• Analytical Science and Technology
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• 제24권5호
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• pp.336-344
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• 2011

The study attempted to find out any effect to prevent photo aging of epoxy resin used for conservation by way of adding UV stabilizer, one of plastic additives. Specimens were made by adding HALS and UVA UV stabilizer as each concentration to 3 kinds of epoxy resin, which are most frequently used for artifacts joining and restoration process, and aging effects were investigated through Color change, SEM, contact angle, FTIR analysis during UV aging experiments. Last, usage suitability was checked when UV stabilizer was added through Universal Tensile strength tester. In result, it is impossible to prevent decomposition of chemical structure in spite of adding UV stabilizer but in the case of epoxy A and R, it is believed that photo aging such as yellowing or crack can be minimized without giving a big influence to adhesive strength of epoxy resin through adding less than 0.1% of UVA. It is expected that above will solve photo aging problem of epoxy resin used for joining and restoration of artifacts and will extend its life as joining and restoration materials.

• Korean Chemical Engineering Research
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• 제50권3호
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• pp.588-593
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• 2012

Compatibility of unsaturated polyester (UP) and low profile agent (LPA) of polystyrene (PS) have been investigated under various mixing conditions such as the ratio of UP and LPA, mixing time, mixing temperature, and input amount of 2nd UP. It was possible to obtain mixture with small particle size and low phase separation in condition of 35 g of LPA, 25 g of 1st UP input, 5 min of mixing time, 1700 rpm of mixing speed, and 45 g of 2nd UP input. It was found that compatibility of UP and LPA was very sensitive to mixing conditions. In addition, molded sample using sheet molding compound prepared by stable mixing condition appeared good properties such as low water adsorption, low shrinkage, and high gloss.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• 제4권2호
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• pp.133-138
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• 2006

Chemical wastes containing small amounts of uranium can not be disposed of them after treatment as an industrial waste, because the uranium concentration in the final dry cake exceeds the exemption level. Especially for the removal of uranium in this study, the method for immobilizing Diphosil powder within alginate beads is adopted to make a bead form from a powdered resin. Sodium alginate bead itself showed a capability to uptake uranium to above 60%, but the value was decreased to below 30% after equilibrium. The adsorption rate of uranium increased with the increasing content of Diphosil in the sodium alginate bead. Diphosil resin itself showed very fast uptake of uranium from early stages, and then the rates were leveled off. Diphosil bead showed an improved capability to uptake uranium considering the pure Diphosil content in the composite bead, and provide a considerable potential for further applications of a continuous process by using Diphosil as a bead form.

• Journal of the Korean Chemical Society
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• 제40권1호
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• pp.81-86
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• 1996

The physical properties of epoxy molding compound (EMC) according to the change of softening point of epoxy resin have been investigated in order to study the relationship between the properties of o-cresol novolac epoxy resin, which is main component of EMC for semiconductor encapsulation, and EMC. The softening points of used epoxy resin are 65.1 $^{\circ}C$, 72.2 $^{\circ}C$, and 83.0 $^{\circ}C$, respectively. The flexural strength and flexural modulus as mechanical properties were measured, and thermal expansion coefficient, thermal conductivity and glass transition temperature (Tg) as thermal properties, and spiral flow as moldability have been investigated to see the change of physical properties of EMC. The flexural modulus, thermal expansion coefficients in the glass state (${\alpha}_1$), and thermal conductivity of EMC were found to be keep constant value irrespective of the change of softening point, but Tg increased with softening point of epoxy resin, and the spiral flow decreased with that. It can be considered that these phenomena are due to the increase of crosslinking density of EMC according to the increase of softening point. The transition points were found out in the thermal expansion coefficient data in the rubbery state (${\alpha}_2$) and the flexural strength data. These can show the decrease of filler dispersion according to increase of epoxy resin viscosity.

• Proceedings of the Materials Research Society of Korea Conference
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• 한국재료학회 2001년도 춘계학술발표강연 및 논문개요집
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• pp.170-170
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• 2001

• Applied Microscopy
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• 제25권3호
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• pp.82-89
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• 1995

High resolution transmission electron microscopic observations on quaternary $Zn_{1-x}Mg_{x}S_y$ $S_{1-y}$(x=0.13, y=0.16) on (001) GaAs substrate grown up to $1.2{\mu}m$ with 20nm ZnSe buffer layer at $300^{\circ}C$ by RIBER MBE system which has a single growth chamber were investigated by HRTEM working at 300kV with point resolution of 0.18nm. The ZnSe buffer layer maintains the coherency with the GaAs substrate. The stacking faults had begun at ZnSe buffer/$Zn_{1-x}Mg_{x}S_{y}S_{1-y}$ interface, whose length and spacing became larger than 60nm and wider than 40nm, respectively. The inverse triangular stacking fault was bounded by stacking faults which were formed on {111} planes with different variants. There exists rare stacking faults inside the triangular defect. The epilayer surrounded by the straight stacking faults, which had formed in the same direction, became the columnar structure.

• Polymer(Korea)
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• 제27권5호
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• pp.493-501
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• 2003

Poly(methyl methacrylate) (PMMA) particles, denture base resin, were synthesized by suspension polymerization through control of polymerization conditions (stabilizer concentration, co-monomer concentration, and the agitation speed) and evaluated changes in molecular weight and particle size. We also investigated their mechanical properties of compression-molded samples which were from synthesized polymer powder mixed with methyl methacrylate (MMA) solution. under the condition of volumetric ratio as 2:1(PMMA powder and MMA solution). The results shows that the mechanical properties were mainly affected by particle size over 100 ${\mu}$m (in particle size) and by molecular weight under 100 ${\mu}$m (in particle size). From these results, we concluded that the most appropriate particle size of PMMA powder for heat-cured denture base resins is around 100 ${\mu}$m. and its molecular weight is around 300000 (M$\sub$n/).

