• The Korean Journal of Applied Statistics
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• v.33 no.2
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• pp.115-122
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• 2020

K-means clustering uses a spherical or elliptical metric to group data points; however, it does not work well for non-convex data such as the concentric circles. Spectral clustering, based on graph theory, is a generalized and robust technique to deal with non-standard type of data such as non-convex data. Results obtained by spectral clustering often outperform traditional clustering such as K-means. In this paper, we review spectral clustering and show important issues in spectral clustering such as determining the number of clusters K, estimation of scale parameter in the adjacency of two points, and the dimension reduction technique in clustering high-dimensional data.

• Journal of the Korean Society of Safety
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• v.33 no.1
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• pp.118-127
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• 2018

The study aims present data collection on the current state of safety and safety consciousness in universities' laboratories to verify the relation between investigation factors and further draw implications. The first finding is that laboratories with high risk level do not have better safety management performance than those with lower risk level. Secondly, labs that experienced accidents has a higher level of control than those without any. Regarding to the university's acceptance of safety requirements, the group with a high level of risk awareness or accidents were concerned that their universities did not provide sufficient support in safety management. It means that safety is low on the list of priorities in Universities' overall agenda and individual labs are responsible of their own safety. Most of the causes of accidents in the labs are man-made than physical errors. It requires that continuous safety educations and measures through safe research activities are means to eliminate and reduce the individual's safety frigidity. Through the survey, it is known that current education's system and contents are too generalized to reflect the characteristics of each laboratory. Thus, it is difficult to recognize various risk situations and to actually prevent safety accidents. Therefore, it is necessary to shift to customized curriculum and system for various major fields.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.5
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• pp.27-39
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• 2004

In the first part of this study, five homogeneous regions in view of topographical and geographically homogeneous aspects except Jeju and Ulreung islands in Korea were accomplished by K-means clustering method. A total of 57 rain gauges were used for the regional frequency analysis with minimum rainfall series for the consecutive durations. Generalized Extreme Value distribution was confirmed as an optimal one among applied distributions. Drought rainfalls following the return periods were estimated by at-site and regional frequency analysis using L-moments method. It was confirmed that the design drought rainfalls estimated by the regional frequency analysis were shown to be more appropriate than those by the at-site frequency analysis. In the second part of this study, LH-moment ratio diagram and the Kolmogorov-Smirnov test on the Gumbel (GUM), Generalized Extreme Value (GEV), Generalized Logistic (GLO) and Generalized Pareto (GPA) distributions were accomplished to get optimal probability distribution. Design drought rainfalls were estimated by both at-site and regional frequency analysis using LH-moments and GEV distribution, which was confirmed as an optimal one among applied distributions. Design rainfalls were estimated by at-site and regional frequency analysis using LH-moments, the observed and simulated data resulted from Monte Carlotechniques. Design drought rainfalls derived by regional frequency analysis using L1, L2, L3 and L4-moments (LH-moments) method have shown higher reliability than those of at-site frequency analysis in view of RRMSE (Relative Root-Mean-Square Error), RBIAS (Relative Bias) and RR (Relative Reduction) for the estimated design drought rainfalls. Relative efficiency were calculated for the judgment of relative merits and demerits for the design drought rainfalls derived by regional frequency analysis using L-moments and L1, L2, L3 and L4-moments applied in the first report and second report of this study, respectively. Consequently, design drought rainfalls derived by regional frequency analysis using L-moments were shown as more reliable than those using LH-moments. Finally, design drought rainfalls for the classified five homogeneous regions following the various consecutive durations were derived by regional frequency analysis using L-moments, which was confirmed as a more reliable method through this study. Maps for the design drought rainfalls for the classified five homogeneous regions following the various consecutive durations were accomplished by the method of inverse distance weight and Arc-View, which is one of GIS techniques.

• International Commerce and Information Review
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• v.9 no.2
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• pp.103-120
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• 2007

The knowledge based economy requires more and more people to learn new knowledge and skills in a timely and effective manner. These needs and new technology such as computer and Internet are fueling a transition in e-learning. According to specialist's opinion, imagination experience studying is generalized, and learning environment that language barrier by studying, multi-language studying Machine that experience past things that disappear through simulation, and travel area, and experience future changed state disappears is forecasting to come. This is previewing finally that it may become future education that education and IT, element of entertainment is combined. Already, became story that argument for party satellite of e-Learning existence passes one season already. e-Learning is utilized already in all educations that we touch by effectiveness by corporation's competitive power improvement and implement of lifelong education in educational institutions through present e-Learning. It is obvious that when see from our viewpoint which is defining e-Learning by one industry and rear by application to education as well as one new growth power about these, e-Learning industry becomes very important means that can solve dilemma of growth real form. Only, special quality of digital industry that e-Learning is being same with other digital industry and repeat putting out a fire rapidly, and is repeating sudden change that these evolution is not gradual growth of accumulation and improvement of technology that is appearing consider need to. In the meantime, we need to observe about evolution of Information Technology. Because there is some scholars who e-Learning's concept foresees to evolve by u-Learning.(although, a person who see that these concept is not more in marketing terminology by some scholars' opinion is). This u-Learning's concept means e-Learning that take advantage of ubiquitous technology as Ubiquitous-Learning's curtailment speech. Ubiquitous, user means Information-Communication surrounding that can connect to network freely regardless of place without feeling network or computer. There is controversy about introduction time regarding these direction, but e-Learning is judged to evolve by u-Learning necessarily. Because keep in step and age that study all contents that learner wants under environment of 3A (any time, any whrer, any device) by individual order thoroughly is foreseen to come in ubiquitous learning environment that approach more festinately.

