| 摘要 |
The present invention discloses a shaftless acoustic source having a solenoi d, a bullet and driving electronics. The bullet, which is positioned inside the solenoid 's coil, can be accelerated by a magnetic force generated when a current pulse is applied to the coil. Acoustic energies are generated upon the impact of the bullet with an object, such as a borehole wall. This impact force can be described by the Hertzian Contact Theory (also referred to herein as Hertzian Theory) as a point of normal for ce with a time function similar to a half period sine function. A retraction means may be used to retract the bullet back into the solenoid after firing.
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