• ALGAE
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• v.22 no.4
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• pp.297-304
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• 2007

This study is intended to clarify the effects of heated effluents on intertidal benthic marine algal community in Korea. The species composition and biomass of marine algae at the discharge canal of Gori nuclear power plant on the southeastern coast of Korea were investigated seasonally from February 2001 to October 2006. As a result, 54 species (7 blue-green, 12 green, 9 brown and 26 red algae) of marine algae were found at the discharge canal during the past six years. In general, the number of species observed was abundant during winter to spring and less in autumn. Enteromorpha compressa, E. intestinalis, E. prolifera and Caulacanthus ustulatus were common species found more than 80% frequency during the study period. Seasonal fluctuations of mean biomass were 1-440 g dry wt m–2 and dominant species in biomass were Enteromorpha spp. (contribution to a total biomass proportion 28%), Sargassum horneri (14%) and Amphiroa beauvoisii (14%). It is evident from the floristic composition and biomass data that unique micro-environment of the discharge canal support different communities from those on the intake or control area. Results from the large numbers of surveys before and during plant operation showed that, in the regions influenced by thermal effluents such as the discharge canal of power plants, the process of ecological succession has been proceeded. It is assumed that the uni-directional water flow and the time of overhaul largely affect the development and succession of benthic marine algal communities of the discharge canal.

• Journal of the Korean Geosynthetics Society
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• v.7 no.1
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• pp.39-44
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• 2008

Recently, the demand for industrial and residential lands are being increased with economic growth, however, it is difficult to acquire the land for development with good ground condition. For efficient and balanced development of land, new development projects are being carried out not only the areas with inland but those with the soft ground as well. As soft grounds have complex engineering properties and high variations such as ground settlement especially when their strength is low and depth is deep, it needs to accurately analyze the engineering properties of soft grounds and find general measurement for stabilization and economic design and management. Prefabricated vertical drain technology is widely used to accelerate the consolidation of soft clay deposits and dredged soil under the preloading and various types of vertical drain are being used with the discharge capacity. Under field conditions, the discharge capacity is changed with various reason, such as soil condition, confinement pressure, long-term clogging and folding of vertical drains, and so on. Therefore, many researcher and engineer recommend the use of required discharge capacity. In this paper, the experimental study were carried out for two different types of vertical drains by utilizing the large-scale model tests and waste lime.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.902-910
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• 2018

In recent times, development of nanofluid insulation for power transformers is a hot research topic. Many researchers reported the enhancement in dielectric characteristics of nano modified mineral oils. Considering the drawbacks of petroleum based mineral oil, it is necessary to understand the dielectric characteristics of nanofluids developed with natural ester based oils. Palm oil has better insulation characteristics comparable to mineral oil. However very few research reports is available in the area of nanofluids based on palm oil. Partial discharge (PD) is one of the major sources of insulation performance degradation of transformer oil. It is essential to understand the partial discharge(PD) characteristics by collecting huge data base of PD performance of nano modified palm oil which will increase its confidence level for power transformer application. Knowing these facts, in the present work, certain laboratory experiments have been performed on PD characteristics of nano $SiO_2$ modified palm oil at different electrode configurations. Influence of concentration of nano filler material on the PD characteristics is also studied. Partial discharge inception voltage, Phase resolved partial discharge (PRPD) pattern, PD signal time-frequency domain characteristics, PD signal equivalent timelength-bandwidth mapping, Weibull distribution statistical parameters of PRPD pattern, skewness, repetition rate and phase angle variations are evaluated at different test conditions. From the results of the experiments conducted, we came to understand that PD performance of palm oil is considerably enhanced with the addition of $nano-SiO_2$ filler at 0.01%wt and 0.05%wt concentration. Significant reduction in PD inception voltage, repetition rate, Weibull shape parameter and PD magnitude are noticed with addition of $SiO_2$ nanofillers in palm oil. These results will be useful for recommending nano modified palm oil for power transformer applications.

• Clean Technology
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• v.13 no.2
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• pp.115-121
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• 2007

In this study, we analyzed experimently the NO and $SO_2$ removal by the dielectric barrier discharge-photocatalysts hybrid process. The glass spheres were used as a dielectric material for dielectric barrier discharge and the $TiO_2$ photocatalysts were coated onto those spheres by the dip-coating method. The $TiO_2$ particles were coated in the sponge-shape, which has the larger surface area. As the voltage applied to the plasma reactor, the pulse frequency of applied voltage, or the residence time increases, the NO and $SO_2$ removal efficiencies increase. The increase in the supplied concentrations of NO and $SO_2$ leads to the higher energy for NO and $SO_2$ removal and the NO and $SO_2$ removal efficiencies decrease. These experimental results can be used as a basis to design the dielectric barrier discharge-photocatalysts hybrid process to remove NO and $SO_2$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.682-685
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• 2017

