• Korean Journal of Materials Research
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• v.11 no.8
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• pp.708-712
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• 2001

Microwave dielectric properties of $(Pb_{0.2}Ca_{0.8})[(Ca_{1/3}Nb{2/3})_{1-x}Ti_x]O_3$ ceramics were investigated as a function of $Ti^{4+}$ content (0.05$\leq$x$\leq$0.35). A single perovskite phase was obtained from x=0.05 to x=0.15, and $TiO_2$ and $CaNb_2O^6$ were detected as a secondary phase beyond x=0.2. The structure was changed from orthorhombic at x=0.05 to cubic at x=0.35. Dielectric constant(K) was increased with increase of $Ti^{4+}$ content due to increase of rattling effect, and was inversely proportional to the cube of the average radius of B-site cation, however, Qf value was decreased, which was due to the decrease of grain size and the secondary phase. With the increase of $Ti^{4+}$ content, the temperature coefficient of resonant frequency(TCF) was controlled from -27.36 ppm/$^{\circ}C$ value to +18.4 ppm/$^{\circ}C$ value, which was caused by the influence of tolerance factor(t) and the bond valence of B-site. Typically, K of 51.67, Qf of 7268(GHz), TCF of 0 ppm/$^{\circ}C$ were obtained in the $(Pb_{0.2}Ca_{0.8})[(Ca_{1/3}Nb_{2/3})_{0.8}Ti_0.2]O_3$ sintered at 13$50^{\circ}C$ for 3h.

• Tuberculosis and Respiratory Diseases
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• v.59 no.4
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• pp.368-373
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• 2005

Background : Bronchial anthracofibrosis usually manifest as a form of obstructive airway disease, and can be accompanied by parenchymal diseases such as pneumonia, and pulmonary tuberculosis. This study investigated the ventilatory dynamics according to the severity of bronchial stenosis in patients with bronchial anthracofibrosis. Method : One hundred and thirteen patients with bronchial anthracofibrosis that was confirmed by bronchoscopy and who had undergone a pulmonary function test were enrolled in this study group. The correlation coefficients between the pulmonary functional parameters and the number of lobes with bronchial stenosis were investigated. Results : The incidence of ventilatory dysfunction was 56(49.6%) for obstructive, 8(7.1%) for restrictive, 2(1.8%) for mixed, and 47(41.6%) for a normal pattern. The $FEV_1/FVC$, $FEF_{25{\sim}75%}$, $FEF_{25%}$, $FEF_{50%}$, $FEF_{75%}$, and PEF showed a significant negative correlation (p<0.05) and the Raw had a significant positive correlation with the number of lobes with bronchial stenosis(p<0.001). Conclusion : These findings suggest that the most common abnormality of the ventilatory function in bronchial anthracofibrosis is an obstructive pattern with a small airway dysfunction according to the severity of bronchial stenosis.