• Polymer(Korea)
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• v.28 no.3
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• pp.263-272
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• 2004

Using computer simulation, the processibility and properties of the inst겨ment panel of automobile produced by gas injection molding were predicted and evaluated. The P-V-T data of ABS, resin were used in the gas injection molding process in order to estimate the mold filling phenomena. The optimum process conditions were found by adjusting the process parameters including pressure, filling time, the positions of gas channel and runner. The process was simplified and the final instrument panel produced by the gas injection molding was found to have improved dimension stability compared to the one produced by conventional injection molding.

• Journal of the Korean Magnetics Society
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• v.21 no.2
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• pp.56-60
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• 2011

Optical properties of $T_{0.2}Fe_{2.8}O_4$ (T = V, Cr, Mn) thin films derived from ferrimagnetic $Fe_3O_4$ were investigated by spectroscopic ellipsometry in the 1~8 eV photon-energy range. The difference in optical-absorption spectrum between the ternary compounds and $Fe_3O_4$ was analyzed based on preferable sites in spinel structure and iconicity of the doped V, Cr, and Mn ions. The observed absorption spectra from $Fe_3O_4$ and the ternary compounds can be interpreted as mainly due to charge-transfer transitions of Fe d electrons characterized by absorption structures with wide energy width. Also, the observed absorption structures with narrow energy width can be interpreted as due to crystal-field transitions between different d electron configurations of tetrahedral $Fe^{3+}(d^5)$ ion. The transitions were described in terms of spin-polarized electronic states of $Fe_3O_4$.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.301-309
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• 2008

In this study, the effect of formaldehyde to phenol (F/P) molar ratios, catalyst wt%, and reaction temperature on the chemical structure was studied utilizing a two-level full factorial experimental design. The effect of three variables on the chemical structure was analyzed by using three-way ANOVA of SPSS. Concentration of methyrol-substituted phenols after 300 min addition reaction increased with higher the F/P mole ratio, lower the reaction temperature and lower the catalyst wt%. Resol catalysed by barium hydroxide showed higher addition of formaldehyde onto ortho positions of phenolic rings. A simplified elementary reaction model for resole type phenolic resin formation which do not consider the dissociation of phenolic compounds and the fraction of formaldehyde in the form of methylene glycol was proposed and compared with Zavitsas' type models. Elementary reaction model showed error of 2.79% compared to the error of 3.27% in Zavitsas' type models. It was thought that the elementary reaction model could be used to predict the behavior of addition reaction in resol formation.

• Applied Chemistry for Engineering
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• v.28 no.6
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• pp.705-713
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• 2017

A novel material, $Bi_2WO_6-GO-TiO_2$ composite, was successfully synthesized using a facile hydrothermal method. During the hydrothermal reaction, the loading of $Bi_2WO_6$ and $TiO_2$ nanoparticles onto graphene sheets was achieved. The obtained $Bi_2WO_{6-GO-TiO2}$ composite photo-catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis-DRS), and X-ray photoelectron spectroscopy (XPS). The $Bi_2WO_6$ nanoparticle showed an irregular dark-square block nanoplate shape, while $TiO_2$ nanoparticles covered the surface of the graphene sheets with a quantum dot size. The degradation of rhodamine B (RhB), methylene blue trihydrate (MB), and reactive black B (RBB) dyes in an aqueous solution with different initial amount of catalysts was observed by UV spectrophotometry after measuring the decrease in the concentration. As a result, the $Bi_2WO_6-GO-TiO_2$ composite showed good decolorization activity with MB solution under visible light. The $Bi_2WO_6-GO-TiO_2$ composite is expected to become a new potential material for decolorization activity. Photocatalytic reactions with different photocatalysts were explained by the Langmuir-Hinshelwood model and a band theory.

