content_image/369247.jpg
<img src='content_image/369247.jpg'>

central area of the island. The half-lives of these nuclei are in the order of seconds [32], which is much shorter than those of known stable nuclei. The measured short half-lives of nuclei in super-heavy region seem to indicate that the shell corrections of these nuclei are probably not very large. 

Fig.7 shows the deviations of the calculated nuclear masses with the proposed model from the results of FRDM and HFB-17. The shades denote the region with deviations smaller than 2 MeV. The results for highly neutron-rich heavy nuclei from the three models have large deviations. The results of our model are relatively close to those of HFB-17 for most nuclei. 

## IV. SUMMARY 

In this paper we proposed a semi-empirical nuclear mass formula based on the macroscopic-microscopic approach. The isospin effects in both macroscopic and microscopic part of the formula are self-consistently considered, with which the number of model pa- rameters is considerably reduced compared with the finite range droplet model and the rms deviation of the calculated masses from the 2149 measured nuclear masses is reduced by 21% and falls to 0.516 MeV. The CPU time used in the calculation of the nuclear masses 

