• Journal of Institute of Control, Robotics and Systems
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• v.17 no.3
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• pp.241-247
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• 2011

This paper is intended to improve efficiency of two-phase BLDC motor using analytical and statistical methods, and then the stability of the starting for the designed model is investigated. The characteristics of the motor according to magnetization directions of permanent magnet are analyzed through the analytical method, and design variables that affect the efficiency are selected. Preliminary optimal design is performed using the analytical method with the design variable. The RSM (Response Surface Method) based on the FEA (Finite Element Analysis) is applied to complement errors of the analytical method. As a result, the optimal design is determined. Finally, the stability of the starting for the optimal designed model is evaluated by analyzing cogging torque, and it is verified through the FEA.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.905-908
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• 2009

In the management of groundwater in coastal areas, saltwater intrusion associated with extensive groundwater pumping, is an important problem. The groundwater optimization model is an advanced method to study the aquifer and decide the optimal pumping rates or optimal well locations. Cheng and Park gave the analytical solutions to the optimization problems basing on Strack's analytical solution. However, the analytical solutions have some limitations of the property of aquifer, boundary conditions, and so on. A simulation-optimization numerical method presented in this study can deal with non-homogenous aquifers and various complex boundary conditions. This simulation-optimization model includes the sharp interface solution which solves the same governing equation with Strack's analytical solution, therefore, the freshwater head and saltwater thickness should be in the same conditions, that can lead to the comparable results in optimal pumping rates and optimal well locations for both of the solutions. It is noticed that the analytical solutions can only be applied on the infinite domain aquifer, while it is impossible to get a numerical model with infinite domain. To compare the numerical model with the analytical solutions, calculation of the equivalent boundary flux was planted into the numerical model so that the numerical model can have the same conditions in steady state with analytical solutions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.301-309
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• 1995

Shape optimal design of an excavator boom to minimize weight can be formulated as a nonlinear programming problem with an automesh refinement carried out by using the finite element method. The design variables are the radii and the coordinates of the circle to describe the excavator boundary shape. In addition to the displacement and stress constraints, geometric constraints are imposed such that the nodes cannot cross the certain range. The optimum design is obtained by using the PLBA nonlinear programming code. The sensitivity derivatives are calculated using the semi-analytical scheme. Numerical results of an excavator boom show potential for weight reduction of 4.4%(65.6 kgf) when considering the displacement, stress and geometric constraints.

• Journal of Environmental Health Sciences
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• v.35 no.5
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• pp.402-410
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• 2009

This study was carried out to examine the optimal analytical method for determination of urinary toxic arsenic (inorganic arsenic and its metabolites) by HG-AAS (hydride generation-atomic absorption spectrometry). In the analysis of SRMs (standard reference materials), method E (addition of 0.4% L-cysteine to pre-reductant and use 0.04M HCl as carrier acid) showed the most accurate results compared with the reference values. In the analysis of 30 urinary samples, analytical results were significantly different depend on the component of pre-reductant and the concentration of carrier acid. When the concentration of carrier acid was higher, the analytical result was lower. The recovery rates of MMA (monomethylarsonic acid) and DMA (dimethylarsenic acid) were varied by the concentration of pre-treatment acid and carrier acid and hydride generation reagents. When the concentration of carrier acid was 1.62 M (5% HCl), the recovery rates of DMA was 1%. The recovery rates of MMA and DMA in method E (=V) were 102% and 100%, respectively. The results of this study suggest that the component and concentration of pre-reductant and carrier acid must be carefully adjusted in the analysis of urinary arsenic, and method E is recommendable as the most precise analytical method for determination of urinary toxic arsenic.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.581-586
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• 2009

This paper presents an optimal design of magnetorheological(MR) damper based on analytical methodology and finite element analysis. The proposed MR damper consists of MR valve and gas chamber. The MR valve is constrained in a specific volume and the optimization problem identifies geometric dimensions of the valve structure that maximize the pressure drop of the MR valve or damping force of the MR damper. In this work, the single-coil annular MR valve structure is considered. After describing the schematic configuration and operating principle of MR valve and damper, a quasi-static model is derived based on Bingham model of MR fluid. The magnetic circuit of the valve and damper is then analyzed by applying the Kirchoff’s law and magnetic flux conservation rule. Based on the quasi-static modeling and the magnetic circuit analysis, the optimization problem of the MR valve and damper is built. The optimal solution of the optimization problem of the MR valve structure constrained in a specific volume is then obtained and compared with the solution obtained from finite element method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.11
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• pp.1110-1118
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• 2009

