• Journal of applied mathematics & informatics
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• v.4 no.1
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• pp.83-108
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• 1997

Chebysheff-Halley methods are probably the best known cubically convergent iterative procedures for solving nonlinear equa-tions. These methods however require an evaluation of the second Frechet-derivative at each step which means a number of function eval-uations proportional to the cube of the dimension of the space. To re-duce the computational cost we replace the second Frechet derivative with a fixed bounded bilinear operator. Using the majorant method and Newton-Kantorovich type hypotheses we provide sufficient condi-tions for the convergence of our method to a locally unique solution of a nonlinear equation in Banach space. Our method is shown to be faster than Newton's method under the same computational cost. Finally we apply our results to solve nonlinear integral equations appearing in radiative transfer in connection with the problem of determination of the angular distribution of the radiant-flux emerging from a plane radiation field.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.574-578
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• 2003

The objective of this paper is to decide optimal location of pin-hole to minimize stress concenstation around hole in rotating disc. The focus of this investigation is to evaluate the effect of pin-hole for stress distribution around hole using optimum design technic and finite element analysis. Design variables are radial and angular location of pin-hole from center of hole, objective function is maximum stress around hole in rotating disc. We use first order method of optimization technic.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.4
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• pp.645-653
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• 2001

It is well known that natural frequencies increase when a cantilever beam rotates about the axis perpendicular to its longitudinal axis. Such phenomena that are caused by centrifugal inertia forces are often referred to as the stiffening effects. Occasionally it is necessary to control the variation of a natural frequency or the maximum stress of a rotating beam. By changing the thickness of the rotating beam, the modal or the stress characteristics can be changed. The thickness of the rotating beam is assumed to be a cubic spline function in the present work. An optimization method is employed to find the optimal thickness shape of the rotating beam. This method can be utilized for the design of rotating structures such as turbine blades and aircraft rotary wings.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.494-499
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• 2003

This paper concerns the static, dynamic and thermal characteristics analysis of a high-speed spindle system for horizontal machining centers with 45mm x50,000rpm. The spindle system is designed based on the angular contact ceramic ball bearings, built-in motor, oil-air lubrication method and oil jacket cooling method. The structural and thermal analysis models of spindle system are constructed by the finite element method. The static and dynamic characteristics are estimated based on the static deformation, modal parameter, mode shape and frequency response function, and the thermal characteristics are estimated based on the temperature rise, temperature distribution and thermal deformation. The analysis results illustrate that the designed spindle system has excellent structural and thermal stabilities

• The Journal of Korean Institute of Communications and Information Sciences
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• v.8 no.1
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• pp.17-22
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• 1983

Scattering of obliquely incident plane electromagnetic waves by an isotropic plasma coumn which is moving uniformly in the perpendicular direction to its axis is treated analytically on the basis of Lorentz transform and boundary conditions. The scattered field, the total scattering cross-section, the rader cross-section, and the angular distribution of the scattered power for the incident plane waves polarized arbitrarily are derived to find the function of the moving velocity of the plasma column and of the angle of the incident plane waves and to find the scattered field of the H-waves more distinguishable than the E-waves.

• Journal of Magnetics
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• v.10 no.4
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• pp.133-136
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• 2005

The NiMn/NiFe bilayer structure which was short time annealed in order to induce unidirectional anisotropy were studied as a function of annealing temperature. The maximum exchange bias field of NiMn/NiFe bilayer was presented at $250^{\circ}C$ after short time annealing process with no external field. The appearance of exchange bias was due to phase transformation of NiMn layer. In plane angular dependence of a resonance field distribution which measured by FMR was analysed as a combined effect of unidirectional anisotropy and uniaxial anisotropy. The resonance field and the line width from FMR measurement were also analysed with annealing temperature.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.6
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• pp.131-138
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• 2004

