• Structural Engineering and Mechanics
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• v.44 no.4
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• pp.521-538
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• 2012

In this study, the transverse vibrations of an axially moving flexible beams resting on multiple supports are investigated. The time-dependent velocity is assumed to vary harmonically about a constant mean velocity. Simple-simple, fixed-fixed, simple-simple-simple and fixed-simple-fixed boundary conditions are considered. The equation of motion becomes independent from geometry and material properties and boundary conditions, since equation is expressed in terms of dimensionless quantities. Then the equation is obtained by assuming small flexural rigidity. For this case, the fourth order spatial derivative multiplies a small parameter; the mathematical model converts to a boundary layer type of problem. Perturbation techniques (The Method of Multiple Scales and The Method of Matched Asymptotic Expansions) are applied to the equation of motion to obtain approximate analytical solutions. Outer expansion solution is obtained by using MMS (The Method of Multiple Scales) and it is observed that this solution does not satisfy the boundary conditions for moment and incline. In order to eliminate this problem, inner solutions are obtained by employing a second expansion near the both ends of the flexible beam. Then the outer and the inner expansion solutions are combined to obtain composite solution which approximately satisfying all the boundary conditions. Effects of axial speed and flexural rigidity on first and second natural frequency of system are investigated. And obtained results are compared with older studies.

• Journal of The Korean Association For Science Education
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• v.16 no.2
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• pp.217-225
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• 1996

Science-related attitudes, perceptions of science classroom environments, and their relationships were investigated for a sample of 535 primary and secondary school students. Two scales of the Test of Science-Related Attitudes and five scales of the Classroom Environment Scale(CES) were administered. Students' perceptions of preferred science classroom environments were also investigated using the same scales of the CES and compared with those of actual classroom environments. The results indicated the primary school students had the most positive attitudes on Enjoyment of Science Lesson and Career Interest in Science. They also had the highest scores on perceptions of actual classroom environments, while the high school students had the lowest scores. Regarding the relationships between science-related attitudes and perceptions of classroom environments, multiple correlations for the five scales of the CES were found to be significant(p<01). The scores of four scales-Involvement, Teacher Support, Order and Organization, Rule Clarity-are significantly correlated with the scores of Enjoyment of Science Lesson. Students' perceptions of preferred classroom environments on the four scales of the CES are significantly higher than those in actual environments. However, students' perceptions of actual environments on Task Orientation are similar to those of preferred environments, and are not significantly correlated with Enjoyment of Science Lesson. Educational implications are discussed.

• Journal of Preventive Medicine and Public Health
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• v.15 no.1
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• pp.219-228
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• 1982

This study aimed at assessing the industrial workers' mental health status and identifing the relationship between mental health status and socio-demographic variables. We administered psychiatric self report rating scale (SCL-90)to 622 manual workers and 191 office workers in a textile .industry. The study began on 1 November, 1981 and lasted for 30 days The results were as follow: 1. Scores of symptom dimension were higher in female rather than male, younger than older, lower income group than higher one, lower educated group than higher one, manual workers than office workers and unmarried group than married one respectively. 2. The result of dimension scores of total samples showed that the score of Obsessive-compulsive scale was highest. The rest symptom dimension showed the order as follows: Interpersonal sensitivity, Depression, Hostility, Anxiety, Paranoid ideation, Somatization, Psychoticism and Phobic anxiety. 3. In order to identify the partial contribution of each socio-demographic variables on the mental health, multiple regression method was applied, and the result was as follows. 1) Sex was the most important one to explain the Somatization, Phobic-anxiety and Psychoticism scales among the 7 variables in the multiple regression equation. 2) Economic status was the most important variable to explein the Obsessive-compulsive, Depression and Hostility scales. 3) Marital status was the most important variable to explain the Interpersonal-sensitivity and Paranoid ideation scales.

