voluntaryXchange

“Reverse Phone Book” for Algebra

I came across an interesting site called RIES. If you give it a number, it returns equations that approximate that number.

Weird, eh? Usually you have a tough equation, and you approximate a solution to it with a number.

For example, I input 42, and RIES outputs these equations that can be solved for x and which yield an answer close to 42:

• x+7=7^2, an exact solution
• 3x=5^3, approximation is accurate within 1%
• (x+5)^2=3*7, , approximation is accurate within 1%
• x^5=8^9, approximation is accurate within 1%
• 5(x+1)=6^3, approximation is accurate within 1%

An odd thing for someone who isn’t a mathematician: this is sort of like a reverse phone book for algebra.

Via I Love Charts via the details in the fabric via XKCD.

Technorati Tags: reverse,phone,book,algebra,ries

Sweet Home Alabama

Interesting to watch, but the best part (for me) was reading their description of what they did. I copied it from their YouTube page.

These are two gigantic solid state musical Tesla Coils. A Tesla Coil is a special type of transformer invented by Nikola Tesla that is able to generating extremely large voltages using a phenomenon known as electrical resonance. Each coil in this video is capable of generating a 13 foot spark. This equates to about 500,000 volts of electricity.

The primary drive system for the coils consists of high power semiconductors arranged into an H-Bridge switching configuration. During a spark event, the coil is pulsed on for a few hundred millionths of a second. During this short time, thousands of amps circulate within the primary tank circuit and the energy is coupled into the secondary resonator through magnetism.

So what appears to be a continuous burst of sparks is actually a specific number of sparks generated per second. By modulating the number of sparks that emit from the coil each second, different tones can be produced by the coils.

These coils were constructed by Eric Goodchild and Steven Caton.

Eric Goodchild is currently an EE student at ASU Polytechnic. His personal website is: http://www.goodchildengineering.net/

Steven Caton is currently an EE student at UCLA. His personal website is: http://stevencaton.com/

Technorati Tags: sweet,home,alabama,tesla,coils

The New York Times Is Misleading and Deceptive*

They’re selling the idea that hybrids are economical, and The New York Times has to be misleading to do so.

The goal is to tell potential buyers how long it will take to pay off the extra expense of a hybrid car.

But, their method is what’s called Payback Time.

In any basic finance book, this method is discussed, in the very first chapter on valuing net cash flows through time, as the method not to use. It is typically included in that chapter as a foil for better methods like net present value and internal rate of return.

The reason is simple: payback doesn’t include discounting (the idea that you’d rather have cash today than wait for it).

How bad is this problem?

It depends on how lousy the car is to begin with. For example, the Chevy Volt is so bad a deal that even The Times notes that payback would take 26 years.

Internal rate of return (IRR) is the second-best method, but perhaps the easiest to explain. It’s the rate another asset would have to provide to be better.

In the case of the Volt, if you held the car for 30 years … it would still only make sense as a purchase against an alternative investment that earns 0.8%.

Let’s put that in perspective. If your choice is to buy a Volt and drive it for 30 years, or buy a house in Detroit … you should probably buy the house in Detroit.

Things are far better for the Prius (but as most people know, the Prius really isn’t very green to begin with). The Times would have you believe it pays for itself in just under 2 years. That’s true, but only in a sense no one who has half a semester of finance actually uses. But, if you buy the Prius and keep it for 5 years, it’s IRR is 47%. That’s a good investment for you, but it’s not clear if it’s a good loss leader for Toyota: it does not count the trade secret of how much Toyota loses on each Prius — estimates range as high at $17,000 per car … although that estimate gets shouted down in polite conversation.

Somewhere in between is the Nissan Leaf: a seriously green car, whose return is not dragged down by inane UAW contracts. The Times reports that payback for this car is just under 9 years. More realistically, if you keep the car for 10 years your IRR will be 2.5%. That rises to 5.3% if you keep it for 12 years. Those are crappy returns. But, you’d need to keep it for 16 years to beat the 8% return routinely assumed by badly managed public sector pension funds.

I kept a car for more than 16 years. And even my parents made fun of me for that. Realistically … no one keeps a car that long.

It’s time to face the facts: a professional financial advisor could be jailed for recommending that you buy a hybrid car as an investment.

P.S. If you want to see my spreadsheets for these calculations, just ask.

* Yeah … I know … what’s new.

Technorati Tags: hyrbid,prius,leaf,volt,payback,irr,internal,rate,return

Cool Speculation: Stonehenge Is All About Sound

This is way out there, but lots of us have done this experiment in physics class, and no one has made the connection before Steven Waller, a doctoral researcher at Rock Art Acoustics USA:

If two pipers were to play in a field, observers walking around the musicians would hear a strange effect … At certain points, the sound waves produced by each player would cancel each other out, creating spots where the sound is dampened.

