Cr-Ni-N coatings, the Ni content of which was altered from 0 to 6?3 at-%, were deposited by a hybrid coating system consisting of high power impulse magnetron sputtering and radio frequency magnetron sputtering. The effects of Ni addition to Cr-N coatings on the microstructure and mechanical properties of the coatings were investigated in this study. The instrumental analysis revealed that the Ni element was incorporated into Cr-N crystals as solid solutions, while excess Ni was precipitated as nanocrystalline phases at the Cr-N grain boundaries. The toughness of the Cr-Ni-N coatings was significantly improved with Ni content increased. In addition, the hardness of the coatings slightly increased from 30?4 to 32?6 GPa due to the grain refinement effect and solid solution hardening. From the tribological tests, the highest wear resistance was obtained from the sample having a Ni content of 2?7 at-%.
The aim of the study was to investigate the dynamic failure initiation as well as the failure modes of insulation panels of liquefied natural gas (LNG) carriers. Insulation panels of LNG cargo tanks may include mechanical failures such as cracks as well as delaminations within the layers because of impact sloshing loads and fatigue loadings, and these failures cause a significant decrease of the structural safety. In this study, a structural health monitoring system was developed that employs fibre optic sensors for monitoring various failures that can occur in LNG insulation panels. Fibre optic sensors have the advantage of being embedded inside the insulation panels. The measurement signal of embedded fibre optic sensor is used to calculate the strain distribution within insulation panels and is analysed to identify the damage initiation. It has been observed that the presence of defects and delaminations produce noticeable changes in the strain measurement in a predictable manner. In addition, fibre optic sensors are used to measure static and dynamic strain variations with and without damage. It is expected that this study will be used as a fundamental study for the safety assessment of LNG insulation panels.
In order to clarify the impact of sea-wind satellite-data assimilation under fair and calm weather conditions over the Korean Peninsula, several numerical experiments were carried out. The numerical model used in this study was the Fifth Mesoscale Model (MM5), verified by many previous studies; satellite data of sea winds were gathered by the QuikSCAT sensor launched on ADEOS II. During the daytime, the change in mesoscale circulations according to the assimilation of sea-wind data increased in the coastal area and decreased deep inland. Although variations in mesoscale circulations due to satellite-based seawind data assimilation occurred near the coastal area, the mixing height far inland over the Korean Peninsula often changed according to the intensity of inflow from the surrounding seas and that of the topographic effect. In this study, a lower mixing height inland was generated by a numerical simulation using QuikSCAT sea-wind data assimilation. The lower mixing height was caused by strong westerly and weak easterly winds from the Yellow Sea and the East Sea, respectively. The validation of the sea-wind influence was verified quantitatively by RMSD and IOA analyses. The accuracy of weather forecasting increased at the East Sea and Korea Strait and decreased at the Yellow Sea. These different accuracy levels were caused by the inhomogeneity of sea-wind data quality. The maintenance of the uniform quality of satellite-based data on sea wind is an important factor in the reasonable forecasting of mesoscale circulations.
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