• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.173-173
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• 2022

유기 퇴적 오염물은 다양한 형태로 호소 바닥에 축적되어 호소 환경 및 생태계에 악영향을 미치고 있으며 메탄가스와 같은 온실가스의 발생을 유발한다. 또한, 수력 산업, 관개, 이·치수 등 다양한 목적에 의해 수체의 형성이 활발하게 이루어지면서 하천 및 호소에 의한 탄소유출을 전지구적 탄소순환에 적극적으로 포함시켜야 한다는 필요성이 증가하고 있다. 따라서 하천 및 호소에서 발생하는 다양한 생지화학적 반응에 의한 메탄 발생 메커니즘 파악은 유역의 중요한 환경평가 지표를 나타내며 탄소 순환을 이해하는데 매우 중요하다. 수온, 수심, 유기물 조건에 따른 하천 및 호소의 메탄 발생을 분석한 연구들이 선행되었으나 생지화학적 특성을 정리하고 이에 따른메탄 발생을 정량화한 연구들은 거의 없는 상황이다. 본 연구는 호소 내 메탄을 발생시키는 기작을 판별하기 위해 수온과 호소 환경과 유사한 TOC(총유기탄소)와 TP(총인) 조건과 같은 유기물 조건을 설정하여 BMP Test를 수행하였다. 반응수조에서 발생한 가스를 포집한 후 GC(Gas Chromatograpghy) 분석을 통해 메탄 생성량을 산출하였고, 유기물 조건에 따라 이론적인 메탄 생성량 대비 실제 발생한 메탄 생성량을 나타내는 생분해도를 산출하여 호소 환경별 주요 기작에 따른 가스 발생을 정량화 하였다. 실험 결과 수온에 가장 큰 영향을 받았으며, 수온에 따라 TP, TOC 순으로 메탄 발생의 영향성을 확인하였다. 향후에는 호소 환경에서의 유기물 조건을 반영하기 위해 입도비, 점착성/ 비점착성 조건, 수체의 높이 조건을 포함한 추가 실험을 수행하고 메탄수율을 정량화하여 호소 내 유기퇴적물에 대한 생지화학적 및 수환경 영향 평가 기법 개발이 가능할 것으로 기대한다.

• Journal of Aquaculture
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• v.4 no.1
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• pp.1-12
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• 1991

A series of rearing experiments were conducted to determine the growth rates and feed conversion efficiencies of tilapia in accordance with body size or age in nearly total closed system glass aquariums ($270\;\ell$ each in water volume) and concrete tanks ($4000\;\ell$) from April 10 to October 16, 1987. The fish used for the experiments was a Japanese strain of Oreochromis niloticus, and the size of the fish ranged from 7 g to more than 1,000 g in body weight. The starting stocking rates for each experimental lot were 10 to 20 kg in the glass aquarium ($3.7{\%}$ to $7.4{\%}$ of water volume) and 200 kg in the concrete tank ($5{\%}$ of water volume). A single experimental rearing term was 14 days with slight variations on occasions. Water temperature was designed to be kept at $26^{\circ}C$ but slight fluctuations were inevitable. Dissolved oxygen level was designed to be maintained at around $3\;mg/\ell$, but it also showed some variations. The ammonia level in the glass aquarium section once reached up to $18\;mg/\ell$, but generally remained at around $4\;mg/\ell$, and in the concrete tank section it was maintained at around $1\;mg/ell$. The feed was composed of mainly soybean meal with a small amount of fish meal as the protein source, and the crude protein content was about $32{\%}$. Mean daily growth rate was $3.5{\%}$ of body weight with 0.9 in food conversion ratio in the glass aquarium when the mean weight of fish was around 10 g with gradually reduced performances as the fish grew bigger. When the mean weight was 800 g, mean daily growth rate was $0.5{\%}$ with about 1.5 in food coversion for fish in the glass aquarium, and $0.8{\%}$ and 1.6 for fish in the concrete tank, respectively. According to the mean growth rate obtained from this experiment, it was calculated that the fish reared in the concrete tank require 223 days from 50 g to reach 1,000 g which is the ideal size for market in Korea, at the conditions provided as above, and 302 days from 10 g fingerlings to 800 g fish in the glass aquarium conditions of the closed recirculating water system.

