• Journal of the Society of Naval Architects of Korea
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• v.52 no.1
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• pp.8-18
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• 2015

Reduction of the fuel oil consumption and corresponding greenhouse gas exhausted from ships is an important issue for today's ship design and shipping. Several concepts and devices on the superstructure of a container ship were suggested and tested in the wind tunnel to estimate the air drag reduction. As a preliminary performance evaluation, air drag contributions of each part of the superstructure and containers were estimated based on RANS simulation respectively. Air drag reduction efficiency of shape modification and add-on devices on the superstructure and containers was also estimated. Gap-protectors between containers and a visor in front of upper deck were found to be most effective for drag reduction. Wind tunnel tests had been carried out to confirm the drag reduction performance between the baseline(without any modification) configuration and two modified superstructure configurations which were designed and chosen based on the computation results. The test results with the modified configurations show considerable aerodynamic drag reduction, especially the gap-protectors between containers show the largest reduction for the wide range of heading angles. RANS computations for three configurations were performed and compared with the wind tunnel tests. Computation result shows the similar drag reduction trend with experiment for small heading angles. However, the computation result becomes less accurate as heading angle is increasing where the massively separated flow is spread over the leeward side.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.2
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• pp.171-177
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• 2014

A two-dimensional particle image velocimetry (2D PIV) system in a towing tank is employed to measure a wake field of a very large crude oil carrier model with rotating propeller in self propulsion condition, to identify characteristics of wake of a propeller working behind a ship. Phase-averaged and time-averaged flow fields are measured for a horizontal plane. Scale ratio of the model ship is 1/100 and Froude number is 0.142. By phase-averaging technique, trajectories of tip vortex and hub vortex are identified and characteristic secondary vortex distribution is observed in the hub vortex region. Propeller wake on the starboard side is more accelerated than that on the port side, due to the difference of inflow of propeller blades. The hub vortex trajectory tends to face the port side. With the fluctuation part of the phase-averaged velocity field, turbulent kinetic energy (TKE) is also derived. In the center of tip vortex and hub vortex region, high TKE concentration is observed. In addition, a time-averaged vector field is also measured and compared with phase-averaged vector field.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.262-267
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• 2005

The evaporation heat transfer coefficient of $CO_2$ in a horizontal round tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and evaporator(test section). The test section was made of a horizontal stainless steel tube with the inner diameter of 7.75 mm, and length of 5 m. The experiments were conducted at mass flux of 200 to 500 $kg/m^2s$, saturation temperature of $-5^{\circ}C$ to $5^{\circ}C$, and heat flux of 10 to 40 $kW/m^2$. The test results showed the evaporation heat transfer of $CO_2$ has great effect on more nucleate boiling than convective boiling. The evaporation heat transfer coefficients of $CO_2$ are highly dependent on the vapor quality, heat flux and saturation temperature. In comparison with teat results and existing correlations, correlations failed to predict the evaporation heat transfer coefficient of $CO_2$, therefore, it is necessary to develop reliable and accurate predictions determining the evaporation heat transfer coefficient of $CO_2$ in a horizontal tube.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.353-358
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• 2005

The heat transfer and pressure drop of supercritical $CO_2$ cooled in a helically coiled tube was investigated experimentally. The experiments were conducted without oil in the refrigerant loop. The experimental apparatus of the refrigerant loop consist of receiver, a variable speed pump, a mass flowmeter, a pre-heater, a gas cooler(test section) and an isothermal tank. The test section is a helically coiled tube in tube counter flow heat exchanger with $CO_2$ flowed inside the inner tube and coolant( water) flowed along the outside annular passage, It was made of it copper tube with the inner diameter of 4.55[mm]. the outer diameter of 6.35 [mm] and length of 10000 [mm]. The refrigerant mass fluxes were $200^{\sim}600$ [kg/m2s] and the inlet pressure of gas cooler varied from 7.5 [MPa] to 10.0 [MPa]. The main results are summarized as follows : The heat transfer coefficient of supercritical $CO_2$ increases, as the cooling pressure of gas cooler decreases. And the heat transfer coefficient increases with the increase of the refrigerant mass flux. The pressure drop decreases in increase of the gas cooler pressure and increases with increase the refrigerant mass flux.

• Journal of the Korea Society for Simulation
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• v.23 no.2
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• pp.17-24
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• 2014

This study attempts to show an example of developing and applying thermal hydraulic simulation model for Aircraft-EHA. The overview of research procedure is as in the following. First, The unit hydraulic simulation model, which reflects physical quantity answering engineer's purpose is developed. Second, The unit hydraulic simulation model is combined, and then branched out to EHA hydraulic model. Third, a simulation model including flow thermal is developed, and then oil temperature rise time according to 'initial temperature and load' is examined. Finally, the master graph that can be used for designing EHA combined with thermal hydraulic analysis results in several cases is compiled, and suggested. AMESim, commercial software, is used through whole procedure.

