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Gibbsian36
Costa Rica
Registrace 14. 07. 2011
Bicentenario de las _Reflexiones sobre el poder motriz del fuego_ de Sadi Carnot
El documento que funda la ciencia moderna de la termodinámica, _Reflexiones sobre el poder motriz del fuego_, fue publicado por el ingeniero y físico francés Sadi Carnot (1796-1832) en la semana del 12 de junio de 1824. Motivado por esto, di hace unos días una charla patrocinada por la Asociación de Estudiantes de Física y Meteorología de la Universidad de Costa Rica. En este video recapitulo esa conferencia, en la que comento sobre la vida y obra de Carnot, que son altamente inusuales en el contexto de la historia de la física. Concluyo con algunas reflexiones personales, motivadas por el contraste entre el esfuerzo de Carnot por desarrollar una teoría racional de las máquinas de vapor y el desinterés del insigne matemático Leonhard Euler (el fundador de la mecánica analítica) por la operación de las bombas hidráulicas. Esto sugiere que la teoría física se podría beneficiar de un mayor contacto entre la teoría termodinámica de las máquinas cíclicas (en inglés, engines) y la mecánica que describe el comportamiento de los sistemas físicos en el tiempo. --
zhlédnutí: 55
Video
Demonstration of the Gibbs-Marangoni effect
zhlédnutí 590Před 2 měsíci
A thin layer of water (with some red dye to improve its visibility) is laid upon a flat surface. Then drops of alcohol (denatured ethanol) are added. Where the alcohol meets the water, the liquid rushes out, sometimes drying a spot on the surface completely. This is a consequence of the fact that the surface tension of water is significantly greater than the surface tension of alcohol, and the ...
Tacoma bridge & other self-oscillators
zhlédnutí 184Před 3 měsíci
I try to give a clear and succinct explanation, intended for students and teachers of physics at the undergraduate level, of why the famous collapse of the Tacoma Narrows bridge in 1940 can't be described as a resonance, but was rather a self-oscillation. I then explain the concept of self-oscillation and give some examples. I finish with a brief discussion of how the wind raises waves on the s...
El puente de Tacoma y otros auto-osciladores
zhlédnutí 197Před 3 měsíci
Trato de ofrecer una explicación clara y sucinta, dirigida a estudiantes y docentes de la carrera universitaria de física, de por qué el famoso colapso del puente colgante de Tacoma Narrows, en el estado de Washington, EE. UU. en el año 1940, no puede ser descrita como una resonancia, sino que se trata de una auto-oscilación. Luego explico el concepto general de auto-oscilación y ofrezco alguno...
Rayleigh-Bénard convection in the morning
zhlédnutí 341Před 2 lety
By not owning a microwave and adding milk to my tea while I reheat it on the stove, I get to start my morning with a contemplation of the wonders of Rayleigh-Bénard convection.
"El hombre Isaac Newton", Alejandro Jenkins, 24 feb. 2021
zhlédnutí 441Před 3 lety
Coloquio virtual sobre materiales, CICIMA, U. de Costa Rica Resumen: Sin duda la figura individual más importante en la historia de la ciencia, Isaac Newton (1642-1727) fue también un diputado liberal ante el parlamento inglés, el administrador principal de la Casa de la Moneda de Londres, un teólogo cristiano heterodoxo y un secreto alquimista. Se han escrito muchas cosas contradictorias sobre...
A. Jenkins, "How does a battery work? A 220-year old puzzle in physics and chemistry", 25 Nov. 2020
zhlédnutí 195Před 3 lety
Virtual seminars on materials, CICIMA, U. de Costa Rica, 2020 Abstract: Volta invented the electrical battery in 1800. This device was soon reproduced and improved upon, but the debate about the mechanism responsible for what Volta called the battery's "electromotive force" (emf) drew the leading physicists and chemists of the 19th and early 20th centuries, including Biot, Davy, Ohm, Berzelius,...
Quantum theory of triboelectricity
zhlédnutí 97Před 3 lety
Poster presentation prepared for the Quantum Technology International Conference - QTech 2020. For the full paper see: arxiv.org/abs/1904.11997 This work is now published as R. Alicki and A. Jenkins, "Quantum Theory of Triboelectricity", Phys. Rev. Lett. 125, 186101 (2020), doi.org/10.1103/PhysRevLett.125.186101
French press pump
zhlédnutí 113Před 3 lety
An ordinary French press (_cafetière à piston_) is here used to pump water upwards against gravity. Played at 10% of actual speed. Note that pumping occurs only during the compression phase of the piston's motion. I promise that this will eventually be relevant to a research physics paper. :)
"Información, deuda y desequilibrio: Un acercamiento desde la econofísica", Alejandro Jenkins
zhlédnutí 155Před 4 lety
Seminario virtual dictado el 2 de junio del 2020, por invitación del grupo "Integración Económica" de la Universidad Nacional Federico Villareal (UNFV) de Lima, Perú. Resumen: La teoría económica neoclásica del equilibrio general fue construida, en buena parte, por analogía con el equilibrio termodinámico en los sistemas físicos. Las ecuaciones del movimiento browniano fueron derivadas en 1900 ...
Alejandro Jenkins, "Moving quantum baths: from black holes to dry friction" 29 Apr 2020
zhlédnutí 287Před 4 lety
Virtual seminars on materials, CICIMA, U. de Costa Rica, 2020 Abstract: We describe the dynamics of a quantum field coupled to a moving heat bath, in the formalism of the Markovian master equation for the field considered as an open system. This can be easily applied to the superradiance of a rotating black hole, which provides a useful paradigm for understanding other irreversible active proce...
