• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.85-92
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• 2003

Generally, ordinary portland cement(OPC) is widely used for grouting to reduce permeability of ground under the foundations of structures. But, it is hard to be injected into the microscopic voids, fissures and crevices in soil or rock formation for the OPC material. Therefore new method what is called MSG(Micro Silica Grouting) has been developed recently to improve the weak point of the OPC material. In this case study, in order to verify performance of the MSG's water cut-off, trial injections were performed in rear of CIP(Cast in Place Pile) on the site A(weathered soil) and B(alluvial soil) that are constructed for the subway No. 9 nowadays. To take the proper grouting method of the MSG in the trial injecting, the injections are carried out for grouting types(constant pressure or fixed Quantity) and grouting methods(1.5shot or 2.0shot) and to confirm the effects of water cut-off and the injection range of the MSG, the tests of permeability and indicator(phenolphthalein) response were performed before and after the injection. Through the tests results, we could affirm the effects of water cut-off of the MSG and the injection range for the weathered and alluvial soil layers near the Han River. Finally we could make sure the application of the MSG method in actual construction under the layers.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.9
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• pp.1644-1651
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• 2010

VLF $tan{\delta}$ diagnosis technology is introduced in IEEE Std 400 and proposed as evaluation criterion in an effective way of detecting water tree which mainly causes the failure of XLPE insulated cables. In order to inspect the accuracy of the VLF $tan{\delta}$ method for XLPE insulated power cables in Korean distribution system, diagnosis for 41 cables which were being serviced in the fields has been carried out and they were removed for AC breakdown voltage test after. Regarding the 41 cables, it was hard to confirm any relation between the VLF $tan{\delta}$ values and AC breakdown voltages and also water tree in the insulation was not detected. However, the other cables were failed several days after the diagnosis of the 41 cables. Water trees were found and their VLF $tan{\delta}$ values were also much higher than the criterion of IEEE standard. It has been ascertained that we need to change the IEEE criteria in order to improve the accuracy of detecting water trees by additional analyzing of field examples of failure and case studies from overseas countries and therefore amended VLF $tan{\delta}$ test voltage and evaluation criteria have been proposed.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06a
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• pp.43-49
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• 2006

The surface and pore structure of cellulose fibers have a significant impact on the properties and performance in applications. Cellulase enzymatic hydrolysis of cellulose fibers can result in changes to the surface and pore structure thus providing a useful tool for fiber modification. This research characterizes these changes using various test methods such as fiber dimension, water retention value, hard-to-remove water content, freezing and non-freezing bound water content, polymer adsorption, and crystallinity index. For a high-dosage enzyme treatment (0.10 g/g), the fiber length was significantly decreased and the fibers were 'cut' in the cross direction, not in the axial direction. The swelling capacities as measured by the WRV and HR water content increased for the high-dosage treatment. Three independent measurements (non-freezing bound water, polymer adsorption, and crystallinity index) are in good agreement with the statement that the amorphous regions of cellulose fibers are a more readily available substrate relative to crystalline regions. Based on the experimental results obtained herein, a model was proposed to explain surface and pore structure modification of cellulose fibers via enzymatic treatment.

• Geosystem Engineering
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• v.21 no.6
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• pp.344-351
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• 2018

It is reported that the flooding rate in low permeability sandstones is low and the oil recovery is hard to increase after water breakthrough. Understanding characteristics of waterflood is hence important for the recovery improvement. In this work, flooding tests on low permeability sandstones were conducted. The corresponding flooding characteristics were investigated by means of CT scanning and Nuclear Magnetic Resonance. Effects of irreducible water and different rates were also discussed in detail. Experimental results reveal a piston-like displacement at a low rate in low permeability samples. The saturation profile is steep and almost vertical to the forward direction. The results at a low rate confirm that once water broke through, increasing the flooding rate or flooding time can hardly reduce the remaining oil inside the sample. It is probably due to the high pore-throat ratio proven by rate-controlled mercury. Results also confirm that the presence of initial water enhanced sweep efficiency substantially. On one hand, because water had previously occupied the small pores, the subsequent oil can only invade relatively large pores and became more movable. On the other hand, stable collars can not form due to the steep front, which may suppress the snap-off.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.149-149
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• 2022

Accurate quantitative evaluation of baseflow contribution to streamflow is imperative to address seasonal drought vulnerability, flood occurrence and groundwater management concerns for efficient and sustainable water resources management in watersheds. Several baseflow separation algorithms using recursive filters, graphical method and tracer or chemical balance have been developed but resulting baseflow outputs always show wide variations, thereby making it hard to determine best separation technique. Therefore, the current global shift towards implementation of artificial intelligence (AI) in water resources is employed to compare the performance of deep learning models with conventional hydrograph separation techniques to quantify baseflow contribution to streamflow of Piney River watershed, Tennessee from 2001-2021. Streamflow values are obtained from the USGS station 03602500 and modeled to generate values of Baseflow Index (BI) using Web-based Hydrograph Analysis (WHAT) model. Annual and seasonal baseflow outputs from the traditional separation techniques are compared with results of Long Short Term Memory (LSTM) and simple Gated Recurrent Unit (GRU) models. The GRU model gave optimal BFI values during the four seasons with average NSE = 0.98, KGE = 0.97, r = 0.89 and future baseflow volumes are predicted. AI offers easier and more accurate approach to groundwater management and surface runoff modeling to create effective water policy frameworks for disaster management.