The theory is highly speculative, but modern-day experiments do reveal that the layout of the Stonehenge ruins and other rock circles mimics the piper illusion, with stones instead of competing sound waves blocking out sounds made in the center of the circle.

In support of the theory, Waller pointed to myths linking Stonehenge with music, such as the traditional nickname for stone circles in Great Britain: "piper stones." …

Waller experimented by having blindfolded participants walk into a field as two pipers played. He asked the volunteers to tell him whenever they thought a barrier existed between them and the sound. There were no barriers in the field, but acoustic "dead spots" created by sound-wave interference certainly gave the volunteers the impression that there were.

"They drew structures, archways and openings that are very similar to Stonehenge," Waller said.

Read more: http://www.foxnews.com/scitech/2012/02/17/stonehenge-inspired-by-sound-illusion-archaeologist-suggests/?intcmp=features#ixzz1mktzlUYh

Technorati Tags: stonhenge,piper,stone,sound,cancellation

Do Cats Make Us Crazy?

Cats carry a parasite that infects humans and can change behavior.

I’ve known this for a several years, but this longread has a lot more new research results in it.

… Schizophrenia patients who underwent MRI scans, the team found, had reduced gray matter in the brain—and the decrease occurred almost exclusively in those who tested positive for T. gondii.

…

a striking talent of the parasite: it has two genes that allow it to crank up production of the neurotransmitter dopamine in the host brain.

…

The psychiatrist E. Fuller Torrey agrees—though he came to this viewpoint from a completely different angle than either Webster or Flegr. His opinion stems from decades of research into the root causes of schizophrenia. “Textbooks today still make silly statements that schizophrenia has always been around, it’s about the same incidence all over the world, and it’s existed since time immemorial,” he says. “The epidemiology literature contradicts that completely.” In fact, he says, schizophrenia did not rise in prevalence until the latter half of the 18th century, when for the first time people in Paris and London started keeping cats as pets. The so-called cat craze began among “poets and left-wing avant-garde Greenwich Village types,” says Torrey, but the trend spread rapidly—and coinciding with that development, the incidence of schizophrenia soared.

…

the national suicide rate among women increased in direct proportion to the prevalence of the latent Toxo infection in each nation’s female population.

There is no cure or treatment. Fortunately, you need to be exposed to outdoor cats, and:

As for outdoor cats, they shed the parasite for only three weeks of their life, typically when they’re young and have just begun hunting. During that brief period, Flegr simply recommends taking care to keep kitchen counters and tables wiped clean.

Technorati Tags: cats,toxoplasmosis,schizophrenia

Could We Build a Death Star by 2500 A.D.?

The vXboy is into Star Wars; how could I not link to this estimate of how much it would cost to build a death star?

The skinny: 13,000 times the world’s current GDP.

My addition to the meme?

• Suppose the government takes 25% of GDP in taxes, and
• Spends a fifth of that on defense, and
• Spends half of that on building a death star, and
• Global real growth is 3% per year, then:
• We’d need 520,000 times our current global real GDP, and
• That could occur by doubling our real GDP 19 times,
• Which at 3% would take us about 450 years.

That’s right, by 2500 AD we should be able to build a death star, using plausible assumptions.

Technorati Tags: death,star,cost,build,2500 AD

Pediatricians Firing Customers

Firing customers isn’t common, but it is a standard part of the discussion in management classes, programs, and books.

It’s what you’re supposed to do when the customer creates more costs than benefits.

Pediatricians have recognized this, and are starting to drop families who don’t vaccinate their children.

The reason is that these families impose extra costs on the practice and externalities on the pediatricians other patients.

Living in Utah, where many parents don’t vaccinate, I can tell you that this is a source of anxiety every time we’re in a public place and see other sick kids.

Via Kottke.

Technorati Tags: vaccination,pediatrician,ban

Cool Photo: Rocket and Aurora

A rocket being launched during the aurora on Saturday night, near Fairbanks:

Technorati Tags: rocket,aurora,fairbanks

Cool Science: Trees Do Solar Better

Silicon based solar power is never going to amount to much: how arrogant do you have to be to not realize that nature had 4.6 billion years to come up with silicon-based solar cells, and instead came up with trees.

Fortunately, the world has 13-year old boys.

This one recognized that trees spread branches following Fibonacci sequences. So he built a “tree” to hold solar cells, and it collected up to 50% more energy than just pointing solar cells at the sun.

BTW: Solyndra, the $500 million Obama boondoggle, was an investment in a product to rotate solar cells to face the sun instead of just pointing them in different directions.

Technorati Tags: solar,power,tree,fibonacci

Hereditary Psychiatric Disorders and Choice of Major

Members of families with a history of depression, mania or substance abuse are more likely to major in humanities, while those with a history of autism are significantly more likely to major in STEM.

Duh … this is one of those things that you really can’t imagine that no one has ever looked at before.

Via Marginal Revolution.

Technorati Tags: depression,bipolar,mania,substance,abuse,autism,humanities,stem