These tactics work and do not require to much thinking/demunging by the user:
Replace @ by @ (sounds simple, but it is reported to work - so far)
Make mailto links in javascript (Spambots don't appear to parse javascript so far)
Make a CGI that serves the email address in a clickable form after the user presses a button. Spambots don't parse HTML forms - yet. Use POST instead of GET such that there does not exist any URL that will serve the email address. Optionally include a simple question in the form. (I implemented:
Email address of John Doe
I am: (x) a robot; ( ) a human [GET EMAIL ADDRESS]
on a website. (Answering wrong will give you 1000 nonexisting email addresses:-) ) If you suspect that the spammer might want to invest some time in writing a script that harvests all 20000 employees from your website, then make it a Kaptcha (type the digits in the image into the box).
Having to demunge an address is annoying. How many spaces do I have to remove from jl i11@example.com? Did I place the cursor left or right of the whitespace? Damn, one space too many removed.
Spambots are stupid. I've seen a few of them visit a website that I maintain and they do not even parse basic HTML such as the BASE tag (which the parser needs to derive relative URLs), or the presence of & in URLs (HTML does officially not allow bare & symbols).
You are oversampling by 4-16 and keeping 16 bits of resolution? Then you're digitally filtering it and running it out a D/A convertor that can handle 176-705KHz?
Yep. The filter calculations are carried out in more bits in order to prevent roundoff errors, but the output is in 16 or maybe 18 bits resolution at this high sample rate. Google for "dac oversampling bits spectrum", there are plenty of web pages that explain things, e.g. oversampling filters and noise spectra. (I have seen better ones, but I'm not sure what exactly I googled for last time)
It is next to impossible to make a DAC that can create a voltage with more than 18 bits resolution because of the tight tolerances that are required. In a 1-bit DAC, the voltage-resolution problem is translated into a kind of duty-cycle modulation with just 1 bit of resolution. Those DACs oversample with 64x or more and run internally at 3 MHz. It's amusing when people complain that sound cards have too much RF interference with the mother board while the DAC itself is running at 3 MHz together with a DSP processor (pentium-100 performance) integrated on the same chip. This DAC is designed to generate noise in the 200 kHz+ region with a 5 V amplitude... (Cheap-sound-card noise comes from a noisy power supply and a cheap buffer amplifier between the filter and the connector, not from RF interference)
In order to be able to record and playback matching 5KHz sinewaves, you need filters at both the A/D side and the D/A side.
If you downsample the signal to 44KHZ, your filter requirements on the playback side increase.
The hard filtering work (cutting off everything beyond 22 kHz and not touching anything below 20 kHz) on the playback side is done by a digital filter on a 176 (4k oversampling) to 705 kHz (16x oversampling) PCM stream. A digital filter can easily satisfy the high requirements that are needed. The imperfect analog filter that follows after the DAC needs to satisfy only very modest requirements.
What you seem to have forgotten is that there is still another filter after the D/A convertor.
Yes, a soft analog filter (pass for f<20 kHz, stop for f>88 kHz). That's easy enough to construct without introducing significant phase shifts for f<20 kHz. There is no need to fully filter away the range 20-88 kHz, since there is no spectral content in that region (the ADC operates on a 176 kHz PCM stream (4x oversampling)). Moreover, the filter has the same characteristics as the filter that filtered the signal from the microphone during the recording, so if you don't like this filter, then you won't like the filter during recording either. If you want to be safe, use a better DAC that does 16x oversampling, such that the PCM stream becomes 705 kHz and the filter needs to cut off at 352 kHz instead of 88 kHz.
In principle, it is possible to pre-compensate in the DSP for the very small ripples in the analog filter spectrum close to 20 kHz, though I don't think that that is commonly implemented. (DACs are usually not manufactured by the same companies as those who build the filters in the CD players)
92 dB isn't very loud at all.
Well, my comparison with speaker volumes was maybe not so lucky with the current amplifier rating inflation, but let's compare it to typical sound sources (google for decibel levels, all numbers relative to hearing treshold): Large Orchestra (98 dB SPL), heavy traffic (85 dB), tractor (90 dB). Also: Safety limits tell you that 92 dB is permissible for maximum 6 hours per day; moreover. You're probably safe if you listen to music which is mostly soft with short bursts.
