• Journal of the Korean Institute of Gas
• /
• v.20 no.6
• /
• pp.16-22
• /
• 2016

Coating pipe(PLP) has been generally used in buried site for protecting the corrosion. To prevent the damage by occurring the defect, other construction or execution works, an anti-oxidation environment was forcibly made by using protective potential. Coating and protective potential are applied simultaneously, but corrosion rate or defects are not easy to observe because soil composition has many uncertainty. Also, defect of coating pipe can not be directly observed. A corrosion coupon can easily measure a corrosion rate directly. The corrosion rate was measured with 6 scenarios using corrosion coupon during about 1 year(6 scenarios are based on soil type and protective potential or not in this research. Resultingly, the corrosion coupon has not occurred in the case of protected by potential current, but corrosion has occurred in a non-protected site. The corrosion rate was measured at least in the clay, and the propensity of corrosion rate was similar in other soil(sand and loams). The local corrosion has occurred in the clay because of high water content. On the other hand, general corrosion was occurred in sand and loams. Commonly, sand is not to corrosive soil. Although, corrosion occurred in sand can be estimated by chemical component and valid with chemical analysis report.

• Journal of Navigation and Port Research
• /
• v.35 no.5
• /
• pp.393-400
• /
• 2011

The residential complexes in waterfront provide the residents with pleasantness and comfort with their scenety and view in the surrounding watersides. However, it is currently true that there has little been established any designing plan utilizing the environmental characteristics of the waterfront. In this study, a survey was conducted on the residents of a Japanese waterfront. in Nishimiyahama and Lake Biwa, and conducted a comparative and analytic investigation regarding water-friendly activities, residents' consciousness of the housing environment, and reasons for the choice of residenve. From the results, we were able to obtain some suggestive points resulting from the differences of the aforementioned. We also fully comprehended that there are some issues and needs for solution for the environmental characteristics in the waterfront as well as for the damage incurred by salt breeze and insects. In addition, we realized that scenery and view toward watersides are becoming the important factors in the residents' consciousness regarding the housing environment. In case of planning housing complexes located in the waterfront, we keenly understood that "the size of a room", "ventilation", "view and daily lighting", and "securing privacy" are having effects on the residents' consciousness of their housing.

• Resources Recycling
• /
• v.29 no.2
• /
• pp.8-17
• /
• 2020

In this study, adsorption and desorption characteristics of pulverized waste paper-mulberry pellet and bast fiber were measured to confirm the applicability to humidity control products. Paper-mulberry powder was classified by 710-355㎛, 355-100㎛, 100-45㎛ and less than 45㎛ and used in experiment. Specific surface area increased from 1.02㎡/g to 1.35㎡/g as the particle size decreased from 710㎛ to under 45㎛. Adsorption and desorption performance decreased in the order of 355-100㎛, 710-355㎛, 100-45㎛, less than 45㎛ and bast fiber, adsorption content on each particle sizes were 141.1g/㎡, 147.1g/㎡, 135.7g/㎡, 129.0g/㎡ and desorption content were 117.2g/㎡, 123.6g/㎡, 110.2g/㎡, 93.3g/㎡. As a result, adsorption and desorption performance of paper-mulberry powder were superior to those of the bast fiber and these phenomenon can be considered that it caused by pore distribution in pellet and damage of fiber.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.6
• /
• pp.97-104
• /
• 2018

In recent years, more than 5,000 tons of sargassum honeri have been infested in the southern coast and the coast of Jeju Island, causing serious damage to the farms and fisheries, and environmental problems. The alginate contained in the sargassum honeri is a natural polymeric substance mainly used for medicines and foods. However, since there is no way to utilize it in large quantities, a study was carried out to utilize bio polymer obtained from sargassum honeri in producing polymer mortar for repairing deteriorated infrastructures. From the tests of setting time, it was found that the L0BP12 mixture containing 12% of bio polymer increased the setting time by 20% as compared with the L12BP0 mixture using only synthetic polymer. From the tests of water absorbtion, the LOBP12 combination decreased by 0.36% compared to Plain-URHC using ultra rapid hardening cement. This indicated that the watertightness of the mortar was increased by the incorporation of the bio polymer. In the compressive and flexural strength tests, the strength decreased as the amount of bio polymer increased. The incorporation rate of the maximum bio polymer satisfying the KS F 4042 standard was determined to be 12%. In addition, the bond strength of the mortar produced with biopolymer was higher than that of Plain-URHC specimens, and it was confirmed that incorporation of bio polymer improves bond strength of mortar.

• Journal of Conservation Science
• /
• v.34 no.1
• /
• pp.11-21
• /
• 2018

The result of the study on the origin and preservation status of the 'Gongju Junghakdong old missionary house', the Registered Cultural Property No. 233, reveals that the building was approved on October 23, 1921, and missionary Alice H. Sharp was living in the building until her retirement from her missionary life of 39 years in Korea in 1939. In order to review internal and external preservation status of the building, condition of wood material, the composition of the window, the damage of the wall, and the leaning of the building were examined. In particular, in the case of window facilities, it is necessary to restore it to the original upper and lower sliding window. As a result of investigation of the preservation status of the external facilities, it is necessary to restore the original shape of the staircase and a deck of the building on south western side and the well. In addition, the results of the non-destructive diagnosis of the ground revealed that the building was built on uneven surface layer of 2-5 m thickness and the boundary between the surface layer and the upper part of the weathered rock is inclined following geomorphology. This phenomenon shows that when the water content of the ground increases in the rainy season, the bearing capacity of the ground is lowered, and there is a possibility of uneven subsidence. Especially, landslides may occur in case of heavy rain. Therefore, it is desirable to install a masonry facility at the southwest boundary of the site, and it is recommended to install a drainage facility to ensure rapid drainage.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.23 no.3
• /
• pp.215-225
• /
• 2011

