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Wonju, South Korea

Halla University is a private Korean University created in 1995 and located in Wonju. Wikipedia.

Lee E.J.,Halla University | Bukowski W.M.,Concordia University at Montreal
Journal of Adolescence | Year: 2012

Latent growth curve modeling was used to study the co-development of internalizing and externalizing problems in a sample of 2844 Korean fourth graders followed over four years. The project integrated two major theoretical viewpoints positing developmental mechanism: directional model and common vulnerability model. Findings suggest that (a) boys and girls follow different developmental trajectories in both domains in early adolescence; (b) bidirectional progression from initial levels of each domain to the developmental pattern of the other domain emerged among boys, while only unidirectional progression from externalizing to internalizing problem emerged among girls; and (c) all risk factors are not equally risky across domain and gender; parental violence was a common cross-domain risk factor for boys, whereas affiliation with delinquent friends was a common cross-domain risk factor for girls. Implications for future research and intervention were discussed. © 2011 The Foundation for Professionals in Services for Adolescents. Source

Kim E.-S.,Halla University
Journal of Electrical Engineering and Technology | Year: 2012

In this paper, the observer based nonlinear state feedback controller has been developed to control the pressures of the oxygen and the hydrogen in the PEM(Proton Exchange Membrane) fuel cell system. Nonlinear model of the PEM fuel cell system was introduced to study the design problems of the state observer and model based controller. A cascade observer using the filtering technique was used to estimate the pressure derivatives of the cathode and the anode in the system. In order to estimate the pressures of the cathode and the anode, the sliding mode observer was designed by using these pressure derivatives. To estimate the oxygen pressure and the hydrogen pressure in the system, the nonlinear state observer was designed by using the cathode pressure estimates and the anode it. These results will be very useful to design the state feedback controller. The validity of the proposed observers and the controller has been investigated by using the Lyapunov's stability analysis strategy. Source

Yu B.,Inha University | Kum S.-M.,Halla University | Lee C.-E.,Inha University | Lee S.,Inha University
Energy | Year: 2013

This research was conducted to experimentally compare the emission characteristics and thermal efficiency of porous-media types of burners and to determine which types to use with a condensing boiler to be developed later. Three types of porous-media burners; metal fiber (MF), ceramic (CM) and stainless steel fin (SF) were used with a commercial heat exchanger and tested for various equivalence ratios and burner capacities. The MF burner had the lowest CO emissions of the three burner types, and the SF burner had the highest CO emissions. However, The MF burner had the highest NOx emission and thermal efficiency, and the SF burner had the lowest NOx emissions and thermal efficiency. In other words, the smaller the burner porosity was (porosity: SF < CM < MF), the higher the CO emission was and the lower the thermal efficiency was. Based on the thermal efficiency, turn-down ratio and NOx and CO emissions with respect to the Korean industrial standard and European norms, the most appropriate burner type for the condensing boiler is the MF burner. The optimal operating equivalence ratio was 0.80 for the range of experimental factors considered in this research. © 2013 Elsevier Ltd. Source

Yoo Y.K.,Halla University
International Journal of Systems Science | Year: 2011

This article presents some operating characteristics of a failure counting group replacement policy. A group of identical units are put in service together. The maintenance policy applied for them is a group replacement policy based on failure count; they are replaced altogether when a number of failures reaches a certain amount. For the expected cost rate function under the failure counting group replacement policy, this article presents a method to obtain the optimum cost rate. We also show that the optimum cost rate is an increasing function in the fleet size. Numerical examples are presented to demonstrate the results. © 2011 Taylor & Francis. Source

This paper is a study on a nuclear water chiller. It presents a test-verified finite element model of a water chiller to be used at a Nuclear Power Plant. The test-verified model predicts natural frequencies within 5% for all major modes below 50 Hz. This model accurately represents the dynamic characteristics of the actual hardware and is qualified for its use in the final stress analysis for seismic verification. Source

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