• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.3
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• pp.44-51
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• 2004

오늘날 대부분의 에너지를 전기에 의존함에 따라 전력사용이 급증하고 부하가 대용량화되어 및 정적 전력공급이 중요한 문제로 대두되었다. 이러한 추세에 따라 송ㆍ배전 설비도 점차 대용량화 및 고전압화 되고 신뢰성을 요구하게 되며, 각종 배전 설비의 제조기술이 더욱 복합 다양하게 발전하고 있다. 그 중 전력계통에서 뇌 혹은 개폐서지 등의 과전압을 흡수ㆍ억제하여, 전력설비와 계통보호를 위해 설치하는 것이 피뢰기이다. 따라서 어떻게 과전압을 낮게 억제할 수 있을까 하는 것이 피뢰기의 가장 중요한 성능이라고 말할 수 있다. (중략)

• Applied Chemistry for Engineering
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• v.23 no.2
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• pp.210-216
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• 2012

For the recycling of rapid-cooled steel slag, various specimens were prepared with the various replacement ratios of the rapid-cooled steel slag and the addition ratios of polymer binders. The physical properties of these specimens were then investigated by absorption test, compressive strength test, flexural strength test and hot water resistance test, and the pore and the micro-structure analysis was performed using scanning electron microscope. Results showed that the flexural strength increased with the increase of rapid-cooled steel slag and polymer binder, but the compressive strength showed a maximum strength at a certain proportion. By the hot water resistance test, compressive strength and flexural strength decreased remarkably and the total pore volume increased but the pore diameter decreased. SEM observation of the structure before the hot water resistance test revealed a very compact infusion of structure but the decomposition or thermal degradation appeared in polymer binders when observed after the hot water resistance test.

• Polymer(Korea)
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• v.30 no.1
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• pp.50-55
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• 2006

When the monodisperse polystyrene(PS)/HDDA polymer particles were synthesized via one-step polymerization using polystyrene seed particles by dispersion polymerization, the effects of 1) the molecular weight of seed polymer particles, 2) the ratio of the absorbed HDDA to the seed polymer particles (swelling ratio) and 3) seeded polymerization rate on the surface morphology of PS/HDDA polymer particles were investigated. It was observed that the creation of the crater shaped defect on the surface of PS/HDDA polymer particles was irrespective of the molecular weight of seed polymer ant swelling ratio. But its surface morphology could be controlled by the change of the seeded polymerization rate.

• Ecology and Resilient Infrastructure
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• v.5 no.3
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• pp.163-173
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• 2018

The biopolymer (BP) used in this study is mainly composed of xanthan gum and ${\beta}$-glucan derived from microorganism and has been introduced as a novel material for soil stabilization. However, the broad applicability of BP has been suggested in the field of geotechnical engineering while little information is available about the effects of BP on the vegetation. The goal of this study is to find the BP effects on the growth of Camelina sativa L. (Camelina) under drought condition. For more thorough evaluation of BP effects on the plant growth, we examined not only morphological but also physiological traits and gene expression patterns. After 25 days of drought treatment from germination in the soil amended with 0, 0.25, 0.5, and 1% BP, we observed that the BP concentration was strongly correlated the growth of Camelina. When plants were grown under drought stress, Camelina in 0.5% BP mixture showed better physiological parameters of the leaf stomatal conductance, electrolyte leakage and relative water content compared to those in control soil without BP. Plant recovery rate after re-watering was higher and the development of lateral root was lower in BP amended soil. RNA expression of Camelina leaf treated with/without drought for 7 and 10 days showed that aquaporin genes transporting solutes at bio-membrane, CsPIP1;4, 2;1, 2;6 and TIP1;2, 2;1, were induced more in the plants with BP amendment and drought treatment. These results suggest that the soil amended with BP has a positive effect on the transport of nutrients and waters into Camelina by improving water retention in soil under drought condition.

• Applied Chemistry for Engineering
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• v.19 no.6
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• pp.652-660
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• 2008

For the recycling of rapid-chilled steel slag, the mechanical strengths and physical properties of EVA-polymer modified mortars with the various replacement ratios of rapid-chilled steel slag were investigated. Twenty five specimens of polymer modified mortars were prepared with the five different amounts of EVA-polymer modifier (0, 5, 10, 15, 20 wt%) and rapid-chilled steel slag (0, 25, 50, 75, 100 wt%). For the investigation of the characteristics of polymer modified mortars, the measurements such as water-cement ratio, unit volume weight, air content for fresh mortar and compressive strength, flexural strength, water absorption, hot water resistance, porosity and SEM investigation for curing specimens were conducted. As a results, with an increase in the replacement ratio of rapid-chilled steel slag, water-cement ratios decreased but unit volume weight increased remarkably. With increasing EVA-polymer modifier and the replacement ratio of rapid-chilled steel slag, percent of water absorption decreased but compressive and flexural strengths increased remarkably. By the hot water resistance test, mechanical strengths decreased but total pore volume and porosity increased remarkably. In the SEM observation, the components of specimen were shown to stick to each other in the form of co-matrix phase before hot water resistance test, but polymer modifier of co-matrix phase was decomposed or deteriorated after hot water resistance test.

• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.181-187
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• 2014

In order to use the spherical atomizing reduction steel slag (ladle furnace slag, LFS) instead of the fine aggregate of polymer concrete composites, various specimens were prepared with various replacement ratios of atomizing reduction steel slag and the addition ratios of polymer binder. Physical properties of these specimens were investigated through the absorption test, the compressive strength test, the flexural strength test, the hot water resistance test, the pore analysis and the micro-structure using scanning electron microscope. Results showed that the compressive strength and flexural strength of specimens with 7.5% of polymer binders increased with the increase of replacement ratios of atomizing reduction steel slag, but those of the specimens with 8.0% or more of polymer binders showed a maximum strength at a certain replacement ratio due to the material segregation causing the increase of fluidity. By hot water resistance tests, the compressive strength, flexural strength, average pore diameter, and bulk density decreased but the total pore volume and pore diameter increased. It was concluded that the amount of polymer binders could be reduced by maximum 23.8%, because the workability of the polymer concrete was remarkably improved by using the atomizing reduction steel slag instead of fine aggregate. However, since the use of atomizing reduction steel slag decreased the resistance of the polymer concrete to hot water, further studies are required.

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.477-484
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• 2004

As a part of durability improvement of concrete-structure, penetrating water repellency of liquid type is applied to concrete surface. Besides, a related standard is made recently, but the standard has been prescribe for initial settlement state of penetrating water repellency of liquid type, to the exclusion of performance variation depending time and outdoor environment factor. For measurement of performance variation, we measured the weight of outdoor exposure specimen every regular intervals and check a measured value against a measured value of different condition specimen. Moreover, after the application of penetrating water repellent, measured a adhesive strength in tension between cement-polymer modified waterproof coatings and surface of specimen. The applied penetrating water repellent is a emulsified silicon type with a deep penetration depth. In view of the results so far achieved, the more a Quantity of application and active solid content does get, the deeper penetrating water repellency of emulsion type Penetrate get longer and supplied moisture increase in quantity, a penetrating water repellency of liquid type penetrates more deep, but a quantity of water absorption increase gradually. Perhaps this result is caused by a reduction of active solid content on concrete surface, because active ingredient is moved into the concrete by dissolution.

• Polymer(Korea)
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• v.38 no.6
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• pp.760-766
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• 2014

Bead type super-absorbent resins to be used for release-control were prepared by modification of the inverse suspension polymerization, and their physical properties were characterized. Acrylic acid and acrylamide were used as monomers, and N,N-methylenebisacrylamide was used as crosslinker, controlling the viscosity of monomer solution by adding hydroxyethylcellulose (HEC). SEM studies of the synthesized beads verified that the bead surfaces had many pores with their diameters of several tens nm. The bead sizes were in the range of $500{\sim}3000{\mu}m$, depending on the viscosity of the monomer solution. Both absorbent amount and absorbent rate of the beads were inversely proportional to the bead size, and the maximum water absorbent amount of 1 g beads was determined to be ca. 170~200 g for 5 hrs. The absorbent rate was also dependent on pH change of the aqueous solution, exhibiting the maximum rate in pH ranging from 5 to 11. The absorbent rate decreased as the concentration of salt (NaCl and $MgCl_2$) or ethanol and ethylene glycol increased. Release time of the water absorbed into the bead resins was 700 hrs, confirming the usefulness of the resin for the good release-control materials.

• Polymer(Korea)
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• v.33 no.1
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• pp.91-95
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• 2009

We fabricated the electromagnetic (EM) noise absorber films for high temperature use by blending a soft magnetic powder with poly(amide imide) (PAI). The EM noise absorber films of PAI/soft magnet composite were prepared by casting the solution of poly(amide amic acid)/soft magnet powder into glass substrate with casting applicator device and then thermal imidization. The obtained films were fully characterized and their physical properties including thermal behavior, thermal stability and mechanical properties were studied. The EM noise absorption ability was also investigated using micro-strip line method. At 1 GHz, the power loss of composite film with 150 ${\mu}m$ thickness was about 25%.

• Polymer(Korea)
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• v.28 no.6
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• pp.478-486
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• 2004

Small intestinal submucosa (SIS) is consisted with collagen and glycosaminoglycan as well as some growth factors which can stimulate cell activity. Recently, it has been recognized that SIS has been successfully examined in the bio-medical application as biomaterials without xenograft immune-rejection response. We prepared native SIS sheets and acid treated SIS sheets by acetic acid with 1 or 5-layered sheets, respectively. The water uptake ability of native and acid treated SIS sheets was examined to evaluate the possibility as wound dressings. Morphologies of SIS sheets were characterized by SEM and the effects of various buffer solutions and different pH solutions on the water uptake ability were observed for 16 days. We observed that the acid treated SIS sheets had higher water uptake ability than native SIS sheets. Also, the water uptake ability of these was slightly higher in various buffers than distilled water. In conclusion, this study suggests that native and acid treated SIS sheets could be useful for the applications of wound dressing and biodegradable injectable materials.