An experimental study was carried out to investigate the injection characteristics of non-circular effervescent type twin-fluid nozzles. For this purpose, two types of non-circular nozzles (E1, E2) and one kind of circular nozzle (C) were used. At this time, the Aerorator mounted on the nozzle used three different diameters to match the aspect ratio with the nozzle exit area. Therefore, experiments were performed according to three aspect ratios for each nozzle, and a total experiments were conducted. Experiments were carried out by controlling the amount of air flowing after fixing the flow rate of the liquid, and the nozzle internal pressure and SMD were measured, and the jet image was taken from the nozzle. The discharge coefficients of the three kinds of nozzles were compared with the conventional equation and the Jedelsky's equation, and the Jedelsky's equation was found to be about 4 times larger. The droplet size (SMD) injected from the nozzle was found to be smaller in the non-circular shape than in the circular shape, which is expected to be caused by the difference of the discharge coefficient values.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.6
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• pp.594-602
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• 2022

Cast-resin transformers are widely installed in various electrical power systems because of their low operating cost and low influence on external environmental factors. However, when they have an internal defect during the manufacturing process or operation, a partial discharge (PD) occurs, and eventually destroys the insulation. In this paper, a Rogowski-type PD sensor was studied to replace commercial PD sensors used for the insulation diagnosis of power apparatus. The proposed PD sensor was manufactured with four different types of PCB-based winding structures, and it was analyzed in terms of the detection characteristics for standard calibration pulses and the changes of the output voltage according to the distance. The output increased linearly in accordance with the applied discharge amount. It was confirmed that the hexagon structure sensor had the highest sensitivity, because the winding cross-sectional area of the sensor was larger than others. In addition, as the distance from the defect increased, the output voltage of the sensors decreased by 7.32% on average. It was also confirmed that the attenuation rate according to the distance decreased as the input discharge amount increased. For the application of this new type sensor, PD electrode system was designed to simulate the void defect. Waveforms and PRPD patterns measured by the proposed PD sensors at DIV and 120% of DIV were the same as the results measured by MPD 600 based on IEC 60270. The proposed PD sensors can be installed on the inner wall of the transformer tank by coating its surfaces with a non-conductive material; therefore, it is possible to detect internal defects more effectively at a closer distance from the defect than the conventional sensors.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.1
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• pp.163-173
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• 2023

In this study, topographic change analysis was performed on the Nak-dong River estuary area. The factors affecting the changes in the bathymetry of the Nak-dong River estuary were analyzed using data from the discharge, suspended sediments, and rainfall of the Nak-dong River barrier as analysis data. As a result, erosion and sedimentation are judged to appear repeatedly due to complex effects such as discharge of the estuary barrier of the Nak-dong River and invasion of the open sea waves, and it is judged that there is no one-sided tendency. However, as a result of checking the data in the second half of 2020, it was possible to confirm a large amount of erosion, which is different from the past data. It is clear that this is a result beyond the trend of erosion in the first half and sedimentation in the second half. In the summer of 2020, the rainy season lasted for more than a month and torrential rains occurred, which seems to be due to about three times higher rainfall than other periods, and erosion is believed to have occurred as the discharge increased rapidly compared to the time deposited by river water outflow. In addition, compared to other times, the influence of many typhoons in the summer of 2020 is believed to have affected the topographical change at the mouth of the Nak-dong River.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1B
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• pp.1-6
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• 2006

Amount of coastal ground water discharge(CGD) of surficial aquifer via coastlines of Nakdong River watershed, Seomjin River watershed, Youngsan River watershed and Keum River watershed is estimated. Compared to other major hydrological components, such as evapo-transpiration and river discharge, CGD is not so large in the amount. However, it is important since coastal ground water can be developed relatively free of environmental impact on downstream area and since most of coastal areas currently suffers water shortage. Regional groundwater investigation data and assessment based on Darcy's law are used for estimating coastal groundwater discharge. In this work the amount of CGD across the coastlines of the four rivers is estimated as 1.8 billion cubic meter per year and that is about 2.3 percentage of total amount of annual precipitation. Nakdong River watershed is most appropriate region in view of developing groundwater.

