• Korean Journal of Mathematics
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• v.31 no.2
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• pp.123-131
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• 2023

In this paper, we prove existence of best proximity points for 2-convex contraction, 2-sided contraction, and M-weakly cyclic 2-convex contraction mappings in the setting of complete strongly regular generalized modular metric spaces that generalize many results in the literature.

• Journal of the Korean Mathematical Society
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• v.61 no.3
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• pp.515-545
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• 2024

Consider a Noetherian domain R₀ with quotient field K₀. Let K be a finitely generated regular transcendental field extension of K₀. We construct a Noetherian domain R with Quot(R) = K that contains R₀ and embed Spec(R₀) into Spec(R). Then, we prove that key properties of abelian varieties and smooth geometrically integral projective curves over K are preserved under reduction modulo p for "almost all" p ∈ Spec(R₀).

• Journal of the Korean housing association
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• v.21 no.1
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• pp.53-65
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• 2010

Apartment buildings represent the most typical patterns of housing in Korea. The present plans are very different from the previous ones when they appeared for the first time. Although apartment unit plans has changed drastically, they can be classified into several categories. Apartment unit plans reflects the demands of living activities and space dimensions of unit plans have the characteristics of diachronic continuity and carry the values of living culture. Thus this study aims to provide the statistical dimensional data of each room that can be actually used for the design of unit plans by sub-grouping typical unit plans. The statistical data of this study showed that apartment unit plans are shifting from 2bay/3room type to 3bay/3room type in 1990s. It is very peculiar that the typical unit plan of $60\;m^2$ area becomes to resemble that of $85\;m^2$ area. The space arrangement of typical unit plans of both $60\;m^2$ and $85\;m^2$ area is almost identical while only their space dimensions differ slightly. As the mean/mode/median values of space dimensions in a typical unit plan are converging into a range of narrow margin, space dimensions of typical unit plan are contended to be strictly regular. The statistical numeric data of various space dimensions provided in this paper can be applied practically to the design of apartment unit plans for low income class people who are disprivileged in the society.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.265-268
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• 2004

In this paper. we propose an adaptive step-size algorithm for the adaptive interference canceller (AIC) in the space-time trellis coded DS-CDMA system. In the AIC, the performance of the blind LMS algorithms that updates the tap-weight vector of the AIC is heavily dependent on the choice of step-size. To improve the performance of the fixed step-size AIC (FS-AIC), the regular adaptive step-size algorithm is extended in complex domain and applied to the joint AIC and ML decoder scheme. Simulation results show that the joint adaptive step-size AIC (AS-AIC) and ML decoder scheme using the proposed algorithm has boner performance than not only the conventional ML decoder but also the joint FS-AIC and ML decoder scheme without much increase of the decoding delay and complexity.

• Communications of the Korean Mathematical Society
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• v.29 no.2
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• pp.227-237
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• 2014

For an $m{\times}n$ nonnegative integral matrix A, a generalized inverse of A is an $n{\times}m$ nonnegative integral matrix G satisfying AGA = A. In this paper, we characterize nonnegative integral matrices having generalized inverses using the structure of nonnegative integral idempotent matrices. We also define a space decomposition of a nonnegative integral matrix, and prove that a nonnegative integral matrix has a generalized inverse if and only if it has a space decomposition. Using this decomposition, we characterize nonnegative integral matrices having reflexive generalized inverses. And we obtain conditions to have various types of generalized inverses.

• Journal of Astronomy and Space Sciences
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• v.5 no.1
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• pp.53-56
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• 1988

UBV photometric monitoring of Eps Aurigae has been made at Yonsei University Observatory since the 1982-1984 eclipse. Among observatios made in four seasons(1984-5, 1985-6, 1986-7, 1987-8) after the 1982-84 eclips ended the observations of the latest season are presented. Standardized UBV light curves of Eps Aur exhibit a light variation in a semi-regular fashion with the amplitudes of 0.12, 0.19, and 0.29 for V, B, and U, respectively. Duratiohs of this light variation may show a color dependency with the mean value of about 78 days whose minimum light on near JD2447118.

• Journal of Astronomy and Space Sciences
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• v.32 no.2
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• pp.137-140
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• 2015

The results of the study of ionospheric variations in the summer months of 1998-2002 at an ionospheric station of vertical sounding "Petropavlovsk-Kamchatsky" are presented. Anomalous variations of virtual sporadic-E height (h'Es), Es blanketing frequency (fbEs), and the critical frequency of the ionospheric F2 layer (foF2) (which can be attributed to the possible earthquake precursors) are selected. The high efficiency of the selection of ionospheric earthquake precursors based on the several parameters of Es and F2 layers is shown. The empirical dependence, which reflects the connection between the lead-time of the earthquake moment, the distance to the epicenter from the observation point, and the magnitude of the earthquake are obtained. This empirical dependence is consistent with the results of the detection of earthquake precursors by measuring the physical parameters of the Earth's crust in the same region.

• Journal of the Korean Mathematical Society
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• v.53 no.4
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• pp.725-735
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• 2016

A pair of bodies rolling on each other is an interesting example of nonholonomic systems in control theory. There is a geometric condition equivalent to the rolling constraint which enables us to generalize the rolling motions for any two-dimensional Riemannian manifolds. This system has a five-dimensional phase space. In order to study the controllability of the rolling surfaces, we lift the system to a six-dimensional space and show that the lifted system is controllable unless the two surfaces have isometric universal covering spaces. In the non-controllable case there are some three-dimensional orbits each of which corresponds to an isometry of the universal covering spaces.

• Journal of Astronomy and Space Sciences
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• v.26 no.4
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• pp.651-658
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• 2009

Nonlinear sliding surface design in variable structure systems for spacecraft attitude control problems is studied. A robustness analysis is performed for regular form of system, and calculation of actuator bandwidth is presented by reviewing sliding surface dynamics. To achieve non-singular attitude description and minimal parameterization, spacecraft attitude control problems are considered based on modified Rodrigues parameters (MRP). It is shown that the derived controller ensures the sliding motion in pre-determined region irrespective of unmodeled effects and disturbances.

• Communications of the Korean Mathematical Society
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• v.11 no.3
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• pp.725-742
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• 1996

In this paper we give some sharp expressions of the weakly convergent sequence coefficient WCS(X) of a Banach space X. They are used to prove fixed point theorems for involution mappings T from a weakly compact convex subset C of a Banach space X with WCS(X) > 1 into itself which $T^2$ are both of asymptotically nonexpansive type and weakly asymptotically regular on C. We also show that if X satisfies the semi-Opial property, then every nonexpansive mapping $T : C \to C$ has a fixed point. Further, some questions for asymtotically nonexpansive mappings are raised.