No abstract

No abstract

In the absence of mooring condition, the heave and pitch coupled equations are established considering the effect of static stability and wave surface elevation for a truss spar platform. The influence of the change of the pitch period and the external excitation force (combined wave loads and wind loads together) on the stability of the heave-pitch coupling motion is studied by means of numerical iteration method. The results show that when the wave frequency is close to the natural heave frequency besides the heave-pitch frequency ratio is close to 2: 1, both of the amplitude of heave and pitch motion are increased considering the wind loads. It is about 12 percent increase for heave motion, while 8 percent for pitch motion. Meanwhile, there is a penetration phenomenon between heave and pitch. And the wind load play a more important role in pitch motion, the characteristic frequency of pitch motion will have an obvious change between 1/2 times sub harmonic motion frequency component and 1 time forced motion frequency component considering the wind load.

The mesoporous zirconate powders were synthesized by solvent evaporation using P123 as templates. The phase composition, pore size distribution and thermo-physical properties were tested and analysed in this study. The test results show that the samples have mesoporous structure after removing template by heat treatment. Mesoporous pore size are mainly distributed in the range of 5-50nm, and the pore volume less than 50nm accounts for about 24% of the total. The thermal diffusivity and thermal conductivity of mesoporous (La0.8Yb0.2)2Zr2O7 are lower than common alumina and zirconia materials, and the lowest thermal conductivity is only 0.218W/(m•K).

In this paper, BN interfacial phase was prepared on SiC fiber surface and CVD SiC gradient coating was prepared on the surface of SiCf/SiC-CMCs composite. CVD SiC coatings were fabricated by the pyrolysis of methyltrichlorosilane (MTS) in hydrogen at a low pressure of 5-10kPa. The ratio of MTS to hydrogen is 1 to 12.Oxidation behaviour is examined by placing the material with coats in air. The oxidizing temperatures were varied from 100°C to 1200°C. Optical microscope and SEM were used to observe the surface morphology and microstructure of coatings. XRD was used to characterize the phase composition. The results indicated that the Oxidation of SiC/SiC-CMC is the most serious at 800°C. Tensile strength test shows that the fracture strength of the material is the lowest and with the increase of temperature to 1200°C, the tensile strength of the material increases. Tensile strength test shows that the fracture strength of the material is the lowest and with the increase of temperature to 1200°C, the tensile strength of the material increases.