• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.551-560
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• 1988

Gas-particle two phase flow and heat transfer in a cavity receiving thermal radiation through selectively transparent walls have been analyzed by a finite difference method. Particles injected from the upper hole of the cavity are accelerated downward by gravity and exit through the lower hole while they absorb, emit and scatter the incident thermal radiation. Gas phase is heated through convection heat transfer from particles, and consequently buoyancy induced flow field is formed. Two-equation model with two-way coupling is adopted and interaction terms are treated as sources by PSI-Cell method. For the particulate phase, Lagrangian method is employed to describe velocities and temperatures of particles. As thermal radiation is incident upon horizontally, radiative heat transfer in the vertical direction is assumed negligible and two-flux model is used for the solution of radiative heat flus. Gas phase velocity and temperature distributions, and particle trajectories, velocities and temperatures are presented. The effects of particle inlet condition, particle size, injection velocity and particle mass rate are mainly investigated.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.1
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• pp.71-78
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• 1998

The eigenvalue problem is presented for the building with added viscoelastic dampers by using component mode method. The Lagrange multiplier formulation is used to derive the eigenvalue problem which is expressed with the natural frequencies of the building, the mode components at which the dampers are added, and the viscoelastic property of the damper. The derived eigenvalue problem has a nonstandard form for determining the eigenvalues. Therefore, the problem is examined by the graphical depiction to give new insight into the eigenvalues for the building with added viscoelastic dampers. Using the present approach the exact eigenvalues can be found and also upper and lower bounds of the eigenvalues can be obtained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.11
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• pp.1820-1828
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• 2001

The dynamics of the 6-3 Stewart platform manipulator (SPM) is newly derived based on the kinematic relations particularly developed fur the SPM. The essence of the analysis is to deal with three subsystems of the SPM, each consisting of the command and feedback line links associated with two joined neighboring actuators. The dynamics of the command and feedback line links are first formulated using Lagrange and Newton-Euler method and then combined to derive the dynamic equations of motion fur the SPM. The derived nonlinear equations of motion are so computationally effective that it can be easily applied to real-time high-speed tracking control of 6-3 SPM.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.3
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• pp.106-112
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• 2000

Since the oil crisis, we have been concerned about the energy saving techniques of electric generating systems. As a part of the effort to save energy, automatic electric load sharing device was developed. Usually, ship's electric generating system consists of two or three sets of generator. And, electric generating system is operated as single or parallel operation mode according to the demanded electric power. Therefore, it is important to investigate generators operating mode for the supply of required electric power in the ship in order to decrease the operating cost. So, this paper suggests the method to solve the optimal electric load distribution problem by dynamic programming. And, this thesis indicates that the proposed method is superior to the lagrange multiplier's method in obtaining optimal load distribution solution in the ship's electric generating system.

• Nuclear Engineering and Technology
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• v.25 no.1
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• pp.102-109
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• 1993

A PC-computer program RADAP has been developed in this study to perform a quick real-time analysis of dose assessment following an accident in a nuclear facility. RADAP uses an interactive LKagrangian puff model in simulating the transport and diffusion of radioactive plume in the atmosphere. For real-time analysis, RADAP treats one or multiple puffs of ground-level releases, simultaneously. It is assumed to maintain a Gaussian distribution within the puff and the diffusion coefficients are computed using the USNRC's normal sigma curve method. The program, however, does not consider the spatial variations but the temporal variations in wind conditions. Whole body and thyroid doses for 3$\times$31 grid are directed to output files, and they are also displayed through computer graphics on VGA or EGA color monitor. The results show that RADAP can be an excellent tool for quick estimation of accidental doses.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.1
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• pp.59-70
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• 1992

Quadratic programming problems(QP) have been widely used as a direction-finding subproblem in the engineering and structural design optimization. To develop an efficient solution algorithm for the QP subproblems, theoretical aspects and numerical behavior of mathematical programming methods that can be used as QP solver are studied and compared. For the solution of both primal and dual QP, Simplex, gradient projection(GRP), and augmented Lagrange multiplier algorithms are investigated and coded. From the numerical study, it is found that the primal GRP algorithm with potential constraint strategy and the dual Simplex algorithm are more attractive and effective than the others. They have theoretical robustness as well. Moreover, primal GRP algorithm is preferable in case the number of constraints is larger than the number of design variables. Favorable features of GRP and Simplex algorithm are merged into a combined algorithm, which is useful in the structural design optimization.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.1
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• pp.9-16
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• 2014

Using a level set method and topological derivatives, a topological shape optimization method that is independent of an initial design is developed for linearly elastic structures. In the level set method, the initial domain is kept fixed and its boundary is represented by an implicit moving boundary embedded in the level set function, which facilitates to handle complicated topological shape changes. The "Hamilton-Jacobi(H-J)" equation and computationally robust numerical technique of "up-wind scheme" lead the initial implicit boundary to an optimal one according to the normal velocity field while minimizing the objective function of compliance and satisfying the constraint of allowable volume. Based on the asymptotic regularization concept, the topological derivative is considered as the limit of shape derivative as the radius of hole approaches to zero. The required velocity field to update the H-J equation is determined from the descent direction of Lagrangian derived from optimality conditions. It turns out that the initial holes are not required to get the optimal result since the developed method can create holes whenever and wherever necessary using indicators obtained from the topological derivatives. It is demonstrated that the proper choice of control parameters for nucleation is crucial for efficient optimization process.