• Journal of Korean Medical classics
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• v.25 no.1
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• pp.173-196
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• 2012

Object : From the ancient times, the importance of childbirth has been well recognized by Korean Traditional Medicine. Numeral methods have been developed to ease the labor process and keep the mother and child healthy from conception to labor. Bulsusan(佛手散) is one of the main remedies to healthy labor in KTM, both widely known and applied as well. Method : This paper examines the labor theory and practice of KTM focused on Bulsusan which is composed of Angelica gigas Nakai(當歸) and Cnidium officinale MAKINO(川芎). Result : 1. From the ancient times until the Q$\bar{i}$ng period, much attention was placed to the handling of the placenta, as it was conceived as bearing much relation to the health of the mother and her fate, and thus included in the labor process. 2. There was a recognition of the 'birth pulse[離經脈]', an intense change in the pulse that presents itself prior to somatic signs of labor. 3. There were numerous prescriptions that were administered beforehand to ease the process. They are mostly constituted with medicinals that nurture Gi(氣) and stimulate its flow, which in turn makes the fetus firm and reduces the volume, easing the labor process. 4. The medical practice of labor-induction was called 'Choesaeng(催生)'. The prescriptions which functioned as such were mostly constituted with blood medicinals such as Angelica gigas Nakai and Cnidium officinale MAKINO, those which nurture both Gi(氣) and blood, and medicinals that physically lubricate the labor pathway such as honey, oil and Talcum(滑石). Conclusion : Bulsusan can be used in most problems concerning pregnancy and labor, and cases of emergency blood loss due to injury. The term 'bulsu(佛手)' infers to the medical ability of the great doctor who takes care of major blood-loss situations resulting from discharge of dead fetus, cesarean delivery, etc. The prescription name takes after this meaning, as it deals with similar conditions in its effect.

• Journal of the Korea Society of Computer and Information
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• v.21 no.8
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• pp.57-64
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• 2016

Initial prevention activities and rapid propagation conditions is the most important to prevent diffusion of water pollution. If water pollutants flow into streams river or main stresm located in environmental conservation area or water intake facilities, we must predict immediately arrival time and the diffusion concentration to the proactive. National Institute of Environmental Research developed water pollution incident response prediction system linking dam and movable weir. the system is mathematical model which is updated daily. Therefore it can quickly predict the arrival time and the diffusion concentration when there are accident of oil spills and hazardous chemicals. Also we equipped with mathematical model and toxicity model of EFDC(Environmental Fluid Dynamics Code) to calculate the arrival time and the diffusion concentration. However these systems offer the services of an offline manner than real-time control services. we have ensured the reliability of data collection and have developed a real-time water quality measurement data transmission device by using the data linkage utilizing a mode bus communication and a commercial SCADA system, in particular, we implemented to be able to do real-time water quality prediction through information infrastructure of the water quality integrated management business created by utilizing the construction of the real-time prediction system that utilizes the data collected, the Open map, the visual representation using charts API and development of integrated management system development based on web maps.

• Journal of the Korean Society for Railway
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• v.8 no.1
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• pp.15-20
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• 2005

The ministry of Environment, Korea, are designing the TMDL(Total Maximum daily Load) program far 4 major large rivers to improve water quality from possible pollutants. It can be successfully performed as controling of nonpoint pollutants from watershed area. Railway stations are stormwater intensive land use because of high imperviousness and high pollutant mass emissions from various activities. Especially the metal pollutants from the railway station were recognized as an important pollutants because of its toxicities. In order to characterize the washed-off pollutants. the monitoring were performed on a railway station during storms. Pollutant concentrations are exponentially decreasing during the storm duration. The 95％ confidence interval of pollutant concentrations in an hour storm duration ranges from 61.6 to 115.4mg/L for TSS(mean=88.50mg/L),103.8-244.1mg/L for COD(mean=174 mg/L) and 7.68-17.32mg/L for Oil & Grease(mean=12.5mg/L). The ranges of metals were 39.2-84.0 $\mu\textrm{g}$/L for total Cu(mean=61.6$\mu\textrm{g}$/L), 14.0-25.8$\mu\textrm{g}$/L for total Pb(mean=19.9$\mu\textrm{g}$/L) and 182.2-376.l $\mu\textrm{g}$/L for total Zn(mean=279.2$\mu\textrm{g}$/L). The first flush criteria for best management practices can be suggested to 50％ pollutant mass emissions during 30％ of the total flow.

• Proceedings of KOSOMES biannual meeting
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• 2005.05a
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• pp.45-52
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• 2005

In the present maritime traffic conditions of mokpo harbor, there exists many hazardous factors which may lead to huge accidents including marine oil pollution We analyze marine traffic environments including traffic congestion, natural conditions, maritime traffic accidents of the last 10 years, the fishery status, operation of traffic routes and navigational aids of navigational aids and regulations relating ships' routeing both in and out of the country. Consequently, this work is to propose improved marine traffic system in future.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.12
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• pp.579-587
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• 2014

This paper deals with precise analytical state equation modeling of a variable speed refrigeration system (VSRS) for optimum control in state space. The VSRS is described as multi-input and multi-output (MIMO) system, which has two controlled variables and two control inputs. First, the Navier-Stokes equation and mass flow rate were applied to each component of the basic refrigeration cycle to build a dynamic model. The dynamic model, represented by a differential equation, was transformed into the state equation formula. Next, a full-order state observer was built to estimate all of the state variables to compose an optimum control system. Then, an optimum controller was designed to minimize an evaluation function that has input energy and control error. Finally, simulations and experiments were conducted to verify the validity of the proposed modeling and designed optimum controller to regulate target temperature and superheat in a 1RT oil cooler system. The results show that the proposed method, state equation modeling and optimum control, is efficient to ensure optimal control performance of the VSRS.