• The Journal of Engineering Geology
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• v.27 no.4
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• pp.383-392
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• 2017

Excessive abstraction of groundwater near streams for agricultural, domestic, or industrial use can significantly reduce the streamflow. Therefore, proper management of water resources must involve careful monitoring of groundwater use near streams. This study investigates the current status of groundwater intake plans in the Anseongcheon watershed, Korea, in order to understand the portion of groundwater wells according to distance from the stream and the distribution of wells near the stream. Among all the wells in the watershed, 20.5% were permitted and 31.3% were declared within 300m from the stream. In particular, among the wells located near streams, 11.4% were permitted and 88.6% were declared among the wells near streams. Therefore, the total amount of groundwater pumping rates from the declared wells is much higher than that from the permitted wells near the stream. Under current guidelines, investigations of the impact of groundwater use near a stream on streamflow depletion should only consider wells permitted by groundwater law. However, prudent management should also pay attention to declared wells, given their large number.

• Journal of Wetlands Research
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• v.14 no.4
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• pp.687-698
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• 2012

This study was conducted to monitor and prevent outbreak of insect pestsin dredged soil dumping area after completion of dredging construction in Masan City. Monitoring was carried out using tent trap, colored sticky trap, and CDC light trap. A total of 217,073 individuals belonging to 23 species from 10 families in 3 orders were collected. In overwintering survey using tent trap, 3 species were collected. 2 species (Leptocera fuscipennis (Haliday) and Ephydra japonica Miyagi) of them were outbreak species. In color sticky trap, more than 96% of total individuals were comprised of five species: Urolepis maritima Walker (43%), E. japonica (19%), Fucellia sp. 1 (13%), Philotelma sp. 1 (10%), and Homalometopus sp. 1 (9%). In CDC light trap, three dominant species were Homalometopus sp. 1 (91%), Glyptotendipes tokunagai Sasa (6%), and L. fuscipennis (1%), representing about 98% of the total. To prevent damage caused by outbreak of insect pests, we carried out ecological control methods such as covering the fresh soil in outbreak area, using light trap, pumping up water and so on, minimizing use of thermal fogging and insect growth regulatorwhen the insect pest population was rapidly increasing.

• Journal of the Korea Institute of Building Construction
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• v.17 no.5
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• pp.453-463
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• 2017

Due to the increase in the size of buildings and scale, the importance of construction engineering that reflects the constructability from the design stage of the project is increasing. Especially, engineering efforts related to facilities, equipment and construction methods for temporary work at the design stage can significantly contribute to improvement of constructability and project performance. The purpose of this study is to derive construction engineering tasks on temporary work at the design phase of the high-rise building projects. 27 preliminary tasks were firstly investigated through literature review and experts' group interview, and the necessity and importance analysis of each tasks were then performed based on questionnaire survey. Most of the tasks related to plans on structural framework and lifting equipment were analyzed as relatively more important ones. Lastly, 21 engineering tasks, which are classified into 5 factors, were proposed through factor analysis. The factors were determined as 1) structural framework, measurement and circulation, 2) lifting equipment and pumping, 3) space zoning, 4) water supply, 5) temporary facility, electric power supply and lighting. The results of this study can be used as basic data for establishing efficient work process of construction engineering on temporary work at the design phase.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.230-236
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• 2020

A trash screen is installed in front of the inflow channel of a drainage pumping station, sewage treatment plant, and a power plant to block floating contaminants. The bottleneck phenomenon, which decreases the water inflow, causes damage to the damper as a result of clogging in between the screen if string type obstacles are not removed. In this paper, the apron was removed, and the screen was expanded, to prevent breakage of the bottleneck phenomenon and string type obstacles. This was designed using an extended rake by adding an inner rake in between the screen interspace to remove the bottleneck phenomenon and string type obstacles. To design the inner rake that satisfies the allowable stresses of the existing damper rake, the experiment points were determined according to the experimental design method using the inner rake vertical length and the thickness of the reinforced section as parameters. The use of the ANSYS static structural module and statistical analysis tool R software gives the optimized shape according to the response surface method. The relative error between the response surface analysis results and the simulation results was 1.63% of the determined optimal design-point rake length of 210.2 mm and the reinforcement section thickness of 2 mm. Through empirical experiments, a test rake was constructed to the actual size, and approximately 97% of the bottleneck phenomenon and string type obstacles could be removed.