Suppose that your Wagner/Mahler music has a typical -20 dB (relative to the maximum that's possible on a CD) level. Then the quantization noise level is at 72 dB below listening level, but you playback at 90 dB, so the absolute level of the quantization noise is at 18 dB SPL. That's comparable to whispering at 5 feet distance. I find it hard to believe that one can hear someone whispering at 5 feet while standing next to a tractor or a passing truck.
However, it is defendable, if you really want to stay on the safe side, to encode in 24 bits, in order to capture the entire range between hearing treshold and instant hearing damage.
I still don't think that it makes sense to use 196 kHz as a sample rate for a transport medium. If you want more realistic sound, then spend the space on surround encoding.
But there is a way to run one Linux kernel on top of another; I forget what it's called but I know it exists. The point being that the "secondary" kernel can have been compiled without certain features.
Sounds to me like hitting a musquito with a sledgehammer, and hard to configure (imagine having 40 kernels, each with different parameters):-) An extension to the ulimit concept inside the main kernel would be enough for me: an application can restrict its permissions, but cannot undo these restrictions. Example:
ulimit -d 10000 # max 10 MB data
ulimit --onlywrite/tmp # only write permission in/tmp
ulimit --tcp 1-1024 # no TCP/IP on ports 1-1024 ./untrusted_application
If I install a text editor, I probably don't want it to be able to access the Internet. It should be possible to say, "for this app here, don't let it do anything network related".
For Windows (sigh), you can use ZoneAlarm (free edition) to do exactly this. It would be nice to have something like that in the Linux kernel.
it was just a pain in the ass to recompile the alsa-driver package each time I upgraded the kernel
After struggling for a while with the Kernel Versioning Hell (A few major releases ago, compiling a kernel was as simple as make dep; make zImage; make modules, but nowadays that doesn't seem to work without endless tweaking), I found Up-to-date Alsa RPMs for all major Linux distributions.
To prevent high frequencies from messing up your recording, you must place a filter before the A/D convertor. This will block those high frequencies from being digitized, but it introduces a new problem:
no filter is perfect.
Yes, 96/192 kHz sampling is a good thing for recording studios for the reason that you explain. Moreover, >=24 bit recording means that you don't get aliasing problems if the signals are amplified or attenuated during the mixing process.
However, this is all on the recording side. After sampling at >=96 kHz, you can apply a digital filter with a perfectly flat passband up to 20 kHz and stopband above 22.05 kHz, and then downsample to 44.1 kHz. In any CD player, the opposite process is performed (the famous "oversampling"): it is hard to filter the noise above 20 kHz in the raw 44.1-kHz signal. Therefore, the DAC converts the signal digitally to a 4 to 16 times higher sampling rate and with a slightly higher bitresolution (e.g. 18 or 20 bits). Then, the DAC digitally filters out everything above 22 kHz while leaving everything below 20 kHz.
The (still digital) signal is now a "smooth line" through the supplied data points at 44 kHz. This signal is converted to a voltage by the true (non-signal-processing part of the) DAC. The part of the spectrum below 20 kHz will be exactly the same independent on whether the original input to the DAC was 44, 96, or 192 kHz. (Note: 1-bit DA convertors use a slightly different approach, but with the same result).
As far as the bit resolution is concerned: in the final signal, 16 bits is enough for a dynamic range of 92 dB. If the hearing treshold is at 0 dB, that means that for peak levels of less than 92 dB, the resolution is fully sufficient to encode even the softest audible sounds. Note that 92 dB is quite loud: about 4 W power to a typical 87 dB/W loudspeaker at 1 m distance. It is defendable to use a bitresolution higher than 16, if you want to hear a ticking watch in the background while the music is playing at the pain treshold of 120 dB. For that, you need 5 more bits: 21 bits. On the consumer end, 24 or 32 bits is a waste of storage space.
it sounds like this kind of technology could be applied to all sorts of food.
A water jet cutter works better (certainly faster) for any products that can stand contact with water. Bread may not be a good candidate, but meat and sticky candy bars are. See the website of a water jet manufacturer for more information.
