• Geophysics and Geophysical Exploration
• /
• v.8 no.2
• /
• pp.177-183
• /
• 2005

The subject of this paper is research into the application of electrical resistivity monitoring to detecting the water leakage of water utilization facilities. For this purpose, we installed a comprehensive monitoring system consisting of resistivity measurement, inclinometer, piezometer, and water gauge at an embankment. Using this monitoring system, we monitored the various kinds of measurement data and compared the resistivity structures and that of hydrological and engineering data in order to investigate the water leakage and stability of the embankment. The variant images of electrical resistivity at the embankment were provided from the monitoring data and we could accurately locate the portion of which resistivities have sharply changed. Furthermore, we could estimate the stability of the embankment more effectively and quantitatively by jointly interpreting the monitoring data of resistivity, water level, pore water pressure, and subsurface displacement. The monitoring experiments in this study led us to the conclusion that for the efficient maintenance of the water utilization facilities, monitoring the resistivity data and hydrological data would be much more preferable to performing the just one-time measurements.

• Restorative Dentistry and Endodontics
• /
• v.17 no.1
• /
• pp.95-103
• /
• 1992

The purpose of this study was to evaluate the effect of the dentin pretreatment on the marginal leakage of a glassionomer cement. 1n this study, 60 molars with sound and healthy crown portion were used. The dentin surface of these teeth were exposed and polished with 600 grit silicon carbide paper. Square - shaped cavities were prepared on the flattened dentin surfaces and these were divided into 4 groups according to the dentin pretreatment procedures. Group I : Dentin pretreatment with distilled water as a control group. Group II : Dentin pretreatment with 5% sodium hypochlorite solution. Group III : Dentin pretreatment with Ketac conditioner. Group IV : Dentin pretreatment with 40% polyacrylic acid. The degrees of dye penetration in the cavity walls were assessed using a stereoscope at ${\times}40$ magnification according to the maximum dye penetration. The results were analyzed by using Mann - Whitney U test. The results were as follows : 1. All groups showed varying depth of dye penetration. 2. Distilled water group showed the most severe marginal leakage when compared with the other groups(P<0.05). 3. 40% polyacrylic acid group showed the least amount of marginal leakage compared with the other groups (P<0.05). 4. There were significant differences between Goup I(distilled water) and Group IV (40% polyacrylic acid)(P<0.05), but there were no significant differences among Group I(distilled water), Group II(sodium hypochlorite), Group III(Ketac conditioner) (P>0.05).

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2017.05a
• /
• pp.142-143
• /
• 2017

An analysis of the current water leak status of understand structure (underground parking lots, staircases, plumbing systems, water reservoirs, etc.) of multi-family housing in South Korea shows that water leaks are found from cracks in all areas of the underground structure caused by the degradation environment (water pressure by underground water, humidity, temperature, earth pressure, soil behaviour and vibration, etc.), which result in various problems, including mold, malodour, debonding of finishing materials, exfoliation, breakout, water leaks in electrical boxes, efflorescence, sedimentation of calcium hydroxide, decoloration, rusting, damages and pollution among others. Therefore, this study aims to analyse the current status of water leaks in underground structure and use the results as the basic data for developing a standard guideline for water leaks and maintenance by parts of the underground structure of multi-family housing.

• Journal of Magnetics
• /
• v.22 no.1
• /
• pp.34-42
• /
• 2017

Material defects in the Steam Generator Tubes (SGT) of sodium cooled fast breeder reactor (PFBR) can lead to leakage of water into sodium. The water and sodium reaction will lead to major accidents. Therefore, the examination of steam generator tubes for the early detection of defects is an important requirement for safety and economic considerations. In this work, the Magnetic Flux Leakage (MFL) based Non Destructive Testing (NDT) technique is used to perform the defect detection process. The rectangular notch defects on the outer surface of steam generator tubes are modeled using COMSOL multiphysics 4.3a software. The obtained MFL images are de-noised to improve the integrity of flaw related information. Grey Level Co-occurrence Matrix (GLCM) features are extracted from MFL images and taken as input parameter to train the neural network. A comparative study on characterization have been carried out using feed-forward back propagation (FFBP) and cascade-forward back propagation (CFBP) algorithms. The results of both algorithms are evaluated with Mean Square Error (MSE) as a prediction performance measure. The average percentage error for length, depth and width are also computed. The result shows that the feed-forward back propagation network model performs better in characterizing the defects.

