• Journal of The Korean Astronomical Society
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• v.47 no.6
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• pp.209-214
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• 2014

In this study we develop a set of solar proton event (SPE) forecast models with NOAA scales by Multi Layer Perceptron (MLP), one of neural network methods, using GOES solar X-ray flare data from 1976 to 2011. Our MLP models are the first attempt to forecast the SPE scales by the neural network method. The combinations of X-ray flare class, impulsive time, and location are used for input data. For this study we make a number of trials by changing the number of layers and nodes as well as combinations of the input data. To find the best model, we use the summation of F-scores weighted by SPE scales, where F-score is the harmonic mean of PODy (recall) and precision (positive predictive value), in order to minimize both misses and false alarms. We find that the MLP models are much better than the multiple linear regression model and one layer MLP model gives the best result.

• Language and Information
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• v.17 no.2
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• pp.29-50
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• 2013

Multiple Nominative Constructions (MNCs) and Multiple Accusative Constructions (MACs) have been some of the hottest and interesting topics in Korean syntax. This paper took empirical approaches to these constructions and examined native speakers' grammaticality judgements of these constructions. Though there are lots of previous studies on these constructions, Ryu (2010, 2013a, 2013b, 2013c) recently tried to unify MNCs and MACs into Multiple Case Constructions (MCCs) and to classify them into 16 types based on the semantic relations. This paper includes experiments which were performed on these 16 different types. The experiments were designed following Johnson (2008); and the native speakers' intuition was measured with two scales, numerical estimates and line drawing, though the latter was adopted in the actual analyses. Through the experiment, the following facts were observed: (i) the grammaticality of the MCCs varies depending on their semantic relations, (ii) MNCs were more grammatical than MACs if both constructions occurred in similar environments, and (iii) the sentences in some MAC types had much lower grammaticality than those in the others, as Ryu (2013b, 2013c) mentioned.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.275-281
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• 1996

In order to examine the validity of an asymptotic solution obtained from the method of multiple scales, we investigate a third-order subharmonic resonance response of a bar constrained by a nonlinear spring to a harmonic excitation. The motion of the bar is governed by a linear partial differential equation with a nonlinear boundary condition. The nonlinear boundary value problem is solved by using the finite difference method. The numerical solution is compared with the asymptotic solution.

• Journal of Preventive Medicine and Public Health
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• v.38 no.3
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• pp.298-306
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• 2005

Objectives : To develop measurement scales of Internet addiction, and propose a Korean Internet Addiction Index (K-IAI) and classification criteria for Internet addiction from the threshold scores developed. Methods : The identification of the concept of 'Internet addiction' was based on the literature review. To select the scales, an exploratory factor analysis was applied. A construct validation was tested by a confirmatory factor analysis (CFA) with a structured equation model (SEM). In testing the validity of the classification criteria, ANOVA and non-recursive models with SEM were applied. Results : Out of 1,080 questionnaires distributed, 1,037 were returned,; a response rate of 96%. The Cronbach-$\alpha$ of all items was over 0.75. Using an exploratory factor analysis in the condition of a 6 factor constrain as the study model proposed, 23 of the initial 28 items were identified. In testing the discriminant and convergent validity of the selected 23 scales using CFA with SEM, the Internet addiction model explained about 93% of all variances of the data collected, and all the latent variables significantly explained the designated scales. A K-IAI was proposed using the T-scores of the sum of all factor averages. In the classification of users, the basic concept was a twostandard deviation approach of the K-IAI as the criteria of MMPI. The addiction group had a score ${\geq}70$ in the K-IAI, the pre-addiction group between ${\geq}50$ and <70, and the average user group <50. The Internet use times of the classified groups were statistically different in the ANOVA and multiple comparisons. Conclusions : The K-IAI is a reliable and valid instrument for measuring Internet addiction. Moreover, the taxonomy of the groups was also verified using various methods.

• Sleep Medicine and Psychophysiology
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• v.1 no.2
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• pp.125-144
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• 1994

Recently excessive daytime sleepiness was found to have relations with various social, occupational, and health problems. This condition is common symptom of several sleep disorders, among which sleep apnea syndrome is most contributive. It is essential to assess daytime sleepiness exactly for the diagnosis of such sleep disorders. Multiple sleep latency test which is a valid and objective measurement technique of sleepiness is time and cost consuming, and so there is increasing need of scales measuring general level of daytime sleepiness which are quick and simple to perform for clinical and research purpose. And also, there have been a lot of sleep researches viewing sleep as a chronobiological process, especially in the study of circadian type of shift workers. In these studies they used various techniques of multiple demensions to assess sleepiness or circadian rhythm which concerns various psychological variables. Of these measurement techniques circadian type questionnaires might have some problems in their psychometric properties. So some of these morningness-eveningness questionnaires have been revised and more valid scales are being suggested by different authors. The author briefly reviewed various measurement techniques of sleepiness and circadian rhythm and introduced recently developed scales which are more valid allegedly, and finally discussed psychometric properties of these morningness-eveningness questionnaires.

