• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.5
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• pp.90-98
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• 2007

The objective of this investigation was to reveal the cause of the faulted cable(LV URD(low voltage underground) cable). For the analysis, various types or equipments such as external pattern, thermal pattern, surface structure, thermal analysis, and property distribution were deployed. The international standards and the specification provided by the manufacturer of faulted cable were examined whether it fit the standards. The summary is as follows. (1) Discovered as a factor lowering insulation performance of the faulted cable: minimum thickness of the insulation layer specified by IEC 60502-1 and IEC 60811-1-1 was not fit. (2) Infrared absorption peaks measured by FT-IR spectrometer revealed that the measurements made for the same material did not conform and it is an important basis for proving heterogeneous composition of the insulation material. (3) It was found that PVC bedding was thermally fragile and therefore long term exposure at the site could cause similar fault pattern.

• Proceedings of the KAIS Fall Conference
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• 2010.11a
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• pp.28-31
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• 2010

충청남도 서해안은 생태환경의 보고로서 갯벌, 사구, 해안습지 등 독특한 자연적 특성을 갖고 있는 지역이다. 그러나 다른 지역에 비해 대규모 간척 및 매립으로 인한 해양생태계 피해에 현저히 노출되어 있고, 최근 산업화 및 관광권화가 진행되고 있으며 해안선 침식 방지를 위한 연안정비사업으로 각종 연안 방호구조물이 건설되었다. 이 중 가장 많이 건설된 연안 호안구조물은 배후지역의 안정성 확보, 해안도로의 건설 등 다양한 목적으로 축조되었다. 그러나 성장위주의 경제정책으로 연안 호안구조물이 무분별하게 설치되어 파도와 호안 구조물의 접촉 시 호안구조물이 파랑을 견디지 못해 사면피복재가 산란되어 외관상 주변 환경을 해칠 뿐만아니라 2차 피해까지 야기 시킬 우려가 있다. 본 연구에서는 호안구조물의 리모델링을 통해 안정성을 증대시키기 위해 서해 연안지역의 4개 시 군 29개 지점을 대상으로 호안구조물 현황에 대해 조사하고 호안구조물의 리모델링을 통해 붕괴된 지역을 대상으로 파랑에 대해 안정한 사석재 소요질량을 호안구조물의 경사 별로 산정하여 비교하였다. 피복재 소요질량 산정을 위한 설계파고는 유의파고를 적용하였으며, 산정공식은 허드슨공식(Hudson, 1959)을 사용하였다. 추가적으로 사석 층의 두께와 단위면적당 수용해야할 사석재의 개수를 산정하여 호안구조물 설계 시 사석재의 배치를 용이하게 할 수 있도록 하였다. 본 연구에서 산정된 값들은 초기설계로서 파랑에 안정한 호안구조물의 설계 조건 중 일부분으로 호안구조물의 최종 설계 시 조파실험을 통하여 안정성을 검증 해야 할 것으로 판단된다.

• Tunnel and Underground Space
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• v.26 no.5
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• pp.441-453
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• 2016

This study aimed to develop a two-component TSL suitable for reducing dust and guaranteeing homogeneous qualities during its spraying. Its performance was evaluated by a series of laboratory and field tests. High ductility of two-component TSL prototypes resulted in increasing their elongation at break even though their tensile strengths were slightly lower than those of one-component powder TSLs. One prototype of the two-component TSLs developed in this study was verified to satisfy every criterion specified by EFNARC (2008). Especially, it increased the average compressive strength of mortar specimens by 50% even when it coated them only with the thickness of 3 mm. From a preliminary spraying test, a spraying machine suitable for the developed TSL prototype was derived and modified. After its field application, dust and rebound generated during its spraying works were found to be very minimal. Its spraying rate was recorded to be approximately $60m^2/hr$. In addition, it showed a very rapid hardening characteristic compared with general sprayable waterproofing membranes.

• Journal of the Korea Concrete Institute
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• v.22 no.6
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• pp.753-760
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• 2010

Ultra high performance concrete (UHPC), is characterized by its high compressive strength and advanced tensile behavior that is much superior to those of conventional concrete. In order to apply this new material in practice, the bond characteristics of UHPC were evaluated in this study. Pull-out tests between UHPC and deformed steel rebar were carried out according to the modified RILEM test method, and were verified by finite element analysis. From the test results showed that UHPC presents 5 to 10 times higher bond strength compared to normal strength concrete, this study suggested remarkably reduced development length and concrete cover comparing to existing specifications. The test results of 700 MPa high strength steel rebar demonstrated the applicability of high strength steel to UHPC. In addition, the transfer length measurements of seven-wire strand in UHPC specimens indicated that the transfer length limit set by the current design code is very conservative for UHPC.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.299-306
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• 2014

