Archive for the ‘thermodynamics’ Category

Meet Maxwell’s gambling demon—smart enough to quit while it’s ahead

March 4th, 2021
In a new version of the classic 19th century thought experiment, Maxwell’s demon plays the role of a gambler who knows when to quit while it's ahead.

Enlarge / In a new version of the classic 19th century thought experiment, Maxwell’s demon plays the role of a gambler who knows when to quit while it's ahead. (credit: Aurich Lawson / Getty Images)

Entropy (aka the second law of thermodynamics) is a harsh mistress. If you think of the universe as a cosmic casino, the laws of thermodynamics amount to the house edge: you can't win, you can't break even, and—barring opening a portal to an alternate universe with different physical laws—you can't get out of the game. You just have to keep playing, and hopefully come up with successful strategies to minimize your losses as much as possible—and maybe even come out ahead occasionally, at least in the short term.

That's the essence of a new paper published in the journal Physical Review Letters, updating a classic 19th century thought experiment known as Maxwell's demon, which provides a potential loophole to subvert the second law—at least temporarily. Now physicists have proposed a gambling version of the demon playing a slot machine, unable to control when the machine pays out (in terms of free energy available for work), but able to choose when to stop playing to maximize its "winnings." The research might one day lead to improved efficiency of microscopic heat engines and motors.

As we've reported previously, around 1870, James Clerk Maxwell envisioned a tiny imp capable of creating order out of disorder in a closed container filled with gas. The imp accomplished this by making heat flow from a cold compartment to a hot one in apparent violation of the second law. The two compartments would be separated by a wall with a shutter covering a pinhole just large enough for a gas molecule to pass through. 

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Posted in entropy, Maxwell's demon, Physics, science, second law of thermodynamics, thermodynamics | Comments (0)

Georgia Tech physicists unlock the secret to perfect wok-tossed fried rice

February 23rd, 2020
Wok tossing has long been suspected of causing the high shoulder injury rate among Chinese chefs.

Enlarge / Wok tossing has long been suspected of causing the high shoulder injury rate among Chinese chefs. (credit: Hunting Ko and David Hu/Georgia Tech)

Fried rice is a classic dish in pretty much every Chinese restaurant, and the strenuous process of tossing the rice in a wok over high heat is key to producing the perfect final product. There's always chemistry involved in cooking, but there's also a fair amount of physics. Scientists at the Georgia Institute of Technology have devised a model for the kinematics of wok-tossing to explain how it produces fried rice that is nicely browned, but not burnt. They described their work in a recent paper published in the Journal of the Royal Society: Interface.

This work hails from David Hu's lab at Georgia Tech, known for investigating such diverse phenomena as the collective behavior of fire ants, water striders, snakes, various climbing insects, mosquitos, the unique properties of cat tongues, and animal bodily functions like urination and defecation—including a 2019 Ig Nobel Prize winning study on why wombats produce cubed poo. Hu and his graduate student, Hungtang Ko—also a co-author on a 2019 paper on the physics of how fire ants band together to build rafts—discovered they shared a common interest in the physics of cooking, particularly Chinese stir-fry.  

Hu and Ko chose to focus their investigation on fried rice (or "scattered golden rice"), a classic dish dating back some 1500 years. According to the authors, tossing the ingredients in the wok while stir-frying ensures that the dish is browned, but not burned. Something about this cooking process creates the so-called "Maillard reaction": the chemical interaction of amino acids and carbohydrates subjected to high heat that is responsible for the browning of meats, for instance.

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Posted in applied physics, fluid mechanics, kinematics, Maillard reaction, mmmm fried rice, Physics, science, thermodynamics, wok tossing | Comments (0)