This paper presents an optimal design of magnetorheological(MR) damper based on analytical methodology and finite element analysis. The proposed MR damper consists of MR valve and gas chamber. The MR valve is constrained in a specific volume and the optimization problem identifies geometric dimensions of the valve structure that maximize the pressure drop of the MR valve or damping force of the MR damper. In this work, the single-coil annular MR valve structure is considered. After describing the schematic configuration and operating principle of MR valve and damper, a quasi-static model is derived based on Bingham model of MR fluid. The magnetic circuit of the valve and damper is then analyzed by applying the Kirchoff' s law and magnetic flux conservation rule. Based on the quasi-static modeling and the magnetic circuit analysis, the optimization problem of the MR valve and damper is built. The optimal solution of the optimization problem of the MR valve structure constrained in a specific volume is then obtained and compared with the solution obtained from finite element method.

• Journal of the Korea Society for Simulation
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• v.10 no.3
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• pp.83-94
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• 2001

In this paper, the consumable spare parts requirement determination problem of newly procured equipment systems is considered. The problem is formulated as the cost minimization problem with operational availability constraint. Assuming part failure rate is constant during operational period, an analytical method is developed to obtain spare part requirements. Since this solution tends to overestimate the requirements, a fast search simulation procedure is introduced to adjust it to the realistic solution. The analytical solution procedure and the simulation procedure are performed recursively until a near optimal solution is achieved. The experimental results show that the near optimal solution is approached in a fairly short amount of time.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.156-161
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• 1994

In this paper, we consider an optimal control problem of a nonlinear stochastic system. Dynamic programming approach is employed for the formulation of a stochastic optimal control problem. As an optimality condition, dynamic programming equation so called the Bellman equation is obtained, which seldom yields an analytical solution, even very difficult to solve numerically. We obtain the numerical solution of the Bellman equation using an algorithm based on the finite difference approximation and the contraction mapping method. Optimal controls are constructed through the solution process of the Bellman equation. We also construct a test case in order to investigate the actual performance of the algorithm.

• Smart Structures and Systems
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• v.33 no.1
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• pp.27-39
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• 2024

The effectiveness of conventional tuned liquid dampers (TLDs) in controlling the wind-induced response of tall flexible structures has been indicated. However, the impaired control effect in the detuning condition or a considerably high mass cost of liquid may be incurred in ensuring the high-level serviceability. To provide an efficient TLD-based solution for wind-induced vibration control, this study proposes a serviceability-oriented optimal design method for isolated TLDs (ILDs) and derives analytical design formulae. The ILD is implemented by mounting the TLD on the linear isolators. Stochastic response analysis is performed for the ILD-equipped structure subjected to stochastic wind and white noise, and the results are considered to derive the closed-form responses. Correspondingly, an extensive parametric analysis is conducted to clarify a serviceability-oriented optimal design framework by incorporating the comfort demand. The obtained results show that the high-level serviceability demand can be satisfied by the ILD based on the proposed optimal design framework. Analytical design formulae can be preliminarily adopted to ensure the target serviceability demand while enhancing the structural displacement performance to increase the safety level. Compared with conventional TLD systems, the ILD exhibits higher effectiveness and a larger frequency bandwidth for wind-induced vibration control at a small mass ratio.

• Journal of Astronomy and Space Sciences
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• v.16 no.2
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• pp.167-176
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• 1999

The optimal initial inclination for minimizing the variation of the Local Time of Ascending Node(LTAN) during the three year mission of the KOMPSAT is investigated. At first, the analytical equation for the inclination change by the Sun is derived and the optimal initial inclination by analytical method is derived. Then the analytically derived optimal inclination is checked by the numerical orbit propagation with including all major perturbations. Four different cases of the initial orbital elements are used for monitoring the LTAN variation of the LTAN. Therefore, a new optimal initial inclination by numerical orbit propagation for the KOMPSAT is found. In addition, the variations of the mean and osculating semi-major axis are investigated with the different atmospheric density values. The mean eccentricity vs. argument of perigee diagram for the frozen orbit is obtained.