• Journal of Advanced Marine Engineering and Technology
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• v.41 no.4
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• pp.296-301
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• 2017

In various industrial places such as power generation plants, petrochemical and unit factories, the demands of systems that produce hot water by utilizing wasted or surplus steam have been increased. Compact steam unit(CSU) is a system that can meet these demands and produce hot water by using surplus or wasted steam, and it is also one of the good solutions in view of energy reuse. The new CSU with a capacity of 1,600 kW was developed with a hybrid plate heat exchanger of which thermal performances are better than a conventional plate heat exchanger, an improved temperature control valve, a user-friendly control system, and other components in this study. The purpose of this study was to obtain performance data of the new CSU through various experiments and utilize them for the CSU commercialization. The experimental results show that heat balances between the hot side(steam) and the cold side(cold water) were within ${\pm}0.77%$, and the fluctuations of outlet temperature of the secondary side which are one of the most important evaluation factors in the CSU were $(0{\sim}0.3)^{\circ}C$.

• Journal of Navigation and Port Research
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• v.28 no.1
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• pp.97-104
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• 2004

Introduction of wave model, take into account the effect of tide, wind and wave induced currents at the coastal waters of complex bathymetry, is a very important factor for most coastal engineering design and disaster protection problems. As the steady state spectral wave model could simulate depth induced wave shoaling and refraction, current induced refraction effect, steepness induced wave breaking, diffraction, wind wave growth, wave-wave interaction, and wave-current interaction that redistribute energy, this would support and compensate the gap in the real field of design where other wave models could not deal and cause wrong estimation. In this study, for better understanding and analysis of wave transformation process, we applied the spectral wave model to the large coastal waters near Gaduck Island where the Busan new port construction project is going on. We also compared the simulation results with the calculatea from the existing model. From such a trial of this study, we hope that broader and safer use of the spectral model in the area of port design and disaster prevention system come through in near future.

• Journal of Navigation and Port Research
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• v.33 no.10
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• pp.659-664
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• 2009

LNG carriers have, up to 2006, mainly been driven by steam turbines. The Boil-Off Gas from the LNG cargo tanks has so far been used as fuel. This is a costly solution that requires special skills during construction and operation. Alternative propulsion systems offer far better fuel economical efficiency than steam turbines. Instead of previous practice using Boil-Off Gas as a fuel, the Re-liquefaction system establishes a solution to liquefy the Boil-Off Gas and return the LNG to the cargo tanks. This Re-liquefaction of Boil-Off Gases on LNG carriers results in increased cargo deliveries and allows owners and operators to choose the most optimum propulsion system. In this study, thermodynamic cycle analysis has been performed on two type of LNG Re-liquefaction system which was designed and adopted for the Q-Flex(216,000$m^3$) and Q-Max(266,000$m^3$) LNG carrier under construction at Korea ship yards and variable key factor was simulated to compare efficiency, power and nitrogen consumption of each Re-liquefaction system.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.6
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• pp.453-457
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• 2016

In various industrial plants such as power generation plants, petrochemical plants, and unit factories, there is an increasing demand for a system that generates hot water using waste or surplus steam. Compact steam unit (CSU), which produces hot water by using steam, is a good solution considering energy reuse. In this study, as a basic study to develop a high-pressure CSU, heat transfer characteristics of a hybrid heat exchanger were investigated through experiments, in order to use the hybrid heat exchanger instead of a conventional plate heat exchanger as the core component of CSU. The experimental results are the followings. Heat balance between the hot side and cold side was satisfied within ${\pm}5%$. Overall heat transfer coefficient increased linearly as the Reynolds number increased and exceeded $5,524W/m^2K$ when the flow velocity was above 0.5 m/s. In addition, pressure drop also increased as the Reynolds number increased, and pressure drop per unit length was below 50 kPa/m.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.294-299
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• 2001

Effects of the surface fluorination on the electrochemical charge-discharge properties of $Mg_2$Ni electrode in Ni-MH batteries fabricated by mechanical alloying were investigated. After 20h ball milling, Mg and Ni powder formed nanocrystalline $Mg_2$Ni. Discharge capacity of this alloy increased greatly at first one cycle, but due to the formation of Mg(OH)$_2$ passive layer, it showed a rapid degradation in alkaline solution within 10cyc1es. In case of 6N KOH +xN KF electrolyte (x = 0.5, 1, 2), a continuous and stable fluorinated layer formed by adding excess F$^{[-10]}$ ion, increased durability of $Mg_2$Ni electrode greatly and high rate discharge capability(90-100mAh/g). 2N KF addition led to the highest durability of all tested here. The reason of the improvement is due to thin MgF$_2$, which can prevent the $Mg_2$Ni electrode from forming Mg(OH)$_2$layer that is the main cause of degradation.

• Korean Journal of Cognitive Science
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• v.27 no.3
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• pp.407-420
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• 2016

We live under the consequences of countless decisions, among which significant number of decisions is made by representatives acting on behalf of us. However, individuals often make disparate decisions depending on which identity they are assigned as an agent or with which opponent they are interplaying. In the current research, behavioral discontinuity depending upon actor identity and social relationship was investigated using the ultimatum game. Participants behaved in a more economically rational way when they acted as a group representative compared with when they made decisions as a private individual. However, the direction of the individual-representative discontinuity was reversed when rivalry came into play. Furthermore, more fairness was requested to accept the offers in the interaction with the rival compared with the neutral countergroup. Especially when interacting with the rival group, participants showed contrasting level of decision bias - measured by rejection rate toward unfair offers - according to the degree of mind attribution to the opponent. Specifically, the greater participants attributed a mind to the rival group, the more they rejected the unfair offers from it. The present research is important in that it provides insight into individuals' decision-making in a group context, which sometimes forgoes the financial gain of the entire group and ultimately leads to the sub-optimization of social welfare.

