从图12a中可以看出，纤维的表面是不光滑的，有因双扩散各向收缩不均匀导

It can be seen from Figure 12a that the surface of the fiber is not smooth, and there are longitudinally distributed grooves caused by the uneven shrinkage of the double diffusion, but the fiber structure is dense and uniform in thickness, and the cross section is close to circular. The fiber formation is relatively sufficient, and there is no thick skin layer, which is close to the full-core structure fiber.

As can be seen from Figure 12a, the surface of the fiber is not smooth, there is the presence of vertical distribution grooves caused by uneven double diffusion of each direction, but the fiber structure is dense and uniform in thickness, the cross-section is close to the circle, which indicates that the fiber forming is relatively adequate, there is no thicker cortex, close to the whole core layer structure fiber.

It can be seen from Fig. 12a that the surface of the fiber is not smooth, and there are longitudinal distribution grooves caused by the uneven shrinkage of double diffusion, but the fiber structure is dense and uniform in thickness, and the cross section is close to circular, which indicates that the fiber is fully formed, and there is no thicker cortex, which is close to the full core structure fiber.<br>