• Journal of the Korean Institute of Gas
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• v.15 no.2
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• pp.63-68
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• 2011

As an effective utilization of biomass, organic wastes and coal, attention has been made to use syngas to a reciprocating engine to generate power. However, significant component variation of syngas depending upon origin and gasification conditions, and its lower heating value than that of LPG and CNG can create difficulties in stable engine operation. Thus it is necessary to address these issues in order to successfully develop power generation engines. As a primary step to resolve these problems, effects of H2 content variation in syngas on engine performance and emission characteristics were discussed in this study. The results show that as H2 % in syngas increases, more stable combustion was achieved with retarded MBT spark timing and engine efficiency becomes maximum with syngas of 10% H2. In addition, NOx emission increased while THC emission decreased as H2 % rises in the syngas.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.351-355
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• 2014

Graphite electrodes are used for secondary batteries, fuel cells, and super capacitors. Research is underway to increased the reaction area of graphite electrodes used carbon nanotube (CNT) and porous carbon. CNT is limited to device utilization in order to used a metal catalyst by lack of surface area to improve. In contrast carbon nanowall (CNW) is chemically very stable. So this paper, microwave plasma enhanced chemical vapor deposition (PECVD) system was used to grow carbon nanowall (CNW) on Si substrate with methane ($CH_4$) and hydrogen ($H_2$) gases. To find the growth properties of CNW according to the reaction gas ratio, we have changed the methane to hydrogen gas ratios (4:1, 2:1, 1:2, and 1:4). The vertical and surficial conditions of the grown CNW according to the gas ratios were characterized by a field emission scanning electron microscopy (FE-SEM) and Raman spectroscopy measurements showed structure variations.

• Progress in Superconductivity and Cryogenics
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• v.16 no.1
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• pp.9-13
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• 2014

Effects of neutron irradiation on the superconducting properties of the undoped $MgB_2$ and the carbon(C)-doped $MgB_2$ bulk superconductors, prepared by an in situ reaction process using Mg and B powder, were investigated. The prepared $MgB_2$ samples were neutron-irradiated at the neutron fluence of $10^{16}-10^{18}n/cm^2$ in a Hanaro nuclear reactor of KAERI involving both fast and thermal neutron. The magnetic moment-temperature (M-T) and magnetization-magnetic field (M-H) curves before/after irradiation were obtained using magnetic property measurement system (MPMS). The superconducting critical temperature ($T_c$) and transition width were estimated from the M-T curves and critical current density ($J_c$) was estimated from the M-H curves using a Bean's critical model. The $T_cs$ of the undoped $MgB_2$ and C-doped $MgB_2$ before irradiation were 36.9-37.0 K and 36.6-36.8 K, respectively. The $T_cs$ decreased to 33.2 K and 31.6 K, respectively after irradiation at neutron fluence of $7.16{\times}10^{17}n/cm^2$, and decreased to 22.6 K and 24.0 K, respectively, at $3.13{\times}10^{18}n/cm^2$. The $J_c$ cross-over was observed at the high magnetic field of 5.2 T for the undoped $MgB_2$ irradiated at $7.16{\times}10^{17}n/cm^2$. The $T_c$ and $J_c$ variation after the neutron irradiation at various neutron fluences were explained in terms of the defect formation in the superconducting matrix by neutron irradiation.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.6
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• pp.120-130
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• 2013

A study was conducted for the performance characteristics of methane taking recently the limelight in the world as a next-generation propellant, with the survey for state of the art in the development of methane/oxygen rocket engine being accompanied. Liquid methane as a rocket fuel has the favorable characteristics such as non-toxic, low cost, regenerative cooling capability, and potential for in-situ resource utilization (ISRU). The combination of liquid methane and liquid oxygen also provides the excellent performance including high specific impulse and low system mass. For these reasons, many researches have been actively carried out on the methane/oxygen engine, nevertheless, its technology readiness level is not that high enough just yet. Therefore, it is judged that it is the time to mitigate the technical gap with the space technology of advanced countries through a swift onset of the development of methane rocket engine.

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.349-353
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• 2001

Korea has a variety of favorable conditions for utilizing wind as energy. First of all, as a geographical characteristic, it is a peninsular country with its three frontiers surrounded by sea. Such a location makes the country influenced, all the year round, both by sea winds and by seasonal winds, so that it has a good possibility of putting its rich wind resources to use as an energy source. Particularly, in view of the results of observations and analysis of actual data about wind sources, it is quite possible to build wind paver plants in many regions across the country, such as inhabited islands dotted on its southern and western coasts around the Korean peninsular, a number of uninhabited islets attached the main islands, large-scaled reclaimed lands, and major inland areas. In Korea, the attempt to develop the technology of wind paver generation started in the 1970's. It was since 1988, when the Law on the promotion of Alternative Energy Development was enacted, that research and development activities for employing the wind force as a part of energy source have got into full swing. At that moment, however, due to the low level of domestic technological development, such efforts were mainly focused on the attainment of basic technologies with regard to wind power generation. Recently, there have been many noticeable changes in the international as well as domestic environments, such as the conclusion of the International Climate Treaty and the increase in public concerns of natural environment. It is quite possible to predict that the demand for wind paver generation will increase in the near future. Therefore, recognizing that wind, as a clean energy source, can be a promising method for coping with the International Climate Treaty and for replacing the fossil fuel, oil, this essay investigates the development history of wind paver generation systems and the status of technological development in Korea and presents an appropriate model for the development of the paver generation system that can compete with other energy sources.

