• Journal of the Microelectronics and Packaging Society
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• v.6 no.2
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• pp.31-36
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• 1999

An efficient method for thermal modeling of QFP is Proposed. Thermal measurement data are given to verify the method. In parallel with the experiment, an exact full 3-D model calculation is also provided. One fonds that there is an excellent agreement between validation data and the efficient model data.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.157-160
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• 1989

The most serious difficulty in using the finite element method is the appearance of the so-called spurious, nonphysical modes. We have proposed the finite element formulation of the variational expression in the three-component magnetic field based on Galerkin's method. In this approach, the divergence relation H is satisfied and spurious modes does not appear and finite-element solutions agree with the exact solutions.

• Bulletin of the Korean Chemical Society
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• v.7 no.4
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• pp.271-275
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• 1986

The Smoluchowski equation with a step potential is solved in one-dimensional case and three-dimensional case with spherical symmetry. Exact analytic expressions for the solution and the remaining probability are obtained in one-dimensional case for the reflecting boundary condition and the long time behavior of the remaining probability is compared with the earlier work. In three-dimensional case, only the long time behavior is evaluated. More general case with the radiation boundary condition is also investigated and the results are shown to approach correct limits of the reflecting boundary condition.

• Journal of the Korean Mathematical Society
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• v.59 no.1
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• pp.171-192
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• 2022

For any category with a distinguished collection of sequences, such as n-exangulated category, category of N-complexes and category of precomplexes, we consider its Grothendieck group and similar results of Bergh-Thaule for n-angulated categories [1] are proven. A classification result of dense complete subcategories is given and we give a formal definition of K-groups for these categories following Grayson's algebraic approach of K-theory for exact categories [4].

• Journal of Korean Society of Industrial and Systems Engineering
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• v.35 no.2
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• pp.57-63
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• 2012

Software release planning model of software product lines was formulated as a precedence-constrained multiple 0-1 knapsack problem. The purpose of the model was to maximize the total profit of an entire set of selected features in a software product line over a multi-release planning horizon. The solution approach is a dynamic programming procedure. Feasible solutions at each stage in dynamic programming are determined by using backward dynamic programming approach while dynamic programming for multi-release planning is forward approach. The pre-processing procedure with a heuristic and reduction algorithm was applied to the single-release problems corresponding to each stage in multi-release dynamic programming in order to reduce the problem size. The heuristic algorithm is used to find a lower bound to the problem. The reduction method makes use of the lower bound to fix a number of variables at either 0 or 1. Then the reduced problem can be solved easily by the dynamic programming approaches. These procedures keep on going until release t = T. A numerical example was developed to show how well the solution procedures in this research works on it. Future work in this area could include the development of a heuristic to obtain lower bounds closer to the optimal solution to the model in this article, as well as computational test of the heuristic algorithm and the exact solution approach developed in this paper. Also, more constraints reflecting the characteristics of software product lines may be added to the model. For instance, other resources such as multiple teams, each developing one product or a platform in a software product line could be added to the model.

• Korean Journal of Head & Neck Oncology
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• v.15 no.2
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• pp.172-176
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• 1999

Background: An increasing number of traumatic, infectious, degenerative, benign, and malignant lesions of the clivus and cervical spine are treated by head and neck surgeons. Surgical techniques vary according to the exact level of the lesion. Objectives: The purpose of this article are to introduce the surgical approach and to discript our experience and to analyze the advantage of the each methods. Materials and Methods: Transpalatal approach in clivus chordoma, transoral approach in C2 fibrous dysplasia, trans mandibular approach in clivus meningioma and transcervical approach in neulilemmoma were reviewed from the medical record. Results: Postoperative complications occured. Otitis media with effusion were observed in transoral and trans mandibular approach. Cranial nerve paralysis was observed in transcervical approach. But other complications such as swallowing difficulty persisting over 6 weeks, malunion of mandible, orocutaneous fistula, hemorrhage from major vessel were not observed. Conclusion: The various surgical techniques to be described herein serve to give the best exposure of each level of the lesions. Therefore head and neck surgeon plays a major role in the treatment of lesion in the clivus and anterior cervical spine according to the lower incidence of postoperative morbidity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.811-825
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• 1998

An approximate line search is presented for dynamic response optimization with Augmented Lagrange Multiplier(ALM) method. This study empolys the approximate a augmented Lagrangian, which can improve the efficiency of the ALM method, while maintaining the global convergence of the ALM method. Although the approximate augmented Lagragian is composed of only the linearized cost and constraint functions, the quality of this approximation should be good since an approximate penalty term is found to have almost second-order accuracy near the optimum. Typical unconstrained optimization algorithms such as quasi-Newton and conjugate gradient methods are directly used to find exact search directions and a golden section method followed by a cubic polynomial approximation is empolyed for approximate line search since the approximate augmented Lagrangian is a nonlinear function of design variable vector. The numberical performance of the proposed approach is investigated by solving three typical dynamic response optimization problems and comparing the results with those in the literature. This comparison shows that the suggested approach is robust and efficient.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.264-270
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• 2002

This paper presents roughness effects on flow characteristics and efficiency of multi-stage axial compressor using numerical simulation. which is carried out with a commercially available software, CFX-TASCflow. In this paper, the third of four stages of GE low pressure compressor is considered including me stator and rue rotor. Mixing-plane approach is adopted to model the interface between the stator and the rotor: it is appropriate for steady state simulation. First, a flat plate simulation was performed to validate how exact the numerical simulation predicts the roughness effect for smooth and rough walls. Then GE compressor model was calculated about at each roughness height. Concluding, very small roughness height largely affects the performance of compressor and the increasing rate of loss decrease as roughness height increase.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.1967-1973
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• 1994

The free vibration of a thin plate with three different boundary conditions is discussed in this paper. A semi-analytical approach to the plate problems has been exploited using computer algebra system(CAS). The approximate solutions are assumed as algebraic polynomials that satisfy the appropriate boundary conditions. In order to solve problems, Galerkin method is used, which is known as an ineffective tool for practical engineering problems, being involved with a large number of multiple integration and differentiation. All the admissible functions used in this paper are generated automatically by CAS otherwise a tedious algebraic manipulations should be done by hand. One, six and fifteen-term solutions in terms of frequency parameters are presented and compared with exact solutions. Even using one-term solution, the comparison with existing data shows good agreement and accuracy of the present method.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.352-357
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• 2002

Some interaction characteristics, i.e., light scattering characteristics, of infrared (IR) radiation with small ice crystals are investigated systematically by using the exact T-matrix approach. Some important facts are obtained, which reveal, especially, that the combination of both the 25 and 3.979$\mu$m together has some advantages and potential applications for remote sensing of cirrus and other ice clouds. A new far-IR channel at the wavelength of 25$\mu$m is proposed.