• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.06a
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• pp.517-521
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• 1998

DEA(data envelopment analysis) is a non-parametric technique for measuring and evaluating the relative efficiencies of a set of entities with common crisp inputs and outputs. In fact, in a real evaluation problem input and output data of entities often flucturate. These fluctuating data can be represented as linguistic variables characterized by fuzzy numbers. Based on a fundamental CCR model, a fuzzy DEA model is proposed to deal with fuzzy input and output data, Furthermore, a model that extends a fuzzy DEA to a more general case is also proposed with considering the relation between DEA and RA (regression analysis) . the crisp efficiency in CCR modelis extended to an L-R fuzzy number in fuzzy DEA problems to reflect some uncertainty in real evaluation problems.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.47.1-47.1
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• 2015

The formation mechanism of supermassive black holes (SMBHs) at the center of galaxies remains an open fundamental question. Black holes (BHs) are believed to grow by accretion of gas or by merging with other BHs. Motivated by the observation of luminous quasar around redshift z ~ 7 with SMBH mass up to 109 solar mass, we follow the growth of the early assembly of SMBHs that trace the hierarchical evolution of dark matter halos derived from large cosmological simulations. The initial masses of BH seeds in the first halos were set up according to the BH mass - halo mass relation. We assume that mergers of host galaxies cause loss of angular momentum of gas and trigger episodes of gas accretion onto BHs for available durations and at the end of each episode of accretion, BHs merge immediately. We trace the evolution of BH masses for various scenarios for central gas properties in halos. We estimate the BH to halo mass ratio and BH mass function at each redshift.

• Journal of The Korean Astronomical Society
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• v.47 no.4
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• pp.153-158
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• 2014

I show that the standard microlensing technique to measure the angular radius of a star using color/surface-brightness relations can be inverted, via late-time proper motion measurements, to calibrate these relations. The method is especially useful for very metal-rich stars because such stars are in short supply in the solar neighborhood where other methods are most effective, but very abundant in Galactic bulge microlensing fields. I provide a list of eight spectroscopically identified high-metallicity bulge stars with the requisite finite-source effects, seven of which will be suitable calibrators when the Giant Magellan Telescope comes on line. Many more such sources can be extracted from current and future microlensing surveys.

• Journal of applied mathematics & informatics
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• v.10 no.1_2
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• pp.51-62
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• 2002

The present paper gives a new construction of a quotient BCI(BCK)-algebra X/${\mu}$ by a fuzzy ideal ${\mu}$ in X and establishes the Fuzzy Homomorphism Fundamental Theorem. We show that if ${\mu}$ is a fuzzy ideal (closed fuzzy ideal) of X, then X/${\mu}$ is a commutative (resp. positive implicative, implicative) BCK(BCI)-algebra if and only if It is a fuzzy commutative (resp. positive implicative, implicative) ideal of X Moreover we prove that a fuzzy ideal of a BCI-algebra is closed if and only if it is a fuzzy subalgebra of X We show that if the period of every element in a BCI-algebra X is finite, then any fuzzy ideal of X is closed. Especiatly, in a well (resp. finite, associative, quasi-associative, simple) BCI-algebra, any fuzzy ideal must be closed.

• The Pure and Applied Mathematics
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• v.25 no.3
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• pp.203-218
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• 2018

An old result of Whitehead says that the set of derivations of a group with values in a crossed G-module has a natural monoid structure. In this paper we introduce derivation of crossed polymodule and actor crossed polymodules by using Lue's and Norrie's constructions. We prove that the set of derivations of a crossed polygroup has a semihypergroup structure with identity. Then, we consider the polygroup of invertible and reversible elements of it and we obtain actor crossed polymodule.

• International Journal of Quality Innovation
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• v.4 no.1
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• pp.54-76
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• 2003

The concept of quality is revisited to evidence its applicability beyond the product and economic transaction level, to cover every kind of human and social relation. A very important extension indeed in this globalization era, where an increasingly interconnected world badly needs rules and means to improve quality, both at economic and political level. To that aim, some commonplaces about quality need to be exposed to criticism and the close connection between ″value″ and ″quality″ concepts must be highlighted. Generalization of the quality related concepts could appear to be just a theoretical issue were it not for the fact that it opens the door to the extension of ″quality management″ concepts to every kind of organization: from the company to the state to the planet. ″Managing for quality″ appears to be a fundamental issue for all human-made systems.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.3
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• pp.83-93
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• 1990

The characteristics of servo systems are desired to be independent for any unpredicted operational condition. The relation between input current and output flowrate of the servovalve is dependent on the load pressure and the idea of compensation using the load pressure feedback is fundamental theory in this paper. With this idea, this paper researches the performance improvement of hydraulic position control system. Static characteristics of compensated system is analyzed by means of analog computer simulation, digital computer simulation and experiment for nonlinear model and linearized model, respectively.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.269-278
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• 1998

The Planning characteristics of the canals linking river basins and estuary reservoirs have been reviewed in relation to the trend widening the areas of water resources planning. It has been also tried to justify the characteristics of the link canals in the history of irrigation development. It was concluded that the link canals were resulted from the most recent technology as far as irrigation systems were concerned, why these were long- and large-scale multipurpose canals ； the hydraulic heads of the link canals could be controlled easily ； and which consisted of open channels, pipelines and control reservoirs. The types and general characteristics of the canals have been reviewed, and the fundamental concept and characteristics in the planning of the canals have been described.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.11
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• pp.927-932
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• 2001

When people write a character with a pen stably, proper compliance planning is necessary. In this paper, after investigating the property of character writing task, we propose a fundamental grasp model for character writing and also analyze compliance characteristics for effective character writing using multi-fingered hands. For this, the general stiffness relation of multi-fingered hand is firstly described. Next, we investigate the grasp configurations for grasping a pen and then, we analyze the conditions of the specified stiffness matrix in the operational space to successfully and more effectively achieve the given character writing task. Through the analysis, an effective grasp modeling for successful character writing is shown. And also, we conclude that the operational compliance characteristics should be properly planned for character writing, stably and precisely.

• Proceedings of the Acoustical Society of Korea Conference
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• 1992.06a
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• pp.3-8
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• 1992

The theory of subjective preference with temporal and spatial factors which include sound signals arriving at both ears is described. Then, auditory evoked potentials which may relate to a primitive subjective response namely subjective preference are discussed. According to such fundamental phenomena, a workable model of human auditory-brain system is proposed. For eample, important subjective attributes, such as loudness, coloration, threshold of preception of a reflection and echo distrubance as well as subjective preference in relation to the initial time delay gap between the direct sound and the first reflection, and the subsequent reverberation time are well described by the autocorrelation function of source signals. Speech clarity, subjective diffuseness as well as subjective preference are related to the magnitude of inter-aural crosscorrelation function (IACC). Even the caktail party effects may be eplained by spatialization of human brain, i.e., independence of temporal and spatial factors.