Driving potential and fission-fragment charge distributions

We propose an efficient approach to describe the fission-fragment charge yields for actinides based on the driving potential of the fissioning system.Considering the properties of primary fission fragments at their ground states,the driving potential,which represents the potential energies of the system around scission configuration and closely relates to the yields of fragments,can be unambiguously and quickly obtained from the Skyrme energy-density functional together with the Weizs?cker-Skyrme mass model.The fission-fragment charge distributions for thermal-neutron-induced fission and spontaneous fission of a series of actinides,especially the odd-even staggering in the charge distributions,can be well reproduced.Nuclear dynamical deformations and pairing corrections of fragments play an important role in the charge distributions.

The role of deformations and orientations in an alpha ternary fission of Thorium

The alpha ternary fission half-lives of thorium isotopes have been studied using the Coulomb and proximity potential models.The role of the deformation effects and the angle of orientation were included during the evaluation of the total potential.Fragment combinations were identified using cold valley plots of the driving potential.The half-lives and yields were evaluated using the penetration probability.The dependence of the logarithmic half-lives on different angles of orientation was studied.The evaluated alpha ternary fission yield was compared with that of the available experiments with and without deformations.The half-lives obtained in the present work were compared with those of the available data.Possible alpha ternary fission fragments were identified in the isotopes of thorium.The alpha ternary fission half-lives were compared to the binary fission half-lives.The binary fission half-lives are dominant in the ^(209-225)Th nuclei,and the ternary fission half-lives are dominant in the isotopes of the ^(226-238)Th nuclei.

Spatiotemporal variations of maximum seasonal freeze depth in 1950s–2007 over the Heihe River Basin, Northwest China

Investigation on spatiotemporal variations of maximum seasonal freeze depth （MSFD） over the Heihe River Basin is of great importance for systematic understanding of regional climate and environmental change, ecological-hydrological processes, water resources assessment, construction and resource development. Based on soil and air temperatures at the meteorological stations of the China Meteorological Administration （CMA） over the Heihe River Basin, MSFDs time series are structured into a composite time series over the 1960-2007 period. Evaluating the averaged MSFD time series for 1960 2007 reveals a statistically significant trend of 4.0 cm/decade or a net change of-19.2 cm for the 48-year period over the basin. The MSFD had significantly negative correlation with mean annual air temperature （MAAT）, winter air temperature, mean annual ground surface temperature （MAGST）, degree days of thawing for the air （DDTa） as well as for the surface （DDTs）, and degree days of freezing for the surface （DDFs）. While there was significantly positive correlation between DDF,. and MSFD time series, MSFD was deeper and changed greatly in the Heihe River source area. It was shallower in the east-central basin and gradually deepened in other sections of the basin. The MSFD distribution pattern in 2003-2005 is consistent with that of averaged degree days of freezing for air （DDFa） in 1960-2007. However, the maximum of MSFD may not be accurate, because there is no long term observation data in the deep seasonally frozen ground regions near the lower boundary of permafrost. With increasing elevation, averaged DDFa increased at a rate of 51.6 ℃-day/100m, therefore, the MSFG and the date reaching MSFG became deeper and later, respectively.