• Journal of Ecology and Environment
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• v.45 no.4
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• pp.190-202
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• 2021

Background: Landscape metrics have been widely applied to quantifying the relationship between land surface temperature and urban spatial patterns and have received acceptable verification from landscape ecologists but some studies have shown their inaccurate results. The objective of the study is to compare landscape metrics and texture-based measures as alternative indices in measuring urban heterogeneity effects on LST at multiple scales. Results: The statistical results showed that the correlation between urban landscape heterogeneity and LST increased as the spatial extent (scale) of under-study landscapes increased. Overall, landscape metrics showed that the less fragmented, the more complex, larger, and the higher number of patches, the lower LST. The most significant relationship was seen between edge density (ED) and LST (r = - 0.47) at the sub-region scale. Texture measures showed a stronger relationship (R² = 34.84% on average) with LST than landscape metrics (R² = 15.33% on average) at all spatial scales, meaning that these measures had a greater ability to describe landscape heterogeneity than the landscape metrics. Conclusion: This study suggests alternative measures for overcoming landscape metrics shortcomings in estimating the effects of landscape heterogeneity on LST variations and gives land managers and urban planners new insights into urban design.

• Journal of applied mathematics & informatics
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• v.33 no.1_2
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• pp.1-12
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• 2015

This paper is concerned with boundary value problems for systems of n-th order dynamic equations on time scales. Under the suitable conditions, the existence and multiplicity of positive solutions are established by using abstract fixed-point theorems.

• The International Journal of Costume Culture
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• v.5 no.1
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• pp.58-66
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• 2002

The objectives of this study are to develope sensibility image scales for Korean traditional motifs by quantitatively measuring their images and preference and to classify them into clusters. Data were collected via a questionnaire from seven hundred twenty five Korean undergraduate students. Re experimental materials were forty eight stimuli of Korean traditional motifs with different categories, interpretation types, composition types, and application objects. The instruments consisted of 7-point polar semantic differential scales of twenty three bipolar adjectives including preference. Data were analyzed by correspondence analysis, cluster analysis, ANOVA and Duncan's multiple range test. Re major results are as follows; image scales for textile patterns and dress designs using Korean traditional motifs were constructed. The axes of sensibility image scales for both textile patterns and dress designs were defined by quality level and degree of simplicity. Second, four clusters on the scale of textile patterns and two clusters on the scale dress designs were identified. Third, in the case of textile Patterns, the preferred cluster had high-quality and classical images, while the cluster that was not preferred had a complex image. In the case of dress designs, the preferred cluster had simple and high-quality images, while the cluster that was not preferred had complex and low-quality images.

• Journal of Mechanical Science and Technology
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• v.14 no.1
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• pp.48-56
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• 2000

The bifurcation problem of thin walled structures in contact with rigid surfaces is formulated by adopting the multiple scales asymptotic technique. The general theory developed in this paper is very useful for the bifurcation analysis of waviness instabilities in the sheet metal forming. The formulation is presented in a full Lagrangian formulation. Through this general formulation, the bifurcation functional is derived within an error of O($(E^4)$) (E: shell's thickness parameter). This functional can be used in numerical solutions to sheet metal forming instability problem.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.916-923
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• 1998

In this paper, an infinite determinant method is presenstd for stability analysis of parametrically excited systems. Unstable regions of the combination parametric resonance as well as principal resonance can be identified with the method. A numerical problem of relatively large amplitude of excitation is solved, and the results of the presented method are compared to those of the multiple scales perturbation method. It is found that the presented method obtains more accurate transition curves which divide stable and unstables in the parameter plane than those of the multiple scales perturbation method.

• Journal of KSNVE
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• v.11 no.1
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• pp.118-124
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• 2001

The effect of a concentrated mass on the regions of dynamic instability of an axially oscillating cantilever beam is investigated in this paper. The equations of motion are derived using Kane's method and the assumed mode method. It is found that the bending stiffness is harmonically varied by axial inertia forces due to oscillating motion. Under the certain conditions between oscillating frequency and the natural frequencies, dynamic instability may occur and the magnitude of the bending vibration increase without bound. By using the multiple time scales method, the regions of dynamic instability are obtained. The regions of dynamic instability are found to be depend on the magnitude of a concentrated mass or its location.

• Structural Engineering and Mechanics
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• v.75 no.1
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• pp.87-100
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• 2020

The present paper investigates the combination resonance behavior of imperfect spiral stiffened functionally graded (SSFG) cylindrical shells with internal and external functionally graded stiffeners under 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, to account for the vibration hardening/softening phenomena and damping considerations. With regard to classical plate theory of shells, 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 combination resonance is obtained by using the multiple scales method. Finally, the influences of the stiffeners angles, foundation type, the nonlinear elastic foundation coefficients, material distribution, and excitation amplitude on the system resonances are investigated comprehensively.