• Journal of Power Electronics
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• v.8 no.2
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• pp.121-130
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• 2008

This paper introduces a design and implementation of a digital control unit for an Oxygenaire Servo Baby Incubator. The control unit is designed and implemented according to international standards. The control unit is based on an AVR Atmel microcontroller unit. It is built for monitoring and control and displays the three main temperature values: set point temperature, baby skin temperature and air temperature. User friendly software is implemented. The implemented control unit was tested in the laboratory as well as in the field. The control unit is sensitive to change of $0.1^{\circ}C$. At startup, based on a unique control strategy, the incubator reaches its steady state in about 14 minutes. The system schematic diagrams are shown in the paper. Also, programs flow charts are presented. The control unit was designed and implemented based on a contract between the Electronics Research Institute (ERI) and ENGIMED Company. The authors would like to thank ERI and ENGIMED for introducing all required finance and shoring to complete this work.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.624-626
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• 1993

The Electrical Charge generated by friction in flowing insulating oil can create hazadous accidents. Neutralization of static charges in the oil during transportation is an obvious method of overcoming the problem of internal electric charge. It is known that SCR(Static Charge Reducer) can neutralize much of this charge by the needle electrode and mixing it with the original charge. In our experiment, a filter to generate static charge was set just befor a measurement pipe, and streaming current from the filter to the earth $I_s$, current from the electrode to the earth $I_e$ and current from the receiving tank to the earth $I_f$ were measured in a steady state. As a result, charge density and needle electrode current increases with increasing of oil temperature. Charge elimination rate decreases with increasing of oil flow rate, and increases with increases of oil temperature. Faraday Cage current decreases with increasing of oil temperature.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.195-200
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• 2004

In this study, a component map generation method using experimental data and the genetic algorithms are newly proposed. In order to generate the performance map for components of this engine, after obtaining engine performance data through many experimental tests, and then the third order equations which have relationships the mass flow function the pressure ratio and the isentropic efficiency as to the engine rotational speed were derived by using the genetic algorithms. A steady-state performance analysis was peformed with the generated maps of the compressor by the commercial gas turbine performance analysis program GASTURB(1). In comparison, it was found that the component maps can be generated from the experimental test data by using the genetic algorithms, and it was confirmed that the analysis results using the generated maps were very similar to those using the scaled maps from the GASTURB.

• Asian Journal of Turfgrass Science
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• v.11 no.4
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• pp.303-309
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• 1997

The investigation was cycle of aluminum of surface soil elements in dynamic grassland ecosystems at a steady state in a Zoysia japonica and a Miscanthus sinensis ecosystem in Mt. Kwanak, Korea. Average amounts of total storage for aluminum in Z japonica and M. sinensis grasslands were 8,426mg /$m^2$ and 7,849mg /$m^2$ respectively. Decay constants estimated on the base of experimental and mathematical model, were 0.04 in Z japonica grassland, and 0.08 in M. sinensis grassland. Half time to decay aluminum of litter soils were 17.33 years in Z japonica grass-land, and 8.66 years in Al. sinensis grassland. 95% decay times in Z japonica, and in M. sinensis grassland were 75.0 years and 35.0 years respectively. Needed times to lose almost all of elements in Z japonica and M. sinensis grassland were 125.0 years, and 62.50 years respectively. The metals were losed more rapidly in M. sinensis than in Z japonica grassland. The cycle of aluminum was investigated to be related with soil acidity. Key words: Cycle of aluminum, Zoysia japonica. Miscanthus sinensis, Mt. Kwanak, Decay constants, Soil acidity.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.483-488
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• 2009

When a train enters into the tunnel with high speed, a compression wave generated inside the tunnel has been studied as a one-dimensional phenomenon. However, one-dimensional approach can't analyze 3-dimensional flow effect in the vicinity of the train body. In this research, so as to overcome this weak point, a prediction method of the wavefront of a compression wave using steady state solution has been used for the parametric study considering 3-dimensional effects of the interactions between trains and tunnels. The effective hood shapes were deduced in both cases of the train's entry into the tunnel on the single track and on a side of the double track. As a result, in case of the train's entry on a side of the double track, the increase of compression wave value propagated to the tunnel inside have appeared compared with the train's entry on the single track. Also, a horizontally convex elliptic hood shape is more effective at the train's entry on a side of the double track for the purpose of a decrease of wavefront gradient of a compression wave.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.965-969
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• 2006

This study investigated heat transfer characteristics between absorber and heat pipe used to extract heat from concentric evacuated tubular collectors. In order to experiment, T-type thermocouples are attached to a evaporator of heat pipe and absorber of inner tube. A wall temperature distribution of absorber and heat pipe were carried out by experimental method under actual various ir-radiance and outdoor conditions. As a result, As to increase an irradiance, a wall temperature of absorber and heat pipe is gradually increased. The heat pipe was required about 20min to obtain steady state operation after start up and operates stable during various irradiance conditions. And the collector efficiency was about $50{\sim}70%$ when a mass flow rate is about $1.3{\ell}/min$.

