• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.22-22
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• 2010

배기속도 2500 L/s, 최고진공도 $10^{-10}$ mbar를 구현할 대용량 복합 분자펌프 설계를 위한 3차원 유동해석을 실시하였다. 진공도가 $10^{-5}$ mbar 이상이 되는 고진공도에서는 Knudsen 수가 $10^2{\sim}10^7$에 이르러 분자간 충돌을 거의 무시할 수 있게 되며, 이때의 유체해석 방법으로서는 통상 희박기체 해석법으로 많이 쓰이는 Direct simulation Monte Carlo 방법보다, 충돌이 없는 분자의 자유운동을 모사하는 Monte Carlo 방법이 더 적합하게 된다. 본 연구에서는 다단계 rotor와 stator로 구성되는 복합분자 내 유동장에 Monte Carlo 해석법을 적용하여 유동해석을 실시하였다. 먼저 2차원 해석을 실시하여 분자펌프의 성능에 중요한 영향을 미치는 설계변수들을 도출하고, 이 설계변수들의 최적값을 다양한 3차원 유동해석을 통해 도출하였다. 해석결과는 펌프설계에 적용되어 펌프 성능시험결과를 통해 확증된다.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.4
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• pp.861-866
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• 2012

The distance optimizing between coil and magnetic materials never be specified in the magnetic materials acceleration using the coil till now. We can know to be the distance which optimizes when being in the half position about the distance of intercoil by the result of the max point on the Differential calculus. Whether several top and bottom current segment coil structures were made and the steel ball in which the current segment coil structure is the magnetic materials could be accelerated in the optimizing distance or not confirmed. When the coil valley current about the mass of the steel ball was known as the experiment and it was but to be the nose consequently it applied to the magnetic materials and magnetic fluid, the optimal distance was solved between the coil and material.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1992.04b
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• pp.457-465
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• 1992

현재 또는 장래에 예견되는 거의 모든 통신서비스를 통합적으로 제공할 수 있는 B-ISDN환경하에서 음성통화와 비디오정보, 데이타들이 각기 다른 bit rate와 서비스 요구조건(통화시간, 질등)를 가지고 전송서비스를 받으려 하기때문에 매우 다양한 서비스들의 조합을 고려하여 교환시스팀을 구현해야 한다. B-ISDN에 적합한 전송기술로서 ATM(Asynchronous Transfer Mode)이 일반적으로 제안되고 있는데 이미 10여종의 독특한 ATM시스팀들이 이론적, 실험적 연구단계를 거쳐 거의 실용화 단계까지 이르렀다고 주장되고 있다. 본 논문에서는 ATM교환시스팀의 설계요건과 비교기준을 제시하여 설계 대자인을 주어진 기술제약하에 최적화 할 수 있는 조건을 제시한다. 이때 우선 기본 스위치의 구조를 단단계로 할 것인가 다단계로 할 것인가에 대한 정량적, 확률적인 비교가 행해지고 특히 이미 많은 ATM스위치에서 채택되고 있는 Banyan형태의 망의 성능분석을 보다 현실에 근접하게 할 수 있는 이산적 마코프체인에 의한 모형과 계산방법이 확립된다. 이를 통해 단위스위치내부에 버퍼의 유무, 버퍼를 두는 위치, 또한 버퍼사이즈에 의한 영향등이 세부적으로 분석된다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.144-151
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• 2003

In this paper, an optimum design problem for endosseous implant in dentistry is studied to find best implant design. An optimum design problem is formulated to reduce stresses arising at the cortical as well as cancellous bones, in which sufficient design parameters are chosen fur design definition that encompasses major implants in popular use. Optimization at once (OAO) with the large number of design variables, however, causes too costly solution or even failure to converge. A concept of multilevel optimization (MLO) is employed to this end, which is to group the design variables of similar nature, solve the sub-problem of smaller size fur each group in sequence, and this is iterated until convergence. Each sub-problem is solved based on the response surface method (RSM) due to its efficiency for small sized problem. Favorable solution is obtained by the MLO, which is compared to both solutions made by RSM and sequential quadratic programming (SQP) in the OAO problem.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2055-2067
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• 1997

Values of process parameters in sheet metal forming can be estimated by various one-step inverse methods. One-step inverse methods based on deformation theory, however, cause some amount of error. The amount of error is generally increased as the deformation path becomes more complex. As a remedy, a new three dimensional multi-step inverse method is introduced for optimum design of blank shapes and strain distributions from desired final shapes. The approach extends a one-step inverse method to a multi-step inverse method in order to reduce the amount of error. The algorithm developed is applied to square cup drawing to confirm its validity by demonstrating reasonably accurate numerical results. Rapid calculation with this algorithm enables easy determination of an initial blank of sheet metal forming.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.2
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• pp.251-256
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• 2006

