In order to clarify anisotropy effects on body wave propagation, exact transient solutions radiated from horizontal line sources of stress discontinuities in a transversely isotropic medium with a vertical axis of symmetry are formulated by a modified Cagniard method which gives the inverse Laplace transform in an ingenious manner. The advantage of the exact transient solutions is the clear onset of elastic displacements at the time of body wave arrivals that are defined by corresponding group velocities. The exact transient solutions display three principal effects of anisotropy: (1) noncircular propagation of wave fronts; (2) deviation of polarizations of particle motions of qP, qSV, and qSH waves from those in an isotropic medium; and (3) separation of group velocity from phase velocity, depending on the relative orientation of anisotropy and wave propagation directions. homogeneous and transversely isotropic medium [e.g., ticle motion displacements near the cusps of S V wave tVhite and Tongtaow, 1981; White, 1982]. Martynov and travel time branching with respect to a propagation di-Mikhailenko [1984] calculated the elastic wave field by rection. A horizontal line source of stress discontinuity is .the finite difference method, in which the high-frequency located along one of the horizontal axes of the reference component of elastic displacements was truncated. They coordinate system. assumed Gaussian-type source time function to avoid severe truncation effects.Another approach has been seismic wave transmission through generally anisotropic layers using the ex-1Now at Once anisotropy is introduced, wave fronts of P, SV, and SH waves do not spread cyhndrically. Particle motion directions of the three body waves do not display purely radial, angular, and transverse polarizations, respectively. Rather, they are obliquely inchned and tilted, and group velocity directions do not coincide with those of phase velocities. In this sense, Crampin [1977] called these body waves, quasi-P waves, quasi-SV waves, and quasi-SH waves, for which we use his abbreviated symbols, qP, qSV and qSH, respectively.In a transversely isotropic medium, the symmetry axis of which is taken as vertical, qSH waves are decou-11,333

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We have developed a gas-fired immersion heater tube for use with melting furnaces for the processing of molten zinc. The tubes are made out of a pressureless sintered silicon carbide. The tubes single-ended have dimensions of either φ230 × φ210 × 2300mm or φ310 × φ290 × 1000mm. In this study, we examined thermal shock resistance upon water quenching, measured the gas temperature along the tubes, and simulated their tube wall temperature strength/stress distributions. Maximum stress of tube occurs just above the ring of contact with the surface of the molten zinc, where the temperature differential is the maximum. By inserting a thermal insulation sleeve (alumina silicate cloth) within the immersion heater tube, stress is decreased from 51.5MPa to 22.5MPa. The stress on dipping slant, which occurred at mechanical fixing part of tube, were not so large. We also checked the resistance of immersion heater tubes to molten zinc corrosion within actual production furnaces. We have found that within industrial zinc furnaces, the tubes can keep to operate on good condition (i.e., corrode only partially) after 6 years of service with normal burners and 4 years of service with regenerative burners.

We have developed a heat-transfer tube for use as a heat exchanger in waste gasification and melting systems. This heat-transfer tube, which is made of a pressureless-sintered silicon carbide material, is a single end-type with cantilever support. Ceramic heat-transfer tubes fixed both ends to a metallic heat exchanger body are easily broken, due to differences in thermal expansion at high temperatures, but silicon carbide tubes on a cantilever support do not have this problem. We measure basic properties of the heat-transfer tube such as the coefficient of heat transfer and corrosion resistance, and discuss ash removal. We conduct a low-temperature heat transfer experiment, using saturated steam at 0.4 MPa pressure as a heating medium, and actual exhaust gas from a waste gasification and melting system at about 1150 K as a high-temperature range. Air of 290 K, 79.2 m 3 [normal]/h reaches 820 K after two heat exchanger passes. Near the dew point, silicon carbide shows high corrosion resistance to the exhaust gas. Regarding ash removal, sandblasting effectively cleans the tube surface, because of hardness of a pressureless-sintered silicon carbide material. We simulate application of a large heat transfer tube, about ϕ200 × ϕ179 × 1800 mm, in a furnace. Results indicate that a heat transfer tube made of pressureless-sintered silicon carbide is suited to waste gasification and melting systems.