• Journal of the Korean Operations Research and Management Science Society
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• v.21 no.1
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• pp.1-17
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• 1996

There have been considerable researches for solving large-scale separable convex optimization ptoblems. In this paper we present a method for large-scale nonseparable smooth convex optimization problems with block-angular linear constraints. One of them is occurred in reconfiguration of the virtual path network which finds the routing path and assigns the bandwidth of the path for each traffic class in ATM (Asynchronous Transfer Mode) network [1]. The solution is approximated by solving a sequence of the block-angular structured separable quadratic programming problems. Bundle-based decomposition method [10, 11, 12]is applied to each large-scale separable quadratic programming problem. We implement the method and present some computational experiences.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.118-119
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• 2005

Recently, fire extinguishing systems based on water mists have been attracting public attentions in marine engineering. Performance of the fire extinguishing systems is influenced by the size and distribution of spayed water mists. Droplet analyzing method based on image processing technique for measuring droplet size and distribution has been developed. The morphological method based on partial curvature information of pre-processed images was adopted for recognition and separation of overlapped particles. Tested results show that the present method may be reliable for the analysis of the size and distribution of droplets produced by water mist spay flow.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.359-369
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• 1999

The paper describes the study of concurrent subspace optimization(CSSO) for coupled multidisciplinary design optimization (MDO) techniques in mechanical systems. This method is a solution to large scale coupled multidisciplinary system, wherein the original problem is decomposed into a set of smaller, more tractable subproblems. Key elements in CSSO are consisted of global sensitivity equation(GSE), subspace optimization (SSO), optimum sensitivity analysis(OSA), and coordination optimization problem(COP) so as to inquiry valanced design solutions finally, Automatic differentiation has an ability to provide a robust sensitivity solution, and have shown the numerical numerical effectiveness over finite difference schemes wherein the perturbed step size in design variable is required. The present paper will develop the automatic differentiation based concurrent subspace optimization(AD-CSSO) in MDO. An automatic differentiation tool in FORTRAN(ADIFOR) will be employed to evaluate sensitivities. The use of exact function derivatives in GSE, OSA and COP makes Possible to enhance the numerical accuracy during the iterative design process. The paper discusses how much influence on final optimal design compared with traditional all-in-one approach, finite difference based CSSO and AD-CSSO applying coupled design variables.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04b
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• pp.1037-1040
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• 2002

본 연구에서는 효율적인 학습알고리즘을 가지는 신경망 기반 독립성분분석 기법을 제안하였다. 제안된 기법은 할선법에 기초를 둔 fixed point 알고리즘의 신경망 기반 독립성분분석 기법이다. 여기서 할선법은 독립성분 상호간의 정보를 최소화하기 위해 negentropy를 최대화는 과정에서 요구되는 1차 미분에 따른 계산량을 줄이기 위함이다. 제안된 기법을 500개의 데이터를 가지는 4개 신호들로부터 임의의 혼합 행렬에 따라 발생되는 혼합신호들을 각각 대상으로 시뮬레이션 한 결과, 우수한 분리성능과 빠른 학습 속도가 있음을 확인하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.83-83
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• 2000

MBE법으로 성장시킨 Cd1-xMgxTe 박막을 조성비 (x=0, 0.23, 0.32, 0.43)에 따라 타원편광 분석기로 측정하여 연구하였다. E0 critical point energy 아래에서 나타나는 간섭무늬를 제거하기 위해 multilayer calculation을 수행했고 ellipsometric data를 2번 미분하여 계산하는 Critical Point Parabolic Band(CPPB) model을 사용하여 E0, E0+Δ0, E1, E1,+Δ1, and E0'critical point energy 들을 구할 수 있었다. 특히 E2 peak region 에서는 종전의 고상시료 (bulk)에서 측정 발표된 값보다도 매우 높고 명확한 <$\varepsilon$2>값이 측정되어, E2와 E、0 peak가 명확하게 분리되는 것을 볼 수 있었다. 또한 Mg의 조성비에 따라 critical point energy 가 linear 하게 변화됨이 관측되었다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.6 s.111
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• pp.634-642
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• 2006

