• Journal of Korean Tunnelling and Underground Space Association
• /
• v.20 no.2
• /
• pp.405-421
• /
• 2018

In most of cases, the wall friction coefficients applied for local tunnel design are quoted directly from foreign data or local design guideline. In the previous studies, the wall friction coefficient was estimated using the velocity decay method. However, it is difficult to estimate the wall friction coefficient when the convergence wind velocity in the tunnel is negative (-) or if there is a change in the natural wind. Therefore, in this study, the wall friction coefficient is estimated by applying the dynamic simulation technique in addition to the conventional the velocity decay method. As a result of the analysis, the coefficient of wall friction in the tunnels for the total of 9 tunnels (18 tubes both directions) was 0.011~0.025, and the mean value was estimated to be 0.020. In addition, the wall friction coefficient obtained quantitatively through this study was compared with the current design criteria.

• KSBB Journal
• /
• v.9 no.4
• /
• pp.395-399
• /
• 1994

P. stipitis CBS5776 was cultivated to examine the characteristics of ethanol fermentation for hexoses (mannose, g1ucose, and galactose) and pentoses(xylose and arabinose). Glucose was the best carbon source among the sugars used in terms of ethanol yield. Glucose was used to produce ethanol with an yield coefficient 0.376g ethanol/g glucose, whereas mannose was converted to produce ethanol with an yield coefficient 0.326g ethanol/g mannose. P. stipitis CBS5776 was also grown in a mixture of sugars to study the pattern of carbon utilization. The yeast utilized glucose and mannose firsts and then galastose and xylose as carbon sources. Arabinose was partially used for biomass when it was present as a sole carbon source, but it was not metabolized at all in a mixture of carbon sources. P. stipitis produced $12.2g/\ell$ ethanol with a yield coefficient 0.332 g ethano1/g sugar in a mixture of sugars.

• Journal of Environmental Science International
• /
• v.14 no.9
• /
• pp.827-835
• /
• 2005

A three-dimensional ecological model (EMT -3D) was applied to Nonylphenol in Tokyo Bay. EMT -3D was calibrated with data obtained in the study area. The simulated results of dissolved Nonylphenol were in good agreement with the observed values, with a correlation coefficient(R) of 0.7707 and a coefficient of determination (R2) of 0.5940. The results of sensitivity analysis showed that biodegradation rate and bioconcentration factor are most important factors for dissolved Nonylphenol and Nonylphenol in phytoplankton, respectively. In the case of Nonylphenol in particulate organic carbon, biodegradation rate and partition coefficient were important factors. Therefore, the parameters must be carefully considered in the modeling. The mass balance results showed that standing stocks of Nonylphenol in water, in particulate organic carbon and in phytoplankton are $8.60\times 10^5\;g,\;2.19\times 10^2\;g\;and\;3.78\times 10^0\;g$ respectively. With respect to the flux of dissolved Nonylphenol, biodegradation in the water column, effluent to the open sea and partition to particulate organic carbon were $6.02\times10^3\;g/day,\;6.02\times10^2\;g/day\;and\;1.02\times10^1\;g/day$, respectively.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.2097-2101
• /
• 2007

This paper presents an optimal design of a micro evaporator which maximizes the heat transfer coefficient. Number of gaps, spanwise distance and streamwise distance are selected as the geometric design parameters. Mass flow rate of the refrigerant is selected as the non-geometric design parameter. Temperature at the surface of the heater is measured to valuate the heat transfer coefficient. Nine experiments are conducted using $L_9(3^4)$ orthogonal array. Maximum heat transfer coefficient is 640 W/$m^2K$ at the parameters of 2 gaps, 0.2 mm spanwise distance, 1.0 mm streamwise distance and 0.72 g/s mass flow rate. Among the 3 geometric parameters, the spanwise distance is the most sensitive parameter influencing the heat transfer coefficient. We conduct a second stage of experiment to increase the heat transfer coefficient by reselecting the mass flow rate. We concluded that 0.87 g/s is the optimized flow rate for an active micro cooler resulting in a heat transfer coefficient of 651 W/$m^2K$.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.4
• /
• pp.1146-1153
• /
• 1996

The properties of FRP(fiber-reinforced plastics) depend not only on the characteristics of the matrix but also on the structure of fiber mat and the fiber type of reinforcement. Therefore it is very important to study the characteristics of reinforcement and matrix. In this paper, a method is proposed which can be used to measure the mean coeffcient of separation for the press molding of FRP, and the mean equivalent coefficient of separation is obtained from the separation coefficient. And the relationship between the mean equivalent coefficient of separation and the structure of fiber mat is discussed. The effects of corrlelation coefficient between separation and orientation on the mean equivalent coefficient are also presented.

