• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.56-61
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• 2012

The most common deterioration cause of concrete structures over the world is chloride ions attacks. Thus, service life modeling of concrete is a crucial issue in civil engineering society. Many studies on the durability of concrete have been accomplished, however, it is not easy to review literatures about environmental analysis. Since the durability of concrete depends on the properties of the surface concrete. micro-climatic condition which influences on surface concrete realistically should be considered. This study is devoted to analysis the micro-climatic condition of concrete structures, based on the in-situ monitoring of weather in marine environment. The effect of degree of saturation on chloride diffusivity of concrete is also examined. It is expected that the result of this work should be available for the prediction of chloride profile of marine concrete.

• Advances in concrete construction
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• v.12 no.5
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• pp.411-418
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• 2021

Roller compacted concrete (RCC) used in the island reef airport runway will be subjected to the coupling actions of the fatigue impacts and the salt spray cycles, which will accelerate the deterioration of runway concrete and even threaten the flight safety. A cyclic impact testing machine and a climatic chamber were used to simulate the low-velocity fatigue impact and the salt spray cycles, respectively. The physical properties, the microstructures and the porosity of RCC were investigated. The results show the flexural strength firstly increases and then decreases with the increase of the fatigue impacts and the salt spray cycles. However, the decrease in the flexural strength is significantly earlier than the compressive strength of RCC only subjected to the salt spray cycles. The chlorine, sulfur and magnesium elements significantly increase in the pores of RCC subjected to 30000 fatigue impacts and 300 salt spray cycles, which causes the decrease in the porosity of RCC. The coupling effects of the fatigue impacts and the salt spray cycles in the later period accelerates the deterioration of RCC.

• Journal of the Korean earth science society
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• v.31 no.7
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• pp.698-707
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• 2010

The Late Pleistocene pollen record from the Poil-dong, Uiwang, Kyunggi-do, reveals that mixed coniferous and deciduous broadleaved forests were spread along with herb and fern understory. Palynofloral changes reflect climate fluctuations. From ca. 43,100 to 41,900 cal. yr BP, a mixed coniferous and deciduous broadleaved forest combined with open grassland occupied the study area, which indicates cooler condition than today. During the period of ca. 41,900-41,200 cal. yr BP, along with fern understory a decrease in subalpine conifers and an increase in temperate deciduous broadleaved trees suggest a climatic amelioration. A climatic deterioration, as evidenced by an increase in subalpine conifers and a decrease in the density of vegetation cover, occurred from ca. 41,200 to 39,700 cal. yr BP.

• Journal of Conservation Science
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• v.25 no.2
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• pp.179-196
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• 2009

The Gaetaesajiseokbulibsang (Treasure No. 219) consists of light gray and coarse to medium-grained granodiorite with feldspar phenocrysts in part. Magnetic susceptibility of the rock material was measured as 12.06(${\times}10^{-3}$ SI unit), being different from the granite($0.19{\times}10^{-3}$ SI unit) in the Mt. Cheonho. This indicates the raw material has been supplied from the outside. As a result of deterioration assessment, exfoliation of the Right Buddha, cement and dust of the Main Buddha were estimated as 35.2%, 21.1% and 25.0%. The ultrasonic velocity was measured as 2850.2m/s(Main Buddha), 2648.4m/s(Left Buddha) and 2644.5m/s(Right Buddha). The compressive strength calculated from the velocity showed low in the Right Buddha among three and the all pedestal parts which corresponds to the result of deterioration assessment. The indoor mean temperature and relative humidity of the shelter were $13.7^{\circ}C$ and 79.0%. It is evaluated that the indoor microclimate was stable and the shelter functioned to reduce climatic fluctuation of the outdoor. However, water condensation was occurred on the surface of the pedestal part during spring and summer, and freezing in winter season might also be done. These factors were probable to be a main cause of the surface exfoliation of the Triad Buddha Statues. Therefore, dehumidification and heating system in the shelter should be applied to prevent further deterioration.

• Journal of Ecology and Environment
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• v.38 no.4
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• pp.437-442
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• 2015

Studies to estimate seed longevity and dormancy of creeping bentgrass (Agrostis stolonifera L.) were conducted from 2000 to 2005 at Corvallis and Hermiston, Oregon. Seeds from three transgenic glyphosate resistant creeping bentgrass lines, 48-10, 48-13, and ASR368, and one non-transgenic glyphosate susceptible line, SR1020, were used. Creeping bentgrass seeds were buried at 3, 18 and 31 cm in 2000 and removed 6, 12, 18, 24, and 51 months later. Soil type and climatic conditions were different at the two locations. At Corvallis, the soil was a Malabon silty clay loam, and the winters wet and mild. The soil at Hermiston was an Adkins fine sandy loam, and winters drier and colder. Seeds of all creeping bentgrass lines deteriorated faster at Corvallis than at Hermiston. The estimated half-lives of creeping bentgrass lines buried at Corvallis were 8.4 to 20.2 months, while those buried at Hermiston were 8.4 to 37.7 months. At both sites, seeds of the glyphosate resistant lines, 48-10 and 48-13, deteriorated faster than the susceptible line, SR1020. However, seed deterioration in the resistant line, ASR368, was slower than all other creeping bentgrass lines. Based on the germination test, exhumed intact seeds at Corvallis were more dormant than those at Hermiston. If buried, it could be expected that viable creeping bentgrass seeds will persist more than 4 years after the seeds are introduced to a site, but environmental conditions can influence both seed longevity and dormancy.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1037-1040
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• 2008

