• Proceedings of the Korea Water Resources Association Conference
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• 1988.07a
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• pp.29-36
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• 1988

A general scheme is developed which determines the Lagrangian motions of water particles by the Eulerian velocity at their mean positions by use of Taylor's theorem. Utilizing the Stokes finite-amplitude wave theory, the mass transport velocity which includes the effects of higher-order wave components is determined. The fifth-order theory predicts the mass transport velocity less than that given by the existing second-order theory over the whole depth. Limited experimental data for changes in wave celerity in closed wave flumes are compared with the theoretical predictions.

• Carbon letters
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• v.23
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• pp.30-37
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• 2017

Dyes are widely used in various industries including textile, cosmetic, paper, plastics, rubber, and coating, and their discharge into waterways causes serious environmental and health problems. Four different carbon nanostructures, graphene oxide, oxidized multi-walled carbon nanotubes, activated carbon and multi-walled carbon nanotubes, were used as adsorbents for the removal of Nile Blue A (NBA) dye from aqueous solution. The four carbon nanostructures were characterized by scanning electron microscope and X-ray diffractometer. The effects of various parameters were investigated. Kinetic adsorption data were analyzed using the first-order model and the pseudo-second-order model. The regression results showed that the adsorption kinetics were more accurately represented by the pseudo-second-order model. The equilibrium data for the aqueous solutions were fitted to Langmuir and Freundlich isotherms, and the equilibrium adsorption of NBA was best described by the Langmuir isotherm model. This is the first research on the removal of dye using four carbon nanostructures adsorbents.

• Journal of Institute of Convergence Technology
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• v.3 no.2
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• pp.23-29
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• 2013

When a human operator interacts with a virtual wall that is modeled as a virtual spring model, the lager the stiffness of the virtual spring is, the more realistic the operator feels that the virtual wall is. In the previous studies, it is shown that the maximum available stiffness of a virtual spring to guarantee the stability can be increased when the first-order-hold method is applied, however the effects of a human impedance on the stability are not considered. This paper presents the effects of a human impedance on stability of haptic system with a virtual spring and a first-order-hold (FOH) method. The human impedance model is modeled as a linear second-order system model. The relations between the maximum available stiffness of a virtual spring and the human impedance such as a mass, a damping and a stiffness are analyzed through the MATLAB simulation. It is shown that the maximum available stiffness is proportional to the square root of the human mass or damping respectively.

• Journal of Advanced Research in Ocean Engineering
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• v.3 no.4
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• pp.193-203
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• 2017

This study investigated the steady-flow effects present in the numerical computation of the resistance added to a ship in waves. For a ship advancing in the forward direction, a time-domain 3D Rankine panel method is applied to solve the ship motion problem, and the added resistance due to waves is calculated using a near-field method, with the direct integration of the second-order pressure on the hull surface. In the linear potential theory, the steady flow is approximated by the basis potential of a uniform flow or double-body flow in order to linearize the boundary conditions. By applying these two different linearization schemes, the coupling effects between steady and unsteady solutions were examined. Furthermore, in order to analyze the steady-flow effects on the hull geometry, the computation results for two realistic hull forms, a KVLCC2 tanker and DTC containership, were compared. In particular, the mj term, which represents the coupling effects under the body boundary condition, was evaluated considering the geometry of a non-wall-sided ship. Lastly, the characteristics of the linearization schemes were examined in relation to the disturbed waves around a ship and the components of added resistance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.1 s.256
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• pp.40-50
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• 2007

The present contribution describes the application of elliptic-blending second moment closure to predict the gas cooling process of turbulent super-critical carbon dioxide flow in a square cross-sectioned duct. The gas cooling process under super-critical state experiences a drastic change in thermodynamic and transport properties. Redistributive terms in the Reynolds stress and turbulent heat flux equations are modeled by an elliptic-blending second moment closure in order to represent strongly non-homogeneous effects produced by the presence of walls. The main feature of Durbin's elliptic relaxation second moment closure that accounts for the nonlocal character of pressure-velocity gradient correlation and the near-wall inhomogeneity guaranteed by the elliptic blending second moment closure.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.11
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• pp.483-493
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• 2002

