• Journal of the Korean Society for Precision Engineering
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• v.23 no.8 s.185
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• pp.127-136
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• 2006

Metallic sandwich plates with inner dimpled shell subject to 3-point bending have been analyzed and then optimized for minimum weight. Inner dimpled shells can be easily fabricated by press or roll with high precision and bonded with same material skin sheets by resistance welding or adhesive bonding. Metallic sandwich plates with inner dimpled shell structure can be optimally designed for minimum weight subject to prescribed combination of bending and transverse shear loads. Fundamental findings for lightweight design are presented through constrained optimization. Failure responses of sandwich plates are predicted and formulated with an assumption of narrow sandwich beam theory. Failure is attributed to four kinds of mechanisms: face yielding, face buckling, dimple buckling and dimple collapse. Optimized shape of inner dimpled shell structure is a hemispherical shell to minimize weight without failure. It is demonstrated that bending stiffness of sandwich plate is 2 or 3 times larger than solid plates with the same strength. Failure mode boundaries and iso-strength lines dependent upon the geometry and yield strain of the material are plotted with respect to geometric parameters on the failure map. Because optimal parameters of maximum strength for given material weight can be selected from the map, analytic solutions for maximum strength are expressed as a function of only material property and proposed strength. These optimal parameters match well with numerical optimal parameters.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.36-39
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• 2009

We developed an optimal design interface based on VBA(Visual Basic Application) that takes advantage of API(Application Program Interface) function of commonly used EM analysis software. The developed interface is adopted for an optimal design of a septum in a waveguide tee junction using PSO(Particle Swarm Optimization) algorithm. The objective function of the optimal design is defined by $S_{11}$-parameter of the waveguide tee junction Design variables are established as position of the septum, that are changed to satisfy the design goal Using the developed design interface and PSO algorithm, the objective function converged to the smallest value, showing the validity of the proposed method. The design interface was developed using Microsoft Excel software, enabling easy control of design parameters for user. Also, various analysis parameters can be set in the Excel interface, including waveguide input mode and frequency. After completion of the design, field solutions at user-specified positrons can be extracted to the output files in complex number form.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.7
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• pp.891-898
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• 2011

The present work was conducted to get the best geometric information for the optimum design of the complex heat exchanger. The objective function for optimal design was expressed as a combination of pressure drop and heat transfer rate. The geometric parameters for the variables of louver pitch and height, tube width, etc., were limited to ranges set by manufacturing conditions. The optimum geometric parameters were calculated by using empirical correlations and theory. The sensitivity of the parameters and optimum values are shown and discussed. The weighting factor in the objective function is important in the selection of the louver fin-tube heat exchanger.

• Journal of the Semiconductor & Display Technology
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• v.8 no.3
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• pp.7-11
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• 2009

In this paper, we developed and presented a design result for optimizing the geometry of Ag circular SPP waveguide for subwavelength waveguide applications. We investigated the effect of the design parameters on the light propagation and find the optimum design for small modal size, high coupling coefficient, and low sensitivity. The results show that the globally optimal design locates optimal waveguide geometries more efficiently than individual optimal points for multivalued objective function.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.451-458
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• 2002

To secure structures from strong earthquakes occurred recently and design economically seismic isolation design is spread rapidly. Specially, frictional isolator has superiority in application to bridge because it has many advantages. however, because isolator lies between pier and girder, responses of pier and superstructure contradict each other and we need to control the two responses to minimize the bridge's failure probability. In this study, frictional coefficient and horizontal stiffness is defined as design parameters of frictional isolator. the optimal design parameters of frictional isolator to minimize the bridge's failure probability are presented according to strength of earthquake and soil conditions. The result says that optimal friction coefficient is higher as the strength of earthquake is increased. And it is also higher as the soils are more flexible. But, optimal horizontal stiffness of rubber spring is insensitive to strength of earthquake and soil condition.

• Transactions of Materials Processing
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• v.24 no.5
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• pp.332-339
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• 2015

In the current paper, a cold forging sequence was developed to manufacture a precisely cold forged H/Lower, which is used as the air back unit in commercial automobiles. The preform shape of the H/Lower influences the dimensional accuracy and stiffness of the final product. The shape factor (SF) ratio and shape of the tools are considered as the design parameters to achieve adequate backward extrusion height and maintain appropriate thickness variations. The optimal conditions of the design parameters were determined by using an artificial neural network (ANN). To experimentally verify the optimal preform and tool shapes, the experiments of the backward extrusion of the H/Lower were executed. The process design methodology proposed in the current paper, can provide a more systematic and economically feasible means for designing the preform and tool shapes for cold forging.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.4
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• pp.1-8
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• 2004

Various controllable parameters of an experiment have influence on grinding process. In order to get good products with a high quality, these parameters should be considered whether each parameter has relations to the quality. This paper describes the use of the design of experiments to minimize geometric error in surface grinding. Controllable parameters for the design of experiments were selected as spindle speed, table speed, depth of cut and grain size. From the experimental results, a degree of influence between these parameters and the geometric error was evaluated. An optimal set of grinding conditions was obtained by means of analysis of variance(ANOVA).

• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.488-492
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• 1986

This paper presents a design method for PID controller using optimal control theory. The procedures of the applied method consist of (1) sampling the system response to the test signal, (2) processing the sampled data using RPE method to identify the parameters of the plant, (3) calculating the optimal value of the PID controller parameters using LQ theory. This controller is implemented on the digital computer and applied to real servomechanism, yielding satisfactory result.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.1 s.94
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• pp.116-124
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• 1999

In most conventional design optimization of dynamic system, design sensitivities are utilized. However, design sensitivities based optimization method has numbers of drawback. First, computing design sensitivities for dynamic system is mathematically difficult, and almost impossible for many complex problems as well. Second, local optimum is obtained. On the other hand, Genetic Algorithm is the search technique based on the performance of system, not on the design sensitivities. It is the search algorithm based on the mechanics of natural selection and natural genetics. GA search, differing from conventional search techniques, starts with an initial set of random solutions called a population. Each individual in the population is called a chromosome, representing a solution to the problem at hand. The chromosomes evolve through successive iterations, called generations. As the generation is repeated, the fitness values of chromosomes were maximized, and design parameters converge to the optimal. In this study, Genetic Algorithm is applied to the actual dynamic optimization problems, to determine the optimal design parameters of the dynamic system.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.4
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• pp.422-434
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• 1997

In this paper, a two-stage kinematic optimal design for a 3 degree of-freedom (DOF) excavator subsystem, which consists of boom, arm and bucket, is performed. The objective of the first stage is to find the optimal parameters of the joint-actuating mechanisms which maximize the force-torque transmission ratio between the hydraulic actuator and the rotating joint. The objective of the second stage is to find the optimal link parameters which maximize the isotropic characteristic of the excavator subsystem throughout the workspace. It is illustrated that kinematic/dynamic performances of the kinematically optimized excavator subsystem have improved compared to those of original HE280 excavator, with respect to three performance indices such as maximum load handling capacity, maximum velocity capability, and acceleration capability.