Most galaxy associations are small and have a low density contrast . 大多数星系协是小的，密度反衬低。
2.
It is often impossible to differentiate between structure and density contrast in determining the source of a gravity anomaly . 在确定重力异常源时，不可能在构造与密度差之间作出抉择。
3.
The separation algorithm based on boundary tracing do not need the acute angle and / or the low density contrast at the points where the objects touched and get better separation result 基于边界跟踪的分离算法能够克服聚堆目标连接处的凹陷比较明显并且或者在连接处存在灰度局部最小边缘的要求，取得了较好的分离效果。