• Nuclear Engineering and Technology
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• v.42 no.6
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• pp.690-703
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• 2010

Sampling based uncertainty analysis was carried out to quantify uncertainty in predictions of best estimate code RELAP5/MOD3.2 for a thermal hydraulic test (10% hot leg break LOCA) performed in the Large Scale Test Facility (LSTF) as a part of an IAEA coordinated research project. The nodalisation of the test facility was qualified for both steady state and transient level by systematically applying the procedures led by uncertainty methodology based on accuracy extrapolation (UMAE); uncertainty analysis was carried out using the Latin hypercube sampling (LHS) method to evaluate uncertainty for ten input parameters. Sixteen output parameters were selected for uncertainty evaluation and uncertainty band between $5^{th}$ and $95^{th}$ percentile of the output parameters were evaluated. It was observed that the uncertainty band for the primary pressure during two phase blowdown is larger than that of the remaining period. Similarly, a larger uncertainty band is observed relating to accumulator injection flow during reflood phase. Importance analysis was also carried out and standard rank regression coefficients were computed to quantify the effect of each individual input parameter on output parameters. It was observed that the break discharge coefficient is the most important uncertain parameter relating to the prediction of all the primary side parameters and that the steam generator (SG) relief pressure setting is the most important parameter in predicting the SG secondary pressure.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.6
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• pp.1435-1441
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• 2014

The fire took place in the synthetic heat transfer fluid boiler used in production process of medium density fiberboard. This study investigated pressure distribution of the first, second and third passes and the temperature in the fire burner. The boiler's internal fluid is unsteady due to the out of order inverter. As the operation continues, the flame's flow and speed are unsteady. The synthetic heat transfer fluid leak spouted about 120kg/min in the form of vapor in the early period of the fire. The flame extended to the second and third passes. The highest temperature of the second and third pass is $1059^{\circ}C$ and $1007^{\circ}C$, respectively. The synthetic heat transfer fluid spouted through the cracked part of the fire box in the first pass and accumulated on the turn table. Therefore, it is expected that the temperature of the interior of the fire box is above $1200^{\circ}C$. The temperature of the burner rises to a maximum level several times in a short period. On account of that, several explosions occur in the fire burner. Pressure distribution at steady state in combustion furnace is 2~5mAq and pressure distribution at inverter under fault condition in combustion furnace is 10~-53mAq. The decrement of coil thickness measurement for synthetic heat transfer fluid boiler is 0~5mm.

• Geomechanics and Engineering
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• v.18 no.3
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• pp.235-245
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• 2019

This paper presents a novel methodology for face stability assessment of rock tunnels under water table by combining the kinematical approach of limit analysis and numerical simulation. The tunnels considered in this paper are excavated in fractured rock masses characterized by the Hoek-Brown failure criterion. In terms of natural rock deposition, a more convincing case of depth-dependent mi, GSI, D and ${\sigma}_c$ is taken into account by proposing the horizontally layered discretization technique, which enables us to generate the failure surface of tunnel face point by point. The vertical distance between any two adjacent points is fixed, which is beneficial to deal with stability problems involving depth-dependent rock parameters. The pore water pressure is numerically computed by means of 3D steady-state flow analyses. Accordingly, the pore water pressure for each discretized point on the failure surface is obtained by interpolation. The parametric analysis is performed to show the influence of depth-dependent parameters of $m_i$, GSI, D, ${\sigma}_c$ and the variation of water table elevation on tunnel face stability. Finally, several design charts for an undisturbed tunnel are presented for quick calculations of critical support pressures against face failure.

• Journal of the Korean Society of Safety
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• v.36 no.2
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• pp.111-119
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• 2021

Multi-dimensional analysis of reactor safety-KINS standard (MARS-KS) is a thermal-hydraulic code to simulate multiple design basis accidents in reactors. The code has been essential to assess nuclear safety, but has mainly focused on light water reactors, which are in the majority in South Korea. Few previous studies considered pressurized heavy water reactor (PHWR) applications. To verify the code applicability for PHWRs, it is necessary to develop MARS-KS input decks under various transient conditions. This study proposes an input model to simulate small-break loss of coolant accidents for PHWRs. The input model includes major equipment and experimental conditions for test B9802. Calculation results for selected variables during steady-state closely follow test data within ±4%. We adopted the Henry-Fauske model to simulate break flow, with coefficients having similar trends to integrated break mass and trip time for the power supply. Transient calculation results for major thermal-hydraulic factors showed good agreement with experimental data, but further study is required to analyze heat transfer and void condensation inside steam generator u-tubes.