• Fire Science and Engineering
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• 제31권6호
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• pp.83-90
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• 2017

If an overcurrent exceeding the rated value is applied to an electric wire, the temperature of the electric wire increases, and the electric wire covering deteriorates to cause a short circuit. The upper limit temperature of the wire varies according to the magnitude of the overcurrent. When a short circuit occurs at each upper temperature limit, a cooling speed difference occurs during the solidification process due to the temperature difference between the short circuit temperature and the wire surface temperature. At this time, the pattern characteristics of the dendritic structure formed on the molten cross section are different. In this study, the upper temperature limit, which varied according to the overcurrent magnitude, was measured. At the time a short circuit occurred, the second branch spacing (dendrite Arm Spacing : DAS) of the dendrite was analyzed and the numerical value was quantified. The experimental results showed that the upper temperature limit increases with the magnitude of the overcurrent, and that the second branch spacing increases with increasing wire temperature.

• Korean Journal of Plant Taxonomy
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• 제44권2호
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• pp.91-99
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• 2014

Leaf anatomical study of Pinus thunbergii collected from 12 different coastal regions of Korea was conducted to understand the adaptive variation on leaf traits. Basic anatomical features are typical pine needle type with fibrous epidermis, 2-3 layered hypodermis, sunken stomata, monomorphic mesophyll, and well-represented bundle sheath. The bundle sheath surrounds a couple of vascular bundle separated by parenchyma bands. On the basis of their position, the resin ducts are of three types; external, medial and internal of the bundle sheath. The total number of resin ducts in all samples varies from 4 to 12. The stomata were found on stomatal bands throughout the leaf surface. Important dissimilarities observed on P. thunburgii leaf are the number and position of resin ducts and the number of stomata rows in leaf surface.

• Proceedings of the ESK Conference
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• 대한인간공학회 1993년도 추계학술대회논문집
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• pp.33-37
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• 1993

근래 우리나라에서도 평균수명이 길어져 노동의욕이 있는 중고령자가 증가하는 한편, 출산율이저 하되어 젊은 근로자의 수가 감소되고 있다. 통계청의 인구통계과의 추계에 의하면 2000년에는 60세 이 상이 총인구에 점하는 비율이 10.7%, 65세 이상은 6.8%가 되고, 2020년에는 60세 이상이 19.5%, 65세 이 상도 12.5%에 도달한다는 것이다. 인구노령화로 인한 고령화 사회에 대한 준비를 서둘러야 할 때라고 생각된다. 또 고령화 사회로 되면 젊은 연령층의 경제적 부담이 증가되므로 중고령자의 노동인구를 이대 로 방치해 두는 것은 국가적으로나 사회복지적으로나 불경제라고 할 수 있다. 그런데, 문제가 되는 것은, 중고령자를 취업시키는 것이 오히려 사회의 생산성을 저하시키거나 경제적으로 불리하게 되어서는 안되는 것과 중고령노동자 자신의 안전을 확보해야 하는 것이다. 이러한 문제를 해결하기 위해서는 고용에 있어 서 어떠한 점에서 중고령노동자에게 특징과 문제가 있는가를 분명히 할 필요가 있다. 고령자는 청년자 보다 노동능력이 떨어지는 특징과 문제가 있는가를 분명히 할 필요가 있다. 고령자는 청년자 보다 노동능력이 떨어지는 경향이 있지만 개인차도 크고 고령자 중에는 청년자의 기능에 비교해도 뒤떨어지지 않는 자도 있다. 연령만으로 노동능력을 판정하는 것은 적절한 방법이라고 할 수 없다. 문헌에 의하면 역연령(chornological age)이 25세의 경우, 생리적 연령은 23세에서 27세로 4년 차이가 있다고 한다. 이러한 생리적 연령의 차이는 역연령이 더해감에 따라서 점차 크게 되어 역연령이 45세에서는 12년, 80세 에서는 20년이나 된다는 것이다. 이것은 인간에 있어서 시간적 경과를 나타내는 역연령 이외에 신체적 기능연령(functional age)가 있다는 것을 의미하는 것이다. 한편, 생산현장에서는 자동화, 기계화가 진보되어 육체적인 노동이 경감된 결과, 중고령자라도 할 수 있는 작업이 많아지고 있다. 또, VDT (Visual Dislay Terminal) 작업과 같은 정보처리 작업의 수요가 증가하여 그 인재의 부족이 지적되고 있다. 따라서 중고령자의 기능을 조사하여 어떠한 작업에 적합한가를 판단하는 것이 중요한 과제로 되었다. 그러나 노동에는 많은 기능이 관여 하고, 그 내용에 따라서 요구되는 기능이 서로 다르기 때문에 노동적응능력의 기본적인 기능으로 보여지는 것에 좁혀서 작업능력의 연령증가 변화에 대하여다원적 평가를 하는 것이 실제적이라고 할 수 있다. 따라서 본 연구에서는 인간이 가지고 있는 다수의 기능중에서 수지교 치성과 연령증가와의 관계를 조사한다. 만약 연령증가 만으로 수지교치성을 평가 할 수 없는 경우에는 어떠한 요인이 수지기민성의 변화에 영향을 미치는가를 검토한다.