• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.571-573
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• 2010

Most real world system such as world economy, management, medical and engineering applications contain a series of complex phenomena. One of common methods to understand these system is to build a model and analyze the behavior of the system. As a first step, Determining the best clusters on data. As a second step, Determining the model of the cluster. In this paper, we investigated heuristic search methods for efficient clustering.

• Bulletin of the Korean Chemical Society
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• v.18 no.1
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• pp.18-23
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• 1997

Data from structure/activity studies in vir gene induction system have led to evaluate the working hypothesis of interaction between phenolic inducers and phenol binding proteins. The primary specificity in the association of a phenolic inducer with its receptor in our system is hypothesized to be the hydrogen bonding interactions through the ortho methoxy substituents as well as the proton transfer between the inducer and the binding protein. In this paper the proposed working model for phenol-mediating signal transduction was evaluated in several ways. The importance of the general acid-base catalysis was first addressed by the presence of an acidic residue and a basic residue in the phenol binding protein. Series of compounds were tested for vir gene expression activity to confirm the generation of a strong nucleophile by an acidic residue and an involvement of a basic residue as a proton acceptor. An attempt was made to correlate the pKa values of the phenolic compounds with vir gene induction activities as inducers to further support the proposed proton transfer mechanism. Finally, it was also observed that the regioselectively attached methoxy group on phenol compounds is required as the proper hydrogen bond acceptor.

• International Journal of Reliability and Applications
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• v.14 no.2
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• pp.97-105
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• 2013

A stress-strength model is formulated for a multi-component system consisting of k identical components. The k components of the system with random strengths ($X_1$, $X_2$, ${\ldots}$, $X_k$) are subjected to one of the r random stresses ($X_{k+1}$, $X_{k+2}$, ${\ldots}$, $X_{k+r}$). The estimation of system reliability based on maximum likelihood estimates (MLEs) and Bayes estimators in k component system are obtained when the system is either parallel or series with the assumption that strengths and stresses follow exponential distribution. A simulation study is conducted to compare MLE and Bayes estimator through the mean squared errors of the estimators.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.6
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• pp.951-963
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• 2015

The water wave characteristics of Bragg reflections from a train of fixed floating pontoon breakwaters was studied numerically. A numerical model of boundary discretization type was developed to calculate the wave field. The model was verified by comparing to analytical data in literature and good agreements were achieved. Series of parametric studies were conducted systematically to investigate the dependence of the reflected coefficients by the Bragg scattering on the design variables, including the spacing between the breakwaters, the total number of installed breakwaters, the draft and width do the breakwater, and wave length. Certain wave characteristics of the Bragg reflections were observed and discussed in details which might be of help for practical engineering applications in shoreline protection from incident waves.

• Computers and Concrete
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• v.24 no.1
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• pp.51-61
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• 2019

Compressive ability is one of the most important mechanical properties of concrete material. The compressive failure process of concrete is pretty complex with internal tension, shear damage and friction between cracks. To simulate the complex fracture process of concrete at meso level, methodology for meso-structural analysis of concrete specimens is developed; the zero thickness cohesive elements are pre-inserted to simulate the crack initiation and propagation; the constitutive applied in cohesive element is established to describe the mechanism of crack separation, closure and friction behavior between the fracture surfaces. A series of simulations were carried out based on the model proposed in this paper. The results reproduced the main fracture and mechanical feature of concrete under compression condition. The effect of key material parameters, structure size, and aggregate content on the concrete fracture pattern and loading carrying capacities was investigated. It is found that the inner friction coefficient has a significant influence on the compression character of concrete, the compression strength raises linearly with the increase of the inner friction coefficient, and the fracture pattern is sensitive to the mesostructure of concrete.

• Ocean Systems Engineering
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• v.9 no.1
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• pp.1-19
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• 2019

Latching control was applied to a Wave Energy Converter (WEC) buoy with direct linear electric Power Take-Off (PTO) systems oscillating in heave direction in waves. The equation of the motion of the WEC buoy in the time-domain is characterized by the wave exciting, hydrostatic, radiation forces and by several damping forces (PTO, brake, and viscous). By applying numerical schemes, such as the semi-analytical and Newmark ${\beta}$ methods, the time series of the heave motion and velocity, and the corresponding extracted power may be obtained. The numerical prediction with the latching control is in accordance with the experimental results from the systematic 1:10-model test in a wave tank at Seoul National University. It was found that the extraction of wave energy may be improved by applying latching control to the WEC, which particularly affects waves longer than the resonant period.

• Communications for Statistical Applications and Methods
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• v.26 no.5
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• pp.463-471
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• 2019

The variable transformations are useful ways to guarantee the functional relationships in the model. However, the presence of outliers may undermine the accuracy of transformation. This paper deals with response transformations in the partial linear models under the existence of outliers. A new procedure for response transformation and outliers detection is proposed. The procedure uses a sequential method for identifying outliers and dynamic graphical methods for an appropriate transformation. The graphical tools make it possible to catch diagnostic information by monitoring the movement of points in the data. The procedure is illustrated with several examples. Examples show that visual clues regarding the optimal transformation, the fittness of the model and the outlyness of the observations can be checked from the series of plots.

• Structural Engineering and Mechanics
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• v.69 no.5
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• pp.487-497
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• 2019

Rapid advances in the engineering applications can bring further areas to provide the opportunity to manipulate anisotropic structures for direct productivity in design of micro/nano-structures. For the first time, magnetic affected wave characteristics of nanosize plates made of anisotropic material is investigated via the three-dimensional bi-Helmholtz nonlocal strain gradient theory. Three small scale parameters are used to predict the size-dependent behavior of the nanoplates more accurately. After owing governing equations of wave motion, an analytical approach based harmonic series is utilized to fine the wave frequency as well as phase velocity. It is observed that the small scale parameters, magnetic field and wave number have considerable influence on the wave characteristics of anisotropic nanoplates. Due to the lack of any study on the mechanics of three-dimensional bi-Helmholtz gradient plates made of anisotropic materials, it is hoped that the present exact model may be used as a benchmark for future works of such nanostructures.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.285-293
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• 2019

In the present paper, model tests of suppressing sloshing fitted with two perforated floating plates are carried out. The study involves identification of system performance such as the suppression and the solidity ratio. Three different solidity ratios of perforated plates have been tried out as potential positive slosh damping devices. A series of painstaking experiments have been conducted in a rigid rectangular tank on six degrees of freedom motion platform under roll harmonic excitation. Comparison of the clean tank shows that the three types of perforated plates are all effective on damping the run-up and impact pressure along the bulkhead. The parametric study indicates that the perforated plate with the median solidity ratio is the most optimal one in suppressing sloshing among three configurations.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.202-210
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• 2019

The obstacles modeling is a fundamental and significant issue for path planning and automatic navigation of Unmanned Surface Vehicle (USV). In this study, we propose a novel obstacles modeling method based on high resolution satellite images. It involves two main steps: extraction of obstacle features and construction of convex hulls. To extract the obstacle features, a series of operations such as sea-land segmentation, obstacles details enhancement, and morphological transformations are applied. Furthermore, an efficient algorithm is proposed to mask the obstacles into convex hulls, which mainly includes the cluster analysis of obstacles area and the determination rules of edge points. Experimental results demonstrate that the models achieved by the proposed method and the manual have high similarity. As an application, the model is used to find the optimal path for USV. The study shows that the obstacles modeling method is feasible, and it can be applied to USV path planning.