Although its visual effect is so pronounced, dust is only a minor constituent of the material, extremely low in density, that lies between the stars.
尽管它的视觉效果如此显著，但尘埃只是位于恒星之间的物质的一个次要组成部分，其密度极低。
2
The technique was found to be a better prognostic tool than conventional visual analysis of receptor density.
人们发现这项技术可以很好地进行病情预测，这种手段优于对受体密度进行目测的传统方法。
3
A measuring instrument about diffuse visual transmission density is introduced, and a numerical calculating method is discussed, which is applied in the advanced research.