We investigate the effects of Yb2O3 and calcium aluminosilicate (CAS) glass as sintering additives on the sintering behavior of AlN. The AlN specimens are sintered at temperatures between 1700oC and 1900oC for 2 h in a nitrogen atmosphere. When the Yb2O3 content is low (within 3 wt.%), an isolated shape of secondary phase is observed at the AlN grain boundary. In contrast, when 3 wt.% Yb2O3 and 1 wt.% CAS glass are added, a continuous secondary phase is formed at the AlN grain boundary. The thermal conductivity decreases when the CAS glass is added, but the sintering density does not decrease. In particular, when 10 wt.% Yb2O3 and 1 wt.% CAS glass are added to AlN, the flexural strength is the highest, at 463 MPa. These results are considered to be influenced by changes in the microstructure of the secondary phase of AlN.
Piezoelectric ceramic specimens with the Pb(Mg1/3Nb2/3)0.65Ti0.35O3 (PMN-PT) composition are prepared by the solid state reaction method known as the “columbite precursor” method. Moreover, the effects of the Li2O-Bi2O3 additive on the microstructure, crystal structure, and piezoelectric properties of sintered PMN-PT ceramic samples are investigated. The addition of Li2O-Bi2O3 lowers the sintering temperature from 1,200oC to 950oC. Moreover, with the addition of >5 wt.% additive, the crystal structure changes from tetragonal to rhombohedral. Notably, the sample with 3 wt.% additive exhibits excellent piezoelectric properties (d33 = 596 pC/N and Kp = 57%) and a sintered density of 7.92 g/cm3 after sintering at 950oC. In addition, the sample exhibits a curie temperature of 138.6oC at 1 kHz. Finally, the compatibility of the sample with a Cu electrode is examined, because the energy-dispersive X-ray spectroscopy data indicate the absence of interdiffusion between Cu and the ceramic material.
In this paper, quality properties and antioxidant capacity of cooked black carrot has been studied. Five different cooking methods have been applied: microwave (45 sec), boiling (100℃, 14 min), steaming (100℃, 20 min), sous vide (75℃, 80 min), sous-vide (95℃, 30 min). The color value was slightly different (p<0.05), the boiling method was the highest in L-value and Sous vide 75℃ method was the lowest. The steaming method indicated the highest a-value at 5.50. The b-value was significantly different between the samples (p<0.05). The microwave method was the highest at 3.49 while the sous vide 95℃ method was the lowest at －0.34. No significant difference was observed between the samples when only the moisture content results were considered. The highest pH was observed in samples cooked using the boiling method. The softening (%) was higher when the cooking water was in contact with samples and it was dependent on the temperatures. In addition, this study shows that not only temperature but also cooking time and cooking media are very crucial in the preparation and cooking of black carrot to prevent the loss of the antioxidant compound. In conclusion, the comparison of the quality characteristics and antioxidant properties of black carrots indicated that the most appropriate cooking method is sous-vide method.
Cordierite composed of an alumina-silica-magnesia compound has a low coefficient of thermal expansion(CTE) and excellent thermal shock resistance. It also has a low dielectric constant and high electrical insulation. However, due to low mechanical strength, it is limited for use in a ceramic heater. In this study, ZrO2 is added to an 80 wt% cordierite-20 wt% mullite composition, and the effect of ZrO2 addition on the mechanical strength and thermal shock resistance is investigated. With an increasing addition of ZrO2, cordierite-mullite formed ZrO2, ZrSiO4 and spinel phases. With sintering conducted at 1400 °C with the addition of 5 wt% ZrO2 to 80 wt% cordierite-20 wt% mullite, the most dense microstructure forms along with an excellent mechanical strength with a 3-point flexural strength of 238MPa. When this composition is quenched in water at ΔT = 400℃ , the 3-point flexural strength is maintained. Moreover, when this composition is cooled from 800℃ to air, the 3-point flexural strength is maintained even after 100 cycles. In addition, the CTE is measured as 3.00 × 10−6·K−1 at 1000℃ . Therefore, 80 wt% cordierite-20 wt% mullite with 5 wt% ZrO2 is considered to be appropriate as material for a ceramic heater.
기업의 생존력과 경쟁력을 위하여 기술혁신을 지속적이고 장기적으로 추구하 고 추진하려는 기업의 전반적인 사고방향을 나타내는 기술혁신지향성의 중요성이 대두하고 있다. 기술혁신지향성이 기업의 지속적인 경쟁우위 확보에 개념적으로나 실무적으로 중요한 의미를 내포하고 있지만, 기업의 성공적인 기술혁신과 성과를 위한 기술혁신지향성의 역할에 대한 체계적인 연구는 현재까지 제한적으로 수행되어 왔다. 기술혁신지향성에 대한 기존 연 구의 미비점을 인지하여, 본 연구에서는 기술혁신지향성에 영향을 미칠 수 있는 기업 내외부 의 핵심적인 요인들을 선택하여, 선행요인들과 기술혁신지향성 및 기술혁신지향성 사이의 상 황관계를 나타내는 연구모델과 가설들을 제안하고 이를 실증분석 하였다. 제안된 연구모델 에서 선택된 기술혁신지향성의 선행요인들은 최고경영자의 기술기능 직무경력과 기능 간 상호통합(cross-functional integration)의 두 내부요인과 환경 불확실성과 경쟁강도의 두 외부 요인을 포함하였고 이 요인들이 결과적으로 기술혁신지향성을 매개로 기업의 기술혁신성과 에 영향을 미치는 것으로 제시하였다. 또한 이 연구모델에서는 환경 불확실성과 경쟁강도의 두 환경요인이 기술혁신지향성과 기술혁신성과 사이의 관계를 긍정적으로 조절하는 효과를 갖는 것으로 제시하였다. 86개의 국내 IT중소기업을 대상으로 분석한 결과, 최고경영자의 기 술기능 직무경력, 기능 간 상호통합, 그리고 환경 불확실성이 기업의 기술혁신지향성에 긍정 적인 영향을 미치고 기술혁신지향성이 기업의 기술혁신성과에 긍정적인 영향을 미치는 것으 로 나타났다. 또한, 환경 불확실성은 기업의 기술혁신지향성과 기술혁신성과간의 관계를 긍 정적으로 조절하는 효과를 갖는 것으로 나타났다. 본 연구결과가 제시하는 이론적, 실무적 시사점의 중요성에 대해서 논의하였다.
This study attempts to utilize the economic efficiency analysis results focused on the break-even point as an indicator for the decision making of commanders and staff. We suggested a method of determining economic life by utilizing logistics information system and commercial program Minitab with a focus on the equipment’s operational environment and performance data, whereas previously the equipment’s retirement period was simply determined by the current equipment prices and sustainable period.