• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.8
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• pp.773-778
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• 2009

Chevron rubber springs are used in primary suspensions for rail vehicle. Chevron rubber spring have function which reduce vibration and noise, support load carried in operation of rail vehicle. Prediction and evaluation of characteristics are very important in design procedure to assure the safety and reliability of the rubber spring. The computer simulation using the nonlinear finite element analysis program executed to predict and evaluate the load capacity and stiffness for the chevron spring. The non-linear properties of rubber which are described as strain energy functions are important parameters. These are determined by material tests which are uniaxial tension, equi-biaxial tension and shear test. The appropriate shape and material properties are proposed to adjust the required characteristics of rubber springs in the three modes of flexibility.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.105-110
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• 2011

Catwalk structures are temporary walk ways for erection of main cables in suspension bridge. The aerodynamic characteristics of the catwalk structures are not well studied even though the catwalk structures are sensitive to wind action because of its flexibility. Present study demonstrates technical results obtained from wind tunnel tests of various catwalk structures. To obtain the aerostatic force coefficients of the floor system of catwalk, 1/14 and 1/4 scaled partial rigid models were fabricated and tested at the wind tunnel. In order to investigate the Reynolds number effects, the aerostatic force coefficients were measured at various wind velocities ranged from 5m/s to 30m/s. The test results revealed that the Reynolds number effects on aerostatic coefficients were not significant for the catwalk floor systems. An empirical equation for aerostatic force coefficients of catwalk are proposed based on the measured results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.10a
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• pp.87-94
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• 1997

The circular plate resting on Boussinesq's half-space model under axisymmetric loading is studied by a finite element procedure to evaluate the distribution of contact pressure between plate and elastic half-space. The displacement of half-space due to axisymmetric surface loading can be evaluated by double integration of Boussinesq's solution. On that case the analytical integration can be executed for the radial direction but the analytical integration for the circumferential direction is impossible and the numerical integration should be considered. With the radial integration we can get non-dimensional function. Then the numerical integration for the formula is executed for the circumferential direction and the results are approximated 5th order Polynomials by using the least square method. With these 5th order approximate formula, the flexibility matrix of half-space is constructed as the coefficient matrix of nodal contact pressure by the finite element procedures. Iteration procedures are attempted by using this method to determine the separated region.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.1
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• pp.99-104
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• 1998

It is a good flexibility of bending body and non-interaction of outer bodies for slit antenna to be being studied and developed in this paper. The characteristics of leaked EM waves in slit transmission line are applied to antennas of tele-communication systems. The computer simulations using a special software adapt to design a new slit antenna, and to apply to tele-communications systems with frequencies of land mobile communication (800-900MHz). The good results of which reflection coefficient 511 is 0.21 and directivity is 2.9 and band-widths are 1.5MHz in 851MHz are shown.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.4
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• pp.443-447
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• 2004

In this study, we investigated the necessity of encapsulation layer to maximize flexibility of brittle indium-tin-oxide (ITO) on polymer substrates. And, Young's modulus (E) of encapsulation layer han a significant effect on external bending stress and the coefficient of thermal expansion (CTE) of that han a significant effect on internal thermal stress. To compare the magnitude of total mechanical stress including both bending stress and thermal stress, the mechanical stress of triple-layer structure (substrate / ITO / encapsulation layer or substrate / buffer layer / ITO) can be quantified and numerically analyzed through the farthest cracked island position. As a result, it should be noted that multi-layer structures with more elastic encapsulation material have small mechanical stress compared to that of buffer and encapsulation structure of large Young's modulus material when they were externally bent.

