• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07b
• /
• pp.1129-1131
• /
• 2002

Zinc Air battery obtain their energy density advantage over the other batteries by utilizing ambient oxygen as the cathode materials, and reusing cathode as recycled form. And specific capacity of zinc powder is as high as 820mAh/g. When Zinc Air battery discharged by low rate current discharge voltage profile has very flat pattern until end of voltage. But, when Zinc Air battery discharged by high rate current discharge voltage and capacity become lower. Therefore, we focused on effects of catalyst size in cathode. So we examined performance of zinc air batteries, average discharge voltage, capacity, energy, resistance. And we also obtained resistance by the GSM pulse discharge. So we have got optimum size of catalyst for Zinc Air battery.

• Proceedings of the KIEE Conference
• /
• 2005.07a
• /
• pp.902-904
• /
• 2005

The AC-DC converter, which has three-phase AC power as input and isolated DC power as output is used for the regulated DC power supply of the telecommunication power processing system for several kilowatt class applications. The conventional DC power supply for the telecommunication power system comprises a PWM rectifier with sine-wave shaping input current unity power factor and a DC/DC converter connected to the PWM converter, which obtains DC 48[V]. Since power passes through these two power stage converters, the conversion power loss is difficult to provide high efficiency. To resolve these problems, this paper presents a new PWM rectified as a 1-stage power conversion method. It simulation and experimental results as proved from a practical point of view that 92.1[%]of conversion efficiency and input current which can meet harmonics regulation of the Class-A in IEC61000-3-3 are achieved.

• Proceedings of the KIEE Conference
• /
• 2005.07d
• /
• pp.3114-3116
• /
• 2005

The AC-DC converter, which has three-phase AC power as input and isolated DC power as output is used for the regulated DC power supply of the telecommunication power processing system for several kilowatt class applications. The conventional DC power supply for the telecommunication power system comprises a PWM rectifier with sine-wave shaping input current unity power factor and a DC/DC converter connected to the PWM converter, which obtains DC 48[V]. Since power passes through these two power stage converters, the conversion power loss is difficult to provide high efficiency. To resolve these problems, this paper presents a new PWM rectified as a 1-stage power conversion method. It simulation and experimental results as proved from a practical point of view that 92.1[%] of conversion efficiency and input current which can meet harmonics regulation of the Class-A in IEC61000-3-3 are achieved.

• Journal of Environmental Science International
• /
• v.11 no.9
• /
• pp.881-895
• /
• 2002

Sediments and river waters form the channel of Hwasun-cheon were studied in sedimentological size and geochemical analyses of metallic elements for the purposes of identification of depositional environments and geochemical characteristics. The sizes of sediments are assigned to pebble to coarse sand in mean size and polymodal in distribution. And the sediments are poorly to very poorly sorted and positively skewed. According to the grain size distributions of the sediments, the Hwasun-cheon belongs to gravel-bed river on the basis of the grain size distribution of the sediments. The behaviors of metallic elements in the sediments mainly depend on not grain size distribution but the geology connected with geomorphological reliefs near the stream. Contamination indices(CI) of Zn, Cu and Pb are 2.83 to 6.96 with average 4.31 in the sediments. Hwasun-cheon is assigned to general stream type in accordance with water quality of physical factors and chemical characteristics by Piper's diagram. Though meaningful values of BOD, T-N, T-P were locally depicted near Masan-ri, Hwasun-eup and Jiseok-cheon areas, artificial metal concentration do not represent in the most area of the stream. Sediments and river water are considered that the relatively more or less high metallic contents in the stream are originated from coal mine and urban area.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07b
• /
• pp.1159-1162
• /
• 2003

Recently we suffered lot of failures of polymer surge arresters made by same manufacture after one year field operation. In order to set up countermeasures we investigated the causes of failures. We extracted faulted arresters and sound ones which were installed in same pole with faulted ones for the electrical test and dissection. 44 arresters were removed from 8 branch offices. Almost all of faulted arresters hadtracking damage on the interface between inner module and housing and the surface of inner module was very rough and irregular. It was possible to occur moisture ingress into the interface between inner module and housing due to the void of the interface and non tight sealing caps. Lots of sound arresters were failed during the moisture ingress test. This result must relate with tracking damage of faulted arresters. Therefore we can say that arresters had poor interface and sealing system. But we could not found aging and defects of ZnO elements because the electrical performance except moisture ingress test of arresters showed good.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.33 no.4
• /
• pp.337-345
• /
• 2009

