**7. Acknowledgments**

Supports by the National Science Council (NSC-96-2116-M-006-012, NSC-96-2738-M-006- 004, NSC-97-2745-M-006-001, NSC-98-2116-M-006-016, and NSC-99-2116-M-006-019) and Central Geological Surveys (98-5226904000-05-02 and 99-5226904000-05-02), Radiation Monitoring Center, and Institute Earth Sciences of Academia Sinica of Taiwan are appreciated.
