• Proceedings of the Optical Society of Korea Conference
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• 1999.08a
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• pp.188-189
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• 1999

• Water for future
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• v.17 no.2
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• pp.72-79
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• 1984

This investagation was carried out by analyzing water types and measuring the environmetal isotopes (tritium and deuterium) for development of water resources and protection of ground waters from sea water intrusion. The water sample were taken monthly from April to June, 1983 from sixteen sites in the Cheju metropolitan area; three sea, three spring, and ten ground waters. The ground water in the midwest area of the city contained 20 TU of tritium and-46 per mille of deuterium, classified as the $NaHCO_3$ type of ground water, generally deep seated. The spring water and ground water in the southern part of the city contained 15 to of tritium and-39 per mile of deuterium, and appeared to the $CaHCO_3$ type of shallow ground water, easily affected 표 precipitation. The results of tritium and deuterium analyses showed that the ground water in the coastal area were not affected by sea water intrusion, although they changed from $NaHCO_3$ or $CaHCO_3$ type to NaCl type in May and June. It is concluded that the high Na and Cl content in those ground waters might come from municipal sewage. The sea water in the Yong-duam area was influenced by sping water.

• Journal of Fisheries and Marine Sciences Education
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• v.3 no.2
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• pp.73-82
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• 1991

In recent years, the communication and the trade between the Republic of Korea(South Korea) and the Communist bloc has been activated. The simultaneous entrance of South Korea and North Korea to the United Nations will accelerate the political dialogue and also the trade which is indirectly carried out through a third country at present will be turned into direct way. Fisheries products are also treated as one of the important trade goods and there is a hopeful prospect that the amount of trade will be steeply increased in the near future. Furthermore, there is a great possibility of development up to the joint utilization of fishing grounds or the joint investment in fisheries projects. Concerning such points, since it is very much important to understand the present status of fisheries in North Korea, the author made a study on this field as requested by the Board of Unification, and report a part of the study here. The prominent character of North Korea's ruling sea area is that the sea is completely separated into two regions-the East Sea Region and the West Sea Region-and no continuity exists between them. The East Sea Region locates in the fringe of the biggest fishing ground of the world-the North Pacific Ocean-and very rich in resources not only warm water fishes but also cold water fishes. Especially alaska pollack, Theragra chalcogramma, is caught abundantly in this region. Contrary to that, fishing activity in the West Sea Region seems to be interrupted in winter. Even though some valuable warm water fishes-yellow corvenia, Pseudosciaena manchurica, and hair tail, Trichiurus lepturus, and so forth-come to this region from spring to summer along the coast line of this region for spawning, and vigorous fishing activity is carried out. But the most of them migrate southward to the neighboring waters of Cheju Island for wintering from autumn to winter, and so the fishing activity in this region seems to be interrupted greatly during winter. The total number of fishing boats in North Korea is estimated at 36 thousand and the rate of mechnization at about 70% compared with 99 thousand and 78% in South Korea. North Korea proclaimed an exclusive economic zone of 200 nautical miles in 1977. Specific character of this zone is setting of military boundary zone, up to 50 miles from the base line in the East Sea Region and also it covers whole region of the economic zone in the West Sea Region. Especially in the East Sea Region she set up a straight base line which can not be permissible by the international law. North Korea's statistics on fisheries product has not been announced officially on account of her unique isolationism, but it can be estimated through several data procured. At the first, the amount of fisheries products in the North Korea is reported as about 1.7 million ${\frac{M}{T}}$ by Fisheries Statistics which issued by the FAO in 1987, but a North Korea's trade organization announced the amount as 3.5 million ${\frac{M}{T}}$ in 1988. The former seems to be underestimated and the latter must be an exaggeration. According to Chikuni, who is a Japanese worker for FAO, prepared the unofficial statistics based on the evidence which he collected through the fineries development plan of the FAO/UNDP, and estimated the mean amount between 1982 and 1984 was 2.4 million ${\frac{M}{T}}$ or so. The Board of Unification estimated on the basis of various factors that the amount was 2.2 million ${\frac{M}{T}}$ or so in 1987 and in 1988. This seems to be the most reasonable. To solve the chronic lack of foreign currency, North Korea makes effort on the development of fisheries, and has even aimed fisheries product at 11 million ${\frac{M}{T}}$ by 1993, but this target looks unrealistic under the present circumstances. Somehow, we can exploit her extreme policy which has gone so far as to establish such an excessive and impractical target. Nevertheless this will be helpful to promote the joint development of the fishery activity between South Korea and North Korea.

• Journal of Korea Multimedia Society
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• v.13 no.7
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• pp.1044-1050
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• 2010

Endoscopic ultrasonography is a medical procedure in endoscopy combined with ultrasound to obtain images of the internal organs. It is useful to have a predictive pathological manifestation since a doctor can observe tumors under mucosa. However, it is often subjective to judge the degree of malignant degeneration of tumors. Thus, in this paper, we propose a feature analysis procedure to make the pathological manifestation more objective so as to improve the accuracy and recall of the diagnosis. In the process, we extract the ultrasound region from the image obtained by endoscopic ultrasonography. It is necessary to standardize the intensity of this region with the intensity of water region as a base since frequently found small intensity difference is only to be inefficient in the analysis. Then, we analyze the spot region with high echo and calcium deposited region by applying LVQ algorithm and bit plane partitioning procedure to tumor regions selected by medical expert. For detailed analysis, features such as intensity value, intensity information included within two random points chosen by medical expert in tumor region, and the slant of outline of tumor region in order to decide the degree of malignant degeneration. Such procedure is proven to be helpful for medical experts in tumor analysis.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.1
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• pp.40-48
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• 2001

