• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.39-44
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• 1996

A nodal transport method based on the F$_{N}$ method is developed for the transport calculation in x- y geometry and tested for benchmark problems. Using transverse integration, the two-dimensional transport equation is converted to one-dimensional equations for x, y-directions and the one-dimensional equations are integrated over azimuthal angle. With proper approximations for the transverse leakage, the one-dimensional equations are discretized by using the F$_{N}$ method without truncation error. At present, isotropic approximation of the transverse with a quadratic or flat shape in spatial variable is tested.ted.

• Journal of the Korean Society of Combustion
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• v.9 no.4
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• pp.35-46
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• 2004

Activation energy asymptotics (AEA) for Linan#s premixed-flame regime is revisited in this paper. First, the detailed AEA procedure for the premixed-flame regime is demonstrated, so that the practitioners of AEA could easily apply the method to their own problems. In addition, the controversies surrounding the premixed-flame regime, namely the closure controversy and fast-time instability paradox, are explained. Finally, the limitation of AEA, mainly arising from the wrong prediction of fuel leakage through the reaction zone, is examined and the Zel#dovich-Linan kinetics is introduced as an alternative to meet the needs of modern combustion analysis, where the detailed chemical structure of flame is demanded.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1175-1180
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• 2001

Reinforced concrete deck slabs are directly affected by traffic loads and they are also susceptible to weather-related problems, such as cracking, reinforcement corrosion, spatting, scaling, delamination, leakage, efflorescence and so on. Some of these defects are caused by water which seeps through pavements and trapped between pavements and deck slabs. For durability of reinforced concrete deck slabs and pavements, it is very important to protect deck slabs and drain the trapped water out. To develop the trapped water drainage system, the following studies have been performed in Korea Highway Cooperation: related researches are reviewed; for six bridges, deck slabs are thoroughly investigated; new system to effectively drain the trapped water out is proposed; the proposed system is installed and evaluated. The proposed system is proved to be effective to drain the trapped water out and is expected to increase the durability of reinforced concrete deck slabs.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1702-1707
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• 2007

The reduction of pipe-thickness induced by flow accelerated corrosion (FAC) is one of the most serious problems on the maintenance of piping system in nuclear power plants (NNP). If the thickness of a pipe component is reduced below the critical level, it cannot sustain pressure and consequently results in leakage or rupture. For this reason, wall thinning by FAC has been inspected in secondary side piping systems in NPPs. In this research Round Robin Test (RRT) was conducted to verify confidence of wall thinning measurement system in NPP. 12 inspectors from 3 companies participated and 23 specimens were used according to standard practice in RRT. The gage R&R analysis was introduced in regard to repeatability and reproducibility that are affected to measurement system errors. Confidence intervals of thickness measurement system were obtained.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.12 no.2
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• pp.25-33
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• 2016

The thermal stratification phenomenon in the nuclear power plant can cause abnormal deformation of the piping, contact with the support, damage to the support system. Repetition of the thermal stratification phenomenon or variation of the thermal boundary layer can cause thermal fatigue. Thermal stratification phenomenon in nuclear power plants is still an ongoing issue and active research has been carried out. In this paper, the current situation in Korean nuclear power plants is described, followed by the status of research and the future problems on the thermal stratification phenomenon in Korea.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.1
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• pp.87-94
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• 2003

Recently, LPLi(Liquied-Phase LPG injection) system is studied for the new stringent emission regulations. But , there are some problems to be solved such as injector tip icing and fuel leakage for LPLi system development. In this paper, the icing problem near injector tip which leads to difficulty of accurate A/F control was studied and reported. Icing of injector tip and port wall was observed at all the cases in this study regardless of injection duration and angle, air humidity change. The spray angle of LPLi was observed approximately two times wider than that of Gasoline injection. This makes the LPLi spray collide with intake port around injector tip. Temperature of the wetted area was decreased and icing of water vapor contained in intake air because of evaporation of the fuel film. The ice of the injector tip and port wall is also affected by the materials related to heat transfer.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.267-276
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• 1993

A kinetmatic stirling engine with a domed heater was designed, fabricated and test. In designing and fabrication of the engine various problems were confronted and solved. Among various parts of the engine, cooler and main seal needed sophisticated techniques to fabricated in order to prevent leakage of working gas from the parts and to ensure their proper functions in the engine. The engine had a series of experiment at various working gas pressure, heater temperatures and engine speeds to evaluate its performance. Indicated and brake power outputs and indicated and brake thermal efficiencies were determined from the experimental data. The engine resulted a little inferior performance to that of the GPU-3 engine of which performance was well reported . Several recommendations were made to improve the performance of the engine during the evaluation of its performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.09a
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• pp.19-22
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• 2001

For stabilization and improving power factor in the power lines, various Static Var Compensators(SVC) have been considered to be installed and partly applicated already. With all these merits of the SVC, it stil has demerits, principally evoking harmonic problems. So far, many harmonic reduction type inverters have been used in various parts. In this paper, the reactive power is controlled by amplitude of the output voltage. This paper propose that the multiple voltage source inverter have controllable power factor made by load vary at receive-stage as lagging and leakage control. The theoretical analysis on this system was confirmed through the computer simulation and the experiments.

• Proceedings of the KIPE Conference
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• 2014.11a
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• pp.25-26
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• 2014

Renewable energy sources such as wind and solar power are free and can be easily harvested everywhere. However, one of the biggest problems when using this kind of energy source is how to increase the efficiency of power conversion system. This paper introduces a modified 3-phase inverter in order to increase the power conversion efficiency. By adding 3 bi-directional switches at output of the inverter, the current flow back DC source during zero state is prevented to minimize leakage current, so that the efficiency of whole system is increased. The proposed topology also improves the power quality to satisfy the total harmonics distortion (THD) requirement. In order to verify the effectiveness of the proposed topology, simulation results are carried out using Simulink in MATLAB.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.170-170
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• 2006

[ ${\pi}-conjugated$ ] organic and polymeric semiconductors are receiving considerable attention because of their suitability as an active layer for electronic devices. An organic inverter with a full swing and a high gain can be obtained through the good qualities of the transfer characteristics of organic thin-film transistors (OTFTs); for example, a low leakage current, a threshold voltage ($V_{th}$) close to 0 V, and a low sub-threshold swing. One of the most critical problems with traditional organic inverters is the high operating voltage, which is often greater than 20 V. The high operating voltage may result in not only high power consumption but also device instabilities such as hysteresis and a shift of $V_{th}$ during operation. In this paper, low-voltage and little-hysteresis pentacene OTFTs and inverters in conjunction with PEALD $Al_{2}O_{3}\;and\;ZrO_{2}$ as the gate dielectrics are demonstrated and the relationships between the transfer characteristics of OTFT and the voltage transfer characteristics (VTCs) of inverter are investigated.