• Journal of the Chungcheong Mathematical Society
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• v.33 no.2
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• pp.237-253
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• 2020

This article studies asymptotic stability of non-auto nomous linear systems with time-dependent coefficient matrices {A(t)}_t∈ℝ. The classical theorem of Levinson has been widely used to science and engineering non-autonomous systems, but systems with defective eigenvalues could not be covered because such a family does not allow continuous diagonalization. We study systems where the family allows to have upper triangulation and to have defective eigenvalues. In addition to the wider applicability, working with upper triangular matrices in place of Jordan form matrices offers more flexibility. We interpret our and earlier works including Levinson's theorem from the perspective of invariant manifold theory.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.177-185
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• 2000

The characteristics of multi-leaf feil bearing are investigated. The Foil bearing is preloaded and has several leaf foils modeled by curved beams. An analysis of the air foil bearing was performed, considering effects of foil deflection and compressible lubrication equation simultaneously. A parametric study shows that the number of foils significantly affect the static characteristics of air foil bearings and describes what the minimum film thickness means. The results include pressure profile, load capacity, dimensionless torque and minimum film thickness in the foil bearing.

• Textile Coloration and Finishing
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• v.13 no.4
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• pp.249-255
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• 2001

To interpret the dyeing behavior of PTT fiber with C. I. Disperse Violet 1, the thermodynamic Parameters of dyeing, such as standard affinity, heat of dyeing(enthalpy change), entropy change, diffusion coefficient, and activation energy of diffusion, were obtained from isotherms and dyeing rates at various temperatures and compared with those of PET fiber. The heat of dyeing(enthalpy change) and the entropy change of PTT fiber showed smaller negative values than those of PET fiber. This means that the dye molecules in the PTT fiber are combined more loosely than in the PET fiber and that is due to the flexibility of polymer chains of PTT fiber. The diffusion coefficients of C. I. Disperse Violet 1 into the PTT fiber were larger than those for PET fiber, and the activation energy of diffusion on PTT fiber was smaller than that on PET fiber.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.16 no.3
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• pp.295-304
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• 1987

The purpose of this study is to develop a computer model for simulating the water-lit hium bromide absorption heat transformer (AHT) Including all major components and to find the flexibility in operation. The effect of source hot water temperature, cooling water temperature, useful hot water flow rate, cooling water flow rate and evaporator circulation flow rate were investigated. The coefficient of performance (COP), temperature boost $({\Delta}T\;=\;T_A\;-\;Ti)$ and concentration variations can be predicted. The performance study indicates that the performance of AHT increases for the waste hot water temperature increasing and with a decrease of the cooling water temperature. The effect on performances of useful hot water flow rape is significant except on temperature boost. Also the effects on performance of cooling water flow rate and evaporator circulation flow rate are small. It is shown that the computer program is valuable to predict the performance of absorp-tion heat transformer units at various working corditions.

• Korean Journal of Human Ecology
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• v.20 no.5
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• pp.1025-1034
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• 2011

The purpose of this study was to examine the evaluation of fabric characteristics on the drapability, texture image and preference of blouse fabrics, and to analyze the effects of the texture image, objective and subjective drapability on the preference. As specimen, silk and polyester fabrics were collected. 52 female subjects evaluated 16 specimens with semantic differential scale of 18 fabric image and 20 sensibility. Data were analyzed through factor analysis, pearson correlational coefficient using spss win 12.0. For the evaluation, structural characteristics such as fiber contents, weave type, weight and thickness were analyzed. The results were as follows: The evaluation results of objective and subjective drapability showed differences. Sensory image factors of blouse fabrics were 'surface smoothness', 'elasticity', 'weight' and 'flexibility'. Sensibility image factors were 'elegance', 'classic', 'characteristic' and 'mannish'. 'Elegance', 'classic' and 'characteristic' of sensibility images showed high correlation with 'surface smoothness' and 'elasticity' of sensory image, also 'mannish' of sensibility image showed significant correlation with 'weight' of sensory image. The significant fabric characteristics affecting objective drapability were density, weight, thickness. The significant texture image factors affecting objective drapability were 'weight', 'flexibility' of sensory image and 'elegance' of sensibility image. On the other hand, the significant factors affecting subjective drapability were thickness of fabric characteristics and 'elegance', 'characteristic', 'mannish' of sensibility images. 'Elegance', 'characteristic' and 'classic' of sensibility image, 'elasticity' of sensory image and subjective drapability affected on the purchase preference.