• Korea Journal of Hospital Management
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• v.17 no.4
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• pp.167-187
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• 2012

Organizational growth is achieved through the process of finding opportunities in the environment and establishing a business model with internal and external resources. Bestian Hospital, which primarily focuses on saving the lives of patients with severe burns, has enlarged its business domain through deep understanding of burn patients' problems, including pain and complications during treatments, long-term treatments, skin reconstruction, and so on. Now Bestian is accelerating research for development of antipyretics and cosmetics for burn patients. The success of Bestian has been due to utilization of human and material resources that are essential to performance in the medical field. Also, Bestian properly used a management service organization(MSO) model and constructed an information technology(IT) system for supporting its businesses. However, previous successes do not guarantee continued success. Bestian is entering a new domain with different challenges than it has experienced so far, and how it deals with these challenges will decide its future.

• Ocean Systems Engineering
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• v.4 no.1
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• pp.63-82
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• 2014

Declutching control is applied to a hemispherical wave energy converter with direct linear electric Power-Take-Off systems oscillating in heave direction in both regular and irregular waves. The direct linear Power-Take-Off system can be simplified as a mechanical spring and damper system. Time domain model is applied to dynamics of the hemispherical wave energy converter in both regular and irregular waves. And state space model is used to replace the convolution term in time domain equation of the heave oscillation of the converter due to its inconvenience in analyzing the controlled motion of the converters. The declutching control strategy is conducted by optimal command theory based on Pontryagin's maximum principle to gain the controlled optimum sequence of Power-Take-Off forces. The results show that the wave energy converter with declutching control captures more energy than that without control and the former's amplitude and velocity is relatively larger. However, the amplification ratio of the absorbed power by declutching control is only slightly larger than 1. This may indicate that declutching control method may be inapplicable for oscillating wave energy converters with direct linear Power-Take-Off systems in real random sea state, considering the error of prediction of the wave excitation force.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.3
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• pp.976-990
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• 2020

The k-means algorithm is widely used in academia and industry due to easy and simple implementation, enabling fast learning for complex datasets. However, k-means struggles to classify datasets without prior knowledge of specific domains. We proposed the repulsive k-means (RK-means) algorithm in a previous study to improve the k-means algorithm, using the repulsive force concept, which allows deleting unnecessary cluster centroids. Accordingly, the RK-means enables to classifying of a dataset without domain knowledge. However, three main problems remain. The RK-means algorithm includes a cluster repulsive force offset, for clusters confined in other clusters, which can cause cluster locking; we were unable to prove RK-means provided optimal convergence in the previous study; and RK-means shown better performance only normalize term and weight. Therefore, this paper proposes the advanced RK-means (ARK-means) algorithm to resolve the RK-means problems. We establish an initialization strategy for deploying cluster centroids and define a metric for the ARK-means algorithm. Finally, we redefine the mass and normalize terms to close to the general dataset. We show ARK-means feasibility experimentally using blob and iris datasets. Experiment results verify the proposed ARK-means algorithm provides better performance than k-means, k'-means, and RK-means.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.5
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• pp.501-510
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• 2016

Capabilities of several beamforming techniques are compared for estimating the position of a moving source. Beamforming has enabled to widen our perspective of aeroacoustics in wind tunnel experiments and has provided useful approach in array measurements. Meanwhile beamforming techniques have been developed in a way to improve estimation accuracy and to save ing effort at the same time. In order to achieve reasonable outcome from aeroacoustic measurement, it is important to identify the spectral characteristics of source and to select an appropriate beamformer. Though aeroacoustic sources normally generates broadband noises, many array signal processing have been focused on narrowband processing which makes calculation numerically efficient. However, calculation in frequency-domain requires selection of single frequency of interest which affects spatial resolution and sidelobe level as a consequence. To be able to localize broadband noise source, it is proposed to use broadband beamforming. The formulas implements the deletion of diagonal term from cross spectral matrix. In this study, trajectory of flying source emitting broadband noise was simulated and several beamformers are applied.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.4
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• pp.565-574
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• 2000

A new ground penetrating radar imaging method for the estimation of buried artificial structures location and their approximate shapes in dispersive lossy ground is investigated. Fundamental idea is based on estimating delayed time and amplitude retrieval coefficients from scattered signals by buried scatterers. Using absolute value integration of each scanning site not only improve the accuracy of measured scattered signal, but also offers convenient ways to extract the image of buried structures. Multi-term Debye model was employed to describe a dispersive and lossy ground medium. We used the finite difference time domain method to discretize the wave equation in continuous form into the machine suitable form. This imaging method uses a new wave path tracing technique in time domain, which is helpful to identify the exact position of buried structures against the ground surface fluctuations.

• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.1
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• pp.95-104
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• 2011

As sea state harsher in the ocean space, more large motion and wave loads occurs on ships hull by non-linear phenomena. To consider nonlinear effect on ships hull in the structural design verification, the direct calculation method with numerical approach is used rather than rule values for the reliable accuracy. In this paper, the non-linear wave loads analysis in time domain is performed by using a Rankine Panel Method together with numerical schemes. Linear calculations have been carried out based on DNV CSA-2 notation to generate the motion responses and wave loads of large ships. By short and long term analysis, the design wave amplitudes are selected for the nonlinear analysis. The maximum wave induced bending moment in hogging and sagging conditions are calculated in the nonlinear analysis. Also, the green water effect on the wave induced vertical bending moment was investigated. The results show the vertical bending moments are more influenced by green water in sagging condition than in hogging condition due to green water loading.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1509-1513
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• 2009

The research of applying reinforced retaining wall due to support the land pressure that given from train's load has been accomplished actively in domestic area. After the retaining wall has been installed, the collapse or partial destruction that generated by effect of train's vibration and repetitive load of train may be induced. Accordingly in the period of using this, the sufficient durability should be guaranteed and years of durability are one hundred and as these are longer than road structure's, the technique that introduced to wall and monitor the long-term strain is necessary. In this paper, the optical fibre is induced vertically to the reinforced retaining wall and after the subsistence of optical fibre is confirmed, the early strain that applied to optical fibre after insertion is monitored. Before and after the concrete placing, damage feasibility of optical fibre is measured by using OTDR(Optical Time Domain Reflectometer) and after concrete is cultivated, the early strain induced to optical fibre is measured by application of BOCDA (Brillouin Correlation Domain Analysis) system.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.3
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• pp.232-248
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• 2009

Numerical methodology to solve ship springing problem, which is basically fluid-structure interaction problem, was explored in this study. Solution of this hydroelasticity problem was sought by coupling higher order B-spline Rankine panel method and finite element method in time domain, each of which is introduced for fluid and structure domain respectively. Even though varieties of different combinations in terms of numerical scheme are possible and have been tried by many researchers to solve the problem, no systematic study regarding the characteristics of each scheme has been done so far. Here, extensive case studies have been done on the numerical schemes especially focusing on the iteration method, FE analysis of beam-like structure, handling of forward speed problem and so on. Two different iteration scheme, Newton style one and fixed point iteration, were tried in this study and results were compared between the two. For the solution of the FE-based equation of motion, direct integration and modal superposition method were compared with each other from the viewpoint of its efficiency and accuracy. Finally, calculation of second derivative of basis potential, which is difficult to obtain with accuracy within grid-based method like BEM was discussed.

• Wind and Structures
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• v.13 no.3
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• pp.235-256
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• 2010

The aeroelastic stability of bridge decks equipped with multiple tuned mass dampers is studied. The problem is attacked in the time domain, by representing self-excited loads with the aid of aerodynamic indicial functions approximated by truncated series of exponential filters. This approach allows to reduce the aeroelastic stability analysis in the form of a direct eigenvalue problem, by introducing an additional state variable for each exponential term adopted in the approximation of indicial functions. A general probabilistic framework for the optimal robust design of multiple tuned mass dampers is proposed, in which all possible sources of uncertainties can be accounted for. For the purposes of this study, the method is also simplified in a form which requires a lower computational effort and it is then applied to a general case study in order to analyze the control effectiveness of regular and irregular multiple tuned mass dampers. A special care is devoted to mistuning effects caused by random variations of the target frequency. Regular multiple tuned mass dampers are seen to improve both control effectiveness and robustness with respect to single tuned mass dampers. However, those devices exhibit an asymmetric behavior with respect to frequency mistuning, which may weaken their feasibility for technical applications. In order to overcome this drawback, an irregular multiple tuned mass damper is conceived which is based on unequal mass distribution. The optimal design of this device is finally pursued via a full domain search, which evidences a remarkable robustness against frequency mistuning, in the sense of the simplified design approach.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.2108-2113
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• 2010

The Long Term Evolution (LTE) system is based on the Orthogonal Frequency Division Multiplexing (OFDM) and relies its channel estimation on the lattice-type pilot samples in the multipath fading channel environment. The estimation of the channel frequency response (CFR) makes use of the least squares estimate (LSE) for each pilot samples, followed by an interpolation both in time- and in frequency-domain to fill up the channel estimates for subcarriers corresponding to data samples. Any interpolation scheme could be adopted for this purpose. Depending on the requirements of the target system, we may choose a simple linear interpolation or a sophisticated one. For any choice of an interpolation scheme, these is a trade-off between estimation accuracy and numerical cost. For those wireless communication systems based on the OFDM and the preamble-type pilot structure, the DFT-based channel estimation and its variants have been successfully. Yet, it may not be suitable for the lattice-type pilot structure, since the pilot samples are not sufficient to provide an accurate estimate and it is known to be sensitive to the location as well as the length of the time-domain window. In this paper, we propose a simple interpolated based on the upsampling mechanism in the multirate signal processing. The proposed method provides an excellent alternative to the DFT-based methods in terms of numerical cost and accuracy. The performance of the proposed technique is verified on a multipath environment suggested on a 3GPP LTE specification.