Many Shoes actually trigger metal detectors because they have nails in it.
The problem isn't the nails, it's the shanks (steel stampings used to stiffen shoes, especially high heels). I've got a few pairs of New Balance velcro fastened sneakers that I thought were metal free - turns out the reinforcing for the slots for the straps are metal.
What we're doing with muslims is in some ways not as bad as what happened to the japanese in WW2 (not rounding everyone up), and in some ways it is worse ( removal of citizenship status, sanctioned torture, indefinite detention outside of both non-us and non-international law, invading an unrelated country).
This reminded me of a concern that a former co-worker had when she found out about the internment of the Japanese in the US during WW2. What was ironic was that she was from Germany and I refrained from asking her whether she'd rather be a Japanese in the US during WW2 or a Jew in Germany during WW2 - the one difference was that the German government now is not the same as in WW2. OTOH, the Japanese had been committing atrocities in China years before Germany got started on theirs.
Probably the most shameful aspect of the whole affair was the indifference of one of the primary supporters of the internment program - Earl Warren.
I thought it was pretty cool, remember going through it in 1965. What's kinds of freaky about it was that its design was a bit like the second story of the house in Heinlein's 'And he built a Crooked House' (an unfolded tesseract for those who haven't read the story.
The SI base unit of length is the metre. Your wacky "meter" is, in some circles, accepted as an alternative spelling.
Making snide remarks about the spelling of meter/metre is one of the worst ways of convincing the US in adopting the metric system for common usage (bearing in mind that 1 inch is defined as 25.4mm - except for the USGS). Don't get me started on the letter vs A4 paper size.
Now a truly rational standard for length would be the distance traveled by light in a vacuum in a nanosecond - which works out to be 0.984 feet. One of Jefferson's ideas was to have the units of length as decimal fractions of a nautical mile (which is still useful if latitude and longitude are given in degrees minutes seconds) - another was to base it on the length of a second's rod (a pedulum of that length would have a period of 1 second), which could be determined in any laboratory.
if you actually talk to any officers on a campus PD anywhere, they're among the most tolerant and least likely to overreact officers on any police force in the world.
That was pretty much my impression of the Uni cops when I was at Cal (BSEE '76, MSNE '78). One memory sticks out about how one was dealing with a fellow who appeared to be having a bad trip - the officer very pleasantly addressed the fellow and suggested that he may be in need of medical attention.
The one on-campus murder during my years there was committed by a non-student.
Interesting and insightful analysis, the system operation sounds similar to a gas turbine (but the turbine produces more power than the compressor consumes).
Current thermoelectric elements are not yet efficient enough to compete with closed cycle refrigeration systems.
That's a bit of an understatement - one of the goals for the gadolinium coolers was to replace thermoelectric coolers in low power applications. If I recall correctly, thermoelectric modules are doing well to move 1 watt of heat across 30C with 3 watts of power, where a mechanical system can easily move three watts of heat per watt of power. If he can reach 'halfway' between mechanical and thermoelectric refrigeration for small systems, he'd still have a winner.
If he can get 1/3rd of Carnot efficiency at 200C, that still have useful applications for recovering heat from internal combustion engines.
I thought my New Balance sneakers would be metal free, but the oval grommets for the velcro straps are metal. I also had one pair of shoes that would invariably set off the metal detectors and I stopped wearing them when going on a flight.
This is the first time that I've heard about false alarms as being the reason for taking shoes off.
In at least a couple of Heinlein stories, he mentions that it is much easier to hide something under a skirt (kilt) than it pants. OTOH, a terrorist could hide a big chunk of explosive on his inner thigh and claim that he makes John C Holmes look small - probably be best if the explosive was anatomically correct shape.
BSD is probably better referred to as a fork of AT&T UNIX (e.g. paging versus swapping). It is ironic that you used that example as UNIX could rightfully be considered a clone of Multics.
A railroad is a little more than an extremely hard and smooth road to minimize rolling resistance. What makes the railroad practical is the flanged wheel (with the flanges on the inside) - See the first chapter in The Railroad, what it is and what it does by John Armstrong.
HEI did a very clever job on shrinking a Pulsed Fast Neutron Activation (PFNA) system. The term neutron backscatter is misleading - the technique actually involves looking for characteristic gammas from inelastic scattering. What it allows for is a spatial mapping of elemental composition - note elemental, not chemical composition.
The problem with the HEI system is that it uses 14 MeV neutrons from the D-T reaction and those are a bitch to stop (think a couple of feet of borated water). And unlike x-rays, neutrons scatter, scatter and scatter, so you have to make sure that the neutron shielding doesn't have much in the way of gaps.
A lithium battery in checked luggage that shorts out could be a major disaster. Take a look at what happened when some oxygen generators where not shipped properly.
Good point wrt the oxygen generators.
I seem to recall that the rules on shipping Li batteries via airfreight were due to an incident on an air cargo plane. I presume the flaming laptop pictures were also on the minds of the group that drafted the new regs. The Li-phosphate batteries are probably a lot safer, but it may take a while for that info to wind its way through the TSA.