• Journal of fish pathology
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• v.17 no.2
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• pp.99-103
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• 2004

White spot disease by Cryptocaryon irritans broke out among cultured river puffer (Takifugu obscurus) cultured in sea water in Oct. 2001 and May 2004. Many white spots were easily observed on the gills with the naked eyes. The parasites attached on the gills at the base of the gill lamellae. The trophonts penetrated the interlamellar epithelium. Epithelial cell proliferation in interlamellar spaces occurred. PAS- positive mucous cells were prominent in the proliferated epithelium.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.341-344
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• 2003

There communicates using tire supersonic waves in tire underwater, that is different from tire ground that use tire propagation. Because using Law frequency to come under tire waves, bandwidth that is able to communicate is very smaller that tire mobile communication of tire ground. Also, The channel environment changes rapidly in tire shallow underwater than tire ground. Due to such a reason, data transmission technic that is able to tire maximum application to restricted bandwidth and tire signal processing technics that is able to conquer tire rapid changes of tire channel environment are being used. Algorithm is used at tire application of these technic has a lot of tire calculating quantity. So this research reveals small bulk and equal performance using one DSP chip and then implements QPSK transmitter, that uses SHARC DSP of Analog Device company, for tire underwater supersonic waves communication rapidly decrease tire calculating quantity.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2003.05a
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• pp.132-138
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• 2003

In order to evaluate properly ship motion relating to the berthing maneuver, the hydrodynamic forces acting on ship hull in berthing maneuver need to be estimated rightly. CFD has been employed for time-domain simulation of transient flow induced by Wigley model moving laterally from rest in shallow water. The numerical solutions successfully captured not only the characteristics of the transitional hydrodynamic forces but also some interesting features of the flow field around a berthing ship according to the water depth. In this paper, the consideration is carried out on the approximate formula based on the CFD results, which can estimate hydrodynamic forces especially lateral drag coefficient starting from the rest to the uniform movement.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.6
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• pp.561-567
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• 1987

The purpose of this study was to find out the removal capacity of harmful ammonia by different filter media in the submerged biological filters in a given space of chamber. Four materials, pile cloth, corrugated skylight roofing plate, embossed plastic plate, and gravel, were used as the experimental filter media. Each filter medium was placed in two aquariums, each aquarium measuring $90cm\times60cm\times60cm\;(depth)$. Under the normal operating condition, the average of mean ammonia removal rates during the first and second functioning periods by each filter material which occupied tile space in the filter chamber (aquarium) was as follows: 1. Pile cloth: $8.381\;g{\cdot}m^{-3}.\;day^{-1}$ 2. Corrugated skylight roofing plate: $7.834\;g{\cdot}m^{-3}.\;day^{-1}$ 3. Embossed plastic plate: $7.797\;g{\cdot}m^{-3}.\;day^{-1}$ 4. Gravel: $7.051\;g{\cdot}m^{-3}.\;day^{-1}$ Thus, there were no significant differences between the media, but at the time of practical application of these materials, some other factors such as investment cost, easiness for the removal of excess detritus accumulated in tile interstices of filter media, etc. should be fallen into consideration. When large units are required, in particular, removal of excess detritus from tile gravel bed is extremely difficult, and in case of pile cloth filters the installation work is much complicated and a problem in supporting the structure when drained also exists. In these respects, corrugated skylight roofing plate and embossed plastic plate seem to be more optimal, but again in practice the local situation for the availability and the price of the materials should be rechecked and the fitness of tile materials in the particular filter chambers under use or under consideration for construction must be taken into account.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.4
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• pp.457-468
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• 1995

In order to develop a more practical culture system from the present running seawater tank system, two experiments of environmental factors, growth, survival rate and rearing density of olive flounder (Paralichthys olivaceus) were carried out for two consecutive years. Two groups of fish in initially averaging 7.5cm of total length, and 3.4g of body weight (EXP. I) and 5.0cm and 1.8g (EXP. II) were reared in the semi-closed recirculating seawater system equipped with the rotating biological contactors with the commercial culture scale. The dissolved inorganic nitrogen concentrations is EXP. I ranged 0,247-0.512 ppm of $NH_4-N$ (0.010-0.043 ppm of$NO_2-N$, and 0.108-0.342 ppm of $NO_3-N$, and those in EXP. II were 0.091-0.715 ppm, 0.002-0.045 ppm, and 0.007-0.277 ppm, respectively. Daily feeding rates of the fish were $0.67-2.41\%$ in EXP. I and $0.69-2.22\%$ in EXP_ II, and teed efficiency were $34.8-59.8\%\;and\;40.5-88.4\%$ in EXP. I and II, respectively. The average total ten說h and body weight were 40.0-42.8cm and 695.0-852.69g after 340 days culture in EXP. I, and 36.7-39.7cm and 552.4-706.4 g after 365 days culture in EXP. II, respectively. Survival rates of the fish at the end of EXP. I and II were $92.0\%\;and\;96.0\%,$ respectively. The ratio to body surface area of non-ocular side in all fish to bottom area of rearing tank, so-called covering rate, was used as an indicator of rearing density. The highest cowering rate and weight density of fish per $m^2$ of rearing tank at the end of experimental period were 2.2 and 34.1kg in EXP. I, and 2.6 and 36.3kg in EXP. II, respectively. For the commercial culture of olive flounder, the semi-closed recirculating seawater system was found to be more effective than the running seawater tank system in aspect to the fish productivity and protection of marine environment.

