• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.4
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• pp.418-425
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• 2021

The effects of an aquaponic system based on biofloc technology (BFT-AP) were analyzed for eel Anguilla japonica as aquaculture species and caipira Lactuca sativa as the cultivated crops. The rate of weight gain rate by the eels was 178% (BFT-AP 200 head) > 136% (BFT-AP 100 head) > 100% (BFT). The eel body weight in the BFT-AP (200 head) significantly increased when compared to the BFT only eel group (P<0.05). The weight of the upper layer of caipira was 91±8.5 g (200 head) > 90±8.9 g (100 head) > 48±8.3 g (Hydroponic crop, HP). The crop growth in all BFT-AP groups was higher than the control, the hydroponic group. The total ammonia nitrogen (TAN) and NO₂^--N concentrations decreased in the BFT-AP group when compared to the BFT group. It was possible to remove nitric acid from the aquaponics system and reuse it as eel rearing water. Although some nutrient concentrations were low in BFT when compared to HP, the nutrient concentration was sufficient for plant growth. The results show that BFT has the potentially to provide a sustainable aquaponic system.

• Journal of Korea Water Resources Association
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• v.49 no.12
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• pp.961-969
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• 2016

Due to the recent requirement of installing low-head structures considering environmental aspects, various types of fixed weir have been suggested. However, the design guideline of transverse structures for practical application is very limited. The purpose of the present study is to analyze the hydraulic properties of the fixed weirs installed at the small and middle sized rivers of Korea depending on the physical specifications to provide fundamental data that may be reflected to the design of a low-head fixed weir considering the relevant environmental aspects. The basic discharge coefficient of slope-type and step-type weirs depending on change of crest was estimated, and a stage-discharge curve was developed. In addition, the flow properties under free flow and submerged flow conditions were analyzed by varying the hydraulic conditions such as discharge and crest.

• Journal of Navigation and Port Research
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• v.37 no.6
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• pp.637-645
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• 2013

Masan bay with a semi-enclosed waters has serious water quality problems due to the low flow and river pollution load from land, and shows the vulnerable locational characteristics to storm surge. We are seeking the way of both operating disaster prevention facilities and water quality improvement measures in the bay. That is, the water was exchanged using the head difference occurred by operating disaster prevention facilities. The location of disaster prevention facilities was assumed to be in the inlet of the bay, in the vicinity of Machang bridge, and in the vicinity of Dot island and the operation time was assumed to be early morning hours(01~05) considering the number of shipping passage and annual tide, and spring tide of the largest head difference. In addition, the experiment case of water exchange including the in-outflow feeder pipe was tested. According to the simulation results, water exchange rate in all experiments has shown a steady increase. Water exchange rate of the whole of Masan bay in the case of present is 38.62%. The water exchange rate of the inside of Masan bay compared with the inlet of bay, appeared to be very low. Thus, we judged that the characteristics of semi-enclosed waters were well reproduced. On the results of the experiment of disaster prevention facilities and in-outflow feeder pipe, the case of the operation of disaster prevention facilities, water exchage rate is high compared with the case of present. And, the higer the operating frequency, the more water exchange is appeared. The cases of water exchange prevention facilities through the in-outflow feeder pipe caused by the head difference, also showed the higest improvement of the water quality. Compared with the south of Machang bridge, the effect of water exchange was better in the inlet of Masan bay and Dot island. On the other hand, the inlet of Masan bay is higer than Dot island as for water exchange of the whole of Masan bay, but opposite, water change rate including Masan inside was higher in the case of Dot island.