Re:That can me more harmful than regular lasers
on
The Cheese Slicing Laser
·
· Score: 3, Informative
Using a non-visible laser can generate much more accidents
I've done experiments with 266 nm laser beams. Ultraviolet light makes nearly every organic molecule fluoresce. It is usually quite easy to see the spot where the laser beam (even if it is just a few milliwatts) hits a surface.
>along with your energy savings (by switching to fluroescents) comes ugly green light and occasionally that annoying flicker.
There are roughly two types of phosphors in fluorescent lamps: halophosphate and triphosphor.
Halophosphate emits mainly in a band around yellow, plus a narrow violet line. The result looks white to the eye, but surfaces that mainly reflect green and blue/green wavelengths or deep red wavelengths look strange, since these wavelengths are not present in the light. This is probably what you refer to as "ugly green light". These are mainly used in cheap tube-type fluorescents. In this building, they are used to illuminate the corridors, but not the offices.
The triphosphor emits mainly five lines: red, yellow, green, blue/green, and violet, evenly distributed over the spectrum of visible light. This type tends to give good color reproduction. All compact fluorescents that I've seen so far use these triphoshpor mixtures, presumably because a compact fluorescent does not need a large amount of phosphor compared to a 120-cm tube. (I played around with looking at diffraction patterns from various light sources through a CD) As other people pointed out, CF lamps are electronically ballasted and do not flicker at frequencies visible to the human eye.
>This may be my imagination, but CDs that I bought in the early 90s felt a little heavier and appeared a little bit thicker than CDs that I buy now.
That's not imagination. I once attended a talk by someone from Philips Research. Accordig to the CD specs, the plastic layer on the playing side of the disc should be 1.0 mm thick with a tolerance of +/- 0.1 mm (I don't recall the exact numbers). According to him, after a few years, all CDs on the market had 0.905-mm-thick plastic layers because it was possible to manufacture them with much tighter tolerances and this way, the manufacturers save 10% on the raw material.
In the DVD specification, the tolerances are much tighter, which is necessary because the laser needs to be focused onto a much smaller spot than in a CD.
> $3,000 of CDs. [...] A $299 device that makes available all your music, especially if it's $6,000 worth of music, is so totally worth it:)
You'll probably get tired of your iPod within 3 years because something hotter appears on the market. So that's $300 every 3 years. Compare that to the fact that you spent those $3000 for CDs over the course of, say, 15 years, that's $600 per 3-year-period. Then $300 is not trivial.
Reduce energy use (do you NEED an electric razor when a manual one works fine? Toothbrush? Does that tivo REALLY need to be on 24/7 with disks spinning?
Though energy reduction is a good thing, it doesn't hurt to see things in proportions.
Electrical razor: 10 W, 3 minutes per day: 0.18 kWh per year or 0.66 MJ.
Shaving with a manual razor: 1 liter of hot water per day: 73 MJ (megajoule) per year (20 kWh if you use electricity to heat the water).
Driving a car, 10000 km per year: 800 liters of fuel or 30000 MJ.
If every new electrical meter put it were REQUIRED to run both directions, then it would be a simple matter to run 2, 4 solar panels and just push it back on the grid.
The price of electricity incorporates the costs of infrastructure to meet peak demands. That is the main reason why selling back electricity to the grid from an unpredictable source such as a wind turbine or a solar panel should cost less than what you pay for your electricity. The electricity companies need to have fuel/nuclear power plants on standby and sufficiently thick cables to supply your house, just in case there is no wind/sun when the need for electricity is high.
You suggest that the electricity price should be dependent on the time. This would only make sense (with the above) if the electricity cost per kWh were the true incremental costs, not involving any infrastructure. The infrastructure would have to be financed completely from the fixed costs, which is not the case. The variable costs are just the costs of the coal or nuclear fuel and maintenance of the power plants; the fixed costs are the installation and maintenance of the complete grid, which costs far more than what can be covered by the connection fee and the nominal monthly fee.
> when you have an accident with liquid nitrogen you lose a finger.