During the past decade, the performance-based design method of caisson breakwaters has been developed, which allows a certain damage while maintaining the function of the structure. However, the existing method does not consider the changing coastal environment due to climate change impacts so that the stability of the structure is not guaranteed over the lifetime of the structure. In this paper, a time-dependent performance-based design method is developed, which is able to estimate the expected sliding distance and the probability of failure of a caisson breakwater considering the influence of sea level rise and wave height increase due to climate change. Especially, time-dependent probability of failure is calculated by considering the sea level rise and wave height increase as a function of time. The developed method was applied to the East Breakwater of the Hitachinaka Port which is located on the east coast of Japan. It was shown that the influence of wave height increase is much greater than that of sea level rise, because the magnitude of sea level rise is negligibly small compared with the water depth at the breakwater site. Moreover, investigation was made for the change of caisson width due to climate change impacts, which is the main concern of harbor engineers. The longer the structure lifetime, the greater was the increase of caisson width. The required increase of caisson width of the Hitachinaka breakwater whose width is 22 m at present was about 0.5 m and 1.5 m respectively for parabolic and linear wave height increase due to climate change.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.6 no.2
• /
• pp.3-15
• /
• 2003

Recently more than 450 incidents of oil spill a year have occurred in nearshore of Korea, which caused unmeasurelable losses in fisheries and severe damage in marine ecosystem. Two approaches remain paramount in any response to marine oil spill : the enhancement of natural dispersion of the oil by using dispersants, and mechanical recovery using booms and skimmers. A technique currently receiving fresh attention is the enhancement of the natural bioremediation of oil through the application of micro-organisms and/or nutrient. Oil, like many natural substances, will biodegrade over a period of time into simple compounds such as carbon dioxide, water and biomass. Bioremediation is the term used to describe a range of processes which can be used to accelerate natural biodegradation. More specifically biostimulation is the application of nutrients, and bioaugremetation or seeding is the addition of microbes specially selected to degrade oil. Bioremediation is an economically attractive method for the clean-up of oil-contaminated area. Bioremediation has been demonstrated to be an effective oil spill countermeasure for use in cobble, sand beach, salt marsh, and mud flat environment.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.15 no.2
• /
• pp.493-500
• /
• 2011

Recently, there has been an increase in the number of disaster victims locally due to climate change and a variety of frequently occurring natural disasters. The damage caused by abrupt weather change in local area by typical weather forecasting techniques is very limited and difficult. Recently local area weather monitoring system using wireless sensor network technology has been very actively studied. Thus an IEEE 802.15.4-based weather field server to measure and monitor the local weather changes was designed and developed in this study. The proposed weather field server utilizes a wireless sensor node and weather sensors to collect weather information such as temperature, humidity, illumination, dew point, barometric pressure, and water level. The integrated weather sensor board was designed to respond quickly to weather changes, and provide feedback to the server PC. Each weather information is analyzed in the server PC to establish a program to monitor and analyze the local area or the area of abrupt climate change in order to provide warning signals in case of disaster events in local.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.2
• /
• pp.1500-1506
• /
• 2015

The headcut erosion at the confluence section of a mainstream and tributary can migrate up the tributary streams, and rapid degradation can threaten the stability of hydraulic structures installed in the channel. Therefore, quantitative analysis for the development and mechanism of headcut erosion is needed to prevent damage due to the headcut. In this study, hydraulic experiments for headcut erosion in the channel with noncohesive materials were performed and the knickpoint movement and final bed slope change were analyzed based on the different hydraulic conditions. As a result, the knickpoint movement was 1.5 times faster when the difference in velocity between the upstream and downstream sections was 2.5 times greater and the central part of the cross-section was eroded and collapsed earlier than the left and right sides. The movement length of headcut erosion was longer and the final bed slope was milder as the velocity difference between the upstream and downstream sections was increased. This study showed that a correlation between the knickpoint movement and bed slope change by headcut erosion and the water level difference of upstream and downstream sections was not constant compared to the velocity difference.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.20 no.4
• /
• pp.136-143
• /
• 2016

There are various method for evaluating the durability life of concrete structures due to salt damage. The best way is to perform a corrosion test for a rebar embedded in concrete specimen was exposure to marine environment. However, this method has the disadvantage that it takes a long period of time. Also, accelerated corrosion test which was complemented complements the time-consuming weakness is limited to apply because it could not reveal a correlation between long-term exposure test. Accordingly, the purpose of this study is to derive a correlation coefficient between cycle drying-wetting accelerated corrosion test and long-term exposure test. Corrosion initiation time was measured in four types of concrete samples, i.e., two samples mixed with fly ash(FA) and blast furnace slag(BS), and the other two samples having two water/cement ratio(W/C = 0.6, 0.35) without admixture(OPC 60 and OPC 35). The accelerated corrosion test was carried out by two case, i.e., one is a cyclic drying-wetting method(case 1), and the other is a artificial seawater ponding test method(case 2). Whether corrosion occurs, it was measures using half-cell potential method. The results indicated that case 1 is to accelerated the corrosion of rebar about 24~36% as compared with case 2, then the corrosion of rebar embedded in concrete occurred according to the order of OPC60, FA, BS, OPC35. Correlation coefficient between accelerated corrosion test and long-term exposure test, case 1 is 4.23 to 5.42, and case 2 is 6.54 to 7.82.