• Korean Journal of Optics and Photonics
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• v.11 no.3
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• pp.202-205
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• 2000

One step thermal potassium ion exchange process was carried out to form optical channel waveguides in an ErNb co-doped phosphate glass. Flowing oxygen gas into KN03 melt during ion exchange was effective to prevent glass surface damage that causes an increase of waveguide propagation loss. Amplification characteristics of the waveguides were evaluated at $1.5{\mu}m$ signal wavelength with 980 om laser diode pump. A 45 mm long waveguide whose processing parameters had been optimized exhibited a small signal net gain of 7.5 dB at the launched pump power of 160 mW.160 mW.

• KCID journal
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• v.17 no.2
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• pp.71-81
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• 2010

Stream Pilot Project, which began in May 2003 and finished in December 2003, was selected to develop effective methods applicable to nature-like streams. Stream restoration projects aim to maintain or increase ecosystem goods and services while protecting downstream and coastal ecosystems. Fields environmental monitoring such as flow discharge and precipitation were conducted along the Idong stream for amount of channel zone change in 2007. This study selected three monitoring positions to measure the water level and discharge of flowing water. A stage-discharge relation is obtained from direct discharge measurements for three stations by fitting an empirical relationship to the data set. Since discharge measures are made only for low flow conditions, a curve of discharge against stage can then be built by fitting these data with a power curve. And this study used data obtained from floodmark checkup as well as HEC-RAS model to analyze the hydrodynamic characteristics of monitoring sites. Reach-averaged hydraulic parameters for the supply reach were calculated from the small area's HEC-RAS model for Idong stream, and a HEC-RAS model used to analyze hydraulics for a period in 2007, after the stream was considered bank stabilization.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.131-136
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• 2008

Using ultrasonic standing waves, micro particles submerged or flowing in fluid can be manipulated. Due to acoustic radiation force of ultrasound, particles are forced to move to pressure nodal or antinodal lines. In this work, we propose a method to control the position of micro particle in a flow by adjusting the frequency of the standing wave. To this end, standing wave field generation system including a few millimeter thick micro channel was established using an immersible ultrasonic transducer. The present generation system works valid in a frequency range between 2.0 MHz and 2.5 MHz. We observed the SiC particles in water moved to pressure nodal lines by the standing wave. The effect of the channel thickness and operating frequency was also investigated. Interestingly, it was shown that the operating frequency have a close relation with the location of the pressure nodal line. Consequently, it fan be said that the position of particle movement rail be controlled by adjusting the ultrasound frequency. The maximum range of the controllable position was about 261 micrometers under the given condition. The resulted observations reveal the possibility of various applications of the ultrasonic standing wave to the manipulation of particles submerged in a fluid.

• Journal of Korea Water Resources Association
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• v.38 no.3 s.152
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• pp.235-244
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• 2005

This study was carried out in Osan river to quantitatively investigate behavior of attacked microbial community (AMC) for enhancing self-purification process of river. We gained the results such as follows throughout long-term monitoring at in-situ river. The biomass of AMC had higher in the riffle than the almost stagnant pool and they were more developed in the riffle with high current velocity (HCV). Although the fast flowing current affects negatively to growth of the AMC during the early phase when the community gets attached to the benthic substrate, it was observed that it affected positively to their growth during the intermediate and later phase after the community is adapted to the substrate. When turbulence due to external pressure (storm or discharge of dam and reservoir) occurs, the degree of separation depends upon the flowing strength and the type of the external pressure. Since the community is not all separated, recovery is rather fast. Therefore, this study found that the degree of reduction of the pollutant by self-purification of the stream is depended upon the riverbed shape and the AMC contributes to self-purification positively or negatively in river. Therefore, the riverbed shape must be constructed in accordance with the characteristics of water quality in stream. Furthermore, the technique of installing the water channel structure appropriate for each section must be developed to maximize self-purification ability.

• Journal of The Geomorphological Association of Korea
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• v.27 no.4
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• pp.71-88
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• 2020

This study modified the properties and boundaries of the inland wetland types through the structural edit of the National Wetland DB, and analyzed the characteristics of the different land cover by area and the entire inland wetlands of South Korea. The inland wetlands of the Gangwon Basin had a small area of waters. In addition, the ratio of natural barren was high, reflecting the characteristics of the upper reaches of the large river in the east and west part of Gangwon Province. The Geum River Basin had a high percentage of aggregate land due to the development of large alluvial land, and the ratio of artistic barren was low, so various ecosystem service of wetland elements were distributed evenly. The Nakdong River Basin had a high proportion of waters as water level in the channel rose due to the installation of 4 Major Rivers Beam, and the ratio of Natural barren was low. Moreover, the water level of the main attributes flowing into the Nakdong River drainage system was not high, so the ratio of vegetation concentration was high. The Yeongsan River Basin showed that Waters had the high proportion. And the distribution of Natural barrens represented differently according to the Yeongsan River Basin and the Seomjin River Basin. Finally, Sand and Gravels supplied to rivers during precipitation were deposited in the main stream of the Han River Basin, and the differences between the side and high side was large in the area, reflecting the characteristics of the mouth of a river, so the Natural barren of Clay was distributed.

