Atmosphere Control of Interface Migration and Its Effect on Dielectric Property of CuO-Infiltrated Strontium Titanate

The control of interface migration and its effect on dielectric properties of SrTiO₃ based materials have been investigated. SrTiO₃ specimens with or without Nb₂O₅ doping were prepared, and the atmospheres of sintering and heat treatment were varied during the processing. It has been demonstrated that the change in defect structure at the interface of Nb-doped SrTiO₃ grains by atmosphere change was the cause of interface migration observed during CuO infiltration or heat treatment. The interface migration caused by sintering in a reducing atmosphere and infiltration in air could be suppressed by preoxidizing grain interfaces before the CuO infiltration in air. The suppression of migration increased the effective dielectric constant of the material.     

A tabu search algorithm for unrelated parallel machine scheduling with sequence- and machine-dependent setups: minimizing total tardiness

This study considers the problem of scheduling independent jobs on unrelated parallel machines with machine- and sequence-dependent setup times for the objective of minimizing the total tardiness, i.e., R _m │S _ijk │∑T _j . Since the parallel machines are unrelated, sequence-dependent setup times must depend on machines. To the best of the authors’ knowledge, the simulated annealing and the iterated greedy algorithms are two existing ones for the new class of scheduling problem with an additional constraint of strict due date constraints for some jobs, i.e., deadlines. In this study, we suggest a tabu search algorithm that incorporates various neighborhood generation methods. A computational experiment was done on the instances generated by the method used in the two previous research articles, and the results show that the tabu search algorithm outperforms the simulated annealing algorithm significantly. In particular, it gave optimal solutions for more than 50 % of small-sized test instances. Also, an additional test was done to compare the performances of the tabu search and the existing iterated greedy algorithms, and the result shows that the tabu search algorithm gives quicker solutions than the iterated greedy algorithm although it gives less quality solutions.     

Comparison of atomic scale etching of poly-Si in inductively coupled Ar and He plasmas

Atomic scale etching (ASE) of poly-Si, which can give etching with atomic scale accuracy, was investigated in inductively coupled Ar and He plasmas. ASE used a cyclic operation of gas adsorption and ion beam irradiation, which is the same concept as atomic layer etching of single crystal substrates. The etch rate gradually increased, reached the saturated region, and then rapidly increased with increasing bias voltage (or ion energy) in both Ar and He plasmas. This saturation region offered a process window for the realization of ASE. At the bias voltage within the process window for ASE, the etch rate was self-limited with respect to the duration of ion beam irradiation for both Ar and He plasmas, confirming that ASE of poly-Si was successfully achieved in both Ar and He plasmas. The range of the process window for ASE using He plasmas was about 10 times wider than that using Ar plasmas. This is because heavier Ar ions impart a greater fraction of ion energy to the surface atoms compared to lighter He ions.     

Sperm abnormalities in high- and low-dose-rate Gamma-irradiated Korean dark-striped field mice, Apodemus agrarius coreae

To evaluate the in vivo effects of low-dose-rate (0.7 mGy h(-1)) gamma radiation, abnormal shapes of sperm in the caudal epidydimus of Apodemus agrarius coreae (A. a. coreae) were used. The six categories of abnormal forms (amorphous heads, blunt hooks, excessive hooks, two heads and tails, folded tails and short tails) of sperm were observed eight days after gamma irradiation (0, 0.5, 1 and 2 Gy) with a high dose rate (0.8 Gy min(-1)) and a low dose rate. The frequency of total abnormal sperm gradually increased starting from 0.5 Gy after high-dose-rate radiation. Blunt hooks and short tails shaped sperm, in particular, were gradually increasing in the high-dose-rate irradiated mice. Dose rate reduction effects for the frequency of abnormal sperms in low-dose-rate irradiated mice to high-dose-rate irradiated mice were 1 at 0.5 Gy, 0.7 at 1 Gy and 0.5 at 2 Gy. Our results indicate that low-dose-rate radiation is not detrimental to spermatogenic cells.     