Good point wrt class-D extinguishers. One substitute is sand, but you're pretty much out of luck unless flying a DC-2 (which had a 1,000 lbm of sand in the back to fix weight and balance problems).
Restrictions on shipping lithium primary batteries by air cargo have been in place for over a year now and this also applied to equipment with lithium primary batteries. There are similar restriction for shipping large lithium secondary batteries.
The news rules do make sense, a in-flight fire on an airliner is pretty serious, especially if there is no nearby place to land (e.g. halfway between California and Hawaii).
The 640K limit was an issue with the design of the IBM and clones. DOS had no trouble addressing over 900K of memory in systems that didn't set aside huge amounts of address space for ROM and video buffers. Keep in mind that DOS was not originally written for the IBM PC, nor was it originally written by Micro$oft.
Low efficiency solar cells will dramatically increase global warming. Instead of 90% of the sun's rays being reflected back off into space by nice light sand or white roofing materials, 90% will be absorbed by photovoltaic panels, and turned into heat either immediate (solar cells are inefficient) or after being used in the form of electricity.
That would be another reason to continue work on high-efficiency PV - the albedo of most roofing material is pretty low, so a conversion efficiency of 40% would be a net gain. The more important reason for high efficiency is that the structural support cost per watt goes down as efficiency goes up.
You did bring up a good point about roofing material. Going to a higher albedo saves in two ways, one being that it cools the local enviroment (especially if the material has a high emissivity at 10-20um), the second is that it reduces air-conditioning loads, which reduces electrical demand. Similarly, local warming can be reduced by increasing the albedo of pavement.
Actually, it's not structural, it's more the fact that the air inlets are fixed rather than variable, so the engines can't get the optimal amount of air intake at different flight envelopes. Because of this, pushing the aircraft beyond mach 2.0 for any extended period of time will cause structural failures in the air intake.
The first sentence is correct, the second is not.
The problem with a fixed geometry inlet is that it is inefficient. At Mach 2.0 and above, a significant portion of the thrust from a properly designed inlet is coming from the inlet itself. The A-12/F-12/SR-71 cruising at Mach 3.0 gets between 55 and 60% of the total thrust from the inlet - this is accomplished by the positioning the shock wave just inside the inlet (the cons on the front of the engine can be moved in and out specifically for this purpose). One of the early issues with the Blackbirds was figuring out how to handle "unstarts" where the shock wave pops out of the inlet - and gives the crew a wild ride in the process - this was also a problem with the B-58.
The F-16 was also limited to Mach 2.0 because of the fixed geometry wing. OTOH, the F-104 was rated top speed was Mach 2.2, but it could easily achieve Mach 2.4, but at the cost of weakening the aluminum alloy in the airframe.
Seeing that fission neutrons on average thermalise after diffusing through about 18cm of reactor-grade graphite, and are absorbed after about 50cm, detecting only fast neutrons is probably not going to give many counts compared to the background.
The key word here is "average", prompt neutrons from fission have energies ranging up to 15MeV, and total cross-sections trend downward with increasing energy for almost all materials (for En>1MeV). In addition, a large chunk of 235U will probably have more more fissions induced by cosmic ray induced neutrons than spontaneous fissions.
You're right in that Pu is a lot easier to detect than 235U.
I was checking what was left in the Encinitas CompUSA store a couple of days before it closed for good. About the only thing left in quantity were UPS's and Zune's. Bear in mind that CompUSA had cut prices by at least 40% to clear out the store (they were even selling the racks that held the merchandise).
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The problem isn't the nails, it's the shanks (steel stampings used to stiffen shoes, especially high heels). I've got a few pairs of New Balance velcro fastened sneakers that I thought were metal free - turns out the reinforcing for the slots for the straps are metal.
This reminded me of a concern that a former co-worker had when she found out about the internment of the Japanese in the US during WW2. What was ironic was that she was from Germany and I refrained from asking her whether she'd rather be a Japanese in the US during WW2 or a Jew in Germany during WW2 - the one difference was that the German government now is not the same as in WW2. OTOH, the Japanese had been committing atrocities in China years before Germany got started on theirs.
Probably the most shameful aspect of the whole affair was the indifference of one of the primary supporters of the internment program - Earl Warren.
I thought it was pretty cool, remember going through it in 1965. What's kinds of freaky about it was that its design was a bit like the second story of the house in Heinlein's 'And he built a Crooked House' (an unfolded tesseract for those who haven't read the story.
Good one - though I wonder how many Slashdot readers would be familiar with that song - first heard it on Genesis Live.
Making snide remarks about the spelling of meter/metre is one of the worst ways of convincing the US in adopting the metric system for common usage (bearing in mind that 1 inch is defined as 25.4mm - except for the USGS). Don't get me started on the letter vs A4 paper size.
Now a truly rational standard for length would be the distance traveled by light in a vacuum in a nanosecond - which works out to be 0.984 feet. One of Jefferson's ideas was to have the units of length as decimal fractions of a nautical mile (which is still useful if latitude and longitude are given in degrees minutes seconds) - another was to base it on the length of a second's rod (a pedulum of that length would have a period of 1 second), which could be determined in any laboratory.