Actually, it is not a problem to bring your skin into contact with liquid nitrogen for 1 or 2 seconds. Between the skin and the LN2, a thin layer of gaseous nitrogen will form which will act as a thermal insulator. I've done that many times (I won't take responsibility in case anyone else tries this at home). After a few seconds, the skin will have cooled down sufficiently for the gas layer to disappear and only then you will get frostbite.
The gas layer also prevents the LN2 from sticking to surfaces. It will just roll of the surface, similar to water droplets that float on a very hot surface (e.g. a hot plate in the kitchen). Hence, if you spill LN2 over your body, you will probably not suffer any damage, unless you are wearing shoes/clothes that can act as a reservoir.
Liquid helium is not very dangerous either: because of its low temperature (4 K), nitrogen and oxygen in the air will immediately start condensing, thereby increasing the helium temperature and forming gaseous helium and liquid air, to which the same comments as above apply. LHe can only be used in closed circuits for this reason.
>Never use anything less than 14 points, preferably at least 18. People in the back of the room and people with less-than-perfect vision need to be able to see.
I've never understood what the idea is of point sizes on something that is going to be projected on a 3 meter-wide screen. Is it going to be 14 points if you print it landscape on standard A4/letter paper, or if it will be portrait (covering half the paper)?
I have found that from the last row in a typical lecture hall, the projected image is typically as big as a QUARTER A4 (=A6) or Letter sheet at normal reading distance (30 cm/1 ft). So if you want to judge the legibility, then print it on reduced size, or turn down the contrast of your 17 inch monitor and look at it from 60 cm (2 ft) at a 30 degree angle.
I've recently discovered Prosper, a LaTeX document class for generating slides. Most importantly, it is designed to generate PDFs with partial changes within a slide (e.g. a bulleted list that appears one point at a time).
It turns out that you can do rather complicated graphical tricks with LaTeX, as the example slide shows demonstrate. Furthermore, it has some rather nice background color schemes, that unfortunately don't always have good contrast.
Re:One very interesting thing about this
on
AOL's $299 PC
·
· Score: 1
Are you trying to get these people spammed by providing their e-mail address publicly?
> Do we have, anywhere, a listing of all the emails that have been sent by our users? Preferably arranged in chronoligical order, with timestamps? If we had that, why all we'd have to do is a little grep and wc action
I'd guess that they would be violating the privacy of the users by doing that retroactively. Maybe what they are really saying is: if more than 20 emails in 10 minutes are sent from your computer, then it will be registered and used for spam-analysis statistics.
>That reduces skipping commercials to hitting a single button labeled [>>] 1-3 times
Why do you have to do that by hand? Can't those PVR boxes detect whether there is a channel logo in the corner of the screen to decide whether it is an ad or not?
A. Programming enthusiast - a happily married father of two kids who spends an hour or so on a typical evening writing his own Visual Basic address book program.
B. hacker - a person that rarely sees daylight who programs in C and assembler until 3 AM to reverse-engineer an obscure protocol, with a pile of pizza boxes and cola cans next to his desk.
The elitists in category B of course do not want to be confused with those belonging in category A. We need a word that conveys these subtle differences.
Slashdot Mirror
- Replace @ by @ (sounds simple, but it is reported to work - so far)
- Make mailto links in javascript (Spambots don't appear to parse javascript so far)
- Make a CGI that serves the email address in a clickable form after the user presses a button. Spambots don't parse HTML forms - yet. Use POST instead of GET such that there does not exist any URL that will serve the email address. Optionally include a simple question in the form. (I implemented:
Having to demunge an address is annoying. How many spaces do I have to remove from jl i11@exampleEmail address of John Doe
I am: (x) a robot; ( ) a human [GET EMAIL ADDRESS]
on a website. (Answering wrong will give you 1000 nonexisting email addresses :-) ) If you suspect that the spammer might want to invest some time in writing a script that harvests all 20000 employees from your website, then make it a Kaptcha (type the digits in the image into the box).
Spambots are stupid. I've seen a few of them visit a website that I maintain and they do not even parse basic HTML such as the BASE tag (which the parser needs to derive relative URLs), or the presence of & in URLs (HTML does officially not allow bare & symbols).