The objective of this paper is to decide optimal location of a pin-hole to minimize stress concentration around the hole in a rotating disc. The focus of this investigation is to evaluate the effect of pin-hole on stress distribution around the hole using optimum design technique and finite element analysis. Design variables are the radial and the angular location of pin-hole from center of the hole and objective function is the maximum stress around hole in a rotating disc. Using first order method of optimization technique, we found that the maximum equivalent stress around the hole with optimized pin-hole could be reduced by 15.1% compared to that without pin-hole.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.59.3-60
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• 2015

We investigate the clustering properties of Lyman-break galaxies (LBGs) at z ~ 4. Using the hierarchical galaxy formation model GALFORM, we predict the angular correlation function (ACF) of LBGs and compare this with the measured ACF from combined survey fields consisting of the Hubble eXtreme Deep Field (XDF) and CANDELS. We find that the predicted ACF is in a good agreement with the measured ACFs. However, when we divide the model LBGs into bright and faint subset, the predicted ACFs are less consistent with observations. We quantify the dependence of clustering on luminosity and show that the fraction of satellite LBGs is important for determining the amplitude of ACF at small scales. We find that central LBGs predominantly reside in ${\sim}10^{11}h^{-1}M_{solar}$ haloes and satellites reside in haloes of mass ${\sim}10^{12}-10^{13}h^{-1}M_{solar}$. The model predicts fewer bright satellite LBGs than is inferred from the observation. LBGs in the tails of the redshift distribution contribute significant additional clustering signal, especially on small scales. This spurious clustering may affect the interpretation of the halo occupation distribution, including the minimum halo mass and abundance of satellite LBGs.

• Journal of Astronomy and Space Sciences
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• v.19 no.1
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• pp.1-6
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• 2002

Recently, one interesting possibility is proposed that a magnetar can be a progenitor of short and hard gamma-ray bursts (GRBs). If this is true, one may expect that the short and hard GRBs, at least some of GRBs in this class, are distributed in the Euclidean space and that the angular position of these GRBs is correlated with galaxy clusters. Even though it is reported that the correlation is statistically marginal, the observed value of < $V/V_{max}$ > deviates from the Euclidean value. The latter fact is often used as evidence against a local extragalactic origin for short GRB class. We demonstrate that GRB sample of which the value of < $V/V_{max}$ > deviates from the Euclidean value can be spatially confined within the low value of z. We select very short bursts (TgO < 0.3 sec) from the BATSE 4B catalog. The value of < $V/V_{max}$ > of the short bursts is 0.4459. Considering a conic-beam and a cylindrical beam for the luminosity function, we deduce the corresponding spatial distribution of the GRB sources. We also calculate the fraction of bursts whose redshifts are larger than a certain redshift z', i.e. f>z'. We find that GRBs may be distributed near to us, despite the non-Euclidean value of < $V/V_{max}$ >. A broad and uniform beam pattern seems compatible with the magnetar model in that the magnetar model requires a small $z_{max}$.

• Korean Journal of Remote Sensing
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• v.30 no.3
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• pp.367-373
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• 2014

Albedo is one of the critical parameters for understanding global climate change and energy/water balance. In this study, we used red and NIR reflectance from Satellite Pour I'Obervation de la Terre (SPOT)/Vegetation (VGT) S1 product. The product is preprocessed for users that they are atmospherically corrected using Simple Method Atmospheric Correction (SMAC) by Vision on Technology (VITO) for calculating broadband albedo. Roujean's Bi-directional Reflectance Distribution Function (BRDF) model is a semi-empirical method used for BRDF angular integration and inversion. Each kernel of Roujean's model was multi integrated by angle components (i.e., viewing zenith, solar zenith, and relative azimuth angle). Black-sky hemispherical function is integrated by observational angle; whereas, white-sky hemispherical efficient is integrated by incident angle. Estimated spectral albedo of red ($0.61{\sim}0.68{\mu}m$, B2) and near infrared ($0.79{\sim}0.89{\mu}m$, B3) have a good agreement with MODIS albedo products.