• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.165-165
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• 2013

희토류 발광 물질은 4f 껍질에 위치하는 전자의 독특한 특성 때문에 발광 소자와 디스플레이에 그 응용성을 확장하고 있다. 본 연구에서는 고효율의 적색과 주황색 형광체를 합성하기 위하여 모체 격자 CaNb2O6에 희토류 이온인 유로퓸과 사마륨을 치환 고용하여 최적의 합성 조건을 조사하였다. Ca1-1.5xNb2O6:REx3+ (RE=Eu, Sm) 형광체 분말 시료는 고상반응법을 사용하여 활성제 이온인 Eu3+와 Sm3+의 농도비를 0, 0.01, 0.05, 0.10, 0.15, 0.20 mol 로 변화시키면서 합성하였다. 초기 물질 CaO, Nb2O5, Eu2O3와 Sm2O3을 화학 적량으로 측정하고, 400 rpm의 속도로 24시간 밀링 작업을 수행한 후에, 건조기 $60^{\circ}C$에서 28시간 건조하고, 시료를 막자 사발에서 갈아 세라믹 도가니에 담아 튜브형 전기로에서 분당 $5^{\circ}C$의 비율로 승온시켜 $500^{\circ}C$에서 5시간 동안 하소와 $1,100^{\circ}C$에서 6시간 소결하여 합성하였다. Eu3+가 도핑된 경우에, 발광 스펙트럼은 Eu3+ 이온의 농도비에 관계없이 강한 적색 발광 스펙트럼이 616 nm에서 관측되었다. 이외에도, 596 nm와 708 nm에서 상대적으로 발광 세기가 약한 주황색 발광과 적색 발광 신호가 검출되었으며, 541 nm에서는 매우 약한 녹색스펙트럼이 관측되었다. Eu3+ 이온의 농도비에 0.01 mol에서 0.15 mol로 증가함에 따라 주발광 신호의 세기는 점점 증가하였으며, 0.15 mol에서 최대 발광 세기를 나타내었다. Eu3+ 이온의 농도비가 0.20 mol 로 더욱 증가함에 따라 주 피크의 세기는 농도 소강 현상에 의하여 현저히 감소함을 보였다. 한편, 주된 흡광 스펙트럼은 279 nm에서 나타났는데, 이것은 전하전달밴드 신호이다. Sm3+가 도핑된 형광체 분말의 발광 스펙트럼은 모든 시료의 경우에 613 nm에서 강한 적주황색 발광 스펙트럼이 관측되었고, 상대적으로 세기가 약한 570 nm와 660 nm에 피크를 갖는 황색과 적색 발광 스펙트럼이 발생하였다. 흡광과 발광 스펙트럼의 최대 세기는 0.05 mol에서 나타났으며, Sm3+ 이온의 농도비가 더욱 증가함에 따라 흡광과 발광 세기는 급격하게 감소하였다.

• Journal of Korean Academy of Dental Administration
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• v.6 no.1
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• pp.11-18
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• 2018

The aim of this study was to evaluate the competency of the Easyperio test, a genetic test method based on real time PCR for the detection of bacteria that cause dental caries and periodontal disease. To verify the validity of this text, various dental health evaluations were administered to 33 boys between the ages of 12 to 14, as this age group commonly experiences dental caries. These evaluations included a dental caries experience survey, a first molar health evaluation, the Dentocult Streptococcus mutans (SM) strip mutans, the Dentocult Lactobacillus spp (LB) test, and the Easyperio test. The correlation coefficients between the level of the Dentocult SM strip mutans and the dental caries experience were DT (R=0.570, p=0.001), DMFT (R=0.376, p=0.031), and first molar health (R=-0.395, p=0.023). The correlation coefficients between the amount of SM in the Easyperio test and dental caries experience were DT (R=0.528, p=0.002), DMFT (R=0.369, p=0.035), and first molar health (R=-0.426, p=0.013). The correlation coefficients between the level of the dentocult SM strip mutans and the SM amounts of the Easyperio test were S.mi (R=0.564 p=0.001) and S.mu (R=0.621, p=0.002). The correlation coefficients between the level of the Dentocult LB test and the SM amount of Easyperio test was S.mi (R=0.495, p=0.003). In conclusion, Easyperio test may be an easy and effective method for the differentiation and diagnosis of dental caries through quantitative and qualitative analysis of oral bacteria.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.218-225
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• 2004

A study has been performed to investigate the applicability of the high-strength steel to the medium-span composite girder bridges. A two- and four-girder simple and continuous bridges are considered. A proper span-to-depth ratio for the model bridges with SM490 and SM570 was evaluated by using the section optimization program, respectively. For the determined span-to-depth ratio, deflections and fatigue performance were also investigated. It was acknowledged that the high-strength steel reduces the weight of girder but the increase of deflection and fatigue stress should be considered especially in the positive moment area.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.120-121
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• 2016

Recently, the building has been changed into high-rise and long span and this yields a development of high performance structural steels in construction market. According to this effect, the SM 520 and the SM 570 were developed and utilized into steel building industry. However, the study for fire resistance of them were not done actively. In this study, to know and comparative the fire resistance performance of long span beams built up with high strength structural steels an analytical method is going to applied using mechanical and thermal properties at high temperature.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.565-570
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• 1999

In this paper, we developed a windows 95 version Off-Line Programming system which can simulate a Robot model in 3D Graphics space. 4axes SCARA Robot (especially FARA SM5) was adopted as an objective model. Forward kinematics, inverse kinematics and robot dynamics modeling were included in the developed program. The interface between users and the OLP system in the Windows 95's GUI environment was also studied. The developing language is Microsoft Visual C++. Graphic libraries, OpenGL, by silicon Graphics, Inc. were utilized for 3D Graphics.