• Journal of the Korean School Mathematics Society
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• v.11 no.1
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• pp.133-157
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• 2008

This paper is based on theory of Usiskin who defined inclusively the various concepts of algebra among many theories classifying a type of the algebra. For this purpose, we examined the curriculum of the algebra of Korea, America and Japan, then analyzed where the problems in "Letter and Formula" of the textbooks fall under Usiskin's concepts of algebra.

• Proceedings of the Korean Magnestics Society Conference
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• 2004.12a
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• pp.200-201
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• 2004

The $H_{EB}$ was investigated for exchange coupling $20\;{\AA}\;Fe/x\;{\AA}\;NiO\;(type-I samples)$, $20\;{\AA}\;Fe/x\;{\AA}$ nonmagnetic layer $(MgO, Ag, Cu)/(500-x{\AA})$ NiO (type-II smaples). In type-I samples, the $H_{EB}$ is long-range coupling when looking from the point of view of the AFM. The $H_{EB}$ consistent with a generalized Meiklejohn-Bean approach. The critical thickness, which $H_{EB}$ is observed, is $130\;{\AA}$. In type-II samples, MgO layer more decouples the thin interfacial NiO from bottom NiO than other nonmagnetic layer. Nd the decoupling of Ag smallest. This means that the Ag layer has strong coupling the thin interfacial NiO with bottom NiO.

• Honam Mathematical Journal
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• v.42 no.2
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• pp.251-268
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• 2020

In this paper, we estimate the degree of approximation by means of the complete modulus of continuity, the partial modulus of continuity, the Lipschitz-type class and Petree's K-functional for the bivariate Szász-Kantorovich operators based on Brenke-type polynomials. Later, we construct Generalized Boolean Sum operators associated with combinations of the Szász-Kantorovich operators based on Brenke-type polynomials. In addition, we obtain the rate of convergence for the GBS operators with the help of the mixed modulus of continuity and the Lipschitz class of the Bögel continuous functions.

• Communications for Statistical Applications and Methods
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• v.5 no.2
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• pp.491-501
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• 1998

Motivated by bioequivalence studies which involve comparisons of pharmaceutically equivalent dosage forms, we propose a more general decision rule for showing equivalence simultaneously between multiple means and a control mean. Namely, this testing procedure is concerned with the situation in that one must make decisions as to the bioequivalence of an original drug product and several generic formulations of that drug. This general test is developed by considering a spherical confidence region, which is a direct extension of the usual t-based confidence interval rule formally approved by the U.S. Food and Drug Administration. We characterize the test by the probability of rejection curves and assess its performance via Monte-Carlo simulation. Since the manufacturer's main concern is the proper choice of sample sizes, we provide optimal sample sizes from the Monte-Carlo simulation results. We also consider an application of the generalized equivalence test to a repeated measures design.

• Speech Sciences
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• v.9 no.3
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• pp.99-112
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• 2002

The purpose of the present study was to investigate the effectiveness of self-monitoring on spontaneously initiating speech behavior of the hearing-impaired preschoolers. Three hearing-impaired preschoolers were selected from a special school for the deaf. They showed some vocalizations and words under intensive instruction settings, but never spontaneously spoke as a means of communication. Multiple probe design was applied in this study. During the self-monitoring intervention, each child was trained to assess whether his own initiating speech behavior was occurred or not, and then record his own behavior's occurrence on the self-recording sheets and self-graphing sheets. The vibration of handphone was used as a tactile cue for self-monitoring. The results of the present study were as follows: (1) self-monitoring significantly increased the percentage of occurrence of spontaneously initiating speech behaviors. (2) Increased level of spontaneously initiating speech behavior were generalized into another natural instruction (cognitive) settings. (3) Increased level of spontaneously initiating speech behavior were maintained after four weeks from the termination of the intervention.

• Journal of computational fluids engineering
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• v.9 no.2
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• pp.43-51
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• 2004

Interaction between fluid flow and thermal radiation has received considerable attention due to its numerous applications in engineering field. In this case the thermofluid properties of radiating fluid vary with the variation of temperature field caused by absorption and emission of radiant heat. To analyze the radiation heat transfer in radiating fluid, the simultaneous solution of the radiative transfer equation (RTE) and the fluid dynamics equations is required. This means that the numerical procedure used for the RTE must be computationally efficient to permit its inclusion in the other submodels, and must be compatible with the other transport equations. The finite volume method (FVM) and the discrete ordinates method (DOM) are usually employed to simulate radiation problems in generalized coordinates. These two representative methods are examined and compared, especially in view of the numerical integration of the radiation intensity over solid angle. The FVM shows better accuracy than the DOM owing to less constraints of the selection of control angle.