• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.67-67
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• 2003

자동차, 항공기, 산업기계, 운반기계, 철도차량, 공작기계 등 거의 모든 산업부문에서 사용되는 베벨기어의 냉간단조 공정 및 금형 설계를 위한 해석을 수행하였다. 소성가공에 의해 생산된 베벨기어는 기계적 성질이 우수하여 동력 전달장치의 수명연장 및 신뢰성, 소형화 등을 달성할 수 있으며 생산 원가 절감의 효과가 크기 때문에 냉간 단조의 공정설계는 매우 중요하다. 베벨기어의 단조에 대한 상계해석 결과는 금형 설계 시 프레스에 필요한 단조하중을 예측할 수 있으므로 프레스의 최적성형과 안전한 금형 설계를 도모할 수 있다. 따라서 본 연구에서는 베벨기어의 냉간 단조시의 내부 동적 가용속도 장을 제시하였고 단조하중, 금속유동 등을 계산하였다. 또한 강소성 유한요소해석을 동시에 수행하여 제시한 동적 가용속도장의 적절성을 비교 검토하였다. 본 연구의 결과는 베벨기어의 적절한 냉간 단조 성형공정 및 공정설계를 위한 기초자료로 활용될 수 있을 것이다.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.581-589
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• 2011

Viscosity and diffusion coefficients for the gaseous binary mixtures of benzene- toluene, benzene-phenol and benzene-p-xylene over a wide range of temperature and composition have been predicted using the semi-empirical inversion method. The accuracies are within 3% and 4% for viscosities and diffusion coefficients, respectively.

• Analytical Science and Technology
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• v.17 no.1
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• pp.60-68
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• 2004

The core-shell polyolefin nonwovon fabric (PNF), wherein the PNF comprises at least about 60% of polyethylene having a melting temperature at ${\sim}132^{\circ}C$ and no more than about 40% of second polypropylene having a lower melting temperature at ${\sim}162^{\circ}C$. The sulfonic acid group for battery separators were prepared by radiation-induced grafting of styrene onto PNF and by the subsequent sulfonation of polystyrene graft chains. The sulfonated PNF was characterized by XPS, SEM, DSC, TGA and porosimeter. The electrochemical properties such as electrolyte retension, electrical resistance, and transport number of the $K^+ions$ were evaluated after sulfonation. It was found that the electrolyte retension increased, whereas the electrical resistance decreased with increasing sulfonic acid content. The transport number of $K^+$ in PNF with sulfonic acid of 0.22 ~ 3.60 mmol/g was to be 0.90 ~ 0.93.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.284-285
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• 2000

광굴절률 현상은 optical signal processing과 홀로그램 기억소자로 널리 응용 될 수 있기 때문에 지금까지 광범위하게 연구되어져 왔다. 광굴절률 현상에서 중요한 변수는 빛이 있는 동안 drift, diffusion 과 photovoltaic current와 같은 전하 운반 메카니즘을 통해서 local charge의 재분포에 따른 공간전하장(Space-charge field, $E_{sc}$ )이다. 지금까지 single beam에 의한 공간전하장을 측정하는 방법으로 birefringenc $e^{1.2}$ 와 interference metho $d^{3}$을 이용하여 굴절률 변화를 측정함으로써 얻을 수 있었다. 그러나 이런 방법들은 공간전하장의 변화를 측정하기위해서 전기광학계수를 측정하여 얻는 간접적인 방법이고 또한 실험방법도 다소 복잡하다. 따라서 본 투고에서는 이미 발표된 광굴절률 현상시 제 2 고조파 세기(SHG)의 변화로부터 공간전하장을 간단하게 측정하는 방법을 이용하여 congruent, MgO가 4mole%, F $e_2$O가 0.1mole% 첨가된 LiNb $O_3$ 단결정의 공간전하장에 대해서 연구를 하였다. 이 방법은 전기광학물질인 LiNb $O_3$에서 SHG 위상정합조건이 dc 전기장에 의존하는 성질을 이용한 것이다. 그리고 온도가 일정할 경우 전기장의 변화에 따라 SHG의 크기가 변함을 이용하였다. (중략)

• Analytical Science and Technology
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• v.6 no.5
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• pp.479-487
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• 1993

Potassium-Graphite Fiber Intercalation Compounds(K-GFIC) have been prepared from well oriented pitch-based Graphite fiber by the transformed two-bulbs method with variation of reaction temperatures of graphite($T_g$ : $450^{\circ}C$, $400^{\circ}C$, $350^{\circ}C$, $300^{\circ}C$, $250^{\circ}C$). The stage transition process of K-GFICs was studied by X-ray diffraction methods, and we have observed peaks with d-values of (001) diffraction of $5.40{\AA}$ and $8.78({\pm}0.01){\AA}$, which are charecteristic for the stage 1 and stage 2, respectively. The stage stability and energy states of K-GFICs were studied by UV/VIS spectrophotometer. As a results, We found that the minimum values of reflactance of K-GFICs with pure stage was moved to higher energy pristine Graphite fiber's. But because of mixtured stage, we could not observe minimum reflectance in the visible region at high reaction temperatures($400^{\circ}C$, $450^{\circ}C$). From X-ray diffraction and UV/VIS sepctrophotometry data, we can suggest that K-GFICs with lower stage has many charge carriers existed between C atoms of graphite Layers. And then, these results also provides information on the electrical and other physical properties of K-GFICs.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.4
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• pp.646-650
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• 2001