• Journal of the Korean Professional Engineers Association
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• v.33 no.1
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• pp.51-60
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• 2000

The mitigation technique is to minimize influences to the environments, and it is one of the environmental management(or administration) to techniques. Its objective is to create sustainable environment by keeping human assistance to the environment as minimal as possible. It restores, creates, enhances, and most importantly preserves the environment by avoiding, minizing, rectifying, eliminating, and compensating the natural circumstances The evaluation of adverse effects to the environment and their reduction is as follow: HEP(Habitat Evaluation Procedure) WET(Wet land evaluation technique) HGM(Hydro Geomorphic Assessment) BEST(Biological Evaluation Standardized Technique) Since there are both pro and cons in the American and Japanese mitigation methods, it is hard to choose which one is better.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.232.1-232.1
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• 2003

Purpose. To develop a hard gelatine capsule containing meloxicam (Yuhan Meloxam capsule$\^$TM/), in vitro dissolution characteristics and bioavailability in beagle dog were compared with commercial product (Mobic capsule$\^$TM/). Methods. Meloxicam capsule$\^$TM/ was prepared by powder filling method using meloxicam, lactose, magnesium stearate, and others. The release of Meloxicam capsule$\^$TM/ and Mobic capsule$\^$Tm/ were monitored by USP dissolution method under various dissolution donditions - dissolution medium (pH 1.2, 4.0, 6.8 and water). (omitted)

• Environmental Engineering Research
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• v.18 no.2
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• pp.95-101
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• 2013

Alternative sources of water are sought in some water stressed communities in the study area. The study focuses on the Aguata-Awka area of southeastern Nigeria. Aquifers occur at great depths, and surface waters may be far from homesteads. The scarcity of water has necessitated the people to adopt various local technologies for harvesting rainfall. The local technology includes collecting rainwater from roofs and channeling the water into large underground tanks, shallow wells and surface reservoirs. Large concrete tanks of $6m{\times}6m{\times}4m$ dimensions are often built underground and can store $144m^3$ of water. Surface reservoirs built on 4 m concrete pillar supports having dimensions of $10m{\times}10m{\times}4m$ and have a storage capacity of $400m^3$. Water samples were collected at 3 different locations of Agulu, Ekwulobia, and Awka and were analyzed for their physical, chemical, and bacteriological parameters. Results indicate a range of values for pH, 5.9 to 7.1; turbidity, 0.9 to 2.7; total dissolved solids, 80 to 170 mg/L; total hardness, 4.5 to 6.4 mg/L; magnesium, 1.2 to 1.4 mg/L; bicarbonate, 19.4 to 83.6 mg/L; and sulfate, 3.6 to 6.4 mg/L. Bacteriological analysis results were negative for fecal and total coliform counts. All parameters, with the exception of pH where aluminum and galvanized iron roofs are used for collection, fall within the recommended guidelines for drinking water quality of the World Health Organization, and the Standard Organization of Nigeria, new Nigerian standards for drinking water quality. Magnesium is above the maximum permitted level for consumer acceptability of the Nigerian standards for drinking water quality. The water can be classified as fresh moderately hard and soft. The water can be described as a calcium and bicarbonate type.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.864-868
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• 2008

Water transmission and distribution systems play a important role to deliver safe and clean water and are responsible for the most direct impacts of water utilities to customers. Although the performance of WDS(Water Distribution Systems) should be evaluated by a certain standards, interests has not been in WDS and developed due to invisible, hard-working and insufficient information in the evaluation process in Korea till now. The investigations and researches were carried out to develop software to assist the evaluation of WDS with respects to hydraulics, water quality and structural analysis methods. The methodologies have been developed which can be used to estimate the performance to water distribution network and software are implemented by the process. Developed systems are consisted with database, analysis techniques, simulation models, decision support systems and other tools. The concepts and functions are introduced in this paper and the performance index are discussed for accurate assessment of water distribution systems.

• Spatial Information Research
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• v.3 no.1
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• pp.39-46
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• 1995

Rural water resources systems may be largely constituted by two parts. One is rural water supply systems such as reservoirs, wells, pumping stations. The other is rural water demand systems which include municipal water, irrigation water, industrial water, livestocks water, inland fisheries water and envir¬onmental water in rural areas. planning to develop rural water resources systems is a very hard task because of their complicated factors and the large number of spatial data to investigate and manipulate. A Geographic Information SystemCGIS) will be a powerful and efficient tool to handle the spatial data and to plan the land use. All data can be efficiently maintained and easily updated. This paper refers to the construction of a GIS for planning rural water resources systems applied to Kokseong County, Cheonnam Province, Republic of Korea. The Geographic Informa¬tion was constituted by 4 layers of base map and 11 layers of thematic map.