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相关概念视频

Atomic Nuclei: Larmor Precession Frequency01:11

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The earth's gravitational field produces a 'twisting force' perpendicular to the angular momentum of a spinning mass (such as a spinning top) that causes the mass to 'wobble' around the gravitational field axis in a phenomenon called precession. Similarly, the magnetic moment (μ) of a spinning nucleus precesses due to an external magnetic field directed along the z-axis. The precession of the magnetic moment vector about the magnetic field is called Larmor precession,...
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Electromagnetic waves are consistent with Ampere's law. Assuming there is no conduction current Ampere's law is given as:
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A pulse is a short burst of radio waves distributed over a range of frequencies that simultaneously excites all the nuclei in the sample. Upon passing a radio frequency pulse along the x-axis, the nuclei absorb energy corresponding to their Larmor frequencies and achieve resonance. This shifts the net magnetization vector from the z-axis toward the transverse plane. This angle of rotation of the magnetization vector, or the flip angle, is proportional to the duration and intensity of the pulse.
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Electromagnetic Waves01:30

Electromagnetic Waves

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James Clerk Maxwell formulated a single theory combining all the electric and magnetic effects scientists knew during that time, calling the phenomena his theory predicted “Electromagnetic waves”. He brought together all the work that had been done by brilliant physicists such as Oersted, Coulomb, Gauss, and Faraday and added his own insights to develop the overarching theory of electromagnetism. Maxwell’s equations, combined with the Lorentz force law, encompass all the laws...
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Standing Electromagnetic Waves01:15

Standing Electromagnetic Waves

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Electromagnetic waves can be reflected; the surface of a conductor or a dielectric can act as a reflector. As electric and magnetic fields obey the superposition principle, so do electromagnetic waves. The superposition of an incident wave and a reflected electromagnetic wave produces a standing wave analogous to the standing waves created on a stretched string.
Suppose a sheet of a perfect conductor is placed in the yz-plane, and a linearly polarized electromagnetic wave traveling in the...
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The Principle of Superposition and the Gravitational Field01:17

The Principle of Superposition and the Gravitational Field

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The principle of superposition applies to gravitational forces of objects that are sufficiently far apart. It states that the net gravitational force on a point object is the vector sum of the gravitational forces on it due to various objects. The principle helps calculate the force by listing the individual forces and then vectorially summing them up. However, it should be noted that the principle of superposition is not always apparent. In the presence of a second force, the first force could...
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相关实验视频

Updated: Sep 30, 2025

Rapid Repetition Rate Fluctuation Measurement of Soliton Crystals in a Microresonator
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统一重复的快速无线电爆发

Manisha Caleb1

  • 1Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia.

Science (New York, N.Y.)
|March 17, 2022
PubMed
概括

神秘的高能无线电爆发被称为快速无线电爆发 (FRB), 这一发现有助于理解这些神秘的宇宙信号的起源.

科学领域:

  • 天文学
  • 天体物理学
  • 宇宙无线电源

背景情况:

  • 快速无线电爆发 (FRB) 是来自银河系外的强烈,持续数毫秒的无线电信号.
  • 在FRB背后的确切起源和机制在很大程度上是未知的,在天体物理学中是一个重要的难题.

研究的目的:

  • 在观察到的快速无线电爆发样本中调查共同的特性.
  • 找出潜在的模式,可以揭示FRB的祖先和发射过程.

主要方法:

  • 来自多个射电望远镜检测快速射电爆发的观测数据的分析.
  • 对爆发的参数进行统计检查,例如持续时间,光谱特性和极化.

主要成果:

  • 一个快速无线电爆发的子集在它们的发射特征中显示出共同的特征.
  • 在不同FRB中发现了特定的光谱特征和偏振模式.

结论:

  • 观察到的共同点表明某些FRB的潜在统一机制或有限的源类型.
  • 进一步研究这些共同的特性对于推进FRB生成和演变模型至关重要.

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