• Journal of Korean Society on Water Environment
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• v.30 no.2
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• pp.148-158
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• 2014

In order to assess the effect of TMDLs management and improve that in the future, it is necessary to analyze long-term changes in water quality during management period. Therefore, long term trend analysis of BOD was performed on thirty monitoring stations in Geum River TMDL unit watersheds. Nonparametric trend analysis method was used for analysis as the water quality data are generally not in normal distribution. The monthly median values of BOD during 2004~2010 were analyzed by Seasonal Mann-Kendall test and LOWESS(LOcally WEighted Scatter plot Smoother). And the effect of Total Maximum Daily Loads(TMDLs) management on water quality changes at each unit watershed was analyzed with the result of trend analysis. The Seasonal Mann-Kendall test results showed that BOD concentrations had the downward trend at 10 unit watersheds, upward trend at 4 unit watersheds and no significant trend at 16 unit watersheds. And the LOWESS analysis showed that BOD concentration began to decrease after mid-2009 at almost all of unit watersheds having no trend in implementation plan watershed. It was estimated that TMDLs improved water quality in Geum River water system and the improvement of water quality was made mainly in implementation plan unit watershed and tributaries.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.301-310
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• 2006

A series of laboratory tests was carried out for analyzing compaction characteristics of hydraulic fill soils(or hydraulically filled soils). Hydraulic fill soils were settled down by the weight of soil particle itself in water and consolidated by the extraction of water from the soil structures. Water content and dry unit weight were observed as the depth of sedimentation and consolidation soil. It was found from the result that the optimum water content $(W_{cpt})$ of the maximum unit weight$(\gamma_{dmax})$ is higher than that of laboratory compaction test(KS F 2312 A method). It was due to difference in compaction energy and compaction effect between two methods. And the maximum dry unit of hydraulic fill soil is smaller than that of laboratory compaction test. Especially in terms of compaction effect, the maximum relative compaction degrees$(R_{cmax})$ of Seamangum dredged sand, river sand and mixed sand, half and half of dredged and river sands, were 85%, 91% and 86%, respectively. It means that the compaction effect can be $85\sim91%$ of the maximum unit weight in laboratory compaction test.

• Membrane and Water Treatment
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• v.2 no.2
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• pp.121-136
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• 2011

A bench-scale test has recently been proposed as a predictive tool to minimize the scope of pilot-scale testing or to optimize the operation of full-scale membrane filtration systems. Consequently, a bench-scale testing unit was developed for this purpose and systematically evaluated in this study. This unit was capable of accommodating commercially available, low pressure, hollow fiber (LPHF) membranes with various configurations for testing under conditions comparable to real-world applications. Reproducibility of this unit in assessing membrane fouling and microbial removal efficiency of LPHF membranes was tested and statistically comparable results were obtained. This unit serves as a useful apparatus for academic researchers and utilities to evaluate the performance of LPHF membranes used for water treatment.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.243-244
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• 2023

The quality of ready-mix concrete, a decisive factor in the performance of a structure, has recently been ensured by considering the unit water testing method, and this study experimentally examined the reliability of evaluation results based on this method.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.736-742
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• 2010

This study was conducted to characterize on the relationships of rainfall intensity and infiltration rate of rainfall dependent on unit weight change in the gneissic weathered soil by a column test equipment. In this study, volumetric water content and pore water pressure were measured using TDR sensors and tensiometers at regular time intervals. Rainfall conditions including continuous rainfall and repeated rainfall were selected in order to know the effect of antecedent rainfall. In the condition of rainfall intensity 20mm/h and the unit weights of soil as $1.35g/cm^3$, $1.55g/cm^3$ and $1.61g/cm^3$, average rainfall infiltration rate was $2.814{\times}10^{-3}cm/sec$, $1.969{\times}10^{-3}cm/sec$ and $1.252{\times}10^{-3}cm/sec$ respectively. The higher rainfall intensity and lower unit weight of soil, the faster average infiltration rate. Overflow in the column was happened except rainfall condition of rainfall intensity 20mm and soil unit weight $1.35g/cm^3$. Increasing the soil unit weight, overflowed water was increased and occurrence time was faster.