• Journal of fish pathology
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• v.34 no.2
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• pp.161-168
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• 2021

Quantitative analysis of myxosporean parasites (Enteromyxum leei and Parvicapsula anisocaudata) were performed using real-time PCR on the internal organs (head kidney, body kidney, intestine, spleen, brain, liver, heart, muscle, blood, and eye) of emaciated Paralichthys olivaceus from farm-A. The highest DNA copy number of E. leei was shown in the intestine (1.3 × 10⁸ copies/mg tissue) of emaciatied P. olivaceus and DNA copy number in the other internal organs (1.3 × 10³~4.6 × 10⁵ copies/mg tissue) showed lower than in intestine. From the result of real-time PCR for P. anisocaudata, it was considered mildly infected, due to the low DNA copy numbers of the head kidney (1.3 × 10³ copies/mg tissue) and body kidney (9.1 × 10³ copies/mg tissue). In order to investigate whether myxosporean parasites can be detected in a non-invasive way, quantitative analysis of E. leei and P. anisocaudata from rearing water of three farms were performed by real-time PCR. The DNA copy number of E. leei from rearing water of farm-A and farm-B were 8 × 10⁴ and 5 × 10⁵ copies/L, respectively. However, it was not detected in farm-C. For P. anisocaudata from rearing water, farm-A, farm-B and farm-C showed 0, 2.0 × 10⁶ and 5.1 × 10⁶ copies/L, respectively.

• Journal of Welding and Joining
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• v.34 no.5
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• pp.13-18
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• 2016

Toshiba has developed a laser peening system for PWRs(pressurized water reactors) as well after the one for BWRs(boiling water reactors), and applied it for BMI(bottom-mounted instrumentation) nozzles, core deluge line nozzles and primary water inlet nozzles of Ikata Unit 1 and 2 of Shikoku Electric Power Company since 2004, which are Japanese operating PWR power plants. Laser pulses were delivered through twin optical fibers and irradiated on two portions in parallel to reduce operation time. For BMI nozzles, we developed a tiny irradiation head for small tubes and we peened the inner surface around J-groove welds after laser ultrasonic testing (LUT) as the remote inspection, and we peened the outer surface and the weld for Ikata Unit 2 supplementary. For core deluge line nozzles and primary water inlet nozzles, we peened the inner surface of the dissimilar metal welding, which is of nickel base alloy, joining a safe end and a low alloy metal nozzle. In this paper, the development and the actual application of the laser peening system for PWR power plants will be described.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09b
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• pp.192-199
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• 2010

This research produced internal model tester ($2.0m{\times}2.0m{\times}1.0m$) to evaluate the field application of Paju Unjeong District water recycling system for small streams eco-friendly river bed disparity method for the first time in Korea and conducted comparative analysis of the Paju Unjeong District water recycling system field test results and infiltration rate result of internal tests by each rainfall intensity following surface material. Infiltration rate result of internal tests concrete pavement by rainfall intensity following surface material, asphalt pavement, bentonite mate, stabilized soil construction and mixed soil construction manifested low infiltration rate. On the contrary, compaction soil, grassland and water permeable packaging materials resulted in significant amount of infiltration rate. As for the field permeability test results, they were manifested similar tendency as indoor permeability test results and they satisfied the standard for standard of water permeability of domestic disparity facility (less than $1.0{\times}10-7cm$/sec). As compaction rate increased, unconfined compression strength increased as well while coefficient of water permeability decreased.

• Korean Journal of Soil Science and Fertilizer
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• v.8 no.4
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• pp.195-198
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• 1975

Boron deficiency appeared as a cause of poor growth of sunflower(Helianthus annuus) according to soil and plant analysis. The investigated results are as follows; 1. Boron deficiency was due to low content of available boron (hot water soluble) in soil and clitical concentration appeared as 0.17 ppm. 2. Clitical concentrations in plant appeared to be 20 ppm for head(flower), 25 for leaf, 15 for stem and 10 for root. Boron concentration among positional leaves was greatly decreasing in the upper leaves. 3. Soils low in boron were relatively higher in calcium, silica and pH than in normal soil but relationship between boron and organic matter or other nutrients was uncertain. 4. The content of Ca and P is high in the head of boron deficient plant but low in root. Plants deficient in boron also showed a tendency of high N and low K but no clear tendency was shown in Mg and Fe. 5. Symptoms of boron deficinicy were yellowing of upper leaves, browning and drying of upper part of stem, cracking and blackening of stem and roots resulting short stem and poor growth.