The vertical distributions of temperature, salinity, dissolved oxygen, nutrients, chlorophyll, and primary production were investigated within the top 200m water depth in the south Pacific Ocean in February,2000. The study area ($24^{\circ}-41^{\circ}S,\;81^{\circ}-168^{\circ}W$) can be hydrologically divided into two regions. Upwelling was actively occurring in the eastern region of the $110^{\circ}S$ line, meanwhile it was not active in the western region. Accordingly, chemical properties in the surface waters were different between the two regions; nitrate+nitrite and phosphate concentrations were much higher in the eastern region than in the western region due to the active upwelling, but silicate concentration was higher in the western region. Among the nutrients, the major element influencing primary production was also different between the two regions; silicon would be a major element influencing primary production in the eastern region, but nitrogen may act as a major element for primary production in the western region. Primary production showed similar values in the two regions in spite of the large differences of nutrient concentrations in the surface waters, but the total chlorophyll integrated within the 200 m water depth was almost twice as much as in the western region than that in the eastern legion.

• Journal of Environmental Impact Assessment
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• v.3 no.2
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• pp.33-45
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• 1994

Water quality of Chongju and Daejeon Water Intake Tower Region, embayments in Daechong Reservoir was found to be worse than that of main lake after analysis of water which were sampled during April, July, October in 1993. Concentration of COD and SS at those two water intake tower sites were 2.8-5.6 mg/l and 2.2-3.2 mg/l, higher than that of main lake. T-N concentration of those two sites was 1.1-1.9 mg/l similar to that of main lake, and T-P concentration of those two sites was 0.14-0.18 mg/l, higher than that of main lake. This study used water quality model of embayment which can analyse pollutant loads from stream and surrounding land use, advection, decay, and diffusion transport between embayment and main lake. The model can predict water quality of embayment according to the change of pollutant load, water elevation of embayment, quantity of water intake in order to suggest water quality management. This study suggests embayment water quality management alternatives, 1) construction of waste water treatment facilities at embayment and main lake for the decrease of pollutant loading, 2) water intake at main lake less polluted or eutrophicated than embayment, and 3) outflow elevation selection for polluted hypolimnion water outflow during stratification.

• Proceedings of the Korea Society of Environmental Biology Conference
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• 2004.05a
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• pp.27-27
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• 2004

We studied algal growth-related water quality of the Sangsa lake which is the drinking water reservoir for the south-eastern region of Jeonnam province. Peridinium cinctum and several diatomic algal species frequently caused water bloom throughout the lake from early spring to late autumn. With the heaviest predominance of Peridinium cintum in May 2003, COD was 22.7 mg/l in the surface layer. Highly turbid surface water of 15 NTU was also caused by Perdinium bloom. Cyanobacterial growth was effectively prohibited by dominant growth of Peridinium in the Sangsa lake, otherwise confronted with cyanobacterial bloom. Dense algal layer was confined in the upper several meters of the water column above the thermocline, which gives relatively algae-free water in deeper layer suitable for drinking source water supply. Upon collapse of thermocline, water quality of the surface layer was improved while deeper layer was deteriorated. This paper deals with some details of water quality changes with algal growth in the Sangsa lake past two years.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.103-107
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• 2001

The major studies of an ocean circulation of the East/Japan Sea related to evaluate the feasibility and utilization of deep ocean water are reviewed. The major feature of surface current system of the East/Japan Sea is an inflow of the Tsushima Warm Current through the Korea/Tsushima Strait and the outflow through the Tsugaru and Soya Straits. The Tsushima Warm Current has been known to split into two or three branches in the southern region of the East/Japan Sea. In the cold water region of the East/Japan Sea, the North Korean Cold Current turns to the east near 39$^{\circ}$N after meeting the East Korean Warm Current, then flows eastward. The degree of penetration depends on the strength of the positive wind stress curl, according to the ventilation theory. Various current meter moorings indicate strong and oscillatory deep currents in various parts of the basin. According to some numerical experiments, these currents may be induced by pressure-topography or eddy-topography interaction. However, more investigations are needed to explain clearly the presence of these strong bottom currents. This study concludes the importance of topographical coupling, isopycnal outcropping, different wind forcing and the branching of the Tsushima Warm Current on the circulation of the East/Japan Sea.

• Journal of Ocean Engineering and Technology
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• v.28 no.4
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• pp.268-273
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• 2014

To investigate the turbulence characteristics within the boundary layer over a flat plate, an experimental study was performed using a PIV technique in a circular water channel. For two water velocities, 0.92 and 1.99 m/s, the water velocity profiles were taken and analyzed to determine turbulent characteristics such as the Reynolds stress, Taylor micro-length scale, and Kolmogorov length scale within the defect law region of the boundary layer. These analysis methods may be applied to research on the friction drag reduction technology using micro-bubbles or an air sheet over the surface of a ship's hull, because the physical reason for the friction drag reduction could be found by understanding the variation of the turbulence characteristics and structures in the boundary layer.

• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.3
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• pp.139-145
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• 2010

In the present study, we conducted resistance test, propeller open water test and self-propulsion test for a ship's resistance and propulsion performance, using computational fluid dynamics techniques, where a Reynolds-averaged Navier-Stokes equations solver was employed. For convenience of mesh generation, unstructured meshes were used in the bow and stern region of a ship, where the hull shape is formed of delicate curved surfaces. On the other hand, structured meshes were generated for the middle part of the hull and the rest of the domain, i.e., the region of relatively simple geometry. To facilitate the rotating propeller for propeller open water test and self-propulsion test, a sliding mesh technique was adopted. Free-surface effects were included by employing the volume of fluid method for multi-phase flows. The computational results were validated by comparing with the existing experimental data.