• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2006.05a
• /
• pp.225-227
• /
• 2006

Active power factor correction methods for electronic ballast are reviewed in this paper. PFC technology becomes more important due to various wattage ratings of new light sources. Expecially, most popular two method critical conduction mode and average mode, are described. Each characteristics are compared in relation to application target and power rating.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1999.03a
• /
• pp.331-338
• /
• 1999

In the present study, a searching technique for critical slip surface in two dimensional slope stability analysis is proposed. The failure surface generation and analysis has been usually limited to simple geometric shapes. However, more random surfaces need to be examined for some particular ground conditions. For this purpose, random searching technique is developed using genetic algorithm. The generalized limit equilibrium method is employed as the method of stability analysis. Using this technique, the factor of safety is compared with the result by using simplified Bishop's method. In addition, the convergent trend of fitness value is analyzed.

• Progress in Superconductivity and Cryogenics
• /
• v.20 no.1
• /
• pp.1-10
• /
• 2018

The improvement of critical current properties of $REBa_2Cu_3O_{7-x}$ (REBCO) coated conductors by introducing artificial pinning centers (APCs) is examined with respect to the field-angle anisotropy, high-field performance and relaxation property with time. Nano-rods along the c-axis introduced by PLD method and isotropic nano-particles introduced by TFA-MOD method are treated. The theoretical analysis is also shown to understand the effect of APCs quantitatively. The effects of superconducting layer thickness that influences the high-field performance and relaxation property are also discussed. It is shown that the upper critical field, which is another important factor to determine the high-field property, can be improved by introduction of APCs through electron scattering at interfaces with the superconducting matrix. The optimum critical current property can be obtained by properly designing the morphology and number density of APCs and the superconducting layer thickness.

• Knowledge Management Research
• /
• v.9 no.2
• /
• pp.35-61
• /
• 2008

The demands for knowledge in the rapid social change and the competitive environment are being increased day by day. As to reflect the demands, much scholarly and practical work has been done on the topics of Knowledge Management (KM). However, the study of KM in nonprofit organizations (NPOs) is insufficient. This study, while discussing the nature of NPOs, which have the different purposes of existence and characteristics from for-profit organizations, has the purpose of finding out the special strategy for KM in NPOs. Through understanding the characteristics and the status of NPOs, this study suggests that that the interorganizational KM is the method to lead successful KM in NPOs. And the critical success factors (CSFs) are presented in the three major factors, such as the systematical, the interorganizational and internal consideration factor for organization. This not only provides the successful KM strategy of NPOs but also enlarges the understandings about interorganizational KM.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.8 no.2
• /
• pp.141-144
• /
• 1984

The fatigue limits of crack initiation and propagation on the edge elliptical notched semi-infinite plate under completely reversed fatigue stress are determined theoretically. Assuming that the crack initiation and propagation occur when stress intensity factors of notched plate reach the critical values obtained from critical micro-crack length under plain fatigue limit loading and the threshold stress intensity factory, respectively, the fatigue limits of crack initiation and propagation are obtained. The induced theoretical fatigue limit of crack initiation is expressed in terms of plain fatigue limit, critical micro-crack length and notch shape. The one of crack propagation is in terms of threshold stress intensity factor, plain fatigue limit and notch shape. These theoretical results are showed to be in good agreement of Frost's experimental data.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2001.03a
• /
• pp.273-280
• /
• 2001

In order to evaluate the stability of railway cut-slope under rainfall, explanatory variables and subordinate variables were selected for multivariate analysis. Furthermore the site which had occurred failure due to rainfall was investigated, and by executing multivariate analysis for 121 cases, critical rainfall was defined by the case that had high value of correlation factor. The 0.3 square value of maximum hourly rainfall during 24 hours before failure caused the collapse of railway cut-slope and could be used to estimate the stability of railway cut-slope. From the result of application to a collapse example, the evaluaton method by critical rainfall curve is satisfactory.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.9 s.180
• /
• pp.2344-2352
• /
• 2000

Mechanical joints such as bolted or riveted joints are widely used in mechanical components. The reliable determination of the stress intensity factors for cracks in bolted joints is needed to evaluate the safety and fatigue life of them. The weight function method is an efficient technique to calculate the stress intensity factors for various loading conditions because only the stress analysis of an uncracked model is required. In this paper the mixed-mode stress intensity factors for cracks in bolted joints are obtained by weight function method, in which the coefficients of weight function are determined by finite element analyses for reference loadings. Critical inclined angle that mode I stress intensity factor becomes maximum is determined and the effects of crack length and the magnitude of clearance on critical inclined angle are investigated.

• International Commerce and Information Review
• /
• v.7 no.1
• /
• pp.3-18
• /
• 2005

The purpose of this study is to investigate the determinants of critical success and to analyze the main factors which are affecting the successful implementation of Internet shopping mall. The major findings of empirical analysis are as follows : 1) The degree of searching easuness in the internet shopping mall is statistical significance. 2) The degree of customer response is the important success factor. 3) The speed of connection exert a beneficial influence upon the performance of shopping mall. 4) The standard of security system is be in direct proportion to the performance of shopping mall The result of this study will be useful for the chief executive officers to make more rational decision making for e-Business strategies is related to the Internet shopping mall. The paper also strives to provoke debate in this area with to encouraging further research on the topic.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1994.11a
• /
• pp.192-197
• /
• 1994

High-Tc superconducting magnet properties were dependent upon design conditions such as its radius, length, critical current and notch size. In order to study, design and the simulation for small size magnet were implemented. We know that intensity of magnetic fields controled by critical current and factor ${\alpha}$( R$_2$/R$_1$) and uniformity controled by notch size. The optimal condition of intensity and uniformity magnetic field in this experiments are R$_1$=3[cm], R$_2$=12[cm], Z=10[cm], ${\alpha}$=4, notch=6[cm], critical current=12[A].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1996.05a
• /
• pp.252-255
• /
• 1996

Superconducting current lead is one of the promising applications of the oxide high-Tc superconductors, because they have the advantage of decreasing heat conduction to low temperature region, comparing with a conventional cooper alloy lead. High critical current density is a key factor for the applications such as current lead. (Bi,Pb)$_2$Sr$_2$Ca$_2$Cu$_3$O$\_$x/ high Tc superconductor haute been investigated in terms of critical current density. Bi-2223 superconducting current lead made by CIP and solid state sintering process. Bi-2223 current lead that heat treated at 836$^{\circ}C$ for 240 h in 1/13 P$\_$O$_2$/ had over 150 A/$\textrm{cm}^2$ of critical current density at 77K. We knew that the superconducting properties of tube type current leads were better than rods type of them. And we investigated the relation of Bi-2223 formation and heat treatment condition by XRD and SEM analysis.