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Precipitations in Mg-Li-Zn ternary alloys containing 4 to 13%Li and 4 to 5%Zn (in mass%) with or single phase, or with ( þ ) dual phases were investigated using a micro-Vickers hardness measurement and transmission electron microscopy. Age hardening in the phase alloy was found to occur, which was attributed to the precipitation of the stable (MgLiZn) phase with the following orientation relationships: ½10 1 10 k ½110 , ð0001Þ k ð1 1 1 1 1Þ . In the ( þ ) phases alloy, the precipitation of the phase together with the metastable 0 (MgLi 2 Zn) phase occurred at grain boundaries between the and , and also and grains. The orientation relationships between the and 0 were as follows; ð0001Þ k ð01 1 1Þ 0 , ½0 1 110 k ½111 0 . Age hardening in the alloy was caused by the precipitation of the 0 phase and over-aging was attributed to the precipitation of the and phases.

Bathymetric mapping is traditionally implemented using shipborne single-beam, multi-beam, and side-scan sonar sensors. Procuring bathymetric data near coastlines using shipborne sensors is difficult, however, this type of data is important for maritime safety, marine territory management, climate change monitoring, and disaster preparedness. In recent years, the bathymetric light detection and ranging (LiDAR) technique has been tried to get seamless geospatial data from land to submarine topography. This paper evaluated the accuracy of bathymetry generated near coastlines from satellite altimetry-derived gravity anomalies and multi-beam bathymetry using a tuning density contrast of 5000 kg/m3 determined by the gravity-geologic method. Comparing with the predicted bathymetry of using only multi-beam depth data, 78% root mean square error from both multi-beam and airborne bathymetric LiDAR was improved in shallow waters of nearshore coastlines of the western Korea. As a result, the satellite-derived bathymetry estimated from the multi-beam and the airborne bathymetric LiDAR was enhanced to the accuracy of about 0.2 m.

The downward continuation (DWC) method was used to determine the density contrast between the seawater and the ocean bottom topographic mass to estimate accurate bathymetry using the gravity-geologic method (GGM) in two study areas, which are located south of Greenland (Test Area #1: 40 -50°W and 50 -60°N) and south of Alaska (Test Area #2: 140 -150°W and 45 -55°N). The data used in this study include altimetry-derived gravity anomalies, shipborne depths and gravity anomalies. Density contrasts of 1.47 and 1.30 g cm -3 were estimated by DWC for the two test areas. The considerations of predicted density contrasts can enhance the accuracy of 3 ~ 4 m for GGM.The GGM model provided results closer to the NGDC (National Geophysical Data Center) model than the ETOPO1 (Earth topographical database 1) model. The differences along the shipborne tracks between the GGM and NGDC models for Test Areas #1 and #2 were 35.8 and 50.4 m in standard deviation, respectively. Furthermore, these differences were more strongly correlated with gravity anomalies than bathymetry in the test areas. It is shown that an accuracy of under 40 m can be obtained with comparisons to shipborne depths only in Test Area #1.

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