• Journal of the Korean Data and Information Science Society
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• v.20 no.5
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• pp.829-835
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• 2009

Parameter design is an approach to reducing performance variation of quality characteristic value in products and processes. Taguchi has used the signal-to-noise ratio to achieve the appropriate set of operating conditions where variability around target is low in the Taguchi parameter design. However, there are difficulties in practical application, such as complexity and nonlinear relationships among quality characteristics and control factors (design factors), and interactions occurred among control factors. Neural networks have a learning capability and model free characteristics. There characteristics support neural networks as a competitive tool in processing multivariable input-output implementation. In this paper we propose a substantially simpler optimization procedure for parameter design using neural network. An example is illustrated to compare the difference between the Taguchi method and neural network method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.79-82
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• 2003

본 논문은 마이크로파발진기의 위상잡음 특성에 영향을 미치는 P-HEMT의 비선형 파라미터를 선정하고, 3개의 비선형 파라미터와 최소 위상잡음을 분석하였다. 분석된 P-HEMT가 저 위상잡음을 가지는 최적의 바이어스 동작점을 선정하여, 선정된 바이어스 동작점에서 두 가지 형태의 발진기를 설계하므로 서 발진기의 물리적 구조에 의한 위상 잡음의 영향을 비교하고 위상잡음의 감소방안을 제시하였으며, 이를 이용하여 ku-대역 위상동기유전체공진 발진기를 설계 제작하였다.

• Journal of Navigation and Port Research
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• v.36 no.10
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• pp.787-793
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• 2012

A hull form design technique to enhance the wave-making resistance performance for a medium size high speed Ro-Pax ship was studied introducing an optimization method and an automatic hull form modification method. SQP(sequential quadratic programming) was applied as the optimization algorithm and the geometry of hull surface was represented and modified using the NURBS(Non-Uniform Rational B-Spline). The wave-making resistance performance as an objective function in the optimization procedure was evaluated using the Rankine source panel method in which nonlinearity of the free surface boundary conditions and the trim and sinkage of the ship was fully taken into account. Using the Ro-Pax ship as a base hull, the hull-form optimization method was applied to obtain the hull shape that produced the lower wave-making resistance. To verify the validity of the hull-form optimization method, the numerical results was compared with the model test results.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.24.3-24.3
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• 2011

우주발사체를 이용하여 인공위성을 궤도에 올리는 문제에서 가장 중요시해야 할 부분은 임무의 성공, 즉 정밀한 궤도 진입이다. 이것이 만족되어졌을 때, 비용의 최소화 또한 설계 시 중요한 고려사항이 된다. 이 두 가지 문제를 동시에 해결하기 위해선 최적 제어 전략이 필요한데, 통상적으로 이 과정은 발사 전에 최적화 기법 등을 이용하여 계산되고 검증된다. 그러나 기존의 최적화 기법은 대부분 선형 시스템에 적합한 기법들 이고, 우주발사체와 같이 매우 복잡하고 강한 비선형을 가진 운동방정식을 최적화 하려면 많은 계산이 소요된다. 계산 소모 시간을 줄이기 위해서는 선형화 등의 기법이 사용되는데, 그러한 경우 최적 해에 대한 신뢰도가 낮아질 수밖에 없다. 이 논문에서는 그러한 문제를 해결하기 위해 최근 활발히 연구되고 있는 비선형 최적화 기법인 상태 의존 Riccati 방정식 기법 (SDRE)을 이용하여 인공위성을 주어진 궤도에 진입시키는 우주발사체의 최적궤도를 계산하였다. 또한 Hamiltonian 을 이용하여 산출된 궤도의 최적성을 보이고, 목표한 궤도와의 비교를 통해 제어기의 정밀성을 확인하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1996.11a
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• pp.97-104
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• 1996

DYGABCD 프로그램을 이용해 선형모델의 구성에 필요한 시스템 행렬을 구하고 최소자승법을 이용하여 실시간 선형모사를 행한 후 DYNGEN 프로그램을 이용한 비선형 모사와 비교하여 그 타당성을 입증하였다. 그리고 가제어성과 가안정성을 시험하여 시스템에 대해 제어기설계가 가능한지 확인하고 엔진의 성능과 직결되는 터빈입구 온도의 Overshoot 제어를 위해 고전적 제어기법인 PI제어기와 현대적 최적제어기법인 LQR 제어기를 설계하여 각각의 성능을 비교해 보았다.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.48-55
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• 2003

