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The effects of calibration phantoms on the correction results of the empirical artifacts correction method (ECCU) for the case of tube modulation were investigated. To improve the validity of the ECCU method, the effect of the geometry parameter of a typical single-material calibration phantom (water calibration phantom) on the ECCU algorithm was investigated. Dual-material calibration phantoms (such as water-bone calibration phantom), geometry arrangement, and the area-ratio of dual-material calibration phantoms were also studied. Preliminary results implied that, to assure the effectiveness of the ECCU algorithm, the polychromatic projections of calibration phantoms must cover the polychromatic projection data of the scanning object. However, the projection range of a water calibration phantom is limited by the scan field of view (SFOV), thus leading to methodological limitations. A dual-material phantom of a proper size and material can overcome the limitations of a single-material phantom and achieve good correction effects. [ABSTRACT FROM AUTHOR]

Freeze casting was used to fabricate unoriented three dimension framework of fibrous porous ceramics. Compared with vacuum filtration, this method was helpful in keeping the original three-dimensional dispersion which led to both high porosity and strength. The results indicated that the optimum fibers and silica sol content were 2 vol% and 5 wt% respectively for mechanical and other properties. The high-temperature stability of fibrous porous ceramics prepared by freeze casting and vacuum filtration are discussed in this paper. The samples showed lower thermal shrinkage and better stability because of the three dimensional orientations under a high temperature environment with a pressure of 0.8 MPa. The maximal tolerable temperature of samples preparing by freeze casting had been as high as 1200 °C. [ABSTRACT FROM AUTHOR]