• 천문학논총
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• 제30권2호
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• pp.367-369
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• 2015

The FastSound project is a galaxy redshift survey using Subaru/FMOS to detect $H{\alpha}$ emitting galaxies at z ~ 1:3, for the purpose of probing the origin of the accelerated expansion of the universe. The survey has detected ~4,000 galaxy redshifts in a total area of $30deg^2$, and detected the redshift space distortion at this redshift range for the first time. The redshift space distortion (RSD) signal will be used to derive a measurement of the growth rate of large scale structure, which will provide a test for modified gravity as a possible origin of accelerated cosmic explansion. Here we present an overview and the current status of the project.

• 천문학회보
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• 제37권2호
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• pp.72.2-72.2
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• 2012

We analyzed the properties of shock waves in galaxy clusters, by using the data of simulations for the large-scale structure of the universe with the spatial resolution of up to 25 kpc/h. In a substantial fraction of clusters, we found that strong shocks with Mach number of several or larger exist in outskirts within the virial radius. They are produced by the accretion of warm gas flowing from filaments to clusters, and generate large cosmic-ray fluxes. The cosmic rays advect into cluster cores, but may temporally induce the population inversion, that is, larger population at larger radius, suggested by recent radio and ${\gamma}$-ray observations.

• 산업경영시스템학회지
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• 제18권36호
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• pp.133-141
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• 1995

One of the problems brought up in the effective execution of genetic algorithms is that if they come under any influences according as the population size is large or small. In the case of small population size the opportunities of premature convergence are increased when the greatly powerful or no good individual is generated during search of the solution space. And searching the solution space in the case of large population size, the difficulties under the execution cause to searching all for one by one individual in every generation applied is limited, this gives the many interruptions to the convergence of final solution. Now this paper gives a suggestion to set up the adaptive population size which could compute the more correct solution and simplify the development of computation performance.

• 한국환경과학회지
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• 제4권1호
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• pp.71-80
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• 1995

생화학적 산소요구량(BOD) 및 용존 산소(DO)을 이용하여 여러구간이 있는 강에 대한 이산 상태공간모델은 설정하였다. 상호작용 예측방법을 이용하여, 상태변수에 시간지연이 존재하는 대규모 시스템에 적용가능한 계층적 최적화 방법을 기술하였다. 정상상태 오차를 해석적으로 구하고, 상수 목표티 추적문제에 있어서 정상상태 오차가 발생하지 않을 필요충분조겆을 규명하였다. 수질오염 모델에 대한 컴퓨터 모사를 통하여 기술한 알고리듬의 타당성을 확인하였다.

• 대한기계학회논문집
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• 제16권5호
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• pp.1011-1018
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• 1992

A series of experiment has been performed on the spray characteristics in a cylindrical confined space with the injection pressure taken as a parameter. By using a single-hole patternator and the Malvern particle sizer, the spray mass flux, drop size and volume concentration distributions along the radial and axial directions were obtained ; the line-of- sight data by Malvern particle sizer have been converted to the ring-of-sight data by using the tomographical transformation techniqe. The experimental results show that, due to the restriction on the ambient gas entrainment by the wall boundary, the effective spray angle is increasing. The spray drops were measured to be smaller in the confined space because of a large number of floating small drops by recirculation of the gas phase and the breakup of large drops by the wall collision. Also the details on the flow behavior of the confined spray are discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(I)
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• pp.185-189
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• 1987

An analysis and design of large-scale linear multivariable systems often requires to be block triangularized form for good sensitivity of the systems when their poles and zeros are varied. But the decomposition algorithms presented up to now need a procedure of permutation, rescaling and a solution of nonlinear algebraic equations, which are usually burden. To avoid these problem, in this paper we develop a newly alternative block triangular decomposition algorithm which used the generalized matrix sign function on the Z-plane. Also, the decomposition algorithm demonstrated using the fifth order linear model of a distillation tower system.

• 대한수학회보
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• 제59권4호
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• pp.879-895
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• 2022

This paper establishes the Baum-Katz type theorem and the Marcinkiewicz-Zymund type strong law of large numbers for sequences of coordinatewise negatively associated and identically distributed random vectors {X, X_n, n ≥ 1} taking values in a Hilbert space H with general normalizing constants $b_n=n^{\alpha}{\tilde{L}}(n^{\alpha})$, where ${\tilde{L}}({\cdot})$ is the de Bruijn conjugate of a slowly varying function L(·). The main result extends and unifies many results in the literature. The sharpness of the result is illustrated by two examples.

• 천문학회보
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• 제45권1호
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• pp.58.2-58.2
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• 2020

We present a method for determining the abundance ratio of nitrogen to iron ([N/Fe]) from low-resolution (R~2000) stellar spectra from large spectroscopic surveys such as Sloan Digital Sky Survey (SDSS) and Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). The basic idea of the method is to match a grid of synthetic spectra with an observed spectrum in the CN band region around 3883 Å. To calibrate our estimate of [N/Fe], we make use of the giants observed in Apache Point Observatory Galaxy Evolution Experiment (APOGEE), which are also observed in the SDSS. This method will be applied to the Galactic halo stars to determine [N/Fe], and the measured nitrogen abundance ratios will be used to investigate the C-N anti-correlation, which is observed in globular clusters, to trace their origin with their kinematic properties.

• 천문학회보
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• 제40권1호
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• pp.56.2-56.2
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• 2015

The KMTNet Supernovae Project utilizes the large $2^{\circ}{\times}2^{\circ}$ field of view of the three KMTNet telescopes to search and monitor supernovae, especially early ones, and other optical transients. A key component of the project is to build a data pipeline with a descent latency and an early alerting system that can handle the large volume of the data in an efficient and a prompt way, while minimizing false alarms, which casts a significant challenge to the software development. Here we present the current status of their development. The pipeline utilizes a difference image analysis technique to discover candidate transient sources after making correction of image distortion. In the early phase of the program, final selection of transient sources from candidates will mainly rely on multi-filter, multi-epoch and multi-site screening as well as human inspection, and an interactive web-based system is being developed for this purpose. Eventually, machine learning algorithms, based on the training set collected in the early phase, will be used to select true transient sources from candidates.

• 호남수학학술지
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• 제37권4호
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• pp.441-455
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• 2015

In this paper, we perform a comparison study of explicit and implicit numerical methods for the equity-linked securities (ELS). The option prices of the two-asset ELS are typically computed using an implicit finite diffrence method because an explicit finite diffrence scheme has a restriction for time steps. Nowadays, the three-asset ELS is getting popularity in the real world financial market. In practical applications of the finite diffrence methods in computational finance, we typically use relatively large space steps and small time steps. Therefore, we can use an accurate and effient explicit finite diffrence method because the implementation is simple and the computation is fast. The computational results demonstrate that if we use a large space step, then the explicit scheme is better than the implicit one. On the other hand, if the space step size is small, then the implicit scheme is more effient than the explicit one.