Nanostructured films as a novel substrate for chondrocytes growth

We fabricated a large area silica nano-particle monolayer on glass substrates for the cell growth by the Langmuir-Blodgett technique. A thin film of 300 nm sized mono-dispersed silica particles was constructed on the air-water interface and transferred onto a glass substrate. Chondrocytes were cultured on nano-structured substrates and bare glass substrates for 8 days. The characterizations of chondrocytes on nano-structured substrate were conducted on 3rd and 6th day using confocal laser microscopy and with MTT assay for 8 days. The chondrocytes cultured on nano-structured substrate showed podia like spike and their size was larger than that formed on bare glass substrate. The metabolic activity of chondrocytes on nano-structured substrate was lower than that on bare glass substrate at early-stage, but it was recovered after 4 days.     

Hydrothermal synthesis and characterization of (Bi,K)TiO3 ferroelectrics

A lead-free ferroelectric (Bi,K)TiO₃ (BKT) was synthesized by a hydrothermal process and characterized systematically at various temperatures. Well-crystallized BKT in the tetragonal phase was identified at a hydrothermal temperature over 220 °C. Small cubic particles were observed, regardless of hydrothermal temperature. The BKT sintered at 1050 °C was observed to be a typical relaxor behavior and very stable against frequency and temperatures, respectively. The sintered-BKT ceramics exhibited a high temperature of maximum dielectric permittivity (T_max = 356 °C at 10⁶ Hz) with piezoelectric constant (d₃₃ = 65 pC/N) and electromechanical coupling factors (k_p = 0.22, k_t = 0.43). Thus, the sintered-BKT showed excellent temperature stability with a high-T_max and piezoelectric properties.     

残余氧化硼对钛酸锶钡晶胞参数及相变温度的影响

研究了氧化硼掺杂（B2O3）烧结钛酸锶钡（Ba1-xSrxTiO3，x=0、0．4、1）陶瓷钙钛矿结构的稳定性、晶胞参数以及相变温度．结果表明，随着掺杂量的增加，钛酸锶钡仍保持原来的钙钛矿结构，但晶胞参数有所变化．晶格常数c与a并非单调变化，但轴比c／a单调递减而晶胞体积a^2c却单调增大．和未掺杂钛酸锶钡相比，掺杂钛酸锶钡陶瓷的相变温度有所升高．同一掺杂含量下，随着烧结温度的升高，因钛酸锶与钛酸钡相互固溶引起晶胞体积明显收缩，相变温度逐渐降低．但在同一烧结温度下，随着掺杂量的增加，相变温度几乎不变．说明硼离子半径虽然很小，氧化硼对钛酸锶钡晶胞参数的影响还是存在的，而且只能以填隙方式存在于晶胞，但其固溶能力非常有限．     

Theoretical and experimental study on junction temperature of packaged Fabry-Perot laser diode

Characterization of laser diode at high temperature for the issue of long-term reliability to detect and screen the initial failures originated from internal stress and optical instability is performed. Estimation of junction temperature of 1.55 /spl mu/m Fabry-Perot laser diode was theoretically approached by using thermal resistance of materials regarding the heat path from analytically modeling laser diode. Under the condition of burn-in test, experiments measuring the junction temperature with current injection at controlled temperature verify the result compared to that of analysis.     

Design of axial fan using inverse design method

The axial fans for cooling condensers were designed by inverse design code TURBOdesign-1. The parameters of the inverse design were set by DOE (design of experiments). By changing the design parameters, such as the distribution of the blade loading, spanwise circulation distribution and stacking, 32 different fan designs were created for the screening of parameters. The overall performance and the local flow field of these fans were computed using a commercial CFD code. The results of the CFD computations were analyzed by DOE. The pressure rise and efficiency were selected as the main responses, and the main effects of the design parameters on the responses were discussed. The main design parameters for the optimum design of the fan were decided from the results of the screening procedure. We designed the optimum axial fan by RSM (response surface method). The design center fan was made by RP (rapid prototype) and the performance was tested using a fan tester based on AMCA standards. These procedures ensured proper screening of parameters and optimum design of the axial fan. This paper was presented at the 9^th Asian International Conference on Fluid Machinery (AICFM9), Jeju, Korea, October 16–19, 2007.