• Journal of Navigation and Port Research
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• v.37 no.6
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• pp.655-662
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• 2013

Recently, by the problems owing to utilization of fossil fuel, various green energies receive attention. Wind, the impetus for the wind power generation as one of the green energies, is observed higher quality value in the offshore than onshore. Also, the development of offshore wind turbines is in the spotlight as alternative to solve the problems of onshore wind farm such as securing sites, noise, and electromagnetic waves, and to get efficient wind energy. Therefore, the many researches on offshore wind energy have been carried out. As wind towers are advanced to ocean, offshore wind towers have been enlarged. Thus, stability is required to endure wind force and wave force. In this study, the external forces act on the foundation in multi-layered are calculated by p-y relation.

• Fire Science and Engineering
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• v.31 no.4
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• pp.43-51
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• 2017

In this study, new design fire curves were suggested for the utilization in fire simulations. Numerical simulations with the Fire Dynamics Simulator (FDS) were performed for the n-octane and n-heptane pool fires in the ISO 9705 compartment to evaluate the prediction performance of the previous quadratic, exponential design fire curves and newly suggested ones. The numerical results were compared with the experimental temperature and concentrations of $O_2$ and $CO_2$. The numerical results with the previous quadratic and exponential curves showed slow increase and decrease trend than experiments. However, the numerical results with the newly suggested 2 design fire curves showed more similar variation trend in temperature, $O_2$ and $CO_2$ concentrations than the quadratic and exponential curves. It was found that the newly suggested design fire curves can be possibly used in the numerical simulation of fires in a practical respect.

• Journal of the Korea Society of Computer and Information
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• v.17 no.2
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• pp.23-29
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• 2012

To recently, light of the sun and fuel cell etc. which is new and renewable energy is developed with the direct current energy source mostly. And it is necessary that the utilization plan which does supply it properly. In this case, the direct current illumination system can be a typical alternative of it. The system similar to the development system is composed of type which connects to each other the photovoltaic pannel, the charge kit, and the battery bank. I develop all-in-one system which the power supply system and photovoltaic pannel which can charge and use efficiently. Additionally, I exploit the DC lamp module of three wave which can separate the electronic ballasts from the module. Developed the DC Lamp module of all-in-one which can turn on or can turn off, by operation of ON/OFF button. It can be used semipermanently by changing just only electronic ballasts.

• Journal of Korean Society for Quality Management
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• v.46 no.4
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• pp.899-910
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• 2018

Purpose: Generally, since the population density is lower in suburban areas, the distance to school is inevitably long. Therefore, schools in suburban areas often operate school buses to improve student welfare. However, since school buses are usually used only during going to and from school, the utilization rates are relatively low. Therefore, this study aims to establish integrated operation plan of public school bus covering all schools. Methods: It is necessary to decide which school buses will serve the specific demand node which want to go to certain school in order to design an integrated operation plan for school buses. Therefore, a mathematical model is developed for minimizing the total number of vehicles and the distance of transportation by reflecting the characteristics of school buses and students as constraints. To solve the proposed mathematical model, CPLEX, a commercial solver, is applied. Results: To validate and to confirm the proposed process, numerical example is designed with the comparison between before and after integrated operations of school buses in terms of total operation cost. The result shows that the integrated operation can lead the reduction of the number of school buses as well as the decreasing of the fuel cost. Conclusion: This study provides the quantitative method to perform the integrated operation of school buses in suburban areas. The optimal operation strategy is required because there are more complex decision-making elements considering the integrated operation. It is expected to apply this research result at real situation to expand this services based on an optimal operation.

• Journal of the Korean Wood Science and Technology
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• v.32 no.4
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• pp.46-51
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• 2004

The objective of this study was to evaluate the applicability of high temperature drying to pitch pine (Pinus rigida) lumber, especially intended for use as lamina of structural glued laminated timber (glulam), to enhance the efficient utilization and provide added-value to that species. The high temperature schedule and drying procedures utilized were shown to be reasonable for drying glulam lamina due to the occurrence of small moisture gradients, minimal residual drying stress, and low warpage. Through preliminary tests, it was confirmed that residual resin at lamina surfaces did not adversely affect the gluing process. However, quantitative analysis of resin is required for developing a method to constrain the occurrence of pitch trouble with respect to decreasing long-term adhesive and finish durability of glulam in use after manufacturing. The final moisture content of high temperature dried lamina was much lower than target moisture content and discoloration was more severe than anticipated. In a further study, it will be necessary to determine the optimal drying conditions, such as temperature, humidity, drying time, and top load restraint level, which could best control discoloration, warpage, and moisture content of the lamina, while minimizing fuel expense.