• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.290-293
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• 1996

This paper presents an EMQ model which determines an optimal production run length in a deteriorating machine. It is assumed that a machine is subject to a random deterioration from an in-control state to an out-of-control state with an arbitrary distribution and thus producing constant proportion of defective items. An average cost function and an optimal production run length are determined. A mistake in previous model is found and discussed. A mistake in previous model is found and discussed. Numerical experiments are carried out to see the behavior of the proposed model depending on the cost factors as well as machine parameters, and some interesting behaviors are observed.

• Journal of the Korean Society of Mechanical Technology
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• v.20 no.6
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• pp.809-817
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• 2018

The model predictive controller performance of the mobile robot is set to an arbitrary value because it is difficult to select an accurate value with respect to the controller parameter. The general model predictive control uses a quadratic cost function to minimize the difference between the reference tracking error and the predicted trajectory error of the actual robot. In this study, we construct a predictive controller by transforming it into a quadratic programming problem considering velocity and acceleration constraints. The control parameters of the predictive controller, which determines the control performance of the mobile robot, are used a simple weighting matrix Q, R without the reference model matrix $A_r$ by applying a quadratic cost function from which the reference tracking error vector is removed. Therefore, we designed the predictive controller 1 and 2 of the mobile robot considering the constraints, and optimized the controller parameters of the predictive controller using a genetic algorithm with excellent optimization capability.

• Smart Structures and Systems
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• v.15 no.4
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• pp.1041-1062
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• 2015

In this paper a method of finding optimal positions for piezoelectric actuators and sensors on different structures is presented. The genetic algorithm and multi-objective genetic algorithm are selected for optimization and $H_{\infty}$ norm is defined as a cost function for the optimization process. To optimize the placement concerning the selected modes simultaneously, the multi-objective genetic algorithm is used. The optimization is investigated for two different structures: a cantilever beam and a simply supported plate. Vibrating structures are controlled in a closed loop with feedback gains, which are obtained using optimal LQ control strategy. Finally, output of a structure with optimized placement is compared with the output of the structure with an arbitrary, non-optimal placement of piezoelectric patches.

• International Journal of CAD/CAM
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• v.6 no.1
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• pp.89-97
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• 2006

This paper presents a novel approach for non-iterative surface smoothing with feature preservation on arbitrary meshes. Laplacian operator is performed in a global way over the mesh. The surface smoothing is formulated as a quadratic optimization problem, which is easily solved by a sparse linear system. The cost function to be optimized penalizes deviations from the global Laplacian operator while maintaining the overall shape of the original mesh. The features of the original mesh can be preserved by adding feature constraints and barycenter constraints in the system. Our approach is simple and fast, and does not cause surface shrinkage and distortion. Many experimental results are presented to show the applicability and flexibility of the approach.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.159-162
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• 1993

A new approach using fuzzy dynamic programming is proposed for the flexible long-term generation mix under uncertain circumstances. A characteristic feature of the presented approach is that not only fuzziness in fuel and construction cost. load growth and reliability but also many constraints of generation mix can easily be taken into account by using fuzzy dynamic programming. The method can accommodate arbitrary shape of membership function as well as the operation of pump-generator. And so more realistic solution can be obtained. The effectiveness of the proposed approach is demonstrated by the best generation mix problem of KEPCO-system which contains nuclear, coal, LNG, oil and pump-generator hydro plant in multi-years.

• Journal of Korean Society of Transportation
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• v.23 no.6 s.84
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• pp.7-18
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• 2005

Currently, design speed selection is chosen by highway function, terrain type and area type. But some standards in classifing highway function let designer decide design speed in an arbitrary manner and too rough a highway function classification system leads to a road function which can not reflect road design, and some ambiguity of terrain type leads to a road which can not reflect land use pattern. Highway design based on traffic volume level without considering area type can result high construction cost. This research paper provides new highway design standards which are based on the refinement of highway design speed selection procedure. The new design speed is summarized to be determined by a more detailed highway function, terrain type, and area type that were made considering South Korean characteristics. The new highway function is established by adopting highway function reclassification and design volumes and rural town center reclassification and new design standards for terrain type selection are developed in this research by analyzing South Korean GIS Data Base obtained over the national government offices.

