• Journal of the Korea Society of Computer and Information
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• v.18 no.4
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• pp.113-121
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• 2013

In this paper, simulations were carried out to determine the efficiency of the rotation efficiency according to the draft of waterwheel in open rectangular channel. In the small hydroelectric generators to get the highest efficiency of waterwheel is very important. But the presence of various elements(free water surface flow, non-uniform velocity distribution because of the waterways wall friction etc) makes it difficult to create a mathematical formula. In this paper, we made a scale model and perform a physical simulation where the draft, gradient and flux is variable. Scale modelling with 10-step draft, 3-step gradients and 2-step flux, as well were constructed then computerized automatic experimental system were configured to acquire the rotational efficiency vs. draft of itself. Rotational efficiency is analyzed as for the draft of waterwheel using the acquired data by varying the gradient and flux of canal. Reviewing the analyzed data, it is confirmed that phenomena of efficiency shown at previous and present experiment is similar and revealed that computerized system shows more sophisticated numerical figures.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.4
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• pp.323-329
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• 2012

In this study, a new optical method for oil detection using an analysis the light-absorption image of separate oil-water mixture with a LED illumination is described. To obtain an information about the presence of oil on water and the thickness of oil, the intensity of light-absorption images acquired through CCD is analyzed. To select the optimal wavelength of the light source, the experiment is conducted using several LEDs having four different wavelength. In the case of using a blue LED having 465 nm wavelength, an intensity decreasing tendency of light-absorption image is obvious and clear. To identify the applicability of sensing system at the real sea condition, experiments are conducted as varying the brightness and water surface angle. Through this research, new optical oil detection methodology is proposed using the absorption difference between water and oil with single-wavelength LED and CCD.

• Applied Microscopy
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• v.30 no.2
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• pp.233-240
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• 2000

Aspects of structural differentiation of the free -floating hydrophyte, Spirodela polyrhira, has been investigated. The hydrophyte exhibited highly reduced structures having only fronds, connective stalks, and roots as a mature plant. The fronds were major photosynthetic and vegetatively reproducing organ during the growth. Daughter fronds which developed early in the mother frond were also chlorenchymatous, but they remained within foliage sheaths of the mother frond before separation from connecting stalks. Although the stalks and roots originated from the same meristematic region of the frond, they exhibited the distinct polarity showing former lateral growth and latter axial growth. Air chambers were formed only in the fronds and roots. Cellular components were scattered throughout the diffuse cytoplasm in most of the actively growing stalk cells. Root cells protected by the root cap demonstrated relatively complex organization, showing dense cytoplasm with Golgi, rER, mitochondria, and chloroplasts in the cortical cells. Cells in the root cap were highly vacuolated within the peripheral cytoplasm. Such reduction and differentiation of the plant body in Spirodela polyrhiza most effectively contributes to the better adaptation of smaller plants to superficial aquatic environments, while also enabling the rapid growth.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.986-990
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• 2005

The present study aims to illuminate the vertical velocity profile of outer region of open-channel flow. Two sets of experiments were performed with PIV and propeller velocimeter. The first set was conducted to investigate the effect of bed roughness on the velocity distribution. The second set of experiments was carried out to find the effect of the Froude number on the velocity profile under the same bed roughness. The results reveal that the wake-law fits well with the experimental data from the bottom to the depth of maximum velocity, but it deviates from the experimental data above the maximum velocity point due to velocity-dip phenomenon, and that the velocity profile of the outer region is more influenced by the Froude number than the roughness. It is also shown that both the velocity difference between maximum velocity and surface velocity and the ratio of the average velocity to surface velocity become larger as the Froude number increases.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.2
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• pp.41-50
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• 1985

The mathematical analysis of the outflow hydrograph resulting from earth dam-break was studied. DBFW(Dam Break Flood Wave) model based on the breach mechanism and reservoir storage equation was developed and was applied to the Teton and Buffalo-Creek dam. The modeling results showed that the shape of outflow hydrograph, peak discharge and failure duration time had a good agreement with the data analyzed by NWS. The breach mechanisms which exert influence on the outflow hydrograph were consisted of geomorphological characteristics of the reservoir, breach mode, breach width and failure duration time. The earth dams in Korea were classified into four types by the reservoir geomorphology, and water surface elevation-failure duration time-peak discharge relationships were also presented. The methodological procedure made in this paper will provide a basic contribution to dam-break study in river system.

