• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.6
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• pp.607-613
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• 2009

In this paper, we made a simple paper feeding system which is one of MTS (media transport system) and controllers. The plant has a flexible paper and two driving rollers and two driven rollers. The control system has two conventional PID controllers. Skew angle and feeding speed of MTS deteriorate the quality of feeding system. In order to control a feeding speed and skew of feeding paper, we control rotational velocity of two driving rollers. Therefore, this controller has two inputs and two outputs as MIMO (multi-input and multi-output) system. The control inputs were the feeding speed and the skew displacement of the paper. The control outputs were the rotational velocity to each driving roller. To find appropriate PID gains of two controllers, we proposed an optimization technique. We assume the system variables and performance of a whole system as follows. PID gains of two controllers for skew and feeding speed are system variables. System performance is both skew and feeding speed. We simulates to making mathematical correlation using global Kriging interpolation. To find appropriate value of system variables, optimization method is simulation in sequence as following method. First, the optimization solver simulates with DOE (design of experiment) tables to find correlation equation of both system variable and performances. Then, the solver guesses the appropriate values and simulates if the system variables are appropriate or not. If the result of validation doesn't satisfy the convergence and iteration tolerance, the solver makes a new Kriging models and iterates this sequence until satisfy the tolerances.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.3
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• pp.259-266
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• 2011

We present a new dual sequential approximate optimization (SAO) algorithm called SD-TDQAO (sequential dual two-point diagonal quadratic approximate optimization). This algorithm solves engineering optimization problems with a nonlinear objective and nonlinear inequality constraints. The two-point diagonal quadratic approximation (TDQA) was originally non-convex and inseparable quadratic approximation in the primal design variable space. To use the dual method, SD-TDQAO uses diagonal quadratic explicit separable approximation; this can easily ensure convexity and separability. An important feature is that the second-derivative terms of the quadratic approximation are approximated by TDQA, which uses only information on the function and the derivative values at two consecutive iteration points. The algorithm will be illustrated using mathematical and topological test problems, and its performance will be compared with that of the MMA algorithm.

• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.4
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• pp.185-191
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• 2004

A mooring system can be applied to keep the position of a floating structures. In this study, the structural analysis is carried out to analyze the dynamic characteristics of a mooring line for a floating breakwater. A three-dimensional equations of motion for a submerged chain are derived. Bending stiffness is considered for the necessary restoring force in the regions of zero tension. A fortran program is to be developed by employing finite difference method. In the algorithm, an implicit time integration and Newton-Raphson iteration are adopted. The results of simulation show good agreement in tension response pattern with the experimental results of a reference. The results of this study can contribute for the design of mooring system for a floating breakwater.

• Journal of the Korean Magnetics Society
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• v.21 no.1
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• pp.15-22
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• 2011

It is necessary to describe the hysteresis characteristics of magnetic material precisely for the analysis or design of system with ferromagnetic materials. Although Preisach model is regarded as the most accurate method to describe the hysteresis characteristics, it is not widely applied to the real systems because of some difficulties. The conventional Preisach model shows the numerical instabilities during the iterative computations because the density distribution obtained from the sets of M-H curves are strongly localized. To remove such numerical instabilities, M-B instead of M-H is adopted as an implementation variable in normal Preisach modeling. The two dimensional computations with hysteresis characteristics by using normal Preisach modeling are tested and the result showed that the modeling by using M-B variables showed better stabilities than M-H variables.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.7
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• pp.677-684
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• 2003

This paper addresses the subblock phase weighting(SPW) method to reduce the PAPR in OFDM system. This method divides the input block of OFDM signal into many subblocks and lower the peak power by weighting the phase of each subblocks properly. SPW method can be realized by only one IFFT. PAPR reduction performance is novelly examined when the adjacent, interleaved and random subblock partitioning schemes are used in the SPW system. The random subblock partition scheme has the most effective. More subblocks can effectively reduce the PAPR, but there is a problem that the processing time of iteration is increased. We propose a new weighting factor combination of the complementary sequence characteristic with threshold technique. OFDM data can be recovered by the inserted side information of weighting factor in the feed forward type. Also, BER performance of this SPW system is analyzed when error happens in the side information.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.10
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• pp.5015-5038
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• 2018