Yep. The filter calculations are carried out in more bits in order to prevent roundoff errors, but the output is in 16 or maybe 18 bits resolution at this high sample rate. Google for "dac oversampling bits spectrum", there are plenty of web pages that explain things, e.g. oversampling filters and noise spectra. (I have seen better ones, but I'm not sure what exactly I googled for last time)
It is next to impossible to make a DAC that can create a voltage with more than 18 bits resolution because of the tight tolerances that are required. In a 1-bit DAC, the voltage-resolution problem is translated into a kind of duty-cycle modulation with just 1 bit of resolution. Those DACs oversample with 64x or more and run internally at 3 MHz. It's amusing when people complain that sound cards have too much RF interference with the mother board while the DAC itself is running at 3 MHz together with a DSP processor (pentium-100 performance) integrated on the same chip. This DAC is designed to generate noise in the 200 kHz+ region with a 5 V amplitude... (Cheap-sound-card noise comes from a noisy power supply and a cheap buffer amplifier between the filter and the connector, not from RF interference)
In order to be able to record and playback matching 5KHz sinewaves, you need filters at both the A/D side and the D/A side. If you downsample the signal to 44KHZ, your filter requirements on the playback side increase.
The hard filtering work (cutting off everything beyond 22 kHz and not touching anything below 20 kHz) on the playback side is done by a digital filter on a 176 (4k oversampling) to 705 kHz (16x oversampling) PCM stream. A digital filter can easily satisfy the high requirements that are needed. The imperfect analog filter that follows after the DAC needs to satisfy only very modest requirements.
Yes, a soft analog filter (pass for f<20 kHz, stop for f>88 kHz). That's easy enough to construct without introducing significant phase shifts for f<20 kHz. There is no need to fully filter away the range 20-88 kHz, since there is no spectral content in that region (the ADC operates on a 176 kHz PCM stream (4x oversampling)). Moreover, the filter has the same characteristics as the filter that filtered the signal from the microphone during the recording, so if you don't like this filter, then you won't like the filter during recording either. If you want to be safe, use a better DAC that does 16x oversampling, such that the PCM stream becomes 705 kHz and the filter needs to cut off at 352 kHz instead of 88 kHz.
In principle, it is possible to pre-compensate in the DSP for the very small ripples in the analog filter spectrum close to 20 kHz, though I don't think that that is commonly implemented. (DACs are usually not manufactured by the same companies as those who build the filters in the CD players)
92 dB isn't very loud at all.
Well, my comparison with speaker volumes was maybe not so lucky with the current amplifier rating inflation, but let's compare it to typical sound sources (google for decibel levels, all numbers relative to hearing treshold): Large Orchestra (98 dB SPL), heavy traffic (85 dB), tractor (90 dB). Also: Safety limits tell you that 92 dB is permissible for maximum 6 hours per day; moreover. You're probably safe if you listen to music which is mostly soft with short bursts.
Suppose that your Wagner/Mahler music has a typical -20 dB (relative to the maximum that's possible on a CD) level. Then the quantization noise level is at 72 dB below listening level, but you playback at 90 dB, so the absolute level of the quantization noise is at 18 dB SPL. That's comparable to whispering at 5 feet distance. I find it hard to believe that one can hear someone whispering at 5 feet while standing next to a tractor or a passing truck.
However, it is defendable, if you really want to stay on the safe side, to encode in 24 bits, in order to capture the entire range between hearing treshold and instant hearing damage.
I still don't think that it makes sense to use 196 kHz as a sample rate for a transport medium. If you want more realistic sound, then spend the space on surround encoding.
Sounds to me like hitting a musquito with a sledgehammer, and hard to configure (imagine having 40 kernels, each with different parameters) :-) An extension to the ulimit concept inside the main kernel would be enough for me: an application can restrict its permissions, but cannot undo these restrictions. Example:
ulimit -d 10000 # max 10 MB data /tmp # only write permission in /tmp
./untrusted_application
ulimit --onlywrite
ulimit --tcp 1-1024 # no TCP/IP on ports 1-1024
For Windows (sigh), you can use ZoneAlarm (free edition) to do exactly this. It would be nice to have something like that in the Linux kernel.