In this paper we consider multi-stage, multi-product production, inventory systems which have assembly-tree-structure. We propose a new mathematical model for pull type ordering systems based on JIT manufacturing systems. To apply the model to an actual automobile parts manufacturer, the objective of proposed model is to minimize the sum of inventory and setup costs. Finally, a numerical example and computational results are given to illustrate the proposed model.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.1
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• pp.130-136
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• 1998

A procedure of stress and strength analysis has been proposed for the centrifuge rotor of composite materials of quasi-isotropic laminates. The goal in this study is to maximize the allowable rotating speed, that is, to minimize maximum strength ratio with the given path length by changing the geometric parameter-outer radius and ply angles in quasi-isotropic laminates. Optimum values of the geometric parameter-outer radius and ply angles are obtained by multilevel optimization. All the geometric dimensions and stresses are normalized such that the result can be extended to a general case. Two dimensional analysis at each cross section with an elliptic tube hole subjected to internal hydrostatic pressures by samples as well as the centrifugal body forces has been performed along the height to calculate the stress distribution with the plane stress assumption, and Tsai-Wu failure criterion is used to calculate the strength ratio. The maximum allowable rotating speed can be increased by changing the radii of the outer surface along the height with the maximum strength ratio under the unit value : The optimal number of ply angles maximizing the allowable rotating speed in quasi-isotropic laminates is found to be the half number of tube hole, and the optimal laminate rotation angle is the half of $[{\pi}/m]$. A $[{\pi}/3]$ laminate, for instance, is stronger than a $[{\pi}/4]$ laminate for the centrifuge rotor of 6 tube hole number even though they have the same stiffness.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.2035-2042
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• 1997

We consider the design of soft decision functions for each stage of multistage detection for coherent demodulation in an asynchronous code-division multiple-access(CDMA) system. In particular, the sigmoid function, which is shown to be optimal under the mean square error(MSE) criterion, andmultilevel quantizers that best approximate the sigmoid function are derived. At each stage of multistage detection, the parameters of these decision functions are adjusted depending on estimated input statistics. Computer simulation results demonstrate that multistage detectors employing these soft decision functions perform considerably better than those with hard decision.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.215-215
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• 2012

사회는 우리의 예상보다 빠르게 혹은 느리게 발전할 수 있고, 정부의 법령이나 규정은 때때로 수정되며, 대중의 선호도나 정서 등도 시시각각 변화한다. 이러한 불확실하고 변화가 많은 환경하에서 수자원기술자들은 시스템의 구축에 있어서 종종 딜레마에 직면하게 된다. 즉, 언제(when), 얼마만한(how big) 규모의 시스템을 구축해야 불투명한 미래에 충분히 대비할 수 있을까란 의문이 바로 그것이다. 시스템의 계획단계(planning stage)에서 시스템과 관련된 여러 가지 불확실성을 고려할 수 있는 가장 강력하면서 또한 직감적인 방법은 바로 여러 가지 미래에 대한 가상 시나리오(scenario)를 구성하여 그것에 대비하는 방법이다. 최근 들어 시나리오에 기반한 시스템 플래닝 기법이 수자원분야에서 주목을 받고 있다. 미래에 발생 가능한 여러 가지 시나리오를 고려하여 구축된 시스템은 그 자체로 유연성을 발휘하여 미래에 발생할 수 있는 (예측에 어긋난) 다양한 변화에도 큰 사회적인 혼란 없이 최소의 추가비용만으로도 본래의 역할을 수행해 나갈 수 있다. 본 연구에서는 최적화 기법을 시나리오 플래닝 기법 (scenario planning technique)과 접목하여 분산형 용수공급 시스템(decentralized water supply system)의 최적설계에 적용하였다. 대상지역은 미국의 대표적인 준사막지역의 하나인 애리조나주에 위치한 투산시의 통합 물공급시스템으로 향후 20년을 대비한 시스템의 최적화에 본 연구에서 제안된 기법을 적용하여, 그 결과를 정리하였다.

• Journal of Korea Water Resources Association
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• v.31 no.3
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• pp.327-335
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• 1998

The distribution network is an essential part of all water supply systems. The cost of this portion of any sizable water supply system may amount to most of the entire cost of the project. This study tried to reduce the cost of the distribution system through optimization in system design. To determine pipe diameter considered in water distribution system design, a iterative procedure linked the flow analysis model and optimization model was used. Linear theory was introduced to analyze flowrate and revised-simplex method based on linear programming is used to optimize pipe diameter. This model was applied to wter distribution system with 22 and 35 pipes, and rapidly determine optimized commercial pipe diameters. Keywords : water distribution system, revised simplex method, optimum pipe diameters.