• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.247-252
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• 2004

To secure stability and availability of Rammed Aggregate Pier method as the foundation of a structure, the bearing capacity and failure behavior characteristics was studied through soil laboratory tests in a model ground. In this study, soil laboratory tests use carried out to find the applicability of RAP method as the foundation of a structure. And bearing capacity and the failure mechanism of RAP method was studied according to relative density($60\%,\;70\%,\;90\%$), diameter(45mm, 60mm, 70mm) of each pier ana depth(5cm, l0cm, 15cm, 20cm, 25cm, 30cm). Earth pressure cell is set up approach RAP and 1.0D space at RAP center. Bearing acpacity and the failure mechanism of RAP is investigated by load test As a result, bulging failure was happened in $5\~10cm\;(1.0D\~2.00)$ depth which the maximum lateral earth pressure is acting. Especially, diameter changing of RAP are in inverse proportion to the relative density and the lateral stress is very much influenced by the lateral earth pressure in every layer and tends to decrease according to depth.

• KSBB Journal
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• v.8 no.5
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• pp.465-472
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• 1993

The comparison of the capabilities of cell growth of four different kinds of commercially available microcarriers was carried out by culturing anchorage-dependent animal cells, Vero-6, in a spinner flask. Using 3 g/l of Cytodex 3, the maximum final cell density was about $1.4{\times}10^6$ cells/ml and increased up to $2.0{\times}10^6$ cells/ml by increasing microcarrier concentration up to 5 g/l. The macroporous collagen microcarriers, VX-100, informatrix, and Cultispher-G showed the final cell concentration of $4{\times}10^6$ cells/ml, $2.1{\times}10^6$ cells/ml, and $3.2{\times}10^6$ cells/ml, respectively at the microcarrier concentration of 5g/1. According to this result, VX-100 showed better cell growth than informatrix and cultispher-G and also showed about 2 fold increase in final cell density comparing to Cytodex 3 solid bead. When the intermittent bead-to-bead transfer technique was introduced in the culture using Cytodex 3 bead and cultispher-G, the result was very successful and the cells grew out very well. The recovered cells by dissolving collagen microcarrier using collagenase enzyme were mostly viable and grew out very well on the surface of the fresh microcarriers.

• Journal of the Korea Organic Resources Recycling Association
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• v.23 no.1
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• pp.45-51
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• 2015

In this study, continuous microbial fuel cells (MFCs) were operated using non-precious metal catalysts such as iron(II) phthalocyanine (FePc) and cobalt tetramethoxyphenylporphyrin (CoTMPP)) as alternative cathode catalysts for platinum. To evaluate MFCs performance, operational conditions of organic loading rate (OLR) (0.5~3 g COD/L/d) and hydraulic retention rate (HRT) (0.25~1 day) were changed. Power density of MFCs were determined by cathode electrode performance. The maximum power density was $3.3W/m^3$ with platinum at OLR 3 g COD/L/d. Given each HRTs at 1 g COD/L/d, FePc showed to be a better alternative for platinum than CoTMPP because the power density of MFC with FePc was similar to that of MFC with platinum. CoTMPP catalyst, however, showed the lowest power density due to increase of internal resistance during continuous operation.

• Journal of the Korean Ceramic Society
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• v.43 no.5 s.288
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• pp.299-303
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• 2006

In this paper, anode supported SOFC with columnar structured YSZ electrolyte was fabricated via Electron Beam Physical Vapor Deposition (EBPVD) method. Liquid condensation process was employed for the preparation of NiO-YSZ substrate and the high power electron beam deposition method was used for the deposition of YSZ electrolyte film. Double layered cathode with LSM-YSZ and LSM was printed on electrolyte via screen-printing method and fired at $1150^{\circ}C$ in air atmosphere for 3 h. The electrochemical performance and the long-term stability of $5{\times}5cm^2$ single cell were investigated with DC current-voltage characteristics and AC-impedance spectroscopy. According to the investigation, $5{\times}5cm^2$ sized unit cell showed the maximum power density of around $0.76W/cm^2$ at $800^{\circ}C$ and maintained the stable performance over 400 h.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.3
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• pp.283-289
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• 2016

In this study, electrochemical characterizations of PdCu/C catalysts that are synthesized by modified polyol method are investigated. Most of all, amount of ethylene glycol (EG) that is used as main component for catalyst synthesis is mainly modulated to optimize synthetic condition of the PdCu/C catalyst, For evaluations about catalytic activity and performance of direct formic acid fuel cell (DFAFC), half cell and full cell tests are implemented. As a result, when amount of EG is 4M, catalytic activities of the PdCu/C catalyst such as peak current of formic acid oxidation and active surface area are best, while maximum power density of DFAFC using the optimized PdCu/C catalyst is better than that using commercial Pd/C (30 wt%) by 6%. Based on that, PdCu/C catalyst synthesized by modified polyol method plays a critical role in improving (i) catalytic activity for formic acid oxidation and (ii) DFAFC performance by employing as anodic catalyst.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.5
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• pp.557-565
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• 2022

