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Wednesday, October 14, 2020

 So Daoist,



"Life in its manifestation is vibration (道 & 常道 constant vibration).
Electricity is vibration.
But vibration that is creative* (名 & 常名) is one thing.
Vibration that is destructive** is another.
Yet they are from the same source (此兩者,同出而異名,同謂之玄。)"

Edgar Cayce reading 1861-16


*   creative by resonance
** natural frequency resonance

    Resonance is when a driving force is at a frequency that is close to the natural oscillation frequency of a system. This makes the amplitude of the oscillation of the system greatly increase.

Interference is when two waves at similar frequencies are superimposed which results in either constructive interference when the waves are in phase and add together, or destructive interference when the waves are out of phase and interfere with each other.

  • Every object does have its own natural frequency.
  • The reason for a destructive resonance to occur is because a frequency matches the system's natural frequency of vibration.
  • There are some destructive resonance cases such as Tacoma Narrows Bridge and glass.

Resonance

Resonance is the constructive interference of two waves with the same frequency.


Destructive Interference

A type of interference that occurs at any location along with the medium where the two interfering waves have a displacement in the opposite direction.


“The principle cannot fail. It is as powerful when applied to the earth as it is when applied to a [violin note shattering a] wineglass, a [boy pushing a man on a] swing, or a steel link. Anyone who doubts should only bear in mind the illustration of the swing. A small boy, by each time adding a pound to the force with which a 200-pound man swings, can soon set the man swinging with the force of 500 pounds. It is necessary only to keep adding a little force at the right time."
Nikola Tesla – the master of resonance.

Every object depending on its mass and stiffness when excited vibrates at its natural frequency. Watches, musical instruments, microwave ovens, mobile phones and many other devices in our day-to-day life make use of this phenomenon. However, there is an undesirable side to these vibrations that can lead to the failure of structures and components. This failure mode, resonance failures, is equally applicable to large structures and small machine parts alike. Not only bridges, towers and skyscrapers, but also blades, bearings, piping and fasteners can fail due to resonance. Air and gas vapour columns can also resonate at their natural frequencies, in the same way that percussion instruments work, and this can lead to failures.

The war cries and the pounding of the foot of marauding armies in history aimed at the destruction of the enemy’s defences by the principle of resonance. The Biblical myth of the Fall of the Walls of Jericho (Joshua 6:3-5) seems to assert this fact.

Large towers and buildings swaying during an earthquake can fail if the swaying coincides with the natural frequency of the structure. Architects consider this while designing these buildings. The Taipei 101, one the tallest building in the world, has a 660 Ton pendulum acting as a mass damper to cancel any resonance.

There are many examples of resonance failures in all fields of engineering.

  • Excitation by the acoustic frequency of the marching soldiers led to the collapse of the Broughton suspension bridge in 1831 and the Angers Bridge in France in 1850. Failure of the Tacoma Narrows Bridge is the most documented and had a great influence on bridge designs world over.
  • Resonance of the wheels to the interaction of the wind on the rotating wheels was the possible reason for the catastrophic failures of Spinenergy-Rev X bicycle wheels. Even though this was a high-performance lightweight Carbon fibre wheel, these failures resulted in the withdrawal of the product.
  • The failure of many midrise buildings during the 1985 Mexico earthquake was due to resonance.
  • Total destruction of multi-bladed helicopters while on the ground is a case of resonance of the helicopter due to shocks from the landing gear known as “ground resonance.”

Today design software can model and predict the natural frequency of a given object.

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