• Annals of Occupational and Environmental Medicine
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• v.35
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• pp.34.1-34.8
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• 2023

Background: Hydrogen sulfide is a toxic substance that humans can be exposed to occupationally, and cases of hydrogen sulfide poisoning of workers in industrial sites are commonly reported. However, there have been no cases of poisoning of the public due to an unauthorized discharge of wastewater, so it is important to describe this incident. Case presentation: In a small village in Jeollanam-do, Republic of Korea, accounts of a terrible stench had been reported. A 26-year-old man who lived and worked in a foul-smelling area was taken to the emergency room with a headache, dizziness, nausea, and repeated syncope. A subsequent police and Ministry of Environment investigation determined that the cause of the stench was the unauthorized discharge of 9 tons of wastewater containing hydrogen sulfide through a stormwater pipe while the villagers were sleeping. The patient had no previous medical history or experience of symptoms. Leukocytes and cardiac markers were elevated, an electrocardiogram indicated biatrial enlargement, left ventricular hypertrophy, and corrected QT interval prolongation. Myocardial hypertrophy was detected on a chest computed tomography scan, and hypertrophic cardiomyopathy was confirmed on echocardiography. After hospitalization, cardiac marker concentrations declined, symptoms improved, and the patient was discharged after 7 days of hospitalization. There was no recurrence of symptoms after discharge. Conclusions: We suspect that previously unrecognized heart disease manifested or was aggravated in this patient due to exposure to hydrogen sulfide. Attention should be paid to the possibility of unauthorized discharge of hydrogen sulfide, etc., in occasional local incidents and damage to public health. In the event of such an accident, it is necessary to have government guidelines in place to investigate health impact and follow-up clinical management of exposed residents.

• Journal of the Korean Geographical Society
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• v.30 no.3
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• pp.242-254
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• 1995

The Hadano Basin is located at a distance of about 70kms and 60kms from Tokyo and Yokohama and lies in the south-west part of the Kanto region in Japan. The basin area, which correspoends to the catchment of the Kaname River, is about areal size of 60.7$\textrm{km}^2$ and extends about length of 8kms in E-W direction and about width of 5kms in N-S direction (Fig.1). The Hadano basin is filled with thick pile of the alluvum from deposits composed of volcanic materials, mostly came from the Hakone Volcano and overlain by Fuji Volcanic ashes. Fluvial deposits form the good aquifer, therefore water resources of Handano City has been largely depending upon the eroundwater. Urbanization and industrialization of the basin has been rapid in the last thirty years, after activation of "Factory Attraction Policy of Hadano City" in 1956. Growth in population and number of factory due to urbanization changed the land-use pattern of the basin rapidly and increased the water demands. Therefore, Hadano City exploited a new source of water supply, and have introduced the prefectureal waterworks since 1976. On the other hand, the rapid urbanization has brought about the pollution of streams in the basin by domestic sewage and industrial waste water. Diffusion rate of sewerage systems in Hadano City is 38% in 1993. In ordcr to examine the impact of anthropogenic factors on river environments, the author took up the change of land-use and diffusion area of sewerage as parameters, and performed field surveys on water discharge and quality. The survey has been made at upstream and downstream of the main stream regularly per month, to get informati ons about the variation of discharge and water quality aiong the stream and its diurnal fluctuation. Annual variation has been analyzed based the data from Hadano City Office. The results are summarized as follows. 1. Stream discharge has been increasing by urbanization (Fig.3). Water quality (C $l^{-10}$ , N $H^{+}$$_{ 4}$-N, BOD) has been improving gradually after the application of sewerage service, yet water pollution load at the lower station has increased than that at the upper one because of the larger anthropogenic discharge volumes (Fig.4). 2. Corrclation coefficient of discharges between upper and lower was 0.81-0.92. Pollutant loads of the R. Kamame after the confluence with R. Kuzuha grew up by 2.4-3.7 times as compared with its upper reaches, and it increased to 3.7-6.9 times after the confluence with the R. Muro (Fig.5). 3. The changes of water quality along the stream can be divided into two groups (Fig.6a). First: water quality of the R. Kaname and R. Shijuhachisse is becoming worse towards the lower reaches because the water from branches are polluted. Second: water quality are improved in the lower where spring and small branch streams supply clear water, for example R. Mizunashi, R. Muro and R. Kuzuha. 4. Measured discharge at the upper station in the R. Shijuhachisse is 0.153㎥/sec, and about 55% of this is recharged until it reaches to the lower point. The R. Mizunashi has a discharge of 1.155㎥/sec at the upper point, is recharged 0.24㎥/sec until the midstream and groundwater spring 0.2㎥/sec at the lower reaches. R. Kuzuha recharged all the mountain runoff (0.2㎥/sec) at the upper reaches. The R. Muro is supplied by many springs and the estimated discharge of spring was 0.47㎥/sec (Fig.6b). 5. Diurmal variations in discharge and water quality are influenced clearly by domestic and industrial waste waters (Fig.7, 8).ed clearly by domestic and industrial waste waters (Fig.7, 8).