• Proceedings of the Computational Structural Engineering Institute Conference
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• 1995.04a
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• pp.62-69
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• 1995

The differential equations governing both the free vibrations and buckling loads of the beam-columns with constant volumes are derived and solved numerically. The axial load effects are included in the differential equations. The Runge-Kutta method and Regula-Falsi method are used to compute the eigenvalues corresponding to the natural frequencies. and buckling loads. In numerical examples, the simple end constraint is considered.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.4B no.2
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• pp.73-79
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• 2004

For the global microwave market, high RF power or deluxe model is applying for inverter gradually. In this paper, 120[V]/1200[W] high power inverter is proposed and verified by an optimized design of PFM type. Especially the steady power output control was fulfilling at ＋/－ 10[％] input voltage variation.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.298-300
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• 2001

This paper presents a forecasting method for production volume of each model manufactured goods by using Back-Propagation technique of Neural Networks. As the learning constant and the momentum constant are respectively 0.65 and 0.94, the learning number is the least, and the forecating accuracy is the highest. When the learning process is more than 1,000 times, the accurate forecating was possible regardless of kind of product.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.46.2-46.2
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• 2015

Modern methods in determining the value of the Hubble constant are divided into two main ways: the classical distance ladder method and the inverse distance ladder method. The classical distance ladder method is based on Cepheid calibrated Type Ia supernovae (SNe Ia), which are known as powerful distance indicator. The inverse distance ladder method uses cosmic microwave background radiation, which emitted from the high-z universe, and the cosmological model. Recent estimations of the Hubble constant based on these two methods show a $2{\sim}3{\sigma}$ difference, which called the "Hubble tension". It is currently an issue in the modern cosmology. We have been working on the luminosity calibration of SNe Ia based on the Tip of the Red Giant Branch (TRGB), which is a precise population I distance indicator. We present the TRGB distance estimates of 5 SNe Ia host galaxies with the archival Hubble Space Telescope image data. We derive the mean absolute maximum magnitude of 5 SNe Ia and the value of the Hubble constant. Cosmological implications of our estimate will be discussed.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.1964-1967
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• 1997

The rotor time constant variation has a large effect on the vector controlled system of induction motor. In this paper, the algorithm which compensate the misalignment of the rotor flux vector as an error caused by incorrect rotor time constant are presented. The simulations show that the proposed algorithm suitably compensates the rotor time constant.

• Journal of the Korean Society of Industry Convergence
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• v.6 no.3
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• pp.193-200
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• 2003

In the production of internal combustion engines, there has been a move towards the development of high performance engines with improved fuel efficiency, lighter weight and smaller sizes. These trends help to answer problems in engines related to thermal load and abnormal combustion. In order to investigate these problems, a thin film-type probe for instantaneously measuring temperatures has been suggested. A method for manufacturing such a probe was established in this study. The instantaneous surface temperature of a constant volume combustion chamber was measured by this probe and the heat flux was obtained through Fourier analysis. In order to thoroughly understand the characteristics of combustion, the authors measured the wall temperature of the combustion chamber and computed heat flux through a cylinder wall while varying the protrusion height of the probe. For achieving the above goals, a instantaneous temperature probe was developed, thereby making possible the analysis of the instantaneous temperature of wall surface and the detection of unsteady heat flux in the constant volume combustion chamber.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.716-720
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• 2006

In order to examine the effect of constant excitation on nonlinear interactions in vibrating modes of circular plates, we added a constant term to a harmonic excitation. A two-degree-of freedom system is derived by using the Galerkin's procedure. The system is shown to have quadratic and cubic nonlinearities subjected to a harmonic excitation.

• Journal of computational fluids engineering
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• v.17 no.4
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• pp.87-92
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• 2012

A numerical study of transient conjugate heat transfer on micro heater in a micro-channel substrate under pulsed heating was conducted. It was found that the time constant is not affected by the pulse heating magnitude at same operating condition. Furthermore, the time constant increases with low substrate thermal diffusivity, low Reynolds number, and large channel diameter. Since the time constant is a dominant parameter to characterize transient heat transfer, it should be considered for transient convective heat transfer coefficient.

• Journal of Powder Materials
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• v.21 no.2
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• pp.114-118
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• 2014

In this study, an aluminum oxide layer for sealing treatment of nano-diamond powder was synthesized by anodizing under constant current. The produced pore size and oxide thickness were investigated using scanning electron microscopy. The pore size increased as the treatment time increased, current density increased, sulfuric acid concentration decreased, which is different from the results under constant voltage, due to a dissolution of the oxide layers. The oxide layer thickness by the anodizing increased as temperature, time, and current density increased. The results of this study can be applied to optimize the sealing treatment process of nano-diamond particles of 4-10 nm to enhance the resistances of corrosion and wear of the matrix.

• Bulletin of the Korean Mathematical Society
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• v.54 no.2
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• pp.507-519
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• 2017

We present an upper bound on the Cheeger constant of a distance-regular graph. Recently, the authors found an upper bound on the Cheeger constant of distance-regular graph under a certain restriction in their previous work. Our new bound in the current paper is much better than the previous bound, and it is a general bound with no restriction. We point out that our bound is explicitly computable by using the valencies and the intersection matrix of a distance-regular graph. As a major tool, we use the discrete Green's function, which is defined as the inverse of ${\beta}$-Laplacian for some positive real number ${\beta}$. We present some examples of distance-regular graphs, where we compute our upper bound on their Cheeger constants.