• Journal of the Korean Society of Clothing and Textiles
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• v.20 no.2
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• pp.241-256
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• 1996

The purposee of this study was to identify the effect of perceiver's clothing attitude on male impressions created by the clothing cues and contexts. In addition, the effect of perceiver's evaluations of clothing appropriateness on male impressions. The subjects consisted of 256 male undergraduate students and 256 middle aged men. The experimental materials developed for this study were a set of stimuli and response scales. The stimuli were 8 color Photographs of drawings of a male figure in clothing which were minipulated in two levels, each of three clothing cues including type, style and color. The experimental design was full factorial design of 2(contexts$\times$clothing types$\times$clothing style$\times$clothing color). Each of the 16 sub-samples includes 16 subjects from the two perceiver group. Questionnaires used to measure perceivers responses to the stimuli were 7-point semantic differential scales composed of 37 bipolar adjectives representing personal traits. Four aspects of clothing attitude(fashion interest, status symbols consiousness, clothing conformity, practicality & comfort)were used to classify subjects into groups of 20 five-point likers type questionnaires adapted from the previous research. Clothing appropriateness were developed 5 point likest scales for evaluation of a stimulus person in each context. The data was processed by factor analysis, ANOVA, multiple classification analysis, Duncan's multiple range test, cluster analysis, MANOVA and pearson's product moment correlations. The major findings drawn from this study were as follows: 1. Perceiver's clothing attitude influenced impression formed by the social contexts and clothing crises. In three groups classified by their clothing attitude, the status symbol-oriented group was most affected by the social contexts and clothing cues. 2. Perceiver's evaluation of clothing appropriateness was related with impressions by a stimulus person. In summary the effect of contexts and clothing cues on impression formation varied according to perceiver's clothing attitude and clothing approopiateness.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1897-1907
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• 1991

An analysis is presented for the primary resonance of a clamped-hinged beam, which occurs when the frequency of excitation is near one of the natural frequencies, .omega.$_{n}$. Three mode interactions, .omega.$_{2}$=3.omega.$_{1}$, and .omega.$_{3}$=.omega.$_{1}$+2.omega.$_{2}$, are considered and their influence on the response is studied. The case of two mode interaction, .omega.$_{2}$=3.omega.$_{1}$, is also considered in order to compare it with the case of three mode interactions. The straight beam experiencing mid-plane stretching is governed by a nonlinear partial differential equation. By using Galerkin's method the governing equation is reduced to a system of nonautonomous nonlinear ordinary differential equations. The method of multiple scales is applied to obtain steady-state responses of the system. Results of numerical investions show that there exists no significant difference between both modal interactions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.11
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• pp.2098-2110
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• 1992

An analysis is presented for the combination resonance of a clamped circular plate, which occurs when the frequency of the excitation is near the combination of the natural frequencies, that is, when ohm.=2.0mega.／sub 1／+omega.／sub 2／. The internal resonance, Omega.／sub 3／=omega.／sub 1／+2.omega.／sub 2／, is considered and its influence on the response is studied. The clamped circular plate experiencing mid-plane stretching is governed by a nonlinear partial differential equation. By using Galerkin's method the governing equation is reduced to a system of nonautonomous ordinary differential equations. The method of multiple scales is used to obtain steady-state responses of the system. Results of numerical investigations show that the increase of the excitation amplitude can reduce the amplitudes of steady-state responses. We can not find this kind of results in linear systems.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.1
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• pp.21-28
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• 2002

This paper intends to investigate the effects of speed fluctuation caused by the cogging torque in permanent magnetic motors on the stability of the transverse vibration for a spinning disk. Based on the Kirchhoff\`s plate theory and the assumed mode methods, a set of discretized equations of motion were derived for an annular disk rotating with a harmonically varying speed. Then, a perturbation method using the multiple time scales was employed and stability boundaries were determined explicitly in terms of the magnitude and frequency of speed fluctuation, a nominal sped and the modal characteristics of the disk. It is found that parametric resonance occurs at several speed ranges and a single mode or a combination of two modes are involved to cause instability. It is also observed that unstable regions become broadened as the spinning speed increases or two modes are combined in parametric instability. As numerical simulations, stability analysis of a conventional CD-ROM drive was performed. Results of this work can e used as guidelines for motor design and operations with low vibration.

• Steel and Composite Structures
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• v.37 no.1
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• pp.51-73
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• 2020

The present paper investigates the simultaneous resonance behavior of spiral stiffened multilayer functionally graded (SSMFG) cylindrical shells with internal and external functionally graded stiffeners under the two-term large amplitude excitations. The structure is embedded within a generalized nonlinear viscoelastic foundation which is composed of a two-parameter Winkler-Pasternak foundation augmented by a Kelvin-Voigt viscoelastic model with a nonlinear cubic stiffness. The cylindrical shell has three layers consist of ceramic, FGM, and metal. The exterior layer of the cylindrical shell is rich ceramic while the interior layer is rich metal and the functionally graded material layer is located between these layers. With regard to classical shells theory, von-Kármán equation, and Hook law, the relations of stress-strain are derived for shell and stiffeners. The spiral stiffeners of the cylindrical shell are modeled according to the smeared stiffener technique. According to the Galerkin method, the discretized motion equation is obtained. The simultaneous resonance is obtained using the multiple scales method. Finally, the influences of different material and geometrical parameters on the system resonances are investigated comprehensively.