The effect of flow configuration in ammonia-fed solid oxide fuel cell are investigated by using a three-dimensional numerical model. Typical flow configurations including co-flow and counter-flow are considered. The ammonia is directly fed into the stack without any external reforming process, resulting in an internal decomposition of NH3 in the anode electrode of the stack. The result showed that temperature profile in the case of counter-flow is more uniform than the co-flow configuration. The counter-flow cell, the temperature is highest at the middle of the channel while in the case of co-flow, the temperature is continuously increased and reached maximum value at the outlet area. This leads to a higher averaged current density in counter-flow compared to that of co-flow, about 5%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.1
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• pp.161-174
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• 1996

Addressed in this paper is performance analysis of the maximum-likelihood code acquisition technique for slotted-mode preamble search in the CDMA reverse link. The probabilities of detection, miss, and false alarm are derived analytically for a multiple $H_{1}$ cell case in a frequency-selective Rayleigh fading channel, based on the statics of the CDMA noncoherent demodulator output. the probability density function of the decision variable consisting of successive demodulator outputs is also derived by considering the fading characteristics of the received signal for both single and dual antenna cases. The performance of the code acquisition technique is evaluated numerically with an emphasis on investigating the effects of post-detection integration, fading rate, and antenna diversity on the detection performance.

• Preventive Nutrition and Food Science
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• v.13 no.2
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• pp.104-111
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• 2008

As a way to account for the variability of the primary model parameters in the secondary modeling of microbial growth, three different regression approaches were compared in determining the confidence interval of the temperature-dependent primary model parameters and the estimated microbial growth during storage: bootstrapped regression with all the individual primary model parameter values; bootstrapped regression with average values at each temperature; and simple regression with regression lines of 2.5% and 97.5% percentile values. Temperature dependences of converted parameters (log $q_o$, ${\mu}_{max}^{1/2}$, log $N_{max}$) of hypothetical initial physiological state, maximum specific growth rate, and maximum cell density in Baranyi's model were subjected to the regression by quadratic, linear, and linear function, respectively. With an advantage of extracting the primary model parameters instantaneously at any temperature by using mathematical functions, regression lines of 2.5% and 97.5% percentile values were capable of accounting for variation in experimental data of microbial growth under constant and fluctuating temperature conditions.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.48-52
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• 2009

Micro-hole targets are studied to generate energetic protons from laser-thin foil targets by using 2-dimensional particle-in-cell simulations. By using a small hole, the maximum energy of the accelerated proton is increased to 4 times higher than that from a simple planar target. The main proton acceleration mechanism of the hole-targets is the electrostatic field created between the fast electrons accelerated by the laser pulse ponderomotive force combined with the vacuum heating and the target rear surface. But in this case, the proton angular distribution shows double-peak shape, which means poor collimation and low current density. By using a small cone-shaped hole, the maximum proton energy is increased 3 times higher than that from a simple planar target. Furthermore, the angular distribution of the accelerated protons shows good collimation.

• ALGAE
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• v.18 no.2
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• pp.145-156
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• 2003

Seasonal investigations were conducted to determine the major aquatic environmental factors and the variation of phytoplankton in Pyeongtaek Reservoir in March, June, September, and December 2000. Heavy rainfall mainly occurs from late June to mid-September, and water quality of reservoir was high in the influent zone of stream and riverine zone of reservoir. The biomass of phytoplankton was related to aquatic environmental factors. In particular, its value increased where nutrient concentration was high. Likewise, the increase of turbidity was found to have anthropogenic effects on the varying quantity of phytoplankton. The phytoplankton composition in quantitative survey identified into 43 genera and 71 species. Species numbers of Bacillariophyceae, Cyanophyceae, and Chlorophyceae accounted for 17%, 15%, and 49%, respectively, with the remainder constituting less than 3-7%. The distribution of such phyla also significantly varied according to seasons, accounting for 25%, 37%, 61%, and 14% in March, June, September, and December, respectively. Bacillariophyceae and Chlorophyceae were observed throughout the year, while Cyanophyceae proliferated in June and September. Euglenophyceae and Dinophyceae were prevalent in March and September, while Cryptophyceae occurred in March and December. The succession trend of phytoplankton showed the maximum cell density was followed by Bacillariophyceae (6.8$\times$$10^3$ cells ${\cdot}$ml)$\rightarrow$ Chlorophyceae (3.7$\times$$10^3$ cells ${\cdot}$ml)$\rightarrow$Cyanophyceae (1.3$\times$$10^4$ cells ${\cdot}$ml)$\rightarrow$Cryptophyceae (1.2$\times$$10^3$ cells ${\cdot}$ml). The cell density was the highest in the upstream. Dominant species were composed of Aulacoseira ambigua, Stephanodiscus hantzschii f. tenuis of Bacillariophyceae, Anabaena spiroides var. crassa, Microcystis aeruginosa, Oscillatoria amphibia of Cyanophyceae, Actinastrum hantzschii var. fluviatile, Pediastrum duplex var. reticulatum of Chlorophyceae, Euglena gracilis, Trachelomonas spp. of Euglenophyceae, and Chroomonas spp., Cryptomonas spp. of Cryptophyceae. As a results, seasonal variation of phytoplankton in Pyeongtaek Reservoir was evident in spite of inflow the high concentration of nutrients from watershed streams, because hydrological control and anthropogenic disturbance in reservoir were found to have major effects on the retention time of water.