• 설비공학논문집
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• 제11권4호
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• pp.440-447
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• 1999

The frosting characteristics on the vertical parallel plates with three cooling plates were experimentally investigated. The experimental parameters were the cooling plate temperature, the air humidity, the air temperature, the air Reynolds number, and the location. The frosting conditions were limited to air temperatures from 10 to $15^{\circ}C$ , air Reynolds numbers from 1600 to 2270, air humidity ratios from 0.00275 to 0.0037kgw/kga and cooling plate temperatures from -10 to $-20^{\circ}C$. Frost growth and density toward the front of the plate were more thick and dense than toward the rear. Frost growth increased with decreasing plate temperature and increasing humidity. In the conditions of the laminar flow, dew point below $0^{\circ}C$and non-cyclic frosting period, frost thickness increased with increasing air temperature. The reason of increasing frost thickness with increasing air temperature was sublimation-ablimation process. The average growth thickness along the locations showed little dependence on the Reynolds numbers.

• Journal of Advanced Marine Engineering and Technology
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• 제39권8호
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• pp.833-837
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• 2015

Li-air batteries have a promising future for because of their high energy density, which could theoretically be equal to that of gasoline. However, substantial Li-air cell performance limitations exist, which are related to the air cathode. The cell discharge products are deposited on the surfaces of the porous carbon materials in the air electrode, which blocks oxygen from diffusing to the reaction sites. Hence, the real capacity of a Li-air battery is determined by the carbon air electrode, especially by the pore volume available for the deposition of the discharged products. In this study, a simple and fast method is reported for the large-scale synthesis of carbon nanoballs (CNBs) consisting of a highly mesoporous structure for Li-air battery cathodes. The CNBs were synthesized by the solution plasma process from benzene solution, without the need for a graphite electrode for carbon growth. The CNBs so formed were then annealed to improve their electrical conductivity. Structural characterization revealed that the CNBs exhibited both an pore structure and high conductivity.

• 한국항공운항학회지
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• 제21권4호
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• pp.90-105
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• 2013

As witnessed in September 11 attacks, air terrorism is often the most effective means to achieve their goals, and thereby requires a sophisticated level of security measures. Moreover, considering the nature of air transportation, the prevention of air terrorism demands a wide range of international cooperation and joint efforts such as timely sharing of information related to air terrorism (such as latest terror techniques and list of terrorists) between nations, International Air Transport Association (IATA) and International Civil Aviation Organization (ICAO) As most air terrorism can be effectively prevented through security and search activities in airports, this study has focused on researching security measures and issues in major airports around the world, along with the potential measures to improve them. To achieve this effect, this paper offers solutions to preventing air terrorism by exploring appropriate responses to various type of air terrorism, deployment of advanced security and search equipment, techniques to identify terrorists, R&D on equipments to physically take down terrorists and systematic improvements on airport security search process.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2004년도 추계학술대회 논문집
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• pp.189-190
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• 2004

• 대한설비공학회지:설비저널
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• 제17권5호
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• pp.519-528
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• 1988

• 설비공학논문집
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• 제10권6호
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• pp.795-802
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• 1998

For measuring the thermal diffusivity by laser flash method, raw data have to be calibrated using temperature data. We have developed in-process calibration method and polynomial calibration in which thermal diffusivity can be calibrated during measuring, This method is different from existing temperature pre-process calibration method and exponential calibration having various source of error. Using this new calibration method, measurement accuracy was improved about 1∼2% compare to the value by the existing method. We also studied more accurate fitting curve as in Figure 4 was shown the result of measuring output characteristics of IR radiometer with temperature. As illustrated in data, in-process calibration method and polynomial calibration equation is proper than pre-process calibration method and exponential calibration.

• 한국레이저가공학회지
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• 제6권2호
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• pp.27-33
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• 2003

A laser shock cleaning technology is a new dry cleaning methodology for the effective removal of small particles from the surface. This technique uses a plasma shock wave produced by a breakdown of air due to an intense laser pulse. In order to optimize the laser shock cleaning process, it needs to evaluate the cleaning performance quantitatively by using a monitoring technique. In this paper, an acoustic monitoring technique was attempted to investigate the laser shock cleaning process with an aim to optimize the cleaning process. A wide-band microphone with high sensitivity was utilized to detect acoustic signals during the cleaning process. It was found that the intensity of the shock wave was strongly dependent on the power density of laser beam and the gas species at the laser beam focus. As a power density was larger, the shock wave became stronger. It was also seen that the shock wave became stronger in the case of Ar gas compared with air and N$_2$ gas.

• Journal of Mechanical Science and Technology
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• 제20권8호
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• pp.1217-1223
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• 2006

Induction heating is a process that is accompanied with magnetic and thermal situation. This paper presents a simulation of a magneto-thermal coupled problem of an induction heating process for moving inductor coil. In the magnetic and thermal analyses, temperature-dependent magnetic and thermal material properties were considered. As the inductor coil moves in the process, solution domains corresponding to inductor changes into those of the air, and the solution domains of air change into those of the inductor. For these reasons, modeling of induction heating process is very difficult with general purpose commercial programs. In this paper, induction heating process for moving coil was simulated with the concept of traveling the position of the heating planes. Finite element program was developed and finite element results were compared with the experimental results.

• 설비공학논문집
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• 제23권1호
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• pp.38-46
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• 2011

The hybrid defrost process combined with hot-gas bypass defrost and electric heater defrost was experimentally evaluated about its defrost performance in the fin-tube evaporators of household refrigerators. Also the hybrid defrost process was compared with only electric heater defrost process. The defrost efficiency of the hybrid defrost process was shown two times higher than electric heater defrost process. The defrost time of the hybrid defrost process was shorten about 10%~50% than electric heater defrost process. Thermal shock after defrost process was decreased about 50% for the case of the hybrid defrost. It was found that energy consumption ratio of defrost process was reduced up to 7.4% compared with 22.4% of electric heater defrost at the condition of $25^{\circ}C$ ambient temperature.

• 한국전산유체공학회지
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• 제13권4호
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• pp.1-7
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• 2008

In the process of continuous hot-dip galvanizing, it is well known that the gas wiping through an air knife system is most effective because of its uniformity in coating thickness, possibility of thin coating, workability in high speed, and simplicity of control. However, gas wiping used in the galvanizing process brings about a problem of splashing at the strip edge above a certain high speed of process. It is also known that the problem of edge splashing is more harmful than that at the mid strip surface. For a given liquid(of a certain viscosity and surface tension), the onset of splashing mainly depends upon the strip velocity, the gas-jet pressure, and the nozzle's stand-off distance. In these connections in the present study, we proposed three kinds of air knife system having nozzles of constant expansion rate, and compared the jet structures issuing from newly proposed nozzle systems with the result by a conventional one. In numerical analysis, the governing equations are consisted of two-dimensional time dependent Navier-Stokes equations, and the standard k-${\varepsilon}$ turbulence model is employed to solve turbulence stress and so on. As the result, it is found that we had better use the constant expansion-rate nozzle which can be interpreted from the point view of the energy saving for the same coating thickness. Also, we better reduce the size of separation bubble and enhance the cutting ability at the strip surface, by using an air-knife having constant expansion-rate nozzle.