The damping ratio ${\xi}$ of the unit-step response of a second-order discrete system is a function of only the location of the closed-loop poles and is not directly related to the location of the system zero. However, the peak overshoot of the response is the function of both the damping ratio ${\xi}$ and an angle ${\alpha}$, which is the phasor angle of the damped sinusoidal response and is determined by the relative location of the zero with respect to the closed-loop poles. Therefore, if the zero and the open-loop poles are relatively adjusted, through pole-zero cancellation, to maintain the desired (or designed) closed-loop poles, the damping ratio ${\xi}$ will also be maintained, while the angle ${\alpha}$ changes. Accordingly, when the closed-loop system poles are fixed, the peak overshoot is considered as a function of the angle ${\alpha}$ or the system zero location. In this paper the effects of the relative location of the zero on the system performance of a second-order discrete system is studied, and a design method of digital compensator which achieves a minimum peak overshoot while maintaining the desired system mode and the damping ratio of the unit step response is presented.

• Fashion & Textile Research Journal
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• v.24 no.6
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• pp.731-743
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• 2022

This study examined the effects of platforms' attributes(economy, convenience, ease of use, and security) on perceived usefulness, perceived enjoyment, trust, and the continuance intention to use. Data were collected through a survey conducted with 327 users of second-hand luxury goods trading platforms in their twenties and thirties; 300 were used for statistical analysis using SPSS26.0 for exploratory factor analysis and correlation analysis, and AMOS 26.0 for confirmatory factor analysis and structural equation modeling. For the attributes of second-hand luxury goods trading platforms, four factors were extracted: economy, convenience, ease of use and security. The results showed that only the security of second-hand luxury goods platforms had a positive effect on the perceived usefulness of the platform, but other attributes did not influence perceived usefulness. In contrast, all attributes of the platform showed positive effects on perceived enjoyment. Perceived enjoyment had a strong effect on trust; however, perceived usefulness did not affect trust. The continuance intention to use the platforms was most influenced by perceived usefulness, trust, and perceived enjoyment, in that order. The current findings can help marketers of second-hand luxury goods platforms optimize the platforms' attributes based on the marketing objectives and develop strategies to build perceived usefulness and enjoyment first, and in turn, trust and intention to use.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.485-496
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• 2006

Practical stability design method of main members of cable-stayed bridges is proposed and discussed through a design example. For this purpose, initial tensions of stay cables and axial forces of main members are firstly determined using initial shaping analysis of bridges under dead loads. And then the effective buckling length using system elastic/inelastic buckling analysis and bending moments considering $P-{\delta}-{\Delta}$ effect by second-order elastic analysis are calculated for main girder and pylon members subjected to both axial forces and moments, respectively. Particularly, three load combinations of dead and live loads, in which maximum load effects due to live loads are obtained, are taken into account and effects of live loads on effective buckling lengths are investigated.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.570-577
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• 2001

Three-dimensional time-dependent flow past a circular cylinder is numerically investigated using direct numerical simulation for Reynolds number 280 and 300. The higher-order finite difference scheme is employed for the spatial distributions along with the second order Adams-Bashforth and the first order backward-Euler time integration. In x-y plane, the convection term is applied by the 5th order upwind scheme and the pressure and viscosity terms are applied by the 4th order central difference. And in spanwise, Navier-Stokes equation is distributed using of Spectral Method. At Reynolds number 259 the two-dimensional wake becomes linearly unstable to a second branch of modes with wavelength about 1.0 diameters at onset (B-mode). Present results of three-dimensional effects of in wake of a circular cylinder is represented with spanwise and streamwise vorticity contours as Reynolds numbers.

• Korean Journal of Human Ecology
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• v.17 no.5
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• pp.835-845
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• 2008

The purpose of this study was to identify the effects of maternal depression, adolescent's self-esteem and adolescent's sex, grade, birth order on the adolescent's social anxiety. for this purpose, data from 334 middle school students and their mothers were collected. frequency, percentage, Cronbach's a, MANOVA and multiple regression analysis were used for data analysis. The main results were as follows. First, there were not significant differences of adolescent's social anxiety according to adolescent's sex, grade and birth order. Second, there were not significant effects of adolescent's sex, grade, birth order and maternal depression on three subordinate factors of adolescent's social anxiety, but adolescent's self-esteem had significant effects on fear of negative evaluation, social avoidance and distress(new), and social avoidance and distress(general) as subordinate factors of adolescent's social anxiety.