• Korean Journal of Cognitive Science
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• v.23 no.1
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• pp.73-95
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• 2012

Two experiments were conducted to verify how the factors of attentional dispersion, reason for waiting, and cue of time flow affect the perceived waiting time. In experiment 1, based on the characteristics of waiting experience that Maister(1985) suggested, levels of attentional dispersion and whether or not offering a reason for waiting were manipulated. Participants estimated elapsed time(the objective time was 10 minutes) using either prospective or retrospective estimation method. Overall results were that they overestimated the elapsed time regardless of the experimental conditions. However, both main effects of the attentional dispersion and the reason for waiting were statistically significant. That is, when attention was more dispersed and when the reason was given, overestimation of elapsed time was reduced. No difference was found between the two estimation methods, and none of the interaction was significant. Experiment 2 was a replication of Experiment 1 except that a cue of time flow was added by using scroll bar on a computer screen. Because it has been suggested that the cue can help us to manage the waiting time and result in differences between the two time estimation methods. The results showed that main effects of the attentional dispersion and the reason for waiting were significant as those in Experiment 1. In addition, main effect of time estimation method and the three-way interaction were also significant. None of two-way interaction was significant. That is, the perceived waiting time is much shorter in the retrospective method, and the effects of the attentional dispersion and the reason of waiting were dependent upon the estimation methods. Both experiments showed that offering a clear reason for waiting is more important than the attentional dispersion in reducing the perceived waiting time. Some implications of these results for the service industry and the future direction of research were discussed in the final section.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.2
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• pp.31-38
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• 2001

LCD는 비발광형 소자이므로 배면광이 필요하다. 현재의 LCD 배면광용 냉음극 형광램프는 전기-광학적 특성을 좋게 하기 위하여 수은방전을 사용한다. 그러나 수은의 이용은 외부 온도에 따라 특성이 변하는 결점과 환경 문제가 있다. 이 결점을 보완하기 위하여 원통방전형, 미세방전형 그리고 평면방전형 등 세가지 방식의 무수은 램프가 개발되어 왔다. 원통 방전형 무수은 램프는 수은 대신 Xe을 사용한다. Xe 방전이 수축되는 것을 막기 위하여 한쪽 전극은 외벽에 코일형태로 감아서 사용한다. 그리고 코일형태의 전극의 권선 간격을 조절하여 균일한 방전을 얻는다. 이 형태는 무수은 냉음극 형광램프의 두배의 광속을 얻을 수가 있다. 미세방전형 무수은 램프는 두 개의 절연체로 절연되 금속 전극사이의 방전공간에 수많은 미세방전을 일으켜 발광시킨다. 이 방식은 대향 방전구조와 면 방전구조의 두가지가 있다. 이 방식은 전극이 유전체로 둘러쌓여 있으므로 수명이 높다. 새로운 평면방전형 무수은 램프를 개발하였다. 이 램프는 두 개의 유리평판 사이에 방전공간을 만들고 한쪽 유리면의 양쪽 가장자리에 두 개의 전극을 설치하여 면방전을 유도한다. 양쪽 유리면에는 삼원색 형광체를 도포하고 Xe을 봉입하여 Xe의 진공자외선으로 형광체를 발광시킨다. 이 램프는 전극이 유전체로 덮혀있어 수명이 길다. 실험결과 기체압력 6.7[kPa], 구동전압 1,130[V]에서 최대휘도 9,200[$cd/m^2$], 광효율 20.4[lm/W]을 었었고, 기체 압력 2.7[kPa] 구동전압 1,120[V]에서 최대효율 34.1[lm/W], 휘도 1,080[$cd/m^2$]을 얻었다. 현재 무수은 램프는 수은 램프에 비해서 광학적 특성이 좋지 못하다. 무수은 램프에서 좋은 광학적 특성을 얻기 위해 가장 중요한 것은 수축이 없이 방전을 확산시키는 것이다. 이를 위해서 램프구조와 구동법을 최적화하는 것이 필요하다. 또한 기체압력을 높임으로서 Xe의 여기복사를 얻을 수 있었다.

• Elastomers and Composites
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• v.49 no.1
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• pp.13-23
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• 2014

In this work, glycolide, L-lactide and ${\varepsilon}$-caprolactone monomers were polymerized into the triblock copolymers by two step polymerization method and their non-isothermal crystallization behaviors were studied by combination of modified Avrami and Ozawa formula for further analysis of their behaviors. The result showed that PGCLA21 gave the highest value for supercooling analysis and super cooling degree increased with L-lactide content. Crystallization velocity constant, however, showed no significant change. The result of cooling function in specific relative crystallization degree showed that the increase of L-lactide content made an effect on the more enhancement of crystallization velocity of the PGCLA than PGCL. The result of big logF(T) value with the L-lactide content above critical point for PGCLA41 and PGCLA21 showed that bigger cooling velocity needed to gain same crystal size compared with PGCL. This means that it gives negative effect in the increase of crystallization velocity.