• Journal of Aquaculture
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• v.13 no.1
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• pp.39-46
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• 2000

Successive management of prawn farm is strongly dependent upon monitoring of pond seawater quality which is generally influenced by an excessive food supplied sediment type and phytoplankton composition in the pond. For good condition of seawater quality it must need exchangning of fresh seawater by tidal current. Two distinct shrimp ponds Galha and Yunho which were different in seawater exchanging system and sediment type were selected to understand how some factors affected to seawater and sediment qualities in the pond. Prawn growth was also determined. Galha pond characterized by sand bottom with water exchanging by turn of the tidal current accumulated 1.8 mgS/g-dry as sulfide in sediment while Yunho pond mud- bottomed with seawater exchanging of pumping system showed 4.7mgS/g-dry when it was highest, Ammonia-N and hydrogen sulfide measured in the seawater were 0.31mg/${\ell}$ and 21.2 ${\mu}$${\ell}$/${\ell}$in Yunho and 0.10mg/${\ell}$and 10.8${\mu}$${\ell}$/${\ell}$in Galha pond respectively. Dissolved oxygen remained below 6.0mg/${\ell}$ in Galha and 5.0mg/${\ell}$in Yunho pond from June through August. Less growth of prawn was found in Yunho pond than in Galha pond. Prawn growth expressed as body length and weight were 138.3mm 22.9g in Yunho pond while they were length 158.2mm and 28.9g in Galha pond respectively when they were harvested in October. These results indicate that higher levels of ammonia-N and hydrogen sulfide and lower dissolved oxygen in bottom seawater of Yunho pond might affect the growth of cultured prawn.

• Journal of the Korean Geosynthetics Society
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• v.1 no.1
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• pp.13-21
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• 2002

Geotextile tubes hydraulically or mechanically filled with dredged materials have been applied in hydraulic and coastal engineering in recent years(detached breakwater, groins and jetty). The geotextile tubes are made of sewn geosynthetics sheets. If the sandy soil is use to fill material, these inlets should be spaced closely to assure uniform filling of the tubes because sandy soil and geosynthetic is very pervious. However, the clayey soil or contaminated slurry is used, the inlets can be located relatively long distance. The fine clayey particles tend to rapidly blind the fabric slowing down water escape through the geotextile. This paper presents a field test result of a geotextile tube in the land reclamation project for the Songdo New City construction site. The dredged silty clay was dredged by the dredging ship and hydraulically pumped into the geotextile tube. The height of geotextile tube was measured at every filling stage and also measured width and diameter of geotextile tube with the elapsed time. Based on the test results, if the clayey filling material is used, the pumping step must be divided 3~4 stages for drainage and sediment. After complete drainage, the height of the geotextile tube reduces by approximately 50%.

• Journal of Biosystems Engineering
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• v.9 no.2
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• pp.1-7
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• 1984

