The Economist. Still worth reading.
E = (T2-T1) / T1
Everyone with an engineering degree knows this. Trying to extract much energy from low-grade heat at the output end of an engine is inefficient. This was figured out a long time ago. Here it is in The Manual of the Steam Engine. It's possible to increase steam engine efficiency by compounding, where the exhaust from each cylinder feeds a larger, lower pressure cylinder. This is cost-effective up to about 3 cylinders ("triple expansion"). Engines up to quintuple-expansion have been built, but the additional power from the last two cylinders in the chain isn't worth the trouble.
In 2005, this appeared in SF Weekly, about the gentrification of the Polk St. area of the Tenderloin:
Gay Shame calls the Lower Polk Neighbors Association a "brutal gentrification squad" of wealthy business owners, slumlords and bureaucrats.
"They are trying to transform Polk Street from the city's last remaining gathering place for marginalized queers and street culture into a hip destination for wealthy suburbanites," Mary said. "We want a safe place for marginalized people, and Polk Street has historically been that space.
"The neighborhood may soon be known more for green-apple mojitos and stretch Hummers than trannies and tweakers (methamphetamine users)."
That was back in 2005. Gentrification won.
It's happening. First, take a look at a map of the Tenderloin, from "Areas to Avoid, San Francisco." Twitter HQ is in that area, between 9th and 10th on Market, and the long-standing "mid-Market area" around there is rapidly being rebuilt. In fact, just about everything south of McAlliister has been gentrified, except for parts of 6th St and a small section around 7th and the north side of Market. Rebuilding is underway along the Van Ness corridor too, and has more or less chopped a block off the Tenderloin on the west side. That's the old "Polk Gulch" area, once a gay rent-boy hangout.
So the SF Tenderloin is about half the size it was a few years ago. Progress continues.
After the first dot-com boom collapsed, about half the twentysomethings in SF left. After this one collapses, that will probably happen again. Face it, most of the useful things in "social" have been done.
This is a training program, not a production process. They have a few people doing forging by hand, but not to make production parts. See the original article in the Japan Times. Toyota's process of continuous improvement of production requires that people working on assembly lines understand the process well enough to suggest improvements. They recognize that they've dumbed down the workforce too much.
Ford Motor funded the building of the Detroit TechShop for similar reasons. They need more people who have a good sense of how stuff is made. Who in the US gets a degree in production engineering any more?
Why does a small jet engine have to cost too much? A quick search of jet turbines for model aircraft shows that the 52lbs max thrust P200-SX from JetCat costs $5,495. Sure you would need 6 or 7 of these to get an average sized adult off the ground vertically with some minimal airframe, but we aren't talking about millions of dollars we are talking about something under $100k to put together some sort of ultralight VTOL.
The JetCat isn't man-rated. It's for model aircraft.
A JetCat needs an overhaul every 50 hours of operation. Mean time to failure is maybe a few hundred hours. A commercial jetliner turbine needs an overhaul every 3500 to 5000 hours of operation. Mean time to failure is around 100,000 hours.
A Williams FJ44 is suitable for light aircraft, and could be used for a VTOL, but a pair of them costs over $1M.
Current status: "€140 raised of €2,250,000 goal".
The thing is, it's quite possible to build a flying car. The prototypes of the 1950s make that clear. The world needs some good small VTOL craft. But none of the people doing it seem to be able to bring it off.
Small jet engines cost too much but can make VTOL work. Wankel engines (the Moller embarassment) or electric motors and batteries (this thing) don'tt have the power/weight ratio needed to do it well. It's probably quite possible to build a battery powered VTOL today, but the flight time will be a few minutes, like quadcopters.
Ignoring the performance hit with this (that many application won't take)
Clearing recently used memory is cheap, because it's in the cache. Clearing memory in general is cheap on modern CPUs, because the superscalar features do it really well. MOV is 35% of instructions, so CPUs are designed to do it efficiently.
It's security code. You have to scrub memory.
Anyone can buy Google Glasses right now on eBay. The going rate is about $1100. Google Glass "invitations" have been for sale on eBay for months. The going rate is about $50.
As an "exclusive launch", this is a flop. There have been XBox and Sony PSn launches where pre-order prices exceeded list price. Google Glasses are already selling at a discount before the launch. This thing is overpriced. It needs to launch at $995, and that will only hold until Samsung starts shipping.
Aviation human-factors people call this the "head-down time" problem - pilot looking at panel for too long. Big efforts are made to minimize head-down time during takeoff, approach, and landing. In combat aircraft, huge efforts are made to eliminate it outright, with heads-up displays and all essential controls needed during combat on throttle and stick. Pilot training emphasizes these issues.
Car UI people are just starting to get a clue about this. Early car interfaces were just awful. BMW's original iDrive is considered a classic example of how not to do it. There have some better interfaces since, but the tendency to emulate phones and do everything through a touchscreen is a step backwards.
Phone people have no clue at all. They assume they own the user's attention.
We're getting close to what could be the start of World War III. It looks like a land war between Russia and Ukraine is about to start. Reuters: Ukraine prepares armed response as city seized by pro-Russia forces. This is not about Crimea. Russia has now taken over cities 150Km inside the eastern part of Ukraine.
WWII started very much like this. On 1 September 1939, Germany invaded Poland.
The trouble with drones is that most of them don't have enough sensing to avoid other aircraft. Most don't have aviation transponders. Yet some of them are big enough that they're a hazard to other aircraft. Many of them can get 500 feet above ground level (AGL). (Aircraft other than helicopters are supposed to stay 500' AGL, 1000' AGL in congested areas. Around airports, airspace is controlled all the way to the ground.) This puts them in conflict with other aircraft. Here's a small Parrot drone at 1553 feet in the UK. It's little, but if it was sucked into a jet engine, the engine would definitely be damaged and might fail. In 2013, someone was flying a drone near JFK in New York and the drone had a near miss with a jetliner.
The Academy of Model Aeronautics used to have a 450' AGL rule, and the FAA has a clear rule about doing anything off the ground within 5 miles of an airport without coordination with the tower. That's enough to keep the little guys from interfering with aircraft.
The other side of this is that aircraft regulated by the FAA are considered not to be violating the property rights of the property overflown. Being overflown at 100' by an HDTV camera isn't a hazard to aviation, but property owners may object.
Look at how Occupy Wall Street fizzled out.