This paper investigates the reliability of district heating pipes at thermo-elastic fatigue loading. District heating pipes, subjected to $120^{\circ}C$ and $16kg_f/cm^2$ due to water distributing service through inside the pipes, should endure long term cyclic thermal-mechanical loadings. The heating pipes are the co-centric tubes of steel pipe, poly urethane(PUR) insulator, and high density poly ethylene(HDPE) case. On installation, foam pad is externally wrapped for accommodating stress reduction near the bend sections of pipes. However, there have been frequent reports on the failures of bend sections in the middle of long term service. This study scrutinizes the observed failures near the bend sections through applying the finite element methods. Specially in this study, heating pipes are studied on the influence of foam padding on failures and proposed new designs for reinforced bend without foam pad.

• Journal of Korean Society for Geospatial Information Science
• /
• v.13 no.4 s.34
• /
• pp.47-58
• /
• 2005

Investigation of bedrock quality and the legal restriction for developing the aggregate resources were carried out with GIS in the Wondeung area Gokseong-gun, Jeollanam-do province. Firstly, we surveyed the exposed bedrocks in the field and examined in physical properties in the lab. Secondly we analyzed the legal restriction by using GIS based on bufferzone and viewshed analysis. At the results of this study, the area can be used totally as the crushed stones. However the suitability sites of crushed stone have various regulations. So the legal restriction is the principal standard to develop the crushed stone in the Wondeung area. Suitable site for crushed stones are about 30% in the Wondeung area.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.919-924
• /
• 2004

A CFA(Cooling Fan Assembly) is composed of a fan, motor and shroud, which is at the back of the automotive radiator. By forcing the wind to pass, the CFA controls the cooling performance of the radiator. The noise and vibration of the CFA may be primarily due to the resonance between the CFA and engine. The Interference among the fan, shroud and radiator by deformation is considered when the CFA is designed. In this paper, in order to analyze the structural vibration of the CFA for automobiles, a finite element model of the CFA is established by using a commercial FEM code. After the finite element modeling, the natural frequencies and the mode shapes are obtained from the FE analysis. The natural frequencies are obtained from the vibration test as well. Then, the results of the vibration test are compared with those of the FE analysis. The natural frequencies obtained by experiment have a great similarity to the results from FE model. We have confirmed the validity of the FE model and verify the structural safety for the resonance. The stress and displacements are obtained from FE analysis. We have confirmed the safety for the interference and failure.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2003.09a
• /
• pp.78-82
• /
• 2003

Development of hematite-coated sand was evaluated for the application of the PRB (permeable reactive barrier) in the arsenic-contaminated subsurface of the metal mining areas. The removal efficiency of As(III) and As(V), the effect of anion competition and the capability of arsenic removal in the flow system were investigated through the experiments of adsorption isotherm, arsenic removal kinetics against anion competition and column removal. Hematite-coated sand followed a linear adsorption isotherm with high adsorption capacity at low level concentrations of arsenic (< 1.0 mg/l). When As(III) and As(V) underwent adsorption reactions in the presence of anions (sulfate, nitrate and bicarbonate), sulfate caused strong inhibition of arsenic removal, and bicarbonate and nitrate caused weak inhibition due to specific and nonspecific adsorption onto hematite, respectively. In the column experiments, high content of hematite-coated sand enhance the arsenic removal, but the amount of the arsenic removal decreased due to the higher affinity of As(V) than As(III) and reduced adsorption kinetics in the flow system, Therefore, the amount of hematite-coated sand, the adsorption affinity of arsenic species and removal kinetics determined the removal efficiency of arsenic in the flow system. arsenic, hematite-coated sand, permeable reactive barrier, anion competition, adsorption.

• Geotechnical Engineering
• /
• v.10 no.1
• /
• pp.7-18
• /
• 1994

A new model for describing the behavior of clay under monotonic and cyclic loading is proposed. This model uses the hyperbolic representation for the stress -strain relationship in overconsolidated state and it describes undrained effective stress path on the basis of the critical state theory. The developed constitutive model by using an energy dissipation equation can describe the behavior of clay in heavily overconsolidated state as u.ell as lightly overconsolidated state under monotonic loading. In order to extend the model for the behavior of clay under cyclic loading, a shift function of undrained stress spacing ratio is introduced in the constitutive model developed for monotonlc loading. A single additional parameter is required to represent the cyclic effect and it can be reasonably deter mined from the test results. The measured behavior in undrained cyclic triaxial tests has been easily and precisely predicted by the newly developed constitutive model.