In order to predict the remaining life of marine concrete structures under climatic loads, it is necessary to develop an analytical approach to predict the time and space dependent deterioration of concrete structures due to mainly chloride attack up to corrosion initiation and additional deterioration like cracking of cover concrete. This study aims to introduce FEM model for life-time simulation of concrete structures subjected to chloride attack. In order to consider uncertainties in materials as well as environmental parameters for the prediction, Monte Carlo Simulation is integrated in that FEM modeling for reliability-based remaining service life prediction. The paper is organized as follows: firstly general scheme for reliability-based remaining service life of concrete structures is introduced, then the FEM models for chloride penetration, corrosion product expansion and cover cracking are briefly explained, finally an example is demonstrated and the effects of localization of chloride concentration and corrosion product expansion on service life using above model are discussed.

• Journal of the Korean Society of Industry Convergence
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• v.10 no.4
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• pp.207-211
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• 2007

The durable lifetime of RC structures is shortened by various reasons, which are the generation of cracks in construction and service term, the exterior deterioration according to climatic condition, the surface damage due to chloride attack and the corrosion of reinforced bars. The durability of concrete structures is nevertheless able to be increased by the method and the material of reinforcement and repair. The epoxy resin is widely used for reinforment and repair of concrete because of the superiority in mechanical property, adhesive property, abrasion resistance, impact resistance and chemical resistance. The epoxy cement mortar with hardening agent has a lot of disadvantages that are troublesome mixing work, weakened weatherability and high cost for hardening agent. In this study, the mix proportion of mortar is presented just only with epoxy resin and some admixtures, and the test result of mortar without hardening agent shows the higher strength than the mortar with hardening agent. In the mix proportion, the weight of epoxy resin must be less than 15% of the unit weight of cement, and 10% of unit weight of cement is adequate for the weight of admixtures.

• Proceedings of the Korean Society of Crop Science Conference
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• 2004.10a
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• pp.36-41
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• 2004

Postharvest handling of sweetpotatoes is inevitable procedure for the maintenance, storage, management and utilization of high fresh quality of storage roots. It ranges in degree from simple lifting of roots, carrying them from field to storage house and immediate consumption after cooking, to sophisticated methods of curing, and storage under controlled conditions followed by processing into a high quality food products. Postharvest saleability, quality and nutritional value of roots and the presence or absence in roots of bitter, toxic furanoterpenoid phytoalexins or mycotoxins depends greatly on the degree and types of treatment to which produce is subjected. Climatic and soil conditions before harvest and contamination or attack by microorganisms or insect pests in the field may initiate or enhance subsequent postharvest deterioration. Careless postharvest handling can lead to both quantitative and qualitative losses which may be extremely high in some circumstances. Research has concentrated on the improvement of preharvest conditions to increase yield and lower decrease rates. However, such efforts are wasted unless they go hand in hand with others designed to reduce the high degree of loss associated with careless postharvest handling.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.3
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• pp.239-244
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• 2020

This study examines the feasibility of the image deep learning method using convolution neural networks (CNNs) to maintain a porcelain insulator. Data augmentation is performed to prevent over-fitting, and the classification performance is evaluated by training the age, material, region, and pollution level of the insulator using image data in which the background and labelling are removed. Based on the results, it was difficult to predict the age, but it was possible to classify 76% of the materials, 60% of the pollution level, and more than 90% of the regions. From the results of this study, we identified the potential and limitations of the CNN classification for the four groups currently classified. However, it was possible to detect discoloration of the porcelain insulator resulting from physical, chemical, and climatic factors. Based on this, it will be possible to estimate the corrosion of the cap and discoloration of the porcelain caused by environmental deterioration, abnormal voltage, and lightning.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.1
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• pp.24-28
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• 2018

Insulators used in overhead transmission lines are continuously exposed to a number of mechanical and electrical stresses owing to external environmental factors, resulting in corrosion, reduction in durability, and deterioration. Widely used porcelain insulators are fabricated with cement and porcelain and are especially common in Korea. Changes in the hardness and chemical reactivity of the cement increase the leakage and fault currents and increase the possibility of flashover due to insulation breakdown. Therefore, it is important to evaluate the durability and defects of porcelain insulators. Studies on the reliability of various evaluation methods are needed to prevent accidents by accurately determining the replacement timing and potential defects in porcelain insulators. In this study, the hardness of the cement part of the porcelain insulator was measured using the Vickers hardness test and its composition was analyzed by energy dispersive spectroscopy and X-ray diffraction analysis. The performance of the insulators was compared in two different regions with varying climatic conditions. This study presents an evaluation method of the defects in porcelain insulators by measuring humidity, which can also be used to assess the reliability of the insulators.