* Posts by Brian

6 posts • joined 7 Jan 2008

Dr. Strangevote saves mankind with Luddite voting recipe

Brian
Thumb Up

So they finally caught up

The small Michigan town I live in has been doing this since at least 1998. I can't say how long before that as I moved here in 1997. Nice to know the high tech types in California have finally caught up to small town USA.

Nike pulls Air Stab trainers

Brian
Coat

There goes Tux

After all the partition mounting configuration is kept in the f-stab file. This anti knife hysteria is obviously a plot by MS to expand their monopoly.

The one targeted by the black helicopter

Mars whacked by object bigger than Pluto

Brian
Alien

@Nate

There used to be 10 planets. Pluto's brother-in-law had his status as a planet demoted by the Martians. In a fit of drunken rage he smashed into their planet for revenge. We had better hope Pluto stays sober.

On a serious note. Someone mentioned the theory that the moon was formed by something Mars sized hitting earth. I seem to remember similar evidence of a fairly big impact to the planet Mercury, assuming they haven't demoted Mercury yet. I wonder if Venus has a similar impact. That might suggest the rocky planets originally form in pairs that eventually slam into each other with the larger one surviving.

X Prize comes to earth

Brian
Flame

Re: Fuel requirements By Michael C

<quote>

I think people are misreading the fuel requirement section. "All cars will have to run on petrol, diesel, electricity, natural gas, bio-diesel and E85 - ethanol and petrol."

My read of this is it will have to run one of: petrol, diesel, electric, lpg, or biodiesel, also run e85 (ethanol petrol mix). This means it could be electric/e85, diesel/e85, natural gas/e85, etc.

There's no such engine that by itself can run all of these. To put all fuels under one hood would require as many as 4 engines: diesel/bio-diesel; petrol/e85/ethanol, natural gas/propane, and electric. Sure a petrol engine can be converted to run natural gas, but it has to be converted... you can't reasonably do them all...

</quote>

I downloaded the draft competition guidelines from the site referenced in the Reg. article and you are the one misreading the fuel requirement section. The PERMITTED FUELS (it is all caps in the guideline) section states that all cars must use Automotive X Prize (AXP) provided fuel. The Reg. article provided the list of fuels AXP is planning to provide. The guideline section does not state that a vehicle must run on all of them.

Your misread aside, I can name three engines that can run on all of these fuels: Steam, Sterling, and gas turbines. Steam and Sterling need an external heat source and a way to dispose of waste heat. Any of the listed fuels, even electricity, can be the heat source. Chrysler had a turbine powered car they tested in the 70's with gasoline, kerosene, diesel and according to the Chrysler museum even scotch whiskey (ethanol). Co generation systems run gas turbines on natural gas. It should be possible to replace the gas turbine engine combustion chambers with electric heating elements. I suspect you could even build a single gas turbine engine with electric heating elements and combustion chambers with injectors for liquid and gaseous fuels. Of course such a gas turbine would be silly, but then again so would powering any of these engines on electricity. Using these engines to generate electricity is not silly, in fact steam and gas turbines are used to generate electricity around the world.

Using the fuel rules in the competition guidelines it is still possible to use any of the three engines with only one fuel tank and one engine. You would have to decide between liquid fuels or natural gas. Personally I would go with the liquids since the existing fuel infrastructure can handle them and the energy density is higher than natural gas. The engine would still have a wider fuel selection than any currently mass produced automotive engine I know of.

The following quote from you was too funny to leave alone: "Note Hydrogen and methane are both distinctly left out."

From the US Department of Energy: "The main ingredient in natural gas is methane, a gas (or compound) composed of one carbon atom and four hydrogen atoms."

Link: http://www.eia.doe.gov/kids/energyfacts/sources/non-renewable/naturalgas.html

Arthur C. Clarke dead at 90

Brian
Unhappy

Farewell to a visionary

The first of his books that I read was 2001. It was tedious near the beginning but picked up later and is still one of my favorites. I wished for a 2001 theater re-release back in 2001, it would have been nice to see it on the big screen for once.

One of the ideas from the book that I found most interesting is using magnetic levitation to accelerate space planes, reducing the fuel requirements. The first time I read of NASA research into this, I remembered 2001.

Thank You for your ideas and books Mr. Clark, you will be missed.

Camouflaged code threatens security apps

Brian
Boffin

@ Stephen B Streater

"One way this is done is to use multiple "independent" hash functions. You only have to check the second if the first gives a match, so it isn't significantly slower than using a single hash function."

Initially this seems like a good idea, unfortunately the idea represents at least two fatally flawed assumptions.

1) Significant time savings requires the file to not match the first hash result. This indicates the first hash function is sufficient. If the first is compromised then you have to run both to detect a bad match and you do have significantly slower verification. Since you expect files to verify most of the time, you are significantly slowing the verification process most of the time.

2) Reading the file takes little time compared with calculating the result. Checking the access times for registers, cache, main memory and hard drives should show the flaw. If that is not enough then try this little experiment. Get a copy of md5sum, sha1sum, and whatever other hash functions you want. Create a simple program that reads a file 4KB at a time doing no processing on the data. Run these programs timing how long it takes to process the same really large file, try a DVD ISO or something. You will find it takes nearly the same amount of time to just read the file as it does to calculate the hash results.

The correct solution would be to always calculate two or more independent hash function results using a single program that only reads the file once. That way reading the file, the most time consuming part of the verification, only happens once. You get the benefit of multiple independent checks without significant increase in verification time.

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