Green BaSi2O2N2:0.02Eu2+ phosphor is synthesized through a two-step solid state reaction method. The first firing is for crystallization, and the second firing is for reduction of Eu3+ into Eu2+ and growth of crystal grains. By thermal analysis, the three-time endothermic reaction is confirmed: pyrolysis reaction of BaCO3 at 900 oC and phase transitions at 1,300 oC and 1,400 oC. By structural analysis, it is confirmed that single phase [BaSi2O2N2] is obtained with Cmcm space group of orthorhombic structure. After the first firing the morphology is rod-like type and, after the second firing, the morphology becomes round. Our phosphor shows a green emission with a peak position of 495 nm and a peak width of 32 nm due to the 4f65d1→4f7 transition of Eu2+ ion. An LED package (chip size 5.6 x 3.0 mm) is fabricated with a mixture of our green BaSi2O2N2, and yellow Y3Al5O12 and red Sr2Si5N8 phosphors. The color rendering index (90) is higher than that of the mixture without our green phosphor (82), which indicates that this is an excellent green candidate for white LEDs with a deluxe color rendering index.

본 연구에서는 국내외적으로 환경문제 및 에너지절감의 일환으로 직류배전시스템을 선박에 적용하려는 연구 및 실증이 활발히 수행되고 있으며, 발전기를 직류배전시스템에 적용하기 위해서는 가변속 엔진을 적용하여 저부하 영역에서 발전기의 엔진 회전수를 줄여 연료소모량을 절감할 수 있는 방안이 제시되고 있다. 본 논문에서는 기존의 디젤발전기를 이용하여 발전기 컨트롤러, 가버너, AVR 을 이용하여 직류배전용 가변속발전기를 구성하였으며, 발전기의 시스템 구성 방법, 가변속 발전에 따른 전력품질 시험(전압 및 주파수 변동특성, 부하변동 특성)을 통해 가변속 발전기의 전력특성을 분석 하였다. 가변속 발전기의 전압(250 ~ 440 VAC) 및 주파수(34 ~ 60 Hz)는 정격의 60 ~ 100%로 구성하였으며, 엔진은 1100 ~ 1800 rpm 범위에서 운전되도록 설정 하였다. 부하변동에 따라 발전기의 엔진속도를 변경 시켜서 발전기 출력의 전압, 전류, 주파수가 전력량에 따라 안정적으로 변동되는 것을 확인하였다.

We prepared Y3Al5O12;Ce3+,Pr3+ transparent ceramic phosphor using a solid state reaction method. By XRD pattern analysis and SEM measurement, our phosphors reveal an Ia-3d(230) space group of cubic structure, and the transparent ceramic phosphor has a polycrystal state with some internal cracks and pores. In the Raman scattering measurement with an increasing temperature, lattice vibrations of the transparent ceramic phosphor decrease due to its more perfect crystal structure and symmetry. Thus, low phonon generation is possible at high temperature. Optical properties of the transparent ceramic phosphor have broader excitation spectra due to a large internal reflection. There is a wide emission band from the green to yellow region, and the red color emission between 610 nm and 640 nm is also observed. The red-yellow phosphor optical characteristics enable a high Color Rendering Index (CRI) in combination with blue emitting LED or LD. Due to its good thermal properties of low phonon generation at high temperature and a wide emission range for high CRI characteristics, the transparent ceramic phosphor is shown to be a good candidate for high power solid state white lighting.

The small coastal vessel registered in Korea, small coastal vessels with a gross tonnage of 10 tons or less account for 94.6 % and among them, aged vessels over 16 years age indicate 40.6 %. In order to reduce GHG emissions from small coast vessels, discussions are underway to replace aging ships' propulsion units with eco - friendly propulsion facilities, and the electric propulsion ship is emerging as one of the measures. The electric propulsion system using the DFE rectifier, which was applied in the conventional large commercial vessel, was effective in reducing the harmonics and improving the DC output voltage of the DC link stage, but it occupied a large volume and caused an increase in the overall system price. Therefore, in this paper, we propose an electric propulsion system using AFE rectifier with a small volume of system that can be applied to a small coastal vessel. In order to analyze the effectiveness of the overall system, the load profile was applied to obtain accurate and rapid speed tracking performance of the propulsion motor affected by the speed load. In addition, the power factor and total harmonic distortion factor of the voltage and current on the improved power output side are derived through simulation.