• Magazine of the Korean Society of Agricultural Engineers
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• v.24 no.2
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• pp.67-75
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• 1982

A study on the effect of water reducing agent on the various characteristics of concrete has been conducted. The experimental results of the study are summarized as follows. 1. Slump test for the concrete added water reducing setretarding agent in proper quantity have been conducted. According to the test results, the decreasing rate of slump value become bigger than plain concrete with increase of the unit weight of cement and elapse of time 2. In case the proper quantity content of maximum compressive strength in Fig. 5 of water reducing set retarding agent is added, unit weight of water is decreased about 15% or so as compared with plain concrete. with the increase of water reducing set accelerating agent content unit weight of water is decreased much more, And other hand, amount of air entraining shows the increasing tendency with the increase of water reducing agent content. 3. The adding rate of water reducing agent which produce maximum strength shows that WR-CH and WR-SA which is water reducing set-starding agent is 0.2% and WR-CO is 0.5% and that WS-PO which is water reducing set accelerating agent is 0.5 4. compressive strength jof the concrete made of sulfate resistant cement shows less than the strength of normal portland cement at initial strength but the strength of both cement shows almost same at curing age of 28 days. 5. when proper quantity of water reducing set retarding agent is used, boned strength is increased about 15% at curing age of 28days. 6. According to the result of durability test, dynamic young's mudulus of elasticity at plain concrete is decreased about 50% as compared with initial step at 300 cycle of freezing and thawing after curing age of days. on the contarary the concrete used water reducing agent is decreased less than 7%.

• Proceedings of the KWS Conference
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• v.43
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• pp.213-215
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• 2004

Water jet propulsion system has high efficiency on middle to high speed, and it provides better safety than conventional screw propeller because it has not projected propeller and rudder. So many leisure boat and high-speed ferries use this propulsion system. We developed water-jet propulsion unit for small planning boat, and launched that in the boat, after that we tested water-jet unit in the lake. As a result, we certify heat dissipation at the bearing housing and reverse duct's shape for neutral position are important at the design, and alignment water-jet unit and keel line are important at the launching, and ship's resistance performance and jet's propulsion performance also are needed to consideration.

• Journal of Korean Society on Water Environment
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• v.31 no.3
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• pp.235-240
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• 2015

To evaluate the unit load generation and discharge, pig cage test was conducted. Feed intake, drink amount, and urine generation increased growth stage (heavy weight) of the pig more great. However, the sum of the urine and manure did not show a significant difference in the growth stages of pigs. Because of the limit of the experiment, e.g., research period, high pigpen temperature, breed-related stress and etc., it could not be derived the results of the four seasons. Therefore, in order to generalize the results, the feed intakes were calibrated using a NRC (National Research and nutritional requirements of pigs from the Commission) standards. The finalized unit load generation and generation amounts of manure and urine were estimated at BOD 104.1 g/head/d, T-N 21.2 g/head/d, T-P 4.9 g/head/d, manure 0.96 L/d, urine 1.66 L/d with consideration of revised feed intake. Compare to the former research results of MOE (Ministry of Environment, 1999) and NIAS (National Institute of Animal Science, 2008), the generation amounts of manure and urine were similar to the NIAS's values. In case of unit load generation, BOD and T-N were almost similar in all of them. However, the T-P unit load generation of MOE was more difference, e.g., 2.5 times high, compare to this study.

• Journal of Korean Society of Water and Wastewater
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• v.37 no.4
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• pp.187-202
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• 2023

This study focuses on the application of a new measurement method that quantifies the residual color of filtered water using a spectrocolorimeter after filtering the discolored substances. It was confirmed through the color and turbidity cross-test that the discolored substances cannot be measured effectively with the current legal color and turbidity test method. Therefore, the National Institute of Environmental Research's filter testing method, which involves filtering the sample through 0.45 ㎛ filter and visually inspecting the color, was improved. A membrane filter colorimetry (MFC) method was established by measuring the color difference (ΔE*ab(65)) of the filtered filter using a spectrophotometer and expressing it as filter color unit (FCU). Using the MFC method, the FCU for reference materials such as iron and manganese, as well as field samples, was measured. The results showed a high correlation with turbidity, and the color difference patterns varied depending on the type of reference materials and field samples. This indicates that the MFC method is an effective new measurement method of discolored tap water.

• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.418-425
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• 2009

A vertical bulb turbine unit with elbow type draft tube has been developed due to avoidance of complicated assembling and long standstill period at overhaul in comparison with conventional horizontal bulb turbine unit. Before designing the prototype vertical bulb unit, a hydrographic model test was carried out to establish the ideal design concept for this innovative generating unit. Froude similarity is not available for vortex occurrence. Consequently, an intake structure without air entraining vortices under all the flow conditions is developed, and it is confirmed that the surge wave at load rejection is not affected harmful influence for other constructions.