• Journal of Soil and Groundwater Environment
• /
• v.18 no.3
• /
• pp.82-92
• /
• 2013

This study has investigated naturally occurring radioactive materials (N.O.R.M; $^{238}U$, $^{222}Rn$) for 353 drinking groundwater wells in metamorphic rock areas in Korea. Uranium concentrations ranged from N.D (not detected) to 563.56 ${\mu}g/L$ (median value, 0.68 ${\mu}g/L$) and radon concentrations ranged from 108 to 11,612 pCi/L (median value, 1,400 pCi/L). Uranium and radon concentrations in the groundwater generally are similar to USA with similar geological setting. Uranium concentrations in 9 wells (2.6%) exceeded 30 ${\mu}g/L$, which is the maximum contaminant level (MCL) by the US environmental protection agency (EPA), radon concentrations in 46 wells (13%) exceeded 4,000 pCi/L, which is the Alternative MCL (AMCL) by the US.EPA. The log-log correlation coefficient between uranium and radon was 0.32. The correlation coefficient between uranium and pH was 0.12 and the correlation coefficient between radon and temperature was -0.01. The correlation coefficient between uranium and $HCO_3$ was 0.09 and the correlation coefficient between uranium and Ca was 0.11. The median value of uranium was high Chung-Buk (1.78 ${\mu}g/L$), Gyeong-Buk (1.37 ${\mu}g/L$), In-Cheon (1.06 ${\mu}g/L$) for each province. On the other hand, the median value of radon was high In-Cheon (2,962 pCi/L), Chung-Buk (2,339 pCi/L), Jeon-Buk (2,165 pCi/L) for each province. Jeon-Buk for log-log correlation coefficient is the highest (0.63) among provinces.

• Journal of the Korean Wood Science and Technology
• /
• v.47 no.3
• /
• pp.290-298
• /
• 2019

The sound absorption coefficient and transmission loss of several types of rice hull mats with varying apparent densities and thicknesses are estimated in this paper using the transfer function and matrix methods, respectively, to evaluate the possibility of using rice hull as an acoustic construction material. The mean sound absorption rates of 10-cm-thick rice hull mats with target densities of $0.10g/cm^3$, $0.12g/cm^3$, and $0.14g/cm^3$ were 0.91, 0.92, and 0.95, respectively, while those of the 1-cm-thick plywood attached to the back of the rice hulls were 0.90, 0.92, and 0.92, respectively. The means of the sound transmission loss of the 10 cm-thick rice hull mats with the target densities of $0.10g/cm^3$, $0.12g/cm^3$, and $0.14g/cm^3$ were 7.66 dB, 10.49 dB, and 14.14 dB, respectively, while those of the 1 cm-thick plywood attached to the back of the rice hulls were 33.34 dB, 36.72 dB, and 38.95 dB, respectively. In conclusion, a rice hull mat could be used as acoustic construction materials because of its high sound absorption coefficient and sound transmission loss.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.10a
• /
• pp.1069-1080
• /
• 2008

The mechanical characteristic of Lightweight Foamed Soil(LWFS) are investigated in this research. LWFS is composed of the in-suit soil, cement and foam to reduce the unit-weight and increase compressive strength. The unconfined compressive tests are carried out on the prepared specimens of LWFS with various soil types to investigate the relationship between compressive strength of LWFS and physical properties of soil. The result indicate that coefficient of gradation($C_g$) and liquid limit(LL) are more important factor affecting compressive strength than other physical properties of soil and coefficient of gradation($C_g$) and liquid limit(LL) can standard to determine the optical soil among the in-situ soils for LWFS.

• Bulletin of the Korean Mathematical Society
• /
• v.40 no.2
• /
• pp.309-317
• /
• 2003

In this paper we study the relation of Euler characteristic with respect to cohomology with compact support in F$_{p}$-coefficient for the fibration of ENR's and generalize some properties on proper G-spaces for locally compact Lie group G.G.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2000.11a
• /
• pp.177-184
• /
• 2000

This study is to choose the most proper model for AGV throughout simulation of behavior of suspension to reduce trial and error because there is no AGV treating heavy weight at harbor loading and unloading at home. Therefore, we estimate the vibration modes of the various suspensions applied to AGV, which is over 75 ton included the weight of two containers using the Matlab in the case of G and 5G, one of the simulation programs.