• Journal of Korean Society of Steel Construction
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• v.25 no.5
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• pp.579-585
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• 2013

Shear buckling stresses of steel pipes due to the lateral forces have been analyzed via parametric analysis. Detailed FEM models are prepared, and steel types, thickness, radii and length of steel pipes are selected as parameters. STK400, STK490 and SM570 are used and the thickness of pipe is 2mm and 40mm. The radii(R) and lengths(L) are determined based on the values satisfying the following relationship as R/t=20~400 and L/R=1~3. The shear buckling stresses decrease for all types of considered steels as R/t increase from 20 to 200. High strength steels are more sensitive to R/t, and also have an bigger effect on shear buckling stresses than low strength steels. It is found that shear buckling stresses decrease as L/R increases, showing that the steel pipes become weak as the length of the steel pipe increases.

• Journal of Korean Society of Steel Construction
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• v.20 no.6
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• pp.691-700
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• 2008

Contemporary architectural structures have diverse and complex forms. Such structural variety demands requisite performance from the connections in the steel structure so that the latter could resist a horizontal force, such as an earthquake. The connections are the all-important components that create the discontinuous form and that support stress concentration, determining the stiffness and toughness of the entire steel frame. In this study, a real-scale column-to-beam connection was constructed in the 600MPa-grade high-strength and high-performance steel, to test its behavior. Its material and welding characteristics were examined in this study, and its structural performance was analyzed by conducting seismic-resistance tests on the full-scale, cross-shaped column-to-beam welded connections with non-scallop, ordinary-scallop, and reinforced-scallop details. The weld ability of the high-strength, high-performance steel was also evaluated, and data regarding the seismic design for practical application were provided.

• Journal of Korean Society of Steel Construction
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• v.14 no.5 s.60
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• pp.647-656
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• 2002

High-strength steel in steel bridges is the key to achieving cost-efficiency because it facilitates lightweight construction and rationalizes structure. The future of high-strength steel is bright, with its use projected to expand. As such, it is necessary to evaluate precisely various factors affecting the process of fabricating high-strength steel, i.e., welding heat, strain hardening, and weldability and performance of the welded joints. This study therefore performed the maximum hardness test and y-groove weld crack test using welding processes such as SAW, FCAW, and GMAW, in order to investigate the welding performance and characteristics of welded Joints or high-strength steel produced in Korea such as SM570, POSTEN60, and POSTEN80. In addition, a series of welding tests was carried out to estimate the tensile strength, bending characteristics, absorbed energy, and hardness in welded joints.

• Journal of the Korean Ceramic Society
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• v.51 no.4
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• pp.295-299
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• 2014

Electrical conductivities of complex perovskites, layered perovskite and Sr doped layered perovskite oxides were measured and analyzed for cathode materials of Intermediate Temperature-operating Solid Oxide Fuel Cells (IT-SOFCs). The electrical conductivities of $Sm_{1-x}Sr_xCoO_{3-\delta}$ (x = 0.3 and 0.7) exhibit a metal-insulator transition (MIT) behavior as a function of temperature. However, $Sm_{0.5}Sr_{0.5}CoO_{3-\delta}$ (SSC55) shows metallic conductivity characteristics and the maximum electrical conductivity value compared to the values of $Pr_{0.5}Sr_{0.5}CoO_{3-\delta}$ (PSC55) and $Nd_{0.5}Sr_{0.5}CoO_{3-\delta}$ (NSC55). The electrical conductivity of $SmBaCo_2O_{5+\delta}$ (SBCO) exhibits a MIT at about $250^{\circ}C$. The maximum conductivity is 570 S/cm at $200^{\circ}C$ and its value is higher than 170 S/cm over the whole temperature range tested. $SmBa_{0.5}Sr_{0.5}Co_2O_{5+\delta}$ (SBSCO), 0.5 mol% Sr and Ba substituted at the layered perovskite shows a typically metallic conductivity that is very similar to the behavior of the SSC55 cathode, and the maximum and minimum electrical conductivity in the SBSCO are 1280 S/cm at $50^{\circ}C$ and 280 S/cm at $900^{\circ}C$.

• Journal of the Korean Society of Safety
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• v.33 no.6
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• pp.1-7
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• 2018

The Continuous Ship Unloader (CSU) is an equipment that unloads freight from the ship docked in the port to the land. And the design target life time is designed to be 30 to 50 years, and it is classified as a semi-permanent large facility. However, cracks may occur due to structural defects, abnormal loads, and corrosion, and fatigue failure may occur before the design life is reached. In this study, we predicted the remaining life time of the main component of the CSU considering crack. And also proposed inspection cycle for maintenance of CSU based on the results of the remaining life time prediction. For this purpose, the structure, operational stresses of the CSU were analyzed and main members were selected. And tensile tests and fatigue crack propagation tests were performed with SM490YA and SM570TMC, which are used as main materials for CSU.