variable density logging的用法和樣例：
例句
- The density logger consists of a radiation source.
密度測井儀包括輻射源。 - In this paper, a new-style Gama Ray Spectrometry is developed, that is mainly used in natural Gama Ray Spectrometry Logging Instrument and Lithology Density Logging Instrument.
本文設計了一種新型的伽馬能譜儀，主要應用於自然伽馬能譜測井和岩性密度測井。