In this study, we investigated the thermotropic behavior of Daucus carota L. (DCS) extracts in phosphatidylcholine(PC) liposomes using high-sensitivity differential scanning calorimetry (nano-DSC). We used dipalmitoylphosphatidylcholine (DPPC) bilayers which made most stable liposomes among the other phosphatidylcholine. The sample DCS was extracted and fractionated to four different types, hexane(DCSMH), ethylacetate (DCSMEA), butanol (DCSMB) and aqueous(DCSMA) fractions. Compared to the other fractions of Daucus carota L., the DCSMH and DCSMEA fractions markedly affected the thermotropic properties of DPPC liposomes, broadened and shifted the thermograms of transition to lower temperatures. The incorporation of DCSMH and DCSMEA in DPPC liposomes were preferentially located in the hydrophobic core of DPPC bilayers, where it reduced the lipid packing orderness (cooperative unit) in the gel state compared to it in the liquid-crystalline state. These results suggest that the activities of the Daucus carota L. extracts to enhance the fluidity of the liposomal membrane have implication in their biological activities.

• Korean Journal of Digital Imaging in Medicine
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• v.8 no.1
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• pp.51-55
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• 2006

The effects of Asaddition in amorphous selenium(a-Se) films for digital X-ray conversion material have been studied using the moving photocarrier grating(MPG) technique. This method utilizes the moving interference pattern generated by the superposition of the two frequency shifted laser beams for the illumination of the sample. This moving intensity grating induces a short circuit current, j$_{sc}$ in a-Se:As film. The transport parameters of the sample are extracted from the grating-velocity dependent short circuit current induced in the sample along the modulation direction. The electron and hole mobility, and recombination lifetime of a-Se films with arsenic(As) additions have been obtained. We have found an Increase in hole drift mobility and recombination lifetime, especially when 0.3% As is added into a-Se film, whereas electron mobility decreases with As addition due to the defect density. The transport properties for As doped a-Se films obtained by using MPG technique have been compared with X-ray sensitivity for a-Se:As device. The fabricated a-Se(0.3% As) device film exhibited the highest X-ray sensitivity out of 5 samples.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.2
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• pp.167-175
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• 1993

Lithium-Carbon Intercalation Compounds(Li-CICs) have been synthesized from various carbon ma-terials by use of the modified stainless steel two-bulbs methods. These compounds had various colours by structural character of starting materials. The synthesized Li-CICs were identified to stage formation process by X-ray diffraction data. At these results, well-oriented natural graphite and graphite fiber are formed lower stages(Stage 1, Stage 2), but poor-oriented carbon fiber and petroleum cokes are also formed higher stages(Stage 3, Stage 4, Stage 5). And when we compared with measured d value and calculated d value, these values agreed with each other. But poor-oriented carbon materials are some difference from them. The stage stability and energy stage of Li-CICs were obtained by UV/VIS Spectrophotometric data. X-ray diffraction and UV/VIS Spectrophotometric data suggested that well-oriented carbon materials has distingushible curve between energy and reflectance. In these results, we know that many charge carriers between carbon layers are related to concentration of intercalants. And then, this paper also provides information on high efficiency energy storing materials at intercalation process of Li-CICs.

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.840-848
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• 1992

An ionizable macrocyclic ligand, diaza-18-crown-6-diisopropionic acid(K22DAP) has been synthesized. Protonation constants of this compound and stability constants with some lanthanides were determined by potentiometric titration method. The protonation constants are log$K_1$ = 9.05, log$K_2$ = 8.37, log$K_3$ = 1.88 and log$K_4$ = 0.99. The logarithmic values of stability constants with La(III), Nd(III), Gd(III) and Lu(III) are 11.14, 11.43, 11.74 and 10.88 respectively. Extraction behavior of Ln(III) ion was investigated using TTA(thenoyltrifluoroacetone) as extractant in the presence of K22DAP as macrocyclic ionophore. It was observed that Ln(K22DAP)TTA is the dominating species in aqueous complexes of La(III) and Nd(III).

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.5
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• pp.543-551
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• 2015

Polyurethane Foam(PUF), a outstanding thermal insulation material, is used for various structures as being composed with other materials. These days, PUF composed with glass fiber, Reinforced PUF(R-PUF), is used for a insulation system of LNG Carrier and performs function of not only the thermal insulation but also a structural member for compressive loads like a sloshing load. As PUF is a porous material made by mixing and foaming, mechanical properties depend on volume fraction of voids which is a dominant parameter on density. Thus, In this study, density is considered as the effect parameter on mechanical properties of Polyurethane Foam, and mechanical behavior for compression of the material is described by using modified Gurson damage model.