In this paper, a novel spectral-spatial joint sparse representation algorithm for hyperspectral image classification is proposed based on multi-layer superpixels in various scales. Superpixels of various scales can provide complete yet redundant correlated information of the class attribute for test pixels. Therefore, we design a joint sparse model for a test pixel by sampling similar pixels from its corresponding superpixels combinations. Firstly, multi-layer superpixels are extracted on the false color image of the HSI data by principal components analysis model. Secondly, a group of discriminative sampling pixels are exploited as reconstruction matrix of test pixel which can be jointly represented by the structured dictionary and recovered sparse coefficients. Thirdly, the orthogonal matching pursuit strategy is employed for estimating sparse vector for the test pixel. In each iteration, the approximation can be computed from the dictionary and corresponding sparse vector. Finally, the class label of test pixel can be directly determined with minimum reconstruction error between the reconstruction matrix and its approximation. The advantages of this algorithm lie in the development of complete neighborhood and homogeneous pixels to share a common sparsity pattern, and it is able to achieve more flexible joint sparse coding of spectral-spatial information. Experimental results on three real hyperspectral datasets show that the proposed joint sparse model can achieve better performance than a series of excellent sparse classification methods and superpixels-based classification methods.

• The Journal of the Acoustical Society of Korea
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• v.15 no.5
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• pp.107-112
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• 1996

In this paper we propose a new fast codebook training algorithm for reducing the searching time of LBG algorithm. For each training data, the proposed algorithm stores the indexes of codewords that are close to that training data in the first iteration. It reduces computation time by searching only those codewords, the indexes of which are stored for each training data. Compared to one of the previous fast training algorithm, FSLBG, it obtains a better codebook with less exccution time. In our experiment, the performance of the codebook generated by the proposed algorithm in terms of peak signal-to-noise ratio(TSNR) is very close to that of LBG algorithm. However, the codewords to be searched for each training data of the proposed algorithm is only about 6%, for a codebook size of 256 and 1.6%, for a codebook size of 1.24, of LBG algorithm.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.4 s.70
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• pp.335-345
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• 2005

This paper concentrates on the nonlinear analysis of prestressed concrete (PSC) containment structures. Unlike a commercialized program which adopts the perfect bond assumption between concrete and tendon in the analysis of PSC structures, a numerical algorithm to consider the slip effect, simultaneously with the use of commercialized programs such as DIANA and ABAQUS, is introduced in this paper For bonded tendons, the apparent yield stress of an embedded tendon is determined from the bond slip relationship. And for unbonded tendons, Correction for the strength and stiffness of unbonded internal tendons is achieved on the basis of an iteration scheme derived from the slip behavior of tendon along the entire length. Finally, the developed algorithm is applied to two PSC containment structures of PWR and CANDU to verify its efficiency and applicability in simulating the structural behavior of large complex structures, and the obtained result shows that both containment structures represent the ultimate pressure capacity larger than about 3 times of the design pressure.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.1
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• pp.39-46
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• 2017

In this paper, a model updating procedure based on the response surface method combined with the multi-objective optimization was proposed and applied for updating of the FE models representing a low-rise reinforced concrete building before and after the seismic retrofit. The dynamic properties to be matched were obtained from vibration tests using a small shaker system. By varying the structural parameters according to the central composite design, analysis results from the initial FE model using a commercial software were collected and used to produce two regression functions each of which representing the errors in the natural frequencies and mode shapes. The two functions were used as the objective functions for multi-objective optimization. Final solution was determined by examining the Pareto solutions with one iteration. The parameters representing the stiffnesses of existing concrete, masonry, connection stiffness in expansion joint, new concrete, retrofitted members with steel section jacketing were selected and identified.

• Journal of Korean Society of Steel Construction
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• v.23 no.5
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• pp.607-614
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• 2011

This study deals with thegeometrical nonlinear dynamic behavior of laminated plates made of advanced composite materials (ACMs), which contain central cutouts. Based on the first-order shear deformation plate theory (FSDT), the Newmark method and Newton-Raphson iteration wereused for the nonlinear dynamic solution. The effects of the cutout sizes and lay-up sequences on the nonlinear dynamic response for various parameters werestudied using a nonlinear dynamic finite element program that was developed for this study. The several numerical results agreed well with those reported by other investigators for square composite plates with or without central cutouts, and the new results reported in this paper showed significant interactions between the cutout and the layup sequence in the laminate. Key observation points are discussed and a brief design guide for laminates with central cutouts is given.