The engines mounted on power-tillers are used as power source in various kinds of works such as plowing, harrowing, transporting, spraying, water pumping and threshing, etc. But the engines have not been used effectively from a standpoint of fuel consumption because of lack of proper power transmission system and lack of understanding of fuel consumption characteristics of the engines. Therefore, this study was attempted to establish proper power transmission system between the power-tiller engines and various implements. In order to accomplish the above objective, firstly, power requirement and pulley sizes for various implements, which are driven by the power-tiller engines, were investigated to find out whether the power transmission system is proper. Secondly, partload variable engine-speed test was conducted for 3 different sizes of diesel engines to measure to specific fuel consumption. Thirdly, the present power transmission systems were analyzed in terms of specific fuel consumption, and proper power transmission systems were suggested for various implements. The results of this study are summarized as follows: 1. Power requirement for each fixed-type implement of power-tiller varied from 1.5 ps to 11 ps according to its type and operating conditions, but generally in the range of 2.5 ps to 7 ps. 2. Each power tiller and implement were equipped with only one size of pully with few exeptions. With the present power transmission systems, the engines can't be utilized effectively in terms of fuel economy. The pulley size of engine or implement should be diversified to provide the optimum engine speed for different implements. 3. For a diesel eninge with the rated power output of 6 ps, the optimum engine speed to minimize specific fuel consumption was 2200 rpm for the power reguirement in the range of 6 ps or more, 1700 rpm in the range of 4 to 6 ps, and 1200 rpm in the range of 4 ps or less. 4. For a diesel engine with the rated power output of 8 ps, the optimum engine speed was 2200 rpm for the power requirement in the range of 7 ps or more, 1700 rpm in the range of 4.8 to 7 ps, and 1200 rpm in the range of 4.8 ps or less. 5. For a diesel engine with the rated power output of 10 ps, the optimum engine speed was 2200 rpm for the power requirement in the range of 8.4 ps or more, 1700 rpm in the range of 5.4 ps to 8.4 ps, and 1200 rpm in thr range of 5.4 ps or less. 6. Provided the existing implements are dirven by 8 ps diesel engines, the optimum size of engine pulley should be larger than 120mm for the works of requiring less than 4 ps and 90-110mm for the works requiring 4.5-6.5 ps in order to minimize fuel consumption.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3518-3524
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• 2015

Spatial and time variation of the precipitation in Korea is high, therefore, more than 2/3 of the annual precipitation is concentrated during the rainy season. Climate change also causes the intensive rainfall in the area of dense population, thus the occurrence frequency of the heavy flood in the impervious area has been increased. Therefore, the structural food mitigation measures such as the construction of the higher design frequency stormwater pipes, pumping stations, and/or detention ponds. The flood bypass tunnel or retention storage is also one of the efficient structures to mitigate flood damage in the urban area. However, the economic feasibility has been controversial because the flood bypass tunnel might be used once or twice a year. To solve the problem, the multi-functional tunnel for the urban traffic and flooding bypass has been considered. In this study, the design criteria of the road and water tunnel has been analysed and the composite design criteria is proposed for the multi-functional tunnel which is expected to be constructed.

• Journal of the Korean Geotechnical Society
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• v.34 no.11
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• pp.21-31
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• 2018

Bucket foundations are widely used in offshore areas due to their various benefits such as easy and fast installations. A bucket is installed using self-weight and the hydraulic pressure difference across the lid generated by pumping out water from inside the bucket. When buckets are installed in high permeable soil such as sands, upward seepage flow occurs around the bucket tip and interior, leading to a decrease in the effective stress in the soil inside the buckets. This process reduces the penetration resistance of buckets. However, the soil inside and outside the bucket can be disturbed due to the upward seepage flow and this can change the soil properties around the bucket. Moreover, upward seepage flow can create significant soil plug heave, thereby hindering the penetration of the bucket to the target depth. Despite of these problems, soil disturbance and soil plug heave created by suction installation are not well understood. This study aims to investigate the behavior of soil during suction installation. To comprehend the phenomena of soil plug heave during installation, a series of small-scale model tests were conducted with different testing conditions. From a series of tests, the effects of tip thickness of bucket, penetration rate, and self-weight were identified. Finally, soil properties inside the bucket after installation were approximated from the measured soil plug heave.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.415-421
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• 2021

This study analyzed the effect on the cooling performance of the channel shape of a heat sink for an insulated gate bipolar transistor (IGBT). A serpentine channel was used for this analysis, and the parameter for the analysis was the number of curves. The analysis was conducted using computational fluid dynamics with the commercial software ANSYS fluent. One curve in the channel improved the heat dissipation performance of the heat sink by up to 8% compared to a straight-channel heat sink. However, two curves in the channel could not improve the heat discharge performance further. Instead, the two curves caused a higher pressure drop, which induces parasitic loss for the pumping of coolant. The pressure drop of the two-curve channel case was 2.48-2.55 times larger than that of a one-curve channel. This higher pressure drop decreased the heat discharge efficiency of the heat sink with two curves. The discharge heat per unit pressure drop was calculated, and the result of the straight heat sink was highest among the analyzed cases. This means that the heat discharge efficiency of the straight heat sink is the highest.