• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.321-325
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• 1986

A new control scheme for the state space model of the robot system using the theory of optimal multi-variable structure is presented in this paper. It is proposed to optimize multi-dimensional variable structure systems for obtaining the required stabilizing signal by minimizing a performance index with respect to the state vector in the sliding mode. It is concluded the proposed variable structure controller yields better system dynamic performance than that obtained by using the only linear optimal controller inthat responses for a step disturbance have a shorter setting time, no matter what overshoot values and rising time.

• Journal for History of Mathematics
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• v.22 no.3
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• pp.273-292
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• 2009

According to historical commentators such as Newton and Einstein, bodily behaviors are causally explained by the geometrical structure of space-time whose existence analogous to that of material substance. This essay challenges this conventional wisdom of interpreting space-time geometry within both Newtonian and Einsteinian physics. By tracing recent historical studies on the interpretation of space-time geometry, I defends that space-time structure is a by-product of a more fundamental fact, the laws of motion. From this perspective, I will argue that the causal properties of space-time cannot provide an adequate account of the theory-change from Newtoninan to Einsteinian physics.

• Communications of the Korean Mathematical Society
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• v.34 no.2
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• pp.633-635
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• 2019

In this note we show that Lorentzian Concircular Structure manifolds $(LCS)_n$ coincide with Generalized Robertson-Walker space-times.

• Journal for History of Mathematics
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• v.32 no.1
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• pp.17-25
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• 2019

This essay elucidates the way the geometries of space-time theories explain material bodies' motions. A conventional attempt to interpret the way that space-time geometry explains is to consider the geometrical structure of space-time as involving a causally efficient entity that directs material bodies to follow their trajectories corresponding to the laws of motion. Newtonian substantival space is interpreted as an entity that acts but is not acted on by the motions of material bodies. And Einstein's curved space-time is interpreted as an entity that causes the motions of bodies. This essay argues against this line of thought and provides an alternative understanding of the way space-time geometry explain the laws of motion. The workings of the way that Newton's flat and Einstein's curved space-time explains the law of motion is such that space-time geometry encodes the principle of inertia which specifies straight lines of moving bodies.

• Journal of architectural history
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• v.1 no.2 s.2
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• pp.172-182
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• 1992

The binary classification, Yin & Yang, can be shown in our culture. Yin & Yang thinking reveals the Up/Down (Principal/Subordinate) relation in space, and Before/After relation in time, and it shows the sequence of Contrast${\to}$Reconciliation & Unification${\to}$Contrast. For example, a follower is Yin against King, while Yang as a father against his son in our trational cognitive structure. With Left/Right, Front/Rear, and Upper/Lower, In/Out division is a basic body-space term to grasp the space position. In the traditional Korean house, when we go out from the deepest 'In', Anbang to Daechung, we may call Anbang 'In' and Daechung 'Out'. When from Daechung to Anmadang reversely, we call Daechung 'In' and Anmadang 'Out'. Namely, Daechung is both 'In' and 'Out'. This is a fallacy logic in view of western basic conception. 'The In/Out Structure, system of a series of inner spaces, is defined as a transformation of cognitive structure of Yin & Yang thinking to the Korean architectural space. The space structure is one of the important deep structure in Korean society.' The concept of the space structure, apperred in east Asia, can make humane space, for it is not a physical 'type' of typepology but related to cognitive structure of human thinking, The structure is applicable to space design in modern society, for the cognitive structure exists in living culture by transformation.

• Journal for History of Mathematics
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• v.28 no.4
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• pp.181-190
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• 2015

In spite of various attempts to characterize the ontological status of space-time, Newtonian substantivalism and Leibnizian relationism, what is really at issue in the controversy between the two parties is by no means clear. This essay argues that from the perspective of space-time symmetries, classical space-time can be unambiguously classified as substantival space-time and relational space-time. The symmetries of space-time theories distinguish the invariant geometric relationships between events. The essential difference between the two space-times stems from whether or not there exists the affine structure that distinguishes the inertial trajectories of a given body.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6C
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• pp.481-489
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• 2005

In this letter, we propose an efficient training sequence structure for adaptive linear multiuser detectors in space-time block coded multiuser systems, by exploiting a particular property of the minimum mean square error multiuser detectors used in these systems. The proposed structure wastes less overall system capacity than the straightforward training structure, without any corresponding loss of performance, as confirmed by the simulation results.

• Communications of the Korean Mathematical Society
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• v.11 no.3
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• pp.783-788
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• 1996

We study some causality characterizations in a space-time by considering chronological common future (or past) sets and indecomposable sets that are important roles in studying causal boundary structure of the space-time.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.4
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• pp.523-532
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• 2001

A simultaneous measurement of wall vorticity and near-wall streamwise velocity fluctuations has been performed using a V-type wall vorticity probe and an I-type velocity probe to investigate the relation between them. Long-time averaged space-time correlations show that the wall vorticity is highly correlated with a turbulence structure which is tilted from the wall in the streamwise direction and that there is a streamwise vortex pair near the wall. It is shown that a structure correlated with the streamwise wall vorticity is smaller than and prior to a structure correlated with the spanwise wall vorticity. Tilting angles are obtained from the phase shift between the wall vorticity and streamwise velocity fluctuations. The tilting angle of the structure correlated with the streamwise wall vorticity is larger than that of the structure correlated with the spanwise wall vorticity. The convection velocity of the near-wall streamwise velocity fluctuations obtained from the space-time correlation is in good agreement with previous results.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.3_4
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• pp.145-151
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• 2004

We present an efficient data structure to obtain the range minima in an away in constant time. Recently, suffix ways are extensively used to search DNA sequences fast in bioinformatics. In constructing suffix arrays, solving the range minima problem is necessary When we construct suffix arrays, we should solve the range minima problem not only in a time-efficient way but also in a space-efficient way. The reason is that DNA sequences consist of millions or billions of bases. Until now, the most efficient data structure to find the range minima in an way in constant time is based on the method that converts the range minima problem in an array into the LCA (Lowest Common Ancestor) problem in a Cartesian tree and then converts the LCA problem into the range minima problem in a specific array. This data structure occupies O( n) space and is constructed in O(n) time. However since this data structure includes intermediate data structures required to convert the range minima problem in an array into other problems, it requires large space (=13n) and much time. Our data structure is based on the method that directly solves the range minima problem. Thus, our data structure requires small space (=5n) and less time in practice. As a matter of course, our data structure requires O(n) time and space theoretically.