• Journal of Soil and Groundwater Environment
• /
• v.23 no.6
• /
• pp.1-8
• /
• 2018

In this study, formaldehyde and benzene were selected as the arbitrary chemicals in accidental leakage to environment, and their physicochemical and biological characteristics and toxicity were studied. Also, the fate of these chemicals in soil and groundwater was studied based on the results of previous studies. They can be released into the atmosphere as gas or vapor phase, which then can be photochemically degraded. Since they have relatively high water solubility, they are likely to have high mobility in water and soil. Volatilization of these chemicals from soil is affected by the soil moisture content. Biodegradation of formaldehyde and benzene is one of the important pathways as well. Therefore, it is necessary to study the environmental impacts of leakage accidents of flammable chemicals such as formaldehyde and benzene. Further research on the fate of flammable chemicals in the environment is needed to take appropriate response actions to leakage accidents of flammable chemicals, and this will contribute to the development of practical guidelines to cope with leakage accidents.

• International Journal of Precision Engineering and Manufacturing
• /
• v.8 no.1
• /
• pp.46-51
• /
• 2007

Environmental contamination creates shortages of potable water. In such situations, the leakage of water due to breakage or aging of rubber valve seats is a serious problem. Rubber is apt to break when it is placed between two materials that contact each other. One way to avoid water leakage due to rubber damage and breakdown is to replace the rubber with metal, which is currently taking place in water distribution systems. In tribology, a severe form of wear is characterized by local macroscopic material transfer or removal, or by problems with sliding protrusions when two solid surfaces experience relative sliding under load. One of the major problems when metal slides is the occurrence of galling. Experimentally, various conditions influence incipient galling, such as hardness, surface roughness, temperature, load, velocity, and the external environment. This study sought to verify the galling tendencies of metal according to its hardness, surface roughness, load, and sliding velocity, and determine the quantitative effect of each factor on the galling tendencies.

• Journal of Korean Society of Water and Wastewater
• /
• v.11 no.2
• /
• pp.31-39
• /
• 1997

Between 40,000 and 60,000 liters of light oil were spilled when an underground pipe broke at a newly constructed landfill site in coastal area, Korea. Methods were presented to examine the subsurface distribution of the contaminants in hydrocarbon-contaminated soil. As results, large quantities of oil and grease were found to have migrated horizontally at the site. Oil and grease plume at concentrations of 38-88 mg/kg was formed horizontally through silty sand with gravel fill and the vertical movement of the contaminants was thought to be limited to groundwater level between 2 and 4 m corresponding to sea water level. Right after finding the leakage area, the early action of excavation and pumping out the mixture of groundwater and oil was taken and it was proved to be very effective for preventing further contamination. Two months after the leakage, oil and grease in sea water sample near contaminated area was not detectable.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2015.05a
• /
• pp.15-16
• /
• 2015

In this research, the application of repair methods of water leakage cracks using self-healing technologies for subway tunnels is presented. In order to apply crack self-healing water stop agents and quick setting agents in subway tunnels, laboratory and field tests were performed based on various previous researches. Especially, this study focused on development of crack repair materials and their new repair methods. Therefore, various repair materials were examined for new repair materials with self-healing capability applied to crack sealing method and to patching repair method.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2013.05a
• /
• pp.247-248
• /
• 2013

The waterproof construction for walls and floor in the underground parking lot in the construction of the apartment buildings have been excluded to the introduction of the waterproof design until now, because of the shorten construction period and the reduced construction costs. The concrete structures are existed to the joints in the vertical or horizontal parts commonly. In case of cracks, there are generated due to behavior by subsidence and external changing temperature environment. The cracks are generated by the frequent water leaks. So, the repair methods of the water leaks are proposed as the quick micro-cement and the polyacrylic resin in this study.

• Transactions of The Korea Fluid Power Systems Society
• /
• v.3 no.4
• /
• pp.1-7
• /
• 2006

A water hydraulic pump is likely to have serious problems of high leakage, friction and low energy efficiency. A water hydraulic pump has commonly a fixed displacement type and its outlet flow is adjusted by controlling rotation speed of the pump, which can be implemented by using an electric inverter. This study aims to investigate energy efficiency of the water hydraulic pump system which is driven by an electric inverter. The study is based on the experimental results. The pump which is used in the study shows relatively good efficiency and low leakage, low friction as well. The reasons for the good performance of pump is also investigated.