• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.144-150
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• 2000

In this paper, we introduce a modified six-degrees-of-freedom parallel-link manipulator, which will be applied to the human vibration experiments. We analyze the inverse kinematics and workspace of this manipulator and comprehend the characteristics of kinematics analyzed. Additionally, solutions of forward kinematics are obtained through the iterative Newton-Raphson method known as one of the most used numerical analysis. Finally, dynamic equation of the manipulator is derived in closed form through the Newton-Euler approach, which will be used for the development of control software.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.12
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• pp.25-35
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• 1995

An analysis method of electromagnetic coupling through an arbitrarily shaped aperture on the upper wall of parallel-plate waveguide, when excited by an electromagnetic plane wave from outside, is considered. The mixed-potential integral equation, in which Green's functions are expressed in a computationally efficient closed form by using the Prony's method and the Sommerfeld identity, is formulated. Expanding the unknown equivalent magnetic surface current in terms of two-dimensional rooftop-type basis functions and choosing razor testing, the integral equation is reduced to a linear algebraic equation, which is solved. The results are compared with the previous results. Fairly good agreements between them are observed.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.95-98
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• 2003

In this work, a closed-form analysis is performed to obtain the stiffness coefficients of thin-walled composites beams with elliptical profiles. The analytical model includes the effects of elastic couplings, shell wall thickness, torsion warping and constrained warping. Reissner's semi-complementary energy functional is used to derive the beam force-displacement relations. The theory is validated against MSC/NASTRAN results for coupled composites beams with single-cell elliptical sections. Very good correlation has been noticed for the test cases considered.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.549-554
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• 2000

In this study, using linear and nonlinear deformation theories and by closed-form analysis and finite difference energy methods, respectively, various buckling load factors are obtained for stiffened laminated composite cylindrical panels with rectangular type longitudinal stiffeners and various longitudinal length to radius ratios, which are made from Carbon/Epoxy USN150 prepreg and are simply-supported on four edges under uniaxial compression, and then for them, buckling behavior design analyses are carried out by the nonlinear search optimizer, ADS

• Computers and Concrete
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• v.18 no.6
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• pp.1097-1112
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• 2016

Fire loading causes a critical collapse of RC (Reinforced Concrete) Structures since the embedded steels inside are relative week against high elevated temperature. Several numerical frameworks for fire resistance have been proposed, however they have limitations such as unstable convergence and long calculation period. In the work, 2-D nonlinear FE technique is proposed using Galerkin method for RC structures under fire loading. Closed-form element stiffness with a triangular element is adopted and verified with fire test on three RC slabs with different fire loading conditions. Several simulations are also performed considering fire loading conditions, water contents, and cover depth. The proposed numerical technique can handle time-dependent fire loading, convection, radiation, and material properties. The proposed technique can be improved through early-aged concrete behavior like moisture transport which varies with external temperature.

• Journal of ILASS-Korea
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• v.7 no.1
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• pp.29-35
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• 2002

This study describes the external spray characteristics of deflector nozzle such as the breakup procedures of liquid sheet, spray angle, breakup length and bubble behaviors of spray at deflector nozzle. In order to visualize the spray behaviors shadow graphy technique were used. According to the increase injection pressure, deveopment of the spray passes through the dribbling, distoted jet, closed bubble due to the contraction by form a conical sheet like as the simplex swirl atomizer. As trying the analysis of the ratio of bubble length and width it was found that the ratios is comparable. Spray cone angle was nearly $90^{\circ}$.

• Journal of Korean Society for Quality Management
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• v.11 no.2
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• pp.32-36
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• 1983

2-Unit systems such as series, parallel, standby with two types of failures are considered. Closed form solutions for both the steady-state and time-dependent availability of 2-Unit system with two types of failures are developed.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.6
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• pp.108-113
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• 1999

For cylindrical shells, the closed-form solutions are confined to the specific boundary and/or loading conditions. Though the finite element method is certainly a powerful solution approach for the structural dynamics problems, it has been well known to provide the solution reliable only in the low frequency region due to the inherent high sensitivities of structual and numerical modeling errors. Instead, the spectral element method has been proved to provide accurate dynamic characteristics of a structure even at the ultrasonic frequency region. Since the wave characteristic of a cylindrical shell becomes identical to that fo a flat plate as the frequency increases, an equivalent plate model (EPM) representing the high-frequency dynamic characteristics of the cylindrical shell is introduced herein. The EPM-based spectral element analysis solutions are compared with the known analytical solutions for the cylindrical shells to confirm the validity of the present modeling approach.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.893-900
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• 1994

In this study, workspace analysis has been performed for a Clemens Coupling type parallel robotic wrist with four degrees of freedom such as three angular degrees of freedom and 1 plunge motion. Because of plunge motion, this mechanism has no singular point that the general roll-pitch-roll mechanisms have. Also, proposed mechanism performs larger load, faster motion, with less weight and has better structural characteristics such as higher stiffness and strength to weight ratio compared with serial type mechanisms. As a basic step for position control, the closed form solution of forward and inverse kinematics are proposed and workspace is analyzed and plotted by applying triangle tracer method for workspace boundary tracing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5A
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• pp.574-582
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• 2004

This paper shows the performance comparisons of several different rate scheduling schemes for non-real time data service over the uplink of burst switching-based direct sequencecode division multiple access (DS/CDMA) system to support the integrated voice/data service. The closed-form solution of optimal scheduling formulation, which minimizes average transmission delay when all of the active data users are transmitting simultaneously, is presented and mathematical analyses with other rate scheduling schemes, which provide efficiency criterion of transmission delay for rate scheduling schemes, are performed. Numerical results show the analyses explicitly.