Catch up on stories from the past week (and beyond) at the Slashdot story archive


Forgot your password?
DEAL: For $25 - Add A Second Phone Number To Your Smartphone for life! Use promo code SLASHDOT25. Also, Slashdot's Facebook page has a chat bot now. Message it for stories and more. Check out the new SourceForge HTML5 Internet speed test! ×

Comment HCCI are efficient like diesel (Score 4, Informative) 89

HCCI engines are a really cool technology, but very hard to do.

Efficiency of internal combustion engines is related to the compression ratio - the ratio of the combustion chamber from largest to smallest capacity.

Gasoline engines usually have a compression ratio around 9:1. Higher, and the compressional heating combined with the heat off of the walls can cause "knocking," which detonation of pockets of fuel/air away from the flame front from the spark plug. Engines with premium gas can run higher compression ratios. Higher-octane fuels can be compressed more without burning, but of course there is no benefit to running it on engines rated for regular.

Diesel engines run ratios of around 17:1, resulting in much greater efficiency. Diesel engines of course don't have spark plugs. The fuel is injected just before top dead center, where the air is compressed maximally. This is in contrast to a gasoline engine, where it is well mixed with air before entering the combustion chamber. Due to compressional heating, it spontaneously combusts very quickly, much faster than the combustion in a spark-plug-ignited gas engine.

HCCI well-mixes the air and gas upon intake, but ignites by compression like diesel. This gives diesel efficiency. In addition to the better compression ratio, HCCI controls power by the amount of fuel injected, like a diesel. Gasoline engines use a throttle to choke off the air supply, which induces losses because the engine has to work harder to pull air at lower power. That's how engine braking works, and also why diesel trucks use a separate "jake brake" to use the engine to brake.

It must run under a leaner mixture. It's really hard to have complete burning of fuel, and avoid knocking. That's why it has to be very carefully computer controlled based on temperature and such.

Comment Re:Better metrics for Ubuntu vs other Linux? (Score 1) 125

If you're talking about stackexchange, you are getting into a sysadmin/developer/knowledgeable user community. It's not really a representative sample.

AFAIK, no one has really got a reliable measure. It's pretty much impossible when you are talking about most FOSS. It is pretty clear that Ubuntu is by far and away the most popular for desktop usage.

Comment Re:Mint Debian (Score 1) 125

I have a hard time believing that accounts for a significant percentage of Ubuntu's search volume. If both had the same popularity, for example, and even one third of people wanting info about Mint searched for "Linux Mint," if Ubuntu had a search volume of 166, then Mint would have a search volume of 33. This is a much smaller relative disparity than actually seen. And the likely case is that while some people searching for Mint information query for Ubuntu, most are still going to search for Mint.

Comment Re: Mint Debian (Score 1) 125

Are you fucking kidding me? I have no idea why people ever think of Distrowatch as mattering. All that it measures is page hits to Distrowatch's info page about that distro. It only measures what people who go to Distrowatch click on at Distrowatch. Notice that the numbers are in the low thousands per month at best. Their audience is longer-time Linux users who remember it from like fifteen years ago.

Google search volumes are by far a more accurate gauge of interest, as it is both a much larger sample, and a more uniform sample, as a broader range of people use Google than visit some fucking site that was cool during Slashdot's heyday. Sampling 101.

Comment Re:Mint Debian (Score 4, Interesting) 125

The vast majority of linux users use Ubuntu, with Unity (they don't know what XFCE is). They just don't post on Slashdot. Take a look at this Google Trends frequency of search terms here.

Mint barely registers compared to Ubuntu. (Also, distrowatch really is useless).

The only people I know (aside from a few sysadmins with RHEL) that run another distro are my parents, because I put Mint on their computer. I just use FreeBSD now.

Slashdot Top Deals

Intel CPUs are not defective, they just act that way. -- Henry Spencer