• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.6
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• pp.1351-1362
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• 1995

A method to estimate the torsional critical speed for practical rotors has been developed in this study. First, the rotor with a uniform shaft segment is modeled for undamped torsional motion analysis, while satisfying all the boundary conditions. This eventually generates governing equations for the torsional critical speeds of the system. The set of governing equations has the form of a sparse and banded matrix. The elements of banded matrix can be arranged in partitions, which correspond to the specific boundary of the rotor. This permits an automatic generation of the system matrix using a computer. In order to calculate the determinant generated by the simultaneous equations, which leads to the torsional critical speed, a recurring numerical algorithm for a (3*4) sub-matrix has been used. This numerical algorithm practically examines successive (3*4) sub-matrix, one at a time, instead of treating a huge matrix. The output of the program provides the mode shapes with continuous curves. The method has been implemented to three rotors given as examples : a simple rotor, Prohl's rotor, and Macmillan rotor.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.56-58
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• 1996

The Preisach model needs a density function to simulate the hysteresis phenomena. To obtain this function, many experimental data obtained from the first order transition curves are required to get accurate density function. However, it is difficult to perform this procedure, especially for the hard magnetic materials. In this paper, we compare the density function obtained from the experimental data with that computed from the mathematical function like the Gaussian function, and propose a simple technique to get mathematical equation of the density function or Everett function which is obtained from the initial curve, major and minor loop.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.60.1-60.1
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• 2015

We present the current operation status of StarDB web services by showing its user access statistics. The StarDB web services started its operation in late November, allowing world-wide users to access results of new variability analysis for Northern Sky Variability Survey light curves. New analysis results of various time-series data have been added to the StarDB services. Importantly, our services have supported a simple cone search, which is an internationally well-defined catalog search interface in the international Virtual Observatory systems. We have collected user access statistics such as how users find our analysis data since its operation in later November. We expect our analysis of the StarDB operation to help Korean community members who plan and operate their own web services preparing for a future era of big survey data.

• Journal of the Korean Data and Information Science Society
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• v.28 no.5
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• pp.1179-1189
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• 2017

In this study, we propose an alternative method for discriminant analysis using a multivariate empirical distribution function to express multivariate data as a simple one-dimensional statistic. This method turns to be the estimation process of the optimal threshold based on classification accuracy measures and an empirical distribution function of data composed of classes. This can also be visually represented on a two-dimensional plane and discussed with some measures in ROC curves, surfaces, and manifolds. In order to explore the usefulness of this method for discriminant analysis in the study, we conducted comparisons between the proposed method and the existing methods through simulations and illustrative examples. It is found that the proposed method may have better performances for some cases.

• Proceedings of the Korean Society for Bioinformatics Conference
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• 2005.09a
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• pp.221-227
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• 2005

THEMATICS is a simple computational method for predicting functional sites in proteins. The method computes the theoretical titration curves of the ionizable residues of a protein using its 3D structure, determines the residues with perturbed, non-Henderson-Hasselbalch titration behavior, and identifies clusters of these perturbed residues in physical proximity. We have shown previously that this method is highly successful in predicting catalytic sites in enzymes. In the present study, we apply the method to non-catalytic ligand-binding proteins. It is shown that THEMATICS can predict non-catalytic binding sites. The success rate is better than 80 % for a set of 30 non-catalytic, ligand-binding proteins. The application of the method to Glutamine-binding protein from E. coli is discussed in detail.

• Natural Product Sciences
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• v.19 no.2
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• pp.145-149
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• 2013

A simple reversed phase HPLC method was established for quantitative determination of liquiritigenin (1), genistein (2), isoliquiritigenin (3), and 7-hydroxyflavanone (4) from stems of Spatholobus suberectus Dunn (Leguminosae) using a binary gradient of $H_2O$ and MeOH as a mobile phase with UV detection at 280 nm. All calibration curves showed good linear regression ($r^2$ > 0.998) within test ranges. The detection limits of the four compounds were $0.43{\sim}1.63{\mu}g/mL$. The contents of four flavonoids (1 - 4) from the stem of S. suberectus were 6.54 mg/g, 1.66 mg/g, 6.65 mg/g, and 1.93 mg/g, respectively.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.6
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• pp.59-66
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• 2001

Fatigue strength of the welding structure is governed by the residual stress at the weldment toe and static tensile overloads were known as relieving the residual stresses. In this study, static tensile overloads were applied to the welding structures which caused the relief of residual stresses. The amount of residual stress relief was found as proportional to the change of fatigue limit at the given conditions. Based on the fact of the proportionality between the change of fatigue limit and that of residual stress, simple measurement technique is proposed. Modified stress-life curves base on proposed technique gave good agreement with test results.

• Agricultural and Biosystems Engineering
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• v.1 no.1
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• pp.16-21
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• 2000

Measurement of spray deposit is necessary for evaluation of a chemical application technology. However it is not easy and time consuming. A simple method for measuring the deposition amount of spray using a tracer and a spectrophotometer was developed. Various materials were tested to determine an adequate tracer. Food dye was selected as a tracer, because it was cheep and easily treatable. Using NIRS(Near Infrared Reflection Spectrophotometer), a regression curves between maximum absorbance of a solution and concentration of the tracer were obtained. Yellow food dye solution showed a peak of spectrum at 452 nm, and absorbance of peak showed a tendency to increase as concentration increased. Green or pink food dye were tested and judged to be good tracers. However, tracer concentration should not exceed certain limits in order to measure maximum absorption. Using spraying liquid with known tracer concentration and known amount of washing liquid, spray deposit amount on real targets on leaves could be estimated at less than 13% error level.

• Journal of Power System Engineering
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• v.15 no.3
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• pp.18-24
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• 2011

In this study, the reflection of the L(0,2), axially symmetric guided elastic wave from defects in pipes above ground is examined using finite element method. Phase and group velocity dispersion curves for the pipe were presented for the selection of the excitation mode. Some simple signal processing was applied to determine the amplitude of each of the reflected waves and to calculate the reflection coefficient. The results show the reflection coefficient of this mode is very close to a linear function of the circumferential extent of the defect. The motivation for the work was the development of a technique for inspecting chemical plant pipelines, but the study addresses the nature of the reflection function and its general applicability.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.1
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• pp.33-37
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• 2009

In this paper, a printed small Ultra-Wideband (UWB) antenna with directive radiation characteristics based on combination of electric-magnetic radiators is presented. The combinations of the electric and magnetic type antennas result in the directive radiation patterns for all observed UWB frequency band. Simple combination of dipole antenna and loop antenna is also presented to show that proper configuration of electric radiator and magnetic radiator can produces directive radiation characteristics. The target frequency is from 3.1 GHz to 10.6 GHz with size of $15\;mm{\times}31\;mm$. A proto-type of the combined antenna is simulated, fabricated and measured. Simulation and experimental results of input impedance and gain characteristics of the proposed antenna are presented. There are good agreements between the simulated and measured VSWR curves. Also, the results show the directive radiation characteristics with small antenna form factor over the target frequency range.