That was pretty much my impression of the Uni cops when I was at Cal (BSEE '76, MSNE '78). One memory sticks out about how one was dealing with a fellow who appeared to be having a bad trip - the officer very pleasantly addressed the fellow and suggested that he may be in need of medical attention.
The one on-campus murder during my years there was committed by a non-student.
Interesting and insightful analysis, the system operation sounds similar to a gas turbine (but the turbine produces more power than the compressor consumes).
That's a bit of an understatement - one of the goals for the gadolinium coolers was to replace thermoelectric coolers in low power applications. If I recall correctly, thermoelectric modules are doing well to move 1 watt of heat across 30C with 3 watts of power, where a mechanical system can easily move three watts of heat per watt of power. If he can reach 'halfway' between mechanical and thermoelectric refrigeration for small systems, he'd still have a winner.
If he can get 1/3rd of Carnot efficiency at 200C, that still have useful applications for recovering heat from internal combustion engines.
This is the first time that I've heard about false alarms as being the reason for taking shoes off.
In at least a couple of Heinlein stories, he mentions that it is much easier to hide something under a skirt (kilt) than it pants. OTOH, a terrorist could hide a big chunk of explosive on his inner thigh and claim that he makes John C Holmes look small - probably be best if the explosive was anatomically correct shape.
Canada, back in the late 1990's, prohibited beverages greater than 150 proof from being taken aboard an airliner.
Perhaps you meant "Would the screener be more gentle if she first felt my gun before going for my nuts."
That's one way to get Microsoft's goat.
BSD is probably better referred to as a fork of AT&T UNIX (e.g. paging versus swapping). It is ironic that you used that example as UNIX could rightfully be considered a clone of Multics.
A railroad is a little more than an extremely hard and smooth road to minimize rolling resistance. What makes the railroad practical is the flanged wheel (with the flanges on the inside) - See the first chapter in The Railroad, what it is and what it does by John Armstrong.
The problem with the HEI system is that it uses 14 MeV neutrons from the D-T reaction and those are a bitch to stop (think a couple of feet of borated water). And unlike x-rays, neutrons scatter, scatter and scatter, so you have to make sure that the neutron shielding doesn't have much in the way of gaps.
Good point wrt the oxygen generators.
I seem to recall that the rules on shipping Li batteries via airfreight were due to an incident on an air cargo plane. I presume the flaming laptop pictures were also on the minds of the group that drafted the new regs. The Li-phosphate batteries are probably a lot safer, but it may take a while for that info to wind its way through the TSA.
Good point wrt class-D extinguishers. One substitute is sand, but you're pretty much out of luck unless flying a DC-2 (which had a 1,000 lbm of sand in the back to fix weight and balance problems).
The news rules do make sense, a in-flight fire on an airliner is pretty serious, especially if there is no nearby place to land (e.g. halfway between California and Hawaii).
One former co-worker's comment was the world would have been a much better place had IBM gone with the 68k running something like OS-9.
The 640K limit was an issue with the design of the IBM and clones. DOS had no trouble addressing over 900K of memory in systems that didn't set aside huge amounts of address space for ROM and video buffers. Keep in mind that DOS was not originally written for the IBM PC, nor was it originally written by Micro$oft.
That would be another reason to continue work on high-efficiency PV - the albedo of most roofing material is pretty low, so a conversion efficiency of 40% would be a net gain. The more important reason for high efficiency is that the structural support cost per watt goes down as efficiency goes up.You did bring up a good point about roofing material. Going to a higher albedo saves in two ways, one being that it cools the local enviroment (especially if the material has a high emissivity at 10-20um), the second is that it reduces air-conditioning loads, which reduces electrical demand. Similarly, local warming can be reduced by increasing the albedo of pavement.
The first sentence is correct, the second is not.The problem with a fixed geometry inlet is that it is inefficient. At Mach 2.0 and above, a significant portion of the thrust from a properly designed inlet is coming from the inlet itself. The A-12/F-12/SR-71 cruising at Mach 3.0 gets between 55 and 60% of the total thrust from the inlet - this is accomplished by the positioning the shock wave just inside the inlet (the cons on the front of the engine can be moved in and out specifically for this purpose). One of the early issues with the Blackbirds was figuring out how to handle "unstarts" where the shock wave pops out of the inlet - and gives the crew a wild ride in the process - this was also a problem with the B-58.
The F-16 was also limited to Mach 2.0 because of the fixed geometry wing. OTOH, the F-104 was rated top speed was Mach 2.2, but it could easily achieve Mach 2.4, but at the cost of weakening the aluminum alloy in the airframe.
The key word here is "average", prompt neutrons from fission have energies ranging up to 15MeV, and total cross-sections trend downward with increasing energy for almost all materials (for En>1MeV). In addition, a large chunk of 235U will probably have more more fissions induced by cosmic ray induced neutrons than spontaneous fissions.You're right in that Pu is a lot easier to detect than 235U.
I was checking what was left in the Encinitas CompUSA store a couple of days before it closed for good. About the only thing left in quantity were UPS's and Zune's. Bear in mind that CompUSA had cut prices by at least 40% to clear out the store (they were even selling the racks that held the merchandise).