Video Experimental Relacionado
Updated: Jan 27, 2026
10:41
The Effect of Charging and Discharging Lithium Iron Phosphate-graphite Cells at Different Temperatures on Degradation
Published on: July 18, 2018
16.1K
Observación del segundo sonido en el grafito a temperaturas superiores a 100 K
S Huberman1, R A Duncan2, K Chen1
1Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Science (New York, N.Y.)
|March 16, 2019
Resumen
El segundo sonido, un transporte térmico en forma de onda, se observó en el grafito por encima de los 100 grados Kelvin. Este hallazgo amplía el potencial del segundo sonido en el transporte de calor a microescala para materiales en capas.
Área de la Ciencia:
- Física de la materia condensada
- Ciencias de los materiales
- Fenómenos de transporte térmico
Sus antecedentes:
- El segundo sonido, un transporte térmico en forma de onda, es un fenómeno exótico típicamente observado en sólidos solo a bajas temperaturas.
- Su rara aparición tiene aplicaciones científicas y prácticas limitadas.
Objetivo del estudio:
- Para observar directamente el segundo sonido en grafito a temperaturas superiores a 100 grados Kelvin.
- Investigar el papel potencial del segundo sonido en el transporte de calor transitorio a microescala.
Principales métodos:
- Utilizó mediciones ópticas con resolución de tiempo.
- Centrado en el transporte térmico en la escala de longitud micrométrica.
Principales resultados:
- Se ha observado con éxito un segundo sonido en grafito a temperaturas superiores a los 100 grados Kelvin.
- Los resultados experimentales se alinean con los cálculos ab initio que predicen la hidrodinámica de fonones tipo onda.
Conclusiones:
- La observación directa del segundo sonido en grafito a temperaturas accesibles es un avance significativo.
- El segundo sonido puede desempeñar un papel crucial en el transporte de calor a microescala en materiales bidimensionales y en capas a través de un amplio rango de temperatura.
Videos de Conceptos Relacionados
01:17Soundness of Cement
559
The soundness of cement refers to the ability of cement paste to retain its volume after setting. Unsound cement can lead to expansion and structural damage due to the presence of free lime, magnesia, and calcium sulfate. Free lime hydrates very slowly, expanding and causing unsoundness, which is difficult to detect because it intercrystallizes with other compounds. Magnesia also reacts with water, forming crystals that can disrupt the cement's structure. Calcium sulfate can create...
559
01:15Heart Sounds
3.5K
Heart sounds are generated by the turbulence in blood flow due to the closing of heart valves. These sounds are best perceived slightly away from the valves, where the blood flow disseminates the sound.
Auscultation is the process of listening to these internal body sounds using a stethoscope. The heart produces four types of sounds, but only two—S1 and S2—can usually be heard with a stethoscope.
S1, also known as the "lub" sound, is caused by the closure of atrioventricular (A-V)...
Auscultation is the process of listening to these internal body sounds using a stethoscope. The heart produces four types of sounds, but only two—S1 and S2—can usually be heard with a stethoscope.
S1, also known as the "lub" sound, is caused by the closure of atrioventricular (A-V)...
3.5K
01:12Korotkoff Sounds
7.9K
Korotkoff sounds are the specific sounds heard while measuring blood pressure using a sphygmomanometer, typically with a stethoscope or a Doppler device. They are named after Russian physician Nikolai Korotkov, who first described them in 1905. These sounds correspond to turbulent blood flow in the artery as the blood pressure cuff is gradually released after inflation.
During blood pressure assessment, inflating the cuff 30 millimeters of mercury above the patient's systolic blood pressure...
During blood pressure assessment, inflating the cuff 30 millimeters of mercury above the patient's systolic blood pressure...
7.9K
01:01Sound Waves
12.9K
Sound waves can be thought of as fluctuations in the pressure of a medium through which they propagate. Since the pressure also makes the medium's particles vibrate along its direction of motion, the waves can be modeled as the displacement of the medium's particles from their mean position.
Sound waves are longitudinal in most fluids because fluids cannot sustain any lateral pressure. In solids, however, shear forces help in propagating the disturbance in the lateral direction as well....
Sound waves are longitudinal in most fluids because fluids cannot sustain any lateral pressure. In solids, however, shear forces help in propagating the disturbance in the lateral direction as well....
12.9K
00:58Sound Intensity
4.8K
The loudness of a sound source is related to how energetically the source is vibrating, consequently making the molecules of the propagation medium vibrate. To measure the loudness of a source, the physical quantity of interest is the intensity. This is defined as the energy emitted per unit of time per unit of area perpendicular to the sound wave's propagation direction. Since the total energy is greater if the source vibrates for a longer duration and over a larger area, dividing the...
4.8K
01:08Speed of Sound in Gases
4.0K
The speed of sound in a gaseous medium depends on various factors. Since gases constitute molecules that are free to move, they are highly compressible. Hence, sound waves travel slowly through gases. Thermodynamics helps us understand the relationship between pressure, volume, and temperature of gases, thus, the speed of sound in an ideal gas can be determined using the laws of thermodynamics. At the same time, Newton's laws of motion and the continuity equation of fluid dynamics also come...
4.0K