After struggling for a while with the Kernel Versioning Hell (A few major releases ago, compiling a kernel was as simple as make dep; make zImage; make modules, but nowadays that doesn't seem to work without endless tweaking), I found Up-to-date Alsa RPMs for all major Linux distributions.
Yes, 96/192 kHz sampling is a good thing for recording studios for the reason that you explain. Moreover, >=24 bit recording means that you don't get aliasing problems if the signals are amplified or attenuated during the mixing process.
However, this is all on the recording side. After sampling at >=96 kHz, you can apply a digital filter with a perfectly flat passband up to 20 kHz and stopband above 22.05 kHz, and then downsample to 44.1 kHz. In any CD player, the opposite process is performed (the famous "oversampling"): it is hard to filter the noise above 20 kHz in the raw 44.1-kHz signal. Therefore, the DAC converts the signal digitally to a 4 to 16 times higher sampling rate and with a slightly higher bitresolution (e.g. 18 or 20 bits). Then, the DAC digitally filters out everything above 22 kHz while leaving everything below 20 kHz.
The (still digital) signal is now a "smooth line" through the supplied data points at 44 kHz. This signal is converted to a voltage by the true (non-signal-processing part of the) DAC. The part of the spectrum below 20 kHz will be exactly the same independent on whether the original input to the DAC was 44, 96, or 192 kHz. (Note: 1-bit DA convertors use a slightly different approach, but with the same result).
As far as the bit resolution is concerned: in the final signal, 16 bits is enough for a dynamic range of 92 dB. If the hearing treshold is at 0 dB, that means that for peak levels of less than 92 dB, the resolution is fully sufficient to encode even the softest audible sounds. Note that 92 dB is quite loud: about 4 W power to a typical 87 dB/W loudspeaker at 1 m distance. It is defendable to use a bitresolution higher than 16, if you want to hear a ticking watch in the background while the music is playing at the pain treshold of 120 dB. For that, you need 5 more bits: 21 bits. On the consumer end, 24 or 32 bits is a waste of storage space.
A water jet cutter works better (certainly faster) for any products that can stand contact with water. Bread may not be a good candidate, but meat and sticky candy bars are. See the website of a water jet manufacturer for more information.
I've done experiments with 266 nm laser beams. Ultraviolet light makes nearly every organic molecule fluoresce. It is usually quite easy to see the spot where the laser beam (even if it is just a few milliwatts) hits a surface.
Actually, Philips used to have their own video format, Video 2000, which flopped.
There are roughly two types of phosphors in fluorescent lamps: halophosphate and triphosphor.
Halophosphate emits mainly in a band around yellow, plus a narrow violet line. The result looks white to the eye, but surfaces that mainly reflect green and blue/green wavelengths or deep red wavelengths look strange, since these wavelengths are not present in the light. This is probably what you refer to as "ugly green light". These are mainly used in cheap tube-type fluorescents. In this building, they are used to illuminate the corridors, but not the offices.
The triphosphor emits mainly five lines: red, yellow, green, blue/green, and violet, evenly distributed over the spectrum of visible light. This type tends to give good color reproduction. All compact fluorescents that I've seen so far use these triphoshpor mixtures, presumably because a compact fluorescent does not need a large amount of phosphor compared to a 120-cm tube. (I played around with looking at diffraction patterns from various light sources through a CD) As other people pointed out, CF lamps are electronically ballasted and do not flicker at frequencies visible to the human eye.
That's not imagination. I once attended a talk by someone from Philips Research. Accordig to the CD specs, the plastic layer on the playing side of the disc should be 1.0 mm thick with a tolerance of +/- 0.1 mm (I don't recall the exact numbers). According to him, after a few years, all CDs on the market had 0.905-mm-thick plastic layers because it was possible to manufacture them with much tighter tolerances and this way, the manufacturers save 10% on the raw material.
In the DVD specification, the tolerances are much tighter, which is necessary because the laser needs to be focused onto a much smaller spot than in a CD.
You'll probably get tired of your iPod within 3 years because something hotter appears on the market. So that's $300 every 3 years. Compare that to the fact that you spent those $3000 for CDs over the course of, say, 15 years, that's $600 per 3-year-period. Then $300 is not trivial.
