• Journal of the Society of Naval Architects of Korea
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• v.54 no.2
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• pp.132-142
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• 2017

As the International Maritime Organization (IMO) recently introduced the Energy Efficiency Design Index (EEDI) for new ships building and the Energy Efficiency Operational Indicator (EEOI) for ship operation, thus an accurate estimation of added resistance of ships advancing in waves has become necessary. In the present study, OpenFOAM, computational fluid dynamics libraries of which source codes are opened to the public, was used to calculate the added resistance and motions of the KCS. Unstructured grid using a hanging-node and cut-cell method was used to generate dense grid around a wave and KCS. A dynamic deformation mesh method was used to consider the motions of the KCS. Five wavelengths from a short wavelength (${\lambda}/LPP=0.65$) to a long wavelength (${\lambda}/LPP=1.95$) were considered. The added resistance and the heave & pitch motions calculated for various waves were compared with the results of model experiments.

• Journal of Sensor Science and Technology
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• v.25 no.1
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• pp.13-19
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• 2016

Nowadays, most major automobile manufacturers are very interested, and actively involved, in developing driver alcohol detection system for safety (DADSS) that serves to prevent driving under the influence. DADSS measures the blood alcohol concentration (BAC) from the driver's breath and limits the ignition of the engine of the vehicle if the BAC exceeds the reference value. In this study, to optimize the sensor array of the DADSS, we selected sensors by using three different methods, configured the sensor arrays, and then compared their performance. The Wilks' lambda, stepwise elimination and filter method (using a principal component) were used as the sensor selection methods [2,3]. We compared the performance of the arrays, by using the selectivity and sensitivity as criteria, and Sammon mapping for the analysis of the cluster type of each gas. The sensor array configured by using the stepwise elimination method exhibited the highest sensitivity and selectivity and yielded the best visual result after Sammon mapping.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.976-983
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• 1988

An efficient unbalance response analysis method for rotor-bearing systems with spin speed dependent parameters is developed by utilizing a generalized modal analysis scheme. The spin speed dependent eigenvalue problem of the original system is transformed into the spin speed independent eigenvalue problem by introducing a lambda matrix, assuming the bearing dynamic coefficients are well approximated by polynomial functions of spin speed. This method features that it requires far less computational effort in unbalance response calculations and that the influence coefficients are readily available. In addition, the critical speeds and the corresponding logarithmic decrements can be readily identified from the resulting eigenvalues.

• Journal of Power Electronics
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• v.19 no.1
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• pp.278-287
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• 2019

In this study, a zero-crossing spike current issue in a totem-pole bridgeless power factor correction (PFC) converter is comprehensively investigated for the first time. Spike current occurs when input voltage crosses zero, becomes a noise source, and causes severe common mode emission issues. A generation mechanism for electromagnetic interference (EMI) is presented to investigate the EMI problem caused by zero-crossing issue, and a noise spectrum due to this issue is predicted by a theoretical analysis based on the Fourier coefficient of an approximate spike current waveform. Furthermore, a noise reduction method is proposed and then improved to reduce the spike current. Experimental measurements are implemented on a GaN-based totem-pole bridgeless PFC converter, and the spike current can be effectively suppressed through the proposed method. Furthermore, the noise spectrums measured without and with the reduced zero-crossing spike current are compared. Experimental results validate the analysis of the noise spectrum caused by the zero-crossing spike current issue.

• Korean Journal of Food Science and Technology
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• v.30 no.5
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• pp.1029-1034
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• 1998

Chick antibodies (IgY) raised against Streptococcus mutans (serotype c) were separated from egg yolk and their properties were investigated. The purity of IgY extracts prepared by the method of ${\lambda}-carrageenan$, $gammaYolk^{TM}$, and $EGGstract^{TM}$ was 20%, 46%, and 48%, respectively, and the yields of IgY extracts from a gram yolk were 11. 3 mg, 1.7 mg, and 1.8mg, respectively. Quantitative immunoprecipitation test showed that specific IgY content of crude IgY prepared by ${\lambda}-carrageenan$ method was 12.2%, which means that 0.85 g of crude IgY from an egg yolk (15 g) contains about 100 mg of specific IgY. When the reactivity of the specific IgY towards 3 caries-inducing strains (serotype: b, c, f) was examined, the strains cultured in sucrose-added medium showed higher reactivity (the orders were c(+), f(+), b(+)) than those cultured in sucrose-free medium. Heat and pH stability of specific IgY was good, for crude IgY contained 50% of antibody activity after heat treatment at $70^{\circ}C$ for 5 min and they were stable at pH $4{\sim}8$.

