This paper first develops the approaches to determine the geopotential of the local mean sea level,and then investigates the offset of the 1985 vertical datum surface defined by the mean sea level of Yellow Sea at the Dagang Tide Gauge in Qingdao city using the developed approaches and GPS/leveling data.It shows that the geopotential of the local mean sea level at the tide gauge is equal to 62 636 853.5±0.2 m2·s -2 and that the 1985 vertical datum surface is 24.6±5.4 cm above the geoid realized by the geopotential W 0= 62 636 856.0±0.5 m2·s -2.
Sand casting process ad directional solidification technique combining thermal-rate treatment(TRT) were used.The influence of process parameters on TRT was investigated according to the values of impact toughness.At the same time,the mechanism of TRT was discussed.The results showed that TRT can improve the impact toughness of this alloy,while the hardness is basically constant.The time of heat preservation should not be more than 5 min.Different forms of cooling intensification additive have different effects among which the zinc ingot solidified in graphite mold is the best one that can improve impact toughness of samples by more than 80%.With increasing the cooling temperature,the value of α(Al)crystal lattice constant increases.The element Sb has negative effect on TRT.