The 40 GB iHP-140 is described in English on their Northern Europe website. You have to click on the English flag in the upper right corner.
Test-achats's original press release in French, Dutch, and Google's translation to English.
Though energy reduction is a good thing, it doesn't hurt to see things in proportions.
Electrical razor: 10 W, 3 minutes per day: 0.18 kWh per year or 0.66 MJ.
Shaving with a manual razor: 1 liter of hot water per day: 73 MJ (megajoule) per year (20 kWh if you use electricity to heat the water).
Driving a car, 10000 km per year: 800 liters of fuel or 30000 MJ.
If every new electrical meter put it were REQUIRED to run both directions, then it would be a simple matter to run 2, 4 solar panels and just push it back on the grid.
The price of electricity incorporates the costs of infrastructure to meet peak demands. That is the main reason why selling back electricity to the grid from an unpredictable source such as a wind turbine or a solar panel should cost less than what you pay for your electricity. The electricity companies need to have fuel/nuclear power plants on standby and sufficiently thick cables to supply your house, just in case there is no wind/sun when the need for electricity is high.
You suggest that the electricity price should be dependent on the time. This would only make sense (with the above) if the electricity cost per kWh were the true incremental costs, not involving any infrastructure. The infrastructure would have to be financed completely from the fixed costs, which is not the case. The variable costs are just the costs of the coal or nuclear fuel and maintenance of the power plants; the fixed costs are the installation and maintenance of the complete grid, which costs far more than what can be covered by the connection fee and the nominal monthly fee.
Actually, it is not a problem to bring your skin into contact with liquid nitrogen for 1 or 2 seconds. Between the skin and the LN2, a thin layer of gaseous nitrogen will form which will act as a thermal insulator. I've done that many times (I won't take responsibility in case anyone else tries this at home). After a few seconds, the skin will have cooled down sufficiently for the gas layer to disappear and only then you will get frostbite.
The gas layer also prevents the LN2 from sticking to surfaces. It will just roll of the surface, similar to water droplets that float on a very hot surface (e.g. a hot plate in the kitchen). Hence, if you spill LN2 over your body, you will probably not suffer any damage, unless you are wearing shoes/clothes that can act as a reservoir.
Liquid helium is not very dangerous either: because of its low temperature (4 K), nitrogen and oxygen in the air will immediately start condensing, thereby increasing the helium temperature and forming gaseous helium and liquid air, to which the same comments as above apply. LHe can only be used in closed circuits for this reason.
I've never understood what the idea is of point sizes on something that is going to be projected on a 3 meter-wide screen. Is it going to be 14 points if you print it landscape on standard A4/letter paper, or if it will be portrait (covering half the paper)?
I have found that from the last row in a typical lecture hall, the projected image is typically as big as a QUARTER A4 (=A6) or Letter sheet at normal reading distance (30 cm/1 ft). So if you want to judge the legibility, then print it on reduced size, or turn down the contrast of your 17 inch monitor and look at it from 60 cm (2 ft) at a 30 degree angle.
It turns out that you can do rather complicated graphical tricks with LaTeX, as the example slide shows demonstrate. Furthermore, it has some rather nice background color schemes, that unfortunately don't always have good contrast.
Are you trying to get these people spammed by providing their e-mail address publicly?
I'd guess that they would be violating the privacy of the users by doing that retroactively. Maybe what they are really saying is: if more than 20 emails in 10 minutes are sent from your computer, then it will be registered and used for spam-analysis statistics.
Why do you have to do that by hand? Can't those PVR boxes detect whether there is a channel logo in the corner of the screen to decide whether it is an ad or not?
A. Programming enthusiast - a happily married father of two kids who spends an hour or so on a typical evening writing his own Visual Basic address book program.
B. hacker - a person that rarely sees daylight who programs in C and assembler until 3 AM to reverse-engineer an obscure protocol, with a pile of pizza boxes and cola cans next to his desk.
The elitists in category B of course do not want to be confused with those belonging in category A. We need a word that conveys these subtle differences.
Then which word do you suggest for someone who enjoys programming and using [their own] computers in creative ways?