We prepared nanostructured Ca3Co4O9 (CCO) thin films by promoting localized epitaxial growth on polycrystalline Al2O3 substrates. The thermoelectric properties of the CCO films were studied in the temperature range 300 to 1023 K. We confirmed that localized epitaxial growth occurred on the seed grains that dominate the (006) plane. The nanostructured CCO thin films were found to have a maximum Seebeck coefficient of 206 μV/K and a power factor (at 920 K) of 0.514 mW/mK2. Moreover, the presence of nanostructure was found to reduce the thermal conductivity, and thus, should enhance the overall performance of CCO films in thermoelectric devices.

No abstract

High-frequency induction is an efficient way to heat mold surface by non-contact electromagnetic induction. It has been recently applied to injection molding because of its capability to heat and cool mold surface rapidly. This study applies high-frequency induction heating to eliminate weldlines in an injection-molded plastic part. To eliminate or reduce weldlines, the mold temperature at the corresponding weld locations should be maintained higher than the glass transition temperature of the resin material. Through 3 s of induction heating, the maximum temperature of 143 °C is obtained on the mold surface around the elliptic coil, while the temperature of the mold plate is lower than 60 °C. An injection molding experiment is then performed with the aid of induction heating, and the effect of induction heating conditions on the surface appearance of the weldline is investigated. The weldline on the heated region is almost eliminated, from which we can obtain the good surface appearance of the part.

Cytogenetic dosimetry is useful for evaluating the absorbed dose of ionizing radiation based on analysis of radiation-induced chromosomal aberrations. We created two types of dose-response calibration curves for dicentric chromosomes (DC) and translocations (TR) induced by X-ray irradiation, using an electron linear accelerator, which is the most frequently used medical device in radiotherapy. We irradiated samples from four healthy Korean individuals and compared the resultant curves between individuals. Aberration yields were studied in a total of 31,800 and 31,725 metaphases for DC and TR, respectively, obtained from 11 X-ray irradiation dose-points (0, 0.05, 0.1, 0.25, 0.5, 0.75, 1, 2, 3, 4, and 5 Gy). The dose-response relationship followed a linear-quadratic equation, Y=C+αD+βD², with the coefficients C=0.0011 for DC and 0.0015 for TR, α=0.0119 for DC and 0.0048 for TR, and β=0.0617 for DC and 0.0237 for TR. Correlation coefficients between irradiation doses and chromosomal aberrations were 0.971 for DC and 0.6 for TR, indicating a very strong and a moderate correlation, respectively. This is the first study implementing cytogenetic dosimetry following exposure to ionizing X-radiation.

We demonstrated a way to fabricate the crystalline Ba0.6Sr0.4TiO3 (BST) thin films using excimer laser annealing technique on the amorphous BST thin films fabricated by sol-gel process. The grain size of the laser-annealed films is larger than that of the conventionally thermal-annealed films. However, an uncrystallized, amorphous layer was observed near the film/substrate interface due to the limited laser absorption depth. The uncrystallized layer has a critical influence on out-of-plane dielectric property of BST films. The significant difference of the relative dielectric permittivity (εr) between in-plane (1383) and out-of-plane (184) directions is observed.