• Journal of KIISE:Information Networking
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• v.29 no.5
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• pp.482-494
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• 2002

In E-mail based accounting system, the remitter does not have need to find collector's account number. To transfer money to a collector's account, what remitter need is just a collector's E-mail address. But the current E-mail based accounting systems are built on SSL technology. Basically SSL provides some security services - confidentiality, user authentication and data integrity, but does not provide non-repudiation. So, in the current E-mail based accounting system, it is possible to deny transaction. And there is no receipt of transaction. In this paper, we design and implementation of a S/MIME applied Secure Payment Mechanism. In our system, every account information - account number, receiver name, amount of money, etc. - is included in a 'check' message. And this message is protected under the Secure Web-mail using S/MIME. In a view point of the convenience, users using our system do not have need to find collector's account number. And in a view point of the security, our system provides confidentiality, user authentication, data integrity and non-repudiation. Moreover our system provides a receipt.

• The Journal of Natural Sciences
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• v.16 no.1
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• pp.143-154
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• 2005

To define the ecological roles of bacterial community in Daechung Reservoir. Vertical variation of total bacterial numbers were estimated at MAN site for one year with DAPI staining. The bacterial numbers were counted, environmental factors were monitored at the surface, -5m, -10m, -15m and -25 m of MAN sited and tried to explain the vertical bacterial numbers with environmental factors. The bacterial number was $1.6-1.7.0 x10^6$ cells/ml at the surface, $2.3-11.0x10^6$ cells/ml at 5 m depth, $1.2-1.4.0x10^6$ cells/ml at 10 m depth, $1.4-15.0x10^6$ cells/ml at 15 m depth and $1.4-1.3.0x10^6$ cells/ml at 25 m depth. The Mean bacterial number at the surface was more that those at any other depth. The explanation of the vertical total bacterial numbers with environmental factors were suggested.

• Animal Systematics, Evolution and Diversity
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• v.17 no.2
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• pp.171-177
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• 2001

The life history of Obelia bicuspidata Clarke, 1975 (Hydrozoa, Campanulariidae) was studied in its habitats, Jak-yk Island, Korea and in the laboratory It grows mainly attaching to the under sides of small rocks immersed in muddy shores, or the shade surfaces of oyster shells. The hydoids liberate medusae. The medusa buds develope twice per year, during from March to June and from September to October The optimum water temperature for the hydroids is between 4$^{\circ}C$ and 8$^{\circ}C$ and at the temperature above 9$^{\circ}C$ the hydroids begin to degenerate. In August the surface water temperature is around $25^{\circ}C$ and the hydrothecae are all disappeared. The hydroids grow best during from February to May. The medusae are small, 0.3 mm high, 0.45 mm wide and require about 9 days at room temperature (about 2$0^{\circ}C$) for mature after releasing. Obelia bicuspidata turned out to be boreal species in this work.

• Geotechnical Engineering
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• v.1 no.1
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• pp.73-84
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• 1985

This Paper aims at investigating the distribution of stresses and the displacement of soft foundation layer subject to embankment load by the finite elements method (FEM). The stresses include the volumetric stress, the Pore water Pressure, the vertical stress. The horizontal stress and the shear stress. The Christian-Boehmer's method was selected as technique for FEM and the general elasticity model and modified Cam-clay model as the governing equations under Plain-strain condition depending on drained and undrained conditions. The results obtained are as follows: 1. The volumetric stress is almost consistent with the pore water pressure. This means that the total stress is the same value with the pore water pressure under the undrined condition 2. The vertical stress appears in the same value regardless of the drained or undrained condition and the model of the constitutive equations. 3. The horizontal stress has almost same value with the drain condition model. 4. depending on the constitutive model. The shear stress is affected by both the drain condition and the constitute model. The resulted value by the modified Cam-clay model has the largest. 5. The direction of the displacement vector turns outward near the tip of load during the increasing load. 6. The magnitude of displacement due to the modified Cam.clay model is as twice large as that due to elastic model.

• Journal of Environmental Science International
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• v.21 no.6
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• pp.739-747
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• 2012

Due to the difficulties for measuring flood discharge in the dangerous field conditions, conventional instruments with relatively low accuracy such as float still have been widely utilized for the field survey. It is also limited to use simple stage-discharge relationship for assessment of the flood discharge, since the stage-discharge relationship during the flood becomes complicated loop shape. In recent years, various non-intrusive velocity measurement techniques such as electromagnetic wave or surface images have been developed, which is quite adequate for the flood discharge measurements. However, these new non-intrusive techniques have little tested in the flood condition, though they promised efficiency and accuracy. Throughout the field observations, we evaluated the validity of these techniques by comparing discharge and velocity measurements acquired concurrently during the flood in a mountain stream. As a result, the flood discharge measurements between electromagnetic wave and surface image processing techniques showed high positive relationship, but velocities did not matched very well particularly for the high current speed more 3 m/s. Therefore, it should be noted here that special cares are required when the velocity measurements by those two different techniques are used, for instance, for the validation of the numerical models. In addition, authors assured that, for the more accurate flood discharge measurements, velocity observation as well as stage height is strongly necessary owing that the unsteady flow occurs during the flood.