• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.5
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• pp.646-651
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• 2012

This paper is about the experiment which is throughput of WLANs based on 802.11 due to interference each other. Recently, WLAN has been increased due to generalization of smart-phone and potable notebook. Therefore, the decrease of throughput because of interference between WLANs is expected. In regard of this, the throughput of WLANs according to channelling is measured in order to figure out efficient channelling and the throughput of WLANs according to the number of AP was measured in order to get relation between number of AP and throughput. Then, more efficient channelling of 1, 5, 9, 13 is suggested and the throughput of WLAN is decreased as increasing of number of AP.

• KSBB Journal
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• v.8 no.4
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• pp.351-357
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• 1993

Three immobilization techniques and free cell system were tested to determine the most effective technique for the treatment of pulp waste effluent. The tests were conducted using Phanerochaete chrysosporium as a biocatalyst in a process designed to treat pulp waste effluent. The results show that Ca-alginate gel was the best immobilization material. The chosen material improved the stability and increased the removal efficiency of the system. The experiment using the chosen material was mom- bored for 400 hours with no significant changes in the state of the fungus. Common problems with other immobilization materials and free cell system were oxygen transfer resistance caused by air channelling and clogging in the bioreactor.

• Journal of the Korean GEO-environmental Society
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• v.14 no.4
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• pp.5-13
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• 2013

The water leakage of reservoir embankment usually occurs around channelling pipes, which gives little influence on the embankment in a normal state. However, the embankment can be destroyed when the water level of reservoir increases with heavy rain and the rainy season in summer. Investigating the water vein and its path is therefore very important from the viewpoint of disaster prevention and embankment maintenance. The water leakage in dams and levees where the channelling pipes are working as weak zone was analyzed by using both numerical simulation and experimental method in this study. To detect the water leakage, an electrical resistivity survey was used and investigated for its' usability. The numerical results show the size and location of weak zone increases the importance of selection of electrode spacing. The leakage experiments of model embankment present the best result is obtained under the conditions of electrode spacing of 0.3m and dipole-dipole array. By studying the water leakage in dams and levees, the electrical resistivity survey is observed it is a very useful method to predict the leakage.

• Wind and Structures
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• v.8 no.6
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• pp.389-406
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• 2005

The results of reference wind speed calculation in Croatia as a base for the revision of the Croatian standards for wind loads upon structures are presented. Wind speed averaged over 10 minutes, at 10 m height, in a flat, open terrain, with a 50-year mean return period is given for 27 meteorological stations in Croatia. It is shown that the greatest part of Croatia is covered with expected reference wind speeds up to 25 m/s. Exceptions are stations with specific anemometer location open to the bura wind which is accelerated due to the channelling effects of local orography and the nearby mountain passes where the expected reference wind speed ranges between 38 m/s and 55 m/s. The methodology for unifying all available information from wind measurements regardless of the averaging period is discussed by analysing wind speed variability at the meteorological station in Hvar.

• KSBB Journal
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• v.5 no.4
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• pp.329-334
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• 1990

In an attempt to develop a novel process for ethanol production from starch, a simultaneous saccharification and fermentation (SSF) process using Zymomonas mobilis and amyloglucosidase (AMG) was studied in continuous modes. Compared with a conventional cylindrical column type of fermentor, the tapered column type of fermentor was found to be superior in terms of reactor performance for ethanol fermentation. The tapered columm fermentor packed with coimmobilized Z. mobilis and AMG alleviated the problems which were associated with CO2 evolution and provided a significantly better flow pattern for both liquid and gas phases in the fermentor without channelling. However, the fluidized bed type of tapered column fermentor using flocculent strain of Z. mobiles and immobilized AMG showed lower productivity (5.2g/1/h) than that of packed bed type of tapered column fermentor(9.2g/l/h).

• Korean Journal of Microbiology
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• v.25 no.3
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• pp.189-197
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• 1987

The aim of the present study was to investigate the effect of glutamate on the biosynthesis of tylosin. Activities of enzymes involved in the metabolic pathway of glutamate to form tylactone, an essential precursor of tylosin, were determined using Streptomyces fradiae grown at different concentration of glutamate. As results, it was found that cell growth and tylactone formation was controlled by the metabolic flux of oxaloacetate. It was clear that cell growth was favored by the activities of citrate synthase and aspartate aminotransferase, while the tylactone synthesis was stimulated by the activity of methylmalonyl-CoA carboxyltransferase. Therefore it was concluded that channelling of oxaloacetate was a point for favoring either cell growth or tylosin biosynthesis.

