• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.04a
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• pp.119-126
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• 2004

A continuum-based design sensitivity analysis and topology optimization methods are developed for power flow analysis. Efficient adjoint sensitivity analysis method is employed and further extended to topology optimization problems. Young's moduli of all the finite elements are selected as design variables and parameterized using a bulk material density function. The objective function and constraint are an energy compliance of the system and an allowable volume fraction, respectively. A gradient-based optimization, the modified method of feasible direction, is used to obtain the optimal material layout. Through several numerical examples, we notice that the developed design sensitivity analysis method is very accurate and efficient compared with the finite difference sensitivity. Also, the topology optimization method provides physically meaningful results. The developed is design sensitivity analysis method is very useful to systematically predict the impact on the design variations. Furthermore, the topology optimization method can be utilized in the layout design of structural systems.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.2825-2836
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• 1994

The engineering optimization has been developed for the automatic design of engineering systems. Since the conventional optimum is determined without considering noise factors, applications to practical problems can be limited. Current design practice tends to account for these noises by the specification of closer tolerances or the use of safety factors. However, these approaches may be very expensive. Thus the consideration on the noises of design variables is needed for optimal design. A method is presented to find robust solutions for unconstrained optimization problems. The method is applied to discrete and continuous variables. The orthogonal array is utilized based on the Taguchi concept. Through mathematical proofs and numerical examples, it is verified that solutions from the suggested method are more insensitive than the conventional optimum within the range of variations for design variables.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.225-228
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• 2005

In this paper, an example of nonlinear analysis for partial prestressing design is presented. For partial prestressing design, the stress redistribution, after concrete cracking has occurred, should be accurately investigated by nonlinear analysis tools. Direct and iterative methods of nonlinear analyses were adopted for the tender design of the Incheon Bridge viaducts. Stress variations in the prestressing tendons and reinforcing bars were investigated and presented in this paper for both the in-service condition and during construction.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.205-209
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• 2000

The performances of cascade-type thermoelectric modules are analysed by numerical simulations. The geometrical variations are used as design parameters.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.628-631
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• 1992

The position control for DC motor under the unpredictable load variations is presented. Neural network controller trained to deal with this problem provide the estimates of system parameters. Pole placement is also performed in accordance with them. The proposed method is validated through computer simulation.

• Korean Journal of Hydrosciences
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• v.1
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• pp.15-25
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• 1990

Spatially varied unsteady flow in a groave-like channel of a sloping roof is analyzed by numerical solution of Saint Venant equations. Depth variations are discussed with different slopes and bed roughness of the channel. Time to equilibrium is found to be inversely proportional to the kinematic flow number. The design of roof drainage system by different schemes is included.

• Journal of Ocean Engineering and Technology
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• v.14 no.2
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• pp.112-116
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• 2000

To determine a preliminary hull form with a minimum viscous resistance this study considers the systematic variations of full form and calculations of the viscous resistance for varied hull forms. A preliminary hull form can be determined from a parametric study of viscous resistance.

• The Research Journal of the Costume Culture
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• v.24 no.5
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• pp.617-625
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• 2016

In women's clothing the shoulders are distorted and exaggerated. Consequently, the wearers' bodies are transformed and interpreted according to modern standards. We therefore refer to this aspect of women's clothing as the power shoulder. This study aims to analyze the differences in sensibility images on variations in the shoulder shape of power shoulder jackets. Nine samples were examined that involved combinations of three variations of the shoulder height and three variations of the shoulder width. The data was evaluated by 123 fashion design majors. Four factors were selected: attractiveness, personality, activity, and self-respect. Among these factors, attractiveness is the most important. The study results indicated that changes in shoulder height acted as a major effect that had an independent influence on all four factors. In contrast, changes in shoulder width acted as a major effect that had an independent influence on attractiveness, personality, and activity but not on self-respect. It also had an influence on the interaction effect of attractiveness, personality, activity, and self-respect. We anticipate that this study will help individual customers select clothing that is suitable for their preference and body shape because it is now possible for them to estimate images of power shoulder jackets.

• The KSFM Journal of Fluid Machinery
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• v.18 no.4
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• pp.30-35
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• 2015

This study analyzed the variations in the performance and operation of a 200 kW class micro gas turbine according to performance degradation of compressor and turbine. An in-house code, developed by the present authors and presented in the first part of these series of papers, were used for the analysis. The degradation of compressor and turbine were simulated by modifications in the their performance maps: mass flow rate, pressure ratio and efficiency were decreased from the reference values. Firstly, the variations in the operating conditions (air flow rate, pressure ratio) were predicted for the full load condition. Then, the same analysis were performed for a wide partial load operating range. The change in engine's performance (power output and efficiency) due to the component degradation was predicted. In addition, the change in the compressor surge margin, which is an important indicator for safe engine operation, was evaluated.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.559-563
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• 1991

Permanent magnet synchronous motor (PMSM) is receiving increased attention for servo drive applications in recent years because of its high torque to inertia ratio, superior power density and high efficiency. Vector-controlled PMSM has the same operating characteristics as separately excited dc motor. The drive system of servo motor is requested to have an accurate response for the speed reference and a quick recovery for the disturbance such as load torque. However the dynamics of PMSM drive change greately by parameter variations. Morever, when the unkown and inaccessible disturbances are imposed on PMSM, the drive system is given a significant effect by them. As a result, the drive system with both a fast drive performance and a reduced sensitivity to parameter variations is requested. In this paper, the robust control system of PMSM with torque feedforward using load torque observer is presented. In the proposed system, load torque is estimated by the reduced order observer, and the robust control system against load torque variation is realized using the torque feedforward. Moreover, the design of speed controller with the torque observer is discussed. Simulation results show that the proposed method is effective for suppression of parameter variations and load disturbance.