• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.384-387
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• 2003

A new Direct Nonlinear Strut-Tie Model design method performing iterative calculations using secant stiffness was developed. Since basically the proposed design method uses elastic analysis, it has the advantages of convenience and stability in numerical analysis. At the same time, the proposed design method can accurately estimate the strength and ductility demands on the members because it analyzes the inelastic behavior of structure using iterative calculation. In the present study, the procedure of the proposed design method was established, and a computer program incorporating the proposed method was developed. The proposed design method, as an integrated method of analysis and design, can address the earthquake design strategy devised by the engineer, such as ductility limit on each member. Through iterative calculations on the structure preliminary designed with member sizes, the strength and ductility demands of each member can be estimated so that they satisfy the given design strategy, and as the result economical and safe design is achieved.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1549-1557
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• 2018

Optimizing the design of large-scale electric machines based on nonlinear finite element analysis (FEA) requires longer computation time than other applications of FEA, mainly due to the huge size of the machines. This paper addresses a new region decision method (RDM) with mesh adaptive direct search (MADS) for the optimal design of wind generators in order to reduce the computation time. The validity of the proposed algorithm is evaluated using Rastrigin and Goldstein-Price benchmark function. Moreover, the algorithm is employed for the optimal design of a 5.6MW interior permanent magnet synchronous generator to minimize the torque ripple. Additionally, mechanical stress analysis as well as electromagnetic field analysis have been implemented to prevent breakdown caused by large centrifugal forces of the modified design.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1590-1595
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• 2003

Direct drive servovalve(DDV) is a kind of one-stage valve since the rotary motion of DC motor is directly transferred to the linear motion of valve spool through the link. Since the structure of DDV is simple, it is less expensive, more reliable and offers reduced internal leakage and reduced sensitivity to fluid contamination. However, the flow force effect on the spool motion is significant such that it induces large steady-state error in a step response. If the proportional control gain is increased to reduce the steady-state error, the system becomes unstable. In order to satisfy the system design requirements, the lead-lag controller is designed using the complex method that is one kind of constrained direct search method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1719-1726
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• 2004

Direct drive servovalve(DDV) is a kind of one-stage valve because the main spool valve is directly driven by the DC motor. Since the structure of DDV is simple, it is less expensive, more reliable and offers reduced internal leakage and reduced sensitivity to fluid contamination. However, the flow force effect on the spool motion is significant such that it induces large steady-state error in a step response. If the proportional control gain is increased to reduce the steady-state error, the system becomes unstable. In order to satisfy the system design requirements, the lead-lag controller is designed using the complex method that is one kind of constrained direct search method.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.398-401
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• 2001

There are two methods to calculate design sensitivity such as direct differentiation method and adjoint method. A sort of direct differentiation method for design sensitivity analysis costs too much when number of design variables is much larger than the number of response functions whose design sensitivity analyses are required. Therefore, an adjoint method is suggested for the case that the dimension of design variables is lager than the number of response function. An adjoint method is required to compute adjoint variables from the simultaneous linear system equation, the so-called adjoint equation, requiring only the eigenvalue and its associated eigenvectors for mode being differentiated. This method has been extended to the repeated eigenvalue problem. In this paper, we propose an adjoint method for deign sensitivity analysis of damped vibratory systems with distinct eigenvalues.

• Proceedings of the Korea Society for Simulation Conference
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• 1999.04a
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• pp.212-216
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• 1999

We propose a method for simulation optimization using stochastic genetic algorithm(GA) to get the best design and operating policies in a Direct-Input-Output Automated Manufacturing System (DIOMS).

• Transactions of The Korea Fluid Power Systems Society
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• v.1 no.4
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• pp.1-8
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• 2004

The optimum design parameters of several hydraulic systems are obtained using the complex method that is one kind of constrained direct search method. First, the parameters of lead-lag controller of the direct drive servovalve is designed using the complex method to satisfy the steady-state error requirement. Second, the optimum locating point of hydraulic cylinder Is determined to minimize the cylinder force in the operation range of rotational sluice gate. For the third application case, the optimum piston area of hydraulic cylinder is determined to minimize the man power to elevate the manually operated sluice gate.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.559-564
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• 2002

Cross-talk cancellation, inverse filter design or deconvolution in a generic term, is a vital process for a virtual sound realization in the stereo sound reproduction system. Most, if not all, of the design algorithms available for the inverse filter are based on a linearized model of the real physical plant. The result of such a plant-based design method, which may be referred to here as the indirect method, is biased due to both modelling and inversion errors. This paper presents a novel direct cross-talk cancellation method that may be free from the inversion error. The direct method can directly models the inverse filter by a suitable rearrangement of the input and output ports of the original plant so that no inversion is required here. Advantages are discussed with various experiments in an anechoic chamber using a PC soundcard. Binaural reproduction tests conducted showed that the conventional indirect method yields about 8 % reproduction performance error on both ear positions, whereas the direct method offers about 3 %.

• Journal of Welding and Joining
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• v.16 no.3
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• pp.141-147
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• 1998

Design sensitivity analysis of a vehicle system is an essential tool for design optimization and trade-off studies. Most optimization algorithms require the derivatives of cost and constraint function with respect to design in order to calculate the next improved design. This paper presents an efficient algorithm application for the design sensitivity analysis, using the direct differentiation method. A mounting area of suspension that welded on chassis frame is analyzed to show the validity and the efficiency of the proposed method. A mounting area of suspension that welded on chassis frame is analyzed to show the validity and the efficiency of the proposed method.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.4 s.142
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• pp.421-426
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• 2005

Scattering center extraction schemes for radar cross section reduction of large complex targets, like warships, was developed, which are an 1-D radar image method(range profile), and a direct analysis based on an object precision method. The analysis result of partial dihedral model shows that the presented direct analysis method is more efficient than the 1-D radar image method for scattering center extraction of interested targets, in terms of radar cross section reduction design, not signal processing. In order to verify the accuracy of the direct analysis method, a scattering center analysis of an naval weapon system was carried out, and the result was coincident with that of another well-known RCS analysis program. Finally, an analysis result of RCS and its scattering center of an 120m class warship-like model presented that the direct analysis method can be an efficient and powerful tools for radar cross section reduction of large complex targets.