• Journal of the Korean Data and Information Science Society
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• v.18 no.4
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• pp.869-878
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• 2007

In this paper a new process capability index $C_{psks}$ is introduced for non-normal process. $C_{psks}$ that is proposed by transformation of the $C_{psks}$ incorporates an additional skewness correction factor in the denominator of $C_{psks}$. The use of each technique is illustrated by reference to a distribution system which includes the Pearson and Johnson functions. Accordingly, $C_{psks}$ is proposed as the process capability measure for non-normal process.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.312-313
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• 2015

For the traceability of high current measuring sensors of high power testing department II(HPTD II) in Korea Electrotechnology Research Institute(KERI), additional comparison tests with reference test object were performed repeatedly. The first intercomparison has been carried out between the reference shunt for Asia and high current shunt of HPTD II in 2013. This paper compares the test results of the calibration in 2014 with them in 2015. The assigned new scale factor of high current sensors will be applied to high power tests in HPTD II until the next high current intercomparison.

• Journal of the Korean Society of Safety
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• v.35 no.3
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• pp.49-57
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• 2020

In comparison with the existing static reliability analysis methods, the dynamic reliability analysis(DyRA) method is more suitable for estimating the failure probability of a structure subjected to earthquake excitations because it can take into account the frequency characteristics and damping capacity of the structure. However, the DyRA is known to have an issue of numerical stability due to the uncertainty in random sampling of the earthquake excitations. In order to solve this numerical stability issue in the DyRA approach, this study proposed two earthquake-scale factors. The first factor is defined as the ratio of the first earthquake excitation over the maximum value of the remaining excitations, and the second factor is defined as the condition number of the matrix consisting of the earthquake excitations. Then, we have performed parametric studies of two factors on numerical stability of the DyRA method. In illustrative example, it was clearly confirmed that the two factors can be used to verify the numerical stability of the proposed DyRA method. However, there exists a difference between the two factors. The first factor showed some overlapping region between the stable results and the unstable results so that it requires some additional reliability analysis to guarantee the stability of the DyRA method. On the contrary, the second factor clearly distinguished the stable and unstable results of the DyRA method without any overlapping region. Therefore, the second factor can be said to be better than the first factor as the criterion to determine whether or not the proposed DyRA method guarantees its numerical stability. In addition, the accuracy of the numerical analysis results of the proposed DyRA has been verified in comparison with those of the existing first-order reliability method(FORM), Monte Carlo simulation(MCS) method and subset simulation method(SSM). The comparative results confirmed that the proposed DyRA method can provide accurate and reliable estimation of the structural failure probability while maintaining the superior numerical efficiency over the existing methods.

• Journal of Industrial Convergence
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• v.20 no.11
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• pp.191-196
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• 2022

In the fintech field, financial transactions with smart phones are actively conducted. User authentication technology is essential for safe financial transactions. PIN authentication through the existing security keypads is convenient to input but has weaknesses in security and others. The biometric authentication technique is secure, but there is a possibility of false positive and false negative authentication. To compensate for this, two-factor authentication is used. In this paper, we propose the 1.5-factor authentication that can increase convenience and security through PIN input with biometric authentication. It provides the stability of fingerprint authentication and convenience of two or three PIN inputs, and this makes safe financial transaction possible. Since biometric authentication is performed at the same time when entering PIN, while security is required by applying fingerprint authentication to the area touched while entering PIN. The User authentication is performed while ensuring convenience to input through additional PIN input in situations where high safety is required, and Safe financial transactions are possible.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.986-989
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• 2002

This paper proposes a new single stage power factor correction (PFC) full bridge converter which operates at continuous conduction mode(CCM). The proposed single stage PFC consists of typical zero voltage switching(ZVS) full bridge DC/DC converter, two transformer auxiliary windings, and two small inductors, and two diodes. Neither additional active switch nor any control circuit are added for PFC resulting in very low cost. The proposed converter provides input power factor correction with CCM control and tight output voltage regulation. All switching devices are operated under ZVS with minimum voltage stress. Operation principle and analysis are explained and verified with computer simulation and experimental results on a 1.2kW, 100kHz prototype.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.1
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• pp.67-74
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• 2017

This study proposes a novel random pulse-width modulation (PWM) technique with a constant switching frequency utilizing a random offset voltage. The proposed PWM technique spreads switching harmonics by varying the position of an active voltage vector without a switching frequency variation. The implementation of the proposed PWM technique is simple because it does not require additional hardware and complex algorithm. The proposed random PWM technique is compared with the conventional PWM technique on the factors of harmonic spectrum, total harmonic distortion, and harmonic spread factor to confirm the harmonic spread effect. The validity of the proposed method is verified by simulations and experiments on a three-phase inverter drive system.

• KIEAE Journal
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• v.11 no.4
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• pp.71-78
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• 2011

The goal of this study is to analyze the impact of load factors on building energy consumption by using EnergyPlus program. We selected a campus building and monitored energy consumption from January 2009 to November 2010. First, we simulated energy consumption basically with weather data, building heat gain and EHP performance data. And then we simulated energy consumption with three additional parameter(infiltration, OA control and schedule). Simulation results are verified by MBE and Cv(RMSE) proposed by M&V guideline 3.0. Simulated total energy consumption was 104.3% of measurements, 4.33% of MBE, and 13.62% of Cv(RMSE). Results show infiltration and schedule were revealed as the most dominant factor of heating energy consumption and of cooling energy consumption, respectively.

• Journal of the Korean Data and Information Science Society
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• v.19 no.3
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• pp.831-844
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• 2008

Since cooperatives consist of many distinct members in the management environment and characteristics, it is necessary to make similar cooperatives into a few groups for the effective risk management of cooperatives' mutuality bank. This paper is a priori research for suggesting a guidance for effective risk management of cooperatives with different management strategy. For such purpose, we propose a way to group the members of cooperative's mutuality bank. The 30 continuous variables which is relative to cooperatives' management status are considered and six factors are extracted from those variables through factor analysis with empirical consideration to avoid wrong grouping and to enhance the practical interpretation. Based on extracted six factors and additional 3 categorical variables, six representative groups are derived by the two step clustering analysis. These findings are useful to execute a discriminatory risk management and other management strategy for a mutuality bank and others.

• Journal of Environmental Science International
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• v.7 no.4
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• pp.549-558
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• 1998

determine the distribution of heavy metals in estuarine sediments, forty surface sediment samples were collected from the Youngsan estuary, and analysed for their contents of Fe, Mn, Co, Cr, Cu, Ni, Zn and Pb. Contents of most analysed metals were comparable to those in the near shore environment around Korean peninsula, and little anthropogenic effect was identified. However, there was a contrasting behavior among the metals with respect to their relationship with the grain-size of sediments. Contents of Fe, Co, Cr and Ni demonstrated a fairly linear relationship with the grain-size of sediments whereas those of Mn, Cu, Zn and Pb did not. This different behavior In these metals was Interpreted as being the result of the additional inputs. The R-mode factor analysis also confirmed the different behavior of Cu, Zn, Pb and Mn from that of Fe, Co, Cr and Ni.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.147-148
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• 2011

In this paper, implementation of digital control for critical conduction mode power factor correction (PFC) rectifier is presented. Critical conduction mode is widely used in medium and low power conversion application due to its minimized MOSFET turn-on loss and diode reverse-recovery problem. However, it needs additional zero current detection circuit and maximum frequency limit to properly turn the MOSFET on and avoid the excessive switching loss in light load operation. This paper explains the digital IC implementation and verifies its operation with 200-W prototype PFC rectifier.