• Journal of Environmental Science International
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• v.23 no.9
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• pp.1551-1562
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• 2014

To clarify the characteristics of TKE (Turbulence Kinetic Energy) variation for offshore wind power development, several numerical experiments using WRF were carried out in three different coastal area of the Korean Peninsula. Buoyancy, mechanical and shear production term of the TKE budget are fundamental elements in the production or dissipation of turbulence. Turbulent kinetic energy of the south coast region was higher than in other sea areas due to the higher sea surface temperature and strong wind speed. In south coast region, strong wind passing through the Korea Strait is caused by channelling effect of the terrain of the Geoje Island. Although wind speed is weak in east coast, because of large difference in wind speed between the upper and lower layer, the development of mechanical turbulence tend to be predominant. Since lower sea surface temperature and smaller wind shear were detected in west coastal region, the possibility of turbulence production not so great in comparison with other regions. The understanding of the characteristics of turbulence in three different coastal region can be reduced the uncertainty of offshore wind construction.

• Journal of Environmental Science International
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• v.13 no.7
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• pp.655-660
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• 2004

This paper demonstrates the numerical simulation of three dimensional flow pattern for vehicular exhaust dispersion in the street canyons. The wind flow around buildings in urban is computed by the SIMPLEST method. The convection-diffusion equation was used to compute the $NO_X$ concentration level near buildings. Details are given of important boundary conditions and turbulence quantities variations. The simple turbulence model was used for unisotropic viscous effect. A control-volume based finite-difference method with the upwind scheme is employed for discretization equation. The simple turbulence model applied in this study has been verified through comparison between predicted and measured data near buildings. By the predictive results, the updraft induced by the presence of high-rise buildings is important in the transport of street level pollutant out from the street canyons. Our suggestion for reducing ground level pollution is to have high-rise buildings constructed or to reduce the channelling effect of street canyons.

• Journal of Korean Society for Atmospheric Environment
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• v.7 no.3
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• pp.169-179
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• 1991

Atmospheric $O_3$ in the biosphere is formed under the favourable meteorological condition, when the primary pollutants, such as $NO_2, HC, CO, CH_4$, etc., react with over constituents. Observed annual average concentrations for 1989 and 1990 were 11.8 and 10.4 ppb, respectively. THe number of days measured ozone over 80 ppb in Seoul were 36 in 1989 and 39 in 1990. In general, monthly maximum values occurred in May and August. In comparison with 1 $\sim$ 2 maxima of $O_3$ distribution in large cities in other countries, it was found that there were 3 $\sim$ 4 maxima in Seoul and its suburbs. Topographic effects, resulted by wind channelling in the Han River valley and by the blocking of air pollutants in the mountain, appeared to produce multiple centres of $O_3$ maxima in Seoul. Surface $O_3$ values were low with decreasing solar radiation, when the cloudiness increased and precipitation occurred. According to 12 cases examined, 2 cases shown here, $O_3$ values exceeding 80 ppb were occurred when the Korean peninsular was under the influence of the backside airflows with high intensity of solar radiation. Occasionally, sea breezes were observed to occur in warm seasons, and the chanelling effect of the Han River valley appeared to increase the general wind (speed) to the east side of Seoul. In this meso-scale situation $O_3$ in downwind is highly correlated with precursors. The sea breeze of 2 $\sim$ 4 m $s^{-1}$ will take 3 $\sim$ 5 hours to transport photochemical precursors for 20 $\sim$ 50 km. In turn the areas of maximum $O_3$ occurrence in Seoul are in the range of meso-scale transport of air pollutants.

• International Area Studies Review
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• v.12 no.3
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• pp.293-319
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• 2008

Medium and small-sized venture firms as well as multinational companies pay liabilities of foreignness. We defined these costs as three different factors which are liability of handicaps(deficit of time, money, experience and, increase of financial risk), overseas market entry costs(information gathering costs, network building costs, marketing costs, channelling costs, monitoring costs), internationalization preparing costs(forecasting and market research of local markets, ex-ante cooperation with local firms), and then empirically tested how each of these factors affects on their business performances. The more important both Taiwanese and Korean firms consider liability of handicaps, the more bigger they pay overseas market entry costs(H1). On the contrary, the more important they consider overseas entry costs, the more they focus on internationalization preparation(H4) and get the better business performances(H5). The more important Korean firms consider liability of handicaps, the bigger they focus on internationalization preparation, on the contrary, the less Taiwanese firms do this(H2). Taiwanese firms as well as Korean firms rejected Hypothesis 3 and 6 which mean both liability of handicaps and internationalization preparation are no relation with their own business performances.