The design and analysis of a three-phase 6/8 structure SRM(switched reluctance motor) art described. The range of the stator ole arc and the rotor pole arc of the motor we analyzed in the linear region. The optimum range of the stator pole arc and the turn-off angle of the main switches in the power converter are given with the 2-D finite element electro-magnetic field calculation of the motor and the nonlinear simulation. Test results of the prototype are discussed. This type is good for high efficiency drive because the drive circuit is simple and current density and copper loss of the winding are law.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.3
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• pp.1-15
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• 1992

A Practical and easily applicable methods for the numerical analysis and the optimum design of continuous and horizontally curved two-way slab systems with twelve possible edge conditions are presented. The proposed method for the numerical structural analysis is based on the use of design moment coefficients which are derived from the elastic theory of thin curved plates. The optimum values are selected from within the feasible region in the design space defined by the limit state requirements. The sequential linear programming is introduced as an analytical method of nonlinear optimization. The optimum design variables, including a effective depth and transformed steel ratios per unit width of middle and column strips of slabs, are then determined.

• Journal of Korean Society of Steel Construction
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• v.16 no.2 s.69
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• pp.201-213
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• 2004

A GA-based optimum design algorithm and a program for plane steel frame structures with semi-rigid connections are presented. The algorithm is incorporated with the refined plastic hinge analysis method wherein geometric nonlinearity is considered by using the stability functions of beam-column members, and material nonlinearity, by using the gradual stiffness degradation model that includes the effects of residual stresses, moment redistribution through the occurrence of plastic hinges, semi-rigid connections, and geometric imperfection of members. In the genetic algorithm, the tournament selection method and micro-GAs are employed. The fitness function for the genetic algorithm is expressed as an unconstrained function composed of objective and penalty functions. The objective and penalty functions are expressed as the weight of steel frames and the constraint functions, respectively. In particular, the constraint functions fulfill the requirements of load-carrying capacity, serviceability, ductility, and construction workability. To verify the appropriateness of the present method, the optimal design results of two plane steel frames with rigid and semi-rigid connections are compared.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.12
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• pp.1165-1172
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• 2007

The spacer grid set is a part of a nuclear fuel assembly. The set has a spring and the spring supports the fuel rods safely. Although material nonlinearity is involved in the deformation of the spring, nonlinearity has not been considered in design of the spring. Recently a nonlinear response structural optimization method has been developed using equivalent loads. It is called nonlinear response optimization equivalent loads (NROEL). In NROEL, the external loads are transformed to the equivalent loads (EL) for linear static analysis and linear response optimization is carried out based on the EL in a cyclic manner until the convergence criteria are satisfied. EL is the load set which generates the same response field of linear analysis as that of nonlinear analysis. Shape optimization of the spring is carried out based on EL. The objective function is defined by minimizing the maximum stress in the spring while mass is limited and the support force of the spring is larger than a certain value. The results are verified by nonlinear response analysis. ABAQUS is used for nonlinear response analysis and GENESIS is employed for linear response optimization.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.694-699
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• 2007

The spacer grid set is a part of a nuclear fuel assembly. The set has a spring and the spring supports the fuel rods safely. Although material nonlinearity is involved in the deformation of the spring,nonlinearity has not been considered in design of the spring. Recently a nonlinear response structural optimization method has been developed using equivalent loads. It is called nonlinear response optimization equivalent loads (NROEL). In NROEL, the external loads are teansformed to the equivalent loads (EL) for linear static analysis and linear response optimization is carried out based on the EL in a cyclic manner until the convergence criteria are satisfied. EL is the load set which generates the same response no EL. The objective function is defined by minimizing the maximum stress in the spring while is limited and the support force of the spring is larger than a certain value. The results are verified by nonlinear. ABAQUS is used for nonlinear response analysis and GENESIS is employed for linear response optimization.