in case I don't have a laptop around. The portable charger is good for about 2/3 recharge of the built in battery of my htc Desire S.
According to TFA they didn't account for Coriolis effects. The overall rotation causes 60 pixels of shift per hour, whereas the differences in rotation speed are only good for 3 pixels per hour.
I don't know much about hydrodynamics of gas giants, but I suppose that there is a mechanism that prevents the formation of hurricane-like structures that are big enough and rotating fast enough to show up on photos of this resolution. Typical photos of Jupiter show only small scale eddies. Except for Jupiter's big spot, but even that one doesn't change shape on a timescale of a few hours.
"make your router and computers with directional antennas so your gear can just ignore interference. using a phased array antenna"
I've built improvised directional antennas for wifi routers out of cardboard, paper, and aluminum foil. Bend a sheet of aluminum foil on paper (25x15 cm will do) into a curved shape and mount it on the router antenna. Convenient if placing the router in the center of the house is impractical. Because the wavelength is 12 cm at 2.4 GHz it won't generate a tighly focused beam, but it will help reducing interference with transmitters behind the reflector and boost the signal in front.
See e.g. here for inspiration.
http://www.freeantennas.com/projects/template/
"...many data centers use gycol as it caries more heat than pure water."
No it doesn't. The heat capacity of ethylene glycol is only half that of water. But mixed with water it acts as anti-freeze, which is convenient since the evaporator that cools the water may reach freezing temperatures occasionally.
A friend of me lost his phone that way, so it does happen. (busy station in Amsterdam at 9 am).
I once received such a request. I let him tell me the phone number and the message and I made the actual call. (in the train)
I once made such a request myself (flat battery, on the platform at 6 pm, needed to tell that my train was 2 hours late). Fortunately the other one didn't make a big deal out of lending me his 40 euro feature phone. Composing an sms on a phone with a different UI is tough, though...
I'm fiddling with my phone most of the time when I'm waiting for something in public (often reading slashdot, see signature). I might be an easy target for someone who just sneaks up on me, grabs it, and runs away with it.
If you have been hacking for a week to squeeze a complex program into 2 kB (excluding whitespace), which by itself will lead to hard-to-read code, then spending another half hour on creative formatting is just the icing on the cake. Actually, the contest rules state that ascii obfuscation doesn't count towards the scoring; the jury will run it through a C beautifier anyway.
That said, the program endoh2 generates an ascii-art obfuscated program. The program 'deckmyn' uses the white space in the source code as data.
I find it pretty impressive what the authors manage to squeeze in tiny programs. Notable things in previous years that I remember include a C compiler and an x86 virtual machine, if I recall correctly. This year, the 'tromp' program is an interpreter - although I don't fully get what it does. :-)
Too bad that this slashdot story draws so few comments.
"we need two levels of driver's license. A higher level ... which brings privileges like ... exceed speed limits on certain roads like divided highways."
Surely you believe that you will pass the test, since you know that you are an above-average driver?
http://en.wikipedia.org/wiki/Illusory_superiority#Driving_ability
Well, "vigorously enforced"... Typically, about 30% of the cyclists in the cities don't have a light. In practice the enforcement means that the police sets up a trap when it's dark during rush hour and fines everyone cycling through without light. That would happen a couple of times at various locations in the bigger cities every winter. I think a car driver has a far greater chance of being caught speeding than a cyclist cycling being caught without lights.
The freezing-point depression of ice induced by pressure is 13 MPa/K. If you concentrate 100 kg (1 kN) on 1 cm2 of ice, the freezing point will go down from 0 C to -0.8 C. So that won't make much of a difference. And even if it would, it's not clear to me why this would help you while cycling in the snow.
That argument of course becomes less valid once L.A. (from TFA) has built those 1600 mi of bike lanes, supposedly with maintenance costs for special traffic lights, road markings, and damage from weather and tree roots.