For the analysis of dynamic contact between a catenary and a pantograph of high-speed electrical train, the numerical solution of the equations of motion of the vehicle pantograph and the catenary system subjected to the contact condition is obtained. The whole equations of motion of the catenary and the pantograph are simultaneously time integrated with the strict application of the contact condition. For the stability of the numerical solution, with the cubic spline interpolation of the catenary displacement, the velocity and acceleration constraints as well as the displacement constraint are imposed on the contact point. Especially it is shown that the Coriolis and centripetal accelerations are critical for the accuracy and stability of the computation.

• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.295-301
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• 2015

A theoretical analysis was carried out to examine the concentration behavior of methane from a biogas using a polysulfone membrane. After the governing equations were derived for the cocurrent flow mode in a membrane module, the coupled nonlinear differential equations were numerically solved with the Compaq Visual Fortran 6.6 software. At the typical operating condition of mole fraction of 0.7 in a feed stream, the mole fraction of methane in the retentate increased to 0.76 while the normalized retentate flow rate to the feed flow rate decreased from 1 to 0.79. When either the mole fraction of methane in a feed increased or the pressure of the feed stream increased, the methane mole fraction in the retentate increased. On the other hand, it was found that as either the membrane area decreased or the ratio of the permeate pressure to the feed pressure increased, the methane mole fraction in the retentate decreased. In case that the stage cut increased, the methane mole fraction in the retentate increased while the recovery of methane slightly decreased.

• The KIPS Transactions:PartB
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• v.13B no.1 s.104
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• pp.27-34
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• 2006

In this study, we propose this new algorithm that generates score function in ICA(Independent Component Analysis) using entropy theory. To generate score function, estimation of probability density function about original signals are certainly necessary and density function should be differentiated. Therefore, we used kernel density estimation method in order to derive differential equation of score function by original signal. After changing formula to convolution form to increase speed of density estimation, we used FFT algorithm that can calculate convolution faster. Proposed score function generation method reduces the errors, it is density difference of recovered signals and originals signals. In the result of computer simulation, we estimate density function more similar to original signals compared with Extended Infomax and Fixed Point ICA in blind source separation problem and get improved performance at the SNR(Signal to Noise Ratio) between recovered signals and original signal.

• Applied Biological Chemistry
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• v.28 no.3
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• pp.149-155
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• 1985

590 strains of Rhizobia were isolated from root nodules of the legumes collected at 223 sites in Korea. According to their host specificities they were classified into R. japonicum(218 strains), R. phaseoli(101 strains), R. trifolii(97 strains), R. meliloti(4 strains), R. leguminosarium(1 strain), Rhizobium species(101 strains), and unidentified species(159 strains). 3 potent strains R-138, R-168, and R-214 of R. japonicum have been selected based on the infectivity to soybean cultivar and effeciency of nitrogen fixation. It was observed that the fast-growing strains of R. japonicum contained 1 to 4 plasmids of M.W. of 35-300 Md. However, plasmids were hardly detected for the slow-growing strains.

• Nuclear Engineering and Technology
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• v.14 no.2
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• pp.78-85
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• 1982

The steady-state rotation of plasma centrifuge is theoretically analyzed to understand the physics of rotating plasmas and its feasibility for isotope separation. The centrifuge system under consideration consists of an annular gap between coaxial cylindrical anode and cathode in the presence of an externally-applied axial magnetic field. A problem for coupled partial differential equations describing centrifuge fields is formulated on the basis of the magnetohydrodynamic equations. Two-dimensional solutions are found analytically in the form of Fourier-Bessel series. The current density and velocity distributions are discussed in terms of the Hartmann number and the geometrical parameter of the system. At typical conditions, rotational speeds of the plasma up to the order of 10$^4$m/sec are achievable, and increase either with increasing Hartmann number, or with increasing ratio of the axial length to the inner radius of the cylinder. In view of much higher speeds of rotation which can be achieved in plasma centrifuge, it is expected that its efficiency is superior to mechanically driven gas centrifuges.