This study was conducted to investigate the actual condition of fine particles (PM2.5) pollution and to verify the necessity of managing PM2.5 in the indoor environment of public use facilities in Gyeonggi-do. As a result, it was found that PM2.5 concentrations measured for 24 hours ranged from 15.9 to 113.5 μg/m3 and averaged 42.5 μg/ m3, and for 6 hours, ranged from 20.4 to 167.1 μg/m3 and averaged 65.6 μg/m3. Average concentration was highest in subway stations, followed by nursery schools and indoor parking lots. 49 of the 55 sites investigated exceeded the 24hr-PM2.5 standard specified in WHO guidelines (25 μg/m3). The ratio of PM2.5 to PM10 was 70.2% for 24hr and 70.7% for 6hr on average. This means that PM2.5 tends to account for a large proportion of the total particulate pollution in the indoor environment, and that it is essential to control fine particulate matter in order to reduce total particulate matter in the indoor environment. In addition, it was found that the time to be sampled and total sampling time are one of important factors which affect PM2.5 concentration in indoor air quality; therefore, I think that it is necessary to concretely specify the time to be sampled and maximum range of total sampling time in the test method of PM2.5. Recently, regulations on PM2.5 in indoor environments have been strengthened in other countries due to its high risk to human health; however, there is currently no enforceable regulation in Korea. Given that PM2.5 is more harmful to human health than PM10, it is urgently necessary to establish proper policies and regulations to control PM2.5 in indoor environments.

적색 K2SiF6:Mn4+ 형광체는 SiO2 in/HF/KMnO4H2O solution 용액의 산화환원 반응에 의해 합성된다. 이 형광체 는 450 nm 이하의 파장에서 여기되어 Mn4+의 2Eg → 4A2g에 의해 반치폭이 10 nm인 약 634 nm의 적색 빛을 발광한다. 입자의 크기는 약 5 ㎛이고 결정구조는 Fm-3m (225)의 공간군을 가지는 입방정계이다 (JCPDS85-1382). 온도의존 발광 스펙트럼에서는 약 175 ℃에서의 발광강도가 상온에서보다 66 %까지 감소하였다. 이 형광체는 청색 발광을 하는 InGaN LED에 의해 효과적으로 여기 될 수 있어서 녹색이나 황색 형광체와 함께 사용하여 연색지수가 높은 백색 LED를 만들 수 있다.

본 논문은 녹색을 발광하는 가넷 형광체 (Lu1-xGdx)3(Al1-yGay)5O12:Ce3+에 관하여 연구하였다. 모든 시편은 입방구조를 가진다. x 증가에 따라 x = 0.20 일 때 559 nm의 peak에서 x = 0.40 일 때 576 nm의 peak로 발광 스펙트럼의 적색편이가 일어나고, x = 0 일 때와 비교하면 x = 0.40 일 때 휘도가 24 %정도 감소한다. 그리고 광여기스펙트럼 또한 유사한 적색편이를 보여준다. y 증가에 따라 y = 0.20 일 때 534 nm의 peak에서 y = 0.40 일 때 524 nm의 peak로 발광 스펙트럼의 청색편이가 일어나고, y = 0 일 때와 비교하면 y = 0.40 일 때 휘도가 46 %정도 감소한다. 그리고 광여기스펙트럼 또한 유사한 청색편이를 보여준다. 본 논문의 가넷 형광체 (Lu1-xGdx)3(Al1-yGay)5O12:Ce3+는 우수한 녹색과 노란색의 색채조정 능력으로 백색발광소자의 색변환 형광체로써 적용될 수 있다.