• 한국군사과학기술학회지
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• 제27권2호
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• pp.238-246
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• 2024

Modern military operations rely heavily on broadband communication and data transmission. Recently, the rising use of intelligent unmanned technology necessitates more frequencies. Free-space optical(FSO) communication can offer high-data-rate communications with high security and no need for licensing. Therefore, the FSO communication holds significant interest and potential in the defense industry. In this paper, we present design of a FSO communication terminal taking Korean domestic weather conditions into account. The domestic atmospheric attenuation is analyzed using several models and two-year meteorological information for a city in Korea, and this analysis is utilized to design the FSO communication terminal. The design results were verified using an FSO communication test bed, and we achieved an Ethernet bandwidth of approximately 1.86 Gbps at a distance of 1.3 km with the optical amplifier output power of the test bed set to about 20 dBm.

• 우주기술과 응용
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• 제3권4호
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• pp.322-332
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• 2023

Satellite attitude-control actuators are equipped with a reaction wheel for three-axis attitude control. The reaction wheel rotates a motor inside the actuator to generate torque in the vector direction. When using the reaction wheel, there are restrictions on the torque values generated as the motor rotates. The torque value of the reaction wheels mounted on small satellites is approximately 10 mNm, and high values are not used. Therefore, three-axis attitude control of a small satellite is possible using a reaction wheel, but this method is not suitable for missions that require rapid attitude control at a specific time. As a technology to overcome the small torque value of the reaction wheel, the control moment gyro (CMG) is currently in wide use as a rapid attitude-control actuator in space satellites. The CMG has an internal gimbal mounted at a right angle to the rotation motor and generates a large torque value. In general, when the gimbal operates, a torque value approximately 100 times greater is generated, making it suitable for rapid posture maneuvering. Currently, we are developing a technology for mounting a controlled moment gyro on a small satellite, and here we share the development status of an 800 mNm CMG.

• 로봇학회논문지
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• 제4권2호
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• pp.147-154
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• 2009

Visions of ubiquitous robotics and ambient intelligence involve distributing information, knowledge, computation over a wide range of servers and data storage devices located all over the world, and integrating tiny microprocessors, actuators, and sensors into everyday objects as well in order to make them smart. In this paper, we introduce our ongoing research effort aimed at realizing ubiquitous robots in an information structured space. For this, a ubiquitous space and ambient intelligent systems for a librarian robot are introduced and the RFID technology based approach for these systems is described.

• 충청수학회지
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• 제17권1호
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• pp.1-17
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• 2004

In this paper, the concept of semi-compatibility in Menger space is introduced and it is used to prove results on the existence of a unique common fixed point of four self-maps. These results are a very wide improvement of Mishra [8], Dedeic and Sarapa [3, 4], Cain and Kasril [1], and Sehgal and Bharucha Reid [10].

• East Asian mathematical journal
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• 제28권5호
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• pp.533-541
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• 2012

A common fixed point result of Gregus type for subcompatible mappings defined on a complete linear metric space is obtained. The considered underlying space is generalized from Banach space to complete linear metric spaces, which include Banach space and complete metrizable locally convex spaces. Invariant approximation results have also been determined as its application.

• 대한수학회논문집
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• 제10권3호
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• pp.699-705
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• 1995

We first generalize the Volodin space which Volodin constructed in order to define a new algebraic K-theory. We investigate the topological (homotopy) properties of the general Volodin space. We also provide a theorem which seems to be useful in pure homotopy theory. We prove that $V(*_\alpha G_\alpha, {G_\alpha})$ is simply connected.

• 대한수학회지
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• 제38권1호
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• pp.135-146
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• 2001

Let M(sup)n be a space-ike submanifold in a de Sitter space M(sub)p(sup)n+p (c) with constant scalar curvature. We firstly extend Cheng-Yau's Technique to higher codimensional cases. Then we study the rigidity problem for M(sup)n with parallel normalized mean curvature vector field.

• East Asian mathematical journal
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• 제21권1호
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• pp.65-76
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• 2005

In this paper the concept of semi-compatibility has been introduced in Menger space and it has been applied to prove results on existence of unique common fixed point of four self maps satisfying an implicit relation. It results in a generalization of Banach contraction principle established by Sehgal and Bharucha-Reid in [8] All the result presented in this paper are new.

• 천문학회보
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• 제26권2호
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• pp.56-56
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• 2001

• Journal of applied mathematics & informatics
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• 제19권1_2호
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• pp.297-310
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• 2005

The concept of the Moore-Penrose inverse in an indefinite inner product space is introduced. Extensions of some of the formulae in the Euclidean space to an indefinite inner product space are studied. In particular range-hermitianness is completely characterized. Equivalence of a weighted generalized inverse and the Moore-Penrose inverse is proved. Finally, methods of computing the Moore-Penrose inverse are presented.