• Journal of Veterinary Clinics
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• v.30 no.4
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• pp.223-229
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• 2013

Because colostrum is considered to be the sole source of passively acquired maternal antibodies for calves, newborn calves must consume colostrum to gain disease resistance during their early years of life. Storage of surplus colostrum from dairy cows right after calving and feeding newborn calves in deficiency of colostrum to assure adequate uptake of IgG for protection of the calf has been a common practice in the bovine production. In the current study, 35 colostrums were randomly collected from 3 colostrum banks located in different regions of Korea and monitored for general bacterial contamination and major bovine pathogens. Immunoglobulin concentrations and BVDV-specific antibodies were also determined to evaluate the immune quality of the colostrums. Moderate to severe bacterial contamination (up to 72,000,000 CFU/ml) was observed in most of the colostrums collected from colostrum banks. General immune quality of the colostrums was under the satisfactory level since most of the colostrums contained less than 50 g/L of IgG, which is the minimum concentration for good quality colostrums. Therefore, colostrum for colostrum bank should be collected at the first 2-3 post-partum milkings according to proper harvesting and handling procedures to guarantee the safety and quality of colostrum. In addition, it was recommended that colostrum should be heat-treated before frozen and stored in the bank because pasteurization at $63^{\circ}C$ for 30 min was very effective reducing the risk of disease transmission without causing significant degradation of immunoglobulins.

• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.393-402
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• 1993

Redox flow secondary battery have been studied actively as one of the most promising electrochemical energy storage devices for a wide range of applications, such as electric vehicles, photovoltaic arrays, and excess power generated by electric power plants. In all-vanadium redox flow battery using solution of vanadium-sulfuric acid as a active material, the difficulty in developing an efficient ion selective membrane can still be identified. The asymmetric cation exchange membrane(M-30) as a separator of all-vanadium redox flow battery which were obtained by the reaction of chlorosulfonation for 30 minutes under the irradiation of UV, showed its superiority in the transport number of 0.94 and electrical resistivity of $0.5{\Omega}{\cdot}cm^2$. The base membrane were prepared by lamination a low density polyethlene film of $10{\mu}m$ thickness on polyolefin membrane(HIPORE 120). The electrical resistivity of M-30 membrane in real solution of vanadium-sulfuric acid was $3.79{\Omega}{\cdot}cm^2$ and it was similar to that of Nafion 117 membrane. Also the cell resistivity was $6.6{\Omega}{\cdot}cm^2$and lower than that of Nafion 117. In considertion of electrochemical properties and costs of membranes, M-30 membrane was better than that of Nafion 117 and CMV of Asahi glass Co. as a separator of all-vanadium redox flow battery.

• Journal of Animal Environmental Science
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• v.17 no.3
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• pp.155-162
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• 2011

This study was conducted to suggest the measurement procedure and to build up national greenhouse gas inventory database of animal agricultural sector by assessing methane and nitrous oxide emissions according to IPCC guidelines for national greenhouse gas inventory report in order to correspond to the Climate Change Convention. Ten house-made steady-state Half dome floating chambers were used to collect air samples emitted from slurry stored in the pit under the slat. Those chambers were spread out in order that air samples might represent the whole area of slurry under the slat. Fresh air was pumped into the chambers by $5{\sim}9{\ell}/min$ and air inside the chambers was sampled by $1{\ell}/min$. Surplus air by the higher flow rate of fresh air than sampling flow rate was passed through a hole on the top of chambers. Nitrous oxide fluxes measured from 10 locations would be negligible as concentrations between background air and sampled air from the chambers were within the error range. However, mean $CH_4$ fluxes were $0.15{\sim}1.02mg/m^2{\cdot}s$. The application of continuous greenhouse gas measurement techniques would be preferred if the patterns of greenhouse gas emissions are considered.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.360-369
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• 2008

The solar cells should be operated at the maximum power point because its output characteristics were greatly fluctuated on the variation of insolation, temperature and load. It is necessary to install an inverter among electric power converts by means of the output power of solar cell is DC. The inverter is operated supply a sinusoidal current and voltage to the load and the interactive utility line. In this paper, the proposes a photovoltaic system is designed with a step up chopper and single phase PWM voltage source inverter. Synchronous signal and control signal was processed by one-chip microprocessor for stable modulation. The step up chopper is operated in continuous mode by adjusting the duty ratio so that the photovoltaic system tracks the maximum power point of solar cell without any influence on the variation of insolation and temperature for solar cell has typical dropping character. The single phase PWM voltage source inverter is consists of complex type of electric power converter to compensate for the defect, that is, solar cell cannot be develop continuously by connecting with the source of electric power for ordinary using. It can be cause the efect of saving electric power, from 10 to 20%. The single phase PWM voltage source inverter operates in situation, that its output voltage is in same phase with the utility voltage. The inverter are supplies an ac power with high factor and low level of harmonics to the load and the utility power system.