• Journal of Conservation Science
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• v.29 no.3
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• pp.231-241
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• 2013

Analysis of the bronze bodhisattva from Pangyo-dong sites in Seongnam by computed tomography, ICP-AES, metallurgical microscope and SEM-EDS had to know manufacturing technique. And the origin of the raw material, was investigated using TIMS. Results with computed tomography, two bronze bodhisattva produced by lost-wax casting technique with hollow inside and could see the core of the inside. Result of component analysis and microstructure observation, material is alloy of copper-tin-lead and made by casting without artificial treatment. According to lead isotope ratio analysis result of bronze bodhisattva could be made into galena of the Gyeonggi massif in Korea South.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.197-197
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• 2011

고온 스퍼터 공정과 구리 리플로우 공정을 통해 다공성 니켈 지지체에 팔라듐-구리-니켈 삼원계 합금 수소 분리막을 제조하였다. 그러나 스퍼터와 같은 물리적 증착법은 주로 주상정 형태로 증착되기 때문에 다공성 니켈 지지체 표면의 수마이크론 내외의 기공이 존재할 경우 다공성 니켈 지지체에 기인한 많은 기공들 때문에 스퍼터 증착에 영향을 주어 수소 분리막 표면에 기공들이 존재하게 된다. 이를 방지하고 균일한 증착이 이루어지도록 다공성 지지체 표면의 전처리 공정이 필요하다. 본 연구에서는 스퍼터 코팅에 의한 균일한 팔라듐 금속층 형성하고 표면에 미세기공이 없는 수소 분리막을 제조하기 위해 다공성 니켈 지지체를 니켈도금, 알루미나 분말 주입 및 미세연마 전처리 공정을 통하여 다공성 니켈 지지체의 표면기공들을 매립하여 치밀한 팔라듐 합금 층을 형성하였다. 전처리를 하지 않은 다공성 니켈 지지체는 팔라듐 및 구리의 고온 스퍼터 증착 및 구리 리플로우 공정에 의해 표면 기공을 막을 수가 없었고 수소분리기능이 없어 수소 분리막으로 역할을 하지 못했다. Al2O3 분말 주입 전처리 공정을 한 다공성 니켈 지지체에 팔라듐 및 구리 고온 스퍼터 증착과 구리 리플로우 공정을 이용하여 제조된 수소 분리막은 다공성 니켈 지지체에 기인한 기공을 메우기 위해서 팔라듐 합금 층이 두꺼워지는 어려움이 있었다. 니켈도금 전처리 공정을 한 다공성 니켈 지지체에 형성한 수소 분리막은 우수한 선택도를 가졌으나 도금 전처리에 사용된 $2{\mu}m$ 두께의 니켈층이 수소의 확산을 방해하는 저항막 역할을 하여 수소 투과도가 3.96 $ml{\cdot}cm-2{\cdot}min-1{\cdot}atm-1$으로 낮게 나타났다. 미세연마 전처리 공정을 한 다공성 니켈 지지체에 형성한 수소 분리막 역시 우수한 수소 선택도를 가졌으며, 수소의 확산을 방해하는 저항막이 존재하지 않아 13.2 $ml{\cdot}cm-2{\cdot}min-1{\cdot}atm-1$의 우수한 수소 투과도를 나타내었다.

• Analytical Science and Technology
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• v.18 no.3
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• pp.241-249
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• 2005

In this study, instrumental neutron activation analysis was used to measure the concentrations of about 30 trace elements in airborne particulate (PM2.5) samples at urban area of Daejeon city located in the southwestern region of Korea. An inspection of the measurement data indicates that the distribution patterns of trace elements could clearly distinguish the elements with their concentrations ranging over five orders of magnitude. The mean values for Lu and Dy were found to be the lowest at values of 0.01 and $0.04ng/m^3$, while those for K and Fe showed the highest value of 671 and $653ng/m^3$, respectively. The results of correlation analysis showed that PM2.5 concentrations can exhibit much more enhanced correlations with the elements of earth crustal components. The results of factor analysis further indicated that there are no more than six factors with statistical significance, which may exert dominant roles in regulating the elemental concentration levels in the study area. Enrichment factor analysis supports explicit interpretation of results found by this factor analysis.