Spiral motion for 1/r^2 central potential
zhlédnutí 140Před 4 lety
Orbital motion of a point particle under an attractive 1/r^2 central potential. Animation generated on Mathematica.
Orbit of a conical pendulum
zhlédnutí 33Před 4 lety
Non-circular motion of a conical pendulum with non-zero angular momentum. This corresponds to a particle moving under the action of a central force F(r) proportional to sin(r/l). The animation was generated on Mathematica.
Van der Pol oscillator, strongly nonlinear regime (relaxation oscillation)
zhlédnutí 362Před 4 lety
Numerical solution to the Van der Pol equation, x''(t) - a [1 - x^2(t)] x'(t) x(t) = 0 , for a = 5 and initial conditions x(0) = 0.1; x'(0) = 0. Animation generated on Mathematica. The period of the oscillation is controlled by the non-linearity, rather than by the resonant term x(t). This can serve as a model for the heartbeat and other naturally occurring cycles. The first plot (top left) sho...
Van der Pol oscillator, weakly nonlinear regime
zhlédnutí 229Před 4 lety
Van der Pol oscillator, weakly nonlinear regime
Apsidal precession for gravitational potential with 1/r^3 correction
zhlédnutí 423Před 5 lety
Apsidal precession for gravitational potential with 1/r^3 correction
Acoustic self-oscillation of time-flow tap
zhlédnutí 161Před 6 lety
Acoustic self-oscillation of time-flow tap
Pumping a swing by parametric resonance
zhlédnutí 2,2KPřed 6 lety
Pumping a swing by parametric resonance
Apsidal precession in attractive 1/r^(0.8) potential
zhlédnutí 1,1KPřed 6 lety
Apsidal precession in attractive 1/r^(0.8) potential
Rijke tube demonstration (thermoacoustic engine)
zhlédnutí 1,4KPřed 8 lety
Rijke tube demonstration (thermoacoustic engine)
Putt-putt steamboat negotiating the turn at the end of a bathtub
zhlédnutí 1,1KPřed 8 lety
Putt-putt steamboat negotiating the turn at the end of a bathtub
Magnetic heat engine (weakly nonlinear regime)
zhlédnutí 277Před 8 lety
Magnetic heat engine (weakly nonlinear regime)
How it works?
The surface tension is greater for water than for alcohol. I give details and references in the description for this video.
Excellent content !! Keep posting
these things are so cool, science truly does rule
Alright, this just got put in my recommendations for some reason. I'm expecting this video to blow up soon.
amazing video, would you mind sharing the code?
could you please give this code? that would be helpful for my studies....thanks
Cool
Thank you for a nice demonstration! I am currently working on parametric resonance
Dead headphone users
Great! Never knew what a constant central force motion looked like. This is quark confinement-like force.
How did you relate the proportionality to the equation of an ellipse. I am trying to write a program that can do this and I am having some trouble.
First I integrated numerically the differential equation for r(t). Then I used that and the conservation of angular momentum to find the polar angle \theta(t). Finally I animated a parametric plot of x(t) = r(t) * cos[\theta(t)]; y(t) = r(t)*sin[\theta(t)], in equal time steps.
How long does it take for one full apsidal cycle on Earth for it to return back to the original position (or as close to it as it will get)?
This orbit never closes, as per a general mathematical result known as "Bertrand's theorem".
can you plz share the mathematica file
I would love to see the whole 8.85 yr cycle. Thanks for sharing.
Lo único que puedo notar en el video, es que el señor es muy tieso. Le pesan los años
ahahaha
Mine did the same! What Doe's it mean?
Does any of you know if the American Stirling Company is a Fake or scam company. www.stirlingengine.com/ I bougth from them Sterling Engine www.stirlingengine.com/product/mm-1-coffee-cup-stirling-engine and payed with credit card for the sterling engine and shipping. When I finished completed the transaction I got on screen The info I have are : Card Approved. Transaction Reference Number:1381066643 Thank you. Your order is being processed. You will receive an E-mail receipt. E-MAIL ADDRESS: valdimar.helgason@gmail.com ORDER: # 2670 DATE: January 3, 2017 12:38 pm TOTAL: $159.00. Since then I have not got any receipt and I have 5 times filed out their contact form on the website and sent them e-mail too the e-mail address the provide on their website info74@stirlingengine.com but the do not answer and I do not know when or if I will get the product.
I'm pretty sure that it's not a fake company. I bought the engine shown in the video a couple of years ago. I recall some trouble with the online form, which I resolved over e-mail. I got the engine over the mail and it still works perfectly. The product is evidently of very good craftsmanship. But it's probably just one person handling a low volume of orders. Perhaps the company has gone inactive (without the website being taken down), or perhaps the person in charge is just not able to responds to orders at the moment. That's all I can tell you.
Thanks :-) 3 people have told me its a good website and have recommended the product they are selling. So they must be on vacation or something. Tanks again :-)
Since I wrote the comment on American Stirling company I have got good info on the company and many recommendations.
Glad I found this, as I searched for "heat attracts heat". Cool experiment. I think heat might actually attract heat, and I believe you can demonstrate it. Thinking HVAC, convection, etc. Peace.