A Shepard tone, named after Roger Shepard, is a sound consisting of a superposition of sine waves separated by octaves. When played with the bass pitch of the tone moving upward or downward, it is referred to as the Shepard scale. This creates the auditory illusion of a tone that continually ascends or descends in pitch, yet which ultimately seems to get no higher or lower.
Benjamin Zander has two infectious passions: classical music, and helping us all realize our untapped love for it — and by extension, our untapped love for all new possibilities, new experiences, new connections.
In 2009 he was flying 700,000 miles per year. Last year he hit 17 million flown, which would mean 7 million in 5 years or 1.4 million per year — twice his earlier pace. That would be 3835 miles per day which would require flying literally a third of the hours in each year.
This is still one of my favourite mad engineering stories on the web. How to fix a 230kV oil filled electricity cable with Liquid Nitrogen.
It turns out they have a problem with an underground wire. Not just any wire but a 230 KV, many-hundred-amp, 10 mile long coax cable. It shorted out. (Lotta watts!) It feeds (fed) power from the Scattergood Steam Plant in El Segundo to a distribution center near Bundy and S.M. Blvd.
To complicate matters the cable consists of a copper center conductor living inside a 16 inch diameter pipe filled with a pressurized oil dielectric. Hundreds of thousands of gallons live in the entire length of pipe. Finding the fault was hard enough. But having found it they still have a serious problem. They can’t afford to drain the whole pipeline – the old oil (contaminated by temporary storage) would have to be disposed of and replaced with new (pure) stuff which they claim takes months to order (in that volume). The cost of oil replacement would be gigantic given that it is special stuff. They also claimed the down time is costing the costing LA $13,000 per hour. How to fix it and fast?
That’s where the LN-2 comes in. An elegant solution if you ask me. They dig holes on both sides (20-30 feet each way) of the fault, wrap the pipe with giant (asbestos-looking) blankets filled with all kind of tubes and wires, feed LN-2 through the tubes, and *freeze* the oil. Viola! Programmable plugs! The faulty section is drained, sliced, the bad stuff removed, replaced, welded back together, topped off, and the plugs are thawed. I was amazed.
The landscape for the performance-minded developer has changed significantly in the last year or so, with the emergence of HTTP/2 being perhaps the most significant of all. No longer is HTTP/2 a feature we pine for. It has arrived, and with it comes server push!