• Journal of Sensor Science and Technology
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• v.6 no.2
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• pp.145-154
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• 1997

Based on a new search strategy using circuit simulation and simulated annealing with local search, a technique for design automation of high-performance operational amplifiers is proposed. For arbitrary circuit topology and performance specifications, through discrete optimization of a cost function with discrete design variables the design of operational amplifiers is performed. A special-purpose circuit simulator and some heuristics are used to reduce the design time. Through the design of a low-power high-speed fully differential CMOS operational amplifier usable in smart sensors and 10-b 25-MS/s pipelined A/D converters, it has been demonstrated that a design tool developed using the proposed technique can be used for designing high-performance operational amplifiers with less design knowledge and less design effort.

• Current Optics and Photonics
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• v.6 no.2
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• pp.161-170
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• 2022

Three-dimensional (3D) geometric models are introduced to correct vignetting, and a downhill simplex search is applied to determine the coefficients of a 3D model used in digital microscopy. Vignetting is nonuniform illuminance with a geometric regularity on a two-dimensional (2D) image plane, which allows the illuminance distribution to be estimated using 3D models. The 3D models are defined using generalized polynomials and arbitrary coefficients. Because the 3D models are nonlinear, their coefficients are determined using a simplex search. The cost function of the simplex search is defined to minimize the error between the 3D model and the reference image of a standard white board. The conventional and proposed methods for correcting the vignetting are used in experiments on four inspection systems based on machine vision and microscopy. The methods are investigated using various performance indices, including the coefficient of determination, the mean absolute error, and the uniformity after correction. The proposed method is intuitive and shows performance similar to the conventional approach, using a smaller number of coefficients.

• Journal of Biosystems Engineering
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• v.16 no.1
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• pp.60-82
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• 1991

Drying process of red pepper is very important in terms of drying cost and quality of the end product. Recently, many studies on red pepper drying have been performed. Nevertheless, an optimum drying condition is not established yet. Drying characteristics of red pepper is much affected by drying factors such as variety and initial state of red pepper as well as by environmental drying factors such as temperature and relative humidity of drying air. Various varieties of red pepper are being cultivated and the initial state of red pepper at harvest is very ambiguous. For this reason, it is very costly and time-consuming to establish an optimum drying condition of red pepper by experiment. A general drying model to descirbe a drying process has not been developed due to diversity of drying characteristics of red pepper. This study was, therefore, performed to develop a general drying model describing a drying process of red pepper. The results from this study are summarized as follows. 1. A basic model was established to develop an appropriate mositure content model and temperature model describing a drying process of red pepper, and the basic model was validated with experimental data. 2. The bone dry weight of fruit and mositure content were accepted satisfactorily as parameter to define the arbitrary red pepper. 3. The equilibrium moisture content of red pepper was found out to be different according to the variety of red pepper, air temperature and relative humidity. Also, the EMC model was developed using the parameters of air temperature, relative humidity and bone dry weight of fruit. 4. A general drying model for red pepper was developed, parameters of which were expressed as the function of drying factors related with drying phenomena. The developed drying model was found out to describe well the drying process of red pepper.

• Structural Engineering and Mechanics
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• v.71 no.4
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• pp.391-405
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• 2019

Compared to the ambient vibration test mainly identifying the structural modal parameters, such as frequency, damping and mode shapes, the impact testing, which benefits from measuring both impacting forces and structural responses, has the merit to identify not only the structural modal parameters but also more detailed structural parameters, in particular flexibility. However, in traditional impact tests, an impacting hammer or artificial excitation device is employed, which restricts the efficiency of tests on various bridge structures. To resolve this problem, we propose a new method whereby a moving vehicle is taken as a continuous exciter and develop a corresponding flexibility identification theory, in which the continuous wheel forces induced by the moving vehicle is considered as structural input and the acceleration response of the bridge as the output, thus a structural flexibility matrix can be identified and then structural deflections of the bridge under arbitrary static loads can be predicted. The proposed method is more convenient, time-saving and cost-effective compared with traditional impact tests. However, because the proposed test produces a spatially continuous force while classical impact forces are spatially discrete, a new flexibility identification theory is required, and a novel structural identification method involving with equivalent load distribution, the enhanced Frequency Response Function (eFRFs) construction and modal scaling factor identification is proposed to make use of the continuous excitation force to identify the basic modal parameters as well as the structural flexibility. Laboratory and numerical examples are given, which validate the effectiveness of the proposed method. Furthermore, parametric analysis including road roughness, vehicle speed, vehicle weight, vehicle's stiffness and damping are conducted and the results obtained demonstrate that the developed method has strong robustness except that the relative error increases with the increase of measurement noise.