• Journal of Physiology & Pathology in Korean Medicine
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• v.19 no.2
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• pp.329-338
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• 2005

Breast milk is general term for crude milk and mature that is secrete after two-three days of delivery. Because amount of milk secretion is different, disorder of milk secretion is to be classified into galactostasis and spontanous flow of milk. According to this point, we considered thirty four papers and got the conclusion about the concept, cause, therapeutic method and medication of secreation disorder. Therefore we report the result. galactostasis due to deficiency of the qi and blood, depression of liver qi, blood stasis of postpartum, excessiveness and so on. If the qi and blood is deficient, therapeutic method is enriching qi and benefiting blood, if the liver qi is deprssive, treatment is relieving the deprssive liver and regulating the circulation of qi. The milk is flowing spontanously and continously due to a prosperous condition of qi and blood, too deficiency of the qi and blood, depression of liver qi and so on. If the qi and blood is deficient, therapeutic method is tonifying and arresting the qi and blood, if Liver channel is stagnated fire, puring the liver of pathologic fire, relieving the deprssive liver and regulating the circulation of qi. Clinical study for the 1 case of the recurrent cervical cancer patient.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.3
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• pp.879-894
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• 2016

In micro-fluid systems, fluids are injected into extremely narrow polymer channels in small amounts such as micro-, nano-, or pico-liter scales. These channels themselves are embedded on tiny chips. Various specialized structures in the chips including pumps, valves, and channels allow the chips to accept different types of fluids to be entered the channel and along with flowing through the channels, exert their effects in the framework of different reactions. The chips are generally crystal, silicon, or elastomer in texture. These highly organized structures are equipped with discharging channels through which products as well as wastes of the reactions are secreted out. A particular advantage regarding the use of fluids in micro-scales over macro-scales lies in the fact that these fluids are much better processed in the chips when they applied as micro-scales. When the laboratory is miniaturized as a microchip and solutions are injected on a micro-scale, this combination makes a specialized construction referred to as "lab-on-chip". Taken together, micro-fluids are among the novel technologies which further than declining the costs; enhancing the test repeatability, sensitivity, accuracy, and speed; are emerged as widespread technology in laboratory diagnosis. They can be utilized for monitoring a wide spectrum of biological disorders including different types of cancers. When these microchips are used for cancer monitoring, circulatory tumor cells play a fundamental role.

• Journal of Navigation and Port Research
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• v.30 no.5 s.111
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• pp.375-379
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• 2006

The keel attached on bottom of hull part prevents yacht from flowing sideway by sailing posture. The keel remove a heel moment and make the force of stability. The selection of suitable keel is important bemuse it has an influence on the safety. Also the appendage attached on bottom of keel part lower ballast weight center and have influence on hull stability. The optimum shape about the keel is very important. So this study has compared with characteristics of resistance depending on the shape of the lower part of fin keel in the same surface of water submersion, we have attached three different types of models of lower part of fin keels to the model ships using circulating water channel and analyzed resistance characteristics per shape to arrive at the optimum shape of reduction of resistance.

• Journal of Korea Water Resources Association
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• v.45 no.6
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• pp.583-596
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• 2012

The revetment is a installed structure on the slope of river bank to protect against flowing. Through the design standards of domestic and overseas, the maximum tractive force is calculated and applied to the average concept on the slope of river bank. In the case of calculating the method of permissible tractive force on the slope of river bank, there is a need to consider soil sliding. In this study, suggested the tractive force formulae by section of adhesion that have 0 < ${\Phi}$ < $90^{\circ}$ slope of river bank and installed an open channel of length of 20 m and 2 m wide for calculating permissible tractive force and hydraulic model experimented with changing discharge. According to the results, the calculated permissible tractive force of section on the slope is the largest due to the significant effects of surface roughness of different revetment materials. In addition, the permissible tractive force increased in the presence of vegetation but has no the effect by vegetation density.

• Journal of Ecology and Environment
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• v.40 no.1
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• pp.12-19
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• 2016

Background: Direct impact of inorganic carbon (i.e., carbon dioxide ($CO_2$)) on the periphyton community is important to understand how and to what extent atmospheric conditions can affect the structure and dynamics of these communities in lotic systems. We investigated the influence of elevated $CO_2$ concentration on the periphyton community in the artificially constructed channels during the winter period. The channels made of acrylic paneling were continuously supplied with surface water discharged from a small reservoir, which was supported with ground water, at a flow rate of 5 L/min, and water temperature ranging $4-5^{\circ}C$. The effects of elevated $CO_2$ concentrations (790 ppm) were evaluated in comparison with the control (395 ppm $CO_2$) by analyzing pH, water carbon content and nutrients in water, periphyton composition and biomass, chlorophyll-a, ash-free dry-matter at 2-day intervals for 10 days. Results: After the addition of $CO_2$, significant decreases of pH, $NH_3-N$, and $PO_4-P$ (p < 0.05) and increases of chlorophyll-a, ash-free dry-matter, and the cell density of periphyton (p < 0.01) were observed, whereas the species composition of periphyton and water carbon content did not change. Conclusions: These results suggest that elevated $CO_2$ in flowing water system with low temperature could facilitate the growth of periphyton resulting in biomass increase, which could further influence water quality and the consumers throughout the food web.