• Journal of the Korea Society for Simulation
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• v.24 no.3
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• pp.27-35
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• 2015

We analyze an M/G/1/K queueing system with queue-length dependent service and arrival rates. There are a single server and a buffer with finite capacity K including a customer in service. The customers are served by a first-come-first-service basis. We put two thresholds $L_1$ and $L_2$($${\geq_-}L_1$$ ) on the buffer. If the queue length at the service initiation epoch is less than the threshold $L_1$, the service time of customers follows $S_1$ with a mean of ${\mu}_1$ and the arrival of customers follows a Poisson process with a rate of ${\lambda}_1$. When the queue length at the service initiation epoch is equal to or greater than $L_1$ and less than $L_2$, the service time is changed to $S_2$ with a mean of $${\mu}_2{\geq_-}{\mu}_1$$. The arrival rate is still ${\lambda}_1$. Finally, if the queue length at the service initiation epoch is greater than $L_2$, the arrival rate of customers are also changed to a value of $${\lambda}_2({\leq_-}{\lambda}_1)$$ and the mean of the service times is ${\mu}_2$. By using the embedded Markov chain method, we derive queue length distribution at departure epochs. We also obtain the queue length distribution at an arbitrary time by the supplementary variable method. Finally, performance measures such as loss probability and mean waiting time are presented.

• Environmental Engineering Research
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• v.17 no.4
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• pp.205-210
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• 2012

Hydroperoxyl radical/superoxide anion radical ($HO_2{\cdot}/O_2^-{\cdot}$, $pK_a$=4.8) as an intermediate is of considerable importance in oxidation processes. Hence, the method of detecting $HO_2{\cdot}/O_2^-{\cdot}$ with high sensitivity is necessary to be developed. To achieve this objective, this study newly employed terephthalate (TA) as a probe for the measurement of $HO_2{\cdot}/O_2^-{\cdot}$ in the kinetic method presented in our previous study. This method was based on the hydroxylation of TA to produce mainly hydroxyterephthalic acid or hydroxyterephthalate (OHTA), which was analyzed by fluorescence detection (${\lambda}_{ex}$=315nm, ${\lambda}_{ex}$=425nm). The life-time of $HO_2{\cdot}/O_2^-{\cdot}$ and its concentration formed from the photolysis technique of $H_2O_2$ were reported in this study. At range of pH 2-10, the life-time of $HO_2{\cdot}/O_2^-{\cdot}$ was 51-422 sec. In particular, an increase in the life-time with pH was observed. The sensitivities of the kinetic method by using TA were always higher with 1.7-2.5 times at pH 8.0 than those by using benzoic acid. From these results, this study can contribute to understanding the basic functions of $HO_2{\cdot}/O_2^-{\cdot}$ in oxidation processes.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.4
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• pp.187-193
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• 1999

This study investigates the hysteresis phenomena of a Synchronous Reluctance Motor (SynRM) using coupled FEM and Preisach modeling. Preisach's model, which allows accurate prediction of hysteresis, is adopted in this procedure to provide a nonlinear solution. the computer simulation and experimental result for the i$\lambda$loci show the propriety of the proposed method.

• Journal of the Korea Safety Management & Science
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• v.9 no.2
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• pp.149-159
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• 2007

This paper is to propose two computation procedures of reliability measures for large interval data. First method is efficient to verify the relationship among four reliability measures such as F(t), R(t), f(t) and $\lambda(t)$. Another method is effective to interpret the concept of various reliability measures. This study is also to reinterpret and recompute the errors of four reliability measures discovered in the reliability textbooks. Various numerical examples are presented to illustrate the application of two proposed procedures.

• 한국데이터정보과학회:학술대회논문집
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• 2001.10a
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• pp.76-78
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• 2001

Variable selection in oriental medical research is considered. Decision tree analysis algorithms such as CHAID, CART, C4.5 and QUEST have been successfully applied to a medical research. Paralysis disease is a highly dangerous and murderous disease which accompanied with a great deal of severe physical handicap. In this paper, we explore the use of CHAID algorithm for selecting variables for evidence-diagnosis of paralysis, disease. Empirical results comparing our proposed method to the method using Wilks $\lambda$ given.