• Journal of Aquaculture
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• v.13 no.3
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• pp.223-230
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• 2000

A rearing experiment of the olive flounder was performed in a set of water-reuse system to test the reusability of the water in culture system with (i) a foam fractionator to separate particles from water and (ii) a culture tank contain mineral particles to filter the metabolic wastes by adsorption and/or decomposition. Two kinds of commercially processed loess particles and a dolomite particle (all 50 ${\mu}$diameter) were tested. The mineral particles were suspended in the culture tank and the water was pumped into the foam fractionator, where the particles were separated and drained out with foam from the system. In a circular culture tank of 4.8 m in diameter with 10 d water, the juvenile olive flounders (23.1 g/fish, 5,555 fish, 128 kg total body weight) were stocked. 90 % of the rearing water was reused and turnover rate of the water in the tank was two times per hour. Water temperature was maintained 17${\pm}$1$^{\circ}C$. At the end of 75 day-experimental rearing, 5,532 flounders, weighing 468 kg, were harvested. An individual flounder grew to 84.6 g of body weight. The final stocking density was 26.0 kg/$m^2$. No diseases were observed during the experiment.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.7 no.3
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• pp.126-144
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• 1974

Adult female prawn, Macrobrachium japonicum, which used for this work were collected at the river Simanto, Shikoku in Japan, and removed in the laboratory. Newly hatched larvae from an adult reared in circulation-filtered aquaria, which is controlled under the conditions of water temperature $26\pm0.3^{\circ}C$, chlorinity $6.21-6.45\%$ Cl, pH 8.0-8.1, illumination 3000 lux, and fed on Artemia salina nauplius sufficielltly For a period of rearing of zoea larvae, big individuals-individual varying bodies, comparing with standard bodies in the same aged individual group, are occasionally appeared from fifth zoea larva stage, and occurence of it be tempted to relate with the factor of trophic condition. This paper was dealt with a comparative morphological view on big individuals, comparing with standard type in the same aged group, to solve the problem on (1). the existence or nonexistence of stages which it is easier to occurence of big individuals, (2). the rate of development in several appendages of an individual, and (3). a happening of skipping whether it certainly occur or not, during newly hatched zoea larvae develop to post larva stage. The results of the above are as follow: (1). the stages which is easier to occur of big individuals are fifth and seventh stage in this species, (2). even same individual, development of several appendages differs more or less on the rate of growth in accordance with its parts, (3). Evidence which skipping phenomenon is occured, during development through zoea larvae to post larvae, couldn't confirm.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.61-69
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• 2015

The objective of this study is to experimentally investigate the mixed flow behaviors and oxygen transfer characteristics of a vertical orifice ejector. The experimental apparatus consisted of an electric motor-pump, an orifice ejector, a circulation water tank, an air compressor, a high speed camera unit and control or measurement accessories. The mass ratio was calculated using the measured primary flow rate and suction air flow rate with experimental parameters. The visualization images of vertically injected mixed jet issuing from the orifice ejector were qualitatively analyzed. The volumetric oxygen transfer coefficient was calculated using the measured dissolved oxygen concentration. At a constant primary flow rate, the mass ratio and oxygen transfer coefficient increase with the air pressure of compressor. At a constant air pressure of the compressor, the mass ratio decreases and the oxygen transfer coefficient increases as the primary flow rate increases. The residence time and dispersion of fine air bubbles and the penetration of mixed flow were found to be important parameters for the oxygen transfer rate owing to the contact area and time of two phases.