Coating is one of the methods used to solve the problem of corrosion of reinforcement in concrete structures. There are few research reported in the literature regarding the effect of zinc-coating on flexural behavior compared to epoxy coating. The objective of this study was to determine whether zinc-coated rebar adversely affects flexural behavior. Concrete beams reinforced with black or zinc-coated steel were tested in flexure. The test variables included the presence of rebar surface coating with zinc, steel ratio used and cover depth. The study concentrated on comparing crack pattern, crack width, deflection and strain. The ultimate flexural capacity of beams reinforced with zinc-coated bars was not different from that of black steel reinforced beams. The results from deflection and crack width measurements were indicative of no significant variation for the different rebar surface conditions. In addition, it was found that load-strain curve of beam reinforced with zinc-coated steel was similar to that of beam reinforced with zinc-coated steel. Therefore, the test results indicated that the use of zinc-coated rebar had no adverse effect on flexural behavior compared to the use of black rebar.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.935-940
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• 2008

When reinforced concrete is subjected to high temperature as in fire, there is deterioration in its properties of particular importance are loss in compressive strength, cracking and spalling of concrete, destruction of the bond between the cement paste and the aggregates and the gradual deterioration of the hardend cement paste. Assessment of fire-damaged concrete usually starts with visual observation of color change, cracking and spalling of the surface. In this paper, it was reported the trends of research and practical use on the Explosive Spalling Properties and Performance Based of Structural Design of the High-Strength Concrete.

• Journal of the Korean earth science society
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• v.25 no.8
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• pp.764-773
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• 2004

The soil in wildfire area Sacheon-myeon, Gangneung, Gangweon Province, Korea, were investigated to clarify pattern of the soils. The soils were classified into 5 types on the basis of vegetation, types of organic matter. thickness of soil horizons, and completeness of soil profile. Each type showed different erosion pattern and Landsat ETM image. Coverage of plant leaves, litter, root, ash and other organic matter was an important component that affected soil color and reflectance of Landsat image (digital number). Although the NDVI (Normalized Distribution Vegetation Index) method in the wildfire area did not show much difference in soil types, the applied supervised classification method showed characteristic pattern of Landsat ETM image of soil types. This study showed that the applied supervised Landsat TM image classification in wildfire area is an effective way to estimate the distribution of erosion pattern of soil in wildfire area.

• Journal of Bio-Environment Control
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• v.19 no.4
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• pp.372-376
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• 2010

In recent years, the bagging cultivation of summer squash (Cucurbita moschata) is applied for surface protection during harvest and extension of storage period. In this study, the effect of plastic bagging cultivation of summer squash on improvement of quality and extension of storage period was investigated. The yield and the length of fruit didn't have no difference between bagging and control treatment but the bagging treatment significantly made more regular size and light weight of fruits, and increased the number of fruits because of the limitation of their growth. The bagging treatment decreased weight loss and fruit softening during the their storage. Therefore it showed effective means for quality improvement and storage extension of summer squash.

• Journal of Korean Society of Steel Construction
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• v.18 no.5
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• pp.643-654
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• 2006

Thispaper presents the results of an experimental investigation into the fire performances ofsimply supported iTECH composite beams using an ISO834 standard fire. There are very few independent studies on the fire resistance of composite steel and concrete structures of various designs. The iTECH composite beam system has been used in construction, but nothing is known about its influence in a fire. To evaluate the fire resistance performanceof the iTECH beam, a test was conducted for 4.7m-span-length iTECH beams under given conditions in a laboratory. The fire resistance performance of unprotected coatings of the iTECH beam has been examined, and a longer period of fire resistance was achieved by increasing the beam coating's section size and decreasing its load ratio. Coatings for the fire protection of iTECH beams reduce the rate of temperature rise of the beam in case of fire, and the required thickness of spray-on fire protection coatings can be determined by means of tests.

• Korean Journal of Materials Research
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• v.9 no.5
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• pp.452-459
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• 1999

To develop advanced cladding materials, the effect of Nb addition on the microstructure and corrosion characteristics of Zr-0.8Sn-xNb alloys was investigated. As the Nb content increased, the grain size decreased and the volume fraction of precipitates increased. It was observed from the corrosion test at $360^{\circ}C$ that the corrosion resistance increased with decreasing Nb content. The best corrosion resistance was obtained in Zr-0.8Sn-0.2Nb alloy with high volume fraction of tetra-$ZrO_2$in the oxide. Therefore, it is suggested that Nb in theZr-0.85Sn-xNb system should be added within the solubility limit of Nb from the viewpoint of alloy design.