• Journal of the Korean Geotechnical Society
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• v.28 no.5
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• pp.27-39
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• 2012

In this paper, a series of centrifuge tests were performed to evaluate the seepage characteristic of reinforced embankment. The centrifuge models simulated an actual embankment reinforced by enlargement of levee cross-section. The centrifuge models have the same conditions except the locations of enlargement with low permeable material : water-side and land-side. In addition, the prototype embankment is constructed on low permeable clay layer. In the case of water-side reinforcement, the reinforced zone makes water head down and the saturated zone of embankment propagates slowly. In the case of land-side reinforcement embankment, the saturated zone enlarged relatively faster but the amount of exit water at land-side toe was very small because of the land-side reinforcement zone. The low permeable clay foundation layer was being continuously saturated by the inflow from the embankment as well as the uplift flow from the permeable layer induced by the excess pore water pressure.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.6
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• pp.421-428
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• 2014

For the analysis of water supply network, demand-driven and pressure-driven analysis methods have been proposed. Of the two methods, demand-driven analysis (DDA) can only be used in a normal operation condition to evaluate hydraulic status of a pipe network. Under abnormal conditions, i.e., unexpected pipe destruction, or abnormal low pressure conditions, pressure-driven analysis (PDA) method should be used to estimate the suppliable flowrate at each node in a network. In order to carry out the pressure-driven analysis, head-outflow relationship (HOR), which estimates flowrate at a certain pressure at each node, should be first determined. Most previous studies empirically suggested that each node possesses its own characteristic head-outflow relationship, which, therefore, requires verification by using actual field data for proper application in PDA modeling. In this study, a model pipe network was constructed, and various operation scenarios of normal and abnormal conditions, which cannot be realized in real pipe networks, were established. Using the model network, data on pressure and flowrate at each node were obtained at each operation condition. Using the data obtained, previously proposed HOR equations were evaluated. In addition, head-outflow relationship at each node was analyzed especially under multiple pipe destruction events. By analyzing the experimental data obtained from the model network, it was found that flowrate reduction corresponding to a certain pressure drop (by pipe destruction at one or multiple points on the network) followed intrinsic head-outflow relationship of each node. By comparing the experimentally obtained head-outflow relationship with various HOR equations proposed by previous studies, the one proposed by Wagner et al. showed the best agreement with the exponential parameter, m of 3.0.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1315-1318
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• 2001

국내외적으로 배기가스 저감 등 환경규제 강화와 환경의식이 향상되면서 원자력, 석탄, 중유 발전 등은 주변지역의 반대에 직면하여 발전소 건설사업 추진이 순조롭지 못한 실정이다. 또한 석유에너지 자원의 고갈과 국제 고유가 시대에 따라 대체에너지의 개발에 세계 각국이 심혈을 기울이고 있다. 그러나 우리나라의 경우 대규모 수력 발전소 입지를 찾는데는 한계가 있으며, 대부분 개발가능 지점이 15m이하 저낙차의 특징을 갖고 있다. 종래에는 소하천을 가로막아 소수력을 개발하는 것이 주종을 이루었으나, 최근에는 공사비 과다로 인한 경제성 불투명과 각종 주변 지역의 민원으로 개발이 어려워 광역상수도, 하수처리장, 농업용 저수지, 다목적댐 하류 조정지댐 등에 저낙차 유휴에너지를 다각적으로 이용하는 방안이 연구 개발되고 있다. 본 연구에서는 저낙차를 이용한 소수력 발전의 최적설계와 경제성 평가 기법 등을 실 적용한 사례를 중심으로 논하고자 한다.